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000
FXUS63 KILX 270122
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
822 PM CDT TUE MAY 26 2015

.UPDATE...
ISSUED AT 815 PM CDT TUE MAY 26 2015

8 PM SURFACE MAP INDICATES A WEAK COLD FRONT/WIND SHIFT LINE WAS
EDGING SLOWLY TO THE EAST EARLY THIS EVENING AND WEST LOCATED OVER
EXTREME EAST CENTRAL IOWA. THIS BOUNDARY IS FORECAST TO SLOWLY
TRACK INTO OUR FORECAST AREA BY EARLY WEDNESDAY MORNING.
MEANWHILE...THE WATER VAPOR LOOP INDICATES A WEAK UPPER LEVEL WAVE
PUSHING EAST FROM THE MISSOURI RIVER VALLEY WITH ORGANIZED
CONVECTION OCCURRING AHEAD OF THE WAVE ACROSS EAST CENTRAL KS
SOUTH THRU OK AND TX. ILX LOCAL OBJECTIVE ANALYSIS INDICATES MOST
UNSTABLE CAPES AROUND 600 J/KG ACROSS THE WEST WITH MOST OF THE
HI-RES SHORT TERM MODELS SUGGESTING MUCAPES IN THE ORDER OF
500-1000 J/KG LATE TONIGHT AHEAD OF THE APPROACHING SHORTWAVE AND
FRONTAL BOUNDARY. CURRENT FORECAST HAS THE HIGHER POPS ACROSS THE
WEST AND CENTRAL AREAS THIS EVENING WITH A GRADUAL SHIFT TO THE
SOUTH WEDNESDAY MORNING AS THE WEAK BOUNDARY SETTLES SOUTHEAST
ACROSS THE FORECAST AREA. MAKING SOME MINOR ADJUSTMENTS TO THE
GRIDS IN THE POPS AND TEMPS FOR THE OVERNIGHT HOURS. SHOULD HAVE
THE UPDATE OUT BY 845 PM.

&&

.SHORT TERM...(TONIGHT)
ISSUED AT 300 PM CDT TUE MAY 26 2015

2 PM SURFACE MAP SHOWED LOW PRESSURE CENTERED JUST NORTHWEST OF
DUBUQUE. INITIAL BAND OF CONVECTIVE SHOWERS/ISOLATED THUNDERSTORMS
WHICH MOVED THROUGH THE FORECAST AREA EARLIER HAS ADVANCED NORTHEAST
ACROSS THE INDIANA BORDER...WITH A SECONDARY AXIS OF LIGHT SHOWERS
MOVING EAST AHEAD OF AN UPPER DISTURBANCE CROSSING THE MISSISSIPPI
RIVER.

HRRR AND OTHER HIGH-RESOLUTION MODEL GUIDANCE HAS BEEN DOING A
REASONABLE JOB WITH THE ACTIVITY TODAY...AND WAS GENERALLY FOLLOWED
FOR THE RAIN TRENDS TONIGHT. HAVE MADE SOME ADJUSTMENTS WITH GOING
MAINLY ISOLATED SHOWERS/STORMS THIS EVENING EXCEPT WEST OF I-55...
WHERE LOW CHANCE POP`S WERE KEPT AS A WAVE/TROUGH ADVANCES EAST
ACROSS NORTHERN MISSOURI. HAVE LINGERED THESE 30% CHANCES OVERNIGHT
FROM ABOUT DECATUR WESTWARD. SHOULD SEE SKIES BECOME PARTLY CLOUDY
ACROSS THE SOUTHERN CWA THIS EVENING...BEFORE SOME INCREASE IS NOTED
AGAIN AHEAD OF THE INCOMING WAVE.

.LONG TERM...(WEDNESDAY THROUGH TUESDAY)
ISSUED AT 300 PM CDT TUE MAY 26 2015

AN UNSETTLED WEATHER PATTERN LOOKS TO CONTINUE THROUGH MONDAY ACROSS
CENTRAL AND SOUTHEAST IL ALONG WITH WARM AND RATHER HUMID SUMMERLIKE
CONDITIONS THE REST OF THE WEEK. A COLD FRONT MOVING SE THROUGH
CENTRAL AND SOUTHEAST IL DURING SATURDAY WILL BRING COOLER
TEMPERATURES DURING THIS WEEKEND ESPECIALLY ON SUNDAY.

UPPER LEVEL TROF OVER THE UPPER MIDWEST MOVES INTO MI ON WED WHILE
PUSHING A WEAK FRONT SE INTO THE IL RIVER VALLEY WED AFTERNOON. ALSO
HAVE A SHORT WAVE EJECTING NE FROM THE SOUTHERN PLAINS INTO SE IL
AND CENTRAL INDIANA BY 18Z/WED. INCREASE INSTABLITY ON WED WITH
CAPES OF 1000-2000 J/KG AND HIGHEST SOUTH OF I-72 TO RETURN CHANCES
OF SHOWERS AND THUNDERSTORMS WITH LOWER CHANCES NW OF IL RIVER AND
HIGHER CHANCES IN SOUTHEAST IL. SPC HAS MARGINAL RISK OF SEVERE WED
AFTERNOON SE OF A SHELYVILLE TO PARIS LINE. CONVECTION CHANCES WILL
LINGER SOUTH OF I-72 WED NIGHT MAINLY WED EVENING. THEN ISOLATED
CHANCES OF CONVECTION SHIFT INTO SOUTHERN AND SW AREAS ON THU AS
WEAK HIGH PRESSURE DRIFTS ACROSS THE GREAT LAKES AND MORE STABLE AIR
OVER NE CWA FROM I-74 NE WHERE IT SHOULD BE DRY. NAM MODEL IS STILL
RATHER UNSTABLE THU SW OF I-74 BUT THINK IT MAY BE OVERDOING THIS AS
STRONGER INSTABLITY CLOSER MO AND THE OHIO RIVER VALLEY ON THU PLUS
HAVE UPPER LEVEL RIDGE BUILDING OVER THE EASTERN STATES THU.

WARM FRONT LIFTS NORTH ACROSS CENTRAL IL THU NIGHT AND IN BREEZY SSW
FLOW ON FRIDAY WITH CHANCES OF SHOWERS AND THUNDERSTORM HIGHEST OVER
IL RIVER VALLEY (LIKELY CHANCES WEST OF IL RIVER ON FRIDAY) AND
LOWEST NEAR WABASH RIVER. WARM HIGHS IN THE LOWER 80S WED AND MID
80S THU AND FRI AND A FEW AREAS COULD REACH UPPER 80S WITH ENOUGH
SUNSHINE ESPECIALLY NEAR WABASH RIVER WHERE RAIN CHANCES ARE LOWER.

HAVE LIKELY CHANCES OF SHOWERS AND THUNDERSTORMS FRI NIGHT AND SAT
WITH COLD FRONT PUSHING SE THROUGH CENTRAL IL DURING SATURDAY. HIGHS
SAT TO CONTRAST FROM LOWER 70S NW OF IL RIVER TO LOW 80S IN
SOUTHEAST IL. CONTINUE LIKELY CHANCES OF SHOWERS AND THUNDERSTORMS
SAT NIGHT IN SOUTHEAST IL ESPECIALLY SAT EVENING WHILE LOWERED POPS
TO LOW CHANCE NW OVER IL RIVER VALLEY BEHIND COLD FRONT. AREAS NW OF
IL RIVER NOW APPEAR DRY ON SUNDAY WHILE CHANCE OF SHOWERS AND
THUNDERSTORMS LINGERS FROM I-72 SOUTH CLOSER TO FRONTAL BOUNDARY
PUSHING SE OF OHIO RIVER OVER KY/TN. SUNDAY APPEARS TO BE COOLEST
DAY WITH HIGHS IN UPPER 60S CENTRAL IL AND LOWER 70S SE IL.

EXTENDED MODELS LIKE GFS AND ECMWF CONTINUE TO SHOW A WEAK CUTOFF
UPPER LEVEL LOW EJECTING INTO MO BY MON AND TO CONTINUE CHANCES OF
SHOWERS AND ISOLATED THUNDERSTORMS MONDAY AND TUESDAY. HIGHS IN THE
LOW TO MID 70S MONDAY AND MID TO UPPER 70S TUESDAY.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z WEDNESDAY EVENING)
ISSUED AT 600 PM CDT TUE MAY 26 2015

MAIN FORECAST CONCERN WILL BE ANY ADDITIONAL SHOWER ACTIVITY AND
AFFECT ON CLOUD BASES LATER THIS EVENING...AND THE POTENTIAL FOR
SOME MVFR FOG TOWARDS DAWN WED. LATEST SURFACE MAP HAS A WEAK
BOUNDARY/WIND SHIFT LINE OVER CENTRAL IOWA EARLY THIS EVENING
AND THAT FEATURE IS EXPECTED TO SLOWLY PUSH ACROSS THE FORECAST
AREA LATE TONIGHT/WED MORNING. NOT MUCH OF A TEMP OR DEW POINT
DISCONTINUITY ASSOCIATED WITH THE FEATURE AND THE UPPER LEVEL
LIFT IS MEAGER SO NOT EXPECTING MUCH IN THE WAY OF WIDESPREAD
RAINFALL OVERNIGHT AS IT PUSHES THROUGH THE AREA. FORECAST
SOUNDINGS SUGGEST SOME LOW MVFR CIGS AT TIMES AHEAD OF THE
FRONT WITH THE WIND FIELDS QUITE LIGHT ALONG AND JUST BEHIND
THE FRONT WHICH MAY ALLOW SOME MVFR FOG TO FORM TOWARDS WED
MORNING. CURRENT FORECAST SOUNDINGS INDICATE ENOUGH CLOUD
COVER WILL LINGER OVERNIGHT...ESPECIALLY IN THE MID AND UPPER
PORTIONS OF THE ATMOSPHERE THAT MAY LIMIT ANY RESTRICTIONS TO
VSBYS. FOR NOW WILL INTRODUCE A 5 TO 6 MI VSBY AT BMI AND CMI
WHICH WILL BE SEEING THE LIGHTER WINDS OVERNIGHT.

AN UPPER LEVEL WAVE IS FORECAST TO PUSH ACROSS THE SOUTHERN PLAINS
TONIGHT AND EDGE ENE INTO PARTS OF SOUTH CENTRAL IL BY MORNING
WED BRINGING SOME SCATTERED SHOWERS AND THUNDERSTORMS WITH IT.
CURRENT GUIDANCE SUGGESTS THE BULK OF THE RAIN SHOULD REMAIN SOUTH
OF THE TAF SITES WITH MAINLY VFR CONDITIONS EXPECTED FOR THE
REMAINDER OF THE DAY. SOUTHWEST WINDS AROUND 10KTS EXPECTED
TONIGHT WILL VEER MORE INTO A WESTERLY DIRECTION AS THE WEAKENING
BOUNDARY SHIFTS ACROSS THE AREA DURING THE DAY WEDNESDAY. WIND
SPEEDS SHOULD RANGE FROM 10 TO 15 KTS.


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...SMITH
SHORT TERM...GEELHART
LONG TERM...07
AVIATION...SMITH



000
FXUS63 KILX 270122
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
822 PM CDT TUE MAY 26 2015

.UPDATE...
ISSUED AT 815 PM CDT TUE MAY 26 2015

8 PM SURFACE MAP INDICATES A WEAK COLD FRONT/WIND SHIFT LINE WAS
EDGING SLOWLY TO THE EAST EARLY THIS EVENING AND WEST LOCATED OVER
EXTREME EAST CENTRAL IOWA. THIS BOUNDARY IS FORECAST TO SLOWLY
TRACK INTO OUR FORECAST AREA BY EARLY WEDNESDAY MORNING.
MEANWHILE...THE WATER VAPOR LOOP INDICATES A WEAK UPPER LEVEL WAVE
PUSHING EAST FROM THE MISSOURI RIVER VALLEY WITH ORGANIZED
CONVECTION OCCURRING AHEAD OF THE WAVE ACROSS EAST CENTRAL KS
SOUTH THRU OK AND TX. ILX LOCAL OBJECTIVE ANALYSIS INDICATES MOST
UNSTABLE CAPES AROUND 600 J/KG ACROSS THE WEST WITH MOST OF THE
HI-RES SHORT TERM MODELS SUGGESTING MUCAPES IN THE ORDER OF
500-1000 J/KG LATE TONIGHT AHEAD OF THE APPROACHING SHORTWAVE AND
FRONTAL BOUNDARY. CURRENT FORECAST HAS THE HIGHER POPS ACROSS THE
WEST AND CENTRAL AREAS THIS EVENING WITH A GRADUAL SHIFT TO THE
SOUTH WEDNESDAY MORNING AS THE WEAK BOUNDARY SETTLES SOUTHEAST
ACROSS THE FORECAST AREA. MAKING SOME MINOR ADJUSTMENTS TO THE
GRIDS IN THE POPS AND TEMPS FOR THE OVERNIGHT HOURS. SHOULD HAVE
THE UPDATE OUT BY 845 PM.

&&

.SHORT TERM...(TONIGHT)
ISSUED AT 300 PM CDT TUE MAY 26 2015

2 PM SURFACE MAP SHOWED LOW PRESSURE CENTERED JUST NORTHWEST OF
DUBUQUE. INITIAL BAND OF CONVECTIVE SHOWERS/ISOLATED THUNDERSTORMS
WHICH MOVED THROUGH THE FORECAST AREA EARLIER HAS ADVANCED NORTHEAST
ACROSS THE INDIANA BORDER...WITH A SECONDARY AXIS OF LIGHT SHOWERS
MOVING EAST AHEAD OF AN UPPER DISTURBANCE CROSSING THE MISSISSIPPI
RIVER.

HRRR AND OTHER HIGH-RESOLUTION MODEL GUIDANCE HAS BEEN DOING A
REASONABLE JOB WITH THE ACTIVITY TODAY...AND WAS GENERALLY FOLLOWED
FOR THE RAIN TRENDS TONIGHT. HAVE MADE SOME ADJUSTMENTS WITH GOING
MAINLY ISOLATED SHOWERS/STORMS THIS EVENING EXCEPT WEST OF I-55...
WHERE LOW CHANCE POP`S WERE KEPT AS A WAVE/TROUGH ADVANCES EAST
ACROSS NORTHERN MISSOURI. HAVE LINGERED THESE 30% CHANCES OVERNIGHT
FROM ABOUT DECATUR WESTWARD. SHOULD SEE SKIES BECOME PARTLY CLOUDY
ACROSS THE SOUTHERN CWA THIS EVENING...BEFORE SOME INCREASE IS NOTED
AGAIN AHEAD OF THE INCOMING WAVE.

.LONG TERM...(WEDNESDAY THROUGH TUESDAY)
ISSUED AT 300 PM CDT TUE MAY 26 2015

AN UNSETTLED WEATHER PATTERN LOOKS TO CONTINUE THROUGH MONDAY ACROSS
CENTRAL AND SOUTHEAST IL ALONG WITH WARM AND RATHER HUMID SUMMERLIKE
CONDITIONS THE REST OF THE WEEK. A COLD FRONT MOVING SE THROUGH
CENTRAL AND SOUTHEAST IL DURING SATURDAY WILL BRING COOLER
TEMPERATURES DURING THIS WEEKEND ESPECIALLY ON SUNDAY.

UPPER LEVEL TROF OVER THE UPPER MIDWEST MOVES INTO MI ON WED WHILE
PUSHING A WEAK FRONT SE INTO THE IL RIVER VALLEY WED AFTERNOON. ALSO
HAVE A SHORT WAVE EJECTING NE FROM THE SOUTHERN PLAINS INTO SE IL
AND CENTRAL INDIANA BY 18Z/WED. INCREASE INSTABLITY ON WED WITH
CAPES OF 1000-2000 J/KG AND HIGHEST SOUTH OF I-72 TO RETURN CHANCES
OF SHOWERS AND THUNDERSTORMS WITH LOWER CHANCES NW OF IL RIVER AND
HIGHER CHANCES IN SOUTHEAST IL. SPC HAS MARGINAL RISK OF SEVERE WED
AFTERNOON SE OF A SHELYVILLE TO PARIS LINE. CONVECTION CHANCES WILL
LINGER SOUTH OF I-72 WED NIGHT MAINLY WED EVENING. THEN ISOLATED
CHANCES OF CONVECTION SHIFT INTO SOUTHERN AND SW AREAS ON THU AS
WEAK HIGH PRESSURE DRIFTS ACROSS THE GREAT LAKES AND MORE STABLE AIR
OVER NE CWA FROM I-74 NE WHERE IT SHOULD BE DRY. NAM MODEL IS STILL
RATHER UNSTABLE THU SW OF I-74 BUT THINK IT MAY BE OVERDOING THIS AS
STRONGER INSTABLITY CLOSER MO AND THE OHIO RIVER VALLEY ON THU PLUS
HAVE UPPER LEVEL RIDGE BUILDING OVER THE EASTERN STATES THU.

WARM FRONT LIFTS NORTH ACROSS CENTRAL IL THU NIGHT AND IN BREEZY SSW
FLOW ON FRIDAY WITH CHANCES OF SHOWERS AND THUNDERSTORM HIGHEST OVER
IL RIVER VALLEY (LIKELY CHANCES WEST OF IL RIVER ON FRIDAY) AND
LOWEST NEAR WABASH RIVER. WARM HIGHS IN THE LOWER 80S WED AND MID
80S THU AND FRI AND A FEW AREAS COULD REACH UPPER 80S WITH ENOUGH
SUNSHINE ESPECIALLY NEAR WABASH RIVER WHERE RAIN CHANCES ARE LOWER.

HAVE LIKELY CHANCES OF SHOWERS AND THUNDERSTORMS FRI NIGHT AND SAT
WITH COLD FRONT PUSHING SE THROUGH CENTRAL IL DURING SATURDAY. HIGHS
SAT TO CONTRAST FROM LOWER 70S NW OF IL RIVER TO LOW 80S IN
SOUTHEAST IL. CONTINUE LIKELY CHANCES OF SHOWERS AND THUNDERSTORMS
SAT NIGHT IN SOUTHEAST IL ESPECIALLY SAT EVENING WHILE LOWERED POPS
TO LOW CHANCE NW OVER IL RIVER VALLEY BEHIND COLD FRONT. AREAS NW OF
IL RIVER NOW APPEAR DRY ON SUNDAY WHILE CHANCE OF SHOWERS AND
THUNDERSTORMS LINGERS FROM I-72 SOUTH CLOSER TO FRONTAL BOUNDARY
PUSHING SE OF OHIO RIVER OVER KY/TN. SUNDAY APPEARS TO BE COOLEST
DAY WITH HIGHS IN UPPER 60S CENTRAL IL AND LOWER 70S SE IL.

EXTENDED MODELS LIKE GFS AND ECMWF CONTINUE TO SHOW A WEAK CUTOFF
UPPER LEVEL LOW EJECTING INTO MO BY MON AND TO CONTINUE CHANCES OF
SHOWERS AND ISOLATED THUNDERSTORMS MONDAY AND TUESDAY. HIGHS IN THE
LOW TO MID 70S MONDAY AND MID TO UPPER 70S TUESDAY.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z WEDNESDAY EVENING)
ISSUED AT 600 PM CDT TUE MAY 26 2015

MAIN FORECAST CONCERN WILL BE ANY ADDITIONAL SHOWER ACTIVITY AND
AFFECT ON CLOUD BASES LATER THIS EVENING...AND THE POTENTIAL FOR
SOME MVFR FOG TOWARDS DAWN WED. LATEST SURFACE MAP HAS A WEAK
BOUNDARY/WIND SHIFT LINE OVER CENTRAL IOWA EARLY THIS EVENING
AND THAT FEATURE IS EXPECTED TO SLOWLY PUSH ACROSS THE FORECAST
AREA LATE TONIGHT/WED MORNING. NOT MUCH OF A TEMP OR DEW POINT
DISCONTINUITY ASSOCIATED WITH THE FEATURE AND THE UPPER LEVEL
LIFT IS MEAGER SO NOT EXPECTING MUCH IN THE WAY OF WIDESPREAD
RAINFALL OVERNIGHT AS IT PUSHES THROUGH THE AREA. FORECAST
SOUNDINGS SUGGEST SOME LOW MVFR CIGS AT TIMES AHEAD OF THE
FRONT WITH THE WIND FIELDS QUITE LIGHT ALONG AND JUST BEHIND
THE FRONT WHICH MAY ALLOW SOME MVFR FOG TO FORM TOWARDS WED
MORNING. CURRENT FORECAST SOUNDINGS INDICATE ENOUGH CLOUD
COVER WILL LINGER OVERNIGHT...ESPECIALLY IN THE MID AND UPPER
PORTIONS OF THE ATMOSPHERE THAT MAY LIMIT ANY RESTRICTIONS TO
VSBYS. FOR NOW WILL INTRODUCE A 5 TO 6 MI VSBY AT BMI AND CMI
WHICH WILL BE SEEING THE LIGHTER WINDS OVERNIGHT.

AN UPPER LEVEL WAVE IS FORECAST TO PUSH ACROSS THE SOUTHERN PLAINS
TONIGHT AND EDGE ENE INTO PARTS OF SOUTH CENTRAL IL BY MORNING
WED BRINGING SOME SCATTERED SHOWERS AND THUNDERSTORMS WITH IT.
CURRENT GUIDANCE SUGGESTS THE BULK OF THE RAIN SHOULD REMAIN SOUTH
OF THE TAF SITES WITH MAINLY VFR CONDITIONS EXPECTED FOR THE
REMAINDER OF THE DAY. SOUTHWEST WINDS AROUND 10KTS EXPECTED
TONIGHT WILL VEER MORE INTO A WESTERLY DIRECTION AS THE WEAKENING
BOUNDARY SHIFTS ACROSS THE AREA DURING THE DAY WEDNESDAY. WIND
SPEEDS SHOULD RANGE FROM 10 TO 15 KTS.


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...SMITH
SHORT TERM...GEELHART
LONG TERM...07
AVIATION...SMITH



000
FXUS63 KILX 270122
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
822 PM CDT TUE MAY 26 2015

.UPDATE...
ISSUED AT 815 PM CDT TUE MAY 26 2015

8 PM SURFACE MAP INDICATES A WEAK COLD FRONT/WIND SHIFT LINE WAS
EDGING SLOWLY TO THE EAST EARLY THIS EVENING AND WEST LOCATED OVER
EXTREME EAST CENTRAL IOWA. THIS BOUNDARY IS FORECAST TO SLOWLY
TRACK INTO OUR FORECAST AREA BY EARLY WEDNESDAY MORNING.
MEANWHILE...THE WATER VAPOR LOOP INDICATES A WEAK UPPER LEVEL WAVE
PUSHING EAST FROM THE MISSOURI RIVER VALLEY WITH ORGANIZED
CONVECTION OCCURRING AHEAD OF THE WAVE ACROSS EAST CENTRAL KS
SOUTH THRU OK AND TX. ILX LOCAL OBJECTIVE ANALYSIS INDICATES MOST
UNSTABLE CAPES AROUND 600 J/KG ACROSS THE WEST WITH MOST OF THE
HI-RES SHORT TERM MODELS SUGGESTING MUCAPES IN THE ORDER OF
500-1000 J/KG LATE TONIGHT AHEAD OF THE APPROACHING SHORTWAVE AND
FRONTAL BOUNDARY. CURRENT FORECAST HAS THE HIGHER POPS ACROSS THE
WEST AND CENTRAL AREAS THIS EVENING WITH A GRADUAL SHIFT TO THE
SOUTH WEDNESDAY MORNING AS THE WEAK BOUNDARY SETTLES SOUTHEAST
ACROSS THE FORECAST AREA. MAKING SOME MINOR ADJUSTMENTS TO THE
GRIDS IN THE POPS AND TEMPS FOR THE OVERNIGHT HOURS. SHOULD HAVE
THE UPDATE OUT BY 845 PM.

&&

.SHORT TERM...(TONIGHT)
ISSUED AT 300 PM CDT TUE MAY 26 2015

2 PM SURFACE MAP SHOWED LOW PRESSURE CENTERED JUST NORTHWEST OF
DUBUQUE. INITIAL BAND OF CONVECTIVE SHOWERS/ISOLATED THUNDERSTORMS
WHICH MOVED THROUGH THE FORECAST AREA EARLIER HAS ADVANCED NORTHEAST
ACROSS THE INDIANA BORDER...WITH A SECONDARY AXIS OF LIGHT SHOWERS
MOVING EAST AHEAD OF AN UPPER DISTURBANCE CROSSING THE MISSISSIPPI
RIVER.

HRRR AND OTHER HIGH-RESOLUTION MODEL GUIDANCE HAS BEEN DOING A
REASONABLE JOB WITH THE ACTIVITY TODAY...AND WAS GENERALLY FOLLOWED
FOR THE RAIN TRENDS TONIGHT. HAVE MADE SOME ADJUSTMENTS WITH GOING
MAINLY ISOLATED SHOWERS/STORMS THIS EVENING EXCEPT WEST OF I-55...
WHERE LOW CHANCE POP`S WERE KEPT AS A WAVE/TROUGH ADVANCES EAST
ACROSS NORTHERN MISSOURI. HAVE LINGERED THESE 30% CHANCES OVERNIGHT
FROM ABOUT DECATUR WESTWARD. SHOULD SEE SKIES BECOME PARTLY CLOUDY
ACROSS THE SOUTHERN CWA THIS EVENING...BEFORE SOME INCREASE IS NOTED
AGAIN AHEAD OF THE INCOMING WAVE.

.LONG TERM...(WEDNESDAY THROUGH TUESDAY)
ISSUED AT 300 PM CDT TUE MAY 26 2015

AN UNSETTLED WEATHER PATTERN LOOKS TO CONTINUE THROUGH MONDAY ACROSS
CENTRAL AND SOUTHEAST IL ALONG WITH WARM AND RATHER HUMID SUMMERLIKE
CONDITIONS THE REST OF THE WEEK. A COLD FRONT MOVING SE THROUGH
CENTRAL AND SOUTHEAST IL DURING SATURDAY WILL BRING COOLER
TEMPERATURES DURING THIS WEEKEND ESPECIALLY ON SUNDAY.

UPPER LEVEL TROF OVER THE UPPER MIDWEST MOVES INTO MI ON WED WHILE
PUSHING A WEAK FRONT SE INTO THE IL RIVER VALLEY WED AFTERNOON. ALSO
HAVE A SHORT WAVE EJECTING NE FROM THE SOUTHERN PLAINS INTO SE IL
AND CENTRAL INDIANA BY 18Z/WED. INCREASE INSTABLITY ON WED WITH
CAPES OF 1000-2000 J/KG AND HIGHEST SOUTH OF I-72 TO RETURN CHANCES
OF SHOWERS AND THUNDERSTORMS WITH LOWER CHANCES NW OF IL RIVER AND
HIGHER CHANCES IN SOUTHEAST IL. SPC HAS MARGINAL RISK OF SEVERE WED
AFTERNOON SE OF A SHELYVILLE TO PARIS LINE. CONVECTION CHANCES WILL
LINGER SOUTH OF I-72 WED NIGHT MAINLY WED EVENING. THEN ISOLATED
CHANCES OF CONVECTION SHIFT INTO SOUTHERN AND SW AREAS ON THU AS
WEAK HIGH PRESSURE DRIFTS ACROSS THE GREAT LAKES AND MORE STABLE AIR
OVER NE CWA FROM I-74 NE WHERE IT SHOULD BE DRY. NAM MODEL IS STILL
RATHER UNSTABLE THU SW OF I-74 BUT THINK IT MAY BE OVERDOING THIS AS
STRONGER INSTABLITY CLOSER MO AND THE OHIO RIVER VALLEY ON THU PLUS
HAVE UPPER LEVEL RIDGE BUILDING OVER THE EASTERN STATES THU.

WARM FRONT LIFTS NORTH ACROSS CENTRAL IL THU NIGHT AND IN BREEZY SSW
FLOW ON FRIDAY WITH CHANCES OF SHOWERS AND THUNDERSTORM HIGHEST OVER
IL RIVER VALLEY (LIKELY CHANCES WEST OF IL RIVER ON FRIDAY) AND
LOWEST NEAR WABASH RIVER. WARM HIGHS IN THE LOWER 80S WED AND MID
80S THU AND FRI AND A FEW AREAS COULD REACH UPPER 80S WITH ENOUGH
SUNSHINE ESPECIALLY NEAR WABASH RIVER WHERE RAIN CHANCES ARE LOWER.

HAVE LIKELY CHANCES OF SHOWERS AND THUNDERSTORMS FRI NIGHT AND SAT
WITH COLD FRONT PUSHING SE THROUGH CENTRAL IL DURING SATURDAY. HIGHS
SAT TO CONTRAST FROM LOWER 70S NW OF IL RIVER TO LOW 80S IN
SOUTHEAST IL. CONTINUE LIKELY CHANCES OF SHOWERS AND THUNDERSTORMS
SAT NIGHT IN SOUTHEAST IL ESPECIALLY SAT EVENING WHILE LOWERED POPS
TO LOW CHANCE NW OVER IL RIVER VALLEY BEHIND COLD FRONT. AREAS NW OF
IL RIVER NOW APPEAR DRY ON SUNDAY WHILE CHANCE OF SHOWERS AND
THUNDERSTORMS LINGERS FROM I-72 SOUTH CLOSER TO FRONTAL BOUNDARY
PUSHING SE OF OHIO RIVER OVER KY/TN. SUNDAY APPEARS TO BE COOLEST
DAY WITH HIGHS IN UPPER 60S CENTRAL IL AND LOWER 70S SE IL.

EXTENDED MODELS LIKE GFS AND ECMWF CONTINUE TO SHOW A WEAK CUTOFF
UPPER LEVEL LOW EJECTING INTO MO BY MON AND TO CONTINUE CHANCES OF
SHOWERS AND ISOLATED THUNDERSTORMS MONDAY AND TUESDAY. HIGHS IN THE
LOW TO MID 70S MONDAY AND MID TO UPPER 70S TUESDAY.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z WEDNESDAY EVENING)
ISSUED AT 600 PM CDT TUE MAY 26 2015

MAIN FORECAST CONCERN WILL BE ANY ADDITIONAL SHOWER ACTIVITY AND
AFFECT ON CLOUD BASES LATER THIS EVENING...AND THE POTENTIAL FOR
SOME MVFR FOG TOWARDS DAWN WED. LATEST SURFACE MAP HAS A WEAK
BOUNDARY/WIND SHIFT LINE OVER CENTRAL IOWA EARLY THIS EVENING
AND THAT FEATURE IS EXPECTED TO SLOWLY PUSH ACROSS THE FORECAST
AREA LATE TONIGHT/WED MORNING. NOT MUCH OF A TEMP OR DEW POINT
DISCONTINUITY ASSOCIATED WITH THE FEATURE AND THE UPPER LEVEL
LIFT IS MEAGER SO NOT EXPECTING MUCH IN THE WAY OF WIDESPREAD
RAINFALL OVERNIGHT AS IT PUSHES THROUGH THE AREA. FORECAST
SOUNDINGS SUGGEST SOME LOW MVFR CIGS AT TIMES AHEAD OF THE
FRONT WITH THE WIND FIELDS QUITE LIGHT ALONG AND JUST BEHIND
THE FRONT WHICH MAY ALLOW SOME MVFR FOG TO FORM TOWARDS WED
MORNING. CURRENT FORECAST SOUNDINGS INDICATE ENOUGH CLOUD
COVER WILL LINGER OVERNIGHT...ESPECIALLY IN THE MID AND UPPER
PORTIONS OF THE ATMOSPHERE THAT MAY LIMIT ANY RESTRICTIONS TO
VSBYS. FOR NOW WILL INTRODUCE A 5 TO 6 MI VSBY AT BMI AND CMI
WHICH WILL BE SEEING THE LIGHTER WINDS OVERNIGHT.

AN UPPER LEVEL WAVE IS FORECAST TO PUSH ACROSS THE SOUTHERN PLAINS
TONIGHT AND EDGE ENE INTO PARTS OF SOUTH CENTRAL IL BY MORNING
WED BRINGING SOME SCATTERED SHOWERS AND THUNDERSTORMS WITH IT.
CURRENT GUIDANCE SUGGESTS THE BULK OF THE RAIN SHOULD REMAIN SOUTH
OF THE TAF SITES WITH MAINLY VFR CONDITIONS EXPECTED FOR THE
REMAINDER OF THE DAY. SOUTHWEST WINDS AROUND 10KTS EXPECTED
TONIGHT WILL VEER MORE INTO A WESTERLY DIRECTION AS THE WEAKENING
BOUNDARY SHIFTS ACROSS THE AREA DURING THE DAY WEDNESDAY. WIND
SPEEDS SHOULD RANGE FROM 10 TO 15 KTS.


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...SMITH
SHORT TERM...GEELHART
LONG TERM...07
AVIATION...SMITH



000
FXUS63 KILX 270122
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
822 PM CDT TUE MAY 26 2015

.UPDATE...
ISSUED AT 815 PM CDT TUE MAY 26 2015

8 PM SURFACE MAP INDICATES A WEAK COLD FRONT/WIND SHIFT LINE WAS
EDGING SLOWLY TO THE EAST EARLY THIS EVENING AND WEST LOCATED OVER
EXTREME EAST CENTRAL IOWA. THIS BOUNDARY IS FORECAST TO SLOWLY
TRACK INTO OUR FORECAST AREA BY EARLY WEDNESDAY MORNING.
MEANWHILE...THE WATER VAPOR LOOP INDICATES A WEAK UPPER LEVEL WAVE
PUSHING EAST FROM THE MISSOURI RIVER VALLEY WITH ORGANIZED
CONVECTION OCCURRING AHEAD OF THE WAVE ACROSS EAST CENTRAL KS
SOUTH THRU OK AND TX. ILX LOCAL OBJECTIVE ANALYSIS INDICATES MOST
UNSTABLE CAPES AROUND 600 J/KG ACROSS THE WEST WITH MOST OF THE
HI-RES SHORT TERM MODELS SUGGESTING MUCAPES IN THE ORDER OF
500-1000 J/KG LATE TONIGHT AHEAD OF THE APPROACHING SHORTWAVE AND
FRONTAL BOUNDARY. CURRENT FORECAST HAS THE HIGHER POPS ACROSS THE
WEST AND CENTRAL AREAS THIS EVENING WITH A GRADUAL SHIFT TO THE
SOUTH WEDNESDAY MORNING AS THE WEAK BOUNDARY SETTLES SOUTHEAST
ACROSS THE FORECAST AREA. MAKING SOME MINOR ADJUSTMENTS TO THE
GRIDS IN THE POPS AND TEMPS FOR THE OVERNIGHT HOURS. SHOULD HAVE
THE UPDATE OUT BY 845 PM.

&&

.SHORT TERM...(TONIGHT)
ISSUED AT 300 PM CDT TUE MAY 26 2015

2 PM SURFACE MAP SHOWED LOW PRESSURE CENTERED JUST NORTHWEST OF
DUBUQUE. INITIAL BAND OF CONVECTIVE SHOWERS/ISOLATED THUNDERSTORMS
WHICH MOVED THROUGH THE FORECAST AREA EARLIER HAS ADVANCED NORTHEAST
ACROSS THE INDIANA BORDER...WITH A SECONDARY AXIS OF LIGHT SHOWERS
MOVING EAST AHEAD OF AN UPPER DISTURBANCE CROSSING THE MISSISSIPPI
RIVER.

HRRR AND OTHER HIGH-RESOLUTION MODEL GUIDANCE HAS BEEN DOING A
REASONABLE JOB WITH THE ACTIVITY TODAY...AND WAS GENERALLY FOLLOWED
FOR THE RAIN TRENDS TONIGHT. HAVE MADE SOME ADJUSTMENTS WITH GOING
MAINLY ISOLATED SHOWERS/STORMS THIS EVENING EXCEPT WEST OF I-55...
WHERE LOW CHANCE POP`S WERE KEPT AS A WAVE/TROUGH ADVANCES EAST
ACROSS NORTHERN MISSOURI. HAVE LINGERED THESE 30% CHANCES OVERNIGHT
FROM ABOUT DECATUR WESTWARD. SHOULD SEE SKIES BECOME PARTLY CLOUDY
ACROSS THE SOUTHERN CWA THIS EVENING...BEFORE SOME INCREASE IS NOTED
AGAIN AHEAD OF THE INCOMING WAVE.

.LONG TERM...(WEDNESDAY THROUGH TUESDAY)
ISSUED AT 300 PM CDT TUE MAY 26 2015

AN UNSETTLED WEATHER PATTERN LOOKS TO CONTINUE THROUGH MONDAY ACROSS
CENTRAL AND SOUTHEAST IL ALONG WITH WARM AND RATHER HUMID SUMMERLIKE
CONDITIONS THE REST OF THE WEEK. A COLD FRONT MOVING SE THROUGH
CENTRAL AND SOUTHEAST IL DURING SATURDAY WILL BRING COOLER
TEMPERATURES DURING THIS WEEKEND ESPECIALLY ON SUNDAY.

UPPER LEVEL TROF OVER THE UPPER MIDWEST MOVES INTO MI ON WED WHILE
PUSHING A WEAK FRONT SE INTO THE IL RIVER VALLEY WED AFTERNOON. ALSO
HAVE A SHORT WAVE EJECTING NE FROM THE SOUTHERN PLAINS INTO SE IL
AND CENTRAL INDIANA BY 18Z/WED. INCREASE INSTABLITY ON WED WITH
CAPES OF 1000-2000 J/KG AND HIGHEST SOUTH OF I-72 TO RETURN CHANCES
OF SHOWERS AND THUNDERSTORMS WITH LOWER CHANCES NW OF IL RIVER AND
HIGHER CHANCES IN SOUTHEAST IL. SPC HAS MARGINAL RISK OF SEVERE WED
AFTERNOON SE OF A SHELYVILLE TO PARIS LINE. CONVECTION CHANCES WILL
LINGER SOUTH OF I-72 WED NIGHT MAINLY WED EVENING. THEN ISOLATED
CHANCES OF CONVECTION SHIFT INTO SOUTHERN AND SW AREAS ON THU AS
WEAK HIGH PRESSURE DRIFTS ACROSS THE GREAT LAKES AND MORE STABLE AIR
OVER NE CWA FROM I-74 NE WHERE IT SHOULD BE DRY. NAM MODEL IS STILL
RATHER UNSTABLE THU SW OF I-74 BUT THINK IT MAY BE OVERDOING THIS AS
STRONGER INSTABLITY CLOSER MO AND THE OHIO RIVER VALLEY ON THU PLUS
HAVE UPPER LEVEL RIDGE BUILDING OVER THE EASTERN STATES THU.

WARM FRONT LIFTS NORTH ACROSS CENTRAL IL THU NIGHT AND IN BREEZY SSW
FLOW ON FRIDAY WITH CHANCES OF SHOWERS AND THUNDERSTORM HIGHEST OVER
IL RIVER VALLEY (LIKELY CHANCES WEST OF IL RIVER ON FRIDAY) AND
LOWEST NEAR WABASH RIVER. WARM HIGHS IN THE LOWER 80S WED AND MID
80S THU AND FRI AND A FEW AREAS COULD REACH UPPER 80S WITH ENOUGH
SUNSHINE ESPECIALLY NEAR WABASH RIVER WHERE RAIN CHANCES ARE LOWER.

HAVE LIKELY CHANCES OF SHOWERS AND THUNDERSTORMS FRI NIGHT AND SAT
WITH COLD FRONT PUSHING SE THROUGH CENTRAL IL DURING SATURDAY. HIGHS
SAT TO CONTRAST FROM LOWER 70S NW OF IL RIVER TO LOW 80S IN
SOUTHEAST IL. CONTINUE LIKELY CHANCES OF SHOWERS AND THUNDERSTORMS
SAT NIGHT IN SOUTHEAST IL ESPECIALLY SAT EVENING WHILE LOWERED POPS
TO LOW CHANCE NW OVER IL RIVER VALLEY BEHIND COLD FRONT. AREAS NW OF
IL RIVER NOW APPEAR DRY ON SUNDAY WHILE CHANCE OF SHOWERS AND
THUNDERSTORMS LINGERS FROM I-72 SOUTH CLOSER TO FRONTAL BOUNDARY
PUSHING SE OF OHIO RIVER OVER KY/TN. SUNDAY APPEARS TO BE COOLEST
DAY WITH HIGHS IN UPPER 60S CENTRAL IL AND LOWER 70S SE IL.

EXTENDED MODELS LIKE GFS AND ECMWF CONTINUE TO SHOW A WEAK CUTOFF
UPPER LEVEL LOW EJECTING INTO MO BY MON AND TO CONTINUE CHANCES OF
SHOWERS AND ISOLATED THUNDERSTORMS MONDAY AND TUESDAY. HIGHS IN THE
LOW TO MID 70S MONDAY AND MID TO UPPER 70S TUESDAY.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z WEDNESDAY EVENING)
ISSUED AT 600 PM CDT TUE MAY 26 2015

MAIN FORECAST CONCERN WILL BE ANY ADDITIONAL SHOWER ACTIVITY AND
AFFECT ON CLOUD BASES LATER THIS EVENING...AND THE POTENTIAL FOR
SOME MVFR FOG TOWARDS DAWN WED. LATEST SURFACE MAP HAS A WEAK
BOUNDARY/WIND SHIFT LINE OVER CENTRAL IOWA EARLY THIS EVENING
AND THAT FEATURE IS EXPECTED TO SLOWLY PUSH ACROSS THE FORECAST
AREA LATE TONIGHT/WED MORNING. NOT MUCH OF A TEMP OR DEW POINT
DISCONTINUITY ASSOCIATED WITH THE FEATURE AND THE UPPER LEVEL
LIFT IS MEAGER SO NOT EXPECTING MUCH IN THE WAY OF WIDESPREAD
RAINFALL OVERNIGHT AS IT PUSHES THROUGH THE AREA. FORECAST
SOUNDINGS SUGGEST SOME LOW MVFR CIGS AT TIMES AHEAD OF THE
FRONT WITH THE WIND FIELDS QUITE LIGHT ALONG AND JUST BEHIND
THE FRONT WHICH MAY ALLOW SOME MVFR FOG TO FORM TOWARDS WED
MORNING. CURRENT FORECAST SOUNDINGS INDICATE ENOUGH CLOUD
COVER WILL LINGER OVERNIGHT...ESPECIALLY IN THE MID AND UPPER
PORTIONS OF THE ATMOSPHERE THAT MAY LIMIT ANY RESTRICTIONS TO
VSBYS. FOR NOW WILL INTRODUCE A 5 TO 6 MI VSBY AT BMI AND CMI
WHICH WILL BE SEEING THE LIGHTER WINDS OVERNIGHT.

AN UPPER LEVEL WAVE IS FORECAST TO PUSH ACROSS THE SOUTHERN PLAINS
TONIGHT AND EDGE ENE INTO PARTS OF SOUTH CENTRAL IL BY MORNING
WED BRINGING SOME SCATTERED SHOWERS AND THUNDERSTORMS WITH IT.
CURRENT GUIDANCE SUGGESTS THE BULK OF THE RAIN SHOULD REMAIN SOUTH
OF THE TAF SITES WITH MAINLY VFR CONDITIONS EXPECTED FOR THE
REMAINDER OF THE DAY. SOUTHWEST WINDS AROUND 10KTS EXPECTED
TONIGHT WILL VEER MORE INTO A WESTERLY DIRECTION AS THE WEAKENING
BOUNDARY SHIFTS ACROSS THE AREA DURING THE DAY WEDNESDAY. WIND
SPEEDS SHOULD RANGE FROM 10 TO 15 KTS.


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...SMITH
SHORT TERM...GEELHART
LONG TERM...07
AVIATION...SMITH


  [top]

000
FXUS63 KLOT 262349
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
649 PM CDT TUE MAY 26 2015

.SHORT TERM...
253 PM CDT

THROUGH WEDNESDAY...

A SURFACE LOW IS OVER NORTHEAST IA AND SW WI WITH A VORT MAX OVER
IOWA. THE LOWS COLD FRONT REMAINS A BIT FURTHER BACK OVER CENTRAL IA
AND EASTERN KS. THE LOW WILL DEEPEN SLIGHTLY AS IT MOVES OVER
CENTRAL WI AND ITS COLD FRONT SWINGS THROUGH WEDNESDAY. THE MAIN
CONCERN RIGHT NOW IS HOW MUCH CONVECTION WILL DEVELOP THIS
AFTERNOON.  THE LATEST RAP ANALYSIS SUGGESTS A RIBBON OF 1000 J/KG
OF CAPE IS OVER I-39...BUT THINKING THAT CAPE IN REALITY IS AROUND
500 J/KG DUE TO LIMITED HEATING. CAPE VALUES COULD RISE TO AROUND
1000 J/KG AS THERE ARE A FEW BREAKS IN THE CLOUDS...BUT THINKING IN
GENERAL THE BREAKS ARE MOVING TOO QUICKLY AND TOO FEW AND FAR BTWN
TO AMOUNT TO MUCH.  SHEAR VALUES REMAIN VERY FAVORABLE FOR ORGANIZED
STORMS WITH VALUES AROUND 35-40 KT.

THEREFORE EXPECTING SCATTERED SHOWER/TS DEVELOPMENT THIS AFTN IN THE
WAKE OF THE LINE OF SHOWERS THAT IS SHIFTING EAST ACROSS INDIANA
RIGHT NOW.  A SECOND SKINNY LINE OF CONVECTION LIES FROM DIXON IL TO
JERSEYVILLE IL WITH A FEW ADDITIONAL CELLS OUT AHEAD OF IT. DUE TO
LIMITED CAPE AS DISCUSSED ABOVE...THE STRONGER CELLS MAY PRODUCE
DAMAGING WINDS. WINDS HAVE VEERED TO THE SW AND HELICITY IS MUCH
LOWER SO NOT AS CONCERNED ABOUT ISOLATED TORNADOES AS I WAS THIS
MORNING.  PWAT VALUES REMAIN VERY IMPRESSIVE AT 1.4-1.7 INCHES SO
ANY OF THE NEW SHOWERS WILL BE CAPABLE OF ADDITIONAL HEAVY DOWNPOURS.

THE AREA OF SCATTERED SHOWERS AND STORMS SHIFTS EAST OF THE CWA THIS
EVENING...BUT WE ARE NOT DONE YET. ANOTHER ROUND OF SHOWERS AND
PERHAPS OF THUNDERSTORMS MAY FORM THIS EVENING AS THE VORT MAX
APPROACHES. THINKING THE COVERAGE WILL BE BEST ALONG AND WEST OF
GARY INDIANA TO PAXTON IL LINE. HAVE LOW CONFIDENCE IN COVERAGE AND
TIMING OF THIS ROUND OF SHOWERS...BUT NOT EXPECTING MUCH THUNDER AND
NO SEVERE WEATHER.  DEWPOINTS REMAIN IN THE 60S TONIGHT SO THINKING
WE WILL NOT COOL MUCH...SO KEPT LOWS IN THE LOW TO MID 60S.

THE PATTERN REMAINS MESSY TOMORROW BUT NOT AS ACTIVE.  A PAIR OF
VORT STREAMERS AND THE LOWS COLD FRONT ROTATE THROUGH AND SHOWERS
AND STORMS MAY FORM ALONG THEM.  THE FIRST IS ASSOCIATED WITH THE
UPPER LEVEL LOW SHIFTING NE INTO ONTARIO TOMORROW. SHOWERS AND
STORMS WITH THIS VORT STREAMER WOULD CLIP THE NORTHERN CWA...NORTH
OF I-88.  PRECIP MAY SINK SOUTH ACROSS DUPAGE AND COOK COUNTIES IN
THE AFTN...BUT HAVE LOW CONFIDENCE IN HOW FAR SOUTH THE PRECIP WILL
GET.

CLOUD COVER SHIFTS EAST THROUGH THE AFTERNOON WITH AREAS WEST OF I-
55 BECOMING MOSTLY SUNNY BY MID AFTN. DID NOT MAKE TOO MANY CHANGES
TO HIGH TEMPS TOMORROW AS CLOUD COVER WILL PLAY A ROLE.  HAVE TEMPS
IN THE UPPER 70S TO LOW 80S.  A LAKE BREEZE IS POSSIBLE LATE IN THE
AFTN AND EVENING SO EXPECTING LAKE COOLING ESPECIALLY AT WAUKEGAN.

JEE

&&

.LONG TERM...
330 PM CDT

WEDNESDAY NIGHT THROUGH TUESDAY...

LOCAL AREA WILL START OUT FIRMLY UNDER MID/UPPER RIDGING ON
WEDNESDAY NIGHT AND THURSDAY...RESULTING IN A DRY AND WARM PERIOD
AS 925 MB TEMPS CLIMB FROM THE UPPER TEENS CELSISUS BY EARLY
THURSDAY TO THE LOWER 20S CELSISUS EARLY THURSDAY EVENING. INLAND
TEMPERATURES WILL WARM TO THE LOWER-MID 80S ON THURSDAY...BUT
DESPITE SOUTHERLY SURFACE FLOW...GRADIENT WILL BE WEAK ENOUGH TO
ENABLE A LAKE BREEZE TO DEVELOP AND PUSH INLAND FAIRLY EARLY. THIS
WILL KEEP LAKESHORE TEMPS (ESPECIALLY IL SHORE) IN THE UPPER 60S.

CHANGES WILL START TO TAKE PLACE THURSDAY NIGHT WITH UPPER RIDGE
AXIS GETTING SHUNTED EAST AND ALLOWS SHORTWAVE ENERGY TO LIFT
EAST-NORTHEAST ACROSS THE AREA AFTER MIDNIGHT INTO FRIDAY ALONG
WITH STRENGTHENING AND VEERING LOW LEVEL JET. HAVE FOCUSED MID
CHANCE POPS INTO NORTHWEST CWA LATE THURSDAY NIGHT AND THEN SPREAD
LIKELY POPS FOR MUCH OF THE CWA FRIDAY MORNING AND EARLY
AFTERNOON. IT APPEARS THAT BETTER MOISTURE CONVERGENCE AND UPPER
FORCING WILL LIFT NORTH AND REFOCUS INTO NORTHWEST CWA FRIDAY
AFTERNOON AND TAILORED POPS AS SUCH...BUT THEN A STRONGER WAVE
WILL MOVE ACROSS THE AREA SATURDAY NIGHT. CONFIDENCE IS A BIT
LOWER IN HIGH TEMPS FRIDAY DUE TO UNCERTAINTY OVER IMPACT OF
CLOUDS/PRECIP...BUT VERY MILD START TO DAY AND WARM AIRMASS IN
PLACE SHOULD STILL SUPPORT HIGHS INTO THE LOWER-MID 80S...WARMEST
IN SOUTHEAST HALF OF CWA. THE WARM TEMPS...DEWPOINTS WELL INTO THE
60S AND MODEST MIDLEVEL LAPSE RATES WILL YIELD MODEST CAPE
VALUES...SO CANNOT RULE OUT AN ISOLATED SEVERE THREAT FOR DAMAGING
WINDS INTO FRIDAY EVENING. COULD BE SOME WET MICROBURSTS WITH PWAT
VALUES IN 1.5 TO 1.75 INCH RANGE.

A STRONG COLD FRONT WILL SWEEP ACROSS THE AREA FRIDAY
NIGHT...RESULTING IN MUCH COOLER WEATHER FOR THE LAST WEEKEND OF
MAY. HIGHS ON THE LAKEFRONT ARE LIKELY TO STAY IN THE 50S ON BOTH
SATURDAY AND SUNDAY...WITH ONLY 60S AND 70S INLAND ON SATURDAY AND
60S ON SUNDAY. WILL NEED TO WATCH FOR A WAVE OF SURFACE LOW
PRESSURE FORMING SOUTH OF THE AREA ON SATURDAY...SO KEPT HIGHER
CONSENSUS POPS FOR NOW SATURDAY MORNING...BUT IF TRENDS ON MUCH OF
GUIDANCE CONTINUE MAY BE ABLE TO LOWER POPS SATURDAY THROUGH
MONDAY WITH EXPANSIVE COOL HIGH PRESSURE OVER THE GREAT LAKES.
TEMPERATURES WILL THEN WARM BACK TO NEAR NORMAL FOR EARLY JUNE BY
TUESDAY WITH SOUTHERLY FLOW ON BACK SIDE OF HIGH TO EAST...THOUGH
ONSHORE FLOW LOOKS TO CONTINUE FOR AT LEAST A PORTION OF THE
LAKEFRONT.

RC

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 00Z...

* GUSTY SOUTHWEST WINDS THROUGH EARLY EVENING.

* ISOLATED TO SCATTERED SHRA POSSIBLE LATER THIS EVENING.

* MVFR CIGS POSSIBLE OVERNIGHT INTO EARLY WEDNESDAY.

* LAKE BREEZE WIND SHIFT TO NORTHEAST POSSIBLE LATE AFTERNOON
  INTO EARLY EVENING WEDNESDAY.

RC

//DISCUSSION...UPDATED 00Z...

LOW PRESSURE LOCATED OVER CENTRAL WISCONSIN RESULTING IN GUSTY
SOUTHWEST WINDS AND THESE GUSTY WINDS WILL CONTINUE THROUGH MID
EVENING. AFTER NARROW AREA OF SHRA CLEARS THE EASTERN
TERMINALS...ANOTHER UPPER DISTURBANCE ROTATING NORTHEAST FROM IA
SHOULD BRING SCATTERED SHRA INTO NORTHERN ILLINOIS AGAIN BY MID
EVENING...BUT TRAJECTORY WOULD FAVOR RFD AND HAVE LEFT OTHER
TERMINALS DRY FOR NOW. NEXT CONCERN IS FOR POTENTIAL PERIOD OF
LOWER CIGS OVERNIGHT INTO EARLY WEDNESDAY. GUIDANCE VARIES ON HOW
LOW/WIDESPREAD CIGS WILL GET AND TIMING...BUT GIVEN LOWER
CONFIDENCE HAVE MAINTAINED PREVIOUS TIMING. DID PULL MVFR VSBY AS
STEADY SOUTHWEST WINDS SHOULD PREVENT VSBY RESTRICTIONS.

A COLD FRONT AND UPPER TROUGH WILL MOVE ACROSS THE AREA ON
WEDNESDAY...WITH WINDS VEERING TO WEST AND THEN WEST-NORTHWEST.
GUSTS TO 15 TO 20 KT ARE POSSIBLE IN THE MORNING THROUGH EARLY
AFTERNOON. GRADIENT IS EXPECTED TO WEAKEN ENOUGH TO ALLOW LAKE
BREEZE TO SLIP INLAND LATE...BUT SPEEDS SHOULD BE LIGHT BEHIND
SHIFT. AS UPPER TROUGH MOVES OVERHEAD...ONLY VERY MINIMAL
INSTABILITY SHOWN ON FORECAST SOUNDINGS AND SHOWER COVERAGE IS
LIKELY TO BE ISOLATED...SO HAVE BACKED OFF TO A PROB30 DURING THE
AFTERNOON AT THE EASTERN TERMINALS.

RC


//ORD AND MDW CONFIDENCE...UPDATED 00Z...

* MEDIUM-HIGH IN WINDS THROUGH WEDNESDAY AFTERNOON.

* MEDIUM IN LAKE BREEZE LATE WEDNESDAY AFTERNOON.

* LOW IN SHRA LATER THIS EVENING AND ON WEDNESDAY AFTERNOON.

* LOW-MEDIUM IN LOWER CIG TRENDS OVERNIGHT INTO EARLY WEDNESDAY.

RC

//OUTLOOK FOR ORD/MDW FOR 12Z THURSDAY-12Z TUESDAY...UPDATED 00Z...

THURSDAY...MAINLY VFR WITH CHANCE SHRA/TSRA LATE THURSDAY NIGHT.
LAKE BREEZE SHIFT TO EAST WINDS.

FRIDAY...PERIODIC SHRA/TSRA...ESPECIALLY IN MORNING AND THEN AT
NIGHT.

SATURDAY...STRONG NORTH-NORTHEAST WINDS. SHRA AND MVFR
POSSIBLE...MAINLY IN THE MORNING.

SUNDAY AND MONDAY...VFR. NORTHEAST WINDS.

RC

&&

.MARINE...
417 PM CDT

WINDS REMAIN GUSTY THIS AFTERNOON AND DECIDED TO ISSUE A SMALL
CRAFT ADVISORY FOR STRONG WINDS INTO THIS EVENING. THE SOUTH WINDS
BECOME SOUTHWEST THIS EVENING. LOW PRESSURE MOVES OVER QUEBEC
TOMORROW AFTERNOON AND COLD FRONT TRAILING FROM THE LOW SWINGS
THROUGH. WINDS WEAKEN WEDNESDAY AFTERNOON AND A LAKE BREEZE IS
EXPECTED LATE WEDNESDAY AFTERNOON.

MODEST SOUTHERLY FLOW IS EXPECTED ON THURSDAY...WITH LAKE BREEZE
INFLUENCES IN THE SOUTHERN PORTION OF THE LAKE...THEN A PERIOD OF
SLIGHTLY STRONGER SOUTHERLY FLOW ON FRIDAY AHEAD OF A STRONG COLD
FRONT...THOUGH WARM AIRMASS WILL LIMIT MIXING. WILL LIKELY NEED TO
ADD AREAS OF FOG OVER THE LAKE. THE STRONG COLD FRONT WILL SWEEP
ACROSS THE LAKE FRIDAY NIGHT INTO SATURDAY...BRINGING NORTHERLY
WINDS TO 30 KT. WILL NEED TO WATCH FOR A PERIOD OF NORTHERLY GALES
SHOWN ON SOME MODEL GUIDANCE. WILL NEED A SMALL CRAFT ADVISORY
SATURDAY MORNING THROUGH SUNDAY MORNING UNTIL WAVES SUBSIDE.

RC

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 10 PM TUESDAY.

&&

$$

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000
FXUS63 KLOT 262349
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
649 PM CDT TUE MAY 26 2015

.SHORT TERM...
253 PM CDT

THROUGH WEDNESDAY...

A SURFACE LOW IS OVER NORTHEAST IA AND SW WI WITH A VORT MAX OVER
IOWA. THE LOWS COLD FRONT REMAINS A BIT FURTHER BACK OVER CENTRAL IA
AND EASTERN KS. THE LOW WILL DEEPEN SLIGHTLY AS IT MOVES OVER
CENTRAL WI AND ITS COLD FRONT SWINGS THROUGH WEDNESDAY. THE MAIN
CONCERN RIGHT NOW IS HOW MUCH CONVECTION WILL DEVELOP THIS
AFTERNOON.  THE LATEST RAP ANALYSIS SUGGESTS A RIBBON OF 1000 J/KG
OF CAPE IS OVER I-39...BUT THINKING THAT CAPE IN REALITY IS AROUND
500 J/KG DUE TO LIMITED HEATING. CAPE VALUES COULD RISE TO AROUND
1000 J/KG AS THERE ARE A FEW BREAKS IN THE CLOUDS...BUT THINKING IN
GENERAL THE BREAKS ARE MOVING TOO QUICKLY AND TOO FEW AND FAR BTWN
TO AMOUNT TO MUCH.  SHEAR VALUES REMAIN VERY FAVORABLE FOR ORGANIZED
STORMS WITH VALUES AROUND 35-40 KT.

THEREFORE EXPECTING SCATTERED SHOWER/TS DEVELOPMENT THIS AFTN IN THE
WAKE OF THE LINE OF SHOWERS THAT IS SHIFTING EAST ACROSS INDIANA
RIGHT NOW.  A SECOND SKINNY LINE OF CONVECTION LIES FROM DIXON IL TO
JERSEYVILLE IL WITH A FEW ADDITIONAL CELLS OUT AHEAD OF IT. DUE TO
LIMITED CAPE AS DISCUSSED ABOVE...THE STRONGER CELLS MAY PRODUCE
DAMAGING WINDS. WINDS HAVE VEERED TO THE SW AND HELICITY IS MUCH
LOWER SO NOT AS CONCERNED ABOUT ISOLATED TORNADOES AS I WAS THIS
MORNING.  PWAT VALUES REMAIN VERY IMPRESSIVE AT 1.4-1.7 INCHES SO
ANY OF THE NEW SHOWERS WILL BE CAPABLE OF ADDITIONAL HEAVY DOWNPOURS.

THE AREA OF SCATTERED SHOWERS AND STORMS SHIFTS EAST OF THE CWA THIS
EVENING...BUT WE ARE NOT DONE YET. ANOTHER ROUND OF SHOWERS AND
PERHAPS OF THUNDERSTORMS MAY FORM THIS EVENING AS THE VORT MAX
APPROACHES. THINKING THE COVERAGE WILL BE BEST ALONG AND WEST OF
GARY INDIANA TO PAXTON IL LINE. HAVE LOW CONFIDENCE IN COVERAGE AND
TIMING OF THIS ROUND OF SHOWERS...BUT NOT EXPECTING MUCH THUNDER AND
NO SEVERE WEATHER.  DEWPOINTS REMAIN IN THE 60S TONIGHT SO THINKING
WE WILL NOT COOL MUCH...SO KEPT LOWS IN THE LOW TO MID 60S.

THE PATTERN REMAINS MESSY TOMORROW BUT NOT AS ACTIVE.  A PAIR OF
VORT STREAMERS AND THE LOWS COLD FRONT ROTATE THROUGH AND SHOWERS
AND STORMS MAY FORM ALONG THEM.  THE FIRST IS ASSOCIATED WITH THE
UPPER LEVEL LOW SHIFTING NE INTO ONTARIO TOMORROW. SHOWERS AND
STORMS WITH THIS VORT STREAMER WOULD CLIP THE NORTHERN CWA...NORTH
OF I-88.  PRECIP MAY SINK SOUTH ACROSS DUPAGE AND COOK COUNTIES IN
THE AFTN...BUT HAVE LOW CONFIDENCE IN HOW FAR SOUTH THE PRECIP WILL
GET.

CLOUD COVER SHIFTS EAST THROUGH THE AFTERNOON WITH AREAS WEST OF I-
55 BECOMING MOSTLY SUNNY BY MID AFTN. DID NOT MAKE TOO MANY CHANGES
TO HIGH TEMPS TOMORROW AS CLOUD COVER WILL PLAY A ROLE.  HAVE TEMPS
IN THE UPPER 70S TO LOW 80S.  A LAKE BREEZE IS POSSIBLE LATE IN THE
AFTN AND EVENING SO EXPECTING LAKE COOLING ESPECIALLY AT WAUKEGAN.

JEE

&&

.LONG TERM...
330 PM CDT

WEDNESDAY NIGHT THROUGH TUESDAY...

LOCAL AREA WILL START OUT FIRMLY UNDER MID/UPPER RIDGING ON
WEDNESDAY NIGHT AND THURSDAY...RESULTING IN A DRY AND WARM PERIOD
AS 925 MB TEMPS CLIMB FROM THE UPPER TEENS CELSISUS BY EARLY
THURSDAY TO THE LOWER 20S CELSISUS EARLY THURSDAY EVENING. INLAND
TEMPERATURES WILL WARM TO THE LOWER-MID 80S ON THURSDAY...BUT
DESPITE SOUTHERLY SURFACE FLOW...GRADIENT WILL BE WEAK ENOUGH TO
ENABLE A LAKE BREEZE TO DEVELOP AND PUSH INLAND FAIRLY EARLY. THIS
WILL KEEP LAKESHORE TEMPS (ESPECIALLY IL SHORE) IN THE UPPER 60S.

CHANGES WILL START TO TAKE PLACE THURSDAY NIGHT WITH UPPER RIDGE
AXIS GETTING SHUNTED EAST AND ALLOWS SHORTWAVE ENERGY TO LIFT
EAST-NORTHEAST ACROSS THE AREA AFTER MIDNIGHT INTO FRIDAY ALONG
WITH STRENGTHENING AND VEERING LOW LEVEL JET. HAVE FOCUSED MID
CHANCE POPS INTO NORTHWEST CWA LATE THURSDAY NIGHT AND THEN SPREAD
LIKELY POPS FOR MUCH OF THE CWA FRIDAY MORNING AND EARLY
AFTERNOON. IT APPEARS THAT BETTER MOISTURE CONVERGENCE AND UPPER
FORCING WILL LIFT NORTH AND REFOCUS INTO NORTHWEST CWA FRIDAY
AFTERNOON AND TAILORED POPS AS SUCH...BUT THEN A STRONGER WAVE
WILL MOVE ACROSS THE AREA SATURDAY NIGHT. CONFIDENCE IS A BIT
LOWER IN HIGH TEMPS FRIDAY DUE TO UNCERTAINTY OVER IMPACT OF
CLOUDS/PRECIP...BUT VERY MILD START TO DAY AND WARM AIRMASS IN
PLACE SHOULD STILL SUPPORT HIGHS INTO THE LOWER-MID 80S...WARMEST
IN SOUTHEAST HALF OF CWA. THE WARM TEMPS...DEWPOINTS WELL INTO THE
60S AND MODEST MIDLEVEL LAPSE RATES WILL YIELD MODEST CAPE
VALUES...SO CANNOT RULE OUT AN ISOLATED SEVERE THREAT FOR DAMAGING
WINDS INTO FRIDAY EVENING. COULD BE SOME WET MICROBURSTS WITH PWAT
VALUES IN 1.5 TO 1.75 INCH RANGE.

A STRONG COLD FRONT WILL SWEEP ACROSS THE AREA FRIDAY
NIGHT...RESULTING IN MUCH COOLER WEATHER FOR THE LAST WEEKEND OF
MAY. HIGHS ON THE LAKEFRONT ARE LIKELY TO STAY IN THE 50S ON BOTH
SATURDAY AND SUNDAY...WITH ONLY 60S AND 70S INLAND ON SATURDAY AND
60S ON SUNDAY. WILL NEED TO WATCH FOR A WAVE OF SURFACE LOW
PRESSURE FORMING SOUTH OF THE AREA ON SATURDAY...SO KEPT HIGHER
CONSENSUS POPS FOR NOW SATURDAY MORNING...BUT IF TRENDS ON MUCH OF
GUIDANCE CONTINUE MAY BE ABLE TO LOWER POPS SATURDAY THROUGH
MONDAY WITH EXPANSIVE COOL HIGH PRESSURE OVER THE GREAT LAKES.
TEMPERATURES WILL THEN WARM BACK TO NEAR NORMAL FOR EARLY JUNE BY
TUESDAY WITH SOUTHERLY FLOW ON BACK SIDE OF HIGH TO EAST...THOUGH
ONSHORE FLOW LOOKS TO CONTINUE FOR AT LEAST A PORTION OF THE
LAKEFRONT.

RC

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 00Z...

* GUSTY SOUTHWEST WINDS THROUGH EARLY EVENING.

* ISOLATED TO SCATTERED SHRA POSSIBLE LATER THIS EVENING.

* MVFR CIGS POSSIBLE OVERNIGHT INTO EARLY WEDNESDAY.

* LAKE BREEZE WIND SHIFT TO NORTHEAST POSSIBLE LATE AFTERNOON
  INTO EARLY EVENING WEDNESDAY.

RC

//DISCUSSION...UPDATED 00Z...

LOW PRESSURE LOCATED OVER CENTRAL WISCONSIN RESULTING IN GUSTY
SOUTHWEST WINDS AND THESE GUSTY WINDS WILL CONTINUE THROUGH MID
EVENING. AFTER NARROW AREA OF SHRA CLEARS THE EASTERN
TERMINALS...ANOTHER UPPER DISTURBANCE ROTATING NORTHEAST FROM IA
SHOULD BRING SCATTERED SHRA INTO NORTHERN ILLINOIS AGAIN BY MID
EVENING...BUT TRAJECTORY WOULD FAVOR RFD AND HAVE LEFT OTHER
TERMINALS DRY FOR NOW. NEXT CONCERN IS FOR POTENTIAL PERIOD OF
LOWER CIGS OVERNIGHT INTO EARLY WEDNESDAY. GUIDANCE VARIES ON HOW
LOW/WIDESPREAD CIGS WILL GET AND TIMING...BUT GIVEN LOWER
CONFIDENCE HAVE MAINTAINED PREVIOUS TIMING. DID PULL MVFR VSBY AS
STEADY SOUTHWEST WINDS SHOULD PREVENT VSBY RESTRICTIONS.

A COLD FRONT AND UPPER TROUGH WILL MOVE ACROSS THE AREA ON
WEDNESDAY...WITH WINDS VEERING TO WEST AND THEN WEST-NORTHWEST.
GUSTS TO 15 TO 20 KT ARE POSSIBLE IN THE MORNING THROUGH EARLY
AFTERNOON. GRADIENT IS EXPECTED TO WEAKEN ENOUGH TO ALLOW LAKE
BREEZE TO SLIP INLAND LATE...BUT SPEEDS SHOULD BE LIGHT BEHIND
SHIFT. AS UPPER TROUGH MOVES OVERHEAD...ONLY VERY MINIMAL
INSTABILITY SHOWN ON FORECAST SOUNDINGS AND SHOWER COVERAGE IS
LIKELY TO BE ISOLATED...SO HAVE BACKED OFF TO A PROB30 DURING THE
AFTERNOON AT THE EASTERN TERMINALS.

RC


//ORD AND MDW CONFIDENCE...UPDATED 00Z...

* MEDIUM-HIGH IN WINDS THROUGH WEDNESDAY AFTERNOON.

* MEDIUM IN LAKE BREEZE LATE WEDNESDAY AFTERNOON.

* LOW IN SHRA LATER THIS EVENING AND ON WEDNESDAY AFTERNOON.

* LOW-MEDIUM IN LOWER CIG TRENDS OVERNIGHT INTO EARLY WEDNESDAY.

RC

//OUTLOOK FOR ORD/MDW FOR 12Z THURSDAY-12Z TUESDAY...UPDATED 00Z...

THURSDAY...MAINLY VFR WITH CHANCE SHRA/TSRA LATE THURSDAY NIGHT.
LAKE BREEZE SHIFT TO EAST WINDS.

FRIDAY...PERIODIC SHRA/TSRA...ESPECIALLY IN MORNING AND THEN AT
NIGHT.

SATURDAY...STRONG NORTH-NORTHEAST WINDS. SHRA AND MVFR
POSSIBLE...MAINLY IN THE MORNING.

SUNDAY AND MONDAY...VFR. NORTHEAST WINDS.

RC

&&

.MARINE...
417 PM CDT

WINDS REMAIN GUSTY THIS AFTERNOON AND DECIDED TO ISSUE A SMALL
CRAFT ADVISORY FOR STRONG WINDS INTO THIS EVENING. THE SOUTH WINDS
BECOME SOUTHWEST THIS EVENING. LOW PRESSURE MOVES OVER QUEBEC
TOMORROW AFTERNOON AND COLD FRONT TRAILING FROM THE LOW SWINGS
THROUGH. WINDS WEAKEN WEDNESDAY AFTERNOON AND A LAKE BREEZE IS
EXPECTED LATE WEDNESDAY AFTERNOON.

MODEST SOUTHERLY FLOW IS EXPECTED ON THURSDAY...WITH LAKE BREEZE
INFLUENCES IN THE SOUTHERN PORTION OF THE LAKE...THEN A PERIOD OF
SLIGHTLY STRONGER SOUTHERLY FLOW ON FRIDAY AHEAD OF A STRONG COLD
FRONT...THOUGH WARM AIRMASS WILL LIMIT MIXING. WILL LIKELY NEED TO
ADD AREAS OF FOG OVER THE LAKE. THE STRONG COLD FRONT WILL SWEEP
ACROSS THE LAKE FRIDAY NIGHT INTO SATURDAY...BRINGING NORTHERLY
WINDS TO 30 KT. WILL NEED TO WATCH FOR A PERIOD OF NORTHERLY GALES
SHOWN ON SOME MODEL GUIDANCE. WILL NEED A SMALL CRAFT ADVISORY
SATURDAY MORNING THROUGH SUNDAY MORNING UNTIL WAVES SUBSIDE.

RC

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 10 PM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 262349
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
649 PM CDT TUE MAY 26 2015

.SHORT TERM...
253 PM CDT

THROUGH WEDNESDAY...

A SURFACE LOW IS OVER NORTHEAST IA AND SW WI WITH A VORT MAX OVER
IOWA. THE LOWS COLD FRONT REMAINS A BIT FURTHER BACK OVER CENTRAL IA
AND EASTERN KS. THE LOW WILL DEEPEN SLIGHTLY AS IT MOVES OVER
CENTRAL WI AND ITS COLD FRONT SWINGS THROUGH WEDNESDAY. THE MAIN
CONCERN RIGHT NOW IS HOW MUCH CONVECTION WILL DEVELOP THIS
AFTERNOON.  THE LATEST RAP ANALYSIS SUGGESTS A RIBBON OF 1000 J/KG
OF CAPE IS OVER I-39...BUT THINKING THAT CAPE IN REALITY IS AROUND
500 J/KG DUE TO LIMITED HEATING. CAPE VALUES COULD RISE TO AROUND
1000 J/KG AS THERE ARE A FEW BREAKS IN THE CLOUDS...BUT THINKING IN
GENERAL THE BREAKS ARE MOVING TOO QUICKLY AND TOO FEW AND FAR BTWN
TO AMOUNT TO MUCH.  SHEAR VALUES REMAIN VERY FAVORABLE FOR ORGANIZED
STORMS WITH VALUES AROUND 35-40 KT.

THEREFORE EXPECTING SCATTERED SHOWER/TS DEVELOPMENT THIS AFTN IN THE
WAKE OF THE LINE OF SHOWERS THAT IS SHIFTING EAST ACROSS INDIANA
RIGHT NOW.  A SECOND SKINNY LINE OF CONVECTION LIES FROM DIXON IL TO
JERSEYVILLE IL WITH A FEW ADDITIONAL CELLS OUT AHEAD OF IT. DUE TO
LIMITED CAPE AS DISCUSSED ABOVE...THE STRONGER CELLS MAY PRODUCE
DAMAGING WINDS. WINDS HAVE VEERED TO THE SW AND HELICITY IS MUCH
LOWER SO NOT AS CONCERNED ABOUT ISOLATED TORNADOES AS I WAS THIS
MORNING.  PWAT VALUES REMAIN VERY IMPRESSIVE AT 1.4-1.7 INCHES SO
ANY OF THE NEW SHOWERS WILL BE CAPABLE OF ADDITIONAL HEAVY DOWNPOURS.

THE AREA OF SCATTERED SHOWERS AND STORMS SHIFTS EAST OF THE CWA THIS
EVENING...BUT WE ARE NOT DONE YET. ANOTHER ROUND OF SHOWERS AND
PERHAPS OF THUNDERSTORMS MAY FORM THIS EVENING AS THE VORT MAX
APPROACHES. THINKING THE COVERAGE WILL BE BEST ALONG AND WEST OF
GARY INDIANA TO PAXTON IL LINE. HAVE LOW CONFIDENCE IN COVERAGE AND
TIMING OF THIS ROUND OF SHOWERS...BUT NOT EXPECTING MUCH THUNDER AND
NO SEVERE WEATHER.  DEWPOINTS REMAIN IN THE 60S TONIGHT SO THINKING
WE WILL NOT COOL MUCH...SO KEPT LOWS IN THE LOW TO MID 60S.

THE PATTERN REMAINS MESSY TOMORROW BUT NOT AS ACTIVE.  A PAIR OF
VORT STREAMERS AND THE LOWS COLD FRONT ROTATE THROUGH AND SHOWERS
AND STORMS MAY FORM ALONG THEM.  THE FIRST IS ASSOCIATED WITH THE
UPPER LEVEL LOW SHIFTING NE INTO ONTARIO TOMORROW. SHOWERS AND
STORMS WITH THIS VORT STREAMER WOULD CLIP THE NORTHERN CWA...NORTH
OF I-88.  PRECIP MAY SINK SOUTH ACROSS DUPAGE AND COOK COUNTIES IN
THE AFTN...BUT HAVE LOW CONFIDENCE IN HOW FAR SOUTH THE PRECIP WILL
GET.

CLOUD COVER SHIFTS EAST THROUGH THE AFTERNOON WITH AREAS WEST OF I-
55 BECOMING MOSTLY SUNNY BY MID AFTN. DID NOT MAKE TOO MANY CHANGES
TO HIGH TEMPS TOMORROW AS CLOUD COVER WILL PLAY A ROLE.  HAVE TEMPS
IN THE UPPER 70S TO LOW 80S.  A LAKE BREEZE IS POSSIBLE LATE IN THE
AFTN AND EVENING SO EXPECTING LAKE COOLING ESPECIALLY AT WAUKEGAN.

JEE

&&

.LONG TERM...
330 PM CDT

WEDNESDAY NIGHT THROUGH TUESDAY...

LOCAL AREA WILL START OUT FIRMLY UNDER MID/UPPER RIDGING ON
WEDNESDAY NIGHT AND THURSDAY...RESULTING IN A DRY AND WARM PERIOD
AS 925 MB TEMPS CLIMB FROM THE UPPER TEENS CELSISUS BY EARLY
THURSDAY TO THE LOWER 20S CELSISUS EARLY THURSDAY EVENING. INLAND
TEMPERATURES WILL WARM TO THE LOWER-MID 80S ON THURSDAY...BUT
DESPITE SOUTHERLY SURFACE FLOW...GRADIENT WILL BE WEAK ENOUGH TO
ENABLE A LAKE BREEZE TO DEVELOP AND PUSH INLAND FAIRLY EARLY. THIS
WILL KEEP LAKESHORE TEMPS (ESPECIALLY IL SHORE) IN THE UPPER 60S.

CHANGES WILL START TO TAKE PLACE THURSDAY NIGHT WITH UPPER RIDGE
AXIS GETTING SHUNTED EAST AND ALLOWS SHORTWAVE ENERGY TO LIFT
EAST-NORTHEAST ACROSS THE AREA AFTER MIDNIGHT INTO FRIDAY ALONG
WITH STRENGTHENING AND VEERING LOW LEVEL JET. HAVE FOCUSED MID
CHANCE POPS INTO NORTHWEST CWA LATE THURSDAY NIGHT AND THEN SPREAD
LIKELY POPS FOR MUCH OF THE CWA FRIDAY MORNING AND EARLY
AFTERNOON. IT APPEARS THAT BETTER MOISTURE CONVERGENCE AND UPPER
FORCING WILL LIFT NORTH AND REFOCUS INTO NORTHWEST CWA FRIDAY
AFTERNOON AND TAILORED POPS AS SUCH...BUT THEN A STRONGER WAVE
WILL MOVE ACROSS THE AREA SATURDAY NIGHT. CONFIDENCE IS A BIT
LOWER IN HIGH TEMPS FRIDAY DUE TO UNCERTAINTY OVER IMPACT OF
CLOUDS/PRECIP...BUT VERY MILD START TO DAY AND WARM AIRMASS IN
PLACE SHOULD STILL SUPPORT HIGHS INTO THE LOWER-MID 80S...WARMEST
IN SOUTHEAST HALF OF CWA. THE WARM TEMPS...DEWPOINTS WELL INTO THE
60S AND MODEST MIDLEVEL LAPSE RATES WILL YIELD MODEST CAPE
VALUES...SO CANNOT RULE OUT AN ISOLATED SEVERE THREAT FOR DAMAGING
WINDS INTO FRIDAY EVENING. COULD BE SOME WET MICROBURSTS WITH PWAT
VALUES IN 1.5 TO 1.75 INCH RANGE.

A STRONG COLD FRONT WILL SWEEP ACROSS THE AREA FRIDAY
NIGHT...RESULTING IN MUCH COOLER WEATHER FOR THE LAST WEEKEND OF
MAY. HIGHS ON THE LAKEFRONT ARE LIKELY TO STAY IN THE 50S ON BOTH
SATURDAY AND SUNDAY...WITH ONLY 60S AND 70S INLAND ON SATURDAY AND
60S ON SUNDAY. WILL NEED TO WATCH FOR A WAVE OF SURFACE LOW
PRESSURE FORMING SOUTH OF THE AREA ON SATURDAY...SO KEPT HIGHER
CONSENSUS POPS FOR NOW SATURDAY MORNING...BUT IF TRENDS ON MUCH OF
GUIDANCE CONTINUE MAY BE ABLE TO LOWER POPS SATURDAY THROUGH
MONDAY WITH EXPANSIVE COOL HIGH PRESSURE OVER THE GREAT LAKES.
TEMPERATURES WILL THEN WARM BACK TO NEAR NORMAL FOR EARLY JUNE BY
TUESDAY WITH SOUTHERLY FLOW ON BACK SIDE OF HIGH TO EAST...THOUGH
ONSHORE FLOW LOOKS TO CONTINUE FOR AT LEAST A PORTION OF THE
LAKEFRONT.

RC

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 00Z...

* GUSTY SOUTHWEST WINDS THROUGH EARLY EVENING.

* ISOLATED TO SCATTERED SHRA POSSIBLE LATER THIS EVENING.

* MVFR CIGS POSSIBLE OVERNIGHT INTO EARLY WEDNESDAY.

* LAKE BREEZE WIND SHIFT TO NORTHEAST POSSIBLE LATE AFTERNOON
  INTO EARLY EVENING WEDNESDAY.

RC

//DISCUSSION...UPDATED 00Z...

LOW PRESSURE LOCATED OVER CENTRAL WISCONSIN RESULTING IN GUSTY
SOUTHWEST WINDS AND THESE GUSTY WINDS WILL CONTINUE THROUGH MID
EVENING. AFTER NARROW AREA OF SHRA CLEARS THE EASTERN
TERMINALS...ANOTHER UPPER DISTURBANCE ROTATING NORTHEAST FROM IA
SHOULD BRING SCATTERED SHRA INTO NORTHERN ILLINOIS AGAIN BY MID
EVENING...BUT TRAJECTORY WOULD FAVOR RFD AND HAVE LEFT OTHER
TERMINALS DRY FOR NOW. NEXT CONCERN IS FOR POTENTIAL PERIOD OF
LOWER CIGS OVERNIGHT INTO EARLY WEDNESDAY. GUIDANCE VARIES ON HOW
LOW/WIDESPREAD CIGS WILL GET AND TIMING...BUT GIVEN LOWER
CONFIDENCE HAVE MAINTAINED PREVIOUS TIMING. DID PULL MVFR VSBY AS
STEADY SOUTHWEST WINDS SHOULD PREVENT VSBY RESTRICTIONS.

A COLD FRONT AND UPPER TROUGH WILL MOVE ACROSS THE AREA ON
WEDNESDAY...WITH WINDS VEERING TO WEST AND THEN WEST-NORTHWEST.
GUSTS TO 15 TO 20 KT ARE POSSIBLE IN THE MORNING THROUGH EARLY
AFTERNOON. GRADIENT IS EXPECTED TO WEAKEN ENOUGH TO ALLOW LAKE
BREEZE TO SLIP INLAND LATE...BUT SPEEDS SHOULD BE LIGHT BEHIND
SHIFT. AS UPPER TROUGH MOVES OVERHEAD...ONLY VERY MINIMAL
INSTABILITY SHOWN ON FORECAST SOUNDINGS AND SHOWER COVERAGE IS
LIKELY TO BE ISOLATED...SO HAVE BACKED OFF TO A PROB30 DURING THE
AFTERNOON AT THE EASTERN TERMINALS.

RC


//ORD AND MDW CONFIDENCE...UPDATED 00Z...

* MEDIUM-HIGH IN WINDS THROUGH WEDNESDAY AFTERNOON.

* MEDIUM IN LAKE BREEZE LATE WEDNESDAY AFTERNOON.

* LOW IN SHRA LATER THIS EVENING AND ON WEDNESDAY AFTERNOON.

* LOW-MEDIUM IN LOWER CIG TRENDS OVERNIGHT INTO EARLY WEDNESDAY.

RC

//OUTLOOK FOR ORD/MDW FOR 12Z THURSDAY-12Z TUESDAY...UPDATED 00Z...

THURSDAY...MAINLY VFR WITH CHANCE SHRA/TSRA LATE THURSDAY NIGHT.
LAKE BREEZE SHIFT TO EAST WINDS.

FRIDAY...PERIODIC SHRA/TSRA...ESPECIALLY IN MORNING AND THEN AT
NIGHT.

SATURDAY...STRONG NORTH-NORTHEAST WINDS. SHRA AND MVFR
POSSIBLE...MAINLY IN THE MORNING.

SUNDAY AND MONDAY...VFR. NORTHEAST WINDS.

RC

&&

.MARINE...
417 PM CDT

WINDS REMAIN GUSTY THIS AFTERNOON AND DECIDED TO ISSUE A SMALL
CRAFT ADVISORY FOR STRONG WINDS INTO THIS EVENING. THE SOUTH WINDS
BECOME SOUTHWEST THIS EVENING. LOW PRESSURE MOVES OVER QUEBEC
TOMORROW AFTERNOON AND COLD FRONT TRAILING FROM THE LOW SWINGS
THROUGH. WINDS WEAKEN WEDNESDAY AFTERNOON AND A LAKE BREEZE IS
EXPECTED LATE WEDNESDAY AFTERNOON.

MODEST SOUTHERLY FLOW IS EXPECTED ON THURSDAY...WITH LAKE BREEZE
INFLUENCES IN THE SOUTHERN PORTION OF THE LAKE...THEN A PERIOD OF
SLIGHTLY STRONGER SOUTHERLY FLOW ON FRIDAY AHEAD OF A STRONG COLD
FRONT...THOUGH WARM AIRMASS WILL LIMIT MIXING. WILL LIKELY NEED TO
ADD AREAS OF FOG OVER THE LAKE. THE STRONG COLD FRONT WILL SWEEP
ACROSS THE LAKE FRIDAY NIGHT INTO SATURDAY...BRINGING NORTHERLY
WINDS TO 30 KT. WILL NEED TO WATCH FOR A PERIOD OF NORTHERLY GALES
SHOWN ON SOME MODEL GUIDANCE. WILL NEED A SMALL CRAFT ADVISORY
SATURDAY MORNING THROUGH SUNDAY MORNING UNTIL WAVES SUBSIDE.

RC

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 10 PM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 262349
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
649 PM CDT TUE MAY 26 2015

.SHORT TERM...
253 PM CDT

THROUGH WEDNESDAY...

A SURFACE LOW IS OVER NORTHEAST IA AND SW WI WITH A VORT MAX OVER
IOWA. THE LOWS COLD FRONT REMAINS A BIT FURTHER BACK OVER CENTRAL IA
AND EASTERN KS. THE LOW WILL DEEPEN SLIGHTLY AS IT MOVES OVER
CENTRAL WI AND ITS COLD FRONT SWINGS THROUGH WEDNESDAY. THE MAIN
CONCERN RIGHT NOW IS HOW MUCH CONVECTION WILL DEVELOP THIS
AFTERNOON.  THE LATEST RAP ANALYSIS SUGGESTS A RIBBON OF 1000 J/KG
OF CAPE IS OVER I-39...BUT THINKING THAT CAPE IN REALITY IS AROUND
500 J/KG DUE TO LIMITED HEATING. CAPE VALUES COULD RISE TO AROUND
1000 J/KG AS THERE ARE A FEW BREAKS IN THE CLOUDS...BUT THINKING IN
GENERAL THE BREAKS ARE MOVING TOO QUICKLY AND TOO FEW AND FAR BTWN
TO AMOUNT TO MUCH.  SHEAR VALUES REMAIN VERY FAVORABLE FOR ORGANIZED
STORMS WITH VALUES AROUND 35-40 KT.

THEREFORE EXPECTING SCATTERED SHOWER/TS DEVELOPMENT THIS AFTN IN THE
WAKE OF THE LINE OF SHOWERS THAT IS SHIFTING EAST ACROSS INDIANA
RIGHT NOW.  A SECOND SKINNY LINE OF CONVECTION LIES FROM DIXON IL TO
JERSEYVILLE IL WITH A FEW ADDITIONAL CELLS OUT AHEAD OF IT. DUE TO
LIMITED CAPE AS DISCUSSED ABOVE...THE STRONGER CELLS MAY PRODUCE
DAMAGING WINDS. WINDS HAVE VEERED TO THE SW AND HELICITY IS MUCH
LOWER SO NOT AS CONCERNED ABOUT ISOLATED TORNADOES AS I WAS THIS
MORNING.  PWAT VALUES REMAIN VERY IMPRESSIVE AT 1.4-1.7 INCHES SO
ANY OF THE NEW SHOWERS WILL BE CAPABLE OF ADDITIONAL HEAVY DOWNPOURS.

THE AREA OF SCATTERED SHOWERS AND STORMS SHIFTS EAST OF THE CWA THIS
EVENING...BUT WE ARE NOT DONE YET. ANOTHER ROUND OF SHOWERS AND
PERHAPS OF THUNDERSTORMS MAY FORM THIS EVENING AS THE VORT MAX
APPROACHES. THINKING THE COVERAGE WILL BE BEST ALONG AND WEST OF
GARY INDIANA TO PAXTON IL LINE. HAVE LOW CONFIDENCE IN COVERAGE AND
TIMING OF THIS ROUND OF SHOWERS...BUT NOT EXPECTING MUCH THUNDER AND
NO SEVERE WEATHER.  DEWPOINTS REMAIN IN THE 60S TONIGHT SO THINKING
WE WILL NOT COOL MUCH...SO KEPT LOWS IN THE LOW TO MID 60S.

THE PATTERN REMAINS MESSY TOMORROW BUT NOT AS ACTIVE.  A PAIR OF
VORT STREAMERS AND THE LOWS COLD FRONT ROTATE THROUGH AND SHOWERS
AND STORMS MAY FORM ALONG THEM.  THE FIRST IS ASSOCIATED WITH THE
UPPER LEVEL LOW SHIFTING NE INTO ONTARIO TOMORROW. SHOWERS AND
STORMS WITH THIS VORT STREAMER WOULD CLIP THE NORTHERN CWA...NORTH
OF I-88.  PRECIP MAY SINK SOUTH ACROSS DUPAGE AND COOK COUNTIES IN
THE AFTN...BUT HAVE LOW CONFIDENCE IN HOW FAR SOUTH THE PRECIP WILL
GET.

CLOUD COVER SHIFTS EAST THROUGH THE AFTERNOON WITH AREAS WEST OF I-
55 BECOMING MOSTLY SUNNY BY MID AFTN. DID NOT MAKE TOO MANY CHANGES
TO HIGH TEMPS TOMORROW AS CLOUD COVER WILL PLAY A ROLE.  HAVE TEMPS
IN THE UPPER 70S TO LOW 80S.  A LAKE BREEZE IS POSSIBLE LATE IN THE
AFTN AND EVENING SO EXPECTING LAKE COOLING ESPECIALLY AT WAUKEGAN.

JEE

&&

.LONG TERM...
330 PM CDT

WEDNESDAY NIGHT THROUGH TUESDAY...

LOCAL AREA WILL START OUT FIRMLY UNDER MID/UPPER RIDGING ON
WEDNESDAY NIGHT AND THURSDAY...RESULTING IN A DRY AND WARM PERIOD
AS 925 MB TEMPS CLIMB FROM THE UPPER TEENS CELSISUS BY EARLY
THURSDAY TO THE LOWER 20S CELSISUS EARLY THURSDAY EVENING. INLAND
TEMPERATURES WILL WARM TO THE LOWER-MID 80S ON THURSDAY...BUT
DESPITE SOUTHERLY SURFACE FLOW...GRADIENT WILL BE WEAK ENOUGH TO
ENABLE A LAKE BREEZE TO DEVELOP AND PUSH INLAND FAIRLY EARLY. THIS
WILL KEEP LAKESHORE TEMPS (ESPECIALLY IL SHORE) IN THE UPPER 60S.

CHANGES WILL START TO TAKE PLACE THURSDAY NIGHT WITH UPPER RIDGE
AXIS GETTING SHUNTED EAST AND ALLOWS SHORTWAVE ENERGY TO LIFT
EAST-NORTHEAST ACROSS THE AREA AFTER MIDNIGHT INTO FRIDAY ALONG
WITH STRENGTHENING AND VEERING LOW LEVEL JET. HAVE FOCUSED MID
CHANCE POPS INTO NORTHWEST CWA LATE THURSDAY NIGHT AND THEN SPREAD
LIKELY POPS FOR MUCH OF THE CWA FRIDAY MORNING AND EARLY
AFTERNOON. IT APPEARS THAT BETTER MOISTURE CONVERGENCE AND UPPER
FORCING WILL LIFT NORTH AND REFOCUS INTO NORTHWEST CWA FRIDAY
AFTERNOON AND TAILORED POPS AS SUCH...BUT THEN A STRONGER WAVE
WILL MOVE ACROSS THE AREA SATURDAY NIGHT. CONFIDENCE IS A BIT
LOWER IN HIGH TEMPS FRIDAY DUE TO UNCERTAINTY OVER IMPACT OF
CLOUDS/PRECIP...BUT VERY MILD START TO DAY AND WARM AIRMASS IN
PLACE SHOULD STILL SUPPORT HIGHS INTO THE LOWER-MID 80S...WARMEST
IN SOUTHEAST HALF OF CWA. THE WARM TEMPS...DEWPOINTS WELL INTO THE
60S AND MODEST MIDLEVEL LAPSE RATES WILL YIELD MODEST CAPE
VALUES...SO CANNOT RULE OUT AN ISOLATED SEVERE THREAT FOR DAMAGING
WINDS INTO FRIDAY EVENING. COULD BE SOME WET MICROBURSTS WITH PWAT
VALUES IN 1.5 TO 1.75 INCH RANGE.

A STRONG COLD FRONT WILL SWEEP ACROSS THE AREA FRIDAY
NIGHT...RESULTING IN MUCH COOLER WEATHER FOR THE LAST WEEKEND OF
MAY. HIGHS ON THE LAKEFRONT ARE LIKELY TO STAY IN THE 50S ON BOTH
SATURDAY AND SUNDAY...WITH ONLY 60S AND 70S INLAND ON SATURDAY AND
60S ON SUNDAY. WILL NEED TO WATCH FOR A WAVE OF SURFACE LOW
PRESSURE FORMING SOUTH OF THE AREA ON SATURDAY...SO KEPT HIGHER
CONSENSUS POPS FOR NOW SATURDAY MORNING...BUT IF TRENDS ON MUCH OF
GUIDANCE CONTINUE MAY BE ABLE TO LOWER POPS SATURDAY THROUGH
MONDAY WITH EXPANSIVE COOL HIGH PRESSURE OVER THE GREAT LAKES.
TEMPERATURES WILL THEN WARM BACK TO NEAR NORMAL FOR EARLY JUNE BY
TUESDAY WITH SOUTHERLY FLOW ON BACK SIDE OF HIGH TO EAST...THOUGH
ONSHORE FLOW LOOKS TO CONTINUE FOR AT LEAST A PORTION OF THE
LAKEFRONT.

RC

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 00Z...

* GUSTY SOUTHWEST WINDS THROUGH EARLY EVENING.

* ISOLATED TO SCATTERED SHRA POSSIBLE LATER THIS EVENING.

* MVFR CIGS POSSIBLE OVERNIGHT INTO EARLY WEDNESDAY.

* LAKE BREEZE WIND SHIFT TO NORTHEAST POSSIBLE LATE AFTERNOON
  INTO EARLY EVENING WEDNESDAY.

RC

//DISCUSSION...UPDATED 00Z...

LOW PRESSURE LOCATED OVER CENTRAL WISCONSIN RESULTING IN GUSTY
SOUTHWEST WINDS AND THESE GUSTY WINDS WILL CONTINUE THROUGH MID
EVENING. AFTER NARROW AREA OF SHRA CLEARS THE EASTERN
TERMINALS...ANOTHER UPPER DISTURBANCE ROTATING NORTHEAST FROM IA
SHOULD BRING SCATTERED SHRA INTO NORTHERN ILLINOIS AGAIN BY MID
EVENING...BUT TRAJECTORY WOULD FAVOR RFD AND HAVE LEFT OTHER
TERMINALS DRY FOR NOW. NEXT CONCERN IS FOR POTENTIAL PERIOD OF
LOWER CIGS OVERNIGHT INTO EARLY WEDNESDAY. GUIDANCE VARIES ON HOW
LOW/WIDESPREAD CIGS WILL GET AND TIMING...BUT GIVEN LOWER
CONFIDENCE HAVE MAINTAINED PREVIOUS TIMING. DID PULL MVFR VSBY AS
STEADY SOUTHWEST WINDS SHOULD PREVENT VSBY RESTRICTIONS.

A COLD FRONT AND UPPER TROUGH WILL MOVE ACROSS THE AREA ON
WEDNESDAY...WITH WINDS VEERING TO WEST AND THEN WEST-NORTHWEST.
GUSTS TO 15 TO 20 KT ARE POSSIBLE IN THE MORNING THROUGH EARLY
AFTERNOON. GRADIENT IS EXPECTED TO WEAKEN ENOUGH TO ALLOW LAKE
BREEZE TO SLIP INLAND LATE...BUT SPEEDS SHOULD BE LIGHT BEHIND
SHIFT. AS UPPER TROUGH MOVES OVERHEAD...ONLY VERY MINIMAL
INSTABILITY SHOWN ON FORECAST SOUNDINGS AND SHOWER COVERAGE IS
LIKELY TO BE ISOLATED...SO HAVE BACKED OFF TO A PROB30 DURING THE
AFTERNOON AT THE EASTERN TERMINALS.

RC


//ORD AND MDW CONFIDENCE...UPDATED 00Z...

* MEDIUM-HIGH IN WINDS THROUGH WEDNESDAY AFTERNOON.

* MEDIUM IN LAKE BREEZE LATE WEDNESDAY AFTERNOON.

* LOW IN SHRA LATER THIS EVENING AND ON WEDNESDAY AFTERNOON.

* LOW-MEDIUM IN LOWER CIG TRENDS OVERNIGHT INTO EARLY WEDNESDAY.

RC

//OUTLOOK FOR ORD/MDW FOR 12Z THURSDAY-12Z TUESDAY...UPDATED 00Z...

THURSDAY...MAINLY VFR WITH CHANCE SHRA/TSRA LATE THURSDAY NIGHT.
LAKE BREEZE SHIFT TO EAST WINDS.

FRIDAY...PERIODIC SHRA/TSRA...ESPECIALLY IN MORNING AND THEN AT
NIGHT.

SATURDAY...STRONG NORTH-NORTHEAST WINDS. SHRA AND MVFR
POSSIBLE...MAINLY IN THE MORNING.

SUNDAY AND MONDAY...VFR. NORTHEAST WINDS.

RC

&&

.MARINE...
417 PM CDT

WINDS REMAIN GUSTY THIS AFTERNOON AND DECIDED TO ISSUE A SMALL
CRAFT ADVISORY FOR STRONG WINDS INTO THIS EVENING. THE SOUTH WINDS
BECOME SOUTHWEST THIS EVENING. LOW PRESSURE MOVES OVER QUEBEC
TOMORROW AFTERNOON AND COLD FRONT TRAILING FROM THE LOW SWINGS
THROUGH. WINDS WEAKEN WEDNESDAY AFTERNOON AND A LAKE BREEZE IS
EXPECTED LATE WEDNESDAY AFTERNOON.

MODEST SOUTHERLY FLOW IS EXPECTED ON THURSDAY...WITH LAKE BREEZE
INFLUENCES IN THE SOUTHERN PORTION OF THE LAKE...THEN A PERIOD OF
SLIGHTLY STRONGER SOUTHERLY FLOW ON FRIDAY AHEAD OF A STRONG COLD
FRONT...THOUGH WARM AIRMASS WILL LIMIT MIXING. WILL LIKELY NEED TO
ADD AREAS OF FOG OVER THE LAKE. THE STRONG COLD FRONT WILL SWEEP
ACROSS THE LAKE FRIDAY NIGHT INTO SATURDAY...BRINGING NORTHERLY
WINDS TO 30 KT. WILL NEED TO WATCH FOR A PERIOD OF NORTHERLY GALES
SHOWN ON SOME MODEL GUIDANCE. WILL NEED A SMALL CRAFT ADVISORY
SATURDAY MORNING THROUGH SUNDAY MORNING UNTIL WAVES SUBSIDE.

RC

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 10 PM TUESDAY.

&&

$$

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000
FXUS63 KILX 262304
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
604 PM CDT TUE MAY 26 2015

.SHORT TERM...(TONIGHT)
ISSUED AT 300 PM CDT TUE MAY 26 2015

2 PM SURFACE MAP SHOWED LOW PRESSURE CENTERED JUST NORTHWEST OF
DUBUQUE. INITIAL BAND OF CONVECTIVE SHOWERS/ISOLATED THUNDERSTORMS
WHICH MOVED THROUGH THE FORECAST AREA EARLIER HAS ADVANCED NORTHEAST
ACROSS THE INDIANA BORDER...WITH A SECONDARY AXIS OF LIGHT SHOWERS
MOVING EAST AHEAD OF AN UPPER DISTURBANCE CROSSING THE MISSISSIPPI
RIVER.

HRRR AND OTHER HIGH-RESOLUTION MODEL GUIDANCE HAS BEEN DOING A
REASONABLE JOB WITH THE ACTIVITY TODAY...AND WAS GENERALLY FOLLOWED
FOR THE RAIN TRENDS TONIGHT. HAVE MADE SOME ADJUSTMENTS WITH GOING
MAINLY ISOLATED SHOWERS/STORMS THIS EVENING EXCEPT WEST OF I-55...
WHERE LOW CHANCE POP`S WERE KEPT AS A WAVE/TROUGH ADVANCES EAST
ACROSS NORTHERN MISSOURI. HAVE LINGERED THESE 30% CHANCES OVERNIGHT
FROM ABOUT DECATUR WESTWARD. SHOULD SEE SKIES BECOME PARTLY CLOUDY
ACROSS THE SOUTHERN CWA THIS EVENING...BEFORE SOME INCREASE IS NOTED
AGAIN AHEAD OF THE INCOMING WAVE.

.LONG TERM...(WEDNESDAY THROUGH TUESDAY)
ISSUED AT 300 PM CDT TUE MAY 26 2015

AN UNSETTLED WEATHER PATTERN LOOKS TO CONTINUE THROUGH MONDAY ACROSS
CENTRAL AND SOUTHEAST IL ALONG WITH WARM AND RATHER HUMID SUMMERLIKE
CONDITIONS THE REST OF THE WEEK. A COLD FRONT MOVING SE THROUGH
CENTRAL AND SOUTHEAST IL DURING SATURDAY WILL BRING COOLER
TEMPERATURES DURING THIS WEEKEND ESPECIALLY ON SUNDAY.

UPPER LEVEL TROF OVER THE UPPER MIDWEST MOVES INTO MI ON WED WHILE
PUSHING A WEAK FRONT SE INTO THE IL RIVER VALLEY WED AFTERNOON. ALSO
HAVE A SHORT WAVE EJECTING NE FROM THE SOUTHERN PLAINS INTO SE IL
AND CENTRAL INDIANA BY 18Z/WED. INCREASE INSTABLITY ON WED WITH
CAPES OF 1000-2000 J/KG AND HIGHEST SOUTH OF I-72 TO RETURN CHANCES
OF SHOWERS AND THUNDERSTORMS WITH LOWER CHANCES NW OF IL RIVER AND
HIGHER CHANCES IN SOUTHEAST IL. SPC HAS MARGINAL RISK OF SEVERE WED
AFTERNOON SE OF A SHELYVILLE TO PARIS LINE. CONVECTION CHANCES WILL
LINGER SOUTH OF I-72 WED NIGHT MAINLY WED EVENING. THEN ISOLATED
CHANCES OF CONVECTION SHIFT INTO SOUTHERN AND SW AREAS ON THU AS
WEAK HIGH PRESSURE DRIFTS ACROSS THE GREAT LAKES AND MORE STABLE AIR
OVER NE CWA FROM I-74 NE WHERE IT SHOULD BE DRY. NAM MODEL IS STILL
RATHER UNSTABLE THU SW OF I-74 BUT THINK IT MAY BE OVERDOING THIS AS
STRONGER INSTABLITY CLOSER MO AND THE OHIO RIVER VALLEY ON THU PLUS
HAVE UPPER LEVEL RIDGE BUILDING OVER THE EASTERN STATES THU.

WARM FRONT LIFTS NORTH ACROSS CENTRAL IL THU NIGHT AND IN BREEZY SSW
FLOW ON FRIDAY WITH CHANCES OF SHOWERS AND THUNDERSTORM HIGHEST OVER
IL RIVER VALLEY (LIKELY CHANCES WEST OF IL RIVER ON FRIDAY) AND
LOWEST NEAR WABASH RIVER. WARM HIGHS IN THE LOWER 80S WED AND MID
80S THU AND FRI AND A FEW AREAS COULD REACH UPPER 80S WITH ENOUGH
SUNSHINE ESPECIALLY NEAR WABASH RIVER WHERE RAIN CHANCES ARE LOWER.

HAVE LIKELY CHANCES OF SHOWERS AND THUNDERSTORMS FRI NIGHT AND SAT
WITH COLD FRONT PUSHING SE THROUGH CENTRAL IL DURING SATURDAY. HIGHS
SAT TO CONTRAST FROM LOWER 70S NW OF IL RIVER TO LOW 80S IN
SOUTHEAST IL. CONTINUE LIKELY CHANCES OF SHOWERS AND THUNDERSTORMS
SAT NIGHT IN SOUTHEAST IL ESPECIALLY SAT EVENING WHILE LOWERED POPS
TO LOW CHANCE NW OVER IL RIVER VALLEY BEHIND COLD FRONT. AREAS NW OF
IL RIVER NOW APPEAR DRY ON SUNDAY WHILE CHANCE OF SHOWERS AND
THUNDERSTORMS LINGERS FROM I-72 SOUTH CLOSER TO FRONTAL BOUNDARY
PUSHING SE OF OHIO RIVER OVER KY/TN. SUNDAY APPEARS TO BE COOLEST
DAY WITH HIGHS IN UPPER 60S CENTRAL IL AND LOWER 70S SE IL.

EXTENDED MODELS LIKE GFS AND ECMWF CONTINUE TO SHOW A WEAK CUTOFF
UPPER LEVEL LOW EJECTING INTO MO BY MON AND TO CONTINUE CHANCES OF
SHOWERS AND ISOLATED THUNDERSTORMS MONDAY AND TUESDAY. HIGHS IN THE
LOW TO MID 70S MONDAY AND MID TO UPPER 70S TUESDAY.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z WEDNESDAY EVENING)
ISSUED AT 600 PM CDT TUE MAY 26 2015

MAIN FORECAST CONCERN WILL BE ANY ADDITIONAL SHOWER ACTIVITY AND
AFFECT ON CLOUD BASES LATER THIS EVENING...AND THE POTENTIAL FOR
SOME MVFR FOG TOWARDS DAWN WED. LATEST SURFACE MAP HAS A WEAK
BOUNDARY/WIND SHIFT LINE OVER CENTRAL IOWA EARLY THIS EVENING
AND THAT FEATURE IS EXPECTED TO SLOWLY PUSH ACROSS THE FORECAST
AREA LATE TONIGHT/WED MORNING. NOT MUCH OF A TEMP OR DEW POINT
DISCONTINUITY ASSOCIATED WITH THE FEATURE AND THE UPPER LEVEL
LIFT IS MEAGER SO NOT EXPECTING MUCH IN THE WAY OF WIDESPREAD
RAINFALL OVERNIGHT AS IT PUSHES THROUGH THE AREA. FORECAST
SOUNDINGS SUGGEST SOME LOW MVFR CIGS AT TIMES AHEAD OF THE
FRONT WITH THE WIND FIELDS QUITE LIGHT ALONG AND JUST BEHIND
THE FRONT WHICH MAY ALLOW SOME MVFR FOG TO FORM TOWARDS WED
MORNING. CURRENT FORECAST SOUNDINGS INDICATE ENOUGH CLOUD
COVER WILL LINGER OVERNIGHT...ESPECIALLY IN THE MID AND UPPER
PORTIONS OF THE ATMOSPHERE THAT MAY LIMIT ANY RESTRICTIONS TO
VSBYS. FOR NOW WILL INTRODUCE A 5 TO 6 MI VSBY AT BMI AND CMI
WHICH WILL BE SEEING THE LIGHTER WINDS OVERNIGHT.

AN UPPER LEVEL WAVE IS FORECAST TO PUSH ACROSS THE SOUTHERN PLAINS
TONIGHT AND EDGE ENE INTO PARTS OF SOUTH CENTRAL IL BY MORNING
WED BRINGING SOME SCATTERED SHOWERS AND THUNDERSTORMS WITH IT.
CURRENT GUIDANCE SUGGESTS THE BULK OF THE RAIN SHOULD REMAIN SOUTH
OF THE TAF SITES WITH MAINLY VFR CONDITIONS EXPECTED FOR THE
REMAINDER OF THE DAY. SOUTHWEST WINDS AROUND 10KTS EXPECTED
TONIGHT WILL VEER MORE INTO A WESTERLY DIRECTION AS THE WEAKENING
BOUNDARY SHIFTS ACROSS THE AREA DURING THE DAY WEDNESDAY. WIND
SPEEDS SHOULD RANGE FROM 10 TO 15 KTS.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...GEELHART
LONG TERM...07
AVIATION...SMITH




000
FXUS63 KILX 262304
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
604 PM CDT TUE MAY 26 2015

.SHORT TERM...(TONIGHT)
ISSUED AT 300 PM CDT TUE MAY 26 2015

2 PM SURFACE MAP SHOWED LOW PRESSURE CENTERED JUST NORTHWEST OF
DUBUQUE. INITIAL BAND OF CONVECTIVE SHOWERS/ISOLATED THUNDERSTORMS
WHICH MOVED THROUGH THE FORECAST AREA EARLIER HAS ADVANCED NORTHEAST
ACROSS THE INDIANA BORDER...WITH A SECONDARY AXIS OF LIGHT SHOWERS
MOVING EAST AHEAD OF AN UPPER DISTURBANCE CROSSING THE MISSISSIPPI
RIVER.

HRRR AND OTHER HIGH-RESOLUTION MODEL GUIDANCE HAS BEEN DOING A
REASONABLE JOB WITH THE ACTIVITY TODAY...AND WAS GENERALLY FOLLOWED
FOR THE RAIN TRENDS TONIGHT. HAVE MADE SOME ADJUSTMENTS WITH GOING
MAINLY ISOLATED SHOWERS/STORMS THIS EVENING EXCEPT WEST OF I-55...
WHERE LOW CHANCE POP`S WERE KEPT AS A WAVE/TROUGH ADVANCES EAST
ACROSS NORTHERN MISSOURI. HAVE LINGERED THESE 30% CHANCES OVERNIGHT
FROM ABOUT DECATUR WESTWARD. SHOULD SEE SKIES BECOME PARTLY CLOUDY
ACROSS THE SOUTHERN CWA THIS EVENING...BEFORE SOME INCREASE IS NOTED
AGAIN AHEAD OF THE INCOMING WAVE.

.LONG TERM...(WEDNESDAY THROUGH TUESDAY)
ISSUED AT 300 PM CDT TUE MAY 26 2015

AN UNSETTLED WEATHER PATTERN LOOKS TO CONTINUE THROUGH MONDAY ACROSS
CENTRAL AND SOUTHEAST IL ALONG WITH WARM AND RATHER HUMID SUMMERLIKE
CONDITIONS THE REST OF THE WEEK. A COLD FRONT MOVING SE THROUGH
CENTRAL AND SOUTHEAST IL DURING SATURDAY WILL BRING COOLER
TEMPERATURES DURING THIS WEEKEND ESPECIALLY ON SUNDAY.

UPPER LEVEL TROF OVER THE UPPER MIDWEST MOVES INTO MI ON WED WHILE
PUSHING A WEAK FRONT SE INTO THE IL RIVER VALLEY WED AFTERNOON. ALSO
HAVE A SHORT WAVE EJECTING NE FROM THE SOUTHERN PLAINS INTO SE IL
AND CENTRAL INDIANA BY 18Z/WED. INCREASE INSTABLITY ON WED WITH
CAPES OF 1000-2000 J/KG AND HIGHEST SOUTH OF I-72 TO RETURN CHANCES
OF SHOWERS AND THUNDERSTORMS WITH LOWER CHANCES NW OF IL RIVER AND
HIGHER CHANCES IN SOUTHEAST IL. SPC HAS MARGINAL RISK OF SEVERE WED
AFTERNOON SE OF A SHELYVILLE TO PARIS LINE. CONVECTION CHANCES WILL
LINGER SOUTH OF I-72 WED NIGHT MAINLY WED EVENING. THEN ISOLATED
CHANCES OF CONVECTION SHIFT INTO SOUTHERN AND SW AREAS ON THU AS
WEAK HIGH PRESSURE DRIFTS ACROSS THE GREAT LAKES AND MORE STABLE AIR
OVER NE CWA FROM I-74 NE WHERE IT SHOULD BE DRY. NAM MODEL IS STILL
RATHER UNSTABLE THU SW OF I-74 BUT THINK IT MAY BE OVERDOING THIS AS
STRONGER INSTABLITY CLOSER MO AND THE OHIO RIVER VALLEY ON THU PLUS
HAVE UPPER LEVEL RIDGE BUILDING OVER THE EASTERN STATES THU.

WARM FRONT LIFTS NORTH ACROSS CENTRAL IL THU NIGHT AND IN BREEZY SSW
FLOW ON FRIDAY WITH CHANCES OF SHOWERS AND THUNDERSTORM HIGHEST OVER
IL RIVER VALLEY (LIKELY CHANCES WEST OF IL RIVER ON FRIDAY) AND
LOWEST NEAR WABASH RIVER. WARM HIGHS IN THE LOWER 80S WED AND MID
80S THU AND FRI AND A FEW AREAS COULD REACH UPPER 80S WITH ENOUGH
SUNSHINE ESPECIALLY NEAR WABASH RIVER WHERE RAIN CHANCES ARE LOWER.

HAVE LIKELY CHANCES OF SHOWERS AND THUNDERSTORMS FRI NIGHT AND SAT
WITH COLD FRONT PUSHING SE THROUGH CENTRAL IL DURING SATURDAY. HIGHS
SAT TO CONTRAST FROM LOWER 70S NW OF IL RIVER TO LOW 80S IN
SOUTHEAST IL. CONTINUE LIKELY CHANCES OF SHOWERS AND THUNDERSTORMS
SAT NIGHT IN SOUTHEAST IL ESPECIALLY SAT EVENING WHILE LOWERED POPS
TO LOW CHANCE NW OVER IL RIVER VALLEY BEHIND COLD FRONT. AREAS NW OF
IL RIVER NOW APPEAR DRY ON SUNDAY WHILE CHANCE OF SHOWERS AND
THUNDERSTORMS LINGERS FROM I-72 SOUTH CLOSER TO FRONTAL BOUNDARY
PUSHING SE OF OHIO RIVER OVER KY/TN. SUNDAY APPEARS TO BE COOLEST
DAY WITH HIGHS IN UPPER 60S CENTRAL IL AND LOWER 70S SE IL.

EXTENDED MODELS LIKE GFS AND ECMWF CONTINUE TO SHOW A WEAK CUTOFF
UPPER LEVEL LOW EJECTING INTO MO BY MON AND TO CONTINUE CHANCES OF
SHOWERS AND ISOLATED THUNDERSTORMS MONDAY AND TUESDAY. HIGHS IN THE
LOW TO MID 70S MONDAY AND MID TO UPPER 70S TUESDAY.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z WEDNESDAY EVENING)
ISSUED AT 600 PM CDT TUE MAY 26 2015

MAIN FORECAST CONCERN WILL BE ANY ADDITIONAL SHOWER ACTIVITY AND
AFFECT ON CLOUD BASES LATER THIS EVENING...AND THE POTENTIAL FOR
SOME MVFR FOG TOWARDS DAWN WED. LATEST SURFACE MAP HAS A WEAK
BOUNDARY/WIND SHIFT LINE OVER CENTRAL IOWA EARLY THIS EVENING
AND THAT FEATURE IS EXPECTED TO SLOWLY PUSH ACROSS THE FORECAST
AREA LATE TONIGHT/WED MORNING. NOT MUCH OF A TEMP OR DEW POINT
DISCONTINUITY ASSOCIATED WITH THE FEATURE AND THE UPPER LEVEL
LIFT IS MEAGER SO NOT EXPECTING MUCH IN THE WAY OF WIDESPREAD
RAINFALL OVERNIGHT AS IT PUSHES THROUGH THE AREA. FORECAST
SOUNDINGS SUGGEST SOME LOW MVFR CIGS AT TIMES AHEAD OF THE
FRONT WITH THE WIND FIELDS QUITE LIGHT ALONG AND JUST BEHIND
THE FRONT WHICH MAY ALLOW SOME MVFR FOG TO FORM TOWARDS WED
MORNING. CURRENT FORECAST SOUNDINGS INDICATE ENOUGH CLOUD
COVER WILL LINGER OVERNIGHT...ESPECIALLY IN THE MID AND UPPER
PORTIONS OF THE ATMOSPHERE THAT MAY LIMIT ANY RESTRICTIONS TO
VSBYS. FOR NOW WILL INTRODUCE A 5 TO 6 MI VSBY AT BMI AND CMI
WHICH WILL BE SEEING THE LIGHTER WINDS OVERNIGHT.

AN UPPER LEVEL WAVE IS FORECAST TO PUSH ACROSS THE SOUTHERN PLAINS
TONIGHT AND EDGE ENE INTO PARTS OF SOUTH CENTRAL IL BY MORNING
WED BRINGING SOME SCATTERED SHOWERS AND THUNDERSTORMS WITH IT.
CURRENT GUIDANCE SUGGESTS THE BULK OF THE RAIN SHOULD REMAIN SOUTH
OF THE TAF SITES WITH MAINLY VFR CONDITIONS EXPECTED FOR THE
REMAINDER OF THE DAY. SOUTHWEST WINDS AROUND 10KTS EXPECTED
TONIGHT WILL VEER MORE INTO A WESTERLY DIRECTION AS THE WEAKENING
BOUNDARY SHIFTS ACROSS THE AREA DURING THE DAY WEDNESDAY. WIND
SPEEDS SHOULD RANGE FROM 10 TO 15 KTS.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...GEELHART
LONG TERM...07
AVIATION...SMITH



000
FXUS63 KLOT 262215
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
515 PM CDT TUE MAY 26 2015

.SHORT TERM...
253 PM CDT

THROUGH WEDNESDAY...

A SURFACE LOW IS OVER NORTHEAST IA AND SW WI WITH A VORT MAX OVER
IOWA. THE LOWS COLD FRONT REMAINS A BIT FURTHER BACK OVER CENTRAL IA
AND EASTERN KS. THE LOW WILL DEEPEN SLIGHTLY AS IT MOVES OVER
CENTRAL WI AND ITS COLD FRONT SWINGS THROUGH WEDNESDAY. THE MAIN
CONCERN RIGHT NOW IS HOW MUCH CONVECTION WILL DEVELOP THIS
AFTERNOON.  THE LATEST RAP ANALYSIS SUGGESTS A RIBBON OF 1000 J/KG
OF CAPE IS OVER I-39...BUT THINKING THAT CAPE IN REALITY IS AROUND
500 J/KG DUE TO LIMITED HEATING. CAPE VALUES COULD RISE TO AROUND
1000 J/KG AS THERE ARE A FEW BREAKS IN THE CLOUDS...BUT THINKING IN
GENERAL THE BREAKS ARE MOVING TOO QUICKLY AND TOO FEW AND FAR BTWN
TO AMOUNT TO MUCH.  SHEAR VALUES REMAIN VERY FAVORABLE FOR ORGANIZED
STORMS WITH VALUES AROUND 35-40 KT.

THEREFORE EXPECTING SCATTERED SHOWER/TS DEVELOPMENT THIS AFTN IN THE
WAKE OF THE LINE OF SHOWERS THAT IS SHIFTING EAST ACROSS INDIANA
RIGHT NOW.  A SECOND SKINNY LINE OF CONVECTION LIES FROM DIXON IL TO
JERSEYVILLE IL WITH A FEW ADDITIONAL CELLS OUT AHEAD OF IT. DUE TO
LIMITED CAPE AS DISCUSSED ABOVE...THE STRONGER CELLS MAY PRODUCE
DAMAGING WINDS. WINDS HAVE VEERED TO THE SW AND HELICITY IS MUCH
LOWER SO NOT AS CONCERNED ABOUT ISOLATED TORNADOES AS I WAS THIS
MORNING.  PWAT VALUES REMAIN VERY IMPRESSIVE AT 1.4-1.7 INCHES SO
ANY OF THE NEW SHOWERS WILL BE CAPABLE OF ADDITIONAL HEAVY DOWNPOURS.

THE AREA OF SCATTERED SHOWERS AND STORMS SHIFTS EAST OF THE CWA THIS
EVENING...BUT WE ARE NOT DONE YET. ANOTHER ROUND OF SHOWERS AND
PERHAPS OF THUNDERSTORMS MAY FORM THIS EVENING AS THE VORT MAX
APPROACHES. THINKING THE COVERAGE WILL BE BEST ALONG AND WEST OF
GARY INDIANA TO PAXTON IL LINE. HAVE LOW CONFIDENCE IN COVERAGE AND
TIMING OF THIS ROUND OF SHOWERS...BUT NOT EXPECTING MUCH THUNDER AND
NO SEVERE WEATHER.  DEWPOINTS REMAIN IN THE 60S TONIGHT SO THINKING
WE WILL NOT COOL MUCH...SO KEPT LOWS IN THE LOW TO MID 60S.

THE PATTERN REMAINS MESSY TOMORROW BUT NOT AS ACTIVE.  A PAIR OF
VORT STREAMERS AND THE LOWS COLD FRONT ROTATE THROUGH AND SHOWERS
AND STORMS MAY FORM ALONG THEM.  THE FIRST IS ASSOCIATED WITH THE
UPPER LEVEL LOW SHIFTING NE INTO ONTARIO TOMORROW. SHOWERS AND
STORMS WITH THIS VORT STREAMER WOULD CLIP THE NORTHERN CWA...NORTH
OF I-88.  PRECIP MAY SINK SOUTH ACROSS DUPAGE AND COOK COUNTIES IN
THE AFTN...BUT HAVE LOW CONFIDENCE IN HOW FAR SOUTH THE PRECIP WILL
GET.

CLOUD COVER SHIFTS EAST THROUGH THE AFTERNOON WITH AREAS WEST OF I-
55 BECOMING MOSTLY SUNNY BY MID AFTN. DID NOT MAKE TOO MANY CHANGES
TO HIGH TEMPS TOMORROW AS CLOUD COVER WILL PLAY A ROLE.  HAVE TEMPS
IN THE UPPER 70S TO LOW 80S.  A LAKE BREEZE IS POSSIBLE LATE IN THE
AFTN AND EVENING SO EXPECTING LAKE COOLING ESPECIALLY AT WAUKEGAN.

JEE

&&

.LONG TERM...
330 PM CDT

WEDNESDAY NIGHT THROUGH TUESDAY...

LOCAL AREA WILL START OUT FIRMLY UNDER MID/UPPER RIDGING ON
WEDNESDAY NIGHT AND THURSDAY...RESULTING IN A DRY AND WARM PERIOD
AS 925 MB TEMPS CLIMB FROM THE UPPER TEENS CELSISUS BY EARLY
THURSDAY TO THE LOWER 20S CELSISUS EARLY THURSDAY EVENING. INLAND
TEMPERATURES WILL WARM TO THE LOWER-MID 80S ON THURSDAY...BUT
DESPITE SOUTHERLY SURFACE FLOW...GRADIENT WILL BE WEAK ENOUGH TO
ENABLE A LAKE BREEZE TO DEVELOP AND PUSH INLAND FAIRLY EARLY. THIS
WILL KEEP LAKESHORE TEMPS (ESPECIALLY IL SHORE) IN THE UPPER 60S.

CHANGES WILL START TO TAKE PLACE THURSDAY NIGHT WITH UPPER RIDGE
AXIS GETTING SHUNTED EAST AND ALLOWS SHORTWAVE ENERGY TO LIFT
EAST-NORTHEAST ACROSS THE AREA AFTER MIDNIGHT INTO FRIDAY ALONG
WITH STRENGTHENING AND VEERING LOW LEVEL JET. HAVE FOCUSED MID
CHANCE POPS INTO NORTHWEST CWA LATE THURSDAY NIGHT AND THEN SPREAD
LIKELY POPS FOR MUCH OF THE CWA FRIDAY MORNING AND EARLY
AFTERNOON. IT APPEARS THAT BETTER MOISTURE CONVERGENCE AND UPPER
FORCING WILL LIFT NORTH AND REFOCUS INTO NORTHWEST CWA FRIDAY
AFTERNOON AND TAILORED POPS AS SUCH...BUT THEN A STRONGER WAVE
WILL MOVE ACROSS THE AREA SATURDAY NIGHT. CONFIDENCE IS A BIT
LOWER IN HIGH TEMPS FRIDAY DUE TO UNCERTAINTY OVER IMPACT OF
CLOUDS/PRECIP...BUT VERY MILD START TO DAY AND WARM AIRMASS IN
PLACE SHOULD STILL SUPPORT HIGHS INTO THE LOWER-MID 80S...WARMEST
IN SOUTHEAST HALF OF CWA. THE WARM TEMPS...DEWPOINTS WELL INTO THE
60S AND MODEST MIDLEVEL LAPSE RATES WILL YIELD MODEST CAPE
VALUES...SO CANNOT RULE OUT AN ISOLATED SEVERE THREAT FOR DAMAGING
WINDS INTO FRIDAY EVENING. COULD BE SOME WET MICROBURSTS WITH PWAT
VALUES IN 1.5 TO 1.75 INCH RANGE.

A STRONG COLD FRONT WILL SWEEP ACROSS THE AREA FRIDAY
NIGHT...RESULTING IN MUCH COOLER WEATHER FOR THE LAST WEEKEND OF
MAY. HIGHS ON THE LAKEFRONT ARE LIKELY TO STAY IN THE 50S ON BOTH
SATURDAY AND SUNDAY...WITH ONLY 60S AND 70S INLAND ON SATURDAY AND
60S ON SUNDAY. WILL NEED TO WATCH FOR A WAVE OF SURFACE LOW
PRESSURE FORMING SOUTH OF THE AREA ON SATURDAY...SO KEPT HIGHER
CONSENSUS POPS FOR NOW SATURDAY MORNING...BUT IF TRENDS ON MUCH OF
GUIDANCE CONTINUE MAY BE ABLE TO LOWER POPS SATURDAY THROUGH
MONDAY WITH EXPANSIVE COOL HIGH PRESSURE OVER THE GREAT LAKES.
TEMPERATURES WILL THEN WARM BACK TO NEAR NORMAL FOR EARLY JUNE BY
TUESDAY WITH SOUTHERLY FLOW ON BACK SIDE OF HIGH TO EAST...THOUGH
ONSHORE FLOW LOOKS TO CONTINUE FOR AT LEAST A PORTION OF THE
LAKEFRONT.

RC

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 22Z...

* ISOLATED MVFR THIS AFTERNOON.

* RAIN SHOWERS POSSIBLY DROPPING TO MVFR THIS AFTERNOON.

* SOUTH TO SOUTHWEST WINDS...GUSTING TO MID/UPPER 20KTS.

* MVFR IN FOG AND LOW CLOUDS WEDNESDAY MORNING.

MM/RODRIGUEZ

//DISCUSSION...UPDATED 20Z...

LINE OF SHOWERS HAS DECREASED VSBYS TO 1 MILE UPSTREAM EARLY THIS
AFTERNOON. AS THE LINE PROGRESSES NORTHEASTWARD...COULD SEE SOME
STRONGER POCKETS OF RAIN AND TALLER EMBEDDED CELLS PRODUCE
ISOLATED LIGHTNING. LOW CHANCE/CONFIDENCE OF ANY OF THESE CELLS
HITTING THE TERMINALS...SO KEPT VCTS IN THE TAFS THROUGH 19Z.

LOOKING TOWARD WEDNESDAY MORNING...LOW LEVEL MOISTURE AND A WEAK
INVERSION WILL ALLOW A CHANCE FOR MVFR FOG AND CIGS TO WORK INTO
THE TERMINALS. THE AFTERNOON WILL FEATURE A SCATTERED TO POSSIBLY
BROKEN DECK AT 025. INTO THE EVENING...EXPECT OVERCAST CONDITIONS
WITH LIGHT RAIN POSSIBLE. THERE IS A CHANCE FOR THE LAKE BREEZE TO
WORK INTO ORD NEAR OR JUST AFTER 00Z WEDNESDAY EVENING.

MM

//ORD AND MDW CONFIDENCE...UPDATED 22Z...

* MEDIUM HIGH CONFIDENCE WITH TEMPO MVFR THIS AFTERNOON.

* HIGH CONFIDENCE WITH RAIN TRENDS THIS AFTERNOON.

* MEDIUM HIGH CONFIDENCE WITH WIND SPEED/DIRECTION.

* LOW-MEDIUM CONFIDENCE IN FOG AND MVFR CONDITIONS WEDNESDAY
  MORNING.

MM/RODRIGUEZ

//OUTLOOK FOR ORD/MDW FOR 00Z THURSDAY-12Z TUESDAY...UPDATED 12Z...

WEDNESDAY NIGHT...WX NIL/VFR. SOUTHEAST WINDS.

THURSDAY...SLIGHT CHANCE OF TSRA AT NIGHT. SOUTHEAST WINDS.

FRIDAY...TSRA/SHRA LIKELY THROUGH THE DAY AND NIGHT. MVFR
POSSIBLE. SOUTHWEST WINDS.

SATURDAY...SHRA LIKELY WITH A CHANCE OF TSRA DURING THE DAY.
NORTHEAST WINDS.

SUNDAY...CHANCE OF SHRA. EAST WINDS. MVFR POSSIBLE.

MONDAY...CHANCE OF SHRA. SOUTHEAST WINDS. MVFR POSSIBLE.

KREIN

&&

.MARINE...
417 PM CDT

WINDS REMAIN GUSTY THIS AFTERNOON AND DECIDED TO ISSUE A SMALL
CRAFT ADVISORY FOR STRONG WINDS INTO THIS EVENING. THE SOUTH WINDS
BECOME SOUTHWEST THIS EVENING. LOW PRESSURE MOVES OVER QUEBEC
TOMORROW AFTERNOON AND COLD FRONT TRAILING FROM THE LOW SWINGS
THROUGH. WINDS WEAKEN WEDNESDAY AFTERNOON AND A LAKE BREEZE IS
EXPECTED LATE WEDNESDAY AFTERNOON.

MODEST SOUTHERLY FLOW IS EXPECTED ON THURSDAY...WITH LAKE BREEZE
INFLUENCES IN THE SOUTHERN PORTION OF THE LAKE...THEN A PERIOD OF
SLIGHTLY STRONGER SOUTHERLY FLOW ON FRIDAY AHEAD OF A STRONG COLD
FRONT...THOUGH WARM AIRMASS WILL LIMIT MIXING. WILL LIKELY NEED TO
ADD AREAS OF FOG OVER THE LAKE. THE STRONG COLD FRONT WILL SWEEP
ACROSS THE LAKE FRIDAY NIGHT INTO SATURDAY...BRINGING NORTHERLY
WINDS TO 30 KT. WILL NEED TO WATCH FOR A PERIOD OF NORTHERLY GALES
SHOWN ON SOME MODEL GUIDANCE. WILL NEED A SMALL CRAFT ADVISORY
SATURDAY MORNING THROUGH SUNDAY MORNING UNTIL WAVES SUBSIDE.

RC

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 10 PM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 262215
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
515 PM CDT TUE MAY 26 2015

.SHORT TERM...
253 PM CDT

THROUGH WEDNESDAY...

A SURFACE LOW IS OVER NORTHEAST IA AND SW WI WITH A VORT MAX OVER
IOWA. THE LOWS COLD FRONT REMAINS A BIT FURTHER BACK OVER CENTRAL IA
AND EASTERN KS. THE LOW WILL DEEPEN SLIGHTLY AS IT MOVES OVER
CENTRAL WI AND ITS COLD FRONT SWINGS THROUGH WEDNESDAY. THE MAIN
CONCERN RIGHT NOW IS HOW MUCH CONVECTION WILL DEVELOP THIS
AFTERNOON.  THE LATEST RAP ANALYSIS SUGGESTS A RIBBON OF 1000 J/KG
OF CAPE IS OVER I-39...BUT THINKING THAT CAPE IN REALITY IS AROUND
500 J/KG DUE TO LIMITED HEATING. CAPE VALUES COULD RISE TO AROUND
1000 J/KG AS THERE ARE A FEW BREAKS IN THE CLOUDS...BUT THINKING IN
GENERAL THE BREAKS ARE MOVING TOO QUICKLY AND TOO FEW AND FAR BTWN
TO AMOUNT TO MUCH.  SHEAR VALUES REMAIN VERY FAVORABLE FOR ORGANIZED
STORMS WITH VALUES AROUND 35-40 KT.

THEREFORE EXPECTING SCATTERED SHOWER/TS DEVELOPMENT THIS AFTN IN THE
WAKE OF THE LINE OF SHOWERS THAT IS SHIFTING EAST ACROSS INDIANA
RIGHT NOW.  A SECOND SKINNY LINE OF CONVECTION LIES FROM DIXON IL TO
JERSEYVILLE IL WITH A FEW ADDITIONAL CELLS OUT AHEAD OF IT. DUE TO
LIMITED CAPE AS DISCUSSED ABOVE...THE STRONGER CELLS MAY PRODUCE
DAMAGING WINDS. WINDS HAVE VEERED TO THE SW AND HELICITY IS MUCH
LOWER SO NOT AS CONCERNED ABOUT ISOLATED TORNADOES AS I WAS THIS
MORNING.  PWAT VALUES REMAIN VERY IMPRESSIVE AT 1.4-1.7 INCHES SO
ANY OF THE NEW SHOWERS WILL BE CAPABLE OF ADDITIONAL HEAVY DOWNPOURS.

THE AREA OF SCATTERED SHOWERS AND STORMS SHIFTS EAST OF THE CWA THIS
EVENING...BUT WE ARE NOT DONE YET. ANOTHER ROUND OF SHOWERS AND
PERHAPS OF THUNDERSTORMS MAY FORM THIS EVENING AS THE VORT MAX
APPROACHES. THINKING THE COVERAGE WILL BE BEST ALONG AND WEST OF
GARY INDIANA TO PAXTON IL LINE. HAVE LOW CONFIDENCE IN COVERAGE AND
TIMING OF THIS ROUND OF SHOWERS...BUT NOT EXPECTING MUCH THUNDER AND
NO SEVERE WEATHER.  DEWPOINTS REMAIN IN THE 60S TONIGHT SO THINKING
WE WILL NOT COOL MUCH...SO KEPT LOWS IN THE LOW TO MID 60S.

THE PATTERN REMAINS MESSY TOMORROW BUT NOT AS ACTIVE.  A PAIR OF
VORT STREAMERS AND THE LOWS COLD FRONT ROTATE THROUGH AND SHOWERS
AND STORMS MAY FORM ALONG THEM.  THE FIRST IS ASSOCIATED WITH THE
UPPER LEVEL LOW SHIFTING NE INTO ONTARIO TOMORROW. SHOWERS AND
STORMS WITH THIS VORT STREAMER WOULD CLIP THE NORTHERN CWA...NORTH
OF I-88.  PRECIP MAY SINK SOUTH ACROSS DUPAGE AND COOK COUNTIES IN
THE AFTN...BUT HAVE LOW CONFIDENCE IN HOW FAR SOUTH THE PRECIP WILL
GET.

CLOUD COVER SHIFTS EAST THROUGH THE AFTERNOON WITH AREAS WEST OF I-
55 BECOMING MOSTLY SUNNY BY MID AFTN. DID NOT MAKE TOO MANY CHANGES
TO HIGH TEMPS TOMORROW AS CLOUD COVER WILL PLAY A ROLE.  HAVE TEMPS
IN THE UPPER 70S TO LOW 80S.  A LAKE BREEZE IS POSSIBLE LATE IN THE
AFTN AND EVENING SO EXPECTING LAKE COOLING ESPECIALLY AT WAUKEGAN.

JEE

&&

.LONG TERM...
330 PM CDT

WEDNESDAY NIGHT THROUGH TUESDAY...

LOCAL AREA WILL START OUT FIRMLY UNDER MID/UPPER RIDGING ON
WEDNESDAY NIGHT AND THURSDAY...RESULTING IN A DRY AND WARM PERIOD
AS 925 MB TEMPS CLIMB FROM THE UPPER TEENS CELSISUS BY EARLY
THURSDAY TO THE LOWER 20S CELSISUS EARLY THURSDAY EVENING. INLAND
TEMPERATURES WILL WARM TO THE LOWER-MID 80S ON THURSDAY...BUT
DESPITE SOUTHERLY SURFACE FLOW...GRADIENT WILL BE WEAK ENOUGH TO
ENABLE A LAKE BREEZE TO DEVELOP AND PUSH INLAND FAIRLY EARLY. THIS
WILL KEEP LAKESHORE TEMPS (ESPECIALLY IL SHORE) IN THE UPPER 60S.

CHANGES WILL START TO TAKE PLACE THURSDAY NIGHT WITH UPPER RIDGE
AXIS GETTING SHUNTED EAST AND ALLOWS SHORTWAVE ENERGY TO LIFT
EAST-NORTHEAST ACROSS THE AREA AFTER MIDNIGHT INTO FRIDAY ALONG
WITH STRENGTHENING AND VEERING LOW LEVEL JET. HAVE FOCUSED MID
CHANCE POPS INTO NORTHWEST CWA LATE THURSDAY NIGHT AND THEN SPREAD
LIKELY POPS FOR MUCH OF THE CWA FRIDAY MORNING AND EARLY
AFTERNOON. IT APPEARS THAT BETTER MOISTURE CONVERGENCE AND UPPER
FORCING WILL LIFT NORTH AND REFOCUS INTO NORTHWEST CWA FRIDAY
AFTERNOON AND TAILORED POPS AS SUCH...BUT THEN A STRONGER WAVE
WILL MOVE ACROSS THE AREA SATURDAY NIGHT. CONFIDENCE IS A BIT
LOWER IN HIGH TEMPS FRIDAY DUE TO UNCERTAINTY OVER IMPACT OF
CLOUDS/PRECIP...BUT VERY MILD START TO DAY AND WARM AIRMASS IN
PLACE SHOULD STILL SUPPORT HIGHS INTO THE LOWER-MID 80S...WARMEST
IN SOUTHEAST HALF OF CWA. THE WARM TEMPS...DEWPOINTS WELL INTO THE
60S AND MODEST MIDLEVEL LAPSE RATES WILL YIELD MODEST CAPE
VALUES...SO CANNOT RULE OUT AN ISOLATED SEVERE THREAT FOR DAMAGING
WINDS INTO FRIDAY EVENING. COULD BE SOME WET MICROBURSTS WITH PWAT
VALUES IN 1.5 TO 1.75 INCH RANGE.

A STRONG COLD FRONT WILL SWEEP ACROSS THE AREA FRIDAY
NIGHT...RESULTING IN MUCH COOLER WEATHER FOR THE LAST WEEKEND OF
MAY. HIGHS ON THE LAKEFRONT ARE LIKELY TO STAY IN THE 50S ON BOTH
SATURDAY AND SUNDAY...WITH ONLY 60S AND 70S INLAND ON SATURDAY AND
60S ON SUNDAY. WILL NEED TO WATCH FOR A WAVE OF SURFACE LOW
PRESSURE FORMING SOUTH OF THE AREA ON SATURDAY...SO KEPT HIGHER
CONSENSUS POPS FOR NOW SATURDAY MORNING...BUT IF TRENDS ON MUCH OF
GUIDANCE CONTINUE MAY BE ABLE TO LOWER POPS SATURDAY THROUGH
MONDAY WITH EXPANSIVE COOL HIGH PRESSURE OVER THE GREAT LAKES.
TEMPERATURES WILL THEN WARM BACK TO NEAR NORMAL FOR EARLY JUNE BY
TUESDAY WITH SOUTHERLY FLOW ON BACK SIDE OF HIGH TO EAST...THOUGH
ONSHORE FLOW LOOKS TO CONTINUE FOR AT LEAST A PORTION OF THE
LAKEFRONT.

RC

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 22Z...

* ISOLATED MVFR THIS AFTERNOON.

* RAIN SHOWERS POSSIBLY DROPPING TO MVFR THIS AFTERNOON.

* SOUTH TO SOUTHWEST WINDS...GUSTING TO MID/UPPER 20KTS.

* MVFR IN FOG AND LOW CLOUDS WEDNESDAY MORNING.

MM/RODRIGUEZ

//DISCUSSION...UPDATED 20Z...

LINE OF SHOWERS HAS DECREASED VSBYS TO 1 MILE UPSTREAM EARLY THIS
AFTERNOON. AS THE LINE PROGRESSES NORTHEASTWARD...COULD SEE SOME
STRONGER POCKETS OF RAIN AND TALLER EMBEDDED CELLS PRODUCE
ISOLATED LIGHTNING. LOW CHANCE/CONFIDENCE OF ANY OF THESE CELLS
HITTING THE TERMINALS...SO KEPT VCTS IN THE TAFS THROUGH 19Z.

LOOKING TOWARD WEDNESDAY MORNING...LOW LEVEL MOISTURE AND A WEAK
INVERSION WILL ALLOW A CHANCE FOR MVFR FOG AND CIGS TO WORK INTO
THE TERMINALS. THE AFTERNOON WILL FEATURE A SCATTERED TO POSSIBLY
BROKEN DECK AT 025. INTO THE EVENING...EXPECT OVERCAST CONDITIONS
WITH LIGHT RAIN POSSIBLE. THERE IS A CHANCE FOR THE LAKE BREEZE TO
WORK INTO ORD NEAR OR JUST AFTER 00Z WEDNESDAY EVENING.

MM

//ORD AND MDW CONFIDENCE...UPDATED 22Z...

* MEDIUM HIGH CONFIDENCE WITH TEMPO MVFR THIS AFTERNOON.

* HIGH CONFIDENCE WITH RAIN TRENDS THIS AFTERNOON.

* MEDIUM HIGH CONFIDENCE WITH WIND SPEED/DIRECTION.

* LOW-MEDIUM CONFIDENCE IN FOG AND MVFR CONDITIONS WEDNESDAY
  MORNING.

MM/RODRIGUEZ

//OUTLOOK FOR ORD/MDW FOR 00Z THURSDAY-12Z TUESDAY...UPDATED 12Z...

WEDNESDAY NIGHT...WX NIL/VFR. SOUTHEAST WINDS.

THURSDAY...SLIGHT CHANCE OF TSRA AT NIGHT. SOUTHEAST WINDS.

FRIDAY...TSRA/SHRA LIKELY THROUGH THE DAY AND NIGHT. MVFR
POSSIBLE. SOUTHWEST WINDS.

SATURDAY...SHRA LIKELY WITH A CHANCE OF TSRA DURING THE DAY.
NORTHEAST WINDS.

SUNDAY...CHANCE OF SHRA. EAST WINDS. MVFR POSSIBLE.

MONDAY...CHANCE OF SHRA. SOUTHEAST WINDS. MVFR POSSIBLE.

KREIN

&&

.MARINE...
417 PM CDT

WINDS REMAIN GUSTY THIS AFTERNOON AND DECIDED TO ISSUE A SMALL
CRAFT ADVISORY FOR STRONG WINDS INTO THIS EVENING. THE SOUTH WINDS
BECOME SOUTHWEST THIS EVENING. LOW PRESSURE MOVES OVER QUEBEC
TOMORROW AFTERNOON AND COLD FRONT TRAILING FROM THE LOW SWINGS
THROUGH. WINDS WEAKEN WEDNESDAY AFTERNOON AND A LAKE BREEZE IS
EXPECTED LATE WEDNESDAY AFTERNOON.

MODEST SOUTHERLY FLOW IS EXPECTED ON THURSDAY...WITH LAKE BREEZE
INFLUENCES IN THE SOUTHERN PORTION OF THE LAKE...THEN A PERIOD OF
SLIGHTLY STRONGER SOUTHERLY FLOW ON FRIDAY AHEAD OF A STRONG COLD
FRONT...THOUGH WARM AIRMASS WILL LIMIT MIXING. WILL LIKELY NEED TO
ADD AREAS OF FOG OVER THE LAKE. THE STRONG COLD FRONT WILL SWEEP
ACROSS THE LAKE FRIDAY NIGHT INTO SATURDAY...BRINGING NORTHERLY
WINDS TO 30 KT. WILL NEED TO WATCH FOR A PERIOD OF NORTHERLY GALES
SHOWN ON SOME MODEL GUIDANCE. WILL NEED A SMALL CRAFT ADVISORY
SATURDAY MORNING THROUGH SUNDAY MORNING UNTIL WAVES SUBSIDE.

RC

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 10 PM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 262215
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
515 PM CDT TUE MAY 26 2015

.SHORT TERM...
253 PM CDT

THROUGH WEDNESDAY...

A SURFACE LOW IS OVER NORTHEAST IA AND SW WI WITH A VORT MAX OVER
IOWA. THE LOWS COLD FRONT REMAINS A BIT FURTHER BACK OVER CENTRAL IA
AND EASTERN KS. THE LOW WILL DEEPEN SLIGHTLY AS IT MOVES OVER
CENTRAL WI AND ITS COLD FRONT SWINGS THROUGH WEDNESDAY. THE MAIN
CONCERN RIGHT NOW IS HOW MUCH CONVECTION WILL DEVELOP THIS
AFTERNOON.  THE LATEST RAP ANALYSIS SUGGESTS A RIBBON OF 1000 J/KG
OF CAPE IS OVER I-39...BUT THINKING THAT CAPE IN REALITY IS AROUND
500 J/KG DUE TO LIMITED HEATING. CAPE VALUES COULD RISE TO AROUND
1000 J/KG AS THERE ARE A FEW BREAKS IN THE CLOUDS...BUT THINKING IN
GENERAL THE BREAKS ARE MOVING TOO QUICKLY AND TOO FEW AND FAR BTWN
TO AMOUNT TO MUCH.  SHEAR VALUES REMAIN VERY FAVORABLE FOR ORGANIZED
STORMS WITH VALUES AROUND 35-40 KT.

THEREFORE EXPECTING SCATTERED SHOWER/TS DEVELOPMENT THIS AFTN IN THE
WAKE OF THE LINE OF SHOWERS THAT IS SHIFTING EAST ACROSS INDIANA
RIGHT NOW.  A SECOND SKINNY LINE OF CONVECTION LIES FROM DIXON IL TO
JERSEYVILLE IL WITH A FEW ADDITIONAL CELLS OUT AHEAD OF IT. DUE TO
LIMITED CAPE AS DISCUSSED ABOVE...THE STRONGER CELLS MAY PRODUCE
DAMAGING WINDS. WINDS HAVE VEERED TO THE SW AND HELICITY IS MUCH
LOWER SO NOT AS CONCERNED ABOUT ISOLATED TORNADOES AS I WAS THIS
MORNING.  PWAT VALUES REMAIN VERY IMPRESSIVE AT 1.4-1.7 INCHES SO
ANY OF THE NEW SHOWERS WILL BE CAPABLE OF ADDITIONAL HEAVY DOWNPOURS.

THE AREA OF SCATTERED SHOWERS AND STORMS SHIFTS EAST OF THE CWA THIS
EVENING...BUT WE ARE NOT DONE YET. ANOTHER ROUND OF SHOWERS AND
PERHAPS OF THUNDERSTORMS MAY FORM THIS EVENING AS THE VORT MAX
APPROACHES. THINKING THE COVERAGE WILL BE BEST ALONG AND WEST OF
GARY INDIANA TO PAXTON IL LINE. HAVE LOW CONFIDENCE IN COVERAGE AND
TIMING OF THIS ROUND OF SHOWERS...BUT NOT EXPECTING MUCH THUNDER AND
NO SEVERE WEATHER.  DEWPOINTS REMAIN IN THE 60S TONIGHT SO THINKING
WE WILL NOT COOL MUCH...SO KEPT LOWS IN THE LOW TO MID 60S.

THE PATTERN REMAINS MESSY TOMORROW BUT NOT AS ACTIVE.  A PAIR OF
VORT STREAMERS AND THE LOWS COLD FRONT ROTATE THROUGH AND SHOWERS
AND STORMS MAY FORM ALONG THEM.  THE FIRST IS ASSOCIATED WITH THE
UPPER LEVEL LOW SHIFTING NE INTO ONTARIO TOMORROW. SHOWERS AND
STORMS WITH THIS VORT STREAMER WOULD CLIP THE NORTHERN CWA...NORTH
OF I-88.  PRECIP MAY SINK SOUTH ACROSS DUPAGE AND COOK COUNTIES IN
THE AFTN...BUT HAVE LOW CONFIDENCE IN HOW FAR SOUTH THE PRECIP WILL
GET.

CLOUD COVER SHIFTS EAST THROUGH THE AFTERNOON WITH AREAS WEST OF I-
55 BECOMING MOSTLY SUNNY BY MID AFTN. DID NOT MAKE TOO MANY CHANGES
TO HIGH TEMPS TOMORROW AS CLOUD COVER WILL PLAY A ROLE.  HAVE TEMPS
IN THE UPPER 70S TO LOW 80S.  A LAKE BREEZE IS POSSIBLE LATE IN THE
AFTN AND EVENING SO EXPECTING LAKE COOLING ESPECIALLY AT WAUKEGAN.

JEE

&&

.LONG TERM...
330 PM CDT

WEDNESDAY NIGHT THROUGH TUESDAY...

LOCAL AREA WILL START OUT FIRMLY UNDER MID/UPPER RIDGING ON
WEDNESDAY NIGHT AND THURSDAY...RESULTING IN A DRY AND WARM PERIOD
AS 925 MB TEMPS CLIMB FROM THE UPPER TEENS CELSISUS BY EARLY
THURSDAY TO THE LOWER 20S CELSISUS EARLY THURSDAY EVENING. INLAND
TEMPERATURES WILL WARM TO THE LOWER-MID 80S ON THURSDAY...BUT
DESPITE SOUTHERLY SURFACE FLOW...GRADIENT WILL BE WEAK ENOUGH TO
ENABLE A LAKE BREEZE TO DEVELOP AND PUSH INLAND FAIRLY EARLY. THIS
WILL KEEP LAKESHORE TEMPS (ESPECIALLY IL SHORE) IN THE UPPER 60S.

CHANGES WILL START TO TAKE PLACE THURSDAY NIGHT WITH UPPER RIDGE
AXIS GETTING SHUNTED EAST AND ALLOWS SHORTWAVE ENERGY TO LIFT
EAST-NORTHEAST ACROSS THE AREA AFTER MIDNIGHT INTO FRIDAY ALONG
WITH STRENGTHENING AND VEERING LOW LEVEL JET. HAVE FOCUSED MID
CHANCE POPS INTO NORTHWEST CWA LATE THURSDAY NIGHT AND THEN SPREAD
LIKELY POPS FOR MUCH OF THE CWA FRIDAY MORNING AND EARLY
AFTERNOON. IT APPEARS THAT BETTER MOISTURE CONVERGENCE AND UPPER
FORCING WILL LIFT NORTH AND REFOCUS INTO NORTHWEST CWA FRIDAY
AFTERNOON AND TAILORED POPS AS SUCH...BUT THEN A STRONGER WAVE
WILL MOVE ACROSS THE AREA SATURDAY NIGHT. CONFIDENCE IS A BIT
LOWER IN HIGH TEMPS FRIDAY DUE TO UNCERTAINTY OVER IMPACT OF
CLOUDS/PRECIP...BUT VERY MILD START TO DAY AND WARM AIRMASS IN
PLACE SHOULD STILL SUPPORT HIGHS INTO THE LOWER-MID 80S...WARMEST
IN SOUTHEAST HALF OF CWA. THE WARM TEMPS...DEWPOINTS WELL INTO THE
60S AND MODEST MIDLEVEL LAPSE RATES WILL YIELD MODEST CAPE
VALUES...SO CANNOT RULE OUT AN ISOLATED SEVERE THREAT FOR DAMAGING
WINDS INTO FRIDAY EVENING. COULD BE SOME WET MICROBURSTS WITH PWAT
VALUES IN 1.5 TO 1.75 INCH RANGE.

A STRONG COLD FRONT WILL SWEEP ACROSS THE AREA FRIDAY
NIGHT...RESULTING IN MUCH COOLER WEATHER FOR THE LAST WEEKEND OF
MAY. HIGHS ON THE LAKEFRONT ARE LIKELY TO STAY IN THE 50S ON BOTH
SATURDAY AND SUNDAY...WITH ONLY 60S AND 70S INLAND ON SATURDAY AND
60S ON SUNDAY. WILL NEED TO WATCH FOR A WAVE OF SURFACE LOW
PRESSURE FORMING SOUTH OF THE AREA ON SATURDAY...SO KEPT HIGHER
CONSENSUS POPS FOR NOW SATURDAY MORNING...BUT IF TRENDS ON MUCH OF
GUIDANCE CONTINUE MAY BE ABLE TO LOWER POPS SATURDAY THROUGH
MONDAY WITH EXPANSIVE COOL HIGH PRESSURE OVER THE GREAT LAKES.
TEMPERATURES WILL THEN WARM BACK TO NEAR NORMAL FOR EARLY JUNE BY
TUESDAY WITH SOUTHERLY FLOW ON BACK SIDE OF HIGH TO EAST...THOUGH
ONSHORE FLOW LOOKS TO CONTINUE FOR AT LEAST A PORTION OF THE
LAKEFRONT.

RC

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 22Z...

* ISOLATED MVFR THIS AFTERNOON.

* RAIN SHOWERS POSSIBLY DROPPING TO MVFR THIS AFTERNOON.

* SOUTH TO SOUTHWEST WINDS...GUSTING TO MID/UPPER 20KTS.

* MVFR IN FOG AND LOW CLOUDS WEDNESDAY MORNING.

MM/RODRIGUEZ

//DISCUSSION...UPDATED 20Z...

LINE OF SHOWERS HAS DECREASED VSBYS TO 1 MILE UPSTREAM EARLY THIS
AFTERNOON. AS THE LINE PROGRESSES NORTHEASTWARD...COULD SEE SOME
STRONGER POCKETS OF RAIN AND TALLER EMBEDDED CELLS PRODUCE
ISOLATED LIGHTNING. LOW CHANCE/CONFIDENCE OF ANY OF THESE CELLS
HITTING THE TERMINALS...SO KEPT VCTS IN THE TAFS THROUGH 19Z.

LOOKING TOWARD WEDNESDAY MORNING...LOW LEVEL MOISTURE AND A WEAK
INVERSION WILL ALLOW A CHANCE FOR MVFR FOG AND CIGS TO WORK INTO
THE TERMINALS. THE AFTERNOON WILL FEATURE A SCATTERED TO POSSIBLY
BROKEN DECK AT 025. INTO THE EVENING...EXPECT OVERCAST CONDITIONS
WITH LIGHT RAIN POSSIBLE. THERE IS A CHANCE FOR THE LAKE BREEZE TO
WORK INTO ORD NEAR OR JUST AFTER 00Z WEDNESDAY EVENING.

MM

//ORD AND MDW CONFIDENCE...UPDATED 22Z...

* MEDIUM HIGH CONFIDENCE WITH TEMPO MVFR THIS AFTERNOON.

* HIGH CONFIDENCE WITH RAIN TRENDS THIS AFTERNOON.

* MEDIUM HIGH CONFIDENCE WITH WIND SPEED/DIRECTION.

* LOW-MEDIUM CONFIDENCE IN FOG AND MVFR CONDITIONS WEDNESDAY
  MORNING.

MM/RODRIGUEZ

//OUTLOOK FOR ORD/MDW FOR 00Z THURSDAY-12Z TUESDAY...UPDATED 12Z...

WEDNESDAY NIGHT...WX NIL/VFR. SOUTHEAST WINDS.

THURSDAY...SLIGHT CHANCE OF TSRA AT NIGHT. SOUTHEAST WINDS.

FRIDAY...TSRA/SHRA LIKELY THROUGH THE DAY AND NIGHT. MVFR
POSSIBLE. SOUTHWEST WINDS.

SATURDAY...SHRA LIKELY WITH A CHANCE OF TSRA DURING THE DAY.
NORTHEAST WINDS.

SUNDAY...CHANCE OF SHRA. EAST WINDS. MVFR POSSIBLE.

MONDAY...CHANCE OF SHRA. SOUTHEAST WINDS. MVFR POSSIBLE.

KREIN

&&

.MARINE...
417 PM CDT

WINDS REMAIN GUSTY THIS AFTERNOON AND DECIDED TO ISSUE A SMALL
CRAFT ADVISORY FOR STRONG WINDS INTO THIS EVENING. THE SOUTH WINDS
BECOME SOUTHWEST THIS EVENING. LOW PRESSURE MOVES OVER QUEBEC
TOMORROW AFTERNOON AND COLD FRONT TRAILING FROM THE LOW SWINGS
THROUGH. WINDS WEAKEN WEDNESDAY AFTERNOON AND A LAKE BREEZE IS
EXPECTED LATE WEDNESDAY AFTERNOON.

MODEST SOUTHERLY FLOW IS EXPECTED ON THURSDAY...WITH LAKE BREEZE
INFLUENCES IN THE SOUTHERN PORTION OF THE LAKE...THEN A PERIOD OF
SLIGHTLY STRONGER SOUTHERLY FLOW ON FRIDAY AHEAD OF A STRONG COLD
FRONT...THOUGH WARM AIRMASS WILL LIMIT MIXING. WILL LIKELY NEED TO
ADD AREAS OF FOG OVER THE LAKE. THE STRONG COLD FRONT WILL SWEEP
ACROSS THE LAKE FRIDAY NIGHT INTO SATURDAY...BRINGING NORTHERLY
WINDS TO 30 KT. WILL NEED TO WATCH FOR A PERIOD OF NORTHERLY GALES
SHOWN ON SOME MODEL GUIDANCE. WILL NEED A SMALL CRAFT ADVISORY
SATURDAY MORNING THROUGH SUNDAY MORNING UNTIL WAVES SUBSIDE.

RC

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 10 PM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 262117
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
417 PM CDT TUE MAY 26 2015

.SHORT TERM...
253 PM CDT

THROUGH WEDNESDAY...

A SURFACE LOW IS OVER NORTHEAST IA AND SW WI WITH A VORT MAX OVER
IOWA. THE LOWS COLD FRONT REMAINS A BIT FURTHER BACK OVER CENTRAL IA
AND EASTERN KS. THE LOW WILL DEEPEN SLIGHTLY AS IT MOVES OVER
CENTRAL WI AND ITS COLD FRONT SWINGS THROUGH WEDNESDAY. THE MAIN
CONCERN RIGHT NOW IS HOW MUCH CONVECTION WILL DEVELOP THIS
AFTERNOON.  THE LATEST RAP ANALYSIS SUGGESTS A RIBBON OF 1000 J/KG
OF CAPE IS OVER I-39...BUT THINKING THAT CAPE IN REALITY IS AROUND
500 J/KG DUE TO LIMITED HEATING. CAPE VALUES COULD RISE TO AROUND
1000 J/KG AS THERE ARE A FEW BREAKS IN THE CLOUDS...BUT THINKING IN
GENERAL THE BREAKS ARE MOVING TOO QUICKLY AND TOO FEW AND FAR BTWN
TO AMOUNT TO MUCH.  SHEAR VALUES REMAIN VERY FAVORABLE FOR ORGANIZED
STORMS WITH VALUES AROUND 35-40 KT.

THEREFORE EXPECTING SCATTERED SHOWER/TS DEVELOPMENT THIS AFTN IN THE
WAKE OF THE LINE OF SHOWERS THAT IS SHIFTING EAST ACROSS INDIANA
RIGHT NOW.  A SECOND SKINNY LINE OF CONVECTION LIES FROM DIXON IL TO
JERSEYVILLE IL WITH A FEW ADDITIONAL CELLS OUT AHEAD OF IT. DUE TO
LIMITED CAPE AS DISCUSSED ABOVE...THE STRONGER CELLS MAY PRODUCE
DAMAGING WINDS. WINDS HAVE VEERED TO THE SW AND HELICITY IS MUCH
LOWER SO NOT AS CONCERNED ABOUT ISOLATED TORNADOES AS I WAS THIS
MORNING.  PWAT VALUES REMAIN VERY IMPRESSIVE AT 1.4-1.7 INCHES SO
ANY OF THE NEW SHOWERS WILL BE CAPABLE OF ADDITIONAL HEAVY DOWNPOURS.

THE AREA OF SCATTERED SHOWERS AND STORMS SHIFTS EAST OF THE CWA THIS
EVENING...BUT WE ARE NOT DONE YET. ANOTHER ROUND OF SHOWERS AND
PERHAPS OF THUNDERSTORMS MAY FORM THIS EVENING AS THE VORT MAX
APPROACHES. THINKING THE COVERAGE WILL BE BEST ALONG AND WEST OF
GARY INDIANA TO PAXTON IL LINE. HAVE LOW CONFIDENCE IN COVERAGE AND
TIMING OF THIS ROUND OF SHOWERS...BUT NOT EXPECTING MUCH THUNDER AND
NO SEVERE WEATHER.  DEWPOINTS REMAIN IN THE 60S TONIGHT SO THINKING
WE WILL NOT COOL MUCH...SO KEPT LOWS IN THE LOW TO MID 60S.

THE PATTERN REMAINS MESSY TOMORROW BUT NOT AS ACTIVE.  A PAIR OF
VORT STREAMERS AND THE LOWS COLD FRONT ROTATE THROUGH AND SHOWERS
AND STORMS MAY FORM ALONG THEM.  THE FIRST IS ASSOCIATED WITH THE
UPPER LEVEL LOW SHIFTING NE INTO ONTARIO TOMORROW. SHOWERS AND
STORMS WITH THIS VORT STREAMER WOULD CLIP THE NORTHERN CWA...NORTH
OF I-88.  PRECIP MAY SINK SOUTH ACROSS DUPAGE AND COOK COUNTIES IN
THE AFTN...BUT HAVE LOW CONFIDENCE IN HOW FAR SOUTH THE PRECIP WILL
GET.

CLOUD COVER SHIFTS EAST THROUGH THE AFTERNOON WITH AREAS WEST OF I-
55 BECOMING MOSTLY SUNNY BY MID AFTN. DID NOT MAKE TOO MANY CHANGES
TO HIGH TEMPS TOMORROW AS CLOUD COVER WILL PLAY A ROLE.  HAVE TEMPS
IN THE UPPER 70S TO LOW 80S.  A LAKE BREEZE IS POSSIBLE LATE IN THE
AFTN AND EVENING SO EXPECTING LAKE COOLING ESPECIALLY AT WAUKEGAN.

JEE

&&

.LONG TERM...
330 PM CDT

WEDNESDAY NIGHT THROUGH TUESDAY...

LOCAL AREA WILL START OUT FIRMLY UNDER MID/UPPER RIDGING ON
WEDNESDAY NIGHT AND THURSDAY...RESULTING IN A DRY AND WARM PERIOD
AS 925 MB TEMPS CLIMB FROM THE UPPER TEENS CELSISUS BY EARLY
THURSDAY TO THE LOWER 20S CELSISUS EARLY THURSDAY EVENING. INLAND
TEMPERATURES WILL WARM TO THE LOWER-MID 80S ON THURSDAY...BUT
DESPITE SOUTHERLY SURFACE FLOW...GRADIENT WILL BE WEAK ENOUGH TO
ENABLE A LAKE BREEZE TO DEVELOP AND PUSH INLAND FAIRLY EARLY. THIS
WILL KEEP LAKESHORE TEMPS (ESPECIALLY IL SHORE) IN THE UPPER 60S.

CHANGES WILL START TO TAKE PLACE THURSDAY NIGHT WITH UPPER RIDGE
AXIS GETTING SHUNTED EAST AND ALLOWS SHORTWAVE ENERGY TO LIFT
EAST-NORTHEAST ACROSS THE AREA AFTER MIDNIGHT INTO FRIDAY ALONG
WITH STRENGTHENING AND VEERING LOW LEVEL JET. HAVE FOCUSED MID
CHANCE POPS INTO NORTHWEST CWA LATE THURSDAY NIGHT AND THEN SPREAD
LIKELY POPS FOR MUCH OF THE CWA FRIDAY MORNING AND EARLY
AFTERNOON. IT APPEARS THAT BETTER MOISTURE CONVERGENCE AND UPPER
FORCING WILL LIFT NORTH AND REFOCUS INTO NORTHWEST CWA FRIDAY
AFTERNOON AND TAILORED POPS AS SUCH...BUT THEN A STRONGER WAVE
WILL MOVE ACROSS THE AREA SATURDAY NIGHT. CONFIDENCE IS A BIT
LOWER IN HIGH TEMPS FRIDAY DUE TO UNCERTAINTY OVER IMPACT OF
CLOUDS/PRECIP...BUT VERY MILD START TO DAY AND WARM AIRMASS IN
PLACE SHOULD STILL SUPPORT HIGHS INTO THE LOWER-MID 80S...WARMEST
IN SOUTHEAST HALF OF CWA. THE WARM TEMPS...DEWPOINTS WELL INTO THE
60S AND MODEST MIDLEVEL LAPSE RATES WILL YIELD MODEST CAPE
VALUES...SO CANNOT RULE OUT AN ISOLATED SEVERE THREAT FOR DAMAGING
WINDS INTO FRIDAY EVENING. COULD BE SOME WET MICROBURSTS WITH PWAT
VALUES IN 1.5 TO 1.75 INCH RANGE.

A STRONG COLD FRONT WILL SWEEP ACROSS THE AREA FRIDAY
NIGHT...RESULTING IN MUCH COOLER WEATHER FOR THE LAST WEEKEND OF
MAY. HIGHS ON THE LAKEFRONT ARE LIKELY TO STAY IN THE 50S ON BOTH
SATURDAY AND SUNDAY...WITH ONLY 60S AND 70S INLAND ON SATURDAY AND
60S ON SUNDAY. WILL NEED TO WATCH FOR A WAVE OF SURFACE LOW
PRESSURE FORMING SOUTH OF THE AREA ON SATURDAY...SO KEPT HIGHER
CONSENSUS POPS FOR NOW SATURDAY MORNING...BUT IF TRENDS ON MUCH OF
GUIDANCE CONTINUE MAY BE ABLE TO LOWER POPS SATURDAY THROUGH
MONDAY WITH EXPANSIVE COOL HIGH PRESSURE OVER THE GREAT LAKES.
TEMPERATURES WILL THEN WARM BACK TO NEAR NORMAL FOR EARLY JUNE BY
TUESDAY WITH SOUTHERLY FLOW ON BACK SIDE OF HIGH TO EAST...THOUGH
ONSHORE FLOW LOOKS TO CONTINUE FOR AT LEAST A PORTION OF THE
LAKEFRONT.

RC

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 20Z...

* ISOLATED MVFR THIS AFTERNOON

* RAIN SHOWERS POSSIBLY DROPPING TO MVFR

* SOUTH WINDS VARYING FROM SOUTH-SOUTHWEST THIS EVENING.

* MVFR IN FOG AND LOW CLOUDS WEDNESDAY MORNING.

MM

//DISCUSSION...UPDATED 20Z...

LINE OF SHOWERS HAS DECREASED VSBYS TO 1 MILE UPSTREAM EARLY THIS
AFTERNOON. AS THE LINE PROGRESSES NORTHEASTWARD...COULD SEE SOME
STRONGER POCKETS OF RAIN AND TALLER EMBEDDED CELLS PRODUCE
ISOLATED LIGHTNING. LOW CHANCE/CONFIDENCE OF ANY OF THESE CELLS
HITTING THE TERMINALS...SO KEPT VCTS IN THE TAFS THROUGH 19Z.

LOOKING TOWARD WEDNESDAY MORNING...LOW LEVEL MOISTURE AND A WEAK
INVERSION WILL ALLOW A CHANCE FOR MVFR FOG AND CIGS TO WORK INTO
THE TERMINALS. THE AFTERNOON WILL FEATURE A SCATTERED TO POSSIBLY
BROKEN DECK AT 025. INTO THE EVENING...EXPECT OVERCAST CONDITIONS
WITH LIGHT RAIN POSSIBLE. THERE IS A CHANCE FOR THE LAKE BREEZE TO
WORK INTO ORD NEAR OR JUST AFTER 00Z WEDNESDAY EVENING.

MM

//ORD AND MDW CONFIDENCE...UPDATED 18Z...

* MEDIUM CONFIDENCE IN TEMPO MVFR THIS AFTERNOON.

* HIGH CONFIDENCE IN RAIN TIMING THIS AFTERNOON. LOW CONFIDENCE ON
  THUNDER CHANCES.

* MEDIUM TO HIGH CONFIDENCE IN WIND DIRECTION WITH HIGH CONFIDENCE
  IN WIND SPEED.

* LOW-MEDIUM CONFIDENCE IN FOG AND MVFR CONDITIONS WEDNESDAY
  MORNING.

MM

//OUTLOOK FOR ORD/MDW FOR 00Z THURSDAY-12Z TUESDAY...UPDATED 12Z...

WEDNESDAY NIGHT...WX NIL/VFR. SOUTHEAST WINDS.

THURSDAY...SLIGHT CHANCE OF TSRA AT NIGHT. SOUTHEAST WINDS.

FRIDAY...TSRA/SHRA LIKELY THROUGH THE DAY AND NIGHT. MVFR
POSSIBLE. SOUTHWEST WINDS.

SATURDAY...SHRA LIKELY WITH A CHANCE OF TSRA DURING THE DAY.
NORTHEAST WINDS.

SUNDAY...CHANCE OF SHRA. EAST WINDS. MVFR POSSIBLE.

MONDAY...CHANCE OF SHRA. SOUTHEAST WINDS. MVFR POSSIBLE.

KREIN

&&

.MARINE...
417 PM CDT

WINDS REMAIN GUSTY THIS AFTERNOON AND DECIDED TO ISSUE A SMALL
CRAFT ADVISORY FOR STRONG WINDS INTO THIS EVENING. THE SOUTH WINDS
BECOME SOUTHWEST THIS EVENING. LOW PRESSURE MOVES OVER QUEBEC
TOMORROW AFTERNOON AND COLD FRONT TRAILING FROM THE LOW SWINGS
THROUGH. WINDS WEAKEN WEDNESDAY AFTERNOON AND A LAKE BREEZE IS
EXPECTED LATE WEDNESDAY AFTERNOON.

MODEST SOUTHERLY FLOW IS EXPECTED ON THURSDAY...WITH LAKE BREEZE
INFLUENCES IN THE SOUTHERN PORTION OF THE LAKE...THEN A PERIOD OF
SLIGHTLY STRONGER SOUTHERLY FLOW ON FRIDAY AHEAD OF A STRONG COLD
FRONT...THOUGH WARM AIRMASS WILL LIMIT MIXING. WILL LIKELY NEED TO
ADD AREAS OF FOG OVER THE LAKE. THE STRONG COLD FRONT WILL SWEEP
ACROSS THE LAKE FRIDAY NIGHT INTO SATURDAY...BRINGING NORTHERLY
WINDS TO 30 KT. WILL NEED TO WATCH FOR A PERIOD OF NORTHERLY GALES
SHOWN ON SOME MODEL GUIDANCE. WILL NEED A SMALL CRAFT ADVISORY
SATURDAY MORNING THROUGH SUNDAY MORNING UNTIL WAVES SUBSIDE.

RC

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 10 PM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 262117
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
417 PM CDT TUE MAY 26 2015

.SHORT TERM...
253 PM CDT

THROUGH WEDNESDAY...

A SURFACE LOW IS OVER NORTHEAST IA AND SW WI WITH A VORT MAX OVER
IOWA. THE LOWS COLD FRONT REMAINS A BIT FURTHER BACK OVER CENTRAL IA
AND EASTERN KS. THE LOW WILL DEEPEN SLIGHTLY AS IT MOVES OVER
CENTRAL WI AND ITS COLD FRONT SWINGS THROUGH WEDNESDAY. THE MAIN
CONCERN RIGHT NOW IS HOW MUCH CONVECTION WILL DEVELOP THIS
AFTERNOON.  THE LATEST RAP ANALYSIS SUGGESTS A RIBBON OF 1000 J/KG
OF CAPE IS OVER I-39...BUT THINKING THAT CAPE IN REALITY IS AROUND
500 J/KG DUE TO LIMITED HEATING. CAPE VALUES COULD RISE TO AROUND
1000 J/KG AS THERE ARE A FEW BREAKS IN THE CLOUDS...BUT THINKING IN
GENERAL THE BREAKS ARE MOVING TOO QUICKLY AND TOO FEW AND FAR BTWN
TO AMOUNT TO MUCH.  SHEAR VALUES REMAIN VERY FAVORABLE FOR ORGANIZED
STORMS WITH VALUES AROUND 35-40 KT.

THEREFORE EXPECTING SCATTERED SHOWER/TS DEVELOPMENT THIS AFTN IN THE
WAKE OF THE LINE OF SHOWERS THAT IS SHIFTING EAST ACROSS INDIANA
RIGHT NOW.  A SECOND SKINNY LINE OF CONVECTION LIES FROM DIXON IL TO
JERSEYVILLE IL WITH A FEW ADDITIONAL CELLS OUT AHEAD OF IT. DUE TO
LIMITED CAPE AS DISCUSSED ABOVE...THE STRONGER CELLS MAY PRODUCE
DAMAGING WINDS. WINDS HAVE VEERED TO THE SW AND HELICITY IS MUCH
LOWER SO NOT AS CONCERNED ABOUT ISOLATED TORNADOES AS I WAS THIS
MORNING.  PWAT VALUES REMAIN VERY IMPRESSIVE AT 1.4-1.7 INCHES SO
ANY OF THE NEW SHOWERS WILL BE CAPABLE OF ADDITIONAL HEAVY DOWNPOURS.

THE AREA OF SCATTERED SHOWERS AND STORMS SHIFTS EAST OF THE CWA THIS
EVENING...BUT WE ARE NOT DONE YET. ANOTHER ROUND OF SHOWERS AND
PERHAPS OF THUNDERSTORMS MAY FORM THIS EVENING AS THE VORT MAX
APPROACHES. THINKING THE COVERAGE WILL BE BEST ALONG AND WEST OF
GARY INDIANA TO PAXTON IL LINE. HAVE LOW CONFIDENCE IN COVERAGE AND
TIMING OF THIS ROUND OF SHOWERS...BUT NOT EXPECTING MUCH THUNDER AND
NO SEVERE WEATHER.  DEWPOINTS REMAIN IN THE 60S TONIGHT SO THINKING
WE WILL NOT COOL MUCH...SO KEPT LOWS IN THE LOW TO MID 60S.

THE PATTERN REMAINS MESSY TOMORROW BUT NOT AS ACTIVE.  A PAIR OF
VORT STREAMERS AND THE LOWS COLD FRONT ROTATE THROUGH AND SHOWERS
AND STORMS MAY FORM ALONG THEM.  THE FIRST IS ASSOCIATED WITH THE
UPPER LEVEL LOW SHIFTING NE INTO ONTARIO TOMORROW. SHOWERS AND
STORMS WITH THIS VORT STREAMER WOULD CLIP THE NORTHERN CWA...NORTH
OF I-88.  PRECIP MAY SINK SOUTH ACROSS DUPAGE AND COOK COUNTIES IN
THE AFTN...BUT HAVE LOW CONFIDENCE IN HOW FAR SOUTH THE PRECIP WILL
GET.

CLOUD COVER SHIFTS EAST THROUGH THE AFTERNOON WITH AREAS WEST OF I-
55 BECOMING MOSTLY SUNNY BY MID AFTN. DID NOT MAKE TOO MANY CHANGES
TO HIGH TEMPS TOMORROW AS CLOUD COVER WILL PLAY A ROLE.  HAVE TEMPS
IN THE UPPER 70S TO LOW 80S.  A LAKE BREEZE IS POSSIBLE LATE IN THE
AFTN AND EVENING SO EXPECTING LAKE COOLING ESPECIALLY AT WAUKEGAN.

JEE

&&

.LONG TERM...
330 PM CDT

WEDNESDAY NIGHT THROUGH TUESDAY...

LOCAL AREA WILL START OUT FIRMLY UNDER MID/UPPER RIDGING ON
WEDNESDAY NIGHT AND THURSDAY...RESULTING IN A DRY AND WARM PERIOD
AS 925 MB TEMPS CLIMB FROM THE UPPER TEENS CELSISUS BY EARLY
THURSDAY TO THE LOWER 20S CELSISUS EARLY THURSDAY EVENING. INLAND
TEMPERATURES WILL WARM TO THE LOWER-MID 80S ON THURSDAY...BUT
DESPITE SOUTHERLY SURFACE FLOW...GRADIENT WILL BE WEAK ENOUGH TO
ENABLE A LAKE BREEZE TO DEVELOP AND PUSH INLAND FAIRLY EARLY. THIS
WILL KEEP LAKESHORE TEMPS (ESPECIALLY IL SHORE) IN THE UPPER 60S.

CHANGES WILL START TO TAKE PLACE THURSDAY NIGHT WITH UPPER RIDGE
AXIS GETTING SHUNTED EAST AND ALLOWS SHORTWAVE ENERGY TO LIFT
EAST-NORTHEAST ACROSS THE AREA AFTER MIDNIGHT INTO FRIDAY ALONG
WITH STRENGTHENING AND VEERING LOW LEVEL JET. HAVE FOCUSED MID
CHANCE POPS INTO NORTHWEST CWA LATE THURSDAY NIGHT AND THEN SPREAD
LIKELY POPS FOR MUCH OF THE CWA FRIDAY MORNING AND EARLY
AFTERNOON. IT APPEARS THAT BETTER MOISTURE CONVERGENCE AND UPPER
FORCING WILL LIFT NORTH AND REFOCUS INTO NORTHWEST CWA FRIDAY
AFTERNOON AND TAILORED POPS AS SUCH...BUT THEN A STRONGER WAVE
WILL MOVE ACROSS THE AREA SATURDAY NIGHT. CONFIDENCE IS A BIT
LOWER IN HIGH TEMPS FRIDAY DUE TO UNCERTAINTY OVER IMPACT OF
CLOUDS/PRECIP...BUT VERY MILD START TO DAY AND WARM AIRMASS IN
PLACE SHOULD STILL SUPPORT HIGHS INTO THE LOWER-MID 80S...WARMEST
IN SOUTHEAST HALF OF CWA. THE WARM TEMPS...DEWPOINTS WELL INTO THE
60S AND MODEST MIDLEVEL LAPSE RATES WILL YIELD MODEST CAPE
VALUES...SO CANNOT RULE OUT AN ISOLATED SEVERE THREAT FOR DAMAGING
WINDS INTO FRIDAY EVENING. COULD BE SOME WET MICROBURSTS WITH PWAT
VALUES IN 1.5 TO 1.75 INCH RANGE.

A STRONG COLD FRONT WILL SWEEP ACROSS THE AREA FRIDAY
NIGHT...RESULTING IN MUCH COOLER WEATHER FOR THE LAST WEEKEND OF
MAY. HIGHS ON THE LAKEFRONT ARE LIKELY TO STAY IN THE 50S ON BOTH
SATURDAY AND SUNDAY...WITH ONLY 60S AND 70S INLAND ON SATURDAY AND
60S ON SUNDAY. WILL NEED TO WATCH FOR A WAVE OF SURFACE LOW
PRESSURE FORMING SOUTH OF THE AREA ON SATURDAY...SO KEPT HIGHER
CONSENSUS POPS FOR NOW SATURDAY MORNING...BUT IF TRENDS ON MUCH OF
GUIDANCE CONTINUE MAY BE ABLE TO LOWER POPS SATURDAY THROUGH
MONDAY WITH EXPANSIVE COOL HIGH PRESSURE OVER THE GREAT LAKES.
TEMPERATURES WILL THEN WARM BACK TO NEAR NORMAL FOR EARLY JUNE BY
TUESDAY WITH SOUTHERLY FLOW ON BACK SIDE OF HIGH TO EAST...THOUGH
ONSHORE FLOW LOOKS TO CONTINUE FOR AT LEAST A PORTION OF THE
LAKEFRONT.

RC

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 20Z...

* ISOLATED MVFR THIS AFTERNOON

* RAIN SHOWERS POSSIBLY DROPPING TO MVFR

* SOUTH WINDS VARYING FROM SOUTH-SOUTHWEST THIS EVENING.

* MVFR IN FOG AND LOW CLOUDS WEDNESDAY MORNING.

MM

//DISCUSSION...UPDATED 20Z...

LINE OF SHOWERS HAS DECREASED VSBYS TO 1 MILE UPSTREAM EARLY THIS
AFTERNOON. AS THE LINE PROGRESSES NORTHEASTWARD...COULD SEE SOME
STRONGER POCKETS OF RAIN AND TALLER EMBEDDED CELLS PRODUCE
ISOLATED LIGHTNING. LOW CHANCE/CONFIDENCE OF ANY OF THESE CELLS
HITTING THE TERMINALS...SO KEPT VCTS IN THE TAFS THROUGH 19Z.

LOOKING TOWARD WEDNESDAY MORNING...LOW LEVEL MOISTURE AND A WEAK
INVERSION WILL ALLOW A CHANCE FOR MVFR FOG AND CIGS TO WORK INTO
THE TERMINALS. THE AFTERNOON WILL FEATURE A SCATTERED TO POSSIBLY
BROKEN DECK AT 025. INTO THE EVENING...EXPECT OVERCAST CONDITIONS
WITH LIGHT RAIN POSSIBLE. THERE IS A CHANCE FOR THE LAKE BREEZE TO
WORK INTO ORD NEAR OR JUST AFTER 00Z WEDNESDAY EVENING.

MM

//ORD AND MDW CONFIDENCE...UPDATED 18Z...

* MEDIUM CONFIDENCE IN TEMPO MVFR THIS AFTERNOON.

* HIGH CONFIDENCE IN RAIN TIMING THIS AFTERNOON. LOW CONFIDENCE ON
  THUNDER CHANCES.

* MEDIUM TO HIGH CONFIDENCE IN WIND DIRECTION WITH HIGH CONFIDENCE
  IN WIND SPEED.

* LOW-MEDIUM CONFIDENCE IN FOG AND MVFR CONDITIONS WEDNESDAY
  MORNING.

MM

//OUTLOOK FOR ORD/MDW FOR 00Z THURSDAY-12Z TUESDAY...UPDATED 12Z...

WEDNESDAY NIGHT...WX NIL/VFR. SOUTHEAST WINDS.

THURSDAY...SLIGHT CHANCE OF TSRA AT NIGHT. SOUTHEAST WINDS.

FRIDAY...TSRA/SHRA LIKELY THROUGH THE DAY AND NIGHT. MVFR
POSSIBLE. SOUTHWEST WINDS.

SATURDAY...SHRA LIKELY WITH A CHANCE OF TSRA DURING THE DAY.
NORTHEAST WINDS.

SUNDAY...CHANCE OF SHRA. EAST WINDS. MVFR POSSIBLE.

MONDAY...CHANCE OF SHRA. SOUTHEAST WINDS. MVFR POSSIBLE.

KREIN

&&

.MARINE...
417 PM CDT

WINDS REMAIN GUSTY THIS AFTERNOON AND DECIDED TO ISSUE A SMALL
CRAFT ADVISORY FOR STRONG WINDS INTO THIS EVENING. THE SOUTH WINDS
BECOME SOUTHWEST THIS EVENING. LOW PRESSURE MOVES OVER QUEBEC
TOMORROW AFTERNOON AND COLD FRONT TRAILING FROM THE LOW SWINGS
THROUGH. WINDS WEAKEN WEDNESDAY AFTERNOON AND A LAKE BREEZE IS
EXPECTED LATE WEDNESDAY AFTERNOON.

MODEST SOUTHERLY FLOW IS EXPECTED ON THURSDAY...WITH LAKE BREEZE
INFLUENCES IN THE SOUTHERN PORTION OF THE LAKE...THEN A PERIOD OF
SLIGHTLY STRONGER SOUTHERLY FLOW ON FRIDAY AHEAD OF A STRONG COLD
FRONT...THOUGH WARM AIRMASS WILL LIMIT MIXING. WILL LIKELY NEED TO
ADD AREAS OF FOG OVER THE LAKE. THE STRONG COLD FRONT WILL SWEEP
ACROSS THE LAKE FRIDAY NIGHT INTO SATURDAY...BRINGING NORTHERLY
WINDS TO 30 KT. WILL NEED TO WATCH FOR A PERIOD OF NORTHERLY GALES
SHOWN ON SOME MODEL GUIDANCE. WILL NEED A SMALL CRAFT ADVISORY
SATURDAY MORNING THROUGH SUNDAY MORNING UNTIL WAVES SUBSIDE.

RC

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 10 PM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 262032
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
332 PM CDT TUE MAY 26 2015

.SHORT TERM...
253 PM CDT

THROUGH WEDNESDAY...

A SURFACE LOW IS OVER NORTHEAST IA AND SW WI WITH A VORT MAX OVER
IOWA. THE LOWS COLD FRONT REMAINS A BIT FURTHER BACK OVER CENTRAL IA
AND EASTERN KS. THE LOW WILL DEEPEN SLIGHTLY AS IT MOVES OVER
CENTRAL WI AND ITS COLD FRONT SWINGS THROUGH WEDNESDAY. THE MAIN
CONCERN RIGHT NOW IS HOW MUCH CONVECTION WILL DEVELOP THIS
AFTERNOON.  THE LATEST RAP ANALYSIS SUGGESTS A RIBBON OF 1000 J/KG
OF CAPE IS OVER I-39...BUT THINKING THAT CAPE IN REALITY IS AROUND
500 J/KG DUE TO LIMITED HEATING. CAPE VALUES COULD RISE TO AROUND
1000 J/KG AS THERE ARE A FEW BREAKS IN THE CLOUDS...BUT THINKING IN
GENERAL THE BREAKS ARE MOVING TOO QUICKLY AND TOO FEW AND FAR BTWN
TO AMOUNT TO MUCH.  SHEAR VALUES REMAIN VERY FAVORABLE FOR ORGANIZED
STORMS WITH VALUES AROUND 35-40 KT.

THEREFORE EXPECTING SCATTERED SHOWER/TS DEVELOPMENT THIS AFTN IN THE
WAKE OF THE LINE OF SHOWERS THAT IS SHIFTING EAST ACROSS INDIANA
RIGHT NOW.  A SECOND SKINNY LINE OF CONVECTION LIES FROM DIXON IL TO
JERSEYVILLE IL WITH A FEW ADDITIONAL CELLS OUT AHEAD OF IT. DUE TO
LIMITED CAPE AS DISCUSSED ABOVE...THE STRONGER CELLS MAY PRODUCE
DAMAGING WINDS. WINDS HAVE VEERED TO THE SW AND HELICITY IS MUCH
LOWER SO NOT AS CONCERNED ABOUT ISOLATED TORNADOES AS I WAS THIS
MORNING.  PWAT VALUES REMAIN VERY IMPRESSIVE AT 1.4-1.7 INCHES SO
ANY OF THE NEW SHOWERS WILL BE CAPABLE OF ADDITIONAL HEAVY DOWNPOURS.

THE AREA OF SCATTERED SHOWERS AND STORMS SHIFTS EAST OF THE CWA THIS
EVENING...BUT WE ARE NOT DONE YET. ANOTHER ROUND OF SHOWERS AND
PERHAPS OF THUNDERSTORMS MAY FORM THIS EVENING AS THE VORT MAX
APPROACHES. THINKING THE COVERAGE WILL BE BEST ALONG AND WEST OF
GARY INDIANA TO PAXTON IL LINE. HAVE LOW CONFIDENCE IN COVERAGE AND
TIMING OF THIS ROUND OF SHOWERS...BUT NOT EXPECTING MUCH THUNDER AND
NO SEVERE WEATHER.  DEWPOINTS REMAIN IN THE 60S TONIGHT SO THINKING
WE WILL NOT COOL MUCH...SO KEPT LOWS IN THE LOW TO MID 60S.

THE PATTERN REMAINS MESSY TOMORROW BUT NOT AS ACTIVE.  A PAIR OF
VORT STREAMERS AND THE LOWS COLD FRONT ROTATE THROUGH AND SHOWERS
AND STORMS MAY FORM ALONG THEM.  THE FIRST IS ASSOCIATED WITH THE
UPPER LEVEL LOW SHIFTING NE INTO ONTARIO TOMORROW. SHOWERS AND
STORMS WITH THIS VORT STREAMER WOULD CLIP THE NORTHERN CWA...NORTH
OF I-88.  PRECIP MAY SINK SOUTH ACROSS DUPAGE AND COOK COUNTIES IN
THE AFTN...BUT HAVE LOW CONFIDENCE IN HOW FAR SOUTH THE PRECIP WILL
GET.

CLOUD COVER SHIFTS EAST THROUGH THE AFTERNOON WITH AREAS WEST OF I-
55 BECOMING MOSTLY SUNNY BY MID AFTN. DID NOT MAKE TOO MANY CHANGES
TO HIGH TEMPS TOMORROW AS CLOUD COVER WILL PLAY A ROLE.  HAVE TEMPS
IN THE UPPER 70S TO LOW 80S.  A LAKE BREEZE IS POSSIBLE LATE IN THE
AFTN AND EVENING SO EXPECTING LAKE COOLING ESPECIALLY AT WAUKEGAN.

JEE

&&

.LONG TERM...
330 PM CDT

WEDNESDAY NIGHT THROUGH TUESDAY...

LOCAL AREA WILL START OUT FIRMLY UNDER MID/UPPER RIDGING ON
WEDNESDAY NIGHT AND THURSDAY...RESULTING IN A DRY AND WARM PERIOD
AS 925 MB TEMPS CLIMB FROM THE UPPER TEENS CELSISUS BY EARLY
THURSDAY TO THE LOWER 20S CELSISUS EARLY THURSDAY EVENING. INLAND
TEMPERATURES WILL WARM TO THE LOWER-MID 80S ON THURSDAY...BUT
DESPITE SOUTHERLY SURFACE FLOW...GRADIENT WILL BE WEAK ENOUGH TO
ENABLE A LAKE BREEZE TO DEVELOP AND PUSH INLAND FAIRLY EARLY. THIS
WILL KEEP LAKESHORE TEMPS (ESPECIALLY IL SHORE) IN THE UPPER 60S.

CHANGES WILL START TO TAKE PLACE THURSDAY NIGHT WITH UPPER RIDGE
AXIS GETTING SHUNTED EAST AND ALLOWS SHORTWAVE ENERGY TO LIFT
EAST-NORTHEAST ACROSS THE AREA AFTER MIDNIGHT INTO FRIDAY ALONG
WITH STRENGTHENING AND VEERING LOW LEVEL JET. HAVE FOCUSED MID
CHANCE POPS INTO NORTHWEST CWA LATE THURSDAY NIGHT AND THEN SPREAD
LIKELY POPS FOR MUCH OF THE CWA FRIDAY MORNING AND EARLY
AFTERNOON. IT APPEARS THAT BETTER MOISTURE CONVERGENCE AND UPPER
FORCING WILL LIFT NORTH AND REFOCUS INTO NORTHWEST CWA FRIDAY
AFTERNOON AND TAILORED POPS AS SUCH...BUT THEN A STRONGER WAVE
WILL MOVE ACROSS THE AREA SATURDAY NIGHT. CONFIDENCE IS A BIT
LOWER IN HIGH TEMPS FRIDAY DUE TO UNCERTAINTY OVER IMPACT OF
CLOUDS/PRECIP...BUT VERY MILD START TO DAY AND WARM AIRMASS IN
PLACE SHOULD STILL SUPPORT HIGHS INTO THE LOWER-MID 80S...WARMEST
IN SOUTHEAST HALF OF CWA. THE WARM TEMPS...DEWPOINTS WELL INTO THE
60S AND MODEST MIDLEVEL LAPSE RATES WILL YIELD MODEST CAPE
VALUES...SO CANNOT RULE OUT AN ISOLATED SEVERE THREAT FOR DAMAGING
WINDS INTO FRIDAY EVENING. COULD BE SOME WET MICROBURSTS WITH PWAT
VALUES IN 1.5 TO 1.75 INCH RANGE.

A STRONG COLD FRONT WILL SWEEP ACROSS THE AREA FRIDAY
NIGHT...RESULTING IN MUCH COOLER WEATHER FOR THE LAST WEEKEND OF
MAY. HIGHS ON THE LAKEFRONT ARE LIKELY TO STAY IN THE 50S ON BOTH
SATURDAY AND SUNDAY...WITH ONLY 60S AND 70S INLAND ON SATURDAY AND
60S ON SUNDAY. WILL NEED TO WATCH FOR A WAVE OF SURFACE LOW
PRESSURE FORMING SOUTH OF THE AREA ON SATURDAY...SO KEPT HIGHER
CONSENSUS POPS FOR NOW SATURDAY MORNING...BUT IF TRENDS ON MUCH OF
GUIDANCE CONTINUE MAY BE ABLE TO LOWER POPS SATURDAY THROUGH
MONDAY WITH EXPANSIVE COOL HIGH PRESSURE OVER THE GREAT LAKES.
TEMPERATURES WILL THEN WARM BACK TO NEAR NORMAL FOR EARLY JUNE BY
TUESDAY WITH SOUTHERLY FLOW ON BACK SIDE OF HIGH TO EAST...THOUGH
ONSHORE FLOW LOOKS TO CONTINUE FOR AT LEAST A PORTION OF THE
LAKEFRONT.

RC

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 20Z...

* ISOLATED MVFR THIS AFTERNOON

* RAIN SHOWERS POSSIBLY DROPPING TO MVFR

* SOUTH WINDS VARYING FROM SOUTH-SOUTHWEST THIS EVENING.

* MVFR IN FOG AND LOW CLOUDS WEDNESDAY MORNING.

MM

//DISCUSSION...UPDATED 20Z...

LINE OF SHOWERS HAS DECREASED VSBYS TO 1 MILE UPSTREAM EARLY THIS
AFTERNOON. AS THE LINE PROGRESSES NORTHEASTWARD...COULD SEE SOME
STRONGER POCKETS OF RAIN AND TALLER EMBEDDED CELLS PRODUCE
ISOLATED LIGHTNING. LOW CHANCE/CONFIDENCE OF ANY OF THESE CELLS
HITTING THE TERMINALS...SO KEPT VCTS IN THE TAFS THROUGH 19Z.

LOOKING TOWARD WEDNESDAY MORNING...LOW LEVEL MOISTURE AND A WEAK
INVERSION WILL ALLOW A CHANCE FOR MVFR FOG AND CIGS TO WORK INTO
THE TERMINALS. THE AFTERNOON WILL FEATURE A SCATTERED TO POSSIBLY
BROKEN DECK AT 025. INTO THE EVENING...EXPECT OVERCAST CONDITIONS
WITH LIGHT RAIN POSSIBLE. THERE IS A CHANCE FOR THE LAKE BREEZE TO
WORK INTO ORD NEAR OR JUST AFTER 00Z WEDNESDAY EVENING.

MM

//ORD AND MDW CONFIDENCE...UPDATED 18Z...

* MEDIUM CONFIDENCE IN TEMPO MVFR THIS AFTERNOON.

* HIGH CONFIDENCE IN RAIN TIMING THIS AFTERNOON. LOW CONFIDENCE ON
  THUNDER CHANCES.

* MEDIUM TO HIGH CONFIDENCE IN WIND DIRECTION WITH HIGH CONFIDENCE
  IN WIND SPEED.

* LOW-MEDIUM CONFIDENCE IN FOG AND MVFR CONDITIONS WEDNESDAY
  MORNING.

MM

//OUTLOOK FOR ORD/MDW FOR 00Z THURSDAY-12Z TUESDAY...UPDATED 12Z...

WEDNESDAY NIGHT...WX NIL/VFR. SOUTHEAST WINDS.

THURSDAY...SLIGHT CHANCE OF TSRA AT NIGHT. SOUTHEAST WINDS.

FRIDAY...TSRA/SHRA LIKELY THROUGH THE DAY AND NIGHT. MVFR
POSSIBLE. SOUTHWEST WINDS.

SATURDAY...SHRA LIKELY WITH A CHANCE OF TSRA DURING THE DAY.
NORTHEAST WINDS.

SUNDAY...CHANCE OF SHRA. EAST WINDS. MVFR POSSIBLE.

MONDAY...CHANCE OF SHRA. SOUTHEAST WINDS. MVFR POSSIBLE.

KREIN

&&

.MARINE...
229 AM CDT

WARM MOIST AIR CONTINUES TO FEED NORTH ACROSS THE LAKE
TODAY...WHICH MAY HELP TO FURTHER ENHANCE ANY AREAS OF FOG THAT
HAVE ALREADY DEVELOPED. IT IS POSSIBLE PATCHY DENSE FOG MAY
DEVELOP...ALTHOUGH WINDS MAY BE JUST STRONG ENOUGH TO LIMIT THE
COVERAGE AND INTENSITY OF THE FOG. A SURFACE LOW PRESSURE SYSTEM
WILL BE LIFTING NORTH ACROSS EASTERN IOWA INTO CENTRAL WISCONSIN
THIS EVENING. THE GRADIENT WILL TIGHTEN ACROSS THE
CENTRAL/SOUTHERN PORTIONS OF THE LAKE...WHICH WITH WARMER
NEARSHORE WATERS EXPECT SOME SLIGHTLY BETTER MIXING TO OCCUR.
FURTHER OUT ACROSS THE OPEN WATERS THE WATER REMAINS COLD AND
EXPECT THE STABILITY TO MAKE IT DIFFICULT TO MIX TO THE SFC THE
HIGHER GUSTS. HIGH PRESSURE THEN ARRIVES LATE WEDNESDAY WITH LIGHT
WINDS DEVELOPING. THEN HIGH PRESSURE SHIFTS EAST THURSDAY
NIGHT...WITH SOUTHERLY WINDS DEVELOPING AGAIN FRIDAY. A FRONTAL
BOUNDARY WILL APPROACH LAKE MICHIGAN LATE FRIDAY NIGHT THEN
STEADILY SLIDE SOUTH ALONG THE LAKE. THIS WILL ALLOW WINDS TO
QUICKLY VEER FROM SOUTH TO NORTH/NORTHEAST SATURDAY. ALONG WITH
THIS QUICK WIND SHIFT WILL BE COOLER AIR SLIDING SOUTH OVER THE
LAKE. WAVES SHOULD EASILY BUILD SATURDAY FOR THE CENTRAL/SOUTHERN
PORTIONS OF THE LAKE.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 10 PM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
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WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 262032
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
332 PM CDT TUE MAY 26 2015

.SHORT TERM...
253 PM CDT

THROUGH WEDNESDAY...

A SURFACE LOW IS OVER NORTHEAST IA AND SW WI WITH A VORT MAX OVER
IOWA. THE LOWS COLD FRONT REMAINS A BIT FURTHER BACK OVER CENTRAL IA
AND EASTERN KS. THE LOW WILL DEEPEN SLIGHTLY AS IT MOVES OVER
CENTRAL WI AND ITS COLD FRONT SWINGS THROUGH WEDNESDAY. THE MAIN
CONCERN RIGHT NOW IS HOW MUCH CONVECTION WILL DEVELOP THIS
AFTERNOON.  THE LATEST RAP ANALYSIS SUGGESTS A RIBBON OF 1000 J/KG
OF CAPE IS OVER I-39...BUT THINKING THAT CAPE IN REALITY IS AROUND
500 J/KG DUE TO LIMITED HEATING. CAPE VALUES COULD RISE TO AROUND
1000 J/KG AS THERE ARE A FEW BREAKS IN THE CLOUDS...BUT THINKING IN
GENERAL THE BREAKS ARE MOVING TOO QUICKLY AND TOO FEW AND FAR BTWN
TO AMOUNT TO MUCH.  SHEAR VALUES REMAIN VERY FAVORABLE FOR ORGANIZED
STORMS WITH VALUES AROUND 35-40 KT.

THEREFORE EXPECTING SCATTERED SHOWER/TS DEVELOPMENT THIS AFTN IN THE
WAKE OF THE LINE OF SHOWERS THAT IS SHIFTING EAST ACROSS INDIANA
RIGHT NOW.  A SECOND SKINNY LINE OF CONVECTION LIES FROM DIXON IL TO
JERSEYVILLE IL WITH A FEW ADDITIONAL CELLS OUT AHEAD OF IT. DUE TO
LIMITED CAPE AS DISCUSSED ABOVE...THE STRONGER CELLS MAY PRODUCE
DAMAGING WINDS. WINDS HAVE VEERED TO THE SW AND HELICITY IS MUCH
LOWER SO NOT AS CONCERNED ABOUT ISOLATED TORNADOES AS I WAS THIS
MORNING.  PWAT VALUES REMAIN VERY IMPRESSIVE AT 1.4-1.7 INCHES SO
ANY OF THE NEW SHOWERS WILL BE CAPABLE OF ADDITIONAL HEAVY DOWNPOURS.

THE AREA OF SCATTERED SHOWERS AND STORMS SHIFTS EAST OF THE CWA THIS
EVENING...BUT WE ARE NOT DONE YET. ANOTHER ROUND OF SHOWERS AND
PERHAPS OF THUNDERSTORMS MAY FORM THIS EVENING AS THE VORT MAX
APPROACHES. THINKING THE COVERAGE WILL BE BEST ALONG AND WEST OF
GARY INDIANA TO PAXTON IL LINE. HAVE LOW CONFIDENCE IN COVERAGE AND
TIMING OF THIS ROUND OF SHOWERS...BUT NOT EXPECTING MUCH THUNDER AND
NO SEVERE WEATHER.  DEWPOINTS REMAIN IN THE 60S TONIGHT SO THINKING
WE WILL NOT COOL MUCH...SO KEPT LOWS IN THE LOW TO MID 60S.

THE PATTERN REMAINS MESSY TOMORROW BUT NOT AS ACTIVE.  A PAIR OF
VORT STREAMERS AND THE LOWS COLD FRONT ROTATE THROUGH AND SHOWERS
AND STORMS MAY FORM ALONG THEM.  THE FIRST IS ASSOCIATED WITH THE
UPPER LEVEL LOW SHIFTING NE INTO ONTARIO TOMORROW. SHOWERS AND
STORMS WITH THIS VORT STREAMER WOULD CLIP THE NORTHERN CWA...NORTH
OF I-88.  PRECIP MAY SINK SOUTH ACROSS DUPAGE AND COOK COUNTIES IN
THE AFTN...BUT HAVE LOW CONFIDENCE IN HOW FAR SOUTH THE PRECIP WILL
GET.

CLOUD COVER SHIFTS EAST THROUGH THE AFTERNOON WITH AREAS WEST OF I-
55 BECOMING MOSTLY SUNNY BY MID AFTN. DID NOT MAKE TOO MANY CHANGES
TO HIGH TEMPS TOMORROW AS CLOUD COVER WILL PLAY A ROLE.  HAVE TEMPS
IN THE UPPER 70S TO LOW 80S.  A LAKE BREEZE IS POSSIBLE LATE IN THE
AFTN AND EVENING SO EXPECTING LAKE COOLING ESPECIALLY AT WAUKEGAN.

JEE

&&

.LONG TERM...
330 PM CDT

WEDNESDAY NIGHT THROUGH TUESDAY...

LOCAL AREA WILL START OUT FIRMLY UNDER MID/UPPER RIDGING ON
WEDNESDAY NIGHT AND THURSDAY...RESULTING IN A DRY AND WARM PERIOD
AS 925 MB TEMPS CLIMB FROM THE UPPER TEENS CELSISUS BY EARLY
THURSDAY TO THE LOWER 20S CELSISUS EARLY THURSDAY EVENING. INLAND
TEMPERATURES WILL WARM TO THE LOWER-MID 80S ON THURSDAY...BUT
DESPITE SOUTHERLY SURFACE FLOW...GRADIENT WILL BE WEAK ENOUGH TO
ENABLE A LAKE BREEZE TO DEVELOP AND PUSH INLAND FAIRLY EARLY. THIS
WILL KEEP LAKESHORE TEMPS (ESPECIALLY IL SHORE) IN THE UPPER 60S.

CHANGES WILL START TO TAKE PLACE THURSDAY NIGHT WITH UPPER RIDGE
AXIS GETTING SHUNTED EAST AND ALLOWS SHORTWAVE ENERGY TO LIFT
EAST-NORTHEAST ACROSS THE AREA AFTER MIDNIGHT INTO FRIDAY ALONG
WITH STRENGTHENING AND VEERING LOW LEVEL JET. HAVE FOCUSED MID
CHANCE POPS INTO NORTHWEST CWA LATE THURSDAY NIGHT AND THEN SPREAD
LIKELY POPS FOR MUCH OF THE CWA FRIDAY MORNING AND EARLY
AFTERNOON. IT APPEARS THAT BETTER MOISTURE CONVERGENCE AND UPPER
FORCING WILL LIFT NORTH AND REFOCUS INTO NORTHWEST CWA FRIDAY
AFTERNOON AND TAILORED POPS AS SUCH...BUT THEN A STRONGER WAVE
WILL MOVE ACROSS THE AREA SATURDAY NIGHT. CONFIDENCE IS A BIT
LOWER IN HIGH TEMPS FRIDAY DUE TO UNCERTAINTY OVER IMPACT OF
CLOUDS/PRECIP...BUT VERY MILD START TO DAY AND WARM AIRMASS IN
PLACE SHOULD STILL SUPPORT HIGHS INTO THE LOWER-MID 80S...WARMEST
IN SOUTHEAST HALF OF CWA. THE WARM TEMPS...DEWPOINTS WELL INTO THE
60S AND MODEST MIDLEVEL LAPSE RATES WILL YIELD MODEST CAPE
VALUES...SO CANNOT RULE OUT AN ISOLATED SEVERE THREAT FOR DAMAGING
WINDS INTO FRIDAY EVENING. COULD BE SOME WET MICROBURSTS WITH PWAT
VALUES IN 1.5 TO 1.75 INCH RANGE.

A STRONG COLD FRONT WILL SWEEP ACROSS THE AREA FRIDAY
NIGHT...RESULTING IN MUCH COOLER WEATHER FOR THE LAST WEEKEND OF
MAY. HIGHS ON THE LAKEFRONT ARE LIKELY TO STAY IN THE 50S ON BOTH
SATURDAY AND SUNDAY...WITH ONLY 60S AND 70S INLAND ON SATURDAY AND
60S ON SUNDAY. WILL NEED TO WATCH FOR A WAVE OF SURFACE LOW
PRESSURE FORMING SOUTH OF THE AREA ON SATURDAY...SO KEPT HIGHER
CONSENSUS POPS FOR NOW SATURDAY MORNING...BUT IF TRENDS ON MUCH OF
GUIDANCE CONTINUE MAY BE ABLE TO LOWER POPS SATURDAY THROUGH
MONDAY WITH EXPANSIVE COOL HIGH PRESSURE OVER THE GREAT LAKES.
TEMPERATURES WILL THEN WARM BACK TO NEAR NORMAL FOR EARLY JUNE BY
TUESDAY WITH SOUTHERLY FLOW ON BACK SIDE OF HIGH TO EAST...THOUGH
ONSHORE FLOW LOOKS TO CONTINUE FOR AT LEAST A PORTION OF THE
LAKEFRONT.

RC

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 20Z...

* ISOLATED MVFR THIS AFTERNOON

* RAIN SHOWERS POSSIBLY DROPPING TO MVFR

* SOUTH WINDS VARYING FROM SOUTH-SOUTHWEST THIS EVENING.

* MVFR IN FOG AND LOW CLOUDS WEDNESDAY MORNING.

MM

//DISCUSSION...UPDATED 20Z...

LINE OF SHOWERS HAS DECREASED VSBYS TO 1 MILE UPSTREAM EARLY THIS
AFTERNOON. AS THE LINE PROGRESSES NORTHEASTWARD...COULD SEE SOME
STRONGER POCKETS OF RAIN AND TALLER EMBEDDED CELLS PRODUCE
ISOLATED LIGHTNING. LOW CHANCE/CONFIDENCE OF ANY OF THESE CELLS
HITTING THE TERMINALS...SO KEPT VCTS IN THE TAFS THROUGH 19Z.

LOOKING TOWARD WEDNESDAY MORNING...LOW LEVEL MOISTURE AND A WEAK
INVERSION WILL ALLOW A CHANCE FOR MVFR FOG AND CIGS TO WORK INTO
THE TERMINALS. THE AFTERNOON WILL FEATURE A SCATTERED TO POSSIBLY
BROKEN DECK AT 025. INTO THE EVENING...EXPECT OVERCAST CONDITIONS
WITH LIGHT RAIN POSSIBLE. THERE IS A CHANCE FOR THE LAKE BREEZE TO
WORK INTO ORD NEAR OR JUST AFTER 00Z WEDNESDAY EVENING.

MM

//ORD AND MDW CONFIDENCE...UPDATED 18Z...

* MEDIUM CONFIDENCE IN TEMPO MVFR THIS AFTERNOON.

* HIGH CONFIDENCE IN RAIN TIMING THIS AFTERNOON. LOW CONFIDENCE ON
  THUNDER CHANCES.

* MEDIUM TO HIGH CONFIDENCE IN WIND DIRECTION WITH HIGH CONFIDENCE
  IN WIND SPEED.

* LOW-MEDIUM CONFIDENCE IN FOG AND MVFR CONDITIONS WEDNESDAY
  MORNING.

MM

//OUTLOOK FOR ORD/MDW FOR 00Z THURSDAY-12Z TUESDAY...UPDATED 12Z...

WEDNESDAY NIGHT...WX NIL/VFR. SOUTHEAST WINDS.

THURSDAY...SLIGHT CHANCE OF TSRA AT NIGHT. SOUTHEAST WINDS.

FRIDAY...TSRA/SHRA LIKELY THROUGH THE DAY AND NIGHT. MVFR
POSSIBLE. SOUTHWEST WINDS.

SATURDAY...SHRA LIKELY WITH A CHANCE OF TSRA DURING THE DAY.
NORTHEAST WINDS.

SUNDAY...CHANCE OF SHRA. EAST WINDS. MVFR POSSIBLE.

MONDAY...CHANCE OF SHRA. SOUTHEAST WINDS. MVFR POSSIBLE.

KREIN

&&

.MARINE...
229 AM CDT

WARM MOIST AIR CONTINUES TO FEED NORTH ACROSS THE LAKE
TODAY...WHICH MAY HELP TO FURTHER ENHANCE ANY AREAS OF FOG THAT
HAVE ALREADY DEVELOPED. IT IS POSSIBLE PATCHY DENSE FOG MAY
DEVELOP...ALTHOUGH WINDS MAY BE JUST STRONG ENOUGH TO LIMIT THE
COVERAGE AND INTENSITY OF THE FOG. A SURFACE LOW PRESSURE SYSTEM
WILL BE LIFTING NORTH ACROSS EASTERN IOWA INTO CENTRAL WISCONSIN
THIS EVENING. THE GRADIENT WILL TIGHTEN ACROSS THE
CENTRAL/SOUTHERN PORTIONS OF THE LAKE...WHICH WITH WARMER
NEARSHORE WATERS EXPECT SOME SLIGHTLY BETTER MIXING TO OCCUR.
FURTHER OUT ACROSS THE OPEN WATERS THE WATER REMAINS COLD AND
EXPECT THE STABILITY TO MAKE IT DIFFICULT TO MIX TO THE SFC THE
HIGHER GUSTS. HIGH PRESSURE THEN ARRIVES LATE WEDNESDAY WITH LIGHT
WINDS DEVELOPING. THEN HIGH PRESSURE SHIFTS EAST THURSDAY
NIGHT...WITH SOUTHERLY WINDS DEVELOPING AGAIN FRIDAY. A FRONTAL
BOUNDARY WILL APPROACH LAKE MICHIGAN LATE FRIDAY NIGHT THEN
STEADILY SLIDE SOUTH ALONG THE LAKE. THIS WILL ALLOW WINDS TO
QUICKLY VEER FROM SOUTH TO NORTH/NORTHEAST SATURDAY. ALONG WITH
THIS QUICK WIND SHIFT WILL BE COOLER AIR SLIDING SOUTH OVER THE
LAKE. WAVES SHOULD EASILY BUILD SATURDAY FOR THE CENTRAL/SOUTHERN
PORTIONS OF THE LAKE.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 10 PM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KILX 262000
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
300 PM CDT TUE MAY 26 2015

.SHORT TERM...(TONIGHT)
ISSUED AT 300 PM CDT TUE MAY 26 2015

2 PM SURFACE MAP SHOWED LOW PRESSURE CENTERED JUST NORTHWEST OF
DUBUQUE. INITIAL BAND OF CONVECTIVE SHOWERS/ISOLATED THUNDERSTORMS
WHICH MOVED THROUGH THE FORECAST AREA EARLIER HAS ADVANCED NORTHEAST
ACROSS THE INDIANA BORDER...WITH A SECONDARY AXIS OF LIGHT SHOWERS
MOVING EAST AHEAD OF AN UPPER DISTURBANCE CROSSING THE MISSISSIPPI
RIVER.

HRRR AND OTHER HIGH-RESOLUTION MODEL GUIDANCE HAS BEEN DOING A
REASONABLE JOB WITH THE ACTIVITY TODAY...AND WAS GENERALLY FOLLOWED
FOR THE RAIN TRENDS TONIGHT. HAVE MADE SOME ADJUSTMENTS WITH GOING
MAINLY ISOLATED SHOWERS/STORMS THIS EVENING EXCEPT WEST OF I-55...
WHERE LOW CHANCE POP`S WERE KEPT AS A WAVE/TROUGH ADVANCES EAST
ACROSS NORTHERN MISSOURI. HAVE LINGERED THESE 30% CHANCES OVERNIGHT
FROM ABOUT DECATUR WESTWARD. SHOULD SEE SKIES BECOME PARTLY CLOUDY
ACROSS THE SOUTHERN CWA THIS EVENING...BEFORE SOME INCREASE IS NOTED
AGAIN AHEAD OF THE INCOMING WAVE.

&&

.LONG TERM...(WEDNESDAY THROUGH TUESDAY)
ISSUED AT 300 PM CDT TUE MAY 26 2015

AN UNSETTLED WEATHER PATTERN LOOKS TO CONTINUE THROUGH MONDAY ACROSS
CENTRAL AND SOUTHEAST IL ALONG WITH WARM AND RATHER HUMID SUMMERLIKE
CONDITIONS THE REST OF THE WEEK. A COLD FRONT MOVING SE THROUGH
CENTRAL AND SOUTHEAST IL DURING SATURDAY WILL BRING COOLER
TEMPERATURES DURING THIS WEEKEND ESPECIALLY ON SUNDAY.

UPPER LEVEL TROF OVER THE UPPER MIDWEST MOVES INTO MI ON WED WHILE
PUSHING A WEAK FRONT SE INTO THE IL RIVER VALLEY WED AFTERNOON. ALSO
HAVE A SHORT WAVE EJECTING NE FROM THE SOUTHERN PLAINS INTO SE IL
AND CENTRAL INDIANA BY 18Z/WED. INCREASE INSTABLITY ON WED WITH
CAPES OF 1000-2000 J/KG AND HIGHEST SOUTH OF I-72 TO RETURN CHANCES
OF SHOWERS AND THUNDERSTORMS WITH LOWER CHANCES NW OF IL RIVER AND
HIGHER CHANCES IN SOUTHEAST IL. SPC HAS MARGINAL RISK OF SEVERE WED
AFTERNOON SE OF A SHELYVILLE TO PARIS LINE. CONVECTION CHANCES WILL
LINGER SOUTH OF I-72 WED NIGHT MAINLY WED EVENING. THEN ISOLATED
CHANCES OF CONVECTION SHIFT INTO SOUTHERN AND SW AREAS ON THU AS
WEAK HIGH PRESSURE DRIFTS ACROSS THE GREAT LAKES AND MORE STABLE AIR
OVER NE CWA FROM I-74 NE WHERE IT SHOULD BE DRY. NAM MODEL IS STILL
RATHER UNSTABLE THU SW OF I-74 BUT THINK IT MAY BE OVERDOING THIS AS
STRONGER INSTABLITY CLOSER MO AND THE OHIO RIVER VALLEY ON THU PLUS
HAVE UPPER LEVEL RIDGE BUILDING OVER THE EASTERN STATES THU.

WARM FRONT LIFTS NORTH ACROSS CENTRAL IL THU NIGHT AND IN BREEZY SSW
FLOW ON FRIDAY WITH CHANCES OF SHOWERS AND THUNDERSTORM HIGHEST OVER
IL RIVER VALLEY (LIKELY CHANCES WEST OF IL RIVER ON FRIDAY) AND
LOWEST NEAR WABASH RIVER. WARM HIGHS IN THE LOWER 80S WED AND MID
80S THU AND FRI AND A FEW AREAS COULD REACH UPPER 80S WITH ENOUGH
SUNSHINE ESPECIALLY NEAR WABASH RIVER WHERE RAIN CHANCES ARE LOWER.

HAVE LIKELY CHANCES OF SHOWERS AND THUNDERSTORMS FRI NIGHT AND SAT
WITH COLD FRONT PUSHING SE THROUGH CENTRAL IL DURING SATURDAY. HIGHS
SAT TO CONTRAST FROM LOWER 70S NW OF IL RIVER TO LOW 80S IN
SOUTHEAST IL. CONTINUE LIKELY CHANCES OF SHOWERS AND THUNDERSTORMS
SAT NIGHT IN SOUTHEAST IL ESPECIALLY SAT EVENING WHILE LOWERED POPS
TO LOW CHANCE NW OVER IL RIVER VALLEY BEHIND COLD FRONT. AREAS NW OF
IL RIVER NOW APPEAR DRY ON SUNDAY WHILE CHANCE OF SHOWERS AND
THUNDERSTORMS LINGERS FROM I-72 SOUTH CLOSER TO FRONTAL BOUNDARY
PUSHING SE OF OHIO RIVER OVER KY/TN. SUNDAY APPEARS TO BE COOLEST
DAY WITH HIGHS IN UPPER 60S CENTRAL IL AND LOWER 70S SE IL.

EXTENDED MODELS LIKE GFS AND ECMWF CONTINUE TO SHOW A WEAK CUTOFF
UPPER LEVEL LOW EJECTING INTO MO BY MON AND TO CONTINUE CHANCES OF
SHOWERS AND ISOLATED THUNDERSTORMS MONDAY AND TUESDAY. HIGHS IN THE
LOW TO MID 70S MONDAY AND MID TO UPPER 70S TUESDAY.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z WEDNESDAY AFTERNOON)
ISSUED AT 1240 PM CDT TUE MAY 26 2015

PERIODS OF SHOWERS AND ISOLATED THUNDERSTORMS CAN BE EXPECTED AT
TIMES THE NEXT 12-15 HOURS, BETWEEN 18Z AND 08Z, ACROSS CENTRAL
AND EASTERN IL.

THE LATEST HRRR REFLECTIVITY FORECAST HAD A PRETTY GOOD HANDLE ON
THE LOW TOPPED CONVECTION THAT HAS FIRED UP IN THE MS RIVER VALLEY
AROUND THE NOON HOUR. THIS IS EXPECTED TO MOVE INTO CENTRAL IL
FROM 19-21Z AND THEN EASTERN IL FROM 21-23Z. GENERALLY VFR
CONDITIONS ARE ANTICIPATED, BUT WOULD ANTICIPATE MVFR FOR A VERY
SHORT PERIOD OF TIME DURING ANY HEAVY DOWNPOURS.

AFTER A BRIEF BREAK IN CONVECTION EARLY THIS EVENING, THE MAIN
COLD FRONT IS EXPECTED TO MOVE TOWARD CENTRAL IL JUST AFTER
SUNSET. THIS WILL RESULT IN MORE SCATTERED SHOWERS. DECIDED NOT TO
INCLUDE ANY MENTION OF THUNDER AT THIS POINT SINCE INSTABILITY IS
EXPECTED TO BE QUITE LIMITED. AFTER THE FRONTAL PASSAGE THE WIND
IS EXPECTED TO GRADUALLY SHIFT FROM SW TO WSW. THIS WILL ALSO BE
ACCOMPANIED BY VFR CEILINGS/STRATOCUMULUS CLOUDS WRAPPING AROUND
THE LOW LEVEL CYCLONIC FLOW THROUGH MUCH OF WEDNESDAY MORNING.


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...GEELHART
LONG TERM...07
AVIATION...MILLER




000
FXUS63 KILX 262000
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
300 PM CDT TUE MAY 26 2015

.SHORT TERM...(TONIGHT)
ISSUED AT 300 PM CDT TUE MAY 26 2015

2 PM SURFACE MAP SHOWED LOW PRESSURE CENTERED JUST NORTHWEST OF
DUBUQUE. INITIAL BAND OF CONVECTIVE SHOWERS/ISOLATED THUNDERSTORMS
WHICH MOVED THROUGH THE FORECAST AREA EARLIER HAS ADVANCED NORTHEAST
ACROSS THE INDIANA BORDER...WITH A SECONDARY AXIS OF LIGHT SHOWERS
MOVING EAST AHEAD OF AN UPPER DISTURBANCE CROSSING THE MISSISSIPPI
RIVER.

HRRR AND OTHER HIGH-RESOLUTION MODEL GUIDANCE HAS BEEN DOING A
REASONABLE JOB WITH THE ACTIVITY TODAY...AND WAS GENERALLY FOLLOWED
FOR THE RAIN TRENDS TONIGHT. HAVE MADE SOME ADJUSTMENTS WITH GOING
MAINLY ISOLATED SHOWERS/STORMS THIS EVENING EXCEPT WEST OF I-55...
WHERE LOW CHANCE POP`S WERE KEPT AS A WAVE/TROUGH ADVANCES EAST
ACROSS NORTHERN MISSOURI. HAVE LINGERED THESE 30% CHANCES OVERNIGHT
FROM ABOUT DECATUR WESTWARD. SHOULD SEE SKIES BECOME PARTLY CLOUDY
ACROSS THE SOUTHERN CWA THIS EVENING...BEFORE SOME INCREASE IS NOTED
AGAIN AHEAD OF THE INCOMING WAVE.

&&

.LONG TERM...(WEDNESDAY THROUGH TUESDAY)
ISSUED AT 300 PM CDT TUE MAY 26 2015

AN UNSETTLED WEATHER PATTERN LOOKS TO CONTINUE THROUGH MONDAY ACROSS
CENTRAL AND SOUTHEAST IL ALONG WITH WARM AND RATHER HUMID SUMMERLIKE
CONDITIONS THE REST OF THE WEEK. A COLD FRONT MOVING SE THROUGH
CENTRAL AND SOUTHEAST IL DURING SATURDAY WILL BRING COOLER
TEMPERATURES DURING THIS WEEKEND ESPECIALLY ON SUNDAY.

UPPER LEVEL TROF OVER THE UPPER MIDWEST MOVES INTO MI ON WED WHILE
PUSHING A WEAK FRONT SE INTO THE IL RIVER VALLEY WED AFTERNOON. ALSO
HAVE A SHORT WAVE EJECTING NE FROM THE SOUTHERN PLAINS INTO SE IL
AND CENTRAL INDIANA BY 18Z/WED. INCREASE INSTABLITY ON WED WITH
CAPES OF 1000-2000 J/KG AND HIGHEST SOUTH OF I-72 TO RETURN CHANCES
OF SHOWERS AND THUNDERSTORMS WITH LOWER CHANCES NW OF IL RIVER AND
HIGHER CHANCES IN SOUTHEAST IL. SPC HAS MARGINAL RISK OF SEVERE WED
AFTERNOON SE OF A SHELYVILLE TO PARIS LINE. CONVECTION CHANCES WILL
LINGER SOUTH OF I-72 WED NIGHT MAINLY WED EVENING. THEN ISOLATED
CHANCES OF CONVECTION SHIFT INTO SOUTHERN AND SW AREAS ON THU AS
WEAK HIGH PRESSURE DRIFTS ACROSS THE GREAT LAKES AND MORE STABLE AIR
OVER NE CWA FROM I-74 NE WHERE IT SHOULD BE DRY. NAM MODEL IS STILL
RATHER UNSTABLE THU SW OF I-74 BUT THINK IT MAY BE OVERDOING THIS AS
STRONGER INSTABLITY CLOSER MO AND THE OHIO RIVER VALLEY ON THU PLUS
HAVE UPPER LEVEL RIDGE BUILDING OVER THE EASTERN STATES THU.

WARM FRONT LIFTS NORTH ACROSS CENTRAL IL THU NIGHT AND IN BREEZY SSW
FLOW ON FRIDAY WITH CHANCES OF SHOWERS AND THUNDERSTORM HIGHEST OVER
IL RIVER VALLEY (LIKELY CHANCES WEST OF IL RIVER ON FRIDAY) AND
LOWEST NEAR WABASH RIVER. WARM HIGHS IN THE LOWER 80S WED AND MID
80S THU AND FRI AND A FEW AREAS COULD REACH UPPER 80S WITH ENOUGH
SUNSHINE ESPECIALLY NEAR WABASH RIVER WHERE RAIN CHANCES ARE LOWER.

HAVE LIKELY CHANCES OF SHOWERS AND THUNDERSTORMS FRI NIGHT AND SAT
WITH COLD FRONT PUSHING SE THROUGH CENTRAL IL DURING SATURDAY. HIGHS
SAT TO CONTRAST FROM LOWER 70S NW OF IL RIVER TO LOW 80S IN
SOUTHEAST IL. CONTINUE LIKELY CHANCES OF SHOWERS AND THUNDERSTORMS
SAT NIGHT IN SOUTHEAST IL ESPECIALLY SAT EVENING WHILE LOWERED POPS
TO LOW CHANCE NW OVER IL RIVER VALLEY BEHIND COLD FRONT. AREAS NW OF
IL RIVER NOW APPEAR DRY ON SUNDAY WHILE CHANCE OF SHOWERS AND
THUNDERSTORMS LINGERS FROM I-72 SOUTH CLOSER TO FRONTAL BOUNDARY
PUSHING SE OF OHIO RIVER OVER KY/TN. SUNDAY APPEARS TO BE COOLEST
DAY WITH HIGHS IN UPPER 60S CENTRAL IL AND LOWER 70S SE IL.

EXTENDED MODELS LIKE GFS AND ECMWF CONTINUE TO SHOW A WEAK CUTOFF
UPPER LEVEL LOW EJECTING INTO MO BY MON AND TO CONTINUE CHANCES OF
SHOWERS AND ISOLATED THUNDERSTORMS MONDAY AND TUESDAY. HIGHS IN THE
LOW TO MID 70S MONDAY AND MID TO UPPER 70S TUESDAY.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z WEDNESDAY AFTERNOON)
ISSUED AT 1240 PM CDT TUE MAY 26 2015

PERIODS OF SHOWERS AND ISOLATED THUNDERSTORMS CAN BE EXPECTED AT
TIMES THE NEXT 12-15 HOURS, BETWEEN 18Z AND 08Z, ACROSS CENTRAL
AND EASTERN IL.

THE LATEST HRRR REFLECTIVITY FORECAST HAD A PRETTY GOOD HANDLE ON
THE LOW TOPPED CONVECTION THAT HAS FIRED UP IN THE MS RIVER VALLEY
AROUND THE NOON HOUR. THIS IS EXPECTED TO MOVE INTO CENTRAL IL
FROM 19-21Z AND THEN EASTERN IL FROM 21-23Z. GENERALLY VFR
CONDITIONS ARE ANTICIPATED, BUT WOULD ANTICIPATE MVFR FOR A VERY
SHORT PERIOD OF TIME DURING ANY HEAVY DOWNPOURS.

AFTER A BRIEF BREAK IN CONVECTION EARLY THIS EVENING, THE MAIN
COLD FRONT IS EXPECTED TO MOVE TOWARD CENTRAL IL JUST AFTER
SUNSET. THIS WILL RESULT IN MORE SCATTERED SHOWERS. DECIDED NOT TO
INCLUDE ANY MENTION OF THUNDER AT THIS POINT SINCE INSTABILITY IS
EXPECTED TO BE QUITE LIMITED. AFTER THE FRONTAL PASSAGE THE WIND
IS EXPECTED TO GRADUALLY SHIFT FROM SW TO WSW. THIS WILL ALSO BE
ACCOMPANIED BY VFR CEILINGS/STRATOCUMULUS CLOUDS WRAPPING AROUND
THE LOW LEVEL CYCLONIC FLOW THROUGH MUCH OF WEDNESDAY MORNING.


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...GEELHART
LONG TERM...07
AVIATION...MILLER



000
FXUS63 KLOT 261959
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
259 PM CDT TUE MAY 26 2015

.SHORT TERM...
253 PM CDT

THROUGH WEDNESDAY...

A SURFACE LOW IS OVER NORTHEAST IA AND SW WI WITH A VORT MAX OVER
IOWA. THE LOWS COLD FRONT REMAINS A BIT FURTHER BACK OVER CENTRAL IA
AND EASTERN KS. THE LOW WILL DEEPEN SLIGHTLY AS IT MOVES OVER
CENTRAL WI AND ITS COLD FRONT SWINGS THROUGH WEDNESDAY. THE MAIN
CONCERN RIGHT NOW IS HOW MUCH CONVECTION WILL DEVELOP THIS
AFTERNOON.  THE LATEST RAP ANALYSIS SUGGESTS A RIBBON OF 1000 J/KG
OF CAPE IS OVER I-39...BUT THINKING THAT CAPE IN REALITY IS AROUND
500 J/KG DUE TO LIMITED HEATING. CAPE VALUES COULD RISE TO AROUND
1000 J/KG AS THERE ARE A FEW BREAKS IN THE CLOUDS...BUT THINKING IN
GENERAL THE BREAKS ARE MOVING TOO QUICKLY AND TOO FEW AND FAR BTWN
TO AMOUNT TO MUCH.  SHEAR VALUES REMAIN VERY FAVORABLE FOR ORGANIZED
STORMS WITH VALUES AROUND 35-40 KT.

THEREFORE EXPECTING SCATTERED SHOWER/TS DEVELOPMENT THIS AFTN IN THE
WAKE OF THE LINE OF SHOWERS THAT IS SHIFTING EAST ACROSS INDIANA
RIGHT NOW.  A SECOND SKINNY LINE OF CONVECTION LIES FROM DIXON IL TO
JERSEYVILLE IL WITH A FEW ADDITIONAL CELLS OUT AHEAD OF IT. DUE TO
LIMITED CAPE AS DISCUSSED ABOVE...THE STRONGER CELLS MAY PRODUCE
DAMAGING WINDS. WINDS HAVE VEERED TO THE SW AND HELICITY IS MUCH
LOWER SO NOT AS CONCERNED ABOUT ISOLATED TORNADOES AS I WAS THIS
MORNING.  PWAT VALUES REMAIN VERY IMPRESSIVE AT 1.4-1.7 INCHES SO
ANY OF THE NEW SHOWERS WILL BE CAPABLE OF ADDITIONAL HEAVY DOWNPOURS.

THE AREA OF SCATTERED SHOWERS AND STORMS SHIFTS EAST OF THE CWA THIS
EVENING...BUT WE ARE NOT DONE YET. ANOTHER ROUND OF SHOWERS AND
PERHAPS OF THUNDERSTORMS MAY FORM THIS EVENING AS THE VORT MAX
APPROACHES. THINKING THE COVERAGE WILL BE BEST ALONG AND WEST OF
GARY INDIANA TO PAXTON IL LINE. HAVE LOW CONFIDENCE IN COVERAGE AND
TIMING OF THIS ROUND OF SHOWERS...BUT NOT EXPECTING MUCH THUNDER AND
NO SEVERE WEATHER.  DEWPOINTS REMAIN IN THE 60S TONIGHT SO THINKING
WE WILL NOT COOL MUCH...SO KEPT LOWS IN THE LOW TO MID 60S.

THE PATTERN REMAINS MESSY TOMORROW BUT NOT AS ACTIVE.  A PAIR OF
VORT STREAMERS AND THE LOWS COLD FRONT ROTATE THROUGH AND SHOWERS
AND STORMS MAY FORM ALONG THEM.  THE FIRST IS ASSOCIATED WITH THE
UPPER LEVEL LOW SHIFTING NE INTO ONTARIO TOMORROW. SHOWERS AND
STORMS WITH THIS VORT STREAMER WOULD CLIP THE NORTHERN CWA...NORTH
OF I-88.  PRECIP MAY SINK SOUTH ACROSS DUPAGE AND COOK COUNTIES IN
THE AFTN...BUT HAVE LOW CONFIDENCE IN HOW FAR SOUTH THE PRECIP WILL
GET.

CLOUD COVER SHIFTS EAST THROUGH THE AFTERNOON WITH AREAS WEST OF I-
55 BECOMING MOSTLY SUNNY BY MID AFTN. DID NOT MAKE TOO MANY CHANGES
TO HIGH TEMPS TOMORROW AS CLOUD COVER WILL PLAY A ROLE.  HAVE TEMPS
IN THE UPPER 70S TO LOW 80S.  A LAKE BREEZE IS POSSIBLE LATE IN THE
AFTN AND EVENING SO EXPECTING LAKE COOLING ESPECIALLY AT WAUKEGAN.

JEE

&&

.LONG TERM...
229 AM CDT

WEDNESDAY THROUGH MONDAY...

WEDNESDAY THROUGH THURSDAY...
OPEN 500MB WAVE WILL BE LIFTING NORTHEAST ACROSS THE UPPER MIDWEST
INTO ONTARIO AND EVENTUALLY QUEBEC...WITH HEIGHTS SLOWLY INCREASING
WED AFTN. SFC FEATURES REMAIN DISORGANIZED WED...WITH A BOUNDARY
SLOWLY SHIFTING EAST. OPER GUIDANCE DIFFERS ON HOW QUICKLY PRECIP
WILL DEPART THE REGION. ENSEMBLE DATA SUGGESTS HOLDING ONTO CHC TO
SLIGHT CHC POPS MAINLY FOR THE CENTRAL/EASTERN CWFA WED/WED EVE.
ALTHOUGH WITH SOME HINT OF SFC HEIGHTS NUDGING UP...IT IS POSSIBLE
THAT SOME DRY AIR COULD FILTER IN AND KICK PRECIP EAST BY MIDDAY AND
ALLOW FOR A MAINLY DRY WED. SFC WINDS WILL BE TURNING SOUTHWEST TO
WEST...KEEPING AN OFFSHORE FLOW FOR LOCATIONS CLOSE TO LAKE
MICHIGAN. TEMPS SHOULD YET AGAIN TOUCH UPR 70S TO ARND 80 WED...IF
CLOUDS AND PRECIP CAN PUSH EAST BY MIDDAY...SOME CLEARING WOULD
ALLOW SFC TEMPS TO PUSH A COUPLE DEGREES WARMER INTO THE LOW 80S IN
SOME LOCATIONS. LATE IN THE EVENING THE GRADIENT SLACKENS
FURTHER...AND COULD ALLOW A LATE DAY ONSHORE FLOW TO DEVELOP FOR
AREAS ADJACENT TO LAKE MICHIGAN.

MID-LVL FLOW BEGINS TO FLATTEN AS A WEAK SFC RIDGE BECOMES ORIENTED
FROM WESTERN QUEBEC SOUTH THROUGH THE EASTERN OHIO RIVER VALLEY.
THIS WILL GENERALLY ALLOW A SOUTHERLY FLOW...ALTHOUGH THE GRADIENT
IS NOT VERY STRONG. THIS SHOULD SET THE STAGE FOR A LAKE
BREEZE/ONSHORE FLOW TO DEVELOP THUR. TIMING COULD END UP BEING
SLIGHTLY EARLIER GIVEN THE LIGHT SFC GRADIENT. GUIDANCE HAS BEEN
CONSISTENT IN HOLDING PRECIP WEST/SOUTH OF THE FORECAST AREA
THUR...AS A RESULT OF THE WEAK SFC RIDGING. SO ONE MORE MILD DAY
WITH HIGHS WARMING BACK INTO THE UPR 70S/LOW 80S...HOWEVER AS
PREVIOUSLY NOTED...A LAKE BREEZE IS LIKELY TO DEVELOP. THIS WILL
BLEED THE MUCH COOLER MARINE AIR WEST ACROSS NORTHEAST IL AND
DOWNTOWN CHICAGO. IF THE TIMING IS EARLIER IN THE DAY THUR...TEMPS
MAY NOT WARM BEYOND THE LOW/MID 60S ALONG THE CHICAGO LAKEFRONT.

FLOW THEN TURNS SOUTHERLY THUR NIGHT WITH THE MORE PROGRESSIVE FLOW
IN THE MID-LVLS PUSHING THE RIDGING EAST. A RETURN FLOW MOISTURE
WILL CONTINUE TO BE FOCUSED ACROSS THE CENTRAL CONUS THUR EVE...WITH
A SLOW MOVING FRONTAL BOUNDARY NUDGING EAST THUR NIGHT TOWARDS
WESTERN IL. THIS FRONTAL BOUNDARY WILL BECOME ENERGIZED AS A ROBUST
500MB VORT MAX BREAKS SOUTH FROM CENTRAL CANADA LATE THUR NIGHT.

THIS SHOULD ALLOW FOR AN ATMOSPHERIC RIVER TO DEVELOP FROM THE
SOUTHERN PLAINS STRETCHING NORTH THROUGH THE MID-MISSOURI VALLEY
INTO THE WESTERN GREAT LAKES EARLY FRI MORNING.

FRIDAY THROUGH EARLY NEXT WEEK...
ENSEMBLES CONTINUE TO PROG A ROBUST TROUGH SLIDING SOUTH FROM
CENTRAL CANADA FRI. THIS COUPLED WITH DOWNSTREAM MID-LVL RIDGING
ACROSS THE SOUTHEAST CONUS WILL STRENGTHEN THE FRONTAL BOUNDARY
THAT WILL BE ORIENTED FROM THE SOUTHERN PLAINS STRETCHING
NORTHEAST THROUGH THE GREAT LAKES REGION INTO WESTERN QUEBEC.

THIS SETUP IS IDEAL FOR THE DEVELOPMENT OF AN ATMOSPHERIC RIVER WITH
ABUNDANT LOW LEVEL MOISTURE AND EFFICIENT PRECIP PRODUCING
CONVECTION.

OPER GUIDANCE HAS BEEN RELATIVELY CONSISTENT WITH BRINGING A SERIES
OF WAVES ALONG THE SLOW MOVING FRONTAL BOUNDARY FRI AFTN/EVE...THEN
THE BOUNDARY SHOULD SLIDE EAST WITH WINDS QUICKLY VEERING
NORTH/NORTHEAST FOR SAT AND USHERING IN MUCH COOLER AIR TO THE
REGION.

CURRENT INDICATIONS ARE THAT HIGHS SAT MAY STRUGGLE TO WARM BEYOND
THE UPR 50S ACROSS NORTHEAST IL/NORTHWEST IN...WITH ONLY LOW 60S
ELSEWHERE. STRONG SFC RIDGE WILL REMAIN NORTH OF THE REGION...SO THE
PRIOR FRONTAL BOUNDARY MAY BECOME QUASI-STATIONARY FOR THE WEEKEND
ALONG THE OHIO VALLEY AND CONTINUE TO FEED PRECIP CHANCES TO THE
SOUTHERN CWFA.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 20Z...

* ISOLATED MVFR THIS AFTERNOON

* RAIN SHOWERS POSSIBLY DROPPING TO MVFR

* SOUTH WINDS VARYING FROM SOUTH-SOUTHWEST THIS EVENING.

* MVFR IN FOG AND LOW CLOUDS WEDNESDAY MORNING.

MM

//DISCUSSION...UPDATED 20Z...

LINE OF SHOWERS HAS DECREASED VSBYS TO 1 MILE UPSTREAM EARLY THIS
AFTERNOON. AS THE LINE PROGRESSES NORTHEASTWARD...COULD SEE SOME
STRONGER POCKETS OF RAIN AND TALLER EMBEDDED CELLS PRODUCE
ISOLATED LIGHTNING. LOW CHANCE/CONFIDENCE OF ANY OF THESE CELLS
HITTING THE TERMINALS...SO KEPT VCTS IN THE TAFS THROUGH 19Z.

LOOKING TOWARD WEDNESDAY MORNING...LOW LEVEL MOISTURE AND A WEAK
INVERSION WILL ALLOW A CHANCE FOR MVFR FOG AND CIGS TO WORK INTO
THE TERMINALS. THE AFTERNOON WILL FEATURE A SCATTERED TO POSSIBLY
BROKEN DECK AT 025. INTO THE EVENING...EXPECT OVERCAST CONDITIONS
WITH LIGHT RAIN POSSIBLE. THERE IS A CHANCE FOR THE LAKE BREEZE TO
WORK INTO ORD NEAR OR JUST AFTER 00Z WEDNESDAY EVENING.

MM

//ORD AND MDW CONFIDENCE...UPDATED 18Z...

* MEDIUM CONFIDENCE IN TEMPO MVFR THIS AFTERNOON.

* HIGH CONFIDENCE IN RAIN TIMING THIS AFTERNOON. LOW CONFIDENCE ON
  THUNDER CHANCES.

* MEDIUM TO HIGH CONFIDENCE IN WIND DIRECTION WITH HIGH CONFIDENCE
  IN WIND SPEED.

* LOW-MEDIUM CONFIDENCE IN FOG AND MVFR CONDITIONS WEDNESDAY
  MORNING.

MM

//OUTLOOK FOR ORD/MDW FOR 00Z THURSDAY-12Z TUESDAY...UPDATED 12Z...

WEDNESDAY NIGHT...WX NIL/VFR. SOUTHEAST WINDS.

THURSDAY...SLIGHT CHANCE OF TSRA AT NIGHT. SOUTHEAST WINDS.

FRIDAY...TSRA/SHRA LIKELY THROUGH THE DAY AND NIGHT. MVFR
POSSIBLE. SOUTHWEST WINDS.

SATURDAY...SHRA LIKELY WITH A CHANCE OF TSRA DURING THE DAY.
NORTHEAST WINDS.

SUNDAY...CHANCE OF SHRA. EAST WINDS. MVFR POSSIBLE.

MONDAY...CHANCE OF SHRA. SOUTHEAST WINDS. MVFR POSSIBLE.

KREIN

&&

.MARINE...
229 AM CDT

WARM MOIST AIR CONTINUES TO FEED NORTH ACROSS THE LAKE
TODAY...WHICH MAY HELP TO FURTHER ENHANCE ANY AREAS OF FOG THAT
HAVE ALREADY DEVELOPED. IT IS POSSIBLE PATCHY DENSE FOG MAY
DEVELOP...ALTHOUGH WINDS MAY BE JUST STRONG ENOUGH TO LIMIT THE
COVERAGE AND INTENSITY OF THE FOG. A SURFACE LOW PRESSURE SYSTEM
WILL BE LIFTING NORTH ACROSS EASTERN IOWA INTO CENTRAL WISCONSIN
THIS EVENING. THE GRADIENT WILL TIGHTEN ACROSS THE
CENTRAL/SOUTHERN PORTIONS OF THE LAKE...WHICH WITH WARMER
NEARSHORE WATERS EXPECT SOME SLIGHTLY BETTER MIXING TO OCCUR.
FURTHER OUT ACROSS THE OPEN WATERS THE WATER REMAINS COLD AND
EXPECT THE STABILITY TO MAKE IT DIFFICULT TO MIX TO THE SFC THE
HIGHER GUSTS. HIGH PRESSURE THEN ARRIVES LATE WEDNESDAY WITH LIGHT
WINDS DEVELOPING. THEN HIGH PRESSURE SHIFTS EAST THURSDAY
NIGHT...WITH SOUTHERLY WINDS DEVELOPING AGAIN FRIDAY. A FRONTAL
BOUNDARY WILL APPROACH LAKE MICHIGAN LATE FRIDAY NIGHT THEN
STEADILY SLIDE SOUTH ALONG THE LAKE. THIS WILL ALLOW WINDS TO
QUICKLY VEER FROM SOUTH TO NORTH/NORTHEAST SATURDAY. ALONG WITH
THIS QUICK WIND SHIFT WILL BE COOLER AIR SLIDING SOUTH OVER THE
LAKE. WAVES SHOULD EASILY BUILD SATURDAY FOR THE CENTRAL/SOUTHERN
PORTIONS OF THE LAKE.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 10 PM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 261953
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
253 PM CDT TUE MAY 26 2015

.SHORT TERM...
253 PM CDT

THROUGH WEDNESDAY...

A SURFACE LOW IS OVER NORTHEAST IA AND SW WI WITH A VORT MAX OVER
IOWA. THE LOWS COLD FRONT REMAINS A BIT FURTHER BACK OVER CENTRAL IA
AND EASTERN KS. THE LOW WILL DEEPEN SLIGHTLY AS IT MOVES OVER
CENTRAL WI AND ITS COLD FRONT SWINGS THROUGH WEDNESDAY. THE MAIN
CONCERN RIGHT NOW IS HOW MUCH CONVECTION WILL DEVELOP THIS
AFTERNOON.  THE LATEST RAP ANALYSIS SUGGESTS A RIBBON OF 1000 J/KG
OF CAPE IS OVER I-39...BUT THINKING THAT CAPE IN REALITY IS AROUND
500 J/KG DUE TO LIMITED HEATING. CAPE VALUES COULD RISE TO AROUND
1000 J/KG AS THERE ARE A FEW BREAKS IN THE CLOUDS...BUT THINKING IN
GENERAL THE BREAKS ARE MOVING TOO QUICKLY AND TOO FEW AND FAR BTWN
TO AMOUNT TO MUCH.  SHEAR VALUES REMAIN VERY FAVORABLE FOR ORGANIZED
STORMS WITH VALUES AROUND 35-40 KT.

THEREFORE EXPECTING SCATTERED SHOWER/TS DEVELOPMENT THIS AFTN IN THE
WAKE OF THE LINE OF SHOWERS THAT IS SHIFTING EAST ACROSS INDIANA
RIGHT NOW.  A SECOND SKINNY LINE OF CONVECTION LIES FROM DIXON IL TO
JERSEYVILLE IL WITH A FEW ADDITIONAL CELLS OUT AHEAD OF IT. DUE TO
LIMITED CAPE AS DISCUSSED ABOVE...THE STRONGER CELLS MAY PRODUCE
DAMAGING WINDS. WINDS HAVE VEERED TO THE SW AND HELICITY IS MUCH
LOWER SO NOT AS CONCERNED ABOUT ISOLATED TORNADOES AS I WAS THIS
MORNING.  PWAT VALUES REMAIN VERY IMPRESSIVE AT 1.4-1.7 INCHES SO
ANY OF THE NEW SHOWERS WILL BE CAPABLE OF ADDITIONAL HEAVY DOWNPOURS.

THE AREA OF SCATTERED SHOWERS AND STORMS SHIFTS EAST OF THE CWA THIS
EVENING...BUT WE ARE NOT DONE YET. ANOTHER ROUND OF SHOWERS AND
PERHAPS OF THUNDERSTORMS MAY FORM THIS EVENING AS THE VORT MAX
APPROACHES. THINKING THE COVERAGE WILL BE BEST ALONG AND WEST OF
GARY INDIANA TO PAXTON IL LINE. HAVE LOW CONFIDENCE IN COVERAGE AND
TIMING OF THIS ROUND OF SHOWERS...BUT NOT EXPECTING MUCH THUNDER AND
NO SEVERE WEATHER.  DEWPOINTS REMAIN IN THE 60S TONIGHT SO THINKING
WE WILL NOT COOL MUCH...SO KEPT LOWS IN THE LOW TO MID 60S.

THE PATTERN REMAINS MESSY TOMORROW BUT NOT AS ACTIVE.  A PAIR OF
VORT STREAMERS AND THE LOWS COLD FRONT ROTATE THROUGH AND SHOWERS
AND STORMS MAY FORM ALONG THEM.  THE FIRST IS ASSOCIATED WITH THE
UPPER LEVEL LOW SHIFTING NE INTO ONTARIO TOMORROW. SHOWERS AND
STORMS WITH THIS VORT STREAMER WOULD CLIP THE NORTHERN CWA...NORTH
OF I-88.  PRECIP MAY SINK SOUTH ACROSS DUPAGE AND COOK COUNTIES IN
THE AFTN...BUT HAVE LOW CONFIDENCE IN HOW FAR SOUTH THE PRECIP WILL
GET.

CLOUD COVER SHIFTS EAST THROUGH THE AFTERNOON WITH AREAS WEST OF I-
55 BECOMING MOSTLY SUNNY BY MID AFTN. DID NOT MAKE TOO MANY CHANGES
TO HIGH TEMPS TOMORROW AS CLOUD COVER WILL PLAY A ROLE.  HAVE TEMPS
IN THE UPPER 70S TO LOW 80S.  A LAKE BREEZE IS POSSIBLE LATE IN THE
AFTN AND EVENING SO EXPECTING LAKE COOLING ESPECIALLY AT WAUKEGAN.

JEE

&&

.LONG TERM...
229 AM CDT

WEDNESDAY THROUGH MONDAY...

WEDNESDAY THROUGH THURSDAY...
OPEN 500MB WAVE WILL BE LIFTING NORTHEAST ACROSS THE UPPER MIDWEST
INTO ONTARIO AND EVENTUALLY QUEBEC...WITH HEIGHTS SLOWLY INCREASING
WED AFTN. SFC FEATURES REMAIN DISORGANIZED WED...WITH A BOUNDARY
SLOWLY SHIFTING EAST. OPER GUIDANCE DIFFERS ON HOW QUICKLY PRECIP
WILL DEPART THE REGION. ENSEMBLE DATA SUGGESTS HOLDING ONTO CHC TO
SLIGHT CHC POPS MAINLY FOR THE CENTRAL/EASTERN CWFA WED/WED EVE.
ALTHOUGH WITH SOME HINT OF SFC HEIGHTS NUDGING UP...IT IS POSSIBLE
THAT SOME DRY AIR COULD FILTER IN AND KICK PRECIP EAST BY MIDDAY AND
ALLOW FOR A MAINLY DRY WED. SFC WINDS WILL BE TURNING SOUTHWEST TO
WEST...KEEPING AN OFFSHORE FLOW FOR LOCATIONS CLOSE TO LAKE
MICHIGAN. TEMPS SHOULD YET AGAIN TOUCH UPR 70S TO ARND 80 WED...IF
CLOUDS AND PRECIP CAN PUSH EAST BY MIDDAY...SOME CLEARING WOULD
ALLOW SFC TEMPS TO PUSH A COUPLE DEGREES WARMER INTO THE LOW 80S IN
SOME LOCATIONS. LATE IN THE EVENING THE GRADIENT SLACKENS
FURTHER...AND COULD ALLOW A LATE DAY ONSHORE FLOW TO DEVELOP FOR
AREAS ADJACENT TO LAKE MICHIGAN.

MID-LVL FLOW BEGINS TO FLATTEN AS A WEAK SFC RIDGE BECOMES ORIENTED
FROM WESTERN QUEBEC SOUTH THROUGH THE EASTERN OHIO RIVER VALLEY.
THIS WILL GENERALLY ALLOW A SOUTHERLY FLOW...ALTHOUGH THE GRADIENT
IS NOT VERY STRONG. THIS SHOULD SET THE STAGE FOR A LAKE
BREEZE/ONSHORE FLOW TO DEVELOP THUR. TIMING COULD END UP BEING
SLIGHTLY EARLIER GIVEN THE LIGHT SFC GRADIENT. GUIDANCE HAS BEEN
CONSISTENT IN HOLDING PRECIP WEST/SOUTH OF THE FORECAST AREA
THUR...AS A RESULT OF THE WEAK SFC RIDGING. SO ONE MORE MILD DAY
WITH HIGHS WARMING BACK INTO THE UPR 70S/LOW 80S...HOWEVER AS
PREVIOUSLY NOTED...A LAKE BREEZE IS LIKELY TO DEVELOP. THIS WILL
BLEED THE MUCH COOLER MARINE AIR WEST ACROSS NORTHEAST IL AND
DOWNTOWN CHICAGO. IF THE TIMING IS EARLIER IN THE DAY THUR...TEMPS
MAY NOT WARM BEYOND THE LOW/MID 60S ALONG THE CHICAGO LAKEFRONT.

FLOW THEN TURNS SOUTHERLY THUR NIGHT WITH THE MORE PROGRESSIVE FLOW
IN THE MID-LVLS PUSHING THE RIDGING EAST. A RETURN FLOW MOISTURE
WILL CONTINUE TO BE FOCUSED ACROSS THE CENTRAL CONUS THUR EVE...WITH
A SLOW MOVING FRONTAL BOUNDARY NUDGING EAST THUR NIGHT TOWARDS
WESTERN IL. THIS FRONTAL BOUNDARY WILL BECOME ENERGIZED AS A ROBUST
500MB VORT MAX BREAKS SOUTH FROM CENTRAL CANADA LATE THUR NIGHT.

THIS SHOULD ALLOW FOR AN ATMOSPHERIC RIVER TO DEVELOP FROM THE
SOUTHERN PLAINS STRETCHING NORTH THROUGH THE MID-MISSOURI VALLEY
INTO THE WESTERN GREAT LAKES EARLY FRI MORNING.

FRIDAY THROUGH EARLY NEXT WEEK...
ENSEMBLES CONTINUE TO PROG A ROBUST TROUGH SLIDING SOUTH FROM
CENTRAL CANADA FRI. THIS COUPLED WITH DOWNSTREAM MID-LVL RIDGING
ACROSS THE SOUTHEAST CONUS WILL STRENGTHEN THE FRONTAL BOUNDARY
THAT WILL BE ORIENTED FROM THE SOUTHERN PLAINS STRETCHING
NORTHEAST THROUGH THE GREAT LAKES REGION INTO WESTERN QUEBEC.

THIS SETUP IS IDEAL FOR THE DEVELOPMENT OF AN ATMOSPHERIC RIVER WITH
ABUNDANT LOW LEVEL MOISTURE AND EFFICIENT PRECIP PRODUCING
CONVECTION.

OPER GUIDANCE HAS BEEN RELATIVELY CONSISTENT WITH BRINGING A SERIES
OF WAVES ALONG THE SLOW MOVING FRONTAL BOUNDARY FRI AFTN/EVE...THEN
THE BOUNDARY SHOULD SLIDE EAST WITH WINDS QUICKLY VEERING
NORTH/NORTHEAST FOR SAT AND USHERING IN MUCH COOLER AIR TO THE
REGION.

CURRENT INDICATIONS ARE THAT HIGHS SAT MAY STRUGGLE TO WARM BEYOND
THE UPR 50S ACROSS NORTHEAST IL/NORTHWEST IN...WITH ONLY LOW 60S
ELSEWHERE. STRONG SFC RIDGE WILL REMAIN NORTH OF THE REGION...SO THE
PRIOR FRONTAL BOUNDARY MAY BECOME QUASI-STATIONARY FOR THE WEEKEND
ALONG THE OHIO VALLEY AND CONTINUE TO FEED PRECIP CHANCES TO THE
SOUTHERN CWFA.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 18Z...

* MVFR THIS AFTERNOON

* RAIN WITH EMBEDDED THUNDER POSSIBLE

* SOUTH WINDS VARYING FROM SOUTHEAST EARLY TO SOUTHWEST THIS
  EVENING.

* MVFR IN FOG AND LOW CLOUDS WEDNESDAY MORNING.

MM

//DISCUSSION...UPDATED 18Z...

LINE OF SHOWERS HAS DECREASED VSBYS TO 1 MILE UPSTREAM EARLY THIS
AFTERNOON. AS THE LINE PROGRESSES NORTHEASTWARD...COULD SEE SOME
STRONGER POCKETS OF RAIN AND TALLER EMBEDDED CELLS PRODUCE
ISOLATED LIGHTNING. LOW CHANCE/CONFIDENCE OF ANY OF THESE CELLS
HITTING THE TERMINALS...SO KEPT VCTS IN THE TAFS THROUGH 19Z.

LOOKING TOWARD WEDNESDAY MORNING...LOW LEVEL MOISTURE AND A WEAK
INVERSION WILL ALLOW A CHANCE FOR MVFR FOG AND CIGS TO WORK INTO
THE TERMINALS. THE AFTERNOON WILL FEATURE A SCATTERED TO POSSIBLY
BROKEN DECK AT 025. INTO THE EVENING...EXPECT OVERCAST CONDITIONS
WITH LIGHT RAIN POSSIBLE. THERE IS A CHANCE FOR THE LAKE BREEZE TO
WORK INTO ORD NEAR OR JUST AFTER 00Z WEDNESDAY EVENING.

MM

//ORD AND MDW CONFIDENCE...UPDATED 18Z...

* HIGH CONFIDENCE REMAINING MVFR THIS AFTERNOON.

* HIGH CONFIDENCE IN RAIN TIMING THIS AFTERNOON. LOW CONFIDENCE ON
  THUNDER CHANCES.

* MEDIUM TO HIGH CONFIDENCE IN WIND DIRECTION WITH HIGH CONFIDENCE
  IN WIND SPEED EXCEPT LOW CONFIDENCE IF THUNDERSTORMS OCCUR.

* LOW-MEDIUM CONFIDENCE IN FOG AND MVFR CONDITIONS WEDNESDAY
  MORNING.

*

MM

//OUTLOOK FOR ORD/MDW FOR 00Z THURSDAY-12Z TUESDAY...UPDATED 12Z...

WEDNESDAY NIGHT...WX NIL/VFR. SOUTHEAST WINDS.

THURSDAY...SLIGHT CHANCE OF TSRA AT NIGHT. SOUTHEAST WINDS.

FRIDAY...TSRA/SHRA LIKELY THROUGH THE DAY AND NIGHT. MVFR
POSSIBLE. SOUTHWEST WINDS.

SATURDAY...SHRA LIKELY WITH A CHANCE OF TSRA DURING THE DAY.
NORTHEAST WINDS.

SUNDAY...CHANCE OF SHRA. EAST WINDS. MVFR POSSIBLE.

MONDAY...CHANCE OF SHRA. SOUTHEAST WINDS. MVFR POSSIBLE.

KREIN

&&

.MARINE...
229 AM CDT

WARM MOIST AIR CONTINUES TO FEED NORTH ACROSS THE LAKE
TODAY...WHICH MAY HELP TO FURTHER ENHANCE ANY AREAS OF FOG THAT
HAVE ALREADY DEVELOPED. IT IS POSSIBLE PATCHY DENSE FOG MAY
DEVELOP...ALTHOUGH WINDS MAY BE JUST STRONG ENOUGH TO LIMIT THE
COVERAGE AND INTENSITY OF THE FOG. A SURFACE LOW PRESSURE SYSTEM
WILL BE LIFTING NORTH ACROSS EASTERN IOWA INTO CENTRAL WISCONSIN
THIS EVENING. THE GRADIENT WILL TIGHTEN ACROSS THE
CENTRAL/SOUTHERN PORTIONS OF THE LAKE...WHICH WITH WARMER
NEARSHORE WATERS EXPECT SOME SLIGHTLY BETTER MIXING TO OCCUR.
FURTHER OUT ACROSS THE OPEN WATERS THE WATER REMAINS COLD AND
EXPECT THE STABILITY TO MAKE IT DIFFICULT TO MIX TO THE SFC THE
HIGHER GUSTS. HIGH PRESSURE THEN ARRIVES LATE WEDNESDAY WITH LIGHT
WINDS DEVELOPING. THEN HIGH PRESSURE SHIFTS EAST THURSDAY
NIGHT...WITH SOUTHERLY WINDS DEVELOPING AGAIN FRIDAY. A FRONTAL
BOUNDARY WILL APPROACH LAKE MICHIGAN LATE FRIDAY NIGHT THEN
STEADILY SLIDE SOUTH ALONG THE LAKE. THIS WILL ALLOW WINDS TO
QUICKLY VEER FROM SOUTH TO NORTH/NORTHEAST SATURDAY. ALONG WITH
THIS QUICK WIND SHIFT WILL BE COOLER AIR SLIDING SOUTH OVER THE
LAKE. WAVES SHOULD EASILY BUILD SATURDAY FOR THE CENTRAL/SOUTHERN
PORTIONS OF THE LAKE.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 10 PM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 261953
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
253 PM CDT TUE MAY 26 2015

.SHORT TERM...
253 PM CDT

THROUGH WEDNESDAY...

A SURFACE LOW IS OVER NORTHEAST IA AND SW WI WITH A VORT MAX OVER
IOWA. THE LOWS COLD FRONT REMAINS A BIT FURTHER BACK OVER CENTRAL IA
AND EASTERN KS. THE LOW WILL DEEPEN SLIGHTLY AS IT MOVES OVER
CENTRAL WI AND ITS COLD FRONT SWINGS THROUGH WEDNESDAY. THE MAIN
CONCERN RIGHT NOW IS HOW MUCH CONVECTION WILL DEVELOP THIS
AFTERNOON.  THE LATEST RAP ANALYSIS SUGGESTS A RIBBON OF 1000 J/KG
OF CAPE IS OVER I-39...BUT THINKING THAT CAPE IN REALITY IS AROUND
500 J/KG DUE TO LIMITED HEATING. CAPE VALUES COULD RISE TO AROUND
1000 J/KG AS THERE ARE A FEW BREAKS IN THE CLOUDS...BUT THINKING IN
GENERAL THE BREAKS ARE MOVING TOO QUICKLY AND TOO FEW AND FAR BTWN
TO AMOUNT TO MUCH.  SHEAR VALUES REMAIN VERY FAVORABLE FOR ORGANIZED
STORMS WITH VALUES AROUND 35-40 KT.

THEREFORE EXPECTING SCATTERED SHOWER/TS DEVELOPMENT THIS AFTN IN THE
WAKE OF THE LINE OF SHOWERS THAT IS SHIFTING EAST ACROSS INDIANA
RIGHT NOW.  A SECOND SKINNY LINE OF CONVECTION LIES FROM DIXON IL TO
JERSEYVILLE IL WITH A FEW ADDITIONAL CELLS OUT AHEAD OF IT. DUE TO
LIMITED CAPE AS DISCUSSED ABOVE...THE STRONGER CELLS MAY PRODUCE
DAMAGING WINDS. WINDS HAVE VEERED TO THE SW AND HELICITY IS MUCH
LOWER SO NOT AS CONCERNED ABOUT ISOLATED TORNADOES AS I WAS THIS
MORNING.  PWAT VALUES REMAIN VERY IMPRESSIVE AT 1.4-1.7 INCHES SO
ANY OF THE NEW SHOWERS WILL BE CAPABLE OF ADDITIONAL HEAVY DOWNPOURS.

THE AREA OF SCATTERED SHOWERS AND STORMS SHIFTS EAST OF THE CWA THIS
EVENING...BUT WE ARE NOT DONE YET. ANOTHER ROUND OF SHOWERS AND
PERHAPS OF THUNDERSTORMS MAY FORM THIS EVENING AS THE VORT MAX
APPROACHES. THINKING THE COVERAGE WILL BE BEST ALONG AND WEST OF
GARY INDIANA TO PAXTON IL LINE. HAVE LOW CONFIDENCE IN COVERAGE AND
TIMING OF THIS ROUND OF SHOWERS...BUT NOT EXPECTING MUCH THUNDER AND
NO SEVERE WEATHER.  DEWPOINTS REMAIN IN THE 60S TONIGHT SO THINKING
WE WILL NOT COOL MUCH...SO KEPT LOWS IN THE LOW TO MID 60S.

THE PATTERN REMAINS MESSY TOMORROW BUT NOT AS ACTIVE.  A PAIR OF
VORT STREAMERS AND THE LOWS COLD FRONT ROTATE THROUGH AND SHOWERS
AND STORMS MAY FORM ALONG THEM.  THE FIRST IS ASSOCIATED WITH THE
UPPER LEVEL LOW SHIFTING NE INTO ONTARIO TOMORROW. SHOWERS AND
STORMS WITH THIS VORT STREAMER WOULD CLIP THE NORTHERN CWA...NORTH
OF I-88.  PRECIP MAY SINK SOUTH ACROSS DUPAGE AND COOK COUNTIES IN
THE AFTN...BUT HAVE LOW CONFIDENCE IN HOW FAR SOUTH THE PRECIP WILL
GET.

CLOUD COVER SHIFTS EAST THROUGH THE AFTERNOON WITH AREAS WEST OF I-
55 BECOMING MOSTLY SUNNY BY MID AFTN. DID NOT MAKE TOO MANY CHANGES
TO HIGH TEMPS TOMORROW AS CLOUD COVER WILL PLAY A ROLE.  HAVE TEMPS
IN THE UPPER 70S TO LOW 80S.  A LAKE BREEZE IS POSSIBLE LATE IN THE
AFTN AND EVENING SO EXPECTING LAKE COOLING ESPECIALLY AT WAUKEGAN.

JEE

&&

.LONG TERM...
229 AM CDT

WEDNESDAY THROUGH MONDAY...

WEDNESDAY THROUGH THURSDAY...
OPEN 500MB WAVE WILL BE LIFTING NORTHEAST ACROSS THE UPPER MIDWEST
INTO ONTARIO AND EVENTUALLY QUEBEC...WITH HEIGHTS SLOWLY INCREASING
WED AFTN. SFC FEATURES REMAIN DISORGANIZED WED...WITH A BOUNDARY
SLOWLY SHIFTING EAST. OPER GUIDANCE DIFFERS ON HOW QUICKLY PRECIP
WILL DEPART THE REGION. ENSEMBLE DATA SUGGESTS HOLDING ONTO CHC TO
SLIGHT CHC POPS MAINLY FOR THE CENTRAL/EASTERN CWFA WED/WED EVE.
ALTHOUGH WITH SOME HINT OF SFC HEIGHTS NUDGING UP...IT IS POSSIBLE
THAT SOME DRY AIR COULD FILTER IN AND KICK PRECIP EAST BY MIDDAY AND
ALLOW FOR A MAINLY DRY WED. SFC WINDS WILL BE TURNING SOUTHWEST TO
WEST...KEEPING AN OFFSHORE FLOW FOR LOCATIONS CLOSE TO LAKE
MICHIGAN. TEMPS SHOULD YET AGAIN TOUCH UPR 70S TO ARND 80 WED...IF
CLOUDS AND PRECIP CAN PUSH EAST BY MIDDAY...SOME CLEARING WOULD
ALLOW SFC TEMPS TO PUSH A COUPLE DEGREES WARMER INTO THE LOW 80S IN
SOME LOCATIONS. LATE IN THE EVENING THE GRADIENT SLACKENS
FURTHER...AND COULD ALLOW A LATE DAY ONSHORE FLOW TO DEVELOP FOR
AREAS ADJACENT TO LAKE MICHIGAN.

MID-LVL FLOW BEGINS TO FLATTEN AS A WEAK SFC RIDGE BECOMES ORIENTED
FROM WESTERN QUEBEC SOUTH THROUGH THE EASTERN OHIO RIVER VALLEY.
THIS WILL GENERALLY ALLOW A SOUTHERLY FLOW...ALTHOUGH THE GRADIENT
IS NOT VERY STRONG. THIS SHOULD SET THE STAGE FOR A LAKE
BREEZE/ONSHORE FLOW TO DEVELOP THUR. TIMING COULD END UP BEING
SLIGHTLY EARLIER GIVEN THE LIGHT SFC GRADIENT. GUIDANCE HAS BEEN
CONSISTENT IN HOLDING PRECIP WEST/SOUTH OF THE FORECAST AREA
THUR...AS A RESULT OF THE WEAK SFC RIDGING. SO ONE MORE MILD DAY
WITH HIGHS WARMING BACK INTO THE UPR 70S/LOW 80S...HOWEVER AS
PREVIOUSLY NOTED...A LAKE BREEZE IS LIKELY TO DEVELOP. THIS WILL
BLEED THE MUCH COOLER MARINE AIR WEST ACROSS NORTHEAST IL AND
DOWNTOWN CHICAGO. IF THE TIMING IS EARLIER IN THE DAY THUR...TEMPS
MAY NOT WARM BEYOND THE LOW/MID 60S ALONG THE CHICAGO LAKEFRONT.

FLOW THEN TURNS SOUTHERLY THUR NIGHT WITH THE MORE PROGRESSIVE FLOW
IN THE MID-LVLS PUSHING THE RIDGING EAST. A RETURN FLOW MOISTURE
WILL CONTINUE TO BE FOCUSED ACROSS THE CENTRAL CONUS THUR EVE...WITH
A SLOW MOVING FRONTAL BOUNDARY NUDGING EAST THUR NIGHT TOWARDS
WESTERN IL. THIS FRONTAL BOUNDARY WILL BECOME ENERGIZED AS A ROBUST
500MB VORT MAX BREAKS SOUTH FROM CENTRAL CANADA LATE THUR NIGHT.

THIS SHOULD ALLOW FOR AN ATMOSPHERIC RIVER TO DEVELOP FROM THE
SOUTHERN PLAINS STRETCHING NORTH THROUGH THE MID-MISSOURI VALLEY
INTO THE WESTERN GREAT LAKES EARLY FRI MORNING.

FRIDAY THROUGH EARLY NEXT WEEK...
ENSEMBLES CONTINUE TO PROG A ROBUST TROUGH SLIDING SOUTH FROM
CENTRAL CANADA FRI. THIS COUPLED WITH DOWNSTREAM MID-LVL RIDGING
ACROSS THE SOUTHEAST CONUS WILL STRENGTHEN THE FRONTAL BOUNDARY
THAT WILL BE ORIENTED FROM THE SOUTHERN PLAINS STRETCHING
NORTHEAST THROUGH THE GREAT LAKES REGION INTO WESTERN QUEBEC.

THIS SETUP IS IDEAL FOR THE DEVELOPMENT OF AN ATMOSPHERIC RIVER WITH
ABUNDANT LOW LEVEL MOISTURE AND EFFICIENT PRECIP PRODUCING
CONVECTION.

OPER GUIDANCE HAS BEEN RELATIVELY CONSISTENT WITH BRINGING A SERIES
OF WAVES ALONG THE SLOW MOVING FRONTAL BOUNDARY FRI AFTN/EVE...THEN
THE BOUNDARY SHOULD SLIDE EAST WITH WINDS QUICKLY VEERING
NORTH/NORTHEAST FOR SAT AND USHERING IN MUCH COOLER AIR TO THE
REGION.

CURRENT INDICATIONS ARE THAT HIGHS SAT MAY STRUGGLE TO WARM BEYOND
THE UPR 50S ACROSS NORTHEAST IL/NORTHWEST IN...WITH ONLY LOW 60S
ELSEWHERE. STRONG SFC RIDGE WILL REMAIN NORTH OF THE REGION...SO THE
PRIOR FRONTAL BOUNDARY MAY BECOME QUASI-STATIONARY FOR THE WEEKEND
ALONG THE OHIO VALLEY AND CONTINUE TO FEED PRECIP CHANCES TO THE
SOUTHERN CWFA.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 18Z...

* MVFR THIS AFTERNOON

* RAIN WITH EMBEDDED THUNDER POSSIBLE

* SOUTH WINDS VARYING FROM SOUTHEAST EARLY TO SOUTHWEST THIS
  EVENING.

* MVFR IN FOG AND LOW CLOUDS WEDNESDAY MORNING.

MM

//DISCUSSION...UPDATED 18Z...

LINE OF SHOWERS HAS DECREASED VSBYS TO 1 MILE UPSTREAM EARLY THIS
AFTERNOON. AS THE LINE PROGRESSES NORTHEASTWARD...COULD SEE SOME
STRONGER POCKETS OF RAIN AND TALLER EMBEDDED CELLS PRODUCE
ISOLATED LIGHTNING. LOW CHANCE/CONFIDENCE OF ANY OF THESE CELLS
HITTING THE TERMINALS...SO KEPT VCTS IN THE TAFS THROUGH 19Z.

LOOKING TOWARD WEDNESDAY MORNING...LOW LEVEL MOISTURE AND A WEAK
INVERSION WILL ALLOW A CHANCE FOR MVFR FOG AND CIGS TO WORK INTO
THE TERMINALS. THE AFTERNOON WILL FEATURE A SCATTERED TO POSSIBLY
BROKEN DECK AT 025. INTO THE EVENING...EXPECT OVERCAST CONDITIONS
WITH LIGHT RAIN POSSIBLE. THERE IS A CHANCE FOR THE LAKE BREEZE TO
WORK INTO ORD NEAR OR JUST AFTER 00Z WEDNESDAY EVENING.

MM

//ORD AND MDW CONFIDENCE...UPDATED 18Z...

* HIGH CONFIDENCE REMAINING MVFR THIS AFTERNOON.

* HIGH CONFIDENCE IN RAIN TIMING THIS AFTERNOON. LOW CONFIDENCE ON
  THUNDER CHANCES.

* MEDIUM TO HIGH CONFIDENCE IN WIND DIRECTION WITH HIGH CONFIDENCE
  IN WIND SPEED EXCEPT LOW CONFIDENCE IF THUNDERSTORMS OCCUR.

* LOW-MEDIUM CONFIDENCE IN FOG AND MVFR CONDITIONS WEDNESDAY
  MORNING.

*

MM

//OUTLOOK FOR ORD/MDW FOR 00Z THURSDAY-12Z TUESDAY...UPDATED 12Z...

WEDNESDAY NIGHT...WX NIL/VFR. SOUTHEAST WINDS.

THURSDAY...SLIGHT CHANCE OF TSRA AT NIGHT. SOUTHEAST WINDS.

FRIDAY...TSRA/SHRA LIKELY THROUGH THE DAY AND NIGHT. MVFR
POSSIBLE. SOUTHWEST WINDS.

SATURDAY...SHRA LIKELY WITH A CHANCE OF TSRA DURING THE DAY.
NORTHEAST WINDS.

SUNDAY...CHANCE OF SHRA. EAST WINDS. MVFR POSSIBLE.

MONDAY...CHANCE OF SHRA. SOUTHEAST WINDS. MVFR POSSIBLE.

KREIN

&&

.MARINE...
229 AM CDT

WARM MOIST AIR CONTINUES TO FEED NORTH ACROSS THE LAKE
TODAY...WHICH MAY HELP TO FURTHER ENHANCE ANY AREAS OF FOG THAT
HAVE ALREADY DEVELOPED. IT IS POSSIBLE PATCHY DENSE FOG MAY
DEVELOP...ALTHOUGH WINDS MAY BE JUST STRONG ENOUGH TO LIMIT THE
COVERAGE AND INTENSITY OF THE FOG. A SURFACE LOW PRESSURE SYSTEM
WILL BE LIFTING NORTH ACROSS EASTERN IOWA INTO CENTRAL WISCONSIN
THIS EVENING. THE GRADIENT WILL TIGHTEN ACROSS THE
CENTRAL/SOUTHERN PORTIONS OF THE LAKE...WHICH WITH WARMER
NEARSHORE WATERS EXPECT SOME SLIGHTLY BETTER MIXING TO OCCUR.
FURTHER OUT ACROSS THE OPEN WATERS THE WATER REMAINS COLD AND
EXPECT THE STABILITY TO MAKE IT DIFFICULT TO MIX TO THE SFC THE
HIGHER GUSTS. HIGH PRESSURE THEN ARRIVES LATE WEDNESDAY WITH LIGHT
WINDS DEVELOPING. THEN HIGH PRESSURE SHIFTS EAST THURSDAY
NIGHT...WITH SOUTHERLY WINDS DEVELOPING AGAIN FRIDAY. A FRONTAL
BOUNDARY WILL APPROACH LAKE MICHIGAN LATE FRIDAY NIGHT THEN
STEADILY SLIDE SOUTH ALONG THE LAKE. THIS WILL ALLOW WINDS TO
QUICKLY VEER FROM SOUTH TO NORTH/NORTHEAST SATURDAY. ALONG WITH
THIS QUICK WIND SHIFT WILL BE COOLER AIR SLIDING SOUTH OVER THE
LAKE. WAVES SHOULD EASILY BUILD SATURDAY FOR THE CENTRAL/SOUTHERN
PORTIONS OF THE LAKE.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 10 PM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KILX 261740
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1240 PM CDT TUE MAY 26 2015

.UPDATE...
ISSUED AT 1038 AM CDT TUE MAY 26 2015

MADE A FEW UPDATES TO POPS/WEATHER AND HOURLY TEMPS FOR TODAY
BASED ON TRENDS OF CURRENT CONVECTION MOVING THROUGH CENTRAL IL
LATE THIS MORNING INTO EAST CENTRAL IL BY THE NOON HOUR. A GENERAL
WEAKENING TREND HAS BEEN NOTED THE PAST HOUR, SO ONLY A BRIEF
HEAVY DOWNPOUR IS ANTICIPATED WITH THE LINE OF SHOWERS-ISOLATED
THUNDERSTORMS.

A VERY BRIEF PERIOD OF PARTIAL CLEARING IS ANTICIPATED AFTER THE
SHOWERS MOVE THROUGH, WHICH MAY HELP TO SLIGHTLY INCREASE THE
INSTABILITY IN CENTRAL AND EASTERN IL THIS AFTERNOON. HOWEVER,
SATELLITE IS SHOWING THAT CUMULUS WILL MOST LIKELY RAPIDLY FILL
IN. THE HRRR, NAM12 AND RAP ALL SEEM TO HAVE A FAIRLY GOOD HANDLE
ON THE WEAKENING TREND OF THE LINE OF CONVECTION, WITH SCATTERED
SHOWERS AND THUNDERSTORMS REDEVELOPING THIS AFTERNOON. A SHORTWAVE
TROUGH MOVING NORTHEAST FROM THE OZARKS WILL PROVIDE UPPER LEVEL
SUPPORT TO SOUTHEAST AND EAST CENTRAL IL, BUT INSTABILITY WILL BE
MARGINAL AT BEST. THUS, STRONG/SEVERE STORMS SHOULD BE QUITE
LIMITED IN COVERAGE, IF THEY DEVELOP AT ALL.

&&

.SHORT TERM...(TODAY)
ISSUED AT 343 AM CDT TUE MAY 26 2015

LOW CLOUDS HAVE BEEN ADVECTING INTO THE AREA AND WILL REMAIN OVER
THE AREA THIS MORNING. LOWER CLOUDS INDICATING LOTS OF LOW LEVEL
MOISTURE BEING ADVECTED INTO THE AREA AHEAD OF THE WEATHER SYSTEM
THAT STILL IS WEST OF THE CWA. RADAR AND SATELLITE LOOPS SHOW
SEVERAL MCVS WEST OF THE AREA WITH SOME SHOWERS MOVING NORTH THROUGH
SOUTHEASTERN MO. MODELS CONTINUE TO INDICATE PCPN REDEVELOPING
TODAY. CLOUDS WILL LIMIT THE DEGREE OF INSTABILITY BUT STILL
EXPECTING ENOUGH FOR THUNDERSTORMS, JUST NOT ENOUGH FOR ANYTHING
SEVERE, WHICH SHOULD BE EAST AND SOUTHEAST OF THE AREA WHERE LESS
CLOUDS WILL BE. CLOUD COVER WILL ALSO TEMPER WARM UP AS WELL SO ONLY
EXPECTING UPPER 70S FOR HIGHS WHICH IS MUCH LESS THAN PAST TWO DAYS.
POPS WILL BE A GRADUAL INCREASE TODAY REACHING LIKELY LATER THIS
MORNING AND THEN MOVING NORTH AND EAST THIS AFTERNOON, BECOMING
CHANCE CATEGORY BY LATE AFTERNOON AS THE PCPN MOVES EAST OF THE
AREA. SOUTHERLY WINDS WILL BE A TAD GUSTY AGAIN, JUST NOT AS MUCH AS
YESTERDAY.

.LONG TERM...(TONIGHT THROUGH MONDAY)
ISSUED AT 343 AM CDT TUE MAY 26 2015

UNTIL THE UPPER WAVE PULLS INTO THE GREAT LAKES REGION, LINGERING
POPS WILL REMAIN OVER THE FA FOR THIS EVENING.  BETTER CHANCES WILL
REMAIN TO THE EAST OVERNIGHT. REMAINS OF THE FRONT WILL STALL OUT
ALONG THE OHIO RIVER VALLEY AND PROVIDE A BIT OF FOCUS FOR ANOTHER
PIECE OF ENERGY EJECTING OUT OF THE SOUTHWEST.  MODELS DIFFERING
WITH THE NORTHERLY EXTENT OF THE PRECIP, BUT LAST FEW RUNS BRINGING
IN SOME PRECIPITATION FOR WEDNESDAY IN THE SOUTHEAST.  NAM IS A
LITTLE MORE WIDESPREAD, BUT CONCENTRATING THE POPS TO THE SOUTH AND
EAST FOR NOW.  TIMING ISSUES REMAIN IN PLACE FOR THIS SYNOPTIC RUN
FOR THE NEXT SYSTEM QUICK ON THE HEELS AS THE DEEP WAVE OVER THE SW
STARTS TO MOVE OUT INTO THE PLAINS. CONVECTION AND PRECIP STARTS TO
SPREAD OVER THE EASTERN HALF OF THE COUNTRY IN THE MODELS WITH  WEAK
SOUTHWESTERLY FLOW ALOFT SHIFTING TO WEAK FLOW OVERALL.  WARM AND
MUGGY CONDITIONS CONTINUE IN A MORE SUMMERLIKE AIRMASS THROUGHOUT
THE WEEK...BUT THAT NEXT SYSTEM WILL BRING A COLD FRONT INTO THE
REGION FOR THE FIRST HALF OF THE WEEKEND TO FOCUS THE RAIN, WITH A
COOLER AIRMASS BEHIND IT DROPPING THE TEMPS FOR THE WEEKEND OUT OF
THE 80S FOR A COUPLE DAYS.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z WEDNESDAY AFTERNOON)
ISSUED AT 1240 PM CDT TUE MAY 26 2015

PERIODS OF SHOWERS AND ISOLATED THUNDERSTORMS CAN BE EXPECTED AT
TIMES THE NEXT 12-15 HOURS, BETWEEN 18Z AND 08Z, ACROSS CENTRAL
AND EASTERN IL.

THE LATEST HRRR REFLECTIVITY FORECAST HAD A PRETTY GOOD HANDLE ON
THE LOW TOPPED CONVECTION THAT HAS FIRED UP IN THE MS RIVER VALLEY
AROUND THE NOON HOUR. THIS IS EXPECTED TO MOVE INTO CENTRAL IL
FROM 19-21Z AND THEN EASTERN IL FROM 21-23Z. GENERALLY VFR
CONDITIONS ARE ANTICIPATED, BUT WOULD ANTICIPATE MVFR FOR A VERY
SHORT PERIOD OF TIME DURING ANY HEAVY DOWNPOURS.

AFTER A BRIEF BREAK IN CONVECTION EARLY THIS EVENING, THE MAIN
COLD FRONT IS EXPECTED TO MOVE TOWARD CENTRAL IL JUST AFTER
SUNSET. THIS WILL RESULT IN MORE SCATTERED SHOWERS. DECIDED NOT TO
INCLUDE ANY MENTION OF THUNDER AT THIS POINT SINCE INSTABILITY IS
EXPECTED TO BE QUITE LIMITED. AFTER THE FRONTAL PASSAGE THE WIND
IS EXPECTED TO GRADUALLY SHIFT FROM SW TO WSW. THIS WILL ALSO BE
ACCOMPANIED BY VFR CEILINGS/STRATOCUMULUS CLOUDS WRAPPING AROUND
THE LOW LEVEL CYCLONIC FLOW THROUGH MUCH OF WEDNESDAY MORNING.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...MILLER
SHORT TERM...AUTEN
LONG TERM...HJS
AVIATION...MILLER




000
FXUS63 KILX 261740
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1240 PM CDT TUE MAY 26 2015

.UPDATE...
ISSUED AT 1038 AM CDT TUE MAY 26 2015

MADE A FEW UPDATES TO POPS/WEATHER AND HOURLY TEMPS FOR TODAY
BASED ON TRENDS OF CURRENT CONVECTION MOVING THROUGH CENTRAL IL
LATE THIS MORNING INTO EAST CENTRAL IL BY THE NOON HOUR. A GENERAL
WEAKENING TREND HAS BEEN NOTED THE PAST HOUR, SO ONLY A BRIEF
HEAVY DOWNPOUR IS ANTICIPATED WITH THE LINE OF SHOWERS-ISOLATED
THUNDERSTORMS.

A VERY BRIEF PERIOD OF PARTIAL CLEARING IS ANTICIPATED AFTER THE
SHOWERS MOVE THROUGH, WHICH MAY HELP TO SLIGHTLY INCREASE THE
INSTABILITY IN CENTRAL AND EASTERN IL THIS AFTERNOON. HOWEVER,
SATELLITE IS SHOWING THAT CUMULUS WILL MOST LIKELY RAPIDLY FILL
IN. THE HRRR, NAM12 AND RAP ALL SEEM TO HAVE A FAIRLY GOOD HANDLE
ON THE WEAKENING TREND OF THE LINE OF CONVECTION, WITH SCATTERED
SHOWERS AND THUNDERSTORMS REDEVELOPING THIS AFTERNOON. A SHORTWAVE
TROUGH MOVING NORTHEAST FROM THE OZARKS WILL PROVIDE UPPER LEVEL
SUPPORT TO SOUTHEAST AND EAST CENTRAL IL, BUT INSTABILITY WILL BE
MARGINAL AT BEST. THUS, STRONG/SEVERE STORMS SHOULD BE QUITE
LIMITED IN COVERAGE, IF THEY DEVELOP AT ALL.

&&

.SHORT TERM...(TODAY)
ISSUED AT 343 AM CDT TUE MAY 26 2015

LOW CLOUDS HAVE BEEN ADVECTING INTO THE AREA AND WILL REMAIN OVER
THE AREA THIS MORNING. LOWER CLOUDS INDICATING LOTS OF LOW LEVEL
MOISTURE BEING ADVECTED INTO THE AREA AHEAD OF THE WEATHER SYSTEM
THAT STILL IS WEST OF THE CWA. RADAR AND SATELLITE LOOPS SHOW
SEVERAL MCVS WEST OF THE AREA WITH SOME SHOWERS MOVING NORTH THROUGH
SOUTHEASTERN MO. MODELS CONTINUE TO INDICATE PCPN REDEVELOPING
TODAY. CLOUDS WILL LIMIT THE DEGREE OF INSTABILITY BUT STILL
EXPECTING ENOUGH FOR THUNDERSTORMS, JUST NOT ENOUGH FOR ANYTHING
SEVERE, WHICH SHOULD BE EAST AND SOUTHEAST OF THE AREA WHERE LESS
CLOUDS WILL BE. CLOUD COVER WILL ALSO TEMPER WARM UP AS WELL SO ONLY
EXPECTING UPPER 70S FOR HIGHS WHICH IS MUCH LESS THAN PAST TWO DAYS.
POPS WILL BE A GRADUAL INCREASE TODAY REACHING LIKELY LATER THIS
MORNING AND THEN MOVING NORTH AND EAST THIS AFTERNOON, BECOMING
CHANCE CATEGORY BY LATE AFTERNOON AS THE PCPN MOVES EAST OF THE
AREA. SOUTHERLY WINDS WILL BE A TAD GUSTY AGAIN, JUST NOT AS MUCH AS
YESTERDAY.

.LONG TERM...(TONIGHT THROUGH MONDAY)
ISSUED AT 343 AM CDT TUE MAY 26 2015

UNTIL THE UPPER WAVE PULLS INTO THE GREAT LAKES REGION, LINGERING
POPS WILL REMAIN OVER THE FA FOR THIS EVENING.  BETTER CHANCES WILL
REMAIN TO THE EAST OVERNIGHT. REMAINS OF THE FRONT WILL STALL OUT
ALONG THE OHIO RIVER VALLEY AND PROVIDE A BIT OF FOCUS FOR ANOTHER
PIECE OF ENERGY EJECTING OUT OF THE SOUTHWEST.  MODELS DIFFERING
WITH THE NORTHERLY EXTENT OF THE PRECIP, BUT LAST FEW RUNS BRINGING
IN SOME PRECIPITATION FOR WEDNESDAY IN THE SOUTHEAST.  NAM IS A
LITTLE MORE WIDESPREAD, BUT CONCENTRATING THE POPS TO THE SOUTH AND
EAST FOR NOW.  TIMING ISSUES REMAIN IN PLACE FOR THIS SYNOPTIC RUN
FOR THE NEXT SYSTEM QUICK ON THE HEELS AS THE DEEP WAVE OVER THE SW
STARTS TO MOVE OUT INTO THE PLAINS. CONVECTION AND PRECIP STARTS TO
SPREAD OVER THE EASTERN HALF OF THE COUNTRY IN THE MODELS WITH  WEAK
SOUTHWESTERLY FLOW ALOFT SHIFTING TO WEAK FLOW OVERALL.  WARM AND
MUGGY CONDITIONS CONTINUE IN A MORE SUMMERLIKE AIRMASS THROUGHOUT
THE WEEK...BUT THAT NEXT SYSTEM WILL BRING A COLD FRONT INTO THE
REGION FOR THE FIRST HALF OF THE WEEKEND TO FOCUS THE RAIN, WITH A
COOLER AIRMASS BEHIND IT DROPPING THE TEMPS FOR THE WEEKEND OUT OF
THE 80S FOR A COUPLE DAYS.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z WEDNESDAY AFTERNOON)
ISSUED AT 1240 PM CDT TUE MAY 26 2015

PERIODS OF SHOWERS AND ISOLATED THUNDERSTORMS CAN BE EXPECTED AT
TIMES THE NEXT 12-15 HOURS, BETWEEN 18Z AND 08Z, ACROSS CENTRAL
AND EASTERN IL.

THE LATEST HRRR REFLECTIVITY FORECAST HAD A PRETTY GOOD HANDLE ON
THE LOW TOPPED CONVECTION THAT HAS FIRED UP IN THE MS RIVER VALLEY
AROUND THE NOON HOUR. THIS IS EXPECTED TO MOVE INTO CENTRAL IL
FROM 19-21Z AND THEN EASTERN IL FROM 21-23Z. GENERALLY VFR
CONDITIONS ARE ANTICIPATED, BUT WOULD ANTICIPATE MVFR FOR A VERY
SHORT PERIOD OF TIME DURING ANY HEAVY DOWNPOURS.

AFTER A BRIEF BREAK IN CONVECTION EARLY THIS EVENING, THE MAIN
COLD FRONT IS EXPECTED TO MOVE TOWARD CENTRAL IL JUST AFTER
SUNSET. THIS WILL RESULT IN MORE SCATTERED SHOWERS. DECIDED NOT TO
INCLUDE ANY MENTION OF THUNDER AT THIS POINT SINCE INSTABILITY IS
EXPECTED TO BE QUITE LIMITED. AFTER THE FRONTAL PASSAGE THE WIND
IS EXPECTED TO GRADUALLY SHIFT FROM SW TO WSW. THIS WILL ALSO BE
ACCOMPANIED BY VFR CEILINGS/STRATOCUMULUS CLOUDS WRAPPING AROUND
THE LOW LEVEL CYCLONIC FLOW THROUGH MUCH OF WEDNESDAY MORNING.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...MILLER
SHORT TERM...AUTEN
LONG TERM...HJS
AVIATION...MILLER



000
FXUS63 KLOT 261732
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1232 PM CDT TUE MAY 26 2015

.UPDATE...
1007 AM CDT

A SFC LOW IS OVER IOWA AND ITS WARM/STATIONARY FRONT IS WELL TO
OUR NORTH OVER CENTRAL WI. ITS COLD FRONT STRETCHES FROM THE LOW
THROUGH CENTRAL KANSAS. AN AREA OF MAINLY RAIN AND A FEW
THUNDERSTORMS IS SLOWLY SPREADING NNE ACROSS NORTH CENTRAL IL. SO
FAR THE SHOWERS HAVE BEEN BEHAVING ACROSS MY CWA...BUT A FEW CELLS
TO THE WEST HAVE SHOWN SIGNS OF ROTATION.

LIKING THE LATEST RAP GUIDANCE WHICH KEEPS CAPE VALUES ON THE LOW
SIDE WITH ONLY A FEW HUNDREDS J/KG OF CAPE TO WORK WITH. THIS IS
ASSUMING SKIES STAY OVERCAST...AND THINKING WE WILL BE OVERCAST
TODAY. THAT BEING SAID...ANY LOCATIONS THAT SEE SUNSHINE COULD
DEVELOP ENOUGH CAPE TO SUPPORT TALLER CELLS AND POSSIBLY SEVERE
WEATHER. IN GENERAL THINKING DAMAGING WINDS AND AN ISOLATED
TORNADO ARE THE MAIN THREATS...BUT STRONGER STORMS WITH HIGHER
CAPE VALUES COULD SUPPORT HAIL. RADAR IMAGERY IS SHOWING GRAVITY
WAVE TAGS MOVING ALONG THE LINE OF STORMS AND WHEN THE TAGS
INTERSECT THE LINE...STORMS BEGIN TO SPIN. THEREFORE THE TORNADO
THREAT IS NOT ZERO.

THIS FIRST BATCH OF PRECIP WILL PUSH EAST THROUGH THE EARLY AFTN
HOURS AND EXPECTING ADDITIONAL SCATTERED TO NUMEROUS THUNDERSTORMS
DEVELOPMENT BEHIND THE LINE OVER NORTH CENTRAL IL. THE SECOND
WAVE SHIFTS EAST THROUGH THE EARLY EVENING HOURS. PWAT VALUES ARE
1.2-1.5 INCHES SO HEAVY DOWNPOURS ARE PSBL.

JEE

&&

.SHORT TERM...
319 AM CDT

THROUGH TUESDAY NIGHT...

FOR THE REMAINDER OF THE OVERNIGHT HOURS...CONDITIONS WILL REMAIN
QUIET ACROSS THE CWA AS A SERIES OF SHORT WAVES CONTINUE TO TRACK
NORTH AROUND THE TOP OF A PERSISTENT UPPER LEVEL RIDGE WHICH EXTENDS
FROM THE SERN CONUS THROUGH THE UPPER MISSISSIPPI VALLEY.  THIS
UPPER RIDGE HAS BEEN THE FEATURE WHICH HAS CONTROLLED THE PATH OF
THE SERIES OF SHORTWAVES LIFTING OUT OF THE SOUTHERN PLAINS...AND
WILL CONTINUE TO DO SO THROUGH THE DAY TODAY. SLY...MODERATELY
STRONG...WINDS WILL PERSIST THROUGH THE NIGHT...AND MUCH OF THE DAY
ALLOWING FOR SFC DEWPOINTS TO REMAIN CONSISTENT OR POSSIBLE INCH A
LITTLE HIGHER.

MAIN CONCERN FOR THE MORNING HOURS WILL BE THE TRACK OF A STRONG
SHORT WAVE AND ASSOCIATED SFC LOW LIFTING NORTHWARD THROUGH THE
MIDDLE MISSISSIPPI VALLEY.  THIS FEATURE WILL PREDOMINANTLY IMPACT
ERN IOWA AND WRN IL BY ARND DAYBREAK.  THROUGH THE MORNING...THE
COMBINATION OF ISENTROPIC LIFT IN THE WARM SECTOR OF THE
SYSTEM...ALL OF IL AND INTO NWRN IN...WILL LEAD TO SOME
DESTABILIZATION ACROSS THE REGION. A SFC TROUGH...AS WELL INDICATED
BY THE LATEST HIGH RES GUIDANCE...WITH LIFT THROUGH NRN IL/IN
THROUGH THE DAY...COINCIDENT WITH A STRONG SSWLY LOW LEVEL JET OF 45-
50 KT...WITH PROVIDE THE POTENTIAL FOR SHOWERS AND STRONG TO SEVERE
THUNDERSTORMS ACROSS THE CWA.  BASED ON WIND PROFILES AND MID LEVEL
DRYING...THE PRIMARY CONCERN WITH REGARD TO SEVERE WEATHER WILL BE
STRONG WIND GUSTS.  HOWEVER...SOME OF THE HIGH RES SFC WIND GUIDANCE
SUGGEST SOME SLIGHT BACKING OF SFC WINDS FROM 180-190 DEGREES TO 160-
170 DEGREES...WHILE WINDS ALOFT REMAIN SWLY.  THIS SLIGHT BACKING OF
THE SFC WINDS COULD PROVIDE ENOUGH DIRECTIONAL SHEAR THROUGH THE
LOWER LEVELS TO BRING AN ISOLD TORNADO THREAT. LOCALLY HEAVY
RAINFALL WILL ALSO BE CONCERNED WITH PWATS REACHING 1.75 INCHES
LATER THIS MORNING.  HOWEVER...FLOODING WILL LIKELY NOT BE A
SIGNIFICANT CONCERN AS THE SWLY WINDS RIGHT OFF THE DECK WILL RANGE
FROM ARND 45 KT ABOVE THE BOUNDARY LAYER TO ARND 90KT AT UPPER
LEVELS WHICH SHOULD ALLOW ANY OF THE STRONGER STORMS THAT DO DEVELOP
TO MOVE QUICKLY.

BY EARLY AFTERNOON...THE MAIN SHORT WAVE WILL LIFT INTO WISCONSIN
WHILE A SFC TROUGH TRACKS EAST ACROSS THE AREA.  THIS WILL LEAD TO
WINDS AT THE SFC VEERING TO SWLY...SETTING UP A UNIDIRECTIONAL WIND
PROFILE...EFFECTIVELY MINIMIZING THE SEVERE WEATHER THREAT TO THE
REGION.  BY LATE AFTERNOON AND INTO THE EVENING THE MODELS ARE
ADVERTISING THAT A DRY SLOW SHOULD NOSE INTO NRN IL...EFFECTIVELY
CUTTING OFF THE PCPN AREA INTO 2 SEPARATE AREA...ONE OVER WISCONSIN
AND ERN IOWA AND ANOTHER MORE FOCUSED OVER INDIANA.  THE NWRN
INDIANA COUNTIES WILL STILL HAVE A CHANCE FOR SOME SHOWERS AND
THUNDERSTORMS INTO THE EVENING...WHILE PCPN CHANCES OVER NRN IL
BEGIN TO WANE.  MUCH OF THE MODEL GUIDANCE ALSO INDICATED THAT THE
SHORTWAVE SHOULD SLOW IT`S PROGRESSION THROUGH WISCONSIN AS IT
APPROACHES THE APEX OF THE UPPER RIDGE.  AN ASSOCIATED SFC
TROUGH/COLD FRONT EXTENDING SOUTHWEST FROM THE SFC LOW WILL LINGER
OVER ERN IOWA IN THE EARLY EVENING BEFORE STEADILY PUSHING ACROSS
NRN IL AND INTO NWRN IN OVERNIGHT.  THROUGH THE NIGHT...THE
STRONGEST UPPER LEVEL FORCING WILL BE WELL NORTH OF THE CWA...SO ANY
LINGERING CHANCES FOR PCPN OVERNIGHT WILL BE LOW AND LIKELY CONFINED
TO THE NRN TIER COUNTIES OF IL...ALONG THE WI BORDER.

KREIN

&&

.LONG TERM...
229 AM CDT

WEDNESDAY THROUGH MONDAY...

WEDNESDAY THROUGH THURSDAY...
OPEN 500MB WAVE WILL BE LIFTING NORTHEAST ACROSS THE UPPER MIDWEST
INTO ONTARIO AND EVENTUALLY QUEBEC...WITH HEIGHTS SLOWLY INCREASING
WED AFTN. SFC FEATURES REMAIN DISORGANIZED WED...WITH A BOUNDARY
SLOWLY SHIFTING EAST. OPER GUIDANCE DIFFERS ON HOW QUICKLY PRECIP
WILL DEPART THE REGION. ENSEMBLE DATA SUGGESTS HOLDING ONTO CHC TO
SLIGHT CHC POPS MAINLY FOR THE CENTRAL/EASTERN CWFA WED/WED EVE.
ALTHOUGH WITH SOME HINT OF SFC HEIGHTS NUDGING UP...IT IS POSSIBLE
THAT SOME DRY AIR COULD FILTER IN AND KICK PRECIP EAST BY MIDDAY AND
ALLOW FOR A MAINLY DRY WED. SFC WINDS WILL BE TURNING SOUTHWEST TO
WEST...KEEPING AN OFFSHORE FLOW FOR LOCATIONS CLOSE TO LAKE
MICHIGAN. TEMPS SHOULD YET AGAIN TOUCH UPR 70S TO ARND 80 WED...IF
CLOUDS AND PRECIP CAN PUSH EAST BY MIDDAY...SOME CLEARING WOULD
ALLOW SFC TEMPS TO PUSH A COUPLE DEGREES WARMER INTO THE LOW 80S IN
SOME LOCATIONS. LATE IN THE EVENING THE GRADIENT SLACKENS
FURTHER...AND COULD ALLOW A LATE DAY ONSHORE FLOW TO DEVELOP FOR
AREAS ADJACENT TO LAKE MICHIGAN.

MID-LVL FLOW BEGINS TO FLATTEN AS A WEAK SFC RIDGE BECOMES ORIENTED
FROM WESTERN QUEBEC SOUTH THROUGH THE EASTERN OHIO RIVER VALLEY.
THIS WILL GENERALLY ALLOW A SOUTHERLY FLOW...ALTHOUGH THE GRADIENT
IS NOT VERY STRONG. THIS SHOULD SET THE STAGE FOR A LAKE
BREEZE/ONSHORE FLOW TO DEVELOP THUR. TIMING COULD END UP BEING
SLIGHTLY EARLIER GIVEN THE LIGHT SFC GRADIENT. GUIDANCE HAS BEEN
CONSISTENT IN HOLDING PRECIP WEST/SOUTH OF THE FORECAST AREA
THUR...AS A RESULT OF THE WEAK SFC RIDGING. SO ONE MORE MILD DAY
WITH HIGHS WARMING BACK INTO THE UPR 70S/LOW 80S...HOWEVER AS
PREVIOUSLY NOTED...A LAKE BREEZE IS LIKELY TO DEVELOP. THIS WILL
BLEED THE MUCH COOLER MARINE AIR WEST ACROSS NORTHEAST IL AND
DOWNTOWN CHICAGO. IF THE TIMING IS EARLIER IN THE DAY THUR...TEMPS
MAY NOT WARM BEYOND THE LOW/MID 60S ALONG THE CHICAGO LAKEFRONT.

FLOW THEN TURNS SOUTHERLY THUR NIGHT WITH THE MORE PROGRESSIVE FLOW
IN THE MID-LVLS PUSHING THE RIDGING EAST. A RETURN FLOW MOISTURE
WILL CONTINUE TO BE FOCUSED ACROSS THE CENTRAL CONUS THUR EVE...WITH
A SLOW MOVING FRONTAL BOUNDARY NUDGING EAST THUR NIGHT TOWARDS
WESTERN IL. THIS FRONTAL BOUNDARY WILL BECOME ENERGIZED AS A ROBUST
500MB VORT MAX BREAKS SOUTH FROM CENTRAL CANADA LATE THUR NIGHT.

THIS SHOULD ALLOW FOR AN ATMOSPHERIC RIVER TO DEVELOP FROM THE
SOUTHERN PLAINS STRETCHING NORTH THROUGH THE MID-MISSOURI VALLEY
INTO THE WESTERN GREAT LAKES EARLY FRI MORNING.

FRIDAY THROUGH EARLY NEXT WEEK...
ENSEMBLES CONTINUE TO PROG A ROBUST TROUGH SLIDING SOUTH FROM
CENTRAL CANADA FRI. THIS COUPLED WITH DOWNSTREAM MID-LVL RIDGING
ACROSS THE SOUTHEAST CONUS WILL STRENGTHEN THE FRONTAL BOUNDARY
THAT WILL BE ORIENTED FROM THE SOUTHERN PLAINS STRETCHING
NORTHEAST THROUGH THE GREAT LAKES REGION INTO WESTERN QUEBEC.

THIS SETUP IS IDEAL FOR THE DEVELOPMENT OF AN ATMOSPHERIC RIVER WITH
ABUNDANT LOW LEVEL MOISTURE AND EFFICIENT PRECIP PRODUCING
CONVECTION.

OPER GUIDANCE HAS BEEN RELATIVELY CONSISTENT WITH BRINGING A SERIES
OF WAVES ALONG THE SLOW MOVING FRONTAL BOUNDARY FRI AFTN/EVE...THEN
THE BOUNDARY SHOULD SLIDE EAST WITH WINDS QUICKLY VEERING
NORTH/NORTHEAST FOR SAT AND USHERING IN MUCH COOLER AIR TO THE
REGION.

CURRENT INDICATIONS ARE THAT HIGHS SAT MAY STRUGGLE TO WARM BEYOND
THE UPR 50S ACROSS NORTHEAST IL/NORTHWEST IN...WITH ONLY LOW 60S
ELSEWHERE. STRONG SFC RIDGE WILL REMAIN NORTH OF THE REGION...SO THE
PRIOR FRONTAL BOUNDARY MAY BECOME QUASI-STATIONARY FOR THE WEEKEND
ALONG THE OHIO VALLEY AND CONTINUE TO FEED PRECIP CHANCES TO THE
SOUTHERN CWFA.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 18Z...

* MVFR THIS AFTERNOON

* RAIN WITH EMBEDDED THUNDER POSSIBLE

* SOUTH WINDS VARYING FROM SOUTHEAST EARLY TO SOUTHWEST THIS
  EVENING.

* MVFR IN FOG AND LOW CLOUDS WEDNESDAY MORNING.

MM

//DISCUSSION...UPDATED 18Z...

LINE OF SHOWERS HAS DECREASED VSBYS TO 1 MILE UPSTREAM EARLY THIS
AFTERNOON. AS THE LINE PROGRESSES NORTHEASTWARD...COULD SEE SOME
STRONGER POCKETS OF RAIN AND TALLER EMBEDDED CELLS PRODUCE
ISOLATED LIGHTNING. LOW CHANCE/CONFIDENCE OF ANY OF THESE CELLS
HITTING THE TERMINALS...SO KEPT VCTS IN THE TAFS THROUGH 19Z.

LOOKING TOWARD WEDNESDAY MORNING...LOW LEVEL MOISTURE AND A WEAK
INVERSION WILL ALLOW A CHANCE FOR MVFR FOG AND CIGS TO WORK INTO
THE TERMINALS. THE AFTERNOON WILL FEATURE A SCATTERED TO POSSIBLY
BROKEN DECK AT 025. INTO THE EVENING...EXPECT OVERCAST CONDITIONS
WITH LIGHT RAIN POSSIBLE. THERE IS A CHANCE FOR THE LAKE BREEZE TO
WORK INTO ORD NEAR OR JUST AFTER 00Z WEDNESDAY EVENING.

MM

//ORD AND MDW CONFIDENCE...UPDATED 18Z...

* HIGH CONFIDENCE REMAINING MVFR THIS AFTERNOON.

* HIGH CONFIDENCE IN RAIN TIMING THIS AFTERNOON. LOW CONFIDENCE ON
  THUNDER CHANCES.

* MEDIUM TO HIGH CONFIDENCE IN WIND DIRECTION WITH HIGH CONFIDENCE
  IN WIND SPEED EXCEPT LOW CONFIDENCE IF THUNDERSTORMS OCCUR.

* LOW-MEDIUM CONFIDENCE IN FOG AND MVFR CONDITIONS WEDNESDAY
  MORNING.

*

MM

//OUTLOOK FOR ORD/MDW FOR 00Z THURSDAY-12Z TUESDAY...UPDATED 12Z...

WEDNESDAY NIGHT...WX NIL/VFR. SOUTHEAST WINDS.

THURSDAY...SLIGHT CHANCE OF TSRA AT NIGHT. SOUTHEAST WINDS.

FRIDAY...TSRA/SHRA LIKELY THROUGH THE DAY AND NIGHT. MVFR
POSSIBLE. SOUTHWEST WINDS.

SATURDAY...SHRA LIKELY WITH A CHANCE OF TSRA DURING THE DAY.
NORTHEAST WINDS.

SUNDAY...CHANCE OF SHRA. EAST WINDS. MVFR POSSIBLE.

MONDAY...CHANCE OF SHRA. SOUTHEAST WINDS. MVFR POSSIBLE.

KREIN

&&

.MARINE...
229 AM CDT

WARM MOIST AIR CONTINUES TO FEED NORTH ACROSS THE LAKE
TODAY...WHICH MAY HELP TO FURTHER ENHANCE ANY AREAS OF FOG THAT
HAVE ALREADY DEVELOPED. IT IS POSSIBLE PATCHY DENSE FOG MAY
DEVELOP...ALTHOUGH WINDS MAY BE JUST STRONG ENOUGH TO LIMIT THE
COVERAGE AND INTENSITY OF THE FOG. A SURFACE LOW PRESSURE SYSTEM
WILL BE LIFTING NORTH ACROSS EASTERN IOWA INTO CENTRAL WISCONSIN
THIS EVENING. THE GRADIENT WILL TIGHTEN ACROSS THE
CENTRAL/SOUTHERN PORTIONS OF THE LAKE...WHICH WITH WARMER
NEARSHORE WATERS EXPECT SOME SLIGHTLY BETTER MIXING TO OCCUR.
FURTHER OUT ACROSS THE OPEN WATERS THE WATER REMAINS COLD AND
EXPECT THE STABILITY TO MAKE IT DIFFICULT TO MIX TO THE SFC THE
HIGHER GUSTS. HIGH PRESSURE THEN ARRIVES LATE WEDNESDAY WITH LIGHT
WINDS DEVELOPING. THEN HIGH PRESSURE SHIFTS EAST THURSDAY
NIGHT...WITH SOUTHERLY WINDS DEVELOPING AGAIN FRIDAY. A FRONTAL
BOUNDARY WILL APPROACH LAKE MICHIGAN LATE FRIDAY NIGHT THEN
STEADILY SLIDE SOUTH ALONG THE LAKE. THIS WILL ALLOW WINDS TO
QUICKLY VEER FROM SOUTH TO NORTH/NORTHEAST SATURDAY. ALONG WITH
THIS QUICK WIND SHIFT WILL BE COOLER AIR SLIDING SOUTH OVER THE
LAKE. WAVES SHOULD EASILY BUILD SATURDAY FOR THE CENTRAL/SOUTHERN
PORTIONS OF THE LAKE.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
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WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 261732
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1232 PM CDT TUE MAY 26 2015

.UPDATE...
1007 AM CDT

A SFC LOW IS OVER IOWA AND ITS WARM/STATIONARY FRONT IS WELL TO
OUR NORTH OVER CENTRAL WI. ITS COLD FRONT STRETCHES FROM THE LOW
THROUGH CENTRAL KANSAS. AN AREA OF MAINLY RAIN AND A FEW
THUNDERSTORMS IS SLOWLY SPREADING NNE ACROSS NORTH CENTRAL IL. SO
FAR THE SHOWERS HAVE BEEN BEHAVING ACROSS MY CWA...BUT A FEW CELLS
TO THE WEST HAVE SHOWN SIGNS OF ROTATION.

LIKING THE LATEST RAP GUIDANCE WHICH KEEPS CAPE VALUES ON THE LOW
SIDE WITH ONLY A FEW HUNDREDS J/KG OF CAPE TO WORK WITH. THIS IS
ASSUMING SKIES STAY OVERCAST...AND THINKING WE WILL BE OVERCAST
TODAY. THAT BEING SAID...ANY LOCATIONS THAT SEE SUNSHINE COULD
DEVELOP ENOUGH CAPE TO SUPPORT TALLER CELLS AND POSSIBLY SEVERE
WEATHER. IN GENERAL THINKING DAMAGING WINDS AND AN ISOLATED
TORNADO ARE THE MAIN THREATS...BUT STRONGER STORMS WITH HIGHER
CAPE VALUES COULD SUPPORT HAIL. RADAR IMAGERY IS SHOWING GRAVITY
WAVE TAGS MOVING ALONG THE LINE OF STORMS AND WHEN THE TAGS
INTERSECT THE LINE...STORMS BEGIN TO SPIN. THEREFORE THE TORNADO
THREAT IS NOT ZERO.

THIS FIRST BATCH OF PRECIP WILL PUSH EAST THROUGH THE EARLY AFTN
HOURS AND EXPECTING ADDITIONAL SCATTERED TO NUMEROUS THUNDERSTORMS
DEVELOPMENT BEHIND THE LINE OVER NORTH CENTRAL IL. THE SECOND
WAVE SHIFTS EAST THROUGH THE EARLY EVENING HOURS. PWAT VALUES ARE
1.2-1.5 INCHES SO HEAVY DOWNPOURS ARE PSBL.

JEE

&&

.SHORT TERM...
319 AM CDT

THROUGH TUESDAY NIGHT...

FOR THE REMAINDER OF THE OVERNIGHT HOURS...CONDITIONS WILL REMAIN
QUIET ACROSS THE CWA AS A SERIES OF SHORT WAVES CONTINUE TO TRACK
NORTH AROUND THE TOP OF A PERSISTENT UPPER LEVEL RIDGE WHICH EXTENDS
FROM THE SERN CONUS THROUGH THE UPPER MISSISSIPPI VALLEY.  THIS
UPPER RIDGE HAS BEEN THE FEATURE WHICH HAS CONTROLLED THE PATH OF
THE SERIES OF SHORTWAVES LIFTING OUT OF THE SOUTHERN PLAINS...AND
WILL CONTINUE TO DO SO THROUGH THE DAY TODAY. SLY...MODERATELY
STRONG...WINDS WILL PERSIST THROUGH THE NIGHT...AND MUCH OF THE DAY
ALLOWING FOR SFC DEWPOINTS TO REMAIN CONSISTENT OR POSSIBLE INCH A
LITTLE HIGHER.

MAIN CONCERN FOR THE MORNING HOURS WILL BE THE TRACK OF A STRONG
SHORT WAVE AND ASSOCIATED SFC LOW LIFTING NORTHWARD THROUGH THE
MIDDLE MISSISSIPPI VALLEY.  THIS FEATURE WILL PREDOMINANTLY IMPACT
ERN IOWA AND WRN IL BY ARND DAYBREAK.  THROUGH THE MORNING...THE
COMBINATION OF ISENTROPIC LIFT IN THE WARM SECTOR OF THE
SYSTEM...ALL OF IL AND INTO NWRN IN...WILL LEAD TO SOME
DESTABILIZATION ACROSS THE REGION. A SFC TROUGH...AS WELL INDICATED
BY THE LATEST HIGH RES GUIDANCE...WITH LIFT THROUGH NRN IL/IN
THROUGH THE DAY...COINCIDENT WITH A STRONG SSWLY LOW LEVEL JET OF 45-
50 KT...WITH PROVIDE THE POTENTIAL FOR SHOWERS AND STRONG TO SEVERE
THUNDERSTORMS ACROSS THE CWA.  BASED ON WIND PROFILES AND MID LEVEL
DRYING...THE PRIMARY CONCERN WITH REGARD TO SEVERE WEATHER WILL BE
STRONG WIND GUSTS.  HOWEVER...SOME OF THE HIGH RES SFC WIND GUIDANCE
SUGGEST SOME SLIGHT BACKING OF SFC WINDS FROM 180-190 DEGREES TO 160-
170 DEGREES...WHILE WINDS ALOFT REMAIN SWLY.  THIS SLIGHT BACKING OF
THE SFC WINDS COULD PROVIDE ENOUGH DIRECTIONAL SHEAR THROUGH THE
LOWER LEVELS TO BRING AN ISOLD TORNADO THREAT. LOCALLY HEAVY
RAINFALL WILL ALSO BE CONCERNED WITH PWATS REACHING 1.75 INCHES
LATER THIS MORNING.  HOWEVER...FLOODING WILL LIKELY NOT BE A
SIGNIFICANT CONCERN AS THE SWLY WINDS RIGHT OFF THE DECK WILL RANGE
FROM ARND 45 KT ABOVE THE BOUNDARY LAYER TO ARND 90KT AT UPPER
LEVELS WHICH SHOULD ALLOW ANY OF THE STRONGER STORMS THAT DO DEVELOP
TO MOVE QUICKLY.

BY EARLY AFTERNOON...THE MAIN SHORT WAVE WILL LIFT INTO WISCONSIN
WHILE A SFC TROUGH TRACKS EAST ACROSS THE AREA.  THIS WILL LEAD TO
WINDS AT THE SFC VEERING TO SWLY...SETTING UP A UNIDIRECTIONAL WIND
PROFILE...EFFECTIVELY MINIMIZING THE SEVERE WEATHER THREAT TO THE
REGION.  BY LATE AFTERNOON AND INTO THE EVENING THE MODELS ARE
ADVERTISING THAT A DRY SLOW SHOULD NOSE INTO NRN IL...EFFECTIVELY
CUTTING OFF THE PCPN AREA INTO 2 SEPARATE AREA...ONE OVER WISCONSIN
AND ERN IOWA AND ANOTHER MORE FOCUSED OVER INDIANA.  THE NWRN
INDIANA COUNTIES WILL STILL HAVE A CHANCE FOR SOME SHOWERS AND
THUNDERSTORMS INTO THE EVENING...WHILE PCPN CHANCES OVER NRN IL
BEGIN TO WANE.  MUCH OF THE MODEL GUIDANCE ALSO INDICATED THAT THE
SHORTWAVE SHOULD SLOW IT`S PROGRESSION THROUGH WISCONSIN AS IT
APPROACHES THE APEX OF THE UPPER RIDGE.  AN ASSOCIATED SFC
TROUGH/COLD FRONT EXTENDING SOUTHWEST FROM THE SFC LOW WILL LINGER
OVER ERN IOWA IN THE EARLY EVENING BEFORE STEADILY PUSHING ACROSS
NRN IL AND INTO NWRN IN OVERNIGHT.  THROUGH THE NIGHT...THE
STRONGEST UPPER LEVEL FORCING WILL BE WELL NORTH OF THE CWA...SO ANY
LINGERING CHANCES FOR PCPN OVERNIGHT WILL BE LOW AND LIKELY CONFINED
TO THE NRN TIER COUNTIES OF IL...ALONG THE WI BORDER.

KREIN

&&

.LONG TERM...
229 AM CDT

WEDNESDAY THROUGH MONDAY...

WEDNESDAY THROUGH THURSDAY...
OPEN 500MB WAVE WILL BE LIFTING NORTHEAST ACROSS THE UPPER MIDWEST
INTO ONTARIO AND EVENTUALLY QUEBEC...WITH HEIGHTS SLOWLY INCREASING
WED AFTN. SFC FEATURES REMAIN DISORGANIZED WED...WITH A BOUNDARY
SLOWLY SHIFTING EAST. OPER GUIDANCE DIFFERS ON HOW QUICKLY PRECIP
WILL DEPART THE REGION. ENSEMBLE DATA SUGGESTS HOLDING ONTO CHC TO
SLIGHT CHC POPS MAINLY FOR THE CENTRAL/EASTERN CWFA WED/WED EVE.
ALTHOUGH WITH SOME HINT OF SFC HEIGHTS NUDGING UP...IT IS POSSIBLE
THAT SOME DRY AIR COULD FILTER IN AND KICK PRECIP EAST BY MIDDAY AND
ALLOW FOR A MAINLY DRY WED. SFC WINDS WILL BE TURNING SOUTHWEST TO
WEST...KEEPING AN OFFSHORE FLOW FOR LOCATIONS CLOSE TO LAKE
MICHIGAN. TEMPS SHOULD YET AGAIN TOUCH UPR 70S TO ARND 80 WED...IF
CLOUDS AND PRECIP CAN PUSH EAST BY MIDDAY...SOME CLEARING WOULD
ALLOW SFC TEMPS TO PUSH A COUPLE DEGREES WARMER INTO THE LOW 80S IN
SOME LOCATIONS. LATE IN THE EVENING THE GRADIENT SLACKENS
FURTHER...AND COULD ALLOW A LATE DAY ONSHORE FLOW TO DEVELOP FOR
AREAS ADJACENT TO LAKE MICHIGAN.

MID-LVL FLOW BEGINS TO FLATTEN AS A WEAK SFC RIDGE BECOMES ORIENTED
FROM WESTERN QUEBEC SOUTH THROUGH THE EASTERN OHIO RIVER VALLEY.
THIS WILL GENERALLY ALLOW A SOUTHERLY FLOW...ALTHOUGH THE GRADIENT
IS NOT VERY STRONG. THIS SHOULD SET THE STAGE FOR A LAKE
BREEZE/ONSHORE FLOW TO DEVELOP THUR. TIMING COULD END UP BEING
SLIGHTLY EARLIER GIVEN THE LIGHT SFC GRADIENT. GUIDANCE HAS BEEN
CONSISTENT IN HOLDING PRECIP WEST/SOUTH OF THE FORECAST AREA
THUR...AS A RESULT OF THE WEAK SFC RIDGING. SO ONE MORE MILD DAY
WITH HIGHS WARMING BACK INTO THE UPR 70S/LOW 80S...HOWEVER AS
PREVIOUSLY NOTED...A LAKE BREEZE IS LIKELY TO DEVELOP. THIS WILL
BLEED THE MUCH COOLER MARINE AIR WEST ACROSS NORTHEAST IL AND
DOWNTOWN CHICAGO. IF THE TIMING IS EARLIER IN THE DAY THUR...TEMPS
MAY NOT WARM BEYOND THE LOW/MID 60S ALONG THE CHICAGO LAKEFRONT.

FLOW THEN TURNS SOUTHERLY THUR NIGHT WITH THE MORE PROGRESSIVE FLOW
IN THE MID-LVLS PUSHING THE RIDGING EAST. A RETURN FLOW MOISTURE
WILL CONTINUE TO BE FOCUSED ACROSS THE CENTRAL CONUS THUR EVE...WITH
A SLOW MOVING FRONTAL BOUNDARY NUDGING EAST THUR NIGHT TOWARDS
WESTERN IL. THIS FRONTAL BOUNDARY WILL BECOME ENERGIZED AS A ROBUST
500MB VORT MAX BREAKS SOUTH FROM CENTRAL CANADA LATE THUR NIGHT.

THIS SHOULD ALLOW FOR AN ATMOSPHERIC RIVER TO DEVELOP FROM THE
SOUTHERN PLAINS STRETCHING NORTH THROUGH THE MID-MISSOURI VALLEY
INTO THE WESTERN GREAT LAKES EARLY FRI MORNING.

FRIDAY THROUGH EARLY NEXT WEEK...
ENSEMBLES CONTINUE TO PROG A ROBUST TROUGH SLIDING SOUTH FROM
CENTRAL CANADA FRI. THIS COUPLED WITH DOWNSTREAM MID-LVL RIDGING
ACROSS THE SOUTHEAST CONUS WILL STRENGTHEN THE FRONTAL BOUNDARY
THAT WILL BE ORIENTED FROM THE SOUTHERN PLAINS STRETCHING
NORTHEAST THROUGH THE GREAT LAKES REGION INTO WESTERN QUEBEC.

THIS SETUP IS IDEAL FOR THE DEVELOPMENT OF AN ATMOSPHERIC RIVER WITH
ABUNDANT LOW LEVEL MOISTURE AND EFFICIENT PRECIP PRODUCING
CONVECTION.

OPER GUIDANCE HAS BEEN RELATIVELY CONSISTENT WITH BRINGING A SERIES
OF WAVES ALONG THE SLOW MOVING FRONTAL BOUNDARY FRI AFTN/EVE...THEN
THE BOUNDARY SHOULD SLIDE EAST WITH WINDS QUICKLY VEERING
NORTH/NORTHEAST FOR SAT AND USHERING IN MUCH COOLER AIR TO THE
REGION.

CURRENT INDICATIONS ARE THAT HIGHS SAT MAY STRUGGLE TO WARM BEYOND
THE UPR 50S ACROSS NORTHEAST IL/NORTHWEST IN...WITH ONLY LOW 60S
ELSEWHERE. STRONG SFC RIDGE WILL REMAIN NORTH OF THE REGION...SO THE
PRIOR FRONTAL BOUNDARY MAY BECOME QUASI-STATIONARY FOR THE WEEKEND
ALONG THE OHIO VALLEY AND CONTINUE TO FEED PRECIP CHANCES TO THE
SOUTHERN CWFA.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 18Z...

* MVFR THIS AFTERNOON

* RAIN WITH EMBEDDED THUNDER POSSIBLE

* SOUTH WINDS VARYING FROM SOUTHEAST EARLY TO SOUTHWEST THIS
  EVENING.

* MVFR IN FOG AND LOW CLOUDS WEDNESDAY MORNING.

MM

//DISCUSSION...UPDATED 18Z...

LINE OF SHOWERS HAS DECREASED VSBYS TO 1 MILE UPSTREAM EARLY THIS
AFTERNOON. AS THE LINE PROGRESSES NORTHEASTWARD...COULD SEE SOME
STRONGER POCKETS OF RAIN AND TALLER EMBEDDED CELLS PRODUCE
ISOLATED LIGHTNING. LOW CHANCE/CONFIDENCE OF ANY OF THESE CELLS
HITTING THE TERMINALS...SO KEPT VCTS IN THE TAFS THROUGH 19Z.

LOOKING TOWARD WEDNESDAY MORNING...LOW LEVEL MOISTURE AND A WEAK
INVERSION WILL ALLOW A CHANCE FOR MVFR FOG AND CIGS TO WORK INTO
THE TERMINALS. THE AFTERNOON WILL FEATURE A SCATTERED TO POSSIBLY
BROKEN DECK AT 025. INTO THE EVENING...EXPECT OVERCAST CONDITIONS
WITH LIGHT RAIN POSSIBLE. THERE IS A CHANCE FOR THE LAKE BREEZE TO
WORK INTO ORD NEAR OR JUST AFTER 00Z WEDNESDAY EVENING.

MM

//ORD AND MDW CONFIDENCE...UPDATED 18Z...

* HIGH CONFIDENCE REMAINING MVFR THIS AFTERNOON.

* HIGH CONFIDENCE IN RAIN TIMING THIS AFTERNOON. LOW CONFIDENCE ON
  THUNDER CHANCES.

* MEDIUM TO HIGH CONFIDENCE IN WIND DIRECTION WITH HIGH CONFIDENCE
  IN WIND SPEED EXCEPT LOW CONFIDENCE IF THUNDERSTORMS OCCUR.

* LOW-MEDIUM CONFIDENCE IN FOG AND MVFR CONDITIONS WEDNESDAY
  MORNING.

*

MM

//OUTLOOK FOR ORD/MDW FOR 00Z THURSDAY-12Z TUESDAY...UPDATED 12Z...

WEDNESDAY NIGHT...WX NIL/VFR. SOUTHEAST WINDS.

THURSDAY...SLIGHT CHANCE OF TSRA AT NIGHT. SOUTHEAST WINDS.

FRIDAY...TSRA/SHRA LIKELY THROUGH THE DAY AND NIGHT. MVFR
POSSIBLE. SOUTHWEST WINDS.

SATURDAY...SHRA LIKELY WITH A CHANCE OF TSRA DURING THE DAY.
NORTHEAST WINDS.

SUNDAY...CHANCE OF SHRA. EAST WINDS. MVFR POSSIBLE.

MONDAY...CHANCE OF SHRA. SOUTHEAST WINDS. MVFR POSSIBLE.

KREIN

&&

.MARINE...
229 AM CDT

WARM MOIST AIR CONTINUES TO FEED NORTH ACROSS THE LAKE
TODAY...WHICH MAY HELP TO FURTHER ENHANCE ANY AREAS OF FOG THAT
HAVE ALREADY DEVELOPED. IT IS POSSIBLE PATCHY DENSE FOG MAY
DEVELOP...ALTHOUGH WINDS MAY BE JUST STRONG ENOUGH TO LIMIT THE
COVERAGE AND INTENSITY OF THE FOG. A SURFACE LOW PRESSURE SYSTEM
WILL BE LIFTING NORTH ACROSS EASTERN IOWA INTO CENTRAL WISCONSIN
THIS EVENING. THE GRADIENT WILL TIGHTEN ACROSS THE
CENTRAL/SOUTHERN PORTIONS OF THE LAKE...WHICH WITH WARMER
NEARSHORE WATERS EXPECT SOME SLIGHTLY BETTER MIXING TO OCCUR.
FURTHER OUT ACROSS THE OPEN WATERS THE WATER REMAINS COLD AND
EXPECT THE STABILITY TO MAKE IT DIFFICULT TO MIX TO THE SFC THE
HIGHER GUSTS. HIGH PRESSURE THEN ARRIVES LATE WEDNESDAY WITH LIGHT
WINDS DEVELOPING. THEN HIGH PRESSURE SHIFTS EAST THURSDAY
NIGHT...WITH SOUTHERLY WINDS DEVELOPING AGAIN FRIDAY. A FRONTAL
BOUNDARY WILL APPROACH LAKE MICHIGAN LATE FRIDAY NIGHT THEN
STEADILY SLIDE SOUTH ALONG THE LAKE. THIS WILL ALLOW WINDS TO
QUICKLY VEER FROM SOUTH TO NORTH/NORTHEAST SATURDAY. ALONG WITH
THIS QUICK WIND SHIFT WILL BE COOLER AIR SLIDING SOUTH OVER THE
LAKE. WAVES SHOULD EASILY BUILD SATURDAY FOR THE CENTRAL/SOUTHERN
PORTIONS OF THE LAKE.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 261732
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1232 PM CDT TUE MAY 26 2015

.UPDATE...
1007 AM CDT

A SFC LOW IS OVER IOWA AND ITS WARM/STATIONARY FRONT IS WELL TO
OUR NORTH OVER CENTRAL WI. ITS COLD FRONT STRETCHES FROM THE LOW
THROUGH CENTRAL KANSAS. AN AREA OF MAINLY RAIN AND A FEW
THUNDERSTORMS IS SLOWLY SPREADING NNE ACROSS NORTH CENTRAL IL. SO
FAR THE SHOWERS HAVE BEEN BEHAVING ACROSS MY CWA...BUT A FEW CELLS
TO THE WEST HAVE SHOWN SIGNS OF ROTATION.

LIKING THE LATEST RAP GUIDANCE WHICH KEEPS CAPE VALUES ON THE LOW
SIDE WITH ONLY A FEW HUNDREDS J/KG OF CAPE TO WORK WITH. THIS IS
ASSUMING SKIES STAY OVERCAST...AND THINKING WE WILL BE OVERCAST
TODAY. THAT BEING SAID...ANY LOCATIONS THAT SEE SUNSHINE COULD
DEVELOP ENOUGH CAPE TO SUPPORT TALLER CELLS AND POSSIBLY SEVERE
WEATHER. IN GENERAL THINKING DAMAGING WINDS AND AN ISOLATED
TORNADO ARE THE MAIN THREATS...BUT STRONGER STORMS WITH HIGHER
CAPE VALUES COULD SUPPORT HAIL. RADAR IMAGERY IS SHOWING GRAVITY
WAVE TAGS MOVING ALONG THE LINE OF STORMS AND WHEN THE TAGS
INTERSECT THE LINE...STORMS BEGIN TO SPIN. THEREFORE THE TORNADO
THREAT IS NOT ZERO.

THIS FIRST BATCH OF PRECIP WILL PUSH EAST THROUGH THE EARLY AFTN
HOURS AND EXPECTING ADDITIONAL SCATTERED TO NUMEROUS THUNDERSTORMS
DEVELOPMENT BEHIND THE LINE OVER NORTH CENTRAL IL. THE SECOND
WAVE SHIFTS EAST THROUGH THE EARLY EVENING HOURS. PWAT VALUES ARE
1.2-1.5 INCHES SO HEAVY DOWNPOURS ARE PSBL.

JEE

&&

.SHORT TERM...
319 AM CDT

THROUGH TUESDAY NIGHT...

FOR THE REMAINDER OF THE OVERNIGHT HOURS...CONDITIONS WILL REMAIN
QUIET ACROSS THE CWA AS A SERIES OF SHORT WAVES CONTINUE TO TRACK
NORTH AROUND THE TOP OF A PERSISTENT UPPER LEVEL RIDGE WHICH EXTENDS
FROM THE SERN CONUS THROUGH THE UPPER MISSISSIPPI VALLEY.  THIS
UPPER RIDGE HAS BEEN THE FEATURE WHICH HAS CONTROLLED THE PATH OF
THE SERIES OF SHORTWAVES LIFTING OUT OF THE SOUTHERN PLAINS...AND
WILL CONTINUE TO DO SO THROUGH THE DAY TODAY. SLY...MODERATELY
STRONG...WINDS WILL PERSIST THROUGH THE NIGHT...AND MUCH OF THE DAY
ALLOWING FOR SFC DEWPOINTS TO REMAIN CONSISTENT OR POSSIBLE INCH A
LITTLE HIGHER.

MAIN CONCERN FOR THE MORNING HOURS WILL BE THE TRACK OF A STRONG
SHORT WAVE AND ASSOCIATED SFC LOW LIFTING NORTHWARD THROUGH THE
MIDDLE MISSISSIPPI VALLEY.  THIS FEATURE WILL PREDOMINANTLY IMPACT
ERN IOWA AND WRN IL BY ARND DAYBREAK.  THROUGH THE MORNING...THE
COMBINATION OF ISENTROPIC LIFT IN THE WARM SECTOR OF THE
SYSTEM...ALL OF IL AND INTO NWRN IN...WILL LEAD TO SOME
DESTABILIZATION ACROSS THE REGION. A SFC TROUGH...AS WELL INDICATED
BY THE LATEST HIGH RES GUIDANCE...WITH LIFT THROUGH NRN IL/IN
THROUGH THE DAY...COINCIDENT WITH A STRONG SSWLY LOW LEVEL JET OF 45-
50 KT...WITH PROVIDE THE POTENTIAL FOR SHOWERS AND STRONG TO SEVERE
THUNDERSTORMS ACROSS THE CWA.  BASED ON WIND PROFILES AND MID LEVEL
DRYING...THE PRIMARY CONCERN WITH REGARD TO SEVERE WEATHER WILL BE
STRONG WIND GUSTS.  HOWEVER...SOME OF THE HIGH RES SFC WIND GUIDANCE
SUGGEST SOME SLIGHT BACKING OF SFC WINDS FROM 180-190 DEGREES TO 160-
170 DEGREES...WHILE WINDS ALOFT REMAIN SWLY.  THIS SLIGHT BACKING OF
THE SFC WINDS COULD PROVIDE ENOUGH DIRECTIONAL SHEAR THROUGH THE
LOWER LEVELS TO BRING AN ISOLD TORNADO THREAT. LOCALLY HEAVY
RAINFALL WILL ALSO BE CONCERNED WITH PWATS REACHING 1.75 INCHES
LATER THIS MORNING.  HOWEVER...FLOODING WILL LIKELY NOT BE A
SIGNIFICANT CONCERN AS THE SWLY WINDS RIGHT OFF THE DECK WILL RANGE
FROM ARND 45 KT ABOVE THE BOUNDARY LAYER TO ARND 90KT AT UPPER
LEVELS WHICH SHOULD ALLOW ANY OF THE STRONGER STORMS THAT DO DEVELOP
TO MOVE QUICKLY.

BY EARLY AFTERNOON...THE MAIN SHORT WAVE WILL LIFT INTO WISCONSIN
WHILE A SFC TROUGH TRACKS EAST ACROSS THE AREA.  THIS WILL LEAD TO
WINDS AT THE SFC VEERING TO SWLY...SETTING UP A UNIDIRECTIONAL WIND
PROFILE...EFFECTIVELY MINIMIZING THE SEVERE WEATHER THREAT TO THE
REGION.  BY LATE AFTERNOON AND INTO THE EVENING THE MODELS ARE
ADVERTISING THAT A DRY SLOW SHOULD NOSE INTO NRN IL...EFFECTIVELY
CUTTING OFF THE PCPN AREA INTO 2 SEPARATE AREA...ONE OVER WISCONSIN
AND ERN IOWA AND ANOTHER MORE FOCUSED OVER INDIANA.  THE NWRN
INDIANA COUNTIES WILL STILL HAVE A CHANCE FOR SOME SHOWERS AND
THUNDERSTORMS INTO THE EVENING...WHILE PCPN CHANCES OVER NRN IL
BEGIN TO WANE.  MUCH OF THE MODEL GUIDANCE ALSO INDICATED THAT THE
SHORTWAVE SHOULD SLOW IT`S PROGRESSION THROUGH WISCONSIN AS IT
APPROACHES THE APEX OF THE UPPER RIDGE.  AN ASSOCIATED SFC
TROUGH/COLD FRONT EXTENDING SOUTHWEST FROM THE SFC LOW WILL LINGER
OVER ERN IOWA IN THE EARLY EVENING BEFORE STEADILY PUSHING ACROSS
NRN IL AND INTO NWRN IN OVERNIGHT.  THROUGH THE NIGHT...THE
STRONGEST UPPER LEVEL FORCING WILL BE WELL NORTH OF THE CWA...SO ANY
LINGERING CHANCES FOR PCPN OVERNIGHT WILL BE LOW AND LIKELY CONFINED
TO THE NRN TIER COUNTIES OF IL...ALONG THE WI BORDER.

KREIN

&&

.LONG TERM...
229 AM CDT

WEDNESDAY THROUGH MONDAY...

WEDNESDAY THROUGH THURSDAY...
OPEN 500MB WAVE WILL BE LIFTING NORTHEAST ACROSS THE UPPER MIDWEST
INTO ONTARIO AND EVENTUALLY QUEBEC...WITH HEIGHTS SLOWLY INCREASING
WED AFTN. SFC FEATURES REMAIN DISORGANIZED WED...WITH A BOUNDARY
SLOWLY SHIFTING EAST. OPER GUIDANCE DIFFERS ON HOW QUICKLY PRECIP
WILL DEPART THE REGION. ENSEMBLE DATA SUGGESTS HOLDING ONTO CHC TO
SLIGHT CHC POPS MAINLY FOR THE CENTRAL/EASTERN CWFA WED/WED EVE.
ALTHOUGH WITH SOME HINT OF SFC HEIGHTS NUDGING UP...IT IS POSSIBLE
THAT SOME DRY AIR COULD FILTER IN AND KICK PRECIP EAST BY MIDDAY AND
ALLOW FOR A MAINLY DRY WED. SFC WINDS WILL BE TURNING SOUTHWEST TO
WEST...KEEPING AN OFFSHORE FLOW FOR LOCATIONS CLOSE TO LAKE
MICHIGAN. TEMPS SHOULD YET AGAIN TOUCH UPR 70S TO ARND 80 WED...IF
CLOUDS AND PRECIP CAN PUSH EAST BY MIDDAY...SOME CLEARING WOULD
ALLOW SFC TEMPS TO PUSH A COUPLE DEGREES WARMER INTO THE LOW 80S IN
SOME LOCATIONS. LATE IN THE EVENING THE GRADIENT SLACKENS
FURTHER...AND COULD ALLOW A LATE DAY ONSHORE FLOW TO DEVELOP FOR
AREAS ADJACENT TO LAKE MICHIGAN.

MID-LVL FLOW BEGINS TO FLATTEN AS A WEAK SFC RIDGE BECOMES ORIENTED
FROM WESTERN QUEBEC SOUTH THROUGH THE EASTERN OHIO RIVER VALLEY.
THIS WILL GENERALLY ALLOW A SOUTHERLY FLOW...ALTHOUGH THE GRADIENT
IS NOT VERY STRONG. THIS SHOULD SET THE STAGE FOR A LAKE
BREEZE/ONSHORE FLOW TO DEVELOP THUR. TIMING COULD END UP BEING
SLIGHTLY EARLIER GIVEN THE LIGHT SFC GRADIENT. GUIDANCE HAS BEEN
CONSISTENT IN HOLDING PRECIP WEST/SOUTH OF THE FORECAST AREA
THUR...AS A RESULT OF THE WEAK SFC RIDGING. SO ONE MORE MILD DAY
WITH HIGHS WARMING BACK INTO THE UPR 70S/LOW 80S...HOWEVER AS
PREVIOUSLY NOTED...A LAKE BREEZE IS LIKELY TO DEVELOP. THIS WILL
BLEED THE MUCH COOLER MARINE AIR WEST ACROSS NORTHEAST IL AND
DOWNTOWN CHICAGO. IF THE TIMING IS EARLIER IN THE DAY THUR...TEMPS
MAY NOT WARM BEYOND THE LOW/MID 60S ALONG THE CHICAGO LAKEFRONT.

FLOW THEN TURNS SOUTHERLY THUR NIGHT WITH THE MORE PROGRESSIVE FLOW
IN THE MID-LVLS PUSHING THE RIDGING EAST. A RETURN FLOW MOISTURE
WILL CONTINUE TO BE FOCUSED ACROSS THE CENTRAL CONUS THUR EVE...WITH
A SLOW MOVING FRONTAL BOUNDARY NUDGING EAST THUR NIGHT TOWARDS
WESTERN IL. THIS FRONTAL BOUNDARY WILL BECOME ENERGIZED AS A ROBUST
500MB VORT MAX BREAKS SOUTH FROM CENTRAL CANADA LATE THUR NIGHT.

THIS SHOULD ALLOW FOR AN ATMOSPHERIC RIVER TO DEVELOP FROM THE
SOUTHERN PLAINS STRETCHING NORTH THROUGH THE MID-MISSOURI VALLEY
INTO THE WESTERN GREAT LAKES EARLY FRI MORNING.

FRIDAY THROUGH EARLY NEXT WEEK...
ENSEMBLES CONTINUE TO PROG A ROBUST TROUGH SLIDING SOUTH FROM
CENTRAL CANADA FRI. THIS COUPLED WITH DOWNSTREAM MID-LVL RIDGING
ACROSS THE SOUTHEAST CONUS WILL STRENGTHEN THE FRONTAL BOUNDARY
THAT WILL BE ORIENTED FROM THE SOUTHERN PLAINS STRETCHING
NORTHEAST THROUGH THE GREAT LAKES REGION INTO WESTERN QUEBEC.

THIS SETUP IS IDEAL FOR THE DEVELOPMENT OF AN ATMOSPHERIC RIVER WITH
ABUNDANT LOW LEVEL MOISTURE AND EFFICIENT PRECIP PRODUCING
CONVECTION.

OPER GUIDANCE HAS BEEN RELATIVELY CONSISTENT WITH BRINGING A SERIES
OF WAVES ALONG THE SLOW MOVING FRONTAL BOUNDARY FRI AFTN/EVE...THEN
THE BOUNDARY SHOULD SLIDE EAST WITH WINDS QUICKLY VEERING
NORTH/NORTHEAST FOR SAT AND USHERING IN MUCH COOLER AIR TO THE
REGION.

CURRENT INDICATIONS ARE THAT HIGHS SAT MAY STRUGGLE TO WARM BEYOND
THE UPR 50S ACROSS NORTHEAST IL/NORTHWEST IN...WITH ONLY LOW 60S
ELSEWHERE. STRONG SFC RIDGE WILL REMAIN NORTH OF THE REGION...SO THE
PRIOR FRONTAL BOUNDARY MAY BECOME QUASI-STATIONARY FOR THE WEEKEND
ALONG THE OHIO VALLEY AND CONTINUE TO FEED PRECIP CHANCES TO THE
SOUTHERN CWFA.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 18Z...

* MVFR THIS AFTERNOON

* RAIN WITH EMBEDDED THUNDER POSSIBLE

* SOUTH WINDS VARYING FROM SOUTHEAST EARLY TO SOUTHWEST THIS
  EVENING.

* MVFR IN FOG AND LOW CLOUDS WEDNESDAY MORNING.

MM

//DISCUSSION...UPDATED 18Z...

LINE OF SHOWERS HAS DECREASED VSBYS TO 1 MILE UPSTREAM EARLY THIS
AFTERNOON. AS THE LINE PROGRESSES NORTHEASTWARD...COULD SEE SOME
STRONGER POCKETS OF RAIN AND TALLER EMBEDDED CELLS PRODUCE
ISOLATED LIGHTNING. LOW CHANCE/CONFIDENCE OF ANY OF THESE CELLS
HITTING THE TERMINALS...SO KEPT VCTS IN THE TAFS THROUGH 19Z.

LOOKING TOWARD WEDNESDAY MORNING...LOW LEVEL MOISTURE AND A WEAK
INVERSION WILL ALLOW A CHANCE FOR MVFR FOG AND CIGS TO WORK INTO
THE TERMINALS. THE AFTERNOON WILL FEATURE A SCATTERED TO POSSIBLY
BROKEN DECK AT 025. INTO THE EVENING...EXPECT OVERCAST CONDITIONS
WITH LIGHT RAIN POSSIBLE. THERE IS A CHANCE FOR THE LAKE BREEZE TO
WORK INTO ORD NEAR OR JUST AFTER 00Z WEDNESDAY EVENING.

MM

//ORD AND MDW CONFIDENCE...UPDATED 18Z...

* HIGH CONFIDENCE REMAINING MVFR THIS AFTERNOON.

* HIGH CONFIDENCE IN RAIN TIMING THIS AFTERNOON. LOW CONFIDENCE ON
  THUNDER CHANCES.

* MEDIUM TO HIGH CONFIDENCE IN WIND DIRECTION WITH HIGH CONFIDENCE
  IN WIND SPEED EXCEPT LOW CONFIDENCE IF THUNDERSTORMS OCCUR.

* LOW-MEDIUM CONFIDENCE IN FOG AND MVFR CONDITIONS WEDNESDAY
  MORNING.

*

MM

//OUTLOOK FOR ORD/MDW FOR 00Z THURSDAY-12Z TUESDAY...UPDATED 12Z...

WEDNESDAY NIGHT...WX NIL/VFR. SOUTHEAST WINDS.

THURSDAY...SLIGHT CHANCE OF TSRA AT NIGHT. SOUTHEAST WINDS.

FRIDAY...TSRA/SHRA LIKELY THROUGH THE DAY AND NIGHT. MVFR
POSSIBLE. SOUTHWEST WINDS.

SATURDAY...SHRA LIKELY WITH A CHANCE OF TSRA DURING THE DAY.
NORTHEAST WINDS.

SUNDAY...CHANCE OF SHRA. EAST WINDS. MVFR POSSIBLE.

MONDAY...CHANCE OF SHRA. SOUTHEAST WINDS. MVFR POSSIBLE.

KREIN

&&

.MARINE...
229 AM CDT

WARM MOIST AIR CONTINUES TO FEED NORTH ACROSS THE LAKE
TODAY...WHICH MAY HELP TO FURTHER ENHANCE ANY AREAS OF FOG THAT
HAVE ALREADY DEVELOPED. IT IS POSSIBLE PATCHY DENSE FOG MAY
DEVELOP...ALTHOUGH WINDS MAY BE JUST STRONG ENOUGH TO LIMIT THE
COVERAGE AND INTENSITY OF THE FOG. A SURFACE LOW PRESSURE SYSTEM
WILL BE LIFTING NORTH ACROSS EASTERN IOWA INTO CENTRAL WISCONSIN
THIS EVENING. THE GRADIENT WILL TIGHTEN ACROSS THE
CENTRAL/SOUTHERN PORTIONS OF THE LAKE...WHICH WITH WARMER
NEARSHORE WATERS EXPECT SOME SLIGHTLY BETTER MIXING TO OCCUR.
FURTHER OUT ACROSS THE OPEN WATERS THE WATER REMAINS COLD AND
EXPECT THE STABILITY TO MAKE IT DIFFICULT TO MIX TO THE SFC THE
HIGHER GUSTS. HIGH PRESSURE THEN ARRIVES LATE WEDNESDAY WITH LIGHT
WINDS DEVELOPING. THEN HIGH PRESSURE SHIFTS EAST THURSDAY
NIGHT...WITH SOUTHERLY WINDS DEVELOPING AGAIN FRIDAY. A FRONTAL
BOUNDARY WILL APPROACH LAKE MICHIGAN LATE FRIDAY NIGHT THEN
STEADILY SLIDE SOUTH ALONG THE LAKE. THIS WILL ALLOW WINDS TO
QUICKLY VEER FROM SOUTH TO NORTH/NORTHEAST SATURDAY. ALONG WITH
THIS QUICK WIND SHIFT WILL BE COOLER AIR SLIDING SOUTH OVER THE
LAKE. WAVES SHOULD EASILY BUILD SATURDAY FOR THE CENTRAL/SOUTHERN
PORTIONS OF THE LAKE.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 261732
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1232 PM CDT TUE MAY 26 2015

.UPDATE...
1007 AM CDT

A SFC LOW IS OVER IOWA AND ITS WARM/STATIONARY FRONT IS WELL TO
OUR NORTH OVER CENTRAL WI. ITS COLD FRONT STRETCHES FROM THE LOW
THROUGH CENTRAL KANSAS. AN AREA OF MAINLY RAIN AND A FEW
THUNDERSTORMS IS SLOWLY SPREADING NNE ACROSS NORTH CENTRAL IL. SO
FAR THE SHOWERS HAVE BEEN BEHAVING ACROSS MY CWA...BUT A FEW CELLS
TO THE WEST HAVE SHOWN SIGNS OF ROTATION.

LIKING THE LATEST RAP GUIDANCE WHICH KEEPS CAPE VALUES ON THE LOW
SIDE WITH ONLY A FEW HUNDREDS J/KG OF CAPE TO WORK WITH. THIS IS
ASSUMING SKIES STAY OVERCAST...AND THINKING WE WILL BE OVERCAST
TODAY. THAT BEING SAID...ANY LOCATIONS THAT SEE SUNSHINE COULD
DEVELOP ENOUGH CAPE TO SUPPORT TALLER CELLS AND POSSIBLY SEVERE
WEATHER. IN GENERAL THINKING DAMAGING WINDS AND AN ISOLATED
TORNADO ARE THE MAIN THREATS...BUT STRONGER STORMS WITH HIGHER
CAPE VALUES COULD SUPPORT HAIL. RADAR IMAGERY IS SHOWING GRAVITY
WAVE TAGS MOVING ALONG THE LINE OF STORMS AND WHEN THE TAGS
INTERSECT THE LINE...STORMS BEGIN TO SPIN. THEREFORE THE TORNADO
THREAT IS NOT ZERO.

THIS FIRST BATCH OF PRECIP WILL PUSH EAST THROUGH THE EARLY AFTN
HOURS AND EXPECTING ADDITIONAL SCATTERED TO NUMEROUS THUNDERSTORMS
DEVELOPMENT BEHIND THE LINE OVER NORTH CENTRAL IL. THE SECOND
WAVE SHIFTS EAST THROUGH THE EARLY EVENING HOURS. PWAT VALUES ARE
1.2-1.5 INCHES SO HEAVY DOWNPOURS ARE PSBL.

JEE

&&

.SHORT TERM...
319 AM CDT

THROUGH TUESDAY NIGHT...

FOR THE REMAINDER OF THE OVERNIGHT HOURS...CONDITIONS WILL REMAIN
QUIET ACROSS THE CWA AS A SERIES OF SHORT WAVES CONTINUE TO TRACK
NORTH AROUND THE TOP OF A PERSISTENT UPPER LEVEL RIDGE WHICH EXTENDS
FROM THE SERN CONUS THROUGH THE UPPER MISSISSIPPI VALLEY.  THIS
UPPER RIDGE HAS BEEN THE FEATURE WHICH HAS CONTROLLED THE PATH OF
THE SERIES OF SHORTWAVES LIFTING OUT OF THE SOUTHERN PLAINS...AND
WILL CONTINUE TO DO SO THROUGH THE DAY TODAY. SLY...MODERATELY
STRONG...WINDS WILL PERSIST THROUGH THE NIGHT...AND MUCH OF THE DAY
ALLOWING FOR SFC DEWPOINTS TO REMAIN CONSISTENT OR POSSIBLE INCH A
LITTLE HIGHER.

MAIN CONCERN FOR THE MORNING HOURS WILL BE THE TRACK OF A STRONG
SHORT WAVE AND ASSOCIATED SFC LOW LIFTING NORTHWARD THROUGH THE
MIDDLE MISSISSIPPI VALLEY.  THIS FEATURE WILL PREDOMINANTLY IMPACT
ERN IOWA AND WRN IL BY ARND DAYBREAK.  THROUGH THE MORNING...THE
COMBINATION OF ISENTROPIC LIFT IN THE WARM SECTOR OF THE
SYSTEM...ALL OF IL AND INTO NWRN IN...WILL LEAD TO SOME
DESTABILIZATION ACROSS THE REGION. A SFC TROUGH...AS WELL INDICATED
BY THE LATEST HIGH RES GUIDANCE...WITH LIFT THROUGH NRN IL/IN
THROUGH THE DAY...COINCIDENT WITH A STRONG SSWLY LOW LEVEL JET OF 45-
50 KT...WITH PROVIDE THE POTENTIAL FOR SHOWERS AND STRONG TO SEVERE
THUNDERSTORMS ACROSS THE CWA.  BASED ON WIND PROFILES AND MID LEVEL
DRYING...THE PRIMARY CONCERN WITH REGARD TO SEVERE WEATHER WILL BE
STRONG WIND GUSTS.  HOWEVER...SOME OF THE HIGH RES SFC WIND GUIDANCE
SUGGEST SOME SLIGHT BACKING OF SFC WINDS FROM 180-190 DEGREES TO 160-
170 DEGREES...WHILE WINDS ALOFT REMAIN SWLY.  THIS SLIGHT BACKING OF
THE SFC WINDS COULD PROVIDE ENOUGH DIRECTIONAL SHEAR THROUGH THE
LOWER LEVELS TO BRING AN ISOLD TORNADO THREAT. LOCALLY HEAVY
RAINFALL WILL ALSO BE CONCERNED WITH PWATS REACHING 1.75 INCHES
LATER THIS MORNING.  HOWEVER...FLOODING WILL LIKELY NOT BE A
SIGNIFICANT CONCERN AS THE SWLY WINDS RIGHT OFF THE DECK WILL RANGE
FROM ARND 45 KT ABOVE THE BOUNDARY LAYER TO ARND 90KT AT UPPER
LEVELS WHICH SHOULD ALLOW ANY OF THE STRONGER STORMS THAT DO DEVELOP
TO MOVE QUICKLY.

BY EARLY AFTERNOON...THE MAIN SHORT WAVE WILL LIFT INTO WISCONSIN
WHILE A SFC TROUGH TRACKS EAST ACROSS THE AREA.  THIS WILL LEAD TO
WINDS AT THE SFC VEERING TO SWLY...SETTING UP A UNIDIRECTIONAL WIND
PROFILE...EFFECTIVELY MINIMIZING THE SEVERE WEATHER THREAT TO THE
REGION.  BY LATE AFTERNOON AND INTO THE EVENING THE MODELS ARE
ADVERTISING THAT A DRY SLOW SHOULD NOSE INTO NRN IL...EFFECTIVELY
CUTTING OFF THE PCPN AREA INTO 2 SEPARATE AREA...ONE OVER WISCONSIN
AND ERN IOWA AND ANOTHER MORE FOCUSED OVER INDIANA.  THE NWRN
INDIANA COUNTIES WILL STILL HAVE A CHANCE FOR SOME SHOWERS AND
THUNDERSTORMS INTO THE EVENING...WHILE PCPN CHANCES OVER NRN IL
BEGIN TO WANE.  MUCH OF THE MODEL GUIDANCE ALSO INDICATED THAT THE
SHORTWAVE SHOULD SLOW IT`S PROGRESSION THROUGH WISCONSIN AS IT
APPROACHES THE APEX OF THE UPPER RIDGE.  AN ASSOCIATED SFC
TROUGH/COLD FRONT EXTENDING SOUTHWEST FROM THE SFC LOW WILL LINGER
OVER ERN IOWA IN THE EARLY EVENING BEFORE STEADILY PUSHING ACROSS
NRN IL AND INTO NWRN IN OVERNIGHT.  THROUGH THE NIGHT...THE
STRONGEST UPPER LEVEL FORCING WILL BE WELL NORTH OF THE CWA...SO ANY
LINGERING CHANCES FOR PCPN OVERNIGHT WILL BE LOW AND LIKELY CONFINED
TO THE NRN TIER COUNTIES OF IL...ALONG THE WI BORDER.

KREIN

&&

.LONG TERM...
229 AM CDT

WEDNESDAY THROUGH MONDAY...

WEDNESDAY THROUGH THURSDAY...
OPEN 500MB WAVE WILL BE LIFTING NORTHEAST ACROSS THE UPPER MIDWEST
INTO ONTARIO AND EVENTUALLY QUEBEC...WITH HEIGHTS SLOWLY INCREASING
WED AFTN. SFC FEATURES REMAIN DISORGANIZED WED...WITH A BOUNDARY
SLOWLY SHIFTING EAST. OPER GUIDANCE DIFFERS ON HOW QUICKLY PRECIP
WILL DEPART THE REGION. ENSEMBLE DATA SUGGESTS HOLDING ONTO CHC TO
SLIGHT CHC POPS MAINLY FOR THE CENTRAL/EASTERN CWFA WED/WED EVE.
ALTHOUGH WITH SOME HINT OF SFC HEIGHTS NUDGING UP...IT IS POSSIBLE
THAT SOME DRY AIR COULD FILTER IN AND KICK PRECIP EAST BY MIDDAY AND
ALLOW FOR A MAINLY DRY WED. SFC WINDS WILL BE TURNING SOUTHWEST TO
WEST...KEEPING AN OFFSHORE FLOW FOR LOCATIONS CLOSE TO LAKE
MICHIGAN. TEMPS SHOULD YET AGAIN TOUCH UPR 70S TO ARND 80 WED...IF
CLOUDS AND PRECIP CAN PUSH EAST BY MIDDAY...SOME CLEARING WOULD
ALLOW SFC TEMPS TO PUSH A COUPLE DEGREES WARMER INTO THE LOW 80S IN
SOME LOCATIONS. LATE IN THE EVENING THE GRADIENT SLACKENS
FURTHER...AND COULD ALLOW A LATE DAY ONSHORE FLOW TO DEVELOP FOR
AREAS ADJACENT TO LAKE MICHIGAN.

MID-LVL FLOW BEGINS TO FLATTEN AS A WEAK SFC RIDGE BECOMES ORIENTED
FROM WESTERN QUEBEC SOUTH THROUGH THE EASTERN OHIO RIVER VALLEY.
THIS WILL GENERALLY ALLOW A SOUTHERLY FLOW...ALTHOUGH THE GRADIENT
IS NOT VERY STRONG. THIS SHOULD SET THE STAGE FOR A LAKE
BREEZE/ONSHORE FLOW TO DEVELOP THUR. TIMING COULD END UP BEING
SLIGHTLY EARLIER GIVEN THE LIGHT SFC GRADIENT. GUIDANCE HAS BEEN
CONSISTENT IN HOLDING PRECIP WEST/SOUTH OF THE FORECAST AREA
THUR...AS A RESULT OF THE WEAK SFC RIDGING. SO ONE MORE MILD DAY
WITH HIGHS WARMING BACK INTO THE UPR 70S/LOW 80S...HOWEVER AS
PREVIOUSLY NOTED...A LAKE BREEZE IS LIKELY TO DEVELOP. THIS WILL
BLEED THE MUCH COOLER MARINE AIR WEST ACROSS NORTHEAST IL AND
DOWNTOWN CHICAGO. IF THE TIMING IS EARLIER IN THE DAY THUR...TEMPS
MAY NOT WARM BEYOND THE LOW/MID 60S ALONG THE CHICAGO LAKEFRONT.

FLOW THEN TURNS SOUTHERLY THUR NIGHT WITH THE MORE PROGRESSIVE FLOW
IN THE MID-LVLS PUSHING THE RIDGING EAST. A RETURN FLOW MOISTURE
WILL CONTINUE TO BE FOCUSED ACROSS THE CENTRAL CONUS THUR EVE...WITH
A SLOW MOVING FRONTAL BOUNDARY NUDGING EAST THUR NIGHT TOWARDS
WESTERN IL. THIS FRONTAL BOUNDARY WILL BECOME ENERGIZED AS A ROBUST
500MB VORT MAX BREAKS SOUTH FROM CENTRAL CANADA LATE THUR NIGHT.

THIS SHOULD ALLOW FOR AN ATMOSPHERIC RIVER TO DEVELOP FROM THE
SOUTHERN PLAINS STRETCHING NORTH THROUGH THE MID-MISSOURI VALLEY
INTO THE WESTERN GREAT LAKES EARLY FRI MORNING.

FRIDAY THROUGH EARLY NEXT WEEK...
ENSEMBLES CONTINUE TO PROG A ROBUST TROUGH SLIDING SOUTH FROM
CENTRAL CANADA FRI. THIS COUPLED WITH DOWNSTREAM MID-LVL RIDGING
ACROSS THE SOUTHEAST CONUS WILL STRENGTHEN THE FRONTAL BOUNDARY
THAT WILL BE ORIENTED FROM THE SOUTHERN PLAINS STRETCHING
NORTHEAST THROUGH THE GREAT LAKES REGION INTO WESTERN QUEBEC.

THIS SETUP IS IDEAL FOR THE DEVELOPMENT OF AN ATMOSPHERIC RIVER WITH
ABUNDANT LOW LEVEL MOISTURE AND EFFICIENT PRECIP PRODUCING
CONVECTION.

OPER GUIDANCE HAS BEEN RELATIVELY CONSISTENT WITH BRINGING A SERIES
OF WAVES ALONG THE SLOW MOVING FRONTAL BOUNDARY FRI AFTN/EVE...THEN
THE BOUNDARY SHOULD SLIDE EAST WITH WINDS QUICKLY VEERING
NORTH/NORTHEAST FOR SAT AND USHERING IN MUCH COOLER AIR TO THE
REGION.

CURRENT INDICATIONS ARE THAT HIGHS SAT MAY STRUGGLE TO WARM BEYOND
THE UPR 50S ACROSS NORTHEAST IL/NORTHWEST IN...WITH ONLY LOW 60S
ELSEWHERE. STRONG SFC RIDGE WILL REMAIN NORTH OF THE REGION...SO THE
PRIOR FRONTAL BOUNDARY MAY BECOME QUASI-STATIONARY FOR THE WEEKEND
ALONG THE OHIO VALLEY AND CONTINUE TO FEED PRECIP CHANCES TO THE
SOUTHERN CWFA.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 18Z...

* MVFR THIS AFTERNOON

* RAIN WITH EMBEDDED THUNDER POSSIBLE

* SOUTH WINDS VARYING FROM SOUTHEAST EARLY TO SOUTHWEST THIS
  EVENING.

* MVFR IN FOG AND LOW CLOUDS WEDNESDAY MORNING.

MM

//DISCUSSION...UPDATED 18Z...

LINE OF SHOWERS HAS DECREASED VSBYS TO 1 MILE UPSTREAM EARLY THIS
AFTERNOON. AS THE LINE PROGRESSES NORTHEASTWARD...COULD SEE SOME
STRONGER POCKETS OF RAIN AND TALLER EMBEDDED CELLS PRODUCE
ISOLATED LIGHTNING. LOW CHANCE/CONFIDENCE OF ANY OF THESE CELLS
HITTING THE TERMINALS...SO KEPT VCTS IN THE TAFS THROUGH 19Z.

LOOKING TOWARD WEDNESDAY MORNING...LOW LEVEL MOISTURE AND A WEAK
INVERSION WILL ALLOW A CHANCE FOR MVFR FOG AND CIGS TO WORK INTO
THE TERMINALS. THE AFTERNOON WILL FEATURE A SCATTERED TO POSSIBLY
BROKEN DECK AT 025. INTO THE EVENING...EXPECT OVERCAST CONDITIONS
WITH LIGHT RAIN POSSIBLE. THERE IS A CHANCE FOR THE LAKE BREEZE TO
WORK INTO ORD NEAR OR JUST AFTER 00Z WEDNESDAY EVENING.

MM

//ORD AND MDW CONFIDENCE...UPDATED 18Z...

* HIGH CONFIDENCE REMAINING MVFR THIS AFTERNOON.

* HIGH CONFIDENCE IN RAIN TIMING THIS AFTERNOON. LOW CONFIDENCE ON
  THUNDER CHANCES.

* MEDIUM TO HIGH CONFIDENCE IN WIND DIRECTION WITH HIGH CONFIDENCE
  IN WIND SPEED EXCEPT LOW CONFIDENCE IF THUNDERSTORMS OCCUR.

* LOW-MEDIUM CONFIDENCE IN FOG AND MVFR CONDITIONS WEDNESDAY
  MORNING.

*

MM

//OUTLOOK FOR ORD/MDW FOR 00Z THURSDAY-12Z TUESDAY...UPDATED 12Z...

WEDNESDAY NIGHT...WX NIL/VFR. SOUTHEAST WINDS.

THURSDAY...SLIGHT CHANCE OF TSRA AT NIGHT. SOUTHEAST WINDS.

FRIDAY...TSRA/SHRA LIKELY THROUGH THE DAY AND NIGHT. MVFR
POSSIBLE. SOUTHWEST WINDS.

SATURDAY...SHRA LIKELY WITH A CHANCE OF TSRA DURING THE DAY.
NORTHEAST WINDS.

SUNDAY...CHANCE OF SHRA. EAST WINDS. MVFR POSSIBLE.

MONDAY...CHANCE OF SHRA. SOUTHEAST WINDS. MVFR POSSIBLE.

KREIN

&&

.MARINE...
229 AM CDT

WARM MOIST AIR CONTINUES TO FEED NORTH ACROSS THE LAKE
TODAY...WHICH MAY HELP TO FURTHER ENHANCE ANY AREAS OF FOG THAT
HAVE ALREADY DEVELOPED. IT IS POSSIBLE PATCHY DENSE FOG MAY
DEVELOP...ALTHOUGH WINDS MAY BE JUST STRONG ENOUGH TO LIMIT THE
COVERAGE AND INTENSITY OF THE FOG. A SURFACE LOW PRESSURE SYSTEM
WILL BE LIFTING NORTH ACROSS EASTERN IOWA INTO CENTRAL WISCONSIN
THIS EVENING. THE GRADIENT WILL TIGHTEN ACROSS THE
CENTRAL/SOUTHERN PORTIONS OF THE LAKE...WHICH WITH WARMER
NEARSHORE WATERS EXPECT SOME SLIGHTLY BETTER MIXING TO OCCUR.
FURTHER OUT ACROSS THE OPEN WATERS THE WATER REMAINS COLD AND
EXPECT THE STABILITY TO MAKE IT DIFFICULT TO MIX TO THE SFC THE
HIGHER GUSTS. HIGH PRESSURE THEN ARRIVES LATE WEDNESDAY WITH LIGHT
WINDS DEVELOPING. THEN HIGH PRESSURE SHIFTS EAST THURSDAY
NIGHT...WITH SOUTHERLY WINDS DEVELOPING AGAIN FRIDAY. A FRONTAL
BOUNDARY WILL APPROACH LAKE MICHIGAN LATE FRIDAY NIGHT THEN
STEADILY SLIDE SOUTH ALONG THE LAKE. THIS WILL ALLOW WINDS TO
QUICKLY VEER FROM SOUTH TO NORTH/NORTHEAST SATURDAY. ALONG WITH
THIS QUICK WIND SHIFT WILL BE COOLER AIR SLIDING SOUTH OVER THE
LAKE. WAVES SHOULD EASILY BUILD SATURDAY FOR THE CENTRAL/SOUTHERN
PORTIONS OF THE LAKE.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 261610
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1110 AM CDT TUE MAY 26 2015

.UPDATE...
1007 AM CDT

A SFC LOW IS OVER IOWA AND ITS WARM/STATIONARY FRONT IS WELL TO
OUR NORTH OVER CENTRAL WI. ITS COLD FRONT STRETCHES FROM THE LOW
THROUGH CENTRAL KANSAS. AN AREA OF MAINLY RAIN AND A FEW
THUNDERSTORMS IS SLOWLY SPREADING NNE ACROSS NORTH CENTRAL IL. SO
FAR THE SHOWERS HAVE BEEN BEHAVING ACROSS MY CWA...BUT A FEW CELLS
TO THE WEST HAVE SHOWN SIGNS OF ROTATION.

LIKING THE LATEST RAP GUIDANCE WHICH KEEPS CAPE VALUES ON THE LOW
SIDE WITH ONLY A FEW HUNDREDS J/KG OF CAPE TO WORK WITH. THIS IS
ASSUMING SKIES STAY OVERCAST...AND THINKING WE WILL BE OVERCAST
TODAY. THAT BEING SAID...ANY LOCATIONS THAT SEE SUNSHINE COULD
DEVELOP ENOUGH CAPE TO SUPPORT TALLER CELLS AND POSSIBLY SEVERE
WEATHER. IN GENERAL THINKING DAMAGING WINDS AND AN ISOLATED
TORNADO ARE THE MAIN THREATS...BUT STRONGER STORMS WITH HIGHER
CAPE VALUES COULD SUPPORT HAIL. RADAR IMAGERY IS SHOWING GRAVITY
WAVE TAGS MOVING ALONG THE LINE OF STORMS AND WHEN THE TAGS
INTERSECT THE LINE...STORMS BEGIN TO SPIN. THEREFORE THE TORNADO
THREAT IS NOT ZERO.

THIS FIRST BATCH OF PRECIP WILL PUSH EAST THROUGH THE EARLY AFTN
HOURS AND EXPECTING ADDITIONAL SCATTERED TO NUMEROUS THUNDERSTORMS
DEVELOPMENT BEHIND THE LINE OVER NORTH CENTRAL IL. THE SECOND
WAVE SHIFTS EAST THROUGH THE EARLY EVENING HOURS. PWAT VALUES ARE
1.2-1.5 INCHES SO HEAVY DOWNPOURS ARE PSBL.

JEE

&&

.SHORT TERM...
319 AM CDT

THROUGH TUESDAY NIGHT...

FOR THE REMAINDER OF THE OVERNIGHT HOURS...CONDITIONS WILL REMAIN
QUIET ACROSS THE CWA AS A SERIES OF SHORT WAVES CONTINUE TO TRACK
NORTH AROUND THE TOP OF A PERSISTENT UPPER LEVEL RIDGE WHICH EXTENDS
FROM THE SERN CONUS THROUGH THE UPPER MISSISSIPPI VALLEY.  THIS
UPPER RIDGE HAS BEEN THE FEATURE WHICH HAS CONTROLLED THE PATH OF
THE SERIES OF SHORTWAVES LIFTING OUT OF THE SOUTHERN PLAINS...AND
WILL CONTINUE TO DO SO THROUGH THE DAY TODAY. SLY...MODERATELY
STRONG...WINDS WILL PERSIST THROUGH THE NIGHT...AND MUCH OF THE DAY
ALLOWING FOR SFC DEWPOINTS TO REMAIN CONSISTENT OR POSSIBLE INCH A
LITTLE HIGHER.

MAIN CONCERN FOR THE MORNING HOURS WILL BE THE TRACK OF A STRONG
SHORT WAVE AND ASSOCIATED SFC LOW LIFTING NORTHWARD THROUGH THE
MIDDLE MISSISSIPPI VALLEY.  THIS FEATURE WILL PREDOMINANTLY IMPACT
ERN IOWA AND WRN IL BY ARND DAYBREAK.  THROUGH THE MORNING...THE
COMBINATION OF ISENTROPIC LIFT IN THE WARM SECTOR OF THE
SYSTEM...ALL OF IL AND INTO NWRN IN...WILL LEAD TO SOME
DESTABILIZATION ACROSS THE REGION. A SFC TROUGH...AS WELL INDICATED
BY THE LATEST HIGH RES GUIDANCE...WITH LIFT THROUGH NRN IL/IN
THROUGH THE DAY...COINCIDENT WITH A STRONG SSWLY LOW LEVEL JET OF 45-
50 KT...WITH PROVIDE THE POTENTIAL FOR SHOWERS AND STRONG TO SEVERE
THUNDERSTORMS ACROSS THE CWA.  BASED ON WIND PROFILES AND MID LEVEL
DRYING...THE PRIMARY CONCERN WITH REGARD TO SEVERE WEATHER WILL BE
STRONG WIND GUSTS.  HOWEVER...SOME OF THE HIGH RES SFC WIND GUIDANCE
SUGGEST SOME SLIGHT BACKING OF SFC WINDS FROM 180-190 DEGREES TO 160-
170 DEGREES...WHILE WINDS ALOFT REMAIN SWLY.  THIS SLIGHT BACKING OF
THE SFC WINDS COULD PROVIDE ENOUGH DIRECTIONAL SHEAR THROUGH THE
LOWER LEVELS TO BRING AN ISOLD TORNADO THREAT. LOCALLY HEAVY
RAINFALL WILL ALSO BE CONCERNED WITH PWATS REACHING 1.75 INCHES
LATER THIS MORNING.  HOWEVER...FLOODING WILL LIKELY NOT BE A
SIGNIFICANT CONCERN AS THE SWLY WINDS RIGHT OFF THE DECK WILL RANGE
FROM ARND 45 KT ABOVE THE BOUNDARY LAYER TO ARND 90KT AT UPPER
LEVELS WHICH SHOULD ALLOW ANY OF THE STRONGER STORMS THAT DO DEVELOP
TO MOVE QUICKLY.

BY EARLY AFTERNOON...THE MAIN SHORT WAVE WILL LIFT INTO WISCONSIN
WHILE A SFC TROUGH TRACKS EAST ACROSS THE AREA.  THIS WILL LEAD TO
WINDS AT THE SFC VEERING TO SWLY...SETTING UP A UNIDIRECTIONAL WIND
PROFILE...EFFECTIVELY MINIMIZING THE SEVERE WEATHER THREAT TO THE
REGION.  BY LATE AFTERNOON AND INTO THE EVENING THE MODELS ARE
ADVERTISING THAT A DRY SLOW SHOULD NOSE INTO NRN IL...EFFECTIVELY
CUTTING OFF THE PCPN AREA INTO 2 SEPARATE AREA...ONE OVER WISCONSIN
AND ERN IOWA AND ANOTHER MORE FOCUSED OVER INDIANA.  THE NWRN
INDIANA COUNTIES WILL STILL HAVE A CHANCE FOR SOME SHOWERS AND
THUNDERSTORMS INTO THE EVENING...WHILE PCPN CHANCES OVER NRN IL
BEGIN TO WANE.  MUCH OF THE MODEL GUIDANCE ALSO INDICATED THAT THE
SHORTWAVE SHOULD SLOW IT`S PROGRESSION THROUGH WISCONSIN AS IT
APPROACHES THE APEX OF THE UPPER RIDGE.  AN ASSOCIATED SFC
TROUGH/COLD FRONT EXTENDING SOUTHWEST FROM THE SFC LOW WILL LINGER
OVER ERN IOWA IN THE EARLY EVENING BEFORE STEADILY PUSHING ACROSS
NRN IL AND INTO NWRN IN OVERNIGHT.  THROUGH THE NIGHT...THE
STRONGEST UPPER LEVEL FORCING WILL BE WELL NORTH OF THE CWA...SO ANY
LINGERING CHANCES FOR PCPN OVERNIGHT WILL BE LOW AND LIKELY CONFINED
TO THE NRN TIER COUNTIES OF IL...ALONG THE WI BORDER.

KREIN

&&

.LONG TERM...
229 AM CDT

WEDNESDAY THROUGH MONDAY...

WEDNESDAY THROUGH THURSDAY...
OPEN 500MB WAVE WILL BE LIFTING NORTHEAST ACROSS THE UPPER MIDWEST
INTO ONTARIO AND EVENTUALLY QUEBEC...WITH HEIGHTS SLOWLY INCREASING
WED AFTN. SFC FEATURES REMAIN DISORGANIZED WED...WITH A BOUNDARY
SLOWLY SHIFTING EAST. OPER GUIDANCE DIFFERS ON HOW QUICKLY PRECIP
WILL DEPART THE REGION. ENSEMBLE DATA SUGGESTS HOLDING ONTO CHC TO
SLIGHT CHC POPS MAINLY FOR THE CENTRAL/EASTERN CWFA WED/WED EVE.
ALTHOUGH WITH SOME HINT OF SFC HEIGHTS NUDGING UP...IT IS POSSIBLE
THAT SOME DRY AIR COULD FILTER IN AND KICK PRECIP EAST BY MIDDAY AND
ALLOW FOR A MAINLY DRY WED. SFC WINDS WILL BE TURNING SOUTHWEST TO
WEST...KEEPING AN OFFSHORE FLOW FOR LOCATIONS CLOSE TO LAKE
MICHIGAN. TEMPS SHOULD YET AGAIN TOUCH UPR 70S TO ARND 80 WED...IF
CLOUDS AND PRECIP CAN PUSH EAST BY MIDDAY...SOME CLEARING WOULD
ALLOW SFC TEMPS TO PUSH A COUPLE DEGREES WARMER INTO THE LOW 80S IN
SOME LOCATIONS. LATE IN THE EVENING THE GRADIENT SLACKENS
FURTHER...AND COULD ALLOW A LATE DAY ONSHORE FLOW TO DEVELOP FOR
AREAS ADJACENT TO LAKE MICHIGAN.

MID-LVL FLOW BEGINS TO FLATTEN AS A WEAK SFC RIDGE BECOMES ORIENTED
FROM WESTERN QUEBEC SOUTH THROUGH THE EASTERN OHIO RIVER VALLEY.
THIS WILL GENERALLY ALLOW A SOUTHERLY FLOW...ALTHOUGH THE GRADIENT
IS NOT VERY STRONG. THIS SHOULD SET THE STAGE FOR A LAKE
BREEZE/ONSHORE FLOW TO DEVELOP THUR. TIMING COULD END UP BEING
SLIGHTLY EARLIER GIVEN THE LIGHT SFC GRADIENT. GUIDANCE HAS BEEN
CONSISTENT IN HOLDING PRECIP WEST/SOUTH OF THE FORECAST AREA
THUR...AS A RESULT OF THE WEAK SFC RIDGING. SO ONE MORE MILD DAY
WITH HIGHS WARMING BACK INTO THE UPR 70S/LOW 80S...HOWEVER AS
PREVIOUSLY NOTED...A LAKE BREEZE IS LIKELY TO DEVELOP. THIS WILL
BLEED THE MUCH COOLER MARINE AIR WEST ACROSS NORTHEAST IL AND
DOWNTOWN CHICAGO. IF THE TIMING IS EARLIER IN THE DAY THUR...TEMPS
MAY NOT WARM BEYOND THE LOW/MID 60S ALONG THE CHICAGO LAKEFRONT.

FLOW THEN TURNS SOUTHERLY THUR NIGHT WITH THE MORE PROGRESSIVE FLOW
IN THE MID-LVLS PUSHING THE RIDGING EAST. A RETURN FLOW MOISTURE
WILL CONTINUE TO BE FOCUSED ACROSS THE CENTRAL CONUS THUR EVE...WITH
A SLOW MOVING FRONTAL BOUNDARY NUDGING EAST THUR NIGHT TOWARDS
WESTERN IL. THIS FRONTAL BOUNDARY WILL BECOME ENERGIZED AS A ROBUST
500MB VORT MAX BREAKS SOUTH FROM CENTRAL CANADA LATE THUR NIGHT.

THIS SHOULD ALLOW FOR AN ATMOSPHERIC RIVER TO DEVELOP FROM THE
SOUTHERN PLAINS STRETCHING NORTH THROUGH THE MID-MISSOURI VALLEY
INTO THE WESTERN GREAT LAKES EARLY FRI MORNING.

FRIDAY THROUGH EARLY NEXT WEEK...
ENSEMBLES CONTINUE TO PROG A ROBUST TROUGH SLIDING SOUTH FROM
CENTRAL CANADA FRI. THIS COUPLED WITH DOWNSTREAM MID-LVL RIDGING
ACROSS THE SOUTHEAST CONUS WILL STRENGTHEN THE FRONTAL BOUNDARY
THAT WILL BE ORIENTED FROM THE SOUTHERN PLAINS STRETCHING
NORTHEAST THROUGH THE GREAT LAKES REGION INTO WESTERN QUEBEC.

THIS SETUP IS IDEAL FOR THE DEVELOPMENT OF AN ATMOSPHERIC RIVER WITH
ABUNDANT LOW LEVEL MOISTURE AND EFFICIENT PRECIP PRODUCING
CONVECTION.

OPER GUIDANCE HAS BEEN RELATIVELY CONSISTENT WITH BRINGING A SERIES
OF WAVES ALONG THE SLOW MOVING FRONTAL BOUNDARY FRI AFTN/EVE...THEN
THE BOUNDARY SHOULD SLIDE EAST WITH WINDS QUICKLY VEERING
NORTH/NORTHEAST FOR SAT AND USHERING IN MUCH COOLER AIR TO THE
REGION.

CURRENT INDICATIONS ARE THAT HIGHS SAT MAY STRUGGLE TO WARM BEYOND
THE UPR 50S ACROSS NORTHEAST IL/NORTHWEST IN...WITH ONLY LOW 60S
ELSEWHERE. STRONG SFC RIDGE WILL REMAIN NORTH OF THE REGION...SO THE
PRIOR FRONTAL BOUNDARY MAY BECOME QUASI-STATIONARY FOR THE WEEKEND
ALONG THE OHIO VALLEY AND CONTINUE TO FEED PRECIP CHANCES TO THE
SOUTHERN CWFA.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 16Z...

* MVFR CEILINGS CONTINUE INTO THIS AFTERNOON

* LINE OF RA APPROACHING TERMINALS WITH VCTS POSSIBLE

* SOUTH WINDS VARYING FROM SSE BECOMING SSW AFTER 23Z...GUSTING
  OVER 20KT

MM

//DISCUSSION...UPDATED 16Z...

DECREASING CONFIDENCE IN ANY THUNDER REACHING THE TAF SITES THIS
AFTERNOON...SO DROPPED GROUP TO VCTS FOR A LIMITED TIME. HIGHER
CONFIDENCE IN LINE OF LIGHT TO MODERATE SHOWER ACTIVITY
APPROACHING FROM THE SOUTH-SOUTHWEST. VISIBLE SATELLITE SHOWS
CLEARING BEHIND THE LINE OF RAIN...WHICH WILL BE MONITORED FOR ANY
ADDITIONAL INSTABILITY DEVELOPING. AT THIS POINT...ONLY CONFIDENT
IN A CHANCE OF SHOWERS REDEVELOPING BEHIND THE LINE.

MM

//ORD AND MDW CONFIDENCE...UPDATED 16Z...

* HIGH CONFIDENCE IN MVFR CEILINGS.

* MEDIUM HIGH CONFIDENCE IN WIND SPEEDS AND MEDIUM IN WIND
  DIRECTION.

* HIGH CONFIDENCE IN SHOWERS AND RAIN WITH MEDIUM CONFIDENCE IN
  VCTS AND LOW CONFIDENCE IN ADDITIONAL TS DEVELOPMENT AFTER 21Z.

MM

//OUTLOOK FOR ORD/MDW FOR 00Z THURSDAY-12Z TUESDAY...UPDATED 12Z...

WEDNESDAY NIGHT...WX NIL/VFR. SOUTHEAST WINDS.

THURSDAY...SLIGHT CHANCE OF TSRA AT NIGHT. SOUTHEAST WINDS.

FRIDAY...TSRA/SHRA LIKELY THROUGH THE DAY AND NIGHT. MVFR
POSSIBLE. SOUTHWEST WINDS.

SATURDAY...SHRA LIKELY WITH A CHANCE OF TSRA DURING THE DAY.
NORTHEAST WINDS.

SUNDAY...CHANCE OF SHRA. EAST WINDS. MVFR POSSIBLE.

MONDAY...CHANCE OF SHRA. SOUTHEAST WINDS. MVFR POSSIBLE.

KREIN

&&

.MARINE...
229 AM CDT

WARM MOIST AIR CONTINUES TO FEED NORTH ACROSS THE LAKE
TODAY...WHICH MAY HELP TO FURTHER ENHANCE ANY AREAS OF FOG THAT
HAVE ALREADY DEVELOPED. IT IS POSSIBLE PATCHY DENSE FOG MAY
DEVELOP...ALTHOUGH WINDS MAY BE JUST STRONG ENOUGH TO LIMIT THE
COVERAGE AND INTENSITY OF THE FOG. A SURFACE LOW PRESSURE SYSTEM
WILL BE LIFTING NORTH ACROSS EASTERN IOWA INTO CENTRAL WISCONSIN
THIS EVENING. THE GRADIENT WILL TIGHTEN ACROSS THE
CENTRAL/SOUTHERN PORTIONS OF THE LAKE...WHICH WITH WARMER
NEARSHORE WATERS EXPECT SOME SLIGHTLY BETTER MIXING TO OCCUR.
FURTHER OUT ACROSS THE OPEN WATERS THE WATER REMAINS COLD AND
EXPECT THE STABILITY TO MAKE IT DIFFICULT TO MIX TO THE SFC THE
HIGHER GUSTS. HIGH PRESSURE THEN ARRIVES LATE WEDNESDAY WITH LIGHT
WINDS DEVELOPING. THEN HIGH PRESSURE SHIFTS EAST THURSDAY
NIGHT...WITH SOUTHERLY WINDS DEVELOPING AGAIN FRIDAY. A FRONTAL
BOUNDARY WILL APPROACH LAKE MICHIGAN LATE FRIDAY NIGHT THEN
STEADILY SLIDE SOUTH ALONG THE LAKE. THIS WILL ALLOW WINDS TO
QUICKLY VEER FROM SOUTH TO NORTH/NORTHEAST SATURDAY. ALONG WITH
THIS QUICK WIND SHIFT WILL BE COOLER AIR SLIDING SOUTH OVER THE
LAKE. WAVES SHOULD EASILY BUILD SATURDAY FOR THE CENTRAL/SOUTHERN
PORTIONS OF THE LAKE.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KILX 261550
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1050 AM CDT TUE MAY 26 2015

.UPDATE...
ISSUED AT 1038 AM CDT TUE MAY 26 2015

MADE A FEW UPDATES TO POPS/WEATHER AND HOURLY TEMPS FOR TODAY
BASED ON TRENDS OF CURRENT CONVECTION MOVING THROUGH CENTRAL IL
LATE THIS MORNING INTO EAST CENTRAL IL BY THE NOON HOUR. A GENERAL
WEAKENING TREND HAS BEEN NOTED THE PAST HOUR, SO ONLY A BRIEF
HEAVY DOWNPOUR IS ANTICIPATED WITH THE LINE OF SHOWERS-ISOLATED
THUNDERSTORMS.

A VERY BRIEF PERIOD OF PARTIAL CLEARING IS ANTICIPATED AFTER THE
SHOWERS MOVE THROUGH, WHICH MAY HELP TO SLIGHTLY INCREASE THE
INSTABILITY IN CENTRAL AND EASTERN IL THIS AFTERNOON. HOWEVER,
SATELLITE IS SHOWING THAT CUMULUS WILL MOST LIKELY RAPIDLY FILL
IN. THE HRRR, NAM12 AND RAP ALL SEEM TO HAVE A FAIRLY GOOD HANDLE
ON THE WEAKENING TREND OF THE LINE OF CONVECTION, WITH SCATTERED
SHOWERS AND THUNDERSTORMS REDEVELOPING THIS AFTERNOON. A SHORTWAVE
TROUGH MOVING NORTHEAST FROM THE OZARKS WILL PROVIDE UPPER LEVEL
SUPPORT TO SOUTHEAST AND EAST CENTRAL IL, BUT INSTABILITY WILL BE
MARGINAL AT BEST. THUS, STRONG/SEVERE STORMS SHOULD BE QUITE
LIMITED IN COVERAGE, IF THEY DEVELOP AT ALL.

&&

.SHORT TERM...(TODAY)
ISSUED AT 343 AM CDT TUE MAY 26 2015

LOW CLOUDS HAVE BEEN ADVECTING INTO THE AREA AND WILL REMAIN OVER
THE AREA THIS MORNING. LOWER CLOUDS INDICATING LOTS OF LOW LEVEL
MOISTURE BEING ADVECTED INTO THE AREA AHEAD OF THE WEATHER SYSTEM
THAT STILL IS WEST OF THE CWA. RADAR AND SATELLITE LOOPS SHOW
SEVERAL MCVS WEST OF THE AREA WITH SOME SHOWERS MOVING NORTH THROUGH
SOUTHEASTERN MO. MODELS CONTINUE TO INDICATE PCPN REDEVELOPING
TODAY. CLOUDS WILL LIMIT THE DEGREE OF INSTABILITY BUT STILL
EXPECTING ENOUGH FOR THUNDERSTORMS, JUST NOT ENOUGH FOR ANYTHING
SEVERE, WHICH SHOULD BE EAST AND SOUTHEAST OF THE AREA WHERE LESS
CLOUDS WILL BE. CLOUD COVER WILL ALSO TEMPER WARM UP AS WELL SO ONLY
EXPECTING UPPER 70S FOR HIGHS WHICH IS MUCH LESS THAN PAST TWO DAYS.
POPS WILL BE A GRADUAL INCREASE TODAY REACHING LIKELY LATER THIS
MORNING AND THEN MOVING NORTH AND EAST THIS AFTERNOON, BECOMING
CHANCE CATEGORY BY LATE AFTERNOON AS THE PCPN MOVES EAST OF THE
AREA. SOUTHERLY WINDS WILL BE A TAD GUSTY AGAIN, JUST NOT AS MUCH AS
YESTERDAY.

.LONG TERM...(TONIGHT THROUGH MONDAY)
ISSUED AT 343 AM CDT TUE MAY 26 2015

UNTIL THE UPPER WAVE PULLS INTO THE GREAT LAKES REGION, LINGERING
POPS WILL REMAIN OVER THE FA FOR THIS EVENING.  BETTER CHANCES WILL
REMAIN TO THE EAST OVERNIGHT. REMAINS OF THE FRONT WILL STALL OUT
ALONG THE OHIO RIVER VALLEY AND PROVIDE A BIT OF FOCUS FOR ANOTHER
PIECE OF ENERGY EJECTING OUT OF THE SOUTHWEST.  MODELS DIFFERING
WITH THE NORTHERLY EXTENT OF THE PRECIP, BUT LAST FEW RUNS BRINGING
IN SOME PRECIPITATION FOR WEDNESDAY IN THE SOUTHEAST.  NAM IS A
LITTLE MORE WIDESPREAD, BUT CONCENTRATING THE POPS TO THE SOUTH AND
EAST FOR NOW.  TIMING ISSUES REMAIN IN PLACE FOR THIS SYNOPTIC RUN
FOR THE NEXT SYSTEM QUICK ON THE HEELS AS THE DEEP WAVE OVER THE SW
STARTS TO MOVE OUT INTO THE PLAINS. CONVECTION AND PRECIP STARTS TO
SPREAD OVER THE EASTERN HALF OF THE COUNTRY IN THE MODELS WITH  WEAK
SOUTHWESTERLY FLOW ALOFT SHIFTING TO WEAK FLOW OVERALL.  WARM AND
MUGGY CONDITIONS CONTINUE IN A MORE SUMMERLIKE AIRMASS THROUGHOUT
THE WEEK...BUT THAT NEXT SYSTEM WILL BRING A COLD FRONT INTO THE
REGION FOR THE FIRST HALF OF THE WEEKEND TO FOCUS THE RAIN, WITH A
COOLER AIRMASS BEHIND IT DROPPING THE TEMPS FOR THE WEEKEND OUT OF
THE 80S FOR A COUPLE DAYS.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z WEDNESDAY MORNING)
ISSUED AT 708 AM CDT TUE MAY 26 2015

LOW STRATUS HAS OVERSPREAD ALL TAF SITES THIS MORNING. THIS LOW
STRATUS LOOKS TO REMAIN OVER ALL SITES UNTIL SOMETIME THIS
AFTERNOON AFTER A NARROW BAND OF SHOWERS MOVES THROUGH THE AREA.
SPI IS THE ONLY ONE AT MVFR STATUS RIGHT NOW. ALL OTHER TAF SITES
ARE MVFR. BY THIS AFTERNOON ALL SITES SHOULD BE MVFR WITH HIGHER
CIGS AROUND 2.5KFT. SHOWERS WILL BE POSSIBLE THIS MORNING AS RADAR
LOOPS SHOWS. THEN HAS THE DAY HEATS UP THUNDERSTORMS WILL BE
POSSIBLE. WILL GO WITH VCTS FOR NOW GIVEN UNCERTAINTY OF LOCATION
OF ANY THUNDERSTORMS. THESE SHOULD END SOMETIME EARLY THIS
EVENING. SKIES SHOULD THEN BE VFR AS THE AREA SHOULD BE WELL IN
THE WARM SECTOR. THERE COULD BE MORE PCPN OVERNIGHT TONIGHT...BUT
LOTS OF UNCERTAINTY THERE SO WILL NOT INCLUDE AT THIS TIME. WINDS
WILL BECOME SOUTHERLY WITH SOME GUSTINESS THIS AFTERNOON.


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...MILLER
SHORT TERM...AUTEN
LONG TERM...HJS
AVIATION...AUTEN



000
FXUS63 KILX 261550
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1050 AM CDT TUE MAY 26 2015

.UPDATE...
ISSUED AT 1038 AM CDT TUE MAY 26 2015

MADE A FEW UPDATES TO POPS/WEATHER AND HOURLY TEMPS FOR TODAY
BASED ON TRENDS OF CURRENT CONVECTION MOVING THROUGH CENTRAL IL
LATE THIS MORNING INTO EAST CENTRAL IL BY THE NOON HOUR. A GENERAL
WEAKENING TREND HAS BEEN NOTED THE PAST HOUR, SO ONLY A BRIEF
HEAVY DOWNPOUR IS ANTICIPATED WITH THE LINE OF SHOWERS-ISOLATED
THUNDERSTORMS.

A VERY BRIEF PERIOD OF PARTIAL CLEARING IS ANTICIPATED AFTER THE
SHOWERS MOVE THROUGH, WHICH MAY HELP TO SLIGHTLY INCREASE THE
INSTABILITY IN CENTRAL AND EASTERN IL THIS AFTERNOON. HOWEVER,
SATELLITE IS SHOWING THAT CUMULUS WILL MOST LIKELY RAPIDLY FILL
IN. THE HRRR, NAM12 AND RAP ALL SEEM TO HAVE A FAIRLY GOOD HANDLE
ON THE WEAKENING TREND OF THE LINE OF CONVECTION, WITH SCATTERED
SHOWERS AND THUNDERSTORMS REDEVELOPING THIS AFTERNOON. A SHORTWAVE
TROUGH MOVING NORTHEAST FROM THE OZARKS WILL PROVIDE UPPER LEVEL
SUPPORT TO SOUTHEAST AND EAST CENTRAL IL, BUT INSTABILITY WILL BE
MARGINAL AT BEST. THUS, STRONG/SEVERE STORMS SHOULD BE QUITE
LIMITED IN COVERAGE, IF THEY DEVELOP AT ALL.

&&

.SHORT TERM...(TODAY)
ISSUED AT 343 AM CDT TUE MAY 26 2015

LOW CLOUDS HAVE BEEN ADVECTING INTO THE AREA AND WILL REMAIN OVER
THE AREA THIS MORNING. LOWER CLOUDS INDICATING LOTS OF LOW LEVEL
MOISTURE BEING ADVECTED INTO THE AREA AHEAD OF THE WEATHER SYSTEM
THAT STILL IS WEST OF THE CWA. RADAR AND SATELLITE LOOPS SHOW
SEVERAL MCVS WEST OF THE AREA WITH SOME SHOWERS MOVING NORTH THROUGH
SOUTHEASTERN MO. MODELS CONTINUE TO INDICATE PCPN REDEVELOPING
TODAY. CLOUDS WILL LIMIT THE DEGREE OF INSTABILITY BUT STILL
EXPECTING ENOUGH FOR THUNDERSTORMS, JUST NOT ENOUGH FOR ANYTHING
SEVERE, WHICH SHOULD BE EAST AND SOUTHEAST OF THE AREA WHERE LESS
CLOUDS WILL BE. CLOUD COVER WILL ALSO TEMPER WARM UP AS WELL SO ONLY
EXPECTING UPPER 70S FOR HIGHS WHICH IS MUCH LESS THAN PAST TWO DAYS.
POPS WILL BE A GRADUAL INCREASE TODAY REACHING LIKELY LATER THIS
MORNING AND THEN MOVING NORTH AND EAST THIS AFTERNOON, BECOMING
CHANCE CATEGORY BY LATE AFTERNOON AS THE PCPN MOVES EAST OF THE
AREA. SOUTHERLY WINDS WILL BE A TAD GUSTY AGAIN, JUST NOT AS MUCH AS
YESTERDAY.

.LONG TERM...(TONIGHT THROUGH MONDAY)
ISSUED AT 343 AM CDT TUE MAY 26 2015

UNTIL THE UPPER WAVE PULLS INTO THE GREAT LAKES REGION, LINGERING
POPS WILL REMAIN OVER THE FA FOR THIS EVENING.  BETTER CHANCES WILL
REMAIN TO THE EAST OVERNIGHT. REMAINS OF THE FRONT WILL STALL OUT
ALONG THE OHIO RIVER VALLEY AND PROVIDE A BIT OF FOCUS FOR ANOTHER
PIECE OF ENERGY EJECTING OUT OF THE SOUTHWEST.  MODELS DIFFERING
WITH THE NORTHERLY EXTENT OF THE PRECIP, BUT LAST FEW RUNS BRINGING
IN SOME PRECIPITATION FOR WEDNESDAY IN THE SOUTHEAST.  NAM IS A
LITTLE MORE WIDESPREAD, BUT CONCENTRATING THE POPS TO THE SOUTH AND
EAST FOR NOW.  TIMING ISSUES REMAIN IN PLACE FOR THIS SYNOPTIC RUN
FOR THE NEXT SYSTEM QUICK ON THE HEELS AS THE DEEP WAVE OVER THE SW
STARTS TO MOVE OUT INTO THE PLAINS. CONVECTION AND PRECIP STARTS TO
SPREAD OVER THE EASTERN HALF OF THE COUNTRY IN THE MODELS WITH  WEAK
SOUTHWESTERLY FLOW ALOFT SHIFTING TO WEAK FLOW OVERALL.  WARM AND
MUGGY CONDITIONS CONTINUE IN A MORE SUMMERLIKE AIRMASS THROUGHOUT
THE WEEK...BUT THAT NEXT SYSTEM WILL BRING A COLD FRONT INTO THE
REGION FOR THE FIRST HALF OF THE WEEKEND TO FOCUS THE RAIN, WITH A
COOLER AIRMASS BEHIND IT DROPPING THE TEMPS FOR THE WEEKEND OUT OF
THE 80S FOR A COUPLE DAYS.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z WEDNESDAY MORNING)
ISSUED AT 708 AM CDT TUE MAY 26 2015

LOW STRATUS HAS OVERSPREAD ALL TAF SITES THIS MORNING. THIS LOW
STRATUS LOOKS TO REMAIN OVER ALL SITES UNTIL SOMETIME THIS
AFTERNOON AFTER A NARROW BAND OF SHOWERS MOVES THROUGH THE AREA.
SPI IS THE ONLY ONE AT MVFR STATUS RIGHT NOW. ALL OTHER TAF SITES
ARE MVFR. BY THIS AFTERNOON ALL SITES SHOULD BE MVFR WITH HIGHER
CIGS AROUND 2.5KFT. SHOWERS WILL BE POSSIBLE THIS MORNING AS RADAR
LOOPS SHOWS. THEN HAS THE DAY HEATS UP THUNDERSTORMS WILL BE
POSSIBLE. WILL GO WITH VCTS FOR NOW GIVEN UNCERTAINTY OF LOCATION
OF ANY THUNDERSTORMS. THESE SHOULD END SOMETIME EARLY THIS
EVENING. SKIES SHOULD THEN BE VFR AS THE AREA SHOULD BE WELL IN
THE WARM SECTOR. THERE COULD BE MORE PCPN OVERNIGHT TONIGHT...BUT
LOTS OF UNCERTAINTY THERE SO WILL NOT INCLUDE AT THIS TIME. WINDS
WILL BECOME SOUTHERLY WITH SOME GUSTINESS THIS AFTERNOON.


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...MILLER
SHORT TERM...AUTEN
LONG TERM...HJS
AVIATION...AUTEN




000
FXUS63 KLOT 261528
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1028 AM CDT TUE MAY 26 2015

.UPDATE...
1007 AM CDT

A SFC LOW IS OVER IOWA AND ITS WARM/STATIONARY FRONT IS WELL TO
OUR NORTH OVER CENTRAL WI. ITS COLD FRONT STRETCHES FROM THE LOW
THROUGH CENTRAL KANSAS. AN AREA OF MAINLY RAIN AND A FEW
THUNDERSTORMS IS SLOWLY SPREADING NNE ACROSS NORTH CENTRAL IL. SO
FAR THE SHOWERS HAVE BEEN BEHAVING ACROSS MY CWA...BUT A FEW CELLS
TO THE WEST HAVE SHOWN SIGNS OF ROTATION.

LIKING THE LATEST RAP GUIDANCE WHICH KEEPS CAPE VALUES ON THE LOW
SIDE WITH ONLY A FEW HUNDREDS J/KG OF CAPE TO WORK WITH. THIS IS
ASSUMING SKIES STAY OVERCAST...AND THINKING WE WILL BE OVERCAST
TODAY. THAT BEING SAID...ANY LOCATIONS THAT SEE SUNSHINE COULD
DEVELOP ENOUGH CAPE TO SUPPORT TALLER CELLS AND POSSIBLY SEVERE
WEATHER. IN GENERAL THINKING DAMAGING WINDS AND AN ISOLATED
TORNADO ARE THE MAIN THREATS...BUT STRONGER STORMS WITH HIGHER
CAPE VALUES COULD SUPPORT HAIL. RADAR IMAGERY IS SHOWING GRAVITY
WAVE TAGS MOVING ALONG THE LINE OF STORMS AND WHEN THE TAGS
INTERSECT THE LINE...STORMS BEGIN TO SPIN. THEREFORE THE TORNADO
THREAT IS NOT ZERO.

THIS FIRST BATCH OF PRECIP WILL PUSH EAST THROUGH THE EARLY AFTN
HOURS AND EXPECTING ADDITIONAL SCATTERED TO NUMEROUS THUNDERSTORMS
DEVELOPMENT BEHIND THE LINE OVER NORTH CENTRAL IL. THE SECOND
WAVE SHIFTS EAST THROUGH THE EARLY EVENING HOURS. PWAT VALUES ARE
1.2-1.5 INCHES SO HEAVY DOWNPOURS ARE PSBL.

JEE

&&

.SHORT TERM...
319 AM CDT

THROUGH TUESDAY NIGHT...

FOR THE REMAINDER OF THE OVERNIGHT HOURS...CONDITIONS WILL REMAIN
QUIET ACROSS THE CWA AS A SERIES OF SHORT WAVES CONTINUE TO TRACK
NORTH AROUND THE TOP OF A PERSISTENT UPPER LEVEL RIDGE WHICH EXTENDS
FROM THE SERN CONUS THROUGH THE UPPER MISSISSIPPI VALLEY.  THIS
UPPER RIDGE HAS BEEN THE FEATURE WHICH HAS CONTROLLED THE PATH OF
THE SERIES OF SHORTWAVES LIFTING OUT OF THE SOUTHERN PLAINS...AND
WILL CONTINUE TO DO SO THROUGH THE DAY TODAY. SLY...MODERATELY
STRONG...WINDS WILL PERSIST THROUGH THE NIGHT...AND MUCH OF THE DAY
ALLOWING FOR SFC DEWPOINTS TO REMAIN CONSISTENT OR POSSIBLE INCH A
LITTLE HIGHER.

MAIN CONCERN FOR THE MORNING HOURS WILL BE THE TRACK OF A STRONG
SHORT WAVE AND ASSOCIATED SFC LOW LIFTING NORTHWARD THROUGH THE
MIDDLE MISSISSIPPI VALLEY.  THIS FEATURE WILL PREDOMINANTLY IMPACT
ERN IOWA AND WRN IL BY ARND DAYBREAK.  THROUGH THE MORNING...THE
COMBINATION OF ISENTROPIC LIFT IN THE WARM SECTOR OF THE
SYSTEM...ALL OF IL AND INTO NWRN IN...WILL LEAD TO SOME
DESTABILIZATION ACROSS THE REGION. A SFC TROUGH...AS WELL INDICATED
BY THE LATEST HIGH RES GUIDANCE...WITH LIFT THROUGH NRN IL/IN
THROUGH THE DAY...COINCIDENT WITH A STRONG SSWLY LOW LEVEL JET OF 45-
50 KT...WITH PROVIDE THE POTENTIAL FOR SHOWERS AND STRONG TO SEVERE
THUNDERSTORMS ACROSS THE CWA.  BASED ON WIND PROFILES AND MID LEVEL
DRYING...THE PRIMARY CONCERN WITH REGARD TO SEVERE WEATHER WILL BE
STRONG WIND GUSTS.  HOWEVER...SOME OF THE HIGH RES SFC WIND GUIDANCE
SUGGEST SOME SLIGHT BACKING OF SFC WINDS FROM 180-190 DEGREES TO 160-
170 DEGREES...WHILE WINDS ALOFT REMAIN SWLY.  THIS SLIGHT BACKING OF
THE SFC WINDS COULD PROVIDE ENOUGH DIRECTIONAL SHEAR THROUGH THE
LOWER LEVELS TO BRING AN ISOLD TORNADO THREAT. LOCALLY HEAVY
RAINFALL WILL ALSO BE CONCERNED WITH PWATS REACHING 1.75 INCHES
LATER THIS MORNING.  HOWEVER...FLOODING WILL LIKELY NOT BE A
SIGNIFICANT CONCERN AS THE SWLY WINDS RIGHT OFF THE DECK WILL RANGE
FROM ARND 45 KT ABOVE THE BOUNDARY LAYER TO ARND 90KT AT UPPER
LEVELS WHICH SHOULD ALLOW ANY OF THE STRONGER STORMS THAT DO DEVELOP
TO MOVE QUICKLY.

BY EARLY AFTERNOON...THE MAIN SHORT WAVE WILL LIFT INTO WISCONSIN
WHILE A SFC TROUGH TRACKS EAST ACROSS THE AREA.  THIS WILL LEAD TO
WINDS AT THE SFC VEERING TO SWLY...SETTING UP A UNIDIRECTIONAL WIND
PROFILE...EFFECTIVELY MINIMIZING THE SEVERE WEATHER THREAT TO THE
REGION.  BY LATE AFTERNOON AND INTO THE EVENING THE MODELS ARE
ADVERTISING THAT A DRY SLOW SHOULD NOSE INTO NRN IL...EFFECTIVELY
CUTTING OFF THE PCPN AREA INTO 2 SEPARATE AREA...ONE OVER WISCONSIN
AND ERN IOWA AND ANOTHER MORE FOCUSED OVER INDIANA.  THE NWRN
INDIANA COUNTIES WILL STILL HAVE A CHANCE FOR SOME SHOWERS AND
THUNDERSTORMS INTO THE EVENING...WHILE PCPN CHANCES OVER NRN IL
BEGIN TO WANE.  MUCH OF THE MODEL GUIDANCE ALSO INDICATED THAT THE
SHORTWAVE SHOULD SLOW IT`S PROGRESSION THROUGH WISCONSIN AS IT
APPROACHES THE APEX OF THE UPPER RIDGE.  AN ASSOCIATED SFC
TROUGH/COLD FRONT EXTENDING SOUTHWEST FROM THE SFC LOW WILL LINGER
OVER ERN IOWA IN THE EARLY EVENING BEFORE STEADILY PUSHING ACROSS
NRN IL AND INTO NWRN IN OVERNIGHT.  THROUGH THE NIGHT...THE
STRONGEST UPPER LEVEL FORCING WILL BE WELL NORTH OF THE CWA...SO ANY
LINGERING CHANCES FOR PCPN OVERNIGHT WILL BE LOW AND LIKELY CONFINED
TO THE NRN TIER COUNTIES OF IL...ALONG THE WI BORDER.

KREIN

&&

.LONG TERM...
229 AM CDT

WEDNESDAY THROUGH MONDAY...

WEDNESDAY THROUGH THURSDAY...
OPEN 500MB WAVE WILL BE LIFTING NORTHEAST ACROSS THE UPPER MIDWEST
INTO ONTARIO AND EVENTUALLY QUEBEC...WITH HEIGHTS SLOWLY INCREASING
WED AFTN. SFC FEATURES REMAIN DISORGANIZED WED...WITH A BOUNDARY
SLOWLY SHIFTING EAST. OPER GUIDANCE DIFFERS ON HOW QUICKLY PRECIP
WILL DEPART THE REGION. ENSEMBLE DATA SUGGESTS HOLDING ONTO CHC TO
SLIGHT CHC POPS MAINLY FOR THE CENTRAL/EASTERN CWFA WED/WED EVE.
ALTHOUGH WITH SOME HINT OF SFC HEIGHTS NUDGING UP...IT IS POSSIBLE
THAT SOME DRY AIR COULD FILTER IN AND KICK PRECIP EAST BY MIDDAY AND
ALLOW FOR A MAINLY DRY WED. SFC WINDS WILL BE TURNING SOUTHWEST TO
WEST...KEEPING AN OFFSHORE FLOW FOR LOCATIONS CLOSE TO LAKE
MICHIGAN. TEMPS SHOULD YET AGAIN TOUCH UPR 70S TO ARND 80 WED...IF
CLOUDS AND PRECIP CAN PUSH EAST BY MIDDAY...SOME CLEARING WOULD
ALLOW SFC TEMPS TO PUSH A COUPLE DEGREES WARMER INTO THE LOW 80S IN
SOME LOCATIONS. LATE IN THE EVENING THE GRADIENT SLACKENS
FURTHER...AND COULD ALLOW A LATE DAY ONSHORE FLOW TO DEVELOP FOR
AREAS ADJACENT TO LAKE MICHIGAN.

MID-LVL FLOW BEGINS TO FLATTEN AS A WEAK SFC RIDGE BECOMES ORIENTED
FROM WESTERN QUEBEC SOUTH THROUGH THE EASTERN OHIO RIVER VALLEY.
THIS WILL GENERALLY ALLOW A SOUTHERLY FLOW...ALTHOUGH THE GRADIENT
IS NOT VERY STRONG. THIS SHOULD SET THE STAGE FOR A LAKE
BREEZE/ONSHORE FLOW TO DEVELOP THUR. TIMING COULD END UP BEING
SLIGHTLY EARLIER GIVEN THE LIGHT SFC GRADIENT. GUIDANCE HAS BEEN
CONSISTENT IN HOLDING PRECIP WEST/SOUTH OF THE FORECAST AREA
THUR...AS A RESULT OF THE WEAK SFC RIDGING. SO ONE MORE MILD DAY
WITH HIGHS WARMING BACK INTO THE UPR 70S/LOW 80S...HOWEVER AS
PREVIOUSLY NOTED...A LAKE BREEZE IS LIKELY TO DEVELOP. THIS WILL
BLEED THE MUCH COOLER MARINE AIR WEST ACROSS NORTHEAST IL AND
DOWNTOWN CHICAGO. IF THE TIMING IS EARLIER IN THE DAY THUR...TEMPS
MAY NOT WARM BEYOND THE LOW/MID 60S ALONG THE CHICAGO LAKEFRONT.

FLOW THEN TURNS SOUTHERLY THUR NIGHT WITH THE MORE PROGRESSIVE FLOW
IN THE MID-LVLS PUSHING THE RIDGING EAST. A RETURN FLOW MOISTURE
WILL CONTINUE TO BE FOCUSED ACROSS THE CENTRAL CONUS THUR EVE...WITH
A SLOW MOVING FRONTAL BOUNDARY NUDGING EAST THUR NIGHT TOWARDS
WESTERN IL. THIS FRONTAL BOUNDARY WILL BECOME ENERGIZED AS A ROBUST
500MB VORT MAX BREAKS SOUTH FROM CENTRAL CANADA LATE THUR NIGHT.

THIS SHOULD ALLOW FOR AN ATMOSPHERIC RIVER TO DEVELOP FROM THE
SOUTHERN PLAINS STRETCHING NORTH THROUGH THE MID-MISSOURI VALLEY
INTO THE WESTERN GREAT LAKES EARLY FRI MORNING.

FRIDAY THROUGH EARLY NEXT WEEK...
ENSEMBLES CONTINUE TO PROG A ROBUST TROUGH SLIDING SOUTH FROM
CENTRAL CANADA FRI. THIS COUPLED WITH DOWNSTREAM MID-LVL RIDGING
ACROSS THE SOUTHEAST CONUS WILL STRENGTHEN THE FRONTAL BOUNDARY
THAT WILL BE ORIENTED FROM THE SOUTHERN PLAINS STRETCHING
NORTHEAST THROUGH THE GREAT LAKES REGION INTO WESTERN QUEBEC.

THIS SETUP IS IDEAL FOR THE DEVELOPMENT OF AN ATMOSPHERIC RIVER WITH
ABUNDANT LOW LEVEL MOISTURE AND EFFICIENT PRECIP PRODUCING
CONVECTION.

OPER GUIDANCE HAS BEEN RELATIVELY CONSISTENT WITH BRINGING A SERIES
OF WAVES ALONG THE SLOW MOVING FRONTAL BOUNDARY FRI AFTN/EVE...THEN
THE BOUNDARY SHOULD SLIDE EAST WITH WINDS QUICKLY VEERING
NORTH/NORTHEAST FOR SAT AND USHERING IN MUCH COOLER AIR TO THE
REGION.

CURRENT INDICATIONS ARE THAT HIGHS SAT MAY STRUGGLE TO WARM BEYOND
THE UPR 50S ACROSS NORTHEAST IL/NORTHWEST IN...WITH ONLY LOW 60S
ELSEWHERE. STRONG SFC RIDGE WILL REMAIN NORTH OF THE REGION...SO THE
PRIOR FRONTAL BOUNDARY MAY BECOME QUASI-STATIONARY FOR THE WEEKEND
ALONG THE OHIO VALLEY AND CONTINUE TO FEED PRECIP CHANCES TO THE
SOUTHERN CWFA.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 14Z...

* MVFR CEILINGS CONTINUE THIS MORNING.

* PERIODS OF -SHRA WITH PERIODIC TSRA THIS AFTERNOON.

* SOUTH TO SOUTH-SOUTHWEST WINDS INCREASING THROUGH THE MORNING TO
  GUST OVER 20KT

KREIN/MM

//DISCUSSION...UPDATED 12Z...

A MID LEVEL DISTURBANCE MOVING FROM THE SOUTHERN PLAINS TO NRN IL
BY THIS AFTERNOON MAY BRING ANOTHER ROUND OF SHOWERS WITH SCT
THUNDERSTORMS TO THE REGION. UPPER LEVEL FORCING FROM THE MID
LEVEL DISTURBANCE AND AN UPPER LEVEL JET STREAM WILL ENHANCE THE
LIKELIHOOD FOR PCPN AND THE CHANCE FOR TSRA...WITH THE MOST
LIKELY CHANCE FOR ACTIVITY FROM LATE MORNING THROUGH EARLY
EVENING. SOME UNCERTAINTY REMAINS IN PINNING DOWN THE EXACT
PERIOD FOR THE TSRA...SO WILL MAINTAIN THE GOING TEMPO FOR LATE
MORNING THROUGH EARLY AFTERNOON. HOWEVER...THE PCPN TIMING COULD
BE SHIFTED OR EXPANDED IN TIME.

LOW LEVEL MOISTURE STREAMING NORTHWARD AHEAD OF LOW PRESSURE OVER
THE MID MISSISSIPPI VALLEY HAS BROUGHT A LOW MVFR STRATUS DECK
ACROSS THE REGION. SOME SITES ARE REPORTING CIGS DROPPING INTO IFR
RANGE...SO WILL INCLUDE THE POSSIBILITY IN A TEMPO GROUP THROUGH
LATE MORNING. DAYTIME WARMING SHOULD ALLOW FOR INCREASE DEEP LAYER
MIXING WHICH SHOULD SCATTER OUT THE STRATUS DECK.

WINDS WILL BE GENERALLY SOUTHERLY TODAY...THOUGH DIRECTION MAY BE
A BIT VARIABLE AROUND CONVECTIVE ACTIVITY. SOME GUSTINESS IS
LIKELY TO BEGIN BY LATE MORNING...WITH THE LATEST GUIDANCE
SUGGESTING THAT WINDS COULD STRENGTHEN AND BECOME EVEN MORE GUSTY
TONIGHT WITH WINDS VEERING SWLY AS SURFACE LOW PRESSURE MOVES
NORTHEAST ACROSS SOUTHERN WISCONSIN.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 14Z...

* HIGH CONFIDENCE IN WIND TRENDS TODAY. MEDIUM IN WIND TRENDS
  TONIGHT.

* HIGH CONFIDENCE IN MVFR CIGS THIS MORNING.

* HIGH CONFIDENCE IN SHOWERS AND MEDIUM CONFIDENCE OF A PERIOD OF
  TSRA. LOW CONFIDENCE IN SPECIFIC TSRA TIMING AND IMPACT ON THE
  TERMINALS WITH MULTIPLE ROUNDS POSSIBLE BETWEEN 18Z AND 02Z.

KREIN/MM

//OUTLOOK FOR ORD/MDW FOR 00Z THURSDAY-12Z TUESDAY...UPDATED 12Z...

WEDNESDAY NIGHT...WX NIL/VFR. SOUTHEAST WINDS.

THURSDAY...SLIGHT CHANCE OF TSRA AT NIGHT. SOUTHEAST WINDS.

FRIDAY...TSRA/SHRA LIKELY THROUGH THE DAY AND NIGHT. MVFR
POSSIBLE. SOUTHWEST WINDS.

SATURDAY...SHRA LIKELY WITH A CHANCE OF TSRA DURING THE DAY.
NORTHEAST WINDS.

SUNDAY...CHANCE OF SHRA. EAST WINDS. MVFR POSSIBLE.

MONDAY...CHANCE OF SHRA. SOUTHEAST WINDS. MVFR POSSIBLE.

KREIN

&&

.MARINE...
229 AM CDT

WARM MOIST AIR CONTINUES TO FEED NORTH ACROSS THE LAKE
TODAY...WHICH MAY HELP TO FURTHER ENHANCE ANY AREAS OF FOG THAT
HAVE ALREADY DEVELOPED. IT IS POSSIBLE PATCHY DENSE FOG MAY
DEVELOP...ALTHOUGH WINDS MAY BE JUST STRONG ENOUGH TO LIMIT THE
COVERAGE AND INTENSITY OF THE FOG. A SURFACE LOW PRESSURE SYSTEM
WILL BE LIFTING NORTH ACROSS EASTERN IOWA INTO CENTRAL WISCONSIN
THIS EVENING. THE GRADIENT WILL TIGHTEN ACROSS THE
CENTRAL/SOUTHERN PORTIONS OF THE LAKE...WHICH WITH WARMER
NEARSHORE WATERS EXPECT SOME SLIGHTLY BETTER MIXING TO OCCUR.
FURTHER OUT ACROSS THE OPEN WATERS THE WATER REMAINS COLD AND
EXPECT THE STABILITY TO MAKE IT DIFFICULT TO MIX TO THE SFC THE
HIGHER GUSTS. HIGH PRESSURE THEN ARRIVES LATE WEDNESDAY WITH LIGHT
WINDS DEVELOPING. THEN HIGH PRESSURE SHIFTS EAST THURSDAY
NIGHT...WITH SOUTHERLY WINDS DEVELOPING AGAIN FRIDAY. A FRONTAL
BOUNDARY WILL APPROACH LAKE MICHIGAN LATE FRIDAY NIGHT THEN
STEADILY SLIDE SOUTH ALONG THE LAKE. THIS WILL ALLOW WINDS TO
QUICKLY VEER FROM SOUTH TO NORTH/NORTHEAST SATURDAY. ALONG WITH
THIS QUICK WIND SHIFT WILL BE COOLER AIR SLIDING SOUTH OVER THE
LAKE. WAVES SHOULD EASILY BUILD SATURDAY FOR THE CENTRAL/SOUTHERN
PORTIONS OF THE LAKE.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

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000
FXUS63 KLOT 261528
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1028 AM CDT TUE MAY 26 2015

.UPDATE...
1007 AM CDT

A SFC LOW IS OVER IOWA AND ITS WARM/STATIONARY FRONT IS WELL TO
OUR NORTH OVER CENTRAL WI. ITS COLD FRONT STRETCHES FROM THE LOW
THROUGH CENTRAL KANSAS. AN AREA OF MAINLY RAIN AND A FEW
THUNDERSTORMS IS SLOWLY SPREADING NNE ACROSS NORTH CENTRAL IL. SO
FAR THE SHOWERS HAVE BEEN BEHAVING ACROSS MY CWA...BUT A FEW CELLS
TO THE WEST HAVE SHOWN SIGNS OF ROTATION.

LIKING THE LATEST RAP GUIDANCE WHICH KEEPS CAPE VALUES ON THE LOW
SIDE WITH ONLY A FEW HUNDREDS J/KG OF CAPE TO WORK WITH. THIS IS
ASSUMING SKIES STAY OVERCAST...AND THINKING WE WILL BE OVERCAST
TODAY. THAT BEING SAID...ANY LOCATIONS THAT SEE SUNSHINE COULD
DEVELOP ENOUGH CAPE TO SUPPORT TALLER CELLS AND POSSIBLY SEVERE
WEATHER. IN GENERAL THINKING DAMAGING WINDS AND AN ISOLATED
TORNADO ARE THE MAIN THREATS...BUT STRONGER STORMS WITH HIGHER
CAPE VALUES COULD SUPPORT HAIL. RADAR IMAGERY IS SHOWING GRAVITY
WAVE TAGS MOVING ALONG THE LINE OF STORMS AND WHEN THE TAGS
INTERSECT THE LINE...STORMS BEGIN TO SPIN. THEREFORE THE TORNADO
THREAT IS NOT ZERO.

THIS FIRST BATCH OF PRECIP WILL PUSH EAST THROUGH THE EARLY AFTN
HOURS AND EXPECTING ADDITIONAL SCATTERED TO NUMEROUS THUNDERSTORMS
DEVELOPMENT BEHIND THE LINE OVER NORTH CENTRAL IL. THE SECOND
WAVE SHIFTS EAST THROUGH THE EARLY EVENING HOURS. PWAT VALUES ARE
1.2-1.5 INCHES SO HEAVY DOWNPOURS ARE PSBL.

JEE

&&

.SHORT TERM...
319 AM CDT

THROUGH TUESDAY NIGHT...

FOR THE REMAINDER OF THE OVERNIGHT HOURS...CONDITIONS WILL REMAIN
QUIET ACROSS THE CWA AS A SERIES OF SHORT WAVES CONTINUE TO TRACK
NORTH AROUND THE TOP OF A PERSISTENT UPPER LEVEL RIDGE WHICH EXTENDS
FROM THE SERN CONUS THROUGH THE UPPER MISSISSIPPI VALLEY.  THIS
UPPER RIDGE HAS BEEN THE FEATURE WHICH HAS CONTROLLED THE PATH OF
THE SERIES OF SHORTWAVES LIFTING OUT OF THE SOUTHERN PLAINS...AND
WILL CONTINUE TO DO SO THROUGH THE DAY TODAY. SLY...MODERATELY
STRONG...WINDS WILL PERSIST THROUGH THE NIGHT...AND MUCH OF THE DAY
ALLOWING FOR SFC DEWPOINTS TO REMAIN CONSISTENT OR POSSIBLE INCH A
LITTLE HIGHER.

MAIN CONCERN FOR THE MORNING HOURS WILL BE THE TRACK OF A STRONG
SHORT WAVE AND ASSOCIATED SFC LOW LIFTING NORTHWARD THROUGH THE
MIDDLE MISSISSIPPI VALLEY.  THIS FEATURE WILL PREDOMINANTLY IMPACT
ERN IOWA AND WRN IL BY ARND DAYBREAK.  THROUGH THE MORNING...THE
COMBINATION OF ISENTROPIC LIFT IN THE WARM SECTOR OF THE
SYSTEM...ALL OF IL AND INTO NWRN IN...WILL LEAD TO SOME
DESTABILIZATION ACROSS THE REGION. A SFC TROUGH...AS WELL INDICATED
BY THE LATEST HIGH RES GUIDANCE...WITH LIFT THROUGH NRN IL/IN
THROUGH THE DAY...COINCIDENT WITH A STRONG SSWLY LOW LEVEL JET OF 45-
50 KT...WITH PROVIDE THE POTENTIAL FOR SHOWERS AND STRONG TO SEVERE
THUNDERSTORMS ACROSS THE CWA.  BASED ON WIND PROFILES AND MID LEVEL
DRYING...THE PRIMARY CONCERN WITH REGARD TO SEVERE WEATHER WILL BE
STRONG WIND GUSTS.  HOWEVER...SOME OF THE HIGH RES SFC WIND GUIDANCE
SUGGEST SOME SLIGHT BACKING OF SFC WINDS FROM 180-190 DEGREES TO 160-
170 DEGREES...WHILE WINDS ALOFT REMAIN SWLY.  THIS SLIGHT BACKING OF
THE SFC WINDS COULD PROVIDE ENOUGH DIRECTIONAL SHEAR THROUGH THE
LOWER LEVELS TO BRING AN ISOLD TORNADO THREAT. LOCALLY HEAVY
RAINFALL WILL ALSO BE CONCERNED WITH PWATS REACHING 1.75 INCHES
LATER THIS MORNING.  HOWEVER...FLOODING WILL LIKELY NOT BE A
SIGNIFICANT CONCERN AS THE SWLY WINDS RIGHT OFF THE DECK WILL RANGE
FROM ARND 45 KT ABOVE THE BOUNDARY LAYER TO ARND 90KT AT UPPER
LEVELS WHICH SHOULD ALLOW ANY OF THE STRONGER STORMS THAT DO DEVELOP
TO MOVE QUICKLY.

BY EARLY AFTERNOON...THE MAIN SHORT WAVE WILL LIFT INTO WISCONSIN
WHILE A SFC TROUGH TRACKS EAST ACROSS THE AREA.  THIS WILL LEAD TO
WINDS AT THE SFC VEERING TO SWLY...SETTING UP A UNIDIRECTIONAL WIND
PROFILE...EFFECTIVELY MINIMIZING THE SEVERE WEATHER THREAT TO THE
REGION.  BY LATE AFTERNOON AND INTO THE EVENING THE MODELS ARE
ADVERTISING THAT A DRY SLOW SHOULD NOSE INTO NRN IL...EFFECTIVELY
CUTTING OFF THE PCPN AREA INTO 2 SEPARATE AREA...ONE OVER WISCONSIN
AND ERN IOWA AND ANOTHER MORE FOCUSED OVER INDIANA.  THE NWRN
INDIANA COUNTIES WILL STILL HAVE A CHANCE FOR SOME SHOWERS AND
THUNDERSTORMS INTO THE EVENING...WHILE PCPN CHANCES OVER NRN IL
BEGIN TO WANE.  MUCH OF THE MODEL GUIDANCE ALSO INDICATED THAT THE
SHORTWAVE SHOULD SLOW IT`S PROGRESSION THROUGH WISCONSIN AS IT
APPROACHES THE APEX OF THE UPPER RIDGE.  AN ASSOCIATED SFC
TROUGH/COLD FRONT EXTENDING SOUTHWEST FROM THE SFC LOW WILL LINGER
OVER ERN IOWA IN THE EARLY EVENING BEFORE STEADILY PUSHING ACROSS
NRN IL AND INTO NWRN IN OVERNIGHT.  THROUGH THE NIGHT...THE
STRONGEST UPPER LEVEL FORCING WILL BE WELL NORTH OF THE CWA...SO ANY
LINGERING CHANCES FOR PCPN OVERNIGHT WILL BE LOW AND LIKELY CONFINED
TO THE NRN TIER COUNTIES OF IL...ALONG THE WI BORDER.

KREIN

&&

.LONG TERM...
229 AM CDT

WEDNESDAY THROUGH MONDAY...

WEDNESDAY THROUGH THURSDAY...
OPEN 500MB WAVE WILL BE LIFTING NORTHEAST ACROSS THE UPPER MIDWEST
INTO ONTARIO AND EVENTUALLY QUEBEC...WITH HEIGHTS SLOWLY INCREASING
WED AFTN. SFC FEATURES REMAIN DISORGANIZED WED...WITH A BOUNDARY
SLOWLY SHIFTING EAST. OPER GUIDANCE DIFFERS ON HOW QUICKLY PRECIP
WILL DEPART THE REGION. ENSEMBLE DATA SUGGESTS HOLDING ONTO CHC TO
SLIGHT CHC POPS MAINLY FOR THE CENTRAL/EASTERN CWFA WED/WED EVE.
ALTHOUGH WITH SOME HINT OF SFC HEIGHTS NUDGING UP...IT IS POSSIBLE
THAT SOME DRY AIR COULD FILTER IN AND KICK PRECIP EAST BY MIDDAY AND
ALLOW FOR A MAINLY DRY WED. SFC WINDS WILL BE TURNING SOUTHWEST TO
WEST...KEEPING AN OFFSHORE FLOW FOR LOCATIONS CLOSE TO LAKE
MICHIGAN. TEMPS SHOULD YET AGAIN TOUCH UPR 70S TO ARND 80 WED...IF
CLOUDS AND PRECIP CAN PUSH EAST BY MIDDAY...SOME CLEARING WOULD
ALLOW SFC TEMPS TO PUSH A COUPLE DEGREES WARMER INTO THE LOW 80S IN
SOME LOCATIONS. LATE IN THE EVENING THE GRADIENT SLACKENS
FURTHER...AND COULD ALLOW A LATE DAY ONSHORE FLOW TO DEVELOP FOR
AREAS ADJACENT TO LAKE MICHIGAN.

MID-LVL FLOW BEGINS TO FLATTEN AS A WEAK SFC RIDGE BECOMES ORIENTED
FROM WESTERN QUEBEC SOUTH THROUGH THE EASTERN OHIO RIVER VALLEY.
THIS WILL GENERALLY ALLOW A SOUTHERLY FLOW...ALTHOUGH THE GRADIENT
IS NOT VERY STRONG. THIS SHOULD SET THE STAGE FOR A LAKE
BREEZE/ONSHORE FLOW TO DEVELOP THUR. TIMING COULD END UP BEING
SLIGHTLY EARLIER GIVEN THE LIGHT SFC GRADIENT. GUIDANCE HAS BEEN
CONSISTENT IN HOLDING PRECIP WEST/SOUTH OF THE FORECAST AREA
THUR...AS A RESULT OF THE WEAK SFC RIDGING. SO ONE MORE MILD DAY
WITH HIGHS WARMING BACK INTO THE UPR 70S/LOW 80S...HOWEVER AS
PREVIOUSLY NOTED...A LAKE BREEZE IS LIKELY TO DEVELOP. THIS WILL
BLEED THE MUCH COOLER MARINE AIR WEST ACROSS NORTHEAST IL AND
DOWNTOWN CHICAGO. IF THE TIMING IS EARLIER IN THE DAY THUR...TEMPS
MAY NOT WARM BEYOND THE LOW/MID 60S ALONG THE CHICAGO LAKEFRONT.

FLOW THEN TURNS SOUTHERLY THUR NIGHT WITH THE MORE PROGRESSIVE FLOW
IN THE MID-LVLS PUSHING THE RIDGING EAST. A RETURN FLOW MOISTURE
WILL CONTINUE TO BE FOCUSED ACROSS THE CENTRAL CONUS THUR EVE...WITH
A SLOW MOVING FRONTAL BOUNDARY NUDGING EAST THUR NIGHT TOWARDS
WESTERN IL. THIS FRONTAL BOUNDARY WILL BECOME ENERGIZED AS A ROBUST
500MB VORT MAX BREAKS SOUTH FROM CENTRAL CANADA LATE THUR NIGHT.

THIS SHOULD ALLOW FOR AN ATMOSPHERIC RIVER TO DEVELOP FROM THE
SOUTHERN PLAINS STRETCHING NORTH THROUGH THE MID-MISSOURI VALLEY
INTO THE WESTERN GREAT LAKES EARLY FRI MORNING.

FRIDAY THROUGH EARLY NEXT WEEK...
ENSEMBLES CONTINUE TO PROG A ROBUST TROUGH SLIDING SOUTH FROM
CENTRAL CANADA FRI. THIS COUPLED WITH DOWNSTREAM MID-LVL RIDGING
ACROSS THE SOUTHEAST CONUS WILL STRENGTHEN THE FRONTAL BOUNDARY
THAT WILL BE ORIENTED FROM THE SOUTHERN PLAINS STRETCHING
NORTHEAST THROUGH THE GREAT LAKES REGION INTO WESTERN QUEBEC.

THIS SETUP IS IDEAL FOR THE DEVELOPMENT OF AN ATMOSPHERIC RIVER WITH
ABUNDANT LOW LEVEL MOISTURE AND EFFICIENT PRECIP PRODUCING
CONVECTION.

OPER GUIDANCE HAS BEEN RELATIVELY CONSISTENT WITH BRINGING A SERIES
OF WAVES ALONG THE SLOW MOVING FRONTAL BOUNDARY FRI AFTN/EVE...THEN
THE BOUNDARY SHOULD SLIDE EAST WITH WINDS QUICKLY VEERING
NORTH/NORTHEAST FOR SAT AND USHERING IN MUCH COOLER AIR TO THE
REGION.

CURRENT INDICATIONS ARE THAT HIGHS SAT MAY STRUGGLE TO WARM BEYOND
THE UPR 50S ACROSS NORTHEAST IL/NORTHWEST IN...WITH ONLY LOW 60S
ELSEWHERE. STRONG SFC RIDGE WILL REMAIN NORTH OF THE REGION...SO THE
PRIOR FRONTAL BOUNDARY MAY BECOME QUASI-STATIONARY FOR THE WEEKEND
ALONG THE OHIO VALLEY AND CONTINUE TO FEED PRECIP CHANCES TO THE
SOUTHERN CWFA.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 14Z...

* MVFR CEILINGS CONTINUE THIS MORNING.

* PERIODS OF -SHRA WITH PERIODIC TSRA THIS AFTERNOON.

* SOUTH TO SOUTH-SOUTHWEST WINDS INCREASING THROUGH THE MORNING TO
  GUST OVER 20KT

KREIN/MM

//DISCUSSION...UPDATED 12Z...

A MID LEVEL DISTURBANCE MOVING FROM THE SOUTHERN PLAINS TO NRN IL
BY THIS AFTERNOON MAY BRING ANOTHER ROUND OF SHOWERS WITH SCT
THUNDERSTORMS TO THE REGION. UPPER LEVEL FORCING FROM THE MID
LEVEL DISTURBANCE AND AN UPPER LEVEL JET STREAM WILL ENHANCE THE
LIKELIHOOD FOR PCPN AND THE CHANCE FOR TSRA...WITH THE MOST
LIKELY CHANCE FOR ACTIVITY FROM LATE MORNING THROUGH EARLY
EVENING. SOME UNCERTAINTY REMAINS IN PINNING DOWN THE EXACT
PERIOD FOR THE TSRA...SO WILL MAINTAIN THE GOING TEMPO FOR LATE
MORNING THROUGH EARLY AFTERNOON. HOWEVER...THE PCPN TIMING COULD
BE SHIFTED OR EXPANDED IN TIME.

LOW LEVEL MOISTURE STREAMING NORTHWARD AHEAD OF LOW PRESSURE OVER
THE MID MISSISSIPPI VALLEY HAS BROUGHT A LOW MVFR STRATUS DECK
ACROSS THE REGION. SOME SITES ARE REPORTING CIGS DROPPING INTO IFR
RANGE...SO WILL INCLUDE THE POSSIBILITY IN A TEMPO GROUP THROUGH
LATE MORNING. DAYTIME WARMING SHOULD ALLOW FOR INCREASE DEEP LAYER
MIXING WHICH SHOULD SCATTER OUT THE STRATUS DECK.

WINDS WILL BE GENERALLY SOUTHERLY TODAY...THOUGH DIRECTION MAY BE
A BIT VARIABLE AROUND CONVECTIVE ACTIVITY. SOME GUSTINESS IS
LIKELY TO BEGIN BY LATE MORNING...WITH THE LATEST GUIDANCE
SUGGESTING THAT WINDS COULD STRENGTHEN AND BECOME EVEN MORE GUSTY
TONIGHT WITH WINDS VEERING SWLY AS SURFACE LOW PRESSURE MOVES
NORTHEAST ACROSS SOUTHERN WISCONSIN.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 14Z...

* HIGH CONFIDENCE IN WIND TRENDS TODAY. MEDIUM IN WIND TRENDS
  TONIGHT.

* HIGH CONFIDENCE IN MVFR CIGS THIS MORNING.

* HIGH CONFIDENCE IN SHOWERS AND MEDIUM CONFIDENCE OF A PERIOD OF
  TSRA. LOW CONFIDENCE IN SPECIFIC TSRA TIMING AND IMPACT ON THE
  TERMINALS WITH MULTIPLE ROUNDS POSSIBLE BETWEEN 18Z AND 02Z.

KREIN/MM

//OUTLOOK FOR ORD/MDW FOR 00Z THURSDAY-12Z TUESDAY...UPDATED 12Z...

WEDNESDAY NIGHT...WX NIL/VFR. SOUTHEAST WINDS.

THURSDAY...SLIGHT CHANCE OF TSRA AT NIGHT. SOUTHEAST WINDS.

FRIDAY...TSRA/SHRA LIKELY THROUGH THE DAY AND NIGHT. MVFR
POSSIBLE. SOUTHWEST WINDS.

SATURDAY...SHRA LIKELY WITH A CHANCE OF TSRA DURING THE DAY.
NORTHEAST WINDS.

SUNDAY...CHANCE OF SHRA. EAST WINDS. MVFR POSSIBLE.

MONDAY...CHANCE OF SHRA. SOUTHEAST WINDS. MVFR POSSIBLE.

KREIN

&&

.MARINE...
229 AM CDT

WARM MOIST AIR CONTINUES TO FEED NORTH ACROSS THE LAKE
TODAY...WHICH MAY HELP TO FURTHER ENHANCE ANY AREAS OF FOG THAT
HAVE ALREADY DEVELOPED. IT IS POSSIBLE PATCHY DENSE FOG MAY
DEVELOP...ALTHOUGH WINDS MAY BE JUST STRONG ENOUGH TO LIMIT THE
COVERAGE AND INTENSITY OF THE FOG. A SURFACE LOW PRESSURE SYSTEM
WILL BE LIFTING NORTH ACROSS EASTERN IOWA INTO CENTRAL WISCONSIN
THIS EVENING. THE GRADIENT WILL TIGHTEN ACROSS THE
CENTRAL/SOUTHERN PORTIONS OF THE LAKE...WHICH WITH WARMER
NEARSHORE WATERS EXPECT SOME SLIGHTLY BETTER MIXING TO OCCUR.
FURTHER OUT ACROSS THE OPEN WATERS THE WATER REMAINS COLD AND
EXPECT THE STABILITY TO MAKE IT DIFFICULT TO MIX TO THE SFC THE
HIGHER GUSTS. HIGH PRESSURE THEN ARRIVES LATE WEDNESDAY WITH LIGHT
WINDS DEVELOPING. THEN HIGH PRESSURE SHIFTS EAST THURSDAY
NIGHT...WITH SOUTHERLY WINDS DEVELOPING AGAIN FRIDAY. A FRONTAL
BOUNDARY WILL APPROACH LAKE MICHIGAN LATE FRIDAY NIGHT THEN
STEADILY SLIDE SOUTH ALONG THE LAKE. THIS WILL ALLOW WINDS TO
QUICKLY VEER FROM SOUTH TO NORTH/NORTHEAST SATURDAY. ALONG WITH
THIS QUICK WIND SHIFT WILL BE COOLER AIR SLIDING SOUTH OVER THE
LAKE. WAVES SHOULD EASILY BUILD SATURDAY FOR THE CENTRAL/SOUTHERN
PORTIONS OF THE LAKE.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
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000
FXUS63 KLOT 261528
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1028 AM CDT TUE MAY 26 2015

.UPDATE...
1007 AM CDT

A SFC LOW IS OVER IOWA AND ITS WARM/STATIONARY FRONT IS WELL TO
OUR NORTH OVER CENTRAL WI. ITS COLD FRONT STRETCHES FROM THE LOW
THROUGH CENTRAL KANSAS. AN AREA OF MAINLY RAIN AND A FEW
THUNDERSTORMS IS SLOWLY SPREADING NNE ACROSS NORTH CENTRAL IL. SO
FAR THE SHOWERS HAVE BEEN BEHAVING ACROSS MY CWA...BUT A FEW CELLS
TO THE WEST HAVE SHOWN SIGNS OF ROTATION.

LIKING THE LATEST RAP GUIDANCE WHICH KEEPS CAPE VALUES ON THE LOW
SIDE WITH ONLY A FEW HUNDREDS J/KG OF CAPE TO WORK WITH. THIS IS
ASSUMING SKIES STAY OVERCAST...AND THINKING WE WILL BE OVERCAST
TODAY. THAT BEING SAID...ANY LOCATIONS THAT SEE SUNSHINE COULD
DEVELOP ENOUGH CAPE TO SUPPORT TALLER CELLS AND POSSIBLY SEVERE
WEATHER. IN GENERAL THINKING DAMAGING WINDS AND AN ISOLATED
TORNADO ARE THE MAIN THREATS...BUT STRONGER STORMS WITH HIGHER
CAPE VALUES COULD SUPPORT HAIL. RADAR IMAGERY IS SHOWING GRAVITY
WAVE TAGS MOVING ALONG THE LINE OF STORMS AND WHEN THE TAGS
INTERSECT THE LINE...STORMS BEGIN TO SPIN. THEREFORE THE TORNADO
THREAT IS NOT ZERO.

THIS FIRST BATCH OF PRECIP WILL PUSH EAST THROUGH THE EARLY AFTN
HOURS AND EXPECTING ADDITIONAL SCATTERED TO NUMEROUS THUNDERSTORMS
DEVELOPMENT BEHIND THE LINE OVER NORTH CENTRAL IL. THE SECOND
WAVE SHIFTS EAST THROUGH THE EARLY EVENING HOURS. PWAT VALUES ARE
1.2-1.5 INCHES SO HEAVY DOWNPOURS ARE PSBL.

JEE

&&

.SHORT TERM...
319 AM CDT

THROUGH TUESDAY NIGHT...

FOR THE REMAINDER OF THE OVERNIGHT HOURS...CONDITIONS WILL REMAIN
QUIET ACROSS THE CWA AS A SERIES OF SHORT WAVES CONTINUE TO TRACK
NORTH AROUND THE TOP OF A PERSISTENT UPPER LEVEL RIDGE WHICH EXTENDS
FROM THE SERN CONUS THROUGH THE UPPER MISSISSIPPI VALLEY.  THIS
UPPER RIDGE HAS BEEN THE FEATURE WHICH HAS CONTROLLED THE PATH OF
THE SERIES OF SHORTWAVES LIFTING OUT OF THE SOUTHERN PLAINS...AND
WILL CONTINUE TO DO SO THROUGH THE DAY TODAY. SLY...MODERATELY
STRONG...WINDS WILL PERSIST THROUGH THE NIGHT...AND MUCH OF THE DAY
ALLOWING FOR SFC DEWPOINTS TO REMAIN CONSISTENT OR POSSIBLE INCH A
LITTLE HIGHER.

MAIN CONCERN FOR THE MORNING HOURS WILL BE THE TRACK OF A STRONG
SHORT WAVE AND ASSOCIATED SFC LOW LIFTING NORTHWARD THROUGH THE
MIDDLE MISSISSIPPI VALLEY.  THIS FEATURE WILL PREDOMINANTLY IMPACT
ERN IOWA AND WRN IL BY ARND DAYBREAK.  THROUGH THE MORNING...THE
COMBINATION OF ISENTROPIC LIFT IN THE WARM SECTOR OF THE
SYSTEM...ALL OF IL AND INTO NWRN IN...WILL LEAD TO SOME
DESTABILIZATION ACROSS THE REGION. A SFC TROUGH...AS WELL INDICATED
BY THE LATEST HIGH RES GUIDANCE...WITH LIFT THROUGH NRN IL/IN
THROUGH THE DAY...COINCIDENT WITH A STRONG SSWLY LOW LEVEL JET OF 45-
50 KT...WITH PROVIDE THE POTENTIAL FOR SHOWERS AND STRONG TO SEVERE
THUNDERSTORMS ACROSS THE CWA.  BASED ON WIND PROFILES AND MID LEVEL
DRYING...THE PRIMARY CONCERN WITH REGARD TO SEVERE WEATHER WILL BE
STRONG WIND GUSTS.  HOWEVER...SOME OF THE HIGH RES SFC WIND GUIDANCE
SUGGEST SOME SLIGHT BACKING OF SFC WINDS FROM 180-190 DEGREES TO 160-
170 DEGREES...WHILE WINDS ALOFT REMAIN SWLY.  THIS SLIGHT BACKING OF
THE SFC WINDS COULD PROVIDE ENOUGH DIRECTIONAL SHEAR THROUGH THE
LOWER LEVELS TO BRING AN ISOLD TORNADO THREAT. LOCALLY HEAVY
RAINFALL WILL ALSO BE CONCERNED WITH PWATS REACHING 1.75 INCHES
LATER THIS MORNING.  HOWEVER...FLOODING WILL LIKELY NOT BE A
SIGNIFICANT CONCERN AS THE SWLY WINDS RIGHT OFF THE DECK WILL RANGE
FROM ARND 45 KT ABOVE THE BOUNDARY LAYER TO ARND 90KT AT UPPER
LEVELS WHICH SHOULD ALLOW ANY OF THE STRONGER STORMS THAT DO DEVELOP
TO MOVE QUICKLY.

BY EARLY AFTERNOON...THE MAIN SHORT WAVE WILL LIFT INTO WISCONSIN
WHILE A SFC TROUGH TRACKS EAST ACROSS THE AREA.  THIS WILL LEAD TO
WINDS AT THE SFC VEERING TO SWLY...SETTING UP A UNIDIRECTIONAL WIND
PROFILE...EFFECTIVELY MINIMIZING THE SEVERE WEATHER THREAT TO THE
REGION.  BY LATE AFTERNOON AND INTO THE EVENING THE MODELS ARE
ADVERTISING THAT A DRY SLOW SHOULD NOSE INTO NRN IL...EFFECTIVELY
CUTTING OFF THE PCPN AREA INTO 2 SEPARATE AREA...ONE OVER WISCONSIN
AND ERN IOWA AND ANOTHER MORE FOCUSED OVER INDIANA.  THE NWRN
INDIANA COUNTIES WILL STILL HAVE A CHANCE FOR SOME SHOWERS AND
THUNDERSTORMS INTO THE EVENING...WHILE PCPN CHANCES OVER NRN IL
BEGIN TO WANE.  MUCH OF THE MODEL GUIDANCE ALSO INDICATED THAT THE
SHORTWAVE SHOULD SLOW IT`S PROGRESSION THROUGH WISCONSIN AS IT
APPROACHES THE APEX OF THE UPPER RIDGE.  AN ASSOCIATED SFC
TROUGH/COLD FRONT EXTENDING SOUTHWEST FROM THE SFC LOW WILL LINGER
OVER ERN IOWA IN THE EARLY EVENING BEFORE STEADILY PUSHING ACROSS
NRN IL AND INTO NWRN IN OVERNIGHT.  THROUGH THE NIGHT...THE
STRONGEST UPPER LEVEL FORCING WILL BE WELL NORTH OF THE CWA...SO ANY
LINGERING CHANCES FOR PCPN OVERNIGHT WILL BE LOW AND LIKELY CONFINED
TO THE NRN TIER COUNTIES OF IL...ALONG THE WI BORDER.

KREIN

&&

.LONG TERM...
229 AM CDT

WEDNESDAY THROUGH MONDAY...

WEDNESDAY THROUGH THURSDAY...
OPEN 500MB WAVE WILL BE LIFTING NORTHEAST ACROSS THE UPPER MIDWEST
INTO ONTARIO AND EVENTUALLY QUEBEC...WITH HEIGHTS SLOWLY INCREASING
WED AFTN. SFC FEATURES REMAIN DISORGANIZED WED...WITH A BOUNDARY
SLOWLY SHIFTING EAST. OPER GUIDANCE DIFFERS ON HOW QUICKLY PRECIP
WILL DEPART THE REGION. ENSEMBLE DATA SUGGESTS HOLDING ONTO CHC TO
SLIGHT CHC POPS MAINLY FOR THE CENTRAL/EASTERN CWFA WED/WED EVE.
ALTHOUGH WITH SOME HINT OF SFC HEIGHTS NUDGING UP...IT IS POSSIBLE
THAT SOME DRY AIR COULD FILTER IN AND KICK PRECIP EAST BY MIDDAY AND
ALLOW FOR A MAINLY DRY WED. SFC WINDS WILL BE TURNING SOUTHWEST TO
WEST...KEEPING AN OFFSHORE FLOW FOR LOCATIONS CLOSE TO LAKE
MICHIGAN. TEMPS SHOULD YET AGAIN TOUCH UPR 70S TO ARND 80 WED...IF
CLOUDS AND PRECIP CAN PUSH EAST BY MIDDAY...SOME CLEARING WOULD
ALLOW SFC TEMPS TO PUSH A COUPLE DEGREES WARMER INTO THE LOW 80S IN
SOME LOCATIONS. LATE IN THE EVENING THE GRADIENT SLACKENS
FURTHER...AND COULD ALLOW A LATE DAY ONSHORE FLOW TO DEVELOP FOR
AREAS ADJACENT TO LAKE MICHIGAN.

MID-LVL FLOW BEGINS TO FLATTEN AS A WEAK SFC RIDGE BECOMES ORIENTED
FROM WESTERN QUEBEC SOUTH THROUGH THE EASTERN OHIO RIVER VALLEY.
THIS WILL GENERALLY ALLOW A SOUTHERLY FLOW...ALTHOUGH THE GRADIENT
IS NOT VERY STRONG. THIS SHOULD SET THE STAGE FOR A LAKE
BREEZE/ONSHORE FLOW TO DEVELOP THUR. TIMING COULD END UP BEING
SLIGHTLY EARLIER GIVEN THE LIGHT SFC GRADIENT. GUIDANCE HAS BEEN
CONSISTENT IN HOLDING PRECIP WEST/SOUTH OF THE FORECAST AREA
THUR...AS A RESULT OF THE WEAK SFC RIDGING. SO ONE MORE MILD DAY
WITH HIGHS WARMING BACK INTO THE UPR 70S/LOW 80S...HOWEVER AS
PREVIOUSLY NOTED...A LAKE BREEZE IS LIKELY TO DEVELOP. THIS WILL
BLEED THE MUCH COOLER MARINE AIR WEST ACROSS NORTHEAST IL AND
DOWNTOWN CHICAGO. IF THE TIMING IS EARLIER IN THE DAY THUR...TEMPS
MAY NOT WARM BEYOND THE LOW/MID 60S ALONG THE CHICAGO LAKEFRONT.

FLOW THEN TURNS SOUTHERLY THUR NIGHT WITH THE MORE PROGRESSIVE FLOW
IN THE MID-LVLS PUSHING THE RIDGING EAST. A RETURN FLOW MOISTURE
WILL CONTINUE TO BE FOCUSED ACROSS THE CENTRAL CONUS THUR EVE...WITH
A SLOW MOVING FRONTAL BOUNDARY NUDGING EAST THUR NIGHT TOWARDS
WESTERN IL. THIS FRONTAL BOUNDARY WILL BECOME ENERGIZED AS A ROBUST
500MB VORT MAX BREAKS SOUTH FROM CENTRAL CANADA LATE THUR NIGHT.

THIS SHOULD ALLOW FOR AN ATMOSPHERIC RIVER TO DEVELOP FROM THE
SOUTHERN PLAINS STRETCHING NORTH THROUGH THE MID-MISSOURI VALLEY
INTO THE WESTERN GREAT LAKES EARLY FRI MORNING.

FRIDAY THROUGH EARLY NEXT WEEK...
ENSEMBLES CONTINUE TO PROG A ROBUST TROUGH SLIDING SOUTH FROM
CENTRAL CANADA FRI. THIS COUPLED WITH DOWNSTREAM MID-LVL RIDGING
ACROSS THE SOUTHEAST CONUS WILL STRENGTHEN THE FRONTAL BOUNDARY
THAT WILL BE ORIENTED FROM THE SOUTHERN PLAINS STRETCHING
NORTHEAST THROUGH THE GREAT LAKES REGION INTO WESTERN QUEBEC.

THIS SETUP IS IDEAL FOR THE DEVELOPMENT OF AN ATMOSPHERIC RIVER WITH
ABUNDANT LOW LEVEL MOISTURE AND EFFICIENT PRECIP PRODUCING
CONVECTION.

OPER GUIDANCE HAS BEEN RELATIVELY CONSISTENT WITH BRINGING A SERIES
OF WAVES ALONG THE SLOW MOVING FRONTAL BOUNDARY FRI AFTN/EVE...THEN
THE BOUNDARY SHOULD SLIDE EAST WITH WINDS QUICKLY VEERING
NORTH/NORTHEAST FOR SAT AND USHERING IN MUCH COOLER AIR TO THE
REGION.

CURRENT INDICATIONS ARE THAT HIGHS SAT MAY STRUGGLE TO WARM BEYOND
THE UPR 50S ACROSS NORTHEAST IL/NORTHWEST IN...WITH ONLY LOW 60S
ELSEWHERE. STRONG SFC RIDGE WILL REMAIN NORTH OF THE REGION...SO THE
PRIOR FRONTAL BOUNDARY MAY BECOME QUASI-STATIONARY FOR THE WEEKEND
ALONG THE OHIO VALLEY AND CONTINUE TO FEED PRECIP CHANCES TO THE
SOUTHERN CWFA.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 14Z...

* MVFR CEILINGS CONTINUE THIS MORNING.

* PERIODS OF -SHRA WITH PERIODIC TSRA THIS AFTERNOON.

* SOUTH TO SOUTH-SOUTHWEST WINDS INCREASING THROUGH THE MORNING TO
  GUST OVER 20KT

KREIN/MM

//DISCUSSION...UPDATED 12Z...

A MID LEVEL DISTURBANCE MOVING FROM THE SOUTHERN PLAINS TO NRN IL
BY THIS AFTERNOON MAY BRING ANOTHER ROUND OF SHOWERS WITH SCT
THUNDERSTORMS TO THE REGION. UPPER LEVEL FORCING FROM THE MID
LEVEL DISTURBANCE AND AN UPPER LEVEL JET STREAM WILL ENHANCE THE
LIKELIHOOD FOR PCPN AND THE CHANCE FOR TSRA...WITH THE MOST
LIKELY CHANCE FOR ACTIVITY FROM LATE MORNING THROUGH EARLY
EVENING. SOME UNCERTAINTY REMAINS IN PINNING DOWN THE EXACT
PERIOD FOR THE TSRA...SO WILL MAINTAIN THE GOING TEMPO FOR LATE
MORNING THROUGH EARLY AFTERNOON. HOWEVER...THE PCPN TIMING COULD
BE SHIFTED OR EXPANDED IN TIME.

LOW LEVEL MOISTURE STREAMING NORTHWARD AHEAD OF LOW PRESSURE OVER
THE MID MISSISSIPPI VALLEY HAS BROUGHT A LOW MVFR STRATUS DECK
ACROSS THE REGION. SOME SITES ARE REPORTING CIGS DROPPING INTO IFR
RANGE...SO WILL INCLUDE THE POSSIBILITY IN A TEMPO GROUP THROUGH
LATE MORNING. DAYTIME WARMING SHOULD ALLOW FOR INCREASE DEEP LAYER
MIXING WHICH SHOULD SCATTER OUT THE STRATUS DECK.

WINDS WILL BE GENERALLY SOUTHERLY TODAY...THOUGH DIRECTION MAY BE
A BIT VARIABLE AROUND CONVECTIVE ACTIVITY. SOME GUSTINESS IS
LIKELY TO BEGIN BY LATE MORNING...WITH THE LATEST GUIDANCE
SUGGESTING THAT WINDS COULD STRENGTHEN AND BECOME EVEN MORE GUSTY
TONIGHT WITH WINDS VEERING SWLY AS SURFACE LOW PRESSURE MOVES
NORTHEAST ACROSS SOUTHERN WISCONSIN.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 14Z...

* HIGH CONFIDENCE IN WIND TRENDS TODAY. MEDIUM IN WIND TRENDS
  TONIGHT.

* HIGH CONFIDENCE IN MVFR CIGS THIS MORNING.

* HIGH CONFIDENCE IN SHOWERS AND MEDIUM CONFIDENCE OF A PERIOD OF
  TSRA. LOW CONFIDENCE IN SPECIFIC TSRA TIMING AND IMPACT ON THE
  TERMINALS WITH MULTIPLE ROUNDS POSSIBLE BETWEEN 18Z AND 02Z.

KREIN/MM

//OUTLOOK FOR ORD/MDW FOR 00Z THURSDAY-12Z TUESDAY...UPDATED 12Z...

WEDNESDAY NIGHT...WX NIL/VFR. SOUTHEAST WINDS.

THURSDAY...SLIGHT CHANCE OF TSRA AT NIGHT. SOUTHEAST WINDS.

FRIDAY...TSRA/SHRA LIKELY THROUGH THE DAY AND NIGHT. MVFR
POSSIBLE. SOUTHWEST WINDS.

SATURDAY...SHRA LIKELY WITH A CHANCE OF TSRA DURING THE DAY.
NORTHEAST WINDS.

SUNDAY...CHANCE OF SHRA. EAST WINDS. MVFR POSSIBLE.

MONDAY...CHANCE OF SHRA. SOUTHEAST WINDS. MVFR POSSIBLE.

KREIN

&&

.MARINE...
229 AM CDT

WARM MOIST AIR CONTINUES TO FEED NORTH ACROSS THE LAKE
TODAY...WHICH MAY HELP TO FURTHER ENHANCE ANY AREAS OF FOG THAT
HAVE ALREADY DEVELOPED. IT IS POSSIBLE PATCHY DENSE FOG MAY
DEVELOP...ALTHOUGH WINDS MAY BE JUST STRONG ENOUGH TO LIMIT THE
COVERAGE AND INTENSITY OF THE FOG. A SURFACE LOW PRESSURE SYSTEM
WILL BE LIFTING NORTH ACROSS EASTERN IOWA INTO CENTRAL WISCONSIN
THIS EVENING. THE GRADIENT WILL TIGHTEN ACROSS THE
CENTRAL/SOUTHERN PORTIONS OF THE LAKE...WHICH WITH WARMER
NEARSHORE WATERS EXPECT SOME SLIGHTLY BETTER MIXING TO OCCUR.
FURTHER OUT ACROSS THE OPEN WATERS THE WATER REMAINS COLD AND
EXPECT THE STABILITY TO MAKE IT DIFFICULT TO MIX TO THE SFC THE
HIGHER GUSTS. HIGH PRESSURE THEN ARRIVES LATE WEDNESDAY WITH LIGHT
WINDS DEVELOPING. THEN HIGH PRESSURE SHIFTS EAST THURSDAY
NIGHT...WITH SOUTHERLY WINDS DEVELOPING AGAIN FRIDAY. A FRONTAL
BOUNDARY WILL APPROACH LAKE MICHIGAN LATE FRIDAY NIGHT THEN
STEADILY SLIDE SOUTH ALONG THE LAKE. THIS WILL ALLOW WINDS TO
QUICKLY VEER FROM SOUTH TO NORTH/NORTHEAST SATURDAY. ALONG WITH
THIS QUICK WIND SHIFT WILL BE COOLER AIR SLIDING SOUTH OVER THE
LAKE. WAVES SHOULD EASILY BUILD SATURDAY FOR THE CENTRAL/SOUTHERN
PORTIONS OF THE LAKE.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 261528
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1028 AM CDT TUE MAY 26 2015

.UPDATE...
1007 AM CDT

A SFC LOW IS OVER IOWA AND ITS WARM/STATIONARY FRONT IS WELL TO
OUR NORTH OVER CENTRAL WI. ITS COLD FRONT STRETCHES FROM THE LOW
THROUGH CENTRAL KANSAS. AN AREA OF MAINLY RAIN AND A FEW
THUNDERSTORMS IS SLOWLY SPREADING NNE ACROSS NORTH CENTRAL IL. SO
FAR THE SHOWERS HAVE BEEN BEHAVING ACROSS MY CWA...BUT A FEW CELLS
TO THE WEST HAVE SHOWN SIGNS OF ROTATION.

LIKING THE LATEST RAP GUIDANCE WHICH KEEPS CAPE VALUES ON THE LOW
SIDE WITH ONLY A FEW HUNDREDS J/KG OF CAPE TO WORK WITH. THIS IS
ASSUMING SKIES STAY OVERCAST...AND THINKING WE WILL BE OVERCAST
TODAY. THAT BEING SAID...ANY LOCATIONS THAT SEE SUNSHINE COULD
DEVELOP ENOUGH CAPE TO SUPPORT TALLER CELLS AND POSSIBLY SEVERE
WEATHER. IN GENERAL THINKING DAMAGING WINDS AND AN ISOLATED
TORNADO ARE THE MAIN THREATS...BUT STRONGER STORMS WITH HIGHER
CAPE VALUES COULD SUPPORT HAIL. RADAR IMAGERY IS SHOWING GRAVITY
WAVE TAGS MOVING ALONG THE LINE OF STORMS AND WHEN THE TAGS
INTERSECT THE LINE...STORMS BEGIN TO SPIN. THEREFORE THE TORNADO
THREAT IS NOT ZERO.

THIS FIRST BATCH OF PRECIP WILL PUSH EAST THROUGH THE EARLY AFTN
HOURS AND EXPECTING ADDITIONAL SCATTERED TO NUMEROUS THUNDERSTORMS
DEVELOPMENT BEHIND THE LINE OVER NORTH CENTRAL IL. THE SECOND
WAVE SHIFTS EAST THROUGH THE EARLY EVENING HOURS. PWAT VALUES ARE
1.2-1.5 INCHES SO HEAVY DOWNPOURS ARE PSBL.

JEE

&&

.SHORT TERM...
319 AM CDT

THROUGH TUESDAY NIGHT...

FOR THE REMAINDER OF THE OVERNIGHT HOURS...CONDITIONS WILL REMAIN
QUIET ACROSS THE CWA AS A SERIES OF SHORT WAVES CONTINUE TO TRACK
NORTH AROUND THE TOP OF A PERSISTENT UPPER LEVEL RIDGE WHICH EXTENDS
FROM THE SERN CONUS THROUGH THE UPPER MISSISSIPPI VALLEY.  THIS
UPPER RIDGE HAS BEEN THE FEATURE WHICH HAS CONTROLLED THE PATH OF
THE SERIES OF SHORTWAVES LIFTING OUT OF THE SOUTHERN PLAINS...AND
WILL CONTINUE TO DO SO THROUGH THE DAY TODAY. SLY...MODERATELY
STRONG...WINDS WILL PERSIST THROUGH THE NIGHT...AND MUCH OF THE DAY
ALLOWING FOR SFC DEWPOINTS TO REMAIN CONSISTENT OR POSSIBLE INCH A
LITTLE HIGHER.

MAIN CONCERN FOR THE MORNING HOURS WILL BE THE TRACK OF A STRONG
SHORT WAVE AND ASSOCIATED SFC LOW LIFTING NORTHWARD THROUGH THE
MIDDLE MISSISSIPPI VALLEY.  THIS FEATURE WILL PREDOMINANTLY IMPACT
ERN IOWA AND WRN IL BY ARND DAYBREAK.  THROUGH THE MORNING...THE
COMBINATION OF ISENTROPIC LIFT IN THE WARM SECTOR OF THE
SYSTEM...ALL OF IL AND INTO NWRN IN...WILL LEAD TO SOME
DESTABILIZATION ACROSS THE REGION. A SFC TROUGH...AS WELL INDICATED
BY THE LATEST HIGH RES GUIDANCE...WITH LIFT THROUGH NRN IL/IN
THROUGH THE DAY...COINCIDENT WITH A STRONG SSWLY LOW LEVEL JET OF 45-
50 KT...WITH PROVIDE THE POTENTIAL FOR SHOWERS AND STRONG TO SEVERE
THUNDERSTORMS ACROSS THE CWA.  BASED ON WIND PROFILES AND MID LEVEL
DRYING...THE PRIMARY CONCERN WITH REGARD TO SEVERE WEATHER WILL BE
STRONG WIND GUSTS.  HOWEVER...SOME OF THE HIGH RES SFC WIND GUIDANCE
SUGGEST SOME SLIGHT BACKING OF SFC WINDS FROM 180-190 DEGREES TO 160-
170 DEGREES...WHILE WINDS ALOFT REMAIN SWLY.  THIS SLIGHT BACKING OF
THE SFC WINDS COULD PROVIDE ENOUGH DIRECTIONAL SHEAR THROUGH THE
LOWER LEVELS TO BRING AN ISOLD TORNADO THREAT. LOCALLY HEAVY
RAINFALL WILL ALSO BE CONCERNED WITH PWATS REACHING 1.75 INCHES
LATER THIS MORNING.  HOWEVER...FLOODING WILL LIKELY NOT BE A
SIGNIFICANT CONCERN AS THE SWLY WINDS RIGHT OFF THE DECK WILL RANGE
FROM ARND 45 KT ABOVE THE BOUNDARY LAYER TO ARND 90KT AT UPPER
LEVELS WHICH SHOULD ALLOW ANY OF THE STRONGER STORMS THAT DO DEVELOP
TO MOVE QUICKLY.

BY EARLY AFTERNOON...THE MAIN SHORT WAVE WILL LIFT INTO WISCONSIN
WHILE A SFC TROUGH TRACKS EAST ACROSS THE AREA.  THIS WILL LEAD TO
WINDS AT THE SFC VEERING TO SWLY...SETTING UP A UNIDIRECTIONAL WIND
PROFILE...EFFECTIVELY MINIMIZING THE SEVERE WEATHER THREAT TO THE
REGION.  BY LATE AFTERNOON AND INTO THE EVENING THE MODELS ARE
ADVERTISING THAT A DRY SLOW SHOULD NOSE INTO NRN IL...EFFECTIVELY
CUTTING OFF THE PCPN AREA INTO 2 SEPARATE AREA...ONE OVER WISCONSIN
AND ERN IOWA AND ANOTHER MORE FOCUSED OVER INDIANA.  THE NWRN
INDIANA COUNTIES WILL STILL HAVE A CHANCE FOR SOME SHOWERS AND
THUNDERSTORMS INTO THE EVENING...WHILE PCPN CHANCES OVER NRN IL
BEGIN TO WANE.  MUCH OF THE MODEL GUIDANCE ALSO INDICATED THAT THE
SHORTWAVE SHOULD SLOW IT`S PROGRESSION THROUGH WISCONSIN AS IT
APPROACHES THE APEX OF THE UPPER RIDGE.  AN ASSOCIATED SFC
TROUGH/COLD FRONT EXTENDING SOUTHWEST FROM THE SFC LOW WILL LINGER
OVER ERN IOWA IN THE EARLY EVENING BEFORE STEADILY PUSHING ACROSS
NRN IL AND INTO NWRN IN OVERNIGHT.  THROUGH THE NIGHT...THE
STRONGEST UPPER LEVEL FORCING WILL BE WELL NORTH OF THE CWA...SO ANY
LINGERING CHANCES FOR PCPN OVERNIGHT WILL BE LOW AND LIKELY CONFINED
TO THE NRN TIER COUNTIES OF IL...ALONG THE WI BORDER.

KREIN

&&

.LONG TERM...
229 AM CDT

WEDNESDAY THROUGH MONDAY...

WEDNESDAY THROUGH THURSDAY...
OPEN 500MB WAVE WILL BE LIFTING NORTHEAST ACROSS THE UPPER MIDWEST
INTO ONTARIO AND EVENTUALLY QUEBEC...WITH HEIGHTS SLOWLY INCREASING
WED AFTN. SFC FEATURES REMAIN DISORGANIZED WED...WITH A BOUNDARY
SLOWLY SHIFTING EAST. OPER GUIDANCE DIFFERS ON HOW QUICKLY PRECIP
WILL DEPART THE REGION. ENSEMBLE DATA SUGGESTS HOLDING ONTO CHC TO
SLIGHT CHC POPS MAINLY FOR THE CENTRAL/EASTERN CWFA WED/WED EVE.
ALTHOUGH WITH SOME HINT OF SFC HEIGHTS NUDGING UP...IT IS POSSIBLE
THAT SOME DRY AIR COULD FILTER IN AND KICK PRECIP EAST BY MIDDAY AND
ALLOW FOR A MAINLY DRY WED. SFC WINDS WILL BE TURNING SOUTHWEST TO
WEST...KEEPING AN OFFSHORE FLOW FOR LOCATIONS CLOSE TO LAKE
MICHIGAN. TEMPS SHOULD YET AGAIN TOUCH UPR 70S TO ARND 80 WED...IF
CLOUDS AND PRECIP CAN PUSH EAST BY MIDDAY...SOME CLEARING WOULD
ALLOW SFC TEMPS TO PUSH A COUPLE DEGREES WARMER INTO THE LOW 80S IN
SOME LOCATIONS. LATE IN THE EVENING THE GRADIENT SLACKENS
FURTHER...AND COULD ALLOW A LATE DAY ONSHORE FLOW TO DEVELOP FOR
AREAS ADJACENT TO LAKE MICHIGAN.

MID-LVL FLOW BEGINS TO FLATTEN AS A WEAK SFC RIDGE BECOMES ORIENTED
FROM WESTERN QUEBEC SOUTH THROUGH THE EASTERN OHIO RIVER VALLEY.
THIS WILL GENERALLY ALLOW A SOUTHERLY FLOW...ALTHOUGH THE GRADIENT
IS NOT VERY STRONG. THIS SHOULD SET THE STAGE FOR A LAKE
BREEZE/ONSHORE FLOW TO DEVELOP THUR. TIMING COULD END UP BEING
SLIGHTLY EARLIER GIVEN THE LIGHT SFC GRADIENT. GUIDANCE HAS BEEN
CONSISTENT IN HOLDING PRECIP WEST/SOUTH OF THE FORECAST AREA
THUR...AS A RESULT OF THE WEAK SFC RIDGING. SO ONE MORE MILD DAY
WITH HIGHS WARMING BACK INTO THE UPR 70S/LOW 80S...HOWEVER AS
PREVIOUSLY NOTED...A LAKE BREEZE IS LIKELY TO DEVELOP. THIS WILL
BLEED THE MUCH COOLER MARINE AIR WEST ACROSS NORTHEAST IL AND
DOWNTOWN CHICAGO. IF THE TIMING IS EARLIER IN THE DAY THUR...TEMPS
MAY NOT WARM BEYOND THE LOW/MID 60S ALONG THE CHICAGO LAKEFRONT.

FLOW THEN TURNS SOUTHERLY THUR NIGHT WITH THE MORE PROGRESSIVE FLOW
IN THE MID-LVLS PUSHING THE RIDGING EAST. A RETURN FLOW MOISTURE
WILL CONTINUE TO BE FOCUSED ACROSS THE CENTRAL CONUS THUR EVE...WITH
A SLOW MOVING FRONTAL BOUNDARY NUDGING EAST THUR NIGHT TOWARDS
WESTERN IL. THIS FRONTAL BOUNDARY WILL BECOME ENERGIZED AS A ROBUST
500MB VORT MAX BREAKS SOUTH FROM CENTRAL CANADA LATE THUR NIGHT.

THIS SHOULD ALLOW FOR AN ATMOSPHERIC RIVER TO DEVELOP FROM THE
SOUTHERN PLAINS STRETCHING NORTH THROUGH THE MID-MISSOURI VALLEY
INTO THE WESTERN GREAT LAKES EARLY FRI MORNING.

FRIDAY THROUGH EARLY NEXT WEEK...
ENSEMBLES CONTINUE TO PROG A ROBUST TROUGH SLIDING SOUTH FROM
CENTRAL CANADA FRI. THIS COUPLED WITH DOWNSTREAM MID-LVL RIDGING
ACROSS THE SOUTHEAST CONUS WILL STRENGTHEN THE FRONTAL BOUNDARY
THAT WILL BE ORIENTED FROM THE SOUTHERN PLAINS STRETCHING
NORTHEAST THROUGH THE GREAT LAKES REGION INTO WESTERN QUEBEC.

THIS SETUP IS IDEAL FOR THE DEVELOPMENT OF AN ATMOSPHERIC RIVER WITH
ABUNDANT LOW LEVEL MOISTURE AND EFFICIENT PRECIP PRODUCING
CONVECTION.

OPER GUIDANCE HAS BEEN RELATIVELY CONSISTENT WITH BRINGING A SERIES
OF WAVES ALONG THE SLOW MOVING FRONTAL BOUNDARY FRI AFTN/EVE...THEN
THE BOUNDARY SHOULD SLIDE EAST WITH WINDS QUICKLY VEERING
NORTH/NORTHEAST FOR SAT AND USHERING IN MUCH COOLER AIR TO THE
REGION.

CURRENT INDICATIONS ARE THAT HIGHS SAT MAY STRUGGLE TO WARM BEYOND
THE UPR 50S ACROSS NORTHEAST IL/NORTHWEST IN...WITH ONLY LOW 60S
ELSEWHERE. STRONG SFC RIDGE WILL REMAIN NORTH OF THE REGION...SO THE
PRIOR FRONTAL BOUNDARY MAY BECOME QUASI-STATIONARY FOR THE WEEKEND
ALONG THE OHIO VALLEY AND CONTINUE TO FEED PRECIP CHANCES TO THE
SOUTHERN CWFA.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 14Z...

* MVFR CEILINGS CONTINUE THIS MORNING.

* PERIODS OF -SHRA WITH PERIODIC TSRA THIS AFTERNOON.

* SOUTH TO SOUTH-SOUTHWEST WINDS INCREASING THROUGH THE MORNING TO
  GUST OVER 20KT

KREIN/MM

//DISCUSSION...UPDATED 12Z...

A MID LEVEL DISTURBANCE MOVING FROM THE SOUTHERN PLAINS TO NRN IL
BY THIS AFTERNOON MAY BRING ANOTHER ROUND OF SHOWERS WITH SCT
THUNDERSTORMS TO THE REGION. UPPER LEVEL FORCING FROM THE MID
LEVEL DISTURBANCE AND AN UPPER LEVEL JET STREAM WILL ENHANCE THE
LIKELIHOOD FOR PCPN AND THE CHANCE FOR TSRA...WITH THE MOST
LIKELY CHANCE FOR ACTIVITY FROM LATE MORNING THROUGH EARLY
EVENING. SOME UNCERTAINTY REMAINS IN PINNING DOWN THE EXACT
PERIOD FOR THE TSRA...SO WILL MAINTAIN THE GOING TEMPO FOR LATE
MORNING THROUGH EARLY AFTERNOON. HOWEVER...THE PCPN TIMING COULD
BE SHIFTED OR EXPANDED IN TIME.

LOW LEVEL MOISTURE STREAMING NORTHWARD AHEAD OF LOW PRESSURE OVER
THE MID MISSISSIPPI VALLEY HAS BROUGHT A LOW MVFR STRATUS DECK
ACROSS THE REGION. SOME SITES ARE REPORTING CIGS DROPPING INTO IFR
RANGE...SO WILL INCLUDE THE POSSIBILITY IN A TEMPO GROUP THROUGH
LATE MORNING. DAYTIME WARMING SHOULD ALLOW FOR INCREASE DEEP LAYER
MIXING WHICH SHOULD SCATTER OUT THE STRATUS DECK.

WINDS WILL BE GENERALLY SOUTHERLY TODAY...THOUGH DIRECTION MAY BE
A BIT VARIABLE AROUND CONVECTIVE ACTIVITY. SOME GUSTINESS IS
LIKELY TO BEGIN BY LATE MORNING...WITH THE LATEST GUIDANCE
SUGGESTING THAT WINDS COULD STRENGTHEN AND BECOME EVEN MORE GUSTY
TONIGHT WITH WINDS VEERING SWLY AS SURFACE LOW PRESSURE MOVES
NORTHEAST ACROSS SOUTHERN WISCONSIN.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 14Z...

* HIGH CONFIDENCE IN WIND TRENDS TODAY. MEDIUM IN WIND TRENDS
  TONIGHT.

* HIGH CONFIDENCE IN MVFR CIGS THIS MORNING.

* HIGH CONFIDENCE IN SHOWERS AND MEDIUM CONFIDENCE OF A PERIOD OF
  TSRA. LOW CONFIDENCE IN SPECIFIC TSRA TIMING AND IMPACT ON THE
  TERMINALS WITH MULTIPLE ROUNDS POSSIBLE BETWEEN 18Z AND 02Z.

KREIN/MM

//OUTLOOK FOR ORD/MDW FOR 00Z THURSDAY-12Z TUESDAY...UPDATED 12Z...

WEDNESDAY NIGHT...WX NIL/VFR. SOUTHEAST WINDS.

THURSDAY...SLIGHT CHANCE OF TSRA AT NIGHT. SOUTHEAST WINDS.

FRIDAY...TSRA/SHRA LIKELY THROUGH THE DAY AND NIGHT. MVFR
POSSIBLE. SOUTHWEST WINDS.

SATURDAY...SHRA LIKELY WITH A CHANCE OF TSRA DURING THE DAY.
NORTHEAST WINDS.

SUNDAY...CHANCE OF SHRA. EAST WINDS. MVFR POSSIBLE.

MONDAY...CHANCE OF SHRA. SOUTHEAST WINDS. MVFR POSSIBLE.

KREIN

&&

.MARINE...
229 AM CDT

WARM MOIST AIR CONTINUES TO FEED NORTH ACROSS THE LAKE
TODAY...WHICH MAY HELP TO FURTHER ENHANCE ANY AREAS OF FOG THAT
HAVE ALREADY DEVELOPED. IT IS POSSIBLE PATCHY DENSE FOG MAY
DEVELOP...ALTHOUGH WINDS MAY BE JUST STRONG ENOUGH TO LIMIT THE
COVERAGE AND INTENSITY OF THE FOG. A SURFACE LOW PRESSURE SYSTEM
WILL BE LIFTING NORTH ACROSS EASTERN IOWA INTO CENTRAL WISCONSIN
THIS EVENING. THE GRADIENT WILL TIGHTEN ACROSS THE
CENTRAL/SOUTHERN PORTIONS OF THE LAKE...WHICH WITH WARMER
NEARSHORE WATERS EXPECT SOME SLIGHTLY BETTER MIXING TO OCCUR.
FURTHER OUT ACROSS THE OPEN WATERS THE WATER REMAINS COLD AND
EXPECT THE STABILITY TO MAKE IT DIFFICULT TO MIX TO THE SFC THE
HIGHER GUSTS. HIGH PRESSURE THEN ARRIVES LATE WEDNESDAY WITH LIGHT
WINDS DEVELOPING. THEN HIGH PRESSURE SHIFTS EAST THURSDAY
NIGHT...WITH SOUTHERLY WINDS DEVELOPING AGAIN FRIDAY. A FRONTAL
BOUNDARY WILL APPROACH LAKE MICHIGAN LATE FRIDAY NIGHT THEN
STEADILY SLIDE SOUTH ALONG THE LAKE. THIS WILL ALLOW WINDS TO
QUICKLY VEER FROM SOUTH TO NORTH/NORTHEAST SATURDAY. ALONG WITH
THIS QUICK WIND SHIFT WILL BE COOLER AIR SLIDING SOUTH OVER THE
LAKE. WAVES SHOULD EASILY BUILD SATURDAY FOR THE CENTRAL/SOUTHERN
PORTIONS OF THE LAKE.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 261528
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1028 AM CDT TUE MAY 26 2015

.UPDATE...
1007 AM CDT

A SFC LOW IS OVER IOWA AND ITS WARM/STATIONARY FRONT IS WELL TO
OUR NORTH OVER CENTRAL WI. ITS COLD FRONT STRETCHES FROM THE LOW
THROUGH CENTRAL KANSAS. AN AREA OF MAINLY RAIN AND A FEW
THUNDERSTORMS IS SLOWLY SPREADING NNE ACROSS NORTH CENTRAL IL. SO
FAR THE SHOWERS HAVE BEEN BEHAVING ACROSS MY CWA...BUT A FEW CELLS
TO THE WEST HAVE SHOWN SIGNS OF ROTATION.

LIKING THE LATEST RAP GUIDANCE WHICH KEEPS CAPE VALUES ON THE LOW
SIDE WITH ONLY A FEW HUNDREDS J/KG OF CAPE TO WORK WITH. THIS IS
ASSUMING SKIES STAY OVERCAST...AND THINKING WE WILL BE OVERCAST
TODAY. THAT BEING SAID...ANY LOCATIONS THAT SEE SUNSHINE COULD
DEVELOP ENOUGH CAPE TO SUPPORT TALLER CELLS AND POSSIBLY SEVERE
WEATHER. IN GENERAL THINKING DAMAGING WINDS AND AN ISOLATED
TORNADO ARE THE MAIN THREATS...BUT STRONGER STORMS WITH HIGHER
CAPE VALUES COULD SUPPORT HAIL. RADAR IMAGERY IS SHOWING GRAVITY
WAVE TAGS MOVING ALONG THE LINE OF STORMS AND WHEN THE TAGS
INTERSECT THE LINE...STORMS BEGIN TO SPIN. THEREFORE THE TORNADO
THREAT IS NOT ZERO.

THIS FIRST BATCH OF PRECIP WILL PUSH EAST THROUGH THE EARLY AFTN
HOURS AND EXPECTING ADDITIONAL SCATTERED TO NUMEROUS THUNDERSTORMS
DEVELOPMENT BEHIND THE LINE OVER NORTH CENTRAL IL. THE SECOND
WAVE SHIFTS EAST THROUGH THE EARLY EVENING HOURS. PWAT VALUES ARE
1.2-1.5 INCHES SO HEAVY DOWNPOURS ARE PSBL.

JEE

&&

.SHORT TERM...
319 AM CDT

THROUGH TUESDAY NIGHT...

FOR THE REMAINDER OF THE OVERNIGHT HOURS...CONDITIONS WILL REMAIN
QUIET ACROSS THE CWA AS A SERIES OF SHORT WAVES CONTINUE TO TRACK
NORTH AROUND THE TOP OF A PERSISTENT UPPER LEVEL RIDGE WHICH EXTENDS
FROM THE SERN CONUS THROUGH THE UPPER MISSISSIPPI VALLEY.  THIS
UPPER RIDGE HAS BEEN THE FEATURE WHICH HAS CONTROLLED THE PATH OF
THE SERIES OF SHORTWAVES LIFTING OUT OF THE SOUTHERN PLAINS...AND
WILL CONTINUE TO DO SO THROUGH THE DAY TODAY. SLY...MODERATELY
STRONG...WINDS WILL PERSIST THROUGH THE NIGHT...AND MUCH OF THE DAY
ALLOWING FOR SFC DEWPOINTS TO REMAIN CONSISTENT OR POSSIBLE INCH A
LITTLE HIGHER.

MAIN CONCERN FOR THE MORNING HOURS WILL BE THE TRACK OF A STRONG
SHORT WAVE AND ASSOCIATED SFC LOW LIFTING NORTHWARD THROUGH THE
MIDDLE MISSISSIPPI VALLEY.  THIS FEATURE WILL PREDOMINANTLY IMPACT
ERN IOWA AND WRN IL BY ARND DAYBREAK.  THROUGH THE MORNING...THE
COMBINATION OF ISENTROPIC LIFT IN THE WARM SECTOR OF THE
SYSTEM...ALL OF IL AND INTO NWRN IN...WILL LEAD TO SOME
DESTABILIZATION ACROSS THE REGION. A SFC TROUGH...AS WELL INDICATED
BY THE LATEST HIGH RES GUIDANCE...WITH LIFT THROUGH NRN IL/IN
THROUGH THE DAY...COINCIDENT WITH A STRONG SSWLY LOW LEVEL JET OF 45-
50 KT...WITH PROVIDE THE POTENTIAL FOR SHOWERS AND STRONG TO SEVERE
THUNDERSTORMS ACROSS THE CWA.  BASED ON WIND PROFILES AND MID LEVEL
DRYING...THE PRIMARY CONCERN WITH REGARD TO SEVERE WEATHER WILL BE
STRONG WIND GUSTS.  HOWEVER...SOME OF THE HIGH RES SFC WIND GUIDANCE
SUGGEST SOME SLIGHT BACKING OF SFC WINDS FROM 180-190 DEGREES TO 160-
170 DEGREES...WHILE WINDS ALOFT REMAIN SWLY.  THIS SLIGHT BACKING OF
THE SFC WINDS COULD PROVIDE ENOUGH DIRECTIONAL SHEAR THROUGH THE
LOWER LEVELS TO BRING AN ISOLD TORNADO THREAT. LOCALLY HEAVY
RAINFALL WILL ALSO BE CONCERNED WITH PWATS REACHING 1.75 INCHES
LATER THIS MORNING.  HOWEVER...FLOODING WILL LIKELY NOT BE A
SIGNIFICANT CONCERN AS THE SWLY WINDS RIGHT OFF THE DECK WILL RANGE
FROM ARND 45 KT ABOVE THE BOUNDARY LAYER TO ARND 90KT AT UPPER
LEVELS WHICH SHOULD ALLOW ANY OF THE STRONGER STORMS THAT DO DEVELOP
TO MOVE QUICKLY.

BY EARLY AFTERNOON...THE MAIN SHORT WAVE WILL LIFT INTO WISCONSIN
WHILE A SFC TROUGH TRACKS EAST ACROSS THE AREA.  THIS WILL LEAD TO
WINDS AT THE SFC VEERING TO SWLY...SETTING UP A UNIDIRECTIONAL WIND
PROFILE...EFFECTIVELY MINIMIZING THE SEVERE WEATHER THREAT TO THE
REGION.  BY LATE AFTERNOON AND INTO THE EVENING THE MODELS ARE
ADVERTISING THAT A DRY SLOW SHOULD NOSE INTO NRN IL...EFFECTIVELY
CUTTING OFF THE PCPN AREA INTO 2 SEPARATE AREA...ONE OVER WISCONSIN
AND ERN IOWA AND ANOTHER MORE FOCUSED OVER INDIANA.  THE NWRN
INDIANA COUNTIES WILL STILL HAVE A CHANCE FOR SOME SHOWERS AND
THUNDERSTORMS INTO THE EVENING...WHILE PCPN CHANCES OVER NRN IL
BEGIN TO WANE.  MUCH OF THE MODEL GUIDANCE ALSO INDICATED THAT THE
SHORTWAVE SHOULD SLOW IT`S PROGRESSION THROUGH WISCONSIN AS IT
APPROACHES THE APEX OF THE UPPER RIDGE.  AN ASSOCIATED SFC
TROUGH/COLD FRONT EXTENDING SOUTHWEST FROM THE SFC LOW WILL LINGER
OVER ERN IOWA IN THE EARLY EVENING BEFORE STEADILY PUSHING ACROSS
NRN IL AND INTO NWRN IN OVERNIGHT.  THROUGH THE NIGHT...THE
STRONGEST UPPER LEVEL FORCING WILL BE WELL NORTH OF THE CWA...SO ANY
LINGERING CHANCES FOR PCPN OVERNIGHT WILL BE LOW AND LIKELY CONFINED
TO THE NRN TIER COUNTIES OF IL...ALONG THE WI BORDER.

KREIN

&&

.LONG TERM...
229 AM CDT

WEDNESDAY THROUGH MONDAY...

WEDNESDAY THROUGH THURSDAY...
OPEN 500MB WAVE WILL BE LIFTING NORTHEAST ACROSS THE UPPER MIDWEST
INTO ONTARIO AND EVENTUALLY QUEBEC...WITH HEIGHTS SLOWLY INCREASING
WED AFTN. SFC FEATURES REMAIN DISORGANIZED WED...WITH A BOUNDARY
SLOWLY SHIFTING EAST. OPER GUIDANCE DIFFERS ON HOW QUICKLY PRECIP
WILL DEPART THE REGION. ENSEMBLE DATA SUGGESTS HOLDING ONTO CHC TO
SLIGHT CHC POPS MAINLY FOR THE CENTRAL/EASTERN CWFA WED/WED EVE.
ALTHOUGH WITH SOME HINT OF SFC HEIGHTS NUDGING UP...IT IS POSSIBLE
THAT SOME DRY AIR COULD FILTER IN AND KICK PRECIP EAST BY MIDDAY AND
ALLOW FOR A MAINLY DRY WED. SFC WINDS WILL BE TURNING SOUTHWEST TO
WEST...KEEPING AN OFFSHORE FLOW FOR LOCATIONS CLOSE TO LAKE
MICHIGAN. TEMPS SHOULD YET AGAIN TOUCH UPR 70S TO ARND 80 WED...IF
CLOUDS AND PRECIP CAN PUSH EAST BY MIDDAY...SOME CLEARING WOULD
ALLOW SFC TEMPS TO PUSH A COUPLE DEGREES WARMER INTO THE LOW 80S IN
SOME LOCATIONS. LATE IN THE EVENING THE GRADIENT SLACKENS
FURTHER...AND COULD ALLOW A LATE DAY ONSHORE FLOW TO DEVELOP FOR
AREAS ADJACENT TO LAKE MICHIGAN.

MID-LVL FLOW BEGINS TO FLATTEN AS A WEAK SFC RIDGE BECOMES ORIENTED
FROM WESTERN QUEBEC SOUTH THROUGH THE EASTERN OHIO RIVER VALLEY.
THIS WILL GENERALLY ALLOW A SOUTHERLY FLOW...ALTHOUGH THE GRADIENT
IS NOT VERY STRONG. THIS SHOULD SET THE STAGE FOR A LAKE
BREEZE/ONSHORE FLOW TO DEVELOP THUR. TIMING COULD END UP BEING
SLIGHTLY EARLIER GIVEN THE LIGHT SFC GRADIENT. GUIDANCE HAS BEEN
CONSISTENT IN HOLDING PRECIP WEST/SOUTH OF THE FORECAST AREA
THUR...AS A RESULT OF THE WEAK SFC RIDGING. SO ONE MORE MILD DAY
WITH HIGHS WARMING BACK INTO THE UPR 70S/LOW 80S...HOWEVER AS
PREVIOUSLY NOTED...A LAKE BREEZE IS LIKELY TO DEVELOP. THIS WILL
BLEED THE MUCH COOLER MARINE AIR WEST ACROSS NORTHEAST IL AND
DOWNTOWN CHICAGO. IF THE TIMING IS EARLIER IN THE DAY THUR...TEMPS
MAY NOT WARM BEYOND THE LOW/MID 60S ALONG THE CHICAGO LAKEFRONT.

FLOW THEN TURNS SOUTHERLY THUR NIGHT WITH THE MORE PROGRESSIVE FLOW
IN THE MID-LVLS PUSHING THE RIDGING EAST. A RETURN FLOW MOISTURE
WILL CONTINUE TO BE FOCUSED ACROSS THE CENTRAL CONUS THUR EVE...WITH
A SLOW MOVING FRONTAL BOUNDARY NUDGING EAST THUR NIGHT TOWARDS
WESTERN IL. THIS FRONTAL BOUNDARY WILL BECOME ENERGIZED AS A ROBUST
500MB VORT MAX BREAKS SOUTH FROM CENTRAL CANADA LATE THUR NIGHT.

THIS SHOULD ALLOW FOR AN ATMOSPHERIC RIVER TO DEVELOP FROM THE
SOUTHERN PLAINS STRETCHING NORTH THROUGH THE MID-MISSOURI VALLEY
INTO THE WESTERN GREAT LAKES EARLY FRI MORNING.

FRIDAY THROUGH EARLY NEXT WEEK...
ENSEMBLES CONTINUE TO PROG A ROBUST TROUGH SLIDING SOUTH FROM
CENTRAL CANADA FRI. THIS COUPLED WITH DOWNSTREAM MID-LVL RIDGING
ACROSS THE SOUTHEAST CONUS WILL STRENGTHEN THE FRONTAL BOUNDARY
THAT WILL BE ORIENTED FROM THE SOUTHERN PLAINS STRETCHING
NORTHEAST THROUGH THE GREAT LAKES REGION INTO WESTERN QUEBEC.

THIS SETUP IS IDEAL FOR THE DEVELOPMENT OF AN ATMOSPHERIC RIVER WITH
ABUNDANT LOW LEVEL MOISTURE AND EFFICIENT PRECIP PRODUCING
CONVECTION.

OPER GUIDANCE HAS BEEN RELATIVELY CONSISTENT WITH BRINGING A SERIES
OF WAVES ALONG THE SLOW MOVING FRONTAL BOUNDARY FRI AFTN/EVE...THEN
THE BOUNDARY SHOULD SLIDE EAST WITH WINDS QUICKLY VEERING
NORTH/NORTHEAST FOR SAT AND USHERING IN MUCH COOLER AIR TO THE
REGION.

CURRENT INDICATIONS ARE THAT HIGHS SAT MAY STRUGGLE TO WARM BEYOND
THE UPR 50S ACROSS NORTHEAST IL/NORTHWEST IN...WITH ONLY LOW 60S
ELSEWHERE. STRONG SFC RIDGE WILL REMAIN NORTH OF THE REGION...SO THE
PRIOR FRONTAL BOUNDARY MAY BECOME QUASI-STATIONARY FOR THE WEEKEND
ALONG THE OHIO VALLEY AND CONTINUE TO FEED PRECIP CHANCES TO THE
SOUTHERN CWFA.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 14Z...

* MVFR CEILINGS CONTINUE THIS MORNING.

* PERIODS OF -SHRA WITH PERIODIC TSRA THIS AFTERNOON.

* SOUTH TO SOUTH-SOUTHWEST WINDS INCREASING THROUGH THE MORNING TO
  GUST OVER 20KT

KREIN/MM

//DISCUSSION...UPDATED 12Z...

A MID LEVEL DISTURBANCE MOVING FROM THE SOUTHERN PLAINS TO NRN IL
BY THIS AFTERNOON MAY BRING ANOTHER ROUND OF SHOWERS WITH SCT
THUNDERSTORMS TO THE REGION. UPPER LEVEL FORCING FROM THE MID
LEVEL DISTURBANCE AND AN UPPER LEVEL JET STREAM WILL ENHANCE THE
LIKELIHOOD FOR PCPN AND THE CHANCE FOR TSRA...WITH THE MOST
LIKELY CHANCE FOR ACTIVITY FROM LATE MORNING THROUGH EARLY
EVENING. SOME UNCERTAINTY REMAINS IN PINNING DOWN THE EXACT
PERIOD FOR THE TSRA...SO WILL MAINTAIN THE GOING TEMPO FOR LATE
MORNING THROUGH EARLY AFTERNOON. HOWEVER...THE PCPN TIMING COULD
BE SHIFTED OR EXPANDED IN TIME.

LOW LEVEL MOISTURE STREAMING NORTHWARD AHEAD OF LOW PRESSURE OVER
THE MID MISSISSIPPI VALLEY HAS BROUGHT A LOW MVFR STRATUS DECK
ACROSS THE REGION. SOME SITES ARE REPORTING CIGS DROPPING INTO IFR
RANGE...SO WILL INCLUDE THE POSSIBILITY IN A TEMPO GROUP THROUGH
LATE MORNING. DAYTIME WARMING SHOULD ALLOW FOR INCREASE DEEP LAYER
MIXING WHICH SHOULD SCATTER OUT THE STRATUS DECK.

WINDS WILL BE GENERALLY SOUTHERLY TODAY...THOUGH DIRECTION MAY BE
A BIT VARIABLE AROUND CONVECTIVE ACTIVITY. SOME GUSTINESS IS
LIKELY TO BEGIN BY LATE MORNING...WITH THE LATEST GUIDANCE
SUGGESTING THAT WINDS COULD STRENGTHEN AND BECOME EVEN MORE GUSTY
TONIGHT WITH WINDS VEERING SWLY AS SURFACE LOW PRESSURE MOVES
NORTHEAST ACROSS SOUTHERN WISCONSIN.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 14Z...

* HIGH CONFIDENCE IN WIND TRENDS TODAY. MEDIUM IN WIND TRENDS
  TONIGHT.

* HIGH CONFIDENCE IN MVFR CIGS THIS MORNING.

* HIGH CONFIDENCE IN SHOWERS AND MEDIUM CONFIDENCE OF A PERIOD OF
  TSRA. LOW CONFIDENCE IN SPECIFIC TSRA TIMING AND IMPACT ON THE
  TERMINALS WITH MULTIPLE ROUNDS POSSIBLE BETWEEN 18Z AND 02Z.

KREIN/MM

//OUTLOOK FOR ORD/MDW FOR 00Z THURSDAY-12Z TUESDAY...UPDATED 12Z...

WEDNESDAY NIGHT...WX NIL/VFR. SOUTHEAST WINDS.

THURSDAY...SLIGHT CHANCE OF TSRA AT NIGHT. SOUTHEAST WINDS.

FRIDAY...TSRA/SHRA LIKELY THROUGH THE DAY AND NIGHT. MVFR
POSSIBLE. SOUTHWEST WINDS.

SATURDAY...SHRA LIKELY WITH A CHANCE OF TSRA DURING THE DAY.
NORTHEAST WINDS.

SUNDAY...CHANCE OF SHRA. EAST WINDS. MVFR POSSIBLE.

MONDAY...CHANCE OF SHRA. SOUTHEAST WINDS. MVFR POSSIBLE.

KREIN

&&

.MARINE...
229 AM CDT

WARM MOIST AIR CONTINUES TO FEED NORTH ACROSS THE LAKE
TODAY...WHICH MAY HELP TO FURTHER ENHANCE ANY AREAS OF FOG THAT
HAVE ALREADY DEVELOPED. IT IS POSSIBLE PATCHY DENSE FOG MAY
DEVELOP...ALTHOUGH WINDS MAY BE JUST STRONG ENOUGH TO LIMIT THE
COVERAGE AND INTENSITY OF THE FOG. A SURFACE LOW PRESSURE SYSTEM
WILL BE LIFTING NORTH ACROSS EASTERN IOWA INTO CENTRAL WISCONSIN
THIS EVENING. THE GRADIENT WILL TIGHTEN ACROSS THE
CENTRAL/SOUTHERN PORTIONS OF THE LAKE...WHICH WITH WARMER
NEARSHORE WATERS EXPECT SOME SLIGHTLY BETTER MIXING TO OCCUR.
FURTHER OUT ACROSS THE OPEN WATERS THE WATER REMAINS COLD AND
EXPECT THE STABILITY TO MAKE IT DIFFICULT TO MIX TO THE SFC THE
HIGHER GUSTS. HIGH PRESSURE THEN ARRIVES LATE WEDNESDAY WITH LIGHT
WINDS DEVELOPING. THEN HIGH PRESSURE SHIFTS EAST THURSDAY
NIGHT...WITH SOUTHERLY WINDS DEVELOPING AGAIN FRIDAY. A FRONTAL
BOUNDARY WILL APPROACH LAKE MICHIGAN LATE FRIDAY NIGHT THEN
STEADILY SLIDE SOUTH ALONG THE LAKE. THIS WILL ALLOW WINDS TO
QUICKLY VEER FROM SOUTH TO NORTH/NORTHEAST SATURDAY. ALONG WITH
THIS QUICK WIND SHIFT WILL BE COOLER AIR SLIDING SOUTH OVER THE
LAKE. WAVES SHOULD EASILY BUILD SATURDAY FOR THE CENTRAL/SOUTHERN
PORTIONS OF THE LAKE.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 261406
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
906 AM CDT TUE MAY 26 2015

.SHORT TERM...
319 AM CDT

THROUGH TUESDAY NIGHT...

FOR THE REMAINDER OF THE OVERNIGHT HOURS...CONDITIONS WILL REMAIN
QUIET ACROSS THE CWA AS A SERIES OF SHORT WAVES CONTINUE TO TRACK
NORTH AROUND THE TOP OF A PERSISTENT UPPER LEVEL RIDGE WHICH EXTENDS
FROM THE SERN CONUS THROUGH THE UPPER MISSISSIPPI VALLEY.  THIS
UPPER RIDGE HAS BEEN THE FEATURE WHICH HAS CONTROLLED THE PATH OF
THE SERIES OF SHORTWAVES LIFTING OUT OF THE SOUTHERN PLAINS...AND
WILL CONTINUE TO DO SO THROUGH THE DAY TODAY. SLY...MODERATELY
STRONG...WINDS WILL PERSIST THROUGH THE NIGHT...AND MUCH OF THE DAY
ALLOWING FOR SFC DEWPOINTS TO REMAIN CONSISTENT OR POSSIBLE INCH A
LITTLE HIGHER.

MAIN CONCERN FOR THE MORNING HOURS WILL BE THE TRACK OF A STRONG
SHORT WAVE AND ASSOCIATED SFC LOW LIFTING NORTHWARD THROUGH THE
MIDDLE MISSISSIPPI VALLEY.  THIS FEATURE WILL PREDOMINANTLY IMPACT
ERN IOWA AND WRN IL BY ARND DAYBREAK.  THROUGH THE MORNING...THE
COMBINATION OF ISENTROPIC LIFT IN THE WARM SECTOR OF THE
SYSTEM...ALL OF IL AND INTO NWRN IN...WILL LEAD TO SOME
DESTABILIZATION ACROSS THE REGION. A SFC TROUGH...AS WELL INDICATED
BY THE LATEST HIGH RES GUIDANCE...WITH LIFT THROUGH NRN IL/IN
THROUGH THE DAY...COINCIDENT WITH A STRONG SSWLY LOW LEVEL JET OF 45-
50 KT...WITH PROVIDE THE POTENTIAL FOR SHOWERS AND STRONG TO SEVERE
THUNDERSTORMS ACROSS THE CWA.  BASED ON WIND PROFILES AND MID LEVEL
DRYING...THE PRIMARY CONCERN WITH REGARD TO SEVERE WEATHER WILL BE
STRONG WIND GUSTS.  HOWEVER...SOME OF THE HIGH RES SFC WIND GUIDANCE
SUGGEST SOME SLIGHT BACKING OF SFC WINDS FROM 180-190 DEGREES TO 160-
170 DEGREES...WHILE WINDS ALOFT REMAIN SWLY.  THIS SLIGHT BACKING OF
THE SFC WINDS COULD PROVIDE ENOUGH DIRECTIONAL SHEAR THROUGH THE
LOWER LEVELS TO BRING AN ISOLD TORNADO THREAT. LOCALLY HEAVY
RAINFALL WILL ALSO BE CONCERNED WITH PWATS REACHING 1.75 INCHES
LATER THIS MORNING.  HOWEVER...FLOODING WILL LIKELY NOT BE A
SIGNIFICANT CONCERN AS THE SWLY WINDS RIGHT OFF THE DECK WILL RANGE
FROM ARND 45 KT ABOVE THE BOUNDARY LAYER TO ARND 90KT AT UPPER
LEVELS WHICH SHOULD ALLOW ANY OF THE STRONGER STORMS THAT DO DEVELOP
TO MOVE QUICKLY.

BY EARLY AFTERNOON...THE MAIN SHORT WAVE WILL LIFT INTO WISCONSIN
WHILE A SFC TROUGH TRACKS EAST ACROSS THE AREA.  THIS WILL LEAD TO
WINDS AT THE SFC VEERING TO SWLY...SETTING UP A UNIDIRECTIONAL WIND
PROFILE...EFFECTIVELY MINIMIZING THE SEVERE WEATHER THREAT TO THE
REGION.  BY LATE AFTERNOON AND INTO THE EVENING THE MODELS ARE
ADVERTISING THAT A DRY SLOW SHOULD NOSE INTO NRN IL...EFFECTIVELY
CUTTING OFF THE PCPN AREA INTO 2 SEPARATE AREA...ONE OVER WISCONSIN
AND ERN IOWA AND ANOTHER MORE FOCUSED OVER INDIANA.  THE NWRN
INDIANA COUNTIES WILL STILL HAVE A CHANCE FOR SOME SHOWERS AND
THUNDERSTORMS INTO THE EVENING...WHILE PCPN CHANCES OVER NRN IL
BEGIN TO WANE.  MUCH OF THE MODEL GUIDANCE ALSO INDICATED THAT THE
SHORTWAVE SHOULD SLOW IT`S PROGRESSION THROUGH WISCONSIN AS IT
APPROACHES THE APEX OF THE UPPER RIDGE.  AN ASSOCIATED SFC
TROUGH/COLD FRONT EXTENDING SOUTHWEST FROM THE SFC LOW WILL LINGER
OVER ERN IOWA IN THE EARLY EVENING BEFORE STEADILY PUSHING ACROSS
NRN IL AND INTO NWRN IN OVERNIGHT.  THROUGH THE NIGHT...THE
STRONGEST UPPER LEVEL FORCING WILL BE WELL NORTH OF THE CWA...SO ANY
LINGERING CHANCES FOR PCPN OVERNIGHT WILL BE LOW AND LIKELY CONFINED
TO THE NRN TIER COUNTIES OF IL...ALONG THE WI BORDER.

KREIN

&&

.LONG TERM...
229 AM CDT

WEDNESDAY THROUGH MONDAY...

WEDNESDAY THROUGH THURSDAY...
OPEN 500MB WAVE WILL BE LIFTING NORTHEAST ACROSS THE UPPER MIDWEST
INTO ONTARIO AND EVENTUALLY QUEBEC...WITH HEIGHTS SLOWLY INCREASING
WED AFTN. SFC FEATURES REMAIN DISORGANIZED WED...WITH A BOUNDARY
SLOWLY SHIFTING EAST. OPER GUIDANCE DIFFERS ON HOW QUICKLY PRECIP
WILL DEPART THE REGION. ENSEMBLE DATA SUGGESTS HOLDING ONTO CHC TO
SLIGHT CHC POPS MAINLY FOR THE CENTRAL/EASTERN CWFA WED/WED EVE.
ALTHOUGH WITH SOME HINT OF SFC HEIGHTS NUDGING UP...IT IS POSSIBLE
THAT SOME DRY AIR COULD FILTER IN AND KICK PRECIP EAST BY MIDDAY AND
ALLOW FOR A MAINLY DRY WED. SFC WINDS WILL BE TURNING SOUTHWEST TO
WEST...KEEPING AN OFFSHORE FLOW FOR LOCATIONS CLOSE TO LAKE
MICHIGAN. TEMPS SHOULD YET AGAIN TOUCH UPR 70S TO ARND 80 WED...IF
CLOUDS AND PRECIP CAN PUSH EAST BY MIDDAY...SOME CLEARING WOULD
ALLOW SFC TEMPS TO PUSH A COUPLE DEGREES WARMER INTO THE LOW 80S IN
SOME LOCATIONS. LATE IN THE EVENING THE GRADIENT SLACKENS
FURTHER...AND COULD ALLOW A LATE DAY ONSHORE FLOW TO DEVELOP FOR
AREAS ADJACENT TO LAKE MICHIGAN.

MID-LVL FLOW BEGINS TO FLATTEN AS A WEAK SFC RIDGE BECOMES ORIENTED
FROM WESTERN QUEBEC SOUTH THROUGH THE EASTERN OHIO RIVER VALLEY.
THIS WILL GENERALLY ALLOW A SOUTHERLY FLOW...ALTHOUGH THE GRADIENT
IS NOT VERY STRONG. THIS SHOULD SET THE STAGE FOR A LAKE
BREEZE/ONSHORE FLOW TO DEVELOP THUR. TIMING COULD END UP BEING
SLIGHTLY EARLIER GIVEN THE LIGHT SFC GRADIENT. GUIDANCE HAS BEEN
CONSISTENT IN HOLDING PRECIP WEST/SOUTH OF THE FORECAST AREA
THUR...AS A RESULT OF THE WEAK SFC RIDGING. SO ONE MORE MILD DAY
WITH HIGHS WARMING BACK INTO THE UPR 70S/LOW 80S...HOWEVER AS
PREVIOUSLY NOTED...A LAKE BREEZE IS LIKELY TO DEVELOP. THIS WILL
BLEED THE MUCH COOLER MARINE AIR WEST ACROSS NORTHEAST IL AND
DOWNTOWN CHICAGO. IF THE TIMING IS EARLIER IN THE DAY THUR...TEMPS
MAY NOT WARM BEYOND THE LOW/MID 60S ALONG THE CHICAGO LAKEFRONT.

FLOW THEN TURNS SOUTHERLY THUR NIGHT WITH THE MORE PROGRESSIVE FLOW
IN THE MID-LVLS PUSHING THE RIDGING EAST. A RETURN FLOW MOISTURE
WILL CONTINUE TO BE FOCUSED ACROSS THE CENTRAL CONUS THUR EVE...WITH
A SLOW MOVING FRONTAL BOUNDARY NUDGING EAST THUR NIGHT TOWARDS
WESTERN IL. THIS FRONTAL BOUNDARY WILL BECOME ENERGIZED AS A ROBUST
500MB VORT MAX BREAKS SOUTH FROM CENTRAL CANADA LATE THUR NIGHT.

THIS SHOULD ALLOW FOR AN ATMOSPHERIC RIVER TO DEVELOP FROM THE
SOUTHERN PLAINS STRETCHING NORTH THROUGH THE MID-MISSOURI VALLEY
INTO THE WESTERN GREAT LAKES EARLY FRI MORNING.

FRIDAY THROUGH EARLY NEXT WEEK...
ENSEMBLES CONTINUE TO PROG A ROBUST TROUGH SLIDING SOUTH FROM
CENTRAL CANADA FRI. THIS COUPLED WITH DOWNSTREAM MID-LVL RIDGING
ACROSS THE SOUTHEAST CONUS WILL STRENGTHEN THE FRONTAL BOUNDARY
THAT WILL BE ORIENTED FROM THE SOUTHERN PLAINS STRETCHING
NORTHEAST THROUGH THE GREAT LAKES REGION INTO WESTERN QUEBEC.

THIS SETUP IS IDEAL FOR THE DEVELOPMENT OF AN ATMOSPHERIC RIVER WITH
ABUNDANT LOW LEVEL MOISTURE AND EFFICIENT PRECIP PRODUCING
CONVECTION.

OPER GUIDANCE HAS BEEN RELATIVELY CONSISTENT WITH BRINGING A SERIES
OF WAVES ALONG THE SLOW MOVING FRONTAL BOUNDARY FRI AFTN/EVE...THEN
THE BOUNDARY SHOULD SLIDE EAST WITH WINDS QUICKLY VEERING
NORTH/NORTHEAST FOR SAT AND USHERING IN MUCH COOLER AIR TO THE
REGION.

CURRENT INDICATIONS ARE THAT HIGHS SAT MAY STRUGGLE TO WARM BEYOND
THE UPR 50S ACROSS NORTHEAST IL/NORTHWEST IN...WITH ONLY LOW 60S
ELSEWHERE. STRONG SFC RIDGE WILL REMAIN NORTH OF THE REGION...SO THE
PRIOR FRONTAL BOUNDARY MAY BECOME QUASI-STATIONARY FOR THE WEEKEND
ALONG THE OHIO VALLEY AND CONTINUE TO FEED PRECIP CHANCES TO THE
SOUTHERN CWFA.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 14Z...

* MVFR CEILINGS CONTINUE THIS MORNING.

* PERIODS OF -SHRA WITH PERIODIC TSRA THIS AFTERNOON.

* SOUTH TO SOUTH-SOUTHWEST WINDS INCREASING THROUGH THE MORNING TO
  GUST OVER 20KT

KREIN/MM

//DISCUSSION...UPDATED 12Z...

A MID LEVEL DISTURBANCE MOVING FROM THE SOUTHERN PLAINS TO NRN IL
BY THIS AFTERNOON MAY BRING ANOTHER ROUND OF SHOWERS WITH SCT
THUNDERSTORMS TO THE REGION. UPPER LEVEL FORCING FROM THE MID
LEVEL DISTURBANCE AND AN UPPER LEVEL JET STREAM WILL ENHANCE THE
LIKELIHOOD FOR PCPN AND THE CHANCE FOR TSRA...WITH THE MOST
LIKELY CHANCE FOR ACTIVITY FROM LATE MORNING THROUGH EARLY
EVENING. SOME UNCERTAINTY REMAINS IN PINNING DOWN THE EXACT
PERIOD FOR THE TSRA...SO WILL MAINTAIN THE GOING TEMPO FOR LATE
MORNING THROUGH EARLY AFTERNOON. HOWEVER...THE PCPN TIMING COULD
BE SHIFTED OR EXPANDED IN TIME.

LOW LEVEL MOISTURE STREAMING NORTHWARD AHEAD OF LOW PRESSURE OVER
THE MID MISSISSIPPI VALLEY HAS BROUGHT A LOW MVFR STRATUS DECK
ACROSS THE REGION. SOME SITES ARE REPORTING CIGS DROPPING INTO IFR
RANGE...SO WILL INCLUDE THE POSSIBILITY IN A TEMPO GROUP THROUGH
LATE MORNING. DAYTIME WARMING SHOULD ALLOW FOR INCREASE DEEP LAYER
MIXING WHICH SHOULD SCATTER OUT THE STRATUS DECK.

WINDS WILL BE GENERALLY SOUTHERLY TODAY...THOUGH DIRECTION MAY BE
A BIT VARIABLE AROUND CONVECTIVE ACTIVITY. SOME GUSTINESS IS
LIKELY TO BEGIN BY LATE MORNING...WITH THE LATEST GUIDANCE
SUGGESTING THAT WINDS COULD STRENGTHEN AND BECOME EVEN MORE GUSTY
TONIGHT WITH WINDS VEERING SWLY AS SURFACE LOW PRESSURE MOVES
NORTHEAST ACROSS SOUTHERN WISCONSIN.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 14Z...

* HIGH CONFIDENCE IN WIND TRENDS TODAY. MEDIUM IN WIND TRENDS
  TONIGHT.

* HIGH CONFIDENCE IN MVFR CIGS THIS MORNING.

* HIGH CONFIDENCE IN SHOWERS AND MEDIUM CONFIDENCE OF A PERIOD OF
  TSRA. LOW CONFIDENCE IN SPECIFIC TSRA TIMING AND IMPACT ON THE
  TERMINALS WITH MULTIPLE ROUNDS POSSIBLE BETWEEN 18Z AND 02Z.

KREIN/MM

//OUTLOOK FOR ORD/MDW FOR 00Z THURSDAY-12Z TUESDAY...UPDATED 12Z...

WEDNESDAY NIGHT...WX NIL/VFR. SOUTHEAST WINDS.

THURSDAY...SLIGHT CHANCE OF TSRA AT NIGHT. SOUTHEAST WINDS.

FRIDAY...TSRA/SHRA LIKELY THROUGH THE DAY AND NIGHT. MVFR
POSSIBLE. SOUTHWEST WINDS.

SATURDAY...SHRA LIKELY WITH A CHANCE OF TSRA DURING THE DAY.
NORTHEAST WINDS.

SUNDAY...CHANCE OF SHRA. EAST WINDS. MVFR POSSIBLE.

MONDAY...CHANCE OF SHRA. SOUTHEAST WINDS. MVFR POSSIBLE.

KREIN

&&

.MARINE...
229 AM CDT

WARM MOIST AIR CONTINUES TO FEED NORTH ACROSS THE LAKE
TODAY...WHICH MAY HELP TO FURTHER ENHANCE ANY AREAS OF FOG THAT
HAVE ALREADY DEVELOPED. IT IS POSSIBLE PATCHY DENSE FOG MAY
DEVELOP...ALTHOUGH WINDS MAY BE JUST STRONG ENOUGH TO LIMIT THE
COVERAGE AND INTENSITY OF THE FOG. A SURFACE LOW PRESSURE SYSTEM
WILL BE LIFTING NORTH ACROSS EASTERN IOWA INTO CENTRAL WISCONSIN
THIS EVENING. THE GRADIENT WILL TIGHTEN ACROSS THE
CENTRAL/SOUTHERN PORTIONS OF THE LAKE...WHICH WITH WARMER
NEARSHORE WATERS EXPECT SOME SLIGHTLY BETTER MIXING TO OCCUR.
FURTHER OUT ACROSS THE OPEN WATERS THE WATER REMAINS COLD AND
EXPECT THE STABILITY TO MAKE IT DIFFICULT TO MIX TO THE SFC THE
HIGHER GUSTS. HIGH PRESSURE THEN ARRIVES LATE WEDNESDAY WITH LIGHT
WINDS DEVELOPING. THEN HIGH PRESSURE SHIFTS EAST THURSDAY
NIGHT...WITH SOUTHERLY WINDS DEVELOPING AGAIN FRIDAY. A FRONTAL
BOUNDARY WILL APPROACH LAKE MICHIGAN LATE FRIDAY NIGHT THEN
STEADILY SLIDE SOUTH ALONG THE LAKE. THIS WILL ALLOW WINDS TO
QUICKLY VEER FROM SOUTH TO NORTH/NORTHEAST SATURDAY. ALONG WITH
THIS QUICK WIND SHIFT WILL BE COOLER AIR SLIDING SOUTH OVER THE
LAKE. WAVES SHOULD EASILY BUILD SATURDAY FOR THE CENTRAL/SOUTHERN
PORTIONS OF THE LAKE.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 261406
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
906 AM CDT TUE MAY 26 2015

.SHORT TERM...
319 AM CDT

THROUGH TUESDAY NIGHT...

FOR THE REMAINDER OF THE OVERNIGHT HOURS...CONDITIONS WILL REMAIN
QUIET ACROSS THE CWA AS A SERIES OF SHORT WAVES CONTINUE TO TRACK
NORTH AROUND THE TOP OF A PERSISTENT UPPER LEVEL RIDGE WHICH EXTENDS
FROM THE SERN CONUS THROUGH THE UPPER MISSISSIPPI VALLEY.  THIS
UPPER RIDGE HAS BEEN THE FEATURE WHICH HAS CONTROLLED THE PATH OF
THE SERIES OF SHORTWAVES LIFTING OUT OF THE SOUTHERN PLAINS...AND
WILL CONTINUE TO DO SO THROUGH THE DAY TODAY. SLY...MODERATELY
STRONG...WINDS WILL PERSIST THROUGH THE NIGHT...AND MUCH OF THE DAY
ALLOWING FOR SFC DEWPOINTS TO REMAIN CONSISTENT OR POSSIBLE INCH A
LITTLE HIGHER.

MAIN CONCERN FOR THE MORNING HOURS WILL BE THE TRACK OF A STRONG
SHORT WAVE AND ASSOCIATED SFC LOW LIFTING NORTHWARD THROUGH THE
MIDDLE MISSISSIPPI VALLEY.  THIS FEATURE WILL PREDOMINANTLY IMPACT
ERN IOWA AND WRN IL BY ARND DAYBREAK.  THROUGH THE MORNING...THE
COMBINATION OF ISENTROPIC LIFT IN THE WARM SECTOR OF THE
SYSTEM...ALL OF IL AND INTO NWRN IN...WILL LEAD TO SOME
DESTABILIZATION ACROSS THE REGION. A SFC TROUGH...AS WELL INDICATED
BY THE LATEST HIGH RES GUIDANCE...WITH LIFT THROUGH NRN IL/IN
THROUGH THE DAY...COINCIDENT WITH A STRONG SSWLY LOW LEVEL JET OF 45-
50 KT...WITH PROVIDE THE POTENTIAL FOR SHOWERS AND STRONG TO SEVERE
THUNDERSTORMS ACROSS THE CWA.  BASED ON WIND PROFILES AND MID LEVEL
DRYING...THE PRIMARY CONCERN WITH REGARD TO SEVERE WEATHER WILL BE
STRONG WIND GUSTS.  HOWEVER...SOME OF THE HIGH RES SFC WIND GUIDANCE
SUGGEST SOME SLIGHT BACKING OF SFC WINDS FROM 180-190 DEGREES TO 160-
170 DEGREES...WHILE WINDS ALOFT REMAIN SWLY.  THIS SLIGHT BACKING OF
THE SFC WINDS COULD PROVIDE ENOUGH DIRECTIONAL SHEAR THROUGH THE
LOWER LEVELS TO BRING AN ISOLD TORNADO THREAT. LOCALLY HEAVY
RAINFALL WILL ALSO BE CONCERNED WITH PWATS REACHING 1.75 INCHES
LATER THIS MORNING.  HOWEVER...FLOODING WILL LIKELY NOT BE A
SIGNIFICANT CONCERN AS THE SWLY WINDS RIGHT OFF THE DECK WILL RANGE
FROM ARND 45 KT ABOVE THE BOUNDARY LAYER TO ARND 90KT AT UPPER
LEVELS WHICH SHOULD ALLOW ANY OF THE STRONGER STORMS THAT DO DEVELOP
TO MOVE QUICKLY.

BY EARLY AFTERNOON...THE MAIN SHORT WAVE WILL LIFT INTO WISCONSIN
WHILE A SFC TROUGH TRACKS EAST ACROSS THE AREA.  THIS WILL LEAD TO
WINDS AT THE SFC VEERING TO SWLY...SETTING UP A UNIDIRECTIONAL WIND
PROFILE...EFFECTIVELY MINIMIZING THE SEVERE WEATHER THREAT TO THE
REGION.  BY LATE AFTERNOON AND INTO THE EVENING THE MODELS ARE
ADVERTISING THAT A DRY SLOW SHOULD NOSE INTO NRN IL...EFFECTIVELY
CUTTING OFF THE PCPN AREA INTO 2 SEPARATE AREA...ONE OVER WISCONSIN
AND ERN IOWA AND ANOTHER MORE FOCUSED OVER INDIANA.  THE NWRN
INDIANA COUNTIES WILL STILL HAVE A CHANCE FOR SOME SHOWERS AND
THUNDERSTORMS INTO THE EVENING...WHILE PCPN CHANCES OVER NRN IL
BEGIN TO WANE.  MUCH OF THE MODEL GUIDANCE ALSO INDICATED THAT THE
SHORTWAVE SHOULD SLOW IT`S PROGRESSION THROUGH WISCONSIN AS IT
APPROACHES THE APEX OF THE UPPER RIDGE.  AN ASSOCIATED SFC
TROUGH/COLD FRONT EXTENDING SOUTHWEST FROM THE SFC LOW WILL LINGER
OVER ERN IOWA IN THE EARLY EVENING BEFORE STEADILY PUSHING ACROSS
NRN IL AND INTO NWRN IN OVERNIGHT.  THROUGH THE NIGHT...THE
STRONGEST UPPER LEVEL FORCING WILL BE WELL NORTH OF THE CWA...SO ANY
LINGERING CHANCES FOR PCPN OVERNIGHT WILL BE LOW AND LIKELY CONFINED
TO THE NRN TIER COUNTIES OF IL...ALONG THE WI BORDER.

KREIN

&&

.LONG TERM...
229 AM CDT

WEDNESDAY THROUGH MONDAY...

WEDNESDAY THROUGH THURSDAY...
OPEN 500MB WAVE WILL BE LIFTING NORTHEAST ACROSS THE UPPER MIDWEST
INTO ONTARIO AND EVENTUALLY QUEBEC...WITH HEIGHTS SLOWLY INCREASING
WED AFTN. SFC FEATURES REMAIN DISORGANIZED WED...WITH A BOUNDARY
SLOWLY SHIFTING EAST. OPER GUIDANCE DIFFERS ON HOW QUICKLY PRECIP
WILL DEPART THE REGION. ENSEMBLE DATA SUGGESTS HOLDING ONTO CHC TO
SLIGHT CHC POPS MAINLY FOR THE CENTRAL/EASTERN CWFA WED/WED EVE.
ALTHOUGH WITH SOME HINT OF SFC HEIGHTS NUDGING UP...IT IS POSSIBLE
THAT SOME DRY AIR COULD FILTER IN AND KICK PRECIP EAST BY MIDDAY AND
ALLOW FOR A MAINLY DRY WED. SFC WINDS WILL BE TURNING SOUTHWEST TO
WEST...KEEPING AN OFFSHORE FLOW FOR LOCATIONS CLOSE TO LAKE
MICHIGAN. TEMPS SHOULD YET AGAIN TOUCH UPR 70S TO ARND 80 WED...IF
CLOUDS AND PRECIP CAN PUSH EAST BY MIDDAY...SOME CLEARING WOULD
ALLOW SFC TEMPS TO PUSH A COUPLE DEGREES WARMER INTO THE LOW 80S IN
SOME LOCATIONS. LATE IN THE EVENING THE GRADIENT SLACKENS
FURTHER...AND COULD ALLOW A LATE DAY ONSHORE FLOW TO DEVELOP FOR
AREAS ADJACENT TO LAKE MICHIGAN.

MID-LVL FLOW BEGINS TO FLATTEN AS A WEAK SFC RIDGE BECOMES ORIENTED
FROM WESTERN QUEBEC SOUTH THROUGH THE EASTERN OHIO RIVER VALLEY.
THIS WILL GENERALLY ALLOW A SOUTHERLY FLOW...ALTHOUGH THE GRADIENT
IS NOT VERY STRONG. THIS SHOULD SET THE STAGE FOR A LAKE
BREEZE/ONSHORE FLOW TO DEVELOP THUR. TIMING COULD END UP BEING
SLIGHTLY EARLIER GIVEN THE LIGHT SFC GRADIENT. GUIDANCE HAS BEEN
CONSISTENT IN HOLDING PRECIP WEST/SOUTH OF THE FORECAST AREA
THUR...AS A RESULT OF THE WEAK SFC RIDGING. SO ONE MORE MILD DAY
WITH HIGHS WARMING BACK INTO THE UPR 70S/LOW 80S...HOWEVER AS
PREVIOUSLY NOTED...A LAKE BREEZE IS LIKELY TO DEVELOP. THIS WILL
BLEED THE MUCH COOLER MARINE AIR WEST ACROSS NORTHEAST IL AND
DOWNTOWN CHICAGO. IF THE TIMING IS EARLIER IN THE DAY THUR...TEMPS
MAY NOT WARM BEYOND THE LOW/MID 60S ALONG THE CHICAGO LAKEFRONT.

FLOW THEN TURNS SOUTHERLY THUR NIGHT WITH THE MORE PROGRESSIVE FLOW
IN THE MID-LVLS PUSHING THE RIDGING EAST. A RETURN FLOW MOISTURE
WILL CONTINUE TO BE FOCUSED ACROSS THE CENTRAL CONUS THUR EVE...WITH
A SLOW MOVING FRONTAL BOUNDARY NUDGING EAST THUR NIGHT TOWARDS
WESTERN IL. THIS FRONTAL BOUNDARY WILL BECOME ENERGIZED AS A ROBUST
500MB VORT MAX BREAKS SOUTH FROM CENTRAL CANADA LATE THUR NIGHT.

THIS SHOULD ALLOW FOR AN ATMOSPHERIC RIVER TO DEVELOP FROM THE
SOUTHERN PLAINS STRETCHING NORTH THROUGH THE MID-MISSOURI VALLEY
INTO THE WESTERN GREAT LAKES EARLY FRI MORNING.

FRIDAY THROUGH EARLY NEXT WEEK...
ENSEMBLES CONTINUE TO PROG A ROBUST TROUGH SLIDING SOUTH FROM
CENTRAL CANADA FRI. THIS COUPLED WITH DOWNSTREAM MID-LVL RIDGING
ACROSS THE SOUTHEAST CONUS WILL STRENGTHEN THE FRONTAL BOUNDARY
THAT WILL BE ORIENTED FROM THE SOUTHERN PLAINS STRETCHING
NORTHEAST THROUGH THE GREAT LAKES REGION INTO WESTERN QUEBEC.

THIS SETUP IS IDEAL FOR THE DEVELOPMENT OF AN ATMOSPHERIC RIVER WITH
ABUNDANT LOW LEVEL MOISTURE AND EFFICIENT PRECIP PRODUCING
CONVECTION.

OPER GUIDANCE HAS BEEN RELATIVELY CONSISTENT WITH BRINGING A SERIES
OF WAVES ALONG THE SLOW MOVING FRONTAL BOUNDARY FRI AFTN/EVE...THEN
THE BOUNDARY SHOULD SLIDE EAST WITH WINDS QUICKLY VEERING
NORTH/NORTHEAST FOR SAT AND USHERING IN MUCH COOLER AIR TO THE
REGION.

CURRENT INDICATIONS ARE THAT HIGHS SAT MAY STRUGGLE TO WARM BEYOND
THE UPR 50S ACROSS NORTHEAST IL/NORTHWEST IN...WITH ONLY LOW 60S
ELSEWHERE. STRONG SFC RIDGE WILL REMAIN NORTH OF THE REGION...SO THE
PRIOR FRONTAL BOUNDARY MAY BECOME QUASI-STATIONARY FOR THE WEEKEND
ALONG THE OHIO VALLEY AND CONTINUE TO FEED PRECIP CHANCES TO THE
SOUTHERN CWFA.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 14Z...

* MVFR CEILINGS CONTINUE THIS MORNING.

* PERIODS OF -SHRA WITH PERIODIC TSRA THIS AFTERNOON.

* SOUTH TO SOUTH-SOUTHWEST WINDS INCREASING THROUGH THE MORNING TO
  GUST OVER 20KT

KREIN/MM

//DISCUSSION...UPDATED 12Z...

A MID LEVEL DISTURBANCE MOVING FROM THE SOUTHERN PLAINS TO NRN IL
BY THIS AFTERNOON MAY BRING ANOTHER ROUND OF SHOWERS WITH SCT
THUNDERSTORMS TO THE REGION. UPPER LEVEL FORCING FROM THE MID
LEVEL DISTURBANCE AND AN UPPER LEVEL JET STREAM WILL ENHANCE THE
LIKELIHOOD FOR PCPN AND THE CHANCE FOR TSRA...WITH THE MOST
LIKELY CHANCE FOR ACTIVITY FROM LATE MORNING THROUGH EARLY
EVENING. SOME UNCERTAINTY REMAINS IN PINNING DOWN THE EXACT
PERIOD FOR THE TSRA...SO WILL MAINTAIN THE GOING TEMPO FOR LATE
MORNING THROUGH EARLY AFTERNOON. HOWEVER...THE PCPN TIMING COULD
BE SHIFTED OR EXPANDED IN TIME.

LOW LEVEL MOISTURE STREAMING NORTHWARD AHEAD OF LOW PRESSURE OVER
THE MID MISSISSIPPI VALLEY HAS BROUGHT A LOW MVFR STRATUS DECK
ACROSS THE REGION. SOME SITES ARE REPORTING CIGS DROPPING INTO IFR
RANGE...SO WILL INCLUDE THE POSSIBILITY IN A TEMPO GROUP THROUGH
LATE MORNING. DAYTIME WARMING SHOULD ALLOW FOR INCREASE DEEP LAYER
MIXING WHICH SHOULD SCATTER OUT THE STRATUS DECK.

WINDS WILL BE GENERALLY SOUTHERLY TODAY...THOUGH DIRECTION MAY BE
A BIT VARIABLE AROUND CONVECTIVE ACTIVITY. SOME GUSTINESS IS
LIKELY TO BEGIN BY LATE MORNING...WITH THE LATEST GUIDANCE
SUGGESTING THAT WINDS COULD STRENGTHEN AND BECOME EVEN MORE GUSTY
TONIGHT WITH WINDS VEERING SWLY AS SURFACE LOW PRESSURE MOVES
NORTHEAST ACROSS SOUTHERN WISCONSIN.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 14Z...

* HIGH CONFIDENCE IN WIND TRENDS TODAY. MEDIUM IN WIND TRENDS
  TONIGHT.

* HIGH CONFIDENCE IN MVFR CIGS THIS MORNING.

* HIGH CONFIDENCE IN SHOWERS AND MEDIUM CONFIDENCE OF A PERIOD OF
  TSRA. LOW CONFIDENCE IN SPECIFIC TSRA TIMING AND IMPACT ON THE
  TERMINALS WITH MULTIPLE ROUNDS POSSIBLE BETWEEN 18Z AND 02Z.

KREIN/MM

//OUTLOOK FOR ORD/MDW FOR 00Z THURSDAY-12Z TUESDAY...UPDATED 12Z...

WEDNESDAY NIGHT...WX NIL/VFR. SOUTHEAST WINDS.

THURSDAY...SLIGHT CHANCE OF TSRA AT NIGHT. SOUTHEAST WINDS.

FRIDAY...TSRA/SHRA LIKELY THROUGH THE DAY AND NIGHT. MVFR
POSSIBLE. SOUTHWEST WINDS.

SATURDAY...SHRA LIKELY WITH A CHANCE OF TSRA DURING THE DAY.
NORTHEAST WINDS.

SUNDAY...CHANCE OF SHRA. EAST WINDS. MVFR POSSIBLE.

MONDAY...CHANCE OF SHRA. SOUTHEAST WINDS. MVFR POSSIBLE.

KREIN

&&

.MARINE...
229 AM CDT

WARM MOIST AIR CONTINUES TO FEED NORTH ACROSS THE LAKE
TODAY...WHICH MAY HELP TO FURTHER ENHANCE ANY AREAS OF FOG THAT
HAVE ALREADY DEVELOPED. IT IS POSSIBLE PATCHY DENSE FOG MAY
DEVELOP...ALTHOUGH WINDS MAY BE JUST STRONG ENOUGH TO LIMIT THE
COVERAGE AND INTENSITY OF THE FOG. A SURFACE LOW PRESSURE SYSTEM
WILL BE LIFTING NORTH ACROSS EASTERN IOWA INTO CENTRAL WISCONSIN
THIS EVENING. THE GRADIENT WILL TIGHTEN ACROSS THE
CENTRAL/SOUTHERN PORTIONS OF THE LAKE...WHICH WITH WARMER
NEARSHORE WATERS EXPECT SOME SLIGHTLY BETTER MIXING TO OCCUR.
FURTHER OUT ACROSS THE OPEN WATERS THE WATER REMAINS COLD AND
EXPECT THE STABILITY TO MAKE IT DIFFICULT TO MIX TO THE SFC THE
HIGHER GUSTS. HIGH PRESSURE THEN ARRIVES LATE WEDNESDAY WITH LIGHT
WINDS DEVELOPING. THEN HIGH PRESSURE SHIFTS EAST THURSDAY
NIGHT...WITH SOUTHERLY WINDS DEVELOPING AGAIN FRIDAY. A FRONTAL
BOUNDARY WILL APPROACH LAKE MICHIGAN LATE FRIDAY NIGHT THEN
STEADILY SLIDE SOUTH ALONG THE LAKE. THIS WILL ALLOW WINDS TO
QUICKLY VEER FROM SOUTH TO NORTH/NORTHEAST SATURDAY. ALONG WITH
THIS QUICK WIND SHIFT WILL BE COOLER AIR SLIDING SOUTH OVER THE
LAKE. WAVES SHOULD EASILY BUILD SATURDAY FOR THE CENTRAL/SOUTHERN
PORTIONS OF THE LAKE.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 261406
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
906 AM CDT TUE MAY 26 2015

.SHORT TERM...
319 AM CDT

THROUGH TUESDAY NIGHT...

FOR THE REMAINDER OF THE OVERNIGHT HOURS...CONDITIONS WILL REMAIN
QUIET ACROSS THE CWA AS A SERIES OF SHORT WAVES CONTINUE TO TRACK
NORTH AROUND THE TOP OF A PERSISTENT UPPER LEVEL RIDGE WHICH EXTENDS
FROM THE SERN CONUS THROUGH THE UPPER MISSISSIPPI VALLEY.  THIS
UPPER RIDGE HAS BEEN THE FEATURE WHICH HAS CONTROLLED THE PATH OF
THE SERIES OF SHORTWAVES LIFTING OUT OF THE SOUTHERN PLAINS...AND
WILL CONTINUE TO DO SO THROUGH THE DAY TODAY. SLY...MODERATELY
STRONG...WINDS WILL PERSIST THROUGH THE NIGHT...AND MUCH OF THE DAY
ALLOWING FOR SFC DEWPOINTS TO REMAIN CONSISTENT OR POSSIBLE INCH A
LITTLE HIGHER.

MAIN CONCERN FOR THE MORNING HOURS WILL BE THE TRACK OF A STRONG
SHORT WAVE AND ASSOCIATED SFC LOW LIFTING NORTHWARD THROUGH THE
MIDDLE MISSISSIPPI VALLEY.  THIS FEATURE WILL PREDOMINANTLY IMPACT
ERN IOWA AND WRN IL BY ARND DAYBREAK.  THROUGH THE MORNING...THE
COMBINATION OF ISENTROPIC LIFT IN THE WARM SECTOR OF THE
SYSTEM...ALL OF IL AND INTO NWRN IN...WILL LEAD TO SOME
DESTABILIZATION ACROSS THE REGION. A SFC TROUGH...AS WELL INDICATED
BY THE LATEST HIGH RES GUIDANCE...WITH LIFT THROUGH NRN IL/IN
THROUGH THE DAY...COINCIDENT WITH A STRONG SSWLY LOW LEVEL JET OF 45-
50 KT...WITH PROVIDE THE POTENTIAL FOR SHOWERS AND STRONG TO SEVERE
THUNDERSTORMS ACROSS THE CWA.  BASED ON WIND PROFILES AND MID LEVEL
DRYING...THE PRIMARY CONCERN WITH REGARD TO SEVERE WEATHER WILL BE
STRONG WIND GUSTS.  HOWEVER...SOME OF THE HIGH RES SFC WIND GUIDANCE
SUGGEST SOME SLIGHT BACKING OF SFC WINDS FROM 180-190 DEGREES TO 160-
170 DEGREES...WHILE WINDS ALOFT REMAIN SWLY.  THIS SLIGHT BACKING OF
THE SFC WINDS COULD PROVIDE ENOUGH DIRECTIONAL SHEAR THROUGH THE
LOWER LEVELS TO BRING AN ISOLD TORNADO THREAT. LOCALLY HEAVY
RAINFALL WILL ALSO BE CONCERNED WITH PWATS REACHING 1.75 INCHES
LATER THIS MORNING.  HOWEVER...FLOODING WILL LIKELY NOT BE A
SIGNIFICANT CONCERN AS THE SWLY WINDS RIGHT OFF THE DECK WILL RANGE
FROM ARND 45 KT ABOVE THE BOUNDARY LAYER TO ARND 90KT AT UPPER
LEVELS WHICH SHOULD ALLOW ANY OF THE STRONGER STORMS THAT DO DEVELOP
TO MOVE QUICKLY.

BY EARLY AFTERNOON...THE MAIN SHORT WAVE WILL LIFT INTO WISCONSIN
WHILE A SFC TROUGH TRACKS EAST ACROSS THE AREA.  THIS WILL LEAD TO
WINDS AT THE SFC VEERING TO SWLY...SETTING UP A UNIDIRECTIONAL WIND
PROFILE...EFFECTIVELY MINIMIZING THE SEVERE WEATHER THREAT TO THE
REGION.  BY LATE AFTERNOON AND INTO THE EVENING THE MODELS ARE
ADVERTISING THAT A DRY SLOW SHOULD NOSE INTO NRN IL...EFFECTIVELY
CUTTING OFF THE PCPN AREA INTO 2 SEPARATE AREA...ONE OVER WISCONSIN
AND ERN IOWA AND ANOTHER MORE FOCUSED OVER INDIANA.  THE NWRN
INDIANA COUNTIES WILL STILL HAVE A CHANCE FOR SOME SHOWERS AND
THUNDERSTORMS INTO THE EVENING...WHILE PCPN CHANCES OVER NRN IL
BEGIN TO WANE.  MUCH OF THE MODEL GUIDANCE ALSO INDICATED THAT THE
SHORTWAVE SHOULD SLOW IT`S PROGRESSION THROUGH WISCONSIN AS IT
APPROACHES THE APEX OF THE UPPER RIDGE.  AN ASSOCIATED SFC
TROUGH/COLD FRONT EXTENDING SOUTHWEST FROM THE SFC LOW WILL LINGER
OVER ERN IOWA IN THE EARLY EVENING BEFORE STEADILY PUSHING ACROSS
NRN IL AND INTO NWRN IN OVERNIGHT.  THROUGH THE NIGHT...THE
STRONGEST UPPER LEVEL FORCING WILL BE WELL NORTH OF THE CWA...SO ANY
LINGERING CHANCES FOR PCPN OVERNIGHT WILL BE LOW AND LIKELY CONFINED
TO THE NRN TIER COUNTIES OF IL...ALONG THE WI BORDER.

KREIN

&&

.LONG TERM...
229 AM CDT

WEDNESDAY THROUGH MONDAY...

WEDNESDAY THROUGH THURSDAY...
OPEN 500MB WAVE WILL BE LIFTING NORTHEAST ACROSS THE UPPER MIDWEST
INTO ONTARIO AND EVENTUALLY QUEBEC...WITH HEIGHTS SLOWLY INCREASING
WED AFTN. SFC FEATURES REMAIN DISORGANIZED WED...WITH A BOUNDARY
SLOWLY SHIFTING EAST. OPER GUIDANCE DIFFERS ON HOW QUICKLY PRECIP
WILL DEPART THE REGION. ENSEMBLE DATA SUGGESTS HOLDING ONTO CHC TO
SLIGHT CHC POPS MAINLY FOR THE CENTRAL/EASTERN CWFA WED/WED EVE.
ALTHOUGH WITH SOME HINT OF SFC HEIGHTS NUDGING UP...IT IS POSSIBLE
THAT SOME DRY AIR COULD FILTER IN AND KICK PRECIP EAST BY MIDDAY AND
ALLOW FOR A MAINLY DRY WED. SFC WINDS WILL BE TURNING SOUTHWEST TO
WEST...KEEPING AN OFFSHORE FLOW FOR LOCATIONS CLOSE TO LAKE
MICHIGAN. TEMPS SHOULD YET AGAIN TOUCH UPR 70S TO ARND 80 WED...IF
CLOUDS AND PRECIP CAN PUSH EAST BY MIDDAY...SOME CLEARING WOULD
ALLOW SFC TEMPS TO PUSH A COUPLE DEGREES WARMER INTO THE LOW 80S IN
SOME LOCATIONS. LATE IN THE EVENING THE GRADIENT SLACKENS
FURTHER...AND COULD ALLOW A LATE DAY ONSHORE FLOW TO DEVELOP FOR
AREAS ADJACENT TO LAKE MICHIGAN.

MID-LVL FLOW BEGINS TO FLATTEN AS A WEAK SFC RIDGE BECOMES ORIENTED
FROM WESTERN QUEBEC SOUTH THROUGH THE EASTERN OHIO RIVER VALLEY.
THIS WILL GENERALLY ALLOW A SOUTHERLY FLOW...ALTHOUGH THE GRADIENT
IS NOT VERY STRONG. THIS SHOULD SET THE STAGE FOR A LAKE
BREEZE/ONSHORE FLOW TO DEVELOP THUR. TIMING COULD END UP BEING
SLIGHTLY EARLIER GIVEN THE LIGHT SFC GRADIENT. GUIDANCE HAS BEEN
CONSISTENT IN HOLDING PRECIP WEST/SOUTH OF THE FORECAST AREA
THUR...AS A RESULT OF THE WEAK SFC RIDGING. SO ONE MORE MILD DAY
WITH HIGHS WARMING BACK INTO THE UPR 70S/LOW 80S...HOWEVER AS
PREVIOUSLY NOTED...A LAKE BREEZE IS LIKELY TO DEVELOP. THIS WILL
BLEED THE MUCH COOLER MARINE AIR WEST ACROSS NORTHEAST IL AND
DOWNTOWN CHICAGO. IF THE TIMING IS EARLIER IN THE DAY THUR...TEMPS
MAY NOT WARM BEYOND THE LOW/MID 60S ALONG THE CHICAGO LAKEFRONT.

FLOW THEN TURNS SOUTHERLY THUR NIGHT WITH THE MORE PROGRESSIVE FLOW
IN THE MID-LVLS PUSHING THE RIDGING EAST. A RETURN FLOW MOISTURE
WILL CONTINUE TO BE FOCUSED ACROSS THE CENTRAL CONUS THUR EVE...WITH
A SLOW MOVING FRONTAL BOUNDARY NUDGING EAST THUR NIGHT TOWARDS
WESTERN IL. THIS FRONTAL BOUNDARY WILL BECOME ENERGIZED AS A ROBUST
500MB VORT MAX BREAKS SOUTH FROM CENTRAL CANADA LATE THUR NIGHT.

THIS SHOULD ALLOW FOR AN ATMOSPHERIC RIVER TO DEVELOP FROM THE
SOUTHERN PLAINS STRETCHING NORTH THROUGH THE MID-MISSOURI VALLEY
INTO THE WESTERN GREAT LAKES EARLY FRI MORNING.

FRIDAY THROUGH EARLY NEXT WEEK...
ENSEMBLES CONTINUE TO PROG A ROBUST TROUGH SLIDING SOUTH FROM
CENTRAL CANADA FRI. THIS COUPLED WITH DOWNSTREAM MID-LVL RIDGING
ACROSS THE SOUTHEAST CONUS WILL STRENGTHEN THE FRONTAL BOUNDARY
THAT WILL BE ORIENTED FROM THE SOUTHERN PLAINS STRETCHING
NORTHEAST THROUGH THE GREAT LAKES REGION INTO WESTERN QUEBEC.

THIS SETUP IS IDEAL FOR THE DEVELOPMENT OF AN ATMOSPHERIC RIVER WITH
ABUNDANT LOW LEVEL MOISTURE AND EFFICIENT PRECIP PRODUCING
CONVECTION.

OPER GUIDANCE HAS BEEN RELATIVELY CONSISTENT WITH BRINGING A SERIES
OF WAVES ALONG THE SLOW MOVING FRONTAL BOUNDARY FRI AFTN/EVE...THEN
THE BOUNDARY SHOULD SLIDE EAST WITH WINDS QUICKLY VEERING
NORTH/NORTHEAST FOR SAT AND USHERING IN MUCH COOLER AIR TO THE
REGION.

CURRENT INDICATIONS ARE THAT HIGHS SAT MAY STRUGGLE TO WARM BEYOND
THE UPR 50S ACROSS NORTHEAST IL/NORTHWEST IN...WITH ONLY LOW 60S
ELSEWHERE. STRONG SFC RIDGE WILL REMAIN NORTH OF THE REGION...SO THE
PRIOR FRONTAL BOUNDARY MAY BECOME QUASI-STATIONARY FOR THE WEEKEND
ALONG THE OHIO VALLEY AND CONTINUE TO FEED PRECIP CHANCES TO THE
SOUTHERN CWFA.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 14Z...

* MVFR CEILINGS CONTINUE THIS MORNING.

* PERIODS OF -SHRA WITH PERIODIC TSRA THIS AFTERNOON.

* SOUTH TO SOUTH-SOUTHWEST WINDS INCREASING THROUGH THE MORNING TO
  GUST OVER 20KT

KREIN/MM

//DISCUSSION...UPDATED 12Z...

A MID LEVEL DISTURBANCE MOVING FROM THE SOUTHERN PLAINS TO NRN IL
BY THIS AFTERNOON MAY BRING ANOTHER ROUND OF SHOWERS WITH SCT
THUNDERSTORMS TO THE REGION. UPPER LEVEL FORCING FROM THE MID
LEVEL DISTURBANCE AND AN UPPER LEVEL JET STREAM WILL ENHANCE THE
LIKELIHOOD FOR PCPN AND THE CHANCE FOR TSRA...WITH THE MOST
LIKELY CHANCE FOR ACTIVITY FROM LATE MORNING THROUGH EARLY
EVENING. SOME UNCERTAINTY REMAINS IN PINNING DOWN THE EXACT
PERIOD FOR THE TSRA...SO WILL MAINTAIN THE GOING TEMPO FOR LATE
MORNING THROUGH EARLY AFTERNOON. HOWEVER...THE PCPN TIMING COULD
BE SHIFTED OR EXPANDED IN TIME.

LOW LEVEL MOISTURE STREAMING NORTHWARD AHEAD OF LOW PRESSURE OVER
THE MID MISSISSIPPI VALLEY HAS BROUGHT A LOW MVFR STRATUS DECK
ACROSS THE REGION. SOME SITES ARE REPORTING CIGS DROPPING INTO IFR
RANGE...SO WILL INCLUDE THE POSSIBILITY IN A TEMPO GROUP THROUGH
LATE MORNING. DAYTIME WARMING SHOULD ALLOW FOR INCREASE DEEP LAYER
MIXING WHICH SHOULD SCATTER OUT THE STRATUS DECK.

WINDS WILL BE GENERALLY SOUTHERLY TODAY...THOUGH DIRECTION MAY BE
A BIT VARIABLE AROUND CONVECTIVE ACTIVITY. SOME GUSTINESS IS
LIKELY TO BEGIN BY LATE MORNING...WITH THE LATEST GUIDANCE
SUGGESTING THAT WINDS COULD STRENGTHEN AND BECOME EVEN MORE GUSTY
TONIGHT WITH WINDS VEERING SWLY AS SURFACE LOW PRESSURE MOVES
NORTHEAST ACROSS SOUTHERN WISCONSIN.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 14Z...

* HIGH CONFIDENCE IN WIND TRENDS TODAY. MEDIUM IN WIND TRENDS
  TONIGHT.

* HIGH CONFIDENCE IN MVFR CIGS THIS MORNING.

* HIGH CONFIDENCE IN SHOWERS AND MEDIUM CONFIDENCE OF A PERIOD OF
  TSRA. LOW CONFIDENCE IN SPECIFIC TSRA TIMING AND IMPACT ON THE
  TERMINALS WITH MULTIPLE ROUNDS POSSIBLE BETWEEN 18Z AND 02Z.

KREIN/MM

//OUTLOOK FOR ORD/MDW FOR 00Z THURSDAY-12Z TUESDAY...UPDATED 12Z...

WEDNESDAY NIGHT...WX NIL/VFR. SOUTHEAST WINDS.

THURSDAY...SLIGHT CHANCE OF TSRA AT NIGHT. SOUTHEAST WINDS.

FRIDAY...TSRA/SHRA LIKELY THROUGH THE DAY AND NIGHT. MVFR
POSSIBLE. SOUTHWEST WINDS.

SATURDAY...SHRA LIKELY WITH A CHANCE OF TSRA DURING THE DAY.
NORTHEAST WINDS.

SUNDAY...CHANCE OF SHRA. EAST WINDS. MVFR POSSIBLE.

MONDAY...CHANCE OF SHRA. SOUTHEAST WINDS. MVFR POSSIBLE.

KREIN

&&

.MARINE...
229 AM CDT

WARM MOIST AIR CONTINUES TO FEED NORTH ACROSS THE LAKE
TODAY...WHICH MAY HELP TO FURTHER ENHANCE ANY AREAS OF FOG THAT
HAVE ALREADY DEVELOPED. IT IS POSSIBLE PATCHY DENSE FOG MAY
DEVELOP...ALTHOUGH WINDS MAY BE JUST STRONG ENOUGH TO LIMIT THE
COVERAGE AND INTENSITY OF THE FOG. A SURFACE LOW PRESSURE SYSTEM
WILL BE LIFTING NORTH ACROSS EASTERN IOWA INTO CENTRAL WISCONSIN
THIS EVENING. THE GRADIENT WILL TIGHTEN ACROSS THE
CENTRAL/SOUTHERN PORTIONS OF THE LAKE...WHICH WITH WARMER
NEARSHORE WATERS EXPECT SOME SLIGHTLY BETTER MIXING TO OCCUR.
FURTHER OUT ACROSS THE OPEN WATERS THE WATER REMAINS COLD AND
EXPECT THE STABILITY TO MAKE IT DIFFICULT TO MIX TO THE SFC THE
HIGHER GUSTS. HIGH PRESSURE THEN ARRIVES LATE WEDNESDAY WITH LIGHT
WINDS DEVELOPING. THEN HIGH PRESSURE SHIFTS EAST THURSDAY
NIGHT...WITH SOUTHERLY WINDS DEVELOPING AGAIN FRIDAY. A FRONTAL
BOUNDARY WILL APPROACH LAKE MICHIGAN LATE FRIDAY NIGHT THEN
STEADILY SLIDE SOUTH ALONG THE LAKE. THIS WILL ALLOW WINDS TO
QUICKLY VEER FROM SOUTH TO NORTH/NORTHEAST SATURDAY. ALONG WITH
THIS QUICK WIND SHIFT WILL BE COOLER AIR SLIDING SOUTH OVER THE
LAKE. WAVES SHOULD EASILY BUILD SATURDAY FOR THE CENTRAL/SOUTHERN
PORTIONS OF THE LAKE.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KILX 261208
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
708 AM CDT TUE MAY 26 2015

.SHORT TERM...(TODAY)
ISSUED AT 343 AM CDT TUE MAY 26 2015

LOW CLOUDS HAVE BEEN ADVECTING INTO THE AREA AND WILL REMAIN OVER
THE AREA THIS MORNING. LOWER CLOUDS INDICATING LOTS OF LOW LEVEL
MOISTURE BEING ADVECTED INTO THE AREA AHEAD OF THE WEATHER SYSTEM
THAT STILL IS WEST OF THE CWA. RADAR AND SATELLITE LOOPS SHOW
SEVERAL MCVS WEST OF THE AREA WITH SOME SHOWERS MOVING NORTH THROUGH
SOUTHEASTERN MO. MODELS CONTINUE TO INDICATE PCPN REDEVELOPING
TODAY. CLOUDS WILL LIMIT THE DEGREE OF INSTABILITY BUT STILL
EXPECTING ENOUGH FOR THUNDERSTORMS, JUST NOT ENOUGH FOR ANYTHING
SEVERE, WHICH SHOULD BE EAST AND SOUTHEAST OF THE AREA WHERE LESS
CLOUDS WILL BE. CLOUD COVER WILL ALSO TEMPER WARM UP AS WELL SO ONLY
EXPECTING UPPER 70S FOR HIGHS WHICH IS MUCH LESS THAN PAST TWO DAYS.
POPS WILL BE A GRADUAL INCREASE TODAY REACHING LIKELY LATER THIS
MORNING AND THEN MOVING NORTH AND EAST THIS AFTERNOON, BECOMING
CHANCE CATEGORY BY LATE AFTERNOON AS THE PCPN MOVES EAST OF THE
AREA. SOUTHERLY WINDS WILL BE A TAD GUSTY AGAIN, JUST NOT AS MUCH AS
YESTERDAY.

.LONG TERM...(TONIGHT THROUGH MONDAY)
ISSUED AT 343 AM CDT TUE MAY 26 2015

UNTIL THE UPPER WAVE PULLS INTO THE GREAT LAKES REGION, LINGERING
POPS WILL REMAIN OVER THE FA FOR THIS EVENING.  BETTER CHANCES WILL
REMAIN TO THE EAST OVERNIGHT. REMAINS OF THE FRONT WILL STALL OUT
ALONG THE OHIO RIVER VALLEY AND PROVIDE A BIT OF FOCUS FOR ANOTHER
PIECE OF ENERGY EJECTING OUT OF THE SOUTHWEST.  MODELS DIFFERING
WITH THE NORTHERLY EXTENT OF THE PRECIP, BUT LAST FEW RUNS BRINGING
IN SOME PRECIPITATION FOR WEDNESDAY IN THE SOUTHEAST.  NAM IS A
LITTLE MORE WIDESPREAD, BUT CONCENTRATING THE POPS TO THE SOUTH AND
EAST FOR NOW.  TIMING ISSUES REMAIN IN PLACE FOR THIS SYNOPTIC RUN
FOR THE NEXT SYSTEM QUICK ON THE HEELS AS THE DEEP WAVE OVER THE SW
STARTS TO MOVE OUT INTO THE PLAINS. CONVECTION AND PRECIP STARTS TO
SPREAD OVER THE EASTERN HALF OF THE COUNTRY IN THE MODELS WITH  WEAK
SOUTHWESTERLY FLOW ALOFT SHIFTING TO WEAK FLOW OVERALL.  WARM AND
MUGGY CONDITIONS CONTINUE IN A MORE SUMMERLIKE AIRMASS THROUGHOUT
THE WEEK...BUT THAT NEXT SYSTEM WILL BRING A COLD FRONT INTO THE
REGION FOR THE FIRST HALF OF THE WEEKEND TO FOCUS THE RAIN, WITH A
COOLER AIRMASS BEHIND IT DROPPING THE TEMPS FOR THE WEEKEND OUT OF
THE 80S FOR A COUPLE DAYS.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z WEDNESDAY MORNING)
ISSUED AT 708 AM CDT TUE MAY 26 2015

LOW STRATUS HAS OVERSPREAD ALL TAF SITES THIS MORNING. THIS LOW
STRATUS LOOKS TO REMAIN OVER ALL SITES UNTIL SOMETIME THIS
AFTERNOON AFTER A NARROW BAND OF SHOWERS MOVES THROUGH THE AREA.
SPI IS THE ONLY ONE AT MVFR STATUS RIGHT NOW. ALL OTHER TAF SITES
ARE MVFR. BY THIS AFTERNOON ALL SITES SHOULD BE MVFR WITH HIGHER
CIGS AROUND 2.5KFT. SHOWERS WILL BE POSSIBLE THIS MORNING AS RADAR
LOOPS SHOWS. THEN HAS THE DAY HEATS UP THUNDERSTORMS WILL BE
POSSIBLE. WILL GO WITH VCTS FOR NOW GIVEN UNCERTAINTY OF LOCATION
OF ANY THUNDERSTORMS. THESE SHOULD END SOMETIME EARLY THIS
EVENING. SKIES SHOULD THEN BE VFR AS THE AREA SHOULD BE WELL IN
THE WARM SECTOR. THERE COULD BE MORE PCPN OVERNIGHT TONIGHT...BUT
LOTS OF UNCERTAINTY THERE SO WILL NOT INCLUDE AT THIS TIME. WINDS
WILL BECOME SOUTHERLY WITH SOME GUSTINESS THIS AFTERNOON.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...AUTEN
LONG TERM...HJS
AVIATION...AUTEN




000
FXUS63 KILX 261208
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
708 AM CDT TUE MAY 26 2015

.SHORT TERM...(TODAY)
ISSUED AT 343 AM CDT TUE MAY 26 2015

LOW CLOUDS HAVE BEEN ADVECTING INTO THE AREA AND WILL REMAIN OVER
THE AREA THIS MORNING. LOWER CLOUDS INDICATING LOTS OF LOW LEVEL
MOISTURE BEING ADVECTED INTO THE AREA AHEAD OF THE WEATHER SYSTEM
THAT STILL IS WEST OF THE CWA. RADAR AND SATELLITE LOOPS SHOW
SEVERAL MCVS WEST OF THE AREA WITH SOME SHOWERS MOVING NORTH THROUGH
SOUTHEASTERN MO. MODELS CONTINUE TO INDICATE PCPN REDEVELOPING
TODAY. CLOUDS WILL LIMIT THE DEGREE OF INSTABILITY BUT STILL
EXPECTING ENOUGH FOR THUNDERSTORMS, JUST NOT ENOUGH FOR ANYTHING
SEVERE, WHICH SHOULD BE EAST AND SOUTHEAST OF THE AREA WHERE LESS
CLOUDS WILL BE. CLOUD COVER WILL ALSO TEMPER WARM UP AS WELL SO ONLY
EXPECTING UPPER 70S FOR HIGHS WHICH IS MUCH LESS THAN PAST TWO DAYS.
POPS WILL BE A GRADUAL INCREASE TODAY REACHING LIKELY LATER THIS
MORNING AND THEN MOVING NORTH AND EAST THIS AFTERNOON, BECOMING
CHANCE CATEGORY BY LATE AFTERNOON AS THE PCPN MOVES EAST OF THE
AREA. SOUTHERLY WINDS WILL BE A TAD GUSTY AGAIN, JUST NOT AS MUCH AS
YESTERDAY.

.LONG TERM...(TONIGHT THROUGH MONDAY)
ISSUED AT 343 AM CDT TUE MAY 26 2015

UNTIL THE UPPER WAVE PULLS INTO THE GREAT LAKES REGION, LINGERING
POPS WILL REMAIN OVER THE FA FOR THIS EVENING.  BETTER CHANCES WILL
REMAIN TO THE EAST OVERNIGHT. REMAINS OF THE FRONT WILL STALL OUT
ALONG THE OHIO RIVER VALLEY AND PROVIDE A BIT OF FOCUS FOR ANOTHER
PIECE OF ENERGY EJECTING OUT OF THE SOUTHWEST.  MODELS DIFFERING
WITH THE NORTHERLY EXTENT OF THE PRECIP, BUT LAST FEW RUNS BRINGING
IN SOME PRECIPITATION FOR WEDNESDAY IN THE SOUTHEAST.  NAM IS A
LITTLE MORE WIDESPREAD, BUT CONCENTRATING THE POPS TO THE SOUTH AND
EAST FOR NOW.  TIMING ISSUES REMAIN IN PLACE FOR THIS SYNOPTIC RUN
FOR THE NEXT SYSTEM QUICK ON THE HEELS AS THE DEEP WAVE OVER THE SW
STARTS TO MOVE OUT INTO THE PLAINS. CONVECTION AND PRECIP STARTS TO
SPREAD OVER THE EASTERN HALF OF THE COUNTRY IN THE MODELS WITH  WEAK
SOUTHWESTERLY FLOW ALOFT SHIFTING TO WEAK FLOW OVERALL.  WARM AND
MUGGY CONDITIONS CONTINUE IN A MORE SUMMERLIKE AIRMASS THROUGHOUT
THE WEEK...BUT THAT NEXT SYSTEM WILL BRING A COLD FRONT INTO THE
REGION FOR THE FIRST HALF OF THE WEEKEND TO FOCUS THE RAIN, WITH A
COOLER AIRMASS BEHIND IT DROPPING THE TEMPS FOR THE WEEKEND OUT OF
THE 80S FOR A COUPLE DAYS.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z WEDNESDAY MORNING)
ISSUED AT 708 AM CDT TUE MAY 26 2015

LOW STRATUS HAS OVERSPREAD ALL TAF SITES THIS MORNING. THIS LOW
STRATUS LOOKS TO REMAIN OVER ALL SITES UNTIL SOMETIME THIS
AFTERNOON AFTER A NARROW BAND OF SHOWERS MOVES THROUGH THE AREA.
SPI IS THE ONLY ONE AT MVFR STATUS RIGHT NOW. ALL OTHER TAF SITES
ARE MVFR. BY THIS AFTERNOON ALL SITES SHOULD BE MVFR WITH HIGHER
CIGS AROUND 2.5KFT. SHOWERS WILL BE POSSIBLE THIS MORNING AS RADAR
LOOPS SHOWS. THEN HAS THE DAY HEATS UP THUNDERSTORMS WILL BE
POSSIBLE. WILL GO WITH VCTS FOR NOW GIVEN UNCERTAINTY OF LOCATION
OF ANY THUNDERSTORMS. THESE SHOULD END SOMETIME EARLY THIS
EVENING. SKIES SHOULD THEN BE VFR AS THE AREA SHOULD BE WELL IN
THE WARM SECTOR. THERE COULD BE MORE PCPN OVERNIGHT TONIGHT...BUT
LOTS OF UNCERTAINTY THERE SO WILL NOT INCLUDE AT THIS TIME. WINDS
WILL BECOME SOUTHERLY WITH SOME GUSTINESS THIS AFTERNOON.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...AUTEN
LONG TERM...HJS
AVIATION...AUTEN



000
FXUS63 KILX 261208
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
708 AM CDT TUE MAY 26 2015

.SHORT TERM...(TODAY)
ISSUED AT 343 AM CDT TUE MAY 26 2015

LOW CLOUDS HAVE BEEN ADVECTING INTO THE AREA AND WILL REMAIN OVER
THE AREA THIS MORNING. LOWER CLOUDS INDICATING LOTS OF LOW LEVEL
MOISTURE BEING ADVECTED INTO THE AREA AHEAD OF THE WEATHER SYSTEM
THAT STILL IS WEST OF THE CWA. RADAR AND SATELLITE LOOPS SHOW
SEVERAL MCVS WEST OF THE AREA WITH SOME SHOWERS MOVING NORTH THROUGH
SOUTHEASTERN MO. MODELS CONTINUE TO INDICATE PCPN REDEVELOPING
TODAY. CLOUDS WILL LIMIT THE DEGREE OF INSTABILITY BUT STILL
EXPECTING ENOUGH FOR THUNDERSTORMS, JUST NOT ENOUGH FOR ANYTHING
SEVERE, WHICH SHOULD BE EAST AND SOUTHEAST OF THE AREA WHERE LESS
CLOUDS WILL BE. CLOUD COVER WILL ALSO TEMPER WARM UP AS WELL SO ONLY
EXPECTING UPPER 70S FOR HIGHS WHICH IS MUCH LESS THAN PAST TWO DAYS.
POPS WILL BE A GRADUAL INCREASE TODAY REACHING LIKELY LATER THIS
MORNING AND THEN MOVING NORTH AND EAST THIS AFTERNOON, BECOMING
CHANCE CATEGORY BY LATE AFTERNOON AS THE PCPN MOVES EAST OF THE
AREA. SOUTHERLY WINDS WILL BE A TAD GUSTY AGAIN, JUST NOT AS MUCH AS
YESTERDAY.

.LONG TERM...(TONIGHT THROUGH MONDAY)
ISSUED AT 343 AM CDT TUE MAY 26 2015

UNTIL THE UPPER WAVE PULLS INTO THE GREAT LAKES REGION, LINGERING
POPS WILL REMAIN OVER THE FA FOR THIS EVENING.  BETTER CHANCES WILL
REMAIN TO THE EAST OVERNIGHT. REMAINS OF THE FRONT WILL STALL OUT
ALONG THE OHIO RIVER VALLEY AND PROVIDE A BIT OF FOCUS FOR ANOTHER
PIECE OF ENERGY EJECTING OUT OF THE SOUTHWEST.  MODELS DIFFERING
WITH THE NORTHERLY EXTENT OF THE PRECIP, BUT LAST FEW RUNS BRINGING
IN SOME PRECIPITATION FOR WEDNESDAY IN THE SOUTHEAST.  NAM IS A
LITTLE MORE WIDESPREAD, BUT CONCENTRATING THE POPS TO THE SOUTH AND
EAST FOR NOW.  TIMING ISSUES REMAIN IN PLACE FOR THIS SYNOPTIC RUN
FOR THE NEXT SYSTEM QUICK ON THE HEELS AS THE DEEP WAVE OVER THE SW
STARTS TO MOVE OUT INTO THE PLAINS. CONVECTION AND PRECIP STARTS TO
SPREAD OVER THE EASTERN HALF OF THE COUNTRY IN THE MODELS WITH  WEAK
SOUTHWESTERLY FLOW ALOFT SHIFTING TO WEAK FLOW OVERALL.  WARM AND
MUGGY CONDITIONS CONTINUE IN A MORE SUMMERLIKE AIRMASS THROUGHOUT
THE WEEK...BUT THAT NEXT SYSTEM WILL BRING A COLD FRONT INTO THE
REGION FOR THE FIRST HALF OF THE WEEKEND TO FOCUS THE RAIN, WITH A
COOLER AIRMASS BEHIND IT DROPPING THE TEMPS FOR THE WEEKEND OUT OF
THE 80S FOR A COUPLE DAYS.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z WEDNESDAY MORNING)
ISSUED AT 708 AM CDT TUE MAY 26 2015

LOW STRATUS HAS OVERSPREAD ALL TAF SITES THIS MORNING. THIS LOW
STRATUS LOOKS TO REMAIN OVER ALL SITES UNTIL SOMETIME THIS
AFTERNOON AFTER A NARROW BAND OF SHOWERS MOVES THROUGH THE AREA.
SPI IS THE ONLY ONE AT MVFR STATUS RIGHT NOW. ALL OTHER TAF SITES
ARE MVFR. BY THIS AFTERNOON ALL SITES SHOULD BE MVFR WITH HIGHER
CIGS AROUND 2.5KFT. SHOWERS WILL BE POSSIBLE THIS MORNING AS RADAR
LOOPS SHOWS. THEN HAS THE DAY HEATS UP THUNDERSTORMS WILL BE
POSSIBLE. WILL GO WITH VCTS FOR NOW GIVEN UNCERTAINTY OF LOCATION
OF ANY THUNDERSTORMS. THESE SHOULD END SOMETIME EARLY THIS
EVENING. SKIES SHOULD THEN BE VFR AS THE AREA SHOULD BE WELL IN
THE WARM SECTOR. THERE COULD BE MORE PCPN OVERNIGHT TONIGHT...BUT
LOTS OF UNCERTAINTY THERE SO WILL NOT INCLUDE AT THIS TIME. WINDS
WILL BECOME SOUTHERLY WITH SOME GUSTINESS THIS AFTERNOON.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...AUTEN
LONG TERM...HJS
AVIATION...AUTEN




000
FXUS63 KILX 261208
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
708 AM CDT TUE MAY 26 2015

.SHORT TERM...(TODAY)
ISSUED AT 343 AM CDT TUE MAY 26 2015

LOW CLOUDS HAVE BEEN ADVECTING INTO THE AREA AND WILL REMAIN OVER
THE AREA THIS MORNING. LOWER CLOUDS INDICATING LOTS OF LOW LEVEL
MOISTURE BEING ADVECTED INTO THE AREA AHEAD OF THE WEATHER SYSTEM
THAT STILL IS WEST OF THE CWA. RADAR AND SATELLITE LOOPS SHOW
SEVERAL MCVS WEST OF THE AREA WITH SOME SHOWERS MOVING NORTH THROUGH
SOUTHEASTERN MO. MODELS CONTINUE TO INDICATE PCPN REDEVELOPING
TODAY. CLOUDS WILL LIMIT THE DEGREE OF INSTABILITY BUT STILL
EXPECTING ENOUGH FOR THUNDERSTORMS, JUST NOT ENOUGH FOR ANYTHING
SEVERE, WHICH SHOULD BE EAST AND SOUTHEAST OF THE AREA WHERE LESS
CLOUDS WILL BE. CLOUD COVER WILL ALSO TEMPER WARM UP AS WELL SO ONLY
EXPECTING UPPER 70S FOR HIGHS WHICH IS MUCH LESS THAN PAST TWO DAYS.
POPS WILL BE A GRADUAL INCREASE TODAY REACHING LIKELY LATER THIS
MORNING AND THEN MOVING NORTH AND EAST THIS AFTERNOON, BECOMING
CHANCE CATEGORY BY LATE AFTERNOON AS THE PCPN MOVES EAST OF THE
AREA. SOUTHERLY WINDS WILL BE A TAD GUSTY AGAIN, JUST NOT AS MUCH AS
YESTERDAY.

.LONG TERM...(TONIGHT THROUGH MONDAY)
ISSUED AT 343 AM CDT TUE MAY 26 2015

UNTIL THE UPPER WAVE PULLS INTO THE GREAT LAKES REGION, LINGERING
POPS WILL REMAIN OVER THE FA FOR THIS EVENING.  BETTER CHANCES WILL
REMAIN TO THE EAST OVERNIGHT. REMAINS OF THE FRONT WILL STALL OUT
ALONG THE OHIO RIVER VALLEY AND PROVIDE A BIT OF FOCUS FOR ANOTHER
PIECE OF ENERGY EJECTING OUT OF THE SOUTHWEST.  MODELS DIFFERING
WITH THE NORTHERLY EXTENT OF THE PRECIP, BUT LAST FEW RUNS BRINGING
IN SOME PRECIPITATION FOR WEDNESDAY IN THE SOUTHEAST.  NAM IS A
LITTLE MORE WIDESPREAD, BUT CONCENTRATING THE POPS TO THE SOUTH AND
EAST FOR NOW.  TIMING ISSUES REMAIN IN PLACE FOR THIS SYNOPTIC RUN
FOR THE NEXT SYSTEM QUICK ON THE HEELS AS THE DEEP WAVE OVER THE SW
STARTS TO MOVE OUT INTO THE PLAINS. CONVECTION AND PRECIP STARTS TO
SPREAD OVER THE EASTERN HALF OF THE COUNTRY IN THE MODELS WITH  WEAK
SOUTHWESTERLY FLOW ALOFT SHIFTING TO WEAK FLOW OVERALL.  WARM AND
MUGGY CONDITIONS CONTINUE IN A MORE SUMMERLIKE AIRMASS THROUGHOUT
THE WEEK...BUT THAT NEXT SYSTEM WILL BRING A COLD FRONT INTO THE
REGION FOR THE FIRST HALF OF THE WEEKEND TO FOCUS THE RAIN, WITH A
COOLER AIRMASS BEHIND IT DROPPING THE TEMPS FOR THE WEEKEND OUT OF
THE 80S FOR A COUPLE DAYS.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z WEDNESDAY MORNING)
ISSUED AT 708 AM CDT TUE MAY 26 2015

LOW STRATUS HAS OVERSPREAD ALL TAF SITES THIS MORNING. THIS LOW
STRATUS LOOKS TO REMAIN OVER ALL SITES UNTIL SOMETIME THIS
AFTERNOON AFTER A NARROW BAND OF SHOWERS MOVES THROUGH THE AREA.
SPI IS THE ONLY ONE AT MVFR STATUS RIGHT NOW. ALL OTHER TAF SITES
ARE MVFR. BY THIS AFTERNOON ALL SITES SHOULD BE MVFR WITH HIGHER
CIGS AROUND 2.5KFT. SHOWERS WILL BE POSSIBLE THIS MORNING AS RADAR
LOOPS SHOWS. THEN HAS THE DAY HEATS UP THUNDERSTORMS WILL BE
POSSIBLE. WILL GO WITH VCTS FOR NOW GIVEN UNCERTAINTY OF LOCATION
OF ANY THUNDERSTORMS. THESE SHOULD END SOMETIME EARLY THIS
EVENING. SKIES SHOULD THEN BE VFR AS THE AREA SHOULD BE WELL IN
THE WARM SECTOR. THERE COULD BE MORE PCPN OVERNIGHT TONIGHT...BUT
LOTS OF UNCERTAINTY THERE SO WILL NOT INCLUDE AT THIS TIME. WINDS
WILL BECOME SOUTHERLY WITH SOME GUSTINESS THIS AFTERNOON.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...AUTEN
LONG TERM...HJS
AVIATION...AUTEN



000
FXUS63 KLOT 261130
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
630 AM CDT TUE MAY 26 2015

.SHORT TERM...
319 AM CDT

THROUGH TUESDAY NIGHT...

FOR THE REMAINDER OF THE OVERNIGHT HOURS...CONDITIONS WILL REMAIN
QUIET ACROSS THE CWA AS A SERIES OF SHORT WAVES CONTINUE TO TRACK
NORTH AROUND THE TOP OF A PERSISTENT UPPER LEVEL RIDGE WHICH EXTENDS
FROM THE SERN CONUS THROUGH THE UPPER MISSISSIPPI VALLEY.  THIS
UPPER RIDGE HAS BEEN THE FEATURE WHICH HAS CONTROLLED THE PATH OF
THE SERIES OF SHORTWAVES LIFTING OUT OF THE SOUTHERN PLAINS...AND
WILL CONTINUE TO DO SO THROUGH THE DAY TODAY. SLY...MODERATELY
STRONG...WINDS WILL PERSIST THROUGH THE NIGHT...AND MUCH OF THE DAY
ALLOWING FOR SFC DEWPOINTS TO REMAIN CONSISTENT OR POSSIBLE INCH A
LITTLE HIGHER.

MAIN CONCERN FOR THE MORNING HOURS WILL BE THE TRACK OF A STRONG
SHORT WAVE AND ASSOCIATED SFC LOW LIFTING NORTHWARD THROUGH THE
MIDDLE MISSISSIPPI VALLEY.  THIS FEATURE WILL PREDOMINANTLY IMPACT
ERN IOWA AND WRN IL BY ARND DAYBREAK.  THROUGH THE MORNING...THE
COMBINATION OF ISENTROPIC LIFT IN THE WARM SECTOR OF THE
SYSTEM...ALL OF IL AND INTO NWRN IN...WILL LEAD TO SOME
DESTABILIZATION ACROSS THE REGION. A SFC TROUGH...AS WELL INDICATED
BY THE LATEST HIGH RES GUIDANCE...WITH LIFT THROUGH NRN IL/IN
THROUGH THE DAY...COINCIDENT WITH A STRONG SSWLY LOW LEVEL JET OF 45-
50 KT...WITH PROVIDE THE POTENTIAL FOR SHOWERS AND STRONG TO SEVERE
THUNDERSTORMS ACROSS THE CWA.  BASED ON WIND PROFILES AND MID LEVEL
DRYING...THE PRIMARY CONCERN WITH REGARD TO SEVERE WEATHER WILL BE
STRONG WIND GUSTS.  HOWEVER...SOME OF THE HIGH RES SFC WIND GUIDANCE
SUGGEST SOME SLIGHT BACKING OF SFC WINDS FROM 180-190 DEGREES TO 160-
170 DEGREES...WHILE WINDS ALOFT REMAIN SWLY.  THIS SLIGHT BACKING OF
THE SFC WINDS COULD PROVIDE ENOUGH DIRECTIONAL SHEAR THROUGH THE
LOWER LEVELS TO BRING AN ISOLD TORNADO THREAT. LOCALLY HEAVY
RAINFALL WILL ALSO BE CONCERNED WITH PWATS REACHING 1.75 INCHES
LATER THIS MORNING.  HOWEVER...FLOODING WILL LIKELY NOT BE A
SIGNIFICANT CONCERN AS THE SWLY WINDS RIGHT OFF THE DECK WILL RANGE
FROM ARND 45 KT ABOVE THE BOUNDARY LAYER TO ARND 90KT AT UPPER
LEVELS WHICH SHOULD ALLOW ANY OF THE STRONGER STORMS THAT DO DEVELOP
TO MOVE QUICKLY.

BY EARLY AFTERNOON...THE MAIN SHORT WAVE WILL LIFT INTO WISCONSIN
WHILE A SFC TROUGH TRACKS EAST ACROSS THE AREA.  THIS WILL LEAD TO
WINDS AT THE SFC VEERING TO SWLY...SETTING UP A UNIDIRECTIONAL WIND
PROFILE...EFFECTIVELY MINIMIZING THE SEVERE WEATHER THREAT TO THE
REGION.  BY LATE AFTERNOON AND INTO THE EVENING THE MODELS ARE
ADVERTISING THAT A DRY SLOW SHOULD NOSE INTO NRN IL...EFFECTIVELY
CUTTING OFF THE PCPN AREA INTO 2 SEPARATE AREA...ONE OVER WISCONSIN
AND ERN IOWA AND ANOTHER MORE FOCUSED OVER INDIANA.  THE NWRN
INDIANA COUNTIES WILL STILL HAVE A CHANCE FOR SOME SHOWERS AND
THUNDERSTORMS INTO THE EVENING...WHILE PCPN CHANCES OVER NRN IL
BEGIN TO WANE.  MUCH OF THE MODEL GUIDANCE ALSO INDICATED THAT THE
SHORTWAVE SHOULD SLOW IT`S PROGRESSION THROUGH WISCONSIN AS IT
APPROACHES THE APEX OF THE UPPER RIDGE.  AN ASSOCIATED SFC
TROUGH/COLD FRONT EXTENDING SOUTHWEST FROM THE SFC LOW WILL LINGER
OVER ERN IOWA IN THE EARLY EVENING BEFORE STEADILY PUSHING ACROSS
NRN IL AND INTO NWRN IN OVERNIGHT.  THROUGH THE NIGHT...THE
STRONGEST UPPER LEVEL FORCING WILL BE WELL NORTH OF THE CWA...SO ANY
LINGERING CHANCES FOR PCPN OVERNIGHT WILL BE LOW AND LIKELY CONFINED
TO THE NRN TIER COUNTIES OF IL...ALONG THE WI BORDER.

KREIN

&&

.LONG TERM...
229 AM CDT

WEDNESDAY THROUGH MONDAY...

WEDNESDAY THROUGH THURSDAY...
OPEN 500MB WAVE WILL BE LIFTING NORTHEAST ACROSS THE UPPER MIDWEST
INTO ONTARIO AND EVENTUALLY QUEBEC...WITH HEIGHTS SLOWLY INCREASING
WED AFTN. SFC FEATURES REMAIN DISORGANIZED WED...WITH A BOUNDARY
SLOWLY SHIFTING EAST. OPER GUIDANCE DIFFERS ON HOW QUICKLY PRECIP
WILL DEPART THE REGION. ENSEMBLE DATA SUGGESTS HOLDING ONTO CHC TO
SLIGHT CHC POPS MAINLY FOR THE CENTRAL/EASTERN CWFA WED/WED EVE.
ALTHOUGH WITH SOME HINT OF SFC HEIGHTS NUDGING UP...IT IS POSSIBLE
THAT SOME DRY AIR COULD FILTER IN AND KICK PRECIP EAST BY MIDDAY AND
ALLOW FOR A MAINLY DRY WED. SFC WINDS WILL BE TURNING SOUTHWEST TO
WEST...KEEPING AN OFFSHORE FLOW FOR LOCATIONS CLOSE TO LAKE
MICHIGAN. TEMPS SHOULD YET AGAIN TOUCH UPR 70S TO ARND 80 WED...IF
CLOUDS AND PRECIP CAN PUSH EAST BY MIDDAY...SOME CLEARING WOULD
ALLOW SFC TEMPS TO PUSH A COUPLE DEGREES WARMER INTO THE LOW 80S IN
SOME LOCATIONS. LATE IN THE EVENING THE GRADIENT SLACKENS
FURTHER...AND COULD ALLOW A LATE DAY ONSHORE FLOW TO DEVELOP FOR
AREAS ADJACENT TO LAKE MICHIGAN.

MID-LVL FLOW BEGINS TO FLATTEN AS A WEAK SFC RIDGE BECOMES ORIENTED
FROM WESTERN QUEBEC SOUTH THROUGH THE EASTERN OHIO RIVER VALLEY.
THIS WILL GENERALLY ALLOW A SOUTHERLY FLOW...ALTHOUGH THE GRADIENT
IS NOT VERY STRONG. THIS SHOULD SET THE STAGE FOR A LAKE
BREEZE/ONSHORE FLOW TO DEVELOP THUR. TIMING COULD END UP BEING
SLIGHTLY EARLIER GIVEN THE LIGHT SFC GRADIENT. GUIDANCE HAS BEEN
CONSISTENT IN HOLDING PRECIP WEST/SOUTH OF THE FORECAST AREA
THUR...AS A RESULT OF THE WEAK SFC RIDGING. SO ONE MORE MILD DAY
WITH HIGHS WARMING BACK INTO THE UPR 70S/LOW 80S...HOWEVER AS
PREVIOUSLY NOTED...A LAKE BREEZE IS LIKELY TO DEVELOP. THIS WILL
BLEED THE MUCH COOLER MARINE AIR WEST ACROSS NORTHEAST IL AND
DOWNTOWN CHICAGO. IF THE TIMING IS EARLIER IN THE DAY THUR...TEMPS
MAY NOT WARM BEYOND THE LOW/MID 60S ALONG THE CHICAGO LAKEFRONT.

FLOW THEN TURNS SOUTHERLY THUR NIGHT WITH THE MORE PROGRESSIVE FLOW
IN THE MID-LVLS PUSHING THE RIDGING EAST. A RETURN FLOW MOISTURE
WILL CONTINUE TO BE FOCUSED ACROSS THE CENTRAL CONUS THUR EVE...WITH
A SLOW MOVING FRONTAL BOUNDARY NUDGING EAST THUR NIGHT TOWARDS
WESTERN IL. THIS FRONTAL BOUNDARY WILL BECOME ENERGIZED AS A ROBUST
500MB VORT MAX BREAKS SOUTH FROM CENTRAL CANADA LATE THUR NIGHT.

THIS SHOULD ALLOW FOR AN ATMOSPHERIC RIVER TO DEVELOP FROM THE
SOUTHERN PLAINS STRETCHING NORTH THROUGH THE MID-MISSOURI VALLEY
INTO THE WESTERN GREAT LAKES EARLY FRI MORNING.

FRIDAY THROUGH EARLY NEXT WEEK...
ENSEMBLES CONTINUE TO PROG A ROBUST TROUGH SLIDING SOUTH FROM
CENTRAL CANADA FRI. THIS COUPLED WITH DOWNSTREAM MID-LVL RIDGING
ACROSS THE SOUTHEAST CONUS WILL STRENGTHEN THE FRONTAL BOUNDARY
THAT WILL BE ORIENTED FROM THE SOUTHERN PLAINS STRETCHING
NORTHEAST THROUGH THE GREAT LAKES REGION INTO WESTERN QUEBEC.

THIS SETUP IS IDEAL FOR THE DEVELOPMENT OF AN ATMOSPHERIC RIVER WITH
ABUNDANT LOW LEVEL MOISTURE AND EFFICIENT PRECIP PRODUCING
CONVECTION.

OPER GUIDANCE HAS BEEN RELATIVELY CONSISTENT WITH BRINGING A SERIES
OF WAVES ALONG THE SLOW MOVING FRONTAL BOUNDARY FRI AFTN/EVE...THEN
THE BOUNDARY SHOULD SLIDE EAST WITH WINDS QUICKLY VEERING
NORTH/NORTHEAST FOR SAT AND USHERING IN MUCH COOLER AIR TO THE
REGION.

CURRENT INDICATIONS ARE THAT HIGHS SAT MAY STRUGGLE TO WARM BEYOND
THE UPR 50S ACROSS NORTHEAST IL/NORTHWEST IN...WITH ONLY LOW 60S
ELSEWHERE. STRONG SFC RIDGE WILL REMAIN NORTH OF THE REGION...SO THE
PRIOR FRONTAL BOUNDARY MAY BECOME QUASI-STATIONARY FOR THE WEEKEND
ALONG THE OHIO VALLEY AND CONTINUE TO FEED PRECIP CHANCES TO THE
SOUTHERN CWFA.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 12Z...

* SOUTH-SOUTHWEST WINDS OF AROUND 40 KT AT 1000 FT
  OVERNIGHT...SETTING UP THE POTENTIAL FOR LOW LEVEL WIND SHEAR.

* MVFR CEILINGS THIS MORNING WITH A CHANCE FOR TEMPORARY IFR.

* PERIODS OF SHRA WITH PERIODIC TSRA FROM LATE THIS MORNING
  THROUGH THE AFTERNOON.

* NEAR DUE SOUTH WINDS ON TUESDAY WITH PERIODIC GUSTS POSSIBLE
  AND SOME VARIABILITY BETWEEN SOUTHEAST AND SOUTHWEST.

KREIN

//DISCUSSION...UPDATED 12Z...

A MID LEVEL DISTURBANCE MOVING FROM THE SOUTHERN PLAINS TO NRN IL
BY THIS AFTERNOON MAY BRING ANOTHER ROUND OF SHOWERS WITH SCT
THUNDERSTORMS TO THE REGION. UPPER LEVEL FORCING FROM THE MID
LEVEL DISTURBANCE AND AN UPPER LEVEL JET STREAM WILL ENHANCE THE
LIKELIHOOD FOR PCPN AND THE CHANCE FOR TSRA...WITH THE MOST
LIKELY CHANCE FOR ACTIVITY FROM LATE MORNING THROUGH EARLY
EVENING. SOME UNCERTAINTY REMAINS IN PINNING DOWN THE EXACT
PERIOD FOR THE TSRA...SO WILL MAINTAIN THE GOING TEMPO FOR LATE
MORNING THROUGH EARLY AFTERNOON. HOWEVER...THE PCPN TIMING COULD
BE SHIFTED OR EXPANDED IN TIME.

LOW LEVEL MOISTURE STREAMING NORTHWARD AHEAD OF LOW PRESSURE OVER
THE MID MISSISSIPPI VALLEY HAS BROUGHT A LOW MVFR STRATUS DECK
ACROSS THE REGION. SOME SITES ARE REPORTING CIGS DROPPING INTO IFR
RANGE...SO WILL INCLUDE THE POSSIBILITY IN A TEMPO GROUP THROUGH
LATE MORNING. DAYTIME WARMING SHOULD ALLOW FOR INCREASE DEEP LAYER
MIXING WHICH SHOULD SCATTER OUT THE STRATUS DECK.

WINDS WILL BE GENERALLY SOUTHERLY TODAY...THOUGH DIRECTION MAY BE
A BIT VARIABLE AROUND CONVECTIVE ACTIVITY. SOME GUSTINESS IS
LIKELY TO BEGIN BY LATE MORNING...WITH THE LATEST GUIDANCE
SUGGESTING THAT WINDS COULD STRENGTHEN AND BECOME EVEN MORE GUSTY
TONIGHT WITH WINDS VEERING SWLY AS SURFACE LOW PRESSURE MOVES
NORTHEAST ACROSS SOUTHERN WISCONSIN.

KREIN


//ORD AND MDW CONFIDENCE...UPDATED 12Z...

* HIGH CONFIDENCE IN WIND TRENDS TODAY. MEDIUM IN WIND TRENDS
  TONIGHT.

* HIGH CONFIDENCE IN MVFR CIGS TUESDAY MORNING WITH LOWER
  CONFIDENCE IN DURATION AND IF CIGS WILL DROP TO IFR.

* HIGH CONFIDENCE IN SHOWERS AND AT LEAST A PERIOD OF TSRA. LOW
  CONFIDENCE IN SPECIFIC TSRA TIMING AND IMPACT ON THE TERMINALS
  WITH MULTIPLE ROUNDS POSSIBLE BETWEEN 16Z AND 02Z.

KREIN

//OUTLOOK FOR ORD/MDW FOR 00Z THURSDAY-12Z TUESDAY...UPDATED 12Z...

WEDNESDAY NIGHT...WX NIL/VFR. SOUTHEAST WINDS.

THURSDAY...SLIGHT CHANCE OF TSRA AT NIGHT. SOUTHEAST WINDS.

FRIDAY...TSRA/SHRA LIKELY THROUGH THE DAY AND NIGHT. MVFR
POSSIBLE. SOUTHWEST WINDS.

SATURDAY...SHRA LIKELY WITH A CHANCE OF TSRA DURING THE DAY.
NORTHEAST WINDS.

SUNDAY...CHANCE OF SHRA. EAST WINDS. MVFR POSSIBLE.

MONDAY...CHANCE OF SHRA. SOUTHEAST WINDS. MVFR POSSIBLE.

KREIN

&&

.MARINE...
229 AM CDT

WARM MOIST AIR CONTINUES TO FEED NORTH ACROSS THE LAKE
TODAY...WHICH MAY HELP TO FURTHER ENHANCE ANY AREAS OF FOG THAT
HAVE ALREADY DEVELOPED. IT IS POSSIBLE PATCHY DENSE FOG MAY
DEVELOP...ALTHOUGH WINDS MAY BE JUST STRONG ENOUGH TO LIMIT THE
COVERAGE AND INTENSITY OF THE FOG. A SURFACE LOW PRESSURE SYSTEM
WILL BE LIFTING NORTH ACROSS EASTERN IOWA INTO CENTRAL WISCONSIN
THIS EVENING. THE GRADIENT WILL TIGHTEN ACROSS THE
CENTRAL/SOUTHERN PORTIONS OF THE LAKE...WHICH WITH WARMER
NEARSHORE WATERS EXPECT SOME SLIGHTLY BETTER MIXING TO OCCUR.
FURTHER OUT ACROSS THE OPEN WATERS THE WATER REMAINS COLD AND
EXPECT THE STABILITY TO MAKE IT DIFFICULT TO MIX TO THE SFC THE
HIGHER GUSTS. HIGH PRESSURE THEN ARRIVES LATE WEDNESDAY WITH LIGHT
WINDS DEVELOPING. THEN HIGH PRESSURE SHIFTS EAST THURSDAY
NIGHT...WITH SOUTHERLY WINDS DEVELOPING AGAIN FRIDAY. A FRONTAL
BOUNDARY WILL APPROACH LAKE MICHIGAN LATE FRIDAY NIGHT THEN
STEADILY SLIDE SOUTH ALONG THE LAKE. THIS WILL ALLOW WINDS TO
QUICKLY VEER FROM SOUTH TO NORTH/NORTHEAST SATURDAY. ALONG WITH
THIS QUICK WIND SHIFT WILL BE COOLER AIR SLIDING SOUTH OVER THE
LAKE. WAVES SHOULD EASILY BUILD SATURDAY FOR THE CENTRAL/SOUTHERN
PORTIONS OF THE LAKE.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 261130
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
630 AM CDT TUE MAY 26 2015

.SHORT TERM...
319 AM CDT

THROUGH TUESDAY NIGHT...

FOR THE REMAINDER OF THE OVERNIGHT HOURS...CONDITIONS WILL REMAIN
QUIET ACROSS THE CWA AS A SERIES OF SHORT WAVES CONTINUE TO TRACK
NORTH AROUND THE TOP OF A PERSISTENT UPPER LEVEL RIDGE WHICH EXTENDS
FROM THE SERN CONUS THROUGH THE UPPER MISSISSIPPI VALLEY.  THIS
UPPER RIDGE HAS BEEN THE FEATURE WHICH HAS CONTROLLED THE PATH OF
THE SERIES OF SHORTWAVES LIFTING OUT OF THE SOUTHERN PLAINS...AND
WILL CONTINUE TO DO SO THROUGH THE DAY TODAY. SLY...MODERATELY
STRONG...WINDS WILL PERSIST THROUGH THE NIGHT...AND MUCH OF THE DAY
ALLOWING FOR SFC DEWPOINTS TO REMAIN CONSISTENT OR POSSIBLE INCH A
LITTLE HIGHER.

MAIN CONCERN FOR THE MORNING HOURS WILL BE THE TRACK OF A STRONG
SHORT WAVE AND ASSOCIATED SFC LOW LIFTING NORTHWARD THROUGH THE
MIDDLE MISSISSIPPI VALLEY.  THIS FEATURE WILL PREDOMINANTLY IMPACT
ERN IOWA AND WRN IL BY ARND DAYBREAK.  THROUGH THE MORNING...THE
COMBINATION OF ISENTROPIC LIFT IN THE WARM SECTOR OF THE
SYSTEM...ALL OF IL AND INTO NWRN IN...WILL LEAD TO SOME
DESTABILIZATION ACROSS THE REGION. A SFC TROUGH...AS WELL INDICATED
BY THE LATEST HIGH RES GUIDANCE...WITH LIFT THROUGH NRN IL/IN
THROUGH THE DAY...COINCIDENT WITH A STRONG SSWLY LOW LEVEL JET OF 45-
50 KT...WITH PROVIDE THE POTENTIAL FOR SHOWERS AND STRONG TO SEVERE
THUNDERSTORMS ACROSS THE CWA.  BASED ON WIND PROFILES AND MID LEVEL
DRYING...THE PRIMARY CONCERN WITH REGARD TO SEVERE WEATHER WILL BE
STRONG WIND GUSTS.  HOWEVER...SOME OF THE HIGH RES SFC WIND GUIDANCE
SUGGEST SOME SLIGHT BACKING OF SFC WINDS FROM 180-190 DEGREES TO 160-
170 DEGREES...WHILE WINDS ALOFT REMAIN SWLY.  THIS SLIGHT BACKING OF
THE SFC WINDS COULD PROVIDE ENOUGH DIRECTIONAL SHEAR THROUGH THE
LOWER LEVELS TO BRING AN ISOLD TORNADO THREAT. LOCALLY HEAVY
RAINFALL WILL ALSO BE CONCERNED WITH PWATS REACHING 1.75 INCHES
LATER THIS MORNING.  HOWEVER...FLOODING WILL LIKELY NOT BE A
SIGNIFICANT CONCERN AS THE SWLY WINDS RIGHT OFF THE DECK WILL RANGE
FROM ARND 45 KT ABOVE THE BOUNDARY LAYER TO ARND 90KT AT UPPER
LEVELS WHICH SHOULD ALLOW ANY OF THE STRONGER STORMS THAT DO DEVELOP
TO MOVE QUICKLY.

BY EARLY AFTERNOON...THE MAIN SHORT WAVE WILL LIFT INTO WISCONSIN
WHILE A SFC TROUGH TRACKS EAST ACROSS THE AREA.  THIS WILL LEAD TO
WINDS AT THE SFC VEERING TO SWLY...SETTING UP A UNIDIRECTIONAL WIND
PROFILE...EFFECTIVELY MINIMIZING THE SEVERE WEATHER THREAT TO THE
REGION.  BY LATE AFTERNOON AND INTO THE EVENING THE MODELS ARE
ADVERTISING THAT A DRY SLOW SHOULD NOSE INTO NRN IL...EFFECTIVELY
CUTTING OFF THE PCPN AREA INTO 2 SEPARATE AREA...ONE OVER WISCONSIN
AND ERN IOWA AND ANOTHER MORE FOCUSED OVER INDIANA.  THE NWRN
INDIANA COUNTIES WILL STILL HAVE A CHANCE FOR SOME SHOWERS AND
THUNDERSTORMS INTO THE EVENING...WHILE PCPN CHANCES OVER NRN IL
BEGIN TO WANE.  MUCH OF THE MODEL GUIDANCE ALSO INDICATED THAT THE
SHORTWAVE SHOULD SLOW IT`S PROGRESSION THROUGH WISCONSIN AS IT
APPROACHES THE APEX OF THE UPPER RIDGE.  AN ASSOCIATED SFC
TROUGH/COLD FRONT EXTENDING SOUTHWEST FROM THE SFC LOW WILL LINGER
OVER ERN IOWA IN THE EARLY EVENING BEFORE STEADILY PUSHING ACROSS
NRN IL AND INTO NWRN IN OVERNIGHT.  THROUGH THE NIGHT...THE
STRONGEST UPPER LEVEL FORCING WILL BE WELL NORTH OF THE CWA...SO ANY
LINGERING CHANCES FOR PCPN OVERNIGHT WILL BE LOW AND LIKELY CONFINED
TO THE NRN TIER COUNTIES OF IL...ALONG THE WI BORDER.

KREIN

&&

.LONG TERM...
229 AM CDT

WEDNESDAY THROUGH MONDAY...

WEDNESDAY THROUGH THURSDAY...
OPEN 500MB WAVE WILL BE LIFTING NORTHEAST ACROSS THE UPPER MIDWEST
INTO ONTARIO AND EVENTUALLY QUEBEC...WITH HEIGHTS SLOWLY INCREASING
WED AFTN. SFC FEATURES REMAIN DISORGANIZED WED...WITH A BOUNDARY
SLOWLY SHIFTING EAST. OPER GUIDANCE DIFFERS ON HOW QUICKLY PRECIP
WILL DEPART THE REGION. ENSEMBLE DATA SUGGESTS HOLDING ONTO CHC TO
SLIGHT CHC POPS MAINLY FOR THE CENTRAL/EASTERN CWFA WED/WED EVE.
ALTHOUGH WITH SOME HINT OF SFC HEIGHTS NUDGING UP...IT IS POSSIBLE
THAT SOME DRY AIR COULD FILTER IN AND KICK PRECIP EAST BY MIDDAY AND
ALLOW FOR A MAINLY DRY WED. SFC WINDS WILL BE TURNING SOUTHWEST TO
WEST...KEEPING AN OFFSHORE FLOW FOR LOCATIONS CLOSE TO LAKE
MICHIGAN. TEMPS SHOULD YET AGAIN TOUCH UPR 70S TO ARND 80 WED...IF
CLOUDS AND PRECIP CAN PUSH EAST BY MIDDAY...SOME CLEARING WOULD
ALLOW SFC TEMPS TO PUSH A COUPLE DEGREES WARMER INTO THE LOW 80S IN
SOME LOCATIONS. LATE IN THE EVENING THE GRADIENT SLACKENS
FURTHER...AND COULD ALLOW A LATE DAY ONSHORE FLOW TO DEVELOP FOR
AREAS ADJACENT TO LAKE MICHIGAN.

MID-LVL FLOW BEGINS TO FLATTEN AS A WEAK SFC RIDGE BECOMES ORIENTED
FROM WESTERN QUEBEC SOUTH THROUGH THE EASTERN OHIO RIVER VALLEY.
THIS WILL GENERALLY ALLOW A SOUTHERLY FLOW...ALTHOUGH THE GRADIENT
IS NOT VERY STRONG. THIS SHOULD SET THE STAGE FOR A LAKE
BREEZE/ONSHORE FLOW TO DEVELOP THUR. TIMING COULD END UP BEING
SLIGHTLY EARLIER GIVEN THE LIGHT SFC GRADIENT. GUIDANCE HAS BEEN
CONSISTENT IN HOLDING PRECIP WEST/SOUTH OF THE FORECAST AREA
THUR...AS A RESULT OF THE WEAK SFC RIDGING. SO ONE MORE MILD DAY
WITH HIGHS WARMING BACK INTO THE UPR 70S/LOW 80S...HOWEVER AS
PREVIOUSLY NOTED...A LAKE BREEZE IS LIKELY TO DEVELOP. THIS WILL
BLEED THE MUCH COOLER MARINE AIR WEST ACROSS NORTHEAST IL AND
DOWNTOWN CHICAGO. IF THE TIMING IS EARLIER IN THE DAY THUR...TEMPS
MAY NOT WARM BEYOND THE LOW/MID 60S ALONG THE CHICAGO LAKEFRONT.

FLOW THEN TURNS SOUTHERLY THUR NIGHT WITH THE MORE PROGRESSIVE FLOW
IN THE MID-LVLS PUSHING THE RIDGING EAST. A RETURN FLOW MOISTURE
WILL CONTINUE TO BE FOCUSED ACROSS THE CENTRAL CONUS THUR EVE...WITH
A SLOW MOVING FRONTAL BOUNDARY NUDGING EAST THUR NIGHT TOWARDS
WESTERN IL. THIS FRONTAL BOUNDARY WILL BECOME ENERGIZED AS A ROBUST
500MB VORT MAX BREAKS SOUTH FROM CENTRAL CANADA LATE THUR NIGHT.

THIS SHOULD ALLOW FOR AN ATMOSPHERIC RIVER TO DEVELOP FROM THE
SOUTHERN PLAINS STRETCHING NORTH THROUGH THE MID-MISSOURI VALLEY
INTO THE WESTERN GREAT LAKES EARLY FRI MORNING.

FRIDAY THROUGH EARLY NEXT WEEK...
ENSEMBLES CONTINUE TO PROG A ROBUST TROUGH SLIDING SOUTH FROM
CENTRAL CANADA FRI. THIS COUPLED WITH DOWNSTREAM MID-LVL RIDGING
ACROSS THE SOUTHEAST CONUS WILL STRENGTHEN THE FRONTAL BOUNDARY
THAT WILL BE ORIENTED FROM THE SOUTHERN PLAINS STRETCHING
NORTHEAST THROUGH THE GREAT LAKES REGION INTO WESTERN QUEBEC.

THIS SETUP IS IDEAL FOR THE DEVELOPMENT OF AN ATMOSPHERIC RIVER WITH
ABUNDANT LOW LEVEL MOISTURE AND EFFICIENT PRECIP PRODUCING
CONVECTION.

OPER GUIDANCE HAS BEEN RELATIVELY CONSISTENT WITH BRINGING A SERIES
OF WAVES ALONG THE SLOW MOVING FRONTAL BOUNDARY FRI AFTN/EVE...THEN
THE BOUNDARY SHOULD SLIDE EAST WITH WINDS QUICKLY VEERING
NORTH/NORTHEAST FOR SAT AND USHERING IN MUCH COOLER AIR TO THE
REGION.

CURRENT INDICATIONS ARE THAT HIGHS SAT MAY STRUGGLE TO WARM BEYOND
THE UPR 50S ACROSS NORTHEAST IL/NORTHWEST IN...WITH ONLY LOW 60S
ELSEWHERE. STRONG SFC RIDGE WILL REMAIN NORTH OF THE REGION...SO THE
PRIOR FRONTAL BOUNDARY MAY BECOME QUASI-STATIONARY FOR THE WEEKEND
ALONG THE OHIO VALLEY AND CONTINUE TO FEED PRECIP CHANCES TO THE
SOUTHERN CWFA.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 12Z...

* SOUTH-SOUTHWEST WINDS OF AROUND 40 KT AT 1000 FT
  OVERNIGHT...SETTING UP THE POTENTIAL FOR LOW LEVEL WIND SHEAR.

* MVFR CEILINGS THIS MORNING WITH A CHANCE FOR TEMPORARY IFR.

* PERIODS OF SHRA WITH PERIODIC TSRA FROM LATE THIS MORNING
  THROUGH THE AFTERNOON.

* NEAR DUE SOUTH WINDS ON TUESDAY WITH PERIODIC GUSTS POSSIBLE
  AND SOME VARIABILITY BETWEEN SOUTHEAST AND SOUTHWEST.

KREIN

//DISCUSSION...UPDATED 12Z...

A MID LEVEL DISTURBANCE MOVING FROM THE SOUTHERN PLAINS TO NRN IL
BY THIS AFTERNOON MAY BRING ANOTHER ROUND OF SHOWERS WITH SCT
THUNDERSTORMS TO THE REGION. UPPER LEVEL FORCING FROM THE MID
LEVEL DISTURBANCE AND AN UPPER LEVEL JET STREAM WILL ENHANCE THE
LIKELIHOOD FOR PCPN AND THE CHANCE FOR TSRA...WITH THE MOST
LIKELY CHANCE FOR ACTIVITY FROM LATE MORNING THROUGH EARLY
EVENING. SOME UNCERTAINTY REMAINS IN PINNING DOWN THE EXACT
PERIOD FOR THE TSRA...SO WILL MAINTAIN THE GOING TEMPO FOR LATE
MORNING THROUGH EARLY AFTERNOON. HOWEVER...THE PCPN TIMING COULD
BE SHIFTED OR EXPANDED IN TIME.

LOW LEVEL MOISTURE STREAMING NORTHWARD AHEAD OF LOW PRESSURE OVER
THE MID MISSISSIPPI VALLEY HAS BROUGHT A LOW MVFR STRATUS DECK
ACROSS THE REGION. SOME SITES ARE REPORTING CIGS DROPPING INTO IFR
RANGE...SO WILL INCLUDE THE POSSIBILITY IN A TEMPO GROUP THROUGH
LATE MORNING. DAYTIME WARMING SHOULD ALLOW FOR INCREASE DEEP LAYER
MIXING WHICH SHOULD SCATTER OUT THE STRATUS DECK.

WINDS WILL BE GENERALLY SOUTHERLY TODAY...THOUGH DIRECTION MAY BE
A BIT VARIABLE AROUND CONVECTIVE ACTIVITY. SOME GUSTINESS IS
LIKELY TO BEGIN BY LATE MORNING...WITH THE LATEST GUIDANCE
SUGGESTING THAT WINDS COULD STRENGTHEN AND BECOME EVEN MORE GUSTY
TONIGHT WITH WINDS VEERING SWLY AS SURFACE LOW PRESSURE MOVES
NORTHEAST ACROSS SOUTHERN WISCONSIN.

KREIN


//ORD AND MDW CONFIDENCE...UPDATED 12Z...

* HIGH CONFIDENCE IN WIND TRENDS TODAY. MEDIUM IN WIND TRENDS
  TONIGHT.

* HIGH CONFIDENCE IN MVFR CIGS TUESDAY MORNING WITH LOWER
  CONFIDENCE IN DURATION AND IF CIGS WILL DROP TO IFR.

* HIGH CONFIDENCE IN SHOWERS AND AT LEAST A PERIOD OF TSRA. LOW
  CONFIDENCE IN SPECIFIC TSRA TIMING AND IMPACT ON THE TERMINALS
  WITH MULTIPLE ROUNDS POSSIBLE BETWEEN 16Z AND 02Z.

KREIN

//OUTLOOK FOR ORD/MDW FOR 00Z THURSDAY-12Z TUESDAY...UPDATED 12Z...

WEDNESDAY NIGHT...WX NIL/VFR. SOUTHEAST WINDS.

THURSDAY...SLIGHT CHANCE OF TSRA AT NIGHT. SOUTHEAST WINDS.

FRIDAY...TSRA/SHRA LIKELY THROUGH THE DAY AND NIGHT. MVFR
POSSIBLE. SOUTHWEST WINDS.

SATURDAY...SHRA LIKELY WITH A CHANCE OF TSRA DURING THE DAY.
NORTHEAST WINDS.

SUNDAY...CHANCE OF SHRA. EAST WINDS. MVFR POSSIBLE.

MONDAY...CHANCE OF SHRA. SOUTHEAST WINDS. MVFR POSSIBLE.

KREIN

&&

.MARINE...
229 AM CDT

WARM MOIST AIR CONTINUES TO FEED NORTH ACROSS THE LAKE
TODAY...WHICH MAY HELP TO FURTHER ENHANCE ANY AREAS OF FOG THAT
HAVE ALREADY DEVELOPED. IT IS POSSIBLE PATCHY DENSE FOG MAY
DEVELOP...ALTHOUGH WINDS MAY BE JUST STRONG ENOUGH TO LIMIT THE
COVERAGE AND INTENSITY OF THE FOG. A SURFACE LOW PRESSURE SYSTEM
WILL BE LIFTING NORTH ACROSS EASTERN IOWA INTO CENTRAL WISCONSIN
THIS EVENING. THE GRADIENT WILL TIGHTEN ACROSS THE
CENTRAL/SOUTHERN PORTIONS OF THE LAKE...WHICH WITH WARMER
NEARSHORE WATERS EXPECT SOME SLIGHTLY BETTER MIXING TO OCCUR.
FURTHER OUT ACROSS THE OPEN WATERS THE WATER REMAINS COLD AND
EXPECT THE STABILITY TO MAKE IT DIFFICULT TO MIX TO THE SFC THE
HIGHER GUSTS. HIGH PRESSURE THEN ARRIVES LATE WEDNESDAY WITH LIGHT
WINDS DEVELOPING. THEN HIGH PRESSURE SHIFTS EAST THURSDAY
NIGHT...WITH SOUTHERLY WINDS DEVELOPING AGAIN FRIDAY. A FRONTAL
BOUNDARY WILL APPROACH LAKE MICHIGAN LATE FRIDAY NIGHT THEN
STEADILY SLIDE SOUTH ALONG THE LAKE. THIS WILL ALLOW WINDS TO
QUICKLY VEER FROM SOUTH TO NORTH/NORTHEAST SATURDAY. ALONG WITH
THIS QUICK WIND SHIFT WILL BE COOLER AIR SLIDING SOUTH OVER THE
LAKE. WAVES SHOULD EASILY BUILD SATURDAY FOR THE CENTRAL/SOUTHERN
PORTIONS OF THE LAKE.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 260856
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
356 AM CDT TUE MAY 26 2015

.SHORT TERM...
319 AM CDT

THROUGH TUESDAY NIGHT...

FOR THE REMAINDER OF THE OVERNIGHT HOURS...CONDITIONS WILL REMAIN
QUIET ACROSS THE CWA AS A SERIES OF SHORT WAVES CONTINUE TO TRACK
NORTH AROUND THE TOP OF A PERSISTENT UPPER LEVEL RIDGE WHICH EXTENDS
FROM THE SERN CONUS THROUGH THE UPPER MISSISSIPPI VALLEY.  THIS
UPPER RIDGE HAS BEEN THE FEATURE WHICH HAS CONTROLLED THE PATH OF
THE SERIES OF SHORTWAVES LIFTING OUT OF THE SOUTHERN PLAINS...AND
WILL CONTINUE TO DO SO THROUGH THE DAY TODAY. SLY...MODERATELY
STRONG...WINDS WILL PERSIST THROUGH THE NIGHT...AND MUCH OF THE DAY
ALLOWING FOR SFC DEWPOINTS TO REMAIN CONSISTENT OR POSSIBLE INCH A
LITTLE HIGHER.

MAIN CONCERN FOR THE MORNING HOURS WILL BE THE TRACK OF A STRONG
SHORT WAVE AND ASSOCIATED SFC LOW LIFTING NORTHWARD THROUGH THE
MIDDLE MISSISSIPPI VALLEY.  THIS FEATURE WILL PREDOMINANTLY IMPACT
ERN IOWA AND WRN IL BY ARND DAYBREAK.  THROUGH THE MORNING...THE
COMBINATION OF ISENTROPIC LIFT IN THE WARM SECTOR OF THE
SYSTEM...ALL OF IL AND INTO NWRN IN...WILL LEAD TO SOME
DESTABILIZATION ACROSS THE REGION. A SFC TROUGH...AS WELL INDICATED
BY THE LATEST HIGH RES GUIDANCE...WITH LIFT THROUGH NRN IL/IN
THROUGH THE DAY...COINCIDENT WITH A STRONG SSWLY LOW LEVEL JET OF 45-
50 KT...WITH PROVIDE THE POTENTIAL FOR SHOWERS AND STRONG TO SEVERE
THUNDERSTORMS ACROSS THE CWA.  BASED ON WIND PROFILES AND MID LEVEL
DRYING...THE PRIMARY CONCERN WITH REGARD TO SEVERE WEATHER WILL BE
STRONG WIND GUSTS.  HOWEVER...SOME OF THE HIGH RES SFC WIND GUIDANCE
SUGGEST SOME SLIGHT BACKING OF SFC WINDS FROM 180-190 DEGREES TO 160-
170 DEGREES...WHILE WINDS ALOFT REMAIN SWLY.  THIS SLIGHT BACKING OF
THE SFC WINDS COULD PROVIDE ENOUGH DIRECTIONAL SHEAR THROUGH THE
LOWER LEVELS TO BRING AN ISOLD TORNADO THREAT. LOCALLY HEAVY
RAINFALL WILL ALSO BE CONCERNED WITH PWATS REACHING 1.75 INCHES
LATER THIS MORNING.  HOWEVER...FLOODING WILL LIKELY NOT BE A
SIGNIFICANT CONCERN AS THE SWLY WINDS RIGHT OFF THE DECK WILL RANGE
FROM ARND 45 KT ABOVE THE BOUNDARY LAYER TO ARND 90KT AT UPPER
LEVELS WHICH SHOULD ALLOW ANY OF THE STRONGER STORMS THAT DO DEVELOP
TO MOVE QUICKLY.

BY EARLY AFTERNOON...THE MAIN SHORT WAVE WILL LIFT INTO WISCONSIN
WHILE A SFC TROUGH TRACKS EAST ACROSS THE AREA.  THIS WILL LEAD TO
WINDS AT THE SFC VEERING TO SWLY...SETTING UP A UNIDIRECTIONAL WIND
PROFILE...EFFECTIVELY MINIMIZING THE SEVERE WEATHER THREAT TO THE
REGION.  BY LATE AFTERNOON AND INTO THE EVENING THE MODELS ARE
ADVERTISING THAT A DRY SLOW SHOULD NOSE INTO NRN IL...EFFECTIVELY
CUTTING OFF THE PCPN AREA INTO 2 SEPARATE AREA...ONE OVER WISCONSIN
AND ERN IOWA AND ANOTHER MORE FOCUSED OVER INDIANA.  THE NWRN
INDIANA COUNTIES WILL STILL HAVE A CHANCE FOR SOME SHOWERS AND
THUNDERSTORMS INTO THE EVENING...WHILE PCPN CHANCES OVER NRN IL
BEGIN TO WANE.  MUCH OF THE MODEL GUIDANCE ALSO INDICATED THAT THE
SHORTWAVE SHOULD SLOW IT`S PROGRESSION THROUGH WISCONSIN AS IT
APPROACHES THE APEX OF THE UPPER RIDGE.  AN ASSOCIATED SFC
TROUGH/COLD FRONT EXTENDING SOUTHWEST FROM THE SFC LOW WILL LINGER
OVER ERN IOWA IN THE EARLY EVENING BEFORE STEADILY PUSHING ACROSS
NRN IL AND INTO NWRN IN OVERNIGHT.  THROUGH THE NIGHT...THE
STRONGEST UPPER LEVEL FORCING WILL BE WELL NORTH OF THE CWA...SO ANY
LINGERING CHANCES FOR PCPN OVERNIGHT WILL BE LOW AND LIKELY CONFINED
TO THE NRN TIER COUNTIES OF IL...ALONG THE WI BORDER.

KREIN

&&

.LONG TERM...
229 AM CDT

WEDNESDAY THROUGH MONDAY...

WEDNESDAY THROUGH THURSDAY...
OPEN 500MB WAVE WILL BE LIFTING NORTHEAST ACROSS THE UPPER MIDWEST
INTO ONTARIO AND EVENTUALLY QUEBEC...WITH HEIGHTS SLOWLY INCREASING
WED AFTN. SFC FEATURES REMAIN DISORGANIZED WED...WITH A BOUNDARY
SLOWLY SHIFTING EAST. OPER GUIDANCE DIFFERS ON HOW QUICKLY PRECIP
WILL DEPART THE REGION. ENSEMBLE DATA SUGGESTS HOLDING ONTO CHC TO
SLIGHT CHC POPS MAINLY FOR THE CENTRAL/EASTERN CWFA WED/WED EVE.
ALTHOUGH WITH SOME HINT OF SFC HEIGHTS NUDGING UP...IT IS POSSIBLE
THAT SOME DRY AIR COULD FILTER IN AND KICK PRECIP EAST BY MIDDAY AND
ALLOW FOR A MAINLY DRY WED. SFC WINDS WILL BE TURNING SOUTHWEST TO
WEST...KEEPING AN OFFSHORE FLOW FOR LOCATIONS CLOSE TO LAKE
MICHIGAN. TEMPS SHOULD YET AGAIN TOUCH UPR 70S TO ARND 80 WED...IF
CLOUDS AND PRECIP CAN PUSH EAST BY MIDDAY...SOME CLEARING WOULD
ALLOW SFC TEMPS TO PUSH A COUPLE DEGREES WARMER INTO THE LOW 80S IN
SOME LOCATIONS. LATE IN THE EVENING THE GRADIENT SLACKENS
FURTHER...AND COULD ALLOW A LATE DAY ONSHORE FLOW TO DEVELOP FOR
AREAS ADJACENT TO LAKE MICHIGAN.

MID-LVL FLOW BEGINS TO FLATTEN AS A WEAK SFC RIDGE BECOMES ORIENTED
FROM WESTERN QUEBEC SOUTH THROUGH THE EASTERN OHIO RIVER VALLEY.
THIS WILL GENERALLY ALLOW A SOUTHERLY FLOW...ALTHOUGH THE GRADIENT
IS NOT VERY STRONG. THIS SHOULD SET THE STAGE FOR A LAKE
BREEZE/ONSHORE FLOW TO DEVELOP THUR. TIMING COULD END UP BEING
SLIGHTLY EARLIER GIVEN THE LIGHT SFC GRADIENT. GUIDANCE HAS BEEN
CONSISTENT IN HOLDING PRECIP WEST/SOUTH OF THE FORECAST AREA
THUR...AS A RESULT OF THE WEAK SFC RIDGING. SO ONE MORE MILD DAY
WITH HIGHS WARMING BACK INTO THE UPR 70S/LOW 80S...HOWEVER AS
PREVIOUSLY NOTED...A LAKE BREEZE IS LIKELY TO DEVELOP. THIS WILL
BLEED THE MUCH COOLER MARINE AIR WEST ACROSS NORTHEAST IL AND
DOWNTOWN CHICAGO. IF THE TIMING IS EARLIER IN THE DAY THUR...TEMPS
MAY NOT WARM BEYONG THE LOW/MID 60S ALONG THE CHICAGO LAKEFRONT.

FLOW THEN TURNS SOUTHERLY THUR NIGHT WITH THE MORE PROGRESSIVE FLOW
IN THE MID-LVLS PUSHING THE RIDGING EAST. A RETURN FLOW MOISTURE
WILL CONTINUE TO BE FOCUSED ACROSS THE CENTRAL CONUS THUR EVE...WITH
A SLOW MOVING FRONTAL BOUNDARY NUDGING EAST THUR NIGHT TOWARDS
WESTERN IL. THIS FRONTAL BOUNDARY WILL BECOME ENERGIZED AS A ROBUST
500MB VORT MAX BREAKS SOUTH FROM CENTRAL CANADA LATE THUR NIGHT.

THIS SHOULD ALLOW FOR AN ATMOSPHERIC RIVER TO DEVELOP FROM THE
SOUTHERN PLAINS STRETCHING NORTH THROUGH THE MID-MISSOURI VALLEY
INTO THE WESTERN GREAT LAKES EARLY FRI MORNING.

FRIDAY THROUGH EARLY NEXT WEEK...
ENSEMBLES CONTINUE TO PROG A ROBUST TROUGH SLIDING SOUTH FROM
CENTRAL CANADA FRI. THIS COUPLED WITH DOWNSTREAM MID-LVL RIDGING
ACROSS THE SOUTHEAST CONUS WILL STRENGTHEN THE FRONTAL BOUNDARY
THAT WILL BE ORIENTED FROM THE SOUTHERN PLAINS STRETCHING
NORTHEAST THROUGH THE GREAT LAKES REGION INTO WESTERN QUEBEC.

THIS SETUP IS IDEAL FOR THE DEVELOPMENT OF AN ATMOSPHERIC RIVER WITH
ABUNDANT LOW LEVEL MOISTURE AND EFFICIENT PRECIP PRODUCING
CONVECTION.

OPER GUIDANCE HAS BEEN RELATIVELY CONSISTENT WITH BRINGING A SERIES
OF WAVES ALONG THE SLOW MOVING FRONTAL BOUNDARY FRI AFTN/EVE...THEN
THE BOUNDARY SHOULD SLIDE EAST WITH WINDS QUICKLY VEERING
NORTH/NORTHEAST FOR SAT AND USHERING IN MUCH COOLER AIR TO THE
REGION.

CURRENT INDICATIONS ARE THAT HIGHS SAT MAY STRUGGLE TO WARM BEYOND
THE UPR 50S ACROSS NORTHEAST IL/NORTHWEST IN...WITH ONLY LOW 60S
ELSEWHERE. STRONG SFC RIDGE WILL REMAIN NORTH OF THE REGION...SO THE
PRIOR FRONTAL BOUNDARY MAY BECOME QUASI-STATIONARY FOR THE WEEKEND
ALONG THE OHIO VALLEY AND CONTINUE TO FEED PRECIP CHANCES TO THE
SOUTHERN CWFA.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 09Z...

* SOUTH-SOUTHWEST WINDS OF AROUND 40 KT AT 1000 FT
  OVERNIGHT...SETTING UP THE POTENTIAL FOR LOW LEVEL WIND SHEAR.

* MVFR CEILINGS PROBABLE AT TIMES TUESDAY WITH A CHANCE FOR
  TEMPORARY IFR.

* PERIODS OF SHRA WITH PERIODIC TSRA FROM LATE TUESDAY MORNING
  THROUGH THE AFTERNOON.

* NEAR DUE SOUTH WINDS ON TUESDAY WITH PERIODIC GUSTS POSSIBLE
  AND SOME VARIABILITY BETWEEN SOUTHEAST AND SOUTHWEST.

KREIN

//DISCUSSION...UPDATED 06Z...

GUSTY SOUTH-SOUTHWEST WINDS HAVE DIMINISHED TO 10 KT OR LESS AND
BECOME SOUTHERLY. A LOW-LEVEL JET WILL DEVELOP OVERHEAD WITH
SSWLY-SWLY WINDS OF 40 KT TO 45 KT FLOW AT 1500-2000 FT UNTIL
ARND 12Z. SOME THUNDERSTORMS MAY DEVELOP THROUGH OVERNIGHT AHEAD
OF A FRONT FROM NRN MO THROUGH ERN IA AND INTO WI. THESE STORMS
WILL ONLY MAKE SLOW PROGRESS EASTWARD DUE TO THE STRONG SSWLY-SWLY
WINDS ALOFT SO...AND STORMS THAT DO DEVELOP SHOULD REMAIN NORTH
AND NORTHWEST OF AREA TAF SITES...THOUGH THERE IS A CHANCE THAT A
FEW STORMS COULD APPROACH THE RFD TERMINAL AREA VERY LATE
TONIGHT.

AS AN MID LEVEL DISTURBANCE MOVING FROM THE SOUTHERN PLAINS TO
NRN IL BY TUESDAY AFTERNOON MAY BRING ANOTHER ROUND OF SHOWERS
WITH SCT EMBEDDED THUNDERSTORMS TO THE REGION. UPPER LEVEL FORCING
FROM THE MID LEVEL DISTURBANCE AND AN UPPER LEVEL JET STREAM WILL
ENHANCE THE LIKELIHOOD FOR SHRA AND THE CHANCE FOR TSRA...WITH THE
MOST LIKELY CHANCE FOR ACTIVITY FROM 15Z THROUGH 02Z. SOME
UNCERTAINTY REMAINS IN PINNING DOWN THE EXACT PERIOD FOR THE
TSRA...SO WILL MAINTAIN THE GOING TEMPO FOR LATE MORNING THROUGH
EARLY AFTERNOON. HOWEVER...THE PCPN ACTIVITY COULD BE SHIFTED OR
EXPANDED IN TIME.

WINDS WILL BE SOUTHERLY ON TUESDAY...THOUGH DIRECTION MAY BE A BIT
VARIABLE AROUND CONVECTIVE ACTIVITY...THOUGH A GENERALLY SOUTHERLY
DIRECTION SHOULD PREVAIL THROUGH THE NIGHT AND MUCH OF THE DAY
TUESDAY. SOME GUSTINESS IS POSSIBLE THROUGH THE ENTIRE DAY...WITH
THE LATEST GUIDANCE SUGGESTING THAT WINDS COULD STRENGTHEN AND
BECOME EVEN MORE GUSTY THROUGH THE NIGHT TOMORROW NIGHT WITH WINDS
VEERING SWLY AS SURFACE LOW PRESSURE MOVES NORTHEAST ACROSS
SOUTHERN WISCONSIN.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 09Z...

* HIGH CONFIDENCE IN 40-45 KT SSWLY-SWLY FLOW ALOFT OVERNIGHT...BUT
  MEDIUM IN TRUE LLWS OCCURRING.

* HIGH CONFIDENCE IN WIND TRENDS OVERNIGHT AND TUESDAY MORNING.
  MEDIUM IN WIND TRENDS TOMORROW EVENING.

* MEDIUM CONFIDENCE IN MVFR CIGS TUESDAY MORNING WITH LOWER
  CONFIDENCE IN DURATION AND HOW LOW CIGS WILL DROP.

* HIGH CONFIDENCE IN SHOWERS AND AT LEAST A PERIOD OF TSRA. LOW
  CONFIDENCE IN SPECIFIC TSRA TIMING AND IMPACT ON THE TERMINALS
  WITH MULTIPLE ROUNDS POSSIBLE BETWEEN 15Z AND 02Z.

KREIN

//OUTLOOK FOR ORD/MDW FOR 12Z WEDNESDAY-12Z MONDAY...UPDATED 00Z...

WEDNESDAY...CHANCE OF TSRA. WEST WINDS.
THURSDAY...SLIGHT CHANCE OF TSRA LATE AT NIGHT. SOUTHEAST WINDS.
FRIDAY...INCREASING CHANCE OF TSRA THROUGH THE DAY AND NIGHT.
         SOUTHWEST WINDS.
SATURDAY...SHRA LIKELY WITH A CHANCE OF TSRA. NORTHEAST WINDS.
SUNDAY...CHANCE OF SHRA. EAST WINDS.

MTF

&&

.MARINE...
229 AM CDT

WARM MOIST AIR CONTINUES TO FEED NORTH ACROSS THE LAKE
TODAY...WHICH MAY HELP TO FURTHER ENHANCE ANY AREAS OF FOG THAT
HAVE ALREADY DEVELOPED. IT IS POSSIBLE PATCHY DENSE FOG MAY
DEVELOP...ALTHOUGH WINDS MAY BE JUST STRONG ENOUGH TO LIMIT THE
COVERAGE AND INTENSITY OF THE FOG. A SURFACE LOW PRESSURE SYSTEM
WILL BE LIFTING NORTH ACROSS EASTERN IOWA INTO CENTRAL WISCONSIN
THIS EVENING. THE GRADIENT WILL TIGHTEN ACROSS THE
CENTRAL/SOUTHERN PORTIONS OF THE LAKE...WHICH WITH WARMER
NEARSHORE WATERS EXPECT SOME SLIGHTLY BETTER MIXING TO OCCUR.
FURTHER OUT ACROSS THE OPEN WATERS THE WATER REMAINS COLD AND
EXPECT THE STABILITY TO MAKE IT DIFFICULT TO MIX TO THE SFC THE
HIGHER GUSTS. HIGH PRESSURE THEN ARRIVES LATE WEDNESDAY WITH LIGHT
WINDS DEVELOPING. THEN HIGH PRESSURE SHIFTS EAST THURSDAY
NIGHT...WITH SOUTHERLY WINDS DEVELOPING AGAIN FRIDAY. A FRONTAL
BOUNDARY WILL APPROACH LAKE MICHIGAN LATE FRIDAY NIGHT THEN
STEADILY SLIDE SOUTH ALONG THE LAKE. THIS WILL ALLOW WINDS TO
QUICKLY VEER FROM SOUTH TO NORTH/NORTHEAST SATURDAY. ALONG WITH
THIS QUICK WIND SHIFT WILL BE COOLER AIR SLIDING SOUTH OVER THE
LAKE. WAVES SHOULD EASILY BUILD SATURDAY FOR THE CENTRAL/SOUTHERN
PORTIONS OF THE LAKE.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 260856
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
356 AM CDT TUE MAY 26 2015

.SHORT TERM...
319 AM CDT

THROUGH TUESDAY NIGHT...

FOR THE REMAINDER OF THE OVERNIGHT HOURS...CONDITIONS WILL REMAIN
QUIET ACROSS THE CWA AS A SERIES OF SHORT WAVES CONTINUE TO TRACK
NORTH AROUND THE TOP OF A PERSISTENT UPPER LEVEL RIDGE WHICH EXTENDS
FROM THE SERN CONUS THROUGH THE UPPER MISSISSIPPI VALLEY.  THIS
UPPER RIDGE HAS BEEN THE FEATURE WHICH HAS CONTROLLED THE PATH OF
THE SERIES OF SHORTWAVES LIFTING OUT OF THE SOUTHERN PLAINS...AND
WILL CONTINUE TO DO SO THROUGH THE DAY TODAY. SLY...MODERATELY
STRONG...WINDS WILL PERSIST THROUGH THE NIGHT...AND MUCH OF THE DAY
ALLOWING FOR SFC DEWPOINTS TO REMAIN CONSISTENT OR POSSIBLE INCH A
LITTLE HIGHER.

MAIN CONCERN FOR THE MORNING HOURS WILL BE THE TRACK OF A STRONG
SHORT WAVE AND ASSOCIATED SFC LOW LIFTING NORTHWARD THROUGH THE
MIDDLE MISSISSIPPI VALLEY.  THIS FEATURE WILL PREDOMINANTLY IMPACT
ERN IOWA AND WRN IL BY ARND DAYBREAK.  THROUGH THE MORNING...THE
COMBINATION OF ISENTROPIC LIFT IN THE WARM SECTOR OF THE
SYSTEM...ALL OF IL AND INTO NWRN IN...WILL LEAD TO SOME
DESTABILIZATION ACROSS THE REGION. A SFC TROUGH...AS WELL INDICATED
BY THE LATEST HIGH RES GUIDANCE...WITH LIFT THROUGH NRN IL/IN
THROUGH THE DAY...COINCIDENT WITH A STRONG SSWLY LOW LEVEL JET OF 45-
50 KT...WITH PROVIDE THE POTENTIAL FOR SHOWERS AND STRONG TO SEVERE
THUNDERSTORMS ACROSS THE CWA.  BASED ON WIND PROFILES AND MID LEVEL
DRYING...THE PRIMARY CONCERN WITH REGARD TO SEVERE WEATHER WILL BE
STRONG WIND GUSTS.  HOWEVER...SOME OF THE HIGH RES SFC WIND GUIDANCE
SUGGEST SOME SLIGHT BACKING OF SFC WINDS FROM 180-190 DEGREES TO 160-
170 DEGREES...WHILE WINDS ALOFT REMAIN SWLY.  THIS SLIGHT BACKING OF
THE SFC WINDS COULD PROVIDE ENOUGH DIRECTIONAL SHEAR THROUGH THE
LOWER LEVELS TO BRING AN ISOLD TORNADO THREAT. LOCALLY HEAVY
RAINFALL WILL ALSO BE CONCERNED WITH PWATS REACHING 1.75 INCHES
LATER THIS MORNING.  HOWEVER...FLOODING WILL LIKELY NOT BE A
SIGNIFICANT CONCERN AS THE SWLY WINDS RIGHT OFF THE DECK WILL RANGE
FROM ARND 45 KT ABOVE THE BOUNDARY LAYER TO ARND 90KT AT UPPER
LEVELS WHICH SHOULD ALLOW ANY OF THE STRONGER STORMS THAT DO DEVELOP
TO MOVE QUICKLY.

BY EARLY AFTERNOON...THE MAIN SHORT WAVE WILL LIFT INTO WISCONSIN
WHILE A SFC TROUGH TRACKS EAST ACROSS THE AREA.  THIS WILL LEAD TO
WINDS AT THE SFC VEERING TO SWLY...SETTING UP A UNIDIRECTIONAL WIND
PROFILE...EFFECTIVELY MINIMIZING THE SEVERE WEATHER THREAT TO THE
REGION.  BY LATE AFTERNOON AND INTO THE EVENING THE MODELS ARE
ADVERTISING THAT A DRY SLOW SHOULD NOSE INTO NRN IL...EFFECTIVELY
CUTTING OFF THE PCPN AREA INTO 2 SEPARATE AREA...ONE OVER WISCONSIN
AND ERN IOWA AND ANOTHER MORE FOCUSED OVER INDIANA.  THE NWRN
INDIANA COUNTIES WILL STILL HAVE A CHANCE FOR SOME SHOWERS AND
THUNDERSTORMS INTO THE EVENING...WHILE PCPN CHANCES OVER NRN IL
BEGIN TO WANE.  MUCH OF THE MODEL GUIDANCE ALSO INDICATED THAT THE
SHORTWAVE SHOULD SLOW IT`S PROGRESSION THROUGH WISCONSIN AS IT
APPROACHES THE APEX OF THE UPPER RIDGE.  AN ASSOCIATED SFC
TROUGH/COLD FRONT EXTENDING SOUTHWEST FROM THE SFC LOW WILL LINGER
OVER ERN IOWA IN THE EARLY EVENING BEFORE STEADILY PUSHING ACROSS
NRN IL AND INTO NWRN IN OVERNIGHT.  THROUGH THE NIGHT...THE
STRONGEST UPPER LEVEL FORCING WILL BE WELL NORTH OF THE CWA...SO ANY
LINGERING CHANCES FOR PCPN OVERNIGHT WILL BE LOW AND LIKELY CONFINED
TO THE NRN TIER COUNTIES OF IL...ALONG THE WI BORDER.

KREIN

&&

.LONG TERM...
229 AM CDT

WEDNESDAY THROUGH MONDAY...

WEDNESDAY THROUGH THURSDAY...
OPEN 500MB WAVE WILL BE LIFTING NORTHEAST ACROSS THE UPPER MIDWEST
INTO ONTARIO AND EVENTUALLY QUEBEC...WITH HEIGHTS SLOWLY INCREASING
WED AFTN. SFC FEATURES REMAIN DISORGANIZED WED...WITH A BOUNDARY
SLOWLY SHIFTING EAST. OPER GUIDANCE DIFFERS ON HOW QUICKLY PRECIP
WILL DEPART THE REGION. ENSEMBLE DATA SUGGESTS HOLDING ONTO CHC TO
SLIGHT CHC POPS MAINLY FOR THE CENTRAL/EASTERN CWFA WED/WED EVE.
ALTHOUGH WITH SOME HINT OF SFC HEIGHTS NUDGING UP...IT IS POSSIBLE
THAT SOME DRY AIR COULD FILTER IN AND KICK PRECIP EAST BY MIDDAY AND
ALLOW FOR A MAINLY DRY WED. SFC WINDS WILL BE TURNING SOUTHWEST TO
WEST...KEEPING AN OFFSHORE FLOW FOR LOCATIONS CLOSE TO LAKE
MICHIGAN. TEMPS SHOULD YET AGAIN TOUCH UPR 70S TO ARND 80 WED...IF
CLOUDS AND PRECIP CAN PUSH EAST BY MIDDAY...SOME CLEARING WOULD
ALLOW SFC TEMPS TO PUSH A COUPLE DEGREES WARMER INTO THE LOW 80S IN
SOME LOCATIONS. LATE IN THE EVENING THE GRADIENT SLACKENS
FURTHER...AND COULD ALLOW A LATE DAY ONSHORE FLOW TO DEVELOP FOR
AREAS ADJACENT TO LAKE MICHIGAN.

MID-LVL FLOW BEGINS TO FLATTEN AS A WEAK SFC RIDGE BECOMES ORIENTED
FROM WESTERN QUEBEC SOUTH THROUGH THE EASTERN OHIO RIVER VALLEY.
THIS WILL GENERALLY ALLOW A SOUTHERLY FLOW...ALTHOUGH THE GRADIENT
IS NOT VERY STRONG. THIS SHOULD SET THE STAGE FOR A LAKE
BREEZE/ONSHORE FLOW TO DEVELOP THUR. TIMING COULD END UP BEING
SLIGHTLY EARLIER GIVEN THE LIGHT SFC GRADIENT. GUIDANCE HAS BEEN
CONSISTENT IN HOLDING PRECIP WEST/SOUTH OF THE FORECAST AREA
THUR...AS A RESULT OF THE WEAK SFC RIDGING. SO ONE MORE MILD DAY
WITH HIGHS WARMING BACK INTO THE UPR 70S/LOW 80S...HOWEVER AS
PREVIOUSLY NOTED...A LAKE BREEZE IS LIKELY TO DEVELOP. THIS WILL
BLEED THE MUCH COOLER MARINE AIR WEST ACROSS NORTHEAST IL AND
DOWNTOWN CHICAGO. IF THE TIMING IS EARLIER IN THE DAY THUR...TEMPS
MAY NOT WARM BEYONG THE LOW/MID 60S ALONG THE CHICAGO LAKEFRONT.

FLOW THEN TURNS SOUTHERLY THUR NIGHT WITH THE MORE PROGRESSIVE FLOW
IN THE MID-LVLS PUSHING THE RIDGING EAST. A RETURN FLOW MOISTURE
WILL CONTINUE TO BE FOCUSED ACROSS THE CENTRAL CONUS THUR EVE...WITH
A SLOW MOVING FRONTAL BOUNDARY NUDGING EAST THUR NIGHT TOWARDS
WESTERN IL. THIS FRONTAL BOUNDARY WILL BECOME ENERGIZED AS A ROBUST
500MB VORT MAX BREAKS SOUTH FROM CENTRAL CANADA LATE THUR NIGHT.

THIS SHOULD ALLOW FOR AN ATMOSPHERIC RIVER TO DEVELOP FROM THE
SOUTHERN PLAINS STRETCHING NORTH THROUGH THE MID-MISSOURI VALLEY
INTO THE WESTERN GREAT LAKES EARLY FRI MORNING.

FRIDAY THROUGH EARLY NEXT WEEK...
ENSEMBLES CONTINUE TO PROG A ROBUST TROUGH SLIDING SOUTH FROM
CENTRAL CANADA FRI. THIS COUPLED WITH DOWNSTREAM MID-LVL RIDGING
ACROSS THE SOUTHEAST CONUS WILL STRENGTHEN THE FRONTAL BOUNDARY
THAT WILL BE ORIENTED FROM THE SOUTHERN PLAINS STRETCHING
NORTHEAST THROUGH THE GREAT LAKES REGION INTO WESTERN QUEBEC.

THIS SETUP IS IDEAL FOR THE DEVELOPMENT OF AN ATMOSPHERIC RIVER WITH
ABUNDANT LOW LEVEL MOISTURE AND EFFICIENT PRECIP PRODUCING
CONVECTION.

OPER GUIDANCE HAS BEEN RELATIVELY CONSISTENT WITH BRINGING A SERIES
OF WAVES ALONG THE SLOW MOVING FRONTAL BOUNDARY FRI AFTN/EVE...THEN
THE BOUNDARY SHOULD SLIDE EAST WITH WINDS QUICKLY VEERING
NORTH/NORTHEAST FOR SAT AND USHERING IN MUCH COOLER AIR TO THE
REGION.

CURRENT INDICATIONS ARE THAT HIGHS SAT MAY STRUGGLE TO WARM BEYOND
THE UPR 50S ACROSS NORTHEAST IL/NORTHWEST IN...WITH ONLY LOW 60S
ELSEWHERE. STRONG SFC RIDGE WILL REMAIN NORTH OF THE REGION...SO THE
PRIOR FRONTAL BOUNDARY MAY BECOME QUASI-STATIONARY FOR THE WEEKEND
ALONG THE OHIO VALLEY AND CONTINUE TO FEED PRECIP CHANCES TO THE
SOUTHERN CWFA.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 09Z...

* SOUTH-SOUTHWEST WINDS OF AROUND 40 KT AT 1000 FT
  OVERNIGHT...SETTING UP THE POTENTIAL FOR LOW LEVEL WIND SHEAR.

* MVFR CEILINGS PROBABLE AT TIMES TUESDAY WITH A CHANCE FOR
  TEMPORARY IFR.

* PERIODS OF SHRA WITH PERIODIC TSRA FROM LATE TUESDAY MORNING
  THROUGH THE AFTERNOON.

* NEAR DUE SOUTH WINDS ON TUESDAY WITH PERIODIC GUSTS POSSIBLE
  AND SOME VARIABILITY BETWEEN SOUTHEAST AND SOUTHWEST.

KREIN

//DISCUSSION...UPDATED 06Z...

GUSTY SOUTH-SOUTHWEST WINDS HAVE DIMINISHED TO 10 KT OR LESS AND
BECOME SOUTHERLY. A LOW-LEVEL JET WILL DEVELOP OVERHEAD WITH
SSWLY-SWLY WINDS OF 40 KT TO 45 KT FLOW AT 1500-2000 FT UNTIL
ARND 12Z. SOME THUNDERSTORMS MAY DEVELOP THROUGH OVERNIGHT AHEAD
OF A FRONT FROM NRN MO THROUGH ERN IA AND INTO WI. THESE STORMS
WILL ONLY MAKE SLOW PROGRESS EASTWARD DUE TO THE STRONG SSWLY-SWLY
WINDS ALOFT SO...AND STORMS THAT DO DEVELOP SHOULD REMAIN NORTH
AND NORTHWEST OF AREA TAF SITES...THOUGH THERE IS A CHANCE THAT A
FEW STORMS COULD APPROACH THE RFD TERMINAL AREA VERY LATE
TONIGHT.

AS AN MID LEVEL DISTURBANCE MOVING FROM THE SOUTHERN PLAINS TO
NRN IL BY TUESDAY AFTERNOON MAY BRING ANOTHER ROUND OF SHOWERS
WITH SCT EMBEDDED THUNDERSTORMS TO THE REGION. UPPER LEVEL FORCING
FROM THE MID LEVEL DISTURBANCE AND AN UPPER LEVEL JET STREAM WILL
ENHANCE THE LIKELIHOOD FOR SHRA AND THE CHANCE FOR TSRA...WITH THE
MOST LIKELY CHANCE FOR ACTIVITY FROM 15Z THROUGH 02Z. SOME
UNCERTAINTY REMAINS IN PINNING DOWN THE EXACT PERIOD FOR THE
TSRA...SO WILL MAINTAIN THE GOING TEMPO FOR LATE MORNING THROUGH
EARLY AFTERNOON. HOWEVER...THE PCPN ACTIVITY COULD BE SHIFTED OR
EXPANDED IN TIME.

WINDS WILL BE SOUTHERLY ON TUESDAY...THOUGH DIRECTION MAY BE A BIT
VARIABLE AROUND CONVECTIVE ACTIVITY...THOUGH A GENERALLY SOUTHERLY
DIRECTION SHOULD PREVAIL THROUGH THE NIGHT AND MUCH OF THE DAY
TUESDAY. SOME GUSTINESS IS POSSIBLE THROUGH THE ENTIRE DAY...WITH
THE LATEST GUIDANCE SUGGESTING THAT WINDS COULD STRENGTHEN AND
BECOME EVEN MORE GUSTY THROUGH THE NIGHT TOMORROW NIGHT WITH WINDS
VEERING SWLY AS SURFACE LOW PRESSURE MOVES NORTHEAST ACROSS
SOUTHERN WISCONSIN.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 09Z...

* HIGH CONFIDENCE IN 40-45 KT SSWLY-SWLY FLOW ALOFT OVERNIGHT...BUT
  MEDIUM IN TRUE LLWS OCCURRING.

* HIGH CONFIDENCE IN WIND TRENDS OVERNIGHT AND TUESDAY MORNING.
  MEDIUM IN WIND TRENDS TOMORROW EVENING.

* MEDIUM CONFIDENCE IN MVFR CIGS TUESDAY MORNING WITH LOWER
  CONFIDENCE IN DURATION AND HOW LOW CIGS WILL DROP.

* HIGH CONFIDENCE IN SHOWERS AND AT LEAST A PERIOD OF TSRA. LOW
  CONFIDENCE IN SPECIFIC TSRA TIMING AND IMPACT ON THE TERMINALS
  WITH MULTIPLE ROUNDS POSSIBLE BETWEEN 15Z AND 02Z.

KREIN

//OUTLOOK FOR ORD/MDW FOR 12Z WEDNESDAY-12Z MONDAY...UPDATED 00Z...

WEDNESDAY...CHANCE OF TSRA. WEST WINDS.
THURSDAY...SLIGHT CHANCE OF TSRA LATE AT NIGHT. SOUTHEAST WINDS.
FRIDAY...INCREASING CHANCE OF TSRA THROUGH THE DAY AND NIGHT.
         SOUTHWEST WINDS.
SATURDAY...SHRA LIKELY WITH A CHANCE OF TSRA. NORTHEAST WINDS.
SUNDAY...CHANCE OF SHRA. EAST WINDS.

MTF

&&

.MARINE...
229 AM CDT

WARM MOIST AIR CONTINUES TO FEED NORTH ACROSS THE LAKE
TODAY...WHICH MAY HELP TO FURTHER ENHANCE ANY AREAS OF FOG THAT
HAVE ALREADY DEVELOPED. IT IS POSSIBLE PATCHY DENSE FOG MAY
DEVELOP...ALTHOUGH WINDS MAY BE JUST STRONG ENOUGH TO LIMIT THE
COVERAGE AND INTENSITY OF THE FOG. A SURFACE LOW PRESSURE SYSTEM
WILL BE LIFTING NORTH ACROSS EASTERN IOWA INTO CENTRAL WISCONSIN
THIS EVENING. THE GRADIENT WILL TIGHTEN ACROSS THE
CENTRAL/SOUTHERN PORTIONS OF THE LAKE...WHICH WITH WARMER
NEARSHORE WATERS EXPECT SOME SLIGHTLY BETTER MIXING TO OCCUR.
FURTHER OUT ACROSS THE OPEN WATERS THE WATER REMAINS COLD AND
EXPECT THE STABILITY TO MAKE IT DIFFICULT TO MIX TO THE SFC THE
HIGHER GUSTS. HIGH PRESSURE THEN ARRIVES LATE WEDNESDAY WITH LIGHT
WINDS DEVELOPING. THEN HIGH PRESSURE SHIFTS EAST THURSDAY
NIGHT...WITH SOUTHERLY WINDS DEVELOPING AGAIN FRIDAY. A FRONTAL
BOUNDARY WILL APPROACH LAKE MICHIGAN LATE FRIDAY NIGHT THEN
STEADILY SLIDE SOUTH ALONG THE LAKE. THIS WILL ALLOW WINDS TO
QUICKLY VEER FROM SOUTH TO NORTH/NORTHEAST SATURDAY. ALONG WITH
THIS QUICK WIND SHIFT WILL BE COOLER AIR SLIDING SOUTH OVER THE
LAKE. WAVES SHOULD EASILY BUILD SATURDAY FOR THE CENTRAL/SOUTHERN
PORTIONS OF THE LAKE.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 260856
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
356 AM CDT TUE MAY 26 2015

.SHORT TERM...
319 AM CDT

THROUGH TUESDAY NIGHT...

FOR THE REMAINDER OF THE OVERNIGHT HOURS...CONDITIONS WILL REMAIN
QUIET ACROSS THE CWA AS A SERIES OF SHORT WAVES CONTINUE TO TRACK
NORTH AROUND THE TOP OF A PERSISTENT UPPER LEVEL RIDGE WHICH EXTENDS
FROM THE SERN CONUS THROUGH THE UPPER MISSISSIPPI VALLEY.  THIS
UPPER RIDGE HAS BEEN THE FEATURE WHICH HAS CONTROLLED THE PATH OF
THE SERIES OF SHORTWAVES LIFTING OUT OF THE SOUTHERN PLAINS...AND
WILL CONTINUE TO DO SO THROUGH THE DAY TODAY. SLY...MODERATELY
STRONG...WINDS WILL PERSIST THROUGH THE NIGHT...AND MUCH OF THE DAY
ALLOWING FOR SFC DEWPOINTS TO REMAIN CONSISTENT OR POSSIBLE INCH A
LITTLE HIGHER.

MAIN CONCERN FOR THE MORNING HOURS WILL BE THE TRACK OF A STRONG
SHORT WAVE AND ASSOCIATED SFC LOW LIFTING NORTHWARD THROUGH THE
MIDDLE MISSISSIPPI VALLEY.  THIS FEATURE WILL PREDOMINANTLY IMPACT
ERN IOWA AND WRN IL BY ARND DAYBREAK.  THROUGH THE MORNING...THE
COMBINATION OF ISENTROPIC LIFT IN THE WARM SECTOR OF THE
SYSTEM...ALL OF IL AND INTO NWRN IN...WILL LEAD TO SOME
DESTABILIZATION ACROSS THE REGION. A SFC TROUGH...AS WELL INDICATED
BY THE LATEST HIGH RES GUIDANCE...WITH LIFT THROUGH NRN IL/IN
THROUGH THE DAY...COINCIDENT WITH A STRONG SSWLY LOW LEVEL JET OF 45-
50 KT...WITH PROVIDE THE POTENTIAL FOR SHOWERS AND STRONG TO SEVERE
THUNDERSTORMS ACROSS THE CWA.  BASED ON WIND PROFILES AND MID LEVEL
DRYING...THE PRIMARY CONCERN WITH REGARD TO SEVERE WEATHER WILL BE
STRONG WIND GUSTS.  HOWEVER...SOME OF THE HIGH RES SFC WIND GUIDANCE
SUGGEST SOME SLIGHT BACKING OF SFC WINDS FROM 180-190 DEGREES TO 160-
170 DEGREES...WHILE WINDS ALOFT REMAIN SWLY.  THIS SLIGHT BACKING OF
THE SFC WINDS COULD PROVIDE ENOUGH DIRECTIONAL SHEAR THROUGH THE
LOWER LEVELS TO BRING AN ISOLD TORNADO THREAT. LOCALLY HEAVY
RAINFALL WILL ALSO BE CONCERNED WITH PWATS REACHING 1.75 INCHES
LATER THIS MORNING.  HOWEVER...FLOODING WILL LIKELY NOT BE A
SIGNIFICANT CONCERN AS THE SWLY WINDS RIGHT OFF THE DECK WILL RANGE
FROM ARND 45 KT ABOVE THE BOUNDARY LAYER TO ARND 90KT AT UPPER
LEVELS WHICH SHOULD ALLOW ANY OF THE STRONGER STORMS THAT DO DEVELOP
TO MOVE QUICKLY.

BY EARLY AFTERNOON...THE MAIN SHORT WAVE WILL LIFT INTO WISCONSIN
WHILE A SFC TROUGH TRACKS EAST ACROSS THE AREA.  THIS WILL LEAD TO
WINDS AT THE SFC VEERING TO SWLY...SETTING UP A UNIDIRECTIONAL WIND
PROFILE...EFFECTIVELY MINIMIZING THE SEVERE WEATHER THREAT TO THE
REGION.  BY LATE AFTERNOON AND INTO THE EVENING THE MODELS ARE
ADVERTISING THAT A DRY SLOW SHOULD NOSE INTO NRN IL...EFFECTIVELY
CUTTING OFF THE PCPN AREA INTO 2 SEPARATE AREA...ONE OVER WISCONSIN
AND ERN IOWA AND ANOTHER MORE FOCUSED OVER INDIANA.  THE NWRN
INDIANA COUNTIES WILL STILL HAVE A CHANCE FOR SOME SHOWERS AND
THUNDERSTORMS INTO THE EVENING...WHILE PCPN CHANCES OVER NRN IL
BEGIN TO WANE.  MUCH OF THE MODEL GUIDANCE ALSO INDICATED THAT THE
SHORTWAVE SHOULD SLOW IT`S PROGRESSION THROUGH WISCONSIN AS IT
APPROACHES THE APEX OF THE UPPER RIDGE.  AN ASSOCIATED SFC
TROUGH/COLD FRONT EXTENDING SOUTHWEST FROM THE SFC LOW WILL LINGER
OVER ERN IOWA IN THE EARLY EVENING BEFORE STEADILY PUSHING ACROSS
NRN IL AND INTO NWRN IN OVERNIGHT.  THROUGH THE NIGHT...THE
STRONGEST UPPER LEVEL FORCING WILL BE WELL NORTH OF THE CWA...SO ANY
LINGERING CHANCES FOR PCPN OVERNIGHT WILL BE LOW AND LIKELY CONFINED
TO THE NRN TIER COUNTIES OF IL...ALONG THE WI BORDER.

KREIN

&&

.LONG TERM...
229 AM CDT

WEDNESDAY THROUGH MONDAY...

WEDNESDAY THROUGH THURSDAY...
OPEN 500MB WAVE WILL BE LIFTING NORTHEAST ACROSS THE UPPER MIDWEST
INTO ONTARIO AND EVENTUALLY QUEBEC...WITH HEIGHTS SLOWLY INCREASING
WED AFTN. SFC FEATURES REMAIN DISORGANIZED WED...WITH A BOUNDARY
SLOWLY SHIFTING EAST. OPER GUIDANCE DIFFERS ON HOW QUICKLY PRECIP
WILL DEPART THE REGION. ENSEMBLE DATA SUGGESTS HOLDING ONTO CHC TO
SLIGHT CHC POPS MAINLY FOR THE CENTRAL/EASTERN CWFA WED/WED EVE.
ALTHOUGH WITH SOME HINT OF SFC HEIGHTS NUDGING UP...IT IS POSSIBLE
THAT SOME DRY AIR COULD FILTER IN AND KICK PRECIP EAST BY MIDDAY AND
ALLOW FOR A MAINLY DRY WED. SFC WINDS WILL BE TURNING SOUTHWEST TO
WEST...KEEPING AN OFFSHORE FLOW FOR LOCATIONS CLOSE TO LAKE
MICHIGAN. TEMPS SHOULD YET AGAIN TOUCH UPR 70S TO ARND 80 WED...IF
CLOUDS AND PRECIP CAN PUSH EAST BY MIDDAY...SOME CLEARING WOULD
ALLOW SFC TEMPS TO PUSH A COUPLE DEGREES WARMER INTO THE LOW 80S IN
SOME LOCATIONS. LATE IN THE EVENING THE GRADIENT SLACKENS
FURTHER...AND COULD ALLOW A LATE DAY ONSHORE FLOW TO DEVELOP FOR
AREAS ADJACENT TO LAKE MICHIGAN.

MID-LVL FLOW BEGINS TO FLATTEN AS A WEAK SFC RIDGE BECOMES ORIENTED
FROM WESTERN QUEBEC SOUTH THROUGH THE EASTERN OHIO RIVER VALLEY.
THIS WILL GENERALLY ALLOW A SOUTHERLY FLOW...ALTHOUGH THE GRADIENT
IS NOT VERY STRONG. THIS SHOULD SET THE STAGE FOR A LAKE
BREEZE/ONSHORE FLOW TO DEVELOP THUR. TIMING COULD END UP BEING
SLIGHTLY EARLIER GIVEN THE LIGHT SFC GRADIENT. GUIDANCE HAS BEEN
CONSISTENT IN HOLDING PRECIP WEST/SOUTH OF THE FORECAST AREA
THUR...AS A RESULT OF THE WEAK SFC RIDGING. SO ONE MORE MILD DAY
WITH HIGHS WARMING BACK INTO THE UPR 70S/LOW 80S...HOWEVER AS
PREVIOUSLY NOTED...A LAKE BREEZE IS LIKELY TO DEVELOP. THIS WILL
BLEED THE MUCH COOLER MARINE AIR WEST ACROSS NORTHEAST IL AND
DOWNTOWN CHICAGO. IF THE TIMING IS EARLIER IN THE DAY THUR...TEMPS
MAY NOT WARM BEYONG THE LOW/MID 60S ALONG THE CHICAGO LAKEFRONT.

FLOW THEN TURNS SOUTHERLY THUR NIGHT WITH THE MORE PROGRESSIVE FLOW
IN THE MID-LVLS PUSHING THE RIDGING EAST. A RETURN FLOW MOISTURE
WILL CONTINUE TO BE FOCUSED ACROSS THE CENTRAL CONUS THUR EVE...WITH
A SLOW MOVING FRONTAL BOUNDARY NUDGING EAST THUR NIGHT TOWARDS
WESTERN IL. THIS FRONTAL BOUNDARY WILL BECOME ENERGIZED AS A ROBUST
500MB VORT MAX BREAKS SOUTH FROM CENTRAL CANADA LATE THUR NIGHT.

THIS SHOULD ALLOW FOR AN ATMOSPHERIC RIVER TO DEVELOP FROM THE
SOUTHERN PLAINS STRETCHING NORTH THROUGH THE MID-MISSOURI VALLEY
INTO THE WESTERN GREAT LAKES EARLY FRI MORNING.

FRIDAY THROUGH EARLY NEXT WEEK...
ENSEMBLES CONTINUE TO PROG A ROBUST TROUGH SLIDING SOUTH FROM
CENTRAL CANADA FRI. THIS COUPLED WITH DOWNSTREAM MID-LVL RIDGING
ACROSS THE SOUTHEAST CONUS WILL STRENGTHEN THE FRONTAL BOUNDARY
THAT WILL BE ORIENTED FROM THE SOUTHERN PLAINS STRETCHING
NORTHEAST THROUGH THE GREAT LAKES REGION INTO WESTERN QUEBEC.

THIS SETUP IS IDEAL FOR THE DEVELOPMENT OF AN ATMOSPHERIC RIVER WITH
ABUNDANT LOW LEVEL MOISTURE AND EFFICIENT PRECIP PRODUCING
CONVECTION.

OPER GUIDANCE HAS BEEN RELATIVELY CONSISTENT WITH BRINGING A SERIES
OF WAVES ALONG THE SLOW MOVING FRONTAL BOUNDARY FRI AFTN/EVE...THEN
THE BOUNDARY SHOULD SLIDE EAST WITH WINDS QUICKLY VEERING
NORTH/NORTHEAST FOR SAT AND USHERING IN MUCH COOLER AIR TO THE
REGION.

CURRENT INDICATIONS ARE THAT HIGHS SAT MAY STRUGGLE TO WARM BEYOND
THE UPR 50S ACROSS NORTHEAST IL/NORTHWEST IN...WITH ONLY LOW 60S
ELSEWHERE. STRONG SFC RIDGE WILL REMAIN NORTH OF THE REGION...SO THE
PRIOR FRONTAL BOUNDARY MAY BECOME QUASI-STATIONARY FOR THE WEEKEND
ALONG THE OHIO VALLEY AND CONTINUE TO FEED PRECIP CHANCES TO THE
SOUTHERN CWFA.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 09Z...

* SOUTH-SOUTHWEST WINDS OF AROUND 40 KT AT 1000 FT
  OVERNIGHT...SETTING UP THE POTENTIAL FOR LOW LEVEL WIND SHEAR.

* MVFR CEILINGS PROBABLE AT TIMES TUESDAY WITH A CHANCE FOR
  TEMPORARY IFR.

* PERIODS OF SHRA WITH PERIODIC TSRA FROM LATE TUESDAY MORNING
  THROUGH THE AFTERNOON.

* NEAR DUE SOUTH WINDS ON TUESDAY WITH PERIODIC GUSTS POSSIBLE
  AND SOME VARIABILITY BETWEEN SOUTHEAST AND SOUTHWEST.

KREIN

//DISCUSSION...UPDATED 06Z...

GUSTY SOUTH-SOUTHWEST WINDS HAVE DIMINISHED TO 10 KT OR LESS AND
BECOME SOUTHERLY. A LOW-LEVEL JET WILL DEVELOP OVERHEAD WITH
SSWLY-SWLY WINDS OF 40 KT TO 45 KT FLOW AT 1500-2000 FT UNTIL
ARND 12Z. SOME THUNDERSTORMS MAY DEVELOP THROUGH OVERNIGHT AHEAD
OF A FRONT FROM NRN MO THROUGH ERN IA AND INTO WI. THESE STORMS
WILL ONLY MAKE SLOW PROGRESS EASTWARD DUE TO THE STRONG SSWLY-SWLY
WINDS ALOFT SO...AND STORMS THAT DO DEVELOP SHOULD REMAIN NORTH
AND NORTHWEST OF AREA TAF SITES...THOUGH THERE IS A CHANCE THAT A
FEW STORMS COULD APPROACH THE RFD TERMINAL AREA VERY LATE
TONIGHT.

AS AN MID LEVEL DISTURBANCE MOVING FROM THE SOUTHERN PLAINS TO
NRN IL BY TUESDAY AFTERNOON MAY BRING ANOTHER ROUND OF SHOWERS
WITH SCT EMBEDDED THUNDERSTORMS TO THE REGION. UPPER LEVEL FORCING
FROM THE MID LEVEL DISTURBANCE AND AN UPPER LEVEL JET STREAM WILL
ENHANCE THE LIKELIHOOD FOR SHRA AND THE CHANCE FOR TSRA...WITH THE
MOST LIKELY CHANCE FOR ACTIVITY FROM 15Z THROUGH 02Z. SOME
UNCERTAINTY REMAINS IN PINNING DOWN THE EXACT PERIOD FOR THE
TSRA...SO WILL MAINTAIN THE GOING TEMPO FOR LATE MORNING THROUGH
EARLY AFTERNOON. HOWEVER...THE PCPN ACTIVITY COULD BE SHIFTED OR
EXPANDED IN TIME.

WINDS WILL BE SOUTHERLY ON TUESDAY...THOUGH DIRECTION MAY BE A BIT
VARIABLE AROUND CONVECTIVE ACTIVITY...THOUGH A GENERALLY SOUTHERLY
DIRECTION SHOULD PREVAIL THROUGH THE NIGHT AND MUCH OF THE DAY
TUESDAY. SOME GUSTINESS IS POSSIBLE THROUGH THE ENTIRE DAY...WITH
THE LATEST GUIDANCE SUGGESTING THAT WINDS COULD STRENGTHEN AND
BECOME EVEN MORE GUSTY THROUGH THE NIGHT TOMORROW NIGHT WITH WINDS
VEERING SWLY AS SURFACE LOW PRESSURE MOVES NORTHEAST ACROSS
SOUTHERN WISCONSIN.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 09Z...

* HIGH CONFIDENCE IN 40-45 KT SSWLY-SWLY FLOW ALOFT OVERNIGHT...BUT
  MEDIUM IN TRUE LLWS OCCURRING.

* HIGH CONFIDENCE IN WIND TRENDS OVERNIGHT AND TUESDAY MORNING.
  MEDIUM IN WIND TRENDS TOMORROW EVENING.

* MEDIUM CONFIDENCE IN MVFR CIGS TUESDAY MORNING WITH LOWER
  CONFIDENCE IN DURATION AND HOW LOW CIGS WILL DROP.

* HIGH CONFIDENCE IN SHOWERS AND AT LEAST A PERIOD OF TSRA. LOW
  CONFIDENCE IN SPECIFIC TSRA TIMING AND IMPACT ON THE TERMINALS
  WITH MULTIPLE ROUNDS POSSIBLE BETWEEN 15Z AND 02Z.

KREIN

//OUTLOOK FOR ORD/MDW FOR 12Z WEDNESDAY-12Z MONDAY...UPDATED 00Z...

WEDNESDAY...CHANCE OF TSRA. WEST WINDS.
THURSDAY...SLIGHT CHANCE OF TSRA LATE AT NIGHT. SOUTHEAST WINDS.
FRIDAY...INCREASING CHANCE OF TSRA THROUGH THE DAY AND NIGHT.
         SOUTHWEST WINDS.
SATURDAY...SHRA LIKELY WITH A CHANCE OF TSRA. NORTHEAST WINDS.
SUNDAY...CHANCE OF SHRA. EAST WINDS.

MTF

&&

.MARINE...
229 AM CDT

WARM MOIST AIR CONTINUES TO FEED NORTH ACROSS THE LAKE
TODAY...WHICH MAY HELP TO FURTHER ENHANCE ANY AREAS OF FOG THAT
HAVE ALREADY DEVELOPED. IT IS POSSIBLE PATCHY DENSE FOG MAY
DEVELOP...ALTHOUGH WINDS MAY BE JUST STRONG ENOUGH TO LIMIT THE
COVERAGE AND INTENSITY OF THE FOG. A SURFACE LOW PRESSURE SYSTEM
WILL BE LIFTING NORTH ACROSS EASTERN IOWA INTO CENTRAL WISCONSIN
THIS EVENING. THE GRADIENT WILL TIGHTEN ACROSS THE
CENTRAL/SOUTHERN PORTIONS OF THE LAKE...WHICH WITH WARMER
NEARSHORE WATERS EXPECT SOME SLIGHTLY BETTER MIXING TO OCCUR.
FURTHER OUT ACROSS THE OPEN WATERS THE WATER REMAINS COLD AND
EXPECT THE STABILITY TO MAKE IT DIFFICULT TO MIX TO THE SFC THE
HIGHER GUSTS. HIGH PRESSURE THEN ARRIVES LATE WEDNESDAY WITH LIGHT
WINDS DEVELOPING. THEN HIGH PRESSURE SHIFTS EAST THURSDAY
NIGHT...WITH SOUTHERLY WINDS DEVELOPING AGAIN FRIDAY. A FRONTAL
BOUNDARY WILL APPROACH LAKE MICHIGAN LATE FRIDAY NIGHT THEN
STEADILY SLIDE SOUTH ALONG THE LAKE. THIS WILL ALLOW WINDS TO
QUICKLY VEER FROM SOUTH TO NORTH/NORTHEAST SATURDAY. ALONG WITH
THIS QUICK WIND SHIFT WILL BE COOLER AIR SLIDING SOUTH OVER THE
LAKE. WAVES SHOULD EASILY BUILD SATURDAY FOR THE CENTRAL/SOUTHERN
PORTIONS OF THE LAKE.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
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WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KILX 260843
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
343 AM CDT TUE MAY 26 2015

.SHORT TERM...(TODAY)
ISSUED AT 343 AM CDT TUE MAY 26 2015

LOW CLOUDS HAVE BEEN ADVECTING INTO THE AREA AND WILL REMAIN OVER
THE AREA THIS MORNING. LOWER CLOUDS INDICATING LOTS OF LOW LEVEL
MOISTURE BEING ADVECTED INTO THE AREA AHEAD OF THE WEATHER SYSTEM
THAT STILL IS WEST OF THE CWA. RADAR AND SATELLITE LOOPS SHOW
SEVERAL MCVS WEST OF THE AREA WITH SOME SHOWERS MOVING NORTH THROUGH
SOUTHEASTERN MO. MODELS CONTINUE TO INDICATE PCPN REDEVELOPING
TODAY. CLOUDS WILL LIMIT THE DEGREE OF INSTABILITY BUT STILL
EXPECTING ENOUGH FOR THUNDERSTORMS, JUST NOT ENOUGH FOR ANYTHING
SEVERE, WHICH SHOULD BE EAST AND SOUTHEAST OF THE AREA WHERE LESS
CLOUDS WILL BE. CLOUD COVER WILL ALSO TEMPER WARM UP AS WELL SO ONLY
EXPECTING UPPER 70S FOR HIGHS WHICH IS MUCH LESS THAN PAST TWO DAYS.
POPS WILL BE A GRADUAL INCREASE TODAY REACHING LIKELY LATER THIS
MORNING AND THEN MOVING NORTH AND EAST THIS AFTERNOON, BECOMING
CHANCE CATEGORY BY LATE AFTERNOON AS THE PCPN MOVES EAST OF THE
AREA. SOUTHERLY WINDS WILL BE A TAD GUSTY AGAIN, JUST NOT AS MUCH AS
YESTERDAY.

&&

.LONG TERM...(TONIGHT THROUGH MONDAY)
ISSUED AT 343 AM CDT TUE MAY 26 2015

UNTIL THE UPPER WAVE PULLS INTO THE GREAT LAKES REGION, LINGERING
POPS WILL REMAIN OVER THE FA FOR THIS EVENING.  BETTER CHANCES WILL
REMAIN TO THE EAST OVERNIGHT. REMAINS OF THE FRONT WILL STALL OUT
ALONG THE OHIO RIVER VALLEY AND PROVIDE A BIT OF FOCUS FOR ANOTHER
PIECE OF ENERGY EJECTING OUT OF THE SOUTHWEST.  MODELS DIFFERING
WITH THE NORTHERLY EXTENT OF THE PRECIP, BUT LAST FEW RUNS BRINGING
IN SOME PRECIPITATION FOR WEDNESDAY IN THE SOUTHEAST.  NAM IS A
LITTLE MORE WIDESPREAD, BUT CONCENTRATING THE POPS TO THE SOUTH AND
EAST FOR NOW.  TIMING ISSUES REMAIN IN PLACE FOR THIS SYNOPTIC RUN
FOR THE NEXT SYSTEM QUICK ON THE HEELS AS THE DEEP WAVE OVER THE SW
STARTS TO MOVE OUT INTO THE PLAINS. CONVECTION AND PRECIP STARTS TO
SPREAD OVER THE EASTERN HALF OF THE COUNTRY IN THE MODELS WITH  WEAK
SOUTHWESTERLY FLOW ALOFT SHIFTING TO WEAK FLOW OVERALL.  WARM AND
MUGGY CONDITIONS CONTINUE IN A MORE SUMMERLIKE AIRMASS THROUGHOUT
THE WEEK...BUT THAT NEXT SYSTEM WILL BRING A COLD FRONT INTO THE
REGION FOR THE FIRST HALF OF THE WEEKEND TO FOCUS THE RAIN, WITH A
COOLER AIRMASS BEHIND IT DROPPING THE TEMPS FOR THE WEEKEND OUT OF
THE 80S FOR A COUPLE DAYS.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z TUESDAY NIGHT)
ISSUED AT 1151 PM CDT MON MAY 25 2015

VFR CONDITIONS IN SCATTERED HIGH CLOUD COVER WITH SOUTH WINDS
10-12 KTS THIS EVENING ACROSS CENTRAL IL. HIGH CLOUD ASSOCIATED
WITH A SHORTWAVE OVER NORTHEAST OKLAHOMA WILL CONTINUE MOVING INTO
THE REGION OVERNIGHT. CURRENT TIMING OF LIFT AND MOISTURE WITH
THE APPROACHING SHORTWAVE INDICATE PREDOMINANT MVFR CONDITIONS IN
SHRA/ISOLD TSRA LIKELY TO BEGIN 10-12Z. SOME LIFTING OF
PREDOMINANT CEILINGS LIKELY IN AFTERNOON WITH DAYTIME HEATING AND
ACCORDING TO MODEL TIME-HEIGHT SECTIONS SO HAVE INCLUDED VCTS
WITH CIGS ABOVE MVFR THRESHOLD. SHORTWAVE AXIS EXPECTED TO CROSS
LATE AFTERNOON/EARLY EVENING TUESDAY BRINGING A DECREASE IN
SHOWER/THUNDERSTORM ACTIVITY BY 00Z AND HAVE ENDED VCTS AND 4 KFT
AGL CIGS. WINDS CONTINUING S 10-12 KTS UNTIL 14Z...INCREASING TO
15-20 KTS WITH GUSTS 25-30KTS AND SHIFTING TOWARD SW. WINDS
DECREASING AFTER 00Z.


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...AUTEN
LONG TERM...HJS
AVIATION...ONTON




000
FXUS63 KILX 260843
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
343 AM CDT TUE MAY 26 2015

.SHORT TERM...(TODAY)
ISSUED AT 343 AM CDT TUE MAY 26 2015

LOW CLOUDS HAVE BEEN ADVECTING INTO THE AREA AND WILL REMAIN OVER
THE AREA THIS MORNING. LOWER CLOUDS INDICATING LOTS OF LOW LEVEL
MOISTURE BEING ADVECTED INTO THE AREA AHEAD OF THE WEATHER SYSTEM
THAT STILL IS WEST OF THE CWA. RADAR AND SATELLITE LOOPS SHOW
SEVERAL MCVS WEST OF THE AREA WITH SOME SHOWERS MOVING NORTH THROUGH
SOUTHEASTERN MO. MODELS CONTINUE TO INDICATE PCPN REDEVELOPING
TODAY. CLOUDS WILL LIMIT THE DEGREE OF INSTABILITY BUT STILL
EXPECTING ENOUGH FOR THUNDERSTORMS, JUST NOT ENOUGH FOR ANYTHING
SEVERE, WHICH SHOULD BE EAST AND SOUTHEAST OF THE AREA WHERE LESS
CLOUDS WILL BE. CLOUD COVER WILL ALSO TEMPER WARM UP AS WELL SO ONLY
EXPECTING UPPER 70S FOR HIGHS WHICH IS MUCH LESS THAN PAST TWO DAYS.
POPS WILL BE A GRADUAL INCREASE TODAY REACHING LIKELY LATER THIS
MORNING AND THEN MOVING NORTH AND EAST THIS AFTERNOON, BECOMING
CHANCE CATEGORY BY LATE AFTERNOON AS THE PCPN MOVES EAST OF THE
AREA. SOUTHERLY WINDS WILL BE A TAD GUSTY AGAIN, JUST NOT AS MUCH AS
YESTERDAY.

&&

.LONG TERM...(TONIGHT THROUGH MONDAY)
ISSUED AT 343 AM CDT TUE MAY 26 2015

UNTIL THE UPPER WAVE PULLS INTO THE GREAT LAKES REGION, LINGERING
POPS WILL REMAIN OVER THE FA FOR THIS EVENING.  BETTER CHANCES WILL
REMAIN TO THE EAST OVERNIGHT. REMAINS OF THE FRONT WILL STALL OUT
ALONG THE OHIO RIVER VALLEY AND PROVIDE A BIT OF FOCUS FOR ANOTHER
PIECE OF ENERGY EJECTING OUT OF THE SOUTHWEST.  MODELS DIFFERING
WITH THE NORTHERLY EXTENT OF THE PRECIP, BUT LAST FEW RUNS BRINGING
IN SOME PRECIPITATION FOR WEDNESDAY IN THE SOUTHEAST.  NAM IS A
LITTLE MORE WIDESPREAD, BUT CONCENTRATING THE POPS TO THE SOUTH AND
EAST FOR NOW.  TIMING ISSUES REMAIN IN PLACE FOR THIS SYNOPTIC RUN
FOR THE NEXT SYSTEM QUICK ON THE HEELS AS THE DEEP WAVE OVER THE SW
STARTS TO MOVE OUT INTO THE PLAINS. CONVECTION AND PRECIP STARTS TO
SPREAD OVER THE EASTERN HALF OF THE COUNTRY IN THE MODELS WITH  WEAK
SOUTHWESTERLY FLOW ALOFT SHIFTING TO WEAK FLOW OVERALL.  WARM AND
MUGGY CONDITIONS CONTINUE IN A MORE SUMMERLIKE AIRMASS THROUGHOUT
THE WEEK...BUT THAT NEXT SYSTEM WILL BRING A COLD FRONT INTO THE
REGION FOR THE FIRST HALF OF THE WEEKEND TO FOCUS THE RAIN, WITH A
COOLER AIRMASS BEHIND IT DROPPING THE TEMPS FOR THE WEEKEND OUT OF
THE 80S FOR A COUPLE DAYS.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z TUESDAY NIGHT)
ISSUED AT 1151 PM CDT MON MAY 25 2015

VFR CONDITIONS IN SCATTERED HIGH CLOUD COVER WITH SOUTH WINDS
10-12 KTS THIS EVENING ACROSS CENTRAL IL. HIGH CLOUD ASSOCIATED
WITH A SHORTWAVE OVER NORTHEAST OKLAHOMA WILL CONTINUE MOVING INTO
THE REGION OVERNIGHT. CURRENT TIMING OF LIFT AND MOISTURE WITH
THE APPROACHING SHORTWAVE INDICATE PREDOMINANT MVFR CONDITIONS IN
SHRA/ISOLD TSRA LIKELY TO BEGIN 10-12Z. SOME LIFTING OF
PREDOMINANT CEILINGS LIKELY IN AFTERNOON WITH DAYTIME HEATING AND
ACCORDING TO MODEL TIME-HEIGHT SECTIONS SO HAVE INCLUDED VCTS
WITH CIGS ABOVE MVFR THRESHOLD. SHORTWAVE AXIS EXPECTED TO CROSS
LATE AFTERNOON/EARLY EVENING TUESDAY BRINGING A DECREASE IN
SHOWER/THUNDERSTORM ACTIVITY BY 00Z AND HAVE ENDED VCTS AND 4 KFT
AGL CIGS. WINDS CONTINUING S 10-12 KTS UNTIL 14Z...INCREASING TO
15-20 KTS WITH GUSTS 25-30KTS AND SHIFTING TOWARD SW. WINDS
DECREASING AFTER 00Z.


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...AUTEN
LONG TERM...HJS
AVIATION...ONTON



000
FXUS63 KILX 260843
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
343 AM CDT TUE MAY 26 2015

.SHORT TERM...(TODAY)
ISSUED AT 343 AM CDT TUE MAY 26 2015

LOW CLOUDS HAVE BEEN ADVECTING INTO THE AREA AND WILL REMAIN OVER
THE AREA THIS MORNING. LOWER CLOUDS INDICATING LOTS OF LOW LEVEL
MOISTURE BEING ADVECTED INTO THE AREA AHEAD OF THE WEATHER SYSTEM
THAT STILL IS WEST OF THE CWA. RADAR AND SATELLITE LOOPS SHOW
SEVERAL MCVS WEST OF THE AREA WITH SOME SHOWERS MOVING NORTH THROUGH
SOUTHEASTERN MO. MODELS CONTINUE TO INDICATE PCPN REDEVELOPING
TODAY. CLOUDS WILL LIMIT THE DEGREE OF INSTABILITY BUT STILL
EXPECTING ENOUGH FOR THUNDERSTORMS, JUST NOT ENOUGH FOR ANYTHING
SEVERE, WHICH SHOULD BE EAST AND SOUTHEAST OF THE AREA WHERE LESS
CLOUDS WILL BE. CLOUD COVER WILL ALSO TEMPER WARM UP AS WELL SO ONLY
EXPECTING UPPER 70S FOR HIGHS WHICH IS MUCH LESS THAN PAST TWO DAYS.
POPS WILL BE A GRADUAL INCREASE TODAY REACHING LIKELY LATER THIS
MORNING AND THEN MOVING NORTH AND EAST THIS AFTERNOON, BECOMING
CHANCE CATEGORY BY LATE AFTERNOON AS THE PCPN MOVES EAST OF THE
AREA. SOUTHERLY WINDS WILL BE A TAD GUSTY AGAIN, JUST NOT AS MUCH AS
YESTERDAY.

&&

.LONG TERM...(TONIGHT THROUGH MONDAY)
ISSUED AT 343 AM CDT TUE MAY 26 2015

UNTIL THE UPPER WAVE PULLS INTO THE GREAT LAKES REGION, LINGERING
POPS WILL REMAIN OVER THE FA FOR THIS EVENING.  BETTER CHANCES WILL
REMAIN TO THE EAST OVERNIGHT. REMAINS OF THE FRONT WILL STALL OUT
ALONG THE OHIO RIVER VALLEY AND PROVIDE A BIT OF FOCUS FOR ANOTHER
PIECE OF ENERGY EJECTING OUT OF THE SOUTHWEST.  MODELS DIFFERING
WITH THE NORTHERLY EXTENT OF THE PRECIP, BUT LAST FEW RUNS BRINGING
IN SOME PRECIPITATION FOR WEDNESDAY IN THE SOUTHEAST.  NAM IS A
LITTLE MORE WIDESPREAD, BUT CONCENTRATING THE POPS TO THE SOUTH AND
EAST FOR NOW.  TIMING ISSUES REMAIN IN PLACE FOR THIS SYNOPTIC RUN
FOR THE NEXT SYSTEM QUICK ON THE HEELS AS THE DEEP WAVE OVER THE SW
STARTS TO MOVE OUT INTO THE PLAINS. CONVECTION AND PRECIP STARTS TO
SPREAD OVER THE EASTERN HALF OF THE COUNTRY IN THE MODELS WITH  WEAK
SOUTHWESTERLY FLOW ALOFT SHIFTING TO WEAK FLOW OVERALL.  WARM AND
MUGGY CONDITIONS CONTINUE IN A MORE SUMMERLIKE AIRMASS THROUGHOUT
THE WEEK...BUT THAT NEXT SYSTEM WILL BRING A COLD FRONT INTO THE
REGION FOR THE FIRST HALF OF THE WEEKEND TO FOCUS THE RAIN, WITH A
COOLER AIRMASS BEHIND IT DROPPING THE TEMPS FOR THE WEEKEND OUT OF
THE 80S FOR A COUPLE DAYS.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z TUESDAY NIGHT)
ISSUED AT 1151 PM CDT MON MAY 25 2015

VFR CONDITIONS IN SCATTERED HIGH CLOUD COVER WITH SOUTH WINDS
10-12 KTS THIS EVENING ACROSS CENTRAL IL. HIGH CLOUD ASSOCIATED
WITH A SHORTWAVE OVER NORTHEAST OKLAHOMA WILL CONTINUE MOVING INTO
THE REGION OVERNIGHT. CURRENT TIMING OF LIFT AND MOISTURE WITH
THE APPROACHING SHORTWAVE INDICATE PREDOMINANT MVFR CONDITIONS IN
SHRA/ISOLD TSRA LIKELY TO BEGIN 10-12Z. SOME LIFTING OF
PREDOMINANT CEILINGS LIKELY IN AFTERNOON WITH DAYTIME HEATING AND
ACCORDING TO MODEL TIME-HEIGHT SECTIONS SO HAVE INCLUDED VCTS
WITH CIGS ABOVE MVFR THRESHOLD. SHORTWAVE AXIS EXPECTED TO CROSS
LATE AFTERNOON/EARLY EVENING TUESDAY BRINGING A DECREASE IN
SHOWER/THUNDERSTORM ACTIVITY BY 00Z AND HAVE ENDED VCTS AND 4 KFT
AGL CIGS. WINDS CONTINUING S 10-12 KTS UNTIL 14Z...INCREASING TO
15-20 KTS WITH GUSTS 25-30KTS AND SHIFTING TOWARD SW. WINDS
DECREASING AFTER 00Z.


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...AUTEN
LONG TERM...HJS
AVIATION...ONTON



000
FXUS63 KILX 260843
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
343 AM CDT TUE MAY 26 2015

.SHORT TERM...(TODAY)
ISSUED AT 343 AM CDT TUE MAY 26 2015

LOW CLOUDS HAVE BEEN ADVECTING INTO THE AREA AND WILL REMAIN OVER
THE AREA THIS MORNING. LOWER CLOUDS INDICATING LOTS OF LOW LEVEL
MOISTURE BEING ADVECTED INTO THE AREA AHEAD OF THE WEATHER SYSTEM
THAT STILL IS WEST OF THE CWA. RADAR AND SATELLITE LOOPS SHOW
SEVERAL MCVS WEST OF THE AREA WITH SOME SHOWERS MOVING NORTH THROUGH
SOUTHEASTERN MO. MODELS CONTINUE TO INDICATE PCPN REDEVELOPING
TODAY. CLOUDS WILL LIMIT THE DEGREE OF INSTABILITY BUT STILL
EXPECTING ENOUGH FOR THUNDERSTORMS, JUST NOT ENOUGH FOR ANYTHING
SEVERE, WHICH SHOULD BE EAST AND SOUTHEAST OF THE AREA WHERE LESS
CLOUDS WILL BE. CLOUD COVER WILL ALSO TEMPER WARM UP AS WELL SO ONLY
EXPECTING UPPER 70S FOR HIGHS WHICH IS MUCH LESS THAN PAST TWO DAYS.
POPS WILL BE A GRADUAL INCREASE TODAY REACHING LIKELY LATER THIS
MORNING AND THEN MOVING NORTH AND EAST THIS AFTERNOON, BECOMING
CHANCE CATEGORY BY LATE AFTERNOON AS THE PCPN MOVES EAST OF THE
AREA. SOUTHERLY WINDS WILL BE A TAD GUSTY AGAIN, JUST NOT AS MUCH AS
YESTERDAY.

&&

.LONG TERM...(TONIGHT THROUGH MONDAY)
ISSUED AT 343 AM CDT TUE MAY 26 2015

UNTIL THE UPPER WAVE PULLS INTO THE GREAT LAKES REGION, LINGERING
POPS WILL REMAIN OVER THE FA FOR THIS EVENING.  BETTER CHANCES WILL
REMAIN TO THE EAST OVERNIGHT. REMAINS OF THE FRONT WILL STALL OUT
ALONG THE OHIO RIVER VALLEY AND PROVIDE A BIT OF FOCUS FOR ANOTHER
PIECE OF ENERGY EJECTING OUT OF THE SOUTHWEST.  MODELS DIFFERING
WITH THE NORTHERLY EXTENT OF THE PRECIP, BUT LAST FEW RUNS BRINGING
IN SOME PRECIPITATION FOR WEDNESDAY IN THE SOUTHEAST.  NAM IS A
LITTLE MORE WIDESPREAD, BUT CONCENTRATING THE POPS TO THE SOUTH AND
EAST FOR NOW.  TIMING ISSUES REMAIN IN PLACE FOR THIS SYNOPTIC RUN
FOR THE NEXT SYSTEM QUICK ON THE HEELS AS THE DEEP WAVE OVER THE SW
STARTS TO MOVE OUT INTO THE PLAINS. CONVECTION AND PRECIP STARTS TO
SPREAD OVER THE EASTERN HALF OF THE COUNTRY IN THE MODELS WITH  WEAK
SOUTHWESTERLY FLOW ALOFT SHIFTING TO WEAK FLOW OVERALL.  WARM AND
MUGGY CONDITIONS CONTINUE IN A MORE SUMMERLIKE AIRMASS THROUGHOUT
THE WEEK...BUT THAT NEXT SYSTEM WILL BRING A COLD FRONT INTO THE
REGION FOR THE FIRST HALF OF THE WEEKEND TO FOCUS THE RAIN, WITH A
COOLER AIRMASS BEHIND IT DROPPING THE TEMPS FOR THE WEEKEND OUT OF
THE 80S FOR A COUPLE DAYS.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z TUESDAY NIGHT)
ISSUED AT 1151 PM CDT MON MAY 25 2015

VFR CONDITIONS IN SCATTERED HIGH CLOUD COVER WITH SOUTH WINDS
10-12 KTS THIS EVENING ACROSS CENTRAL IL. HIGH CLOUD ASSOCIATED
WITH A SHORTWAVE OVER NORTHEAST OKLAHOMA WILL CONTINUE MOVING INTO
THE REGION OVERNIGHT. CURRENT TIMING OF LIFT AND MOISTURE WITH
THE APPROACHING SHORTWAVE INDICATE PREDOMINANT MVFR CONDITIONS IN
SHRA/ISOLD TSRA LIKELY TO BEGIN 10-12Z. SOME LIFTING OF
PREDOMINANT CEILINGS LIKELY IN AFTERNOON WITH DAYTIME HEATING AND
ACCORDING TO MODEL TIME-HEIGHT SECTIONS SO HAVE INCLUDED VCTS
WITH CIGS ABOVE MVFR THRESHOLD. SHORTWAVE AXIS EXPECTED TO CROSS
LATE AFTERNOON/EARLY EVENING TUESDAY BRINGING A DECREASE IN
SHOWER/THUNDERSTORM ACTIVITY BY 00Z AND HAVE ENDED VCTS AND 4 KFT
AGL CIGS. WINDS CONTINUING S 10-12 KTS UNTIL 14Z...INCREASING TO
15-20 KTS WITH GUSTS 25-30KTS AND SHIFTING TOWARD SW. WINDS
DECREASING AFTER 00Z.


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...AUTEN
LONG TERM...HJS
AVIATION...ONTON



000
FXUS63 KILX 260843
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
343 AM CDT TUE MAY 26 2015

.SHORT TERM...(TODAY)
ISSUED AT 343 AM CDT TUE MAY 26 2015

LOW CLOUDS HAVE BEEN ADVECTING INTO THE AREA AND WILL REMAIN OVER
THE AREA THIS MORNING. LOWER CLOUDS INDICATING LOTS OF LOW LEVEL
MOISTURE BEING ADVECTED INTO THE AREA AHEAD OF THE WEATHER SYSTEM
THAT STILL IS WEST OF THE CWA. RADAR AND SATELLITE LOOPS SHOW
SEVERAL MCVS WEST OF THE AREA WITH SOME SHOWERS MOVING NORTH THROUGH
SOUTHEASTERN MO. MODELS CONTINUE TO INDICATE PCPN REDEVELOPING
TODAY. CLOUDS WILL LIMIT THE DEGREE OF INSTABILITY BUT STILL
EXPECTING ENOUGH FOR THUNDERSTORMS, JUST NOT ENOUGH FOR ANYTHING
SEVERE, WHICH SHOULD BE EAST AND SOUTHEAST OF THE AREA WHERE LESS
CLOUDS WILL BE. CLOUD COVER WILL ALSO TEMPER WARM UP AS WELL SO ONLY
EXPECTING UPPER 70S FOR HIGHS WHICH IS MUCH LESS THAN PAST TWO DAYS.
POPS WILL BE A GRADUAL INCREASE TODAY REACHING LIKELY LATER THIS
MORNING AND THEN MOVING NORTH AND EAST THIS AFTERNOON, BECOMING
CHANCE CATEGORY BY LATE AFTERNOON AS THE PCPN MOVES EAST OF THE
AREA. SOUTHERLY WINDS WILL BE A TAD GUSTY AGAIN, JUST NOT AS MUCH AS
YESTERDAY.

&&

.LONG TERM...(TONIGHT THROUGH MONDAY)
ISSUED AT 343 AM CDT TUE MAY 26 2015

UNTIL THE UPPER WAVE PULLS INTO THE GREAT LAKES REGION, LINGERING
POPS WILL REMAIN OVER THE FA FOR THIS EVENING.  BETTER CHANCES WILL
REMAIN TO THE EAST OVERNIGHT. REMAINS OF THE FRONT WILL STALL OUT
ALONG THE OHIO RIVER VALLEY AND PROVIDE A BIT OF FOCUS FOR ANOTHER
PIECE OF ENERGY EJECTING OUT OF THE SOUTHWEST.  MODELS DIFFERING
WITH THE NORTHERLY EXTENT OF THE PRECIP, BUT LAST FEW RUNS BRINGING
IN SOME PRECIPITATION FOR WEDNESDAY IN THE SOUTHEAST.  NAM IS A
LITTLE MORE WIDESPREAD, BUT CONCENTRATING THE POPS TO THE SOUTH AND
EAST FOR NOW.  TIMING ISSUES REMAIN IN PLACE FOR THIS SYNOPTIC RUN
FOR THE NEXT SYSTEM QUICK ON THE HEELS AS THE DEEP WAVE OVER THE SW
STARTS TO MOVE OUT INTO THE PLAINS. CONVECTION AND PRECIP STARTS TO
SPREAD OVER THE EASTERN HALF OF THE COUNTRY IN THE MODELS WITH  WEAK
SOUTHWESTERLY FLOW ALOFT SHIFTING TO WEAK FLOW OVERALL.  WARM AND
MUGGY CONDITIONS CONTINUE IN A MORE SUMMERLIKE AIRMASS THROUGHOUT
THE WEEK...BUT THAT NEXT SYSTEM WILL BRING A COLD FRONT INTO THE
REGION FOR THE FIRST HALF OF THE WEEKEND TO FOCUS THE RAIN, WITH A
COOLER AIRMASS BEHIND IT DROPPING THE TEMPS FOR THE WEEKEND OUT OF
THE 80S FOR A COUPLE DAYS.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z TUESDAY NIGHT)
ISSUED AT 1151 PM CDT MON MAY 25 2015

VFR CONDITIONS IN SCATTERED HIGH CLOUD COVER WITH SOUTH WINDS
10-12 KTS THIS EVENING ACROSS CENTRAL IL. HIGH CLOUD ASSOCIATED
WITH A SHORTWAVE OVER NORTHEAST OKLAHOMA WILL CONTINUE MOVING INTO
THE REGION OVERNIGHT. CURRENT TIMING OF LIFT AND MOISTURE WITH
THE APPROACHING SHORTWAVE INDICATE PREDOMINANT MVFR CONDITIONS IN
SHRA/ISOLD TSRA LIKELY TO BEGIN 10-12Z. SOME LIFTING OF
PREDOMINANT CEILINGS LIKELY IN AFTERNOON WITH DAYTIME HEATING AND
ACCORDING TO MODEL TIME-HEIGHT SECTIONS SO HAVE INCLUDED VCTS
WITH CIGS ABOVE MVFR THRESHOLD. SHORTWAVE AXIS EXPECTED TO CROSS
LATE AFTERNOON/EARLY EVENING TUESDAY BRINGING A DECREASE IN
SHOWER/THUNDERSTORM ACTIVITY BY 00Z AND HAVE ENDED VCTS AND 4 KFT
AGL CIGS. WINDS CONTINUING S 10-12 KTS UNTIL 14Z...INCREASING TO
15-20 KTS WITH GUSTS 25-30KTS AND SHIFTING TOWARD SW. WINDS
DECREASING AFTER 00Z.


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...AUTEN
LONG TERM...HJS
AVIATION...ONTON



000
FXUS63 KILX 260843
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
343 AM CDT TUE MAY 26 2015

.SHORT TERM...(TODAY)
ISSUED AT 343 AM CDT TUE MAY 26 2015

LOW CLOUDS HAVE BEEN ADVECTING INTO THE AREA AND WILL REMAIN OVER
THE AREA THIS MORNING. LOWER CLOUDS INDICATING LOTS OF LOW LEVEL
MOISTURE BEING ADVECTED INTO THE AREA AHEAD OF THE WEATHER SYSTEM
THAT STILL IS WEST OF THE CWA. RADAR AND SATELLITE LOOPS SHOW
SEVERAL MCVS WEST OF THE AREA WITH SOME SHOWERS MOVING NORTH THROUGH
SOUTHEASTERN MO. MODELS CONTINUE TO INDICATE PCPN REDEVELOPING
TODAY. CLOUDS WILL LIMIT THE DEGREE OF INSTABILITY BUT STILL
EXPECTING ENOUGH FOR THUNDERSTORMS, JUST NOT ENOUGH FOR ANYTHING
SEVERE, WHICH SHOULD BE EAST AND SOUTHEAST OF THE AREA WHERE LESS
CLOUDS WILL BE. CLOUD COVER WILL ALSO TEMPER WARM UP AS WELL SO ONLY
EXPECTING UPPER 70S FOR HIGHS WHICH IS MUCH LESS THAN PAST TWO DAYS.
POPS WILL BE A GRADUAL INCREASE TODAY REACHING LIKELY LATER THIS
MORNING AND THEN MOVING NORTH AND EAST THIS AFTERNOON, BECOMING
CHANCE CATEGORY BY LATE AFTERNOON AS THE PCPN MOVES EAST OF THE
AREA. SOUTHERLY WINDS WILL BE A TAD GUSTY AGAIN, JUST NOT AS MUCH AS
YESTERDAY.

&&

.LONG TERM...(TONIGHT THROUGH MONDAY)
ISSUED AT 343 AM CDT TUE MAY 26 2015

UNTIL THE UPPER WAVE PULLS INTO THE GREAT LAKES REGION, LINGERING
POPS WILL REMAIN OVER THE FA FOR THIS EVENING.  BETTER CHANCES WILL
REMAIN TO THE EAST OVERNIGHT. REMAINS OF THE FRONT WILL STALL OUT
ALONG THE OHIO RIVER VALLEY AND PROVIDE A BIT OF FOCUS FOR ANOTHER
PIECE OF ENERGY EJECTING OUT OF THE SOUTHWEST.  MODELS DIFFERING
WITH THE NORTHERLY EXTENT OF THE PRECIP, BUT LAST FEW RUNS BRINGING
IN SOME PRECIPITATION FOR WEDNESDAY IN THE SOUTHEAST.  NAM IS A
LITTLE MORE WIDESPREAD, BUT CONCENTRATING THE POPS TO THE SOUTH AND
EAST FOR NOW.  TIMING ISSUES REMAIN IN PLACE FOR THIS SYNOPTIC RUN
FOR THE NEXT SYSTEM QUICK ON THE HEELS AS THE DEEP WAVE OVER THE SW
STARTS TO MOVE OUT INTO THE PLAINS. CONVECTION AND PRECIP STARTS TO
SPREAD OVER THE EASTERN HALF OF THE COUNTRY IN THE MODELS WITH  WEAK
SOUTHWESTERLY FLOW ALOFT SHIFTING TO WEAK FLOW OVERALL.  WARM AND
MUGGY CONDITIONS CONTINUE IN A MORE SUMMERLIKE AIRMASS THROUGHOUT
THE WEEK...BUT THAT NEXT SYSTEM WILL BRING A COLD FRONT INTO THE
REGION FOR THE FIRST HALF OF THE WEEKEND TO FOCUS THE RAIN, WITH A
COOLER AIRMASS BEHIND IT DROPPING THE TEMPS FOR THE WEEKEND OUT OF
THE 80S FOR A COUPLE DAYS.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z TUESDAY NIGHT)
ISSUED AT 1151 PM CDT MON MAY 25 2015

VFR CONDITIONS IN SCATTERED HIGH CLOUD COVER WITH SOUTH WINDS
10-12 KTS THIS EVENING ACROSS CENTRAL IL. HIGH CLOUD ASSOCIATED
WITH A SHORTWAVE OVER NORTHEAST OKLAHOMA WILL CONTINUE MOVING INTO
THE REGION OVERNIGHT. CURRENT TIMING OF LIFT AND MOISTURE WITH
THE APPROACHING SHORTWAVE INDICATE PREDOMINANT MVFR CONDITIONS IN
SHRA/ISOLD TSRA LIKELY TO BEGIN 10-12Z. SOME LIFTING OF
PREDOMINANT CEILINGS LIKELY IN AFTERNOON WITH DAYTIME HEATING AND
ACCORDING TO MODEL TIME-HEIGHT SECTIONS SO HAVE INCLUDED VCTS
WITH CIGS ABOVE MVFR THRESHOLD. SHORTWAVE AXIS EXPECTED TO CROSS
LATE AFTERNOON/EARLY EVENING TUESDAY BRINGING A DECREASE IN
SHOWER/THUNDERSTORM ACTIVITY BY 00Z AND HAVE ENDED VCTS AND 4 KFT
AGL CIGS. WINDS CONTINUING S 10-12 KTS UNTIL 14Z...INCREASING TO
15-20 KTS WITH GUSTS 25-30KTS AND SHIFTING TOWARD SW. WINDS
DECREASING AFTER 00Z.


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...AUTEN
LONG TERM...HJS
AVIATION...ONTON



000
FXUS63 KLOT 260820
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
320 AM CDT TUE MAY 26 2015

.SHORT TERM...
319 AM CDT

THROUGH TUESDAY NIGHT...

FOR THE REMAINDER OF THE OVERNIGHT HOURS...CONDITIONS WILL REMAIN
QUIET ACROSS THE CWA AS A SERIES OF SHORT WAVES CONTINUE TO TRACK
NORTH AROUND THE TOP OF A PERSISTENT UPPER LEVEL RIDGE WHICH EXTENDS
FROM THE SERN CONUS THROUGH THE UPPER MISSISSIPPI VALLEY.  THIS
UPPER RIDGE HAS BEEN THE FEATURE WHICH HAS CONTROLLED THE PATH OF
THE SERIES OF SHORTWAVES LIFTING OUT OF THE SOUTHERN PLAINS...AND
WILL CONTINUE TO DO SO THROUGH THE DAY TODAY. SLY...MODERATELY
STRONG...WINDS WILL PERSIST THROUGH THE NIGHT...AND MUCH OF THE DAY
ALLOWING FOR SFC DEWPOINTS TO REMAIN CONSISTENT OR POSSIBLE INCH A
LITTLE HIGHER.

MAIN CONCERN FOR THE MORNING HOURS WILL BE THE TRACK OF A STRONG
SHORT WAVE AND ASSOCIATED SFC LOW LIFTING NORTHWARD THROUGH THE
MIDDLE MISSISSIPPI VALLEY.  THIS FEATURE WILL PREDOMINANTLY IMPACT
ERN IOWA AND WRN IL BY ARND DAYBREAK.  THROUGH THE MORNING...THE
COMBINATION OF ISENTROPIC LIFT IN THE WARM SECTOR OF THE
SYSTEM...ALL OF IL AND INTO NWRN IN...WILL LEAD TO SOME
DESTABILIZATION ACROSS THE REGION. A SFC TROUGH...AS WELL INDICATED
BY THE LATEST HIGH RES GUIDANCE...WITH LIFT THROUGH NRN IL/IN
THROUGH THE DAY...COINCIDENT WITH A STRONG SSWLY LOW LEVEL JET OF 45-
50 KT...WITH PROVIDE THE POTENTIAL FOR SHOWERS AND STRONG TO SEVERE
THUNDERSTORMS ACROSS THE CWA.  BASED ON WIND PROFILES AND MID LEVEL
DRYING...THE PRIMARY CONCERN WITH REGARD TO SEVERE WEATHER WILL BE
STRONG WIND GUSTS.  HOWEVER...SOME OF THE HIGH RES SFC WIND GUIDANCE
SUGGEST SOME SLIGHT BACKING OF SFC WINDS FROM 180-190 DEGREES TO 160-
170 DEGREES...WHILE WINDS ALOFT REMAIN SWLY.  THIS SLIGHT BACKING OF
THE SFC WINDS COULD PROVIDE ENOUGH DIRECTIONAL SHEAR THROUGH THE
LOWER LEVELS TO BRING AN ISOLD TORNADO THREAT. LOCALLY HEAVY
RAINFALL WILL ALSO BE CONCERNED WITH PWATS REACHING 1.75 INCHES
LATER THIS MORNING.  HOWEVER...FLOODING WILL LIKELY NOT BE A
SIGNIFICANT CONCERN AS THE SWLY WINDS RIGHT OFF THE DECK WILL RANGE
FROM ARND 45 KT ABOVE THE BOUNDARY LAYER TO ARND 90KT AT UPPER
LEVELS WHICH SHOULD ALLOW ANY OF THE STRONGER STORMS THAT DO DEVELOP
TO MOVE QUICKLY.

BY EARLY AFTERNOON...THE MAIN SHORT WAVE WILL LIFT INTO WISCONSIN
WHILE A SFC TROUGH TRACKS EAST ACROSS THE AREA.  THIS WILL LEAD TO
WINDS AT THE SFC VEERING TO SWLY...SETTING UP A UNIDIRECTIONAL WIND
PROFILE...EFFECTIVELY MINIMIZING THE SEVERE WEATHER THREAT TO THE
REGION.  BY LATE AFTERNOON AND INTO THE EVENING THE MODELS ARE
ADVERTISING THAT A DRY SLOW SHOULD NOSE INTO NRN IL...EFFECTIVELY
CUTTING OFF THE PCPN AREA INTO 2 SEPARATE AREA...ONE OVER WISCONSIN
AND ERN IOWA AND ANOTHER MORE FOCUSED OVER INDIANA.  THE NWRN
INDIANA COUNTIES WILL STILL HAVE A CHANCE FOR SOME SHOWERS AND
THUNDERSTORMS INTO THE EVENING...WHILE PCPN CHANCES OVER NRN IL
BEGIN TO WANE.  MUCH OF THE MODEL GUIDANCE ALSO INDICATED THAT THE
SHORTWAVE SHOULD SLOW IT`S PROGRESSION THROUGH WISCONSIN AS IT
APPROACHES THE APEX OF THE UPPER RIDGE.  AN ASSOCIATED SFC
TROUGH/COLD FRONT EXTENDING SOUTHWEST FROM THE SFC LOW WILL LINGER
OVER ERN IOWA IN THE EARLY EVENING BEFORE STEADILY PUSHING ACROSS
NRN IL AND INTO NWRN IN OVERNIGHT.  THROUGH THE NIGHT...THE
STRONGEST UPPER LEVEL FORCING WILL BE WELL NORTH OF THE CWA...SO ANY
LINGERING CHANCES FOR PCPN OVERNIGHT WILL BE LOW AND LIKELY CONFINED
TO THE NRN TIER COUNTIES OF IL...ALONG THE WI BORDER.

KREIN

&&

.LONG TERM...
229 AM CDT

WEDNESDAY THROUGH MONDAY...

WEDNESDAY THROUGH THURSDAY...
OPEN 500MB WAVE WILL BE LIFTING NORTHEAST ACROSS THE UPPER MIDWEST
INTO ONTARIO AND EVENTUALLY QUEBEC...WITH HEIGHTS SLOWLY INCREASING
WED AFTN. SFC FEATURES REMAIN DISORGANIZED WED...WITH A BOUNDARY
SLOWLY SHIFTING EAST. OPER GUIDANCE DIFFERS ON HOW QUICKLY PRECIP
WILL DEPART THE REGION. ENSEMBLE DATA SUGGESTS HOLDING ONTO CHC TO
SLIGHT CHC POPS MAINLY FOR THE CENTRAL/EASTERN CWFA WED/WED EVE.
ALTHOUGH WITH SOME HINT OF SFC HEIGHTS NUDGING UP...IT IS POSSIBLE
THAT SOME DRY AIR COULD FILTER IN AND KICK PRECIP EAST BY MIDDAY AND
ALLOW FOR A MAINLY DRY WED. SFC WINDS WILL BE TURNING SOUTHWEST TO
WEST...KEEPING AN OFFSHORE FLOW FOR LOCATIONS CLOSE TO LAKE
MICHIGAN. TEMPS SHOULD YET AGAIN TOUCH UPR 70S TO ARND 80 WED...IF
CLOUDS AND PRECIP CAN PUSH EAST BY MIDDAY...SOME CLEARING WOULD
ALLOW SFC TEMPS TO PUSH A COUPLE DEGREES WARMER INTO THE LOW 80S IN
SOME LOCATIONS. LATE IN THE EVENING THE GRADIENT SLACKENS
FURTHER...AND COULD ALLOW A LATE DAY ONSHORE FLOW TO DEVELOP FOR
AREAS ADJACENT TO LAKE MICHIGAN.

MID-LVL FLOW BEGINS TO FLATTEN AS A WEAK SFC RIDGE BECOMES ORIENTED
FROM WESTERN QUEBEC SOUTH THROUGH THE EASTERN OHIO RIVER VALLEY.
THIS WILL GENERALLY ALLOW A SOUTHERLY FLOW...ALTHOUGH THE GRADIENT
IS NOT VERY STRONG. THIS SHOULD SET THE STAGE FOR A LAKE
BREEZE/ONSHORE FLOW TO DEVELOP THUR. TIMING COULD END UP BEING
SLIGHTLY EARLIER GIVEN THE LIGHT SFC GRADIENT. GUIDANCE HAS BEEN
CONSISTENT IN HOLDING PRECIP WEST/SOUTH OF THE FORECAST AREA
THUR...AS A RESULT OF THE WEAK SFC RIDGING. SO ONE MORE MILD DAY
WITH HIGHS WARMING BACK INTO THE UPR 70S/LOW 80S...HOWEVER AS
PREVIOUSLY NOTED...A LAKE BREEZE IS LIKELY TO DEVELOP. THIS WILL
BLEED THE MUCH COOLER MARINE AIR WEST ACROSS NORTHEAST IL AND
DOWNTOWN CHICAGO. IF THE TIMING IS EARLIER IN THE DAY THUR...TEMPS
MAY NOT WARM BEYONG THE LOW/MID 60S ALONG THE CHICAGO LAKEFRONT.

FLOW THEN TURNS SOUTHERLY THUR NIGHT WITH THE MORE PROGRESSIVE FLOW
IN THE MID-LVLS PUSHING THE RIDGING EAST. A RETURN FLOW MOISTURE
WILL CONTINUE TO BE FOCUSED ACROSS THE CENTRAL CONUS THUR EVE...WITH
A SLOW MOVING FRONTAL BOUNDARY NUDGING EAST THUR NIGHT TOWARDS
WESTERN IL. THIS FRONTAL BOUNDARY WILL BECOME ENERGIZED AS A ROBUST
500MB VORT MAX BREAKS SOUTH FROM CENTRAL CANADA LATE THUR NIGHT.

THIS SHOULD ALLOW FOR AN ATMOSPHERIC RIVER TO DEVELOP FROM THE
SOUTHERN PLAINS STRETCHING NORTH THROUGH THE MID-MISSOURI VALLEY
INTO THE WESTERN GREAT LAKES EARLY FRI MORNING.

FRIDAY THROUGH EARLY NEXT WEEK...
ENSEMBLES CONTINUE TO PROG A ROBUST TROUGH SLIDING SOUTH FROM
CENTRAL CANADA FRI. THIS COUPLED WITH DOWNSTREAM MID-LVL RIDGING
ACROSS THE SOUTHEAST CONUS WILL STRENGTHEN THE FRONTAL BOUNDARY
THAT WILL BE ORIENTED FROM THE SOUTHERN PLAINS STRETCHING
NORTHEAST THROUGH THE GREAT LAKES REGION INTO WESTERN QUEBEC.

THIS SETUP IS IDEAL FOR THE DEVELOPMENT OF AN ATMOSPHERIC RIVER WITH
ABUNDANT LOW LEVEL MOISTURE AND EFFICIENT PRECIP PRODUCING
CONVECTION.

OPER GUIDANCE HAS BEEN RELATIVELY CONSISTENT WITH BRINGING A SERIES
OF WAVES ALONG THE SLOW MOVING FRONTAL BOUNDARY FRI AFTN/EVE...THEN
THE BOUNDARY SHOULD SLIDE EAST WITH WINDS QUICKLY VEERING
NORTH/NORTHEAST FOR SAT AND USHERING IN MUCH COOLER AIR TO THE
REGION.

CURRENT INDICATIONS ARE THAT HIGHS SAT MAY STRUGGLE TO WARM BEYOND
THE UPR 50S ACROSS NORTHEAST IL/NORTHWEST IN...WITH ONLY LOW 60S
ELSEWHERE. STRONG SFC RIDGE WILL REMAIN NORTH OF THE REGION...SO THE
PRIOR FRONTAL BOUNDARY MAY BECOME QUASI-STATIONARY FOR THE WEEKEND
ALONG THE OHIO VALLEY AND CONTINUE TO FEED PRECIP CHANCES TO THE
SOUTHERN CWFA.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* SOUTH-SOUTHWEST WINDS OF AROUND 40 KT AT 1000 FT
  OVERNIGHT...SETTING UP LOW LEVEL WIND SHEAR.

* MVFR CEILINGS PROBABLE AT TIMES TUESDAY WITH A CHANCE FOR
  TEMPORARY IFR.

* PERIODS OF SHRA WITH PERIODIC TSRA FROM LATE TUESDAY MORNING
  THROUGH THE AFTERNOON.

* NEAR DUE SOUTH WINDS ON TUESDAY WITH PERIODIC GUSTS POSSIBLE
  AND SOME VARIABILITY BETWEEN SOUTHEAST AND SOUTHWEST.

KREIN

//DISCUSSION...UPDATED 06Z...

GUSTY SOUTH-SOUTHWEST WINDS HAVE DIMINISHED TO 10 KT OR LESS AND
BECOME SOUTHERLY. A LOW-LEVEL JET WILL DEVELOP OVERHEAD WITH
SSWLY-SWLY WINDS OF 40 KT TO 45 KT FLOW AT 1500-2000 FT UNTIL
ARND 12Z. SOME THUNDERSTORMS MAY DEVELOP THROUGH OVERNIGHT AHEAD
OF A FRONT FROM NRN MO THROUGH ERN IA AND INTO WI. THESE STORMS
WILL ONLY MAKE SLOW PROGRESS EASTWARD DUE TO THE STRONG SSWLY-SWLY
WINDS ALOFT SO...AND STORMS THAT DO DEVELOP SHOULD REMAIN NORTH
AND NORTHWEST OF AREA TAF SITES...THOUGH THERE IS A CHANCE THAT A
FEW STORMS COULD APPROACH THE RFD TERMINAL AREA VERY LATE
TONIGHT.

AS AN MID LEVEL DISTURBANCE MOVING FROM THE SOUTHERN PLAINS TO
NRN IL BY TUESDAY AFTERNOON MAY BRING ANOTHER ROUND OF SHOWERS
WITH SCT EMBEDDED THUNDERSTORMS TO THE REGION. UPPER LEVEL FORCING
FROM THE MID LEVEL DISTURBANCE AND AN UPPER LEVEL JET STREAM WILL
ENHANCE THE LIKELIHOOD FOR SHRA AND THE CHANCE FOR TSRA...WITH THE
MOST LIKELY CHANCE FOR ACTIVITY FROM 15Z THROUGH 02Z. SOME
UNCERTAINTY REMAINS IN PINNING DOWN THE EXACT PERIOD FOR THE
TSRA...SO WILL MAINTAIN THE GOING TEMPO FOR LATE MORNING THROUGH
EARLY AFTERNOON. HOWEVER...THE PCPN ACTIVITY COULD BE SHIFTED OR
EXPANDED IN TIME.

WINDS WILL BE SOUTHERLY ON TUESDAY...THOUGH DIRECTION MAY BE A BIT
VARIABLE AROUND CONVECTIVE ACTIVITY...THOUGH A GENERALLY SOUTHERLY
DIRECTION SHOULD PREVAIL THROUGH THE NIGHT AND MUCH OF THE DAY
TUESDAY. SOME GUSTINESS IS POSSIBLE THROUGH THE ENTIRE DAY...WITH
THE LATEST GUIDANCE SUGGESTING THAT WINDS COULD STRENGTHEN AND
BECOME EVEN MORE GUSTY THROUGH THE NIGHT TOMORROW NIGHT WITH WINDS
VEERING SWLY AS SURFACE LOW PRESSURE MOVES NORTHEAST ACROSS
SOUTHERN WISCONSIN.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* HIGH CONFIDENCE IN 40-45 KT SSWLY-SWLY FLOW ALOFT OVERNIGHT...BUT
  MEDIUM IN TRUE LLWS OCCURRING.

* HIGH CONFIDENCE IN WIND TRENDS OVERNIGHT AND TUESDAY MORNING.
  MEDIUM IN WIND TRENDS TOMORROW EVENING.

* MEDIUM CONFIDENCE IN MVFR CIGS TUESDAY MORNING WITH LOWER
  CONFIDENCE IN DURATION AND HOW LOW CIGS WILL DROP.

* HIGH CONFIDENCE IN SHOWERS AND AT LEAST A PERIOD OF TSRA. LOW
  CONFIDENCE IN SPECIFIC TSRA TIMING AND IMPACT ON THE TERMINALS
  WITH MULTIPLE ROUNDS POSSIBLE BETWEEN 15Z AND 02Z.

KREIN

//OUTLOOK FOR ORD/MDW FOR 12Z WEDNESDAY-12Z MONDAY...UPDATED 00Z...

WEDNESDAY...CHANCE OF TSRA. WEST WINDS.
THURSDAY...SLIGHT CHANCE OF TSRA LATE AT NIGHT. SOUTHEAST WINDS.
FRIDAY...INCREASING CHANCE OF TSRA THROUGH THE DAY AND NIGHT.
         SOUTHWEST WINDS.
SATURDAY...SHRA LIKELY WITH A CHANCE OF TSRA. NORTHEAST WINDS.
SUNDAY...CHANCE OF SHRA. EAST WINDS.

MTF

&&

.MARINE...
229 AM CDT

WARM MOIST AIR CONTINUES TO FEED NORTH ACROSS THE LAKE
TODAY...WHICH MAY HELP TO FURTHER ENHANCE ANY AREAS OF FOG THAT
HAVE ALREADY DEVELOPED. IT IS POSSIBLE PATCHY DENSE FOG MAY
DEVELOP...ALTHOUGH WINDS MAY BE JUST STRONG ENOUGH TO LIMIT THE
COVERAGE AND INTENSITY OF THE FOG. A SURFACE LOW PRESSURE SYSTEM
WILL BE LIFTING NORTH ACROSS EASTERN IOWA INTO CENTRAL WISCONSIN
THIS EVENING. THE GRADIENT WILL TIGHTEN ACROSS THE
CENTRAL/SOUTHERN PORTIONS OF THE LAKE...WHICH WITH WARMER
NEARSHORE WATERS EXPECT SOME SLIGHTLY BETTER MIXING TO OCCUR.
FURTHER OUT ACROSS THE OPEN WATERS THE WATER REMAINS COLD AND
EXPECT THE STABILITY TO MAKE IT DIFFICULT TO MIX TO THE SFC THE
HIGHER GUSTS. HIGH PRESSURE THEN ARRIVES LATE WEDNESDAY WITH LIGHT
WINDS DEVELOPING. THEN HIGH PRESSURE SHIFTS EAST THURSDAY
NIGHT...WITH SOUTHERLY WINDS DEVELOPING AGAIN FRIDAY. A FRONTAL
BOUNDARY WILL APPROACH LAKE MICHIGAN LATE FRIDAY NIGHT THEN
STEADILY SLIDE SOUTH ALONG THE LAKE. THIS WILL ALLOW WINDS TO
QUICKLY VEER FROM SOUTH TO NORTH/NORTHEAST SATURDAY. ALONG WITH
THIS QUICK WIND SHIFT WILL BE COOLER AIR SLIDING SOUTH OVER THE
LAKE. WAVES SHOULD EASILY BUILD SATURDAY FOR THE CENTRAL/SOUTHERN
PORTIONS OF THE LAKE.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 260820
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
320 AM CDT TUE MAY 26 2015

.SHORT TERM...
319 AM CDT

THROUGH TUESDAY NIGHT...

FOR THE REMAINDER OF THE OVERNIGHT HOURS...CONDITIONS WILL REMAIN
QUIET ACROSS THE CWA AS A SERIES OF SHORT WAVES CONTINUE TO TRACK
NORTH AROUND THE TOP OF A PERSISTENT UPPER LEVEL RIDGE WHICH EXTENDS
FROM THE SERN CONUS THROUGH THE UPPER MISSISSIPPI VALLEY.  THIS
UPPER RIDGE HAS BEEN THE FEATURE WHICH HAS CONTROLLED THE PATH OF
THE SERIES OF SHORTWAVES LIFTING OUT OF THE SOUTHERN PLAINS...AND
WILL CONTINUE TO DO SO THROUGH THE DAY TODAY. SLY...MODERATELY
STRONG...WINDS WILL PERSIST THROUGH THE NIGHT...AND MUCH OF THE DAY
ALLOWING FOR SFC DEWPOINTS TO REMAIN CONSISTENT OR POSSIBLE INCH A
LITTLE HIGHER.

MAIN CONCERN FOR THE MORNING HOURS WILL BE THE TRACK OF A STRONG
SHORT WAVE AND ASSOCIATED SFC LOW LIFTING NORTHWARD THROUGH THE
MIDDLE MISSISSIPPI VALLEY.  THIS FEATURE WILL PREDOMINANTLY IMPACT
ERN IOWA AND WRN IL BY ARND DAYBREAK.  THROUGH THE MORNING...THE
COMBINATION OF ISENTROPIC LIFT IN THE WARM SECTOR OF THE
SYSTEM...ALL OF IL AND INTO NWRN IN...WILL LEAD TO SOME
DESTABILIZATION ACROSS THE REGION. A SFC TROUGH...AS WELL INDICATED
BY THE LATEST HIGH RES GUIDANCE...WITH LIFT THROUGH NRN IL/IN
THROUGH THE DAY...COINCIDENT WITH A STRONG SSWLY LOW LEVEL JET OF 45-
50 KT...WITH PROVIDE THE POTENTIAL FOR SHOWERS AND STRONG TO SEVERE
THUNDERSTORMS ACROSS THE CWA.  BASED ON WIND PROFILES AND MID LEVEL
DRYING...THE PRIMARY CONCERN WITH REGARD TO SEVERE WEATHER WILL BE
STRONG WIND GUSTS.  HOWEVER...SOME OF THE HIGH RES SFC WIND GUIDANCE
SUGGEST SOME SLIGHT BACKING OF SFC WINDS FROM 180-190 DEGREES TO 160-
170 DEGREES...WHILE WINDS ALOFT REMAIN SWLY.  THIS SLIGHT BACKING OF
THE SFC WINDS COULD PROVIDE ENOUGH DIRECTIONAL SHEAR THROUGH THE
LOWER LEVELS TO BRING AN ISOLD TORNADO THREAT. LOCALLY HEAVY
RAINFALL WILL ALSO BE CONCERNED WITH PWATS REACHING 1.75 INCHES
LATER THIS MORNING.  HOWEVER...FLOODING WILL LIKELY NOT BE A
SIGNIFICANT CONCERN AS THE SWLY WINDS RIGHT OFF THE DECK WILL RANGE
FROM ARND 45 KT ABOVE THE BOUNDARY LAYER TO ARND 90KT AT UPPER
LEVELS WHICH SHOULD ALLOW ANY OF THE STRONGER STORMS THAT DO DEVELOP
TO MOVE QUICKLY.

BY EARLY AFTERNOON...THE MAIN SHORT WAVE WILL LIFT INTO WISCONSIN
WHILE A SFC TROUGH TRACKS EAST ACROSS THE AREA.  THIS WILL LEAD TO
WINDS AT THE SFC VEERING TO SWLY...SETTING UP A UNIDIRECTIONAL WIND
PROFILE...EFFECTIVELY MINIMIZING THE SEVERE WEATHER THREAT TO THE
REGION.  BY LATE AFTERNOON AND INTO THE EVENING THE MODELS ARE
ADVERTISING THAT A DRY SLOW SHOULD NOSE INTO NRN IL...EFFECTIVELY
CUTTING OFF THE PCPN AREA INTO 2 SEPARATE AREA...ONE OVER WISCONSIN
AND ERN IOWA AND ANOTHER MORE FOCUSED OVER INDIANA.  THE NWRN
INDIANA COUNTIES WILL STILL HAVE A CHANCE FOR SOME SHOWERS AND
THUNDERSTORMS INTO THE EVENING...WHILE PCPN CHANCES OVER NRN IL
BEGIN TO WANE.  MUCH OF THE MODEL GUIDANCE ALSO INDICATED THAT THE
SHORTWAVE SHOULD SLOW IT`S PROGRESSION THROUGH WISCONSIN AS IT
APPROACHES THE APEX OF THE UPPER RIDGE.  AN ASSOCIATED SFC
TROUGH/COLD FRONT EXTENDING SOUTHWEST FROM THE SFC LOW WILL LINGER
OVER ERN IOWA IN THE EARLY EVENING BEFORE STEADILY PUSHING ACROSS
NRN IL AND INTO NWRN IN OVERNIGHT.  THROUGH THE NIGHT...THE
STRONGEST UPPER LEVEL FORCING WILL BE WELL NORTH OF THE CWA...SO ANY
LINGERING CHANCES FOR PCPN OVERNIGHT WILL BE LOW AND LIKELY CONFINED
TO THE NRN TIER COUNTIES OF IL...ALONG THE WI BORDER.

KREIN

&&

.LONG TERM...
229 AM CDT

WEDNESDAY THROUGH MONDAY...

WEDNESDAY THROUGH THURSDAY...
OPEN 500MB WAVE WILL BE LIFTING NORTHEAST ACROSS THE UPPER MIDWEST
INTO ONTARIO AND EVENTUALLY QUEBEC...WITH HEIGHTS SLOWLY INCREASING
WED AFTN. SFC FEATURES REMAIN DISORGANIZED WED...WITH A BOUNDARY
SLOWLY SHIFTING EAST. OPER GUIDANCE DIFFERS ON HOW QUICKLY PRECIP
WILL DEPART THE REGION. ENSEMBLE DATA SUGGESTS HOLDING ONTO CHC TO
SLIGHT CHC POPS MAINLY FOR THE CENTRAL/EASTERN CWFA WED/WED EVE.
ALTHOUGH WITH SOME HINT OF SFC HEIGHTS NUDGING UP...IT IS POSSIBLE
THAT SOME DRY AIR COULD FILTER IN AND KICK PRECIP EAST BY MIDDAY AND
ALLOW FOR A MAINLY DRY WED. SFC WINDS WILL BE TURNING SOUTHWEST TO
WEST...KEEPING AN OFFSHORE FLOW FOR LOCATIONS CLOSE TO LAKE
MICHIGAN. TEMPS SHOULD YET AGAIN TOUCH UPR 70S TO ARND 80 WED...IF
CLOUDS AND PRECIP CAN PUSH EAST BY MIDDAY...SOME CLEARING WOULD
ALLOW SFC TEMPS TO PUSH A COUPLE DEGREES WARMER INTO THE LOW 80S IN
SOME LOCATIONS. LATE IN THE EVENING THE GRADIENT SLACKENS
FURTHER...AND COULD ALLOW A LATE DAY ONSHORE FLOW TO DEVELOP FOR
AREAS ADJACENT TO LAKE MICHIGAN.

MID-LVL FLOW BEGINS TO FLATTEN AS A WEAK SFC RIDGE BECOMES ORIENTED
FROM WESTERN QUEBEC SOUTH THROUGH THE EASTERN OHIO RIVER VALLEY.
THIS WILL GENERALLY ALLOW A SOUTHERLY FLOW...ALTHOUGH THE GRADIENT
IS NOT VERY STRONG. THIS SHOULD SET THE STAGE FOR A LAKE
BREEZE/ONSHORE FLOW TO DEVELOP THUR. TIMING COULD END UP BEING
SLIGHTLY EARLIER GIVEN THE LIGHT SFC GRADIENT. GUIDANCE HAS BEEN
CONSISTENT IN HOLDING PRECIP WEST/SOUTH OF THE FORECAST AREA
THUR...AS A RESULT OF THE WEAK SFC RIDGING. SO ONE MORE MILD DAY
WITH HIGHS WARMING BACK INTO THE UPR 70S/LOW 80S...HOWEVER AS
PREVIOUSLY NOTED...A LAKE BREEZE IS LIKELY TO DEVELOP. THIS WILL
BLEED THE MUCH COOLER MARINE AIR WEST ACROSS NORTHEAST IL AND
DOWNTOWN CHICAGO. IF THE TIMING IS EARLIER IN THE DAY THUR...TEMPS
MAY NOT WARM BEYONG THE LOW/MID 60S ALONG THE CHICAGO LAKEFRONT.

FLOW THEN TURNS SOUTHERLY THUR NIGHT WITH THE MORE PROGRESSIVE FLOW
IN THE MID-LVLS PUSHING THE RIDGING EAST. A RETURN FLOW MOISTURE
WILL CONTINUE TO BE FOCUSED ACROSS THE CENTRAL CONUS THUR EVE...WITH
A SLOW MOVING FRONTAL BOUNDARY NUDGING EAST THUR NIGHT TOWARDS
WESTERN IL. THIS FRONTAL BOUNDARY WILL BECOME ENERGIZED AS A ROBUST
500MB VORT MAX BREAKS SOUTH FROM CENTRAL CANADA LATE THUR NIGHT.

THIS SHOULD ALLOW FOR AN ATMOSPHERIC RIVER TO DEVELOP FROM THE
SOUTHERN PLAINS STRETCHING NORTH THROUGH THE MID-MISSOURI VALLEY
INTO THE WESTERN GREAT LAKES EARLY FRI MORNING.

FRIDAY THROUGH EARLY NEXT WEEK...
ENSEMBLES CONTINUE TO PROG A ROBUST TROUGH SLIDING SOUTH FROM
CENTRAL CANADA FRI. THIS COUPLED WITH DOWNSTREAM MID-LVL RIDGING
ACROSS THE SOUTHEAST CONUS WILL STRENGTHEN THE FRONTAL BOUNDARY
THAT WILL BE ORIENTED FROM THE SOUTHERN PLAINS STRETCHING
NORTHEAST THROUGH THE GREAT LAKES REGION INTO WESTERN QUEBEC.

THIS SETUP IS IDEAL FOR THE DEVELOPMENT OF AN ATMOSPHERIC RIVER WITH
ABUNDANT LOW LEVEL MOISTURE AND EFFICIENT PRECIP PRODUCING
CONVECTION.

OPER GUIDANCE HAS BEEN RELATIVELY CONSISTENT WITH BRINGING A SERIES
OF WAVES ALONG THE SLOW MOVING FRONTAL BOUNDARY FRI AFTN/EVE...THEN
THE BOUNDARY SHOULD SLIDE EAST WITH WINDS QUICKLY VEERING
NORTH/NORTHEAST FOR SAT AND USHERING IN MUCH COOLER AIR TO THE
REGION.

CURRENT INDICATIONS ARE THAT HIGHS SAT MAY STRUGGLE TO WARM BEYOND
THE UPR 50S ACROSS NORTHEAST IL/NORTHWEST IN...WITH ONLY LOW 60S
ELSEWHERE. STRONG SFC RIDGE WILL REMAIN NORTH OF THE REGION...SO THE
PRIOR FRONTAL BOUNDARY MAY BECOME QUASI-STATIONARY FOR THE WEEKEND
ALONG THE OHIO VALLEY AND CONTINUE TO FEED PRECIP CHANCES TO THE
SOUTHERN CWFA.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* SOUTH-SOUTHWEST WINDS OF AROUND 40 KT AT 1000 FT
  OVERNIGHT...SETTING UP LOW LEVEL WIND SHEAR.

* MVFR CEILINGS PROBABLE AT TIMES TUESDAY WITH A CHANCE FOR
  TEMPORARY IFR.

* PERIODS OF SHRA WITH PERIODIC TSRA FROM LATE TUESDAY MORNING
  THROUGH THE AFTERNOON.

* NEAR DUE SOUTH WINDS ON TUESDAY WITH PERIODIC GUSTS POSSIBLE
  AND SOME VARIABILITY BETWEEN SOUTHEAST AND SOUTHWEST.

KREIN

//DISCUSSION...UPDATED 06Z...

GUSTY SOUTH-SOUTHWEST WINDS HAVE DIMINISHED TO 10 KT OR LESS AND
BECOME SOUTHERLY. A LOW-LEVEL JET WILL DEVELOP OVERHEAD WITH
SSWLY-SWLY WINDS OF 40 KT TO 45 KT FLOW AT 1500-2000 FT UNTIL
ARND 12Z. SOME THUNDERSTORMS MAY DEVELOP THROUGH OVERNIGHT AHEAD
OF A FRONT FROM NRN MO THROUGH ERN IA AND INTO WI. THESE STORMS
WILL ONLY MAKE SLOW PROGRESS EASTWARD DUE TO THE STRONG SSWLY-SWLY
WINDS ALOFT SO...AND STORMS THAT DO DEVELOP SHOULD REMAIN NORTH
AND NORTHWEST OF AREA TAF SITES...THOUGH THERE IS A CHANCE THAT A
FEW STORMS COULD APPROACH THE RFD TERMINAL AREA VERY LATE
TONIGHT.

AS AN MID LEVEL DISTURBANCE MOVING FROM THE SOUTHERN PLAINS TO
NRN IL BY TUESDAY AFTERNOON MAY BRING ANOTHER ROUND OF SHOWERS
WITH SCT EMBEDDED THUNDERSTORMS TO THE REGION. UPPER LEVEL FORCING
FROM THE MID LEVEL DISTURBANCE AND AN UPPER LEVEL JET STREAM WILL
ENHANCE THE LIKELIHOOD FOR SHRA AND THE CHANCE FOR TSRA...WITH THE
MOST LIKELY CHANCE FOR ACTIVITY FROM 15Z THROUGH 02Z. SOME
UNCERTAINTY REMAINS IN PINNING DOWN THE EXACT PERIOD FOR THE
TSRA...SO WILL MAINTAIN THE GOING TEMPO FOR LATE MORNING THROUGH
EARLY AFTERNOON. HOWEVER...THE PCPN ACTIVITY COULD BE SHIFTED OR
EXPANDED IN TIME.

WINDS WILL BE SOUTHERLY ON TUESDAY...THOUGH DIRECTION MAY BE A BIT
VARIABLE AROUND CONVECTIVE ACTIVITY...THOUGH A GENERALLY SOUTHERLY
DIRECTION SHOULD PREVAIL THROUGH THE NIGHT AND MUCH OF THE DAY
TUESDAY. SOME GUSTINESS IS POSSIBLE THROUGH THE ENTIRE DAY...WITH
THE LATEST GUIDANCE SUGGESTING THAT WINDS COULD STRENGTHEN AND
BECOME EVEN MORE GUSTY THROUGH THE NIGHT TOMORROW NIGHT WITH WINDS
VEERING SWLY AS SURFACE LOW PRESSURE MOVES NORTHEAST ACROSS
SOUTHERN WISCONSIN.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* HIGH CONFIDENCE IN 40-45 KT SSWLY-SWLY FLOW ALOFT OVERNIGHT...BUT
  MEDIUM IN TRUE LLWS OCCURRING.

* HIGH CONFIDENCE IN WIND TRENDS OVERNIGHT AND TUESDAY MORNING.
  MEDIUM IN WIND TRENDS TOMORROW EVENING.

* MEDIUM CONFIDENCE IN MVFR CIGS TUESDAY MORNING WITH LOWER
  CONFIDENCE IN DURATION AND HOW LOW CIGS WILL DROP.

* HIGH CONFIDENCE IN SHOWERS AND AT LEAST A PERIOD OF TSRA. LOW
  CONFIDENCE IN SPECIFIC TSRA TIMING AND IMPACT ON THE TERMINALS
  WITH MULTIPLE ROUNDS POSSIBLE BETWEEN 15Z AND 02Z.

KREIN

//OUTLOOK FOR ORD/MDW FOR 12Z WEDNESDAY-12Z MONDAY...UPDATED 00Z...

WEDNESDAY...CHANCE OF TSRA. WEST WINDS.
THURSDAY...SLIGHT CHANCE OF TSRA LATE AT NIGHT. SOUTHEAST WINDS.
FRIDAY...INCREASING CHANCE OF TSRA THROUGH THE DAY AND NIGHT.
         SOUTHWEST WINDS.
SATURDAY...SHRA LIKELY WITH A CHANCE OF TSRA. NORTHEAST WINDS.
SUNDAY...CHANCE OF SHRA. EAST WINDS.

MTF

&&

.MARINE...
229 AM CDT

WARM MOIST AIR CONTINUES TO FEED NORTH ACROSS THE LAKE
TODAY...WHICH MAY HELP TO FURTHER ENHANCE ANY AREAS OF FOG THAT
HAVE ALREADY DEVELOPED. IT IS POSSIBLE PATCHY DENSE FOG MAY
DEVELOP...ALTHOUGH WINDS MAY BE JUST STRONG ENOUGH TO LIMIT THE
COVERAGE AND INTENSITY OF THE FOG. A SURFACE LOW PRESSURE SYSTEM
WILL BE LIFTING NORTH ACROSS EASTERN IOWA INTO CENTRAL WISCONSIN
THIS EVENING. THE GRADIENT WILL TIGHTEN ACROSS THE
CENTRAL/SOUTHERN PORTIONS OF THE LAKE...WHICH WITH WARMER
NEARSHORE WATERS EXPECT SOME SLIGHTLY BETTER MIXING TO OCCUR.
FURTHER OUT ACROSS THE OPEN WATERS THE WATER REMAINS COLD AND
EXPECT THE STABILITY TO MAKE IT DIFFICULT TO MIX TO THE SFC THE
HIGHER GUSTS. HIGH PRESSURE THEN ARRIVES LATE WEDNESDAY WITH LIGHT
WINDS DEVELOPING. THEN HIGH PRESSURE SHIFTS EAST THURSDAY
NIGHT...WITH SOUTHERLY WINDS DEVELOPING AGAIN FRIDAY. A FRONTAL
BOUNDARY WILL APPROACH LAKE MICHIGAN LATE FRIDAY NIGHT THEN
STEADILY SLIDE SOUTH ALONG THE LAKE. THIS WILL ALLOW WINDS TO
QUICKLY VEER FROM SOUTH TO NORTH/NORTHEAST SATURDAY. ALONG WITH
THIS QUICK WIND SHIFT WILL BE COOLER AIR SLIDING SOUTH OVER THE
LAKE. WAVES SHOULD EASILY BUILD SATURDAY FOR THE CENTRAL/SOUTHERN
PORTIONS OF THE LAKE.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 260820
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
320 AM CDT TUE MAY 26 2015

.SHORT TERM...
319 AM CDT

THROUGH TUESDAY NIGHT...

FOR THE REMAINDER OF THE OVERNIGHT HOURS...CONDITIONS WILL REMAIN
QUIET ACROSS THE CWA AS A SERIES OF SHORT WAVES CONTINUE TO TRACK
NORTH AROUND THE TOP OF A PERSISTENT UPPER LEVEL RIDGE WHICH EXTENDS
FROM THE SERN CONUS THROUGH THE UPPER MISSISSIPPI VALLEY.  THIS
UPPER RIDGE HAS BEEN THE FEATURE WHICH HAS CONTROLLED THE PATH OF
THE SERIES OF SHORTWAVES LIFTING OUT OF THE SOUTHERN PLAINS...AND
WILL CONTINUE TO DO SO THROUGH THE DAY TODAY. SLY...MODERATELY
STRONG...WINDS WILL PERSIST THROUGH THE NIGHT...AND MUCH OF THE DAY
ALLOWING FOR SFC DEWPOINTS TO REMAIN CONSISTENT OR POSSIBLE INCH A
LITTLE HIGHER.

MAIN CONCERN FOR THE MORNING HOURS WILL BE THE TRACK OF A STRONG
SHORT WAVE AND ASSOCIATED SFC LOW LIFTING NORTHWARD THROUGH THE
MIDDLE MISSISSIPPI VALLEY.  THIS FEATURE WILL PREDOMINANTLY IMPACT
ERN IOWA AND WRN IL BY ARND DAYBREAK.  THROUGH THE MORNING...THE
COMBINATION OF ISENTROPIC LIFT IN THE WARM SECTOR OF THE
SYSTEM...ALL OF IL AND INTO NWRN IN...WILL LEAD TO SOME
DESTABILIZATION ACROSS THE REGION. A SFC TROUGH...AS WELL INDICATED
BY THE LATEST HIGH RES GUIDANCE...WITH LIFT THROUGH NRN IL/IN
THROUGH THE DAY...COINCIDENT WITH A STRONG SSWLY LOW LEVEL JET OF 45-
50 KT...WITH PROVIDE THE POTENTIAL FOR SHOWERS AND STRONG TO SEVERE
THUNDERSTORMS ACROSS THE CWA.  BASED ON WIND PROFILES AND MID LEVEL
DRYING...THE PRIMARY CONCERN WITH REGARD TO SEVERE WEATHER WILL BE
STRONG WIND GUSTS.  HOWEVER...SOME OF THE HIGH RES SFC WIND GUIDANCE
SUGGEST SOME SLIGHT BACKING OF SFC WINDS FROM 180-190 DEGREES TO 160-
170 DEGREES...WHILE WINDS ALOFT REMAIN SWLY.  THIS SLIGHT BACKING OF
THE SFC WINDS COULD PROVIDE ENOUGH DIRECTIONAL SHEAR THROUGH THE
LOWER LEVELS TO BRING AN ISOLD TORNADO THREAT. LOCALLY HEAVY
RAINFALL WILL ALSO BE CONCERNED WITH PWATS REACHING 1.75 INCHES
LATER THIS MORNING.  HOWEVER...FLOODING WILL LIKELY NOT BE A
SIGNIFICANT CONCERN AS THE SWLY WINDS RIGHT OFF THE DECK WILL RANGE
FROM ARND 45 KT ABOVE THE BOUNDARY LAYER TO ARND 90KT AT UPPER
LEVELS WHICH SHOULD ALLOW ANY OF THE STRONGER STORMS THAT DO DEVELOP
TO MOVE QUICKLY.

BY EARLY AFTERNOON...THE MAIN SHORT WAVE WILL LIFT INTO WISCONSIN
WHILE A SFC TROUGH TRACKS EAST ACROSS THE AREA.  THIS WILL LEAD TO
WINDS AT THE SFC VEERING TO SWLY...SETTING UP A UNIDIRECTIONAL WIND
PROFILE...EFFECTIVELY MINIMIZING THE SEVERE WEATHER THREAT TO THE
REGION.  BY LATE AFTERNOON AND INTO THE EVENING THE MODELS ARE
ADVERTISING THAT A DRY SLOW SHOULD NOSE INTO NRN IL...EFFECTIVELY
CUTTING OFF THE PCPN AREA INTO 2 SEPARATE AREA...ONE OVER WISCONSIN
AND ERN IOWA AND ANOTHER MORE FOCUSED OVER INDIANA.  THE NWRN
INDIANA COUNTIES WILL STILL HAVE A CHANCE FOR SOME SHOWERS AND
THUNDERSTORMS INTO THE EVENING...WHILE PCPN CHANCES OVER NRN IL
BEGIN TO WANE.  MUCH OF THE MODEL GUIDANCE ALSO INDICATED THAT THE
SHORTWAVE SHOULD SLOW IT`S PROGRESSION THROUGH WISCONSIN AS IT
APPROACHES THE APEX OF THE UPPER RIDGE.  AN ASSOCIATED SFC
TROUGH/COLD FRONT EXTENDING SOUTHWEST FROM THE SFC LOW WILL LINGER
OVER ERN IOWA IN THE EARLY EVENING BEFORE STEADILY PUSHING ACROSS
NRN IL AND INTO NWRN IN OVERNIGHT.  THROUGH THE NIGHT...THE
STRONGEST UPPER LEVEL FORCING WILL BE WELL NORTH OF THE CWA...SO ANY
LINGERING CHANCES FOR PCPN OVERNIGHT WILL BE LOW AND LIKELY CONFINED
TO THE NRN TIER COUNTIES OF IL...ALONG THE WI BORDER.

KREIN

&&

.LONG TERM...
229 AM CDT

WEDNESDAY THROUGH MONDAY...

WEDNESDAY THROUGH THURSDAY...
OPEN 500MB WAVE WILL BE LIFTING NORTHEAST ACROSS THE UPPER MIDWEST
INTO ONTARIO AND EVENTUALLY QUEBEC...WITH HEIGHTS SLOWLY INCREASING
WED AFTN. SFC FEATURES REMAIN DISORGANIZED WED...WITH A BOUNDARY
SLOWLY SHIFTING EAST. OPER GUIDANCE DIFFERS ON HOW QUICKLY PRECIP
WILL DEPART THE REGION. ENSEMBLE DATA SUGGESTS HOLDING ONTO CHC TO
SLIGHT CHC POPS MAINLY FOR THE CENTRAL/EASTERN CWFA WED/WED EVE.
ALTHOUGH WITH SOME HINT OF SFC HEIGHTS NUDGING UP...IT IS POSSIBLE
THAT SOME DRY AIR COULD FILTER IN AND KICK PRECIP EAST BY MIDDAY AND
ALLOW FOR A MAINLY DRY WED. SFC WINDS WILL BE TURNING SOUTHWEST TO
WEST...KEEPING AN OFFSHORE FLOW FOR LOCATIONS CLOSE TO LAKE
MICHIGAN. TEMPS SHOULD YET AGAIN TOUCH UPR 70S TO ARND 80 WED...IF
CLOUDS AND PRECIP CAN PUSH EAST BY MIDDAY...SOME CLEARING WOULD
ALLOW SFC TEMPS TO PUSH A COUPLE DEGREES WARMER INTO THE LOW 80S IN
SOME LOCATIONS. LATE IN THE EVENING THE GRADIENT SLACKENS
FURTHER...AND COULD ALLOW A LATE DAY ONSHORE FLOW TO DEVELOP FOR
AREAS ADJACENT TO LAKE MICHIGAN.

MID-LVL FLOW BEGINS TO FLATTEN AS A WEAK SFC RIDGE BECOMES ORIENTED
FROM WESTERN QUEBEC SOUTH THROUGH THE EASTERN OHIO RIVER VALLEY.
THIS WILL GENERALLY ALLOW A SOUTHERLY FLOW...ALTHOUGH THE GRADIENT
IS NOT VERY STRONG. THIS SHOULD SET THE STAGE FOR A LAKE
BREEZE/ONSHORE FLOW TO DEVELOP THUR. TIMING COULD END UP BEING
SLIGHTLY EARLIER GIVEN THE LIGHT SFC GRADIENT. GUIDANCE HAS BEEN
CONSISTENT IN HOLDING PRECIP WEST/SOUTH OF THE FORECAST AREA
THUR...AS A RESULT OF THE WEAK SFC RIDGING. SO ONE MORE MILD DAY
WITH HIGHS WARMING BACK INTO THE UPR 70S/LOW 80S...HOWEVER AS
PREVIOUSLY NOTED...A LAKE BREEZE IS LIKELY TO DEVELOP. THIS WILL
BLEED THE MUCH COOLER MARINE AIR WEST ACROSS NORTHEAST IL AND
DOWNTOWN CHICAGO. IF THE TIMING IS EARLIER IN THE DAY THUR...TEMPS
MAY NOT WARM BEYONG THE LOW/MID 60S ALONG THE CHICAGO LAKEFRONT.

FLOW THEN TURNS SOUTHERLY THUR NIGHT WITH THE MORE PROGRESSIVE FLOW
IN THE MID-LVLS PUSHING THE RIDGING EAST. A RETURN FLOW MOISTURE
WILL CONTINUE TO BE FOCUSED ACROSS THE CENTRAL CONUS THUR EVE...WITH
A SLOW MOVING FRONTAL BOUNDARY NUDGING EAST THUR NIGHT TOWARDS
WESTERN IL. THIS FRONTAL BOUNDARY WILL BECOME ENERGIZED AS A ROBUST
500MB VORT MAX BREAKS SOUTH FROM CENTRAL CANADA LATE THUR NIGHT.

THIS SHOULD ALLOW FOR AN ATMOSPHERIC RIVER TO DEVELOP FROM THE
SOUTHERN PLAINS STRETCHING NORTH THROUGH THE MID-MISSOURI VALLEY
INTO THE WESTERN GREAT LAKES EARLY FRI MORNING.

FRIDAY THROUGH EARLY NEXT WEEK...
ENSEMBLES CONTINUE TO PROG A ROBUST TROUGH SLIDING SOUTH FROM
CENTRAL CANADA FRI. THIS COUPLED WITH DOWNSTREAM MID-LVL RIDGING
ACROSS THE SOUTHEAST CONUS WILL STRENGTHEN THE FRONTAL BOUNDARY
THAT WILL BE ORIENTED FROM THE SOUTHERN PLAINS STRETCHING
NORTHEAST THROUGH THE GREAT LAKES REGION INTO WESTERN QUEBEC.

THIS SETUP IS IDEAL FOR THE DEVELOPMENT OF AN ATMOSPHERIC RIVER WITH
ABUNDANT LOW LEVEL MOISTURE AND EFFICIENT PRECIP PRODUCING
CONVECTION.

OPER GUIDANCE HAS BEEN RELATIVELY CONSISTENT WITH BRINGING A SERIES
OF WAVES ALONG THE SLOW MOVING FRONTAL BOUNDARY FRI AFTN/EVE...THEN
THE BOUNDARY SHOULD SLIDE EAST WITH WINDS QUICKLY VEERING
NORTH/NORTHEAST FOR SAT AND USHERING IN MUCH COOLER AIR TO THE
REGION.

CURRENT INDICATIONS ARE THAT HIGHS SAT MAY STRUGGLE TO WARM BEYOND
THE UPR 50S ACROSS NORTHEAST IL/NORTHWEST IN...WITH ONLY LOW 60S
ELSEWHERE. STRONG SFC RIDGE WILL REMAIN NORTH OF THE REGION...SO THE
PRIOR FRONTAL BOUNDARY MAY BECOME QUASI-STATIONARY FOR THE WEEKEND
ALONG THE OHIO VALLEY AND CONTINUE TO FEED PRECIP CHANCES TO THE
SOUTHERN CWFA.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* SOUTH-SOUTHWEST WINDS OF AROUND 40 KT AT 1000 FT
  OVERNIGHT...SETTING UP LOW LEVEL WIND SHEAR.

* MVFR CEILINGS PROBABLE AT TIMES TUESDAY WITH A CHANCE FOR
  TEMPORARY IFR.

* PERIODS OF SHRA WITH PERIODIC TSRA FROM LATE TUESDAY MORNING
  THROUGH THE AFTERNOON.

* NEAR DUE SOUTH WINDS ON TUESDAY WITH PERIODIC GUSTS POSSIBLE
  AND SOME VARIABILITY BETWEEN SOUTHEAST AND SOUTHWEST.

KREIN

//DISCUSSION...UPDATED 06Z...

GUSTY SOUTH-SOUTHWEST WINDS HAVE DIMINISHED TO 10 KT OR LESS AND
BECOME SOUTHERLY. A LOW-LEVEL JET WILL DEVELOP OVERHEAD WITH
SSWLY-SWLY WINDS OF 40 KT TO 45 KT FLOW AT 1500-2000 FT UNTIL
ARND 12Z. SOME THUNDERSTORMS MAY DEVELOP THROUGH OVERNIGHT AHEAD
OF A FRONT FROM NRN MO THROUGH ERN IA AND INTO WI. THESE STORMS
WILL ONLY MAKE SLOW PROGRESS EASTWARD DUE TO THE STRONG SSWLY-SWLY
WINDS ALOFT SO...AND STORMS THAT DO DEVELOP SHOULD REMAIN NORTH
AND NORTHWEST OF AREA TAF SITES...THOUGH THERE IS A CHANCE THAT A
FEW STORMS COULD APPROACH THE RFD TERMINAL AREA VERY LATE
TONIGHT.

AS AN MID LEVEL DISTURBANCE MOVING FROM THE SOUTHERN PLAINS TO
NRN IL BY TUESDAY AFTERNOON MAY BRING ANOTHER ROUND OF SHOWERS
WITH SCT EMBEDDED THUNDERSTORMS TO THE REGION. UPPER LEVEL FORCING
FROM THE MID LEVEL DISTURBANCE AND AN UPPER LEVEL JET STREAM WILL
ENHANCE THE LIKELIHOOD FOR SHRA AND THE CHANCE FOR TSRA...WITH THE
MOST LIKELY CHANCE FOR ACTIVITY FROM 15Z THROUGH 02Z. SOME
UNCERTAINTY REMAINS IN PINNING DOWN THE EXACT PERIOD FOR THE
TSRA...SO WILL MAINTAIN THE GOING TEMPO FOR LATE MORNING THROUGH
EARLY AFTERNOON. HOWEVER...THE PCPN ACTIVITY COULD BE SHIFTED OR
EXPANDED IN TIME.

WINDS WILL BE SOUTHERLY ON TUESDAY...THOUGH DIRECTION MAY BE A BIT
VARIABLE AROUND CONVECTIVE ACTIVITY...THOUGH A GENERALLY SOUTHERLY
DIRECTION SHOULD PREVAIL THROUGH THE NIGHT AND MUCH OF THE DAY
TUESDAY. SOME GUSTINESS IS POSSIBLE THROUGH THE ENTIRE DAY...WITH
THE LATEST GUIDANCE SUGGESTING THAT WINDS COULD STRENGTHEN AND
BECOME EVEN MORE GUSTY THROUGH THE NIGHT TOMORROW NIGHT WITH WINDS
VEERING SWLY AS SURFACE LOW PRESSURE MOVES NORTHEAST ACROSS
SOUTHERN WISCONSIN.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* HIGH CONFIDENCE IN 40-45 KT SSWLY-SWLY FLOW ALOFT OVERNIGHT...BUT
  MEDIUM IN TRUE LLWS OCCURRING.

* HIGH CONFIDENCE IN WIND TRENDS OVERNIGHT AND TUESDAY MORNING.
  MEDIUM IN WIND TRENDS TOMORROW EVENING.

* MEDIUM CONFIDENCE IN MVFR CIGS TUESDAY MORNING WITH LOWER
  CONFIDENCE IN DURATION AND HOW LOW CIGS WILL DROP.

* HIGH CONFIDENCE IN SHOWERS AND AT LEAST A PERIOD OF TSRA. LOW
  CONFIDENCE IN SPECIFIC TSRA TIMING AND IMPACT ON THE TERMINALS
  WITH MULTIPLE ROUNDS POSSIBLE BETWEEN 15Z AND 02Z.

KREIN

//OUTLOOK FOR ORD/MDW FOR 12Z WEDNESDAY-12Z MONDAY...UPDATED 00Z...

WEDNESDAY...CHANCE OF TSRA. WEST WINDS.
THURSDAY...SLIGHT CHANCE OF TSRA LATE AT NIGHT. SOUTHEAST WINDS.
FRIDAY...INCREASING CHANCE OF TSRA THROUGH THE DAY AND NIGHT.
         SOUTHWEST WINDS.
SATURDAY...SHRA LIKELY WITH A CHANCE OF TSRA. NORTHEAST WINDS.
SUNDAY...CHANCE OF SHRA. EAST WINDS.

MTF

&&

.MARINE...
229 AM CDT

WARM MOIST AIR CONTINUES TO FEED NORTH ACROSS THE LAKE
TODAY...WHICH MAY HELP TO FURTHER ENHANCE ANY AREAS OF FOG THAT
HAVE ALREADY DEVELOPED. IT IS POSSIBLE PATCHY DENSE FOG MAY
DEVELOP...ALTHOUGH WINDS MAY BE JUST STRONG ENOUGH TO LIMIT THE
COVERAGE AND INTENSITY OF THE FOG. A SURFACE LOW PRESSURE SYSTEM
WILL BE LIFTING NORTH ACROSS EASTERN IOWA INTO CENTRAL WISCONSIN
THIS EVENING. THE GRADIENT WILL TIGHTEN ACROSS THE
CENTRAL/SOUTHERN PORTIONS OF THE LAKE...WHICH WITH WARMER
NEARSHORE WATERS EXPECT SOME SLIGHTLY BETTER MIXING TO OCCUR.
FURTHER OUT ACROSS THE OPEN WATERS THE WATER REMAINS COLD AND
EXPECT THE STABILITY TO MAKE IT DIFFICULT TO MIX TO THE SFC THE
HIGHER GUSTS. HIGH PRESSURE THEN ARRIVES LATE WEDNESDAY WITH LIGHT
WINDS DEVELOPING. THEN HIGH PRESSURE SHIFTS EAST THURSDAY
NIGHT...WITH SOUTHERLY WINDS DEVELOPING AGAIN FRIDAY. A FRONTAL
BOUNDARY WILL APPROACH LAKE MICHIGAN LATE FRIDAY NIGHT THEN
STEADILY SLIDE SOUTH ALONG THE LAKE. THIS WILL ALLOW WINDS TO
QUICKLY VEER FROM SOUTH TO NORTH/NORTHEAST SATURDAY. ALONG WITH
THIS QUICK WIND SHIFT WILL BE COOLER AIR SLIDING SOUTH OVER THE
LAKE. WAVES SHOULD EASILY BUILD SATURDAY FOR THE CENTRAL/SOUTHERN
PORTIONS OF THE LAKE.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 260820
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
320 AM CDT TUE MAY 26 2015

.SHORT TERM...
319 AM CDT

THROUGH TUESDAY NIGHT...

FOR THE REMAINDER OF THE OVERNIGHT HOURS...CONDITIONS WILL REMAIN
QUIET ACROSS THE CWA AS A SERIES OF SHORT WAVES CONTINUE TO TRACK
NORTH AROUND THE TOP OF A PERSISTENT UPPER LEVEL RIDGE WHICH EXTENDS
FROM THE SERN CONUS THROUGH THE UPPER MISSISSIPPI VALLEY.  THIS
UPPER RIDGE HAS BEEN THE FEATURE WHICH HAS CONTROLLED THE PATH OF
THE SERIES OF SHORTWAVES LIFTING OUT OF THE SOUTHERN PLAINS...AND
WILL CONTINUE TO DO SO THROUGH THE DAY TODAY. SLY...MODERATELY
STRONG...WINDS WILL PERSIST THROUGH THE NIGHT...AND MUCH OF THE DAY
ALLOWING FOR SFC DEWPOINTS TO REMAIN CONSISTENT OR POSSIBLE INCH A
LITTLE HIGHER.

MAIN CONCERN FOR THE MORNING HOURS WILL BE THE TRACK OF A STRONG
SHORT WAVE AND ASSOCIATED SFC LOW LIFTING NORTHWARD THROUGH THE
MIDDLE MISSISSIPPI VALLEY.  THIS FEATURE WILL PREDOMINANTLY IMPACT
ERN IOWA AND WRN IL BY ARND DAYBREAK.  THROUGH THE MORNING...THE
COMBINATION OF ISENTROPIC LIFT IN THE WARM SECTOR OF THE
SYSTEM...ALL OF IL AND INTO NWRN IN...WILL LEAD TO SOME
DESTABILIZATION ACROSS THE REGION. A SFC TROUGH...AS WELL INDICATED
BY THE LATEST HIGH RES GUIDANCE...WITH LIFT THROUGH NRN IL/IN
THROUGH THE DAY...COINCIDENT WITH A STRONG SSWLY LOW LEVEL JET OF 45-
50 KT...WITH PROVIDE THE POTENTIAL FOR SHOWERS AND STRONG TO SEVERE
THUNDERSTORMS ACROSS THE CWA.  BASED ON WIND PROFILES AND MID LEVEL
DRYING...THE PRIMARY CONCERN WITH REGARD TO SEVERE WEATHER WILL BE
STRONG WIND GUSTS.  HOWEVER...SOME OF THE HIGH RES SFC WIND GUIDANCE
SUGGEST SOME SLIGHT BACKING OF SFC WINDS FROM 180-190 DEGREES TO 160-
170 DEGREES...WHILE WINDS ALOFT REMAIN SWLY.  THIS SLIGHT BACKING OF
THE SFC WINDS COULD PROVIDE ENOUGH DIRECTIONAL SHEAR THROUGH THE
LOWER LEVELS TO BRING AN ISOLD TORNADO THREAT. LOCALLY HEAVY
RAINFALL WILL ALSO BE CONCERNED WITH PWATS REACHING 1.75 INCHES
LATER THIS MORNING.  HOWEVER...FLOODING WILL LIKELY NOT BE A
SIGNIFICANT CONCERN AS THE SWLY WINDS RIGHT OFF THE DECK WILL RANGE
FROM ARND 45 KT ABOVE THE BOUNDARY LAYER TO ARND 90KT AT UPPER
LEVELS WHICH SHOULD ALLOW ANY OF THE STRONGER STORMS THAT DO DEVELOP
TO MOVE QUICKLY.

BY EARLY AFTERNOON...THE MAIN SHORT WAVE WILL LIFT INTO WISCONSIN
WHILE A SFC TROUGH TRACKS EAST ACROSS THE AREA.  THIS WILL LEAD TO
WINDS AT THE SFC VEERING TO SWLY...SETTING UP A UNIDIRECTIONAL WIND
PROFILE...EFFECTIVELY MINIMIZING THE SEVERE WEATHER THREAT TO THE
REGION.  BY LATE AFTERNOON AND INTO THE EVENING THE MODELS ARE
ADVERTISING THAT A DRY SLOW SHOULD NOSE INTO NRN IL...EFFECTIVELY
CUTTING OFF THE PCPN AREA INTO 2 SEPARATE AREA...ONE OVER WISCONSIN
AND ERN IOWA AND ANOTHER MORE FOCUSED OVER INDIANA.  THE NWRN
INDIANA COUNTIES WILL STILL HAVE A CHANCE FOR SOME SHOWERS AND
THUNDERSTORMS INTO THE EVENING...WHILE PCPN CHANCES OVER NRN IL
BEGIN TO WANE.  MUCH OF THE MODEL GUIDANCE ALSO INDICATED THAT THE
SHORTWAVE SHOULD SLOW IT`S PROGRESSION THROUGH WISCONSIN AS IT
APPROACHES THE APEX OF THE UPPER RIDGE.  AN ASSOCIATED SFC
TROUGH/COLD FRONT EXTENDING SOUTHWEST FROM THE SFC LOW WILL LINGER
OVER ERN IOWA IN THE EARLY EVENING BEFORE STEADILY PUSHING ACROSS
NRN IL AND INTO NWRN IN OVERNIGHT.  THROUGH THE NIGHT...THE
STRONGEST UPPER LEVEL FORCING WILL BE WELL NORTH OF THE CWA...SO ANY
LINGERING CHANCES FOR PCPN OVERNIGHT WILL BE LOW AND LIKELY CONFINED
TO THE NRN TIER COUNTIES OF IL...ALONG THE WI BORDER.

KREIN

&&

.LONG TERM...
229 AM CDT

WEDNESDAY THROUGH MONDAY...

WEDNESDAY THROUGH THURSDAY...
OPEN 500MB WAVE WILL BE LIFTING NORTHEAST ACROSS THE UPPER MIDWEST
INTO ONTARIO AND EVENTUALLY QUEBEC...WITH HEIGHTS SLOWLY INCREASING
WED AFTN. SFC FEATURES REMAIN DISORGANIZED WED...WITH A BOUNDARY
SLOWLY SHIFTING EAST. OPER GUIDANCE DIFFERS ON HOW QUICKLY PRECIP
WILL DEPART THE REGION. ENSEMBLE DATA SUGGESTS HOLDING ONTO CHC TO
SLIGHT CHC POPS MAINLY FOR THE CENTRAL/EASTERN CWFA WED/WED EVE.
ALTHOUGH WITH SOME HINT OF SFC HEIGHTS NUDGING UP...IT IS POSSIBLE
THAT SOME DRY AIR COULD FILTER IN AND KICK PRECIP EAST BY MIDDAY AND
ALLOW FOR A MAINLY DRY WED. SFC WINDS WILL BE TURNING SOUTHWEST TO
WEST...KEEPING AN OFFSHORE FLOW FOR LOCATIONS CLOSE TO LAKE
MICHIGAN. TEMPS SHOULD YET AGAIN TOUCH UPR 70S TO ARND 80 WED...IF
CLOUDS AND PRECIP CAN PUSH EAST BY MIDDAY...SOME CLEARING WOULD
ALLOW SFC TEMPS TO PUSH A COUPLE DEGREES WARMER INTO THE LOW 80S IN
SOME LOCATIONS. LATE IN THE EVENING THE GRADIENT SLACKENS
FURTHER...AND COULD ALLOW A LATE DAY ONSHORE FLOW TO DEVELOP FOR
AREAS ADJACENT TO LAKE MICHIGAN.

MID-LVL FLOW BEGINS TO FLATTEN AS A WEAK SFC RIDGE BECOMES ORIENTED
FROM WESTERN QUEBEC SOUTH THROUGH THE EASTERN OHIO RIVER VALLEY.
THIS WILL GENERALLY ALLOW A SOUTHERLY FLOW...ALTHOUGH THE GRADIENT
IS NOT VERY STRONG. THIS SHOULD SET THE STAGE FOR A LAKE
BREEZE/ONSHORE FLOW TO DEVELOP THUR. TIMING COULD END UP BEING
SLIGHTLY EARLIER GIVEN THE LIGHT SFC GRADIENT. GUIDANCE HAS BEEN
CONSISTENT IN HOLDING PRECIP WEST/SOUTH OF THE FORECAST AREA
THUR...AS A RESULT OF THE WEAK SFC RIDGING. SO ONE MORE MILD DAY
WITH HIGHS WARMING BACK INTO THE UPR 70S/LOW 80S...HOWEVER AS
PREVIOUSLY NOTED...A LAKE BREEZE IS LIKELY TO DEVELOP. THIS WILL
BLEED THE MUCH COOLER MARINE AIR WEST ACROSS NORTHEAST IL AND
DOWNTOWN CHICAGO. IF THE TIMING IS EARLIER IN THE DAY THUR...TEMPS
MAY NOT WARM BEYONG THE LOW/MID 60S ALONG THE CHICAGO LAKEFRONT.

FLOW THEN TURNS SOUTHERLY THUR NIGHT WITH THE MORE PROGRESSIVE FLOW
IN THE MID-LVLS PUSHING THE RIDGING EAST. A RETURN FLOW MOISTURE
WILL CONTINUE TO BE FOCUSED ACROSS THE CENTRAL CONUS THUR EVE...WITH
A SLOW MOVING FRONTAL BOUNDARY NUDGING EAST THUR NIGHT TOWARDS
WESTERN IL. THIS FRONTAL BOUNDARY WILL BECOME ENERGIZED AS A ROBUST
500MB VORT MAX BREAKS SOUTH FROM CENTRAL CANADA LATE THUR NIGHT.

THIS SHOULD ALLOW FOR AN ATMOSPHERIC RIVER TO DEVELOP FROM THE
SOUTHERN PLAINS STRETCHING NORTH THROUGH THE MID-MISSOURI VALLEY
INTO THE WESTERN GREAT LAKES EARLY FRI MORNING.

FRIDAY THROUGH EARLY NEXT WEEK...
ENSEMBLES CONTINUE TO PROG A ROBUST TROUGH SLIDING SOUTH FROM
CENTRAL CANADA FRI. THIS COUPLED WITH DOWNSTREAM MID-LVL RIDGING
ACROSS THE SOUTHEAST CONUS WILL STRENGTHEN THE FRONTAL BOUNDARY
THAT WILL BE ORIENTED FROM THE SOUTHERN PLAINS STRETCHING
NORTHEAST THROUGH THE GREAT LAKES REGION INTO WESTERN QUEBEC.

THIS SETUP IS IDEAL FOR THE DEVELOPMENT OF AN ATMOSPHERIC RIVER WITH
ABUNDANT LOW LEVEL MOISTURE AND EFFICIENT PRECIP PRODUCING
CONVECTION.

OPER GUIDANCE HAS BEEN RELATIVELY CONSISTENT WITH BRINGING A SERIES
OF WAVES ALONG THE SLOW MOVING FRONTAL BOUNDARY FRI AFTN/EVE...THEN
THE BOUNDARY SHOULD SLIDE EAST WITH WINDS QUICKLY VEERING
NORTH/NORTHEAST FOR SAT AND USHERING IN MUCH COOLER AIR TO THE
REGION.

CURRENT INDICATIONS ARE THAT HIGHS SAT MAY STRUGGLE TO WARM BEYOND
THE UPR 50S ACROSS NORTHEAST IL/NORTHWEST IN...WITH ONLY LOW 60S
ELSEWHERE. STRONG SFC RIDGE WILL REMAIN NORTH OF THE REGION...SO THE
PRIOR FRONTAL BOUNDARY MAY BECOME QUASI-STATIONARY FOR THE WEEKEND
ALONG THE OHIO VALLEY AND CONTINUE TO FEED PRECIP CHANCES TO THE
SOUTHERN CWFA.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* SOUTH-SOUTHWEST WINDS OF AROUND 40 KT AT 1000 FT
  OVERNIGHT...SETTING UP LOW LEVEL WIND SHEAR.

* MVFR CEILINGS PROBABLE AT TIMES TUESDAY WITH A CHANCE FOR
  TEMPORARY IFR.

* PERIODS OF SHRA WITH PERIODIC TSRA FROM LATE TUESDAY MORNING
  THROUGH THE AFTERNOON.

* NEAR DUE SOUTH WINDS ON TUESDAY WITH PERIODIC GUSTS POSSIBLE
  AND SOME VARIABILITY BETWEEN SOUTHEAST AND SOUTHWEST.

KREIN

//DISCUSSION...UPDATED 06Z...

GUSTY SOUTH-SOUTHWEST WINDS HAVE DIMINISHED TO 10 KT OR LESS AND
BECOME SOUTHERLY. A LOW-LEVEL JET WILL DEVELOP OVERHEAD WITH
SSWLY-SWLY WINDS OF 40 KT TO 45 KT FLOW AT 1500-2000 FT UNTIL
ARND 12Z. SOME THUNDERSTORMS MAY DEVELOP THROUGH OVERNIGHT AHEAD
OF A FRONT FROM NRN MO THROUGH ERN IA AND INTO WI. THESE STORMS
WILL ONLY MAKE SLOW PROGRESS EASTWARD DUE TO THE STRONG SSWLY-SWLY
WINDS ALOFT SO...AND STORMS THAT DO DEVELOP SHOULD REMAIN NORTH
AND NORTHWEST OF AREA TAF SITES...THOUGH THERE IS A CHANCE THAT A
FEW STORMS COULD APPROACH THE RFD TERMINAL AREA VERY LATE
TONIGHT.

AS AN MID LEVEL DISTURBANCE MOVING FROM THE SOUTHERN PLAINS TO
NRN IL BY TUESDAY AFTERNOON MAY BRING ANOTHER ROUND OF SHOWERS
WITH SCT EMBEDDED THUNDERSTORMS TO THE REGION. UPPER LEVEL FORCING
FROM THE MID LEVEL DISTURBANCE AND AN UPPER LEVEL JET STREAM WILL
ENHANCE THE LIKELIHOOD FOR SHRA AND THE CHANCE FOR TSRA...WITH THE
MOST LIKELY CHANCE FOR ACTIVITY FROM 15Z THROUGH 02Z. SOME
UNCERTAINTY REMAINS IN PINNING DOWN THE EXACT PERIOD FOR THE
TSRA...SO WILL MAINTAIN THE GOING TEMPO FOR LATE MORNING THROUGH
EARLY AFTERNOON. HOWEVER...THE PCPN ACTIVITY COULD BE SHIFTED OR
EXPANDED IN TIME.

WINDS WILL BE SOUTHERLY ON TUESDAY...THOUGH DIRECTION MAY BE A BIT
VARIABLE AROUND CONVECTIVE ACTIVITY...THOUGH A GENERALLY SOUTHERLY
DIRECTION SHOULD PREVAIL THROUGH THE NIGHT AND MUCH OF THE DAY
TUESDAY. SOME GUSTINESS IS POSSIBLE THROUGH THE ENTIRE DAY...WITH
THE LATEST GUIDANCE SUGGESTING THAT WINDS COULD STRENGTHEN AND
BECOME EVEN MORE GUSTY THROUGH THE NIGHT TOMORROW NIGHT WITH WINDS
VEERING SWLY AS SURFACE LOW PRESSURE MOVES NORTHEAST ACROSS
SOUTHERN WISCONSIN.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* HIGH CONFIDENCE IN 40-45 KT SSWLY-SWLY FLOW ALOFT OVERNIGHT...BUT
  MEDIUM IN TRUE LLWS OCCURRING.

* HIGH CONFIDENCE IN WIND TRENDS OVERNIGHT AND TUESDAY MORNING.
  MEDIUM IN WIND TRENDS TOMORROW EVENING.

* MEDIUM CONFIDENCE IN MVFR CIGS TUESDAY MORNING WITH LOWER
  CONFIDENCE IN DURATION AND HOW LOW CIGS WILL DROP.

* HIGH CONFIDENCE IN SHOWERS AND AT LEAST A PERIOD OF TSRA. LOW
  CONFIDENCE IN SPECIFIC TSRA TIMING AND IMPACT ON THE TERMINALS
  WITH MULTIPLE ROUNDS POSSIBLE BETWEEN 15Z AND 02Z.

KREIN

//OUTLOOK FOR ORD/MDW FOR 12Z WEDNESDAY-12Z MONDAY...UPDATED 00Z...

WEDNESDAY...CHANCE OF TSRA. WEST WINDS.
THURSDAY...SLIGHT CHANCE OF TSRA LATE AT NIGHT. SOUTHEAST WINDS.
FRIDAY...INCREASING CHANCE OF TSRA THROUGH THE DAY AND NIGHT.
         SOUTHWEST WINDS.
SATURDAY...SHRA LIKELY WITH A CHANCE OF TSRA. NORTHEAST WINDS.
SUNDAY...CHANCE OF SHRA. EAST WINDS.

MTF

&&

.MARINE...
229 AM CDT

WARM MOIST AIR CONTINUES TO FEED NORTH ACROSS THE LAKE
TODAY...WHICH MAY HELP TO FURTHER ENHANCE ANY AREAS OF FOG THAT
HAVE ALREADY DEVELOPED. IT IS POSSIBLE PATCHY DENSE FOG MAY
DEVELOP...ALTHOUGH WINDS MAY BE JUST STRONG ENOUGH TO LIMIT THE
COVERAGE AND INTENSITY OF THE FOG. A SURFACE LOW PRESSURE SYSTEM
WILL BE LIFTING NORTH ACROSS EASTERN IOWA INTO CENTRAL WISCONSIN
THIS EVENING. THE GRADIENT WILL TIGHTEN ACROSS THE
CENTRAL/SOUTHERN PORTIONS OF THE LAKE...WHICH WITH WARMER
NEARSHORE WATERS EXPECT SOME SLIGHTLY BETTER MIXING TO OCCUR.
FURTHER OUT ACROSS THE OPEN WATERS THE WATER REMAINS COLD AND
EXPECT THE STABILITY TO MAKE IT DIFFICULT TO MIX TO THE SFC THE
HIGHER GUSTS. HIGH PRESSURE THEN ARRIVES LATE WEDNESDAY WITH LIGHT
WINDS DEVELOPING. THEN HIGH PRESSURE SHIFTS EAST THURSDAY
NIGHT...WITH SOUTHERLY WINDS DEVELOPING AGAIN FRIDAY. A FRONTAL
BOUNDARY WILL APPROACH LAKE MICHIGAN LATE FRIDAY NIGHT THEN
STEADILY SLIDE SOUTH ALONG THE LAKE. THIS WILL ALLOW WINDS TO
QUICKLY VEER FROM SOUTH TO NORTH/NORTHEAST SATURDAY. ALONG WITH
THIS QUICK WIND SHIFT WILL BE COOLER AIR SLIDING SOUTH OVER THE
LAKE. WAVES SHOULD EASILY BUILD SATURDAY FOR THE CENTRAL/SOUTHERN
PORTIONS OF THE LAKE.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 260739
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
239 AM CDT TUE MAY 26 2015

.SHORT TERM...
255 PM CDT

THROUGH TUESDAY...

SHOWERS CONTINUE TO DIMINISH AS WE GET ON THE SUBSIDENT SIDE OF THE
DEPARTING UPPER TROUGH AXIS THAT WILL QUICKLY EXIT TO THE NORTHEAST
TONIGHT. SURFACE LOW PRESSURE IS PUSHING INTO UPPER MICHIGAN WHILE
LEAVING MODEST PRESSURE RISES IN ITS WAKE. WIND GUSTS TO 30 TO
LOCALLY 35 MPH WILL CONTINUE THROUGH THE AFTERNOON. EXPECT TO SEE
A LITTLE MORE BLUE SKY THROUGH THE AFTERNOON/EARLY EVENING WHICH
WILL ALLOW TEMPERATURES TO SLOWLY INCH UPWARD TO THE UPPER 70S TO
LOW 80S...THOUGH WITH MOIST SW FLOW EXPECT THESE LOWER CLOUDS TO
LINGER AROUND A BIT LONGER.

THE ACTIVE PATTERN CONTINUES ACROSS THE AREA FOR THE NEXT 24 HOURS.
SEVERAL UPPER LEVEL LOW PRESSURE SYSTEMS ARE NOTED IN AFTERNOON
WATER VAPOR IMAGERY. THE FIRST IS OVER THE NEBRASKA PANHANDLE...WITH
ASSOCIATED LEADING SHORTWAVE ENERGY TRIGGERING SOME SHOWERS AND T-
STORMS ACROSS IOWA...THEN THE BIGGER SHOWS TO THE SOUTH WITH THE
COMPLEX OF STRONG/SEVERE THUNDERSTORMS ASSOCIATED WITH A NEGATIVELY
TILTED TROUGH IN THE TEXAS. THE NORTHERN SHORTWAVE IS EXPECTED TO
CONTINUE DEVELOPING SHOWERS AND STORMS ACROSS IOWA AND INTO FAR
WESTERN ILLINOIS AND WISCONSIN. SOME OF THIS MAY CLIP OUR FAR
NORTHWESTERN COUNTIES...INCLUDING THE ROCKFORD AREA...BUT FEEL AT
THIS POINT THAT IT SHOULD LARGELY BE OFF FARTHER NW. HAVE HELD OFF
AND KEPT THIS ACTIVITY OUT OF AREA.

THEN TONIGHT THE LOWER LEVEL FRONTAL BOUNDARY ASSOCIATED WITH THE
NORTHERN WAVE WILL SAG SOUTHEAST TOWARD THE AREA LATE TONIGHT. MUCH
OF THE GUIDANCE THEN BRINGS THE SOUTHERN SHORTWAVE TOWARD OUR AREA
LATE TONIGHT AND MORE SO ON TUESDAY ON A DECENT UPPER LEVEL JET. THE
LARGE SUITE OF GUIDANCE KEEPS THESE TWO LOWS SEPARATE...ALLOWING
MUCH OF THE NORTHERN STREAM SHOWERS/STORMS TO LARGELY REMAIN OUT OF
AREA...BUT THEY MAY BEGIN TO AFFECT AREAS WEST OF I-39 IN ILLINOIS
OVERNIGHT.

TUESDAY MORNING IS WHEN BETTER CHANCES OF SHOWERS AND SCATTERED
THUNDERSTORMS WOULD BE. THIS MID MORNING/EARLY AFTERNOON PERIOD
FEATURES MODEST LOW/MID LEVEL ISENTROPIC LIFT/PW VALUES APPROACHING
1.5 INCHES AND THETA-E RIDGE NOSING IN FROM THE SOUTH. WE SHOULD
HAVE SOME SHOWERS AND THUNDERSTORMS MOVING FROM SOUTH TO NORTH
DURING THIS TIME FRAME.  DEPENDING ON THE INTERACTION OF THESE TWO
SYSTEMS AND IF THINGS SLOW DOWN A BIT...BETTER INSTABILITY WILL BE
TAPPED INTO IN THE AFTERNOON. THE NAM WOULD SUGGEST THIS
SOLUTION...WHILE THE GLOBAL GFS/ECMWF SUGGEST THE MID-MORNING TO
EARLY AFTERNOON PERIOD WOULD BE THE MOST LIKELY PERIOD WHERE DEEPER
MOISTURE IS AVAILABLE AND CO-LOCATED WITH THE UPPER FORCING.
CONFIDENCE ON TIMING IS ONLY MEDIUM WHICH REQUIRED CARRYING AN
EXTENDED PERIOD OF LIKELY POPS FOR MUCH OF THE DAY.

KMD

&&

.LONG TERM...
229 AM CDT

WEDNESDAY THROUGH MONDAY...

WEDNESDAY THROUGH THURSDAY...
OPEN 500MB WAVE WILL BE LIFTING NORTHEAST ACROSS THE UPPER MIDWEST
INTO ONTARIO AND EVENTUALLY QUEBEC...WITH HEIGHTS SLOWLY INCREASING
WED AFTN. SFC FEATURES REMAIN DISORGANIZED WED...WITH A BOUNDARY
SLOWLY SHIFTING EAST. OPER GUIDANCE DIFFERS ON HOW QUICKLY PRECIP
WILL DEPART THE REGION. ENSEMBLE DATA SUGGESTS HOLDING ONTO CHC TO
SLIGHT CHC POPS MAINLY FOR THE CENTRAL/EASTERN CWFA WED/WED EVE.
ALTHOUGH WITH SOME HINT OF SFC HEIGHTS NUDGING UP...IT IS POSSIBLE
THAT SOME DRY AIR COULD FILTER IN AND KICK PRECIP EAST BY MIDDAY AND
ALLOW FOR A MAINLY DRY WED. SFC WINDS WILL BE TURNING SOUTHWEST TO
WEST...KEEPING AN OFFSHORE FLOW FOR LOCATIONS CLOSE TO LAKE
MICHIGAN. TEMPS SHOULD YET AGAIN TOUCH UPR 70S TO ARND 80 WED...IF
CLOUDS AND PRECIP CAN PUSH EAST BY MIDDAY...SOME CLEARING WOULD
ALLOW SFC TEMPS TO PUSH A COUPLE DEGREES WARMER INTO THE LOW 80S IN
SOME LOCATIONS. LATE IN THE EVENING THE GRADIENT SLACKENS
FURTHER...AND COULD ALLOW A LATE DAY ONSHORE FLOW TO DEVELOP FOR
AREAS ADJACENT TO LAKE MICHIGAN.

MID-LVL FLOW BEGINS TO FLATTEN AS A WEAK SFC RIDGE BECOMES ORIENTED
FROM WESTERN QUEBEC SOUTH THROUGH THE EASTERN OHIO RIVER VALLEY.
THIS WILL GENERALLY ALLOW A SOUTHERLY FLOW...ALTHOUGH THE GRADIENT
IS NOT VERY STRONG. THIS SHOULD SET THE STAGE FOR A LAKE
BREEZE/ONSHORE FLOW TO DEVELOP THUR. TIMING COULD END UP BEING
SLIGHTLY EARLIER GIVEN THE LIGHT SFC GRADIENT. GUIDANCE HAS BEEN
CONSISTENT IN HOLDING PRECIP WEST/SOUTH OF THE FORECAST AREA
THUR...AS A RESULT OF THE WEAK SFC RIDGING. SO ONE MORE MILD DAY
WITH HIGHS WARMING BACK INTO THE UPR 70S/LOW 80S...HOWEVER AS
PREVIOUSLY NOTED...A LAKE BREEZE IS LIKELY TO DEVELOP. THIS WILL
BLEED THE MUCH COOLER MARINE AIR WEST ACROSS NORTHEAST IL AND
DOWNTOWN CHICAGO. IF THE TIMING IS EARLIER IN THE DAY THUR...TEMPS
MAY NOT WARM BEYONG THE LOW/MID 60S ALONG THE CHICAGO LAKEFRONT.

FLOW THEN TURNS SOUTHERLY THUR NIGHT WITH THE MORE PROGRESSIVE FLOW
IN THE MID-LVLS PUSHING THE RIDGING EAST. A RETURN FLOW MOISTURE
WILL CONTINUE TO BE FOCUSED ACROSS THE CENTRAL CONUS THUR EVE...WITH
A SLOW MOVING FRONTAL BOUNDARY NUDGING EAST THUR NIGHT TOWARDS
WESTERN IL. THIS FRONTAL BOUNDARY WILL BECOME ENERGIZED AS A ROBUST
500MB VORT MAX BREAKS SOUTH FROM CENTRAL CANADA LATE THUR NIGHT.

THIS SHOULD ALLOW FOR AN ATMOSPHERIC RIVER TO DEVELOP FROM THE
SOUTHERN PLAINS STRETCHING NORTH THROUGH THE MID-MISSOURI VALLEY
INTO THE WESTERN GREAT LAKES EARLY FRI MORNING.


FRIDAY THROUGH EARLY NEXT WEEK...
ENSEMBLES CONTINUE TO PROG A ROBUST TROUGH SLIDING SOUTH FROM
CENTRAL CANADA FRI. THIS COUPLED WITH DOWNSTREAM MID-LVL RIDGING
ACROSS THE SOUTHEAST CONUS WILL STRENGTHEN THE FRONTAL BOUNDARY
THAT WILL BE ORIENTED FROM THE SOUTHERN PLAINS STRETCHING
NORTHEAST THROUGH THE GREAT LAKES REGION INTO WESTERN QUEBEC.

THIS SETUP IS IDEAL FOR THE DEVELOPMENT OF AN ATMOSPHERIC RIVER WITH
ABUNDANT LOW LEVEL MOISTURE AND EFFICIENT PRECIP PRODUCING
CONVECTION.

OPER GUIDANCE HAS BEEN RELATIVELY CONSISTENT WITH BRINGING A SERIES
OF WAVES ALONG THE SLOW MOVING FRONTAL BOUNDARY FRI AFTN/EVE...THEN
THE BOUNDARY SHOULD SLIDE EAST WITH WINDS QUICKLY VEERING
NORTH/NORTHEAST FOR SAT AND USHERING IN MUCH COOLER AIR TO THE
REGION.

CURRENT INDICATIONS ARE THAT HIGHS SAT MAY STRUGGLE TO WARM BEYOND
THE UPR 50S ACROSS NORTHEAST IL/NORTHWEST IN...WITH ONLY LOW 60S
ELSEWHERE. STRONG SFC RIDGE WILL REMAIN NORTH OF THE REGION...SO THE
PRIOR FRONTAL BOUNDARY MAY BECOME QUASI-STATIONARY FOR THE WEEKEND
ALONG THE OHIO VALLEY AND CONTINUE TO FEED PRECIP CHANCES TO THE
SOUTHERN CWFA.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* SOUTH-SOUTHWEST WINDS OF AROUND 40 KT AT 1000 FT
  OVERNIGHT...SETTING UP LOW LEVEL WIND SHEAR.

* MVFR CEILINGS PROBABLE AT TIMES TUESDAY WITH A CHANCE FOR
  TEMPORARY IFR.

* PERIODS OF SHRA WITH PERIODIC TSRA FROM LATE TUESDAY MORNING
  THROUGH THE AFTERNOON.

* NEAR DUE SOUTH WINDS ON TUESDAY WITH PERIODIC GUSTS POSSIBLE
  AND SOME VARIABILITY BETWEEN SOUTHEAST AND SOUTHWEST.

KREIN

//DISCUSSION...UPDATED 06Z...

GUSTY SOUTH-SOUTHWEST WINDS HAVE DIMINISHED TO 10 KT OR LESS AND
BECOME SOUTHERLY. A LOW-LEVEL JET WILL DEVELOP OVERHEAD WITH
SSWLY-SWLY WINDS OF 40 KT TO 45 KT FLOW AT 1500-2000 FT UNTIL
ARND 12Z. SOME THUNDERSTORMS MAY DEVELOP THROUGH OVERNIGHT AHEAD
OF A FRONT FROM NRN MO THROUGH ERN IA AND INTO WI. THESE STORMS
WILL ONLY MAKE SLOW PROGRESS EASTWARD DUE TO THE STRONG SSWLY-SWLY
WINDS ALOFT SO...AND STORMS THAT DO DEVELOP SHOULD REMAIN NORTH
AND NORTHWEST OF AREA TAF SITES...THOUGH THERE IS A CHANCE THAT A
FEW STORMS COULD APPROACH THE RFD TERMINAL AREA VERY LATE
TONIGHT.

AS AN MID LEVEL DISTURBANCE MOVING FROM THE SOUTHERN PLAINS TO
NRN IL BY TUESDAY AFTERNOON MAY BRING ANOTHER ROUND OF SHOWERS
WITH SCT EMBEDDED THUNDERSTORMS TO THE REGION. UPPER LEVEL FORCING
FROM THE MID LEVEL DISTURBANCE AND AN UPPER LEVEL JET STREAM WILL
ENHANCE THE LIKELIHOOD FOR SHRA AND THE CHANCE FOR TSRA...WITH THE
MOST LIKELY CHANCE FOR ACTIVITY FROM 15Z THROUGH 02Z. SOME
UNCERTAINTY REMAINS IN PINNING DOWN THE EXACT PERIOD FOR THE
TSRA...SO WILL MAINTAIN THE GOING TEMPO FOR LATE MORNING THROUGH
EARLY AFTERNOON. HOWEVER...THE PCPN ACTIVITY COULD BE SHIFTED OR
EXPANDED IN TIME.

WINDS WILL BE SOUTHERLY ON TUESDAY...THOUGH DIRECTION MAY BE A BIT
VARIABLE AROUND CONVECTIVE ACTIVITY...THOUGH A GENERALLY SOUTHERLY
DIRECTION SHOULD PREVAIL THROUGH THE NIGHT AND MUCH OF THE DAY
TUESDAY. SOME GUSTINESS IS POSSIBLE THROUGH THE ENTIRE DAY...WITH
THE LATEST GUIDANCE SUGGESTING THAT WINDS COULD STRENGTHEN AND
BECOME EVEN MORE GUSTY THROUGH THE NIGHT TOMORROW NIGHT WITH WINDS
VEERING SWLY AS SURFACE LOW PRESSURE MOVES NORTHEAST ACROSS
SOUTHERN WISCONSIN.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* HIGH CONFIDENCE IN 40-45 KT SSWLY-SWLY FLOW ALOFT OVERNIGHT...BUT
  MEDIUM IN TRUE LLWS OCCURRING.

* HIGH CONFIDENCE IN WIND TRENDS OVERNIGHT AND TUESDAY MORNING.
  MEDIUM IN WIND TRENDS TOMORROW EVENING.

* MEDIUM CONFIDENCE IN MVFR CIGS TUESDAY MORNING WITH LOWER
  CONFIDENCE IN DURATION AND HOW LOW CIGS WILL DROP.

* HIGH CONFIDENCE IN SHOWERS AND AT LEAST A PERIOD OF TSRA. LOW
  CONFIDENCE IN SPECIFIC TSRA TIMING AND IMPACT ON THE TERMINALS
  WITH MULTIPLE ROUNDS POSSIBLE BETWEEN 15Z AND 02Z.

KREIN

//OUTLOOK FOR ORD/MDW FOR 12Z WEDNESDAY-12Z MONDAY...UPDATED 00Z...

WEDNESDAY...CHANCE OF TSRA. WEST WINDS.
THURSDAY...SLIGHT CHANCE OF TSRA LATE AT NIGHT. SOUTHEAST WINDS.
FRIDAY...INCREASING CHANCE OF TSRA THROUGH THE DAY AND NIGHT.
         SOUTHWEST WINDS.
SATURDAY...SHRA LIKELY WITH A CHANCE OF TSRA. NORTHEAST WINDS.
SUNDAY...CHANCE OF SHRA. EAST WINDS.

MTF

&&

.MARINE...
229 AM CDT

WARM MOIST AIR CONTINUES TO FEED NORTH ACROSS THE LAKE
TODAY...WHICH MAY HELP TO FURTHER ENHANCE ANY AREAS OF FOG THAT
HAVE ALREADY DEVELOPED. IT IS POSSIBLE PATCHY DENSE FOG MAY
DEVELOP...ALTHOUGH WINDS MAY BE JUST STRONG ENOUGH TO LIMIT THE
COVERAGE AND INTENSITY OF THE FOG. A SURFACE LOW PRESSURE SYSTEM
WILL BE LIFTING NORTH ACROSS EASTERN IOWA INTO CENTRAL WISCONSIN
THIS EVENING. THE GRADIENT WILL TIGHTEN ACROSS THE
CENTRAL/SOUTHERN PORTIONS OF THE LAKE...WHICH WITH WARMER
NEARSHORE WATERS EXPECT SOME SLIGHTLY BETTER MIXING TO OCCUR.
FURTHER OUT ACROSS THE OPEN WATERS THE WATER REMAINS COLD AND
EXPECT THE STABILITY TO MAKE IT DIFFICULT TO MIX TO THE SFC THE
HIGHER GUSTS. HIGH PRESSURE THEN ARRIVES LATE WEDNESDAY WITH LIGHT
WINDS DEVELOPING. THEN HIGH PRESSURE SHIFTS EAST THURSDAY
NIGHT...WITH SOUTHERLY WINDS DEVELOPING AGAIN FRIDAY. A FRONTAL
BOUNDARY WILL APPROACH LAKE MICHIGAN LATE FRIDAY NIGHT THEN
STEADILY SLIDE SOUTH ALONG THE LAKE. THIS WILL ALLOW WINDS TO
QUICKLY VEER FROM SOUTH TO NORTH/NORTHEAST SATURDAY. ALONG WITH
THIS QUICK WIND SHIFT WILL BE COOLER AIR SLIDING SOUTH OVER THE
LAKE. WAVES SHOULD EASILY BUILD SATURDAY FOR THE CENTRAL/SOUTHERN
PORTIONS OF THE LAKE.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 260555
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1255 AM CDT TUE MAY 26 2015

.SHORT TERM...
255 PM CDT

THROUGH TUESDAY...

SHOWERS CONTINUE TO DIMINISH AS WE GET ON THE SUBSIDENT SIDE OF THE
DEPARTING UPPER TROUGH AXIS THAT WILL QUICKLY EXIT TO THE NORTHEAST
TONIGHT. SURFACE LOW PRESSURE IS PUSHING INTO UPPER MICHIGAN WHILE
LEAVING MODEST PRESSURE RISES IN ITS WAKE. WIND GUSTS TO 30 TO
LOCALLY 35 MPH WILL CONTINUE THROUGH THE AFTERNOON. EXPECT TO SEE
A LITTLE MORE BLUE SKY THROUGH THE AFTERNOON/EARLY EVENING WHICH
WILL ALLOW TEMPERATURES TO SLOWLY INCH UPWARD TO THE UPPER 70S TO
LOW 80S...THOUGH WITH MOIST SW FLOW EXPECT THESE LOWER CLOUDS TO
LINGER AROUND A BIT LONGER.

THE ACTIVE PATTERN CONTINUES ACROSS THE AREA FOR THE NEXT 24 HOURS.
SEVERAL UPPER LEVEL LOW PRESSURE SYSTEMS ARE NOTED IN AFTERNOON
WATER VAPOR IMAGERY. THE FIRST IS OVER THE NEBRASKA PANHANDLE...WITH
ASSOCIATED LEADING SHORTWAVE ENERGY TRIGGERING SOME SHOWERS AND T-
STORMS ACROSS IOWA...THEN THE BIGGER SHOWS TO THE SOUTH WITH THE
COMPLEX OF STRONG/SEVERE THUNDERSTORMS ASSOCIATED WITH A NEGATIVELY
TILTED TROUGH IN THE TEXAS. THE NORTHERN SHORTWAVE IS EXPECTED TO
CONTINUE DEVELOPING SHOWERS AND STORMS ACROSS IOWA AND INTO FAR
WESTERN ILLINOIS AND WISCONSIN. SOME OF THIS MAY CLIP OUR FAR
NORTHWESTERN COUNTIES...INCLUDING THE ROCKFORD AREA...BUT FEEL AT
THIS POINT THAT IT SHOULD LARGELY BE OFF FARTHER NW. HAVE HELD OFF
AND KEPT THIS ACTIVITY OUT OF AREA.

THEN TONIGHT THE LOWER LEVEL FRONTAL BOUNDARY ASSOCIATED WITH THE
NORTHERN WAVE WILL SAG SOUTHEAST TOWARD THE AREA LATE TONIGHT. MUCH
OF THE GUIDANCE THEN BRINGS THE SOUTHERN SHORTWAVE TOWARD OUR AREA
LATE TONIGHT AND MORE SO ON TUESDAY ON A DECENT UPPER LEVEL JET. THE
LARGE SUITE OF GUIDANCE KEEPS THESE TWO LOWS SEPARATE...ALLOWING
MUCH OF THE NORTHERN STREAM SHOWERS/STORMS TO LARGELY REMAIN OUT OF
AREA...BUT THEY MAY BEGIN TO AFFECT AREAS WEST OF I-39 IN ILLINOIS
OVERNIGHT.

TUESDAY MORNING IS WHEN BETTER CHANCES OF SHOWERS AND SCATTERED
THUNDERSTORMS WOULD BE. THIS MID MORNING/EARLY AFTERNOON PERIOD
FEATURES MODEST LOW/MID LEVEL ISENTROPIC LIFT/PW VALUES APPROACHING
1.5 INCHES AND THETA-E RIDGE NOSING IN FROM THE SOUTH. WE SHOULD
HAVE SOME SHOWERS AND THUNDERSTORMS MOVING FROM SOUTH TO NORTH
DURING THIS TIME FRAME.  DEPENDING ON THE INTERACTION OF THESE TWO
SYSTEMS AND IF THINGS SLOW DOWN A BIT...BETTER INSTABILITY WILL BE
TAPPED INTO IN THE AFTERNOON. THE NAM WOULD SUGGEST THIS
SOLUTION...WHILE THE GLOBAL GFS/ECMWF SUGGEST THE MID-MORNING TO
EARLY AFTERNOON PERIOD WOULD BE THE MOST LIKELY PERIOD WHERE DEEPER
MOISTURE IS AVAILABLE AND CO-LOCATED WITH THE UPPER FORCING.
CONFIDENCE ON TIMING IS ONLY MEDIUM WHICH REQUIRED CARRYING AN
EXTENDED PERIOD OF LIKELY POPS FOR MUCH OF THE DAY.

KMD

&&

.LONG TERM...
319 PM CDT

WEDNESDAY NIGHT THROUGH MONDAY...

AN UPPER LEVEL SHORTWAVE TROUGH PASSES OVERHEAD TUESDAY NIGHT
THROUGH WEDNESDAY WITH NUMEROUS PERIODS OF SHOWERS AND THUNDERSTORMS
EXPECTED.  THE SFC FCST ALSO FEATURES A BOUNDARY MOVING THROUGH THE
CWA WEDNESDAY WHICH COULD HELP FORCE SHOWERS AND STORMS. HAVE HIGHER
CONFIDENCE IN PRECIP TUESDAY NIGHT THAN WEDNESDAY. CAPE LOOKS
MARGINAL OUTSIDE OF THE TYPICALLY TOO ROBUST NAM SOUNDINGS. FCST
SOUNDINGS LACK SHEAR...BUT THEY DO FEATURE INVERTED V/S AT THE SFC
AND SOME DRY AIR ALOFT. THIS SUGGESTS GUSTY WINDS ARE PSBL BUT FLOW
IS LESS THAN 40 KT ALOFT SO DAMAGING WINDS ARE NOT EXPECTED. PWAT
VALUES ARE FORECASTED TO BE ARND 1.3 INCHES WHICH IS ABOVE NORMAL
FOR THIS TIME OF YEAR...THEREFORE HEAVY DOWNPOURS ARE POSSIBLE.

WITH 925MB TEMPS BTWN +18 TO +20C...WARMED TEMPS SLIGHTLY FOR
WEDNESDAY INTO THE UPPER 70S TO AROUND 80.

HIGH PRESSURE THEN SPREADS ACROSS THE REGION WEDNESDAY NIGHT AND
HANGS AROUND THROUGH THURSDAY. THIS SHOULD RESULT IN DRY CONDITIONS
OUTSIDE OF POSSIBLE ISOLATED SHOWERS OVER LAKE MI. WINDS TURN OFF OF
THE LAKE THURSDAY SO AREAS ALONG THE LAKE WILL BE IN THE LOW
70S...WHILE AREAS AWAY FROM THE LAKE WILL GET INTO THE LOW TO MID
80S.

THE NEXT SFC LOW FORMS OVER THE PLAINS THURSDAY EVENING AND PASSES
OVER ONTARIO LATE THURSDAY NIGHT THROUGH FRIDAY MORNING. A LOW
PRESSURE TROUGH ACCOMPANIES THE LOW/S COLD FRONT WHICH SLIDES
THROUGH LATE THIS WEEK. GUIDANCE DIFFERS ON HOW QUICKLY THE FRONT
WILL TRAVEL WITH THE GFS BEING THE QUICKER MODEL.  THE MODELS DO
AGREE THAT THE LOWS WARM FRONT WILL LIFT NORTH OF THE CWA BY FRIDAY
MORNING LEADING TO A WARM AND MUGGY DAY WITH HIGHS IN THE MID 80S.
IF CLOUD COVER REMAINS SCARCE...COULD SEE TEMPS GET INTO THE UPPER
80S. GUSTY WINDS ARE ALSO EXPECTED WITH GUSTS ARND 25 MPH. PRECIP
CHANCES WILL INCREASE THROUGH FRIDAY NIGHT AS THE COLD FRONT MOVES
CLOSER TO THE CWA. THINKING FRIDAY WILL NOT BE A TOTAL WASHOUT...BUT
THERE WILL BE MULTIPLE PERIODS OF STORMS. PWAT VALUES INCREASE
FURTHER TO 1.5 INCHES SO ANY SHOWERS AND STORMS WILL BE CAPABLE OF
HEAVY DOWNPOURS.

SHOWERS AND STORMS ARE ALSO EXPECTED SATURDAY AHEAD OF AND ALONG THE
COLD FRONT. ANOTHER ROUND OF SHOWERS IS POSSIBLE BEHIND THE COLD
FRONT ALONG A VORT STREAMER SATURDAY EVENING AND SUNDAY. THE GFS
KEEPS PRECIP IN THE REGION INTO EARLY NEXT WEEK WHILE THE ECMWF HAS
A RIDGE OVERHEAD.  THEREFORE HAVE LOW CONFIDENCE IN PRECIP CHANCES
NEXT WEEK.  BELOW NORMAL TEMPS MOVE IN LATE THIS WEEK INTO NEXT WEEK
WITH HIGHS POSSIBLY IN THE 60S OVER THE WEEKEND.

JEE

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* SOUTH-SOUTHWEST WINDS OF AROUND 40 KT AT 1000 FT
  OVERNIGHT...SETTING UP LOW LEVEL WIND SHEAR.

* MVFR CEILINGS PROBABLE AT TIMES TUESDAY WITH A CHANCE FOR
  TEMPORARY IFR.

* PERIODS OF SHRA WITH PERIODIC TSRA FROM LATE TUESDAY MORNING
  THROUGH THE AFTERNOON.

* NEAR DUE SOUTH WINDS ON TUESDAY WITH PERIODIC GUSTS POSSIBLE
  AND SOME VARIABILITY BETWEEN SOUTHEAST AND SOUTHWEST.

KREIN

//DISCUSSION...UPDATED 06Z...

GUSTY SOUTH-SOUTHWEST WINDS HAVE DIMINISHED TO 10 KT OR LESS AND
BECOME SOUTHERLY. A LOW-LEVEL JET WILL DEVELOP OVERHEAD WITH
SSWLY-SWLY WINDS OF 40 KT TO 45 KT FLOW AT 1500-2000 FT UNTIL
ARND 12Z. SOME THUNDERSTORMS MAY DEVELOP THROUGH OVERNIGHT AHEAD
OF A FRONT FROM NRN MO THROUGH ERN IA AND INTO WI. THESE STORMS
WILL ONLY MAKE SLOW PROGRESS EASTWARD DUE TO THE STRONG SSWLY-SWLY
WINDS ALOFT SO...AND STORMS THAT DO DEVELOP SHOULD REMAIN NORTH
AND NORTHWEST OF AREA TAF SITES...THOUGH THERE IS A CHANCE THAT A
FEW STORMS COULD APPROACH THE RFD TERMINAL AREA VERY LATE
TONIGHT.

AS AN MID LEVEL DISTURBANCE MOVING FROM THE SOUTHERN PLAINS TO
NRN IL BY TUESDAY AFTERNOON MAY BRING ANOTHER ROUND OF SHOWERS
WITH SCT EMBEDDED THUNDERSTORMS TO THE REGION. UPPER LEVEL FORCING
FROM THE MID LEVEL DISTURBANCE AND AN UPPER LEVEL JET STREAM WILL
ENHANCE THE LIKELIHOOD FOR SHRA AND THE CHANCE FOR TSRA...WITH THE
MOST LIKELY CHANCE FOR ACTIVITY FROM 15Z THROUGH 02Z. SOME
UNCERTAINTY REMAINS IN PINNING DOWN THE EXACT PERIOD FOR THE
TSRA...SO WILL MAINTAIN THE GOING TEMPO FOR LATE MORNING THROUGH
EARLY AFTERNOON. HOWEVER...THE PCPN ACTIVITY COULD BE SHIFTED OR
EXPANDED IN TIME.

WINDS WILL BE SOUTHERLY ON TUESDAY...THOUGH DIRECTION MAY BE A BIT
VARIABLE AROUND CONVECTIVE ACTIVITY...THOUGH A GENERALLY SOUTHERLY
DIRECTION SHOULD PREVAIL THROUGH THE NIGHT AND MUCH OF THE DAY
TUESDAY. SOME GUSTINESS IS POSSIBLE THROUGH THE ENTIRE DAY...WITH
THE LATEST GUIDANCE SUGGESTING THAT WINDS COULD STRENGTHEN AND
BECOME EVEN MORE GUSTY THROUGH THE NIGHT TOMORROW NIGHT WITH WINDS
VEERING SWLY AS SURFACE LOW PRESSURE MOVES NORTHEAST ACROSS
SOUTHERN WISCONSIN.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* HIGH CONFIDENCE IN 40-45 KT SSWLY-SWLY FLOW ALOFT OVERNIGHT...BUT
  MEDIUM IN TRUE LLWS OCCURRING.

* HIGH CONFIDENCE IN WIND TRENDS OVERNIGHT AND TUESDAY MORNING.
  MEDIUM IN WIND TRENDS TOMORROW EVENING.

* MEDIUM CONFIDENCE IN MVFR CIGS TUESDAY MORNING WITH LOWER
  CONFIDENCE IN DURATION AND HOW LOW CIGS WILL DROP.

* HIGH CONFIDENCE IN SHOWERS AND AT LEAST A PERIOD OF TSRA. LOW
  CONFIDENCE IN SPECIFIC TSRA TIMING AND IMPACT ON THE TERMINALS
  WITH MULTIPLE ROUNDS POSSIBLE BETWEEN 15Z AND 02Z.

KREIN

//OUTLOOK FOR ORD/MDW FOR 12Z WEDNESDAY-12Z MONDAY...UPDATED 00Z...

WEDNESDAY...CHANCE OF TSRA. WEST WINDS.
THURSDAY...SLIGHT CHANCE OF TSRA LATE AT NIGHT. SOUTHEAST WINDS.
FRIDAY...INCREASING CHANCE OF TSRA THROUGH THE DAY AND NIGHT.
         SOUTHWEST WINDS.
SATURDAY...SHRA LIKELY WITH A CHANCE OF TSRA. NORTHEAST WINDS.
SUNDAY...CHANCE OF SHRA. EAST WINDS.

MTF

&&

.MARINE...
334 PM CDT

WIND GUSTS ARE BEGINNING TO COME DOWN AND THE GALE WARNING FOR THE
NEARSHORE ZONES HAS BEEN DROPPED. A SMALL CRAFT ADVISORY WILL GO
THROUGH 9PM CDT THIS EVENING FOR LINGERING STRONG WINDS AND HIGH
WAVES.  LOW PRESSURE CURRENTLY OVER THE UPPER MIDWEST WILL MOVE OVER
QUEBEC TUESDAY MORNING. THE LOWS STATIONARY FRONT REMAINS NORTH OF
THE LAKE BUT STABLE CONDITIONS OVER THE LAKE WILL RESULT IN AREAS OF
FOG THROUGH TUESDAY NIGHT. SOUTH WINDS ARE EXPECTED WITH SPEEDS TO
20 KT. HIGH PRESSURE SPREADS OVER THE LAKE WEDNESDAY NIGHT WITH
WINDS REMAINING LIGHT AND VARYING BTWN WEST AND SOUTHEAST THROUGH
FRIDAY. A COLD FRONT THEN SWEEPS DOWN THE LAKE LATE IN THE WEEK WITH
WINDS BCMG NORTH BEHIND IT.

JEE

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KILX 260451
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1151 PM CDT MON MAY 25 2015

.UPDATE...
ISSUED AT 900 PM CDT MON MAY 25 2015

A SHORTWAVE CURRENTLY OVER EASTERN TX/OK WILL BE THE MAIN WEATHER
FEATURE FOR CENTRAL IL LATE TONIGHT AND TOMORROW. AS THE SHORTWAVE
EJECTS OFF TO THE NORTHEAST OF ITS CURRENT POSITION...LIFT AND
MOISTURE ASSOCIATED WITH THE FEATURE WILL DEVELOP RAIN SHOWERS AND
THUNDERSTORMS AFTER MIDNIGHT. CURRENT SHORT TERM MODELS TENDING TO
HOLD OFF PRECIPITATION UNTIL LATER THAN PREVIOUS MODELS SO HAVE
TRENDED PRECIPITATION LATER...HOWEVER MAINTAINING LIKELY
PRECIPITATION BY 7 AM ACROSS CENTRAL IL. CORRIDOR OF PREFERRED
SHEAR/INSTABILITY OVERLAP LOOKS TO SKIRT THROUGH SOUTHERN IL
DURING THE MORNING...LIMITING SEVERE WEATHER POTENTIAL DUE TO
LIMITED SURFACE HEATING. HAVE UPDATED GRIDDED FORECASTS FOR THESE
TRENDS AND EVENING TEMPERATURE/WIND TRENDS.

&&

.SHORT TERM...(TONIGHT)
ISSUED AT 259 PM CDT MON MAY 25 2015

LOWER CLOUDS ARE LIFTING AND BREAKING UP ACROSS THE EAST HALF OF THE
FORECAST AREA THIS AFTERNOON...BUT EXTENSIVE CIRRUS SHIELD KEEPING
SKIES PARTLY SUNNY AT BEST THERE. THE WESTERN CWA HAS HAD SOME
DIURNAL CUMULUS AS IT IS OUTSIDE THE CIRRUS SHIELD...BUT THIS SHOULD
FADE LATER THIS AFTERNOON AS SOME SUBSIDENCE OCCURS ACROSS THAT
AREA. SKIES WILL BE PARTLY CLOUDY FOR A TIME THIS EVENING...BUT THEN
CLOUD UP AGAIN LATER AS SOME OF THE CONVECTIVE BLOWOFF ARRIVES FROM
THE SEVERE ACTIVITY CURRENTLY ACROSS THE SOUTHERN PLAINS. LATEST
HIGH-RESOLUTION MODELS KEEP THE FORECAST AREA DRY THIS EVENING WITH
SEVERAL SUGGESTING PERHAPS TAKING UNTIL EVEN 3-4 AM BEFORE WE SEE
ANY SHOWERS AND STORMS MOVE BACK IN. HOWEVER...I HAVE RAMPED UP THE
POP`S QUICKLY AFTER MIDNIGHT ACROSS THE WEST AND AFTER 3 AM IN THE
EAST. WITH SOUTHERLY WINDS STAYING UP AROUND 10 MPH OR SO...LITTLE
CHANGE NEEDED TO THE OVERNIGHT LOWS...WHICH SHOULD BE IN THE 66-68
DEGREE RANGE.

.LONG TERM...(TUESDAY THROUGH MONDAY)
ISSUED AT 259 PM CDT MON MAY 25 2015

SHORT WAVE NEAR THE RED RIVER ALONG THE WESTERN TX/OK BORDER TO
EJECT NE INTO IL ON TUE LIKELY BRINGING SHOWERS AND THUNDERSTORMS
MOST OF THE DAY. HAVE INCREASING LOW LEVEL JET AHEAD OF THIS FEATURE
LATER TONIGHT THAT WILL INCREASE CHANCES OF SHOWERS AND
THUNDERSTORMS FROM SW TO NE. SHOWERS AND THUNDERSTORMS WILL BECOME
MORE WIDELY SCATTERED SW AREAS LATER TUE AFTERNOON AND OVER REST OF
CENTRAL/EASTERN IL TUE EVENING. SPC SHIFTED SLIGHT RISK SOUTHEAST OF
IL ON TUE AND NOW MAINLY OVER KY/TN/MS/AL WHERE BETTER INSTABILITY
WILL BE PRESENT. STILL HAVE A MARGINAL RISK OF SEVERE STORMS TUE
AFTERNOON FROM SHELBYVILLE TO DANVILLE SE FOR HAIL AND GUSTY WINDS.
HIGHS IN THE UPPER 70S TUE WITH LAWRENCEVILLE NEAR 80F WITH
DEWPOINTS IN THE MID TO UPPER 60S (HIGHEST IN SE IL).

RATHER WARM AND HUMID WEATHER PATTERN LOOKS TO CONTINUE ACROSS IL
DURING THE REST OF THE WEEK WITH DAILY CHANCE OF SHOWERS AND
THUNDERSTORMS. BETWEEN 1.5 AND 2 INCHES OF RAIN IS EXPECTED OVER
AREA THE REST OF THIS WEEK. CHANCE OF SHOWERS AND THUNDERSTORMS
LOOK HIGHER IN SOUTHEAST IL ON WED WITH JUST SLIGHT CHANCE NW OF
THE IL RIVER BY GALESBURG AS MORE SHORT WAVE ENERGY EJECT NE INTO
THE MID MS AND OHIO RIVER VALLEY. SPC HAS MARGINAL RISK OF SEVERE
STORMS WED AFTERNOON MAINLY SOUTH OF I-72. LOWS TONIGHT MOSTLY IN
THE MID 60S WITH SOME LOWER 60S NW OF THE IL RIVER. HIGHS WED IN
THE LOWER 80S AND DEWPOINTS IN THE LOW TO MID 60S.

UPPER LEVEL RIDGE BUILDING A BIT OVER THE EASTERN STATES WED NIGHT
AND THU SO CONVECTION CHANCES LOOK MORE WIDELY SCATTERED OVER
CENTRAL AND SOUTHEAST IL. AREAS FROM I-72 NORTH LOOK DRIER DURING
THIS TIME FRAME CLOSER TO WEAK HIGH PRESSURE DRIFTING OVER THE GREAT
LAKES. HIGHS THU IN THE LOW TO MID 80S WITH MORE SUNSHINE POSSIBLE
AND MID 80S ON FRIDAY.

CHANCES OF SHOWERS AND THUNDERSTORMS INCREASE AGAIN FRI/SAT WITH A
FRONTAL BOUNDARY PUSHING SE ACROSS CENTRAL IL SATURDAY AND SAT
NIGHT. TEMPERATURES TO COOL BEHIND THIS FRONT DURING THE WEEKEND
INTO EARLY NEXT WEEK WITH HIGHS IN THE LOW TO MID 70S SUNDAY. A
CUTOFF UPPER LEVEL LOW EJECTING FROM THE ROCKIES INTO TEH CENTRAL
PLAINS BY EARLY NEXT WEEK TO CONTINUE CHANCES OF SHOWERS AND A FEW
THUNDERSTORMS.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z TUESDAY NIGHT)
ISSUED AT 1151 PM CDT MON MAY 25 2015

VFR CONDITIONS IN SCATTERED HIGH CLOUD COVER WITH SOUTH WINDS
10-12 KTS THIS EVENING ACROSS CENTRAL IL. HIGH CLOUD ASSOCIATED
WITH A SHORTWAVE OVER NORTHEAST OKLAHOMA WILL CONTINUE MOVING INTO
THE REGION OVERNIGHT. CURRENT TIMING OF LIFT AND MOISTURE WITH
THE APPROACHING SHORTWAVE INDICATE PREDOMINANT MVFR CONDITIONS IN
SHRA/ISOLD TSRA LIKELY TO BEGIN 10-12Z. SOME LIFTING OF
PREDOMINANT CEILINGS LIKELY IN AFTERNOON WITH DAYTIME HEATING AND
ACCORDING TO MODEL TIME-HEIGHT SECTIONS SO HAVE INCLUDED VCTS
WITH CIGS ABOVE MVFR THRESHOLD. SHORTWAVE AXIS EXPECTED TO CROSS
LATE AFTERNOON/EARLY EVENING TUESDAY BRINGING A DECREASE IN
SHOWER/THUNDERSTORM ACTIVITY BY 00Z AND HAVE ENDED VCTS AND 4 KFT
AGL CIGS. WINDS CONTINUING S 10-12 KTS UNTIL 14Z...INCREASING TO
15-20 KTS WITH GUSTS 25-30KTS AND SHIFTING TOWARD SW. WINDS
DECREASING AFTER 00Z.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...ONTON
SHORT TERM...GEELHART
LONG TERM...07
AVIATION...ONTON




000
FXUS63 KILX 260451
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1151 PM CDT MON MAY 25 2015

.UPDATE...
ISSUED AT 900 PM CDT MON MAY 25 2015

A SHORTWAVE CURRENTLY OVER EASTERN TX/OK WILL BE THE MAIN WEATHER
FEATURE FOR CENTRAL IL LATE TONIGHT AND TOMORROW. AS THE SHORTWAVE
EJECTS OFF TO THE NORTHEAST OF ITS CURRENT POSITION...LIFT AND
MOISTURE ASSOCIATED WITH THE FEATURE WILL DEVELOP RAIN SHOWERS AND
THUNDERSTORMS AFTER MIDNIGHT. CURRENT SHORT TERM MODELS TENDING TO
HOLD OFF PRECIPITATION UNTIL LATER THAN PREVIOUS MODELS SO HAVE
TRENDED PRECIPITATION LATER...HOWEVER MAINTAINING LIKELY
PRECIPITATION BY 7 AM ACROSS CENTRAL IL. CORRIDOR OF PREFERRED
SHEAR/INSTABILITY OVERLAP LOOKS TO SKIRT THROUGH SOUTHERN IL
DURING THE MORNING...LIMITING SEVERE WEATHER POTENTIAL DUE TO
LIMITED SURFACE HEATING. HAVE UPDATED GRIDDED FORECASTS FOR THESE
TRENDS AND EVENING TEMPERATURE/WIND TRENDS.

&&

.SHORT TERM...(TONIGHT)
ISSUED AT 259 PM CDT MON MAY 25 2015

LOWER CLOUDS ARE LIFTING AND BREAKING UP ACROSS THE EAST HALF OF THE
FORECAST AREA THIS AFTERNOON...BUT EXTENSIVE CIRRUS SHIELD KEEPING
SKIES PARTLY SUNNY AT BEST THERE. THE WESTERN CWA HAS HAD SOME
DIURNAL CUMULUS AS IT IS OUTSIDE THE CIRRUS SHIELD...BUT THIS SHOULD
FADE LATER THIS AFTERNOON AS SOME SUBSIDENCE OCCURS ACROSS THAT
AREA. SKIES WILL BE PARTLY CLOUDY FOR A TIME THIS EVENING...BUT THEN
CLOUD UP AGAIN LATER AS SOME OF THE CONVECTIVE BLOWOFF ARRIVES FROM
THE SEVERE ACTIVITY CURRENTLY ACROSS THE SOUTHERN PLAINS. LATEST
HIGH-RESOLUTION MODELS KEEP THE FORECAST AREA DRY THIS EVENING WITH
SEVERAL SUGGESTING PERHAPS TAKING UNTIL EVEN 3-4 AM BEFORE WE SEE
ANY SHOWERS AND STORMS MOVE BACK IN. HOWEVER...I HAVE RAMPED UP THE
POP`S QUICKLY AFTER MIDNIGHT ACROSS THE WEST AND AFTER 3 AM IN THE
EAST. WITH SOUTHERLY WINDS STAYING UP AROUND 10 MPH OR SO...LITTLE
CHANGE NEEDED TO THE OVERNIGHT LOWS...WHICH SHOULD BE IN THE 66-68
DEGREE RANGE.

.LONG TERM...(TUESDAY THROUGH MONDAY)
ISSUED AT 259 PM CDT MON MAY 25 2015

SHORT WAVE NEAR THE RED RIVER ALONG THE WESTERN TX/OK BORDER TO
EJECT NE INTO IL ON TUE LIKELY BRINGING SHOWERS AND THUNDERSTORMS
MOST OF THE DAY. HAVE INCREASING LOW LEVEL JET AHEAD OF THIS FEATURE
LATER TONIGHT THAT WILL INCREASE CHANCES OF SHOWERS AND
THUNDERSTORMS FROM SW TO NE. SHOWERS AND THUNDERSTORMS WILL BECOME
MORE WIDELY SCATTERED SW AREAS LATER TUE AFTERNOON AND OVER REST OF
CENTRAL/EASTERN IL TUE EVENING. SPC SHIFTED SLIGHT RISK SOUTHEAST OF
IL ON TUE AND NOW MAINLY OVER KY/TN/MS/AL WHERE BETTER INSTABILITY
WILL BE PRESENT. STILL HAVE A MARGINAL RISK OF SEVERE STORMS TUE
AFTERNOON FROM SHELBYVILLE TO DANVILLE SE FOR HAIL AND GUSTY WINDS.
HIGHS IN THE UPPER 70S TUE WITH LAWRENCEVILLE NEAR 80F WITH
DEWPOINTS IN THE MID TO UPPER 60S (HIGHEST IN SE IL).

RATHER WARM AND HUMID WEATHER PATTERN LOOKS TO CONTINUE ACROSS IL
DURING THE REST OF THE WEEK WITH DAILY CHANCE OF SHOWERS AND
THUNDERSTORMS. BETWEEN 1.5 AND 2 INCHES OF RAIN IS EXPECTED OVER
AREA THE REST OF THIS WEEK. CHANCE OF SHOWERS AND THUNDERSTORMS
LOOK HIGHER IN SOUTHEAST IL ON WED WITH JUST SLIGHT CHANCE NW OF
THE IL RIVER BY GALESBURG AS MORE SHORT WAVE ENERGY EJECT NE INTO
THE MID MS AND OHIO RIVER VALLEY. SPC HAS MARGINAL RISK OF SEVERE
STORMS WED AFTERNOON MAINLY SOUTH OF I-72. LOWS TONIGHT MOSTLY IN
THE MID 60S WITH SOME LOWER 60S NW OF THE IL RIVER. HIGHS WED IN
THE LOWER 80S AND DEWPOINTS IN THE LOW TO MID 60S.

UPPER LEVEL RIDGE BUILDING A BIT OVER THE EASTERN STATES WED NIGHT
AND THU SO CONVECTION CHANCES LOOK MORE WIDELY SCATTERED OVER
CENTRAL AND SOUTHEAST IL. AREAS FROM I-72 NORTH LOOK DRIER DURING
THIS TIME FRAME CLOSER TO WEAK HIGH PRESSURE DRIFTING OVER THE GREAT
LAKES. HIGHS THU IN THE LOW TO MID 80S WITH MORE SUNSHINE POSSIBLE
AND MID 80S ON FRIDAY.

CHANCES OF SHOWERS AND THUNDERSTORMS INCREASE AGAIN FRI/SAT WITH A
FRONTAL BOUNDARY PUSHING SE ACROSS CENTRAL IL SATURDAY AND SAT
NIGHT. TEMPERATURES TO COOL BEHIND THIS FRONT DURING THE WEEKEND
INTO EARLY NEXT WEEK WITH HIGHS IN THE LOW TO MID 70S SUNDAY. A
CUTOFF UPPER LEVEL LOW EJECTING FROM THE ROCKIES INTO TEH CENTRAL
PLAINS BY EARLY NEXT WEEK TO CONTINUE CHANCES OF SHOWERS AND A FEW
THUNDERSTORMS.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z TUESDAY NIGHT)
ISSUED AT 1151 PM CDT MON MAY 25 2015

VFR CONDITIONS IN SCATTERED HIGH CLOUD COVER WITH SOUTH WINDS
10-12 KTS THIS EVENING ACROSS CENTRAL IL. HIGH CLOUD ASSOCIATED
WITH A SHORTWAVE OVER NORTHEAST OKLAHOMA WILL CONTINUE MOVING INTO
THE REGION OVERNIGHT. CURRENT TIMING OF LIFT AND MOISTURE WITH
THE APPROACHING SHORTWAVE INDICATE PREDOMINANT MVFR CONDITIONS IN
SHRA/ISOLD TSRA LIKELY TO BEGIN 10-12Z. SOME LIFTING OF
PREDOMINANT CEILINGS LIKELY IN AFTERNOON WITH DAYTIME HEATING AND
ACCORDING TO MODEL TIME-HEIGHT SECTIONS SO HAVE INCLUDED VCTS
WITH CIGS ABOVE MVFR THRESHOLD. SHORTWAVE AXIS EXPECTED TO CROSS
LATE AFTERNOON/EARLY EVENING TUESDAY BRINGING A DECREASE IN
SHOWER/THUNDERSTORM ACTIVITY BY 00Z AND HAVE ENDED VCTS AND 4 KFT
AGL CIGS. WINDS CONTINUING S 10-12 KTS UNTIL 14Z...INCREASING TO
15-20 KTS WITH GUSTS 25-30KTS AND SHIFTING TOWARD SW. WINDS
DECREASING AFTER 00Z.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...ONTON
SHORT TERM...GEELHART
LONG TERM...07
AVIATION...ONTON



000
FXUS63 KILX 260451
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1151 PM CDT MON MAY 25 2015

.UPDATE...
ISSUED AT 900 PM CDT MON MAY 25 2015

A SHORTWAVE CURRENTLY OVER EASTERN TX/OK WILL BE THE MAIN WEATHER
FEATURE FOR CENTRAL IL LATE TONIGHT AND TOMORROW. AS THE SHORTWAVE
EJECTS OFF TO THE NORTHEAST OF ITS CURRENT POSITION...LIFT AND
MOISTURE ASSOCIATED WITH THE FEATURE WILL DEVELOP RAIN SHOWERS AND
THUNDERSTORMS AFTER MIDNIGHT. CURRENT SHORT TERM MODELS TENDING TO
HOLD OFF PRECIPITATION UNTIL LATER THAN PREVIOUS MODELS SO HAVE
TRENDED PRECIPITATION LATER...HOWEVER MAINTAINING LIKELY
PRECIPITATION BY 7 AM ACROSS CENTRAL IL. CORRIDOR OF PREFERRED
SHEAR/INSTABILITY OVERLAP LOOKS TO SKIRT THROUGH SOUTHERN IL
DURING THE MORNING...LIMITING SEVERE WEATHER POTENTIAL DUE TO
LIMITED SURFACE HEATING. HAVE UPDATED GRIDDED FORECASTS FOR THESE
TRENDS AND EVENING TEMPERATURE/WIND TRENDS.

&&

.SHORT TERM...(TONIGHT)
ISSUED AT 259 PM CDT MON MAY 25 2015

LOWER CLOUDS ARE LIFTING AND BREAKING UP ACROSS THE EAST HALF OF THE
FORECAST AREA THIS AFTERNOON...BUT EXTENSIVE CIRRUS SHIELD KEEPING
SKIES PARTLY SUNNY AT BEST THERE. THE WESTERN CWA HAS HAD SOME
DIURNAL CUMULUS AS IT IS OUTSIDE THE CIRRUS SHIELD...BUT THIS SHOULD
FADE LATER THIS AFTERNOON AS SOME SUBSIDENCE OCCURS ACROSS THAT
AREA. SKIES WILL BE PARTLY CLOUDY FOR A TIME THIS EVENING...BUT THEN
CLOUD UP AGAIN LATER AS SOME OF THE CONVECTIVE BLOWOFF ARRIVES FROM
THE SEVERE ACTIVITY CURRENTLY ACROSS THE SOUTHERN PLAINS. LATEST
HIGH-RESOLUTION MODELS KEEP THE FORECAST AREA DRY THIS EVENING WITH
SEVERAL SUGGESTING PERHAPS TAKING UNTIL EVEN 3-4 AM BEFORE WE SEE
ANY SHOWERS AND STORMS MOVE BACK IN. HOWEVER...I HAVE RAMPED UP THE
POP`S QUICKLY AFTER MIDNIGHT ACROSS THE WEST AND AFTER 3 AM IN THE
EAST. WITH SOUTHERLY WINDS STAYING UP AROUND 10 MPH OR SO...LITTLE
CHANGE NEEDED TO THE OVERNIGHT LOWS...WHICH SHOULD BE IN THE 66-68
DEGREE RANGE.

.LONG TERM...(TUESDAY THROUGH MONDAY)
ISSUED AT 259 PM CDT MON MAY 25 2015

SHORT WAVE NEAR THE RED RIVER ALONG THE WESTERN TX/OK BORDER TO
EJECT NE INTO IL ON TUE LIKELY BRINGING SHOWERS AND THUNDERSTORMS
MOST OF THE DAY. HAVE INCREASING LOW LEVEL JET AHEAD OF THIS FEATURE
LATER TONIGHT THAT WILL INCREASE CHANCES OF SHOWERS AND
THUNDERSTORMS FROM SW TO NE. SHOWERS AND THUNDERSTORMS WILL BECOME
MORE WIDELY SCATTERED SW AREAS LATER TUE AFTERNOON AND OVER REST OF
CENTRAL/EASTERN IL TUE EVENING. SPC SHIFTED SLIGHT RISK SOUTHEAST OF
IL ON TUE AND NOW MAINLY OVER KY/TN/MS/AL WHERE BETTER INSTABILITY
WILL BE PRESENT. STILL HAVE A MARGINAL RISK OF SEVERE STORMS TUE
AFTERNOON FROM SHELBYVILLE TO DANVILLE SE FOR HAIL AND GUSTY WINDS.
HIGHS IN THE UPPER 70S TUE WITH LAWRENCEVILLE NEAR 80F WITH
DEWPOINTS IN THE MID TO UPPER 60S (HIGHEST IN SE IL).

RATHER WARM AND HUMID WEATHER PATTERN LOOKS TO CONTINUE ACROSS IL
DURING THE REST OF THE WEEK WITH DAILY CHANCE OF SHOWERS AND
THUNDERSTORMS. BETWEEN 1.5 AND 2 INCHES OF RAIN IS EXPECTED OVER
AREA THE REST OF THIS WEEK. CHANCE OF SHOWERS AND THUNDERSTORMS
LOOK HIGHER IN SOUTHEAST IL ON WED WITH JUST SLIGHT CHANCE NW OF
THE IL RIVER BY GALESBURG AS MORE SHORT WAVE ENERGY EJECT NE INTO
THE MID MS AND OHIO RIVER VALLEY. SPC HAS MARGINAL RISK OF SEVERE
STORMS WED AFTERNOON MAINLY SOUTH OF I-72. LOWS TONIGHT MOSTLY IN
THE MID 60S WITH SOME LOWER 60S NW OF THE IL RIVER. HIGHS WED IN
THE LOWER 80S AND DEWPOINTS IN THE LOW TO MID 60S.

UPPER LEVEL RIDGE BUILDING A BIT OVER THE EASTERN STATES WED NIGHT
AND THU SO CONVECTION CHANCES LOOK MORE WIDELY SCATTERED OVER
CENTRAL AND SOUTHEAST IL. AREAS FROM I-72 NORTH LOOK DRIER DURING
THIS TIME FRAME CLOSER TO WEAK HIGH PRESSURE DRIFTING OVER THE GREAT
LAKES. HIGHS THU IN THE LOW TO MID 80S WITH MORE SUNSHINE POSSIBLE
AND MID 80S ON FRIDAY.

CHANCES OF SHOWERS AND THUNDERSTORMS INCREASE AGAIN FRI/SAT WITH A
FRONTAL BOUNDARY PUSHING SE ACROSS CENTRAL IL SATURDAY AND SAT
NIGHT. TEMPERATURES TO COOL BEHIND THIS FRONT DURING THE WEEKEND
INTO EARLY NEXT WEEK WITH HIGHS IN THE LOW TO MID 70S SUNDAY. A
CUTOFF UPPER LEVEL LOW EJECTING FROM THE ROCKIES INTO TEH CENTRAL
PLAINS BY EARLY NEXT WEEK TO CONTINUE CHANCES OF SHOWERS AND A FEW
THUNDERSTORMS.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z TUESDAY NIGHT)
ISSUED AT 1151 PM CDT MON MAY 25 2015

VFR CONDITIONS IN SCATTERED HIGH CLOUD COVER WITH SOUTH WINDS
10-12 KTS THIS EVENING ACROSS CENTRAL IL. HIGH CLOUD ASSOCIATED
WITH A SHORTWAVE OVER NORTHEAST OKLAHOMA WILL CONTINUE MOVING INTO
THE REGION OVERNIGHT. CURRENT TIMING OF LIFT AND MOISTURE WITH
THE APPROACHING SHORTWAVE INDICATE PREDOMINANT MVFR CONDITIONS IN
SHRA/ISOLD TSRA LIKELY TO BEGIN 10-12Z. SOME LIFTING OF
PREDOMINANT CEILINGS LIKELY IN AFTERNOON WITH DAYTIME HEATING AND
ACCORDING TO MODEL TIME-HEIGHT SECTIONS SO HAVE INCLUDED VCTS
WITH CIGS ABOVE MVFR THRESHOLD. SHORTWAVE AXIS EXPECTED TO CROSS
LATE AFTERNOON/EARLY EVENING TUESDAY BRINGING A DECREASE IN
SHOWER/THUNDERSTORM ACTIVITY BY 00Z AND HAVE ENDED VCTS AND 4 KFT
AGL CIGS. WINDS CONTINUING S 10-12 KTS UNTIL 14Z...INCREASING TO
15-20 KTS WITH GUSTS 25-30KTS AND SHIFTING TOWARD SW. WINDS
DECREASING AFTER 00Z.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...ONTON
SHORT TERM...GEELHART
LONG TERM...07
AVIATION...ONTON




000
FXUS63 KILX 260451
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1151 PM CDT MON MAY 25 2015

.UPDATE...
ISSUED AT 900 PM CDT MON MAY 25 2015

A SHORTWAVE CURRENTLY OVER EASTERN TX/OK WILL BE THE MAIN WEATHER
FEATURE FOR CENTRAL IL LATE TONIGHT AND TOMORROW. AS THE SHORTWAVE
EJECTS OFF TO THE NORTHEAST OF ITS CURRENT POSITION...LIFT AND
MOISTURE ASSOCIATED WITH THE FEATURE WILL DEVELOP RAIN SHOWERS AND
THUNDERSTORMS AFTER MIDNIGHT. CURRENT SHORT TERM MODELS TENDING TO
HOLD OFF PRECIPITATION UNTIL LATER THAN PREVIOUS MODELS SO HAVE
TRENDED PRECIPITATION LATER...HOWEVER MAINTAINING LIKELY
PRECIPITATION BY 7 AM ACROSS CENTRAL IL. CORRIDOR OF PREFERRED
SHEAR/INSTABILITY OVERLAP LOOKS TO SKIRT THROUGH SOUTHERN IL
DURING THE MORNING...LIMITING SEVERE WEATHER POTENTIAL DUE TO
LIMITED SURFACE HEATING. HAVE UPDATED GRIDDED FORECASTS FOR THESE
TRENDS AND EVENING TEMPERATURE/WIND TRENDS.

&&

.SHORT TERM...(TONIGHT)
ISSUED AT 259 PM CDT MON MAY 25 2015

LOWER CLOUDS ARE LIFTING AND BREAKING UP ACROSS THE EAST HALF OF THE
FORECAST AREA THIS AFTERNOON...BUT EXTENSIVE CIRRUS SHIELD KEEPING
SKIES PARTLY SUNNY AT BEST THERE. THE WESTERN CWA HAS HAD SOME
DIURNAL CUMULUS AS IT IS OUTSIDE THE CIRRUS SHIELD...BUT THIS SHOULD
FADE LATER THIS AFTERNOON AS SOME SUBSIDENCE OCCURS ACROSS THAT
AREA. SKIES WILL BE PARTLY CLOUDY FOR A TIME THIS EVENING...BUT THEN
CLOUD UP AGAIN LATER AS SOME OF THE CONVECTIVE BLOWOFF ARRIVES FROM
THE SEVERE ACTIVITY CURRENTLY ACROSS THE SOUTHERN PLAINS. LATEST
HIGH-RESOLUTION MODELS KEEP THE FORECAST AREA DRY THIS EVENING WITH
SEVERAL SUGGESTING PERHAPS TAKING UNTIL EVEN 3-4 AM BEFORE WE SEE
ANY SHOWERS AND STORMS MOVE BACK IN. HOWEVER...I HAVE RAMPED UP THE
POP`S QUICKLY AFTER MIDNIGHT ACROSS THE WEST AND AFTER 3 AM IN THE
EAST. WITH SOUTHERLY WINDS STAYING UP AROUND 10 MPH OR SO...LITTLE
CHANGE NEEDED TO THE OVERNIGHT LOWS...WHICH SHOULD BE IN THE 66-68
DEGREE RANGE.

.LONG TERM...(TUESDAY THROUGH MONDAY)
ISSUED AT 259 PM CDT MON MAY 25 2015

SHORT WAVE NEAR THE RED RIVER ALONG THE WESTERN TX/OK BORDER TO
EJECT NE INTO IL ON TUE LIKELY BRINGING SHOWERS AND THUNDERSTORMS
MOST OF THE DAY. HAVE INCREASING LOW LEVEL JET AHEAD OF THIS FEATURE
LATER TONIGHT THAT WILL INCREASE CHANCES OF SHOWERS AND
THUNDERSTORMS FROM SW TO NE. SHOWERS AND THUNDERSTORMS WILL BECOME
MORE WIDELY SCATTERED SW AREAS LATER TUE AFTERNOON AND OVER REST OF
CENTRAL/EASTERN IL TUE EVENING. SPC SHIFTED SLIGHT RISK SOUTHEAST OF
IL ON TUE AND NOW MAINLY OVER KY/TN/MS/AL WHERE BETTER INSTABILITY
WILL BE PRESENT. STILL HAVE A MARGINAL RISK OF SEVERE STORMS TUE
AFTERNOON FROM SHELBYVILLE TO DANVILLE SE FOR HAIL AND GUSTY WINDS.
HIGHS IN THE UPPER 70S TUE WITH LAWRENCEVILLE NEAR 80F WITH
DEWPOINTS IN THE MID TO UPPER 60S (HIGHEST IN SE IL).

RATHER WARM AND HUMID WEATHER PATTERN LOOKS TO CONTINUE ACROSS IL
DURING THE REST OF THE WEEK WITH DAILY CHANCE OF SHOWERS AND
THUNDERSTORMS. BETWEEN 1.5 AND 2 INCHES OF RAIN IS EXPECTED OVER
AREA THE REST OF THIS WEEK. CHANCE OF SHOWERS AND THUNDERSTORMS
LOOK HIGHER IN SOUTHEAST IL ON WED WITH JUST SLIGHT CHANCE NW OF
THE IL RIVER BY GALESBURG AS MORE SHORT WAVE ENERGY EJECT NE INTO
THE MID MS AND OHIO RIVER VALLEY. SPC HAS MARGINAL RISK OF SEVERE
STORMS WED AFTERNOON MAINLY SOUTH OF I-72. LOWS TONIGHT MOSTLY IN
THE MID 60S WITH SOME LOWER 60S NW OF THE IL RIVER. HIGHS WED IN
THE LOWER 80S AND DEWPOINTS IN THE LOW TO MID 60S.

UPPER LEVEL RIDGE BUILDING A BIT OVER THE EASTERN STATES WED NIGHT
AND THU SO CONVECTION CHANCES LOOK MORE WIDELY SCATTERED OVER
CENTRAL AND SOUTHEAST IL. AREAS FROM I-72 NORTH LOOK DRIER DURING
THIS TIME FRAME CLOSER TO WEAK HIGH PRESSURE DRIFTING OVER THE GREAT
LAKES. HIGHS THU IN THE LOW TO MID 80S WITH MORE SUNSHINE POSSIBLE
AND MID 80S ON FRIDAY.

CHANCES OF SHOWERS AND THUNDERSTORMS INCREASE AGAIN FRI/SAT WITH A
FRONTAL BOUNDARY PUSHING SE ACROSS CENTRAL IL SATURDAY AND SAT
NIGHT. TEMPERATURES TO COOL BEHIND THIS FRONT DURING THE WEEKEND
INTO EARLY NEXT WEEK WITH HIGHS IN THE LOW TO MID 70S SUNDAY. A
CUTOFF UPPER LEVEL LOW EJECTING FROM THE ROCKIES INTO TEH CENTRAL
PLAINS BY EARLY NEXT WEEK TO CONTINUE CHANCES OF SHOWERS AND A FEW
THUNDERSTORMS.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z TUESDAY NIGHT)
ISSUED AT 1151 PM CDT MON MAY 25 2015

VFR CONDITIONS IN SCATTERED HIGH CLOUD COVER WITH SOUTH WINDS
10-12 KTS THIS EVENING ACROSS CENTRAL IL. HIGH CLOUD ASSOCIATED
WITH A SHORTWAVE OVER NORTHEAST OKLAHOMA WILL CONTINUE MOVING INTO
THE REGION OVERNIGHT. CURRENT TIMING OF LIFT AND MOISTURE WITH
THE APPROACHING SHORTWAVE INDICATE PREDOMINANT MVFR CONDITIONS IN
SHRA/ISOLD TSRA LIKELY TO BEGIN 10-12Z. SOME LIFTING OF
PREDOMINANT CEILINGS LIKELY IN AFTERNOON WITH DAYTIME HEATING AND
ACCORDING TO MODEL TIME-HEIGHT SECTIONS SO HAVE INCLUDED VCTS
WITH CIGS ABOVE MVFR THRESHOLD. SHORTWAVE AXIS EXPECTED TO CROSS
LATE AFTERNOON/EARLY EVENING TUESDAY BRINGING A DECREASE IN
SHOWER/THUNDERSTORM ACTIVITY BY 00Z AND HAVE ENDED VCTS AND 4 KFT
AGL CIGS. WINDS CONTINUING S 10-12 KTS UNTIL 14Z...INCREASING TO
15-20 KTS WITH GUSTS 25-30KTS AND SHIFTING TOWARD SW. WINDS
DECREASING AFTER 00Z.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...ONTON
SHORT TERM...GEELHART
LONG TERM...07
AVIATION...ONTON




000
FXUS63 KILX 260451
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1151 PM CDT MON MAY 25 2015

.UPDATE...
ISSUED AT 900 PM CDT MON MAY 25 2015

A SHORTWAVE CURRENTLY OVER EASTERN TX/OK WILL BE THE MAIN WEATHER
FEATURE FOR CENTRAL IL LATE TONIGHT AND TOMORROW. AS THE SHORTWAVE
EJECTS OFF TO THE NORTHEAST OF ITS CURRENT POSITION...LIFT AND
MOISTURE ASSOCIATED WITH THE FEATURE WILL DEVELOP RAIN SHOWERS AND
THUNDERSTORMS AFTER MIDNIGHT. CURRENT SHORT TERM MODELS TENDING TO
HOLD OFF PRECIPITATION UNTIL LATER THAN PREVIOUS MODELS SO HAVE
TRENDED PRECIPITATION LATER...HOWEVER MAINTAINING LIKELY
PRECIPITATION BY 7 AM ACROSS CENTRAL IL. CORRIDOR OF PREFERRED
SHEAR/INSTABILITY OVERLAP LOOKS TO SKIRT THROUGH SOUTHERN IL
DURING THE MORNING...LIMITING SEVERE WEATHER POTENTIAL DUE TO
LIMITED SURFACE HEATING. HAVE UPDATED GRIDDED FORECASTS FOR THESE
TRENDS AND EVENING TEMPERATURE/WIND TRENDS.

&&

.SHORT TERM...(TONIGHT)
ISSUED AT 259 PM CDT MON MAY 25 2015

LOWER CLOUDS ARE LIFTING AND BREAKING UP ACROSS THE EAST HALF OF THE
FORECAST AREA THIS AFTERNOON...BUT EXTENSIVE CIRRUS SHIELD KEEPING
SKIES PARTLY SUNNY AT BEST THERE. THE WESTERN CWA HAS HAD SOME
DIURNAL CUMULUS AS IT IS OUTSIDE THE CIRRUS SHIELD...BUT THIS SHOULD
FADE LATER THIS AFTERNOON AS SOME SUBSIDENCE OCCURS ACROSS THAT
AREA. SKIES WILL BE PARTLY CLOUDY FOR A TIME THIS EVENING...BUT THEN
CLOUD UP AGAIN LATER AS SOME OF THE CONVECTIVE BLOWOFF ARRIVES FROM
THE SEVERE ACTIVITY CURRENTLY ACROSS THE SOUTHERN PLAINS. LATEST
HIGH-RESOLUTION MODELS KEEP THE FORECAST AREA DRY THIS EVENING WITH
SEVERAL SUGGESTING PERHAPS TAKING UNTIL EVEN 3-4 AM BEFORE WE SEE
ANY SHOWERS AND STORMS MOVE BACK IN. HOWEVER...I HAVE RAMPED UP THE
POP`S QUICKLY AFTER MIDNIGHT ACROSS THE WEST AND AFTER 3 AM IN THE
EAST. WITH SOUTHERLY WINDS STAYING UP AROUND 10 MPH OR SO...LITTLE
CHANGE NEEDED TO THE OVERNIGHT LOWS...WHICH SHOULD BE IN THE 66-68
DEGREE RANGE.

.LONG TERM...(TUESDAY THROUGH MONDAY)
ISSUED AT 259 PM CDT MON MAY 25 2015

SHORT WAVE NEAR THE RED RIVER ALONG THE WESTERN TX/OK BORDER TO
EJECT NE INTO IL ON TUE LIKELY BRINGING SHOWERS AND THUNDERSTORMS
MOST OF THE DAY. HAVE INCREASING LOW LEVEL JET AHEAD OF THIS FEATURE
LATER TONIGHT THAT WILL INCREASE CHANCES OF SHOWERS AND
THUNDERSTORMS FROM SW TO NE. SHOWERS AND THUNDERSTORMS WILL BECOME
MORE WIDELY SCATTERED SW AREAS LATER TUE AFTERNOON AND OVER REST OF
CENTRAL/EASTERN IL TUE EVENING. SPC SHIFTED SLIGHT RISK SOUTHEAST OF
IL ON TUE AND NOW MAINLY OVER KY/TN/MS/AL WHERE BETTER INSTABILITY
WILL BE PRESENT. STILL HAVE A MARGINAL RISK OF SEVERE STORMS TUE
AFTERNOON FROM SHELBYVILLE TO DANVILLE SE FOR HAIL AND GUSTY WINDS.
HIGHS IN THE UPPER 70S TUE WITH LAWRENCEVILLE NEAR 80F WITH
DEWPOINTS IN THE MID TO UPPER 60S (HIGHEST IN SE IL).

RATHER WARM AND HUMID WEATHER PATTERN LOOKS TO CONTINUE ACROSS IL
DURING THE REST OF THE WEEK WITH DAILY CHANCE OF SHOWERS AND
THUNDERSTORMS. BETWEEN 1.5 AND 2 INCHES OF RAIN IS EXPECTED OVER
AREA THE REST OF THIS WEEK. CHANCE OF SHOWERS AND THUNDERSTORMS
LOOK HIGHER IN SOUTHEAST IL ON WED WITH JUST SLIGHT CHANCE NW OF
THE IL RIVER BY GALESBURG AS MORE SHORT WAVE ENERGY EJECT NE INTO
THE MID MS AND OHIO RIVER VALLEY. SPC HAS MARGINAL RISK OF SEVERE
STORMS WED AFTERNOON MAINLY SOUTH OF I-72. LOWS TONIGHT MOSTLY IN
THE MID 60S WITH SOME LOWER 60S NW OF THE IL RIVER. HIGHS WED IN
THE LOWER 80S AND DEWPOINTS IN THE LOW TO MID 60S.

UPPER LEVEL RIDGE BUILDING A BIT OVER THE EASTERN STATES WED NIGHT
AND THU SO CONVECTION CHANCES LOOK MORE WIDELY SCATTERED OVER
CENTRAL AND SOUTHEAST IL. AREAS FROM I-72 NORTH LOOK DRIER DURING
THIS TIME FRAME CLOSER TO WEAK HIGH PRESSURE DRIFTING OVER THE GREAT
LAKES. HIGHS THU IN THE LOW TO MID 80S WITH MORE SUNSHINE POSSIBLE
AND MID 80S ON FRIDAY.

CHANCES OF SHOWERS AND THUNDERSTORMS INCREASE AGAIN FRI/SAT WITH A
FRONTAL BOUNDARY PUSHING SE ACROSS CENTRAL IL SATURDAY AND SAT
NIGHT. TEMPERATURES TO COOL BEHIND THIS FRONT DURING THE WEEKEND
INTO EARLY NEXT WEEK WITH HIGHS IN THE LOW TO MID 70S SUNDAY. A
CUTOFF UPPER LEVEL LOW EJECTING FROM THE ROCKIES INTO TEH CENTRAL
PLAINS BY EARLY NEXT WEEK TO CONTINUE CHANCES OF SHOWERS AND A FEW
THUNDERSTORMS.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z TUESDAY NIGHT)
ISSUED AT 1151 PM CDT MON MAY 25 2015

VFR CONDITIONS IN SCATTERED HIGH CLOUD COVER WITH SOUTH WINDS
10-12 KTS THIS EVENING ACROSS CENTRAL IL. HIGH CLOUD ASSOCIATED
WITH A SHORTWAVE OVER NORTHEAST OKLAHOMA WILL CONTINUE MOVING INTO
THE REGION OVERNIGHT. CURRENT TIMING OF LIFT AND MOISTURE WITH
THE APPROACHING SHORTWAVE INDICATE PREDOMINANT MVFR CONDITIONS IN
SHRA/ISOLD TSRA LIKELY TO BEGIN 10-12Z. SOME LIFTING OF
PREDOMINANT CEILINGS LIKELY IN AFTERNOON WITH DAYTIME HEATING AND
ACCORDING TO MODEL TIME-HEIGHT SECTIONS SO HAVE INCLUDED VCTS
WITH CIGS ABOVE MVFR THRESHOLD. SHORTWAVE AXIS EXPECTED TO CROSS
LATE AFTERNOON/EARLY EVENING TUESDAY BRINGING A DECREASE IN
SHOWER/THUNDERSTORM ACTIVITY BY 00Z AND HAVE ENDED VCTS AND 4 KFT
AGL CIGS. WINDS CONTINUING S 10-12 KTS UNTIL 14Z...INCREASING TO
15-20 KTS WITH GUSTS 25-30KTS AND SHIFTING TOWARD SW. WINDS
DECREASING AFTER 00Z.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...ONTON
SHORT TERM...GEELHART
LONG TERM...07
AVIATION...ONTON




000
FXUS63 KILX 260451
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1151 PM CDT MON MAY 25 2015

.UPDATE...
ISSUED AT 900 PM CDT MON MAY 25 2015

A SHORTWAVE CURRENTLY OVER EASTERN TX/OK WILL BE THE MAIN WEATHER
FEATURE FOR CENTRAL IL LATE TONIGHT AND TOMORROW. AS THE SHORTWAVE
EJECTS OFF TO THE NORTHEAST OF ITS CURRENT POSITION...LIFT AND
MOISTURE ASSOCIATED WITH THE FEATURE WILL DEVELOP RAIN SHOWERS AND
THUNDERSTORMS AFTER MIDNIGHT. CURRENT SHORT TERM MODELS TENDING TO
HOLD OFF PRECIPITATION UNTIL LATER THAN PREVIOUS MODELS SO HAVE
TRENDED PRECIPITATION LATER...HOWEVER MAINTAINING LIKELY
PRECIPITATION BY 7 AM ACROSS CENTRAL IL. CORRIDOR OF PREFERRED
SHEAR/INSTABILITY OVERLAP LOOKS TO SKIRT THROUGH SOUTHERN IL
DURING THE MORNING...LIMITING SEVERE WEATHER POTENTIAL DUE TO
LIMITED SURFACE HEATING. HAVE UPDATED GRIDDED FORECASTS FOR THESE
TRENDS AND EVENING TEMPERATURE/WIND TRENDS.

&&

.SHORT TERM...(TONIGHT)
ISSUED AT 259 PM CDT MON MAY 25 2015

LOWER CLOUDS ARE LIFTING AND BREAKING UP ACROSS THE EAST HALF OF THE
FORECAST AREA THIS AFTERNOON...BUT EXTENSIVE CIRRUS SHIELD KEEPING
SKIES PARTLY SUNNY AT BEST THERE. THE WESTERN CWA HAS HAD SOME
DIURNAL CUMULUS AS IT IS OUTSIDE THE CIRRUS SHIELD...BUT THIS SHOULD
FADE LATER THIS AFTERNOON AS SOME SUBSIDENCE OCCURS ACROSS THAT
AREA. SKIES WILL BE PARTLY CLOUDY FOR A TIME THIS EVENING...BUT THEN
CLOUD UP AGAIN LATER AS SOME OF THE CONVECTIVE BLOWOFF ARRIVES FROM
THE SEVERE ACTIVITY CURRENTLY ACROSS THE SOUTHERN PLAINS. LATEST
HIGH-RESOLUTION MODELS KEEP THE FORECAST AREA DRY THIS EVENING WITH
SEVERAL SUGGESTING PERHAPS TAKING UNTIL EVEN 3-4 AM BEFORE WE SEE
ANY SHOWERS AND STORMS MOVE BACK IN. HOWEVER...I HAVE RAMPED UP THE
POP`S QUICKLY AFTER MIDNIGHT ACROSS THE WEST AND AFTER 3 AM IN THE
EAST. WITH SOUTHERLY WINDS STAYING UP AROUND 10 MPH OR SO...LITTLE
CHANGE NEEDED TO THE OVERNIGHT LOWS...WHICH SHOULD BE IN THE 66-68
DEGREE RANGE.

.LONG TERM...(TUESDAY THROUGH MONDAY)
ISSUED AT 259 PM CDT MON MAY 25 2015

SHORT WAVE NEAR THE RED RIVER ALONG THE WESTERN TX/OK BORDER TO
EJECT NE INTO IL ON TUE LIKELY BRINGING SHOWERS AND THUNDERSTORMS
MOST OF THE DAY. HAVE INCREASING LOW LEVEL JET AHEAD OF THIS FEATURE
LATER TONIGHT THAT WILL INCREASE CHANCES OF SHOWERS AND
THUNDERSTORMS FROM SW TO NE. SHOWERS AND THUNDERSTORMS WILL BECOME
MORE WIDELY SCATTERED SW AREAS LATER TUE AFTERNOON AND OVER REST OF
CENTRAL/EASTERN IL TUE EVENING. SPC SHIFTED SLIGHT RISK SOUTHEAST OF
IL ON TUE AND NOW MAINLY OVER KY/TN/MS/AL WHERE BETTER INSTABILITY
WILL BE PRESENT. STILL HAVE A MARGINAL RISK OF SEVERE STORMS TUE
AFTERNOON FROM SHELBYVILLE TO DANVILLE SE FOR HAIL AND GUSTY WINDS.
HIGHS IN THE UPPER 70S TUE WITH LAWRENCEVILLE NEAR 80F WITH
DEWPOINTS IN THE MID TO UPPER 60S (HIGHEST IN SE IL).

RATHER WARM AND HUMID WEATHER PATTERN LOOKS TO CONTINUE ACROSS IL
DURING THE REST OF THE WEEK WITH DAILY CHANCE OF SHOWERS AND
THUNDERSTORMS. BETWEEN 1.5 AND 2 INCHES OF RAIN IS EXPECTED OVER
AREA THE REST OF THIS WEEK. CHANCE OF SHOWERS AND THUNDERSTORMS
LOOK HIGHER IN SOUTHEAST IL ON WED WITH JUST SLIGHT CHANCE NW OF
THE IL RIVER BY GALESBURG AS MORE SHORT WAVE ENERGY EJECT NE INTO
THE MID MS AND OHIO RIVER VALLEY. SPC HAS MARGINAL RISK OF SEVERE
STORMS WED AFTERNOON MAINLY SOUTH OF I-72. LOWS TONIGHT MOSTLY IN
THE MID 60S WITH SOME LOWER 60S NW OF THE IL RIVER. HIGHS WED IN
THE LOWER 80S AND DEWPOINTS IN THE LOW TO MID 60S.

UPPER LEVEL RIDGE BUILDING A BIT OVER THE EASTERN STATES WED NIGHT
AND THU SO CONVECTION CHANCES LOOK MORE WIDELY SCATTERED OVER
CENTRAL AND SOUTHEAST IL. AREAS FROM I-72 NORTH LOOK DRIER DURING
THIS TIME FRAME CLOSER TO WEAK HIGH PRESSURE DRIFTING OVER THE GREAT
LAKES. HIGHS THU IN THE LOW TO MID 80S WITH MORE SUNSHINE POSSIBLE
AND MID 80S ON FRIDAY.

CHANCES OF SHOWERS AND THUNDERSTORMS INCREASE AGAIN FRI/SAT WITH A
FRONTAL BOUNDARY PUSHING SE ACROSS CENTRAL IL SATURDAY AND SAT
NIGHT. TEMPERATURES TO COOL BEHIND THIS FRONT DURING THE WEEKEND
INTO EARLY NEXT WEEK WITH HIGHS IN THE LOW TO MID 70S SUNDAY. A
CUTOFF UPPER LEVEL LOW EJECTING FROM THE ROCKIES INTO TEH CENTRAL
PLAINS BY EARLY NEXT WEEK TO CONTINUE CHANCES OF SHOWERS AND A FEW
THUNDERSTORMS.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z TUESDAY NIGHT)
ISSUED AT 1151 PM CDT MON MAY 25 2015

VFR CONDITIONS IN SCATTERED HIGH CLOUD COVER WITH SOUTH WINDS
10-12 KTS THIS EVENING ACROSS CENTRAL IL. HIGH CLOUD ASSOCIATED
WITH A SHORTWAVE OVER NORTHEAST OKLAHOMA WILL CONTINUE MOVING INTO
THE REGION OVERNIGHT. CURRENT TIMING OF LIFT AND MOISTURE WITH
THE APPROACHING SHORTWAVE INDICATE PREDOMINANT MVFR CONDITIONS IN
SHRA/ISOLD TSRA LIKELY TO BEGIN 10-12Z. SOME LIFTING OF
PREDOMINANT CEILINGS LIKELY IN AFTERNOON WITH DAYTIME HEATING AND
ACCORDING TO MODEL TIME-HEIGHT SECTIONS SO HAVE INCLUDED VCTS
WITH CIGS ABOVE MVFR THRESHOLD. SHORTWAVE AXIS EXPECTED TO CROSS
LATE AFTERNOON/EARLY EVENING TUESDAY BRINGING A DECREASE IN
SHOWER/THUNDERSTORM ACTIVITY BY 00Z AND HAVE ENDED VCTS AND 4 KFT
AGL CIGS. WINDS CONTINUING S 10-12 KTS UNTIL 14Z...INCREASING TO
15-20 KTS WITH GUSTS 25-30KTS AND SHIFTING TOWARD SW. WINDS
DECREASING AFTER 00Z.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...ONTON
SHORT TERM...GEELHART
LONG TERM...07
AVIATION...ONTON




000
FXUS63 KLOT 260308
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1008 PM CDT MON MAY 25 2015

.SHORT TERM...
255 PM CDT

THROUGH TUESDAY...

SHOWERS CONTINUE TO DIMINISH AS WE GET ON THE SUBSIDENT SIDE OF THE
DEPARTING UPPER TROUGH AXIS THAT WILL QUICKLY EXIT TO THE NORTHEAST
TONIGHT. SURFACE LOW PRESSURE IS PUSHING INTO UPPER MICHIGAN WHILE
LEAVING MODEST PRESSURE RISES IN ITS WAKE. WIND GUSTS TO 30 TO
LOCALLY 35 MPH WILL CONTINUE THROUGH THE AFTERNOON. EXPECT TO SEE
A LITTLE MORE BLUE SKY THROUGH THE AFTERNOON/EARLY EVENING WHICH
WILL ALLOW TEMPERATURES TO SLOWLY INCH UPWARD TO THE UPPER 70S TO
LOW 80S...THOUGH WITH MOIST SW FLOW EXPECT THESE LOWER CLOUDS TO
LINGER AROUND A BIT LONGER.

THE ACTIVE PATTERN CONTINUES ACROSS THE AREA FOR THE NEXT 24 HOURS.
SEVERAL UPPER LEVEL LOW PRESSURE SYSTEMS ARE NOTED IN AFTERNOON
WATER VAPOR IMAGERY. THE FIRST IS OVER THE NEBRASKA PANHANDLE...WITH
ASSOCIATED LEADING SHORTWAVE ENERGY TRIGGERING SOME SHOWERS AND T-
STORMS ACROSS IOWA...THEN THE BIGGER SHOWS TO THE SOUTH WITH THE
COMPLEX OF STRONG/SEVERE THUNDERSTORMS ASSOCIATED WITH A NEGATIVELY
TILTED TROUGH IN THE TEXAS. THE NORTHERN SHORTWAVE IS EXPECTED TO
CONTINUE DEVELOPING SHOWERS AND STORMS ACROSS IOWA AND INTO FAR
WESTERN ILLINOIS AND WISCONSIN. SOME OF THIS MAY CLIP OUR FAR
NORTHWESTERN COUNTIES...INCLUDING THE ROCKFORD AREA...BUT FEEL AT
THIS POINT THAT IT SHOULD LARGELY BE OFF FARTHER NW. HAVE HELD OFF
AND KEPT THIS ACTIVITY OUT OF AREA.

THEN TONIGHT THE LOWER LEVEL FRONTAL BOUNDARY ASSOCIATED WITH THE
NORTHERN WAVE WILL SAG SOUTHEAST TOWARD THE AREA LATE TONIGHT. MUCH
OF THE GUIDANCE THEN BRINGS THE SOUTHERN SHORTWAVE TOWARD OUR AREA
LATE TONIGHT AND MORE SO ON TUESDAY ON A DECENT UPPER LEVEL JET. THE
LARGE SUITE OF GUIDANCE KEEPS THESE TWO LOWS SEPARATE...ALLOWING
MUCH OF THE NORTHERN STREAM SHOWERS/STORMS TO LARGELY REMAIN OUT OF
AREA...BUT THEY MAY BEGIN TO AFFECT AREAS WEST OF I-39 IN ILLINOIS
OVERNIGHT.

TUESDAY MORNING IS WHEN BETTER CHANCES OF SHOWERS AND SCATTERED
THUNDERSTORMS WOULD BE. THIS MID MORNING/EARLY AFTERNOON PERIOD
FEATURES MODEST LOW/MID LEVEL ISENTROPIC LIFT/PW VALUES APPROACHING
1.5 INCHES AND THETA-E RIDGE NOSING IN FROM THE SOUTH. WE SHOULD
HAVE SOME SHOWERS AND THUNDERSTORMS MOVING FROM SOUTH TO NORTH
DURING THIS TIME FRAME.  DEPENDING ON THE INTERACTION OF THESE TWO
SYSTEMS AND IF THINGS SLOW DOWN A BIT...BETTER INSTABILITY WILL BE
TAPPED INTO IN THE AFTERNOON. THE NAM WOULD SUGGEST THIS
SOLUTION...WHILE THE GLOBAL GFS/ECMWF SUGGEST THE MID-MORNING TO
EARLY AFTERNOON PERIOD WOULD BE THE MOST LIKELY PERIOD WHERE DEEPER
MOISTURE IS AVAILABLE AND CO-LOCATED WITH THE UPPER FORCING.
CONFIDENCE ON TIMING IS ONLY MEDIUM WHICH REQUIRED CARRYING AN
EXTENDED PERIOD OF LIKELY POPS FOR MUCH OF THE DAY.

KMD

&&

.LONG TERM...
319 PM CDT

WEDNESDAY NIGHT THROUGH MONDAY...

AN UPPER LEVEL SHORTWAVE TROUGH PASSES OVERHEAD TUESDAY NIGHT
THROUGH WEDNESDAY WITH NUMEROUS PERIODS OF SHOWERS AND THUNDERSTORMS
EXPECTED.  THE SFC FCST ALSO FEATURES A BOUNDARY MOVING THROUGH THE
CWA WEDNESDAY WHICH COULD HELP FORCE SHOWERS AND STORMS. HAVE HIGHER
CONFIDENCE IN PRECIP TUESDAY NIGHT THAN WEDNESDAY. CAPE LOOKS
MARGINAL OUTSIDE OF THE TYPICALLY TOO ROBUST NAM SOUNDINGS. FCST
SOUNDINGS LACK SHEAR...BUT THEY DO FEATURE INVERTED V/S AT THE SFC
AND SOME DRY AIR ALOFT. THIS SUGGESTS GUSTY WINDS ARE PSBL BUT FLOW
IS LESS THAN 40 KT ALOFT SO DAMAGING WINDS ARE NOT EXPECTED. PWAT
VALUES ARE FORECASTED TO BE ARND 1.3 INCHES WHICH IS ABOVE NORMAL
FOR THIS TIME OF YEAR...THEREFORE HEAVY DOWNPOURS ARE POSSIBLE.

WITH 925MB TEMPS BTWN +18 TO +20C...WARMED TEMPS SLIGHTLY FOR
WEDNESDAY INTO THE UPPER 70S TO AROUND 80.

HIGH PRESSURE THEN SPREADS ACROSS THE REGION WEDNESDAY NIGHT AND
HANGS AROUND THROUGH THURSDAY. THIS SHOULD RESULT IN DRY CONDITIONS
OUTSIDE OF POSSIBLE ISOLATED SHOWERS OVER LAKE MI. WINDS TURN OFF OF
THE LAKE THURSDAY SO AREAS ALONG THE LAKE WILL BE IN THE LOW
70S...WHILE AREAS AWAY FROM THE LAKE WILL GET INTO THE LOW TO MID
80S.

THE NEXT SFC LOW FORMS OVER THE PLAINS THURSDAY EVENING AND PASSES
OVER ONTARIO LATE THURSDAY NIGHT THROUGH FRIDAY MORNING. A LOW
PRESSURE TROUGH ACCOMPANIES THE LOW/S COLD FRONT WHICH SLIDES
THROUGH LATE THIS WEEK. GUIDANCE DIFFERS ON HOW QUICKLY THE FRONT
WILL TRAVEL WITH THE GFS BEING THE QUICKER MODEL.  THE MODELS DO
AGREE THAT THE LOWS WARM FRONT WILL LIFT NORTH OF THE CWA BY FRIDAY
MORNING LEADING TO A WARM AND MUGGY DAY WITH HIGHS IN THE MID 80S.
IF CLOUD COVER REMAINS SCARCE...COULD SEE TEMPS GET INTO THE UPPER
80S. GUSTY WINDS ARE ALSO EXPECTED WITH GUSTS ARND 25 MPH. PRECIP
CHANCES WILL INCREASE THROUGH FRIDAY NIGHT AS THE COLD FRONT MOVES
CLOSER TO THE CWA. THINKING FRIDAY WILL NOT BE A TOTAL WASHOUT...BUT
THERE WILL BE MULTIPLE PERIODS OF STORMS. PWAT VALUES INCREASE
FURTHER TO 1.5 INCHES SO ANY SHOWERS AND STORMS WILL BE CAPABLE OF
HEAVY DOWNPOURS.

SHOWERS AND STORMS ARE ALSO EXPECTED SATURDAY AHEAD OF AND ALONG THE
COLD FRONT. ANOTHER ROUND OF SHOWERS IS POSSIBLE BEHIND THE COLD
FRONT ALONG A VORT STREAMER SATURDAY EVENING AND SUNDAY. THE GFS
KEEPS PRECIP IN THE REGION INTO EARLY NEXT WEEK WHILE THE ECMWF HAS
A RIDGE OVERHEAD.  THEREFORE HAVE LOW CONFIDENCE IN PRECIP CHANCES
NEXT WEEK.  BELOW NORMAL TEMPS MOVE IN LATE THIS WEEK INTO NEXT WEEK
WITH HIGHS POSSIBLY IN THE 60S OVER THE WEEKEND.

JEE

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 03Z...

* SOUTH-SOUTHWEST WINDS OF AROUND 40 KT AT 1000 FT OVERNIGHT.

* MVFR CEILINGS PROBABLE AT TIMES TUESDAY WITH A CHANCE FOR
  TEMPORARY IFR.

* PERIODS OF SHRA WITH PERIODIC TSRA FROM LATE TUESDAY MORNING
  THROUGH THE AFTERNOON.

* NEAR DUE SOUTH WINDS ON TUESDAY WITH PERIODIC GUSTS POSSIBLE
  AND SOME VARIABILITY BETWEEN SOUTHEAST AND SOUTHWEST.


//DISCUSSION...UPDATED 00Z...

GUSTY SOUTH-SOUTHWEST WINDS HAVE ALREADY BEGUN TO EASE AND SHOULD
CONTINUE TO EARLY THIS EVENING. A LOW-LEVEL JET WILL DEVELOP
OVERHEAD WITH SOME 40 KT AND POSSIBLY 45 KT FLOW AT 1500-2000 FT
FROM 05Z-12Z. STORMS ARE EXPECTED TO DEVELOP THROUGH THE EVE AHEAD
OF A FRONT FROM NORTHERN MO THROUGH IA AND INTO WI. WHILE THESE
WILL INCH EASTWARD SOME...THEY ARE GENERALLY EXPECTED TO REMAIN
NORTH AND NORTHWEST OF AREA TAF SITES...POSSIBLY CLOSING IN ON
RFD VERY LATE TONIGHT.

AS AN UPPER DISTURBANCE...PARTLY CONVECTIVELY ENHANCED...MOVES
FROM THE SOUTHERN PLAINS THIS EVENING TO NORTHERN IL BY LATE DAY
TUESDAY...SHOWERS AND SOME STORMS ARE EXPECTED TO EVOLVE INTO THE
REGION. GIVEN THE SUPPORT FOR LIFT ACROSS THE AREA THROUGHOUT THE
DAY THANKS TO BEING IN A FAVORABLE UPPER JET REGION...THE
LIKELIHOOD FOR SHRA AND THE CHANCE FOR TSRA LASTS BASICALLY FROM
15Z THROUGH 02Z. THIS MAKES IT DIFFICULT TO TARGET A SPECIFIC
WINDOW FOR THUNDER. HAVE MADE OUR BEST FORECAST FOR EARLY TO MID
AFTERNOON...BUT COULD VERY WELL BE SHIFTED OR EXPANDED IN TIME.

WINDS WILL BE SOUTHERLY ON TUESDAY AND AT TIMES MAY BE SHIFTING
SOME FROM SOUTHEAST TO SOUTHWEST DEPENDING ON CONVECTIVE ACTIVITY
COVERAGE. GUSTS ARE POSSIBLE THROUGH THE ENTIRE DAY AND APPEAR TO
BE EVEN MORE LIKELY IN THE EVENING AS SURFACE LOW PRESSURE MOVES
NORTHEAST ACROSS SOUTHERN WISCONSIN.


//ORD AND MDW CONFIDENCE...UPDATED 03Z...

* HIGH IN 40 KT SSW FLOW AROUND 1000-1500 FT OVERNIGHT...BUT LOW
  IN TRUE LLWS OCCURRING.

* HIGH IN WINDS TONIGHT AND TUESDAY MORNING. MEDIUM ON SPECIFICS
  AFTER.

* MEDIUM ON MVFR CIGS TUESDAY MORNING AND LOW-MEDIUM ON START TIME
  AND HOW LOW CIGS WILL DROP.

* HIGH ON SHOWERS AND AT LEAST A PERIOD OF TSRA. LOW ON SPECIFIC
  TSRA TIMING WITH MULTIPLE ROUNDS POSSIBLE BETWEEN 15Z AND 02Z.


//OUTLOOK FOR ORD/MDW FOR 12Z WEDNESDAY-12Z MONDAY...UPDATED 00Z...

WEDNESDAY...CHANCE OF TSRA. WEST WINDS.
THURSDAY...SLIGHT CHANCE OF TSRA LATE AT NIGHT. SOUTHEAST WINDS.
FRIDAY...INCREASING CHANCE OF TSRA THROUGH THE DAY AND NIGHT.
         SOUTHWEST WINDS.
SATURDAY...SHRA LIKELY WITH A CHANCE OF TSRA. NORTHEAST WINDS.
SUNDAY...CHANCE OF SHRA. EAST WINDS.

MTF

&&

.MARINE...
334 PM CDT

WIND GUSTS ARE BEGINNING TO COME DOWN AND THE GALE WARNING FOR THE
NEARSHORE ZONES HAS BEEN DROPPED. A SMALL CRAFT ADVISORY WILL GO
THROUGH 9PM CDT THIS EVENING FOR LINGERING STRONG WINDS AND HIGH
WAVES.  LOW PRESSURE CURRENTLY OVER THE UPPER MIDWEST WILL MOVE OVER
QUEBEC TUESDAY MORNING. THE LOWS STATIONARY FRONT REMAINS NORTH OF
THE LAKE BUT STABLE CONDITIONS OVER THE LAKE WILL RESULT IN AREAS OF
FOG THROUGH TUESDAY NIGHT. SOUTH WINDS ARE EXPECTED WITH SPEEDS TO
20 KT. HIGH PRESSURE SPREADS OVER THE LAKE WEDNESDAY NIGHT WITH
WINDS REMAINING LIGHT AND VARYING BTWN WEST AND SOUTHEAST THROUGH
FRIDAY. A COLD FRONT THEN SWEEPS DOWN THE LAKE LATE IN THE WEEK WITH
WINDS BCMG NORTH BEHIND IT.

JEE

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

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000
FXUS63 KLOT 260308
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1008 PM CDT MON MAY 25 2015

.SHORT TERM...
255 PM CDT

THROUGH TUESDAY...

SHOWERS CONTINUE TO DIMINISH AS WE GET ON THE SUBSIDENT SIDE OF THE
DEPARTING UPPER TROUGH AXIS THAT WILL QUICKLY EXIT TO THE NORTHEAST
TONIGHT. SURFACE LOW PRESSURE IS PUSHING INTO UPPER MICHIGAN WHILE
LEAVING MODEST PRESSURE RISES IN ITS WAKE. WIND GUSTS TO 30 TO
LOCALLY 35 MPH WILL CONTINUE THROUGH THE AFTERNOON. EXPECT TO SEE
A LITTLE MORE BLUE SKY THROUGH THE AFTERNOON/EARLY EVENING WHICH
WILL ALLOW TEMPERATURES TO SLOWLY INCH UPWARD TO THE UPPER 70S TO
LOW 80S...THOUGH WITH MOIST SW FLOW EXPECT THESE LOWER CLOUDS TO
LINGER AROUND A BIT LONGER.

THE ACTIVE PATTERN CONTINUES ACROSS THE AREA FOR THE NEXT 24 HOURS.
SEVERAL UPPER LEVEL LOW PRESSURE SYSTEMS ARE NOTED IN AFTERNOON
WATER VAPOR IMAGERY. THE FIRST IS OVER THE NEBRASKA PANHANDLE...WITH
ASSOCIATED LEADING SHORTWAVE ENERGY TRIGGERING SOME SHOWERS AND T-
STORMS ACROSS IOWA...THEN THE BIGGER SHOWS TO THE SOUTH WITH THE
COMPLEX OF STRONG/SEVERE THUNDERSTORMS ASSOCIATED WITH A NEGATIVELY
TILTED TROUGH IN THE TEXAS. THE NORTHERN SHORTWAVE IS EXPECTED TO
CONTINUE DEVELOPING SHOWERS AND STORMS ACROSS IOWA AND INTO FAR
WESTERN ILLINOIS AND WISCONSIN. SOME OF THIS MAY CLIP OUR FAR
NORTHWESTERN COUNTIES...INCLUDING THE ROCKFORD AREA...BUT FEEL AT
THIS POINT THAT IT SHOULD LARGELY BE OFF FARTHER NW. HAVE HELD OFF
AND KEPT THIS ACTIVITY OUT OF AREA.

THEN TONIGHT THE LOWER LEVEL FRONTAL BOUNDARY ASSOCIATED WITH THE
NORTHERN WAVE WILL SAG SOUTHEAST TOWARD THE AREA LATE TONIGHT. MUCH
OF THE GUIDANCE THEN BRINGS THE SOUTHERN SHORTWAVE TOWARD OUR AREA
LATE TONIGHT AND MORE SO ON TUESDAY ON A DECENT UPPER LEVEL JET. THE
LARGE SUITE OF GUIDANCE KEEPS THESE TWO LOWS SEPARATE...ALLOWING
MUCH OF THE NORTHERN STREAM SHOWERS/STORMS TO LARGELY REMAIN OUT OF
AREA...BUT THEY MAY BEGIN TO AFFECT AREAS WEST OF I-39 IN ILLINOIS
OVERNIGHT.

TUESDAY MORNING IS WHEN BETTER CHANCES OF SHOWERS AND SCATTERED
THUNDERSTORMS WOULD BE. THIS MID MORNING/EARLY AFTERNOON PERIOD
FEATURES MODEST LOW/MID LEVEL ISENTROPIC LIFT/PW VALUES APPROACHING
1.5 INCHES AND THETA-E RIDGE NOSING IN FROM THE SOUTH. WE SHOULD
HAVE SOME SHOWERS AND THUNDERSTORMS MOVING FROM SOUTH TO NORTH
DURING THIS TIME FRAME.  DEPENDING ON THE INTERACTION OF THESE TWO
SYSTEMS AND IF THINGS SLOW DOWN A BIT...BETTER INSTABILITY WILL BE
TAPPED INTO IN THE AFTERNOON. THE NAM WOULD SUGGEST THIS
SOLUTION...WHILE THE GLOBAL GFS/ECMWF SUGGEST THE MID-MORNING TO
EARLY AFTERNOON PERIOD WOULD BE THE MOST LIKELY PERIOD WHERE DEEPER
MOISTURE IS AVAILABLE AND CO-LOCATED WITH THE UPPER FORCING.
CONFIDENCE ON TIMING IS ONLY MEDIUM WHICH REQUIRED CARRYING AN
EXTENDED PERIOD OF LIKELY POPS FOR MUCH OF THE DAY.

KMD

&&

.LONG TERM...
319 PM CDT

WEDNESDAY NIGHT THROUGH MONDAY...

AN UPPER LEVEL SHORTWAVE TROUGH PASSES OVERHEAD TUESDAY NIGHT
THROUGH WEDNESDAY WITH NUMEROUS PERIODS OF SHOWERS AND THUNDERSTORMS
EXPECTED.  THE SFC FCST ALSO FEATURES A BOUNDARY MOVING THROUGH THE
CWA WEDNESDAY WHICH COULD HELP FORCE SHOWERS AND STORMS. HAVE HIGHER
CONFIDENCE IN PRECIP TUESDAY NIGHT THAN WEDNESDAY. CAPE LOOKS
MARGINAL OUTSIDE OF THE TYPICALLY TOO ROBUST NAM SOUNDINGS. FCST
SOUNDINGS LACK SHEAR...BUT THEY DO FEATURE INVERTED V/S AT THE SFC
AND SOME DRY AIR ALOFT. THIS SUGGESTS GUSTY WINDS ARE PSBL BUT FLOW
IS LESS THAN 40 KT ALOFT SO DAMAGING WINDS ARE NOT EXPECTED. PWAT
VALUES ARE FORECASTED TO BE ARND 1.3 INCHES WHICH IS ABOVE NORMAL
FOR THIS TIME OF YEAR...THEREFORE HEAVY DOWNPOURS ARE POSSIBLE.

WITH 925MB TEMPS BTWN +18 TO +20C...WARMED TEMPS SLIGHTLY FOR
WEDNESDAY INTO THE UPPER 70S TO AROUND 80.

HIGH PRESSURE THEN SPREADS ACROSS THE REGION WEDNESDAY NIGHT AND
HANGS AROUND THROUGH THURSDAY. THIS SHOULD RESULT IN DRY CONDITIONS
OUTSIDE OF POSSIBLE ISOLATED SHOWERS OVER LAKE MI. WINDS TURN OFF OF
THE LAKE THURSDAY SO AREAS ALONG THE LAKE WILL BE IN THE LOW
70S...WHILE AREAS AWAY FROM THE LAKE WILL GET INTO THE LOW TO MID
80S.

THE NEXT SFC LOW FORMS OVER THE PLAINS THURSDAY EVENING AND PASSES
OVER ONTARIO LATE THURSDAY NIGHT THROUGH FRIDAY MORNING. A LOW
PRESSURE TROUGH ACCOMPANIES THE LOW/S COLD FRONT WHICH SLIDES
THROUGH LATE THIS WEEK. GUIDANCE DIFFERS ON HOW QUICKLY THE FRONT
WILL TRAVEL WITH THE GFS BEING THE QUICKER MODEL.  THE MODELS DO
AGREE THAT THE LOWS WARM FRONT WILL LIFT NORTH OF THE CWA BY FRIDAY
MORNING LEADING TO A WARM AND MUGGY DAY WITH HIGHS IN THE MID 80S.
IF CLOUD COVER REMAINS SCARCE...COULD SEE TEMPS GET INTO THE UPPER
80S. GUSTY WINDS ARE ALSO EXPECTED WITH GUSTS ARND 25 MPH. PRECIP
CHANCES WILL INCREASE THROUGH FRIDAY NIGHT AS THE COLD FRONT MOVES
CLOSER TO THE CWA. THINKING FRIDAY WILL NOT BE A TOTAL WASHOUT...BUT
THERE WILL BE MULTIPLE PERIODS OF STORMS. PWAT VALUES INCREASE
FURTHER TO 1.5 INCHES SO ANY SHOWERS AND STORMS WILL BE CAPABLE OF
HEAVY DOWNPOURS.

SHOWERS AND STORMS ARE ALSO EXPECTED SATURDAY AHEAD OF AND ALONG THE
COLD FRONT. ANOTHER ROUND OF SHOWERS IS POSSIBLE BEHIND THE COLD
FRONT ALONG A VORT STREAMER SATURDAY EVENING AND SUNDAY. THE GFS
KEEPS PRECIP IN THE REGION INTO EARLY NEXT WEEK WHILE THE ECMWF HAS
A RIDGE OVERHEAD.  THEREFORE HAVE LOW CONFIDENCE IN PRECIP CHANCES
NEXT WEEK.  BELOW NORMAL TEMPS MOVE IN LATE THIS WEEK INTO NEXT WEEK
WITH HIGHS POSSIBLY IN THE 60S OVER THE WEEKEND.

JEE

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 03Z...

* SOUTH-SOUTHWEST WINDS OF AROUND 40 KT AT 1000 FT OVERNIGHT.

* MVFR CEILINGS PROBABLE AT TIMES TUESDAY WITH A CHANCE FOR
  TEMPORARY IFR.

* PERIODS OF SHRA WITH PERIODIC TSRA FROM LATE TUESDAY MORNING
  THROUGH THE AFTERNOON.

* NEAR DUE SOUTH WINDS ON TUESDAY WITH PERIODIC GUSTS POSSIBLE
  AND SOME VARIABILITY BETWEEN SOUTHEAST AND SOUTHWEST.


//DISCUSSION...UPDATED 00Z...

GUSTY SOUTH-SOUTHWEST WINDS HAVE ALREADY BEGUN TO EASE AND SHOULD
CONTINUE TO EARLY THIS EVENING. A LOW-LEVEL JET WILL DEVELOP
OVERHEAD WITH SOME 40 KT AND POSSIBLY 45 KT FLOW AT 1500-2000 FT
FROM 05Z-12Z. STORMS ARE EXPECTED TO DEVELOP THROUGH THE EVE AHEAD
OF A FRONT FROM NORTHERN MO THROUGH IA AND INTO WI. WHILE THESE
WILL INCH EASTWARD SOME...THEY ARE GENERALLY EXPECTED TO REMAIN
NORTH AND NORTHWEST OF AREA TAF SITES...POSSIBLY CLOSING IN ON
RFD VERY LATE TONIGHT.

AS AN UPPER DISTURBANCE...PARTLY CONVECTIVELY ENHANCED...MOVES
FROM THE SOUTHERN PLAINS THIS EVENING TO NORTHERN IL BY LATE DAY
TUESDAY...SHOWERS AND SOME STORMS ARE EXPECTED TO EVOLVE INTO THE
REGION. GIVEN THE SUPPORT FOR LIFT ACROSS THE AREA THROUGHOUT THE
DAY THANKS TO BEING IN A FAVORABLE UPPER JET REGION...THE
LIKELIHOOD FOR SHRA AND THE CHANCE FOR TSRA LASTS BASICALLY FROM
15Z THROUGH 02Z. THIS MAKES IT DIFFICULT TO TARGET A SPECIFIC
WINDOW FOR THUNDER. HAVE MADE OUR BEST FORECAST FOR EARLY TO MID
AFTERNOON...BUT COULD VERY WELL BE SHIFTED OR EXPANDED IN TIME.

WINDS WILL BE SOUTHERLY ON TUESDAY AND AT TIMES MAY BE SHIFTING
SOME FROM SOUTHEAST TO SOUTHWEST DEPENDING ON CONVECTIVE ACTIVITY
COVERAGE. GUSTS ARE POSSIBLE THROUGH THE ENTIRE DAY AND APPEAR TO
BE EVEN MORE LIKELY IN THE EVENING AS SURFACE LOW PRESSURE MOVES
NORTHEAST ACROSS SOUTHERN WISCONSIN.


//ORD AND MDW CONFIDENCE...UPDATED 03Z...

* HIGH IN 40 KT SSW FLOW AROUND 1000-1500 FT OVERNIGHT...BUT LOW
  IN TRUE LLWS OCCURRING.

* HIGH IN WINDS TONIGHT AND TUESDAY MORNING. MEDIUM ON SPECIFICS
  AFTER.

* MEDIUM ON MVFR CIGS TUESDAY MORNING AND LOW-MEDIUM ON START TIME
  AND HOW LOW CIGS WILL DROP.

* HIGH ON SHOWERS AND AT LEAST A PERIOD OF TSRA. LOW ON SPECIFIC
  TSRA TIMING WITH MULTIPLE ROUNDS POSSIBLE BETWEEN 15Z AND 02Z.


//OUTLOOK FOR ORD/MDW FOR 12Z WEDNESDAY-12Z MONDAY...UPDATED 00Z...

WEDNESDAY...CHANCE OF TSRA. WEST WINDS.
THURSDAY...SLIGHT CHANCE OF TSRA LATE AT NIGHT. SOUTHEAST WINDS.
FRIDAY...INCREASING CHANCE OF TSRA THROUGH THE DAY AND NIGHT.
         SOUTHWEST WINDS.
SATURDAY...SHRA LIKELY WITH A CHANCE OF TSRA. NORTHEAST WINDS.
SUNDAY...CHANCE OF SHRA. EAST WINDS.

MTF

&&

.MARINE...
334 PM CDT

WIND GUSTS ARE BEGINNING TO COME DOWN AND THE GALE WARNING FOR THE
NEARSHORE ZONES HAS BEEN DROPPED. A SMALL CRAFT ADVISORY WILL GO
THROUGH 9PM CDT THIS EVENING FOR LINGERING STRONG WINDS AND HIGH
WAVES.  LOW PRESSURE CURRENTLY OVER THE UPPER MIDWEST WILL MOVE OVER
QUEBEC TUESDAY MORNING. THE LOWS STATIONARY FRONT REMAINS NORTH OF
THE LAKE BUT STABLE CONDITIONS OVER THE LAKE WILL RESULT IN AREAS OF
FOG THROUGH TUESDAY NIGHT. SOUTH WINDS ARE EXPECTED WITH SPEEDS TO
20 KT. HIGH PRESSURE SPREADS OVER THE LAKE WEDNESDAY NIGHT WITH
WINDS REMAINING LIGHT AND VARYING BTWN WEST AND SOUTHEAST THROUGH
FRIDAY. A COLD FRONT THEN SWEEPS DOWN THE LAKE LATE IN THE WEEK WITH
WINDS BCMG NORTH BEHIND IT.

JEE

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

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000
FXUS63 KILX 260201
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
901 PM CDT MON MAY 25 2015

.UPDATE...
ISSUED AT 900 PM CDT MON MAY 25 2015

A SHORTWAVE CURRENTLY OVER EASTERN TX/OK WILL BE THE MAIN WEATHER
FEATURE FOR CENTRAL IL LATE TONIGHT AND TOMORROW. AS THE SHORTWAVE
EJECTS OFF TO THE NORTHEAST OF ITS CURRENT POSITION...LIFT AND
MOISTURE ASSOCIATED WITH THE FEATURE WILL DEVELOP RAIN SHOWERS AND
THUNDERSTORMS AFTER MIDNIGHT. CURRENT SHORT TERM MODELS TENDING TO
HOLD OFF PRECIPITATION UNTIL LATER THAN PREVIOUS MODELS SO HAVE
TRENDED PRECIPITATION LATER...HOWEVER MAINTAINING LIKELY
PRECIPITATION BY 7 AM ACROSS CENTRAL IL. CORRIDOR OF PREFERRED
SHEAR/INSTABILITY OVERLAP LOOKS TO SKIRT THROUGH SOUTHERN IL
DURING THE MORNING...LIMITING SEVERE WEATHER POTENTIAL DUE TO
LIMITED SURFACE HEATING. HAVE UPDATED GRIDDED FORECASTS FOR THESE
TRENDS AND EVENING TEMPERATURE/WIND TRENDS.

&&

.SHORT TERM...(TONIGHT)
ISSUED AT 259 PM CDT MON MAY 25 2015

LOWER CLOUDS ARE LIFTING AND BREAKING UP ACROSS THE EAST HALF OF THE
FORECAST AREA THIS AFTERNOON...BUT EXTENSIVE CIRRUS SHIELD KEEPING
SKIES PARTLY SUNNY AT BEST THERE. THE WESTERN CWA HAS HAD SOME
DIURNAL CUMULUS AS IT IS OUTSIDE THE CIRRUS SHIELD...BUT THIS SHOULD
FADE LATER THIS AFTERNOON AS SOME SUBSIDENCE OCCURS ACROSS THAT
AREA. SKIES WILL BE PARTLY CLOUDY FOR A TIME THIS EVENING...BUT THEN
CLOUD UP AGAIN LATER AS SOME OF THE CONVECTIVE BLOWOFF ARRIVES FROM
THE SEVERE ACTIVITY CURRENTLY ACROSS THE SOUTHERN PLAINS. LATEST
HIGH-RESOLUTION MODELS KEEP THE FORECAST AREA DRY THIS EVENING WITH
SEVERAL SUGGESTING PERHAPS TAKING UNTIL EVEN 3-4 AM BEFORE WE SEE
ANY SHOWERS AND STORMS MOVE BACK IN. HOWEVER...I HAVE RAMPED UP THE
POP`S QUICKLY AFTER MIDNIGHT ACROSS THE WEST AND AFTER 3 AM IN THE
EAST. WITH SOUTHERLY WINDS STAYING UP AROUND 10 MPH OR SO...LITTLE
CHANGE NEEDED TO THE OVERNIGHT LOWS...WHICH SHOULD BE IN THE 66-68
DEGREE RANGE.

.LONG TERM...(TUESDAY THROUGH MONDAY)
ISSUED AT 259 PM CDT MON MAY 25 2015

SHORT WAVE NEAR THE RED RIVER ALONG THE WESTERN TX/OK BORDER TO
EJECT NE INTO IL ON TUE LIKELY BRINGING SHOWERS AND THUNDERSTORMS
MOST OF THE DAY. HAVE INCREASING LOW LEVEL JET AHEAD OF THIS FEATURE
LATER TONIGHT THAT WILL INCREASE CHANCES OF SHOWERS AND
THUNDERSTORMS FROM SW TO NE. SHOWERS AND THUNDERSTORMS WILL BECOME
MORE WIDELY SCATTERED SW AREAS LATER TUE AFTERNOON AND OVER REST OF
CENTRAL/EASTERN IL TUE EVENING. SPC SHIFTED SLIGHT RISK SOUTHEAST OF
IL ON TUE AND NOW MAINLY OVER KY/TN/MS/AL WHERE BETTER INSTABILITY
WILL BE PRESENT. STILL HAVE A MARGINAL RISK OF SEVERE STORMS TUE
AFTERNOON FROM SHELBYVILLE TO DANVILLE SE FOR HAIL AND GUSTY WINDS.
HIGHS IN THE UPPER 70S TUE WITH LAWRENCEVILLE NEAR 80F WITH
DEWPOINTS IN THE MID TO UPPER 60S (HIGHEST IN SE IL).

RATHER WARM AND HUMID WEATHER PATTERN LOOKS TO CONTINUE ACROSS IL
DURING THE REST OF THE WEEK WITH DAILY CHANCE OF SHOWERS AND
THUNDERSTORMS. BETWEEN 1.5 AND 2 INCHES OF RAIN IS EXPECTED OVER
AREA THE REST OF THIS WEEK. CHANCE OF SHOWERS AND THUNDERSTORMS
LOOK HIGHER IN SOUTHEAST IL ON WED WITH JUST SLIGHT CHANCE NW OF
THE IL RIVER BY GALESBURG AS MORE SHORT WAVE ENERGY EJECT NE INTO
THE MID MS AND OHIO RIVER VALLEY. SPC HAS MARGINAL RISK OF SEVERE
STORMS WED AFTERNOON MAINLY SOUTH OF I-72. LOWS TONIGHT MOSTLY IN
THE MID 60S WITH SOME LOWER 60S NW OF THE IL RIVER. HIGHS WED IN
THE LOWER 80S AND DEWPOINTS IN THE LOW TO MID 60S.

UPPER LEVEL RIDGE BUILDING A BIT OVER THE EASTERN STATES WED NIGHT
AND THU SO CONVECTION CHANCES LOOK MORE WIDELY SCATTERED OVER
CENTRAL AND SOUTHEAST IL. AREAS FROM I-72 NORTH LOOK DRIER DURING
THIS TIME FRAME CLOSER TO WEAK HIGH PRESSURE DRIFTING OVER THE GREAT
LAKES. HIGHS THU IN THE LOW TO MID 80S WITH MORE SUNSHINE POSSIBLE
AND MID 80S ON FRIDAY.

CHANCES OF SHOWERS AND THUNDERSTORMS INCREASE AGAIN FRI/SAT WITH A
FRONTAL BOUNDARY PUSHING SE ACROSS CENTRAL IL SATURDAY AND SAT
NIGHT. TEMPERATURES TO COOL BEHIND THIS FRONT DURING THE WEEKEND
INTO EARLY NEXT WEEK WITH HIGHS IN THE LOW TO MID 70S SUNDAY. A
CUTOFF UPPER LEVEL LOW EJECTING FROM THE ROCKIES INTO TEH CENTRAL
PLAINS BY EARLY NEXT WEEK TO CONTINUE CHANCES OF SHOWERS AND A FEW
THUNDERSTORMS.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z TUESDAY EVENING)
ISSUED AT 659 PM CDT MON MAY 25 2015

VFR CONDITIONS IN AREAS OF SCT025-050 CLOUD COVER WITH SOUTH
WINDS 10-18 KTS THIS EVENING. LOW CLOUD COVER WILL DISSIPATE AFTER
SUNSET THEN HIGH CLOUD ASSOCIATED WITH A SHORTWAVE OVER EAST TX
AND OK WILL BEGIN MOVING INTO THE REGION. CURRENT TIMING OF LIFT
AND MOISTURE WITH THE APPROACHING SHORTWAVE INDICATE PREDOMINANT
MVFR CONDITIONS IN SHRA/ISOLD TSRA LIKELY TO BEGIN 10-12Z. SOME
LIFTING OF PREDOMINANT CEILINGS LIKELY IN AFTERNOON SO HAVE
INCLUDED VCTS WITH CIGS ABOVE MVFR THRESHOLD. SHORTWAVE AXIS
EXPECTED TO CROSS LATE AFTERNOON/EARLY EVENING TUESDAY BRINGING A
DECREASE IN SHOWER/THUNDERSTORM ACTIVITY TOWARD THE END OF THE
24-HOUR TAF FORECAST PERIOD. WINDS CONTINUING S 10-18 KTS UNTIL
18Z...SHIFTING TOWARD SW IN AFTERNOON.


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...ONTON
SHORT TERM...GEELHART
LONG TERM...07
AVIATION...ONTON




000
FXUS63 KILX 252359
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
659 PM CDT MON MAY 25 2015

.SHORT TERM...(TONIGHT)
ISSUED AT 259 PM CDT MON MAY 25 2015

LOWER CLOUDS ARE LIFTING AND BREAKING UP ACROSS THE EAST HALF OF THE
FORECAST AREA THIS AFTERNOON...BUT EXTENSIVE CIRRUS SHIELD KEEPING
SKIES PARTLY SUNNY AT BEST THERE. THE WESTERN CWA HAS HAD SOME
DIURNAL CUMULUS AS IT IS OUTSIDE THE CIRRUS SHIELD...BUT THIS SHOULD
FADE LATER THIS AFTERNOON AS SOME SUBSIDENCE OCCURS ACROSS THAT
AREA. SKIES WILL BE PARTLY CLOUDY FOR A TIME THIS EVENING...BUT THEN
CLOUD UP AGAIN LATER AS SOME OF THE CONVECTIVE BLOWOFF ARRIVES FROM
THE SEVERE ACTIVITY CURRENTLY ACROSS THE SOUTHERN PLAINS. LATEST
HIGH-RESOLUTION MODELS KEEP THE FORECAST AREA DRY THIS EVENING WITH
SEVERAL SUGGESTING PERHAPS TAKING UNTIL EVEN 3-4 AM BEFORE WE SEE
ANY SHOWERS AND STORMS MOVE BACK IN. HOWEVER...I HAVE RAMPED UP THE
POP`S QUICKLY AFTER MIDNIGHT ACROSS THE WEST AND AFTER 3 AM IN THE
EAST. WITH SOUTHERLY WINDS STAYING UP AROUND 10 MPH OR SO...LITTLE
CHANGE NEEDED TO THE OVERNIGHT LOWS...WHICH SHOULD BE IN THE 66-68
DEGREE RANGE.

.LONG TERM...(TUESDAY THROUGH MONDAY)
ISSUED AT 259 PM CDT MON MAY 25 2015

SHORT WAVE NEAR THE RED RIVER ALONG THE WESTERN TX/OK BORDER TO
EJECT NE INTO IL ON TUE LIKELY BRINGING SHOWERS AND THUNDERSTORMS
MOST OF THE DAY. HAVE INCREASING LOW LEVEL JET AHEAD OF THIS FEATURE
LATER TONIGHT THAT WILL INCREASE CHANCES OF SHOWERS AND
THUNDERSTORMS FROM SW TO NE. SHOWERS AND THUNDERSTORMS WILL BECOME
MORE WIDELY SCATTERED SW AREAS LATER TUE AFTERNOON AND OVER REST OF
CENTRAL/EASTERN IL TUE EVENING. SPC SHIFTED SLIGHT RISK SOUTHEAST OF
IL ON TUE AND NOW MAINLY OVER KY/TN/MS/AL WHERE BETTER INSTABILITY
WILL BE PRESENT. STILL HAVE A MARGINAL RISK OF SEVERE STORMS TUE
AFTERNOON FROM SHELBYVILLE TO DANVILLE SE FOR HAIL AND GUSTY WINDS.
HIGHS IN THE UPPER 70S TUE WITH LAWRENCEVILLE NEAR 80F WITH
DEWPOINTS IN THE MID TO UPPER 60S (HIGHEST IN SE IL).

RATHER WARM AND HUMID WEATHER PATTERN LOOKS TO CONTINUE ACROSS IL
DURING THE REST OF THE WEEK WITH DAILY CHANCE OF SHOWERS AND
THUNDERSTORMS. BETWEEN 1.5 AND 2 INCHES OF RAIN IS EXPECTED OVER
AREA THE REST OF THIS WEEK. CHANCE OF SHOWERS AND THUNDERSTORMS
LOOK HIGHER IN SOUTHEAST IL ON WED WITH JUST SLIGHT CHANCE NW OF
THE IL RIVER BY GALESBURG AS MORE SHORT WAVE ENERGY EJECT NE INTO
THE MID MS AND OHIO RIVER VALLEY. SPC HAS MARGINAL RISK OF SEVERE
STORMS WED AFTERNOON MAINLY SOUTH OF I-72. LOWS TONIGHT MOSTLY IN
THE MID 60S WITH SOME LOWER 60S NW OF THE IL RIVER. HIGHS WED IN
THE LOWER 80S AND DEWPOINTS IN THE LOW TO MID 60S.

UPPER LEVEL RIDGE BUILDING A BIT OVER THE EASTERN STATES WED NIGHT
AND THU SO CONVECTION CHANCES LOOK MORE WIDELY SCATTERED OVER
CENTRAL AND SOUTHEAST IL. AREAS FROM I-72 NORTH LOOK DRIER DURING
THIS TIME FRAME CLOSER TO WEAK HIGH PRESSURE DRIFTING OVER THE GREAT
LAKES. HIGHS THU IN THE LOW TO MID 80S WITH MORE SUNSHINE POSSIBLE
AND MID 80S ON FRIDAY.

CHANCES OF SHOWERS AND THUNDERSTORMS INCREASE AGAIN FRI/SAT WITH A
FRONTAL BOUNDARY PUSHING SE ACROSS CENTRAL IL SATURDAY AND SAT
NIGHT. TEMPERATURES TO COOL BEHIND THIS FRONT DURING THE WEEKEND
INTO EARLY NEXT WEEK WITH HIGHS IN THE LOW TO MID 70S SUNDAY. A
CUTOFF UPPER LEVEL LOW EJECTING FROM THE ROCKIES INTO TEH CENTRAL
PLAINS BY EARLY NEXT WEEK TO CONTINUE CHANCES OF SHOWERS AND A FEW
THUNDERSTORMS.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z TUESDAY EVENING)
ISSUED AT 659 PM CDT MON MAY 25 2015

VFR CONDITIONS IN AREAS OF SCT025-050 CLOUD COVER WITH SOUTH
WINDS 10-18 KTS THIS EVENING. LOW CLOUD COVER WILL DISSIPATE AFTER
SUNSET THEN HIGH CLOUD ASSOCIATED WITH A SHORTWAVE OVER EAST TX
AND OK WILL BEGIN MOVING INTO THE REGION. CURRENT TIMING OF LIFT
AND MOISTURE WITH THE APPROACHING SHORTWAVE INDICATE PREDOMINANT
MVFR CONDITIONS IN SHRA/ISOLD TSRA LIKELY TO BEGIN 10-12Z. SOME
LIFTING OF PREDOMINANT CEILINGS LIKELY IN AFTERNOON SO HAVE
INCLUDED VCTS WITH CIGS ABOVE MVFR THRESHOLD. SHORTWAVE AXIS
EXPECTED TO CROSS LATE AFTERNOON/EARLY EVENING TUESDAY BRINGING A
DECREASE IN SHOWER/THUNDERSTORM ACTIVITY TOWARD THE END OF THE
24-HOUR TAF FORECAST PERIOD. WINDS CONTINUING S 10-18 KTS UNTIL
18Z...SHIFTING TOWARD SW IN AFTERNOON.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...GEELHART
LONG TERM...07
AVIATION...ONTON




000
FXUS63 KILX 252359
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
659 PM CDT MON MAY 25 2015

.SHORT TERM...(TONIGHT)
ISSUED AT 259 PM CDT MON MAY 25 2015

LOWER CLOUDS ARE LIFTING AND BREAKING UP ACROSS THE EAST HALF OF THE
FORECAST AREA THIS AFTERNOON...BUT EXTENSIVE CIRRUS SHIELD KEEPING
SKIES PARTLY SUNNY AT BEST THERE. THE WESTERN CWA HAS HAD SOME
DIURNAL CUMULUS AS IT IS OUTSIDE THE CIRRUS SHIELD...BUT THIS SHOULD
FADE LATER THIS AFTERNOON AS SOME SUBSIDENCE OCCURS ACROSS THAT
AREA. SKIES WILL BE PARTLY CLOUDY FOR A TIME THIS EVENING...BUT THEN
CLOUD UP AGAIN LATER AS SOME OF THE CONVECTIVE BLOWOFF ARRIVES FROM
THE SEVERE ACTIVITY CURRENTLY ACROSS THE SOUTHERN PLAINS. LATEST
HIGH-RESOLUTION MODELS KEEP THE FORECAST AREA DRY THIS EVENING WITH
SEVERAL SUGGESTING PERHAPS TAKING UNTIL EVEN 3-4 AM BEFORE WE SEE
ANY SHOWERS AND STORMS MOVE BACK IN. HOWEVER...I HAVE RAMPED UP THE
POP`S QUICKLY AFTER MIDNIGHT ACROSS THE WEST AND AFTER 3 AM IN THE
EAST. WITH SOUTHERLY WINDS STAYING UP AROUND 10 MPH OR SO...LITTLE
CHANGE NEEDED TO THE OVERNIGHT LOWS...WHICH SHOULD BE IN THE 66-68
DEGREE RANGE.

.LONG TERM...(TUESDAY THROUGH MONDAY)
ISSUED AT 259 PM CDT MON MAY 25 2015

SHORT WAVE NEAR THE RED RIVER ALONG THE WESTERN TX/OK BORDER TO
EJECT NE INTO IL ON TUE LIKELY BRINGING SHOWERS AND THUNDERSTORMS
MOST OF THE DAY. HAVE INCREASING LOW LEVEL JET AHEAD OF THIS FEATURE
LATER TONIGHT THAT WILL INCREASE CHANCES OF SHOWERS AND
THUNDERSTORMS FROM SW TO NE. SHOWERS AND THUNDERSTORMS WILL BECOME
MORE WIDELY SCATTERED SW AREAS LATER TUE AFTERNOON AND OVER REST OF
CENTRAL/EASTERN IL TUE EVENING. SPC SHIFTED SLIGHT RISK SOUTHEAST OF
IL ON TUE AND NOW MAINLY OVER KY/TN/MS/AL WHERE BETTER INSTABILITY
WILL BE PRESENT. STILL HAVE A MARGINAL RISK OF SEVERE STORMS TUE
AFTERNOON FROM SHELBYVILLE TO DANVILLE SE FOR HAIL AND GUSTY WINDS.
HIGHS IN THE UPPER 70S TUE WITH LAWRENCEVILLE NEAR 80F WITH
DEWPOINTS IN THE MID TO UPPER 60S (HIGHEST IN SE IL).

RATHER WARM AND HUMID WEATHER PATTERN LOOKS TO CONTINUE ACROSS IL
DURING THE REST OF THE WEEK WITH DAILY CHANCE OF SHOWERS AND
THUNDERSTORMS. BETWEEN 1.5 AND 2 INCHES OF RAIN IS EXPECTED OVER
AREA THE REST OF THIS WEEK. CHANCE OF SHOWERS AND THUNDERSTORMS
LOOK HIGHER IN SOUTHEAST IL ON WED WITH JUST SLIGHT CHANCE NW OF
THE IL RIVER BY GALESBURG AS MORE SHORT WAVE ENERGY EJECT NE INTO
THE MID MS AND OHIO RIVER VALLEY. SPC HAS MARGINAL RISK OF SEVERE
STORMS WED AFTERNOON MAINLY SOUTH OF I-72. LOWS TONIGHT MOSTLY IN
THE MID 60S WITH SOME LOWER 60S NW OF THE IL RIVER. HIGHS WED IN
THE LOWER 80S AND DEWPOINTS IN THE LOW TO MID 60S.

UPPER LEVEL RIDGE BUILDING A BIT OVER THE EASTERN STATES WED NIGHT
AND THU SO CONVECTION CHANCES LOOK MORE WIDELY SCATTERED OVER
CENTRAL AND SOUTHEAST IL. AREAS FROM I-72 NORTH LOOK DRIER DURING
THIS TIME FRAME CLOSER TO WEAK HIGH PRESSURE DRIFTING OVER THE GREAT
LAKES. HIGHS THU IN THE LOW TO MID 80S WITH MORE SUNSHINE POSSIBLE
AND MID 80S ON FRIDAY.

CHANCES OF SHOWERS AND THUNDERSTORMS INCREASE AGAIN FRI/SAT WITH A
FRONTAL BOUNDARY PUSHING SE ACROSS CENTRAL IL SATURDAY AND SAT
NIGHT. TEMPERATURES TO COOL BEHIND THIS FRONT DURING THE WEEKEND
INTO EARLY NEXT WEEK WITH HIGHS IN THE LOW TO MID 70S SUNDAY. A
CUTOFF UPPER LEVEL LOW EJECTING FROM THE ROCKIES INTO TEH CENTRAL
PLAINS BY EARLY NEXT WEEK TO CONTINUE CHANCES OF SHOWERS AND A FEW
THUNDERSTORMS.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z TUESDAY EVENING)
ISSUED AT 659 PM CDT MON MAY 25 2015

VFR CONDITIONS IN AREAS OF SCT025-050 CLOUD COVER WITH SOUTH
WINDS 10-18 KTS THIS EVENING. LOW CLOUD COVER WILL DISSIPATE AFTER
SUNSET THEN HIGH CLOUD ASSOCIATED WITH A SHORTWAVE OVER EAST TX
AND OK WILL BEGIN MOVING INTO THE REGION. CURRENT TIMING OF LIFT
AND MOISTURE WITH THE APPROACHING SHORTWAVE INDICATE PREDOMINANT
MVFR CONDITIONS IN SHRA/ISOLD TSRA LIKELY TO BEGIN 10-12Z. SOME
LIFTING OF PREDOMINANT CEILINGS LIKELY IN AFTERNOON SO HAVE
INCLUDED VCTS WITH CIGS ABOVE MVFR THRESHOLD. SHORTWAVE AXIS
EXPECTED TO CROSS LATE AFTERNOON/EARLY EVENING TUESDAY BRINGING A
DECREASE IN SHOWER/THUNDERSTORM ACTIVITY TOWARD THE END OF THE
24-HOUR TAF FORECAST PERIOD. WINDS CONTINUING S 10-18 KTS UNTIL
18Z...SHIFTING TOWARD SW IN AFTERNOON.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...GEELHART
LONG TERM...07
AVIATION...ONTON



000
FXUS63 KLOT 252352
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
652 PM CDT MON MAY 25 2015

.SHORT TERM...
255 PM CDT

THROUGH TUESDAY...

SHOWERS CONTINUE TO DIMINISH AS WE GET ON THE SUBSIDENT SIDE OF THE
DEPARTING UPPER TROUGH AXIS THAT WILL QUICKLY EXIT TO THE NORTHEAST
TONIGHT. SURFACE LOW PRESSURE IS PUSHING INTO UPPER MICHIGAN WHILE
LEAVING MODEST PRESSURE RISES IN ITS WAKE. WIND GUSTS TO 30 TO
LOCALLY 35 MPH WILL CONTINUE THROUGH THE AFTERNOON. EXPECT TO SEE
A LITTLE MORE BLUE SKY THROUGH THE AFTERNOON/EARLY EVENING WHICH
WILL ALLOW TEMPERATURES TO SLOWLY INCH UPWARD TO THE UPPER 70S TO
LOW 80S...THOUGH WITH MOIST SW FLOW EXPECT THESE LOWER CLOUDS TO
LINGER AROUND A BIT LONGER.

THE ACTIVE PATTERN CONTINUES ACROSS THE AREA FOR THE NEXT 24 HOURS.
SEVERAL UPPER LEVEL LOW PRESSURE SYSTEMS ARE NOTED IN AFTERNOON
WATER VAPOR IMAGERY. THE FIRST IS OVER THE NEBRASKA PANHANDLE...WITH
ASSOCIATED LEADING SHORTWAVE ENERGY TRIGGERING SOME SHOWERS AND T-
STORMS ACROSS IOWA...THEN THE BIGGER SHOWS TO THE SOUTH WITH THE
COMPLEX OF STRONG/SEVERE THUNDERSTORMS ASSOCIATED WITH A NEGATIVELY
TILTED TROUGH IN THE TEXAS. THE NORTHERN SHORTWAVE IS EXPECTED TO
CONTINUE DEVELOPING SHOWERS AND STORMS ACROSS IOWA AND INTO FAR
WESTERN ILLINOIS AND WISCONSIN. SOME OF THIS MAY CLIP OUR FAR
NORTHWESTERN COUNTIES...INCLUDING THE ROCKFORD AREA...BUT FEEL AT
THIS POINT THAT IT SHOULD LARGELY BE OFF FARTHER NW. HAVE HELD OFF
AND KEPT THIS ACTIVITY OUT OF AREA.

THEN TONIGHT THE LOWER LEVEL FRONTAL BOUNDARY ASSOCIATED WITH THE
NORTHERN WAVE WILL SAG SOUTHEAST TOWARD THE AREA LATE TONIGHT. MUCH
OF THE GUIDANCE THEN BRINGS THE SOUTHERN SHORTWAVE TOWARD OUR AREA
LATE TONIGHT AND MORE SO ON TUESDAY ON A DECENT UPPER LEVEL JET. THE
LARGE SUITE OF GUIDANCE KEEPS THESE TWO LOWS SEPARATE...ALLOWING
MUCH OF THE NORTHERN STREAM SHOWERS/STORMS TO LARGELY REMAIN OUT OF
AREA...BUT THEY MAY BEGIN TO AFFECT AREAS WEST OF I-39 IN ILLINOIS
OVERNIGHT.

TUESDAY MORNING IS WHEN BETTER CHANCES OF SHOWERS AND SCATTERED
THUNDERSTORMS WOULD BE. THIS MID MORNING/EARLY AFTERNOON PERIOD
FEATURES MODEST LOW/MID LEVEL ISENTROPIC LIFT/PW VALUES APPROACHING
1.5 INCHES AND THETA-E RIDGE NOSING IN FROM THE SOUTH. WE SHOULD
HAVE SOME SHOWERS AND THUNDERSTORMS MOVING FROM SOUTH TO NORTH
DURING THIS TIME FRAME.  DEPENDING ON THE INTERACTION OF THESE TWO
SYSTEMS AND IF THINGS SLOW DOWN A BIT...BETTER INSTABILITY WILL BE
TAPPED INTO IN THE AFTERNOON. THE NAM WOULD SUGGEST THIS
SOLUTION...WHILE THE GLOBAL GFS/ECMWF SUGGEST THE MID-MORNING TO
EARLY AFTERNOON PERIOD WOULD BE THE MOST LIKELY PERIOD WHERE DEEPER
MOISTURE IS AVAILABLE AND CO-LOCATED WITH THE UPPER FORCING.
CONFIDENCE ON TIMING IS ONLY MEDIUM WHICH REQUIRED CARRYING AN
EXTENDED PERIOD OF LIKELY POPS FOR MUCH OF THE DAY.

KMD

&&

.LONG TERM...
319 PM CDT

WEDNESDAY NIGHT THROUGH MONDAY...

AN UPPER LEVEL SHORTWAVE TROUGH PASSES OVERHEAD TUESDAY NIGHT
THROUGH WEDNESDAY WITH NUMEROUS PERIODS OF SHOWERS AND THUNDERSTORMS
EXPECTED.  THE SFC FCST ALSO FEATURES A BOUNDARY MOVING THROUGH THE
CWA WEDNESDAY WHICH COULD HELP FORCE SHOWERS AND STORMS. HAVE HIGHER
CONFIDENCE IN PRECIP TUESDAY NIGHT THAN WEDNESDAY. CAPE LOOKS
MARGINAL OUTSIDE OF THE TYPICALLY TOO ROBUST NAM SOUNDINGS. FCST
SOUNDINGS LACK SHEAR...BUT THEY DO FEATURE INVERTED V/S AT THE SFC
AND SOME DRY AIR ALOFT. THIS SUGGESTS GUSTY WINDS ARE PSBL BUT FLOW
IS LESS THAN 40 KT ALOFT SO DAMAGING WINDS ARE NOT EXPECTED. PWAT
VALUES ARE FORECASTED TO BE ARND 1.3 INCHES WHICH IS ABOVE NORMAL
FOR THIS TIME OF YEAR...THEREFORE HEAVY DOWNPOURS ARE POSSIBLE.

WITH 925MB TEMPS BTWN +18 TO +20C...WARMED TEMPS SLIGHTLY FOR
WEDNESDAY INTO THE UPPER 70S TO AROUND 80.

HIGH PRESSURE THEN SPREADS ACROSS THE REGION WEDNESDAY NIGHT AND
HANGS AROUND THROUGH THURSDAY. THIS SHOULD RESULT IN DRY CONDITIONS
OUTSIDE OF POSSIBLE ISOLATED SHOWERS OVER LAKE MI. WINDS TURN OFF OF
THE LAKE THURSDAY SO AREAS ALONG THE LAKE WILL BE IN THE LOW
70S...WHILE AREAS AWAY FROM THE LAKE WILL GET INTO THE LOW TO MID
80S.

THE NEXT SFC LOW FORMS OVER THE PLAINS THURSDAY EVENING AND PASSES
OVER ONTARIO LATE THURSDAY NIGHT THROUGH FRIDAY MORNING. A LOW
PRESSURE TROUGH ACCOMPANIES THE LOW/S COLD FRONT WHICH SLIDES
THROUGH LATE THIS WEEK. GUIDANCE DIFFERS ON HOW QUICKLY THE FRONT
WILL TRAVEL WITH THE GFS BEING THE QUICKER MODEL.  THE MODELS DO
AGREE THAT THE LOWS WARM FRONT WILL LIFT NORTH OF THE CWA BY FRIDAY
MORNING LEADING TO A WARM AND MUGGY DAY WITH HIGHS IN THE MID 80S.
IF CLOUD COVER REMAINS SCARCE...COULD SEE TEMPS GET INTO THE UPPER
80S. GUSTY WINDS ARE ALSO EXPECTED WITH GUSTS ARND 25 MPH. PRECIP
CHANCES WILL INCREASE THROUGH FRIDAY NIGHT AS THE COLD FRONT MOVES
CLOSER TO THE CWA. THINKING FRIDAY WILL NOT BE A TOTAL WASHOUT...BUT
THERE WILL BE MULTIPLE PERIODS OF STORMS. PWAT VALUES INCREASE
FURTHER TO 1.5 INCHES SO ANY SHOWERS AND STORMS WILL BE CAPABLE OF
HEAVY DOWNPOURS.

SHOWERS AND STORMS ARE ALSO EXPECTED SATURDAY AHEAD OF AND ALONG THE
COLD FRONT. ANOTHER ROUND OF SHOWERS IS POSSIBLE BEHIND THE COLD
FRONT ALONG A VORT STREAMER SATURDAY EVENING AND SUNDAY. THE GFS
KEEPS PRECIP IN THE REGION INTO EARLY NEXT WEEK WHILE THE ECMWF HAS
A RIDGE OVERHEAD.  THEREFORE HAVE LOW CONFIDENCE IN PRECIP CHANCES
NEXT WEEK.  BELOW NORMAL TEMPS MOVE IN LATE THIS WEEK INTO NEXT WEEK
WITH HIGHS POSSIBLY IN THE 60S OVER THE WEEKEND.

JEE

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 00Z...

* GUSTY SOUTHWEST WINDS EASING EARLY THIS EVE AND TURNING DUE
  SOUTH.

* MVFR CEILINGS PROBABLE AT TIMES TUESDAY WITH A CHANCE FOR
  TEMPORARY IFR.

* PERIODS OF SHRA WITH PERIODIC TSRA FROM LATE TUESDAY MORNING
  THROUGH THE AFTERNOON.

* NEAR DUE SOUTH WINDS ON TUESDAY WITH PERIODIC GUSTS POSSIBLE
  AND SOME VARIABILITY BETWEEN SOUTHEAST AND SOUTHWEST.


//DISCUSSION...UPDATED 00Z...

GUSTY SOUTH-SOUTHWEST WINDS HAVE ALREADY BEGUN TO EASE AND SHOULD
CONTINUE TO EARLY THIS EVENING. A LOW-LEVEL JET WILL DEVELOP
OVERHEAD WITH SOME 40 KT AND POSSIBLY 45 KT FLOW AT 1500-2000 FT
FROM 05Z-12Z. STORMS ARE EXPECTED TO DEVELOP THROUGH THE EVE AHEAD
OF A FRONT FROM NORTHERN MO THROUGH IA AND INTO WI. WHILE THESE
WILL INCH EASTWARD SOME...THEY ARE GENERALLY EXPECTED TO REMAIN
NORTH AND NORTHWEST OF AREA TAF SITES...POSSIBLY CLOSING IN ON
RFD VERY LATE TONIGHT.

AS AN UPPER DISTURBANCE...PARTLY CONVECTIVELY ENHANCED...MOVES
FROM THE SOUTHERN PLAINS THIS EVENING TO NORTHERN IL BY LATE DAY
TUESDAY...SHOWERS AND SOME STORMS ARE EXPECTED TO EVOLVE INTO THE
REGION. GIVEN THE SUPPORT FOR LIFT ACROSS THE AREA THROUGHOUT THE
DAY THANKS TO BEING IN A FAVORABLE UPPER JET REGION...THE
LIKELIHOOD FOR SHRA AND THE CHANCE FOR TSRA LASTS BASICALLY FROM
15Z THROUGH 02Z. THIS MAKES IT DIFFICULT TO TARGET A SPECIFIC
WINDOW FOR THUNDER. HAVE MADE OUR BEST FORECAST FOR EARLY TO MID
AFTERNOON...BUT COULD VERY WELL BE SHIFTED OR EXPANDED IN TIME.

WINDS WILL BE SOUTHERLY ON TUESDAY AND AT TIMES MAY BE SHIFTING
SOME FROM SOUTHEAST TO SOUTHWEST DEPENDING ON CONVECTIVE ACTIVITY
COVERAGE. GUSTS ARE POSSIBLE THROUGH THE ENTIRE DAY AND APPEAR TO
BE EVEN MORE LIKELY IN THE EVENING AS SURFACE LOW PRESSURE MOVES
NORTHEAST ACROSS SOUTHERN WISCONSIN.


//ORD AND MDW CONFIDENCE...UPDATED 00Z...

* HIGH IN WINDS TONIGHT AND TUESDAY MORNING. MEDIUM ON SPECIFICS
  AFTER.

* MEDIUM ON MVFR CIGS TUESDAY MORNING AND LOW-MEDIUM ON START TIME
  AND HOW LOW CIGS WILL DROP.

* HIGH ON SHOWERS AND AT LEAST A PERIOD OF TSRA. LOW ON SPECIFIC
  TSRA TIMING WITH MULTIPLE ROUNDS POSSIBLE BETWEEN 15Z AND 02Z.


//OUTLOOK FOR ORD/MDW FOR 12Z WEDNESDAY-12Z MONDAY...UPDATED 00Z...

WEDNESDAY...CHANCE OF TSRA. WEST WINDS.
THURSDAY...SLIGHT CHANCE OF TSRA LATE AT NIGHT. SOUTHEAST WINDS.
FRIDAY...INCREASING CHANCE OF TSRA THROUGH THE DAY AND NIGHT.
         SOUTHWEST WINDS.
SATURDAY...SHRA LIKELY WITH A CHANCE OF TSRA. NORTHEAST WINDS.
SUNDAY...CHANCE OF SHRA. EAST WINDS.

MTF

&&

.MARINE...
334 PM CDT

WIND GUSTS ARE BEGINNING TO COME DOWN AND THE GALE WARNING FOR THE
NEARSHORE ZONES HAS BEEN DROPPED. A SMALL CRAFT ADVISORY WILL GO
THROUGH 9PM CDT THIS EVENING FOR LINGERING STRONG WINDS AND HIGH
WAVES.  LOW PRESSURE CURRENTLY OVER THE UPPER MIDWEST WILL MOVE OVER
QUEBEC TUESDAY MORNING. THE LOWS STATIONARY FRONT REMAINS NORTH OF
THE LAKE BUT STABLE CONDITIONS OVER THE LAKE WILL RESULT IN AREAS OF
FOG THROUGH TUESDAY NIGHT. SOUTH WINDS ARE EXPECTED WITH SPEEDS TO
20 KT. HIGH PRESSURE SPREADS OVER THE LAKE WEDNESDAY NIGHT WITH
WINDS REMAINING LIGHT AND VARYING BTWN WEST AND SOUTHEAST THROUGH
FRIDAY. A COLD FRONT THEN SWEEPS DOWN THE LAKE LATE IN THE WEEK WITH
WINDS BCMG NORTH BEHIND IT.

JEE

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 9 PM MONDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 252352
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
652 PM CDT MON MAY 25 2015

.SHORT TERM...
255 PM CDT

THROUGH TUESDAY...

SHOWERS CONTINUE TO DIMINISH AS WE GET ON THE SUBSIDENT SIDE OF THE
DEPARTING UPPER TROUGH AXIS THAT WILL QUICKLY EXIT TO THE NORTHEAST
TONIGHT. SURFACE LOW PRESSURE IS PUSHING INTO UPPER MICHIGAN WHILE
LEAVING MODEST PRESSURE RISES IN ITS WAKE. WIND GUSTS TO 30 TO
LOCALLY 35 MPH WILL CONTINUE THROUGH THE AFTERNOON. EXPECT TO SEE
A LITTLE MORE BLUE SKY THROUGH THE AFTERNOON/EARLY EVENING WHICH
WILL ALLOW TEMPERATURES TO SLOWLY INCH UPWARD TO THE UPPER 70S TO
LOW 80S...THOUGH WITH MOIST SW FLOW EXPECT THESE LOWER CLOUDS TO
LINGER AROUND A BIT LONGER.

THE ACTIVE PATTERN CONTINUES ACROSS THE AREA FOR THE NEXT 24 HOURS.
SEVERAL UPPER LEVEL LOW PRESSURE SYSTEMS ARE NOTED IN AFTERNOON
WATER VAPOR IMAGERY. THE FIRST IS OVER THE NEBRASKA PANHANDLE...WITH
ASSOCIATED LEADING SHORTWAVE ENERGY TRIGGERING SOME SHOWERS AND T-
STORMS ACROSS IOWA...THEN THE BIGGER SHOWS TO THE SOUTH WITH THE
COMPLEX OF STRONG/SEVERE THUNDERSTORMS ASSOCIATED WITH A NEGATIVELY
TILTED TROUGH IN THE TEXAS. THE NORTHERN SHORTWAVE IS EXPECTED TO
CONTINUE DEVELOPING SHOWERS AND STORMS ACROSS IOWA AND INTO FAR
WESTERN ILLINOIS AND WISCONSIN. SOME OF THIS MAY CLIP OUR FAR
NORTHWESTERN COUNTIES...INCLUDING THE ROCKFORD AREA...BUT FEEL AT
THIS POINT THAT IT SHOULD LARGELY BE OFF FARTHER NW. HAVE HELD OFF
AND KEPT THIS ACTIVITY OUT OF AREA.

THEN TONIGHT THE LOWER LEVEL FRONTAL BOUNDARY ASSOCIATED WITH THE
NORTHERN WAVE WILL SAG SOUTHEAST TOWARD THE AREA LATE TONIGHT. MUCH
OF THE GUIDANCE THEN BRINGS THE SOUTHERN SHORTWAVE TOWARD OUR AREA
LATE TONIGHT AND MORE SO ON TUESDAY ON A DECENT UPPER LEVEL JET. THE
LARGE SUITE OF GUIDANCE KEEPS THESE TWO LOWS SEPARATE...ALLOWING
MUCH OF THE NORTHERN STREAM SHOWERS/STORMS TO LARGELY REMAIN OUT OF
AREA...BUT THEY MAY BEGIN TO AFFECT AREAS WEST OF I-39 IN ILLINOIS
OVERNIGHT.

TUESDAY MORNING IS WHEN BETTER CHANCES OF SHOWERS AND SCATTERED
THUNDERSTORMS WOULD BE. THIS MID MORNING/EARLY AFTERNOON PERIOD
FEATURES MODEST LOW/MID LEVEL ISENTROPIC LIFT/PW VALUES APPROACHING
1.5 INCHES AND THETA-E RIDGE NOSING IN FROM THE SOUTH. WE SHOULD
HAVE SOME SHOWERS AND THUNDERSTORMS MOVING FROM SOUTH TO NORTH
DURING THIS TIME FRAME.  DEPENDING ON THE INTERACTION OF THESE TWO
SYSTEMS AND IF THINGS SLOW DOWN A BIT...BETTER INSTABILITY WILL BE
TAPPED INTO IN THE AFTERNOON. THE NAM WOULD SUGGEST THIS
SOLUTION...WHILE THE GLOBAL GFS/ECMWF SUGGEST THE MID-MORNING TO
EARLY AFTERNOON PERIOD WOULD BE THE MOST LIKELY PERIOD WHERE DEEPER
MOISTURE IS AVAILABLE AND CO-LOCATED WITH THE UPPER FORCING.
CONFIDENCE ON TIMING IS ONLY MEDIUM WHICH REQUIRED CARRYING AN
EXTENDED PERIOD OF LIKELY POPS FOR MUCH OF THE DAY.

KMD

&&

.LONG TERM...
319 PM CDT

WEDNESDAY NIGHT THROUGH MONDAY...

AN UPPER LEVEL SHORTWAVE TROUGH PASSES OVERHEAD TUESDAY NIGHT
THROUGH WEDNESDAY WITH NUMEROUS PERIODS OF SHOWERS AND THUNDERSTORMS
EXPECTED.  THE SFC FCST ALSO FEATURES A BOUNDARY MOVING THROUGH THE
CWA WEDNESDAY WHICH COULD HELP FORCE SHOWERS AND STORMS. HAVE HIGHER
CONFIDENCE IN PRECIP TUESDAY NIGHT THAN WEDNESDAY. CAPE LOOKS
MARGINAL OUTSIDE OF THE TYPICALLY TOO ROBUST NAM SOUNDINGS. FCST
SOUNDINGS LACK SHEAR...BUT THEY DO FEATURE INVERTED V/S AT THE SFC
AND SOME DRY AIR ALOFT. THIS SUGGESTS GUSTY WINDS ARE PSBL BUT FLOW
IS LESS THAN 40 KT ALOFT SO DAMAGING WINDS ARE NOT EXPECTED. PWAT
VALUES ARE FORECASTED TO BE ARND 1.3 INCHES WHICH IS ABOVE NORMAL
FOR THIS TIME OF YEAR...THEREFORE HEAVY DOWNPOURS ARE POSSIBLE.

WITH 925MB TEMPS BTWN +18 TO +20C...WARMED TEMPS SLIGHTLY FOR
WEDNESDAY INTO THE UPPER 70S TO AROUND 80.

HIGH PRESSURE THEN SPREADS ACROSS THE REGION WEDNESDAY NIGHT AND
HANGS AROUND THROUGH THURSDAY. THIS SHOULD RESULT IN DRY CONDITIONS
OUTSIDE OF POSSIBLE ISOLATED SHOWERS OVER LAKE MI. WINDS TURN OFF OF
THE LAKE THURSDAY SO AREAS ALONG THE LAKE WILL BE IN THE LOW
70S...WHILE AREAS AWAY FROM THE LAKE WILL GET INTO THE LOW TO MID
80S.

THE NEXT SFC LOW FORMS OVER THE PLAINS THURSDAY EVENING AND PASSES
OVER ONTARIO LATE THURSDAY NIGHT THROUGH FRIDAY MORNING. A LOW
PRESSURE TROUGH ACCOMPANIES THE LOW/S COLD FRONT WHICH SLIDES
THROUGH LATE THIS WEEK. GUIDANCE DIFFERS ON HOW QUICKLY THE FRONT
WILL TRAVEL WITH THE GFS BEING THE QUICKER MODEL.  THE MODELS DO
AGREE THAT THE LOWS WARM FRONT WILL LIFT NORTH OF THE CWA BY FRIDAY
MORNING LEADING TO A WARM AND MUGGY DAY WITH HIGHS IN THE MID 80S.
IF CLOUD COVER REMAINS SCARCE...COULD SEE TEMPS GET INTO THE UPPER
80S. GUSTY WINDS ARE ALSO EXPECTED WITH GUSTS ARND 25 MPH. PRECIP
CHANCES WILL INCREASE THROUGH FRIDAY NIGHT AS THE COLD FRONT MOVES
CLOSER TO THE CWA. THINKING FRIDAY WILL NOT BE A TOTAL WASHOUT...BUT
THERE WILL BE MULTIPLE PERIODS OF STORMS. PWAT VALUES INCREASE
FURTHER TO 1.5 INCHES SO ANY SHOWERS AND STORMS WILL BE CAPABLE OF
HEAVY DOWNPOURS.

SHOWERS AND STORMS ARE ALSO EXPECTED SATURDAY AHEAD OF AND ALONG THE
COLD FRONT. ANOTHER ROUND OF SHOWERS IS POSSIBLE BEHIND THE COLD
FRONT ALONG A VORT STREAMER SATURDAY EVENING AND SUNDAY. THE GFS
KEEPS PRECIP IN THE REGION INTO EARLY NEXT WEEK WHILE THE ECMWF HAS
A RIDGE OVERHEAD.  THEREFORE HAVE LOW CONFIDENCE IN PRECIP CHANCES
NEXT WEEK.  BELOW NORMAL TEMPS MOVE IN LATE THIS WEEK INTO NEXT WEEK
WITH HIGHS POSSIBLY IN THE 60S OVER THE WEEKEND.

JEE

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 00Z...

* GUSTY SOUTHWEST WINDS EASING EARLY THIS EVE AND TURNING DUE
  SOUTH.

* MVFR CEILINGS PROBABLE AT TIMES TUESDAY WITH A CHANCE FOR
  TEMPORARY IFR.

* PERIODS OF SHRA WITH PERIODIC TSRA FROM LATE TUESDAY MORNING
  THROUGH THE AFTERNOON.

* NEAR DUE SOUTH WINDS ON TUESDAY WITH PERIODIC GUSTS POSSIBLE
  AND SOME VARIABILITY BETWEEN SOUTHEAST AND SOUTHWEST.


//DISCUSSION...UPDATED 00Z...

GUSTY SOUTH-SOUTHWEST WINDS HAVE ALREADY BEGUN TO EASE AND SHOULD
CONTINUE TO EARLY THIS EVENING. A LOW-LEVEL JET WILL DEVELOP
OVERHEAD WITH SOME 40 KT AND POSSIBLY 45 KT FLOW AT 1500-2000 FT
FROM 05Z-12Z. STORMS ARE EXPECTED TO DEVELOP THROUGH THE EVE AHEAD
OF A FRONT FROM NORTHERN MO THROUGH IA AND INTO WI. WHILE THESE
WILL INCH EASTWARD SOME...THEY ARE GENERALLY EXPECTED TO REMAIN
NORTH AND NORTHWEST OF AREA TAF SITES...POSSIBLY CLOSING IN ON
RFD VERY LATE TONIGHT.

AS AN UPPER DISTURBANCE...PARTLY CONVECTIVELY ENHANCED...MOVES
FROM THE SOUTHERN PLAINS THIS EVENING TO NORTHERN IL BY LATE DAY
TUESDAY...SHOWERS AND SOME STORMS ARE EXPECTED TO EVOLVE INTO THE
REGION. GIVEN THE SUPPORT FOR LIFT ACROSS THE AREA THROUGHOUT THE
DAY THANKS TO BEING IN A FAVORABLE UPPER JET REGION...THE
LIKELIHOOD FOR SHRA AND THE CHANCE FOR TSRA LASTS BASICALLY FROM
15Z THROUGH 02Z. THIS MAKES IT DIFFICULT TO TARGET A SPECIFIC
WINDOW FOR THUNDER. HAVE MADE OUR BEST FORECAST FOR EARLY TO MID
AFTERNOON...BUT COULD VERY WELL BE SHIFTED OR EXPANDED IN TIME.

WINDS WILL BE SOUTHERLY ON TUESDAY AND AT TIMES MAY BE SHIFTING
SOME FROM SOUTHEAST TO SOUTHWEST DEPENDING ON CONVECTIVE ACTIVITY
COVERAGE. GUSTS ARE POSSIBLE THROUGH THE ENTIRE DAY AND APPEAR TO
BE EVEN MORE LIKELY IN THE EVENING AS SURFACE LOW PRESSURE MOVES
NORTHEAST ACROSS SOUTHERN WISCONSIN.


//ORD AND MDW CONFIDENCE...UPDATED 00Z...

* HIGH IN WINDS TONIGHT AND TUESDAY MORNING. MEDIUM ON SPECIFICS
  AFTER.

* MEDIUM ON MVFR CIGS TUESDAY MORNING AND LOW-MEDIUM ON START TIME
  AND HOW LOW CIGS WILL DROP.

* HIGH ON SHOWERS AND AT LEAST A PERIOD OF TSRA. LOW ON SPECIFIC
  TSRA TIMING WITH MULTIPLE ROUNDS POSSIBLE BETWEEN 15Z AND 02Z.


//OUTLOOK FOR ORD/MDW FOR 12Z WEDNESDAY-12Z MONDAY...UPDATED 00Z...

WEDNESDAY...CHANCE OF TSRA. WEST WINDS.
THURSDAY...SLIGHT CHANCE OF TSRA LATE AT NIGHT. SOUTHEAST WINDS.
FRIDAY...INCREASING CHANCE OF TSRA THROUGH THE DAY AND NIGHT.
         SOUTHWEST WINDS.
SATURDAY...SHRA LIKELY WITH A CHANCE OF TSRA. NORTHEAST WINDS.
SUNDAY...CHANCE OF SHRA. EAST WINDS.

MTF

&&

.MARINE...
334 PM CDT

WIND GUSTS ARE BEGINNING TO COME DOWN AND THE GALE WARNING FOR THE
NEARSHORE ZONES HAS BEEN DROPPED. A SMALL CRAFT ADVISORY WILL GO
THROUGH 9PM CDT THIS EVENING FOR LINGERING STRONG WINDS AND HIGH
WAVES.  LOW PRESSURE CURRENTLY OVER THE UPPER MIDWEST WILL MOVE OVER
QUEBEC TUESDAY MORNING. THE LOWS STATIONARY FRONT REMAINS NORTH OF
THE LAKE BUT STABLE CONDITIONS OVER THE LAKE WILL RESULT IN AREAS OF
FOG THROUGH TUESDAY NIGHT. SOUTH WINDS ARE EXPECTED WITH SPEEDS TO
20 KT. HIGH PRESSURE SPREADS OVER THE LAKE WEDNESDAY NIGHT WITH
WINDS REMAINING LIGHT AND VARYING BTWN WEST AND SOUTHEAST THROUGH
FRIDAY. A COLD FRONT THEN SWEEPS DOWN THE LAKE LATE IN THE WEEK WITH
WINDS BCMG NORTH BEHIND IT.

JEE

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 9 PM MONDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 252146
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
446 PM CDT MON MAY 25 2015

.SHORT TERM...
255 PM CDT

THROUGH TUESDAY...

SHOWERS CONTINUE TO DIMINISH AS WE GET ON THE SUBSIDENT SIDE OF THE
DEPARTING UPPER TROUGH AXIS THAT WILL QUICKLY EXIT TO THE NORTHEAST
TONIGHT. SURFACE LOW PRESSURE IS PUSHING INTO UPPER MICHIGAN WHILE
LEAVING MODEST PRESSURE RISES IN ITS WAKE. WIND GUSTS TO 30 TO
LOCALLY 35 MPH WILL CONTINUE THROUGH THE AFTERNOON. EXPECT TO SEE
A LITTLE MORE BLUE SKY THROUGH THE AFTERNOON/EARLY EVENING WHICH
WILL ALLOW TEMPERATURES TO SLOWLY INCH UPWARD TO THE UPPER 70S TO
LOW 80S...THOUGH WITH MOIST SW FLOW EXPECT THESE LOWER CLOUDS TO
LINGER AROUND A BIT LONGER.

THE ACTIVE PATTERN CONTINUES ACROSS THE AREA FOR THE NEXT 24 HOURS.
SEVERAL UPPER LEVEL LOW PRESSURE SYSTEMS ARE NOTED IN AFTERNOON
WATER VAPOR IMAGERY. THE FIRST IS OVER THE NEBRASKA PANHANDLE...WITH
ASSOCIATED LEADING SHORTWAVE ENERGY TRIGGERING SOME SHOWERS AND T-
STORMS ACROSS IOWA...THEN THE BIGGER SHOWS TO THE SOUTH WITH THE
COMPLEX OF STRONG/SEVERE THUNDERSTORMS ASSOCIATED WITH A NEGATIVELY
TILTED TROUGH IN THE TEXAS. THE NORTHERN SHORTWAVE IS EXPECTED TO
CONTINUE DEVELOPING SHOWERS AND STORMS ACROSS IOWA AND INTO FAR
WESTERN ILLINOIS AND WISCONSIN. SOME OF THIS MAY CLIP OUR FAR
NORTHWESTERN COUNTIES...INCLUDING THE ROCKFORD AREA...BUT FEEL AT
THIS POINT THAT IT SHOULD LARGELY BE OFF FARTHER NW. HAVE HELD OFF
AND KEPT THIS ACTIVITY OUT OF AREA.

THEN TONIGHT THE LOWER LEVEL FRONTAL BOUNDARY ASSOCIATED WITH THE
NORTHERN WAVE WILL SAG SOUTHEAST TOWARD THE AREA LATE TONIGHT. MUCH
OF THE GUIDANCE THEN BRINGS THE SOUTHERN SHORTWAVE TOWARD OUR AREA
LATE TONIGHT AND MORE SO ON TUESDAY ON A DECENT UPPER LEVEL JET. THE
LARGE SUITE OF GUIDANCE KEEPS THESE TWO LOWS SEPARATE...ALLOWING
MUCH OF THE NORTHERN STREAM SHOWERS/STORMS TO LARGELY REMAIN OUT OF
AREA...BUT THEY MAY BEGIN TO AFFECT AREAS WEST OF I-39 IN ILLINOIS
OVERNIGHT.

TUESDAY MORNING IS WHEN BETTER CHANCES OF SHOWERS AND SCATTERED
THUNDERSTORMS WOULD BE. THIS MID MORNING/EARLY AFTERNOON PERIOD
FEATURES MODEST LOW/MID LEVEL ISENTROPIC LIFT/PW VALUES APPROACHING
1.5 INCHES AND THETA-E RIDGE NOSING IN FROM THE SOUTH. WE SHOULD
HAVE SOME SHOWERS AND THUNDERSTORMS MOVING FROM SOUTH TO NORTH
DURING THIS TIME FRAME.  DEPENDING ON THE INTERACTION OF THESE TWO
SYSTEMS AND IF THINGS SLOW DOWN A BIT...BETTER INSTABILITY WILL BE
TAPPED INTO IN THE AFTERNOON. THE NAM WOULD SUGGEST THIS
SOLUTION...WHILE THE GLOBAL GFS/ECMWF SUGGEST THE MID-MORNING TO
EARLY AFTERNOON PERIOD WOULD BE THE MOST LIKELY PERIOD WHERE DEEPER
MOISTURE IS AVAILABLE AND CO-LOCATED WITH THE UPPER FORCING.
CONFIDENCE ON TIMING IS ONLY MEDIUM WHICH REQUIRED CARRYING AN
EXTENDED PERIOD OF LIKELY POPS FOR MUCH OF THE DAY.

KMD

&&

.LONG TERM...
319 PM CDT

WEDNESDAY NIGHT THROUGH MONDAY...

AN UPPER LEVEL SHORTWAVE TROUGH PASSES OVERHEAD TUESDAY NIGHT
THROUGH WEDNESDAY WITH NUMEROUS PERIODS OF SHOWERS AND THUNDERSTORMS
EXPECTED.  THE SFC FCST ALSO FEATURES A BOUNDARY MOVING THROUGH THE
CWA WEDNESDAY WHICH COULD HELP FORCE SHOWERS AND STORMS. HAVE HIGHER
CONFIDENCE IN PRECIP TUESDAY NIGHT THAN WEDNESDAY. CAPE LOOKS
MARGINAL OUTSIDE OF THE TYPICALLY TOO ROBUST NAM SOUNDINGS. FCST
SOUNDINGS LACK SHEAR...BUT THEY DO FEATURE INVERTED V/S AT THE SFC
AND SOME DRY AIR ALOFT. THIS SUGGESTS GUSTY WINDS ARE PSBL BUT FLOW
IS LESS THAN 40 KT ALOFT SO DAMAGING WINDS ARE NOT EXPECTED. PWAT
VALUES ARE FORECASTED TO BE ARND 1.3 INCHES WHICH IS ABOVE NORMAL
FOR THIS TIME OF YEAR...THEREFORE HEAVY DOWNPOURS ARE POSSIBLE.

WITH 925MB TEMPS BTWN +18 TO +20C...WARMED TEMPS SLIGHTLY FOR
WEDNESDAY INTO THE UPPER 70S TO AROUND 80.

HIGH PRESSURE THEN SPREADS ACROSS THE REGION WEDNESDAY NIGHT AND
HANGS AROUND THROUGH THURSDAY. THIS SHOULD RESULT IN DRY CONDITIONS
OUTSIDE OF POSSIBLE ISOLATED SHOWERS OVER LAKE MI. WINDS TURN OFF OF
THE LAKE THURSDAY SO AREAS ALONG THE LAKE WILL BE IN THE LOW
70S...WHILE AREAS AWAY FROM THE LAKE WILL GET INTO THE LOW TO MID
80S.

THE NEXT SFC LOW FORMS OVER THE PLAINS THURSDAY EVENING AND PASSES
OVER ONTARIO LATE THURSDAY NIGHT THROUGH FRIDAY MORNING. A LOW
PRESSURE TROUGH ACCOMPANIES THE LOW/S COLD FRONT WHICH SLIDES
THROUGH LATE THIS WEEK. GUIDANCE DIFFERS ON HOW QUICKLY THE FRONT
WILL TRAVEL WITH THE GFS BEING THE QUICKER MODEL.  THE MODELS DO
AGREE THAT THE LOWS WARM FRONT WILL LIFT NORTH OF THE CWA BY FRIDAY
MORNING LEADING TO A WARM AND MUGGY DAY WITH HIGHS IN THE MID 80S.
IF CLOUD COVER REMAINS SCARCE...COULD SEE TEMPS GET INTO THE UPPER
80S. GUSTY WINDS ARE ALSO EXPECTED WITH GUSTS ARND 25 MPH. PRECIP
CHANCES WILL INCREASE THROUGH FRIDAY NIGHT AS THE COLD FRONT MOVES
CLOSER TO THE CWA. THINKING FRIDAY WILL NOT BE A TOTAL WASHOUT...BUT
THERE WILL BE MULTIPLE PERIODS OF STORMS. PWAT VALUES INCREASE
FURTHER TO 1.5 INCHES SO ANY SHOWERS AND STORMS WILL BE CAPABLE OF
HEAVY DOWNPOURS.

SHOWERS AND STORMS ARE ALSO EXPECTED SATURDAY AHEAD OF AND ALONG THE
COLD FRONT. ANOTHER ROUND OF SHOWERS IS POSSIBLE BEHIND THE COLD
FRONT ALONG A VORT STREAMER SATURDAY EVENING AND SUNDAY. THE GFS
KEEPS PRECIP IN THE REGION INTO EARLY NEXT WEEK WHILE THE ECMWF HAS
A RIDGE OVERHEAD.  THEREFORE HAVE LOW CONFIDENCE IN PRECIP CHANCES
NEXT WEEK.  BELOW NORMAL TEMPS MOVE IN LATE THIS WEEK INTO NEXT WEEK
WITH HIGHS POSSIBLY IN THE 60S OVER THE WEEKEND.

JEE

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 22Z...

* GUSTY SOUTHWEST WINDS EASING THIS EVE AND TURNING NEAR DUE
  SOUTH.

* MVFR CEILINGS POSSIBLE EARLY TUESDAY MORNING.

* SHOWERS LIKELY WITH PERIODIC THUNDERSTORMS LATE IN THE FORECAST
  PERIOD.

MTF/RODRIGUEZ

//DISCUSSION...UPDATED 18Z...

MUCH OF THE SHOWERS ARE EXITING THE AREA EARLY THIS AFTERNOON.
HOWEVER...AN ISOLATED LIGHT SHOWER WILL STILL BE POSSIBLE OVER THE
NEXT HOUR BEFORE PREVAILING DRY CONDITIONS ARE EXPECTED THIS
AFTERNOON AND TONIGHT. LINGERING MVFR CEILINGS WILL LIFT TO VFR
THROUGH 20-21Z THIS AFTERNOON WITH SKIES THEN SCATTERING THIS
EVENING...AS THE SOUTHWEST WINDS/GUSTS DIMINISH INTO THE EVENING.
WITH FAIRLY MOIST CONDITIONS REMAINING IN PLACE TONIGHT INTO
TUESDAY...REDEVELOPING LOW CEILINGS DO APPEAR TO BE A POSSIBILITY.
OVERALL CONFIDENCE IS LOWER DURING THIS PERIOD...BUT DID MAKE
MENTION OF AT LEAST MVFR CEILINGS...AND WILL NEED TO MONITOR FOR
POTENTIALLY LOWER CEILINGS. HAVE PUSHED BACK TIMING OF PRECIP LATE
IN THE PERIOD...BUT WITH INSTABILITY AND FORCING
INCREASING...SHOWERS AND THUNDERSTORMS DO APPEAR LIKELY TUESDAY.
STILL SOME UNCERTAINTY WITH EXACT TIMING AND DURATION...AND EVEN
THE POSSIBILITY FOR AN ADDITIONAL PERIOD OF THUNDERSTORMS TUESDAY
AFTERNOON.

RODRIGUEZ


//ORD AND MDW CONFIDENCE...UPDATED 22Z...

* HIGH IN WIND SPEED/DIRECTION.

* MEDIUM-HIGH IN CEILINGS.

* HIGH IN SHOWERS/THUNDERSTORMS...MEDIUM IN TIMING/DURATION.

MTF/RODRIGUEZ


//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/TSRA LATE. SOUTHEAST WINDS.

FRIDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. SOUTHWEST WINDS
BECOMING NORTHEAST OVERNIGHT.

SATURDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. NORTHEAST
WINDS.

SUNDAY...CHANCE TSRA. MVFR POSSIBLE. NORTHEAST WINDS.

KREIN

&&

.MARINE...
334 PM CDT

WIND GUSTS ARE BEGINNING TO COME DOWN AND THE GALE WARNING FOR THE
NEARSHORE ZONES HAS BEEN DROPPED. A SMALL CRAFT ADVISORY WILL GO
THROUGH 9PM CDT THIS EVENING FOR LINGERING STRONG WINDS AND HIGH
WAVES.  LOW PRESSURE CURRENTLY OVER THE UPPER MIDWEST WILL MOVE OVER
QUEBEC TUESDAY MORNING. THE LOWS STATIONARY FRONT REMAINS NORTH OF
THE LAKE BUT STABLE CONDITIONS OVER THE LAKE WILL RESULT IN AREAS OF
FOG THROUGH TUESDAY NIGHT. SOUTH WINDS ARE EXPECTED WITH SPEEDS TO
20 KT. HIGH PRESSURE SPREADS OVER THE LAKE WEDNESDAY NIGHT WITH
WINDS REMAINING LIGHT AND VARYING BTWN WEST AND SOUTHEAST THROUGH
FRIDAY. A COLD FRONT THEN SWEEPS DOWN THE LAKE LATE IN THE WEEK WITH
WINDS BCMG NORTH BEHIND IT.

JEE

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 9 PM MONDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 252146
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
446 PM CDT MON MAY 25 2015

.SHORT TERM...
255 PM CDT

THROUGH TUESDAY...

SHOWERS CONTINUE TO DIMINISH AS WE GET ON THE SUBSIDENT SIDE OF THE
DEPARTING UPPER TROUGH AXIS THAT WILL QUICKLY EXIT TO THE NORTHEAST
TONIGHT. SURFACE LOW PRESSURE IS PUSHING INTO UPPER MICHIGAN WHILE
LEAVING MODEST PRESSURE RISES IN ITS WAKE. WIND GUSTS TO 30 TO
LOCALLY 35 MPH WILL CONTINUE THROUGH THE AFTERNOON. EXPECT TO SEE
A LITTLE MORE BLUE SKY THROUGH THE AFTERNOON/EARLY EVENING WHICH
WILL ALLOW TEMPERATURES TO SLOWLY INCH UPWARD TO THE UPPER 70S TO
LOW 80S...THOUGH WITH MOIST SW FLOW EXPECT THESE LOWER CLOUDS TO
LINGER AROUND A BIT LONGER.

THE ACTIVE PATTERN CONTINUES ACROSS THE AREA FOR THE NEXT 24 HOURS.
SEVERAL UPPER LEVEL LOW PRESSURE SYSTEMS ARE NOTED IN AFTERNOON
WATER VAPOR IMAGERY. THE FIRST IS OVER THE NEBRASKA PANHANDLE...WITH
ASSOCIATED LEADING SHORTWAVE ENERGY TRIGGERING SOME SHOWERS AND T-
STORMS ACROSS IOWA...THEN THE BIGGER SHOWS TO THE SOUTH WITH THE
COMPLEX OF STRONG/SEVERE THUNDERSTORMS ASSOCIATED WITH A NEGATIVELY
TILTED TROUGH IN THE TEXAS. THE NORTHERN SHORTWAVE IS EXPECTED TO
CONTINUE DEVELOPING SHOWERS AND STORMS ACROSS IOWA AND INTO FAR
WESTERN ILLINOIS AND WISCONSIN. SOME OF THIS MAY CLIP OUR FAR
NORTHWESTERN COUNTIES...INCLUDING THE ROCKFORD AREA...BUT FEEL AT
THIS POINT THAT IT SHOULD LARGELY BE OFF FARTHER NW. HAVE HELD OFF
AND KEPT THIS ACTIVITY OUT OF AREA.

THEN TONIGHT THE LOWER LEVEL FRONTAL BOUNDARY ASSOCIATED WITH THE
NORTHERN WAVE WILL SAG SOUTHEAST TOWARD THE AREA LATE TONIGHT. MUCH
OF THE GUIDANCE THEN BRINGS THE SOUTHERN SHORTWAVE TOWARD OUR AREA
LATE TONIGHT AND MORE SO ON TUESDAY ON A DECENT UPPER LEVEL JET. THE
LARGE SUITE OF GUIDANCE KEEPS THESE TWO LOWS SEPARATE...ALLOWING
MUCH OF THE NORTHERN STREAM SHOWERS/STORMS TO LARGELY REMAIN OUT OF
AREA...BUT THEY MAY BEGIN TO AFFECT AREAS WEST OF I-39 IN ILLINOIS
OVERNIGHT.

TUESDAY MORNING IS WHEN BETTER CHANCES OF SHOWERS AND SCATTERED
THUNDERSTORMS WOULD BE. THIS MID MORNING/EARLY AFTERNOON PERIOD
FEATURES MODEST LOW/MID LEVEL ISENTROPIC LIFT/PW VALUES APPROACHING
1.5 INCHES AND THETA-E RIDGE NOSING IN FROM THE SOUTH. WE SHOULD
HAVE SOME SHOWERS AND THUNDERSTORMS MOVING FROM SOUTH TO NORTH
DURING THIS TIME FRAME.  DEPENDING ON THE INTERACTION OF THESE TWO
SYSTEMS AND IF THINGS SLOW DOWN A BIT...BETTER INSTABILITY WILL BE
TAPPED INTO IN THE AFTERNOON. THE NAM WOULD SUGGEST THIS
SOLUTION...WHILE THE GLOBAL GFS/ECMWF SUGGEST THE MID-MORNING TO
EARLY AFTERNOON PERIOD WOULD BE THE MOST LIKELY PERIOD WHERE DEEPER
MOISTURE IS AVAILABLE AND CO-LOCATED WITH THE UPPER FORCING.
CONFIDENCE ON TIMING IS ONLY MEDIUM WHICH REQUIRED CARRYING AN
EXTENDED PERIOD OF LIKELY POPS FOR MUCH OF THE DAY.

KMD

&&

.LONG TERM...
319 PM CDT

WEDNESDAY NIGHT THROUGH MONDAY...

AN UPPER LEVEL SHORTWAVE TROUGH PASSES OVERHEAD TUESDAY NIGHT
THROUGH WEDNESDAY WITH NUMEROUS PERIODS OF SHOWERS AND THUNDERSTORMS
EXPECTED.  THE SFC FCST ALSO FEATURES A BOUNDARY MOVING THROUGH THE
CWA WEDNESDAY WHICH COULD HELP FORCE SHOWERS AND STORMS. HAVE HIGHER
CONFIDENCE IN PRECIP TUESDAY NIGHT THAN WEDNESDAY. CAPE LOOKS
MARGINAL OUTSIDE OF THE TYPICALLY TOO ROBUST NAM SOUNDINGS. FCST
SOUNDINGS LACK SHEAR...BUT THEY DO FEATURE INVERTED V/S AT THE SFC
AND SOME DRY AIR ALOFT. THIS SUGGESTS GUSTY WINDS ARE PSBL BUT FLOW
IS LESS THAN 40 KT ALOFT SO DAMAGING WINDS ARE NOT EXPECTED. PWAT
VALUES ARE FORECASTED TO BE ARND 1.3 INCHES WHICH IS ABOVE NORMAL
FOR THIS TIME OF YEAR...THEREFORE HEAVY DOWNPOURS ARE POSSIBLE.

WITH 925MB TEMPS BTWN +18 TO +20C...WARMED TEMPS SLIGHTLY FOR
WEDNESDAY INTO THE UPPER 70S TO AROUND 80.

HIGH PRESSURE THEN SPREADS ACROSS THE REGION WEDNESDAY NIGHT AND
HANGS AROUND THROUGH THURSDAY. THIS SHOULD RESULT IN DRY CONDITIONS
OUTSIDE OF POSSIBLE ISOLATED SHOWERS OVER LAKE MI. WINDS TURN OFF OF
THE LAKE THURSDAY SO AREAS ALONG THE LAKE WILL BE IN THE LOW
70S...WHILE AREAS AWAY FROM THE LAKE WILL GET INTO THE LOW TO MID
80S.

THE NEXT SFC LOW FORMS OVER THE PLAINS THURSDAY EVENING AND PASSES
OVER ONTARIO LATE THURSDAY NIGHT THROUGH FRIDAY MORNING. A LOW
PRESSURE TROUGH ACCOMPANIES THE LOW/S COLD FRONT WHICH SLIDES
THROUGH LATE THIS WEEK. GUIDANCE DIFFERS ON HOW QUICKLY THE FRONT
WILL TRAVEL WITH THE GFS BEING THE QUICKER MODEL.  THE MODELS DO
AGREE THAT THE LOWS WARM FRONT WILL LIFT NORTH OF THE CWA BY FRIDAY
MORNING LEADING TO A WARM AND MUGGY DAY WITH HIGHS IN THE MID 80S.
IF CLOUD COVER REMAINS SCARCE...COULD SEE TEMPS GET INTO THE UPPER
80S. GUSTY WINDS ARE ALSO EXPECTED WITH GUSTS ARND 25 MPH. PRECIP
CHANCES WILL INCREASE THROUGH FRIDAY NIGHT AS THE COLD FRONT MOVES
CLOSER TO THE CWA. THINKING FRIDAY WILL NOT BE A TOTAL WASHOUT...BUT
THERE WILL BE MULTIPLE PERIODS OF STORMS. PWAT VALUES INCREASE
FURTHER TO 1.5 INCHES SO ANY SHOWERS AND STORMS WILL BE CAPABLE OF
HEAVY DOWNPOURS.

SHOWERS AND STORMS ARE ALSO EXPECTED SATURDAY AHEAD OF AND ALONG THE
COLD FRONT. ANOTHER ROUND OF SHOWERS IS POSSIBLE BEHIND THE COLD
FRONT ALONG A VORT STREAMER SATURDAY EVENING AND SUNDAY. THE GFS
KEEPS PRECIP IN THE REGION INTO EARLY NEXT WEEK WHILE THE ECMWF HAS
A RIDGE OVERHEAD.  THEREFORE HAVE LOW CONFIDENCE IN PRECIP CHANCES
NEXT WEEK.  BELOW NORMAL TEMPS MOVE IN LATE THIS WEEK INTO NEXT WEEK
WITH HIGHS POSSIBLY IN THE 60S OVER THE WEEKEND.

JEE

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 22Z...

* GUSTY SOUTHWEST WINDS EASING THIS EVE AND TURNING NEAR DUE
  SOUTH.

* MVFR CEILINGS POSSIBLE EARLY TUESDAY MORNING.

* SHOWERS LIKELY WITH PERIODIC THUNDERSTORMS LATE IN THE FORECAST
  PERIOD.

MTF/RODRIGUEZ

//DISCUSSION...UPDATED 18Z...

MUCH OF THE SHOWERS ARE EXITING THE AREA EARLY THIS AFTERNOON.
HOWEVER...AN ISOLATED LIGHT SHOWER WILL STILL BE POSSIBLE OVER THE
NEXT HOUR BEFORE PREVAILING DRY CONDITIONS ARE EXPECTED THIS
AFTERNOON AND TONIGHT. LINGERING MVFR CEILINGS WILL LIFT TO VFR
THROUGH 20-21Z THIS AFTERNOON WITH SKIES THEN SCATTERING THIS
EVENING...AS THE SOUTHWEST WINDS/GUSTS DIMINISH INTO THE EVENING.
WITH FAIRLY MOIST CONDITIONS REMAINING IN PLACE TONIGHT INTO
TUESDAY...REDEVELOPING LOW CEILINGS DO APPEAR TO BE A POSSIBILITY.
OVERALL CONFIDENCE IS LOWER DURING THIS PERIOD...BUT DID MAKE
MENTION OF AT LEAST MVFR CEILINGS...AND WILL NEED TO MONITOR FOR
POTENTIALLY LOWER CEILINGS. HAVE PUSHED BACK TIMING OF PRECIP LATE
IN THE PERIOD...BUT WITH INSTABILITY AND FORCING
INCREASING...SHOWERS AND THUNDERSTORMS DO APPEAR LIKELY TUESDAY.
STILL SOME UNCERTAINTY WITH EXACT TIMING AND DURATION...AND EVEN
THE POSSIBILITY FOR AN ADDITIONAL PERIOD OF THUNDERSTORMS TUESDAY
AFTERNOON.

RODRIGUEZ


//ORD AND MDW CONFIDENCE...UPDATED 22Z...

* HIGH IN WIND SPEED/DIRECTION.

* MEDIUM-HIGH IN CEILINGS.

* HIGH IN SHOWERS/THUNDERSTORMS...MEDIUM IN TIMING/DURATION.

MTF/RODRIGUEZ


//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/TSRA LATE. SOUTHEAST WINDS.

FRIDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. SOUTHWEST WINDS
BECOMING NORTHEAST OVERNIGHT.

SATURDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. NORTHEAST
WINDS.

SUNDAY...CHANCE TSRA. MVFR POSSIBLE. NORTHEAST WINDS.

KREIN

&&

.MARINE...
334 PM CDT

WIND GUSTS ARE BEGINNING TO COME DOWN AND THE GALE WARNING FOR THE
NEARSHORE ZONES HAS BEEN DROPPED. A SMALL CRAFT ADVISORY WILL GO
THROUGH 9PM CDT THIS EVENING FOR LINGERING STRONG WINDS AND HIGH
WAVES.  LOW PRESSURE CURRENTLY OVER THE UPPER MIDWEST WILL MOVE OVER
QUEBEC TUESDAY MORNING. THE LOWS STATIONARY FRONT REMAINS NORTH OF
THE LAKE BUT STABLE CONDITIONS OVER THE LAKE WILL RESULT IN AREAS OF
FOG THROUGH TUESDAY NIGHT. SOUTH WINDS ARE EXPECTED WITH SPEEDS TO
20 KT. HIGH PRESSURE SPREADS OVER THE LAKE WEDNESDAY NIGHT WITH
WINDS REMAINING LIGHT AND VARYING BTWN WEST AND SOUTHEAST THROUGH
FRIDAY. A COLD FRONT THEN SWEEPS DOWN THE LAKE LATE IN THE WEEK WITH
WINDS BCMG NORTH BEHIND IT.

JEE

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 9 PM MONDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 252034
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
334 PM CDT MON MAY 25 2015

.SHORT TERM...
255 PM CDT

THROUGH TUESDAY...

SHOWERS CONTINUE TO DIMINISH AS WE GET ON THE SUBSIDENT SIDE OF THE
DEPARTING UPPER TROUGH AXIS THAT WILL QUICKLY EXIT TO THE NORTHEAST
TONIGHT. SURFACE LOW PRESSURE IS PUSHING INTO UPPER MICHIGAN WHILE
LEAVING MODEST PRESSURE RISES IN ITS WAKE. WIND GUSTS TO 30 TO
LOCALLY 35 MPH WILL CONTINUE THROUGH THE AFTERNOON. EXPECT TO SEE
ALITTLE MORE BLUE SKY THROUGH THE AFTERNOON/EARLY EVENING WHICH
WILL ALLOW TEMPERATURES TO SLOWLY INCH UPWARD TO THE UPPER 70S TO
LOW 80S...THOUGH WITH MOIST SW FLOW EXPECT THESE LOWER CLOUDS TO
LINGER AROUND A BIT LONGER.

THE ACTIVE PATTERN CONTINUES ACROSS THE AREA FOR THE NEXT 24 HOURS.
SEVERAL UPPER LEVEL LOW PRESSURE SYSTEMS ARE NOTED IN AFTERNOON
WATER VAPOR IMAGERY. THE FIRST IS OVER THE NEBRASKA PANHANDLE...WITH
ASSOCIATED LEADING SHORTWAVE ENERGY TRIGGERING SOME SHOWERS AND T-
STORMS ACROSS IOWA...THEN THE BIGGER SHOWS TO THE SOUTH WITH THE
COMPLEX OF STRONG/SEVERE THUNDERSTORMS ASSOCIATED WITH A NEGATIVELY
TILTED TROUGH IN THE TEXAS. THE NORTHERN SHORTWAVE IS EXPECTED TO
CONTINUE DEVELOPING SHOWERS AND STORMS ACROSS IOWA AND INTO FAR
WESTERN ILLINOIS AND WISCONSIN. SOME OF THIS MAY CLIP OUR FAR
NORTHWESTERN COUNTIES...INCLUDING THE ROCKFORD AREA...BUT FEEL AT
THIS POINT THAT IT SHOULD LARGELY BE OFF FARTHER NW. HAVE HELD OFF
AND KEPT THIS ACTIVITY OUT OF AREA.

THEN TONIGHT THE LOWER LEVEL FRONTAL BOUNDARY ASSOCIATED WITH THE
NORTHERN WAVE WILL SAG SOUTHEAST TOWARD THE AREA LATE TONIGHT. MUCH
OF THE GUIDANCE THEN BRINGS THE SOUTHERN SHORTWAVE TOWARD OUR AREA
LATE TONIGHT AND MORE SO ON TUESDAY ON A DECENT UPPER LEVEL JET. THE
LARGE SUITE OF GUIDANCE KEEPS THESE TWO LOWS SEPARATE...ALLOWING
MUCH OF THE NORTHERN STREAM SHOWERS/STORMS TO LARGELY REMAIN OUT OF
AREA...BUT THEY MAY BEGIN TO AFFECT AREAS WEST OF I-39 IN ILLINOIS
OVERNIGHT.

TUESDAY MORNING IS WHEN BETTER CHANCES OF SHOWERS AND SCATTERED
THUNDERSTORMS WOULD BE. THIS MID MORNING/EARLY AFTERNOON PERIOD
FEATURES MODEST LOW/MID LEVEL ISENTROPIC LIFT/PW VALUES APPROACHING
1.5 INCHES AND THETA-E RIDGE NOSING IN FROM THE SOUTH. WE SHOULD
HAVE SOME SHOWERS AND THUNDERSTORMS MOVING FROM SOUTH TO NORTH
DURING THIS TIME FRAME.  DEPENDING ON THE INTERACTION OF THESE TWO
SYSTEMS AND IF THINGS SLOW DOWN A BIT...BETTER INSTABILITY WILL BE
TAPPED INTO IN THE AFTERNOON. THE NAM WOULD SUGGEST THIS
SOLUTION...WHILE THE GLOBAL GFS/ECMWF SUGGEST THE MID-MORNING TO
EARLY AFTERNOON PERIOD WOULD BE THE MOST LIKELY PERIOD WHERE DEEPER
MOISTURE IS AVAILABLE AND CO-LOCATED WITH THE UPPER FORCING.
CONFIDENCE ON TIMING IS ONLY MEDIUM WHICH REQUIRED CARRYING AN
EXTENDED PERIOD OF LIKELY POPS FOR MUCH OF THE DAY.

KMD

&&

.LONG TERM...
319 PM CDT

WEDNESDAY NIGHT THROUGH MONDAY...

AN UPPER LEVEL SHORTWAVE TROUGH PASSES OVERHEAD TUESDAY NIGHT
THROUGH WEDNESDAY WITH NUMEROUS PERIODS OF SHOWERS AND THUNDERSTORMS
EXPECTED.  THE SFC FCST ALSO FEATURES A BOUNDARY MOVING THROUGH THE
CWA WEDNESDAY WHICH COULD HELP FORCE SHOWERS AND STORMS. HAVE HIGHER
CONFIDENCE IN PRECIP TUESDAY NIGHT THAN WEDNESDAY. CAPE LOOKS
MARGINAL OUTSIDE OF THE TYPICALLY TOO ROBUST NAM SOUNDINGS. FCST
SOUNDINGS LACK SHEAR...BUT THEY DO FEATURE INVERTED V/S AT THE SFC
AND SOME DRY AIR ALOFT. THIS SUGGESTS GUSTY WINDS ARE PSBL BUT FLOW
IS LESS THAN 40 KT ALOFT SO DAMAGING WINDS ARE NOT EXPECTED. PWAT
VALUES ARE FORECASTED TO BE ARND 1.3 INCHES WHICH IS ABOVE NORMAL
FOR THIS TIME OF YEAR...THEREFORE HEAVY DOWNPOURS ARE POSSIBLE.

WITH 925MB TEMPS BTWN +18 TO +20C...WARMED TEMPS SLIGHTLY FOR
WEDNESDAY INTO THE UPPER 70S TO AROUND 80.

HIGH PRESSURE THEN SPREADS ACROSS THE REGION WEDNESDAY NIGHT AND
HANGS AROUND THROUGH THURSDAY. THIS SHOULD RESULT IN DRY CONDITIONS
OUTSIDE OF POSSIBLE ISOLATED SHOWERS OVER LAKE MI. WINDS TURN OFF OF
THE LAKE THURSDAY SO AREAS ALONG THE LAKE WILL BE IN THE LOW
70S...WHILE AREAS AWAY FROM THE LAKE WILL GET INTO THE LOW TO MID
80S.

THE NEXT SFC LOW FORMS OVER THE PLAINS THURSDAY EVENING AND PASSES
OVER ONTARIO LATE THURSDAY NIGHT THROUGH FRIDAY MORNING. A LOW
PRESSURE TROUGH ACCOMPANIES THE LOW/S COLD FRONT WHICH SLIDES
THROUGH LATE THIS WEEK. GUIDANCE DIFFERS ON HOW QUICKLY THE FRONT
WILL TRAVEL WITH THE GFS BEING THE QUICKER MODEL.  THE MODELS DO
AGREE THAT THE LOWS WARM FRONT WILL LIFT NORTH OF THE CWA BY FRIDAY
MORNING LEADING TO A WARM AND MUGGY DAY WITH HIGHS IN THE MID 80S.
IF CLOUD COVER REMAINS SCARCE...COULD SEE TEMPS GET INTO THE UPPER
80S. GUSTY WINDS ARE ALSO EXPECTED WITH GUSTS ARND 25 MPH. PRECIP
CHANCES WILL INCREASE THROUGH FRIDAY NIGHT AS THE COLD FRONT MOVES
CLOSER TO THE CWA. THINKING FRIDAY WILL NOT BE A TOTAL WASHOUT...BUT
THERE WILL BE MULTIPLE PERIODS OF STORMS. PWAT VALUES INCREASE
FURTHER TO 1.5 INCHES SO ANY SHOWERS AND STORMS WILL BE CAPABLE OF
HEAVY DOWNPOURS.

SHOWERS AND STORMS ARE ALSO EXPECTED SATURDAY AHEAD OF AND ALONG THE
COLD FRONT. ANOTHER ROUND OF SHOWERS IS POSSIBLE BEHIND THE COLD
FRONT ALONG A VORT STREAMER SATURDAY EVENING AND SUNDAY. THE GFS
KEEPS PRECIP IN THE REGION INTO EARLY NEXT WEEK WHILE THE ECMWF HAS
A RIDGE OVERHEAD.  THEREFORE HAVE LOW CONFIDENCE IN PRECIP CHANCES
NEXT WEEK.  BELOW NORMAL TEMPS MOVE IN LATE THIS WEEK INTO NEXT WEEK
WITH HIGHS POSSIBLY IN THE 60S OVER THE WEEKEND.

JEE

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 20Z...

* GUSTY SOUTHWEST WINDS.

* MVFR CEILINGS POSSIBLE EARLY TUESDAY MORNING.

* SHOWERS LIKELY WITH PERIODIC THUNDERSTORMS LATE IN THE FORECAST
  PERIOD.

RODRIGUEZ

//DISCUSSION...UPDATED 18Z...

MUCH OF THE SHOWERS ARE EXITING THE AREA EARLY THIS AFTERNOON.
HOWEVER...AN ISOLATED LIGHT SHOWER WILL STILL BE POSSIBLE OVER THE
NEXT HOUR BEFORE PREVAILING DRY CONDITIONS ARE EXPECTED THIS
AFTERNOON AND TONIGHT. LINGERING MVFR CEILINGS WILL LIFT TO VFR
THROUGH 20-21Z THIS AFTERNOON WITH SKIES THEN SCATTERING THIS
EVENING...AS THE SOUTHWEST WINDS/GUSTS DIMINISH INTO THE EVENING.
WITH FAIRLY MOIST CONDITIONS REMAINING IN PLACE TONIGHT INTO
TUESDAY...REDEVELOPING LOW CEILINGS DO APPEAR TO BE A POSSIBILITY.
OVERALL CONFIDENCE IS LOWER DURING THIS PERIOD...BUT DID MAKE
MENTION OF AT LEAST MVFR CEILINGS...AND WILL NEED TO MONITOR FOR
POTENTIALLY LOWER CEILINGS. HAVE PUSHED BACK TIMING OF PRECIP LATE
IN THE PERIOD...BUT WITH INSTABILITY AND FORCING
INCREASING...SHOWERS AND THUNDERSTORMS DO APPEAR LIKELY TUESDAY.
STILL SOME UNCERTAINTY WITH EXACT TIMING AND DURATION...AND EVEN
THE POSSIBILITY FOR AN ADDITIONAL PERIOD OF THUNDERSTORMS TUESDAY
AFTERNOON.

RODRIGUEZ

//ORD AND MDW CONFIDENCE...UPDATED 20Z...

* HIGH CONFIDENCE WITH WIND SPEED/DIRECTION.

* MEDIUM HIGH CONFIDENCE WITH CEILINGS.

* HIGH CONFIDENCE OF SHOWERS/THUNDERSTORMS...MEDIUM CONFIDENCE
  WITH TIMING/DURATION.

RODRIGUEZ

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/TSRA LATE. SOUTHEAST WINDS.

FRIDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. SOUTHWEST WINDS
BECOMING NORTHEAST OVERNIGHT.

SATURDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. NORTHEAST
WINDS.

SUNDAY...CHANCE TSRA. MVFR POSSIBLE. NORTHEAST WINDS.

KREIN

&&

.MARINE...
334 PM CDT

WIND GUSTS ARE BEGINNING TO COME DOWN AND THE GALE WARNING FOR THE
NEARSHORE ZONES HAS BEEN DROPPED. A SMALL CRAFT ADVISORY WILL GO
THROUGH 9PM CDT THIS EVENING FOR LINGERING STRONG WINDS AND HIGH
WAVES.  LOW PRESSURE CURRENTLY OVER THE UPPER MIDWEST WILL MOVE OVER
QUEBEC TUESDAY MORNING. THE LOWS STATIONARY FRONT REMAINS NORTH OF
THE LAKE BUT STABLE CONDITIONS OVER THE LAKE WILL RESULT IN AREAS OF
FOG THROUGH TUESDAY NIGHT. SOUTH WINDS ARE EXPECTED WITH SPEEDS TO
20 KT. HIGH PRESSURE SPREADS OVER THE LAKE WEDNESDAY NIGHT WITH
WINDS REMAINING LIGHT AND VARYING BTWN WEST AND SOUTHEAST THROUGH
FRIDAY. A COLD FRONT THEN SWEEPS DOWN THE LAKE LATE IN THE WEEK WITH
WINDS BCMG NORTH BEHIND IT.

JEE

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 9 PM MONDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 252034
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
334 PM CDT MON MAY 25 2015

.SHORT TERM...
255 PM CDT

THROUGH TUESDAY...

SHOWERS CONTINUE TO DIMINISH AS WE GET ON THE SUBSIDENT SIDE OF THE
DEPARTING UPPER TROUGH AXIS THAT WILL QUICKLY EXIT TO THE NORTHEAST
TONIGHT. SURFACE LOW PRESSURE IS PUSHING INTO UPPER MICHIGAN WHILE
LEAVING MODEST PRESSURE RISES IN ITS WAKE. WIND GUSTS TO 30 TO
LOCALLY 35 MPH WILL CONTINUE THROUGH THE AFTERNOON. EXPECT TO SEE
ALITTLE MORE BLUE SKY THROUGH THE AFTERNOON/EARLY EVENING WHICH
WILL ALLOW TEMPERATURES TO SLOWLY INCH UPWARD TO THE UPPER 70S TO
LOW 80S...THOUGH WITH MOIST SW FLOW EXPECT THESE LOWER CLOUDS TO
LINGER AROUND A BIT LONGER.

THE ACTIVE PATTERN CONTINUES ACROSS THE AREA FOR THE NEXT 24 HOURS.
SEVERAL UPPER LEVEL LOW PRESSURE SYSTEMS ARE NOTED IN AFTERNOON
WATER VAPOR IMAGERY. THE FIRST IS OVER THE NEBRASKA PANHANDLE...WITH
ASSOCIATED LEADING SHORTWAVE ENERGY TRIGGERING SOME SHOWERS AND T-
STORMS ACROSS IOWA...THEN THE BIGGER SHOWS TO THE SOUTH WITH THE
COMPLEX OF STRONG/SEVERE THUNDERSTORMS ASSOCIATED WITH A NEGATIVELY
TILTED TROUGH IN THE TEXAS. THE NORTHERN SHORTWAVE IS EXPECTED TO
CONTINUE DEVELOPING SHOWERS AND STORMS ACROSS IOWA AND INTO FAR
WESTERN ILLINOIS AND WISCONSIN. SOME OF THIS MAY CLIP OUR FAR
NORTHWESTERN COUNTIES...INCLUDING THE ROCKFORD AREA...BUT FEEL AT
THIS POINT THAT IT SHOULD LARGELY BE OFF FARTHER NW. HAVE HELD OFF
AND KEPT THIS ACTIVITY OUT OF AREA.

THEN TONIGHT THE LOWER LEVEL FRONTAL BOUNDARY ASSOCIATED WITH THE
NORTHERN WAVE WILL SAG SOUTHEAST TOWARD THE AREA LATE TONIGHT. MUCH
OF THE GUIDANCE THEN BRINGS THE SOUTHERN SHORTWAVE TOWARD OUR AREA
LATE TONIGHT AND MORE SO ON TUESDAY ON A DECENT UPPER LEVEL JET. THE
LARGE SUITE OF GUIDANCE KEEPS THESE TWO LOWS SEPARATE...ALLOWING
MUCH OF THE NORTHERN STREAM SHOWERS/STORMS TO LARGELY REMAIN OUT OF
AREA...BUT THEY MAY BEGIN TO AFFECT AREAS WEST OF I-39 IN ILLINOIS
OVERNIGHT.

TUESDAY MORNING IS WHEN BETTER CHANCES OF SHOWERS AND SCATTERED
THUNDERSTORMS WOULD BE. THIS MID MORNING/EARLY AFTERNOON PERIOD
FEATURES MODEST LOW/MID LEVEL ISENTROPIC LIFT/PW VALUES APPROACHING
1.5 INCHES AND THETA-E RIDGE NOSING IN FROM THE SOUTH. WE SHOULD
HAVE SOME SHOWERS AND THUNDERSTORMS MOVING FROM SOUTH TO NORTH
DURING THIS TIME FRAME.  DEPENDING ON THE INTERACTION OF THESE TWO
SYSTEMS AND IF THINGS SLOW DOWN A BIT...BETTER INSTABILITY WILL BE
TAPPED INTO IN THE AFTERNOON. THE NAM WOULD SUGGEST THIS
SOLUTION...WHILE THE GLOBAL GFS/ECMWF SUGGEST THE MID-MORNING TO
EARLY AFTERNOON PERIOD WOULD BE THE MOST LIKELY PERIOD WHERE DEEPER
MOISTURE IS AVAILABLE AND CO-LOCATED WITH THE UPPER FORCING.
CONFIDENCE ON TIMING IS ONLY MEDIUM WHICH REQUIRED CARRYING AN
EXTENDED PERIOD OF LIKELY POPS FOR MUCH OF THE DAY.

KMD

&&

.LONG TERM...
319 PM CDT

WEDNESDAY NIGHT THROUGH MONDAY...

AN UPPER LEVEL SHORTWAVE TROUGH PASSES OVERHEAD TUESDAY NIGHT
THROUGH WEDNESDAY WITH NUMEROUS PERIODS OF SHOWERS AND THUNDERSTORMS
EXPECTED.  THE SFC FCST ALSO FEATURES A BOUNDARY MOVING THROUGH THE
CWA WEDNESDAY WHICH COULD HELP FORCE SHOWERS AND STORMS. HAVE HIGHER
CONFIDENCE IN PRECIP TUESDAY NIGHT THAN WEDNESDAY. CAPE LOOKS
MARGINAL OUTSIDE OF THE TYPICALLY TOO ROBUST NAM SOUNDINGS. FCST
SOUNDINGS LACK SHEAR...BUT THEY DO FEATURE INVERTED V/S AT THE SFC
AND SOME DRY AIR ALOFT. THIS SUGGESTS GUSTY WINDS ARE PSBL BUT FLOW
IS LESS THAN 40 KT ALOFT SO DAMAGING WINDS ARE NOT EXPECTED. PWAT
VALUES ARE FORECASTED TO BE ARND 1.3 INCHES WHICH IS ABOVE NORMAL
FOR THIS TIME OF YEAR...THEREFORE HEAVY DOWNPOURS ARE POSSIBLE.

WITH 925MB TEMPS BTWN +18 TO +20C...WARMED TEMPS SLIGHTLY FOR
WEDNESDAY INTO THE UPPER 70S TO AROUND 80.

HIGH PRESSURE THEN SPREADS ACROSS THE REGION WEDNESDAY NIGHT AND
HANGS AROUND THROUGH THURSDAY. THIS SHOULD RESULT IN DRY CONDITIONS
OUTSIDE OF POSSIBLE ISOLATED SHOWERS OVER LAKE MI. WINDS TURN OFF OF
THE LAKE THURSDAY SO AREAS ALONG THE LAKE WILL BE IN THE LOW
70S...WHILE AREAS AWAY FROM THE LAKE WILL GET INTO THE LOW TO MID
80S.

THE NEXT SFC LOW FORMS OVER THE PLAINS THURSDAY EVENING AND PASSES
OVER ONTARIO LATE THURSDAY NIGHT THROUGH FRIDAY MORNING. A LOW
PRESSURE TROUGH ACCOMPANIES THE LOW/S COLD FRONT WHICH SLIDES
THROUGH LATE THIS WEEK. GUIDANCE DIFFERS ON HOW QUICKLY THE FRONT
WILL TRAVEL WITH THE GFS BEING THE QUICKER MODEL.  THE MODELS DO
AGREE THAT THE LOWS WARM FRONT WILL LIFT NORTH OF THE CWA BY FRIDAY
MORNING LEADING TO A WARM AND MUGGY DAY WITH HIGHS IN THE MID 80S.
IF CLOUD COVER REMAINS SCARCE...COULD SEE TEMPS GET INTO THE UPPER
80S. GUSTY WINDS ARE ALSO EXPECTED WITH GUSTS ARND 25 MPH. PRECIP
CHANCES WILL INCREASE THROUGH FRIDAY NIGHT AS THE COLD FRONT MOVES
CLOSER TO THE CWA. THINKING FRIDAY WILL NOT BE A TOTAL WASHOUT...BUT
THERE WILL BE MULTIPLE PERIODS OF STORMS. PWAT VALUES INCREASE
FURTHER TO 1.5 INCHES SO ANY SHOWERS AND STORMS WILL BE CAPABLE OF
HEAVY DOWNPOURS.

SHOWERS AND STORMS ARE ALSO EXPECTED SATURDAY AHEAD OF AND ALONG THE
COLD FRONT. ANOTHER ROUND OF SHOWERS IS POSSIBLE BEHIND THE COLD
FRONT ALONG A VORT STREAMER SATURDAY EVENING AND SUNDAY. THE GFS
KEEPS PRECIP IN THE REGION INTO EARLY NEXT WEEK WHILE THE ECMWF HAS
A RIDGE OVERHEAD.  THEREFORE HAVE LOW CONFIDENCE IN PRECIP CHANCES
NEXT WEEK.  BELOW NORMAL TEMPS MOVE IN LATE THIS WEEK INTO NEXT WEEK
WITH HIGHS POSSIBLY IN THE 60S OVER THE WEEKEND.

JEE

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 20Z...

* GUSTY SOUTHWEST WINDS.

* MVFR CEILINGS POSSIBLE EARLY TUESDAY MORNING.

* SHOWERS LIKELY WITH PERIODIC THUNDERSTORMS LATE IN THE FORECAST
  PERIOD.

RODRIGUEZ

//DISCUSSION...UPDATED 18Z...

MUCH OF THE SHOWERS ARE EXITING THE AREA EARLY THIS AFTERNOON.
HOWEVER...AN ISOLATED LIGHT SHOWER WILL STILL BE POSSIBLE OVER THE
NEXT HOUR BEFORE PREVAILING DRY CONDITIONS ARE EXPECTED THIS
AFTERNOON AND TONIGHT. LINGERING MVFR CEILINGS WILL LIFT TO VFR
THROUGH 20-21Z THIS AFTERNOON WITH SKIES THEN SCATTERING THIS
EVENING...AS THE SOUTHWEST WINDS/GUSTS DIMINISH INTO THE EVENING.
WITH FAIRLY MOIST CONDITIONS REMAINING IN PLACE TONIGHT INTO
TUESDAY...REDEVELOPING LOW CEILINGS DO APPEAR TO BE A POSSIBILITY.
OVERALL CONFIDENCE IS LOWER DURING THIS PERIOD...BUT DID MAKE
MENTION OF AT LEAST MVFR CEILINGS...AND WILL NEED TO MONITOR FOR
POTENTIALLY LOWER CEILINGS. HAVE PUSHED BACK TIMING OF PRECIP LATE
IN THE PERIOD...BUT WITH INSTABILITY AND FORCING
INCREASING...SHOWERS AND THUNDERSTORMS DO APPEAR LIKELY TUESDAY.
STILL SOME UNCERTAINTY WITH EXACT TIMING AND DURATION...AND EVEN
THE POSSIBILITY FOR AN ADDITIONAL PERIOD OF THUNDERSTORMS TUESDAY
AFTERNOON.

RODRIGUEZ

//ORD AND MDW CONFIDENCE...UPDATED 20Z...

* HIGH CONFIDENCE WITH WIND SPEED/DIRECTION.

* MEDIUM HIGH CONFIDENCE WITH CEILINGS.

* HIGH CONFIDENCE OF SHOWERS/THUNDERSTORMS...MEDIUM CONFIDENCE
  WITH TIMING/DURATION.

RODRIGUEZ

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/TSRA LATE. SOUTHEAST WINDS.

FRIDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. SOUTHWEST WINDS
BECOMING NORTHEAST OVERNIGHT.

SATURDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. NORTHEAST
WINDS.

SUNDAY...CHANCE TSRA. MVFR POSSIBLE. NORTHEAST WINDS.

KREIN

&&

.MARINE...
334 PM CDT

WIND GUSTS ARE BEGINNING TO COME DOWN AND THE GALE WARNING FOR THE
NEARSHORE ZONES HAS BEEN DROPPED. A SMALL CRAFT ADVISORY WILL GO
THROUGH 9PM CDT THIS EVENING FOR LINGERING STRONG WINDS AND HIGH
WAVES.  LOW PRESSURE CURRENTLY OVER THE UPPER MIDWEST WILL MOVE OVER
QUEBEC TUESDAY MORNING. THE LOWS STATIONARY FRONT REMAINS NORTH OF
THE LAKE BUT STABLE CONDITIONS OVER THE LAKE WILL RESULT IN AREAS OF
FOG THROUGH TUESDAY NIGHT. SOUTH WINDS ARE EXPECTED WITH SPEEDS TO
20 KT. HIGH PRESSURE SPREADS OVER THE LAKE WEDNESDAY NIGHT WITH
WINDS REMAINING LIGHT AND VARYING BTWN WEST AND SOUTHEAST THROUGH
FRIDAY. A COLD FRONT THEN SWEEPS DOWN THE LAKE LATE IN THE WEEK WITH
WINDS BCMG NORTH BEHIND IT.

JEE

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 9 PM MONDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 252034
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
334 PM CDT MON MAY 25 2015

.SHORT TERM...
255 PM CDT

THROUGH TUESDAY...

SHOWERS CONTINUE TO DIMINISH AS WE GET ON THE SUBSIDENT SIDE OF THE
DEPARTING UPPER TROUGH AXIS THAT WILL QUICKLY EXIT TO THE NORTHEAST
TONIGHT. SURFACE LOW PRESSURE IS PUSHING INTO UPPER MICHIGAN WHILE
LEAVING MODEST PRESSURE RISES IN ITS WAKE. WIND GUSTS TO 30 TO
LOCALLY 35 MPH WILL CONTINUE THROUGH THE AFTERNOON. EXPECT TO SEE
ALITTLE MORE BLUE SKY THROUGH THE AFTERNOON/EARLY EVENING WHICH
WILL ALLOW TEMPERATURES TO SLOWLY INCH UPWARD TO THE UPPER 70S TO
LOW 80S...THOUGH WITH MOIST SW FLOW EXPECT THESE LOWER CLOUDS TO
LINGER AROUND A BIT LONGER.

THE ACTIVE PATTERN CONTINUES ACROSS THE AREA FOR THE NEXT 24 HOURS.
SEVERAL UPPER LEVEL LOW PRESSURE SYSTEMS ARE NOTED IN AFTERNOON
WATER VAPOR IMAGERY. THE FIRST IS OVER THE NEBRASKA PANHANDLE...WITH
ASSOCIATED LEADING SHORTWAVE ENERGY TRIGGERING SOME SHOWERS AND T-
STORMS ACROSS IOWA...THEN THE BIGGER SHOWS TO THE SOUTH WITH THE
COMPLEX OF STRONG/SEVERE THUNDERSTORMS ASSOCIATED WITH A NEGATIVELY
TILTED TROUGH IN THE TEXAS. THE NORTHERN SHORTWAVE IS EXPECTED TO
CONTINUE DEVELOPING SHOWERS AND STORMS ACROSS IOWA AND INTO FAR
WESTERN ILLINOIS AND WISCONSIN. SOME OF THIS MAY CLIP OUR FAR
NORTHWESTERN COUNTIES...INCLUDING THE ROCKFORD AREA...BUT FEEL AT
THIS POINT THAT IT SHOULD LARGELY BE OFF FARTHER NW. HAVE HELD OFF
AND KEPT THIS ACTIVITY OUT OF AREA.

THEN TONIGHT THE LOWER LEVEL FRONTAL BOUNDARY ASSOCIATED WITH THE
NORTHERN WAVE WILL SAG SOUTHEAST TOWARD THE AREA LATE TONIGHT. MUCH
OF THE GUIDANCE THEN BRINGS THE SOUTHERN SHORTWAVE TOWARD OUR AREA
LATE TONIGHT AND MORE SO ON TUESDAY ON A DECENT UPPER LEVEL JET. THE
LARGE SUITE OF GUIDANCE KEEPS THESE TWO LOWS SEPARATE...ALLOWING
MUCH OF THE NORTHERN STREAM SHOWERS/STORMS TO LARGELY REMAIN OUT OF
AREA...BUT THEY MAY BEGIN TO AFFECT AREAS WEST OF I-39 IN ILLINOIS
OVERNIGHT.

TUESDAY MORNING IS WHEN BETTER CHANCES OF SHOWERS AND SCATTERED
THUNDERSTORMS WOULD BE. THIS MID MORNING/EARLY AFTERNOON PERIOD
FEATURES MODEST LOW/MID LEVEL ISENTROPIC LIFT/PW VALUES APPROACHING
1.5 INCHES AND THETA-E RIDGE NOSING IN FROM THE SOUTH. WE SHOULD
HAVE SOME SHOWERS AND THUNDERSTORMS MOVING FROM SOUTH TO NORTH
DURING THIS TIME FRAME.  DEPENDING ON THE INTERACTION OF THESE TWO
SYSTEMS AND IF THINGS SLOW DOWN A BIT...BETTER INSTABILITY WILL BE
TAPPED INTO IN THE AFTERNOON. THE NAM WOULD SUGGEST THIS
SOLUTION...WHILE THE GLOBAL GFS/ECMWF SUGGEST THE MID-MORNING TO
EARLY AFTERNOON PERIOD WOULD BE THE MOST LIKELY PERIOD WHERE DEEPER
MOISTURE IS AVAILABLE AND CO-LOCATED WITH THE UPPER FORCING.
CONFIDENCE ON TIMING IS ONLY MEDIUM WHICH REQUIRED CARRYING AN
EXTENDED PERIOD OF LIKELY POPS FOR MUCH OF THE DAY.

KMD

&&

.LONG TERM...
319 PM CDT

WEDNESDAY NIGHT THROUGH MONDAY...

AN UPPER LEVEL SHORTWAVE TROUGH PASSES OVERHEAD TUESDAY NIGHT
THROUGH WEDNESDAY WITH NUMEROUS PERIODS OF SHOWERS AND THUNDERSTORMS
EXPECTED.  THE SFC FCST ALSO FEATURES A BOUNDARY MOVING THROUGH THE
CWA WEDNESDAY WHICH COULD HELP FORCE SHOWERS AND STORMS. HAVE HIGHER
CONFIDENCE IN PRECIP TUESDAY NIGHT THAN WEDNESDAY. CAPE LOOKS
MARGINAL OUTSIDE OF THE TYPICALLY TOO ROBUST NAM SOUNDINGS. FCST
SOUNDINGS LACK SHEAR...BUT THEY DO FEATURE INVERTED V/S AT THE SFC
AND SOME DRY AIR ALOFT. THIS SUGGESTS GUSTY WINDS ARE PSBL BUT FLOW
IS LESS THAN 40 KT ALOFT SO DAMAGING WINDS ARE NOT EXPECTED. PWAT
VALUES ARE FORECASTED TO BE ARND 1.3 INCHES WHICH IS ABOVE NORMAL
FOR THIS TIME OF YEAR...THEREFORE HEAVY DOWNPOURS ARE POSSIBLE.

WITH 925MB TEMPS BTWN +18 TO +20C...WARMED TEMPS SLIGHTLY FOR
WEDNESDAY INTO THE UPPER 70S TO AROUND 80.

HIGH PRESSURE THEN SPREADS ACROSS THE REGION WEDNESDAY NIGHT AND
HANGS AROUND THROUGH THURSDAY. THIS SHOULD RESULT IN DRY CONDITIONS
OUTSIDE OF POSSIBLE ISOLATED SHOWERS OVER LAKE MI. WINDS TURN OFF OF
THE LAKE THURSDAY SO AREAS ALONG THE LAKE WILL BE IN THE LOW
70S...WHILE AREAS AWAY FROM THE LAKE WILL GET INTO THE LOW TO MID
80S.

THE NEXT SFC LOW FORMS OVER THE PLAINS THURSDAY EVENING AND PASSES
OVER ONTARIO LATE THURSDAY NIGHT THROUGH FRIDAY MORNING. A LOW
PRESSURE TROUGH ACCOMPANIES THE LOW/S COLD FRONT WHICH SLIDES
THROUGH LATE THIS WEEK. GUIDANCE DIFFERS ON HOW QUICKLY THE FRONT
WILL TRAVEL WITH THE GFS BEING THE QUICKER MODEL.  THE MODELS DO
AGREE THAT THE LOWS WARM FRONT WILL LIFT NORTH OF THE CWA BY FRIDAY
MORNING LEADING TO A WARM AND MUGGY DAY WITH HIGHS IN THE MID 80S.
IF CLOUD COVER REMAINS SCARCE...COULD SEE TEMPS GET INTO THE UPPER
80S. GUSTY WINDS ARE ALSO EXPECTED WITH GUSTS ARND 25 MPH. PRECIP
CHANCES WILL INCREASE THROUGH FRIDAY NIGHT AS THE COLD FRONT MOVES
CLOSER TO THE CWA. THINKING FRIDAY WILL NOT BE A TOTAL WASHOUT...BUT
THERE WILL BE MULTIPLE PERIODS OF STORMS. PWAT VALUES INCREASE
FURTHER TO 1.5 INCHES SO ANY SHOWERS AND STORMS WILL BE CAPABLE OF
HEAVY DOWNPOURS.

SHOWERS AND STORMS ARE ALSO EXPECTED SATURDAY AHEAD OF AND ALONG THE
COLD FRONT. ANOTHER ROUND OF SHOWERS IS POSSIBLE BEHIND THE COLD
FRONT ALONG A VORT STREAMER SATURDAY EVENING AND SUNDAY. THE GFS
KEEPS PRECIP IN THE REGION INTO EARLY NEXT WEEK WHILE THE ECMWF HAS
A RIDGE OVERHEAD.  THEREFORE HAVE LOW CONFIDENCE IN PRECIP CHANCES
NEXT WEEK.  BELOW NORMAL TEMPS MOVE IN LATE THIS WEEK INTO NEXT WEEK
WITH HIGHS POSSIBLY IN THE 60S OVER THE WEEKEND.

JEE

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 20Z...

* GUSTY SOUTHWEST WINDS.

* MVFR CEILINGS POSSIBLE EARLY TUESDAY MORNING.

* SHOWERS LIKELY WITH PERIODIC THUNDERSTORMS LATE IN THE FORECAST
  PERIOD.

RODRIGUEZ

//DISCUSSION...UPDATED 18Z...

MUCH OF THE SHOWERS ARE EXITING THE AREA EARLY THIS AFTERNOON.
HOWEVER...AN ISOLATED LIGHT SHOWER WILL STILL BE POSSIBLE OVER THE
NEXT HOUR BEFORE PREVAILING DRY CONDITIONS ARE EXPECTED THIS
AFTERNOON AND TONIGHT. LINGERING MVFR CEILINGS WILL LIFT TO VFR
THROUGH 20-21Z THIS AFTERNOON WITH SKIES THEN SCATTERING THIS
EVENING...AS THE SOUTHWEST WINDS/GUSTS DIMINISH INTO THE EVENING.
WITH FAIRLY MOIST CONDITIONS REMAINING IN PLACE TONIGHT INTO
TUESDAY...REDEVELOPING LOW CEILINGS DO APPEAR TO BE A POSSIBILITY.
OVERALL CONFIDENCE IS LOWER DURING THIS PERIOD...BUT DID MAKE
MENTION OF AT LEAST MVFR CEILINGS...AND WILL NEED TO MONITOR FOR
POTENTIALLY LOWER CEILINGS. HAVE PUSHED BACK TIMING OF PRECIP LATE
IN THE PERIOD...BUT WITH INSTABILITY AND FORCING
INCREASING...SHOWERS AND THUNDERSTORMS DO APPEAR LIKELY TUESDAY.
STILL SOME UNCERTAINTY WITH EXACT TIMING AND DURATION...AND EVEN
THE POSSIBILITY FOR AN ADDITIONAL PERIOD OF THUNDERSTORMS TUESDAY
AFTERNOON.

RODRIGUEZ

//ORD AND MDW CONFIDENCE...UPDATED 20Z...

* HIGH CONFIDENCE WITH WIND SPEED/DIRECTION.

* MEDIUM HIGH CONFIDENCE WITH CEILINGS.

* HIGH CONFIDENCE OF SHOWERS/THUNDERSTORMS...MEDIUM CONFIDENCE
  WITH TIMING/DURATION.

RODRIGUEZ

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/TSRA LATE. SOUTHEAST WINDS.

FRIDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. SOUTHWEST WINDS
BECOMING NORTHEAST OVERNIGHT.

SATURDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. NORTHEAST
WINDS.

SUNDAY...CHANCE TSRA. MVFR POSSIBLE. NORTHEAST WINDS.

KREIN

&&

.MARINE...
334 PM CDT

WIND GUSTS ARE BEGINNING TO COME DOWN AND THE GALE WARNING FOR THE
NEARSHORE ZONES HAS BEEN DROPPED. A SMALL CRAFT ADVISORY WILL GO
THROUGH 9PM CDT THIS EVENING FOR LINGERING STRONG WINDS AND HIGH
WAVES.  LOW PRESSURE CURRENTLY OVER THE UPPER MIDWEST WILL MOVE OVER
QUEBEC TUESDAY MORNING. THE LOWS STATIONARY FRONT REMAINS NORTH OF
THE LAKE BUT STABLE CONDITIONS OVER THE LAKE WILL RESULT IN AREAS OF
FOG THROUGH TUESDAY NIGHT. SOUTH WINDS ARE EXPECTED WITH SPEEDS TO
20 KT. HIGH PRESSURE SPREADS OVER THE LAKE WEDNESDAY NIGHT WITH
WINDS REMAINING LIGHT AND VARYING BTWN WEST AND SOUTHEAST THROUGH
FRIDAY. A COLD FRONT THEN SWEEPS DOWN THE LAKE LATE IN THE WEEK WITH
WINDS BCMG NORTH BEHIND IT.

JEE

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 9 PM MONDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 252034
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
334 PM CDT MON MAY 25 2015

.SHORT TERM...
255 PM CDT

THROUGH TUESDAY...

SHOWERS CONTINUE TO DIMINISH AS WE GET ON THE SUBSIDENT SIDE OF THE
DEPARTING UPPER TROUGH AXIS THAT WILL QUICKLY EXIT TO THE NORTHEAST
TONIGHT. SURFACE LOW PRESSURE IS PUSHING INTO UPPER MICHIGAN WHILE
LEAVING MODEST PRESSURE RISES IN ITS WAKE. WIND GUSTS TO 30 TO
LOCALLY 35 MPH WILL CONTINUE THROUGH THE AFTERNOON. EXPECT TO SEE
ALITTLE MORE BLUE SKY THROUGH THE AFTERNOON/EARLY EVENING WHICH
WILL ALLOW TEMPERATURES TO SLOWLY INCH UPWARD TO THE UPPER 70S TO
LOW 80S...THOUGH WITH MOIST SW FLOW EXPECT THESE LOWER CLOUDS TO
LINGER AROUND A BIT LONGER.

THE ACTIVE PATTERN CONTINUES ACROSS THE AREA FOR THE NEXT 24 HOURS.
SEVERAL UPPER LEVEL LOW PRESSURE SYSTEMS ARE NOTED IN AFTERNOON
WATER VAPOR IMAGERY. THE FIRST IS OVER THE NEBRASKA PANHANDLE...WITH
ASSOCIATED LEADING SHORTWAVE ENERGY TRIGGERING SOME SHOWERS AND T-
STORMS ACROSS IOWA...THEN THE BIGGER SHOWS TO THE SOUTH WITH THE
COMPLEX OF STRONG/SEVERE THUNDERSTORMS ASSOCIATED WITH A NEGATIVELY
TILTED TROUGH IN THE TEXAS. THE NORTHERN SHORTWAVE IS EXPECTED TO
CONTINUE DEVELOPING SHOWERS AND STORMS ACROSS IOWA AND INTO FAR
WESTERN ILLINOIS AND WISCONSIN. SOME OF THIS MAY CLIP OUR FAR
NORTHWESTERN COUNTIES...INCLUDING THE ROCKFORD AREA...BUT FEEL AT
THIS POINT THAT IT SHOULD LARGELY BE OFF FARTHER NW. HAVE HELD OFF
AND KEPT THIS ACTIVITY OUT OF AREA.

THEN TONIGHT THE LOWER LEVEL FRONTAL BOUNDARY ASSOCIATED WITH THE
NORTHERN WAVE WILL SAG SOUTHEAST TOWARD THE AREA LATE TONIGHT. MUCH
OF THE GUIDANCE THEN BRINGS THE SOUTHERN SHORTWAVE TOWARD OUR AREA
LATE TONIGHT AND MORE SO ON TUESDAY ON A DECENT UPPER LEVEL JET. THE
LARGE SUITE OF GUIDANCE KEEPS THESE TWO LOWS SEPARATE...ALLOWING
MUCH OF THE NORTHERN STREAM SHOWERS/STORMS TO LARGELY REMAIN OUT OF
AREA...BUT THEY MAY BEGIN TO AFFECT AREAS WEST OF I-39 IN ILLINOIS
OVERNIGHT.

TUESDAY MORNING IS WHEN BETTER CHANCES OF SHOWERS AND SCATTERED
THUNDERSTORMS WOULD BE. THIS MID MORNING/EARLY AFTERNOON PERIOD
FEATURES MODEST LOW/MID LEVEL ISENTROPIC LIFT/PW VALUES APPROACHING
1.5 INCHES AND THETA-E RIDGE NOSING IN FROM THE SOUTH. WE SHOULD
HAVE SOME SHOWERS AND THUNDERSTORMS MOVING FROM SOUTH TO NORTH
DURING THIS TIME FRAME.  DEPENDING ON THE INTERACTION OF THESE TWO
SYSTEMS AND IF THINGS SLOW DOWN A BIT...BETTER INSTABILITY WILL BE
TAPPED INTO IN THE AFTERNOON. THE NAM WOULD SUGGEST THIS
SOLUTION...WHILE THE GLOBAL GFS/ECMWF SUGGEST THE MID-MORNING TO
EARLY AFTERNOON PERIOD WOULD BE THE MOST LIKELY PERIOD WHERE DEEPER
MOISTURE IS AVAILABLE AND CO-LOCATED WITH THE UPPER FORCING.
CONFIDENCE ON TIMING IS ONLY MEDIUM WHICH REQUIRED CARRYING AN
EXTENDED PERIOD OF LIKELY POPS FOR MUCH OF THE DAY.

KMD

&&

.LONG TERM...
319 PM CDT

WEDNESDAY NIGHT THROUGH MONDAY...

AN UPPER LEVEL SHORTWAVE TROUGH PASSES OVERHEAD TUESDAY NIGHT
THROUGH WEDNESDAY WITH NUMEROUS PERIODS OF SHOWERS AND THUNDERSTORMS
EXPECTED.  THE SFC FCST ALSO FEATURES A BOUNDARY MOVING THROUGH THE
CWA WEDNESDAY WHICH COULD HELP FORCE SHOWERS AND STORMS. HAVE HIGHER
CONFIDENCE IN PRECIP TUESDAY NIGHT THAN WEDNESDAY. CAPE LOOKS
MARGINAL OUTSIDE OF THE TYPICALLY TOO ROBUST NAM SOUNDINGS. FCST
SOUNDINGS LACK SHEAR...BUT THEY DO FEATURE INVERTED V/S AT THE SFC
AND SOME DRY AIR ALOFT. THIS SUGGESTS GUSTY WINDS ARE PSBL BUT FLOW
IS LESS THAN 40 KT ALOFT SO DAMAGING WINDS ARE NOT EXPECTED. PWAT
VALUES ARE FORECASTED TO BE ARND 1.3 INCHES WHICH IS ABOVE NORMAL
FOR THIS TIME OF YEAR...THEREFORE HEAVY DOWNPOURS ARE POSSIBLE.

WITH 925MB TEMPS BTWN +18 TO +20C...WARMED TEMPS SLIGHTLY FOR
WEDNESDAY INTO THE UPPER 70S TO AROUND 80.

HIGH PRESSURE THEN SPREADS ACROSS THE REGION WEDNESDAY NIGHT AND
HANGS AROUND THROUGH THURSDAY. THIS SHOULD RESULT IN DRY CONDITIONS
OUTSIDE OF POSSIBLE ISOLATED SHOWERS OVER LAKE MI. WINDS TURN OFF OF
THE LAKE THURSDAY SO AREAS ALONG THE LAKE WILL BE IN THE LOW
70S...WHILE AREAS AWAY FROM THE LAKE WILL GET INTO THE LOW TO MID
80S.

THE NEXT SFC LOW FORMS OVER THE PLAINS THURSDAY EVENING AND PASSES
OVER ONTARIO LATE THURSDAY NIGHT THROUGH FRIDAY MORNING. A LOW
PRESSURE TROUGH ACCOMPANIES THE LOW/S COLD FRONT WHICH SLIDES
THROUGH LATE THIS WEEK. GUIDANCE DIFFERS ON HOW QUICKLY THE FRONT
WILL TRAVEL WITH THE GFS BEING THE QUICKER MODEL.  THE MODELS DO
AGREE THAT THE LOWS WARM FRONT WILL LIFT NORTH OF THE CWA BY FRIDAY
MORNING LEADING TO A WARM AND MUGGY DAY WITH HIGHS IN THE MID 80S.
IF CLOUD COVER REMAINS SCARCE...COULD SEE TEMPS GET INTO THE UPPER
80S. GUSTY WINDS ARE ALSO EXPECTED WITH GUSTS ARND 25 MPH. PRECIP
CHANCES WILL INCREASE THROUGH FRIDAY NIGHT AS THE COLD FRONT MOVES
CLOSER TO THE CWA. THINKING FRIDAY WILL NOT BE A TOTAL WASHOUT...BUT
THERE WILL BE MULTIPLE PERIODS OF STORMS. PWAT VALUES INCREASE
FURTHER TO 1.5 INCHES SO ANY SHOWERS AND STORMS WILL BE CAPABLE OF
HEAVY DOWNPOURS.

SHOWERS AND STORMS ARE ALSO EXPECTED SATURDAY AHEAD OF AND ALONG THE
COLD FRONT. ANOTHER ROUND OF SHOWERS IS POSSIBLE BEHIND THE COLD
FRONT ALONG A VORT STREAMER SATURDAY EVENING AND SUNDAY. THE GFS
KEEPS PRECIP IN THE REGION INTO EARLY NEXT WEEK WHILE THE ECMWF HAS
A RIDGE OVERHEAD.  THEREFORE HAVE LOW CONFIDENCE IN PRECIP CHANCES
NEXT WEEK.  BELOW NORMAL TEMPS MOVE IN LATE THIS WEEK INTO NEXT WEEK
WITH HIGHS POSSIBLY IN THE 60S OVER THE WEEKEND.

JEE

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 20Z...

* GUSTY SOUTHWEST WINDS.

* MVFR CEILINGS POSSIBLE EARLY TUESDAY MORNING.

* SHOWERS LIKELY WITH PERIODIC THUNDERSTORMS LATE IN THE FORECAST
  PERIOD.

RODRIGUEZ

//DISCUSSION...UPDATED 18Z...

MUCH OF THE SHOWERS ARE EXITING THE AREA EARLY THIS AFTERNOON.
HOWEVER...AN ISOLATED LIGHT SHOWER WILL STILL BE POSSIBLE OVER THE
NEXT HOUR BEFORE PREVAILING DRY CONDITIONS ARE EXPECTED THIS
AFTERNOON AND TONIGHT. LINGERING MVFR CEILINGS WILL LIFT TO VFR
THROUGH 20-21Z THIS AFTERNOON WITH SKIES THEN SCATTERING THIS
EVENING...AS THE SOUTHWEST WINDS/GUSTS DIMINISH INTO THE EVENING.
WITH FAIRLY MOIST CONDITIONS REMAINING IN PLACE TONIGHT INTO
TUESDAY...REDEVELOPING LOW CEILINGS DO APPEAR TO BE A POSSIBILITY.
OVERALL CONFIDENCE IS LOWER DURING THIS PERIOD...BUT DID MAKE
MENTION OF AT LEAST MVFR CEILINGS...AND WILL NEED TO MONITOR FOR
POTENTIALLY LOWER CEILINGS. HAVE PUSHED BACK TIMING OF PRECIP LATE
IN THE PERIOD...BUT WITH INSTABILITY AND FORCING
INCREASING...SHOWERS AND THUNDERSTORMS DO APPEAR LIKELY TUESDAY.
STILL SOME UNCERTAINTY WITH EXACT TIMING AND DURATION...AND EVEN
THE POSSIBILITY FOR AN ADDITIONAL PERIOD OF THUNDERSTORMS TUESDAY
AFTERNOON.

RODRIGUEZ

//ORD AND MDW CONFIDENCE...UPDATED 20Z...

* HIGH CONFIDENCE WITH WIND SPEED/DIRECTION.

* MEDIUM HIGH CONFIDENCE WITH CEILINGS.

* HIGH CONFIDENCE OF SHOWERS/THUNDERSTORMS...MEDIUM CONFIDENCE
  WITH TIMING/DURATION.

RODRIGUEZ

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/TSRA LATE. SOUTHEAST WINDS.

FRIDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. SOUTHWEST WINDS
BECOMING NORTHEAST OVERNIGHT.

SATURDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. NORTHEAST
WINDS.

SUNDAY...CHANCE TSRA. MVFR POSSIBLE. NORTHEAST WINDS.

KREIN

&&

.MARINE...
334 PM CDT

WIND GUSTS ARE BEGINNING TO COME DOWN AND THE GALE WARNING FOR THE
NEARSHORE ZONES HAS BEEN DROPPED. A SMALL CRAFT ADVISORY WILL GO
THROUGH 9PM CDT THIS EVENING FOR LINGERING STRONG WINDS AND HIGH
WAVES.  LOW PRESSURE CURRENTLY OVER THE UPPER MIDWEST WILL MOVE OVER
QUEBEC TUESDAY MORNING. THE LOWS STATIONARY FRONT REMAINS NORTH OF
THE LAKE BUT STABLE CONDITIONS OVER THE LAKE WILL RESULT IN AREAS OF
FOG THROUGH TUESDAY NIGHT. SOUTH WINDS ARE EXPECTED WITH SPEEDS TO
20 KT. HIGH PRESSURE SPREADS OVER THE LAKE WEDNESDAY NIGHT WITH
WINDS REMAINING LIGHT AND VARYING BTWN WEST AND SOUTHEAST THROUGH
FRIDAY. A COLD FRONT THEN SWEEPS DOWN THE LAKE LATE IN THE WEEK WITH
WINDS BCMG NORTH BEHIND IT.

JEE

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 9 PM MONDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 252034
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
334 PM CDT MON MAY 25 2015

.SHORT TERM...
255 PM CDT

THROUGH TUESDAY...

SHOWERS CONTINUE TO DIMINISH AS WE GET ON THE SUBSIDENT SIDE OF THE
DEPARTING UPPER TROUGH AXIS THAT WILL QUICKLY EXIT TO THE NORTHEAST
TONIGHT. SURFACE LOW PRESSURE IS PUSHING INTO UPPER MICHIGAN WHILE
LEAVING MODEST PRESSURE RISES IN ITS WAKE. WIND GUSTS TO 30 TO
LOCALLY 35 MPH WILL CONTINUE THROUGH THE AFTERNOON. EXPECT TO SEE
ALITTLE MORE BLUE SKY THROUGH THE AFTERNOON/EARLY EVENING WHICH
WILL ALLOW TEMPERATURES TO SLOWLY INCH UPWARD TO THE UPPER 70S TO
LOW 80S...THOUGH WITH MOIST SW FLOW EXPECT THESE LOWER CLOUDS TO
LINGER AROUND A BIT LONGER.

THE ACTIVE PATTERN CONTINUES ACROSS THE AREA FOR THE NEXT 24 HOURS.
SEVERAL UPPER LEVEL LOW PRESSURE SYSTEMS ARE NOTED IN AFTERNOON
WATER VAPOR IMAGERY. THE FIRST IS OVER THE NEBRASKA PANHANDLE...WITH
ASSOCIATED LEADING SHORTWAVE ENERGY TRIGGERING SOME SHOWERS AND T-
STORMS ACROSS IOWA...THEN THE BIGGER SHOWS TO THE SOUTH WITH THE
COMPLEX OF STRONG/SEVERE THUNDERSTORMS ASSOCIATED WITH A NEGATIVELY
TILTED TROUGH IN THE TEXAS. THE NORTHERN SHORTWAVE IS EXPECTED TO
CONTINUE DEVELOPING SHOWERS AND STORMS ACROSS IOWA AND INTO FAR
WESTERN ILLINOIS AND WISCONSIN. SOME OF THIS MAY CLIP OUR FAR
NORTHWESTERN COUNTIES...INCLUDING THE ROCKFORD AREA...BUT FEEL AT
THIS POINT THAT IT SHOULD LARGELY BE OFF FARTHER NW. HAVE HELD OFF
AND KEPT THIS ACTIVITY OUT OF AREA.

THEN TONIGHT THE LOWER LEVEL FRONTAL BOUNDARY ASSOCIATED WITH THE
NORTHERN WAVE WILL SAG SOUTHEAST TOWARD THE AREA LATE TONIGHT. MUCH
OF THE GUIDANCE THEN BRINGS THE SOUTHERN SHORTWAVE TOWARD OUR AREA
LATE TONIGHT AND MORE SO ON TUESDAY ON A DECENT UPPER LEVEL JET. THE
LARGE SUITE OF GUIDANCE KEEPS THESE TWO LOWS SEPARATE...ALLOWING
MUCH OF THE NORTHERN STREAM SHOWERS/STORMS TO LARGELY REMAIN OUT OF
AREA...BUT THEY MAY BEGIN TO AFFECT AREAS WEST OF I-39 IN ILLINOIS
OVERNIGHT.

TUESDAY MORNING IS WHEN BETTER CHANCES OF SHOWERS AND SCATTERED
THUNDERSTORMS WOULD BE. THIS MID MORNING/EARLY AFTERNOON PERIOD
FEATURES MODEST LOW/MID LEVEL ISENTROPIC LIFT/PW VALUES APPROACHING
1.5 INCHES AND THETA-E RIDGE NOSING IN FROM THE SOUTH. WE SHOULD
HAVE SOME SHOWERS AND THUNDERSTORMS MOVING FROM SOUTH TO NORTH
DURING THIS TIME FRAME.  DEPENDING ON THE INTERACTION OF THESE TWO
SYSTEMS AND IF THINGS SLOW DOWN A BIT...BETTER INSTABILITY WILL BE
TAPPED INTO IN THE AFTERNOON. THE NAM WOULD SUGGEST THIS
SOLUTION...WHILE THE GLOBAL GFS/ECMWF SUGGEST THE MID-MORNING TO
EARLY AFTERNOON PERIOD WOULD BE THE MOST LIKELY PERIOD WHERE DEEPER
MOISTURE IS AVAILABLE AND CO-LOCATED WITH THE UPPER FORCING.
CONFIDENCE ON TIMING IS ONLY MEDIUM WHICH REQUIRED CARRYING AN
EXTENDED PERIOD OF LIKELY POPS FOR MUCH OF THE DAY.

KMD

&&

.LONG TERM...
319 PM CDT

WEDNESDAY NIGHT THROUGH MONDAY...

AN UPPER LEVEL SHORTWAVE TROUGH PASSES OVERHEAD TUESDAY NIGHT
THROUGH WEDNESDAY WITH NUMEROUS PERIODS OF SHOWERS AND THUNDERSTORMS
EXPECTED.  THE SFC FCST ALSO FEATURES A BOUNDARY MOVING THROUGH THE
CWA WEDNESDAY WHICH COULD HELP FORCE SHOWERS AND STORMS. HAVE HIGHER
CONFIDENCE IN PRECIP TUESDAY NIGHT THAN WEDNESDAY. CAPE LOOKS
MARGINAL OUTSIDE OF THE TYPICALLY TOO ROBUST NAM SOUNDINGS. FCST
SOUNDINGS LACK SHEAR...BUT THEY DO FEATURE INVERTED V/S AT THE SFC
AND SOME DRY AIR ALOFT. THIS SUGGESTS GUSTY WINDS ARE PSBL BUT FLOW
IS LESS THAN 40 KT ALOFT SO DAMAGING WINDS ARE NOT EXPECTED. PWAT
VALUES ARE FORECASTED TO BE ARND 1.3 INCHES WHICH IS ABOVE NORMAL
FOR THIS TIME OF YEAR...THEREFORE HEAVY DOWNPOURS ARE POSSIBLE.

WITH 925MB TEMPS BTWN +18 TO +20C...WARMED TEMPS SLIGHTLY FOR
WEDNESDAY INTO THE UPPER 70S TO AROUND 80.

HIGH PRESSURE THEN SPREADS ACROSS THE REGION WEDNESDAY NIGHT AND
HANGS AROUND THROUGH THURSDAY. THIS SHOULD RESULT IN DRY CONDITIONS
OUTSIDE OF POSSIBLE ISOLATED SHOWERS OVER LAKE MI. WINDS TURN OFF OF
THE LAKE THURSDAY SO AREAS ALONG THE LAKE WILL BE IN THE LOW
70S...WHILE AREAS AWAY FROM THE LAKE WILL GET INTO THE LOW TO MID
80S.

THE NEXT SFC LOW FORMS OVER THE PLAINS THURSDAY EVENING AND PASSES
OVER ONTARIO LATE THURSDAY NIGHT THROUGH FRIDAY MORNING. A LOW
PRESSURE TROUGH ACCOMPANIES THE LOW/S COLD FRONT WHICH SLIDES
THROUGH LATE THIS WEEK. GUIDANCE DIFFERS ON HOW QUICKLY THE FRONT
WILL TRAVEL WITH THE GFS BEING THE QUICKER MODEL.  THE MODELS DO
AGREE THAT THE LOWS WARM FRONT WILL LIFT NORTH OF THE CWA BY FRIDAY
MORNING LEADING TO A WARM AND MUGGY DAY WITH HIGHS IN THE MID 80S.
IF CLOUD COVER REMAINS SCARCE...COULD SEE TEMPS GET INTO THE UPPER
80S. GUSTY WINDS ARE ALSO EXPECTED WITH GUSTS ARND 25 MPH. PRECIP
CHANCES WILL INCREASE THROUGH FRIDAY NIGHT AS THE COLD FRONT MOVES
CLOSER TO THE CWA. THINKING FRIDAY WILL NOT BE A TOTAL WASHOUT...BUT
THERE WILL BE MULTIPLE PERIODS OF STORMS. PWAT VALUES INCREASE
FURTHER TO 1.5 INCHES SO ANY SHOWERS AND STORMS WILL BE CAPABLE OF
HEAVY DOWNPOURS.

SHOWERS AND STORMS ARE ALSO EXPECTED SATURDAY AHEAD OF AND ALONG THE
COLD FRONT. ANOTHER ROUND OF SHOWERS IS POSSIBLE BEHIND THE COLD
FRONT ALONG A VORT STREAMER SATURDAY EVENING AND SUNDAY. THE GFS
KEEPS PRECIP IN THE REGION INTO EARLY NEXT WEEK WHILE THE ECMWF HAS
A RIDGE OVERHEAD.  THEREFORE HAVE LOW CONFIDENCE IN PRECIP CHANCES
NEXT WEEK.  BELOW NORMAL TEMPS MOVE IN LATE THIS WEEK INTO NEXT WEEK
WITH HIGHS POSSIBLY IN THE 60S OVER THE WEEKEND.

JEE

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 20Z...

* GUSTY SOUTHWEST WINDS.

* MVFR CEILINGS POSSIBLE EARLY TUESDAY MORNING.

* SHOWERS LIKELY WITH PERIODIC THUNDERSTORMS LATE IN THE FORECAST
  PERIOD.

RODRIGUEZ

//DISCUSSION...UPDATED 18Z...

MUCH OF THE SHOWERS ARE EXITING THE AREA EARLY THIS AFTERNOON.
HOWEVER...AN ISOLATED LIGHT SHOWER WILL STILL BE POSSIBLE OVER THE
NEXT HOUR BEFORE PREVAILING DRY CONDITIONS ARE EXPECTED THIS
AFTERNOON AND TONIGHT. LINGERING MVFR CEILINGS WILL LIFT TO VFR
THROUGH 20-21Z THIS AFTERNOON WITH SKIES THEN SCATTERING THIS
EVENING...AS THE SOUTHWEST WINDS/GUSTS DIMINISH INTO THE EVENING.
WITH FAIRLY MOIST CONDITIONS REMAINING IN PLACE TONIGHT INTO
TUESDAY...REDEVELOPING LOW CEILINGS DO APPEAR TO BE A POSSIBILITY.
OVERALL CONFIDENCE IS LOWER DURING THIS PERIOD...BUT DID MAKE
MENTION OF AT LEAST MVFR CEILINGS...AND WILL NEED TO MONITOR FOR
POTENTIALLY LOWER CEILINGS. HAVE PUSHED BACK TIMING OF PRECIP LATE
IN THE PERIOD...BUT WITH INSTABILITY AND FORCING
INCREASING...SHOWERS AND THUNDERSTORMS DO APPEAR LIKELY TUESDAY.
STILL SOME UNCERTAINTY WITH EXACT TIMING AND DURATION...AND EVEN
THE POSSIBILITY FOR AN ADDITIONAL PERIOD OF THUNDERSTORMS TUESDAY
AFTERNOON.

RODRIGUEZ

//ORD AND MDW CONFIDENCE...UPDATED 20Z...

* HIGH CONFIDENCE WITH WIND SPEED/DIRECTION.

* MEDIUM HIGH CONFIDENCE WITH CEILINGS.

* HIGH CONFIDENCE OF SHOWERS/THUNDERSTORMS...MEDIUM CONFIDENCE
  WITH TIMING/DURATION.

RODRIGUEZ

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/TSRA LATE. SOUTHEAST WINDS.

FRIDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. SOUTHWEST WINDS
BECOMING NORTHEAST OVERNIGHT.

SATURDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. NORTHEAST
WINDS.

SUNDAY...CHANCE TSRA. MVFR POSSIBLE. NORTHEAST WINDS.

KREIN

&&

.MARINE...
334 PM CDT

WIND GUSTS ARE BEGINNING TO COME DOWN AND THE GALE WARNING FOR THE
NEARSHORE ZONES HAS BEEN DROPPED. A SMALL CRAFT ADVISORY WILL GO
THROUGH 9PM CDT THIS EVENING FOR LINGERING STRONG WINDS AND HIGH
WAVES.  LOW PRESSURE CURRENTLY OVER THE UPPER MIDWEST WILL MOVE OVER
QUEBEC TUESDAY MORNING. THE LOWS STATIONARY FRONT REMAINS NORTH OF
THE LAKE BUT STABLE CONDITIONS OVER THE LAKE WILL RESULT IN AREAS OF
FOG THROUGH TUESDAY NIGHT. SOUTH WINDS ARE EXPECTED WITH SPEEDS TO
20 KT. HIGH PRESSURE SPREADS OVER THE LAKE WEDNESDAY NIGHT WITH
WINDS REMAINING LIGHT AND VARYING BTWN WEST AND SOUTHEAST THROUGH
FRIDAY. A COLD FRONT THEN SWEEPS DOWN THE LAKE LATE IN THE WEEK WITH
WINDS BCMG NORTH BEHIND IT.

JEE

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 9 PM MONDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 252019
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
319 PM CDT MON MAY 25 2015

.SHORT TERM...
255 PM CDT

THROUGH TUESDAY...

SHOWERS CONTINUE TO DIMINISH AS WE GET ON THE SUBSIDENT SIDE OF THE
DEPARTING UPPER TROUGH AXIS THAT WILL QUICKLY EXIT TO THE NORTHEAST
TONIGHT. SURFACE LOW PRESSURE IS PUSHING INTO UPPER MICHIGAN WHILE
LEAVING MODEST PRESSURE RISES IN ITS WAKE. WIND GUSTS TO 30 TO
LOCALLY 35 MPH WILL CONTINUE THROUGH THE AFTERNOON. EXPECT TO SEE
ALITTLE MORE BLUE SKY THROUGH THE AFTERNOON/EARLY EVENING WHICH
WILL ALLOW TEMPERATURES TO SLOWLY INCH UPWARD TO THE UPPER 70S TO
LOW 80S...THOUGH WITH MOIST SW FLOW EXPECT THESE LOWER CLOUDS TO
LINGER AROUND A BIT LONGER.

THE ACTIVE PATTERN CONTINUES ACROSS THE AREA FOR THE NEXT 24 HOURS.
SEVERAL UPPER LEVEL LOW PRESSURE SYSTEMS ARE NOTED IN AFTERNOON
WATER VAPOR IMAGERY. THE FIRST IS OVER THE NEBRASKA PANHANDLE...WITH
ASSOCIATED LEADING SHORTWAVE ENERGY TRIGGERING SOME SHOWERS AND T-
STORMS ACROSS IOWA...THEN THE BIGGER SHOWS TO THE SOUTH WITH THE
COMPLEX OF STRONG/SEVERE THUNDERSTORMS ASSOCIATED WITH A NEGATIVELY
TILTED TROUGH IN THE TEXAS. THE NORTHERN SHORTWAVE IS EXPECTED TO
CONTINUE DEVELOPING SHOWERS AND STORMS ACROSS IOWA AND INTO FAR
WESTERN ILLINOIS AND WISCONSIN. SOME OF THIS MAY CLIP OUR FAR
NORTHWESTERN COUNTIES...INCLUDING THE ROCKFORD AREA...BUT FEEL AT
THIS POINT THAT IT SHOULD LARGELY BE OFF FARTHER NW. HAVE HELD OFF
AND KEPT THIS ACTIVITY OUT OF AREA.

THEN TONIGHT THE LOWER LEVEL FRONTAL BOUNDARY ASSOCIATED WITH THE
NORTHERN WAVE WILL SAG SOUTHEAST TOWARD THE AREA LATE TONIGHT. MUCH
OF THE GUIDANCE THEN BRINGS THE SOUTHERN SHORTWAVE TOWARD OUR AREA
LATE TONIGHT AND MORE SO ON TUESDAY ON A DECENT UPPER LEVEL JET. THE
LARGE SUITE OF GUIDANCE KEEPS THESE TWO LOWS SEPARATE...ALLOWING
MUCH OF THE NORTHERN STREAM SHOWERS/STORMS TO LARGELY REMAIN OUT OF
AREA...BUT THEY MAY BEGIN TO AFFECT AREAS WEST OF I-39 IN ILLINOIS
OVERNIGHT.

TUESDAY MORNING IS WHEN BETTER CHANCES OF SHOWERS AND SCATTERED
THUNDERSTORMS WOULD BE. THIS MID MORNING/EARLY AFTERNOON PERIOD
FEATURES MODEST LOW/MID LEVEL ISENTROPIC LIFT/PW VALUES APPROACHING
1.5 INCHES AND THETA-E RIDGE NOSING IN FROM THE SOUTH. WE SHOULD
HAVE SOME SHOWERS AND THUNDERSTORMS MOVING FROM SOUTH TO NORTH
DURING THIS TIME FRAME.  DEPENDING ON THE INTERACTION OF THESE TWO
SYSTEMS AND IF THINGS SLOW DOWN A BIT...BETTER INSTABILITY WILL BE
TAPPED INTO IN THE AFTERNOON. THE NAM WOULD SUGGEST THIS
SOLUTION...WHILE THE GLOBAL GFS/ECMWF SUGGEST THE MID-MORNING TO
EARLY AFTERNOON PERIOD WOULD BE THE MOST LIKELY PERIOD WHERE DEEPER
MOISTURE IS AVAILABLE AND CO-LOCATED WITH THE UPPER FORCING.
CONFIDENCE ON TIMING IS ONLY MEDIUM WHICH REQUIRED CARRYING AN
EXTENDED PERIOD OF LIKELY POPS FOR MUCH OF THE DAY.

KMD

&&

.LONG TERM...
319 PM CDT

WEDNESDAY NIGHT THROUGH MONDAY...

AN UPPER LEVEL SHORTWAVE TROUGH PASSES OVERHEAD TUESDAY NIGHT
THROUGH WEDNESDAY WITH NUMEROUS PERIODS OF SHOWERS AND THUNDERSTORMS
EXPECTED.  THE SFC FCST ALSO FEATURES A BOUNDARY MOVING THROUGH THE
CWA WEDNESDAY WHICH COULD HELP FORCE SHOWERS AND STORMS. HAVE HIGHER
CONFIDENCE IN PRECIP TUESDAY NIGHT THAN WEDNESDAY. CAPE LOOKS
MARGINAL OUTSIDE OF THE TYPICALLY TOO ROBUST NAM SOUNDINGS. FCST
SOUNDINGS LACK SHEAR...BUT THEY DO FEATURE INVERTED V/S AT THE SFC
AND SOME DRY AIR ALOFT. THIS SUGGESTS GUSTY WINDS ARE PSBL BUT FLOW
IS LESS THAN 40 KT ALOFT SO DAMAGING WINDS ARE NOT EXPECTED. PWAT
VALUES ARE FORECASTED TO BE ARND 1.3 INCHES WHICH IS ABOVE NORMAL
FOR THIS TIME OF YEAR...THEREFORE HEAVY DOWNPOURS ARE POSSIBLE.

WITH 925MB TEMPS BTWN +18 TO +20C...WARMED TEMPS SLIGHTLY FOR
WEDNESDAY INTO THE UPPER 70S TO AROUND 80.

HIGH PRESSURE THEN SPREADS ACROSS THE REGION WEDNESDAY NIGHT AND
HANGS AROUND THROUGH THURSDAY. THIS SHOULD RESULT IN DRY CONDITIONS
OUTSIDE OF POSSIBLE ISOLATED SHOWERS OVER LAKE MI. WINDS TURN OFF OF
THE LAKE THURSDAY SO AREAS ALONG THE LAKE WILL BE IN THE LOW
70S...WHILE AREAS AWAY FROM THE LAKE WILL GET INTO THE LOW TO MID
80S.

THE NEXT SFC LOW FORMS OVER THE PLAINS THURSDAY EVENING AND PASSES
OVER ONTARIO LATE THURSDAY NIGHT THROUGH FRIDAY MORNING. A LOW
PRESSURE TROUGH ACCOMPANIES THE LOW/S COLD FRONT WHICH SLIDES
THROUGH LATE THIS WEEK. GUIDANCE DIFFERS ON HOW QUICKLY THE FRONT
WILL TRAVEL WITH THE GFS BEING THE QUICKER MODEL.  THE MODELS DO
AGREE THAT THE LOWS WARM FRONT WILL LIFT NORTH OF THE CWA BY FRIDAY
MORNING LEADING TO A WARM AND MUGGY DAY WITH HIGHS IN THE MID 80S.
IF CLOUD COVER REMAINS SCARCE...COULD SEE TEMPS GET INTO THE UPPER
80S. GUSTY WINDS ARE ALSO EXPECTED WITH GUSTS ARND 25 MPH. PRECIP
CHANCES WILL INCREASE THROUGH FRIDAY NIGHT AS THE COLD FRONT MOVES
CLOSER TO THE CWA. THINKING FRIDAY WILL NOT BE A TOTAL WASHOUT...BUT
THERE WILL BE MULTIPLE PERIODS OF STORMS. PWAT VALUES INCREASE
FURTHER TO 1.5 INCHES SO ANY SHOWERS AND STORMS WILL BE CAPABLE OF
HEAVY DOWNPOURS.

SHOWERS AND STORMS ARE ALSO EXPECTED SATURDAY AHEAD OF AND ALONG THE
COLD FRONT. ANOTHER ROUND OF SHOWERS IS POSSIBLE BEHIND THE COLD
FRONT ALONG A VORT STREAMER SATURDAY EVENING AND SUNDAY. THE GFS
KEEPS PRECIP IN THE REGION INTO EARLY NEXT WEEK WHILE THE ECMWF HAS
A RIDGE OVERHEAD.  THEREFORE HAVE LOW CONFIDENCE IN PRECIP CHANCES
NEXT WEEK.  BELOW NORMAL TEMPS MOVE IN LATE THIS WEEK INTO NEXT WEEK
WITH HIGHS POSSIBLY IN THE 60S OVER THE WEEKEND.

JEE

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 20Z...

* GUSTY SOUTHWEST WINDS.

* MVFR CEILINGS POSSIBLE EARLY TUESDAY MORNING.

* SHOWERS LIKELY WITH PERIODIC THUNDERSTORMS LATE IN THE FORECAST
  PERIOD.

RODRIGUEZ

//DISCUSSION...UPDATED 18Z...

MUCH OF THE SHOWERS ARE EXITING THE AREA EARLY THIS AFTERNOON.
HOWEVER...AN ISOLATED LIGHT SHOWER WILL STILL BE POSSIBLE OVER THE
NEXT HOUR BEFORE PREVAILING DRY CONDITIONS ARE EXPECTED THIS
AFTERNOON AND TONIGHT. LINGERING MVFR CEILINGS WILL LIFT TO VFR
THROUGH 20-21Z THIS AFTERNOON WITH SKIES THEN SCATTERING THIS
EVENING...AS THE SOUTHWEST WINDS/GUSTS DIMINISH INTO THE EVENING.
WITH FAIRLY MOIST CONDITIONS REMAINING IN PLACE TONIGHT INTO
TUESDAY...REDEVELOPING LOW CEILINGS DO APPEAR TO BE A POSSIBILITY.
OVERALL CONFIDENCE IS LOWER DURING THIS PERIOD...BUT DID MAKE
MENTION OF AT LEAST MVFR CEILINGS...AND WILL NEED TO MONITOR FOR
POTENTIALLY LOWER CEILINGS. HAVE PUSHED BACK TIMING OF PRECIP LATE
IN THE PERIOD...BUT WITH INSTABILITY AND FORCING
INCREASING...SHOWERS AND THUNDERSTORMS DO APPEAR LIKELY TUESDAY.
STILL SOME UNCERTAINTY WITH EXACT TIMING AND DURATION...AND EVEN
THE POSSIBILITY FOR AN ADDITIONAL PERIOD OF THUNDERSTORMS TUESDAY
AFTERNOON.

RODRIGUEZ

//ORD AND MDW CONFIDENCE...UPDATED 20Z...

* HIGH CONFIDENCE WITH WIND SPEED/DIRECTION.

* MEDIUM HIGH CONFIDENCE WITH CEILINGS.

* HIGH CONFIDENCE OF SHOWERS/THUNDERSTORMS...MEDIUM CONFIDENCE
  WITH TIMING/DURATION.

RODRIGUEZ

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/TSRA LATE. SOUTHEAST WINDS.

FRIDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. SOUTHWEST WINDS
BECOMING NORTHEAST OVERNIGHT.

SATURDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. NORTHEAST
WINDS.

SUNDAY...CHANCE TSRA. MVFR POSSIBLE. NORTHEAST WINDS.

KREIN

&&

.MARINE...
304 AM CDT

LOW PRESSURE WILL BE STEADILY LIFTING NORTH ACROSS THE MISSOURI
VALLEY THIS MORNING...REACHING LAKE SUPERIOR BY THIS EVENING AND
CONTINUING TO SLIDE EAST/NORTHEAST TOWARDS QUEBEC BY TUESDAY
MORNING. A FRONTAL BOUNDARY WILL REMAIN OVER THE FAR NORTHERN
PORTIONS OF LAKE MICHIGAN. MEANWHILE GUSTY SOUTHERLY WINDS ARE
EXPECTED TO INCREASE THIS MORNING...WITH OCCASIONAL GALES FOR THE
NEARSHORE WATERS OF IL/IN. ACROSS THE OPEN WATERS...EXPECT THE
WARM/MOIST AIR TO STRUGGLE TO REACH THE SFC OF THE LAKE WITH SOME
DEGREE OF LAKE STABILITY. WAVES WILL STEADILY BUILD ACROSS THE
NORTHERN HALF OF THE LAKE AS A RESULT OF THE LONG FETCH. STILL
FEEL THAT GUSTS WILL REACH 30KT ACROSS THE LAKE...HOWEVER
CONFIDENCE HAS DIMINISHED SLIGHTLY AS NEW GUIDANCE HAS BECOME A
LITTLE LESS WITH THE WIND FIELDS. NONETHELESS...WAVES FOR THE
NORTHERN HALF OF THE LAKE WILL LIKELY TOP OUT IN THE 4 TO 7 FT
RANGE WITH OCCASIONAL WAVES REACHING 9 FT THIS AFTERNOON/EVENING.

THE GRADIENT QUICKLY DIMINISHES THIS EVENING...BUT EXPECT
SOUTHERLY WINDS TO PERSIST. THIS WILL ALLOW WAVES TO SUBSIDE TO 3
TO 5 FT. ANOTHER LOW WILL ARRIVE TUE...WITH WINDS NUDGING BACK UP
HOWEVER WARM AIR WILL CONTINUE TO FLOW ACROSS THE LAKE AND COULD
FURTHER ENHANCE THE LAKE STABILITY AND KEEP WAVES FROM BUILDING TO
LARGE.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 9 PM MONDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 252001 CCA
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
256 PM CDT MON MAY 25 2015


.SHORT TERM...
255 PM CDT

THROUGH TUESDAY...

SHOWERS CONTINUE TO DIMINISH AS WE GET ON THE SUBSIDENT SIDE OF THE
DEPARTING UPPER TROUGH AXIS THAT WILL QUICKLY EXIT TO THE NORTHEAST
TONIGHT. SURFACE LOW PRESSURE IS PUSHING INTO UPPER MICHIGAN WHILE
LEAVING MODEST PRESSURE RISES IN ITS WAKE. WIND GUSTS TO 30 TO
LOCALLY 35 MPH WILL CONTINUE THROUGH THE AFTERNOON. EXPECT TO SEE
ALITTLE MORE BLUE SKY THROUGH THE AFTERNOON/EARLY EVENING WHICH
WILL ALLOW TEMPERATURES TO SLOWLY INCH UPWARD TO THE UPPER 70S TO
LOW 80S...THOUGH WITH MOIST SW FLOW EXPECT THESE LOWER CLOUDS TO
LINGER AROUND A BIT LONGER.

THE ACTIVE PATTERN CONTINUES ACROSS THE AREA FOR THE NEXT 24 HOURS.
SEVERAL UPPER LEVEL LOW PRESSURE SYSTEMS ARE NOTED IN AFTERNOON
WATER VAPOR IMAGERY. THE FIRST IS OVER THE NEBRASKA PANHANDLE...WITH
ASSOCIATED LEADING SHORTWAVE ENERGY TRIGGERING SOME SHOWERS AND T-
STORMS ACROSS IOWA...THEN THE BIGGER SHOWS TO THE SOUTH WITH THE
COMPLEX OF STRONG/SEVERE THUNDERSTORMS ASSOCIATED WITH A NEGATIVELY
TILTED TROUGH IN THE TEXAS. THE NORTHERN SHORTWAVE IS EXPECTED TO
CONTINUE DEVELOPING SHOWERS AND STORMS ACROSS IOWA AND INTO FAR
WESTERN ILLINOIS AND WISCONSIN. SOME OF THIS MAY CLIP OUR FAR
NORTHWESTERN COUNTIES...INCLUDING THE ROCKFORD AREA...BUT FEEL AT
THIS POINT THAT IT SHOULD LARGELY BE OFF FARTHER NW. HAVE HELD OFF
AND KEPT THIS ACTIVITY OUT OF AREA.

THEN TONIGHT THE LOWER LEVEL FRONTAL BOUNDARY ASSOCIATED WITH THE
NORTHERN WAVE WILL SAG SOUTHEAST TOWARD THE AREA LATE TONIGHT. MUCH
OF THE GUIDANCE THEN BRINGS THE SOUTHERN SHORTWAVE TOWARD OUR AREA
LATE TONIGHT AND MORE SO ON TUESDAY ON A DECENT UPPER LEVEL JET. THE
LARGE SUITE OF GUIDANCE KEEPS THESE TWO LOWS SEPARATE...ALLOWING
MUCH OF THE NORTHERN STREAM SHOWERS/STORMS TO LARGELY REMAIN OUT OF
AREA...BUT THEY MAY BEGIN TO AFFECT AREAS WEST OF I-39 IN ILLINOIS
OVERNIGHT.

TUESDAY MORNING IS WHEN BETTER CHANCES OF SHOWERS AND SCATTERED
THUNDERSTORMS WOULD BE. THIS MID MORNING/EARLY AFTERNOON PERIOD
FEATURES MODEST LOW/MID LEVEL ISENTROPIC LIFT/PW VALUES APPROACHING
1.5 INCHES AND THETA-E RIDGE NOSING IN FROM THE SOUTH. WE SHOULD
HAVE SOME SHOWERS AND THUNDERSTORMS MOVING FROM SOUTH TO NORTH
DURING THIS TIME FRAME.  DEPENDING ON THE INTERACTION OF THESE TWO
SYSTEMS AND IF THINGS SLOW DOWN A BIT...BETTER INSTABILITY WILL BE
TAPPED INTO IN THE AFTERNOON. THE NAM WOULD SUGGEST THIS
SOLUTION...WHILE THE GLOBAL GFS/ECMWF SUGGEST THE MID-MORNING TO
EARLY AFTERNOON PERIOD WOULD BE THE MOST LIKELY PERIOD WHERE DEEPER
MOISTURE IS AVAILABLE AND CO-LOCATED WITH THE UPPER FORCING.
CONFIDENCE ON TIMING IS ONLY MEDIUM WHICH REQUIRED CARRYING AN
EXTENDED PERIOD OF LIKELY POPS FOR MUCH OF THE DAY.

KMD

&&

.LONG TERM...
239 AM CDT

TUESDAY THROUGH SUNDAY...

TUESDAY THROUGH WEDNESDAY...
500MB TROUGH AXIS WILL SLOWLY PIVOT EAST ACROSS THE CENTRAL PLAINS
INTO THE MID-MISSOURI VALLEY TUE...WITH A SFC WAVE SLIDING NORTH
ACROSS IOWA INTO CENTRAL WISC LATE TUE. THE SFC FEATURE IS NOT
EXPECTED TO BE STRONG...HOWEVER THE GRADIENT DOES TIGHTEN WITH
MODEST HEIGHT FALLS IN THE LOWEST LAYERS OF THE ATMOSPHERE. SOME
INSTABILITY DOES REMAIN ALONG WITH RELATIVELY MOIST SFC CONDS AS
DEW PTS WILL REMAIN IN THE UPR 50S/LOW 60S. PWAT VALUES WILL ALSO
HOVER JUST OVER 1 INCH...WHICH IS SEASONAL. WILL HOLD ONTO MENTION
OF RAIN AND THUNDER...BUT COULD SEE THIS MAINLY FOCUSED IN THE TUE
MORNING TIMEFRAME.

WITH CONSIDERABLE SOLAR SHIELDING PROGGED FOR TUE...TEMPS MAY
STRUGGLE TO WARM BEYOND THE MID/UPR 70S. BUT WITH GUIDANCE HINTING
AT A DRY SLOT LIFTING NORTHEAST ACROSS THE REGION TUE EVE...THIS
COULD INTRODUCE SOME EROSION TO THE CLOUD COVER IN THE AFTN HOURS
TUE AND ALLOW SOME SFC HEATING TO OCCUR AND PUSH TEMPS TO ARND 80.

GUIDANCE LIFTS THE DRY SLOT OVERHEAD LATE TUE NGT...WITH THE 500MB
TROUGH AXIS ARRIVING ARND DAYBREAK WED AND LIFTING EAST ACROSS LOWER
MICHIGAN. THIS WILL BRING DRY ONLY SLIGHT CHANCE POPS AS WEAK SFC
RIDGING BEGINS TO NUDGE EAST ACROSS THE MISSOURI VALLEY TOWARDS THE
FORECAST AREA MIDDAY WED. IT IS POSSIBLE THAT ENOUGH DRY AIR
INFLUENCE COULD ALLOW FOR REMOVAL OF THE SLIGHT CHANCE POPS WED
AFTN. THERMAL TROUGH LAGS BEHIND THE FRONTAL BOUNDARY WED...SO TEMPS
COULD STILL WARM BACK TO ARND 80 AND PERHAPS THE LOW 80S IN THE
SOUTHERN CWFA.

THURSDAY THROUGH SUNDAY...
ANTI-CYCLONIC FLOW ARRIVES THUR WITH AT LEAST ONE PERIOD OF DRY
WEATHER EXPECTED FOR NORTHERN IL/NORTHWEST IN. ONLY A COUPLE
ENSEMBLE MEMBERS CONTINUE TO PROG POPS ALONG THE SOUTHERN FORECAST
AREA THUR...BUT COULD SEE THIS TRENDING DRY IN THE NEXT FEW
SOLUTIONS. WITH WARM TEMPS ALOFT EXPECTED THUR AND THIN CLOUD
COVER...THUR HIGHS COULD PEAK IN THE LOW 80S.

THEN FOCUS TURNS TOWARDS THE UPCOMING WEEKEND AND A PATTERN SHIFT
AWAY FROM THE WARM/HUMID CONDITIONS. ENSEMBLES SHOW MINIMAL SPREAD
IN THE LATE WEEK PERIODS...WITH THE UPSTREAM RIDGE OVER
ALASKA/WESTERN CANADA AND A DOWNSTREAM MID-LVL RIDGE ACROSS THE
SOUTHEAST CONUS. BOTH OF THESE FEATURES IN TIME BEGIN TO
WEAKEN...WITH THE LONGWAVE PATTERN TRANSITIONING INTO A SEMI-ZONAL
ORIENTATION BY THE SECOND HALF OF THE WEEKEND.

OPER GUIDANCE HAS BEEN CONSISTENT WITH PROGGING A ROBUST 500MB
TROUGH TO SLIDE SOUTH FROM CENTRAL CANADA FRI...ALONG WITH A STRONG
CANADIAN SFC RIDGE ON IT/S HEELS. WITH A CHANNEL OF MOISTURE
REMAINING ACROSS THE SOUTHERN PLAINS STRETCHING NORTHEAST THROUGH
THE UPPER MIDWEST...THIS BOUNDARY WILL BECOME ACTIVE WITH A SFC WAVE
DEVELOPING ACROSS THE SOUTHERN PLAINS. THIS LOW WILL THEN LIFT
NORTHEAST TOWARDS THE CWFA FRI WITH A COLD FRONT ARRIVING ACROSS THE
FORECAST AREA SAT. WINDS LOOK TO SHIFT TO THE NORTH...WITH MUCH
COOLER AIR SLIDING SOUTH AND LIKELY KNOCKING TEMPS BACK TO SUB-
SEASONAL CONDS IN THE UPR 60S/NEAR 70 DEGREE RANGE SAT/SUN. IF
NORTHEAST WINDS MATERIALIZE...NEXT WEEKEND AREAS ADJACENT TO LAKE
MICHIGAN ALONG THE IL/IN SHORELINE COULD BE LOCKED IN THE UPR 50S TO
LOW 60S FOR HIGHS WITH A COLD FLOW OFF OF LAKE MICHIGAN.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 20Z...

* GUSTY SOUTHWEST WINDS.

* MVFR CEILINGS POSSIBLE EARLY TUESDAY MORNING.

* SHOWERS LIKELY WITH PERIODIC THUNDERSTORMS LATE IN THE FORECAST
  PERIOD.

RODRIGUEZ

//DISCUSSION...UPDATED 18Z...

MUCH OF THE SHOWERS ARE EXITING THE AREA EARLY THIS AFTERNOON.
HOWEVER...AN ISOLATED LIGHT SHOWER WILL STILL BE POSSIBLE OVER THE
NEXT HOUR BEFORE PREVAILING DRY CONDITIONS ARE EXPECTED THIS
AFTERNOON AND TONIGHT. LINGERING MVFR CEILINGS WILL LIFT TO VFR
THROUGH 20-21Z THIS AFTERNOON WITH SKIES THEN SCATTERING THIS
EVENING...AS THE SOUTHWEST WINDS/GUSTS DIMINISH INTO THE EVENING.
WITH FAIRLY MOIST CONDITIONS REMAINING IN PLACE TONIGHT INTO
TUESDAY...REDEVELOPING LOW CEILINGS DO APPEAR TO BE A POSSIBILITY.
OVERALL CONFIDENCE IS LOWER DURING THIS PERIOD...BUT DID MAKE
MENTION OF AT LEAST MVFR CEILINGS...AND WILL NEED TO MONITOR FOR
POTENTIALLY LOWER CEILINGS. HAVE PUSHED BACK TIMING OF PRECIP LATE
IN THE PERIOD...BUT WITH INSTABILITY AND FORCING
INCREASING...SHOWERS AND THUNDERSTORMS DO APPEAR LIKELY TUESDAY.
STILL SOME UNCERTAINTY WITH EXACT TIMING AND DURATION...AND EVEN
THE POSSIBILITY FOR AN ADDITIONAL PERIOD OF THUNDERSTORMS TUESDAY
AFTERNOON.

RODRIGUEZ

//ORD AND MDW CONFIDENCE...UPDATED 20Z...

* HIGH CONFIDENCE WITH WIND SPEED/DIRECTION.

* MEDIUM HIGH CONFIDENCE WITH CEILINGS.

* HIGH CONFIDENCE OF SHOWERS/THUNDERSTORMS...MEDIUM CONFIDENCE
  WITH TIMING/DURATION.

RODRIGUEZ

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/TSRA LATE. SOUTHEAST WINDS.

FRIDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. SOUTHWEST WINDS
BECOMING NORTHEAST OVERNIGHT.

SATURDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. NORTHEAST
WINDS.

SUNDAY...CHANCE TSRA. MVFR POSSIBLE. NORTHEAST WINDS.

KREIN

&&

.MARINE...
304 AM CDT

LOW PRESSURE WILL BE STEADILY LIFTING NORTH ACROSS THE MISSOURI
VALLEY THIS MORNING...REACHING LAKE SUPERIOR BY THIS EVENING AND
CONTINUING TO SLIDE EAST/NORTHEAST TOWARDS QUEBEC BY TUESDAY
MORNING. A FRONTAL BOUNDARY WILL REMAIN OVER THE FAR NORTHERN
PORTIONS OF LAKE MICHIGAN. MEANWHILE GUSTY SOUTHERLY WINDS ARE
EXPECTED TO INCREASE THIS MORNING...WITH OCCASIONAL GALES FOR THE
NEARSHORE WATERS OF IL/IN. ACROSS THE OPEN WATERS...EXPECT THE
WARM/MOIST AIR TO STRUGGLE TO REACH THE SFC OF THE LAKE WITH SOME
DEGREE OF LAKE STABILITY. WAVES WILL STEADILY BUILD ACROSS THE
NORTHERN HALF OF THE LAKE AS A RESULT OF THE LONG FETCH. STILL
FEEL THAT GUSTS WILL REACH 30KT ACROSS THE LAKE...HOWEVER
CONFIDENCE HAS DIMINISHED SLIGHTLY AS NEW GUIDANCE HAS BECOME A
LITTLE LESS WITH THE WIND FIELDS. NONETHELESS...WAVES FOR THE
NORTHERN HALF OF THE LAKE WILL LIKELY TOP OUT IN THE 4 TO 7 FT
RANGE WITH OCCASIONAL WAVES REACHING 9 FT THIS AFTERNOON/EVENING.

THE GRADIENT QUICKLY DIMINISHES THIS EVENING...BUT EXPECT
SOUTHERLY WINDS TO PERSIST. THIS WILL ALLOW WAVES TO SUBSIDE TO 3
TO 5 FT. ANOTHER LOW WILL ARRIVE TUE...WITH WINDS NUDGING BACK UP
HOWEVER WARM AIR WILL CONTINUE TO FLOW ACROSS THE LAKE AND COULD
FURTHER ENHANCE THE LAKE STABILITY AND KEEP WAVES FROM BUILDING TO
LARGE.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...NEARSHORE WATERS UNTIL 3
     PM MONDAY.

     SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 252001 CCA
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
256 PM CDT MON MAY 25 2015


.SHORT TERM...
255 PM CDT

THROUGH TUESDAY...

SHOWERS CONTINUE TO DIMINISH AS WE GET ON THE SUBSIDENT SIDE OF THE
DEPARTING UPPER TROUGH AXIS THAT WILL QUICKLY EXIT TO THE NORTHEAST
TONIGHT. SURFACE LOW PRESSURE IS PUSHING INTO UPPER MICHIGAN WHILE
LEAVING MODEST PRESSURE RISES IN ITS WAKE. WIND GUSTS TO 30 TO
LOCALLY 35 MPH WILL CONTINUE THROUGH THE AFTERNOON. EXPECT TO SEE
ALITTLE MORE BLUE SKY THROUGH THE AFTERNOON/EARLY EVENING WHICH
WILL ALLOW TEMPERATURES TO SLOWLY INCH UPWARD TO THE UPPER 70S TO
LOW 80S...THOUGH WITH MOIST SW FLOW EXPECT THESE LOWER CLOUDS TO
LINGER AROUND A BIT LONGER.

THE ACTIVE PATTERN CONTINUES ACROSS THE AREA FOR THE NEXT 24 HOURS.
SEVERAL UPPER LEVEL LOW PRESSURE SYSTEMS ARE NOTED IN AFTERNOON
WATER VAPOR IMAGERY. THE FIRST IS OVER THE NEBRASKA PANHANDLE...WITH
ASSOCIATED LEADING SHORTWAVE ENERGY TRIGGERING SOME SHOWERS AND T-
STORMS ACROSS IOWA...THEN THE BIGGER SHOWS TO THE SOUTH WITH THE
COMPLEX OF STRONG/SEVERE THUNDERSTORMS ASSOCIATED WITH A NEGATIVELY
TILTED TROUGH IN THE TEXAS. THE NORTHERN SHORTWAVE IS EXPECTED TO
CONTINUE DEVELOPING SHOWERS AND STORMS ACROSS IOWA AND INTO FAR
WESTERN ILLINOIS AND WISCONSIN. SOME OF THIS MAY CLIP OUR FAR
NORTHWESTERN COUNTIES...INCLUDING THE ROCKFORD AREA...BUT FEEL AT
THIS POINT THAT IT SHOULD LARGELY BE OFF FARTHER NW. HAVE HELD OFF
AND KEPT THIS ACTIVITY OUT OF AREA.

THEN TONIGHT THE LOWER LEVEL FRONTAL BOUNDARY ASSOCIATED WITH THE
NORTHERN WAVE WILL SAG SOUTHEAST TOWARD THE AREA LATE TONIGHT. MUCH
OF THE GUIDANCE THEN BRINGS THE SOUTHERN SHORTWAVE TOWARD OUR AREA
LATE TONIGHT AND MORE SO ON TUESDAY ON A DECENT UPPER LEVEL JET. THE
LARGE SUITE OF GUIDANCE KEEPS THESE TWO LOWS SEPARATE...ALLOWING
MUCH OF THE NORTHERN STREAM SHOWERS/STORMS TO LARGELY REMAIN OUT OF
AREA...BUT THEY MAY BEGIN TO AFFECT AREAS WEST OF I-39 IN ILLINOIS
OVERNIGHT.

TUESDAY MORNING IS WHEN BETTER CHANCES OF SHOWERS AND SCATTERED
THUNDERSTORMS WOULD BE. THIS MID MORNING/EARLY AFTERNOON PERIOD
FEATURES MODEST LOW/MID LEVEL ISENTROPIC LIFT/PW VALUES APPROACHING
1.5 INCHES AND THETA-E RIDGE NOSING IN FROM THE SOUTH. WE SHOULD
HAVE SOME SHOWERS AND THUNDERSTORMS MOVING FROM SOUTH TO NORTH
DURING THIS TIME FRAME.  DEPENDING ON THE INTERACTION OF THESE TWO
SYSTEMS AND IF THINGS SLOW DOWN A BIT...BETTER INSTABILITY WILL BE
TAPPED INTO IN THE AFTERNOON. THE NAM WOULD SUGGEST THIS
SOLUTION...WHILE THE GLOBAL GFS/ECMWF SUGGEST THE MID-MORNING TO
EARLY AFTERNOON PERIOD WOULD BE THE MOST LIKELY PERIOD WHERE DEEPER
MOISTURE IS AVAILABLE AND CO-LOCATED WITH THE UPPER FORCING.
CONFIDENCE ON TIMING IS ONLY MEDIUM WHICH REQUIRED CARRYING AN
EXTENDED PERIOD OF LIKELY POPS FOR MUCH OF THE DAY.

KMD

&&

.LONG TERM...
239 AM CDT

TUESDAY THROUGH SUNDAY...

TUESDAY THROUGH WEDNESDAY...
500MB TROUGH AXIS WILL SLOWLY PIVOT EAST ACROSS THE CENTRAL PLAINS
INTO THE MID-MISSOURI VALLEY TUE...WITH A SFC WAVE SLIDING NORTH
ACROSS IOWA INTO CENTRAL WISC LATE TUE. THE SFC FEATURE IS NOT
EXPECTED TO BE STRONG...HOWEVER THE GRADIENT DOES TIGHTEN WITH
MODEST HEIGHT FALLS IN THE LOWEST LAYERS OF THE ATMOSPHERE. SOME
INSTABILITY DOES REMAIN ALONG WITH RELATIVELY MOIST SFC CONDS AS
DEW PTS WILL REMAIN IN THE UPR 50S/LOW 60S. PWAT VALUES WILL ALSO
HOVER JUST OVER 1 INCH...WHICH IS SEASONAL. WILL HOLD ONTO MENTION
OF RAIN AND THUNDER...BUT COULD SEE THIS MAINLY FOCUSED IN THE TUE
MORNING TIMEFRAME.

WITH CONSIDERABLE SOLAR SHIELDING PROGGED FOR TUE...TEMPS MAY
STRUGGLE TO WARM BEYOND THE MID/UPR 70S. BUT WITH GUIDANCE HINTING
AT A DRY SLOT LIFTING NORTHEAST ACROSS THE REGION TUE EVE...THIS
COULD INTRODUCE SOME EROSION TO THE CLOUD COVER IN THE AFTN HOURS
TUE AND ALLOW SOME SFC HEATING TO OCCUR AND PUSH TEMPS TO ARND 80.

GUIDANCE LIFTS THE DRY SLOT OVERHEAD LATE TUE NGT...WITH THE 500MB
TROUGH AXIS ARRIVING ARND DAYBREAK WED AND LIFTING EAST ACROSS LOWER
MICHIGAN. THIS WILL BRING DRY ONLY SLIGHT CHANCE POPS AS WEAK SFC
RIDGING BEGINS TO NUDGE EAST ACROSS THE MISSOURI VALLEY TOWARDS THE
FORECAST AREA MIDDAY WED. IT IS POSSIBLE THAT ENOUGH DRY AIR
INFLUENCE COULD ALLOW FOR REMOVAL OF THE SLIGHT CHANCE POPS WED
AFTN. THERMAL TROUGH LAGS BEHIND THE FRONTAL BOUNDARY WED...SO TEMPS
COULD STILL WARM BACK TO ARND 80 AND PERHAPS THE LOW 80S IN THE
SOUTHERN CWFA.

THURSDAY THROUGH SUNDAY...
ANTI-CYCLONIC FLOW ARRIVES THUR WITH AT LEAST ONE PERIOD OF DRY
WEATHER EXPECTED FOR NORTHERN IL/NORTHWEST IN. ONLY A COUPLE
ENSEMBLE MEMBERS CONTINUE TO PROG POPS ALONG THE SOUTHERN FORECAST
AREA THUR...BUT COULD SEE THIS TRENDING DRY IN THE NEXT FEW
SOLUTIONS. WITH WARM TEMPS ALOFT EXPECTED THUR AND THIN CLOUD
COVER...THUR HIGHS COULD PEAK IN THE LOW 80S.

THEN FOCUS TURNS TOWARDS THE UPCOMING WEEKEND AND A PATTERN SHIFT
AWAY FROM THE WARM/HUMID CONDITIONS. ENSEMBLES SHOW MINIMAL SPREAD
IN THE LATE WEEK PERIODS...WITH THE UPSTREAM RIDGE OVER
ALASKA/WESTERN CANADA AND A DOWNSTREAM MID-LVL RIDGE ACROSS THE
SOUTHEAST CONUS. BOTH OF THESE FEATURES IN TIME BEGIN TO
WEAKEN...WITH THE LONGWAVE PATTERN TRANSITIONING INTO A SEMI-ZONAL
ORIENTATION BY THE SECOND HALF OF THE WEEKEND.

OPER GUIDANCE HAS BEEN CONSISTENT WITH PROGGING A ROBUST 500MB
TROUGH TO SLIDE SOUTH FROM CENTRAL CANADA FRI...ALONG WITH A STRONG
CANADIAN SFC RIDGE ON IT/S HEELS. WITH A CHANNEL OF MOISTURE
REMAINING ACROSS THE SOUTHERN PLAINS STRETCHING NORTHEAST THROUGH
THE UPPER MIDWEST...THIS BOUNDARY WILL BECOME ACTIVE WITH A SFC WAVE
DEVELOPING ACROSS THE SOUTHERN PLAINS. THIS LOW WILL THEN LIFT
NORTHEAST TOWARDS THE CWFA FRI WITH A COLD FRONT ARRIVING ACROSS THE
FORECAST AREA SAT. WINDS LOOK TO SHIFT TO THE NORTH...WITH MUCH
COOLER AIR SLIDING SOUTH AND LIKELY KNOCKING TEMPS BACK TO SUB-
SEASONAL CONDS IN THE UPR 60S/NEAR 70 DEGREE RANGE SAT/SUN. IF
NORTHEAST WINDS MATERIALIZE...NEXT WEEKEND AREAS ADJACENT TO LAKE
MICHIGAN ALONG THE IL/IN SHORELINE COULD BE LOCKED IN THE UPR 50S TO
LOW 60S FOR HIGHS WITH A COLD FLOW OFF OF LAKE MICHIGAN.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 20Z...

* GUSTY SOUTHWEST WINDS.

* MVFR CEILINGS POSSIBLE EARLY TUESDAY MORNING.

* SHOWERS LIKELY WITH PERIODIC THUNDERSTORMS LATE IN THE FORECAST
  PERIOD.

RODRIGUEZ

//DISCUSSION...UPDATED 18Z...

MUCH OF THE SHOWERS ARE EXITING THE AREA EARLY THIS AFTERNOON.
HOWEVER...AN ISOLATED LIGHT SHOWER WILL STILL BE POSSIBLE OVER THE
NEXT HOUR BEFORE PREVAILING DRY CONDITIONS ARE EXPECTED THIS
AFTERNOON AND TONIGHT. LINGERING MVFR CEILINGS WILL LIFT TO VFR
THROUGH 20-21Z THIS AFTERNOON WITH SKIES THEN SCATTERING THIS
EVENING...AS THE SOUTHWEST WINDS/GUSTS DIMINISH INTO THE EVENING.
WITH FAIRLY MOIST CONDITIONS REMAINING IN PLACE TONIGHT INTO
TUESDAY...REDEVELOPING LOW CEILINGS DO APPEAR TO BE A POSSIBILITY.
OVERALL CONFIDENCE IS LOWER DURING THIS PERIOD...BUT DID MAKE
MENTION OF AT LEAST MVFR CEILINGS...AND WILL NEED TO MONITOR FOR
POTENTIALLY LOWER CEILINGS. HAVE PUSHED BACK TIMING OF PRECIP LATE
IN THE PERIOD...BUT WITH INSTABILITY AND FORCING
INCREASING...SHOWERS AND THUNDERSTORMS DO APPEAR LIKELY TUESDAY.
STILL SOME UNCERTAINTY WITH EXACT TIMING AND DURATION...AND EVEN
THE POSSIBILITY FOR AN ADDITIONAL PERIOD OF THUNDERSTORMS TUESDAY
AFTERNOON.

RODRIGUEZ

//ORD AND MDW CONFIDENCE...UPDATED 20Z...

* HIGH CONFIDENCE WITH WIND SPEED/DIRECTION.

* MEDIUM HIGH CONFIDENCE WITH CEILINGS.

* HIGH CONFIDENCE OF SHOWERS/THUNDERSTORMS...MEDIUM CONFIDENCE
  WITH TIMING/DURATION.

RODRIGUEZ

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/TSRA LATE. SOUTHEAST WINDS.

FRIDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. SOUTHWEST WINDS
BECOMING NORTHEAST OVERNIGHT.

SATURDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. NORTHEAST
WINDS.

SUNDAY...CHANCE TSRA. MVFR POSSIBLE. NORTHEAST WINDS.

KREIN

&&

.MARINE...
304 AM CDT

LOW PRESSURE WILL BE STEADILY LIFTING NORTH ACROSS THE MISSOURI
VALLEY THIS MORNING...REACHING LAKE SUPERIOR BY THIS EVENING AND
CONTINUING TO SLIDE EAST/NORTHEAST TOWARDS QUEBEC BY TUESDAY
MORNING. A FRONTAL BOUNDARY WILL REMAIN OVER THE FAR NORTHERN
PORTIONS OF LAKE MICHIGAN. MEANWHILE GUSTY SOUTHERLY WINDS ARE
EXPECTED TO INCREASE THIS MORNING...WITH OCCASIONAL GALES FOR THE
NEARSHORE WATERS OF IL/IN. ACROSS THE OPEN WATERS...EXPECT THE
WARM/MOIST AIR TO STRUGGLE TO REACH THE SFC OF THE LAKE WITH SOME
DEGREE OF LAKE STABILITY. WAVES WILL STEADILY BUILD ACROSS THE
NORTHERN HALF OF THE LAKE AS A RESULT OF THE LONG FETCH. STILL
FEEL THAT GUSTS WILL REACH 30KT ACROSS THE LAKE...HOWEVER
CONFIDENCE HAS DIMINISHED SLIGHTLY AS NEW GUIDANCE HAS BECOME A
LITTLE LESS WITH THE WIND FIELDS. NONETHELESS...WAVES FOR THE
NORTHERN HALF OF THE LAKE WILL LIKELY TOP OUT IN THE 4 TO 7 FT
RANGE WITH OCCASIONAL WAVES REACHING 9 FT THIS AFTERNOON/EVENING.

THE GRADIENT QUICKLY DIMINISHES THIS EVENING...BUT EXPECT
SOUTHERLY WINDS TO PERSIST. THIS WILL ALLOW WAVES TO SUBSIDE TO 3
TO 5 FT. ANOTHER LOW WILL ARRIVE TUE...WITH WINDS NUDGING BACK UP
HOWEVER WARM AIR WILL CONTINUE TO FLOW ACROSS THE LAKE AND COULD
FURTHER ENHANCE THE LAKE STABILITY AND KEEP WAVES FROM BUILDING TO
LARGE.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...NEARSHORE WATERS UNTIL 3
     PM MONDAY.

     SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
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WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KILX 252000
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
300 PM CDT MON MAY 25 2015

.SHORT TERM...(TONIGHT)
ISSUED AT 259 PM CDT MON MAY 25 2015

LOWER CLOUDS ARE LIFTING AND BREAKING UP ACROSS THE EAST HALF OF THE
FORECAST AREA THIS AFTERNOON...BUT EXTENSIVE CIRRUS SHIELD KEEPING
SKIES PARTLY SUNNY AT BEST THERE. THE WESTERN CWA HAS HAD SOME
DIURNAL CUMULUS AS IT IS OUTSIDE THE CIRRUS SHIELD...BUT THIS SHOULD
FADE LATER THIS AFTERNOON AS SOME SUBSIDENCE OCCURS ACROSS THAT
AREA. SKIES WILL BE PARTLY CLOUDY FOR A TIME THIS EVENING...BUT THEN
CLOUD UP AGAIN LATER AS SOME OF THE CONVECTIVE BLOWOFF ARRIVES FROM
THE SEVERE ACTIVITY CURRENTLY ACROSS THE SOUTHERN PLAINS. LATEST
HIGH-RESOLUTION MODELS KEEP THE FORECAST AREA DRY THIS EVENING WITH
SEVERAL SUGGESTING PERHAPS TAKING UNTIL EVEN 3-4 AM BEFORE WE SEE
ANY SHOWERS AND STORMS MOVE BACK IN. HOWEVER...I HAVE RAMPED UP THE
POP`S QUICKLY AFTER MIDNIGHT ACROSS THE WEST AND AFTER 3 AM IN THE
EAST. WITH SOUTHERLY WINDS STAYING UP AROUND 10 MPH OR SO...LITTLE
CHANGE NEEDED TO THE OVERNIGHT LOWS...WHICH SHOULD BE IN THE 66-68
DEGREE RANGE.

&&

.LONG TERM...(TUESDAY THROUGH MONDAY)
ISSUED AT 259 PM CDT MON MAY 25 2015

SHORT WAVE NEAR THE RED RIVER ALONG THE WESTERN TX/OK BORDER TO
EJECT NE INTO IL ON TUE LIKELY BRINGING SHOWERS AND THUNDERSTORMS
MOST OF THE DAY. HAVE INCREASING LOW LEVEL JET AHEAD OF THIS FEATURE
LATER TONIGHT THAT WILL INCREASE CHANCES OF SHOWERS AND
THUNDERSTORMS FROM SW TO NE. SHOWERS AND THUNDERSTORMS WILL BECOME
MORE WIDELY SCATTERED SW AREAS LATER TUE AFTERNOON AND OVER REST OF
CENTRAL/EASTERN IL TUE EVENING. SPC SHIFTED SLIGHT RISK SOUTHEAST OF
IL ON TUE AND NOW MAINLY OVER KY/TN/MS/AL WHERE BETTER INSTABILITY
WILL BE PRESENT. STILL HAVE A MARGINAL RISK OF SEVERE STORMS TUE
AFTERNOON FROM SHELBYVILLE TO DANVILLE SE FOR HAIL AND GUSTY WINDS.
HIGHS IN THE UPPER 70S TUE WITH LAWRENCEVILLE NEAR 80F WITH
DEWPOINTS IN THE MID TO UPPER 60S (HIGHEST IN SE IL).

RATHER WARM AND HUMID WEATHER PATTERN LOOKS TO CONTINUE ACROSS IL
DURING THE REST OF THE WEEK WITH DAILY CHANCE OF SHOWERS AND
THUNDERSTORMS. BETWEEN 1.5 AND 2 INCHES OF RAIN IS EXPECTED OVER
AREA THE REST OF THIS WEEK. CHANCE OF SHOWERS AND THUNDERSTORMS
LOOK HIGHER IN SOUTHEAST IL ON WED WITH JUST SLIGHT CHANCE NW OF
THE IL RIVER BY GALESBURG AS MORE SHORT WAVE ENERGY EJECT NE INTO
THE MID MS AND OHIO RIVER VALLEY. SPC HAS MARGINAL RISK OF SEVERE
STORMS WED AFTERNOON MAINLY SOUTH OF I-72. LOWS TONIGHT MOSTLY IN
THE MID 60S WITH SOME LOWER 60S NW OF THE IL RIVER. HIGHS WED IN
THE LOWER 80S AND DEWPOINTS IN THE LOW TO MID 60S.

UPPER LEVEL RIDGE BUILDING A BIT OVER THE EASTERN STATES WED NIGHT
AND THU SO CONVECTION CHANCES LOOK MORE WIDELY SCATTERED OVER
CENTRAL AND SOUTHEAST IL. AREAS FROM I-72 NORTH LOOK DRIER DURING
THIS TIME FRAME CLOSER TO WEAK HIGH PRESSURE DRIFTING OVER THE GREAT
LAKES. HIGHS THU IN THE LOW TO MID 80S WITH MORE SUNSHINE POSSIBLE
AND MID 80S ON FRIDAY.

CHANCES OF SHOWERS AND THUNDERSTORMS INCREASE AGAIN FRI/SAT WITH A
FRONTAL BOUNDARY PUSHING SE ACROSS CENTRAL IL SATURDAY AND SAT
NIGHT. TEMPERATURES TO COOL BEHIND THIS FRONT DURING THE WEEKEND
INTO EARLY NEXT WEEK WITH HIGHS IN THE LOW TO MID 70S SUNDAY. A
CUTOFF UPPER LEVEL LOW EJECTING FROM THE ROCKIES INTO TEH CENTRAL
PLAINS BY EARLY NEXT WEEK TO CONTINUE CHANCES OF SHOWERS AND A FEW
THUNDERSTORMS.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z TUESDAY AFTERNOON)
ISSUED AT 1244 PM CDT MON MAY 25 2015

LINGERING MVFR CEILINGS ARE LIFTING AND ALL SITES SHOULD BE VFR BY
18-19Z. THE STRONGEST OF THE SOUTHWEST WINDS HAVE SHIFTED AWAY
FROM KCMI...BUT WINDS THERE SHOULD STILL GUST TO AROUND 30 KNOTS
OR SO FOR A FEW MORE HOURS. THE REMAINING TAF SITES WILL HAVE
GUSTS MORE IN THE 25 KNOT RANGE...BUT THESE SHOULD SUBSIDE TOWARD
00Z. NEXT PERIOD FOR CONVECTIVE CONCERN APPEARS TO START AROUND
08-09Z WITH STORMS TRACKING IN FROM THE SOUTHWEST. HIGH-RESOLUTION
MODELS SUGGEST SOME BREAKS IN BETWEEN STORMS TUESDAY MORNING...SO
WILL GO WITH VCTS MENTION LATE IN THE PERIOD. TAIL END OF THE RAP
MODEL SUGGESTS SOME MVFR CEILINGS DEVELOPING LATE TONIGHT IN
SOUTHERN ILLINOIS AND BUILDING NORTHWARD...AND HAVE ADDED THESE
FOR KBMI/KDEC/KCMI.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.

&&

$$

SHORT TERM...GEELHART
LONG TERM...07
AVIATION...GEELHART



000
FXUS63 KILX 252000
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
300 PM CDT MON MAY 25 2015

.SHORT TERM...(TONIGHT)
ISSUED AT 259 PM CDT MON MAY 25 2015

LOWER CLOUDS ARE LIFTING AND BREAKING UP ACROSS THE EAST HALF OF THE
FORECAST AREA THIS AFTERNOON...BUT EXTENSIVE CIRRUS SHIELD KEEPING
SKIES PARTLY SUNNY AT BEST THERE. THE WESTERN CWA HAS HAD SOME
DIURNAL CUMULUS AS IT IS OUTSIDE THE CIRRUS SHIELD...BUT THIS SHOULD
FADE LATER THIS AFTERNOON AS SOME SUBSIDENCE OCCURS ACROSS THAT
AREA. SKIES WILL BE PARTLY CLOUDY FOR A TIME THIS EVENING...BUT THEN
CLOUD UP AGAIN LATER AS SOME OF THE CONVECTIVE BLOWOFF ARRIVES FROM
THE SEVERE ACTIVITY CURRENTLY ACROSS THE SOUTHERN PLAINS. LATEST
HIGH-RESOLUTION MODELS KEEP THE FORECAST AREA DRY THIS EVENING WITH
SEVERAL SUGGESTING PERHAPS TAKING UNTIL EVEN 3-4 AM BEFORE WE SEE
ANY SHOWERS AND STORMS MOVE BACK IN. HOWEVER...I HAVE RAMPED UP THE
POP`S QUICKLY AFTER MIDNIGHT ACROSS THE WEST AND AFTER 3 AM IN THE
EAST. WITH SOUTHERLY WINDS STAYING UP AROUND 10 MPH OR SO...LITTLE
CHANGE NEEDED TO THE OVERNIGHT LOWS...WHICH SHOULD BE IN THE 66-68
DEGREE RANGE.

&&

.LONG TERM...(TUESDAY THROUGH MONDAY)
ISSUED AT 259 PM CDT MON MAY 25 2015

SHORT WAVE NEAR THE RED RIVER ALONG THE WESTERN TX/OK BORDER TO
EJECT NE INTO IL ON TUE LIKELY BRINGING SHOWERS AND THUNDERSTORMS
MOST OF THE DAY. HAVE INCREASING LOW LEVEL JET AHEAD OF THIS FEATURE
LATER TONIGHT THAT WILL INCREASE CHANCES OF SHOWERS AND
THUNDERSTORMS FROM SW TO NE. SHOWERS AND THUNDERSTORMS WILL BECOME
MORE WIDELY SCATTERED SW AREAS LATER TUE AFTERNOON AND OVER REST OF
CENTRAL/EASTERN IL TUE EVENING. SPC SHIFTED SLIGHT RISK SOUTHEAST OF
IL ON TUE AND NOW MAINLY OVER KY/TN/MS/AL WHERE BETTER INSTABILITY
WILL BE PRESENT. STILL HAVE A MARGINAL RISK OF SEVERE STORMS TUE
AFTERNOON FROM SHELBYVILLE TO DANVILLE SE FOR HAIL AND GUSTY WINDS.
HIGHS IN THE UPPER 70S TUE WITH LAWRENCEVILLE NEAR 80F WITH
DEWPOINTS IN THE MID TO UPPER 60S (HIGHEST IN SE IL).

RATHER WARM AND HUMID WEATHER PATTERN LOOKS TO CONTINUE ACROSS IL
DURING THE REST OF THE WEEK WITH DAILY CHANCE OF SHOWERS AND
THUNDERSTORMS. BETWEEN 1.5 AND 2 INCHES OF RAIN IS EXPECTED OVER
AREA THE REST OF THIS WEEK. CHANCE OF SHOWERS AND THUNDERSTORMS
LOOK HIGHER IN SOUTHEAST IL ON WED WITH JUST SLIGHT CHANCE NW OF
THE IL RIVER BY GALESBURG AS MORE SHORT WAVE ENERGY EJECT NE INTO
THE MID MS AND OHIO RIVER VALLEY. SPC HAS MARGINAL RISK OF SEVERE
STORMS WED AFTERNOON MAINLY SOUTH OF I-72. LOWS TONIGHT MOSTLY IN
THE MID 60S WITH SOME LOWER 60S NW OF THE IL RIVER. HIGHS WED IN
THE LOWER 80S AND DEWPOINTS IN THE LOW TO MID 60S.

UPPER LEVEL RIDGE BUILDING A BIT OVER THE EASTERN STATES WED NIGHT
AND THU SO CONVECTION CHANCES LOOK MORE WIDELY SCATTERED OVER
CENTRAL AND SOUTHEAST IL. AREAS FROM I-72 NORTH LOOK DRIER DURING
THIS TIME FRAME CLOSER TO WEAK HIGH PRESSURE DRIFTING OVER THE GREAT
LAKES. HIGHS THU IN THE LOW TO MID 80S WITH MORE SUNSHINE POSSIBLE
AND MID 80S ON FRIDAY.

CHANCES OF SHOWERS AND THUNDERSTORMS INCREASE AGAIN FRI/SAT WITH A
FRONTAL BOUNDARY PUSHING SE ACROSS CENTRAL IL SATURDAY AND SAT
NIGHT. TEMPERATURES TO COOL BEHIND THIS FRONT DURING THE WEEKEND
INTO EARLY NEXT WEEK WITH HIGHS IN THE LOW TO MID 70S SUNDAY. A
CUTOFF UPPER LEVEL LOW EJECTING FROM THE ROCKIES INTO TEH CENTRAL
PLAINS BY EARLY NEXT WEEK TO CONTINUE CHANCES OF SHOWERS AND A FEW
THUNDERSTORMS.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z TUESDAY AFTERNOON)
ISSUED AT 1244 PM CDT MON MAY 25 2015

LINGERING MVFR CEILINGS ARE LIFTING AND ALL SITES SHOULD BE VFR BY
18-19Z. THE STRONGEST OF THE SOUTHWEST WINDS HAVE SHIFTED AWAY
FROM KCMI...BUT WINDS THERE SHOULD STILL GUST TO AROUND 30 KNOTS
OR SO FOR A FEW MORE HOURS. THE REMAINING TAF SITES WILL HAVE
GUSTS MORE IN THE 25 KNOT RANGE...BUT THESE SHOULD SUBSIDE TOWARD
00Z. NEXT PERIOD FOR CONVECTIVE CONCERN APPEARS TO START AROUND
08-09Z WITH STORMS TRACKING IN FROM THE SOUTHWEST. HIGH-RESOLUTION
MODELS SUGGEST SOME BREAKS IN BETWEEN STORMS TUESDAY MORNING...SO
WILL GO WITH VCTS MENTION LATE IN THE PERIOD. TAIL END OF THE RAP
MODEL SUGGESTS SOME MVFR CEILINGS DEVELOPING LATE TONIGHT IN
SOUTHERN ILLINOIS AND BUILDING NORTHWARD...AND HAVE ADDED THESE
FOR KBMI/KDEC/KCMI.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.

&&

$$

SHORT TERM...GEELHART
LONG TERM...07
AVIATION...GEELHART



000
FXUS63 KILX 252000
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
300 PM CDT MON MAY 25 2015

.SHORT TERM...(TONIGHT)
ISSUED AT 259 PM CDT MON MAY 25 2015

LOWER CLOUDS ARE LIFTING AND BREAKING UP ACROSS THE EAST HALF OF THE
FORECAST AREA THIS AFTERNOON...BUT EXTENSIVE CIRRUS SHIELD KEEPING
SKIES PARTLY SUNNY AT BEST THERE. THE WESTERN CWA HAS HAD SOME
DIURNAL CUMULUS AS IT IS OUTSIDE THE CIRRUS SHIELD...BUT THIS SHOULD
FADE LATER THIS AFTERNOON AS SOME SUBSIDENCE OCCURS ACROSS THAT
AREA. SKIES WILL BE PARTLY CLOUDY FOR A TIME THIS EVENING...BUT THEN
CLOUD UP AGAIN LATER AS SOME OF THE CONVECTIVE BLOWOFF ARRIVES FROM
THE SEVERE ACTIVITY CURRENTLY ACROSS THE SOUTHERN PLAINS. LATEST
HIGH-RESOLUTION MODELS KEEP THE FORECAST AREA DRY THIS EVENING WITH
SEVERAL SUGGESTING PERHAPS TAKING UNTIL EVEN 3-4 AM BEFORE WE SEE
ANY SHOWERS AND STORMS MOVE BACK IN. HOWEVER...I HAVE RAMPED UP THE
POP`S QUICKLY AFTER MIDNIGHT ACROSS THE WEST AND AFTER 3 AM IN THE
EAST. WITH SOUTHERLY WINDS STAYING UP AROUND 10 MPH OR SO...LITTLE
CHANGE NEEDED TO THE OVERNIGHT LOWS...WHICH SHOULD BE IN THE 66-68
DEGREE RANGE.

&&

.LONG TERM...(TUESDAY THROUGH MONDAY)
ISSUED AT 259 PM CDT MON MAY 25 2015

SHORT WAVE NEAR THE RED RIVER ALONG THE WESTERN TX/OK BORDER TO
EJECT NE INTO IL ON TUE LIKELY BRINGING SHOWERS AND THUNDERSTORMS
MOST OF THE DAY. HAVE INCREASING LOW LEVEL JET AHEAD OF THIS FEATURE
LATER TONIGHT THAT WILL INCREASE CHANCES OF SHOWERS AND
THUNDERSTORMS FROM SW TO NE. SHOWERS AND THUNDERSTORMS WILL BECOME
MORE WIDELY SCATTERED SW AREAS LATER TUE AFTERNOON AND OVER REST OF
CENTRAL/EASTERN IL TUE EVENING. SPC SHIFTED SLIGHT RISK SOUTHEAST OF
IL ON TUE AND NOW MAINLY OVER KY/TN/MS/AL WHERE BETTER INSTABILITY
WILL BE PRESENT. STILL HAVE A MARGINAL RISK OF SEVERE STORMS TUE
AFTERNOON FROM SHELBYVILLE TO DANVILLE SE FOR HAIL AND GUSTY WINDS.
HIGHS IN THE UPPER 70S TUE WITH LAWRENCEVILLE NEAR 80F WITH
DEWPOINTS IN THE MID TO UPPER 60S (HIGHEST IN SE IL).

RATHER WARM AND HUMID WEATHER PATTERN LOOKS TO CONTINUE ACROSS IL
DURING THE REST OF THE WEEK WITH DAILY CHANCE OF SHOWERS AND
THUNDERSTORMS. BETWEEN 1.5 AND 2 INCHES OF RAIN IS EXPECTED OVER
AREA THE REST OF THIS WEEK. CHANCE OF SHOWERS AND THUNDERSTORMS
LOOK HIGHER IN SOUTHEAST IL ON WED WITH JUST SLIGHT CHANCE NW OF
THE IL RIVER BY GALESBURG AS MORE SHORT WAVE ENERGY EJECT NE INTO
THE MID MS AND OHIO RIVER VALLEY. SPC HAS MARGINAL RISK OF SEVERE
STORMS WED AFTERNOON MAINLY SOUTH OF I-72. LOWS TONIGHT MOSTLY IN
THE MID 60S WITH SOME LOWER 60S NW OF THE IL RIVER. HIGHS WED IN
THE LOWER 80S AND DEWPOINTS IN THE LOW TO MID 60S.

UPPER LEVEL RIDGE BUILDING A BIT OVER THE EASTERN STATES WED NIGHT
AND THU SO CONVECTION CHANCES LOOK MORE WIDELY SCATTERED OVER
CENTRAL AND SOUTHEAST IL. AREAS FROM I-72 NORTH LOOK DRIER DURING
THIS TIME FRAME CLOSER TO WEAK HIGH PRESSURE DRIFTING OVER THE GREAT
LAKES. HIGHS THU IN THE LOW TO MID 80S WITH MORE SUNSHINE POSSIBLE
AND MID 80S ON FRIDAY.

CHANCES OF SHOWERS AND THUNDERSTORMS INCREASE AGAIN FRI/SAT WITH A
FRONTAL BOUNDARY PUSHING SE ACROSS CENTRAL IL SATURDAY AND SAT
NIGHT. TEMPERATURES TO COOL BEHIND THIS FRONT DURING THE WEEKEND
INTO EARLY NEXT WEEK WITH HIGHS IN THE LOW TO MID 70S SUNDAY. A
CUTOFF UPPER LEVEL LOW EJECTING FROM THE ROCKIES INTO TEH CENTRAL
PLAINS BY EARLY NEXT WEEK TO CONTINUE CHANCES OF SHOWERS AND A FEW
THUNDERSTORMS.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z TUESDAY AFTERNOON)
ISSUED AT 1244 PM CDT MON MAY 25 2015

LINGERING MVFR CEILINGS ARE LIFTING AND ALL SITES SHOULD BE VFR BY
18-19Z. THE STRONGEST OF THE SOUTHWEST WINDS HAVE SHIFTED AWAY
FROM KCMI...BUT WINDS THERE SHOULD STILL GUST TO AROUND 30 KNOTS
OR SO FOR A FEW MORE HOURS. THE REMAINING TAF SITES WILL HAVE
GUSTS MORE IN THE 25 KNOT RANGE...BUT THESE SHOULD SUBSIDE TOWARD
00Z. NEXT PERIOD FOR CONVECTIVE CONCERN APPEARS TO START AROUND
08-09Z WITH STORMS TRACKING IN FROM THE SOUTHWEST. HIGH-RESOLUTION
MODELS SUGGEST SOME BREAKS IN BETWEEN STORMS TUESDAY MORNING...SO
WILL GO WITH VCTS MENTION LATE IN THE PERIOD. TAIL END OF THE RAP
MODEL SUGGESTS SOME MVFR CEILINGS DEVELOPING LATE TONIGHT IN
SOUTHERN ILLINOIS AND BUILDING NORTHWARD...AND HAVE ADDED THESE
FOR KBMI/KDEC/KCMI.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.

&&

$$

SHORT TERM...GEELHART
LONG TERM...07
AVIATION...GEELHART



000
FXUS63 KILX 252000
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
300 PM CDT MON MAY 25 2015

.SHORT TERM...(TONIGHT)
ISSUED AT 259 PM CDT MON MAY 25 2015

LOWER CLOUDS ARE LIFTING AND BREAKING UP ACROSS THE EAST HALF OF THE
FORECAST AREA THIS AFTERNOON...BUT EXTENSIVE CIRRUS SHIELD KEEPING
SKIES PARTLY SUNNY AT BEST THERE. THE WESTERN CWA HAS HAD SOME
DIURNAL CUMULUS AS IT IS OUTSIDE THE CIRRUS SHIELD...BUT THIS SHOULD
FADE LATER THIS AFTERNOON AS SOME SUBSIDENCE OCCURS ACROSS THAT
AREA. SKIES WILL BE PARTLY CLOUDY FOR A TIME THIS EVENING...BUT THEN
CLOUD UP AGAIN LATER AS SOME OF THE CONVECTIVE BLOWOFF ARRIVES FROM
THE SEVERE ACTIVITY CURRENTLY ACROSS THE SOUTHERN PLAINS. LATEST
HIGH-RESOLUTION MODELS KEEP THE FORECAST AREA DRY THIS EVENING WITH
SEVERAL SUGGESTING PERHAPS TAKING UNTIL EVEN 3-4 AM BEFORE WE SEE
ANY SHOWERS AND STORMS MOVE BACK IN. HOWEVER...I HAVE RAMPED UP THE
POP`S QUICKLY AFTER MIDNIGHT ACROSS THE WEST AND AFTER 3 AM IN THE
EAST. WITH SOUTHERLY WINDS STAYING UP AROUND 10 MPH OR SO...LITTLE
CHANGE NEEDED TO THE OVERNIGHT LOWS...WHICH SHOULD BE IN THE 66-68
DEGREE RANGE.

&&

.LONG TERM...(TUESDAY THROUGH MONDAY)
ISSUED AT 259 PM CDT MON MAY 25 2015

SHORT WAVE NEAR THE RED RIVER ALONG THE WESTERN TX/OK BORDER TO
EJECT NE INTO IL ON TUE LIKELY BRINGING SHOWERS AND THUNDERSTORMS
MOST OF THE DAY. HAVE INCREASING LOW LEVEL JET AHEAD OF THIS FEATURE
LATER TONIGHT THAT WILL INCREASE CHANCES OF SHOWERS AND
THUNDERSTORMS FROM SW TO NE. SHOWERS AND THUNDERSTORMS WILL BECOME
MORE WIDELY SCATTERED SW AREAS LATER TUE AFTERNOON AND OVER REST OF
CENTRAL/EASTERN IL TUE EVENING. SPC SHIFTED SLIGHT RISK SOUTHEAST OF
IL ON TUE AND NOW MAINLY OVER KY/TN/MS/AL WHERE BETTER INSTABILITY
WILL BE PRESENT. STILL HAVE A MARGINAL RISK OF SEVERE STORMS TUE
AFTERNOON FROM SHELBYVILLE TO DANVILLE SE FOR HAIL AND GUSTY WINDS.
HIGHS IN THE UPPER 70S TUE WITH LAWRENCEVILLE NEAR 80F WITH
DEWPOINTS IN THE MID TO UPPER 60S (HIGHEST IN SE IL).

RATHER WARM AND HUMID WEATHER PATTERN LOOKS TO CONTINUE ACROSS IL
DURING THE REST OF THE WEEK WITH DAILY CHANCE OF SHOWERS AND
THUNDERSTORMS. BETWEEN 1.5 AND 2 INCHES OF RAIN IS EXPECTED OVER
AREA THE REST OF THIS WEEK. CHANCE OF SHOWERS AND THUNDERSTORMS
LOOK HIGHER IN SOUTHEAST IL ON WED WITH JUST SLIGHT CHANCE NW OF
THE IL RIVER BY GALESBURG AS MORE SHORT WAVE ENERGY EJECT NE INTO
THE MID MS AND OHIO RIVER VALLEY. SPC HAS MARGINAL RISK OF SEVERE
STORMS WED AFTERNOON MAINLY SOUTH OF I-72. LOWS TONIGHT MOSTLY IN
THE MID 60S WITH SOME LOWER 60S NW OF THE IL RIVER. HIGHS WED IN
THE LOWER 80S AND DEWPOINTS IN THE LOW TO MID 60S.

UPPER LEVEL RIDGE BUILDING A BIT OVER THE EASTERN STATES WED NIGHT
AND THU SO CONVECTION CHANCES LOOK MORE WIDELY SCATTERED OVER
CENTRAL AND SOUTHEAST IL. AREAS FROM I-72 NORTH LOOK DRIER DURING
THIS TIME FRAME CLOSER TO WEAK HIGH PRESSURE DRIFTING OVER THE GREAT
LAKES. HIGHS THU IN THE LOW TO MID 80S WITH MORE SUNSHINE POSSIBLE
AND MID 80S ON FRIDAY.

CHANCES OF SHOWERS AND THUNDERSTORMS INCREASE AGAIN FRI/SAT WITH A
FRONTAL BOUNDARY PUSHING SE ACROSS CENTRAL IL SATURDAY AND SAT
NIGHT. TEMPERATURES TO COOL BEHIND THIS FRONT DURING THE WEEKEND
INTO EARLY NEXT WEEK WITH HIGHS IN THE LOW TO MID 70S SUNDAY. A
CUTOFF UPPER LEVEL LOW EJECTING FROM THE ROCKIES INTO TEH CENTRAL
PLAINS BY EARLY NEXT WEEK TO CONTINUE CHANCES OF SHOWERS AND A FEW
THUNDERSTORMS.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z TUESDAY AFTERNOON)
ISSUED AT 1244 PM CDT MON MAY 25 2015

LINGERING MVFR CEILINGS ARE LIFTING AND ALL SITES SHOULD BE VFR BY
18-19Z. THE STRONGEST OF THE SOUTHWEST WINDS HAVE SHIFTED AWAY
FROM KCMI...BUT WINDS THERE SHOULD STILL GUST TO AROUND 30 KNOTS
OR SO FOR A FEW MORE HOURS. THE REMAINING TAF SITES WILL HAVE
GUSTS MORE IN THE 25 KNOT RANGE...BUT THESE SHOULD SUBSIDE TOWARD
00Z. NEXT PERIOD FOR CONVECTIVE CONCERN APPEARS TO START AROUND
08-09Z WITH STORMS TRACKING IN FROM THE SOUTHWEST. HIGH-RESOLUTION
MODELS SUGGEST SOME BREAKS IN BETWEEN STORMS TUESDAY MORNING...SO
WILL GO WITH VCTS MENTION LATE IN THE PERIOD. TAIL END OF THE RAP
MODEL SUGGESTS SOME MVFR CEILINGS DEVELOPING LATE TONIGHT IN
SOUTHERN ILLINOIS AND BUILDING NORTHWARD...AND HAVE ADDED THESE
FOR KBMI/KDEC/KCMI.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.

&&

$$

SHORT TERM...GEELHART
LONG TERM...07
AVIATION...GEELHART



000
FXUS63 KLOT 251956
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
256 PM CDT MON MAY 25 2015


.SHORT TERM...
255 PM CDT

THROUGH WEDNESDAY...

.SHORT TERM...THROUGH TUESDAY...

SHOWERS CONTINUE TO DIMINISH AS WE GET ON THE SUBSIDENT SIDE OF THE
DEPARTING UPPER TROUGH AXIS THAT WILL QUICKLY EXIT TO THE NORTHEAST
TONIGHT. SURFACE LOW PRESSURE IS PUSHING INTO UPPER MICHIGAN WHILE
LEAVING MODEST PRESSURE RISES IN ITS WAKE. WIND GUSTS TO 30 TO
LOCALLY 35 MPH WILL CONTINUE THROUGH THE AFTERNOON. EXPECT TO SEE
ALITTLE MORE BLUE SKY THROUGH THE AFTERNOON/EARLY EVENING WHICH
WILL ALLOW TEMPERATURES TO SLOWLY INCH UPWARD TO THE UPPER 70S TO
LOW 80S...THOUGH WITH MOIST SW FLOW EXPECT THESE LOWER CLOUDS TO
LINGER AROUND A BIT LONGER.

THE ACTIVE PATTERN CONTINUES ACROSS THE AREA FOR THE NEXT 24 HOURS.
SEVERAL UPPER LEVEL LOW PRESSURE SYSTEMS ARE NOTED IN AFTERNOON
WATER VAPOR IMAGERY. THE FIRST IS OVER THE NEBRASKA PANHANDLE...WITH
ASSOCIATED LEADING SHORTWAVE ENERGY TRIGGERING SOME SHOWERS AND T-
STORMS ACROSS IOWA...THEN THE BIGGER SHOWS TO THE SOUTH WITH THE
COMPLEX OF STRONG/SEVERE THUNDERSTORMS ASSOCIATED WITH A NEGATIVELY
TILTED TROUGH IN THE TEXAS. THE NORTHERN SHORTWAVE IS EXPECTED TO
CONTINUE DEVELOPING SHOWERS AND STORMS ACROSS IOWA AND INTO FAR
WESTERN ILLINOIS AND WISCONSIN. SOME OF THIS MAY CLIP OUR FAR
NORTHWESTERN COUNTIES...INCLUDING THE ROCKFORD AREA...BUT FEEL AT
THIS POINT THAT IT SHOULD LARGELY BE OFF FARTHER NW. HAVE HELD OFF
AND KEPT THIS ACTIVITY OUT OF AREA.

THEN TONIGHT THE LOWER LEVEL FRONTAL BOUNDARY ASSOCIATED WITH THE
NORTHERN WAVE WILL SAG SOUTHEAST TOWARD THE AREA LATE TONIGHT. MUCH
OF THE GUIDANCE THEN BRINGS THE SOUTHERN SHORTWAVE TOWARD OUR AREA
LATE TONIGHT AND MORE SO ON TUESDAY ON A DECENT UPPER LEVEL JET. THE
LARGE SUITE OF GUIDANCE KEEPS THESE TWO LOWS SEPARATE...ALLOWING
MUCH OF THE NORTHERN STREAM SHOWERS/STORMS TO LARGELY REMAIN OUT OF
AREA...BUT THEY MAY BEGIN TO AFFECT AREAS WEST OF I-39 IN ILLINOIS
OVERNIGHT.

TUESDAY MORNING IS WHEN BETTER CHANCES OF SHOWERS AND SCATTERED
THUNDERSTORMS WOULD BE. THIS MID MORNING/EARLY AFTERNOON PERIOD
FEATURES MODEST LOW/MID LEVEL ISENTROPIC LIFT/PW VALUES APPROACHING
1.5 INCHES AND THETA-E RIDGE NOSING IN FROM THE SOUTH. WE SHOULD
HAVE SOME SHOWERS AND THUNDERSTORMS MOVING FROM SOUTH TO NORTH
DURING THIS TIME FRAME.  DEPENDING ON THE INTERACTION OF THESE TWO
SYSTEMS AND IF THINGS SLOW DOWN A BIT...BETTER INSTABILITY WILL BE
TAPPED INTO IN THE AFTERNOON. THE NAM WOULD SUGGEST THIS
SOLUTION...WHILE THE GLOBAL GFS/ECMWF SUGGEST THE MID-MORNING TO
EARLY AFTERNOON PERIOD WOULD BE THE MOST LIKELY PERIOD WHERE DEEPER
MOISTURE IS AVAILABLE AND CO-LOCATED WITH THE UPPER FORCING.
CONFIDENCE ON TIMING IS ONLY MEDIUM WHICH REQUIRED CARRYING AN
EXTENDED PERIOD OF LIKELY POPS FOR MUCH OF THE DAY.

KMD

&&

.LONG TERM...
239 AM CDT

TUESDAY THROUGH SUNDAY...

TUESDAY THROUGH WEDNESDAY...
500MB TROUGH AXIS WILL SLOWLY PIVOT EAST ACROSS THE CENTRAL PLAINS
INTO THE MID-MISSOURI VALLEY TUE...WITH A SFC WAVE SLIDING NORTH
ACROSS IOWA INTO CENTRAL WISC LATE TUE. THE SFC FEATURE IS NOT
EXPECTED TO BE STRONG...HOWEVER THE GRADIENT DOES TIGHTEN WITH
MODEST HEIGHT FALLS IN THE LOWEST LAYERS OF THE ATMOSPHERE. SOME
INSTABILITY DOES REMAIN ALONG WITH RELATIVELY MOIST SFC CONDS AS
DEW PTS WILL REMAIN IN THE UPR 50S/LOW 60S. PWAT VALUES WILL ALSO
HOVER JUST OVER 1 INCH...WHICH IS SEASONAL. WILL HOLD ONTO MENTION
OF RAIN AND THUNDER...BUT COULD SEE THIS MAINLY FOCUSED IN THE TUE
MORNING TIMEFRAME.

WITH CONSIDERABLE SOLAR SHIELDING PROGGED FOR TUE...TEMPS MAY
STRUGGLE TO WARM BEYOND THE MID/UPR 70S. BUT WITH GUIDANCE HINTING
AT A DRY SLOT LIFTING NORTHEAST ACROSS THE REGION TUE EVE...THIS
COULD INTRODUCE SOME EROSION TO THE CLOUD COVER IN THE AFTN HOURS
TUE AND ALLOW SOME SFC HEATING TO OCCUR AND PUSH TEMPS TO ARND 80.

GUIDANCE LIFTS THE DRY SLOT OVERHEAD LATE TUE NGT...WITH THE 500MB
TROUGH AXIS ARRIVING ARND DAYBREAK WED AND LIFTING EAST ACROSS LOWER
MICHIGAN. THIS WILL BRING DRY ONLY SLIGHT CHANCE POPS AS WEAK SFC
RIDGING BEGINS TO NUDGE EAST ACROSS THE MISSOURI VALLEY TOWARDS THE
FORECAST AREA MIDDAY WED. IT IS POSSIBLE THAT ENOUGH DRY AIR
INFLUENCE COULD ALLOW FOR REMOVAL OF THE SLIGHT CHANCE POPS WED
AFTN. THERMAL TROUGH LAGS BEHIND THE FRONTAL BOUNDARY WED...SO TEMPS
COULD STILL WARM BACK TO ARND 80 AND PERHAPS THE LOW 80S IN THE
SOUTHERN CWFA.

THURSDAY THROUGH SUNDAY...
ANTI-CYCLONIC FLOW ARRIVES THUR WITH AT LEAST ONE PERIOD OF DRY
WEATHER EXPECTED FOR NORTHERN IL/NORTHWEST IN. ONLY A COUPLE
ENSEMBLE MEMBERS CONTINUE TO PROG POPS ALONG THE SOUTHERN FORECAST
AREA THUR...BUT COULD SEE THIS TRENDING DRY IN THE NEXT FEW
SOLUTIONS. WITH WARM TEMPS ALOFT EXPECTED THUR AND THIN CLOUD
COVER...THUR HIGHS COULD PEAK IN THE LOW 80S.

THEN FOCUS TURNS TOWARDS THE UPCOMING WEEKEND AND A PATTERN SHIFT
AWAY FROM THE WARM/HUMID CONDITIONS. ENSEMBLES SHOW MINIMAL SPREAD
IN THE LATE WEEK PERIODS...WITH THE UPSTREAM RIDGE OVER
ALASKA/WESTERN CANADA AND A DOWNSTREAM MID-LVL RIDGE ACROSS THE
SOUTHEAST CONUS. BOTH OF THESE FEATURES IN TIME BEGIN TO
WEAKEN...WITH THE LONGWAVE PATTERN TRANSITIONING INTO A SEMI-ZONAL
ORIENTATION BY THE SECOND HALF OF THE WEEKEND.

OPER GUIDANCE HAS BEEN CONSISTENT WITH PROGGING A ROBUST 500MB
TROUGH TO SLIDE SOUTH FROM CENTRAL CANADA FRI...ALONG WITH A STRONG
CANADIAN SFC RIDGE ON IT/S HEELS. WITH A CHANNEL OF MOISTURE
REMAINING ACROSS THE SOUTHERN PLAINS STRETCHING NORTHEAST THROUGH
THE UPPER MIDWEST...THIS BOUNDARY WILL BECOME ACTIVE WITH A SFC WAVE
DEVELOPING ACROSS THE SOUTHERN PLAINS. THIS LOW WILL THEN LIFT
NORTHEAST TOWARDS THE CWFA FRI WITH A COLD FRONT ARRIVING ACROSS THE
FORECAST AREA SAT. WINDS LOOK TO SHIFT TO THE NORTH...WITH MUCH
COOLER AIR SLIDING SOUTH AND LIKELY KNOCKING TEMPS BACK TO SUB-
SEASONAL CONDS IN THE UPR 60S/NEAR 70 DEGREE RANGE SAT/SUN. IF
NORTHEAST WINDS MATERIALIZE...NEXT WEEKEND AREAS ADJACENT TO LAKE
MICHIGAN ALONG THE IL/IN SHORELINE COULD BE LOCKED IN THE UPR 50S TO
LOW 60S FOR HIGHS WITH A COLD FLOW OFF OF LAKE MICHIGAN.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 20Z...

* GUSTY SOUTHWEST WINDS.

* MVFR CEILINGS POSSIBLE EARLY TUESDAY MORNING.

* SHOWERS LIKELY WITH PERIODIC THUNDERSTORMS LATE IN THE FORECAST
  PERIOD.

RODRIGUEZ

//DISCUSSION...UPDATED 18Z...

MUCH OF THE SHOWERS ARE EXITING THE AREA EARLY THIS AFTERNOON.
HOWEVER...AN ISOLATED LIGHT SHOWER WILL STILL BE POSSIBLE OVER THE
NEXT HOUR BEFORE PREVAILING DRY CONDITIONS ARE EXPECTED THIS
AFTERNOON AND TONIGHT. LINGERING MVFR CEILINGS WILL LIFT TO VFR
THROUGH 20-21Z THIS AFTERNOON WITH SKIES THEN SCATTERING THIS
EVENING...AS THE SOUTHWEST WINDS/GUSTS DIMINISH INTO THE EVENING.
WITH FAIRLY MOIST CONDITIONS REMAINING IN PLACE TONIGHT INTO
TUESDAY...REDEVELOPING LOW CEILINGS DO APPEAR TO BE A POSSIBILITY.
OVERALL CONFIDENCE IS LOWER DURING THIS PERIOD...BUT DID MAKE
MENTION OF AT LEAST MVFR CEILINGS...AND WILL NEED TO MONITOR FOR
POTENTIALLY LOWER CEILINGS. HAVE PUSHED BACK TIMING OF PRECIP LATE
IN THE PERIOD...BUT WITH INSTABILITY AND FORCING
INCREASING...SHOWERS AND THUNDERSTORMS DO APPEAR LIKELY TUESDAY.
STILL SOME UNCERTAINTY WITH EXACT TIMING AND DURATION...AND EVEN
THE POSSIBILITY FOR AN ADDITIONAL PERIOD OF THUNDERSTORMS TUESDAY
AFTERNOON.

RODRIGUEZ

//ORD AND MDW CONFIDENCE...UPDATED 20Z...

* HIGH CONFIDENCE WITH WIND SPEED/DIRECTION.

* MEDIUM HIGH CONFIDENCE WITH CEILINGS.

* HIGH CONFIDENCE OF SHOWERS/THUNDERSTORMS...MEDIUM CONFIDENCE
  WITH TIMING/DURATION.

RODRIGUEZ

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/TSRA LATE. SOUTHEAST WINDS.

FRIDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. SOUTHWEST WINDS
BECOMING NORTHEAST OVERNIGHT.

SATURDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. NORTHEAST
WINDS.

SUNDAY...CHANCE TSRA. MVFR POSSIBLE. NORTHEAST WINDS.

KREIN

&&

.MARINE...
304 AM CDT

LOW PRESSURE WILL BE STEADILY LIFTING NORTH ACROSS THE MISSOURI
VALLEY THIS MORNING...REACHING LAKE SUPERIOR BY THIS EVENING AND
CONTINUING TO SLIDE EAST/NORTHEAST TOWARDS QUEBEC BY TUESDAY
MORNING. A FRONTAL BOUNDARY WILL REMAIN OVER THE FAR NORTHERN
PORTIONS OF LAKE MICHIGAN. MEANWHILE GUSTY SOUTHERLY WINDS ARE
EXPECTED TO INCREASE THIS MORNING...WITH OCCASIONAL GALES FOR THE
NEARSHORE WATERS OF IL/IN. ACROSS THE OPEN WATERS...EXPECT THE
WARM/MOIST AIR TO STRUGGLE TO REACH THE SFC OF THE LAKE WITH SOME
DEGREE OF LAKE STABILITY. WAVES WILL STEADILY BUILD ACROSS THE
NORTHERN HALF OF THE LAKE AS A RESULT OF THE LONG FETCH. STILL
FEEL THAT GUSTS WILL REACH 30KT ACROSS THE LAKE...HOWEVER
CONFIDENCE HAS DIMINISHED SLIGHTLY AS NEW GUIDANCE HAS BECOME A
LITTLE LESS WITH THE WIND FIELDS. NONETHELESS...WAVES FOR THE
NORTHERN HALF OF THE LAKE WILL LIKELY TOP OUT IN THE 4 TO 7 FT
RANGE WITH OCCASIONAL WAVES REACHING 9 FT THIS AFTERNOON/EVENING.

THE GRADIENT QUICKLY DIMINISHES THIS EVENING...BUT EXPECT
SOUTHERLY WINDS TO PERSIST. THIS WILL ALLOW WAVES TO SUBSIDE TO 3
TO 5 FT. ANOTHER LOW WILL ARRIVE TUE...WITH WINDS NUDGING BACK UP
HOWEVER WARM AIR WILL CONTINUE TO FLOW ACROSS THE LAKE AND COULD
FURTHER ENHANCE THE LAKE STABILITY AND KEEP WAVES FROM BUILDING TO
LARGE.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...NEARSHORE WATERS UNTIL 3
     PM MONDAY.

     SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 251956
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
256 PM CDT MON MAY 25 2015


.SHORT TERM...
255 PM CDT

THROUGH WEDNESDAY...

.SHORT TERM...THROUGH TUESDAY...

SHOWERS CONTINUE TO DIMINISH AS WE GET ON THE SUBSIDENT SIDE OF THE
DEPARTING UPPER TROUGH AXIS THAT WILL QUICKLY EXIT TO THE NORTHEAST
TONIGHT. SURFACE LOW PRESSURE IS PUSHING INTO UPPER MICHIGAN WHILE
LEAVING MODEST PRESSURE RISES IN ITS WAKE. WIND GUSTS TO 30 TO
LOCALLY 35 MPH WILL CONTINUE THROUGH THE AFTERNOON. EXPECT TO SEE
ALITTLE MORE BLUE SKY THROUGH THE AFTERNOON/EARLY EVENING WHICH
WILL ALLOW TEMPERATURES TO SLOWLY INCH UPWARD TO THE UPPER 70S TO
LOW 80S...THOUGH WITH MOIST SW FLOW EXPECT THESE LOWER CLOUDS TO
LINGER AROUND A BIT LONGER.

THE ACTIVE PATTERN CONTINUES ACROSS THE AREA FOR THE NEXT 24 HOURS.
SEVERAL UPPER LEVEL LOW PRESSURE SYSTEMS ARE NOTED IN AFTERNOON
WATER VAPOR IMAGERY. THE FIRST IS OVER THE NEBRASKA PANHANDLE...WITH
ASSOCIATED LEADING SHORTWAVE ENERGY TRIGGERING SOME SHOWERS AND T-
STORMS ACROSS IOWA...THEN THE BIGGER SHOWS TO THE SOUTH WITH THE
COMPLEX OF STRONG/SEVERE THUNDERSTORMS ASSOCIATED WITH A NEGATIVELY
TILTED TROUGH IN THE TEXAS. THE NORTHERN SHORTWAVE IS EXPECTED TO
CONTINUE DEVELOPING SHOWERS AND STORMS ACROSS IOWA AND INTO FAR
WESTERN ILLINOIS AND WISCONSIN. SOME OF THIS MAY CLIP OUR FAR
NORTHWESTERN COUNTIES...INCLUDING THE ROCKFORD AREA...BUT FEEL AT
THIS POINT THAT IT SHOULD LARGELY BE OFF FARTHER NW. HAVE HELD OFF
AND KEPT THIS ACTIVITY OUT OF AREA.

THEN TONIGHT THE LOWER LEVEL FRONTAL BOUNDARY ASSOCIATED WITH THE
NORTHERN WAVE WILL SAG SOUTHEAST TOWARD THE AREA LATE TONIGHT. MUCH
OF THE GUIDANCE THEN BRINGS THE SOUTHERN SHORTWAVE TOWARD OUR AREA
LATE TONIGHT AND MORE SO ON TUESDAY ON A DECENT UPPER LEVEL JET. THE
LARGE SUITE OF GUIDANCE KEEPS THESE TWO LOWS SEPARATE...ALLOWING
MUCH OF THE NORTHERN STREAM SHOWERS/STORMS TO LARGELY REMAIN OUT OF
AREA...BUT THEY MAY BEGIN TO AFFECT AREAS WEST OF I-39 IN ILLINOIS
OVERNIGHT.

TUESDAY MORNING IS WHEN BETTER CHANCES OF SHOWERS AND SCATTERED
THUNDERSTORMS WOULD BE. THIS MID MORNING/EARLY AFTERNOON PERIOD
FEATURES MODEST LOW/MID LEVEL ISENTROPIC LIFT/PW VALUES APPROACHING
1.5 INCHES AND THETA-E RIDGE NOSING IN FROM THE SOUTH. WE SHOULD
HAVE SOME SHOWERS AND THUNDERSTORMS MOVING FROM SOUTH TO NORTH
DURING THIS TIME FRAME.  DEPENDING ON THE INTERACTION OF THESE TWO
SYSTEMS AND IF THINGS SLOW DOWN A BIT...BETTER INSTABILITY WILL BE
TAPPED INTO IN THE AFTERNOON. THE NAM WOULD SUGGEST THIS
SOLUTION...WHILE THE GLOBAL GFS/ECMWF SUGGEST THE MID-MORNING TO
EARLY AFTERNOON PERIOD WOULD BE THE MOST LIKELY PERIOD WHERE DEEPER
MOISTURE IS AVAILABLE AND CO-LOCATED WITH THE UPPER FORCING.
CONFIDENCE ON TIMING IS ONLY MEDIUM WHICH REQUIRED CARRYING AN
EXTENDED PERIOD OF LIKELY POPS FOR MUCH OF THE DAY.

KMD

&&

.LONG TERM...
239 AM CDT

TUESDAY THROUGH SUNDAY...

TUESDAY THROUGH WEDNESDAY...
500MB TROUGH AXIS WILL SLOWLY PIVOT EAST ACROSS THE CENTRAL PLAINS
INTO THE MID-MISSOURI VALLEY TUE...WITH A SFC WAVE SLIDING NORTH
ACROSS IOWA INTO CENTRAL WISC LATE TUE. THE SFC FEATURE IS NOT
EXPECTED TO BE STRONG...HOWEVER THE GRADIENT DOES TIGHTEN WITH
MODEST HEIGHT FALLS IN THE LOWEST LAYERS OF THE ATMOSPHERE. SOME
INSTABILITY DOES REMAIN ALONG WITH RELATIVELY MOIST SFC CONDS AS
DEW PTS WILL REMAIN IN THE UPR 50S/LOW 60S. PWAT VALUES WILL ALSO
HOVER JUST OVER 1 INCH...WHICH IS SEASONAL. WILL HOLD ONTO MENTION
OF RAIN AND THUNDER...BUT COULD SEE THIS MAINLY FOCUSED IN THE TUE
MORNING TIMEFRAME.

WITH CONSIDERABLE SOLAR SHIELDING PROGGED FOR TUE...TEMPS MAY
STRUGGLE TO WARM BEYOND THE MID/UPR 70S. BUT WITH GUIDANCE HINTING
AT A DRY SLOT LIFTING NORTHEAST ACROSS THE REGION TUE EVE...THIS
COULD INTRODUCE SOME EROSION TO THE CLOUD COVER IN THE AFTN HOURS
TUE AND ALLOW SOME SFC HEATING TO OCCUR AND PUSH TEMPS TO ARND 80.

GUIDANCE LIFTS THE DRY SLOT OVERHEAD LATE TUE NGT...WITH THE 500MB
TROUGH AXIS ARRIVING ARND DAYBREAK WED AND LIFTING EAST ACROSS LOWER
MICHIGAN. THIS WILL BRING DRY ONLY SLIGHT CHANCE POPS AS WEAK SFC
RIDGING BEGINS TO NUDGE EAST ACROSS THE MISSOURI VALLEY TOWARDS THE
FORECAST AREA MIDDAY WED. IT IS POSSIBLE THAT ENOUGH DRY AIR
INFLUENCE COULD ALLOW FOR REMOVAL OF THE SLIGHT CHANCE POPS WED
AFTN. THERMAL TROUGH LAGS BEHIND THE FRONTAL BOUNDARY WED...SO TEMPS
COULD STILL WARM BACK TO ARND 80 AND PERHAPS THE LOW 80S IN THE
SOUTHERN CWFA.

THURSDAY THROUGH SUNDAY...
ANTI-CYCLONIC FLOW ARRIVES THUR WITH AT LEAST ONE PERIOD OF DRY
WEATHER EXPECTED FOR NORTHERN IL/NORTHWEST IN. ONLY A COUPLE
ENSEMBLE MEMBERS CONTINUE TO PROG POPS ALONG THE SOUTHERN FORECAST
AREA THUR...BUT COULD SEE THIS TRENDING DRY IN THE NEXT FEW
SOLUTIONS. WITH WARM TEMPS ALOFT EXPECTED THUR AND THIN CLOUD
COVER...THUR HIGHS COULD PEAK IN THE LOW 80S.

THEN FOCUS TURNS TOWARDS THE UPCOMING WEEKEND AND A PATTERN SHIFT
AWAY FROM THE WARM/HUMID CONDITIONS. ENSEMBLES SHOW MINIMAL SPREAD
IN THE LATE WEEK PERIODS...WITH THE UPSTREAM RIDGE OVER
ALASKA/WESTERN CANADA AND A DOWNSTREAM MID-LVL RIDGE ACROSS THE
SOUTHEAST CONUS. BOTH OF THESE FEATURES IN TIME BEGIN TO
WEAKEN...WITH THE LONGWAVE PATTERN TRANSITIONING INTO A SEMI-ZONAL
ORIENTATION BY THE SECOND HALF OF THE WEEKEND.

OPER GUIDANCE HAS BEEN CONSISTENT WITH PROGGING A ROBUST 500MB
TROUGH TO SLIDE SOUTH FROM CENTRAL CANADA FRI...ALONG WITH A STRONG
CANADIAN SFC RIDGE ON IT/S HEELS. WITH A CHANNEL OF MOISTURE
REMAINING ACROSS THE SOUTHERN PLAINS STRETCHING NORTHEAST THROUGH
THE UPPER MIDWEST...THIS BOUNDARY WILL BECOME ACTIVE WITH A SFC WAVE
DEVELOPING ACROSS THE SOUTHERN PLAINS. THIS LOW WILL THEN LIFT
NORTHEAST TOWARDS THE CWFA FRI WITH A COLD FRONT ARRIVING ACROSS THE
FORECAST AREA SAT. WINDS LOOK TO SHIFT TO THE NORTH...WITH MUCH
COOLER AIR SLIDING SOUTH AND LIKELY KNOCKING TEMPS BACK TO SUB-
SEASONAL CONDS IN THE UPR 60S/NEAR 70 DEGREE RANGE SAT/SUN. IF
NORTHEAST WINDS MATERIALIZE...NEXT WEEKEND AREAS ADJACENT TO LAKE
MICHIGAN ALONG THE IL/IN SHORELINE COULD BE LOCKED IN THE UPR 50S TO
LOW 60S FOR HIGHS WITH A COLD FLOW OFF OF LAKE MICHIGAN.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 20Z...

* GUSTY SOUTHWEST WINDS.

* MVFR CEILINGS POSSIBLE EARLY TUESDAY MORNING.

* SHOWERS LIKELY WITH PERIODIC THUNDERSTORMS LATE IN THE FORECAST
  PERIOD.

RODRIGUEZ

//DISCUSSION...UPDATED 18Z...

MUCH OF THE SHOWERS ARE EXITING THE AREA EARLY THIS AFTERNOON.
HOWEVER...AN ISOLATED LIGHT SHOWER WILL STILL BE POSSIBLE OVER THE
NEXT HOUR BEFORE PREVAILING DRY CONDITIONS ARE EXPECTED THIS
AFTERNOON AND TONIGHT. LINGERING MVFR CEILINGS WILL LIFT TO VFR
THROUGH 20-21Z THIS AFTERNOON WITH SKIES THEN SCATTERING THIS
EVENING...AS THE SOUTHWEST WINDS/GUSTS DIMINISH INTO THE EVENING.
WITH FAIRLY MOIST CONDITIONS REMAINING IN PLACE TONIGHT INTO
TUESDAY...REDEVELOPING LOW CEILINGS DO APPEAR TO BE A POSSIBILITY.
OVERALL CONFIDENCE IS LOWER DURING THIS PERIOD...BUT DID MAKE
MENTION OF AT LEAST MVFR CEILINGS...AND WILL NEED TO MONITOR FOR
POTENTIALLY LOWER CEILINGS. HAVE PUSHED BACK TIMING OF PRECIP LATE
IN THE PERIOD...BUT WITH INSTABILITY AND FORCING
INCREASING...SHOWERS AND THUNDERSTORMS DO APPEAR LIKELY TUESDAY.
STILL SOME UNCERTAINTY WITH EXACT TIMING AND DURATION...AND EVEN
THE POSSIBILITY FOR AN ADDITIONAL PERIOD OF THUNDERSTORMS TUESDAY
AFTERNOON.

RODRIGUEZ

//ORD AND MDW CONFIDENCE...UPDATED 20Z...

* HIGH CONFIDENCE WITH WIND SPEED/DIRECTION.

* MEDIUM HIGH CONFIDENCE WITH CEILINGS.

* HIGH CONFIDENCE OF SHOWERS/THUNDERSTORMS...MEDIUM CONFIDENCE
  WITH TIMING/DURATION.

RODRIGUEZ

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/TSRA LATE. SOUTHEAST WINDS.

FRIDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. SOUTHWEST WINDS
BECOMING NORTHEAST OVERNIGHT.

SATURDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. NORTHEAST
WINDS.

SUNDAY...CHANCE TSRA. MVFR POSSIBLE. NORTHEAST WINDS.

KREIN

&&

.MARINE...
304 AM CDT

LOW PRESSURE WILL BE STEADILY LIFTING NORTH ACROSS THE MISSOURI
VALLEY THIS MORNING...REACHING LAKE SUPERIOR BY THIS EVENING AND
CONTINUING TO SLIDE EAST/NORTHEAST TOWARDS QUEBEC BY TUESDAY
MORNING. A FRONTAL BOUNDARY WILL REMAIN OVER THE FAR NORTHERN
PORTIONS OF LAKE MICHIGAN. MEANWHILE GUSTY SOUTHERLY WINDS ARE
EXPECTED TO INCREASE THIS MORNING...WITH OCCASIONAL GALES FOR THE
NEARSHORE WATERS OF IL/IN. ACROSS THE OPEN WATERS...EXPECT THE
WARM/MOIST AIR TO STRUGGLE TO REACH THE SFC OF THE LAKE WITH SOME
DEGREE OF LAKE STABILITY. WAVES WILL STEADILY BUILD ACROSS THE
NORTHERN HALF OF THE LAKE AS A RESULT OF THE LONG FETCH. STILL
FEEL THAT GUSTS WILL REACH 30KT ACROSS THE LAKE...HOWEVER
CONFIDENCE HAS DIMINISHED SLIGHTLY AS NEW GUIDANCE HAS BECOME A
LITTLE LESS WITH THE WIND FIELDS. NONETHELESS...WAVES FOR THE
NORTHERN HALF OF THE LAKE WILL LIKELY TOP OUT IN THE 4 TO 7 FT
RANGE WITH OCCASIONAL WAVES REACHING 9 FT THIS AFTERNOON/EVENING.

THE GRADIENT QUICKLY DIMINISHES THIS EVENING...BUT EXPECT
SOUTHERLY WINDS TO PERSIST. THIS WILL ALLOW WAVES TO SUBSIDE TO 3
TO 5 FT. ANOTHER LOW WILL ARRIVE TUE...WITH WINDS NUDGING BACK UP
HOWEVER WARM AIR WILL CONTINUE TO FLOW ACROSS THE LAKE AND COULD
FURTHER ENHANCE THE LAKE STABILITY AND KEEP WAVES FROM BUILDING TO
LARGE.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...NEARSHORE WATERS UNTIL 3
     PM MONDAY.

     SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 251956
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
256 PM CDT MON MAY 25 2015


.SHORT TERM...
255 PM CDT

THROUGH WEDNESDAY...

.SHORT TERM...THROUGH TUESDAY...

SHOWERS CONTINUE TO DIMINISH AS WE GET ON THE SUBSIDENT SIDE OF THE
DEPARTING UPPER TROUGH AXIS THAT WILL QUICKLY EXIT TO THE NORTHEAST
TONIGHT. SURFACE LOW PRESSURE IS PUSHING INTO UPPER MICHIGAN WHILE
LEAVING MODEST PRESSURE RISES IN ITS WAKE. WIND GUSTS TO 30 TO
LOCALLY 35 MPH WILL CONTINUE THROUGH THE AFTERNOON. EXPECT TO SEE
ALITTLE MORE BLUE SKY THROUGH THE AFTERNOON/EARLY EVENING WHICH
WILL ALLOW TEMPERATURES TO SLOWLY INCH UPWARD TO THE UPPER 70S TO
LOW 80S...THOUGH WITH MOIST SW FLOW EXPECT THESE LOWER CLOUDS TO
LINGER AROUND A BIT LONGER.

THE ACTIVE PATTERN CONTINUES ACROSS THE AREA FOR THE NEXT 24 HOURS.
SEVERAL UPPER LEVEL LOW PRESSURE SYSTEMS ARE NOTED IN AFTERNOON
WATER VAPOR IMAGERY. THE FIRST IS OVER THE NEBRASKA PANHANDLE...WITH
ASSOCIATED LEADING SHORTWAVE ENERGY TRIGGERING SOME SHOWERS AND T-
STORMS ACROSS IOWA...THEN THE BIGGER SHOWS TO THE SOUTH WITH THE
COMPLEX OF STRONG/SEVERE THUNDERSTORMS ASSOCIATED WITH A NEGATIVELY
TILTED TROUGH IN THE TEXAS. THE NORTHERN SHORTWAVE IS EXPECTED TO
CONTINUE DEVELOPING SHOWERS AND STORMS ACROSS IOWA AND INTO FAR
WESTERN ILLINOIS AND WISCONSIN. SOME OF THIS MAY CLIP OUR FAR
NORTHWESTERN COUNTIES...INCLUDING THE ROCKFORD AREA...BUT FEEL AT
THIS POINT THAT IT SHOULD LARGELY BE OFF FARTHER NW. HAVE HELD OFF
AND KEPT THIS ACTIVITY OUT OF AREA.

THEN TONIGHT THE LOWER LEVEL FRONTAL BOUNDARY ASSOCIATED WITH THE
NORTHERN WAVE WILL SAG SOUTHEAST TOWARD THE AREA LATE TONIGHT. MUCH
OF THE GUIDANCE THEN BRINGS THE SOUTHERN SHORTWAVE TOWARD OUR AREA
LATE TONIGHT AND MORE SO ON TUESDAY ON A DECENT UPPER LEVEL JET. THE
LARGE SUITE OF GUIDANCE KEEPS THESE TWO LOWS SEPARATE...ALLOWING
MUCH OF THE NORTHERN STREAM SHOWERS/STORMS TO LARGELY REMAIN OUT OF
AREA...BUT THEY MAY BEGIN TO AFFECT AREAS WEST OF I-39 IN ILLINOIS
OVERNIGHT.

TUESDAY MORNING IS WHEN BETTER CHANCES OF SHOWERS AND SCATTERED
THUNDERSTORMS WOULD BE. THIS MID MORNING/EARLY AFTERNOON PERIOD
FEATURES MODEST LOW/MID LEVEL ISENTROPIC LIFT/PW VALUES APPROACHING
1.5 INCHES AND THETA-E RIDGE NOSING IN FROM THE SOUTH. WE SHOULD
HAVE SOME SHOWERS AND THUNDERSTORMS MOVING FROM SOUTH TO NORTH
DURING THIS TIME FRAME.  DEPENDING ON THE INTERACTION OF THESE TWO
SYSTEMS AND IF THINGS SLOW DOWN A BIT...BETTER INSTABILITY WILL BE
TAPPED INTO IN THE AFTERNOON. THE NAM WOULD SUGGEST THIS
SOLUTION...WHILE THE GLOBAL GFS/ECMWF SUGGEST THE MID-MORNING TO
EARLY AFTERNOON PERIOD WOULD BE THE MOST LIKELY PERIOD WHERE DEEPER
MOISTURE IS AVAILABLE AND CO-LOCATED WITH THE UPPER FORCING.
CONFIDENCE ON TIMING IS ONLY MEDIUM WHICH REQUIRED CARRYING AN
EXTENDED PERIOD OF LIKELY POPS FOR MUCH OF THE DAY.

KMD

&&

.LONG TERM...
239 AM CDT

TUESDAY THROUGH SUNDAY...

TUESDAY THROUGH WEDNESDAY...
500MB TROUGH AXIS WILL SLOWLY PIVOT EAST ACROSS THE CENTRAL PLAINS
INTO THE MID-MISSOURI VALLEY TUE...WITH A SFC WAVE SLIDING NORTH
ACROSS IOWA INTO CENTRAL WISC LATE TUE. THE SFC FEATURE IS NOT
EXPECTED TO BE STRONG...HOWEVER THE GRADIENT DOES TIGHTEN WITH
MODEST HEIGHT FALLS IN THE LOWEST LAYERS OF THE ATMOSPHERE. SOME
INSTABILITY DOES REMAIN ALONG WITH RELATIVELY MOIST SFC CONDS AS
DEW PTS WILL REMAIN IN THE UPR 50S/LOW 60S. PWAT VALUES WILL ALSO
HOVER JUST OVER 1 INCH...WHICH IS SEASONAL. WILL HOLD ONTO MENTION
OF RAIN AND THUNDER...BUT COULD SEE THIS MAINLY FOCUSED IN THE TUE
MORNING TIMEFRAME.

WITH CONSIDERABLE SOLAR SHIELDING PROGGED FOR TUE...TEMPS MAY
STRUGGLE TO WARM BEYOND THE MID/UPR 70S. BUT WITH GUIDANCE HINTING
AT A DRY SLOT LIFTING NORTHEAST ACROSS THE REGION TUE EVE...THIS
COULD INTRODUCE SOME EROSION TO THE CLOUD COVER IN THE AFTN HOURS
TUE AND ALLOW SOME SFC HEATING TO OCCUR AND PUSH TEMPS TO ARND 80.

GUIDANCE LIFTS THE DRY SLOT OVERHEAD LATE TUE NGT...WITH THE 500MB
TROUGH AXIS ARRIVING ARND DAYBREAK WED AND LIFTING EAST ACROSS LOWER
MICHIGAN. THIS WILL BRING DRY ONLY SLIGHT CHANCE POPS AS WEAK SFC
RIDGING BEGINS TO NUDGE EAST ACROSS THE MISSOURI VALLEY TOWARDS THE
FORECAST AREA MIDDAY WED. IT IS POSSIBLE THAT ENOUGH DRY AIR
INFLUENCE COULD ALLOW FOR REMOVAL OF THE SLIGHT CHANCE POPS WED
AFTN. THERMAL TROUGH LAGS BEHIND THE FRONTAL BOUNDARY WED...SO TEMPS
COULD STILL WARM BACK TO ARND 80 AND PERHAPS THE LOW 80S IN THE
SOUTHERN CWFA.

THURSDAY THROUGH SUNDAY...
ANTI-CYCLONIC FLOW ARRIVES THUR WITH AT LEAST ONE PERIOD OF DRY
WEATHER EXPECTED FOR NORTHERN IL/NORTHWEST IN. ONLY A COUPLE
ENSEMBLE MEMBERS CONTINUE TO PROG POPS ALONG THE SOUTHERN FORECAST
AREA THUR...BUT COULD SEE THIS TRENDING DRY IN THE NEXT FEW
SOLUTIONS. WITH WARM TEMPS ALOFT EXPECTED THUR AND THIN CLOUD
COVER...THUR HIGHS COULD PEAK IN THE LOW 80S.

THEN FOCUS TURNS TOWARDS THE UPCOMING WEEKEND AND A PATTERN SHIFT
AWAY FROM THE WARM/HUMID CONDITIONS. ENSEMBLES SHOW MINIMAL SPREAD
IN THE LATE WEEK PERIODS...WITH THE UPSTREAM RIDGE OVER
ALASKA/WESTERN CANADA AND A DOWNSTREAM MID-LVL RIDGE ACROSS THE
SOUTHEAST CONUS. BOTH OF THESE FEATURES IN TIME BEGIN TO
WEAKEN...WITH THE LONGWAVE PATTERN TRANSITIONING INTO A SEMI-ZONAL
ORIENTATION BY THE SECOND HALF OF THE WEEKEND.

OPER GUIDANCE HAS BEEN CONSISTENT WITH PROGGING A ROBUST 500MB
TROUGH TO SLIDE SOUTH FROM CENTRAL CANADA FRI...ALONG WITH A STRONG
CANADIAN SFC RIDGE ON IT/S HEELS. WITH A CHANNEL OF MOISTURE
REMAINING ACROSS THE SOUTHERN PLAINS STRETCHING NORTHEAST THROUGH
THE UPPER MIDWEST...THIS BOUNDARY WILL BECOME ACTIVE WITH A SFC WAVE
DEVELOPING ACROSS THE SOUTHERN PLAINS. THIS LOW WILL THEN LIFT
NORTHEAST TOWARDS THE CWFA FRI WITH A COLD FRONT ARRIVING ACROSS THE
FORECAST AREA SAT. WINDS LOOK TO SHIFT TO THE NORTH...WITH MUCH
COOLER AIR SLIDING SOUTH AND LIKELY KNOCKING TEMPS BACK TO SUB-
SEASONAL CONDS IN THE UPR 60S/NEAR 70 DEGREE RANGE SAT/SUN. IF
NORTHEAST WINDS MATERIALIZE...NEXT WEEKEND AREAS ADJACENT TO LAKE
MICHIGAN ALONG THE IL/IN SHORELINE COULD BE LOCKED IN THE UPR 50S TO
LOW 60S FOR HIGHS WITH A COLD FLOW OFF OF LAKE MICHIGAN.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 20Z...

* GUSTY SOUTHWEST WINDS.

* MVFR CEILINGS POSSIBLE EARLY TUESDAY MORNING.

* SHOWERS LIKELY WITH PERIODIC THUNDERSTORMS LATE IN THE FORECAST
  PERIOD.

RODRIGUEZ

//DISCUSSION...UPDATED 18Z...

MUCH OF THE SHOWERS ARE EXITING THE AREA EARLY THIS AFTERNOON.
HOWEVER...AN ISOLATED LIGHT SHOWER WILL STILL BE POSSIBLE OVER THE
NEXT HOUR BEFORE PREVAILING DRY CONDITIONS ARE EXPECTED THIS
AFTERNOON AND TONIGHT. LINGERING MVFR CEILINGS WILL LIFT TO VFR
THROUGH 20-21Z THIS AFTERNOON WITH SKIES THEN SCATTERING THIS
EVENING...AS THE SOUTHWEST WINDS/GUSTS DIMINISH INTO THE EVENING.
WITH FAIRLY MOIST CONDITIONS REMAINING IN PLACE TONIGHT INTO
TUESDAY...REDEVELOPING LOW CEILINGS DO APPEAR TO BE A POSSIBILITY.
OVERALL CONFIDENCE IS LOWER DURING THIS PERIOD...BUT DID MAKE
MENTION OF AT LEAST MVFR CEILINGS...AND WILL NEED TO MONITOR FOR
POTENTIALLY LOWER CEILINGS. HAVE PUSHED BACK TIMING OF PRECIP LATE
IN THE PERIOD...BUT WITH INSTABILITY AND FORCING
INCREASING...SHOWERS AND THUNDERSTORMS DO APPEAR LIKELY TUESDAY.
STILL SOME UNCERTAINTY WITH EXACT TIMING AND DURATION...AND EVEN
THE POSSIBILITY FOR AN ADDITIONAL PERIOD OF THUNDERSTORMS TUESDAY
AFTERNOON.

RODRIGUEZ

//ORD AND MDW CONFIDENCE...UPDATED 20Z...

* HIGH CONFIDENCE WITH WIND SPEED/DIRECTION.

* MEDIUM HIGH CONFIDENCE WITH CEILINGS.

* HIGH CONFIDENCE OF SHOWERS/THUNDERSTORMS...MEDIUM CONFIDENCE
  WITH TIMING/DURATION.

RODRIGUEZ

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/TSRA LATE. SOUTHEAST WINDS.

FRIDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. SOUTHWEST WINDS
BECOMING NORTHEAST OVERNIGHT.

SATURDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. NORTHEAST
WINDS.

SUNDAY...CHANCE TSRA. MVFR POSSIBLE. NORTHEAST WINDS.

KREIN

&&

.MARINE...
304 AM CDT

LOW PRESSURE WILL BE STEADILY LIFTING NORTH ACROSS THE MISSOURI
VALLEY THIS MORNING...REACHING LAKE SUPERIOR BY THIS EVENING AND
CONTINUING TO SLIDE EAST/NORTHEAST TOWARDS QUEBEC BY TUESDAY
MORNING. A FRONTAL BOUNDARY WILL REMAIN OVER THE FAR NORTHERN
PORTIONS OF LAKE MICHIGAN. MEANWHILE GUSTY SOUTHERLY WINDS ARE
EXPECTED TO INCREASE THIS MORNING...WITH OCCASIONAL GALES FOR THE
NEARSHORE WATERS OF IL/IN. ACROSS THE OPEN WATERS...EXPECT THE
WARM/MOIST AIR TO STRUGGLE TO REACH THE SFC OF THE LAKE WITH SOME
DEGREE OF LAKE STABILITY. WAVES WILL STEADILY BUILD ACROSS THE
NORTHERN HALF OF THE LAKE AS A RESULT OF THE LONG FETCH. STILL
FEEL THAT GUSTS WILL REACH 30KT ACROSS THE LAKE...HOWEVER
CONFIDENCE HAS DIMINISHED SLIGHTLY AS NEW GUIDANCE HAS BECOME A
LITTLE LESS WITH THE WIND FIELDS. NONETHELESS...WAVES FOR THE
NORTHERN HALF OF THE LAKE WILL LIKELY TOP OUT IN THE 4 TO 7 FT
RANGE WITH OCCASIONAL WAVES REACHING 9 FT THIS AFTERNOON/EVENING.

THE GRADIENT QUICKLY DIMINISHES THIS EVENING...BUT EXPECT
SOUTHERLY WINDS TO PERSIST. THIS WILL ALLOW WAVES TO SUBSIDE TO 3
TO 5 FT. ANOTHER LOW WILL ARRIVE TUE...WITH WINDS NUDGING BACK UP
HOWEVER WARM AIR WILL CONTINUE TO FLOW ACROSS THE LAKE AND COULD
FURTHER ENHANCE THE LAKE STABILITY AND KEEP WAVES FROM BUILDING TO
LARGE.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...NEARSHORE WATERS UNTIL 3
     PM MONDAY.

     SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 251955
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
255 PM CDT MON MAY 25 2015

.UPDATE...

COMPACT NEGATIVELY TILTED TROUGH AXIS IS SLIDING NORTHEAST THROUGH
IOWA AND WESTERN ILLINOIS. EASTERN EDGE OF THE TROUGH WILL MOVE
THROUGH NORTHEAST ILLINOIS THIS MORNING. NOTED UPTICK IN SHOWER
ACTIVITY ASSOCIATED WITH THIS WAVE IS PRODUCING MORE ORGANIZED BUT
STILL LARGELY SCATTERED SHOWERS. STILL TRACKING THIS FEATURE WILL
BRING THE BEST CHANCE FOR SOME BRIEF DOWNPOURS IN THE COMING
HOURS...AND THESE WILL SPREAD INTO THE WEST METRO AREA IN THE NEXT
HOUR...SPREADING INTO CHICAGOLAND SHORTLY THERE AFTER. THE CLOUDS
PRODUCING THE SHOWER ACTIVITY ARE SHALLOW AND MID LEVEL LAPSE
RATES ARE SUBPAR...THUS THUNDER SHOULD BE LIMITED AT BEST. SOME
WEAK INSTABILITY IS NOTED SOUTH OF I-80 WHICH DOES NOT PRECLUDE AN
ISOLATED STRIKE IN ANY STRONGER ACTIVITY.

REGARDING WINDS...WITH THE BROKEN TO OVERCAST LOW CLOUD
DECK...MIXING IS BEING LIMITED AND GETING GUSTS TO AROUND 30 KT OR
SO. ANY STRONGER GUSTS WOULD BE IN THE NEXT HOUR BEFORE A RAPID
DROP OFF LATER THIS MORNING.

KMD

&&

.SHORT TERM...
345 AM CDT

THROUGH MONDAY NIGHT...
FOR THE REMAINDER OF THE NIGHT AND INTO MONDAY MORNING...PCPN
CHANCES CONTINUE TO WANE AS LATEST RADAR TRENDS ONLY SHOW SOME SCT
SHRA WHICH ARE DECREASING IN INTENSITY.  IN SPITE OF DEWPOINTS IN
THE LOW 60S...AND A STRONG LOW LEVEL JET...50 KT AT 925 MB...THERE
IS AN ELEMENT LACKING WHICH IS SEEMS TO BE PREVENTING THE
MAINTENANCE OF SHRA/TSRA OVER NERN IL/NWRN IN.  THE MAIN MISSING
ELEMENTS IS FORCING.  THE SFC AND UPPER LEVEL LOW ARE WAY TO THE
WEST...OVER THE NRN PLAINS. THE SHORTWAVE CLIMBING UP THE NWRN
PERIPHERY OF THE HIGH AMPLITUDE RIDGE IS BEING SLOWED BY THE HIGH
AMPLITUDE...AND IS BEING FORCED TO A MORE WLY TRACK THROUGH THE
UPPER MISSISSIPPI VALLEY THAN PREVIOUSLY ANTICIPATED.  SO...FOR THE
REMAINDER OF THE OVERNIGHT HOURS AND THE DAYTIME HOURS MONDAY...HAVE
BACK OF TO ISOLD-SCT SHRA.  WILL KEEP ISOLD TS MENTION FOR THE LATE
MORNING HOURS...THROUGH AROUND NOON...WITH THE DAYTIME HEATING...BUT
CONFIDENCE IN ANY TS IS RATHER LOW AT THIS TIME.  BY THIS
AFTERNOON...A MID LEVEL DRY SLOT IS EXPECTED TO MOVE ACROSS THE
REGION...FURTHER LIMITING PCPN CHANCES AND IT IS QUITE LIKELY THAT
THE REGION WILL REMAIN DRY THROUGH THE DAY.  HOWEVER...WHILE THE
PCPN CHANCES ARE DIMINISHING...THE LIKELIHOOD OF STRONG WINDS IS
STILL A CONCERN.  WITH THE DIMINISHING PCPN CHANCES...LESS SKY COVER
THAN PREVIOUSLY ANTICIPATED IS ALSO POSSIBLE.  A STRONG SWLY
PRESSURE GRADIENT IS SETTING UP ACROSS THE REGION BETWEEN SFC
RIDGING ACROSS THE SERN CONUS AND AND LOW PRESSURE FROM THE UPPER
MISSISSIPPI VALLEY TO THE WESTERN PLAINS.  THE STRONG GRADIENT WILL
HELP DRIVE THE SFC WINDS AND THE DIMINISHING CLOUD COVER COULD HELP
ENHANCE DEEP LAYER MIXING...TAPPING STRONGER WINDS ALOFT.  SUSTAINED
25-25 MPH WINDS ARE LIKELY WITH GUSTS OF 30-35 MPH.
ALSO...PERSISTENT WARM/MOIST ADVECTION AT THE SFC WILL BRING
TEMPERATURES INTO THE LOW TO MIDDLE 80S WITH DEWPOINTS IN THE LOWER
60S.

FOR MONDAY NIGHT...THE BREEZY CONDITIONS WILL PERSIST INTO THE AS
THERE SHOULD BE LITTLE CHANGE TO THE SFC AND UPPER LEVEL PATTERNS.
THE UPPER RIDGE WILL LOSE A LITTLE AMPLITUDE AS SHORT WAVE ENERGY
OVERTOPS THE RIDGE...BUT GENERAL TROUGHING WILL PERSIST ACROSS THE
UPPER MISSISSIPPI VALLEY THROUGH THE CENTRAL PLAINS.  THE NEXT
CHANCE FOR PCPN WILL HOLD OFF UNTIL LATE TONIGHT/EARLY TUESDAY
MORNING AND THE NEXT SHORTWAVE LIFTS OUT OF THE SRN PLAINS AND INTO
THE MIDDLE MISSISSIPPI VALLEY.  AMPLE LOW LEVEL MOISTURE WILL
ALREADY BE IN PLACE SO IT WILL JUST A MATTER OF WHEN THE FORCING
WILL GET HERE.  AGAIN...THERE IS SOME CONCERN THAT THE FORCING WILL
BE TO THE WEST...WITH THE SHORTWAVE TRACKING THROUGH THE MIDDLE
MISSISSIPPI VALLEY AND INTO WI.  SO...WILL CARRY CHANCE POPS FOR THE
REGION...WITH LIKELY POPS APPROACHING THE PONTIAC AREA BY EARLY
TUESDAY MORNING.  THE PERSISTENT WARM/MOIST ADVECTIVE PATTERN AND
BREEZY CONDITIONS SHOULD KEEP TEMPERATURES FROM DROPPING OFF
SIGNIFICANTLY OVERNIGHT AND LOWS SHOULD BE IN THE MIDDLE TO UPPER
60S.

KREIN

&&

.LONG TERM...
239 AM CDT

TUESDAY THROUGH SUNDAY...

TUESDAY THROUGH WEDNESDAY...
500MB TROUGH AXIS WILL SLOWLY PIVOT EAST ACROSS THE CENTRAL PLAINS
INTO THE MID-MISSOURI VALLEY TUE...WITH A SFC WAVE SLIDING NORTH
ACROSS IOWA INTO CENTRAL WISC LATE TUE. THE SFC FEATURE IS NOT
EXPECTED TO BE STRONG...HOWEVER THE GRADIENT DOES TIGHTEN WITH
MODEST HEIGHT FALLS IN THE LOWEST LAYERS OF THE ATMOSPHERE. SOME
INSTABILITY DOES REMAIN ALONG WITH RELATIVELY MOIST SFC CONDS AS
DEW PTS WILL REMAIN IN THE UPR 50S/LOW 60S. PWAT VALUES WILL ALSO
HOVER JUST OVER 1 INCH...WHICH IS SEASONAL. WILL HOLD ONTO MENTION
OF RAIN AND THUNDER...BUT COULD SEE THIS MAINLY FOCUSED IN THE TUE
MORNING TIMEFRAME.

WITH CONSIDERABLE SOLAR SHIELDING PROGGED FOR TUE...TEMPS MAY
STRUGGLE TO WARM BEYOND THE MID/UPR 70S. BUT WITH GUIDANCE HINTING
AT A DRY SLOT LIFTING NORTHEAST ACROSS THE REGION TUE EVE...THIS
COULD INTRODUCE SOME EROSION TO THE CLOUD COVER IN THE AFTN HOURS
TUE AND ALLOW SOME SFC HEATING TO OCCUR AND PUSH TEMPS TO ARND 80.

GUIDANCE LIFTS THE DRY SLOT OVERHEAD LATE TUE NGT...WITH THE 500MB
TROUGH AXIS ARRIVING ARND DAYBREAK WED AND LIFTING EAST ACROSS LOWER
MICHIGAN. THIS WILL BRING DRY ONLY SLIGHT CHANCE POPS AS WEAK SFC
RIDGING BEGINS TO NUDGE EAST ACROSS THE MISSOURI VALLEY TOWARDS THE
FORECAST AREA MIDDAY WED. IT IS POSSIBLE THAT ENOUGH DRY AIR
INFLUENCE COULD ALLOW FOR REMOVAL OF THE SLIGHT CHANCE POPS WED
AFTN. THERMAL TROUGH LAGS BEHIND THE FRONTAL BOUNDARY WED...SO TEMPS
COULD STILL WARM BACK TO ARND 80 AND PERHAPS THE LOW 80S IN THE
SOUTHERN CWFA.

THURSDAY THROUGH SUNDAY...
ANTI-CYCLONIC FLOW ARRIVES THUR WITH AT LEAST ONE PERIOD OF DRY
WEATHER EXPECTED FOR NORTHERN IL/NORTHWEST IN. ONLY A COUPLE
ENSEMBLE MEMBERS CONTINUE TO PROG POPS ALONG THE SOUTHERN FORECAST
AREA THUR...BUT COULD SEE THIS TRENDING DRY IN THE NEXT FEW
SOLUTIONS. WITH WARM TEMPS ALOFT EXPECTED THUR AND THIN CLOUD
COVER...THUR HIGHS COULD PEAK IN THE LOW 80S.

THEN FOCUS TURNS TOWARDS THE UPCOMING WEEKEND AND A PATTERN SHIFT
AWAY FROM THE WARM/HUMID CONDITIONS. ENSEMBLES SHOW MINIMAL SPREAD
IN THE LATE WEEK PERIODS...WITH THE UPSTREAM RIDGE OVER
ALASKA/WESTERN CANADA AND A DOWNSTREAM MID-LVL RIDGE ACROSS THE
SOUTHEAST CONUS. BOTH OF THESE FEATURES IN TIME BEGIN TO
WEAKEN...WITH THE LONGWAVE PATTERN TRANSITIONING INTO A SEMI-ZONAL
ORIENTATION BY THE SECOND HALF OF THE WEEKEND.

OPER GUIDANCE HAS BEEN CONSISTENT WITH PROGGING A ROBUST 500MB
TROUGH TO SLIDE SOUTH FROM CENTRAL CANADA FRI...ALONG WITH A STRONG
CANADIAN SFC RIDGE ON IT/S HEELS. WITH A CHANNEL OF MOISTURE
REMAINING ACROSS THE SOUTHERN PLAINS STRETCHING NORTHEAST THROUGH
THE UPPER MIDWEST...THIS BOUNDARY WILL BECOME ACTIVE WITH A SFC WAVE
DEVELOPING ACROSS THE SOUTHERN PLAINS. THIS LOW WILL THEN LIFT
NORTHEAST TOWARDS THE CWFA FRI WITH A COLD FRONT ARRIVING ACROSS THE
FORECAST AREA SAT. WINDS LOOK TO SHIFT TO THE NORTH...WITH MUCH
COOLER AIR SLIDING SOUTH AND LIKELY KNOCKING TEMPS BACK TO SUB-
SEASONAL CONDS IN THE UPR 60S/NEAR 70 DEGREE RANGE SAT/SUN. IF
NORTHEAST WINDS MATERIALIZE...NEXT WEEKEND AREAS ADJACENT TO LAKE
MICHIGAN ALONG THE IL/IN SHORELINE COULD BE LOCKED IN THE UPR 50S TO
LOW 60S FOR HIGHS WITH A COLD FLOW OFF OF LAKE MICHIGAN.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 20Z...

* GUSTY SOUTHWEST WINDS.

* MVFR CEILINGS POSSIBLE EARLY TUESDAY MORNING.

* SHOWERS LIKELY WITH PERIODIC THUNDERSTORMS LATE IN THE FORECAST
  PERIOD.

RODRIGUEZ

//DISCUSSION...UPDATED 18Z...

MUCH OF THE SHOWERS ARE EXITING THE AREA EARLY THIS AFTERNOON.
HOWEVER...AN ISOLATED LIGHT SHOWER WILL STILL BE POSSIBLE OVER THE
NEXT HOUR BEFORE PREVAILING DRY CONDITIONS ARE EXPECTED THIS
AFTERNOON AND TONIGHT. LINGERING MVFR CEILINGS WILL LIFT TO VFR
THROUGH 20-21Z THIS AFTERNOON WITH SKIES THEN SCATTERING THIS
EVENING...AS THE SOUTHWEST WINDS/GUSTS DIMINISH INTO THE EVENING.
WITH FAIRLY MOIST CONDITIONS REMAINING IN PLACE TONIGHT INTO
TUESDAY...REDEVELOPING LOW CEILINGS DO APPEAR TO BE A POSSIBILITY.
OVERALL CONFIDENCE IS LOWER DURING THIS PERIOD...BUT DID MAKE
MENTION OF AT LEAST MVFR CEILINGS...AND WILL NEED TO MONITOR FOR
POTENTIALLY LOWER CEILINGS. HAVE PUSHED BACK TIMING OF PRECIP LATE
IN THE PERIOD...BUT WITH INSTABILITY AND FORCING
INCREASING...SHOWERS AND THUNDERSTORMS DO APPEAR LIKELY TUESDAY.
STILL SOME UNCERTAINTY WITH EXACT TIMING AND DURATION...AND EVEN
THE POSSIBILITY FOR AN ADDITIONAL PERIOD OF THUNDERSTORMS TUESDAY
AFTERNOON.

RODRIGUEZ

//ORD AND MDW CONFIDENCE...UPDATED 20Z...

* HIGH CONFIDENCE WITH WIND SPEED/DIRECTION.

* MEDIUM HIGH CONFIDENCE WITH CEILINGS.

* HIGH CONFIDENCE OF SHOWERS/THUNDERSTORMS...MEDIUM CONFIDENCE
  WITH TIMING/DURATION.

RODRIGUEZ

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/TSRA LATE. SOUTHEAST WINDS.

FRIDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. SOUTHWEST WINDS
BECOMING NORTHEAST OVERNIGHT.

SATURDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. NORTHEAST
WINDS.

SUNDAY...CHANCE TSRA. MVFR POSSIBLE. NORTHEAST WINDS.

KREIN

&&

.MARINE...
304 AM CDT

LOW PRESSURE WILL BE STEADILY LIFTING NORTH ACROSS THE MISSOURI
VALLEY THIS MORNING...REACHING LAKE SUPERIOR BY THIS EVENING AND
CONTINUING TO SLIDE EAST/NORTHEAST TOWARDS QUEBEC BY TUESDAY
MORNING. A FRONTAL BOUNDARY WILL REMAIN OVER THE FAR NORTHERN
PORTIONS OF LAKE MICHIGAN. MEANWHILE GUSTY SOUTHERLY WINDS ARE
EXPECTED TO INCREASE THIS MORNING...WITH OCCASIONAL GALES FOR THE
NEARSHORE WATERS OF IL/IN. ACROSS THE OPEN WATERS...EXPECT THE
WARM/MOIST AIR TO STRUGGLE TO REACH THE SFC OF THE LAKE WITH SOME
DEGREE OF LAKE STABILITY. WAVES WILL STEADILY BUILD ACROSS THE
NORTHERN HALF OF THE LAKE AS A RESULT OF THE LONG FETCH. STILL
FEEL THAT GUSTS WILL REACH 30KT ACROSS THE LAKE...HOWEVER
CONFIDENCE HAS DIMINISHED SLIGHTLY AS NEW GUIDANCE HAS BECOME A
LITTLE LESS WITH THE WIND FIELDS. NONETHELESS...WAVES FOR THE
NORTHERN HALF OF THE LAKE WILL LIKELY TOP OUT IN THE 4 TO 7 FT
RANGE WITH OCCASIONAL WAVES REACHING 9 FT THIS AFTERNOON/EVENING.

THE GRADIENT QUICKLY DIMINISHES THIS EVENING...BUT EXPECT
SOUTHERLY WINDS TO PERSIST. THIS WILL ALLOW WAVES TO SUBSIDE TO 3
TO 5 FT. ANOTHER LOW WILL ARRIVE TUE...WITH WINDS NUDGING BACK UP
HOWEVER WARM AIR WILL CONTINUE TO FLOW ACROSS THE LAKE AND COULD
FURTHER ENHANCE THE LAKE STABILITY AND KEEP WAVES FROM BUILDING TO
LARGE.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...NEARSHORE WATERS UNTIL 3
     PM MONDAY.

     SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 251955
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
255 PM CDT MON MAY 25 2015

.UPDATE...

COMPACT NEGATIVELY TILTED TROUGH AXIS IS SLIDING NORTHEAST THROUGH
IOWA AND WESTERN ILLINOIS. EASTERN EDGE OF THE TROUGH WILL MOVE
THROUGH NORTHEAST ILLINOIS THIS MORNING. NOTED UPTICK IN SHOWER
ACTIVITY ASSOCIATED WITH THIS WAVE IS PRODUCING MORE ORGANIZED BUT
STILL LARGELY SCATTERED SHOWERS. STILL TRACKING THIS FEATURE WILL
BRING THE BEST CHANCE FOR SOME BRIEF DOWNPOURS IN THE COMING
HOURS...AND THESE WILL SPREAD INTO THE WEST METRO AREA IN THE NEXT
HOUR...SPREADING INTO CHICAGOLAND SHORTLY THERE AFTER. THE CLOUDS
PRODUCING THE SHOWER ACTIVITY ARE SHALLOW AND MID LEVEL LAPSE
RATES ARE SUBPAR...THUS THUNDER SHOULD BE LIMITED AT BEST. SOME
WEAK INSTABILITY IS NOTED SOUTH OF I-80 WHICH DOES NOT PRECLUDE AN
ISOLATED STRIKE IN ANY STRONGER ACTIVITY.

REGARDING WINDS...WITH THE BROKEN TO OVERCAST LOW CLOUD
DECK...MIXING IS BEING LIMITED AND GETING GUSTS TO AROUND 30 KT OR
SO. ANY STRONGER GUSTS WOULD BE IN THE NEXT HOUR BEFORE A RAPID
DROP OFF LATER THIS MORNING.

KMD

&&

.SHORT TERM...
345 AM CDT

THROUGH MONDAY NIGHT...
FOR THE REMAINDER OF THE NIGHT AND INTO MONDAY MORNING...PCPN
CHANCES CONTINUE TO WANE AS LATEST RADAR TRENDS ONLY SHOW SOME SCT
SHRA WHICH ARE DECREASING IN INTENSITY.  IN SPITE OF DEWPOINTS IN
THE LOW 60S...AND A STRONG LOW LEVEL JET...50 KT AT 925 MB...THERE
IS AN ELEMENT LACKING WHICH IS SEEMS TO BE PREVENTING THE
MAINTENANCE OF SHRA/TSRA OVER NERN IL/NWRN IN.  THE MAIN MISSING
ELEMENTS IS FORCING.  THE SFC AND UPPER LEVEL LOW ARE WAY TO THE
WEST...OVER THE NRN PLAINS. THE SHORTWAVE CLIMBING UP THE NWRN
PERIPHERY OF THE HIGH AMPLITUDE RIDGE IS BEING SLOWED BY THE HIGH
AMPLITUDE...AND IS BEING FORCED TO A MORE WLY TRACK THROUGH THE
UPPER MISSISSIPPI VALLEY THAN PREVIOUSLY ANTICIPATED.  SO...FOR THE
REMAINDER OF THE OVERNIGHT HOURS AND THE DAYTIME HOURS MONDAY...HAVE
BACK OF TO ISOLD-SCT SHRA.  WILL KEEP ISOLD TS MENTION FOR THE LATE
MORNING HOURS...THROUGH AROUND NOON...WITH THE DAYTIME HEATING...BUT
CONFIDENCE IN ANY TS IS RATHER LOW AT THIS TIME.  BY THIS
AFTERNOON...A MID LEVEL DRY SLOT IS EXPECTED TO MOVE ACROSS THE
REGION...FURTHER LIMITING PCPN CHANCES AND IT IS QUITE LIKELY THAT
THE REGION WILL REMAIN DRY THROUGH THE DAY.  HOWEVER...WHILE THE
PCPN CHANCES ARE DIMINISHING...THE LIKELIHOOD OF STRONG WINDS IS
STILL A CONCERN.  WITH THE DIMINISHING PCPN CHANCES...LESS SKY COVER
THAN PREVIOUSLY ANTICIPATED IS ALSO POSSIBLE.  A STRONG SWLY
PRESSURE GRADIENT IS SETTING UP ACROSS THE REGION BETWEEN SFC
RIDGING ACROSS THE SERN CONUS AND AND LOW PRESSURE FROM THE UPPER
MISSISSIPPI VALLEY TO THE WESTERN PLAINS.  THE STRONG GRADIENT WILL
HELP DRIVE THE SFC WINDS AND THE DIMINISHING CLOUD COVER COULD HELP
ENHANCE DEEP LAYER MIXING...TAPPING STRONGER WINDS ALOFT.  SUSTAINED
25-25 MPH WINDS ARE LIKELY WITH GUSTS OF 30-35 MPH.
ALSO...PERSISTENT WARM/MOIST ADVECTION AT THE SFC WILL BRING
TEMPERATURES INTO THE LOW TO MIDDLE 80S WITH DEWPOINTS IN THE LOWER
60S.

FOR MONDAY NIGHT...THE BREEZY CONDITIONS WILL PERSIST INTO THE AS
THERE SHOULD BE LITTLE CHANGE TO THE SFC AND UPPER LEVEL PATTERNS.
THE UPPER RIDGE WILL LOSE A LITTLE AMPLITUDE AS SHORT WAVE ENERGY
OVERTOPS THE RIDGE...BUT GENERAL TROUGHING WILL PERSIST ACROSS THE
UPPER MISSISSIPPI VALLEY THROUGH THE CENTRAL PLAINS.  THE NEXT
CHANCE FOR PCPN WILL HOLD OFF UNTIL LATE TONIGHT/EARLY TUESDAY
MORNING AND THE NEXT SHORTWAVE LIFTS OUT OF THE SRN PLAINS AND INTO
THE MIDDLE MISSISSIPPI VALLEY.  AMPLE LOW LEVEL MOISTURE WILL
ALREADY BE IN PLACE SO IT WILL JUST A MATTER OF WHEN THE FORCING
WILL GET HERE.  AGAIN...THERE IS SOME CONCERN THAT THE FORCING WILL
BE TO THE WEST...WITH THE SHORTWAVE TRACKING THROUGH THE MIDDLE
MISSISSIPPI VALLEY AND INTO WI.  SO...WILL CARRY CHANCE POPS FOR THE
REGION...WITH LIKELY POPS APPROACHING THE PONTIAC AREA BY EARLY
TUESDAY MORNING.  THE PERSISTENT WARM/MOIST ADVECTIVE PATTERN AND
BREEZY CONDITIONS SHOULD KEEP TEMPERATURES FROM DROPPING OFF
SIGNIFICANTLY OVERNIGHT AND LOWS SHOULD BE IN THE MIDDLE TO UPPER
60S.

KREIN

&&

.LONG TERM...
239 AM CDT

TUESDAY THROUGH SUNDAY...

TUESDAY THROUGH WEDNESDAY...
500MB TROUGH AXIS WILL SLOWLY PIVOT EAST ACROSS THE CENTRAL PLAINS
INTO THE MID-MISSOURI VALLEY TUE...WITH A SFC WAVE SLIDING NORTH
ACROSS IOWA INTO CENTRAL WISC LATE TUE. THE SFC FEATURE IS NOT
EXPECTED TO BE STRONG...HOWEVER THE GRADIENT DOES TIGHTEN WITH
MODEST HEIGHT FALLS IN THE LOWEST LAYERS OF THE ATMOSPHERE. SOME
INSTABILITY DOES REMAIN ALONG WITH RELATIVELY MOIST SFC CONDS AS
DEW PTS WILL REMAIN IN THE UPR 50S/LOW 60S. PWAT VALUES WILL ALSO
HOVER JUST OVER 1 INCH...WHICH IS SEASONAL. WILL HOLD ONTO MENTION
OF RAIN AND THUNDER...BUT COULD SEE THIS MAINLY FOCUSED IN THE TUE
MORNING TIMEFRAME.

WITH CONSIDERABLE SOLAR SHIELDING PROGGED FOR TUE...TEMPS MAY
STRUGGLE TO WARM BEYOND THE MID/UPR 70S. BUT WITH GUIDANCE HINTING
AT A DRY SLOT LIFTING NORTHEAST ACROSS THE REGION TUE EVE...THIS
COULD INTRODUCE SOME EROSION TO THE CLOUD COVER IN THE AFTN HOURS
TUE AND ALLOW SOME SFC HEATING TO OCCUR AND PUSH TEMPS TO ARND 80.

GUIDANCE LIFTS THE DRY SLOT OVERHEAD LATE TUE NGT...WITH THE 500MB
TROUGH AXIS ARRIVING ARND DAYBREAK WED AND LIFTING EAST ACROSS LOWER
MICHIGAN. THIS WILL BRING DRY ONLY SLIGHT CHANCE POPS AS WEAK SFC
RIDGING BEGINS TO NUDGE EAST ACROSS THE MISSOURI VALLEY TOWARDS THE
FORECAST AREA MIDDAY WED. IT IS POSSIBLE THAT ENOUGH DRY AIR
INFLUENCE COULD ALLOW FOR REMOVAL OF THE SLIGHT CHANCE POPS WED
AFTN. THERMAL TROUGH LAGS BEHIND THE FRONTAL BOUNDARY WED...SO TEMPS
COULD STILL WARM BACK TO ARND 80 AND PERHAPS THE LOW 80S IN THE
SOUTHERN CWFA.

THURSDAY THROUGH SUNDAY...
ANTI-CYCLONIC FLOW ARRIVES THUR WITH AT LEAST ONE PERIOD OF DRY
WEATHER EXPECTED FOR NORTHERN IL/NORTHWEST IN. ONLY A COUPLE
ENSEMBLE MEMBERS CONTINUE TO PROG POPS ALONG THE SOUTHERN FORECAST
AREA THUR...BUT COULD SEE THIS TRENDING DRY IN THE NEXT FEW
SOLUTIONS. WITH WARM TEMPS ALOFT EXPECTED THUR AND THIN CLOUD
COVER...THUR HIGHS COULD PEAK IN THE LOW 80S.

THEN FOCUS TURNS TOWARDS THE UPCOMING WEEKEND AND A PATTERN SHIFT
AWAY FROM THE WARM/HUMID CONDITIONS. ENSEMBLES SHOW MINIMAL SPREAD
IN THE LATE WEEK PERIODS...WITH THE UPSTREAM RIDGE OVER
ALASKA/WESTERN CANADA AND A DOWNSTREAM MID-LVL RIDGE ACROSS THE
SOUTHEAST CONUS. BOTH OF THESE FEATURES IN TIME BEGIN TO
WEAKEN...WITH THE LONGWAVE PATTERN TRANSITIONING INTO A SEMI-ZONAL
ORIENTATION BY THE SECOND HALF OF THE WEEKEND.

OPER GUIDANCE HAS BEEN CONSISTENT WITH PROGGING A ROBUST 500MB
TROUGH TO SLIDE SOUTH FROM CENTRAL CANADA FRI...ALONG WITH A STRONG
CANADIAN SFC RIDGE ON IT/S HEELS. WITH A CHANNEL OF MOISTURE
REMAINING ACROSS THE SOUTHERN PLAINS STRETCHING NORTHEAST THROUGH
THE UPPER MIDWEST...THIS BOUNDARY WILL BECOME ACTIVE WITH A SFC WAVE
DEVELOPING ACROSS THE SOUTHERN PLAINS. THIS LOW WILL THEN LIFT
NORTHEAST TOWARDS THE CWFA FRI WITH A COLD FRONT ARRIVING ACROSS THE
FORECAST AREA SAT. WINDS LOOK TO SHIFT TO THE NORTH...WITH MUCH
COOLER AIR SLIDING SOUTH AND LIKELY KNOCKING TEMPS BACK TO SUB-
SEASONAL CONDS IN THE UPR 60S/NEAR 70 DEGREE RANGE SAT/SUN. IF
NORTHEAST WINDS MATERIALIZE...NEXT WEEKEND AREAS ADJACENT TO LAKE
MICHIGAN ALONG THE IL/IN SHORELINE COULD BE LOCKED IN THE UPR 50S TO
LOW 60S FOR HIGHS WITH A COLD FLOW OFF OF LAKE MICHIGAN.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 20Z...

* GUSTY SOUTHWEST WINDS.

* MVFR CEILINGS POSSIBLE EARLY TUESDAY MORNING.

* SHOWERS LIKELY WITH PERIODIC THUNDERSTORMS LATE IN THE FORECAST
  PERIOD.

RODRIGUEZ

//DISCUSSION...UPDATED 18Z...

MUCH OF THE SHOWERS ARE EXITING THE AREA EARLY THIS AFTERNOON.
HOWEVER...AN ISOLATED LIGHT SHOWER WILL STILL BE POSSIBLE OVER THE
NEXT HOUR BEFORE PREVAILING DRY CONDITIONS ARE EXPECTED THIS
AFTERNOON AND TONIGHT. LINGERING MVFR CEILINGS WILL LIFT TO VFR
THROUGH 20-21Z THIS AFTERNOON WITH SKIES THEN SCATTERING THIS
EVENING...AS THE SOUTHWEST WINDS/GUSTS DIMINISH INTO THE EVENING.
WITH FAIRLY MOIST CONDITIONS REMAINING IN PLACE TONIGHT INTO
TUESDAY...REDEVELOPING LOW CEILINGS DO APPEAR TO BE A POSSIBILITY.
OVERALL CONFIDENCE IS LOWER DURING THIS PERIOD...BUT DID MAKE
MENTION OF AT LEAST MVFR CEILINGS...AND WILL NEED TO MONITOR FOR
POTENTIALLY LOWER CEILINGS. HAVE PUSHED BACK TIMING OF PRECIP LATE
IN THE PERIOD...BUT WITH INSTABILITY AND FORCING
INCREASING...SHOWERS AND THUNDERSTORMS DO APPEAR LIKELY TUESDAY.
STILL SOME UNCERTAINTY WITH EXACT TIMING AND DURATION...AND EVEN
THE POSSIBILITY FOR AN ADDITIONAL PERIOD OF THUNDERSTORMS TUESDAY
AFTERNOON.

RODRIGUEZ

//ORD AND MDW CONFIDENCE...UPDATED 20Z...

* HIGH CONFIDENCE WITH WIND SPEED/DIRECTION.

* MEDIUM HIGH CONFIDENCE WITH CEILINGS.

* HIGH CONFIDENCE OF SHOWERS/THUNDERSTORMS...MEDIUM CONFIDENCE
  WITH TIMING/DURATION.

RODRIGUEZ

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/TSRA LATE. SOUTHEAST WINDS.

FRIDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. SOUTHWEST WINDS
BECOMING NORTHEAST OVERNIGHT.

SATURDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. NORTHEAST
WINDS.

SUNDAY...CHANCE TSRA. MVFR POSSIBLE. NORTHEAST WINDS.

KREIN

&&

.MARINE...
304 AM CDT

LOW PRESSURE WILL BE STEADILY LIFTING NORTH ACROSS THE MISSOURI
VALLEY THIS MORNING...REACHING LAKE SUPERIOR BY THIS EVENING AND
CONTINUING TO SLIDE EAST/NORTHEAST TOWARDS QUEBEC BY TUESDAY
MORNING. A FRONTAL BOUNDARY WILL REMAIN OVER THE FAR NORTHERN
PORTIONS OF LAKE MICHIGAN. MEANWHILE GUSTY SOUTHERLY WINDS ARE
EXPECTED TO INCREASE THIS MORNING...WITH OCCASIONAL GALES FOR THE
NEARSHORE WATERS OF IL/IN. ACROSS THE OPEN WATERS...EXPECT THE
WARM/MOIST AIR TO STRUGGLE TO REACH THE SFC OF THE LAKE WITH SOME
DEGREE OF LAKE STABILITY. WAVES WILL STEADILY BUILD ACROSS THE
NORTHERN HALF OF THE LAKE AS A RESULT OF THE LONG FETCH. STILL
FEEL THAT GUSTS WILL REACH 30KT ACROSS THE LAKE...HOWEVER
CONFIDENCE HAS DIMINISHED SLIGHTLY AS NEW GUIDANCE HAS BECOME A
LITTLE LESS WITH THE WIND FIELDS. NONETHELESS...WAVES FOR THE
NORTHERN HALF OF THE LAKE WILL LIKELY TOP OUT IN THE 4 TO 7 FT
RANGE WITH OCCASIONAL WAVES REACHING 9 FT THIS AFTERNOON/EVENING.

THE GRADIENT QUICKLY DIMINISHES THIS EVENING...BUT EXPECT
SOUTHERLY WINDS TO PERSIST. THIS WILL ALLOW WAVES TO SUBSIDE TO 3
TO 5 FT. ANOTHER LOW WILL ARRIVE TUE...WITH WINDS NUDGING BACK UP
HOWEVER WARM AIR WILL CONTINUE TO FLOW ACROSS THE LAKE AND COULD
FURTHER ENHANCE THE LAKE STABILITY AND KEEP WAVES FROM BUILDING TO
LARGE.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...NEARSHORE WATERS UNTIL 3
     PM MONDAY.

     SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 251803
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
103 PM CDT MON MAY 25 2015

.UPDATE...

COMPACT NEGATIVELY TILTED TROUGH AXIS IS SLIDING NORTHEAST THROUGH
IOWA AND WESTERN ILLINOIS. EASTERN EDGE OF THE TROUGH WILL MOVE
THROUGH NORTHEAST ILLINOIS THIS MORNING. NOTED UPTICK IN SHOWER
ACTIVITY ASSOCIATED WITH THIS WAVE IS PRODUCING MORE ORGANIZED BUT
STILL LARGELY SCATTERED SHOWERS. STILL TRACKING THIS FEATURE WILL
BRING THE BEST CHANCE FOR SOME BRIEF DOWNPOURS IN THE COMING
HOURS...AND THESE WILL SPREAD INTO THE WEST METRO AREA IN THE NEXT
HOUR...SPREADING INTO CHICAGOLAND SHORTLY THERE AFTER. THE CLOUDS
PRODUCING THE SHOWER ACTIVITY ARE SHALLOW AND MID LEVEL LAPSE
RATES ARE SUBPAR...THUS THUNDER SHOULD BE LIMITED AT BEST. SOME
WEAK INSTABILITY IS NOTED SOUTH OF I-80 WHICH DOES NOT PRECLUDE AN
ISOLATED STRIKE IN ANY STRONGER ACTIVITY.

REGARDING WINDS...WITH THE BROKEN TO OVERCAST LOW CLOUD
DECK...MIXING IS BEING LIMITED AND GETING GUSTS TO AROUND 30 KT OR
SO. ANY STRONGER GUSTS WOULD BE IN THE NEXT HOUR BEFORE A RAPID
DROP OFF LATER THIS MORNING.

KMD

&&

.SHORT TERM...
345 AM CDT

THROUGH MONDAY NIGHT...
FOR THE REMAINDER OF THE NIGHT AND INTO MONDAY MORNING...PCPN
CHANCES CONTINUE TO WANE AS LATEST RADAR TRENDS ONLY SHOW SOME SCT
SHRA WHICH ARE DECREASING IN INTENSITY.  IN SPITE OF DEWPOINTS IN
THE LOW 60S...AND A STRONG LOW LEVEL JET...50 KT AT 925 MB...THERE
IS AN ELEMENT LACKING WHICH IS SEEMS TO BE PREVENTING THE
MAINTENANCE OF SHRA/TSRA OVER NERN IL/NWRN IN.  THE MAIN MISSING
ELEMENTS IS FORCING.  THE SFC AND UPPER LEVEL LOW ARE WAY TO THE
WEST...OVER THE NRN PLAINS. THE SHORTWAVE CLIMBING UP THE NWRN
PERIPHERY OF THE HIGH AMPLITUDE RIDGE IS BEING SLOWED BY THE HIGH
AMPLITUDE...AND IS BEING FORCED TO A MORE WLY TRACK THROUGH THE
UPPER MISSISSIPPI VALLEY THAN PREVIOUSLY ANTICIPATED.  SO...FOR THE
REMAINDER OF THE OVERNIGHT HOURS AND THE DAYTIME HOURS MONDAY...HAVE
BACK OF TO ISOLD-SCT SHRA.  WILL KEEP ISOLD TS MENTION FOR THE LATE
MORNING HOURS...THROUGH AROUND NOON...WITH THE DAYTIME HEATING...BUT
CONFIDENCE IN ANY TS IS RATHER LOW AT THIS TIME.  BY THIS
AFTERNOON...A MID LEVEL DRY SLOT IS EXPECTED TO MOVE ACROSS THE
REGION...FURTHER LIMITING PCPN CHANCES AND IT IS QUITE LIKELY THAT
THE REGION WILL REMAIN DRY THROUGH THE DAY.  HOWEVER...WHILE THE
PCPN CHANCES ARE DIMINISHING...THE LIKELIHOOD OF STRONG WINDS IS
STILL A CONCERN.  WITH THE DIMINISHING PCPN CHANCES...LESS SKY COVER
THAN PREVIOUSLY ANTICIPATED IS ALSO POSSIBLE.  A STRONG SWLY
PRESSURE GRADIENT IS SETTING UP ACROSS THE REGION BETWEEN SFC
RIDGING ACROSS THE SERN CONUS AND AND LOW PRESSURE FROM THE UPPER
MISSISSIPPI VALLEY TO THE WESTERN PLAINS.  THE STRONG GRADIENT WILL
HELP DRIVE THE SFC WINDS AND THE DIMINISHING CLOUD COVER COULD HELP
ENHANCE DEEP LAYER MIXING...TAPPING STRONGER WINDS ALOFT.  SUSTAINED
25-25 MPH WINDS ARE LIKELY WITH GUSTS OF 30-35 MPH.
ALSO...PERSISTENT WARM/MOIST ADVECTION AT THE SFC WILL BRING
TEMPERATURES INTO THE LOW TO MIDDLE 80S WITH DEWPOINTS IN THE LOWER
60S.

FOR MONDAY NIGHT...THE BREEZY CONDITIONS WILL PERSIST INTO THE AS
THERE SHOULD BE LITTLE CHANGE TO THE SFC AND UPPER LEVEL PATTERNS.
THE UPPER RIDGE WILL LOSE A LITTLE AMPLITUDE AS SHORT WAVE ENERGY
OVERTOPS THE RIDGE...BUT GENERAL TROUGHING WILL PERSIST ACROSS THE
UPPER MISSISSIPPI VALLEY THROUGH THE CENTRAL PLAINS.  THE NEXT
CHANCE FOR PCPN WILL HOLD OFF UNTIL LATE TONIGHT/EARLY TUESDAY
MORNING AND THE NEXT SHORTWAVE LIFTS OUT OF THE SRN PLAINS AND INTO
THE MIDDLE MISSISSIPPI VALLEY.  AMPLE LOW LEVEL MOISTURE WILL
ALREADY BE IN PLACE SO IT WILL JUST A MATTER OF WHEN THE FORCING
WILL GET HERE.  AGAIN...THERE IS SOME CONCERN THAT THE FORCING WILL
BE TO THE WEST...WITH THE SHORTWAVE TRACKING THROUGH THE MIDDLE
MISSISSIPPI VALLEY AND INTO WI.  SO...WILL CARRY CHANCE POPS FOR THE
REGION...WITH LIKELY POPS APPROACHING THE PONTIAC AREA BY EARLY
TUESDAY MORNING.  THE PERSISTENT WARM/MOIST ADVECTIVE PATTERN AND
BREEZY CONDITIONS SHOULD KEEP TEMPERATURES FROM DROPPING OFF
SIGNIFICANTLY OVERNIGHT AND LOWS SHOULD BE IN THE MIDDLE TO UPPER
60S.

KREIN

&&

.LONG TERM...
239 AM CDT

TUESDAY THROUGH SUNDAY...

TUESDAY THROUGH WEDNESDAY...
500MB TROUGH AXIS WILL SLOWLY PIVOT EAST ACROSS THE CENTRAL PLAINS
INTO THE MID-MISSOURI VALLEY TUE...WITH A SFC WAVE SLIDING NORTH
ACROSS IOWA INTO CENTRAL WISC LATE TUE. THE SFC FEATURE IS NOT
EXPECTED TO BE STRONG...HOWEVER THE GRADIENT DOES TIGHTEN WITH
MODEST HEIGHT FALLS IN THE LOWEST LAYERS OF THE ATMOSPHERE. SOME
INSTABILITY DOES REMAIN ALONG WITH RELATIVELY MOIST SFC CONDS AS
DEW PTS WILL REMAIN IN THE UPR 50S/LOW 60S. PWAT VALUES WILL ALSO
HOVER JUST OVER 1 INCH...WHICH IS SEASONAL. WILL HOLD ONTO MENTION
OF RAIN AND THUNDER...BUT COULD SEE THIS MAINLY FOCUSED IN THE TUE
MORNING TIMEFRAME.

WITH CONSIDERABLE SOLAR SHIELDING PROGGED FOR TUE...TEMPS MAY
STRUGGLE TO WARM BEYOND THE MID/UPR 70S. BUT WITH GUIDANCE HINTING
AT A DRY SLOT LIFTING NORTHEAST ACROSS THE REGION TUE EVE...THIS
COULD INTRODUCE SOME EROSION TO THE CLOUD COVER IN THE AFTN HOURS
TUE AND ALLOW SOME SFC HEATING TO OCCUR AND PUSH TEMPS TO ARND 80.

GUIDANCE LIFTS THE DRY SLOT OVERHEAD LATE TUE NGT...WITH THE 500MB
TROUGH AXIS ARRIVING ARND DAYBREAK WED AND LIFTING EAST ACROSS LOWER
MICHIGAN. THIS WILL BRING DRY ONLY SLIGHT CHANCE POPS AS WEAK SFC
RIDGING BEGINS TO NUDGE EAST ACROSS THE MISSOURI VALLEY TOWARDS THE
FORECAST AREA MIDDAY WED. IT IS POSSIBLE THAT ENOUGH DRY AIR
INFLUENCE COULD ALLOW FOR REMOVAL OF THE SLIGHT CHANCE POPS WED
AFTN. THERMAL TROUGH LAGS BEHIND THE FRONTAL BOUNDARY WED...SO TEMPS
COULD STILL WARM BACK TO ARND 80 AND PERHAPS THE LOW 80S IN THE
SOUTHERN CWFA.

THURSDAY THROUGH SUNDAY...
ANTI-CYCLONIC FLOW ARRIVES THUR WITH AT LEAST ONE PERIOD OF DRY
WEATHER EXPECTED FOR NORTHERN IL/NORTHWEST IN. ONLY A COUPLE
ENSEMBLE MEMBERS CONTINUE TO PROG POPS ALONG THE SOUTHERN FORECAST
AREA THUR...BUT COULD SEE THIS TRENDING DRY IN THE NEXT FEW
SOLUTIONS. WITH WARM TEMPS ALOFT EXPECTED THUR AND THIN CLOUD
COVER...THUR HIGHS COULD PEAK IN THE LOW 80S.

THEN FOCUS TURNS TOWARDS THE UPCOMING WEEKEND AND A PATTERN SHIFT
AWAY FROM THE WARM/HUMID CONDITIONS. ENSEMBLES SHOW MINIMAL SPREAD
IN THE LATE WEEK PERIODS...WITH THE UPSTREAM RIDGE OVER
ALASKA/WESTERN CANADA AND A DOWNSTREAM MID-LVL RIDGE ACROSS THE
SOUTHEAST CONUS. BOTH OF THESE FEATURES IN TIME BEGIN TO
WEAKEN...WITH THE LONGWAVE PATTERN TRANSITIONING INTO A SEMI-ZONAL
ORIENTATION BY THE SECOND HALF OF THE WEEKEND.

OPER GUIDANCE HAS BEEN CONSISTENT WITH PROGGING A ROBUST 500MB
TROUGH TO SLIDE SOUTH FROM CENTRAL CANADA FRI...ALONG WITH A STRONG
CANADIAN SFC RIDGE ON IT/S HEELS. WITH A CHANNEL OF MOISTURE
REMAINING ACROSS THE SOUTHERN PLAINS STRETCHING NORTHEAST THROUGH
THE UPPER MIDWEST...THIS BOUNDARY WILL BECOME ACTIVE WITH A SFC WAVE
DEVELOPING ACROSS THE SOUTHERN PLAINS. THIS LOW WILL THEN LIFT
NORTHEAST TOWARDS THE CWFA FRI WITH A COLD FRONT ARRIVING ACROSS THE
FORECAST AREA SAT. WINDS LOOK TO SHIFT TO THE NORTH...WITH MUCH
COOLER AIR SLIDING SOUTH AND LIKELY KNOCKING TEMPS BACK TO SUB-
SEASONAL CONDS IN THE UPR 60S/NEAR 70 DEGREE RANGE SAT/SUN. IF
NORTHEAST WINDS MATERIALIZE...NEXT WEEKEND AREAS ADJACENT TO LAKE
MICHIGAN ALONG THE IL/IN SHORELINE COULD BE LOCKED IN THE UPR 50S TO
LOW 60S FOR HIGHS WITH A COLD FLOW OFF OF LAKE MICHIGAN.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 18Z...

* GUSTY SOUTHWEST WINDS.

* HIGH END MVFR CEILINGS POSSIBLE EARLY THIS AFTERNOON...MVFR
  POSSIBLE AGAIN EARLY TUESDAY MORNING.

* SHOWERS LIKELY WITH PERIODIC THUNDERSTORMS LATE IN THE FORECAST
  PERIOD.

RODRIGUEZ

//DISCUSSION...UPDATED 18Z...

MUCH OF THE SHOWERS ARE EXITING THE AREA EARLY THIS AFTERNOON.
HOWEVER...AN ISOLATED LIGHT SHOWER WILL STILL BE POSSIBLE OVER THE
NEXT HOUR BEFORE PREVAILING DRY CONDITIONS ARE EXPECTED THIS
AFTERNOON AND TONIGHT. LINGERING MVFR CEILINGS WILL LIFT TO VFR
THROUGH 20-21Z THIS AFTERNOON WITH SKIES THEN SCATTERING THIS
EVENING...AS THE SOUTHWEST WINDS/GUSTS DIMINISH INTO THE EVENING.
WITH FAIRLY MOIST CONDITIONS REMAINING IN PLACE TONIGHT INTO
TUESDAY...REDEVELOPING LOW CEILINGS DO APPEAR TO BE A POSSIBILITY.
OVERALL CONFIDENCE IS LOWER DURING THIS PERIOD...BUT DID MAKE
MENTION OF AT LEAST MVFR CEILINGS...AND WILL NEED TO MONITOR FOR
POTENTIALLY LOWER CEILINGS. HAVE PUSHED BACK TIMING OF PRECIP LATE
IN THE PERIOD...BUT WITH INSTABILITY AND FORCING
INCREASING...SHOWERS AND THUNDERSTORMS DO APPEAR LIKELY TUESDAY.
STILL SOME UNCERTAINTY WITH EXACT TIMING AND DURATION...AND EVEN
THE POSSIBILITY FOR AN ADDITIONAL PERIOD OF THUNDERSTORMS TUESDAY
AFTERNOON.

RODRIGUEZ


//ORD AND MDW CONFIDENCE...UPDATED 18Z...

* HIGH CONFIDENCE WITH WIND SPEED/DIRECTION.

* MEDIUM HIGH CONFIDENCE WITH CEILINGS.

* HIGH CONFIDENCE OF SHOWERS/THUNDERSTORMS...MEDIUM CONFIDENCE
  WITH TIMING/DURATION.

RODRIGUEZ

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/TSRA LATE. SOUTHEAST WINDS.

FRIDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. SOUTHWEST WINDS
BECOMING NORTHEAST OVERNIGHT.

SATURDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. NORTHEAST
WINDS.

SUNDAY...CHANCE TSRA. MVFR POSSIBLE. NORTHEAST WINDS.

KREIN

&&

.MARINE...
304 AM CDT

LOW PRESSURE WILL BE STEADILY LIFTING NORTH ACROSS THE MISSOURI
VALLEY THIS MORNING...REACHING LAKE SUPERIOR BY THIS EVENING AND
CONTINUING TO SLIDE EAST/NORTHEAST TOWARDS QUEBEC BY TUESDAY
MORNING. A FRONTAL BOUNDARY WILL REMAIN OVER THE FAR NORTHERN
PORTIONS OF LAKE MICHIGAN. MEANWHILE GUSTY SOUTHERLY WINDS ARE
EXPECTED TO INCREASE THIS MORNING...WITH OCCASIONAL GALES FOR THE
NEARSHORE WATERS OF IL/IN. ACROSS THE OPEN WATERS...EXPECT THE
WARM/MOIST AIR TO STRUGGLE TO REACH THE SFC OF THE LAKE WITH SOME
DEGREE OF LAKE STABILITY. WAVES WILL STEADILY BUILD ACROSS THE
NORTHERN HALF OF THE LAKE AS A RESULT OF THE LONG FETCH. STILL
FEEL THAT GUSTS WILL REACH 30KT ACROSS THE LAKE...HOWEVER
CONFIDENCE HAS DIMINISHED SLIGHTLY AS NEW GUIDANCE HAS BECOME A
LITTLE LESS WITH THE WIND FIELDS. NONETHELESS...WAVES FOR THE
NORTHERN HALF OF THE LAKE WILL LIKELY TOP OUT IN THE 4 TO 7 FT
RANGE WITH OCCASIONAL WAVES REACHING 9 FT THIS AFTERNOON/EVENING.

THE GRADIENT QUICKLY DIMINISHES THIS EVENING...BUT EXPECT
SOUTHERLY WINDS TO PERSIST. THIS WILL ALLOW WAVES TO SUBSIDE TO 3
TO 5 FT. ANOTHER LOW WILL ARRIVE TUE...WITH WINDS NUDGING BACK UP
HOWEVER WARM AIR WILL CONTINUE TO FLOW ACROSS THE LAKE AND COULD
FURTHER ENHANCE THE LAKE STABILITY AND KEEP WAVES FROM BUILDING TO
LARGE.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...NEARSHORE WATERS UNTIL 3
     PM MONDAY.

     SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 251803
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
103 PM CDT MON MAY 25 2015

.UPDATE...

COMPACT NEGATIVELY TILTED TROUGH AXIS IS SLIDING NORTHEAST THROUGH
IOWA AND WESTERN ILLINOIS. EASTERN EDGE OF THE TROUGH WILL MOVE
THROUGH NORTHEAST ILLINOIS THIS MORNING. NOTED UPTICK IN SHOWER
ACTIVITY ASSOCIATED WITH THIS WAVE IS PRODUCING MORE ORGANIZED BUT
STILL LARGELY SCATTERED SHOWERS. STILL TRACKING THIS FEATURE WILL
BRING THE BEST CHANCE FOR SOME BRIEF DOWNPOURS IN THE COMING
HOURS...AND THESE WILL SPREAD INTO THE WEST METRO AREA IN THE NEXT
HOUR...SPREADING INTO CHICAGOLAND SHORTLY THERE AFTER. THE CLOUDS
PRODUCING THE SHOWER ACTIVITY ARE SHALLOW AND MID LEVEL LAPSE
RATES ARE SUBPAR...THUS THUNDER SHOULD BE LIMITED AT BEST. SOME
WEAK INSTABILITY IS NOTED SOUTH OF I-80 WHICH DOES NOT PRECLUDE AN
ISOLATED STRIKE IN ANY STRONGER ACTIVITY.

REGARDING WINDS...WITH THE BROKEN TO OVERCAST LOW CLOUD
DECK...MIXING IS BEING LIMITED AND GETING GUSTS TO AROUND 30 KT OR
SO. ANY STRONGER GUSTS WOULD BE IN THE NEXT HOUR BEFORE A RAPID
DROP OFF LATER THIS MORNING.

KMD

&&

.SHORT TERM...
345 AM CDT

THROUGH MONDAY NIGHT...
FOR THE REMAINDER OF THE NIGHT AND INTO MONDAY MORNING...PCPN
CHANCES CONTINUE TO WANE AS LATEST RADAR TRENDS ONLY SHOW SOME SCT
SHRA WHICH ARE DECREASING IN INTENSITY.  IN SPITE OF DEWPOINTS IN
THE LOW 60S...AND A STRONG LOW LEVEL JET...50 KT AT 925 MB...THERE
IS AN ELEMENT LACKING WHICH IS SEEMS TO BE PREVENTING THE
MAINTENANCE OF SHRA/TSRA OVER NERN IL/NWRN IN.  THE MAIN MISSING
ELEMENTS IS FORCING.  THE SFC AND UPPER LEVEL LOW ARE WAY TO THE
WEST...OVER THE NRN PLAINS. THE SHORTWAVE CLIMBING UP THE NWRN
PERIPHERY OF THE HIGH AMPLITUDE RIDGE IS BEING SLOWED BY THE HIGH
AMPLITUDE...AND IS BEING FORCED TO A MORE WLY TRACK THROUGH THE
UPPER MISSISSIPPI VALLEY THAN PREVIOUSLY ANTICIPATED.  SO...FOR THE
REMAINDER OF THE OVERNIGHT HOURS AND THE DAYTIME HOURS MONDAY...HAVE
BACK OF TO ISOLD-SCT SHRA.  WILL KEEP ISOLD TS MENTION FOR THE LATE
MORNING HOURS...THROUGH AROUND NOON...WITH THE DAYTIME HEATING...BUT
CONFIDENCE IN ANY TS IS RATHER LOW AT THIS TIME.  BY THIS
AFTERNOON...A MID LEVEL DRY SLOT IS EXPECTED TO MOVE ACROSS THE
REGION...FURTHER LIMITING PCPN CHANCES AND IT IS QUITE LIKELY THAT
THE REGION WILL REMAIN DRY THROUGH THE DAY.  HOWEVER...WHILE THE
PCPN CHANCES ARE DIMINISHING...THE LIKELIHOOD OF STRONG WINDS IS
STILL A CONCERN.  WITH THE DIMINISHING PCPN CHANCES...LESS SKY COVER
THAN PREVIOUSLY ANTICIPATED IS ALSO POSSIBLE.  A STRONG SWLY
PRESSURE GRADIENT IS SETTING UP ACROSS THE REGION BETWEEN SFC
RIDGING ACROSS THE SERN CONUS AND AND LOW PRESSURE FROM THE UPPER
MISSISSIPPI VALLEY TO THE WESTERN PLAINS.  THE STRONG GRADIENT WILL
HELP DRIVE THE SFC WINDS AND THE DIMINISHING CLOUD COVER COULD HELP
ENHANCE DEEP LAYER MIXING...TAPPING STRONGER WINDS ALOFT.  SUSTAINED
25-25 MPH WINDS ARE LIKELY WITH GUSTS OF 30-35 MPH.
ALSO...PERSISTENT WARM/MOIST ADVECTION AT THE SFC WILL BRING
TEMPERATURES INTO THE LOW TO MIDDLE 80S WITH DEWPOINTS IN THE LOWER
60S.

FOR MONDAY NIGHT...THE BREEZY CONDITIONS WILL PERSIST INTO THE AS
THERE SHOULD BE LITTLE CHANGE TO THE SFC AND UPPER LEVEL PATTERNS.
THE UPPER RIDGE WILL LOSE A LITTLE AMPLITUDE AS SHORT WAVE ENERGY
OVERTOPS THE RIDGE...BUT GENERAL TROUGHING WILL PERSIST ACROSS THE
UPPER MISSISSIPPI VALLEY THROUGH THE CENTRAL PLAINS.  THE NEXT
CHANCE FOR PCPN WILL HOLD OFF UNTIL LATE TONIGHT/EARLY TUESDAY
MORNING AND THE NEXT SHORTWAVE LIFTS OUT OF THE SRN PLAINS AND INTO
THE MIDDLE MISSISSIPPI VALLEY.  AMPLE LOW LEVEL MOISTURE WILL
ALREADY BE IN PLACE SO IT WILL JUST A MATTER OF WHEN THE FORCING
WILL GET HERE.  AGAIN...THERE IS SOME CONCERN THAT THE FORCING WILL
BE TO THE WEST...WITH THE SHORTWAVE TRACKING THROUGH THE MIDDLE
MISSISSIPPI VALLEY AND INTO WI.  SO...WILL CARRY CHANCE POPS FOR THE
REGION...WITH LIKELY POPS APPROACHING THE PONTIAC AREA BY EARLY
TUESDAY MORNING.  THE PERSISTENT WARM/MOIST ADVECTIVE PATTERN AND
BREEZY CONDITIONS SHOULD KEEP TEMPERATURES FROM DROPPING OFF
SIGNIFICANTLY OVERNIGHT AND LOWS SHOULD BE IN THE MIDDLE TO UPPER
60S.

KREIN

&&

.LONG TERM...
239 AM CDT

TUESDAY THROUGH SUNDAY...

TUESDAY THROUGH WEDNESDAY...
500MB TROUGH AXIS WILL SLOWLY PIVOT EAST ACROSS THE CENTRAL PLAINS
INTO THE MID-MISSOURI VALLEY TUE...WITH A SFC WAVE SLIDING NORTH
ACROSS IOWA INTO CENTRAL WISC LATE TUE. THE SFC FEATURE IS NOT
EXPECTED TO BE STRONG...HOWEVER THE GRADIENT DOES TIGHTEN WITH
MODEST HEIGHT FALLS IN THE LOWEST LAYERS OF THE ATMOSPHERE. SOME
INSTABILITY DOES REMAIN ALONG WITH RELATIVELY MOIST SFC CONDS AS
DEW PTS WILL REMAIN IN THE UPR 50S/LOW 60S. PWAT VALUES WILL ALSO
HOVER JUST OVER 1 INCH...WHICH IS SEASONAL. WILL HOLD ONTO MENTION
OF RAIN AND THUNDER...BUT COULD SEE THIS MAINLY FOCUSED IN THE TUE
MORNING TIMEFRAME.

WITH CONSIDERABLE SOLAR SHIELDING PROGGED FOR TUE...TEMPS MAY
STRUGGLE TO WARM BEYOND THE MID/UPR 70S. BUT WITH GUIDANCE HINTING
AT A DRY SLOT LIFTING NORTHEAST ACROSS THE REGION TUE EVE...THIS
COULD INTRODUCE SOME EROSION TO THE CLOUD COVER IN THE AFTN HOURS
TUE AND ALLOW SOME SFC HEATING TO OCCUR AND PUSH TEMPS TO ARND 80.

GUIDANCE LIFTS THE DRY SLOT OVERHEAD LATE TUE NGT...WITH THE 500MB
TROUGH AXIS ARRIVING ARND DAYBREAK WED AND LIFTING EAST ACROSS LOWER
MICHIGAN. THIS WILL BRING DRY ONLY SLIGHT CHANCE POPS AS WEAK SFC
RIDGING BEGINS TO NUDGE EAST ACROSS THE MISSOURI VALLEY TOWARDS THE
FORECAST AREA MIDDAY WED. IT IS POSSIBLE THAT ENOUGH DRY AIR
INFLUENCE COULD ALLOW FOR REMOVAL OF THE SLIGHT CHANCE POPS WED
AFTN. THERMAL TROUGH LAGS BEHIND THE FRONTAL BOUNDARY WED...SO TEMPS
COULD STILL WARM BACK TO ARND 80 AND PERHAPS THE LOW 80S IN THE
SOUTHERN CWFA.

THURSDAY THROUGH SUNDAY...
ANTI-CYCLONIC FLOW ARRIVES THUR WITH AT LEAST ONE PERIOD OF DRY
WEATHER EXPECTED FOR NORTHERN IL/NORTHWEST IN. ONLY A COUPLE
ENSEMBLE MEMBERS CONTINUE TO PROG POPS ALONG THE SOUTHERN FORECAST
AREA THUR...BUT COULD SEE THIS TRENDING DRY IN THE NEXT FEW
SOLUTIONS. WITH WARM TEMPS ALOFT EXPECTED THUR AND THIN CLOUD
COVER...THUR HIGHS COULD PEAK IN THE LOW 80S.

THEN FOCUS TURNS TOWARDS THE UPCOMING WEEKEND AND A PATTERN SHIFT
AWAY FROM THE WARM/HUMID CONDITIONS. ENSEMBLES SHOW MINIMAL SPREAD
IN THE LATE WEEK PERIODS...WITH THE UPSTREAM RIDGE OVER
ALASKA/WESTERN CANADA AND A DOWNSTREAM MID-LVL RIDGE ACROSS THE
SOUTHEAST CONUS. BOTH OF THESE FEATURES IN TIME BEGIN TO
WEAKEN...WITH THE LONGWAVE PATTERN TRANSITIONING INTO A SEMI-ZONAL
ORIENTATION BY THE SECOND HALF OF THE WEEKEND.

OPER GUIDANCE HAS BEEN CONSISTENT WITH PROGGING A ROBUST 500MB
TROUGH TO SLIDE SOUTH FROM CENTRAL CANADA FRI...ALONG WITH A STRONG
CANADIAN SFC RIDGE ON IT/S HEELS. WITH A CHANNEL OF MOISTURE
REMAINING ACROSS THE SOUTHERN PLAINS STRETCHING NORTHEAST THROUGH
THE UPPER MIDWEST...THIS BOUNDARY WILL BECOME ACTIVE WITH A SFC WAVE
DEVELOPING ACROSS THE SOUTHERN PLAINS. THIS LOW WILL THEN LIFT
NORTHEAST TOWARDS THE CWFA FRI WITH A COLD FRONT ARRIVING ACROSS THE
FORECAST AREA SAT. WINDS LOOK TO SHIFT TO THE NORTH...WITH MUCH
COOLER AIR SLIDING SOUTH AND LIKELY KNOCKING TEMPS BACK TO SUB-
SEASONAL CONDS IN THE UPR 60S/NEAR 70 DEGREE RANGE SAT/SUN. IF
NORTHEAST WINDS MATERIALIZE...NEXT WEEKEND AREAS ADJACENT TO LAKE
MICHIGAN ALONG THE IL/IN SHORELINE COULD BE LOCKED IN THE UPR 50S TO
LOW 60S FOR HIGHS WITH A COLD FLOW OFF OF LAKE MICHIGAN.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 18Z...

* GUSTY SOUTHWEST WINDS.

* HIGH END MVFR CEILINGS POSSIBLE EARLY THIS AFTERNOON...MVFR
  POSSIBLE AGAIN EARLY TUESDAY MORNING.

* SHOWERS LIKELY WITH PERIODIC THUNDERSTORMS LATE IN THE FORECAST
  PERIOD.

RODRIGUEZ

//DISCUSSION...UPDATED 18Z...

MUCH OF THE SHOWERS ARE EXITING THE AREA EARLY THIS AFTERNOON.
HOWEVER...AN ISOLATED LIGHT SHOWER WILL STILL BE POSSIBLE OVER THE
NEXT HOUR BEFORE PREVAILING DRY CONDITIONS ARE EXPECTED THIS
AFTERNOON AND TONIGHT. LINGERING MVFR CEILINGS WILL LIFT TO VFR
THROUGH 20-21Z THIS AFTERNOON WITH SKIES THEN SCATTERING THIS
EVENING...AS THE SOUTHWEST WINDS/GUSTS DIMINISH INTO THE EVENING.
WITH FAIRLY MOIST CONDITIONS REMAINING IN PLACE TONIGHT INTO
TUESDAY...REDEVELOPING LOW CEILINGS DO APPEAR TO BE A POSSIBILITY.
OVERALL CONFIDENCE IS LOWER DURING THIS PERIOD...BUT DID MAKE
MENTION OF AT LEAST MVFR CEILINGS...AND WILL NEED TO MONITOR FOR
POTENTIALLY LOWER CEILINGS. HAVE PUSHED BACK TIMING OF PRECIP LATE
IN THE PERIOD...BUT WITH INSTABILITY AND FORCING
INCREASING...SHOWERS AND THUNDERSTORMS DO APPEAR LIKELY TUESDAY.
STILL SOME UNCERTAINTY WITH EXACT TIMING AND DURATION...AND EVEN
THE POSSIBILITY FOR AN ADDITIONAL PERIOD OF THUNDERSTORMS TUESDAY
AFTERNOON.

RODRIGUEZ


//ORD AND MDW CONFIDENCE...UPDATED 18Z...

* HIGH CONFIDENCE WITH WIND SPEED/DIRECTION.

* MEDIUM HIGH CONFIDENCE WITH CEILINGS.

* HIGH CONFIDENCE OF SHOWERS/THUNDERSTORMS...MEDIUM CONFIDENCE
  WITH TIMING/DURATION.

RODRIGUEZ

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/TSRA LATE. SOUTHEAST WINDS.

FRIDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. SOUTHWEST WINDS
BECOMING NORTHEAST OVERNIGHT.

SATURDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. NORTHEAST
WINDS.

SUNDAY...CHANCE TSRA. MVFR POSSIBLE. NORTHEAST WINDS.

KREIN

&&

.MARINE...
304 AM CDT

LOW PRESSURE WILL BE STEADILY LIFTING NORTH ACROSS THE MISSOURI
VALLEY THIS MORNING...REACHING LAKE SUPERIOR BY THIS EVENING AND
CONTINUING TO SLIDE EAST/NORTHEAST TOWARDS QUEBEC BY TUESDAY
MORNING. A FRONTAL BOUNDARY WILL REMAIN OVER THE FAR NORTHERN
PORTIONS OF LAKE MICHIGAN. MEANWHILE GUSTY SOUTHERLY WINDS ARE
EXPECTED TO INCREASE THIS MORNING...WITH OCCASIONAL GALES FOR THE
NEARSHORE WATERS OF IL/IN. ACROSS THE OPEN WATERS...EXPECT THE
WARM/MOIST AIR TO STRUGGLE TO REACH THE SFC OF THE LAKE WITH SOME
DEGREE OF LAKE STABILITY. WAVES WILL STEADILY BUILD ACROSS THE
NORTHERN HALF OF THE LAKE AS A RESULT OF THE LONG FETCH. STILL
FEEL THAT GUSTS WILL REACH 30KT ACROSS THE LAKE...HOWEVER
CONFIDENCE HAS DIMINISHED SLIGHTLY AS NEW GUIDANCE HAS BECOME A
LITTLE LESS WITH THE WIND FIELDS. NONETHELESS...WAVES FOR THE
NORTHERN HALF OF THE LAKE WILL LIKELY TOP OUT IN THE 4 TO 7 FT
RANGE WITH OCCASIONAL WAVES REACHING 9 FT THIS AFTERNOON/EVENING.

THE GRADIENT QUICKLY DIMINISHES THIS EVENING...BUT EXPECT
SOUTHERLY WINDS TO PERSIST. THIS WILL ALLOW WAVES TO SUBSIDE TO 3
TO 5 FT. ANOTHER LOW WILL ARRIVE TUE...WITH WINDS NUDGING BACK UP
HOWEVER WARM AIR WILL CONTINUE TO FLOW ACROSS THE LAKE AND COULD
FURTHER ENHANCE THE LAKE STABILITY AND KEEP WAVES FROM BUILDING TO
LARGE.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...NEARSHORE WATERS UNTIL 3
     PM MONDAY.

     SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
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000
FXUS63 KLOT 251803
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
103 PM CDT MON MAY 25 2015

.UPDATE...

COMPACT NEGATIVELY TILTED TROUGH AXIS IS SLIDING NORTHEAST THROUGH
IOWA AND WESTERN ILLINOIS. EASTERN EDGE OF THE TROUGH WILL MOVE
THROUGH NORTHEAST ILLINOIS THIS MORNING. NOTED UPTICK IN SHOWER
ACTIVITY ASSOCIATED WITH THIS WAVE IS PRODUCING MORE ORGANIZED BUT
STILL LARGELY SCATTERED SHOWERS. STILL TRACKING THIS FEATURE WILL
BRING THE BEST CHANCE FOR SOME BRIEF DOWNPOURS IN THE COMING
HOURS...AND THESE WILL SPREAD INTO THE WEST METRO AREA IN THE NEXT
HOUR...SPREADING INTO CHICAGOLAND SHORTLY THERE AFTER. THE CLOUDS
PRODUCING THE SHOWER ACTIVITY ARE SHALLOW AND MID LEVEL LAPSE
RATES ARE SUBPAR...THUS THUNDER SHOULD BE LIMITED AT BEST. SOME
WEAK INSTABILITY IS NOTED SOUTH OF I-80 WHICH DOES NOT PRECLUDE AN
ISOLATED STRIKE IN ANY STRONGER ACTIVITY.

REGARDING WINDS...WITH THE BROKEN TO OVERCAST LOW CLOUD
DECK...MIXING IS BEING LIMITED AND GETING GUSTS TO AROUND 30 KT OR
SO. ANY STRONGER GUSTS WOULD BE IN THE NEXT HOUR BEFORE A RAPID
DROP OFF LATER THIS MORNING.

KMD

&&

.SHORT TERM...
345 AM CDT

THROUGH MONDAY NIGHT...
FOR THE REMAINDER OF THE NIGHT AND INTO MONDAY MORNING...PCPN
CHANCES CONTINUE TO WANE AS LATEST RADAR TRENDS ONLY SHOW SOME SCT
SHRA WHICH ARE DECREASING IN INTENSITY.  IN SPITE OF DEWPOINTS IN
THE LOW 60S...AND A STRONG LOW LEVEL JET...50 KT AT 925 MB...THERE
IS AN ELEMENT LACKING WHICH IS SEEMS TO BE PREVENTING THE
MAINTENANCE OF SHRA/TSRA OVER NERN IL/NWRN IN.  THE MAIN MISSING
ELEMENTS IS FORCING.  THE SFC AND UPPER LEVEL LOW ARE WAY TO THE
WEST...OVER THE NRN PLAINS. THE SHORTWAVE CLIMBING UP THE NWRN
PERIPHERY OF THE HIGH AMPLITUDE RIDGE IS BEING SLOWED BY THE HIGH
AMPLITUDE...AND IS BEING FORCED TO A MORE WLY TRACK THROUGH THE
UPPER MISSISSIPPI VALLEY THAN PREVIOUSLY ANTICIPATED.  SO...FOR THE
REMAINDER OF THE OVERNIGHT HOURS AND THE DAYTIME HOURS MONDAY...HAVE
BACK OF TO ISOLD-SCT SHRA.  WILL KEEP ISOLD TS MENTION FOR THE LATE
MORNING HOURS...THROUGH AROUND NOON...WITH THE DAYTIME HEATING...BUT
CONFIDENCE IN ANY TS IS RATHER LOW AT THIS TIME.  BY THIS
AFTERNOON...A MID LEVEL DRY SLOT IS EXPECTED TO MOVE ACROSS THE
REGION...FURTHER LIMITING PCPN CHANCES AND IT IS QUITE LIKELY THAT
THE REGION WILL REMAIN DRY THROUGH THE DAY.  HOWEVER...WHILE THE
PCPN CHANCES ARE DIMINISHING...THE LIKELIHOOD OF STRONG WINDS IS
STILL A CONCERN.  WITH THE DIMINISHING PCPN CHANCES...LESS SKY COVER
THAN PREVIOUSLY ANTICIPATED IS ALSO POSSIBLE.  A STRONG SWLY
PRESSURE GRADIENT IS SETTING UP ACROSS THE REGION BETWEEN SFC
RIDGING ACROSS THE SERN CONUS AND AND LOW PRESSURE FROM THE UPPER
MISSISSIPPI VALLEY TO THE WESTERN PLAINS.  THE STRONG GRADIENT WILL
HELP DRIVE THE SFC WINDS AND THE DIMINISHING CLOUD COVER COULD HELP
ENHANCE DEEP LAYER MIXING...TAPPING STRONGER WINDS ALOFT.  SUSTAINED
25-25 MPH WINDS ARE LIKELY WITH GUSTS OF 30-35 MPH.
ALSO...PERSISTENT WARM/MOIST ADVECTION AT THE SFC WILL BRING
TEMPERATURES INTO THE LOW TO MIDDLE 80S WITH DEWPOINTS IN THE LOWER
60S.

FOR MONDAY NIGHT...THE BREEZY CONDITIONS WILL PERSIST INTO THE AS
THERE SHOULD BE LITTLE CHANGE TO THE SFC AND UPPER LEVEL PATTERNS.
THE UPPER RIDGE WILL LOSE A LITTLE AMPLITUDE AS SHORT WAVE ENERGY
OVERTOPS THE RIDGE...BUT GENERAL TROUGHING WILL PERSIST ACROSS THE
UPPER MISSISSIPPI VALLEY THROUGH THE CENTRAL PLAINS.  THE NEXT
CHANCE FOR PCPN WILL HOLD OFF UNTIL LATE TONIGHT/EARLY TUESDAY
MORNING AND THE NEXT SHORTWAVE LIFTS OUT OF THE SRN PLAINS AND INTO
THE MIDDLE MISSISSIPPI VALLEY.  AMPLE LOW LEVEL MOISTURE WILL
ALREADY BE IN PLACE SO IT WILL JUST A MATTER OF WHEN THE FORCING
WILL GET HERE.  AGAIN...THERE IS SOME CONCERN THAT THE FORCING WILL
BE TO THE WEST...WITH THE SHORTWAVE TRACKING THROUGH THE MIDDLE
MISSISSIPPI VALLEY AND INTO WI.  SO...WILL CARRY CHANCE POPS FOR THE
REGION...WITH LIKELY POPS APPROACHING THE PONTIAC AREA BY EARLY
TUESDAY MORNING.  THE PERSISTENT WARM/MOIST ADVECTIVE PATTERN AND
BREEZY CONDITIONS SHOULD KEEP TEMPERATURES FROM DROPPING OFF
SIGNIFICANTLY OVERNIGHT AND LOWS SHOULD BE IN THE MIDDLE TO UPPER
60S.

KREIN

&&

.LONG TERM...
239 AM CDT

TUESDAY THROUGH SUNDAY...

TUESDAY THROUGH WEDNESDAY...
500MB TROUGH AXIS WILL SLOWLY PIVOT EAST ACROSS THE CENTRAL PLAINS
INTO THE MID-MISSOURI VALLEY TUE...WITH A SFC WAVE SLIDING NORTH
ACROSS IOWA INTO CENTRAL WISC LATE TUE. THE SFC FEATURE IS NOT
EXPECTED TO BE STRONG...HOWEVER THE GRADIENT DOES TIGHTEN WITH
MODEST HEIGHT FALLS IN THE LOWEST LAYERS OF THE ATMOSPHERE. SOME
INSTABILITY DOES REMAIN ALONG WITH RELATIVELY MOIST SFC CONDS AS
DEW PTS WILL REMAIN IN THE UPR 50S/LOW 60S. PWAT VALUES WILL ALSO
HOVER JUST OVER 1 INCH...WHICH IS SEASONAL. WILL HOLD ONTO MENTION
OF RAIN AND THUNDER...BUT COULD SEE THIS MAINLY FOCUSED IN THE TUE
MORNING TIMEFRAME.

WITH CONSIDERABLE SOLAR SHIELDING PROGGED FOR TUE...TEMPS MAY
STRUGGLE TO WARM BEYOND THE MID/UPR 70S. BUT WITH GUIDANCE HINTING
AT A DRY SLOT LIFTING NORTHEAST ACROSS THE REGION TUE EVE...THIS
COULD INTRODUCE SOME EROSION TO THE CLOUD COVER IN THE AFTN HOURS
TUE AND ALLOW SOME SFC HEATING TO OCCUR AND PUSH TEMPS TO ARND 80.

GUIDANCE LIFTS THE DRY SLOT OVERHEAD LATE TUE NGT...WITH THE 500MB
TROUGH AXIS ARRIVING ARND DAYBREAK WED AND LIFTING EAST ACROSS LOWER
MICHIGAN. THIS WILL BRING DRY ONLY SLIGHT CHANCE POPS AS WEAK SFC
RIDGING BEGINS TO NUDGE EAST ACROSS THE MISSOURI VALLEY TOWARDS THE
FORECAST AREA MIDDAY WED. IT IS POSSIBLE THAT ENOUGH DRY AIR
INFLUENCE COULD ALLOW FOR REMOVAL OF THE SLIGHT CHANCE POPS WED
AFTN. THERMAL TROUGH LAGS BEHIND THE FRONTAL BOUNDARY WED...SO TEMPS
COULD STILL WARM BACK TO ARND 80 AND PERHAPS THE LOW 80S IN THE
SOUTHERN CWFA.

THURSDAY THROUGH SUNDAY...
ANTI-CYCLONIC FLOW ARRIVES THUR WITH AT LEAST ONE PERIOD OF DRY
WEATHER EXPECTED FOR NORTHERN IL/NORTHWEST IN. ONLY A COUPLE
ENSEMBLE MEMBERS CONTINUE TO PROG POPS ALONG THE SOUTHERN FORECAST
AREA THUR...BUT COULD SEE THIS TRENDING DRY IN THE NEXT FEW
SOLUTIONS. WITH WARM TEMPS ALOFT EXPECTED THUR AND THIN CLOUD
COVER...THUR HIGHS COULD PEAK IN THE LOW 80S.

THEN FOCUS TURNS TOWARDS THE UPCOMING WEEKEND AND A PATTERN SHIFT
AWAY FROM THE WARM/HUMID CONDITIONS. ENSEMBLES SHOW MINIMAL SPREAD
IN THE LATE WEEK PERIODS...WITH THE UPSTREAM RIDGE OVER
ALASKA/WESTERN CANADA AND A DOWNSTREAM MID-LVL RIDGE ACROSS THE
SOUTHEAST CONUS. BOTH OF THESE FEATURES IN TIME BEGIN TO
WEAKEN...WITH THE LONGWAVE PATTERN TRANSITIONING INTO A SEMI-ZONAL
ORIENTATION BY THE SECOND HALF OF THE WEEKEND.

OPER GUIDANCE HAS BEEN CONSISTENT WITH PROGGING A ROBUST 500MB
TROUGH TO SLIDE SOUTH FROM CENTRAL CANADA FRI...ALONG WITH A STRONG
CANADIAN SFC RIDGE ON IT/S HEELS. WITH A CHANNEL OF MOISTURE
REMAINING ACROSS THE SOUTHERN PLAINS STRETCHING NORTHEAST THROUGH
THE UPPER MIDWEST...THIS BOUNDARY WILL BECOME ACTIVE WITH A SFC WAVE
DEVELOPING ACROSS THE SOUTHERN PLAINS. THIS LOW WILL THEN LIFT
NORTHEAST TOWARDS THE CWFA FRI WITH A COLD FRONT ARRIVING ACROSS THE
FORECAST AREA SAT. WINDS LOOK TO SHIFT TO THE NORTH...WITH MUCH
COOLER AIR SLIDING SOUTH AND LIKELY KNOCKING TEMPS BACK TO SUB-
SEASONAL CONDS IN THE UPR 60S/NEAR 70 DEGREE RANGE SAT/SUN. IF
NORTHEAST WINDS MATERIALIZE...NEXT WEEKEND AREAS ADJACENT TO LAKE
MICHIGAN ALONG THE IL/IN SHORELINE COULD BE LOCKED IN THE UPR 50S TO
LOW 60S FOR HIGHS WITH A COLD FLOW OFF OF LAKE MICHIGAN.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 18Z...

* GUSTY SOUTHWEST WINDS.

* HIGH END MVFR CEILINGS POSSIBLE EARLY THIS AFTERNOON...MVFR
  POSSIBLE AGAIN EARLY TUESDAY MORNING.

* SHOWERS LIKELY WITH PERIODIC THUNDERSTORMS LATE IN THE FORECAST
  PERIOD.

RODRIGUEZ

//DISCUSSION...UPDATED 18Z...

MUCH OF THE SHOWERS ARE EXITING THE AREA EARLY THIS AFTERNOON.
HOWEVER...AN ISOLATED LIGHT SHOWER WILL STILL BE POSSIBLE OVER THE
NEXT HOUR BEFORE PREVAILING DRY CONDITIONS ARE EXPECTED THIS
AFTERNOON AND TONIGHT. LINGERING MVFR CEILINGS WILL LIFT TO VFR
THROUGH 20-21Z THIS AFTERNOON WITH SKIES THEN SCATTERING THIS
EVENING...AS THE SOUTHWEST WINDS/GUSTS DIMINISH INTO THE EVENING.
WITH FAIRLY MOIST CONDITIONS REMAINING IN PLACE TONIGHT INTO
TUESDAY...REDEVELOPING LOW CEILINGS DO APPEAR TO BE A POSSIBILITY.
OVERALL CONFIDENCE IS LOWER DURING THIS PERIOD...BUT DID MAKE
MENTION OF AT LEAST MVFR CEILINGS...AND WILL NEED TO MONITOR FOR
POTENTIALLY LOWER CEILINGS. HAVE PUSHED BACK TIMING OF PRECIP LATE
IN THE PERIOD...BUT WITH INSTABILITY AND FORCING
INCREASING...SHOWERS AND THUNDERSTORMS DO APPEAR LIKELY TUESDAY.
STILL SOME UNCERTAINTY WITH EXACT TIMING AND DURATION...AND EVEN
THE POSSIBILITY FOR AN ADDITIONAL PERIOD OF THUNDERSTORMS TUESDAY
AFTERNOON.

RODRIGUEZ


//ORD AND MDW CONFIDENCE...UPDATED 18Z...

* HIGH CONFIDENCE WITH WIND SPEED/DIRECTION.

* MEDIUM HIGH CONFIDENCE WITH CEILINGS.

* HIGH CONFIDENCE OF SHOWERS/THUNDERSTORMS...MEDIUM CONFIDENCE
  WITH TIMING/DURATION.

RODRIGUEZ

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/TSRA LATE. SOUTHEAST WINDS.

FRIDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. SOUTHWEST WINDS
BECOMING NORTHEAST OVERNIGHT.

SATURDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. NORTHEAST
WINDS.

SUNDAY...CHANCE TSRA. MVFR POSSIBLE. NORTHEAST WINDS.

KREIN

&&

.MARINE...
304 AM CDT

LOW PRESSURE WILL BE STEADILY LIFTING NORTH ACROSS THE MISSOURI
VALLEY THIS MORNING...REACHING LAKE SUPERIOR BY THIS EVENING AND
CONTINUING TO SLIDE EAST/NORTHEAST TOWARDS QUEBEC BY TUESDAY
MORNING. A FRONTAL BOUNDARY WILL REMAIN OVER THE FAR NORTHERN
PORTIONS OF LAKE MICHIGAN. MEANWHILE GUSTY SOUTHERLY WINDS ARE
EXPECTED TO INCREASE THIS MORNING...WITH OCCASIONAL GALES FOR THE
NEARSHORE WATERS OF IL/IN. ACROSS THE OPEN WATERS...EXPECT THE
WARM/MOIST AIR TO STRUGGLE TO REACH THE SFC OF THE LAKE WITH SOME
DEGREE OF LAKE STABILITY. WAVES WILL STEADILY BUILD ACROSS THE
NORTHERN HALF OF THE LAKE AS A RESULT OF THE LONG FETCH. STILL
FEEL THAT GUSTS WILL REACH 30KT ACROSS THE LAKE...HOWEVER
CONFIDENCE HAS DIMINISHED SLIGHTLY AS NEW GUIDANCE HAS BECOME A
LITTLE LESS WITH THE WIND FIELDS. NONETHELESS...WAVES FOR THE
NORTHERN HALF OF THE LAKE WILL LIKELY TOP OUT IN THE 4 TO 7 FT
RANGE WITH OCCASIONAL WAVES REACHING 9 FT THIS AFTERNOON/EVENING.

THE GRADIENT QUICKLY DIMINISHES THIS EVENING...BUT EXPECT
SOUTHERLY WINDS TO PERSIST. THIS WILL ALLOW WAVES TO SUBSIDE TO 3
TO 5 FT. ANOTHER LOW WILL ARRIVE TUE...WITH WINDS NUDGING BACK UP
HOWEVER WARM AIR WILL CONTINUE TO FLOW ACROSS THE LAKE AND COULD
FURTHER ENHANCE THE LAKE STABILITY AND KEEP WAVES FROM BUILDING TO
LARGE.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...NEARSHORE WATERS UNTIL 3
     PM MONDAY.

     SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 251803
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
103 PM CDT MON MAY 25 2015

.UPDATE...

COMPACT NEGATIVELY TILTED TROUGH AXIS IS SLIDING NORTHEAST THROUGH
IOWA AND WESTERN ILLINOIS. EASTERN EDGE OF THE TROUGH WILL MOVE
THROUGH NORTHEAST ILLINOIS THIS MORNING. NOTED UPTICK IN SHOWER
ACTIVITY ASSOCIATED WITH THIS WAVE IS PRODUCING MORE ORGANIZED BUT
STILL LARGELY SCATTERED SHOWERS. STILL TRACKING THIS FEATURE WILL
BRING THE BEST CHANCE FOR SOME BRIEF DOWNPOURS IN THE COMING
HOURS...AND THESE WILL SPREAD INTO THE WEST METRO AREA IN THE NEXT
HOUR...SPREADING INTO CHICAGOLAND SHORTLY THERE AFTER. THE CLOUDS
PRODUCING THE SHOWER ACTIVITY ARE SHALLOW AND MID LEVEL LAPSE
RATES ARE SUBPAR...THUS THUNDER SHOULD BE LIMITED AT BEST. SOME
WEAK INSTABILITY IS NOTED SOUTH OF I-80 WHICH DOES NOT PRECLUDE AN
ISOLATED STRIKE IN ANY STRONGER ACTIVITY.

REGARDING WINDS...WITH THE BROKEN TO OVERCAST LOW CLOUD
DECK...MIXING IS BEING LIMITED AND GETING GUSTS TO AROUND 30 KT OR
SO. ANY STRONGER GUSTS WOULD BE IN THE NEXT HOUR BEFORE A RAPID
DROP OFF LATER THIS MORNING.

KMD

&&

.SHORT TERM...
345 AM CDT

THROUGH MONDAY NIGHT...
FOR THE REMAINDER OF THE NIGHT AND INTO MONDAY MORNING...PCPN
CHANCES CONTINUE TO WANE AS LATEST RADAR TRENDS ONLY SHOW SOME SCT
SHRA WHICH ARE DECREASING IN INTENSITY.  IN SPITE OF DEWPOINTS IN
THE LOW 60S...AND A STRONG LOW LEVEL JET...50 KT AT 925 MB...THERE
IS AN ELEMENT LACKING WHICH IS SEEMS TO BE PREVENTING THE
MAINTENANCE OF SHRA/TSRA OVER NERN IL/NWRN IN.  THE MAIN MISSING
ELEMENTS IS FORCING.  THE SFC AND UPPER LEVEL LOW ARE WAY TO THE
WEST...OVER THE NRN PLAINS. THE SHORTWAVE CLIMBING UP THE NWRN
PERIPHERY OF THE HIGH AMPLITUDE RIDGE IS BEING SLOWED BY THE HIGH
AMPLITUDE...AND IS BEING FORCED TO A MORE WLY TRACK THROUGH THE
UPPER MISSISSIPPI VALLEY THAN PREVIOUSLY ANTICIPATED.  SO...FOR THE
REMAINDER OF THE OVERNIGHT HOURS AND THE DAYTIME HOURS MONDAY...HAVE
BACK OF TO ISOLD-SCT SHRA.  WILL KEEP ISOLD TS MENTION FOR THE LATE
MORNING HOURS...THROUGH AROUND NOON...WITH THE DAYTIME HEATING...BUT
CONFIDENCE IN ANY TS IS RATHER LOW AT THIS TIME.  BY THIS
AFTERNOON...A MID LEVEL DRY SLOT IS EXPECTED TO MOVE ACROSS THE
REGION...FURTHER LIMITING PCPN CHANCES AND IT IS QUITE LIKELY THAT
THE REGION WILL REMAIN DRY THROUGH THE DAY.  HOWEVER...WHILE THE
PCPN CHANCES ARE DIMINISHING...THE LIKELIHOOD OF STRONG WINDS IS
STILL A CONCERN.  WITH THE DIMINISHING PCPN CHANCES...LESS SKY COVER
THAN PREVIOUSLY ANTICIPATED IS ALSO POSSIBLE.  A STRONG SWLY
PRESSURE GRADIENT IS SETTING UP ACROSS THE REGION BETWEEN SFC
RIDGING ACROSS THE SERN CONUS AND AND LOW PRESSURE FROM THE UPPER
MISSISSIPPI VALLEY TO THE WESTERN PLAINS.  THE STRONG GRADIENT WILL
HELP DRIVE THE SFC WINDS AND THE DIMINISHING CLOUD COVER COULD HELP
ENHANCE DEEP LAYER MIXING...TAPPING STRONGER WINDS ALOFT.  SUSTAINED
25-25 MPH WINDS ARE LIKELY WITH GUSTS OF 30-35 MPH.
ALSO...PERSISTENT WARM/MOIST ADVECTION AT THE SFC WILL BRING
TEMPERATURES INTO THE LOW TO MIDDLE 80S WITH DEWPOINTS IN THE LOWER
60S.

FOR MONDAY NIGHT...THE BREEZY CONDITIONS WILL PERSIST INTO THE AS
THERE SHOULD BE LITTLE CHANGE TO THE SFC AND UPPER LEVEL PATTERNS.
THE UPPER RIDGE WILL LOSE A LITTLE AMPLITUDE AS SHORT WAVE ENERGY
OVERTOPS THE RIDGE...BUT GENERAL TROUGHING WILL PERSIST ACROSS THE
UPPER MISSISSIPPI VALLEY THROUGH THE CENTRAL PLAINS.  THE NEXT
CHANCE FOR PCPN WILL HOLD OFF UNTIL LATE TONIGHT/EARLY TUESDAY
MORNING AND THE NEXT SHORTWAVE LIFTS OUT OF THE SRN PLAINS AND INTO
THE MIDDLE MISSISSIPPI VALLEY.  AMPLE LOW LEVEL MOISTURE WILL
ALREADY BE IN PLACE SO IT WILL JUST A MATTER OF WHEN THE FORCING
WILL GET HERE.  AGAIN...THERE IS SOME CONCERN THAT THE FORCING WILL
BE TO THE WEST...WITH THE SHORTWAVE TRACKING THROUGH THE MIDDLE
MISSISSIPPI VALLEY AND INTO WI.  SO...WILL CARRY CHANCE POPS FOR THE
REGION...WITH LIKELY POPS APPROACHING THE PONTIAC AREA BY EARLY
TUESDAY MORNING.  THE PERSISTENT WARM/MOIST ADVECTIVE PATTERN AND
BREEZY CONDITIONS SHOULD KEEP TEMPERATURES FROM DROPPING OFF
SIGNIFICANTLY OVERNIGHT AND LOWS SHOULD BE IN THE MIDDLE TO UPPER
60S.

KREIN

&&

.LONG TERM...
239 AM CDT

TUESDAY THROUGH SUNDAY...

TUESDAY THROUGH WEDNESDAY...
500MB TROUGH AXIS WILL SLOWLY PIVOT EAST ACROSS THE CENTRAL PLAINS
INTO THE MID-MISSOURI VALLEY TUE...WITH A SFC WAVE SLIDING NORTH
ACROSS IOWA INTO CENTRAL WISC LATE TUE. THE SFC FEATURE IS NOT
EXPECTED TO BE STRONG...HOWEVER THE GRADIENT DOES TIGHTEN WITH
MODEST HEIGHT FALLS IN THE LOWEST LAYERS OF THE ATMOSPHERE. SOME
INSTABILITY DOES REMAIN ALONG WITH RELATIVELY MOIST SFC CONDS AS
DEW PTS WILL REMAIN IN THE UPR 50S/LOW 60S. PWAT VALUES WILL ALSO
HOVER JUST OVER 1 INCH...WHICH IS SEASONAL. WILL HOLD ONTO MENTION
OF RAIN AND THUNDER...BUT COULD SEE THIS MAINLY FOCUSED IN THE TUE
MORNING TIMEFRAME.

WITH CONSIDERABLE SOLAR SHIELDING PROGGED FOR TUE...TEMPS MAY
STRUGGLE TO WARM BEYOND THE MID/UPR 70S. BUT WITH GUIDANCE HINTING
AT A DRY SLOT LIFTING NORTHEAST ACROSS THE REGION TUE EVE...THIS
COULD INTRODUCE SOME EROSION TO THE CLOUD COVER IN THE AFTN HOURS
TUE AND ALLOW SOME SFC HEATING TO OCCUR AND PUSH TEMPS TO ARND 80.

GUIDANCE LIFTS THE DRY SLOT OVERHEAD LATE TUE NGT...WITH THE 500MB
TROUGH AXIS ARRIVING ARND DAYBREAK WED AND LIFTING EAST ACROSS LOWER
MICHIGAN. THIS WILL BRING DRY ONLY SLIGHT CHANCE POPS AS WEAK SFC
RIDGING BEGINS TO NUDGE EAST ACROSS THE MISSOURI VALLEY TOWARDS THE
FORECAST AREA MIDDAY WED. IT IS POSSIBLE THAT ENOUGH DRY AIR
INFLUENCE COULD ALLOW FOR REMOVAL OF THE SLIGHT CHANCE POPS WED
AFTN. THERMAL TROUGH LAGS BEHIND THE FRONTAL BOUNDARY WED...SO TEMPS
COULD STILL WARM BACK TO ARND 80 AND PERHAPS THE LOW 80S IN THE
SOUTHERN CWFA.

THURSDAY THROUGH SUNDAY...
ANTI-CYCLONIC FLOW ARRIVES THUR WITH AT LEAST ONE PERIOD OF DRY
WEATHER EXPECTED FOR NORTHERN IL/NORTHWEST IN. ONLY A COUPLE
ENSEMBLE MEMBERS CONTINUE TO PROG POPS ALONG THE SOUTHERN FORECAST
AREA THUR...BUT COULD SEE THIS TRENDING DRY IN THE NEXT FEW
SOLUTIONS. WITH WARM TEMPS ALOFT EXPECTED THUR AND THIN CLOUD
COVER...THUR HIGHS COULD PEAK IN THE LOW 80S.

THEN FOCUS TURNS TOWARDS THE UPCOMING WEEKEND AND A PATTERN SHIFT
AWAY FROM THE WARM/HUMID CONDITIONS. ENSEMBLES SHOW MINIMAL SPREAD
IN THE LATE WEEK PERIODS...WITH THE UPSTREAM RIDGE OVER
ALASKA/WESTERN CANADA AND A DOWNSTREAM MID-LVL RIDGE ACROSS THE
SOUTHEAST CONUS. BOTH OF THESE FEATURES IN TIME BEGIN TO
WEAKEN...WITH THE LONGWAVE PATTERN TRANSITIONING INTO A SEMI-ZONAL
ORIENTATION BY THE SECOND HALF OF THE WEEKEND.

OPER GUIDANCE HAS BEEN CONSISTENT WITH PROGGING A ROBUST 500MB
TROUGH TO SLIDE SOUTH FROM CENTRAL CANADA FRI...ALONG WITH A STRONG
CANADIAN SFC RIDGE ON IT/S HEELS. WITH A CHANNEL OF MOISTURE
REMAINING ACROSS THE SOUTHERN PLAINS STRETCHING NORTHEAST THROUGH
THE UPPER MIDWEST...THIS BOUNDARY WILL BECOME ACTIVE WITH A SFC WAVE
DEVELOPING ACROSS THE SOUTHERN PLAINS. THIS LOW WILL THEN LIFT
NORTHEAST TOWARDS THE CWFA FRI WITH A COLD FRONT ARRIVING ACROSS THE
FORECAST AREA SAT. WINDS LOOK TO SHIFT TO THE NORTH...WITH MUCH
COOLER AIR SLIDING SOUTH AND LIKELY KNOCKING TEMPS BACK TO SUB-
SEASONAL CONDS IN THE UPR 60S/NEAR 70 DEGREE RANGE SAT/SUN. IF
NORTHEAST WINDS MATERIALIZE...NEXT WEEKEND AREAS ADJACENT TO LAKE
MICHIGAN ALONG THE IL/IN SHORELINE COULD BE LOCKED IN THE UPR 50S TO
LOW 60S FOR HIGHS WITH A COLD FLOW OFF OF LAKE MICHIGAN.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 18Z...

* GUSTY SOUTHWEST WINDS.

* HIGH END MVFR CEILINGS POSSIBLE EARLY THIS AFTERNOON...MVFR
  POSSIBLE AGAIN EARLY TUESDAY MORNING.

* SHOWERS LIKELY WITH PERIODIC THUNDERSTORMS LATE IN THE FORECAST
  PERIOD.

RODRIGUEZ

//DISCUSSION...UPDATED 18Z...

MUCH OF THE SHOWERS ARE EXITING THE AREA EARLY THIS AFTERNOON.
HOWEVER...AN ISOLATED LIGHT SHOWER WILL STILL BE POSSIBLE OVER THE
NEXT HOUR BEFORE PREVAILING DRY CONDITIONS ARE EXPECTED THIS
AFTERNOON AND TONIGHT. LINGERING MVFR CEILINGS WILL LIFT TO VFR
THROUGH 20-21Z THIS AFTERNOON WITH SKIES THEN SCATTERING THIS
EVENING...AS THE SOUTHWEST WINDS/GUSTS DIMINISH INTO THE EVENING.
WITH FAIRLY MOIST CONDITIONS REMAINING IN PLACE TONIGHT INTO
TUESDAY...REDEVELOPING LOW CEILINGS DO APPEAR TO BE A POSSIBILITY.
OVERALL CONFIDENCE IS LOWER DURING THIS PERIOD...BUT DID MAKE
MENTION OF AT LEAST MVFR CEILINGS...AND WILL NEED TO MONITOR FOR
POTENTIALLY LOWER CEILINGS. HAVE PUSHED BACK TIMING OF PRECIP LATE
IN THE PERIOD...BUT WITH INSTABILITY AND FORCING
INCREASING...SHOWERS AND THUNDERSTORMS DO APPEAR LIKELY TUESDAY.
STILL SOME UNCERTAINTY WITH EXACT TIMING AND DURATION...AND EVEN
THE POSSIBILITY FOR AN ADDITIONAL PERIOD OF THUNDERSTORMS TUESDAY
AFTERNOON.

RODRIGUEZ


//ORD AND MDW CONFIDENCE...UPDATED 18Z...

* HIGH CONFIDENCE WITH WIND SPEED/DIRECTION.

* MEDIUM HIGH CONFIDENCE WITH CEILINGS.

* HIGH CONFIDENCE OF SHOWERS/THUNDERSTORMS...MEDIUM CONFIDENCE
  WITH TIMING/DURATION.

RODRIGUEZ

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/TSRA LATE. SOUTHEAST WINDS.

FRIDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. SOUTHWEST WINDS
BECOMING NORTHEAST OVERNIGHT.

SATURDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. NORTHEAST
WINDS.

SUNDAY...CHANCE TSRA. MVFR POSSIBLE. NORTHEAST WINDS.

KREIN

&&

.MARINE...
304 AM CDT

LOW PRESSURE WILL BE STEADILY LIFTING NORTH ACROSS THE MISSOURI
VALLEY THIS MORNING...REACHING LAKE SUPERIOR BY THIS EVENING AND
CONTINUING TO SLIDE EAST/NORTHEAST TOWARDS QUEBEC BY TUESDAY
MORNING. A FRONTAL BOUNDARY WILL REMAIN OVER THE FAR NORTHERN
PORTIONS OF LAKE MICHIGAN. MEANWHILE GUSTY SOUTHERLY WINDS ARE
EXPECTED TO INCREASE THIS MORNING...WITH OCCASIONAL GALES FOR THE
NEARSHORE WATERS OF IL/IN. ACROSS THE OPEN WATERS...EXPECT THE
WARM/MOIST AIR TO STRUGGLE TO REACH THE SFC OF THE LAKE WITH SOME
DEGREE OF LAKE STABILITY. WAVES WILL STEADILY BUILD ACROSS THE
NORTHERN HALF OF THE LAKE AS A RESULT OF THE LONG FETCH. STILL
FEEL THAT GUSTS WILL REACH 30KT ACROSS THE LAKE...HOWEVER
CONFIDENCE HAS DIMINISHED SLIGHTLY AS NEW GUIDANCE HAS BECOME A
LITTLE LESS WITH THE WIND FIELDS. NONETHELESS...WAVES FOR THE
NORTHERN HALF OF THE LAKE WILL LIKELY TOP OUT IN THE 4 TO 7 FT
RANGE WITH OCCASIONAL WAVES REACHING 9 FT THIS AFTERNOON/EVENING.

THE GRADIENT QUICKLY DIMINISHES THIS EVENING...BUT EXPECT
SOUTHERLY WINDS TO PERSIST. THIS WILL ALLOW WAVES TO SUBSIDE TO 3
TO 5 FT. ANOTHER LOW WILL ARRIVE TUE...WITH WINDS NUDGING BACK UP
HOWEVER WARM AIR WILL CONTINUE TO FLOW ACROSS THE LAKE AND COULD
FURTHER ENHANCE THE LAKE STABILITY AND KEEP WAVES FROM BUILDING TO
LARGE.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...NEARSHORE WATERS UNTIL 3
     PM MONDAY.

     SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 251803
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
103 PM CDT MON MAY 25 2015

.UPDATE...

COMPACT NEGATIVELY TILTED TROUGH AXIS IS SLIDING NORTHEAST THROUGH
IOWA AND WESTERN ILLINOIS. EASTERN EDGE OF THE TROUGH WILL MOVE
THROUGH NORTHEAST ILLINOIS THIS MORNING. NOTED UPTICK IN SHOWER
ACTIVITY ASSOCIATED WITH THIS WAVE IS PRODUCING MORE ORGANIZED BUT
STILL LARGELY SCATTERED SHOWERS. STILL TRACKING THIS FEATURE WILL
BRING THE BEST CHANCE FOR SOME BRIEF DOWNPOURS IN THE COMING
HOURS...AND THESE WILL SPREAD INTO THE WEST METRO AREA IN THE NEXT
HOUR...SPREADING INTO CHICAGOLAND SHORTLY THERE AFTER. THE CLOUDS
PRODUCING THE SHOWER ACTIVITY ARE SHALLOW AND MID LEVEL LAPSE
RATES ARE SUBPAR...THUS THUNDER SHOULD BE LIMITED AT BEST. SOME
WEAK INSTABILITY IS NOTED SOUTH OF I-80 WHICH DOES NOT PRECLUDE AN
ISOLATED STRIKE IN ANY STRONGER ACTIVITY.

REGARDING WINDS...WITH THE BROKEN TO OVERCAST LOW CLOUD
DECK...MIXING IS BEING LIMITED AND GETING GUSTS TO AROUND 30 KT OR
SO. ANY STRONGER GUSTS WOULD BE IN THE NEXT HOUR BEFORE A RAPID
DROP OFF LATER THIS MORNING.

KMD

&&

.SHORT TERM...
345 AM CDT

THROUGH MONDAY NIGHT...
FOR THE REMAINDER OF THE NIGHT AND INTO MONDAY MORNING...PCPN
CHANCES CONTINUE TO WANE AS LATEST RADAR TRENDS ONLY SHOW SOME SCT
SHRA WHICH ARE DECREASING IN INTENSITY.  IN SPITE OF DEWPOINTS IN
THE LOW 60S...AND A STRONG LOW LEVEL JET...50 KT AT 925 MB...THERE
IS AN ELEMENT LACKING WHICH IS SEEMS TO BE PREVENTING THE
MAINTENANCE OF SHRA/TSRA OVER NERN IL/NWRN IN.  THE MAIN MISSING
ELEMENTS IS FORCING.  THE SFC AND UPPER LEVEL LOW ARE WAY TO THE
WEST...OVER THE NRN PLAINS. THE SHORTWAVE CLIMBING UP THE NWRN
PERIPHERY OF THE HIGH AMPLITUDE RIDGE IS BEING SLOWED BY THE HIGH
AMPLITUDE...AND IS BEING FORCED TO A MORE WLY TRACK THROUGH THE
UPPER MISSISSIPPI VALLEY THAN PREVIOUSLY ANTICIPATED.  SO...FOR THE
REMAINDER OF THE OVERNIGHT HOURS AND THE DAYTIME HOURS MONDAY...HAVE
BACK OF TO ISOLD-SCT SHRA.  WILL KEEP ISOLD TS MENTION FOR THE LATE
MORNING HOURS...THROUGH AROUND NOON...WITH THE DAYTIME HEATING...BUT
CONFIDENCE IN ANY TS IS RATHER LOW AT THIS TIME.  BY THIS
AFTERNOON...A MID LEVEL DRY SLOT IS EXPECTED TO MOVE ACROSS THE
REGION...FURTHER LIMITING PCPN CHANCES AND IT IS QUITE LIKELY THAT
THE REGION WILL REMAIN DRY THROUGH THE DAY.  HOWEVER...WHILE THE
PCPN CHANCES ARE DIMINISHING...THE LIKELIHOOD OF STRONG WINDS IS
STILL A CONCERN.  WITH THE DIMINISHING PCPN CHANCES...LESS SKY COVER
THAN PREVIOUSLY ANTICIPATED IS ALSO POSSIBLE.  A STRONG SWLY
PRESSURE GRADIENT IS SETTING UP ACROSS THE REGION BETWEEN SFC
RIDGING ACROSS THE SERN CONUS AND AND LOW PRESSURE FROM THE UPPER
MISSISSIPPI VALLEY TO THE WESTERN PLAINS.  THE STRONG GRADIENT WILL
HELP DRIVE THE SFC WINDS AND THE DIMINISHING CLOUD COVER COULD HELP
ENHANCE DEEP LAYER MIXING...TAPPING STRONGER WINDS ALOFT.  SUSTAINED
25-25 MPH WINDS ARE LIKELY WITH GUSTS OF 30-35 MPH.
ALSO...PERSISTENT WARM/MOIST ADVECTION AT THE SFC WILL BRING
TEMPERATURES INTO THE LOW TO MIDDLE 80S WITH DEWPOINTS IN THE LOWER
60S.

FOR MONDAY NIGHT...THE BREEZY CONDITIONS WILL PERSIST INTO THE AS
THERE SHOULD BE LITTLE CHANGE TO THE SFC AND UPPER LEVEL PATTERNS.
THE UPPER RIDGE WILL LOSE A LITTLE AMPLITUDE AS SHORT WAVE ENERGY
OVERTOPS THE RIDGE...BUT GENERAL TROUGHING WILL PERSIST ACROSS THE
UPPER MISSISSIPPI VALLEY THROUGH THE CENTRAL PLAINS.  THE NEXT
CHANCE FOR PCPN WILL HOLD OFF UNTIL LATE TONIGHT/EARLY TUESDAY
MORNING AND THE NEXT SHORTWAVE LIFTS OUT OF THE SRN PLAINS AND INTO
THE MIDDLE MISSISSIPPI VALLEY.  AMPLE LOW LEVEL MOISTURE WILL
ALREADY BE IN PLACE SO IT WILL JUST A MATTER OF WHEN THE FORCING
WILL GET HERE.  AGAIN...THERE IS SOME CONCERN THAT THE FORCING WILL
BE TO THE WEST...WITH THE SHORTWAVE TRACKING THROUGH THE MIDDLE
MISSISSIPPI VALLEY AND INTO WI.  SO...WILL CARRY CHANCE POPS FOR THE
REGION...WITH LIKELY POPS APPROACHING THE PONTIAC AREA BY EARLY
TUESDAY MORNING.  THE PERSISTENT WARM/MOIST ADVECTIVE PATTERN AND
BREEZY CONDITIONS SHOULD KEEP TEMPERATURES FROM DROPPING OFF
SIGNIFICANTLY OVERNIGHT AND LOWS SHOULD BE IN THE MIDDLE TO UPPER
60S.

KREIN

&&

.LONG TERM...
239 AM CDT

TUESDAY THROUGH SUNDAY...

TUESDAY THROUGH WEDNESDAY...
500MB TROUGH AXIS WILL SLOWLY PIVOT EAST ACROSS THE CENTRAL PLAINS
INTO THE MID-MISSOURI VALLEY TUE...WITH A SFC WAVE SLIDING NORTH
ACROSS IOWA INTO CENTRAL WISC LATE TUE. THE SFC FEATURE IS NOT
EXPECTED TO BE STRONG...HOWEVER THE GRADIENT DOES TIGHTEN WITH
MODEST HEIGHT FALLS IN THE LOWEST LAYERS OF THE ATMOSPHERE. SOME
INSTABILITY DOES REMAIN ALONG WITH RELATIVELY MOIST SFC CONDS AS
DEW PTS WILL REMAIN IN THE UPR 50S/LOW 60S. PWAT VALUES WILL ALSO
HOVER JUST OVER 1 INCH...WHICH IS SEASONAL. WILL HOLD ONTO MENTION
OF RAIN AND THUNDER...BUT COULD SEE THIS MAINLY FOCUSED IN THE TUE
MORNING TIMEFRAME.

WITH CONSIDERABLE SOLAR SHIELDING PROGGED FOR TUE...TEMPS MAY
STRUGGLE TO WARM BEYOND THE MID/UPR 70S. BUT WITH GUIDANCE HINTING
AT A DRY SLOT LIFTING NORTHEAST ACROSS THE REGION TUE EVE...THIS
COULD INTRODUCE SOME EROSION TO THE CLOUD COVER IN THE AFTN HOURS
TUE AND ALLOW SOME SFC HEATING TO OCCUR AND PUSH TEMPS TO ARND 80.

GUIDANCE LIFTS THE DRY SLOT OVERHEAD LATE TUE NGT...WITH THE 500MB
TROUGH AXIS ARRIVING ARND DAYBREAK WED AND LIFTING EAST ACROSS LOWER
MICHIGAN. THIS WILL BRING DRY ONLY SLIGHT CHANCE POPS AS WEAK SFC
RIDGING BEGINS TO NUDGE EAST ACROSS THE MISSOURI VALLEY TOWARDS THE
FORECAST AREA MIDDAY WED. IT IS POSSIBLE THAT ENOUGH DRY AIR
INFLUENCE COULD ALLOW FOR REMOVAL OF THE SLIGHT CHANCE POPS WED
AFTN. THERMAL TROUGH LAGS BEHIND THE FRONTAL BOUNDARY WED...SO TEMPS
COULD STILL WARM BACK TO ARND 80 AND PERHAPS THE LOW 80S IN THE
SOUTHERN CWFA.

THURSDAY THROUGH SUNDAY...
ANTI-CYCLONIC FLOW ARRIVES THUR WITH AT LEAST ONE PERIOD OF DRY
WEATHER EXPECTED FOR NORTHERN IL/NORTHWEST IN. ONLY A COUPLE
ENSEMBLE MEMBERS CONTINUE TO PROG POPS ALONG THE SOUTHERN FORECAST
AREA THUR...BUT COULD SEE THIS TRENDING DRY IN THE NEXT FEW
SOLUTIONS. WITH WARM TEMPS ALOFT EXPECTED THUR AND THIN CLOUD
COVER...THUR HIGHS COULD PEAK IN THE LOW 80S.

THEN FOCUS TURNS TOWARDS THE UPCOMING WEEKEND AND A PATTERN SHIFT
AWAY FROM THE WARM/HUMID CONDITIONS. ENSEMBLES SHOW MINIMAL SPREAD
IN THE LATE WEEK PERIODS...WITH THE UPSTREAM RIDGE OVER
ALASKA/WESTERN CANADA AND A DOWNSTREAM MID-LVL RIDGE ACROSS THE
SOUTHEAST CONUS. BOTH OF THESE FEATURES IN TIME BEGIN TO
WEAKEN...WITH THE LONGWAVE PATTERN TRANSITIONING INTO A SEMI-ZONAL
ORIENTATION BY THE SECOND HALF OF THE WEEKEND.

OPER GUIDANCE HAS BEEN CONSISTENT WITH PROGGING A ROBUST 500MB
TROUGH TO SLIDE SOUTH FROM CENTRAL CANADA FRI...ALONG WITH A STRONG
CANADIAN SFC RIDGE ON IT/S HEELS. WITH A CHANNEL OF MOISTURE
REMAINING ACROSS THE SOUTHERN PLAINS STRETCHING NORTHEAST THROUGH
THE UPPER MIDWEST...THIS BOUNDARY WILL BECOME ACTIVE WITH A SFC WAVE
DEVELOPING ACROSS THE SOUTHERN PLAINS. THIS LOW WILL THEN LIFT
NORTHEAST TOWARDS THE CWFA FRI WITH A COLD FRONT ARRIVING ACROSS THE
FORECAST AREA SAT. WINDS LOOK TO SHIFT TO THE NORTH...WITH MUCH
COOLER AIR SLIDING SOUTH AND LIKELY KNOCKING TEMPS BACK TO SUB-
SEASONAL CONDS IN THE UPR 60S/NEAR 70 DEGREE RANGE SAT/SUN. IF
NORTHEAST WINDS MATERIALIZE...NEXT WEEKEND AREAS ADJACENT TO LAKE
MICHIGAN ALONG THE IL/IN SHORELINE COULD BE LOCKED IN THE UPR 50S TO
LOW 60S FOR HIGHS WITH A COLD FLOW OFF OF LAKE MICHIGAN.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 18Z...

* GUSTY SOUTHWEST WINDS.

* HIGH END MVFR CEILINGS POSSIBLE EARLY THIS AFTERNOON...MVFR
  POSSIBLE AGAIN EARLY TUESDAY MORNING.

* SHOWERS LIKELY WITH PERIODIC THUNDERSTORMS LATE IN THE FORECAST
  PERIOD.

RODRIGUEZ

//DISCUSSION...UPDATED 18Z...

MUCH OF THE SHOWERS ARE EXITING THE AREA EARLY THIS AFTERNOON.
HOWEVER...AN ISOLATED LIGHT SHOWER WILL STILL BE POSSIBLE OVER THE
NEXT HOUR BEFORE PREVAILING DRY CONDITIONS ARE EXPECTED THIS
AFTERNOON AND TONIGHT. LINGERING MVFR CEILINGS WILL LIFT TO VFR
THROUGH 20-21Z THIS AFTERNOON WITH SKIES THEN SCATTERING THIS
EVENING...AS THE SOUTHWEST WINDS/GUSTS DIMINISH INTO THE EVENING.
WITH FAIRLY MOIST CONDITIONS REMAINING IN PLACE TONIGHT INTO
TUESDAY...REDEVELOPING LOW CEILINGS DO APPEAR TO BE A POSSIBILITY.
OVERALL CONFIDENCE IS LOWER DURING THIS PERIOD...BUT DID MAKE
MENTION OF AT LEAST MVFR CEILINGS...AND WILL NEED TO MONITOR FOR
POTENTIALLY LOWER CEILINGS. HAVE PUSHED BACK TIMING OF PRECIP LATE
IN THE PERIOD...BUT WITH INSTABILITY AND FORCING
INCREASING...SHOWERS AND THUNDERSTORMS DO APPEAR LIKELY TUESDAY.
STILL SOME UNCERTAINTY WITH EXACT TIMING AND DURATION...AND EVEN
THE POSSIBILITY FOR AN ADDITIONAL PERIOD OF THUNDERSTORMS TUESDAY
AFTERNOON.

RODRIGUEZ


//ORD AND MDW CONFIDENCE...UPDATED 18Z...

* HIGH CONFIDENCE WITH WIND SPEED/DIRECTION.

* MEDIUM HIGH CONFIDENCE WITH CEILINGS.

* HIGH CONFIDENCE OF SHOWERS/THUNDERSTORMS...MEDIUM CONFIDENCE
  WITH TIMING/DURATION.

RODRIGUEZ

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/TSRA LATE. SOUTHEAST WINDS.

FRIDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. SOUTHWEST WINDS
BECOMING NORTHEAST OVERNIGHT.

SATURDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. NORTHEAST
WINDS.

SUNDAY...CHANCE TSRA. MVFR POSSIBLE. NORTHEAST WINDS.

KREIN

&&

.MARINE...
304 AM CDT

LOW PRESSURE WILL BE STEADILY LIFTING NORTH ACROSS THE MISSOURI
VALLEY THIS MORNING...REACHING LAKE SUPERIOR BY THIS EVENING AND
CONTINUING TO SLIDE EAST/NORTHEAST TOWARDS QUEBEC BY TUESDAY
MORNING. A FRONTAL BOUNDARY WILL REMAIN OVER THE FAR NORTHERN
PORTIONS OF LAKE MICHIGAN. MEANWHILE GUSTY SOUTHERLY WINDS ARE
EXPECTED TO INCREASE THIS MORNING...WITH OCCASIONAL GALES FOR THE
NEARSHORE WATERS OF IL/IN. ACROSS THE OPEN WATERS...EXPECT THE
WARM/MOIST AIR TO STRUGGLE TO REACH THE SFC OF THE LAKE WITH SOME
DEGREE OF LAKE STABILITY. WAVES WILL STEADILY BUILD ACROSS THE
NORTHERN HALF OF THE LAKE AS A RESULT OF THE LONG FETCH. STILL
FEEL THAT GUSTS WILL REACH 30KT ACROSS THE LAKE...HOWEVER
CONFIDENCE HAS DIMINISHED SLIGHTLY AS NEW GUIDANCE HAS BECOME A
LITTLE LESS WITH THE WIND FIELDS. NONETHELESS...WAVES FOR THE
NORTHERN HALF OF THE LAKE WILL LIKELY TOP OUT IN THE 4 TO 7 FT
RANGE WITH OCCASIONAL WAVES REACHING 9 FT THIS AFTERNOON/EVENING.

THE GRADIENT QUICKLY DIMINISHES THIS EVENING...BUT EXPECT
SOUTHERLY WINDS TO PERSIST. THIS WILL ALLOW WAVES TO SUBSIDE TO 3
TO 5 FT. ANOTHER LOW WILL ARRIVE TUE...WITH WINDS NUDGING BACK UP
HOWEVER WARM AIR WILL CONTINUE TO FLOW ACROSS THE LAKE AND COULD
FURTHER ENHANCE THE LAKE STABILITY AND KEEP WAVES FROM BUILDING TO
LARGE.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...NEARSHORE WATERS UNTIL 3
     PM MONDAY.

     SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
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000
FXUS63 KLOT 251803
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
103 PM CDT MON MAY 25 2015

.UPDATE...

COMPACT NEGATIVELY TILTED TROUGH AXIS IS SLIDING NORTHEAST THROUGH
IOWA AND WESTERN ILLINOIS. EASTERN EDGE OF THE TROUGH WILL MOVE
THROUGH NORTHEAST ILLINOIS THIS MORNING. NOTED UPTICK IN SHOWER
ACTIVITY ASSOCIATED WITH THIS WAVE IS PRODUCING MORE ORGANIZED BUT
STILL LARGELY SCATTERED SHOWERS. STILL TRACKING THIS FEATURE WILL
BRING THE BEST CHANCE FOR SOME BRIEF DOWNPOURS IN THE COMING
HOURS...AND THESE WILL SPREAD INTO THE WEST METRO AREA IN THE NEXT
HOUR...SPREADING INTO CHICAGOLAND SHORTLY THERE AFTER. THE CLOUDS
PRODUCING THE SHOWER ACTIVITY ARE SHALLOW AND MID LEVEL LAPSE
RATES ARE SUBPAR...THUS THUNDER SHOULD BE LIMITED AT BEST. SOME
WEAK INSTABILITY IS NOTED SOUTH OF I-80 WHICH DOES NOT PRECLUDE AN
ISOLATED STRIKE IN ANY STRONGER ACTIVITY.

REGARDING WINDS...WITH THE BROKEN TO OVERCAST LOW CLOUD
DECK...MIXING IS BEING LIMITED AND GETING GUSTS TO AROUND 30 KT OR
SO. ANY STRONGER GUSTS WOULD BE IN THE NEXT HOUR BEFORE A RAPID
DROP OFF LATER THIS MORNING.

KMD

&&

.SHORT TERM...
345 AM CDT

THROUGH MONDAY NIGHT...
FOR THE REMAINDER OF THE NIGHT AND INTO MONDAY MORNING...PCPN
CHANCES CONTINUE TO WANE AS LATEST RADAR TRENDS ONLY SHOW SOME SCT
SHRA WHICH ARE DECREASING IN INTENSITY.  IN SPITE OF DEWPOINTS IN
THE LOW 60S...AND A STRONG LOW LEVEL JET...50 KT AT 925 MB...THERE
IS AN ELEMENT LACKING WHICH IS SEEMS TO BE PREVENTING THE
MAINTENANCE OF SHRA/TSRA OVER NERN IL/NWRN IN.  THE MAIN MISSING
ELEMENTS IS FORCING.  THE SFC AND UPPER LEVEL LOW ARE WAY TO THE
WEST...OVER THE NRN PLAINS. THE SHORTWAVE CLIMBING UP THE NWRN
PERIPHERY OF THE HIGH AMPLITUDE RIDGE IS BEING SLOWED BY THE HIGH
AMPLITUDE...AND IS BEING FORCED TO A MORE WLY TRACK THROUGH THE
UPPER MISSISSIPPI VALLEY THAN PREVIOUSLY ANTICIPATED.  SO...FOR THE
REMAINDER OF THE OVERNIGHT HOURS AND THE DAYTIME HOURS MONDAY...HAVE
BACK OF TO ISOLD-SCT SHRA.  WILL KEEP ISOLD TS MENTION FOR THE LATE
MORNING HOURS...THROUGH AROUND NOON...WITH THE DAYTIME HEATING...BUT
CONFIDENCE IN ANY TS IS RATHER LOW AT THIS TIME.  BY THIS
AFTERNOON...A MID LEVEL DRY SLOT IS EXPECTED TO MOVE ACROSS THE
REGION...FURTHER LIMITING PCPN CHANCES AND IT IS QUITE LIKELY THAT
THE REGION WILL REMAIN DRY THROUGH THE DAY.  HOWEVER...WHILE THE
PCPN CHANCES ARE DIMINISHING...THE LIKELIHOOD OF STRONG WINDS IS
STILL A CONCERN.  WITH THE DIMINISHING PCPN CHANCES...LESS SKY COVER
THAN PREVIOUSLY ANTICIPATED IS ALSO POSSIBLE.  A STRONG SWLY
PRESSURE GRADIENT IS SETTING UP ACROSS THE REGION BETWEEN SFC
RIDGING ACROSS THE SERN CONUS AND AND LOW PRESSURE FROM THE UPPER
MISSISSIPPI VALLEY TO THE WESTERN PLAINS.  THE STRONG GRADIENT WILL
HELP DRIVE THE SFC WINDS AND THE DIMINISHING CLOUD COVER COULD HELP
ENHANCE DEEP LAYER MIXING...TAPPING STRONGER WINDS ALOFT.  SUSTAINED
25-25 MPH WINDS ARE LIKELY WITH GUSTS OF 30-35 MPH.
ALSO...PERSISTENT WARM/MOIST ADVECTION AT THE SFC WILL BRING
TEMPERATURES INTO THE LOW TO MIDDLE 80S WITH DEWPOINTS IN THE LOWER
60S.

FOR MONDAY NIGHT...THE BREEZY CONDITIONS WILL PERSIST INTO THE AS
THERE SHOULD BE LITTLE CHANGE TO THE SFC AND UPPER LEVEL PATTERNS.
THE UPPER RIDGE WILL LOSE A LITTLE AMPLITUDE AS SHORT WAVE ENERGY
OVERTOPS THE RIDGE...BUT GENERAL TROUGHING WILL PERSIST ACROSS THE
UPPER MISSISSIPPI VALLEY THROUGH THE CENTRAL PLAINS.  THE NEXT
CHANCE FOR PCPN WILL HOLD OFF UNTIL LATE TONIGHT/EARLY TUESDAY
MORNING AND THE NEXT SHORTWAVE LIFTS OUT OF THE SRN PLAINS AND INTO
THE MIDDLE MISSISSIPPI VALLEY.  AMPLE LOW LEVEL MOISTURE WILL
ALREADY BE IN PLACE SO IT WILL JUST A MATTER OF WHEN THE FORCING
WILL GET HERE.  AGAIN...THERE IS SOME CONCERN THAT THE FORCING WILL
BE TO THE WEST...WITH THE SHORTWAVE TRACKING THROUGH THE MIDDLE
MISSISSIPPI VALLEY AND INTO WI.  SO...WILL CARRY CHANCE POPS FOR THE
REGION...WITH LIKELY POPS APPROACHING THE PONTIAC AREA BY EARLY
TUESDAY MORNING.  THE PERSISTENT WARM/MOIST ADVECTIVE PATTERN AND
BREEZY CONDITIONS SHOULD KEEP TEMPERATURES FROM DROPPING OFF
SIGNIFICANTLY OVERNIGHT AND LOWS SHOULD BE IN THE MIDDLE TO UPPER
60S.

KREIN

&&

.LONG TERM...
239 AM CDT

TUESDAY THROUGH SUNDAY...

TUESDAY THROUGH WEDNESDAY...
500MB TROUGH AXIS WILL SLOWLY PIVOT EAST ACROSS THE CENTRAL PLAINS
INTO THE MID-MISSOURI VALLEY TUE...WITH A SFC WAVE SLIDING NORTH
ACROSS IOWA INTO CENTRAL WISC LATE TUE. THE SFC FEATURE IS NOT
EXPECTED TO BE STRONG...HOWEVER THE GRADIENT DOES TIGHTEN WITH
MODEST HEIGHT FALLS IN THE LOWEST LAYERS OF THE ATMOSPHERE. SOME
INSTABILITY DOES REMAIN ALONG WITH RELATIVELY MOIST SFC CONDS AS
DEW PTS WILL REMAIN IN THE UPR 50S/LOW 60S. PWAT VALUES WILL ALSO
HOVER JUST OVER 1 INCH...WHICH IS SEASONAL. WILL HOLD ONTO MENTION
OF RAIN AND THUNDER...BUT COULD SEE THIS MAINLY FOCUSED IN THE TUE
MORNING TIMEFRAME.

WITH CONSIDERABLE SOLAR SHIELDING PROGGED FOR TUE...TEMPS MAY
STRUGGLE TO WARM BEYOND THE MID/UPR 70S. BUT WITH GUIDANCE HINTING
AT A DRY SLOT LIFTING NORTHEAST ACROSS THE REGION TUE EVE...THIS
COULD INTRODUCE SOME EROSION TO THE CLOUD COVER IN THE AFTN HOURS
TUE AND ALLOW SOME SFC HEATING TO OCCUR AND PUSH TEMPS TO ARND 80.

GUIDANCE LIFTS THE DRY SLOT OVERHEAD LATE TUE NGT...WITH THE 500MB
TROUGH AXIS ARRIVING ARND DAYBREAK WED AND LIFTING EAST ACROSS LOWER
MICHIGAN. THIS WILL BRING DRY ONLY SLIGHT CHANCE POPS AS WEAK SFC
RIDGING BEGINS TO NUDGE EAST ACROSS THE MISSOURI VALLEY TOWARDS THE
FORECAST AREA MIDDAY WED. IT IS POSSIBLE THAT ENOUGH DRY AIR
INFLUENCE COULD ALLOW FOR REMOVAL OF THE SLIGHT CHANCE POPS WED
AFTN. THERMAL TROUGH LAGS BEHIND THE FRONTAL BOUNDARY WED...SO TEMPS
COULD STILL WARM BACK TO ARND 80 AND PERHAPS THE LOW 80S IN THE
SOUTHERN CWFA.

THURSDAY THROUGH SUNDAY...
ANTI-CYCLONIC FLOW ARRIVES THUR WITH AT LEAST ONE PERIOD OF DRY
WEATHER EXPECTED FOR NORTHERN IL/NORTHWEST IN. ONLY A COUPLE
ENSEMBLE MEMBERS CONTINUE TO PROG POPS ALONG THE SOUTHERN FORECAST
AREA THUR...BUT COULD SEE THIS TRENDING DRY IN THE NEXT FEW
SOLUTIONS. WITH WARM TEMPS ALOFT EXPECTED THUR AND THIN CLOUD
COVER...THUR HIGHS COULD PEAK IN THE LOW 80S.

THEN FOCUS TURNS TOWARDS THE UPCOMING WEEKEND AND A PATTERN SHIFT
AWAY FROM THE WARM/HUMID CONDITIONS. ENSEMBLES SHOW MINIMAL SPREAD
IN THE LATE WEEK PERIODS...WITH THE UPSTREAM RIDGE OVER
ALASKA/WESTERN CANADA AND A DOWNSTREAM MID-LVL RIDGE ACROSS THE
SOUTHEAST CONUS. BOTH OF THESE FEATURES IN TIME BEGIN TO
WEAKEN...WITH THE LONGWAVE PATTERN TRANSITIONING INTO A SEMI-ZONAL
ORIENTATION BY THE SECOND HALF OF THE WEEKEND.

OPER GUIDANCE HAS BEEN CONSISTENT WITH PROGGING A ROBUST 500MB
TROUGH TO SLIDE SOUTH FROM CENTRAL CANADA FRI...ALONG WITH A STRONG
CANADIAN SFC RIDGE ON IT/S HEELS. WITH A CHANNEL OF MOISTURE
REMAINING ACROSS THE SOUTHERN PLAINS STRETCHING NORTHEAST THROUGH
THE UPPER MIDWEST...THIS BOUNDARY WILL BECOME ACTIVE WITH A SFC WAVE
DEVELOPING ACROSS THE SOUTHERN PLAINS. THIS LOW WILL THEN LIFT
NORTHEAST TOWARDS THE CWFA FRI WITH A COLD FRONT ARRIVING ACROSS THE
FORECAST AREA SAT. WINDS LOOK TO SHIFT TO THE NORTH...WITH MUCH
COOLER AIR SLIDING SOUTH AND LIKELY KNOCKING TEMPS BACK TO SUB-
SEASONAL CONDS IN THE UPR 60S/NEAR 70 DEGREE RANGE SAT/SUN. IF
NORTHEAST WINDS MATERIALIZE...NEXT WEEKEND AREAS ADJACENT TO LAKE
MICHIGAN ALONG THE IL/IN SHORELINE COULD BE LOCKED IN THE UPR 50S TO
LOW 60S FOR HIGHS WITH A COLD FLOW OFF OF LAKE MICHIGAN.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 18Z...

* GUSTY SOUTHWEST WINDS.

* HIGH END MVFR CEILINGS POSSIBLE EARLY THIS AFTERNOON...MVFR
  POSSIBLE AGAIN EARLY TUESDAY MORNING.

* SHOWERS LIKELY WITH PERIODIC THUNDERSTORMS LATE IN THE FORECAST
  PERIOD.

RODRIGUEZ

//DISCUSSION...UPDATED 18Z...

MUCH OF THE SHOWERS ARE EXITING THE AREA EARLY THIS AFTERNOON.
HOWEVER...AN ISOLATED LIGHT SHOWER WILL STILL BE POSSIBLE OVER THE
NEXT HOUR BEFORE PREVAILING DRY CONDITIONS ARE EXPECTED THIS
AFTERNOON AND TONIGHT. LINGERING MVFR CEILINGS WILL LIFT TO VFR
THROUGH 20-21Z THIS AFTERNOON WITH SKIES THEN SCATTERING THIS
EVENING...AS THE SOUTHWEST WINDS/GUSTS DIMINISH INTO THE EVENING.
WITH FAIRLY MOIST CONDITIONS REMAINING IN PLACE TONIGHT INTO
TUESDAY...REDEVELOPING LOW CEILINGS DO APPEAR TO BE A POSSIBILITY.
OVERALL CONFIDENCE IS LOWER DURING THIS PERIOD...BUT DID MAKE
MENTION OF AT LEAST MVFR CEILINGS...AND WILL NEED TO MONITOR FOR
POTENTIALLY LOWER CEILINGS. HAVE PUSHED BACK TIMING OF PRECIP LATE
IN THE PERIOD...BUT WITH INSTABILITY AND FORCING
INCREASING...SHOWERS AND THUNDERSTORMS DO APPEAR LIKELY TUESDAY.
STILL SOME UNCERTAINTY WITH EXACT TIMING AND DURATION...AND EVEN
THE POSSIBILITY FOR AN ADDITIONAL PERIOD OF THUNDERSTORMS TUESDAY
AFTERNOON.

RODRIGUEZ


//ORD AND MDW CONFIDENCE...UPDATED 18Z...

* HIGH CONFIDENCE WITH WIND SPEED/DIRECTION.

* MEDIUM HIGH CONFIDENCE WITH CEILINGS.

* HIGH CONFIDENCE OF SHOWERS/THUNDERSTORMS...MEDIUM CONFIDENCE
  WITH TIMING/DURATION.

RODRIGUEZ

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/TSRA LATE. SOUTHEAST WINDS.

FRIDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. SOUTHWEST WINDS
BECOMING NORTHEAST OVERNIGHT.

SATURDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. NORTHEAST
WINDS.

SUNDAY...CHANCE TSRA. MVFR POSSIBLE. NORTHEAST WINDS.

KREIN

&&

.MARINE...
304 AM CDT

LOW PRESSURE WILL BE STEADILY LIFTING NORTH ACROSS THE MISSOURI
VALLEY THIS MORNING...REACHING LAKE SUPERIOR BY THIS EVENING AND
CONTINUING TO SLIDE EAST/NORTHEAST TOWARDS QUEBEC BY TUESDAY
MORNING. A FRONTAL BOUNDARY WILL REMAIN OVER THE FAR NORTHERN
PORTIONS OF LAKE MICHIGAN. MEANWHILE GUSTY SOUTHERLY WINDS ARE
EXPECTED TO INCREASE THIS MORNING...WITH OCCASIONAL GALES FOR THE
NEARSHORE WATERS OF IL/IN. ACROSS THE OPEN WATERS...EXPECT THE
WARM/MOIST AIR TO STRUGGLE TO REACH THE SFC OF THE LAKE WITH SOME
DEGREE OF LAKE STABILITY. WAVES WILL STEADILY BUILD ACROSS THE
NORTHERN HALF OF THE LAKE AS A RESULT OF THE LONG FETCH. STILL
FEEL THAT GUSTS WILL REACH 30KT ACROSS THE LAKE...HOWEVER
CONFIDENCE HAS DIMINISHED SLIGHTLY AS NEW GUIDANCE HAS BECOME A
LITTLE LESS WITH THE WIND FIELDS. NONETHELESS...WAVES FOR THE
NORTHERN HALF OF THE LAKE WILL LIKELY TOP OUT IN THE 4 TO 7 FT
RANGE WITH OCCASIONAL WAVES REACHING 9 FT THIS AFTERNOON/EVENING.

THE GRADIENT QUICKLY DIMINISHES THIS EVENING...BUT EXPECT
SOUTHERLY WINDS TO PERSIST. THIS WILL ALLOW WAVES TO SUBSIDE TO 3
TO 5 FT. ANOTHER LOW WILL ARRIVE TUE...WITH WINDS NUDGING BACK UP
HOWEVER WARM AIR WILL CONTINUE TO FLOW ACROSS THE LAKE AND COULD
FURTHER ENHANCE THE LAKE STABILITY AND KEEP WAVES FROM BUILDING TO
LARGE.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...NEARSHORE WATERS UNTIL 3
     PM MONDAY.

     SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
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WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KILX 251744
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1244 PM CDT MON MAY 25 2015

.UPDATE...
ISSUED AT 1004 AM CDT MON MAY 25 2015

A FEW SHOWERS LINGER EAST OF I-55...BUT THESE WILL BE EXITING OVER THE
NEXT COUPLE HOURS. HAVE KEPT SOME SLIGHT CHANCE POP`S EAST OF I-57
INTO THE AFTERNOON...BUT CONDITIONS SHOULD LARGELY BE DRY OVER THE
FORECAST AREA INTO THE EVENING HOURS. HIGH-RESOLUTION VISIBLE
SATELLITE IMAGERY SHOWING SKIES BECOMING PARTLY SUNNY ALREADY
NORTHWEST OF THE ILLINOIS RIVER...AND A LARGER HOLE IN THE CLOUDS
OVER NORTH CENTRAL MISSOURI SHOULD BE MOVING INTO THE FORECAST
AREA EARLY AFTERNOON PER THE RAP MODEL...ALTHOUGH THE SOUTHEAST
CWA WILL LIKELY SEE MORE PERSISTENT CLOUDS. HAVE HAD SOME GUSTS
40-45 MPH AROUND DECATUR AND CHAMPAIGN ON THE LATEST OBS...BUT THE
HRRR MODEL SHOWS THESE HIGH WINDS SHIFTING INTO INDIANA OVER THE
NEXT COUPLE HOURS.

&&

.SHORT TERM...(TODAY)
ISSUED AT 337 AM CDT MON MAY 25 2015

LOW PRESSURE CENTER STILL WELL OFF TO THE SOUTHWEST THIS
MORNING...AND A WARM FRONT DRAPED ACROSS THE IL/WI BORDER THIS
MORNING.  SCATTERED SHOWERS AND ISOLATED THUNDER STILL IN THE
REGION, BUT MAINLY CONFINED TO AREAS IN THE SOUTHEAST AS WELL AS THE
NW.  ILX SITUATED IN A GAP AS THE MAJORITY OF THE SYSTEM CONTINUES
TO LIFT NORTH AND NORTHEAST THIS MORNING.  MODELS PRETTY CONSISTENT
WITH THE MOVING OUT OF THE SYSTEM, WITH SOME SCATTERED SHOWERS
POSSIBLY AT LEAST THROUGH MIDDAY.  ISOLATED THUNDER CANNOT BE RULED
OUT WITH THE INCREASING INSTABILITY AFTER SUNRISE...BUT MAJORITY OF
THE ACTIVITY SCOURS OUT IN ALL OF THE MODELS SHORTLY AFTER MIDDAY.
LINGERED SOME SLIGHT CHANCES AFTER 18Z TO COVER AT LEAST THE
POTENTIAL FOR ACTIVITY WITH ANY REMNANT MESOSCALE BOUNDARIES.
PLENTY OF INSTABILITY STILL WITHIN THE ATMOSPHERE SHOULD IT GET THE
CHANCE TO RECOVER/RESTRATIFY.  HOWEVER, A SMALL AREA OF MIDLEVEL
RIDGING BEHIND THE SHORTWAVE THIS MORNING MAY GIVE US ENOUGH
SUBSIDENCE TO COUNTER THE EFFECTS...SO HAVE FOLLOWED SUIT WITH THE
END OF DAYTIME HEATING AND THE EARLY EVENING AND DROPPED THE POPS
BACK DOWN BEFORE 06Z. EITHER WAY...WINDS ALOFT WITH THE PASSING OF
THE SHORTWAVE AND DAYTIME MIXING WILL RESULT IN SOME GUSTY WINDS
TODAY...GUSTING 25 TO 35 MPH BY MID DAY AND SLOWLY BACKING OFF AS
THE LOW LIFTS OUT OF THE REGION.

.LONG TERM...(TONIGHT THROUGH SUNDAY)
ISSUED AT 337 AM CDT MON MAY 25 2015

FORECAST REMAINS WARM AND MUGGY WITH SEVERAL CHANCES FOR SHOWERS AND
THUNDERSTORMS THROUGHOUT. REGION DOMINATED BY SOUTHWESTERLY FLOW AND
A SERIES OF SHORT WAVES EJECTING OUT OF THE UPPER TROF IN THE SW
THROUGH THE FIRST HALF OF THE WEEK.  A BRIEF BREAK IN THE PATTERN
MID WEEK IS ONLY TEMPORARY AS TEMPS REMAIN WARM WITH PLENTY OF
MOISTURE ONLY REINFORCED BY PERIODIC SHOWERS ENHANCING THE BOUNDARY
LAYER RH. YET ANOTHER SURFACE LOW LIFTS INTO THE MIDWEST MOVING
ALONG THE SOUTHWESTERLY FLOW ALOFT ON TUESDAY.  MORE SHOWERS
ANTICIPATED FOR TUESDAY/TUESDAY NIGHT WITH THE MUGGY AIRMASS.  FRONT
ASSOCIATED WITH THIS SYSTEM WEAK AT BEST AND WILL ONLY SEE A BRIEF
SFC WIND SHIFT TO MORE WESTERLY FROM SOUTHERLY FOR WED AND WED NIGHT
ACCOMPANIED BY A BRIEF PATTERN SHIFT ALOFT.  CHANGE IS ONLY
TEMPORARY AS SOUTHERLY SFC WINDS REESTABLISH BY THE END OF THE WEEK.
WEAK SOUTHWESTERLY FLOW ALOFT SLOWLY SHIFTS TO WEAK FLOW OVERALL
GOING INTO THE WEEKEND SETTING UP CHANCES FOR PERIODIC DIURNALLY
DRIVEN CONVECTION YET AGAIN.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z TUESDAY AFTERNOON)
ISSUED AT 1244 PM CDT MON MAY 25 2015

LINGERING MVFR CEILINGS ARE LIFTING AND ALL SITES SHOULD BE VFR BY
18-19Z. THE STRONGEST OF THE SOUTHWEST WINDS HAVE SHIFTED AWAY
FROM KCMI...BUT WINDS THERE SHOULD STILL GUST TO AROUND 30 KNOTS
OR SO FOR A FEW MORE HOURS. THE REMAINING TAF SITES WILL HAVE
GUSTS MORE IN THE 25 KNOT RANGE...BUT THESE SHOULD SUBSIDE TOWARD
00Z. NEXT PERIOD FOR CONVECTIVE CONCERN APPEARS TO START AROUND
08-09Z WITH STORMS TRACKING IN FROM THE SOUTHWEST. HIGH-RESOLUTION
MODELS SUGGEST SOME BREAKS IN BETWEEN STORMS TUESDAY MORNING...SO
WILL GO WITH VCTS MENTION LATE IN THE PERIOD. TAIL END OF THE RAP
MODEL SUGGESTS SOME MVFR CEILINGS DEVELOPING LATE TONIGHT IN
SOUTHERN ILLINOIS AND BUILDING NORTHWARD...AND HAVE ADDED THESE
FOR KBMI/KDEC/KCMI.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...GEELHART
SHORT TERM...HJS
LONG TERM...HJS
AVIATION...GEELHART



000
FXUS63 KILX 251744
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1244 PM CDT MON MAY 25 2015

.UPDATE...
ISSUED AT 1004 AM CDT MON MAY 25 2015

A FEW SHOWERS LINGER EAST OF I-55...BUT THESE WILL BE EXITING OVER THE
NEXT COUPLE HOURS. HAVE KEPT SOME SLIGHT CHANCE POP`S EAST OF I-57
INTO THE AFTERNOON...BUT CONDITIONS SHOULD LARGELY BE DRY OVER THE
FORECAST AREA INTO THE EVENING HOURS. HIGH-RESOLUTION VISIBLE
SATELLITE IMAGERY SHOWING SKIES BECOMING PARTLY SUNNY ALREADY
NORTHWEST OF THE ILLINOIS RIVER...AND A LARGER HOLE IN THE CLOUDS
OVER NORTH CENTRAL MISSOURI SHOULD BE MOVING INTO THE FORECAST
AREA EARLY AFTERNOON PER THE RAP MODEL...ALTHOUGH THE SOUTHEAST
CWA WILL LIKELY SEE MORE PERSISTENT CLOUDS. HAVE HAD SOME GUSTS
40-45 MPH AROUND DECATUR AND CHAMPAIGN ON THE LATEST OBS...BUT THE
HRRR MODEL SHOWS THESE HIGH WINDS SHIFTING INTO INDIANA OVER THE
NEXT COUPLE HOURS.

&&

.SHORT TERM...(TODAY)
ISSUED AT 337 AM CDT MON MAY 25 2015

LOW PRESSURE CENTER STILL WELL OFF TO THE SOUTHWEST THIS
MORNING...AND A WARM FRONT DRAPED ACROSS THE IL/WI BORDER THIS
MORNING.  SCATTERED SHOWERS AND ISOLATED THUNDER STILL IN THE
REGION, BUT MAINLY CONFINED TO AREAS IN THE SOUTHEAST AS WELL AS THE
NW.  ILX SITUATED IN A GAP AS THE MAJORITY OF THE SYSTEM CONTINUES
TO LIFT NORTH AND NORTHEAST THIS MORNING.  MODELS PRETTY CONSISTENT
WITH THE MOVING OUT OF THE SYSTEM, WITH SOME SCATTERED SHOWERS
POSSIBLY AT LEAST THROUGH MIDDAY.  ISOLATED THUNDER CANNOT BE RULED
OUT WITH THE INCREASING INSTABILITY AFTER SUNRISE...BUT MAJORITY OF
THE ACTIVITY SCOURS OUT IN ALL OF THE MODELS SHORTLY AFTER MIDDAY.
LINGERED SOME SLIGHT CHANCES AFTER 18Z TO COVER AT LEAST THE
POTENTIAL FOR ACTIVITY WITH ANY REMNANT MESOSCALE BOUNDARIES.
PLENTY OF INSTABILITY STILL WITHIN THE ATMOSPHERE SHOULD IT GET THE
CHANCE TO RECOVER/RESTRATIFY.  HOWEVER, A SMALL AREA OF MIDLEVEL
RIDGING BEHIND THE SHORTWAVE THIS MORNING MAY GIVE US ENOUGH
SUBSIDENCE TO COUNTER THE EFFECTS...SO HAVE FOLLOWED SUIT WITH THE
END OF DAYTIME HEATING AND THE EARLY EVENING AND DROPPED THE POPS
BACK DOWN BEFORE 06Z. EITHER WAY...WINDS ALOFT WITH THE PASSING OF
THE SHORTWAVE AND DAYTIME MIXING WILL RESULT IN SOME GUSTY WINDS
TODAY...GUSTING 25 TO 35 MPH BY MID DAY AND SLOWLY BACKING OFF AS
THE LOW LIFTS OUT OF THE REGION.

.LONG TERM...(TONIGHT THROUGH SUNDAY)
ISSUED AT 337 AM CDT MON MAY 25 2015

FORECAST REMAINS WARM AND MUGGY WITH SEVERAL CHANCES FOR SHOWERS AND
THUNDERSTORMS THROUGHOUT. REGION DOMINATED BY SOUTHWESTERLY FLOW AND
A SERIES OF SHORT WAVES EJECTING OUT OF THE UPPER TROF IN THE SW
THROUGH THE FIRST HALF OF THE WEEK.  A BRIEF BREAK IN THE PATTERN
MID WEEK IS ONLY TEMPORARY AS TEMPS REMAIN WARM WITH PLENTY OF
MOISTURE ONLY REINFORCED BY PERIODIC SHOWERS ENHANCING THE BOUNDARY
LAYER RH. YET ANOTHER SURFACE LOW LIFTS INTO THE MIDWEST MOVING
ALONG THE SOUTHWESTERLY FLOW ALOFT ON TUESDAY.  MORE SHOWERS
ANTICIPATED FOR TUESDAY/TUESDAY NIGHT WITH THE MUGGY AIRMASS.  FRONT
ASSOCIATED WITH THIS SYSTEM WEAK AT BEST AND WILL ONLY SEE A BRIEF
SFC WIND SHIFT TO MORE WESTERLY FROM SOUTHERLY FOR WED AND WED NIGHT
ACCOMPANIED BY A BRIEF PATTERN SHIFT ALOFT.  CHANGE IS ONLY
TEMPORARY AS SOUTHERLY SFC WINDS REESTABLISH BY THE END OF THE WEEK.
WEAK SOUTHWESTERLY FLOW ALOFT SLOWLY SHIFTS TO WEAK FLOW OVERALL
GOING INTO THE WEEKEND SETTING UP CHANCES FOR PERIODIC DIURNALLY
DRIVEN CONVECTION YET AGAIN.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z TUESDAY AFTERNOON)
ISSUED AT 1244 PM CDT MON MAY 25 2015

LINGERING MVFR CEILINGS ARE LIFTING AND ALL SITES SHOULD BE VFR BY
18-19Z. THE STRONGEST OF THE SOUTHWEST WINDS HAVE SHIFTED AWAY
FROM KCMI...BUT WINDS THERE SHOULD STILL GUST TO AROUND 30 KNOTS
OR SO FOR A FEW MORE HOURS. THE REMAINING TAF SITES WILL HAVE
GUSTS MORE IN THE 25 KNOT RANGE...BUT THESE SHOULD SUBSIDE TOWARD
00Z. NEXT PERIOD FOR CONVECTIVE CONCERN APPEARS TO START AROUND
08-09Z WITH STORMS TRACKING IN FROM THE SOUTHWEST. HIGH-RESOLUTION
MODELS SUGGEST SOME BREAKS IN BETWEEN STORMS TUESDAY MORNING...SO
WILL GO WITH VCTS MENTION LATE IN THE PERIOD. TAIL END OF THE RAP
MODEL SUGGESTS SOME MVFR CEILINGS DEVELOPING LATE TONIGHT IN
SOUTHERN ILLINOIS AND BUILDING NORTHWARD...AND HAVE ADDED THESE
FOR KBMI/KDEC/KCMI.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...GEELHART
SHORT TERM...HJS
LONG TERM...HJS
AVIATION...GEELHART



000
FXUS63 KILX 251744
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1244 PM CDT MON MAY 25 2015

.UPDATE...
ISSUED AT 1004 AM CDT MON MAY 25 2015

A FEW SHOWERS LINGER EAST OF I-55...BUT THESE WILL BE EXITING OVER THE
NEXT COUPLE HOURS. HAVE KEPT SOME SLIGHT CHANCE POP`S EAST OF I-57
INTO THE AFTERNOON...BUT CONDITIONS SHOULD LARGELY BE DRY OVER THE
FORECAST AREA INTO THE EVENING HOURS. HIGH-RESOLUTION VISIBLE
SATELLITE IMAGERY SHOWING SKIES BECOMING PARTLY SUNNY ALREADY
NORTHWEST OF THE ILLINOIS RIVER...AND A LARGER HOLE IN THE CLOUDS
OVER NORTH CENTRAL MISSOURI SHOULD BE MOVING INTO THE FORECAST
AREA EARLY AFTERNOON PER THE RAP MODEL...ALTHOUGH THE SOUTHEAST
CWA WILL LIKELY SEE MORE PERSISTENT CLOUDS. HAVE HAD SOME GUSTS
40-45 MPH AROUND DECATUR AND CHAMPAIGN ON THE LATEST OBS...BUT THE
HRRR MODEL SHOWS THESE HIGH WINDS SHIFTING INTO INDIANA OVER THE
NEXT COUPLE HOURS.

&&

.SHORT TERM...(TODAY)
ISSUED AT 337 AM CDT MON MAY 25 2015

LOW PRESSURE CENTER STILL WELL OFF TO THE SOUTHWEST THIS
MORNING...AND A WARM FRONT DRAPED ACROSS THE IL/WI BORDER THIS
MORNING.  SCATTERED SHOWERS AND ISOLATED THUNDER STILL IN THE
REGION, BUT MAINLY CONFINED TO AREAS IN THE SOUTHEAST AS WELL AS THE
NW.  ILX SITUATED IN A GAP AS THE MAJORITY OF THE SYSTEM CONTINUES
TO LIFT NORTH AND NORTHEAST THIS MORNING.  MODELS PRETTY CONSISTENT
WITH THE MOVING OUT OF THE SYSTEM, WITH SOME SCATTERED SHOWERS
POSSIBLY AT LEAST THROUGH MIDDAY.  ISOLATED THUNDER CANNOT BE RULED
OUT WITH THE INCREASING INSTABILITY AFTER SUNRISE...BUT MAJORITY OF
THE ACTIVITY SCOURS OUT IN ALL OF THE MODELS SHORTLY AFTER MIDDAY.
LINGERED SOME SLIGHT CHANCES AFTER 18Z TO COVER AT LEAST THE
POTENTIAL FOR ACTIVITY WITH ANY REMNANT MESOSCALE BOUNDARIES.
PLENTY OF INSTABILITY STILL WITHIN THE ATMOSPHERE SHOULD IT GET THE
CHANCE TO RECOVER/RESTRATIFY.  HOWEVER, A SMALL AREA OF MIDLEVEL
RIDGING BEHIND THE SHORTWAVE THIS MORNING MAY GIVE US ENOUGH
SUBSIDENCE TO COUNTER THE EFFECTS...SO HAVE FOLLOWED SUIT WITH THE
END OF DAYTIME HEATING AND THE EARLY EVENING AND DROPPED THE POPS
BACK DOWN BEFORE 06Z. EITHER WAY...WINDS ALOFT WITH THE PASSING OF
THE SHORTWAVE AND DAYTIME MIXING WILL RESULT IN SOME GUSTY WINDS
TODAY...GUSTING 25 TO 35 MPH BY MID DAY AND SLOWLY BACKING OFF AS
THE LOW LIFTS OUT OF THE REGION.

.LONG TERM...(TONIGHT THROUGH SUNDAY)
ISSUED AT 337 AM CDT MON MAY 25 2015

FORECAST REMAINS WARM AND MUGGY WITH SEVERAL CHANCES FOR SHOWERS AND
THUNDERSTORMS THROUGHOUT. REGION DOMINATED BY SOUTHWESTERLY FLOW AND
A SERIES OF SHORT WAVES EJECTING OUT OF THE UPPER TROF IN THE SW
THROUGH THE FIRST HALF OF THE WEEK.  A BRIEF BREAK IN THE PATTERN
MID WEEK IS ONLY TEMPORARY AS TEMPS REMAIN WARM WITH PLENTY OF
MOISTURE ONLY REINFORCED BY PERIODIC SHOWERS ENHANCING THE BOUNDARY
LAYER RH. YET ANOTHER SURFACE LOW LIFTS INTO THE MIDWEST MOVING
ALONG THE SOUTHWESTERLY FLOW ALOFT ON TUESDAY.  MORE SHOWERS
ANTICIPATED FOR TUESDAY/TUESDAY NIGHT WITH THE MUGGY AIRMASS.  FRONT
ASSOCIATED WITH THIS SYSTEM WEAK AT BEST AND WILL ONLY SEE A BRIEF
SFC WIND SHIFT TO MORE WESTERLY FROM SOUTHERLY FOR WED AND WED NIGHT
ACCOMPANIED BY A BRIEF PATTERN SHIFT ALOFT.  CHANGE IS ONLY
TEMPORARY AS SOUTHERLY SFC WINDS REESTABLISH BY THE END OF THE WEEK.
WEAK SOUTHWESTERLY FLOW ALOFT SLOWLY SHIFTS TO WEAK FLOW OVERALL
GOING INTO THE WEEKEND SETTING UP CHANCES FOR PERIODIC DIURNALLY
DRIVEN CONVECTION YET AGAIN.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z TUESDAY AFTERNOON)
ISSUED AT 1244 PM CDT MON MAY 25 2015

LINGERING MVFR CEILINGS ARE LIFTING AND ALL SITES SHOULD BE VFR BY
18-19Z. THE STRONGEST OF THE SOUTHWEST WINDS HAVE SHIFTED AWAY
FROM KCMI...BUT WINDS THERE SHOULD STILL GUST TO AROUND 30 KNOTS
OR SO FOR A FEW MORE HOURS. THE REMAINING TAF SITES WILL HAVE
GUSTS MORE IN THE 25 KNOT RANGE...BUT THESE SHOULD SUBSIDE TOWARD
00Z. NEXT PERIOD FOR CONVECTIVE CONCERN APPEARS TO START AROUND
08-09Z WITH STORMS TRACKING IN FROM THE SOUTHWEST. HIGH-RESOLUTION
MODELS SUGGEST SOME BREAKS IN BETWEEN STORMS TUESDAY MORNING...SO
WILL GO WITH VCTS MENTION LATE IN THE PERIOD. TAIL END OF THE RAP
MODEL SUGGESTS SOME MVFR CEILINGS DEVELOPING LATE TONIGHT IN
SOUTHERN ILLINOIS AND BUILDING NORTHWARD...AND HAVE ADDED THESE
FOR KBMI/KDEC/KCMI.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...GEELHART
SHORT TERM...HJS
LONG TERM...HJS
AVIATION...GEELHART



000
FXUS63 KILX 251744
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1244 PM CDT MON MAY 25 2015

.UPDATE...
ISSUED AT 1004 AM CDT MON MAY 25 2015

A FEW SHOWERS LINGER EAST OF I-55...BUT THESE WILL BE EXITING OVER THE
NEXT COUPLE HOURS. HAVE KEPT SOME SLIGHT CHANCE POP`S EAST OF I-57
INTO THE AFTERNOON...BUT CONDITIONS SHOULD LARGELY BE DRY OVER THE
FORECAST AREA INTO THE EVENING HOURS. HIGH-RESOLUTION VISIBLE
SATELLITE IMAGERY SHOWING SKIES BECOMING PARTLY SUNNY ALREADY
NORTHWEST OF THE ILLINOIS RIVER...AND A LARGER HOLE IN THE CLOUDS
OVER NORTH CENTRAL MISSOURI SHOULD BE MOVING INTO THE FORECAST
AREA EARLY AFTERNOON PER THE RAP MODEL...ALTHOUGH THE SOUTHEAST
CWA WILL LIKELY SEE MORE PERSISTENT CLOUDS. HAVE HAD SOME GUSTS
40-45 MPH AROUND DECATUR AND CHAMPAIGN ON THE LATEST OBS...BUT THE
HRRR MODEL SHOWS THESE HIGH WINDS SHIFTING INTO INDIANA OVER THE
NEXT COUPLE HOURS.

&&

.SHORT TERM...(TODAY)
ISSUED AT 337 AM CDT MON MAY 25 2015

LOW PRESSURE CENTER STILL WELL OFF TO THE SOUTHWEST THIS
MORNING...AND A WARM FRONT DRAPED ACROSS THE IL/WI BORDER THIS
MORNING.  SCATTERED SHOWERS AND ISOLATED THUNDER STILL IN THE
REGION, BUT MAINLY CONFINED TO AREAS IN THE SOUTHEAST AS WELL AS THE
NW.  ILX SITUATED IN A GAP AS THE MAJORITY OF THE SYSTEM CONTINUES
TO LIFT NORTH AND NORTHEAST THIS MORNING.  MODELS PRETTY CONSISTENT
WITH THE MOVING OUT OF THE SYSTEM, WITH SOME SCATTERED SHOWERS
POSSIBLY AT LEAST THROUGH MIDDAY.  ISOLATED THUNDER CANNOT BE RULED
OUT WITH THE INCREASING INSTABILITY AFTER SUNRISE...BUT MAJORITY OF
THE ACTIVITY SCOURS OUT IN ALL OF THE MODELS SHORTLY AFTER MIDDAY.
LINGERED SOME SLIGHT CHANCES AFTER 18Z TO COVER AT LEAST THE
POTENTIAL FOR ACTIVITY WITH ANY REMNANT MESOSCALE BOUNDARIES.
PLENTY OF INSTABILITY STILL WITHIN THE ATMOSPHERE SHOULD IT GET THE
CHANCE TO RECOVER/RESTRATIFY.  HOWEVER, A SMALL AREA OF MIDLEVEL
RIDGING BEHIND THE SHORTWAVE THIS MORNING MAY GIVE US ENOUGH
SUBSIDENCE TO COUNTER THE EFFECTS...SO HAVE FOLLOWED SUIT WITH THE
END OF DAYTIME HEATING AND THE EARLY EVENING AND DROPPED THE POPS
BACK DOWN BEFORE 06Z. EITHER WAY...WINDS ALOFT WITH THE PASSING OF
THE SHORTWAVE AND DAYTIME MIXING WILL RESULT IN SOME GUSTY WINDS
TODAY...GUSTING 25 TO 35 MPH BY MID DAY AND SLOWLY BACKING OFF AS
THE LOW LIFTS OUT OF THE REGION.

.LONG TERM...(TONIGHT THROUGH SUNDAY)
ISSUED AT 337 AM CDT MON MAY 25 2015

FORECAST REMAINS WARM AND MUGGY WITH SEVERAL CHANCES FOR SHOWERS AND
THUNDERSTORMS THROUGHOUT. REGION DOMINATED BY SOUTHWESTERLY FLOW AND
A SERIES OF SHORT WAVES EJECTING OUT OF THE UPPER TROF IN THE SW
THROUGH THE FIRST HALF OF THE WEEK.  A BRIEF BREAK IN THE PATTERN
MID WEEK IS ONLY TEMPORARY AS TEMPS REMAIN WARM WITH PLENTY OF
MOISTURE ONLY REINFORCED BY PERIODIC SHOWERS ENHANCING THE BOUNDARY
LAYER RH. YET ANOTHER SURFACE LOW LIFTS INTO THE MIDWEST MOVING
ALONG THE SOUTHWESTERLY FLOW ALOFT ON TUESDAY.  MORE SHOWERS
ANTICIPATED FOR TUESDAY/TUESDAY NIGHT WITH THE MUGGY AIRMASS.  FRONT
ASSOCIATED WITH THIS SYSTEM WEAK AT BEST AND WILL ONLY SEE A BRIEF
SFC WIND SHIFT TO MORE WESTERLY FROM SOUTHERLY FOR WED AND WED NIGHT
ACCOMPANIED BY A BRIEF PATTERN SHIFT ALOFT.  CHANGE IS ONLY
TEMPORARY AS SOUTHERLY SFC WINDS REESTABLISH BY THE END OF THE WEEK.
WEAK SOUTHWESTERLY FLOW ALOFT SLOWLY SHIFTS TO WEAK FLOW OVERALL
GOING INTO THE WEEKEND SETTING UP CHANCES FOR PERIODIC DIURNALLY
DRIVEN CONVECTION YET AGAIN.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z TUESDAY AFTERNOON)
ISSUED AT 1244 PM CDT MON MAY 25 2015

LINGERING MVFR CEILINGS ARE LIFTING AND ALL SITES SHOULD BE VFR BY
18-19Z. THE STRONGEST OF THE SOUTHWEST WINDS HAVE SHIFTED AWAY
FROM KCMI...BUT WINDS THERE SHOULD STILL GUST TO AROUND 30 KNOTS
OR SO FOR A FEW MORE HOURS. THE REMAINING TAF SITES WILL HAVE
GUSTS MORE IN THE 25 KNOT RANGE...BUT THESE SHOULD SUBSIDE TOWARD
00Z. NEXT PERIOD FOR CONVECTIVE CONCERN APPEARS TO START AROUND
08-09Z WITH STORMS TRACKING IN FROM THE SOUTHWEST. HIGH-RESOLUTION
MODELS SUGGEST SOME BREAKS IN BETWEEN STORMS TUESDAY MORNING...SO
WILL GO WITH VCTS MENTION LATE IN THE PERIOD. TAIL END OF THE RAP
MODEL SUGGESTS SOME MVFR CEILINGS DEVELOPING LATE TONIGHT IN
SOUTHERN ILLINOIS AND BUILDING NORTHWARD...AND HAVE ADDED THESE
FOR KBMI/KDEC/KCMI.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...GEELHART
SHORT TERM...HJS
LONG TERM...HJS
AVIATION...GEELHART



000
FXUS63 KILX 251744
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1244 PM CDT MON MAY 25 2015

.UPDATE...
ISSUED AT 1004 AM CDT MON MAY 25 2015

A FEW SHOWERS LINGER EAST OF I-55...BUT THESE WILL BE EXITING OVER THE
NEXT COUPLE HOURS. HAVE KEPT SOME SLIGHT CHANCE POP`S EAST OF I-57
INTO THE AFTERNOON...BUT CONDITIONS SHOULD LARGELY BE DRY OVER THE
FORECAST AREA INTO THE EVENING HOURS. HIGH-RESOLUTION VISIBLE
SATELLITE IMAGERY SHOWING SKIES BECOMING PARTLY SUNNY ALREADY
NORTHWEST OF THE ILLINOIS RIVER...AND A LARGER HOLE IN THE CLOUDS
OVER NORTH CENTRAL MISSOURI SHOULD BE MOVING INTO THE FORECAST
AREA EARLY AFTERNOON PER THE RAP MODEL...ALTHOUGH THE SOUTHEAST
CWA WILL LIKELY SEE MORE PERSISTENT CLOUDS. HAVE HAD SOME GUSTS
40-45 MPH AROUND DECATUR AND CHAMPAIGN ON THE LATEST OBS...BUT THE
HRRR MODEL SHOWS THESE HIGH WINDS SHIFTING INTO INDIANA OVER THE
NEXT COUPLE HOURS.

&&

.SHORT TERM...(TODAY)
ISSUED AT 337 AM CDT MON MAY 25 2015

LOW PRESSURE CENTER STILL WELL OFF TO THE SOUTHWEST THIS
MORNING...AND A WARM FRONT DRAPED ACROSS THE IL/WI BORDER THIS
MORNING.  SCATTERED SHOWERS AND ISOLATED THUNDER STILL IN THE
REGION, BUT MAINLY CONFINED TO AREAS IN THE SOUTHEAST AS WELL AS THE
NW.  ILX SITUATED IN A GAP AS THE MAJORITY OF THE SYSTEM CONTINUES
TO LIFT NORTH AND NORTHEAST THIS MORNING.  MODELS PRETTY CONSISTENT
WITH THE MOVING OUT OF THE SYSTEM, WITH SOME SCATTERED SHOWERS
POSSIBLY AT LEAST THROUGH MIDDAY.  ISOLATED THUNDER CANNOT BE RULED
OUT WITH THE INCREASING INSTABILITY AFTER SUNRISE...BUT MAJORITY OF
THE ACTIVITY SCOURS OUT IN ALL OF THE MODELS SHORTLY AFTER MIDDAY.
LINGERED SOME SLIGHT CHANCES AFTER 18Z TO COVER AT LEAST THE
POTENTIAL FOR ACTIVITY WITH ANY REMNANT MESOSCALE BOUNDARIES.
PLENTY OF INSTABILITY STILL WITHIN THE ATMOSPHERE SHOULD IT GET THE
CHANCE TO RECOVER/RESTRATIFY.  HOWEVER, A SMALL AREA OF MIDLEVEL
RIDGING BEHIND THE SHORTWAVE THIS MORNING MAY GIVE US ENOUGH
SUBSIDENCE TO COUNTER THE EFFECTS...SO HAVE FOLLOWED SUIT WITH THE
END OF DAYTIME HEATING AND THE EARLY EVENING AND DROPPED THE POPS
BACK DOWN BEFORE 06Z. EITHER WAY...WINDS ALOFT WITH THE PASSING OF
THE SHORTWAVE AND DAYTIME MIXING WILL RESULT IN SOME GUSTY WINDS
TODAY...GUSTING 25 TO 35 MPH BY MID DAY AND SLOWLY BACKING OFF AS
THE LOW LIFTS OUT OF THE REGION.

.LONG TERM...(TONIGHT THROUGH SUNDAY)
ISSUED AT 337 AM CDT MON MAY 25 2015

FORECAST REMAINS WARM AND MUGGY WITH SEVERAL CHANCES FOR SHOWERS AND
THUNDERSTORMS THROUGHOUT. REGION DOMINATED BY SOUTHWESTERLY FLOW AND
A SERIES OF SHORT WAVES EJECTING OUT OF THE UPPER TROF IN THE SW
THROUGH THE FIRST HALF OF THE WEEK.  A BRIEF BREAK IN THE PATTERN
MID WEEK IS ONLY TEMPORARY AS TEMPS REMAIN WARM WITH PLENTY OF
MOISTURE ONLY REINFORCED BY PERIODIC SHOWERS ENHANCING THE BOUNDARY
LAYER RH. YET ANOTHER SURFACE LOW LIFTS INTO THE MIDWEST MOVING
ALONG THE SOUTHWESTERLY FLOW ALOFT ON TUESDAY.  MORE SHOWERS
ANTICIPATED FOR TUESDAY/TUESDAY NIGHT WITH THE MUGGY AIRMASS.  FRONT
ASSOCIATED WITH THIS SYSTEM WEAK AT BEST AND WILL ONLY SEE A BRIEF
SFC WIND SHIFT TO MORE WESTERLY FROM SOUTHERLY FOR WED AND WED NIGHT
ACCOMPANIED BY A BRIEF PATTERN SHIFT ALOFT.  CHANGE IS ONLY
TEMPORARY AS SOUTHERLY SFC WINDS REESTABLISH BY THE END OF THE WEEK.
WEAK SOUTHWESTERLY FLOW ALOFT SLOWLY SHIFTS TO WEAK FLOW OVERALL
GOING INTO THE WEEKEND SETTING UP CHANCES FOR PERIODIC DIURNALLY
DRIVEN CONVECTION YET AGAIN.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z TUESDAY AFTERNOON)
ISSUED AT 1244 PM CDT MON MAY 25 2015

LINGERING MVFR CEILINGS ARE LIFTING AND ALL SITES SHOULD BE VFR BY
18-19Z. THE STRONGEST OF THE SOUTHWEST WINDS HAVE SHIFTED AWAY
FROM KCMI...BUT WINDS THERE SHOULD STILL GUST TO AROUND 30 KNOTS
OR SO FOR A FEW MORE HOURS. THE REMAINING TAF SITES WILL HAVE
GUSTS MORE IN THE 25 KNOT RANGE...BUT THESE SHOULD SUBSIDE TOWARD
00Z. NEXT PERIOD FOR CONVECTIVE CONCERN APPEARS TO START AROUND
08-09Z WITH STORMS TRACKING IN FROM THE SOUTHWEST. HIGH-RESOLUTION
MODELS SUGGEST SOME BREAKS IN BETWEEN STORMS TUESDAY MORNING...SO
WILL GO WITH VCTS MENTION LATE IN THE PERIOD. TAIL END OF THE RAP
MODEL SUGGESTS SOME MVFR CEILINGS DEVELOPING LATE TONIGHT IN
SOUTHERN ILLINOIS AND BUILDING NORTHWARD...AND HAVE ADDED THESE
FOR KBMI/KDEC/KCMI.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...GEELHART
SHORT TERM...HJS
LONG TERM...HJS
AVIATION...GEELHART



000
FXUS63 KLOT 251602
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1102 AM CDT MON MAY 25 2015

.UPDATE...

COMPACT NEGATIVELY TILTED TROUGH AXIS IS SLIDING NORTHEAST THROUGH
IOWA AND WESTERN ILLINOIS. EASTERN EDGE OF THE TROUGH WILL MOVE
THROUGH NORTHEAST ILLINOIS THIS MORNING. NOTED UPTICK IN SHOWER
ACTIVITY ASSOCIATED WITH THIS WAVE IS PRODUCING MORE ORGANIZED BUT
STILL LARGELY SCATTERED SHOWERS. STILL TRACKING THIS FEATURE WILL
BRING THE BEST CHANCE FOR SOME BRIEF DOWNPOURS IN THE COMING
HOURS...AND THESE WILL SPREAD INTO THE WEST METRO AREA IN THE NEXT
HOUR...SPREADING INTO CHICAGOLAND SHORTLY THERE AFTER. THE CLOUDS
PRODUCING THE SHOWER ACTIVITY ARE SHALLOW AND MID LEVEL LAPSE
RATES ARE SUBPAR...THUS THUNDER SHOULD BE LIMITED AT BEST. SOME
WEAK INSTABILITY IS NOTED SOUTH OF I-80 WHICH DOES NOT PRECLUDE AN
ISOLATED STRIKE IN ANY STRONGER ACTIVITY.

REGARDING WINDS...WITH THE BROKEN TO OVERCAST LOW CLOUD
DECK...MIXING IS BEING LIMITED AND GETING GUSTS TO AROUND 30 KT OR
SO. ANY STRONGER GUSTS WOULD BE IN THE NEXT HOUR BEFORE A RAPID
DROP OFF LATER THIS MORNING.

KMD

&&

.SHORT TERM...
345 AM CDT

THROUGH MONDAY NIGHT...
FOR THE REMAINDER OF THE NIGHT AND INTO MONDAY MORNING...PCPN
CHANCES CONTINUE TO WANE AS LATEST RADAR TRENDS ONLY SHOW SOME SCT
SHRA WHICH ARE DECREASING IN INTENSITY.  IN SPITE OF DEWPOINTS IN
THE LOW 60S...AND A STRONG LOW LEVEL JET...50 KT AT 925 MB...THERE
IS AN ELEMENT LACKING WHICH IS SEEMS TO BE PREVENTING THE
MAINTENANCE OF SHRA/TSRA OVER NERN IL/NWRN IN.  THE MAIN MISSING
ELEMENTS IS FORCING.  THE SFC AND UPPER LEVEL LOW ARE WAY TO THE
WEST...OVER THE NRN PLAINS. THE SHORTWAVE CLIMBING UP THE NWRN
PERIPHERY OF THE HIGH AMPLITUDE RIDGE IS BEING SLOWED BY THE HIGH
AMPLITUDE...AND IS BEING FORCED TO A MORE WLY TRACK THROUGH THE
UPPER MISSISSIPPI VALLEY THAN PREVIOUSLY ANTICIPATED.  SO...FOR THE
REMAINDER OF THE OVERNIGHT HOURS AND THE DAYTIME HOURS MONDAY...HAVE
BACK OF TO ISOLD-SCT SHRA.  WILL KEEP ISOLD TS MENTION FOR THE LATE
MORNING HOURS...THROUGH AROUND NOON...WITH THE DAYTIME HEATING...BUT
CONFIDENCE IN ANY TS IS RATHER LOW AT THIS TIME.  BY THIS
AFTERNOON...A MID LEVEL DRY SLOT IS EXPECTED TO MOVE ACROSS THE
REGION...FURTHER LIMITING PCPN CHANCES AND IT IS QUITE LIKELY THAT
THE REGION WILL REMAIN DRY THROUGH THE DAY.  HOWEVER...WHILE THE
PCPN CHANCES ARE DIMINISHING...THE LIKELIHOOD OF STRONG WINDS IS
STILL A CONCERN.  WITH THE DIMINISHING PCPN CHANCES...LESS SKY COVER
THAN PREVIOUSLY ANTICIPATED IS ALSO POSSIBLE.  A STRONG SWLY
PRESSURE GRADIENT IS SETTING UP ACROSS THE REGION BETWEEN SFC
RIDGING ACROSS THE SERN CONUS AND AND LOW PRESSURE FROM THE UPPER
MISSISSIPPI VALLEY TO THE WESTERN PLAINS.  THE STRONG GRADIENT WILL
HELP DRIVE THE SFC WINDS AND THE DIMINISHING CLOUD COVER COULD HELP
ENHANCE DEEP LAYER MIXING...TAPPING STRONGER WINDS ALOFT.  SUSTAINED
25-25 MPH WINDS ARE LIKELY WITH GUSTS OF 30-35 MPH.
ALSO...PERSISTENT WARM/MOIST ADVECTION AT THE SFC WILL BRING
TEMPERATURES INTO THE LOW TO MIDDLE 80S WITH DEWPOINTS IN THE LOWER
60S.

FOR MONDAY NIGHT...THE BREEZY CONDITIONS WILL PERSIST INTO THE AS
THERE SHOULD BE LITTLE CHANGE TO THE SFC AND UPPER LEVEL PATTERNS.
THE UPPER RIDGE WILL LOSE A LITTLE AMPLITUDE AS SHORT WAVE ENERGY
OVERTOPS THE RIDGE...BUT GENERAL TROUGHING WILL PERSIST ACROSS THE
UPPER MISSISSIPPI VALLEY THROUGH THE CENTRAL PLAINS.  THE NEXT
CHANCE FOR PCPN WILL HOLD OFF UNTIL LATE TONIGHT/EARLY TUESDAY
MORNING AND THE NEXT SHORTWAVE LIFTS OUT OF THE SRN PLAINS AND INTO
THE MIDDLE MISSISSIPPI VALLEY.  AMPLE LOW LEVEL MOISTURE WILL
ALREADY BE IN PLACE SO IT WILL JUST A MATTER OF WHEN THE FORCING
WILL GET HERE.  AGAIN...THERE IS SOME CONCERN THAT THE FORCING WILL
BE TO THE WEST...WITH THE SHORTWAVE TRACKING THROUGH THE MIDDLE
MISSISSIPPI VALLEY AND INTO WI.  SO...WILL CARRY CHANCE POPS FOR THE
REGION...WITH LIKELY POPS APPROACHING THE PONTIAC AREA BY EARLY
TUESDAY MORNING.  THE PERSISTENT WARM/MOIST ADVECTIVE PATTERN AND
BREEZY CONDITIONS SHOULD KEEP TEMPERATURES FROM DROPPING OFF
SIGNIFICANTLY OVERNIGHT AND LOWS SHOULD BE IN THE MIDDLE TO UPPER
60S.

KREIN

&&

.LONG TERM...
239 AM CDT

TUESDAY THROUGH SUNDAY...

TUESDAY THROUGH WEDNESDAY...
500MB TROUGH AXIS WILL SLOWLY PIVOT EAST ACROSS THE CENTRAL PLAINS
INTO THE MID-MISSOURI VALLEY TUE...WITH A SFC WAVE SLIDING NORTH
ACROSS IOWA INTO CENTRAL WISC LATE TUE. THE SFC FEATURE IS NOT
EXPECTED TO BE STRONG...HOWEVER THE GRADIENT DOES TIGHTEN WITH
MODEST HEIGHT FALLS IN THE LOWEST LAYERS OF THE ATMOSPHERE. SOME
INSTABILITY DOES REMAIN ALONG WITH RELATIVELY MOIST SFC CONDS AS
DEW PTS WILL REMAIN IN THE UPR 50S/LOW 60S. PWAT VALUES WILL ALSO
HOVER JUST OVER 1 INCH...WHICH IS SEASONAL. WILL HOLD ONTO MENTION
OF RAIN AND THUNDER...BUT COULD SEE THIS MAINLY FOCUSED IN THE TUE
MORNING TIMEFRAME.

WITH CONSIDERABLE SOLAR SHIELDING PROGGED FOR TUE...TEMPS MAY
STRUGGLE TO WARM BEYOND THE MID/UPR 70S. BUT WITH GUIDANCE HINTING
AT A DRY SLOT LIFTING NORTHEAST ACROSS THE REGION TUE EVE...THIS
COULD INTRODUCE SOME EROSION TO THE CLOUD COVER IN THE AFTN HOURS
TUE AND ALLOW SOME SFC HEATING TO OCCUR AND PUSH TEMPS TO ARND 80.

GUIDANCE LIFTS THE DRY SLOT OVERHEAD LATE TUE NGT...WITH THE 500MB
TROUGH AXIS ARRIVING ARND DAYBREAK WED AND LIFTING EAST ACROSS LOWER
MICHIGAN. THIS WILL BRING DRY ONLY SLIGHT CHANCE POPS AS WEAK SFC
RIDGING BEGINS TO NUDGE EAST ACROSS THE MISSOURI VALLEY TOWARDS THE
FORECAST AREA MIDDAY WED. IT IS POSSIBLE THAT ENOUGH DRY AIR
INFLUENCE COULD ALLOW FOR REMOVAL OF THE SLIGHT CHANCE POPS WED
AFTN. THERMAL TROUGH LAGS BEHIND THE FRONTAL BOUNDARY WED...SO TEMPS
COULD STILL WARM BACK TO ARND 80 AND PERHAPS THE LOW 80S IN THE
SOUTHERN CWFA.

THURSDAY THROUGH SUNDAY...
ANTI-CYCLONIC FLOW ARRIVES THUR WITH AT LEAST ONE PERIOD OF DRY
WEATHER EXPECTED FOR NORTHERN IL/NORTHWEST IN. ONLY A COUPLE
ENSEMBLE MEMBERS CONTINUE TO PROG POPS ALONG THE SOUTHERN FORECAST
AREA THUR...BUT COULD SEE THIS TRENDING DRY IN THE NEXT FEW
SOLUTIONS. WITH WARM TEMPS ALOFT EXPECTED THUR AND THIN CLOUD
COVER...THUR HIGHS COULD PEAK IN THE LOW 80S.

THEN FOCUS TURNS TOWARDS THE UPCOMING WEEKEND AND A PATTERN SHIFT
AWAY FROM THE WARM/HUMID CONDITIONS. ENSEMBLES SHOW MINIMAL SPREAD
IN THE LATE WEEK PERIODS...WITH THE UPSTREAM RIDGE OVER
ALASKA/WESTERN CANADA AND A DOWNSTREAM MID-LVL RIDGE ACROSS THE
SOUTHEAST CONUS. BOTH OF THESE FEATURES IN TIME BEGIN TO
WEAKEN...WITH THE LONGWAVE PATTERN TRANSITIONING INTO A SEMI-ZONAL
ORIENTATION BY THE SECOND HALF OF THE WEEKEND.

OPER GUIDANCE HAS BEEN CONSISTENT WITH PROGGING A ROBUST 500MB
TROUGH TO SLIDE SOUTH FROM CENTRAL CANADA FRI...ALONG WITH A STRONG
CANADIAN SFC RIDGE ON IT/S HEELS. WITH A CHANNEL OF MOISTURE
REMAINING ACROSS THE SOUTHERN PLAINS STRETCHING NORTHEAST THROUGH
THE UPPER MIDWEST...THIS BOUNDARY WILL BECOME ACTIVE WITH A SFC WAVE
DEVELOPING ACROSS THE SOUTHERN PLAINS. THIS LOW WILL THEN LIFT
NORTHEAST TOWARDS THE CWFA FRI WITH A COLD FRONT ARRIVING ACROSS THE
FORECAST AREA SAT. WINDS LOOK TO SHIFT TO THE NORTH...WITH MUCH
COOLER AIR SLIDING SOUTH AND LIKELY KNOCKING TEMPS BACK TO SUB-
SEASONAL CONDS IN THE UPR 60S/NEAR 70 DEGREE RANGE SAT/SUN. IF
NORTHEAST WINDS MATERIALIZE...NEXT WEEKEND AREAS ADJACENT TO LAKE
MICHIGAN ALONG THE IL/IN SHORELINE COULD BE LOCKED IN THE UPR 50S TO
LOW 60S FOR HIGHS WITH A COLD FLOW OFF OF LAKE MICHIGAN.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 16Z...

* GUSTY SOUTH/SOUTHWEST WINDS THROUGH MIDDAY.

* CHANCE OF -RA THIS MORNING.

* MVFR CEILINGS STILL POSSIBLE THIS MORNING.

* CHANCE SHRA/TSRA LATE TONIGHT THROUGH TOMORROW.

KREIN/RODRIGUEZ

//DISCUSSION...UPDATED 12Z...

MAIN CONCERN FOR TODAY WILL BE STRONG...GUSTY SOUTH WINDS. AS OF
11Z THIS MORNING...WINDS ARE ALREADY GUSTING TO 25-30KT AND EXPECT
THAT WITH DEEPER MIXING LATER THIS MORNING...SHOULD BE ABLE TO TAP
INTO A 50 KT LOW LEVEL JET TO MIX DOWN GUSTS TO 35 KT OR EVEN
SLIGHTLY HIGHER. THE STRONG LOW LEVEL JET SHOULD MOVE OFF TO THE
EAST BY EARLY AFTERNOON...SO WHILE WINDS SHOULD STILL BE STRONG
AND GUSTY...PEAK GUSTS SHOULD LOWER TO ARND 25KT.

WITH THE PERSISTENT FETCH OF LOW LEVEL MOISTURE INTO THE
REGION...A LAYER OF MVFR STRATOCU HAS OVERSPREAD THE REGION.
EXPECT THAT BASES SHOULD NOT LOWER MUCH LESS THAT 1800FT AGL.
THERE IS SOME UNCERTAINTY AS TO THE DURATION OF THE MVFR CLOUD
LAYER...BUT WITH LITTLE CHANGE TO THE OVERALL PATTERN THROUGH THE
DAY...THERE IS A CHANCE THAT THE MVFR CIGS COULD HANG IN THROUGH
MUCH OF THE DAY. HOWEVER...THERE IS ALSO A CHANCE THAT STRONGER
MIXING IN THE AFTERNOON HOURS COULD ALLOW FOR THE MVFR DECK TO
SCATTER OUT.

LATEST RADAR TRENDS INDICATE THAT AN AREA OF SHRA LIFTING NEWD
FROM CNTRL IL INTO INDIANA. THE TRAJECTORY OF THE PCPN AREA SHOULD
KEEP THE BULK OF THE PCPN EAST AND SOUTH OF GYY...THOUGH A FEW SCT
SHRA AREA NOT OUT OF THE QUESTION. ALSO...SOME SHRA ASSOCIATED
WITH A MID LEVEL IMPULSE LIFTING NORTH THROUGH IOWA AND INTO WRN
WI IS GENERATING SCT SHRA AS WELL. IT IS ALSO POSSIBLE THAT RFD
COULD SEE A FEW SHRA THIS MORNING...BUT THE PROBABILITY IS TOO LOW
TO INCLUDE IN THE TAF AS THE LATEST RADAR TRENDS INDICATE A
WEAKENING TREND THERE.

A SECONDARY LOW IS EXPECTED TO DEVELOP OVER THE UPPER MISSOURI
VALLEY THIS EVENING...KEEPING A MODEST PRESSURE GRADIENT OVER THE
REGION. SO MODERATE...GUSTY WINDS SHOULD PERSIST WELL INTO
TONIGHT. ANOTHER STRONG MID LEVEL IMPULSE IS EXPECTED TO TRACK
THROUGH THE MIDDLE MISSISSIPPI VALLEY AND INTO WISCONSIN LATE
TONIGHT...BRINGING A RENEWED CHANCE FOR SHRA/TSRA TO THE REGION
LATE TONIGHT AND TOMORROW.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 16Z...

* MEDIUM TO HIGH CONFIDENCE IN WIND TRENDS.

* HIGH CONFIDENCE WITH -RA TRENDS THIS MORNING.

* MEDIUM HIGH CONFIDENCE IN CIG TRENDS.

* MEDIUM CONFIDENCE IN PCPN TIMING LATE TONIGHT.

KREIN/RODRIGUEZ

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/TSRA LATE. SOUTHEAST WINDS.

FRIDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. SOUTHWEST WINDS
BECOMING NORTHEAST OVERNIGHT.

SATURDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. NORTHEAST
WINDS.

SUNDAY...CHANCE TSRA. MVFR POSSIBLE. NORTHEAST WINDS.

KREIN

&&

.MARINE...
304 AM CDT

LOW PRESSURE WILL BE STEADILY LIFTING NORTH ACROSS THE MISSOURI
VALLEY THIS MORNING...REACHING LAKE SUPERIOR BY THIS EVENING AND
CONTINUING TO SLIDE EAST/NORTHEAST TOWARDS QUEBEC BY TUESDAY
MORNING. A FRONTAL BOUNDARY WILL REMAIN OVER THE FAR NORTHERN
PORTIONS OF LAKE MICHIGAN. MEANWHILE GUSTY SOUTHERLY WINDS ARE
EXPECTED TO INCREASE THIS MORNING...WITH OCCASIONAL GALES FOR THE
NEARSHORE WATERS OF IL/IN. ACROSS THE OPEN WATERS...EXPECT THE
WARM/MOIST AIR TO STRUGGLE TO REACH THE SFC OF THE LAKE WITH SOME
DEGREE OF LAKE STABILITY. WAVES WILL STEADILY BUILD ACROSS THE
NORTHERN HALF OF THE LAKE AS A RESULT OF THE LONG FETCH. STILL
FEEL THAT GUSTS WILL REACH 30KT ACROSS THE LAKE...HOWEVER
CONFIDENCE HAS DIMINISHED SLIGHTLY AS NEW GUIDANCE HAS BECOME A
LITTLE LESS WITH THE WIND FIELDS. NONETHELESS...WAVES FOR THE
NORTHERN HALF OF THE LAKE WILL LIKELY TOP OUT IN THE 4 TO 7 FT
RANGE WITH OCCASIONAL WAVES REACHING 9 FT THIS AFTERNOON/EVENING.

THE GRADIENT QUICKLY DIMINISHES THIS EVENING...BUT EXPECT
SOUTHERLY WINDS TO PERSIST. THIS WILL ALLOW WAVES TO SUBSIDE TO 3
TO 5 FT. ANOTHER LOW WILL ARRIVE TUE...WITH WINDS NUDGING BACK UP
HOWEVER WARM AIR WILL CONTINUE TO FLOW ACROSS THE LAKE AND COULD
FURTHER ENHANCE THE LAKE STABILITY AND KEEP WAVES FROM BUILDING TO
LARGE.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...NEARSHORE WATERS UNTIL 3
     PM MONDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...3 PM MONDAY TO 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 251602
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1102 AM CDT MON MAY 25 2015

.UPDATE...

COMPACT NEGATIVELY TILTED TROUGH AXIS IS SLIDING NORTHEAST THROUGH
IOWA AND WESTERN ILLINOIS. EASTERN EDGE OF THE TROUGH WILL MOVE
THROUGH NORTHEAST ILLINOIS THIS MORNING. NOTED UPTICK IN SHOWER
ACTIVITY ASSOCIATED WITH THIS WAVE IS PRODUCING MORE ORGANIZED BUT
STILL LARGELY SCATTERED SHOWERS. STILL TRACKING THIS FEATURE WILL
BRING THE BEST CHANCE FOR SOME BRIEF DOWNPOURS IN THE COMING
HOURS...AND THESE WILL SPREAD INTO THE WEST METRO AREA IN THE NEXT
HOUR...SPREADING INTO CHICAGOLAND SHORTLY THERE AFTER. THE CLOUDS
PRODUCING THE SHOWER ACTIVITY ARE SHALLOW AND MID LEVEL LAPSE
RATES ARE SUBPAR...THUS THUNDER SHOULD BE LIMITED AT BEST. SOME
WEAK INSTABILITY IS NOTED SOUTH OF I-80 WHICH DOES NOT PRECLUDE AN
ISOLATED STRIKE IN ANY STRONGER ACTIVITY.

REGARDING WINDS...WITH THE BROKEN TO OVERCAST LOW CLOUD
DECK...MIXING IS BEING LIMITED AND GETING GUSTS TO AROUND 30 KT OR
SO. ANY STRONGER GUSTS WOULD BE IN THE NEXT HOUR BEFORE A RAPID
DROP OFF LATER THIS MORNING.

KMD

&&

.SHORT TERM...
345 AM CDT

THROUGH MONDAY NIGHT...
FOR THE REMAINDER OF THE NIGHT AND INTO MONDAY MORNING...PCPN
CHANCES CONTINUE TO WANE AS LATEST RADAR TRENDS ONLY SHOW SOME SCT
SHRA WHICH ARE DECREASING IN INTENSITY.  IN SPITE OF DEWPOINTS IN
THE LOW 60S...AND A STRONG LOW LEVEL JET...50 KT AT 925 MB...THERE
IS AN ELEMENT LACKING WHICH IS SEEMS TO BE PREVENTING THE
MAINTENANCE OF SHRA/TSRA OVER NERN IL/NWRN IN.  THE MAIN MISSING
ELEMENTS IS FORCING.  THE SFC AND UPPER LEVEL LOW ARE WAY TO THE
WEST...OVER THE NRN PLAINS. THE SHORTWAVE CLIMBING UP THE NWRN
PERIPHERY OF THE HIGH AMPLITUDE RIDGE IS BEING SLOWED BY THE HIGH
AMPLITUDE...AND IS BEING FORCED TO A MORE WLY TRACK THROUGH THE
UPPER MISSISSIPPI VALLEY THAN PREVIOUSLY ANTICIPATED.  SO...FOR THE
REMAINDER OF THE OVERNIGHT HOURS AND THE DAYTIME HOURS MONDAY...HAVE
BACK OF TO ISOLD-SCT SHRA.  WILL KEEP ISOLD TS MENTION FOR THE LATE
MORNING HOURS...THROUGH AROUND NOON...WITH THE DAYTIME HEATING...BUT
CONFIDENCE IN ANY TS IS RATHER LOW AT THIS TIME.  BY THIS
AFTERNOON...A MID LEVEL DRY SLOT IS EXPECTED TO MOVE ACROSS THE
REGION...FURTHER LIMITING PCPN CHANCES AND IT IS QUITE LIKELY THAT
THE REGION WILL REMAIN DRY THROUGH THE DAY.  HOWEVER...WHILE THE
PCPN CHANCES ARE DIMINISHING...THE LIKELIHOOD OF STRONG WINDS IS
STILL A CONCERN.  WITH THE DIMINISHING PCPN CHANCES...LESS SKY COVER
THAN PREVIOUSLY ANTICIPATED IS ALSO POSSIBLE.  A STRONG SWLY
PRESSURE GRADIENT IS SETTING UP ACROSS THE REGION BETWEEN SFC
RIDGING ACROSS THE SERN CONUS AND AND LOW PRESSURE FROM THE UPPER
MISSISSIPPI VALLEY TO THE WESTERN PLAINS.  THE STRONG GRADIENT WILL
HELP DRIVE THE SFC WINDS AND THE DIMINISHING CLOUD COVER COULD HELP
ENHANCE DEEP LAYER MIXING...TAPPING STRONGER WINDS ALOFT.  SUSTAINED
25-25 MPH WINDS ARE LIKELY WITH GUSTS OF 30-35 MPH.
ALSO...PERSISTENT WARM/MOIST ADVECTION AT THE SFC WILL BRING
TEMPERATURES INTO THE LOW TO MIDDLE 80S WITH DEWPOINTS IN THE LOWER
60S.

FOR MONDAY NIGHT...THE BREEZY CONDITIONS WILL PERSIST INTO THE AS
THERE SHOULD BE LITTLE CHANGE TO THE SFC AND UPPER LEVEL PATTERNS.
THE UPPER RIDGE WILL LOSE A LITTLE AMPLITUDE AS SHORT WAVE ENERGY
OVERTOPS THE RIDGE...BUT GENERAL TROUGHING WILL PERSIST ACROSS THE
UPPER MISSISSIPPI VALLEY THROUGH THE CENTRAL PLAINS.  THE NEXT
CHANCE FOR PCPN WILL HOLD OFF UNTIL LATE TONIGHT/EARLY TUESDAY
MORNING AND THE NEXT SHORTWAVE LIFTS OUT OF THE SRN PLAINS AND INTO
THE MIDDLE MISSISSIPPI VALLEY.  AMPLE LOW LEVEL MOISTURE WILL
ALREADY BE IN PLACE SO IT WILL JUST A MATTER OF WHEN THE FORCING
WILL GET HERE.  AGAIN...THERE IS SOME CONCERN THAT THE FORCING WILL
BE TO THE WEST...WITH THE SHORTWAVE TRACKING THROUGH THE MIDDLE
MISSISSIPPI VALLEY AND INTO WI.  SO...WILL CARRY CHANCE POPS FOR THE
REGION...WITH LIKELY POPS APPROACHING THE PONTIAC AREA BY EARLY
TUESDAY MORNING.  THE PERSISTENT WARM/MOIST ADVECTIVE PATTERN AND
BREEZY CONDITIONS SHOULD KEEP TEMPERATURES FROM DROPPING OFF
SIGNIFICANTLY OVERNIGHT AND LOWS SHOULD BE IN THE MIDDLE TO UPPER
60S.

KREIN

&&

.LONG TERM...
239 AM CDT

TUESDAY THROUGH SUNDAY...

TUESDAY THROUGH WEDNESDAY...
500MB TROUGH AXIS WILL SLOWLY PIVOT EAST ACROSS THE CENTRAL PLAINS
INTO THE MID-MISSOURI VALLEY TUE...WITH A SFC WAVE SLIDING NORTH
ACROSS IOWA INTO CENTRAL WISC LATE TUE. THE SFC FEATURE IS NOT
EXPECTED TO BE STRONG...HOWEVER THE GRADIENT DOES TIGHTEN WITH
MODEST HEIGHT FALLS IN THE LOWEST LAYERS OF THE ATMOSPHERE. SOME
INSTABILITY DOES REMAIN ALONG WITH RELATIVELY MOIST SFC CONDS AS
DEW PTS WILL REMAIN IN THE UPR 50S/LOW 60S. PWAT VALUES WILL ALSO
HOVER JUST OVER 1 INCH...WHICH IS SEASONAL. WILL HOLD ONTO MENTION
OF RAIN AND THUNDER...BUT COULD SEE THIS MAINLY FOCUSED IN THE TUE
MORNING TIMEFRAME.

WITH CONSIDERABLE SOLAR SHIELDING PROGGED FOR TUE...TEMPS MAY
STRUGGLE TO WARM BEYOND THE MID/UPR 70S. BUT WITH GUIDANCE HINTING
AT A DRY SLOT LIFTING NORTHEAST ACROSS THE REGION TUE EVE...THIS
COULD INTRODUCE SOME EROSION TO THE CLOUD COVER IN THE AFTN HOURS
TUE AND ALLOW SOME SFC HEATING TO OCCUR AND PUSH TEMPS TO ARND 80.

GUIDANCE LIFTS THE DRY SLOT OVERHEAD LATE TUE NGT...WITH THE 500MB
TROUGH AXIS ARRIVING ARND DAYBREAK WED AND LIFTING EAST ACROSS LOWER
MICHIGAN. THIS WILL BRING DRY ONLY SLIGHT CHANCE POPS AS WEAK SFC
RIDGING BEGINS TO NUDGE EAST ACROSS THE MISSOURI VALLEY TOWARDS THE
FORECAST AREA MIDDAY WED. IT IS POSSIBLE THAT ENOUGH DRY AIR
INFLUENCE COULD ALLOW FOR REMOVAL OF THE SLIGHT CHANCE POPS WED
AFTN. THERMAL TROUGH LAGS BEHIND THE FRONTAL BOUNDARY WED...SO TEMPS
COULD STILL WARM BACK TO ARND 80 AND PERHAPS THE LOW 80S IN THE
SOUTHERN CWFA.

THURSDAY THROUGH SUNDAY...
ANTI-CYCLONIC FLOW ARRIVES THUR WITH AT LEAST ONE PERIOD OF DRY
WEATHER EXPECTED FOR NORTHERN IL/NORTHWEST IN. ONLY A COUPLE
ENSEMBLE MEMBERS CONTINUE TO PROG POPS ALONG THE SOUTHERN FORECAST
AREA THUR...BUT COULD SEE THIS TRENDING DRY IN THE NEXT FEW
SOLUTIONS. WITH WARM TEMPS ALOFT EXPECTED THUR AND THIN CLOUD
COVER...THUR HIGHS COULD PEAK IN THE LOW 80S.

THEN FOCUS TURNS TOWARDS THE UPCOMING WEEKEND AND A PATTERN SHIFT
AWAY FROM THE WARM/HUMID CONDITIONS. ENSEMBLES SHOW MINIMAL SPREAD
IN THE LATE WEEK PERIODS...WITH THE UPSTREAM RIDGE OVER
ALASKA/WESTERN CANADA AND A DOWNSTREAM MID-LVL RIDGE ACROSS THE
SOUTHEAST CONUS. BOTH OF THESE FEATURES IN TIME BEGIN TO
WEAKEN...WITH THE LONGWAVE PATTERN TRANSITIONING INTO A SEMI-ZONAL
ORIENTATION BY THE SECOND HALF OF THE WEEKEND.

OPER GUIDANCE HAS BEEN CONSISTENT WITH PROGGING A ROBUST 500MB
TROUGH TO SLIDE SOUTH FROM CENTRAL CANADA FRI...ALONG WITH A STRONG
CANADIAN SFC RIDGE ON IT/S HEELS. WITH A CHANNEL OF MOISTURE
REMAINING ACROSS THE SOUTHERN PLAINS STRETCHING NORTHEAST THROUGH
THE UPPER MIDWEST...THIS BOUNDARY WILL BECOME ACTIVE WITH A SFC WAVE
DEVELOPING ACROSS THE SOUTHERN PLAINS. THIS LOW WILL THEN LIFT
NORTHEAST TOWARDS THE CWFA FRI WITH A COLD FRONT ARRIVING ACROSS THE
FORECAST AREA SAT. WINDS LOOK TO SHIFT TO THE NORTH...WITH MUCH
COOLER AIR SLIDING SOUTH AND LIKELY KNOCKING TEMPS BACK TO SUB-
SEASONAL CONDS IN THE UPR 60S/NEAR 70 DEGREE RANGE SAT/SUN. IF
NORTHEAST WINDS MATERIALIZE...NEXT WEEKEND AREAS ADJACENT TO LAKE
MICHIGAN ALONG THE IL/IN SHORELINE COULD BE LOCKED IN THE UPR 50S TO
LOW 60S FOR HIGHS WITH A COLD FLOW OFF OF LAKE MICHIGAN.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 16Z...

* GUSTY SOUTH/SOUTHWEST WINDS THROUGH MIDDAY.

* CHANCE OF -RA THIS MORNING.

* MVFR CEILINGS STILL POSSIBLE THIS MORNING.

* CHANCE SHRA/TSRA LATE TONIGHT THROUGH TOMORROW.

KREIN/RODRIGUEZ

//DISCUSSION...UPDATED 12Z...

MAIN CONCERN FOR TODAY WILL BE STRONG...GUSTY SOUTH WINDS. AS OF
11Z THIS MORNING...WINDS ARE ALREADY GUSTING TO 25-30KT AND EXPECT
THAT WITH DEEPER MIXING LATER THIS MORNING...SHOULD BE ABLE TO TAP
INTO A 50 KT LOW LEVEL JET TO MIX DOWN GUSTS TO 35 KT OR EVEN
SLIGHTLY HIGHER. THE STRONG LOW LEVEL JET SHOULD MOVE OFF TO THE
EAST BY EARLY AFTERNOON...SO WHILE WINDS SHOULD STILL BE STRONG
AND GUSTY...PEAK GUSTS SHOULD LOWER TO ARND 25KT.

WITH THE PERSISTENT FETCH OF LOW LEVEL MOISTURE INTO THE
REGION...A LAYER OF MVFR STRATOCU HAS OVERSPREAD THE REGION.
EXPECT THAT BASES SHOULD NOT LOWER MUCH LESS THAT 1800FT AGL.
THERE IS SOME UNCERTAINTY AS TO THE DURATION OF THE MVFR CLOUD
LAYER...BUT WITH LITTLE CHANGE TO THE OVERALL PATTERN THROUGH THE
DAY...THERE IS A CHANCE THAT THE MVFR CIGS COULD HANG IN THROUGH
MUCH OF THE DAY. HOWEVER...THERE IS ALSO A CHANCE THAT STRONGER
MIXING IN THE AFTERNOON HOURS COULD ALLOW FOR THE MVFR DECK TO
SCATTER OUT.

LATEST RADAR TRENDS INDICATE THAT AN AREA OF SHRA LIFTING NEWD
FROM CNTRL IL INTO INDIANA. THE TRAJECTORY OF THE PCPN AREA SHOULD
KEEP THE BULK OF THE PCPN EAST AND SOUTH OF GYY...THOUGH A FEW SCT
SHRA AREA NOT OUT OF THE QUESTION. ALSO...SOME SHRA ASSOCIATED
WITH A MID LEVEL IMPULSE LIFTING NORTH THROUGH IOWA AND INTO WRN
WI IS GENERATING SCT SHRA AS WELL. IT IS ALSO POSSIBLE THAT RFD
COULD SEE A FEW SHRA THIS MORNING...BUT THE PROBABILITY IS TOO LOW
TO INCLUDE IN THE TAF AS THE LATEST RADAR TRENDS INDICATE A
WEAKENING TREND THERE.

A SECONDARY LOW IS EXPECTED TO DEVELOP OVER THE UPPER MISSOURI
VALLEY THIS EVENING...KEEPING A MODEST PRESSURE GRADIENT OVER THE
REGION. SO MODERATE...GUSTY WINDS SHOULD PERSIST WELL INTO
TONIGHT. ANOTHER STRONG MID LEVEL IMPULSE IS EXPECTED TO TRACK
THROUGH THE MIDDLE MISSISSIPPI VALLEY AND INTO WISCONSIN LATE
TONIGHT...BRINGING A RENEWED CHANCE FOR SHRA/TSRA TO THE REGION
LATE TONIGHT AND TOMORROW.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 16Z...

* MEDIUM TO HIGH CONFIDENCE IN WIND TRENDS.

* HIGH CONFIDENCE WITH -RA TRENDS THIS MORNING.

* MEDIUM HIGH CONFIDENCE IN CIG TRENDS.

* MEDIUM CONFIDENCE IN PCPN TIMING LATE TONIGHT.

KREIN/RODRIGUEZ

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/TSRA LATE. SOUTHEAST WINDS.

FRIDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. SOUTHWEST WINDS
BECOMING NORTHEAST OVERNIGHT.

SATURDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. NORTHEAST
WINDS.

SUNDAY...CHANCE TSRA. MVFR POSSIBLE. NORTHEAST WINDS.

KREIN

&&

.MARINE...
304 AM CDT

LOW PRESSURE WILL BE STEADILY LIFTING NORTH ACROSS THE MISSOURI
VALLEY THIS MORNING...REACHING LAKE SUPERIOR BY THIS EVENING AND
CONTINUING TO SLIDE EAST/NORTHEAST TOWARDS QUEBEC BY TUESDAY
MORNING. A FRONTAL BOUNDARY WILL REMAIN OVER THE FAR NORTHERN
PORTIONS OF LAKE MICHIGAN. MEANWHILE GUSTY SOUTHERLY WINDS ARE
EXPECTED TO INCREASE THIS MORNING...WITH OCCASIONAL GALES FOR THE
NEARSHORE WATERS OF IL/IN. ACROSS THE OPEN WATERS...EXPECT THE
WARM/MOIST AIR TO STRUGGLE TO REACH THE SFC OF THE LAKE WITH SOME
DEGREE OF LAKE STABILITY. WAVES WILL STEADILY BUILD ACROSS THE
NORTHERN HALF OF THE LAKE AS A RESULT OF THE LONG FETCH. STILL
FEEL THAT GUSTS WILL REACH 30KT ACROSS THE LAKE...HOWEVER
CONFIDENCE HAS DIMINISHED SLIGHTLY AS NEW GUIDANCE HAS BECOME A
LITTLE LESS WITH THE WIND FIELDS. NONETHELESS...WAVES FOR THE
NORTHERN HALF OF THE LAKE WILL LIKELY TOP OUT IN THE 4 TO 7 FT
RANGE WITH OCCASIONAL WAVES REACHING 9 FT THIS AFTERNOON/EVENING.

THE GRADIENT QUICKLY DIMINISHES THIS EVENING...BUT EXPECT
SOUTHERLY WINDS TO PERSIST. THIS WILL ALLOW WAVES TO SUBSIDE TO 3
TO 5 FT. ANOTHER LOW WILL ARRIVE TUE...WITH WINDS NUDGING BACK UP
HOWEVER WARM AIR WILL CONTINUE TO FLOW ACROSS THE LAKE AND COULD
FURTHER ENHANCE THE LAKE STABILITY AND KEEP WAVES FROM BUILDING TO
LARGE.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...NEARSHORE WATERS UNTIL 3
     PM MONDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...3 PM MONDAY TO 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 251602
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1102 AM CDT MON MAY 25 2015

.UPDATE...

COMPACT NEGATIVELY TILTED TROUGH AXIS IS SLIDING NORTHEAST THROUGH
IOWA AND WESTERN ILLINOIS. EASTERN EDGE OF THE TROUGH WILL MOVE
THROUGH NORTHEAST ILLINOIS THIS MORNING. NOTED UPTICK IN SHOWER
ACTIVITY ASSOCIATED WITH THIS WAVE IS PRODUCING MORE ORGANIZED BUT
STILL LARGELY SCATTERED SHOWERS. STILL TRACKING THIS FEATURE WILL
BRING THE BEST CHANCE FOR SOME BRIEF DOWNPOURS IN THE COMING
HOURS...AND THESE WILL SPREAD INTO THE WEST METRO AREA IN THE NEXT
HOUR...SPREADING INTO CHICAGOLAND SHORTLY THERE AFTER. THE CLOUDS
PRODUCING THE SHOWER ACTIVITY ARE SHALLOW AND MID LEVEL LAPSE
RATES ARE SUBPAR...THUS THUNDER SHOULD BE LIMITED AT BEST. SOME
WEAK INSTABILITY IS NOTED SOUTH OF I-80 WHICH DOES NOT PRECLUDE AN
ISOLATED STRIKE IN ANY STRONGER ACTIVITY.

REGARDING WINDS...WITH THE BROKEN TO OVERCAST LOW CLOUD
DECK...MIXING IS BEING LIMITED AND GETING GUSTS TO AROUND 30 KT OR
SO. ANY STRONGER GUSTS WOULD BE IN THE NEXT HOUR BEFORE A RAPID
DROP OFF LATER THIS MORNING.

KMD

&&

.SHORT TERM...
345 AM CDT

THROUGH MONDAY NIGHT...
FOR THE REMAINDER OF THE NIGHT AND INTO MONDAY MORNING...PCPN
CHANCES CONTINUE TO WANE AS LATEST RADAR TRENDS ONLY SHOW SOME SCT
SHRA WHICH ARE DECREASING IN INTENSITY.  IN SPITE OF DEWPOINTS IN
THE LOW 60S...AND A STRONG LOW LEVEL JET...50 KT AT 925 MB...THERE
IS AN ELEMENT LACKING WHICH IS SEEMS TO BE PREVENTING THE
MAINTENANCE OF SHRA/TSRA OVER NERN IL/NWRN IN.  THE MAIN MISSING
ELEMENTS IS FORCING.  THE SFC AND UPPER LEVEL LOW ARE WAY TO THE
WEST...OVER THE NRN PLAINS. THE SHORTWAVE CLIMBING UP THE NWRN
PERIPHERY OF THE HIGH AMPLITUDE RIDGE IS BEING SLOWED BY THE HIGH
AMPLITUDE...AND IS BEING FORCED TO A MORE WLY TRACK THROUGH THE
UPPER MISSISSIPPI VALLEY THAN PREVIOUSLY ANTICIPATED.  SO...FOR THE
REMAINDER OF THE OVERNIGHT HOURS AND THE DAYTIME HOURS MONDAY...HAVE
BACK OF TO ISOLD-SCT SHRA.  WILL KEEP ISOLD TS MENTION FOR THE LATE
MORNING HOURS...THROUGH AROUND NOON...WITH THE DAYTIME HEATING...BUT
CONFIDENCE IN ANY TS IS RATHER LOW AT THIS TIME.  BY THIS
AFTERNOON...A MID LEVEL DRY SLOT IS EXPECTED TO MOVE ACROSS THE
REGION...FURTHER LIMITING PCPN CHANCES AND IT IS QUITE LIKELY THAT
THE REGION WILL REMAIN DRY THROUGH THE DAY.  HOWEVER...WHILE THE
PCPN CHANCES ARE DIMINISHING...THE LIKELIHOOD OF STRONG WINDS IS
STILL A CONCERN.  WITH THE DIMINISHING PCPN CHANCES...LESS SKY COVER
THAN PREVIOUSLY ANTICIPATED IS ALSO POSSIBLE.  A STRONG SWLY
PRESSURE GRADIENT IS SETTING UP ACROSS THE REGION BETWEEN SFC
RIDGING ACROSS THE SERN CONUS AND AND LOW PRESSURE FROM THE UPPER
MISSISSIPPI VALLEY TO THE WESTERN PLAINS.  THE STRONG GRADIENT WILL
HELP DRIVE THE SFC WINDS AND THE DIMINISHING CLOUD COVER COULD HELP
ENHANCE DEEP LAYER MIXING...TAPPING STRONGER WINDS ALOFT.  SUSTAINED
25-25 MPH WINDS ARE LIKELY WITH GUSTS OF 30-35 MPH.
ALSO...PERSISTENT WARM/MOIST ADVECTION AT THE SFC WILL BRING
TEMPERATURES INTO THE LOW TO MIDDLE 80S WITH DEWPOINTS IN THE LOWER
60S.

FOR MONDAY NIGHT...THE BREEZY CONDITIONS WILL PERSIST INTO THE AS
THERE SHOULD BE LITTLE CHANGE TO THE SFC AND UPPER LEVEL PATTERNS.
THE UPPER RIDGE WILL LOSE A LITTLE AMPLITUDE AS SHORT WAVE ENERGY
OVERTOPS THE RIDGE...BUT GENERAL TROUGHING WILL PERSIST ACROSS THE
UPPER MISSISSIPPI VALLEY THROUGH THE CENTRAL PLAINS.  THE NEXT
CHANCE FOR PCPN WILL HOLD OFF UNTIL LATE TONIGHT/EARLY TUESDAY
MORNING AND THE NEXT SHORTWAVE LIFTS OUT OF THE SRN PLAINS AND INTO
THE MIDDLE MISSISSIPPI VALLEY.  AMPLE LOW LEVEL MOISTURE WILL
ALREADY BE IN PLACE SO IT WILL JUST A MATTER OF WHEN THE FORCING
WILL GET HERE.  AGAIN...THERE IS SOME CONCERN THAT THE FORCING WILL
BE TO THE WEST...WITH THE SHORTWAVE TRACKING THROUGH THE MIDDLE
MISSISSIPPI VALLEY AND INTO WI.  SO...WILL CARRY CHANCE POPS FOR THE
REGION...WITH LIKELY POPS APPROACHING THE PONTIAC AREA BY EARLY
TUESDAY MORNING.  THE PERSISTENT WARM/MOIST ADVECTIVE PATTERN AND
BREEZY CONDITIONS SHOULD KEEP TEMPERATURES FROM DROPPING OFF
SIGNIFICANTLY OVERNIGHT AND LOWS SHOULD BE IN THE MIDDLE TO UPPER
60S.

KREIN

&&

.LONG TERM...
239 AM CDT

TUESDAY THROUGH SUNDAY...

TUESDAY THROUGH WEDNESDAY...
500MB TROUGH AXIS WILL SLOWLY PIVOT EAST ACROSS THE CENTRAL PLAINS
INTO THE MID-MISSOURI VALLEY TUE...WITH A SFC WAVE SLIDING NORTH
ACROSS IOWA INTO CENTRAL WISC LATE TUE. THE SFC FEATURE IS NOT
EXPECTED TO BE STRONG...HOWEVER THE GRADIENT DOES TIGHTEN WITH
MODEST HEIGHT FALLS IN THE LOWEST LAYERS OF THE ATMOSPHERE. SOME
INSTABILITY DOES REMAIN ALONG WITH RELATIVELY MOIST SFC CONDS AS
DEW PTS WILL REMAIN IN THE UPR 50S/LOW 60S. PWAT VALUES WILL ALSO
HOVER JUST OVER 1 INCH...WHICH IS SEASONAL. WILL HOLD ONTO MENTION
OF RAIN AND THUNDER...BUT COULD SEE THIS MAINLY FOCUSED IN THE TUE
MORNING TIMEFRAME.

WITH CONSIDERABLE SOLAR SHIELDING PROGGED FOR TUE...TEMPS MAY
STRUGGLE TO WARM BEYOND THE MID/UPR 70S. BUT WITH GUIDANCE HINTING
AT A DRY SLOT LIFTING NORTHEAST ACROSS THE REGION TUE EVE...THIS
COULD INTRODUCE SOME EROSION TO THE CLOUD COVER IN THE AFTN HOURS
TUE AND ALLOW SOME SFC HEATING TO OCCUR AND PUSH TEMPS TO ARND 80.

GUIDANCE LIFTS THE DRY SLOT OVERHEAD LATE TUE NGT...WITH THE 500MB
TROUGH AXIS ARRIVING ARND DAYBREAK WED AND LIFTING EAST ACROSS LOWER
MICHIGAN. THIS WILL BRING DRY ONLY SLIGHT CHANCE POPS AS WEAK SFC
RIDGING BEGINS TO NUDGE EAST ACROSS THE MISSOURI VALLEY TOWARDS THE
FORECAST AREA MIDDAY WED. IT IS POSSIBLE THAT ENOUGH DRY AIR
INFLUENCE COULD ALLOW FOR REMOVAL OF THE SLIGHT CHANCE POPS WED
AFTN. THERMAL TROUGH LAGS BEHIND THE FRONTAL BOUNDARY WED...SO TEMPS
COULD STILL WARM BACK TO ARND 80 AND PERHAPS THE LOW 80S IN THE
SOUTHERN CWFA.

THURSDAY THROUGH SUNDAY...
ANTI-CYCLONIC FLOW ARRIVES THUR WITH AT LEAST ONE PERIOD OF DRY
WEATHER EXPECTED FOR NORTHERN IL/NORTHWEST IN. ONLY A COUPLE
ENSEMBLE MEMBERS CONTINUE TO PROG POPS ALONG THE SOUTHERN FORECAST
AREA THUR...BUT COULD SEE THIS TRENDING DRY IN THE NEXT FEW
SOLUTIONS. WITH WARM TEMPS ALOFT EXPECTED THUR AND THIN CLOUD
COVER...THUR HIGHS COULD PEAK IN THE LOW 80S.

THEN FOCUS TURNS TOWARDS THE UPCOMING WEEKEND AND A PATTERN SHIFT
AWAY FROM THE WARM/HUMID CONDITIONS. ENSEMBLES SHOW MINIMAL SPREAD
IN THE LATE WEEK PERIODS...WITH THE UPSTREAM RIDGE OVER
ALASKA/WESTERN CANADA AND A DOWNSTREAM MID-LVL RIDGE ACROSS THE
SOUTHEAST CONUS. BOTH OF THESE FEATURES IN TIME BEGIN TO
WEAKEN...WITH THE LONGWAVE PATTERN TRANSITIONING INTO A SEMI-ZONAL
ORIENTATION BY THE SECOND HALF OF THE WEEKEND.

OPER GUIDANCE HAS BEEN CONSISTENT WITH PROGGING A ROBUST 500MB
TROUGH TO SLIDE SOUTH FROM CENTRAL CANADA FRI...ALONG WITH A STRONG
CANADIAN SFC RIDGE ON IT/S HEELS. WITH A CHANNEL OF MOISTURE
REMAINING ACROSS THE SOUTHERN PLAINS STRETCHING NORTHEAST THROUGH
THE UPPER MIDWEST...THIS BOUNDARY WILL BECOME ACTIVE WITH A SFC WAVE
DEVELOPING ACROSS THE SOUTHERN PLAINS. THIS LOW WILL THEN LIFT
NORTHEAST TOWARDS THE CWFA FRI WITH A COLD FRONT ARRIVING ACROSS THE
FORECAST AREA SAT. WINDS LOOK TO SHIFT TO THE NORTH...WITH MUCH
COOLER AIR SLIDING SOUTH AND LIKELY KNOCKING TEMPS BACK TO SUB-
SEASONAL CONDS IN THE UPR 60S/NEAR 70 DEGREE RANGE SAT/SUN. IF
NORTHEAST WINDS MATERIALIZE...NEXT WEEKEND AREAS ADJACENT TO LAKE
MICHIGAN ALONG THE IL/IN SHORELINE COULD BE LOCKED IN THE UPR 50S TO
LOW 60S FOR HIGHS WITH A COLD FLOW OFF OF LAKE MICHIGAN.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 16Z...

* GUSTY SOUTH/SOUTHWEST WINDS THROUGH MIDDAY.

* CHANCE OF -RA THIS MORNING.

* MVFR CEILINGS STILL POSSIBLE THIS MORNING.

* CHANCE SHRA/TSRA LATE TONIGHT THROUGH TOMORROW.

KREIN/RODRIGUEZ

//DISCUSSION...UPDATED 12Z...

MAIN CONCERN FOR TODAY WILL BE STRONG...GUSTY SOUTH WINDS. AS OF
11Z THIS MORNING...WINDS ARE ALREADY GUSTING TO 25-30KT AND EXPECT
THAT WITH DEEPER MIXING LATER THIS MORNING...SHOULD BE ABLE TO TAP
INTO A 50 KT LOW LEVEL JET TO MIX DOWN GUSTS TO 35 KT OR EVEN
SLIGHTLY HIGHER. THE STRONG LOW LEVEL JET SHOULD MOVE OFF TO THE
EAST BY EARLY AFTERNOON...SO WHILE WINDS SHOULD STILL BE STRONG
AND GUSTY...PEAK GUSTS SHOULD LOWER TO ARND 25KT.

WITH THE PERSISTENT FETCH OF LOW LEVEL MOISTURE INTO THE
REGION...A LAYER OF MVFR STRATOCU HAS OVERSPREAD THE REGION.
EXPECT THAT BASES SHOULD NOT LOWER MUCH LESS THAT 1800FT AGL.
THERE IS SOME UNCERTAINTY AS TO THE DURATION OF THE MVFR CLOUD
LAYER...BUT WITH LITTLE CHANGE TO THE OVERALL PATTERN THROUGH THE
DAY...THERE IS A CHANCE THAT THE MVFR CIGS COULD HANG IN THROUGH
MUCH OF THE DAY. HOWEVER...THERE IS ALSO A CHANCE THAT STRONGER
MIXING IN THE AFTERNOON HOURS COULD ALLOW FOR THE MVFR DECK TO
SCATTER OUT.

LATEST RADAR TRENDS INDICATE THAT AN AREA OF SHRA LIFTING NEWD
FROM CNTRL IL INTO INDIANA. THE TRAJECTORY OF THE PCPN AREA SHOULD
KEEP THE BULK OF THE PCPN EAST AND SOUTH OF GYY...THOUGH A FEW SCT
SHRA AREA NOT OUT OF THE QUESTION. ALSO...SOME SHRA ASSOCIATED
WITH A MID LEVEL IMPULSE LIFTING NORTH THROUGH IOWA AND INTO WRN
WI IS GENERATING SCT SHRA AS WELL. IT IS ALSO POSSIBLE THAT RFD
COULD SEE A FEW SHRA THIS MORNING...BUT THE PROBABILITY IS TOO LOW
TO INCLUDE IN THE TAF AS THE LATEST RADAR TRENDS INDICATE A
WEAKENING TREND THERE.

A SECONDARY LOW IS EXPECTED TO DEVELOP OVER THE UPPER MISSOURI
VALLEY THIS EVENING...KEEPING A MODEST PRESSURE GRADIENT OVER THE
REGION. SO MODERATE...GUSTY WINDS SHOULD PERSIST WELL INTO
TONIGHT. ANOTHER STRONG MID LEVEL IMPULSE IS EXPECTED TO TRACK
THROUGH THE MIDDLE MISSISSIPPI VALLEY AND INTO WISCONSIN LATE
TONIGHT...BRINGING A RENEWED CHANCE FOR SHRA/TSRA TO THE REGION
LATE TONIGHT AND TOMORROW.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 16Z...

* MEDIUM TO HIGH CONFIDENCE IN WIND TRENDS.

* HIGH CONFIDENCE WITH -RA TRENDS THIS MORNING.

* MEDIUM HIGH CONFIDENCE IN CIG TRENDS.

* MEDIUM CONFIDENCE IN PCPN TIMING LATE TONIGHT.

KREIN/RODRIGUEZ

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/TSRA LATE. SOUTHEAST WINDS.

FRIDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. SOUTHWEST WINDS
BECOMING NORTHEAST OVERNIGHT.

SATURDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. NORTHEAST
WINDS.

SUNDAY...CHANCE TSRA. MVFR POSSIBLE. NORTHEAST WINDS.

KREIN

&&

.MARINE...
304 AM CDT

LOW PRESSURE WILL BE STEADILY LIFTING NORTH ACROSS THE MISSOURI
VALLEY THIS MORNING...REACHING LAKE SUPERIOR BY THIS EVENING AND
CONTINUING TO SLIDE EAST/NORTHEAST TOWARDS QUEBEC BY TUESDAY
MORNING. A FRONTAL BOUNDARY WILL REMAIN OVER THE FAR NORTHERN
PORTIONS OF LAKE MICHIGAN. MEANWHILE GUSTY SOUTHERLY WINDS ARE
EXPECTED TO INCREASE THIS MORNING...WITH OCCASIONAL GALES FOR THE
NEARSHORE WATERS OF IL/IN. ACROSS THE OPEN WATERS...EXPECT THE
WARM/MOIST AIR TO STRUGGLE TO REACH THE SFC OF THE LAKE WITH SOME
DEGREE OF LAKE STABILITY. WAVES WILL STEADILY BUILD ACROSS THE
NORTHERN HALF OF THE LAKE AS A RESULT OF THE LONG FETCH. STILL
FEEL THAT GUSTS WILL REACH 30KT ACROSS THE LAKE...HOWEVER
CONFIDENCE HAS DIMINISHED SLIGHTLY AS NEW GUIDANCE HAS BECOME A
LITTLE LESS WITH THE WIND FIELDS. NONETHELESS...WAVES FOR THE
NORTHERN HALF OF THE LAKE WILL LIKELY TOP OUT IN THE 4 TO 7 FT
RANGE WITH OCCASIONAL WAVES REACHING 9 FT THIS AFTERNOON/EVENING.

THE GRADIENT QUICKLY DIMINISHES THIS EVENING...BUT EXPECT
SOUTHERLY WINDS TO PERSIST. THIS WILL ALLOW WAVES TO SUBSIDE TO 3
TO 5 FT. ANOTHER LOW WILL ARRIVE TUE...WITH WINDS NUDGING BACK UP
HOWEVER WARM AIR WILL CONTINUE TO FLOW ACROSS THE LAKE AND COULD
FURTHER ENHANCE THE LAKE STABILITY AND KEEP WAVES FROM BUILDING TO
LARGE.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...NEARSHORE WATERS UNTIL 3
     PM MONDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...3 PM MONDAY TO 4 AM TUESDAY.

&&

$$

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000
FXUS63 KLOT 251602
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1102 AM CDT MON MAY 25 2015

.UPDATE...

COMPACT NEGATIVELY TILTED TROUGH AXIS IS SLIDING NORTHEAST THROUGH
IOWA AND WESTERN ILLINOIS. EASTERN EDGE OF THE TROUGH WILL MOVE
THROUGH NORTHEAST ILLINOIS THIS MORNING. NOTED UPTICK IN SHOWER
ACTIVITY ASSOCIATED WITH THIS WAVE IS PRODUCING MORE ORGANIZED BUT
STILL LARGELY SCATTERED SHOWERS. STILL TRACKING THIS FEATURE WILL
BRING THE BEST CHANCE FOR SOME BRIEF DOWNPOURS IN THE COMING
HOURS...AND THESE WILL SPREAD INTO THE WEST METRO AREA IN THE NEXT
HOUR...SPREADING INTO CHICAGOLAND SHORTLY THERE AFTER. THE CLOUDS
PRODUCING THE SHOWER ACTIVITY ARE SHALLOW AND MID LEVEL LAPSE
RATES ARE SUBPAR...THUS THUNDER SHOULD BE LIMITED AT BEST. SOME
WEAK INSTABILITY IS NOTED SOUTH OF I-80 WHICH DOES NOT PRECLUDE AN
ISOLATED STRIKE IN ANY STRONGER ACTIVITY.

REGARDING WINDS...WITH THE BROKEN TO OVERCAST LOW CLOUD
DECK...MIXING IS BEING LIMITED AND GETING GUSTS TO AROUND 30 KT OR
SO. ANY STRONGER GUSTS WOULD BE IN THE NEXT HOUR BEFORE A RAPID
DROP OFF LATER THIS MORNING.

KMD

&&

.SHORT TERM...
345 AM CDT

THROUGH MONDAY NIGHT...
FOR THE REMAINDER OF THE NIGHT AND INTO MONDAY MORNING...PCPN
CHANCES CONTINUE TO WANE AS LATEST RADAR TRENDS ONLY SHOW SOME SCT
SHRA WHICH ARE DECREASING IN INTENSITY.  IN SPITE OF DEWPOINTS IN
THE LOW 60S...AND A STRONG LOW LEVEL JET...50 KT AT 925 MB...THERE
IS AN ELEMENT LACKING WHICH IS SEEMS TO BE PREVENTING THE
MAINTENANCE OF SHRA/TSRA OVER NERN IL/NWRN IN.  THE MAIN MISSING
ELEMENTS IS FORCING.  THE SFC AND UPPER LEVEL LOW ARE WAY TO THE
WEST...OVER THE NRN PLAINS. THE SHORTWAVE CLIMBING UP THE NWRN
PERIPHERY OF THE HIGH AMPLITUDE RIDGE IS BEING SLOWED BY THE HIGH
AMPLITUDE...AND IS BEING FORCED TO A MORE WLY TRACK THROUGH THE
UPPER MISSISSIPPI VALLEY THAN PREVIOUSLY ANTICIPATED.  SO...FOR THE
REMAINDER OF THE OVERNIGHT HOURS AND THE DAYTIME HOURS MONDAY...HAVE
BACK OF TO ISOLD-SCT SHRA.  WILL KEEP ISOLD TS MENTION FOR THE LATE
MORNING HOURS...THROUGH AROUND NOON...WITH THE DAYTIME HEATING...BUT
CONFIDENCE IN ANY TS IS RATHER LOW AT THIS TIME.  BY THIS
AFTERNOON...A MID LEVEL DRY SLOT IS EXPECTED TO MOVE ACROSS THE
REGION...FURTHER LIMITING PCPN CHANCES AND IT IS QUITE LIKELY THAT
THE REGION WILL REMAIN DRY THROUGH THE DAY.  HOWEVER...WHILE THE
PCPN CHANCES ARE DIMINISHING...THE LIKELIHOOD OF STRONG WINDS IS
STILL A CONCERN.  WITH THE DIMINISHING PCPN CHANCES...LESS SKY COVER
THAN PREVIOUSLY ANTICIPATED IS ALSO POSSIBLE.  A STRONG SWLY
PRESSURE GRADIENT IS SETTING UP ACROSS THE REGION BETWEEN SFC
RIDGING ACROSS THE SERN CONUS AND AND LOW PRESSURE FROM THE UPPER
MISSISSIPPI VALLEY TO THE WESTERN PLAINS.  THE STRONG GRADIENT WILL
HELP DRIVE THE SFC WINDS AND THE DIMINISHING CLOUD COVER COULD HELP
ENHANCE DEEP LAYER MIXING...TAPPING STRONGER WINDS ALOFT.  SUSTAINED
25-25 MPH WINDS ARE LIKELY WITH GUSTS OF 30-35 MPH.
ALSO...PERSISTENT WARM/MOIST ADVECTION AT THE SFC WILL BRING
TEMPERATURES INTO THE LOW TO MIDDLE 80S WITH DEWPOINTS IN THE LOWER
60S.

FOR MONDAY NIGHT...THE BREEZY CONDITIONS WILL PERSIST INTO THE AS
THERE SHOULD BE LITTLE CHANGE TO THE SFC AND UPPER LEVEL PATTERNS.
THE UPPER RIDGE WILL LOSE A LITTLE AMPLITUDE AS SHORT WAVE ENERGY
OVERTOPS THE RIDGE...BUT GENERAL TROUGHING WILL PERSIST ACROSS THE
UPPER MISSISSIPPI VALLEY THROUGH THE CENTRAL PLAINS.  THE NEXT
CHANCE FOR PCPN WILL HOLD OFF UNTIL LATE TONIGHT/EARLY TUESDAY
MORNING AND THE NEXT SHORTWAVE LIFTS OUT OF THE SRN PLAINS AND INTO
THE MIDDLE MISSISSIPPI VALLEY.  AMPLE LOW LEVEL MOISTURE WILL
ALREADY BE IN PLACE SO IT WILL JUST A MATTER OF WHEN THE FORCING
WILL GET HERE.  AGAIN...THERE IS SOME CONCERN THAT THE FORCING WILL
BE TO THE WEST...WITH THE SHORTWAVE TRACKING THROUGH THE MIDDLE
MISSISSIPPI VALLEY AND INTO WI.  SO...WILL CARRY CHANCE POPS FOR THE
REGION...WITH LIKELY POPS APPROACHING THE PONTIAC AREA BY EARLY
TUESDAY MORNING.  THE PERSISTENT WARM/MOIST ADVECTIVE PATTERN AND
BREEZY CONDITIONS SHOULD KEEP TEMPERATURES FROM DROPPING OFF
SIGNIFICANTLY OVERNIGHT AND LOWS SHOULD BE IN THE MIDDLE TO UPPER
60S.

KREIN

&&

.LONG TERM...
239 AM CDT

TUESDAY THROUGH SUNDAY...

TUESDAY THROUGH WEDNESDAY...
500MB TROUGH AXIS WILL SLOWLY PIVOT EAST ACROSS THE CENTRAL PLAINS
INTO THE MID-MISSOURI VALLEY TUE...WITH A SFC WAVE SLIDING NORTH
ACROSS IOWA INTO CENTRAL WISC LATE TUE. THE SFC FEATURE IS NOT
EXPECTED TO BE STRONG...HOWEVER THE GRADIENT DOES TIGHTEN WITH
MODEST HEIGHT FALLS IN THE LOWEST LAYERS OF THE ATMOSPHERE. SOME
INSTABILITY DOES REMAIN ALONG WITH RELATIVELY MOIST SFC CONDS AS
DEW PTS WILL REMAIN IN THE UPR 50S/LOW 60S. PWAT VALUES WILL ALSO
HOVER JUST OVER 1 INCH...WHICH IS SEASONAL. WILL HOLD ONTO MENTION
OF RAIN AND THUNDER...BUT COULD SEE THIS MAINLY FOCUSED IN THE TUE
MORNING TIMEFRAME.

WITH CONSIDERABLE SOLAR SHIELDING PROGGED FOR TUE...TEMPS MAY
STRUGGLE TO WARM BEYOND THE MID/UPR 70S. BUT WITH GUIDANCE HINTING
AT A DRY SLOT LIFTING NORTHEAST ACROSS THE REGION TUE EVE...THIS
COULD INTRODUCE SOME EROSION TO THE CLOUD COVER IN THE AFTN HOURS
TUE AND ALLOW SOME SFC HEATING TO OCCUR AND PUSH TEMPS TO ARND 80.

GUIDANCE LIFTS THE DRY SLOT OVERHEAD LATE TUE NGT...WITH THE 500MB
TROUGH AXIS ARRIVING ARND DAYBREAK WED AND LIFTING EAST ACROSS LOWER
MICHIGAN. THIS WILL BRING DRY ONLY SLIGHT CHANCE POPS AS WEAK SFC
RIDGING BEGINS TO NUDGE EAST ACROSS THE MISSOURI VALLEY TOWARDS THE
FORECAST AREA MIDDAY WED. IT IS POSSIBLE THAT ENOUGH DRY AIR
INFLUENCE COULD ALLOW FOR REMOVAL OF THE SLIGHT CHANCE POPS WED
AFTN. THERMAL TROUGH LAGS BEHIND THE FRONTAL BOUNDARY WED...SO TEMPS
COULD STILL WARM BACK TO ARND 80 AND PERHAPS THE LOW 80S IN THE
SOUTHERN CWFA.

THURSDAY THROUGH SUNDAY...
ANTI-CYCLONIC FLOW ARRIVES THUR WITH AT LEAST ONE PERIOD OF DRY
WEATHER EXPECTED FOR NORTHERN IL/NORTHWEST IN. ONLY A COUPLE
ENSEMBLE MEMBERS CONTINUE TO PROG POPS ALONG THE SOUTHERN FORECAST
AREA THUR...BUT COULD SEE THIS TRENDING DRY IN THE NEXT FEW
SOLUTIONS. WITH WARM TEMPS ALOFT EXPECTED THUR AND THIN CLOUD
COVER...THUR HIGHS COULD PEAK IN THE LOW 80S.

THEN FOCUS TURNS TOWARDS THE UPCOMING WEEKEND AND A PATTERN SHIFT
AWAY FROM THE WARM/HUMID CONDITIONS. ENSEMBLES SHOW MINIMAL SPREAD
IN THE LATE WEEK PERIODS...WITH THE UPSTREAM RIDGE OVER
ALASKA/WESTERN CANADA AND A DOWNSTREAM MID-LVL RIDGE ACROSS THE
SOUTHEAST CONUS. BOTH OF THESE FEATURES IN TIME BEGIN TO
WEAKEN...WITH THE LONGWAVE PATTERN TRANSITIONING INTO A SEMI-ZONAL
ORIENTATION BY THE SECOND HALF OF THE WEEKEND.

OPER GUIDANCE HAS BEEN CONSISTENT WITH PROGGING A ROBUST 500MB
TROUGH TO SLIDE SOUTH FROM CENTRAL CANADA FRI...ALONG WITH A STRONG
CANADIAN SFC RIDGE ON IT/S HEELS. WITH A CHANNEL OF MOISTURE
REMAINING ACROSS THE SOUTHERN PLAINS STRETCHING NORTHEAST THROUGH
THE UPPER MIDWEST...THIS BOUNDARY WILL BECOME ACTIVE WITH A SFC WAVE
DEVELOPING ACROSS THE SOUTHERN PLAINS. THIS LOW WILL THEN LIFT
NORTHEAST TOWARDS THE CWFA FRI WITH A COLD FRONT ARRIVING ACROSS THE
FORECAST AREA SAT. WINDS LOOK TO SHIFT TO THE NORTH...WITH MUCH
COOLER AIR SLIDING SOUTH AND LIKELY KNOCKING TEMPS BACK TO SUB-
SEASONAL CONDS IN THE UPR 60S/NEAR 70 DEGREE RANGE SAT/SUN. IF
NORTHEAST WINDS MATERIALIZE...NEXT WEEKEND AREAS ADJACENT TO LAKE
MICHIGAN ALONG THE IL/IN SHORELINE COULD BE LOCKED IN THE UPR 50S TO
LOW 60S FOR HIGHS WITH A COLD FLOW OFF OF LAKE MICHIGAN.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 16Z...

* GUSTY SOUTH/SOUTHWEST WINDS THROUGH MIDDAY.

* CHANCE OF -RA THIS MORNING.

* MVFR CEILINGS STILL POSSIBLE THIS MORNING.

* CHANCE SHRA/TSRA LATE TONIGHT THROUGH TOMORROW.

KREIN/RODRIGUEZ

//DISCUSSION...UPDATED 12Z...

MAIN CONCERN FOR TODAY WILL BE STRONG...GUSTY SOUTH WINDS. AS OF
11Z THIS MORNING...WINDS ARE ALREADY GUSTING TO 25-30KT AND EXPECT
THAT WITH DEEPER MIXING LATER THIS MORNING...SHOULD BE ABLE TO TAP
INTO A 50 KT LOW LEVEL JET TO MIX DOWN GUSTS TO 35 KT OR EVEN
SLIGHTLY HIGHER. THE STRONG LOW LEVEL JET SHOULD MOVE OFF TO THE
EAST BY EARLY AFTERNOON...SO WHILE WINDS SHOULD STILL BE STRONG
AND GUSTY...PEAK GUSTS SHOULD LOWER TO ARND 25KT.

WITH THE PERSISTENT FETCH OF LOW LEVEL MOISTURE INTO THE
REGION...A LAYER OF MVFR STRATOCU HAS OVERSPREAD THE REGION.
EXPECT THAT BASES SHOULD NOT LOWER MUCH LESS THAT 1800FT AGL.
THERE IS SOME UNCERTAINTY AS TO THE DURATION OF THE MVFR CLOUD
LAYER...BUT WITH LITTLE CHANGE TO THE OVERALL PATTERN THROUGH THE
DAY...THERE IS A CHANCE THAT THE MVFR CIGS COULD HANG IN THROUGH
MUCH OF THE DAY. HOWEVER...THERE IS ALSO A CHANCE THAT STRONGER
MIXING IN THE AFTERNOON HOURS COULD ALLOW FOR THE MVFR DECK TO
SCATTER OUT.

LATEST RADAR TRENDS INDICATE THAT AN AREA OF SHRA LIFTING NEWD
FROM CNTRL IL INTO INDIANA. THE TRAJECTORY OF THE PCPN AREA SHOULD
KEEP THE BULK OF THE PCPN EAST AND SOUTH OF GYY...THOUGH A FEW SCT
SHRA AREA NOT OUT OF THE QUESTION. ALSO...SOME SHRA ASSOCIATED
WITH A MID LEVEL IMPULSE LIFTING NORTH THROUGH IOWA AND INTO WRN
WI IS GENERATING SCT SHRA AS WELL. IT IS ALSO POSSIBLE THAT RFD
COULD SEE A FEW SHRA THIS MORNING...BUT THE PROBABILITY IS TOO LOW
TO INCLUDE IN THE TAF AS THE LATEST RADAR TRENDS INDICATE A
WEAKENING TREND THERE.

A SECONDARY LOW IS EXPECTED TO DEVELOP OVER THE UPPER MISSOURI
VALLEY THIS EVENING...KEEPING A MODEST PRESSURE GRADIENT OVER THE
REGION. SO MODERATE...GUSTY WINDS SHOULD PERSIST WELL INTO
TONIGHT. ANOTHER STRONG MID LEVEL IMPULSE IS EXPECTED TO TRACK
THROUGH THE MIDDLE MISSISSIPPI VALLEY AND INTO WISCONSIN LATE
TONIGHT...BRINGING A RENEWED CHANCE FOR SHRA/TSRA TO THE REGION
LATE TONIGHT AND TOMORROW.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 16Z...

* MEDIUM TO HIGH CONFIDENCE IN WIND TRENDS.

* HIGH CONFIDENCE WITH -RA TRENDS THIS MORNING.

* MEDIUM HIGH CONFIDENCE IN CIG TRENDS.

* MEDIUM CONFIDENCE IN PCPN TIMING LATE TONIGHT.

KREIN/RODRIGUEZ

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/TSRA LATE. SOUTHEAST WINDS.

FRIDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. SOUTHWEST WINDS
BECOMING NORTHEAST OVERNIGHT.

SATURDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. NORTHEAST
WINDS.

SUNDAY...CHANCE TSRA. MVFR POSSIBLE. NORTHEAST WINDS.

KREIN

&&

.MARINE...
304 AM CDT

LOW PRESSURE WILL BE STEADILY LIFTING NORTH ACROSS THE MISSOURI
VALLEY THIS MORNING...REACHING LAKE SUPERIOR BY THIS EVENING AND
CONTINUING TO SLIDE EAST/NORTHEAST TOWARDS QUEBEC BY TUESDAY
MORNING. A FRONTAL BOUNDARY WILL REMAIN OVER THE FAR NORTHERN
PORTIONS OF LAKE MICHIGAN. MEANWHILE GUSTY SOUTHERLY WINDS ARE
EXPECTED TO INCREASE THIS MORNING...WITH OCCASIONAL GALES FOR THE
NEARSHORE WATERS OF IL/IN. ACROSS THE OPEN WATERS...EXPECT THE
WARM/MOIST AIR TO STRUGGLE TO REACH THE SFC OF THE LAKE WITH SOME
DEGREE OF LAKE STABILITY. WAVES WILL STEADILY BUILD ACROSS THE
NORTHERN HALF OF THE LAKE AS A RESULT OF THE LONG FETCH. STILL
FEEL THAT GUSTS WILL REACH 30KT ACROSS THE LAKE...HOWEVER
CONFIDENCE HAS DIMINISHED SLIGHTLY AS NEW GUIDANCE HAS BECOME A
LITTLE LESS WITH THE WIND FIELDS. NONETHELESS...WAVES FOR THE
NORTHERN HALF OF THE LAKE WILL LIKELY TOP OUT IN THE 4 TO 7 FT
RANGE WITH OCCASIONAL WAVES REACHING 9 FT THIS AFTERNOON/EVENING.

THE GRADIENT QUICKLY DIMINISHES THIS EVENING...BUT EXPECT
SOUTHERLY WINDS TO PERSIST. THIS WILL ALLOW WAVES TO SUBSIDE TO 3
TO 5 FT. ANOTHER LOW WILL ARRIVE TUE...WITH WINDS NUDGING BACK UP
HOWEVER WARM AIR WILL CONTINUE TO FLOW ACROSS THE LAKE AND COULD
FURTHER ENHANCE THE LAKE STABILITY AND KEEP WAVES FROM BUILDING TO
LARGE.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...NEARSHORE WATERS UNTIL 3
     PM MONDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...3 PM MONDAY TO 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
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000
FXUS63 KILX 251505
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1005 AM CDT MON MAY 25 2015

.UPDATE...
ISSUED AT 1004 AM CDT MON MAY 25 2015

A FEW SHOWERS LINGER EAST OF I-55...BUT THESE WILL BE EXITING OVER THE
NEXT COUPLE HOURS. HAVE KEPT SOME SLIGHT CHANCE POP`S EAST OF I-57
INTO THE AFTERNOON...BUT CONDITIONS SHOULD LARGELY BE DRY OVER THE
FORECAST AREA INTO THE EVENING HOURS. HIGH-RESOLUTION VISIBLE
SATELLITE IMAGERY SHOWING SKIES BECOMING PARTLY SUNNY ALREADY
NORTHWEST OF THE ILLINOIS RIVER...AND A LARGER HOLE IN THE CLOUDS
OVER NORTH CENTRAL MISSOURI SHOULD BE MOVING INTO THE FORECAST
AREA EARLY AFTERNOON PER THE RAP MODEL...ALTHOUGH THE SOUTHEAST
CWA WILL LIKELY SEE MORE PERSISTENT CLOUDS. HAVE HAD SOME GUSTS
40-45 MPH AROUND DECATUR AND CHAMPAIGN ON THE LATEST OBS...BUT THE
HRRR MODEL SHOWS THESE HIGH WINDS SHIFTING INTO INDIANA OVER THE
NEXT COUPLE HOURS.


&&

.SHORT TERM...(TODAY)
ISSUED AT 337 AM CDT MON MAY 25 2015

LOW PRESSURE CENTER STILL WELL OFF TO THE SOUTHWEST THIS
MORNING...AND A WARM FRONT DRAPED ACROSS THE IL/WI BORDER THIS
MORNING.  SCATTERED SHOWERS AND ISOLATED THUNDER STILL IN THE
REGION, BUT MAINLY CONFINED TO AREAS IN THE SOUTHEAST AS WELL AS THE
NW.  ILX SITUATED IN A GAP AS THE MAJORITY OF THE SYSTEM CONTINUES
TO LIFT NORTH AND NORTHEAST THIS MORNING.  MODELS PRETTY CONSISTENT
WITH THE MOVING OUT OF THE SYSTEM, WITH SOME SCATTERED SHOWERS
POSSIBLY AT LEAST THROUGH MIDDAY.  ISOLATED THUNDER CANNOT BE RULED
OUT WITH THE INCREASING INSTABILITY AFTER SUNRISE...BUT MAJORITY OF
THE ACTIVITY SCOURS OUT IN ALL OF THE MODELS SHORTLY AFTER MIDDAY.
LINGERED SOME SLIGHT CHANCES AFTER 18Z TO COVER AT LEAST THE
POTENTIAL FOR ACTIVITY WITH ANY REMNANT MESOSCALE BOUNDARIES.
PLENTY OF INSTABILITY STILL WITHIN THE ATMOSPHERE SHOULD IT GET THE
CHANCE TO RECOVER/RESTRATIFY.  HOWEVER, A SMALL AREA OF MIDLEVEL
RIDGING BEHIND THE SHORTWAVE THIS MORNING MAY GIVE US ENOUGH
SUBSIDENCE TO COUNTER THE EFFECTS...SO HAVE FOLLOWED SUIT WITH THE
END OF DAYTIME HEATING AND THE EARLY EVENING AND DROPPED THE POPS
BACK DOWN BEFORE 06Z. EITHER WAY...WINDS ALOFT WITH THE PASSING OF
THE SHORTWAVE AND DAYTIME MIXING WILL RESULT IN SOME GUSTY WINDS
TODAY...GUSTING 25 TO 35 MPH BY MID DAY AND SLOWLY BACKING OFF AS
THE LOW LIFTS OUT OF THE REGION.

.LONG TERM...(TONIGHT THROUGH SUNDAY)
ISSUED AT 337 AM CDT MON MAY 25 2015

FORECAST REMAINS WARM AND MUGGY WITH SEVERAL CHANCES FOR SHOWERS AND
THUNDERSTORMS THROUGHOUT. REGION DOMINATED BY SOUTHWESTERLY FLOW AND
A SERIES OF SHORT WAVES EJECTING OUT OF THE UPPER TROF IN THE SW
THROUGH THE FIRST HALF OF THE WEEK.  A BRIEF BREAK IN THE PATTERN
MID WEEK IS ONLY TEMPORARY AS TEMPS REMAIN WARM WITH PLENTY OF
MOISTURE ONLY REINFORCED BY PERIODIC SHOWERS ENHANCING THE BOUNDARY
LAYER RH. YET ANOTHER SURFACE LOW LIFTS INTO THE MIDWEST MOVING
ALONG THE SOUTHWESTERLY FLOW ALOFT ON TUESDAY.  MORE SHOWERS
ANTICIPATED FOR TUESDAY/TUESDAY NIGHT WITH THE MUGGY AIRMASS.  FRONT
ASSOCIATED WITH THIS SYSTEM WEAK AT BEST AND WILL ONLY SEE A BRIEF
SFC WIND SHIFT TO MORE WESTERLY FROM SOUTHERLY FOR WED AND WED NIGHT
ACCOMPANIED BY A BRIEF PATTERN SHIFT ALOFT.  CHANGE IS ONLY
TEMPORARY AS SOUTHERLY SFC WINDS REESTABLISH BY THE END OF THE WEEK.
WEAK SOUTHWESTERLY FLOW ALOFT SLOWLY SHIFTS TO WEAK FLOW OVERALL
GOING INTO THE WEEKEND SETTING UP CHANCES FOR PERIODIC DIURNALLY
DRIVEN CONVECTION YET AGAIN.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z TUESDAY MORNING)
ISSUED AT 654 AM CDT MON MAY 25 2015

SCATTERED SHOWERS CONTINUE TO MOVE THROUGH THE AREA THIS MORNING.
THE SHOWERS IN WEST CENTRAL ILLINOIS WILL BE LIFTING NORTH TO
NORTHEAST AND SHOULD EFFECT PIA/SPI THIS MORNING. FOR OTHER TAF
SITES WILL JUST KEEP VCSH IN THE MORNING HOURS. ONCE THE PCPN
MOVES OUT, SKIES WILL BEGIN TO GRADUALLY SCATTER OUT. THIS WILL BE
SHORT LIVED AS ANOTHER WAVE/BOUNDARY WILL PUSH INTO THE AREA FOR
TUE NIGHT...WITH MOVE SHOWERS AND STORMS. EXCEPT FOR EARLY THIS
AFTERNOON AND THIS EVENING...ALL TAF SITES WILL BE MVFR CIGS
THROUGH THE PERIOD. LATE TONIGHT ALL TAF SITES WILL HAVE
PREDOMINATE SHOWERS WITH VCTS. WINDS WILL BE VERY GUSTY THIS
MORNING OUT OF THE SOUTH BUT THEN TAPER SOME DURING THE AFTERNOON.
THEN WILL LOOSE THE GUSTINESS DURING THE EVENING.


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...GEELHART
SHORT TERM...HJS
LONG TERM...HJS
AVIATION...AUTEN



000
FXUS63 KILX 251505
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1005 AM CDT MON MAY 25 2015

.UPDATE...
ISSUED AT 1004 AM CDT MON MAY 25 2015

A FEW SHOWERS LINGER EAST OF I-55...BUT THESE WILL BE EXITING OVER THE
NEXT COUPLE HOURS. HAVE KEPT SOME SLIGHT CHANCE POP`S EAST OF I-57
INTO THE AFTERNOON...BUT CONDITIONS SHOULD LARGELY BE DRY OVER THE
FORECAST AREA INTO THE EVENING HOURS. HIGH-RESOLUTION VISIBLE
SATELLITE IMAGERY SHOWING SKIES BECOMING PARTLY SUNNY ALREADY
NORTHWEST OF THE ILLINOIS RIVER...AND A LARGER HOLE IN THE CLOUDS
OVER NORTH CENTRAL MISSOURI SHOULD BE MOVING INTO THE FORECAST
AREA EARLY AFTERNOON PER THE RAP MODEL...ALTHOUGH THE SOUTHEAST
CWA WILL LIKELY SEE MORE PERSISTENT CLOUDS. HAVE HAD SOME GUSTS
40-45 MPH AROUND DECATUR AND CHAMPAIGN ON THE LATEST OBS...BUT THE
HRRR MODEL SHOWS THESE HIGH WINDS SHIFTING INTO INDIANA OVER THE
NEXT COUPLE HOURS.


&&

.SHORT TERM...(TODAY)
ISSUED AT 337 AM CDT MON MAY 25 2015

LOW PRESSURE CENTER STILL WELL OFF TO THE SOUTHWEST THIS
MORNING...AND A WARM FRONT DRAPED ACROSS THE IL/WI BORDER THIS
MORNING.  SCATTERED SHOWERS AND ISOLATED THUNDER STILL IN THE
REGION, BUT MAINLY CONFINED TO AREAS IN THE SOUTHEAST AS WELL AS THE
NW.  ILX SITUATED IN A GAP AS THE MAJORITY OF THE SYSTEM CONTINUES
TO LIFT NORTH AND NORTHEAST THIS MORNING.  MODELS PRETTY CONSISTENT
WITH THE MOVING OUT OF THE SYSTEM, WITH SOME SCATTERED SHOWERS
POSSIBLY AT LEAST THROUGH MIDDAY.  ISOLATED THUNDER CANNOT BE RULED
OUT WITH THE INCREASING INSTABILITY AFTER SUNRISE...BUT MAJORITY OF
THE ACTIVITY SCOURS OUT IN ALL OF THE MODELS SHORTLY AFTER MIDDAY.
LINGERED SOME SLIGHT CHANCES AFTER 18Z TO COVER AT LEAST THE
POTENTIAL FOR ACTIVITY WITH ANY REMNANT MESOSCALE BOUNDARIES.
PLENTY OF INSTABILITY STILL WITHIN THE ATMOSPHERE SHOULD IT GET THE
CHANCE TO RECOVER/RESTRATIFY.  HOWEVER, A SMALL AREA OF MIDLEVEL
RIDGING BEHIND THE SHORTWAVE THIS MORNING MAY GIVE US ENOUGH
SUBSIDENCE TO COUNTER THE EFFECTS...SO HAVE FOLLOWED SUIT WITH THE
END OF DAYTIME HEATING AND THE EARLY EVENING AND DROPPED THE POPS
BACK DOWN BEFORE 06Z. EITHER WAY...WINDS ALOFT WITH THE PASSING OF
THE SHORTWAVE AND DAYTIME MIXING WILL RESULT IN SOME GUSTY WINDS
TODAY...GUSTING 25 TO 35 MPH BY MID DAY AND SLOWLY BACKING OFF AS
THE LOW LIFTS OUT OF THE REGION.

.LONG TERM...(TONIGHT THROUGH SUNDAY)
ISSUED AT 337 AM CDT MON MAY 25 2015

FORECAST REMAINS WARM AND MUGGY WITH SEVERAL CHANCES FOR SHOWERS AND
THUNDERSTORMS THROUGHOUT. REGION DOMINATED BY SOUTHWESTERLY FLOW AND
A SERIES OF SHORT WAVES EJECTING OUT OF THE UPPER TROF IN THE SW
THROUGH THE FIRST HALF OF THE WEEK.  A BRIEF BREAK IN THE PATTERN
MID WEEK IS ONLY TEMPORARY AS TEMPS REMAIN WARM WITH PLENTY OF
MOISTURE ONLY REINFORCED BY PERIODIC SHOWERS ENHANCING THE BOUNDARY
LAYER RH. YET ANOTHER SURFACE LOW LIFTS INTO THE MIDWEST MOVING
ALONG THE SOUTHWESTERLY FLOW ALOFT ON TUESDAY.  MORE SHOWERS
ANTICIPATED FOR TUESDAY/TUESDAY NIGHT WITH THE MUGGY AIRMASS.  FRONT
ASSOCIATED WITH THIS SYSTEM WEAK AT BEST AND WILL ONLY SEE A BRIEF
SFC WIND SHIFT TO MORE WESTERLY FROM SOUTHERLY FOR WED AND WED NIGHT
ACCOMPANIED BY A BRIEF PATTERN SHIFT ALOFT.  CHANGE IS ONLY
TEMPORARY AS SOUTHERLY SFC WINDS REESTABLISH BY THE END OF THE WEEK.
WEAK SOUTHWESTERLY FLOW ALOFT SLOWLY SHIFTS TO WEAK FLOW OVERALL
GOING INTO THE WEEKEND SETTING UP CHANCES FOR PERIODIC DIURNALLY
DRIVEN CONVECTION YET AGAIN.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z TUESDAY MORNING)
ISSUED AT 654 AM CDT MON MAY 25 2015

SCATTERED SHOWERS CONTINUE TO MOVE THROUGH THE AREA THIS MORNING.
THE SHOWERS IN WEST CENTRAL ILLINOIS WILL BE LIFTING NORTH TO
NORTHEAST AND SHOULD EFFECT PIA/SPI THIS MORNING. FOR OTHER TAF
SITES WILL JUST KEEP VCSH IN THE MORNING HOURS. ONCE THE PCPN
MOVES OUT, SKIES WILL BEGIN TO GRADUALLY SCATTER OUT. THIS WILL BE
SHORT LIVED AS ANOTHER WAVE/BOUNDARY WILL PUSH INTO THE AREA FOR
TUE NIGHT...WITH MOVE SHOWERS AND STORMS. EXCEPT FOR EARLY THIS
AFTERNOON AND THIS EVENING...ALL TAF SITES WILL BE MVFR CIGS
THROUGH THE PERIOD. LATE TONIGHT ALL TAF SITES WILL HAVE
PREDOMINATE SHOWERS WITH VCTS. WINDS WILL BE VERY GUSTY THIS
MORNING OUT OF THE SOUTH BUT THEN TAPER SOME DURING THE AFTERNOON.
THEN WILL LOOSE THE GUSTINESS DURING THE EVENING.


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...GEELHART
SHORT TERM...HJS
LONG TERM...HJS
AVIATION...AUTEN



000
FXUS63 KILX 251505
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1005 AM CDT MON MAY 25 2015

.UPDATE...
ISSUED AT 1004 AM CDT MON MAY 25 2015

A FEW SHOWERS LINGER EAST OF I-55...BUT THESE WILL BE EXITING OVER THE
NEXT COUPLE HOURS. HAVE KEPT SOME SLIGHT CHANCE POP`S EAST OF I-57
INTO THE AFTERNOON...BUT CONDITIONS SHOULD LARGELY BE DRY OVER THE
FORECAST AREA INTO THE EVENING HOURS. HIGH-RESOLUTION VISIBLE
SATELLITE IMAGERY SHOWING SKIES BECOMING PARTLY SUNNY ALREADY
NORTHWEST OF THE ILLINOIS RIVER...AND A LARGER HOLE IN THE CLOUDS
OVER NORTH CENTRAL MISSOURI SHOULD BE MOVING INTO THE FORECAST
AREA EARLY AFTERNOON PER THE RAP MODEL...ALTHOUGH THE SOUTHEAST
CWA WILL LIKELY SEE MORE PERSISTENT CLOUDS. HAVE HAD SOME GUSTS
40-45 MPH AROUND DECATUR AND CHAMPAIGN ON THE LATEST OBS...BUT THE
HRRR MODEL SHOWS THESE HIGH WINDS SHIFTING INTO INDIANA OVER THE
NEXT COUPLE HOURS.


&&

.SHORT TERM...(TODAY)
ISSUED AT 337 AM CDT MON MAY 25 2015

LOW PRESSURE CENTER STILL WELL OFF TO THE SOUTHWEST THIS
MORNING...AND A WARM FRONT DRAPED ACROSS THE IL/WI BORDER THIS
MORNING.  SCATTERED SHOWERS AND ISOLATED THUNDER STILL IN THE
REGION, BUT MAINLY CONFINED TO AREAS IN THE SOUTHEAST AS WELL AS THE
NW.  ILX SITUATED IN A GAP AS THE MAJORITY OF THE SYSTEM CONTINUES
TO LIFT NORTH AND NORTHEAST THIS MORNING.  MODELS PRETTY CONSISTENT
WITH THE MOVING OUT OF THE SYSTEM, WITH SOME SCATTERED SHOWERS
POSSIBLY AT LEAST THROUGH MIDDAY.  ISOLATED THUNDER CANNOT BE RULED
OUT WITH THE INCREASING INSTABILITY AFTER SUNRISE...BUT MAJORITY OF
THE ACTIVITY SCOURS OUT IN ALL OF THE MODELS SHORTLY AFTER MIDDAY.
LINGERED SOME SLIGHT CHANCES AFTER 18Z TO COVER AT LEAST THE
POTENTIAL FOR ACTIVITY WITH ANY REMNANT MESOSCALE BOUNDARIES.
PLENTY OF INSTABILITY STILL WITHIN THE ATMOSPHERE SHOULD IT GET THE
CHANCE TO RECOVER/RESTRATIFY.  HOWEVER, A SMALL AREA OF MIDLEVEL
RIDGING BEHIND THE SHORTWAVE THIS MORNING MAY GIVE US ENOUGH
SUBSIDENCE TO COUNTER THE EFFECTS...SO HAVE FOLLOWED SUIT WITH THE
END OF DAYTIME HEATING AND THE EARLY EVENING AND DROPPED THE POPS
BACK DOWN BEFORE 06Z. EITHER WAY...WINDS ALOFT WITH THE PASSING OF
THE SHORTWAVE AND DAYTIME MIXING WILL RESULT IN SOME GUSTY WINDS
TODAY...GUSTING 25 TO 35 MPH BY MID DAY AND SLOWLY BACKING OFF AS
THE LOW LIFTS OUT OF THE REGION.

.LONG TERM...(TONIGHT THROUGH SUNDAY)
ISSUED AT 337 AM CDT MON MAY 25 2015

FORECAST REMAINS WARM AND MUGGY WITH SEVERAL CHANCES FOR SHOWERS AND
THUNDERSTORMS THROUGHOUT. REGION DOMINATED BY SOUTHWESTERLY FLOW AND
A SERIES OF SHORT WAVES EJECTING OUT OF THE UPPER TROF IN THE SW
THROUGH THE FIRST HALF OF THE WEEK.  A BRIEF BREAK IN THE PATTERN
MID WEEK IS ONLY TEMPORARY AS TEMPS REMAIN WARM WITH PLENTY OF
MOISTURE ONLY REINFORCED BY PERIODIC SHOWERS ENHANCING THE BOUNDARY
LAYER RH. YET ANOTHER SURFACE LOW LIFTS INTO THE MIDWEST MOVING
ALONG THE SOUTHWESTERLY FLOW ALOFT ON TUESDAY.  MORE SHOWERS
ANTICIPATED FOR TUESDAY/TUESDAY NIGHT WITH THE MUGGY AIRMASS.  FRONT
ASSOCIATED WITH THIS SYSTEM WEAK AT BEST AND WILL ONLY SEE A BRIEF
SFC WIND SHIFT TO MORE WESTERLY FROM SOUTHERLY FOR WED AND WED NIGHT
ACCOMPANIED BY A BRIEF PATTERN SHIFT ALOFT.  CHANGE IS ONLY
TEMPORARY AS SOUTHERLY SFC WINDS REESTABLISH BY THE END OF THE WEEK.
WEAK SOUTHWESTERLY FLOW ALOFT SLOWLY SHIFTS TO WEAK FLOW OVERALL
GOING INTO THE WEEKEND SETTING UP CHANCES FOR PERIODIC DIURNALLY
DRIVEN CONVECTION YET AGAIN.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z TUESDAY MORNING)
ISSUED AT 654 AM CDT MON MAY 25 2015

SCATTERED SHOWERS CONTINUE TO MOVE THROUGH THE AREA THIS MORNING.
THE SHOWERS IN WEST CENTRAL ILLINOIS WILL BE LIFTING NORTH TO
NORTHEAST AND SHOULD EFFECT PIA/SPI THIS MORNING. FOR OTHER TAF
SITES WILL JUST KEEP VCSH IN THE MORNING HOURS. ONCE THE PCPN
MOVES OUT, SKIES WILL BEGIN TO GRADUALLY SCATTER OUT. THIS WILL BE
SHORT LIVED AS ANOTHER WAVE/BOUNDARY WILL PUSH INTO THE AREA FOR
TUE NIGHT...WITH MOVE SHOWERS AND STORMS. EXCEPT FOR EARLY THIS
AFTERNOON AND THIS EVENING...ALL TAF SITES WILL BE MVFR CIGS
THROUGH THE PERIOD. LATE TONIGHT ALL TAF SITES WILL HAVE
PREDOMINATE SHOWERS WITH VCTS. WINDS WILL BE VERY GUSTY THIS
MORNING OUT OF THE SOUTH BUT THEN TAPER SOME DURING THE AFTERNOON.
THEN WILL LOOSE THE GUSTINESS DURING THE EVENING.


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...GEELHART
SHORT TERM...HJS
LONG TERM...HJS
AVIATION...AUTEN



000
FXUS63 KILX 251505
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1005 AM CDT MON MAY 25 2015

.UPDATE...
ISSUED AT 1004 AM CDT MON MAY 25 2015

A FEW SHOWERS LINGER EAST OF I-55...BUT THESE WILL BE EXITING OVER THE
NEXT COUPLE HOURS. HAVE KEPT SOME SLIGHT CHANCE POP`S EAST OF I-57
INTO THE AFTERNOON...BUT CONDITIONS SHOULD LARGELY BE DRY OVER THE
FORECAST AREA INTO THE EVENING HOURS. HIGH-RESOLUTION VISIBLE
SATELLITE IMAGERY SHOWING SKIES BECOMING PARTLY SUNNY ALREADY
NORTHWEST OF THE ILLINOIS RIVER...AND A LARGER HOLE IN THE CLOUDS
OVER NORTH CENTRAL MISSOURI SHOULD BE MOVING INTO THE FORECAST
AREA EARLY AFTERNOON PER THE RAP MODEL...ALTHOUGH THE SOUTHEAST
CWA WILL LIKELY SEE MORE PERSISTENT CLOUDS. HAVE HAD SOME GUSTS
40-45 MPH AROUND DECATUR AND CHAMPAIGN ON THE LATEST OBS...BUT THE
HRRR MODEL SHOWS THESE HIGH WINDS SHIFTING INTO INDIANA OVER THE
NEXT COUPLE HOURS.


&&

.SHORT TERM...(TODAY)
ISSUED AT 337 AM CDT MON MAY 25 2015

LOW PRESSURE CENTER STILL WELL OFF TO THE SOUTHWEST THIS
MORNING...AND A WARM FRONT DRAPED ACROSS THE IL/WI BORDER THIS
MORNING.  SCATTERED SHOWERS AND ISOLATED THUNDER STILL IN THE
REGION, BUT MAINLY CONFINED TO AREAS IN THE SOUTHEAST AS WELL AS THE
NW.  ILX SITUATED IN A GAP AS THE MAJORITY OF THE SYSTEM CONTINUES
TO LIFT NORTH AND NORTHEAST THIS MORNING.  MODELS PRETTY CONSISTENT
WITH THE MOVING OUT OF THE SYSTEM, WITH SOME SCATTERED SHOWERS
POSSIBLY AT LEAST THROUGH MIDDAY.  ISOLATED THUNDER CANNOT BE RULED
OUT WITH THE INCREASING INSTABILITY AFTER SUNRISE...BUT MAJORITY OF
THE ACTIVITY SCOURS OUT IN ALL OF THE MODELS SHORTLY AFTER MIDDAY.
LINGERED SOME SLIGHT CHANCES AFTER 18Z TO COVER AT LEAST THE
POTENTIAL FOR ACTIVITY WITH ANY REMNANT MESOSCALE BOUNDARIES.
PLENTY OF INSTABILITY STILL WITHIN THE ATMOSPHERE SHOULD IT GET THE
CHANCE TO RECOVER/RESTRATIFY.  HOWEVER, A SMALL AREA OF MIDLEVEL
RIDGING BEHIND THE SHORTWAVE THIS MORNING MAY GIVE US ENOUGH
SUBSIDENCE TO COUNTER THE EFFECTS...SO HAVE FOLLOWED SUIT WITH THE
END OF DAYTIME HEATING AND THE EARLY EVENING AND DROPPED THE POPS
BACK DOWN BEFORE 06Z. EITHER WAY...WINDS ALOFT WITH THE PASSING OF
THE SHORTWAVE AND DAYTIME MIXING WILL RESULT IN SOME GUSTY WINDS
TODAY...GUSTING 25 TO 35 MPH BY MID DAY AND SLOWLY BACKING OFF AS
THE LOW LIFTS OUT OF THE REGION.

.LONG TERM...(TONIGHT THROUGH SUNDAY)
ISSUED AT 337 AM CDT MON MAY 25 2015

FORECAST REMAINS WARM AND MUGGY WITH SEVERAL CHANCES FOR SHOWERS AND
THUNDERSTORMS THROUGHOUT. REGION DOMINATED BY SOUTHWESTERLY FLOW AND
A SERIES OF SHORT WAVES EJECTING OUT OF THE UPPER TROF IN THE SW
THROUGH THE FIRST HALF OF THE WEEK.  A BRIEF BREAK IN THE PATTERN
MID WEEK IS ONLY TEMPORARY AS TEMPS REMAIN WARM WITH PLENTY OF
MOISTURE ONLY REINFORCED BY PERIODIC SHOWERS ENHANCING THE BOUNDARY
LAYER RH. YET ANOTHER SURFACE LOW LIFTS INTO THE MIDWEST MOVING
ALONG THE SOUTHWESTERLY FLOW ALOFT ON TUESDAY.  MORE SHOWERS
ANTICIPATED FOR TUESDAY/TUESDAY NIGHT WITH THE MUGGY AIRMASS.  FRONT
ASSOCIATED WITH THIS SYSTEM WEAK AT BEST AND WILL ONLY SEE A BRIEF
SFC WIND SHIFT TO MORE WESTERLY FROM SOUTHERLY FOR WED AND WED NIGHT
ACCOMPANIED BY A BRIEF PATTERN SHIFT ALOFT.  CHANGE IS ONLY
TEMPORARY AS SOUTHERLY SFC WINDS REESTABLISH BY THE END OF THE WEEK.
WEAK SOUTHWESTERLY FLOW ALOFT SLOWLY SHIFTS TO WEAK FLOW OVERALL
GOING INTO THE WEEKEND SETTING UP CHANCES FOR PERIODIC DIURNALLY
DRIVEN CONVECTION YET AGAIN.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z TUESDAY MORNING)
ISSUED AT 654 AM CDT MON MAY 25 2015

SCATTERED SHOWERS CONTINUE TO MOVE THROUGH THE AREA THIS MORNING.
THE SHOWERS IN WEST CENTRAL ILLINOIS WILL BE LIFTING NORTH TO
NORTHEAST AND SHOULD EFFECT PIA/SPI THIS MORNING. FOR OTHER TAF
SITES WILL JUST KEEP VCSH IN THE MORNING HOURS. ONCE THE PCPN
MOVES OUT, SKIES WILL BEGIN TO GRADUALLY SCATTER OUT. THIS WILL BE
SHORT LIVED AS ANOTHER WAVE/BOUNDARY WILL PUSH INTO THE AREA FOR
TUE NIGHT...WITH MOVE SHOWERS AND STORMS. EXCEPT FOR EARLY THIS
AFTERNOON AND THIS EVENING...ALL TAF SITES WILL BE MVFR CIGS
THROUGH THE PERIOD. LATE TONIGHT ALL TAF SITES WILL HAVE
PREDOMINATE SHOWERS WITH VCTS. WINDS WILL BE VERY GUSTY THIS
MORNING OUT OF THE SOUTH BUT THEN TAPER SOME DURING THE AFTERNOON.
THEN WILL LOOSE THE GUSTINESS DURING THE EVENING.


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...GEELHART
SHORT TERM...HJS
LONG TERM...HJS
AVIATION...AUTEN



000
FXUS63 KLOT 251413
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
913 AM CDT MON MAY 25 2015

.UPDATE...

COMPACT NEGATIVELY TILTED TROUGH AXIS IS SLIDING NORTHEAST THROUGH
IOWA AND WESTERN ILLINOIS. EASTERN EDGE OF THE TROUGH WILL MOVE
THROUGH NORTHEAST ILLINOIS THIS MORNING. NOTED UPTICK IN SHOWER
ACTIVITY ASSOCIATED WITH THIS WAVE IS PRODUCING MORE ORGANIZED BUT
STILL LARGELY SCATTERED SHOWERS. STILL TRACKING THIS FEATURE WILL
BRING THE BEST CHANCE FOR SOME BRIEF DOWNPOURS IN THE COMING
HOURS...AND THESE WILL SPREAD INTO THE WEST METRO AREA IN THE NEXT
HOUR...SPREADING INTO CHICAGOLAND SHORTLY THERE AFTER. THE CLOUDS
PRODUCING THE SHOWER ACTIVITY ARE SHALLOW AND MID LEVEL LAPSE
RATES ARE SUBPAR...THUS THUNDER SHOULD BE LIMITED AT BEST. SOME
WEAK INSTABILITY IS NOTED SOUTH OF I-80 WHICH DOES NOT PRECLUDE AN
ISOLATED STRIKE IN ANY STRONGER ACTIVITY.

REGARDING WINDS...WITH THE BROKEN TO OVERCAST LOW CLOUD
DECK...MIXING IS BEING LIMITED AND GETING GUSTS TO AROUND 30 KT OR
SO. ANY STRONGER GUSTS WOULD BE IN THE NEXT HOUR BEFORE A RAPID
DROP OFF LATER THIS MORNING.

KMD

&&

.SHORT TERM...
345 AM CDT

THROUGH MONDAY NIGHT...
FOR THE REMAINDER OF THE NIGHT AND INTO MONDAY MORNING...PCPN
CHANCES CONTINUE TO WANE AS LATEST RADAR TRENDS ONLY SHOW SOME SCT
SHRA WHICH ARE DECREASING IN INTENSITY.  IN SPITE OF DEWPOINTS IN
THE LOW 60S...AND A STRONG LOW LEVEL JET...50 KT AT 925 MB...THERE
IS AN ELEMENT LACKING WHICH IS SEEMS TO BE PREVENTING THE
MAINTENANCE OF SHRA/TSRA OVER NERN IL/NWRN IN.  THE MAIN MISSING
ELEMENTS IS FORCING.  THE SFC AND UPPER LEVEL LOW ARE WAY TO THE
WEST...OVER THE NRN PLAINS. THE SHORTWAVE CLIMBING UP THE NWRN
PERIPHERY OF THE HIGH AMPLITUDE RIDGE IS BEING SLOWED BY THE HIGH
AMPLITUDE...AND IS BEING FORCED TO A MORE WLY TRACK THROUGH THE
UPPER MISSISSIPPI VALLEY THAN PREVIOUSLY ANTICIPATED.  SO...FOR THE
REMAINDER OF THE OVERNIGHT HOURS AND THE DAYTIME HOURS MONDAY...HAVE
BACK OF TO ISOLD-SCT SHRA.  WILL KEEP ISOLD TS MENTION FOR THE LATE
MORNING HOURS...THROUGH AROUND NOON...WITH THE DAYTIME HEATING...BUT
CONFIDENCE IN ANY TS IS RATHER LOW AT THIS TIME.  BY THIS
AFTERNOON...A MID LEVEL DRY SLOT IS EXPECTED TO MOVE ACROSS THE
REGION...FURTHER LIMITING PCPN CHANCES AND IT IS QUITE LIKELY THAT
THE REGION WILL REMAIN DRY THROUGH THE DAY.  HOWEVER...WHILE THE
PCPN CHANCES ARE DIMINISHING...THE LIKELIHOOD OF STRONG WINDS IS
STILL A CONCERN.  WITH THE DIMINISHING PCPN CHANCES...LESS SKY COVER
THAN PREVIOUSLY ANTICIPATED IS ALSO POSSIBLE.  A STRONG SWLY
PRESSURE GRADIENT IS SETTING UP ACROSS THE REGION BETWEEN SFC
RIDGING ACROSS THE SERN CONUS AND AND LOW PRESSURE FROM THE UPPER
MISSISSIPPI VALLEY TO THE WESTERN PLAINS.  THE STRONG GRADIENT WILL
HELP DRIVE THE SFC WINDS AND THE DIMINISHING CLOUD COVER COULD HELP
ENHANCE DEEP LAYER MIXING...TAPPING STRONGER WINDS ALOFT.  SUSTAINED
25-25 MPH WINDS ARE LIKELY WITH GUSTS OF 30-35 MPH.
ALSO...PERSISTENT WARM/MOIST ADVECTION AT THE SFC WILL BRING
TEMPERATURES INTO THE LOW TO MIDDLE 80S WITH DEWPOINTS IN THE LOWER
60S.

FOR MONDAY NIGHT...THE BREEZY CONDITIONS WILL PERSIST INTO THE AS
THERE SHOULD BE LITTLE CHANGE TO THE SFC AND UPPER LEVEL PATTERNS.
THE UPPER RIDGE WILL LOSE A LITTLE AMPLITUDE AS SHORT WAVE ENERGY
OVERTOPS THE RIDGE...BUT GENERAL TROUGHING WILL PERSIST ACROSS THE
UPPER MISSISSIPPI VALLEY THROUGH THE CENTRAL PLAINS.  THE NEXT
CHANCE FOR PCPN WILL HOLD OFF UNTIL LATE TONIGHT/EARLY TUESDAY
MORNING AND THE NEXT SHORTWAVE LIFTS OUT OF THE SRN PLAINS AND INTO
THE MIDDLE MISSISSIPPI VALLEY.  AMPLE LOW LEVEL MOISTURE WILL
ALREADY BE IN PLACE SO IT WILL JUST A MATTER OF WHEN THE FORCING
WILL GET HERE.  AGAIN...THERE IS SOME CONCERN THAT THE FORCING WILL
BE TO THE WEST...WITH THE SHORTWAVE TRACKING THROUGH THE MIDDLE
MISSISSIPPI VALLEY AND INTO WI.  SO...WILL CARRY CHANCE POPS FOR THE
REGION...WITH LIKELY POPS APPROACHING THE PONTIAC AREA BY EARLY
TUESDAY MORNING.  THE PERSISTENT WARM/MOIST ADVECTIVE PATTERN AND
BREEZY CONDITIONS SHOULD KEEP TEMPERATURES FROM DROPPING OFF
SIGNIFICANTLY OVERNIGHT AND LOWS SHOULD BE IN THE MIDDLE TO UPPER
60S.

KREIN

&&

.LONG TERM...
239 AM CDT

TUESDAY THROUGH SUNDAY...

TUESDAY THROUGH WEDNESDAY...
500MB TROUGH AXIS WILL SLOWLY PIVOT EAST ACROSS THE CENTRAL PLAINS
INTO THE MID-MISSOURI VALLEY TUE...WITH A SFC WAVE SLIDING NORTH
ACROSS IOWA INTO CENTRAL WISC LATE TUE. THE SFC FEATURE IS NOT
EXPECTED TO BE STRONG...HOWEVER THE GRADIENT DOES TIGHTEN WITH
MODEST HEIGHT FALLS IN THE LOWEST LAYERS OF THE ATMOSPHERE. SOME
INSTABILITY DOES REMAIN ALONG WITH RELATIVELY MOIST SFC CONDS AS
DEW PTS WILL REMAIN IN THE UPR 50S/LOW 60S. PWAT VALUES WILL ALSO
HOVER JUST OVER 1 INCH...WHICH IS SEASONAL. WILL HOLD ONTO MENTION
OF RAIN AND THUNDER...BUT COULD SEE THIS MAINLY FOCUSED IN THE TUE
MORNING TIMEFRAME.

WITH CONSIDERABLE SOLAR SHIELDING PROGGED FOR TUE...TEMPS MAY
STRUGGLE TO WARM BEYOND THE MID/UPR 70S. BUT WITH GUIDANCE HINTING
AT A DRY SLOT LIFTING NORTHEAST ACROSS THE REGION TUE EVE...THIS
COULD INTRODUCE SOME EROSION TO THE CLOUD COVER IN THE AFTN HOURS
TUE AND ALLOW SOME SFC HEATING TO OCCUR AND PUSH TEMPS TO ARND 80.

GUIDANCE LIFTS THE DRY SLOT OVERHEAD LATE TUE NGT...WITH THE 500MB
TROUGH AXIS ARRIVING ARND DAYBREAK WED AND LIFTING EAST ACROSS LOWER
MICHIGAN. THIS WILL BRING DRY ONLY SLIGHT CHANCE POPS AS WEAK SFC
RIDGING BEGINS TO NUDGE EAST ACROSS THE MISSOURI VALLEY TOWARDS THE
FORECAST AREA MIDDAY WED. IT IS POSSIBLE THAT ENOUGH DRY AIR
INFLUENCE COULD ALLOW FOR REMOVAL OF THE SLIGHT CHANCE POPS WED
AFTN. THERMAL TROUGH LAGS BEHIND THE FRONTAL BOUNDARY WED...SO TEMPS
COULD STILL WARM BACK TO ARND 80 AND PERHAPS THE LOW 80S IN THE
SOUTHERN CWFA.

THURSDAY THROUGH SUNDAY...
ANTI-CYCLONIC FLOW ARRIVES THUR WITH AT LEAST ONE PERIOD OF DRY
WEATHER EXPECTED FOR NORTHERN IL/NORTHWEST IN. ONLY A COUPLE
ENSEMBLE MEMBERS CONTINUE TO PROG POPS ALONG THE SOUTHERN FORECAST
AREA THUR...BUT COULD SEE THIS TRENDING DRY IN THE NEXT FEW
SOLUTIONS. WITH WARM TEMPS ALOFT EXPECTED THUR AND THIN CLOUD
COVER...THUR HIGHS COULD PEAK IN THE LOW 80S.

THEN FOCUS TURNS TOWARDS THE UPCOMING WEEKEND AND A PATTERN SHIFT
AWAY FROM THE WARM/HUMID CONDITIONS. ENSEMBLES SHOW MINIMAL SPREAD
IN THE LATE WEEK PERIODS...WITH THE UPSTREAM RIDGE OVER
ALASKA/WESTERN CANADA AND A DOWNSTREAM MID-LVL RIDGE ACROSS THE
SOUTHEAST CONUS. BOTH OF THESE FEATURES IN TIME BEGIN TO
WEAKEN...WITH THE LONGWAVE PATTERN TRANSITIONING INTO A SEMI-ZONAL
ORIENTATION BY THE SECOND HALF OF THE WEEKEND.

OPER GUIDANCE HAS BEEN CONSISTENT WITH PROGGING A ROBUST 500MB
TROUGH TO SLIDE SOUTH FROM CENTRAL CANADA FRI...ALONG WITH A STRONG
CANADIAN SFC RIDGE ON IT/S HEELS. WITH A CHANNEL OF MOISTURE
REMAINING ACROSS THE SOUTHERN PLAINS STRETCHING NORTHEAST THROUGH
THE UPPER MIDWEST...THIS BOUNDARY WILL BECOME ACTIVE WITH A SFC WAVE
DEVELOPING ACROSS THE SOUTHERN PLAINS. THIS LOW WILL THEN LIFT
NORTHEAST TOWARDS THE CWFA FRI WITH A COLD FRONT ARRIVING ACROSS THE
FORECAST AREA SAT. WINDS LOOK TO SHIFT TO THE NORTH...WITH MUCH
COOLER AIR SLIDING SOUTH AND LIKELY KNOCKING TEMPS BACK TO SUB-
SEASONAL CONDS IN THE UPR 60S/NEAR 70 DEGREE RANGE SAT/SUN. IF
NORTHEAST WINDS MATERIALIZE...NEXT WEEKEND AREAS ADJACENT TO LAKE
MICHIGAN ALONG THE IL/IN SHORELINE COULD BE LOCKED IN THE UPR 50S TO
LOW 60S FOR HIGHS WITH A COLD FLOW OFF OF LAKE MICHIGAN.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 14Z...

* GUSTY SOUTH/SOUTHWEST WINDS THROUGH MIDDAY.

* CHANCE OF -RA THIS MORNING.

* MVFR CEILINGS THIS MORNING.

* CHANCE SHRA/TSRA LATE TONIGHT THROUGH TOMORROW.

KREIN/RODRIGUEZ

//DISCUSSION...UPDATED 12Z...

MAIN CONCERN FOR TODAY WILL BE STRONG...GUSTY SOUTH WINDS. AS OF
11Z THIS MORNING...WINDS ARE ALREADY GUSTING TO 25-30KT AND EXPECT
THAT WITH DEEPER MIXING LATER THIS MORNING...SHOULD BE ABLE TO TAP
INTO A 50 KT LOW LEVEL JET TO MIX DOWN GUSTS TO 35 KT OR EVEN
SLIGHTLY HIGHER. THE STRONG LOW LEVEL JET SHOULD MOVE OFF TO THE
EAST BY EARLY AFTERNOON...SO WHILE WINDS SHOULD STILL BE STRONG
AND GUSTY...PEAK GUSTS SHOULD LOWER TO ARND 25KT.

WITH THE PERSISTENT FETCH OF LOW LEVEL MOISTURE INTO THE
REGION...A LAYER OF MVFR STRATOCU HAS OVERSPREAD THE REGION.
EXPECT THAT BASES SHOULD NOT LOWER MUCH LESS THAT 1800FT AGL.
THERE IS SOME UNCERTAINTY AS TO THE DURATION OF THE MVFR CLOUD
LAYER...BUT WITH LITTLE CHANGE TO THE OVERALL PATTERN THROUGH THE
DAY...THERE IS A CHANCE THAT THE MVFR CIGS COULD HANG IN THROUGH
MUCH OF THE DAY. HOWEVER...THERE IS ALSO A CHANCE THAT STRONGER
MIXING IN THE AFTERNOON HOURS COULD ALLOW FOR THE MVFR DECK TO
SCATTER OUT.

LATEST RADAR TRENDS INDICATE THAT AN AREA OF SHRA LIFTING NEWD
FROM CNTRL IL INTO INDIANA. THE TRAJECTORY OF THE PCPN AREA SHOULD
KEEP THE BULK OF THE PCPN EAST AND SOUTH OF GYY...THOUGH A FEW SCT
SHRA AREA NOT OUT OF THE QUESTION. ALSO...SOME SHRA ASSOCIATED
WITH A MID LEVEL IMPULSE LIFTING NORTH THROUGH IOWA AND INTO WRN
WI IS GENERATING SCT SHRA AS WELL. IT IS ALSO POSSIBLE THAT RFD
COULD SEE A FEW SHRA THIS MORNING...BUT THE PROBABILITY IS TOO LOW
TO INCLUDE IN THE TAF AS THE LATEST RADAR TRENDS INDICATE A
WEAKENING TREND THERE.

A SECONDARY LOW IS EXPECTED TO DEVELOP OVER THE UPPER MISSOURI
VALLEY THIS EVENING...KEEPING A MODEST PRESSURE GRADIENT OVER THE
REGION. SO MODERATE...GUSTY WINDS SHOULD PERSIST WELL INTO
TONIGHT. ANOTHER STRONG MID LEVEL IMPULSE IS EXPECTED TO TRACK
THROUGH THE MIDDLE MISSISSIPPI VALLEY AND INTO WISCONSIN LATE
TONIGHT...BRINGING A RENEWED CHANCE FOR SHRA/TSRA TO THE REGION
LATE TONIGHT AND TOMORROW.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 14Z...

* MEDIUM TO HIGH CONFIDENCE IN WIND TRENDS.

* HIGH CONFIDENCE WITH -RA TRENDS THIS MORNING.

* MEDIUM HIGH CONFIDENCE IN CIG TRENDS.

* MEDIUM CONFIDENCE IN PCPN TIMING LATE TONIGHT.

KREIN/RODRIGUEZ

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/TSRA LATE. SOUTHEAST WINDS.

FRIDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. SOUTHWEST WINDS
BECOMING NORTHEAST OVERNIGHT.

SATURDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. NORTHEAST
WINDS.

SUNDAY...CHANCE TSRA. MVFR POSSIBLE. NORTHEAST WINDS.

KREIN

&&

.MARINE...
304 AM CDT

LOW PRESSURE WILL BE STEADILY LIFTING NORTH ACROSS THE MISSOURI
VALLEY THIS MORNING...REACHING LAKE SUPERIOR BY THIS EVENING AND
CONTINUING TO SLIDE EAST/NORTHEAST TOWARDS QUEBEC BY TUESDAY
MORNING. A FRONTAL BOUNDARY WILL REMAIN OVER THE FAR NORTHERN
PORTIONS OF LAKE MICHIGAN. MEANWHILE GUSTY SOUTHERLY WINDS ARE
EXPECTED TO INCREASE THIS MORNING...WITH OCCASIONAL GALES FOR THE
NEARSHORE WATERS OF IL/IN. ACROSS THE OPEN WATERS...EXPECT THE
WARM/MOIST AIR TO STRUGGLE TO REACH THE SFC OF THE LAKE WITH SOME
DEGREE OF LAKE STABILITY. WAVES WILL STEADILY BUILD ACROSS THE
NORTHERN HALF OF THE LAKE AS A RESULT OF THE LONG FETCH. STILL
FEEL THAT GUSTS WILL REACH 30KT ACROSS THE LAKE...HOWEVER
CONFIDENCE HAS DIMINISHED SLIGHTLY AS NEW GUIDANCE HAS BECOME A
LITTLE LESS WITH THE WIND FIELDS. NONETHELESS...WAVES FOR THE
NORTHERN HALF OF THE LAKE WILL LIKELY TOP OUT IN THE 4 TO 7 FT
RANGE WITH OCCASIONAL WAVES REACHING 9 FT THIS AFTERNOON/EVENING.

THE GRADIENT QUICKLY DIMINISHES THIS EVENING...BUT EXPECT
SOUTHERLY WINDS TO PERSIST. THIS WILL ALLOW WAVES TO SUBSIDE TO 3
TO 5 FT. ANOTHER LOW WILL ARRIVE TUE...WITH WINDS NUDGING BACK UP
HOWEVER WARM AIR WILL CONTINUE TO FLOW ACROSS THE LAKE AND COULD
FURTHER ENHANCE THE LAKE STABILITY AND KEEP WAVES FROM BUILDING TO
LARGE.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...NEARSHORE WATERS UNTIL 3
     PM MONDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...3 PM MONDAY TO 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

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000
FXUS63 KLOT 251413
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
913 AM CDT MON MAY 25 2015

.UPDATE...

COMPACT NEGATIVELY TILTED TROUGH AXIS IS SLIDING NORTHEAST THROUGH
IOWA AND WESTERN ILLINOIS. EASTERN EDGE OF THE TROUGH WILL MOVE
THROUGH NORTHEAST ILLINOIS THIS MORNING. NOTED UPTICK IN SHOWER
ACTIVITY ASSOCIATED WITH THIS WAVE IS PRODUCING MORE ORGANIZED BUT
STILL LARGELY SCATTERED SHOWERS. STILL TRACKING THIS FEATURE WILL
BRING THE BEST CHANCE FOR SOME BRIEF DOWNPOURS IN THE COMING
HOURS...AND THESE WILL SPREAD INTO THE WEST METRO AREA IN THE NEXT
HOUR...SPREADING INTO CHICAGOLAND SHORTLY THERE AFTER. THE CLOUDS
PRODUCING THE SHOWER ACTIVITY ARE SHALLOW AND MID LEVEL LAPSE
RATES ARE SUBPAR...THUS THUNDER SHOULD BE LIMITED AT BEST. SOME
WEAK INSTABILITY IS NOTED SOUTH OF I-80 WHICH DOES NOT PRECLUDE AN
ISOLATED STRIKE IN ANY STRONGER ACTIVITY.

REGARDING WINDS...WITH THE BROKEN TO OVERCAST LOW CLOUD
DECK...MIXING IS BEING LIMITED AND GETING GUSTS TO AROUND 30 KT OR
SO. ANY STRONGER GUSTS WOULD BE IN THE NEXT HOUR BEFORE A RAPID
DROP OFF LATER THIS MORNING.

KMD

&&

.SHORT TERM...
345 AM CDT

THROUGH MONDAY NIGHT...
FOR THE REMAINDER OF THE NIGHT AND INTO MONDAY MORNING...PCPN
CHANCES CONTINUE TO WANE AS LATEST RADAR TRENDS ONLY SHOW SOME SCT
SHRA WHICH ARE DECREASING IN INTENSITY.  IN SPITE OF DEWPOINTS IN
THE LOW 60S...AND A STRONG LOW LEVEL JET...50 KT AT 925 MB...THERE
IS AN ELEMENT LACKING WHICH IS SEEMS TO BE PREVENTING THE
MAINTENANCE OF SHRA/TSRA OVER NERN IL/NWRN IN.  THE MAIN MISSING
ELEMENTS IS FORCING.  THE SFC AND UPPER LEVEL LOW ARE WAY TO THE
WEST...OVER THE NRN PLAINS. THE SHORTWAVE CLIMBING UP THE NWRN
PERIPHERY OF THE HIGH AMPLITUDE RIDGE IS BEING SLOWED BY THE HIGH
AMPLITUDE...AND IS BEING FORCED TO A MORE WLY TRACK THROUGH THE
UPPER MISSISSIPPI VALLEY THAN PREVIOUSLY ANTICIPATED.  SO...FOR THE
REMAINDER OF THE OVERNIGHT HOURS AND THE DAYTIME HOURS MONDAY...HAVE
BACK OF TO ISOLD-SCT SHRA.  WILL KEEP ISOLD TS MENTION FOR THE LATE
MORNING HOURS...THROUGH AROUND NOON...WITH THE DAYTIME HEATING...BUT
CONFIDENCE IN ANY TS IS RATHER LOW AT THIS TIME.  BY THIS
AFTERNOON...A MID LEVEL DRY SLOT IS EXPECTED TO MOVE ACROSS THE
REGION...FURTHER LIMITING PCPN CHANCES AND IT IS QUITE LIKELY THAT
THE REGION WILL REMAIN DRY THROUGH THE DAY.  HOWEVER...WHILE THE
PCPN CHANCES ARE DIMINISHING...THE LIKELIHOOD OF STRONG WINDS IS
STILL A CONCERN.  WITH THE DIMINISHING PCPN CHANCES...LESS SKY COVER
THAN PREVIOUSLY ANTICIPATED IS ALSO POSSIBLE.  A STRONG SWLY
PRESSURE GRADIENT IS SETTING UP ACROSS THE REGION BETWEEN SFC
RIDGING ACROSS THE SERN CONUS AND AND LOW PRESSURE FROM THE UPPER
MISSISSIPPI VALLEY TO THE WESTERN PLAINS.  THE STRONG GRADIENT WILL
HELP DRIVE THE SFC WINDS AND THE DIMINISHING CLOUD COVER COULD HELP
ENHANCE DEEP LAYER MIXING...TAPPING STRONGER WINDS ALOFT.  SUSTAINED
25-25 MPH WINDS ARE LIKELY WITH GUSTS OF 30-35 MPH.
ALSO...PERSISTENT WARM/MOIST ADVECTION AT THE SFC WILL BRING
TEMPERATURES INTO THE LOW TO MIDDLE 80S WITH DEWPOINTS IN THE LOWER
60S.

FOR MONDAY NIGHT...THE BREEZY CONDITIONS WILL PERSIST INTO THE AS
THERE SHOULD BE LITTLE CHANGE TO THE SFC AND UPPER LEVEL PATTERNS.
THE UPPER RIDGE WILL LOSE A LITTLE AMPLITUDE AS SHORT WAVE ENERGY
OVERTOPS THE RIDGE...BUT GENERAL TROUGHING WILL PERSIST ACROSS THE
UPPER MISSISSIPPI VALLEY THROUGH THE CENTRAL PLAINS.  THE NEXT
CHANCE FOR PCPN WILL HOLD OFF UNTIL LATE TONIGHT/EARLY TUESDAY
MORNING AND THE NEXT SHORTWAVE LIFTS OUT OF THE SRN PLAINS AND INTO
THE MIDDLE MISSISSIPPI VALLEY.  AMPLE LOW LEVEL MOISTURE WILL
ALREADY BE IN PLACE SO IT WILL JUST A MATTER OF WHEN THE FORCING
WILL GET HERE.  AGAIN...THERE IS SOME CONCERN THAT THE FORCING WILL
BE TO THE WEST...WITH THE SHORTWAVE TRACKING THROUGH THE MIDDLE
MISSISSIPPI VALLEY AND INTO WI.  SO...WILL CARRY CHANCE POPS FOR THE
REGION...WITH LIKELY POPS APPROACHING THE PONTIAC AREA BY EARLY
TUESDAY MORNING.  THE PERSISTENT WARM/MOIST ADVECTIVE PATTERN AND
BREEZY CONDITIONS SHOULD KEEP TEMPERATURES FROM DROPPING OFF
SIGNIFICANTLY OVERNIGHT AND LOWS SHOULD BE IN THE MIDDLE TO UPPER
60S.

KREIN

&&

.LONG TERM...
239 AM CDT

TUESDAY THROUGH SUNDAY...

TUESDAY THROUGH WEDNESDAY...
500MB TROUGH AXIS WILL SLOWLY PIVOT EAST ACROSS THE CENTRAL PLAINS
INTO THE MID-MISSOURI VALLEY TUE...WITH A SFC WAVE SLIDING NORTH
ACROSS IOWA INTO CENTRAL WISC LATE TUE. THE SFC FEATURE IS NOT
EXPECTED TO BE STRONG...HOWEVER THE GRADIENT DOES TIGHTEN WITH
MODEST HEIGHT FALLS IN THE LOWEST LAYERS OF THE ATMOSPHERE. SOME
INSTABILITY DOES REMAIN ALONG WITH RELATIVELY MOIST SFC CONDS AS
DEW PTS WILL REMAIN IN THE UPR 50S/LOW 60S. PWAT VALUES WILL ALSO
HOVER JUST OVER 1 INCH...WHICH IS SEASONAL. WILL HOLD ONTO MENTION
OF RAIN AND THUNDER...BUT COULD SEE THIS MAINLY FOCUSED IN THE TUE
MORNING TIMEFRAME.

WITH CONSIDERABLE SOLAR SHIELDING PROGGED FOR TUE...TEMPS MAY
STRUGGLE TO WARM BEYOND THE MID/UPR 70S. BUT WITH GUIDANCE HINTING
AT A DRY SLOT LIFTING NORTHEAST ACROSS THE REGION TUE EVE...THIS
COULD INTRODUCE SOME EROSION TO THE CLOUD COVER IN THE AFTN HOURS
TUE AND ALLOW SOME SFC HEATING TO OCCUR AND PUSH TEMPS TO ARND 80.

GUIDANCE LIFTS THE DRY SLOT OVERHEAD LATE TUE NGT...WITH THE 500MB
TROUGH AXIS ARRIVING ARND DAYBREAK WED AND LIFTING EAST ACROSS LOWER
MICHIGAN. THIS WILL BRING DRY ONLY SLIGHT CHANCE POPS AS WEAK SFC
RIDGING BEGINS TO NUDGE EAST ACROSS THE MISSOURI VALLEY TOWARDS THE
FORECAST AREA MIDDAY WED. IT IS POSSIBLE THAT ENOUGH DRY AIR
INFLUENCE COULD ALLOW FOR REMOVAL OF THE SLIGHT CHANCE POPS WED
AFTN. THERMAL TROUGH LAGS BEHIND THE FRONTAL BOUNDARY WED...SO TEMPS
COULD STILL WARM BACK TO ARND 80 AND PERHAPS THE LOW 80S IN THE
SOUTHERN CWFA.

THURSDAY THROUGH SUNDAY...
ANTI-CYCLONIC FLOW ARRIVES THUR WITH AT LEAST ONE PERIOD OF DRY
WEATHER EXPECTED FOR NORTHERN IL/NORTHWEST IN. ONLY A COUPLE
ENSEMBLE MEMBERS CONTINUE TO PROG POPS ALONG THE SOUTHERN FORECAST
AREA THUR...BUT COULD SEE THIS TRENDING DRY IN THE NEXT FEW
SOLUTIONS. WITH WARM TEMPS ALOFT EXPECTED THUR AND THIN CLOUD
COVER...THUR HIGHS COULD PEAK IN THE LOW 80S.

THEN FOCUS TURNS TOWARDS THE UPCOMING WEEKEND AND A PATTERN SHIFT
AWAY FROM THE WARM/HUMID CONDITIONS. ENSEMBLES SHOW MINIMAL SPREAD
IN THE LATE WEEK PERIODS...WITH THE UPSTREAM RIDGE OVER
ALASKA/WESTERN CANADA AND A DOWNSTREAM MID-LVL RIDGE ACROSS THE
SOUTHEAST CONUS. BOTH OF THESE FEATURES IN TIME BEGIN TO
WEAKEN...WITH THE LONGWAVE PATTERN TRANSITIONING INTO A SEMI-ZONAL
ORIENTATION BY THE SECOND HALF OF THE WEEKEND.

OPER GUIDANCE HAS BEEN CONSISTENT WITH PROGGING A ROBUST 500MB
TROUGH TO SLIDE SOUTH FROM CENTRAL CANADA FRI...ALONG WITH A STRONG
CANADIAN SFC RIDGE ON IT/S HEELS. WITH A CHANNEL OF MOISTURE
REMAINING ACROSS THE SOUTHERN PLAINS STRETCHING NORTHEAST THROUGH
THE UPPER MIDWEST...THIS BOUNDARY WILL BECOME ACTIVE WITH A SFC WAVE
DEVELOPING ACROSS THE SOUTHERN PLAINS. THIS LOW WILL THEN LIFT
NORTHEAST TOWARDS THE CWFA FRI WITH A COLD FRONT ARRIVING ACROSS THE
FORECAST AREA SAT. WINDS LOOK TO SHIFT TO THE NORTH...WITH MUCH
COOLER AIR SLIDING SOUTH AND LIKELY KNOCKING TEMPS BACK TO SUB-
SEASONAL CONDS IN THE UPR 60S/NEAR 70 DEGREE RANGE SAT/SUN. IF
NORTHEAST WINDS MATERIALIZE...NEXT WEEKEND AREAS ADJACENT TO LAKE
MICHIGAN ALONG THE IL/IN SHORELINE COULD BE LOCKED IN THE UPR 50S TO
LOW 60S FOR HIGHS WITH A COLD FLOW OFF OF LAKE MICHIGAN.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 14Z...

* GUSTY SOUTH/SOUTHWEST WINDS THROUGH MIDDAY.

* CHANCE OF -RA THIS MORNING.

* MVFR CEILINGS THIS MORNING.

* CHANCE SHRA/TSRA LATE TONIGHT THROUGH TOMORROW.

KREIN/RODRIGUEZ

//DISCUSSION...UPDATED 12Z...

MAIN CONCERN FOR TODAY WILL BE STRONG...GUSTY SOUTH WINDS. AS OF
11Z THIS MORNING...WINDS ARE ALREADY GUSTING TO 25-30KT AND EXPECT
THAT WITH DEEPER MIXING LATER THIS MORNING...SHOULD BE ABLE TO TAP
INTO A 50 KT LOW LEVEL JET TO MIX DOWN GUSTS TO 35 KT OR EVEN
SLIGHTLY HIGHER. THE STRONG LOW LEVEL JET SHOULD MOVE OFF TO THE
EAST BY EARLY AFTERNOON...SO WHILE WINDS SHOULD STILL BE STRONG
AND GUSTY...PEAK GUSTS SHOULD LOWER TO ARND 25KT.

WITH THE PERSISTENT FETCH OF LOW LEVEL MOISTURE INTO THE
REGION...A LAYER OF MVFR STRATOCU HAS OVERSPREAD THE REGION.
EXPECT THAT BASES SHOULD NOT LOWER MUCH LESS THAT 1800FT AGL.
THERE IS SOME UNCERTAINTY AS TO THE DURATION OF THE MVFR CLOUD
LAYER...BUT WITH LITTLE CHANGE TO THE OVERALL PATTERN THROUGH THE
DAY...THERE IS A CHANCE THAT THE MVFR CIGS COULD HANG IN THROUGH
MUCH OF THE DAY. HOWEVER...THERE IS ALSO A CHANCE THAT STRONGER
MIXING IN THE AFTERNOON HOURS COULD ALLOW FOR THE MVFR DECK TO
SCATTER OUT.

LATEST RADAR TRENDS INDICATE THAT AN AREA OF SHRA LIFTING NEWD
FROM CNTRL IL INTO INDIANA. THE TRAJECTORY OF THE PCPN AREA SHOULD
KEEP THE BULK OF THE PCPN EAST AND SOUTH OF GYY...THOUGH A FEW SCT
SHRA AREA NOT OUT OF THE QUESTION. ALSO...SOME SHRA ASSOCIATED
WITH A MID LEVEL IMPULSE LIFTING NORTH THROUGH IOWA AND INTO WRN
WI IS GENERATING SCT SHRA AS WELL. IT IS ALSO POSSIBLE THAT RFD
COULD SEE A FEW SHRA THIS MORNING...BUT THE PROBABILITY IS TOO LOW
TO INCLUDE IN THE TAF AS THE LATEST RADAR TRENDS INDICATE A
WEAKENING TREND THERE.

A SECONDARY LOW IS EXPECTED TO DEVELOP OVER THE UPPER MISSOURI
VALLEY THIS EVENING...KEEPING A MODEST PRESSURE GRADIENT OVER THE
REGION. SO MODERATE...GUSTY WINDS SHOULD PERSIST WELL INTO
TONIGHT. ANOTHER STRONG MID LEVEL IMPULSE IS EXPECTED TO TRACK
THROUGH THE MIDDLE MISSISSIPPI VALLEY AND INTO WISCONSIN LATE
TONIGHT...BRINGING A RENEWED CHANCE FOR SHRA/TSRA TO THE REGION
LATE TONIGHT AND TOMORROW.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 14Z...

* MEDIUM TO HIGH CONFIDENCE IN WIND TRENDS.

* HIGH CONFIDENCE WITH -RA TRENDS THIS MORNING.

* MEDIUM HIGH CONFIDENCE IN CIG TRENDS.

* MEDIUM CONFIDENCE IN PCPN TIMING LATE TONIGHT.

KREIN/RODRIGUEZ

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/TSRA LATE. SOUTHEAST WINDS.

FRIDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. SOUTHWEST WINDS
BECOMING NORTHEAST OVERNIGHT.

SATURDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. NORTHEAST
WINDS.

SUNDAY...CHANCE TSRA. MVFR POSSIBLE. NORTHEAST WINDS.

KREIN

&&

.MARINE...
304 AM CDT

LOW PRESSURE WILL BE STEADILY LIFTING NORTH ACROSS THE MISSOURI
VALLEY THIS MORNING...REACHING LAKE SUPERIOR BY THIS EVENING AND
CONTINUING TO SLIDE EAST/NORTHEAST TOWARDS QUEBEC BY TUESDAY
MORNING. A FRONTAL BOUNDARY WILL REMAIN OVER THE FAR NORTHERN
PORTIONS OF LAKE MICHIGAN. MEANWHILE GUSTY SOUTHERLY WINDS ARE
EXPECTED TO INCREASE THIS MORNING...WITH OCCASIONAL GALES FOR THE
NEARSHORE WATERS OF IL/IN. ACROSS THE OPEN WATERS...EXPECT THE
WARM/MOIST AIR TO STRUGGLE TO REACH THE SFC OF THE LAKE WITH SOME
DEGREE OF LAKE STABILITY. WAVES WILL STEADILY BUILD ACROSS THE
NORTHERN HALF OF THE LAKE AS A RESULT OF THE LONG FETCH. STILL
FEEL THAT GUSTS WILL REACH 30KT ACROSS THE LAKE...HOWEVER
CONFIDENCE HAS DIMINISHED SLIGHTLY AS NEW GUIDANCE HAS BECOME A
LITTLE LESS WITH THE WIND FIELDS. NONETHELESS...WAVES FOR THE
NORTHERN HALF OF THE LAKE WILL LIKELY TOP OUT IN THE 4 TO 7 FT
RANGE WITH OCCASIONAL WAVES REACHING 9 FT THIS AFTERNOON/EVENING.

THE GRADIENT QUICKLY DIMINISHES THIS EVENING...BUT EXPECT
SOUTHERLY WINDS TO PERSIST. THIS WILL ALLOW WAVES TO SUBSIDE TO 3
TO 5 FT. ANOTHER LOW WILL ARRIVE TUE...WITH WINDS NUDGING BACK UP
HOWEVER WARM AIR WILL CONTINUE TO FLOW ACROSS THE LAKE AND COULD
FURTHER ENHANCE THE LAKE STABILITY AND KEEP WAVES FROM BUILDING TO
LARGE.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...NEARSHORE WATERS UNTIL 3
     PM MONDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...3 PM MONDAY TO 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 251307
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
807 AM CDT MON MAY 25 2015

.UPDATE...756 AM CDT

COMPACT NEGATIVELY TILTED TROUGH AXIS IS SLIDING NORTHEAST THROUGH
IOWA AND WESTERN ILLINOIS. EASTERN EDGE OF THE TROUGH WILL MOVE
THROUGH NORTHEAST ILLINOIS THIS MORNING. NOTED UPTICK IN SHOWER
ACTIVITY ASSOCIATED WITH THIS WAVE IS PRODUCING MORE ORGANIZED BUT
STILL LARGELY SCATTERED SHOWERS. STILL TRACKING THIS FEATURE WILL
BRING THE BEST CHANCE FOR SOME BRIEF DOWNPOURS IN THE COMING
HOURS...AND THESE WILL SPREAD INTO THE WEST METRO AREA IN THE NEXT
HOUR...SPREADING INTO CHICAGOLAND SHORTLY THERE AFTER. THE CLOUDS
PRODUCING THE SHOWER ACTIVITY ARE SHALLOW AND MID LEVEL LAPSE
RATES ARE SUBPAR...THUS THUNDER SHOULD BE LIMITED AT BEST. SOME
WEAK INSTABILITY IS NOTED SOUTH OF I-80 WHICH DOES NOT PRECLUDE AN
ISOLATED STRIKE IN ANY STRONGER ACTIVITY.

REGARDING WINDS...WITH THE BROKEN TO OVERCAST LOW CLOUD
DECK...MIXING IS BEING LIMITED AND GETING GUSTS TO AROUND 30 KT OR
SO. ANY STRONGER GUSTS WOULD BE IN THE NEXT HOUR BEFORE A RAPID
DROP OFF LATER THIS MORNING.

KMD

&&

.SHORT TERM...
345 AM CDT

THROUGH MONDAY NIGHT...
FOR THE REMAINDER OF THE NIGHT AND INTO MONDAY MORNING...PCPN
CHANCES CONTINUE TO WANE AS LATEST RADAR TRENDS ONLY SHOW SOME SCT
SHRA WHICH ARE DECREASING IN INTENSITY.  IN SPITE OF DEWPOINTS IN
THE LOW 60S...AND A STRONG LOW LEVEL JET...50 KT AT 925 MB...THERE
IS AN ELEMENT LACKING WHICH IS SEEMS TO BE PREVENTING THE
MAINTENANCE OF SHRA/TSRA OVER NERN IL/NWRN IN.  THE MAIN MISSING
ELEMENTS IS FORCING.  THE SFC AND UPPER LEVEL LOW ARE WAY TO THE
WEST...OVER THE NRN PLAINS. THE SHORTWAVE CLIMBING UP THE NWRN
PERIPHERY OF THE HIGH AMPLITUDE RIDGE IS BEING SLOWED BY THE HIGH
AMPLITUDE...AND IS BEING FORCED TO A MORE WLY TRACK THROUGH THE
UPPER MISSISSIPPI VALLEY THAN PREVIOUSLY ANTICIPATED.  SO...FOR THE
REMAINDER OF THE OVERNIGHT HOURS AND THE DAYTIME HOURS MONDAY...HAVE
BACK OF TO ISOLD-SCT SHRA.  WILL KEEP ISOLD TS MENTION FOR THE LATE
MORNING HOURS...THROUGH AROUND NOON...WITH THE DAYTIME HEATING...BUT
CONFIDENCE IN ANY TS IS RATHER LOW AT THIS TIME.  BY THIS
AFTERNOON...A MID LEVEL DRY SLOT IS EXPECTED TO MOVE ACROSS THE
REGION...FURTHER LIMITING PCPN CHANCES AND IT IS QUITE LIKELY THAT
THE REGION WILL REMAIN DRY THROUGH THE DAY.  HOWEVER...WHILE THE
PCPN CHANCES ARE DIMINISHING...THE LIKELIHOOD OF STRONG WINDS IS
STILL A CONCERN.  WITH THE DIMINISHING PCPN CHANCES...LESS SKY COVER
THAN PREVIOUSLY ANTICIPATED IS ALSO POSSIBLE.  A STRONG SWLY
PRESSURE GRADIENT IS SETTING UP ACROSS THE REGION BETWEEN SFC
RIDGING ACROSS THE SERN CONUS AND AND LOW PRESSURE FROM THE UPPER
MISSISSIPPI VALLEY TO THE WESTERN PLAINS.  THE STRONG GRADIENT WILL
HELP DRIVE THE SFC WINDS AND THE DIMINISHING CLOUD COVER COULD HELP
ENHANCE DEEP LAYER MIXING...TAPPING STRONGER WINDS ALOFT.  SUSTAINED
25-25 MPH WINDS ARE LIKELY WITH GUSTS OF 30-35 MPH.
ALSO...PERSISTENT WARM/MOIST ADVECTION AT THE SFC WILL BRING
TEMPERATURES INTO THE LOW TO MIDDLE 80S WITH DEWPOINTS IN THE LOWER
60S.

FOR MONDAY NIGHT...THE BREEZY CONDITIONS WILL PERSIST INTO THE AS
THERE SHOULD BE LITTLE CHANGE TO THE SFC AND UPPER LEVEL PATTERNS.
THE UPPER RIDGE WILL LOSE A LITTLE AMPLITUDE AS SHORT WAVE ENERGY
OVERTOPS THE RIDGE...BUT GENERAL TROUGHING WILL PERSIST ACROSS THE
UPPER MISSISSIPPI VALLEY THROUGH THE CENTRAL PLAINS.  THE NEXT
CHANCE FOR PCPN WILL HOLD OFF UNTIL LATE TONIGHT/EARLY TUESDAY
MORNING AND THE NEXT SHORTWAVE LIFTS OUT OF THE SRN PLAINS AND INTO
THE MIDDLE MISSISSIPPI VALLEY.  AMPLE LOW LEVEL MOISTURE WILL
ALREADY BE IN PLACE SO IT WILL JUST A MATTER OF WHEN THE FORCING
WILL GET HERE.  AGAIN...THERE IS SOME CONCERN THAT THE FORCING WILL
BE TO THE WEST...WITH THE SHORTWAVE TRACKING THROUGH THE MIDDLE
MISSISSIPPI VALLEY AND INTO WI.  SO...WILL CARRY CHANCE POPS FOR THE
REGION...WITH LIKELY POPS APPROACHING THE PONTIAC AREA BY EARLY
TUESDAY MORNING.  THE PERSISTENT WARM/MOIST ADVECTIVE PATTERN AND
BREEZY CONDITIONS SHOULD KEEP TEMPERATURES FROM DROPPING OFF
SIGNIFICANTLY OVERNIGHT AND LOWS SHOULD BE IN THE MIDDLE TO UPPER
60S.

KREIN

&&

.LONG TERM...
239 AM CDT

TUESDAY THROUGH SUNDAY...

TUESDAY THROUGH WEDNESDAY...
500MB TROUGH AXIS WILL SLOWLY PIVOT EAST ACROSS THE CENTRAL PLAINS
INTO THE MID-MISSOURI VALLEY TUE...WITH A SFC WAVE SLIDING NORTH
ACROSS IOWA INTO CENTRAL WISC LATE TUE. THE SFC FEATURE IS NOT
EXPECTED TO BE STRONG...HOWEVER THE GRADIENT DOES TIGHTEN WITH
MODEST HEIGHT FALLS IN THE LOWEST LAYERS OF THE ATMOSPHERE. SOME
INSTABILITY DOES REMAIN ALONG WITH RELATIVELY MOIST SFC CONDS AS
DEW PTS WILL REMAIN IN THE UPR 50S/LOW 60S. PWAT VALUES WILL ALSO
HOVER JUST OVER 1 INCH...WHICH IS SEASONAL. WILL HOLD ONTO MENTION
OF RAIN AND THUNDER...BUT COULD SEE THIS MAINLY FOCUSED IN THE TUE
MORNING TIMEFRAME.

WITH CONSIDERABLE SOLAR SHIELDING PROGGED FOR TUE...TEMPS MAY
STRUGGLE TO WARM BEYOND THE MID/UPR 70S. BUT WITH GUIDANCE HINTING
AT A DRY SLOT LIFTING NORTHEAST ACROSS THE REGION TUE EVE...THIS
COULD INTRODUCE SOME EROSION TO THE CLOUD COVER IN THE AFTN HOURS
TUE AND ALLOW SOME SFC HEATING TO OCCUR AND PUSH TEMPS TO ARND 80.

GUIDANCE LIFTS THE DRY SLOT OVERHEAD LATE TUE NGT...WITH THE 500MB
TROUGH AXIS ARRIVING ARND DAYBREAK WED AND LIFTING EAST ACROSS LOWER
MICHIGAN. THIS WILL BRING DRY ONLY SLIGHT CHANCE POPS AS WEAK SFC
RIDGING BEGINS TO NUDGE EAST ACROSS THE MISSOURI VALLEY TOWARDS THE
FORECAST AREA MIDDAY WED. IT IS POSSIBLE THAT ENOUGH DRY AIR
INFLUENCE COULD ALLOW FOR REMOVAL OF THE SLIGHT CHANCE POPS WED
AFTN. THERMAL TROUGH LAGS BEHIND THE FRONTAL BOUNDARY WED...SO TEMPS
COULD STILL WARM BACK TO ARND 80 AND PERHAPS THE LOW 80S IN THE
SOUTHERN CWFA.

THURSDAY THROUGH SUNDAY...
ANTI-CYCLONIC FLOW ARRIVES THUR WITH AT LEAST ONE PERIOD OF DRY
WEATHER EXPECTED FOR NORTHERN IL/NORTHWEST IN. ONLY A COUPLE
ENSEMBLE MEMBERS CONTINUE TO PROG POPS ALONG THE SOUTHERN FORECAST
AREA THUR...BUT COULD SEE THIS TRENDING DRY IN THE NEXT FEW
SOLUTIONS. WITH WARM TEMPS ALOFT EXPECTED THUR AND THIN CLOUD
COVER...THUR HIGHS COULD PEAK IN THE LOW 80S.

THEN FOCUS TURNS TOWARDS THE UPCOMING WEEKEND AND A PATTERN SHIFT
AWAY FROM THE WARM/HUMID CONDITIONS. ENSEMBLES SHOW MINIMAL SPREAD
IN THE LATE WEEK PERIODS...WITH THE UPSTREAM RIDGE OVER
ALASKA/WESTERN CANADA AND A DOWNSTREAM MID-LVL RIDGE ACROSS THE
SOUTHEAST CONUS. BOTH OF THESE FEATURES IN TIME BEGIN TO
WEAKEN...WITH THE LONGWAVE PATTERN TRANSITIONING INTO A SEMI-ZONAL
ORIENTATION BY THE SECOND HALF OF THE WEEKEND.

OPER GUIDANCE HAS BEEN CONSISTENT WITH PROGGING A ROBUST 500MB
TROUGH TO SLIDE SOUTH FROM CENTRAL CANADA FRI...ALONG WITH A STRONG
CANADIAN SFC RIDGE ON IT/S HEELS. WITH A CHANNEL OF MOISTURE
REMAINING ACROSS THE SOUTHERN PLAINS STRETCHING NORTHEAST THROUGH
THE UPPER MIDWEST...THIS BOUNDARY WILL BECOME ACTIVE WITH A SFC WAVE
DEVELOPING ACROSS THE SOUTHERN PLAINS. THIS LOW WILL THEN LIFT
NORTHEAST TOWARDS THE CWFA FRI WITH A COLD FRONT ARRIVING ACROSS THE
FORECAST AREA SAT. WINDS LOOK TO SHIFT TO THE NORTH...WITH MUCH
COOLER AIR SLIDING SOUTH AND LIKELY KNOCKING TEMPS BACK TO SUB-
SEASONAL CONDS IN THE UPR 60S/NEAR 70 DEGREE RANGE SAT/SUN. IF
NORTHEAST WINDS MATERIALIZE...NEXT WEEKEND AREAS ADJACENT TO LAKE
MICHIGAN ALONG THE IL/IN SHORELINE COULD BE LOCKED IN THE UPR 50S TO
LOW 60S FOR HIGHS WITH A COLD FLOW OFF OF LAKE MICHIGAN.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 12Z...

* STRONG AND GUSTY SOUTH WINDS THROUGH EARLY EVENING.

* CHANCE SHRA/TSRA LATE TONIGHT THROUGH TOMORROW.

KREIN

//DISCUSSION...UPDATED 12Z...

MAIN CONCERN FOR TODAY WILL BE STRONG...GUSTY SOUTH WINDS. AS OF
11Z THIS MORNING...WINDS ARE ALREADY GUSTING TO 25-30KT AND EXPECT
THAT WITH DEEPER MIXING LATER THIS MORNING...SHOULD BE ABLE TO TAP
INTO A 50 KT LOW LEVEL JET TO MIX DOWN GUSTS TO 35 KT OR EVEN
SLIGHTLY HIGHER. THE STRONG LOW LEVEL JET SHOULD MOVE OFF TO THE
EAST BY EARLY AFTERNOON...SO WHILE WINDS SHOULD STILL BE STRONG
AND GUSTY...PEAK GUSTS SHOULD LOWER TO ARND 25KT.

WITH THE PERSISTENT FETCH OF LOW LEVEL MOISTURE INTO THE
REGION...A LAYER OF MVFR STRATOCU HAS OVERSPREAD THE REGION.
EXPECT THAT BASES SHOULD NOT LOWER MUCH LESS THAT 1800FT AGL.
THERE IS SOME UNCERTAINTY AS TO THE DURATION OF THE MVFR CLOUD
LAYER...BUT WITH LITTLE CHANGE TO THE OVERALL PATTERN THROUGH THE
DAY...THERE IS A CHANCE THAT THE MVFR CIGS COULD HANG IN THROUGH
MUCH OF THE DAY. HOWEVER...THERE IS ALSO A CHANCE THAT STRONGER
MIXING IN THE AFTERNOON HOURS COULD ALLOW FOR THE MVFR DECK TO
SCATTER OUT.

LATEST RADAR TRENDS INDICATE THAT AN AREA OF SHRA LIFTING NEWD
FROM CNTRL IL INTO INDIANA. THE TRAJECTORY OF THE PCPN AREA SHOULD
KEEP THE BULK OF THE PCPN EAST AND SOUTH OF GYY...THOUGH A FEW SCT
SHRA AREA NOT OUT OF THE QUESTION. ALSO...SOME SHRA ASSOCIATED
WITH A MID LEVEL IMPULSE LIFTING NORTH THROUGH IOWA AND INTO WRN
WI IS GENERATING SCT SHRA AS WELL. IT IS ALSO POSSIBLE THAT RFD
COULD SEE A FEW SHRA THIS MORNING...BUT THE PROBABILITY IS TOO LOW
TO INCLUDE IN THE TAF AS THE LATEST RADAR TRENDS INDICATE A
WEAKENING TREND THERE.

A SECONDARY LOW IS EXPECTED TO DEVELOP OVER THE UPPER MISSOURI
VALLEY THIS EVENING...KEEPING A MODEST PRESSURE GRADIENT OVER THE
REGION. SO MODERATE...GUSTY WINDS SHOULD PERSIST WELL INTO
TONIGHT. ANOTHER STRONG MID LEVEL IMPULSE IS EXPECTED TO TRACK
THROUGH THE MIDDLE MISSISSIPPI VALLEY AND INTO WISCONSIN LATE
TONIGHT...BRINGING A RENEWED CHANCE FOR SHRA/TSRA TO THE REGION
LATE TONIGHT AND TOMORROW.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 12Z...

* MEDIUM TO HIGH CONFIDENCE IN WIND TRENDS.

* MEDIUM TO HIGH CONFIDENCE THAT THE TERMINALS SHOULD REMAIN
  DRY...THOUGH THERE IS A SMALL CHANCE FOR SOME SHRA INVOF THE
  TERMINALS THROUGH THE MORNING HOURS.

* MEDIUM CONFIDENCE IN CIG TRENDS.

* MEDIUM CONFIDENCE IN PCPN TIMING LATE TONIGHT.

KREIN

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/TSRA LATE. SOUTHEAST WINDS.

FRIDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. SOUTHWEST WINDS
BECOMING NORTHEAST OVERNIGHT.

SATURDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. NORTHEAST
WINDS.

SUNDAY...CHANCE TSRA. MVFR POSSIBLE. NORTHEAST WINDS.

KREIN

&&

.MARINE...
304 AM CDT

LOW PRESSURE WILL BE STEADILY LIFTING NORTH ACROSS THE MISSOURI
VALLEY THIS MORNING...REACHING LAKE SUPERIOR BY THIS EVENING AND
CONTINUING TO SLIDE EAST/NORTHEAST TOWARDS QUEBEC BY TUESDAY
MORNING. A FRONTAL BOUNDARY WILL REMAIN OVER THE FAR NORTHERN
PORTIONS OF LAKE MICHIGAN. MEANWHILE GUSTY SOUTHERLY WINDS ARE
EXPECTED TO INCREASE THIS MORNING...WITH OCCASIONAL GALES FOR THE
NEARSHORE WATERS OF IL/IN. ACROSS THE OPEN WATERS...EXPECT THE
WARM/MOIST AIR TO STRUGGLE TO REACH THE SFC OF THE LAKE WITH SOME
DEGREE OF LAKE STABILITY. WAVES WILL STEADILY BUILD ACROSS THE
NORTHERN HALF OF THE LAKE AS A RESULT OF THE LONG FETCH. STILL
FEEL THAT GUSTS WILL REACH 30KT ACROSS THE LAKE...HOWEVER
CONFIDENCE HAS DIMINISHED SLIGHTLY AS NEW GUIDANCE HAS BECOME A
LITTLE LESS WITH THE WIND FIELDS. NONETHELESS...WAVES FOR THE
NORTHERN HALF OF THE LAKE WILL LIKELY TOP OUT IN THE 4 TO 7 FT
RANGE WITH OCCASIONAL WAVES REACHING 9 FT THIS AFTERNOON/EVENING.

THE GRADIENT QUICKLY DIMINISHES THIS EVENING...BUT EXPECT
SOUTHERLY WINDS TO PERSIST. THIS WILL ALLOW WAVES TO SUBSIDE TO 3
TO 5 FT. ANOTHER LOW WILL ARRIVE TUE...WITH WINDS NUDGING BACK UP
HOWEVER WARM AIR WILL CONTINUE TO FLOW ACROSS THE LAKE AND COULD
FURTHER ENHANCE THE LAKE STABILITY AND KEEP WAVES FROM BUILDING TO
LARGE.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 9 AM MONDAY.

     GALE WARNING...NEARSHORE WATERS UNTIL 3
     PM MONDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...3 PM MONDAY TO 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 251307
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
807 AM CDT MON MAY 25 2015

.UPDATE...756 AM CDT

COMPACT NEGATIVELY TILTED TROUGH AXIS IS SLIDING NORTHEAST THROUGH
IOWA AND WESTERN ILLINOIS. EASTERN EDGE OF THE TROUGH WILL MOVE
THROUGH NORTHEAST ILLINOIS THIS MORNING. NOTED UPTICK IN SHOWER
ACTIVITY ASSOCIATED WITH THIS WAVE IS PRODUCING MORE ORGANIZED BUT
STILL LARGELY SCATTERED SHOWERS. STILL TRACKING THIS FEATURE WILL
BRING THE BEST CHANCE FOR SOME BRIEF DOWNPOURS IN THE COMING
HOURS...AND THESE WILL SPREAD INTO THE WEST METRO AREA IN THE NEXT
HOUR...SPREADING INTO CHICAGOLAND SHORTLY THERE AFTER. THE CLOUDS
PRODUCING THE SHOWER ACTIVITY ARE SHALLOW AND MID LEVEL LAPSE
RATES ARE SUBPAR...THUS THUNDER SHOULD BE LIMITED AT BEST. SOME
WEAK INSTABILITY IS NOTED SOUTH OF I-80 WHICH DOES NOT PRECLUDE AN
ISOLATED STRIKE IN ANY STRONGER ACTIVITY.

REGARDING WINDS...WITH THE BROKEN TO OVERCAST LOW CLOUD
DECK...MIXING IS BEING LIMITED AND GETING GUSTS TO AROUND 30 KT OR
SO. ANY STRONGER GUSTS WOULD BE IN THE NEXT HOUR BEFORE A RAPID
DROP OFF LATER THIS MORNING.

KMD

&&

.SHORT TERM...
345 AM CDT

THROUGH MONDAY NIGHT...
FOR THE REMAINDER OF THE NIGHT AND INTO MONDAY MORNING...PCPN
CHANCES CONTINUE TO WANE AS LATEST RADAR TRENDS ONLY SHOW SOME SCT
SHRA WHICH ARE DECREASING IN INTENSITY.  IN SPITE OF DEWPOINTS IN
THE LOW 60S...AND A STRONG LOW LEVEL JET...50 KT AT 925 MB...THERE
IS AN ELEMENT LACKING WHICH IS SEEMS TO BE PREVENTING THE
MAINTENANCE OF SHRA/TSRA OVER NERN IL/NWRN IN.  THE MAIN MISSING
ELEMENTS IS FORCING.  THE SFC AND UPPER LEVEL LOW ARE WAY TO THE
WEST...OVER THE NRN PLAINS. THE SHORTWAVE CLIMBING UP THE NWRN
PERIPHERY OF THE HIGH AMPLITUDE RIDGE IS BEING SLOWED BY THE HIGH
AMPLITUDE...AND IS BEING FORCED TO A MORE WLY TRACK THROUGH THE
UPPER MISSISSIPPI VALLEY THAN PREVIOUSLY ANTICIPATED.  SO...FOR THE
REMAINDER OF THE OVERNIGHT HOURS AND THE DAYTIME HOURS MONDAY...HAVE
BACK OF TO ISOLD-SCT SHRA.  WILL KEEP ISOLD TS MENTION FOR THE LATE
MORNING HOURS...THROUGH AROUND NOON...WITH THE DAYTIME HEATING...BUT
CONFIDENCE IN ANY TS IS RATHER LOW AT THIS TIME.  BY THIS
AFTERNOON...A MID LEVEL DRY SLOT IS EXPECTED TO MOVE ACROSS THE
REGION...FURTHER LIMITING PCPN CHANCES AND IT IS QUITE LIKELY THAT
THE REGION WILL REMAIN DRY THROUGH THE DAY.  HOWEVER...WHILE THE
PCPN CHANCES ARE DIMINISHING...THE LIKELIHOOD OF STRONG WINDS IS
STILL A CONCERN.  WITH THE DIMINISHING PCPN CHANCES...LESS SKY COVER
THAN PREVIOUSLY ANTICIPATED IS ALSO POSSIBLE.  A STRONG SWLY
PRESSURE GRADIENT IS SETTING UP ACROSS THE REGION BETWEEN SFC
RIDGING ACROSS THE SERN CONUS AND AND LOW PRESSURE FROM THE UPPER
MISSISSIPPI VALLEY TO THE WESTERN PLAINS.  THE STRONG GRADIENT WILL
HELP DRIVE THE SFC WINDS AND THE DIMINISHING CLOUD COVER COULD HELP
ENHANCE DEEP LAYER MIXING...TAPPING STRONGER WINDS ALOFT.  SUSTAINED
25-25 MPH WINDS ARE LIKELY WITH GUSTS OF 30-35 MPH.
ALSO...PERSISTENT WARM/MOIST ADVECTION AT THE SFC WILL BRING
TEMPERATURES INTO THE LOW TO MIDDLE 80S WITH DEWPOINTS IN THE LOWER
60S.

FOR MONDAY NIGHT...THE BREEZY CONDITIONS WILL PERSIST INTO THE AS
THERE SHOULD BE LITTLE CHANGE TO THE SFC AND UPPER LEVEL PATTERNS.
THE UPPER RIDGE WILL LOSE A LITTLE AMPLITUDE AS SHORT WAVE ENERGY
OVERTOPS THE RIDGE...BUT GENERAL TROUGHING WILL PERSIST ACROSS THE
UPPER MISSISSIPPI VALLEY THROUGH THE CENTRAL PLAINS.  THE NEXT
CHANCE FOR PCPN WILL HOLD OFF UNTIL LATE TONIGHT/EARLY TUESDAY
MORNING AND THE NEXT SHORTWAVE LIFTS OUT OF THE SRN PLAINS AND INTO
THE MIDDLE MISSISSIPPI VALLEY.  AMPLE LOW LEVEL MOISTURE WILL
ALREADY BE IN PLACE SO IT WILL JUST A MATTER OF WHEN THE FORCING
WILL GET HERE.  AGAIN...THERE IS SOME CONCERN THAT THE FORCING WILL
BE TO THE WEST...WITH THE SHORTWAVE TRACKING THROUGH THE MIDDLE
MISSISSIPPI VALLEY AND INTO WI.  SO...WILL CARRY CHANCE POPS FOR THE
REGION...WITH LIKELY POPS APPROACHING THE PONTIAC AREA BY EARLY
TUESDAY MORNING.  THE PERSISTENT WARM/MOIST ADVECTIVE PATTERN AND
BREEZY CONDITIONS SHOULD KEEP TEMPERATURES FROM DROPPING OFF
SIGNIFICANTLY OVERNIGHT AND LOWS SHOULD BE IN THE MIDDLE TO UPPER
60S.

KREIN

&&

.LONG TERM...
239 AM CDT

TUESDAY THROUGH SUNDAY...

TUESDAY THROUGH WEDNESDAY...
500MB TROUGH AXIS WILL SLOWLY PIVOT EAST ACROSS THE CENTRAL PLAINS
INTO THE MID-MISSOURI VALLEY TUE...WITH A SFC WAVE SLIDING NORTH
ACROSS IOWA INTO CENTRAL WISC LATE TUE. THE SFC FEATURE IS NOT
EXPECTED TO BE STRONG...HOWEVER THE GRADIENT DOES TIGHTEN WITH
MODEST HEIGHT FALLS IN THE LOWEST LAYERS OF THE ATMOSPHERE. SOME
INSTABILITY DOES REMAIN ALONG WITH RELATIVELY MOIST SFC CONDS AS
DEW PTS WILL REMAIN IN THE UPR 50S/LOW 60S. PWAT VALUES WILL ALSO
HOVER JUST OVER 1 INCH...WHICH IS SEASONAL. WILL HOLD ONTO MENTION
OF RAIN AND THUNDER...BUT COULD SEE THIS MAINLY FOCUSED IN THE TUE
MORNING TIMEFRAME.

WITH CONSIDERABLE SOLAR SHIELDING PROGGED FOR TUE...TEMPS MAY
STRUGGLE TO WARM BEYOND THE MID/UPR 70S. BUT WITH GUIDANCE HINTING
AT A DRY SLOT LIFTING NORTHEAST ACROSS THE REGION TUE EVE...THIS
COULD INTRODUCE SOME EROSION TO THE CLOUD COVER IN THE AFTN HOURS
TUE AND ALLOW SOME SFC HEATING TO OCCUR AND PUSH TEMPS TO ARND 80.

GUIDANCE LIFTS THE DRY SLOT OVERHEAD LATE TUE NGT...WITH THE 500MB
TROUGH AXIS ARRIVING ARND DAYBREAK WED AND LIFTING EAST ACROSS LOWER
MICHIGAN. THIS WILL BRING DRY ONLY SLIGHT CHANCE POPS AS WEAK SFC
RIDGING BEGINS TO NUDGE EAST ACROSS THE MISSOURI VALLEY TOWARDS THE
FORECAST AREA MIDDAY WED. IT IS POSSIBLE THAT ENOUGH DRY AIR
INFLUENCE COULD ALLOW FOR REMOVAL OF THE SLIGHT CHANCE POPS WED
AFTN. THERMAL TROUGH LAGS BEHIND THE FRONTAL BOUNDARY WED...SO TEMPS
COULD STILL WARM BACK TO ARND 80 AND PERHAPS THE LOW 80S IN THE
SOUTHERN CWFA.

THURSDAY THROUGH SUNDAY...
ANTI-CYCLONIC FLOW ARRIVES THUR WITH AT LEAST ONE PERIOD OF DRY
WEATHER EXPECTED FOR NORTHERN IL/NORTHWEST IN. ONLY A COUPLE
ENSEMBLE MEMBERS CONTINUE TO PROG POPS ALONG THE SOUTHERN FORECAST
AREA THUR...BUT COULD SEE THIS TRENDING DRY IN THE NEXT FEW
SOLUTIONS. WITH WARM TEMPS ALOFT EXPECTED THUR AND THIN CLOUD
COVER...THUR HIGHS COULD PEAK IN THE LOW 80S.

THEN FOCUS TURNS TOWARDS THE UPCOMING WEEKEND AND A PATTERN SHIFT
AWAY FROM THE WARM/HUMID CONDITIONS. ENSEMBLES SHOW MINIMAL SPREAD
IN THE LATE WEEK PERIODS...WITH THE UPSTREAM RIDGE OVER
ALASKA/WESTERN CANADA AND A DOWNSTREAM MID-LVL RIDGE ACROSS THE
SOUTHEAST CONUS. BOTH OF THESE FEATURES IN TIME BEGIN TO
WEAKEN...WITH THE LONGWAVE PATTERN TRANSITIONING INTO A SEMI-ZONAL
ORIENTATION BY THE SECOND HALF OF THE WEEKEND.

OPER GUIDANCE HAS BEEN CONSISTENT WITH PROGGING A ROBUST 500MB
TROUGH TO SLIDE SOUTH FROM CENTRAL CANADA FRI...ALONG WITH A STRONG
CANADIAN SFC RIDGE ON IT/S HEELS. WITH A CHANNEL OF MOISTURE
REMAINING ACROSS THE SOUTHERN PLAINS STRETCHING NORTHEAST THROUGH
THE UPPER MIDWEST...THIS BOUNDARY WILL BECOME ACTIVE WITH A SFC WAVE
DEVELOPING ACROSS THE SOUTHERN PLAINS. THIS LOW WILL THEN LIFT
NORTHEAST TOWARDS THE CWFA FRI WITH A COLD FRONT ARRIVING ACROSS THE
FORECAST AREA SAT. WINDS LOOK TO SHIFT TO THE NORTH...WITH MUCH
COOLER AIR SLIDING SOUTH AND LIKELY KNOCKING TEMPS BACK TO SUB-
SEASONAL CONDS IN THE UPR 60S/NEAR 70 DEGREE RANGE SAT/SUN. IF
NORTHEAST WINDS MATERIALIZE...NEXT WEEKEND AREAS ADJACENT TO LAKE
MICHIGAN ALONG THE IL/IN SHORELINE COULD BE LOCKED IN THE UPR 50S TO
LOW 60S FOR HIGHS WITH A COLD FLOW OFF OF LAKE MICHIGAN.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 12Z...

* STRONG AND GUSTY SOUTH WINDS THROUGH EARLY EVENING.

* CHANCE SHRA/TSRA LATE TONIGHT THROUGH TOMORROW.

KREIN

//DISCUSSION...UPDATED 12Z...

MAIN CONCERN FOR TODAY WILL BE STRONG...GUSTY SOUTH WINDS. AS OF
11Z THIS MORNING...WINDS ARE ALREADY GUSTING TO 25-30KT AND EXPECT
THAT WITH DEEPER MIXING LATER THIS MORNING...SHOULD BE ABLE TO TAP
INTO A 50 KT LOW LEVEL JET TO MIX DOWN GUSTS TO 35 KT OR EVEN
SLIGHTLY HIGHER. THE STRONG LOW LEVEL JET SHOULD MOVE OFF TO THE
EAST BY EARLY AFTERNOON...SO WHILE WINDS SHOULD STILL BE STRONG
AND GUSTY...PEAK GUSTS SHOULD LOWER TO ARND 25KT.

WITH THE PERSISTENT FETCH OF LOW LEVEL MOISTURE INTO THE
REGION...A LAYER OF MVFR STRATOCU HAS OVERSPREAD THE REGION.
EXPECT THAT BASES SHOULD NOT LOWER MUCH LESS THAT 1800FT AGL.
THERE IS SOME UNCERTAINTY AS TO THE DURATION OF THE MVFR CLOUD
LAYER...BUT WITH LITTLE CHANGE TO THE OVERALL PATTERN THROUGH THE
DAY...THERE IS A CHANCE THAT THE MVFR CIGS COULD HANG IN THROUGH
MUCH OF THE DAY. HOWEVER...THERE IS ALSO A CHANCE THAT STRONGER
MIXING IN THE AFTERNOON HOURS COULD ALLOW FOR THE MVFR DECK TO
SCATTER OUT.

LATEST RADAR TRENDS INDICATE THAT AN AREA OF SHRA LIFTING NEWD
FROM CNTRL IL INTO INDIANA. THE TRAJECTORY OF THE PCPN AREA SHOULD
KEEP THE BULK OF THE PCPN EAST AND SOUTH OF GYY...THOUGH A FEW SCT
SHRA AREA NOT OUT OF THE QUESTION. ALSO...SOME SHRA ASSOCIATED
WITH A MID LEVEL IMPULSE LIFTING NORTH THROUGH IOWA AND INTO WRN
WI IS GENERATING SCT SHRA AS WELL. IT IS ALSO POSSIBLE THAT RFD
COULD SEE A FEW SHRA THIS MORNING...BUT THE PROBABILITY IS TOO LOW
TO INCLUDE IN THE TAF AS THE LATEST RADAR TRENDS INDICATE A
WEAKENING TREND THERE.

A SECONDARY LOW IS EXPECTED TO DEVELOP OVER THE UPPER MISSOURI
VALLEY THIS EVENING...KEEPING A MODEST PRESSURE GRADIENT OVER THE
REGION. SO MODERATE...GUSTY WINDS SHOULD PERSIST WELL INTO
TONIGHT. ANOTHER STRONG MID LEVEL IMPULSE IS EXPECTED TO TRACK
THROUGH THE MIDDLE MISSISSIPPI VALLEY AND INTO WISCONSIN LATE
TONIGHT...BRINGING A RENEWED CHANCE FOR SHRA/TSRA TO THE REGION
LATE TONIGHT AND TOMORROW.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 12Z...

* MEDIUM TO HIGH CONFIDENCE IN WIND TRENDS.

* MEDIUM TO HIGH CONFIDENCE THAT THE TERMINALS SHOULD REMAIN
  DRY...THOUGH THERE IS A SMALL CHANCE FOR SOME SHRA INVOF THE
  TERMINALS THROUGH THE MORNING HOURS.

* MEDIUM CONFIDENCE IN CIG TRENDS.

* MEDIUM CONFIDENCE IN PCPN TIMING LATE TONIGHT.

KREIN

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/TSRA LATE. SOUTHEAST WINDS.

FRIDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. SOUTHWEST WINDS
BECOMING NORTHEAST OVERNIGHT.

SATURDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. NORTHEAST
WINDS.

SUNDAY...CHANCE TSRA. MVFR POSSIBLE. NORTHEAST WINDS.

KREIN

&&

.MARINE...
304 AM CDT

LOW PRESSURE WILL BE STEADILY LIFTING NORTH ACROSS THE MISSOURI
VALLEY THIS MORNING...REACHING LAKE SUPERIOR BY THIS EVENING AND
CONTINUING TO SLIDE EAST/NORTHEAST TOWARDS QUEBEC BY TUESDAY
MORNING. A FRONTAL BOUNDARY WILL REMAIN OVER THE FAR NORTHERN
PORTIONS OF LAKE MICHIGAN. MEANWHILE GUSTY SOUTHERLY WINDS ARE
EXPECTED TO INCREASE THIS MORNING...WITH OCCASIONAL GALES FOR THE
NEARSHORE WATERS OF IL/IN. ACROSS THE OPEN WATERS...EXPECT THE
WARM/MOIST AIR TO STRUGGLE TO REACH THE SFC OF THE LAKE WITH SOME
DEGREE OF LAKE STABILITY. WAVES WILL STEADILY BUILD ACROSS THE
NORTHERN HALF OF THE LAKE AS A RESULT OF THE LONG FETCH. STILL
FEEL THAT GUSTS WILL REACH 30KT ACROSS THE LAKE...HOWEVER
CONFIDENCE HAS DIMINISHED SLIGHTLY AS NEW GUIDANCE HAS BECOME A
LITTLE LESS WITH THE WIND FIELDS. NONETHELESS...WAVES FOR THE
NORTHERN HALF OF THE LAKE WILL LIKELY TOP OUT IN THE 4 TO 7 FT
RANGE WITH OCCASIONAL WAVES REACHING 9 FT THIS AFTERNOON/EVENING.

THE GRADIENT QUICKLY DIMINISHES THIS EVENING...BUT EXPECT
SOUTHERLY WINDS TO PERSIST. THIS WILL ALLOW WAVES TO SUBSIDE TO 3
TO 5 FT. ANOTHER LOW WILL ARRIVE TUE...WITH WINDS NUDGING BACK UP
HOWEVER WARM AIR WILL CONTINUE TO FLOW ACROSS THE LAKE AND COULD
FURTHER ENHANCE THE LAKE STABILITY AND KEEP WAVES FROM BUILDING TO
LARGE.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 9 AM MONDAY.

     GALE WARNING...NEARSHORE WATERS UNTIL 3
     PM MONDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...3 PM MONDAY TO 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 251307
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
807 AM CDT MON MAY 25 2015

.UPDATE...756 AM CDT

COMPACT NEGATIVELY TILTED TROUGH AXIS IS SLIDING NORTHEAST THROUGH
IOWA AND WESTERN ILLINOIS. EASTERN EDGE OF THE TROUGH WILL MOVE
THROUGH NORTHEAST ILLINOIS THIS MORNING. NOTED UPTICK IN SHOWER
ACTIVITY ASSOCIATED WITH THIS WAVE IS PRODUCING MORE ORGANIZED BUT
STILL LARGELY SCATTERED SHOWERS. STILL TRACKING THIS FEATURE WILL
BRING THE BEST CHANCE FOR SOME BRIEF DOWNPOURS IN THE COMING
HOURS...AND THESE WILL SPREAD INTO THE WEST METRO AREA IN THE NEXT
HOUR...SPREADING INTO CHICAGOLAND SHORTLY THERE AFTER. THE CLOUDS
PRODUCING THE SHOWER ACTIVITY ARE SHALLOW AND MID LEVEL LAPSE
RATES ARE SUBPAR...THUS THUNDER SHOULD BE LIMITED AT BEST. SOME
WEAK INSTABILITY IS NOTED SOUTH OF I-80 WHICH DOES NOT PRECLUDE AN
ISOLATED STRIKE IN ANY STRONGER ACTIVITY.

REGARDING WINDS...WITH THE BROKEN TO OVERCAST LOW CLOUD
DECK...MIXING IS BEING LIMITED AND GETING GUSTS TO AROUND 30 KT OR
SO. ANY STRONGER GUSTS WOULD BE IN THE NEXT HOUR BEFORE A RAPID
DROP OFF LATER THIS MORNING.

KMD

&&

.SHORT TERM...
345 AM CDT

THROUGH MONDAY NIGHT...
FOR THE REMAINDER OF THE NIGHT AND INTO MONDAY MORNING...PCPN
CHANCES CONTINUE TO WANE AS LATEST RADAR TRENDS ONLY SHOW SOME SCT
SHRA WHICH ARE DECREASING IN INTENSITY.  IN SPITE OF DEWPOINTS IN
THE LOW 60S...AND A STRONG LOW LEVEL JET...50 KT AT 925 MB...THERE
IS AN ELEMENT LACKING WHICH IS SEEMS TO BE PREVENTING THE
MAINTENANCE OF SHRA/TSRA OVER NERN IL/NWRN IN.  THE MAIN MISSING
ELEMENTS IS FORCING.  THE SFC AND UPPER LEVEL LOW ARE WAY TO THE
WEST...OVER THE NRN PLAINS. THE SHORTWAVE CLIMBING UP THE NWRN
PERIPHERY OF THE HIGH AMPLITUDE RIDGE IS BEING SLOWED BY THE HIGH
AMPLITUDE...AND IS BEING FORCED TO A MORE WLY TRACK THROUGH THE
UPPER MISSISSIPPI VALLEY THAN PREVIOUSLY ANTICIPATED.  SO...FOR THE
REMAINDER OF THE OVERNIGHT HOURS AND THE DAYTIME HOURS MONDAY...HAVE
BACK OF TO ISOLD-SCT SHRA.  WILL KEEP ISOLD TS MENTION FOR THE LATE
MORNING HOURS...THROUGH AROUND NOON...WITH THE DAYTIME HEATING...BUT
CONFIDENCE IN ANY TS IS RATHER LOW AT THIS TIME.  BY THIS
AFTERNOON...A MID LEVEL DRY SLOT IS EXPECTED TO MOVE ACROSS THE
REGION...FURTHER LIMITING PCPN CHANCES AND IT IS QUITE LIKELY THAT
THE REGION WILL REMAIN DRY THROUGH THE DAY.  HOWEVER...WHILE THE
PCPN CHANCES ARE DIMINISHING...THE LIKELIHOOD OF STRONG WINDS IS
STILL A CONCERN.  WITH THE DIMINISHING PCPN CHANCES...LESS SKY COVER
THAN PREVIOUSLY ANTICIPATED IS ALSO POSSIBLE.  A STRONG SWLY
PRESSURE GRADIENT IS SETTING UP ACROSS THE REGION BETWEEN SFC
RIDGING ACROSS THE SERN CONUS AND AND LOW PRESSURE FROM THE UPPER
MISSISSIPPI VALLEY TO THE WESTERN PLAINS.  THE STRONG GRADIENT WILL
HELP DRIVE THE SFC WINDS AND THE DIMINISHING CLOUD COVER COULD HELP
ENHANCE DEEP LAYER MIXING...TAPPING STRONGER WINDS ALOFT.  SUSTAINED
25-25 MPH WINDS ARE LIKELY WITH GUSTS OF 30-35 MPH.
ALSO...PERSISTENT WARM/MOIST ADVECTION AT THE SFC WILL BRING
TEMPERATURES INTO THE LOW TO MIDDLE 80S WITH DEWPOINTS IN THE LOWER
60S.

FOR MONDAY NIGHT...THE BREEZY CONDITIONS WILL PERSIST INTO THE AS
THERE SHOULD BE LITTLE CHANGE TO THE SFC AND UPPER LEVEL PATTERNS.
THE UPPER RIDGE WILL LOSE A LITTLE AMPLITUDE AS SHORT WAVE ENERGY
OVERTOPS THE RIDGE...BUT GENERAL TROUGHING WILL PERSIST ACROSS THE
UPPER MISSISSIPPI VALLEY THROUGH THE CENTRAL PLAINS.  THE NEXT
CHANCE FOR PCPN WILL HOLD OFF UNTIL LATE TONIGHT/EARLY TUESDAY
MORNING AND THE NEXT SHORTWAVE LIFTS OUT OF THE SRN PLAINS AND INTO
THE MIDDLE MISSISSIPPI VALLEY.  AMPLE LOW LEVEL MOISTURE WILL
ALREADY BE IN PLACE SO IT WILL JUST A MATTER OF WHEN THE FORCING
WILL GET HERE.  AGAIN...THERE IS SOME CONCERN THAT THE FORCING WILL
BE TO THE WEST...WITH THE SHORTWAVE TRACKING THROUGH THE MIDDLE
MISSISSIPPI VALLEY AND INTO WI.  SO...WILL CARRY CHANCE POPS FOR THE
REGION...WITH LIKELY POPS APPROACHING THE PONTIAC AREA BY EARLY
TUESDAY MORNING.  THE PERSISTENT WARM/MOIST ADVECTIVE PATTERN AND
BREEZY CONDITIONS SHOULD KEEP TEMPERATURES FROM DROPPING OFF
SIGNIFICANTLY OVERNIGHT AND LOWS SHOULD BE IN THE MIDDLE TO UPPER
60S.

KREIN

&&

.LONG TERM...
239 AM CDT

TUESDAY THROUGH SUNDAY...

TUESDAY THROUGH WEDNESDAY...
500MB TROUGH AXIS WILL SLOWLY PIVOT EAST ACROSS THE CENTRAL PLAINS
INTO THE MID-MISSOURI VALLEY TUE...WITH A SFC WAVE SLIDING NORTH
ACROSS IOWA INTO CENTRAL WISC LATE TUE. THE SFC FEATURE IS NOT
EXPECTED TO BE STRONG...HOWEVER THE GRADIENT DOES TIGHTEN WITH
MODEST HEIGHT FALLS IN THE LOWEST LAYERS OF THE ATMOSPHERE. SOME
INSTABILITY DOES REMAIN ALONG WITH RELATIVELY MOIST SFC CONDS AS
DEW PTS WILL REMAIN IN THE UPR 50S/LOW 60S. PWAT VALUES WILL ALSO
HOVER JUST OVER 1 INCH...WHICH IS SEASONAL. WILL HOLD ONTO MENTION
OF RAIN AND THUNDER...BUT COULD SEE THIS MAINLY FOCUSED IN THE TUE
MORNING TIMEFRAME.

WITH CONSIDERABLE SOLAR SHIELDING PROGGED FOR TUE...TEMPS MAY
STRUGGLE TO WARM BEYOND THE MID/UPR 70S. BUT WITH GUIDANCE HINTING
AT A DRY SLOT LIFTING NORTHEAST ACROSS THE REGION TUE EVE...THIS
COULD INTRODUCE SOME EROSION TO THE CLOUD COVER IN THE AFTN HOURS
TUE AND ALLOW SOME SFC HEATING TO OCCUR AND PUSH TEMPS TO ARND 80.

GUIDANCE LIFTS THE DRY SLOT OVERHEAD LATE TUE NGT...WITH THE 500MB
TROUGH AXIS ARRIVING ARND DAYBREAK WED AND LIFTING EAST ACROSS LOWER
MICHIGAN. THIS WILL BRING DRY ONLY SLIGHT CHANCE POPS AS WEAK SFC
RIDGING BEGINS TO NUDGE EAST ACROSS THE MISSOURI VALLEY TOWARDS THE
FORECAST AREA MIDDAY WED. IT IS POSSIBLE THAT ENOUGH DRY AIR
INFLUENCE COULD ALLOW FOR REMOVAL OF THE SLIGHT CHANCE POPS WED
AFTN. THERMAL TROUGH LAGS BEHIND THE FRONTAL BOUNDARY WED...SO TEMPS
COULD STILL WARM BACK TO ARND 80 AND PERHAPS THE LOW 80S IN THE
SOUTHERN CWFA.

THURSDAY THROUGH SUNDAY...
ANTI-CYCLONIC FLOW ARRIVES THUR WITH AT LEAST ONE PERIOD OF DRY
WEATHER EXPECTED FOR NORTHERN IL/NORTHWEST IN. ONLY A COUPLE
ENSEMBLE MEMBERS CONTINUE TO PROG POPS ALONG THE SOUTHERN FORECAST
AREA THUR...BUT COULD SEE THIS TRENDING DRY IN THE NEXT FEW
SOLUTIONS. WITH WARM TEMPS ALOFT EXPECTED THUR AND THIN CLOUD
COVER...THUR HIGHS COULD PEAK IN THE LOW 80S.

THEN FOCUS TURNS TOWARDS THE UPCOMING WEEKEND AND A PATTERN SHIFT
AWAY FROM THE WARM/HUMID CONDITIONS. ENSEMBLES SHOW MINIMAL SPREAD
IN THE LATE WEEK PERIODS...WITH THE UPSTREAM RIDGE OVER
ALASKA/WESTERN CANADA AND A DOWNSTREAM MID-LVL RIDGE ACROSS THE
SOUTHEAST CONUS. BOTH OF THESE FEATURES IN TIME BEGIN TO
WEAKEN...WITH THE LONGWAVE PATTERN TRANSITIONING INTO A SEMI-ZONAL
ORIENTATION BY THE SECOND HALF OF THE WEEKEND.

OPER GUIDANCE HAS BEEN CONSISTENT WITH PROGGING A ROBUST 500MB
TROUGH TO SLIDE SOUTH FROM CENTRAL CANADA FRI...ALONG WITH A STRONG
CANADIAN SFC RIDGE ON IT/S HEELS. WITH A CHANNEL OF MOISTURE
REMAINING ACROSS THE SOUTHERN PLAINS STRETCHING NORTHEAST THROUGH
THE UPPER MIDWEST...THIS BOUNDARY WILL BECOME ACTIVE WITH A SFC WAVE
DEVELOPING ACROSS THE SOUTHERN PLAINS. THIS LOW WILL THEN LIFT
NORTHEAST TOWARDS THE CWFA FRI WITH A COLD FRONT ARRIVING ACROSS THE
FORECAST AREA SAT. WINDS LOOK TO SHIFT TO THE NORTH...WITH MUCH
COOLER AIR SLIDING SOUTH AND LIKELY KNOCKING TEMPS BACK TO SUB-
SEASONAL CONDS IN THE UPR 60S/NEAR 70 DEGREE RANGE SAT/SUN. IF
NORTHEAST WINDS MATERIALIZE...NEXT WEEKEND AREAS ADJACENT TO LAKE
MICHIGAN ALONG THE IL/IN SHORELINE COULD BE LOCKED IN THE UPR 50S TO
LOW 60S FOR HIGHS WITH A COLD FLOW OFF OF LAKE MICHIGAN.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 12Z...

* STRONG AND GUSTY SOUTH WINDS THROUGH EARLY EVENING.

* CHANCE SHRA/TSRA LATE TONIGHT THROUGH TOMORROW.

KREIN

//DISCUSSION...UPDATED 12Z...

MAIN CONCERN FOR TODAY WILL BE STRONG...GUSTY SOUTH WINDS. AS OF
11Z THIS MORNING...WINDS ARE ALREADY GUSTING TO 25-30KT AND EXPECT
THAT WITH DEEPER MIXING LATER THIS MORNING...SHOULD BE ABLE TO TAP
INTO A 50 KT LOW LEVEL JET TO MIX DOWN GUSTS TO 35 KT OR EVEN
SLIGHTLY HIGHER. THE STRONG LOW LEVEL JET SHOULD MOVE OFF TO THE
EAST BY EARLY AFTERNOON...SO WHILE WINDS SHOULD STILL BE STRONG
AND GUSTY...PEAK GUSTS SHOULD LOWER TO ARND 25KT.

WITH THE PERSISTENT FETCH OF LOW LEVEL MOISTURE INTO THE
REGION...A LAYER OF MVFR STRATOCU HAS OVERSPREAD THE REGION.
EXPECT THAT BASES SHOULD NOT LOWER MUCH LESS THAT 1800FT AGL.
THERE IS SOME UNCERTAINTY AS TO THE DURATION OF THE MVFR CLOUD
LAYER...BUT WITH LITTLE CHANGE TO THE OVERALL PATTERN THROUGH THE
DAY...THERE IS A CHANCE THAT THE MVFR CIGS COULD HANG IN THROUGH
MUCH OF THE DAY. HOWEVER...THERE IS ALSO A CHANCE THAT STRONGER
MIXING IN THE AFTERNOON HOURS COULD ALLOW FOR THE MVFR DECK TO
SCATTER OUT.

LATEST RADAR TRENDS INDICATE THAT AN AREA OF SHRA LIFTING NEWD
FROM CNTRL IL INTO INDIANA. THE TRAJECTORY OF THE PCPN AREA SHOULD
KEEP THE BULK OF THE PCPN EAST AND SOUTH OF GYY...THOUGH A FEW SCT
SHRA AREA NOT OUT OF THE QUESTION. ALSO...SOME SHRA ASSOCIATED
WITH A MID LEVEL IMPULSE LIFTING NORTH THROUGH IOWA AND INTO WRN
WI IS GENERATING SCT SHRA AS WELL. IT IS ALSO POSSIBLE THAT RFD
COULD SEE A FEW SHRA THIS MORNING...BUT THE PROBABILITY IS TOO LOW
TO INCLUDE IN THE TAF AS THE LATEST RADAR TRENDS INDICATE A
WEAKENING TREND THERE.

A SECONDARY LOW IS EXPECTED TO DEVELOP OVER THE UPPER MISSOURI
VALLEY THIS EVENING...KEEPING A MODEST PRESSURE GRADIENT OVER THE
REGION. SO MODERATE...GUSTY WINDS SHOULD PERSIST WELL INTO
TONIGHT. ANOTHER STRONG MID LEVEL IMPULSE IS EXPECTED TO TRACK
THROUGH THE MIDDLE MISSISSIPPI VALLEY AND INTO WISCONSIN LATE
TONIGHT...BRINGING A RENEWED CHANCE FOR SHRA/TSRA TO THE REGION
LATE TONIGHT AND TOMORROW.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 12Z...

* MEDIUM TO HIGH CONFIDENCE IN WIND TRENDS.

* MEDIUM TO HIGH CONFIDENCE THAT THE TERMINALS SHOULD REMAIN
  DRY...THOUGH THERE IS A SMALL CHANCE FOR SOME SHRA INVOF THE
  TERMINALS THROUGH THE MORNING HOURS.

* MEDIUM CONFIDENCE IN CIG TRENDS.

* MEDIUM CONFIDENCE IN PCPN TIMING LATE TONIGHT.

KREIN

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/TSRA LATE. SOUTHEAST WINDS.

FRIDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. SOUTHWEST WINDS
BECOMING NORTHEAST OVERNIGHT.

SATURDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. NORTHEAST
WINDS.

SUNDAY...CHANCE TSRA. MVFR POSSIBLE. NORTHEAST WINDS.

KREIN

&&

.MARINE...
304 AM CDT

LOW PRESSURE WILL BE STEADILY LIFTING NORTH ACROSS THE MISSOURI
VALLEY THIS MORNING...REACHING LAKE SUPERIOR BY THIS EVENING AND
CONTINUING TO SLIDE EAST/NORTHEAST TOWARDS QUEBEC BY TUESDAY
MORNING. A FRONTAL BOUNDARY WILL REMAIN OVER THE FAR NORTHERN
PORTIONS OF LAKE MICHIGAN. MEANWHILE GUSTY SOUTHERLY WINDS ARE
EXPECTED TO INCREASE THIS MORNING...WITH OCCASIONAL GALES FOR THE
NEARSHORE WATERS OF IL/IN. ACROSS THE OPEN WATERS...EXPECT THE
WARM/MOIST AIR TO STRUGGLE TO REACH THE SFC OF THE LAKE WITH SOME
DEGREE OF LAKE STABILITY. WAVES WILL STEADILY BUILD ACROSS THE
NORTHERN HALF OF THE LAKE AS A RESULT OF THE LONG FETCH. STILL
FEEL THAT GUSTS WILL REACH 30KT ACROSS THE LAKE...HOWEVER
CONFIDENCE HAS DIMINISHED SLIGHTLY AS NEW GUIDANCE HAS BECOME A
LITTLE LESS WITH THE WIND FIELDS. NONETHELESS...WAVES FOR THE
NORTHERN HALF OF THE LAKE WILL LIKELY TOP OUT IN THE 4 TO 7 FT
RANGE WITH OCCASIONAL WAVES REACHING 9 FT THIS AFTERNOON/EVENING.

THE GRADIENT QUICKLY DIMINISHES THIS EVENING...BUT EXPECT
SOUTHERLY WINDS TO PERSIST. THIS WILL ALLOW WAVES TO SUBSIDE TO 3
TO 5 FT. ANOTHER LOW WILL ARRIVE TUE...WITH WINDS NUDGING BACK UP
HOWEVER WARM AIR WILL CONTINUE TO FLOW ACROSS THE LAKE AND COULD
FURTHER ENHANCE THE LAKE STABILITY AND KEEP WAVES FROM BUILDING TO
LARGE.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 9 AM MONDAY.

     GALE WARNING...NEARSHORE WATERS UNTIL 3
     PM MONDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...3 PM MONDAY TO 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 251307
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
807 AM CDT MON MAY 25 2015

.UPDATE...756 AM CDT

COMPACT NEGATIVELY TILTED TROUGH AXIS IS SLIDING NORTHEAST THROUGH
IOWA AND WESTERN ILLINOIS. EASTERN EDGE OF THE TROUGH WILL MOVE
THROUGH NORTHEAST ILLINOIS THIS MORNING. NOTED UPTICK IN SHOWER
ACTIVITY ASSOCIATED WITH THIS WAVE IS PRODUCING MORE ORGANIZED BUT
STILL LARGELY SCATTERED SHOWERS. STILL TRACKING THIS FEATURE WILL
BRING THE BEST CHANCE FOR SOME BRIEF DOWNPOURS IN THE COMING
HOURS...AND THESE WILL SPREAD INTO THE WEST METRO AREA IN THE NEXT
HOUR...SPREADING INTO CHICAGOLAND SHORTLY THERE AFTER. THE CLOUDS
PRODUCING THE SHOWER ACTIVITY ARE SHALLOW AND MID LEVEL LAPSE
RATES ARE SUBPAR...THUS THUNDER SHOULD BE LIMITED AT BEST. SOME
WEAK INSTABILITY IS NOTED SOUTH OF I-80 WHICH DOES NOT PRECLUDE AN
ISOLATED STRIKE IN ANY STRONGER ACTIVITY.

REGARDING WINDS...WITH THE BROKEN TO OVERCAST LOW CLOUD
DECK...MIXING IS BEING LIMITED AND GETING GUSTS TO AROUND 30 KT OR
SO. ANY STRONGER GUSTS WOULD BE IN THE NEXT HOUR BEFORE A RAPID
DROP OFF LATER THIS MORNING.

KMD

&&

.SHORT TERM...
345 AM CDT

THROUGH MONDAY NIGHT...
FOR THE REMAINDER OF THE NIGHT AND INTO MONDAY MORNING...PCPN
CHANCES CONTINUE TO WANE AS LATEST RADAR TRENDS ONLY SHOW SOME SCT
SHRA WHICH ARE DECREASING IN INTENSITY.  IN SPITE OF DEWPOINTS IN
THE LOW 60S...AND A STRONG LOW LEVEL JET...50 KT AT 925 MB...THERE
IS AN ELEMENT LACKING WHICH IS SEEMS TO BE PREVENTING THE
MAINTENANCE OF SHRA/TSRA OVER NERN IL/NWRN IN.  THE MAIN MISSING
ELEMENTS IS FORCING.  THE SFC AND UPPER LEVEL LOW ARE WAY TO THE
WEST...OVER THE NRN PLAINS. THE SHORTWAVE CLIMBING UP THE NWRN
PERIPHERY OF THE HIGH AMPLITUDE RIDGE IS BEING SLOWED BY THE HIGH
AMPLITUDE...AND IS BEING FORCED TO A MORE WLY TRACK THROUGH THE
UPPER MISSISSIPPI VALLEY THAN PREVIOUSLY ANTICIPATED.  SO...FOR THE
REMAINDER OF THE OVERNIGHT HOURS AND THE DAYTIME HOURS MONDAY...HAVE
BACK OF TO ISOLD-SCT SHRA.  WILL KEEP ISOLD TS MENTION FOR THE LATE
MORNING HOURS...THROUGH AROUND NOON...WITH THE DAYTIME HEATING...BUT
CONFIDENCE IN ANY TS IS RATHER LOW AT THIS TIME.  BY THIS
AFTERNOON...A MID LEVEL DRY SLOT IS EXPECTED TO MOVE ACROSS THE
REGION...FURTHER LIMITING PCPN CHANCES AND IT IS QUITE LIKELY THAT
THE REGION WILL REMAIN DRY THROUGH THE DAY.  HOWEVER...WHILE THE
PCPN CHANCES ARE DIMINISHING...THE LIKELIHOOD OF STRONG WINDS IS
STILL A CONCERN.  WITH THE DIMINISHING PCPN CHANCES...LESS SKY COVER
THAN PREVIOUSLY ANTICIPATED IS ALSO POSSIBLE.  A STRONG SWLY
PRESSURE GRADIENT IS SETTING UP ACROSS THE REGION BETWEEN SFC
RIDGING ACROSS THE SERN CONUS AND AND LOW PRESSURE FROM THE UPPER
MISSISSIPPI VALLEY TO THE WESTERN PLAINS.  THE STRONG GRADIENT WILL
HELP DRIVE THE SFC WINDS AND THE DIMINISHING CLOUD COVER COULD HELP
ENHANCE DEEP LAYER MIXING...TAPPING STRONGER WINDS ALOFT.  SUSTAINED
25-25 MPH WINDS ARE LIKELY WITH GUSTS OF 30-35 MPH.
ALSO...PERSISTENT WARM/MOIST ADVECTION AT THE SFC WILL BRING
TEMPERATURES INTO THE LOW TO MIDDLE 80S WITH DEWPOINTS IN THE LOWER
60S.

FOR MONDAY NIGHT...THE BREEZY CONDITIONS WILL PERSIST INTO THE AS
THERE SHOULD BE LITTLE CHANGE TO THE SFC AND UPPER LEVEL PATTERNS.
THE UPPER RIDGE WILL LOSE A LITTLE AMPLITUDE AS SHORT WAVE ENERGY
OVERTOPS THE RIDGE...BUT GENERAL TROUGHING WILL PERSIST ACROSS THE
UPPER MISSISSIPPI VALLEY THROUGH THE CENTRAL PLAINS.  THE NEXT
CHANCE FOR PCPN WILL HOLD OFF UNTIL LATE TONIGHT/EARLY TUESDAY
MORNING AND THE NEXT SHORTWAVE LIFTS OUT OF THE SRN PLAINS AND INTO
THE MIDDLE MISSISSIPPI VALLEY.  AMPLE LOW LEVEL MOISTURE WILL
ALREADY BE IN PLACE SO IT WILL JUST A MATTER OF WHEN THE FORCING
WILL GET HERE.  AGAIN...THERE IS SOME CONCERN THAT THE FORCING WILL
BE TO THE WEST...WITH THE SHORTWAVE TRACKING THROUGH THE MIDDLE
MISSISSIPPI VALLEY AND INTO WI.  SO...WILL CARRY CHANCE POPS FOR THE
REGION...WITH LIKELY POPS APPROACHING THE PONTIAC AREA BY EARLY
TUESDAY MORNING.  THE PERSISTENT WARM/MOIST ADVECTIVE PATTERN AND
BREEZY CONDITIONS SHOULD KEEP TEMPERATURES FROM DROPPING OFF
SIGNIFICANTLY OVERNIGHT AND LOWS SHOULD BE IN THE MIDDLE TO UPPER
60S.

KREIN

&&

.LONG TERM...
239 AM CDT

TUESDAY THROUGH SUNDAY...

TUESDAY THROUGH WEDNESDAY...
500MB TROUGH AXIS WILL SLOWLY PIVOT EAST ACROSS THE CENTRAL PLAINS
INTO THE MID-MISSOURI VALLEY TUE...WITH A SFC WAVE SLIDING NORTH
ACROSS IOWA INTO CENTRAL WISC LATE TUE. THE SFC FEATURE IS NOT
EXPECTED TO BE STRONG...HOWEVER THE GRADIENT DOES TIGHTEN WITH
MODEST HEIGHT FALLS IN THE LOWEST LAYERS OF THE ATMOSPHERE. SOME
INSTABILITY DOES REMAIN ALONG WITH RELATIVELY MOIST SFC CONDS AS
DEW PTS WILL REMAIN IN THE UPR 50S/LOW 60S. PWAT VALUES WILL ALSO
HOVER JUST OVER 1 INCH...WHICH IS SEASONAL. WILL HOLD ONTO MENTION
OF RAIN AND THUNDER...BUT COULD SEE THIS MAINLY FOCUSED IN THE TUE
MORNING TIMEFRAME.

WITH CONSIDERABLE SOLAR SHIELDING PROGGED FOR TUE...TEMPS MAY
STRUGGLE TO WARM BEYOND THE MID/UPR 70S. BUT WITH GUIDANCE HINTING
AT A DRY SLOT LIFTING NORTHEAST ACROSS THE REGION TUE EVE...THIS
COULD INTRODUCE SOME EROSION TO THE CLOUD COVER IN THE AFTN HOURS
TUE AND ALLOW SOME SFC HEATING TO OCCUR AND PUSH TEMPS TO ARND 80.

GUIDANCE LIFTS THE DRY SLOT OVERHEAD LATE TUE NGT...WITH THE 500MB
TROUGH AXIS ARRIVING ARND DAYBREAK WED AND LIFTING EAST ACROSS LOWER
MICHIGAN. THIS WILL BRING DRY ONLY SLIGHT CHANCE POPS AS WEAK SFC
RIDGING BEGINS TO NUDGE EAST ACROSS THE MISSOURI VALLEY TOWARDS THE
FORECAST AREA MIDDAY WED. IT IS POSSIBLE THAT ENOUGH DRY AIR
INFLUENCE COULD ALLOW FOR REMOVAL OF THE SLIGHT CHANCE POPS WED
AFTN. THERMAL TROUGH LAGS BEHIND THE FRONTAL BOUNDARY WED...SO TEMPS
COULD STILL WARM BACK TO ARND 80 AND PERHAPS THE LOW 80S IN THE
SOUTHERN CWFA.

THURSDAY THROUGH SUNDAY...
ANTI-CYCLONIC FLOW ARRIVES THUR WITH AT LEAST ONE PERIOD OF DRY
WEATHER EXPECTED FOR NORTHERN IL/NORTHWEST IN. ONLY A COUPLE
ENSEMBLE MEMBERS CONTINUE TO PROG POPS ALONG THE SOUTHERN FORECAST
AREA THUR...BUT COULD SEE THIS TRENDING DRY IN THE NEXT FEW
SOLUTIONS. WITH WARM TEMPS ALOFT EXPECTED THUR AND THIN CLOUD
COVER...THUR HIGHS COULD PEAK IN THE LOW 80S.

THEN FOCUS TURNS TOWARDS THE UPCOMING WEEKEND AND A PATTERN SHIFT
AWAY FROM THE WARM/HUMID CONDITIONS. ENSEMBLES SHOW MINIMAL SPREAD
IN THE LATE WEEK PERIODS...WITH THE UPSTREAM RIDGE OVER
ALASKA/WESTERN CANADA AND A DOWNSTREAM MID-LVL RIDGE ACROSS THE
SOUTHEAST CONUS. BOTH OF THESE FEATURES IN TIME BEGIN TO
WEAKEN...WITH THE LONGWAVE PATTERN TRANSITIONING INTO A SEMI-ZONAL
ORIENTATION BY THE SECOND HALF OF THE WEEKEND.

OPER GUIDANCE HAS BEEN CONSISTENT WITH PROGGING A ROBUST 500MB
TROUGH TO SLIDE SOUTH FROM CENTRAL CANADA FRI...ALONG WITH A STRONG
CANADIAN SFC RIDGE ON IT/S HEELS. WITH A CHANNEL OF MOISTURE
REMAINING ACROSS THE SOUTHERN PLAINS STRETCHING NORTHEAST THROUGH
THE UPPER MIDWEST...THIS BOUNDARY WILL BECOME ACTIVE WITH A SFC WAVE
DEVELOPING ACROSS THE SOUTHERN PLAINS. THIS LOW WILL THEN LIFT
NORTHEAST TOWARDS THE CWFA FRI WITH A COLD FRONT ARRIVING ACROSS THE
FORECAST AREA SAT. WINDS LOOK TO SHIFT TO THE NORTH...WITH MUCH
COOLER AIR SLIDING SOUTH AND LIKELY KNOCKING TEMPS BACK TO SUB-
SEASONAL CONDS IN THE UPR 60S/NEAR 70 DEGREE RANGE SAT/SUN. IF
NORTHEAST WINDS MATERIALIZE...NEXT WEEKEND AREAS ADJACENT TO LAKE
MICHIGAN ALONG THE IL/IN SHORELINE COULD BE LOCKED IN THE UPR 50S TO
LOW 60S FOR HIGHS WITH A COLD FLOW OFF OF LAKE MICHIGAN.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 12Z...

* STRONG AND GUSTY SOUTH WINDS THROUGH EARLY EVENING.

* CHANCE SHRA/TSRA LATE TONIGHT THROUGH TOMORROW.

KREIN

//DISCUSSION...UPDATED 12Z...

MAIN CONCERN FOR TODAY WILL BE STRONG...GUSTY SOUTH WINDS. AS OF
11Z THIS MORNING...WINDS ARE ALREADY GUSTING TO 25-30KT AND EXPECT
THAT WITH DEEPER MIXING LATER THIS MORNING...SHOULD BE ABLE TO TAP
INTO A 50 KT LOW LEVEL JET TO MIX DOWN GUSTS TO 35 KT OR EVEN
SLIGHTLY HIGHER. THE STRONG LOW LEVEL JET SHOULD MOVE OFF TO THE
EAST BY EARLY AFTERNOON...SO WHILE WINDS SHOULD STILL BE STRONG
AND GUSTY...PEAK GUSTS SHOULD LOWER TO ARND 25KT.

WITH THE PERSISTENT FETCH OF LOW LEVEL MOISTURE INTO THE
REGION...A LAYER OF MVFR STRATOCU HAS OVERSPREAD THE REGION.
EXPECT THAT BASES SHOULD NOT LOWER MUCH LESS THAT 1800FT AGL.
THERE IS SOME UNCERTAINTY AS TO THE DURATION OF THE MVFR CLOUD
LAYER...BUT WITH LITTLE CHANGE TO THE OVERALL PATTERN THROUGH THE
DAY...THERE IS A CHANCE THAT THE MVFR CIGS COULD HANG IN THROUGH
MUCH OF THE DAY. HOWEVER...THERE IS ALSO A CHANCE THAT STRONGER
MIXING IN THE AFTERNOON HOURS COULD ALLOW FOR THE MVFR DECK TO
SCATTER OUT.

LATEST RADAR TRENDS INDICATE THAT AN AREA OF SHRA LIFTING NEWD
FROM CNTRL IL INTO INDIANA. THE TRAJECTORY OF THE PCPN AREA SHOULD
KEEP THE BULK OF THE PCPN EAST AND SOUTH OF GYY...THOUGH A FEW SCT
SHRA AREA NOT OUT OF THE QUESTION. ALSO...SOME SHRA ASSOCIATED
WITH A MID LEVEL IMPULSE LIFTING NORTH THROUGH IOWA AND INTO WRN
WI IS GENERATING SCT SHRA AS WELL. IT IS ALSO POSSIBLE THAT RFD
COULD SEE A FEW SHRA THIS MORNING...BUT THE PROBABILITY IS TOO LOW
TO INCLUDE IN THE TAF AS THE LATEST RADAR TRENDS INDICATE A
WEAKENING TREND THERE.

A SECONDARY LOW IS EXPECTED TO DEVELOP OVER THE UPPER MISSOURI
VALLEY THIS EVENING...KEEPING A MODEST PRESSURE GRADIENT OVER THE
REGION. SO MODERATE...GUSTY WINDS SHOULD PERSIST WELL INTO
TONIGHT. ANOTHER STRONG MID LEVEL IMPULSE IS EXPECTED TO TRACK
THROUGH THE MIDDLE MISSISSIPPI VALLEY AND INTO WISCONSIN LATE
TONIGHT...BRINGING A RENEWED CHANCE FOR SHRA/TSRA TO THE REGION
LATE TONIGHT AND TOMORROW.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 12Z...

* MEDIUM TO HIGH CONFIDENCE IN WIND TRENDS.

* MEDIUM TO HIGH CONFIDENCE THAT THE TERMINALS SHOULD REMAIN
  DRY...THOUGH THERE IS A SMALL CHANCE FOR SOME SHRA INVOF THE
  TERMINALS THROUGH THE MORNING HOURS.

* MEDIUM CONFIDENCE IN CIG TRENDS.

* MEDIUM CONFIDENCE IN PCPN TIMING LATE TONIGHT.

KREIN

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/TSRA LATE. SOUTHEAST WINDS.

FRIDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. SOUTHWEST WINDS
BECOMING NORTHEAST OVERNIGHT.

SATURDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. NORTHEAST
WINDS.

SUNDAY...CHANCE TSRA. MVFR POSSIBLE. NORTHEAST WINDS.

KREIN

&&

.MARINE...
304 AM CDT

LOW PRESSURE WILL BE STEADILY LIFTING NORTH ACROSS THE MISSOURI
VALLEY THIS MORNING...REACHING LAKE SUPERIOR BY THIS EVENING AND
CONTINUING TO SLIDE EAST/NORTHEAST TOWARDS QUEBEC BY TUESDAY
MORNING. A FRONTAL BOUNDARY WILL REMAIN OVER THE FAR NORTHERN
PORTIONS OF LAKE MICHIGAN. MEANWHILE GUSTY SOUTHERLY WINDS ARE
EXPECTED TO INCREASE THIS MORNING...WITH OCCASIONAL GALES FOR THE
NEARSHORE WATERS OF IL/IN. ACROSS THE OPEN WATERS...EXPECT THE
WARM/MOIST AIR TO STRUGGLE TO REACH THE SFC OF THE LAKE WITH SOME
DEGREE OF LAKE STABILITY. WAVES WILL STEADILY BUILD ACROSS THE
NORTHERN HALF OF THE LAKE AS A RESULT OF THE LONG FETCH. STILL
FEEL THAT GUSTS WILL REACH 30KT ACROSS THE LAKE...HOWEVER
CONFIDENCE HAS DIMINISHED SLIGHTLY AS NEW GUIDANCE HAS BECOME A
LITTLE LESS WITH THE WIND FIELDS. NONETHELESS...WAVES FOR THE
NORTHERN HALF OF THE LAKE WILL LIKELY TOP OUT IN THE 4 TO 7 FT
RANGE WITH OCCASIONAL WAVES REACHING 9 FT THIS AFTERNOON/EVENING.

THE GRADIENT QUICKLY DIMINISHES THIS EVENING...BUT EXPECT
SOUTHERLY WINDS TO PERSIST. THIS WILL ALLOW WAVES TO SUBSIDE TO 3
TO 5 FT. ANOTHER LOW WILL ARRIVE TUE...WITH WINDS NUDGING BACK UP
HOWEVER WARM AIR WILL CONTINUE TO FLOW ACROSS THE LAKE AND COULD
FURTHER ENHANCE THE LAKE STABILITY AND KEEP WAVES FROM BUILDING TO
LARGE.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 9 AM MONDAY.

     GALE WARNING...NEARSHORE WATERS UNTIL 3
     PM MONDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...3 PM MONDAY TO 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
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000
FXUS63 KLOT 251302
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
802 AM CDT MON MAY 25 2015

.UPDATE...
756 AM CDT

COMPACT NEGATIVELY TILTED TROUGH AXIS IS SLIDING NORTHEAST THROUGH
IOWA AND WESTERN ILLINOIS. EASTERN EDGE OF THE TROUGH WILL MOVE
THROUGH NORTHEAST ILLINOIS THIS MORNING. NOTED UPTICK IN SHOWER
ACTIVITY ASSOCIATED WITH THIS WAVE IS PRODUCING MORE ORGANIZED BUT
STILL LARGELY SCATTERED SHOWERS. STILL TRACKING THIS FEATURE WILL
BRING THE BEST CHANCE FOR SOME BRIEF DOWNPOURS IN THE COMING
HOURS...AND THESE WILL SPREAD INTO THE WEST METRO AREA IN THE NEXT
HOUR...SPREADING INTO CHICAGOLAND SHORTLY THERE AFTER. THE CLOUDS
PRODUCING THE SHOWER ACTIVITY ARE SHALLOW AND MID LEVEL LAPSE
RATES ARE SUBPAR...THUS THUNDER SHOULD BE LIMITED AT BEST. SOME
WEAK INSTABILITY IS NOTED SOUTH OF I-80 WHICH DOES NOT PRECLUDE AN
ISOLATED STRIKE IN ANY STRONGER ACTIVITY.

KMD

KMD

&&

.SHORT TERM...
345 AM CDT

THROUGH MONDAY NIGHT...
FOR THE REMAINDER OF THE NIGHT AND INTO MONDAY MORNING...PCPN
CHANCES CONTINUE TO WANE AS LATEST RADAR TRENDS ONLY SHOW SOME SCT
SHRA WHICH ARE DECREASING IN INTENSITY.  IN SPITE OF DEWPOINTS IN
THE LOW 60S...AND A STRONG LOW LEVEL JET...50 KT AT 925 MB...THERE
IS AN ELEMENT LACKING WHICH IS SEEMS TO BE PREVENTING THE
MAINTENANCE OF SHRA/TSRA OVER NERN IL/NWRN IN.  THE MAIN MISSING
ELEMENTS IS FORCING.  THE SFC AND UPPER LEVEL LOW ARE WAY TO THE
WEST...OVER THE NRN PLAINS. THE SHORTWAVE CLIMBING UP THE NWRN
PERIPHERY OF THE HIGH AMPLITUDE RIDGE IS BEING SLOWED BY THE HIGH
AMPLITUDE...AND IS BEING FORCED TO A MORE WLY TRACK THROUGH THE
UPPER MISSISSIPPI VALLEY THAN PREVIOUSLY ANTICIPATED.  SO...FOR THE
REMAINDER OF THE OVERNIGHT HOURS AND THE DAYTIME HOURS MONDAY...HAVE
BACK OF TO ISOLD-SCT SHRA.  WILL KEEP ISOLD TS MENTION FOR THE LATE
MORNING HOURS...THROUGH AROUND NOON...WITH THE DAYTIME HEATING...BUT
CONFIDENCE IN ANY TS IS RATHER LOW AT THIS TIME.  BY THIS
AFTERNOON...A MID LEVEL DRY SLOT IS EXPECTED TO MOVE ACROSS THE
REGION...FURTHER LIMITING PCPN CHANCES AND IT IS QUITE LIKELY THAT
THE REGION WILL REMAIN DRY THROUGH THE DAY.  HOWEVER...WHILE THE
PCPN CHANCES ARE DIMINISHING...THE LIKELIHOOD OF STRONG WINDS IS
STILL A CONCERN.  WITH THE DIMINISHING PCPN CHANCES...LESS SKY COVER
THAN PREVIOUSLY ANTICIPATED IS ALSO POSSIBLE.  A STRONG SWLY
PRESSURE GRADIENT IS SETTING UP ACROSS THE REGION BETWEEN SFC
RIDGING ACROSS THE SERN CONUS AND AND LOW PRESSURE FROM THE UPPER
MISSISSIPPI VALLEY TO THE WESTERN PLAINS.  THE STRONG GRADIENT WILL
HELP DRIVE THE SFC WINDS AND THE DIMINISHING CLOUD COVER COULD HELP
ENHANCE DEEP LAYER MIXING...TAPPING STRONGER WINDS ALOFT.  SUSTAINED
25-25 MPH WINDS ARE LIKELY WITH GUSTS OF 30-35 MPH.
ALSO...PERSISTENT WARM/MOIST ADVECTION AT THE SFC WILL BRING
TEMPERATURES INTO THE LOW TO MIDDLE 80S WITH DEWPOINTS IN THE LOWER
60S.

FOR MONDAY NIGHT...THE BREEZY CONDITIONS WILL PERSIST INTO THE AS
THERE SHOULD BE LITTLE CHANGE TO THE SFC AND UPPER LEVEL PATTERNS.
THE UPPER RIDGE WILL LOSE A LITTLE AMPLITUDE AS SHORT WAVE ENERGY
OVERTOPS THE RIDGE...BUT GENERAL TROUGHING WILL PERSIST ACROSS THE
UPPER MISSISSIPPI VALLEY THROUGH THE CENTRAL PLAINS.  THE NEXT
CHANCE FOR PCPN WILL HOLD OFF UNTIL LATE TONIGHT/EARLY TUESDAY
MORNING AND THE NEXT SHORTWAVE LIFTS OUT OF THE SRN PLAINS AND INTO
THE MIDDLE MISSISSIPPI VALLEY.  AMPLE LOW LEVEL MOISTURE WILL
ALREADY BE IN PLACE SO IT WILL JUST A MATTER OF WHEN THE FORCING
WILL GET HERE.  AGAIN...THERE IS SOME CONCERN THAT THE FORCING WILL
BE TO THE WEST...WITH THE SHORTWAVE TRACKING THROUGH THE MIDDLE
MISSISSIPPI VALLEY AND INTO WI.  SO...WILL CARRY CHANCE POPS FOR THE
REGION...WITH LIKELY POPS APPROACHING THE PONTIAC AREA BY EARLY
TUESDAY MORNING.  THE PERSISTENT WARM/MOIST ADVECTIVE PATTERN AND
BREEZY CONDITIONS SHOULD KEEP TEMPERATURES FROM DROPPING OFF
SIGNIFICANTLY OVERNIGHT AND LOWS SHOULD BE IN THE MIDDLE TO UPPER
60S.

KREIN

&&

.LONG TERM...
239 AM CDT

TUESDAY THROUGH SUNDAY...

TUESDAY THROUGH WEDNESDAY...
500MB TROUGH AXIS WILL SLOWLY PIVOT EAST ACROSS THE CENTRAL PLAINS
INTO THE MID-MISSOURI VALLEY TUE...WITH A SFC WAVE SLIDING NORTH
ACROSS IOWA INTO CENTRAL WISC LATE TUE. THE SFC FEATURE IS NOT
EXPECTED TO BE STRONG...HOWEVER THE GRADIENT DOES TIGHTEN WITH
MODEST HEIGHT FALLS IN THE LOWEST LAYERS OF THE ATMOSPHERE. SOME
INSTABILITY DOES REMAIN ALONG WITH RELATIVELY MOIST SFC CONDS AS
DEW PTS WILL REMAIN IN THE UPR 50S/LOW 60S. PWAT VALUES WILL ALSO
HOVER JUST OVER 1 INCH...WHICH IS SEASONAL. WILL HOLD ONTO MENTION
OF RAIN AND THUNDER...BUT COULD SEE THIS MAINLY FOCUSED IN THE TUE
MORNING TIMEFRAME.

WITH CONSIDERABLE SOLAR SHIELDING PROGGED FOR TUE...TEMPS MAY
STRUGGLE TO WARM BEYOND THE MID/UPR 70S. BUT WITH GUIDANCE HINTING
AT A DRY SLOT LIFTING NORTHEAST ACROSS THE REGION TUE EVE...THIS
COULD INTRODUCE SOME EROSION TO THE CLOUD COVER IN THE AFTN HOURS
TUE AND ALLOW SOME SFC HEATING TO OCCUR AND PUSH TEMPS TO ARND 80.

GUIDANCE LIFTS THE DRY SLOT OVERHEAD LATE TUE NGT...WITH THE 500MB
TROUGH AXIS ARRIVING ARND DAYBREAK WED AND LIFTING EAST ACROSS LOWER
MICHIGAN. THIS WILL BRING DRY ONLY SLIGHT CHANCE POPS AS WEAK SFC
RIDGING BEGINS TO NUDGE EAST ACROSS THE MISSOURI VALLEY TOWARDS THE
FORECAST AREA MIDDAY WED. IT IS POSSIBLE THAT ENOUGH DRY AIR
INFLUENCE COULD ALLOW FOR REMOVAL OF THE SLIGHT CHANCE POPS WED
AFTN. THERMAL TROUGH LAGS BEHIND THE FRONTAL BOUNDARY WED...SO TEMPS
COULD STILL WARM BACK TO ARND 80 AND PERHAPS THE LOW 80S IN THE
SOUTHERN CWFA.

THURSDAY THROUGH SUNDAY...
ANTI-CYCLONIC FLOW ARRIVES THUR WITH AT LEAST ONE PERIOD OF DRY
WEATHER EXPECTED FOR NORTHERN IL/NORTHWEST IN. ONLY A COUPLE
ENSEMBLE MEMBERS CONTINUE TO PROG POPS ALONG THE SOUTHERN FORECAST
AREA THUR...BUT COULD SEE THIS TRENDING DRY IN THE NEXT FEW
SOLUTIONS. WITH WARM TEMPS ALOFT EXPECTED THUR AND THIN CLOUD
COVER...THUR HIGHS COULD PEAK IN THE LOW 80S.

THEN FOCUS TURNS TOWARDS THE UPCOMING WEEKEND AND A PATTERN SHIFT
AWAY FROM THE WARM/HUMID CONDITIONS. ENSEMBLES SHOW MINIMAL SPREAD
IN THE LATE WEEK PERIODS...WITH THE UPSTREAM RIDGE OVER
ALASKA/WESTERN CANADA AND A DOWNSTREAM MID-LVL RIDGE ACROSS THE
SOUTHEAST CONUS. BOTH OF THESE FEATURES IN TIME BEGIN TO
WEAKEN...WITH THE LONGWAVE PATTERN TRANSITIONING INTO A SEMI-ZONAL
ORIENTATION BY THE SECOND HALF OF THE WEEKEND.

OPER GUIDANCE HAS BEEN CONSISTENT WITH PROGGING A ROBUST 500MB
TROUGH TO SLIDE SOUTH FROM CENTRAL CANADA FRI...ALONG WITH A STRONG
CANADIAN SFC RIDGE ON IT/S HEELS. WITH A CHANNEL OF MOISTURE
REMAINING ACROSS THE SOUTHERN PLAINS STRETCHING NORTHEAST THROUGH
THE UPPER MIDWEST...THIS BOUNDARY WILL BECOME ACTIVE WITH A SFC WAVE
DEVELOPING ACROSS THE SOUTHERN PLAINS. THIS LOW WILL THEN LIFT
NORTHEAST TOWARDS THE CWFA FRI WITH A COLD FRONT ARRIVING ACROSS THE
FORECAST AREA SAT. WINDS LOOK TO SHIFT TO THE NORTH...WITH MUCH
COOLER AIR SLIDING SOUTH AND LIKELY KNOCKING TEMPS BACK TO SUB-
SEASONAL CONDS IN THE UPR 60S/NEAR 70 DEGREE RANGE SAT/SUN. IF
NORTHEAST WINDS MATERIALIZE...NEXT WEEKEND AREAS ADJACENT TO LAKE
MICHIGAN ALONG THE IL/IN SHORELINE COULD BE LOCKED IN THE UPR 50S TO
LOW 60S FOR HIGHS WITH A COLD FLOW OFF OF LAKE MICHIGAN.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 12Z...

* STRONG AND GUSTY SOUTH WINDS THROUGH EARLY EVENING.

* CHANCE SHRA/TSRA LATE TONIGHT THROUGH TOMORROW.

KREIN

//DISCUSSION...UPDATED 12Z...

MAIN CONCERN FOR TODAY WILL BE STRONG...GUSTY SOUTH WINDS. AS OF
11Z THIS MORNING...WINDS ARE ALREADY GUSTING TO 25-30KT AND EXPECT
THAT WITH DEEPER MIXING LATER THIS MORNING...SHOULD BE ABLE TO TAP
INTO A 50 KT LOW LEVEL JET TO MIX DOWN GUSTS TO 35 KT OR EVEN
SLIGHTLY HIGHER. THE STRONG LOW LEVEL JET SHOULD MOVE OFF TO THE
EAST BY EARLY AFTERNOON...SO WHILE WINDS SHOULD STILL BE STRONG
AND GUSTY...PEAK GUSTS SHOULD LOWER TO ARND 25KT.

WITH THE PERSISTENT FETCH OF LOW LEVEL MOISTURE INTO THE
REGION...A LAYER OF MVFR STRATOCU HAS OVERSPREAD THE REGION.
EXPECT THAT BASES SHOULD NOT LOWER MUCH LESS THAT 1800FT AGL.
THERE IS SOME UNCERTAINTY AS TO THE DURATION OF THE MVFR CLOUD
LAYER...BUT WITH LITTLE CHANGE TO THE OVERALL PATTERN THROUGH THE
DAY...THERE IS A CHANCE THAT THE MVFR CIGS COULD HANG IN THROUGH
MUCH OF THE DAY. HOWEVER...THERE IS ALSO A CHANCE THAT STRONGER
MIXING IN THE AFTERNOON HOURS COULD ALLOW FOR THE MVFR DECK TO
SCATTER OUT.

LATEST RADAR TRENDS INDICATE THAT AN AREA OF SHRA LIFTING NEWD
FROM CNTRL IL INTO INDIANA. THE TRAJECTORY OF THE PCPN AREA SHOULD
KEEP THE BULK OF THE PCPN EAST AND SOUTH OF GYY...THOUGH A FEW SCT
SHRA AREA NOT OUT OF THE QUESTION. ALSO...SOME SHRA ASSOCIATED
WITH A MID LEVEL IMPULSE LIFTING NORTH THROUGH IOWA AND INTO WRN
WI IS GENERATING SCT SHRA AS WELL. IT IS ALSO POSSIBLE THAT RFD
COULD SEE A FEW SHRA THIS MORNING...BUT THE PROBABILITY IS TOO LOW
TO INCLUDE IN THE TAF AS THE LATEST RADAR TRENDS INDICATE A
WEAKENING TREND THERE.

A SECONDARY LOW IS EXPECTED TO DEVELOP OVER THE UPPER MISSOURI
VALLEY THIS EVENING...KEEPING A MODEST PRESSURE GRADIENT OVER THE
REGION. SO MODERATE...GUSTY WINDS SHOULD PERSIST WELL INTO
TONIGHT. ANOTHER STRONG MID LEVEL IMPULSE IS EXPECTED TO TRACK
THROUGH THE MIDDLE MISSISSIPPI VALLEY AND INTO WISCONSIN LATE
TONIGHT...BRINGING A RENEWED CHANCE FOR SHRA/TSRA TO THE REGION
LATE TONIGHT AND TOMORROW.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 12Z...

* MEDIUM TO HIGH CONFIDENCE IN WIND TRENDS.

* MEDIUM TO HIGH CONFIDENCE THAT THE TERMINALS SHOULD REMAIN
  DRY...THOUGH THERE IS A SMALL CHANCE FOR SOME SHRA INVOF THE
  TERMINALS THROUGH THE MORNING HOURS.

* MEDIUM CONFIDENCE IN CIG TRENDS.

* MEDIUM CONFIDENCE IN PCPN TIMING LATE TONIGHT.

KREIN

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/TSRA LATE. SOUTHEAST WINDS.

FRIDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. SOUTHWEST WINDS
BECOMING NORTHEAST OVERNIGHT.

SATURDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. NORTHEAST
WINDS.

SUNDAY...CHANCE TSRA. MVFR POSSIBLE. NORTHEAST WINDS.

KREIN

&&

.MARINE...
304 AM CDT

LOW PRESSURE WILL BE STEADILY LIFTING NORTH ACROSS THE MISSOURI
VALLEY THIS MORNING...REACHING LAKE SUPERIOR BY THIS EVENING AND
CONTINUING TO SLIDE EAST/NORTHEAST TOWARDS QUEBEC BY TUESDAY
MORNING. A FRONTAL BOUNDARY WILL REMAIN OVER THE FAR NORTHERN
PORTIONS OF LAKE MICHIGAN. MEANWHILE GUSTY SOUTHERLY WINDS ARE
EXPECTED TO INCREASE THIS MORNING...WITH OCCASIONAL GALES FOR THE
NEARSHORE WATERS OF IL/IN. ACROSS THE OPEN WATERS...EXPECT THE
WARM/MOIST AIR TO STRUGGLE TO REACH THE SFC OF THE LAKE WITH SOME
DEGREE OF LAKE STABILITY. WAVES WILL STEADILY BUILD ACROSS THE
NORTHERN HALF OF THE LAKE AS A RESULT OF THE LONG FETCH. STILL
FEEL THAT GUSTS WILL REACH 30KT ACROSS THE LAKE...HOWEVER
CONFIDENCE HAS DIMINISHED SLIGHTLY AS NEW GUIDANCE HAS BECOME A
LITTLE LESS WITH THE WIND FIELDS. NONETHELESS...WAVES FOR THE
NORTHERN HALF OF THE LAKE WILL LIKELY TOP OUT IN THE 4 TO 7 FT
RANGE WITH OCCASIONAL WAVES REACHING 9 FT THIS AFTERNOON/EVENING.

THE GRADIENT QUICKLY DIMINISHES THIS EVENING...BUT EXPECT
SOUTHERLY WINDS TO PERSIST. THIS WILL ALLOW WAVES TO SUBSIDE TO 3
TO 5 FT. ANOTHER LOW WILL ARRIVE TUE...WITH WINDS NUDGING BACK UP
HOWEVER WARM AIR WILL CONTINUE TO FLOW ACROSS THE LAKE AND COULD
FURTHER ENHANCE THE LAKE STABILITY AND KEEP WAVES FROM BUILDING TO
LARGE.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 9 AM MONDAY.

     GALE WARNING...NEARSHORE WATERS UNTIL 3
     PM MONDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...3 PM MONDAY TO 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
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000
FXUS63 KLOT 251302
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
802 AM CDT MON MAY 25 2015

.UPDATE...
756 AM CDT

COMPACT NEGATIVELY TILTED TROUGH AXIS IS SLIDING NORTHEAST THROUGH
IOWA AND WESTERN ILLINOIS. EASTERN EDGE OF THE TROUGH WILL MOVE
THROUGH NORTHEAST ILLINOIS THIS MORNING. NOTED UPTICK IN SHOWER
ACTIVITY ASSOCIATED WITH THIS WAVE IS PRODUCING MORE ORGANIZED BUT
STILL LARGELY SCATTERED SHOWERS. STILL TRACKING THIS FEATURE WILL
BRING THE BEST CHANCE FOR SOME BRIEF DOWNPOURS IN THE COMING
HOURS...AND THESE WILL SPREAD INTO THE WEST METRO AREA IN THE NEXT
HOUR...SPREADING INTO CHICAGOLAND SHORTLY THERE AFTER. THE CLOUDS
PRODUCING THE SHOWER ACTIVITY ARE SHALLOW AND MID LEVEL LAPSE
RATES ARE SUBPAR...THUS THUNDER SHOULD BE LIMITED AT BEST. SOME
WEAK INSTABILITY IS NOTED SOUTH OF I-80 WHICH DOES NOT PRECLUDE AN
ISOLATED STRIKE IN ANY STRONGER ACTIVITY.

KMD

KMD

&&

.SHORT TERM...
345 AM CDT

THROUGH MONDAY NIGHT...
FOR THE REMAINDER OF THE NIGHT AND INTO MONDAY MORNING...PCPN
CHANCES CONTINUE TO WANE AS LATEST RADAR TRENDS ONLY SHOW SOME SCT
SHRA WHICH ARE DECREASING IN INTENSITY.  IN SPITE OF DEWPOINTS IN
THE LOW 60S...AND A STRONG LOW LEVEL JET...50 KT AT 925 MB...THERE
IS AN ELEMENT LACKING WHICH IS SEEMS TO BE PREVENTING THE
MAINTENANCE OF SHRA/TSRA OVER NERN IL/NWRN IN.  THE MAIN MISSING
ELEMENTS IS FORCING.  THE SFC AND UPPER LEVEL LOW ARE WAY TO THE
WEST...OVER THE NRN PLAINS. THE SHORTWAVE CLIMBING UP THE NWRN
PERIPHERY OF THE HIGH AMPLITUDE RIDGE IS BEING SLOWED BY THE HIGH
AMPLITUDE...AND IS BEING FORCED TO A MORE WLY TRACK THROUGH THE
UPPER MISSISSIPPI VALLEY THAN PREVIOUSLY ANTICIPATED.  SO...FOR THE
REMAINDER OF THE OVERNIGHT HOURS AND THE DAYTIME HOURS MONDAY...HAVE
BACK OF TO ISOLD-SCT SHRA.  WILL KEEP ISOLD TS MENTION FOR THE LATE
MORNING HOURS...THROUGH AROUND NOON...WITH THE DAYTIME HEATING...BUT
CONFIDENCE IN ANY TS IS RATHER LOW AT THIS TIME.  BY THIS
AFTERNOON...A MID LEVEL DRY SLOT IS EXPECTED TO MOVE ACROSS THE
REGION...FURTHER LIMITING PCPN CHANCES AND IT IS QUITE LIKELY THAT
THE REGION WILL REMAIN DRY THROUGH THE DAY.  HOWEVER...WHILE THE
PCPN CHANCES ARE DIMINISHING...THE LIKELIHOOD OF STRONG WINDS IS
STILL A CONCERN.  WITH THE DIMINISHING PCPN CHANCES...LESS SKY COVER
THAN PREVIOUSLY ANTICIPATED IS ALSO POSSIBLE.  A STRONG SWLY
PRESSURE GRADIENT IS SETTING UP ACROSS THE REGION BETWEEN SFC
RIDGING ACROSS THE SERN CONUS AND AND LOW PRESSURE FROM THE UPPER
MISSISSIPPI VALLEY TO THE WESTERN PLAINS.  THE STRONG GRADIENT WILL
HELP DRIVE THE SFC WINDS AND THE DIMINISHING CLOUD COVER COULD HELP
ENHANCE DEEP LAYER MIXING...TAPPING STRONGER WINDS ALOFT.  SUSTAINED
25-25 MPH WINDS ARE LIKELY WITH GUSTS OF 30-35 MPH.
ALSO...PERSISTENT WARM/MOIST ADVECTION AT THE SFC WILL BRING
TEMPERATURES INTO THE LOW TO MIDDLE 80S WITH DEWPOINTS IN THE LOWER
60S.

FOR MONDAY NIGHT...THE BREEZY CONDITIONS WILL PERSIST INTO THE AS
THERE SHOULD BE LITTLE CHANGE TO THE SFC AND UPPER LEVEL PATTERNS.
THE UPPER RIDGE WILL LOSE A LITTLE AMPLITUDE AS SHORT WAVE ENERGY
OVERTOPS THE RIDGE...BUT GENERAL TROUGHING WILL PERSIST ACROSS THE
UPPER MISSISSIPPI VALLEY THROUGH THE CENTRAL PLAINS.  THE NEXT
CHANCE FOR PCPN WILL HOLD OFF UNTIL LATE TONIGHT/EARLY TUESDAY
MORNING AND THE NEXT SHORTWAVE LIFTS OUT OF THE SRN PLAINS AND INTO
THE MIDDLE MISSISSIPPI VALLEY.  AMPLE LOW LEVEL MOISTURE WILL
ALREADY BE IN PLACE SO IT WILL JUST A MATTER OF WHEN THE FORCING
WILL GET HERE.  AGAIN...THERE IS SOME CONCERN THAT THE FORCING WILL
BE TO THE WEST...WITH THE SHORTWAVE TRACKING THROUGH THE MIDDLE
MISSISSIPPI VALLEY AND INTO WI.  SO...WILL CARRY CHANCE POPS FOR THE
REGION...WITH LIKELY POPS APPROACHING THE PONTIAC AREA BY EARLY
TUESDAY MORNING.  THE PERSISTENT WARM/MOIST ADVECTIVE PATTERN AND
BREEZY CONDITIONS SHOULD KEEP TEMPERATURES FROM DROPPING OFF
SIGNIFICANTLY OVERNIGHT AND LOWS SHOULD BE IN THE MIDDLE TO UPPER
60S.

KREIN

&&

.LONG TERM...
239 AM CDT

TUESDAY THROUGH SUNDAY...

TUESDAY THROUGH WEDNESDAY...
500MB TROUGH AXIS WILL SLOWLY PIVOT EAST ACROSS THE CENTRAL PLAINS
INTO THE MID-MISSOURI VALLEY TUE...WITH A SFC WAVE SLIDING NORTH
ACROSS IOWA INTO CENTRAL WISC LATE TUE. THE SFC FEATURE IS NOT
EXPECTED TO BE STRONG...HOWEVER THE GRADIENT DOES TIGHTEN WITH
MODEST HEIGHT FALLS IN THE LOWEST LAYERS OF THE ATMOSPHERE. SOME
INSTABILITY DOES REMAIN ALONG WITH RELATIVELY MOIST SFC CONDS AS
DEW PTS WILL REMAIN IN THE UPR 50S/LOW 60S. PWAT VALUES WILL ALSO
HOVER JUST OVER 1 INCH...WHICH IS SEASONAL. WILL HOLD ONTO MENTION
OF RAIN AND THUNDER...BUT COULD SEE THIS MAINLY FOCUSED IN THE TUE
MORNING TIMEFRAME.

WITH CONSIDERABLE SOLAR SHIELDING PROGGED FOR TUE...TEMPS MAY
STRUGGLE TO WARM BEYOND THE MID/UPR 70S. BUT WITH GUIDANCE HINTING
AT A DRY SLOT LIFTING NORTHEAST ACROSS THE REGION TUE EVE...THIS
COULD INTRODUCE SOME EROSION TO THE CLOUD COVER IN THE AFTN HOURS
TUE AND ALLOW SOME SFC HEATING TO OCCUR AND PUSH TEMPS TO ARND 80.

GUIDANCE LIFTS THE DRY SLOT OVERHEAD LATE TUE NGT...WITH THE 500MB
TROUGH AXIS ARRIVING ARND DAYBREAK WED AND LIFTING EAST ACROSS LOWER
MICHIGAN. THIS WILL BRING DRY ONLY SLIGHT CHANCE POPS AS WEAK SFC
RIDGING BEGINS TO NUDGE EAST ACROSS THE MISSOURI VALLEY TOWARDS THE
FORECAST AREA MIDDAY WED. IT IS POSSIBLE THAT ENOUGH DRY AIR
INFLUENCE COULD ALLOW FOR REMOVAL OF THE SLIGHT CHANCE POPS WED
AFTN. THERMAL TROUGH LAGS BEHIND THE FRONTAL BOUNDARY WED...SO TEMPS
COULD STILL WARM BACK TO ARND 80 AND PERHAPS THE LOW 80S IN THE
SOUTHERN CWFA.

THURSDAY THROUGH SUNDAY...
ANTI-CYCLONIC FLOW ARRIVES THUR WITH AT LEAST ONE PERIOD OF DRY
WEATHER EXPECTED FOR NORTHERN IL/NORTHWEST IN. ONLY A COUPLE
ENSEMBLE MEMBERS CONTINUE TO PROG POPS ALONG THE SOUTHERN FORECAST
AREA THUR...BUT COULD SEE THIS TRENDING DRY IN THE NEXT FEW
SOLUTIONS. WITH WARM TEMPS ALOFT EXPECTED THUR AND THIN CLOUD
COVER...THUR HIGHS COULD PEAK IN THE LOW 80S.

THEN FOCUS TURNS TOWARDS THE UPCOMING WEEKEND AND A PATTERN SHIFT
AWAY FROM THE WARM/HUMID CONDITIONS. ENSEMBLES SHOW MINIMAL SPREAD
IN THE LATE WEEK PERIODS...WITH THE UPSTREAM RIDGE OVER
ALASKA/WESTERN CANADA AND A DOWNSTREAM MID-LVL RIDGE ACROSS THE
SOUTHEAST CONUS. BOTH OF THESE FEATURES IN TIME BEGIN TO
WEAKEN...WITH THE LONGWAVE PATTERN TRANSITIONING INTO A SEMI-ZONAL
ORIENTATION BY THE SECOND HALF OF THE WEEKEND.

OPER GUIDANCE HAS BEEN CONSISTENT WITH PROGGING A ROBUST 500MB
TROUGH TO SLIDE SOUTH FROM CENTRAL CANADA FRI...ALONG WITH A STRONG
CANADIAN SFC RIDGE ON IT/S HEELS. WITH A CHANNEL OF MOISTURE
REMAINING ACROSS THE SOUTHERN PLAINS STRETCHING NORTHEAST THROUGH
THE UPPER MIDWEST...THIS BOUNDARY WILL BECOME ACTIVE WITH A SFC WAVE
DEVELOPING ACROSS THE SOUTHERN PLAINS. THIS LOW WILL THEN LIFT
NORTHEAST TOWARDS THE CWFA FRI WITH A COLD FRONT ARRIVING ACROSS THE
FORECAST AREA SAT. WINDS LOOK TO SHIFT TO THE NORTH...WITH MUCH
COOLER AIR SLIDING SOUTH AND LIKELY KNOCKING TEMPS BACK TO SUB-
SEASONAL CONDS IN THE UPR 60S/NEAR 70 DEGREE RANGE SAT/SUN. IF
NORTHEAST WINDS MATERIALIZE...NEXT WEEKEND AREAS ADJACENT TO LAKE
MICHIGAN ALONG THE IL/IN SHORELINE COULD BE LOCKED IN THE UPR 50S TO
LOW 60S FOR HIGHS WITH A COLD FLOW OFF OF LAKE MICHIGAN.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 12Z...

* STRONG AND GUSTY SOUTH WINDS THROUGH EARLY EVENING.

* CHANCE SHRA/TSRA LATE TONIGHT THROUGH TOMORROW.

KREIN

//DISCUSSION...UPDATED 12Z...

MAIN CONCERN FOR TODAY WILL BE STRONG...GUSTY SOUTH WINDS. AS OF
11Z THIS MORNING...WINDS ARE ALREADY GUSTING TO 25-30KT AND EXPECT
THAT WITH DEEPER MIXING LATER THIS MORNING...SHOULD BE ABLE TO TAP
INTO A 50 KT LOW LEVEL JET TO MIX DOWN GUSTS TO 35 KT OR EVEN
SLIGHTLY HIGHER. THE STRONG LOW LEVEL JET SHOULD MOVE OFF TO THE
EAST BY EARLY AFTERNOON...SO WHILE WINDS SHOULD STILL BE STRONG
AND GUSTY...PEAK GUSTS SHOULD LOWER TO ARND 25KT.

WITH THE PERSISTENT FETCH OF LOW LEVEL MOISTURE INTO THE
REGION...A LAYER OF MVFR STRATOCU HAS OVERSPREAD THE REGION.
EXPECT THAT BASES SHOULD NOT LOWER MUCH LESS THAT 1800FT AGL.
THERE IS SOME UNCERTAINTY AS TO THE DURATION OF THE MVFR CLOUD
LAYER...BUT WITH LITTLE CHANGE TO THE OVERALL PATTERN THROUGH THE
DAY...THERE IS A CHANCE THAT THE MVFR CIGS COULD HANG IN THROUGH
MUCH OF THE DAY. HOWEVER...THERE IS ALSO A CHANCE THAT STRONGER
MIXING IN THE AFTERNOON HOURS COULD ALLOW FOR THE MVFR DECK TO
SCATTER OUT.

LATEST RADAR TRENDS INDICATE THAT AN AREA OF SHRA LIFTING NEWD
FROM CNTRL IL INTO INDIANA. THE TRAJECTORY OF THE PCPN AREA SHOULD
KEEP THE BULK OF THE PCPN EAST AND SOUTH OF GYY...THOUGH A FEW SCT
SHRA AREA NOT OUT OF THE QUESTION. ALSO...SOME SHRA ASSOCIATED
WITH A MID LEVEL IMPULSE LIFTING NORTH THROUGH IOWA AND INTO WRN
WI IS GENERATING SCT SHRA AS WELL. IT IS ALSO POSSIBLE THAT RFD
COULD SEE A FEW SHRA THIS MORNING...BUT THE PROBABILITY IS TOO LOW
TO INCLUDE IN THE TAF AS THE LATEST RADAR TRENDS INDICATE A
WEAKENING TREND THERE.

A SECONDARY LOW IS EXPECTED TO DEVELOP OVER THE UPPER MISSOURI
VALLEY THIS EVENING...KEEPING A MODEST PRESSURE GRADIENT OVER THE
REGION. SO MODERATE...GUSTY WINDS SHOULD PERSIST WELL INTO
TONIGHT. ANOTHER STRONG MID LEVEL IMPULSE IS EXPECTED TO TRACK
THROUGH THE MIDDLE MISSISSIPPI VALLEY AND INTO WISCONSIN LATE
TONIGHT...BRINGING A RENEWED CHANCE FOR SHRA/TSRA TO THE REGION
LATE TONIGHT AND TOMORROW.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 12Z...

* MEDIUM TO HIGH CONFIDENCE IN WIND TRENDS.

* MEDIUM TO HIGH CONFIDENCE THAT THE TERMINALS SHOULD REMAIN
  DRY...THOUGH THERE IS A SMALL CHANCE FOR SOME SHRA INVOF THE
  TERMINALS THROUGH THE MORNING HOURS.

* MEDIUM CONFIDENCE IN CIG TRENDS.

* MEDIUM CONFIDENCE IN PCPN TIMING LATE TONIGHT.

KREIN

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/TSRA LATE. SOUTHEAST WINDS.

FRIDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. SOUTHWEST WINDS
BECOMING NORTHEAST OVERNIGHT.

SATURDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. NORTHEAST
WINDS.

SUNDAY...CHANCE TSRA. MVFR POSSIBLE. NORTHEAST WINDS.

KREIN

&&

.MARINE...
304 AM CDT

LOW PRESSURE WILL BE STEADILY LIFTING NORTH ACROSS THE MISSOURI
VALLEY THIS MORNING...REACHING LAKE SUPERIOR BY THIS EVENING AND
CONTINUING TO SLIDE EAST/NORTHEAST TOWARDS QUEBEC BY TUESDAY
MORNING. A FRONTAL BOUNDARY WILL REMAIN OVER THE FAR NORTHERN
PORTIONS OF LAKE MICHIGAN. MEANWHILE GUSTY SOUTHERLY WINDS ARE
EXPECTED TO INCREASE THIS MORNING...WITH OCCASIONAL GALES FOR THE
NEARSHORE WATERS OF IL/IN. ACROSS THE OPEN WATERS...EXPECT THE
WARM/MOIST AIR TO STRUGGLE TO REACH THE SFC OF THE LAKE WITH SOME
DEGREE OF LAKE STABILITY. WAVES WILL STEADILY BUILD ACROSS THE
NORTHERN HALF OF THE LAKE AS A RESULT OF THE LONG FETCH. STILL
FEEL THAT GUSTS WILL REACH 30KT ACROSS THE LAKE...HOWEVER
CONFIDENCE HAS DIMINISHED SLIGHTLY AS NEW GUIDANCE HAS BECOME A
LITTLE LESS WITH THE WIND FIELDS. NONETHELESS...WAVES FOR THE
NORTHERN HALF OF THE LAKE WILL LIKELY TOP OUT IN THE 4 TO 7 FT
RANGE WITH OCCASIONAL WAVES REACHING 9 FT THIS AFTERNOON/EVENING.

THE GRADIENT QUICKLY DIMINISHES THIS EVENING...BUT EXPECT
SOUTHERLY WINDS TO PERSIST. THIS WILL ALLOW WAVES TO SUBSIDE TO 3
TO 5 FT. ANOTHER LOW WILL ARRIVE TUE...WITH WINDS NUDGING BACK UP
HOWEVER WARM AIR WILL CONTINUE TO FLOW ACROSS THE LAKE AND COULD
FURTHER ENHANCE THE LAKE STABILITY AND KEEP WAVES FROM BUILDING TO
LARGE.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 9 AM MONDAY.

     GALE WARNING...NEARSHORE WATERS UNTIL 3
     PM MONDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...3 PM MONDAY TO 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KILX 251154
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
654 AM CDT MON MAY 25 2015

.SHORT TERM...(TODAY)
ISSUED AT 337 AM CDT MON MAY 25 2015

LOW PRESSURE CENTER STILL WELL OFF TO THE SOUTHWEST THIS
MORNING...AND A WARM FRONT DRAPED ACROSS THE IL/WI BORDER THIS
MORNING.  SCATTERED SHOWERS AND ISOLATED THUNDER STILL IN THE
REGION, BUT MAINLY CONFINED TO AREAS IN THE SOUTHEAST AS WELL AS THE
NW.  ILX SITUATED IN A GAP AS THE MAJORITY OF THE SYSTEM CONTINUES
TO LIFT NORTH AND NORTHEAST THIS MORNING.  MODELS PRETTY CONSISTENT
WITH THE MOVING OUT OF THE SYSTEM, WITH SOME SCATTERED SHOWERS
POSSIBLY AT LEAST THROUGH MIDDAY.  ISOLATED THUNDER CANNOT BE RULED
OUT WITH THE INCREASING INSTABILITY AFTER SUNRISE...BUT MAJORITY OF
THE ACTIVITY SCOURS OUT IN ALL OF THE MODELS SHORTLY AFTER MIDDAY.
LINGERED SOME SLIGHT CHANCES AFTER 18Z TO COVER AT LEAST THE
POTENTIAL FOR ACTIVITY WITH ANY REMNANT MESOSCALE BOUNDARIES.
PLENTY OF INSTABILITY STILL WITHIN THE ATMOSPHERE SHOULD IT GET THE
CHANCE TO RECOVER/RESTRATIFY.  HOWEVER, A SMALL AREA OF MIDLEVEL
RIDGING BEHIND THE SHORTWAVE THIS MORNING MAY GIVE US ENOUGH
SUBSIDENCE TO COUNTER THE EFFECTS...SO HAVE FOLLOWED SUIT WITH THE
END OF DAYTIME HEATING AND THE EARLY EVENING AND DROPPED THE POPS
BACK DOWN BEFORE 06Z. EITHER WAY...WINDS ALOFT WITH THE PASSING OF
THE SHORTWAVE AND DAYTIME MIXING WILL RESULT IN SOME GUSTY WINDS
TODAY...GUSTING 25 TO 35 MPH BY MID DAY AND SLOWLY BACKING OFF AS
THE LOW LIFTS OUT OF THE REGION.

.LONG TERM...(TONIGHT THROUGH SUNDAY)
ISSUED AT 337 AM CDT MON MAY 25 2015

FORECAST REMAINS WARM AND MUGGY WITH SEVERAL CHANCES FOR SHOWERS AND
THUNDERSTORMS THROUGHOUT. REGION DOMINATED BY SOUTHWESTERLY FLOW AND
A SERIES OF SHORT WAVES EJECTING OUT OF THE UPPER TROF IN THE SW
THROUGH THE FIRST HALF OF THE WEEK.  A BRIEF BREAK IN THE PATTERN
MID WEEK IS ONLY TEMPORARY AS TEMPS REMAIN WARM WITH PLENTY OF
MOISTURE ONLY REINFORCED BY PERIODIC SHOWERS ENHANCING THE BOUNDARY
LAYER RH. YET ANOTHER SURFACE LOW LIFTS INTO THE MIDWEST MOVING
ALONG THE SOUTHWESTERLY FLOW ALOFT ON TUESDAY.  MORE SHOWERS
ANTICIPATED FOR TUESDAY/TUESDAY NIGHT WITH THE MUGGY AIRMASS.  FRONT
ASSOCIATED WITH THIS SYSTEM WEAK AT BEST AND WILL ONLY SEE A BRIEF
SFC WIND SHIFT TO MORE WESTERLY FROM SOUTHERLY FOR WED AND WED NIGHT
ACCOMPANIED BY A BRIEF PATTERN SHIFT ALOFT.  CHANGE IS ONLY
TEMPORARY AS SOUTHERLY SFC WINDS REESTABLISH BY THE END OF THE WEEK.
WEAK SOUTHWESTERLY FLOW ALOFT SLOWLY SHIFTS TO WEAK FLOW OVERALL
GOING INTO THE WEEKEND SETTING UP CHANCES FOR PERIODIC DIURNALLY
DRIVEN CONVECTION YET AGAIN.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z TUESDAY MORNING)
ISSUED AT 654 AM CDT MON MAY 25 2015

SCATTERED SHOWERS CONTINUE TO MOVE THROUGH THE AREA THIS MORNING.
THE SHOWERS IN WEST CENTRAL ILLINOIS WILL BE LIFTING NORTH TO
NORTHEAST AND SHOULD EFFECT PIA/SPI THIS MORNING. FOR OTHER TAF
SITES WILL JUST KEEP VCSH IN THE MORNING HOURS. ONCE THE PCPN
MOVES OUT, SKIES WILL BEGIN TO GRADUALLY SCATTER OUT. THIS WILL BE
SHORT LIVED AS ANOTHER WAVE/BOUNDARY WILL PUSH INTO THE AREA FOR
TUE NIGHT...WITH MOVE SHOWERS AND STORMS. EXCEPT FOR EARLY THIS
AFTERNOON AND THIS EVENING...ALL TAF SITES WILL BE MVFR CIGS
THROUGH THE PERIOD. LATE TONIGHT ALL TAF SITES WILL HAVE
PREDOMINATE SHOWERS WITH VCTS. WINDS WILL BE VERY GUSTY THIS
MORNING OUT OF THE SOUTH BUT THEN TAPER SOME DURING THE AFTERNOON.
THEN WILL LOOSE THE GUSTINESS DURING THE EVENING.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...HJS
LONG TERM...HJS
AVIATION...AUTEN



000
FXUS63 KILX 251154
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
654 AM CDT MON MAY 25 2015

.SHORT TERM...(TODAY)
ISSUED AT 337 AM CDT MON MAY 25 2015

LOW PRESSURE CENTER STILL WELL OFF TO THE SOUTHWEST THIS
MORNING...AND A WARM FRONT DRAPED ACROSS THE IL/WI BORDER THIS
MORNING.  SCATTERED SHOWERS AND ISOLATED THUNDER STILL IN THE
REGION, BUT MAINLY CONFINED TO AREAS IN THE SOUTHEAST AS WELL AS THE
NW.  ILX SITUATED IN A GAP AS THE MAJORITY OF THE SYSTEM CONTINUES
TO LIFT NORTH AND NORTHEAST THIS MORNING.  MODELS PRETTY CONSISTENT
WITH THE MOVING OUT OF THE SYSTEM, WITH SOME SCATTERED SHOWERS
POSSIBLY AT LEAST THROUGH MIDDAY.  ISOLATED THUNDER CANNOT BE RULED
OUT WITH THE INCREASING INSTABILITY AFTER SUNRISE...BUT MAJORITY OF
THE ACTIVITY SCOURS OUT IN ALL OF THE MODELS SHORTLY AFTER MIDDAY.
LINGERED SOME SLIGHT CHANCES AFTER 18Z TO COVER AT LEAST THE
POTENTIAL FOR ACTIVITY WITH ANY REMNANT MESOSCALE BOUNDARIES.
PLENTY OF INSTABILITY STILL WITHIN THE ATMOSPHERE SHOULD IT GET THE
CHANCE TO RECOVER/RESTRATIFY.  HOWEVER, A SMALL AREA OF MIDLEVEL
RIDGING BEHIND THE SHORTWAVE THIS MORNING MAY GIVE US ENOUGH
SUBSIDENCE TO COUNTER THE EFFECTS...SO HAVE FOLLOWED SUIT WITH THE
END OF DAYTIME HEATING AND THE EARLY EVENING AND DROPPED THE POPS
BACK DOWN BEFORE 06Z. EITHER WAY...WINDS ALOFT WITH THE PASSING OF
THE SHORTWAVE AND DAYTIME MIXING WILL RESULT IN SOME GUSTY WINDS
TODAY...GUSTING 25 TO 35 MPH BY MID DAY AND SLOWLY BACKING OFF AS
THE LOW LIFTS OUT OF THE REGION.

.LONG TERM...(TONIGHT THROUGH SUNDAY)
ISSUED AT 337 AM CDT MON MAY 25 2015

FORECAST REMAINS WARM AND MUGGY WITH SEVERAL CHANCES FOR SHOWERS AND
THUNDERSTORMS THROUGHOUT. REGION DOMINATED BY SOUTHWESTERLY FLOW AND
A SERIES OF SHORT WAVES EJECTING OUT OF THE UPPER TROF IN THE SW
THROUGH THE FIRST HALF OF THE WEEK.  A BRIEF BREAK IN THE PATTERN
MID WEEK IS ONLY TEMPORARY AS TEMPS REMAIN WARM WITH PLENTY OF
MOISTURE ONLY REINFORCED BY PERIODIC SHOWERS ENHANCING THE BOUNDARY
LAYER RH. YET ANOTHER SURFACE LOW LIFTS INTO THE MIDWEST MOVING
ALONG THE SOUTHWESTERLY FLOW ALOFT ON TUESDAY.  MORE SHOWERS
ANTICIPATED FOR TUESDAY/TUESDAY NIGHT WITH THE MUGGY AIRMASS.  FRONT
ASSOCIATED WITH THIS SYSTEM WEAK AT BEST AND WILL ONLY SEE A BRIEF
SFC WIND SHIFT TO MORE WESTERLY FROM SOUTHERLY FOR WED AND WED NIGHT
ACCOMPANIED BY A BRIEF PATTERN SHIFT ALOFT.  CHANGE IS ONLY
TEMPORARY AS SOUTHERLY SFC WINDS REESTABLISH BY THE END OF THE WEEK.
WEAK SOUTHWESTERLY FLOW ALOFT SLOWLY SHIFTS TO WEAK FLOW OVERALL
GOING INTO THE WEEKEND SETTING UP CHANCES FOR PERIODIC DIURNALLY
DRIVEN CONVECTION YET AGAIN.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z TUESDAY MORNING)
ISSUED AT 654 AM CDT MON MAY 25 2015

SCATTERED SHOWERS CONTINUE TO MOVE THROUGH THE AREA THIS MORNING.
THE SHOWERS IN WEST CENTRAL ILLINOIS WILL BE LIFTING NORTH TO
NORTHEAST AND SHOULD EFFECT PIA/SPI THIS MORNING. FOR OTHER TAF
SITES WILL JUST KEEP VCSH IN THE MORNING HOURS. ONCE THE PCPN
MOVES OUT, SKIES WILL BEGIN TO GRADUALLY SCATTER OUT. THIS WILL BE
SHORT LIVED AS ANOTHER WAVE/BOUNDARY WILL PUSH INTO THE AREA FOR
TUE NIGHT...WITH MOVE SHOWERS AND STORMS. EXCEPT FOR EARLY THIS
AFTERNOON AND THIS EVENING...ALL TAF SITES WILL BE MVFR CIGS
THROUGH THE PERIOD. LATE TONIGHT ALL TAF SITES WILL HAVE
PREDOMINATE SHOWERS WITH VCTS. WINDS WILL BE VERY GUSTY THIS
MORNING OUT OF THE SOUTH BUT THEN TAPER SOME DURING THE AFTERNOON.
THEN WILL LOOSE THE GUSTINESS DURING THE EVENING.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...HJS
LONG TERM...HJS
AVIATION...AUTEN




000
FXUS63 KILX 251154
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
654 AM CDT MON MAY 25 2015

.SHORT TERM...(TODAY)
ISSUED AT 337 AM CDT MON MAY 25 2015

LOW PRESSURE CENTER STILL WELL OFF TO THE SOUTHWEST THIS
MORNING...AND A WARM FRONT DRAPED ACROSS THE IL/WI BORDER THIS
MORNING.  SCATTERED SHOWERS AND ISOLATED THUNDER STILL IN THE
REGION, BUT MAINLY CONFINED TO AREAS IN THE SOUTHEAST AS WELL AS THE
NW.  ILX SITUATED IN A GAP AS THE MAJORITY OF THE SYSTEM CONTINUES
TO LIFT NORTH AND NORTHEAST THIS MORNING.  MODELS PRETTY CONSISTENT
WITH THE MOVING OUT OF THE SYSTEM, WITH SOME SCATTERED SHOWERS
POSSIBLY AT LEAST THROUGH MIDDAY.  ISOLATED THUNDER CANNOT BE RULED
OUT WITH THE INCREASING INSTABILITY AFTER SUNRISE...BUT MAJORITY OF
THE ACTIVITY SCOURS OUT IN ALL OF THE MODELS SHORTLY AFTER MIDDAY.
LINGERED SOME SLIGHT CHANCES AFTER 18Z TO COVER AT LEAST THE
POTENTIAL FOR ACTIVITY WITH ANY REMNANT MESOSCALE BOUNDARIES.
PLENTY OF INSTABILITY STILL WITHIN THE ATMOSPHERE SHOULD IT GET THE
CHANCE TO RECOVER/RESTRATIFY.  HOWEVER, A SMALL AREA OF MIDLEVEL
RIDGING BEHIND THE SHORTWAVE THIS MORNING MAY GIVE US ENOUGH
SUBSIDENCE TO COUNTER THE EFFECTS...SO HAVE FOLLOWED SUIT WITH THE
END OF DAYTIME HEATING AND THE EARLY EVENING AND DROPPED THE POPS
BACK DOWN BEFORE 06Z. EITHER WAY...WINDS ALOFT WITH THE PASSING OF
THE SHORTWAVE AND DAYTIME MIXING WILL RESULT IN SOME GUSTY WINDS
TODAY...GUSTING 25 TO 35 MPH BY MID DAY AND SLOWLY BACKING OFF AS
THE LOW LIFTS OUT OF THE REGION.

.LONG TERM...(TONIGHT THROUGH SUNDAY)
ISSUED AT 337 AM CDT MON MAY 25 2015

FORECAST REMAINS WARM AND MUGGY WITH SEVERAL CHANCES FOR SHOWERS AND
THUNDERSTORMS THROUGHOUT. REGION DOMINATED BY SOUTHWESTERLY FLOW AND
A SERIES OF SHORT WAVES EJECTING OUT OF THE UPPER TROF IN THE SW
THROUGH THE FIRST HALF OF THE WEEK.  A BRIEF BREAK IN THE PATTERN
MID WEEK IS ONLY TEMPORARY AS TEMPS REMAIN WARM WITH PLENTY OF
MOISTURE ONLY REINFORCED BY PERIODIC SHOWERS ENHANCING THE BOUNDARY
LAYER RH. YET ANOTHER SURFACE LOW LIFTS INTO THE MIDWEST MOVING
ALONG THE SOUTHWESTERLY FLOW ALOFT ON TUESDAY.  MORE SHOWERS
ANTICIPATED FOR TUESDAY/TUESDAY NIGHT WITH THE MUGGY AIRMASS.  FRONT
ASSOCIATED WITH THIS SYSTEM WEAK AT BEST AND WILL ONLY SEE A BRIEF
SFC WIND SHIFT TO MORE WESTERLY FROM SOUTHERLY FOR WED AND WED NIGHT
ACCOMPANIED BY A BRIEF PATTERN SHIFT ALOFT.  CHANGE IS ONLY
TEMPORARY AS SOUTHERLY SFC WINDS REESTABLISH BY THE END OF THE WEEK.
WEAK SOUTHWESTERLY FLOW ALOFT SLOWLY SHIFTS TO WEAK FLOW OVERALL
GOING INTO THE WEEKEND SETTING UP CHANCES FOR PERIODIC DIURNALLY
DRIVEN CONVECTION YET AGAIN.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z TUESDAY MORNING)
ISSUED AT 654 AM CDT MON MAY 25 2015

SCATTERED SHOWERS CONTINUE TO MOVE THROUGH THE AREA THIS MORNING.
THE SHOWERS IN WEST CENTRAL ILLINOIS WILL BE LIFTING NORTH TO
NORTHEAST AND SHOULD EFFECT PIA/SPI THIS MORNING. FOR OTHER TAF
SITES WILL JUST KEEP VCSH IN THE MORNING HOURS. ONCE THE PCPN
MOVES OUT, SKIES WILL BEGIN TO GRADUALLY SCATTER OUT. THIS WILL BE
SHORT LIVED AS ANOTHER WAVE/BOUNDARY WILL PUSH INTO THE AREA FOR
TUE NIGHT...WITH MOVE SHOWERS AND STORMS. EXCEPT FOR EARLY THIS
AFTERNOON AND THIS EVENING...ALL TAF SITES WILL BE MVFR CIGS
THROUGH THE PERIOD. LATE TONIGHT ALL TAF SITES WILL HAVE
PREDOMINATE SHOWERS WITH VCTS. WINDS WILL BE VERY GUSTY THIS
MORNING OUT OF THE SOUTH BUT THEN TAPER SOME DURING THE AFTERNOON.
THEN WILL LOOSE THE GUSTINESS DURING THE EVENING.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...HJS
LONG TERM...HJS
AVIATION...AUTEN




000
FXUS63 KLOT 251139
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
639 AM CDT MON MAY 25 2015

.SHORT TERM...
345 AM CDT

THROUGH MONDAY NIGHT...
FOR THE REMAINDER OF THE NIGHT AND INTO MONDAY MORNING...PCPN
CHANCES CONTINUE TO WANE AS LATEST RADAR TRENDS ONLY SHOW SOME SCT
SHRA WHICH ARE DECREASING IN INTENSITY.  IN SPITE OF DEWPOINTS IN
THE LOW 60S...AND A STRONG LOW LEVEL JET...50 KT AT 925 MB...THERE
IS AN ELEMENT LACKING WHICH IS SEEMS TO BE PREVENTING THE
MAINTENANCE OF SHRA/TSRA OVER NERN IL/NWRN IN.  THE MAIN MISSING
ELEMENTS IS FORCING.  THE SFC AND UPPER LEVEL LOW ARE WAY TO THE
WEST...OVER THE NRN PLAINS. THE SHORTWAVE CLIMBING UP THE NWRN
PERIPHERY OF THE HIGH AMPLITUDE RIDGE IS BEING SLOWED BY THE HIGH
AMPLITUDE...AND IS BEING FORCED TO A MORE WLY TRACK THROUGH THE
UPPER MISSISSIPPI VALLEY THAN PREVIOUSLY ANTICIPATED.  SO...FOR THE
REMAINDER OF THE OVERNIGHT HOURS AND THE DAYTIME HOURS MONDAY...HAVE
BACK OF TO ISOLD-SCT SHRA.  WILL KEEP ISOLD TS MENTION FOR THE LATE
MORNING HOURS...THROUGH AROUND NOON...WITH THE DAYTIME HEATING...BUT
CONFIDENCE IN ANY TS IS RATHER LOW AT THIS TIME.  BY THIS
AFTERNOON...A MID LEVEL DRY SLOT IS EXPECTED TO MOVE ACROSS THE
REGION...FURTHER LIMITING PCPN CHANCES AND IT IS QUITE LIKELY THAT
THE REGION WILL REMAIN DRY THROUGH THE DAY.  HOWEVER...WHILE THE
PCPN CHANCES ARE DIMINISHING...THE LIKELIHOOD OF STRONG WINDS IS
STILL A CONCERN.  WITH THE DIMINISHING PCPN CHANCES...LESS SKY COVER
THAN PREVIOUSLY ANTICIPATED IS ALSO POSSIBLE.  A STRONG SWLY
PRESSURE GRADIENT IS SETTING UP ACROSS THE REGION BETWEEN SFC
RIDGING ACROSS THE SERN CONUS AND AND LOW PRESSURE FROM THE UPPER
MISSISSIPPI VALLEY TO THE WESTERN PLAINS.  THE STRONG GRADIENT WILL
HELP DRIVE THE SFC WINDS AND THE DIMINISHING CLOUD COVER COULD HELP
ENHANCE DEEP LAYER MIXING...TAPPING STRONGER WINDS ALOFT.  SUSTAINED
25-25 MPH WINDS ARE LIKELY WITH GUSTS OF 30-35 MPH.
ALSO...PERSISTENT WARM/MOIST ADVECTION AT THE SFC WILL BRING
TEMPERATURES INTO THE LOW TO MIDDLE 80S WITH DEWPOINTS IN THE LOWER
60S.

FOR MONDAY NIGHT...THE BREEZY CONDITIONS WILL PERSIST INTO THE AS
THERE SHOULD BE LITTLE CHANGE TO THE SFC AND UPPER LEVEL PATTERNS.
THE UPPER RIDGE WILL LOSE A LITTLE AMPLITUDE AS SHORT WAVE ENERGY
OVERTOPS THE RIDGE...BUT GENERAL TROUGHING WILL PERSIST ACROSS THE
UPPER MISSISSIPPI VALLEY THROUGH THE CENTRAL PLAINS.  THE NEXT
CHANCE FOR PCPN WILL HOLD OFF UNTIL LATE TONIGHT/EARLY TUESDAY
MORNING AND THE NEXT SHORTWAVE LIFTS OUT OF THE SRN PLAINS AND INTO
THE MIDDLE MISSISSIPPI VALLEY.  AMPLE LOW LEVEL MOISTURE WILL
ALREADY BE IN PLACE SO IT WILL JUST A MATTER OF WHEN THE FORCING
WILL GET HERE.  AGAIN...THERE IS SOME CONCERN THAT THE FORCING WILL
BE TO THE WEST...WITH THE SHORTWAVE TRACKING THROUGH THE MIDDLE
MISSISSIPPI VALLEY AND INTO WI.  SO...WILL CARRY CHANCE POPS FOR THE
REGION...WITH LIKELY POPS APPROACHING THE PONTIAC AREA BY EARLY
TUESDAY MORNING.  THE PERSISTENT WARM/MOIST ADVECTIVE PATTERN AND
BREEZY CONDITIONS SHOULD KEEP TEMPERATURES FROM DROPPING OFF
SIGNIFICANTLY OVERNIGHT AND LOWS SHOULD BE IN THE MIDDLE TO UPPER
60S.

KREIN

&&

.LONG TERM...
239 AM CDT

TUESDAY THROUGH SUNDAY...

TUESDAY THROUGH WEDNESDAY...
500MB TROUGH AXIS WILL SLOWLY PIVOT EAST ACROSS THE CENTRAL PLAINS
INTO THE MID-MISSOURI VALLEY TUE...WITH A SFC WAVE SLIDING NORTH
ACROSS IOWA INTO CENTRAL WISC LATE TUE. THE SFC FEATURE IS NOT
EXPECTED TO BE STRONG...HOWEVER THE GRADIENT DOES TIGHTEN WITH
MODEST HEIGHT FALLS IN THE LOWEST LAYERS OF THE ATMOSPHERE. SOME
INSTABILITY DOES REMAIN ALONG WITH RELATIVELY MOIST SFC CONDS AS
DEW PTS WILL REMAIN IN THE UPR 50S/LOW 60S. PWAT VALUES WILL ALSO
HOVER JUST OVER 1 INCH...WHICH IS SEASONAL. WILL HOLD ONTO MENTION
OF RAIN AND THUNDER...BUT COULD SEE THIS MAINLY FOCUSED IN THE TUE
MORNING TIMEFRAME.

WITH CONSIDERABLE SOLAR SHIELDING PROGGED FOR TUE...TEMPS MAY
STRUGGLE TO WARM BEYOND THE MID/UPR 70S. BUT WITH GUIDANCE HINTING
AT A DRY SLOT LIFTING NORTHEAST ACROSS THE REGION TUE EVE...THIS
COULD INTRODUCE SOME EROSION TO THE CLOUD COVER IN THE AFTN HOURS
TUE AND ALLOW SOME SFC HEATING TO OCCUR AND PUSH TEMPS TO ARND 80.

GUIDANCE LIFTS THE DRY SLOT OVERHEAD LATE TUE NGT...WITH THE 500MB
TROUGH AXIS ARRIVING ARND DAYBREAK WED AND LIFTING EAST ACROSS LOWER
MICHIGAN. THIS WILL BRING DRY ONLY SLIGHT CHANCE POPS AS WEAK SFC
RIDGING BEGINS TO NUDGE EAST ACROSS THE MISSOURI VALLEY TOWARDS THE
FORECAST AREA MIDDAY WED. IT IS POSSIBLE THAT ENOUGH DRY AIR
INFLUENCE COULD ALLOW FOR REMOVAL OF THE SLIGHT CHANCE POPS WED
AFTN. THERMAL TROUGH LAGS BEHIND THE FRONTAL BOUNDARY WED...SO TEMPS
COULD STILL WARM BACK TO ARND 80 AND PERHAPS THE LOW 80S IN THE
SOUTHERN CWFA.

THURSDAY THROUGH SUNDAY...
ANTI-CYCLONIC FLOW ARRIVES THUR WITH AT LEAST ONE PERIOD OF DRY
WEATHER EXPECTED FOR NORTHERN IL/NORTHWEST IN. ONLY A COUPLE
ENSEMBLE MEMBERS CONTINUE TO PROG POPS ALONG THE SOUTHERN FORECAST
AREA THUR...BUT COULD SEE THIS TRENDING DRY IN THE NEXT FEW
SOLUTIONS. WITH WARM TEMPS ALOFT EXPECTED THUR AND THIN CLOUD
COVER...THUR HIGHS COULD PEAK IN THE LOW 80S.

THEN FOCUS TURNS TOWARDS THE UPCOMING WEEKEND AND A PATTERN SHIFT
AWAY FROM THE WARM/HUMID CONDITIONS. ENSEMBLES SHOW MINIMAL SPREAD
IN THE LATE WEEK PERIODS...WITH THE UPSTREAM RIDGE OVER
ALASKA/WESTERN CANADA AND A DOWNSTREAM MID-LVL RIDGE ACROSS THE
SOUTHEAST CONUS. BOTH OF THESE FEATURES IN TIME BEGIN TO
WEAKEN...WITH THE LONGWAVE PATTERN TRANSITIONING INTO A SEMI-ZONAL
ORIENTATION BY THE SECOND HALF OF THE WEEKEND.

OPER GUIDANCE HAS BEEN CONSISTENT WITH PROGGING A ROBUST 500MB
TROUGH TO SLIDE SOUTH FROM CENTRAL CANADA FRI...ALONG WITH A STRONG
CANADIAN SFC RIDGE ON IT/S HEELS. WITH A CHANNEL OF MOISTURE
REMAINING ACROSS THE SOUTHERN PLAINS STRETCHING NORTHEAST THROUGH
THE UPPER MIDWEST...THIS BOUNDARY WILL BECOME ACTIVE WITH A SFC WAVE
DEVELOPING ACROSS THE SOUTHERN PLAINS. THIS LOW WILL THEN LIFT
NORTHEAST TOWARDS THE CWFA FRI WITH A COLD FRONT ARRIVING ACROSS THE
FORECAST AREA SAT. WINDS LOOK TO SHIFT TO THE NORTH...WITH MUCH
COOLER AIR SLIDING SOUTH AND LIKELY KNOCKING TEMPS BACK TO SUB-
SEASONAL CONDS IN THE UPR 60S/NEAR 70 DEGREE RANGE SAT/SUN. IF
NORTHEAST WINDS MATERIALIZE...NEXT WEEKEND AREAS ADJACENT TO LAKE
MICHIGAN ALONG THE IL/IN SHORELINE COULD BE LOCKED IN THE UPR 50S TO
LOW 60S FOR HIGHS WITH A COLD FLOW OFF OF LAKE MICHIGAN.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 12Z...

* STRONG AND GUSTY SOUTH WINDS THROUGH EARLY EVENING.

* CHANCE SHRA/TSRA LATE TONIGHT THROUGH TOMORROW.

KREIN

//DISCUSSION...UPDATED 12Z...

MAIN CONCERN FOR TODAY WILL BE STRONG...GUSTY SOUTH WINDS. AS OF
11Z THIS MORNING...WINDS ARE ALREADY GUSTING TO 25-30KT AND EXPECT
THAT WITH DEEPER MIXING LATER THIS MORNING...SHOULD BE ABLE TO TAP
INTO A 50 KT LOW LEVEL JET TO MIX DOWN GUSTS TO 35 KT OR EVEN
SLIGHTLY HIGHER. THE STRONG LOW LEVEL JET SHOULD MOVE OFF TO THE
EAST BY EARLY AFTERNOON...SO WHILE WINDS SHOULD STILL BE STRONG
AND GUSTY...PEAK GUSTS SHOULD LOWER TO ARND 25KT.

WITH THE PERSISTENT FETCH OF LOW LEVEL MOISTURE INTO THE
REGION...A LAYER OF MVFR STRATOCU HAS OVERSPREAD THE REGION.
EXPECT THAT BASES SHOULD NOT LOWER MUCH LESS THAT 1800FT AGL.
THERE IS SOME UNCERTAINTY AS TO THE DURATION OF THE MVFR CLOUD
LAYER...BUT WITH LITTLE CHANGE TO THE OVERALL PATTERN THROUGH THE
DAY...THERE IS A CHANCE THAT THE MVFR CIGS COULD HANG IN THROUGH
MUCH OF THE DAY. HOWEVER...THERE IS ALSO A CHANCE THAT STRONGER
MIXING IN THE AFTERNOON HOURS COULD ALLOW FOR THE MVFR DECK TO
SCATTER OUT.

LATEST RADAR TRENDS INDICATE THAT AN AREA OF SHRA LIFTING NEWD
FROM CNTRL IL INTO INDIANA. THE TRAJECTORY OF THE PCPN AREA SHOULD
KEEP THE BULK OF THE PCPN EAST AND SOUTH OF GYY...THOUGH A FEW SCT
SHRA AREA NOT OUT OF THE QUESTION. ALSO...SOME SHRA ASSOCIATED
WITH A MID LEVEL IMPULSE LIFTING NORTH THROUGH IOWA AND INTO WRN
WI IS GENERATING SCT SHRA AS WELL. IT IS ALSO POSSIBLE THAT RFD
COULD SEE A FEW SHRA THIS MORNING...BUT THE PROBABILITY IS TOO LOW
TO INCLUDE IN THE TAF AS THE LATEST RADAR TRENDS INDICATE A
WEAKENING TREND THERE.

A SECONDARY LOW IS EXPECTED TO DEVELOP OVER THE UPPER MISSOURI
VALLEY THIS EVENING...KEEPING A MODEST PRESSURE GRADIENT OVER THE
REGION. SO MODERATE...GUSTY WINDS SHOULD PERSIST WELL INTO
TONIGHT. ANOTHER STRONG MID LEVEL IMPULSE IS EXPECTED TO TRACK
THROUGH THE MIDDLE MISSISSIPPI VALLEY AND INTO WISCONSIN LATE
TONIGHT...BRINGING A RENEWED CHANCE FOR SHRA/TSRA TO THE REGION
LATE TONIGHT AND TOMORROW.

KREIN


//ORD AND MDW CONFIDENCE...UPDATED 12Z...

* MEDIUM TO HIGH CONFIDENCE IN WIND TRENDS.

* MEDIUM TO HIGH CONFIDENCE THAT THE TERMINALS SHOULD REMAIN
  DRY...THOUGH THERE IS A SMALL CHANCE FOR SOME SHRA INVOF THE
  TERMINALS THROUGH THE MORNING HOURS.

* MEDIUM CONFIDENCE IN CIG TRENDS.

* MEDIUM CONFIDENCE IN PCPN TIMING LATE TONIGHT.

KREIN

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/TSRA LATE. SOUTHEAST WINDS.

FRIDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. SOUTHWEST WINDS
BECOMING NORTHEAST OVERNIGHT.

SATURDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. NORTHEAST
WINDS.

SUNDAY...CHANCE TSRA. MVFR POSSIBLE. NORTHEAST WINDS.

KREIN

&&

.MARINE...
304 AM CDT

LOW PRESSURE WILL BE STEADILY LIFTING NORTH ACROSS THE MISSOURI
VALLEY THIS MORNING...REACHING LAKE SUPERIOR BY THIS EVENING AND
CONTINUING TO SLIDE EAST/NORTHEAST TOWARDS QUEBEC BY TUESDAY
MORNING. A FRONTAL BOUNDARY WILL REMAIN OVER THE FAR NORTHERN
PORTIONS OF LAKE MICHIGAN. MEANWHILE GUSTY SOUTHERLY WINDS ARE
EXPECTED TO INCREASE THIS MORNING...WITH OCCASIONAL GALES FOR THE
NEARSHORE WATERS OF IL/IN. ACROSS THE OPEN WATERS...EXPECT THE
WARM/MOIST AIR TO STRUGGLE TO REACH THE SFC OF THE LAKE WITH SOME
DEGREE OF LAKE STABILITY. WAVES WILL STEADILY BUILD ACROSS THE
NORTHERN HALF OF THE LAKE AS A RESULT OF THE LONG FETCH. STILL
FEEL THAT GUSTS WILL REACH 30KT ACROSS THE LAKE...HOWEVER
CONFIDENCE HAS DIMINISHED SLIGHTLY AS NEW GUIDANCE HAS BECOME A
LITTLE LESS WITH THE WIND FIELDS. NONETHELESS...WAVES FOR THE
NORTHERN HALF OF THE LAKE WILL LIKELY TOP OUT IN THE 4 TO 7 FT
RANGE WITH OCCASIONAL WAVES REACHING 9 FT THIS AFTERNOON/EVENING.

THE GRADIENT QUICKLY DIMINISHES THIS EVENING...BUT EXPECT
SOUTHERLY WINDS TO PERSIST. THIS WILL ALLOW WAVES TO SUBSIDE TO 3
TO 5 FT. ANOTHER LOW WILL ARRIVE TUE...WITH WINDS NUDGING BACK UP
HOWEVER WARM AIR WILL CONTINUE TO FLOW ACROSS THE LAKE AND COULD
FURTHER ENHANCE THE LAKE STABILITY AND KEEP WAVES FROM BUILDING TO
LARGE.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 9 AM MONDAY.

     GALE WARNING...NEARSHORE WATERS UNTIL 3
     PM MONDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...3 PM MONDAY TO 4 AM TUESDAY.

&&

$$

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000
FXUS63 KLOT 251139
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
639 AM CDT MON MAY 25 2015

.SHORT TERM...
345 AM CDT

THROUGH MONDAY NIGHT...
FOR THE REMAINDER OF THE NIGHT AND INTO MONDAY MORNING...PCPN
CHANCES CONTINUE TO WANE AS LATEST RADAR TRENDS ONLY SHOW SOME SCT
SHRA WHICH ARE DECREASING IN INTENSITY.  IN SPITE OF DEWPOINTS IN
THE LOW 60S...AND A STRONG LOW LEVEL JET...50 KT AT 925 MB...THERE
IS AN ELEMENT LACKING WHICH IS SEEMS TO BE PREVENTING THE
MAINTENANCE OF SHRA/TSRA OVER NERN IL/NWRN IN.  THE MAIN MISSING
ELEMENTS IS FORCING.  THE SFC AND UPPER LEVEL LOW ARE WAY TO THE
WEST...OVER THE NRN PLAINS. THE SHORTWAVE CLIMBING UP THE NWRN
PERIPHERY OF THE HIGH AMPLITUDE RIDGE IS BEING SLOWED BY THE HIGH
AMPLITUDE...AND IS BEING FORCED TO A MORE WLY TRACK THROUGH THE
UPPER MISSISSIPPI VALLEY THAN PREVIOUSLY ANTICIPATED.  SO...FOR THE
REMAINDER OF THE OVERNIGHT HOURS AND THE DAYTIME HOURS MONDAY...HAVE
BACK OF TO ISOLD-SCT SHRA.  WILL KEEP ISOLD TS MENTION FOR THE LATE
MORNING HOURS...THROUGH AROUND NOON...WITH THE DAYTIME HEATING...BUT
CONFIDENCE IN ANY TS IS RATHER LOW AT THIS TIME.  BY THIS
AFTERNOON...A MID LEVEL DRY SLOT IS EXPECTED TO MOVE ACROSS THE
REGION...FURTHER LIMITING PCPN CHANCES AND IT IS QUITE LIKELY THAT
THE REGION WILL REMAIN DRY THROUGH THE DAY.  HOWEVER...WHILE THE
PCPN CHANCES ARE DIMINISHING...THE LIKELIHOOD OF STRONG WINDS IS
STILL A CONCERN.  WITH THE DIMINISHING PCPN CHANCES...LESS SKY COVER
THAN PREVIOUSLY ANTICIPATED IS ALSO POSSIBLE.  A STRONG SWLY
PRESSURE GRADIENT IS SETTING UP ACROSS THE REGION BETWEEN SFC
RIDGING ACROSS THE SERN CONUS AND AND LOW PRESSURE FROM THE UPPER
MISSISSIPPI VALLEY TO THE WESTERN PLAINS.  THE STRONG GRADIENT WILL
HELP DRIVE THE SFC WINDS AND THE DIMINISHING CLOUD COVER COULD HELP
ENHANCE DEEP LAYER MIXING...TAPPING STRONGER WINDS ALOFT.  SUSTAINED
25-25 MPH WINDS ARE LIKELY WITH GUSTS OF 30-35 MPH.
ALSO...PERSISTENT WARM/MOIST ADVECTION AT THE SFC WILL BRING
TEMPERATURES INTO THE LOW TO MIDDLE 80S WITH DEWPOINTS IN THE LOWER
60S.

FOR MONDAY NIGHT...THE BREEZY CONDITIONS WILL PERSIST INTO THE AS
THERE SHOULD BE LITTLE CHANGE TO THE SFC AND UPPER LEVEL PATTERNS.
THE UPPER RIDGE WILL LOSE A LITTLE AMPLITUDE AS SHORT WAVE ENERGY
OVERTOPS THE RIDGE...BUT GENERAL TROUGHING WILL PERSIST ACROSS THE
UPPER MISSISSIPPI VALLEY THROUGH THE CENTRAL PLAINS.  THE NEXT
CHANCE FOR PCPN WILL HOLD OFF UNTIL LATE TONIGHT/EARLY TUESDAY
MORNING AND THE NEXT SHORTWAVE LIFTS OUT OF THE SRN PLAINS AND INTO
THE MIDDLE MISSISSIPPI VALLEY.  AMPLE LOW LEVEL MOISTURE WILL
ALREADY BE IN PLACE SO IT WILL JUST A MATTER OF WHEN THE FORCING
WILL GET HERE.  AGAIN...THERE IS SOME CONCERN THAT THE FORCING WILL
BE TO THE WEST...WITH THE SHORTWAVE TRACKING THROUGH THE MIDDLE
MISSISSIPPI VALLEY AND INTO WI.  SO...WILL CARRY CHANCE POPS FOR THE
REGION...WITH LIKELY POPS APPROACHING THE PONTIAC AREA BY EARLY
TUESDAY MORNING.  THE PERSISTENT WARM/MOIST ADVECTIVE PATTERN AND
BREEZY CONDITIONS SHOULD KEEP TEMPERATURES FROM DROPPING OFF
SIGNIFICANTLY OVERNIGHT AND LOWS SHOULD BE IN THE MIDDLE TO UPPER
60S.

KREIN

&&

.LONG TERM...
239 AM CDT

TUESDAY THROUGH SUNDAY...

TUESDAY THROUGH WEDNESDAY...
500MB TROUGH AXIS WILL SLOWLY PIVOT EAST ACROSS THE CENTRAL PLAINS
INTO THE MID-MISSOURI VALLEY TUE...WITH A SFC WAVE SLIDING NORTH
ACROSS IOWA INTO CENTRAL WISC LATE TUE. THE SFC FEATURE IS NOT
EXPECTED TO BE STRONG...HOWEVER THE GRADIENT DOES TIGHTEN WITH
MODEST HEIGHT FALLS IN THE LOWEST LAYERS OF THE ATMOSPHERE. SOME
INSTABILITY DOES REMAIN ALONG WITH RELATIVELY MOIST SFC CONDS AS
DEW PTS WILL REMAIN IN THE UPR 50S/LOW 60S. PWAT VALUES WILL ALSO
HOVER JUST OVER 1 INCH...WHICH IS SEASONAL. WILL HOLD ONTO MENTION
OF RAIN AND THUNDER...BUT COULD SEE THIS MAINLY FOCUSED IN THE TUE
MORNING TIMEFRAME.

WITH CONSIDERABLE SOLAR SHIELDING PROGGED FOR TUE...TEMPS MAY
STRUGGLE TO WARM BEYOND THE MID/UPR 70S. BUT WITH GUIDANCE HINTING
AT A DRY SLOT LIFTING NORTHEAST ACROSS THE REGION TUE EVE...THIS
COULD INTRODUCE SOME EROSION TO THE CLOUD COVER IN THE AFTN HOURS
TUE AND ALLOW SOME SFC HEATING TO OCCUR AND PUSH TEMPS TO ARND 80.

GUIDANCE LIFTS THE DRY SLOT OVERHEAD LATE TUE NGT...WITH THE 500MB
TROUGH AXIS ARRIVING ARND DAYBREAK WED AND LIFTING EAST ACROSS LOWER
MICHIGAN. THIS WILL BRING DRY ONLY SLIGHT CHANCE POPS AS WEAK SFC
RIDGING BEGINS TO NUDGE EAST ACROSS THE MISSOURI VALLEY TOWARDS THE
FORECAST AREA MIDDAY WED. IT IS POSSIBLE THAT ENOUGH DRY AIR
INFLUENCE COULD ALLOW FOR REMOVAL OF THE SLIGHT CHANCE POPS WED
AFTN. THERMAL TROUGH LAGS BEHIND THE FRONTAL BOUNDARY WED...SO TEMPS
COULD STILL WARM BACK TO ARND 80 AND PERHAPS THE LOW 80S IN THE
SOUTHERN CWFA.

THURSDAY THROUGH SUNDAY...
ANTI-CYCLONIC FLOW ARRIVES THUR WITH AT LEAST ONE PERIOD OF DRY
WEATHER EXPECTED FOR NORTHERN IL/NORTHWEST IN. ONLY A COUPLE
ENSEMBLE MEMBERS CONTINUE TO PROG POPS ALONG THE SOUTHERN FORECAST
AREA THUR...BUT COULD SEE THIS TRENDING DRY IN THE NEXT FEW
SOLUTIONS. WITH WARM TEMPS ALOFT EXPECTED THUR AND THIN CLOUD
COVER...THUR HIGHS COULD PEAK IN THE LOW 80S.

THEN FOCUS TURNS TOWARDS THE UPCOMING WEEKEND AND A PATTERN SHIFT
AWAY FROM THE WARM/HUMID CONDITIONS. ENSEMBLES SHOW MINIMAL SPREAD
IN THE LATE WEEK PERIODS...WITH THE UPSTREAM RIDGE OVER
ALASKA/WESTERN CANADA AND A DOWNSTREAM MID-LVL RIDGE ACROSS THE
SOUTHEAST CONUS. BOTH OF THESE FEATURES IN TIME BEGIN TO
WEAKEN...WITH THE LONGWAVE PATTERN TRANSITIONING INTO A SEMI-ZONAL
ORIENTATION BY THE SECOND HALF OF THE WEEKEND.

OPER GUIDANCE HAS BEEN CONSISTENT WITH PROGGING A ROBUST 500MB
TROUGH TO SLIDE SOUTH FROM CENTRAL CANADA FRI...ALONG WITH A STRONG
CANADIAN SFC RIDGE ON IT/S HEELS. WITH A CHANNEL OF MOISTURE
REMAINING ACROSS THE SOUTHERN PLAINS STRETCHING NORTHEAST THROUGH
THE UPPER MIDWEST...THIS BOUNDARY WILL BECOME ACTIVE WITH A SFC WAVE
DEVELOPING ACROSS THE SOUTHERN PLAINS. THIS LOW WILL THEN LIFT
NORTHEAST TOWARDS THE CWFA FRI WITH A COLD FRONT ARRIVING ACROSS THE
FORECAST AREA SAT. WINDS LOOK TO SHIFT TO THE NORTH...WITH MUCH
COOLER AIR SLIDING SOUTH AND LIKELY KNOCKING TEMPS BACK TO SUB-
SEASONAL CONDS IN THE UPR 60S/NEAR 70 DEGREE RANGE SAT/SUN. IF
NORTHEAST WINDS MATERIALIZE...NEXT WEEKEND AREAS ADJACENT TO LAKE
MICHIGAN ALONG THE IL/IN SHORELINE COULD BE LOCKED IN THE UPR 50S TO
LOW 60S FOR HIGHS WITH A COLD FLOW OFF OF LAKE MICHIGAN.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 12Z...

* STRONG AND GUSTY SOUTH WINDS THROUGH EARLY EVENING.

* CHANCE SHRA/TSRA LATE TONIGHT THROUGH TOMORROW.

KREIN

//DISCUSSION...UPDATED 12Z...

MAIN CONCERN FOR TODAY WILL BE STRONG...GUSTY SOUTH WINDS. AS OF
11Z THIS MORNING...WINDS ARE ALREADY GUSTING TO 25-30KT AND EXPECT
THAT WITH DEEPER MIXING LATER THIS MORNING...SHOULD BE ABLE TO TAP
INTO A 50 KT LOW LEVEL JET TO MIX DOWN GUSTS TO 35 KT OR EVEN
SLIGHTLY HIGHER. THE STRONG LOW LEVEL JET SHOULD MOVE OFF TO THE
EAST BY EARLY AFTERNOON...SO WHILE WINDS SHOULD STILL BE STRONG
AND GUSTY...PEAK GUSTS SHOULD LOWER TO ARND 25KT.

WITH THE PERSISTENT FETCH OF LOW LEVEL MOISTURE INTO THE
REGION...A LAYER OF MVFR STRATOCU HAS OVERSPREAD THE REGION.
EXPECT THAT BASES SHOULD NOT LOWER MUCH LESS THAT 1800FT AGL.
THERE IS SOME UNCERTAINTY AS TO THE DURATION OF THE MVFR CLOUD
LAYER...BUT WITH LITTLE CHANGE TO THE OVERALL PATTERN THROUGH THE
DAY...THERE IS A CHANCE THAT THE MVFR CIGS COULD HANG IN THROUGH
MUCH OF THE DAY. HOWEVER...THERE IS ALSO A CHANCE THAT STRONGER
MIXING IN THE AFTERNOON HOURS COULD ALLOW FOR THE MVFR DECK TO
SCATTER OUT.

LATEST RADAR TRENDS INDICATE THAT AN AREA OF SHRA LIFTING NEWD
FROM CNTRL IL INTO INDIANA. THE TRAJECTORY OF THE PCPN AREA SHOULD
KEEP THE BULK OF THE PCPN EAST AND SOUTH OF GYY...THOUGH A FEW SCT
SHRA AREA NOT OUT OF THE QUESTION. ALSO...SOME SHRA ASSOCIATED
WITH A MID LEVEL IMPULSE LIFTING NORTH THROUGH IOWA AND INTO WRN
WI IS GENERATING SCT SHRA AS WELL. IT IS ALSO POSSIBLE THAT RFD
COULD SEE A FEW SHRA THIS MORNING...BUT THE PROBABILITY IS TOO LOW
TO INCLUDE IN THE TAF AS THE LATEST RADAR TRENDS INDICATE A
WEAKENING TREND THERE.

A SECONDARY LOW IS EXPECTED TO DEVELOP OVER THE UPPER MISSOURI
VALLEY THIS EVENING...KEEPING A MODEST PRESSURE GRADIENT OVER THE
REGION. SO MODERATE...GUSTY WINDS SHOULD PERSIST WELL INTO
TONIGHT. ANOTHER STRONG MID LEVEL IMPULSE IS EXPECTED TO TRACK
THROUGH THE MIDDLE MISSISSIPPI VALLEY AND INTO WISCONSIN LATE
TONIGHT...BRINGING A RENEWED CHANCE FOR SHRA/TSRA TO THE REGION
LATE TONIGHT AND TOMORROW.

KREIN


//ORD AND MDW CONFIDENCE...UPDATED 12Z...

* MEDIUM TO HIGH CONFIDENCE IN WIND TRENDS.

* MEDIUM TO HIGH CONFIDENCE THAT THE TERMINALS SHOULD REMAIN
  DRY...THOUGH THERE IS A SMALL CHANCE FOR SOME SHRA INVOF THE
  TERMINALS THROUGH THE MORNING HOURS.

* MEDIUM CONFIDENCE IN CIG TRENDS.

* MEDIUM CONFIDENCE IN PCPN TIMING LATE TONIGHT.

KREIN

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/TSRA LATE. SOUTHEAST WINDS.

FRIDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. SOUTHWEST WINDS
BECOMING NORTHEAST OVERNIGHT.

SATURDAY...LIKELY SHRA/CHANCE TSRA. MVFR POSSIBLE. NORTHEAST
WINDS.

SUNDAY...CHANCE TSRA. MVFR POSSIBLE. NORTHEAST WINDS.

KREIN

&&

.MARINE...
304 AM CDT

LOW PRESSURE WILL BE STEADILY LIFTING NORTH ACROSS THE MISSOURI
VALLEY THIS MORNING...REACHING LAKE SUPERIOR BY THIS EVENING AND
CONTINUING TO SLIDE EAST/NORTHEAST TOWARDS QUEBEC BY TUESDAY
MORNING. A FRONTAL BOUNDARY WILL REMAIN OVER THE FAR NORTHERN
PORTIONS OF LAKE MICHIGAN. MEANWHILE GUSTY SOUTHERLY WINDS ARE
EXPECTED TO INCREASE THIS MORNING...WITH OCCASIONAL GALES FOR THE
NEARSHORE WATERS OF IL/IN. ACROSS THE OPEN WATERS...EXPECT THE
WARM/MOIST AIR TO STRUGGLE TO REACH THE SFC OF THE LAKE WITH SOME
DEGREE OF LAKE STABILITY. WAVES WILL STEADILY BUILD ACROSS THE
NORTHERN HALF OF THE LAKE AS A RESULT OF THE LONG FETCH. STILL
FEEL THAT GUSTS WILL REACH 30KT ACROSS THE LAKE...HOWEVER
CONFIDENCE HAS DIMINISHED SLIGHTLY AS NEW GUIDANCE HAS BECOME A
LITTLE LESS WITH THE WIND FIELDS. NONETHELESS...WAVES FOR THE
NORTHERN HALF OF THE LAKE WILL LIKELY TOP OUT IN THE 4 TO 7 FT
RANGE WITH OCCASIONAL WAVES REACHING 9 FT THIS AFTERNOON/EVENING.

THE GRADIENT QUICKLY DIMINISHES THIS EVENING...BUT EXPECT
SOUTHERLY WINDS TO PERSIST. THIS WILL ALLOW WAVES TO SUBSIDE TO 3
TO 5 FT. ANOTHER LOW WILL ARRIVE TUE...WITH WINDS NUDGING BACK UP
HOWEVER WARM AIR WILL CONTINUE TO FLOW ACROSS THE LAKE AND COULD
FURTHER ENHANCE THE LAKE STABILITY AND KEEP WAVES FROM BUILDING TO
LARGE.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 9 AM MONDAY.

     GALE WARNING...NEARSHORE WATERS UNTIL 3
     PM MONDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...3 PM MONDAY TO 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 250845
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
345 AM CDT MON MAY 25 2015

.SHORT TERM...
345 AM CDT

THROUGH MONDAY NIGHT...
FOR THE REMAINDER OF THE NIGHT AND INTO MONDAY MORNING...PCPN
CHANCES CONTINUE TO WANE AS LATEST RADAR TRENDS ONLY SHOW SOME SCT
SHRA WHICH ARE DECREASING IN INTENSITY.  IN SPITE OF DEWPOINTS IN
THE LOW 60S...AND A STRONG LOW LEVEL JET...50 KT AT 925 MB...THERE
IS AN ELEMENT LACKING WHICH IS SEEMS TO BE PREVENTING THE
MAINTENANCE OF SHRA/TSRA OVER NERN IL/NWRN IN.  THE MAIN MISSING
ELEMENTS IS FORCING.  THE SFC AND UPPER LEVEL LOW ARE WAY TO THE
WEST...OVER THE NRN PLAINS. THE SHORTWAVE CLIMBING UP THE NWRN
PERIPHERY OF THE HIGH AMPLITUDE RIDGE IS BEING SLOWED BY THE HIGH
AMPLITUDE...AND IS BEING FORCED TO A MORE WLY TRACK THROUGH THE
UPPER MISSISSIPPI VALLEY THAN PREVIOUSLY ANTICIPATED.  SO...FOR THE
REMAINDER OF THE OVERNIGHT HOURS AND THE DAYTIME HOURS MONDAY...HAVE
BACK OF TO ISOLD-SCT SHRA.  WILL KEEP ISOLD TS MENTION FOR THE LATE
MORNING HOURS...THROUGH AROUND NOON...WITH THE DAYTIME HEATING...BUT
CONFIDENCE IN ANY TS IS RATHER LOW AT THIS TIME.  BY THIS
AFTERNOON...A MID LEVEL DRY SLOT IS EXPECTED TO MOVE ACROSS THE
REGION...FURTHER LIMITING PCPN CHANCES AND IT IS QUITE LIKELY THAT
THE REGION WILL REMAIN DRY THROUGH THE DAY.  HOWEVER...WHILE THE
PCPN CHANCES ARE DIMINISHING...THE LIKELIHOOD OF STRONG WINDS IS
STILL A CONCERN.  WITH THE DIMINISHING PCPN CHANCES...LESS SKY COVER
THAN PREVIOUSLY ANTICIPATED IS ALSO POSSIBLE.  A STRONG SWLY
PRESSURE GRADIENT IS SETTING UP ACROSS THE REGION BETWEEN SFC
RIDGING ACROSS THE SERN CONUS AND AND LOW PRESSURE FROM THE UPPER
MISSISSIPPI VALLEY TO THE WESTERN PLAINS.  THE STRONG GRADIENT WILL
HELP DRIVE THE SFC WINDS AND THE DIMINISHING CLOUD COVER COULD HELP
ENHANCE DEEP LAYER MIXING...TAPPING STRONGER WINDS ALOFT.  SUSTAINED
25-25 MPH WINDS ARE LIKELY WITH GUSTS OF 30-35 MPH.
ALSO...PERSISTENT WARM/MOIST ADVECTION AT THE SFC WILL BRING
TEMPERATURES INTO THE LOW TO MIDDLE 80S WITH DEWPOINTS IN THE LOWER
60S.

FOR MONDAY NIGHT...THE BREEZY CONDITIONS WILL PERSIST INTO THE AS
THERE SHOULD BE LITTLE CHANGE TO THE SFC AND UPPER LEVEL PATTERNS.
THE UPPER RIDGE WILL LOSE A LITTLE AMPLITUDE AS SHORT WAVE ENERGY
OVERTOPS THE RIDGE...BUT GENERAL TROUGHING WILL PERSIST ACROSS THE
UPPER MISSISSIPPI VALLEY THROUGH THE CENTRAL PLAINS.  THE NEXT
CHANCE FOR PCPN WILL HOLD OFF UNTIL LATE TONIGHT/EARLY TUESDAY
MORNING AND THE NEXT SHORTWAVE LIFTS OUT OF THE SRN PLAINS AND INTO
THE MIDDLE MISSISSIPPI VALLEY.  AMPLE LOW LEVEL MOISTURE WILL
ALREADY BE IN PLACE SO IT WILL JUST A MATTER OF WHEN THE FORCING
WILL GET HERE.  AGAIN...THERE IS SOME CONCERN THAT THE FORCING WILL
BE TO THE WEST...WITH THE SHORTWAVE TRACKING THROUGH THE MIDDLE
MISSISSIPPI VALLEY AND INTO WI.  SO...WILL CARRY CHANCE POPS FOR THE
REGION...WITH LIKELY POPS APPROACHING THE PONTIAC AREA BY EARLY
TUESDAY MORNING.  THE PERSISTENT WARM/MOIST ADVECTIVE PATTERN AND
BREEZY CONDITIONS SHOULD KEEP TEMPERATURES FROM DROPPING OFF
SIGNIFICANTLY OVERNIGHT AND LOWS SHOULD BE IN THE MIDDLE TO UPPER
60S.

KREIN

&&

.LONG TERM...
239 AM CDT

TUESDAY THROUGH SUNDAY...

TUESDAY THROUGH WEDNESDAY...
500MB TROUGH AXIS WILL SLOWLY PIVOT EAST ACROSS THE CENTRAL PLAINS
INTO THE MID-MISSOURI VALLEY TUE...WITH A SFC WAVE SLIDING NORTH
ACROSS IOWA INTO CENTRAL WISC LATE TUE. THE SFC FEATURE IS NOT
EXPECTED TO BE STRONG...HOWEVER THE GRAIDENT DOES TIGHTEN WITH
MODEST HEIGHT FALLS IN THE LOWEST LAYERS OF THE ATMOSPHERE. SOME
INSTABILITY DOES REMAIN ALONG WITH RELATIELY MOIST SFC CONDS AS DEW
PTS WILL REMAIN IN THE UPR 50S/LOW 60S. PWAT VALUES WILL ALSO HOVER
JUST OVER 1 INCH...WHICH IS SEASONAL. WILL HOLD ONTO MENTION OF RAIN
AND THUNDER...BUT COULD SEE THIS MAINLY FOCUSED IN THE TUE MORING
TIMEFRAME.

WITH CONSIDERABLE SOLAR SHIELDING PROGGED FOR TUE...TEMPS MAY
STRUGGLE TO WARM BEYOND THE MID/UPR 70S. BUT WITH GUIDANCE HINTING
AT A DRY SLOT LIFTING NORTHEAST ACROSS THE REGION TUE EVE...THIS
COULD INTRODUCE SOME EROSION TO THE CLOUD COVER IN THE AFTN HOURS
TUE AND ALLOW SOME SFC HEATING TO OCCUR AND PUSH TEMPS TO ARND 80.

GUIDANCE LIFTS THE DRY SLOT OVERHEAD LATE TUE NGT...WITH THE 500MB
TROUGH AXIS ARRIVING ARND DAYBREAK WED AND LIFTING EAST ACROSS LOWER
MICHIGAN. THIS WILL BRING DRY ONLY SLIGHT CHANCE POPS AS WEAK SFC
RIDGING BEGINS TO NUDGE EAST ACROSS THE MISSOURI VALLEY TOWARDS THE
FORECAST AREA MIDDAY WED. IT IS POSSIBLE THAT ENOUGH DRY AIR
INFLUENCE COULD ALLOW FOR REMOVAL OF THE SLIGHT CHANCE POPS WED
AFTN. THERMAL TROUGH LAGS BEHIND THE FRONTAL BOUNDARY WED...SO TEMPS
COULD STILL WARM BACK TO ARND 80 AND PERHAPS THE LOW 80S IN THE
SOUTHERN CWFA.

THURSDAY THROUGH SUNDAY...
ANTI-CYCLONIC FLOW ARRIVES THUR WITH AT LEAST ONE PERIOD OF DRY
WEATHER EXPECTED FOR NORTHERN IL/NORTHWEST IN. ONLY A COUPLE
ENSEMBLE MEMBERS CONTINUE TO PROG POPS ALONG THE SOUTHERN FORECAST
AREA THUR...BUT COULD SEE THIS TRENDING DRY IN THE NEXT FEW
SOLUTIONS. WITH WARM TEMPS ALOFT EXPECTED THUR AND THIN CLOUD
COVER...THUR HIGHS COULD PEAK IN THE LOW 80S.

THEN FOCUS TURNS TOWARDS THE UPCOMING WEEKEND AND A PATTERN SHIFT
AWAY FROM THE WARM/HUMID CONDITIONS. ENSEMBLES SHOW MINIMAL SPREAD
IN THE LATE WEEK PERIODS...WITH THE UPSTREAM RIDGE OVER
ALASKA/WESTERN CANADA AND A DOWNSTREAM MID-LVL RIDGE ACROSS THE
SOUTHEAST CONUS. BOTH OF THESE FEATURES IN TIME BEGIN TO
WEAKEN...WITH THE LONGWAVE PATTERN TRANSITIONING INTO A SEMI-ZONAL
ORIENTATION BY THE SECOND HALF OF THE WEEKEND.

OPER GUIDANCE HAS BEEN CONSISTENT WITH PROGGING A ROBUST 500MB
TROUGH TO SLIDE SOUTH FROM CENTRAL CANADA FRI...ALONG WITH A STRONG
CANADIAN SFC RIDGE ON IT/S HEELS. WITH A CHANNEL OF MOISTURE
REMAINING ACROSS THE SOUTHERN PLAINS STRETCHING NORTHEAST THROUGH
THE UPPER MIDWEST...THIS BOUNDARY WILL BECOME ACTIVE WITH A SFC WAVE
DEVELOPING ACROSS THE SOUTHERN PLAINS. THIS LOW WILL THEN LIFT
NORTHEAST TOWARDS THE CWFA FRI WITH A COLD FRONT ARRIVING ACROSS THE
FORECAST AREA SAT. WINDS LOOK TO SHIFT TO THE NORTH...WITH MUCH
COOLER AIR SLIDING SOUTH AND LIKELY KNOCKING TEMPS BACK TO SUB-
SEASONAL CONDS IN THE UPR 60S/NEAR 70 DEGREE RANGE SAT/SUN. IF
NORTHEAST WINDS MATERIALIZE...NEXT WEEKEND AREAS ADJACENT TO LAKE
MICHIGAN ALONG THE IL/IN SHORELINE COULD BE LOCKED IN THE UPR 50S TO
LOW 60S FOR HIGHS WITH A COLD FLOW OFF OF LAKE MICHIGAN.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* SCATTERED SHOWERS AND ISOLATED TSRA OVERNIGHT.

* WINDS...TURNING SOUTH AND INCREASING OVERNIGHT.

* STRONG AND GUSTY SOUTH WINDS MONDAY MORNING THROUGH EARLY
  AFTERNOON.

KREIN

//DISCUSSION...UPDATED 06Z...

MAIN CONCERN FOR THE OVERNIGHT HOURS WILL BE STRENGTHENING WINDS
BECOMING PREVAILING SOUTHERLY. AT 06S...WINS HAVE INCREASE T0
10-15KT AND SHOULD GRADUALLY INCREASE THROUGH THE NIGHT...BECOMING
GUSTY TO 20-25KT THROUGH THE EARLY MORNING HOURS AS THE SFC
PRESSURE GRADIENT TIGHTENS WITH THE SFC LOW MOVING INTO NWRN WI.
LATEST RADAR TRENDS INDICATE THAT PCPN HAS ENDED OVER NERN
IL...BUT AN AREA OF SCT SHRA/ISOLD TSRA PERSISTS FROM NCNTRL IL
WEST INTO ERN IOWA...INCLUDING THE RFD AREA. THERE IS A BAND OF
PCPN OVER CNTRL IL TRACKING ENELY WHICH COULD REACH THE CHICAGO
AREA TERMINALS DURG THE EARLY MORNING HOURS...SO WILL MAINTAIN THE
GOING FORECAST OF THE TEMPO TSRA FOR 07-10Z.

WINDS WILL THEN BECOME THE PRIMARY CONCERN BY THE PREDAWN HOURS AS
SFC RIDGING BUILDS THROUGH THE OHIO VALLEY WHILE THE SFC LOW MOVES
INTO NRN WI WITH TROUGHING EXTENDING TO THE EAST. THIS WILL SET
OF A STRONG SWLY GRADIENT AT THE SFC. ALSO...LATEST MODEL GUIDANCE
SUGGESTS THAT A STRONG LOW LEVEL JET WILL MOVE OVER THE
AREA...WITH 925MB WINDS OF 45-50KT. SINCE THE LOWER LEVELS SHOULD
REMAIN WELL MIXED OVERNIGHT...STRONGER GUSTS SHOULD HAVE LITTLE
TROUBLE MIXING DOWN TO THE SFC...WITH GUSTS OF 30-35KT LIKELY
THROUGH ARND NOON. INTO THE EARLY AFTERNOON...THE LOW LEVEL JET
WILL WEAKEN TO ABOUT 30KT WHILE VEERING MORE WLY...SO SFC GUSTS
SHOULD DROP OFF INTO THE AFTERNOON AS WELL. A SECONDARY LOW IS
EXPECTED TO DEVELOP OVER THE UPPER MISSOURI VALLEY TOMORROW
EVENING...KEEPING A MODEST PRESSURE GRADIENT OVER THE REGION...SO
MODERATE...GUSTY WINDS SHOULD PERSIST INTO TOMORROW NIGHT.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* MEDIUM CONFIDENCE IN WIND TRENDS OVERNIGHT BUT HIGH TOMORROW.

* MEDIUM CONFIDENCE IN CONVECTIVE TRENDS OVERNIGHT.

* MEDIUM CONFIDENCE IN CIG TRENDS OVERNIGHT...ESPECIALLY INVOF
  PCPN/TSRA.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

KREIN

//OUTLOOK FOR ORD/MDW FOR 12Z TUESDAY-12Z SUNDAY...UPDATED 00Z...

TUESDAY...SHRA LIKELY/CHANCE TSRA. GUSTY SOUTHWEST WINDS.

WEDNESDAY...CHANCE OF SHRA/TSRA EARLY. WEST WINDS TURNING EAST.

THURSDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHEAST WINDS.

FRIDAY...CHANCE SHRA/SLIGHT CHANCE TSRA. SOUTHWEST WINDS.

SATURDAY...CHANCE SHRA. EAST WINDS.

LENNING

&&

.MARINE...
304 AM CDT

LOW PRESSURE WILL BE STEADILY LIFTING NORTH ACROSS THE MISSOURI
VALLEY THIS MORNING...REACHING LAKE SUPERIOR BY THIS EVENING AND
CONTINUEING TO SLIDE EAST/NORTHEAST TOWARDS QUEBEC BY TUESDAY
MORNING. A FRONTAL BOUNDARY WILL REMAIN OVER THE FAR NORTHERN
PORTIONS OF LAKE MICHIGAN. MEANWHILE GUSTY SOUTHERLY WINDS ARE
EXPECTED TO INCREASE THIS MORNING...WITH OCCASIONAL GALES FOR THE
NEARSHORE WATERS OF IL/IN. ACROSS THE OPEN WATERS...EXPECT THE
WARM/MOIST AIR TO STRUGGLE TO REACH THE SFC OF THE LAKE WITH SOME
DEGREE OF LAKE STABILITY. WAVES WILL STEADILY BUILD ACROSS THE
NORTHERN HALF OF THE LAKE AS A RESULT OF THE LONG FETCH. STILL
FEEL THAT GUSTS WILL REACH 30KT ACROSS THE LAKE...HOWEVER
CONFIDENCE HAS DIMINISHED SLIGHTLY AS NEW GUIDANCE HAS BECOME A
LITTLE LESS WITH THE WIND FIELDS. NONETHELESS...WAVES FOR THE
NORTHERN HALF OF THE LAKE WILL LIKELY TOP OUT IN THE 4 TO 7 FT
RANGE WITH OCCASIONAL WAVES REACHING 9 FT THIS AFTERNOON/EVENING.

THE GRADIENT QUICKLY DIMINISHES THIS EVENING...BUT EXPECT
SOUTHERLY WINDS TO PERSIST. THIS WILL ALLOW WAVES TO SUBSIDE TO 3
TO 5 FT. ANOTHER LOW WILL ARRIVE TUE...WITH WINDS NUDGING BACK UP
HOWEVER WARM AIR WILL CONTINUE TO FLOW ACROSS THE LAKE AND COULD
FURTHER ENHANCE THE LAKE STABILITY AND KEEP WAVES FROM BUILDING TO
LARGE.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 9 AM MONDAY.

     GALE WARNING...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745...9 AM
     MONDAY TO 3 PM MONDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...3 PM MONDAY TO 4 AM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 250845
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
345 AM CDT MON MAY 25 2015

.SHORT TERM...
345 AM CDT

THROUGH MONDAY NIGHT...
FOR THE REMAINDER OF THE NIGHT AND INTO MONDAY MORNING...PCPN
CHANCES CONTINUE TO WANE AS LATEST RADAR TRENDS ONLY SHOW SOME SCT
SHRA WHICH ARE DECREASING IN INTENSITY.  IN SPITE OF DEWPOINTS IN
THE LOW 60S...AND A STRONG LOW LEVEL JET...50 KT AT 925 MB...THERE
IS AN ELEMENT LACKING WHICH IS SEEMS TO BE PREVENTING THE
MAINTENANCE OF SHRA/TSRA OVER NERN IL/NWRN IN.  THE MAIN MISSING
ELEMENTS IS FORCING.  THE SFC AND UPPER LEVEL LOW ARE WAY TO THE
WEST...OVER THE NRN PLAINS. THE SHORTWAVE CLIMBING UP THE NWRN
PERIPHERY OF THE HIGH AMPLITUDE RIDGE IS BEING SLOWED BY THE HIGH
AMPLITUDE...AND IS BEING FORCED TO A MORE WLY TRACK THROUGH THE
UPPER MISSISSIPPI VALLEY THAN PREVIOUSLY ANTICIPATED.  SO...FOR THE
REMAINDER OF THE OVERNIGHT HOURS AND THE DAYTIME HOURS MONDAY...HAVE
BACK OF TO ISOLD-SCT SHRA.  WILL KEEP ISOLD TS MENTION FOR THE LATE
MORNING HOURS...THROUGH AROUND NOON...WITH THE DAYTIME HEATING...BUT
CONFIDENCE IN ANY TS IS RATHER LOW AT THIS TIME.  BY THIS
AFTERNOON...A MID LEVEL DRY SLOT IS EXPECTED TO MOVE ACROSS THE
REGION...FURTHER LIMITING PCPN CHANCES AND IT IS QUITE LIKELY THAT
THE REGION WILL REMAIN DRY THROUGH THE DAY.  HOWEVER...WHILE THE
PCPN CHANCES ARE DIMINISHING...THE LIKELIHOOD OF STRONG WINDS IS
STILL A CONCERN.  WITH THE DIMINISHING PCPN CHANCES...LESS SKY COVER
THAN PREVIOUSLY ANTICIPATED IS ALSO POSSIBLE.  A STRONG SWLY
PRESSURE GRADIENT IS SETTING UP ACROSS THE REGION BETWEEN SFC
RIDGING ACROSS THE SERN CONUS AND AND LOW PRESSURE FROM THE UPPER
MISSISSIPPI VALLEY TO THE WESTERN PLAINS.  THE STRONG GRADIENT WILL
HELP DRIVE THE SFC WINDS AND THE DIMINISHING CLOUD COVER COULD HELP
ENHANCE DEEP LAYER MIXING...TAPPING STRONGER WINDS ALOFT.  SUSTAINED
25-25 MPH WINDS ARE LIKELY WITH GUSTS OF 30-35 MPH.
ALSO...PERSISTENT WARM/MOIST ADVECTION AT THE SFC WILL BRING
TEMPERATURES INTO THE LOW TO MIDDLE 80S WITH DEWPOINTS IN THE LOWER
60S.

FOR MONDAY NIGHT...THE BREEZY CONDITIONS WILL PERSIST INTO THE AS
THERE SHOULD BE LITTLE CHANGE TO THE SFC AND UPPER LEVEL PATTERNS.
THE UPPER RIDGE WILL LOSE A LITTLE AMPLITUDE AS SHORT WAVE ENERGY
OVERTOPS THE RIDGE...BUT GENERAL TROUGHING WILL PERSIST ACROSS THE
UPPER MISSISSIPPI VALLEY THROUGH THE CENTRAL PLAINS.  THE NEXT
CHANCE FOR PCPN WILL HOLD OFF UNTIL LATE TONIGHT/EARLY TUESDAY
MORNING AND THE NEXT SHORTWAVE LIFTS OUT OF THE SRN PLAINS AND INTO
THE MIDDLE MISSISSIPPI VALLEY.  AMPLE LOW LEVEL MOISTURE WILL
ALREADY BE IN PLACE SO IT WILL JUST A MATTER OF WHEN THE FORCING
WILL GET HERE.  AGAIN...THERE IS SOME CONCERN THAT THE FORCING WILL
BE TO THE WEST...WITH THE SHORTWAVE TRACKING THROUGH THE MIDDLE
MISSISSIPPI VALLEY AND INTO WI.  SO...WILL CARRY CHANCE POPS FOR THE
REGION...WITH LIKELY POPS APPROACHING THE PONTIAC AREA BY EARLY
TUESDAY MORNING.  THE PERSISTENT WARM/MOIST ADVECTIVE PATTERN AND
BREEZY CONDITIONS SHOULD KEEP TEMPERATURES FROM DROPPING OFF
SIGNIFICANTLY OVERNIGHT AND LOWS SHOULD BE IN THE MIDDLE TO UPPER
60S.

KREIN

&&

.LONG TERM...
239 AM CDT

TUESDAY THROUGH SUNDAY...

TUESDAY THROUGH WEDNESDAY...
500MB TROUGH AXIS WILL SLOWLY PIVOT EAST ACROSS THE CENTRAL PLAINS
INTO THE MID-MISSOURI VALLEY TUE...WITH A SFC WAVE SLIDING NORTH
ACROSS IOWA INTO CENTRAL WISC LATE TUE. THE SFC FEATURE IS NOT
EXPECTED TO BE STRONG...HOWEVER THE GRAIDENT DOES TIGHTEN WITH
MODEST HEIGHT FALLS IN THE LOWEST LAYERS OF THE ATMOSPHERE. SOME
INSTABILITY DOES REMAIN ALONG WITH RELATIELY MOIST SFC CONDS AS DEW
PTS WILL REMAIN IN THE UPR 50S/LOW 60S. PWAT VALUES WILL ALSO HOVER
JUST OVER 1 INCH...WHICH IS SEASONAL. WILL HOLD ONTO MENTION OF RAIN
AND THUNDER...BUT COULD SEE THIS MAINLY FOCUSED IN THE TUE MORING
TIMEFRAME.

WITH CONSIDERABLE SOLAR SHIELDING PROGGED FOR TUE...TEMPS MAY
STRUGGLE TO WARM BEYOND THE MID/UPR 70S. BUT WITH GUIDANCE HINTING
AT A DRY SLOT LIFTING NORTHEAST ACROSS THE REGION TUE EVE...THIS
COULD INTRODUCE SOME EROSION TO THE CLOUD COVER IN THE AFTN HOURS
TUE AND ALLOW SOME SFC HEATING TO OCCUR AND PUSH TEMPS TO ARND 80.

GUIDANCE LIFTS THE DRY SLOT OVERHEAD LATE TUE NGT...WITH THE 500MB
TROUGH AXIS ARRIVING ARND DAYBREAK WED AND LIFTING EAST ACROSS LOWER
MICHIGAN. THIS WILL BRING DRY ONLY SLIGHT CHANCE POPS AS WEAK SFC
RIDGING BEGINS TO NUDGE EAST ACROSS THE MISSOURI VALLEY TOWARDS THE
FORECAST AREA MIDDAY WED. IT IS POSSIBLE THAT ENOUGH DRY AIR
INFLUENCE COULD ALLOW FOR REMOVAL OF THE SLIGHT CHANCE POPS WED
AFTN. THERMAL TROUGH LAGS BEHIND THE FRONTAL BOUNDARY WED...SO TEMPS
COULD STILL WARM BACK TO ARND 80 AND PERHAPS THE LOW 80S IN THE
SOUTHERN CWFA.

THURSDAY THROUGH SUNDAY...
ANTI-CYCLONIC FLOW ARRIVES THUR WITH AT LEAST ONE PERIOD OF DRY
WEATHER EXPECTED FOR NORTHERN IL/NORTHWEST IN. ONLY A COUPLE
ENSEMBLE MEMBERS CONTINUE TO PROG POPS ALONG THE SOUTHERN FORECAST
AREA THUR...BUT COULD SEE THIS TRENDING DRY IN THE NEXT FEW
SOLUTIONS. WITH WARM TEMPS ALOFT EXPECTED THUR AND THIN CLOUD
COVER...THUR HIGHS COULD PEAK IN THE LOW 80S.

THEN FOCUS TURNS TOWARDS THE UPCOMING WEEKEND AND A PATTERN SHIFT
AWAY FROM THE WARM/HUMID CONDITIONS. ENSEMBLES SHOW MINIMAL SPREAD
IN THE LATE WEEK PERIODS...WITH THE UPSTREAM RIDGE OVER
ALASKA/WESTERN CANADA AND A DOWNSTREAM MID-LVL RIDGE ACROSS THE
SOUTHEAST CONUS. BOTH OF THESE FEATURES IN TIME BEGIN TO
WEAKEN...WITH THE LONGWAVE PATTERN TRANSITIONING INTO A SEMI-ZONAL
ORIENTATION BY THE SECOND HALF OF THE WEEKEND.

OPER GUIDANCE HAS BEEN CONSISTENT WITH PROGGING A ROBUST 500MB
TROUGH TO SLIDE SOUTH FROM CENTRAL CANADA FRI...ALONG WITH A STRONG
CANADIAN SFC RIDGE ON IT/S HEELS. WITH A CHANNEL OF MOISTURE
REMAINING ACROSS THE SOUTHERN PLAINS STRETCHING NORTHEAST THROUGH
THE UPPER MIDWEST...THIS BOUNDARY WILL BECOME ACTIVE WITH A SFC WAVE
DEVELOPING ACROSS THE SOUTHERN PLAINS. THIS LOW WILL THEN LIFT
NORTHEAST TOWARDS THE CWFA FRI WITH A COLD FRONT ARRIVING ACROSS THE
FORECAST AREA SAT. WINDS LOOK TO SHIFT TO THE NORTH...WITH MUCH
COOLER AIR SLIDING SOUTH AND LIKELY KNOCKING TEMPS BACK TO SUB-
SEASONAL CONDS IN THE UPR 60S/NEAR 70 DEGREE RANGE SAT/SUN. IF
NORTHEAST WINDS MATERIALIZE...NEXT WEEKEND AREAS ADJACENT TO LAKE
MICHIGAN ALONG THE IL/IN SHORELINE COULD BE LOCKED IN THE UPR 50S TO
LOW 60S FOR HIGHS WITH A COLD FLOW OFF OF LAKE MICHIGAN.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* SCATTERED SHOWERS AND ISOLATED TSRA OVERNIGHT.

* WINDS...TURNING SOUTH AND INCREASING OVERNIGHT.

* STRONG AND GUSTY SOUTH WINDS MONDAY MORNING THROUGH EARLY
  AFTERNOON.

KREIN

//DISCUSSION...UPDATED 06Z...

MAIN CONCERN FOR THE OVERNIGHT HOURS WILL BE STRENGTHENING WINDS
BECOMING PREVAILING SOUTHERLY. AT 06S...WINS HAVE INCREASE T0
10-15KT AND SHOULD GRADUALLY INCREASE THROUGH THE NIGHT...BECOMING
GUSTY TO 20-25KT THROUGH THE EARLY MORNING HOURS AS THE SFC
PRESSURE GRADIENT TIGHTENS WITH THE SFC LOW MOVING INTO NWRN WI.
LATEST RADAR TRENDS INDICATE THAT PCPN HAS ENDED OVER NERN
IL...BUT AN AREA OF SCT SHRA/ISOLD TSRA PERSISTS FROM NCNTRL IL
WEST INTO ERN IOWA...INCLUDING THE RFD AREA. THERE IS A BAND OF
PCPN OVER CNTRL IL TRACKING ENELY WHICH COULD REACH THE CHICAGO
AREA TERMINALS DURG THE EARLY MORNING HOURS...SO WILL MAINTAIN THE
GOING FOREC