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000
FXUS63 KLOT 292348
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
648 PM CDT FRI AUG 29 2014

.MESOSCALE DISCUSSION...
411 PM CDT

THUNDERSTORMS ARE GENERALLY ISOLATED IN NORTHEAST ILLINOIS THIS
AFTERNOON WITH SCATTERED ACTIVITY EAST OF INTERSTATE 57 IN
ILLNOIS AND ALONG THE INTERSTATE 65 CORRIDOR IN NW INDIANA. RADAR
ESTIMATES A QUICK THREE QUARTERS OF AN INCH TO 1 INCH HAS FALLEN
IN THE HEAVIER DOWNPOURS...WITH STREET FLOODING REPORTED IN
LANSING. EXPECT HEAVY RAIN AND LOCALIZED PONDING OF WATER TO
REMAIN A THREAT INTO THE EARLY EVENING...ESPECIALLY IN NW
INDIANA...THOUGH STORMS MAY INCREASE AS THE WARM FRONT TO THE
SOUTH AND DEEPER MOISTURE SPREAD NORTHWARD.

KMD

&&

.DISCUSSION...
221 PM CDT

SYNOPSIS...UNSETTLED WEATHER CONTINUES THROUGH TOMORROW WITH
SCATTERED THUNDERSTORMS EXPECTED.  CONFIDENCE REMAINS LOW IN WHEN
AND WHERE THUNDERSTORMS WILL FORM.  SUNDAY STILL LOOKS DRY BUT
MULTIPLE CHANCES FOR STORMS RETURN MONDAY THROUGH THE END OF THE
WEEK. ABOVE NORMAL TEMPERATURES ARE ALSO EXPECTED THROUGH THE PERIOD
AS WELL.

//NEAR TERM FORECAST//

THROUGH TONIGHT...
A LARGE RIDGE IS OVER THE EAST COAST WHILE A TROUGH IS OVER THE
PLAINS.  THE TROUGH WILL WEAKEN AS IT APPROACHES OUR AREA AND PASS
OVERHEAD LATE SATURDAY NIGHT INTO SUNDAY MORNING. AT THE SURFACE THE
HIGH HAS PUSHED EAST WHILE A DEVELOPING LOW PRESSURE SYSTEM IS OVER
MINNESOTA.  THE LOWS WARM FRONT LIES TO OUR SOUTH ACROSS SOUTHERN
IL...AND IT WILL LIFT NORTH THROUGH THE REGION THIS AFTERNOON.

HAVE VERY LOW CONFIDENCE IN EXACT TIMING AND LOCATION OF
THUNDERSTORMS THROUGH THIS EVENING.  THERE IS NO CLEAR FORCING
MECHANISM BUT WITH AROUND 2000 J/KG OF CAPE AVAILABLE...STORMS ARE
CERTAINLY POSSIBLE. PWAT VALUES ARE AROUND 2 INCHES SO THE MAIN
CONCERN REMAINS HEAVY DOWNPOURS. THE STRONGEST STORMS MAY PRODUCE
WIND GUSTS TO 50 KT BUT NO SEVERE WEATHER IS EXPECTED AS WIND SHEAR
IS BASICALLY NIL.

FOR POPS USED A BLEND OF NEAR TERM GUIDANCE WHICH HAS BEEN DOING
REASONABLY WELL THIS MORNING.  HOWEVER...KEPT A CHANCE OF STORMS
ACROSS THE REGION THIS AFTERNOON AND EVENING DUE TO THE SCATTERED
NATURE OF THE STORMS THAT ARE EXPECTED.  A WASH OUT IS NOT
EXPECTED.  THE BEST CHANCE FOR WIDESPREAD STORMS WILL BE OVERNIGHT
AS THE UPPER LEVEL TROUGH APPROACHES. IN FACT THE STORMS ASSOCIATED
WITH THE TROUGH STRETCH FROM MINNESOTA THROUGH ARKANSAS.  MODELS
DIFFER IN HOW WELL THIS AREA OF PRECIP WILL HOLD TOGETHER SO LIMITED
POPS TO THE LIKELY CATEGORY.

LOWS WILL BE IN THE UPPER 60S TO LOWER 70S TONIGHT AND FOG IS
POSSIBLE. GIVEN THAT WE HAVE NOT SEEN MUCH RAIN TODAY...HAVE LIMITED
CONFIDENCE SO LEFT FOG OUT OF THE FORECAST FOR NOW.

SATURDAY AND SATURDAY NIGHT...
THE SURFACE LOW PASSES OVER LAKE MICHIGAN SATURDAY AFTERNOON WHILE
ITS COLD FRONT GETS DRAGGED THROUGH THE AREA SATURDAY
AFTERNOON/EVENING.  SCATTERED STORMS ARE AGAIN POSSIBLE IN THE
MORNING IN THE WARM AND MOIST ENVIRONMENT WITH LINGERING 2 INCH PWAT
VALUES. STORMS WILL THEN FORM ALONG THE COLD FRONT SOUTH OF A GARY
IN TO PONTIAC IL LINE. STORMS ARE POSSIBLE NORTH AND WEST OF THIS
LINE...BUT CONFIDENCE IS SIGNIFICANTLY LOWER.

CAPE VALUES WILL BE AROUND 1000 J/KG TOMORROW WITH WEAK SHEAR ONCE
AGAIN. THEREFORE EXPECTING STORMS TO PRODUCE HEAVY DOWNPOURS AND THE
STRONGEST MAY BE CAPABLE OF GUSTY WINDS.  SEVERE WEATHER IS NOT
EXPECTED.

TOMORROW LOOKS LIKE ANOTHER WARM AND STICKY DAY AHEAD OF THE COLD
FRONT.  LOWS WILL BE IN THE 60S AND FOG IS POSSIBLE OVERNIGHT.

JEE

//EXTENDED FORECAST//

SUNDAY...
EXPECT A BRIEF LULL IN THE PRECIP CHANCES DURING MUCH OF THE DAY
SUNDAY AS THE FIRST COLD FRONT DEPARTS TO THE EAST AND ANOTHER LOW
TAKES SHAPE OVER THE NORTHERN PLAINS. IN BETWEEN THESE TWO
SYSTEMS...WEAK INDUCED SURFACE HIGH SHOULD RESULT IN QUIET WEATHER
LOCALLY...WITH THE H85 THERMAL RIDGE ADVECTING OVERHEARD THROUGHOUT
THE DAY. RETURN FLOW WILL HELP PUSH THE DEWPOINTS BACK UP TO AROUND
70 WITH AFTERNOON HIGH TEMPS EXPECTED TO BE IN THE MID 80S. STEEP
LOW/MID LEVEL LAPSE RATES WILL RESULT IN MODERATE INSTABILITY
DEVELOPING DURING THE AFTERNOON...BUT MODEST SBCIN IS PROGGED TO
STAY IN PLACE CAPPING ANY SURFACE BASED CONVECTION. IN ADDITION...
THE AREA SHOULD BE SQUARELY UNDER AREA OF MID LEVEL HEIGHT RISES
WHICH SHOULD HELP REINFORCE THE INVERSION...AND NO SIGNIFICANT
FORCING NOTED OVER THE AREA.

MONDAY...
TROUGHING CURRENTLY MOVING ONSHORE OVER THE PAC NORTHWEST TODAY WILL
MOVE ACROSS THE CENTRAL PLAINS THIS WEEKEND...THEN BEGIN TO LIFT
ACROSS THE UPPER MIDWEST EARLY NEXT WEEK. SURFACE LOW IS PROGGED TO
DEEPEN FROM THE NORTHERN PLAINS SUNDAY AS IT LIFTS TO NEAR HUDSON
BAY LATE ON MONDAY. THIS WILL DRAG A COLD FRONT ACROSS THE REGION ON
MONDAY. WITH THE LOW LIFTING AWAY FROM THE AREA...CONVERGENCE ALONG
THE FRONT IS PROGGED TO WEAKEN AS IT COMES ACROSS NORTHERN ILLINOIS
EARLY MONDAY WITH THE BETTER DYNAMICS STAYING TO OUR NORTH.
MEANWHILE...THE LOCAL AREA APPEARS TO LIE ON THE NORTHERN PERIPHERY
OF THE BETTER INSTABILITY TO OUR SOUTH. GFS SHOWS SOME HINTS THAT
PARTICULARLY NORTH CENTRAL ILLINOIS MAY BE SPLIT BY THE
PRECIP...ESPECIALLY CONSIDERING THE CAPPING EARLY IN THE DAY...BUT
WILL HOLD OFF ON FINE TUNING THIS DETAIL FOR NOW. IN ADDITION...THE
REGION DOES FALL WITHIN AN OVERLAPPED AREA OF FAVORABLE
SHEAR/INSTABILITY THAT COULD POTENTIALLY SUPPORT A SEVERE WEATHER
THREAT.

TUESDAY THROUGH FRIDAY...
FRONTAL BOUNDARY IS PROGGED TO STALL ACROSS/NEAR CENTRAL ILLINOIS
TUESDAY GRADUALLY LIFTING BACK NORTH ACROSS THE FORECAST AREA BY THE
END OF THE WORK WEEK AS A SERIES OF UPPER LEVEL DISTURBANCES MOVE
ACROSS THE REGION. THIS WILL RESULT IN PERIODIC CHANCES FOR SHOWERS
AND THUNDERSTORMS ACROSS THE AREA...THOUGH TIMING AND LOCATION
DETAILS WILL BE DIFFICULT TO PIN DOWN THIS FAR OUT GIVEN THE
PATTERN. THE ATMOSPHERE REMAINS QUITE SOUPY IN THE VICINITY OF THE
FRONT WHERE PWATS REMAIN AROUND 2 INCHES. THUS THE HEAVY RAIN AND
FLOODING THREAT WILL HAVE TO BE CLOSELY MONITORED THROUGH MUCH OF
THE UPCOMING WEEK.

DEUBELBEISS

&&

.AVIATION...

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

* SLIGHT CHANCE OF BRIEF WIND SHIFT TO MORE EASTERLY WITH TS
  OUTFLOW/LAKE BREEZE EARLY THIS EVENING
* ISOLD TSRA MOSTLY JUST AVOIDING TERMINALS THRU MID EVENING
* CHANCE OF SHRA/TSRA LATE EVENING THRU MIDDAY SATURDAY

IZZI

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

ISOLD TSRA HAVE BEEN DOTTING THE AREA EARLY THIS EVENING WITH A
COUPLE CELLS EAST OF ORD/MDW HELPING PUSH THE LAKE BREEZE WEST A
BIT. EXPECT LAKE BREEZE/OUTFLOW TO STAY EAST OF TERMINALS...BUT IT
IS WITHIN A COUPLE MILES OF ORD NOW AND THERE IS A SLIGHT CHANCE
IT COULD PUSH A BIT FARTHER WEST RESULTING IN WIND SHIFT TO A
MORE EASTERLY DIRECTION FOR A SHORT TIME EARLY THIS EVENING.
ISOLD TSRA LIKELY TO LINGER THRU EARLY EVENING...BUT CURRENT
TRENDS SUGGEST THE STORMS WILL PROBABLY STAY OUT OF THE IMMEDIATE
VICINITY OF THE TERMINALS. BAND OF SHRA/TSRA TOWARD THE
MISSISSIPPI RIVER WILL LIKELY WEAKEN AND COULD EVEN DISSIPATE
BEFORE ARRIVING INTO THE REGION LATE THIS EVENING INTO THE EARLY
OVERNIGHT HOURS. PLAUSIBLE THAT THERE COULD BE ADDITIONAL
DEVELOPMENT BEHIND THIS BAND OVERNIGHT...BUT WITH NO OBVIOUS FOCUS
FOR PRECIP HAVE GONE DRY IN TAFS OVERNIGHT INTO EARLY SATURDAY
MORNING. WEAK TROUGH WILL MOVE THROUGH THE TERMINAL MIDDAY
SATURDAY AND COULD SEE SHRA/TSRA DEVELOP WITH THIS
FEATURE...THOUGH BETTER CHANCES LOOK TO BE SOUTHEAST OF THE
TERMINALS LATER IN THE AFTERNOON.

IZZI


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

* LOW-MEDIUM CONFIDENCE IN PRECIP TRENDS
* MEDIUM-HIGH CONFIDENCE IN WINDS

IZZI

//OUTLOOK FOR ORD/MDW FOR 12Z SUNDAY-12Z FRIDAY...UPDATED 00Z...

SUNDAY...VFR.

MONDAY...PERIOD OF TSRA LIKELY.

TUESDAY AND WEDNESDAY...PREDOMINANTLY VFR.

THURSDAY...CHANCE TSRA.

IZZI

&&

.MARINE...
221 PM CDT

MODERATE SOUTHERLY WINDS ARE IN PLACE TODAY AHEAD OF LOW PRESSURE
OVER THE NORTHERN PLAINS. SOUTH TO SOUTHWEST WINDS 20 TO 25 KT
WITH AN OCCASIONAL 30 KT GUSTS POSSIBLE WILL BE IN PLACE THROUGH
TOMORROW...THEN A COLD FRONT WILL START TO PUSH ACROSS THE LAKE
TURNING WINDS NORTHWESTERLY. HIGH PRESSURE WILL PROVIDE A BRIEF
LULL IN THE WINDS SUNDAY ALLOWING LAKE BREEZES TO DEVELOP...BUT
THEN SOUTHERLY WINDS RAMP BACK UP TO 25 TO 30 KT SUNDAY NIGHT INTO
MONDAY AHEAD OF ANOTHER LOW. THIS LOW IS PROGGED TO DEEPEN AS IT
LIFTS FROM THE NORTHERN PLAINS SUNDAY TO HUDSON BAY LATE MONDAY.

BMD

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 292348
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
648 PM CDT FRI AUG 29 2014

.MESOSCALE DISCUSSION...
411 PM CDT

THUNDERSTORMS ARE GENERALLY ISOLATED IN NORTHEAST ILLINOIS THIS
AFTERNOON WITH SCATTERED ACTIVITY EAST OF INTERSTATE 57 IN
ILLNOIS AND ALONG THE INTERSTATE 65 CORRIDOR IN NW INDIANA. RADAR
ESTIMATES A QUICK THREE QUARTERS OF AN INCH TO 1 INCH HAS FALLEN
IN THE HEAVIER DOWNPOURS...WITH STREET FLOODING REPORTED IN
LANSING. EXPECT HEAVY RAIN AND LOCALIZED PONDING OF WATER TO
REMAIN A THREAT INTO THE EARLY EVENING...ESPECIALLY IN NW
INDIANA...THOUGH STORMS MAY INCREASE AS THE WARM FRONT TO THE
SOUTH AND DEEPER MOISTURE SPREAD NORTHWARD.

KMD

&&

.DISCUSSION...
221 PM CDT

SYNOPSIS...UNSETTLED WEATHER CONTINUES THROUGH TOMORROW WITH
SCATTERED THUNDERSTORMS EXPECTED.  CONFIDENCE REMAINS LOW IN WHEN
AND WHERE THUNDERSTORMS WILL FORM.  SUNDAY STILL LOOKS DRY BUT
MULTIPLE CHANCES FOR STORMS RETURN MONDAY THROUGH THE END OF THE
WEEK. ABOVE NORMAL TEMPERATURES ARE ALSO EXPECTED THROUGH THE PERIOD
AS WELL.

//NEAR TERM FORECAST//

THROUGH TONIGHT...
A LARGE RIDGE IS OVER THE EAST COAST WHILE A TROUGH IS OVER THE
PLAINS.  THE TROUGH WILL WEAKEN AS IT APPROACHES OUR AREA AND PASS
OVERHEAD LATE SATURDAY NIGHT INTO SUNDAY MORNING. AT THE SURFACE THE
HIGH HAS PUSHED EAST WHILE A DEVELOPING LOW PRESSURE SYSTEM IS OVER
MINNESOTA.  THE LOWS WARM FRONT LIES TO OUR SOUTH ACROSS SOUTHERN
IL...AND IT WILL LIFT NORTH THROUGH THE REGION THIS AFTERNOON.

HAVE VERY LOW CONFIDENCE IN EXACT TIMING AND LOCATION OF
THUNDERSTORMS THROUGH THIS EVENING.  THERE IS NO CLEAR FORCING
MECHANISM BUT WITH AROUND 2000 J/KG OF CAPE AVAILABLE...STORMS ARE
CERTAINLY POSSIBLE. PWAT VALUES ARE AROUND 2 INCHES SO THE MAIN
CONCERN REMAINS HEAVY DOWNPOURS. THE STRONGEST STORMS MAY PRODUCE
WIND GUSTS TO 50 KT BUT NO SEVERE WEATHER IS EXPECTED AS WIND SHEAR
IS BASICALLY NIL.

FOR POPS USED A BLEND OF NEAR TERM GUIDANCE WHICH HAS BEEN DOING
REASONABLY WELL THIS MORNING.  HOWEVER...KEPT A CHANCE OF STORMS
ACROSS THE REGION THIS AFTERNOON AND EVENING DUE TO THE SCATTERED
NATURE OF THE STORMS THAT ARE EXPECTED.  A WASH OUT IS NOT
EXPECTED.  THE BEST CHANCE FOR WIDESPREAD STORMS WILL BE OVERNIGHT
AS THE UPPER LEVEL TROUGH APPROACHES. IN FACT THE STORMS ASSOCIATED
WITH THE TROUGH STRETCH FROM MINNESOTA THROUGH ARKANSAS.  MODELS
DIFFER IN HOW WELL THIS AREA OF PRECIP WILL HOLD TOGETHER SO LIMITED
POPS TO THE LIKELY CATEGORY.

LOWS WILL BE IN THE UPPER 60S TO LOWER 70S TONIGHT AND FOG IS
POSSIBLE. GIVEN THAT WE HAVE NOT SEEN MUCH RAIN TODAY...HAVE LIMITED
CONFIDENCE SO LEFT FOG OUT OF THE FORECAST FOR NOW.

SATURDAY AND SATURDAY NIGHT...
THE SURFACE LOW PASSES OVER LAKE MICHIGAN SATURDAY AFTERNOON WHILE
ITS COLD FRONT GETS DRAGGED THROUGH THE AREA SATURDAY
AFTERNOON/EVENING.  SCATTERED STORMS ARE AGAIN POSSIBLE IN THE
MORNING IN THE WARM AND MOIST ENVIRONMENT WITH LINGERING 2 INCH PWAT
VALUES. STORMS WILL THEN FORM ALONG THE COLD FRONT SOUTH OF A GARY
IN TO PONTIAC IL LINE. STORMS ARE POSSIBLE NORTH AND WEST OF THIS
LINE...BUT CONFIDENCE IS SIGNIFICANTLY LOWER.

CAPE VALUES WILL BE AROUND 1000 J/KG TOMORROW WITH WEAK SHEAR ONCE
AGAIN. THEREFORE EXPECTING STORMS TO PRODUCE HEAVY DOWNPOURS AND THE
STRONGEST MAY BE CAPABLE OF GUSTY WINDS.  SEVERE WEATHER IS NOT
EXPECTED.

TOMORROW LOOKS LIKE ANOTHER WARM AND STICKY DAY AHEAD OF THE COLD
FRONT.  LOWS WILL BE IN THE 60S AND FOG IS POSSIBLE OVERNIGHT.

JEE

//EXTENDED FORECAST//

SUNDAY...
EXPECT A BRIEF LULL IN THE PRECIP CHANCES DURING MUCH OF THE DAY
SUNDAY AS THE FIRST COLD FRONT DEPARTS TO THE EAST AND ANOTHER LOW
TAKES SHAPE OVER THE NORTHERN PLAINS. IN BETWEEN THESE TWO
SYSTEMS...WEAK INDUCED SURFACE HIGH SHOULD RESULT IN QUIET WEATHER
LOCALLY...WITH THE H85 THERMAL RIDGE ADVECTING OVERHEARD THROUGHOUT
THE DAY. RETURN FLOW WILL HELP PUSH THE DEWPOINTS BACK UP TO AROUND
70 WITH AFTERNOON HIGH TEMPS EXPECTED TO BE IN THE MID 80S. STEEP
LOW/MID LEVEL LAPSE RATES WILL RESULT IN MODERATE INSTABILITY
DEVELOPING DURING THE AFTERNOON...BUT MODEST SBCIN IS PROGGED TO
STAY IN PLACE CAPPING ANY SURFACE BASED CONVECTION. IN ADDITION...
THE AREA SHOULD BE SQUARELY UNDER AREA OF MID LEVEL HEIGHT RISES
WHICH SHOULD HELP REINFORCE THE INVERSION...AND NO SIGNIFICANT
FORCING NOTED OVER THE AREA.

MONDAY...
TROUGHING CURRENTLY MOVING ONSHORE OVER THE PAC NORTHWEST TODAY WILL
MOVE ACROSS THE CENTRAL PLAINS THIS WEEKEND...THEN BEGIN TO LIFT
ACROSS THE UPPER MIDWEST EARLY NEXT WEEK. SURFACE LOW IS PROGGED TO
DEEPEN FROM THE NORTHERN PLAINS SUNDAY AS IT LIFTS TO NEAR HUDSON
BAY LATE ON MONDAY. THIS WILL DRAG A COLD FRONT ACROSS THE REGION ON
MONDAY. WITH THE LOW LIFTING AWAY FROM THE AREA...CONVERGENCE ALONG
THE FRONT IS PROGGED TO WEAKEN AS IT COMES ACROSS NORTHERN ILLINOIS
EARLY MONDAY WITH THE BETTER DYNAMICS STAYING TO OUR NORTH.
MEANWHILE...THE LOCAL AREA APPEARS TO LIE ON THE NORTHERN PERIPHERY
OF THE BETTER INSTABILITY TO OUR SOUTH. GFS SHOWS SOME HINTS THAT
PARTICULARLY NORTH CENTRAL ILLINOIS MAY BE SPLIT BY THE
PRECIP...ESPECIALLY CONSIDERING THE CAPPING EARLY IN THE DAY...BUT
WILL HOLD OFF ON FINE TUNING THIS DETAIL FOR NOW. IN ADDITION...THE
REGION DOES FALL WITHIN AN OVERLAPPED AREA OF FAVORABLE
SHEAR/INSTABILITY THAT COULD POTENTIALLY SUPPORT A SEVERE WEATHER
THREAT.

TUESDAY THROUGH FRIDAY...
FRONTAL BOUNDARY IS PROGGED TO STALL ACROSS/NEAR CENTRAL ILLINOIS
TUESDAY GRADUALLY LIFTING BACK NORTH ACROSS THE FORECAST AREA BY THE
END OF THE WORK WEEK AS A SERIES OF UPPER LEVEL DISTURBANCES MOVE
ACROSS THE REGION. THIS WILL RESULT IN PERIODIC CHANCES FOR SHOWERS
AND THUNDERSTORMS ACROSS THE AREA...THOUGH TIMING AND LOCATION
DETAILS WILL BE DIFFICULT TO PIN DOWN THIS FAR OUT GIVEN THE
PATTERN. THE ATMOSPHERE REMAINS QUITE SOUPY IN THE VICINITY OF THE
FRONT WHERE PWATS REMAIN AROUND 2 INCHES. THUS THE HEAVY RAIN AND
FLOODING THREAT WILL HAVE TO BE CLOSELY MONITORED THROUGH MUCH OF
THE UPCOMING WEEK.

DEUBELBEISS

&&

.AVIATION...

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

* SLIGHT CHANCE OF BRIEF WIND SHIFT TO MORE EASTERLY WITH TS
  OUTFLOW/LAKE BREEZE EARLY THIS EVENING
* ISOLD TSRA MOSTLY JUST AVOIDING TERMINALS THRU MID EVENING
* CHANCE OF SHRA/TSRA LATE EVENING THRU MIDDAY SATURDAY

IZZI

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

ISOLD TSRA HAVE BEEN DOTTING THE AREA EARLY THIS EVENING WITH A
COUPLE CELLS EAST OF ORD/MDW HELPING PUSH THE LAKE BREEZE WEST A
BIT. EXPECT LAKE BREEZE/OUTFLOW TO STAY EAST OF TERMINALS...BUT IT
IS WITHIN A COUPLE MILES OF ORD NOW AND THERE IS A SLIGHT CHANCE
IT COULD PUSH A BIT FARTHER WEST RESULTING IN WIND SHIFT TO A
MORE EASTERLY DIRECTION FOR A SHORT TIME EARLY THIS EVENING.
ISOLD TSRA LIKELY TO LINGER THRU EARLY EVENING...BUT CURRENT
TRENDS SUGGEST THE STORMS WILL PROBABLY STAY OUT OF THE IMMEDIATE
VICINITY OF THE TERMINALS. BAND OF SHRA/TSRA TOWARD THE
MISSISSIPPI RIVER WILL LIKELY WEAKEN AND COULD EVEN DISSIPATE
BEFORE ARRIVING INTO THE REGION LATE THIS EVENING INTO THE EARLY
OVERNIGHT HOURS. PLAUSIBLE THAT THERE COULD BE ADDITIONAL
DEVELOPMENT BEHIND THIS BAND OVERNIGHT...BUT WITH NO OBVIOUS FOCUS
FOR PRECIP HAVE GONE DRY IN TAFS OVERNIGHT INTO EARLY SATURDAY
MORNING. WEAK TROUGH WILL MOVE THROUGH THE TERMINAL MIDDAY
SATURDAY AND COULD SEE SHRA/TSRA DEVELOP WITH THIS
FEATURE...THOUGH BETTER CHANCES LOOK TO BE SOUTHEAST OF THE
TERMINALS LATER IN THE AFTERNOON.

IZZI


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

* LOW-MEDIUM CONFIDENCE IN PRECIP TRENDS
* MEDIUM-HIGH CONFIDENCE IN WINDS

IZZI

//OUTLOOK FOR ORD/MDW FOR 12Z SUNDAY-12Z FRIDAY...UPDATED 00Z...

SUNDAY...VFR.

MONDAY...PERIOD OF TSRA LIKELY.

TUESDAY AND WEDNESDAY...PREDOMINANTLY VFR.

THURSDAY...CHANCE TSRA.

IZZI

&&

.MARINE...
221 PM CDT

MODERATE SOUTHERLY WINDS ARE IN PLACE TODAY AHEAD OF LOW PRESSURE
OVER THE NORTHERN PLAINS. SOUTH TO SOUTHWEST WINDS 20 TO 25 KT
WITH AN OCCASIONAL 30 KT GUSTS POSSIBLE WILL BE IN PLACE THROUGH
TOMORROW...THEN A COLD FRONT WILL START TO PUSH ACROSS THE LAKE
TURNING WINDS NORTHWESTERLY. HIGH PRESSURE WILL PROVIDE A BRIEF
LULL IN THE WINDS SUNDAY ALLOWING LAKE BREEZES TO DEVELOP...BUT
THEN SOUTHERLY WINDS RAMP BACK UP TO 25 TO 30 KT SUNDAY NIGHT INTO
MONDAY AHEAD OF ANOTHER LOW. THIS LOW IS PROGGED TO DEEPEN AS IT
LIFTS FROM THE NORTHERN PLAINS SUNDAY TO HUDSON BAY LATE MONDAY.

BMD

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO







000
FXUS63 KLOT 292220
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
520 PM CDT FRI AUG 29 2014

.MESOSCALE DISCUSSION...
411 PM CDT

THUNDERSTORMS ARE GENERALLY ISOLATED IN NORTHEAST ILLNOIS THIS
AFTERNOON WITH SCATTERED ACTIVITY EAST OF INTERSTATE 57 IN
ILLNOIS AND ALONG THE INTERSTATE 65 CORRIDOR IN NW INDIANA. RADAR
ESTIMATES A QUICK THREE QUARTERS OF AN INCH TO 1 INCH HAS FALLEN
IN THE HEAVIER DOWNPOURS...WITH STREET FLOODING REPORTED IN
LANSING. EXPECT HEAVY RAIN AND LOCALIZED PONDING OF WATER TO
REMAIN A THREAT INTO THE EARLY EVENING...ESPECIALLY IN NW
INDIANA...THOUGH STORMS MAY INCREASE AS THE WARM FRONT TO THE
SOUTH AND DEEPER MOISTURE SPREAD NORTHWARD.

KMD

&&

.DISCUSSION...
221 PM CDT

SYNOPSIS...UNSETTLED WEATHER CONTINUES THROUGH TOMORROW WITH
SCATTERED THUNDERSTORMS EXPECTED.  CONFIDENCE REMAINS LOW IN WHEN
AND WHERE THUNDERSTORMS WILL FORM.  SUNDAY STILL LOOKS DRY BUT
MULTIPLE CHANCES FOR STORMS RETURN MONDAY THROUGH THE END OF THE
WEEK. ABOVE NORMAL TEMPERATURES ARE ALSO EXPECTED THROUGH THE PERIOD
AS WELL.

//NEAR TERM FORECAST//

THROUGH TONIGHT...
A LARGE RIDGE IS OVER THE EAST COAST WHILE A TROUGH IS OVER THE
PLAINS.  THE TROUGH WILL WEAKEN AS IT APPROACHES OUR AREA AND PASS
OVERHEAD LATE SATURDAY NIGHT INTO SUNDAY MORNING. AT THE SURFACE THE
HIGH HAS PUSHED EAST WHILE A DEVELOPING LOW PRESSURE SYSTEM IS OVER
MINNESOTA.  THE LOWS WARM FRONT LIES TO OUR SOUTH ACROSS SOUTHERN
IL...AND IT WILL LIFT NORTH THROUGH THE REGION THIS AFTERNOON.

HAVE VERY LOW CONFIDENCE IN EXACT TIMING AND LOCATION OF
THUNDERSTORMS THROUGH THIS EVENING.  THERE IS NO CLEAR FORCING
MECHANISM BUT WITH AROUND 2000 J/KG OF CAPE AVAILABLE...STORMS ARE
CERTAINLY POSSIBLE. PWAT VALUES ARE AROUND 2 INCHES SO THE MAIN
CONCERN REMAINS HEAVY DOWNPOURS. THE STRONGEST STORMS MAY PRODUCE
WIND GUSTS TO 50 KT BUT NO SEVERE WEATHER IS EXPECTED AS WIND SHEAR
IS BASICALLY NIL.

FOR POPS USED A BLEND OF NEAR TERM GUIDANCE WHICH HAS BEEN DOING
REASONABLY WELL THIS MORNING.  HOWEVER...KEPT A CHANCE OF STORMS
ACROSS THE REGION THIS AFTERNOON AND EVENING DUE TO THE SCATTERED
NATURE OF THE STORMS THAT ARE EXPECTED.  A WASH OUT IS NOT
EXPECTED.  THE BEST CHANCE FOR WIDESPREAD STORMS WILL BE OVERNIGHT
AS THE UPPER LEVEL TROUGH APPROACHES. IN FACT THE STORMS ASSOCIATED
WITH THE TROUGH STRETCH FROM MINNESOTA THROUGH ARKANSAS.  MODELS
DIFFER IN HOW WELL THIS AREA OF PRECIP WILL HOLD TOGETHER SO LIMITED
POPS TO THE LIKELY CATEGORY.

LOWS WILL BE IN THE UPPER 60S TO LOWER 70S TONIGHT AND FOG IS
POSSIBLE. GIVEN THAT WE HAVE NOT SEEN MUCH RAIN TODAY...HAVE LIMITED
CONFIDENCE SO LEFT FOG OUT OF THE FORECAST FOR NOW.

SATURDAY AND SATURDAY NIGHT...
THE SURFACE LOW PASSES OVER LAKE MICHIGAN SATURDAY AFTERNOON WHILE
ITS COLD FRONT GETS DRAGGED THROUGH THE AREA SATURDAY
AFTERNOON/EVENING.  SCATTERED STORMS ARE AGAIN POSSIBLE IN THE
MORNING IN THE WARM AND MOIST ENVIRONMENT WITH LINGERING 2 INCH PWAT
VALUES. STORMS WILL THEN FORM ALONG THE COLD FRONT SOUTH OF A GARY
IN TO PONTIAC IL LINE. STORMS ARE POSSIBLE NORTH AND WEST OF THIS
LINE...BUT CONFIDENCE IS SIGNIFICANTLY LOWER.

CAPE VALUES WILL BE AROUND 1000 J/KG TOMORROW WITH WEAK SHEAR ONCE
AGAIN. THEREFORE EXPECTING STORMS TO PRODUCE HEAVY DOWNPOURS AND THE
STRONGEST MAY BE CAPABLE OF GUSTY WINDS.  SEVERE WEATHER IS NOT
EXPECTED.

TOMORROW LOOKS LIKE ANOTHER WARM AND STICKY DAY AHEAD OF THE COLD
FRONT.  LOWS WILL BE IN THE 60S AND FOG IS POSSIBLE OVERNIGHT.

JEE

//EXTENDED FORECAST//

SUNDAY...
EXPECT A BRIEF LULL IN THE PRECIP CHANCES DURING MUCH OF THE DAY
SUNDAY AS THE FIRST COLD FRONT DEPARTS TO THE EAST AND ANOTHER LOW
TAKES SHAPE OVER THE NORTHERN PLAINS. IN BETWEEN THESE TWO
SYSTEMS...WEAK INDUCED SURFACE HIGH SHOULD RESULT IN QUIET WEATHER
LOCALLY...WITH THE H85 THERMAL RIDGE ADVECTING OVERHEARD THROUGHOUT
THE DAY. RETURN FLOW WILL HELP PUSH THE DEWPOINTS BACK UP TO AROUND
70 WITH AFTERNOON HIGH TEMPS EXPECTED TO BE IN THE MID 80S. STEEP
LOW/MID LEVEL LAPSE RATES WILL RESULT IN MODERATE INSTABILITY
DEVELOPING DURING THE AFTERNOON...BUT MODEST SBCIN IS PROGGED TO
STAY IN PLACE CAPPING ANY SURFACE BASED CONVECTION. IN ADDITION...
THE AREA SHOULD BE SQUARELY UNDER AREA OF MID LEVEL HEIGHT RISES
WHICH SHOULD HELP REINFORCE THE INVERSION...AND NO SIGNIFICANT
FORCING NOTED OVER THE AREA.

MONDAY...
TROUGHING CURRENTLY MOVING ONSHORE OVER THE PAC NORTHWEST TODAY WILL
MOVE ACROSS THE CENTRAL PLAINS THIS WEEKEND...THEN BEGIN TO LIFT
ACROSS THE UPPER MIDWEST EARLY NEXT WEEK. SURFACE LOW IS PROGGED TO
DEEPEN FROM THE NORTHERN PLAINS SUNDAY AS IT LIFTS TO NEAR HUDSON
BAY LATE ON MONDAY. THIS WILL DRAG A COLD FRONT ACROSS THE REGION ON
MONDAY. WITH THE LOW LIFTING AWAY FROM THE AREA...CONVERGENCE ALONG
THE FRONT IS PROGGED TO WEAKEN AS IT COMES ACROSS NORTHERN ILLINOIS
EARLY MONDAY WITH THE BETTER DYNAMICS STAYING TO OUR NORTH.
MEANWHILE...THE LOCAL AREA APPEARS TO LIE ON THE NORTHERN PERIPHERY
OF THE BETTER INSTABILITY TO OUR SOUTH. GFS SHOWS SOME HINTS THAT
PARTICULARLY NORTH CENTRAL ILLINOIS MAY BE SPLIT BY THE
PRECIP...ESPECIALLY CONSIDERING THE CAPPING EARLY IN THE DAY...BUT
WILL HOLD OFF ON FINE TUNING THIS DETAIL FOR NOW. IN ADDITION...THE
REGION DOES FALL WITHIN AN OVERLAPPED AREA OF FAVORABLE
SHEAR/INSTABILITY THAT COULD POTENTIALLY SUPPORT A SEVERE WEATHER
THREAT.

TUESDAY THROUGH FRIDAY...
FRONTAL BOUNDARY IS PROGGED TO STALL ACROSS/NEAR CENTRAL ILLINOIS
TUESDAY GRADUALLY LIFTING BACK NORTH ACROSS THE FORECAST AREA BY THE
END OF THE WORK WEEK AS A SERIES OF UPPER LEVEL DISTURBANCES MOVE
ACROSS THE REGION. THIS WILL RESULT IN PERIODIC CHANCES FOR SHOWERS
AND THUNDERSTORMS ACROSS THE AREA...THOUGH TIMING AND LOCATION
DETAILS WILL BE DIFFICULT TO PIN DOWN THIS FAR OUT GIVEN THE
PATTERN. THE ATMOSPHERE REMAINS QUITE SOUPY IN THE VICINITY OF THE
FRONT WHERE PWATS REMAIN AROUND 2 INCHES. THUS THE HEAVY RAIN AND
FLOODING THREAT WILL HAVE TO BE CLOSELY MONITORED THROUGH MUCH OF
THE UPCOMING WEEK.

DEUBELBEISS

&&

.AVIATION...

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

* ISOLATED SHRA/TSRA THRU EARLY EVENING

* S-SSE WINDS 10-14KT THRU EARLY EVENING

* ANOTHER PERIOD OF SHRA/TSRA TOWARD MIDNIGHT INTO SATURDAY
  MORNING.

* SOUTHWEST WINDS GUSTING AROUND 20 KT SATURDAY.

RATZER/IZZI

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

ISOLATED TSRA WILL CONTINUE TO DEVELOP IN VC OF THE TERMINALS
THROUGH EARLY EVENING. COVERAGE WILL BE LOW BUT COULD SEE BRIEF
SHRA OR TSRA AT CHICAGO AREA TERMINALS THROUGH ABOUT 00-01Z.

IZZI

PREVIOUS DISCUSSION FROM 18Z...

FAIRLY LOW CONFIDENCE CONVECTIVE FORECAST THIS PERIOD...WITH
TERMINALS WITHIN A BROAD AREA OF SOUTH WARM/MOIST ADVECTION
DOWNSTREAM OF AN UPPER TROUGH OVER THE CENTRAL PLAINS BUT WITH
OTHERWISE LITTLE ORGANIZED FOCUS FOR TSRA.

SATELLITE EVIDENCE OF WEAK MID-LEVEL DISTURBANCE OVER NORTHEAST
IL EARLY THIS AFTERNOON...WITH MORNING ELEVATED SHRA/TSRA DECAYING
OVER NORTH CENTRAL IL. DIURNAL TSRA WERE FORMING IN LOW LEVEL
INSTABILITY AXIS ALONG IL/IN BORDER REGION GENERALLY ALONG A DEC-
GIJ-MKG LINE...AND THIS LOOKS TO REMAIN THE FOCUS REGION FOR
HIGHEST COVERAGE TSRA THIS AFTERNOON. HIGH-RES GUIDANCE STILL
DEVELOPS SOME ISOLATED SHRA/TSRA INTO THE TERMINAL REGION IN
ASSOCIATION WITH AFOREMENTIONED MID-LEVEL DISTURBANCE AND NORTH
OF SURFACE WARM FRONT WHICH IS ACROSS DOWNSTATE IL AT THIS TIME...
THOUGH COVERAGE IS EXPECTED TO REMAIN LOW. A GREATER CHANCE OF
SHRA/TSRA APPEARS TO BE LATE TONIGHT AND EARLY SATURDAY AS THE
MAIN UPPER TROUGH APPROACHES. WEAK COLD FRONT APPROACHES FROM THE
WEST SATURDAY MIDDAY AND AFTERNOON...WITH THUNDERSTORMS EXPECTED
TO DEVELOP ALONG THE FRONT BY EARLY AFTERNOON. CURRENT SUITE OF
HIGH-RES GUIDANCE SUGGESTS TSRA POTENTIAL MAY BE GREATER JUST
EAST/SOUTH OF CHICAGO TERMINALS SATURDAY AFTERNOON. OUTSIDE OF ANY
PRECIP VIS REDUCTION EARLY SATURDAY...SOME MVFR HAZE POSSIBLE
OVERNIGHT IN MOIST WARM SECTOR AIR.

WINDS...GENERALLY SOUTH 10-12 KT WITH GUSTS TO 20 KT OR SO
POSSIBLE THIS AFTERNOON. WIND MAY BACK A BIT TO THE SOUTH-
SOUTHEAST LATE THIS AFTERNOON/EARLY EVENING AS SURFACE WARM
FRONT APPROACHES...BEFORE SHIFTING SOUTHWEST OVERNIGHT AND SUNDAY
AHEAD OF THE COLD FRONT. DEEPER MIXING SUNDAY SUGGESTS GUSTS AGAIN
IN THE 20 KT RANGE OR A LITTLE HIGHER DURING THE LATE MORNING AND
AFTERNOON.

RATZER

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

* MEDIUM IN SHRA/TSRA BEING LOW IN COVERAGE IN IMMEDIATE TERMINAL
  AREA THIS AFTERNOON...GREATER COVERAGE EAST/SOUTH OF CHICAGO.

* LOW IN TSRA TIMING/COVERAGE LATER TONIGHT/SATURDAY.

* MEDIUM-HIGH IN WIND TRENDS THROUGH PERIOD.

RATZER/IZZI

//OUTLOOK FOR ORD/MDW FOR 00Z SUNDAY-12Z FRIDAY...UPDATED 12Z...

* SATURDAY NIGHT THROUGH SUNDAY NIGHT...VFR. WX NIL.

* MONDAY...CHANCE OF TSRA.

* TUESDAY...VFR. WX NIL.

* WEDNESDAY THROUGH THURSDAY NIGHT...SLIGHT CHANCE OF TSRA

KREIN

&&

.MARINE...
221 PM CDT

MODERATE SOUTHERLY WINDS ARE IN PLACE TODAY AHEAD OF LOW PRESSURE
OVER THE NORTHERN PLAINS. SOUTH TO SOUTHWEST WINDS 20 TO 25 KT
WITH AN OCCASIONAL 30 KT GUSTS POSSIBLE WILL BE IN PLACE THROUGH
TOMORROW...THEN A COLD FRONT WILL START TO PUSH ACROSS THE LAKE
TURNING WINDS NORTHWESTERLY. HIGH PRESSURE WILL PROVIDE A BRIEF
LULL IN THE WINDS SUNDAY ALLOWING LAKE BREEZES TO DEVELOP...BUT
THEN SOUTHERLY WINDS RAMP BACK UP TO 25 TO 30 KT SUNDAY NIGHT INTO
MONDAY AHEAD OF ANOTHER LOW. THIS LOW IS PROGGED TO DEEPEN AS IT
LIFTS FROM THE NORTHERN PLAINS SUNDAY TO HUDSON BAY LATE MONDAY.

BMD

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 292220
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
520 PM CDT FRI AUG 29 2014

.MESOSCALE DISCUSSION...
411 PM CDT

THUNDERSTORMS ARE GENERALLY ISOLATED IN NORTHEAST ILLNOIS THIS
AFTERNOON WITH SCATTERED ACTIVITY EAST OF INTERSTATE 57 IN
ILLNOIS AND ALONG THE INTERSTATE 65 CORRIDOR IN NW INDIANA. RADAR
ESTIMATES A QUICK THREE QUARTERS OF AN INCH TO 1 INCH HAS FALLEN
IN THE HEAVIER DOWNPOURS...WITH STREET FLOODING REPORTED IN
LANSING. EXPECT HEAVY RAIN AND LOCALIZED PONDING OF WATER TO
REMAIN A THREAT INTO THE EARLY EVENING...ESPECIALLY IN NW
INDIANA...THOUGH STORMS MAY INCREASE AS THE WARM FRONT TO THE
SOUTH AND DEEPER MOISTURE SPREAD NORTHWARD.

KMD

&&

.DISCUSSION...
221 PM CDT

SYNOPSIS...UNSETTLED WEATHER CONTINUES THROUGH TOMORROW WITH
SCATTERED THUNDERSTORMS EXPECTED.  CONFIDENCE REMAINS LOW IN WHEN
AND WHERE THUNDERSTORMS WILL FORM.  SUNDAY STILL LOOKS DRY BUT
MULTIPLE CHANCES FOR STORMS RETURN MONDAY THROUGH THE END OF THE
WEEK. ABOVE NORMAL TEMPERATURES ARE ALSO EXPECTED THROUGH THE PERIOD
AS WELL.

//NEAR TERM FORECAST//

THROUGH TONIGHT...
A LARGE RIDGE IS OVER THE EAST COAST WHILE A TROUGH IS OVER THE
PLAINS.  THE TROUGH WILL WEAKEN AS IT APPROACHES OUR AREA AND PASS
OVERHEAD LATE SATURDAY NIGHT INTO SUNDAY MORNING. AT THE SURFACE THE
HIGH HAS PUSHED EAST WHILE A DEVELOPING LOW PRESSURE SYSTEM IS OVER
MINNESOTA.  THE LOWS WARM FRONT LIES TO OUR SOUTH ACROSS SOUTHERN
IL...AND IT WILL LIFT NORTH THROUGH THE REGION THIS AFTERNOON.

HAVE VERY LOW CONFIDENCE IN EXACT TIMING AND LOCATION OF
THUNDERSTORMS THROUGH THIS EVENING.  THERE IS NO CLEAR FORCING
MECHANISM BUT WITH AROUND 2000 J/KG OF CAPE AVAILABLE...STORMS ARE
CERTAINLY POSSIBLE. PWAT VALUES ARE AROUND 2 INCHES SO THE MAIN
CONCERN REMAINS HEAVY DOWNPOURS. THE STRONGEST STORMS MAY PRODUCE
WIND GUSTS TO 50 KT BUT NO SEVERE WEATHER IS EXPECTED AS WIND SHEAR
IS BASICALLY NIL.

FOR POPS USED A BLEND OF NEAR TERM GUIDANCE WHICH HAS BEEN DOING
REASONABLY WELL THIS MORNING.  HOWEVER...KEPT A CHANCE OF STORMS
ACROSS THE REGION THIS AFTERNOON AND EVENING DUE TO THE SCATTERED
NATURE OF THE STORMS THAT ARE EXPECTED.  A WASH OUT IS NOT
EXPECTED.  THE BEST CHANCE FOR WIDESPREAD STORMS WILL BE OVERNIGHT
AS THE UPPER LEVEL TROUGH APPROACHES. IN FACT THE STORMS ASSOCIATED
WITH THE TROUGH STRETCH FROM MINNESOTA THROUGH ARKANSAS.  MODELS
DIFFER IN HOW WELL THIS AREA OF PRECIP WILL HOLD TOGETHER SO LIMITED
POPS TO THE LIKELY CATEGORY.

LOWS WILL BE IN THE UPPER 60S TO LOWER 70S TONIGHT AND FOG IS
POSSIBLE. GIVEN THAT WE HAVE NOT SEEN MUCH RAIN TODAY...HAVE LIMITED
CONFIDENCE SO LEFT FOG OUT OF THE FORECAST FOR NOW.

SATURDAY AND SATURDAY NIGHT...
THE SURFACE LOW PASSES OVER LAKE MICHIGAN SATURDAY AFTERNOON WHILE
ITS COLD FRONT GETS DRAGGED THROUGH THE AREA SATURDAY
AFTERNOON/EVENING.  SCATTERED STORMS ARE AGAIN POSSIBLE IN THE
MORNING IN THE WARM AND MOIST ENVIRONMENT WITH LINGERING 2 INCH PWAT
VALUES. STORMS WILL THEN FORM ALONG THE COLD FRONT SOUTH OF A GARY
IN TO PONTIAC IL LINE. STORMS ARE POSSIBLE NORTH AND WEST OF THIS
LINE...BUT CONFIDENCE IS SIGNIFICANTLY LOWER.

CAPE VALUES WILL BE AROUND 1000 J/KG TOMORROW WITH WEAK SHEAR ONCE
AGAIN. THEREFORE EXPECTING STORMS TO PRODUCE HEAVY DOWNPOURS AND THE
STRONGEST MAY BE CAPABLE OF GUSTY WINDS.  SEVERE WEATHER IS NOT
EXPECTED.

TOMORROW LOOKS LIKE ANOTHER WARM AND STICKY DAY AHEAD OF THE COLD
FRONT.  LOWS WILL BE IN THE 60S AND FOG IS POSSIBLE OVERNIGHT.

JEE

//EXTENDED FORECAST//

SUNDAY...
EXPECT A BRIEF LULL IN THE PRECIP CHANCES DURING MUCH OF THE DAY
SUNDAY AS THE FIRST COLD FRONT DEPARTS TO THE EAST AND ANOTHER LOW
TAKES SHAPE OVER THE NORTHERN PLAINS. IN BETWEEN THESE TWO
SYSTEMS...WEAK INDUCED SURFACE HIGH SHOULD RESULT IN QUIET WEATHER
LOCALLY...WITH THE H85 THERMAL RIDGE ADVECTING OVERHEARD THROUGHOUT
THE DAY. RETURN FLOW WILL HELP PUSH THE DEWPOINTS BACK UP TO AROUND
70 WITH AFTERNOON HIGH TEMPS EXPECTED TO BE IN THE MID 80S. STEEP
LOW/MID LEVEL LAPSE RATES WILL RESULT IN MODERATE INSTABILITY
DEVELOPING DURING THE AFTERNOON...BUT MODEST SBCIN IS PROGGED TO
STAY IN PLACE CAPPING ANY SURFACE BASED CONVECTION. IN ADDITION...
THE AREA SHOULD BE SQUARELY UNDER AREA OF MID LEVEL HEIGHT RISES
WHICH SHOULD HELP REINFORCE THE INVERSION...AND NO SIGNIFICANT
FORCING NOTED OVER THE AREA.

MONDAY...
TROUGHING CURRENTLY MOVING ONSHORE OVER THE PAC NORTHWEST TODAY WILL
MOVE ACROSS THE CENTRAL PLAINS THIS WEEKEND...THEN BEGIN TO LIFT
ACROSS THE UPPER MIDWEST EARLY NEXT WEEK. SURFACE LOW IS PROGGED TO
DEEPEN FROM THE NORTHERN PLAINS SUNDAY AS IT LIFTS TO NEAR HUDSON
BAY LATE ON MONDAY. THIS WILL DRAG A COLD FRONT ACROSS THE REGION ON
MONDAY. WITH THE LOW LIFTING AWAY FROM THE AREA...CONVERGENCE ALONG
THE FRONT IS PROGGED TO WEAKEN AS IT COMES ACROSS NORTHERN ILLINOIS
EARLY MONDAY WITH THE BETTER DYNAMICS STAYING TO OUR NORTH.
MEANWHILE...THE LOCAL AREA APPEARS TO LIE ON THE NORTHERN PERIPHERY
OF THE BETTER INSTABILITY TO OUR SOUTH. GFS SHOWS SOME HINTS THAT
PARTICULARLY NORTH CENTRAL ILLINOIS MAY BE SPLIT BY THE
PRECIP...ESPECIALLY CONSIDERING THE CAPPING EARLY IN THE DAY...BUT
WILL HOLD OFF ON FINE TUNING THIS DETAIL FOR NOW. IN ADDITION...THE
REGION DOES FALL WITHIN AN OVERLAPPED AREA OF FAVORABLE
SHEAR/INSTABILITY THAT COULD POTENTIALLY SUPPORT A SEVERE WEATHER
THREAT.

TUESDAY THROUGH FRIDAY...
FRONTAL BOUNDARY IS PROGGED TO STALL ACROSS/NEAR CENTRAL ILLINOIS
TUESDAY GRADUALLY LIFTING BACK NORTH ACROSS THE FORECAST AREA BY THE
END OF THE WORK WEEK AS A SERIES OF UPPER LEVEL DISTURBANCES MOVE
ACROSS THE REGION. THIS WILL RESULT IN PERIODIC CHANCES FOR SHOWERS
AND THUNDERSTORMS ACROSS THE AREA...THOUGH TIMING AND LOCATION
DETAILS WILL BE DIFFICULT TO PIN DOWN THIS FAR OUT GIVEN THE
PATTERN. THE ATMOSPHERE REMAINS QUITE SOUPY IN THE VICINITY OF THE
FRONT WHERE PWATS REMAIN AROUND 2 INCHES. THUS THE HEAVY RAIN AND
FLOODING THREAT WILL HAVE TO BE CLOSELY MONITORED THROUGH MUCH OF
THE UPCOMING WEEK.

DEUBELBEISS

&&

.AVIATION...

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

* ISOLATED SHRA/TSRA THRU EARLY EVENING

* S-SSE WINDS 10-14KT THRU EARLY EVENING

* ANOTHER PERIOD OF SHRA/TSRA TOWARD MIDNIGHT INTO SATURDAY
  MORNING.

* SOUTHWEST WINDS GUSTING AROUND 20 KT SATURDAY.

RATZER/IZZI

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

ISOLATED TSRA WILL CONTINUE TO DEVELOP IN VC OF THE TERMINALS
THROUGH EARLY EVENING. COVERAGE WILL BE LOW BUT COULD SEE BRIEF
SHRA OR TSRA AT CHICAGO AREA TERMINALS THROUGH ABOUT 00-01Z.

IZZI

PREVIOUS DISCUSSION FROM 18Z...

FAIRLY LOW CONFIDENCE CONVECTIVE FORECAST THIS PERIOD...WITH
TERMINALS WITHIN A BROAD AREA OF SOUTH WARM/MOIST ADVECTION
DOWNSTREAM OF AN UPPER TROUGH OVER THE CENTRAL PLAINS BUT WITH
OTHERWISE LITTLE ORGANIZED FOCUS FOR TSRA.

SATELLITE EVIDENCE OF WEAK MID-LEVEL DISTURBANCE OVER NORTHEAST
IL EARLY THIS AFTERNOON...WITH MORNING ELEVATED SHRA/TSRA DECAYING
OVER NORTH CENTRAL IL. DIURNAL TSRA WERE FORMING IN LOW LEVEL
INSTABILITY AXIS ALONG IL/IN BORDER REGION GENERALLY ALONG A DEC-
GIJ-MKG LINE...AND THIS LOOKS TO REMAIN THE FOCUS REGION FOR
HIGHEST COVERAGE TSRA THIS AFTERNOON. HIGH-RES GUIDANCE STILL
DEVELOPS SOME ISOLATED SHRA/TSRA INTO THE TERMINAL REGION IN
ASSOCIATION WITH AFOREMENTIONED MID-LEVEL DISTURBANCE AND NORTH
OF SURFACE WARM FRONT WHICH IS ACROSS DOWNSTATE IL AT THIS TIME...
THOUGH COVERAGE IS EXPECTED TO REMAIN LOW. A GREATER CHANCE OF
SHRA/TSRA APPEARS TO BE LATE TONIGHT AND EARLY SATURDAY AS THE
MAIN UPPER TROUGH APPROACHES. WEAK COLD FRONT APPROACHES FROM THE
WEST SATURDAY MIDDAY AND AFTERNOON...WITH THUNDERSTORMS EXPECTED
TO DEVELOP ALONG THE FRONT BY EARLY AFTERNOON. CURRENT SUITE OF
HIGH-RES GUIDANCE SUGGESTS TSRA POTENTIAL MAY BE GREATER JUST
EAST/SOUTH OF CHICAGO TERMINALS SATURDAY AFTERNOON. OUTSIDE OF ANY
PRECIP VIS REDUCTION EARLY SATURDAY...SOME MVFR HAZE POSSIBLE
OVERNIGHT IN MOIST WARM SECTOR AIR.

WINDS...GENERALLY SOUTH 10-12 KT WITH GUSTS TO 20 KT OR SO
POSSIBLE THIS AFTERNOON. WIND MAY BACK A BIT TO THE SOUTH-
SOUTHEAST LATE THIS AFTERNOON/EARLY EVENING AS SURFACE WARM
FRONT APPROACHES...BEFORE SHIFTING SOUTHWEST OVERNIGHT AND SUNDAY
AHEAD OF THE COLD FRONT. DEEPER MIXING SUNDAY SUGGESTS GUSTS AGAIN
IN THE 20 KT RANGE OR A LITTLE HIGHER DURING THE LATE MORNING AND
AFTERNOON.

RATZER

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

* MEDIUM IN SHRA/TSRA BEING LOW IN COVERAGE IN IMMEDIATE TERMINAL
  AREA THIS AFTERNOON...GREATER COVERAGE EAST/SOUTH OF CHICAGO.

* LOW IN TSRA TIMING/COVERAGE LATER TONIGHT/SATURDAY.

* MEDIUM-HIGH IN WIND TRENDS THROUGH PERIOD.

RATZER/IZZI

//OUTLOOK FOR ORD/MDW FOR 00Z SUNDAY-12Z FRIDAY...UPDATED 12Z...

* SATURDAY NIGHT THROUGH SUNDAY NIGHT...VFR. WX NIL.

* MONDAY...CHANCE OF TSRA.

* TUESDAY...VFR. WX NIL.

* WEDNESDAY THROUGH THURSDAY NIGHT...SLIGHT CHANCE OF TSRA

KREIN

&&

.MARINE...
221 PM CDT

MODERATE SOUTHERLY WINDS ARE IN PLACE TODAY AHEAD OF LOW PRESSURE
OVER THE NORTHERN PLAINS. SOUTH TO SOUTHWEST WINDS 20 TO 25 KT
WITH AN OCCASIONAL 30 KT GUSTS POSSIBLE WILL BE IN PLACE THROUGH
TOMORROW...THEN A COLD FRONT WILL START TO PUSH ACROSS THE LAKE
TURNING WINDS NORTHWESTERLY. HIGH PRESSURE WILL PROVIDE A BRIEF
LULL IN THE WINDS SUNDAY ALLOWING LAKE BREEZES TO DEVELOP...BUT
THEN SOUTHERLY WINDS RAMP BACK UP TO 25 TO 30 KT SUNDAY NIGHT INTO
MONDAY AHEAD OF ANOTHER LOW. THIS LOW IS PROGGED TO DEEPEN AS IT
LIFTS FROM THE NORTHERN PLAINS SUNDAY TO HUDSON BAY LATE MONDAY.

BMD

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO







000
FXUS63 KLOT 292120 CCA
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
420 PM CDT FRI AUG 29 2014

.MESOSCALE DISCUSSION...
411 PM CDT

THUNDERSTORMS ARE GENERALLY ISOLATED IN NORTHEAST ILLNOIS THIS
AFTERNOON WITH SCATTERED ACTIVITY EAST OF INTERSTATE 57 IN
ILLNOIS AND ALONG THE INTERSTATE 65 CORRIDOR IN NW INDIANA. RADAR
ESTIMATES A QUICK THREE QUARTERS OF AN INCH TO 1 INCH HAS FALLEN
IN THE HEAVIER DOWNPOURS...WITH STREET FLOODING REPORTED IN
LANSING. EXPECT HEAVY RAIN AND LOCALIZED PONDING OF WATER TO
REMAIN A THREAT INTO THE EARLY EVENING...ESPECIALLY IN NW
INDIANA...THOUGH STORMS MAY INCREASE AS THE WARM FRONT TO THE
SOUTH AND DEEPER MOISTURE SPREAD NORTHWARD.

KMD

&&

.DISCUSSION...
221 PM CDT

SYNOPSIS...UNSETTLED WEATHER CONTINUES THROUGH TOMORROW WITH
SCATTERED THUNDERSTORMS EXPECTED.  CONFIDENCE REMAINS LOW IN WHEN
AND WHERE THUNDERSTORMS WILL FORM.  SUNDAY STILL LOOKS DRY BUT
MULTIPLE CHANCES FOR STORMS RETURN MONDAY THROUGH THE END OF THE
WEEK. ABOVE NORMAL TEMPERATURES ARE ALSO EXPECTED THROUGH THE PERIOD
AS WELL.

//NEAR TERM FORECAST//

THROUGH TONIGHT...
A LARGE RIDGE IS OVER THE EAST COAST WHILE A TROUGH IS OVER THE
PLAINS.  THE TROUGH WILL WEAKEN AS IT APPROACHES OUR AREA AND PASS
OVERHEAD LATE SATURDAY NIGHT INTO SUNDAY MORNING. AT THE SURFACE THE
HIGH HAS PUSHED EAST WHILE A DEVELOPING LOW PRESSURE SYSTEM IS OVER
MINNESOTA.  THE LOWS WARM FRONT LIES TO OUR SOUTH ACROSS SOUTHERN
IL...AND IT WILL LIFT NORTH THROUGH THE REGION THIS AFTERNOON.

HAVE VERY LOW CONFIDENCE IN EXACT TIMING AND LOCATION OF
THUNDERSTORMS THROUGH THIS EVENING.  THERE IS NO CLEAR FORCING
MECHANISM BUT WITH AROUND 2000 J/KG OF CAPE AVAILABLE...STORMS ARE
CERTAINLY POSSIBLE. PWAT VALUES ARE AROUND 2 INCHES SO THE MAIN
CONCERN REMAINS HEAVY DOWNPOURS. THE STRONGEST STORMS MAY PRODUCE
WIND GUSTS TO 50 KT BUT NO SEVERE WEATHER IS EXPECTED AS WIND SHEAR
IS BASICALLY NIL.

FOR POPS USED A BLEND OF NEAR TERM GUIDANCE WHICH HAS BEEN DOING
REASONABLY WELL THIS MORNING.  HOWEVER...KEPT A CHANCE OF STORMS
ACROSS THE REGION THIS AFTERNOON AND EVENING DUE TO THE SCATTERED
NATURE OF THE STORMS THAT ARE EXPECTED.  A WASH OUT IS NOT
EXPECTED.  THE BEST CHANCE FOR WIDESPREAD STORMS WILL BE OVERNIGHT
AS THE UPPER LEVEL TROUGH APPROACHES. IN FACT THE STORMS ASSOCIATED
WITH THE TROUGH STRETCH FROM MINNESOTA THROUGH ARKANSAS.  MODELS
DIFFER IN HOW WELL THIS AREA OF PRECIP WILL HOLD TOGETHER SO LIMITED
POPS TO THE LIKELY CATEGORY.

LOWS WILL BE IN THE UPPER 60S TO LOWER 70S TONIGHT AND FOG IS
POSSIBLE. GIVEN THAT WE HAVE NOT SEEN MUCH RAIN TODAY...HAVE LIMITED
CONFIDENCE SO LEFT FOG OUT OF THE FORECAST FOR NOW.

SATURDAY AND SATURDAY NIGHT...
THE SURFACE LOW PASSES OVER LAKE MICHIGAN SATURDAY AFTERNOON WHILE
ITS COLD FRONT GETS DRAGGED THROUGH THE AREA SATURDAY
AFTERNOON/EVENING.  SCATTERED STORMS ARE AGAIN POSSIBLE IN THE
MORNING IN THE WARM AND MOIST ENVIRONMENT WITH LINGERING 2 INCH PWAT
VALUES. STORMS WILL THEN FORM ALONG THE COLD FRONT SOUTH OF A GARY
IN TO PONTIAC IL LINE. STORMS ARE POSSIBLE NORTH AND WEST OF THIS
LINE...BUT CONFIDENCE IS SIGNIFICANTLY LOWER.

CAPE VALUES WILL BE AROUND 1000 J/KG TOMORROW WITH WEAK SHEAR ONCE
AGAIN. THEREFORE EXPECTING STORMS TO PRODUCE HEAVY DOWNPOURS AND THE
STRONGEST MAY BE CAPABLE OF GUSTY WINDS.  SEVERE WEATHER IS NOT
EXPECTED.

TOMORROW LOOKS LIKE ANOTHER WARM AND STICKY DAY AHEAD OF THE COLD
FRONT.  LOWS WILL BE IN THE 60S AND FOG IS POSSIBLE OVERNIGHT.

JEE

//EXTENDED FORECAST//

SUNDAY...
EXPECT A BRIEF LULL IN THE PRECIP CHANCES DURING MUCH OF THE DAY
SUNDAY AS THE FIRST COLD FRONT DEPARTS TO THE EAST AND ANOTHER LOW
TAKES SHAPE OVER THE NORTHERN PLAINS. IN BETWEEN THESE TWO
SYSTEMS...WEAK INDUCED SURFACE HIGH SHOULD RESULT IN QUIET WEATHER
LOCALLY...WITH THE H85 THERMAL RIDGE ADVECTING OVERHEARD THROUGHOUT
THE DAY. RETURN FLOW WILL HELP PUSH THE DEWPOINTS BACK UP TO AROUND
70 WITH AFTERNOON HIGH TEMPS EXPECTED TO BE IN THE MID 80S. STEEP
LOW/MID LEVEL LAPSE RATES WILL RESULT IN MODERATE INSTABILITY
DEVELOPING DURING THE AFTERNOON...BUT MODEST SBCIN IS PROGGED TO
STAY IN PLACE CAPPING ANY SURFACE BASED CONVECTION. IN ADDITION...
THE AREA SHOULD BE SQUARELY UNDER AREA OF MID LEVEL HEIGHT RISES
WHICH SHOULD HELP REINFORCE THE INVERSION...AND NO SIGNIFICANT
FORCING NOTED OVER THE AREA.

MONDAY...
TROUGHING CURRENTLY MOVING ONSHORE OVER THE PAC NORTHWEST TODAY WILL
MOVE ACROSS THE CENTRAL PLAINS THIS WEEKEND...THEN BEGIN TO LIFT
ACROSS THE UPPER MIDWEST EARLY NEXT WEEK. SURFACE LOW IS PROGGED TO
DEEPEN FROM THE NORTHERN PLAINS SUNDAY AS IT LIFTS TO NEAR HUDSON
BAY LATE ON MONDAY. THIS WILL DRAG A COLD FRONT ACROSS THE REGION ON
MONDAY. WITH THE LOW LIFTING AWAY FROM THE AREA...CONVERGENCE ALONG
THE FRONT IS PROGGED TO WEAKEN AS IT COMES ACROSS NORTHERN ILLINOIS
EARLY MONDAY WITH THE BETTER DYNAMICS STAYING TO OUR NORTH.
MEANWHILE...THE LOCAL AREA APPEARS TO LIE ON THE NORTHERN PERIPHERY
OF THE BETTER INSTABILITY TO OUR SOUTH. GFS SHOWS SOME HINTS THAT
PARTICULARLY NORTH CENTRAL ILLINOIS MAY BE SPLIT BY THE
PRECIP...ESPECIALLY CONSIDERING THE CAPPING EARLY IN THE DAY...BUT
WILL HOLD OFF ON FINE TUNING THIS DETAIL FOR NOW. IN ADDITION...THE
REGION DOES FALL WITHIN AN OVERLAPPED AREA OF FAVORABLE
SHEAR/INSTABILITY THAT COULD POTENTIALLY SUPPORT A SEVERE WEATHER
THREAT.

TUESDAY THROUGH FRIDAY...
FRONTAL BOUNDARY IS PROGGED TO STALL ACROSS/NEAR CENTRAL ILLINOIS
TUESDAY GRADUALLY LIFTING BACK NORTH ACROSS THE FORECAST AREA BY THE
END OF THE WORK WEEK AS A SERIES OF UPPER LEVEL DISTURBANCES MOVE
ACROSS THE REGION. THIS WILL RESULT IN PERIODIC CHANCES FOR SHOWERS
AND THUNDERSTORMS ACROSS THE AREA...THOUGH TIMING AND LOCATION
DETAILS WILL BE DIFFICULT TO PIN DOWN THIS FAR OUT GIVEN THE
PATTERN. THE ATMOSPHERE REMAINS QUITE SOUPY IN THE VICINITY OF THE
FRONT WHERE PWATS REMAIN AROUND 2 INCHES. THUS THE HEAVY RAIN AND
FLOODING THREAT WILL HAVE TO BE CLOSELY MONITORED THROUGH MUCH OF
THE UPCOMING WEEK.

DEUBELBEISS

&&

.AVIATION...

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

* ISOLATED-SCATTERED SHRA/TSRA THIS AFTERNOON THRU EARLY EVENING.

* SOUTH WINDS WITH GUSTS 15-20 KT THIS AFTERNOON.

* ANOTHER PERIOD OF SHRA/TSRA LIKELY AFTER MIDNIGHT INTO SATURDAY
  MORNING.

* SOUTHWEST WINDS GUSTING AROUND 20 KT SATURDAY.

RATZER

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

ISOLATED TSRA DEVELOPING FROM NORTHEAST OF DOWNTOWN CHICAGO SOUTH
INTO IKK AREA. THINK COVERAGE WILL REMAIN FAIRLY LOW...THOUGH HAVE
ADDED VCTS FOR THE NEXT FEW HOURS FOR CHICAGO TERMINALS AS THEY
WILL BE SPARSE BUT IN THE NEIGHBORHOOD SO TO SPEAK.

RATZER

PREVIOUS DISCUSSION FROM 18Z...

FAIRLY LOW CONFIDENCE CONVECTIVE FORECAST THIS PERIOD...WITH
TERMINALS WITHIN A BROAD AREA OF SOUTH WARM/MOIST ADVECTION
DOWNSTREAM OF AN UPPER TROUGH OVER THE CENTRAL PLAINS BUT WITH
OTHERWISE LITTLE ORGANIZED FOCUS FOR TSRA.

SATELLITE EVIDENCE OF WEAK MID-LEVEL DISTURBANCE OVER NORTHEAST
IL EARLY THIS AFTERNOON...WITH MORNING ELEVATED SHRA/TSRA DECAYING
OVER NORTH CENTRAL IL. DIURNAL TSRA WERE FORMING IN LOW LEVEL
INSTABILITY AXIS ALONG IL/IN BORDER REGION GENERALLY ALONG A DEC-
GIJ-MKG LINE...AND THIS LOOKS TO REMAIN THE FOCUS REGION FOR
HIGHEST COVERAGE TSRA THIS AFTERNOON. HIGH-RES GUIDANCE STILL
DEVELOPS SOME ISOLATED SHRA/TSRA INTO THE TERMINAL REGION IN
ASSOCIATION WITH AFOREMENTIONED MID-LEVEL DISTURBANCE AND NORTH
OF SURFACE WARM FRONT WHICH IS ACROSS DOWNSTATE IL AT THIS TIME...
THOUGH COVERAGE IS EXPECTED TO REMAIN LOW. A GREATER CHANCE OF
SHRA/TSRA APPEARS TO BE LATE TONIGHT AND EARLY SATURDAY AS THE
MAIN UPPER TROUGH APPROACHES. WEAK COLD FRONT APPROACHES FROM THE
WEST SATURDAY MIDDAY AND AFTERNOON...WITH THUNDERSTORMS EXPECTED
TO DEVELOP ALONG THE FRONT BY EARLY AFTERNOON. CURRENT SUITE OF
HIGH-RES GUIDANCE SUGGESTS TSRA POTENTIAL MAY BE GREATER JUST
EAST/SOUTH OF CHICAGO TERMINALS SATURDAY AFTERNOON. OUTSIDE OF ANY
PRECIP VIS REDUCTION EARLY SATURDAY...SOME MVFR HAZE POSSIBLE
OVERNIGHT IN MOIST WARM SECTOR AIR.

WINDS...GENERALLY SOUTH 10-12 KT WITH GUSTS TO 20 KT OR SO
POSSIBLE THIS AFTERNOON. WIND MAY BACK A BIT TO THE SOUTH-
SOUTHEAST LATE THIS AFTERNOON/EARLY EVENING AS SURFACE WARM
FRONT APPROACHES...BEFORE SHIFTING SOUTHWEST OVERNIGHT AND SUNDAY
AHEAD OF THE COLD FRONT. DEEPER MIXING SUNDAY SUGGESTS GUSTS AGAIN
IN THE 20 KT RANGE OR A LITTLE HIGHER DURING THE LATE MORNING AND
AFTERNOON.

RATZER

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

* MEDIUM IN SHRA/TSRA BEING LOW IN COVERAGE IN IMMEDIATE TERMINAL
  AREA THIS AFTERNOON...GREATER COVERAGE EAST/SOUTH OF CHICAGO.

* LOW IN TSRA TIMING/COVERAGE LATER TONIGHT/SATURDAY.

* MEDIUM-HIGH IN WIND TRENDS THROUGH PERIOD.

RATZER

//OUTLOOK FOR ORD/MDW FOR 00Z SUNDAY-12Z FRIDAY...UPDATED 12Z...

* SATURDAY NIGHT THROUGH SUNDAY NIGHT...VFR. WX NIL.

* MONDAY...CHANCE OF TSRA.

* TUESDAY...VFR. WX NIL.

* WEDNESDAY THROUGH THURSDAY NIGHT...SLIGHT CHANCE OF TSRA

KREIN

&&

.MARINE...
221 PM CDT

MODERATE SOUTHERLY WINDS ARE IN PLACE TODAY AHEAD OF LOW PRESSURE
OVER THE NORTHERN PLAINS. SOUTH TO SOUTHWEST WINDS 20 TO 25 KT
WITH AN OCCASIONAL 30 KT GUSTS POSSIBLE WILL BE IN PLACE THROUGH
TOMORROW...THEN A COLD FRONT WILL START TO PUSH ACROSS THE LAKE
TURNING WINDS NORTHWESTERLY. HIGH PRESSURE WILL PROVIDE A BRIEF
LULL IN THE WINDS SUNDAY ALLOWING LAKE BREEZES TO DEVELOP...BUT
THEN SOUTHERLY WINDS RAMP BACK UP TO 25 TO 30 KT SUNDAY NIGHT INTO
MONDAY AHEAD OF ANOTHER LOW. THIS LOW IS PROGGED TO DEEPEN AS IT
LIFTS FROM THE NORTHERN PLAINS SUNDAY TO HUDSON BAY LATE MONDAY.

BMD

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO









000
FXUS63 KLOT 292120 CCA
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
420 PM CDT FRI AUG 29 2014

.MESOSCALE DISCUSSION...
411 PM CDT

THUNDERSTORMS ARE GENERALLY ISOLATED IN NORTHEAST ILLNOIS THIS
AFTERNOON WITH SCATTERED ACTIVITY EAST OF INTERSTATE 57 IN
ILLNOIS AND ALONG THE INTERSTATE 65 CORRIDOR IN NW INDIANA. RADAR
ESTIMATES A QUICK THREE QUARTERS OF AN INCH TO 1 INCH HAS FALLEN
IN THE HEAVIER DOWNPOURS...WITH STREET FLOODING REPORTED IN
LANSING. EXPECT HEAVY RAIN AND LOCALIZED PONDING OF WATER TO
REMAIN A THREAT INTO THE EARLY EVENING...ESPECIALLY IN NW
INDIANA...THOUGH STORMS MAY INCREASE AS THE WARM FRONT TO THE
SOUTH AND DEEPER MOISTURE SPREAD NORTHWARD.

KMD

&&

.DISCUSSION...
221 PM CDT

SYNOPSIS...UNSETTLED WEATHER CONTINUES THROUGH TOMORROW WITH
SCATTERED THUNDERSTORMS EXPECTED.  CONFIDENCE REMAINS LOW IN WHEN
AND WHERE THUNDERSTORMS WILL FORM.  SUNDAY STILL LOOKS DRY BUT
MULTIPLE CHANCES FOR STORMS RETURN MONDAY THROUGH THE END OF THE
WEEK. ABOVE NORMAL TEMPERATURES ARE ALSO EXPECTED THROUGH THE PERIOD
AS WELL.

//NEAR TERM FORECAST//

THROUGH TONIGHT...
A LARGE RIDGE IS OVER THE EAST COAST WHILE A TROUGH IS OVER THE
PLAINS.  THE TROUGH WILL WEAKEN AS IT APPROACHES OUR AREA AND PASS
OVERHEAD LATE SATURDAY NIGHT INTO SUNDAY MORNING. AT THE SURFACE THE
HIGH HAS PUSHED EAST WHILE A DEVELOPING LOW PRESSURE SYSTEM IS OVER
MINNESOTA.  THE LOWS WARM FRONT LIES TO OUR SOUTH ACROSS SOUTHERN
IL...AND IT WILL LIFT NORTH THROUGH THE REGION THIS AFTERNOON.

HAVE VERY LOW CONFIDENCE IN EXACT TIMING AND LOCATION OF
THUNDERSTORMS THROUGH THIS EVENING.  THERE IS NO CLEAR FORCING
MECHANISM BUT WITH AROUND 2000 J/KG OF CAPE AVAILABLE...STORMS ARE
CERTAINLY POSSIBLE. PWAT VALUES ARE AROUND 2 INCHES SO THE MAIN
CONCERN REMAINS HEAVY DOWNPOURS. THE STRONGEST STORMS MAY PRODUCE
WIND GUSTS TO 50 KT BUT NO SEVERE WEATHER IS EXPECTED AS WIND SHEAR
IS BASICALLY NIL.

FOR POPS USED A BLEND OF NEAR TERM GUIDANCE WHICH HAS BEEN DOING
REASONABLY WELL THIS MORNING.  HOWEVER...KEPT A CHANCE OF STORMS
ACROSS THE REGION THIS AFTERNOON AND EVENING DUE TO THE SCATTERED
NATURE OF THE STORMS THAT ARE EXPECTED.  A WASH OUT IS NOT
EXPECTED.  THE BEST CHANCE FOR WIDESPREAD STORMS WILL BE OVERNIGHT
AS THE UPPER LEVEL TROUGH APPROACHES. IN FACT THE STORMS ASSOCIATED
WITH THE TROUGH STRETCH FROM MINNESOTA THROUGH ARKANSAS.  MODELS
DIFFER IN HOW WELL THIS AREA OF PRECIP WILL HOLD TOGETHER SO LIMITED
POPS TO THE LIKELY CATEGORY.

LOWS WILL BE IN THE UPPER 60S TO LOWER 70S TONIGHT AND FOG IS
POSSIBLE. GIVEN THAT WE HAVE NOT SEEN MUCH RAIN TODAY...HAVE LIMITED
CONFIDENCE SO LEFT FOG OUT OF THE FORECAST FOR NOW.

SATURDAY AND SATURDAY NIGHT...
THE SURFACE LOW PASSES OVER LAKE MICHIGAN SATURDAY AFTERNOON WHILE
ITS COLD FRONT GETS DRAGGED THROUGH THE AREA SATURDAY
AFTERNOON/EVENING.  SCATTERED STORMS ARE AGAIN POSSIBLE IN THE
MORNING IN THE WARM AND MOIST ENVIRONMENT WITH LINGERING 2 INCH PWAT
VALUES. STORMS WILL THEN FORM ALONG THE COLD FRONT SOUTH OF A GARY
IN TO PONTIAC IL LINE. STORMS ARE POSSIBLE NORTH AND WEST OF THIS
LINE...BUT CONFIDENCE IS SIGNIFICANTLY LOWER.

CAPE VALUES WILL BE AROUND 1000 J/KG TOMORROW WITH WEAK SHEAR ONCE
AGAIN. THEREFORE EXPECTING STORMS TO PRODUCE HEAVY DOWNPOURS AND THE
STRONGEST MAY BE CAPABLE OF GUSTY WINDS.  SEVERE WEATHER IS NOT
EXPECTED.

TOMORROW LOOKS LIKE ANOTHER WARM AND STICKY DAY AHEAD OF THE COLD
FRONT.  LOWS WILL BE IN THE 60S AND FOG IS POSSIBLE OVERNIGHT.

JEE

//EXTENDED FORECAST//

SUNDAY...
EXPECT A BRIEF LULL IN THE PRECIP CHANCES DURING MUCH OF THE DAY
SUNDAY AS THE FIRST COLD FRONT DEPARTS TO THE EAST AND ANOTHER LOW
TAKES SHAPE OVER THE NORTHERN PLAINS. IN BETWEEN THESE TWO
SYSTEMS...WEAK INDUCED SURFACE HIGH SHOULD RESULT IN QUIET WEATHER
LOCALLY...WITH THE H85 THERMAL RIDGE ADVECTING OVERHEARD THROUGHOUT
THE DAY. RETURN FLOW WILL HELP PUSH THE DEWPOINTS BACK UP TO AROUND
70 WITH AFTERNOON HIGH TEMPS EXPECTED TO BE IN THE MID 80S. STEEP
LOW/MID LEVEL LAPSE RATES WILL RESULT IN MODERATE INSTABILITY
DEVELOPING DURING THE AFTERNOON...BUT MODEST SBCIN IS PROGGED TO
STAY IN PLACE CAPPING ANY SURFACE BASED CONVECTION. IN ADDITION...
THE AREA SHOULD BE SQUARELY UNDER AREA OF MID LEVEL HEIGHT RISES
WHICH SHOULD HELP REINFORCE THE INVERSION...AND NO SIGNIFICANT
FORCING NOTED OVER THE AREA.

MONDAY...
TROUGHING CURRENTLY MOVING ONSHORE OVER THE PAC NORTHWEST TODAY WILL
MOVE ACROSS THE CENTRAL PLAINS THIS WEEKEND...THEN BEGIN TO LIFT
ACROSS THE UPPER MIDWEST EARLY NEXT WEEK. SURFACE LOW IS PROGGED TO
DEEPEN FROM THE NORTHERN PLAINS SUNDAY AS IT LIFTS TO NEAR HUDSON
BAY LATE ON MONDAY. THIS WILL DRAG A COLD FRONT ACROSS THE REGION ON
MONDAY. WITH THE LOW LIFTING AWAY FROM THE AREA...CONVERGENCE ALONG
THE FRONT IS PROGGED TO WEAKEN AS IT COMES ACROSS NORTHERN ILLINOIS
EARLY MONDAY WITH THE BETTER DYNAMICS STAYING TO OUR NORTH.
MEANWHILE...THE LOCAL AREA APPEARS TO LIE ON THE NORTHERN PERIPHERY
OF THE BETTER INSTABILITY TO OUR SOUTH. GFS SHOWS SOME HINTS THAT
PARTICULARLY NORTH CENTRAL ILLINOIS MAY BE SPLIT BY THE
PRECIP...ESPECIALLY CONSIDERING THE CAPPING EARLY IN THE DAY...BUT
WILL HOLD OFF ON FINE TUNING THIS DETAIL FOR NOW. IN ADDITION...THE
REGION DOES FALL WITHIN AN OVERLAPPED AREA OF FAVORABLE
SHEAR/INSTABILITY THAT COULD POTENTIALLY SUPPORT A SEVERE WEATHER
THREAT.

TUESDAY THROUGH FRIDAY...
FRONTAL BOUNDARY IS PROGGED TO STALL ACROSS/NEAR CENTRAL ILLINOIS
TUESDAY GRADUALLY LIFTING BACK NORTH ACROSS THE FORECAST AREA BY THE
END OF THE WORK WEEK AS A SERIES OF UPPER LEVEL DISTURBANCES MOVE
ACROSS THE REGION. THIS WILL RESULT IN PERIODIC CHANCES FOR SHOWERS
AND THUNDERSTORMS ACROSS THE AREA...THOUGH TIMING AND LOCATION
DETAILS WILL BE DIFFICULT TO PIN DOWN THIS FAR OUT GIVEN THE
PATTERN. THE ATMOSPHERE REMAINS QUITE SOUPY IN THE VICINITY OF THE
FRONT WHERE PWATS REMAIN AROUND 2 INCHES. THUS THE HEAVY RAIN AND
FLOODING THREAT WILL HAVE TO BE CLOSELY MONITORED THROUGH MUCH OF
THE UPCOMING WEEK.

DEUBELBEISS

&&

.AVIATION...

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

* ISOLATED-SCATTERED SHRA/TSRA THIS AFTERNOON THRU EARLY EVENING.

* SOUTH WINDS WITH GUSTS 15-20 KT THIS AFTERNOON.

* ANOTHER PERIOD OF SHRA/TSRA LIKELY AFTER MIDNIGHT INTO SATURDAY
  MORNING.

* SOUTHWEST WINDS GUSTING AROUND 20 KT SATURDAY.

RATZER

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

ISOLATED TSRA DEVELOPING FROM NORTHEAST OF DOWNTOWN CHICAGO SOUTH
INTO IKK AREA. THINK COVERAGE WILL REMAIN FAIRLY LOW...THOUGH HAVE
ADDED VCTS FOR THE NEXT FEW HOURS FOR CHICAGO TERMINALS AS THEY
WILL BE SPARSE BUT IN THE NEIGHBORHOOD SO TO SPEAK.

RATZER

PREVIOUS DISCUSSION FROM 18Z...

FAIRLY LOW CONFIDENCE CONVECTIVE FORECAST THIS PERIOD...WITH
TERMINALS WITHIN A BROAD AREA OF SOUTH WARM/MOIST ADVECTION
DOWNSTREAM OF AN UPPER TROUGH OVER THE CENTRAL PLAINS BUT WITH
OTHERWISE LITTLE ORGANIZED FOCUS FOR TSRA.

SATELLITE EVIDENCE OF WEAK MID-LEVEL DISTURBANCE OVER NORTHEAST
IL EARLY THIS AFTERNOON...WITH MORNING ELEVATED SHRA/TSRA DECAYING
OVER NORTH CENTRAL IL. DIURNAL TSRA WERE FORMING IN LOW LEVEL
INSTABILITY AXIS ALONG IL/IN BORDER REGION GENERALLY ALONG A DEC-
GIJ-MKG LINE...AND THIS LOOKS TO REMAIN THE FOCUS REGION FOR
HIGHEST COVERAGE TSRA THIS AFTERNOON. HIGH-RES GUIDANCE STILL
DEVELOPS SOME ISOLATED SHRA/TSRA INTO THE TERMINAL REGION IN
ASSOCIATION WITH AFOREMENTIONED MID-LEVEL DISTURBANCE AND NORTH
OF SURFACE WARM FRONT WHICH IS ACROSS DOWNSTATE IL AT THIS TIME...
THOUGH COVERAGE IS EXPECTED TO REMAIN LOW. A GREATER CHANCE OF
SHRA/TSRA APPEARS TO BE LATE TONIGHT AND EARLY SATURDAY AS THE
MAIN UPPER TROUGH APPROACHES. WEAK COLD FRONT APPROACHES FROM THE
WEST SATURDAY MIDDAY AND AFTERNOON...WITH THUNDERSTORMS EXPECTED
TO DEVELOP ALONG THE FRONT BY EARLY AFTERNOON. CURRENT SUITE OF
HIGH-RES GUIDANCE SUGGESTS TSRA POTENTIAL MAY BE GREATER JUST
EAST/SOUTH OF CHICAGO TERMINALS SATURDAY AFTERNOON. OUTSIDE OF ANY
PRECIP VIS REDUCTION EARLY SATURDAY...SOME MVFR HAZE POSSIBLE
OVERNIGHT IN MOIST WARM SECTOR AIR.

WINDS...GENERALLY SOUTH 10-12 KT WITH GUSTS TO 20 KT OR SO
POSSIBLE THIS AFTERNOON. WIND MAY BACK A BIT TO THE SOUTH-
SOUTHEAST LATE THIS AFTERNOON/EARLY EVENING AS SURFACE WARM
FRONT APPROACHES...BEFORE SHIFTING SOUTHWEST OVERNIGHT AND SUNDAY
AHEAD OF THE COLD FRONT. DEEPER MIXING SUNDAY SUGGESTS GUSTS AGAIN
IN THE 20 KT RANGE OR A LITTLE HIGHER DURING THE LATE MORNING AND
AFTERNOON.

RATZER

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

* MEDIUM IN SHRA/TSRA BEING LOW IN COVERAGE IN IMMEDIATE TERMINAL
  AREA THIS AFTERNOON...GREATER COVERAGE EAST/SOUTH OF CHICAGO.

* LOW IN TSRA TIMING/COVERAGE LATER TONIGHT/SATURDAY.

* MEDIUM-HIGH IN WIND TRENDS THROUGH PERIOD.

RATZER

//OUTLOOK FOR ORD/MDW FOR 00Z SUNDAY-12Z FRIDAY...UPDATED 12Z...

* SATURDAY NIGHT THROUGH SUNDAY NIGHT...VFR. WX NIL.

* MONDAY...CHANCE OF TSRA.

* TUESDAY...VFR. WX NIL.

* WEDNESDAY THROUGH THURSDAY NIGHT...SLIGHT CHANCE OF TSRA

KREIN

&&

.MARINE...
221 PM CDT

MODERATE SOUTHERLY WINDS ARE IN PLACE TODAY AHEAD OF LOW PRESSURE
OVER THE NORTHERN PLAINS. SOUTH TO SOUTHWEST WINDS 20 TO 25 KT
WITH AN OCCASIONAL 30 KT GUSTS POSSIBLE WILL BE IN PLACE THROUGH
TOMORROW...THEN A COLD FRONT WILL START TO PUSH ACROSS THE LAKE
TURNING WINDS NORTHWESTERLY. HIGH PRESSURE WILL PROVIDE A BRIEF
LULL IN THE WINDS SUNDAY ALLOWING LAKE BREEZES TO DEVELOP...BUT
THEN SOUTHERLY WINDS RAMP BACK UP TO 25 TO 30 KT SUNDAY NIGHT INTO
MONDAY AHEAD OF ANOTHER LOW. THIS LOW IS PROGGED TO DEEPEN AS IT
LIFTS FROM THE NORTHERN PLAINS SUNDAY TO HUDSON BAY LATE MONDAY.

BMD

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO










000
FXUS63 KLOT 292120
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
420 PM CDT FRI AUG 29 2014

.MESOSCALE DISCUSSION...
411 PM CDT

THUNDERSTORMS ARE GENERALLY ISOLATED IN NORTHEAST ILLNOIS THIS
AFTERNOON WITH SCATTERED ACTIVITY EAST OF INTERSTATE 57 IN
ILLNOIS AND ALONG THE INTERSTATE CORRIDOR IN NW INDIANA. RADAR
ESTIMATES A QUICK THREE QUARTERS OF AN INCH TO 1 INCH HAS FALLEN
IN THE HEAVIER DOWNPOURS...WITH STREET FLOODING REPORTED IN
LANSING. EXPECT HEAVY RAIN AND LOCALIZED PONDING OF WATER TO
REMAIN A THREAT INTO THE EARLY EVENING...ESPECIALLY IN NW
INDIANA...THOUGH STORMS MAY INCREASE AS THE WARM FRONT TO THE
SOUTH AND DEEPER MOISTURE SPREAD NORTHWARD.

KMD

&&

.DISCUSSION...
221 PM CDT

SYNOPSIS...UNSETTLED WEATHER CONTINUES THROUGH TOMORROW WITH
SCATTERED THUNDERSTORMS EXPECTED.  CONFIDENCE REMAINS LOW IN WHEN
AND WHERE THUNDERSTORMS WILL FORM.  SUNDAY STILL LOOKS DRY BUT
MULTIPLE CHANCES FOR STORMS RETURN MONDAY THROUGH THE END OF THE
WEEK. ABOVE NORMAL TEMPERATURES ARE ALSO EXPECTED THROUGH THE PERIOD
AS WELL.

//NEAR TERM FORECAST//

THROUGH TONIGHT...
A LARGE RIDGE IS OVER THE EAST COAST WHILE A TROUGH IS OVER THE
PLAINS.  THE TROUGH WILL WEAKEN AS IT APPROACHES OUR AREA AND PASS
OVERHEAD LATE SATURDAY NIGHT INTO SUNDAY MORNING. AT THE SURFACE THE
HIGH HAS PUSHED EAST WHILE A DEVELOPING LOW PRESSURE SYSTEM IS OVER
MINNESOTA.  THE LOWS WARM FRONT LIES TO OUR SOUTH ACROSS SOUTHERN
IL...AND IT WILL LIFT NORTH THROUGH THE REGION THIS AFTERNOON.

HAVE VERY LOW CONFIDENCE IN EXACT TIMING AND LOCATION OF
THUNDERSTORMS THROUGH THIS EVENING.  THERE IS NO CLEAR FORCING
MECHANISM BUT WITH AROUND 2000 J/KG OF CAPE AVAILABLE...STORMS ARE
CERTAINLY POSSIBLE. PWAT VALUES ARE AROUND 2 INCHES SO THE MAIN
CONCERN REMAINS HEAVY DOWNPOURS. THE STRONGEST STORMS MAY PRODUCE
WIND GUSTS TO 50 KT BUT NO SEVERE WEATHER IS EXPECTED AS WIND SHEAR
IS BASICALLY NIL.

FOR POPS USED A BLEND OF NEAR TERM GUIDANCE WHICH HAS BEEN DOING
REASONABLY WELL THIS MORNING.  HOWEVER...KEPT A CHANCE OF STORMS
ACROSS THE REGION THIS AFTERNOON AND EVENING DUE TO THE SCATTERED
NATURE OF THE STORMS THAT ARE EXPECTED.  A WASH OUT IS NOT
EXPECTED.  THE BEST CHANCE FOR WIDESPREAD STORMS WILL BE OVERNIGHT
AS THE UPPER LEVEL TROUGH APPROACHES. IN FACT THE STORMS ASSOCIATED
WITH THE TROUGH STRETCH FROM MINNESOTA THROUGH ARKANSAS.  MODELS
DIFFER IN HOW WELL THIS AREA OF PRECIP WILL HOLD TOGETHER SO LIMITED
POPS TO THE LIKELY CATEGORY.

LOWS WILL BE IN THE UPPER 60S TO LOWER 70S TONIGHT AND FOG IS
POSSIBLE. GIVEN THAT WE HAVE NOT SEEN MUCH RAIN TODAY...HAVE LIMITED
CONFIDENCE SO LEFT FOG OUT OF THE FORECAST FOR NOW.

SATURDAY AND SATURDAY NIGHT...
THE SURFACE LOW PASSES OVER LAKE MICHIGAN SATURDAY AFTERNOON WHILE
ITS COLD FRONT GETS DRAGGED THROUGH THE AREA SATURDAY
AFTERNOON/EVENING.  SCATTERED STORMS ARE AGAIN POSSIBLE IN THE
MORNING IN THE WARM AND MOIST ENVIRONMENT WITH LINGERING 2 INCH PWAT
VALUES. STORMS WILL THEN FORM ALONG THE COLD FRONT SOUTH OF A GARY
IN TO PONTIAC IL LINE. STORMS ARE POSSIBLE NORTH AND WEST OF THIS
LINE...BUT CONFIDENCE IS SIGNIFICANTLY LOWER.

CAPE VALUES WILL BE AROUND 1000 J/KG TOMORROW WITH WEAK SHEAR ONCE
AGAIN. THEREFORE EXPECTING STORMS TO PRODUCE HEAVY DOWNPOURS AND THE
STRONGEST MAY BE CAPABLE OF GUSTY WINDS.  SEVERE WEATHER IS NOT
EXPECTED.

TOMORROW LOOKS LIKE ANOTHER WARM AND STICKY DAY AHEAD OF THE COLD
FRONT.  LOWS WILL BE IN THE 60S AND FOG IS POSSIBLE OVERNIGHT.

JEE

//EXTENDED FORECAST//

SUNDAY...
EXPECT A BRIEF LULL IN THE PRECIP CHANCES DURING MUCH OF THE DAY
SUNDAY AS THE FIRST COLD FRONT DEPARTS TO THE EAST AND ANOTHER LOW
TAKES SHAPE OVER THE NORTHERN PLAINS. IN BETWEEN THESE TWO
SYSTEMS...WEAK INDUCED SURFACE HIGH SHOULD RESULT IN QUIET WEATHER
LOCALLY...WITH THE H85 THERMAL RIDGE ADVECTING OVERHEARD THROUGHOUT
THE DAY. RETURN FLOW WILL HELP PUSH THE DEWPOINTS BACK UP TO AROUND
70 WITH AFTERNOON HIGH TEMPS EXPECTED TO BE IN THE MID 80S. STEEP
LOW/MID LEVEL LAPSE RATES WILL RESULT IN MODERATE INSTABILITY
DEVELOPING DURING THE AFTERNOON...BUT MODEST SBCIN IS PROGGED TO
STAY IN PLACE CAPPING ANY SURFACE BASED CONVECTION. IN ADDITION...
THE AREA SHOULD BE SQUARELY UNDER AREA OF MID LEVEL HEIGHT RISES
WHICH SHOULD HELP REINFORCE THE INVERSION...AND NO SIGNIFICANT
FORCING NOTED OVER THE AREA.

MONDAY...
TROUGHING CURRENTLY MOVING ONSHORE OVER THE PAC NORTHWEST TODAY WILL
MOVE ACROSS THE CENTRAL PLAINS THIS WEEKEND...THEN BEGIN TO LIFT
ACROSS THE UPPER MIDWEST EARLY NEXT WEEK. SURFACE LOW IS PROGGED TO
DEEPEN FROM THE NORTHERN PLAINS SUNDAY AS IT LIFTS TO NEAR HUDSON
BAY LATE ON MONDAY. THIS WILL DRAG A COLD FRONT ACROSS THE REGION ON
MONDAY. WITH THE LOW LIFTING AWAY FROM THE AREA...CONVERGENCE ALONG
THE FRONT IS PROGGED TO WEAKEN AS IT COMES ACROSS NORTHERN ILLINOIS
EARLY MONDAY WITH THE BETTER DYNAMICS STAYING TO OUR NORTH.
MEANWHILE...THE LOCAL AREA APPEARS TO LIE ON THE NORTHERN PERIPHERY
OF THE BETTER INSTABILITY TO OUR SOUTH. GFS SHOWS SOME HINTS THAT
PARTICULARLY NORTH CENTRAL ILLINOIS MAY BE SPLIT BY THE
PRECIP...ESPECIALLY CONSIDERING THE CAPPING EARLY IN THE DAY...BUT
WILL HOLD OFF ON FINE TUNING THIS DETAIL FOR NOW. IN ADDITION...THE
REGION DOES FALL WITHIN AN OVERLAPPED AREA OF FAVORABLE
SHEAR/INSTABILITY THAT COULD POTENTIALLY SUPPORT A SEVERE WEATHER
THREAT.

TUESDAY THROUGH FRIDAY...
FRONTAL BOUNDARY IS PROGGED TO STALL ACROSS/NEAR CENTRAL ILLINOIS
TUESDAY GRADUALLY LIFTING BACK NORTH ACROSS THE FORECAST AREA BY THE
END OF THE WORK WEEK AS A SERIES OF UPPER LEVEL DISTURBANCES MOVE
ACROSS THE REGION. THIS WILL RESULT IN PERIODIC CHANCES FOR SHOWERS
AND THUNDERSTORMS ACROSS THE AREA...THOUGH TIMING AND LOCATION
DETAILS WILL BE DIFFICULT TO PIN DOWN THIS FAR OUT GIVEN THE
PATTERN. THE ATMOSPHERE REMAINS QUITE SOUPY IN THE VICINITY OF THE
FRONT WHERE PWATS REMAIN AROUND 2 INCHES. THUS THE HEAVY RAIN AND
FLOODING THREAT WILL HAVE TO BE CLOSELY MONITORED THROUGH MUCH OF
THE UPCOMING WEEK.

DEUBELBEISS

&&

.AVIATION...

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

* ISOLATED-SCATTERED SHRA/TSRA THIS AFTERNOON THRU EARLY EVENING.

* SOUTH WINDS WITH GUSTS 15-20 KT THIS AFTERNOON.

* ANOTHER PERIOD OF SHRA/TSRA LIKELY AFTER MIDNIGHT INTO SATURDAY
  MORNING.

* SOUTHWEST WINDS GUSTING AROUND 20 KT SATURDAY.

RATZER

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

ISOLATED TSRA DEVELOPING FROM NORTHEAST OF DOWNTOWN CHICAGO SOUTH
INTO IKK AREA. THINK COVERAGE WILL REMAIN FAIRLY LOW...THOUGH HAVE
ADDED VCTS FOR THE NEXT FEW HOURS FOR CHICAGO TERMINALS AS THEY
WILL BE SPARSE BUT IN THE NEIGHBORHOOD SO TO SPEAK.

RATZER

PREVIOUS DISCUSSION FROM 18Z...

FAIRLY LOW CONFIDENCE CONVECTIVE FORECAST THIS PERIOD...WITH
TERMINALS WITHIN A BROAD AREA OF SOUTH WARM/MOIST ADVECTION
DOWNSTREAM OF AN UPPER TROUGH OVER THE CENTRAL PLAINS BUT WITH
OTHERWISE LITTLE ORGANIZED FOCUS FOR TSRA.

SATELLITE EVIDENCE OF WEAK MID-LEVEL DISTURBANCE OVER NORTHEAST
IL EARLY THIS AFTERNOON...WITH MORNING ELEVATED SHRA/TSRA DECAYING
OVER NORTH CENTRAL IL. DIURNAL TSRA WERE FORMING IN LOW LEVEL
INSTABILITY AXIS ALONG IL/IN BORDER REGION GENERALLY ALONG A DEC-
GIJ-MKG LINE...AND THIS LOOKS TO REMAIN THE FOCUS REGION FOR
HIGHEST COVERAGE TSRA THIS AFTERNOON. HIGH-RES GUIDANCE STILL
DEVELOPS SOME ISOLATED SHRA/TSRA INTO THE TERMINAL REGION IN
ASSOCIATION WITH AFOREMENTIONED MID-LEVEL DISTURBANCE AND NORTH
OF SURFACE WARM FRONT WHICH IS ACROSS DOWNSTATE IL AT THIS TIME...
THOUGH COVERAGE IS EXPECTED TO REMAIN LOW. A GREATER CHANCE OF
SHRA/TSRA APPEARS TO BE LATE TONIGHT AND EARLY SATURDAY AS THE
MAIN UPPER TROUGH APPROACHES. WEAK COLD FRONT APPROACHES FROM THE
WEST SATURDAY MIDDAY AND AFTERNOON...WITH THUNDERSTORMS EXPECTED
TO DEVELOP ALONG THE FRONT BY EARLY AFTERNOON. CURRENT SUITE OF
HIGH-RES GUIDANCE SUGGESTS TSRA POTENTIAL MAY BE GREATER JUST
EAST/SOUTH OF CHICAGO TERMINALS SATURDAY AFTERNOON. OUTSIDE OF ANY
PRECIP VIS REDUCTION EARLY SATURDAY...SOME MVFR HAZE POSSIBLE
OVERNIGHT IN MOIST WARM SECTOR AIR.

WINDS...GENERALLY SOUTH 10-12 KT WITH GUSTS TO 20 KT OR SO
POSSIBLE THIS AFTERNOON. WIND MAY BACK A BIT TO THE SOUTH-
SOUTHEAST LATE THIS AFTERNOON/EARLY EVENING AS SURFACE WARM
FRONT APPROACHES...BEFORE SHIFTING SOUTHWEST OVERNIGHT AND SUNDAY
AHEAD OF THE COLD FRONT. DEEPER MIXING SUNDAY SUGGESTS GUSTS AGAIN
IN THE 20 KT RANGE OR A LITTLE HIGHER DURING THE LATE MORNING AND
AFTERNOON.

RATZER

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

* MEDIUM IN SHRA/TSRA BEING LOW IN COVERAGE IN IMMEDIATE TERMINAL
  AREA THIS AFTERNOON...GREATER COVERAGE EAST/SOUTH OF CHICAGO.

* LOW IN TSRA TIMING/COVERAGE LATER TONIGHT/SATURDAY.

* MEDIUM-HIGH IN WIND TRENDS THROUGH PERIOD.

RATZER

//OUTLOOK FOR ORD/MDW FOR 00Z SUNDAY-12Z FRIDAY...UPDATED 12Z...

* SATURDAY NIGHT THROUGH SUNDAY NIGHT...VFR. WX NIL.

* MONDAY...CHANCE OF TSRA.

* TUESDAY...VFR. WX NIL.

* WEDNESDAY THROUGH THURSDAY NIGHT...SLIGHT CHANCE OF TSRA

KREIN

&&

.MARINE...
221 PM CDT

MODERATE SOUTHERLY WINDS ARE IN PLACE TODAY AHEAD OF LOW PRESSURE
OVER THE NORTHERN PLAINS. SOUTH TO SOUTHWEST WINDS 20 TO 25 KT
WITH AN OCCASIONAL 30 KT GUSTS POSSIBLE WILL BE IN PLACE THROUGH
TOMORROW...THEN A COLD FRONT WILL START TO PUSH ACROSS THE LAKE
TURNING WINDS NORTHWESTERLY. HIGH PRESSURE WILL PROVIDE A BRIEF
LULL IN THE WINDS SUNDAY ALLOWING LAKE BREEZES TO DEVELOP...BUT
THEN SOUTHERLY WINDS RAMP BACK UP TO 25 TO 30 KT SUNDAY NIGHT INTO
MONDAY AHEAD OF ANOTHER LOW. THIS LOW IS PROGGED TO DEEPEN AS IT
LIFTS FROM THE NORTHERN PLAINS SUNDAY TO HUDSON BAY LATE MONDAY.

BMD

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO







000
FXUS63 KLOT 292120
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
420 PM CDT FRI AUG 29 2014

.MESOSCALE DISCUSSION...
411 PM CDT

THUNDERSTORMS ARE GENERALLY ISOLATED IN NORTHEAST ILLNOIS THIS
AFTERNOON WITH SCATTERED ACTIVITY EAST OF INTERSTATE 57 IN
ILLNOIS AND ALONG THE INTERSTATE CORRIDOR IN NW INDIANA. RADAR
ESTIMATES A QUICK THREE QUARTERS OF AN INCH TO 1 INCH HAS FALLEN
IN THE HEAVIER DOWNPOURS...WITH STREET FLOODING REPORTED IN
LANSING. EXPECT HEAVY RAIN AND LOCALIZED PONDING OF WATER TO
REMAIN A THREAT INTO THE EARLY EVENING...ESPECIALLY IN NW
INDIANA...THOUGH STORMS MAY INCREASE AS THE WARM FRONT TO THE
SOUTH AND DEEPER MOISTURE SPREAD NORTHWARD.

KMD

&&

.DISCUSSION...
221 PM CDT

SYNOPSIS...UNSETTLED WEATHER CONTINUES THROUGH TOMORROW WITH
SCATTERED THUNDERSTORMS EXPECTED.  CONFIDENCE REMAINS LOW IN WHEN
AND WHERE THUNDERSTORMS WILL FORM.  SUNDAY STILL LOOKS DRY BUT
MULTIPLE CHANCES FOR STORMS RETURN MONDAY THROUGH THE END OF THE
WEEK. ABOVE NORMAL TEMPERATURES ARE ALSO EXPECTED THROUGH THE PERIOD
AS WELL.

//NEAR TERM FORECAST//

THROUGH TONIGHT...
A LARGE RIDGE IS OVER THE EAST COAST WHILE A TROUGH IS OVER THE
PLAINS.  THE TROUGH WILL WEAKEN AS IT APPROACHES OUR AREA AND PASS
OVERHEAD LATE SATURDAY NIGHT INTO SUNDAY MORNING. AT THE SURFACE THE
HIGH HAS PUSHED EAST WHILE A DEVELOPING LOW PRESSURE SYSTEM IS OVER
MINNESOTA.  THE LOWS WARM FRONT LIES TO OUR SOUTH ACROSS SOUTHERN
IL...AND IT WILL LIFT NORTH THROUGH THE REGION THIS AFTERNOON.

HAVE VERY LOW CONFIDENCE IN EXACT TIMING AND LOCATION OF
THUNDERSTORMS THROUGH THIS EVENING.  THERE IS NO CLEAR FORCING
MECHANISM BUT WITH AROUND 2000 J/KG OF CAPE AVAILABLE...STORMS ARE
CERTAINLY POSSIBLE. PWAT VALUES ARE AROUND 2 INCHES SO THE MAIN
CONCERN REMAINS HEAVY DOWNPOURS. THE STRONGEST STORMS MAY PRODUCE
WIND GUSTS TO 50 KT BUT NO SEVERE WEATHER IS EXPECTED AS WIND SHEAR
IS BASICALLY NIL.

FOR POPS USED A BLEND OF NEAR TERM GUIDANCE WHICH HAS BEEN DOING
REASONABLY WELL THIS MORNING.  HOWEVER...KEPT A CHANCE OF STORMS
ACROSS THE REGION THIS AFTERNOON AND EVENING DUE TO THE SCATTERED
NATURE OF THE STORMS THAT ARE EXPECTED.  A WASH OUT IS NOT
EXPECTED.  THE BEST CHANCE FOR WIDESPREAD STORMS WILL BE OVERNIGHT
AS THE UPPER LEVEL TROUGH APPROACHES. IN FACT THE STORMS ASSOCIATED
WITH THE TROUGH STRETCH FROM MINNESOTA THROUGH ARKANSAS.  MODELS
DIFFER IN HOW WELL THIS AREA OF PRECIP WILL HOLD TOGETHER SO LIMITED
POPS TO THE LIKELY CATEGORY.

LOWS WILL BE IN THE UPPER 60S TO LOWER 70S TONIGHT AND FOG IS
POSSIBLE. GIVEN THAT WE HAVE NOT SEEN MUCH RAIN TODAY...HAVE LIMITED
CONFIDENCE SO LEFT FOG OUT OF THE FORECAST FOR NOW.

SATURDAY AND SATURDAY NIGHT...
THE SURFACE LOW PASSES OVER LAKE MICHIGAN SATURDAY AFTERNOON WHILE
ITS COLD FRONT GETS DRAGGED THROUGH THE AREA SATURDAY
AFTERNOON/EVENING.  SCATTERED STORMS ARE AGAIN POSSIBLE IN THE
MORNING IN THE WARM AND MOIST ENVIRONMENT WITH LINGERING 2 INCH PWAT
VALUES. STORMS WILL THEN FORM ALONG THE COLD FRONT SOUTH OF A GARY
IN TO PONTIAC IL LINE. STORMS ARE POSSIBLE NORTH AND WEST OF THIS
LINE...BUT CONFIDENCE IS SIGNIFICANTLY LOWER.

CAPE VALUES WILL BE AROUND 1000 J/KG TOMORROW WITH WEAK SHEAR ONCE
AGAIN. THEREFORE EXPECTING STORMS TO PRODUCE HEAVY DOWNPOURS AND THE
STRONGEST MAY BE CAPABLE OF GUSTY WINDS.  SEVERE WEATHER IS NOT
EXPECTED.

TOMORROW LOOKS LIKE ANOTHER WARM AND STICKY DAY AHEAD OF THE COLD
FRONT.  LOWS WILL BE IN THE 60S AND FOG IS POSSIBLE OVERNIGHT.

JEE

//EXTENDED FORECAST//

SUNDAY...
EXPECT A BRIEF LULL IN THE PRECIP CHANCES DURING MUCH OF THE DAY
SUNDAY AS THE FIRST COLD FRONT DEPARTS TO THE EAST AND ANOTHER LOW
TAKES SHAPE OVER THE NORTHERN PLAINS. IN BETWEEN THESE TWO
SYSTEMS...WEAK INDUCED SURFACE HIGH SHOULD RESULT IN QUIET WEATHER
LOCALLY...WITH THE H85 THERMAL RIDGE ADVECTING OVERHEARD THROUGHOUT
THE DAY. RETURN FLOW WILL HELP PUSH THE DEWPOINTS BACK UP TO AROUND
70 WITH AFTERNOON HIGH TEMPS EXPECTED TO BE IN THE MID 80S. STEEP
LOW/MID LEVEL LAPSE RATES WILL RESULT IN MODERATE INSTABILITY
DEVELOPING DURING THE AFTERNOON...BUT MODEST SBCIN IS PROGGED TO
STAY IN PLACE CAPPING ANY SURFACE BASED CONVECTION. IN ADDITION...
THE AREA SHOULD BE SQUARELY UNDER AREA OF MID LEVEL HEIGHT RISES
WHICH SHOULD HELP REINFORCE THE INVERSION...AND NO SIGNIFICANT
FORCING NOTED OVER THE AREA.

MONDAY...
TROUGHING CURRENTLY MOVING ONSHORE OVER THE PAC NORTHWEST TODAY WILL
MOVE ACROSS THE CENTRAL PLAINS THIS WEEKEND...THEN BEGIN TO LIFT
ACROSS THE UPPER MIDWEST EARLY NEXT WEEK. SURFACE LOW IS PROGGED TO
DEEPEN FROM THE NORTHERN PLAINS SUNDAY AS IT LIFTS TO NEAR HUDSON
BAY LATE ON MONDAY. THIS WILL DRAG A COLD FRONT ACROSS THE REGION ON
MONDAY. WITH THE LOW LIFTING AWAY FROM THE AREA...CONVERGENCE ALONG
THE FRONT IS PROGGED TO WEAKEN AS IT COMES ACROSS NORTHERN ILLINOIS
EARLY MONDAY WITH THE BETTER DYNAMICS STAYING TO OUR NORTH.
MEANWHILE...THE LOCAL AREA APPEARS TO LIE ON THE NORTHERN PERIPHERY
OF THE BETTER INSTABILITY TO OUR SOUTH. GFS SHOWS SOME HINTS THAT
PARTICULARLY NORTH CENTRAL ILLINOIS MAY BE SPLIT BY THE
PRECIP...ESPECIALLY CONSIDERING THE CAPPING EARLY IN THE DAY...BUT
WILL HOLD OFF ON FINE TUNING THIS DETAIL FOR NOW. IN ADDITION...THE
REGION DOES FALL WITHIN AN OVERLAPPED AREA OF FAVORABLE
SHEAR/INSTABILITY THAT COULD POTENTIALLY SUPPORT A SEVERE WEATHER
THREAT.

TUESDAY THROUGH FRIDAY...
FRONTAL BOUNDARY IS PROGGED TO STALL ACROSS/NEAR CENTRAL ILLINOIS
TUESDAY GRADUALLY LIFTING BACK NORTH ACROSS THE FORECAST AREA BY THE
END OF THE WORK WEEK AS A SERIES OF UPPER LEVEL DISTURBANCES MOVE
ACROSS THE REGION. THIS WILL RESULT IN PERIODIC CHANCES FOR SHOWERS
AND THUNDERSTORMS ACROSS THE AREA...THOUGH TIMING AND LOCATION
DETAILS WILL BE DIFFICULT TO PIN DOWN THIS FAR OUT GIVEN THE
PATTERN. THE ATMOSPHERE REMAINS QUITE SOUPY IN THE VICINITY OF THE
FRONT WHERE PWATS REMAIN AROUND 2 INCHES. THUS THE HEAVY RAIN AND
FLOODING THREAT WILL HAVE TO BE CLOSELY MONITORED THROUGH MUCH OF
THE UPCOMING WEEK.

DEUBELBEISS

&&

.AVIATION...

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

* ISOLATED-SCATTERED SHRA/TSRA THIS AFTERNOON THRU EARLY EVENING.

* SOUTH WINDS WITH GUSTS 15-20 KT THIS AFTERNOON.

* ANOTHER PERIOD OF SHRA/TSRA LIKELY AFTER MIDNIGHT INTO SATURDAY
  MORNING.

* SOUTHWEST WINDS GUSTING AROUND 20 KT SATURDAY.

RATZER

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

ISOLATED TSRA DEVELOPING FROM NORTHEAST OF DOWNTOWN CHICAGO SOUTH
INTO IKK AREA. THINK COVERAGE WILL REMAIN FAIRLY LOW...THOUGH HAVE
ADDED VCTS FOR THE NEXT FEW HOURS FOR CHICAGO TERMINALS AS THEY
WILL BE SPARSE BUT IN THE NEIGHBORHOOD SO TO SPEAK.

RATZER

PREVIOUS DISCUSSION FROM 18Z...

FAIRLY LOW CONFIDENCE CONVECTIVE FORECAST THIS PERIOD...WITH
TERMINALS WITHIN A BROAD AREA OF SOUTH WARM/MOIST ADVECTION
DOWNSTREAM OF AN UPPER TROUGH OVER THE CENTRAL PLAINS BUT WITH
OTHERWISE LITTLE ORGANIZED FOCUS FOR TSRA.

SATELLITE EVIDENCE OF WEAK MID-LEVEL DISTURBANCE OVER NORTHEAST
IL EARLY THIS AFTERNOON...WITH MORNING ELEVATED SHRA/TSRA DECAYING
OVER NORTH CENTRAL IL. DIURNAL TSRA WERE FORMING IN LOW LEVEL
INSTABILITY AXIS ALONG IL/IN BORDER REGION GENERALLY ALONG A DEC-
GIJ-MKG LINE...AND THIS LOOKS TO REMAIN THE FOCUS REGION FOR
HIGHEST COVERAGE TSRA THIS AFTERNOON. HIGH-RES GUIDANCE STILL
DEVELOPS SOME ISOLATED SHRA/TSRA INTO THE TERMINAL REGION IN
ASSOCIATION WITH AFOREMENTIONED MID-LEVEL DISTURBANCE AND NORTH
OF SURFACE WARM FRONT WHICH IS ACROSS DOWNSTATE IL AT THIS TIME...
THOUGH COVERAGE IS EXPECTED TO REMAIN LOW. A GREATER CHANCE OF
SHRA/TSRA APPEARS TO BE LATE TONIGHT AND EARLY SATURDAY AS THE
MAIN UPPER TROUGH APPROACHES. WEAK COLD FRONT APPROACHES FROM THE
WEST SATURDAY MIDDAY AND AFTERNOON...WITH THUNDERSTORMS EXPECTED
TO DEVELOP ALONG THE FRONT BY EARLY AFTERNOON. CURRENT SUITE OF
HIGH-RES GUIDANCE SUGGESTS TSRA POTENTIAL MAY BE GREATER JUST
EAST/SOUTH OF CHICAGO TERMINALS SATURDAY AFTERNOON. OUTSIDE OF ANY
PRECIP VIS REDUCTION EARLY SATURDAY...SOME MVFR HAZE POSSIBLE
OVERNIGHT IN MOIST WARM SECTOR AIR.

WINDS...GENERALLY SOUTH 10-12 KT WITH GUSTS TO 20 KT OR SO
POSSIBLE THIS AFTERNOON. WIND MAY BACK A BIT TO THE SOUTH-
SOUTHEAST LATE THIS AFTERNOON/EARLY EVENING AS SURFACE WARM
FRONT APPROACHES...BEFORE SHIFTING SOUTHWEST OVERNIGHT AND SUNDAY
AHEAD OF THE COLD FRONT. DEEPER MIXING SUNDAY SUGGESTS GUSTS AGAIN
IN THE 20 KT RANGE OR A LITTLE HIGHER DURING THE LATE MORNING AND
AFTERNOON.

RATZER

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

* MEDIUM IN SHRA/TSRA BEING LOW IN COVERAGE IN IMMEDIATE TERMINAL
  AREA THIS AFTERNOON...GREATER COVERAGE EAST/SOUTH OF CHICAGO.

* LOW IN TSRA TIMING/COVERAGE LATER TONIGHT/SATURDAY.

* MEDIUM-HIGH IN WIND TRENDS THROUGH PERIOD.

RATZER

//OUTLOOK FOR ORD/MDW FOR 00Z SUNDAY-12Z FRIDAY...UPDATED 12Z...

* SATURDAY NIGHT THROUGH SUNDAY NIGHT...VFR. WX NIL.

* MONDAY...CHANCE OF TSRA.

* TUESDAY...VFR. WX NIL.

* WEDNESDAY THROUGH THURSDAY NIGHT...SLIGHT CHANCE OF TSRA

KREIN

&&

.MARINE...
221 PM CDT

MODERATE SOUTHERLY WINDS ARE IN PLACE TODAY AHEAD OF LOW PRESSURE
OVER THE NORTHERN PLAINS. SOUTH TO SOUTHWEST WINDS 20 TO 25 KT
WITH AN OCCASIONAL 30 KT GUSTS POSSIBLE WILL BE IN PLACE THROUGH
TOMORROW...THEN A COLD FRONT WILL START TO PUSH ACROSS THE LAKE
TURNING WINDS NORTHWESTERLY. HIGH PRESSURE WILL PROVIDE A BRIEF
LULL IN THE WINDS SUNDAY ALLOWING LAKE BREEZES TO DEVELOP...BUT
THEN SOUTHERLY WINDS RAMP BACK UP TO 25 TO 30 KT SUNDAY NIGHT INTO
MONDAY AHEAD OF ANOTHER LOW. THIS LOW IS PROGGED TO DEEPEN AS IT
LIFTS FROM THE NORTHERN PLAINS SUNDAY TO HUDSON BAY LATE MONDAY.

BMD

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 291958
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
258 PM CDT FRI AUG 29 2014

.DISCUSSION...
221 PM CDT

SYNOPSIS...UNSETTLED WEATHER CONTINUES THROUGH TOMORROW WITH
SCATTERED THUNDERSTORMS EXPECTED.  CONFIDENCE REMAINS LOW IN WHEN
AND WHERE THUNDERSTORMS WILL FORM.  SUNDAY STILL LOOKS DRY BUT
MULTIPLE CHANCES FOR STORMS RETURN MONDAY THROUGH THE END OF THE
WEEK. ABOVE NORMAL TEMPERATURES ARE ALSO EXPECTED THROUGH THE PERIOD
AS WELL.

//NEAR TERM FORECAST//

THROUGH TONIGHT...
A LARGE RIDGE IS OVER THE EAST COAST WHILE A TROUGH IS OVER THE
PLAINS.  THE TROUGH WILL WEAKEN AS IT APPROACHES OUR AREA AND PASS
OVERHEAD LATE SATURDAY NIGHT INTO SUNDAY MORNING. AT THE SURFACE THE
HIGH HAS PUSHED EAST WHILE A DEVELOPING LOW PRESSURE SYSTEM IS OVER
MINNESOTA.  THE LOWS WARM FRONT LIES TO OUR SOUTH ACROSS SOUTHERN
IL...AND IT WILL LIFT NORTH THROUGH THE REGION THIS AFTERNOON.

HAVE VERY LOW CONFIDENCE IN EXACT TIMING AND LOCATION OF
THUNDERSTORMS THROUGH THIS EVENING.  THERE IS NO CLEAR FORCING
MECHANISM BUT WITH AROUND 2000 J/KG OF CAPE AVAILABLE...STORMS ARE
CERTAINLY POSSIBLE. PWAT VALUES ARE AROUND 2 INCHES SO THE MAIN
CONCERN REMAINS HEAVY DOWNPOURS. THE STRONGEST STORMS MAY PRODUCE
WIND GUSTS TO 50 KT BUT NO SEVERE WEATHER IS EXPECTED AS WIND SHEAR
IS BASICALLY NIL.

FOR POPS USED A BLEND OF NEAR TERM GUIDANCE WHICH HAS BEEN DOING
REASONABLY WELL THIS MORNING.  HOWEVER...KEPT A CHANCE OF STORMS
ACROSS THE REGION THIS AFTERNOON AND EVENING DUE TO THE SCATTERED
NATURE OF THE STORMS THAT ARE EXPECTED.  A WASH OUT IS NOT
EXPECTED.  THE BEST CHANCE FOR WIDESPREAD STORMS WILL BE OVERNIGHT
AS THE UPPER LEVEL TROUGH APPROACHES. IN FACT THE STORMS ASSOCIATED
WITH THE TROUGH STRETCH FROM MINNESOTA THROUGH ARKANSAS.  MODELS
DIFFER IN HOW WELL THIS AREA OF PRECIP WILL HOLD TOGETHER SO LIMITED
POPS TO THE LIKELY CATEGORY.

LOWS WILL BE IN THE UPPER 60S TO LOWER 70S TONIGHT AND FOG IS
POSSIBLE. GIVEN THAT WE HAVE NOT SEEN MUCH RAIN TODAY...HAVE LIMITED
CONFIDENCE SO LEFT FOG OUT OF THE FORECAST FOR NOW.

SATURDAY AND SATURDAY NIGHT...
THE SURFACE LOW PASSES OVER LAKE MICHIGAN SATURDAY AFTERNOON WHILE
ITS COLD FRONT GETS DRAGGED THROUGH THE AREA SATURDAY
AFTERNOON/EVENING.  SCATTERED STORMS ARE AGAIN POSSIBLE IN THE
MORNING IN THE WARM AND MOIST ENVIRONMENT WITH LINGERING 2 INCH PWAT
VALUES. STORMS WILL THEN FORM ALONG THE COLD FRONT SOUTH OF A GARY
IN TO PONTIAC IL LINE. STORMS ARE POSSIBLE NORTH AND WEST OF THIS
LINE...BUT CONFIDENCE IS SIGNIFICANTLY LOWER.

CAPE VALUES WILL BE AROUND 1000 J/KG TOMORROW WITH WEAK SHEAR ONCE
AGAIN. THEREFORE EXPECTING STORMS TO PRODUCE HEAVY DOWNPOURS AND THE
STRONGEST MAY BE CAPABLE OF GUSTY WINDS.  SEVERE WEATHER IS NOT
EXPECTED.

TOMORROW LOOKS LIKE ANOTHER WARM AND STICKY DAY AHEAD OF THE COLD
FRONT.  LOWS WILL BE IN THE 60S AND FOG IS POSSIBLE OVERNIGHT.

JEE

//EXTENDED FORECAST//

SUNDAY...
EXPECT A BRIEF LULL IN THE PRECIP CHANCES DURING MUCH OF THE DAY
SUNDAY AS THE FIRST COLD FRONT DEPARTS TO THE EAST AND ANOTHER LOW
TAKES SHAPE OVER THE NORTHERN PLAINS. IN BETWEEN THESE TWO
SYSTEMS...WEAK INDUCED SURFACE HIGH SHOULD RESULT IN QUIET WEATHER
LOCALLY...WITH THE H85 THERMAL RIDGE ADVECTING OVERHEARD THROUGHOUT
THE DAY. RETURN FLOW WILL HELP PUSH THE DEWPOINTS BACK UP TO AROUND
70 WITH AFTERNOON HIGH TEMPS EXPECTED TO BE IN THE MID 80S. STEEP
LOW/MID LEVEL LAPSE RATES WILL RESULT IN MODERATE INSTABILITY
DEVELOPING DURING THE AFTERNOON...BUT MODEST SBCIN IS PROGGED TO
STAY IN PLACE CAPPING ANY SURFACE BASED CONVECTION. IN ADDITION...
THE AREA SHOULD BE SQUARELY UNDER AREA OF MID LEVEL HEIGHT RISES
WHICH SHOULD HELP REINFORCE THE INVERSION...AND NO SIGNIFICANT
FORCING NOTED OVER THE AREA.

MONDAY...
TROUGHING CURRENTLY MOVING ONSHORE OVER THE PAC NORTHWEST TODAY WILL
MOVE ACROSS THE CENTRAL PLAINS THIS WEEKEND...THEN BEGIN TO LIFT
ACROSS THE UPPER MIDWEST EARLY NEXT WEEK. SURFACE LOW IS PROGGED TO
DEEPEN FROM THE NORTHERN PLAINS SUNDAY AS IT LIFTS TO NEAR HUDSON
BAY LATE ON MONDAY. THIS WILL DRAG A COLD FRONT ACROSS THE REGION ON
MONDAY. WITH THE LOW LIFTING AWAY FROM THE AREA...CONVERGENCE ALONG
THE FRONT IS PROGGED TO WEAKEN AS IT COMES ACROSS NORTHERN ILLINOIS
EARLY MONDAY WITH THE BETTER DYNAMICS STAYING TO OUR NORTH.
MEANWHILE...THE LOCAL AREA APPEARS TO LIE ON THE NORTHERN PERIPHERY
OF THE BETTER INSTABILITY TO OUR SOUTH. GFS SHOWS SOME HINTS THAT
PARTICULARLY NORTH CENTRAL ILLINOIS MAY BE SPLIT BY THE
PRECIP...ESPECIALLY CONSIDERING THE CAPPING EARLY IN THE DAY...BUT
WILL HOLD OFF ON FINE TUNING THIS DETAIL FOR NOW. IN ADDITION...THE
REGION DOES FALL WITHIN AN OVERLAPPED AREA OF FAVORABLE
SHEAR/INSTABILITY THAT COULD POTENTIALLY SUPPORT A SEVERE WEATHER
THREAT.

TUESDAY THROUGH FRIDAY...
FRONTAL BOUNDARY IS PROGGED TO STALL ACROSS/NEAR CENTRAL ILLINOIS
TUESDAY GRADUALLY LIFTING BACK NORTH ACROSS THE FORECAST AREA BY THE
END OF THE WORK WEEK AS A SERIES OF UPPER LEVEL DISTURBANCES MOVE
ACROSS THE REGION. THIS WILL RESULT IN PERIODIC CHANCES FOR SHOWERS
AND THUNDERSTORMS ACROSS THE AREA...THOUGH TIMING AND LOCATION
DETAILS WILL BE DIFFICULT TO PIN DOWN THIS FAR OUT GIVEN THE
PATTERN. THE ATMOSPHERE REMAINS QUITE SOUPY IN THE VICINITY OF THE
FRONT WHERE PWATS REMAIN AROUND 2 INCHES. THUS THE HEAVY RAIN AND
FLOODING THREAT WILL HAVE TO BE CLOSELY MONITORED THROUGH MUCH OF
THE UPCOMING WEEK.

DEUBELBEISS

&&

.AVIATION...

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

* ISOLATED-SCATTERED SHRA/TSRA THIS AFTERNOON THRU EARLY EVENING.

* SOUTH WINDS WITH GUSTS 15-20 KT THIS AFTERNOON.

* ANOTHER PERIOD OF SHRA/TSRA LIKELY AFTER MIDNIGHT INTO SATURDAY
  MORNING.

* SOUTHWEST WINDS GUSTING AROUND 20 KT SATURDAY.

RATZER

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

ISOLATED TSRA DEVELOPING FROM NORTHEAST OF DOWNTOWN CHICAGO SOUTH
INTO IKK AREA. THINK COVERAGE WILL REMAIN FAIRLY LOW...THOUGH HAVE
ADDED VCTS FOR THE NEXT FEW HOURS FOR CHICAGO TERMINALS AS THEY
WILL BE SPARSE BUT IN THE NEIGHBORHOOD SO TO SPEAK.

RATZER

PREVIOUS DISCUSSION FROM 18Z...

FAIRLY LOW CONFIDENCE CONVECTIVE FORECAST THIS PERIOD...WITH
TERMINALS WITHIN A BROAD AREA OF SOUTH WARM/MOIST ADVECTION
DOWNSTREAM OF AN UPPER TROUGH OVER THE CENTRAL PLAINS BUT WITH
OTHERWISE LITTLE ORGANIZED FOCUS FOR TSRA.

SATELLITE EVIDENCE OF WEAK MID-LEVEL DISTURBANCE OVER NORTHEAST
IL EARLY THIS AFTERNOON...WITH MORNING ELEVATED SHRA/TSRA DECAYING
OVER NORTH CENTRAL IL. DIURNAL TSRA WERE FORMING IN LOW LEVEL
INSTABILITY AXIS ALONG IL/IN BORDER REGION GENERALLY ALONG A DEC-
GIJ-MKG LINE...AND THIS LOOKS TO REMAIN THE FOCUS REGION FOR
HIGHEST COVERAGE TSRA THIS AFTERNOON. HIGH-RES GUIDANCE STILL
DEVELOPS SOME ISOLATED SHRA/TSRA INTO THE TERMINAL REGION IN
ASSOCIATION WITH AFOREMENTIONED MID-LEVEL DISTURBANCE AND NORTH
OF SURFACE WARM FRONT WHICH IS ACROSS DOWNSTATE IL AT THIS TIME...
THOUGH COVERAGE IS EXPECTED TO REMAIN LOW. A GREATER CHANCE OF
SHRA/TSRA APPEARS TO BE LATE TONIGHT AND EARLY SATURDAY AS THE
MAIN UPPER TROUGH APPROACHES. WEAK COLD FRONT APPROACHES FROM THE
WEST SATURDAY MIDDAY AND AFTERNOON...WITH THUNDERSTORMS EXPECTED
TO DEVELOP ALONG THE FRONT BY EARLY AFTERNOON. CURRENT SUITE OF
HIGH-RES GUIDANCE SUGGESTS TSRA POTENTIAL MAY BE GREATER JUST
EAST/SOUTH OF CHICAGO TERMINALS SATURDAY AFTERNOON. OUTSIDE OF ANY
PRECIP VIS REDUCTION EARLY SATURDAY...SOME MVFR HAZE POSSIBLE
OVERNIGHT IN MOIST WARM SECTOR AIR.

WINDS...GENERALLY SOUTH 10-12 KT WITH GUSTS TO 20 KT OR SO
POSSIBLE THIS AFTERNOON. WIND MAY BACK A BIT TO THE SOUTH-
SOUTHEAST LATE THIS AFTERNOON/EARLY EVENING AS SURFACE WARM
FRONT APPROACHES...BEFORE SHIFTING SOUTHWEST OVERNIGHT AND SUNDAY
AHEAD OF THE COLD FRONT. DEEPER MIXING SUNDAY SUGGESTS GUSTS AGAIN
IN THE 20 KT RANGE OR A LITTLE HIGHER DURING THE LATE MORNING AND
AFTERNOON.

RATZER

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

* MEDIUM IN SHRA/TSRA BEING LOW IN COVERAGE IN IMMEDIATE TERMINAL
  AREA THIS AFTERNOON...GREATER COVERAGE EAST/SOUTH OF CHICAGO.

* LOW IN TSRA TIMING/COVERAGE LATER TONIGHT/SATURDAY.

* MEDIUM-HIGH IN WIND TRENDS THROUGH PERIOD.

RATZER

//OUTLOOK FOR ORD/MDW FOR 00Z SUNDAY-12Z FRIDAY...UPDATED 12Z...

* SATURDAY NIGHT THROUGH SUNDAY NIGHT...VFR. WX NIL.

* MONDAY...CHANCE OF TSRA.

* TUESDAY...VFR. WX NIL.

* WEDNESDAY THROUGH THURSDAY NIGHT...SLIGHT CHANCE OF TSRA

KREIN

&&

.MARINE...
221 PM CDT

MODERATE SOUTHERLY WINDS ARE IN PLACE TODAY AHEAD OF LOW PRESSURE
OVER THE NORTHERN PLAINS. SOUTH TO SOUTHWEST WINDS 20 TO 25 KT
WITH AN OCCASIONAL 30 KT GUSTS POSSIBLE WILL BE IN PLACE THROUGH
TOMORROW...THEN A COLD FRONT WILL START TO PUSH ACROSS THE LAKE
TURNING WINDS NORTHWESTERLY. HIGH PRESSURE WILL PROVIDE A BRIEF
LULL IN THE WINDS SUNDAY ALLOWING LAKE BREEZES TO DEVELOP...BUT
THEN SOUTHERLY WINDS RAMP BACK UP TO 25 TO 30 KT SUNDAY NIGHT INTO
MONDAY AHEAD OF ANOTHER LOW. THIS LOW IS PROGGED TO DEEPEN AS IT
LIFTS FROM THE NORTHERN PLAINS SUNDAY TO HUDSON BAY LATE MONDAY.

BMD

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO










000
FXUS63 KLOT 291958
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
258 PM CDT FRI AUG 29 2014

.DISCUSSION...
221 PM CDT

SYNOPSIS...UNSETTLED WEATHER CONTINUES THROUGH TOMORROW WITH
SCATTERED THUNDERSTORMS EXPECTED.  CONFIDENCE REMAINS LOW IN WHEN
AND WHERE THUNDERSTORMS WILL FORM.  SUNDAY STILL LOOKS DRY BUT
MULTIPLE CHANCES FOR STORMS RETURN MONDAY THROUGH THE END OF THE
WEEK. ABOVE NORMAL TEMPERATURES ARE ALSO EXPECTED THROUGH THE PERIOD
AS WELL.

//NEAR TERM FORECAST//

THROUGH TONIGHT...
A LARGE RIDGE IS OVER THE EAST COAST WHILE A TROUGH IS OVER THE
PLAINS.  THE TROUGH WILL WEAKEN AS IT APPROACHES OUR AREA AND PASS
OVERHEAD LATE SATURDAY NIGHT INTO SUNDAY MORNING. AT THE SURFACE THE
HIGH HAS PUSHED EAST WHILE A DEVELOPING LOW PRESSURE SYSTEM IS OVER
MINNESOTA.  THE LOWS WARM FRONT LIES TO OUR SOUTH ACROSS SOUTHERN
IL...AND IT WILL LIFT NORTH THROUGH THE REGION THIS AFTERNOON.

HAVE VERY LOW CONFIDENCE IN EXACT TIMING AND LOCATION OF
THUNDERSTORMS THROUGH THIS EVENING.  THERE IS NO CLEAR FORCING
MECHANISM BUT WITH AROUND 2000 J/KG OF CAPE AVAILABLE...STORMS ARE
CERTAINLY POSSIBLE. PWAT VALUES ARE AROUND 2 INCHES SO THE MAIN
CONCERN REMAINS HEAVY DOWNPOURS. THE STRONGEST STORMS MAY PRODUCE
WIND GUSTS TO 50 KT BUT NO SEVERE WEATHER IS EXPECTED AS WIND SHEAR
IS BASICALLY NIL.

FOR POPS USED A BLEND OF NEAR TERM GUIDANCE WHICH HAS BEEN DOING
REASONABLY WELL THIS MORNING.  HOWEVER...KEPT A CHANCE OF STORMS
ACROSS THE REGION THIS AFTERNOON AND EVENING DUE TO THE SCATTERED
NATURE OF THE STORMS THAT ARE EXPECTED.  A WASH OUT IS NOT
EXPECTED.  THE BEST CHANCE FOR WIDESPREAD STORMS WILL BE OVERNIGHT
AS THE UPPER LEVEL TROUGH APPROACHES. IN FACT THE STORMS ASSOCIATED
WITH THE TROUGH STRETCH FROM MINNESOTA THROUGH ARKANSAS.  MODELS
DIFFER IN HOW WELL THIS AREA OF PRECIP WILL HOLD TOGETHER SO LIMITED
POPS TO THE LIKELY CATEGORY.

LOWS WILL BE IN THE UPPER 60S TO LOWER 70S TONIGHT AND FOG IS
POSSIBLE. GIVEN THAT WE HAVE NOT SEEN MUCH RAIN TODAY...HAVE LIMITED
CONFIDENCE SO LEFT FOG OUT OF THE FORECAST FOR NOW.

SATURDAY AND SATURDAY NIGHT...
THE SURFACE LOW PASSES OVER LAKE MICHIGAN SATURDAY AFTERNOON WHILE
ITS COLD FRONT GETS DRAGGED THROUGH THE AREA SATURDAY
AFTERNOON/EVENING.  SCATTERED STORMS ARE AGAIN POSSIBLE IN THE
MORNING IN THE WARM AND MOIST ENVIRONMENT WITH LINGERING 2 INCH PWAT
VALUES. STORMS WILL THEN FORM ALONG THE COLD FRONT SOUTH OF A GARY
IN TO PONTIAC IL LINE. STORMS ARE POSSIBLE NORTH AND WEST OF THIS
LINE...BUT CONFIDENCE IS SIGNIFICANTLY LOWER.

CAPE VALUES WILL BE AROUND 1000 J/KG TOMORROW WITH WEAK SHEAR ONCE
AGAIN. THEREFORE EXPECTING STORMS TO PRODUCE HEAVY DOWNPOURS AND THE
STRONGEST MAY BE CAPABLE OF GUSTY WINDS.  SEVERE WEATHER IS NOT
EXPECTED.

TOMORROW LOOKS LIKE ANOTHER WARM AND STICKY DAY AHEAD OF THE COLD
FRONT.  LOWS WILL BE IN THE 60S AND FOG IS POSSIBLE OVERNIGHT.

JEE

//EXTENDED FORECAST//

SUNDAY...
EXPECT A BRIEF LULL IN THE PRECIP CHANCES DURING MUCH OF THE DAY
SUNDAY AS THE FIRST COLD FRONT DEPARTS TO THE EAST AND ANOTHER LOW
TAKES SHAPE OVER THE NORTHERN PLAINS. IN BETWEEN THESE TWO
SYSTEMS...WEAK INDUCED SURFACE HIGH SHOULD RESULT IN QUIET WEATHER
LOCALLY...WITH THE H85 THERMAL RIDGE ADVECTING OVERHEARD THROUGHOUT
THE DAY. RETURN FLOW WILL HELP PUSH THE DEWPOINTS BACK UP TO AROUND
70 WITH AFTERNOON HIGH TEMPS EXPECTED TO BE IN THE MID 80S. STEEP
LOW/MID LEVEL LAPSE RATES WILL RESULT IN MODERATE INSTABILITY
DEVELOPING DURING THE AFTERNOON...BUT MODEST SBCIN IS PROGGED TO
STAY IN PLACE CAPPING ANY SURFACE BASED CONVECTION. IN ADDITION...
THE AREA SHOULD BE SQUARELY UNDER AREA OF MID LEVEL HEIGHT RISES
WHICH SHOULD HELP REINFORCE THE INVERSION...AND NO SIGNIFICANT
FORCING NOTED OVER THE AREA.

MONDAY...
TROUGHING CURRENTLY MOVING ONSHORE OVER THE PAC NORTHWEST TODAY WILL
MOVE ACROSS THE CENTRAL PLAINS THIS WEEKEND...THEN BEGIN TO LIFT
ACROSS THE UPPER MIDWEST EARLY NEXT WEEK. SURFACE LOW IS PROGGED TO
DEEPEN FROM THE NORTHERN PLAINS SUNDAY AS IT LIFTS TO NEAR HUDSON
BAY LATE ON MONDAY. THIS WILL DRAG A COLD FRONT ACROSS THE REGION ON
MONDAY. WITH THE LOW LIFTING AWAY FROM THE AREA...CONVERGENCE ALONG
THE FRONT IS PROGGED TO WEAKEN AS IT COMES ACROSS NORTHERN ILLINOIS
EARLY MONDAY WITH THE BETTER DYNAMICS STAYING TO OUR NORTH.
MEANWHILE...THE LOCAL AREA APPEARS TO LIE ON THE NORTHERN PERIPHERY
OF THE BETTER INSTABILITY TO OUR SOUTH. GFS SHOWS SOME HINTS THAT
PARTICULARLY NORTH CENTRAL ILLINOIS MAY BE SPLIT BY THE
PRECIP...ESPECIALLY CONSIDERING THE CAPPING EARLY IN THE DAY...BUT
WILL HOLD OFF ON FINE TUNING THIS DETAIL FOR NOW. IN ADDITION...THE
REGION DOES FALL WITHIN AN OVERLAPPED AREA OF FAVORABLE
SHEAR/INSTABILITY THAT COULD POTENTIALLY SUPPORT A SEVERE WEATHER
THREAT.

TUESDAY THROUGH FRIDAY...
FRONTAL BOUNDARY IS PROGGED TO STALL ACROSS/NEAR CENTRAL ILLINOIS
TUESDAY GRADUALLY LIFTING BACK NORTH ACROSS THE FORECAST AREA BY THE
END OF THE WORK WEEK AS A SERIES OF UPPER LEVEL DISTURBANCES MOVE
ACROSS THE REGION. THIS WILL RESULT IN PERIODIC CHANCES FOR SHOWERS
AND THUNDERSTORMS ACROSS THE AREA...THOUGH TIMING AND LOCATION
DETAILS WILL BE DIFFICULT TO PIN DOWN THIS FAR OUT GIVEN THE
PATTERN. THE ATMOSPHERE REMAINS QUITE SOUPY IN THE VICINITY OF THE
FRONT WHERE PWATS REMAIN AROUND 2 INCHES. THUS THE HEAVY RAIN AND
FLOODING THREAT WILL HAVE TO BE CLOSELY MONITORED THROUGH MUCH OF
THE UPCOMING WEEK.

DEUBELBEISS

&&

.AVIATION...

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

* ISOLATED-SCATTERED SHRA/TSRA THIS AFTERNOON THRU EARLY EVENING.

* SOUTH WINDS WITH GUSTS 15-20 KT THIS AFTERNOON.

* ANOTHER PERIOD OF SHRA/TSRA LIKELY AFTER MIDNIGHT INTO SATURDAY
  MORNING.

* SOUTHWEST WINDS GUSTING AROUND 20 KT SATURDAY.

RATZER

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

ISOLATED TSRA DEVELOPING FROM NORTHEAST OF DOWNTOWN CHICAGO SOUTH
INTO IKK AREA. THINK COVERAGE WILL REMAIN FAIRLY LOW...THOUGH HAVE
ADDED VCTS FOR THE NEXT FEW HOURS FOR CHICAGO TERMINALS AS THEY
WILL BE SPARSE BUT IN THE NEIGHBORHOOD SO TO SPEAK.

RATZER

PREVIOUS DISCUSSION FROM 18Z...

FAIRLY LOW CONFIDENCE CONVECTIVE FORECAST THIS PERIOD...WITH
TERMINALS WITHIN A BROAD AREA OF SOUTH WARM/MOIST ADVECTION
DOWNSTREAM OF AN UPPER TROUGH OVER THE CENTRAL PLAINS BUT WITH
OTHERWISE LITTLE ORGANIZED FOCUS FOR TSRA.

SATELLITE EVIDENCE OF WEAK MID-LEVEL DISTURBANCE OVER NORTHEAST
IL EARLY THIS AFTERNOON...WITH MORNING ELEVATED SHRA/TSRA DECAYING
OVER NORTH CENTRAL IL. DIURNAL TSRA WERE FORMING IN LOW LEVEL
INSTABILITY AXIS ALONG IL/IN BORDER REGION GENERALLY ALONG A DEC-
GIJ-MKG LINE...AND THIS LOOKS TO REMAIN THE FOCUS REGION FOR
HIGHEST COVERAGE TSRA THIS AFTERNOON. HIGH-RES GUIDANCE STILL
DEVELOPS SOME ISOLATED SHRA/TSRA INTO THE TERMINAL REGION IN
ASSOCIATION WITH AFOREMENTIONED MID-LEVEL DISTURBANCE AND NORTH
OF SURFACE WARM FRONT WHICH IS ACROSS DOWNSTATE IL AT THIS TIME...
THOUGH COVERAGE IS EXPECTED TO REMAIN LOW. A GREATER CHANCE OF
SHRA/TSRA APPEARS TO BE LATE TONIGHT AND EARLY SATURDAY AS THE
MAIN UPPER TROUGH APPROACHES. WEAK COLD FRONT APPROACHES FROM THE
WEST SATURDAY MIDDAY AND AFTERNOON...WITH THUNDERSTORMS EXPECTED
TO DEVELOP ALONG THE FRONT BY EARLY AFTERNOON. CURRENT SUITE OF
HIGH-RES GUIDANCE SUGGESTS TSRA POTENTIAL MAY BE GREATER JUST
EAST/SOUTH OF CHICAGO TERMINALS SATURDAY AFTERNOON. OUTSIDE OF ANY
PRECIP VIS REDUCTION EARLY SATURDAY...SOME MVFR HAZE POSSIBLE
OVERNIGHT IN MOIST WARM SECTOR AIR.

WINDS...GENERALLY SOUTH 10-12 KT WITH GUSTS TO 20 KT OR SO
POSSIBLE THIS AFTERNOON. WIND MAY BACK A BIT TO THE SOUTH-
SOUTHEAST LATE THIS AFTERNOON/EARLY EVENING AS SURFACE WARM
FRONT APPROACHES...BEFORE SHIFTING SOUTHWEST OVERNIGHT AND SUNDAY
AHEAD OF THE COLD FRONT. DEEPER MIXING SUNDAY SUGGESTS GUSTS AGAIN
IN THE 20 KT RANGE OR A LITTLE HIGHER DURING THE LATE MORNING AND
AFTERNOON.

RATZER

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

* MEDIUM IN SHRA/TSRA BEING LOW IN COVERAGE IN IMMEDIATE TERMINAL
  AREA THIS AFTERNOON...GREATER COVERAGE EAST/SOUTH OF CHICAGO.

* LOW IN TSRA TIMING/COVERAGE LATER TONIGHT/SATURDAY.

* MEDIUM-HIGH IN WIND TRENDS THROUGH PERIOD.

RATZER

//OUTLOOK FOR ORD/MDW FOR 00Z SUNDAY-12Z FRIDAY...UPDATED 12Z...

* SATURDAY NIGHT THROUGH SUNDAY NIGHT...VFR. WX NIL.

* MONDAY...CHANCE OF TSRA.

* TUESDAY...VFR. WX NIL.

* WEDNESDAY THROUGH THURSDAY NIGHT...SLIGHT CHANCE OF TSRA

KREIN

&&

.MARINE...
221 PM CDT

MODERATE SOUTHERLY WINDS ARE IN PLACE TODAY AHEAD OF LOW PRESSURE
OVER THE NORTHERN PLAINS. SOUTH TO SOUTHWEST WINDS 20 TO 25 KT
WITH AN OCCASIONAL 30 KT GUSTS POSSIBLE WILL BE IN PLACE THROUGH
TOMORROW...THEN A COLD FRONT WILL START TO PUSH ACROSS THE LAKE
TURNING WINDS NORTHWESTERLY. HIGH PRESSURE WILL PROVIDE A BRIEF
LULL IN THE WINDS SUNDAY ALLOWING LAKE BREEZES TO DEVELOP...BUT
THEN SOUTHERLY WINDS RAMP BACK UP TO 25 TO 30 KT SUNDAY NIGHT INTO
MONDAY AHEAD OF ANOTHER LOW. THIS LOW IS PROGGED TO DEEPEN AS IT
LIFTS FROM THE NORTHERN PLAINS SUNDAY TO HUDSON BAY LATE MONDAY.

BMD

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO











000
FXUS63 KLOT 291950
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
250 PM CDT FRI AUG 29 2014

.DISCUSSION...
326 AM CDT

THE MAIN FORECAST CONCERNS WILL CENTER AROUND CONVECTIVE CHANCES AND
TIMING...AS WELL AS TEMPERATURES TODAY...AND THROUGH THE HOLIDAY WEEKEND.

CURRENTLY...THE REMNANT MCV FROM YESTERDAY EVENINGS SHOWERS AND
STORMS CONTINUES TO SHIFT ACROSS MY SOUTHERN COUNTIES EARLY THIS
MORNING. HOWEVER...ONLY A FEW LIGHT SHOWERS/SPRINKLES REMAIN ACROSS
THIS AREA...WITH DRIER AND FAIRLY STABLE CONDITIONS IN PLACE TO THE EAST.

ANOTHER AREA OF CONVECTION IS ONGOING TO OUR WEST ACROSS IOWA AND
INTO SOUTHERN MN. THIS ACTIVITY IS OCCURRING WITHIN A REGION OF GOOD
LOWER LEVEL WARM AIR ADVECTION/ISENTROPIC ASCENT ON THE DOWNSTREAM
PERIPHERY OF A REMNANT MID/UPPER LEVEL TROUGH OVER THE PLAINS STATES.
DOWN STREAM UPPER RIDGING OVER THE GREAT LAKES REGION IS LEADING TO A
STEERING FLOW TO THE NORTHEAST. THEREFORE...MOST IF NOT ALL OF THIS
CONVECTIVE ACTIVITY WILL SHIFT INTO SOUTHERN WISCONSIN AND PERHAPS
FAR NORTHWESTERN ILLINOIS THIS MORNING. IN SPITE OF THIS...I HAVE
LEFT SLIGHT CHANCE POPS IN THIS MORNING AS IT IS POSSIBLE THAT SOME
ADDITIONAL CELLS COULD DEVELOP IN ASSOCIATION WITH AN EASTWARD MOVING
OUTFLOW BOUNDARY...AS EVIDENT OFF OF THE DMX RADAR MOVING TOWARDS
EASTERN IOWA. THIS ACTIVITY...IF IT OCCURS IN ANY OF NORTHERN
ILLINOIS EARLY THIS MORNING...WOULD LIKELY BE ISOLATED TO WIDELY
SCATTERED...WITH THE MAIN FOCUS REMAINING NORTH.

A SURFACE WARM FRONT IS EXPECTED TO LIFT NORTHWARD OVER THE AREA
INTO THIS AFTERNOON...WITH A WARMER AIRMASS EXPECTED IN ITS WAKE. IN
SPITE OF THIS...HOWEVER...HIGH TEMPERATURES ACROSS THE AREA WILL BE
TRICKY AS IT APPEARS THAT SOME SCATTERED THUNDERSTORMS COULD DEVELOP
ACROSS PORTIONS OF THE AREA THIS AFTERNOON...AND HAMPER THE MAGNITUDE
OF THE WARMTH ACROSS SOME AREAS. MODEST HEIGHT FALLS ALOFT ARE FORECAST
ACROSS NORTHERN ILLINOIS IN ASSOCIATION WITH THE AFOREMENTIONED UPPER
TROUGH SHIFTING EASTWARD OVER THE MID MISSOURI VALLEY THIS
AFTERNOON. IN SPITE OF THE FACT THAT THE BEST LARGE SCALE FORCING
FOR ASCENT WITH THIS DISTURBANCE SHOULD REMAIN WEST OF THE AREA THIS
AFTERNOON...THE EXPECTED INCREASE IN LOW-LEVEL THETA E IS EXPECTED
TO PRODUCE AN UNCAPPED ATMOSPHERE FEATURING MLCAPES OF AROUND 1500
J/KG BY THIS AFTERNOON. A MAJORITY OF THE GLOBAL MODELS...AS WELL AS
THE HIRES CONVECTIVE ALLOWING MODELS FIRE UP ACTIVITY WITHIN THIS
REGIME THIS AFTERNOON. IT APPEARS WE WILL HAVE TO WATCH MORNING
CLOUD COVER...HOWEVER...AS THIS COULD INHIBIT THE DEGREE OF
WARMING A BIT THROUGH THE MORNING...AND POSSIBLY LEAD TO WEAKER
INSTABILITY THAN WHAT THE MODELS ARE CURRENTLY ADVERTISING.

IF THE CONVECTION DOES DEVELOP AS  EXPECTED...MARGINAL DEEP LAYER
SHEAR OF 25 TO 30 KT COULD ALLOW FOR A FEW STRONGER STORMS CAPABLE
OF SOME ISOLATED HIGH WIND GUSTS. SOME TORRENTIAL DOWNPOURS WOULD
ALSO BE A THREAT FROM THESE STORMS GIVEN THE JUICY AIRMASS FEATURING
PWATS UP AROUND 1.75 INCHES. HOWEVER...EXTREME RAINFALL AMOUNTS
APPEAR UNLIKELY GIVEN STORM MOTIONS SHOULD BE TO THE NORTHEAST
AROUND 30 KT. SO THE STORMS SHOULD NOT BE OVER A GIVEN AREA TOO
LONG. MUCH OF THIS ACTIVITY APPEARS TO BE HIGHLY DIURNAL IN
NATURE...SO A RAPID DOWNWARD TREND IS EXPECTED AFTER SUNSET THIS
EVENING.

ANOTHER ROUND OF THUNDERSTORMS APPEARS LIKELY ON
SATURDAY...ESPECIALLY DURING THE MORNING AS THE UPPER LEVEL
TROUGH...AND AN ASSOCIATED SURFACE LOW AND COLD FRONT SHIFTS
EASTWARD ACROSS ACROSS SOUTHERN WI AND NORTHERN IL. THIS ACTIVITY
COULD LINGER INTO SATURDAY EVENING ACROSS MY FAR SOUTHEASTERN
COUNTIES. HOWEVER...IT APPEARS THAT FOLLOWING THIS FRONTAL PASSAGE
WE WILL BE GREETED WITH A NICE DRY SUNDAY ACROSS THE AREA.

UNFORTUNATELY...LABOR DAY APPEARS THAT IT COULD BE ANOTHER ACTIVE
WEATHER DAY ACROSS THE REGION. ANOTHER POTENT UPPER LEVEL
DISTURBANCE AND SURFACE FRONT IS FORECAST TO SHIFT OVER THE AREA BY
MONDAY. WE WILL ALSO HAVE TO WATCH FOR THE THREAT OF SEVERE
THUNDERSTORMS ON MONDAY AND MONDAY NIGHT AS A 45 TO 50 KT MID LEVEL
JET IS PROGGED TO DEVELOP ACROSS THE AREA. THIS COULD RESULT IN DEEP
LAYER SHEAR STRONG ENOUGH TO PRODUCE MORE ORGANIZED STRONG TO SEVERE
CONVECTION. VERY HEAVY RAINFALL WOULD AGAIN BE A CONCERN WITH THIS
ACTIVITY...ESPECIALLY IF THE FRONTAL ZONE STALLS OUT OVER THE AREA
MONDAY NIGHT. AT THIS TIME...HOWEVER...UNCERTAINTY IS HIGH ON WHERE
THE SURFACE FRONT MAY STALL AND HENCE WHAT AREAS COULD BE FAVORED FOR
EXTENDED PERIODS OF VERY HEAVY RAINFALL.

THE ACTIVE WEATHER PATTERN COULD SHIFT SOUTH OF THE AREA FOR A DAY
OR TWO INTO MID TO LATE WEEK BEFORE MORE PERIODS OF CONVECTION ARE
POSSIBLE. OVERALL...IT APPEARS TEMPERATURES WILL REMAIN ON THE WARM
SIDE OF AVERAGE...WITH THE POTENTIAL FOR SOME VERY WARM AND HUMID DAYS
LATER NEXT WEEK.

KJB

&&

.AVIATION...

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

* ISOLATED-SCATTERED SHRA/TSRA THIS AFTERNOON THRU EARLY EVENING.

* SOUTH WINDS WITH GUSTS 15-20 KT THIS AFTERNOON.

* ANOTHER PERIOD OF SHRA/TSRA LIKELY AFTER MIDNIGHT INTO SATURDAY
  MORNING.

* SOUTHWEST WINDS GUSTING AROUND 20 KT SATURDAY.

RATZER

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

ISOLATED TSRA DEVELOPING FROM NORTHEAST OF DOWNTOWN CHICAGO SOUTH
INTO IKK AREA. THINK COVERAGE WILL REMAIN FAIRLY LOW...THOUGH HAVE
ADDED VCTS FOR THE NEXT FEW HOURS FOR CHICAGO TERMINALS AS THEY
WILL BE SPARSE BUT IN THE NEIGHBORHOOD SO TO SPEAK.

RATZER

PREVIOUS DISCUSSION FROM 18Z...

FAIRLY LOW CONFIDENCE CONVECTIVE FORECAST THIS PERIOD...WITH
TERMINALS WITHIN A BROAD AREA OF SOUTH WARM/MOIST ADVECTION
DOWNSTREAM OF AN UPPER TROUGH OVER THE CENTRAL PLAINS BUT WITH
OTHERWISE LITTLE ORGANIZED FOCUS FOR TSRA.

SATELLITE EVIDENCE OF WEAK MID-LEVEL DISTURBANCE OVER NORTHEAST
IL EARLY THIS AFTERNOON...WITH MORNING ELEVATED SHRA/TSRA DECAYING
OVER NORTH CENTRAL IL. DIURNAL TSRA WERE FORMING IN LOW LEVEL
INSTABILITY AXIS ALONG IL/IN BORDER REGION GENERALLY ALONG A DEC-
GIJ-MKG LINE...AND THIS LOOKS TO REMAIN THE FOCUS REGION FOR
HIGHEST COVERAGE TSRA THIS AFTERNOON. HIGH-RES GUIDANCE STILL
DEVELOPS SOME ISOLATED SHRA/TSRA INTO THE TERMINAL REGION IN
ASSOCIATION WITH AFOREMENTIONED MID-LEVEL DISTURBANCE AND NORTH
OF SURFACE WARM FRONT WHICH IS ACROSS DOWNSTATE IL AT THIS TIME...
THOUGH COVERAGE IS EXPECTED TO REMAIN LOW. A GREATER CHANCE OF
SHRA/TSRA APPEARS TO BE LATE TONIGHT AND EARLY SATURDAY AS THE
MAIN UPPER TROUGH APPROACHES. WEAK COLD FRONT APPROACHES FROM THE
WEST SATURDAY MIDDAY AND AFTERNOON...WITH THUNDERSTORMS EXPECTED
TO DEVELOP ALONG THE FRONT BY EARLY AFTERNOON. CURRENT SUITE OF
HIGH-RES GUIDANCE SUGGESTS TSRA POTENTIAL MAY BE GREATER JUST
EAST/SOUTH OF CHICAGO TERMINALS SATURDAY AFTERNOON. OUTSIDE OF ANY
PRECIP VIS REDUCTION EARLY SATURDAY...SOME MVFR HAZE POSSIBLE
OVERNIGHT IN MOIST WARM SECTOR AIR.

WINDS...GENERALLY SOUTH 10-12 KT WITH GUSTS TO 20 KT OR SO
POSSIBLE THIS AFTERNOON. WIND MAY BACK A BIT TO THE SOUTH-
SOUTHEAST LATE THIS AFTERNOON/EARLY EVENING AS SURFACE WARM
FRONT APPROACHES...BEFORE SHIFTING SOUTHWEST OVERNIGHT AND SUNDAY
AHEAD OF THE COLD FRONT. DEEPER MIXING SUNDAY SUGGESTS GUSTS AGAIN
IN THE 20 KT RANGE OR A LITTLE HIGHER DURING THE LATE MORNING AND
AFTERNOON.

RATZER

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

* MEDIUM IN SHRA/TSRA BEING LOW IN COVERAGE IN IMMEDIATE TERMINAL
  AREA THIS AFTERNOON...GREATER COVERAGE EAST/SOUTH OF CHICAGO.

* LOW IN TSRA TIMING/COVERAGE LATER TONIGHT/SATURDAY.

* MEDIUM-HIGH IN WIND TRENDS THROUGH PERIOD.

RATZER

//OUTLOOK FOR ORD/MDW FOR 00Z SUNDAY-12Z FRIDAY...UPDATED 12Z...

* SATURDAY NIGHT THROUGH SUNDAY NIGHT...VFR. WX NIL.

* MONDAY...CHANCE OF TSRA.

* TUESDAY...VFR. WX NIL.

* WEDNESDAY THROUGH THURSDAY NIGHT...SLIGHT CHANCE OF TSRA

KREIN

&&

.MARINE...
315 AM CDT

HIGH PRESSURE OVER THE EASTERN GREAT LAKES WILL MOVE EAST OFF THE
NEW ENGLAND COAST FRIDAY EVENING...WHILE A TROUGH OF LOW PRESSURE
DEVELOPS ACROSS THE CENTRAL PLAINS AND UPPER MIDWEST. THIS WILL
SET UP A PERIOD OF SOUTHERLY WINDS AND AS THE TROUGH MOVES
EAST...THE GRADIENT OVER THE LAKE WILL STRENGTHEN AND WINDS SHOULD
INCREASE TO THE 20-25 KT RANGE. A DEEPENING LOW CENTER WITHIN THE
TROUGH WILL MOVE TO WISCONSIN SATURDAY AND ACROSS NORTHERN LAKE
MICHIGAN SATURDAY EVENING. AS THE LOW TRACKS TO THE NORTHEAST...AN
ASSOCIATED COLD FRONT WILL MOVE DOWN THE LAKE SATURDAY AFTERNOON
AND EVENING...QUICKLY SHIFTING WINDS TO NWLY FOLLOWING THE FROPA.
THE LATEST MODEL GUIDANCE SUGGESTS THAT THE FRONT WILL WASH OUT
LATE SATURDAY NIGHT BEFORE REACHING THE SOUTH END OF THE LAKE AND
WINDS THERE SHOULD NEVER TRULY SHIFT NWLY...BUT RATHER BECOMING
LIGHT AND VARIABLE LATE SATURDAY NIGHT THROUGH SUNDAY MORNING. A
DEEPER LOW IS EXPECTED TO DEVELOP OVER THE DAKOTAS AND LIFT
THROUGH WESTERN ONTARIO SUNDAY NIGHT AND MONDAY BRINGING A RETURN
TO BRISK SOUTH TO SOUTHWEST WINDS TO THE LAKE FOR MONDAY AND
TUESDAY.

KREIN

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO







000
FXUS63 KLOT 291950
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
250 PM CDT FRI AUG 29 2014

.DISCUSSION...
326 AM CDT

THE MAIN FORECAST CONCERNS WILL CENTER AROUND CONVECTIVE CHANCES AND
TIMING...AS WELL AS TEMPERATURES TODAY...AND THROUGH THE HOLIDAY WEEKEND.

CURRENTLY...THE REMNANT MCV FROM YESTERDAY EVENINGS SHOWERS AND
STORMS CONTINUES TO SHIFT ACROSS MY SOUTHERN COUNTIES EARLY THIS
MORNING. HOWEVER...ONLY A FEW LIGHT SHOWERS/SPRINKLES REMAIN ACROSS
THIS AREA...WITH DRIER AND FAIRLY STABLE CONDITIONS IN PLACE TO THE EAST.

ANOTHER AREA OF CONVECTION IS ONGOING TO OUR WEST ACROSS IOWA AND
INTO SOUTHERN MN. THIS ACTIVITY IS OCCURRING WITHIN A REGION OF GOOD
LOWER LEVEL WARM AIR ADVECTION/ISENTROPIC ASCENT ON THE DOWNSTREAM
PERIPHERY OF A REMNANT MID/UPPER LEVEL TROUGH OVER THE PLAINS STATES.
DOWN STREAM UPPER RIDGING OVER THE GREAT LAKES REGION IS LEADING TO A
STEERING FLOW TO THE NORTHEAST. THEREFORE...MOST IF NOT ALL OF THIS
CONVECTIVE ACTIVITY WILL SHIFT INTO SOUTHERN WISCONSIN AND PERHAPS
FAR NORTHWESTERN ILLINOIS THIS MORNING. IN SPITE OF THIS...I HAVE
LEFT SLIGHT CHANCE POPS IN THIS MORNING AS IT IS POSSIBLE THAT SOME
ADDITIONAL CELLS COULD DEVELOP IN ASSOCIATION WITH AN EASTWARD MOVING
OUTFLOW BOUNDARY...AS EVIDENT OFF OF THE DMX RADAR MOVING TOWARDS
EASTERN IOWA. THIS ACTIVITY...IF IT OCCURS IN ANY OF NORTHERN
ILLINOIS EARLY THIS MORNING...WOULD LIKELY BE ISOLATED TO WIDELY
SCATTERED...WITH THE MAIN FOCUS REMAINING NORTH.

A SURFACE WARM FRONT IS EXPECTED TO LIFT NORTHWARD OVER THE AREA
INTO THIS AFTERNOON...WITH A WARMER AIRMASS EXPECTED IN ITS WAKE. IN
SPITE OF THIS...HOWEVER...HIGH TEMPERATURES ACROSS THE AREA WILL BE
TRICKY AS IT APPEARS THAT SOME SCATTERED THUNDERSTORMS COULD DEVELOP
ACROSS PORTIONS OF THE AREA THIS AFTERNOON...AND HAMPER THE MAGNITUDE
OF THE WARMTH ACROSS SOME AREAS. MODEST HEIGHT FALLS ALOFT ARE FORECAST
ACROSS NORTHERN ILLINOIS IN ASSOCIATION WITH THE AFOREMENTIONED UPPER
TROUGH SHIFTING EASTWARD OVER THE MID MISSOURI VALLEY THIS
AFTERNOON. IN SPITE OF THE FACT THAT THE BEST LARGE SCALE FORCING
FOR ASCENT WITH THIS DISTURBANCE SHOULD REMAIN WEST OF THE AREA THIS
AFTERNOON...THE EXPECTED INCREASE IN LOW-LEVEL THETA E IS EXPECTED
TO PRODUCE AN UNCAPPED ATMOSPHERE FEATURING MLCAPES OF AROUND 1500
J/KG BY THIS AFTERNOON. A MAJORITY OF THE GLOBAL MODELS...AS WELL AS
THE HIRES CONVECTIVE ALLOWING MODELS FIRE UP ACTIVITY WITHIN THIS
REGIME THIS AFTERNOON. IT APPEARS WE WILL HAVE TO WATCH MORNING
CLOUD COVER...HOWEVER...AS THIS COULD INHIBIT THE DEGREE OF
WARMING A BIT THROUGH THE MORNING...AND POSSIBLY LEAD TO WEAKER
INSTABILITY THAN WHAT THE MODELS ARE CURRENTLY ADVERTISING.

IF THE CONVECTION DOES DEVELOP AS  EXPECTED...MARGINAL DEEP LAYER
SHEAR OF 25 TO 30 KT COULD ALLOW FOR A FEW STRONGER STORMS CAPABLE
OF SOME ISOLATED HIGH WIND GUSTS. SOME TORRENTIAL DOWNPOURS WOULD
ALSO BE A THREAT FROM THESE STORMS GIVEN THE JUICY AIRMASS FEATURING
PWATS UP AROUND 1.75 INCHES. HOWEVER...EXTREME RAINFALL AMOUNTS
APPEAR UNLIKELY GIVEN STORM MOTIONS SHOULD BE TO THE NORTHEAST
AROUND 30 KT. SO THE STORMS SHOULD NOT BE OVER A GIVEN AREA TOO
LONG. MUCH OF THIS ACTIVITY APPEARS TO BE HIGHLY DIURNAL IN
NATURE...SO A RAPID DOWNWARD TREND IS EXPECTED AFTER SUNSET THIS
EVENING.

ANOTHER ROUND OF THUNDERSTORMS APPEARS LIKELY ON
SATURDAY...ESPECIALLY DURING THE MORNING AS THE UPPER LEVEL
TROUGH...AND AN ASSOCIATED SURFACE LOW AND COLD FRONT SHIFTS
EASTWARD ACROSS ACROSS SOUTHERN WI AND NORTHERN IL. THIS ACTIVITY
COULD LINGER INTO SATURDAY EVENING ACROSS MY FAR SOUTHEASTERN
COUNTIES. HOWEVER...IT APPEARS THAT FOLLOWING THIS FRONTAL PASSAGE
WE WILL BE GREETED WITH A NICE DRY SUNDAY ACROSS THE AREA.

UNFORTUNATELY...LABOR DAY APPEARS THAT IT COULD BE ANOTHER ACTIVE
WEATHER DAY ACROSS THE REGION. ANOTHER POTENT UPPER LEVEL
DISTURBANCE AND SURFACE FRONT IS FORECAST TO SHIFT OVER THE AREA BY
MONDAY. WE WILL ALSO HAVE TO WATCH FOR THE THREAT OF SEVERE
THUNDERSTORMS ON MONDAY AND MONDAY NIGHT AS A 45 TO 50 KT MID LEVEL
JET IS PROGGED TO DEVELOP ACROSS THE AREA. THIS COULD RESULT IN DEEP
LAYER SHEAR STRONG ENOUGH TO PRODUCE MORE ORGANIZED STRONG TO SEVERE
CONVECTION. VERY HEAVY RAINFALL WOULD AGAIN BE A CONCERN WITH THIS
ACTIVITY...ESPECIALLY IF THE FRONTAL ZONE STALLS OUT OVER THE AREA
MONDAY NIGHT. AT THIS TIME...HOWEVER...UNCERTAINTY IS HIGH ON WHERE
THE SURFACE FRONT MAY STALL AND HENCE WHAT AREAS COULD BE FAVORED FOR
EXTENDED PERIODS OF VERY HEAVY RAINFALL.

THE ACTIVE WEATHER PATTERN COULD SHIFT SOUTH OF THE AREA FOR A DAY
OR TWO INTO MID TO LATE WEEK BEFORE MORE PERIODS OF CONVECTION ARE
POSSIBLE. OVERALL...IT APPEARS TEMPERATURES WILL REMAIN ON THE WARM
SIDE OF AVERAGE...WITH THE POTENTIAL FOR SOME VERY WARM AND HUMID DAYS
LATER NEXT WEEK.

KJB

&&

.AVIATION...

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

* ISOLATED-SCATTERED SHRA/TSRA THIS AFTERNOON THRU EARLY EVENING.

* SOUTH WINDS WITH GUSTS 15-20 KT THIS AFTERNOON.

* ANOTHER PERIOD OF SHRA/TSRA LIKELY AFTER MIDNIGHT INTO SATURDAY
  MORNING.

* SOUTHWEST WINDS GUSTING AROUND 20 KT SATURDAY.

RATZER

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

ISOLATED TSRA DEVELOPING FROM NORTHEAST OF DOWNTOWN CHICAGO SOUTH
INTO IKK AREA. THINK COVERAGE WILL REMAIN FAIRLY LOW...THOUGH HAVE
ADDED VCTS FOR THE NEXT FEW HOURS FOR CHICAGO TERMINALS AS THEY
WILL BE SPARSE BUT IN THE NEIGHBORHOOD SO TO SPEAK.

RATZER

PREVIOUS DISCUSSION FROM 18Z...

FAIRLY LOW CONFIDENCE CONVECTIVE FORECAST THIS PERIOD...WITH
TERMINALS WITHIN A BROAD AREA OF SOUTH WARM/MOIST ADVECTION
DOWNSTREAM OF AN UPPER TROUGH OVER THE CENTRAL PLAINS BUT WITH
OTHERWISE LITTLE ORGANIZED FOCUS FOR TSRA.

SATELLITE EVIDENCE OF WEAK MID-LEVEL DISTURBANCE OVER NORTHEAST
IL EARLY THIS AFTERNOON...WITH MORNING ELEVATED SHRA/TSRA DECAYING
OVER NORTH CENTRAL IL. DIURNAL TSRA WERE FORMING IN LOW LEVEL
INSTABILITY AXIS ALONG IL/IN BORDER REGION GENERALLY ALONG A DEC-
GIJ-MKG LINE...AND THIS LOOKS TO REMAIN THE FOCUS REGION FOR
HIGHEST COVERAGE TSRA THIS AFTERNOON. HIGH-RES GUIDANCE STILL
DEVELOPS SOME ISOLATED SHRA/TSRA INTO THE TERMINAL REGION IN
ASSOCIATION WITH AFOREMENTIONED MID-LEVEL DISTURBANCE AND NORTH
OF SURFACE WARM FRONT WHICH IS ACROSS DOWNSTATE IL AT THIS TIME...
THOUGH COVERAGE IS EXPECTED TO REMAIN LOW. A GREATER CHANCE OF
SHRA/TSRA APPEARS TO BE LATE TONIGHT AND EARLY SATURDAY AS THE
MAIN UPPER TROUGH APPROACHES. WEAK COLD FRONT APPROACHES FROM THE
WEST SATURDAY MIDDAY AND AFTERNOON...WITH THUNDERSTORMS EXPECTED
TO DEVELOP ALONG THE FRONT BY EARLY AFTERNOON. CURRENT SUITE OF
HIGH-RES GUIDANCE SUGGESTS TSRA POTENTIAL MAY BE GREATER JUST
EAST/SOUTH OF CHICAGO TERMINALS SATURDAY AFTERNOON. OUTSIDE OF ANY
PRECIP VIS REDUCTION EARLY SATURDAY...SOME MVFR HAZE POSSIBLE
OVERNIGHT IN MOIST WARM SECTOR AIR.

WINDS...GENERALLY SOUTH 10-12 KT WITH GUSTS TO 20 KT OR SO
POSSIBLE THIS AFTERNOON. WIND MAY BACK A BIT TO THE SOUTH-
SOUTHEAST LATE THIS AFTERNOON/EARLY EVENING AS SURFACE WARM
FRONT APPROACHES...BEFORE SHIFTING SOUTHWEST OVERNIGHT AND SUNDAY
AHEAD OF THE COLD FRONT. DEEPER MIXING SUNDAY SUGGESTS GUSTS AGAIN
IN THE 20 KT RANGE OR A LITTLE HIGHER DURING THE LATE MORNING AND
AFTERNOON.

RATZER

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

* MEDIUM IN SHRA/TSRA BEING LOW IN COVERAGE IN IMMEDIATE TERMINAL
  AREA THIS AFTERNOON...GREATER COVERAGE EAST/SOUTH OF CHICAGO.

* LOW IN TSRA TIMING/COVERAGE LATER TONIGHT/SATURDAY.

* MEDIUM-HIGH IN WIND TRENDS THROUGH PERIOD.

RATZER

//OUTLOOK FOR ORD/MDW FOR 00Z SUNDAY-12Z FRIDAY...UPDATED 12Z...

* SATURDAY NIGHT THROUGH SUNDAY NIGHT...VFR. WX NIL.

* MONDAY...CHANCE OF TSRA.

* TUESDAY...VFR. WX NIL.

* WEDNESDAY THROUGH THURSDAY NIGHT...SLIGHT CHANCE OF TSRA

KREIN

&&

.MARINE...
315 AM CDT

HIGH PRESSURE OVER THE EASTERN GREAT LAKES WILL MOVE EAST OFF THE
NEW ENGLAND COAST FRIDAY EVENING...WHILE A TROUGH OF LOW PRESSURE
DEVELOPS ACROSS THE CENTRAL PLAINS AND UPPER MIDWEST. THIS WILL
SET UP A PERIOD OF SOUTHERLY WINDS AND AS THE TROUGH MOVES
EAST...THE GRADIENT OVER THE LAKE WILL STRENGTHEN AND WINDS SHOULD
INCREASE TO THE 20-25 KT RANGE. A DEEPENING LOW CENTER WITHIN THE
TROUGH WILL MOVE TO WISCONSIN SATURDAY AND ACROSS NORTHERN LAKE
MICHIGAN SATURDAY EVENING. AS THE LOW TRACKS TO THE NORTHEAST...AN
ASSOCIATED COLD FRONT WILL MOVE DOWN THE LAKE SATURDAY AFTERNOON
AND EVENING...QUICKLY SHIFTING WINDS TO NWLY FOLLOWING THE FROPA.
THE LATEST MODEL GUIDANCE SUGGESTS THAT THE FRONT WILL WASH OUT
LATE SATURDAY NIGHT BEFORE REACHING THE SOUTH END OF THE LAKE AND
WINDS THERE SHOULD NEVER TRULY SHIFT NWLY...BUT RATHER BECOMING
LIGHT AND VARIABLE LATE SATURDAY NIGHT THROUGH SUNDAY MORNING. A
DEEPER LOW IS EXPECTED TO DEVELOP OVER THE DAKOTAS AND LIFT
THROUGH WESTERN ONTARIO SUNDAY NIGHT AND MONDAY BRINGING A RETURN
TO BRISK SOUTH TO SOUTHWEST WINDS TO THE LAKE FOR MONDAY AND
TUESDAY.

KREIN

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO








000
FXUS63 KLOT 291807
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
107 PM CDT FRI AUG 29 2014

.DISCUSSION...
326 AM CDT

THE MAIN FORECAST CONCERNS WILL CENTER AROUND CONVECTIVE CHANCES AND
TIMING...AS WELL AS TEMPERATURES TODAY...AND THROUGH THE HOLIDAY WEEKEND.

CURRENTLY...THE REMNANT MCV FROM YESTERDAY EVENINGS SHOWERS AND
STORMS CONTINUES TO SHIFT ACROSS MY SOUTHERN COUNTIES EARLY THIS
MORNING. HOWEVER...ONLY A FEW LIGHT SHOWERS/SPRINKLES REMAIN ACROSS
THIS AREA...WITH DRIER AND FAIRLY STABLE CONDITIONS IN PLACE TO THE EAST.

ANOTHER AREA OF CONVECTION IS ONGOING TO OUR WEST ACROSS IOWA AND
INTO SOUTHERN MN. THIS ACTIVITY IS OCCURRING WITHIN A REGION OF GOOD
LOWER LEVEL WARM AIR ADVECTION/ISENTROPIC ASCENT ON THE DOWNSTREAM
PERIPHERY OF A REMNANT MID/UPPER LEVEL TROUGH OVER THE PLAINS STATES.
DOWN STREAM UPPER RIDGING OVER THE GREAT LAKES REGION IS LEADING TO A
STEERING FLOW TO THE NORTHEAST. THEREFORE...MOST IF NOT ALL OF THIS
CONVECTIVE ACTIVITY WILL SHIFT INTO SOUTHERN WISCONSIN AND PERHAPS
FAR NORTHWESTERN ILLINOIS THIS MORNING. IN SPITE OF THIS...I HAVE
LEFT SLIGHT CHANCE POPS IN THIS MORNING AS IT IS POSSIBLE THAT SOME
ADDITIONAL CELLS COULD DEVELOP IN ASSOCIATION WITH AN EASTWARD MOVING
OUTFLOW BOUNDARY...AS EVIDENT OFF OF THE DMX RADAR MOVING TOWARDS
EASTERN IOWA. THIS ACTIVITY...IF IT OCCURS IN ANY OF NORTHERN
ILLINOIS EARLY THIS MORNING...WOULD LIKELY BE ISOLATED TO WIDELY
SCATTERED...WITH THE MAIN FOCUS REMAINING NORTH.

A SURFACE WARM FRONT IS EXPECTED TO LIFT NORTHWARD OVER THE AREA
INTO THIS AFTERNOON...WITH A WARMER AIRMASS EXPECTED IN ITS WAKE. IN
SPITE OF THIS...HOWEVER...HIGH TEMPERATURES ACROSS THE AREA WILL BE
TRICKY AS IT APPEARS THAT SOME SCATTERED THUNDERSTORMS COULD DEVELOP
ACROSS PORTIONS OF THE AREA THIS AFTERNOON...AND HAMPER THE MAGNITUDE
OF THE WARMTH ACROSS SOME AREAS. MODEST HEIGHT FALLS ALOFT ARE FORECAST
ACROSS NORTHERN ILLINOIS IN ASSOCIATION WITH THE AFOREMENTIONED UPPER
TROUGH SHIFTING EASTWARD OVER THE MID MISSOURI VALLEY THIS
AFTERNOON. IN SPITE OF THE FACT THAT THE BEST LARGE SCALE FORCING
FOR ASCENT WITH THIS DISTURBANCE SHOULD REMAIN WEST OF THE AREA THIS
AFTERNOON...THE EXPECTED INCREASE IN LOW-LEVEL THETA E IS EXPECTED
TO PRODUCE AN UNCAPPED ATMOSPHERE FEATURING MLCAPES OF AROUND 1500
J/KG BY THIS AFTERNOON. A MAJORITY OF THE GLOBAL MODELS...AS WELL AS
THE HIRES CONVECTIVE ALLOWING MODELS FIRE UP ACTIVITY WITHIN THIS
REGIME THIS AFTERNOON. IT APPEARS WE WILL HAVE TO WATCH MORNING
CLOUD COVER...HOWEVER...AS THIS COULD INHIBIT THE DEGREE OF
WARMING A BIT THROUGH THE MORNING...AND POSSIBLY LEAD TO WEAKER
INSTABILITY THAN WHAT THE MODELS ARE CURRENTLY ADVERTISING.

IF THE CONVECTION DOES DEVELOP AS  EXPECTED...MARGINAL DEEP LAYER
SHEAR OF 25 TO 30 KT COULD ALLOW FOR A FEW STRONGER STORMS CAPABLE
OF SOME ISOLATED HIGH WIND GUSTS. SOME TORRENTIAL DOWNPOURS WOULD
ALSO BE A THREAT FROM THESE STORMS GIVEN THE JUICY AIRMASS FEATURING
PWATS UP AROUND 1.75 INCHES. HOWEVER...EXTREME RAINFALL AMOUNTS
APPEAR UNLIKELY GIVEN STORM MOTIONS SHOULD BE TO THE NORTHEAST
AROUND 30 KT. SO THE STORMS SHOULD NOT BE OVER A GIVEN AREA TOO
LONG. MUCH OF THIS ACTIVITY APPEARS TO BE HIGHLY DIURNAL IN
NATURE...SO A RAPID DOWNWARD TREND IS EXPECTED AFTER SUNSET THIS
EVENING.

ANOTHER ROUND OF THUNDERSTORMS APPEARS LIKELY ON
SATURDAY...ESPECIALLY DURING THE MORNING AS THE UPPER LEVEL
TROUGH...AND AN ASSOCIATED SURFACE LOW AND COLD FRONT SHIFTS
EASTWARD ACROSS ACROSS SOUTHERN WI AND NORTHERN IL. THIS ACTIVITY
COULD LINGER INTO SATURDAY EVENING ACROSS MY FAR SOUTHEASTERN
COUNTIES. HOWEVER...IT APPEARS THAT FOLLOWING THIS FRONTAL PASSAGE
WE WILL BE GREETED WITH A NICE DRY SUNDAY ACROSS THE AREA.

UNFORTUNATELY...LABOR DAY APPEARS THAT IT COULD BE ANOTHER ACTIVE
WEATHER DAY ACROSS THE REGION. ANOTHER POTENT UPPER LEVEL
DISTURBANCE AND SURFACE FRONT IS FORECAST TO SHIFT OVER THE AREA BY
MONDAY. WE WILL ALSO HAVE TO WATCH FOR THE THREAT OF SEVERE
THUNDERSTORMS ON MONDAY AND MONDAY NIGHT AS A 45 TO 50 KT MID LEVEL
JET IS PROGGED TO DEVELOP ACROSS THE AREA. THIS COULD RESULT IN DEEP
LAYER SHEAR STRONG ENOUGH TO PRODUCE MORE ORGANIZED STRONG TO SEVERE
CONVECTION. VERY HEAVY RAINFALL WOULD AGAIN BE A CONCERN WITH THIS
ACTIVITY...ESPECIALLY IF THE FRONTAL ZONE STALLS OUT OVER THE AREA
MONDAY NIGHT. AT THIS TIME...HOWEVER...UNCERTAINTY IS HIGH ON WHERE
THE SURFACE FRONT MAY STALL AND HENCE WHAT AREAS COULD BE FAVORED FOR
EXTENDED PERIODS OF VERY HEAVY RAINFALL.

THE ACTIVE WEATHER PATTERN COULD SHIFT SOUTH OF THE AREA FOR A DAY
OR TWO INTO MID TO LATE WEEK BEFORE MORE PERIODS OF CONVECTION ARE
POSSIBLE. OVERALL...IT APPEARS TEMPERATURES WILL REMAIN ON THE WARM
SIDE OF AVERAGE...WITH THE POTENTIAL FOR SOME VERY WARM AND HUMID DAYS
LATER NEXT WEEK.

KJB

&&

.AVIATION...

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

* ISOLATED-SCATTERED SHRA/TSRA THIS AFTERNOON THRU EARLY EVENING.

* SOUTH WINDS WITH GUSTS 15-20 KT THIS AFTERNOON.

* ANOTHER PERIOD OF SHRA/TSRA LIKELY AFTER MIDNIGHT INTO SATURDAY
  MORNING.

* SOUTHWEST WINDS GUSTING AROUND 20 KT SATURDAY.

RATZER

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

FAIRLY LOW CONFIDENCE CONVECTIVE FORECAST THIS PERIOD...WITH
TERMINALS WITHIN A BROAD AREA OF SOUTH WARM/MOIST ADVECTION
DOWNSTREAM OF AN UPPER TROUGH OVER THE CENTRAL PLAINS BUT WITH
OTHERWISE LITTLE ORGANIZED FOCUS FOR TSRA.

SATELLITE EVIDENCE OF WEAK MID-LEVEL DISTURBANCE OVER NORTHEAST
IL EARLY THIS AFTERNOON...WITH MORNING ELEVATED SHRA/TSRA DECAYING
OVER NORTH CENTRAL IL. DIURNAL TSRA WERE FORMING IN LOW LEVEL
INSTABILITY AXIS ALONG IL/IN BORDER REGION GENERALLY ALONG A DEC-
GIJ-MKG LINE...AND THIS LOOKS TO REMAIN THE FOCUS REGION FOR
HIGHEST COVERAGE TSRA THIS AFTERNOON. HIGH-RES GUIDANCE STILL
DEVELOPS SOME ISOLATED SHRA/TSRA INTO THE TERMINAL REGION IN
ASSOCIATION WITH AFOREMENTIONED MID-LEVEL DISTURBANCE AND NORTH
OF SURFACE WARM FRONT WHICH IS ACROSS DOWNSTATE IL AT THIS TIME...
THOUGH COVERAGE IS EXPECTED TO REMAIN LOW. A GREATER CHANCE OF
SHRA/TSRA APPEARS TO BE LATE TONIGHT AND EARLY SATURDAY AS THE
MAIN UPPER TROUGH APPROACHES. WEAK COLD FRONT APPROACHES FROM THE
WEST SATURDAY MIDDAY AND AFTERNOON...WITH THUNDERSTORMS EXPECTED
TO DEVELOP ALONG THE FRONT BY EARLY AFTERNOON. CURRENT SUITE OF
HIGH-RES GUIDANCE SUGGESTS TSRA POTENTIAL MAY BE GREATER JUST
EAST/SOUTH OF CHICAGO TERMINALS SATURDAY AFTERNOON. OUTSIDE OF ANY
PRECIP VIS REDUCTION EARLY SATURDAY...SOME MVFR HAZE POSSIBLE
OVERNIGHT IN MOIST WARM SECTOR AIR.

WINDS...GENERALLY SOUTH 10-12 KT WITH GUSTS TO 20 KT OR SO
POSSIBLE THIS AFTERNOON. WIND MAY BACK A BIT TO THE SOUTH-
SOUTHEAST LATE THIS AFTERNOON/EARLY EVENING AS SURFACE WARM
FRONT APPROACHES...BEFORE SHIFTING SOUTHWEST OVERNIGHT AND SUNDAY
AHEAD OF THE COLD FRONT. DEEPER MIXING SUNDAY SUGGESTS GUSTS AGAIN
IN THE 20 KT RANGE OR A LITTLE HIGHER DURING THE LATE MORNING AND
AFTERNOON.

RATZER


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

* MEDIUM IN SHRA/TSRA BEING LOW IN COVERAGE IN IMMEDIATE TERMINAL
  AREA THIS AFTERNOON...GREATER COVERAGE EAST/SOUTH OF CHICAGO.

* LOW IN TSRA TIMING/COVERAGE LATER TONIGHT/SATURDAY.

* MEDIUM-HIGH IN WIND TRENDS THROUGH PERIOD.

RATZER

//OUTLOOK FOR ORD/MDW FOR 00Z SUNDAY-12Z FRIDAY...UPDATED 12Z...

* SATURDAY NIGHT THROUGH SUNDAY NIGHT...VFR. WX NIL.

* MONDAY...CHANCE OF TSRA.

* TUESDAY...VFR. WX NIL.

* WEDNESDAY THROUGH THURSDAY NIGHT...SLIGHT CHANCE OF TSRA

KREIN

&&

.MARINE...
315 AM CDT

HIGH PRESSURE OVER THE EASTERN GREAT LAKES WILL MOVE EAST OFF THE
NEW ENGLAND COAST FRIDAY EVENING...WHILE A TROUGH OF LOW PRESSURE
DEVELOPS ACROSS THE CENTRAL PLAINS AND UPPER MIDWEST. THIS WILL
SET UP A PERIOD OF SOUTHERLY WINDS AND AS THE TROUGH MOVES
EAST...THE GRADIENT OVER THE LAKE WILL STRENGTHEN AND WINDS SHOULD
INCREASE TO THE 20-25 KT RANGE. A DEEPENING LOW CENTER WITHIN THE
TROUGH WILL MOVE TO WISCONSIN SATURDAY AND ACROSS NORTHERN LAKE
MICHIGAN SATURDAY EVENING. AS THE LOW TRACKS TO THE NORTHEAST...AN
ASSOCIATED COLD FRONT WILL MOVE DOWN THE LAKE SATURDAY AFTERNOON
AND EVENING...QUICKLY SHIFTING WINDS TO NWLY FOLLOWING THE FROPA.
THE LATEST MODEL GUIDANCE SUGGESTS THAT THE FRONT WILL WASH OUT
LATE SATURDAY NIGHT BEFORE REACHING THE SOUTH END OF THE LAKE AND
WINDS THERE SHOULD NEVER TRULY SHIFT NWLY...BUT RATHER BECOMING
LIGHT AND VARIABLE LATE SATURDAY NIGHT THROUGH SUNDAY MORNING. A
DEEPER LOW IS EXPECTED TO DEVELOP OVER THE DAKOTAS AND LIFT
THROUGH WESTERN ONTARIO SUNDAY NIGHT AND MONDAY BRINGING A RETURN
TO BRISK SOUTH TO SOUTHWEST WINDS TO THE LAKE FOR MONDAY AND
TUESDAY.

KREIN

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO







000
FXUS63 KLOT 291807
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
107 PM CDT FRI AUG 29 2014

.DISCUSSION...
326 AM CDT

THE MAIN FORECAST CONCERNS WILL CENTER AROUND CONVECTIVE CHANCES AND
TIMING...AS WELL AS TEMPERATURES TODAY...AND THROUGH THE HOLIDAY WEEKEND.

CURRENTLY...THE REMNANT MCV FROM YESTERDAY EVENINGS SHOWERS AND
STORMS CONTINUES TO SHIFT ACROSS MY SOUTHERN COUNTIES EARLY THIS
MORNING. HOWEVER...ONLY A FEW LIGHT SHOWERS/SPRINKLES REMAIN ACROSS
THIS AREA...WITH DRIER AND FAIRLY STABLE CONDITIONS IN PLACE TO THE EAST.

ANOTHER AREA OF CONVECTION IS ONGOING TO OUR WEST ACROSS IOWA AND
INTO SOUTHERN MN. THIS ACTIVITY IS OCCURRING WITHIN A REGION OF GOOD
LOWER LEVEL WARM AIR ADVECTION/ISENTROPIC ASCENT ON THE DOWNSTREAM
PERIPHERY OF A REMNANT MID/UPPER LEVEL TROUGH OVER THE PLAINS STATES.
DOWN STREAM UPPER RIDGING OVER THE GREAT LAKES REGION IS LEADING TO A
STEERING FLOW TO THE NORTHEAST. THEREFORE...MOST IF NOT ALL OF THIS
CONVECTIVE ACTIVITY WILL SHIFT INTO SOUTHERN WISCONSIN AND PERHAPS
FAR NORTHWESTERN ILLINOIS THIS MORNING. IN SPITE OF THIS...I HAVE
LEFT SLIGHT CHANCE POPS IN THIS MORNING AS IT IS POSSIBLE THAT SOME
ADDITIONAL CELLS COULD DEVELOP IN ASSOCIATION WITH AN EASTWARD MOVING
OUTFLOW BOUNDARY...AS EVIDENT OFF OF THE DMX RADAR MOVING TOWARDS
EASTERN IOWA. THIS ACTIVITY...IF IT OCCURS IN ANY OF NORTHERN
ILLINOIS EARLY THIS MORNING...WOULD LIKELY BE ISOLATED TO WIDELY
SCATTERED...WITH THE MAIN FOCUS REMAINING NORTH.

A SURFACE WARM FRONT IS EXPECTED TO LIFT NORTHWARD OVER THE AREA
INTO THIS AFTERNOON...WITH A WARMER AIRMASS EXPECTED IN ITS WAKE. IN
SPITE OF THIS...HOWEVER...HIGH TEMPERATURES ACROSS THE AREA WILL BE
TRICKY AS IT APPEARS THAT SOME SCATTERED THUNDERSTORMS COULD DEVELOP
ACROSS PORTIONS OF THE AREA THIS AFTERNOON...AND HAMPER THE MAGNITUDE
OF THE WARMTH ACROSS SOME AREAS. MODEST HEIGHT FALLS ALOFT ARE FORECAST
ACROSS NORTHERN ILLINOIS IN ASSOCIATION WITH THE AFOREMENTIONED UPPER
TROUGH SHIFTING EASTWARD OVER THE MID MISSOURI VALLEY THIS
AFTERNOON. IN SPITE OF THE FACT THAT THE BEST LARGE SCALE FORCING
FOR ASCENT WITH THIS DISTURBANCE SHOULD REMAIN WEST OF THE AREA THIS
AFTERNOON...THE EXPECTED INCREASE IN LOW-LEVEL THETA E IS EXPECTED
TO PRODUCE AN UNCAPPED ATMOSPHERE FEATURING MLCAPES OF AROUND 1500
J/KG BY THIS AFTERNOON. A MAJORITY OF THE GLOBAL MODELS...AS WELL AS
THE HIRES CONVECTIVE ALLOWING MODELS FIRE UP ACTIVITY WITHIN THIS
REGIME THIS AFTERNOON. IT APPEARS WE WILL HAVE TO WATCH MORNING
CLOUD COVER...HOWEVER...AS THIS COULD INHIBIT THE DEGREE OF
WARMING A BIT THROUGH THE MORNING...AND POSSIBLY LEAD TO WEAKER
INSTABILITY THAN WHAT THE MODELS ARE CURRENTLY ADVERTISING.

IF THE CONVECTION DOES DEVELOP AS  EXPECTED...MARGINAL DEEP LAYER
SHEAR OF 25 TO 30 KT COULD ALLOW FOR A FEW STRONGER STORMS CAPABLE
OF SOME ISOLATED HIGH WIND GUSTS. SOME TORRENTIAL DOWNPOURS WOULD
ALSO BE A THREAT FROM THESE STORMS GIVEN THE JUICY AIRMASS FEATURING
PWATS UP AROUND 1.75 INCHES. HOWEVER...EXTREME RAINFALL AMOUNTS
APPEAR UNLIKELY GIVEN STORM MOTIONS SHOULD BE TO THE NORTHEAST
AROUND 30 KT. SO THE STORMS SHOULD NOT BE OVER A GIVEN AREA TOO
LONG. MUCH OF THIS ACTIVITY APPEARS TO BE HIGHLY DIURNAL IN
NATURE...SO A RAPID DOWNWARD TREND IS EXPECTED AFTER SUNSET THIS
EVENING.

ANOTHER ROUND OF THUNDERSTORMS APPEARS LIKELY ON
SATURDAY...ESPECIALLY DURING THE MORNING AS THE UPPER LEVEL
TROUGH...AND AN ASSOCIATED SURFACE LOW AND COLD FRONT SHIFTS
EASTWARD ACROSS ACROSS SOUTHERN WI AND NORTHERN IL. THIS ACTIVITY
COULD LINGER INTO SATURDAY EVENING ACROSS MY FAR SOUTHEASTERN
COUNTIES. HOWEVER...IT APPEARS THAT FOLLOWING THIS FRONTAL PASSAGE
WE WILL BE GREETED WITH A NICE DRY SUNDAY ACROSS THE AREA.

UNFORTUNATELY...LABOR DAY APPEARS THAT IT COULD BE ANOTHER ACTIVE
WEATHER DAY ACROSS THE REGION. ANOTHER POTENT UPPER LEVEL
DISTURBANCE AND SURFACE FRONT IS FORECAST TO SHIFT OVER THE AREA BY
MONDAY. WE WILL ALSO HAVE TO WATCH FOR THE THREAT OF SEVERE
THUNDERSTORMS ON MONDAY AND MONDAY NIGHT AS A 45 TO 50 KT MID LEVEL
JET IS PROGGED TO DEVELOP ACROSS THE AREA. THIS COULD RESULT IN DEEP
LAYER SHEAR STRONG ENOUGH TO PRODUCE MORE ORGANIZED STRONG TO SEVERE
CONVECTION. VERY HEAVY RAINFALL WOULD AGAIN BE A CONCERN WITH THIS
ACTIVITY...ESPECIALLY IF THE FRONTAL ZONE STALLS OUT OVER THE AREA
MONDAY NIGHT. AT THIS TIME...HOWEVER...UNCERTAINTY IS HIGH ON WHERE
THE SURFACE FRONT MAY STALL AND HENCE WHAT AREAS COULD BE FAVORED FOR
EXTENDED PERIODS OF VERY HEAVY RAINFALL.

THE ACTIVE WEATHER PATTERN COULD SHIFT SOUTH OF THE AREA FOR A DAY
OR TWO INTO MID TO LATE WEEK BEFORE MORE PERIODS OF CONVECTION ARE
POSSIBLE. OVERALL...IT APPEARS TEMPERATURES WILL REMAIN ON THE WARM
SIDE OF AVERAGE...WITH THE POTENTIAL FOR SOME VERY WARM AND HUMID DAYS
LATER NEXT WEEK.

KJB

&&

.AVIATION...

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

* ISOLATED-SCATTERED SHRA/TSRA THIS AFTERNOON THRU EARLY EVENING.

* SOUTH WINDS WITH GUSTS 15-20 KT THIS AFTERNOON.

* ANOTHER PERIOD OF SHRA/TSRA LIKELY AFTER MIDNIGHT INTO SATURDAY
  MORNING.

* SOUTHWEST WINDS GUSTING AROUND 20 KT SATURDAY.

RATZER

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

FAIRLY LOW CONFIDENCE CONVECTIVE FORECAST THIS PERIOD...WITH
TERMINALS WITHIN A BROAD AREA OF SOUTH WARM/MOIST ADVECTION
DOWNSTREAM OF AN UPPER TROUGH OVER THE CENTRAL PLAINS BUT WITH
OTHERWISE LITTLE ORGANIZED FOCUS FOR TSRA.

SATELLITE EVIDENCE OF WEAK MID-LEVEL DISTURBANCE OVER NORTHEAST
IL EARLY THIS AFTERNOON...WITH MORNING ELEVATED SHRA/TSRA DECAYING
OVER NORTH CENTRAL IL. DIURNAL TSRA WERE FORMING IN LOW LEVEL
INSTABILITY AXIS ALONG IL/IN BORDER REGION GENERALLY ALONG A DEC-
GIJ-MKG LINE...AND THIS LOOKS TO REMAIN THE FOCUS REGION FOR
HIGHEST COVERAGE TSRA THIS AFTERNOON. HIGH-RES GUIDANCE STILL
DEVELOPS SOME ISOLATED SHRA/TSRA INTO THE TERMINAL REGION IN
ASSOCIATION WITH AFOREMENTIONED MID-LEVEL DISTURBANCE AND NORTH
OF SURFACE WARM FRONT WHICH IS ACROSS DOWNSTATE IL AT THIS TIME...
THOUGH COVERAGE IS EXPECTED TO REMAIN LOW. A GREATER CHANCE OF
SHRA/TSRA APPEARS TO BE LATE TONIGHT AND EARLY SATURDAY AS THE
MAIN UPPER TROUGH APPROACHES. WEAK COLD FRONT APPROACHES FROM THE
WEST SATURDAY MIDDAY AND AFTERNOON...WITH THUNDERSTORMS EXPECTED
TO DEVELOP ALONG THE FRONT BY EARLY AFTERNOON. CURRENT SUITE OF
HIGH-RES GUIDANCE SUGGESTS TSRA POTENTIAL MAY BE GREATER JUST
EAST/SOUTH OF CHICAGO TERMINALS SATURDAY AFTERNOON. OUTSIDE OF ANY
PRECIP VIS REDUCTION EARLY SATURDAY...SOME MVFR HAZE POSSIBLE
OVERNIGHT IN MOIST WARM SECTOR AIR.

WINDS...GENERALLY SOUTH 10-12 KT WITH GUSTS TO 20 KT OR SO
POSSIBLE THIS AFTERNOON. WIND MAY BACK A BIT TO THE SOUTH-
SOUTHEAST LATE THIS AFTERNOON/EARLY EVENING AS SURFACE WARM
FRONT APPROACHES...BEFORE SHIFTING SOUTHWEST OVERNIGHT AND SUNDAY
AHEAD OF THE COLD FRONT. DEEPER MIXING SUNDAY SUGGESTS GUSTS AGAIN
IN THE 20 KT RANGE OR A LITTLE HIGHER DURING THE LATE MORNING AND
AFTERNOON.

RATZER


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

* MEDIUM IN SHRA/TSRA BEING LOW IN COVERAGE IN IMMEDIATE TERMINAL
  AREA THIS AFTERNOON...GREATER COVERAGE EAST/SOUTH OF CHICAGO.

* LOW IN TSRA TIMING/COVERAGE LATER TONIGHT/SATURDAY.

* MEDIUM-HIGH IN WIND TRENDS THROUGH PERIOD.

RATZER

//OUTLOOK FOR ORD/MDW FOR 00Z SUNDAY-12Z FRIDAY...UPDATED 12Z...

* SATURDAY NIGHT THROUGH SUNDAY NIGHT...VFR. WX NIL.

* MONDAY...CHANCE OF TSRA.

* TUESDAY...VFR. WX NIL.

* WEDNESDAY THROUGH THURSDAY NIGHT...SLIGHT CHANCE OF TSRA

KREIN

&&

.MARINE...
315 AM CDT

HIGH PRESSURE OVER THE EASTERN GREAT LAKES WILL MOVE EAST OFF THE
NEW ENGLAND COAST FRIDAY EVENING...WHILE A TROUGH OF LOW PRESSURE
DEVELOPS ACROSS THE CENTRAL PLAINS AND UPPER MIDWEST. THIS WILL
SET UP A PERIOD OF SOUTHERLY WINDS AND AS THE TROUGH MOVES
EAST...THE GRADIENT OVER THE LAKE WILL STRENGTHEN AND WINDS SHOULD
INCREASE TO THE 20-25 KT RANGE. A DEEPENING LOW CENTER WITHIN THE
TROUGH WILL MOVE TO WISCONSIN SATURDAY AND ACROSS NORTHERN LAKE
MICHIGAN SATURDAY EVENING. AS THE LOW TRACKS TO THE NORTHEAST...AN
ASSOCIATED COLD FRONT WILL MOVE DOWN THE LAKE SATURDAY AFTERNOON
AND EVENING...QUICKLY SHIFTING WINDS TO NWLY FOLLOWING THE FROPA.
THE LATEST MODEL GUIDANCE SUGGESTS THAT THE FRONT WILL WASH OUT
LATE SATURDAY NIGHT BEFORE REACHING THE SOUTH END OF THE LAKE AND
WINDS THERE SHOULD NEVER TRULY SHIFT NWLY...BUT RATHER BECOMING
LIGHT AND VARIABLE LATE SATURDAY NIGHT THROUGH SUNDAY MORNING. A
DEEPER LOW IS EXPECTED TO DEVELOP OVER THE DAKOTAS AND LIFT
THROUGH WESTERN ONTARIO SUNDAY NIGHT AND MONDAY BRINGING A RETURN
TO BRISK SOUTH TO SOUTHWEST WINDS TO THE LAKE FOR MONDAY AND
TUESDAY.

KREIN

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 291608
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1108 AM CDT FRI AUG 29 2014

.DISCUSSION...
326 AM CDT

THE MAIN FORECAST CONCERNS WILL CENTER AROUND CONVECTIVE CHANCES AND
TIMING...AS WELL AS TEMPERATURES TODAY...AND THROUGH THE HOLIDAY WEEKEND.

CURRENTLY...THE REMNANT MCV FROM YESTERDAY EVENINGS SHOWERS AND
STORMS CONTINUES TO SHIFT ACROSS MY SOUTHERN COUNTIES EARLY THIS
MORNING. HOWEVER...ONLY A FEW LIGHT SHOWERS/SPRINKLES REMAIN ACROSS
THIS AREA...WITH DRIER AND FAIRLY STABLE CONDITIONS IN PLACE TO THE EAST.

ANOTHER AREA OF CONVECTION IS ONGOING TO OUR WEST ACROSS IOWA AND
INTO SOUTHERN MN. THIS ACTIVITY IS OCCURRING WITHIN A REGION OF GOOD
LOWER LEVEL WARM AIR ADVECTION/ISENTROPIC ASCENT ON THE DOWNSTREAM
PERIPHERY OF A REMNANT MID/UPPER LEVEL TROUGH OVER THE PLAINS STATES.
DOWN STREAM UPPER RIDGING OVER THE GREAT LAKES REGION IS LEADING TO A
STEERING FLOW TO THE NORTHEAST. THEREFORE...MOST IF NOT ALL OF THIS
CONVECTIVE ACTIVITY WILL SHIFT INTO SOUTHERN WISCONSIN AND PERHAPS
FAR NORTHWESTERN ILLINOIS THIS MORNING. IN SPITE OF THIS...I HAVE
LEFT SLIGHT CHANCE POPS IN THIS MORNING AS IT IS POSSIBLE THAT SOME
ADDITIONAL CELLS COULD DEVELOP IN ASSOCIATION WITH AN EASTWARD MOVING
OUTFLOW BOUNDARY...AS EVIDENT OFF OF THE DMX RADAR MOVING TOWARDS
EASTERN IOWA. THIS ACTIVITY...IF IT OCCURS IN ANY OF NORTHERN
ILLINOIS EARLY THIS MORNING...WOULD LIKELY BE ISOLATED TO WIDELY
SCATTERED...WITH THE MAIN FOCUS REMAINING NORTH.

A SURFACE WARM FRONT IS EXPECTED TO LIFT NORTHWARD OVER THE AREA
INTO THIS AFTERNOON...WITH A WARMER AIRMASS EXPECTED IN ITS WAKE. IN
SPITE OF THIS...HOWEVER...HIGH TEMPERATURES ACROSS THE AREA WILL BE
TRICKY AS IT APPEARS THAT SOME SCATTERED THUNDERSTORMS COULD DEVELOP
ACROSS PORTIONS OF THE AREA THIS AFTERNOON...AND HAMPER THE MAGNITUDE
OF THE WARMTH ACROSS SOME AREAS. MODEST HEIGHT FALLS ALOFT ARE FORECAST
ACROSS NORTHERN ILLINOIS IN ASSOCIATION WITH THE AFOREMENTIONED UPPER
TROUGH SHIFTING EASTWARD OVER THE MID MISSOURI VALLEY THIS
AFTERNOON. IN SPITE OF THE FACT THAT THE BEST LARGE SCALE FORCING
FOR ASCENT WITH THIS DISTURBANCE SHOULD REMAIN WEST OF THE AREA THIS
AFTERNOON...THE EXPECTED INCREASE IN LOW-LEVEL THETA E IS EXPECTED
TO PRODUCE AN UNCAPPED ATMOSPHERE FEATURING MLCAPES OF AROUND 1500
J/KG BY THIS AFTERNOON. A MAJORITY OF THE GLOBAL MODELS...AS WELL AS
THE HIRES CONVECTIVE ALLOWING MODELS FIRE UP ACTIVITY WITHIN THIS
REGIME THIS AFTERNOON. IT APPEARS WE WILL HAVE TO WATCH MORNING
CLOUD COVER...HOWEVER...AS THIS COULD INHIBIT THE DEGREE OF
WARMING A BIT THROUGH THE MORNING...AND POSSIBLY LEAD TO WEAKER
INSTABILITY THAN WHAT THE MODELS ARE CURRENTLY ADVERTISING.

IF THE CONVECTION DOES DEVELOP AS  EXPECTED...MARGINAL DEEP LAYER
SHEAR OF 25 TO 30 KT COULD ALLOW FOR A FEW STRONGER STORMS CAPABLE
OF SOME ISOLATED HIGH WIND GUSTS. SOME TORRENTIAL DOWNPOURS WOULD
ALSO BE A THREAT FROM THESE STORMS GIVEN THE JUICY AIRMASS FEATURING
PWATS UP AROUND 1.75 INCHES. HOWEVER...EXTREME RAINFALL AMOUNTS
APPEAR UNLIKELY GIVEN STORM MOTIONS SHOULD BE TO THE NORTHEAST
AROUND 30 KT. SO THE STORMS SHOULD NOT BE OVER A GIVEN AREA TOO
LONG. MUCH OF THIS ACTIVITY APPEARS TO BE HIGHLY DIURNAL IN
NATURE...SO A RAPID DOWNWARD TREND IS EXPECTED AFTER SUNSET THIS
EVENING.

ANOTHER ROUND OF THUNDERSTORMS APPEARS LIKELY ON
SATURDAY...ESPECIALLY DURING THE MORNING AS THE UPPER LEVEL
TROUGH...AND AN ASSOCIATED SURFACE LOW AND COLD FRONT SHIFTS
EASTWARD ACROSS ACROSS SOUTHERN WI AND NORTHERN IL. THIS ACTIVITY
COULD LINGER INTO SATURDAY EVENING ACROSS MY FAR SOUTHEASTERN
COUNTIES. HOWEVER...IT APPEARS THAT FOLLOWING THIS FRONTAL PASSAGE
WE WILL BE GREETED WITH A NICE DRY SUNDAY ACROSS THE AREA.

UNFORTUNATELY...LABOR DAY APPEARS THAT IT COULD BE ANOTHER ACTIVE
WEATHER DAY ACROSS THE REGION. ANOTHER POTENT UPPER LEVEL
DISTURBANCE AND SURFACE FRONT IS FORECAST TO SHIFT OVER THE AREA BY
MONDAY. WE WILL ALSO HAVE TO WATCH FOR THE THREAT OF SEVERE
THUNDERSTORMS ON MONDAY AND MONDAY NIGHT AS A 45 TO 50 KT MID LEVEL
JET IS PROGGED TO DEVELOP ACROSS THE AREA. THIS COULD RESULT IN DEEP
LAYER SHEAR STRONG ENOUGH TO PRODUCE MORE ORGANIZED STRONG TO SEVERE
CONVECTION. VERY HEAVY RAINFALL WOULD AGAIN BE A CONCERN WITH THIS
ACTIVITY...ESPECIALLY IF THE FRONTAL ZONE STALLS OUT OVER THE AREA
MONDAY NIGHT. AT THIS TIME...HOWEVER...UNCERTAINTY IS HIGH ON WHERE
THE SURFACE FRONT MAY STALL AND HENCE WHAT AREAS COULD BE FAVORED FOR
EXTENDED PERIODS OF VERY HEAVY RAINFALL.

THE ACTIVE WEATHER PATTERN COULD SHIFT SOUTH OF THE AREA FOR A DAY
OR TWO INTO MID TO LATE WEEK BEFORE MORE PERIODS OF CONVECTION ARE
POSSIBLE. OVERALL...IT APPEARS TEMPERATURES WILL REMAIN ON THE WARM
SIDE OF AVERAGE...WITH THE POTENTIAL FOR SOME VERY WARM AND HUMID DAYS
LATER NEXT WEEK.

KJB

&&

.AVIATION...

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

* ISOLATED-SCATTERED TSRA THIS AFTERNOON/EARLY EVENING.

* SOUTH-SOUTHEAST WIND AROUND 10 KT BECOMING SOUTH WITH GUSTS NEAR
  20 KT DEVELOPING BY MIDDAY.

* GREATER CHANCE FOR MORE ORGANIZED TSRA TOMORROW.

RATZER

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

FORECAST CONCERNS CONTINUE TO FOCUS ON SHRA/TSRA POTENTIAL
THROUGH THE PERIOD AS WELL AS GUSTY SOUTH WINDS DEVELOPING LATE
FRIDAY MORNING AND PERSISTING INTO THIS EVENING.

A WARM FRONT WILL SLOWLY LIFT NWD THROUGH THE DAY AND PUSH NORTH
OF THE TERMINALS BY LATE MORNING. WHILE THE SFC WARM FRONT IS
STILL TO THE SOUTH OF THE TERMINALS...SCT SHRA HAVE DEVELOPED IN A
ZONE OF WARM ADVECTION ALONG 25-30KT SWLY WINDS ALOFT. THE BULK OF
THE ACTIVITY IS CURRENTLY LOCATED OVER WRN IL...INVOF KRFD. SFC
WINDS ARE STILL SLIGHTLY EAST OF SOUTH...BUT AS THE WARM FRONT
PUSHES NORTH OF THE TERMINALS...WINDS WILL VEER TO SOUTHERLY WITH
GUSTS TO ARND 20KT OR SO.

INSTABILITY WILL INCREASE VERY QUICKLY AS THE WARM FRONT PASSES
TO THE NORTH AND WARM SECTOR AIR OVERSPREADS THE REGION BRINGING
INCREASING TEMPERATURES AND DEWPOINTS. WEAK MID LEVEL IMPULSES
SHOULD TRACK ACROSS THE AREA THIS AFTERNOON AND EVENING IN UPPER
LEVEL SWLY FLOW AS AN UPPER RIDGE PUSHES TO THE EAST AND A LARGER
SCALE UPPER TROUGH MOVES ACROSS THE CENTRAL PLAINS. THESE IMPULSES
WILL BE THE TRIGGERING MECHANISM FOR ADDITIONAL SHRA/TSRA...BUT IN
THE ABSENCE OF ANY SFC FORCING...ACTIVITY SHOULD GENERALLY BE
SCATTERED AND DIFFICULT TO TIME AT THE TERMINALS. HAVE PUSHED BACK
THE TIMING OF THE PCPN MENTION AT THE CHICAGO AREA TERMINALS WHEN
INSTABILITY SHOULD BE THE STRONGEST...BUT THIS IS A LOW CONFIDENCE
CHANGE AS IN SUCH A WARM/MOIST AIRMASS SCT SHRA/ISOLD TSRA COULD
DEVELOP AT ANY TIME.

A BETTER CHANCE FOR MORE ORGANIZED TS WILL COME LATE IN THE
PERIOD...POSSIBLY NOT UNTIL TOMORROW MORNING AS THE MAIN LONGWAVE
UPPER TROUGH AND A WEAK SFC COLD FRONT CROSS THE REGION.

KREIN

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

* MEDIUM-LOW CONFIDENCE IN THUNDER CHANCES/COVERAGE AND SPECIFIC TIMING
  THROUGH THIS EVENING.

* MEDIUM CONFIDENCE IN MORE ORGANIZED TS TOMORROW MORNING.

* HIGH CONFIDENCE IN WIND TRENDS THROUGH THE PERIOD.

KREIN/RATZER

//OUTLOOK FOR ORD/MDW FOR 00Z SUNDAY-12Z FRIDAY...UPDATED 12Z...

* SATURDAY NIGHT THROUGH SUNDAY NIGHT...VFR. WX NIL.

* MONDAY...CHANCE OF TSRA.

* TUESDAY...VFR. WX NIL.

* WEDNESDAY THROUGH THURSDAY NIGHT...SLIGHT CHANCE OF TSRA

KREIN

&&

.MARINE...
315 AM CDT

HIGH PRESSURE OVER THE EASTERN GREAT LAKES WILL MOVE EAST OFF THE
NEW ENGLAND COAST FRIDAY EVENING...WHILE A TROUGH OF LOW PRESSURE
DEVELOPS ACROSS THE CENTRAL PLAINS AND UPPER MIDWEST. THIS WILL
SET UP A PERIOD OF SOUTHERLY WINDS AND AS THE TROUGH MOVES
EAST...THE GRADIENT OVER THE LAKE WILL STRENGTHEN AND WINDS SHOULD
INCREASE TO THE 20-25 KT RANGE. A DEEPENING LOW CENTER WITHIN THE
TROUGH WILL MOVE TO WISCONSIN SATURDAY AND ACROSS NORTHERN LAKE
MICHIGAN SATURDAY EVENING. AS THE LOW TRACKS TO THE NORTHEAST...AN
ASSOCIATED COLD FRONT WILL MOVE DOWN THE LAKE SATURDAY AFTERNOON
AND EVENING...QUICKLY SHIFTING WINDS TO NWLY FOLLOWING THE FROPA.
THE LATEST MODEL GUIDANCE SUGGESTS THAT THE FRONT WILL WASH OUT
LATE SATURDAY NIGHT BEFORE REACHING THE SOUTH END OF THE LAKE AND
WINDS THERE SHOULD NEVER TRULY SHIFT NWLY...BUT RATHER BECOMING
LIGHT AND VARIABLE LATE SATURDAY NIGHT THROUGH SUNDAY MORNING. A
DEEPER LOW IS EXPECTED TO DEVELOP OVER THE DAKOTAS AND LIFT
THROUGH WESTERN ONTARIO SUNDAY NIGHT AND MONDAY BRINGING A RETURN
TO BRISK SOUTH TO SOUTHWEST WINDS TO THE LAKE FOR MONDAY AND
TUESDAY.

KREIN

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO







000
FXUS63 KLOT 291608
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1108 AM CDT FRI AUG 29 2014

.DISCUSSION...
326 AM CDT

THE MAIN FORECAST CONCERNS WILL CENTER AROUND CONVECTIVE CHANCES AND
TIMING...AS WELL AS TEMPERATURES TODAY...AND THROUGH THE HOLIDAY WEEKEND.

CURRENTLY...THE REMNANT MCV FROM YESTERDAY EVENINGS SHOWERS AND
STORMS CONTINUES TO SHIFT ACROSS MY SOUTHERN COUNTIES EARLY THIS
MORNING. HOWEVER...ONLY A FEW LIGHT SHOWERS/SPRINKLES REMAIN ACROSS
THIS AREA...WITH DRIER AND FAIRLY STABLE CONDITIONS IN PLACE TO THE EAST.

ANOTHER AREA OF CONVECTION IS ONGOING TO OUR WEST ACROSS IOWA AND
INTO SOUTHERN MN. THIS ACTIVITY IS OCCURRING WITHIN A REGION OF GOOD
LOWER LEVEL WARM AIR ADVECTION/ISENTROPIC ASCENT ON THE DOWNSTREAM
PERIPHERY OF A REMNANT MID/UPPER LEVEL TROUGH OVER THE PLAINS STATES.
DOWN STREAM UPPER RIDGING OVER THE GREAT LAKES REGION IS LEADING TO A
STEERING FLOW TO THE NORTHEAST. THEREFORE...MOST IF NOT ALL OF THIS
CONVECTIVE ACTIVITY WILL SHIFT INTO SOUTHERN WISCONSIN AND PERHAPS
FAR NORTHWESTERN ILLINOIS THIS MORNING. IN SPITE OF THIS...I HAVE
LEFT SLIGHT CHANCE POPS IN THIS MORNING AS IT IS POSSIBLE THAT SOME
ADDITIONAL CELLS COULD DEVELOP IN ASSOCIATION WITH AN EASTWARD MOVING
OUTFLOW BOUNDARY...AS EVIDENT OFF OF THE DMX RADAR MOVING TOWARDS
EASTERN IOWA. THIS ACTIVITY...IF IT OCCURS IN ANY OF NORTHERN
ILLINOIS EARLY THIS MORNING...WOULD LIKELY BE ISOLATED TO WIDELY
SCATTERED...WITH THE MAIN FOCUS REMAINING NORTH.

A SURFACE WARM FRONT IS EXPECTED TO LIFT NORTHWARD OVER THE AREA
INTO THIS AFTERNOON...WITH A WARMER AIRMASS EXPECTED IN ITS WAKE. IN
SPITE OF THIS...HOWEVER...HIGH TEMPERATURES ACROSS THE AREA WILL BE
TRICKY AS IT APPEARS THAT SOME SCATTERED THUNDERSTORMS COULD DEVELOP
ACROSS PORTIONS OF THE AREA THIS AFTERNOON...AND HAMPER THE MAGNITUDE
OF THE WARMTH ACROSS SOME AREAS. MODEST HEIGHT FALLS ALOFT ARE FORECAST
ACROSS NORTHERN ILLINOIS IN ASSOCIATION WITH THE AFOREMENTIONED UPPER
TROUGH SHIFTING EASTWARD OVER THE MID MISSOURI VALLEY THIS
AFTERNOON. IN SPITE OF THE FACT THAT THE BEST LARGE SCALE FORCING
FOR ASCENT WITH THIS DISTURBANCE SHOULD REMAIN WEST OF THE AREA THIS
AFTERNOON...THE EXPECTED INCREASE IN LOW-LEVEL THETA E IS EXPECTED
TO PRODUCE AN UNCAPPED ATMOSPHERE FEATURING MLCAPES OF AROUND 1500
J/KG BY THIS AFTERNOON. A MAJORITY OF THE GLOBAL MODELS...AS WELL AS
THE HIRES CONVECTIVE ALLOWING MODELS FIRE UP ACTIVITY WITHIN THIS
REGIME THIS AFTERNOON. IT APPEARS WE WILL HAVE TO WATCH MORNING
CLOUD COVER...HOWEVER...AS THIS COULD INHIBIT THE DEGREE OF
WARMING A BIT THROUGH THE MORNING...AND POSSIBLY LEAD TO WEAKER
INSTABILITY THAN WHAT THE MODELS ARE CURRENTLY ADVERTISING.

IF THE CONVECTION DOES DEVELOP AS  EXPECTED...MARGINAL DEEP LAYER
SHEAR OF 25 TO 30 KT COULD ALLOW FOR A FEW STRONGER STORMS CAPABLE
OF SOME ISOLATED HIGH WIND GUSTS. SOME TORRENTIAL DOWNPOURS WOULD
ALSO BE A THREAT FROM THESE STORMS GIVEN THE JUICY AIRMASS FEATURING
PWATS UP AROUND 1.75 INCHES. HOWEVER...EXTREME RAINFALL AMOUNTS
APPEAR UNLIKELY GIVEN STORM MOTIONS SHOULD BE TO THE NORTHEAST
AROUND 30 KT. SO THE STORMS SHOULD NOT BE OVER A GIVEN AREA TOO
LONG. MUCH OF THIS ACTIVITY APPEARS TO BE HIGHLY DIURNAL IN
NATURE...SO A RAPID DOWNWARD TREND IS EXPECTED AFTER SUNSET THIS
EVENING.

ANOTHER ROUND OF THUNDERSTORMS APPEARS LIKELY ON
SATURDAY...ESPECIALLY DURING THE MORNING AS THE UPPER LEVEL
TROUGH...AND AN ASSOCIATED SURFACE LOW AND COLD FRONT SHIFTS
EASTWARD ACROSS ACROSS SOUTHERN WI AND NORTHERN IL. THIS ACTIVITY
COULD LINGER INTO SATURDAY EVENING ACROSS MY FAR SOUTHEASTERN
COUNTIES. HOWEVER...IT APPEARS THAT FOLLOWING THIS FRONTAL PASSAGE
WE WILL BE GREETED WITH A NICE DRY SUNDAY ACROSS THE AREA.

UNFORTUNATELY...LABOR DAY APPEARS THAT IT COULD BE ANOTHER ACTIVE
WEATHER DAY ACROSS THE REGION. ANOTHER POTENT UPPER LEVEL
DISTURBANCE AND SURFACE FRONT IS FORECAST TO SHIFT OVER THE AREA BY
MONDAY. WE WILL ALSO HAVE TO WATCH FOR THE THREAT OF SEVERE
THUNDERSTORMS ON MONDAY AND MONDAY NIGHT AS A 45 TO 50 KT MID LEVEL
JET IS PROGGED TO DEVELOP ACROSS THE AREA. THIS COULD RESULT IN DEEP
LAYER SHEAR STRONG ENOUGH TO PRODUCE MORE ORGANIZED STRONG TO SEVERE
CONVECTION. VERY HEAVY RAINFALL WOULD AGAIN BE A CONCERN WITH THIS
ACTIVITY...ESPECIALLY IF THE FRONTAL ZONE STALLS OUT OVER THE AREA
MONDAY NIGHT. AT THIS TIME...HOWEVER...UNCERTAINTY IS HIGH ON WHERE
THE SURFACE FRONT MAY STALL AND HENCE WHAT AREAS COULD BE FAVORED FOR
EXTENDED PERIODS OF VERY HEAVY RAINFALL.

THE ACTIVE WEATHER PATTERN COULD SHIFT SOUTH OF THE AREA FOR A DAY
OR TWO INTO MID TO LATE WEEK BEFORE MORE PERIODS OF CONVECTION ARE
POSSIBLE. OVERALL...IT APPEARS TEMPERATURES WILL REMAIN ON THE WARM
SIDE OF AVERAGE...WITH THE POTENTIAL FOR SOME VERY WARM AND HUMID DAYS
LATER NEXT WEEK.

KJB

&&

.AVIATION...

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

* ISOLATED-SCATTERED TSRA THIS AFTERNOON/EARLY EVENING.

* SOUTH-SOUTHEAST WIND AROUND 10 KT BECOMING SOUTH WITH GUSTS NEAR
  20 KT DEVELOPING BY MIDDAY.

* GREATER CHANCE FOR MORE ORGANIZED TSRA TOMORROW.

RATZER

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

FORECAST CONCERNS CONTINUE TO FOCUS ON SHRA/TSRA POTENTIAL
THROUGH THE PERIOD AS WELL AS GUSTY SOUTH WINDS DEVELOPING LATE
FRIDAY MORNING AND PERSISTING INTO THIS EVENING.

A WARM FRONT WILL SLOWLY LIFT NWD THROUGH THE DAY AND PUSH NORTH
OF THE TERMINALS BY LATE MORNING. WHILE THE SFC WARM FRONT IS
STILL TO THE SOUTH OF THE TERMINALS...SCT SHRA HAVE DEVELOPED IN A
ZONE OF WARM ADVECTION ALONG 25-30KT SWLY WINDS ALOFT. THE BULK OF
THE ACTIVITY IS CURRENTLY LOCATED OVER WRN IL...INVOF KRFD. SFC
WINDS ARE STILL SLIGHTLY EAST OF SOUTH...BUT AS THE WARM FRONT
PUSHES NORTH OF THE TERMINALS...WINDS WILL VEER TO SOUTHERLY WITH
GUSTS TO ARND 20KT OR SO.

INSTABILITY WILL INCREASE VERY QUICKLY AS THE WARM FRONT PASSES
TO THE NORTH AND WARM SECTOR AIR OVERSPREADS THE REGION BRINGING
INCREASING TEMPERATURES AND DEWPOINTS. WEAK MID LEVEL IMPULSES
SHOULD TRACK ACROSS THE AREA THIS AFTERNOON AND EVENING IN UPPER
LEVEL SWLY FLOW AS AN UPPER RIDGE PUSHES TO THE EAST AND A LARGER
SCALE UPPER TROUGH MOVES ACROSS THE CENTRAL PLAINS. THESE IMPULSES
WILL BE THE TRIGGERING MECHANISM FOR ADDITIONAL SHRA/TSRA...BUT IN
THE ABSENCE OF ANY SFC FORCING...ACTIVITY SHOULD GENERALLY BE
SCATTERED AND DIFFICULT TO TIME AT THE TERMINALS. HAVE PUSHED BACK
THE TIMING OF THE PCPN MENTION AT THE CHICAGO AREA TERMINALS WHEN
INSTABILITY SHOULD BE THE STRONGEST...BUT THIS IS A LOW CONFIDENCE
CHANGE AS IN SUCH A WARM/MOIST AIRMASS SCT SHRA/ISOLD TSRA COULD
DEVELOP AT ANY TIME.

A BETTER CHANCE FOR MORE ORGANIZED TS WILL COME LATE IN THE
PERIOD...POSSIBLY NOT UNTIL TOMORROW MORNING AS THE MAIN LONGWAVE
UPPER TROUGH AND A WEAK SFC COLD FRONT CROSS THE REGION.

KREIN

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

* MEDIUM-LOW CONFIDENCE IN THUNDER CHANCES/COVERAGE AND SPECIFIC TIMING
  THROUGH THIS EVENING.

* MEDIUM CONFIDENCE IN MORE ORGANIZED TS TOMORROW MORNING.

* HIGH CONFIDENCE IN WIND TRENDS THROUGH THE PERIOD.

KREIN/RATZER

//OUTLOOK FOR ORD/MDW FOR 00Z SUNDAY-12Z FRIDAY...UPDATED 12Z...

* SATURDAY NIGHT THROUGH SUNDAY NIGHT...VFR. WX NIL.

* MONDAY...CHANCE OF TSRA.

* TUESDAY...VFR. WX NIL.

* WEDNESDAY THROUGH THURSDAY NIGHT...SLIGHT CHANCE OF TSRA

KREIN

&&

.MARINE...
315 AM CDT

HIGH PRESSURE OVER THE EASTERN GREAT LAKES WILL MOVE EAST OFF THE
NEW ENGLAND COAST FRIDAY EVENING...WHILE A TROUGH OF LOW PRESSURE
DEVELOPS ACROSS THE CENTRAL PLAINS AND UPPER MIDWEST. THIS WILL
SET UP A PERIOD OF SOUTHERLY WINDS AND AS THE TROUGH MOVES
EAST...THE GRADIENT OVER THE LAKE WILL STRENGTHEN AND WINDS SHOULD
INCREASE TO THE 20-25 KT RANGE. A DEEPENING LOW CENTER WITHIN THE
TROUGH WILL MOVE TO WISCONSIN SATURDAY AND ACROSS NORTHERN LAKE
MICHIGAN SATURDAY EVENING. AS THE LOW TRACKS TO THE NORTHEAST...AN
ASSOCIATED COLD FRONT WILL MOVE DOWN THE LAKE SATURDAY AFTERNOON
AND EVENING...QUICKLY SHIFTING WINDS TO NWLY FOLLOWING THE FROPA.
THE LATEST MODEL GUIDANCE SUGGESTS THAT THE FRONT WILL WASH OUT
LATE SATURDAY NIGHT BEFORE REACHING THE SOUTH END OF THE LAKE AND
WINDS THERE SHOULD NEVER TRULY SHIFT NWLY...BUT RATHER BECOMING
LIGHT AND VARIABLE LATE SATURDAY NIGHT THROUGH SUNDAY MORNING. A
DEEPER LOW IS EXPECTED TO DEVELOP OVER THE DAKOTAS AND LIFT
THROUGH WESTERN ONTARIO SUNDAY NIGHT AND MONDAY BRINGING A RETURN
TO BRISK SOUTH TO SOUTHWEST WINDS TO THE LAKE FOR MONDAY AND
TUESDAY.

KREIN

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 291403
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
903 AM CDT FRI AUG 29 2014

.DISCUSSION...
326 AM CDT

THE MAIN FORECAST CONCERNS WILL CENTER AROUND CONVECTIVE CHANCES AND
TIMING...AS WELL AS TEMPERATURES TODAY...AND THROUGH THE HOLIDAY WEEKEND.

CURRENTLY...THE REMNANT MCV FROM YESTERDAY EVENINGS SHOWERS AND
STORMS CONTINUES TO SHIFT ACROSS MY SOUTHERN COUNTIES EARLY THIS
MORNING. HOWEVER...ONLY A FEW LIGHT SHOWERS/SPRINKLES REMAIN ACROSS
THIS AREA...WITH DRIER AND FAIRLY STABLE CONDITIONS IN PLACE TO THE EAST.

ANOTHER AREA OF CONVECTION IS ONGOING TO OUR WEST ACROSS IOWA AND
INTO SOUTHERN MN. THIS ACTIVITY IS OCCURRING WITHIN A REGION OF GOOD
LOWER LEVEL WARM AIR ADVECTION/ISENTROPIC ASCENT ON THE DOWNSTREAM
PERIPHERY OF A REMNANT MID/UPPER LEVEL TROUGH OVER THE PLAINS STATES.
DOWN STREAM UPPER RIDGING OVER THE GREAT LAKES REGION IS LEADING TO A
STEERING FLOW TO THE NORTHEAST. THEREFORE...MOST IF NOT ALL OF THIS
CONVECTIVE ACTIVITY WILL SHIFT INTO SOUTHERN WISCONSIN AND PERHAPS
FAR NORTHWESTERN ILLINOIS THIS MORNING. IN SPITE OF THIS...I HAVE
LEFT SLIGHT CHANCE POPS IN THIS MORNING AS IT IS POSSIBLE THAT SOME
ADDITIONAL CELLS COULD DEVELOP IN ASSOCIATION WITH AN EASTWARD MOVING
OUTFLOW BOUNDARY...AS EVIDENT OFF OF THE DMX RADAR MOVING TOWARDS
EASTERN IOWA. THIS ACTIVITY...IF IT OCCURS IN ANY OF NORTHERN
ILLINOIS EARLY THIS MORNING...WOULD LIKELY BE ISOLATED TO WIDELY
SCATTERED...WITH THE MAIN FOCUS REMAINING NORTH.

A SURFACE WARM FRONT IS EXPECTED TO LIFT NORTHWARD OVER THE AREA
INTO THIS AFTERNOON...WITH A WARMER AIRMASS EXPECTED IN ITS WAKE. IN
SPITE OF THIS...HOWEVER...HIGH TEMPERATURES ACROSS THE AREA WILL BE
TRICKY AS IT APPEARS THAT SOME SCATTERED THUNDERSTORMS COULD DEVELOP
ACROSS PORTIONS OF THE AREA THIS AFTERNOON...AND HAMPER THE MAGNITUDE
OF THE WARMTH ACROSS SOME AREAS. MODEST HEIGHT FALLS ALOFT ARE FORECAST
ACROSS NORTHERN ILLINOIS IN ASSOCIATION WITH THE AFOREMENTIONED UPPER
TROUGH SHIFTING EASTWARD OVER THE MID MISSOURI VALLEY THIS
AFTERNOON. IN SPITE OF THE FACT THAT THE BEST LARGE SCALE FORCING
FOR ASCENT WITH THIS DISTURBANCE SHOULD REMAIN WEST OF THE AREA THIS
AFTERNOON...THE EXPECTED INCREASE IN LOW-LEVEL THETA E IS EXPECTED
TO PRODUCE AN UNCAPPED ATMOSPHERE FEATURING MLCAPES OF AROUND 1500
J/KG BY THIS AFTERNOON. A MAJORITY OF THE GLOBAL MODELS...AS WELL AS
THE HIRES CONVECTIVE ALLOWING MODELS FIRE UP ACTIVITY WITHIN THIS
REGIME THIS AFTERNOON. IT APPEARS WE WILL HAVE TO WATCH MORNING
CLOUD COVER...HOWEVER...AS THIS COULD INHIBIT THE DEGREE OF
WARMING A BIT THROUGH THE MORNING...AND POSSIBLY LEAD TO WEAKER
INSTABILITY THAN WHAT THE MODELS ARE CURRENTLY ADVERTISING.

IF THE CONVECTION DOES DEVELOP AS  EXPECTED...MARGINAL DEEP LAYER
SHEAR OF 25 TO 30 KT COULD ALLOW FOR A FEW STRONGER STORMS CAPABLE
OF SOME ISOLATED HIGH WIND GUSTS. SOME TORRENTIAL DOWNPOURS WOULD
ALSO BE A THREAT FROM THESE STORMS GIVEN THE JUICY AIRMASS FEATURING
PWATS UP AROUND 1.75 INCHES. HOWEVER...EXTREME RAINFALL AMOUNTS
APPEAR UNLIKELY GIVEN STORM MOTIONS SHOULD BE TO THE NORTHEAST
AROUND 30 KT. SO THE STORMS SHOULD NOT BE OVER A GIVEN AREA TOO
LONG. MUCH OF THIS ACTIVITY APPEARS TO BE HIGHLY DIURNAL IN
NATURE...SO A RAPID DOWNWARD TREND IS EXPECTED AFTER SUNSET THIS
EVENING.

ANOTHER ROUND OF THUNDERSTORMS APPEARS LIKELY ON
SATURDAY...ESPECIALLY DURING THE MORNING AS THE UPPER LEVEL
TROUGH...AND AN ASSOCIATED SURFACE LOW AND COLD FRONT SHIFTS
EASTWARD ACROSS ACROSS SOUTHERN WI AND NORTHERN IL. THIS ACTIVITY
COULD LINGER INTO SATURDAY EVENING ACROSS MY FAR SOUTHEASTERN
COUNTIES. HOWEVER...IT APPEARS THAT FOLLOWING THIS FRONTAL PASSAGE
WE WILL BE GREETED WITH A NICE DRY SUNDAY ACROSS THE AREA.

UNFORTUNATELY...LABOR DAY APPEARS THAT IT COULD BE ANOTHER ACTIVE
WEATHER DAY ACROSS THE REGION. ANOTHER POTENT UPPER LEVEL
DISTURBANCE AND SURFACE FRONT IS FORECAST TO SHIFT OVER THE AREA BY
MONDAY. WE WILL ALSO HAVE TO WATCH FOR THE THREAT OF SEVERE
THUNDERSTORMS ON MONDAY AND MONDAY NIGHT AS A 45 TO 50 KT MID LEVEL
JET IS PROGGED TO DEVELOP ACROSS THE AREA. THIS COULD RESULT IN DEEP
LAYER SHEAR STRONG ENOUGH TO PRODUCE MORE ORGANIZED STRONG TO SEVERE
CONVECTION. VERY HEAVY RAINFALL WOULD AGAIN BE A CONCERN WITH THIS
ACTIVITY...ESPECIALLY IF THE FRONTAL ZONE STALLS OUT OVER THE AREA
MONDAY NIGHT. AT THIS TIME...HOWEVER...UNCERTAINTY IS HIGH ON WHERE
THE SURFACE FRONT MAY STALL AND HENCE WHAT AREAS COULD BE FAVORED FOR
EXTENDED PERIODS OF VERY HEAVY RAINFALL.

THE ACTIVE WEATHER PATTERN COULD SHIFT SOUTH OF THE AREA FOR A DAY
OR TWO INTO MID TO LATE WEEK BEFORE MORE PERIODS OF CONVECTION ARE
POSSIBLE. OVERALL...IT APPEARS TEMPERATURES WILL REMAIN ON THE WARM
SIDE OF AVERAGE...WITH THE POTENTIAL FOR SOME VERY WARM AND HUMID DAYS
LATER NEXT WEEK.

KJB

&&

.AVIATION...

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

* ISOLATED-SCATTERED TSRA THIS AFTERNOON/EARLY EVENING.

* SOUTH-SOUTHEAST WIND AROUND 10 KT BECOMING SOUTH WITH GUSTS NEAR
  20 KT DEVELOPING BY MIDDAY.

* GREATER CHANCE FOR MORE ORGANIZED TSRA TOMORROW.

RATZER

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

FORECAST CONCERNS CONTINUE TO FOCUS ON SHRA/TSRA POTENTIAL
THROUGH THE PERIOD AS WELL AS GUSTY SOUTH WINDS DEVELOPING LATE
FRIDAY MORNING AND PERSISTING INTO THIS EVENING.

A WARM FRONT WILL SLOWLY LIFT NWD THROUGH THE DAY AND PUSH NORTH
OF THE TERMINALS BY LATE MORNING. WHILE THE SFC WARM FRONT IS
STILL TO THE SOUTH OF THE TERMINALS...SCT SHRA HAVE DEVELOPED IN A
ZONE OF WARM ADVECTION ALONG 25-30KT SWLY WINDS ALOFT. THE BULK OF
THE ACTIVITY IS CURRENTLY LOCATED OVER WRN IL...INVOF KRFD. SFC
WINDS ARE STILL SLIGHTLY EAST OF SOUTH...BUT AS THE WARM FRONT
PUSHES NORTH OF THE TERMINALS...WINDS WILL VEER TO SOUTHERLY WITH
GUSTS TO ARND 20KT OR SO.

INSTABILITY WILL INCREASE VERY QUICKLY AS THE WARM FRONT PASSES
TO THE NORTH AND WARM SECTOR AIR OVERSPREADS THE REGION BRINGING
INCREASING TEMPERATURES AND DEWPOINTS. WEAK MID LEVEL IMPULSES
SHOULD TRACK ACROSS THE AREA THIS AFTERNOON AND EVENING IN UPPER
LEVEL SWLY FLOW AS AN UPPER RIDGE PUSHES TO THE EAST AND A LARGER
SCALE UPPER TROUGH MOVES ACROSS THE CENTRAL PLAINS. THESE IMPULSES
WILL BE THE TRIGGERING MECHANISM FOR ADDITIONAL SHRA/TSRA...BUT IN
THE ABSENCE OF ANY SFC FORCING...ACTIVITY SHOULD GENERALLY BE
SCATTERED AND DIFFICULT TO TIME AT THE TERMINALS. HAVE PUSHED BACK
THE TIMING OF THE PCPN MENTION AT THE CHICAGO AREA TERMINALS WHEN
INSTABILITY SHOULD BE THE STRONGEST...BUT THIS IS A LOW CONFIDENCE
CHANGE AS IN SUCH A WARM/MOIST AIRMASS SCT SHRA/ISOLD TSRA COULD
DEVELOP AT ANY TIME.

A BETTER CHANCE FOR MORE ORGANIZED TS WILL COME LATE IN THE
PERIOD...POSSIBLY NOT UNTIL TOMORROW MORNING AS THE MAIN LONGWAVE
UPPER TROUGH AND A WEAK SFC COLD FRONT CROSS THE REGION.

KREIN

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

* MEDIUM-LOW CONFIDENCE IN THUNDER CHANCES/COVERAGE AND SPECIFIC TIMING
  THROUGH THIS EVENING.

* MEDIUM CONFIDENCE IN MORE ORGANIZED TS TOMORROW MORNING.

* HIGH CONFIDENCE IN WIND TRENDS THROUGH THE PERIOD.

KREIN/RATZER

//OUTLOOK FOR ORD/MDW FOR 00Z SUNDAY-12Z FRIDAY...UPDATED 12Z...

* SATURDAY NIGHT THROUGH SUNDAY NIGHT...VFR. WX NIL.

* MONDAY...CHANCE OF TSRA.

* TUESDAY...VFR. WX NIL.

* WEDNESDAY THROUGH THURSDAY NIGHT...SLIGHT CHANCE OF TSRA

KREIN

&&

.MARINE...
315 AM CDT

HIGH PRESSURE OVER THE EASTERN GREAT LAKES WILL MOVE EAST OFF THE
NEW ENGLAND COAST FRIDAY EVENING...WHILE A TROUGH OF LOW PRESSURE
DEVELOPS ACROSS THE CENTRAL PLAINS AND UPPER MIDWEST. THIS WILL
SET UP A PERIOD OF SOUTHERLY WINDS AND AS THE TROUGH MOVES
EAST...THE GRADIENT OVER THE LAKE WILL STRENGTHEN AND WINDS SHOULD
INCREASE TO THE 20-25 KT RANGE. A DEEPENING LOW CENTER WITHIN THE
TROUGH WILL MOVE TO WISCONSIN SATURDAY AND ACROSS NORTHERN LAKE
MICHIGAN SATURDAY EVENING. AS THE LOW TRACKS TO THE NORTHEAST...AN
ASSOCIATED COLD FRONT WILL MOVE DOWN THE LAKE SATURDAY AFTERNOON
AND EVENING...QUICKLY SHIFTING WINDS TO NWLY FOLLOWING THE FROPA.
THE LATEST MODEL GUIDANCE SUGGESTS THAT THE FRONT WILL WASH OUT
LATE SATURDAY NIGHT BEFORE REACHING THE SOUTH END OF THE LAKE AND
WINDS THERE SHOULD NEVER TRULY SHIFT NWLY...BUT RATHER BECOMING
LIGHT AND VARIABLE LATE SATURDAY NIGHT THROUGH SUNDAY MORNING. A
DEEPER LOW IS EXPECTED TO DEVELOP OVER THE DAKOTAS AND LIFT
THROUGH WESTERN ONTARIO SUNDAY NIGHT AND MONDAY BRINGING A RETURN
TO BRISK SOUTH TO SOUTHWEST WINDS TO THE LAKE FOR MONDAY AND
TUESDAY.

KREIN

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO







000
FXUS63 KLOT 291152
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
652 AM CDT FRI AUG 29 2014

.DISCUSSION...
326 AM CDT

THE MAIN FORECAST CONCERNS WILL CENTER AROUND CONVECTIVE CHANCES AND
TIMING...AS WELL AS TEMPERATURES TODAY...AND THROUGH THE HOLIDAY WEEKEND.

CURRENTLY...THE REMNANT MCV FROM YESTERDAY EVENINGS SHOWERS AND
STORMS CONTINUES TO SHIFT ACROSS MY SOUTHERN COUNTIES EARLY THIS
MORNING. HOWEVER...ONLY A FEW LIGHT SHOWERS/SPRINKLES REMAIN ACROSS
THIS AREA...WITH DRIER AND FAIRLY STABLE CONDITIONS IN PLACE TO THE EAST.

ANOTHER AREA OF CONVECTION IS ONGOING TO OUR WEST ACROSS IOWA AND
INTO SOUTHERN MN. THIS ACTIVITY IS OCCURRING WITHIN A REGION OF GOOD
LOWER LEVEL WARM AIR ADVECTION/ISENTROPIC ASCENT ON THE DOWNSTREAM
PERIPHERY OF A REMNANT MID/UPPER LEVEL TROUGH OVER THE PLAINS STATES.
DOWN STREAM UPPER RIDGING OVER THE GREAT LAKES REGION IS LEADING TO A
STEERING FLOW TO THE NORTHEAST. THEREFORE...MOST IF NOT ALL OF THIS
CONVECTIVE ACTIVITY WILL SHIFT INTO SOUTHERN WISCONSIN AND PERHAPS
FAR NORTHWESTERN ILLINOIS THIS MORNING. IN SPITE OF THIS...I HAVE
LEFT SLIGHT CHANCE POPS IN THIS MORNING AS IT IS POSSIBLE THAT SOME
ADDITIONAL CELLS COULD DEVELOP IN ASSOCIATION WITH AN EASTWARD MOVING
OUTFLOW BOUNDARY...AS EVIDENT OFF OF THE DMX RADAR MOVING TOWARDS
EASTERN IOWA. THIS ACTIVITY...IF IT OCCURS IN ANY OF NORTHERN
ILLINOIS EARLY THIS MORNING...WOULD LIKELY BE ISOLATED TO WIDELY
SCATTERED...WITH THE MAIN FOCUS REMAINING NORTH.

A SURFACE WARM FRONT IS EXPECTED TO LIFT NORTHWARD OVER THE AREA
INTO THIS AFTERNOON...WITH A WARMER AIRMASS EXPECTED IN ITS WAKE. IN
SPITE OF THIS...HOWEVER...HIGH TEMPERATURES ACROSS THE AREA WILL BE
TRICKY AS IT APPEARS THAT SOME SCATTERED THUNDERSTORMS COULD DEVELOP
ACROSS PORTIONS OF THE AREA THIS AFTERNOON...AND HAMPER THE MAGNITUDE
OF THE WARMTH ACROSS SOME AREAS. MODEST HEIGHT FALLS ALOFT ARE FORECAST
ACROSS NORTHERN ILLINOIS IN ASSOCIATION WITH THE AFOREMENTIONED UPPER
TROUGH SHIFTING EASTWARD OVER THE MID MISSOURI VALLEY THIS
AFTERNOON. IN SPITE OF THE FACT THAT THE BEST LARGE SCALE FORCING
FOR ASCENT WITH THIS DISTURBANCE SHOULD REMAIN WEST OF THE AREA THIS
AFTERNOON...THE EXPECTED INCREASE IN LOW-LEVEL THETA E IS EXPECTED
TO PRODUCE AN UNCAPPED ATMOSPHERE FEATURING MLCAPES OF AROUND 1500
J/KG BY THIS AFTERNOON. A MAJORITY OF THE GLOBAL MODELS...AS WELL AS
THE HIRES CONVECTIVE ALLOWING MODELS FIRE UP ACTIVITY WITHIN THIS
REGIME THIS AFTERNOON. IT APPEARS WE WILL HAVE TO WATCH MORNING
CLOUD COVER...HOWEVER...AS THIS COULD INHIBIT THE DEGREE OF
WARMING A BIT THROUGH THE MORNING...AND POSSIBLY LEAD TO WEAKER
INSTABILITY THAN WHAT THE MODELS ARE CURRENTLY ADVERTISING.

IF THE CONVECTION DOES DEVELOP AS  EXPECTED...MARGINAL DEEP LAYER
SHEAR OF 25 TO 30 KT COULD ALLOW FOR A FEW STRONGER STORMS CAPABLE
OF SOME ISOLATED HIGH WIND GUSTS. SOME TORRENTIAL DOWNPOURS WOULD
ALSO BE A THREAT FROM THESE STORMS GIVEN THE JUICY AIRMASS FEATURING
PWATS UP AROUND 1.75 INCHES. HOWEVER...EXTREME RAINFALL AMOUNTS
APPEAR UNLIKELY GIVEN STORM MOTIONS SHOULD BE TO THE NORTHEAST
AROUND 30 KT. SO THE STORMS SHOULD NOT BE OVER A GIVEN AREA TOO
LONG. MUCH OF THIS ACTIVITY APPEARS TO BE HIGHLY DIURNAL IN
NATURE...SO A RAPID DOWNWARD TREND IS EXPECTED AFTER SUNSET THIS
EVENING.

ANOTHER ROUND OF THUNDERSTORMS APPEARS LIKELY ON
SATURDAY...ESPECIALLY DURING THE MORNING AS THE UPPER LEVEL
TROUGH...AND AN ASSOCIATED SURFACE LOW AND COLD FRONT SHIFTS
EASTWARD ACROSS ACROSS SOUTHERN WI AND NORTHERN IL. THIS ACTIVITY
COULD LINGER INTO SATURDAY EVENING ACROSS MY FAR SOUTHEASTERN
COUNTIES. HOWEVER...IT APPEARS THAT FOLLOWING THIS FRONTAL PASSAGE
WE WILL BE GREETED WITH A NICE DRY SUNDAY ACROSS THE AREA.

UNFORTUNATELY...LABOR DAY APPEARS THAT IT COULD BE ANOTHER ACTIVE
WEATHER DAY ACROSS THE REGION. ANOTHER POTENT UPPER LEVEL
DISTURBANCE AND SURFACE FRONT IS FORECAST TO SHIFT OVER THE AREA BY
MONDAY. WE WILL ALSO HAVE TO WATCH FOR THE THREAT OF SEVERE
THUNDERSTORMS ON MONDAY AND MONDAY NIGHT AS A 45 TO 50 KT MID LEVEL
JET IS PROGGED TO DEVELOP ACROSS THE AREA. THIS COULD RESULT IN DEEP
LAYER SHEAR STRONG ENOUGH TO PRODUCE MORE ORGANIZED STRONG TO SEVERE
CONVECTION. VERY HEAVY RAINFALL WOULD AGAIN BE A CONCERN WITH THIS
ACTIVITY...ESPECIALLY IF THE FRONTAL ZONE STALLS OUT OVER THE AREA
MONDAY NIGHT. AT THIS TIME...HOWEVER...UNCERTAINTY IS HIGH ON WHERE
THE SURFACE FRONT MAY STALL AND HENCE WHAT AREAS COULD BE FAVORED FOR
EXTENDED PERIODS OF VERY HEAVY RAINFALL.

THE ACTIVE WEATHER PATTERN COULD SHIFT SOUTH OF THE AREA FOR A DAY
OR TWO INTO MID TO LATE WEEK BEFORE MORE PERIODS OF CONVECTION ARE
POSSIBLE. OVERALL...IT APPEARS TEMPERATURES WILL REMAIN ON THE WARM
SIDE OF AVERAGE...WITH THE POTENTIAL FOR SOME VERY WARM AND HUMID DAYS
LATER NEXT WEEK.

KJB

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 12Z...

* SCATTERED TSRA/SHRA FRIDAY LATE AFTERNOON/EARLY EVENING.

* SOUTH WIND WITH GUSTS DEVELOPING TO 20KT LATE MORNING FRIDAY.

* GREATER CHANCE FOR MORE ORGANIZED TSRA TOMORROW.

KREIN

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

FORECAST CONCERNS CONTINUE TO FOCUS ON SHRA/TSRA POTENTIAL
THROUGH THE PERIOD AS WELL AS GUSTY SOUTH WINDS DEVELOPING LATE
FRIDAY MORNING AND PERSISTING INTO THIS EVENING.

A WARM FRONT WILL SLOWLY LIFT NWD THROUGH THE DAY AND PUSH NORTH
OF THE TERMINALS BY LATE MORNING. WHILE THE SFC WARM FRONT IS
STILL TO THE SOUTH OF THE TERMINALS...SCT SHRA HAVE DEVELOPED IN A
ZONE OF WARM ADVECTION ALONG 25-30KT SWLY WINDS ALOFT. THE BULK OF
THE ACTIVITY IS CURRENTLY LOCATED OVER WRN IL...INVOF KRFD. SFC
WINDS ARE STILL SLIGHTLY EAST OF SOUTH...BUT AS THE WARM FRONT
PUSHES NORTH OF THE TERMINALS...WINDS WILL VEER TO SOUTHERLY WITH
GUSTS TO ARND 20KT OR SO.

INSTABILITY WILL INCREASE VERY QUICKLY AS THE WARM FRONT PASSES
TO THE NORTH AND WARM SECTOR AIR OVERSPREADS THE REGION BRINGING
INCREASING TEMPERATURES AND DEWPOINTS. WEAK MID LEVEL IMPULSES
SHOULD TRACK ACROSS THE AREA THIS AFTERNOON AND EVENING IN UPPER
LEVEL SWLY FLOW AS AN UPPER RIDGE PUSHES TO THE EAST AND A LARGER
SCALE UPPER TROUGH MOVES ACROSS THE CENTRAL PLAINS. THESE IMPULSES
WILL BE THE TRIGGERING MECHANISM FOR ADDITIONAL SHRA/TSRA...BUT IN
THE ABSENCE OF ANY SFC FORCING...ACTIVITY SHOULD GENERALLY BE
SCATTERED AND DIFFICULT TO TIME AT THE TERMINALS. HAVE PUSHED BACK
THE TIMING OF THE PCPN MENTION AT THE CHICAGO AREA TERMINALS WHEN
INSTABILITY SHOULD BE THE STRONGEST...BUT THIS IS A LOW CONFIDENCE
CHANGE AS IN SUCH A WARM/MOIST AIRMASS SCT SHRA/ISOLD TSRA COULD
DEVELOP AT ANY TIME.

A BETTER CHANCE FOR MORE ORGANIZED TS WILL COME LATE IN THE
PERIOD...POSSIBLY NOT UNTIL TOMORROW MORNING AS THE MAIN LONGWAVE
UPPER TROUGH AND A WEAK SFC COLD FRONT CROSS THE REGION.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 12Z...

* LOW CONFIDENCE IN THUNDER CHANCES/COVERAGE AND SPECIFIC TIMING
  THROUGH THIS EVENING.

* MEDIUM CONFIDENCE IN MORE ORGANIZED TS TOMORROW MORNING.

* HIGH CONFIDENCE IN WIND TRENDS THROUGH THE PERIOD.

KREIN

//OUTLOOK FOR ORD/MDW FOR 00Z SUNDAY-12Z FRIDAY...UPDATED 12Z...

* SATURDAY NIGHT THROUGH SUNDAY NIGHT...VFR. WX NIL.

* MONDAY...CHANCE OF TSRA.

* TUESDAY...VFR. WX NIL.

* WEDNESDAY THROUGH THURSDAY NIGHT...SLIGHT CHANCE OF TSRA

KREIN

&&

.MARINE...
315 AM CDT

HIGH PRESSURE OVER THE EASTERN GREAT LAKES WILL MOVE EAST OFF THE
NEW ENGLAND COAST FRIDAY EVENING...WHILE A TROUGH OF LOW PRESSURE
DEVELOPS ACROSS THE CENTRAL PLAINS AND UPPER MIDWEST. THIS WILL
SET UP A PERIOD OF SOUTHERLY WINDS AND AS THE TROUGH MOVES
EAST...THE GRADIENT OVER THE LAKE WILL STRENGTHEN AND WINDS SHOULD
INCREASE TO THE 20-25 KT RANGE. A DEEPENING LOW CENTER WITHIN THE
TROUGH WILL MOVE TO WISCONSIN SATURDAY AND ACROSS NORTHERN LAKE
MICHIGAN SATURDAY EVENING. AS THE LOW TRACKS TO THE NORTHEAST...AN
ASSOCIATED COLD FRONT WILL MOVE DOWN THE LAKE SATURDAY AFTERNOON
AND EVENING...QUICKLY SHIFTING WINDS TO NWLY FOLLOWING THE FROPA.
THE LATEST MODEL GUIDANCE SUGGESTS THAT THE FRONT WILL WASH OUT
LATE SATURDAY NIGHT BEFORE REACHING THE SOUTH END OF THE LAKE AND
WINDS THERE SHOULD NEVER TRULY SHIFT NWLY...BUT RATHER BECOMING
LIGHT AND VARIABLE LATE SATURDAY NIGHT THROUGH SUNDAY MORNING. A
DEEPER LOW IS EXPECTED TO DEVELOP OVER THE DAKOTAS AND LIFT
THROUGH WESTERN ONTARIO SUNDAY NIGHT AND MONDAY BRINGING A RETURN
TO BRISK SOUTH TO SOUTHWEST WINDS TO THE LAKE FOR MONDAY AND
TUESDAY.

KREIN

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO







000
FXUS63 KLOT 291152
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
652 AM CDT FRI AUG 29 2014

.DISCUSSION...
326 AM CDT

THE MAIN FORECAST CONCERNS WILL CENTER AROUND CONVECTIVE CHANCES AND
TIMING...AS WELL AS TEMPERATURES TODAY...AND THROUGH THE HOLIDAY WEEKEND.

CURRENTLY...THE REMNANT MCV FROM YESTERDAY EVENINGS SHOWERS AND
STORMS CONTINUES TO SHIFT ACROSS MY SOUTHERN COUNTIES EARLY THIS
MORNING. HOWEVER...ONLY A FEW LIGHT SHOWERS/SPRINKLES REMAIN ACROSS
THIS AREA...WITH DRIER AND FAIRLY STABLE CONDITIONS IN PLACE TO THE EAST.

ANOTHER AREA OF CONVECTION IS ONGOING TO OUR WEST ACROSS IOWA AND
INTO SOUTHERN MN. THIS ACTIVITY IS OCCURRING WITHIN A REGION OF GOOD
LOWER LEVEL WARM AIR ADVECTION/ISENTROPIC ASCENT ON THE DOWNSTREAM
PERIPHERY OF A REMNANT MID/UPPER LEVEL TROUGH OVER THE PLAINS STATES.
DOWN STREAM UPPER RIDGING OVER THE GREAT LAKES REGION IS LEADING TO A
STEERING FLOW TO THE NORTHEAST. THEREFORE...MOST IF NOT ALL OF THIS
CONVECTIVE ACTIVITY WILL SHIFT INTO SOUTHERN WISCONSIN AND PERHAPS
FAR NORTHWESTERN ILLINOIS THIS MORNING. IN SPITE OF THIS...I HAVE
LEFT SLIGHT CHANCE POPS IN THIS MORNING AS IT IS POSSIBLE THAT SOME
ADDITIONAL CELLS COULD DEVELOP IN ASSOCIATION WITH AN EASTWARD MOVING
OUTFLOW BOUNDARY...AS EVIDENT OFF OF THE DMX RADAR MOVING TOWARDS
EASTERN IOWA. THIS ACTIVITY...IF IT OCCURS IN ANY OF NORTHERN
ILLINOIS EARLY THIS MORNING...WOULD LIKELY BE ISOLATED TO WIDELY
SCATTERED...WITH THE MAIN FOCUS REMAINING NORTH.

A SURFACE WARM FRONT IS EXPECTED TO LIFT NORTHWARD OVER THE AREA
INTO THIS AFTERNOON...WITH A WARMER AIRMASS EXPECTED IN ITS WAKE. IN
SPITE OF THIS...HOWEVER...HIGH TEMPERATURES ACROSS THE AREA WILL BE
TRICKY AS IT APPEARS THAT SOME SCATTERED THUNDERSTORMS COULD DEVELOP
ACROSS PORTIONS OF THE AREA THIS AFTERNOON...AND HAMPER THE MAGNITUDE
OF THE WARMTH ACROSS SOME AREAS. MODEST HEIGHT FALLS ALOFT ARE FORECAST
ACROSS NORTHERN ILLINOIS IN ASSOCIATION WITH THE AFOREMENTIONED UPPER
TROUGH SHIFTING EASTWARD OVER THE MID MISSOURI VALLEY THIS
AFTERNOON. IN SPITE OF THE FACT THAT THE BEST LARGE SCALE FORCING
FOR ASCENT WITH THIS DISTURBANCE SHOULD REMAIN WEST OF THE AREA THIS
AFTERNOON...THE EXPECTED INCREASE IN LOW-LEVEL THETA E IS EXPECTED
TO PRODUCE AN UNCAPPED ATMOSPHERE FEATURING MLCAPES OF AROUND 1500
J/KG BY THIS AFTERNOON. A MAJORITY OF THE GLOBAL MODELS...AS WELL AS
THE HIRES CONVECTIVE ALLOWING MODELS FIRE UP ACTIVITY WITHIN THIS
REGIME THIS AFTERNOON. IT APPEARS WE WILL HAVE TO WATCH MORNING
CLOUD COVER...HOWEVER...AS THIS COULD INHIBIT THE DEGREE OF
WARMING A BIT THROUGH THE MORNING...AND POSSIBLY LEAD TO WEAKER
INSTABILITY THAN WHAT THE MODELS ARE CURRENTLY ADVERTISING.

IF THE CONVECTION DOES DEVELOP AS  EXPECTED...MARGINAL DEEP LAYER
SHEAR OF 25 TO 30 KT COULD ALLOW FOR A FEW STRONGER STORMS CAPABLE
OF SOME ISOLATED HIGH WIND GUSTS. SOME TORRENTIAL DOWNPOURS WOULD
ALSO BE A THREAT FROM THESE STORMS GIVEN THE JUICY AIRMASS FEATURING
PWATS UP AROUND 1.75 INCHES. HOWEVER...EXTREME RAINFALL AMOUNTS
APPEAR UNLIKELY GIVEN STORM MOTIONS SHOULD BE TO THE NORTHEAST
AROUND 30 KT. SO THE STORMS SHOULD NOT BE OVER A GIVEN AREA TOO
LONG. MUCH OF THIS ACTIVITY APPEARS TO BE HIGHLY DIURNAL IN
NATURE...SO A RAPID DOWNWARD TREND IS EXPECTED AFTER SUNSET THIS
EVENING.

ANOTHER ROUND OF THUNDERSTORMS APPEARS LIKELY ON
SATURDAY...ESPECIALLY DURING THE MORNING AS THE UPPER LEVEL
TROUGH...AND AN ASSOCIATED SURFACE LOW AND COLD FRONT SHIFTS
EASTWARD ACROSS ACROSS SOUTHERN WI AND NORTHERN IL. THIS ACTIVITY
COULD LINGER INTO SATURDAY EVENING ACROSS MY FAR SOUTHEASTERN
COUNTIES. HOWEVER...IT APPEARS THAT FOLLOWING THIS FRONTAL PASSAGE
WE WILL BE GREETED WITH A NICE DRY SUNDAY ACROSS THE AREA.

UNFORTUNATELY...LABOR DAY APPEARS THAT IT COULD BE ANOTHER ACTIVE
WEATHER DAY ACROSS THE REGION. ANOTHER POTENT UPPER LEVEL
DISTURBANCE AND SURFACE FRONT IS FORECAST TO SHIFT OVER THE AREA BY
MONDAY. WE WILL ALSO HAVE TO WATCH FOR THE THREAT OF SEVERE
THUNDERSTORMS ON MONDAY AND MONDAY NIGHT AS A 45 TO 50 KT MID LEVEL
JET IS PROGGED TO DEVELOP ACROSS THE AREA. THIS COULD RESULT IN DEEP
LAYER SHEAR STRONG ENOUGH TO PRODUCE MORE ORGANIZED STRONG TO SEVERE
CONVECTION. VERY HEAVY RAINFALL WOULD AGAIN BE A CONCERN WITH THIS
ACTIVITY...ESPECIALLY IF THE FRONTAL ZONE STALLS OUT OVER THE AREA
MONDAY NIGHT. AT THIS TIME...HOWEVER...UNCERTAINTY IS HIGH ON WHERE
THE SURFACE FRONT MAY STALL AND HENCE WHAT AREAS COULD BE FAVORED FOR
EXTENDED PERIODS OF VERY HEAVY RAINFALL.

THE ACTIVE WEATHER PATTERN COULD SHIFT SOUTH OF THE AREA FOR A DAY
OR TWO INTO MID TO LATE WEEK BEFORE MORE PERIODS OF CONVECTION ARE
POSSIBLE. OVERALL...IT APPEARS TEMPERATURES WILL REMAIN ON THE WARM
SIDE OF AVERAGE...WITH THE POTENTIAL FOR SOME VERY WARM AND HUMID DAYS
LATER NEXT WEEK.

KJB

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 12Z...

* SCATTERED TSRA/SHRA FRIDAY LATE AFTERNOON/EARLY EVENING.

* SOUTH WIND WITH GUSTS DEVELOPING TO 20KT LATE MORNING FRIDAY.

* GREATER CHANCE FOR MORE ORGANIZED TSRA TOMORROW.

KREIN

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

FORECAST CONCERNS CONTINUE TO FOCUS ON SHRA/TSRA POTENTIAL
THROUGH THE PERIOD AS WELL AS GUSTY SOUTH WINDS DEVELOPING LATE
FRIDAY MORNING AND PERSISTING INTO THIS EVENING.

A WARM FRONT WILL SLOWLY LIFT NWD THROUGH THE DAY AND PUSH NORTH
OF THE TERMINALS BY LATE MORNING. WHILE THE SFC WARM FRONT IS
STILL TO THE SOUTH OF THE TERMINALS...SCT SHRA HAVE DEVELOPED IN A
ZONE OF WARM ADVECTION ALONG 25-30KT SWLY WINDS ALOFT. THE BULK OF
THE ACTIVITY IS CURRENTLY LOCATED OVER WRN IL...INVOF KRFD. SFC
WINDS ARE STILL SLIGHTLY EAST OF SOUTH...BUT AS THE WARM FRONT
PUSHES NORTH OF THE TERMINALS...WINDS WILL VEER TO SOUTHERLY WITH
GUSTS TO ARND 20KT OR SO.

INSTABILITY WILL INCREASE VERY QUICKLY AS THE WARM FRONT PASSES
TO THE NORTH AND WARM SECTOR AIR OVERSPREADS THE REGION BRINGING
INCREASING TEMPERATURES AND DEWPOINTS. WEAK MID LEVEL IMPULSES
SHOULD TRACK ACROSS THE AREA THIS AFTERNOON AND EVENING IN UPPER
LEVEL SWLY FLOW AS AN UPPER RIDGE PUSHES TO THE EAST AND A LARGER
SCALE UPPER TROUGH MOVES ACROSS THE CENTRAL PLAINS. THESE IMPULSES
WILL BE THE TRIGGERING MECHANISM FOR ADDITIONAL SHRA/TSRA...BUT IN
THE ABSENCE OF ANY SFC FORCING...ACTIVITY SHOULD GENERALLY BE
SCATTERED AND DIFFICULT TO TIME AT THE TERMINALS. HAVE PUSHED BACK
THE TIMING OF THE PCPN MENTION AT THE CHICAGO AREA TERMINALS WHEN
INSTABILITY SHOULD BE THE STRONGEST...BUT THIS IS A LOW CONFIDENCE
CHANGE AS IN SUCH A WARM/MOIST AIRMASS SCT SHRA/ISOLD TSRA COULD
DEVELOP AT ANY TIME.

A BETTER CHANCE FOR MORE ORGANIZED TS WILL COME LATE IN THE
PERIOD...POSSIBLY NOT UNTIL TOMORROW MORNING AS THE MAIN LONGWAVE
UPPER TROUGH AND A WEAK SFC COLD FRONT CROSS THE REGION.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 12Z...

* LOW CONFIDENCE IN THUNDER CHANCES/COVERAGE AND SPECIFIC TIMING
  THROUGH THIS EVENING.

* MEDIUM CONFIDENCE IN MORE ORGANIZED TS TOMORROW MORNING.

* HIGH CONFIDENCE IN WIND TRENDS THROUGH THE PERIOD.

KREIN

//OUTLOOK FOR ORD/MDW FOR 00Z SUNDAY-12Z FRIDAY...UPDATED 12Z...

* SATURDAY NIGHT THROUGH SUNDAY NIGHT...VFR. WX NIL.

* MONDAY...CHANCE OF TSRA.

* TUESDAY...VFR. WX NIL.

* WEDNESDAY THROUGH THURSDAY NIGHT...SLIGHT CHANCE OF TSRA

KREIN

&&

.MARINE...
315 AM CDT

HIGH PRESSURE OVER THE EASTERN GREAT LAKES WILL MOVE EAST OFF THE
NEW ENGLAND COAST FRIDAY EVENING...WHILE A TROUGH OF LOW PRESSURE
DEVELOPS ACROSS THE CENTRAL PLAINS AND UPPER MIDWEST. THIS WILL
SET UP A PERIOD OF SOUTHERLY WINDS AND AS THE TROUGH MOVES
EAST...THE GRADIENT OVER THE LAKE WILL STRENGTHEN AND WINDS SHOULD
INCREASE TO THE 20-25 KT RANGE. A DEEPENING LOW CENTER WITHIN THE
TROUGH WILL MOVE TO WISCONSIN SATURDAY AND ACROSS NORTHERN LAKE
MICHIGAN SATURDAY EVENING. AS THE LOW TRACKS TO THE NORTHEAST...AN
ASSOCIATED COLD FRONT WILL MOVE DOWN THE LAKE SATURDAY AFTERNOON
AND EVENING...QUICKLY SHIFTING WINDS TO NWLY FOLLOWING THE FROPA.
THE LATEST MODEL GUIDANCE SUGGESTS THAT THE FRONT WILL WASH OUT
LATE SATURDAY NIGHT BEFORE REACHING THE SOUTH END OF THE LAKE AND
WINDS THERE SHOULD NEVER TRULY SHIFT NWLY...BUT RATHER BECOMING
LIGHT AND VARIABLE LATE SATURDAY NIGHT THROUGH SUNDAY MORNING. A
DEEPER LOW IS EXPECTED TO DEVELOP OVER THE DAKOTAS AND LIFT
THROUGH WESTERN ONTARIO SUNDAY NIGHT AND MONDAY BRINGING A RETURN
TO BRISK SOUTH TO SOUTHWEST WINDS TO THE LAKE FOR MONDAY AND
TUESDAY.

KREIN

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 290831
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
331 AM CDT FRI AUG 29 2014

.DISCUSSION...
326 AM CDT

THE MAIN FORECAST CONCERNS WILL CENTER AROUND CONVECTIVE CHANCES AND
TIMING...AS WELL AS TEMPERATURES TODAY...AND THROUGH THE HOLIDAY WEEKEND.

CURRENTLY...THE REMNANT MCV FROM YESTERDAY EVENINGS SHOWERS AND
STORMS CONTINUES TO SHIFT ACROSS MY SOUTHERN COUNTIES EARLY THIS
MORNING. HOWEVER...ONLY A FEW LIGHT SHOWERS/SPRINKLES REMAIN ACROSS
THIS AREA...WITH DRIER AND FAIRLY STABLE CONDITIONS IN PLACE TO THE EAST.

ANOTHER AREA OF CONVECTION IS ONGOING TO OUR WEST ACROSS IOWA AND
INTO SOUTHERN MN. THIS ACTIVITY IS OCCURRING WITHIN A REGION OF GOOD
LOWER LEVEL WARM AIR ADVECTION/ISENTROPIC ASCENT ON THE DOWNSTREAM
PERIPHERY OF A REMNANT MID/UPPER LEVEL TROUGH OVER THE PLAINS STATES.
DOWN STREAM UPPER RIDGING OVER THE GREAT LAKES REGION IS LEADING TO A
STEERING FLOW TO THE NORTHEAST. THEREFORE...MOST IF NOT ALL OF THIS
CONVECTIVE ACTIVITY WILL SHIFT INTO SOUTHERN WISCONSIN AND PERHAPS
FAR NORTHWESTERN ILLINOIS THIS MORNING. IN SPITE OF THIS...I HAVE
LEFT SLIGHT CHANCE POPS IN THIS MORNING AS IT IS POSSIBLE THAT SOME
ADDITIONAL CELLS COULD DEVELOP IN ASSOCIATION WITH AN EASTWARD MOVING
OUTFLOW BOUNDARY...AS EVIDENT OFF OF THE DMX RADAR MOVING TOWARDS
EASTERN IOWA. THIS ACTIVITY...IF IT OCCURS IN ANY OF NORTHERN
ILLINOIS EARLY THIS MORNING...WOULD LIKELY BE ISOLATED TO WIDELY
SCATTERED...WITH THE MAIN FOCUS REMAINING NORTH.

A SURFACE WARM FRONT IS EXPECTED TO LIFT NORTHWARD OVER THE AREA
INTO THIS AFTERNOON...WITH A WARMER AIRMASS EXPECTED IN ITS WAKE. IN
SPITE OF THIS...HOWEVER...HIGH TEMPERATURES ACROSS THE AREA WILL BE
TRICKY AS IT APPEARS THAT SOME SCATTERED THUNDERSTORMS COULD DEVELOP
ACROSS PORTIONS OF THE AREA THIS AFTERNOON...AND HAMPER THE MAGNITUDE
OF THE WARMTH ACROSS SOME AREAS. MODEST HEIGHT FALLS ALOFT ARE FORECAST
ACROSS NORTHERN ILLINOIS IN ASSOCIATION WITH THE AFOREMENTIONED UPPER
TROUGH SHIFTING EASTWARD OVER THE MID MISSOURI VALLEY THIS
AFTERNOON. IN SPITE OF THE FACT THAT THE BEST LARGE SCALE FORCING
FOR ASCENT WITH THIS DISTURBANCE SHOULD REMAIN WEST OF THE AREA THIS
AFTERNOON...THE EXPECTED INCREASE IN LOW-LEVEL THETA E IS EXPECTED
TO PRODUCE AN UNCAPPED ATMOSPHERE FEATURING MLCAPES OF AROUND 1500
J/KG BY THIS AFTERNOON. A MAJORITY OF THE GLOBAL MODELS...AS WELL AS
THE HIRES CONVECTIVE ALLOWING MODELS FIRE UP ACTIVITY WITHIN THIS
REGIME THIS AFTERNOON. IT APPEARS WE WILL HAVE TO WATCH MORNING
CLOUD COVER...HOWEVER...AS THIS COULD INHIBIT THE DEGREE OF
WARMING A BIT THROUGH THE MORNING...AND POSSIBLY LEAD TO WEAKER
INSTABILITY THAN WHAT THE MODELS ARE CURRENTLY ADVERTISING.

IF THE CONVECTION DOES DEVELOP AS  EXPECTED...MARGINAL DEEP LAYER
SHEAR OF 25 TO 30 KT COULD ALLOW FOR A FEW STRONGER STORMS CAPABLE
OF SOME ISOLATED HIGH WIND GUSTS. SOME TORRENTIAL DOWNPOURS WOULD
ALSO BE A THREAT FROM THESE STORMS GIVEN THE JUICY AIRMASS FEATURING
PWATS UP AROUND 1.75 INCHES. HOWEVER...EXTREME RAINFALL AMOUNTS
APPEAR UNLIKELY GIVEN STORM MOTIONS SHOULD BE TO THE NORTHEAST
AROUND 30 KT. SO THE STORMS SHOULD NOT BE OVER A GIVEN AREA TOO
LONG. MUCH OF THIS ACTIVITY APPEARS TO BE HIGHLY DIURNAL IN
NATURE...SO A RAPID DOWNWARD TREND IS EXPECTED AFTER SUNSET THIS
EVENING.

ANOTHER ROUND OF THUNDERSTORMS APPEARS LIKELY ON
SATURDAY...ESPECIALLY DURING THE MORNING AS THE UPPER LEVEL
TROUGH...AND AN ASSOCIATED SURFACE LOW AND COLD FRONT SHIFTS
EASTWARD ACROSS ACROSS SOUTHERN WI AND NORTHERN IL. THIS ACTIVITY
COULD LINGER INTO SATURDAY EVENING ACROSS MY FAR SOUTHEASTERN
COUNTIES. HOWEVER...IT APPEARS THAT FOLLOWING THIS FRONTAL PASSAGE
WE WILL BE GREETED WITH A NICE DRY SUNDAY ACROSS THE AREA.

UNFORTUNATELY...LABOR DAY APPEARS THAT IT COULD BE ANOTHER ACTIVE
WEATHER DAY ACROSS THE REGION. ANOTHER POTENT UPPER LEVEL
DISTURBANCE AND SURFACE FRONT IS FORECAST TO SHIFT OVER THE AREA BY
MONDAY. WE WILL ALSO HAVE TO WATCH FOR THE THREAT OF SEVERE
THUNDERSTORMS ON MONDAY AND MONDAY NIGHT AS A 45 TO 50 KT MID LEVEL
JET IS PROGGED TO DEVELOP ACROSS THE AREA. THIS COULD RESULT IN DEEP
LAYER SHEAR STRONG ENOUGH TO PRODUCE MORE ORGANIZED STRONG TO SEVERE
CONVECTION. VERY HEAVY RAINFALL WOULD AGAIN BE A CONCERN WITH THIS
ACTIVITY...ESPECIALLY IF THE FRONTAL ZONE STALLS OUT OVER THE AREA
MONDAY NIGHT. AT THIS TIME...HOWEVER...UNCERTAINTY IS HIGH ON WHERE
THE SURFACE FRONT MAY STALL AND HENCE WHAT AREAS COULD BE FAVORED FOR
EXTENDED PERIODS OF VERY HEAVY RAINFALL.

THE ACTIVE WEATHER PATTERN COULD SHIFT SOUTH OF THE AREA FOR A DAY
OR TWO INTO MID TO LATE WEEK BEFORE MORE PERIODS OF CONVECTION ARE
POSSIBLE. OVERALL...IT APPEARS TEMPERATURES WILL REMAIN ON THE WARM
SIDE OF AVERAGE...WITH THE POTENTIAL FOR SOME VERY WARM AND HUMID DAYS
LATER NEXT WEEK.

KJB

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 09Z...

* ISOLATED SHRA/TSRA LATE TONIGHT INTO EARLY FRIDAY MORNING.

* SCATTERED TSRA FRIDAY AFTERNOON/EARLY EVENING.

* SOUTH WIND WITH GUSTS DEVELOPING TO 20KT LATE MORNING FRIDAY.

KREIN

//DISCUSSION...UPDATED 06Z...

FORECAST CONCERNS WILL FOCUS ON SHRA/TSRA POTENTIAL THROUGH THE
PERIOD AS WELL AS GUSTY SOUTH WINDS DEVELOPING LATE FRIDAY MORNING
AND PERSISTING INTO EARLY FRIDAY EVENING.

FOR THE REMAINDER OF THE OVERNIGHT HOURS...THE REGION WILL REMAIN
UNDER SELY FLOW...NORTH OF A WARM FRONT CURRENTLY OVER CNTRL MO TO
SRN IL. SOME REMNANT SHOWERS FROM EARLIER CONVECTIVE ACTIVITY ARE
STILL SEEN ON THE LATEST RADAR IMAGERY...BUT THIS ACTIVITY IS
DIMINISHING WITH TIME FOR MUCH OF THE REGION. THE EXCEPTION IS A
SMALL AREA OF RAIN WHICH IS MORE PERSISTENT OVER ECNTRL IL. WITH
MID LEVEL FLOW MORE SOUTHWESTERLY...THERE HAS BEEN A MORE
PERSISTENT FETCH OF LIGHT PCPN INTO NWRN IL...SO KGYY COULD LIKELY
SEE SOME LIGHT RAIN THROUGH THE NIGHT THOUGH NO ADDITION THUNDER
IS ANTICIPATED WITH THIS PCPN. WITH A VERY MOIST AIRMASS IN PLACE
FROM RECENT PCPN ALONG WITH LIGHT WINDS...THERE WILL BE THE
POTENTIAL FOR SOME PATCHY BR WITH KDPA/KRFD BEING THE MORE LIKELY
TAF SITES TO SEE VIS DROP AT LEAST INTO MVFR LEVELS. EXPECT THAT
ORD/MDW SHOULD REMAIN VFR AS WINDS WILL REMAIN A LITTLE STRONGER
AND TEMP/DEWPOINT SPREADS A LITTLE HIGHER.

THE WARM FRONT WILL SLOWLY LIFT NWD THROUGH THE NIGHT AND PUSH
NORTH OF THE TERMINALS BY LATE FRIDAY MORNING. AT THIS
POINT...WINDS WILL SHIFT TO MORE SOUTHERLY. SOME BREAKS IN THE
CLOUD COVER SHOULD ALLOW FOR DEEPER LAYER MIXING...TAPPING
STRONGER WINDS ALOFT AND EXPECT THAT WINDS WILL BEGIN TO GUST TO
20KT FOLLOWING THE WARM FROPA.

INSTABILITY WILL INCREASES VERY QUICKLY AS THE WARM FRONT PASSES
TO THE NORTH AND WARM SECTOR AIR OVERSPREADS THE REGION BRINGING
INCREASING TEMPERATURES AND DEWPOINTS. MID LEVEL IMPULSES SHOULD
TRACK ACROSS THE AREA FRIDAY AFTERNOON AND EVENING IN UPPER LEVEL
SWLY FLOW AS THE UPPER RIDGE PUSHES TO THE EAST AND A LARGER SCALE
UPPER TROUGH MOVES ACROSS THE CENTRAL PLAINS. THESE IMPULSES WILL
BE THE TRIGGERING MECHANISM FOR ADDITIONAL SHRA/TSRA...BUT IN THE
ABSENCE OF ANY SFC FORCING...ACTIVITY WILL GENERALLY BE SCATTERED
AND DIFFICULT TO TIME AT THE TERMINALS. SO...WILL MAINTAIN THE
GOING PROB30 GROUP FOR TSRA WITH THE MOST FAVORABLE TIMING DURG
THE AFTERNOON HOURS. HOWEVER...WITH SCATTERED COVERAGE...ANY OF
THE TERMINALS COULD SEE SOME SHRA/TSRA A LITTLE EARLIER OR A
LITTLE LATER THAN THE GOING PROB30 TIMING.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 09Z...

* LOW CONFIDENCE IN THUNDER CHANCES/COVERAGE AND SPECIFIC TIMING
  FRIDAY AFTERNOON.

* HIGH CONFIDENCE IN WIND TRENDS THROUGH THE PERIOD.

* MEDIUM CONFIDENCE THAT ORD/MDW WILL REMAIN VFR THROUGH THE
  REMAINDER OF THE NIGHT AND INTO EARLY FRIDAY MORNING.

KREIN

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

* SATURDAY...TSRA LIKELY.
* SUNDAY...SLIGHT CHANCE OF TSRA.
* MONDAY AND TUESDAY...CHANCE OF TSRA.
* WEDNESDAY AND THURSDAY...SLIGHT CHANCE OF TSRA

KMD

&&

.MARINE...
315 AM CDT

HIGH PRESSURE OVER THE EASTERN GREAT LAKES WILL MOVE EAST OFF THE
NEW ENGLAND COAST FRIDAY EVENING...WHILE A TROUGH OF LOW PRESSURE
DEVELOPS ACROSS THE CENTRAL PLAINS AND UPPER MIDWEST. THIS WILL
SET UP A PERIOD OF SOUTHERLY WINDS AND AS THE TROUGH MOVES
EAST...THE GRADIENT OVER THE LAKE WILL STRENGTHEN AND WINDS SHOULD
INCREASE TO THE 20-25 KT RANGE. A DEEPENING LOW CENTER WITHIN THE
TROUGH WILL MOVE TO WISCONSIN SATURDAY AND ACROSS NORTHERN LAKE
MICHIGAN SATURDAY EVENING. AS THE LOW TRACKS TO THE NORTHEAST...AN
ASSOCIATED COLD FRONT WILL MOVE DOWN THE LAKE SATURDAY AFTERNOON
AND EVENING...QUICKLY SHIFTING WINDS TO NWLY FOLLOWING THE FROPA.
THE LATEST MODEL GUIDANCE SUGGESTS THAT THE FRONT WILL WASH OUT
LATE SATURDAY NIGHT BEFORE REACHING THE SOUTH END OF THE LAKE AND
WINDS THERE SHOULD NEVER TRULY SHIFT NWLY...BUT RATHER BECOMING
LIGHT AND VARIABLE LATE SATURDAY NIGHT THROUGH SUNDAY MORNING. A
DEEPER LOW IS EXPECTED TO DEVELOP OVER THE DAKOTAS AND LIFT
THROUGH WESTERN ONTARIO SUNDAY NIGHT AND MONDAY BRINGING A RETURN
TO BRISK SOUTH TO SOUTHWEST WINDS TO THE LAKE FOR MONDAY AND
TUESDAY.

KREIN

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO







000
FXUS63 KLOT 290815
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
315 AM CDT FRI AUG 29 2014

.DISCUSSION...
714 PM CDT

PAIR OF MCVS NOTED ON RADAR IMAGERY CONTINUE TO MOVE EASTWARD
DRIVING SLOWLY DECAYING CONVECTIVE COMPLEX EASTWARD INTO OUR CWA
EARLY THIS EVENING DESPITE THE MUCH MORE STABLE AND SOMEWHAT DRIER
AIR MASS OVER THE REGION. HAVE ALREADY UPDATED PRECIP TRENDS A
COUPLE TIME TO ACCOUNT FOR THE RAIN THIS EVENING. ANTICIPATE
CONTINUED WEAKENING TREND...PARTICULARLY FROM THE NORTH...IN THIS
AREA OF LEFT OVER RAIN AND EVEN SOME LINGERING THUNDER. THE THREAT
OF THUNDER WITH THE NORTHERN MCV TRACKING CLOSE TO I-88 LOOKS TO END
VERY SOON...WHILE THE CONVECTION WITH THE SOUTHERN MOST MCV LIES
CLOSE ENOUGH TO MORE UNSTABLE AIR TO POTENTIALLY MAINTAIN
THUNDERSTORMS ACROSS THE SOUTHERN TIER OF OUR CWA THE NEXT FEW
HOURS. IN THE WAKE OF THESE MCVS...WHICH REALLY HAVENT BEEN HANDLED
WELL BY NUMERICAL GUIDANCE...SHOULD SEE A PERIOD OF DRY CONDITIONS
HOWEVER MODELS DO BREAK OUT ADDITIONAL CONVECTION OVERNIGHT WHICH
ISN`T THAT UNREASONABLE GIVEN THE NORTHWARD ADVANCING WARM FRONT.

IZZI

//PREV DISCUSSION...
230 PM CDT

VISIBLE IMAGERY THIS AFTERNOON SHOWS A MID/UPR LEVEL CLOUD DECK
LIFTING NORTHEAST ACROSS NORTHERN IL. REMNANTS FROM A MORNING
COMPLEX OF THUNDERSTORMS RESIDES OVER IOWA...WITH SOME CONVECTIVE
LOOK TO THE CLOUDS LINGERING INTO THIS AFTN. SFC TEMPS ACROSS THE
FORECAST AREA HAVE BEEN ABLE TO WARM INTO THE MID/UPR 70S. A FEW
POINTS SOUTH OF PONTIAC TO KANKAKEE HAVE PUSHED TO ARND 80 DEG...BUT
WITH THE LIGHT EASTERLY FLOW AT THE SFC SOME WEAK SUBSIDENCE HAS
BEEN NOTED WITH DEW POINTS BEING PUSHED INTO THE LOW 50S ALONG THE
LAKESHORE AND MID/UPR 50S INLAND.

THE MAIN CHALLENGE FOR THIS EVENING WILL FOCUS ON CONVECTIVE
CHANCES/COVERAGE...WHICH WILL CONTINUE THROUGH DAYBREAK FRI.
GUIDANCE HAS CONTINUED TO BACK OFF ON THE ARRIVAL OF PRECIP INTO THE
FORECAST AREA...WHICH SEEMS TO LINE UP RELATIVELY WELL WITH THE
CURRENT TRENDS. THE FRONTAL BOUNDARY WILL SLOWLY LIFT NORTH THIS
EVENING...BUT NOT EXPECTING MUCH IN THE WAY OF PRECIP UNTIL PERHAPS
AFT 04Z WITH A GRADUAL UPGLIDE OF PARCELS ALLOWS FOR MOISTENING.
SOME ELEVATED CONVECTION COULD BEGIN TO DEVELOP...ALTHOUGH NOT
EXPECTING MUCH COVERAGE OVERNIGHT. THE FOCUS FOR SLIGHTLY BETTER
PRECIP COVERAGE WILL REMAIN ALONG THE NORTHERN ROW OF COUNTIES IN
NORTHERN IL...HOWEVER CLOSER TO DAYBREAK FRI IT APPEARS SOME
PRECIP/CONVECTION COULD SAG SOUTHEAST AND CLIP NORTHEAST
IL/NORTHWEST IN BEFORE DISSIPATING.

WITH INCREASING CLOUD COVER TONIGHT...IT SHUD LIMIT HOW COOL TEMPS
BECOME. SO HAVE MADE ONLY MINOR ADJUSTMENTS TO THE TEMPS WITH
GENERALLY MID/UPR 60S FOR LOWS.

BEACHLER

FRIDAY AND FRIDAY NIGHT...
CLOSED UPPER LOW CURRENTLY NEAR THE COLORADO FRONT RANGE WILL SLOWLY
TRAVERSE EAST TOWARDS THE MID-MISSOURI VALLEY FRIDAY BECOMING AN
OPEN WAVE. AT THE SURFACE...BROAD AND WEAK SURFACE LOW WILL LIFT
INTO THE UPPER MIDWEST WHILE SOUTHWEST FLOW RAMPS UP THROUGH THE
COLUMN AS THE WARM FRONT LIFTS INTO THE CENTRAL GREAT LAKES. HEAT
AND HUMIDITY WILL MAKE A RETURN AS THIS OCCURS. H85 TEMPS WARMING TO
AROUND 18C WILL HELP SUPPORT MID/UPPER 80S DURING THE DAY
FRIDAY...AND SURFACE DEWPOINTS ARE PROGGED TO PUSH BACK INTO THE LOW
POSSIBLY MID 70S. THIS WILL RESULT IN MODERATE INSTABILITY
DEVELOPING DURING THE DAY...AND ONLY WEAKLY CAPPED DURING THE
AFTERNOON AS BROAD HEIGHT FALLS ASSOCIATED WITH THE UPPER WAVE START
TO OVERSPREAD THE AREA. THERE DOESNT SEEM TO BE MUCH FOCUS IN THE
LOWER LEVELS SO WOULD EXPECT ONLY SCATTERED THUNDERSTORM DEVELOPMENT
ACROSS THE REGION FRIDAY AFTERNOON/EVENING. UPPER WAVE BEGINS TO
MOVE INTO THE UPPER MIDWEST TOMORROW NIGHT AND BROAD WARM ADVECTION
OUT AHEAD DURING THE EVENING AND OVERNIGHT HOURS WILL HELP SUSTAIN
SOME CONVECTION LATE BUT WOULD EXPECT SOME NOCTURNAL DOWNTICK IN
ACTIVITY OVERNIGHT WITH THE LOW LEVEL JET FOCUSED WELL TO OUR NORTH.
GFS/NAM SEEM TO BE OVERDOING POPS MUCH OF THE DAY AND NIGHT
FRIDAY...AND OPTED TO LEAN CLOSER TO ECMWF THESE PERIODS.

THIS WEEKEND...
COLD FRONT WILL SWEEP ACROSS THE FORECAST AREA STARTING VERY EARLY
ON SATURDAY. WHILE NOT A FAVORABLE DIURNAL TIME...WE SHOULD STILL
HAVE SOME VERY MODEST INSTABILITY IN PLACE THAT WILL SUPPORT SOME
EARLY DAY THUNDERSTORMS ALONG THE FRONTAL BOUNDARY...WHICH WOULD BE
ABLE TO EXPAND IN COVERAGE AS THE DAY PROGRESSES AND THE BOUNDARY
LAYER WARMS. IN ADDITION...GUIDANCE SUGGESTS A SECOND SHORTWAVE
WILL WRAP INTO THE AREA THAT WILL PROVIDE ADDITIONAL BROAD SCALE
ASCENT. THE ECMWF IS ABOUT SIX HOURS SLOWER WITH THIS FEATURE
COMPARED TO THE NAM/GFS...WITH THE GEM A COMPROMISE...SO THERE
REMAINS SOME UNCERTAINTY IN TIMING. HIGH PRESSURE WILL BUILD IN
BEHIND THE FRONT SATURDAY NIGHT INTO SUNDAY AND WILL PROVIDE A
BRIEF RESPITE FROM THE ACTIVE WEATHER. THE ATMOSPHERE LOOKS TO
QUICKLY RELOAD HOWEVER WITH THERMAL RIDGE ONCE AGAIN STARTING TO
TILT BACK OVER THE AREA WITH H85 TEMPS AROUND 20C BY LATER IN THE
DAY SUNDAY.

NEXT WEEK...
AN ACTIVE PATTERN LOOKS TO PERSIST THROUGH AT LEAST THE MIDDLE OF
NEXT WEEK WITH A SERIES OF WAVES PUSHING ACROSS THE REGION BRINGING
CONTINUED PERIODIC CHANCES FOR SHOWERS AND THUNDERSTORMS. ANOTHER
COLD FRONT WILL PUSH ACROSS THE AREA LATER ON MONDAY WITH THE
FRONTAL BOUNDARY STALLING JUST TO OUR SOUTH. THEREAFTER...THERE IS
CONSIDERABLE UNCERTAINTY ON HOW FAR NORTH THE BOUNDARY MAY LIFT
WITH THE BEST PRECIP CHANCES FOCUSED IN THE VICINITY OF THE
FRONT AS A SERIES OF UPPER LEVEL DISTURBANCES PUSH ACROSS THE
AREA. PWATS REMAIN JUICY ALONG THE FRONT...AROUND TWO INCHES...AND
GUIDANCE SUGGESTS THAT THERE COULD BE SEVERAL CONVECTIVE COMPLEXES
NEXT WEEK WITH A CONCERN FOR HEAVY RAIN AND FLOODING SHOULD THIS
PAN OUT.

DEUBELBEISS

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* ISOLATED SHRA/TSRA LATE TONIGHT INTO EARLY FRIDAY MORNING.

* SCATTERED TSRA FRIDAY AFTERNOON/EARLY EVENING.

* SOUTH WIND WITH GUSTS DEVELOPING TO 20KT LATE MORNING FRIDAY.

KREIN

//DISCUSSION...UPDATED 06Z...

FORECAST CONCERNS WILL FOCUS ON SHRA/TSRA POTENTIAL THROUGH THE
PERIOD AS WELL AS GUSTY SOUTH WINDS DEVELOPING LATE FRIDAY MORNING
AND PERSISTING INTO EARLY FRIDAY EVENING.

FOR THE REMAINDER OF THE OVERNIGHT HOURS...THE REGION WILL REMAIN
UNDER SELY FLOW...NORTH OF A WARM FRONT CURRENTLY OVER CNTRL MO TO
SRN IL. SOME REMNANT SHOWERS FROM EARLIER CONVECTIVE ACTIVITY ARE
STILL SEEN ON THE LATEST RADAR IMAGERY...BUT THIS ACTIVITY IS
DIMINISHING WITH TIME FOR MUCH OF THE REGION. THE EXCEPTION IS A
SMALL AREA OF RAIN WHICH IS MORE PERSISTENT OVER ECNTRL IL. WITH
MID LEVEL FLOW MORE SOUTHWESTERLY...THERE HAS BEEN A MORE
PERSISTENT FETCH OF LIGHT PCPN INTO NWRN IL...SO KGYY COULD LIKELY
SEE SOME LIGHT RAIN THROUGH THE NIGHT THOUGH NO ADDITION THUNDER
IS ANTICIPATED WITH THIS PCPN. WITH A VERY MOIST AIRMASS IN PLACE
FROM RECENT PCPN ALONG WITH LIGHT WINDS...THERE WILL BE THE
POTENTIAL FOR SOME PATCHY BR WITH KDPA/KRFD BEING THE MORE LIKELY
TAF SITES TO SEE VIS DROP AT LEAST INTO MVFR LEVELS. EXPECT THAT
ORD/MDW SHOULD REMAIN VFR AS WINDS WILL REMAIN A LITTLE STRONGER
AND TEMP/DEWPOINT SPREADS A LITTLE HIGHER.

THE WARM FRONT WILL SLOWLY LIFT NWD THROUGH THE NIGHT AND PUSH
NORTH OF THE TERMINALS BY LATE FRIDAY MORNING. AT THIS
POINT...WINDS WILL SHIFT TO MORE SOUTHERLY. SOME BREAKS IN THE
CLOUD COVER SHOULD ALLOW FOR DEEPER LAYER MIXING...TAPPING
STRONGER WINDS ALOFT AND EXPECT THAT WINDS WILL BEGIN TO GUST TO
20KT FOLLOWING THE WARM FROPA.

INSTABILITY WILL INCREASES VERY QUICKLY AS THE WARM FRONT PASSES
TO THE NORTH AND WARM SECTOR AIR OVERSPREADS THE REGION BRINGING
INCREASING TEMPERATURES AND DEWPOINTS. MID LEVEL IMPULSES SHOULD
TRACK ACROSS THE AREA FRIDAY AFTERNOON AND EVENING IN UPPER LEVEL
SWLY FLOW AS THE UPPER RIDGE PUSHES TO THE EAST AND A LARGER SCALE
UPPER TROUGH MOVES ACROSS THE CENTRAL PLAINS. THESE IMPULSES WILL
BE THE TRIGGERING MECHANISM FOR ADDITIONAL SHRA/TSRA...BUT IN THE
ABSENCE OF ANY SFC FORCING...ACTIVITY WILL GENERALLY BE SCATTERED
AND DIFFICULT TO TIME AT THE TERMINALS. SO...WILL MAINTAIN THE
GOING PROB30 GROUP FOR TSRA WITH THE MOST FAVORABLE TIMING DURG
THE AFTERNOON HOURS. HOWEVER...WITH SCATTERED COVERAGE...ANY OF
THE TERMINALS COULD SEE SOME SHRA/TSRA A LITTLE EARLIER OR A
LITTLE LATER THAN THE GOING PROB30 TIMING.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* LOW CONFIDENCE IN THUNDER CHANCES/COVERAGE AND SPECIFIC TIMING
  FRIDAY AFTERNOON.

* HIGH CONFIDENCE IN WIND TRENDS THROUGH THE PERIOD.

* MEDIUM CONFIDENCE THAT ORD/MDW WILL REMAIN VFR THROUGH THE
  REMAINDER OF THE NIGHT AND INTO EARLY FRIDAY MORNING.

KREIN

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

* SATURDAY...TSRA LIKELY.
* SUNDAY...SLIGHT CHANCE OF TSRA.
* MONDAY AND TUESDAY...CHANCE OF TSRA.
* WEDNESDAY AND THURSDAY...SLIGHT CHANCE OF TSRA

KMD

&&

.MARINE...
315 AM CDT

HIGH PRESSURE OVER THE EASTERN GREAT LAKES WILL MOVE EAST OFF THE
NEW ENGLAND COAST FRIDAY EVENING...WHILE A TROUGH OF LOW PRESSURE
DEVELOPS ACROSS THE CENTRAL PLAINS AND UPPER MIDWEST. THIS WILL
SET UP A PERIOD OF SOUTHERLY WINDS AND AS THE TROUGH MOVES
EAST...THE GRADIENT OVER THE LAKE WILL STRENGTHEN AND WINDS SHOULD
INCREASE TO THE 20-25 KT RANGE. A DEEPENING LOW CENTER WITHIN THE
TROUGH WILL MOVE TO WISCONSIN SATURDAY AND ACROSS NORTHERN LAKE
MICHIGAN SATURDAY EVENING. AS THE LOW TRACKS TO THE NORTHEAST...AN
ASSOCIATED COLD FRONT WILL MOVE DOWN THE LAKE SATURDAY AFTERNOON
AND EVENING...QUICKLY SHIFTING WINDS TO NWLY FOLLOWING THE FROPA.
THE LATEST MODEL GUIDANCE SUGGESTS THAT THE FRONT WILL WASH OUT
LATE SATURDAY NIGHT BEFORE REACHING THE SOUTH END OF THE LAKE AND
WINDS THERE SHOULD NEVER TRULY SHIFT NWLY...BUT RATHER BECOMING
LIGHT AND VARIABLE LATE SATURDAY NIGHT THROUGH SUNDAY MORNING. A
DEEPER LOW IS EXPECTED TO DEVELOP OVER THE DAKOTAS AND LIFT
THROUGH WESTERN ONTARIO SUNDAY NIGHT AND MONDAY BRINGING A RETURN
TO BRISK SOUTH TO SOUTHWEST WINDS TO THE LAKE FOR MONDAY AND
TUESDAY.

KREIN

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 290815
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
315 AM CDT FRI AUG 29 2014

.DISCUSSION...
714 PM CDT

PAIR OF MCVS NOTED ON RADAR IMAGERY CONTINUE TO MOVE EASTWARD
DRIVING SLOWLY DECAYING CONVECTIVE COMPLEX EASTWARD INTO OUR CWA
EARLY THIS EVENING DESPITE THE MUCH MORE STABLE AND SOMEWHAT DRIER
AIR MASS OVER THE REGION. HAVE ALREADY UPDATED PRECIP TRENDS A
COUPLE TIME TO ACCOUNT FOR THE RAIN THIS EVENING. ANTICIPATE
CONTINUED WEAKENING TREND...PARTICULARLY FROM THE NORTH...IN THIS
AREA OF LEFT OVER RAIN AND EVEN SOME LINGERING THUNDER. THE THREAT
OF THUNDER WITH THE NORTHERN MCV TRACKING CLOSE TO I-88 LOOKS TO END
VERY SOON...WHILE THE CONVECTION WITH THE SOUTHERN MOST MCV LIES
CLOSE ENOUGH TO MORE UNSTABLE AIR TO POTENTIALLY MAINTAIN
THUNDERSTORMS ACROSS THE SOUTHERN TIER OF OUR CWA THE NEXT FEW
HOURS. IN THE WAKE OF THESE MCVS...WHICH REALLY HAVENT BEEN HANDLED
WELL BY NUMERICAL GUIDANCE...SHOULD SEE A PERIOD OF DRY CONDITIONS
HOWEVER MODELS DO BREAK OUT ADDITIONAL CONVECTION OVERNIGHT WHICH
ISN`T THAT UNREASONABLE GIVEN THE NORTHWARD ADVANCING WARM FRONT.

IZZI

//PREV DISCUSSION...
230 PM CDT

VISIBLE IMAGERY THIS AFTERNOON SHOWS A MID/UPR LEVEL CLOUD DECK
LIFTING NORTHEAST ACROSS NORTHERN IL. REMNANTS FROM A MORNING
COMPLEX OF THUNDERSTORMS RESIDES OVER IOWA...WITH SOME CONVECTIVE
LOOK TO THE CLOUDS LINGERING INTO THIS AFTN. SFC TEMPS ACROSS THE
FORECAST AREA HAVE BEEN ABLE TO WARM INTO THE MID/UPR 70S. A FEW
POINTS SOUTH OF PONTIAC TO KANKAKEE HAVE PUSHED TO ARND 80 DEG...BUT
WITH THE LIGHT EASTERLY FLOW AT THE SFC SOME WEAK SUBSIDENCE HAS
BEEN NOTED WITH DEW POINTS BEING PUSHED INTO THE LOW 50S ALONG THE
LAKESHORE AND MID/UPR 50S INLAND.

THE MAIN CHALLENGE FOR THIS EVENING WILL FOCUS ON CONVECTIVE
CHANCES/COVERAGE...WHICH WILL CONTINUE THROUGH DAYBREAK FRI.
GUIDANCE HAS CONTINUED TO BACK OFF ON THE ARRIVAL OF PRECIP INTO THE
FORECAST AREA...WHICH SEEMS TO LINE UP RELATIVELY WELL WITH THE
CURRENT TRENDS. THE FRONTAL BOUNDARY WILL SLOWLY LIFT NORTH THIS
EVENING...BUT NOT EXPECTING MUCH IN THE WAY OF PRECIP UNTIL PERHAPS
AFT 04Z WITH A GRADUAL UPGLIDE OF PARCELS ALLOWS FOR MOISTENING.
SOME ELEVATED CONVECTION COULD BEGIN TO DEVELOP...ALTHOUGH NOT
EXPECTING MUCH COVERAGE OVERNIGHT. THE FOCUS FOR SLIGHTLY BETTER
PRECIP COVERAGE WILL REMAIN ALONG THE NORTHERN ROW OF COUNTIES IN
NORTHERN IL...HOWEVER CLOSER TO DAYBREAK FRI IT APPEARS SOME
PRECIP/CONVECTION COULD SAG SOUTHEAST AND CLIP NORTHEAST
IL/NORTHWEST IN BEFORE DISSIPATING.

WITH INCREASING CLOUD COVER TONIGHT...IT SHUD LIMIT HOW COOL TEMPS
BECOME. SO HAVE MADE ONLY MINOR ADJUSTMENTS TO THE TEMPS WITH
GENERALLY MID/UPR 60S FOR LOWS.

BEACHLER

FRIDAY AND FRIDAY NIGHT...
CLOSED UPPER LOW CURRENTLY NEAR THE COLORADO FRONT RANGE WILL SLOWLY
TRAVERSE EAST TOWARDS THE MID-MISSOURI VALLEY FRIDAY BECOMING AN
OPEN WAVE. AT THE SURFACE...BROAD AND WEAK SURFACE LOW WILL LIFT
INTO THE UPPER MIDWEST WHILE SOUTHWEST FLOW RAMPS UP THROUGH THE
COLUMN AS THE WARM FRONT LIFTS INTO THE CENTRAL GREAT LAKES. HEAT
AND HUMIDITY WILL MAKE A RETURN AS THIS OCCURS. H85 TEMPS WARMING TO
AROUND 18C WILL HELP SUPPORT MID/UPPER 80S DURING THE DAY
FRIDAY...AND SURFACE DEWPOINTS ARE PROGGED TO PUSH BACK INTO THE LOW
POSSIBLY MID 70S. THIS WILL RESULT IN MODERATE INSTABILITY
DEVELOPING DURING THE DAY...AND ONLY WEAKLY CAPPED DURING THE
AFTERNOON AS BROAD HEIGHT FALLS ASSOCIATED WITH THE UPPER WAVE START
TO OVERSPREAD THE AREA. THERE DOESNT SEEM TO BE MUCH FOCUS IN THE
LOWER LEVELS SO WOULD EXPECT ONLY SCATTERED THUNDERSTORM DEVELOPMENT
ACROSS THE REGION FRIDAY AFTERNOON/EVENING. UPPER WAVE BEGINS TO
MOVE INTO THE UPPER MIDWEST TOMORROW NIGHT AND BROAD WARM ADVECTION
OUT AHEAD DURING THE EVENING AND OVERNIGHT HOURS WILL HELP SUSTAIN
SOME CONVECTION LATE BUT WOULD EXPECT SOME NOCTURNAL DOWNTICK IN
ACTIVITY OVERNIGHT WITH THE LOW LEVEL JET FOCUSED WELL TO OUR NORTH.
GFS/NAM SEEM TO BE OVERDOING POPS MUCH OF THE DAY AND NIGHT
FRIDAY...AND OPTED TO LEAN CLOSER TO ECMWF THESE PERIODS.

THIS WEEKEND...
COLD FRONT WILL SWEEP ACROSS THE FORECAST AREA STARTING VERY EARLY
ON SATURDAY. WHILE NOT A FAVORABLE DIURNAL TIME...WE SHOULD STILL
HAVE SOME VERY MODEST INSTABILITY IN PLACE THAT WILL SUPPORT SOME
EARLY DAY THUNDERSTORMS ALONG THE FRONTAL BOUNDARY...WHICH WOULD BE
ABLE TO EXPAND IN COVERAGE AS THE DAY PROGRESSES AND THE BOUNDARY
LAYER WARMS. IN ADDITION...GUIDANCE SUGGESTS A SECOND SHORTWAVE
WILL WRAP INTO THE AREA THAT WILL PROVIDE ADDITIONAL BROAD SCALE
ASCENT. THE ECMWF IS ABOUT SIX HOURS SLOWER WITH THIS FEATURE
COMPARED TO THE NAM/GFS...WITH THE GEM A COMPROMISE...SO THERE
REMAINS SOME UNCERTAINTY IN TIMING. HIGH PRESSURE WILL BUILD IN
BEHIND THE FRONT SATURDAY NIGHT INTO SUNDAY AND WILL PROVIDE A
BRIEF RESPITE FROM THE ACTIVE WEATHER. THE ATMOSPHERE LOOKS TO
QUICKLY RELOAD HOWEVER WITH THERMAL RIDGE ONCE AGAIN STARTING TO
TILT BACK OVER THE AREA WITH H85 TEMPS AROUND 20C BY LATER IN THE
DAY SUNDAY.

NEXT WEEK...
AN ACTIVE PATTERN LOOKS TO PERSIST THROUGH AT LEAST THE MIDDLE OF
NEXT WEEK WITH A SERIES OF WAVES PUSHING ACROSS THE REGION BRINGING
CONTINUED PERIODIC CHANCES FOR SHOWERS AND THUNDERSTORMS. ANOTHER
COLD FRONT WILL PUSH ACROSS THE AREA LATER ON MONDAY WITH THE
FRONTAL BOUNDARY STALLING JUST TO OUR SOUTH. THEREAFTER...THERE IS
CONSIDERABLE UNCERTAINTY ON HOW FAR NORTH THE BOUNDARY MAY LIFT
WITH THE BEST PRECIP CHANCES FOCUSED IN THE VICINITY OF THE
FRONT AS A SERIES OF UPPER LEVEL DISTURBANCES PUSH ACROSS THE
AREA. PWATS REMAIN JUICY ALONG THE FRONT...AROUND TWO INCHES...AND
GUIDANCE SUGGESTS THAT THERE COULD BE SEVERAL CONVECTIVE COMPLEXES
NEXT WEEK WITH A CONCERN FOR HEAVY RAIN AND FLOODING SHOULD THIS
PAN OUT.

DEUBELBEISS

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* ISOLATED SHRA/TSRA LATE TONIGHT INTO EARLY FRIDAY MORNING.

* SCATTERED TSRA FRIDAY AFTERNOON/EARLY EVENING.

* SOUTH WIND WITH GUSTS DEVELOPING TO 20KT LATE MORNING FRIDAY.

KREIN

//DISCUSSION...UPDATED 06Z...

FORECAST CONCERNS WILL FOCUS ON SHRA/TSRA POTENTIAL THROUGH THE
PERIOD AS WELL AS GUSTY SOUTH WINDS DEVELOPING LATE FRIDAY MORNING
AND PERSISTING INTO EARLY FRIDAY EVENING.

FOR THE REMAINDER OF THE OVERNIGHT HOURS...THE REGION WILL REMAIN
UNDER SELY FLOW...NORTH OF A WARM FRONT CURRENTLY OVER CNTRL MO TO
SRN IL. SOME REMNANT SHOWERS FROM EARLIER CONVECTIVE ACTIVITY ARE
STILL SEEN ON THE LATEST RADAR IMAGERY...BUT THIS ACTIVITY IS
DIMINISHING WITH TIME FOR MUCH OF THE REGION. THE EXCEPTION IS A
SMALL AREA OF RAIN WHICH IS MORE PERSISTENT OVER ECNTRL IL. WITH
MID LEVEL FLOW MORE SOUTHWESTERLY...THERE HAS BEEN A MORE
PERSISTENT FETCH OF LIGHT PCPN INTO NWRN IL...SO KGYY COULD LIKELY
SEE SOME LIGHT RAIN THROUGH THE NIGHT THOUGH NO ADDITION THUNDER
IS ANTICIPATED WITH THIS PCPN. WITH A VERY MOIST AIRMASS IN PLACE
FROM RECENT PCPN ALONG WITH LIGHT WINDS...THERE WILL BE THE
POTENTIAL FOR SOME PATCHY BR WITH KDPA/KRFD BEING THE MORE LIKELY
TAF SITES TO SEE VIS DROP AT LEAST INTO MVFR LEVELS. EXPECT THAT
ORD/MDW SHOULD REMAIN VFR AS WINDS WILL REMAIN A LITTLE STRONGER
AND TEMP/DEWPOINT SPREADS A LITTLE HIGHER.

THE WARM FRONT WILL SLOWLY LIFT NWD THROUGH THE NIGHT AND PUSH
NORTH OF THE TERMINALS BY LATE FRIDAY MORNING. AT THIS
POINT...WINDS WILL SHIFT TO MORE SOUTHERLY. SOME BREAKS IN THE
CLOUD COVER SHOULD ALLOW FOR DEEPER LAYER MIXING...TAPPING
STRONGER WINDS ALOFT AND EXPECT THAT WINDS WILL BEGIN TO GUST TO
20KT FOLLOWING THE WARM FROPA.

INSTABILITY WILL INCREASES VERY QUICKLY AS THE WARM FRONT PASSES
TO THE NORTH AND WARM SECTOR AIR OVERSPREADS THE REGION BRINGING
INCREASING TEMPERATURES AND DEWPOINTS. MID LEVEL IMPULSES SHOULD
TRACK ACROSS THE AREA FRIDAY AFTERNOON AND EVENING IN UPPER LEVEL
SWLY FLOW AS THE UPPER RIDGE PUSHES TO THE EAST AND A LARGER SCALE
UPPER TROUGH MOVES ACROSS THE CENTRAL PLAINS. THESE IMPULSES WILL
BE THE TRIGGERING MECHANISM FOR ADDITIONAL SHRA/TSRA...BUT IN THE
ABSENCE OF ANY SFC FORCING...ACTIVITY WILL GENERALLY BE SCATTERED
AND DIFFICULT TO TIME AT THE TERMINALS. SO...WILL MAINTAIN THE
GOING PROB30 GROUP FOR TSRA WITH THE MOST FAVORABLE TIMING DURG
THE AFTERNOON HOURS. HOWEVER...WITH SCATTERED COVERAGE...ANY OF
THE TERMINALS COULD SEE SOME SHRA/TSRA A LITTLE EARLIER OR A
LITTLE LATER THAN THE GOING PROB30 TIMING.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* LOW CONFIDENCE IN THUNDER CHANCES/COVERAGE AND SPECIFIC TIMING
  FRIDAY AFTERNOON.

* HIGH CONFIDENCE IN WIND TRENDS THROUGH THE PERIOD.

* MEDIUM CONFIDENCE THAT ORD/MDW WILL REMAIN VFR THROUGH THE
  REMAINDER OF THE NIGHT AND INTO EARLY FRIDAY MORNING.

KREIN

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

* SATURDAY...TSRA LIKELY.
* SUNDAY...SLIGHT CHANCE OF TSRA.
* MONDAY AND TUESDAY...CHANCE OF TSRA.
* WEDNESDAY AND THURSDAY...SLIGHT CHANCE OF TSRA

KMD

&&

.MARINE...
315 AM CDT

HIGH PRESSURE OVER THE EASTERN GREAT LAKES WILL MOVE EAST OFF THE
NEW ENGLAND COAST FRIDAY EVENING...WHILE A TROUGH OF LOW PRESSURE
DEVELOPS ACROSS THE CENTRAL PLAINS AND UPPER MIDWEST. THIS WILL
SET UP A PERIOD OF SOUTHERLY WINDS AND AS THE TROUGH MOVES
EAST...THE GRADIENT OVER THE LAKE WILL STRENGTHEN AND WINDS SHOULD
INCREASE TO THE 20-25 KT RANGE. A DEEPENING LOW CENTER WITHIN THE
TROUGH WILL MOVE TO WISCONSIN SATURDAY AND ACROSS NORTHERN LAKE
MICHIGAN SATURDAY EVENING. AS THE LOW TRACKS TO THE NORTHEAST...AN
ASSOCIATED COLD FRONT WILL MOVE DOWN THE LAKE SATURDAY AFTERNOON
AND EVENING...QUICKLY SHIFTING WINDS TO NWLY FOLLOWING THE FROPA.
THE LATEST MODEL GUIDANCE SUGGESTS THAT THE FRONT WILL WASH OUT
LATE SATURDAY NIGHT BEFORE REACHING THE SOUTH END OF THE LAKE AND
WINDS THERE SHOULD NEVER TRULY SHIFT NWLY...BUT RATHER BECOMING
LIGHT AND VARIABLE LATE SATURDAY NIGHT THROUGH SUNDAY MORNING. A
DEEPER LOW IS EXPECTED TO DEVELOP OVER THE DAKOTAS AND LIFT
THROUGH WESTERN ONTARIO SUNDAY NIGHT AND MONDAY BRINGING A RETURN
TO BRISK SOUTH TO SOUTHWEST WINDS TO THE LAKE FOR MONDAY AND
TUESDAY.

KREIN

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO







000
FXUS63 KLOT 290612
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
112 AM CDT FRI AUG 29 2014

.DISCUSSION...
714 PM CDT

PAIR OF MCVS NOTED ON RADAR IMAGERY CONTINUE TO MOVE EASTWARD
DRIVING SLOWLY DECAYING CONVECTIVE COMPLEX EASTWARD INTO OUR CWA
EARLY THIS EVENING DESPITE THE MUCH MORE STABLE AND SOMEWHAT DRIER
AIR MASS OVER THE REGION. HAVE ALREADY UPDATED PRECIP TRENDS A
COUPLE TIME TO ACCOUNT FOR THE RAIN THIS EVENING. ANTICIPATE
CONTINUED WEAKENING TREND...PARTICULARLY FROM THE NORTH...IN THIS
AREA OF LEFT OVER RAIN AND EVEN SOME LINGERING THUNDER. THE THREAT
OF THUNDER WITH THE NORTHERN MCV TRACKING CLOSE TO I-88 LOOKS TO END
VERY SOON...WHILE THE CONVECTION WITH THE SOUTHERN MOST MCV LIES
CLOSE ENOUGH TO MORE UNSTABLE AIR TO POTENTIALLY MAINTAIN
THUNDERSTORMS ACROSS THE SOUTHERN TIER OF OUR CWA THE NEXT FEW
HOURS. IN THE WAKE OF THESE MCVS...WHICH REALLY HAVENT BEEN HANDLED
WELL BY NUMERICAL GUIDANCE...SHOULD SEE A PERIOD OF DRY CONDITIONS
HOWEVER MODELS DO BREAK OUT ADDITIONAL CONVECTION OVERNIGHT WHICH
ISN`T THAT UNREASONABLE GIVEN THE NORTHWARD ADVANCING WARM FRONT.

IZZI

//PREV DISCUSSION...
230 PM CDT

VISIBLE IMAGERY THIS AFTERNOON SHOWS A MID/UPR LEVEL CLOUD DECK
LIFTING NORTHEAST ACROSS NORTHERN IL. REMNANTS FROM A MORNING
COMPLEX OF THUNDERSTORMS RESIDES OVER IOWA...WITH SOME CONVECTIVE
LOOK TO THE CLOUDS LINGERING INTO THIS AFTN. SFC TEMPS ACROSS THE
FORECAST AREA HAVE BEEN ABLE TO WARM INTO THE MID/UPR 70S. A FEW
POINTS SOUTH OF PONTIAC TO KANKAKEE HAVE PUSHED TO ARND 80 DEG...BUT
WITH THE LIGHT EASTERLY FLOW AT THE SFC SOME WEAK SUBSIDENCE HAS
BEEN NOTED WITH DEW POINTS BEING PUSHED INTO THE LOW 50S ALONG THE
LAKESHORE AND MID/UPR 50S INLAND.

THE MAIN CHALLENGE FOR THIS EVENING WILL FOCUS ON CONVECTIVE
CHANCES/COVERAGE...WHICH WILL CONTINUE THROUGH DAYBREAK FRI.
GUIDANCE HAS CONTINUED TO BACK OFF ON THE ARRIVAL OF PRECIP INTO THE
FORECAST AREA...WHICH SEEMS TO LINE UP RELATIVELY WELL WITH THE
CURRENT TRENDS. THE FRONTAL BOUNDARY WILL SLOWLY LIFT NORTH THIS
EVENING...BUT NOT EXPECTING MUCH IN THE WAY OF PRECIP UNTIL PERHAPS
AFT 04Z WITH A GRADUAL UPGLIDE OF PARCELS ALLOWS FOR MOISTENING.
SOME ELEVATED CONVECTION COULD BEGIN TO DEVELOP...ALTHOUGH NOT
EXPECTING MUCH COVERAGE OVERNIGHT. THE FOCUS FOR SLIGHTLY BETTER
PRECIP COVERAGE WILL REMAIN ALONG THE NORTHERN ROW OF COUNTIES IN
NORTHERN IL...HOWEVER CLOSER TO DAYBREAK FRI IT APPEARS SOME
PRECIP/CONVECTION COULD SAG SOUTHEAST AND CLIP NORTHEAST
IL/NORTHWEST IN BEFORE DISSIPATING.

WITH INCREASING CLOUD COVER TONIGHT...IT SHUD LIMIT HOW COOL TEMPS
BECOME. SO HAVE MADE ONLY MINOR ADJUSTMENTS TO THE TEMPS WITH
GENERALLY MID/UPR 60S FOR LOWS.

BEACHLER

FRIDAY AND FRIDAY NIGHT...
CLOSED UPPER LOW CURRENTLY NEAR THE COLORADO FRONT RANGE WILL SLOWLY
TRAVERSE EAST TOWARDS THE MID-MISSOURI VALLEY FRIDAY BECOMING AN
OPEN WAVE. AT THE SURFACE...BROAD AND WEAK SURFACE LOW WILL LIFT
INTO THE UPPER MIDWEST WHILE SOUTHWEST FLOW RAMPS UP THROUGH THE
COLUMN AS THE WARM FRONT LIFTS INTO THE CENTRAL GREAT LAKES. HEAT
AND HUMIDITY WILL MAKE A RETURN AS THIS OCCURS. H85 TEMPS WARMING TO
AROUND 18C WILL HELP SUPPORT MID/UPPER 80S DURING THE DAY
FRIDAY...AND SURFACE DEWPOINTS ARE PROGGED TO PUSH BACK INTO THE LOW
POSSIBLY MID 70S. THIS WILL RESULT IN MODERATE INSTABILITY
DEVELOPING DURING THE DAY...AND ONLY WEAKLY CAPPED DURING THE
AFTERNOON AS BROAD HEIGHT FALLS ASSOCIATED WITH THE UPPER WAVE START
TO OVERSPREAD THE AREA. THERE DOESNT SEEM TO BE MUCH FOCUS IN THE
LOWER LEVELS SO WOULD EXPECT ONLY SCATTERED THUNDERSTORM DEVELOPMENT
ACROSS THE REGION FRIDAY AFTERNOON/EVENING. UPPER WAVE BEGINS TO
MOVE INTO THE UPPER MIDWEST TOMORROW NIGHT AND BROAD WARM ADVECTION
OUT AHEAD DURING THE EVENING AND OVERNIGHT HOURS WILL HELP SUSTAIN
SOME CONVECTION LATE BUT WOULD EXPECT SOME NOCTURNAL DOWNTICK IN
ACTIVITY OVERNIGHT WITH THE LOW LEVEL JET FOCUSED WELL TO OUR NORTH.
GFS/NAM SEEM TO BE OVERDOING POPS MUCH OF THE DAY AND NIGHT
FRIDAY...AND OPTED TO LEAN CLOSER TO ECMWF THESE PERIODS.

THIS WEEKEND...
COLD FRONT WILL SWEEP ACROSS THE FORECAST AREA STARTING VERY EARLY
ON SATURDAY. WHILE NOT A FAVORABLE DIURNAL TIME...WE SHOULD STILL
HAVE SOME VERY MODEST INSTABILITY IN PLACE THAT WILL SUPPORT SOME
EARLY DAY THUNDERSTORMS ALONG THE FRONTAL BOUNDARY...WHICH WOULD BE
ABLE TO EXPAND IN COVERAGE AS THE DAY PROGRESSES AND THE BOUNDARY
LAYER WARMS. IN ADDITION...GUIDANCE SUGGESTS A SECOND SHORTWAVE
WILL WRAP INTO THE AREA THAT WILL PROVIDE ADDITIONAL BROAD SCALE
ASCENT. THE ECMWF IS ABOUT SIX HOURS SLOWER WITH THIS FEATURE
COMPARED TO THE NAM/GFS...WITH THE GEM A COMPROMISE...SO THERE
REMAINS SOME UNCERTAINTY IN TIMING. HIGH PRESSURE WILL BUILD IN
BEHIND THE FRONT SATURDAY NIGHT INTO SUNDAY AND WILL PROVIDE A
BRIEF RESPITE FROM THE ACTIVE WEATHER. THE ATMOSPHERE LOOKS TO
QUICKLY RELOAD HOWEVER WITH THERMAL RIDGE ONCE AGAIN STARTING TO
TILT BACK OVER THE AREA WITH H85 TEMPS AROUND 20C BY LATER IN THE
DAY SUNDAY.

NEXT WEEK...
AN ACTIVE PATTERN LOOKS TO PERSIST THROUGH AT LEAST THE MIDDLE OF
NEXT WEEK WITH A SERIES OF WAVES PUSHING ACROSS THE REGION BRINGING
CONTINUED PERIODIC CHANCES FOR SHOWERS AND THUNDERSTORMS. ANOTHER
COLD FRONT WILL PUSH ACROSS THE AREA LATER ON MONDAY WITH THE
FRONTAL BOUNDARY STALLING JUST TO OUR SOUTH. THEREAFTER...THERE IS
CONSIDERABLE UNCERTAINTY ON HOW FAR NORTH THE BOUNDARY MAY LIFT
WITH THE BEST PRECIP CHANCES FOCUSED IN THE VICINITY OF THE
FRONT AS A SERIES OF UPPER LEVEL DISTURBANCES PUSH ACROSS THE
AREA. PWATS REMAIN JUICY ALONG THE FRONT...AROUND TWO INCHES...AND
GUIDANCE SUGGESTS THAT THERE COULD BE SEVERAL CONVECTIVE COMPLEXES
NEXT WEEK WITH A CONCERN FOR HEAVY RAIN AND FLOODING SHOULD THIS
PAN OUT.

DEUBELBEISS

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* ISOLATED SHRA/TSRA LATE TONIGHT INTO EARLY FRIDAY MORNING.

* SCATTERED TSRA FRIDAY AFTERNOON/EARLY EVENING.

* SOUTH WIND WITH GUSTS DEVELOPING TO 20KT LATE MORNING FRIDAY.

KREIN

//DISCUSSION...UPDATED 06Z...

FORECAST CONCERNS WILL FOCUS ON SHRA/TSRA POTENTIAL THROUGH THE
PERIOD AS WELL AS GUSTY SOUTH WINDS DEVELOPING LATE FRIDAY MORNING
AND PERSISTING INTO EARLY FRIDAY EVENING.

FOR THE REMAINDER OF THE OVERNIGHT HOURS...THE REGION WILL REMAIN
UNDER SELY FLOW...NORTH OF A WARM FRONT CURRENTLY OVER CNTRL MO TO
SRN IL. SOME REMNANT SHOWERS FROM EARLIER CONVECTIVE ACTIVITY ARE
STILL SEEN ON THE LATEST RADAR IMAGERY...BUT THIS ACTIVITY IS
DIMINISHING WITH TIME FOR MUCH OF THE REGION. THE EXCEPTION IS A
SMALL AREA OF RAIN WHICH IS MORE PERSISTENT OVER ECNTRL IL. WITH
MID LEVEL FLOW MORE SOUTHWESTERLY...THERE HAS BEEN A MORE
PERSISTENT FETCH OF LIGHT PCPN INTO NWRN IL...SO KGYY COULD LIKELY
SEE SOME LIGHT RAIN THROUGH THE NIGHT THOUGH NO ADDITION THUNDER
IS ANTICIPATED WITH THIS PCPN. WITH A VERY MOIST AIRMASS IN PLACE
FROM RECENT PCPN ALONG WITH LIGHT WINDS...THERE WILL BE THE
POTENTIAL FOR SOME PATCHY BR WITH KDPA/KRFD BEING THE MORE LIKELY
TAF SITES TO SEE VIS DROP AT LEAST INTO MVFR LEVELS. EXPECT THAT
ORD/MDW SHOULD REMAIN VFR AS WINDS WILL REMAIN A LITTLE STRONGER
AND TEMP/DEWPOINT SPREADS A LITTLE HIGHER.

THE WARM FRONT WILL SLOWLY LIFT NWD THROUGH THE NIGHT AND PUSH
NORTH OF THE TERMINALS BY LATE FRIDAY MORNING. AT THIS
POINT...WINDS WILL SHIFT TO MORE SOUTHERLY. SOME BREAKS IN THE
CLOUD COVER SHOULD ALLOW FOR DEEPER LAYER MIXING...TAPPING
STRONGER WINDS ALOFT AND EXPECT THAT WINDS WILL BEGIN TO GUST TO
20KT FOLLOWING THE WARM FROPA.

INSTABILITY WILL INCREASES VERY QUICKLY AS THE WARM FRONT PASSES
TO THE NORTH AND WARM SECTOR AIR OVERSPREADS THE REGION BRINGING
INCREASING TEMPERATURES AND DEWPOINTS. MID LEVEL IMPULSES SHOULD
TRACK ACROSS THE AREA FRIDAY AFTERNOON AND EVENING IN UPPER LEVEL
SWLY FLOW AS THE UPPER RIDGE PUSHES TO THE EAST AND A LARGER SCALE
UPPER TROUGH MOVES ACROSS THE CENTRAL PLAINS. THESE IMPULSES WILL
BE THE TRIGGERING MECHANISM FOR ADDITIONAL SHRA/TSRA...BUT IN THE
ABSENCE OF ANY SFC FORCING...ACTIVITY WILL GENERALLY BE SCATTERED
AND DIFFICULT TO TIME AT THE TERMINALS. SO...WILL MAINTAIN THE
GOING PROB30 GROUP FOR TSRA WITH THE MOST FAVORABLE TIMING DURG
THE AFTERNOON HOURS. HOWEVER...WITH SCATTERED COVERAGE...ANY OF
THE TERMINALS COULD SEE SOME SHRA/TSRA A LITTLE EARLIER OR A
LITTLE LATER THAN THE GOING PROB30 TIMING.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* LOW CONFIDENCE IN THUNDER CHANCES/COVERAGE AND SPECIFIC TIMING
  FRIDAY AFTERNOON.

* HIGH CONFIDENCE IN WIND TRENDS THROUGH THE PERIOD.

* MEDIUM CONFIDENCE THAT ORD/MDW WILL REMAIN VFR THROUGH THE
  REMAINDER OF THE NIGHT AND INTO EARLY FRIDAY MORNING.

KREIN

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

* SATURDAY...TSRA LIKELY.
* SUNDAY...SLIGHT CHANCE OF TSRA.
* MONDAY AND TUESDAY...CHANCE OF TSRA.
* WEDNESDAY AND THURSDAY...SLIGHT CHANCE OF TSRA

KMD

&&

.MARINE...
123 PM CDT

SURFACE HIGH PRESSURE OVER THE GREAT LAKES REGION THIS AFTERNOON
WILL DRIFT TO THE EAST TONIGHT IN THE WAKE OF A DEPARTING UPPER
TROUGH OVER NEW ENGLAND/QUEBEC...AND AHEAD OF ANOTHER SURFACE TROUGH
AND WEAK COLD FRONT STRETCHING FROM FAR NORTHWEST ONTARIO TO THE
CENTRAL PLAINS. WINDS ON LAKE MICHIGAN WILL SHIFT TO THE SOUTHEAST
AND EVENTUALLY SOUTH HEADING INTO FRIDAY...AS AN AREA OF SURFACE LOW
PRESSURE DEVELOPS ACROSS THE PLAINS AND LIFTS ACROSS THE UPPER
MISSISSIPPI RIVER VALLEY. TIGHTENING OF THE PRESSURE GRADIENT
SOUTHEAST OF THE LOW TRACK WILL RESULT IN S-SE WINDS INCREASING INTO
THE 15-25 KT RANGE TONIGHT AND FRIDAY...GRADUALLY WEAKENING SATURDAY
AS THE LOW MOVES OFF TO THE NORTHEAST AND A WEAK COLD FRONT TRAILS
ACROSS THE LAKE FOLLOWED BY WEAK HIGH PRESSURE.

THIS COLD FRONT APPEARS TO DISSIPATE OR STALL ACROSS FAR SOUTHERN
LAKE MICHIGAN OR NORTHERN IL/IND LATE SATURDAY NIGHT OR EARLY SUNDAY
BEFORE DEVELOPING BACK TO THE NORTH AS A WARM FRONT SUNDAY NIGHT AS
ANOTHER AREA OF LOW PRESSURE DEVELOPS OVER THE PLAINS AND LIFTS
NORTHEAST INTO THE WESTERN/NORTHERN LAKES LATE SUNDAY NIGHT INTO
MONDAY. AGAIN...A TIGHTENING OF THE PRESSURE GRADIENT ALONG THE
SOUTHEAST PERIPHERY OF THE LOW TRACK IS EXPECTED WITH WINDS AGAIN
BECOMING SOUTHERLY INTO THE 15-25 KT RANGE ON MONDAY. ANOTHER
TRAILING COLD FRONT WILL PASS ACROSS THE LAKE MONDAY NIGHT...WITH
WEAK HIGH PRESSURE AND LIGHTER WINDS DEVELOPING TUESDAY.

RATZER

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 290612
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
112 AM CDT FRI AUG 29 2014

.DISCUSSION...
714 PM CDT

PAIR OF MCVS NOTED ON RADAR IMAGERY CONTINUE TO MOVE EASTWARD
DRIVING SLOWLY DECAYING CONVECTIVE COMPLEX EASTWARD INTO OUR CWA
EARLY THIS EVENING DESPITE THE MUCH MORE STABLE AND SOMEWHAT DRIER
AIR MASS OVER THE REGION. HAVE ALREADY UPDATED PRECIP TRENDS A
COUPLE TIME TO ACCOUNT FOR THE RAIN THIS EVENING. ANTICIPATE
CONTINUED WEAKENING TREND...PARTICULARLY FROM THE NORTH...IN THIS
AREA OF LEFT OVER RAIN AND EVEN SOME LINGERING THUNDER. THE THREAT
OF THUNDER WITH THE NORTHERN MCV TRACKING CLOSE TO I-88 LOOKS TO END
VERY SOON...WHILE THE CONVECTION WITH THE SOUTHERN MOST MCV LIES
CLOSE ENOUGH TO MORE UNSTABLE AIR TO POTENTIALLY MAINTAIN
THUNDERSTORMS ACROSS THE SOUTHERN TIER OF OUR CWA THE NEXT FEW
HOURS. IN THE WAKE OF THESE MCVS...WHICH REALLY HAVENT BEEN HANDLED
WELL BY NUMERICAL GUIDANCE...SHOULD SEE A PERIOD OF DRY CONDITIONS
HOWEVER MODELS DO BREAK OUT ADDITIONAL CONVECTION OVERNIGHT WHICH
ISN`T THAT UNREASONABLE GIVEN THE NORTHWARD ADVANCING WARM FRONT.

IZZI

//PREV DISCUSSION...
230 PM CDT

VISIBLE IMAGERY THIS AFTERNOON SHOWS A MID/UPR LEVEL CLOUD DECK
LIFTING NORTHEAST ACROSS NORTHERN IL. REMNANTS FROM A MORNING
COMPLEX OF THUNDERSTORMS RESIDES OVER IOWA...WITH SOME CONVECTIVE
LOOK TO THE CLOUDS LINGERING INTO THIS AFTN. SFC TEMPS ACROSS THE
FORECAST AREA HAVE BEEN ABLE TO WARM INTO THE MID/UPR 70S. A FEW
POINTS SOUTH OF PONTIAC TO KANKAKEE HAVE PUSHED TO ARND 80 DEG...BUT
WITH THE LIGHT EASTERLY FLOW AT THE SFC SOME WEAK SUBSIDENCE HAS
BEEN NOTED WITH DEW POINTS BEING PUSHED INTO THE LOW 50S ALONG THE
LAKESHORE AND MID/UPR 50S INLAND.

THE MAIN CHALLENGE FOR THIS EVENING WILL FOCUS ON CONVECTIVE
CHANCES/COVERAGE...WHICH WILL CONTINUE THROUGH DAYBREAK FRI.
GUIDANCE HAS CONTINUED TO BACK OFF ON THE ARRIVAL OF PRECIP INTO THE
FORECAST AREA...WHICH SEEMS TO LINE UP RELATIVELY WELL WITH THE
CURRENT TRENDS. THE FRONTAL BOUNDARY WILL SLOWLY LIFT NORTH THIS
EVENING...BUT NOT EXPECTING MUCH IN THE WAY OF PRECIP UNTIL PERHAPS
AFT 04Z WITH A GRADUAL UPGLIDE OF PARCELS ALLOWS FOR MOISTENING.
SOME ELEVATED CONVECTION COULD BEGIN TO DEVELOP...ALTHOUGH NOT
EXPECTING MUCH COVERAGE OVERNIGHT. THE FOCUS FOR SLIGHTLY BETTER
PRECIP COVERAGE WILL REMAIN ALONG THE NORTHERN ROW OF COUNTIES IN
NORTHERN IL...HOWEVER CLOSER TO DAYBREAK FRI IT APPEARS SOME
PRECIP/CONVECTION COULD SAG SOUTHEAST AND CLIP NORTHEAST
IL/NORTHWEST IN BEFORE DISSIPATING.

WITH INCREASING CLOUD COVER TONIGHT...IT SHUD LIMIT HOW COOL TEMPS
BECOME. SO HAVE MADE ONLY MINOR ADJUSTMENTS TO THE TEMPS WITH
GENERALLY MID/UPR 60S FOR LOWS.

BEACHLER

FRIDAY AND FRIDAY NIGHT...
CLOSED UPPER LOW CURRENTLY NEAR THE COLORADO FRONT RANGE WILL SLOWLY
TRAVERSE EAST TOWARDS THE MID-MISSOURI VALLEY FRIDAY BECOMING AN
OPEN WAVE. AT THE SURFACE...BROAD AND WEAK SURFACE LOW WILL LIFT
INTO THE UPPER MIDWEST WHILE SOUTHWEST FLOW RAMPS UP THROUGH THE
COLUMN AS THE WARM FRONT LIFTS INTO THE CENTRAL GREAT LAKES. HEAT
AND HUMIDITY WILL MAKE A RETURN AS THIS OCCURS. H85 TEMPS WARMING TO
AROUND 18C WILL HELP SUPPORT MID/UPPER 80S DURING THE DAY
FRIDAY...AND SURFACE DEWPOINTS ARE PROGGED TO PUSH BACK INTO THE LOW
POSSIBLY MID 70S. THIS WILL RESULT IN MODERATE INSTABILITY
DEVELOPING DURING THE DAY...AND ONLY WEAKLY CAPPED DURING THE
AFTERNOON AS BROAD HEIGHT FALLS ASSOCIATED WITH THE UPPER WAVE START
TO OVERSPREAD THE AREA. THERE DOESNT SEEM TO BE MUCH FOCUS IN THE
LOWER LEVELS SO WOULD EXPECT ONLY SCATTERED THUNDERSTORM DEVELOPMENT
ACROSS THE REGION FRIDAY AFTERNOON/EVENING. UPPER WAVE BEGINS TO
MOVE INTO THE UPPER MIDWEST TOMORROW NIGHT AND BROAD WARM ADVECTION
OUT AHEAD DURING THE EVENING AND OVERNIGHT HOURS WILL HELP SUSTAIN
SOME CONVECTION LATE BUT WOULD EXPECT SOME NOCTURNAL DOWNTICK IN
ACTIVITY OVERNIGHT WITH THE LOW LEVEL JET FOCUSED WELL TO OUR NORTH.
GFS/NAM SEEM TO BE OVERDOING POPS MUCH OF THE DAY AND NIGHT
FRIDAY...AND OPTED TO LEAN CLOSER TO ECMWF THESE PERIODS.

THIS WEEKEND...
COLD FRONT WILL SWEEP ACROSS THE FORECAST AREA STARTING VERY EARLY
ON SATURDAY. WHILE NOT A FAVORABLE DIURNAL TIME...WE SHOULD STILL
HAVE SOME VERY MODEST INSTABILITY IN PLACE THAT WILL SUPPORT SOME
EARLY DAY THUNDERSTORMS ALONG THE FRONTAL BOUNDARY...WHICH WOULD BE
ABLE TO EXPAND IN COVERAGE AS THE DAY PROGRESSES AND THE BOUNDARY
LAYER WARMS. IN ADDITION...GUIDANCE SUGGESTS A SECOND SHORTWAVE
WILL WRAP INTO THE AREA THAT WILL PROVIDE ADDITIONAL BROAD SCALE
ASCENT. THE ECMWF IS ABOUT SIX HOURS SLOWER WITH THIS FEATURE
COMPARED TO THE NAM/GFS...WITH THE GEM A COMPROMISE...SO THERE
REMAINS SOME UNCERTAINTY IN TIMING. HIGH PRESSURE WILL BUILD IN
BEHIND THE FRONT SATURDAY NIGHT INTO SUNDAY AND WILL PROVIDE A
BRIEF RESPITE FROM THE ACTIVE WEATHER. THE ATMOSPHERE LOOKS TO
QUICKLY RELOAD HOWEVER WITH THERMAL RIDGE ONCE AGAIN STARTING TO
TILT BACK OVER THE AREA WITH H85 TEMPS AROUND 20C BY LATER IN THE
DAY SUNDAY.

NEXT WEEK...
AN ACTIVE PATTERN LOOKS TO PERSIST THROUGH AT LEAST THE MIDDLE OF
NEXT WEEK WITH A SERIES OF WAVES PUSHING ACROSS THE REGION BRINGING
CONTINUED PERIODIC CHANCES FOR SHOWERS AND THUNDERSTORMS. ANOTHER
COLD FRONT WILL PUSH ACROSS THE AREA LATER ON MONDAY WITH THE
FRONTAL BOUNDARY STALLING JUST TO OUR SOUTH. THEREAFTER...THERE IS
CONSIDERABLE UNCERTAINTY ON HOW FAR NORTH THE BOUNDARY MAY LIFT
WITH THE BEST PRECIP CHANCES FOCUSED IN THE VICINITY OF THE
FRONT AS A SERIES OF UPPER LEVEL DISTURBANCES PUSH ACROSS THE
AREA. PWATS REMAIN JUICY ALONG THE FRONT...AROUND TWO INCHES...AND
GUIDANCE SUGGESTS THAT THERE COULD BE SEVERAL CONVECTIVE COMPLEXES
NEXT WEEK WITH A CONCERN FOR HEAVY RAIN AND FLOODING SHOULD THIS
PAN OUT.

DEUBELBEISS

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* ISOLATED SHRA/TSRA LATE TONIGHT INTO EARLY FRIDAY MORNING.

* SCATTERED TSRA FRIDAY AFTERNOON/EARLY EVENING.

* SOUTH WIND WITH GUSTS DEVELOPING TO 20KT LATE MORNING FRIDAY.

KREIN

//DISCUSSION...UPDATED 06Z...

FORECAST CONCERNS WILL FOCUS ON SHRA/TSRA POTENTIAL THROUGH THE
PERIOD AS WELL AS GUSTY SOUTH WINDS DEVELOPING LATE FRIDAY MORNING
AND PERSISTING INTO EARLY FRIDAY EVENING.

FOR THE REMAINDER OF THE OVERNIGHT HOURS...THE REGION WILL REMAIN
UNDER SELY FLOW...NORTH OF A WARM FRONT CURRENTLY OVER CNTRL MO TO
SRN IL. SOME REMNANT SHOWERS FROM EARLIER CONVECTIVE ACTIVITY ARE
STILL SEEN ON THE LATEST RADAR IMAGERY...BUT THIS ACTIVITY IS
DIMINISHING WITH TIME FOR MUCH OF THE REGION. THE EXCEPTION IS A
SMALL AREA OF RAIN WHICH IS MORE PERSISTENT OVER ECNTRL IL. WITH
MID LEVEL FLOW MORE SOUTHWESTERLY...THERE HAS BEEN A MORE
PERSISTENT FETCH OF LIGHT PCPN INTO NWRN IL...SO KGYY COULD LIKELY
SEE SOME LIGHT RAIN THROUGH THE NIGHT THOUGH NO ADDITION THUNDER
IS ANTICIPATED WITH THIS PCPN. WITH A VERY MOIST AIRMASS IN PLACE
FROM RECENT PCPN ALONG WITH LIGHT WINDS...THERE WILL BE THE
POTENTIAL FOR SOME PATCHY BR WITH KDPA/KRFD BEING THE MORE LIKELY
TAF SITES TO SEE VIS DROP AT LEAST INTO MVFR LEVELS. EXPECT THAT
ORD/MDW SHOULD REMAIN VFR AS WINDS WILL REMAIN A LITTLE STRONGER
AND TEMP/DEWPOINT SPREADS A LITTLE HIGHER.

THE WARM FRONT WILL SLOWLY LIFT NWD THROUGH THE NIGHT AND PUSH
NORTH OF THE TERMINALS BY LATE FRIDAY MORNING. AT THIS
POINT...WINDS WILL SHIFT TO MORE SOUTHERLY. SOME BREAKS IN THE
CLOUD COVER SHOULD ALLOW FOR DEEPER LAYER MIXING...TAPPING
STRONGER WINDS ALOFT AND EXPECT THAT WINDS WILL BEGIN TO GUST TO
20KT FOLLOWING THE WARM FROPA.

INSTABILITY WILL INCREASES VERY QUICKLY AS THE WARM FRONT PASSES
TO THE NORTH AND WARM SECTOR AIR OVERSPREADS THE REGION BRINGING
INCREASING TEMPERATURES AND DEWPOINTS. MID LEVEL IMPULSES SHOULD
TRACK ACROSS THE AREA FRIDAY AFTERNOON AND EVENING IN UPPER LEVEL
SWLY FLOW AS THE UPPER RIDGE PUSHES TO THE EAST AND A LARGER SCALE
UPPER TROUGH MOVES ACROSS THE CENTRAL PLAINS. THESE IMPULSES WILL
BE THE TRIGGERING MECHANISM FOR ADDITIONAL SHRA/TSRA...BUT IN THE
ABSENCE OF ANY SFC FORCING...ACTIVITY WILL GENERALLY BE SCATTERED
AND DIFFICULT TO TIME AT THE TERMINALS. SO...WILL MAINTAIN THE
GOING PROB30 GROUP FOR TSRA WITH THE MOST FAVORABLE TIMING DURG
THE AFTERNOON HOURS. HOWEVER...WITH SCATTERED COVERAGE...ANY OF
THE TERMINALS COULD SEE SOME SHRA/TSRA A LITTLE EARLIER OR A
LITTLE LATER THAN THE GOING PROB30 TIMING.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* LOW CONFIDENCE IN THUNDER CHANCES/COVERAGE AND SPECIFIC TIMING
  FRIDAY AFTERNOON.

* HIGH CONFIDENCE IN WIND TRENDS THROUGH THE PERIOD.

* MEDIUM CONFIDENCE THAT ORD/MDW WILL REMAIN VFR THROUGH THE
  REMAINDER OF THE NIGHT AND INTO EARLY FRIDAY MORNING.

KREIN

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

* SATURDAY...TSRA LIKELY.
* SUNDAY...SLIGHT CHANCE OF TSRA.
* MONDAY AND TUESDAY...CHANCE OF TSRA.
* WEDNESDAY AND THURSDAY...SLIGHT CHANCE OF TSRA

KMD

&&

.MARINE...
123 PM CDT

SURFACE HIGH PRESSURE OVER THE GREAT LAKES REGION THIS AFTERNOON
WILL DRIFT TO THE EAST TONIGHT IN THE WAKE OF A DEPARTING UPPER
TROUGH OVER NEW ENGLAND/QUEBEC...AND AHEAD OF ANOTHER SURFACE TROUGH
AND WEAK COLD FRONT STRETCHING FROM FAR NORTHWEST ONTARIO TO THE
CENTRAL PLAINS. WINDS ON LAKE MICHIGAN WILL SHIFT TO THE SOUTHEAST
AND EVENTUALLY SOUTH HEADING INTO FRIDAY...AS AN AREA OF SURFACE LOW
PRESSURE DEVELOPS ACROSS THE PLAINS AND LIFTS ACROSS THE UPPER
MISSISSIPPI RIVER VALLEY. TIGHTENING OF THE PRESSURE GRADIENT
SOUTHEAST OF THE LOW TRACK WILL RESULT IN S-SE WINDS INCREASING INTO
THE 15-25 KT RANGE TONIGHT AND FRIDAY...GRADUALLY WEAKENING SATURDAY
AS THE LOW MOVES OFF TO THE NORTHEAST AND A WEAK COLD FRONT TRAILS
ACROSS THE LAKE FOLLOWED BY WEAK HIGH PRESSURE.

THIS COLD FRONT APPEARS TO DISSIPATE OR STALL ACROSS FAR SOUTHERN
LAKE MICHIGAN OR NORTHERN IL/IND LATE SATURDAY NIGHT OR EARLY SUNDAY
BEFORE DEVELOPING BACK TO THE NORTH AS A WARM FRONT SUNDAY NIGHT AS
ANOTHER AREA OF LOW PRESSURE DEVELOPS OVER THE PLAINS AND LIFTS
NORTHEAST INTO THE WESTERN/NORTHERN LAKES LATE SUNDAY NIGHT INTO
MONDAY. AGAIN...A TIGHTENING OF THE PRESSURE GRADIENT ALONG THE
SOUTHEAST PERIPHERY OF THE LOW TRACK IS EXPECTED WITH WINDS AGAIN
BECOMING SOUTHERLY INTO THE 15-25 KT RANGE ON MONDAY. ANOTHER
TRAILING COLD FRONT WILL PASS ACROSS THE LAKE MONDAY NIGHT...WITH
WEAK HIGH PRESSURE AND LIGHTER WINDS DEVELOPING TUESDAY.

RATZER

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO







000
FXUS63 KLOT 290308
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1008 PM CDT THU AUG 28 2014

.DISCUSSION...
714 PM CDT

PAIR OF MCVS NOTED ON RADAR IMAGERY CONTINUE TO MOVE EASTWARD
DRIVING SLOWLY DECAYING CONVECTIVE COMPLEX EASTWARD INTO OUR CWA
EARLY THIS EVENING DESPITE THE MUCH MORE STABLE AND SOMEWHAT DRIER
AIR MASS OVER THE REGION. HAVE ALREADY UPDATED PRECIP TRENDS A
COUPLE TIME TO ACCOUNT FOR THE RAIN THIS EVENING. ANTICIPATE
CONTINUED WEAKENING TREND...PARTICULARLY FROM THE NORTH...IN THIS
AREA OF LEFT OVER RAIN AND EVEN SOME LINGERING THUNDER. THE THREAT
OF THUNDER WITH THE NORTHERN MCV TRACKING CLOSE TO I-88 LOOKS TO END
VERY SOON...WHILE THE CONVECTION WITH THE SOUTHERN MOST MCV LIES
CLOSE ENOUGH TO MORE UNSTABLE AIR TO POTENTIALLY MAINTAIN
THUNDERSTORMS ACROSS THE SOUTHERN TIER OF OUR CWA THE NEXT FEW
HOURS. IN THE WAKE OF THESE MCVS...WHICH REALLY HAVENT BEEN HANDLED
WELL BY NUMERICAL GUIDANCE...SHOULD SEE A PERIOD OF DRY CONDITIONS
HOWEVER MODELS DO BREAK OUT ADDITIONAL CONVECTION OVERNIGHT WHICH
ISN`T THAT UNREASONABLE GIVEN THE NORTHWARD ADVANCING WARM FRONT.

IZZI

//PREV DISCUSSION...
230 PM CDT

VISIBLE IMAGERY THIS AFTERNOON SHOWS A MID/UPR LEVEL CLOUD DECK
LIFTING NORTHEAST ACROSS NORTHERN IL. REMNANTS FROM A MORNING
COMPLEX OF THUNDERSTORMS RESIDES OVER IOWA...WITH SOME CONVECTIVE
LOOK TO THE CLOUDS LINGERING INTO THIS AFTN. SFC TEMPS ACROSS THE
FORECAST AREA HAVE BEEN ABLE TO WARM INTO THE MID/UPR 70S. A FEW
POINTS SOUTH OF PONTIAC TO KANKAKEE HAVE PUSHED TO ARND 80 DEG...BUT
WITH THE LIGHT EASTERLY FLOW AT THE SFC SOME WEAK SUBSIDENCE HAS
BEEN NOTED WITH DEW POINTS BEING PUSHED INTO THE LOW 50S ALONG THE
LAKESHORE AND MID/UPR 50S INLAND.

THE MAIN CHALLENGE FOR THIS EVENING WILL FOCUS ON CONVECTIVE
CHANCES/COVERAGE...WHICH WILL CONTINUE THROUGH DAYBREAK FRI.
GUIDANCE HAS CONTINUED TO BACK OFF ON THE ARRIVAL OF PRECIP INTO THE
FORECAST AREA...WHICH SEEMS TO LINE UP RELATIVELY WELL WITH THE
CURRENT TRENDS. THE FRONTAL BOUNDARY WILL SLOWLY LIFT NORTH THIS
EVENING...BUT NOT EXPECTING MUCH IN THE WAY OF PRECIP UNTIL PERHAPS
AFT 04Z WITH A GRADUAL UPGLIDE OF PARCELS ALLOWS FOR MOISTENING.
SOME ELEVATED CONVECTION COULD BEGIN TO DEVELOP...ALTHOUGH NOT
EXPECTING MUCH COVERAGE OVERNIGHT. THE FOCUS FOR SLIGHTLY BETTER
PRECIP COVERAGE WILL REMAIN ALONG THE NORTHERN ROW OF COUNTIES IN
NORTHERN IL...HOWEVER CLOSER TO DAYBREAK FRI IT APPEARS SOME
PRECIP/CONVECTION COULD SAG SOUTHEAST AND CLIP NORTHEAST
IL/NORTHWEST IN BEFORE DISSIPATING.

WITH INCREASING CLOUD COVER TONIGHT...IT SHUD LIMIT HOW COOL TEMPS
BECOME. SO HAVE MADE ONLY MINOR ADJUSTMENTS TO THE TEMPS WITH
GENERALLY MID/UPR 60S FOR LOWS.

BEACHLER

FRIDAY AND FRIDAY NIGHT...
CLOSED UPPER LOW CURRENTLY NEAR THE COLORADO FRONT RANGE WILL SLOWLY
TRAVERSE EAST TOWARDS THE MID-MISSOURI VALLEY FRIDAY BECOMING AN
OPEN WAVE. AT THE SURFACE...BROAD AND WEAK SURFACE LOW WILL LIFT
INTO THE UPPER MIDWEST WHILE SOUTHWEST FLOW RAMPS UP THROUGH THE
COLUMN AS THE WARM FRONT LIFTS INTO THE CENTRAL GREAT LAKES. HEAT
AND HUMIDITY WILL MAKE A RETURN AS THIS OCCURS. H85 TEMPS WARMING TO
AROUND 18C WILL HELP SUPPORT MID/UPPER 80S DURING THE DAY
FRIDAY...AND SURFACE DEWPOINTS ARE PROGGED TO PUSH BACK INTO THE LOW
POSSIBLY MID 70S. THIS WILL RESULT IN MODERATE INSTABILITY
DEVELOPING DURING THE DAY...AND ONLY WEAKLY CAPPED DURING THE
AFTERNOON AS BROAD HEIGHT FALLS ASSOCIATED WITH THE UPPER WAVE START
TO OVERSPREAD THE AREA. THERE DOESNT SEEM TO BE MUCH FOCUS IN THE
LOWER LEVELS SO WOULD EXPECT ONLY SCATTERED THUNDERSTORM DEVELOPMENT
ACROSS THE REGION FRIDAY AFTERNOON/EVENING. UPPER WAVE BEGINS TO
MOVE INTO THE UPPER MIDWEST TOMORROW NIGHT AND BROAD WARM ADVECTION
OUT AHEAD DURING THE EVENING AND OVERNIGHT HOURS WILL HELP SUSTAIN
SOME CONVECTION LATE BUT WOULD EXPECT SOME NOCTURNAL DOWNTICK IN
ACTIVITY OVERNIGHT WITH THE LOW LEVEL JET FOCUSED WELL TO OUR NORTH.
GFS/NAM SEEM TO BE OVERDOING POPS MUCH OF THE DAY AND NIGHT
FRIDAY...AND OPTED TO LEAN CLOSER TO ECMWF THESE PERIODS.

THIS WEEKEND...
COLD FRONT WILL SWEEP ACROSS THE FORECAST AREA STARTING VERY EARLY
ON SATURDAY. WHILE NOT A FAVORABLE DIURNAL TIME...WE SHOULD STILL
HAVE SOME VERY MODEST INSTABILITY IN PLACE THAT WILL SUPPORT SOME
EARLY DAY THUNDERSTORMS ALONG THE FRONTAL BOUNDARY...WHICH WOULD BE
ABLE TO EXPAND IN COVERAGE AS THE DAY PROGRESSES AND THE BOUNDARY
LAYER WARMS. IN ADDITION...GUIDANCE SUGGESTS A SECOND SHORTWAVE
WILL WRAP INTO THE AREA THAT WILL PROVIDE ADDITIONAL BROAD SCALE
ASCENT. THE ECMWF IS ABOUT SIX HOURS SLOWER WITH THIS FEATURE
COMPARED TO THE NAM/GFS...WITH THE GEM A COMPROMISE...SO THERE
REMAINS SOME UNCERTAINTY IN TIMING. HIGH PRESSURE WILL BUILD IN
BEHIND THE FRONT SATURDAY NIGHT INTO SUNDAY AND WILL PROVIDE A
BRIEF RESPITE FROM THE ACTIVE WEATHER. THE ATMOSPHERE LOOKS TO
QUICKLY RELOAD HOWEVER WITH THERMAL RIDGE ONCE AGAIN STARTING TO
TILT BACK OVER THE AREA WITH H85 TEMPS AROUND 20C BY LATER IN THE
DAY SUNDAY.

NEXT WEEK...
AN ACTIVE PATTERN LOOKS TO PERSIST THROUGH AT LEAST THE MIDDLE OF
NEXT WEEK WITH A SERIES OF WAVES PUSHING ACROSS THE REGION BRINGING
CONTINUED PERIODIC CHANCES FOR SHOWERS AND THUNDERSTORMS. ANOTHER
COLD FRONT WILL PUSH ACROSS THE AREA LATER ON MONDAY WITH THE
FRONTAL BOUNDARY STALLING JUST TO OUR SOUTH. THEREAFTER...THERE IS
CONSIDERABLE UNCERTAINTY ON HOW FAR NORTH THE BOUNDARY MAY LIFT
WITH THE BEST PRECIP CHANCES FOCUSED IN THE VICINITY OF THE
FRONT AS A SERIES OF UPPER LEVEL DISTURBANCES PUSH ACROSS THE
AREA. PWATS REMAIN JUICY ALONG THE FRONT...AROUND TWO INCHES...AND
GUIDANCE SUGGESTS THAT THERE COULD BE SEVERAL CONVECTIVE COMPLEXES
NEXT WEEK WITH A CONCERN FOR HEAVY RAIN AND FLOODING SHOULD THIS
PAN OUT.

DEUBELBEISS

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 03Z...

* ISOLATED SHRA/TSRA LATE TONIGHT INTO EARLY FRIDAY MORNING.

* SCATTERED TSRA FRIDAY AFTERNOON/EARLY EVENING.

* SOUTH WIND WITH GUSTS DEVELOPING TO 20KT MIDDAY FRI.

KMD

//DISCUSSION...UPDATED 00Z...
CHALLENGING FORECAST FOR THE NEXT 24-30 HOURS. AREA OF SHOWERS
WILL CONTINUE TO PUSH EASTWARD AND WEAKEN SOME THIS EVENING.
THUNDER ACTIVITY LOOKS TO REMAIN SOUTH OF THE INTERSTATE 80
CORRIDOR ALONG A LINE FROM KVYS TO KLOT TO KGYY. CIGS AND VSBYS
SHOULD GENERALLY REMAIN VFR THOUGH BRIEF MVFR VISBYS ARE POSSIBLE
MAINLY WEST OF THE MAIN CHICAGO TERMINALS.

EXPECTING A LULL THIS EVENING...THEN AS A WARM FRONT LIFTS THROUGH
TONIGHT...ADDITIONAL CONVECTION IS EXPECTED IN NW IOWA AND
SPREADING INTO WISCONSIN OVERNIGHT. AS AN UPPER RIDGE BUCKLES SOME
LATE TONIGHT INTO EARLY FRIDAY...SOME OF THIS ACTIVITY MAY GRAZE
NORTHEAST ILLINOIS IN THE 12Z-15Z TIME FRAME. INSTABILITY MAY
SUPPORT SHRA WITH ISOLATED TS.

INSTABILITY THEN INCREASES VERY QUICKLY ON FRIDAY AS WE GET IN THE
WARM SECTOR AND DEWPOINTS RISE. UPPER HEIGHT FALLS COMBINED WITH
PEAK HEATING SUGGESTS AFTERNOON AIR MASS THUNDERSTORMS THOUGH
DIFFICULT ON TIMING. COULD BE THUNDERSTORMS AT ANY TIME FRIDAY
AFTERNOON EARLY EVENING WITH NO OBVIOUS SURFACE FOCUS. WITH HIGH
PRECIPITABLE WATER VALUES...HEAVY DOWNPOURS ARE POSSIBLE.

KMD

//ORD AND MDW CONFIDENCE...UPDATED 03Z...

* LOW-MEDIUM IN PRECIP COVERAGE LATE TONIGHT INTO EARLY FRIDAY.

* LOW IN THUNDER CHANCES/COVERAGE AND SPECIFIC TIMING FRIDAY AFTERNOON.

* HIGH IN WIND DIR/SPEED AND TRENDS

KMD

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

* SATURDAY...TSRA LIKELY.
* SUNDAY...SLIGHT CHANCE OF TSRA.
* MONDAY AND TUESDAY...CHANCE OF TSRA.
* WEDNESDAY AND THURSDAY...SLIGHT CHANCE OF TSRA

KMD

&&

.MARINE...
123 PM CDT

SURFACE HIGH PRESSURE OVER THE GREAT LAKES REGION THIS AFTERNOON
WILL DRIFT TO THE EAST TONIGHT IN THE WAKE OF A DEPARTING UPPER
TROUGH OVER NEW ENGLAND/QUEBEC...AND AHEAD OF ANOTHER SURFACE TROUGH
AND WEAK COLD FRONT STRETCHING FROM FAR NORTHWEST ONTARIO TO THE
CENTRAL PLAINS. WINDS ON LAKE MICHIGAN WILL SHIFT TO THE SOUTHEAST
AND EVENTUALLY SOUTH HEADING INTO FRIDAY...AS AN AREA OF SURFACE LOW
PRESSURE DEVELOPS ACROSS THE PLAINS AND LIFTS ACROSS THE UPPER
MISSISSIPPI RIVER VALLEY. TIGHTENING OF THE PRESSURE GRADIENT
SOUTHEAST OF THE LOW TRACK WILL RESULT IN S-SE WINDS INCREASING INTO
THE 15-25 KT RANGE TONIGHT AND FRIDAY...GRADUALLY WEAKENING SATURDAY
AS THE LOW MOVES OFF TO THE NORTHEAST AND A WEAK COLD FRONT TRAILS
ACROSS THE LAKE FOLLOWED BY WEAK HIGH PRESSURE.

THIS COLD FRONT APPEARS TO DISSIPATE OR STALL ACROSS FAR SOUTHERN
LAKE MICHIGAN OR NORTHERN IL/IND LATE SATURDAY NIGHT OR EARLY SUNDAY
BEFORE DEVELOPING BACK TO THE NORTH AS A WARM FRONT SUNDAY NIGHT AS
ANOTHER AREA OF LOW PRESSURE DEVELOPS OVER THE PLAINS AND LIFTS
NORTHEAST INTO THE WESTERN/NORTHERN LAKES LATE SUNDAY NIGHT INTO
MONDAY. AGAIN...A TIGHTENING OF THE PRESSURE GRADIENT ALONG THE
SOUTHEAST PERIPHERY OF THE LOW TRACK IS EXPECTED WITH WINDS AGAIN
BECOMING SOUTHERLY INTO THE 15-25 KT RANGE ON MONDAY. ANOTHER
TRAILING COLD FRONT WILL PASS ACROSS THE LAKE MONDAY NIGHT...WITH
WEAK HIGH PRESSURE AND LIGHTER WINDS DEVELOPING TUESDAY.

RATZER

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 290308
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1008 PM CDT THU AUG 28 2014

.DISCUSSION...
714 PM CDT

PAIR OF MCVS NOTED ON RADAR IMAGERY CONTINUE TO MOVE EASTWARD
DRIVING SLOWLY DECAYING CONVECTIVE COMPLEX EASTWARD INTO OUR CWA
EARLY THIS EVENING DESPITE THE MUCH MORE STABLE AND SOMEWHAT DRIER
AIR MASS OVER THE REGION. HAVE ALREADY UPDATED PRECIP TRENDS A
COUPLE TIME TO ACCOUNT FOR THE RAIN THIS EVENING. ANTICIPATE
CONTINUED WEAKENING TREND...PARTICULARLY FROM THE NORTH...IN THIS
AREA OF LEFT OVER RAIN AND EVEN SOME LINGERING THUNDER. THE THREAT
OF THUNDER WITH THE NORTHERN MCV TRACKING CLOSE TO I-88 LOOKS TO END
VERY SOON...WHILE THE CONVECTION WITH THE SOUTHERN MOST MCV LIES
CLOSE ENOUGH TO MORE UNSTABLE AIR TO POTENTIALLY MAINTAIN
THUNDERSTORMS ACROSS THE SOUTHERN TIER OF OUR CWA THE NEXT FEW
HOURS. IN THE WAKE OF THESE MCVS...WHICH REALLY HAVENT BEEN HANDLED
WELL BY NUMERICAL GUIDANCE...SHOULD SEE A PERIOD OF DRY CONDITIONS
HOWEVER MODELS DO BREAK OUT ADDITIONAL CONVECTION OVERNIGHT WHICH
ISN`T THAT UNREASONABLE GIVEN THE NORTHWARD ADVANCING WARM FRONT.

IZZI

//PREV DISCUSSION...
230 PM CDT

VISIBLE IMAGERY THIS AFTERNOON SHOWS A MID/UPR LEVEL CLOUD DECK
LIFTING NORTHEAST ACROSS NORTHERN IL. REMNANTS FROM A MORNING
COMPLEX OF THUNDERSTORMS RESIDES OVER IOWA...WITH SOME CONVECTIVE
LOOK TO THE CLOUDS LINGERING INTO THIS AFTN. SFC TEMPS ACROSS THE
FORECAST AREA HAVE BEEN ABLE TO WARM INTO THE MID/UPR 70S. A FEW
POINTS SOUTH OF PONTIAC TO KANKAKEE HAVE PUSHED TO ARND 80 DEG...BUT
WITH THE LIGHT EASTERLY FLOW AT THE SFC SOME WEAK SUBSIDENCE HAS
BEEN NOTED WITH DEW POINTS BEING PUSHED INTO THE LOW 50S ALONG THE
LAKESHORE AND MID/UPR 50S INLAND.

THE MAIN CHALLENGE FOR THIS EVENING WILL FOCUS ON CONVECTIVE
CHANCES/COVERAGE...WHICH WILL CONTINUE THROUGH DAYBREAK FRI.
GUIDANCE HAS CONTINUED TO BACK OFF ON THE ARRIVAL OF PRECIP INTO THE
FORECAST AREA...WHICH SEEMS TO LINE UP RELATIVELY WELL WITH THE
CURRENT TRENDS. THE FRONTAL BOUNDARY WILL SLOWLY LIFT NORTH THIS
EVENING...BUT NOT EXPECTING MUCH IN THE WAY OF PRECIP UNTIL PERHAPS
AFT 04Z WITH A GRADUAL UPGLIDE OF PARCELS ALLOWS FOR MOISTENING.
SOME ELEVATED CONVECTION COULD BEGIN TO DEVELOP...ALTHOUGH NOT
EXPECTING MUCH COVERAGE OVERNIGHT. THE FOCUS FOR SLIGHTLY BETTER
PRECIP COVERAGE WILL REMAIN ALONG THE NORTHERN ROW OF COUNTIES IN
NORTHERN IL...HOWEVER CLOSER TO DAYBREAK FRI IT APPEARS SOME
PRECIP/CONVECTION COULD SAG SOUTHEAST AND CLIP NORTHEAST
IL/NORTHWEST IN BEFORE DISSIPATING.

WITH INCREASING CLOUD COVER TONIGHT...IT SHUD LIMIT HOW COOL TEMPS
BECOME. SO HAVE MADE ONLY MINOR ADJUSTMENTS TO THE TEMPS WITH
GENERALLY MID/UPR 60S FOR LOWS.

BEACHLER

FRIDAY AND FRIDAY NIGHT...
CLOSED UPPER LOW CURRENTLY NEAR THE COLORADO FRONT RANGE WILL SLOWLY
TRAVERSE EAST TOWARDS THE MID-MISSOURI VALLEY FRIDAY BECOMING AN
OPEN WAVE. AT THE SURFACE...BROAD AND WEAK SURFACE LOW WILL LIFT
INTO THE UPPER MIDWEST WHILE SOUTHWEST FLOW RAMPS UP THROUGH THE
COLUMN AS THE WARM FRONT LIFTS INTO THE CENTRAL GREAT LAKES. HEAT
AND HUMIDITY WILL MAKE A RETURN AS THIS OCCURS. H85 TEMPS WARMING TO
AROUND 18C WILL HELP SUPPORT MID/UPPER 80S DURING THE DAY
FRIDAY...AND SURFACE DEWPOINTS ARE PROGGED TO PUSH BACK INTO THE LOW
POSSIBLY MID 70S. THIS WILL RESULT IN MODERATE INSTABILITY
DEVELOPING DURING THE DAY...AND ONLY WEAKLY CAPPED DURING THE
AFTERNOON AS BROAD HEIGHT FALLS ASSOCIATED WITH THE UPPER WAVE START
TO OVERSPREAD THE AREA. THERE DOESNT SEEM TO BE MUCH FOCUS IN THE
LOWER LEVELS SO WOULD EXPECT ONLY SCATTERED THUNDERSTORM DEVELOPMENT
ACROSS THE REGION FRIDAY AFTERNOON/EVENING. UPPER WAVE BEGINS TO
MOVE INTO THE UPPER MIDWEST TOMORROW NIGHT AND BROAD WARM ADVECTION
OUT AHEAD DURING THE EVENING AND OVERNIGHT HOURS WILL HELP SUSTAIN
SOME CONVECTION LATE BUT WOULD EXPECT SOME NOCTURNAL DOWNTICK IN
ACTIVITY OVERNIGHT WITH THE LOW LEVEL JET FOCUSED WELL TO OUR NORTH.
GFS/NAM SEEM TO BE OVERDOING POPS MUCH OF THE DAY AND NIGHT
FRIDAY...AND OPTED TO LEAN CLOSER TO ECMWF THESE PERIODS.

THIS WEEKEND...
COLD FRONT WILL SWEEP ACROSS THE FORECAST AREA STARTING VERY EARLY
ON SATURDAY. WHILE NOT A FAVORABLE DIURNAL TIME...WE SHOULD STILL
HAVE SOME VERY MODEST INSTABILITY IN PLACE THAT WILL SUPPORT SOME
EARLY DAY THUNDERSTORMS ALONG THE FRONTAL BOUNDARY...WHICH WOULD BE
ABLE TO EXPAND IN COVERAGE AS THE DAY PROGRESSES AND THE BOUNDARY
LAYER WARMS. IN ADDITION...GUIDANCE SUGGESTS A SECOND SHORTWAVE
WILL WRAP INTO THE AREA THAT WILL PROVIDE ADDITIONAL BROAD SCALE
ASCENT. THE ECMWF IS ABOUT SIX HOURS SLOWER WITH THIS FEATURE
COMPARED TO THE NAM/GFS...WITH THE GEM A COMPROMISE...SO THERE
REMAINS SOME UNCERTAINTY IN TIMING. HIGH PRESSURE WILL BUILD IN
BEHIND THE FRONT SATURDAY NIGHT INTO SUNDAY AND WILL PROVIDE A
BRIEF RESPITE FROM THE ACTIVE WEATHER. THE ATMOSPHERE LOOKS TO
QUICKLY RELOAD HOWEVER WITH THERMAL RIDGE ONCE AGAIN STARTING TO
TILT BACK OVER THE AREA WITH H85 TEMPS AROUND 20C BY LATER IN THE
DAY SUNDAY.

NEXT WEEK...
AN ACTIVE PATTERN LOOKS TO PERSIST THROUGH AT LEAST THE MIDDLE OF
NEXT WEEK WITH A SERIES OF WAVES PUSHING ACROSS THE REGION BRINGING
CONTINUED PERIODIC CHANCES FOR SHOWERS AND THUNDERSTORMS. ANOTHER
COLD FRONT WILL PUSH ACROSS THE AREA LATER ON MONDAY WITH THE
FRONTAL BOUNDARY STALLING JUST TO OUR SOUTH. THEREAFTER...THERE IS
CONSIDERABLE UNCERTAINTY ON HOW FAR NORTH THE BOUNDARY MAY LIFT
WITH THE BEST PRECIP CHANCES FOCUSED IN THE VICINITY OF THE
FRONT AS A SERIES OF UPPER LEVEL DISTURBANCES PUSH ACROSS THE
AREA. PWATS REMAIN JUICY ALONG THE FRONT...AROUND TWO INCHES...AND
GUIDANCE SUGGESTS THAT THERE COULD BE SEVERAL CONVECTIVE COMPLEXES
NEXT WEEK WITH A CONCERN FOR HEAVY RAIN AND FLOODING SHOULD THIS
PAN OUT.

DEUBELBEISS

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 03Z...

* ISOLATED SHRA/TSRA LATE TONIGHT INTO EARLY FRIDAY MORNING.

* SCATTERED TSRA FRIDAY AFTERNOON/EARLY EVENING.

* SOUTH WIND WITH GUSTS DEVELOPING TO 20KT MIDDAY FRI.

KMD

//DISCUSSION...UPDATED 00Z...
CHALLENGING FORECAST FOR THE NEXT 24-30 HOURS. AREA OF SHOWERS
WILL CONTINUE TO PUSH EASTWARD AND WEAKEN SOME THIS EVENING.
THUNDER ACTIVITY LOOKS TO REMAIN SOUTH OF THE INTERSTATE 80
CORRIDOR ALONG A LINE FROM KVYS TO KLOT TO KGYY. CIGS AND VSBYS
SHOULD GENERALLY REMAIN VFR THOUGH BRIEF MVFR VISBYS ARE POSSIBLE
MAINLY WEST OF THE MAIN CHICAGO TERMINALS.

EXPECTING A LULL THIS EVENING...THEN AS A WARM FRONT LIFTS THROUGH
TONIGHT...ADDITIONAL CONVECTION IS EXPECTED IN NW IOWA AND
SPREADING INTO WISCONSIN OVERNIGHT. AS AN UPPER RIDGE BUCKLES SOME
LATE TONIGHT INTO EARLY FRIDAY...SOME OF THIS ACTIVITY MAY GRAZE
NORTHEAST ILLINOIS IN THE 12Z-15Z TIME FRAME. INSTABILITY MAY
SUPPORT SHRA WITH ISOLATED TS.

INSTABILITY THEN INCREASES VERY QUICKLY ON FRIDAY AS WE GET IN THE
WARM SECTOR AND DEWPOINTS RISE. UPPER HEIGHT FALLS COMBINED WITH
PEAK HEATING SUGGESTS AFTERNOON AIR MASS THUNDERSTORMS THOUGH
DIFFICULT ON TIMING. COULD BE THUNDERSTORMS AT ANY TIME FRIDAY
AFTERNOON EARLY EVENING WITH NO OBVIOUS SURFACE FOCUS. WITH HIGH
PRECIPITABLE WATER VALUES...HEAVY DOWNPOURS ARE POSSIBLE.

KMD

//ORD AND MDW CONFIDENCE...UPDATED 03Z...

* LOW-MEDIUM IN PRECIP COVERAGE LATE TONIGHT INTO EARLY FRIDAY.

* LOW IN THUNDER CHANCES/COVERAGE AND SPECIFIC TIMING FRIDAY AFTERNOON.

* HIGH IN WIND DIR/SPEED AND TRENDS

KMD

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

* SATURDAY...TSRA LIKELY.
* SUNDAY...SLIGHT CHANCE OF TSRA.
* MONDAY AND TUESDAY...CHANCE OF TSRA.
* WEDNESDAY AND THURSDAY...SLIGHT CHANCE OF TSRA

KMD

&&

.MARINE...
123 PM CDT

SURFACE HIGH PRESSURE OVER THE GREAT LAKES REGION THIS AFTERNOON
WILL DRIFT TO THE EAST TONIGHT IN THE WAKE OF A DEPARTING UPPER
TROUGH OVER NEW ENGLAND/QUEBEC...AND AHEAD OF ANOTHER SURFACE TROUGH
AND WEAK COLD FRONT STRETCHING FROM FAR NORTHWEST ONTARIO TO THE
CENTRAL PLAINS. WINDS ON LAKE MICHIGAN WILL SHIFT TO THE SOUTHEAST
AND EVENTUALLY SOUTH HEADING INTO FRIDAY...AS AN AREA OF SURFACE LOW
PRESSURE DEVELOPS ACROSS THE PLAINS AND LIFTS ACROSS THE UPPER
MISSISSIPPI RIVER VALLEY. TIGHTENING OF THE PRESSURE GRADIENT
SOUTHEAST OF THE LOW TRACK WILL RESULT IN S-SE WINDS INCREASING INTO
THE 15-25 KT RANGE TONIGHT AND FRIDAY...GRADUALLY WEAKENING SATURDAY
AS THE LOW MOVES OFF TO THE NORTHEAST AND A WEAK COLD FRONT TRAILS
ACROSS THE LAKE FOLLOWED BY WEAK HIGH PRESSURE.

THIS COLD FRONT APPEARS TO DISSIPATE OR STALL ACROSS FAR SOUTHERN
LAKE MICHIGAN OR NORTHERN IL/IND LATE SATURDAY NIGHT OR EARLY SUNDAY
BEFORE DEVELOPING BACK TO THE NORTH AS A WARM FRONT SUNDAY NIGHT AS
ANOTHER AREA OF LOW PRESSURE DEVELOPS OVER THE PLAINS AND LIFTS
NORTHEAST INTO THE WESTERN/NORTHERN LAKES LATE SUNDAY NIGHT INTO
MONDAY. AGAIN...A TIGHTENING OF THE PRESSURE GRADIENT ALONG THE
SOUTHEAST PERIPHERY OF THE LOW TRACK IS EXPECTED WITH WINDS AGAIN
BECOMING SOUTHERLY INTO THE 15-25 KT RANGE ON MONDAY. ANOTHER
TRAILING COLD FRONT WILL PASS ACROSS THE LAKE MONDAY NIGHT...WITH
WEAK HIGH PRESSURE AND LIGHTER WINDS DEVELOPING TUESDAY.

RATZER

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO







000
FXUS63 KLOT 290014
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
714 PM CDT THU AUG 28 2014

.DISCUSSION...
714 PM CDT

PAIR OF MCVS NOTED ON RADAR IMAGERY CONTINUE TO MOVE EASTWARD
DRIVING SLOWLY DECAYING CONVECTIVE COMPLEX EASTWARD INTO OUR CWA
EARLY THIS EVENING DESPITE THE MUCH MORE STABLE AND SOMEWHAT DRIER
AIR MASS OVER THE REGION. HAVE ALREADY UPDATED PRECIP TRENDS A
COUPLE TIME TO ACCOUNT FOR THE RAIN THIS EVENING. ANTICIPATE
CONTINUED WEAKENING TREND...PARTICULARLY FROM THE NORTH...IN THIS
AREA OF LEFT OVER RAIN AND EVEN SOME LINGERING THUNDER. THE THREAT
OF THUNDER WITH THE NORTHERN MCV TRACKING CLOSE TO I-88 LOOKS TO END
VERY SOON...WHILE THE CONVECTION WITH THE SOUTHERN MOST MCV LIES
CLOSE ENOUGH TO MORE UNSTABLE AIR TO POTENTIALLY MAINTAIN
THUNDERSTORMS ACROSS THE SOUTHERN TIER OF OUR CWA THE NEXT FEW
HOURS. IN THE WAKE OF THESE MCVS...WHICH REALLY HAVENT BEEN HANDLED
WELL BY NUMERICAL GUIDANCE...SHOULD SEE A PERIOD OF DRY CONDITIONS
HOWEVER MODELS DO BREAK OUT ADDITIONAL CONVECTION OVERNIGHT WHICH
ISN`T THAT UNREASONABLE GIVEN THE NORTHWARD ADVANCING WARM FRONT.

IZZI

&&

.PREV DISCUSSION...
230 PM CDT

VISIBLE IMAGERY THIS AFTERNOON SHOWS A MID/UPR LEVEL CLOUD DECK
LIFTING NORTHEAST ACROSS NORTHERN IL. REMNANTS FROM A MORNING
COMPLEX OF THUNDERSTORMS RESIDES OVER IOWA...WITH SOME CONVECTIVE
LOOK TO THE CLOUDS LINGERING INTO THIS AFTN. SFC TEMPS ACROSS THE
FORECAST AREA HAVE BEEN ABLE TO WARM INTO THE MID/UPR 70S. A FEW
POINTS SOUTH OF PONTIAC TO KANKAKEE HAVE PUSHED TO ARND 80 DEG...BUT
WITH THE LIGHT EASTERLY FLOW AT THE SFC SOME WEAK SUBSIDENCE HAS
BEEN NOTED WITH DEW POINTS BEING PUSHED INTO THE LOW 50S ALONG THE
LAKESHORE AND MID/UPR 50S INLAND.

THE MAIN CHALLENGE FOR THIS EVENING WILL FOCUS ON CONVECTIVE
CHANCES/COVERAGE...WHICH WILL CONTINUE THROUGH DAYBREAK FRI.
GUIDANCE HAS CONTINUED TO BACK OFF ON THE ARRIVAL OF PRECIP INTO THE
FORECAST AREA...WHICH SEEMS TO LINE UP RELATIVELY WELL WITH THE
CURRENT TRENDS. THE FRONTAL BOUNDARY WILL SLOWLY LIFT NORTH THIS
EVENING...BUT NOT EXPECTING MUCH IN THE WAY OF PRECIP UNTIL PERHAPS
AFT 04Z WITH A GRADUAL UPGLIDE OF PARCELS ALLOWS FOR MOISTENING.
SOME ELEVATED CONVECTION COULD BEGIN TO DEVELOP...ALTHOUGH NOT
EXPECTING MUCH COVERAGE OVERNIGHT. THE FOCUS FOR SLIGHTLY BETTER
PRECIP COVERAGE WILL REMAIN ALONG THE NORTHERN ROW OF COUNTIES IN
NORTHERN IL...HOWEVER CLOSER TO DAYBREAK FRI IT APPEARS SOME
PRECIP/CONVECTION COULD SAG SOUTHEAST AND CLIP NORTHEAST
IL/NORTHWEST IN BEFORE DISSIPATING.

WITH INCREASING CLOUD COVER TONIGHT...IT SHUD LIMIT HOW COOL TEMPS
BECOME. SO HAVE MADE ONLY MINOR ADJUSTMENTS TO THE TEMPS WITH
GENERALLY MID/UPR 60S FOR LOWS.

BEACHLER

FRIDAY AND FRIDAY NIGHT...
CLOSED UPPER LOW CURRENTLY NEAR THE COLORADO FRONT RANGE WILL SLOWLY
TRAVERSE EAST TOWARDS THE MID-MISSOURI VALLEY FRIDAY BECOMING AN
OPEN WAVE. AT THE SURFACE...BROAD AND WEAK SURFACE LOW WILL LIFT
INTO THE UPPER MIDWEST WHILE SOUTHWEST FLOW RAMPS UP THROUGH THE
COLUMN AS THE WARM FRONT LIFTS INTO THE CENTRAL GREAT LAKES. HEAT
AND HUMIDITY WILL MAKE A RETURN AS THIS OCCURS. H85 TEMPS WARMING TO
AROUND 18C WILL HELP SUPPORT MID/UPPER 80S DURING THE DAY
FRIDAY...AND SURFACE DEWPOINTS ARE PROGGED TO PUSH BACK INTO THE LOW
POSSIBLY MID 70S. THIS WILL RESULT IN MODERATE INSTABILITY
DEVELOPING DURING THE DAY...AND ONLY WEAKLY CAPPED DURING THE
AFTERNOON AS BROAD HEIGHT FALLS ASSOCIATED WITH THE UPPER WAVE START
TO OVERSPREAD THE AREA. THERE DOESNT SEEM TO BE MUCH FOCUS IN THE
LOWER LEVELS SO WOULD EXPECT ONLY SCATTERED THUNDERSTORM DEVELOPMENT
ACROSS THE REGION FRIDAY AFTERNOON/EVENING. UPPER WAVE BEGINS TO
MOVE INTO THE UPPER MIDWEST TOMORROW NIGHT AND BROAD WARM ADVECTION
OUT AHEAD DURING THE EVENING AND OVERNIGHT HOURS WILL HELP SUSTAIN
SOME CONVECTION LATE BUT WOULD EXPECT SOME NOCTURNAL DOWNTICK IN
ACTIVITY OVERNIGHT WITH THE LOW LEVEL JET FOCUSED WELL TO OUR NORTH.
GFS/NAM SEEM TO BE OVERDOING POPS MUCH OF THE DAY AND NIGHT
FRIDAY...AND OPTED TO LEAN CLOSER TO ECMWF THESE PERIODS.

THIS WEEKEND...
COLD FRONT WILL SWEEP ACROSS THE FORECAST AREA STARTING VERY EARLY
ON SATURDAY. WHILE NOT A FAVORABLE DIURNAL TIME...WE SHOULD STILL
HAVE SOME VERY MODEST INSTABILITY IN PLACE THAT WILL SUPPORT SOME
EARLY DAY THUNDERSTORMS ALONG THE FRONTAL BOUNDARY...WHICH WOULD BE
ABLE TO EXPAND IN COVERAGE AS THE DAY PROGRESSES AND THE BOUNDARY
LAYER WARMS. IN ADDITION...GUIDANCE SUGGESTS A SECOND SHORTWAVE
WILL WRAP INTO THE AREA THAT WILL PROVIDE ADDITIONAL BROAD SCALE
ASCENT. THE ECMWF IS ABOUT SIX HOURS SLOWER WITH THIS FEATURE
COMPARED TO THE NAM/GFS...WITH THE GEM A COMPROMISE...SO THERE
REMAINS SOME UNCERTAINTY IN TIMING. HIGH PRESSURE WILL BUILD IN
BEHIND THE FRONT SATURDAY NIGHT INTO SUNDAY AND WILL PROVIDE A
BRIEF RESPITE FROM THE ACTIVE WEATHER. THE ATMOSPHERE LOOKS TO
QUICKLY RELOAD HOWEVER WITH THERMAL RIDGE ONCE AGAIN STARTING TO
TILT BACK OVER THE AREA WITH H85 TEMPS AROUND 20C BY LATER IN THE
DAY SUNDAY.

NEXT WEEK...
AN ACTIVE PATTERN LOOKS TO PERSIST THROUGH AT LEAST THE MIDDLE OF
NEXT WEEK WITH A SERIES OF WAVES PUSHING ACROSS THE REGION BRINGING
CONTINUED PERIODIC CHANCES FOR SHOWERS AND THUNDERSTORMS. ANOTHER
COLD FRONT WILL PUSH ACROSS THE AREA LATER ON MONDAY WITH THE
FRONTAL BOUNDARY STALLING JUST TO OUR SOUTH. THEREAFTER...THERE IS
CONSIDERABLE UNCERTAINTY ON HOW FAR NORTH THE BOUNDARY MAY LIFT
WITH THE BEST PRECIP CHANCES FOCUSED IN THE VICINITY OF THE
FRONT AS A SERIES OF UPPER LEVEL DISTURBANCES PUSH ACROSS THE
AREA. PWATS REMAIN JUICY ALONG THE FRONT...AROUND TWO INCHES...AND
GUIDANCE SUGGESTS THAT THERE COULD BE SEVERAL CONVECTIVE COMPLEXES
NEXT WEEK WITH A CONCERN FOR HEAVY RAIN AND FLOODING SHOULD THIS
PAN OUT.

DEUBELBEISS

&&

.AVIATION...

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

* EAST WIND ARND 8-10KT THRU THE EVENING...WINDS TURNING SE LATER THIS
  EVENING.

* SHOWERS MOVING THROUGH BTW 00-03Z...WITH POTENTIAL SHRA/ISOLATED
  TSRA AROUND DAYBREAK FRI.

* MVFR IN -SHRA THIS EVENING.

* SCATTERED TSRA FRIDAY AFTERNOON/EARLY EVENING.

* SOUTH WIND WITH GUSTS DEVELOPING TO 20KT MIDDAY FRI.

KMD

//DISCUSSION...UPDATED 00Z...
CHALLENGING FORECAST FOR THE NEXT 24-30 HOURS. AREA OF SHOWERS
WILL CONTINUE TO PUSH EASTWARD AND WEAKEN SOME THIS EVENING.
THUNDER ACTIVITY LOOKS TO REMAIN SOUTH OF THE INTERSTATE 80
CORRIDOR ALONG A LINE FROM KVYS TO KLOT TO KGYY. CIGS AND VSBYS
SHOULD GENERALLY REMAIN VFR THOUGH BRIEF MVFR VISBYS ARE POSSIBLE
MAINLY WEST OF THE MAIN CHICAGO TERMINALS.

EXPECTING A LULL THIS EVENING...THEN AS A WARM FRONT LIFTS THROUGH
TONIGHT...ADDITIONAL CONVECTION IS EXPECTED IN NW IOWA AND
SPREADING INTO WISCONSIN OVERNIGHT. AS AN UPPER RIDGE BUCKLES SOME
LATE TONIGHT INTO EARLY FRIDAY...SOME OF THIS ACTIVITY MAY GRAZE
NORTHEAST ILLINOIS IN THE 12Z-15Z TIME FRAME. INSTABILITY MAY
SUPPORT SHRA WITH ISOLATED TS.

INSTABILITY THEN INCREASES VERY QUICKLY ON FRIDAY AS WE GET IN THE
WARM SECTOR AND DEWPOINTS RISE. UPPER HEIGHT FALLS COMBINED WITH
PEAK HEATING SUGGESTS AFTERNOON AIR MASS THUNDERSTORMS THOUGH
DIFFICULT ON TIMING. COULD BE THUNDERSTORMS AT ANY TIME FRIDAY
AFTERNOON EARLY EVENING WITH NO OBVIOUS SURFACE FOCUS. WITH HIGH
PRECIPITABLE WATER VALUES...HEAVY DOWNPOURS ARE POSSIBLE.

KMD

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

* HIGH IN WIND DIR/SPEED AND TRENDS.

* MEDIUM-HIGH IN -SHRA 0Z-3Z.

* MEDIUM-HIGH THAT CIGS/VSBY REMAIN VFR WITH SHOWERS.

* LOW-MEDIUM PRECIP COVERAGE LATE TONIGHT INTO EARLY FRIDAY.

* LOW IN THUNDER CHANCES/COVERAGE AND SPECIFIC TIMING FRIDAY AFTERNOON.

KMD

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

* SATURDAY...TSRA LIKELY.
* SUNDAY...SLIGHT CHANCE OF TSRA.
* MONDAY AND TUESDAY...CHANCE OF TSRA.
* WEDNESDAY AND THURSDAY...SLIGHT CHANCE OF TSRA

KMD

&&

.MARINE...
123 PM CDT

SURFACE HIGH PRESSURE OVER THE GREAT LAKES REGION THIS AFTERNOON
WILL DRIFT TO THE EAST TONIGHT IN THE WAKE OF A DEPARTING UPPER
TROUGH OVER NEW ENGLAND/QUEBEC...AND AHEAD OF ANOTHER SURFACE TROUGH
AND WEAK COLD FRONT STRETCHING FROM FAR NORTHWEST ONTARIO TO THE
CENTRAL PLAINS. WINDS ON LAKE MICHIGAN WILL SHIFT TO THE SOUTHEAST
AND EVENTUALLY SOUTH HEADING INTO FRIDAY...AS AN AREA OF SURFACE LOW
PRESSURE DEVELOPS ACROSS THE PLAINS AND LIFTS ACROSS THE UPPER
MISSISSIPPI RIVER VALLEY. TIGHTENING OF THE PRESSURE GRADIENT
SOUTHEAST OF THE LOW TRACK WILL RESULT IN S-SE WINDS INCREASING INTO
THE 15-25 KT RANGE TONIGHT AND FRIDAY...GRADUALLY WEAKENING SATURDAY
AS THE LOW MOVES OFF TO THE NORTHEAST AND A WEAK COLD FRONT TRAILS
ACROSS THE LAKE FOLLOWED BY WEAK HIGH PRESSURE.

THIS COLD FRONT APPEARS TO DISSIPATE OR STALL ACROSS FAR SOUTHERN
LAKE MICHIGAN OR NORTHERN IL/IND LATE SATURDAY NIGHT OR EARLY SUNDAY
BEFORE DEVELOPING BACK TO THE NORTH AS A WARM FRONT SUNDAY NIGHT AS
ANOTHER AREA OF LOW PRESSURE DEVELOPS OVER THE PLAINS AND LIFTS
NORTHEAST INTO THE WESTERN/NORTHERN LAKES LATE SUNDAY NIGHT INTO
MONDAY. AGAIN...A TIGHTENING OF THE PRESSURE GRADIENT ALONG THE
SOUTHEAST PERIPHERY OF THE LOW TRACK IS EXPECTED WITH WINDS AGAIN
BECOMING SOUTHERLY INTO THE 15-25 KT RANGE ON MONDAY. ANOTHER
TRAILING COLD FRONT WILL PASS ACROSS THE LAKE MONDAY NIGHT...WITH
WEAK HIGH PRESSURE AND LIGHTER WINDS DEVELOPING TUESDAY.

RATZER

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO








000
FXUS63 KLOT 290014
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
714 PM CDT THU AUG 28 2014

.DISCUSSION...
714 PM CDT

PAIR OF MCVS NOTED ON RADAR IMAGERY CONTINUE TO MOVE EASTWARD
DRIVING SLOWLY DECAYING CONVECTIVE COMPLEX EASTWARD INTO OUR CWA
EARLY THIS EVENING DESPITE THE MUCH MORE STABLE AND SOMEWHAT DRIER
AIR MASS OVER THE REGION. HAVE ALREADY UPDATED PRECIP TRENDS A
COUPLE TIME TO ACCOUNT FOR THE RAIN THIS EVENING. ANTICIPATE
CONTINUED WEAKENING TREND...PARTICULARLY FROM THE NORTH...IN THIS
AREA OF LEFT OVER RAIN AND EVEN SOME LINGERING THUNDER. THE THREAT
OF THUNDER WITH THE NORTHERN MCV TRACKING CLOSE TO I-88 LOOKS TO END
VERY SOON...WHILE THE CONVECTION WITH THE SOUTHERN MOST MCV LIES
CLOSE ENOUGH TO MORE UNSTABLE AIR TO POTENTIALLY MAINTAIN
THUNDERSTORMS ACROSS THE SOUTHERN TIER OF OUR CWA THE NEXT FEW
HOURS. IN THE WAKE OF THESE MCVS...WHICH REALLY HAVENT BEEN HANDLED
WELL BY NUMERICAL GUIDANCE...SHOULD SEE A PERIOD OF DRY CONDITIONS
HOWEVER MODELS DO BREAK OUT ADDITIONAL CONVECTION OVERNIGHT WHICH
ISN`T THAT UNREASONABLE GIVEN THE NORTHWARD ADVANCING WARM FRONT.

IZZI

&&

.PREV DISCUSSION...
230 PM CDT

VISIBLE IMAGERY THIS AFTERNOON SHOWS A MID/UPR LEVEL CLOUD DECK
LIFTING NORTHEAST ACROSS NORTHERN IL. REMNANTS FROM A MORNING
COMPLEX OF THUNDERSTORMS RESIDES OVER IOWA...WITH SOME CONVECTIVE
LOOK TO THE CLOUDS LINGERING INTO THIS AFTN. SFC TEMPS ACROSS THE
FORECAST AREA HAVE BEEN ABLE TO WARM INTO THE MID/UPR 70S. A FEW
POINTS SOUTH OF PONTIAC TO KANKAKEE HAVE PUSHED TO ARND 80 DEG...BUT
WITH THE LIGHT EASTERLY FLOW AT THE SFC SOME WEAK SUBSIDENCE HAS
BEEN NOTED WITH DEW POINTS BEING PUSHED INTO THE LOW 50S ALONG THE
LAKESHORE AND MID/UPR 50S INLAND.

THE MAIN CHALLENGE FOR THIS EVENING WILL FOCUS ON CONVECTIVE
CHANCES/COVERAGE...WHICH WILL CONTINUE THROUGH DAYBREAK FRI.
GUIDANCE HAS CONTINUED TO BACK OFF ON THE ARRIVAL OF PRECIP INTO THE
FORECAST AREA...WHICH SEEMS TO LINE UP RELATIVELY WELL WITH THE
CURRENT TRENDS. THE FRONTAL BOUNDARY WILL SLOWLY LIFT NORTH THIS
EVENING...BUT NOT EXPECTING MUCH IN THE WAY OF PRECIP UNTIL PERHAPS
AFT 04Z WITH A GRADUAL UPGLIDE OF PARCELS ALLOWS FOR MOISTENING.
SOME ELEVATED CONVECTION COULD BEGIN TO DEVELOP...ALTHOUGH NOT
EXPECTING MUCH COVERAGE OVERNIGHT. THE FOCUS FOR SLIGHTLY BETTER
PRECIP COVERAGE WILL REMAIN ALONG THE NORTHERN ROW OF COUNTIES IN
NORTHERN IL...HOWEVER CLOSER TO DAYBREAK FRI IT APPEARS SOME
PRECIP/CONVECTION COULD SAG SOUTHEAST AND CLIP NORTHEAST
IL/NORTHWEST IN BEFORE DISSIPATING.

WITH INCREASING CLOUD COVER TONIGHT...IT SHUD LIMIT HOW COOL TEMPS
BECOME. SO HAVE MADE ONLY MINOR ADJUSTMENTS TO THE TEMPS WITH
GENERALLY MID/UPR 60S FOR LOWS.

BEACHLER

FRIDAY AND FRIDAY NIGHT...
CLOSED UPPER LOW CURRENTLY NEAR THE COLORADO FRONT RANGE WILL SLOWLY
TRAVERSE EAST TOWARDS THE MID-MISSOURI VALLEY FRIDAY BECOMING AN
OPEN WAVE. AT THE SURFACE...BROAD AND WEAK SURFACE LOW WILL LIFT
INTO THE UPPER MIDWEST WHILE SOUTHWEST FLOW RAMPS UP THROUGH THE
COLUMN AS THE WARM FRONT LIFTS INTO THE CENTRAL GREAT LAKES. HEAT
AND HUMIDITY WILL MAKE A RETURN AS THIS OCCURS. H85 TEMPS WARMING TO
AROUND 18C WILL HELP SUPPORT MID/UPPER 80S DURING THE DAY
FRIDAY...AND SURFACE DEWPOINTS ARE PROGGED TO PUSH BACK INTO THE LOW
POSSIBLY MID 70S. THIS WILL RESULT IN MODERATE INSTABILITY
DEVELOPING DURING THE DAY...AND ONLY WEAKLY CAPPED DURING THE
AFTERNOON AS BROAD HEIGHT FALLS ASSOCIATED WITH THE UPPER WAVE START
TO OVERSPREAD THE AREA. THERE DOESNT SEEM TO BE MUCH FOCUS IN THE
LOWER LEVELS SO WOULD EXPECT ONLY SCATTERED THUNDERSTORM DEVELOPMENT
ACROSS THE REGION FRIDAY AFTERNOON/EVENING. UPPER WAVE BEGINS TO
MOVE INTO THE UPPER MIDWEST TOMORROW NIGHT AND BROAD WARM ADVECTION
OUT AHEAD DURING THE EVENING AND OVERNIGHT HOURS WILL HELP SUSTAIN
SOME CONVECTION LATE BUT WOULD EXPECT SOME NOCTURNAL DOWNTICK IN
ACTIVITY OVERNIGHT WITH THE LOW LEVEL JET FOCUSED WELL TO OUR NORTH.
GFS/NAM SEEM TO BE OVERDOING POPS MUCH OF THE DAY AND NIGHT
FRIDAY...AND OPTED TO LEAN CLOSER TO ECMWF THESE PERIODS.

THIS WEEKEND...
COLD FRONT WILL SWEEP ACROSS THE FORECAST AREA STARTING VERY EARLY
ON SATURDAY. WHILE NOT A FAVORABLE DIURNAL TIME...WE SHOULD STILL
HAVE SOME VERY MODEST INSTABILITY IN PLACE THAT WILL SUPPORT SOME
EARLY DAY THUNDERSTORMS ALONG THE FRONTAL BOUNDARY...WHICH WOULD BE
ABLE TO EXPAND IN COVERAGE AS THE DAY PROGRESSES AND THE BOUNDARY
LAYER WARMS. IN ADDITION...GUIDANCE SUGGESTS A SECOND SHORTWAVE
WILL WRAP INTO THE AREA THAT WILL PROVIDE ADDITIONAL BROAD SCALE
ASCENT. THE ECMWF IS ABOUT SIX HOURS SLOWER WITH THIS FEATURE
COMPARED TO THE NAM/GFS...WITH THE GEM A COMPROMISE...SO THERE
REMAINS SOME UNCERTAINTY IN TIMING. HIGH PRESSURE WILL BUILD IN
BEHIND THE FRONT SATURDAY NIGHT INTO SUNDAY AND WILL PROVIDE A
BRIEF RESPITE FROM THE ACTIVE WEATHER. THE ATMOSPHERE LOOKS TO
QUICKLY RELOAD HOWEVER WITH THERMAL RIDGE ONCE AGAIN STARTING TO
TILT BACK OVER THE AREA WITH H85 TEMPS AROUND 20C BY LATER IN THE
DAY SUNDAY.

NEXT WEEK...
AN ACTIVE PATTERN LOOKS TO PERSIST THROUGH AT LEAST THE MIDDLE OF
NEXT WEEK WITH A SERIES OF WAVES PUSHING ACROSS THE REGION BRINGING
CONTINUED PERIODIC CHANCES FOR SHOWERS AND THUNDERSTORMS. ANOTHER
COLD FRONT WILL PUSH ACROSS THE AREA LATER ON MONDAY WITH THE
FRONTAL BOUNDARY STALLING JUST TO OUR SOUTH. THEREAFTER...THERE IS
CONSIDERABLE UNCERTAINTY ON HOW FAR NORTH THE BOUNDARY MAY LIFT
WITH THE BEST PRECIP CHANCES FOCUSED IN THE VICINITY OF THE
FRONT AS A SERIES OF UPPER LEVEL DISTURBANCES PUSH ACROSS THE
AREA. PWATS REMAIN JUICY ALONG THE FRONT...AROUND TWO INCHES...AND
GUIDANCE SUGGESTS THAT THERE COULD BE SEVERAL CONVECTIVE COMPLEXES
NEXT WEEK WITH A CONCERN FOR HEAVY RAIN AND FLOODING SHOULD THIS
PAN OUT.

DEUBELBEISS

&&

.AVIATION...

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

* EAST WIND ARND 8-10KT THRU THE EVENING...WINDS TURNING SE LATER THIS
  EVENING.

* SHOWERS MOVING THROUGH BTW 00-03Z...WITH POTENTIAL SHRA/ISOLATED
  TSRA AROUND DAYBREAK FRI.

* MVFR IN -SHRA THIS EVENING.

* SCATTERED TSRA FRIDAY AFTERNOON/EARLY EVENING.

* SOUTH WIND WITH GUSTS DEVELOPING TO 20KT MIDDAY FRI.

KMD

//DISCUSSION...UPDATED 00Z...
CHALLENGING FORECAST FOR THE NEXT 24-30 HOURS. AREA OF SHOWERS
WILL CONTINUE TO PUSH EASTWARD AND WEAKEN SOME THIS EVENING.
THUNDER ACTIVITY LOOKS TO REMAIN SOUTH OF THE INTERSTATE 80
CORRIDOR ALONG A LINE FROM KVYS TO KLOT TO KGYY. CIGS AND VSBYS
SHOULD GENERALLY REMAIN VFR THOUGH BRIEF MVFR VISBYS ARE POSSIBLE
MAINLY WEST OF THE MAIN CHICAGO TERMINALS.

EXPECTING A LULL THIS EVENING...THEN AS A WARM FRONT LIFTS THROUGH
TONIGHT...ADDITIONAL CONVECTION IS EXPECTED IN NW IOWA AND
SPREADING INTO WISCONSIN OVERNIGHT. AS AN UPPER RIDGE BUCKLES SOME
LATE TONIGHT INTO EARLY FRIDAY...SOME OF THIS ACTIVITY MAY GRAZE
NORTHEAST ILLINOIS IN THE 12Z-15Z TIME FRAME. INSTABILITY MAY
SUPPORT SHRA WITH ISOLATED TS.

INSTABILITY THEN INCREASES VERY QUICKLY ON FRIDAY AS WE GET IN THE
WARM SECTOR AND DEWPOINTS RISE. UPPER HEIGHT FALLS COMBINED WITH
PEAK HEATING SUGGESTS AFTERNOON AIR MASS THUNDERSTORMS THOUGH
DIFFICULT ON TIMING. COULD BE THUNDERSTORMS AT ANY TIME FRIDAY
AFTERNOON EARLY EVENING WITH NO OBVIOUS SURFACE FOCUS. WITH HIGH
PRECIPITABLE WATER VALUES...HEAVY DOWNPOURS ARE POSSIBLE.

KMD

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

* HIGH IN WIND DIR/SPEED AND TRENDS.

* MEDIUM-HIGH IN -SHRA 0Z-3Z.

* MEDIUM-HIGH THAT CIGS/VSBY REMAIN VFR WITH SHOWERS.

* LOW-MEDIUM PRECIP COVERAGE LATE TONIGHT INTO EARLY FRIDAY.

* LOW IN THUNDER CHANCES/COVERAGE AND SPECIFIC TIMING FRIDAY AFTERNOON.

KMD

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

* SATURDAY...TSRA LIKELY.
* SUNDAY...SLIGHT CHANCE OF TSRA.
* MONDAY AND TUESDAY...CHANCE OF TSRA.
* WEDNESDAY AND THURSDAY...SLIGHT CHANCE OF TSRA

KMD

&&

.MARINE...
123 PM CDT

SURFACE HIGH PRESSURE OVER THE GREAT LAKES REGION THIS AFTERNOON
WILL DRIFT TO THE EAST TONIGHT IN THE WAKE OF A DEPARTING UPPER
TROUGH OVER NEW ENGLAND/QUEBEC...AND AHEAD OF ANOTHER SURFACE TROUGH
AND WEAK COLD FRONT STRETCHING FROM FAR NORTHWEST ONTARIO TO THE
CENTRAL PLAINS. WINDS ON LAKE MICHIGAN WILL SHIFT TO THE SOUTHEAST
AND EVENTUALLY SOUTH HEADING INTO FRIDAY...AS AN AREA OF SURFACE LOW
PRESSURE DEVELOPS ACROSS THE PLAINS AND LIFTS ACROSS THE UPPER
MISSISSIPPI RIVER VALLEY. TIGHTENING OF THE PRESSURE GRADIENT
SOUTHEAST OF THE LOW TRACK WILL RESULT IN S-SE WINDS INCREASING INTO
THE 15-25 KT RANGE TONIGHT AND FRIDAY...GRADUALLY WEAKENING SATURDAY
AS THE LOW MOVES OFF TO THE NORTHEAST AND A WEAK COLD FRONT TRAILS
ACROSS THE LAKE FOLLOWED BY WEAK HIGH PRESSURE.

THIS COLD FRONT APPEARS TO DISSIPATE OR STALL ACROSS FAR SOUTHERN
LAKE MICHIGAN OR NORTHERN IL/IND LATE SATURDAY NIGHT OR EARLY SUNDAY
BEFORE DEVELOPING BACK TO THE NORTH AS A WARM FRONT SUNDAY NIGHT AS
ANOTHER AREA OF LOW PRESSURE DEVELOPS OVER THE PLAINS AND LIFTS
NORTHEAST INTO THE WESTERN/NORTHERN LAKES LATE SUNDAY NIGHT INTO
MONDAY. AGAIN...A TIGHTENING OF THE PRESSURE GRADIENT ALONG THE
SOUTHEAST PERIPHERY OF THE LOW TRACK IS EXPECTED WITH WINDS AGAIN
BECOMING SOUTHERLY INTO THE 15-25 KT RANGE ON MONDAY. ANOTHER
TRAILING COLD FRONT WILL PASS ACROSS THE LAKE MONDAY NIGHT...WITH
WEAK HIGH PRESSURE AND LIGHTER WINDS DEVELOPING TUESDAY.

RATZER

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO







000
FXUS63 KLOT 290013
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
713 PM CDT THU AUG 28 2014

.DISCUSSION...
230 PM CDT

VISIBLE IMAGERY THIS AFTERNOON SHOWS A MID/UPR LEVEL CLOUD DECK
LIFTING NORTHEAST ACROSS NORTHERN IL. REMNANTS FROM A MORNING
COMPLEX OF THUNDERSTORMS RESIDES OVER IOWA...WITH SOME CONVECTIVE
LOOK TO THE CLOUDS LINGERING INTO THIS AFTN. SFC TEMPS ACROSS THE
FORECAST AREA HAVE BEEN ABLE TO WARM INTO THE MID/UPR 70S. A FEW
POINTS SOUTH OF PONTIAC TO KANKAKEE HAVE PUSHED TO ARND 80 DEG...BUT
WITH THE LIGHT EASTERLY FLOW AT THE SFC SOME WEAK SUBSIDENCE HAS
BEEN NOTED WITH DEW POINTS BEING PUSHED INTO THE LOW 50S ALONG THE
LAKESHORE AND MID/UPR 50S INLAND.

THE MAIN CHALLENGE FOR THIS EVENING WILL FOCUS ON CONVECTIVE
CHANCES/COVERAGE...WHICH WILL CONTINUE THROUGH DAYBREAK FRI.
GUIDANCE HAS CONTINUED TO BACK OFF ON THE ARRIVAL OF PRECIP INTO THE
FORECAST AREA...WHICH SEEMS TO LINE UP RELATIVELY WELL WITH THE
CURRENT TRENDS. THE FRONTAL BOUNDARY WILL SLOWLY LIFT NORTH THIS
EVENING...BUT NOT EXPECTING MUCH IN THE WAY OF PRECIP UNTIL PERHAPS
AFT 04Z WITH A GRADUAL UPGLIDE OF PARCELS ALLOWS FOR MOISTENING.
SOME ELEVATED CONVECTION COULD BEGIN TO DEVELOP...ALTHOUGH NOT
EXPECTING MUCH COVERAGE OVERNIGHT. THE FOCUS FOR SLIGHTLY BETTER
PRECIP COVERAGE WILL REMAIN ALONG THE NORTHERN ROW OF COUNTIES IN
NORTHERN IL...HOWEVER CLOSER TO DAYBREAK FRI IT APPEARS SOME
PRECIP/CONVECTION COULD SAG SOUTHEAST AND CLIP NORTHEAST
IL/NORTHWEST IN BEFORE DISSIPATING.

WITH INCREASING CLOUD COVER TONIGHT...IT SHUD LIMIT HOW COOL TEMPS
BECOME. SO HAVE MADE ONLY MINOR ADJUSTMENTS TO THE TEMPS WITH
GENERALLY MID/UPR 60S FOR LOWS.

BEACHLER

FRIDAY AND FRIDAY NIGHT...
CLOSED UPPER LOW CURRENTLY NEAR THE COLORADO FRONT RANGE WILL SLOWLY
TRAVERSE EAST TOWARDS THE MID-MISSOURI VALLEY FRIDAY BECOMING AN
OPEN WAVE. AT THE SURFACE...BROAD AND WEAK SURFACE LOW WILL LIFT
INTO THE UPPER MIDWEST WHILE SOUTHWEST FLOW RAMPS UP THROUGH THE
COLUMN AS THE WARM FRONT LIFTS INTO THE CENTRAL GREAT LAKES. HEAT
AND HUMIDITY WILL MAKE A RETURN AS THIS OCCURS. H85 TEMPS WARMING TO
AROUND 18C WILL HELP SUPPORT MID/UPPER 80S DURING THE DAY
FRIDAY...AND SURFACE DEWPOINTS ARE PROGGED TO PUSH BACK INTO THE LOW
POSSIBLY MID 70S. THIS WILL RESULT IN MODERATE INSTABILITY
DEVELOPING DURING THE DAY...AND ONLY WEAKLY CAPPED DURING THE
AFTERNOON AS BROAD HEIGHT FALLS ASSOCIATED WITH THE UPPER WAVE START
TO OVERSPREAD THE AREA. THERE DOESNT SEEM TO BE MUCH FOCUS IN THE
LOWER LEVELS SO WOULD EXPECT ONLY SCATTERED THUNDERSTORM DEVELOPMENT
ACROSS THE REGION FRIDAY AFTERNOON/EVENING. UPPER WAVE BEGINS TO
MOVE INTO THE UPPER MIDWEST TOMORROW NIGHT AND BROAD WARM ADVECTION
OUT AHEAD DURING THE EVENING AND OVERNIGHT HOURS WILL HELP SUSTAIN
SOME CONVECTION LATE BUT WOULD EXPECT SOME NOCTURNAL DOWNTICK IN
ACTIVITY OVERNIGHT WITH THE LOW LEVEL JET FOCUSED WELL TO OUR NORTH.
GFS/NAM SEEM TO BE OVERDOING POPS MUCH OF THE DAY AND NIGHT
FRIDAY...AND OPTED TO LEAN CLOSER TO ECMWF THESE PERIODS.

THIS WEEKEND...
COLD FRONT WILL SWEEP ACROSS THE FORECAST AREA STARTING VERY EARLY
ON SATURDAY. WHILE NOT A FAVORABLE DIURNAL TIME...WE SHOULD STILL
HAVE SOME VERY MODEST INSTABILITY IN PLACE THAT WILL SUPPORT SOME
EARLY DAY THUNDERSTORMS ALONG THE FRONTAL BOUNDARY...WHICH WOULD BE
ABLE TO EXPAND IN COVERAGE AS THE DAY PROGRESSES AND THE BOUNDARY
LAYER WARMS. IN ADDITION...GUIDANCE SUGGESTS A SECOND SHORTWAVE
WILL WRAP INTO THE AREA THAT WILL PROVIDE ADDITIONAL BROAD SCALE
ASCENT. THE ECMWF IS ABOUT SIX HOURS SLOWER WITH THIS FEATURE
COMPARED TO THE NAM/GFS...WITH THE GEM A COMPROMISE...SO THERE
REMAINS SOME UNCERTAINTY IN TIMING. HIGH PRESSURE WILL BUILD IN
BEHIND THE FRONT SATURDAY NIGHT INTO SUNDAY AND WILL PROVIDE A
BRIEF RESPITE FROM THE ACTIVE WEATHER. THE ATMOSPHERE LOOKS TO
QUICKLY RELOAD HOWEVER WITH THERMAL RIDGE ONCE AGAIN STARTING TO
TILT BACK OVER THE AREA WITH H85 TEMPS AROUND 20C BY LATER IN THE
DAY SUNDAY.

NEXT WEEK...
AN ACTIVE PATTERN LOOKS TO PERSIST THROUGH AT LEAST THE MIDDLE OF
NEXT WEEK WITH A SERIES OF WAVES PUSHING ACROSS THE REGION BRINGING
CONTINUED PERIODIC CHANCES FOR SHOWERS AND THUNDERSTORMS. ANOTHER
COLD FRONT WILL PUSH ACROSS THE AREA LATER ON MONDAY WITH THE
FRONTAL BOUNDARY STALLING JUST TO OUR SOUTH. THEREAFTER...THERE IS
CONSIDERABLE UNCERTAINTY ON HOW FAR NORTH THE BOUNDARY MAY LIFT
WITH THE BEST PRECIP CHANCES FOCUSED IN THE VICINITY OF THE
FRONT AS A SERIES OF UPPER LEVEL DISTURBANCES PUSH ACROSS THE
AREA. PWATS REMAIN JUICY ALONG THE FRONT...AROUND TWO INCHES...AND
GUIDANCE SUGGESTS THAT THERE COULD BE SEVERAL CONVECTIVE COMPLEXES
NEXT WEEK WITH A CONCERN FOR HEAVY RAIN AND FLOODING SHOULD THIS
PAN OUT.

DEUBELBEISS

&&

.AVIATION...

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

* EAST WIND ARND 8-10KT THRU THE EVENING...WINDS TURNING SE LATER THIS
  EVENING.

* SHOWERS MOVING THROUGH BTW 00-03Z...WITH POTENTIAL SHRA/ISOLATED
  TSRA AROUND DAYBREAK FRI.

* MVFR IN -SHRA THIS EVENING.

* SCATTERED TSRA FRIDAY AFTERNOON/EARLY EVENING.

* SOUTH WIND WITH GUSTS DEVELOPING TO 20KT MIDDAY FRI.

KMD

//DISCUSSION...UPDATED 00Z...
CHALLENGING FORECAST FOR THE NEXT 24-30 HOURS. AREA OF SHOWERS
WILL CONTINUE TO PUSH EASTWARD AND WEAKEN SOME THIS EVENING.
THUNDER ACTIVITY LOOKS TO REMAIN SOUTH OF THE INTERSTATE 80
CORRIDOR ALONG A LINE FROM KVYS TO KLOT TO KGYY. CIGS AND VSBYS
SHOULD GENERALLY REMAIN VFR THOUGH BRIEF MVFR VISBYS ARE POSSIBLE
MAINLY WEST OF THE MAIN CHICAGO TERMINALS.

EXPECTING A LULL THIS EVENING...THEN AS A WARM FRONT LIFTS THROUGH
TONIGHT...ADDITIONAL CONVECTION IS EXPECTED IN NW IOWA AND
SPREADING INTO WISCONSIN OVERNIGHT. AS AN UPPER RIDGE BUCKLES SOME
LATE TONIGHT INTO EARLY FRIDAY...SOME OF THIS ACTIVITY MAY GRAZE
NORTHEAST ILLINOIS IN THE 12Z-15Z TIME FRAME. INSTABILITY MAY
SUPPORT SHRA WITH ISOLATED TS.

INSTABILITY THEN INCREASES VERY QUICKLY ON FRIDAY AS WE GET IN THE
WARM SECTOR AND DEWPOINTS RISE. UPPER HEIGHT FALLS COMBINED WITH
PEAK HEATING SUGGESTS AFTERNOON AIR MASS THUNDERSTORMS THOUGH
DIFFICULT ON TIMING. COULD BE THUNDERSTORMS AT ANY TIME FRIDAY
AFTERNOON EARLY EVENING WITH NO OBVIOUS SURFACE FOCUS. WITH HIGH
PRECIPITABLE WATER VALUES...HEAVY DOWNPOURS ARE POSSIBLE.

KMD


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

* HIGH IN WIND DIR/SPEED AND TRENDS.

* MEDIUM-HIGH IN -SHRA 0Z-3Z.

* MEDIUM-HIGH THAT CIGS/VSBY REMAIN VFR WITH SHOWERS.

* LOW-MEDIUM PRECIP COVERAGE LATE TONIGHT INTO EARLY FRIDAY.

* LOW IN THUNDER CHANCES/COVERAGE AND SPECIFIC TIMING FRIDAY AFTERNOON.

KMD

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

* SATURDAY...TSRA LIKELY.
* SUNDAY...SLIGHT CHANCE OF TSRA.
* MONDAY AND TUESDAY...CHANCE OF TSRA.
* WEDNESDAY AND THURSDAY...SLIGHT CHANCE OF TSRA

KMD


&&

.MARINE...
123 PM CDT

SURFACE HIGH PRESSURE OVER THE GREAT LAKES REGION THIS AFTERNOON
WILL DRIFT TO THE EAST TONIGHT IN THE WAKE OF A DEPARTING UPPER
TROUGH OVER NEW ENGLAND/QUEBEC...AND AHEAD OF ANOTHER SURFACE TROUGH
AND WEAK COLD FRONT STRETCHING FROM FAR NORTHWEST ONTARIO TO THE
CENTRAL PLAINS. WINDS ON LAKE MICHIGAN WILL SHIFT TO THE SOUTHEAST
AND EVENTUALLY SOUTH HEADING INTO FRIDAY...AS AN AREA OF SURFACE LOW
PRESSURE DEVELOPS ACROSS THE PLAINS AND LIFTS ACROSS THE UPPER
MISSISSIPPI RIVER VALLEY. TIGHTENING OF THE PRESSURE GRADIENT
SOUTHEAST OF THE LOW TRACK WILL RESULT IN S-SE WINDS INCREASING INTO
THE 15-25 KT RANGE TONIGHT AND FRIDAY...GRADUALLY WEAKENING SATURDAY
AS THE LOW MOVES OFF TO THE NORTHEAST AND A WEAK COLD FRONT TRAILS
ACROSS THE LAKE FOLLOWED BY WEAK HIGH PRESSURE.

THIS COLD FRONT APPEARS TO DISSIPATE OR STALL ACROSS FAR SOUTHERN
LAKE MICHIGAN OR NORTHERN IL/IND LATE SATURDAY NIGHT OR EARLY SUNDAY
BEFORE DEVELOPING BACK TO THE NORTH AS A WARM FRONT SUNDAY NIGHT AS
ANOTHER AREA OF LOW PRESSURE DEVELOPS OVER THE PLAINS AND LIFTS
NORTHEAST INTO THE WESTERN/NORTHERN LAKES LATE SUNDAY NIGHT INTO
MONDAY. AGAIN...A TIGHTENING OF THE PRESSURE GRADIENT ALONG THE
SOUTHEAST PERIPHERY OF THE LOW TRACK IS EXPECTED WITH WINDS AGAIN
BECOMING SOUTHERLY INTO THE 15-25 KT RANGE ON MONDAY. ANOTHER
TRAILING COLD FRONT WILL PASS ACROSS THE LAKE MONDAY NIGHT...WITH
WEAK HIGH PRESSURE AND LIGHTER WINDS DEVELOPING TUESDAY.

RATZER

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 290013
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
713 PM CDT THU AUG 28 2014

.DISCUSSION...
230 PM CDT

VISIBLE IMAGERY THIS AFTERNOON SHOWS A MID/UPR LEVEL CLOUD DECK
LIFTING NORTHEAST ACROSS NORTHERN IL. REMNANTS FROM A MORNING
COMPLEX OF THUNDERSTORMS RESIDES OVER IOWA...WITH SOME CONVECTIVE
LOOK TO THE CLOUDS LINGERING INTO THIS AFTN. SFC TEMPS ACROSS THE
FORECAST AREA HAVE BEEN ABLE TO WARM INTO THE MID/UPR 70S. A FEW
POINTS SOUTH OF PONTIAC TO KANKAKEE HAVE PUSHED TO ARND 80 DEG...BUT
WITH THE LIGHT EASTERLY FLOW AT THE SFC SOME WEAK SUBSIDENCE HAS
BEEN NOTED WITH DEW POINTS BEING PUSHED INTO THE LOW 50S ALONG THE
LAKESHORE AND MID/UPR 50S INLAND.

THE MAIN CHALLENGE FOR THIS EVENING WILL FOCUS ON CONVECTIVE
CHANCES/COVERAGE...WHICH WILL CONTINUE THROUGH DAYBREAK FRI.
GUIDANCE HAS CONTINUED TO BACK OFF ON THE ARRIVAL OF PRECIP INTO THE
FORECAST AREA...WHICH SEEMS TO LINE UP RELATIVELY WELL WITH THE
CURRENT TRENDS. THE FRONTAL BOUNDARY WILL SLOWLY LIFT NORTH THIS
EVENING...BUT NOT EXPECTING MUCH IN THE WAY OF PRECIP UNTIL PERHAPS
AFT 04Z WITH A GRADUAL UPGLIDE OF PARCELS ALLOWS FOR MOISTENING.
SOME ELEVATED CONVECTION COULD BEGIN TO DEVELOP...ALTHOUGH NOT
EXPECTING MUCH COVERAGE OVERNIGHT. THE FOCUS FOR SLIGHTLY BETTER
PRECIP COVERAGE WILL REMAIN ALONG THE NORTHERN ROW OF COUNTIES IN
NORTHERN IL...HOWEVER CLOSER TO DAYBREAK FRI IT APPEARS SOME
PRECIP/CONVECTION COULD SAG SOUTHEAST AND CLIP NORTHEAST
IL/NORTHWEST IN BEFORE DISSIPATING.

WITH INCREASING CLOUD COVER TONIGHT...IT SHUD LIMIT HOW COOL TEMPS
BECOME. SO HAVE MADE ONLY MINOR ADJUSTMENTS TO THE TEMPS WITH
GENERALLY MID/UPR 60S FOR LOWS.

BEACHLER

FRIDAY AND FRIDAY NIGHT...
CLOSED UPPER LOW CURRENTLY NEAR THE COLORADO FRONT RANGE WILL SLOWLY
TRAVERSE EAST TOWARDS THE MID-MISSOURI VALLEY FRIDAY BECOMING AN
OPEN WAVE. AT THE SURFACE...BROAD AND WEAK SURFACE LOW WILL LIFT
INTO THE UPPER MIDWEST WHILE SOUTHWEST FLOW RAMPS UP THROUGH THE
COLUMN AS THE WARM FRONT LIFTS INTO THE CENTRAL GREAT LAKES. HEAT
AND HUMIDITY WILL MAKE A RETURN AS THIS OCCURS. H85 TEMPS WARMING TO
AROUND 18C WILL HELP SUPPORT MID/UPPER 80S DURING THE DAY
FRIDAY...AND SURFACE DEWPOINTS ARE PROGGED TO PUSH BACK INTO THE LOW
POSSIBLY MID 70S. THIS WILL RESULT IN MODERATE INSTABILITY
DEVELOPING DURING THE DAY...AND ONLY WEAKLY CAPPED DURING THE
AFTERNOON AS BROAD HEIGHT FALLS ASSOCIATED WITH THE UPPER WAVE START
TO OVERSPREAD THE AREA. THERE DOESNT SEEM TO BE MUCH FOCUS IN THE
LOWER LEVELS SO WOULD EXPECT ONLY SCATTERED THUNDERSTORM DEVELOPMENT
ACROSS THE REGION FRIDAY AFTERNOON/EVENING. UPPER WAVE BEGINS TO
MOVE INTO THE UPPER MIDWEST TOMORROW NIGHT AND BROAD WARM ADVECTION
OUT AHEAD DURING THE EVENING AND OVERNIGHT HOURS WILL HELP SUSTAIN
SOME CONVECTION LATE BUT WOULD EXPECT SOME NOCTURNAL DOWNTICK IN
ACTIVITY OVERNIGHT WITH THE LOW LEVEL JET FOCUSED WELL TO OUR NORTH.
GFS/NAM SEEM TO BE OVERDOING POPS MUCH OF THE DAY AND NIGHT
FRIDAY...AND OPTED TO LEAN CLOSER TO ECMWF THESE PERIODS.

THIS WEEKEND...
COLD FRONT WILL SWEEP ACROSS THE FORECAST AREA STARTING VERY EARLY
ON SATURDAY. WHILE NOT A FAVORABLE DIURNAL TIME...WE SHOULD STILL
HAVE SOME VERY MODEST INSTABILITY IN PLACE THAT WILL SUPPORT SOME
EARLY DAY THUNDERSTORMS ALONG THE FRONTAL BOUNDARY...WHICH WOULD BE
ABLE TO EXPAND IN COVERAGE AS THE DAY PROGRESSES AND THE BOUNDARY
LAYER WARMS. IN ADDITION...GUIDANCE SUGGESTS A SECOND SHORTWAVE
WILL WRAP INTO THE AREA THAT WILL PROVIDE ADDITIONAL BROAD SCALE
ASCENT. THE ECMWF IS ABOUT SIX HOURS SLOWER WITH THIS FEATURE
COMPARED TO THE NAM/GFS...WITH THE GEM A COMPROMISE...SO THERE
REMAINS SOME UNCERTAINTY IN TIMING. HIGH PRESSURE WILL BUILD IN
BEHIND THE FRONT SATURDAY NIGHT INTO SUNDAY AND WILL PROVIDE A
BRIEF RESPITE FROM THE ACTIVE WEATHER. THE ATMOSPHERE LOOKS TO
QUICKLY RELOAD HOWEVER WITH THERMAL RIDGE ONCE AGAIN STARTING TO
TILT BACK OVER THE AREA WITH H85 TEMPS AROUND 20C BY LATER IN THE
DAY SUNDAY.

NEXT WEEK...
AN ACTIVE PATTERN LOOKS TO PERSIST THROUGH AT LEAST THE MIDDLE OF
NEXT WEEK WITH A SERIES OF WAVES PUSHING ACROSS THE REGION BRINGING
CONTINUED PERIODIC CHANCES FOR SHOWERS AND THUNDERSTORMS. ANOTHER
COLD FRONT WILL PUSH ACROSS THE AREA LATER ON MONDAY WITH THE
FRONTAL BOUNDARY STALLING JUST TO OUR SOUTH. THEREAFTER...THERE IS
CONSIDERABLE UNCERTAINTY ON HOW FAR NORTH THE BOUNDARY MAY LIFT
WITH THE BEST PRECIP CHANCES FOCUSED IN THE VICINITY OF THE
FRONT AS A SERIES OF UPPER LEVEL DISTURBANCES PUSH ACROSS THE
AREA. PWATS REMAIN JUICY ALONG THE FRONT...AROUND TWO INCHES...AND
GUIDANCE SUGGESTS THAT THERE COULD BE SEVERAL CONVECTIVE COMPLEXES
NEXT WEEK WITH A CONCERN FOR HEAVY RAIN AND FLOODING SHOULD THIS
PAN OUT.

DEUBELBEISS

&&

.AVIATION...

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

* EAST WIND ARND 8-10KT THRU THE EVENING...WINDS TURNING SE LATER THIS
  EVENING.

* SHOWERS MOVING THROUGH BTW 00-03Z...WITH POTENTIAL SHRA/ISOLATED
  TSRA AROUND DAYBREAK FRI.

* MVFR IN -SHRA THIS EVENING.

* SCATTERED TSRA FRIDAY AFTERNOON/EARLY EVENING.

* SOUTH WIND WITH GUSTS DEVELOPING TO 20KT MIDDAY FRI.

KMD

//DISCUSSION...UPDATED 00Z...
CHALLENGING FORECAST FOR THE NEXT 24-30 HOURS. AREA OF SHOWERS
WILL CONTINUE TO PUSH EASTWARD AND WEAKEN SOME THIS EVENING.
THUNDER ACTIVITY LOOKS TO REMAIN SOUTH OF THE INTERSTATE 80
CORRIDOR ALONG A LINE FROM KVYS TO KLOT TO KGYY. CIGS AND VSBYS
SHOULD GENERALLY REMAIN VFR THOUGH BRIEF MVFR VISBYS ARE POSSIBLE
MAINLY WEST OF THE MAIN CHICAGO TERMINALS.

EXPECTING A LULL THIS EVENING...THEN AS A WARM FRONT LIFTS THROUGH
TONIGHT...ADDITIONAL CONVECTION IS EXPECTED IN NW IOWA AND
SPREADING INTO WISCONSIN OVERNIGHT. AS AN UPPER RIDGE BUCKLES SOME
LATE TONIGHT INTO EARLY FRIDAY...SOME OF THIS ACTIVITY MAY GRAZE
NORTHEAST ILLINOIS IN THE 12Z-15Z TIME FRAME. INSTABILITY MAY
SUPPORT SHRA WITH ISOLATED TS.

INSTABILITY THEN INCREASES VERY QUICKLY ON FRIDAY AS WE GET IN THE
WARM SECTOR AND DEWPOINTS RISE. UPPER HEIGHT FALLS COMBINED WITH
PEAK HEATING SUGGESTS AFTERNOON AIR MASS THUNDERSTORMS THOUGH
DIFFICULT ON TIMING. COULD BE THUNDERSTORMS AT ANY TIME FRIDAY
AFTERNOON EARLY EVENING WITH NO OBVIOUS SURFACE FOCUS. WITH HIGH
PRECIPITABLE WATER VALUES...HEAVY DOWNPOURS ARE POSSIBLE.

KMD


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

* HIGH IN WIND DIR/SPEED AND TRENDS.

* MEDIUM-HIGH IN -SHRA 0Z-3Z.

* MEDIUM-HIGH THAT CIGS/VSBY REMAIN VFR WITH SHOWERS.

* LOW-MEDIUM PRECIP COVERAGE LATE TONIGHT INTO EARLY FRIDAY.

* LOW IN THUNDER CHANCES/COVERAGE AND SPECIFIC TIMING FRIDAY AFTERNOON.

KMD

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

* SATURDAY...TSRA LIKELY.
* SUNDAY...SLIGHT CHANCE OF TSRA.
* MONDAY AND TUESDAY...CHANCE OF TSRA.
* WEDNESDAY AND THURSDAY...SLIGHT CHANCE OF TSRA

KMD


&&

.MARINE...
123 PM CDT

SURFACE HIGH PRESSURE OVER THE GREAT LAKES REGION THIS AFTERNOON
WILL DRIFT TO THE EAST TONIGHT IN THE WAKE OF A DEPARTING UPPER
TROUGH OVER NEW ENGLAND/QUEBEC...AND AHEAD OF ANOTHER SURFACE TROUGH
AND WEAK COLD FRONT STRETCHING FROM FAR NORTHWEST ONTARIO TO THE
CENTRAL PLAINS. WINDS ON LAKE MICHIGAN WILL SHIFT TO THE SOUTHEAST
AND EVENTUALLY SOUTH HEADING INTO FRIDAY...AS AN AREA OF SURFACE LOW
PRESSURE DEVELOPS ACROSS THE PLAINS AND LIFTS ACROSS THE UPPER
MISSISSIPPI RIVER VALLEY. TIGHTENING OF THE PRESSURE GRADIENT
SOUTHEAST OF THE LOW TRACK WILL RESULT IN S-SE WINDS INCREASING INTO
THE 15-25 KT RANGE TONIGHT AND FRIDAY...GRADUALLY WEAKENING SATURDAY
AS THE LOW MOVES OFF TO THE NORTHEAST AND A WEAK COLD FRONT TRAILS
ACROSS THE LAKE FOLLOWED BY WEAK HIGH PRESSURE.

THIS COLD FRONT APPEARS TO DISSIPATE OR STALL ACROSS FAR SOUTHERN
LAKE MICHIGAN OR NORTHERN IL/IND LATE SATURDAY NIGHT OR EARLY SUNDAY
BEFORE DEVELOPING BACK TO THE NORTH AS A WARM FRONT SUNDAY NIGHT AS
ANOTHER AREA OF LOW PRESSURE DEVELOPS OVER THE PLAINS AND LIFTS
NORTHEAST INTO THE WESTERN/NORTHERN LAKES LATE SUNDAY NIGHT INTO
MONDAY. AGAIN...A TIGHTENING OF THE PRESSURE GRADIENT ALONG THE
SOUTHEAST PERIPHERY OF THE LOW TRACK IS EXPECTED WITH WINDS AGAIN
BECOMING SOUTHERLY INTO THE 15-25 KT RANGE ON MONDAY. ANOTHER
TRAILING COLD FRONT WILL PASS ACROSS THE LAKE MONDAY NIGHT...WITH
WEAK HIGH PRESSURE AND LIGHTER WINDS DEVELOPING TUESDAY.

RATZER

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO







000
FXUS63 KLOT 282234
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
534 PM CDT THU AUG 28 2014

.DISCUSSION...
230 PM CDT

VISIBLE IMAGERY THIS AFTERNOON SHOWS A MID/UPR LEVEL CLOUD DECK
LIFTING NORTHEAST ACROSS NORTHERN IL. REMNANTS FROM A MORNING
COMPLEX OF THUNDERSTORMS RESIDES OVER IOWA...WITH SOME CONVECTIVE
LOOK TO THE CLOUDS LINGERING INTO THIS AFTN. SFC TEMPS ACROSS THE
FORECAST AREA HAVE BEEN ABLE TO WARM INTO THE MID/UPR 70S. A FEW
POINTS SOUTH OF PONTIAC TO KANKAKEE HAVE PUSHED TO ARND 80 DEG...BUT
WITH THE LIGHT EASTERLY FLOW AT THE SFC SOME WEAK SUBSIDENCE HAS
BEEN NOTED WITH DEW POINTS BEING PUSHED INTO THE LOW 50S ALONG THE
LAKESHORE AND MID/UPR 50S INLAND.

THE MAIN CHALLENGE FOR THIS EVENING WILL FOCUS ON CONVECTIVE
CHANCES/COVERAGE...WHICH WILL CONTINUE THROUGH DAYBREAK FRI.
GUIDANCE HAS CONTINUED TO BACK OFF ON THE ARRIVAL OF PRECIP INTO THE
FORECAST AREA...WHICH SEEMS TO LINE UP RELATIVELY WELL WITH THE
CURRENT TRENDS. THE FRONTAL BOUNDARY WILL SLOWLY LIFT NORTH THIS
EVENING...BUT NOT EXPECTING MUCH IN THE WAY OF PRECIP UNTIL PERHAPS
AFT 04Z WITH A GRADUAL UPGLIDE OF PARCELS ALLOWS FOR MOISTENING.
SOME ELEVATED CONVECTION COULD BEGIN TO DEVELOP...ALTHOUGH NOT
EXPECTING MUCH COVERAGE OVERNIGHT. THE FOCUS FOR SLIGHTLY BETTER
PRECIP COVERAGE WILL REMAIN ALONG THE NORTHERN ROW OF COUNTIES IN
NORTHERN IL...HOWEVER CLOSER TO DAYBREAK FRI IT APPEARS SOME
PRECIP/CONVECTION COULD SAG SOUTHEAST AND CLIP NORTHEAST
IL/NORTHWEST IN BEFORE DISSIPATING.

WITH INCREASING CLOUD COVER TONIGHT...IT SHUD LIMIT HOW COOL TEMPS
BECOME. SO HAVE MADE ONLY MINOR ADJUSTMENTS TO THE TEMPS WITH
GENERALLY MID/UPR 60S FOR LOWS.

BEACHLER

FRIDAY AND FRIDAY NIGHT...
CLOSED UPPER LOW CURRENTLY NEAR THE COLORADO FRONT RANGE WILL SLOWLY
TRAVERSE EAST TOWARDS THE MID-MISSOURI VALLEY FRIDAY BECOMING AN
OPEN WAVE. AT THE SURFACE...BROAD AND WEAK SURFACE LOW WILL LIFT
INTO THE UPPER MIDWEST WHILE SOUTHWEST FLOW RAMPS UP THROUGH THE
COLUMN AS THE WARM FRONT LIFTS INTO THE CENTRAL GREAT LAKES. HEAT
AND HUMIDITY WILL MAKE A RETURN AS THIS OCCURS. H85 TEMPS WARMING TO
AROUND 18C WILL HELP SUPPORT MID/UPPER 80S DURING THE DAY
FRIDAY...AND SURFACE DEWPOINTS ARE PROGGED TO PUSH BACK INTO THE LOW
POSSIBLY MID 70S. THIS WILL RESULT IN MODERATE INSTABILITY
DEVELOPING DURING THE DAY...AND ONLY WEAKLY CAPPED DURING THE
AFTERNOON AS BROAD HEIGHT FALLS ASSOCIATED WITH THE UPPER WAVE START
TO OVERSPREAD THE AREA. THERE DOESNT SEEM TO BE MUCH FOCUS IN THE
LOWER LEVELS SO WOULD EXPECT ONLY SCATTERED THUNDERSTORM DEVELOPMENT
ACROSS THE REGION FRIDAY AFTERNOON/EVENING. UPPER WAVE BEGINS TO
MOVE INTO THE UPPER MIDWEST TOMORROW NIGHT AND BROAD WARM ADVECTION
OUT AHEAD DURING THE EVENING AND OVERNIGHT HOURS WILL HELP SUSTAIN
SOME CONVECTION LATE BUT WOULD EXPECT SOME NOCTURNAL DOWNTICK IN
ACTIVITY OVERNIGHT WITH THE LOW LEVEL JET FOCUSED WELL TO OUR NORTH.
GFS/NAM SEEM TO BE OVERDOING POPS MUCH OF THE DAY AND NIGHT
FRIDAY...AND OPTED TO LEAN CLOSER TO ECMWF THESE PERIODS.

THIS WEEKEND...
COLD FRONT WILL SWEEP ACROSS THE FORECAST AREA STARTING VERY EARLY
ON SATURDAY. WHILE NOT A FAVORABLE DIURNAL TIME...WE SHOULD STILL
HAVE SOME VERY MODEST INSTABILITY IN PLACE THAT WILL SUPPORT SOME
EARLY DAY THUNDERSTORMS ALONG THE FRONTAL BOUNDARY...WHICH WOULD BE
ABLE TO EXPAND IN COVERAGE AS THE DAY PROGRESSES AND THE BOUNDARY
LAYER WARMS. IN ADDITION...GUIDANCE SUGGESTS A SECOND SHORTWAVE
WILL WRAP INTO THE AREA THAT WILL PROVIDE ADDITIONAL BROAD SCALE
ASCENT. THE ECMWF IS ABOUT SIX HOURS SLOWER WITH THIS FEATURE
COMPARED TO THE NAM/GFS...WITH THE GEM A COMPROMISE...SO THERE
REMAINS SOME UNCERTAINTY IN TIMING. HIGH PRESSURE WILL BUILD IN
BEHIND THE FRONT SATURDAY NIGHT INTO SUNDAY AND WILL PROVIDE A
BRIEF RESPITE FROM THE ACTIVE WEATHER. THE ATMOSPHERE LOOKS TO
QUICKLY RELOAD HOWEVER WITH THERMAL RIDGE ONCE AGAIN STARTING TO
TILT BACK OVER THE AREA WITH H85 TEMPS AROUND 20C BY LATER IN THE
DAY SUNDAY.

NEXT WEEK...
AN ACTIVE PATTERN LOOKS TO PERSIST THROUGH AT LEAST THE MIDDLE OF
NEXT WEEK WITH A SERIES OF WAVES PUSHING ACROSS THE REGION BRINGING
CONTINUED PERIODIC CHANCES FOR SHOWERS AND THUNDERSTORMS. ANOTHER
COLD FRONT WILL PUSH ACROSS THE AREA LATER ON MONDAY WITH THE
FRONTAL BOUNDARY STALLING JUST TO OUR SOUTH. THEREAFTER...THERE IS
CONSIDERABLE UNCERTAINTY ON HOW FAR NORTH THE BOUNDARY MAY LIFT
WITH THE BEST PRECIP CHANCES FOCUSED IN THE VICINITY OF THE
FRONT AS A SERIES OF UPPER LEVEL DISTURBANCES PUSH ACROSS THE
AREA. PWATS REMAIN JUICY ALONG THE FRONT...AROUND TWO INCHES...AND
GUIDANCE SUGGESTS THAT THERE COULD BE SEVERAL CONVECTIVE COMPLEXES
NEXT WEEK WITH A CONCERN FOR HEAVY RAIN AND FLOODING SHOULD THIS
PAN OUT.

DEUBELBEISS

&&

.AVIATION...

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

* EAST WIND ARND 8-10KT THRU LATE AFTN...WINDS TURNING SE LATER
  THIS EVENING.

* SHOWERS MOVING THROUGH BTW 00-03Z...WITH POTENTIAL TSRA AFT 09Z
  THRU DAYBREAK FRI.

* MVFR IN -SHRA THIS EVENING

* WINDS CONTINUE TO TURN S FRI MORNING...WITH GUSTS DEVELOPING TO
  20KT MIDDAY FRI.

BEACHLER/KMD

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

VISIBLE IMAGERY THIS AFTN SHOWS SOME THIN MID-DECK CLOUDS LIFTING
NORTHEAST ACROSS NORTHERN IL. MUCH THICKER CLOUDS AND SPOTTY
SHOWERS REMAINS OVER IOWA. SFC WINDS CONTINUE TO BE EASTERLY
ACROSS MUCH OF THE REGION...WITH A GRADUAL TURN TOWARDS SOUTHEAST
ACROSS CENTRAL IL/IN. A FRONTAL BOUNDARY WILL BEGIN TO LIFT NORTH
THIS EVENING...WITH INCREASING MOISTURE. THIS COULD AID IN SEEING
ISOLATED SHOWERS AND POSSIBLY A THUNDERSTORM LATER TONIGHT.
GUIDANCE CONTINUES TO LEAN TOWARDS THE 10-14Z FRI TIMEFRAME FOR
THE BEST COVERAGE OF SHOWERS AND ISO-TSRA DEVELOPING...BUT
CONFIDENCE REMAINS LOW WITH COVERAGE OF THUNDER. SO AT THIS TIME
HAVE HELD ONTO JUST A PROB30 GROUP. WINDS BEHIND THE FRONTAL
BOUNDARY WILL BEGIN TO TURN SOUTH AROUND DAYBREAK FRI...WITH
BETTER MIXING DEVELOPING BY LATE MORNING/EARLY AFTN. GUIDANCE
CONTINUES TO SUGGEST CONVETION COULD BEGIN TO DEVELOP YET AGAIN
LATE MORNING THROUGH THE AFTERNOON...HOWEVER FEEL THIS IS A BIT
OVERDONE.

BEACHLER

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

* HIGH CONFIDENCE IN WIND DIR/SPEED AND TRENDS.

* MEDIUM HIGH CONFIDENCE IN -SHRA 0Z-3Z.

* MEDIUM-HIGH CONFIDENCE THAT CIGS/VSBY REMAIN VFR WITH SHOWERS.

* LOW-MEDIUM CONFIDENCE IN TIMING OF PRECIP AND COVERAGE AFTER FIRST
  ROUND OF SHOWERS THIS EVENING.

* LOW CONFIDENCE IN THUNDER CHANCES/COVERAGE.

BEACHLER/KMD

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

* FRIDAY NIGHT...CHANCE OF TSRA.
* SATURDAY...TSRA LIKELY.
* SUNDAY...SLIGHT CHANCE OF TSRA.
* MONDAY AND TUESDAY...CHANCE OF TSRA.
* WEDNESDAY...DRY/VFR.

&&

.MARINE...
123 PM CDT

SURFACE HIGH PRESSURE OVER THE GREAT LAKES REGION THIS AFTERNOON
WILL DRIFT TO THE EAST TONIGHT IN THE WAKE OF A DEPARTING UPPER
TROUGH OVER NEW ENGLAND/QUEBEC...AND AHEAD OF ANOTHER SURFACE TROUGH
AND WEAK COLD FRONT STRETCHING FROM FAR NORTHWEST ONTARIO TO THE
CENTRAL PLAINS. WINDS ON LAKE MICHIGAN WILL SHIFT TO THE SOUTHEAST
AND EVENTUALLY SOUTH HEADING INTO FRIDAY...AS AN AREA OF SURFACE LOW
PRESSURE DEVELOPS ACROSS THE PLAINS AND LIFTS ACROSS THE UPPER
MISSISSIPPI RIVER VALLEY. TIGHTENING OF THE PRESSURE GRADIENT
SOUTHEAST OF THE LOW TRACK WILL RESULT IN S-SE WINDS INCREASING INTO
THE 15-25 KT RANGE TONIGHT AND FRIDAY...GRADUALLY WEAKENING SATURDAY
AS THE LOW MOVES OFF TO THE NORTHEAST AND A WEAK COLD FRONT TRAILS
ACROSS THE LAKE FOLLOWED BY WEAK HIGH PRESSURE.

THIS COLD FRONT APPEARS TO DISSIPATE OR STALL ACROSS FAR SOUTHERN
LAKE MICHIGAN OR NORTHERN IL/IND LATE SATURDAY NIGHT OR EARLY SUNDAY
BEFORE DEVELOPING BACK TO THE NORTH AS A WARM FRONT SUNDAY NIGHT AS
ANOTHER AREA OF LOW PRESSURE DEVELOPS OVER THE PLAINS AND LIFTS
NORTHEAST INTO THE WESTERN/NORTHERN LAKES LATE SUNDAY NIGHT INTO
MONDAY. AGAIN...A TIGHTENING OF THE PRESSURE GRADIENT ALONG THE
SOUTHEAST PERIPHERY OF THE LOW TRACK IS EXPECTED WITH WINDS AGAIN
BECOMING SOUTHERLY INTO THE 15-25 KT RANGE ON MONDAY. ANOTHER
TRAILING COLD FRONT WILL PASS ACROSS THE LAKE MONDAY NIGHT...WITH
WEAK HIGH PRESSURE AND LIGHTER WINDS DEVELOPING TUESDAY.

RATZER

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO







000
FXUS63 KLOT 282234
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
534 PM CDT THU AUG 28 2014

.DISCUSSION...
230 PM CDT

VISIBLE IMAGERY THIS AFTERNOON SHOWS A MID/UPR LEVEL CLOUD DECK
LIFTING NORTHEAST ACROSS NORTHERN IL. REMNANTS FROM A MORNING
COMPLEX OF THUNDERSTORMS RESIDES OVER IOWA...WITH SOME CONVECTIVE
LOOK TO THE CLOUDS LINGERING INTO THIS AFTN. SFC TEMPS ACROSS THE
FORECAST AREA HAVE BEEN ABLE TO WARM INTO THE MID/UPR 70S. A FEW
POINTS SOUTH OF PONTIAC TO KANKAKEE HAVE PUSHED TO ARND 80 DEG...BUT
WITH THE LIGHT EASTERLY FLOW AT THE SFC SOME WEAK SUBSIDENCE HAS
BEEN NOTED WITH DEW POINTS BEING PUSHED INTO THE LOW 50S ALONG THE
LAKESHORE AND MID/UPR 50S INLAND.

THE MAIN CHALLENGE FOR THIS EVENING WILL FOCUS ON CONVECTIVE
CHANCES/COVERAGE...WHICH WILL CONTINUE THROUGH DAYBREAK FRI.
GUIDANCE HAS CONTINUED TO BACK OFF ON THE ARRIVAL OF PRECIP INTO THE
FORECAST AREA...WHICH SEEMS TO LINE UP RELATIVELY WELL WITH THE
CURRENT TRENDS. THE FRONTAL BOUNDARY WILL SLOWLY LIFT NORTH THIS
EVENING...BUT NOT EXPECTING MUCH IN THE WAY OF PRECIP UNTIL PERHAPS
AFT 04Z WITH A GRADUAL UPGLIDE OF PARCELS ALLOWS FOR MOISTENING.
SOME ELEVATED CONVECTION COULD BEGIN TO DEVELOP...ALTHOUGH NOT
EXPECTING MUCH COVERAGE OVERNIGHT. THE FOCUS FOR SLIGHTLY BETTER
PRECIP COVERAGE WILL REMAIN ALONG THE NORTHERN ROW OF COUNTIES IN
NORTHERN IL...HOWEVER CLOSER TO DAYBREAK FRI IT APPEARS SOME
PRECIP/CONVECTION COULD SAG SOUTHEAST AND CLIP NORTHEAST
IL/NORTHWEST IN BEFORE DISSIPATING.

WITH INCREASING CLOUD COVER TONIGHT...IT SHUD LIMIT HOW COOL TEMPS
BECOME. SO HAVE MADE ONLY MINOR ADJUSTMENTS TO THE TEMPS WITH
GENERALLY MID/UPR 60S FOR LOWS.

BEACHLER

FRIDAY AND FRIDAY NIGHT...
CLOSED UPPER LOW CURRENTLY NEAR THE COLORADO FRONT RANGE WILL SLOWLY
TRAVERSE EAST TOWARDS THE MID-MISSOURI VALLEY FRIDAY BECOMING AN
OPEN WAVE. AT THE SURFACE...BROAD AND WEAK SURFACE LOW WILL LIFT
INTO THE UPPER MIDWEST WHILE SOUTHWEST FLOW RAMPS UP THROUGH THE
COLUMN AS THE WARM FRONT LIFTS INTO THE CENTRAL GREAT LAKES. HEAT
AND HUMIDITY WILL MAKE A RETURN AS THIS OCCURS. H85 TEMPS WARMING TO
AROUND 18C WILL HELP SUPPORT MID/UPPER 80S DURING THE DAY
FRIDAY...AND SURFACE DEWPOINTS ARE PROGGED TO PUSH BACK INTO THE LOW
POSSIBLY MID 70S. THIS WILL RESULT IN MODERATE INSTABILITY
DEVELOPING DURING THE DAY...AND ONLY WEAKLY CAPPED DURING THE
AFTERNOON AS BROAD HEIGHT FALLS ASSOCIATED WITH THE UPPER WAVE START
TO OVERSPREAD THE AREA. THERE DOESNT SEEM TO BE MUCH FOCUS IN THE
LOWER LEVELS SO WOULD EXPECT ONLY SCATTERED THUNDERSTORM DEVELOPMENT
ACROSS THE REGION FRIDAY AFTERNOON/EVENING. UPPER WAVE BEGINS TO
MOVE INTO THE UPPER MIDWEST TOMORROW NIGHT AND BROAD WARM ADVECTION
OUT AHEAD DURING THE EVENING AND OVERNIGHT HOURS WILL HELP SUSTAIN
SOME CONVECTION LATE BUT WOULD EXPECT SOME NOCTURNAL DOWNTICK IN
ACTIVITY OVERNIGHT WITH THE LOW LEVEL JET FOCUSED WELL TO OUR NORTH.
GFS/NAM SEEM TO BE OVERDOING POPS MUCH OF THE DAY AND NIGHT
FRIDAY...AND OPTED TO LEAN CLOSER TO ECMWF THESE PERIODS.

THIS WEEKEND...
COLD FRONT WILL SWEEP ACROSS THE FORECAST AREA STARTING VERY EARLY
ON SATURDAY. WHILE NOT A FAVORABLE DIURNAL TIME...WE SHOULD STILL
HAVE SOME VERY MODEST INSTABILITY IN PLACE THAT WILL SUPPORT SOME
EARLY DAY THUNDERSTORMS ALONG THE FRONTAL BOUNDARY...WHICH WOULD BE
ABLE TO EXPAND IN COVERAGE AS THE DAY PROGRESSES AND THE BOUNDARY
LAYER WARMS. IN ADDITION...GUIDANCE SUGGESTS A SECOND SHORTWAVE
WILL WRAP INTO THE AREA THAT WILL PROVIDE ADDITIONAL BROAD SCALE
ASCENT. THE ECMWF IS ABOUT SIX HOURS SLOWER WITH THIS FEATURE
COMPARED TO THE NAM/GFS...WITH THE GEM A COMPROMISE...SO THERE
REMAINS SOME UNCERTAINTY IN TIMING. HIGH PRESSURE WILL BUILD IN
BEHIND THE FRONT SATURDAY NIGHT INTO SUNDAY AND WILL PROVIDE A
BRIEF RESPITE FROM THE ACTIVE WEATHER. THE ATMOSPHERE LOOKS TO
QUICKLY RELOAD HOWEVER WITH THERMAL RIDGE ONCE AGAIN STARTING TO
TILT BACK OVER THE AREA WITH H85 TEMPS AROUND 20C BY LATER IN THE
DAY SUNDAY.

NEXT WEEK...
AN ACTIVE PATTERN LOOKS TO PERSIST THROUGH AT LEAST THE MIDDLE OF
NEXT WEEK WITH A SERIES OF WAVES PUSHING ACROSS THE REGION BRINGING
CONTINUED PERIODIC CHANCES FOR SHOWERS AND THUNDERSTORMS. ANOTHER
COLD FRONT WILL PUSH ACROSS THE AREA LATER ON MONDAY WITH THE
FRONTAL BOUNDARY STALLING JUST TO OUR SOUTH. THEREAFTER...THERE IS
CONSIDERABLE UNCERTAINTY ON HOW FAR NORTH THE BOUNDARY MAY LIFT
WITH THE BEST PRECIP CHANCES FOCUSED IN THE VICINITY OF THE
FRONT AS A SERIES OF UPPER LEVEL DISTURBANCES PUSH ACROSS THE
AREA. PWATS REMAIN JUICY ALONG THE FRONT...AROUND TWO INCHES...AND
GUIDANCE SUGGESTS THAT THERE COULD BE SEVERAL CONVECTIVE COMPLEXES
NEXT WEEK WITH A CONCERN FOR HEAVY RAIN AND FLOODING SHOULD THIS
PAN OUT.

DEUBELBEISS

&&

.AVIATION...

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

* EAST WIND ARND 8-10KT THRU LATE AFTN...WINDS TURNING SE LATER
  THIS EVENING.

* SHOWERS MOVING THROUGH BTW 00-03Z...WITH POTENTIAL TSRA AFT 09Z
  THRU DAYBREAK FRI.

* MVFR IN -SHRA THIS EVENING

* WINDS CONTINUE TO TURN S FRI MORNING...WITH GUSTS DEVELOPING TO
  20KT MIDDAY FRI.

BEACHLER/KMD

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

VISIBLE IMAGERY THIS AFTN SHOWS SOME THIN MID-DECK CLOUDS LIFTING
NORTHEAST ACROSS NORTHERN IL. MUCH THICKER CLOUDS AND SPOTTY
SHOWERS REMAINS OVER IOWA. SFC WINDS CONTINUE TO BE EASTERLY
ACROSS MUCH OF THE REGION...WITH A GRADUAL TURN TOWARDS SOUTHEAST
ACROSS CENTRAL IL/IN. A FRONTAL BOUNDARY WILL BEGIN TO LIFT NORTH
THIS EVENING...WITH INCREASING MOISTURE. THIS COULD AID IN SEEING
ISOLATED SHOWERS AND POSSIBLY A THUNDERSTORM LATER TONIGHT.
GUIDANCE CONTINUES TO LEAN TOWARDS THE 10-14Z FRI TIMEFRAME FOR
THE BEST COVERAGE OF SHOWERS AND ISO-TSRA DEVELOPING...BUT
CONFIDENCE REMAINS LOW WITH COVERAGE OF THUNDER. SO AT THIS TIME
HAVE HELD ONTO JUST A PROB30 GROUP. WINDS BEHIND THE FRONTAL
BOUNDARY WILL BEGIN TO TURN SOUTH AROUND DAYBREAK FRI...WITH
BETTER MIXING DEVELOPING BY LATE MORNING/EARLY AFTN. GUIDANCE
CONTINUES TO SUGGEST CONVETION COULD BEGIN TO DEVELOP YET AGAIN
LATE MORNING THROUGH THE AFTERNOON...HOWEVER FEEL THIS IS A BIT
OVERDONE.

BEACHLER

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

* HIGH CONFIDENCE IN WIND DIR/SPEED AND TRENDS.

* MEDIUM HIGH CONFIDENCE IN -SHRA 0Z-3Z.

* MEDIUM-HIGH CONFIDENCE THAT CIGS/VSBY REMAIN VFR WITH SHOWERS.

* LOW-MEDIUM CONFIDENCE IN TIMING OF PRECIP AND COVERAGE AFTER FIRST
  ROUND OF SHOWERS THIS EVENING.

* LOW CONFIDENCE IN THUNDER CHANCES/COVERAGE.

BEACHLER/KMD

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

* FRIDAY NIGHT...CHANCE OF TSRA.
* SATURDAY...TSRA LIKELY.
* SUNDAY...SLIGHT CHANCE OF TSRA.
* MONDAY AND TUESDAY...CHANCE OF TSRA.
* WEDNESDAY...DRY/VFR.

&&

.MARINE...
123 PM CDT

SURFACE HIGH PRESSURE OVER THE GREAT LAKES REGION THIS AFTERNOON
WILL DRIFT TO THE EAST TONIGHT IN THE WAKE OF A DEPARTING UPPER
TROUGH OVER NEW ENGLAND/QUEBEC...AND AHEAD OF ANOTHER SURFACE TROUGH
AND WEAK COLD FRONT STRETCHING FROM FAR NORTHWEST ONTARIO TO THE
CENTRAL PLAINS. WINDS ON LAKE MICHIGAN WILL SHIFT TO THE SOUTHEAST
AND EVENTUALLY SOUTH HEADING INTO FRIDAY...AS AN AREA OF SURFACE LOW
PRESSURE DEVELOPS ACROSS THE PLAINS AND LIFTS ACROSS THE UPPER
MISSISSIPPI RIVER VALLEY. TIGHTENING OF THE PRESSURE GRADIENT
SOUTHEAST OF THE LOW TRACK WILL RESULT IN S-SE WINDS INCREASING INTO
THE 15-25 KT RANGE TONIGHT AND FRIDAY...GRADUALLY WEAKENING SATURDAY
AS THE LOW MOVES OFF TO THE NORTHEAST AND A WEAK COLD FRONT TRAILS
ACROSS THE LAKE FOLLOWED BY WEAK HIGH PRESSURE.

THIS COLD FRONT APPEARS TO DISSIPATE OR STALL ACROSS FAR SOUTHERN
LAKE MICHIGAN OR NORTHERN IL/IND LATE SATURDAY NIGHT OR EARLY SUNDAY
BEFORE DEVELOPING BACK TO THE NORTH AS A WARM FRONT SUNDAY NIGHT AS
ANOTHER AREA OF LOW PRESSURE DEVELOPS OVER THE PLAINS AND LIFTS
NORTHEAST INTO THE WESTERN/NORTHERN LAKES LATE SUNDAY NIGHT INTO
MONDAY. AGAIN...A TIGHTENING OF THE PRESSURE GRADIENT ALONG THE
SOUTHEAST PERIPHERY OF THE LOW TRACK IS EXPECTED WITH WINDS AGAIN
BECOMING SOUTHERLY INTO THE 15-25 KT RANGE ON MONDAY. ANOTHER
TRAILING COLD FRONT WILL PASS ACROSS THE LAKE MONDAY NIGHT...WITH
WEAK HIGH PRESSURE AND LIGHTER WINDS DEVELOPING TUESDAY.

RATZER

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 281937
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
237 PM CDT THU AUG 28 2014

.DISCUSSION...
230 PM CDT

VISIBLE IMAGERY THIS AFTERNOON SHOWS A MID/UPR LEVEL CLOUD DECK
LIFTING NORTHEAST ACROSS NORTHERN IL. REMNANTS FROM A MORNING
COMPLEX OF THUNDERSTORMS RESIDES OVER IOWA...WITH SOME CONVECTIVE
LOOK TO THE CLOUDS LINGERING INTO THIS AFTN. SFC TEMPS ACROSS THE
FORECAST AREA HAVE BEEN ABLE TO WARM INTO THE MID/UPR 70S. A FEW
POINTS SOUTH OF PONTIAC TO KANKAKEE HAVE PUSHED TO ARND 80 DEG...BUT
WITH THE LIGHT EASTERLY FLOW AT THE SFC SOME WEAK SUBSIDENCE HAS
BEEN NOTED WITH DEW POINTS BEING PUSHED INTO THE LOW 50S ALONG THE
LAKESHORE AND MID/UPR 50S INLAND.

THE MAIN CHALLENGE FOR THIS EVENING WILL FOCUS ON CONVECTIVE
CHANCES/COVERAGE...WHICH WILL CONTINUE THROUGH DAYBREAK FRI.
GUIDANCE HAS CONTINUED TO BACK OFF ON THE ARRIVAL OF PRECIP INTO THE
FORECAST AREA...WHICH SEEMS TO LINE UP RELATIVELY WELL WITH THE
CURRENT TRENDS. THE FRONTAL BOUNDARY WILL SLOWLY LIFT NORTH THIS
EVENING...BUT NOT EXPECTING MUCH IN THE WAY OF PRECIP UNTIL PERHAPS
AFT 04Z WITH A GRADUAL UPGLIDE OF PARCELS ALLOWS FOR MOISTENING.
SOME ELEVATED CONVECTION COULD BEGIN TO DEVELOP...ALTHOUGH NOT
EXPECTING MUCH COVERAGE OVERNIGHT. THE FOCUS FOR SLIGHTLY BETTER
PRECIP COVERAGE WILL REMAIN ALONG THE NORTHERN ROW OF COUNTIES IN
NORTHERN IL...HOWEVER CLOSER TO DAYBREAK FRI IT APPEARS SOME
PRECIP/CONVECTION COULD SAG SOUTHEAST AND CLIP NORTHEAST
IL/NORTHWEST IN BEFORE DISSIPATING.

WITH INCREASING CLOUD COVER TONIGHT...IT SHUD LIMIT HOW COOL TEMPS
BECOME. SO HAVE MADE ONLY MINOR ADJUSTMENTS TO THE TEMPS WITH
GENERALLY MID/UPR 60S FOR LOWS.

BEACHLER


FRIDAY AND FRIDAY NIGHT...
CLOSED UPPER LOW CURRENTLY NEAR THE COLORADO FRONT RANGE WILL SLOWLY
TRAVERSE EAST TOWARDS THE MID-MISSOURI VALLEY FRIDAY BECOMING AN
OPEN WAVE. AT THE SURFACE...BROAD AND WEAK SURFACE LOW WILL LIFT
INTO THE UPPER MIDWEST WHILE SOUTHWEST FLOW RAMPS UP THROUGH THE
COLUMN AS THE WARM FRONT LIFTS INTO THE CENTRAL GREAT LAKES. HEAT
AND HUMIDITY WILL MAKE A RETURN AS THIS OCCURS. H85 TEMPS WARMING TO
AROUND 18C WILL HELP SUPPORT MID/UPPER 80S DURING THE DAY
FRIDAY...AND SURFACE DEWPOINTS ARE PROGGED TO PUSH BACK INTO THE LOW
POSSIBLY MID 70S. THIS WILL RESULT IN MODERATE INSTABILITY
DEVELOPING DURING THE DAY...AND ONLY WEAKLY CAPPED DURING THE
AFTERNOON AS BROAD HEIGHT FALLS ASSOCIATED WITH THE UPPER WAVE START
TO OVERSPREAD THE AREA. THERE DOESNT SEEM TO BE MUCH FOCUS IN THE
LOWER LEVELS SO WOULD EXPECT ONLY SCATTERED THUNDERSTORM DEVELOPMENT
ACROSS THE REGION FRIDAY AFTERNOON/EVENING. UPPER WAVE BEGINS TO
MOVE INTO THE UPPER MIDWEST TOMORROW NIGHT AND BROAD WARM ADVECTION
OUT AHEAD DURING THE EVENING AND OVERNIGHT HOURS WILL HELP SUSTAIN
SOME CONVECTION LATE BUT WOULD EXPECT SOME NOCTURNAL DOWNTICK IN
ACTIVITY OVERNIGHT WITH THE LOW LEVEL JET FOCUSED WELL TO OUR NORTH.
GFS/NAM SEEM TO BE OVERDOING POPS MUCH OF THE DAY AND NIGHT
FRIDAY...AND OPTED TO LEAN CLOSER TO ECMWF THESE PERIODS.

THIS WEEKEND...
COLD FRONT WILL SWEEP ACROSS THE FORECAST AREA STARTING VERY EARLY
ON SATURDAY. WHILE NOT A FAVORABLE DIURNAL TIME...WE SHOULD STILL
HAVE SOME VERY MODEST INSTABILITY IN PLACE THAT WILL SUPPORT SOME
EARLY DAY THUNDERSTORMS ALONG THE FRONTAL BOUNDARY...WHICH WOULD BE
ABLE TO EXPAND IN COVERAGE AS THE DAY PROGRESSES AND THE BOUNDARY
LAYER WARMS. IN ADDITION...GUIDANCE SUGGESTS A SECOND SHORTWAVE
WILL WRAP INTO THE AREA THAT WILL PROVIDE ADDITIONAL BROAD SCALE
ASCENT. THE ECMWF IS ABOUT SIX HOURS SLOWER WITH THIS FEATURE
COMPARED TO THE NAM/GFS...WITH THE GEM A COMPROMISE...SO THERE
REMAINS SOME UNCERTAINTY IN TIMING. HIGH PRESSURE WILL BUILD IN
BEHIND THE FRONT SATURDAY NIGHT INTO SUNDAY AND WILL PROVIDE A
BRIEF RESPITE FROM THE ACTIVE WEATHER. THE ATMOSPHERE LOOKS TO
QUICKLY RELOAD HOWEVER WITH THERMAL RIDGE ONCE AGAIN STARTING TO
TILT BACK OVER THE AREA WITH H85 TEMPS AROUND 20C BY LATER IN THE
DAY SUNDAY.

NEXT WEEK...
AN ACTIVE PATTERN LOOKS TO PERSIST THROUGH AT LEAST THE MIDDLE OF
NEXT WEEK WITH A SERIES OF WAVES PUSHING ACROSS THE REGION BRINGING
CONTINUED PERIODIC CHANCES FOR SHOWERS AND THUNDERSTORMS. ANOTHER
COLD FRONT WILL PUSH ACROSS THE AREA LATER ON MONDAY WITH THE
FRONTAL BOUNDARY STALLING JUST TO OUR SOUTH. THEREAFTER...THERE IS
CONSIDERABLE UNCERTAINTY ON HOW FAR NORTH THE BOUNDARY MAY LIFT
WITH THE BEST PRECIP CHANCES FOCUSED IN THE VICINITY OF THE
FRONT AS A SERIES OF UPPER LEVEL DISTURBANCES PUSH ACROSS THE
AREA. PWATS REMAIN JUICY ALONG THE FRONT...AROUND TWO INCHES...AND
GUIDANCE SUGGESTS THAT THERE COULD BE SEVERAL CONVECTIVE COMPLEXES
NEXT WEEK WITH A CONCERN FOR HEAVY RAIN AND FLOODING SHOULD THIS
PAN OUT.

DEUBELBEISS

&&

.AVIATION...

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

* LIGHT EAST FLOW ARND 5-7KT THRU LATE AFTN...WINDS TURNING SE
  WITH SPEEDS INCREASING TO ARND 10KT.

* POSSIBLE SHOWERS DEVELOPING AFT 03Z...WITH BETTER COVERAGE AND
  POTENTIAL TSRA AFT 09Z THRU DAYBREAK FRI.

* WINDS CONTINUE TO TURN S FRI MORNING...WITH GUSTS DEVELOPING TO
  20KT MIDDAY FRI.

BEACHLER

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

VISIBLE IMAGERY THIS AFTN SHOWS SOME THIN MID-DECK CLOUDS LIFTING
NORTHEAST ACROSS NORTHERN IL. MUCH THICKER CLOUDS AND SPOTTY
SHOWERS REMAINS OVER IOWA. SFC WINDS CONTINUE TO BE EASTERLY
ACROSS MUCH OF THE REGION...WITH A GRADUAL TURN TOWARDS SOUTHEAST
ACROSS CENTRAL IL/IN. A FRONTAL BOUNDARY WILL BEGIN TO LIFT NORTH
THIS EVENING...WITH INCREASING MOISTURE. THIS COULD AID IN SEEING
ISOLATED SHOWERS AND POSSIBLY A THUNDERSTORM LATER TONIGHT.
GUIDANCE CONTINUES TO LEAN TOWARDS THE 10-14Z FRI TIMEFRAME FOR
THE BEST COVERAGE OF SHOWERS AND ISO-TSRA DEVELOPING...BUT
CONFIDENCE REMAINS LOW WITH COVERAGE OF THUNDER. SO AT THIS TIME
HAVE HELD ONTO JUST A PROB30 GROUP. WINDS BEHIND THE FRONTAL
BOUNDARY WILL BEGIN TO TURN SOUTH AROUND DAYBREAK FRI...WITH
BETTER MIXING DEVELOPING BY LATE MORNING/EARLY AFTN. GUIDANCE
CONTINUES TO SUGGEST CONVETION COULD BEGIN TO DEVELOP YET AGAIN
LATE MORNING THROUGH THE AFTERNOON...HOWEVER FEEL THIS IS A BIT
OVERDONE.

BEACHLER

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

* HIGH CONFIDENCE IN WIND DIR/SPEED AND TRENDS.

* HIGH CONFIDENCE IN ALL OTHER ELEMENTS THROUGH 04Z.

* MEDIUM CONFIDENCE IN TIMING OF PRECIP AND COVERAGE.

* LOW CONFIDENCE IN THUNDER CHANCES/COVERAGE.

BEACHLER

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

* FRIDAY NIGHT...CHANCE OF TSRA.
* SATURDAY...TSRA LIKELY.
* SUNDAY...SLIGHT CHANCE OF TSRA.
* MONDAY AND TUESDAY...CHANCE OF TSRA.
* WEDNESDAY...DRY/VFR.

&&

.MARINE...
123 PM CDT

SURFACE HIGH PRESSURE OVER THE GREAT LAKES REGION THIS AFTERNOON
WILL DRIFT TO THE EAST TONIGHT IN THE WAKE OF A DEPARTING UPPER
TROUGH OVER NEW ENGLAND/QUEBEC...AND AHEAD OF ANOTHER SURFACE TROUGH
AND WEAK COLD FRONT STRETCHING FROM FAR NORTHWEST ONTARIO TO THE
CENTRAL PLAINS. WINDS ON LAKE MICHIGAN WILL SHIFT TO THE SOUTHEAST
AND EVENTUALLY SOUTH HEADING INTO FRIDAY...AS AN AREA OF SURFACE LOW
PRESSURE DEVELOPS ACROSS THE PLAINS AND LIFTS ACROSS THE UPPER
MISSISSIPPI RIVER VALLEY. TIGHTENING OF THE PRESSURE GRADIENT
SOUTHEAST OF THE LOW TRACK WILL RESULT IN S-SE WINDS INCREASING INTO
THE 15-25 KT RANGE TONIGHT AND FRIDAY...GRADUALLY WEAKENING SATURDAY
AS THE LOW MOVES OFF TO THE NORTHEAST AND A WEAK COLD FRONT TRAILS
ACROSS THE LAKE FOLLOWED BY WEAK HIGH PRESSURE.

THIS COLD FRONT APPEARS TO DISSIPATE OR STALL ACROSS FAR SOUTHERN
LAKE MICHIGAN OR NORTHERN IL/IND LATE SATURDAY NIGHT OR EARLY SUNDAY
BEFORE DEVELOPING BACK TO THE NORTH AS A WARM FRONT SUNDAY NIGHT AS
ANOTHER AREA OF LOW PRESSURE DEVELOPS OVER THE PLAINS AND LIFTS
NORTHEAST INTO THE WESTERN/NORTHERN LAKES LATE SUNDAY NIGHT INTO
MONDAY. AGAIN...A TIGHTENING OF THE PRESSURE GRADIENT ALONG THE
SOUTHEAST PERIPHERY OF THE LOW TRACK IS EXPECTED WITH WINDS AGAIN
BECOMING SOUTHERLY INTO THE 15-25 KT RANGE ON MONDAY. ANOTHER
TRAILING COLD FRONT WILL PASS ACROSS THE LAKE MONDAY NIGHT...WITH
WEAK HIGH PRESSURE AND LIGHTER WINDS DEVELOPING TUESDAY.

RATZER

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KLOT 281937
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
237 PM CDT THU AUG 28 2014

.DISCUSSION...
230 PM CDT

VISIBLE IMAGERY THIS AFTERNOON SHOWS A MID/UPR LEVEL CLOUD DECK
LIFTING NORTHEAST ACROSS NORTHERN IL. REMNANTS FROM A MORNING
COMPLEX OF THUNDERSTORMS RESIDES OVER IOWA...WITH SOME CONVECTIVE
LOOK TO THE CLOUDS LINGERING INTO THIS AFTN. SFC TEMPS ACROSS THE
FORECAST AREA HAVE BEEN ABLE TO WARM INTO THE MID/UPR 70S. A FEW
POINTS SOUTH OF PONTIAC TO KANKAKEE HAVE PUSHED TO ARND 80 DEG...BUT
WITH THE LIGHT EASTERLY FLOW AT THE SFC SOME WEAK SUBSIDENCE HAS
BEEN NOTED WITH DEW POINTS BEING PUSHED INTO THE LOW 50S ALONG THE
LAKESHORE AND MID/UPR 50S INLAND.

THE MAIN CHALLENGE FOR THIS EVENING WILL FOCUS ON CONVECTIVE
CHANCES/COVERAGE...WHICH WILL CONTINUE THROUGH DAYBREAK FRI.
GUIDANCE HAS CONTINUED TO BACK OFF ON THE ARRIVAL OF PRECIP INTO THE
FORECAST AREA...WHICH SEEMS TO LINE UP RELATIVELY WELL WITH THE
CURRENT TRENDS. THE FRONTAL BOUNDARY WILL SLOWLY LIFT NORTH THIS
EVENING...BUT NOT EXPECTING MUCH IN THE WAY OF PRECIP UNTIL PERHAPS
AFT 04Z WITH A GRADUAL UPGLIDE OF PARCELS ALLOWS FOR MOISTENING.
SOME ELEVATED CONVECTION COULD BEGIN TO DEVELOP...ALTHOUGH NOT
EXPECTING MUCH COVERAGE OVERNIGHT. THE FOCUS FOR SLIGHTLY BETTER
PRECIP COVERAGE WILL REMAIN ALONG THE NORTHERN ROW OF COUNTIES IN
NORTHERN IL...HOWEVER CLOSER TO DAYBREAK FRI IT APPEARS SOME
PRECIP/CONVECTION COULD SAG SOUTHEAST AND CLIP NORTHEAST
IL/NORTHWEST IN BEFORE DISSIPATING.

WITH INCREASING CLOUD COVER TONIGHT...IT SHUD LIMIT HOW COOL TEMPS
BECOME. SO HAVE MADE ONLY MINOR ADJUSTMENTS TO THE TEMPS WITH
GENERALLY MID/UPR 60S FOR LOWS.

BEACHLER


FRIDAY AND FRIDAY NIGHT...
CLOSED UPPER LOW CURRENTLY NEAR THE COLORADO FRONT RANGE WILL SLOWLY
TRAVERSE EAST TOWARDS THE MID-MISSOURI VALLEY FRIDAY BECOMING AN
OPEN WAVE. AT THE SURFACE...BROAD AND WEAK SURFACE LOW WILL LIFT
INTO THE UPPER MIDWEST WHILE SOUTHWEST FLOW RAMPS UP THROUGH THE
COLUMN AS THE WARM FRONT LIFTS INTO THE CENTRAL GREAT LAKES. HEAT
AND HUMIDITY WILL MAKE A RETURN AS THIS OCCURS. H85 TEMPS WARMING TO
AROUND 18C WILL HELP SUPPORT MID/UPPER 80S DURING THE DAY
FRIDAY...AND SURFACE DEWPOINTS ARE PROGGED TO PUSH BACK INTO THE LOW
POSSIBLY MID 70S. THIS WILL RESULT IN MODERATE INSTABILITY
DEVELOPING DURING THE DAY...AND ONLY WEAKLY CAPPED DURING THE
AFTERNOON AS BROAD HEIGHT FALLS ASSOCIATED WITH THE UPPER WAVE START
TO OVERSPREAD THE AREA. THERE DOESNT SEEM TO BE MUCH FOCUS IN THE
LOWER LEVELS SO WOULD EXPECT ONLY SCATTERED THUNDERSTORM DEVELOPMENT
ACROSS THE REGION FRIDAY AFTERNOON/EVENING. UPPER WAVE BEGINS TO
MOVE INTO THE UPPER MIDWEST TOMORROW NIGHT AND BROAD WARM ADVECTION
OUT AHEAD DURING THE EVENING AND OVERNIGHT HOURS WILL HELP SUSTAIN
SOME CONVECTION LATE BUT WOULD EXPECT SOME NOCTURNAL DOWNTICK IN
ACTIVITY OVERNIGHT WITH THE LOW LEVEL JET FOCUSED WELL TO OUR NORTH.
GFS/NAM SEEM TO BE OVERDOING POPS MUCH OF THE DAY AND NIGHT
FRIDAY...AND OPTED TO LEAN CLOSER TO ECMWF THESE PERIODS.

THIS WEEKEND...
COLD FRONT WILL SWEEP ACROSS THE FORECAST AREA STARTING VERY EARLY
ON SATURDAY. WHILE NOT A FAVORABLE DIURNAL TIME...WE SHOULD STILL
HAVE SOME VERY MODEST INSTABILITY IN PLACE THAT WILL SUPPORT SOME
EARLY DAY THUNDERSTORMS ALONG THE FRONTAL BOUNDARY...WHICH WOULD BE
ABLE TO EXPAND IN COVERAGE AS THE DAY PROGRESSES AND THE BOUNDARY
LAYER WARMS. IN ADDITION...GUIDANCE SUGGESTS A SECOND SHORTWAVE
WILL WRAP INTO THE AREA THAT WILL PROVIDE ADDITIONAL BROAD SCALE
ASCENT. THE ECMWF IS ABOUT SIX HOURS SLOWER WITH THIS FEATURE
COMPARED TO THE NAM/GFS...WITH THE GEM A COMPROMISE...SO THERE
REMAINS SOME UNCERTAINTY IN TIMING. HIGH PRESSURE WILL BUILD IN
BEHIND THE FRONT SATURDAY NIGHT INTO SUNDAY AND WILL PROVIDE A
BRIEF RESPITE FROM THE ACTIVE WEATHER. THE ATMOSPHERE LOOKS TO
QUICKLY RELOAD HOWEVER WITH THERMAL RIDGE ONCE AGAIN STARTING TO
TILT BACK OVER THE AREA WITH H85 TEMPS AROUND 20C BY LATER IN THE
DAY SUNDAY.

NEXT WEEK...
AN ACTIVE PATTERN LOOKS TO PERSIST THROUGH AT LEAST THE MIDDLE OF
NEXT WEEK WITH A SERIES OF WAVES PUSHING ACROSS THE REGION BRINGING
CONTINUED PERIODIC CHANCES FOR SHOWERS AND THUNDERSTORMS. ANOTHER
COLD FRONT WILL PUSH ACROSS THE AREA LATER ON MONDAY WITH THE
FRONTAL BOUNDARY STALLING JUST TO OUR SOUTH. THEREAFTER...THERE IS
CONSIDERABLE UNCERTAINTY ON HOW FAR NORTH THE BOUNDARY MAY LIFT
WITH THE BEST PRECIP CHANCES FOCUSED IN THE VICINITY OF THE
FRONT AS A SERIES OF UPPER LEVEL DISTURBANCES PUSH ACROSS THE
AREA. PWATS REMAIN JUICY ALONG THE FRONT...AROUND TWO INCHES...AND
GUIDANCE SUGGESTS THAT THERE COULD BE SEVERAL CONVECTIVE COMPLEXES
NEXT WEEK WITH A CONCERN FOR HEAVY RAIN AND FLOODING SHOULD THIS
PAN OUT.

DEUBELBEISS

&&

.AVIATION...

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

* LIGHT EAST FLOW ARND 5-7KT THRU LATE AFTN...WINDS TURNING SE
  WITH SPEEDS INCREASING TO ARND 10KT.

* POSSIBLE SHOWERS DEVELOPING AFT 03Z...WITH BETTER COVERAGE AND
  POTENTIAL TSRA AFT 09Z THRU DAYBREAK FRI.

* WINDS CONTINUE TO TURN S FRI MORNING...WITH GUSTS DEVELOPING TO
  20KT MIDDAY FRI.

BEACHLER

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

VISIBLE IMAGERY THIS AFTN SHOWS SOME THIN MID-DECK CLOUDS LIFTING
NORTHEAST ACROSS NORTHERN IL. MUCH THICKER CLOUDS AND SPOTTY
SHOWERS REMAINS OVER IOWA. SFC WINDS CONTINUE TO BE EASTERLY
ACROSS MUCH OF THE REGION...WITH A GRADUAL TURN TOWARDS SOUTHEAST
ACROSS CENTRAL IL/IN. A FRONTAL BOUNDARY WILL BEGIN TO LIFT NORTH
THIS EVENING...WITH INCREASING MOISTURE. THIS COULD AID IN SEEING
ISOLATED SHOWERS AND POSSIBLY A THUNDERSTORM LATER TONIGHT.
GUIDANCE CONTINUES TO LEAN TOWARDS THE 10-14Z FRI TIMEFRAME FOR
THE BEST COVERAGE OF SHOWERS AND ISO-TSRA DEVELOPING...BUT
CONFIDENCE REMAINS LOW WITH COVERAGE OF THUNDER. SO AT THIS TIME
HAVE HELD ONTO JUST A PROB30 GROUP. WINDS BEHIND THE FRONTAL
BOUNDARY WILL BEGIN TO TURN SOUTH AROUND DAYBREAK FRI...WITH
BETTER MIXING DEVELOPING BY LATE MORNING/EARLY AFTN. GUIDANCE
CONTINUES TO SUGGEST CONVETION COULD BEGIN TO DEVELOP YET AGAIN
LATE MORNING THROUGH THE AFTERNOON...HOWEVER FEEL THIS IS A BIT
OVERDONE.

BEACHLER

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

* HIGH CONFIDENCE IN WIND DIR/SPEED AND TRENDS.

* HIGH CONFIDENCE IN ALL OTHER ELEMENTS THROUGH 04Z.

* MEDIUM CONFIDENCE IN TIMING OF PRECIP AND COVERAGE.

* LOW CONFIDENCE IN THUNDER CHANCES/COVERAGE.

BEACHLER

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

* FRIDAY NIGHT...CHANCE OF TSRA.
* SATURDAY...TSRA LIKELY.
* SUNDAY...SLIGHT CHANCE OF TSRA.
* MONDAY AND TUESDAY...CHANCE OF TSRA.
* WEDNESDAY...DRY/VFR.

&&

.MARINE...
123 PM CDT

SURFACE HIGH PRESSURE OVER THE GREAT LAKES REGION THIS AFTERNOON
WILL DRIFT TO THE EAST TONIGHT IN THE WAKE OF A DEPARTING UPPER
TROUGH OVER NEW ENGLAND/QUEBEC...AND AHEAD OF ANOTHER SURFACE TROUGH
AND WEAK COLD FRONT STRETCHING FROM FAR NORTHWEST ONTARIO TO THE
CENTRAL PLAINS. WINDS ON LAKE MICHIGAN WILL SHIFT TO THE SOUTHEAST
AND EVENTUALLY SOUTH HEADING INTO FRIDAY...AS AN AREA OF SURFACE LOW
PRESSURE DEVELOPS ACROSS THE PLAINS AND LIFTS ACROSS THE UPPER
MISSISSIPPI RIVER VALLEY. TIGHTENING OF THE PRESSURE GRADIENT
SOUTHEAST OF THE LOW TRACK WILL RESULT IN S-SE WINDS INCREASING INTO
THE 15-25 KT RANGE TONIGHT AND FRIDAY...GRADUALLY WEAKENING SATURDAY
AS THE LOW MOVES OFF TO THE NORTHEAST AND A WEAK COLD FRONT TRAILS
ACROSS THE LAKE FOLLOWED BY WEAK HIGH PRESSURE.

THIS COLD FRONT APPEARS TO DISSIPATE OR STALL ACROSS FAR SOUTHERN
LAKE MICHIGAN OR NORTHERN IL/IND LATE SATURDAY NIGHT OR EARLY SUNDAY
BEFORE DEVELOPING BACK TO THE NORTH AS A WARM FRONT SUNDAY NIGHT AS
ANOTHER AREA OF LOW PRESSURE DEVELOPS OVER THE PLAINS AND LIFTS
NORTHEAST INTO THE WESTERN/NORTHERN LAKES LATE SUNDAY NIGHT INTO
MONDAY. AGAIN...A TIGHTENING OF THE PRESSURE GRADIENT ALONG THE
SOUTHEAST PERIPHERY OF THE LOW TRACK IS EXPECTED WITH WINDS AGAIN
BECOMING SOUTHERLY INTO THE 15-25 KT RANGE ON MONDAY. ANOTHER
TRAILING COLD FRONT WILL PASS ACROSS THE LAKE MONDAY NIGHT...WITH
WEAK HIGH PRESSURE AND LIGHTER WINDS DEVELOPING TUESDAY.

RATZER

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 281823
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
123 PM CDT THU AUG 28 2014

.DISCUSSION...
310 AM CDT

MORE ACTIVE WEATHER WILL TRY TO RETURN TO THE AREA INTO THIS EVENING
FOR AT LEAST PART OF THE AREA FOLLOWING THE RATHER QUIET WEATHER
YESTERDAY. THE FORECAST WILL FOCUS ON TIMING AND COVERAGE OF
SHOWER/THUNDER CHANCES AS WELL AS TEMPERATURES...ESPECIALLY FRIDAY
WHEN THUNDERSTORMS COULD HINDER ANOTHER SUBSTANTIAL WARM UP. THE
MAIN FEATURE ON WATER VAPOR THIS MORNING IS AN UPPER LOW WHICH HAS
BEEN SLOWLY SPINNING EASTWARD ACROSS THE WESTERN U.S. THE LOW IS NOW
MAKING SLIGHTLY FASTER EASTWARD PROGRESS ACROSS COLORADO AND WYOMING
AND AMPLIFYING A RIDGE AHEAD OF IT INTO THE MID AND UPPER
MISSISSIPPI RIVER VALLEY. SEVERAL SMALLER SCALE SHORTWAVES ARE
MOVING NORTHEASTWARD AROUND THE BASE OF THE LOW AND LIFTING INTO
KANSAS AND NEBRASKA. LOOKING FURTHER NORTHWEST...A TROUGH AXIS
EXTENDS SOUTHWESTWARD FROM NORTHERN ALBERTA ACROSS CENTRAL BRITISH
COLUMBIA AND OVER THE PACIFIC WHILE A CLOSED UPPER IS DIGGING
SOUTHEASTWARD OFF THE SOUTHERN ALASKA COAST. AT THE SURFACE...HIGH
PRESSURE IS CENTERED OVER LAKE SUPERIOR WHILE A FRONTAL BOUNDARY
EXTENDS FROM THE MAINE COAST DOWN THE OHIO VALLEY AND BACK INTO THE
CENTRAL PLAINS. SURFACE LOW PRESSURE IS ORGANIZING ACROSS THE
CENTRAL AND SOUTHERN HIGH PLAINS IN CONJUNCTION WITH THE APPROACHING
UPPER LOW.

TODAY AND TONIGHT...THE UPPER RIDGE AXIS WILL BE CRESTING THE AREA
THIS MORNING AS THE ENTIRE RIDGE BROADENS INTO FRIDAY. THE SURFACE
HIGH WILL ACCELERATE EASTWARD AND BE CENTERED OVER THE LOWER ST.
LAWRENCE RIVER VALLEY BY FRIDAY. THE UPPER LOW WILL PUSH INTO THE
CENTRAL PLAINS WHILE THE ATTENDANT SURFACE LOW MOVES NORTHEASTWARD
INTO MINNESOTA TONIGHT. WARM ADVECTION AHEAD OF THE ADVANCING UPPER
TROUGH IS GENERATING SHOWERS AND THUNDERSTORMS ACROSS MUCH OF
NEBRASKA INTO SOUTHERN IOWA AND NORTHERN MISSOURI IN CONJUNCTION
WITH SEVERAL SHORTWAVES. THE WARM ADVECTION WILL SPREAD
NORTHEASTWARD WITH A SURFACE WARM FRONT ALSO MOVING NORTHEASTWARD
AND CROSSING THE LOCAL AREA TODAY. THE FOCUS OF THE ASCENT WILL BE
TO THE WEST AND NORTHWEST OF THE AREA THROUGH THE MORNING KEEPING
THE BULK OF IF NOT ALL OF THE SHOWER ACTIVITY OUT OF THE CWA.
HOWEVER...HAVE BEEN SEEING A FEW LIGHT SPRINKLES/SHOWERS ALONG AND
SOUTH OF THE SOUTHERN CWA BORDER THIS MORNING AS WELL LIKELY IN
CONJUNCTION WITH A SUBTLE MID LEVEL WAVE. EXPECT THESE TO SHIFT EAST
OF THE AREA THROUGH DAYBREAK. PRECIP CHANCES WILL INCREASE THIS
AFTERNOON HOWEVER...MAINLY ACROSS THE WESTERN HALF OF THE AREA AND
IT IS POSSIBLE THIS COULD BE A LITTLE FAST. A BETTER PUSH OF THETA-E
AND INSTABILITY MOVE ACROSS THIS EVENING...ESPECIALLY ACROSS
NORTHERN AREAS SO MAY SEE THE PEAK OF THE ACTIVITY DURING THIS TIME.
SOUTHERN AND EASTERN AREAS MAY END UP STAYING DRY FOR MUCH OF THIS
PERIOD. HIGHS TODAY WILL RANGE FROM THE UPPER 70S NORTH TO LOWER 80S
SOUTH WITH A FAIR AMOUNT OF CLOUD COVER EXPECTED.

FRIDAY...FRIDAY WILL BE A TRICKY FORECAST WITH THE POTENTIAL
FOR A NOTICEABLE WARM UP BUT ALSO A POTENTIAL TO HAVE THAT SPOILED
BY THUNDERSTORMS. THE WESTERN PERIPHERY OF THE MID LEVEL WARM AXIS
WILL BE OVER THE AREA WITH A SOUTH TO SOUTHWEST SURFACE WIND IN
PLACE. H85/H92 HIGH TEMP CLIMATOLOGY SHOWS STRONG SUPPORT FOR HIGHS
NEAR 90 WITH VALUES OF 18/23C. LATEST GUIDANCE SHOWS CONVECTION
DEVELOPING TO THE SOUTH OF THE AREA FRIDAY MORNING AND LIFTING
NORTHWARD ON THE WESTERN FLANK OF THE RIDGE AND CROSSING THE AREA
INTO THE AFTERNOON. TOUGH TO SAY IF THIS WILL BE THE CASE BUT THE
PATTERN IS CERTAINLY SUCH THAT THIS COULD OCCUR SO WILL CONTINUE
WITH POPS PRIMARILY FRIDAY AFTERNOON AND STICK WITH HIGHS IN THE MID
TO UPPER 80S FOR NOW.

FRIDAY NIGHT THROUGH MID NEXT WEEK...LARGER SCALE TROUGHING WILL BE
BUILDING INTO WESTERN NORTH AMERICA INTO SATURDAY WHICH WILL HELP
KICK THE CENTRAL PLAINS UPPER LOW NORTHEASTWARD. ANOTHER SURFACE LOW
WILL DEVELOP AND TRACK NORTHEASTWARD INTO WISCONSIN BY SATURDAY
MORNING. LATE FRIDAY NIGHT THROUGH SATURDAY MORNING WILL PROBABLY
END UP BEING THE BEST CHANCE FOR SHOWERS AND THUNDERSTORMS AS THIS
OCCURS. MORNING FRONTAL PASSAGE IS NOT ALL THAT FAVORABLE FOR SEVERE
WEATHER BUT DO EXPECT THAT SOME SORT OF LINE OR COMPLEX OF STORMS
WOULD AFFECT THE AREA...BRINGING HEAVY RAINFALL IF NOTHING ELSE.
HIGH PRESSURE RIDGING BUILDS IN NORTH OF THE AREA BEHIND THE
DEPARTING LOW. THE BIGGEST ISSUE WITH THIS HAS BEEN TIMING WITH THE
LATEST GUIDANCE FASTER THAN EARLIER RUNS KEEPING THE PRECIP CONFINED
TO SATURDAY MORNING. WILL ADJUST POPS TO BETTER FIT THIS BUT WILL
KEEP CHANCE POPS FOR SATURDAY AFTERNOON FOR NOW. H85 TEMPS COOL
BEHIND THE SYSTEM KEEPING HIGHS IN THE UPPER 70S AND LOWER 80S WITH
SLIGHTLY WARMER TEMPS SUNDAY. THE WESTERN TROUGH WILL AMPLIFY AS IT
MOVES INTO THE NORTHERN PLAINS TAKING A SURFACE LOW NORTHEAST FROM
THE NORTHERN PLAINS TO NORTHWESTERN ONTARIO LATER SUNDAY. TIMING
WILL ONCE AGAIN NEED TO BE BETTER ASSESSED BUT THIS SYSTEM WILL
BRING ANOTHER COOL FRONT ACROSS THE AREA SOME TIME MONDAY. A LOWER
AMPLITUDE UPPER FLOW BECOMES ESTABLISHED AS THE TROUGH DEPARTS WITH
HIGH PRESSURE BUILDING IN AT THE SURFACE. WIDESPREAD POP CHANCES
LOOK LOW INTO MIDWEEK BUT THE FAIRLY ZONAL FLOW WILL BE SUPPORTIVE
OF WEAK PASSING SHORTWAVES WHICH COULD TRIGGER SOME SPOTTY PRECIP AT
TIMES. HIGHS GENERALLY LOOK TO BE AROUND 80 BUT THE FLOW WILL LIKELY
BE WEAK ENOUGH TO SUPPORT LAKE COOLING AS LONG AS THE SURFACE HIGH
IS NEARBY.

MDB

&&

.AVIATION...

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

* LIGHT EAST FLOW ARND 5-7KT THRU LATE AFTN...WINDS TURNING SE
  WITH SPEEDS INCREASING TO ARND 10KT.

* POSSIBLE SHOWERS DEVELOPING AFT 03Z...WITH BETTER COVERAGE AND
  POTENTIAL TSRA AFT 09Z THRU DAYBREAK FRI.

* WINDS CONTINUE TO TURN S FRI MORNING...WITH GUSTS DEVELOPING TO
  20KT MIDDAY FRI.

BEACHLER

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

VISIBLE IMAGERY THIS AFTN SHOWS SOME THIN MID-DECK CLOUDS LIFTING
NORTHEAST ACROSS NORTHERN IL. MUCH THICKER CLOUDS AND SPOTTY
SHOWERS REMAINS OVER IOWA. SFC WINDS CONTINUE TO BE EASTERLY
ACROSS MUCH OF THE REGION...WITH A GRADUAL TURN TOWARDS SOUTHEAST
ACROSS CENTRAL IL/IN. A FRONTAL BOUNDARY WILL BEGIN TO LIFT NORTH
THIS EVENING...WITH INCREASING MOISTURE. THIS COULD AID IN SEEING
ISOLATED SHOWERS AND POSSIBLY A THUNDERSTORM LATER TONIGHT.
GUIDANCE CONTINUES TO LEAN TOWARDS THE 10-14Z FRI TIMEFRAME FOR
THE BEST COVERAGE OF SHOWERS AND ISO-TSRA DEVELOPING...BUT
CONFIDENCE REMAINS LOW WITH COVERAGE OF THUNDER. SO AT THIS TIME
HAVE HELD ONTO JUST A PROB30 GROUP. WINDS BEHIND THE FRONTAL
BOUNDARY WILL BEGIN TO TURN SOUTH AROUND DAYBREAK FRI...WITH
BETTER MIXING DEVELOPING BY LATE MORNING/EARLY AFTN. GUIDANCE
CONTINUES TO SUGGEST CONVETION COULD BEGIN TO DEVELOP YET AGAIN
LATE MORNING THROUGH THE AFTERNOON...HOWEVER FEEL THIS IS A BIT
OVERDONE.

BEACHLER

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

* HIGH CONFIDENCE IN WIND DIR/SPEED AND TRENDS.

* HIGH CONFIDENCE IN ALL OTHER ELEMENTS THROUGH 04Z.

* MEDIUM CONFIDENCE IN TIMING OF PRECIP AND COVERAGE.

* LOW CONFIDENCE IN THUNDER CHANCES/COVERAGE.

BEACHLER

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

* FRIDAY NIGHT...CHANCE OF TSRA.
* SATURDAY...TSRA LIKELY.
* SUNDAY...SLIGHT CHANCE OF TSRA.
* MONDAY AND TUESDAY...CHANCE OF TSRA.
* WEDNESDAY...DRY/VFR.

&&

.MARINE...
123 PM CDT

SURFACE HIGH PRESSURE OVER THE GREAT LAKES REGION THIS AFTERNOON
WILL DRIFT TO THE EAST TONIGHT IN THE WAKE OF A DEPARTING UPPER
TROUGH OVER NEW ENGLAND/QUEBEC...AND AHEAD OF ANOTHER SURFACE TROUGH
AND WEAK COLD FRONT STRETCHING FROM FAR NORTHWEST ONTARIO TO THE
CENTRAL PLAINS. WINDS ON LAKE MICHIGAN WILL SHIFT TO THE SOUTHEAST
AND EVENTUALLY SOUTH HEADING INTO FRIDAY...AS AN AREA OF SURFACE LOW
PRESSURE DEVELOPS ACROSS THE PLAINS AND LIFTS ACROSS THE UPPER
MISSISSIPPI RIVER VALLEY. TIGHTENING OF THE PRESSURE GRADIENT
SOUTHEAST OF THE LOW TRACK WILL RESULT IN S-SE WINDS INCREASING INTO
THE 15-25 KT RANGE TONIGHT AND FRIDAY...GRADUALLY WEAKENING SATURDAY
AS THE LOW MOVES OFF TO THE NORTHEAST AND A WEAK COLD FRONT TRAILS
ACROSS THE LAKE FOLLOWED BY WEAK HIGH PRESSURE.

THIS COLD FRONT APPEARS TO DISSIPATE OR STALL ACROSS FAR SOUTHERN
LAKE MICHIGAN OR NORTHERN IL/IND LATE SATURDAY NIGHT OR EARLY SUNDAY
BEFORE DEVELOPING BACK TO THE NORTH AS A WARM FRONT SUNDAY NIGHT AS
ANOTHER AREA OF LOW PRESSURE DEVELOPS OVER THE PLAINS AND LIFTS
NORTHEAST INTO THE WESTERN/NORTHERN LAKES LATE SUNDAY NIGHT INTO
MONDAY. AGAIN...A TIGHTENING OF THE PRESSURE GRADIENT ALONG THE
SOUTHEAST PERIPHERY OF THE LOW TRACK IS EXPECTED WITH WINDS AGAIN
BECOMING SOUTHERLY INTO THE 15-25 KT RANGE ON MONDAY. ANOTHER
TRAILING COLD FRONT WILL PASS ACROSS THE LAKE MONDAY NIGHT...WITH
WEAK HIGH PRESSURE AND LIGHTER WINDS DEVELOPING TUESDAY.

RATZER

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO








000
FXUS63 KLOT 281823
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
123 PM CDT THU AUG 28 2014

.DISCUSSION...
310 AM CDT

MORE ACTIVE WEATHER WILL TRY TO RETURN TO THE AREA INTO THIS EVENING
FOR AT LEAST PART OF THE AREA FOLLOWING THE RATHER QUIET WEATHER
YESTERDAY. THE FORECAST WILL FOCUS ON TIMING AND COVERAGE OF
SHOWER/THUNDER CHANCES AS WELL AS TEMPERATURES...ESPECIALLY FRIDAY
WHEN THUNDERSTORMS COULD HINDER ANOTHER SUBSTANTIAL WARM UP. THE
MAIN FEATURE ON WATER VAPOR THIS MORNING IS AN UPPER LOW WHICH HAS
BEEN SLOWLY SPINNING EASTWARD ACROSS THE WESTERN U.S. THE LOW IS NOW
MAKING SLIGHTLY FASTER EASTWARD PROGRESS ACROSS COLORADO AND WYOMING
AND AMPLIFYING A RIDGE AHEAD OF IT INTO THE MID AND UPPER
MISSISSIPPI RIVER VALLEY. SEVERAL SMALLER SCALE SHORTWAVES ARE
MOVING NORTHEASTWARD AROUND THE BASE OF THE LOW AND LIFTING INTO
KANSAS AND NEBRASKA. LOOKING FURTHER NORTHWEST...A TROUGH AXIS
EXTENDS SOUTHWESTWARD FROM NORTHERN ALBERTA ACROSS CENTRAL BRITISH
COLUMBIA AND OVER THE PACIFIC WHILE A CLOSED UPPER IS DIGGING
SOUTHEASTWARD OFF THE SOUTHERN ALASKA COAST. AT THE SURFACE...HIGH
PRESSURE IS CENTERED OVER LAKE SUPERIOR WHILE A FRONTAL BOUNDARY
EXTENDS FROM THE MAINE COAST DOWN THE OHIO VALLEY AND BACK INTO THE
CENTRAL PLAINS. SURFACE LOW PRESSURE IS ORGANIZING ACROSS THE
CENTRAL AND SOUTHERN HIGH PLAINS IN CONJUNCTION WITH THE APPROACHING
UPPER LOW.

TODAY AND TONIGHT...THE UPPER RIDGE AXIS WILL BE CRESTING THE AREA
THIS MORNING AS THE ENTIRE RIDGE BROADENS INTO FRIDAY. THE SURFACE
HIGH WILL ACCELERATE EASTWARD AND BE CENTERED OVER THE LOWER ST.
LAWRENCE RIVER VALLEY BY FRIDAY. THE UPPER LOW WILL PUSH INTO THE
CENTRAL PLAINS WHILE THE ATTENDANT SURFACE LOW MOVES NORTHEASTWARD
INTO MINNESOTA TONIGHT. WARM ADVECTION AHEAD OF THE ADVANCING UPPER
TROUGH IS GENERATING SHOWERS AND THUNDERSTORMS ACROSS MUCH OF
NEBRASKA INTO SOUTHERN IOWA AND NORTHERN MISSOURI IN CONJUNCTION
WITH SEVERAL SHORTWAVES. THE WARM ADVECTION WILL SPREAD
NORTHEASTWARD WITH A SURFACE WARM FRONT ALSO MOVING NORTHEASTWARD
AND CROSSING THE LOCAL AREA TODAY. THE FOCUS OF THE ASCENT WILL BE
TO THE WEST AND NORTHWEST OF THE AREA THROUGH THE MORNING KEEPING
THE BULK OF IF NOT ALL OF THE SHOWER ACTIVITY OUT OF THE CWA.
HOWEVER...HAVE BEEN SEEING A FEW LIGHT SPRINKLES/SHOWERS ALONG AND
SOUTH OF THE SOUTHERN CWA BORDER THIS MORNING AS WELL LIKELY IN
CONJUNCTION WITH A SUBTLE MID LEVEL WAVE. EXPECT THESE TO SHIFT EAST
OF THE AREA THROUGH DAYBREAK. PRECIP CHANCES WILL INCREASE THIS
AFTERNOON HOWEVER...MAINLY ACROSS THE WESTERN HALF OF THE AREA AND
IT IS POSSIBLE THIS COULD BE A LITTLE FAST. A BETTER PUSH OF THETA-E
AND INSTABILITY MOVE ACROSS THIS EVENING...ESPECIALLY ACROSS
NORTHERN AREAS SO MAY SEE THE PEAK OF THE ACTIVITY DURING THIS TIME.
SOUTHERN AND EASTERN AREAS MAY END UP STAYING DRY FOR MUCH OF THIS
PERIOD. HIGHS TODAY WILL RANGE FROM THE UPPER 70S NORTH TO LOWER 80S
SOUTH WITH A FAIR AMOUNT OF CLOUD COVER EXPECTED.

FRIDAY...FRIDAY WILL BE A TRICKY FORECAST WITH THE POTENTIAL
FOR A NOTICEABLE WARM UP BUT ALSO A POTENTIAL TO HAVE THAT SPOILED
BY THUNDERSTORMS. THE WESTERN PERIPHERY OF THE MID LEVEL WARM AXIS
WILL BE OVER THE AREA WITH A SOUTH TO SOUTHWEST SURFACE WIND IN
PLACE. H85/H92 HIGH TEMP CLIMATOLOGY SHOWS STRONG SUPPORT FOR HIGHS
NEAR 90 WITH VALUES OF 18/23C. LATEST GUIDANCE SHOWS CONVECTION
DEVELOPING TO THE SOUTH OF THE AREA FRIDAY MORNING AND LIFTING
NORTHWARD ON THE WESTERN FLANK OF THE RIDGE AND CROSSING THE AREA
INTO THE AFTERNOON. TOUGH TO SAY IF THIS WILL BE THE CASE BUT THE
PATTERN IS CERTAINLY SUCH THAT THIS COULD OCCUR SO WILL CONTINUE
WITH POPS PRIMARILY FRIDAY AFTERNOON AND STICK WITH HIGHS IN THE MID
TO UPPER 80S FOR NOW.

FRIDAY NIGHT THROUGH MID NEXT WEEK...LARGER SCALE TROUGHING WILL BE
BUILDING INTO WESTERN NORTH AMERICA INTO SATURDAY WHICH WILL HELP
KICK THE CENTRAL PLAINS UPPER LOW NORTHEASTWARD. ANOTHER SURFACE LOW
WILL DEVELOP AND TRACK NORTHEASTWARD INTO WISCONSIN BY SATURDAY
MORNING. LATE FRIDAY NIGHT THROUGH SATURDAY MORNING WILL PROBABLY
END UP BEING THE BEST CHANCE FOR SHOWERS AND THUNDERSTORMS AS THIS
OCCURS. MORNING FRONTAL PASSAGE IS NOT ALL THAT FAVORABLE FOR SEVERE
WEATHER BUT DO EXPECT THAT SOME SORT OF LINE OR COMPLEX OF STORMS
WOULD AFFECT THE AREA...BRINGING HEAVY RAINFALL IF NOTHING ELSE.
HIGH PRESSURE RIDGING BUILDS IN NORTH OF THE AREA BEHIND THE
DEPARTING LOW. THE BIGGEST ISSUE WITH THIS HAS BEEN TIMING WITH THE
LATEST GUIDANCE FASTER THAN EARLIER RUNS KEEPING THE PRECIP CONFINED
TO SATURDAY MORNING. WILL ADJUST POPS TO BETTER FIT THIS BUT WILL
KEEP CHANCE POPS FOR SATURDAY AFTERNOON FOR NOW. H85 TEMPS COOL
BEHIND THE SYSTEM KEEPING HIGHS IN THE UPPER 70S AND LOWER 80S WITH
SLIGHTLY WARMER TEMPS SUNDAY. THE WESTERN TROUGH WILL AMPLIFY AS IT
MOVES INTO THE NORTHERN PLAINS TAKING A SURFACE LOW NORTHEAST FROM
THE NORTHERN PLAINS TO NORTHWESTERN ONTARIO LATER SUNDAY. TIMING
WILL ONCE AGAIN NEED TO BE BETTER ASSESSED BUT THIS SYSTEM WILL
BRING ANOTHER COOL FRONT ACROSS THE AREA SOME TIME MONDAY. A LOWER
AMPLITUDE UPPER FLOW BECOMES ESTABLISHED AS THE TROUGH DEPARTS WITH
HIGH PRESSURE BUILDING IN AT THE SURFACE. WIDESPREAD POP CHANCES
LOOK LOW INTO MIDWEEK BUT THE FAIRLY ZONAL FLOW WILL BE SUPPORTIVE
OF WEAK PASSING SHORTWAVES WHICH COULD TRIGGER SOME SPOTTY PRECIP AT
TIMES. HIGHS GENERALLY LOOK TO BE AROUND 80 BUT THE FLOW WILL LIKELY
BE WEAK ENOUGH TO SUPPORT LAKE COOLING AS LONG AS THE SURFACE HIGH
IS NEARBY.

MDB

&&

.AVIATION...

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

* LIGHT EAST FLOW ARND 5-7KT THRU LATE AFTN...WINDS TURNING SE
  WITH SPEEDS INCREASING TO ARND 10KT.

* POSSIBLE SHOWERS DEVELOPING AFT 03Z...WITH BETTER COVERAGE AND
  POTENTIAL TSRA AFT 09Z THRU DAYBREAK FRI.

* WINDS CONTINUE TO TURN S FRI MORNING...WITH GUSTS DEVELOPING TO
  20KT MIDDAY FRI.

BEACHLER

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

VISIBLE IMAGERY THIS AFTN SHOWS SOME THIN MID-DECK CLOUDS LIFTING
NORTHEAST ACROSS NORTHERN IL. MUCH THICKER CLOUDS AND SPOTTY
SHOWERS REMAINS OVER IOWA. SFC WINDS CONTINUE TO BE EASTERLY
ACROSS MUCH OF THE REGION...WITH A GRADUAL TURN TOWARDS SOUTHEAST
ACROSS CENTRAL IL/IN. A FRONTAL BOUNDARY WILL BEGIN TO LIFT NORTH
THIS EVENING...WITH INCREASING MOISTURE. THIS COULD AID IN SEEING
ISOLATED SHOWERS AND POSSIBLY A THUNDERSTORM LATER TONIGHT.
GUIDANCE CONTINUES TO LEAN TOWARDS THE 10-14Z FRI TIMEFRAME FOR
THE BEST COVERAGE OF SHOWERS AND ISO-TSRA DEVELOPING...BUT
CONFIDENCE REMAINS LOW WITH COVERAGE OF THUNDER. SO AT THIS TIME
HAVE HELD ONTO JUST A PROB30 GROUP. WINDS BEHIND THE FRONTAL
BOUNDARY WILL BEGIN TO TURN SOUTH AROUND DAYBREAK FRI...WITH
BETTER MIXING DEVELOPING BY LATE MORNING/EARLY AFTN. GUIDANCE
CONTINUES TO SUGGEST CONVETION COULD BEGIN TO DEVELOP YET AGAIN
LATE MORNING THROUGH THE AFTERNOON...HOWEVER FEEL THIS IS A BIT
OVERDONE.

BEACHLER

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

* HIGH CONFIDENCE IN WIND DIR/SPEED AND TRENDS.

* HIGH CONFIDENCE IN ALL OTHER ELEMENTS THROUGH 04Z.

* MEDIUM CONFIDENCE IN TIMING OF PRECIP AND COVERAGE.

* LOW CONFIDENCE IN THUNDER CHANCES/COVERAGE.

BEACHLER

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

* FRIDAY NIGHT...CHANCE OF TSRA.
* SATURDAY...TSRA LIKELY.
* SUNDAY...SLIGHT CHANCE OF TSRA.
* MONDAY AND TUESDAY...CHANCE OF TSRA.
* WEDNESDAY...DRY/VFR.

&&

.MARINE...
123 PM CDT

SURFACE HIGH PRESSURE OVER THE GREAT LAKES REGION THIS AFTERNOON
WILL DRIFT TO THE EAST TONIGHT IN THE WAKE OF A DEPARTING UPPER
TROUGH OVER NEW ENGLAND/QUEBEC...AND AHEAD OF ANOTHER SURFACE TROUGH
AND WEAK COLD FRONT STRETCHING FROM FAR NORTHWEST ONTARIO TO THE
CENTRAL PLAINS. WINDS ON LAKE MICHIGAN WILL SHIFT TO THE SOUTHEAST
AND EVENTUALLY SOUTH HEADING INTO FRIDAY...AS AN AREA OF SURFACE LOW
PRESSURE DEVELOPS ACROSS THE PLAINS AND LIFTS ACROSS THE UPPER
MISSISSIPPI RIVER VALLEY. TIGHTENING OF THE PRESSURE GRADIENT
SOUTHEAST OF THE LOW TRACK WILL RESULT IN S-SE WINDS INCREASING INTO
THE 15-25 KT RANGE TONIGHT AND FRIDAY...GRADUALLY WEAKENING SATURDAY
AS THE LOW MOVES OFF TO THE NORTHEAST AND A WEAK COLD FRONT TRAILS
ACROSS THE LAKE FOLLOWED BY WEAK HIGH PRESSURE.

THIS COLD FRONT APPEARS TO DISSIPATE OR STALL ACROSS FAR SOUTHERN
LAKE MICHIGAN OR NORTHERN IL/IND LATE SATURDAY NIGHT OR EARLY SUNDAY
BEFORE DEVELOPING BACK TO THE NORTH AS A WARM FRONT SUNDAY NIGHT AS
ANOTHER AREA OF LOW PRESSURE DEVELOPS OVER THE PLAINS AND LIFTS
NORTHEAST INTO THE WESTERN/NORTHERN LAKES LATE SUNDAY NIGHT INTO
MONDAY. AGAIN...A TIGHTENING OF THE PRESSURE GRADIENT ALONG THE
SOUTHEAST PERIPHERY OF THE LOW TRACK IS EXPECTED WITH WINDS AGAIN
BECOMING SOUTHERLY INTO THE 15-25 KT RANGE ON MONDAY. ANOTHER
TRAILING COLD FRONT WILL PASS ACROSS THE LAKE MONDAY NIGHT...WITH
WEAK HIGH PRESSURE AND LIGHTER WINDS DEVELOPING TUESDAY.

RATZER

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO







000
FXUS63 KLOT 281805
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
105 PM CDT THU AUG 28 2014

.DISCUSSION...
310 AM CDT

MORE ACTIVE WEATHER WILL TRY TO RETURN TO THE AREA INTO THIS EVENING
FOR AT LEAST PART OF THE AREA FOLLOWING THE RATHER QUIET WEATHER
YESTERDAY. THE FORECAST WILL FOCUS ON TIMING AND COVERAGE OF
SHOWER/THUNDER CHANCES AS WELL AS TEMPERATURES...ESPECIALLY FRIDAY
WHEN THUNDERSTORMS COULD HINDER ANOTHER SUBSTANTIAL WARM UP. THE
MAIN FEATURE ON WATER VAPOR THIS MORNING IS AN UPPER LOW WHICH HAS
BEEN SLOWLY SPINNING EASTWARD ACROSS THE WESTERN U.S. THE LOW IS NOW
MAKING SLIGHTLY FASTER EASTWARD PROGRESS ACROSS COLORADO AND WYOMING
AND AMPLIFYING A RIDGE AHEAD OF IT INTO THE MID AND UPPER
MISSISSIPPI RIVER VALLEY. SEVERAL SMALLER SCALE SHORTWAVES ARE
MOVING NORTHEASTWARD AROUND THE BASE OF THE LOW AND LIFTING INTO
KANSAS AND NEBRASKA. LOOKING FURTHER NORTHWEST...A TROUGH AXIS
EXTENDS SOUTHWESTWARD FROM NORTHERN ALBERTA ACROSS CENTRAL BRITISH
COLUMBIA AND OVER THE PACIFIC WHILE A CLOSED UPPER IS DIGGING
SOUTHEASTWARD OFF THE SOUTHERN ALASKA COAST. AT THE SURFACE...HIGH
PRESSURE IS CENTERED OVER LAKE SUPERIOR WHILE A FRONTAL BOUNDARY
EXTENDS FROM THE MAINE COAST DOWN THE OHIO VALLEY AND BACK INTO THE
CENTRAL PLAINS. SURFACE LOW PRESSURE IS ORGANIZING ACROSS THE
CENTRAL AND SOUTHERN HIGH PLAINS IN CONJUNCTION WITH THE APPROACHING
UPPER LOW.

TODAY AND TONIGHT...THE UPPER RIDGE AXIS WILL BE CRESTING THE AREA
THIS MORNING AS THE ENTIRE RIDGE BROADENS INTO FRIDAY. THE SURFACE
HIGH WILL ACCELERATE EASTWARD AND BE CENTERED OVER THE LOWER ST.
LAWRENCE RIVER VALLEY BY FRIDAY. THE UPPER LOW WILL PUSH INTO THE
CENTRAL PLAINS WHILE THE ATTENDANT SURFACE LOW MOVES NORTHEASTWARD
INTO MINNESOTA TONIGHT. WARM ADVECTION AHEAD OF THE ADVANCING UPPER
TROUGH IS GENERATING SHOWERS AND THUNDERSTORMS ACROSS MUCH OF
NEBRASKA INTO SOUTHERN IOWA AND NORTHERN MISSOURI IN CONJUNCTION
WITH SEVERAL SHORTWAVES. THE WARM ADVECTION WILL SPREAD
NORTHEASTWARD WITH A SURFACE WARM FRONT ALSO MOVING NORTHEASTWARD
AND CROSSING THE LOCAL AREA TODAY. THE FOCUS OF THE ASCENT WILL BE
TO THE WEST AND NORTHWEST OF THE AREA THROUGH THE MORNING KEEPING
THE BULK OF IF NOT ALL OF THE SHOWER ACTIVITY OUT OF THE CWA.
HOWEVER...HAVE BEEN SEEING A FEW LIGHT SPRINKLES/SHOWERS ALONG AND
SOUTH OF THE SOUTHERN CWA BORDER THIS MORNING AS WELL LIKELY IN
CONJUNCTION WITH A SUBTLE MID LEVEL WAVE. EXPECT THESE TO SHIFT EAST
OF THE AREA THROUGH DAYBREAK. PRECIP CHANCES WILL INCREASE THIS
AFTERNOON HOWEVER...MAINLY ACROSS THE WESTERN HALF OF THE AREA AND
IT IS POSSIBLE THIS COULD BE A LITTLE FAST. A BETTER PUSH OF THETA-E
AND INSTABILITY MOVE ACROSS THIS EVENING...ESPECIALLY ACROSS
NORTHERN AREAS SO MAY SEE THE PEAK OF THE ACTIVITY DURING THIS TIME.
SOUTHERN AND EASTERN AREAS MAY END UP STAYING DRY FOR MUCH OF THIS
PERIOD. HIGHS TODAY WILL RANGE FROM THE UPPER 70S NORTH TO LOWER 80S
SOUTH WITH A FAIR AMOUNT OF CLOUD COVER EXPECTED.

FRIDAY...FRIDAY WILL BE A TRICKY FORECAST WITH THE POTENTIAL
FOR A NOTICEABLE WARM UP BUT ALSO A POTENTIAL TO HAVE THAT SPOILED
BY THUNDERSTORMS. THE WESTERN PERIPHERY OF THE MID LEVEL WARM AXIS
WILL BE OVER THE AREA WITH A SOUTH TO SOUTHWEST SURFACE WIND IN
PLACE. H85/H92 HIGH TEMP CLIMATOLOGY SHOWS STRONG SUPPORT FOR HIGHS
NEAR 90 WITH VALUES OF 18/23C. LATEST GUIDANCE SHOWS CONVECTION
DEVELOPING TO THE SOUTH OF THE AREA FRIDAY MORNING AND LIFTING
NORTHWARD ON THE WESTERN FLANK OF THE RIDGE AND CROSSING THE AREA
INTO THE AFTERNOON. TOUGH TO SAY IF THIS WILL BE THE CASE BUT THE
PATTERN IS CERTAINLY SUCH THAT THIS COULD OCCUR SO WILL CONTINUE
WITH POPS PRIMARILY FRIDAY AFTERNOON AND STICK WITH HIGHS IN THE MID
TO UPPER 80S FOR NOW.

FRIDAY NIGHT THROUGH MID NEXT WEEK...LARGER SCALE TROUGHING WILL BE
BUILDING INTO WESTERN NORTH AMERICA INTO SATURDAY WHICH WILL HELP
KICK THE CENTRAL PLAINS UPPER LOW NORTHEASTWARD. ANOTHER SURFACE LOW
WILL DEVELOP AND TRACK NORTHEASTWARD INTO WISCONSIN BY SATURDAY
MORNING. LATE FRIDAY NIGHT THROUGH SATURDAY MORNING WILL PROBABLY
END UP BEING THE BEST CHANCE FOR SHOWERS AND THUNDERSTORMS AS THIS
OCCURS. MORNING FRONTAL PASSAGE IS NOT ALL THAT FAVORABLE FOR SEVERE
WEATHER BUT DO EXPECT THAT SOME SORT OF LINE OR COMPLEX OF STORMS
WOULD AFFECT THE AREA...BRINGING HEAVY RAINFALL IF NOTHING ELSE.
HIGH PRESSURE RIDGING BUILDS IN NORTH OF THE AREA BEHIND THE
DEPARTING LOW. THE BIGGEST ISSUE WITH THIS HAS BEEN TIMING WITH THE
LATEST GUIDANCE FASTER THAN EARLIER RUNS KEEPING THE PRECIP CONFINED
TO SATURDAY MORNING. WILL ADJUST POPS TO BETTER FIT THIS BUT WILL
KEEP CHANCE POPS FOR SATURDAY AFTERNOON FOR NOW. H85 TEMPS COOL
BEHIND THE SYSTEM KEEPING HIGHS IN THE UPPER 70S AND LOWER 80S WITH
SLIGHTLY WARMER TEMPS SUNDAY. THE WESTERN TROUGH WILL AMPLIFY AS IT
MOVES INTO THE NORTHERN PLAINS TAKING A SURFACE LOW NORTHEAST FROM
THE NORTHERN PLAINS TO NORTHWESTERN ONTARIO LATER SUNDAY. TIMING
WILL ONCE AGAIN NEED TO BE BETTER ASSESSED BUT THIS SYSTEM WILL
BRING ANOTHER COOL FRONT ACROSS THE AREA SOME TIME MONDAY. A LOWER
AMPLITUDE UPPER FLOW BECOMES ESTABLISHED AS THE TROUGH DEPARTS WITH
HIGH PRESSURE BUILDING IN AT THE SURFACE. WIDESPREAD POP CHANCES
LOOK LOW INTO MIDWEEK BUT THE FAIRLY ZONAL FLOW WILL BE SUPPORTIVE
OF WEAK PASSING SHORTWAVES WHICH COULD TRIGGER SOME SPOTTY PRECIP AT
TIMES. HIGHS GENERALLY LOOK TO BE AROUND 80 BUT THE FLOW WILL LIKELY
BE WEAK ENOUGH TO SUPPORT LAKE COOLING AS LONG AS THE SURFACE HIGH
IS NEARBY.

MDB

&&

.AVIATION...

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

* LIGHT EAST FLOW ARND 5-7KT THRU LATE AFTN...WINDS TURNING SE
  WITH SPEEDS INCREASING TO ARND 10KT.

* POSSIBLE SHOWERS DEVELOPING AFT 03Z...WITH BETTER COVERAGE AND
  POTENTIAL TSRA AFT 09Z THRU DAYBREAK FRI.

* WINDS CONTINUE TO TURN S FRI MORNING...WITH GUSTS DEVELOPING TO
  20KT MIDDAY FRI.

BEACHLER

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

VISIBLE IMAGERY THIS AFTN SHOWS SOME THIN MID-DECK CLOUDS LIFTING
NORTHEAST ACROSS NORTHERN IL. MUCH THICKER CLOUDS AND SPOTTY
SHOWERS REMAINS OVER IOWA. SFC WINDS CONTINUE TO BE EASTERLY
ACROSS MUCH OF THE REGION...WITH A GRADUAL TURN TOWARDS SOUTHEAST
ACROSS CENTRAL IL/IN. A FRONTAL BOUNDARY WILL BEGIN TO LIFT NORTH
THIS EVENING...WITH INCREASING MOISTURE. THIS COULD AID IN SEEING
ISOLATED SHOWERS AND POSSIBLY A THUNDERSTORM LATER TONIGHT.
GUIDANCE CONTINUES TO LEAN TOWARDS THE 10-14Z FRI TIMEFRAME FOR
THE BEST COVERAGE OF SHOWERS AND ISO-TSRA DEVELOPING...BUT
CONFIDENCE REMAINS LOW WITH COVERAGE OF THUNDER. SO AT THIS TIME
HAVE HELD ONTO JUST A PROB30 GROUP. WINDS BEHIND THE FRONTAL
BOUNDARY WILL BEGIN TO TURN SOUTH AROUND DAYBREAK FRI...WITH
BETTER MIXING DEVELOPING BY LATE MORNING/EARLY AFTN. GUIDANCE
CONTINUES TO SUGGEST CONVETION COULD BEGIN TO DEVELOP YET AGAIN
LATE MORNING THROUGH THE AFTERNOON...HOWEVER FEEL THIS IS A BIT
OVERDONE.

BEACHLER


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

* HIGH CONFIDENCE IN WIND DIR/SPEED AND TRENDS.

* HIGH CONFIDENCE IN ALL OTHER ELEMENTS THROUGH 04Z.

* MEDIUM CONFIDENCE IN TIMING OF PRECIP AND COVERAGE.

* LOW CONFIDENCE IN THUNDER CHANCES/COVERAGE.

BEACHLER

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

* FRIDAY NIGHT...CHANCE OF TSRA.
* SATURDAY...TSRA LIKELY.
* SUNDAY...SLIGHT CHANCE OF TSRA.
* MONDAY AND TUESDAY...CHANCE OF TSRA.
* WEDNESDAY...DRY/VFR.

&&

.MARINE...

300 AM...HIGH PRESSURE OVER THE LAKES REGION WILL MOVE EAST TODAY
AND TONIGHT REACHING NEW ENGLAND FRIDAY MORNING. EAST WINDS 10 TO
15 KTS WILL GRADUALLY TURN SOUTHEASTERLY THIS EVENING THEN MORE
SOUTHERLY OVERNIGHT INTO FRIDAY MORNING AND INCREASE. LOW PRESSURE
OVER THE WESTERN PLAINS WILL MOVE NORTHEAST TO MINNESOTA AND IOWA
BY FRIDAY MORNING THEN TURN NORTHEAST ACROSS THE NORTHERN LAKES
SATURDAY INTO SATURDAY EVENING. THE GRADIENT WILL TIGHTEN AHEAD OF
THIS LOW WITH 15-25KTS EXPECTED FRIDAY. THE GRADIENT WILL SLOWLY
WEAKEN FROM NORTH TO SOUTH FRIDAY NIGHT. A TRAILING COLD FRONT
FROM THIS LOW WILL THEN MOVE SOUTH ACROSS LAKE MICHIGAN SATURDAY
NIGHT INTO SUNDAY MORNING. THIS FRONT WILL THEN LIFT BACK NORTH AS
A WARM FRONT SUNDAY NIGHT AS STRONGER HIGH PRESSURE IS EXPECTED TO
MOVE ACROSS THE NORTHERN LAKES AND ONTARIO SUNDAY NIGHT AND
MONDAY. CMS

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO







000
FXUS63 KLOT 281805
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
105 PM CDT THU AUG 28 2014

.DISCUSSION...
310 AM CDT

MORE ACTIVE WEATHER WILL TRY TO RETURN TO THE AREA INTO THIS EVENING
FOR AT LEAST PART OF THE AREA FOLLOWING THE RATHER QUIET WEATHER
YESTERDAY. THE FORECAST WILL FOCUS ON TIMING AND COVERAGE OF
SHOWER/THUNDER CHANCES AS WELL AS TEMPERATURES...ESPECIALLY FRIDAY
WHEN THUNDERSTORMS COULD HINDER ANOTHER SUBSTANTIAL WARM UP. THE
MAIN FEATURE ON WATER VAPOR THIS MORNING IS AN UPPER LOW WHICH HAS
BEEN SLOWLY SPINNING EASTWARD ACROSS THE WESTERN U.S. THE LOW IS NOW
MAKING SLIGHTLY FASTER EASTWARD PROGRESS ACROSS COLORADO AND WYOMING
AND AMPLIFYING A RIDGE AHEAD OF IT INTO THE MID AND UPPER
MISSISSIPPI RIVER VALLEY. SEVERAL SMALLER SCALE SHORTWAVES ARE
MOVING NORTHEASTWARD AROUND THE BASE OF THE LOW AND LIFTING INTO
KANSAS AND NEBRASKA. LOOKING FURTHER NORTHWEST...A TROUGH AXIS
EXTENDS SOUTHWESTWARD FROM NORTHERN ALBERTA ACROSS CENTRAL BRITISH
COLUMBIA AND OVER THE PACIFIC WHILE A CLOSED UPPER IS DIGGING
SOUTHEASTWARD OFF THE SOUTHERN ALASKA COAST. AT THE SURFACE...HIGH
PRESSURE IS CENTERED OVER LAKE SUPERIOR WHILE A FRONTAL BOUNDARY
EXTENDS FROM THE MAINE COAST DOWN THE OHIO VALLEY AND BACK INTO THE
CENTRAL PLAINS. SURFACE LOW PRESSURE IS ORGANIZING ACROSS THE
CENTRAL AND SOUTHERN HIGH PLAINS IN CONJUNCTION WITH THE APPROACHING
UPPER LOW.

TODAY AND TONIGHT...THE UPPER RIDGE AXIS WILL BE CRESTING THE AREA
THIS MORNING AS THE ENTIRE RIDGE BROADENS INTO FRIDAY. THE SURFACE
HIGH WILL ACCELERATE EASTWARD AND BE CENTERED OVER THE LOWER ST.
LAWRENCE RIVER VALLEY BY FRIDAY. THE UPPER LOW WILL PUSH INTO THE
CENTRAL PLAINS WHILE THE ATTENDANT SURFACE LOW MOVES NORTHEASTWARD
INTO MINNESOTA TONIGHT. WARM ADVECTION AHEAD OF THE ADVANCING UPPER
TROUGH IS GENERATING SHOWERS AND THUNDERSTORMS ACROSS MUCH OF
NEBRASKA INTO SOUTHERN IOWA AND NORTHERN MISSOURI IN CONJUNCTION
WITH SEVERAL SHORTWAVES. THE WARM ADVECTION WILL SPREAD
NORTHEASTWARD WITH A SURFACE WARM FRONT ALSO MOVING NORTHEASTWARD
AND CROSSING THE LOCAL AREA TODAY. THE FOCUS OF THE ASCENT WILL BE
TO THE WEST AND NORTHWEST OF THE AREA THROUGH THE MORNING KEEPING
THE BULK OF IF NOT ALL OF THE SHOWER ACTIVITY OUT OF THE CWA.
HOWEVER...HAVE BEEN SEEING A FEW LIGHT SPRINKLES/SHOWERS ALONG AND
SOUTH OF THE SOUTHERN CWA BORDER THIS MORNING AS WELL LIKELY IN
CONJUNCTION WITH A SUBTLE MID LEVEL WAVE. EXPECT THESE TO SHIFT EAST
OF THE AREA THROUGH DAYBREAK. PRECIP CHANCES WILL INCREASE THIS
AFTERNOON HOWEVER...MAINLY ACROSS THE WESTERN HALF OF THE AREA AND
IT IS POSSIBLE THIS COULD BE A LITTLE FAST. A BETTER PUSH OF THETA-E
AND INSTABILITY MOVE ACROSS THIS EVENING...ESPECIALLY ACROSS
NORTHERN AREAS SO MAY SEE THE PEAK OF THE ACTIVITY DURING THIS TIME.
SOUTHERN AND EASTERN AREAS MAY END UP STAYING DRY FOR MUCH OF THIS
PERIOD. HIGHS TODAY WILL RANGE FROM THE UPPER 70S NORTH TO LOWER 80S
SOUTH WITH A FAIR AMOUNT OF CLOUD COVER EXPECTED.

FRIDAY...FRIDAY WILL BE A TRICKY FORECAST WITH THE POTENTIAL
FOR A NOTICEABLE WARM UP BUT ALSO A POTENTIAL TO HAVE THAT SPOILED
BY THUNDERSTORMS. THE WESTERN PERIPHERY OF THE MID LEVEL WARM AXIS
WILL BE OVER THE AREA WITH A SOUTH TO SOUTHWEST SURFACE WIND IN
PLACE. H85/H92 HIGH TEMP CLIMATOLOGY SHOWS STRONG SUPPORT FOR HIGHS
NEAR 90 WITH VALUES OF 18/23C. LATEST GUIDANCE SHOWS CONVECTION
DEVELOPING TO THE SOUTH OF THE AREA FRIDAY MORNING AND LIFTING
NORTHWARD ON THE WESTERN FLANK OF THE RIDGE AND CROSSING THE AREA
INTO THE AFTERNOON. TOUGH TO SAY IF THIS WILL BE THE CASE BUT THE
PATTERN IS CERTAINLY SUCH THAT THIS COULD OCCUR SO WILL CONTINUE
WITH POPS PRIMARILY FRIDAY AFTERNOON AND STICK WITH HIGHS IN THE MID
TO UPPER 80S FOR NOW.

FRIDAY NIGHT THROUGH MID NEXT WEEK...LARGER SCALE TROUGHING WILL BE
BUILDING INTO WESTERN NORTH AMERICA INTO SATURDAY WHICH WILL HELP
KICK THE CENTRAL PLAINS UPPER LOW NORTHEASTWARD. ANOTHER SURFACE LOW
WILL DEVELOP AND TRACK NORTHEASTWARD INTO WISCONSIN BY SATURDAY
MORNING. LATE FRIDAY NIGHT THROUGH SATURDAY MORNING WILL PROBABLY
END UP BEING THE BEST CHANCE FOR SHOWERS AND THUNDERSTORMS AS THIS
OCCURS. MORNING FRONTAL PASSAGE IS NOT ALL THAT FAVORABLE FOR SEVERE
WEATHER BUT DO EXPECT THAT SOME SORT OF LINE OR COMPLEX OF STORMS
WOULD AFFECT THE AREA...BRINGING HEAVY RAINFALL IF NOTHING ELSE.
HIGH PRESSURE RIDGING BUILDS IN NORTH OF THE AREA BEHIND THE
DEPARTING LOW. THE BIGGEST ISSUE WITH THIS HAS BEEN TIMING WITH THE
LATEST GUIDANCE FASTER THAN EARLIER RUNS KEEPING THE PRECIP CONFINED
TO SATURDAY MORNING. WILL ADJUST POPS TO BETTER FIT THIS BUT WILL
KEEP CHANCE POPS FOR SATURDAY AFTERNOON FOR NOW. H85 TEMPS COOL
BEHIND THE SYSTEM KEEPING HIGHS IN THE UPPER 70S AND LOWER 80S WITH
SLIGHTLY WARMER TEMPS SUNDAY. THE WESTERN TROUGH WILL AMPLIFY AS IT
MOVES INTO THE NORTHERN PLAINS TAKING A SURFACE LOW NORTHEAST FROM
THE NORTHERN PLAINS TO NORTHWESTERN ONTARIO LATER SUNDAY. TIMING
WILL ONCE AGAIN NEED TO BE BETTER ASSESSED BUT THIS SYSTEM WILL
BRING ANOTHER COOL FRONT ACROSS THE AREA SOME TIME MONDAY. A LOWER
AMPLITUDE UPPER FLOW BECOMES ESTABLISHED AS THE TROUGH DEPARTS WITH
HIGH PRESSURE BUILDING IN AT THE SURFACE. WIDESPREAD POP CHANCES
LOOK LOW INTO MIDWEEK BUT THE FAIRLY ZONAL FLOW WILL BE SUPPORTIVE
OF WEAK PASSING SHORTWAVES WHICH COULD TRIGGER SOME SPOTTY PRECIP AT
TIMES. HIGHS GENERALLY LOOK TO BE AROUND 80 BUT THE FLOW WILL LIKELY
BE WEAK ENOUGH TO SUPPORT LAKE COOLING AS LONG AS THE SURFACE HIGH
IS NEARBY.

MDB

&&

.AVIATION...

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

* LIGHT EAST FLOW ARND 5-7KT THRU LATE AFTN...WINDS TURNING SE
  WITH SPEEDS INCREASING TO ARND 10KT.

* POSSIBLE SHOWERS DEVELOPING AFT 03Z...WITH BETTER COVERAGE AND
  POTENTIAL TSRA AFT 09Z THRU DAYBREAK FRI.

* WINDS CONTINUE TO TURN S FRI MORNING...WITH GUSTS DEVELOPING TO
  20KT MIDDAY FRI.

BEACHLER

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

VISIBLE IMAGERY THIS AFTN SHOWS SOME THIN MID-DECK CLOUDS LIFTING
NORTHEAST ACROSS NORTHERN IL. MUCH THICKER CLOUDS AND SPOTTY
SHOWERS REMAINS OVER IOWA. SFC WINDS CONTINUE TO BE EASTERLY
ACROSS MUCH OF THE REGION...WITH A GRADUAL TURN TOWARDS SOUTHEAST
ACROSS CENTRAL IL/IN. A FRONTAL BOUNDARY WILL BEGIN TO LIFT NORTH
THIS EVENING...WITH INCREASING MOISTURE. THIS COULD AID IN SEEING
ISOLATED SHOWERS AND POSSIBLY A THUNDERSTORM LATER TONIGHT.
GUIDANCE CONTINUES TO LEAN TOWARDS THE 10-14Z FRI TIMEFRAME FOR
THE BEST COVERAGE OF SHOWERS AND ISO-TSRA DEVELOPING...BUT
CONFIDENCE REMAINS LOW WITH COVERAGE OF THUNDER. SO AT THIS TIME
HAVE HELD ONTO JUST A PROB30 GROUP. WINDS BEHIND THE FRONTAL
BOUNDARY WILL BEGIN TO TURN SOUTH AROUND DAYBREAK FRI...WITH
BETTER MIXING DEVELOPING BY LATE MORNING/EARLY AFTN. GUIDANCE
CONTINUES TO SUGGEST CONVETION COULD BEGIN TO DEVELOP YET AGAIN
LATE MORNING THROUGH THE AFTERNOON...HOWEVER FEEL THIS IS A BIT
OVERDONE.

BEACHLER


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

* HIGH CONFIDENCE IN WIND DIR/SPEED AND TRENDS.

* HIGH CONFIDENCE IN ALL OTHER ELEMENTS THROUGH 04Z.

* MEDIUM CONFIDENCE IN TIMING OF PRECIP AND COVERAGE.

* LOW CONFIDENCE IN THUNDER CHANCES/COVERAGE.

BEACHLER

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

* FRIDAY NIGHT...CHANCE OF TSRA.
* SATURDAY...TSRA LIKELY.
* SUNDAY...SLIGHT CHANCE OF TSRA.
* MONDAY AND TUESDAY...CHANCE OF TSRA.
* WEDNESDAY...DRY/VFR.

&&

.MARINE...

300 AM...HIGH PRESSURE OVER THE LAKES REGION WILL MOVE EAST TODAY
AND TONIGHT REACHING NEW ENGLAND FRIDAY MORNING. EAST WINDS 10 TO
15 KTS WILL GRADUALLY TURN SOUTHEASTERLY THIS EVENING THEN MORE
SOUTHERLY OVERNIGHT INTO FRIDAY MORNING AND INCREASE. LOW PRESSURE
OVER THE WESTERN PLAINS WILL MOVE NORTHEAST TO MINNESOTA AND IOWA
BY FRIDAY MORNING THEN TURN NORTHEAST ACROSS THE NORTHERN LAKES
SATURDAY INTO SATURDAY EVENING. THE GRADIENT WILL TIGHTEN AHEAD OF
THIS LOW WITH 15-25KTS EXPECTED FRIDAY. THE GRADIENT WILL SLOWLY
WEAKEN FROM NORTH TO SOUTH FRIDAY NIGHT. A TRAILING COLD FRONT
FROM THIS LOW WILL THEN MOVE SOUTH ACROSS LAKE MICHIGAN SATURDAY
NIGHT INTO SUNDAY MORNING. THIS FRONT WILL THEN LIFT BACK NORTH AS
A WARM FRONT SUNDAY NIGHT AS STRONGER HIGH PRESSURE IS EXPECTED TO
MOVE ACROSS THE NORTHERN LAKES AND ONTARIO SUNDAY NIGHT AND
MONDAY. CMS

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 281605
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1105 AM CDT THU AUG 28 2014

.DISCUSSION...
310 AM CDT

MORE ACTIVE WEATHER WILL TRY TO RETURN TO THE AREA INTO THIS EVENING
FOR AT LEAST PART OF THE AREA FOLLOWING THE RATHER QUIET WEATHER
YESTERDAY. THE FORECAST WILL FOCUS ON TIMING AND COVERAGE OF
SHOWER/THUNDER CHANCES AS WELL AS TEMPERATURES...ESPECIALLY FRIDAY
WHEN THUNDERSTORMS COULD HINDER ANOTHER SUBSTANTIAL WARM UP. THE
MAIN FEATURE ON WATER VAPOR THIS MORNING IS AN UPPER LOW WHICH HAS
BEEN SLOWLY SPINNING EASTWARD ACROSS THE WESTERN U.S. THE LOW IS NOW
MAKING SLIGHTLY FASTER EASTWARD PROGRESS ACROSS COLORADO AND WYOMING
AND AMPLIFYING A RIDGE AHEAD OF IT INTO THE MID AND UPPER
MISSISSIPPI RIVER VALLEY. SEVERAL SMALLER SCALE SHORTWAVES ARE
MOVING NORTHEASTWARD AROUND THE BASE OF THE LOW AND LIFTING INTO
KANSAS AND NEBRASKA. LOOKING FURTHER NORTHWEST...A TROUGH AXIS
EXTENDS SOUTHWESTWARD FROM NORTHERN ALBERTA ACROSS CENTRAL BRITISH
COLUMBIA AND OVER THE PACIFIC WHILE A CLOSED UPPER IS DIGGING
SOUTHEASTWARD OFF THE SOUTHERN ALASKA COAST. AT THE SURFACE...HIGH
PRESSURE IS CENTERED OVER LAKE SUPERIOR WHILE A FRONTAL BOUNDARY
EXTENDS FROM THE MAINE COAST DOWN THE OHIO VALLEY AND BACK INTO THE
CENTRAL PLAINS. SURFACE LOW PRESSURE IS ORGANIZING ACROSS THE
CENTRAL AND SOUTHERN HIGH PLAINS IN CONJUNCTION WITH THE APPROACHING
UPPER LOW.

TODAY AND TONIGHT...THE UPPER RIDGE AXIS WILL BE CRESTING THE AREA
THIS MORNING AS THE ENTIRE RIDGE BROADENS INTO FRIDAY. THE SURFACE
HIGH WILL ACCELERATE EASTWARD AND BE CENTERED OVER THE LOWER ST.
LAWRENCE RIVER VALLEY BY FRIDAY. THE UPPER LOW WILL PUSH INTO THE
CENTRAL PLAINS WHILE THE ATTENDANT SURFACE LOW MOVES NORTHEASTWARD
INTO MINNESOTA TONIGHT. WARM ADVECTION AHEAD OF THE ADVANCING UPPER
TROUGH IS GENERATING SHOWERS AND THUNDERSTORMS ACROSS MUCH OF
NEBRASKA INTO SOUTHERN IOWA AND NORTHERN MISSOURI IN CONJUNCTION
WITH SEVERAL SHORTWAVES. THE WARM ADVECTION WILL SPREAD
NORTHEASTWARD WITH A SURFACE WARM FRONT ALSO MOVING NORTHEASTWARD
AND CROSSING THE LOCAL AREA TODAY. THE FOCUS OF THE ASCENT WILL BE
TO THE WEST AND NORTHWEST OF THE AREA THROUGH THE MORNING KEEPING
THE BULK OF IF NOT ALL OF THE SHOWER ACTIVITY OUT OF THE CWA.
HOWEVER...HAVE BEEN SEEING A FEW LIGHT SPRINKLES/SHOWERS ALONG AND
SOUTH OF THE SOUTHERN CWA BORDER THIS MORNING AS WELL LIKELY IN
CONJUNCTION WITH A SUBTLE MID LEVEL WAVE. EXPECT THESE TO SHIFT EAST
OF THE AREA THROUGH DAYBREAK. PRECIP CHANCES WILL INCREASE THIS
AFTERNOON HOWEVER...MAINLY ACROSS THE WESTERN HALF OF THE AREA AND
IT IS POSSIBLE THIS COULD BE A LITTLE FAST. A BETTER PUSH OF THETA-E
AND INSTABILITY MOVE ACROSS THIS EVENING...ESPECIALLY ACROSS
NORTHERN AREAS SO MAY SEE THE PEAK OF THE ACTIVITY DURING THIS TIME.
SOUTHERN AND EASTERN AREAS MAY END UP STAYING DRY FOR MUCH OF THIS
PERIOD. HIGHS TODAY WILL RANGE FROM THE UPPER 70S NORTH TO LOWER 80S
SOUTH WITH A FAIR AMOUNT OF CLOUD COVER EXPECTED.

FRIDAY...FRIDAY WILL BE A TRICKY FORECAST WITH THE POTENTIAL
FOR A NOTICEABLE WARM UP BUT ALSO A POTENTIAL TO HAVE THAT SPOILED
BY THUNDERSTORMS. THE WESTERN PERIPHERY OF THE MID LEVEL WARM AXIS
WILL BE OVER THE AREA WITH A SOUTH TO SOUTHWEST SURFACE WIND IN
PLACE. H85/H92 HIGH TEMP CLIMATOLOGY SHOWS STRONG SUPPORT FOR HIGHS
NEAR 90 WITH VALUES OF 18/23C. LATEST GUIDANCE SHOWS CONVECTION
DEVELOPING TO THE SOUTH OF THE AREA FRIDAY MORNING AND LIFTING
NORTHWARD ON THE WESTERN FLANK OF THE RIDGE AND CROSSING THE AREA
INTO THE AFTERNOON. TOUGH TO SAY IF THIS WILL BE THE CASE BUT THE
PATTERN IS CERTAINLY SUCH THAT THIS COULD OCCUR SO WILL CONTINUE
WITH POPS PRIMARILY FRIDAY AFTERNOON AND STICK WITH HIGHS IN THE MID
TO UPPER 80S FOR NOW.

FRIDAY NIGHT THROUGH MID NEXT WEEK...LARGER SCALE TROUGHING WILL BE
BUILDING INTO WESTERN NORTH AMERICA INTO SATURDAY WHICH WILL HELP
KICK THE CENTRAL PLAINS UPPER LOW NORTHEASTWARD. ANOTHER SURFACE LOW
WILL DEVELOP AND TRACK NORTHEASTWARD INTO WISCONSIN BY SATURDAY
MORNING. LATE FRIDAY NIGHT THROUGH SATURDAY MORNING WILL PROBABLY
END UP BEING THE BEST CHANCE FOR SHOWERS AND THUNDERSTORMS AS THIS
OCCURS. MORNING FRONTAL PASSAGE IS NOT ALL THAT FAVORABLE FOR SEVERE
WEATHER BUT DO EXPECT THAT SOME SORT OF LINE OR COMPLEX OF STORMS
WOULD AFFECT THE AREA...BRINGING HEAVY RAINFALL IF NOTHING ELSE.
HIGH PRESSURE RIDGING BUILDS IN NORTH OF THE AREA BEHIND THE
DEPARTING LOW. THE BIGGEST ISSUE WITH THIS HAS BEEN TIMING WITH THE
LATEST GUIDANCE FASTER THAN EARLIER RUNS KEEPING THE PRECIP CONFINED
TO SATURDAY MORNING. WILL ADJUST POPS TO BETTER FIT THIS BUT WILL
KEEP CHANCE POPS FOR SATURDAY AFTERNOON FOR NOW. H85 TEMPS COOL
BEHIND THE SYSTEM KEEPING HIGHS IN THE UPPER 70S AND LOWER 80S WITH
SLIGHTLY WARMER TEMPS SUNDAY. THE WESTERN TROUGH WILL AMPLIFY AS IT
MOVES INTO THE NORTHERN PLAINS TAKING A SURFACE LOW NORTHEAST FROM
THE NORTHERN PLAINS TO NORTHWESTERN ONTARIO LATER SUNDAY. TIMING
WILL ONCE AGAIN NEED TO BE BETTER ASSESSED BUT THIS SYSTEM WILL
BRING ANOTHER COOL FRONT ACROSS THE AREA SOME TIME MONDAY. A LOWER
AMPLITUDE UPPER FLOW BECOMES ESTABLISHED AS THE TROUGH DEPARTS WITH
HIGH PRESSURE BUILDING IN AT THE SURFACE. WIDESPREAD POP CHANCES
LOOK LOW INTO MIDWEEK BUT THE FAIRLY ZONAL FLOW WILL BE SUPPORTIVE
OF WEAK PASSING SHORTWAVES WHICH COULD TRIGGER SOME SPOTTY PRECIP AT
TIMES. HIGHS GENERALLY LOOK TO BE AROUND 80 BUT THE FLOW WILL LIKELY
BE WEAK ENOUGH TO SUPPORT LAKE COOLING AS LONG AS THE SURFACE HIGH
IS NEARBY.

MDB

&&

.AVIATION...

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

* EASTERLY WINDS AROUND 10KT THRU EARLY EVENING.
* ISOLATED/SCATTERED SHRA THIS EVENING THRU FRIDAY MORNING.
CMS/BEACH

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

GRADIENT HAS TIGHTENED JUST A BIT THIS MORNING WITH EASTERLY WINDS
AROUND 10KT. MAY SEE SOME FLUCTUATION IN WIND SPEEDS BUT OVERALL...
PREVAILING WINDS WILL LIKELY BE EASTERLY AROUND 10KT FOR MUCH OF
THE DAY. WINDS SLOWLY TURN SOUTHEAST THIS EVENING THE SHIFT
SOUTHERLY TOWARD DAYBREAK FRIDAY.

MID CLOUDS WILL VARY FROM SCT TO BKN THIS MORNING BUT SHOULD
EVENTUALLY BECOME BKN/OVC LATER THIS AFTERNOON INTO THIS EVENING
AS THEY SLOWLY LOWER. HIGH MVFR CIGS HAVE DEVELOPED ACROSS EASTERN
IOWA AND FAR WESTERN IL. THESE WILL NEED TO BE MONITORED THIS
MORNING...ESPECIALLY FOR POSSIBLE HIGH MVFR CIGS INTO RFD.

SHRA/TSRA OVER IOWA ARE EXPECTED TO LIFT NORTHEAST THIS AFTERNOON
AND THIS EVENING...POSSIBLY MOVING ACROSS FAR NORTHWEST IL AND
RFD WITH ADDITIONAL SHRA DEVELOPMENT POSSIBLE THRU THE NIGHT AS A
WARM FRONT LIFTS ACROSS THE AREA. OVERALL CONFIDENCE REGARDING
TIMING AND COVERAGE OF PRECIP REMAINS LOW SO MAINTAINED PREVIOUS
PROB MENTION AND ADDED VICINITY MENTION INTO FRIDAY MORNING WITH
THE BEST CHANCES ACROSS FAR NORTHERN IL INTO SOUTHERN WI. CMS

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

* HIGH FOR WINDS THRU THE PERIOD.
* LOW FOR SHRA THIS EVENING THRU FRIDAY MORNING.
CMS/BEACH

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

* FRIDAY NIGHT...CHANCE OF TSRA.
* SATURDAY...TSRA LIKELY.
* SUNDAY...SLIGHT CHANCE OF TSRA.
* MONDAY AND TUESDAY...CHANCE OF TSRA.
* WEDNESDAY...DRY/VFR.

&&

.MARINE...

300 AM...HIGH PRESSURE OVER THE LAKES REGION WILL MOVE EAST TODAY
AND TONIGHT REACHING NEW ENGLAND FRIDAY MORNING. EAST WINDS 10 TO
15 KTS WILL GRADUALLY TURN SOUTHEASTERLY THIS EVENING THEN MORE
SOUTHERLY OVERNIGHT INTO FRIDAY MORNING AND INCREASE. LOW PRESSURE
OVER THE WESTERN PLAINS WILL MOVE NORTHEAST TO MINNESOTA AND IOWA
BY FRIDAY MORNING THEN TURN NORTHEAST ACROSS THE NORTHERN LAKES
SATURDAY INTO SATURDAY EVENING. THE GRADIENT WILL TIGHTEN AHEAD OF
THIS LOW WITH 15-25KTS EXPECTED FRIDAY. THE GRADIENT WILL SLOWLY
WEAKEN FROM NORTH TO SOUTH FRIDAY NIGHT. A TRAILING COLD FRONT
FROM THIS LOW WILL THEN MOVE SOUTH ACROSS LAKE MICHIGAN SATURDAY
NIGHT INTO SUNDAY MORNING. THIS FRONT WILL THEN LIFT BACK NORTH AS
A WARM FRONT SUNDAY NIGHT AS STRONGER HIGH PRESSURE IS EXPECTED TO
MOVE ACROSS THE NORTHERN LAKES AND ONTARIO SUNDAY NIGHT AND
MONDAY. CMS

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 281605
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1105 AM CDT THU AUG 28 2014

.DISCUSSION...
310 AM CDT

MORE ACTIVE WEATHER WILL TRY TO RETURN TO THE AREA INTO THIS EVENING
FOR AT LEAST PART OF THE AREA FOLLOWING THE RATHER QUIET WEATHER
YESTERDAY. THE FORECAST WILL FOCUS ON TIMING AND COVERAGE OF
SHOWER/THUNDER CHANCES AS WELL AS TEMPERATURES...ESPECIALLY FRIDAY
WHEN THUNDERSTORMS COULD HINDER ANOTHER SUBSTANTIAL WARM UP. THE
MAIN FEATURE ON WATER VAPOR THIS MORNING IS AN UPPER LOW WHICH HAS
BEEN SLOWLY SPINNING EASTWARD ACROSS THE WESTERN U.S. THE LOW IS NOW
MAKING SLIGHTLY FASTER EASTWARD PROGRESS ACROSS COLORADO AND WYOMING
AND AMPLIFYING A RIDGE AHEAD OF IT INTO THE MID AND UPPER
MISSISSIPPI RIVER VALLEY. SEVERAL SMALLER SCALE SHORTWAVES ARE
MOVING NORTHEASTWARD AROUND THE BASE OF THE LOW AND LIFTING INTO
KANSAS AND NEBRASKA. LOOKING FURTHER NORTHWEST...A TROUGH AXIS
EXTENDS SOUTHWESTWARD FROM NORTHERN ALBERTA ACROSS CENTRAL BRITISH
COLUMBIA AND OVER THE PACIFIC WHILE A CLOSED UPPER IS DIGGING
SOUTHEASTWARD OFF THE SOUTHERN ALASKA COAST. AT THE SURFACE...HIGH
PRESSURE IS CENTERED OVER LAKE SUPERIOR WHILE A FRONTAL BOUNDARY
EXTENDS FROM THE MAINE COAST DOWN THE OHIO VALLEY AND BACK INTO THE
CENTRAL PLAINS. SURFACE LOW PRESSURE IS ORGANIZING ACROSS THE
CENTRAL AND SOUTHERN HIGH PLAINS IN CONJUNCTION WITH THE APPROACHING
UPPER LOW.

TODAY AND TONIGHT...THE UPPER RIDGE AXIS WILL BE CRESTING THE AREA
THIS MORNING AS THE ENTIRE RIDGE BROADENS INTO FRIDAY. THE SURFACE
HIGH WILL ACCELERATE EASTWARD AND BE CENTERED OVER THE LOWER ST.
LAWRENCE RIVER VALLEY BY FRIDAY. THE UPPER LOW WILL PUSH INTO THE
CENTRAL PLAINS WHILE THE ATTENDANT SURFACE LOW MOVES NORTHEASTWARD
INTO MINNESOTA TONIGHT. WARM ADVECTION AHEAD OF THE ADVANCING UPPER
TROUGH IS GENERATING SHOWERS AND THUNDERSTORMS ACROSS MUCH OF
NEBRASKA INTO SOUTHERN IOWA AND NORTHERN MISSOURI IN CONJUNCTION
WITH SEVERAL SHORTWAVES. THE WARM ADVECTION WILL SPREAD
NORTHEASTWARD WITH A SURFACE WARM FRONT ALSO MOVING NORTHEASTWARD
AND CROSSING THE LOCAL AREA TODAY. THE FOCUS OF THE ASCENT WILL BE
TO THE WEST AND NORTHWEST OF THE AREA THROUGH THE MORNING KEEPING
THE BULK OF IF NOT ALL OF THE SHOWER ACTIVITY OUT OF THE CWA.
HOWEVER...HAVE BEEN SEEING A FEW LIGHT SPRINKLES/SHOWERS ALONG AND
SOUTH OF THE SOUTHERN CWA BORDER THIS MORNING AS WELL LIKELY IN
CONJUNCTION WITH A SUBTLE MID LEVEL WAVE. EXPECT THESE TO SHIFT EAST
OF THE AREA THROUGH DAYBREAK. PRECIP CHANCES WILL INCREASE THIS
AFTERNOON HOWEVER...MAINLY ACROSS THE WESTERN HALF OF THE AREA AND
IT IS POSSIBLE THIS COULD BE A LITTLE FAST. A BETTER PUSH OF THETA-E
AND INSTABILITY MOVE ACROSS THIS EVENING...ESPECIALLY ACROSS
NORTHERN AREAS SO MAY SEE THE PEAK OF THE ACTIVITY DURING THIS TIME.
SOUTHERN AND EASTERN AREAS MAY END UP STAYING DRY FOR MUCH OF THIS
PERIOD. HIGHS TODAY WILL RANGE FROM THE UPPER 70S NORTH TO LOWER 80S
SOUTH WITH A FAIR AMOUNT OF CLOUD COVER EXPECTED.

FRIDAY...FRIDAY WILL BE A TRICKY FORECAST WITH THE POTENTIAL
FOR A NOTICEABLE WARM UP BUT ALSO A POTENTIAL TO HAVE THAT SPOILED
BY THUNDERSTORMS. THE WESTERN PERIPHERY OF THE MID LEVEL WARM AXIS
WILL BE OVER THE AREA WITH A SOUTH TO SOUTHWEST SURFACE WIND IN
PLACE. H85/H92 HIGH TEMP CLIMATOLOGY SHOWS STRONG SUPPORT FOR HIGHS
NEAR 90 WITH VALUES OF 18/23C. LATEST GUIDANCE SHOWS CONVECTION
DEVELOPING TO THE SOUTH OF THE AREA FRIDAY MORNING AND LIFTING
NORTHWARD ON THE WESTERN FLANK OF THE RIDGE AND CROSSING THE AREA
INTO THE AFTERNOON. TOUGH TO SAY IF THIS WILL BE THE CASE BUT THE
PATTERN IS CERTAINLY SUCH THAT THIS COULD OCCUR SO WILL CONTINUE
WITH POPS PRIMARILY FRIDAY AFTERNOON AND STICK WITH HIGHS IN THE MID
TO UPPER 80S FOR NOW.

FRIDAY NIGHT THROUGH MID NEXT WEEK...LARGER SCALE TROUGHING WILL BE
BUILDING INTO WESTERN NORTH AMERICA INTO SATURDAY WHICH WILL HELP
KICK THE CENTRAL PLAINS UPPER LOW NORTHEASTWARD. ANOTHER SURFACE LOW
WILL DEVELOP AND TRACK NORTHEASTWARD INTO WISCONSIN BY SATURDAY
MORNING. LATE FRIDAY NIGHT THROUGH SATURDAY MORNING WILL PROBABLY
END UP BEING THE BEST CHANCE FOR SHOWERS AND THUNDERSTORMS AS THIS
OCCURS. MORNING FRONTAL PASSAGE IS NOT ALL THAT FAVORABLE FOR SEVERE
WEATHER BUT DO EXPECT THAT SOME SORT OF LINE OR COMPLEX OF STORMS
WOULD AFFECT THE AREA...BRINGING HEAVY RAINFALL IF NOTHING ELSE.
HIGH PRESSURE RIDGING BUILDS IN NORTH OF THE AREA BEHIND THE
DEPARTING LOW. THE BIGGEST ISSUE WITH THIS HAS BEEN TIMING WITH THE
LATEST GUIDANCE FASTER THAN EARLIER RUNS KEEPING THE PRECIP CONFINED
TO SATURDAY MORNING. WILL ADJUST POPS TO BETTER FIT THIS BUT WILL
KEEP CHANCE POPS FOR SATURDAY AFTERNOON FOR NOW. H85 TEMPS COOL
BEHIND THE SYSTEM KEEPING HIGHS IN THE UPPER 70S AND LOWER 80S WITH
SLIGHTLY WARMER TEMPS SUNDAY. THE WESTERN TROUGH WILL AMPLIFY AS IT
MOVES INTO THE NORTHERN PLAINS TAKING A SURFACE LOW NORTHEAST FROM
THE NORTHERN PLAINS TO NORTHWESTERN ONTARIO LATER SUNDAY. TIMING
WILL ONCE AGAIN NEED TO BE BETTER ASSESSED BUT THIS SYSTEM WILL
BRING ANOTHER COOL FRONT ACROSS THE AREA SOME TIME MONDAY. A LOWER
AMPLITUDE UPPER FLOW BECOMES ESTABLISHED AS THE TROUGH DEPARTS WITH
HIGH PRESSURE BUILDING IN AT THE SURFACE. WIDESPREAD POP CHANCES
LOOK LOW INTO MIDWEEK BUT THE FAIRLY ZONAL FLOW WILL BE SUPPORTIVE
OF WEAK PASSING SHORTWAVES WHICH COULD TRIGGER SOME SPOTTY PRECIP AT
TIMES. HIGHS GENERALLY LOOK TO BE AROUND 80 BUT THE FLOW WILL LIKELY
BE WEAK ENOUGH TO SUPPORT LAKE COOLING AS LONG AS THE SURFACE HIGH
IS NEARBY.

MDB

&&

.AVIATION...

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

* EASTERLY WINDS AROUND 10KT THRU EARLY EVENING.
* ISOLATED/SCATTERED SHRA THIS EVENING THRU FRIDAY MORNING.
CMS/BEACH

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

GRADIENT HAS TIGHTENED JUST A BIT THIS MORNING WITH EASTERLY WINDS
AROUND 10KT. MAY SEE SOME FLUCTUATION IN WIND SPEEDS BUT OVERALL...
PREVAILING WINDS WILL LIKELY BE EASTERLY AROUND 10KT FOR MUCH OF
THE DAY. WINDS SLOWLY TURN SOUTHEAST THIS EVENING THE SHIFT
SOUTHERLY TOWARD DAYBREAK FRIDAY.

MID CLOUDS WILL VARY FROM SCT TO BKN THIS MORNING BUT SHOULD
EVENTUALLY BECOME BKN/OVC LATER THIS AFTERNOON INTO THIS EVENING
AS THEY SLOWLY LOWER. HIGH MVFR CIGS HAVE DEVELOPED ACROSS EASTERN
IOWA AND FAR WESTERN IL. THESE WILL NEED TO BE MONITORED THIS
MORNING...ESPECIALLY FOR POSSIBLE HIGH MVFR CIGS INTO RFD.

SHRA/TSRA OVER IOWA ARE EXPECTED TO LIFT NORTHEAST THIS AFTERNOON
AND THIS EVENING...POSSIBLY MOVING ACROSS FAR NORTHWEST IL AND
RFD WITH ADDITIONAL SHRA DEVELOPMENT POSSIBLE THRU THE NIGHT AS A
WARM FRONT LIFTS ACROSS THE AREA. OVERALL CONFIDENCE REGARDING
TIMING AND COVERAGE OF PRECIP REMAINS LOW SO MAINTAINED PREVIOUS
PROB MENTION AND ADDED VICINITY MENTION INTO FRIDAY MORNING WITH
THE BEST CHANCES ACROSS FAR NORTHERN IL INTO SOUTHERN WI. CMS

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

* HIGH FOR WINDS THRU THE PERIOD.
* LOW FOR SHRA THIS EVENING THRU FRIDAY MORNING.
CMS/BEACH

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

* FRIDAY NIGHT...CHANCE OF TSRA.
* SATURDAY...TSRA LIKELY.
* SUNDAY...SLIGHT CHANCE OF TSRA.
* MONDAY AND TUESDAY...CHANCE OF TSRA.
* WEDNESDAY...DRY/VFR.

&&

.MARINE...

300 AM...HIGH PRESSURE OVER THE LAKES REGION WILL MOVE EAST TODAY
AND TONIGHT REACHING NEW ENGLAND FRIDAY MORNING. EAST WINDS 10 TO
15 KTS WILL GRADUALLY TURN SOUTHEASTERLY THIS EVENING THEN MORE
SOUTHERLY OVERNIGHT INTO FRIDAY MORNING AND INCREASE. LOW PRESSURE
OVER THE WESTERN PLAINS WILL MOVE NORTHEAST TO MINNESOTA AND IOWA
BY FRIDAY MORNING THEN TURN NORTHEAST ACROSS THE NORTHERN LAKES
SATURDAY INTO SATURDAY EVENING. THE GRADIENT WILL TIGHTEN AHEAD OF
THIS LOW WITH 15-25KTS EXPECTED FRIDAY. THE GRADIENT WILL SLOWLY
WEAKEN FROM NORTH TO SOUTH FRIDAY NIGHT. A TRAILING COLD FRONT
FROM THIS LOW WILL THEN MOVE SOUTH ACROSS LAKE MICHIGAN SATURDAY
NIGHT INTO SUNDAY MORNING. THIS FRONT WILL THEN LIFT BACK NORTH AS
A WARM FRONT SUNDAY NIGHT AS STRONGER HIGH PRESSURE IS EXPECTED TO
MOVE ACROSS THE NORTHERN LAKES AND ONTARIO SUNDAY NIGHT AND
MONDAY. CMS

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO







000
FXUS63 KLOT 281412
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
912 AM CDT THU AUG 28 2014

.DISCUSSION...
310 AM CDT

MORE ACTIVE WEATHER WILL TRY TO RETURN TO THE AREA INTO THIS EVENING
FOR AT LEAST PART OF THE AREA FOLLOWING THE RATHER QUIET WEATHER
YESTERDAY. THE FORECAST WILL FOCUS ON TIMING AND COVERAGE OF
SHOWER/THUNDER CHANCES AS WELL AS TEMPERATURES...ESPECIALLY FRIDAY
WHEN THUNDERSTORMS COULD HINDER ANOTHER SUBSTANTIAL WARM UP. THE
MAIN FEATURE ON WATER VAPOR THIS MORNING IS AN UPPER LOW WHICH HAS
BEEN SLOWLY SPINNING EASTWARD ACROSS THE WESTERN U.S. THE LOW IS NOW
MAKING SLIGHTLY FASTER EASTWARD PROGRESS ACROSS COLORADO AND WYOMING
AND AMPLIFYING A RIDGE AHEAD OF IT INTO THE MID AND UPPER
MISSISSIPPI RIVER VALLEY. SEVERAL SMALLER SCALE SHORTWAVES ARE
MOVING NORTHEASTWARD AROUND THE BASE OF THE LOW AND LIFTING INTO
KANSAS AND NEBRASKA. LOOKING FURTHER NORTHWEST...A TROUGH AXIS
EXTENDS SOUTHWESTWARD FROM NORTHERN ALBERTA ACROSS CENTRAL BRITISH
COLUMBIA AND OVER THE PACIFIC WHILE A CLOSED UPPER IS DIGGING
SOUTHEASTWARD OFF THE SOUTHERN ALASKA COAST. AT THE SURFACE...HIGH
PRESSURE IS CENTERED OVER LAKE SUPERIOR WHILE A FRONTAL BOUNDARY
EXTENDS FROM THE MAINE COAST DOWN THE OHIO VALLEY AND BACK INTO THE
CENTRAL PLAINS. SURFACE LOW PRESSURE IS ORGANIZING ACROSS THE
CENTRAL AND SOUTHERN HIGH PLAINS IN CONJUNCTION WITH THE APPROACHING
UPPER LOW.

TODAY AND TONIGHT...THE UPPER RIDGE AXIS WILL BE CRESTING THE AREA
THIS MORNING AS THE ENTIRE RIDGE BROADENS INTO FRIDAY. THE SURFACE
HIGH WILL ACCELERATE EASTWARD AND BE CENTERED OVER THE LOWER ST.
LAWRENCE RIVER VALLEY BY FRIDAY. THE UPPER LOW WILL PUSH INTO THE
CENTRAL PLAINS WHILE THE ATTENDANT SURFACE LOW MOVES NORTHEASTWARD
INTO MINNESOTA TONIGHT. WARM ADVECTION AHEAD OF THE ADVANCING UPPER
TROUGH IS GENERATING SHOWERS AND THUNDERSTORMS ACROSS MUCH OF
NEBRASKA INTO SOUTHERN IOWA AND NORTHERN MISSOURI IN CONJUNCTION
WITH SEVERAL SHORTWAVES. THE WARM ADVECTION WILL SPREAD
NORTHEASTWARD WITH A SURFACE WARM FRONT ALSO MOVING NORTHEASTWARD
AND CROSSING THE LOCAL AREA TODAY. THE FOCUS OF THE ASCENT WILL BE
TO THE WEST AND NORTHWEST OF THE AREA THROUGH THE MORNING KEEPING
THE BULK OF IF NOT ALL OF THE SHOWER ACTIVITY OUT OF THE CWA.
HOWEVER...HAVE BEEN SEEING A FEW LIGHT SPRINKLES/SHOWERS ALONG AND
SOUTH OF THE SOUTHERN CWA BORDER THIS MORNING AS WELL LIKELY IN
CONJUNCTION WITH A SUBTLE MID LEVEL WAVE. EXPECT THESE TO SHIFT EAST
OF THE AREA THROUGH DAYBREAK. PRECIP CHANCES WILL INCREASE THIS
AFTERNOON HOWEVER...MAINLY ACROSS THE WESTERN HALF OF THE AREA AND
IT IS POSSIBLE THIS COULD BE A LITTLE FAST. A BETTER PUSH OF THETA-E
AND INSTABILITY MOVE ACROSS THIS EVENING...ESPECIALLY ACROSS
NORTHERN AREAS SO MAY SEE THE PEAK OF THE ACTIVITY DURING THIS TIME.
SOUTHERN AND EASTERN AREAS MAY END UP STAYING DRY FOR MUCH OF THIS
PERIOD. HIGHS TODAY WILL RANGE FROM THE UPPER 70S NORTH TO LOWER 80S
SOUTH WITH A FAIR AMOUNT OF CLOUD COVER EXPECTED.

FRIDAY...FRIDAY WILL BE A TRICKY FORECAST WITH THE POTENTIAL
FOR A NOTICEABLE WARM UP BUT ALSO A POTENTIAL TO HAVE THAT SPOILED
BY THUNDERSTORMS. THE WESTERN PERIPHERY OF THE MID LEVEL WARM AXIS
WILL BE OVER THE AREA WITH A SOUTH TO SOUTHWEST SURFACE WIND IN
PLACE. H85/H92 HIGH TEMP CLIMATOLOGY SHOWS STRONG SUPPORT FOR HIGHS
NEAR 90 WITH VALUES OF 18/23C. LATEST GUIDANCE SHOWS CONVECTION
DEVELOPING TO THE SOUTH OF THE AREA FRIDAY MORNING AND LIFTING
NORTHWARD ON THE WESTERN FLANK OF THE RIDGE AND CROSSING THE AREA
INTO THE AFTERNOON. TOUGH TO SAY IF THIS WILL BE THE CASE BUT THE
PATTERN IS CERTAINLY SUCH THAT THIS COULD OCCUR SO WILL CONTINUE
WITH POPS PRIMARILY FRIDAY AFTERNOON AND STICK WITH HIGHS IN THE MID
TO UPPER 80S FOR NOW.

FRIDAY NIGHT THROUGH MID NEXT WEEK...LARGER SCALE TROUGHING WILL BE
BUILDING INTO WESTERN NORTH AMERICA INTO SATURDAY WHICH WILL HELP
KICK THE CENTRAL PLAINS UPPER LOW NORTHEASTWARD. ANOTHER SURFACE LOW
WILL DEVELOP AND TRACK NORTHEASTWARD INTO WISCONSIN BY SATURDAY
MORNING. LATE FRIDAY NIGHT THROUGH SATURDAY MORNING WILL PROBABLY
END UP BEING THE BEST CHANCE FOR SHOWERS AND THUNDERSTORMS AS THIS
OCCURS. MORNING FRONTAL PASSAGE IS NOT ALL THAT FAVORABLE FOR SEVERE
WEATHER BUT DO EXPECT THAT SOME SORT OF LINE OR COMPLEX OF STORMS
WOULD AFFECT THE AREA...BRINGING HEAVY RAINFALL IF NOTHING ELSE.
HIGH PRESSURE RIDGING BUILDS IN NORTH OF THE AREA BEHIND THE
DEPARTING LOW. THE BIGGEST ISSUE WITH THIS HAS BEEN TIMING WITH THE
LATEST GUIDANCE FASTER THAN EARLIER RUNS KEEPING THE PRECIP CONFINED
TO SATURDAY MORNING. WILL ADJUST POPS TO BETTER FIT THIS BUT WILL
KEEP CHANCE POPS FOR SATURDAY AFTERNOON FOR NOW. H85 TEMPS COOL
BEHIND THE SYSTEM KEEPING HIGHS IN THE UPPER 70S AND LOWER 80S WITH
SLIGHTLY WARMER TEMPS SUNDAY. THE WESTERN TROUGH WILL AMPLIFY AS IT
MOVES INTO THE NORTHERN PLAINS TAKING A SURFACE LOW NORTHEAST FROM
THE NORTHERN PLAINS TO NORTHWESTERN ONTARIO LATER SUNDAY. TIMING
WILL ONCE AGAIN NEED TO BE BETTER ASSESSED BUT THIS SYSTEM WILL
BRING ANOTHER COOL FRONT ACROSS THE AREA SOME TIME MONDAY. A LOWER
AMPLITUDE UPPER FLOW BECOMES ESTABLISHED AS THE TROUGH DEPARTS WITH
HIGH PRESSURE BUILDING IN AT THE SURFACE. WIDESPREAD POP CHANCES
LOOK LOW INTO MIDWEEK BUT THE FAIRLY ZONAL FLOW WILL BE SUPPORTIVE
OF WEAK PASSING SHORTWAVES WHICH COULD TRIGGER SOME SPOTTY PRECIP AT
TIMES. HIGHS GENERALLY LOOK TO BE AROUND 80 BUT THE FLOW WILL LIKELY
BE WEAK ENOUGH TO SUPPORT LAKE COOLING AS LONG AS THE SURFACE HIGH
IS NEARBY.

MDB

&&

.AVIATION...

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

* EASTERLY WINDS AROUND 10KT THRU EARLY EVENING.
* ISOLATED/SCATTERED SHRA THIS EVENING THRU FRIDAY MORNING.
CMS/BEACH

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

GRADIENT HAS TIGHTENED JUST A BIT THIS MORNING WITH EASTERLY WINDS
AROUND 10KT. MAY SEE SOME FLUCTUATION IN WIND SPEEDS BUT OVERALL...
PREVAILING WINDS WILL LIKELY BE EASTERLY AROUND 10KT FOR MUCH OF
THE DAY. WINDS SLOWLY TURN SOUTHEAST THIS EVENING THE SHIFT
SOUTHERLY TOWARD DAYBREAK FRIDAY.

MID CLOUDS WILL VARY FROM SCT TO BKN THIS MORNING BUT SHOULD
EVENTUALLY BECOME BKN/OVC LATER THIS AFTERNOON INTO THIS EVENING
AS THEY SLOWLY LOWER. HIGH MVFR CIGS HAVE DEVELOPED ACROSS EASTERN
IOWA AND FAR WESTERN IL. THESE WILL NEED TO BE MONITORED THIS
MORNING...ESPECIALLY FOR POSSIBLE HIGH MVFR CIGS INTO RFD.

SHRA/TSRA OVER IOWA ARE EXPECTED TO LIFT NORTHEAST THIS AFTERNOON
AND THIS EVENING...POSSIBLY MOVING ACROSS FAR NORTHWEST IL AND
RFD WITH ADDITIONAL SHRA DEVELOPMENT POSSIBLE THRU THE NIGHT AS A
WARM FRONT LIFTS ACROSS THE AREA. OVERALL CONFIDENCE REGARDING
TIMING AND COVERAGE OF PRECIP REMAINS LOW SO MAINTAINED PREVIOUS
PROB MENTION AND ADDED VICINITY MENTION INTO FRIDAY MORNING WITH
THE BEST CHANCES ACROSS FAR NORTHERN IL INTO SOUTHERN WI. CMS

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

* HIGH FOR WINDS THRU THE PERIOD.
* LOW FOR SHRA THIS EVENING THRU FRIDAY MORNING.
CMS/BEACH

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

* FRIDAY NIGHT...CHANCE OF TSRA.
* SATURDAY...TSRA LIKELY.
* SUNDAY...SLIGHT CHANCE OF TSRA.
* MONDAY AND TUESDAY...CHANCE OF TSRA.
* WEDNESDAY...DRY/VFR.

&&

.MARINE...

300 AM...HIGH PRESSURE OVER THE LAKES REGION WILL MOVE EAST TODAY
AND TONIGHT REACHING NEW ENGLAND FRIDAY MORNING. EAST WINDS 10 TO
15 KTS WILL GRADUALLY TURN SOUTHEASTERLY THIS EVENING THEN MORE
SOUTHERLY OVERNIGHT INTO FRIDAY MORNING AND INCREASE. LOW PRESSURE
OVER THE WESTERN PLAINS WILL MOVE NORTHEAST TO MINNESOTA AND IOWA
BY FRIDAY MORNING THEN TURN NORTHEAST ACROSS THE NORTHERN LAKES
SATURDAY INTO SATURDAY EVENING. THE GRADIENT WILL TIGHTEN AHEAD OF
THIS LOW WITH 15-25KTS EXPECTED FRIDAY. THE GRADIENT WILL SLOWLY
WEAKEN FROM NORTH TO SOUTH FRIDAY NIGHT. A TRAILING COLD FRONT
FROM THIS LOW WILL THEN MOVE SOUTH ACROSS LAKE MICHIGAN SATURDAY
NIGHT INTO SUNDAY MORNING. THIS FRONT WILL THEN LIFT BACK NORTH AS
A WARM FRONT SUNDAY NIGHT AS STRONGER HIGH PRESSURE IS EXPECTED TO
MOVE ACROSS THE NORTHERN LAKES AND ONTARIO SUNDAY NIGHT AND
MONDAY. CMS

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 281412
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
912 AM CDT THU AUG 28 2014

.DISCUSSION...
310 AM CDT

MORE ACTIVE WEATHER WILL TRY TO RETURN TO THE AREA INTO THIS EVENING
FOR AT LEAST PART OF THE AREA FOLLOWING THE RATHER QUIET WEATHER
YESTERDAY. THE FORECAST WILL FOCUS ON TIMING AND COVERAGE OF
SHOWER/THUNDER CHANCES AS WELL AS TEMPERATURES...ESPECIALLY FRIDAY
WHEN THUNDERSTORMS COULD HINDER ANOTHER SUBSTANTIAL WARM UP. THE
MAIN FEATURE ON WATER VAPOR THIS MORNING IS AN UPPER LOW WHICH HAS
BEEN SLOWLY SPINNING EASTWARD ACROSS THE WESTERN U.S. THE LOW IS NOW
MAKING SLIGHTLY FASTER EASTWARD PROGRESS ACROSS COLORADO AND WYOMING
AND AMPLIFYING A RIDGE AHEAD OF IT INTO THE MID AND UPPER
MISSISSIPPI RIVER VALLEY. SEVERAL SMALLER SCALE SHORTWAVES ARE
MOVING NORTHEASTWARD AROUND THE BASE OF THE LOW AND LIFTING INTO
KANSAS AND NEBRASKA. LOOKING FURTHER NORTHWEST...A TROUGH AXIS
EXTENDS SOUTHWESTWARD FROM NORTHERN ALBERTA ACROSS CENTRAL BRITISH
COLUMBIA AND OVER THE PACIFIC WHILE A CLOSED UPPER IS DIGGING
SOUTHEASTWARD OFF THE SOUTHERN ALASKA COAST. AT THE SURFACE...HIGH
PRESSURE IS CENTERED OVER LAKE SUPERIOR WHILE A FRONTAL BOUNDARY
EXTENDS FROM THE MAINE COAST DOWN THE OHIO VALLEY AND BACK INTO THE
CENTRAL PLAINS. SURFACE LOW PRESSURE IS ORGANIZING ACROSS THE
CENTRAL AND SOUTHERN HIGH PLAINS IN CONJUNCTION WITH THE APPROACHING
UPPER LOW.

TODAY AND TONIGHT...THE UPPER RIDGE AXIS WILL BE CRESTING THE AREA
THIS MORNING AS THE ENTIRE RIDGE BROADENS INTO FRIDAY. THE SURFACE
HIGH WILL ACCELERATE EASTWARD AND BE CENTERED OVER THE LOWER ST.
LAWRENCE RIVER VALLEY BY FRIDAY. THE UPPER LOW WILL PUSH INTO THE
CENTRAL PLAINS WHILE THE ATTENDANT SURFACE LOW MOVES NORTHEASTWARD
INTO MINNESOTA TONIGHT. WARM ADVECTION AHEAD OF THE ADVANCING UPPER
TROUGH IS GENERATING SHOWERS AND THUNDERSTORMS ACROSS MUCH OF
NEBRASKA INTO SOUTHERN IOWA AND NORTHERN MISSOURI IN CONJUNCTION
WITH SEVERAL SHORTWAVES. THE WARM ADVECTION WILL SPREAD
NORTHEASTWARD WITH A SURFACE WARM FRONT ALSO MOVING NORTHEASTWARD
AND CROSSING THE LOCAL AREA TODAY. THE FOCUS OF THE ASCENT WILL BE
TO THE WEST AND NORTHWEST OF THE AREA THROUGH THE MORNING KEEPING
THE BULK OF IF NOT ALL OF THE SHOWER ACTIVITY OUT OF THE CWA.
HOWEVER...HAVE BEEN SEEING A FEW LIGHT SPRINKLES/SHOWERS ALONG AND
SOUTH OF THE SOUTHERN CWA BORDER THIS MORNING AS WELL LIKELY IN
CONJUNCTION WITH A SUBTLE MID LEVEL WAVE. EXPECT THESE TO SHIFT EAST
OF THE AREA THROUGH DAYBREAK. PRECIP CHANCES WILL INCREASE THIS
AFTERNOON HOWEVER...MAINLY ACROSS THE WESTERN HALF OF THE AREA AND
IT IS POSSIBLE THIS COULD BE A LITTLE FAST. A BETTER PUSH OF THETA-E
AND INSTABILITY MOVE ACROSS THIS EVENING...ESPECIALLY ACROSS
NORTHERN AREAS SO MAY SEE THE PEAK OF THE ACTIVITY DURING THIS TIME.
SOUTHERN AND EASTERN AREAS MAY END UP STAYING DRY FOR MUCH OF THIS
PERIOD. HIGHS TODAY WILL RANGE FROM THE UPPER 70S NORTH TO LOWER 80S
SOUTH WITH A FAIR AMOUNT OF CLOUD COVER EXPECTED.

FRIDAY...FRIDAY WILL BE A TRICKY FORECAST WITH THE POTENTIAL
FOR A NOTICEABLE WARM UP BUT ALSO A POTENTIAL TO HAVE THAT SPOILED
BY THUNDERSTORMS. THE WESTERN PERIPHERY OF THE MID LEVEL WARM AXIS
WILL BE OVER THE AREA WITH A SOUTH TO SOUTHWEST SURFACE WIND IN
PLACE. H85/H92 HIGH TEMP CLIMATOLOGY SHOWS STRONG SUPPORT FOR HIGHS
NEAR 90 WITH VALUES OF 18/23C. LATEST GUIDANCE SHOWS CONVECTION
DEVELOPING TO THE SOUTH OF THE AREA FRIDAY MORNING AND LIFTING
NORTHWARD ON THE WESTERN FLANK OF THE RIDGE AND CROSSING THE AREA
INTO THE AFTERNOON. TOUGH TO SAY IF THIS WILL BE THE CASE BUT THE
PATTERN IS CERTAINLY SUCH THAT THIS COULD OCCUR SO WILL CONTINUE
WITH POPS PRIMARILY FRIDAY AFTERNOON AND STICK WITH HIGHS IN THE MID
TO UPPER 80S FOR NOW.

FRIDAY NIGHT THROUGH MID NEXT WEEK...LARGER SCALE TROUGHING WILL BE
BUILDING INTO WESTERN NORTH AMERICA INTO SATURDAY WHICH WILL HELP
KICK THE CENTRAL PLAINS UPPER LOW NORTHEASTWARD. ANOTHER SURFACE LOW
WILL DEVELOP AND TRACK NORTHEASTWARD INTO WISCONSIN BY SATURDAY
MORNING. LATE FRIDAY NIGHT THROUGH SATURDAY MORNING WILL PROBABLY
END UP BEING THE BEST CHANCE FOR SHOWERS AND THUNDERSTORMS AS THIS
OCCURS. MORNING FRONTAL PASSAGE IS NOT ALL THAT FAVORABLE FOR SEVERE
WEATHER BUT DO EXPECT THAT SOME SORT OF LINE OR COMPLEX OF STORMS
WOULD AFFECT THE AREA...BRINGING HEAVY RAINFALL IF NOTHING ELSE.
HIGH PRESSURE RIDGING BUILDS IN NORTH OF THE AREA BEHIND THE
DEPARTING LOW. THE BIGGEST ISSUE WITH THIS HAS BEEN TIMING WITH THE
LATEST GUIDANCE FASTER THAN EARLIER RUNS KEEPING THE PRECIP CONFINED
TO SATURDAY MORNING. WILL ADJUST POPS TO BETTER FIT THIS BUT WILL
KEEP CHANCE POPS FOR SATURDAY AFTERNOON FOR NOW. H85 TEMPS COOL
BEHIND THE SYSTEM KEEPING HIGHS IN THE UPPER 70S AND LOWER 80S WITH
SLIGHTLY WARMER TEMPS SUNDAY. THE WESTERN TROUGH WILL AMPLIFY AS IT
MOVES INTO THE NORTHERN PLAINS TAKING A SURFACE LOW NORTHEAST FROM
THE NORTHERN PLAINS TO NORTHWESTERN ONTARIO LATER SUNDAY. TIMING
WILL ONCE AGAIN NEED TO BE BETTER ASSESSED BUT THIS SYSTEM WILL
BRING ANOTHER COOL FRONT ACROSS THE AREA SOME TIME MONDAY. A LOWER
AMPLITUDE UPPER FLOW BECOMES ESTABLISHED AS THE TROUGH DEPARTS WITH
HIGH PRESSURE BUILDING IN AT THE SURFACE. WIDESPREAD POP CHANCES
LOOK LOW INTO MIDWEEK BUT THE FAIRLY ZONAL FLOW WILL BE SUPPORTIVE
OF WEAK PASSING SHORTWAVES WHICH COULD TRIGGER SOME SPOTTY PRECIP AT
TIMES. HIGHS GENERALLY LOOK TO BE AROUND 80 BUT THE FLOW WILL LIKELY
BE WEAK ENOUGH TO SUPPORT LAKE COOLING AS LONG AS THE SURFACE HIGH
IS NEARBY.

MDB

&&

.AVIATION...

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

* EASTERLY WINDS AROUND 10KT THRU EARLY EVENING.
* ISOLATED/SCATTERED SHRA THIS EVENING THRU FRIDAY MORNING.
CMS/BEACH

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

GRADIENT HAS TIGHTENED JUST A BIT THIS MORNING WITH EASTERLY WINDS
AROUND 10KT. MAY SEE SOME FLUCTUATION IN WIND SPEEDS BUT OVERALL...
PREVAILING WINDS WILL LIKELY BE EASTERLY AROUND 10KT FOR MUCH OF
THE DAY. WINDS SLOWLY TURN SOUTHEAST THIS EVENING THE SHIFT
SOUTHERLY TOWARD DAYBREAK FRIDAY.

MID CLOUDS WILL VARY FROM SCT TO BKN THIS MORNING BUT SHOULD
EVENTUALLY BECOME BKN/OVC LATER THIS AFTERNOON INTO THIS EVENING
AS THEY SLOWLY LOWER. HIGH MVFR CIGS HAVE DEVELOPED ACROSS EASTERN
IOWA AND FAR WESTERN IL. THESE WILL NEED TO BE MONITORED THIS
MORNING...ESPECIALLY FOR POSSIBLE HIGH MVFR CIGS INTO RFD.

SHRA/TSRA OVER IOWA ARE EXPECTED TO LIFT NORTHEAST THIS AFTERNOON
AND THIS EVENING...POSSIBLY MOVING ACROSS FAR NORTHWEST IL AND
RFD WITH ADDITIONAL SHRA DEVELOPMENT POSSIBLE THRU THE NIGHT AS A
WARM FRONT LIFTS ACROSS THE AREA. OVERALL CONFIDENCE REGARDING
TIMING AND COVERAGE OF PRECIP REMAINS LOW SO MAINTAINED PREVIOUS
PROB MENTION AND ADDED VICINITY MENTION INTO FRIDAY MORNING WITH
THE BEST CHANCES ACROSS FAR NORTHERN IL INTO SOUTHERN WI. CMS

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

* HIGH FOR WINDS THRU THE PERIOD.
* LOW FOR SHRA THIS EVENING THRU FRIDAY MORNING.
CMS/BEACH

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

* FRIDAY NIGHT...CHANCE OF TSRA.
* SATURDAY...TSRA LIKELY.
* SUNDAY...SLIGHT CHANCE OF TSRA.
* MONDAY AND TUESDAY...CHANCE OF TSRA.
* WEDNESDAY...DRY/VFR.

&&

.MARINE...

300 AM...HIGH PRESSURE OVER THE LAKES REGION WILL MOVE EAST TODAY
AND TONIGHT REACHING NEW ENGLAND FRIDAY MORNING. EAST WINDS 10 TO
15 KTS WILL GRADUALLY TURN SOUTHEASTERLY THIS EVENING THEN MORE
SOUTHERLY OVERNIGHT INTO FRIDAY MORNING AND INCREASE. LOW PRESSURE
OVER THE WESTERN PLAINS WILL MOVE NORTHEAST TO MINNESOTA AND IOWA
BY FRIDAY MORNING THEN TURN NORTHEAST ACROSS THE NORTHERN LAKES
SATURDAY INTO SATURDAY EVENING. THE GRADIENT WILL TIGHTEN AHEAD OF
THIS LOW WITH 15-25KTS EXPECTED FRIDAY. THE GRADIENT WILL SLOWLY
WEAKEN FROM NORTH TO SOUTH FRIDAY NIGHT. A TRAILING COLD FRONT
FROM THIS LOW WILL THEN MOVE SOUTH ACROSS LAKE MICHIGAN SATURDAY
NIGHT INTO SUNDAY MORNING. THIS FRONT WILL THEN LIFT BACK NORTH AS
A WARM FRONT SUNDAY NIGHT AS STRONGER HIGH PRESSURE IS EXPECTED TO
MOVE ACROSS THE NORTHERN LAKES AND ONTARIO SUNDAY NIGHT AND
MONDAY. CMS

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO







000
FXUS63 KLOT 281141
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
641 AM CDT THU AUG 28 2014

.DISCUSSION...
310 AM CDT

MORE ACTIVE WEATHER WILL TRY TO RETURN TO THE AREA INTO THIS EVENING
FOR AT LEAST PART OF THE AREA FOLLOWING THE RATHER QUIET WEATHER
YESTERDAY. THE FORECAST WILL FOCUS ON TIMING AND COVERAGE OF
SHOWER/THUNDER CHANCES AS WELL AS TEMPERATURES...ESPECIALLY FRIDAY
WHEN THUNDERSTORMS COULD HINDER ANOTHER SUBSTANTIAL WARM UP. THE
MAIN FEATURE ON WATER VAPOR THIS MORNING IS AN UPPER LOW WHICH HAS
BEEN SLOWLY SPINNING EASTWARD ACROSS THE WESTERN U.S. THE LOW IS NOW
MAKING SLIGHTLY FASTER EASTWARD PROGRESS ACROSS COLORADO AND WYOMING
AND AMPLIFYING A RIDGE AHEAD OF IT INTO THE MID AND UPPER
MISSISSIPPI RIVER VALLEY. SEVERAL SMALLER SCALE SHORTWAVES ARE
MOVING NORTHEASTWARD AROUND THE BASE OF THE LOW AND LIFTING INTO
KANSAS AND NEBRASKA. LOOKING FURTHER NORTHWEST...A TROUGH AXIS
EXTENDS SOUTHWESTWARD FROM NORTHERN ALBERTA ACROSS CENTRAL BRITISH
COLUMBIA AND OVER THE PACIFIC WHILE A CLOSED UPPER IS DIGGING
SOUTHEASTWARD OFF THE SOUTHERN ALASKA COAST. AT THE SURFACE...HIGH
PRESSURE IS CENTERED OVER LAKE SUPERIOR WHILE A FRONTAL BOUNDARY
EXTENDS FROM THE MAINE COAST DOWN THE OHIO VALLEY AND BACK INTO THE
CENTRAL PLAINS. SURFACE LOW PRESSURE IS ORGANIZING ACROSS THE
CENTRAL AND SOUTHERN HIGH PLAINS IN CONJUNCTION WITH THE APPROACHING
UPPER LOW.

TODAY AND TONIGHT...THE UPPER RIDGE AXIS WILL BE CRESTING THE AREA
THIS MORNING AS THE ENTIRE RIDGE BROADENS INTO FRIDAY. THE SURFACE
HIGH WILL ACCELERATE EASTWARD AND BE CENTERED OVER THE LOWER ST.
LAWRENCE RIVER VALLEY BY FRIDAY. THE UPPER LOW WILL PUSH INTO THE
CENTRAL PLAINS WHILE THE ATTENDANT SURFACE LOW MOVES NORTHEASTWARD
INTO MINNESOTA TONIGHT. WARM ADVECTION AHEAD OF THE ADVANCING UPPER
TROUGH IS GENERATING SHOWERS AND THUNDERSTORMS ACROSS MUCH OF
NEBRASKA INTO SOUTHERN IOWA AND NORTHERN MISSOURI IN CONJUNCTION
WITH SEVERAL SHORTWAVES. THE WARM ADVECTION WILL SPREAD
NORTHEASTWARD WITH A SURFACE WARM FRONT ALSO MOVING NORTHEASTWARD
AND CROSSING THE LOCAL AREA TODAY. THE FOCUS OF THE ASCENT WILL BE
TO THE WEST AND NORTHWEST OF THE AREA THROUGH THE MORNING KEEPING
THE BULK OF IF NOT ALL OF THE SHOWER ACTIVITY OUT OF THE CWA.
HOWEVER...HAVE BEEN SEEING A FEW LIGHT SPRINKLES/SHOWERS ALONG AND
SOUTH OF THE SOUTHERN CWA BORDER THIS MORNING AS WELL LIKELY IN
CONJUNCTION WITH A SUBTLE MID LEVEL WAVE. EXPECT THESE TO SHIFT EAST
OF THE AREA THROUGH DAYBREAK. PRECIP CHANCES WILL INCREASE THIS
AFTERNOON HOWEVER...MAINLY ACROSS THE WESTERN HALF OF THE AREA AND
IT IS POSSIBLE THIS COULD BE A LITTLE FAST. A BETTER PUSH OF THETA-E
AND INSTABILITY MOVE ACROSS THIS EVENING...ESPECIALLY ACROSS
NORTHERN AREAS SO MAY SEE THE PEAK OF THE ACTIVITY DURING THIS TIME.
SOUTHERN AND EASTERN AREAS MAY END UP STAYING DRY FOR MUCH OF THIS
PERIOD. HIGHS TODAY WILL RANGE FROM THE UPPER 70S NORTH TO LOWER 80S
SOUTH WITH A FAIR AMOUNT OF CLOUD COVER EXPECTED.

FRIDAY...FRIDAY WILL BE A TRICKY FORECAST WITH THE POTENTIAL
FOR A NOTICEABLE WARM UP BUT ALSO A POTENTIAL TO HAVE THAT SPOILED
BY THUNDERSTORMS. THE WESTERN PERIPHERY OF THE MID LEVEL WARM AXIS
WILL BE OVER THE AREA WITH A SOUTH TO SOUTHWEST SURFACE WIND IN
PLACE. H85/H92 HIGH TEMP CLIMATOLOGY SHOWS STRONG SUPPORT FOR HIGHS
NEAR 90 WITH VALUES OF 18/23C. LATEST GUIDANCE SHOWS CONVECTION
DEVELOPING TO THE SOUTH OF THE AREA FRIDAY MORNING AND LIFTING
NORTHWARD ON THE WESTERN FLANK OF THE RIDGE AND CROSSING THE AREA
INTO THE AFTERNOON. TOUGH TO SAY IF THIS WILL BE THE CASE BUT THE
PATTERN IS CERTAINLY SUCH THAT THIS COULD OCCUR SO WILL CONTINUE
WITH POPS PRIMARILY FRIDAY AFTERNOON AND STICK WITH HIGHS IN THE MID
TO UPPER 80S FOR NOW.

FRIDAY NIGHT THROUGH MID NEXT WEEK...LARGER SCALE TROUGHING WILL BE
BUILDING INTO WESTERN NORTH AMERICA INTO SATURDAY WHICH WILL HELP
KICK THE CENTRAL PLAINS UPPER LOW NORTHEASTWARD. ANOTHER SURFACE LOW
WILL DEVELOP AND TRACK NORTHEASTWARD INTO WISCONSIN BY SATURDAY
MORNING. LATE FRIDAY NIGHT THROUGH SATURDAY MORNING WILL PROBABLY
END UP BEING THE BEST CHANCE FOR SHOWERS AND THUNDERSTORMS AS THIS
OCCURS. MORNING FRONTAL PASSAGE IS NOT ALL THAT FAVORABLE FOR SEVERE
WEATHER BUT DO EXPECT THAT SOME SORT OF LINE OR COMPLEX OF STORMS
WOULD AFFECT THE AREA...BRINGING HEAVY RAINFALL IF NOTHING ELSE.
HIGH PRESSURE RIDGING BUILDS IN NORTH OF THE AREA BEHIND THE
DEPARTING LOW. THE BIGGEST ISSUE WITH THIS HAS BEEN TIMING WITH THE
LATEST GUIDANCE FASTER THAN EARLIER RUNS KEEPING THE PRECIP CONFINED
TO SATURDAY MORNING. WILL ADJUST POPS TO BETTER FIT THIS BUT WILL
KEEP CHANCE POPS FOR SATURDAY AFTERNOON FOR NOW. H85 TEMPS COOL
BEHIND THE SYSTEM KEEPING HIGHS IN THE UPPER 70S AND LOWER 80S WITH
SLIGHTLY WARMER TEMPS SUNDAY. THE WESTERN TROUGH WILL AMPLIFY AS IT
MOVES INTO THE NORTHERN PLAINS TAKING A SURFACE LOW NORTHEAST FROM
THE NORTHERN PLAINS TO NORTHWESTERN ONTARIO LATER SUNDAY. TIMING
WILL ONCE AGAIN NEED TO BE BETTER ASSESSED BUT THIS SYSTEM WILL
BRING ANOTHER COOL FRONT ACROSS THE AREA SOME TIME MONDAY. A LOWER
AMPLITUDE UPPER FLOW BECOMES ESTABLISHED AS THE TROUGH DEPARTS WITH
HIGH PRESSURE BUILDING IN AT THE SURFACE. WIDESPREAD POP CHANCES
LOOK LOW INTO MIDWEEK BUT THE FAIRLY ZONAL FLOW WILL BE SUPPORTIVE
OF WEAK PASSING SHORTWAVES WHICH COULD TRIGGER SOME SPOTTY PRECIP AT
TIMES. HIGHS GENERALLY LOOK TO BE AROUND 80 BUT THE FLOW WILL LIKELY
BE WEAK ENOUGH TO SUPPORT LAKE COOLING AS LONG AS THE SURFACE HIGH
IS NEARBY.

MDB

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 12Z...

* EASTERLY WINDS AROUND 10KT THRU EARLY EVENING.
* ISOLATED/SCATTERED SHRA THIS EVENING THRU FRIDAY MORNING. CMS

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

GRADIENT HAS TIGHTENED JUST A BIT THIS MORNING WITH EASTERLY WINDS
AROUND 10KT. MAY SEE SOME FLUCTUATION IN WIND SPEEDS BUT OVERALL...
PREVAILING WINDS WILL LIKELY BE EASTERLY AROUND 10KT FOR MUCH OF
THE DAY. WINDS SLOWLY TURN SOUTHEAST THIS EVENING THE SHIFT
SOUTHERLY TOWARD DAYBREAK FRIDAY.

MID CLOUDS WILL VARY FROM SCT TO BKN THIS MORNING BUT SHOULD
EVENTUALLY BECOME BKN/OVC LATER THIS AFTERNOON INTO THIS EVENING
AS THEY SLOWLY LOWER. HIGH MVFR CIGS HAVE DEVELOPED ACROSS EASTERN
IOWA AND FAR WESTERN IL. THESE WILL NEED TO BE MONITORED THIS
MORNING...ESPECIALLY FOR POSSIBLE HIGH MVFR CIGS INTO RFD.

SHRA/TSRA OVER IOWA ARE EXPECTED TO LIFT NORTHEAST THIS AFTERNOON
AND THIS EVENING...POSSIBLY MOVING ACROSS FAR NORTHWEST IL AND
RFD WITH ADDITIONAL SHRA DEVELOPMENT POSSIBLE THRU THE NIGHT AS A
WARM FRONT LIFTS ACROSS THE AREA. OVERALL CONFIDENCE REGARDING
TIMING AND COVERAGE OF PRECIP REMAINS LOW SO MAINTAINED PREVIOUS
PROB MENTION AND ADDED VICINITY MENTION INTO FRIDAY MORNING WITH
THE BEST CHANCES ACROSS FAR NORTHERN IL INTO SOUTHERN WI. CMS

//ORD AND MDW CONFIDENCE...UPDATED 12Z...

* HIGH FOR WINDS THRU THE PERIOD.
* LOW FOR SHRA THIS EVENING THRU FRIDAY MORNING. CMS

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

* FRIDAY NIGHT...CHANCE OF TSRA.
* SATURDAY...TSRA LIKELY.
* SUNDAY...SLIGHT CHANCE OF TSRA.
* MONDAY AND TUESDAY...CHANCE OF TSRA.
* WEDNESDAY...DRY/VFR.

&&

.MARINE...

300 AM...HIGH PRESSURE OVER THE LAKES REGION WILL MOVE EAST TODAY
AND TONIGHT REACHING NEW ENGLAND FRIDAY MORNING. EAST WINDS 10 TO
15 KTS WILL GRADUALLY TURN SOUTHEASTERLY THIS EVENING THEN MORE
SOUTHERLY OVERNIGHT INTO FRIDAY MORNING AND INCREASE. LOW PRESSURE
OVER THE WESTERN PLAINS WILL MOVE NORTHEAST TO MINNESOTA AND IOWA
BY FRIDAY MORNING THEN TURN NORTHEAST ACROSS THE NORTHERN LAKES
SATURDAY INTO SATURDAY EVENING. THE GRADIENT WILL TIGHTEN AHEAD OF
THIS LOW WITH 15-25KTS EXPECTED FRIDAY. THE GRADIENT WILL SLOWLY
WEAKEN FROM NORTH TO SOUTH FRIDAY NIGHT. A TRAILING COLD FRONT
FROM THIS LOW WILL THEN MOVE SOUTH ACROSS LAKE MICHIGAN SATURDAY
NIGHT INTO SUNDAY MORNING. THIS FRONT WILL THEN LIFT BACK NORTH AS
A WARM FRONT SUNDAY NIGHT AS STRONGER HIGH PRESSURE IS EXPECTED TO
MOVE ACROSS THE NORTHERN LAKES AND ONTARIO SUNDAY NIGHT AND
MONDAY. CMS

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO







000
FXUS63 KLOT 280901
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
401 AM CDT THU AUG 28 2014

.DISCUSSION...
310 AM CDT

MORE ACTIVE WEATHER WILL TRY TO RETURN TO THE AREA INTO THIS EVENING
FOR AT LEAST PART OF THE AREA FOLLOWING THE RATHER QUIET WEATHER
YESTERDAY. THE FORECAST WILL FOCUS ON TIMING AND COVERAGE OF
SHOWER/THUNDER CHANCES AS WELL AS TEMPERATURES...ESPECIALLY FRIDAY
WHEN THUNDERSTORMS COULD HINDER ANOTHER SUBSTANTIAL WARM UP. THE
MAIN FEATURE ON WATER VAPOR THIS MORNING IS AN UPPER LOW WHICH HAS
BEEN SLOWLY SPINNING EASTWARD ACROSS THE WESTERN U.S. THE LOW IS NOW
MAKING SLIGHTLY FASTER EASTWARD PROGRESS ACROSS COLORADO AND WYOMING
AND AMPLIFYING A RIDGE AHEAD OF IT INTO THE MID AND UPPER
MISSISSIPPI RIVER VALLEY. SEVERAL SMALLER SCALE SHORTWAVES ARE
MOVING NORTHEASTWARD AROUND THE BASE OF THE LOW AND LIFTING INTO
KANSAS AND NEBRASKA. LOOKING FURTHER NORTHWEST...A TROUGH AXIS
EXTENDS SOUTHWESTWARD FROM NORTHERN ALBERTA ACROSS CENTRAL BRITISH
COLUMBIA AND OVER THE PACIFIC WHILE A CLOSED UPPER IS DIGGING
SOUTHEASTWARD OFF THE SOUTHERN ALASKA COAST. AT THE SURFACE...HIGH
PRESSURE IS CENTERED OVER LAKE SUPERIOR WHILE A FRONTAL BOUNDARY
EXTENDS FROM THE MAINE COAST DOWN THE OHIO VALLEY AND BACK INTO THE
CENTRAL PLAINS. SURFACE LOW PRESSURE IS ORGANIZING ACROSS THE
CENTRAL AND SOUTHERN HIGH PLAINS IN CONJUNCTION WITH THE APPROACHING
UPPER LOW.

TODAY AND TONIGHT...THE UPPER RIDGE AXIS WILL BE CRESTING THE AREA
THIS MORNING AS THE ENTIRE RIDGE BROADENS INTO FRIDAY. THE SURFACE
HIGH WILL ACCELERATE EASTWARD AND BE CENTERED OVER THE LOWER ST.
LAWRENCE RIVER VALLEY BY FRIDAY. THE UPPER LOW WILL PUSH INTO THE
CENTRAL PLAINS WHILE THE ATTENDANT SURFACE LOW MOVES NORTHEASTWARD
INTO MINNESOTA TONIGHT. WARM ADVECTION AHEAD OF THE ADVANCING UPPER
TROUGH IS GENERATING SHOWERS AND THUNDERSTORMS ACROSS MUCH OF
NEBRASKA INTO SOUTHERN IOWA AND NORTHERN MISSOURI IN CONJUNCTION
WITH SEVERAL SHORTWAVES. THE WARM ADVECTION WILL SPREAD
NORTHEASTWARD WITH A SURFACE WARM FRONT ALSO MOVING NORTHEASTWARD
AND CROSSING THE LOCAL AREA TODAY. THE FOCUS OF THE ASCENT WILL BE
TO THE WEST AND NORTHWEST OF THE AREA THROUGH THE MORNING KEEPING
THE BULK OF IF NOT ALL OF THE SHOWER ACTIVITY OUT OF THE CWA.
HOWEVER...HAVE BEEN SEEING A FEW LIGHT SPRINKLES/SHOWERS ALONG AND
SOUTH OF THE SOUTHERN CWA BORDER THIS MORNING AS WELL LIKELY IN
CONJUNCTION WITH A SUBTLE MID LEVEL WAVE. EXPECT THESE TO SHIFT EAST
OF THE AREA THROUGH DAYBREAK. PRECIP CHANCES WILL INCREASE THIS
AFTERNOON HOWEVER...MAINLY ACROSS THE WESTERN HALF OF THE AREA AND
IT IS POSSIBLE THIS COULD BE A LITTLE FAST. A BETTER PUSH OF THETA-E
AND INSTABILITY MOVE ACROSS THIS EVENING...ESPECIALLY ACROSS
NORTHERN AREAS SO MAY SEE THE PEAK OF THE ACTIVITY DURING THIS TIME.
SOUTHERN AND EASTERN AREAS MAY END UP STAYING DRY FOR MUCH OF THIS
PERIOD. HIGHS TODAY WILL RANGE FROM THE UPPER 70S NORTH TO LOWER 80S
SOUTH WITH A FAIR AMOUNT OF CLOUD COVER EXPECTED.

FRIDAY...FRIDAY WILL BE A TRICKY FORECAST WITH THE POTENTIAL
FOR A NOTICEABLE WARM UP BUT ALSO A POTENTIAL TO HAVE THAT SPOILED
BY THUNDERSTORMS. THE WESTERN PERIPHERY OF THE MID LEVEL WARM AXIS
WILL BE OVER THE AREA WITH A SOUTH TO SOUTHWEST SURFACE WIND IN
PLACE. H85/H92 HIGH TEMP CLIMATOLOGY SHOWS STRONG SUPPORT FOR HIGHS
NEAR 90 WITH VALUES OF 18/23C. LATEST GUIDANCE SHOWS CONVECTION
DEVELOPING TO THE SOUTH OF THE AREA FRIDAY MORNING AND LIFTING
NORTHWARD ON THE WESTERN FLANK OF THE RIDGE AND CROSSING THE AREA
INTO THE AFTERNOON. TOUGH TO SAY IF THIS WILL BE THE CASE BUT THE
PATTERN IS CERTAINLY SUCH THAT THIS COULD OCCUR SO WILL CONTINUE
WITH POPS PRIMARILY FRIDAY AFTERNOON AND STICK WITH HIGHS IN THE MID
TO UPPER 80S FOR NOW.

FRIDAY NIGHT THROUGH MID NEXT WEEK...LARGER SCALE TROUGHING WILL BE
BUILDING INTO WESTERN NORTH AMERICA INTO SATURDAY WHICH WILL HELP
KICK THE CENTRAL PLAINS UPPER LOW NORTHEASTWARD. ANOTHER SURFACE LOW
WILL DEVELOP AND TRACK NORTHEASTWARD INTO WISCONSIN BY SATURDAY
MORNING. LATE FRIDAY NIGHT THROUGH SATURDAY MORNING WILL PROBABLY
END UP BEING THE BEST CHANCE FOR SHOWERS AND THUNDERSTORMS AS THIS
OCCURS. MORNING FRONTAL PASSAGE IS NOT ALL THAT FAVORABLE FOR SEVERE
WEATHER BUT DO EXPECT THAT SOME SORT OF LINE OR COMPLEX OF STORMS
WOULD AFFECT THE AREA...BRINGING HEAVY RAINFALL IF NOTHING ELSE.
HIGH PRESSURE RIDGING BUILDS IN NORTH OF THE AREA BEHIND THE
DEPARTING LOW. THE BIGGEST ISSUE WITH THIS HAS BEEN TIMING WITH THE
LATEST GUIDANCE FASTER THAN EARLIER RUNS KEEPING THE PRECIP CONFINED
TO SATURDAY MORNING. WILL ADJUST POPS TO BETTER FIT THIS BUT WILL
KEEP CHANCE POPS FOR SATURDAY AFTERNOON FOR NOW. H85 TEMPS COOL
BEHIND THE SYSTEM KEEPING HIGHS IN THE UPPER 70S AND LOWER 80S WITH
SLIGHTLY WARMER TEMPS SUNDAY. THE WESTERN TROUGH WILL AMPLIFY AS IT
MOVES INTO THE NORTHERN PLAINS TAKING A SURFACE LOW NORTHEAST FROM
THE NORTHERN PLAINS TO NORTHWESTERN ONTARIO LATER SUNDAY. TIMING
WILL ONCE AGAIN NEED TO BE BETTER ASSESSED BUT THIS SYSTEM WILL
BRING ANOTHER COOL FRONT ACROSS THE AREA SOME TIME MONDAY. A LOWER
AMPLITUDE UPPER FLOW BECOMES ESTABLISHED AS THE TROUGH DEPARTS WITH
HIGH PRESSURE BUILDING IN AT THE SURFACE. WIDESPREAD POP CHANCES
LOOK LOW INTO MIDWEEK BUT THE FAIRLY ZONAL FLOW WILL BE SUPPORTIVE
OF WEAK PASSING SHORTWAVES WHICH COULD TRIGGER SOME SPOTTY PRECIP AT
TIMES. HIGHS GENERALLY LOOK TO BE AROUND 80 BUT THE FLOW WILL LIKELY
BE WEAK ENOUGH TO SUPPORT LAKE COOLING AS LONG AS THE SURFACE HIGH
IS NEARBY.

MDB

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 09Z...

* EASTERLY WINDS THRU THE PERIOD...AND AROUND 10KT THIS AFTERNOON.
* ISOLATED SHRA THIS EVENING/OVERNIGHT. CMS

//DISCUSSION...UPDATED 06Z...

HIGH PRESSURE OVER THE WESTERN GREAT LAKES WILL MOVE EAST TODAY
AND TONIGHT. LIGHT NORTHEAST WINDS EARLY THIS MORNING WILL TURN
MORE EASTERLY TODAY AND INCREASE IN SPEED TO 10KTS BY EARLY THIS
AFTERNOON. A WARM FRONT WILL MOVE ACROSS THE AREA LATER TONIGHT...
SHIFTING WINDS SOUTHEASTERLY THIS EVENING AND THEN MORE SOUTHERLY
BY FRIDAY MORNING.

AS THE WARM FRONT LIFTS NORTH...SCATTERED SHOWERS WILL BE POSSIBLE
STARTING FIRST ACROSS NORTHWEST IL LATE THIS AFTERNOON THEN ACROSS
THE REST OF THE TERMINALS THIS EVENING INTO EARLY FRIDAY MORNING.
INSTABILITY APPEARS FAIRLY WEAK SO NOT EXPECTING MUCH IN THE WAY
OF THUNDER. BUT CONFIDENCE REGARDING OVERALL COVERAGE IS FAIRLY
LOW AND WILL JUST CARRY PROB MENTION EXCEPT AT RFD WHERE CHANCES
ARE A LITTLE BETTER. CMS

//ORD AND MDW CONFIDENCE...UPDATED 09Z...

* HIGH FOR WINDS THRU THE PERIOD.
* LOW FOR SHRA TONIGHT. CMS

//OUTLOOK FOR ORD/MDW FOR 12Z FRIDAY-12Z WEDNESDAY...UPDATED 00Z...

FRIDAY...CHANCE TSRA.

SATURDAY...TSRA LIKELY.

SUNDAY AND MONDAY...CHANCE TSRA.

TUESDAY...SLIGHT CHANCE TSRA.

KMD

&&

.MARINE...

300 AM...HIGH PRESSURE OVER THE LAKES REGION WILL MOVE EAST TODAY
AND TONIGHT REACHING NEW ENGLAND FRIDAY MORNING. EAST WINDS 10 TO
15 KTS WILL GRADUALLY TURN SOUTHEASTERLY THIS EVENING THEN MORE
SOUTHERLY OVERNIGHT INTO FRIDAY MORNING AND INCREASE. LOW PRESSURE
OVER THE WESTERN PLAINS WILL MOVE NORTHEAST TO MINNESOTA AND IOWA
BY FRIDAY MORNING THEN TURN NORTHEAST ACROSS THE NORTHERN LAKES
SATURDAY INTO SATURDAY EVENING. THE GRADIENT WILL TIGHTEN AHEAD OF
THIS LOW WITH 15-25KTS EXPECTED FRIDAY. THE GRADIENT WILL SLOWLY
WEAKEN FROM NORTH TO SOUTH FRIDAY NIGHT. A TRAILING COLD FRONT
FROM THIS LOW WILL THEN MOVE SOUTH ACROSS LAKE MICHIGAN SATURDAY
NIGHT INTO SUNDAY MORNING. THIS FRONT WILL THEN LIFT BACK NORTH AS
A WARM FRONT SUNDAY NIGHT AS STRONGER HIGH PRESSURE IS EXPECTED TO
MOVE ACROSS THE NORTHERN LAKES AND ONTARIO SUNDAY NIGHT AND
MONDAY. CMS

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO







000
FXUS63 KLOT 280901
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
401 AM CDT THU AUG 28 2014

.DISCUSSION...
310 AM CDT

MORE ACTIVE WEATHER WILL TRY TO RETURN TO THE AREA INTO THIS EVENING
FOR AT LEAST PART OF THE AREA FOLLOWING THE RATHER QUIET WEATHER
YESTERDAY. THE FORECAST WILL FOCUS ON TIMING AND COVERAGE OF
SHOWER/THUNDER CHANCES AS WELL AS TEMPERATURES...ESPECIALLY FRIDAY
WHEN THUNDERSTORMS COULD HINDER ANOTHER SUBSTANTIAL WARM UP. THE
MAIN FEATURE ON WATER VAPOR THIS MORNING IS AN UPPER LOW WHICH HAS
BEEN SLOWLY SPINNING EASTWARD ACROSS THE WESTERN U.S. THE LOW IS NOW
MAKING SLIGHTLY FASTER EASTWARD PROGRESS ACROSS COLORADO AND WYOMING
AND AMPLIFYING A RIDGE AHEAD OF IT INTO THE MID AND UPPER
MISSISSIPPI RIVER VALLEY. SEVERAL SMALLER SCALE SHORTWAVES ARE
MOVING NORTHEASTWARD AROUND THE BASE OF THE LOW AND LIFTING INTO
KANSAS AND NEBRASKA. LOOKING FURTHER NORTHWEST...A TROUGH AXIS
EXTENDS SOUTHWESTWARD FROM NORTHERN ALBERTA ACROSS CENTRAL BRITISH
COLUMBIA AND OVER THE PACIFIC WHILE A CLOSED UPPER IS DIGGING
SOUTHEASTWARD OFF THE SOUTHERN ALASKA COAST. AT THE SURFACE...HIGH
PRESSURE IS CENTERED OVER LAKE SUPERIOR WHILE A FRONTAL BOUNDARY
EXTENDS FROM THE MAINE COAST DOWN THE OHIO VALLEY AND BACK INTO THE
CENTRAL PLAINS. SURFACE LOW PRESSURE IS ORGANIZING ACROSS THE
CENTRAL AND SOUTHERN HIGH PLAINS IN CONJUNCTION WITH THE APPROACHING
UPPER LOW.

TODAY AND TONIGHT...THE UPPER RIDGE AXIS WILL BE CRESTING THE AREA
THIS MORNING AS THE ENTIRE RIDGE BROADENS INTO FRIDAY. THE SURFACE
HIGH WILL ACCELERATE EASTWARD AND BE CENTERED OVER THE LOWER ST.
LAWRENCE RIVER VALLEY BY FRIDAY. THE UPPER LOW WILL PUSH INTO THE
CENTRAL PLAINS WHILE THE ATTENDANT SURFACE LOW MOVES NORTHEASTWARD
INTO MINNESOTA TONIGHT. WARM ADVECTION AHEAD OF THE ADVANCING UPPER
TROUGH IS GENERATING SHOWERS AND THUNDERSTORMS ACROSS MUCH OF
NEBRASKA INTO SOUTHERN IOWA AND NORTHERN MISSOURI IN CONJUNCTION
WITH SEVERAL SHORTWAVES. THE WARM ADVECTION WILL SPREAD
NORTHEASTWARD WITH A SURFACE WARM FRONT ALSO MOVING NORTHEASTWARD
AND CROSSING THE LOCAL AREA TODAY. THE FOCUS OF THE ASCENT WILL BE
TO THE WEST AND NORTHWEST OF THE AREA THROUGH THE MORNING KEEPING
THE BULK OF IF NOT ALL OF THE SHOWER ACTIVITY OUT OF THE CWA.
HOWEVER...HAVE BEEN SEEING A FEW LIGHT SPRINKLES/SHOWERS ALONG AND
SOUTH OF THE SOUTHERN CWA BORDER THIS MORNING AS WELL LIKELY IN
CONJUNCTION WITH A SUBTLE MID LEVEL WAVE. EXPECT THESE TO SHIFT EAST
OF THE AREA THROUGH DAYBREAK. PRECIP CHANCES WILL INCREASE THIS
AFTERNOON HOWEVER...MAINLY ACROSS THE WESTERN HALF OF THE AREA AND
IT IS POSSIBLE THIS COULD BE A LITTLE FAST. A BETTER PUSH OF THETA-E
AND INSTABILITY MOVE ACROSS THIS EVENING...ESPECIALLY ACROSS
NORTHERN AREAS SO MAY SEE THE PEAK OF THE ACTIVITY DURING THIS TIME.
SOUTHERN AND EASTERN AREAS MAY END UP STAYING DRY FOR MUCH OF THIS
PERIOD. HIGHS TODAY WILL RANGE FROM THE UPPER 70S NORTH TO LOWER 80S
SOUTH WITH A FAIR AMOUNT OF CLOUD COVER EXPECTED.

FRIDAY...FRIDAY WILL BE A TRICKY FORECAST WITH THE POTENTIAL
FOR A NOTICEABLE WARM UP BUT ALSO A POTENTIAL TO HAVE THAT SPOILED
BY THUNDERSTORMS. THE WESTERN PERIPHERY OF THE MID LEVEL WARM AXIS
WILL BE OVER THE AREA WITH A SOUTH TO SOUTHWEST SURFACE WIND IN
PLACE. H85/H92 HIGH TEMP CLIMATOLOGY SHOWS STRONG SUPPORT FOR HIGHS
NEAR 90 WITH VALUES OF 18/23C. LATEST GUIDANCE SHOWS CONVECTION
DEVELOPING TO THE SOUTH OF THE AREA FRIDAY MORNING AND LIFTING
NORTHWARD ON THE WESTERN FLANK OF THE RIDGE AND CROSSING THE AREA
INTO THE AFTERNOON. TOUGH TO SAY IF THIS WILL BE THE CASE BUT THE
PATTERN IS CERTAINLY SUCH THAT THIS COULD OCCUR SO WILL CONTINUE
WITH POPS PRIMARILY FRIDAY AFTERNOON AND STICK WITH HIGHS IN THE MID
TO UPPER 80S FOR NOW.

FRIDAY NIGHT THROUGH MID NEXT WEEK...LARGER SCALE TROUGHING WILL BE
BUILDING INTO WESTERN NORTH AMERICA INTO SATURDAY WHICH WILL HELP
KICK THE CENTRAL PLAINS UPPER LOW NORTHEASTWARD. ANOTHER SURFACE LOW
WILL DEVELOP AND TRACK NORTHEASTWARD INTO WISCONSIN BY SATURDAY
MORNING. LATE FRIDAY NIGHT THROUGH SATURDAY MORNING WILL PROBABLY
END UP BEING THE BEST CHANCE FOR SHOWERS AND THUNDERSTORMS AS THIS
OCCURS. MORNING FRONTAL PASSAGE IS NOT ALL THAT FAVORABLE FOR SEVERE
WEATHER BUT DO EXPECT THAT SOME SORT OF LINE OR COMPLEX OF STORMS
WOULD AFFECT THE AREA...BRINGING HEAVY RAINFALL IF NOTHING ELSE.
HIGH PRESSURE RIDGING BUILDS IN NORTH OF THE AREA BEHIND THE
DEPARTING LOW. THE BIGGEST ISSUE WITH THIS HAS BEEN TIMING WITH THE
LATEST GUIDANCE FASTER THAN EARLIER RUNS KEEPING THE PRECIP CONFINED
TO SATURDAY MORNING. WILL ADJUST POPS TO BETTER FIT THIS BUT WILL
KEEP CHANCE POPS FOR SATURDAY AFTERNOON FOR NOW. H85 TEMPS COOL
BEHIND THE SYSTEM KEEPING HIGHS IN THE UPPER 70S AND LOWER 80S WITH
SLIGHTLY WARMER TEMPS SUNDAY. THE WESTERN TROUGH WILL AMPLIFY AS IT
MOVES INTO THE NORTHERN PLAINS TAKING A SURFACE LOW NORTHEAST FROM
THE NORTHERN PLAINS TO NORTHWESTERN ONTARIO LATER SUNDAY. TIMING
WILL ONCE AGAIN NEED TO BE BETTER ASSESSED BUT THIS SYSTEM WILL
BRING ANOTHER COOL FRONT ACROSS THE AREA SOME TIME MONDAY. A LOWER
AMPLITUDE UPPER FLOW BECOMES ESTABLISHED AS THE TROUGH DEPARTS WITH
HIGH PRESSURE BUILDING IN AT THE SURFACE. WIDESPREAD POP CHANCES
LOOK LOW INTO MIDWEEK BUT THE FAIRLY ZONAL FLOW WILL BE SUPPORTIVE
OF WEAK PASSING SHORTWAVES WHICH COULD TRIGGER SOME SPOTTY PRECIP AT
TIMES. HIGHS GENERALLY LOOK TO BE AROUND 80 BUT THE FLOW WILL LIKELY
BE WEAK ENOUGH TO SUPPORT LAKE COOLING AS LONG AS THE SURFACE HIGH
IS NEARBY.

MDB

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 09Z...

* EASTERLY WINDS THRU THE PERIOD...AND AROUND 10KT THIS AFTERNOON.
* ISOLATED SHRA THIS EVENING/OVERNIGHT. CMS

//DISCUSSION...UPDATED 06Z...

HIGH PRESSURE OVER THE WESTERN GREAT LAKES WILL MOVE EAST TODAY
AND TONIGHT. LIGHT NORTHEAST WINDS EARLY THIS MORNING WILL TURN
MORE EASTERLY TODAY AND INCREASE IN SPEED TO 10KTS BY EARLY THIS
AFTERNOON. A WARM FRONT WILL MOVE ACROSS THE AREA LATER TONIGHT...
SHIFTING WINDS SOUTHEASTERLY THIS EVENING AND THEN MORE SOUTHERLY
BY FRIDAY MORNING.

AS THE WARM FRONT LIFTS NORTH...SCATTERED SHOWERS WILL BE POSSIBLE
STARTING FIRST ACROSS NORTHWEST IL LATE THIS AFTERNOON THEN ACROSS
THE REST OF THE TERMINALS THIS EVENING INTO EARLY FRIDAY MORNING.
INSTABILITY APPEARS FAIRLY WEAK SO NOT EXPECTING MUCH IN THE WAY
OF THUNDER. BUT CONFIDENCE REGARDING OVERALL COVERAGE IS FAIRLY
LOW AND WILL JUST CARRY PROB MENTION EXCEPT AT RFD WHERE CHANCES
ARE A LITTLE BETTER. CMS

//ORD AND MDW CONFIDENCE...UPDATED 09Z...

* HIGH FOR WINDS THRU THE PERIOD.
* LOW FOR SHRA TONIGHT. CMS

//OUTLOOK FOR ORD/MDW FOR 12Z FRIDAY-12Z WEDNESDAY...UPDATED 00Z...

FRIDAY...CHANCE TSRA.

SATURDAY...TSRA LIKELY.

SUNDAY AND MONDAY...CHANCE TSRA.

TUESDAY...SLIGHT CHANCE TSRA.

KMD

&&

.MARINE...

300 AM...HIGH PRESSURE OVER THE LAKES REGION WILL MOVE EAST TODAY
AND TONIGHT REACHING NEW ENGLAND FRIDAY MORNING. EAST WINDS 10 TO
15 KTS WILL GRADUALLY TURN SOUTHEASTERLY THIS EVENING THEN MORE
SOUTHERLY OVERNIGHT INTO FRIDAY MORNING AND INCREASE. LOW PRESSURE
OVER THE WESTERN PLAINS WILL MOVE NORTHEAST TO MINNESOTA AND IOWA
BY FRIDAY MORNING THEN TURN NORTHEAST ACROSS THE NORTHERN LAKES
SATURDAY INTO SATURDAY EVENING. THE GRADIENT WILL TIGHTEN AHEAD OF
THIS LOW WITH 15-25KTS EXPECTED FRIDAY. THE GRADIENT WILL SLOWLY
WEAKEN FROM NORTH TO SOUTH FRIDAY NIGHT. A TRAILING COLD FRONT
FROM THIS LOW WILL THEN MOVE SOUTH ACROSS LAKE MICHIGAN SATURDAY
NIGHT INTO SUNDAY MORNING. THIS FRONT WILL THEN LIFT BACK NORTH AS
A WARM FRONT SUNDAY NIGHT AS STRONGER HIGH PRESSURE IS EXPECTED TO
MOVE ACROSS THE NORTHERN LAKES AND ONTARIO SUNDAY NIGHT AND
MONDAY. CMS

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 280811
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
311 AM CDT THU AUG 28 2014

.DISCUSSION...
310 AM CDT

MORE ACTIVE WEATHER WILL TRY TO RETURN TO THE AREA INTO THIS EVENING
FOR AT LEAST PART OF THE AREA FOLLOWING THE RATHER QUIET WEATHER
YESTERDAY. THE FORECAST WILL FOCUS ON TIMING AND COVERAGE OF
SHOWER/THUNDER CHANCES AS WELL AS TEMPERATURES...ESPECIALLY FRIDAY
WHEN THUNDERSTORMS COULD HINDER ANOTHER SUBSTANTIAL WARM UP. THE
MAIN FEATURE ON WATER VAPOR THIS MORNING IS AN UPPER LOW WHICH HAS
BEEN SLOWLY SPINNING EASTWARD ACROSS THE WESTERN U.S. THE LOW IS NOW
MAKING SLIGHTLY FASTER EASTWARD PROGRESS ACROSS COLORADO AND WYOMING
AND AMPLIFYING A RIDGE AHEAD OF IT INTO THE MID AND UPPER
MISSISSIPPI RIVER VALLEY. SEVERAL SMALLER SCALE SHORTWAVES ARE
MOVING NORTHEASTWARD AROUND THE BASE OF THE LOW AND LIFTING INTO
KANSAS AND NEBRASKA. LOOKING FURTHER NORTHWEST...A TROUGH AXIS
EXTENDS SOUTHWESTWARD FROM NORTHERN ALBERTA ACROSS CENTRAL BRITISH
COLUMBIA AND OVER THE PACIFIC WHILE A CLOSED UPPER IS DIGGING
SOUTHEASTWARD OFF THE SOUTHERN ALASKA COAST. AT THE SURFACE...HIGH
PRESSURE IS CENTERED OVER LAKE SUPERIOR WHILE A FRONTAL BOUNDARY
EXTENDS FROM THE MAINE COAST DOWN THE OHIO VALLEY AND BACK INTO THE
CENTRAL PLAINS. SURFACE LOW PRESSURE IS ORGANIZING ACROSS THE
CENTRAL AND SOUTHERN HIGH PLAINS IN CONJUNCTION WITH THE APPROACHING
UPPER LOW.

TODAY AND TONIGHT...THE UPPER RIDGE AXIS WILL BE CRESTING THE AREA
THIS MORNING AS THE ENTIRE RIDGE BROADENS INTO FRIDAY. THE SURFACE
HIGH WILL ACCELERATE EASTWARD AND BE CENTERED OVER THE LOWER ST.
LAWRENCE RIVER VALLEY BY FRIDAY. THE UPPER LOW WILL PUSH INTO THE
CENTRAL PLAINS WHILE THE ATTENDANT SURFACE LOW MOVES NORTHEASTWARD
INTO MINNESOTA TONIGHT. WARM ADVECTION AHEAD OF THE ADVANCING UPPER
TROUGH IS GENERATING SHOWERS AND THUNDERSTORMS ACROSS MUCH OF
NEBRASKA INTO SOUTHERN IOWA AND NORTHERN MISSOURI IN CONJUNCTION
WITH SEVERAL SHORTWAVES. THE WARM ADVECTION WILL SPREAD
NORTHEASTWARD WITH A SURFACE WARM FRONT ALSO MOVING NORTHEASTWARD
AND CROSSING THE LOCAL AREA TODAY. THE FOCUS OF THE ASCENT WILL BE
TO THE WEST AND NORTHWEST OF THE AREA THROUGH THE MORNING KEEPING
THE BULK OF IF NOT ALL OF THE SHOWER ACTIVITY OUT OF THE CWA.
HOWEVER...HAVE BEEN SEEING A FEW LIGHT SPRINKLES/SHOWERS ALONG AND
SOUTH OF THE SOUTHERN CWA BORDER THIS MORNING AS WELL LIKELY IN
CONJUNCTION WITH A SUBTLE MID LEVEL WAVE. EXPECT THESE TO SHIFT EAST
OF THE AREA THROUGH DAYBREAK. PRECIP CHANCES WILL INCREASE THIS
AFTERNOON HOWEVER...MAINLY ACROSS THE WESTERN HALF OF THE AREA AND
IT IS POSSIBLE THIS COULD BE A LITTLE FAST. A BETTER PUSH OF THETA-E
AND INSTABILITY MOVE ACROSS THIS EVENING...ESPECIALLY ACROSS
NORTHERN AREAS SO MAY SEE THE PEAK OF THE ACTIVITY DURING THIS TIME.
SOUTHERN AND EASTERN AREAS MAY END UP STAYING DRY FOR MUCH OF THIS
PERIOD. HIGHS TODAY WILL RANGE FROM THE UPPER 70S NORTH TO LOWER 80S
SOUTH WITH A FAIR AMOUNT OF CLOUD COVER EXPECTED.

FRIDAY...FRIDAY WILL BE A TRICKY FORECAST WITH THE POTENTIAL
FOR A NOTICEABLE WARM UP BUT ALSO A POTENTIAL TO HAVE THAT SPOILED
BY THUNDERSTORMS. THE WESTERN PERIPHERY OF THE MID LEVEL WARM AXIS
WILL BE OVER THE AREA WITH A SOUTH TO SOUTHWEST SURFACE WIND IN
PLACE. H85/H92 HIGH TEMP CLIMATOLOGY SHOWS STRONG SUPPORT FOR HIGHS
NEAR 90 WITH VALUES OF 18/23C. LATEST GUIDANCE SHOWS CONVECTION
DEVELOPING TO THE SOUTH OF THE AREA FRIDAY MORNING AND LIFTING
NORTHWARD ON THE WESTERN FLANK OF THE RIDGE AND CROSSING THE AREA
INTO THE AFTERNOON. TOUGH TO SAY IF THIS WILL BE THE CASE BUT THE
PATTERN IS CERTAINLY SUCH THAT THIS COULD OCCUR SO WILL CONTINUE
WITH POPS PRIMARILY FRIDAY AFTERNOON AND STICK WITH HIGHS IN THE MID
TO UPPER 80S FOR NOW.

FRIDAY NIGHT THROUGH MID NEXT WEEK...LARGER SCALE TROUGHING WILL BE
BUILDING INTO WESTERN NORTH AMERICA INTO SATURDAY WHICH WILL HELP
KICK THE CENTRAL PLAINS UPPER LOW NORTHEASTWARD. ANOTHER SURFACE LOW
WILL DEVELOP AND TRACK NORTHEASTWARD INTO WISCONSIN BY SATURDAY
MORNING. LATE FRIDAY NIGHT THROUGH SATURDAY MORNING WILL PROBABLY
END UP BEING THE BEST CHANCE FOR SHOWERS AND THUNDERSTORMS AS THIS
OCCURS. MORNING FRONTAL PASSAGE IS NOT ALL THAT FAVORABLE FOR SEVERE
WEATHER BUT DO EXPECT THAT SOME SORT OF LINE OR COMPLEX OF STORMS
WOULD AFFECT THE AREA...BRINGING HEAVY RAINFALL IF NOTHING ELSE.
HIGH PRESSURE RIDGING BUILDS IN NORTH OF THE AREA BEHIND THE
DEPARTING LOW. THE BIGGEST ISSUE WITH THIS HAS BEEN TIMING WITH THE
LATEST GUIDANCE FASTER THAN EARLIER RUNS KEEPING THE PRECIP CONFINED
TO SATURDAY MORNING. WILL ADJUST POPS TO BETTER FIT THIS BUT WILL
KEEP CHANCE POPS FOR SATURDAY AFTERNOON FOR NOW. H85 TEMPS COOL
BEHIND THE SYSTEM KEEPING HIGHS IN THE UPPER 70S AND LOWER 80S WITH
SLIGHTLY WARMER TEMPS SUNDAY. THE WESTERN TROUGH WILL AMPLIFY AS IT
MOVES INTO THE NORTHERN PLAINS TAKING A SURFACE LOW NORTHEAST FROM
THE NORTHERN PLAINS TO NORTHWESTERN ONTARIO LATER SUNDAY. TIMING
WILL ONCE AGAIN NEED TO BE BETTER ASSESSED BUT THIS SYSTEM WILL
BRING ANOTHER COOL FRONT ACROSS THE AREA SOME TIME MONDAY. A LOWER
AMPLITUDE UPPER FLOW BECOMES ESTABLISHED AS THE TROUGH DEPARTS WITH
HIGH PRESSURE BUILDING IN AT THE SURFACE. WIDESPREAD POP CHANCES
LOOK LOW INTO MIDWEEK BUT THE FAIRLY ZONAL FLOW WILL BE SUPPORTIVE
OF WEAK PASSING SHORTWAVES WHICH COULD TRIGGER SOME SPOTTY PRECIP AT
TIMES. HIGHS GENERALLY LOOK TO BE AROUND 80 BUT THE FLOW WILL LIKELY
BE WEAK ENOUGH TO SUPPORT LAKE COOLING AS LONG AS THE SURFACE HIGH
IS NEARBY.

MDB

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* EASTERLY WINDS THRU THE PERIOD...AND AROUND 10KT THIS AFTERNOON.
* ISOLATED SHRA THIS EVENING/OVERNIGHT. CMS

//DISCUSSION...UPDATED 06Z...

HIGH PRESSURE OVER THE WESTERN GREAT LAKES WILL MOVE EAST TODAY
AND TONIGHT. LIGHT NORTHEAST WINDS EARLY THIS MORNING WILL TURN
MORE EASTERLY TODAY AND INCREASE IN SPEED TO 10KTS BY EARLY THIS
AFTERNOON. A WARM FRONT WILL MOVE ACROSS THE AREA LATER TONIGHT...
SHIFTING WINDS SOUTHEASTERLY THIS EVENING AND THEN MORE SOUTHERLY
BY FRIDAY MORNING.

AS THE WARM FRONT LIFTS NORTH...SCATTERED SHOWERS WILL BE POSSIBLE
STARTING FIRST ACROSS NORTHWEST IL LATE THIS AFTERNOON THEN ACROSS
THE REST OF THE TERMINALS THIS EVENING INTO EARLY FRIDAY MORNING.
INSTABILITY APPEARS FAIRLY WEAK SO NOT EXPECTING MUCH IN THE WAY
OF THUNDER. BUT CONFIDENCE REGARDING OVERALL COVERAGE IS FAIRLY
LOW AND WILL JUST CARRY PROB MENTION EXCEPT AT RFD WHERE CHANCES
ARE A LITTLE BETTER. CMS

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* HIGH FOR WINDS THRU THE PERIOD.
* LOW FOR SHRA TONIGHT. CMS

//OUTLOOK FOR ORD/MDW FOR 12Z FRIDAY-12Z WEDNESDAY...UPDATED 00Z...

FRIDAY...CHANCE TSRA.

SATURDAY...TSRA LIKELY.

SUNDAY AND MONDAY...CHANCE TSRA.

TUESDAY...SLIGHT CHANCE TSRA.

KMD

&&

.MARINE...

300 AM...HIGH PRESSURE OVER THE LAKES REGION WILL MOVE EAST TODAY
AND TONIGHT REACHING NEW ENGLAND FRIDAY MORNING. EAST WINDS 10 TO
15 KTS WILL GRADUALLY TURN SOUTHEASTERLY THIS EVENING THEN MORE
SOUTHERLY OVERNIGHT INTO FRIDAY MORNING AND INCREASE. LOW PRESSURE
OVER THE WESTERN PLAINS WILL MOVE NORTHEAST TO MINNESOTA AND IOWA
BY FRIDAY MORNING THEN TURN NORTHEAST ACROSS THE NORTHERN LAKES
SATURDAY INTO SATURDAY EVENING. THE GRADIENT WILL TIGHTEN AHEAD OF
THIS LOW WITH 15-25KTS EXPECTED FRIDAY. THE GRADIENT WILL SLOWLY
WEAKEN FROM NORTH TO SOUTH FRIDAY NIGHT. A TRAILING COLD FRONT
FROM THIS LOW WILL THEN MOVE SOUTH ACROSS LAKE MICHIGAN SATURDAY
NIGHT INTO SUNDAY MORNING. THIS FRONT WILL THEN LIFT BACK NORTH AS
A WARM FRONT SUNDAY NIGHT AS STRONGER HIGH PRESSURE IS EXPECTED TO
MOVE ACROSS THE NORTHERN LAKES AND ONTARIO SUNDAY NIGHT AND
MONDAY. CMS

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO







000
FXUS63 KLOT 280811
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
311 AM CDT THU AUG 28 2014

.DISCUSSION...
310 AM CDT

MORE ACTIVE WEATHER WILL TRY TO RETURN TO THE AREA INTO THIS EVENING
FOR AT LEAST PART OF THE AREA FOLLOWING THE RATHER QUIET WEATHER
YESTERDAY. THE FORECAST WILL FOCUS ON TIMING AND COVERAGE OF
SHOWER/THUNDER CHANCES AS WELL AS TEMPERATURES...ESPECIALLY FRIDAY
WHEN THUNDERSTORMS COULD HINDER ANOTHER SUBSTANTIAL WARM UP. THE
MAIN FEATURE ON WATER VAPOR THIS MORNING IS AN UPPER LOW WHICH HAS
BEEN SLOWLY SPINNING EASTWARD ACROSS THE WESTERN U.S. THE LOW IS NOW
MAKING SLIGHTLY FASTER EASTWARD PROGRESS ACROSS COLORADO AND WYOMING
AND AMPLIFYING A RIDGE AHEAD OF IT INTO THE MID AND UPPER
MISSISSIPPI RIVER VALLEY. SEVERAL SMALLER SCALE SHORTWAVES ARE
MOVING NORTHEASTWARD AROUND THE BASE OF THE LOW AND LIFTING INTO
KANSAS AND NEBRASKA. LOOKING FURTHER NORTHWEST...A TROUGH AXIS
EXTENDS SOUTHWESTWARD FROM NORTHERN ALBERTA ACROSS CENTRAL BRITISH
COLUMBIA AND OVER THE PACIFIC WHILE A CLOSED UPPER IS DIGGING
SOUTHEASTWARD OFF THE SOUTHERN ALASKA COAST. AT THE SURFACE...HIGH
PRESSURE IS CENTERED OVER LAKE SUPERIOR WHILE A FRONTAL BOUNDARY
EXTENDS FROM THE MAINE COAST DOWN THE OHIO VALLEY AND BACK INTO THE
CENTRAL PLAINS. SURFACE LOW PRESSURE IS ORGANIZING ACROSS THE
CENTRAL AND SOUTHERN HIGH PLAINS IN CONJUNCTION WITH THE APPROACHING
UPPER LOW.

TODAY AND TONIGHT...THE UPPER RIDGE AXIS WILL BE CRESTING THE AREA
THIS MORNING AS THE ENTIRE RIDGE BROADENS INTO FRIDAY. THE SURFACE
HIGH WILL ACCELERATE EASTWARD AND BE CENTERED OVER THE LOWER ST.
LAWRENCE RIVER VALLEY BY FRIDAY. THE UPPER LOW WILL PUSH INTO THE
CENTRAL PLAINS WHILE THE ATTENDANT SURFACE LOW MOVES NORTHEASTWARD
INTO MINNESOTA TONIGHT. WARM ADVECTION AHEAD OF THE ADVANCING UPPER
TROUGH IS GENERATING SHOWERS AND THUNDERSTORMS ACROSS MUCH OF
NEBRASKA INTO SOUTHERN IOWA AND NORTHERN MISSOURI IN CONJUNCTION
WITH SEVERAL SHORTWAVES. THE WARM ADVECTION WILL SPREAD
NORTHEASTWARD WITH A SURFACE WARM FRONT ALSO MOVING NORTHEASTWARD
AND CROSSING THE LOCAL AREA TODAY. THE FOCUS OF THE ASCENT WILL BE
TO THE WEST AND NORTHWEST OF THE AREA THROUGH THE MORNING KEEPING
THE BULK OF IF NOT ALL OF THE SHOWER ACTIVITY OUT OF THE CWA.
HOWEVER...HAVE BEEN SEEING A FEW LIGHT SPRINKLES/SHOWERS ALONG AND
SOUTH OF THE SOUTHERN CWA BORDER THIS MORNING AS WELL LIKELY IN
CONJUNCTION WITH A SUBTLE MID LEVEL WAVE. EXPECT THESE TO SHIFT EAST
OF THE AREA THROUGH DAYBREAK. PRECIP CHANCES WILL INCREASE THIS
AFTERNOON HOWEVER...MAINLY ACROSS THE WESTERN HALF OF THE AREA AND
IT IS POSSIBLE THIS COULD BE A LITTLE FAST. A BETTER PUSH OF THETA-E
AND INSTABILITY MOVE ACROSS THIS EVENING...ESPECIALLY ACROSS
NORTHERN AREAS SO MAY SEE THE PEAK OF THE ACTIVITY DURING THIS TIME.
SOUTHERN AND EASTERN AREAS MAY END UP STAYING DRY FOR MUCH OF THIS
PERIOD. HIGHS TODAY WILL RANGE FROM THE UPPER 70S NORTH TO LOWER 80S
SOUTH WITH A FAIR AMOUNT OF CLOUD COVER EXPECTED.

FRIDAY...FRIDAY WILL BE A TRICKY FORECAST WITH THE POTENTIAL
FOR A NOTICEABLE WARM UP BUT ALSO A POTENTIAL TO HAVE THAT SPOILED
BY THUNDERSTORMS. THE WESTERN PERIPHERY OF THE MID LEVEL WARM AXIS
WILL BE OVER THE AREA WITH A SOUTH TO SOUTHWEST SURFACE WIND IN
PLACE. H85/H92 HIGH TEMP CLIMATOLOGY SHOWS STRONG SUPPORT FOR HIGHS
NEAR 90 WITH VALUES OF 18/23C. LATEST GUIDANCE SHOWS CONVECTION
DEVELOPING TO THE SOUTH OF THE AREA FRIDAY MORNING AND LIFTING
NORTHWARD ON THE WESTERN FLANK OF THE RIDGE AND CROSSING THE AREA
INTO THE AFTERNOON. TOUGH TO SAY IF THIS WILL BE THE CASE BUT THE
PATTERN IS CERTAINLY SUCH THAT THIS COULD OCCUR SO WILL CONTINUE
WITH POPS PRIMARILY FRIDAY AFTERNOON AND STICK WITH HIGHS IN THE MID
TO UPPER 80S FOR NOW.

FRIDAY NIGHT THROUGH MID NEXT WEEK...LARGER SCALE TROUGHING WILL BE
BUILDING INTO WESTERN NORTH AMERICA INTO SATURDAY WHICH WILL HELP
KICK THE CENTRAL PLAINS UPPER LOW NORTHEASTWARD. ANOTHER SURFACE LOW
WILL DEVELOP AND TRACK NORTHEASTWARD INTO WISCONSIN BY SATURDAY
MORNING. LATE FRIDAY NIGHT THROUGH SATURDAY MORNING WILL PROBABLY
END UP BEING THE BEST CHANCE FOR SHOWERS AND THUNDERSTORMS AS THIS
OCCURS. MORNING FRONTAL PASSAGE IS NOT ALL THAT FAVORABLE FOR SEVERE
WEATHER BUT DO EXPECT THAT SOME SORT OF LINE OR COMPLEX OF STORMS
WOULD AFFECT THE AREA...BRINGING HEAVY RAINFALL IF NOTHING ELSE.
HIGH PRESSURE RIDGING BUILDS IN NORTH OF THE AREA BEHIND THE
DEPARTING LOW. THE BIGGEST ISSUE WITH THIS HAS BEEN TIMING WITH THE
LATEST GUIDANCE FASTER THAN EARLIER RUNS KEEPING THE PRECIP CONFINED
TO SATURDAY MORNING. WILL ADJUST POPS TO BETTER FIT THIS BUT WILL
KEEP CHANCE POPS FOR SATURDAY AFTERNOON FOR NOW. H85 TEMPS COOL
BEHIND THE SYSTEM KEEPING HIGHS IN THE UPPER 70S AND LOWER 80S WITH
SLIGHTLY WARMER TEMPS SUNDAY. THE WESTERN TROUGH WILL AMPLIFY AS IT
MOVES INTO THE NORTHERN PLAINS TAKING A SURFACE LOW NORTHEAST FROM
THE NORTHERN PLAINS TO NORTHWESTERN ONTARIO LATER SUNDAY. TIMING
WILL ONCE AGAIN NEED TO BE BETTER ASSESSED BUT THIS SYSTEM WILL
BRING ANOTHER COOL FRONT ACROSS THE AREA SOME TIME MONDAY. A LOWER
AMPLITUDE UPPER FLOW BECOMES ESTABLISHED AS THE TROUGH DEPARTS WITH
HIGH PRESSURE BUILDING IN AT THE SURFACE. WIDESPREAD POP CHANCES
LOOK LOW INTO MIDWEEK BUT THE FAIRLY ZONAL FLOW WILL BE SUPPORTIVE
OF WEAK PASSING SHORTWAVES WHICH COULD TRIGGER SOME SPOTTY PRECIP AT
TIMES. HIGHS GENERALLY LOOK TO BE AROUND 80 BUT THE FLOW WILL LIKELY
BE WEAK ENOUGH TO SUPPORT LAKE COOLING AS LONG AS THE SURFACE HIGH
IS NEARBY.

MDB

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* EASTERLY WINDS THRU THE PERIOD...AND AROUND 10KT THIS AFTERNOON.
* ISOLATED SHRA THIS EVENING/OVERNIGHT. CMS

//DISCUSSION...UPDATED 06Z...

HIGH PRESSURE OVER THE WESTERN GREAT LAKES WILL MOVE EAST TODAY
AND TONIGHT. LIGHT NORTHEAST WINDS EARLY THIS MORNING WILL TURN
MORE EASTERLY TODAY AND INCREASE IN SPEED TO 10KTS BY EARLY THIS
AFTERNOON. A WARM FRONT WILL MOVE ACROSS THE AREA LATER TONIGHT...
SHIFTING WINDS SOUTHEASTERLY THIS EVENING AND THEN MORE SOUTHERLY
BY FRIDAY MORNING.

AS THE WARM FRONT LIFTS NORTH...SCATTERED SHOWERS WILL BE POSSIBLE
STARTING FIRST ACROSS NORTHWEST IL LATE THIS AFTERNOON THEN ACROSS
THE REST OF THE TERMINALS THIS EVENING INTO EARLY FRIDAY MORNING.
INSTABILITY APPEARS FAIRLY WEAK SO NOT EXPECTING MUCH IN THE WAY
OF THUNDER. BUT CONFIDENCE REGARDING OVERALL COVERAGE IS FAIRLY
LOW AND WILL JUST CARRY PROB MENTION EXCEPT AT RFD WHERE CHANCES
ARE A LITTLE BETTER. CMS

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* HIGH FOR WINDS THRU THE PERIOD.
* LOW FOR SHRA TONIGHT. CMS

//OUTLOOK FOR ORD/MDW FOR 12Z FRIDAY-12Z WEDNESDAY...UPDATED 00Z...

FRIDAY...CHANCE TSRA.

SATURDAY...TSRA LIKELY.

SUNDAY AND MONDAY...CHANCE TSRA.

TUESDAY...SLIGHT CHANCE TSRA.

KMD

&&

.MARINE...

300 AM...HIGH PRESSURE OVER THE LAKES REGION WILL MOVE EAST TODAY
AND TONIGHT REACHING NEW ENGLAND FRIDAY MORNING. EAST WINDS 10 TO
15 KTS WILL GRADUALLY TURN SOUTHEASTERLY THIS EVENING THEN MORE
SOUTHERLY OVERNIGHT INTO FRIDAY MORNING AND INCREASE. LOW PRESSURE
OVER THE WESTERN PLAINS WILL MOVE NORTHEAST TO MINNESOTA AND IOWA
BY FRIDAY MORNING THEN TURN NORTHEAST ACROSS THE NORTHERN LAKES
SATURDAY INTO SATURDAY EVENING. THE GRADIENT WILL TIGHTEN AHEAD OF
THIS LOW WITH 15-25KTS EXPECTED FRIDAY. THE GRADIENT WILL SLOWLY
WEAKEN FROM NORTH TO SOUTH FRIDAY NIGHT. A TRAILING COLD FRONT
FROM THIS LOW WILL THEN MOVE SOUTH ACROSS LAKE MICHIGAN SATURDAY
NIGHT INTO SUNDAY MORNING. THIS FRONT WILL THEN LIFT BACK NORTH AS
A WARM FRONT SUNDAY NIGHT AS STRONGER HIGH PRESSURE IS EXPECTED TO
MOVE ACROSS THE NORTHERN LAKES AND ONTARIO SUNDAY NIGHT AND
MONDAY. CMS

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 280800
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
300 AM CDT THU AUG 28 2014

.DISCUSSION...
330 PM CDT

SHORT TERM...WEDNESDAY AFTERNOON THROUGH SATURDAY...

FOR THE REMAINDER OF THE AFTERNOON SHOULD REMAIN QUIET AS THE OLD
STATIONARY BOUNDARY REMAINS WELL TO THE SOUTH ACROSS SRN IL AND THE
OHIO VALLEY.  HAVE MAINTAINED SLIGHT CHANCE POPS ACROSS THE VERY FAR
SOUTH OF THE CWA...A LITTLE NORTH OF THE BOUNDARY IN DEFERENCE TO
THE PROXIMITY TO THE BOUNDARY TO THE SOUTH AND A WARM AND VERY MOIST
AIRMASS...WITH DEWPOINTS STILL IN THE LOW 70S...ACROSS THE AREA.
THROUGH THE LATE EVENING AND INTO THE OVERNIGHT HOURS...ANTICIPATE
INCREASING POPS SPREADING FROM SOUTHWEST TO NORTHEAST AS LOW
PRESSURE OVER THE CENTRAL PLAINS LIFTS NEWD...DRAGGING THE OLD
STATIONARY BOUNDARY BACK NORTH AS A WARM FRONT.  WITH UPPER RIDGING
BUILDING ALOFT WITH THE RIDGE AXIS EXTENDING JUST EAST OF THE
MISSISSIPPI RIVER BY EARLY THURSDAY MORNING...ANTICIPATE THAT SWLY
FLOW ALOFT SHOULD HELP KEEP THE HIGHEST PCPN CHANCES OVER LOCATIONS
WEST OF A LINE FROM ROCKFORD TO WATSEKA.

THROUGH THURSDAY AND THURSDAY NIGHT...THE UPPER RIDGE WILL SLOWLY
BUILD  EAST AS SHORTWAVE ENERGY OVERTOPS THE RIDGE.  THE SHORT RANGE
MODELS ARE RELATIVELY CONSISTENT ON ADVERTISING THIS SCENARIO...SO
ANTICIPATE INCREASING POPS OVER THE WRN PORTIONS OF THE CWA THROUGH
THE EVENING AND THEN THE NORTHERN PORTIONS OF THE CWA THROUGH THE
NIGHT...BUT WITH THE TRACK OF THE MAIN UPPER SHORTWAVE TO THE WEST
AND NORTH OF THE CWA...THE STRONGER UPPER FORCING SHOULD BE OVER
IOWA AND INTO WISCONSIN...SO HAVE LIMITED POPS OVER THE CWA TO
CHANCE LEVELS.  THE LOCAL AREA SHOULD BEGIN TO SEE POPS INCREASING
THROUGH THE DAY FRIDAY AND ESPECIALLY LATER FRIDAY NIGHT AS A STRONG
SHORTWAVE LIFTING OUT OF THE GREAT BASIN TONIGHT SLOWLY TRACKS EAST
ACROSS THE CENTRAL PLAINS AND REACHES THE MIDDLE AND UPPER
MISSISSIPPI VALLEY FRIDAY NIGHT.  WILL INCREASE POPS THROUGH FRIDAY
EVENING WITH LIKELY POPS SPREADING INTO THE WRN PORTIONS OF THE CWA
AFTER MIDNIGHT FRIDAY NIGHT AND EAST ACROSS THE REMAINDER OF THE
AREA THROUGH SATURDAY AND INTO SATURDAY EVENING.

FORM TEMPERATURES...WITH SFC HIGH PRESSURE SLOWLY SLIDING ACROSS THE
GREAT LAKES REGION...THE WARMEST AND MOST HUMID CONDITIONS WILL BE
CONFINED TO THE FAR SOUTHERN PORTIONS OF THE CWA...THOUGH EVEN
LOCATIONS NORTH OF THE I-80 CORRIDOR HAVE SEEN TEMPS CLIMB INTO THE
LOWER 80S EVEN WITH PERSISTENT NELY FLOW AT THE LOWER LEVELS.  THE
HIGH WILL STILL HAVE A MAJOR INFLUENCE ON TEMPS THROUGH
THURSDAY...KEEPING THE NORTHERN PORTIONS OF THE CWA...INCLUDING THE
LAKEFRONT...ON THE COOLER SIDE WITH HIGHS IN THE UPPER 70S TO AROUND
80...WHILE THE SRN LOCATIONS SHOULD WARM INTO THE LOWER 80S.  AS THE
UPPER RIDGE BUILDS ACROSS THE AREA ON FRIDAY AND THE WARM FRONT
LIFTS WELL TO THE NORTH INTO WISCONSIN...EXPECT THAT TEMPS SHOULD
RETURN TO THE MIDDLE TO UPPER 80S WITH DEWPOINTS IN THE LOWER 70S.
THIS COMBINATION OF WARMTH AND MOISTURE SHOULD DRIVE HEAT INDEX
VALUES BACK INTO THE LOWER 90S.  BY FRIDAY NIGHT OR EARLY
SATURDAY...A WEAK COLD FRONT IS EXPECTED TO SWEEP ACROSS THE
AREA...BUT LITTLE SIGNIFICANT AIRMASS CHANGE IS EXPECTED AS THERE
SHOULD BE LITTLE INFLUX OF SIGNIFICANTLY COOLER/DRIER AIR INTO THE
REGION AS SFC HIGH PRESSURE BUILDS ACROSS SRN CANADA AND THE REGION
ONLY EXPERIENCES A BRIEF PERIOD OF LIGHT AND VARIABLE WINDS UNDER
VERY WEAK SFC TROUGHING ASSOCIATED WITH THE COLD FRONT.  BY
SATURDAY...SOUTHERLY FLOW SHOULD RETURN AS A COLD FRONT AND SFC
TROUGH MOVES OUT OVER THE NRN/CNTRL PLAINS AND AND THE BERMUDA HIGH
BUILDS BACK ACROSS THE GULF COAST.

FOR THE LONGER TERM...FROM SUNDAY THROUGH WEDNESDAY...UNSETTLED
WEATHER WILL CONTINUE ACROSS THE REGION FOR SUNDAY AND MONDAY.  THE
LONGER RANGE GUIDANCE IN IN RELATIVELY GOOD AGREEMENT ON A LONG WAVE
TROUGH MOVING ACROSS THE ROCKIES WITH WEAK RIDGING OVER THE ERN
CONUS.  THIS WILL PUT THE UPPER MIDWEST UNDER BROAD SWLY FLOW WITH A
SERIES OF WEAK SRN STREAM SHORT WAVES TRACKING ACROSS THE AREA.  IN
GENERAL...THE UPPER LEVEL PATTERN WILL BE FAIRLY LOW AMPLITUDE...SO
TIMING AND STRENGTH OF INDIVIDUAL WAVES WILL BE QUESTIONABLE...BUT
THE GENERAL TREND SHOULD BE FOR MORE PERIODIC SHOWERS AND
THUNDERSTORMS...THOUGH CONFIDENCE IN TIMING WILL BE LOW.  BY TUESDAY
AND WEDNESDAY...THE LONGER RANGE GUIDANCE IS INDICATING THAT THE
UPPER TROUGH SHOULD BEGIN TO MOVE EAST OF THE AREA...WITH HIGH
PRESSURE SETTLING OVER THE UPPER MISSISSIPPI VALLEY AND WESTERN
GREAT LAKES REGION.  THIS WOULD LEAD TO A PERIOD OF DRIER CONDITIONS
SO HAVE REMOVED POPS FOR TUESDAY AND WEDNESDAY.  UNDER RELATIVELY
LOW AMPLITUDE FLOW ALOFT...THERE SHOULD BE LITTLE DAY TO DAY
TEMPERATURE SWINGS WITH HIGHS GENERALLY IN THE LOWER 80S AND
OVERNIGHT LOWS IN THE 60S.

KREIN

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* EASTERLY WINDS THRU THE PERIOD...AND AROUND 10KT THIS AFTERNOON.
* ISOLATED SHRA THIS EVENING/OVERNIGHT. CMS

//DISCUSSION...UPDATED 06Z...

HIGH PRESSURE OVER THE WESTERN GREAT LAKES WILL MOVE EAST TODAY
AND TONIGHT. LIGHT NORTHEAST WINDS EARLY THIS MORNING WILL TURN
MORE EASTERLY TODAY AND INCREASE IN SPEED TO 10KTS BY EARLY THIS
AFTERNOON. A WARM FRONT WILL MOVE ACROSS THE AREA LATER TONIGHT...
SHIFTING WINDS SOUTHEASTERLY THIS EVENING AND THEN MORE SOUTHERLY
BY FRIDAY MORNING.

AS THE WARM FRONT LIFTS NORTH...SCATTERED SHOWERS WILL BE POSSIBLE
STARTING FIRST ACROSS NORTHWEST IL LATE THIS AFTERNOON THEN ACROSS
THE REST OF THE TERMINALS THIS EVENING INTO EARLY FRIDAY MORNING.
INSTABILITY APPEARS FAIRLY WEAK SO NOT EXPECTING MUCH IN THE WAY
OF THUNDER. BUT CONFIDENCE REGARDING OVERALL COVERAGE IS FAIRLY
LOW AND WILL JUST CARRY PROB MENTION EXCEPT AT RFD WHERE CHANCES
ARE A LITTLE BETTER. CMS

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* HIGH FOR WINDS THRU THE PERIOD.
* LOW FOR SHRA TONIGHT. CMS

//OUTLOOK FOR ORD/MDW FOR 12Z FRIDAY-12Z WEDNESDAY...UPDATED 00Z...

FRIDAY...CHANCE TSRA.

SATURDAY...TSRA LIKELY.

SUNDAY AND MONDAY...CHANCE TSRA.

TUESDAY...SLIGHT CHANCE TSRA.

KMD

&&

.MARINE...

300 AM...HIGH PRESSURE OVER THE LAKES REGION WILL MOVE EAST TODAY
AND TONIGHT REACHING NEW ENGLAND FRIDAY MORNING. EAST WINDS 10 TO
15 KTS WILL GRADUALLY TURN SOUTHEASTERLY THIS EVENING THEN MORE
SOUTHERLY OVERNIGHT INTO FRIDAY MORNING AND INCREASE. LOW PRESSURE
OVER THE WESTERN PLAINS WILL MOVE NORTHEAST TO MINNESOTA AND IOWA
BY FRIDAY MORNING THEN TURN NORTHEAST ACROSS THE NORTHERN LAKES
SATURDAY INTO SATURDAY EVENING. THE GRADIENT WILL TIGHTEN AHEAD OF
THIS LOW WITH 15-25KTS EXPECTED FRIDAY. THE GRADIENT WILL SLOWLY
WEAKEN FROM NORTH TO SOUTH FRIDAY NIGHT. A TRAILING COLD FRONT
FROM THIS LOW WILL THEN MOVE SOUTH ACROSS LAKE MICHIGAN SATURDAY
NIGHT INTO SUNDAY MORNING. THIS FRONT WILL THEN LIFT BACK NORTH AS
A WARM FRONT SUNDAY NIGHT AS STRONGER HIGH PRESSURE IS EXPECTED TO
MOVE ACROSS THE NORTHERN LAKES AND ONTARIO SUNDAY NIGHT AND
MONDAY. CMS

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO







000
FXUS63 KLOT 280800
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
300 AM CDT THU AUG 28 2014

.DISCUSSION...
330 PM CDT

SHORT TERM...WEDNESDAY AFTERNOON THROUGH SATURDAY...

FOR THE REMAINDER OF THE AFTERNOON SHOULD REMAIN QUIET AS THE OLD
STATIONARY BOUNDARY REMAINS WELL TO THE SOUTH ACROSS SRN IL AND THE
OHIO VALLEY.  HAVE MAINTAINED SLIGHT CHANCE POPS ACROSS THE VERY FAR
SOUTH OF THE CWA...A LITTLE NORTH OF THE BOUNDARY IN DEFERENCE TO
THE PROXIMITY TO THE BOUNDARY TO THE SOUTH AND A WARM AND VERY MOIST
AIRMASS...WITH DEWPOINTS STILL IN THE LOW 70S...ACROSS THE AREA.
THROUGH THE LATE EVENING AND INTO THE OVERNIGHT HOURS...ANTICIPATE
INCREASING POPS SPREADING FROM SOUTHWEST TO NORTHEAST AS LOW
PRESSURE OVER THE CENTRAL PLAINS LIFTS NEWD...DRAGGING THE OLD
STATIONARY BOUNDARY BACK NORTH AS A WARM FRONT.  WITH UPPER RIDGING
BUILDING ALOFT WITH THE RIDGE AXIS EXTENDING JUST EAST OF THE
MISSISSIPPI RIVER BY EARLY THURSDAY MORNING...ANTICIPATE THAT SWLY
FLOW ALOFT SHOULD HELP KEEP THE HIGHEST PCPN CHANCES OVER LOCATIONS
WEST OF A LINE FROM ROCKFORD TO WATSEKA.

THROUGH THURSDAY AND THURSDAY NIGHT...THE UPPER RIDGE WILL SLOWLY
BUILD  EAST AS SHORTWAVE ENERGY OVERTOPS THE RIDGE.  THE SHORT RANGE
MODELS ARE RELATIVELY CONSISTENT ON ADVERTISING THIS SCENARIO...SO
ANTICIPATE INCREASING POPS OVER THE WRN PORTIONS OF THE CWA THROUGH
THE EVENING AND THEN THE NORTHERN PORTIONS OF THE CWA THROUGH THE
NIGHT...BUT WITH THE TRACK OF THE MAIN UPPER SHORTWAVE TO THE WEST
AND NORTH OF THE CWA...THE STRONGER UPPER FORCING SHOULD BE OVER
IOWA AND INTO WISCONSIN...SO HAVE LIMITED POPS OVER THE CWA TO
CHANCE LEVELS.  THE LOCAL AREA SHOULD BEGIN TO SEE POPS INCREASING
THROUGH THE DAY FRIDAY AND ESPECIALLY LATER FRIDAY NIGHT AS A STRONG
SHORTWAVE LIFTING OUT OF THE GREAT BASIN TONIGHT SLOWLY TRACKS EAST
ACROSS THE CENTRAL PLAINS AND REACHES THE MIDDLE AND UPPER
MISSISSIPPI VALLEY FRIDAY NIGHT.  WILL INCREASE POPS THROUGH FRIDAY
EVENING WITH LIKELY POPS SPREADING INTO THE WRN PORTIONS OF THE CWA
AFTER MIDNIGHT FRIDAY NIGHT AND EAST ACROSS THE REMAINDER OF THE
AREA THROUGH SATURDAY AND INTO SATURDAY EVENING.

FORM TEMPERATURES...WITH SFC HIGH PRESSURE SLOWLY SLIDING ACROSS THE
GREAT LAKES REGION...THE WARMEST AND MOST HUMID CONDITIONS WILL BE
CONFINED TO THE FAR SOUTHERN PORTIONS OF THE CWA...THOUGH EVEN
LOCATIONS NORTH OF THE I-80 CORRIDOR HAVE SEEN TEMPS CLIMB INTO THE
LOWER 80S EVEN WITH PERSISTENT NELY FLOW AT THE LOWER LEVELS.  THE
HIGH WILL STILL HAVE A MAJOR INFLUENCE ON TEMPS THROUGH
THURSDAY...KEEPING THE NORTHERN PORTIONS OF THE CWA...INCLUDING THE
LAKEFRONT...ON THE COOLER SIDE WITH HIGHS IN THE UPPER 70S TO AROUND
80...WHILE THE SRN LOCATIONS SHOULD WARM INTO THE LOWER 80S.  AS THE
UPPER RIDGE BUILDS ACROSS THE AREA ON FRIDAY AND THE WARM FRONT
LIFTS WELL TO THE NORTH INTO WISCONSIN...EXPECT THAT TEMPS SHOULD
RETURN TO THE MIDDLE TO UPPER 80S WITH DEWPOINTS IN THE LOWER 70S.
THIS COMBINATION OF WARMTH AND MOISTURE SHOULD DRIVE HEAT INDEX
VALUES BACK INTO THE LOWER 90S.  BY FRIDAY NIGHT OR EARLY
SATURDAY...A WEAK COLD FRONT IS EXPECTED TO SWEEP ACROSS THE
AREA...BUT LITTLE SIGNIFICANT AIRMASS CHANGE IS EXPECTED AS THERE
SHOULD BE LITTLE INFLUX OF SIGNIFICANTLY COOLER/DRIER AIR INTO THE
REGION AS SFC HIGH PRESSURE BUILDS ACROSS SRN CANADA AND THE REGION
ONLY EXPERIENCES A BRIEF PERIOD OF LIGHT AND VARIABLE WINDS UNDER
VERY WEAK SFC TROUGHING ASSOCIATED WITH THE COLD FRONT.  BY
SATURDAY...SOUTHERLY FLOW SHOULD RETURN AS A COLD FRONT AND SFC
TROUGH MOVES OUT OVER THE NRN/CNTRL PLAINS AND AND THE BERMUDA HIGH
BUILDS BACK ACROSS THE GULF COAST.

FOR THE LONGER TERM...FROM SUNDAY THROUGH WEDNESDAY...UNSETTLED
WEATHER WILL CONTINUE ACROSS THE REGION FOR SUNDAY AND MONDAY.  THE
LONGER RANGE GUIDANCE IN IN RELATIVELY GOOD AGREEMENT ON A LONG WAVE
TROUGH MOVING ACROSS THE ROCKIES WITH WEAK RIDGING OVER THE ERN
CONUS.  THIS WILL PUT THE UPPER MIDWEST UNDER BROAD SWLY FLOW WITH A
SERIES OF WEAK SRN STREAM SHORT WAVES TRACKING ACROSS THE AREA.  IN
GENERAL...THE UPPER LEVEL PATTERN WILL BE FAIRLY LOW AMPLITUDE...SO
TIMING AND STRENGTH OF INDIVIDUAL WAVES WILL BE QUESTIONABLE...BUT
THE GENERAL TREND SHOULD BE FOR MORE PERIODIC SHOWERS AND
THUNDERSTORMS...THOUGH CONFIDENCE IN TIMING WILL BE LOW.  BY TUESDAY
AND WEDNESDAY...THE LONGER RANGE GUIDANCE IS INDICATING THAT THE
UPPER TROUGH SHOULD BEGIN TO MOVE EAST OF THE AREA...WITH HIGH
PRESSURE SETTLING OVER THE UPPER MISSISSIPPI VALLEY AND WESTERN
GREAT LAKES REGION.  THIS WOULD LEAD TO A PERIOD OF DRIER CONDITIONS
SO HAVE REMOVED POPS FOR TUESDAY AND WEDNESDAY.  UNDER RELATIVELY
LOW AMPLITUDE FLOW ALOFT...THERE SHOULD BE LITTLE DAY TO DAY
TEMPERATURE SWINGS WITH HIGHS GENERALLY IN THE LOWER 80S AND
OVERNIGHT LOWS IN THE 60S.

KREIN

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* EASTERLY WINDS THRU THE PERIOD...AND AROUND 10KT THIS AFTERNOON.
* ISOLATED SHRA THIS EVENING/OVERNIGHT. CMS

//DISCUSSION...UPDATED 06Z...

HIGH PRESSURE OVER THE WESTERN GREAT LAKES WILL MOVE EAST TODAY
AND TONIGHT. LIGHT NORTHEAST WINDS EARLY THIS MORNING WILL TURN
MORE EASTERLY TODAY AND INCREASE IN SPEED TO 10KTS BY EARLY THIS
AFTERNOON. A WARM FRONT WILL MOVE ACROSS THE AREA LATER TONIGHT...
SHIFTING WINDS SOUTHEASTERLY THIS EVENING AND THEN MORE SOUTHERLY
BY FRIDAY MORNING.

AS THE WARM FRONT LIFTS NORTH...SCATTERED SHOWERS WILL BE POSSIBLE
STARTING FIRST ACROSS NORTHWEST IL LATE THIS AFTERNOON THEN ACROSS
THE REST OF THE TERMINALS THIS EVENING INTO EARLY FRIDAY MORNING.
INSTABILITY APPEARS FAIRLY WEAK SO NOT EXPECTING MUCH IN THE WAY
OF THUNDER. BUT CONFIDENCE REGARDING OVERALL COVERAGE IS FAIRLY
LOW AND WILL JUST CARRY PROB MENTION EXCEPT AT RFD WHERE CHANCES
ARE A LITTLE BETTER. CMS

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* HIGH FOR WINDS THRU THE PERIOD.
* LOW FOR SHRA TONIGHT. CMS

//OUTLOOK FOR ORD/MDW FOR 12Z FRIDAY-12Z WEDNESDAY...UPDATED 00Z...

FRIDAY...CHANCE TSRA.

SATURDAY...TSRA LIKELY.

SUNDAY AND MONDAY...CHANCE TSRA.

TUESDAY...SLIGHT CHANCE TSRA.

KMD

&&

.MARINE...

300 AM...HIGH PRESSURE OVER THE LAKES REGION WILL MOVE EAST TODAY
AND TONIGHT REACHING NEW ENGLAND FRIDAY MORNING. EAST WINDS 10 TO
15 KTS WILL GRADUALLY TURN SOUTHEASTERLY THIS EVENING THEN MORE
SOUTHERLY OVERNIGHT INTO FRIDAY MORNING AND INCREASE. LOW PRESSURE
OVER THE WESTERN PLAINS WILL MOVE NORTHEAST TO MINNESOTA AND IOWA
BY FRIDAY MORNING THEN TURN NORTHEAST ACROSS THE NORTHERN LAKES
SATURDAY INTO SATURDAY EVENING. THE GRADIENT WILL TIGHTEN AHEAD OF
THIS LOW WITH 15-25KTS EXPECTED FRIDAY. THE GRADIENT WILL SLOWLY
WEAKEN FROM NORTH TO SOUTH FRIDAY NIGHT. A TRAILING COLD FRONT
FROM THIS LOW WILL THEN MOVE SOUTH ACROSS LAKE MICHIGAN SATURDAY
NIGHT INTO SUNDAY MORNING. THIS FRONT WILL THEN LIFT BACK NORTH AS
A WARM FRONT SUNDAY NIGHT AS STRONGER HIGH PRESSURE IS EXPECTED TO
MOVE ACROSS THE NORTHERN LAKES AND ONTARIO SUNDAY NIGHT AND
MONDAY. CMS

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 280521
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1221 AM CDT THU AUG 28 2014

.DISCUSSION...
330 PM CDT

SHORT TERM...WEDNESDAY AFTERNOON THROUGH SATURDAY...

FOR THE REMAINDER OF THE AFTERNOON SHOULD REMAIN QUIET AS THE OLD
STATIONARY BOUNDARY REMAINS WELL TO THE SOUTH ACROSS SRN IL AND THE
OHIO VALLEY.  HAVE MAINTAINED SLIGHT CHANCE POPS ACROSS THE VERY FAR
SOUTH OF THE CWA...A LITTLE NORTH OF THE BOUNDARY IN DEFERENCE TO
THE PROXIMITY TO THE BOUNDARY TO THE SOUTH AND A WARM AND VERY MOIST
AIRMASS...WITH DEWPOINTS STILL IN THE LOW 70S...ACROSS THE AREA.
THROUGH THE LATE EVENING AND INTO THE OVERNIGHT HOURS...ANTICIPATE
INCREASING POPS SPREADING FROM SOUTHWEST TO NORTHEAST AS LOW
PRESSURE OVER THE CENTRAL PLAINS LIFTS NEWD...DRAGGING THE OLD
STATIONARY BOUNDARY BACK NORTH AS A WARM FRONT.  WITH UPPER RIDGING
BUILDING ALOFT WITH THE RIDGE AXIS EXTENDING JUST EAST OF THE
MISSISSIPPI RIVER BY EARLY THURSDAY MORNING...ANTICIPATE THAT SWLY
FLOW ALOFT SHOULD HELP KEEP THE HIGHEST PCPN CHANCES OVER LOCATIONS
WEST OF A LINE FROM ROCKFORD TO WATSEKA.

THROUGH THURSDAY AND THURSDAY NIGHT...THE UPPER RIDGE WILL SLOWLY
BUILD  EAST AS SHORTWAVE ENERGY OVERTOPS THE RIDGE.  THE SHORT RANGE
MODELS ARE RELATIVELY CONSISTENT ON ADVERTISING THIS SCENARIO...SO
ANTICIPATE INCREASING POPS OVER THE WRN PORTIONS OF THE CWA THROUGH
THE EVENING AND THEN THE NORTHERN PORTIONS OF THE CWA THROUGH THE
NIGHT...BUT WITH THE TRACK OF THE MAIN UPPER SHORTWAVE TO THE WEST
AND NORTH OF THE CWA...THE STRONGER UPPER FORCING SHOULD BE OVER
IOWA AND INTO WISCONSIN...SO HAVE LIMITED POPS OVER THE CWA TO
CHANCE LEVELS.  THE LOCAL AREA SHOULD BEGIN TO SEE POPS INCREASING
THROUGH THE DAY FRIDAY AND ESPECIALLY LATER FRIDAY NIGHT AS A STRONG
SHORTWAVE LIFTING OUT OF THE GREAT BASIN TONIGHT SLOWLY TRACKS EAST
ACROSS THE CENTRAL PLAINS AND REACHES THE MIDDLE AND UPPER
MISSISSIPPI VALLEY FRIDAY NIGHT.  WILL INCREASE POPS THROUGH FRIDAY
EVENING WITH LIKELY POPS SPREADING INTO THE WRN PORTIONS OF THE CWA
AFTER MIDNIGHT FRIDAY NIGHT AND EAST ACROSS THE REMAINDER OF THE
AREA THROUGH SATURDAY AND INTO SATURDAY EVENING.

FORM TEMPERATURES...WITH SFC HIGH PRESSURE SLOWLY SLIDING ACROSS THE
GREAT LAKES REGION...THE WARMEST AND MOST HUMID CONDITIONS WILL BE
CONFINED TO THE FAR SOUTHERN PORTIONS OF THE CWA...THOUGH EVEN
LOCATIONS NORTH OF THE I-80 CORRIDOR HAVE SEEN TEMPS CLIMB INTO THE
LOWER 80S EVEN WITH PERSISTENT NELY FLOW AT THE LOWER LEVELS.  THE
HIGH WILL STILL HAVE A MAJOR INFLUENCE ON TEMPS THROUGH
THURSDAY...KEEPING THE NORTHERN PORTIONS OF THE CWA...INCLUDING THE
LAKEFRONT...ON THE COOLER SIDE WITH HIGHS IN THE UPPER 70S TO AROUND
80...WHILE THE SRN LOCATIONS SHOULD WARM INTO THE LOWER 80S.  AS THE
UPPER RIDGE BUILDS ACROSS THE AREA ON FRIDAY AND THE WARM FRONT
LIFTS WELL TO THE NORTH INTO WISCONSIN...EXPECT THAT TEMPS SHOULD
RETURN TO THE MIDDLE TO UPPER 80S WITH DEWPOINTS IN THE LOWER 70S.
THIS COMBINATION OF WARMTH AND MOISTURE SHOULD DRIVE HEAT INDEX
VALUES BACK INTO THE LOWER 90S.  BY FRIDAY NIGHT OR EARLY
SATURDAY...A WEAK COLD FRONT IS EXPECTED TO SWEEP ACROSS THE
AREA...BUT LITTLE SIGNIFICANT AIRMASS CHANGE IS EXPECTED AS THERE
SHOULD BE LITTLE INFLUX OF SIGNIFICANTLY COOLER/DRIER AIR INTO THE
REGION AS SFC HIGH PRESSURE BUILDS ACROSS SRN CANADA AND THE REGION
ONLY EXPERIENCES A BRIEF PERIOD OF LIGHT AND VARIABLE WINDS UNDER
VERY WEAK SFC TROUGHING ASSOCIATED WITH THE COLD FRONT.  BY
SATURDAY...SOUTHERLY FLOW SHOULD RETURN AS A COLD FRONT AND SFC
TROUGH MOVES OUT OVER THE NRN/CNTRL PLAINS AND AND THE BERMUDA HIGH
BUILDS BACK ACROSS THE GULF COAST.

FOR THE LONGER TERM...FROM SUNDAY THROUGH WEDNESDAY...UNSETTLED
WEATHER WILL CONTINUE ACROSS THE REGION FOR SUNDAY AND MONDAY.  THE
LONGER RANGE GUIDANCE IN IN RELATIVELY GOOD AGREEMENT ON A LONG WAVE
TROUGH MOVING ACROSS THE ROCKIES WITH WEAK RIDGING OVER THE ERN
CONUS.  THIS WILL PUT THE UPPER MIDWEST UNDER BROAD SWLY FLOW WITH A
SERIES OF WEAK SRN STREAM SHORT WAVES TRACKING ACROSS THE AREA.  IN
GENERAL...THE UPPER LEVEL PATTERN WILL BE FAIRLY LOW AMPLITUDE...SO
TIMING AND STRENGTH OF INDIVIDUAL WAVES WILL BE QUESTIONABLE...BUT
THE GENERAL TREND SHOULD BE FOR MORE PERIODIC SHOWERS AND
THUNDERSTORMS...THOUGH CONFIDENCE IN TIMING WILL BE LOW.  BY TUESDAY
AND WEDNESDAY...THE LONGER RANGE GUIDANCE IS INDICATING THAT THE
UPPER TROUGH SHOULD BEGIN TO MOVE EAST OF THE AREA...WITH HIGH
PRESSURE SETTLING OVER THE UPPER MISSISSIPPI VALLEY AND WESTERN
GREAT LAKES REGION.  THIS WOULD LEAD TO A PERIOD OF DRIER CONDITIONS
SO HAVE REMOVED POPS FOR TUESDAY AND WEDNESDAY.  UNDER RELATIVELY
LOW AMPLITUDE FLOW ALOFT...THERE SHOULD BE LITTLE DAY TO DAY
TEMPERATURE SWINGS WITH HIGHS GENERALLY IN THE LOWER 80S AND
OVERNIGHT LOWS IN THE 60S.

KREIN

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* EASTERLY WINDS THRU THE PERIOD...AND AROUND 10KT THIS AFTERNOON.
* ISOLATED SHRA THIS EVENING/OVERNIGHT. CMS

//DISCUSSION...UPDATED 06Z...

HIGH PRESSURE OVER THE WESTERN GREAT LAKES WILL MOVE EAST TODAY
AND TONIGHT. LIGHT NORTHEAST WINDS EARLY THIS MORNING WILL TURN
MORE EASTERLY TODAY AND INCREASE IN SPEED TO 10KTS BY EARLY THIS
AFTERNOON. A WARM FRONT WILL MOVE ACROSS THE AREA LATER TONIGHT...
SHIFTING WINDS SOUTHEASTERLY THIS EVENING AND THEN MORE SOUTHERLY
BY FRIDAY MORNING.

AS THE WARM FRONT LIFTS NORTH...SCATTERED SHOWERS WILL BE POSSIBLE
STARTING FIRST ACROSS NORTHWEST IL LATE THIS AFTERNOON THEN ACROSS
THE REST OF THE TERMINALS THIS EVENING INTO EARLY FRIDAY MORNING.
INSTABILITY APPEARS FAIRLY WEAK SO NOT EXPECTING MUCH IN THE WAY
OF THUNDER. BUT CONFIDENCE REGARDING OVERALL COVERAGE IS FAIRLY
LOW AND WILL JUST CARRY PROB MENTION EXCEPT AT RFD WHERE CHANCES
ARE A LITTLE BETTER. CMS

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* HIGH FOR WINDS THRU THE PERIOD.
* LOW FOR SHRA TONIGHT. CMS

//OUTLOOK FOR ORD/MDW FOR 12Z FRIDAY-12Z WEDNESDAY...UPDATED 00Z...

FRIDAY...CHANCE TSRA.

SATURDAY...TSRA LIKELY.

SUNDAY AND MONDAY...CHANCE TSRA.

TUESDAY...SLIGHT CHANCE TSRA.

KMD

&&

.MARINE...
205 PM CDT

HIGH PRESSURE WILL CONTINUE TO BE OVERHEAD OF LAKE
MICHIGAN...LIKELY LINGERING THROUGH DAYBREAK THURSDAY BEFORE
MOVING EAST TOWARDS LAKE ERIE TOMORROW NIGHT. AS THE HIGH DRIFTS
EAST...WINDS WILL SLOWLY TURN SOUTHEASTERLY THEN SOUTHERLY.
GUIDANCE IS EXPECTING A LOW PRESSURE SYSTEM TO LIFT NORTHEAST
ACROSS THE CENTRAL PLAINS INTO THE UPPER MIDWEST THURSDAY
AFTERNOON. THIS WILL RESULT IN A TIGHTENING GRADIENT FROM SOUTH TO
NORTH ACROSS THE LAKE. AT THIS TIME IT IS POSSIBLE THAT WINDS
COULD HOVER IN THE 15 TO 25 KT RANGE THURSDAY NIGHT INTO FRIDAY.
THEN AS THE LOW PRESSURE LIFTS NORTHEAST OF LAKE MICHIGAN AND A
RIDGE OF HIGH PRESSURE SLIDES SOUTH FROM CENTRAL CANADA INTO THE
UPPER MIDWEST FRIDAY EVENING...A FRONTAL BOUNDARY WILL SAG SOUTH
AND TURN WINDS NORTHERLY FOR THE NORTHERN HALF OF THE LAKE.
MEANWHILE IT DOES APPEAR THE BOUNDARY GETS HUNG UP ACROSS THE
CENTRAL PORTION OF THE LAKE FRIDAY NIGHT/EARLY SATURDAY...WHICH
WILL KEEP SOUTHERLY WINDS FOR THE SOUTHERN HALF OF THE LAKE. THEN
YET ANOTHER AREA OF LOW PRESSURE IS FORECAST TO DEVELOP ACROSS THE
NORTHERN PLAINS SATURDAY AFTERNOON AND DEEPEN AS IT MOVES
NORTHEAST INTO WESTERN ONTARIO. THIS WILL LIKELY CREATE A TIGHT
GRADIENT ACROSS THE LAKE SUNDAY WITH YET ANOTHER PERIOD OF WINDS
NEARING 20-25KT.

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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 280521
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1221 AM CDT THU AUG 28 2014

.DISCUSSION...
330 PM CDT

SHORT TERM...WEDNESDAY AFTERNOON THROUGH SATURDAY...

FOR THE REMAINDER OF THE AFTERNOON SHOULD REMAIN QUIET AS THE OLD
STATIONARY BOUNDARY REMAINS WELL TO THE SOUTH ACROSS SRN IL AND THE
OHIO VALLEY.  HAVE MAINTAINED SLIGHT CHANCE POPS ACROSS THE VERY FAR
SOUTH OF THE CWA...A LITTLE NORTH OF THE BOUNDARY IN DEFERENCE TO
THE PROXIMITY TO THE BOUNDARY TO THE SOUTH AND A WARM AND VERY MOIST
AIRMASS...WITH DEWPOINTS STILL IN THE LOW 70S...ACROSS THE AREA.
THROUGH THE LATE EVENING AND INTO THE OVERNIGHT HOURS...ANTICIPATE
INCREASING POPS SPREADING FROM SOUTHWEST TO NORTHEAST AS LOW
PRESSURE OVER THE CENTRAL PLAINS LIFTS NEWD...DRAGGING THE OLD
STATIONARY BOUNDARY BACK NORTH AS A WARM FRONT.  WITH UPPER RIDGING
BUILDING ALOFT WITH THE RIDGE AXIS EXTENDING JUST EAST OF THE
MISSISSIPPI RIVER BY EARLY THURSDAY MORNING...ANTICIPATE THAT SWLY
FLOW ALOFT SHOULD HELP KEEP THE HIGHEST PCPN CHANCES OVER LOCATIONS
WEST OF A LINE FROM ROCKFORD TO WATSEKA.

THROUGH THURSDAY AND THURSDAY NIGHT...THE UPPER RIDGE WILL SLOWLY
BUILD  EAST AS SHORTWAVE ENERGY OVERTOPS THE RIDGE.  THE SHORT RANGE
MODELS ARE RELATIVELY CONSISTENT ON ADVERTISING THIS SCENARIO...SO
ANTICIPATE INCREASING POPS OVER THE WRN PORTIONS OF THE CWA THROUGH
THE EVENING AND THEN THE NORTHERN PORTIONS OF THE CWA THROUGH THE
NIGHT...BUT WITH THE TRACK OF THE MAIN UPPER SHORTWAVE TO THE WEST
AND NORTH OF THE CWA...THE STRONGER UPPER FORCING SHOULD BE OVER
IOWA AND INTO WISCONSIN...SO HAVE LIMITED POPS OVER THE CWA TO
CHANCE LEVELS.  THE LOCAL AREA SHOULD BEGIN TO SEE POPS INCREASING
THROUGH THE DAY FRIDAY AND ESPECIALLY LATER FRIDAY NIGHT AS A STRONG
SHORTWAVE LIFTING OUT OF THE GREAT BASIN TONIGHT SLOWLY TRACKS EAST
ACROSS THE CENTRAL PLAINS AND REACHES THE MIDDLE AND UPPER
MISSISSIPPI VALLEY FRIDAY NIGHT.  WILL INCREASE POPS THROUGH FRIDAY
EVENING WITH LIKELY POPS SPREADING INTO THE WRN PORTIONS OF THE CWA
AFTER MIDNIGHT FRIDAY NIGHT AND EAST ACROSS THE REMAINDER OF THE
AREA THROUGH SATURDAY AND INTO SATURDAY EVENING.

FORM TEMPERATURES...WITH SFC HIGH PRESSURE SLOWLY SLIDING ACROSS THE
GREAT LAKES REGION...THE WARMEST AND MOST HUMID CONDITIONS WILL BE
CONFINED TO THE FAR SOUTHERN PORTIONS OF THE CWA...THOUGH EVEN
LOCATIONS NORTH OF THE I-80 CORRIDOR HAVE SEEN TEMPS CLIMB INTO THE
LOWER 80S EVEN WITH PERSISTENT NELY FLOW AT THE LOWER LEVELS.  THE
HIGH WILL STILL HAVE A MAJOR INFLUENCE ON TEMPS THROUGH
THURSDAY...KEEPING THE NORTHERN PORTIONS OF THE CWA...INCLUDING THE
LAKEFRONT...ON THE COOLER SIDE WITH HIGHS IN THE UPPER 70S TO AROUND
80...WHILE THE SRN LOCATIONS SHOULD WARM INTO THE LOWER 80S.  AS THE
UPPER RIDGE BUILDS ACROSS THE AREA ON FRIDAY AND THE WARM FRONT
LIFTS WELL TO THE NORTH INTO WISCONSIN...EXPECT THAT TEMPS SHOULD
RETURN TO THE MIDDLE TO UPPER 80S WITH DEWPOINTS IN THE LOWER 70S.
THIS COMBINATION OF WARMTH AND MOISTURE SHOULD DRIVE HEAT INDEX
VALUES BACK INTO THE LOWER 90S.  BY FRIDAY NIGHT OR EARLY
SATURDAY...A WEAK COLD FRONT IS EXPECTED TO SWEEP ACROSS THE
AREA...BUT LITTLE SIGNIFICANT AIRMASS CHANGE IS EXPECTED AS THERE
SHOULD BE LITTLE INFLUX OF SIGNIFICANTLY COOLER/DRIER AIR INTO THE
REGION AS SFC HIGH PRESSURE BUILDS ACROSS SRN CANADA AND THE REGION
ONLY EXPERIENCES A BRIEF PERIOD OF LIGHT AND VARIABLE WINDS UNDER
VERY WEAK SFC TROUGHING ASSOCIATED WITH THE COLD FRONT.  BY
SATURDAY...SOUTHERLY FLOW SHOULD RETURN AS A COLD FRONT AND SFC
TROUGH MOVES OUT OVER THE NRN/CNTRL PLAINS AND AND THE BERMUDA HIGH
BUILDS BACK ACROSS THE GULF COAST.

FOR THE LONGER TERM...FROM SUNDAY THROUGH WEDNESDAY...UNSETTLED
WEATHER WILL CONTINUE ACROSS THE REGION FOR SUNDAY AND MONDAY.  THE
LONGER RANGE GUIDANCE IN IN RELATIVELY GOOD AGREEMENT ON A LONG WAVE
TROUGH MOVING ACROSS THE ROCKIES WITH WEAK RIDGING OVER THE ERN
CONUS.  THIS WILL PUT THE UPPER MIDWEST UNDER BROAD SWLY FLOW WITH A
SERIES OF WEAK SRN STREAM SHORT WAVES TRACKING ACROSS THE AREA.  IN
GENERAL...THE UPPER LEVEL PATTERN WILL BE FAIRLY LOW AMPLITUDE...SO
TIMING AND STRENGTH OF INDIVIDUAL WAVES WILL BE QUESTIONABLE...BUT
THE GENERAL TREND SHOULD BE FOR MORE PERIODIC SHOWERS AND
THUNDERSTORMS...THOUGH CONFIDENCE IN TIMING WILL BE LOW.  BY TUESDAY
AND WEDNESDAY...THE LONGER RANGE GUIDANCE IS INDICATING THAT THE
UPPER TROUGH SHOULD BEGIN TO MOVE EAST OF THE AREA...WITH HIGH
PRESSURE SETTLING OVER THE UPPER MISSISSIPPI VALLEY AND WESTERN
GREAT LAKES REGION.  THIS WOULD LEAD TO A PERIOD OF DRIER CONDITIONS
SO HAVE REMOVED POPS FOR TUESDAY AND WEDNESDAY.  UNDER RELATIVELY
LOW AMPLITUDE FLOW ALOFT...THERE SHOULD BE LITTLE DAY TO DAY
TEMPERATURE SWINGS WITH HIGHS GENERALLY IN THE LOWER 80S AND
OVERNIGHT LOWS IN THE 60S.

KREIN

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* EASTERLY WINDS THRU THE PERIOD...AND AROUND 10KT THIS AFTERNOON.
* ISOLATED SHRA THIS EVENING/OVERNIGHT. CMS

//DISCUSSION...UPDATED 06Z...

HIGH PRESSURE OVER THE WESTERN GREAT LAKES WILL MOVE EAST TODAY
AND TONIGHT. LIGHT NORTHEAST WINDS EARLY THIS MORNING WILL TURN
MORE EASTERLY TODAY AND INCREASE IN SPEED TO 10KTS BY EARLY THIS
AFTERNOON. A WARM FRONT WILL MOVE ACROSS THE AREA LATER TONIGHT...
SHIFTING WINDS SOUTHEASTERLY THIS EVENING AND THEN MORE SOUTHERLY
BY FRIDAY MORNING.

AS THE WARM FRONT LIFTS NORTH...SCATTERED SHOWERS WILL BE POSSIBLE
STARTING FIRST ACROSS NORTHWEST IL LATE THIS AFTERNOON THEN ACROSS
THE REST OF THE TERMINALS THIS EVENING INTO EARLY FRIDAY MORNING.
INSTABILITY APPEARS FAIRLY WEAK SO NOT EXPECTING MUCH IN THE WAY
OF THUNDER. BUT CONFIDENCE REGARDING OVERALL COVERAGE IS FAIRLY
LOW AND WILL JUST CARRY PROB MENTION EXCEPT AT RFD WHERE CHANCES
ARE A LITTLE BETTER. CMS

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* HIGH FOR WINDS THRU THE PERIOD.
* LOW FOR SHRA TONIGHT. CMS

//OUTLOOK FOR ORD/MDW FOR 12Z FRIDAY-12Z WEDNESDAY...UPDATED 00Z...

FRIDAY...CHANCE TSRA.

SATURDAY...TSRA LIKELY.

SUNDAY AND MONDAY...CHANCE TSRA.

TUESDAY...SLIGHT CHANCE TSRA.

KMD

&&

.MARINE...
205 PM CDT

HIGH PRESSURE WILL CONTINUE TO BE OVERHEAD OF LAKE
MICHIGAN...LIKELY LINGERING THROUGH DAYBREAK THURSDAY BEFORE
MOVING EAST TOWARDS LAKE ERIE TOMORROW NIGHT. AS THE HIGH DRIFTS
EAST...WINDS WILL SLOWLY TURN SOUTHEASTERLY THEN SOUTHERLY.
GUIDANCE IS EXPECTING A LOW PRESSURE SYSTEM TO LIFT NORTHEAST
ACROSS THE CENTRAL PLAINS INTO THE UPPER MIDWEST THURSDAY
AFTERNOON. THIS WILL RESULT IN A TIGHTENING GRADIENT FROM SOUTH TO
NORTH ACROSS THE LAKE. AT THIS TIME IT IS POSSIBLE THAT WINDS
COULD HOVER IN THE 15 TO 25 KT RANGE THURSDAY NIGHT INTO FRIDAY.
THEN AS THE LOW PRESSURE LIFTS NORTHEAST OF LAKE MICHIGAN AND A
RIDGE OF HIGH PRESSURE SLIDES SOUTH FROM CENTRAL CANADA INTO THE
UPPER MIDWEST FRIDAY EVENING...A FRONTAL BOUNDARY WILL SAG SOUTH
AND TURN WINDS NORTHERLY FOR THE NORTHERN HALF OF THE LAKE.
MEANWHILE IT DOES APPEAR THE BOUNDARY GETS HUNG UP ACROSS THE
CENTRAL PORTION OF THE LAKE FRIDAY NIGHT/EARLY SATURDAY...WHICH
WILL KEEP SOUTHERLY WINDS FOR THE SOUTHERN HALF OF THE LAKE. THEN
YET ANOTHER AREA OF LOW PRESSURE IS FORECAST TO DEVELOP ACROSS THE
NORTHERN PLAINS SATURDAY AFTERNOON AND DEEPEN AS IT MOVES
NORTHEAST INTO WESTERN ONTARIO. THIS WILL LIKELY CREATE A TIGHT
GRADIENT ACROSS THE LAKE SUNDAY WITH YET ANOTHER PERIOD OF WINDS
NEARING 20-25KT.

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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO







000
FXUS63 KLOT 280315
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1015 PM CDT WED AUG 27 2014

.DISCUSSION...
330 PM CDT

SHORT TERM...WEDNESDAY AFTERNOON THROUGH SATURDAY...

FOR THE REMAINDER OF THE AFTERNOON SHOULD REMAIN QUIET AS THE OLD
STATIONARY BOUNDARY REMAINS WELL TO THE SOUTH ACROSS SRN IL AND THE
OHIO VALLEY.  HAVE MAINTAINED SLIGHT CHANCE POPS ACROSS THE VERY FAR
SOUTH OF THE CWA...A LITTLE NORTH OF THE BOUNDARY IN DEFERENCE TO
THE PROXIMITY TO THE BOUNDARY TO THE SOUTH AND A WARM AND VERY MOIST
AIRMASS...WITH DEWPOINTS STILL IN THE LOW 70S...ACROSS THE AREA.
THROUGH THE LATE EVENING AND INTO THE OVERNIGHT HOURS...ANTICIPATE
INCREASING POPS SPREADING FROM SOUTHWEST TO NORTHEAST AS LOW
PRESSURE OVER THE CENTRAL PLAINS LIFTS NEWD...DRAGGING THE OLD
STATIONARY BOUNDARY BACK NORTH AS A WARM FRONT.  WITH UPPER RIDGING
BUILDING ALOFT WITH THE RIDGE AXIS EXTENDING JUST EAST OF THE
MISSISSIPPI RIVER BY EARLY THURSDAY MORNING...ANTICIPATE THAT SWLY
FLOW ALOFT SHOULD HELP KEEP THE HIGHEST PCPN CHANCES OVER LOCATIONS
WEST OF A LINE FROM ROCKFORD TO WATSEKA.

THROUGH THURSDAY AND THURSDAY NIGHT...THE UPPER RIDGE WILL SLOWLY
BUILD  EAST AS SHORTWAVE ENERGY OVERTOPS THE RIDGE.  THE SHORT RANGE
MODELS ARE RELATIVELY CONSISTENT ON ADVERTISING THIS SCENARIO...SO
ANTICIPATE INCREASING POPS OVER THE WRN PORTIONS OF THE CWA THROUGH
THE EVENING AND THEN THE NORTHERN PORTIONS OF THE CWA THROUGH THE
NIGHT...BUT WITH THE TRACK OF THE MAIN UPPER SHORTWAVE TO THE WEST
AND NORTH OF THE CWA...THE STRONGER UPPER FORCING SHOULD BE OVER
IOWA AND INTO WISCONSIN...SO HAVE LIMITED POPS OVER THE CWA TO
CHANCE LEVELS.  THE LOCAL AREA SHOULD BEGIN TO SEE POPS INCREASING
THROUGH THE DAY FRIDAY AND ESPECIALLY LATER FRIDAY NIGHT AS A STRONG
SHORTWAVE LIFTING OUT OF THE GREAT BASIN TONIGHT SLOWLY TRACKS EAST
ACROSS THE CENTRAL PLAINS AND REACHES THE MIDDLE AND UPPER
MISSISSIPPI VALLEY FRIDAY NIGHT.  WILL INCREASE POPS THROUGH FRIDAY
EVENING WITH LIKELY POPS SPREADING INTO THE WRN PORTIONS OF THE CWA
AFTER MIDNIGHT FRIDAY NIGHT AND EAST ACROSS THE REMAINDER OF THE
AREA THROUGH SATURDAY AND INTO SATURDAY EVENING.

FORM TEMPERATURES...WITH SFC HIGH PRESSURE SLOWLY SLIDING ACROSS THE
GREAT LAKES REGION...THE WARMEST AND MOST HUMID CONDITIONS WILL BE
CONFINED TO THE FAR SOUTHERN PORTIONS OF THE CWA...THOUGH EVEN
LOCATIONS NORTH OF THE I-80 CORRIDOR HAVE SEEN TEMPS CLIMB INTO THE
LOWER 80S EVEN WITH PERSISTENT NELY FLOW AT THE LOWER LEVELS.  THE
HIGH WILL STILL HAVE A MAJOR INFLUENCE ON TEMPS THROUGH
THURSDAY...KEEPING THE NORTHERN PORTIONS OF THE CWA...INCLUDING THE
LAKEFRONT...ON THE COOLER SIDE WITH HIGHS IN THE UPPER 70S TO AROUND
80...WHILE THE SRN LOCATIONS SHOULD WARM INTO THE LOWER 80S.  AS THE
UPPER RIDGE BUILDS ACROSS THE AREA ON FRIDAY AND THE WARM FRONT
LIFTS WELL TO THE NORTH INTO WISCONSIN...EXPECT THAT TEMPS SHOULD
RETURN TO THE MIDDLE TO UPPER 80S WITH DEWPOINTS IN THE LOWER 70S.
THIS COMBINATION OF WARMTH AND MOISTURE SHOULD DRIVE HEAT INDEX
VALUES BACK INTO THE LOWER 90S.  BY FRIDAY NIGHT OR EARLY
SATURDAY...A WEAK COLD FRONT IS EXPECTED TO SWEEP ACROSS THE
AREA...BUT LITTLE SIGNIFICANT AIRMASS CHANGE IS EXPECTED AS THERE
SHOULD BE LITTLE INFLUX OF SIGNIFICANTLY COOLER/DRIER AIR INTO THE
REGION AS SFC HIGH PRESSURE BUILDS ACROSS SRN CANADA AND THE REGION
ONLY EXPERIENCES A BRIEF PERIOD OF LIGHT AND VARIABLE WINDS UNDER
VERY WEAK SFC TROUGHING ASSOCIATED WITH THE COLD FRONT.  BY
SATURDAY...SOUTHERLY FLOW SHOULD RETURN AS A COLD FRONT AND SFC
TROUGH MOVES OUT OVER THE NRN/CNTRL PLAINS AND AND THE BERMUDA HIGH
BUILDS BACK ACROSS THE GULF COAST.

FOR THE LONGER TERM...FROM SUNDAY THROUGH WEDNESDAY...UNSETTLED
WEATHER WILL CONTINUE ACROSS THE REGION FOR SUNDAY AND MONDAY.  THE
LONGER RANGE GUIDANCE IN IN RELATIVELY GOOD AGREEMENT ON A LONG WAVE
TROUGH MOVING ACROSS THE ROCKIES WITH WEAK RIDGING OVER THE ERN
CONUS.  THIS WILL PUT THE UPPER MIDWEST UNDER BROAD SWLY FLOW WITH A
SERIES OF WEAK SRN STREAM SHORT WAVES TRACKING ACROSS THE AREA.  IN
GENERAL...THE UPPER LEVEL PATTERN WILL BE FAIRLY LOW AMPLITUDE...SO
TIMING AND STRENGTH OF INDIVIDUAL WAVES WILL BE QUESTIONABLE...BUT
THE GENERAL TREND SHOULD BE FOR MORE PERIODIC SHOWERS AND
THUNDERSTORMS...THOUGH CONFIDENCE IN TIMING WILL BE LOW.  BY TUESDAY
AND WEDNESDAY...THE LONGER RANGE GUIDANCE IS INDICATING THAT THE
UPPER TROUGH SHOULD BEGIN TO MOVE EAST OF THE AREA...WITH HIGH
PRESSURE SETTLING OVER THE UPPER MISSISSIPPI VALLEY AND WESTERN
GREAT LAKES REGION.  THIS WOULD LEAD TO A PERIOD OF DRIER CONDITIONS
SO HAVE REMOVED POPS FOR TUESDAY AND WEDNESDAY.  UNDER RELATIVELY
LOW AMPLITUDE FLOW ALOFT...THERE SHOULD BE LITTLE DAY TO DAY
TEMPERATURE SWINGS WITH HIGHS GENERALLY IN THE LOWER 80S AND
OVERNIGHT LOWS IN THE 60S.

KREIN

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 03Z...

* EAST WINDS INCREASING AGAIN TO AT OR ABOVE 10 KT THURSDAY
  AFTERNOON.

* SHRA/ISOLATED TSRA THURSDAY AFTERNOON/EVENING

KMD

//DISCUSSION...UPDATED 00Z...
EAST WINDS STILL HOVERING AROUND 10 KT...AND EXPECT THAT TO
CONTINUE UNTIL A LITTLE AFTER SUNSET. HIGH PRESSURE REMAINS IN
CONTROL TONIGHT FOR PASSING HIGH CLOUDS AND LIGHTER EAST
WINDS...THEN CLOUDS INCREASE ON THURSDAY AHEAD OF A WARM FRONT.
DRIER EAST WINDS KEEP MOST AREAS DRY...THOUGH KRFD HAS THE BEST
CHANCE FOR A SHOWER IN THE AFTERNOON. THE WARM FRONT LIFTS THROUGH
THURSDAY EVENING WHICH IS THE BEST CHANCE FOR ANY SHOWERS ACROSS
THE TERMINALS. INSTABILITY PARAMETERS ARE WEAK AND THUS EXPECT
THUNDER ACTIVITY TO BE ISOLATED AND THEREFORE KEPT THE KORD TAF
LIMITED TO SHOWERS FOR NOW. HIGHEST IMPACTS FOR THE AIRSPACE WILL
BE FOR AREAS NORTH AND WEST.

KMD

//ORD AND MDW CONFIDENCE...UPDATED 03Z...

* MEDIUM-HIGH THAT WINDS WILL REACH 10 KT OR HIGHER TOMORROW
  AFTERNOON.

* MEDIUM THAT SHRA REMAIN WEST OF ORD/MDW THROUGH 0Z. MEDIUM IN
  SHRA/ISOLATED TSRA THURSDAY EVENING.

KMD

//OUTLOOK FOR ORD/MDW FOR 12Z FRIDAY-12Z WEDNESDAY...UPDATED 00Z...

FRIDAY...CHANCE TSRA.

SATURDAY...TSRA LIKELY.

SUNDAY AND MONDAY...CHANCE TSRA.

TUESDAY...SLIGHT CHANCE TSRA.

KMD

&&

.MARINE...
205 PM CDT

HIGH PRESSURE WILL CONTINUE TO BE OVERHEAD OF LAKE
MICHIGAN...LIKELY LINGERING THROUGH DAYBREAK THURSDAY BEFORE
MOVING EAST TOWARDS LAKE ERIE TOMORROW NIGHT. AS THE HIGH DRIFTS
EAST...WINDS WILL SLOWLY TURN SOUTHEASTERLY THEN SOUTHERLY.
GUIDANCE IS EXPECTING A LOW PRESSURE SYSTEM TO LIFT NORTHEAST
ACROSS THE CENTRAL PLAINS INTO THE UPPER MIDWEST THURSDAY
AFTERNOON. THIS WILL RESULT IN A TIGHTENING GRADIENT FROM SOUTH TO
NORTH ACROSS THE LAKE. AT THIS TIME IT IS POSSIBLE THAT WINDS
COULD HOVER IN THE 15 TO 25 KT RANGE THURSDAY NIGHT INTO FRIDAY.
THEN AS THE LOW PRESSURE LIFTS NORTHEAST OF LAKE MICHIGAN AND A
RIDGE OF HIGH PRESSURE SLIDES SOUTH FROM CENTRAL CANADA INTO THE
UPPER MIDWEST FRIDAY EVENING...A FRONTAL BOUNDARY WILL SAG SOUTH
AND TURN WINDS NORTHERLY FOR THE NORTHERN HALF OF THE LAKE.
MEANWHILE IT DOES APPEAR THE BOUNDARY GETS HUNG UP ACROSS THE
CENTRAL PORTION OF THE LAKE FRIDAY NIGHT/EARLY SATURDAY...WHICH
WILL KEEP SOUTHERLY WINDS FOR THE SOUTHERN HALF OF THE LAKE. THEN
YET ANOTHER AREA OF LOW PRESSURE IS FORECAST TO DEVELOP ACROSS THE
NORTHERN PLAINS SATURDAY AFTERNOON AND DEEPEN AS IT MOVES
NORTHEAST INTO WESTERN ONTARIO. THIS WILL LIKELY CREATE A TIGHT
GRADIENT ACROSS THE LAKE SUNDAY WITH YET ANOTHER PERIOD OF WINDS
NEARING 20-25KT.

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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO








000
FXUS63 KLOT 280315
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1015 PM CDT WED AUG 27 2014

.DISCUSSION...
330 PM CDT

SHORT TERM...WEDNESDAY AFTERNOON THROUGH SATURDAY...

FOR THE REMAINDER OF THE AFTERNOON SHOULD REMAIN QUIET AS THE OLD
STATIONARY BOUNDARY REMAINS WELL TO THE SOUTH ACROSS SRN IL AND THE
OHIO VALLEY.  HAVE MAINTAINED SLIGHT CHANCE POPS ACROSS THE VERY FAR
SOUTH OF THE CWA...A LITTLE NORTH OF THE BOUNDARY IN DEFERENCE TO
THE PROXIMITY TO THE BOUNDARY TO THE SOUTH AND A WARM AND VERY MOIST
AIRMASS...WITH DEWPOINTS STILL IN THE LOW 70S...ACROSS THE AREA.
THROUGH THE LATE EVENING AND INTO THE OVERNIGHT HOURS...ANTICIPATE
INCREASING POPS SPREADING FROM SOUTHWEST TO NORTHEAST AS LOW
PRESSURE OVER THE CENTRAL PLAINS LIFTS NEWD...DRAGGING THE OLD
STATIONARY BOUNDARY BACK NORTH AS A WARM FRONT.  WITH UPPER RIDGING
BUILDING ALOFT WITH THE RIDGE AXIS EXTENDING JUST EAST OF THE
MISSISSIPPI RIVER BY EARLY THURSDAY MORNING...ANTICIPATE THAT SWLY
FLOW ALOFT SHOULD HELP KEEP THE HIGHEST PCPN CHANCES OVER LOCATIONS
WEST OF A LINE FROM ROCKFORD TO WATSEKA.

THROUGH THURSDAY AND THURSDAY NIGHT...THE UPPER RIDGE WILL SLOWLY
BUILD  EAST AS SHORTWAVE ENERGY OVERTOPS THE RIDGE.  THE SHORT RANGE
MODELS ARE RELATIVELY CONSISTENT ON ADVERTISING THIS SCENARIO...SO
ANTICIPATE INCREASING POPS OVER THE WRN PORTIONS OF THE CWA THROUGH
THE EVENING AND THEN THE NORTHERN PORTIONS OF THE CWA THROUGH THE
NIGHT...BUT WITH THE TRACK OF THE MAIN UPPER SHORTWAVE TO THE WEST
AND NORTH OF THE CWA...THE STRONGER UPPER FORCING SHOULD BE OVER
IOWA AND INTO WISCONSIN...SO HAVE LIMITED POPS OVER THE CWA TO
CHANCE LEVELS.  THE LOCAL AREA SHOULD BEGIN TO SEE POPS INCREASING
THROUGH THE DAY FRIDAY AND ESPECIALLY LATER FRIDAY NIGHT AS A STRONG
SHORTWAVE LIFTING OUT OF THE GREAT BASIN TONIGHT SLOWLY TRACKS EAST
ACROSS THE CENTRAL PLAINS AND REACHES THE MIDDLE AND UPPER
MISSISSIPPI VALLEY FRIDAY NIGHT.  WILL INCREASE POPS THROUGH FRIDAY
EVENING WITH LIKELY POPS SPREADING INTO THE WRN PORTIONS OF THE CWA
AFTER MIDNIGHT FRIDAY NIGHT AND EAST ACROSS THE REMAINDER OF THE
AREA THROUGH SATURDAY AND INTO SATURDAY EVENING.

FORM TEMPERATURES...WITH SFC HIGH PRESSURE SLOWLY SLIDING ACROSS THE
GREAT LAKES REGION...THE WARMEST AND MOST HUMID CONDITIONS WILL BE
CONFINED TO THE FAR SOUTHERN PORTIONS OF THE CWA...THOUGH EVEN
LOCATIONS NORTH OF THE I-80 CORRIDOR HAVE SEEN TEMPS CLIMB INTO THE
LOWER 80S EVEN WITH PERSISTENT NELY FLOW AT THE LOWER LEVELS.  THE
HIGH WILL STILL HAVE A MAJOR INFLUENCE ON TEMPS THROUGH
THURSDAY...KEEPING THE NORTHERN PORTIONS OF THE CWA...INCLUDING THE
LAKEFRONT...ON THE COOLER SIDE WITH HIGHS IN THE UPPER 70S TO AROUND
80...WHILE THE SRN LOCATIONS SHOULD WARM INTO THE LOWER 80S.  AS THE
UPPER RIDGE BUILDS ACROSS THE AREA ON FRIDAY AND THE WARM FRONT
LIFTS WELL TO THE NORTH INTO WISCONSIN...EXPECT THAT TEMPS SHOULD
RETURN TO THE MIDDLE TO UPPER 80S WITH DEWPOINTS IN THE LOWER 70S.
THIS COMBINATION OF WARMTH AND MOISTURE SHOULD DRIVE HEAT INDEX
VALUES BACK INTO THE LOWER 90S.  BY FRIDAY NIGHT OR EARLY
SATURDAY...A WEAK COLD FRONT IS EXPECTED TO SWEEP ACROSS THE
AREA...BUT LITTLE SIGNIFICANT AIRMASS CHANGE IS EXPECTED AS THERE
SHOULD BE LITTLE INFLUX OF SIGNIFICANTLY COOLER/DRIER AIR INTO THE
REGION AS SFC HIGH PRESSURE BUILDS ACROSS SRN CANADA AND THE REGION
ONLY EXPERIENCES A BRIEF PERIOD OF LIGHT AND VARIABLE WINDS UNDER
VERY WEAK SFC TROUGHING ASSOCIATED WITH THE COLD FRONT.  BY
SATURDAY...SOUTHERLY FLOW SHOULD RETURN AS A COLD FRONT AND SFC
TROUGH MOVES OUT OVER THE NRN/CNTRL PLAINS AND AND THE BERMUDA HIGH
BUILDS BACK ACROSS THE GULF COAST.

FOR THE LONGER TERM...FROM SUNDAY THROUGH WEDNESDAY...UNSETTLED
WEATHER WILL CONTINUE ACROSS THE REGION FOR SUNDAY AND MONDAY.  THE
LONGER RANGE GUIDANCE IN IN RELATIVELY GOOD AGREEMENT ON A LONG WAVE
TROUGH MOVING ACROSS THE ROCKIES WITH WEAK RIDGING OVER THE ERN
CONUS.  THIS WILL PUT THE UPPER MIDWEST UNDER BROAD SWLY FLOW WITH A
SERIES OF WEAK SRN STREAM SHORT WAVES TRACKING ACROSS THE AREA.  IN
GENERAL...THE UPPER LEVEL PATTERN WILL BE FAIRLY LOW AMPLITUDE...SO
TIMING AND STRENGTH OF INDIVIDUAL WAVES WILL BE QUESTIONABLE...BUT
THE GENERAL TREND SHOULD BE FOR MORE PERIODIC SHOWERS AND
THUNDERSTORMS...THOUGH CONFIDENCE IN TIMING WILL BE LOW.  BY TUESDAY
AND WEDNESDAY...THE LONGER RANGE GUIDANCE IS INDICATING THAT THE
UPPER TROUGH SHOULD BEGIN TO MOVE EAST OF THE AREA...WITH HIGH
PRESSURE SETTLING OVER THE UPPER MISSISSIPPI VALLEY AND WESTERN
GREAT LAKES REGION.  THIS WOULD LEAD TO A PERIOD OF DRIER CONDITIONS
SO HAVE REMOVED POPS FOR TUESDAY AND WEDNESDAY.  UNDER RELATIVELY
LOW AMPLITUDE FLOW ALOFT...THERE SHOULD BE LITTLE DAY TO DAY
TEMPERATURE SWINGS WITH HIGHS GENERALLY IN THE LOWER 80S AND
OVERNIGHT LOWS IN THE 60S.

KREIN

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 03Z...

* EAST WINDS INCREASING AGAIN TO AT OR ABOVE 10 KT THURSDAY
  AFTERNOON.

* SHRA/ISOLATED TSRA THURSDAY AFTERNOON/EVENING

KMD

//DISCUSSION...UPDATED 00Z...
EAST WINDS STILL HOVERING AROUND 10 KT...AND EXPECT THAT TO
CONTINUE UNTIL A LITTLE AFTER SUNSET. HIGH PRESSURE REMAINS IN
CONTROL TONIGHT FOR PASSING HIGH CLOUDS AND LIGHTER EAST
WINDS...THEN CLOUDS INCREASE ON THURSDAY AHEAD OF A WARM FRONT.
DRIER EAST WINDS KEEP MOST AREAS DRY...THOUGH KRFD HAS THE BEST
CHANCE FOR A SHOWER IN THE AFTERNOON. THE WARM FRONT LIFTS THROUGH
THURSDAY EVENING WHICH IS THE BEST CHANCE FOR ANY SHOWERS ACROSS
THE TERMINALS. INSTABILITY PARAMETERS ARE WEAK AND THUS EXPECT
THUNDER ACTIVITY TO BE ISOLATED AND THEREFORE KEPT THE KORD TAF
LIMITED TO SHOWERS FOR NOW. HIGHEST IMPACTS FOR THE AIRSPACE WILL
BE FOR AREAS NORTH AND WEST.

KMD

//ORD AND MDW CONFIDENCE...UPDATED 03Z...

* MEDIUM-HIGH THAT WINDS WILL REACH 10 KT OR HIGHER TOMORROW
  AFTERNOON.

* MEDIUM THAT SHRA REMAIN WEST OF ORD/MDW THROUGH 0Z. MEDIUM IN
  SHRA/ISOLATED TSRA THURSDAY EVENING.

KMD

//OUTLOOK FOR ORD/MDW FOR 12Z FRIDAY-12Z WEDNESDAY...UPDATED 00Z...

FRIDAY...CHANCE TSRA.

SATURDAY...TSRA LIKELY.

SUNDAY AND MONDAY...CHANCE TSRA.

TUESDAY...SLIGHT CHANCE TSRA.

KMD

&&

.MARINE...
205 PM CDT

HIGH PRESSURE WILL CONTINUE TO BE OVERHEAD OF LAKE
MICHIGAN...LIKELY LINGERING THROUGH DAYBREAK THURSDAY BEFORE
MOVING EAST TOWARDS LAKE ERIE TOMORROW NIGHT. AS THE HIGH DRIFTS
EAST...WINDS WILL SLOWLY TURN SOUTHEASTERLY THEN SOUTHERLY.
GUIDANCE IS EXPECTING A LOW PRESSURE SYSTEM TO LIFT NORTHEAST
ACROSS THE CENTRAL PLAINS INTO THE UPPER MIDWEST THURSDAY
AFTERNOON. THIS WILL RESULT IN A TIGHTENING GRADIENT FROM SOUTH TO
NORTH ACROSS THE LAKE. AT THIS TIME IT IS POSSIBLE THAT WINDS
COULD HOVER IN THE 15 TO 25 KT RANGE THURSDAY NIGHT INTO FRIDAY.
THEN AS THE LOW PRESSURE LIFTS NORTHEAST OF LAKE MICHIGAN AND A
RIDGE OF HIGH PRESSURE SLIDES SOUTH FROM CENTRAL CANADA INTO THE
UPPER MIDWEST FRIDAY EVENING...A FRONTAL BOUNDARY WILL SAG SOUTH
AND TURN WINDS NORTHERLY FOR THE NORTHERN HALF OF THE LAKE.
MEANWHILE IT DOES APPEAR THE BOUNDARY GETS HUNG UP ACROSS THE
CENTRAL PORTION OF THE LAKE FRIDAY NIGHT/EARLY SATURDAY...WHICH
WILL KEEP SOUTHERLY WINDS FOR THE SOUTHERN HALF OF THE LAKE. THEN
YET ANOTHER AREA OF LOW PRESSURE IS FORECAST TO DEVELOP ACROSS THE
NORTHERN PLAINS SATURDAY AFTERNOON AND DEEPEN AS IT MOVES
NORTHEAST INTO WESTERN ONTARIO. THIS WILL LIKELY CREATE A TIGHT
GRADIENT ACROSS THE LAKE SUNDAY WITH YET ANOTHER PERIOD OF WINDS
NEARING 20-25KT.

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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO









000
FXUS63 KLOT 280000
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
700 PM CDT WED AUG 27 2014

.DISCUSSION...
330 PM CDT

SHORT TERM...WEDNESDAY AFTERNOON THROUGH SATURDAY...

FOR THE REMAINDER OF THE AFTERNOON SHOULD REMAIN QUIET AS THE OLD
STATIONARY BOUNDARY REMAINS WELL TO THE SOUTH ACROSS SRN IL AND THE
OHIO VALLEY.  HAVE MAINTAINED SLIGHT CHANCE POPS ACROSS THE VERY FAR
SOUTH OF THE CWA...A LITTLE NORTH OF THE BOUNDARY IN DEFERENCE TO
THE PROXIMITY TO THE BOUNDARY TO THE SOUTH AND A WARM AND VERY MOIST
AIRMASS...WITH DEWPOINTS STILL IN THE LOW 70S...ACROSS THE AREA.
THROUGH THE LATE EVENING AND INTO THE OVERNIGHT HOURS...ANTICIPATE
INCREASING POPS SPREADING FROM SOUTHWEST TO NORTHEAST AS LOW
PRESSURE OVER THE CENTRAL PLAINS LIFTS NEWD...DRAGGING THE OLD
STATIONARY BOUNDARY BACK NORTH AS A WARM FRONT.  WITH UPPER RIDGING
BUILDING ALOFT WITH THE RIDGE AXIS EXTENDING JUST EAST OF THE
MISSISSIPPI RIVER BY EARLY THURSDAY MORNING...ANTICIPATE THAT SWLY
FLOW ALOFT SHOULD HELP KEEP THE HIGHEST PCPN CHANCES OVER LOCATIONS
WEST OF A LINE FROM ROCKFORD TO WATSEKA.

THROUGH THURSDAY AND THURSDAY NIGHT...THE UPPER RIDGE WILL SLOWLY
BUILD  EAST AS SHORTWAVE ENERGY OVERTOPS THE RIDGE.  THE SHORT RANGE
MODELS ARE RELATIVELY CONSISTENT ON ADVERTISING THIS SCENARIO...SO
ANTICIPATE INCREASING POPS OVER THE WRN PORTIONS OF THE CWA THROUGH
THE EVENING AND THEN THE NORTHERN PORTIONS OF THE CWA THROUGH THE
NIGHT...BUT WITH THE TRACK OF THE MAIN UPPER SHORTWAVE TO THE WEST
AND NORTH OF THE CWA...THE STRONGER UPPER FORCING SHOULD BE OVER
IOWA AND INTO WISCONSIN...SO HAVE LIMITED POPS OVER THE CWA TO
CHANCE LEVELS.  THE LOCAL AREA SHOULD BEGIN TO SEE POPS INCREASING
THROUGH THE DAY FRIDAY AND ESPECIALLY LATER FRIDAY NIGHT AS A STRONG
SHORTWAVE LIFTING OUT OF THE GREAT BASIN TONIGHT SLOWLY TRACKS EAST
ACROSS THE CENTRAL PLAINS AND REACHES THE MIDDLE AND UPPER
MISSISSIPPI VALLEY FRIDAY NIGHT.  WILL INCREASE POPS THROUGH FRIDAY
EVENING WITH LIKELY POPS SPREADING INTO THE WRN PORTIONS OF THE CWA
AFTER MIDNIGHT FRIDAY NIGHT AND EAST ACROSS THE REMAINDER OF THE
AREA THROUGH SATURDAY AND INTO SATURDAY EVENING.

FORM TEMPERATURES...WITH SFC HIGH PRESSURE SLOWLY SLIDING ACROSS THE
GREAT LAKES REGION...THE WARMEST AND MOST HUMID CONDITIONS WILL BE
CONFINED TO THE FAR SOUTHERN PORTIONS OF THE CWA...THOUGH EVEN
LOCATIONS NORTH OF THE I-80 CORRIDOR HAVE SEEN TEMPS CLIMB INTO THE
LOWER 80S EVEN WITH PERSISTENT NELY FLOW AT THE LOWER LEVELS.  THE
HIGH WILL STILL HAVE A MAJOR INFLUENCE ON TEMPS THROUGH
THURSDAY...KEEPING THE NORTHERN PORTIONS OF THE CWA...INCLUDING THE
LAKEFRONT...ON THE COOLER SIDE WITH HIGHS IN THE UPPER 70S TO AROUND
80...WHILE THE SRN LOCATIONS SHOULD WARM INTO THE LOWER 80S.  AS THE
UPPER RIDGE BUILDS ACROSS THE AREA ON FRIDAY AND THE WARM FRONT
LIFTS WELL TO THE NORTH INTO WISCONSIN...EXPECT THAT TEMPS SHOULD
RETURN TO THE MIDDLE TO UPPER 80S WITH DEWPOINTS IN THE LOWER 70S.
THIS COMBINATION OF WARMTH AND MOISTURE SHOULD DRIVE HEAT INDEX
VALUES BACK INTO THE LOWER 90S.  BY FRIDAY NIGHT OR EARLY
SATURDAY...A WEAK COLD FRONT IS EXPECTED TO SWEEP ACROSS THE
AREA...BUT LITTLE SIGNIFICANT AIRMASS CHANGE IS EXPECTED AS THERE
SHOULD BE LITTLE INFLUX OF SIGNIFICANTLY COOLER/DRIER AIR INTO THE
REGION AS SFC HIGH PRESSURE BUILDS ACROSS SRN CANADA AND THE REGION
ONLY EXPERIENCES A BRIEF PERIOD OF LIGHT AND VARIABLE WINDS UNDER
VERY WEAK SFC TROUGHING ASSOCIATED WITH THE COLD FRONT.  BY
SATURDAY...SOUTHERLY FLOW SHOULD RETURN AS A COLD FRONT AND SFC
TROUGH MOVES OUT OVER THE NRN/CNTRL PLAINS AND AND THE BERMUDA HIGH
BUILDS BACK ACROSS THE GULF COAST.

FOR THE LONGER TERM...FROM SUNDAY THROUGH WEDNESDAY...UNSETTLED
WEATHER WILL CONTINUE ACROSS THE REGION FOR SUNDAY AND MONDAY.  THE
LONGER RANGE GUIDANCE IN IN RELATIVELY GOOD AGREEMENT ON A LONG WAVE
TROUGH MOVING ACROSS THE ROCKIES WITH WEAK RIDGING OVER THE ERN
CONUS.  THIS WILL PUT THE UPPER MIDWEST UNDER BROAD SWLY FLOW WITH A
SERIES OF WEAK SRN STREAM SHORT WAVES TRACKING ACROSS THE AREA.  IN
GENERAL...THE UPPER LEVEL PATTERN WILL BE FAIRLY LOW AMPLITUDE...SO
TIMING AND STRENGTH OF INDIVIDUAL WAVES WILL BE QUESTIONABLE...BUT
THE GENERAL TREND SHOULD BE FOR MORE PERIODIC SHOWERS AND
THUNDERSTORMS...THOUGH CONFIDENCE IN TIMING WILL BE LOW.  BY TUESDAY
AND WEDNESDAY...THE LONGER RANGE GUIDANCE IS INDICATING THAT THE
UPPER TROUGH SHOULD BEGIN TO MOVE EAST OF THE AREA...WITH HIGH
PRESSURE SETTLING OVER THE UPPER MISSISSIPPI VALLEY AND WESTERN
GREAT LAKES REGION.  THIS WOULD LEAD TO A PERIOD OF DRIER CONDITIONS
SO HAVE REMOVED POPS FOR TUESDAY AND WEDNESDAY.  UNDER RELATIVELY
LOW AMPLITUDE FLOW ALOFT...THERE SHOULD BE LITTLE DAY TO DAY
TEMPERATURE SWINGS WITH HIGHS GENERALLY IN THE LOWER 80S AND
OVERNIGHT LOWS IN THE 60S.

KREIN

&&

.AVIATION...

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

* EAST WINDS AROUND 10 KT THROUGH THE EARLY EVENING...THEN
  INCREASING AGAIN TO AROUND 10 KT THURSDAY AFTERNOON.

* SHRA/ISOLATED TSRA THURSDAY AFTERNOON/EVENING

KMD

//DISCUSSION...UPDATED 00Z...
EAST WINDS STILL HOVERING AROUND 10 KT...AND EXPECT THAT TO
CONTINUE UNTIL A LITTLE AFTER SUNSET. HIGH PRESSURE REMAINS IN
CONTROL TONIGHT FOR PASSING HIGH CLOUDS AND LIGHTER EAST
WINDS...THEN CLOUDS INCREASE ON THURSDAY AHEAD OF A WARM FRONT.
DRIER EAST WINDS KEEP MOST AREAS DRY...THOUGH KRFD HAS THE BEST
CHANCE FOR A SHOWER IN THE AFTERNOON. THE WARM FRONT LIFTS THROUGH
THURSDAY EVENING WHICH IS THE BEST CHANCE FOR ANY SHOWERS ACROSS
THE TERMINALS. INSTABILITY PARAMETERS ARE WEAK AND THUS EXPECT
THUNDER ACTIVITY TO BE ISOLATED AND THEREFORE KEPT THE KORD TAF
LIMITED TO SHOWERS FOR NOW. HIGHEST IMPACTS FOR THE AIRSPACE WILL
BE FOR AREAS NORTH AND WEST.

KMD


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

* HIGH IN WINDS AT OR ABOVE 10 KT THROUGH 1Z. MEDIUM THAT EAST
  WINDS WILL REACH 10 KT OR HIGHER TOMORROW AFTERNOON AND MEDIUM
  ON TIMING.

* MEDIUM THAT SHRA REMAIN WEST OF ORD/MDW THROUGH 0Z. MEDIUM IN
  SHRA THURSDAY EVENING. MEDIUM THAT ANY TSRA WOULD BE ISOLATED
  THROUGH 6Z.

KMD

//OUTLOOK FOR ORD/MDW FOR 12Z FRIDAY-12Z WEDNESDAY...UPDATED 00Z...

FRIDAY...CHANCE TSRA.

SATURDAY...TSRA LIKELY.

SUNDAY AND MONDAY...CHANCE TSRA.

TUESDAY...SLIGHT CHANCE TSRA.

KMD

&&

.MARINE...
205 PM CDT

HIGH PRESSURE WILL CONTINUE TO BE OVERHEAD OF LAKE
MICHIGAN...LIKELY LINGERING THROUGH DAYBREAK THURSDAY BEFORE
MOVING EAST TOWARDS LAKE ERIE TOMORROW NIGHT. AS THE HIGH DRIFTS
EAST...WINDS WILL SLOWLY TURN SOUTHEASTERLY THEN SOUTHERLY.
GUIDANCE IS EXPECTING A LOW PRESSURE SYSTEM TO LIFT NORTHEAST
ACROSS THE CENTRAL PLAINS INTO THE UPPER MIDWEST THURSDAY
AFTERNOON. THIS WILL RESULT IN A TIGHTENING GRADIENT FROM SOUTH TO
NORTH ACROSS THE LAKE. AT THIS TIME IT IS POSSIBLE THAT WINDS
COULD HOVER IN THE 15 TO 25 KT RANGE THURSDAY NIGHT INTO FRIDAY.
THEN AS THE LOW PRESSURE LIFTS NORTHEAST OF LAKE MICHIGAN AND A
RIDGE OF HIGH PRESSURE SLIDES SOUTH FROM CENTRAL CANADA INTO THE
UPPER MIDWEST FRIDAY EVENING...A FRONTAL BOUNDARY WILL SAG SOUTH
AND TURN WINDS NORTHERLY FOR THE NORTHERN HALF OF THE LAKE.
MEANWHILE IT DOES APPEAR THE BOUNDARY GETS HUNG UP ACROSS THE
CENTRAL PORTION OF THE LAKE FRIDAY NIGHT/EARLY SATURDAY...WHICH
WILL KEEP SOUTHERLY WINDS FOR THE SOUTHERN HALF OF THE LAKE. THEN
YET ANOTHER AREA OF LOW PRESSURE IS FORECAST TO DEVELOP ACROSS THE
NORTHERN PLAINS SATURDAY AFTERNOON AND DEEPEN AS IT MOVES
NORTHEAST INTO WESTERN ONTARIO. THIS WILL LIKELY CREATE A TIGHT
GRADIENT ACROSS THE LAKE SUNDAY WITH YET ANOTHER PERIOD OF WINDS
NEARING 20-25KT.

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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 280000
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
700 PM CDT WED AUG 27 2014

.DISCUSSION...
330 PM CDT

SHORT TERM...WEDNESDAY AFTERNOON THROUGH SATURDAY...

FOR THE REMAINDER OF THE AFTERNOON SHOULD REMAIN QUIET AS THE OLD
STATIONARY BOUNDARY REMAINS WELL TO THE SOUTH ACROSS SRN IL AND THE
OHIO VALLEY.  HAVE MAINTAINED SLIGHT CHANCE POPS ACROSS THE VERY FAR
SOUTH OF THE CWA...A LITTLE NORTH OF THE BOUNDARY IN DEFERENCE TO
THE PROXIMITY TO THE BOUNDARY TO THE SOUTH AND A WARM AND VERY MOIST
AIRMASS...WITH DEWPOINTS STILL IN THE LOW 70S...ACROSS THE AREA.
THROUGH THE LATE EVENING AND INTO THE OVERNIGHT HOURS...ANTICIPATE
INCREASING POPS SPREADING FROM SOUTHWEST TO NORTHEAST AS LOW
PRESSURE OVER THE CENTRAL PLAINS LIFTS NEWD...DRAGGING THE OLD
STATIONARY BOUNDARY BACK NORTH AS A WARM FRONT.  WITH UPPER RIDGING
BUILDING ALOFT WITH THE RIDGE AXIS EXTENDING JUST EAST OF THE
MISSISSIPPI RIVER BY EARLY THURSDAY MORNING...ANTICIPATE THAT SWLY
FLOW ALOFT SHOULD HELP KEEP THE HIGHEST PCPN CHANCES OVER LOCATIONS
WEST OF A LINE FROM ROCKFORD TO WATSEKA.

THROUGH THURSDAY AND THURSDAY NIGHT...THE UPPER RIDGE WILL SLOWLY
BUILD  EAST AS SHORTWAVE ENERGY OVERTOPS THE RIDGE.  THE SHORT RANGE
MODELS ARE RELATIVELY CONSISTENT ON ADVERTISING THIS SCENARIO...SO
ANTICIPATE INCREASING POPS OVER THE WRN PORTIONS OF THE CWA THROUGH
THE EVENING AND THEN THE NORTHERN PORTIONS OF THE CWA THROUGH THE
NIGHT...BUT WITH THE TRACK OF THE MAIN UPPER SHORTWAVE TO THE WEST
AND NORTH OF THE CWA...THE STRONGER UPPER FORCING SHOULD BE OVER
IOWA AND INTO WISCONSIN...SO HAVE LIMITED POPS OVER THE CWA TO
CHANCE LEVELS.  THE LOCAL AREA SHOULD BEGIN TO SEE POPS INCREASING
THROUGH THE DAY FRIDAY AND ESPECIALLY LATER FRIDAY NIGHT AS A STRONG
SHORTWAVE LIFTING OUT OF THE GREAT BASIN TONIGHT SLOWLY TRACKS EAST
ACROSS THE CENTRAL PLAINS AND REACHES THE MIDDLE AND UPPER
MISSISSIPPI VALLEY FRIDAY NIGHT.  WILL INCREASE POPS THROUGH FRIDAY
EVENING WITH LIKELY POPS SPREADING INTO THE WRN PORTIONS OF THE CWA
AFTER MIDNIGHT FRIDAY NIGHT AND EAST ACROSS THE REMAINDER OF THE
AREA THROUGH SATURDAY AND INTO SATURDAY EVENING.

FORM TEMPERATURES...WITH SFC HIGH PRESSURE SLOWLY SLIDING ACROSS THE
GREAT LAKES REGION...THE WARMEST AND MOST HUMID CONDITIONS WILL BE
CONFINED TO THE FAR SOUTHERN PORTIONS OF THE CWA...THOUGH EVEN
LOCATIONS NORTH OF THE I-80 CORRIDOR HAVE SEEN TEMPS CLIMB INTO THE
LOWER 80S EVEN WITH PERSISTENT NELY FLOW AT THE LOWER LEVELS.  THE
HIGH WILL STILL HAVE A MAJOR INFLUENCE ON TEMPS THROUGH
THURSDAY...KEEPING THE NORTHERN PORTIONS OF THE CWA...INCLUDING THE
LAKEFRONT...ON THE COOLER SIDE WITH HIGHS IN THE UPPER 70S TO AROUND
80...WHILE THE SRN LOCATIONS SHOULD WARM INTO THE LOWER 80S.  AS THE
UPPER RIDGE BUILDS ACROSS THE AREA ON FRIDAY AND THE WARM FRONT
LIFTS WELL TO THE NORTH INTO WISCONSIN...EXPECT THAT TEMPS SHOULD
RETURN TO THE MIDDLE TO UPPER 80S WITH DEWPOINTS IN THE LOWER 70S.
THIS COMBINATION OF WARMTH AND MOISTURE SHOULD DRIVE HEAT INDEX
VALUES BACK INTO THE LOWER 90S.  BY FRIDAY NIGHT OR EARLY
SATURDAY...A WEAK COLD FRONT IS EXPECTED TO SWEEP ACROSS THE
AREA...BUT LITTLE SIGNIFICANT AIRMASS CHANGE IS EXPECTED AS THERE
SHOULD BE LITTLE INFLUX OF SIGNIFICANTLY COOLER/DRIER AIR INTO THE
REGION AS SFC HIGH PRESSURE BUILDS ACROSS SRN CANADA AND THE REGION
ONLY EXPERIENCES A BRIEF PERIOD OF LIGHT AND VARIABLE WINDS UNDER
VERY WEAK SFC TROUGHING ASSOCIATED WITH THE COLD FRONT.  BY
SATURDAY...SOUTHERLY FLOW SHOULD RETURN AS A COLD FRONT AND SFC
TROUGH MOVES OUT OVER THE NRN/CNTRL PLAINS AND AND THE BERMUDA HIGH
BUILDS BACK ACROSS THE GULF COAST.

FOR THE LONGER TERM...FROM SUNDAY THROUGH WEDNESDAY...UNSETTLED
WEATHER WILL CONTINUE ACROSS THE REGION FOR SUNDAY AND MONDAY.  THE
LONGER RANGE GUIDANCE IN IN RELATIVELY GOOD AGREEMENT ON A LONG WAVE
TROUGH MOVING ACROSS THE ROCKIES WITH WEAK RIDGING OVER THE ERN
CONUS.  THIS WILL PUT THE UPPER MIDWEST UNDER BROAD SWLY FLOW WITH A
SERIES OF WEAK SRN STREAM SHORT WAVES TRACKING ACROSS THE AREA.  IN
GENERAL...THE UPPER LEVEL PATTERN WILL BE FAIRLY LOW AMPLITUDE...SO
TIMING AND STRENGTH OF INDIVIDUAL WAVES WILL BE QUESTIONABLE...BUT
THE GENERAL TREND SHOULD BE FOR MORE PERIODIC SHOWERS AND
THUNDERSTORMS...THOUGH CONFIDENCE IN TIMING WILL BE LOW.  BY TUESDAY
AND WEDNESDAY...THE LONGER RANGE GUIDANCE IS INDICATING THAT THE
UPPER TROUGH SHOULD BEGIN TO MOVE EAST OF THE AREA...WITH HIGH
PRESSURE SETTLING OVER THE UPPER MISSISSIPPI VALLEY AND WESTERN
GREAT LAKES REGION.  THIS WOULD LEAD TO A PERIOD OF DRIER CONDITIONS
SO HAVE REMOVED POPS FOR TUESDAY AND WEDNESDAY.  UNDER RELATIVELY
LOW AMPLITUDE FLOW ALOFT...THERE SHOULD BE LITTLE DAY TO DAY
TEMPERATURE SWINGS WITH HIGHS GENERALLY IN THE LOWER 80S AND
OVERNIGHT LOWS IN THE 60S.

KREIN

&&

.AVIATION...

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

* EAST WINDS AROUND 10 KT THROUGH THE EARLY EVENING...THEN
  INCREASING AGAIN TO AROUND 10 KT THURSDAY AFTERNOON.

* SHRA/ISOLATED TSRA THURSDAY AFTERNOON/EVENING

KMD

//DISCUSSION...UPDATED 00Z...
EAST WINDS STILL HOVERING AROUND 10 KT...AND EXPECT THAT TO
CONTINUE UNTIL A LITTLE AFTER SUNSET. HIGH PRESSURE REMAINS IN
CONTROL TONIGHT FOR PASSING HIGH CLOUDS AND LIGHTER EAST
WINDS...THEN CLOUDS INCREASE ON THURSDAY AHEAD OF A WARM FRONT.
DRIER EAST WINDS KEEP MOST AREAS DRY...THOUGH KRFD HAS THE BEST
CHANCE FOR A SHOWER IN THE AFTERNOON. THE WARM FRONT LIFTS THROUGH
THURSDAY EVENING WHICH IS THE BEST CHANCE FOR ANY SHOWERS ACROSS
THE TERMINALS. INSTABILITY PARAMETERS ARE WEAK AND THUS EXPECT
THUNDER ACTIVITY TO BE ISOLATED AND THEREFORE KEPT THE KORD TAF
LIMITED TO SHOWERS FOR NOW. HIGHEST IMPACTS FOR THE AIRSPACE WILL
BE FOR AREAS NORTH AND WEST.

KMD


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

* HIGH IN WINDS AT OR ABOVE 10 KT THROUGH 1Z. MEDIUM THAT EAST
  WINDS WILL REACH 10 KT OR HIGHER TOMORROW AFTERNOON AND MEDIUM
  ON TIMING.

* MEDIUM THAT SHRA REMAIN WEST OF ORD/MDW THROUGH 0Z. MEDIUM IN
  SHRA THURSDAY EVENING. MEDIUM THAT ANY TSRA WOULD BE ISOLATED
  THROUGH 6Z.

KMD

//OUTLOOK FOR ORD/MDW FOR 12Z FRIDAY-12Z WEDNESDAY...UPDATED 00Z...

FRIDAY...CHANCE TSRA.

SATURDAY...TSRA LIKELY.

SUNDAY AND MONDAY...CHANCE TSRA.

TUESDAY...SLIGHT CHANCE TSRA.

KMD

&&

.MARINE...
205 PM CDT

HIGH PRESSURE WILL CONTINUE TO BE OVERHEAD OF LAKE
MICHIGAN...LIKELY LINGERING THROUGH DAYBREAK THURSDAY BEFORE
MOVING EAST TOWARDS LAKE ERIE TOMORROW NIGHT. AS THE HIGH DRIFTS
EAST...WINDS WILL SLOWLY TURN SOUTHEASTERLY THEN SOUTHERLY.
GUIDANCE IS EXPECTING A LOW PRESSURE SYSTEM TO LIFT NORTHEAST
ACROSS THE CENTRAL PLAINS INTO THE UPPER MIDWEST THURSDAY
AFTERNOON. THIS WILL RESULT IN A TIGHTENING GRADIENT FROM SOUTH TO
NORTH ACROSS THE LAKE. AT THIS TIME IT IS POSSIBLE THAT WINDS
COULD HOVER IN THE 15 TO 25 KT RANGE THURSDAY NIGHT INTO FRIDAY.
THEN AS THE LOW PRESSURE LIFTS NORTHEAST OF LAKE MICHIGAN AND A
RIDGE OF HIGH PRESSURE SLIDES SOUTH FROM CENTRAL CANADA INTO THE
UPPER MIDWEST FRIDAY EVENING...A FRONTAL BOUNDARY WILL SAG SOUTH
AND TURN WINDS NORTHERLY FOR THE NORTHERN HALF OF THE LAKE.
MEANWHILE IT DOES APPEAR THE BOUNDARY GETS HUNG UP ACROSS THE
CENTRAL PORTION OF THE LAKE FRIDAY NIGHT/EARLY SATURDAY...WHICH
WILL KEEP SOUTHERLY WINDS FOR THE SOUTHERN HALF OF THE LAKE. THEN
YET ANOTHER AREA OF LOW PRESSURE IS FORECAST TO DEVELOP ACROSS THE
NORTHERN PLAINS SATURDAY AFTERNOON AND DEEPEN AS IT MOVES
NORTHEAST INTO WESTERN ONTARIO. THIS WILL LIKELY CREATE A TIGHT
GRADIENT ACROSS THE LAKE SUNDAY WITH YET ANOTHER PERIOD OF WINDS
NEARING 20-25KT.

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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO







000
FXUS63 KLOT 272213
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
513 PM CDT WED AUG 27 2014

.DISCUSSION...
330 PM CDT

SHORT TERM...WEDNESDAY AFTERNOON THROUGH SATURDAY...

FOR THE REMAINDER OF THE AFTERNOON SHOULD REMAIN QUIET AS THE OLD
STATIONARY BOUNDARY REMAINS WELL TO THE SOUTH ACROSS SRN IL AND THE
OHIO VALLEY.  HAVE MAINTAINED SLIGHT CHANCE POPS ACROSS THE VERY FAR
SOUTH OF THE CWA...A LITTLE NORTH OF THE BOUNDARY IN DEFERENCE TO
THE PROXIMITY TO THE BOUNDARY TO THE SOUTH AND A WARM AND VERY MOIST
AIRMASS...WITH DEWPOINTS STILL IN THE LOW 70S...ACROSS THE AREA.
THROUGH THE LATE EVENING AND INTO THE OVERNIGHT HOURS...ANTICIPATE
INCREASING POPS SPREADING FROM SOUTHWEST TO NORTHEAST AS LOW
PRESSURE OVER THE CENTRAL PLAINS LIFTS NEWD...DRAGGING THE OLD
STATIONARY BOUNDARY BACK NORTH AS A WARM FRONT.  WITH UPPER RIDGING
BUILDING ALOFT WITH THE RIDGE AXIS EXTENDING JUST EAST OF THE
MISSISSIPPI RIVER BY EARLY THURSDAY MORNING...ANTICIPATE THAT SWLY
FLOW ALOFT SHOULD HELP KEEP THE HIGHEST PCPN CHANCES OVER LOCATIONS
WEST OF A LINE FROM ROCKFORD TO WATSEKA.

THROUGH THURSDAY AND THURSDAY NIGHT...THE UPPER RIDGE WILL SLOWLY
BUILD  EAST AS SHORTWAVE ENERGY OVERTOPS THE RIDGE.  THE SHORT RANGE
MODELS ARE RELATIVELY CONSISTENT ON ADVERTISING THIS SCENARIO...SO
ANTICIPATE INCREASING POPS OVER THE WRN PORTIONS OF THE CWA THROUGH
THE EVENING AND THEN THE NORTHERN PORTIONS OF THE CWA THROUGH THE
NIGHT...BUT WITH THE TRACK OF THE MAIN UPPER SHORTWAVE TO THE WEST
AND NORTH OF THE CWA...THE STRONGER UPPER FORCING SHOULD BE OVER
IOWA AND INTO WISCONSIN...SO HAVE LIMITED POPS OVER THE CWA TO
CHANCE LEVELS.  THE LOCAL AREA SHOULD BEGIN TO SEE POPS INCREASING
THROUGH THE DAY FRIDAY AND ESPECIALLY LATER FRIDAY NIGHT AS A STRONG
SHORTWAVE LIFTING OUT OF THE GREAT BASIN TONIGHT SLOWLY TRACKS EAST
ACROSS THE CENTRAL PLAINS AND REACHES THE MIDDLE AND UPPER
MISSISSIPPI VALLEY FRIDAY NIGHT.  WILL INCREASE POPS THROUGH FRIDAY
EVENING WITH LIKELY POPS SPREADING INTO THE WRN PORTIONS OF THE CWA
AFTER MIDNIGHT FRIDAY NIGHT AND EAST ACROSS THE REMAINDER OF THE
AREA THROUGH SATURDAY AND INTO SATURDAY EVENING.

FORM TEMPERATURES...WITH SFC HIGH PRESSURE SLOWLY SLIDING ACROSS THE
GREAT LAKES REGION...THE WARMEST AND MOST HUMID CONDITIONS WILL BE
CONFINED TO THE FAR SOUTHERN PORTIONS OF THE CWA...THOUGH EVEN
LOCATIONS NORTH OF THE I-80 CORRIDOR HAVE SEEN TEMPS CLIMB INTO THE
LOWER 80S EVEN WITH PERSISTENT NELY FLOW AT THE LOWER LEVELS.  THE
HIGH WILL STILL HAVE A MAJOR INFLUENCE ON TEMPS THROUGH
THURSDAY...KEEPING THE NORTHERN PORTIONS OF THE CWA...INCLUDING THE
LAKEFRONT...ON THE COOLER SIDE WITH HIGHS IN THE UPPER 70S TO AROUND
80...WHILE THE SRN LOCATIONS SHOULD WARM INTO THE LOWER 80S.  AS THE
UPPER RIDGE BUILDS ACROSS THE AREA ON FRIDAY AND THE WARM FRONT
LIFTS WELL TO THE NORTH INTO WISCONSIN...EXPECT THAT TEMPS SHOULD
RETURN TO THE MIDDLE TO UPPER 80S WITH DEWPOINTS IN THE LOWER 70S.
THIS COMBINATION OF WARMTH AND MOISTURE SHOULD DRIVE HEAT INDEX
VALUES BACK INTO THE LOWER 90S.  BY FRIDAY NIGHT OR EARLY
SATURDAY...A WEAK COLD FRONT IS EXPECTED TO SWEEP ACROSS THE
AREA...BUT LITTLE SIGNIFICANT AIRMASS CHANGE IS EXPECTED AS THERE
SHOULD BE LITTLE INFLUX OF SIGNIFICANTLY COOLER/DRIER AIR INTO THE
REGION AS SFC HIGH PRESSURE BUILDS ACROSS SRN CANADA AND THE REGION
ONLY EXPERIENCES A BRIEF PERIOD OF LIGHT AND VARIABLE WINDS UNDER
VERY WEAK SFC TROUGHING ASSOCIATED WITH THE COLD FRONT.  BY
SATURDAY...SOUTHERLY FLOW SHOULD RETURN AS A COLD FRONT AND SFC
TROUGH MOVES OUT OVER THE NRN/CNTRL PLAINS AND AND THE BERMUDA HIGH
BUILDS BACK ACROSS THE GULF COAST.

FOR THE LONGER TERM...FROM SUNDAY THROUGH WEDNESDAY...UNSETTLED
WEATHER WILL CONTINUE ACROSS THE REGION FOR SUNDAY AND MONDAY.  THE
LONGER RANGE GUIDANCE IN IN RELATIVELY GOOD AGREEMENT ON A LONG WAVE
TROUGH MOVING ACROSS THE ROCKIES WITH WEAK RIDGING OVER THE ERN
CONUS.  THIS WILL PUT THE UPPER MIDWEST UNDER BROAD SWLY FLOW WITH A
SERIES OF WEAK SRN STREAM SHORT WAVES TRACKING ACROSS THE AREA.  IN
GENERAL...THE UPPER LEVEL PATTERN WILL BE FAIRLY LOW AMPLITUDE...SO
TIMING AND STRENGTH OF INDIVIDUAL WAVES WILL BE QUESTIONABLE...BUT
THE GENERAL TREND SHOULD BE FOR MORE PERIODIC SHOWERS AND
THUNDERSTORMS...THOUGH CONFIDENCE IN TIMING WILL BE LOW.  BY TUESDAY
AND WEDNESDAY...THE LONGER RANGE GUIDANCE IS INDICATING THAT THE
UPPER TROUGH SHOULD BEGIN TO MOVE EAST OF THE AREA...WITH HIGH
PRESSURE SETTLING OVER THE UPPER MISSISSIPPI VALLEY AND WESTERN
GREAT LAKES REGION.  THIS WOULD LEAD TO A PERIOD OF DRIER CONDITIONS
SO HAVE REMOVED POPS FOR TUESDAY AND WEDNESDAY.  UNDER RELATIVELY
LOW AMPLITUDE FLOW ALOFT...THERE SHOULD BE LITTLE DAY TO DAY
TEMPERATURE SWINGS WITH HIGHS GENERALLY IN THE LOWER 80S AND
OVERNIGHT LOWS IN THE 60S.

KREIN

&&

.AVIATION...

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

* EAST WINDS AROUND 10 KT THROUGH THE EARLY EVENING...THEN
  INCREASING AGAIN TO AROUND 10 KT THURSDAY AFTERNOON.

KMD

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

HIGH PRESSURE IS SPREADING OVER THE REGION WITH VFR CONDITIONS
ACROSS THE REGION. EAST WINDS WILL CONTINUE THROUGH THE PERIOD. AS
WARMING CONTINUES...EXPECTING WINDS TO PICK UP TO ARND 10 KT BY
MID AFTN. WINDS THEN DIMINISH THIS EVENING...AND THEN WILL BE ARND
8 KT TOMORROW.

THE HIGH SHIFTS EAST TONIGHT INTO TOMORROW WITH LOW PRESSURE
APPROACHING FROM THE SOUTHWEST. GUIDANCE HAS THE WARM FRONT
REMAINING SOUTH OF THE TERMINALS THROUGH TOMORROW AFTERNOON.
HOWEVER...SOME MODELS SHOW STORMS REACHING RFD BY LATE
MORNING/EARLY AFTN SO HAVE A PROB30 FOR THOSE. NOT OVERLY
CONFIDENT IN THE TSRA CHANCES AT RFD. THE OTHER TERMINALS WILL SEE
PRECIP PUSH IN AFTER 00Z FRIDAY.

JEE

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

* HIGH IN WINDS AT OR ABOVE 10 KT THROUGH 1Z. MEDIUM-HIGH ON
  TIMING FOR WHEN WINDS EASE BELOW 10 KT. LOW-MEDIUM THAT EAST
  WINDS WILL REACH 10 KT TOMORROW AFTERNOON.

KMD

//OUTLOOK FOR ORD/MDW FOR 00Z FRIDAY-12Z WEDNESDAY...UPDATED 12Z...

* THURSDAY NIGHT AND FRIDAY...CHANCE OF TSRA.
* SATURDAY...TSRA LIKELY.
* SUNDAY THROUGH TUESDAY...CHANCE OF TSRA.

&&

.MARINE...
205 PM CDT

HIGH PRESSURE WILL CONTINUE TO BE OVERHEAD OF LAKE
MICHIGAN...LIKELY LINGERING THROUGH DAYBREAK THURSDAY BEFORE
MOVING EAST TOWARDS LAKE ERIE TOMORROW NIGHT. AS THE HIGH DRIFTS
EAST...WINDS WILL SLOWLY TURN SOUTHEASTERLY THEN SOUTHERLY.
GUIDANCE IS EXPECTING A LOW PRESSURE SYSTEM TO LIFT NORTHEAST
ACROSS THE CENTRAL PLAINS INTO THE UPPER MIDWEST THURSDAY
AFTERNOON. THIS WILL RESULT IN A TIGHTENING GRADIENT FROM SOUTH TO
NORTH ACROSS THE LAKE. AT THIS TIME IT IS POSSIBLE THAT WINDS
COULD HOVER IN THE 15 TO 25 KT RANGE THURSDAY NIGHT INTO FRIDAY.
THEN AS THE LOW PRESSURE LIFTS NORTHEAST OF LAKE MICHIGAN AND A
RIDGE OF HIGH PRESSURE SLIDES SOUTH FROM CENTRAL CANADA INTO THE
UPPER MIDWEST FRIDAY EVENING...A FRONTAL BOUNDARY WILL SAG SOUTH
AND TURN WINDS NORTHERLY FOR THE NORTHERN HALF OF THE LAKE.
MEANWHILE IT DOES APPEAR THE BOUNDARY GETS HUNG UP ACROSS THE
CENTRAL PORTION OF THE LAKE FRIDAY NIGHT/EARLY SATURDAY...WHICH
WILL KEEP SOUTHERLY WINDS FOR THE SOUTHERN HALF OF THE LAKE. THEN
YET ANOTHER AREA OF LOW PRESSURE IS FORECAST TO DEVELOP ACROSS THE
NORTHERN PLAINS SATURDAY AFTERNOON AND DEEPEN AS IT MOVES
NORTHEAST INTO WESTERN ONTARIO. THIS WILL LIKELY CREATE A TIGHT
GRADIENT ACROSS THE LAKE SUNDAY WITH YET ANOTHER PERIOD OF WINDS
NEARING 20-25KT.

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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO







000
FXUS63 KLOT 272213
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
513 PM CDT WED AUG 27 2014

.DISCUSSION...
330 PM CDT

SHORT TERM...WEDNESDAY AFTERNOON THROUGH SATURDAY...

FOR THE REMAINDER OF THE AFTERNOON SHOULD REMAIN QUIET AS THE OLD
STATIONARY BOUNDARY REMAINS WELL TO THE SOUTH ACROSS SRN IL AND THE
OHIO VALLEY.  HAVE MAINTAINED SLIGHT CHANCE POPS ACROSS THE VERY FAR
SOUTH OF THE CWA...A LITTLE NORTH OF THE BOUNDARY IN DEFERENCE TO
THE PROXIMITY TO THE BOUNDARY TO THE SOUTH AND A WARM AND VERY MOIST
AIRMASS...WITH DEWPOINTS STILL IN THE LOW 70S...ACROSS THE AREA.
THROUGH THE LATE EVENING AND INTO THE OVERNIGHT HOURS...ANTICIPATE
INCREASING POPS SPREADING FROM SOUTHWEST TO NORTHEAST AS LOW
PRESSURE OVER THE CENTRAL PLAINS LIFTS NEWD...DRAGGING THE OLD
STATIONARY BOUNDARY BACK NORTH AS A WARM FRONT.  WITH UPPER RIDGING
BUILDING ALOFT WITH THE RIDGE AXIS EXTENDING JUST EAST OF THE
MISSISSIPPI RIVER BY EARLY THURSDAY MORNING...ANTICIPATE THAT SWLY
FLOW ALOFT SHOULD HELP KEEP THE HIGHEST PCPN CHANCES OVER LOCATIONS
WEST OF A LINE FROM ROCKFORD TO WATSEKA.

THROUGH THURSDAY AND THURSDAY NIGHT...THE UPPER RIDGE WILL SLOWLY
BUILD  EAST AS SHORTWAVE ENERGY OVERTOPS THE RIDGE.  THE SHORT RANGE
MODELS ARE RELATIVELY CONSISTENT ON ADVERTISING THIS SCENARIO...SO
ANTICIPATE INCREASING POPS OVER THE WRN PORTIONS OF THE CWA THROUGH
THE EVENING AND THEN THE NORTHERN PORTIONS OF THE CWA THROUGH THE
NIGHT...BUT WITH THE TRACK OF THE MAIN UPPER SHORTWAVE TO THE WEST
AND NORTH OF THE CWA...THE STRONGER UPPER FORCING SHOULD BE OVER
IOWA AND INTO WISCONSIN...SO HAVE LIMITED POPS OVER THE CWA TO
CHANCE LEVELS.  THE LOCAL AREA SHOULD BEGIN TO SEE POPS INCREASING
THROUGH THE DAY FRIDAY AND ESPECIALLY LATER FRIDAY NIGHT AS A STRONG
SHORTWAVE LIFTING OUT OF THE GREAT BASIN TONIGHT SLOWLY TRACKS EAST
ACROSS THE CENTRAL PLAINS AND REACHES THE MIDDLE AND UPPER
MISSISSIPPI VALLEY FRIDAY NIGHT.  WILL INCREASE POPS THROUGH FRIDAY
EVENING WITH LIKELY POPS SPREADING INTO THE WRN PORTIONS OF THE CWA
AFTER MIDNIGHT FRIDAY NIGHT AND EAST ACROSS THE REMAINDER OF THE
AREA THROUGH SATURDAY AND INTO SATURDAY EVENING.

FORM TEMPERATURES...WITH SFC HIGH PRESSURE SLOWLY SLIDING ACROSS THE
GREAT LAKES REGION...THE WARMEST AND MOST HUMID CONDITIONS WILL BE
CONFINED TO THE FAR SOUTHERN PORTIONS OF THE CWA...THOUGH EVEN
LOCATIONS NORTH OF THE I-80 CORRIDOR HAVE SEEN TEMPS CLIMB INTO THE
LOWER 80S EVEN WITH PERSISTENT NELY FLOW AT THE LOWER LEVELS.  THE
HIGH WILL STILL HAVE A MAJOR INFLUENCE ON TEMPS THROUGH
THURSDAY...KEEPING THE NORTHERN PORTIONS OF THE CWA...INCLUDING THE
LAKEFRONT...ON THE COOLER SIDE WITH HIGHS IN THE UPPER 70S TO AROUND
80...WHILE THE SRN LOCATIONS SHOULD WARM INTO THE LOWER 80S.  AS THE
UPPER RIDGE BUILDS ACROSS THE AREA ON FRIDAY AND THE WARM FRONT
LIFTS WELL TO THE NORTH INTO WISCONSIN...EXPECT THAT TEMPS SHOULD
RETURN TO THE MIDDLE TO UPPER 80S WITH DEWPOINTS IN THE LOWER 70S.
THIS COMBINATION OF WARMTH AND MOISTURE SHOULD DRIVE HEAT INDEX
VALUES BACK INTO THE LOWER 90S.  BY FRIDAY NIGHT OR EARLY
SATURDAY...A WEAK COLD FRONT IS EXPECTED TO SWEEP ACROSS THE
AREA...BUT LITTLE SIGNIFICANT AIRMASS CHANGE IS EXPECTED AS THERE
SHOULD BE LITTLE INFLUX OF SIGNIFICANTLY COOLER/DRIER AIR INTO THE
REGION AS SFC HIGH PRESSURE BUILDS ACROSS SRN CANADA AND THE REGION
ONLY EXPERIENCES A BRIEF PERIOD OF LIGHT AND VARIABLE WINDS UNDER
VERY WEAK SFC TROUGHING ASSOCIATED WITH THE COLD FRONT.  BY
SATURDAY...SOUTHERLY FLOW SHOULD RETURN AS A COLD FRONT AND SFC
TROUGH MOVES OUT OVER THE NRN/CNTRL PLAINS AND AND THE BERMUDA HIGH
BUILDS BACK ACROSS THE GULF COAST.

FOR THE LONGER TERM...FROM SUNDAY THROUGH WEDNESDAY...UNSETTLED
WEATHER WILL CONTINUE ACROSS THE REGION FOR SUNDAY AND MONDAY.  THE
LONGER RANGE GUIDANCE IN IN RELATIVELY GOOD AGREEMENT ON A LONG WAVE
TROUGH MOVING ACROSS THE ROCKIES WITH WEAK RIDGING OVER THE ERN
CONUS.  THIS WILL PUT THE UPPER MIDWEST UNDER BROAD SWLY FLOW WITH A
SERIES OF WEAK SRN STREAM SHORT WAVES TRACKING ACROSS THE AREA.  IN
GENERAL...THE UPPER LEVEL PATTERN WILL BE FAIRLY LOW AMPLITUDE...SO
TIMING AND STRENGTH OF INDIVIDUAL WAVES WILL BE QUESTIONABLE...BUT
THE GENERAL TREND SHOULD BE FOR MORE PERIODIC SHOWERS AND
THUNDERSTORMS...THOUGH CONFIDENCE IN TIMING WILL BE LOW.  BY TUESDAY
AND WEDNESDAY...THE LONGER RANGE GUIDANCE IS INDICATING THAT THE
UPPER TROUGH SHOULD BEGIN TO MOVE EAST OF THE AREA...WITH HIGH
PRESSURE SETTLING OVER THE UPPER MISSISSIPPI VALLEY AND WESTERN
GREAT LAKES REGION.  THIS WOULD LEAD TO A PERIOD OF DRIER CONDITIONS
SO HAVE REMOVED POPS FOR TUESDAY AND WEDNESDAY.  UNDER RELATIVELY
LOW AMPLITUDE FLOW ALOFT...THERE SHOULD BE LITTLE DAY TO DAY
TEMPERATURE SWINGS WITH HIGHS GENERALLY IN THE LOWER 80S AND
OVERNIGHT LOWS IN THE 60S.

KREIN

&&

.AVIATION...

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

* EAST WINDS AROUND 10 KT THROUGH THE EARLY EVENING...THEN
  INCREASING AGAIN TO AROUND 10 KT THURSDAY AFTERNOON.

KMD

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

HIGH PRESSURE IS SPREADING OVER THE REGION WITH VFR CONDITIONS
ACROSS THE REGION. EAST WINDS WILL CONTINUE THROUGH THE PERIOD. AS
WARMING CONTINUES...EXPECTING WINDS TO PICK UP TO ARND 10 KT BY
MID AFTN. WINDS THEN DIMINISH THIS EVENING...AND THEN WILL BE ARND
8 KT TOMORROW.

THE HIGH SHIFTS EAST TONIGHT INTO TOMORROW WITH LOW PRESSURE
APPROACHING FROM THE SOUTHWEST. GUIDANCE HAS THE WARM FRONT
REMAINING SOUTH OF THE TERMINALS THROUGH TOMORROW AFTERNOON.
HOWEVER...SOME MODELS SHOW STORMS REACHING RFD BY LATE
MORNING/EARLY AFTN SO HAVE A PROB30 FOR THOSE. NOT OVERLY
CONFIDENT IN THE TSRA CHANCES AT RFD. THE OTHER TERMINALS WILL SEE
PRECIP PUSH IN AFTER 00Z FRIDAY.

JEE

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

* HIGH IN WINDS AT OR ABOVE 10 KT THROUGH 1Z. MEDIUM-HIGH ON
  TIMING FOR WHEN WINDS EASE BELOW 10 KT. LOW-MEDIUM THAT EAST
  WINDS WILL REACH 10 KT TOMORROW AFTERNOON.

KMD

//OUTLOOK FOR ORD/MDW FOR 00Z FRIDAY-12Z WEDNESDAY...UPDATED 12Z...

* THURSDAY NIGHT AND FRIDAY...CHANCE OF TSRA.
* SATURDAY...TSRA LIKELY.
* SUNDAY THROUGH TUESDAY...CHANCE OF TSRA.

&&

.MARINE...
205 PM CDT

HIGH PRESSURE WILL CONTINUE TO BE OVERHEAD OF LAKE
MICHIGAN...LIKELY LINGERING THROUGH DAYBREAK THURSDAY BEFORE
MOVING EAST TOWARDS LAKE ERIE TOMORROW NIGHT. AS THE HIGH DRIFTS
EAST...WINDS WILL SLOWLY TURN SOUTHEASTERLY THEN SOUTHERLY.
GUIDANCE IS EXPECTING A LOW PRESSURE SYSTEM TO LIFT NORTHEAST
ACROSS THE CENTRAL PLAINS INTO THE UPPER MIDWEST THURSDAY
AFTERNOON. THIS WILL RESULT IN A TIGHTENING GRADIENT FROM SOUTH TO
NORTH ACROSS THE LAKE. AT THIS TIME IT IS POSSIBLE THAT WINDS
COULD HOVER IN THE 15 TO 25 KT RANGE THURSDAY NIGHT INTO FRIDAY.
THEN AS THE LOW PRESSURE LIFTS NORTHEAST OF LAKE MICHIGAN AND A
RIDGE OF HIGH PRESSURE SLIDES SOUTH FROM CENTRAL CANADA INTO THE
UPPER MIDWEST FRIDAY EVENING...A FRONTAL BOUNDARY WILL SAG SOUTH
AND TURN WINDS NORTHERLY FOR THE NORTHERN HALF OF THE LAKE.
MEANWHILE IT DOES APPEAR THE BOUNDARY GETS HUNG UP ACROSS THE
CENTRAL PORTION OF THE LAKE FRIDAY NIGHT/EARLY SATURDAY...WHICH
WILL KEEP SOUTHERLY WINDS FOR THE SOUTHERN HALF OF THE LAKE. THEN
YET ANOTHER AREA OF LOW PRESSURE IS FORECAST TO DEVELOP ACROSS THE
NORTHERN PLAINS SATURDAY AFTERNOON AND DEEPEN AS IT MOVES
NORTHEAST INTO WESTERN ONTARIO. THIS WILL LIKELY CREATE A TIGHT
GRADIENT ACROSS THE LAKE SUNDAY WITH YET ANOTHER PERIOD OF WINDS
NEARING 20-25KT.

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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 272031
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
331 PM CDT WED AUG 27 2014

.DISCUSSION...
330 PM CDT

SHORT TERM...WEDNESDAY AFTERNOON THROUGH SATURDAY...

FOR THE REMAINDER OF THE AFTERNOON SHOULD REMAIN QUIET AS THE OLD
STATIONARY BOUNDARY REMAINS WELL TO THE SOUTH ACROSS SRN IL AND THE
OHIO VALLEY.  HAVE MAINTAINED SLIGHT CHANCE POPS ACROSS THE VERY FAR
SOUTH OF THE CWA...A LITTLE NORTH OF THE BOUNDARY IN DEFERENCE TO
THE PROXIMITY TO THE BOUNDARY TO THE SOUTH AND A WARM AND VERY MOIST
AIRMASS...WITH DEWPOINTS STILL IN THE LOW 70S...ACROSS THE AREA.
THROUGH THE LATE EVENING AND INTO THE OVERNIGHT HOURS...ANTICIPATE
INCREASING POPS SPREADING FROM SOUTHWEST TO NORTHEAST AS LOW
PRESSURE OVER THE CENTRAL PLAINS LIFTS NEWD...DRAGGING THE OLD
STATIONARY BOUNDARY BACK NORTH AS A WARM FRONT.  WITH UPPER RIDGING
BUILDING ALOFT WITH THE RIDGE AXIS EXTENDING JUST EAST OF THE
MISSISSIPPI RIVER BY EARLY THURSDAY MORNING...ANTICIPATE THAT SWLY
FLOW ALOFT SHOULD HELP KEEP THE HIGHEST PCPN CHANCES OVER LOCATIONS
WEST OF A LINE FROM ROCKFORD TO WATSEKA.

THROUGH THURSDAY AND THURSDAY NIGHT...THE UPPER RIDGE WILL SLOWLY
BUILD  EAST AS SHORTWAVE ENERGY OVERTOPS THE RIDGE.  THE SHORT RANGE
MODELS ARE RELATIVELY CONSISTENT ON ADVERTISING THIS SCENARIO...SO
ANTICIPATE INCREASING POPS OVER THE WRN PORTIONS OF THE CWA THROUGH
THE EVENING AND THEN THE NORTHERN PORTIONS OF THE CWA THROUGH THE
NIGHT...BUT WITH THE TRACK OF THE MAIN UPPER SHORTWAVE TO THE WEST
AND NORTH OF THE CWA...THE STRONGER UPPER FORCING SHOULD BE OVER
IOWA AND INTO WISCONSIN...SO HAVE LIMITED POPS OVER THE CWA TO
CHANCE LEVELS.  THE LOCAL AREA SHOULD BEGIN TO SEE POPS INCREASING
THROUGH THE DAY FRIDAY AND ESPECIALLY LATER FRIDAY NIGHT AS A STRONG
SHORTWAVE LIFTING OUT OF THE GREAT BASIN TONIGHT SLOWLY TRACKS EAST
ACROSS THE CENTRAL PLAINS AND REACHES THE MIDDLE AND UPPER
MISSISSIPPI VALLEY FRIDAY NIGHT.  WILL INCREASE POPS THROUGH FRIDAY
EVENING WITH LIKELY POPS SPREADING INTO THE WRN PORTIONS OF THE CWA
AFTER MIDNIGHT FRIDAY NIGHT AND EAST ACROSS THE REMAINDER OF THE
AREA THROUGH SATURDAY AND INTO SATURDAY EVENING.

FORM TEMPERATURES...WITH SFC HIGH PRESSURE SLOWLY SLIDING ACROSS THE
GREAT LAKES REGION...THE WARMEST AND MOST HUMID CONDITIONS WILL BE
CONFINED TO THE FAR SOUTHERN PORTIONS OF THE CWA...THOUGH EVEN
LOCATIONS NORTH OF THE I-80 CORRIDOR HAVE SEEN TEMPS CLIMB INTO THE
LOWER 80S EVEN WITH PERSISTENT NELY FLOW AT THE LOWER LEVELS.  THE
HIGH WILL STILL HAVE A MAJOR INFLUENCE ON TEMPS THROUGH
THURSDAY...KEEPING THE NORTHERN PORTIONS OF THE CWA...INCLUDING THE
LAKEFRONT...ON THE COOLER SIDE WITH HIGHS IN THE UPPER 70S TO AROUND
80...WHILE THE SRN LOCATIONS SHOULD WARM INTO THE LOWER 80S.  AS THE
UPPER RIDGE BUILDS ACROSS THE AREA ON FRIDAY AND THE WARM FRONT
LIFTS WELL TO THE NORTH INTO WISCONSIN...EXPECT THAT TEMPS SHOULD
RETURN TO THE MIDDLE TO UPPER 80S WITH DEWPOINTS IN THE LOWER 70S.
THIS COMBINATION OF WARMTH AND MOISTURE SHOULD DRIVE HEAT INDEX
VALUES BACK INTO THE LOWER 90S.  BY FRIDAY NIGHT OR EARLY
SATURDAY...A WEAK COLD FRONT IS EXPECTED TO SWEEP ACROSS THE
AREA...BUT LITTLE SIGNIFICANT AIRMASS CHANGE IS EXPECTED AS THERE
SHOULD BE LITTLE INFLUX OF SIGNIFICANTLY COOLER/DRIER AIR INTO THE
REGION AS SFC HIGH PRESSURE BUILDS ACROSS SRN CANADA AND THE REGION
ONLY EXPERIENCES A BRIEF PERIOD OF LIGHT AND VARIABLE WINDS UNDER
VERY WEAK SFC TROUGHING ASSOCIATED WITH THE COLD FRONT.  BY
SATURDAY...SOUTHERLY FLOW SHOULD RETURN AS A COLD FRONT AND SFC
TROUGH MOVES OUT OVER THE NRN/CNTRL PLAINS AND AND THE BERMUDA HIGH
BUILDS BACK ACROSS THE GULF COAST.

FOR THE LONGER TERM...FROM SUNDAY THROUGH WEDNESDAY...UNSETTLED
WEATHER WILL CONTINUE ACROSS THE REGION FOR SUNDAY AND MONDAY.  THE
LONGER RANGE GUIDANCE IN IN RELATIVELY GOOD AGREEMENT ON A LONG WAVE
TROUGH MOVING ACROSS THE ROCKIES WITH WEAK RIDGING OVER THE ERN
CONUS.  THIS WILL PUT THE UPPER MIDWEST UNDER BROAD SWLY FLOW WITH A
SERIES OF WEAK SRN STREAM SHORT WAVES TRACKING ACROSS THE AREA.  IN
GENERAL...THE UPPER LEVEL PATTERN WILL BE FAIRLY LOW AMPLITUDE...SO
TIMING AND STRENGTH OF INDIVIDUAL WAVES WILL BE QUESTIONABLE...BUT
THE GENERAL TREND SHOULD BE FOR MORE PERIODIC SHOWERS AND
THUNDERSTORMS...THOUGH CONFIDENCE IN TIMING WILL BE LOW.  BY TUESDAY
AND WEDNESDAY...THE LONGER RANGE GUIDANCE IS INDICATING THAT THE
UPPER TROUGH SHOULD BEGIN TO MOVE EAST OF THE AREA...WITH HIGH
PRESSURE SETTLING OVER THE UPPER MISSISSIPPI VALLEY AND WESTERN
GREAT LAKES REGION.  THIS WOULD LEAD TO A PERIOD OF DRIER CONDITIONS
SO HAVE REMOVED POPS FOR TUESDAY AND WEDNESDAY.  UNDER RELATIVELY
LOW AMPLITUDE FLOW ALOFT...THERE SHOULD BE LITTLE DAY TO DAY
TEMPERATURE SWINGS WITH HIGHS GENERALLY IN THE LOWER 80S AND
OVERNIGHT LOWS IN THE 60S.

KREIN

&&

.AVIATION...

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

* EAST WINDS AROUND 10 KT THROUGH THE EARLY EVENING.

JEE

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

HIGH PRESSURE IS SPREADING OVER THE REGION WITH VFR CONDITIONS
ACROSS THE REGION. EAST WINDS WILL CONTINUE THROUGH THE PERIOD. AS
WARMING CONTINUES...EXPECTING WINDS TO PICK UP TO ARND 10 KT BY
MID AFTN. WINDS THEN DIMINISH THIS EVENING...AND THEN WILL BE ARND
8 KT TOMORROW.

THE HIGH SHIFTS EAST TONIGHT INTO TOMORROW WITH LOW PRESSURE
APPROACHING FROM THE SOUTHWEST. GUIDANCE HAS THE WARM FRONT
REMAINING SOUTH OF THE TERMINALS THROUGH TOMORROW AFTERNOON.
HOWEVER...SOME MODELS SHOW STORMS REACHING RFD BY LATE
MORNING/EARLY AFTN SO HAVE A PROB30 FOR THOSE. NOT OVERLY
CONFIDENT IN THE TSRA CHANCES AT RFD. THE OTHER TERMINALS WILL SEE
PRECIP PUSH IN AFTER 00Z FRIDAY.

JEE

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

* HIGH CONFIDENCE IN ALL OTHER FORECAST PARAMETERS.

JEE

//OUTLOOK FOR ORD/MDW FOR 00Z FRIDAY-12Z WEDNESDAY...UPDATED 12Z...

* THURSDAY NIGHT AND FRIDAY...CHANCE OF TSRA.
* SATURDAY...TSRA LIKELY.
* SUNDAY THROUGH TUESDAY...CHANCE OF TSRA.

&&

.MARINE...
205 PM CDT

HIGH PRESSURE WILL CONTINUE TO BE OVERHEAD OF LAKE
MICHIGAN...LIKELY LINGERING THROUGH DAYBREAK THURSDAY BEFORE
MOVING EAST TOWARDS LAKE ERIE TOMORROW NIGHT. AS THE HIGH DRIFTS
EAST...WINDS WILL SLOWLY TURN SOUTHEASTERLY THEN SOUTHERLY.
GUIDANCE IS EXPECTING A LOW PRESSURE SYSTEM TO LIFT NORTHEAST
ACROSS THE CENTRAL PLAINS INTO THE UPPER MIDWEST THURSDAY
AFTERNOON. THIS WILL RESULT IN A TIGHTENING GRADIENT FROM SOUTH TO
NORTH ACROSS THE LAKE. AT THIS TIME IT IS POSSIBLE THAT WINDS
COULD HOVER IN THE 15 TO 25 KT RANGE THURSDAY NIGHT INTO FRIDAY.
THEN AS THE LOW PRESSURE LIFTS NORTHEAST OF LAKE MICHIGAN AND A
RIDGE OF HIGH PRESSURE SLIDES SOUTH FROM CENTRAL CANADA INTO THE
UPPER MIDWEST FRIDAY EVENING...A FRONTAL BOUNDARY WILL SAG SOUTH
AND TURN WINDS NORTHERLY FOR THE NORTHERN HALF OF THE LAKE.
MEANWHILE IT DOES APPEAR THE BOUNDARY GETS HUNG UP ACROSS THE
CENTRAL PORTION OF THE LAKE FRIDAY NIGHT/EARLY SATURDAY...WHICH
WILL KEEP SOUTHERLY WINDS FOR THE SOUTHERN HALF OF THE LAKE. THEN
YET ANOTHER AREA OF LOW PRESSURE IS FORECAST TO DEVELOP ACROSS THE
NORTHERN PLAINS SATURDAY AFTERNOON AND DEEPEN AS IT MOVES
NORTHEAST INTO WESTERN ONTARIO. THIS WILL LIKELY CREATE A TIGHT
GRADIENT ACROSS THE LAKE SUNDAY WITH YET ANOTHER PERIOD OF WINDS
NEARING 20-25KT.

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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO







000
FXUS63 KLOT 272031
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
331 PM CDT WED AUG 27 2014

.DISCUSSION...
330 PM CDT

SHORT TERM...WEDNESDAY AFTERNOON THROUGH SATURDAY...

FOR THE REMAINDER OF THE AFTERNOON SHOULD REMAIN QUIET AS THE OLD
STATIONARY BOUNDARY REMAINS WELL TO THE SOUTH ACROSS SRN IL AND THE
OHIO VALLEY.  HAVE MAINTAINED SLIGHT CHANCE POPS ACROSS THE VERY FAR
SOUTH OF THE CWA...A LITTLE NORTH OF THE BOUNDARY IN DEFERENCE TO
THE PROXIMITY TO THE BOUNDARY TO THE SOUTH AND A WARM AND VERY MOIST
AIRMASS...WITH DEWPOINTS STILL IN THE LOW 70S...ACROSS THE AREA.
THROUGH THE LATE EVENING AND INTO THE OVERNIGHT HOURS...ANTICIPATE
INCREASING POPS SPREADING FROM SOUTHWEST TO NORTHEAST AS LOW
PRESSURE OVER THE CENTRAL PLAINS LIFTS NEWD...DRAGGING THE OLD
STATIONARY BOUNDARY BACK NORTH AS A WARM FRONT.  WITH UPPER RIDGING
BUILDING ALOFT WITH THE RIDGE AXIS EXTENDING JUST EAST OF THE
MISSISSIPPI RIVER BY EARLY THURSDAY MORNING...ANTICIPATE THAT SWLY
FLOW ALOFT SHOULD HELP KEEP THE HIGHEST PCPN CHANCES OVER LOCATIONS
WEST OF A LINE FROM ROCKFORD TO WATSEKA.

THROUGH THURSDAY AND THURSDAY NIGHT...THE UPPER RIDGE WILL SLOWLY
BUILD  EAST AS SHORTWAVE ENERGY OVERTOPS THE RIDGE.  THE SHORT RANGE
MODELS ARE RELATIVELY CONSISTENT ON ADVERTISING THIS SCENARIO...SO
ANTICIPATE INCREASING POPS OVER THE WRN PORTIONS OF THE CWA THROUGH
THE EVENING AND THEN THE NORTHERN PORTIONS OF THE CWA THROUGH THE
NIGHT...BUT WITH THE TRACK OF THE MAIN UPPER SHORTWAVE TO THE WEST
AND NORTH OF THE CWA...THE STRONGER UPPER FORCING SHOULD BE OVER
IOWA AND INTO WISCONSIN...SO HAVE LIMITED POPS OVER THE CWA TO
CHANCE LEVELS.  THE LOCAL AREA SHOULD BEGIN TO SEE POPS INCREASING
THROUGH THE DAY FRIDAY AND ESPECIALLY LATER FRIDAY NIGHT AS A STRONG
SHORTWAVE LIFTING OUT OF THE GREAT BASIN TONIGHT SLOWLY TRACKS EAST
ACROSS THE CENTRAL PLAINS AND REACHES THE MIDDLE AND UPPER
MISSISSIPPI VALLEY FRIDAY NIGHT.  WILL INCREASE POPS THROUGH FRIDAY
EVENING WITH LIKELY POPS SPREADING INTO THE WRN PORTIONS OF THE CWA
AFTER MIDNIGHT FRIDAY NIGHT AND EAST ACROSS THE REMAINDER OF THE
AREA THROUGH SATURDAY AND INTO SATURDAY EVENING.

FORM TEMPERATURES...WITH SFC HIGH PRESSURE SLOWLY SLIDING ACROSS THE
GREAT LAKES REGION...THE WARMEST AND MOST HUMID CONDITIONS WILL BE
CONFINED TO THE FAR SOUTHERN PORTIONS OF THE CWA...THOUGH EVEN
LOCATIONS NORTH OF THE I-80 CORRIDOR HAVE SEEN TEMPS CLIMB INTO THE
LOWER 80S EVEN WITH PERSISTENT NELY FLOW AT THE LOWER LEVELS.  THE
HIGH WILL STILL HAVE A MAJOR INFLUENCE ON TEMPS THROUGH
THURSDAY...KEEPING THE NORTHERN PORTIONS OF THE CWA...INCLUDING THE
LAKEFRONT...ON THE COOLER SIDE WITH HIGHS IN THE UPPER 70S TO AROUND
80...WHILE THE SRN LOCATIONS SHOULD WARM INTO THE LOWER 80S.  AS THE
UPPER RIDGE BUILDS ACROSS THE AREA ON FRIDAY AND THE WARM FRONT
LIFTS WELL TO THE NORTH INTO WISCONSIN...EXPECT THAT TEMPS SHOULD
RETURN TO THE MIDDLE TO UPPER 80S WITH DEWPOINTS IN THE LOWER 70S.
THIS COMBINATION OF WARMTH AND MOISTURE SHOULD DRIVE HEAT INDEX
VALUES BACK INTO THE LOWER 90S.  BY FRIDAY NIGHT OR EARLY
SATURDAY...A WEAK COLD FRONT IS EXPECTED TO SWEEP ACROSS THE
AREA...BUT LITTLE SIGNIFICANT AIRMASS CHANGE IS EXPECTED AS THERE
SHOULD BE LITTLE INFLUX OF SIGNIFICANTLY COOLER/DRIER AIR INTO THE
REGION AS SFC HIGH PRESSURE BUILDS ACROSS SRN CANADA AND THE REGION
ONLY EXPERIENCES A BRIEF PERIOD OF LIGHT AND VARIABLE WINDS UNDER
VERY WEAK SFC TROUGHING ASSOCIATED WITH THE COLD FRONT.  BY
SATURDAY...SOUTHERLY FLOW SHOULD RETURN AS A COLD FRONT AND SFC
TROUGH MOVES OUT OVER THE NRN/CNTRL PLAINS AND AND THE BERMUDA HIGH
BUILDS BACK ACROSS THE GULF COAST.

FOR THE LONGER TERM...FROM SUNDAY THROUGH WEDNESDAY...UNSETTLED
WEATHER WILL CONTINUE ACROSS THE REGION FOR SUNDAY AND MONDAY.  THE
LONGER RANGE GUIDANCE IN IN RELATIVELY GOOD AGREEMENT ON A LONG WAVE
TROUGH MOVING ACROSS THE ROCKIES WITH WEAK RIDGING OVER THE ERN
CONUS.  THIS WILL PUT THE UPPER MIDWEST UNDER BROAD SWLY FLOW WITH A
SERIES OF WEAK SRN STREAM SHORT WAVES TRACKING ACROSS THE AREA.  IN
GENERAL...THE UPPER LEVEL PATTERN WILL BE FAIRLY LOW AMPLITUDE...SO
TIMING AND STRENGTH OF INDIVIDUAL WAVES WILL BE QUESTIONABLE...BUT
THE GENERAL TREND SHOULD BE FOR MORE PERIODIC SHOWERS AND
THUNDERSTORMS...THOUGH CONFIDENCE IN TIMING WILL BE LOW.  BY TUESDAY
AND WEDNESDAY...THE LONGER RANGE GUIDANCE IS INDICATING THAT THE
UPPER TROUGH SHOULD BEGIN TO MOVE EAST OF THE AREA...WITH HIGH
PRESSURE SETTLING OVER THE UPPER MISSISSIPPI VALLEY AND WESTERN
GREAT LAKES REGION.  THIS WOULD LEAD TO A PERIOD OF DRIER CONDITIONS
SO HAVE REMOVED POPS FOR TUESDAY AND WEDNESDAY.  UNDER RELATIVELY
LOW AMPLITUDE FLOW ALOFT...THERE SHOULD BE LITTLE DAY TO DAY
TEMPERATURE SWINGS WITH HIGHS GENERALLY IN THE LOWER 80S AND
OVERNIGHT LOWS IN THE 60S.

KREIN

&&

.AVIATION...

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

* EAST WINDS AROUND 10 KT THROUGH THE EARLY EVENING.

JEE

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

HIGH PRESSURE IS SPREADING OVER THE REGION WITH VFR CONDITIONS
ACROSS THE REGION. EAST WINDS WILL CONTINUE THROUGH THE PERIOD. AS
WARMING CONTINUES...EXPECTING WINDS TO PICK UP TO ARND 10 KT BY
MID AFTN. WINDS THEN DIMINISH THIS EVENING...AND THEN WILL BE ARND
8 KT TOMORROW.

THE HIGH SHIFTS EAST TONIGHT INTO TOMORROW WITH LOW PRESSURE
APPROACHING FROM THE SOUTHWEST. GUIDANCE HAS THE WARM FRONT
REMAINING SOUTH OF THE TERMINALS THROUGH TOMORROW AFTERNOON.
HOWEVER...SOME MODELS SHOW STORMS REACHING RFD BY LATE
MORNING/EARLY AFTN SO HAVE A PROB30 FOR THOSE. NOT OVERLY
CONFIDENT IN THE TSRA CHANCES AT RFD. THE OTHER TERMINALS WILL SEE
PRECIP PUSH IN AFTER 00Z FRIDAY.

JEE

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

* HIGH CONFIDENCE IN ALL OTHER FORECAST PARAMETERS.

JEE

//OUTLOOK FOR ORD/MDW FOR 00Z FRIDAY-12Z WEDNESDAY...UPDATED 12Z...

* THURSDAY NIGHT AND FRIDAY...CHANCE OF TSRA.
* SATURDAY...TSRA LIKELY.
* SUNDAY THROUGH TUESDAY...CHANCE OF TSRA.

&&

.MARINE...
205 PM CDT

HIGH PRESSURE WILL CONTINUE TO BE OVERHEAD OF LAKE
MICHIGAN...LIKELY LINGERING THROUGH DAYBREAK THURSDAY BEFORE
MOVING EAST TOWARDS LAKE ERIE TOMORROW NIGHT. AS THE HIGH DRIFTS
EAST...WINDS WILL SLOWLY TURN SOUTHEASTERLY THEN SOUTHERLY.
GUIDANCE IS EXPECTING A LOW PRESSURE SYSTEM TO LIFT NORTHEAST
ACROSS THE CENTRAL PLAINS INTO THE UPPER MIDWEST THURSDAY
AFTERNOON. THIS WILL RESULT IN A TIGHTENING GRADIENT FROM SOUTH TO
NORTH ACROSS THE LAKE. AT THIS TIME IT IS POSSIBLE THAT WINDS
COULD HOVER IN THE 15 TO 25 KT RANGE THURSDAY NIGHT INTO FRIDAY.
THEN AS THE LOW PRESSURE LIFTS NORTHEAST OF LAKE MICHIGAN AND A
RIDGE OF HIGH PRESSURE SLIDES SOUTH FROM CENTRAL CANADA INTO THE
UPPER MIDWEST FRIDAY EVENING...A FRONTAL BOUNDARY WILL SAG SOUTH
AND TURN WINDS NORTHERLY FOR THE NORTHERN HALF OF THE LAKE.
MEANWHILE IT DOES APPEAR THE BOUNDARY GETS HUNG UP ACROSS THE
CENTRAL PORTION OF THE LAKE FRIDAY NIGHT/EARLY SATURDAY...WHICH
WILL KEEP SOUTHERLY WINDS FOR THE SOUTHERN HALF OF THE LAKE. THEN
YET ANOTHER AREA OF LOW PRESSURE IS FORECAST TO DEVELOP ACROSS THE
NORTHERN PLAINS SATURDAY AFTERNOON AND DEEPEN AS IT MOVES
NORTHEAST INTO WESTERN ONTARIO. THIS WILL LIKELY CREATE A TIGHT
GRADIENT ACROSS THE LAKE SUNDAY WITH YET ANOTHER PERIOD OF WINDS
NEARING 20-25KT.

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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 271952
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
252 PM CDT WED AUG 27 2014

.DISCUSSION...
321 AM CDT

CONVECTIVE TRENDS REMAIN THE MAIN FOCUS OF THE FORECAST THROUGH THE
WEEKEND. WATER VAPOR IMAGERY SHOWS A SPLIT UPPER FLOW WITH A
NORTHERN STREAM OF PROGRESSIVE FLOW RUNNING ACROSS SOUTHERN CANADA
INTO THE UPPER GREAT LAKES. A LOW AMPLITUDE TROUGH AXIS IS
TRAVERSING THE FLOW AND MOVING INTO WISCONSIN AT THE CURRENT TIME.
THE SOUTHERN STREAM FEATURES A CUTOFF UPPER LOW WHICH IS OVER UTAH
AND SLOWLY MOVING EASTWARD. UPPER RIDGING IS STARTING TO BUILD JUST
DOWNSTREAM OF THE UPPER LOW WITH SEVERAL EMBEDDED WAVES MOVING
NORTHEASTWARD AHEAD OF THE LOW. AT THE SURFACE...THE FRONTAL
BOUNDARY WHICH HAS BEEN DISCUSSED OVER THE PAST SEVERAL DAYS IS NOW
SOUTH OF THE CWA AND RUNS EAST-NORTHEAST ACROSS THE LOWER GREAT
LAKES AND ST. LAWRENCE RIVER VALLEY. HIGH PRESSURE HAS SPREAD ACROSS
THE UPPER MIDWEST WITH ITS SOUTHERN FLANK INTO THE FORECAST AREA.

TODAY...THE NORTHERN STREAM UPPER TROUGH AXIS WILL
CROSS THE LOCAL AREA THIS MORNING. THE GREATEST ASCENT ASSOCIATED
WITH IT IS TO THE NORTH AND IS GENERATING BANDS OF SHOWERS ACROSS
WISCONSIN...WITH ADDITIONAL RETURNS WORKING ACROSS CENTRAL IOWA INTO
NORTHERN ILLINOIS. THIS ACTIVITY SEEMS TO BE IN BETTER CONJUNCTION
WITH THE RIGHT ENTRANCE REGION OF AN UPPER JET MAX TO THE NORTH IN
ADDITION TO A BROAD AREA OF HEIGHT FALLS INDUCED BY THE UPPER
TROUGH. A CLUSTER OF THUNDERSTORMS HAS ALSO DEVELOPED ACROSS SW IOWA
IN RESPONSE TO BETTER FOCUSED MID LEVEL WARM ADVECTION. MOST OF THIS
UPPER SUPPORT WILL BE PASSING BY THIS MORNING RESULTING IN A
DECREASE IN ACTIVITY. WITH THE SURFACE FRONT TO THE SOUTH THE
INSTABILITY GRADIENT IS ALSO TO THE SOUTH WITH A WESTERLY LOW LEVEL
JET ABOVE IT SUGGESTING THAT THE CONVECTION ACROSS SOUTHWEST IOWA
WOULD NOT BE A FACTOR TOO FAR NORTH OF ITS CURRENT LATITUDE. ONCE
THE CURRENT SHOWER ACTIVITY EXITS IT APPEARS THAT MOST AREAS WILL
REMAIN DRY FOR THE REST OF THE DAY BUT FAR SOUTHERN AREAS DO HAVE A
CHANCE TO SEE SOME SHOWERS AND STORMS THIS MORNING GIVEN THE
WESTERLY LOW LEVEL JET ALONG THE BOUNDARY AND MID LEVEL MOISTURE
GRADIENT BUT WARM/MOIST ADVECTION IS PRETTY WEAK. HIGH TEMPERATURES
WILL RANGE FROM THE UPPER 70S NORTH TO MID 80S SOUTH WITH A
NORTHEAST WIND HOLDING LAKEFRONT AREAS TO THE LOWER TO MID 70S.

TONIGHT AND THURSDAY...AS THE UPPER TROUGH SHIFTS EAST THE RIDGING
DOWNSTREAM OF THE CUTOFF LOW TO THE WEST WILL PIVOT ACROSS THE
CENTRAL PLAINS. SURFACE LOW PRESSURE WILL BE DEVELOPING ACROSS
EASTERN COLORADO AND WESTERN KANSAS WHICH WILL DRIVE THE FRONTAL
BOUNDARY NORTHEASTWARD ACROSS THE CENTRAL PLAINS WITH THE NEARBY
PORTION OF THE FRONT REMAINING SOUTH OF THE AREA INTO THURSDAY
EVENING. WITH WARM ADVECTION INCREASING ALOFT WITH THE RIDGE
BUILDING BACK IN TONIGHT SHOWERS AND THUNDERSTORMS ARE EXPECTED TO
BE MOVING EAST-NORTHEAST ACROSS IOWA/MISSOURI. SOME OF THIS ACTIVITY
MAY REACH THE WESTERN CWA VERY LATE TONIGHT AND MAY END UP SEEING A
SIMILAR SITUATION TO RECENT DAYS WITH REMNANT CONVECTION FESTERING
AND/OR SPAWNING NEW DEVELOPMENT ACROSS THE CWA THURSDAY
MORNING/AFTERNOON. THE MAIN SURFACE LOW AND UPPER WAVE IS EXPECTED
TO BE MOVING ACROSS IOWA/MINNESOTA/WISCONSIN SO THE BULK OF THE
CONVECTION MAY STAY TO THE NORTHWEST OF THE LOCAL AREA. WILL FOCUS
HIGHEST POPS ACROSS THE WESTERN CWA AND SLOW DOWN THE ARRIVAL UNTIL
LATER TONIGHT. THURSDAY LOOKS TO BE SLIGHTLY WARMER...ESPECIALLY
WITH CONVECTION LOOKING TO BE MORE SCATTERED IN COVERAGE.

FRIDAY THROUGH EARLY NEXT WEEK...THE UPPER TROUGH WILL START TO MAKE
QUICKER EAST-NORTHEAST PROGRESS THANKS TO ANOTHER LARGE SCALE UPPER
TROUGH PUSHING INTO THE WESTERN U.S./CANADA. THIS WILL TAKE ANOTHER
SURFACE LOW NORTHEASTWARD WITH IT WHICH WILL LIKELY TRACK NORTHWEST
OF THE AREA SATURDAY. FRIDAY SHOULD SEE A NOTICEABLE WARM UP WITH
ANOTHER LULL IN WIDESPREAD CONVECTION WITH IT FOCUSING TO THE NORTH
AND WEST. WILL HAVE HIGHER POPS SATURDAY WITH THE LOW PASSING BUT AM
SEEING MIXED SIGNALS IN THE TRACK WHICH WILL AFFECT PRECIP COVERAGE.
CHANCES WILL DIMINISH SATURDAY NIGHT WITH QUESTION MARKS SURROUNDING
SUNDAY INTO EARLY NEXT WEEK WITH THE GFS SHOWING A MORE ACTIVE FLOW
WHILE THE ECMWF IS QUIETER THOUGH IT DOES BRING A FRONT THROUGH THE
AREA TUESDAY. DO NOT SEE MUCH OF A COOL DOWN OVERALL AND A DRY
FORECAST SUNDAY/MONDAY WOULD COINCIDE WITH A WARMING TREND IF IT
COMES TO PASS. WILL CONTINUE WITH MID TO UPPER 80S FRIDAY WITH
READINGS SEVERAL DEGREES COOLER SATURDAY AND SUNDAY.

MDB

&&

.AVIATION...

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

* EAST WINDS AROUND 10 KT THROUGH THE EARLY EVENING.

JEE

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

HIGH PRESSURE IS SPREADING OVER THE REGION WITH VFR CONDITIONS
ACROSS THE REGION. EAST WINDS WILL CONTINUE THROUGH THE PERIOD. AS
WARMING CONTINUES...EXPECTING WINDS TO PICK UP TO ARND 10 KT BY
MID AFTN. WINDS THEN DIMINISH THIS EVENING...AND THEN WILL BE ARND
8 KT TOMORROW.

THE HIGH SHIFTS EAST TONIGHT INTO TOMORROW WITH LOW PRESSURE
APPROACHING FROM THE SOUTHWEST. GUIDANCE HAS THE WARM FRONT
REMAINING SOUTH OF THE TERMINALS THROUGH TOMORROW AFTERNOON.
HOWEVER...SOME MODELS SHOW STORMS REACHING RFD BY LATE
MORNING/EARLY AFTN SO HAVE A PROB30 FOR THOSE. NOT OVERLY
CONFIDENT IN THE TSRA CHANCES AT RFD. THE OTHER TERMINALS WILL SEE
PRECIP PUSH IN AFTER 00Z FRIDAY.

JEE

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

* HIGH CONFIDENCE IN ALL OTHER FORECAST PARAMETERS.

JEE

//OUTLOOK FOR ORD/MDW FOR 00Z FRIDAY-12Z WEDNESDAY...UPDATED 12Z...

* THURSDAY NIGHT AND FRIDAY...CHANCE OF TSRA.
* SATURDAY...TSRA LIKELY.
* SUNDAY THROUGH TUESDAY...CHANCE OF TSRA.

&&

.MARINE...
205 PM CDT

HIGH PRESSURE WILL CONTINUE TO BE OVERHEAD OF LAKE
MICHIGAN...LIKELY LINGERING THROUGH DAYBREAK THURSDAY BEFORE
MOVING EAST TOWARDS LAKE ERIE TOMORROW NIGHT. AS THE HIGH DRIFTS
EAST...WINDS WILL SLOWLY TURN SOUTHEASTERLY THEN SOUTHERLY.
GUIDANCE IS EXPECTING A LOW PRESSURE SYSTEM TO LIFT NORTHEAST
ACROSS THE CENTRAL PLAINS INTO THE UPPER MIDWEST THURSDAY
AFTERNOON. THIS WILL RESULT IN A TIGHTENING GRADIENT FROM SOUTH TO
NORTH ACROSS THE LAKE. AT THIS TIME IT IS POSSIBLE THAT WINDS
COULD HOVER IN THE 15 TO 25 KT RANGE THURSDAY NIGHT INTO FRIDAY.
THEN AS THE LOW PRESSURE LIFTS NORTHEAST OF LAKE MICHIGAN AND A
RIDGE OF HIGH PRESSURE SLIDES SOUTH FROM CENTRAL CANADA INTO THE
UPPER MIDWEST FRIDAY EVENING...A FRONTAL BOUNDARY WILL SAG SOUTH
AND TURN WINDS NORTHERLY FOR THE NORTHERN HALF OF THE LAKE.
MEANWHILE IT DOES APPEAR THE BOUNDARY GETS HUNG UP ACROSS THE
CENTRAL PORTION OF THE LAKE FRIDAY NIGHT/EARLY SATURDAY...WHICH
WILL KEEP SOUTHERLY WINDS FOR THE SOUTHERN HALF OF THE LAKE. THEN
YET ANOTHER AREA OF LOW PRESSURE IS FORECAST TO DEVELOP ACROSS THE
NORTHERN PLAINS SATURDAY AFTERNOON AND DEEPEN AS IT MOVES
NORTHEAST INTO WESTERN ONTARIO. THIS WILL LIKELY CREATE A TIGHT
GRADIENT ACROSS THE LAKE SUNDAY WITH YET ANOTHER PERIOD OF WINDS
NEARING 20-25KT.

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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO







000
FXUS63 KLOT 271952
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
252 PM CDT WED AUG 27 2014

.DISCUSSION...
321 AM CDT

CONVECTIVE TRENDS REMAIN THE MAIN FOCUS OF THE FORECAST THROUGH THE
WEEKEND. WATER VAPOR IMAGERY SHOWS A SPLIT UPPER FLOW WITH A
NORTHERN STREAM OF PROGRESSIVE FLOW RUNNING ACROSS SOUTHERN CANADA
INTO THE UPPER GREAT LAKES. A LOW AMPLITUDE TROUGH AXIS IS
TRAVERSING THE FLOW AND MOVING INTO WISCONSIN AT THE CURRENT TIME.
THE SOUTHERN STREAM FEATURES A CUTOFF UPPER LOW WHICH IS OVER UTAH
AND SLOWLY MOVING EASTWARD. UPPER RIDGING IS STARTING TO BUILD JUST
DOWNSTREAM OF THE UPPER LOW WITH SEVERAL EMBEDDED WAVES MOVING
NORTHEASTWARD AHEAD OF THE LOW. AT THE SURFACE...THE FRONTAL
BOUNDARY WHICH HAS BEEN DISCUSSED OVER THE PAST SEVERAL DAYS IS NOW
SOUTH OF THE CWA AND RUNS EAST-NORTHEAST ACROSS THE LOWER GREAT
LAKES AND ST. LAWRENCE RIVER VALLEY. HIGH PRESSURE HAS SPREAD ACROSS
THE UPPER MIDWEST WITH ITS SOUTHERN FLANK INTO THE FORECAST AREA.

TODAY...THE NORTHERN STREAM UPPER TROUGH AXIS WILL
CROSS THE LOCAL AREA THIS MORNING. THE GREATEST ASCENT ASSOCIATED
WITH IT IS TO THE NORTH AND IS GENERATING BANDS OF SHOWERS ACROSS
WISCONSIN...WITH ADDITIONAL RETURNS WORKING ACROSS CENTRAL IOWA INTO
NORTHERN ILLINOIS. THIS ACTIVITY SEEMS TO BE IN BETTER CONJUNCTION
WITH THE RIGHT ENTRANCE REGION OF AN UPPER JET MAX TO THE NORTH IN
ADDITION TO A BROAD AREA OF HEIGHT FALLS INDUCED BY THE UPPER
TROUGH. A CLUSTER OF THUNDERSTORMS HAS ALSO DEVELOPED ACROSS SW IOWA
IN RESPONSE TO BETTER FOCUSED MID LEVEL WARM ADVECTION. MOST OF THIS
UPPER SUPPORT WILL BE PASSING BY THIS MORNING RESULTING IN A
DECREASE IN ACTIVITY. WITH THE SURFACE FRONT TO THE SOUTH THE
INSTABILITY GRADIENT IS ALSO TO THE SOUTH WITH A WESTERLY LOW LEVEL
JET ABOVE IT SUGGESTING THAT THE CONVECTION ACROSS SOUTHWEST IOWA
WOULD NOT BE A FACTOR TOO FAR NORTH OF ITS CURRENT LATITUDE. ONCE
THE CURRENT SHOWER ACTIVITY EXITS IT APPEARS THAT MOST AREAS WILL
REMAIN DRY FOR THE REST OF THE DAY BUT FAR SOUTHERN AREAS DO HAVE A
CHANCE TO SEE SOME SHOWERS AND STORMS THIS MORNING GIVEN THE
WESTERLY LOW LEVEL JET ALONG THE BOUNDARY AND MID LEVEL MOISTURE
GRADIENT BUT WARM/MOIST ADVECTION IS PRETTY WEAK. HIGH TEMPERATURES
WILL RANGE FROM THE UPPER 70S NORTH TO MID 80S SOUTH WITH A
NORTHEAST WIND HOLDING LAKEFRONT AREAS TO THE LOWER TO MID 70S.

TONIGHT AND THURSDAY...AS THE UPPER TROUGH SHIFTS EAST THE RIDGING
DOWNSTREAM OF THE CUTOFF LOW TO THE WEST WILL PIVOT ACROSS THE
CENTRAL PLAINS. SURFACE LOW PRESSURE WILL BE DEVELOPING ACROSS
EASTERN COLORADO AND WESTERN KANSAS WHICH WILL DRIVE THE FRONTAL
BOUNDARY NORTHEASTWARD ACROSS THE CENTRAL PLAINS WITH THE NEARBY
PORTION OF THE FRONT REMAINING SOUTH OF THE AREA INTO THURSDAY
EVENING. WITH WARM ADVECTION INCREASING ALOFT WITH THE RIDGE
BUILDING BACK IN TONIGHT SHOWERS AND THUNDERSTORMS ARE EXPECTED TO
BE MOVING EAST-NORTHEAST ACROSS IOWA/MISSOURI. SOME OF THIS ACTIVITY
MAY REACH THE WESTERN CWA VERY LATE TONIGHT AND MAY END UP SEEING A
SIMILAR SITUATION TO RECENT DAYS WITH REMNANT CONVECTION FESTERING
AND/OR SPAWNING NEW DEVELOPMENT ACROSS THE CWA THURSDAY
MORNING/AFTERNOON. THE MAIN SURFACE LOW AND UPPER WAVE IS EXPECTED
TO BE MOVING ACROSS IOWA/MINNESOTA/WISCONSIN SO THE BULK OF THE
CONVECTION MAY STAY TO THE NORTHWEST OF THE LOCAL AREA. WILL FOCUS
HIGHEST POPS ACROSS THE WESTERN CWA AND SLOW DOWN THE ARRIVAL UNTIL
LATER TONIGHT. THURSDAY LOOKS TO BE SLIGHTLY WARMER...ESPECIALLY
WITH CONVECTION LOOKING TO BE MORE SCATTERED IN COVERAGE.

FRIDAY THROUGH EARLY NEXT WEEK...THE UPPER TROUGH WILL START TO MAKE
QUICKER EAST-NORTHEAST PROGRESS THANKS TO ANOTHER LARGE SCALE UPPER
TROUGH PUSHING INTO THE WESTERN U.S./CANADA. THIS WILL TAKE ANOTHER
SURFACE LOW NORTHEASTWARD WITH IT WHICH WILL LIKELY TRACK NORTHWEST
OF THE AREA SATURDAY. FRIDAY SHOULD SEE A NOTICEABLE WARM UP WITH
ANOTHER LULL IN WIDESPREAD CONVECTION WITH IT FOCUSING TO THE NORTH
AND WEST. WILL HAVE HIGHER POPS SATURDAY WITH THE LOW PASSING BUT AM
SEEING MIXED SIGNALS IN THE TRACK WHICH WILL AFFECT PRECIP COVERAGE.
CHANCES WILL DIMINISH SATURDAY NIGHT WITH QUESTION MARKS SURROUNDING
SUNDAY INTO EARLY NEXT WEEK WITH THE GFS SHOWING A MORE ACTIVE FLOW
WHILE THE ECMWF IS QUIETER THOUGH IT DOES BRING A FRONT THROUGH THE
AREA TUESDAY. DO NOT SEE MUCH OF A COOL DOWN OVERALL AND A DRY
FORECAST SUNDAY/MONDAY WOULD COINCIDE WITH A WARMING TREND IF IT
COMES TO PASS. WILL CONTINUE WITH MID TO UPPER 80S FRIDAY WITH
READINGS SEVERAL DEGREES COOLER SATURDAY AND SUNDAY.

MDB

&&

.AVIATION...

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

* EAST WINDS AROUND 10 KT THROUGH THE EARLY EVENING.

JEE

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

HIGH PRESSURE IS SPREADING OVER THE REGION WITH VFR CONDITIONS
ACROSS THE REGION. EAST WINDS WILL CONTINUE THROUGH THE PERIOD. AS
WARMING CONTINUES...EXPECTING WINDS TO PICK UP TO ARND 10 KT BY
MID AFTN. WINDS THEN DIMINISH THIS EVENING...AND THEN WILL BE ARND
8 KT TOMORROW.

THE HIGH SHIFTS EAST TONIGHT INTO TOMORROW WITH LOW PRESSURE
APPROACHING FROM THE SOUTHWEST. GUIDANCE HAS THE WARM FRONT
REMAINING SOUTH OF THE TERMINALS THROUGH TOMORROW AFTERNOON.
HOWEVER...SOME MODELS SHOW STORMS REACHING RFD BY LATE
MORNING/EARLY AFTN SO HAVE A PROB30 FOR THOSE. NOT OVERLY
CONFIDENT IN THE TSRA CHANCES AT RFD. THE OTHER TERMINALS WILL SEE
PRECIP PUSH IN AFTER 00Z FRIDAY.

JEE

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

* HIGH CONFIDENCE IN ALL OTHER FORECAST PARAMETERS.

JEE

//OUTLOOK FOR ORD/MDW FOR 00Z FRIDAY-12Z WEDNESDAY...UPDATED 12Z...

* THURSDAY NIGHT AND FRIDAY...CHANCE OF TSRA.
* SATURDAY...TSRA LIKELY.
* SUNDAY THROUGH TUESDAY...CHANCE OF TSRA.

&&

.MARINE...
205 PM CDT

HIGH PRESSURE WILL CONTINUE TO BE OVERHEAD OF LAKE
MICHIGAN...LIKELY LINGERING THROUGH DAYBREAK THURSDAY BEFORE
MOVING EAST TOWARDS LAKE ERIE TOMORROW NIGHT. AS THE HIGH DRIFTS
EAST...WINDS WILL SLOWLY TURN SOUTHEASTERLY THEN SOUTHERLY.
GUIDANCE IS EXPECTING A LOW PRESSURE SYSTEM TO LIFT NORTHEAST
ACROSS THE CENTRAL PLAINS INTO THE UPPER MIDWEST THURSDAY
AFTERNOON. THIS WILL RESULT IN A TIGHTENING GRADIENT FROM SOUTH TO
NORTH ACROSS THE LAKE. AT THIS TIME IT IS POSSIBLE THAT WINDS
COULD HOVER IN THE 15 TO 25 KT RANGE THURSDAY NIGHT INTO FRIDAY.
THEN AS THE LOW PRESSURE LIFTS NORTHEAST OF LAKE MICHIGAN AND A
RIDGE OF HIGH PRESSURE SLIDES SOUTH FROM CENTRAL CANADA INTO THE
UPPER MIDWEST FRIDAY EVENING...A FRONTAL BOUNDARY WILL SAG SOUTH
AND TURN WINDS NORTHERLY FOR THE NORTHERN HALF OF THE LAKE.
MEANWHILE IT DOES APPEAR THE BOUNDARY GETS HUNG UP ACROSS THE
CENTRAL PORTION OF THE LAKE FRIDAY NIGHT/EARLY SATURDAY...WHICH
WILL KEEP SOUTHERLY WINDS FOR THE SOUTHERN HALF OF THE LAKE. THEN
YET ANOTHER AREA OF LOW PRESSURE IS FORECAST TO DEVELOP ACROSS THE
NORTHERN PLAINS SATURDAY AFTERNOON AND DEEPEN AS IT MOVES
NORTHEAST INTO WESTERN ONTARIO. THIS WILL LIKELY CREATE A TIGHT
GRADIENT ACROSS THE LAKE SUNDAY WITH YET ANOTHER PERIOD OF WINDS
NEARING 20-25KT.

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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 271912
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
212 PM CDT WED AUG 27 2014

.DISCUSSION...
321 AM CDT

CONVECTIVE TRENDS REMAIN THE MAIN FOCUS OF THE FORECAST THROUGH THE
WEEKEND. WATER VAPOR IMAGERY SHOWS A SPLIT UPPER FLOW WITH A
NORTHERN STREAM OF PROGRESSIVE FLOW RUNNING ACROSS SOUTHERN CANADA
INTO THE UPPER GREAT LAKES. A LOW AMPLITUDE TROUGH AXIS IS
TRAVERSING THE FLOW AND MOVING INTO WISCONSIN AT THE CURRENT TIME.
THE SOUTHERN STREAM FEATURES A CUTOFF UPPER LOW WHICH IS OVER UTAH
AND SLOWLY MOVING EASTWARD. UPPER RIDGING IS STARTING TO BUILD JUST
DOWNSTREAM OF THE UPPER LOW WITH SEVERAL EMBEDDED WAVES MOVING
NORTHEASTWARD AHEAD OF THE LOW. AT THE SURFACE...THE FRONTAL
BOUNDARY WHICH HAS BEEN DISCUSSED OVER THE PAST SEVERAL DAYS IS NOW
SOUTH OF THE CWA AND RUNS EAST-NORTHEAST ACROSS THE LOWER GREAT
LAKES AND ST. LAWRENCE RIVER VALLEY. HIGH PRESSURE HAS SPREAD ACROSS
THE UPPER MIDWEST WITH ITS SOUTHERN FLANK INTO THE FORECAST AREA.

TODAY...THE NORTHERN STREAM UPPER TROUGH AXIS WILL
CROSS THE LOCAL AREA THIS MORNING. THE GREATEST ASCENT ASSOCIATED
WITH IT IS TO THE NORTH AND IS GENERATING BANDS OF SHOWERS ACROSS
WISCONSIN...WITH ADDITIONAL RETURNS WORKING ACROSS CENTRAL IOWA INTO
NORTHERN ILLINOIS. THIS ACTIVITY SEEMS TO BE IN BETTER CONJUNCTION
WITH THE RIGHT ENTRANCE REGION OF AN UPPER JET MAX TO THE NORTH IN
ADDITION TO A BROAD AREA OF HEIGHT FALLS INDUCED BY THE UPPER
TROUGH. A CLUSTER OF THUNDERSTORMS HAS ALSO DEVELOPED ACROSS SW IOWA
IN RESPONSE TO BETTER FOCUSED MID LEVEL WARM ADVECTION. MOST OF THIS
UPPER SUPPORT WILL BE PASSING BY THIS MORNING RESULTING IN A
DECREASE IN ACTIVITY. WITH THE SURFACE FRONT TO THE SOUTH THE
INSTABILITY GRADIENT IS ALSO TO THE SOUTH WITH A WESTERLY LOW LEVEL
JET ABOVE IT SUGGESTING THAT THE CONVECTION ACROSS SOUTHWEST IOWA
WOULD NOT BE A FACTOR TOO FAR NORTH OF ITS CURRENT LATITUDE. ONCE
THE CURRENT SHOWER ACTIVITY EXITS IT APPEARS THAT MOST AREAS WILL
REMAIN DRY FOR THE REST OF THE DAY BUT FAR SOUTHERN AREAS DO HAVE A
CHANCE TO SEE SOME SHOWERS AND STORMS THIS MORNING GIVEN THE
WESTERLY LOW LEVEL JET ALONG THE BOUNDARY AND MID LEVEL MOISTURE
GRADIENT BUT WARM/MOIST ADVECTION IS PRETTY WEAK. HIGH TEMPERATURES
WILL RANGE FROM THE UPPER 70S NORTH TO MID 80S SOUTH WITH A
NORTHEAST WIND HOLDING LAKEFRONT AREAS TO THE LOWER TO MID 70S.

TONIGHT AND THURSDAY...AS THE UPPER TROUGH SHIFTS EAST THE RIDGING
DOWNSTREAM OF THE CUTOFF LOW TO THE WEST WILL PIVOT ACROSS THE
CENTRAL PLAINS. SURFACE LOW PRESSURE WILL BE DEVELOPING ACROSS
EASTERN COLORADO AND WESTERN KANSAS WHICH WILL DRIVE THE FRONTAL
BOUNDARY NORTHEASTWARD ACROSS THE CENTRAL PLAINS WITH THE NEARBY
PORTION OF THE FRONT REMAINING SOUTH OF THE AREA INTO THURSDAY
EVENING. WITH WARM ADVECTION INCREASING ALOFT WITH THE RIDGE
BUILDING BACK IN TONIGHT SHOWERS AND THUNDERSTORMS ARE EXPECTED TO
BE MOVING EAST-NORTHEAST ACROSS IOWA/MISSOURI. SOME OF THIS ACTIVITY
MAY REACH THE WESTERN CWA VERY LATE TONIGHT AND MAY END UP SEEING A
SIMILAR SITUATION TO RECENT DAYS WITH REMNANT CONVECTION FESTERING
AND/OR SPAWNING NEW DEVELOPMENT ACROSS THE CWA THURSDAY
MORNING/AFTERNOON. THE MAIN SURFACE LOW AND UPPER WAVE IS EXPECTED
TO BE MOVING ACROSS IOWA/MINNESOTA/WISCONSIN SO THE BULK OF THE
CONVECTION MAY STAY TO THE NORTHWEST OF THE LOCAL AREA. WILL FOCUS
HIGHEST POPS ACROSS THE WESTERN CWA AND SLOW DOWN THE ARRIVAL UNTIL
LATER TONIGHT. THURSDAY LOOKS TO BE SLIGHTLY WARMER...ESPECIALLY
WITH CONVECTION LOOKING TO BE MORE SCATTERED IN COVERAGE.

FRIDAY THROUGH EARLY NEXT WEEK...THE UPPER TROUGH WILL START TO MAKE
QUICKER EAST-NORTHEAST PROGRESS THANKS TO ANOTHER LARGE SCALE UPPER
TROUGH PUSHING INTO THE WESTERN U.S./CANADA. THIS WILL TAKE ANOTHER
SURFACE LOW NORTHEASTWARD WITH IT WHICH WILL LIKELY TRACK NORTHWEST
OF THE AREA SATURDAY. FRIDAY SHOULD SEE A NOTICEABLE WARM UP WITH
ANOTHER LULL IN WIDESPREAD CONVECTION WITH IT FOCUSING TO THE NORTH
AND WEST. WILL HAVE HIGHER POPS SATURDAY WITH THE LOW PASSING BUT AM
SEEING MIXED SIGNALS IN THE TRACK WHICH WILL AFFECT PRECIP COVERAGE.
CHANCES WILL DIMINISH SATURDAY NIGHT WITH QUESTION MARKS SURROUNDING
SUNDAY INTO EARLY NEXT WEEK WITH THE GFS SHOWING A MORE ACTIVE FLOW
WHILE THE ECMWF IS QUIETER THOUGH IT DOES BRING A FRONT THROUGH THE
AREA TUESDAY. DO NOT SEE MUCH OF A COOL DOWN OVERALL AND A DRY
FORECAST SUNDAY/MONDAY WOULD COINCIDE WITH A WARMING TREND IF IT
COMES TO PASS. WILL CONTINUE WITH MID TO UPPER 80S FRIDAY WITH
READINGS SEVERAL DEGREES COOLER SATURDAY AND SUNDAY.

MDB

&&

.AVIATION...

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

* E WINDS ARND 10 KT EXPECTED BY MID AFTN.

JEE

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

HIGH PRESSURE IS SPREADING OVER THE REGION WITH VFR CONDITIONS
ACROSS THE REGION. EAST WINDS WILL CONTINUE THROUGH THE PERIOD. AS
WARMING CONTINUES...EXPECTING WINDS TO PICK UP TO ARND 10 KT BY
MID AFTN. WINDS THEN DIMINISH THIS EVENING...AND THEN WILL BE ARND
8 KT TOMORROW.

THE HIGH SHIFTS EAST TONIGHT INTO TOMORROW WITH LOW PRESSURE
APPROACHING FROM THE SOUTHWEST. GUIDANCE HAS THE WARM FRONT
REMAINING SOUTH OF THE TERMINALS THROUGH TOMORROW AFTERNOON.
HOWEVER...SOME MODELS SHOW STORMS REACHING RFD BY LATE
MORNING/EARLY AFTN SO HAVE A PROB30 FOR THOSE. NOT OVERLY
CONFIDENT IN THE TSRA CHANCES AT RFD. THE OTHER TERMINALS WILL SEE
PRECIP PUSH IN AFTER 00Z FRIDAY.

JEE

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

* MEDIUM CONFIDENCE IN WHEN EAST WINDS WILL BE ARND 10 KT THIS AFTN.

* HIGH CONFIDENCE IN ALL OTHER FORECAST PARAMETERS.

JEE

//OUTLOOK FOR ORD/MDW FOR 00Z FRIDAY-12Z WEDNESDAY...UPDATED 12Z...

* THURSDAY NIGHT AND FRIDAY...CHANCE OF TSRA.
* SATURDAY...TSRA LIKELY.
* SUNDAY THROUGH TUESDAY...CHANCE OF TSRA.

&&

.MARINE...
205 PM CDT

HIGH PRESSURE WILL CONTINUE TO BE OVERHEAD OF LAKE
MICHIGAN...LIKELY LINGERING THROUGH DAYBREAK THURSDAY BEFORE
MOVING EAST TOWARDS LAKE ERIE TOMORROW NIGHT. AS THE HIGH DRIFTS
EAST...WINDS WILL SLOWLY TURN SOUTHEASTERLY THEN SOUTHERLY.
GUIDANCE IS EXPECTING A LOW PRESSURE SYSTEM TO LIFT NORTHEAST
ACROSS THE CENTRAL PLAINS INTO THE UPPER MIDWEST THURSDAY
AFTERNOON. THIS WILL RESULT IN A TIGHTENING GRADIENT FROM SOUTH TO
NORTH ACROSS THE LAKE. AT THIS TIME IT IS POSSIBLE THAT WINDS
COULD HOVER IN THE 15 TO 25 KT RANGE THURSDAY NIGHT INTO FRIDAY.
THEN AS THE LOW PRESSURE LIFTS NORTHEAST OF LAKE MICHIGAN AND A
RIDGE OF HIGH PRESSURE SLIDES SOUTH FROM CENTRAL CANADA INTO THE
UPPER MIDWEST FRIDAY EVENING...A FRONTAL BOUNDARY WILL SAG SOUTH
AND TURN WINDS NORTHERLY FOR THE NORTHERN HALF OF THE LAKE.
MEANWHILE IT DOES APPEAR THE BOUNDARY GETS HUNG UP ACROSS THE
CENTRAL PORTION OF THE LAKE FRIDAY NIGHT/EARLY SATURDAY...WHICH
WILL KEEP SOUTHERLY WINDS FOR THE SOUTHERN HALF OF THE LAKE. THEN
YET ANOTHER AREA OF LOW PRESSURE IS FORECAST TO DEVELOP ACROSS THE
NORTHERN PLAINS SATURDAY AFTERNOON AND DEEPEN AS IT MOVES
NORTHEAST INTO WESTERN ONTARIO. THIS WILL LIKELY CREATE A TIGHT
GRADIENT ACROSS THE LAKE SUNDAY WITH YET ANOTHER PERIOD OF WINDS
NEARING 20-25KT.

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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO







000
FXUS63 KLOT 271912
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
212 PM CDT WED AUG 27 2014

.DISCUSSION...
321 AM CDT

CONVECTIVE TRENDS REMAIN THE MAIN FOCUS OF THE FORECAST THROUGH THE
WEEKEND. WATER VAPOR IMAGERY SHOWS A SPLIT UPPER FLOW WITH A
NORTHERN STREAM OF PROGRESSIVE FLOW RUNNING ACROSS SOUTHERN CANADA
INTO THE UPPER GREAT LAKES. A LOW AMPLITUDE TROUGH AXIS IS
TRAVERSING THE FLOW AND MOVING INTO WISCONSIN AT THE CURRENT TIME.
THE SOUTHERN STREAM FEATURES A CUTOFF UPPER LOW WHICH IS OVER UTAH
AND SLOWLY MOVING EASTWARD. UPPER RIDGING IS STARTING TO BUILD JUST
DOWNSTREAM OF THE UPPER LOW WITH SEVERAL EMBEDDED WAVES MOVING
NORTHEASTWARD AHEAD OF THE LOW. AT THE SURFACE...THE FRONTAL
BOUNDARY WHICH HAS BEEN DISCUSSED OVER THE PAST SEVERAL DAYS IS NOW
SOUTH OF THE CWA AND RUNS EAST-NORTHEAST ACROSS THE LOWER GREAT
LAKES AND ST. LAWRENCE RIVER VALLEY. HIGH PRESSURE HAS SPREAD ACROSS
THE UPPER MIDWEST WITH ITS SOUTHERN FLANK INTO THE FORECAST AREA.

TODAY...THE NORTHERN STREAM UPPER TROUGH AXIS WILL
CROSS THE LOCAL AREA THIS MORNING. THE GREATEST ASCENT ASSOCIATED
WITH IT IS TO THE NORTH AND IS GENERATING BANDS OF SHOWERS ACROSS
WISCONSIN...WITH ADDITIONAL RETURNS WORKING ACROSS CENTRAL IOWA INTO
NORTHERN ILLINOIS. THIS ACTIVITY SEEMS TO BE IN BETTER CONJUNCTION
WITH THE RIGHT ENTRANCE REGION OF AN UPPER JET MAX TO THE NORTH IN
ADDITION TO A BROAD AREA OF HEIGHT FALLS INDUCED BY THE UPPER
TROUGH. A CLUSTER OF THUNDERSTORMS HAS ALSO DEVELOPED ACROSS SW IOWA
IN RESPONSE TO BETTER FOCUSED MID LEVEL WARM ADVECTION. MOST OF THIS
UPPER SUPPORT WILL BE PASSING BY THIS MORNING RESULTING IN A
DECREASE IN ACTIVITY. WITH THE SURFACE FRONT TO THE SOUTH THE
INSTABILITY GRADIENT IS ALSO TO THE SOUTH WITH A WESTERLY LOW LEVEL
JET ABOVE IT SUGGESTING THAT THE CONVECTION ACROSS SOUTHWEST IOWA
WOULD NOT BE A FACTOR TOO FAR NORTH OF ITS CURRENT LATITUDE. ONCE
THE CURRENT SHOWER ACTIVITY EXITS IT APPEARS THAT MOST AREAS WILL
REMAIN DRY FOR THE REST OF THE DAY BUT FAR SOUTHERN AREAS DO HAVE A
CHANCE TO SEE SOME SHOWERS AND STORMS THIS MORNING GIVEN THE
WESTERLY LOW LEVEL JET ALONG THE BOUNDARY AND MID LEVEL MOISTURE
GRADIENT BUT WARM/MOIST ADVECTION IS PRETTY WEAK. HIGH TEMPERATURES
WILL RANGE FROM THE UPPER 70S NORTH TO MID 80S SOUTH WITH A
NORTHEAST WIND HOLDING LAKEFRONT AREAS TO THE LOWER TO MID 70S.

TONIGHT AND THURSDAY...AS THE UPPER TROUGH SHIFTS EAST THE RIDGING
DOWNSTREAM OF THE CUTOFF LOW TO THE WEST WILL PIVOT ACROSS THE
CENTRAL PLAINS. SURFACE LOW PRESSURE WILL BE DEVELOPING ACROSS
EASTERN COLORADO AND WESTERN KANSAS WHICH WILL DRIVE THE FRONTAL
BOUNDARY NORTHEASTWARD ACROSS THE CENTRAL PLAINS WITH THE NEARBY
PORTION OF THE FRONT REMAINING SOUTH OF THE AREA INTO THURSDAY
EVENING. WITH WARM ADVECTION INCREASING ALOFT WITH THE RIDGE
BUILDING BACK IN TONIGHT SHOWERS AND THUNDERSTORMS ARE EXPECTED TO
BE MOVING EAST-NORTHEAST ACROSS IOWA/MISSOURI. SOME OF THIS ACTIVITY
MAY REACH THE WESTERN CWA VERY LATE TONIGHT AND MAY END UP SEEING A
SIMILAR SITUATION TO RECENT DAYS WITH REMNANT CONVECTION FESTERING
AND/OR SPAWNING NEW DEVELOPMENT ACROSS THE CWA THURSDAY
MORNING/AFTERNOON. THE MAIN SURFACE LOW AND UPPER WAVE IS EXPECTED
TO BE MOVING ACROSS IOWA/MINNESOTA/WISCONSIN SO THE BULK OF THE
CONVECTION MAY STAY TO THE NORTHWEST OF THE LOCAL AREA. WILL FOCUS
HIGHEST POPS ACROSS THE WESTERN CWA AND SLOW DOWN THE ARRIVAL UNTIL
LATER TONIGHT. THURSDAY LOOKS TO BE SLIGHTLY WARMER...ESPECIALLY
WITH CONVECTION LOOKING TO BE MORE SCATTERED IN COVERAGE.

FRIDAY THROUGH EARLY NEXT WEEK...THE UPPER TROUGH WILL START TO MAKE
QUICKER EAST-NORTHEAST PROGRESS THANKS TO ANOTHER LARGE SCALE UPPER
TROUGH PUSHING INTO THE WESTERN U.S./CANADA. THIS WILL TAKE ANOTHER
SURFACE LOW NORTHEASTWARD WITH IT WHICH WILL LIKELY TRACK NORTHWEST
OF THE AREA SATURDAY. FRIDAY SHOULD SEE A NOTICEABLE WARM UP WITH
ANOTHER LULL IN WIDESPREAD CONVECTION WITH IT FOCUSING TO THE NORTH
AND WEST. WILL HAVE HIGHER POPS SATURDAY WITH THE LOW PASSING BUT AM
SEEING MIXED SIGNALS IN THE TRACK WHICH WILL AFFECT PRECIP COVERAGE.
CHANCES WILL DIMINISH SATURDAY NIGHT WITH QUESTION MARKS SURROUNDING
SUNDAY INTO EARLY NEXT WEEK WITH THE GFS SHOWING A MORE ACTIVE FLOW
WHILE THE ECMWF IS QUIETER THOUGH IT DOES BRING A FRONT THROUGH THE
AREA TUESDAY. DO NOT SEE MUCH OF A COOL DOWN OVERALL AND A DRY
FORECAST SUNDAY/MONDAY WOULD COINCIDE WITH A WARMING TREND IF IT
COMES TO PASS. WILL CONTINUE WITH MID TO UPPER 80S FRIDAY WITH
READINGS SEVERAL DEGREES COOLER SATURDAY AND SUNDAY.

MDB

&&

.AVIATION...

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

* E WINDS ARND 10 KT EXPECTED BY MID AFTN.

JEE

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

HIGH PRESSURE IS SPREADING OVER THE REGION WITH VFR CONDITIONS
ACROSS THE REGION. EAST WINDS WILL CONTINUE THROUGH THE PERIOD. AS
WARMING CONTINUES...EXPECTING WINDS TO PICK UP TO ARND 10 KT BY
MID AFTN. WINDS THEN DIMINISH THIS EVENING...AND THEN WILL BE ARND
8 KT TOMORROW.

THE HIGH SHIFTS EAST TONIGHT INTO TOMORROW WITH LOW PRESSURE
APPROACHING FROM THE SOUTHWEST. GUIDANCE HAS THE WARM FRONT
REMAINING SOUTH OF THE TERMINALS THROUGH TOMORROW AFTERNOON.
HOWEVER...SOME MODELS SHOW STORMS REACHING RFD BY LATE
MORNING/EARLY AFTN SO HAVE A PROB30 FOR THOSE. NOT OVERLY
CONFIDENT IN THE TSRA CHANCES AT RFD. THE OTHER TERMINALS WILL SEE
PRECIP PUSH IN AFTER 00Z FRIDAY.

JEE

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

* MEDIUM CONFIDENCE IN WHEN EAST WINDS WILL BE ARND 10 KT THIS AFTN.

* HIGH CONFIDENCE IN ALL OTHER FORECAST PARAMETERS.

JEE

//OUTLOOK FOR ORD/MDW FOR 00Z FRIDAY-12Z WEDNESDAY...UPDATED 12Z...

* THURSDAY NIGHT AND FRIDAY...CHANCE OF TSRA.
* SATURDAY...TSRA LIKELY.
* SUNDAY THROUGH TUESDAY...CHANCE OF TSRA.

&&

.MARINE...
205 PM CDT

HIGH PRESSURE WILL CONTINUE TO BE OVERHEAD OF LAKE
MICHIGAN...LIKELY LINGERING THROUGH DAYBREAK THURSDAY BEFORE
MOVING EAST TOWARDS LAKE ERIE TOMORROW NIGHT. AS THE HIGH DRIFTS
EAST...WINDS WILL SLOWLY TURN SOUTHEASTERLY THEN SOUTHERLY.
GUIDANCE IS EXPECTING A LOW PRESSURE SYSTEM TO LIFT NORTHEAST
ACROSS THE CENTRAL PLAINS INTO THE UPPER MIDWEST THURSDAY
AFTERNOON. THIS WILL RESULT IN A TIGHTENING GRADIENT FROM SOUTH TO
NORTH ACROSS THE LAKE. AT THIS TIME IT IS POSSIBLE THAT WINDS
COULD HOVER IN THE 15 TO 25 KT RANGE THURSDAY NIGHT INTO FRIDAY.
THEN AS THE LOW PRESSURE LIFTS NORTHEAST OF LAKE MICHIGAN AND A
RIDGE OF HIGH PRESSURE SLIDES SOUTH FROM CENTRAL CANADA INTO THE
UPPER MIDWEST FRIDAY EVENING...A FRONTAL BOUNDARY WILL SAG SOUTH
AND TURN WINDS NORTHERLY FOR THE NORTHERN HALF OF THE LAKE.
MEANWHILE IT DOES APPEAR THE BOUNDARY GETS HUNG UP ACROSS THE
CENTRAL PORTION OF THE LAKE FRIDAY NIGHT/EARLY SATURDAY...WHICH
WILL KEEP SOUTHERLY WINDS FOR THE SOUTHERN HALF OF THE LAKE. THEN
YET ANOTHER AREA OF LOW PRESSURE IS FORECAST TO DEVELOP ACROSS THE
NORTHERN PLAINS SATURDAY AFTERNOON AND DEEPEN AS IT MOVES
NORTHEAST INTO WESTERN ONTARIO. THIS WILL LIKELY CREATE A TIGHT
GRADIENT ACROSS THE LAKE SUNDAY WITH YET ANOTHER PERIOD OF WINDS
NEARING 20-25KT.

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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 271744
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1244 PM CDT WED AUG 27 2014

.DISCUSSION...
321 AM CDT

CONVECTIVE TRENDS REMAIN THE MAIN FOCUS OF THE FORECAST THROUGH THE
WEEKEND. WATER VAPOR IMAGERY SHOWS A SPLIT UPPER FLOW WITH A
NORTHERN STREAM OF PROGRESSIVE FLOW RUNNING ACROSS SOUTHERN CANADA
INTO THE UPPER GREAT LAKES. A LOW AMPLITUDE TROUGH AXIS IS
TRAVERSING THE FLOW AND MOVING INTO WISCONSIN AT THE CURRENT TIME.
THE SOUTHERN STREAM FEATURES A CUTOFF UPPER LOW WHICH IS OVER UTAH
AND SLOWLY MOVING EASTWARD. UPPER RIDGING IS STARTING TO BUILD JUST
DOWNSTREAM OF THE UPPER LOW WITH SEVERAL EMBEDDED WAVES MOVING
NORTHEASTWARD AHEAD OF THE LOW. AT THE SURFACE...THE FRONTAL
BOUNDARY WHICH HAS BEEN DISCUSSED OVER THE PAST SEVERAL DAYS IS NOW
SOUTH OF THE CWA AND RUNS EAST-NORTHEAST ACROSS THE LOWER GREAT
LAKES AND ST. LAWRENCE RIVER VALLEY. HIGH PRESSURE HAS SPREAD ACROSS
THE UPPER MIDWEST WITH ITS SOUTHERN FLANK INTO THE FORECAST AREA.

TODAY...THE NORTHERN STREAM UPPER TROUGH AXIS WILL
CROSS THE LOCAL AREA THIS MORNING. THE GREATEST ASCENT ASSOCIATED
WITH IT IS TO THE NORTH AND IS GENERATING BANDS OF SHOWERS ACROSS
WISCONSIN...WITH ADDITIONAL RETURNS WORKING ACROSS CENTRAL IOWA INTO
NORTHERN ILLINOIS. THIS ACTIVITY SEEMS TO BE IN BETTER CONJUNCTION
WITH THE RIGHT ENTRANCE REGION OF AN UPPER JET MAX TO THE NORTH IN
ADDITION TO A BROAD AREA OF HEIGHT FALLS INDUCED BY THE UPPER
TROUGH. A CLUSTER OF THUNDERSTORMS HAS ALSO DEVELOPED ACROSS SW IOWA
IN RESPONSE TO BETTER FOCUSED MID LEVEL WARM ADVECTION. MOST OF THIS
UPPER SUPPORT WILL BE PASSING BY THIS MORNING RESULTING IN A
DECREASE IN ACTIVITY. WITH THE SURFACE FRONT TO THE SOUTH THE
INSTABILITY GRADIENT IS ALSO TO THE SOUTH WITH A WESTERLY LOW LEVEL
JET ABOVE IT SUGGESTING THAT THE CONVECTION ACROSS SOUTHWEST IOWA
WOULD NOT BE A FACTOR TOO FAR NORTH OF ITS CURRENT LATITUDE. ONCE
THE CURRENT SHOWER ACTIVITY EXITS IT APPEARS THAT MOST AREAS WILL
REMAIN DRY FOR THE REST OF THE DAY BUT FAR SOUTHERN AREAS DO HAVE A
CHANCE TO SEE SOME SHOWERS AND STORMS THIS MORNING GIVEN THE
WESTERLY LOW LEVEL JET ALONG THE BOUNDARY AND MID LEVEL MOISTURE
GRADIENT BUT WARM/MOIST ADVECTION IS PRETTY WEAK. HIGH TEMPERATURES
WILL RANGE FROM THE UPPER 70S NORTH TO MID 80S SOUTH WITH A
NORTHEAST WIND HOLDING LAKEFRONT AREAS TO THE LOWER TO MID 70S.

TONIGHT AND THURSDAY...AS THE UPPER TROUGH SHIFTS EAST THE RIDGING
DOWNSTREAM OF THE CUTOFF LOW TO THE WEST WILL PIVOT ACROSS THE
CENTRAL PLAINS. SURFACE LOW PRESSURE WILL BE DEVELOPING ACROSS
EASTERN COLORADO AND WESTERN KANSAS WHICH WILL DRIVE THE FRONTAL
BOUNDARY NORTHEASTWARD ACROSS THE CENTRAL PLAINS WITH THE NEARBY
PORTION OF THE FRONT REMAINING SOUTH OF THE AREA INTO THURSDAY
EVENING. WITH WARM ADVECTION INCREASING ALOFT WITH THE RIDGE
BUILDING BACK IN TONIGHT SHOWERS AND THUNDERSTORMS ARE EXPECTED TO
BE MOVING EAST-NORTHEAST ACROSS IOWA/MISSOURI. SOME OF THIS ACTIVITY
MAY REACH THE WESTERN CWA VERY LATE TONIGHT AND MAY END UP SEEING A
SIMILAR SITUATION TO RECENT DAYS WITH REMNANT CONVECTION FESTERING
AND/OR SPAWNING NEW DEVELOPMENT ACROSS THE CWA THURSDAY
MORNING/AFTERNOON. THE MAIN SURFACE LOW AND UPPER WAVE IS EXPECTED
TO BE MOVING ACROSS IOWA/MINNESOTA/WISCONSIN SO THE BULK OF THE
CONVECTION MAY STAY TO THE NORTHWEST OF THE LOCAL AREA. WILL FOCUS
HIGHEST POPS ACROSS THE WESTERN CWA AND SLOW DOWN THE ARRIVAL UNTIL
LATER TONIGHT. THURSDAY LOOKS TO BE SLIGHTLY WARMER...ESPECIALLY
WITH CONVECTION LOOKING TO BE MORE SCATTERED IN COVERAGE.

FRIDAY THROUGH EARLY NEXT WEEK...THE UPPER TROUGH WILL START TO MAKE
QUICKER EAST-NORTHEAST PROGRESS THANKS TO ANOTHER LARGE SCALE UPPER
TROUGH PUSHING INTO THE WESTERN U.S./CANADA. THIS WILL TAKE ANOTHER
SURFACE LOW NORTHEASTWARD WITH IT WHICH WILL LIKELY TRACK NORTHWEST
OF THE AREA SATURDAY. FRIDAY SHOULD SEE A NOTICEABLE WARM UP WITH
ANOTHER LULL IN WIDESPREAD CONVECTION WITH IT FOCUSING TO THE NORTH
AND WEST. WILL HAVE HIGHER POPS SATURDAY WITH THE LOW PASSING BUT AM
SEEING MIXED SIGNALS IN THE TRACK WHICH WILL AFFECT PRECIP COVERAGE.
CHANCES WILL DIMINISH SATURDAY NIGHT WITH QUESTION MARKS SURROUNDING
SUNDAY INTO EARLY NEXT WEEK WITH THE GFS SHOWING A MORE ACTIVE FLOW
WHILE THE ECMWF IS QUIETER THOUGH IT DOES BRING A FRONT THROUGH THE
AREA TUESDAY. DO NOT SEE MUCH OF A COOL DOWN OVERALL AND A DRY
FORECAST SUNDAY/MONDAY WOULD COINCIDE WITH A WARMING TREND IF IT
COMES TO PASS. WILL CONTINUE WITH MID TO UPPER 80S FRIDAY WITH
READINGS SEVERAL DEGREES COOLER SATURDAY AND SUNDAY.

MDB

&&

.AVIATION...

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

* E WINDS ARND 10 KT EXPECTED BY MID AFTN.

JEE

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

HIGH PRESSURE IS SPREADING OVER THE REGION WITH VFR CONDITIONS
ACROSS THE REGION. EAST WINDS WILL CONTINUE THROUGH THE PERIOD. AS
WARMING CONTINUES...EXPECTING WINDS TO PICK UP TO ARND 10 KT BY
MID AFTN. WINDS THEN DIMINISH THIS EVENING...AND THEN WILL BE ARND
8 KT TOMORROW.

THE HIGH SHIFTS EAST TONIGHT INTO TOMORROW WITH LOW PRESSURE
APPROACHING FROM THE SOUTHWEST. GUIDANCE HAS THE WARM FRONT
REMAINING SOUTH OF THE TERMINALS THROUGH TOMORROW AFTERNOON.
HOWEVER...SOME MODELS SHOW STORMS REACHING RFD BY LATE
MORNING/EARLY AFTN SO HAVE A PROB30 FOR THOSE. NOT OVERLY
CONFIDENT IN THE TSRA CHANCES AT RFD. THE OTHER TERMINALS WILL SEE
PRECIP PUSH IN AFTER 00Z FRIDAY.

JEE


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

* MEDIUM CONFIDENCE IN WHEN EAST WINDS WILL BE ARND 10 KT THIS AFTN.

* HIGH CONFIDENCE IN ALL OTHER FORECAST PARAMETERS.

JEE

//OUTLOOK FOR ORD/MDW FOR 00Z FRIDAY-12Z WEDNESDAY...UPDATED 12Z...

* THURSDAY NIGHT AND FRIDAY...CHANCE OF TSRA.
* SATURDAY...TSRA LIKELY.
* SUNDAY THROUGH TUESDAY...CHANCE OF TSRA.

&&

.MARINE...

307 AM...HIGH PRESSURE CENTERED OVER MINNESOTA EARLY THIS MORNING
WILL MOVE ACROSS THE LAKES REGION TODAY AND TONIGHT. AS IT DOES
THE GRADIENT WILL SLOWLY WEAKEN OVER NORTHERN LAKE MICHIGAN WHILE
IT SLOWLY TIGHTENS OVER THE SOUTHERN PORTION OF THE LAKE. SPEEDS
WILL INCREASE INTO THE 10-20KT RANGE. AS THE HIGH SHIFTS EAST...
WINDS WILL TURN MORE EASTERLY BY THURSDAY MORNING THEN SHIFT
SOUTHEAST TO SOUTHERLY THURSDAY NIGHT AS A WARM FRONT LIFTS NORTH
ACROSS THE LAKE. THE GRADIENT COULD TIGHTEN ENOUGH FOR A PERIOD OF
15-25 KTS THURSDAY NIGHT INTO FRIDAY. A FRONTAL BOUNDARY IS THEN
EXPECTED TO MOVE SOUTH ACROSS THE LAKE SATURDAY AFTERNOON INTO
SATURDAY EVENING. BUT AT THE SAME TIME...LOW PRESSURE IS EXPECTED
TO DEVELOP OVER THE WESTERN LAKES AND THEN MOVE ACROSS NORTHERN
LAKE MICHIGAN BY SUNDAY MORNING. THIS MAKES FOR A CHALLENGING WIND
FORECAST. IF THE LOW BEGINS TO DEEPEN...NORTHERLY WINDS MAY
INCREASE INTO THE 15-25KT RANGE. CHANGES CAN BE EXPECTED DURING
THIS TIME PERIOD AS TRENDS EMERGE. WINDS THEN QUICKLY TURN BACK
SOUTHERLY SUNDAY NIGHT INTO MONDAY. CMS

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 271744
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1244 PM CDT WED AUG 27 2014

.DISCUSSION...
321 AM CDT

CONVECTIVE TRENDS REMAIN THE MAIN FOCUS OF THE FORECAST THROUGH THE
WEEKEND. WATER VAPOR IMAGERY SHOWS A SPLIT UPPER FLOW WITH A
NORTHERN STREAM OF PROGRESSIVE FLOW RUNNING ACROSS SOUTHERN CANADA
INTO THE UPPER GREAT LAKES. A LOW AMPLITUDE TROUGH AXIS IS
TRAVERSING THE FLOW AND MOVING INTO WISCONSIN AT THE CURRENT TIME.
THE SOUTHERN STREAM FEATURES A CUTOFF UPPER LOW WHICH IS OVER UTAH
AND SLOWLY MOVING EASTWARD. UPPER RIDGING IS STARTING TO BUILD JUST
DOWNSTREAM OF THE UPPER LOW WITH SEVERAL EMBEDDED WAVES MOVING
NORTHEASTWARD AHEAD OF THE LOW. AT THE SURFACE...THE FRONTAL
BOUNDARY WHICH HAS BEEN DISCUSSED OVER THE PAST SEVERAL DAYS IS NOW
SOUTH OF THE CWA AND RUNS EAST-NORTHEAST ACROSS THE LOWER GREAT
LAKES AND ST. LAWRENCE RIVER VALLEY. HIGH PRESSURE HAS SPREAD ACROSS
THE UPPER MIDWEST WITH ITS SOUTHERN FLANK INTO THE FORECAST AREA.

TODAY...THE NORTHERN STREAM UPPER TROUGH AXIS WILL
CROSS THE LOCAL AREA THIS MORNING. THE GREATEST ASCENT ASSOCIATED
WITH IT IS TO THE NORTH AND IS GENERATING BANDS OF SHOWERS ACROSS
WISCONSIN...WITH ADDITIONAL RETURNS WORKING ACROSS CENTRAL IOWA INTO
NORTHERN ILLINOIS. THIS ACTIVITY SEEMS TO BE IN BETTER CONJUNCTION
WITH THE RIGHT ENTRANCE REGION OF AN UPPER JET MAX TO THE NORTH IN
ADDITION TO A BROAD AREA OF HEIGHT FALLS INDUCED BY THE UPPER
TROUGH. A CLUSTER OF THUNDERSTORMS HAS ALSO DEVELOPED ACROSS SW IOWA
IN RESPONSE TO BETTER FOCUSED MID LEVEL WARM ADVECTION. MOST OF THIS
UPPER SUPPORT WILL BE PASSING BY THIS MORNING RESULTING IN A
DECREASE IN ACTIVITY. WITH THE SURFACE FRONT TO THE SOUTH THE
INSTABILITY GRADIENT IS ALSO TO THE SOUTH WITH A WESTERLY LOW LEVEL
JET ABOVE IT SUGGESTING THAT THE CONVECTION ACROSS SOUTHWEST IOWA
WOULD NOT BE A FACTOR TOO FAR NORTH OF ITS CURRENT LATITUDE. ONCE
THE CURRENT SHOWER ACTIVITY EXITS IT APPEARS THAT MOST AREAS WILL
REMAIN DRY FOR THE REST OF THE DAY BUT FAR SOUTHERN AREAS DO HAVE A
CHANCE TO SEE SOME SHOWERS AND STORMS THIS MORNING GIVEN THE
WESTERLY LOW LEVEL JET ALONG THE BOUNDARY AND MID LEVEL MOISTURE
GRADIENT BUT WARM/MOIST ADVECTION IS PRETTY WEAK. HIGH TEMPERATURES
WILL RANGE FROM THE UPPER 70S NORTH TO MID 80S SOUTH WITH A
NORTHEAST WIND HOLDING LAKEFRONT AREAS TO THE LOWER TO MID 70S.

TONIGHT AND THURSDAY...AS THE UPPER TROUGH SHIFTS EAST THE RIDGING
DOWNSTREAM OF THE CUTOFF LOW TO THE WEST WILL PIVOT ACROSS THE
CENTRAL PLAINS. SURFACE LOW PRESSURE WILL BE DEVELOPING ACROSS
EASTERN COLORADO AND WESTERN KANSAS WHICH WILL DRIVE THE FRONTAL
BOUNDARY NORTHEASTWARD ACROSS THE CENTRAL PLAINS WITH THE NEARBY
PORTION OF THE FRONT REMAINING SOUTH OF THE AREA INTO THURSDAY
EVENING. WITH WARM ADVECTION INCREASING ALOFT WITH THE RIDGE
BUILDING BACK IN TONIGHT SHOWERS AND THUNDERSTORMS ARE EXPECTED TO
BE MOVING EAST-NORTHEAST ACROSS IOWA/MISSOURI. SOME OF THIS ACTIVITY
MAY REACH THE WESTERN CWA VERY LATE TONIGHT AND MAY END UP SEEING A
SIMILAR SITUATION TO RECENT DAYS WITH REMNANT CONVECTION FESTERING
AND/OR SPAWNING NEW DEVELOPMENT ACROSS THE CWA THURSDAY
MORNING/AFTERNOON. THE MAIN SURFACE LOW AND UPPER WAVE IS EXPECTED
TO BE MOVING ACROSS IOWA/MINNESOTA/WISCONSIN SO THE BULK OF THE
CONVECTION MAY STAY TO THE NORTHWEST OF THE LOCAL AREA. WILL FOCUS
HIGHEST POPS ACROSS THE WESTERN CWA AND SLOW DOWN THE ARRIVAL UNTIL
LATER TONIGHT. THURSDAY LOOKS TO BE SLIGHTLY WARMER...ESPECIALLY
WITH CONVECTION LOOKING TO BE MORE SCATTERED IN COVERAGE.

FRIDAY THROUGH EARLY NEXT WEEK...THE UPPER TROUGH WILL START TO MAKE
QUICKER EAST-NORTHEAST PROGRESS THANKS TO ANOTHER LARGE SCALE UPPER
TROUGH PUSHING INTO THE WESTERN U.S./CANADA. THIS WILL TAKE ANOTHER
SURFACE LOW NORTHEASTWARD WITH IT WHICH WILL LIKELY TRACK NORTHWEST
OF THE AREA SATURDAY. FRIDAY SHOULD SEE A NOTICEABLE WARM UP WITH
ANOTHER LULL IN WIDESPREAD CONVECTION WITH IT FOCUSING TO THE NORTH
AND WEST. WILL HAVE HIGHER POPS SATURDAY WITH THE LOW PASSING BUT AM
SEEING MIXED SIGNALS IN THE TRACK WHICH WILL AFFECT PRECIP COVERAGE.
CHANCES WILL DIMINISH SATURDAY NIGHT WITH QUESTION MARKS SURROUNDING
SUNDAY INTO EARLY NEXT WEEK WITH THE GFS SHOWING A MORE ACTIVE FLOW
WHILE THE ECMWF IS QUIETER THOUGH IT DOES BRING A FRONT THROUGH THE
AREA TUESDAY. DO NOT SEE MUCH OF A COOL DOWN OVERALL AND A DRY
FORECAST SUNDAY/MONDAY WOULD COINCIDE WITH A WARMING TREND IF IT
COMES TO PASS. WILL CONTINUE WITH MID TO UPPER 80S FRIDAY WITH
READINGS SEVERAL DEGREES COOLER SATURDAY AND SUNDAY.

MDB

&&

.AVIATION...

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

* E WINDS ARND 10 KT EXPECTED BY MID AFTN.

JEE

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

HIGH PRESSURE IS SPREADING OVER THE REGION WITH VFR CONDITIONS
ACROSS THE REGION. EAST WINDS WILL CONTINUE THROUGH THE PERIOD. AS
WARMING CONTINUES...EXPECTING WINDS TO PICK UP TO ARND 10 KT BY
MID AFTN. WINDS THEN DIMINISH THIS EVENING...AND THEN WILL BE ARND
8 KT TOMORROW.

THE HIGH SHIFTS EAST TONIGHT INTO TOMORROW WITH LOW PRESSURE
APPROACHING FROM THE SOUTHWEST. GUIDANCE HAS THE WARM FRONT
REMAINING SOUTH OF THE TERMINALS THROUGH TOMORROW AFTERNOON.
HOWEVER...SOME MODELS SHOW STORMS REACHING RFD BY LATE
MORNING/EARLY AFTN SO HAVE A PROB30 FOR THOSE. NOT OVERLY
CONFIDENT IN THE TSRA CHANCES AT RFD. THE OTHER TERMINALS WILL SEE
PRECIP PUSH IN AFTER 00Z FRIDAY.

JEE


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

* MEDIUM CONFIDENCE IN WHEN EAST WINDS WILL BE ARND 10 KT THIS AFTN.

* HIGH CONFIDENCE IN ALL OTHER FORECAST PARAMETERS.

JEE

//OUTLOOK FOR ORD/MDW FOR 00Z FRIDAY-12Z WEDNESDAY...UPDATED 12Z...

* THURSDAY NIGHT AND FRIDAY...CHANCE OF TSRA.
* SATURDAY...TSRA LIKELY.
* SUNDAY THROUGH TUESDAY...CHANCE OF TSRA.

&&

.MARINE...

307 AM...HIGH PRESSURE CENTERED OVER MINNESOTA EARLY THIS MORNING
WILL MOVE ACROSS THE LAKES REGION TODAY AND TONIGHT. AS IT DOES
THE GRADIENT WILL SLOWLY WEAKEN OVER NORTHERN LAKE MICHIGAN WHILE
IT SLOWLY TIGHTENS OVER THE SOUTHERN PORTION OF THE LAKE. SPEEDS
WILL INCREASE INTO THE 10-20KT RANGE. AS THE HIGH SHIFTS EAST...
WINDS WILL TURN MORE EASTERLY BY THURSDAY MORNING THEN SHIFT
SOUTHEAST TO SOUTHERLY THURSDAY NIGHT AS A WARM FRONT LIFTS NORTH
ACROSS THE LAKE. THE GRADIENT COULD TIGHTEN ENOUGH FOR A PERIOD OF
15-25 KTS THURSDAY NIGHT INTO FRIDAY. A FRONTAL BOUNDARY IS THEN
EXPECTED TO MOVE SOUTH ACROSS THE LAKE SATURDAY AFTERNOON INTO
SATURDAY EVENING. BUT AT THE SAME TIME...LOW PRESSURE IS EXPECTED
TO DEVELOP OVER THE WESTERN LAKES AND THEN MOVE ACROSS NORTHERN
LAKE MICHIGAN BY SUNDAY MORNING. THIS MAKES FOR A CHALLENGING WIND
FORECAST. IF THE LOW BEGINS TO DEEPEN...NORTHERLY WINDS MAY
INCREASE INTO THE 15-25KT RANGE. CHANGES CAN BE EXPECTED DURING
THIS TIME PERIOD AS TRENDS EMERGE. WINDS THEN QUICKLY TURN BACK
SOUTHERLY SUNDAY NIGHT INTO MONDAY. CMS

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO







000
FXUS63 KLOT 271601
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1101 AM CDT WED AUG 27 2014

.DISCUSSION...
321 AM CDT

CONVECTIVE TRENDS REMAIN THE MAIN FOCUS OF THE FORECAST THROUGH THE
WEEKEND. WATER VAPOR IMAGERY SHOWS A SPLIT UPPER FLOW WITH A
NORTHERN STREAM OF PROGRESSIVE FLOW RUNNING ACROSS SOUTHERN CANADA
INTO THE UPPER GREAT LAKES. A LOW AMPLITUDE TROUGH AXIS IS
TRAVERSING THE FLOW AND MOVING INTO WISCONSIN AT THE CURRENT TIME.
THE SOUTHERN STREAM FEATURES A CUTOFF UPPER LOW WHICH IS OVER UTAH
AND SLOWLY MOVING EASTWARD. UPPER RIDGING IS STARTING TO BUILD JUST
DOWNSTREAM OF THE UPPER LOW WITH SEVERAL EMBEDDED WAVES MOVING
NORTHEASTWARD AHEAD OF THE LOW. AT THE SURFACE...THE FRONTAL
BOUNDARY WHICH HAS BEEN DISCUSSED OVER THE PAST SEVERAL DAYS IS NOW
SOUTH OF THE CWA AND RUNS EAST-NORTHEAST ACROSS THE LOWER GREAT
LAKES AND ST. LAWRENCE RIVER VALLEY. HIGH PRESSURE HAS SPREAD ACROSS
THE UPPER MIDWEST WITH ITS SOUTHERN FLANK INTO THE FORECAST AREA.

TODAY...THE NORTHERN STREAM UPPER TROUGH AXIS WILL
CROSS THE LOCAL AREA THIS MORNING. THE GREATEST ASCENT ASSOCIATED
WITH IT IS TO THE NORTH AND IS GENERATING BANDS OF SHOWERS ACROSS
WISCONSIN...WITH ADDITIONAL RETURNS WORKING ACROSS CENTRAL IOWA INTO
NORTHERN ILLINOIS. THIS ACTIVITY SEEMS TO BE IN BETTER CONJUNCTION
WITH THE RIGHT ENTRANCE REGION OF AN UPPER JET MAX TO THE NORTH IN
ADDITION TO A BROAD AREA OF HEIGHT FALLS INDUCED BY THE UPPER
TROUGH. A CLUSTER OF THUNDERSTORMS HAS ALSO DEVELOPED ACROSS SW IOWA
IN RESPONSE TO BETTER FOCUSED MID LEVEL WARM ADVECTION. MOST OF THIS
UPPER SUPPORT WILL BE PASSING BY THIS MORNING RESULTING IN A
DECREASE IN ACTIVITY. WITH THE SURFACE FRONT TO THE SOUTH THE
INSTABILITY GRADIENT IS ALSO TO THE SOUTH WITH A WESTERLY LOW LEVEL
JET ABOVE IT SUGGESTING THAT THE CONVECTION ACROSS SOUTHWEST IOWA
WOULD NOT BE A FACTOR TOO FAR NORTH OF ITS CURRENT LATITUDE. ONCE
THE CURRENT SHOWER ACTIVITY EXITS IT APPEARS THAT MOST AREAS WILL
REMAIN DRY FOR THE REST OF THE DAY BUT FAR SOUTHERN AREAS DO HAVE A
CHANCE TO SEE SOME SHOWERS AND STORMS THIS MORNING GIVEN THE
WESTERLY LOW LEVEL JET ALONG THE BOUNDARY AND MID LEVEL MOISTURE
GRADIENT BUT WARM/MOIST ADVECTION IS PRETTY WEAK. HIGH TEMPERATURES
WILL RANGE FROM THE UPPER 70S NORTH TO MID 80S SOUTH WITH A
NORTHEAST WIND HOLDING LAKEFRONT AREAS TO THE LOWER TO MID 70S.

TONIGHT AND THURSDAY...AS THE UPPER TROUGH SHIFTS EAST THE RIDGING
DOWNSTREAM OF THE CUTOFF LOW TO THE WEST WILL PIVOT ACROSS THE
CENTRAL PLAINS. SURFACE LOW PRESSURE WILL BE DEVELOPING ACROSS
EASTERN COLORADO AND WESTERN KANSAS WHICH WILL DRIVE THE FRONTAL
BOUNDARY NORTHEASTWARD ACROSS THE CENTRAL PLAINS WITH THE NEARBY
PORTION OF THE FRONT REMAINING SOUTH OF THE AREA INTO THURSDAY
EVENING. WITH WARM ADVECTION INCREASING ALOFT WITH THE RIDGE
BUILDING BACK IN TONIGHT SHOWERS AND THUNDERSTORMS ARE EXPECTED TO
BE MOVING EAST-NORTHEAST ACROSS IOWA/MISSOURI. SOME OF THIS ACTIVITY
MAY REACH THE WESTERN CWA VERY LATE TONIGHT AND MAY END UP SEEING A
SIMILAR SITUATION TO RECENT DAYS WITH REMNANT CONVECTION FESTERING
AND/OR SPAWNING NEW DEVELOPMENT ACROSS THE CWA THURSDAY
MORNING/AFTERNOON. THE MAIN SURFACE LOW AND UPPER WAVE IS EXPECTED
TO BE MOVING ACROSS IOWA/MINNESOTA/WISCONSIN SO THE BULK OF THE
CONVECTION MAY STAY TO THE NORTHWEST OF THE LOCAL AREA. WILL FOCUS
HIGHEST POPS ACROSS THE WESTERN CWA AND SLOW DOWN THE ARRIVAL UNTIL
LATER TONIGHT. THURSDAY LOOKS TO BE SLIGHTLY WARMER...ESPECIALLY
WITH CONVECTION LOOKING TO BE MORE SCATTERED IN COVERAGE.

FRIDAY THROUGH EARLY NEXT WEEK...THE UPPER TROUGH WILL START TO MAKE
QUICKER EAST-NORTHEAST PROGRESS THANKS TO ANOTHER LARGE SCALE UPPER
TROUGH PUSHING INTO THE WESTERN U.S./CANADA. THIS WILL TAKE ANOTHER
SURFACE LOW NORTHEASTWARD WITH IT WHICH WILL LIKELY TRACK NORTHWEST
OF THE AREA SATURDAY. FRIDAY SHOULD SEE A NOTICEABLE WARM UP WITH
ANOTHER LULL IN WIDESPREAD CONVECTION WITH IT FOCUSING TO THE NORTH
AND WEST. WILL HAVE HIGHER POPS SATURDAY WITH THE LOW PASSING BUT AM
SEEING MIXED SIGNALS IN THE TRACK WHICH WILL AFFECT PRECIP COVERAGE.
CHANCES WILL DIMINISH SATURDAY NIGHT WITH QUESTION MARKS SURROUNDING
SUNDAY INTO EARLY NEXT WEEK WITH THE GFS SHOWING A MORE ACTIVE FLOW
WHILE THE ECMWF IS QUIETER THOUGH IT DOES BRING A FRONT THROUGH THE
AREA TUESDAY. DO NOT SEE MUCH OF A COOL DOWN OVERALL AND A DRY
FORECAST SUNDAY/MONDAY WOULD COINCIDE WITH A WARMING TREND IF IT
COMES TO PASS. WILL CONTINUE WITH MID TO UPPER 80S FRIDAY WITH
READINGS SEVERAL DEGREES COOLER SATURDAY AND SUNDAY.

MDB

&&

.AVIATION...

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

* NE TO E WINDS ARND 10 KT EARLY THIS AFTN.

* E WINDS THURSDAY MORNING.

JEE

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

HIGH PRESSURE WILL CONTINUE MOVING ACROSS THE UPPER MIDWEST AND
NORTHERN LAKES TODAY AND TONIGHT. THIS WILL MAINTAIN NORTHEAST
WINDS TODAY TURNING MORE EASTERLY OVERNIGHT IN THURSDAY MORNING.
THE GRADIENT MAY TIGHTEN JUST A BIT THIS AFTERNOON ALLOWING SPEEDS
IN THE 10KT RANGE...PERHAPS A BIT HIGHER IN THE MID/LATE AFTERNOON.

LOWER VFR CLOUDS...3-5KFT...HAVE BEEN SCATTERING OUT OVER THE PAST
FEW HOURS. WILL CONTINUE TO SEE MID CLOUDS THIS MORNING WITH HIGH
CLOUDS EXPECTED THIS AFTERNOON AND TONIGHT. MORE MID CLOUDS
POSSIBLE OVERNIGHT INTO THURSDAY MORNING. CMS

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

* HIGH CONFIDENCE IN ALL OTHER FORECAST PARAMETERS.

JEE

//OUTLOOK FOR ORD/MDW FOR 00Z FRIDAY-12Z WEDNESDAY...UPDATED 12Z...

* THURSDAY NIGHT AND FRIDAY...CHANCE OF TSRA.
* SATURDAY...TSRA LIKELY.
* SUNDAY THROUGH TUESDAY...CHANCE OF TSRA.

&&

.MARINE...

307 AM...HIGH PRESSURE CENTERED OVER MINNESOTA EARLY THIS MORNING
WILL MOVE ACROSS THE LAKES REGION TODAY AND TONIGHT. AS IT DOES
THE GRADIENT WILL SLOWLY WEAKEN OVER NORTHERN LAKE MICHIGAN WHILE
IT SLOWLY TIGHTENS OVER THE SOUTHERN PORTION OF THE LAKE. SPEEDS
WILL INCREASE INTO THE 10-20KT RANGE. AS THE HIGH SHIFTS EAST...
WINDS WILL TURN MORE EASTERLY BY THURSDAY MORNING THEN SHIFT
SOUTHEAST TO SOUTHERLY THURSDAY NIGHT AS A WARM FRONT LIFTS NORTH
ACROSS THE LAKE. THE GRADIENT COULD TIGHTEN ENOUGH FOR A PERIOD OF
15-25 KTS THURSDAY NIGHT INTO FRIDAY. A FRONTAL BOUNDARY IS THEN
EXPECTED TO MOVE SOUTH ACROSS THE LAKE SATURDAY AFTERNOON INTO
SATURDAY EVENING. BUT AT THE SAME TIME...LOW PRESSURE IS EXPECTED
TO DEVELOP OVER THE WESTERN LAKES AND THEN MOVE ACROSS NORTHERN
LAKE MICHIGAN BY SUNDAY MORNING. THIS MAKES FOR A CHALLENGING WIND
FORECAST. IF THE LOW BEGINS TO DEEPEN...NORTHERLY WINDS MAY
INCREASE INTO THE 15-25KT RANGE. CHANGES CAN BE EXPECTED DURING
THIS TIME PERIOD AS TRENDS EMERGE. WINDS THEN QUICKLY TURN BACK
SOUTHERLY SUNDAY NIGHT INTO MONDAY. CMS

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO







000
FXUS63 KLOT 271406
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
906 AM CDT WED AUG 27 2014

.DISCUSSION...
321 AM CDT

CONVECTIVE TRENDS REMAIN THE MAIN FOCUS OF THE FORECAST THROUGH THE
WEEKEND. WATER VAPOR IMAGERY SHOWS A SPLIT UPPER FLOW WITH A
NORTHERN STREAM OF PROGRESSIVE FLOW RUNNING ACROSS SOUTHERN CANADA
INTO THE UPPER GREAT LAKES. A LOW AMPLITUDE TROUGH AXIS IS
TRAVERSING THE FLOW AND MOVING INTO WISCONSIN AT THE CURRENT TIME.
THE SOUTHERN STREAM FEATURES A CUTOFF UPPER LOW WHICH IS OVER UTAH
AND SLOWLY MOVING EASTWARD. UPPER RIDGING IS STARTING TO BUILD JUST
DOWNSTREAM OF THE UPPER LOW WITH SEVERAL EMBEDDED WAVES MOVING
NORTHEASTWARD AHEAD OF THE LOW. AT THE SURFACE...THE FRONTAL
BOUNDARY WHICH HAS BEEN DISCUSSED OVER THE PAST SEVERAL DAYS IS NOW
SOUTH OF THE CWA AND RUNS EAST-NORTHEAST ACROSS THE LOWER GREAT
LAKES AND ST. LAWRENCE RIVER VALLEY. HIGH PRESSURE HAS SPREAD ACROSS
THE UPPER MIDWEST WITH ITS SOUTHERN FLANK INTO THE FORECAST AREA.

TODAY...THE NORTHERN STREAM UPPER TROUGH AXIS WILL
CROSS THE LOCAL AREA THIS MORNING. THE GREATEST ASCENT ASSOCIATED
WITH IT IS TO THE NORTH AND IS GENERATING BANDS OF SHOWERS ACROSS
WISCONSIN...WITH ADDITIONAL RETURNS WORKING ACROSS CENTRAL IOWA INTO
NORTHERN ILLINOIS. THIS ACTIVITY SEEMS TO BE IN BETTER CONJUNCTION
WITH THE RIGHT ENTRANCE REGION OF AN UPPER JET MAX TO THE NORTH IN
ADDITION TO A BROAD AREA OF HEIGHT FALLS INDUCED BY THE UPPER
TROUGH. A CLUSTER OF THUNDERSTORMS HAS ALSO DEVELOPED ACROSS SW IOWA
IN RESPONSE TO BETTER FOCUSED MID LEVEL WARM ADVECTION. MOST OF THIS
UPPER SUPPORT WILL BE PASSING BY THIS MORNING RESULTING IN A
DECREASE IN ACTIVITY. WITH THE SURFACE FRONT TO THE SOUTH THE
INSTABILITY GRADIENT IS ALSO TO THE SOUTH WITH A WESTERLY LOW LEVEL
JET ABOVE IT SUGGESTING THAT THE CONVECTION ACROSS SOUTHWEST IOWA
WOULD NOT BE A FACTOR TOO FAR NORTH OF ITS CURRENT LATITUDE. ONCE
THE CURRENT SHOWER ACTIVITY EXITS IT APPEARS THAT MOST AREAS WILL
REMAIN DRY FOR THE REST OF THE DAY BUT FAR SOUTHERN AREAS DO HAVE A
CHANCE TO SEE SOME SHOWERS AND STORMS THIS MORNING GIVEN THE
WESTERLY LOW LEVEL JET ALONG THE BOUNDARY AND MID LEVEL MOISTURE
GRADIENT BUT WARM/MOIST ADVECTION IS PRETTY WEAK. HIGH TEMPERATURES
WILL RANGE FROM THE UPPER 70S NORTH TO MID 80S SOUTH WITH A
NORTHEAST WIND HOLDING LAKEFRONT AREAS TO THE LOWER TO MID 70S.

TONIGHT AND THURSDAY...AS THE UPPER TROUGH SHIFTS EAST THE RIDGING
DOWNSTREAM OF THE CUTOFF LOW TO THE WEST WILL PIVOT ACROSS THE
CENTRAL PLAINS. SURFACE LOW PRESSURE WILL BE DEVELOPING ACROSS
EASTERN COLORADO AND WESTERN KANSAS WHICH WILL DRIVE THE FRONTAL
BOUNDARY NORTHEASTWARD ACROSS THE CENTRAL PLAINS WITH THE NEARBY
PORTION OF THE FRONT REMAINING SOUTH OF THE AREA INTO THURSDAY
EVENING. WITH WARM ADVECTION INCREASING ALOFT WITH THE RIDGE
BUILDING BACK IN TONIGHT SHOWERS AND THUNDERSTORMS ARE EXPECTED TO
BE MOVING EAST-NORTHEAST ACROSS IOWA/MISSOURI. SOME OF THIS ACTIVITY
MAY REACH THE WESTERN CWA VERY LATE TONIGHT AND MAY END UP SEEING A
SIMILAR SITUATION TO RECENT DAYS WITH REMNANT CONVECTION FESTERING
AND/OR SPAWNING NEW DEVELOPMENT ACROSS THE CWA THURSDAY
MORNING/AFTERNOON. THE MAIN SURFACE LOW AND UPPER WAVE IS EXPECTED
TO BE MOVING ACROSS IOWA/MINNESOTA/WISCONSIN SO THE BULK OF THE
CONVECTION MAY STAY TO THE NORTHWEST OF THE LOCAL AREA. WILL FOCUS
HIGHEST POPS ACROSS THE WESTERN CWA AND SLOW DOWN THE ARRIVAL UNTIL
LATER TONIGHT. THURSDAY LOOKS TO BE SLIGHTLY WARMER...ESPECIALLY
WITH CONVECTION LOOKING TO BE MORE SCATTERED IN COVERAGE.

FRIDAY THROUGH EARLY NEXT WEEK...THE UPPER TROUGH WILL START TO MAKE
QUICKER EAST-NORTHEAST PROGRESS THANKS TO ANOTHER LARGE SCALE UPPER
TROUGH PUSHING INTO THE WESTERN U.S./CANADA. THIS WILL TAKE ANOTHER
SURFACE LOW NORTHEASTWARD WITH IT WHICH WILL LIKELY TRACK NORTHWEST
OF THE AREA SATURDAY. FRIDAY SHOULD SEE A NOTICEABLE WARM UP WITH
ANOTHER LULL IN WIDESPREAD CONVECTION WITH IT FOCUSING TO THE NORTH
AND WEST. WILL HAVE HIGHER POPS SATURDAY WITH THE LOW PASSING BUT AM
SEEING MIXED SIGNALS IN THE TRACK WHICH WILL AFFECT PRECIP COVERAGE.
CHANCES WILL DIMINISH SATURDAY NIGHT WITH QUESTION MARKS SURROUNDING
SUNDAY INTO EARLY NEXT WEEK WITH THE GFS SHOWING A MORE ACTIVE FLOW
WHILE THE ECMWF IS QUIETER THOUGH IT DOES BRING A FRONT THROUGH THE
AREA TUESDAY. DO NOT SEE MUCH OF A COOL DOWN OVERALL AND A DRY
FORECAST SUNDAY/MONDAY WOULD COINCIDE WITH A WARMING TREND IF IT
COMES TO PASS. WILL CONTINUE WITH MID TO UPPER 80S FRIDAY WITH
READINGS SEVERAL DEGREES COOLER SATURDAY AND SUNDAY.

MDB

&&

.AVIATION...

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

* NE TO E WINDS ARND 10 KT EARLY THIS AFTN.

* E WINDS THURSDAY MORNING.

JEE

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

HIGH PRESSURE WILL CONTINUE MOVING ACROSS THE UPPER MIDWEST AND
NORTHERN LAKES TODAY AND TONIGHT. THIS WILL MAINTAIN NORTHEAST
WINDS TODAY TURNING MORE EASTERLY OVERNIGHT IN THURSDAY MORNING.
THE GRADIENT MAY TIGHTEN JUST A BIT THIS AFTERNOON ALLOWING SPEEDS
IN THE 10KT RANGE...PERHAPS A BIT HIGHER IN THE MID/LATE AFTERNOON.

LOWER VFR CLOUDS...3-5KFT...HAVE BEEN SCATTERING OUT OVER THE PAST
FEW HOURS. WILL CONTINUE TO SEE MID CLOUDS THIS MORNING WITH HIGH
CLOUDS EXPECTED THIS AFTERNOON AND TONIGHT. MORE MID CLOUDS
POSSIBLE OVERNIGHT INTO THURSDAY MORNING. CMS

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

* MEDIUM CONFIDENCE IN E WIND SPEEDS...MAY BCM 10 KT QUICKER THAN
  FORECAST.

* HIGH CONFIDENCE IN ALL OTHER FORECAST PARAMETERS.

JEE

//OUTLOOK FOR ORD/MDW FOR 00Z FRIDAY-12Z WEDNESDAY...UPDATED 12Z...

* THURSDAY NIGHT AND FRIDAY...CHANCE OF TSRA.
* SATURDAY...TSRA LIKELY.
* SUNDAY THROUGH TUESDAY...CHANCE OF TSRA.

&&

.MARINE...

307 AM...HIGH PRESSURE CENTERED OVER MINNESOTA EARLY THIS MORNING
WILL MOVE ACROSS THE LAKES REGION TODAY AND TONIGHT. AS IT DOES
THE GRADIENT WILL SLOWLY WEAKEN OVER NORTHERN LAKE MICHIGAN WHILE
IT SLOWLY TIGHTENS OVER THE SOUTHERN PORTION OF THE LAKE. SPEEDS
WILL INCREASE INTO THE 10-20KT RANGE. AS THE HIGH SHIFTS EAST...
WINDS WILL TURN MORE EASTERLY BY THURSDAY MORNING THEN SHIFT
SOUTHEAST TO SOUTHERLY THURSDAY NIGHT AS A WARM FRONT LIFTS NORTH
ACROSS THE LAKE. THE GRADIENT COULD TIGHTEN ENOUGH FOR A PERIOD OF
15-25 KTS THURSDAY NIGHT INTO FRIDAY. A FRONTAL BOUNDARY IS THEN
EXPECTED TO MOVE SOUTH ACROSS THE LAKE SATURDAY AFTERNOON INTO
SATURDAY EVENING. BUT AT THE SAME TIME...LOW PRESSURE IS EXPECTED
TO DEVELOP OVER THE WESTERN LAKES AND THEN MOVE ACROSS NORTHERN
LAKE MICHIGAN BY SUNDAY MORNING. THIS MAKES FOR A CHALLENGING WIND
FORECAST. IF THE LOW BEGINS TO DEEPEN...NORTHERLY WINDS MAY
INCREASE INTO THE 15-25KT RANGE. CHANGES CAN BE EXPECTED DURING
THIS TIME PERIOD AS TRENDS EMERGE. WINDS THEN QUICKLY TURN BACK
SOUTHERLY SUNDAY NIGHT INTO MONDAY. CMS

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 271406
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
906 AM CDT WED AUG 27 2014

.DISCUSSION...
321 AM CDT

CONVECTIVE TRENDS REMAIN THE MAIN FOCUS OF THE FORECAST THROUGH THE
WEEKEND. WATER VAPOR IMAGERY SHOWS A SPLIT UPPER FLOW WITH A
NORTHERN STREAM OF PROGRESSIVE FLOW RUNNING ACROSS SOUTHERN CANADA
INTO THE UPPER GREAT LAKES. A LOW AMPLITUDE TROUGH AXIS IS
TRAVERSING THE FLOW AND MOVING INTO WISCONSIN AT THE CURRENT TIME.
THE SOUTHERN STREAM FEATURES A CUTOFF UPPER LOW WHICH IS OVER UTAH
AND SLOWLY MOVING EASTWARD. UPPER RIDGING IS STARTING TO BUILD JUST
DOWNSTREAM OF THE UPPER LOW WITH SEVERAL EMBEDDED WAVES MOVING
NORTHEASTWARD AHEAD OF THE LOW. AT THE SURFACE...THE FRONTAL
BOUNDARY WHICH HAS BEEN DISCUSSED OVER THE PAST SEVERAL DAYS IS NOW
SOUTH OF THE CWA AND RUNS EAST-NORTHEAST ACROSS THE LOWER GREAT
LAKES AND ST. LAWRENCE RIVER VALLEY. HIGH PRESSURE HAS SPREAD ACROSS
THE UPPER MIDWEST WITH ITS SOUTHERN FLANK INTO THE FORECAST AREA.

TODAY...THE NORTHERN STREAM UPPER TROUGH AXIS WILL
CROSS THE LOCAL AREA THIS MORNING. THE GREATEST ASCENT ASSOCIATED
WITH IT IS TO THE NORTH AND IS GENERATING BANDS OF SHOWERS ACROSS
WISCONSIN...WITH ADDITIONAL RETURNS WORKING ACROSS CENTRAL IOWA INTO
NORTHERN ILLINOIS. THIS ACTIVITY SEEMS TO BE IN BETTER CONJUNCTION
WITH THE RIGHT ENTRANCE REGION OF AN UPPER JET MAX TO THE NORTH IN
ADDITION TO A BROAD AREA OF HEIGHT FALLS INDUCED BY THE UPPER
TROUGH. A CLUSTER OF THUNDERSTORMS HAS ALSO DEVELOPED ACROSS SW IOWA
IN RESPONSE TO BETTER FOCUSED MID LEVEL WARM ADVECTION. MOST OF THIS
UPPER SUPPORT WILL BE PASSING BY THIS MORNING RESULTING IN A
DECREASE IN ACTIVITY. WITH THE SURFACE FRONT TO THE SOUTH THE
INSTABILITY GRADIENT IS ALSO TO THE SOUTH WITH A WESTERLY LOW LEVEL
JET ABOVE IT SUGGESTING THAT THE CONVECTION ACROSS SOUTHWEST IOWA
WOULD NOT BE A FACTOR TOO FAR NORTH OF ITS CURRENT LATITUDE. ONCE
THE CURRENT SHOWER ACTIVITY EXITS IT APPEARS THAT MOST AREAS WILL
REMAIN DRY FOR THE REST OF THE DAY BUT FAR SOUTHERN AREAS DO HAVE A
CHANCE TO SEE SOME SHOWERS AND STORMS THIS MORNING GIVEN THE
WESTERLY LOW LEVEL JET ALONG THE BOUNDARY AND MID LEVEL MOISTURE
GRADIENT BUT WARM/MOIST ADVECTION IS PRETTY WEAK. HIGH TEMPERATURES
WILL RANGE FROM THE UPPER 70S NORTH TO MID 80S SOUTH WITH A
NORTHEAST WIND HOLDING LAKEFRONT AREAS TO THE LOWER TO MID 70S.

TONIGHT AND THURSDAY...AS THE UPPER TROUGH SHIFTS EAST THE RIDGING
DOWNSTREAM OF THE CUTOFF LOW TO THE WEST WILL PIVOT ACROSS THE
CENTRAL PLAINS. SURFACE LOW PRESSURE WILL BE DEVELOPING ACROSS
EASTERN COLORADO AND WESTERN KANSAS WHICH WILL DRIVE THE FRONTAL
BOUNDARY NORTHEASTWARD ACROSS THE CENTRAL PLAINS WITH THE NEARBY
PORTION OF THE FRONT REMAINING SOUTH OF THE AREA INTO THURSDAY
EVENING. WITH WARM ADVECTION INCREASING ALOFT WITH THE RIDGE
BUILDING BACK IN TONIGHT SHOWERS AND THUNDERSTORMS ARE EXPECTED TO
BE MOVING EAST-NORTHEAST ACROSS IOWA/MISSOURI. SOME OF THIS ACTIVITY
MAY REACH THE WESTERN CWA VERY LATE TONIGHT AND MAY END UP SEEING A
SIMILAR SITUATION TO RECENT DAYS WITH REMNANT CONVECTION FESTERING
AND/OR SPAWNING NEW DEVELOPMENT ACROSS THE CWA THURSDAY
MORNING/AFTERNOON. THE MAIN SURFACE LOW AND UPPER WAVE IS EXPECTED
TO BE MOVING ACROSS IOWA/MINNESOTA/WISCONSIN SO THE BULK OF THE
CONVECTION MAY STAY TO THE NORTHWEST OF THE LOCAL AREA. WILL FOCUS
HIGHEST POPS ACROSS THE WESTERN CWA AND SLOW DOWN THE ARRIVAL UNTIL
LATER TONIGHT. THURSDAY LOOKS TO BE SLIGHTLY WARMER...ESPECIALLY
WITH CONVECTION LOOKING TO BE MORE SCATTERED IN COVERAGE.

FRIDAY THROUGH EARLY NEXT WEEK...THE UPPER TROUGH WILL START TO MAKE
QUICKER EAST-NORTHEAST PROGRESS THANKS TO ANOTHER LARGE SCALE UPPER
TROUGH PUSHING INTO THE WESTERN U.S./CANADA. THIS WILL TAKE ANOTHER
SURFACE LOW NORTHEASTWARD WITH IT WHICH WILL LIKELY TRACK NORTHWEST
OF THE AREA SATURDAY. FRIDAY SHOULD SEE A NOTICEABLE WARM UP WITH
ANOTHER LULL IN WIDESPREAD CONVECTION WITH IT FOCUSING TO THE NORTH
AND WEST. WILL HAVE HIGHER POPS SATURDAY WITH THE LOW PASSING BUT AM
SEEING MIXED SIGNALS IN THE TRACK WHICH WILL AFFECT PRECIP COVERAGE.
CHANCES WILL DIMINISH SATURDAY NIGHT WITH QUESTION MARKS SURROUNDING
SUNDAY INTO EARLY NEXT WEEK WITH THE GFS SHOWING A MORE ACTIVE FLOW
WHILE THE ECMWF IS QUIETER THOUGH IT DOES BRING A FRONT THROUGH THE
AREA TUESDAY. DO NOT SEE MUCH OF A COOL DOWN OVERALL AND A DRY
FORECAST SUNDAY/MONDAY WOULD COINCIDE WITH A WARMING TREND IF IT
COMES TO PASS. WILL CONTINUE WITH MID TO UPPER 80S FRIDAY WITH
READINGS SEVERAL DEGREES COOLER SATURDAY AND SUNDAY.

MDB

&&

.AVIATION...

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

* NE TO E WINDS ARND 10 KT EARLY THIS AFTN.

* E WINDS THURSDAY MORNING.

JEE

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

HIGH PRESSURE WILL CONTINUE MOVING ACROSS THE UPPER MIDWEST AND
NORTHERN LAKES TODAY AND TONIGHT. THIS WILL MAINTAIN NORTHEAST
WINDS TODAY TURNING MORE EASTERLY OVERNIGHT IN THURSDAY MORNING.
THE GRADIENT MAY TIGHTEN JUST A BIT THIS AFTERNOON ALLOWING SPEEDS
IN THE 10KT RANGE...PERHAPS A BIT HIGHER IN THE MID/LATE AFTERNOON.

LOWER VFR CLOUDS...3-5KFT...HAVE BEEN SCATTERING OUT OVER THE PAST
FEW HOURS. WILL CONTINUE TO SEE MID CLOUDS THIS MORNING WITH HIGH
CLOUDS EXPECTED THIS AFTERNOON AND TONIGHT. MORE MID CLOUDS
POSSIBLE OVERNIGHT INTO THURSDAY MORNING. CMS

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

* MEDIUM CONFIDENCE IN E WIND SPEEDS...MAY BCM 10 KT QUICKER THAN
  FORECAST.

* HIGH CONFIDENCE IN ALL OTHER FORECAST PARAMETERS.

JEE

//OUTLOOK FOR ORD/MDW FOR 00Z FRIDAY-12Z WEDNESDAY...UPDATED 12Z...

* THURSDAY NIGHT AND FRIDAY...CHANCE OF TSRA.
* SATURDAY...TSRA LIKELY.
* SUNDAY THROUGH TUESDAY...CHANCE OF TSRA.

&&

.MARINE...

307 AM...HIGH PRESSURE CENTERED OVER MINNESOTA EARLY THIS MORNING
WILL MOVE ACROSS THE LAKES REGION TODAY AND TONIGHT. AS IT DOES
THE GRADIENT WILL SLOWLY WEAKEN OVER NORTHERN LAKE MICHIGAN WHILE
IT SLOWLY TIGHTENS OVER THE SOUTHERN PORTION OF THE LAKE. SPEEDS
WILL INCREASE INTO THE 10-20KT RANGE. AS THE HIGH SHIFTS EAST...
WINDS WILL TURN MORE EASTERLY BY THURSDAY MORNING THEN SHIFT
SOUTHEAST TO SOUTHERLY THURSDAY NIGHT AS A WARM FRONT LIFTS NORTH
ACROSS THE LAKE. THE GRADIENT COULD TIGHTEN ENOUGH FOR A PERIOD OF
15-25 KTS THURSDAY NIGHT INTO FRIDAY. A FRONTAL BOUNDARY IS THEN
EXPECTED TO MOVE SOUTH ACROSS THE LAKE SATURDAY AFTERNOON INTO
SATURDAY EVENING. BUT AT THE SAME TIME...LOW PRESSURE IS EXPECTED
TO DEVELOP OVER THE WESTERN LAKES AND THEN MOVE ACROSS NORTHERN
LAKE MICHIGAN BY SUNDAY MORNING. THIS MAKES FOR A CHALLENGING WIND
FORECAST. IF THE LOW BEGINS TO DEEPEN...NORTHERLY WINDS MAY
INCREASE INTO THE 15-25KT RANGE. CHANGES CAN BE EXPECTED DURING
THIS TIME PERIOD AS TRENDS EMERGE. WINDS THEN QUICKLY TURN BACK
SOUTHERLY SUNDAY NIGHT INTO MONDAY. CMS

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO







000
FXUS63 KLOT 271132
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
632 AM CDT WED AUG 27 2014

.DISCUSSION...
321 AM CDT

CONVECTIVE TRENDS REMAIN THE MAIN FOCUS OF THE FORECAST THROUGH THE
WEEKEND. WATER VAPOR IMAGERY SHOWS A SPLIT UPPER FLOW WITH A
NORTHERN STREAM OF PROGRESSIVE FLOW RUNNING ACROSS SOUTHERN CANADA
INTO THE UPPER GREAT LAKES. A LOW AMPLITUDE TROUGH AXIS IS
TRAVERSING THE FLOW AND MOVING INTO WISCONSIN AT THE CURRENT TIME.
THE SOUTHERN STREAM FEATURES A CUTOFF UPPER LOW WHICH IS OVER UTAH
AND SLOWLY MOVING EASTWARD. UPPER RIDGING IS STARTING TO BUILD JUST
DOWNSTREAM OF THE UPPER LOW WITH SEVERAL EMBEDDED WAVES MOVING
NORTHEASTWARD AHEAD OF THE LOW. AT THE SURFACE...THE FRONTAL
BOUNDARY WHICH HAS BEEN DISCUSSED OVER THE PAST SEVERAL DAYS IS NOW
SOUTH OF THE CWA AND RUNS EAST-NORTHEAST ACROSS THE LOWER GREAT
LAKES AND ST. LAWRENCE RIVER VALLEY. HIGH PRESSURE HAS SPREAD ACROSS
THE UPPER MIDWEST WITH ITS SOUTHERN FLANK INTO THE FORECAST AREA.

TODAY...THE NORTHERN STREAM UPPER TROUGH AXIS WILL
CROSS THE LOCAL AREA THIS MORNING. THE GREATEST ASCENT ASSOCIATED
WITH IT IS TO THE NORTH AND IS GENERATING BANDS OF SHOWERS ACROSS
WISCONSIN...WITH ADDITIONAL RETURNS WORKING ACROSS CENTRAL IOWA INTO
NORTHERN ILLINOIS. THIS ACTIVITY SEEMS TO BE IN BETTER CONJUNCTION
WITH THE RIGHT ENTRANCE REGION OF AN UPPER JET MAX TO THE NORTH IN
ADDITION TO A BROAD AREA OF HEIGHT FALLS INDUCED BY THE UPPER
TROUGH. A CLUSTER OF THUNDERSTORMS HAS ALSO DEVELOPED ACROSS SW IOWA
IN RESPONSE TO BETTER FOCUSED MID LEVEL WARM ADVECTION. MOST OF THIS
UPPER SUPPORT WILL BE PASSING BY THIS MORNING RESULTING IN A
DECREASE IN ACTIVITY. WITH THE SURFACE FRONT TO THE SOUTH THE
INSTABILITY GRADIENT IS ALSO TO THE SOUTH WITH A WESTERLY LOW LEVEL
JET ABOVE IT SUGGESTING THAT THE CONVECTION ACROSS SOUTHWEST IOWA
WOULD NOT BE A FACTOR TOO FAR NORTH OF ITS CURRENT LATITUDE. ONCE
THE CURRENT SHOWER ACTIVITY EXITS IT APPEARS THAT MOST AREAS WILL
REMAIN DRY FOR THE REST OF THE DAY BUT FAR SOUTHERN AREAS DO HAVE A
CHANCE TO SEE SOME SHOWERS AND STORMS THIS MORNING GIVEN THE
WESTERLY LOW LEVEL JET ALONG THE BOUNDARY AND MID LEVEL MOISTURE
GRADIENT BUT WARM/MOIST ADVECTION IS PRETTY WEAK. HIGH TEMPERATURES
WILL RANGE FROM THE UPPER 70S NORTH TO MID 80S SOUTH WITH A
NORTHEAST WIND HOLDING LAKEFRONT AREAS TO THE LOWER TO MID 70S.

TONIGHT AND THURSDAY...AS THE UPPER TROUGH SHIFTS EAST THE RIDGING
DOWNSTREAM OF THE CUTOFF LOW TO THE WEST WILL PIVOT ACROSS THE
CENTRAL PLAINS. SURFACE LOW PRESSURE WILL BE DEVELOPING ACROSS
EASTERN COLORADO AND WESTERN KANSAS WHICH WILL DRIVE THE FRONTAL
BOUNDARY NORTHEASTWARD ACROSS THE CENTRAL PLAINS WITH THE NEARBY
PORTION OF THE FRONT REMAINING SOUTH OF THE AREA INTO THURSDAY
EVENING. WITH WARM ADVECTION INCREASING ALOFT WITH THE RIDGE
BUILDING BACK IN TONIGHT SHOWERS AND THUNDERSTORMS ARE EXPECTED TO
BE MOVING EAST-NORTHEAST ACROSS IOWA/MISSOURI. SOME OF THIS ACTIVITY
MAY REACH THE WESTERN CWA VERY LATE TONIGHT AND MAY END UP SEEING A
SIMILAR SITUATION TO RECENT DAYS WITH REMNANT CONVECTION FESTERING
AND/OR SPAWNING NEW DEVELOPMENT ACROSS THE CWA THURSDAY
MORNING/AFTERNOON. THE MAIN SURFACE LOW AND UPPER WAVE IS EXPECTED
TO BE MOVING ACROSS IOWA/MINNESOTA/WISCONSIN SO THE BULK OF THE
CONVECTION MAY STAY TO THE NORTHWEST OF THE LOCAL AREA. WILL FOCUS
HIGHEST POPS ACROSS THE WESTERN CWA AND SLOW DOWN THE ARRIVAL UNTIL
LATER TONIGHT. THURSDAY LOOKS TO BE SLIGHTLY WARMER...ESPECIALLY
WITH CONVECTION LOOKING TO BE MORE SCATTERED IN COVERAGE.

FRIDAY THROUGH EARLY NEXT WEEK...THE UPPER TROUGH WILL START TO MAKE
QUICKER EAST-NORTHEAST PROGRESS THANKS TO ANOTHER LARGE SCALE UPPER
TROUGH PUSHING INTO THE WESTERN U.S./CANADA. THIS WILL TAKE ANOTHER
SURFACE LOW NORTHEASTWARD WITH IT WHICH WILL LIKELY TRACK NORTHWEST
OF THE AREA SATURDAY. FRIDAY SHOULD SEE A NOTICEABLE WARM UP WITH
ANOTHER LULL IN WIDESPREAD CONVECTION WITH IT FOCUSING TO THE NORTH
AND WEST. WILL HAVE HIGHER POPS SATURDAY WITH THE LOW PASSING BUT AM
SEEING MIXED SIGNALS IN THE TRACK WHICH WILL AFFECT PRECIP COVERAGE.
CHANCES WILL DIMINISH SATURDAY NIGHT WITH QUESTION MARKS SURROUNDING
SUNDAY INTO EARLY NEXT WEEK WITH THE GFS SHOWING A MORE ACTIVE FLOW
WHILE THE ECMWF IS QUIETER THOUGH IT DOES BRING A FRONT THROUGH THE
AREA TUESDAY. DO NOT SEE MUCH OF A COOL DOWN OVERALL AND A DRY
FORECAST SUNDAY/MONDAY WOULD COINCIDE WITH A WARMING TREND IF IT
COMES TO PASS. WILL CONTINUE WITH MID TO UPPER 80S FRIDAY WITH
READINGS SEVERAL DEGREES COOLER SATURDAY AND SUNDAY.

MDB

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 12Z...

* NORTHEAST WINDS THRU TONIGHT...POSSIBLY AROUND 10KT THIS
  AFTERNOON.
* EAST WINDS THURSDAY MORNING. CMS

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

HIGH PRESSURE WILL CONTINUE MOVING ACROSS THE UPPER MIDWEST AND
NORTHERN LAKES TODAY AND TONIGHT. THIS WILL MAINTAIN NORTHEAST
WINDS TODAY TURNING MORE EASTERLY OVERNIGHT IN THURSDAY MORNING.
THE GRADIENT MAY TIGHTEN JUST A BIT THIS AFTERNOON ALLOWING SPEEDS
IN THE 10KT RANGE...PERHAPS A BIT HIGHER IN THE MID/LATE AFTERNOON.

LOWER VFR CLOUDS...3-5KFT...HAVE BEEN SCATTERING OUT OVER THE PAST
FEW HOURS. WILL CONTINUE TO SEE MID CLOUDS THIS MORNING WITH HIGH
CLOUDS EXPECTED THIS AFTERNOON AND TONIGHT. MORE MID CLOUDS
POSSIBLE OVERNIGHT INTO THURSDAY MORNING. CMS

//ORD AND MDW CONFIDENCE...UPDATED 12Z...

* MEDIUM FOR WINDS THRU THE PERIOD. CMS

//OUTLOOK FOR ORD/MDW FOR 00Z FRIDAY-12Z WEDNESDAY...UPDATED 12Z...

* THURSDAY NIGHT AND FRIDAY...CHANCE OF TSRA.
* SATURDAY...TSRA LIKELY.
* SUNDAY THROUGH TUESDAY...CHANCE OF TSRA.

&&

.MARINE...

307 AM...HIGH PRESSURE CENTERED OVER MINNESOTA EARLY THIS MORNING
WILL MOVE ACROSS THE LAKES REGION TODAY AND TONIGHT. AS IT DOES
THE GRADIENT WILL SLOWLY WEAKEN OVER NORTHERN LAKE MICHIGAN WHILE
IT SLOWLY TIGHTENS OVER THE SOUTHERN PORTION OF THE LAKE. SPEEDS
WILL INCREASE INTO THE 10-20KT RANGE. AS THE HIGH SHIFTS EAST...
WINDS WILL TURN MORE EASTERLY BY THURSDAY MORNING THEN SHIFT
SOUTHEAST TO SOUTHERLY THURSDAY NIGHT AS A WARM FRONT LIFTS NORTH
ACROSS THE LAKE. THE GRADIENT COULD TIGHTEN ENOUGH FOR A PERIOD OF
15-25 KTS THURSDAY NIGHT INTO FRIDAY. A FRONTAL BOUNDARY IS THEN
EXPECTED TO MOVE SOUTH ACROSS THE LAKE SATURDAY AFTERNOON INTO
SATURDAY EVENING. BUT AT THE SAME TIME...LOW PRESSURE IS EXPECTED
TO DEVELOP OVER THE WESTERN LAKES AND THEN MOVE ACROSS NORTHERN
LAKE MICHIGAN BY SUNDAY MORNING. THIS MAKES FOR A CHALLENGING WIND
FORECAST. IF THE LOW BEGINS TO DEEPEN...NORTHERLY WINDS MAY
INCREASE INTO THE 15-25KT RANGE. CHANGES CAN BE EXPECTED DURING
THIS TIME PERIOD AS TRENDS EMERGE. WINDS THEN QUICKLY TURN BACK
SOUTHERLY SUNDAY NIGHT INTO MONDAY. CMS

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO







000
FXUS63 KLOT 270906
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
406 AM CDT WED AUG 27 2014

.DISCUSSION...
321 AM CDT

CONVECTIVE TRENDS REMAIN THE MAIN FOCUS OF THE FORECAST THROUGH THE
WEEKEND. WATER VAPOR IMAGERY SHOWS A SPLIT UPPER FLOW WITH A
NORTHERN STREAM OF PROGRESSIVE FLOW RUNNING ACROSS SOUTHERN CANADA
INTO THE UPPER GREAT LAKES. A LOW AMPLITUDE TROUGH AXIS IS
TRAVERSING THE FLOW AND MOVING INTO WISCONSIN AT THE CURRENT TIME.
THE SOUTHERN STREAM FEATURES A CUTOFF UPPER LOW WHICH IS OVER UTAH
AND SLOWLY MOVING EASTWARD. UPPER RIDGING IS STARTING TO BUILD JUST
DOWNSTREAM OF THE UPPER LOW WITH SEVERAL EMBEDDED WAVES MOVING
NORTHEASTWARD AHEAD OF THE LOW. AT THE SURFACE...THE FRONTAL
BOUNDARY WHICH HAS BEEN DISCUSSED OVER THE PAST SEVERAL DAYS IS NOW
SOUTH OF THE CWA AND RUNS EAST-NORTHEAST ACROSS THE LOWER GREAT
LAKES AND ST. LAWRENCE RIVER VALLEY. HIGH PRESSURE HAS SPREAD ACROSS
THE UPPER MIDWEST WITH ITS SOUTHERN FLANK INTO THE FORECAST AREA.

TODAY...THE NORTHERN STREAM UPPER TROUGH AXIS WILL
CROSS THE LOCAL AREA THIS MORNING. THE GREATEST ASCENT ASSOCIATED
WITH IT IS TO THE NORTH AND IS GENERATING BANDS OF SHOWERS ACROSS
WISCONSIN...WITH ADDITIONAL RETURNS WORKING ACROSS CENTRAL IOWA INTO
NORTHERN ILLINOIS. THIS ACTIVITY SEEMS TO BE IN BETTER CONJUNCTION
WITH THE RIGHT ENTRANCE REGION OF AN UPPER JET MAX TO THE NORTH IN
ADDITION TO A BROAD AREA OF HEIGHT FALLS INDUCED BY THE UPPER
TROUGH. A CLUSTER OF THUNDERSTORMS HAS ALSO DEVELOPED ACROSS SW IOWA
IN RESPONSE TO BETTER FOCUSED MID LEVEL WARM ADVECTION. MOST OF THIS
UPPER SUPPORT WILL BE PASSING BY THIS MORNING RESULTING IN A
DECREASE IN ACTIVITY. WITH THE SURFACE FRONT TO THE SOUTH THE
INSTABILITY GRADIENT IS ALSO TO THE SOUTH WITH A WESTERLY LOW LEVEL
JET ABOVE IT SUGGESTING THAT THE CONVECTION ACROSS SOUTHWEST IOWA
WOULD NOT BE A FACTOR TOO FAR NORTH OF ITS CURRENT LATITUDE. ONCE
THE CURRENT SHOWER ACTIVITY EXITS IT APPEARS THAT MOST AREAS WILL
REMAIN DRY FOR THE REST OF THE DAY BUT FAR SOUTHERN AREAS DO HAVE A
CHANCE TO SEE SOME SHOWERS AND STORMS THIS MORNING GIVEN THE
WESTERLY LOW LEVEL JET ALONG THE BOUNDARY AND MID LEVEL MOISTURE
GRADIENT BUT WARM/MOIST ADVECTION IS PRETTY WEAK. HIGH TEMPERATURES
WILL RANGE FROM THE UPPER 70S NORTH TO MID 80S SOUTH WITH A
NORTHEAST WIND HOLDING LAKEFRONT AREAS TO THE LOWER TO MID 70S.

TONIGHT AND THURSDAY...AS THE UPPER TROUGH SHIFTS EAST THE RIDGING
DOWNSTREAM OF THE CUTOFF LOW TO THE WEST WILL PIVOT ACROSS THE
CENTRAL PLAINS. SURFACE LOW PRESSURE WILL BE DEVELOPING ACROSS
EASTERN COLORADO AND WESTERN KANSAS WHICH WILL DRIVE THE FRONTAL
BOUNDARY NORTHEASTWARD ACROSS THE CENTRAL PLAINS WITH THE NEARBY
PORTION OF THE FRONT REMAINING SOUTH OF THE AREA INTO THURSDAY
EVENING. WITH WARM ADVECTION INCREASING ALOFT WITH THE RIDGE
BUILDING BACK IN TONIGHT SHOWERS AND THUNDERSTORMS ARE EXPECTED TO
BE MOVING EAST-NORTHEAST ACROSS IOWA/MISSOURI. SOME OF THIS ACTIVITY
MAY REACH THE WESTERN CWA VERY LATE TONIGHT AND MAY END UP SEEING A
SIMILAR SITUATION TO RECENT DAYS WITH REMNANT CONVECTION FESTERING
AND/OR SPAWNING NEW DEVELOPMENT ACROSS THE CWA THURSDAY
MORNING/AFTERNOON. THE MAIN SURFACE LOW AND UPPER WAVE IS EXPECTED
TO BE MOVING ACROSS IOWA/MINNESOTA/WISCONSIN SO THE BULK OF THE
CONVECTION MAY STAY TO THE NORTHWEST OF THE LOCAL AREA. WILL FOCUS
HIGHEST POPS ACROSS THE WESTERN CWA AND SLOW DOWN THE ARRIVAL UNTIL
LATER TONIGHT. THURSDAY LOOKS TO BE SLIGHTLY WARMER...ESPECIALLY
WITH CONVECTION LOOKING TO BE MORE SCATTERED IN COVERAGE.

FRIDAY THROUGH EARLY NEXT WEEK...THE UPPER TROUGH WILL START TO MAKE
QUICKER EAST-NORTHEAST PROGRESS THANKS TO ANOTHER LARGE SCALE UPPER
TROUGH PUSHING INTO THE WESTERN U.S./CANADA. THIS WILL TAKE ANOTHER
SURFACE LOW NORTHEASTWARD WITH IT WHICH WILL LIKELY TRACK NORTHWEST
OF THE AREA SATURDAY. FRIDAY SHOULD SEE A NOTICEABLE WARM UP WITH
ANOTHER LULL IN WIDESPREAD CONVECTION WITH IT FOCUSING TO THE NORTH
AND WEST. WILL HAVE HIGHER POPS SATURDAY WITH THE LOW PASSING BUT AM
SEEING MIXED SIGNALS IN THE TRACK WHICH WILL AFFECT PRECIP COVERAGE.
CHANCES WILL DIMINISH SATURDAY NIGHT WITH QUESTION MARKS SURROUNDING
SUNDAY INTO EARLY NEXT WEEK WITH THE GFS SHOWING A MORE ACTIVE FLOW
WHILE THE ECMWF IS QUIETER THOUGH IT DOES BRING A FRONT THROUGH THE
AREA TUESDAY. DO NOT SEE MUCH OF A COOL DOWN OVERALL AND A DRY
FORECAST SUNDAY/MONDAY WOULD COINCIDE WITH A WARMING TREND IF IT
COMES TO PASS. WILL CONTINUE WITH MID TO UPPER 80S FRIDAY WITH
READINGS SEVERAL DEGREES COOLER SATURDAY AND SUNDAY.

MDB

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 09Z...

* ISOLATED SHRA THIS MORNING.
* POSSIBLE MVFR CIGS THRU MID MORNING.
* EAST/NORTHEAST WINDS THRU THE PERIOD...POSSIBLY AROUND 10KT THIS
  AFTERNOON. CMS

//DISCUSSION...UPDATED 09Z...

CIGS IN THE 3-4KFT RANGE SHOULD PREVAIL FOR AT LEAST THE NEXT FEW
HOURS. STILL SOME POTENTIAL THESE COULD DIP INTO HIGH MVFR.
ISOLATED SHRA WILL ALSO BE POSSIBLE ACROSS THE TERMINALS THRU MID
MORNING. ANY TSRA THAT DEVELOP SHOULD REMAIN SOUTH OF THE
TERMINALS...AND PERHAPS ACROSS CENTRAL IL. CMS

PREVIOUS 06Z DISCUSSION...

HIGH PRESSURE OVER THE NORTHERN PLAINS WILL MOVE EAST ACROSS THE
LAKES REGION LATER TODAY AND TONIGHT. THIS WILL MAINTAIN EAST/
NORTHEAST WINDS THROUGH THE PERIOD. SPEEDS COULD INCREASE TO 10KTS
OR SLIGHTLY HIGHER THIS AFTERNOON INTO EARLY THIS EVENING WITH A
POSSIBLE LAKE BREEZE.

CIGS AROUND 3KFT HAVE DEVELOPED ACROSS NORTHEAST IL BUT APPEAR TO
BE SHIFTING EAST AND FOR NOW WILL JUST CARRY SCT MENTION. APPEARS
A BKN/OVC MID DECK WILL SPREAD ACROSS MUCH OF THE REGION OVERNIGHT
AND CONTINUE INTO THIS AFTERNOON. SOME FOG IS POSSIBLE WHERE SKIES
REMAIN MOSTLY CLEAR AND GENERALLY SOUTH AND SOUTHEAST OF THE
TERMINALS. CONTINUED FOG MENTION AT GYY BUT CONFIDENCE TOO LOW
ELSEWHERE.

A FEW ECHOS SHOWING UP ON RADAR NEAR THE QUAD CITIES AND ITS
POSSIBLE FOR A LIGHT SHOWER OR SOME SPRINKLES OUT OF THE MID DECK
THRU MID MORNING. CMS

//ORD AND MDW CONFIDENCE...UPDATED 09Z...

* LOW FOR ISOLATED SHRA THIS MORNING.
* LOW FOR MVFR CIGS THIS MORNING.
* MEDIUM FOR WINDS THRU THE PERIOD. CMS

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

* THURSDAY THROUGH MONDAY...CHANCE OF TSRA.

KJB

&&

.MARINE...

307 AM...HIGH PRESSURE CENTERED OVER MINNESOTA EARLY THIS MORNING
WILL MOVE ACROSS THE LAKES REGION TODAY AND TONIGHT. AS IT DOES
THE GRADIENT WILL SLOWLY WEAKEN OVER NORTHERN LAKE MICHIGAN WHILE
IT SLOWLY TIGHTENS OVER THE SOUTHERN PORTION OF THE LAKE. SPEEDS
WILL INCREASE INTO THE 10-20KT RANGE. AS THE HIGH SHIFTS EAST...
WINDS WILL TURN MORE EASTERLY BY THURSDAY MORNING THEN SHIFT
SOUTHEAST TO SOUTHERLY THURSDAY NIGHT AS A WARM FRONT LIFTS NORTH
ACROSS THE LAKE. THE GRADIENT COULD TIGHTEN ENOUGH FOR A PERIOD OF
15-25 KTS THURSDAY NIGHT INTO FRIDAY. A FRONTAL BOUNDARY IS THEN
EXPECTED TO MOVE SOUTH ACROSS THE LAKE SATURDAY AFTERNOON INTO
SATURDAY EVENING. BUT AT THE SAME TIME...LOW PRESSURE IS EXPECTED
TO DEVELOP OVER THE WESTERN LAKES AND THEN MOVE ACROSS NORTHERN
LAKE MICHIGAN BY SUNDAY MORNING. THIS MAKES FOR A CHALLENGING WIND
FORECAST. IF THE LOW BEGINS TO DEEPEN...NORTHERLY WINDS MAY
INCREASE INTO THE 15-25KT RANGE. CHANGES CAN BE EXPECTED DURING
THIS TIME PERIOD AS TRENDS EMERGE. WINDS THEN QUICKLY TURN BACK
SOUTHERLY SUNDAY NIGHT INTO MONDAY. CMS

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 270906
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
406 AM CDT WED AUG 27 2014

.DISCUSSION...
321 AM CDT

CONVECTIVE TRENDS REMAIN THE MAIN FOCUS OF THE FORECAST THROUGH THE
WEEKEND. WATER VAPOR IMAGERY SHOWS A SPLIT UPPER FLOW WITH A
NORTHERN STREAM OF PROGRESSIVE FLOW RUNNING ACROSS SOUTHERN CANADA
INTO THE UPPER GREAT LAKES. A LOW AMPLITUDE TROUGH AXIS IS
TRAVERSING THE FLOW AND MOVING INTO WISCONSIN AT THE CURRENT TIME.
THE SOUTHERN STREAM FEATURES A CUTOFF UPPER LOW WHICH IS OVER UTAH
AND SLOWLY MOVING EASTWARD. UPPER RIDGING IS STARTING TO BUILD JUST
DOWNSTREAM OF THE UPPER LOW WITH SEVERAL EMBEDDED WAVES MOVING
NORTHEASTWARD AHEAD OF THE LOW. AT THE SURFACE...THE FRONTAL
BOUNDARY WHICH HAS BEEN DISCUSSED OVER THE PAST SEVERAL DAYS IS NOW
SOUTH OF THE CWA AND RUNS EAST-NORTHEAST ACROSS THE LOWER GREAT
LAKES AND ST. LAWRENCE RIVER VALLEY. HIGH PRESSURE HAS SPREAD ACROSS
THE UPPER MIDWEST WITH ITS SOUTHERN FLANK INTO THE FORECAST AREA.

TODAY...THE NORTHERN STREAM UPPER TROUGH AXIS WILL
CROSS THE LOCAL AREA THIS MORNING. THE GREATEST ASCENT ASSOCIATED
WITH IT IS TO THE NORTH AND IS GENERATING BANDS OF SHOWERS ACROSS
WISCONSIN...WITH ADDITIONAL RETURNS WORKING ACROSS CENTRAL IOWA INTO
NORTHERN ILLINOIS. THIS ACTIVITY SEEMS TO BE IN BETTER CONJUNCTION
WITH THE RIGHT ENTRANCE REGION OF AN UPPER JET MAX TO THE NORTH IN
ADDITION TO A BROAD AREA OF HEIGHT FALLS INDUCED BY THE UPPER
TROUGH. A CLUSTER OF THUNDERSTORMS HAS ALSO DEVELOPED ACROSS SW IOWA
IN RESPONSE TO BETTER FOCUSED MID LEVEL WARM ADVECTION. MOST OF THIS
UPPER SUPPORT WILL BE PASSING BY THIS MORNING RESULTING IN A
DECREASE IN ACTIVITY. WITH THE SURFACE FRONT TO THE SOUTH THE
INSTABILITY GRADIENT IS ALSO TO THE SOUTH WITH A WESTERLY LOW LEVEL
JET ABOVE IT SUGGESTING THAT THE CONVECTION ACROSS SOUTHWEST IOWA
WOULD NOT BE A FACTOR TOO FAR NORTH OF ITS CURRENT LATITUDE. ONCE
THE CURRENT SHOWER ACTIVITY EXITS IT APPEARS THAT MOST AREAS WILL
REMAIN DRY FOR THE REST OF THE DAY BUT FAR SOUTHERN AREAS DO HAVE A
CHANCE TO SEE SOME SHOWERS AND STORMS THIS MORNING GIVEN THE
WESTERLY LOW LEVEL JET ALONG THE BOUNDARY AND MID LEVEL MOISTURE
GRADIENT BUT WARM/MOIST ADVECTION IS PRETTY WEAK. HIGH TEMPERATURES
WILL RANGE FROM THE UPPER 70S NORTH TO MID 80S SOUTH WITH A
NORTHEAST WIND HOLDING LAKEFRONT AREAS TO THE LOWER TO MID 70S.

TONIGHT AND THURSDAY...AS THE UPPER TROUGH SHIFTS EAST THE RIDGING
DOWNSTREAM OF THE CUTOFF LOW TO THE WEST WILL PIVOT ACROSS THE
CENTRAL PLAINS. SURFACE LOW PRESSURE WILL BE DEVELOPING ACROSS
EASTERN COLORADO AND WESTERN KANSAS WHICH WILL DRIVE THE FRONTAL
BOUNDARY NORTHEASTWARD ACROSS THE CENTRAL PLAINS WITH THE NEARBY
PORTION OF THE FRONT REMAINING SOUTH OF THE AREA INTO THURSDAY
EVENING. WITH WARM ADVECTION INCREASING ALOFT WITH THE RIDGE
BUILDING BACK IN TONIGHT SHOWERS AND THUNDERSTORMS ARE EXPECTED TO
BE MOVING EAST-NORTHEAST ACROSS IOWA/MISSOURI. SOME OF THIS ACTIVITY
MAY REACH THE WESTERN CWA VERY LATE TONIGHT AND MAY END UP SEEING A
SIMILAR SITUATION TO RECENT DAYS WITH REMNANT CONVECTION FESTERING
AND/OR SPAWNING NEW DEVELOPMENT ACROSS THE CWA THURSDAY
MORNING/AFTERNOON. THE MAIN SURFACE LOW AND UPPER WAVE IS EXPECTED
TO BE MOVING ACROSS IOWA/MINNESOTA/WISCONSIN SO THE BULK OF THE
CONVECTION MAY STAY TO THE NORTHWEST OF THE LOCAL AREA. WILL FOCUS
HIGHEST POPS ACROSS THE WESTERN CWA AND SLOW DOWN THE ARRIVAL UNTIL
LATER TONIGHT. THURSDAY LOOKS TO BE SLIGHTLY WARMER...ESPECIALLY
WITH CONVECTION LOOKING TO BE MORE SCATTERED IN COVERAGE.

FRIDAY THROUGH EARLY NEXT WEEK...THE UPPER TROUGH WILL START TO MAKE
QUICKER EAST-NORTHEAST PROGRESS THANKS TO ANOTHER LARGE SCALE UPPER
TROUGH PUSHING INTO THE WESTERN U.S./CANADA. THIS WILL TAKE ANOTHER
SURFACE LOW NORTHEASTWARD WITH IT WHICH WILL LIKELY TRACK NORTHWEST
OF THE AREA SATURDAY. FRIDAY SHOULD SEE A NOTICEABLE WARM UP WITH
ANOTHER LULL IN WIDESPREAD CONVECTION WITH IT FOCUSING TO THE NORTH
AND WEST. WILL HAVE HIGHER POPS SATURDAY WITH THE LOW PASSING BUT AM
SEEING MIXED SIGNALS IN THE TRACK WHICH WILL AFFECT PRECIP COVERAGE.
CHANCES WILL DIMINISH SATURDAY NIGHT WITH QUESTION MARKS SURROUNDING
SUNDAY INTO EARLY NEXT WEEK WITH THE GFS SHOWING A MORE ACTIVE FLOW
WHILE THE ECMWF IS QUIETER THOUGH IT DOES BRING A FRONT THROUGH THE
AREA TUESDAY. DO NOT SEE MUCH OF A COOL DOWN OVERALL AND A DRY
FORECAST SUNDAY/MONDAY WOULD COINCIDE WITH A WARMING TREND IF IT
COMES TO PASS. WILL CONTINUE WITH MID TO UPPER 80S FRIDAY WITH
READINGS SEVERAL DEGREES COOLER SATURDAY AND SUNDAY.

MDB

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 09Z...

* ISOLATED SHRA THIS MORNING.
* POSSIBLE MVFR CIGS THRU MID MORNING.
* EAST/NORTHEAST WINDS THRU THE PERIOD...POSSIBLY AROUND 10KT THIS
  AFTERNOON. CMS

//DISCUSSION...UPDATED 09Z...

CIGS IN THE 3-4KFT RANGE SHOULD PREVAIL FOR AT LEAST THE NEXT FEW
HOURS. STILL SOME POTENTIAL THESE COULD DIP INTO HIGH MVFR.
ISOLATED SHRA WILL ALSO BE POSSIBLE ACROSS THE TERMINALS THRU MID
MORNING. ANY TSRA THAT DEVELOP SHOULD REMAIN SOUTH OF THE
TERMINALS...AND PERHAPS ACROSS CENTRAL IL. CMS

PREVIOUS 06Z DISCUSSION...

HIGH PRESSURE OVER THE NORTHERN PLAINS WILL MOVE EAST ACROSS THE
LAKES REGION LATER TODAY AND TONIGHT. THIS WILL MAINTAIN EAST/
NORTHEAST WINDS THROUGH THE PERIOD. SPEEDS COULD INCREASE TO 10KTS
OR SLIGHTLY HIGHER THIS AFTERNOON INTO EARLY THIS EVENING WITH A
POSSIBLE LAKE BREEZE.

CIGS AROUND 3KFT HAVE DEVELOPED ACROSS NORTHEAST IL BUT APPEAR TO
BE SHIFTING EAST AND FOR NOW WILL JUST CARRY SCT MENTION. APPEARS
A BKN/OVC MID DECK WILL SPREAD ACROSS MUCH OF THE REGION OVERNIGHT
AND CONTINUE INTO THIS AFTERNOON. SOME FOG IS POSSIBLE WHERE SKIES
REMAIN MOSTLY CLEAR AND GENERALLY SOUTH AND SOUTHEAST OF THE
TERMINALS. CONTINUED FOG MENTION AT GYY BUT CONFIDENCE TOO LOW
ELSEWHERE.

A FEW ECHOS SHOWING UP ON RADAR NEAR THE QUAD CITIES AND ITS
POSSIBLE FOR A LIGHT SHOWER OR SOME SPRINKLES OUT OF THE MID DECK
THRU MID MORNING. CMS

//ORD AND MDW CONFIDENCE...UPDATED 09Z...

* LOW FOR ISOLATED SHRA THIS MORNING.
* LOW FOR MVFR CIGS THIS MORNING.
* MEDIUM FOR WINDS THRU THE PERIOD. CMS

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

* THURSDAY THROUGH MONDAY...CHANCE OF TSRA.

KJB

&&

.MARINE...

307 AM...HIGH PRESSURE CENTERED OVER MINNESOTA EARLY THIS MORNING
WILL MOVE ACROSS THE LAKES REGION TODAY AND TONIGHT. AS IT DOES
THE GRADIENT WILL SLOWLY WEAKEN OVER NORTHERN LAKE MICHIGAN WHILE
IT SLOWLY TIGHTENS OVER THE SOUTHERN PORTION OF THE LAKE. SPEEDS
WILL INCREASE INTO THE 10-20KT RANGE. AS THE HIGH SHIFTS EAST...
WINDS WILL TURN MORE EASTERLY BY THURSDAY MORNING THEN SHIFT
SOUTHEAST TO SOUTHERLY THURSDAY NIGHT AS A WARM FRONT LIFTS NORTH
ACROSS THE LAKE. THE GRADIENT COULD TIGHTEN ENOUGH FOR A PERIOD OF
15-25 KTS THURSDAY NIGHT INTO FRIDAY. A FRONTAL BOUNDARY IS THEN
EXPECTED TO MOVE SOUTH ACROSS THE LAKE SATURDAY AFTERNOON INTO
SATURDAY EVENING. BUT AT THE SAME TIME...LOW PRESSURE IS EXPECTED
TO DEVELOP OVER THE WESTERN LAKES AND THEN MOVE ACROSS NORTHERN
LAKE MICHIGAN BY SUNDAY MORNING. THIS MAKES FOR A CHALLENGING WIND
FORECAST. IF THE LOW BEGINS TO DEEPEN...NORTHERLY WINDS MAY
INCREASE INTO THE 15-25KT RANGE. CHANGES CAN BE EXPECTED DURING
THIS TIME PERIOD AS TRENDS EMERGE. WINDS THEN QUICKLY TURN BACK
SOUTHERLY SUNDAY NIGHT INTO MONDAY. CMS

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
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000
FXUS63 KLOT 270823
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
323 AM CDT WED AUG 27 2014

.DISCUSSION...
321 AM CDT

CONVECTIVE TRENDS REMAIN THE MAIN FOCUS OF THE FORECAST THROUGH THE
WEEKEND. WATER VAPOR IMAGERY SHOWS A SPLIT UPPER FLOW WITH A
NORTHERN STREAM OF PROGRESSIVE FLOW RUNNING ACROSS SOUTHERN CANADA
INTO THE UPPER GREAT LAKES. A LOW AMPLITUDE TROUGH AXIS IS
TRAVERSING THE FLOW AND MOVING INTO WISCONSIN AT THE CURRENT TIME.
THE SOUTHERN STREAM FEATURES A CUTOFF UPPER LOW WHICH IS OVER UTAH
AND SLOWLY MOVING EASTWARD. UPPER RIDGING IS STARTING TO BUILD JUST
DOWNSTREAM OF THE UPPER LOW WITH SEVERAL EMBEDDED WAVES MOVING
NORTHEASTWARD AHEAD OF THE LOW. AT THE SURFACE...THE FRONTAL
BOUNDARY WHICH HAS BEEN DISCUSSED OVER THE PAST SEVERAL DAYS IS NOW
SOUTH OF THE CWA AND RUNS EAST-NORTHEAST ACROSS THE LOWER GREAT
LAKES AND ST. LAWRENCE RIVER VALLEY. HIGH PRESSURE HAS SPREAD ACROSS
THE UPPER MIDWEST WITH ITS SOUTHERN FLANK INTO THE FORECAST AREA.

TODAY...THE NORTHERN STREAM UPPER TROUGH AXIS WILL
CROSS THE LOCAL AREA THIS MORNING. THE GREATEST ASCENT ASSOCIATED
WITH IT IS TO THE NORTH AND IS GENERATING BANDS OF SHOWERS ACROSS
WISCONSIN...WITH ADDITIONAL RETURNS WORKING ACROSS CENTRAL IOWA INTO
NORTHERN ILLINOIS. THIS ACTIVITY SEEMS TO BE IN BETTER CONJUNCTION
WITH THE RIGHT ENTRANCE REGION OF AN UPPER JET MAX TO THE NORTH IN
ADDITION TO A BROAD AREA OF HEIGHT FALLS INDUCED BY THE UPPER
TROUGH. A CLUSTER OF THUNDERSTORMS HAS ALSO DEVELOPED ACROSS SW IOWA
IN RESPONSE TO BETTER FOCUSED MID LEVEL WARM ADVECTION. MOST OF THIS
UPPER SUPPORT WILL BE PASSING BY THIS MORNING RESULTING IN A
DECREASE IN ACTIVITY. WITH THE SURFACE FRONT TO THE SOUTH THE
INSTABILITY GRADIENT IS ALSO TO THE SOUTH WITH A WESTERLY LOW LEVEL
JET ABOVE IT SUGGESTING THAT THE CONVECTION ACROSS SOUTHWEST IOWA
WOULD NOT BE A FACTOR TOO FAR NORTH OF ITS CURRENT LATITUDE. ONCE
THE CURRENT SHOWER ACTIVITY EXITS IT APPEARS THAT MOST AREAS WILL
REMAIN DRY FOR THE REST OF THE DAY BUT FAR SOUTHERN AREAS DO HAVE A
CHANCE TO SEE SOME SHOWERS AND STORMS THIS MORNING GIVEN THE
WESTERLY LOW LEVEL JET ALONG THE BOUNDARY AND MID LEVEL MOISTURE
GRADIENT BUT WARM/MOIST ADVECTION IS PRETTY WEAK. HIGH TEMPERATURES
WILL RANGE FROM THE UPPER 70S NORTH TO MID 80S SOUTH WITH A
NORTHEAST WIND HOLDING LAKEFRONT AREAS TO THE LOWER TO MID 70S.

TONIGHT AND THURSDAY...AS THE UPPER TROUGH SHIFTS EAST THE RIDGING
DOWNSTREAM OF THE CUTOFF LOW TO THE WEST WILL PIVOT ACROSS THE
CENTRAL PLAINS. SURFACE LOW PRESSURE WILL BE DEVELOPING ACROSS
EASTERN COLORADO AND WESTERN KANSAS WHICH WILL DRIVE THE FRONTAL
BOUNDARY NORTHEASTWARD ACROSS THE CENTRAL PLAINS WITH THE NEARBY
PORTION OF THE FRONT REMAINING SOUTH OF THE AREA INTO THURSDAY
EVENING. WITH WARM ADVECTION INCREASING ALOFT WITH THE RIDGE
BUILDING BACK IN TONIGHT SHOWERS AND THUNDERSTORMS ARE EXPECTED TO
BE MOVING EAST-NORTHEAST ACROSS IOWA/MISSOURI. SOME OF THIS ACTIVITY
MAY REACH THE WESTERN CWA VERY LATE TONIGHT AND MAY END UP SEEING A
SIMILAR SITUATION TO RECENT DAYS WITH REMNANT CONVECTION FESTERING
AND/OR SPAWNING NEW DEVELOPMENT ACROSS THE CWA THURSDAY
MORNING/AFTERNOON. THE MAIN SURFACE LOW AND UPPER WAVE IS EXPECTED
TO BE MOVING ACROSS IOWA/MINNESOTA/WISCONSIN SO THE BULK OF THE
CONVECTION MAY STAY TO THE NORTHWEST OF THE LOCAL AREA. WILL FOCUS
HIGHEST POPS ACROSS THE WESTERN CWA AND SLOW DOWN THE ARRIVAL UNTIL
LATER TONIGHT. THURSDAY LOOKS TO BE SLIGHTLY WARMER...ESPECIALLY
WITH CONVECTION LOOKING TO BE MORE SCATTERED IN COVERAGE.

FRIDAY THROUGH EARLY NEXT WEEK...THE UPPER TROUGH WILL START TO MAKE
QUICKER EAST-NORTHEAST PROGRESS THANKS TO ANOTHER LARGE SCALE UPPER
TROUGH PUSHING INTO THE WESTERN U.S./CANADA. THIS WILL TAKE ANOTHER
SURFACE LOW NORTHEASTWARD WITH IT WHICH WILL LIKELY TRACK NORTHWEST
OF THE AREA SATURDAY. FRIDAY SHOULD SEE A NOTICEABLE WARM UP WITH
ANOTHER LULL IN WIDESPREAD CONVECTION WITH IT FOCUSING TO THE NORTH
AND WEST. WILL HAVE HIGHER POPS SATURDAY WITH THE LOW PASSING BUT AM
SEEING MIXED SIGNALS IN THE TRACK WHICH WILL AFFECT PRECIP COVERAGE.
CHANCES WILL DIMINISH SATURDAY NIGHT WITH QUESTION MARKS SURROUNDING
SUNDAY INTO EARLY NEXT WEEK WITH THE GFS SHOWING A MORE ACTIVE FLOW
WHILE THE ECMWF IS QUIETER THOUGH IT DOES BRING A FRONT THROUGH THE
AREA TUESDAY. DO NOT SEE MUCH OF A COOL DOWN OVERALL AND A DRY
FORECAST SUNDAY/MONDAY WOULD COINCIDE WITH A WARMING TREND IF IT
COMES TO PASS. WILL CONTINUE WITH MID TO UPPER 80S FRIDAY WITH
READINGS SEVERAL DEGREES COOLER SATURDAY AND SUNDAY.

MDB

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* POSSIBLE MVFR CIGS EARLY THIS MORNING.
* EAST/NORTHEAST WINDS THRU THE PERIOD...POSSIBLY AROUND 10KT THIS
  AFTERNOON. CMS

//DISCUSSION...UPDATED 06Z...

HIGH PRESSURE OVER THE NORTHERN PLAINS WILL MOVE EAST ACROSS THE
LAKES REGION LATER TODAY AND TONIGHT. THIS WILL MAINTAIN EAST/
NORTHEAST WINDS THROUGH THE PERIOD. SPEEDS COULD INCREASE TO 10KTS
OR SLIGHTLY HIGHER THIS AFTERNOON INTO EARLY THIS EVENING WITH A
POSSIBLE LAKE BREEZE.

CIGS AROUND 3KFT HAVE DEVELOPED ACROSS NORTHEAST IL BUT APPEAR TO
BE SHIFTING EAST AND FOR NOW WILL JUST CARRY SCT MENTION. APPEARS
A BKN/OVC MID DECK WILL SPREAD ACROSS MUCH OF THE REGION OVERNIGHT
AND CONTINUE INTO THIS AFTERNOON. SOME FOG IS POSSIBLE WHERE SKIES
REMAIN MOSTLY CLEAR AND GENERALLY SOUTH AND SOUTHEAST OF THE
TERMINALS. CONTINUED FOG MENTION AT GYY BUT CONFIDENCE TOO LOW
ELSEWHERE.

A FEW ECHOS SHOWING UP ON RADAR NEAR THE QUAD CITIES AND ITS
POSSIBLE FOR A LIGHT SHOWER OR SOME SPRINKLES OUT OF THE MID DECK
THRU MID MORNING. CMS

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* LOW FOR MVFR CIGS EARLY THIS MORNING.
* MEDIUM FOR WINDS THRU THE PERIOD. CMS

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

* THURSDAY THROUGH MONDAY...CHANCE OF TSRA.

KJB

&&

.MARINE...

307 AM...HIGH PRESSURE CENTERED OVER MINNESOTA EARLY THIS MORNING
WILL MOVE ACROSS THE LAKES REGION TODAY AND TONIGHT. AS IT DOES
THE GRADIENT WILL SLOWLY WEAKEN OVER NORTHERN LAKE MICHIGAN WHILE
IT SLOWLY TIGHTENS OVER THE SOUTHERN PORTION OF THE LAKE. SPEEDS
WILL INCREASE INTO THE 10-20KT RANGE. AS THE HIGH SHIFTS EAST...
WINDS WILL TURN MORE EASTERLY BY THURSDAY MORNING THEN SHIFT
SOUTHEAST TO SOUTHERLY THURSDAY NIGHT AS A WARM FRONT LIFTS NORTH
ACROSS THE LAKE. THE GRADIENT COULD TIGHTEN ENOUGH FOR A PERIOD OF
15-25 KTS THURSDAY NIGHT INTO FRIDAY. A FRONTAL BOUNDARY IS THEN
EXPECTED TO MOVE SOUTH ACROSS THE LAKE SATURDAY AFTERNOON INTO
SATURDAY EVENING. BUT AT THE SAME TIME...LOW PRESSURE IS EXPECTED
TO DEVELOP OVER THE WESTERN LAKES AND THEN MOVE ACROSS NORTHERN
LAKE MICHIGAN BY SUNDAY MORNING. THIS MAKES FOR A CHALLENGING WIND
FORECAST. IF THE LOW BEGINS TO DEEPEN...NORTHERLY WINDS MAY
INCREASE INTO THE 15-25KT RANGE. CHANGES CAN BE EXPECTED DURING
THIS TIME PERIOD AS TRENDS EMERGE. WINDS THEN QUICKLY TURN BACK
SOUTHERLY SUNDAY NIGHT INTO MONDAY. CMS

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO







000
FXUS63 KLOT 270823
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
323 AM CDT WED AUG 27 2014

.DISCUSSION...
321 AM CDT

CONVECTIVE TRENDS REMAIN THE MAIN FOCUS OF THE FORECAST THROUGH THE
WEEKEND. WATER VAPOR IMAGERY SHOWS A SPLIT UPPER FLOW WITH A
NORTHERN STREAM OF PROGRESSIVE FLOW RUNNING ACROSS SOUTHERN CANADA
INTO THE UPPER GREAT LAKES. A LOW AMPLITUDE TROUGH AXIS IS
TRAVERSING THE FLOW AND MOVING INTO WISCONSIN AT THE CURRENT TIME.
THE SOUTHERN STREAM FEATURES A CUTOFF UPPER LOW WHICH IS OVER UTAH
AND SLOWLY MOVING EASTWARD. UPPER RIDGING IS STARTING TO BUILD JUST
DOWNSTREAM OF THE UPPER LOW WITH SEVERAL EMBEDDED WAVES MOVING
NORTHEASTWARD AHEAD OF THE LOW. AT THE SURFACE...THE FRONTAL
BOUNDARY WHICH HAS BEEN DISCUSSED OVER THE PAST SEVERAL DAYS IS NOW
SOUTH OF THE CWA AND RUNS EAST-NORTHEAST ACROSS THE LOWER GREAT
LAKES AND ST. LAWRENCE RIVER VALLEY. HIGH PRESSURE HAS SPREAD ACROSS
THE UPPER MIDWEST WITH ITS SOUTHERN FLANK INTO THE FORECAST AREA.

TODAY...THE NORTHERN STREAM UPPER TROUGH AXIS WILL
CROSS THE LOCAL AREA THIS MORNING. THE GREATEST ASCENT ASSOCIATED
WITH IT IS TO THE NORTH AND IS GENERATING BANDS OF SHOWERS ACROSS
WISCONSIN...WITH ADDITIONAL RETURNS WORKING ACROSS CENTRAL IOWA INTO
NORTHERN ILLINOIS. THIS ACTIVITY SEEMS TO BE IN BETTER CONJUNCTION
WITH THE RIGHT ENTRANCE REGION OF AN UPPER JET MAX TO THE NORTH IN
ADDITION TO A BROAD AREA OF HEIGHT FALLS INDUCED BY THE UPPER
TROUGH. A CLUSTER OF THUNDERSTORMS HAS ALSO DEVELOPED ACROSS SW IOWA
IN RESPONSE TO BETTER FOCUSED MID LEVEL WARM ADVECTION. MOST OF THIS
UPPER SUPPORT WILL BE PASSING BY THIS MORNING RESULTING IN A
DECREASE IN ACTIVITY. WITH THE SURFACE FRONT TO THE SOUTH THE
INSTABILITY GRADIENT IS ALSO TO THE SOUTH WITH A WESTERLY LOW LEVEL
JET ABOVE IT SUGGESTING THAT THE CONVECTION ACROSS SOUTHWEST IOWA
WOULD NOT BE A FACTOR TOO FAR NORTH OF ITS CURRENT LATITUDE. ONCE
THE CURRENT SHOWER ACTIVITY EXITS IT APPEARS THAT MOST AREAS WILL
REMAIN DRY FOR THE REST OF THE DAY BUT FAR SOUTHERN AREAS DO HAVE A
CHANCE TO SEE SOME SHOWERS AND STORMS THIS MORNING GIVEN THE
WESTERLY LOW LEVEL JET ALONG THE BOUNDARY AND MID LEVEL MOISTURE
GRADIENT BUT WARM/MOIST ADVECTION IS PRETTY WEAK. HIGH TEMPERATURES
WILL RANGE FROM THE UPPER 70S NORTH TO MID 80S SOUTH WITH A
NORTHEAST WIND HOLDING LAKEFRONT AREAS TO THE LOWER TO MID 70S.

TONIGHT AND THURSDAY...AS THE UPPER TROUGH SHIFTS EAST THE RIDGING
DOWNSTREAM OF THE CUTOFF LOW TO THE WEST WILL PIVOT ACROSS THE
CENTRAL PLAINS. SURFACE LOW PRESSURE WILL BE DEVELOPING ACROSS
EASTERN COLORADO AND WESTERN KANSAS WHICH WILL DRIVE THE FRONTAL
BOUNDARY NORTHEASTWARD ACROSS THE CENTRAL PLAINS WITH THE NEARBY
PORTION OF THE FRONT REMAINING SOUTH OF THE AREA INTO THURSDAY
EVENING. WITH WARM ADVECTION INCREASING ALOFT WITH THE RIDGE
BUILDING BACK IN TONIGHT SHOWERS AND THUNDERSTORMS ARE EXPECTED TO
BE MOVING EAST-NORTHEAST ACROSS IOWA/MISSOURI. SOME OF THIS ACTIVITY
MAY REACH THE WESTERN CWA VERY LATE TONIGHT AND MAY END UP SEEING A
SIMILAR SITUATION TO RECENT DAYS WITH REMNANT CONVECTION FESTERING
AND/OR SPAWNING NEW DEVELOPMENT ACROSS THE CWA THURSDAY
MORNING/AFTERNOON. THE MAIN SURFACE LOW AND UPPER WAVE IS EXPECTED
TO BE MOVING ACROSS IOWA/MINNESOTA/WISCONSIN SO THE BULK OF THE
CONVECTION MAY STAY TO THE NORTHWEST OF THE LOCAL AREA. WILL FOCUS
HIGHEST POPS ACROSS THE WESTERN CWA AND SLOW DOWN THE ARRIVAL UNTIL
LATER TONIGHT. THURSDAY LOOKS TO BE SLIGHTLY WARMER...ESPECIALLY
WITH CONVECTION LOOKING TO BE MORE SCATTERED IN COVERAGE.

FRIDAY THROUGH EARLY NEXT WEEK...THE UPPER TROUGH WILL START TO MAKE
QUICKER EAST-NORTHEAST PROGRESS THANKS TO ANOTHER LARGE SCALE UPPER
TROUGH PUSHING INTO THE WESTERN U.S./CANADA. THIS WILL TAKE ANOTHER
SURFACE LOW NORTHEASTWARD WITH IT WHICH WILL LIKELY TRACK NORTHWEST
OF THE AREA SATURDAY. FRIDAY SHOULD SEE A NOTICEABLE WARM UP WITH
ANOTHER LULL IN WIDESPREAD CONVECTION WITH IT FOCUSING TO THE NORTH
AND WEST. WILL HAVE HIGHER POPS SATURDAY WITH THE LOW PASSING BUT AM
SEEING MIXED SIGNALS IN THE TRACK WHICH WILL AFFECT PRECIP COVERAGE.
CHANCES WILL DIMINISH SATURDAY NIGHT WITH QUESTION MARKS SURROUNDING
SUNDAY INTO EARLY NEXT WEEK WITH THE GFS SHOWING A MORE ACTIVE FLOW
WHILE THE ECMWF IS QUIETER THOUGH IT DOES BRING A FRONT THROUGH THE
AREA TUESDAY. DO NOT SEE MUCH OF A COOL DOWN OVERALL AND A DRY
FORECAST SUNDAY/MONDAY WOULD COINCIDE WITH A WARMING TREND IF IT
COMES TO PASS. WILL CONTINUE WITH MID TO UPPER 80S FRIDAY WITH
READINGS SEVERAL DEGREES COOLER SATURDAY AND SUNDAY.

MDB

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* POSSIBLE MVFR CIGS EARLY THIS MORNING.
* EAST/NORTHEAST WINDS THRU THE PERIOD...POSSIBLY AROUND 10KT THIS
  AFTERNOON. CMS

//DISCUSSION...UPDATED 06Z...

HIGH PRESSURE OVER THE NORTHERN PLAINS WILL MOVE EAST ACROSS THE
LAKES REGION LATER TODAY AND TONIGHT. THIS WILL MAINTAIN EAST/
NORTHEAST WINDS THROUGH THE PERIOD. SPEEDS COULD INCREASE TO 10KTS
OR SLIGHTLY HIGHER THIS AFTERNOON INTO EARLY THIS EVENING WITH A
POSSIBLE LAKE BREEZE.

CIGS AROUND 3KFT HAVE DEVELOPED ACROSS NORTHEAST IL BUT APPEAR TO
BE SHIFTING EAST AND FOR NOW WILL JUST CARRY SCT MENTION. APPEARS
A BKN/OVC MID DECK WILL SPREAD ACROSS MUCH OF THE REGION OVERNIGHT
AND CONTINUE INTO THIS AFTERNOON. SOME FOG IS POSSIBLE WHERE SKIES
REMAIN MOSTLY CLEAR AND GENERALLY SOUTH AND SOUTHEAST OF THE
TERMINALS. CONTINUED FOG MENTION AT GYY BUT CONFIDENCE TOO LOW
ELSEWHERE.

A FEW ECHOS SHOWING UP ON RADAR NEAR THE QUAD CITIES AND ITS
POSSIBLE FOR A LIGHT SHOWER OR SOME SPRINKLES OUT OF THE MID DECK
THRU MID MORNING. CMS

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* LOW FOR MVFR CIGS EARLY THIS MORNING.
* MEDIUM FOR WINDS THRU THE PERIOD. CMS

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

* THURSDAY THROUGH MONDAY...CHANCE OF TSRA.

KJB

&&

.MARINE...

307 AM...HIGH PRESSURE CENTERED OVER MINNESOTA EARLY THIS MORNING
WILL MOVE ACROSS THE LAKES REGION TODAY AND TONIGHT. AS IT DOES
THE GRADIENT WILL SLOWLY WEAKEN OVER NORTHERN LAKE MICHIGAN WHILE
IT SLOWLY TIGHTENS OVER THE SOUTHERN PORTION OF THE LAKE. SPEEDS
WILL INCREASE INTO THE 10-20KT RANGE. AS THE HIGH SHIFTS EAST...
WINDS WILL TURN MORE EASTERLY BY THURSDAY MORNING THEN SHIFT
SOUTHEAST TO SOUTHERLY THURSDAY NIGHT AS A WARM FRONT LIFTS NORTH
ACROSS THE LAKE. THE GRADIENT COULD TIGHTEN ENOUGH FOR A PERIOD OF
15-25 KTS THURSDAY NIGHT INTO FRIDAY. A FRONTAL BOUNDARY IS THEN
EXPECTED TO MOVE SOUTH ACROSS THE LAKE SATURDAY AFTERNOON INTO
SATURDAY EVENING. BUT AT THE SAME TIME...LOW PRESSURE IS EXPECTED
TO DEVELOP OVER THE WESTERN LAKES AND THEN MOVE ACROSS NORTHERN
LAKE MICHIGAN BY SUNDAY MORNING. THIS MAKES FOR A CHALLENGING WIND
FORECAST. IF THE LOW BEGINS TO DEEPEN...NORTHERLY WINDS MAY
INCREASE INTO THE 15-25KT RANGE. CHANGES CAN BE EXPECTED DURING
THIS TIME PERIOD AS TRENDS EMERGE. WINDS THEN QUICKLY TURN BACK
SOUTHERLY SUNDAY NIGHT INTO MONDAY. CMS

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 270807
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
307 AM CDT WED AUG 27 2014

.DISCUSSION...
255 PM CDT

AS HAS BEEN THE NORM IN THE PAST WEEK TO TEN DAYS...THE PRIMARY
FORECAST CHALLENGES ARE TRYING TO DETECT WHEN BETTER THUNDERSTORM
CHANCES MAY BE AND WHAT INFLUENCE THOSE HAVE...IF ANY...ON
TEMPERATURES.

.TONIGHT...

THE INITIAL SYNOPTIC COLD FRONT HAS APPEARED TO CLEAR THE
FORECAST AREA. THIS SURGE WAS CONVECTIVELY ENHANCED AND LINGERING
HIGH DEW POINT AIR...E.G. UPPER 60S TO LOWER 70S...REMAINS ACROSS
THE SOUTH. THERE ALSO ARE ONE OR TWO WESTWARD-PROPAGATING OUTFLOW
BOUNDARIES THAT ARE LIKELY TO LAST INTO LATE THIS AFTERNOON.
CUMULUS HAS FORMED NEAR PONTIAC AND GIBSON CITY...AND BACK TOWARD
PRINCETON TO MENDOTA...WITH THESE FEATURES. WOULD NOT BE TOTALLY
SURPRISED TO SEE ISOLATED STORMS POP ON THESE AS MIXED LAYER
INHIBITION APPEARS SHALLOW WITH RECOVERING TEMPERATURES INTO THE
MID 80S AND EVEN 88 AT PONTIAC. A COUPLE SUBTLE SHORT WAVES ARE
NOTED ON WATER VAPOR...WITH ONE A LITTLE BETTER DEFINED ON
VISIBLE SATELLITE NEARING THE MISSISSIPPI RIVER FROM IA ASSOCIATED
WITH A 35 KT 500MB SPEED MAXIMUM. THIS LOOKS TO PASS OVER NORTH
CENTRAL IL EARLY THIS EVE AND COULD SEE SOME SHOWER/STORM ACTIVITY
WITH THAT...ALTHOUGH CONFIDENCE IS LOW FOR SHORT TERM STORM
CHANCES...SO HAVE KEPT POPS FAIRLY LOW. CONFLUENT 700-850MB FLOW
CONTINUES OVERNIGHT WITH ANOTHER LITTLE RIPPLE IN THE FLOW
FORECAST TO MOVE OVER THE AREA. SO CONTINUE CHANCE FOR A STORM
THROUGH THE ENTIRE NIGHT...BUT NOT EXPECTING ANYTHING WIDESPREAD.

INCOMING CLOUDS FROM THE DISTURBED MID-LEVEL FLOW SHOULD KEEP THE FOG
THREAT MINIMAL...AND TEMP/DEW POINT SPREADS LOOK TO BE MODESTLY
HIGH GOING INTO TONIGHT IN MOST AREAS...OUTSIDE OF THE FAR SOUTH.

MTF

.WEDNESDAY THROUGH TUESDAY...

THE LONGWAVE PATTERN OVER THE CENTRAL CONUS HAS BECOME MORE ZONAL
WITH TROPICAL SYSTEM OVER SERN ATLANTIC...NERN PACIFIC WHILE A BROAD
HIGH SITS OVER THE SRN CONUS AND A CLOSED UPPER LOW SWINGS THROUGH
THE GREAT BASIN.  THE SENSIBLE WEATHER OVER THE CWA WILL CONTINUE TO
BE UNSETTLED AS A STRONG SHORTWAVE QUICKLY MOVES ACROSS THE UPPER
MISSISSIPPI VALLEY AND GREAT LAKES WEDNESDAY.  UPPER RIDGING SHOULD
BUILD ACROSS THE MIDWEST ON THURSDAY AS MORE SHORT WAVE ENERGY
OVERTOPS THE RIDGE AND TRACKS ACROSS THE UPPER MIDWEST AND THE LOWER
GREAT LAKES REGIONS.  BY THURSDAY NIGHT AND FRIDAY...THE UPPER RIDGE
SHOULD BUILD TO THE EAST OF THE REGION AS THE UPPER LOW OVER THE
GREAT BASIN FINALLY OPENS UP AND LIFTS EAST ACROSS THE CENTRAL
PLAINS AS AN OPEN WAVE FRIDAY AND FRIDAY NIGHT.  THIS WAVE WILL
CROSS THE UPPER MIDWEST INTO THE WESTERN GREAT LAKES BY SUNDAY.  THE
LONGER RANGE GUIDANCE SUGGESTS THAT THIS WAVE WILL PHASE WITH
ANOTHER NORTHERN STREAM SHORTWAVE OVER THE UPPER GREAT LAKES BY
SUNDAY.  THE PROGRESSIVE AND RELATIVELY LOW AMPLITUDE UPPER LEVEL
PATTERN OVER THE CONUS WILL LEAD TO A CONTINUES ACTIVE WEATHER
PATTERN FOR THE LOCAL AREA...WITH PERIODIC CHANCES FOR SHOWERS AND
THUNDERSTORMS THROUGH MUCH OF THE PERIOD.  THE SOUTHERN PORTIONS OF
THE CWA WILL BE MORE FAVORABLE FOR ADDITIONAL PCPN WEDNESDAY AS SFC
HIGH PRESSURE SPREADS ACROSS THE GREAT LAKES REGION AND THE OLD
FRONTAL BOUNDARY LAYS OUT ALONG THE OHIO VALLEY INTO SRN ILLINOIS.
AS A SFC LOW DEEPENS OVER THE CENTRAL PLAINS ON THURSDAY...IT WILL
DRAG THE FRONT NORTH AGAIN AS A WARM FRONT...BRINGING GREATER
CHANCES FOR MORE WIDESPREAD PCPN TO THE AREA FOR THURSDAY AND
THURSDAY NIGHT.  WHILE THE FRONT REMAINS TO THE SOUTH AND HIGH
PRESSURE SPREADS ACROSS THE GREAT LAKES REGION...TEMPERATURES WILL
DIP BACK INTO THE MIDDLE 70S ACROSS THE NORTHERN PORTIONS OF THE CWA
WHILE THE SOUTHERN LOCATIONS MAY REACH THE LOWER 80S.  BY
FRIDAY...WHEN THE WARM FRONT LIFTS NORTH OF THE CWA...HOT AND HUMID
CONDITIONS WILL RETURN...WITH HIGHS IN THE MIDDLE 80S...DEWPOINTS IN
THE LOWER 70S AND MAX HEAT INDEX VALUES INTO THE LOWER 90S.  THE
DEVELOPING SFC LOW IS EXPECTED TO SLOWLY LIFT ACROSS THE UPPER
MISSISSIPPI VALLEY ON SATURDAY...KEEPING THE LOCAL AREA UNDER WARM
SECTOR AIR AHEAD OF AN ASSOCIATED COLD FRONT.  WHILE THE AREA
REMAINS IN THE WARM SECTOR THROUGH THE WEEKEND...THERE WILL CONTINUE
TO BE CHANCES FOR SCATTERED SHOWERS AND THUNDERSTORMS...BUT WITHOUT
A STRONG FOCUSING MECHANISM...WILL KEEP POPS IN THE CHANCE RANGE.
BY EARLY NEXT WEEK...THE LONG RANGE GUIDANCE IS SUGGESTING THAT THE
COLD FRONT SHOULD FINALLY PUSH THROUGH THE AREA...BUT THERE SHOULD
BE LITTLE IN THE WAY OF AIRMASS CHANGE WITH THE FROPA AS ANOTHER
DEEPENING TROUGH OVER THE NORTHERN PLAINS SHOULD QUICKLY BRING A
RETURN TO WARM...MOIST SOUTHERLY FLOW FOR EARLY NEXT WEEK...WHICH
WILL...IN TURN...KEEP CONTINUES CHANCES FOR PCPN ACROSS THE REGION.

KREIN

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* POSSIBLE MVFR CIGS EARLY THIS MORNING.
* EAST/NORTHEAST WINDS THRU THE PERIOD...POSSIBLY AROUND 10KT THIS
  AFTERNOON. CMS

//DISCUSSION...UPDATED 06Z...

HIGH PRESSURE OVER THE NORTHERN PLAINS WILL MOVE EAST ACROSS THE
LAKES REGION LATER TODAY AND TONIGHT. THIS WILL MAINTAIN EAST/
NORTHEAST WINDS THROUGH THE PERIOD. SPEEDS COULD INCREASE TO 10KTS
OR SLIGHTLY HIGHER THIS AFTERNOON INTO EARLY THIS EVENING WITH A
POSSIBLE LAKE BREEZE.

CIGS AROUND 3KFT HAVE DEVELOPED ACROSS NORTHEAST IL BUT APPEAR TO
BE SHIFTING EAST AND FOR NOW WILL JUST CARRY SCT MENTION. APPEARS
A BKN/OVC MID DECK WILL SPREAD ACROSS MUCH OF THE REGION OVERNIGHT
AND CONTINUE INTO THIS AFTERNOON. SOME FOG IS POSSIBLE WHERE SKIES
REMAIN MOSTLY CLEAR AND GENERALLY SOUTH AND SOUTHEAST OF THE
TERMINALS. CONTINUED FOG MENTION AT GYY BUT CONFIDENCE TOO LOW
ELSEWHERE.

A FEW ECHOS SHOWING UP ON RADAR NEAR THE QUAD CITIES AND ITS
POSSIBLE FOR A LIGHT SHOWER OR SOME SPRINKLES OUT OF THE MID DECK
THRU MID MORNING. CMS

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* LOW FOR MVFR CIGS EARLY THIS MORNING.
* MEDIUM FOR WINDS THRU THE PERIOD. CMS

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

* THURSDAY THROUGH MONDAY...CHANCE OF TSRA.

KJB

&&

.MARINE...

307 AM...HIGH PRESSURE CENTERED OVER MINNESOTA EARLY THIS MORNING
WILL MOVE ACROSS THE LAKES REGION TODAY AND TONIGHT. AS IT DOES
THE GRADIENT WILL SLOWLY WEAKEN OVER NORTHERN LAKE MICHIGAN WHILE
IT SLOWLY TIGHTENS OVER THE SOUTHERN PORTION OF THE LAKE. SPEEDS
WILL INCREASE INTO THE 10-20KT RANGE. AS THE HIGH SHIFTS EAST...
WINDS WILL TURN MORE EASTERLY BY THURSDAY MORNING THEN SHIFT
SOUTHEAST TO SOUTHERLY THURSDAY NIGHT AS A WARM FRONT LIFTS NORTH
ACROSS THE LAKE. THE GRADIENT COULD TIGHTEN ENOUGH FOR A PERIOD OF
15-25 KTS THURSDAY NIGHT INTO FRIDAY. A FRONTAL BOUNDARY IS THEN
EXPECTED TO MOVE SOUTH ACROSS THE LAKE SATURDAY AFTERNOON INTO
SATURDAY EVENING. BUT AT THE SAME TIME...LOW PRESSURE IS EXPECTED
TO DEVELOP OVER THE WESTERN LAKES AND THEN MOVE ACROSS NORTHERN
LAKE MICHIGAN BY SUNDAY MORNING. THIS MAKES FOR A CHALLENGING WIND
FORECAST. IF THE LOW BEGINS TO DEEPEN...NORTHERLY WINDS MAY
INCREASE INTO THE 15-25KT RANGE. CHANGES CAN BE EXPECTED DURING
THIS TIME PERIOD AS TRENDS EMERGE. WINDS THEN QUICKLY TURN BACK
SOUTHERLY SUNDAY NIGHT INTO MONDAY. CMS

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 270807
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
307 AM CDT WED AUG 27 2014

.DISCUSSION...
255 PM CDT

AS HAS BEEN THE NORM IN THE PAST WEEK TO TEN DAYS...THE PRIMARY
FORECAST CHALLENGES ARE TRYING TO DETECT WHEN BETTER THUNDERSTORM
CHANCES MAY BE AND WHAT INFLUENCE THOSE HAVE...IF ANY...ON
TEMPERATURES.

.TONIGHT...

THE INITIAL SYNOPTIC COLD FRONT HAS APPEARED TO CLEAR THE
FORECAST AREA. THIS SURGE WAS CONVECTIVELY ENHANCED AND LINGERING
HIGH DEW POINT AIR...E.G. UPPER 60S TO LOWER 70S...REMAINS ACROSS
THE SOUTH. THERE ALSO ARE ONE OR TWO WESTWARD-PROPAGATING OUTFLOW
BOUNDARIES THAT ARE LIKELY TO LAST INTO LATE THIS AFTERNOON.
CUMULUS HAS FORMED NEAR PONTIAC AND GIBSON CITY...AND BACK TOWARD
PRINCETON TO MENDOTA...WITH THESE FEATURES. WOULD NOT BE TOTALLY
SURPRISED TO SEE ISOLATED STORMS POP ON THESE AS MIXED LAYER
INHIBITION APPEARS SHALLOW WITH RECOVERING TEMPERATURES INTO THE
MID 80S AND EVEN 88 AT PONTIAC. A COUPLE SUBTLE SHORT WAVES ARE
NOTED ON WATER VAPOR...WITH ONE A LITTLE BETTER DEFINED ON
VISIBLE SATELLITE NEARING THE MISSISSIPPI RIVER FROM IA ASSOCIATED
WITH A 35 KT 500MB SPEED MAXIMUM. THIS LOOKS TO PASS OVER NORTH
CENTRAL IL EARLY THIS EVE AND COULD SEE SOME SHOWER/STORM ACTIVITY
WITH THAT...ALTHOUGH CONFIDENCE IS LOW FOR SHORT TERM STORM
CHANCES...SO HAVE KEPT POPS FAIRLY LOW. CONFLUENT 700-850MB FLOW
CONTINUES OVERNIGHT WITH ANOTHER LITTLE RIPPLE IN THE FLOW
FORECAST TO MOVE OVER THE AREA. SO CONTINUE CHANCE FOR A STORM
THROUGH THE ENTIRE NIGHT...BUT NOT EXPECTING ANYTHING WIDESPREAD.

INCOMING CLOUDS FROM THE DISTURBED MID-LEVEL FLOW SHOULD KEEP THE FOG
THREAT MINIMAL...AND TEMP/DEW POINT SPREADS LOOK TO BE MODESTLY
HIGH GOING INTO TONIGHT IN MOST AREAS...OUTSIDE OF THE FAR SOUTH.

MTF

.WEDNESDAY THROUGH TUESDAY...

THE LONGWAVE PATTERN OVER THE CENTRAL CONUS HAS BECOME MORE ZONAL
WITH TROPICAL SYSTEM OVER SERN ATLANTIC...NERN PACIFIC WHILE A BROAD
HIGH SITS OVER THE SRN CONUS AND A CLOSED UPPER LOW SWINGS THROUGH
THE GREAT BASIN.  THE SENSIBLE WEATHER OVER THE CWA WILL CONTINUE TO
BE UNSETTLED AS A STRONG SHORTWAVE QUICKLY MOVES ACROSS THE UPPER
MISSISSIPPI VALLEY AND GREAT LAKES WEDNESDAY.  UPPER RIDGING SHOULD
BUILD ACROSS THE MIDWEST ON THURSDAY AS MORE SHORT WAVE ENERGY
OVERTOPS THE RIDGE AND TRACKS ACROSS THE UPPER MIDWEST AND THE LOWER
GREAT LAKES REGIONS.  BY THURSDAY NIGHT AND FRIDAY...THE UPPER RIDGE
SHOULD BUILD TO THE EAST OF THE REGION AS THE UPPER LOW OVER THE
GREAT BASIN FINALLY OPENS UP AND LIFTS EAST ACROSS THE CENTRAL
PLAINS AS AN OPEN WAVE FRIDAY AND FRIDAY NIGHT.  THIS WAVE WILL
CROSS THE UPPER MIDWEST INTO THE WESTERN GREAT LAKES BY SUNDAY.  THE
LONGER RANGE GUIDANCE SUGGESTS THAT THIS WAVE WILL PHASE WITH
ANOTHER NORTHERN STREAM SHORTWAVE OVER THE UPPER GREAT LAKES BY
SUNDAY.  THE PROGRESSIVE AND RELATIVELY LOW AMPLITUDE UPPER LEVEL
PATTERN OVER THE CONUS WILL LEAD TO A CONTINUES ACTIVE WEATHER
PATTERN FOR THE LOCAL AREA...WITH PERIODIC CHANCES FOR SHOWERS AND
THUNDERSTORMS THROUGH MUCH OF THE PERIOD.  THE SOUTHERN PORTIONS OF
THE CWA WILL BE MORE FAVORABLE FOR ADDITIONAL PCPN WEDNESDAY AS SFC
HIGH PRESSURE SPREADS ACROSS THE GREAT LAKES REGION AND THE OLD
FRONTAL BOUNDARY LAYS OUT ALONG THE OHIO VALLEY INTO SRN ILLINOIS.
AS A SFC LOW DEEPENS OVER THE CENTRAL PLAINS ON THURSDAY...IT WILL
DRAG THE FRONT NORTH AGAIN AS A WARM FRONT...BRINGING GREATER
CHANCES FOR MORE WIDESPREAD PCPN TO THE AREA FOR THURSDAY AND
THURSDAY NIGHT.  WHILE THE FRONT REMAINS TO THE SOUTH AND HIGH
PRESSURE SPREADS ACROSS THE GREAT LAKES REGION...TEMPERATURES WILL
DIP BACK INTO THE MIDDLE 70S ACROSS THE NORTHERN PORTIONS OF THE CWA
WHILE THE SOUTHERN LOCATIONS MAY REACH THE LOWER 80S.  BY
FRIDAY...WHEN THE WARM FRONT LIFTS NORTH OF THE CWA...HOT AND HUMID
CONDITIONS WILL RETURN...WITH HIGHS IN THE MIDDLE 80S...DEWPOINTS IN
THE LOWER 70S AND MAX HEAT INDEX VALUES INTO THE LOWER 90S.  THE
DEVELOPING SFC LOW IS EXPECTED TO SLOWLY LIFT ACROSS THE UPPER
MISSISSIPPI VALLEY ON SATURDAY...KEEPING THE LOCAL AREA UNDER WARM
SECTOR AIR AHEAD OF AN ASSOCIATED COLD FRONT.  WHILE THE AREA
REMAINS IN THE WARM SECTOR THROUGH THE WEEKEND...THERE WILL CONTINUE
TO BE CHANCES FOR SCATTERED SHOWERS AND THUNDERSTORMS...BUT WITHOUT
A STRONG FOCUSING MECHANISM...WILL KEEP POPS IN THE CHANCE RANGE.
BY EARLY NEXT WEEK...THE LONG RANGE GUIDANCE IS SUGGESTING THAT THE
COLD FRONT SHOULD FINALLY PUSH THROUGH THE AREA...BUT THERE SHOULD
BE LITTLE IN THE WAY OF AIRMASS CHANGE WITH THE FROPA AS ANOTHER
DEEPENING TROUGH OVER THE NORTHERN PLAINS SHOULD QUICKLY BRING A
RETURN TO WARM...MOIST SOUTHERLY FLOW FOR EARLY NEXT WEEK...WHICH
WILL...IN TURN...KEEP CONTINUES CHANCES FOR PCPN ACROSS THE REGION.

KREIN

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* POSSIBLE MVFR CIGS EARLY THIS MORNING.
* EAST/NORTHEAST WINDS THRU THE PERIOD...POSSIBLY AROUND 10KT THIS
  AFTERNOON. CMS

//DISCUSSION...UPDATED 06Z...

HIGH PRESSURE OVER THE NORTHERN PLAINS WILL MOVE EAST ACROSS THE
LAKES REGION LATER TODAY AND TONIGHT. THIS WILL MAINTAIN EAST/
NORTHEAST WINDS THROUGH THE PERIOD. SPEEDS COULD INCREASE TO 10KTS
OR SLIGHTLY HIGHER THIS AFTERNOON INTO EARLY THIS EVENING WITH A
POSSIBLE LAKE BREEZE.

CIGS AROUND 3KFT HAVE DEVELOPED ACROSS NORTHEAST IL BUT APPEAR TO
BE SHIFTING EAST AND FOR NOW WILL JUST CARRY SCT MENTION. APPEARS
A BKN/OVC MID DECK WILL SPREAD ACROSS MUCH OF THE REGION OVERNIGHT
AND CONTINUE INTO THIS AFTERNOON. SOME FOG IS POSSIBLE WHERE SKIES
REMAIN MOSTLY CLEAR AND GENERALLY SOUTH AND SOUTHEAST OF THE
TERMINALS. CONTINUED FOG MENTION AT GYY BUT CONFIDENCE TOO LOW
ELSEWHERE.

A FEW ECHOS SHOWING UP ON RADAR NEAR THE QUAD CITIES AND ITS
POSSIBLE FOR A LIGHT SHOWER OR SOME SPRINKLES OUT OF THE MID DECK
THRU MID MORNING. CMS

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* LOW FOR MVFR CIGS EARLY THIS MORNING.
* MEDIUM FOR WINDS THRU THE PERIOD. CMS

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

* THURSDAY THROUGH MONDAY...CHANCE OF TSRA.

KJB

&&

.MARINE...

307 AM...HIGH PRESSURE CENTERED OVER MINNESOTA EARLY THIS MORNING
WILL MOVE ACROSS THE LAKES REGION TODAY AND TONIGHT. AS IT DOES
THE GRADIENT WILL SLOWLY WEAKEN OVER NORTHERN LAKE MICHIGAN WHILE
IT SLOWLY TIGHTENS OVER THE SOUTHERN PORTION OF THE LAKE. SPEEDS
WILL INCREASE INTO THE 10-20KT RANGE. AS THE HIGH SHIFTS EAST...
WINDS WILL TURN MORE EASTERLY BY THURSDAY MORNING THEN SHIFT
SOUTHEAST TO SOUTHERLY THURSDAY NIGHT AS A WARM FRONT LIFTS NORTH
ACROSS THE LAKE. THE GRADIENT COULD TIGHTEN ENOUGH FOR A PERIOD OF
15-25 KTS THURSDAY NIGHT INTO FRIDAY. A FRONTAL BOUNDARY IS THEN
EXPECTED TO MOVE SOUTH ACROSS THE LAKE SATURDAY AFTERNOON INTO
SATURDAY EVENING. BUT AT THE SAME TIME...LOW PRESSURE IS EXPECTED
TO DEVELOP OVER THE WESTERN LAKES AND THEN MOVE ACROSS NORTHERN
LAKE MICHIGAN BY SUNDAY MORNING. THIS MAKES FOR A CHALLENGING WIND
FORECAST. IF THE LOW BEGINS TO DEEPEN...NORTHERLY WINDS MAY
INCREASE INTO THE 15-25KT RANGE. CHANGES CAN BE EXPECTED DURING
THIS TIME PERIOD AS TRENDS EMERGE. WINDS THEN QUICKLY TURN BACK
SOUTHERLY SUNDAY NIGHT INTO MONDAY. CMS

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO







000
FXUS63 KLOT 270538
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1238 AM CDT WED AUG 27 2014

.DISCUSSION...
255 PM CDT

AS HAS BEEN THE NORM IN THE PAST WEEK TO TEN DAYS...THE PRIMARY
FORECAST CHALLENGES ARE TRYING TO DETECT WHEN BETTER THUNDERSTORM
CHANCES MAY BE AND WHAT INFLUENCE THOSE HAVE...IF ANY...ON
TEMPERATURES.

.TONIGHT...

THE INITIAL SYNOPTIC COLD FRONT HAS APPEARED TO CLEAR THE
FORECAST AREA. THIS SURGE WAS CONVECTIVELY ENHANCED AND LINGERING
HIGH DEW POINT AIR...E.G. UPPER 60S TO LOWER 70S...REMAINS ACROSS
THE SOUTH. THERE ALSO ARE ONE OR TWO WESTWARD-PROPAGATING OUTFLOW
BOUNDARIES THAT ARE LIKELY TO LAST INTO LATE THIS AFTERNOON.
CUMULUS HAS FORMED NEAR PONTIAC AND GIBSON CITY...AND BACK TOWARD
PRINCETON TO MENDOTA...WITH THESE FEATURES. WOULD NOT BE TOTALLY
SURPRISED TO SEE ISOLATED STORMS POP ON THESE AS MIXED LAYER
INHIBITION APPEARS SHALLOW WITH RECOVERING TEMPERATURES INTO THE
MID 80S AND EVEN 88 AT PONTIAC. A COUPLE SUBTLE SHORT WAVES ARE
NOTED ON WATER VAPOR...WITH ONE A LITTLE BETTER DEFINED ON
VISIBLE SATELLITE NEARING THE MISSISSIPPI RIVER FROM IA ASSOCIATED
WITH A 35 KT 500MB SPEED MAXIMUM. THIS LOOKS TO PASS OVER NORTH
CENTRAL IL EARLY THIS EVE AND COULD SEE SOME SHOWER/STORM ACTIVITY
WITH THAT...ALTHOUGH CONFIDENCE IS LOW FOR SHORT TERM STORM
CHANCES...SO HAVE KEPT POPS FAIRLY LOW. CONFLUENT 700-850MB FLOW
CONTINUES OVERNIGHT WITH ANOTHER LITTLE RIPPLE IN THE FLOW
FORECAST TO MOVE OVER THE AREA. SO CONTINUE CHANCE FOR A STORM
THROUGH THE ENTIRE NIGHT...BUT NOT EXPECTING ANYTHING WIDESPREAD.

INCOMING CLOUDS FROM THE DISTURBED MID-LEVEL FLOW SHOULD KEEP THE FOG
THREAT MINIMAL...AND TEMP/DEW POINT SPREADS LOOK TO BE MODESTLY
HIGH GOING INTO TONIGHT IN MOST AREAS...OUTSIDE OF THE FAR SOUTH.

MTF

.WEDNESDAY THROUGH TUESDAY...

THE LONGWAVE PATTERN OVER THE CENTRAL CONUS HAS BECOME MORE ZONAL
WITH TROPICAL SYSTEM OVER SERN ATLANTIC...NERN PACIFIC WHILE A BROAD
HIGH SITS OVER THE SRN CONUS AND A CLOSED UPPER LOW SWINGS THROUGH
THE GREAT BASIN.  THE SENSIBLE WEATHER OVER THE CWA WILL CONTINUE TO
BE UNSETTLED AS A STRONG SHORTWAVE QUICKLY MOVES ACROSS THE UPPER
MISSISSIPPI VALLEY AND GREAT LAKES WEDNESDAY.  UPPER RIDGING SHOULD
BUILD ACROSS THE MIDWEST ON THURSDAY AS MORE SHORT WAVE ENERGY
OVERTOPS THE RIDGE AND TRACKS ACROSS THE UPPER MIDWEST AND THE LOWER
GREAT LAKES REGIONS.  BY THURSDAY NIGHT AND FRIDAY...THE UPPER RIDGE
SHOULD BUILD TO THE EAST OF THE REGION AS THE UPPER LOW OVER THE
GREAT BASIN FINALLY OPENS UP AND LIFTS EAST ACROSS THE CENTRAL
PLAINS AS AN OPEN WAVE FRIDAY AND FRIDAY NIGHT.  THIS WAVE WILL
CROSS THE UPPER MIDWEST INTO THE WESTERN GREAT LAKES BY SUNDAY.  THE
LONGER RANGE GUIDANCE SUGGESTS THAT THIS WAVE WILL PHASE WITH
ANOTHER NORTHERN STREAM SHORTWAVE OVER THE UPPER GREAT LAKES BY
SUNDAY.  THE PROGRESSIVE AND RELATIVELY LOW AMPLITUDE UPPER LEVEL
PATTERN OVER THE CONUS WILL LEAD TO A CONTINUES ACTIVE WEATHER
PATTERN FOR THE LOCAL AREA...WITH PERIODIC CHANCES FOR SHOWERS AND
THUNDERSTORMS THROUGH MUCH OF THE PERIOD.  THE SOUTHERN PORTIONS OF
THE CWA WILL BE MORE FAVORABLE FOR ADDITIONAL PCPN WEDNESDAY AS SFC
HIGH PRESSURE SPREADS ACROSS THE GREAT LAKES REGION AND THE OLD
FRONTAL BOUNDARY LAYS OUT ALONG THE OHIO VALLEY INTO SRN ILLINOIS.
AS A SFC LOW DEEPENS OVER THE CENTRAL PLAINS ON THURSDAY...IT WILL
DRAG THE FRONT NORTH AGAIN AS A WARM FRONT...BRINGING GREATER
CHANCES FOR MORE WIDESPREAD PCPN TO THE AREA FOR THURSDAY AND
THURSDAY NIGHT.  WHILE THE FRONT REMAINS TO THE SOUTH AND HIGH
PRESSURE SPREADS ACROSS THE GREAT LAKES REGION...TEMPERATURES WILL
DIP BACK INTO THE MIDDLE 70S ACROSS THE NORTHERN PORTIONS OF THE CWA
WHILE THE SOUTHERN LOCATIONS MAY REACH THE LOWER 80S.  BY
FRIDAY...WHEN THE WARM FRONT LIFTS NORTH OF THE CWA...HOT AND HUMID
CONDITIONS WILL RETURN...WITH HIGHS IN THE MIDDLE 80S...DEWPOINTS IN
THE LOWER 70S AND MAX HEAT INDEX VALUES INTO THE LOWER 90S.  THE
DEVELOPING SFC LOW IS EXPECTED TO SLOWLY LIFT ACROSS THE UPPER
MISSISSIPPI VALLEY ON SATURDAY...KEEPING THE LOCAL AREA UNDER WARM
SECTOR AIR AHEAD OF AN ASSOCIATED COLD FRONT.  WHILE THE AREA
REMAINS IN THE WARM SECTOR THROUGH THE WEEKEND...THERE WILL CONTINUE
TO BE CHANCES FOR SCATTERED SHOWERS AND THUNDERSTORMS...BUT WITHOUT
A STRONG FOCUSING MECHANISM...WILL KEEP POPS IN THE CHANCE RANGE.
BY EARLY NEXT WEEK...THE LONG RANGE GUIDANCE IS SUGGESTING THAT THE
COLD FRONT SHOULD FINALLY PUSH THROUGH THE AREA...BUT THERE SHOULD
BE LITTLE IN THE WAY OF AIRMASS CHANGE WITH THE FROPA AS ANOTHER
DEEPENING TROUGH OVER THE NORTHERN PLAINS SHOULD QUICKLY BRING A
RETURN TO WARM...MOIST SOUTHERLY FLOW FOR EARLY NEXT WEEK...WHICH
WILL...IN TURN...KEEP CONTINUES CHANCES FOR PCPN ACROSS THE REGION.

KREIN

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* POSSIBLE MVFR CIGS EARLY THIS MORNING.
* EAST/NORTHEAST WINDS THRU THE PERIOD...POSSIBLY AROUND 10KT THIS
  AFTERNOON. CMS

//DISCUSSION...UPDATED 06Z...

HIGH PRESSURE OVER THE NORTHERN PLAINS WILL MOVE EAST ACROSS THE
LAKES REGION LATER TODAY AND TONIGHT. THIS WILL MAINTAIN EAST/
NORTHEAST WINDS THROUGH THE PERIOD. SPEEDS COULD INCREASE TO 10KTS
OR SLIGHTLY HIGHER THIS AFTERNOON INTO EARLY THIS EVENING WITH A
POSSIBLE LAKE BREEZE.

CIGS AROUND 3KFT HAVE DEVELOPED ACROSS NORTHEAST IL BUT APPEAR TO
BE SHIFTING EAST AND FOR NOW WILL JUST CARRY SCT MENTION. APPEARS
A BKN/OVC MID DECK WILL SPREAD ACROSS MUCH OF THE REGION OVERNIGHT
AND CONTINUE INTO THIS AFTERNOON. SOME FOG IS POSSIBLE WHERE SKIES
REMAIN MOSTLY CLEAR AND GENERALLY SOUTH AND SOUTHEAST OF THE
TERMINALS. CONTINUED FOG MENTION AT GYY BUT CONFIDENCE TOO LOW
ELSEWHERE.

A FEW ECHOS SHOWING UP ON RADAR NEAR THE QUAD CITIES AND ITS
POSSIBLE FOR A LIGHT SHOWER OR SOME SPRINKLES OUT OF THE MID DECK
THRU MID MORNING. CMS

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* LOW FOR MVFR CIGS EARLY THIS MORNING.
* MEDIUM FOR WINDS THRU THE PERIOD. CMS

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

* THURSDAY THROUGH MONDAY...CHANCE OF TSRA.

KJB

&&

.MARINE...
250 PM CDT

LOW PRESSURE CONTINUES TO TRACK OUT OF NORTHERN QUEBEC AS A TRAILING
COLD FRONT EXTENDS SOUTHWEST THROUGH NORTHERN INDIANA AND INTO
SOUTHERN ILLINOIS.  THE FRONT SHOULD STALL OUT OVER THE OHIO VALLEY
OVERNIGHT TONIGHT AND HIGH PRESSURE BUILDS ACROSS UPPER MISSISSIPPI
VALLEY AND WESTERN GREAT LAKES.  WINDS OVER THE LAKE HAVE BEEN
DISRUPTED BY THUNDERSTORM ACTIVITY TODAY...BUT SHOULD SETTLE INTO A
MORE NORTHERLY TO NORTHEASTERLY DIRECTION OVERNIGHT TONIGHT.  THE
HIGH IS EXPECTED TO BUILD ACROSS THE UPPER GREAT LAKES WEDNESDAY
NIGHT WHILE LOW PRESSURE DEEPENS OVER THE CENTRAL PLAINS.  WINDS
OVER THE NORTHERN PORTIONS OF THE LAKE SHOULD THEN BECOME SOMEWHAT
VARIABLE IN DIRECTION AS THE CENTER OF THE HIGH MOVES OVER THE FAR
NORTHERN PORTION OF THE LAKE...BUT THE SOUTHERN PORTIONS OF THE LAKE
SHOULD MAINTAIN A NORTHEASTERLY TO EASTERLY FETCH.  THE PERSISTENT
NORTHEASTERLY TO EASTERLY FETCH SHOULD CAUSE WINDS TO PILE UP OVER
THE WESTERN SHORE OF THE LAKE...APPROACHING 3-4FT AS WINDS REACH
10-20KT.  THE HIGH WILL CONTINUE TO BUILD TO THE EAST THURSDAY AND
FRIDAY AS LOW PRESSURE TRACKS NEWD ONTO THE UPPER MISSOURI VALLEY.
THIS WILL...IN TURN...LIFT THE OLD FRONTAL BOUNDARY THAT HAD GONE
STATIONARY OVER THE OHIO VALLEY TO LIFT NORTH AS A WARM FRONT TURING
WINDS THROUGH SOUTHEASTERLY TO SOUTHERLY BY FRIDAY.

AS HAS BEEN THE NORM IN THE PAST WEEK TO TEN DAYS...THE PRIMARY
FORECAST CHALLENGES ARE MUCH WHAT THEY HAVE BEEN...TRYING TO DETECT
WHEN BETTER THUNDERSTORM CHANCES MAY BE AND WHAT INFLUENCE THOSE
CONVECTIVE CHANCES HAVE ON TEMPERATURES.

KREIN

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 270538
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1238 AM CDT WED AUG 27 2014

.DISCUSSION...
255 PM CDT

AS HAS BEEN THE NORM IN THE PAST WEEK TO TEN DAYS...THE PRIMARY
FORECAST CHALLENGES ARE TRYING TO DETECT WHEN BETTER THUNDERSTORM
CHANCES MAY BE AND WHAT INFLUENCE THOSE HAVE...IF ANY...ON
TEMPERATURES.

.TONIGHT...

THE INITIAL SYNOPTIC COLD FRONT HAS APPEARED TO CLEAR THE
FORECAST AREA. THIS SURGE WAS CONVECTIVELY ENHANCED AND LINGERING
HIGH DEW POINT AIR...E.G. UPPER 60S TO LOWER 70S...REMAINS ACROSS
THE SOUTH. THERE ALSO ARE ONE OR TWO WESTWARD-PROPAGATING OUTFLOW
BOUNDARIES THAT ARE LIKELY TO LAST INTO LATE THIS AFTERNOON.
CUMULUS HAS FORMED NEAR PONTIAC AND GIBSON CITY...AND BACK TOWARD
PRINCETON TO MENDOTA...WITH THESE FEATURES. WOULD NOT BE TOTALLY
SURPRISED TO SEE ISOLATED STORMS POP ON THESE AS MIXED LAYER
INHIBITION APPEARS SHALLOW WITH RECOVERING TEMPERATURES INTO THE
MID 80S AND EVEN 88 AT PONTIAC. A COUPLE SUBTLE SHORT WAVES ARE
NOTED ON WATER VAPOR...WITH ONE A LITTLE BETTER DEFINED ON
VISIBLE SATELLITE NEARING THE MISSISSIPPI RIVER FROM IA ASSOCIATED
WITH A 35 KT 500MB SPEED MAXIMUM. THIS LOOKS TO PASS OVER NORTH
CENTRAL IL EARLY THIS EVE AND COULD SEE SOME SHOWER/STORM ACTIVITY
WITH THAT...ALTHOUGH CONFIDENCE IS LOW FOR SHORT TERM STORM
CHANCES...SO HAVE KEPT POPS FAIRLY LOW. CONFLUENT 700-850MB FLOW
CONTINUES OVERNIGHT WITH ANOTHER LITTLE RIPPLE IN THE FLOW
FORECAST TO MOVE OVER THE AREA. SO CONTINUE CHANCE FOR A STORM
THROUGH THE ENTIRE NIGHT...BUT NOT EXPECTING ANYTHING WIDESPREAD.

INCOMING CLOUDS FROM THE DISTURBED MID-LEVEL FLOW SHOULD KEEP THE FOG
THREAT MINIMAL...AND TEMP/DEW POINT SPREADS LOOK TO BE MODESTLY
HIGH GOING INTO TONIGHT IN MOST AREAS...OUTSIDE OF THE FAR SOUTH.

MTF

.WEDNESDAY THROUGH TUESDAY...

THE LONGWAVE PATTERN OVER THE CENTRAL CONUS HAS BECOME MORE ZONAL
WITH TROPICAL SYSTEM OVER SERN ATLANTIC...NERN PACIFIC WHILE A BROAD
HIGH SITS OVER THE SRN CONUS AND A CLOSED UPPER LOW SWINGS THROUGH
THE GREAT BASIN.  THE SENSIBLE WEATHER OVER THE CWA WILL CONTINUE TO
BE UNSETTLED AS A STRONG SHORTWAVE QUICKLY MOVES ACROSS THE UPPER
MISSISSIPPI VALLEY AND GREAT LAKES WEDNESDAY.  UPPER RIDGING SHOULD
BUILD ACROSS THE MIDWEST ON THURSDAY AS MORE SHORT WAVE ENERGY
OVERTOPS THE RIDGE AND TRACKS ACROSS THE UPPER MIDWEST AND THE LOWER
GREAT LAKES REGIONS.  BY THURSDAY NIGHT AND FRIDAY...THE UPPER RIDGE
SHOULD BUILD TO THE EAST OF THE REGION AS THE UPPER LOW OVER THE
GREAT BASIN FINALLY OPENS UP AND LIFTS EAST ACROSS THE CENTRAL
PLAINS AS AN OPEN WAVE FRIDAY AND FRIDAY NIGHT.  THIS WAVE WILL
CROSS THE UPPER MIDWEST INTO THE WESTERN GREAT LAKES BY SUNDAY.  THE
LONGER RANGE GUIDANCE SUGGESTS THAT THIS WAVE WILL PHASE WITH
ANOTHER NORTHERN STREAM SHORTWAVE OVER THE UPPER GREAT LAKES BY
SUNDAY.  THE PROGRESSIVE AND RELATIVELY LOW AMPLITUDE UPPER LEVEL
PATTERN OVER THE CONUS WILL LEAD TO A CONTINUES ACTIVE WEATHER
PATTERN FOR THE LOCAL AREA...WITH PERIODIC CHANCES FOR SHOWERS AND
THUNDERSTORMS THROUGH MUCH OF THE PERIOD.  THE SOUTHERN PORTIONS OF
THE CWA WILL BE MORE FAVORABLE FOR ADDITIONAL PCPN WEDNESDAY AS SFC
HIGH PRESSURE SPREADS ACROSS THE GREAT LAKES REGION AND THE OLD
FRONTAL BOUNDARY LAYS OUT ALONG THE OHIO VALLEY INTO SRN ILLINOIS.
AS A SFC LOW DEEPENS OVER THE CENTRAL PLAINS ON THURSDAY...IT WILL
DRAG THE FRONT NORTH AGAIN AS A WARM FRONT...BRINGING GREATER
CHANCES FOR MORE WIDESPREAD PCPN TO THE AREA FOR THURSDAY AND
THURSDAY NIGHT.  WHILE THE FRONT REMAINS TO THE SOUTH AND HIGH
PRESSURE SPREADS ACROSS THE GREAT LAKES REGION...TEMPERATURES WILL
DIP BACK INTO THE MIDDLE 70S ACROSS THE NORTHERN PORTIONS OF THE CWA
WHILE THE SOUTHERN LOCATIONS MAY REACH THE LOWER 80S.  BY
FRIDAY...WHEN THE WARM FRONT LIFTS NORTH OF THE CWA...HOT AND HUMID
CONDITIONS WILL RETURN...WITH HIGHS IN THE MIDDLE 80S...DEWPOINTS IN
THE LOWER 70S AND MAX HEAT INDEX VALUES INTO THE LOWER 90S.  THE
DEVELOPING SFC LOW IS EXPECTED TO SLOWLY LIFT ACROSS THE UPPER
MISSISSIPPI VALLEY ON SATURDAY...KEEPING THE LOCAL AREA UNDER WARM
SECTOR AIR AHEAD OF AN ASSOCIATED COLD FRONT.  WHILE THE AREA
REMAINS IN THE WARM SECTOR THROUGH THE WEEKEND...THERE WILL CONTINUE
TO BE CHANCES FOR SCATTERED SHOWERS AND THUNDERSTORMS...BUT WITHOUT
A STRONG FOCUSING MECHANISM...WILL KEEP POPS IN THE CHANCE RANGE.
BY EARLY NEXT WEEK...THE LONG RANGE GUIDANCE IS SUGGESTING THAT THE
COLD FRONT SHOULD FINALLY PUSH THROUGH THE AREA...BUT THERE SHOULD
BE LITTLE IN THE WAY OF AIRMASS CHANGE WITH THE FROPA AS ANOTHER
DEEPENING TROUGH OVER THE NORTHERN PLAINS SHOULD QUICKLY BRING A
RETURN TO WARM...MOIST SOUTHERLY FLOW FOR EARLY NEXT WEEK...WHICH
WILL...IN TURN...KEEP CONTINUES CHANCES FOR PCPN ACROSS THE REGION.

KREIN

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* POSSIBLE MVFR CIGS EARLY THIS MORNING.
* EAST/NORTHEAST WINDS THRU THE PERIOD...POSSIBLY AROUND 10KT THIS
  AFTERNOON. CMS

//DISCUSSION...UPDATED 06Z...

HIGH PRESSURE OVER THE NORTHERN PLAINS WILL MOVE EAST ACROSS THE
LAKES REGION LATER TODAY AND TONIGHT. THIS WILL MAINTAIN EAST/
NORTHEAST WINDS THROUGH THE PERIOD. SPEEDS COULD INCREASE TO 10KTS
OR SLIGHTLY HIGHER THIS AFTERNOON INTO EARLY THIS EVENING WITH A
POSSIBLE LAKE BREEZE.

CIGS AROUND 3KFT HAVE DEVELOPED ACROSS NORTHEAST IL BUT APPEAR TO
BE SHIFTING EAST AND FOR NOW WILL JUST CARRY SCT MENTION. APPEARS
A BKN/OVC MID DECK WILL SPREAD ACROSS MUCH OF THE REGION OVERNIGHT
AND CONTINUE INTO THIS AFTERNOON. SOME FOG IS POSSIBLE WHERE SKIES
REMAIN MOSTLY CLEAR AND GENERALLY SOUTH AND SOUTHEAST OF THE
TERMINALS. CONTINUED FOG MENTION AT GYY BUT CONFIDENCE TOO LOW
ELSEWHERE.

A FEW ECHOS SHOWING UP ON RADAR NEAR THE QUAD CITIES AND ITS
POSSIBLE FOR A LIGHT SHOWER OR SOME SPRINKLES OUT OF THE MID DECK
THRU MID MORNING. CMS

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* LOW FOR MVFR CIGS EARLY THIS MORNING.
* MEDIUM FOR WINDS THRU THE PERIOD. CMS

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

* THURSDAY THROUGH MONDAY...CHANCE OF TSRA.

KJB

&&

.MARINE...
250 PM CDT

LOW PRESSURE CONTINUES TO TRACK OUT OF NORTHERN QUEBEC AS A TRAILING
COLD FRONT EXTENDS SOUTHWEST THROUGH NORTHERN INDIANA AND INTO
SOUTHERN ILLINOIS.  THE FRONT SHOULD STALL OUT OVER THE OHIO VALLEY
OVERNIGHT TONIGHT AND HIGH PRESSURE BUILDS ACROSS UPPER MISSISSIPPI
VALLEY AND WESTERN GREAT LAKES.  WINDS OVER THE LAKE HAVE BEEN
DISRUPTED BY THUNDERSTORM ACTIVITY TODAY...BUT SHOULD SETTLE INTO A
MORE NORTHERLY TO NORTHEASTERLY DIRECTION OVERNIGHT TONIGHT.  THE
HIGH IS EXPECTED TO BUILD ACROSS THE UPPER GREAT LAKES WEDNESDAY
NIGHT WHILE LOW PRESSURE DEEPENS OVER THE CENTRAL PLAINS.  WINDS
OVER THE NORTHERN PORTIONS OF THE LAKE SHOULD THEN BECOME SOMEWHAT
VARIABLE IN DIRECTION AS THE CENTER OF THE HIGH MOVES OVER THE FAR
NORTHERN PORTION OF THE LAKE...BUT THE SOUTHERN PORTIONS OF THE LAKE
SHOULD MAINTAIN A NORTHEASTERLY TO EASTERLY FETCH.  THE PERSISTENT
NORTHEASTERLY TO EASTERLY FETCH SHOULD CAUSE WINDS TO PILE UP OVER
THE WESTERN SHORE OF THE LAKE...APPROACHING 3-4FT AS WINDS REACH
10-20KT.  THE HIGH WILL CONTINUE TO BUILD TO THE EAST THURSDAY AND
FRIDAY AS LOW PRESSURE TRACKS NEWD ONTO THE UPPER MISSOURI VALLEY.
THIS WILL...IN TURN...LIFT THE OLD FRONTAL BOUNDARY THAT HAD GONE
STATIONARY OVER THE OHIO VALLEY TO LIFT NORTH AS A WARM FRONT TURING
WINDS THROUGH SOUTHEASTERLY TO SOUTHERLY BY FRIDAY.

AS HAS BEEN THE NORM IN THE PAST WEEK TO TEN DAYS...THE PRIMARY
FORECAST CHALLENGES ARE MUCH WHAT THEY HAVE BEEN...TRYING TO DETECT
WHEN BETTER THUNDERSTORM CHANCES MAY BE AND WHAT INFLUENCE THOSE
CONVECTIVE CHANCES HAVE ON TEMPERATURES.

KREIN

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO







000
FXUS63 KLOT 270249
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
949 PM CDT TUE AUG 26 2014

.DISCUSSION...
255 PM CDT

AS HAS BEEN THE NORM IN THE PAST WEEK TO TEN DAYS...THE PRIMARY
FORECAST CHALLENGES ARE TRYING TO DETECT WHEN BETTER THUNDERSTORM
CHANCES MAY BE AND WHAT INFLUENCE THOSE HAVE...IF ANY...ON
TEMPERATURES.

.TONIGHT...

THE INITIAL SYNOPTIC COLD FRONT HAS APPEARED TO CLEAR THE
FORECAST AREA. THIS SURGE WAS CONVECTIVELY ENHANCED AND LINGERING
HIGH DEW POINT AIR...E.G. UPPER 60S TO LOWER 70S...REMAINS ACROSS
THE SOUTH. THERE ALSO ARE ONE OR TWO WESTWARD-PROPAGATING OUTFLOW
BOUNDARIES THAT ARE LIKELY TO LAST INTO LATE THIS AFTERNOON.
CUMULUS HAS FORMED NEAR PONTIAC AND GIBSON CITY...AND BACK TOWARD
PRINCETON TO MENDOTA...WITH THESE FEATURES. WOULD NOT BE TOTALLY
SURPRISED TO SEE ISOLATED STORMS POP ON THESE AS MIXED LAYER
INHIBITION APPEARS SHALLOW WITH RECOVERING TEMPERATURES INTO THE
MID 80S AND EVEN 88 AT PONTIAC. A COUPLE SUBTLE SHORT WAVES ARE
NOTED ON WATER VAPOR...WITH ONE A LITTLE BETTER DEFINED ON
VISIBLE SATELLITE NEARING THE MISSISSIPPI RIVER FROM IA ASSOCIATED
WITH A 35 KT 500MB SPEED MAXIMUM. THIS LOOKS TO PASS OVER NORTH
CENTRAL IL EARLY THIS EVE AND COULD SEE SOME SHOWER/STORM ACTIVITY
WITH THAT...ALTHOUGH CONFIDENCE IS LOW FOR SHORT TERM STORM
CHANCES...SO HAVE KEPT POPS FAIRLY LOW. CONFLUENT 700-850MB FLOW
CONTINUES OVERNIGHT WITH ANOTHER LITTLE RIPPLE IN THE FLOW
FORECAST TO MOVE OVER THE AREA. SO CONTINUE CHANCE FOR A STORM
THROUGH THE ENTIRE NIGHT...BUT NOT EXPECTING ANYTHING WIDESPREAD.

INCOMING CLOUDS FROM THE DISTURBED MID-LEVEL FLOW SHOULD KEEP THE FOG
THREAT MINIMAL...AND TEMP/DEW POINT SPREADS LOOK TO BE MODESTLY
HIGH GOING INTO TONIGHT IN MOST AREAS...OUTSIDE OF THE FAR SOUTH.

MTF

.WEDNESDAY THROUGH TUESDAY...

THE LONGWAVE PATTERN OVER THE CENTRAL CONUS HAS BECOME MORE ZONAL
WITH TROPICAL SYSTEM OVER SERN ATLANTIC...NERN PACIFIC WHILE A BROAD
HIGH SITS OVER THE SRN CONUS AND A CLOSED UPPER LOW SWINGS THROUGH
THE GREAT BASIN.  THE SENSIBLE WEATHER OVER THE CWA WILL CONTINUE TO
BE UNSETTLED AS A STRONG SHORTWAVE QUICKLY MOVES ACROSS THE UPPER
MISSISSIPPI VALLEY AND GREAT LAKES WEDNESDAY.  UPPER RIDGING SHOULD
BUILD ACROSS THE MIDWEST ON THURSDAY AS MORE SHORT WAVE ENERGY
OVERTOPS THE RIDGE AND TRACKS ACROSS THE UPPER MIDWEST AND THE LOWER
GREAT LAKES REGIONS.  BY THURSDAY NIGHT AND FRIDAY...THE UPPER RIDGE
SHOULD BUILD TO THE EAST OF THE REGION AS THE UPPER LOW OVER THE
GREAT BASIN FINALLY OPENS UP AND LIFTS EAST ACROSS THE CENTRAL
PLAINS AS AN OPEN WAVE FRIDAY AND FRIDAY NIGHT.  THIS WAVE WILL
CROSS THE UPPER MIDWEST INTO THE WESTERN GREAT LAKES BY SUNDAY.  THE
LONGER RANGE GUIDANCE SUGGESTS THAT THIS WAVE WILL PHASE WITH
ANOTHER NORTHERN STREAM SHORTWAVE OVER THE UPPER GREAT LAKES BY
SUNDAY.  THE PROGRESSIVE AND RELATIVELY LOW AMPLITUDE UPPER LEVEL
PATTERN OVER THE CONUS WILL LEAD TO A CONTINUES ACTIVE WEATHER
PATTERN FOR THE LOCAL AREA...WITH PERIODIC CHANCES FOR SHOWERS AND
THUNDERSTORMS THROUGH MUCH OF THE PERIOD.  THE SOUTHERN PORTIONS OF
THE CWA WILL BE MORE FAVORABLE FOR ADDITIONAL PCPN WEDNESDAY AS SFC
HIGH PRESSURE SPREADS ACROSS THE GREAT LAKES REGION AND THE OLD
FRONTAL BOUNDARY LAYS OUT ALONG THE OHIO VALLEY INTO SRN ILLINOIS.
AS A SFC LOW DEEPENS OVER THE CENTRAL PLAINS ON THURSDAY...IT WILL
DRAG THE FRONT NORTH AGAIN AS A WARM FRONT...BRINGING GREATER
CHANCES FOR MORE WIDESPREAD PCPN TO THE AREA FOR THURSDAY AND
THURSDAY NIGHT.  WHILE THE FRONT REMAINS TO THE SOUTH AND HIGH
PRESSURE SPREADS ACROSS THE GREAT LAKES REGION...TEMPERATURES WILL
DIP BACK INTO THE MIDDLE 70S ACROSS THE NORTHERN PORTIONS OF THE CWA
WHILE THE SOUTHERN LOCATIONS MAY REACH THE LOWER 80S.  BY
FRIDAY...WHEN THE WARM FRONT LIFTS NORTH OF THE CWA...HOT AND HUMID
CONDITIONS WILL RETURN...WITH HIGHS IN THE MIDDLE 80S...DEWPOINTS IN
THE LOWER 70S AND MAX HEAT INDEX VALUES INTO THE LOWER 90S.  THE
DEVELOPING SFC LOW IS EXPECTED TO SLOWLY LIFT ACROSS THE UPPER
MISSISSIPPI VALLEY ON SATURDAY...KEEPING THE LOCAL AREA UNDER WARM
SECTOR AIR AHEAD OF AN ASSOCIATED COLD FRONT.  WHILE THE AREA
REMAINS IN THE WARM SECTOR THROUGH THE WEEKEND...THERE WILL CONTINUE
TO BE CHANCES FOR SCATTERED SHOWERS AND THUNDERSTORMS...BUT WITHOUT
A STRONG FOCUSING MECHANISM...WILL KEEP POPS IN THE CHANCE RANGE.
BY EARLY NEXT WEEK...THE LONG RANGE GUIDANCE IS SUGGESTING THAT THE
COLD FRONT SHOULD FINALLY PUSH THROUGH THE AREA...BUT THERE SHOULD
BE LITTLE IN THE WAY OF AIRMASS CHANGE WITH THE FROPA AS ANOTHER
DEEPENING TROUGH OVER THE NORTHERN PLAINS SHOULD QUICKLY BRING A
RETURN TO WARM...MOIST SOUTHERLY FLOW FOR EARLY NEXT WEEK...WHICH
WILL...IN TURN...KEEP CONTINUES CHANCES FOR PCPN ACROSS THE REGION.

KREIN

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 03Z...

* EAST-NORTHEASTERLY WIND SPEEDS WEDNESDAY AFTERNOON...POSSIBLY
  NEAR 10 KT IN THE AFTERNOON.

KJB

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

A LAKE BREEZE IS CURRENTLY MOVING OVER THE EASTERN TERMINALS.
HOWEVER...WIND SPEEDS ARE GENERALLY LESS THAN 8 KT WITH THE
NORTHEASTERLY PUSH. WEATHER CONCERNS AT THE TERMINALS OVER THE NEXT
24 HOURS LOOK TO MAINLY REVOLVE AROUND THE MAGNITUDE OF THE
NORTHEASTERLY WINDS...ESPECIALLY WEDNESDAY AFTERNOON. THE MAIN
THREAT FOR THUNDERSTORMS ON WEDNESDAY LOOKS TO REMAIN SOUTH OF THE
TERMINALS. IT APPEARS THE NORTHEASTERLY WINDS WILL GENERALLY REMAIN
UNDER 10 KT...ESPECIALLY DURING THE MORNING. HOWEVER...WIND SPEEDS
COULD GET TO OR JUST SLIGHTLY ABOVE 10 KT FOR A FEW HOURS TOMORROW
AFTERNOON AS A LAKE BREEZE PUSH COULD LOCALLY ENHANCE WIND SPEEDS A
BIT.

KJB

//ORD AND MDW CONFIDENCE...UPDATED 03Z...

* HIGH WITH ALL FORECAST ELEMENTS.

KJB

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

* THURSDAY THROUGH MONDAY...CHANCE OF TSRA.

KJB

&&

.MARINE...
250 PM CDT

LOW PRESSURE CONTINUES TO TRACK OUT OF NORTHERN QUEBEC AS A TRAILING
COLD FRONT EXTENDS SOUTHWEST THROUGH NORTHERN INDIANA AND INTO
SOUTHERN ILLINOIS.  THE FRONT SHOULD STALL OUT OVER THE OHIO VALLEY
OVERNIGHT TONIGHT AND HIGH PRESSURE BUILDS ACROSS UPPER MISSISSIPPI
VALLEY AND WESTERN GREAT LAKES.  WINDS OVER THE LAKE HAVE BEEN
DISRUPTED BY THUNDERSTORM ACTIVITY TODAY...BUT SHOULD SETTLE INTO A
MORE NORTHERLY TO NORTHEASTERLY DIRECTION OVERNIGHT TONIGHT.  THE
HIGH IS EXPECTED TO BUILD ACROSS THE UPPER GREAT LAKES WEDNESDAY
NIGHT WHILE LOW PRESSURE DEEPENS OVER THE CENTRAL PLAINS.  WINDS
OVER THE NORTHERN PORTIONS OF THE LAKE SHOULD THEN BECOME SOMEWHAT
VARIABLE IN DIRECTION AS THE CENTER OF THE HIGH MOVES OVER THE FAR
NORTHERN PORTION OF THE LAKE...BUT THE SOUTHERN PORTIONS OF THE LAKE
SHOULD MAINTAIN A NORTHEASTERLY TO EASTERLY FETCH.  THE PERSISTENT
NORTHEASTERLY TO EASTERLY FETCH SHOULD CAUSE WINDS TO PILE UP OVER
THE WESTERN SHORE OF THE LAKE...APPROACHING 3-4FT AS WINDS REACH
10-20KT.  THE HIGH WILL CONTINUE TO BUILD TO THE EAST THURSDAY AND
FRIDAY AS LOW PRESSURE TRACKS NEWD ONTO THE UPPER MISSOURI VALLEY.
THIS WILL...IN TURN...LIFT THE OLD FRONTAL BOUNDARY THAT HAD GONE
STATIONARY OVER THE OHIO VALLEY TO LIFT NORTH AS A WARM FRONT TURING
WINDS THROUGH SOUTHEASTERLY TO SOUTHERLY BY FRIDAY.

AS HAS BEEN THE NORM IN THE PAST WEEK TO TEN DAYS...THE PRIMARY
FORECAST CHALLENGES ARE MUCH WHAT THEY HAVE BEEN...TRYING TO DETECT
WHEN BETTER THUNDERSTORM CHANCES MAY BE AND WHAT INFLUENCE THOSE
CONVECTIVE CHANCES HAVE ON TEMPERATURES.

KREIN

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO







000
FXUS63 KLOT 270249
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
949 PM CDT TUE AUG 26 2014

.DISCUSSION...
255 PM CDT

AS HAS BEEN THE NORM IN THE PAST WEEK TO TEN DAYS...THE PRIMARY
FORECAST CHALLENGES ARE TRYING TO DETECT WHEN BETTER THUNDERSTORM
CHANCES MAY BE AND WHAT INFLUENCE THOSE HAVE...IF ANY...ON
TEMPERATURES.

.TONIGHT...

THE INITIAL SYNOPTIC COLD FRONT HAS APPEARED TO CLEAR THE
FORECAST AREA. THIS SURGE WAS CONVECTIVELY ENHANCED AND LINGERING
HIGH DEW POINT AIR...E.G. UPPER 60S TO LOWER 70S...REMAINS ACROSS
THE SOUTH. THERE ALSO ARE ONE OR TWO WESTWARD-PROPAGATING OUTFLOW
BOUNDARIES THAT ARE LIKELY TO LAST INTO LATE THIS AFTERNOON.
CUMULUS HAS FORMED NEAR PONTIAC AND GIBSON CITY...AND BACK TOWARD
PRINCETON TO MENDOTA...WITH THESE FEATURES. WOULD NOT BE TOTALLY
SURPRISED TO SEE ISOLATED STORMS POP ON THESE AS MIXED LAYER
INHIBITION APPEARS SHALLOW WITH RECOVERING TEMPERATURES INTO THE
MID 80S AND EVEN 88 AT PONTIAC. A COUPLE SUBTLE SHORT WAVES ARE
NOTED ON WATER VAPOR...WITH ONE A LITTLE BETTER DEFINED ON
VISIBLE SATELLITE NEARING THE MISSISSIPPI RIVER FROM IA ASSOCIATED
WITH A 35 KT 500MB SPEED MAXIMUM. THIS LOOKS TO PASS OVER NORTH
CENTRAL IL EARLY THIS EVE AND COULD SEE SOME SHOWER/STORM ACTIVITY
WITH THAT...ALTHOUGH CONFIDENCE IS LOW FOR SHORT TERM STORM
CHANCES...SO HAVE KEPT POPS FAIRLY LOW. CONFLUENT 700-850MB FLOW
CONTINUES OVERNIGHT WITH ANOTHER LITTLE RIPPLE IN THE FLOW
FORECAST TO MOVE OVER THE AREA. SO CONTINUE CHANCE FOR A STORM
THROUGH THE ENTIRE NIGHT...BUT NOT EXPECTING ANYTHING WIDESPREAD.

INCOMING CLOUDS FROM THE DISTURBED MID-LEVEL FLOW SHOULD KEEP THE FOG
THREAT MINIMAL...AND TEMP/DEW POINT SPREADS LOOK TO BE MODESTLY
HIGH GOING INTO TONIGHT IN MOST AREAS...OUTSIDE OF THE FAR SOUTH.

MTF

.WEDNESDAY THROUGH TUESDAY...

THE LONGWAVE PATTERN OVER THE CENTRAL CONUS HAS BECOME MORE ZONAL
WITH TROPICAL SYSTEM OVER SERN ATLANTIC...NERN PACIFIC WHILE A BROAD
HIGH SITS OVER THE SRN CONUS AND A CLOSED UPPER LOW SWINGS THROUGH
THE GREAT BASIN.  THE SENSIBLE WEATHER OVER THE CWA WILL CONTINUE TO
BE UNSETTLED AS A STRONG SHORTWAVE QUICKLY MOVES ACROSS THE UPPER
MISSISSIPPI VALLEY AND GREAT LAKES WEDNESDAY.  UPPER RIDGING SHOULD
BUILD ACROSS THE MIDWEST ON THURSDAY AS MORE SHORT WAVE ENERGY
OVERTOPS THE RIDGE AND TRACKS ACROSS THE UPPER MIDWEST AND THE LOWER
GREAT LAKES REGIONS.  BY THURSDAY NIGHT AND FRIDAY...THE UPPER RIDGE
SHOULD BUILD TO THE EAST OF THE REGION AS THE UPPER LOW OVER THE
GREAT BASIN FINALLY OPENS UP AND LIFTS EAST ACROSS THE CENTRAL
PLAINS AS AN OPEN WAVE FRIDAY AND FRIDAY NIGHT.  THIS WAVE WILL
CROSS THE UPPER MIDWEST INTO THE WESTERN GREAT LAKES BY SUNDAY.  THE
LONGER RANGE GUIDANCE SUGGESTS THAT THIS WAVE WILL PHASE WITH
ANOTHER NORTHERN STREAM SHORTWAVE OVER THE UPPER GREAT LAKES BY
SUNDAY.  THE PROGRESSIVE AND RELATIVELY LOW AMPLITUDE UPPER LEVEL
PATTERN OVER THE CONUS WILL LEAD TO A CONTINUES ACTIVE WEATHER
PATTERN FOR THE LOCAL AREA...WITH PERIODIC CHANCES FOR SHOWERS AND
THUNDERSTORMS THROUGH MUCH OF THE PERIOD.  THE SOUTHERN PORTIONS OF
THE CWA WILL BE MORE FAVORABLE FOR ADDITIONAL PCPN WEDNESDAY AS SFC
HIGH PRESSURE SPREADS ACROSS THE GREAT LAKES REGION AND THE OLD
FRONTAL BOUNDARY LAYS OUT ALONG THE OHIO VALLEY INTO SRN ILLINOIS.
AS A SFC LOW DEEPENS OVER THE CENTRAL PLAINS ON THURSDAY...IT WILL
DRAG THE FRONT NORTH AGAIN AS A WARM FRONT...BRINGING GREATER
CHANCES FOR MORE WIDESPREAD PCPN TO THE AREA FOR THURSDAY AND
THURSDAY NIGHT.  WHILE THE FRONT REMAINS TO THE SOUTH AND HIGH
PRESSURE SPREADS ACROSS THE GREAT LAKES REGION...TEMPERATURES WILL
DIP BACK INTO THE MIDDLE 70S ACROSS THE NORTHERN PORTIONS OF THE CWA
WHILE THE SOUTHERN LOCATIONS MAY REACH THE LOWER 80S.  BY
FRIDAY...WHEN THE WARM FRONT LIFTS NORTH OF THE CWA...HOT AND HUMID
CONDITIONS WILL RETURN...WITH HIGHS IN THE MIDDLE 80S...DEWPOINTS IN
THE LOWER 70S AND MAX HEAT INDEX VALUES INTO THE LOWER 90S.  THE
DEVELOPING SFC LOW IS EXPECTED TO SLOWLY LIFT ACROSS THE UPPER
MISSISSIPPI VALLEY ON SATURDAY...KEEPING THE LOCAL AREA UNDER WARM
SECTOR AIR AHEAD OF AN ASSOCIATED COLD FRONT.  WHILE THE AREA
REMAINS IN THE WARM SECTOR THROUGH THE WEEKEND...THERE WILL CONTINUE
TO BE CHANCES FOR SCATTERED SHOWERS AND THUNDERSTORMS...BUT WITHOUT
A STRONG FOCUSING MECHANISM...WILL KEEP POPS IN THE CHANCE RANGE.
BY EARLY NEXT WEEK...THE LONG RANGE GUIDANCE IS SUGGESTING THAT THE
COLD FRONT SHOULD FINALLY PUSH THROUGH THE AREA...BUT THERE SHOULD
BE LITTLE IN THE WAY OF AIRMASS CHANGE WITH THE FROPA AS ANOTHER
DEEPENING TROUGH OVER THE NORTHERN PLAINS SHOULD QUICKLY BRING A
RETURN TO WARM...MOIST SOUTHERLY FLOW FOR EARLY NEXT WEEK...WHICH
WILL...IN TURN...KEEP CONTINUES CHANCES FOR PCPN ACROSS THE REGION.

KREIN

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 03Z...

* EAST-NORTHEASTERLY WIND SPEEDS WEDNESDAY AFTERNOON...POSSIBLY
  NEAR 10 KT IN THE AFTERNOON.

KJB

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

A LAKE BREEZE IS CURRENTLY MOVING OVER THE EASTERN TERMINALS.
HOWEVER...WIND SPEEDS ARE GENERALLY LESS THAN 8 KT WITH THE
NORTHEASTERLY PUSH. WEATHER CONCERNS AT THE TERMINALS OVER THE NEXT
24 HOURS LOOK TO MAINLY REVOLVE AROUND THE MAGNITUDE OF THE
NORTHEASTERLY WINDS...ESPECIALLY WEDNESDAY AFTERNOON. THE MAIN
THREAT FOR THUNDERSTORMS ON WEDNESDAY LOOKS TO REMAIN SOUTH OF THE
TERMINALS. IT APPEARS THE NORTHEASTERLY WINDS WILL GENERALLY REMAIN
UNDER 10 KT...ESPECIALLY DURING THE MORNING. HOWEVER...WIND SPEEDS
COULD GET TO OR JUST SLIGHTLY ABOVE 10 KT FOR A FEW HOURS TOMORROW
AFTERNOON AS A LAKE BREEZE PUSH COULD LOCALLY ENHANCE WIND SPEEDS A
BIT.

KJB

//ORD AND MDW CONFIDENCE...UPDATED 03Z...

* HIGH WITH ALL FORECAST ELEMENTS.

KJB

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

* THURSDAY THROUGH MONDAY...CHANCE OF TSRA.

KJB

&&

.MARINE...
250 PM CDT

LOW PRESSURE CONTINUES TO TRACK OUT OF NORTHERN QUEBEC AS A TRAILING
COLD FRONT EXTENDS SOUTHWEST THROUGH NORTHERN INDIANA AND INTO
SOUTHERN ILLINOIS.  THE FRONT SHOULD STALL OUT OVER THE OHIO VALLEY
OVERNIGHT TONIGHT AND HIGH PRESSURE BUILDS ACROSS UPPER MISSISSIPPI
VALLEY AND WESTERN GREAT LAKES.  WINDS OVER THE LAKE HAVE BEEN
DISRUPTED BY THUNDERSTORM ACTIVITY TODAY...BUT SHOULD SETTLE INTO A
MORE NORTHERLY TO NORTHEASTERLY DIRECTION OVERNIGHT TONIGHT.  THE
HIGH IS EXPECTED TO BUILD ACROSS THE UPPER GREAT LAKES WEDNESDAY
NIGHT WHILE LOW PRESSURE DEEPENS OVER THE CENTRAL PLAINS.  WINDS
OVER THE NORTHERN PORTIONS OF THE LAKE SHOULD THEN BECOME SOMEWHAT
VARIABLE IN DIRECTION AS THE CENTER OF THE HIGH MOVES OVER THE FAR
NORTHERN PORTION OF THE LAKE...BUT THE SOUTHERN PORTIONS OF THE LAKE
SHOULD MAINTAIN A NORTHEASTERLY TO EASTERLY FETCH.  THE PERSISTENT
NORTHEASTERLY TO EASTERLY FETCH SHOULD CAUSE WINDS TO PILE UP OVER
THE WESTERN SHORE OF THE LAKE...APPROACHING 3-4FT AS WINDS REACH
10-20KT.  THE HIGH WILL CONTINUE TO BUILD TO THE EAST THURSDAY AND
FRIDAY AS LOW PRESSURE TRACKS NEWD ONTO THE UPPER MISSOURI VALLEY.
THIS WILL...IN TURN...LIFT THE OLD FRONTAL BOUNDARY THAT HAD GONE
STATIONARY OVER THE OHIO VALLEY TO LIFT NORTH AS A WARM FRONT TURING
WINDS THROUGH SOUTHEASTERLY TO SOUTHERLY BY FRIDAY.

AS HAS BEEN THE NORM IN THE PAST WEEK TO TEN DAYS...THE PRIMARY
FORECAST CHALLENGES ARE MUCH WHAT THEY HAVE BEEN...TRYING TO DETECT
WHEN BETTER THUNDERSTORM CHANCES MAY BE AND WHAT INFLUENCE THOSE
CONVECTIVE CHANCES HAVE ON TEMPERATURES.

KREIN

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






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