000
FXUS63 KLOT 190303
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1003 PM CDT SAT MAY 18 2013
.DISCUSSION...
252 PM...MULTIPLE FORECAST CONCERNS AND CHALLENGES CONTINUE
THROUGH THE MIDDLE OF NEXT WEEK INCLUDING SEVERE POTENTIAL SUNDAY
AFTERNOON THROUGH MONDAY NIGHT...HEAVY RAIN POTENTIAL ESPECIALLY
MONDAY NIGHT THROUGH TUESDAY NIGHT ALONG WITH ASSOCIATED CLOUD
COVER...WINDS OFF THE LAKE/LAKE BREEZES AND THEIR AFFECTS ON
TEMPERATURES.
IN THE SHORT TERM...LOW LEVELS ARE NOW QUITE MOIST WITH DEWPOINTS
GENERALLY IN THE LOWER 60S WEST OF THE LAKE BREEZE. BROKEN TO AT
TIMES OVERCAST CU FIELD DEVELOPED EARLIER THIS MORNING WHICH
HELPED BUT THE BRAKES ON TEMPS MAKING IT INTO THE LOWER 80S...
THOUGH STILL A FEW LOCATIONS TAGGING 80. LACK OF INSTABILITY
HOWEVER HAS LIMITED SHOWER DEVELOPMENT WITH ISOLATED SHOWERS NOW
DEVELOPING SOUTH OF THE KANKAKEE RIVER. OTHER THAN AN ISOLATED
SPRINKLE/SHOWER...DRY WEATHER EXPECTED THROUGH SUNDAY MORNING.
WITH CONTINUED LIGHT WINDS AND CLEARING SKIES AS THE CU DISSIPATE
THIS EVENING...EXPECT AT LEAST SOME PATCHY FOG DEVELOPMENT AS
TEMPS COOL INTO THE LOWER 60S DEWPOINTS. THOUGH CONFIDENCE
REGARDING FOG DEVELOPMENT IS LOW.
CONVECTIVE TRENDS/POTENTIAL FROM SUNDAY AFTERNOON THROUGH MONDAY
NIGHT ARE FAIRLY UNCERTAIN. HOWEVER THERE APPEARS TO BE INCREASING
CONSENSUS...BOTH WITH TIMING AND LOCATION...OF A SHORTWAVE LIFTING
NORTHEAST ACROSS IOWA INTO SOUTHERN WISCONSIN SUNDAY AFTERNOON
INTO SUNDAY EVENING WITH INCREASING CHANCES FOR THUNDERSTORMS
SUNDAY AFTERNOON/EVENING. HOW FAR EAST THIS ACTIVITY MAY SPREAD
APPEARS TO BE THE MOST UNCERTAIN AND POPS MAY NEED TO BE ADJUSTED
AS WELL AS INCREASED AS TRENDS EMERGE. WITH THE UPPER RIDGE
BUILDING ACROSS THE REGION LATE TONIGHT...EXPECT HIGH TEMPS
SUNDAY TO BE WELL INTO THE MID/UPPER 80S WITH PERHAPS A FEW
LOCATIONS TAGGING 90. THESE TEMPS COMBINED WITH DEWPOINTS CREEPING
INTO THE UPPER 60S...PERHAPS EVEN 70 IN SOME LOCATIONS...WILL
PROVIDE PLENTY OF INSTABILITY IF THUNDERSTORMS ARE ABLE TO SPREAD
INTO THE CWA.
AS TIME GOES ON...CONFIDENCE DECREASES REGARDING CONVECTIVE
TRENDS AS TIMING DIFFERENCES AND LOCATIONS OF VARIOUS WAVES THEN
IMPACT FUTURE POTENTIAL CONVECTIVE TIME PERIODS. WITH ENOUGH
SUNSHINE AND ENOUGH OF A DRY PERIOD MIDDAY...EXPECT MONDAY COULD
BE AS WARM PERHAPS A FEW DEGREES WARMER THAN SUNDAY WITH HIGHS
BACK IN THE MID/UPPER 80S. ALSO STILL LOOKS BREEZY WHICH COULD
LOWER DEWPOINTS SOME IN THE AFTERNOON. SHOULD CONVECTION BE ABLE
TO FIRE...ATMOSPHERE REMAINS UNSTABLE AND SHEAR WOULD SUPPORT
CONTINUED SEVERE THREAT.
AS THE UPPER LOW OVER THE PLAINS SLOWLY SPINS EAST INTO THE
WESTERN LAKES TUESDAY AND WEDNESDAY...THIS SEEMS TO BE THE BEST
TIMING FOR A MORE PROLONGED/CONTINUED HEAVY RAIN THREAT. ANY OF
THE STORMS THAT FORM THROUGH THE MIDDLE OF NEXT WEEK WILL HAVE THE
POTENTIAL TO PRODUCE HEAVY RAIN...BUT WAVES OF MORE WIDESPREAD
STORMS WITH HEAVY RAIN APPEAR TO BE POSSIBLE LATE MONDAY NIGHT
INTO TUESDAY AND THEN AGAIN TUESDAY NIGHT INTO WEDNESDAY.
CONFIDENCE REGARDING RAINFALL AMOUNTS REMAINS LOW HOWEVER WITH
MODEL QPF STORM TOTAL AMOUNTS LOWER THAN 24 HOURS AGO. OF
COURSE...THIS DOESN/T DOWNPLAY THE POTENTIAL FOR WHAT COULD END UP
BEING SEVERAL INCHES OF RAIN IN PARTS OF THE AREA BY MIDWEEK...
JUST ADDS TO LOW CONFIDENCE REGARDING LOCATION/AMOUNTS.
LOW TEMPS APPEAR TO BE RATHER WARM IN THE 60S INTO WEDNESDAY
MORNING WITH HIGHS POTENTIALLY IN THE UPPER 70S/LOWER 80S BOTH
TUESDAY AND WEDNESDAY THOUGH CLOUD COVER/PRECIP DURATION/AMOUNTS
WILL DETERMINE JUST HOW WARM TEMPS ARE ABLE TO GO. LAKE BREEZES
AND OUTFLOWS FROM CONVECTIVE WAVES WILL ALSO MAKE TEMPERATURE
FORECASTS DIFFICULT. AS THE MAIN SURFACE LOW PASSES EAST OF THE
AREA THURSDAY/THURSDAY NIGHT...A COLD FRONT WILL PASS THROUGH THE
REGION...ENDING THE PRECIP WITH MUCH COOLER AND DRIER AIR EXPECTED
TO SPREAD ACROSS THE GREAT LAKES REGION INTO THE BEGINNING OF THE
HOLIDAY WEEKEND. CMS
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 03Z...
* MVFR FOG POTENTIAL LATE TONIGHT/EARLY SUN MORNING.
* SSE WINDS GUSTING TO 15-20 KT SUN AFTERNOON.
* A CHANCE FOR TSRA SUN EVE.
//DISCUSSION...UPDATED 00Z...
LOW PRESSURE OVER THE CENTRAL PLAINS WILL DEVELOP SLOWLY EAST AND
NORTH THROUGH THE FIRST HALF OF THE WEEK. A REMNANT STATIONARY
BOUNDARY ACROSS THE AREA...COUPLED WITH THE LAKE BREEZE
INITIALLY...WILL KEEP WINDS ESE OVER ORD AND MDW THROUGH TONIGHT.
SPEEDS SHOULD DIMINISH QUICKLY BY MID-EVE WHICH COUPLED WITH CLEAR
SKIES AND ELEVATED LOW-LEVEL MOISTURE WILL AID IN ANOTHER NIGHT
OF LIKELY AREAS OF MVFR FOG. WHILE SOME WIND COMPONENT GENERALLY
DOES NOT FAVOR FOG THIS TIME OF YEAR AT ORD AND MDW
CLIMATOLOGICALLY...THE TEMPS SHOULD NEAR THE DEW POINTS REGARDLESS
BY OVERNIGHT GIVEN THE HIGH DEW POINTS MOVING IN.
SUNDAY WILL SEE SE TO SSE WINDS INCREASE WITH SOME GUSTINESS IN
THE AFTERNOON. MODEST TO HIGH INSTABILITY WILL DEVELOP AND SHOULD
LEAD TO A FAIRLY WIDESPREAD CU FIELD. FOCUS FOR ANY STORMS LOOKS TO
BE TO THE WEST OF THE TAF SITES THROUGH MID AFTERNOON...BUT BY
LATE IN THE DAY INTO THE EVENING THERE IS A GENERAL TREND IN MODEL
GUIDANCE TO SHOW STEADILY IMPROVING CHANCES ACROSS NORTHERN IL.
ANY CONVECTION IS FAVORED TO BE MAINLY SCATTERED TOMORROW LATE
AFTERNOON INTO THE EVE. COULD BE A FEW GUSTY STORMS TOWARD RFD.
//ORD AND MDW CONFIDENCE...UPDATED 03Z...
* MEDIUM CONFIDENCE ON MVFR VISBY LATE TONIGHT BUT HIGH CONFIDENCE
ON TIMING IF IT OCCURS.
* HIGH CONFIDENCE ON WIND TRENDS ON SUNDAY...AS LAKE BREEZE SHOULD
REMAIN EAST DURING MOST AND LIKELY ALL OF THE AFTERNOON.
* LOW CONFIDENCE ON THUNDER CHANCES SUN EVE.
//OUTLOOK FOR ORD/MDW FOR 12Z MONDAY-12Z SATURDAY...UPDATED 00Z...
MONDAY-TUESDAY...LIKELY PERIODS OF TSRA IN THE REGION BUT WITH SOME
IF NOT MORE BREAKS AS WELL. STILL TOO EARLY
TO REFINE MORE PRECISE TIMING. GUSTY SSW WINDS
ON MONDAY.
WEDNESDAY...LIKELY TSRA DURING THE DAY WITH A CHANCE OF SHRA
DURING THE NIGHT.
THURSDAY...CHANCE OF SHRA.
FRIDAY...VFR LIKELY.
MTF
&&
.MARINE...
151 PM CDT
A SURFACE RIDGE OF HIGH PRESSURE CONTINUES TO BUILD
EASTWARD ACROSS EASTERN QUEBEC AND THE NORTHEASTERN CONUS THIS
AFTERNOON. HOWEVER...ATTENTION IS QUICKLY TURNING OUT WEST ACROSS
THE CENTRAL HIGH PLAINS...WHERE AN AREA OF LOW PRESSURE IS TAKING
SHAPE THIS AFTERNOON. THIS STORM SYSTEM IS EXPECTED TO MOVE
EAST-NORTHEASTWARD TOWARDS THE MID MISSOURI VALLEY BY SUNDAY
EVENING. AN ASSOCIATED SURFACE WARM FRONT...EXTENDING EASTWARD
ACROSS THE MID MISSISSIPPI VALLEY...WILL MOVE NORTHWARD ACROSS AT
LEAST THE SOUTHERN HALF TO TWO THIRDS OF THE LAKE SUNDAY NIGHT AND
MONDAY. BEHIND THIS FRONT WINDS LOOKS TO INCREASE OUT
OF THE SOUTH IN THE 15 TO 25 KT RANGE SUNDAY NIGHT INTO MONDAY.
HOWEVER...TO THE NORTH OF THIS FRONT...WINDS WILL PRIMARILY BE
MORE EASTERLY. THERE IS SOME UNCERTAINTY IN HOW FAR NORTH UP THE LAKE
THIS WARM FRONT WILL REACH. IT IS POSSIBLE THAT IT NEVER REACHES THE
NORTHERN THIRD OF THE LAKE...WHICH WOULD RESULT IN EASTERLY WINDS
REMAINING IN PLACE THERE DURING THE PERIOD.
THE OTHER CONCERN WILL BE THE THREAT FOR PERIODS OF DENSE MARINE FOG
SUNDAY NIGHT AND INTO AT LEAST THE FIRST PART OF THE COMING WEEK. AS
THIS WARM FRONT LIFTS OVER THE LAKE...MUCH HIGHER DEW POINTS WILL
MOVE OVER THE RELATIVELY COLD WATER...POSSIBLY RESULTING IN SOME
FOG DEVELOPMENT.
IT APPEARS THAT THE SURFACE LOW WILL SLOWLY MOVE EASTWARD ACROSS THE
MID MISSISSIPPI VALLEY THROUGH MID WEEK AND THEN ACROSS THE SOUTHERN
LAKES AND THE OHIO VALLEY LATER IN THE WEEK. THIS SHOULD ALLOW WARM
FRONT TO SHIFT BACK SOUTHWARD WITH TIME DURING THE WEEK. DURING THIS
TIME...THE WIND DIRECTIONS WILL PRIMARILY BECOME EAST NORTHEASTWARD
15 TO 25 KT NORTH OF THE FRONT. LATER IN THE WEEK...AS THE SURFACE
LOW PASSES EAST OF LAKE MICHIGAN...THE WINDS LOOK TO BE RATHER STOUT
UP TO 25 TO POSSIBLY AS HIGH AS 30 KT OUT OF THE NORTH FOR A PERIOD
AS A GOOD AREA OF HIGH PRESSURE BUILDS EASTWARD ACROSS ONTARIO AND
THE UPPER GREAT LAKES REGION.
KJB
&&
.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 182357
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
657 PM CDT SAT MAY 18 2013
.DISCUSSION...
252 PM...MULTIPLE FORECAST CONCERNS AND CHALLENGES CONTINUE
THROUGH THE MIDDLE OF NEXT WEEK INCLUDING SEVERE POTENTIAL SUNDAY
AFTERNOON THROUGH MONDAY NIGHT...HEAVY RAIN POTENTIAL ESPECIALLY
MONDAY NIGHT THROUGH TUESDAY NIGHT ALONG WITH ASSOCIATED CLOUD
COVER...WINDS OFF THE LAKE/LAKE BREEZES AND THEIR AFFECTS ON
TEMPERATURES.
IN THE SHORT TERM...LOW LEVELS ARE NOW QUITE MOIST WITH DEWPOINTS
GENERALLY IN THE LOWER 60S WEST OF THE LAKE BREEZE. BROKEN TO AT
TIMES OVERCAST CU FIELD DEVELOPED EARLIER THIS MORNING WHICH
HELPED BUT THE BRAKES ON TEMPS MAKING IT INTO THE LOWER 80S...
THOUGH STILL A FEW LOCATIONS TAGGING 80. LACK OF INSTABILITY
HOWEVER HAS LIMITED SHOWER DEVELOPMENT WITH ISOLATED SHOWERS NOW
DEVELOPING SOUTH OF THE KANKAKEE RIVER. OTHER THAN AN ISOLATED
SPRINKLE/SHOWER...DRY WEATHER EXPECTED THROUGH SUNDAY MORNING.
WITH CONTINUED LIGHT WINDS AND CLEARING SKIES AS THE CU DISSIPATE
THIS EVENING...EXPECT AT LEAST SOME PATCHY FOG DEVELOPMENT AS
TEMPS COOL INTO THE LOWER 60S DEWPOINTS. THOUGH CONFIDENCE
REGARDING FOG DEVELOPMENT IS LOW.
CONVECTIVE TRENDS/POTENTIAL FROM SUNDAY AFTERNOON THROUGH MONDAY
NIGHT ARE FAIRLY UNCERTAIN. HOWEVER THERE APPEARS TO BE INCREASING
CONSENSUS...BOTH WITH TIMING AND LOCATION...OF A SHORTWAVE LIFTING
NORTHEAST ACROSS IOWA INTO SOUTHERN WISCONSIN SUNDAY AFTERNOON
INTO SUNDAY EVENING WITH INCREASING CHANCES FOR THUNDERSTORMS
SUNDAY AFTERNOON/EVENING. HOW FAR EAST THIS ACTIVITY MAY SPREAD
APPEARS TO BE THE MOST UNCERTAIN AND POPS MAY NEED TO BE ADJUSTED
AS WELL AS INCREASED AS TRENDS EMERGE. WITH THE UPPER RIDGE
BUILDING ACROSS THE REGION LATE TONIGHT...EXPECT HIGH TEMPS
SUNDAY TO BE WELL INTO THE MID/UPPER 80S WITH PERHAPS A FEW
LOCATIONS TAGGING 90. THESE TEMPS COMBINED WITH DEWPOINTS CREEPING
INTO THE UPPER 60S...PERHAPS EVEN 70 IN SOME LOCATIONS...WILL
PROVIDE PLENTY OF INSTABILITY IF THUNDERSTORMS ARE ABLE TO SPREAD
INTO THE CWA.
AS TIME GOES ON...CONFIDENCE DECREASES REGARDING CONVECTIVE
TRENDS AS TIMING DIFFERENCES AND LOCATIONS OF VARIOUS WAVES THEN
IMPACT FUTURE POTENTIAL CONVECTIVE TIME PERIODS. WITH ENOUGH
SUNSHINE AND ENOUGH OF A DRY PERIOD MIDDAY...EXPECT MONDAY COULD
BE AS WARM PERHAPS A FEW DEGREES WARMER THAN SUNDAY WITH HIGHS
BACK IN THE MID/UPPER 80S. ALSO STILL LOOKS BREEZY WHICH COULD
LOWER DEWPOINTS SOME IN THE AFTERNOON. SHOULD CONVECTION BE ABLE
TO FIRE...ATMOSPHERE REMAINS UNSTABLE AND SHEAR WOULD SUPPORT
CONTINUED SEVERE THREAT.
AS THE UPPER LOW OVER THE PLAINS SLOWLY SPINS EAST INTO THE
WESTERN LAKES TUESDAY AND WEDNESDAY...THIS SEEMS TO BE THE BEST
TIMING FOR A MORE PROLONGED/CONTINUED HEAVY RAIN THREAT. ANY OF
THE STORMS THAT FORM THROUGH THE MIDDLE OF NEXT WEEK WILL HAVE THE
POTENTIAL TO PRODUCE HEAVY RAIN...BUT WAVES OF MORE WIDESPREAD
STORMS WITH HEAVY RAIN APPEAR TO BE POSSIBLE LATE MONDAY NIGHT
INTO TUESDAY AND THEN AGAIN TUESDAY NIGHT INTO WEDNESDAY.
CONFIDENCE REGARDING RAINFALL AMOUNTS REMAINS LOW HOWEVER WITH
MODEL QPF STORM TOTAL AMOUNTS LOWER THAN 24 HOURS AGO. OF
COURSE...THIS DOESN/T DOWNPLAY THE POTENTIAL FOR WHAT COULD END UP
BEING SEVERAL INCHES OF RAIN IN PARTS OF THE AREA BY MIDWEEK...
JUST ADDS TO LOW CONFIDENCE REGARDING LOCATION/AMOUNTS.
LOW TEMPS APPEAR TO BE RATHER WARM IN THE 60S INTO WEDNESDAY
MORNING WITH HIGHS POTENTIALLY IN THE UPPER 70S/LOWER 80S BOTH
TUESDAY AND WEDNESDAY THOUGH CLOUD COVER/PRECIP DURATION/AMOUNTS
WILL DETERMINE JUST HOW WARM TEMPS ARE ABLE TO GO. LAKE BREEZES
AND OUTFLOWS FROM CONVECTIVE WAVES WILL ALSO MAKE TEMPERATURE
FORECASTS DIFFICULT. AS THE MAIN SURFACE LOW PASSES EAST OF THE
AREA THURSDAY/THURSDAY NIGHT...A COLD FRONT WILL PASS THROUGH THE
REGION...ENDING THE PRECIP WITH MUCH COOLER AND DRIER AIR EXPECTED
TO SPREAD ACROSS THE GREAT LAKES REGION INTO THE BEGINNING OF THE
HOLIDAY WEEKEND. CMS
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 00Z...
* ESE WINDS NEAR 10 KT THROUGH 01Z-02Z.
* MVFR FOG POTENTIAL LATE TONIGHT/EARLY SUN MORNING.
* SSE WINDS GUSTING TO 15-20 KT SUN AFTERNOON.
* A CHANCE FOR TSRA SUN EVE.
//DISCUSSION...UPDATED 00Z...
LOW PRESSURE OVER THE CENTRAL PLAINS WILL DEVELOP SLOWLY EAST AND
NORTH THROUGH THE FIRST HALF OF THE WEEK. A REMNANT STATIONARY
BOUNDARY ACROSS THE AREA...COUPLED WITH THE LAKE BREEZE
INITIALLY...WILL KEEP WINDS ESE OVER ORD AND MDW THROUGH TONIGHT.
SPEEDS SHOULD DIMINISH QUICKLY BY MID-EVE WHICH COUPLED WITH CLEAR
SKIES AND ELEVATED LOW-LEVEL MOISTURE WILL AID IN ANOTHER NIGHT
OF LIKELY AREAS OF MVFR FOG. WHILE SOME WIND COMPONENT GENERALLY
DOES NOT FAVOR FOG THIS TIME OF YEAR AT ORD AND MDW
CLIMATOLOGICALLY...THE TEMPS SHOULD NEAR THE DEW POINTS REGARDLESS
BY OVERNIGHT GIVEN THE HIGH DEW POINTS MOVING IN.
SUNDAY WILL SEE SE TO SSE WINDS INCREASE WITH SOME GUSTINESS IN
THE AFTERNOON. MODEST TO HIGH INSTABILITY WILL DEVELOP AND SHOULD
LEAD TO A FAIRLY WIDESPREAD CU FIELD. FOCUS FOR ANY STORMS LOOKS TO
BE TO THE WEST OF THE TAF SITES THROUGH MID AFTERNOON...BUT BY
LATE IN THE DAY INTO THE EVENING THERE IS A GENERAL TREND IN MODEL
GUIDANCE TO SHOW STEADILY IMPROVING CHANCES ACROSS NORTHERN IL.
ANY CONVECTION IS FAVORED TO BE MAINLY SCATTERED TOMORROW LATE
AFTERNOON INTO THE EVE. COULD BE A FEW GUSTY STORMS TOWARD RFD.
//ORD AND MDW CONFIDENCE...UPDATED 00Z...
* MEDIUM CONFIDENCE ON ESE WIND SPEEDS OF 10 KT THROUGH 02Z...MAY
DROP BELOW THAT PRIOR TO 02Z.
* MEDIUM CONFIDENCE ON MVFR VISBY LATE TONIGHT BUT HIGH CONFIDENCE
ON TIMING IF IT OCCURS.
* HIGH CONFIDENCE ON WIND TRENDS ON SUNDAY...AS LAKE BREEZE SHOULD
REMAIN EAST DURING MOST AND LIKELY ALL OF THE AFTERNOON.
* LOW CONFIDENCE ON THUNDER CHANCES SUN EVE.
//OUTLOOK FOR ORD/MDW FOR 12Z MONDAY-12Z SATURDAY...UPDATED 00Z...
MONDAY-TUESDAY...LIKELY PERIODS OF TSRA IN THE REGION BUT WITH SOME
IF NOT MORE BREAKS AS WELL. STILL TOO EARLY
TO REFINE MORE PRECISE TIMING. GUSTY SSW WINDS
ON MONDAY.
WEDNESDAY...LIKELY TSRA DURING THE DAY WITH A CHANCE OF SHRA
DURING THE NIGHT.
THURSDAY...CHANCE OF SHRA.
FRIDAY...VFR LIKELY.
MTF
&&
.MARINE...
151 PM CDT
A SURFACE RIDGE OF HIGH PRESSURE CONTINUES TO BUILD
EASTWARD ACROSS EASTERN QUEBEC AND THE NORTHEASTERN CONUS THIS
AFTERNOON. HOWEVER...ATTENTION IS QUICKLY TURNING OUT WEST ACROSS
THE CENTRAL HIGH PLAINS...WHERE AN AREA OF LOW PRESSURE IS TAKING
SHAPE THIS AFTERNOON. THIS STORM SYSTEM IS EXPECTED TO MOVE
EAST-NORTHEASTWARD TOWARDS THE MID MISSOURI VALLEY BY SUNDAY
EVENING. AN ASSOCIATED SURFACE WARM FRONT...EXTENDING EASTWARD
ACROSS THE MID MISSISSIPPI VALLEY...WILL MOVE NORTHWARD ACROSS AT
LEAST THE SOUTHERN HALF TO TWO THIRDS OF THE LAKE SUNDAY NIGHT AND
MONDAY. BEHIND THIS FRONT WINDS LOOKS TO INCREASE OUT
OF THE SOUTH IN THE 15 TO 25 KT RANGE SUNDAY NIGHT INTO MONDAY.
HOWEVER...TO THE NORTH OF THIS FRONT...WINDS WILL PRIMARILY BE
MORE EASTERLY. THERE IS SOME UNCERTAINTY IN HOW FAR NORTH UP THE LAKE
THIS WARM FRONT WILL REACH. IT IS POSSIBLE THAT IT NEVER REACHES THE
NORTHERN THIRD OF THE LAKE...WHICH WOULD RESULT IN EASTERLY WINDS
REMAINING IN PLACE THERE DURING THE PERIOD.
THE OTHER CONCERN WILL BE THE THREAT FOR PERIODS OF DENSE MARINE FOG
SUNDAY NIGHT AND INTO AT LEAST THE FIRST PART OF THE COMING WEEK. AS
THIS WARM FRONT LIFTS OVER THE LAKE...MUCH HIGHER DEW POINTS WILL
MOVE OVER THE RELATIVELY COLD WATER...POSSIBLY RESULTING IN SOME
FOG DEVELOPMENT.
IT APPEARS THAT THE SURFACE LOW WILL SLOWLY MOVE EASTWARD ACROSS THE
MID MISSISSIPPI VALLEY THROUGH MID WEEK AND THEN ACROSS THE SOUTHERN
LAKES AND THE OHIO VALLEY LATER IN THE WEEK. THIS SHOULD ALLOW WARM
FRONT TO SHIFT BACK SOUTHWARD WITH TIME DURING THE WEEK. DURING THIS
TIME...THE WIND DIRECTIONS WILL PRIMARILY BECOME EAST NORTHEASTWARD
15 TO 25 KT NORTH OF THE FRONT. LATER IN THE WEEK...AS THE SURFACE
LOW PASSES EAST OF LAKE MICHIGAN...THE WINDS LOOK TO BE RATHER STOUT
UP TO 25 TO POSSIBLY AS HIGH AS 30 KT OUT OF THE NORTH FOR A PERIOD
AS A GOOD AREA OF HIGH PRESSURE BUILDS EASTWARD ACROSS ONTARIO AND
THE UPPER GREAT LAKES REGION.
KJB
&&
.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 182200
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
500 PM CDT SAT MAY 18 2013
.DISCUSSION...
252 PM...MULTIPLE FORECAST CONCERNS AND CHALLENGES CONTINUE
THROUGH THE MIDDLE OF NEXT WEEK INCLUDING SEVERE POTENTIAL SUNDAY
AFTERNOON THROUGH MONDAY NIGHT...HEAVY RAIN POTENTIAL ESPECIALLY
MONDAY NIGHT THROUGH TUESDAY NIGHT ALONG WITH ASSOCIATED CLOUD
COVER...WINDS OFF THE LAKE/LAKE BREEZES AND THEIR AFFECTS ON
TEMPERATURES.
IN THE SHORT TERM...LOW LEVELS ARE NOW QUITE MOIST WITH DEWPOINTS
GENERALLY IN THE LOWER 60S WEST OF THE LAKE BREEZE. BROKEN TO AT
TIMES OVERCAST CU FIELD DEVELOPED EARLIER THIS MORNING WHICH
HELPED BUT THE BRAKES ON TEMPS MAKING IT INTO THE LOWER 80S...
THOUGH STILL A FEW LOCATIONS TAGGING 80. LACK OF INSTABILITY
HOWEVER HAS LIMITED SHOWER DEVELOPMENT WITH ISOLATED SHOWERS NOW
DEVELOPING SOUTH OF THE KANKAKEE RIVER. OTHER THAN AN ISOLATED
SPRINKLE/SHOWER...DRY WEATHER EXPECTED THROUGH SUNDAY MORNING.
WITH CONTINUED LIGHT WINDS AND CLEARING SKIES AS THE CU DISSIPATE
THIS EVENING...EXPECT AT LEAST SOME PATCHY FOG DEVELOPMENT AS
TEMPS COOL INTO THE LOWER 60S DEWPOINTS. THOUGH CONFIDENCE
REGARDING FOG DEVELOPMENT IS LOW.
CONVECTIVE TRENDS/POTENTIAL FROM SUNDAY AFTERNOON THROUGH MONDAY
NIGHT ARE FAIRLY UNCERTAIN. HOWEVER THERE APPEARS TO BE INCREASING
CONSENSUS...BOTH WITH TIMING AND LOCATION...OF A SHORTWAVE LIFTING
NORTHEAST ACROSS IOWA INTO SOUTHERN WISCONSIN SUNDAY AFTERNOON
INTO SUNDAY EVENING WITH INCREASING CHANCES FOR THUNDERSTORMS
SUNDAY AFTERNOON/EVENING. HOW FAR EAST THIS ACTIVITY MAY SPREAD
APPEARS TO BE THE MOST UNCERTAIN AND POPS MAY NEED TO BE ADJUSTED
AS WELL AS INCREASED AS TRENDS EMERGE. WITH THE UPPER RIDGE
BUILDING ACROSS THE REGION LATE TONIGHT...EXPECT HIGH TEMPS
SUNDAY TO BE WELL INTO THE MID/UPPER 80S WITH PERHAPS A FEW
LOCATIONS TAGGING 90. THESE TEMPS COMBINED WITH DEWPOINTS CREEPING
INTO THE UPPER 60S...PERHAPS EVEN 70 IN SOME LOCATIONS...WILL
PROVIDE PLENTY OF INSTABILITY IF THUNDERSTORMS ARE ABLE TO SPREAD
INTO THE CWA.
AS TIME GOES ON...CONFIDENCE DECREASES REGARDING CONVECTIVE
TRENDS AS TIMING DIFFERENCES AND LOCATIONS OF VARIOUS WAVES THEN
IMPACT FUTURE POTENTIAL CONVECTIVE TIME PERIODS. WITH ENOUGH
SUNSHINE AND ENOUGH OF A DRY PERIOD MIDDAY...EXPECT MONDAY COULD
BE AS WARM PERHAPS A FEW DEGREES WARMER THAN SUNDAY WITH HIGHS
BACK IN THE MID/UPPER 80S. ALSO STILL LOOKS BREEZY WHICH COULD
LOWER DEWPOINTS SOME IN THE AFTERNOON. SHOULD CONVECTION BE ABLE
TO FIRE...ATMOSPHERE REMAINS UNSTABLE AND SHEAR WOULD SUPPORT
CONTINUED SEVERE THREAT.
AS THE UPPER LOW OVER THE PLAINS SLOWLY SPINS EAST INTO THE
WESTERN LAKES TUESDAY AND WEDNESDAY...THIS SEEMS TO BE THE BEST
TIMING FOR A MORE PROLONGED/CONTINUED HEAVY RAIN THREAT. ANY OF
THE STORMS THAT FORM THROUGH THE MIDDLE OF NEXT WEEK WILL HAVE THE
POTENTIAL TO PRODUCE HEAVY RAIN...BUT WAVES OF MORE WIDESPREAD
STORMS WITH HEAVY RAIN APPEAR TO BE POSSIBLE LATE MONDAY NIGHT
INTO TUESDAY AND THEN AGAIN TUESDAY NIGHT INTO WEDNESDAY.
CONFIDENCE REGARDING RAINFALL AMOUNTS REMAINS LOW HOWEVER WITH
MODEL QPF STORM TOTAL AMOUNTS LOWER THAN 24 HOURS AGO. OF
COURSE...THIS DOESN/T DOWNPLAY THE POTENTIAL FOR WHAT COULD END UP
BEING SEVERAL INCHES OF RAIN IN PARTS OF THE AREA BY MIDWEEK...
JUST ADDS TO LOW CONFIDENCE REGARDING LOCATION/AMOUNTS.
LOW TEMPS APPEAR TO BE RATHER WARM IN THE 60S INTO WEDNESDAY
MORNING WITH HIGHS POTENTIALLY IN THE UPPER 70S/LOWER 80S BOTH
TUESDAY AND WEDNESDAY THOUGH CLOUD COVER/PRECIP DURATION/AMOUNTS
WILL DETERMINE JUST HOW WARM TEMPS ARE ABLE TO GO. LAKE BREEZES
AND OUTFLOWS FROM CONVECTIVE WAVES WILL ALSO MAKE TEMPERATURE
FORECASTS DIFFICULT. AS THE MAIN SURFACE LOW PASSES EAST OF THE
AREA THURSDAY/THURSDAY NIGHT...A COLD FRONT WILL PASS THROUGH THE
REGION...ENDING THE PRECIP WITH MUCH COOLER AND DRIER AIR EXPECTED
TO SPREAD ACROSS THE GREAT LAKES REGION INTO THE BEGINNING OF THE
HOLIDAY WEEKEND. CMS
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 22Z...
* SE TO ESE WINDS NEAR 10 KT AT TIMES THROUGH EARLY EVE.
* MVFR VSBY POSSIBLE OVERNIGHT THROUGH DAYBREAK SUNDAY.
MDB/MTF
//DISCUSSION...UPDATED 18Z...
LAKE BREEZE BOUNDARY HAS BECOME BETTER DEFINED VIA MESO OBS AND
VISIBLE SATELLITE IMAGERY EXTENDING FROM NEAR PWK TO GYY AND IS
MAKING A SLOW INLAND PUSH. HAVE DECENT CONFIDENCE IN WINDS TURNING
EAST OR NORTHEAST AT ORD/MDW TOWARD MID AFTERNOON BUT AM NOT SURE
HOW FAR PAST THE TERMINALS THE BOUNDARY WILL PUSH. TIMING MAY NEED
TO BE REFINED. SCT-BKN LOWER END VFR CU WILL CONTINUE TO LIFT
THROUGH THE AFTERNOON AND AREAS EAST OF THE LAKE BREEZE WILL
LIKELY SCOUR OUT BASED ON LATEST TRENDS. WINDS WILL DIMINISH THIS
EVENING AND BECOME LIGHT AND VARIABLE OVERNIGHT. THERE IS A BIT
MORE MOISTURE IN THE AIR SO VSBY REDUCTION LOOKS MORE LIKELY THAN
THIS MORNING SO WILL CONTINUE WITH MVFR VSBY TOWARD DAYBREAK. SOME
IFR IS POSSIBLE AT RFD/DPA BUT WILL LEAVE MVFR FOR NOW. WINDS WILL
INCREASE FROM THE SOUTHEAST THROUGH SUNDAY MORNING ALLOWING VSBY
TO IMPROVE. SOME VFR CU MAY ONCE AGAIN DEVELOP. SHRA/TSRA CHANCES
WILL INCREASE FROM THE WEST LATE IN THE DAY AND EVENING.
MDB
//ORD AND MDW CONFIDENCE...UPDATED 22Z...
* MEDIUM-HIGH CONFIDENCE IN WIND DIRECTION FORECAST THROUGH THE
EVE AND THAT SPEEDS WILL REMAIN GENERALLY UNDER 10 KT.
* MEDIUM CONFIDENCE IN MVFR VSBY POTENTIAL EARLY SUNDAY.
MDB/MTF
//OUTLOOK FOR ORD/MDW FOR 00Z MONDAY-12Z SATURDAY...UPDATED 12Z...
SUNDAY NIGHT...VFR TRENDING TO PATCHY MVFR. PERIODS OF TSRA.
MONDAY THROUGH WEDNESDAY...PERIODS OF TSRA
THURSDAY...CHC SHRA.
FRIDAY...VFR. NO SIG WX.
BEACHLER
&&
.MARINE...
151 PM CDT
A SURFACE RIDGE OF HIGH PRESSURE CONTINUES TO BUILD
EASTWARD ACROSS EASTERN QUEBEC AND THE NORTHEASTERN CONUS THIS
AFTERNOON. HOWEVER...ATTENTION IS QUICKLY TURNING OUT WEST ACROSS
THE CENTRAL HIGH PLAINS...WHERE AN AREA OF LOW PRESSURE IS TAKING
SHAPE THIS AFTERNOON. THIS STORM SYSTEM IS EXPECTED TO MOVE
EAST-NORTHEASTWARD TOWARDS THE MID MISSOURI VALLEY BY SUNDAY
EVENING. AN ASSOCIATED SURFACE WARM FRONT...EXTENDING EASTWARD
ACROSS THE MID MISSISSIPPI VALLEY...WILL MOVE NORTHWARD ACROSS AT
LEAST THE SOUTHERN HALF TO TWO THIRDS OF THE LAKE SUNDAY NIGHT AND
MONDAY. BEHIND THIS FRONT WINDS LOOKS TO INCREASE OUT
OF THE SOUTH IN THE 15 TO 25 KT RANGE SUNDAY NIGHT INTO MONDAY.
HOWEVER...TO THE NORTH OF THIS FRONT...WINDS WILL PRIMARILY BE
MORE EASTERLY. THERE IS SOME UNCERTAINTY IN HOW FAR NORTH UP THE LAKE
THIS WARM FRONT WILL REACH. IT IS POSSIBLE THAT IT NEVER REACHES THE
NORTHERN THIRD OF THE LAKE...WHICH WOULD RESULT IN EASTERLY WINDS
REMAINING IN PLACE THERE DURING THE PERIOD.
THE OTHER CONCERN WILL BE THE THREAT FOR PERIODS OF DENSE MARINE FOG
SUNDAY NIGHT AND INTO AT LEAST THE FIRST PART OF THE COMING WEEK. AS
THIS WARM FRONT LIFTS OVER THE LAKE...MUCH HIGHER DEW POINTS WILL
MOVE OVER THE RELATIVELY COLD WATER...POSSIBLY RESULTING IN SOME
FOG DEVELOPMENT.
IT APPEARS THAT THE SURFACE LOW WILL SLOWLY MOVE EASTWARD ACROSS THE
MID MISSISSIPPI VALLEY THROUGH MID WEEK AND THEN ACROSS THE SOUTHERN
LAKES AND THE OHIO VALLEY LATER IN THE WEEK. THIS SHOULD ALLOW WARM
FRONT TO SHIFT BACK SOUTHWARD WITH TIME DURING THE WEEK. DURING THIS
TIME...THE WIND DIRECTIONS WILL PRIMARILY BECOME EAST NORTHEASTWARD
15 TO 25 KT NORTH OF THE FRONT. LATER IN THE WEEK...AS THE SURFACE
LOW PASSES EAST OF LAKE MICHIGAN...THE WINDS LOOK TO BE RATHER STOUT
UP TO 25 TO POSSIBLY AS HIGH AS 30 KT OUT OF THE NORTH FOR A PERIOD
AS A GOOD AREA OF HIGH PRESSURE BUILDS EASTWARD ACROSS ONTARIO AND
THE UPPER GREAT LAKES REGION.
KJB
&&
.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 181956
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
256 PM CDT SAT MAY 18 2013
.DISCUSSION...
252 PM...MULTIPLE FORECAST CONCERNS AND CHALLENGES CONTINUE
THROUGH THE MIDDLE OF NEXT WEEK INCLUDING SEVERE POTENTIAL SUNDAY
AFTERNOON THROUGH MONDAY NIGHT...HEAVY RAIN POTENTIAL ESPECIALLY
MONDAY NIGHT THROUGH TUESDAY NIGHT ALONG WITH ASSOCIATED CLOUD
COVER...WINDS OFF THE LAKE/LAKE BREEZES AND THEIR AFFECTS ON
TEMPERATURES.
IN THE SHORT TERM...LOW LEVELS ARE NOW QUITE MOIST WITH DEWPOINTS
GENERALLY IN THE LOWER 60S WEST OF THE LAKE BREEZE. BROKEN TO AT
TIMES OVERCAST CU FIELD DEVELOPED EARLIER THIS MORNING WHICH
HELPED BUT THE BRAKES ON TEMPS MAKING IT INTO THE LOWER 80S...
THOUGH STILL A FEW LOCATIONS TAGGING 80. LACK OF INSTABILITY
HOWEVER HAS LIMITED SHOWER DEVELOPMENT WITH ISOLATED SHOWERS NOW
DEVELOPING SOUTH OF THE KANKAKEE RIVER. OTHER THAN AN ISOLATED
SPRINKLE/SHOWER...DRY WEATHER EXPECTED THROUGH SUNDAY MORNING.
WITH CONTINUED LIGHT WINDS AND CLEARING SKIES AS THE CU DISSIPATE
THIS EVENING...EXPECT AT LEAST SOME PATCHY FOG DEVELOPMENT AS
TEMPS COOL INTO THE LOWER 60S DEWPOINTS. THOUGH CONFIDENCE
REGARDING FOG DEVELOPMENT IS LOW.
CONVECTIVE TRENDS/POTENTIAL FROM SUNDAY AFTERNOON THROUGH MONDAY
NIGHT ARE FAIRLY UNCERTAIN. HOWEVER THERE APPEARS TO BE INCREASING
CONSENSUS...BOTH WITH TIMING AND LOCATION...OF A SHORTWAVE LIFTING
NORTHEAST ACROSS IOWA INTO SOUTHERN WISCONSIN SUNDAY AFTERNOON
INTO SUNDAY EVENING WITH INCREASING CHANCES FOR THUNDERSTORMS
SUNDAY AFTERNOON/EVENING. HOW FAR EAST THIS ACTIVITY MAY SPREAD
APPEARS TO BE THE MOST UNCERTAIN AND POPS MAY NEED TO BE ADJUSTED
AS WELL AS INCREASED AS TRENDS EMERGE. WITH THE UPPER RIDGE
BUILDING ACROSS THE REGION LATE TONIGHT...EXPECT HIGH TEMPS
SUNDAY TO BE WELL INTO THE MID/UPPER 80S WITH PERHAPS A FEW
LOCATIONS TAGGING 90. THESE TEMPS COMBINED WITH DEWPOINTS CREEPING
INTO THE UPPER 60S...PERHAPS EVEN 70 IN SOME LOCATIONS...WILL
PROVIDE PLENTY OF INSTABILITY IF THUNDERSTORMS ARE ABLE TO SPREAD
INTO THE CWA.
AS TIME GOES ON...CONFIDENCE DECREASES REGARDING CONVECTIVE
TRENDS AS TIMING DIFFERENCES AND LOCATIONS OF VARIOUS WAVES THEN
IMPACT FUTURE POTENTIAL CONVECTIVE TIME PERIODS. WITH ENOUGH
SUNSHINE AND ENOUGH OF A DRY PERIOD MIDDAY...EXPECT MONDAY COULD
BE AS WARM PERHAPS A FEW DEGREES WARMER THAN SUNDAY WITH HIGHS
BACK IN THE MID/UPPER 80S. ALSO STILL LOOKS BREEZY WHICH COULD
LOWER DEWPOINTS SOME IN THE AFTERNOON. SHOULD CONVECTION BE ABLE
TO FIRE...ATMOSPHERE REMAINS UNSTABLE AND SHEAR WOULD SUPPORT
CONTINUED SEVERE THREAT.
AS THE UPPER LOW OVER THE PLAINS SLOWLY SPINS EAST INTO THE
WESTERN LAKES TUESDAY AND WEDNESDAY...THIS SEEMS TO BE THE BEST
TIMING FOR A MORE PROLONGED/CONTINUED HEAVY RAIN THREAT. ANY OF
THE STORMS THAT FORM THROUGH THE MIDDLE OF NEXT WEEK WILL HAVE THE
POTENTIAL TO PRODUCE HEAVY RAIN...BUT WAVES OF MORE WIDESPREAD
STORMS WITH HEAVY RAIN APPEAR TO BE POSSIBLE LATE MONDAY NIGHT
INTO TUESDAY AND THEN AGAIN TUESDAY NIGHT INTO WEDNESDAY.
CONFIDENCE REGARDING RAINFALL AMOUNTS REMAINS LOW HOWEVER WITH
MODEL QPF STORM TOTAL AMOUNTS LOWER THAN 24 HOURS AGO. OF
COURSE...THIS DOESN/T DOWNPLAY THE POTENTIAL FOR WHAT COULD END UP
BEING SEVERAL INCHES OF RAIN IN PARTS OF THE AREA BY MIDWEEK...
JUST ADDS TO LOW CONFIDENCE REGARDING LOCATION/AMOUNTS.
LOW TEMPS APPEAR TO BE RATHER WARM IN THE 60S INTO WEDNESDAY
MORNING WITH HIGHS POTENTIALLY IN THE UPPER 70S/LOWER 80S BOTH
TUESDAY AND WEDNESDAY THOUGH CLOUD COVER/PRECIP DURATION/AMOUNTS
WILL DETERMINE JUST HOW WARM TEMPS ARE ABLE TO GO. LAKE BREEZES
AND OUTFLOWS FROM CONVECTIVE WAVES WILL ALSO MAKE TEMPERATURE
FORECASTS DIFFICULT. AS THE MAIN SURFACE LOW PASSES EAST OF THE
AREA THURSDAY/THURSDAY NIGHT...A COLD FRONT WILL PASS THROUGH THE
REGION...ENDING THE PRECIP WITH MUCH COOLER AND DRIER AIR EXPECTED
TO SPREAD ACROSS THE GREAT LAKES REGION INTO THE BEGINNING OF THE
HOLIDAY WEEKEND. CMS
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 20Z...
* LAKE BREEZE BOUNDARY JUST REACHING ORD...EXPECT EAST TO EAST-
NORTHEAST WINDS THROUGH THE AFTERNOON.
* MVFR VSBY POSSIBLE OVERNIGHT THROUGH DAYBREAK SUNDAY.
MDB
//DISCUSSION...UPDATED 18Z...
LAKE BREEZE BOUNDARY HAS BECOME BETTER DEFINED VIA MESO OBS AND
VISIBLE SATELLITE IMAGERY EXTENDING FROM NEAR PWK TO GYY AND IS
MAKING A SLOW INLAND PUSH. HAVE DECENT CONFIDENCE IN WINDS TURNING
EAST OR NORTHEAST AT ORD/MDW TOWARD MID AFTERNOON BUT AM NOT SURE
HOW FAR PAST THE TERMINALS THE BOUNDARY WILL PUSH. TIMING MAY NEED
TO BE REFINED. SCT-BKN LOWER END VFR CU WILL CONTINUE TO LIFT
THROUGH THE AFTERNOON AND AREAS EAST OF THE LAKE BREEZE WILL
LIKELY SCOUR OUT BASED ON LATEST TRENDS. WINDS WILL DIMINISH THIS
EVENING AND BECOME LIGHT AND VARIABLE OVERNIGHT. THERE IS A BIT
MORE MOISTURE IN THE AIR SO VSBY REDUCTION LOOKS MORE LIKELY THAN
THIS MORNING SO WILL CONTINUE WITH MVFR VSBY TOWARD DAYBREAK. SOME
IFR IS POSSIBLE AT RFD/DPA BUT WILL LEAVE MVFR FOR NOW. WINDS WILL
INCREASE FROM THE SOUTHEAST THROUGH SUNDAY MORNING ALLOWING VSBY
TO IMPROVE. SOME VFR CU MAY ONCE AGAIN DEVELOP. SHRA/TSRA CHANCES
WILL INCREASE FROM THE WEST LATE IN THE DAY AND EVENING.
MDB
//ORD AND MDW CONFIDENCE...UPDATED 20Z...
* MEDIUM-HIGH CONFIDENCE IN WIND FORECAST THROUGH THE EVENING.
* MEDIUM CONFIDENCE IN MVFR VSBY POTENTIAL EARLY SUNDAY.
MDB
//OUTLOOK FOR ORD/MDW FOR 00Z MONDAY-12Z SATURDAY...UPDATED 12Z...
SUNDAY NIGHT...VFR TRENDING TO PATCHY MVFR. PERIODS OF TSRA.
MONDAY THROUGH WEDNESDAY...PERIODS OF TSRA
THURSDAY...CHC SHRA.
FRIDAY...VFR. NO SIG WX.
BEACHLER
&&
.MARINE...
151 PM CDT
A SURFACE RIDGE OF HIGH PRESSURE CONTINUES TO BUILD
EASTWARD ACROSS EASTERN QUEBEC AND THE NORTHEASTERN CONUS THIS
AFTERNOON. HOWEVER...ATTENTION IS QUICKLY TURNING OUT WEST ACROSS
THE CENTRAL HIGH PLAINS...WHERE AN AREA OF LOW PRESSURE IS TAKING
SHAPE THIS AFTERNOON. THIS STORM SYSTEM IS EXPECTED TO MOVE
EAST-NORTHEASTWARD TOWARDS THE MID MISSOURI VALLEY BY SUNDAY
EVENING. AN ASSOCIATED SURFACE WARM FRONT...EXTENDING EASTWARD
ACROSS THE MID MISSISSIPPI VALLEY...WILL MOVE NORTHWARD ACROSS AT
LEAST THE SOUTHERN HALF TO TWO THIRDS OF THE LAKE SUNDAY NIGHT AND
MONDAY. BEHIND THIS FRONT WINDS LOOKS TO INCREASE OUT
OF THE SOUTH IN THE 15 TO 25 KT RANGE SUNDAY NIGHT INTO MONDAY.
HOWEVER...TO THE NORTH OF THIS FRONT...WINDS WILL PRIMARILY BE
MORE EASTERLY. THERE IS SOME UNCERTAINTY IN HOW FAR NORTH UP THE LAKE
THIS WARM FRONT WILL REACH. IT IS POSSIBLE THAT IT NEVER REACHES THE
NORTHERN THIRD OF THE LAKE...WHICH WOULD RESULT IN EASTERLY WINDS
REMAINING IN PLACE THERE DURING THE PERIOD.
THE OTHER CONCERN WILL BE THE THREAT FOR PERIODS OF DENSE MARINE FOG
SUNDAY NIGHT AND INTO AT LEAST THE FIRST PART OF THE COMING WEEK. AS
THIS WARM FRONT LIFTS OVER THE LAKE...MUCH HIGHER DEW POINTS WILL
MOVE OVER THE RELATIVELY COLD WATER...POSSIBLY RESULTING IN SOME
FOG DEVELOPMENT.
IT APPEARS THAT THE SURFACE LOW WILL SLOWLY MOVE EASTWARD ACROSS THE
MID MISSISSIPPI VALLEY THROUGH MID WEEK AND THEN ACROSS THE SOUTHERN
LAKES AND THE OHIO VALLEY LATER IN THE WEEK. THIS SHOULD ALLOW WARM
FRONT TO SHIFT BACK SOUTHWARD WITH TIME DURING THE WEEK. DURING THIS
TIME...THE WIND DIRECTIONS WILL PRIMARILY BECOME EAST NORTHEASTWARD
15 TO 25 KT NORTH OF THE FRONT. LATER IN THE WEEK...AS THE SURFACE
LOW PASSES EAST OF LAKE MICHIGAN...THE WINDS LOOK TO BE RATHER STOUT
UP TO 25 TO POSSIBLY AS HIGH AS 30 KT OUT OF THE NORTH FOR A PERIOD
AS A GOOD AREA OF HIGH PRESSURE BUILDS EASTWARD ACROSS ONTARIO AND
THE UPPER GREAT LAKES REGION.
KJB
&&
.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 181952
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
252 PM CDT SAT MAY 18 2013
.DISCUSSION...
252 PM...MULTIPLE FORECAST CONCERNS AND CHALLENGES CONTINUE
THROUGH THE MIDDLE OF NEXT WEEK INCLUDING SEVERE POTENTIAL SUNDAY
AFTERNOON THROUGH MONDAY NIGHT...HEAVY RAIN POTENTIAL ESPECIALLY
MONDAY NIGHT THROUGH TUESDAY NIGHT ALONG WITH ASSOCIATED CLOUD
COVER...WINDS OFF THE LAKE/LAKE BREEZES AND THEIR AFFECTS ON
TEMPERATURES.
IN THE SHORT TERM...LOW LEVELS ARE NOW QUITE MOIST WITH DEWPOINTS
GENERALLY IN THE LOWER 60S WEST OF THE LAKE BREEZE. BROKEN TO AT
TIMES OVERCAST CU FIELD DEVELOPED EARLIER THIS MORNING WHICH
HELPED BUT THE BRAKES ON TEMPS MAKING IT INTO THE LOWER 80S...
THOUGH STILL A FEW LOCATIONS TAGGING 80. LACK OF INSTABILITY
HOWEVER HAS LIMITED SHOWER DEVELOPMENT WITH ISOLATED SHOWERS NOW
DEVELOPING SOUTH OF THE KANKAKEE RIVER. OTHER THAN AN ISOLATED
SPRINKLE/SHOWER...DRY WEATHER EXPECTED THROUGH SUNDAY MORNING.
WITH CONTINUED LIGHT WINDS AND CLEARING SKIES AS THE CU DISSIPATE
THIS EVENING...EXPECT AT LEAST SOME PATCHY FOG DEVELOPMENT AS
TEMPS COOL INTO THE LOWER 60S DEWPOINTS. THOUGH CONFIDENCE
REGARDING FOG DEVELOPMENT IS LOW.
CONVECTIVE TRENDS/POTENTIAL FROM SUNDAY AFTERNOON THROUGH MONDAY
NIGHT ARE FAIRLY UNCERTAIN. HOWEVER THERE APPEARS TO BE INCREASING
CONSENSUS...BOTH WITH TIMING AND LOCATION...OF A SHORTWAVE LIFTING
NORTHEAST ACROSS IOWA INTO SOUTHERN WISCONSIN SUNDAY AFTERNOON
INTO SUNDAY EVENING WITH INCREASING CHANCES FOR THUNDERSTORMS
SUNDAY AFTERNOON/EVENING. HOW FAR EAST THIS ACTIVITY MAY SPREAD
APPEARS TO BE THE MOST UNCERTAIN AND POPS MAY NEED TO BE ADJUSTED
AS WELL AS INCREASED AS TRENDS EMERGE. WITH THE UPPER RIDGE
BUILDING ACROSS THE REGION LATE TONIGHT...EXPECT HIGH TEMPS
SUNDAY TO BE WELL INTO THE MID/UPPER 80S WITH PERHAPS A FEW
LOCATIONS TAGGING 90. THESE TEMPS COMBINED WITH DEWPOINTS CREEPING
INTO THE UPPER 60S...PERHAPS EVEN 70 IN SOME LOCATIONS...WILL
PROVIDE PLENTY OF INSTABILITY IF THUNDERSTORMS ARE ABLE TO SPREAD
INTO THE CWA.
AS TIME GOES ON...CONFIDENCE DECREASES REGARDING CONVECTIVE
TRENDS AS TIMING DIFFERENCES AND LOCATIONS OF VARIOUS WAVES THEN
IMPACT FUTURE POTENTIAL CONVECTIVE TIME PERIODS. WITH ENOUGH
SUNSHINE AND ENOUGH OF A DRY PERIOD MIDDAY...EXPECT MONDAY COULD
BE AS WARM PERHAPS A FEW DEGREES WARMER THAN SUNDAY WITH HIGHS
BACK IN THE MID/UPPER 80S. ALSO STILL LOOKS BREEZY WHICH COULD
LOWER DEWPOINTS SOME IN THE AFTERNOON. SHOULD CONVECTION BE ABLE
TO FIRE...ATMOSPHERE REMAINS UNSTABLE AND SHEAR WOULD SUPPORT
CONTINUED SEVERE THREAT.
AS THE UPPER LOW OVER THE PLAINS SLOWLY SPINS EAST INTO THE
WESTERN LAKES TUESDAY AND WEDNESDAY...THIS SEEMS TO BE THE BEST
TIMING FOR A MORE PROLONGED/CONTINUED HEAVY RAIN THREAT. ANY OF
THE STORMS THAT FORM THROUGH THE MIDDLE OF NEXT WEEK WILL HAVE THE
POTENTIAL TO PRODUCE HEAVY RAIN...BUT WAVES OF MORE WIDESPREAD
STORMS WITH HEAVY RAIN APPEAR TO BE POSSIBLE LATE MONDAY NIGHT
INTO TUESDAY AND THEN AGAIN TUESDAY NIGHT INTO WEDNESDAY.
CONFIDENCE REGARDING RAINFALL AMOUNTS REMAINS LOW HOWEVER WITH
MODEL QPF STORM TOTAL AMOUNTS LOWER THAN 24 HOURS AGO. OF
COURSE...THIS DOESN/T DOWNPLAY THE POTENTIAL FOR WHAT COULD END UP
BEING SEVERAL INCHES OF RAIN IN PARTS OF THE AREA BY MIDWEEK...
JUST ADDS TO LOW CONFIDENCE REGARDING LOCATION/AMOUNTS.
LOW TEMPS APPEAR TO BE RATHER WARM IN THE 60S INTO WEDNESDAY
MORNING WITH HIGHS POTENTIALLY IN THE UPPER 70S/LOWER 80S BOTH
TUESDAY AND WEDNESDAY THOUGH CLOUD COVER/PRECIP DURATION/AMOUNTS
WILL DETERMINE JUST HOW WARM TEMPS ARE ABLE TO GO. LAKE BREEZES
AND OUTFLOWS FROM CONVECTIVE WAVES WILL ALSO MAKE TEMPERATURE
FORECASTS DIFFICULT. AS THE MAIN SURFACE LOW PASSES EAST OF THE
AREA THURSDAY/THURSDAY NIGHT...A COLD FRONT WILL PASS THROUGH THE
REGION...ENDING THE PRECIP WITH MUCH COOLER AND DRIER AIR EXPECTED
TO SPREAD ACROSS THE GREAT LAKES REGION INTO THE BEGINNING OF THE
HOLIDAY WEEKEND. CMS
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 18Z...
* VARIABLE SOUTHEAST WINDS TURNING EAST OR EAST-NORTHEAST TOWARD
20Z WITH LAKE BREEZE PASSAGE.
* MVFR VSBY POSSIBLE LATE TONIGHT THROUGH DAYBREAK SUNDAY.
MDB
//DISCUSSION...UPDATED 18Z...
LAKE BREEZE BOUNDARY HAS BECOME BETTER DEFINED VIA MESO OBS AND
VISIBLE SATELLITE IMAGERY EXTENDING FROM NEAR PWK TO GYY AND IS
MAKING A SLOW INLAND PUSH. HAVE DECENT CONFIDENCE IN WINDS TURNING
EAST OR NORTHEAST AT ORD/MDW TOWARD MID AFTERNOON BUT AM NOT SURE
HOW FAR PAST THE TERMINALS THE BOUNDARY WILL PUSH. TIMING MAY NEED
TO BE REFINED. SCT-BKN LOWER END VFR CU WILL CONTINUE TO LIFT
THROUGH THE AFTERNOON AND AREAS EAST OF THE LAKE BREEZE WILL
LIKELY SCOUR OUT BASED ON LATEST TRENDS. WINDS WILL DIMINISH THIS
EVENING AND BECOME LIGHT AND VARIABLE OVERNIGHT. THERE IS A BIT
MORE MOISTURE IN THE AIR SO VSBY REDUCTION LOOKS MORE LIKELY THAN
THIS MORNING SO WILL CONTINUE WITH MVFR VSBY TOWARD DAYBREAK. SOME
IFR IS POSSIBLE AT RFD/DPA BUT WILL LEAVE MVFR FOR NOW. WINDS WILL
INCREASE FROM THE SOUTHEAST THROUGH SUNDAY MORNING ALLOWING VSBY
TO IMPROVE. SOME VFR CU MAY ONCE AGAIN DEVELOP. SHRA/TSRA CHANCES
WILL INCREASE FROM THE WEST LATE IN THE DAY AND EVENING.
MDB
//ORD AND MDW CONFIDENCE...UPDATED 18Z...
* MEDIUM-HIGH CONFIDENCE IN WINDS SHIFTING TO EAST OR EAST-
NORTHEAST AND TIMING.
* MEDIUM CONFIDENCE IN MVFR VSBY POTENTIAL EARLY SUNDAY.
MDB
//OUTLOOK FOR ORD/MDW FOR 00Z MONDAY-12Z SATURDAY...UPDATED 12Z...
SUNDAY NIGHT...VFR TRENDING TO PATCHY MVFR. PERIODS OF TSRA.
MONDAY THROUGH WEDNESDAY...PERIODS OF TSRA
THURSDAY...CHC SHRA.
FRIDAY...VFR. NO SIG WX.
BEACHLER
&&
.MARINE...
151 PM CDT
A SURFACE RIDGE OF HIGH PRESSURE CONTINUES TO BUILD
EASTWARD ACROSS EASTERN QUEBEC AND THE NORTHEASTERN CONUS THIS
AFTERNOON. HOWEVER...ATTENTION IS QUICKLY TURNING OUT WEST ACROSS
THE CENTRAL HIGH PLAINS...WHERE AN AREA OF LOW PRESSURE IS TAKING
SHAPE THIS AFTERNOON. THIS STORM SYSTEM IS EXPECTED TO MOVE
EAST-NORTHEASTWARD TOWARDS THE MID MISSOURI VALLEY BY SUNDAY
EVENING. AN ASSOCIATED SURFACE WARM FRONT...EXTENDING EASTWARD
ACROSS THE MID MISSISSIPPI VALLEY...WILL MOVE NORTHWARD ACROSS AT
LEAST THE SOUTHERN HALF TO TWO THIRDS OF THE LAKE SUNDAY NIGHT AND
MONDAY. BEHIND THIS FRONT WINDS LOOKS TO INCREASE OUT
OF THE SOUTH IN THE 15 TO 25 KT RANGE SUNDAY NIGHT INTO MONDAY.
HOWEVER...TO THE NORTH OF THIS FRONT...WINDS WILL PRIMARILY BE
MORE EASTERLY. THERE IS SOME UNCERTAINTY IN HOW FAR NORTH UP THE LAKE
THIS WARM FRONT WILL REACH. IT IS POSSIBLE THAT IT NEVER REACHES THE
NORTHERN THIRD OF THE LAKE...WHICH WOULD RESULT IN EASTERLY WINDS
REMAINING IN PLACE THERE DURING THE PERIOD.
THE OTHER CONCERN WILL BE THE THREAT FOR PERIODS OF DENSE MARINE FOG
SUNDAY NIGHT AND INTO AT LEAST THE FIRST PART OF THE COMING WEEK. AS
THIS WARM FRONT LIFTS OVER THE LAKE...MUCH HIGHER DEW POINTS WILL
MOVE OVER THE RELATIVELY COLD WATER...POSSIBLY RESULTING IN SOME
FOG DEVELOPMENT.
IT APPEARS THAT THE SURFACE LOW WILL SLOWLY MOVE EASTWARD ACROSS THE
MID MISSISSIPPI VALLEY THROUGH MID WEEK AND THEN ACROSS THE SOUTHERN
LAKES AND THE OHIO VALLEY LATER IN THE WEEK. THIS SHOULD ALLOW WARM
FRONT TO SHIFT BACK SOUTHWARD WITH TIME DURING THE WEEK. DURING THIS
TIME...THE WIND DIRECTIONS WILL PRIMARILY BECOME EAST NORTHEASTWARD
15 TO 25 KT NORTH OF THE FRONT. LATER IN THE WEEK...AS THE SURFACE
LOW PASSES EAST OF LAKE MICHIGAN...THE WINDS LOOK TO BE RATHER STOUT
UP TO 25 TO POSSIBLY AS HIGH AS 30 KT OUT OF THE NORTH FOR A PERIOD
AS A GOOD AREA OF HIGH PRESSURE BUILDS EASTWARD ACROSS ONTARIO AND
THE UPPER GREAT LAKES REGION.
KJB
&&
.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 181852
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
152 PM CDT SAT MAY 18 2013
.DISCUSSION...
430 AM CDT
FOCUS OF FORECAST IS ON THE INCREASE IN CHANCES OF SHOWERS AND
THUNDERSTORMS BEGINNING LATE SUNDAY/SUNDAY NIGHT AND CONTINUING TO
GRADUALLY INCREASE THROUGH MONDAY...PERSISTING THROUGH THURSDAY.
TIME FRAME OF GREATEST THREAT OF PRECIP WILL BE MONDAY NIGHT
THROUGH TUESDAY NIGHT.
OTHER MAIN FORECAST ITEM IS THE CONTINUED WARM UP TODAY AND SUNDAY
WITH WARMTH PERSISTING MONDAY BEFORE HIGH TEMPERATURES START
FALLING OFF TUESDAY...WITH HIGHS ONLY IN THE MID 60S TO LOWER 70S
ON THURSDAY AND FRIDAY.
OTHER CONCERNS ARE POTENTIAL FOR SIGNIFICANT AMOUNTS OF RAINFALL
FROM MONDAY NIGHT INTO WEDNESDAY AND SOME POTENTIAL FOR SEVERE
CONVECTION...IN THE WESTERN PORTION OF THE FORECAST AREA LATE
SUNDAY AND SUNDAY NIGHT...AND ACROSS THE AREA MONDAY AND MONDAY
NIGHT.
CHANCES OF ANY PRECIP IN THE AREA ARE LOW FOR TODAY AND TONIGHT
AS AN UPPER RIDGE BUILDING OVER THE MID CONTINENT SHIFTS EASTWARD
TO OVER THE LOCAL AREA LATE TODAY AND TONIGHT RESULTING IN RISING
HEIGHTS AND LARGE SCALE SUBSIDENCE. THE CONVECTION THAT HAS BEEN
OCCURRING DURING THE NIGHT AND EARLY THIS MORNING OVER THE
NORTHERN PLAINS AND UPPER MS VALLEY WILL CONTINUE TO MOVE TO THE
EAST-NORTHEAST OVER THE TOP OF THE BUILDING RIDGE. BY SUNDAY NIGHT
THE UPPER RIDGE WILL HAVE REACHED THE CENTRAL GREAT LAKES AND THE OH
VALLEY REGIONS AS AN UPPER LOW SLOWLY MOVES EAST FROM THE CANADIAN
MARITIMES.
A VERY WARM AIR MASS WAS ACROSS THE HIGH PLAINS FRIDAY UNDER THE
UPPER RIDGE. THIS AIR MASS WILL SPREAD TO THE LOCAL AREA FOR
SUNDAY. DEPENDING ON CLOUD COVER...OF WHICH MUCH WOULD LIKELY BY
CONVECTIVE DEBRIS SPREADING EAST ACROSS THE MS RIVER FROM UPSTREAM
CONVECTION...TEMPERATURES MAY PEAK IN THE UPPER 80S IF THE CIRRUS
DEBRIS CLOUDS ARE NOT TOO THICK. EVEN WITH MORE CLOUDINESS MID 80S
LOOKS PRETTY LIKELY FOR SUNDAY AFTERNOON.
MEANWHILE...MULTIPLE STRONG UPPER WAVES DROPPING INTO AN UPPER
TROUGH EXTENDING FROM WEST OF THE B.C. COAST SOUTHEAST ACROSS THE
PACIFIC NORTHWEST TO THE DESERT SOUTHWEST ARE PROGGED TO CONGEAL
AND FORM AN UPPER LOW TO REACH THE CENTRAL HIGH PLAINS BY SUNDAY
EVENING. INCREASING SOUTH TO SOUTHWEST LOW AND MID LEVEL FLOW
AHEAD OF A SURFACE LOW ASSOCIATED WITH THE UPPER LOW WILL
TRANSPORT SIGNIFICANT MOISTURE FROM THE WESTERN GULF UP ACROSS THE
SOUTHERN PLAINS...MID MO VALLEY AND UPPER MS VALLEY DURING SUNDAY
WITH THE MOISTURE AXIS SHIFTING EAST OVER THE MID MS VALLEY AND
THE UPPER MIDWEST TO OVER IL AND THE WESTERN GREAT LAKES BY MONDAY.
WHILE THE UPPER LOW WILL STILL BE OUT OVER THE CENTRAL PLAINS
LATE SUNDAY AND NOT REACH THE MID MO VALLEY TIL LATER MONDAY
POTENTIAL INSTABILITY WILL BE INCREASING OVER THE LOCAL AREA AND
ANY SMALLER SCALE DISTURBANCES TRAVELING NORTHEASTWARD ACROSS
THE MID MS VALLEY MAY TRIGGER THUNDERSTORMS. GIVEN AMOUNT OF
AVAILABLE CAPE AND LOW LEVEL WIND SHEAR THERE IS THE POTENTIAL
FOR SOME OF THE THUNDERSTORMS THAT MAY DEVELOP TO BE STRONG TO
SEVERE.
WITH THE CORE OF THE WARM AIR DOME SHIFTING TO THE EAST MONDAY
AND MORE CLOUDS AND POSSIBLY MOIST CONVECTION OVER/NEAR THE AREA
TEMPERATURES WILL LIKELY BE HELD DOWN A FEW TO A COUPLE DEGREES
FROM THOSE REACHED SUNDAY.
THE SLOW PROGRESS OF THE UPPER LOW DUE TO BEING IN AN OMEGA BLOCK
TYPE UPPER PATTERN RESULTS IN IT NOT REACHING NEAR/OVER THE LOCAL
AREA UNTIL LATER WEDNESDAY AND WEDNESDAY NIGHT. THIS SLOW MOVEMENT
KEEPS THE THREAT OF THUNDERSTORMS GOING...WITH THE HIGHEST POPS
DURING MONDAY NIGHT THROUGH TUESDAY NIGHT AS THIS IS WHEN THE
HIGHEST THETA E AIR IS IN PLACE WITH SIGNIFICANT CAPE VALUES.
WHILE PRECIPITABLE WATER VALUES ARE NOT EXTREME...GENERALLY AROUND
1.5 INCHES FROM SUNDAY NIGHT INTO WEDNESDAY...THE POTENTIAL FOR
MULTIPLE RAINFALL EVENTS DURING THE PERIOD OF TIME IT TAKES THE
UPPER LOW TO REACH AND EVENTUALLY PASS OVER THE LOCAL AREA DOES
PRESENT THE POSSIBILITY OF SOME 2 TO 3 INCH RAINFALL TOTALS.
SPECIFICS ON WHICH PART OR PARTS OF THE FA WOULD BE MOST PRONE TO
RECEIVING SIGNIFICANT RAINFALL AMOUNTS IS NOT CLEAR AT THIS TIME
SO ALL THAT CAN BE SAID THAT THERE IS THE POTENTIAL.
CHANCES FOR SHOWERS AND SOME THUNDERSTORMS PERSIST WEDNESDAY
THROUGH THURSDAY AS THE UPPER LOW IS TO STILL BE SLUGGISHLY
MOVING EAST TO THE WESTERN GREAT LAKES AND MIDWEST. COOLER AIR
WILL BE DRAWN DOWN ACROSS THE REGION AS THE UPPER FLOW VEERS TO
OUT OF THE NORTHWEST THURSDAY. THIS RESULTS IN HIGHS OF ONLY MID
60S TO LOWER 70S FOR THURSDAY AND FRIDAY. BY THURSDAY NIGHT THE
THREAT OF ANY ADDITIONAL SHOWERS SHOULD HAVE ENDED WITH THE UPPER
LOW OPENING UP TO THE EAST OF THE AREA AND THE LOWER LEVEL FLOW
BECOMING SOMEWHAT ANTICYCLONIC AS A RIDGE OF HIGH PRESSURE
EXTENDING SOUTHWEST FROM ONTARIO DRIFTS EAST ACROSS THE UPPER
MIDWEST AND MID MO VALLEY.
TRS
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 18Z...
* VARIABLE SOUTHEAST WINDS TURNING EAST OR EAST-NORTHEAST TOWARD
20Z WITH LAKE BREEZE PASSAGE.
* MVFR VSBY POSSIBLE LATE TONIGHT THROUGH DAYBREAK SUNDAY.
MDB
//DISCUSSION...UPDATED 18Z...
LAKE BREEZE BOUNDARY HAS BECOME BETTER DEFINED VIA MESO OBS AND
VISIBLE SATELLITE IMAGERY EXTENDING FROM NEAR PWK TO GYY AND IS
MAKING A SLOW INLAND PUSH. HAVE DECENT CONFIDENCE IN WINDS TURNING
EAST OR NORTHEAST AT ORD/MDW TOWARD MID AFTERNOON BUT AM NOT SURE
HOW FAR PAST THE TERMINALS THE BOUNDARY WILL PUSH. TIMING MAY NEED
TO BE REFINED. SCT-BKN LOWER END VFR CU WILL CONTINUE TO LIFT
THROUGH THE AFTERNOON AND AREAS EAST OF THE LAKE BREEZE WILL
LIKELY SCOUR OUT BASED ON LATEST TRENDS. WINDS WILL DIMINISH THIS
EVENING AND BECOME LIGHT AND VARIABLE OVERNIGHT. THERE IS A BIT
MORE MOISTURE IN THE AIR SO VSBY REDUCTION LOOKS MORE LIKELY THAN
THIS MORNING SO WILL CONTINUE WITH MVFR VSBY TOWARD DAYBREAK. SOME
IFR IS POSSIBLE AT RFD/DPA BUT WILL LEAVE MVFR FOR NOW. WINDS WILL
INCREASE FROM THE SOUTHEAST THROUGH SUNDAY MORNING ALLOWING VSBY
TO IMPROVE. SOME VFR CU MAY ONCE AGAIN DEVELOP. SHRA/TSRA CHANCES
WILL INCREASE FROM THE WEST LATE IN THE DAY AND EVENING.
MDB
//ORD AND MDW CONFIDENCE...UPDATED 18Z...
* MEDIUM-HIGH CONFIDENCE IN WINDS SHIFTING TO EAST OR EAST-
NORTHEAST AND TIMING.
* MEDIUM CONFIDENCE IN MVFR VSBY POTENTIAL EARLY SUNDAY.
MDB
//OUTLOOK FOR ORD/MDW FOR 00Z MONDAY-12Z SATURDAY...UPDATED 12Z...
SUNDAY NIGHT...VFR TRENDING TO PATCHY MVFR. PERIODS OF TSRA.
MONDAY THROUGH WEDNESDAY...PERIODS OF TSRA
THURSDAY...CHC SHRA.
FRIDAY...VFR. NO SIG WX.
BEACHLER
&&
.MARINE...
151 PM CDT
A SURFACE RIDGE OF HIGH PRESSURE CONTINUES TO BUILD
EASTWARD ACROSS EASTERN QUEBEC AND THE NORTHEASTERN CONUS THIS
AFTERNOON. HOWEVER...ATTENTION IS QUICKLY TURNING OUT WEST ACROSS
THE CENTRAL HIGH PLAINS...WHERE AN AREA OF LOW PRESSURE IS TAKING
SHAPE THIS AFTERNOON. THIS STORM SYSTEM IS EXPECTED TO MOVE
EAST-NORTHEASTWARD TOWARDS THE MID MISSOURI VALLEY BY SUNDAY
EVENING. AN ASSOCIATED SURFACE WARM FRONT...EXTENDING EASTWARD
ACROSS THE MID MISSISSIPPI VALLEY...WILL MOVE NORTHWARD ACROSS AT
LEAST THE SOUTHERN HALF TO TWO THIRDS OF THE LAKE SUNDAY NIGHT AND
MONDAY. BEHIND THIS FRONT WINDS LOOKS TO INCREASE OUT
OF THE SOUTH IN THE 15 TO 25 KT RANGE SUNDAY NIGHT INTO MONDAY.
HOWEVER...TO THE NORTH OF THIS FRONT...WINDS WILL PRIMARILY BE
MORE EASTERLY. THERE IS SOME UNCERTAINTY IN HOW FAR NORTH UP THE LAKE
THIS WARM FRONT WILL REACH. IT IS POSSIBLE THAT IT NEVER REACHES THE
NORTHERN THIRD OF THE LAKE...WHICH WOULD RESULT IN EASTERLY WINDS
REMAINING IN PLACE THERE DURING THE PERIOD.
THE OTHER CONCERN WILL BE THE THREAT FOR PERIODS OF DENSE MARINE FOG
SUNDAY NIGHT AND INTO AT LEAST THE FIRST PART OF THE COMING WEEK. AS THIS
WARM FRONT LIFTS OVER THE LAKE...MUCH HIGHER DEW POINTS WILL MOVE
OVER THE RELATIVELY COLD WATER...POSSIBLY RESULTING IN SOME FOG
DEVELOPMENT.
IT APPEARS THAT THE SURFACE LOW WILL SLOWLY MOVE EASTWARD ACROSS THE
MID MISSISSIPPI VALLEY THROUGH MID WEEK AND THEN ACROSS THE SOUTHERN
LAKES AND THE OHIO VALLEY LATER IN THE WEEK. THIS SHOULD ALLOW WARM
FRONT TO SHIFT BACK SOUTHWARD WITH TIME DURING THE WEEK. DURING THIS
TIME...THE WIND DIRECTIONS WILL PRIMARILY BECOME EAST NORTHEASTWARD
15 TO 25 KT NORTH OF THE FRONT. LATER IN THE WEEK...AS THE SURFACE
LOW PASSES EAST OF LAKE MICHIGAN...THE WINDS LOOK TO BE RATHER STOUT
UP TO 25 TO POSSIBLY AS HIGH AS 30 KT OUT OF THE NORTH FOR A PERIOD
AS A GOOD AREA OF HIGH PRESSURE BUILDS EASTWARD ACROSS ONTARIO AND
THE UPPER GREAT LAKES REGION.
KJB
&&
.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 181755
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1255 PM CDT SAT MAY 18 2013
.DISCUSSION...
430 AM CDT
FOCUS OF FORECAST IS ON THE INCREASE IN CHANCES OF SHOWERS AND
THUNDERSTORMS BEGINNING LATE SUNDAY/SUNDAY NIGHT AND CONTINUING TO
GRADUALLY INCREASE THROUGH MONDAY...PERSISTING THROUGH THURSDAY.
TIME FRAME OF GREATEST THREAT OF PRECIP WILL BE MONDAY NIGHT
THROUGH TUESDAY NIGHT.
OTHER MAIN FORECAST ITEM IS THE CONTINUED WARM UP TODAY AND SUNDAY
WITH WARMTH PERSISTING MONDAY BEFORE HIGH TEMPERATURES START
FALLING OFF TUESDAY...WITH HIGHS ONLY IN THE MID 60S TO LOWER 70S
ON THURSDAY AND FRIDAY.
OTHER CONCERNS ARE POTENTIAL FOR SIGNIFICANT AMOUNTS OF RAINFALL
FROM MONDAY NIGHT INTO WEDNESDAY AND SOME POTENTIAL FOR SEVERE
CONVECTION...IN THE WESTERN PORTION OF THE FORECAST AREA LATE
SUNDAY AND SUNDAY NIGHT...AND ACROSS THE AREA MONDAY AND MONDAY
NIGHT.
CHANCES OF ANY PRECIP IN THE AREA ARE LOW FOR TODAY AND TONIGHT
AS AN UPPER RIDGE BUILDING OVER THE MID CONTINENT SHIFTS EASTWARD
TO OVER THE LOCAL AREA LATE TODAY AND TONIGHT RESULTING IN RISING
HEIGHTS AND LARGE SCALE SUBSIDENCE. THE CONVECTION THAT HAS BEEN
OCCURRING DURING THE NIGHT AND EARLY THIS MORNING OVER THE
NORTHERN PLAINS AND UPPER MS VALLEY WILL CONTINUE TO MOVE TO THE
EAST-NORTHEAST OVER THE TOP OF THE BUILDING RIDGE. BY SUNDAY NIGHT
THE UPPER RIDGE WILL HAVE REACHED THE CENTRAL GREAT LAKES AND THE OH
VALLEY REGIONS AS AN UPPER LOW SLOWLY MOVES EAST FROM THE CANADIAN
MARITIMES.
A VERY WARM AIR MASS WAS ACROSS THE HIGH PLAINS FRIDAY UNDER THE
UPPER RIDGE. THIS AIR MASS WILL SPREAD TO THE LOCAL AREA FOR
SUNDAY. DEPENDING ON CLOUD COVER...OF WHICH MUCH WOULD LIKELY BY
CONVECTIVE DEBRIS SPREADING EAST ACROSS THE MS RIVER FROM UPSTREAM
CONVECTION...TEMPERATURES MAY PEAK IN THE UPPER 80S IF THE CIRRUS
DEBRIS CLOUDS ARE NOT TOO THICK. EVEN WITH MORE CLOUDINESS MID 80S
LOOKS PRETTY LIKELY FOR SUNDAY AFTERNOON.
MEANWHILE...MULTIPLE STRONG UPPER WAVES DROPPING INTO AN UPPER
TROUGH EXTENDING FROM WEST OF THE B.C. COAST SOUTHEAST ACROSS THE
PACIFIC NORTHWEST TO THE DESERT SOUTHWEST ARE PROGGED TO CONGEAL
AND FORM AN UPPER LOW TO REACH THE CENTRAL HIGH PLAINS BY SUNDAY
EVENING. INCREASING SOUTH TO SOUTHWEST LOW AND MID LEVEL FLOW
AHEAD OF A SURFACE LOW ASSOCIATED WITH THE UPPER LOW WILL
TRANSPORT SIGNIFICANT MOISTURE FROM THE WESTERN GULF UP ACROSS THE
SOUTHERN PLAINS...MID MO VALLEY AND UPPER MS VALLEY DURING SUNDAY
WITH THE MOISTURE AXIS SHIFTING EAST OVER THE MID MS VALLEY AND
THE UPPER MIDWEST TO OVER IL AND THE WESTERN GREAT LAKES BY MONDAY.
WHILE THE UPPER LOW WILL STILL BE OUT OVER THE CENTRAL PLAINS
LATE SUNDAY AND NOT REACH THE MID MO VALLEY TIL LATER MONDAY
POTENTIAL INSTABILITY WILL BE INCREASING OVER THE LOCAL AREA AND
ANY SMALLER SCALE DISTURBANCES TRAVELING NORTHEASTWARD ACROSS
THE MID MS VALLEY MAY TRIGGER THUNDERSTORMS. GIVEN AMOUNT OF
AVAILABLE CAPE AND LOW LEVEL WIND SHEAR THERE IS THE POTENTIAL
FOR SOME OF THE THUNDERSTORMS THAT MAY DEVELOP TO BE STRONG TO
SEVERE.
WITH THE CORE OF THE WARM AIR DOME SHIFTING TO THE EAST MONDAY
AND MORE CLOUDS AND POSSIBLY MOIST CONVECTION OVER/NEAR THE AREA
TEMPERATURES WILL LIKELY BE HELD DOWN A FEW TO A COUPLE DEGREES
FROM THOSE REACHED SUNDAY.
THE SLOW PROGRESS OF THE UPPER LOW DUE TO BEING IN AN OMEGA BLOCK
TYPE UPPER PATTERN RESULTS IN IT NOT REACHING NEAR/OVER THE LOCAL
AREA UNTIL LATER WEDNESDAY AND WEDNESDAY NIGHT. THIS SLOW MOVEMENT
KEEPS THE THREAT OF THUNDERSTORMS GOING...WITH THE HIGHEST POPS
DURING MONDAY NIGHT THROUGH TUESDAY NIGHT AS THIS IS WHEN THE
HIGHEST THETA E AIR IS IN PLACE WITH SIGNIFICANT CAPE VALUES.
WHILE PRECIPITABLE WATER VALUES ARE NOT EXTREME...GENERALLY AROUND
1.5 INCHES FROM SUNDAY NIGHT INTO WEDNESDAY...THE POTENTIAL FOR
MULTIPLE RAINFALL EVENTS DURING THE PERIOD OF TIME IT TAKES THE
UPPER LOW TO REACH AND EVENTUALLY PASS OVER THE LOCAL AREA DOES
PRESENT THE POSSIBILITY OF SOME 2 TO 3 INCH RAINFALL TOTALS.
SPECIFICS ON WHICH PART OR PARTS OF THE FA WOULD BE MOST PRONE TO
RECEIVING SIGNIFICANT RAINFALL AMOUNTS IS NOT CLEAR AT THIS TIME
SO ALL THAT CAN BE SAID THAT THERE IS THE POTENTIAL.
CHANCES FOR SHOWERS AND SOME THUNDERSTORMS PERSIST WEDNESDAY
THROUGH THURSDAY AS THE UPPER LOW IS TO STILL BE SLUGGISHLY
MOVING EAST TO THE WESTERN GREAT LAKES AND MIDWEST. COOLER AIR
WILL BE DRAWN DOWN ACROSS THE REGION AS THE UPPER FLOW VEERS TO
OUT OF THE NORTHWEST THURSDAY. THIS RESULTS IN HIGHS OF ONLY MID
60S TO LOWER 70S FOR THURSDAY AND FRIDAY. BY THURSDAY NIGHT THE
THREAT OF ANY ADDITIONAL SHOWERS SHOULD HAVE ENDED WITH THE UPPER
LOW OPENING UP TO THE EAST OF THE AREA AND THE LOWER LEVEL FLOW
BECOMING SOMEWHAT ANTICYCLONIC AS A RIDGE OF HIGH PRESSURE
EXTENDING SOUTHWEST FROM ONTARIO DRIFTS EAST ACROSS THE UPPER
MIDWEST AND MID MO VALLEY.
TRS
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 18Z...
* VARIABLE SOUTHEAST WINDS TURNING EAST OR EAST-NORTHEAST TOWARD
20Z WITH LAKE BREEZE PASSAGE.
* MVFR VSBY POSSIBLE LATE TONIGHT THROUGH DAYBREAK SUNDAY.
MDB
//DISCUSSION...UPDATED 18Z...
LAKE BREEZE BOUNDARY HAS BECOME BETTER DEFINED VIA MESO OBS AND
VISIBLE SATELLITE IMAGERY EXTENDING FROM NEAR PWK TO GYY AND IS
MAKING A SLOW INLAND PUSH. HAVE DECENT CONFIDENCE IN WINDS TURNING
EAST OR NORTHEAST AT ORD/MDW TOWARD MID AFTERNOON BUT AM NOT SURE
HOW FAR PAST THE TERMINALS THE BOUNDARY WILL PUSH. TIMING MAY NEED
TO BE REFINED. SCT-BKN LOWER END VFR CU WILL CONTINUE TO LIFT
THROUGH THE AFTERNOON AND AREAS EAST OF THE LAKE BREEZE WILL
LIKELY SCOUR OUT BASED ON LATEST TRENDS. WINDS WILL DIMINISH THIS
EVENING AND BECOME LIGHT AND VARIABLE OVERNIGHT. THERE IS A BIT
MORE MOISTURE IN THE AIR SO VSBY REDUCTION LOOKS MORE LIKELY THAN
THIS MORNING SO WILL CONTINUE WITH MVFR VSBY TOWARD DAYBREAK. SOME
IFR IS POSSIBLE AT RFD/DPA BUT WILL LEAVE MVFR FOR NOW. WINDS WILL
INCREASE FROM THE SOUTHEAST THROUGH SUNDAY MORNING ALLOWING VSBY
TO IMPROVE. SOME VFR CU MAY ONCE AGAIN DEVELOP. SHRA/TSRA CHANCES
WILL INCREASE FROM THE WEST LATE IN THE DAY AND EVENING.
MDB
//ORD AND MDW CONFIDENCE...UPDATED 18Z...
* MEDIUM-HIGH CONFIDENCE IN WINDS SHIFTING TO EAST OR EAST-
NORTHEAST AND TIMING.
* MEDIUM CONFIDENCE IN MVFR VSBY POTENTIAL EARLY SUNDAY.
MDB
//OUTLOOK FOR ORD/MDW FOR 00Z MONDAY-12Z SATURDAY...UPDATED 12Z...
SUNDAY NIGHT...VFR TRENDING TO PATCHY MVFR. PERIODS OF TSRA.
MONDAY THROUGH WEDNESDAY...PERIODS OF TSRA
THURSDAY...CHC SHRA.
FRIDAY...VFR. NO SIG WX.
BEACHLER
&&
.MARINE...
221 AM CDT
MINIMAL CHANGES FROM PREVIOUS FORECAST. BROAD SFC RIDGE HAS BECOME
CENTERED ACROSS CENTRAL QUEBEC....HOWEVER THIS FEATURE CONTINUES
TO INFLUENCE THE WESTERN GREAT LAKES WITH A LIGHT EAST FLOW TODAY
ACROSS THE LAKE. AS THE SFC RIDGE WILL DRIFT FURTHER AWAY FROM
LAKE MICHIGAN...WINDS WILL GRADUALLY TURN SOUTHEASTERLY. A STALLED
FRONTAL BOUNDARY STRETCHES FROM CENTRAL MINNESOTA EXTENDING
SOUTHEAST THROUGH WESTERN ILLINOIS INTO CENTRAL INDIANA. IT
APPEARS THE BROAD SFC RIDGE WILL KEEP THIS BOUNDARY JUST SOUTH OF
LAKE MICHIGAN...AND MOST LIKELY WEAKEN. A TROUGH OF LOW PRESSURE
OVER THE NORTHERN PLAINS WILL WEAKEN...AS A SECOND AREA OF LOW
PRESSURE DEVELOPS ALONG A SLOW MOVING COLD FRONT IN THE CENTRAL
PLAINS SUNDAY EVENING. PRIOR TO THE FRONTAL BOUNDARIES
ARRIVAL...WINDS SPEEDS WILL GENERALLY BE 10 TO 20 KT. HOWEVER...AN
OCCASIONAL GUSTS TO 25 KT MAY OCCUR THROUGHOUT THE DAY AS A WEAK
GRADIENT IS FORECAST TO DEVELOP OVER THE CENTRAL PORTION OF THE
LAKE.
AS THE CENTRAL PLAINS LOW PRESSURE DEVELOPS...IT WILL LIFT A WARM
FRONT NORTH ACROSS THE CENTRAL PORTIONS OF THE LAKE SUNDAY
NIGHT/EARLY MON. WINDS WILL TURN SOUTHERLY AND INCREASE BEHIND
THIS BOUNDARY. THIS LOW PRESSURE SYSTEM WILL SLOWLY PUSH EAST INTO
THE MID-MISSISSIPPI VALLEY TUE/WED...THEN DRIFT EAST INTO THE OHIO
VALLEY. WITH THE SLOW MOVING FRONTAL BOUNDARY EXPECTED TO BE OVER
THE CENTRAL PORTIONS OF THE LAKE...WINDS NORTH WILL BE NORTHERLY
AND SOUTHERLY TO THE SOUTH. FORECAST GUIDANCE INDICATES THAT A
TIGHTENING GRADIENT ACROSS THE NORTHERN PORTIONS OF THE LAKE IS
LIKELY...WHICH COULD RESULT IN WINDS BETWEEN 15-25 KT MON/TUE. THEN
THE BOUNDARY WILL EVENTUALLY PUSH BACK TO THE SOUTH OF THE LAKE
TOWARDS THE MIDDLE OF THE UPCOMING WEEK.
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 181613
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1113 AM CDT SAT MAY 18 2013
.DISCUSSION...
430 AM CDT
FOCUS OF FORECAST IS ON THE INCREASE IN CHANCES OF SHOWERS AND
THUNDERSTORMS BEGINNING LATE SUNDAY/SUNDAY NIGHT AND CONTINUING TO
GRADUALLY INCREASE THROUGH MONDAY...PERSISTING THROUGH THURSDAY.
TIME FRAME OF GREATEST THREAT OF PRECIP WILL BE MONDAY NIGHT
THROUGH TUESDAY NIGHT.
OTHER MAIN FORECAST ITEM IS THE CONTINUED WARM UP TODAY AND SUNDAY
WITH WARMTH PERSISTING MONDAY BEFORE HIGH TEMPERATURES START
FALLING OFF TUESDAY...WITH HIGHS ONLY IN THE MID 60S TO LOWER 70S
ON THURSDAY AND FRIDAY.
OTHER CONCERNS ARE POTENTIAL FOR SIGNIFICANT AMOUNTS OF RAINFALL
FROM MONDAY NIGHT INTO WEDNESDAY AND SOME POTENTIAL FOR SEVERE
CONVECTION...IN THE WESTERN PORTION OF THE FORECAST AREA LATE
SUNDAY AND SUNDAY NIGHT...AND ACROSS THE AREA MONDAY AND MONDAY
NIGHT.
CHANCES OF ANY PRECIP IN THE AREA ARE LOW FOR TODAY AND TONIGHT
AS AN UPPER RIDGE BUILDING OVER THE MID CONTINENT SHIFTS EASTWARD
TO OVER THE LOCAL AREA LATE TODAY AND TONIGHT RESULTING IN RISING
HEIGHTS AND LARGE SCALE SUBSIDENCE. THE CONVECTION THAT HAS BEEN
OCCURRING DURING THE NIGHT AND EARLY THIS MORNING OVER THE
NORTHERN PLAINS AND UPPER MS VALLEY WILL CONTINUE TO MOVE TO THE
EAST-NORTHEAST OVER THE TOP OF THE BUILDING RIDGE. BY SUNDAY NIGHT
THE UPPER RIDGE WILL HAVE REACHED THE CENTRAL GREAT LAKES AND THE OH
VALLEY REGIONS AS AN UPPER LOW SLOWLY MOVES EAST FROM THE CANADIAN
MARITIMES.
A VERY WARM AIR MASS WAS ACROSS THE HIGH PLAINS FRIDAY UNDER THE
UPPER RIDGE. THIS AIR MASS WILL SPREAD TO THE LOCAL AREA FOR
SUNDAY. DEPENDING ON CLOUD COVER...OF WHICH MUCH WOULD LIKELY BY
CONVECTIVE DEBRIS SPREADING EAST ACROSS THE MS RIVER FROM UPSTREAM
CONVECTION...TEMPERATURES MAY PEAK IN THE UPPER 80S IF THE CIRRUS
DEBRIS CLOUDS ARE NOT TOO THICK. EVEN WITH MORE CLOUDINESS MID 80S
LOOKS PRETTY LIKELY FOR SUNDAY AFTERNOON.
MEANWHILE...MULTIPLE STRONG UPPER WAVES DROPPING INTO AN UPPER
TROUGH EXTENDING FROM WEST OF THE B.C. COAST SOUTHEAST ACROSS THE
PACIFIC NORTHWEST TO THE DESERT SOUTHWEST ARE PROGGED TO CONGEAL
AND FORM AN UPPER LOW TO REACH THE CENTRAL HIGH PLAINS BY SUNDAY
EVENING. INCREASING SOUTH TO SOUTHWEST LOW AND MID LEVEL FLOW
AHEAD OF A SURFACE LOW ASSOCIATED WITH THE UPPER LOW WILL
TRANSPORT SIGNIFICANT MOISTURE FROM THE WESTERN GULF UP ACROSS THE
SOUTHERN PLAINS...MID MO VALLEY AND UPPER MS VALLEY DURING SUNDAY
WITH THE MOISTURE AXIS SHIFTING EAST OVER THE MID MS VALLEY AND
THE UPPER MIDWEST TO OVER IL AND THE WESTERN GREAT LAKES BY MONDAY.
WHILE THE UPPER LOW WILL STILL BE OUT OVER THE CENTRAL PLAINS
LATE SUNDAY AND NOT REACH THE MID MO VALLEY TIL LATER MONDAY
POTENTIAL INSTABILITY WILL BE INCREASING OVER THE LOCAL AREA AND
ANY SMALLER SCALE DISTURBANCES TRAVELING NORTHEASTWARD ACROSS
THE MID MS VALLEY MAY TRIGGER THUNDERSTORMS. GIVEN AMOUNT OF
AVAILABLE CAPE AND LOW LEVEL WIND SHEAR THERE IS THE POTENTIAL
FOR SOME OF THE THUNDERSTORMS THAT MAY DEVELOP TO BE STRONG TO
SEVERE.
WITH THE CORE OF THE WARM AIR DOME SHIFTING TO THE EAST MONDAY
AND MORE CLOUDS AND POSSIBLY MOIST CONVECTION OVER/NEAR THE AREA
TEMPERATURES WILL LIKELY BE HELD DOWN A FEW TO A COUPLE DEGREES
FROM THOSE REACHED SUNDAY.
THE SLOW PROGRESS OF THE UPPER LOW DUE TO BEING IN AN OMEGA BLOCK
TYPE UPPER PATTERN RESULTS IN IT NOT REACHING NEAR/OVER THE LOCAL
AREA UNTIL LATER WEDNESDAY AND WEDNESDAY NIGHT. THIS SLOW MOVEMENT
KEEPS THE THREAT OF THUNDERSTORMS GOING...WITH THE HIGHEST POPS
DURING MONDAY NIGHT THROUGH TUESDAY NIGHT AS THIS IS WHEN THE
HIGHEST THETA E AIR IS IN PLACE WITH SIGNIFICANT CAPE VALUES.
WHILE PRECIPITABLE WATER VALUES ARE NOT EXTREME...GENERALLY AROUND
1.5 INCHES FROM SUNDAY NIGHT INTO WEDNESDAY...THE POTENTIAL FOR
MULTIPLE RAINFALL EVENTS DURING THE PERIOD OF TIME IT TAKES THE
UPPER LOW TO REACH AND EVENTUALLY PASS OVER THE LOCAL AREA DOES
PRESENT THE POSSIBILITY OF SOME 2 TO 3 INCH RAINFALL TOTALS.
SPECIFICS ON WHICH PART OR PARTS OF THE FA WOULD BE MOST PRONE TO
RECEIVING SIGNIFICANT RAINFALL AMOUNTS IS NOT CLEAR AT THIS TIME
SO ALL THAT CAN BE SAID THAT THERE IS THE POTENTIAL.
CHANCES FOR SHOWERS AND SOME THUNDERSTORMS PERSIST WEDNESDAY
THROUGH THURSDAY AS THE UPPER LOW IS TO STILL BE SLUGGISHLY
MOVING EAST TO THE WESTERN GREAT LAKES AND MIDWEST. COOLER AIR
WILL BE DRAWN DOWN ACROSS THE REGION AS THE UPPER FLOW VEERS TO
OUT OF THE NORTHWEST THURSDAY. THIS RESULTS IN HIGHS OF ONLY MID
60S TO LOWER 70S FOR THURSDAY AND FRIDAY. BY THURSDAY NIGHT THE
THREAT OF ANY ADDITIONAL SHOWERS SHOULD HAVE ENDED WITH THE UPPER
LOW OPENING UP TO THE EAST OF THE AREA AND THE LOWER LEVEL FLOW
BECOMING SOMEWHAT ANTICYCLONIC AS A RIDGE OF HIGH PRESSURE
EXTENDING SOUTHWEST FROM ONTARIO DRIFTS EAST ACROSS THE UPPER
MIDWEST AND MID MO VALLEY.
TRS
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 16Z...
* SOUTHEAST WINDS /VARIABLE 130-170/ BECOMING EAST /VARIABLE
080-120/ NEXT 1-3 HOURS AS LAKE INFLUENCE TAKES HOLD.
* MVFR VSBY POSSIBLE TONIGHT THROUGH DAYBREAK SUNDAY.
MDB
//DISCUSSION...UPDATED 16Z...
LAKE BREEZE/INFLUENCE STARTING TO APPEAR IN MESO OBS AND FAINTLY
IN RADAR DATA WITHIN A FEW MILES OF THE ILLINOIS SHORELINE...AND
SUGGESTED TO BE NEAR GYY WITH A CHANGE TO VARIABLE WINDS THIS PAST
HOUR. EXPECT THE CURRENT VARIABLE SOUTHEAST WINDS TO TURN MORE
EASTERLY WITH CONTINUED VARIABILITY OVER THE NEXT FEW HOURS AT
ORD/MDW/GYY. FEW-SCT CU HAS ALSO DEVELOPED AROUND 030 AND WILL
STEADILY LIFT THROUGH THE MID AFTERNOON. THE INFLUX OF LAKE AIR
MAY BE ABLE TO SCOUR THE CU NEAR ORD/MDW/GYY IF IT IS DEEP ENOUGH.
MDB
FROM 12Z...
IR IMAGERY EARLY THIS MORNING WAS INDICATING SOME LOW CLOUDS
SLIDING NORTHWEST ACROSS GYY...TOWARDS ORD/MDW. THESE CLOUDS HAVE
SINCE DISSIPATED. PATCHY FOG ALSO DEVELOPED...BUT REMAINED
SOUTHWEST OF THE TAF SITES. REDUCED VSBYS AT VARIOUS AIRFIELDS WAS
ARND 1-2SM. IT APPEARS THIS SHUD LIFT BY 14Z...HOWEVER WITH HIGH
CLOUDS BEGINNING TO APPROACH FROM A DECAYING COMPLEX OF
THUNDERSTORMS IN MINNESOTA OVERNIGHT...MAY SLOW THE RATE OF
IMPROVING VSBYS. WINDS HAVE REMAINED LIGHT EARLY THIS
MORNING...THRU DAYBREAK. GENERALLY VRB WITH SPEEDS LESS THAN 4 KT.
AS THE MORNING PROGRESSES...MIXING WILL INCREASE AND WINDS WILL
BRIEFLY TURN SOUTHEASTERLY. SPEEDS WILL GENERALLY BE 10KT OR LESS
THRU LATE MORNING. THEN IT APPEARS A LAKE BREEZE WILL DEVELOP AND
ALLOW WINDS TO TURN EASTERLY OR BETWEEN A 080-100 DEG RANGE. AT
THIS TIME IT APPEARS OCCASIONAL GUSTS MAY ACCOMPANY THE WIND
SHIFT. HOWEVER IT APPEARS THIS MAY ONLY AFFECT ORD/MDW. FOR GYY
WINDS WILL TURN MORE NORTH/NORTHEASTERLY OR A 010-030 DEG RANGE.
VFR CONDS ARE EXPECTED TO PREVAIL THRU THE DAY TODAY...WITH SCT CLOUDS
NOTED IN A 3-4KFT AGL DECK WITH A CIRRUS SHIELD OVERHEAD AT OR
AROUND 15KFT AGL. THEN AFT SUNSET WINDS DIMINISH AND THEN RELAX
BACK TO THE SOUTHEAST. GUIDANCE HAS BACKED OFF ON PRECIP CHCS
TODAY...HOWEVER SOME SPOTTY SHOWERS MAY STILL DEVELOP. THE
COVERAGE DOES NOT LOOK TOO GREAT...AND HAVE OPTED TO MAINTAIN A
DRY TAF. OVERNIGHT IT APPEARS CONDITIONS BECOME FAVORABLE FOR
PATCHY FOG TO DEVELOP. AT THIS TIME FEEL THE TAF SITES MAY ONLY BE
REDUCED TO ARND 3-4SM...HOWEVER ADDITIONAL MOISTURE WILL POOL INTO
THE NORTHERN IL/NORTHWEST IN AIRFIELDS. THIS MAY AID IN FURTHER
REDUCING VSBYS TO ARND 1SM IN LOCATIONS.
BEACHLER
//ORD AND MDW CONFIDENCE...UPDATED 16Z...
* MEDIUM-HIGH CONFIDENCE IN WIND DIRECTION TRENDS AND TIMING
THROUGH THE AFTERNOON.
* MEDIUM CONFIDENCE IN MVFR VSBY OVERNIGHT/SUNDAY MORNING.
MDB
//OUTLOOK FOR ORD/MDW FOR 00Z MONDAY-12Z SATURDAY...UPDATED 12Z...
SUNDAY NIGHT...VFR TRENDING TO PATCHY MVFR. PERIODS OF TSRA.
MONDAY THROUGH WEDNESDAY...PERIODS OF TSRA
THURSDAY...CHC SHRA.
FRIDAY...VFR. NO SIG WX.
BEACHLER
&&
.MARINE...
221 AM CDT
MINIMAL CHANGES FROM PREVIOUS FORECAST. BROAD SFC RIDGE HAS BECOME
CENTERED ACROSS CENTRAL QUEBEC....HOWEVER THIS FEATURE CONTINUES
TO INFLUENCE THE WESTERN GREAT LAKES WITH A LIGHT EAST FLOW TODAY
ACROSS THE LAKE. AS THE SFC RIDGE WILL DRIFT FURTHER AWAY FROM
LAKE MICHIGAN...WINDS WILL GRADUALLY TURN SOUTHEASTERLY. A STALLED
FRONTAL BOUNDARY STRETCHES FROM CENTRAL MINNESOTA EXTENDING
SOUTHEAST THROUGH WESTERN ILLINOIS INTO CENTRAL INDIANA. IT
APPEARS THE BROAD SFC RIDGE WILL KEEP THIS BOUNDARY JUST SOUTH OF
LAKE MICHIGAN...AND MOST LIKELY WEAKEN. A TROUGH OF LOW PRESSURE
OVER THE NORTHERN PLAINS WILL WEAKEN...AS A SECOND AREA OF LOW
PRESSURE DEVELOPS ALONG A SLOW MOVING COLD FRONT IN THE CENTRAL
PLAINS SUNDAY EVENING. PRIOR TO THE FRONTAL BOUNDARIES
ARRIVAL...WINDS SPEEDS WILL GENERALLY BE 10 TO 20 KT. HOWEVER...AN
OCCASIONAL GUSTS TO 25 KT MAY OCCUR THROUGHOUT THE DAY AS A WEAK
GRADIENT IS FORECAST TO DEVELOP OVER THE CENTRAL PORTION OF THE
LAKE.
AS THE CENTRAL PLAINS LOW PRESSURE DEVELOPS...IT WILL LIFT A WARM
FRONT NORTH ACROSS THE CENTRAL PORTIONS OF THE LAKE SUNDAY
NIGHT/EARLY MON. WINDS WILL TURN SOUTHERLY AND INCREASE BEHIND
THIS BOUNDARY. THIS LOW PRESSURE SYSTEM WILL SLOWLY PUSH EAST INTO
THE MID-MISSISSIPPI VALLEY TUE/WED...THEN DRIFT EAST INTO THE OHIO
VALLEY. WITH THE SLOW MOVING FRONTAL BOUNDARY EXPECTED TO BE OVER
THE CENTRAL PORTIONS OF THE LAKE...WINDS NORTH WILL BE NORTHERLY
AND SOUTHERLY TO THE SOUTH. FORECAST GUIDANCE INDICATES THAT A
TIGHTENING GRADIENT ACROSS THE NORTHERN PORTIONS OF THE LAKE IS
LIKELY...WHICH COULD RESULT IN WINDS BETWEEN 15-25 KT MON/TUE. THEN
THE BOUNDARY WILL EVENTUALLY PUSH BACK TO THE SOUTH OF THE LAKE
TOWARDS THE MIDDLE OF THE UPCOMING WEEK.
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 181412
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
912 AM CDT SAT MAY 18 2013
.DISCUSSION...
430 AM CDT
FOCUS OF FORECAST IS ON THE INCREASE IN CHANCES OF SHOWERS AND
THUNDERSTORMS BEGINNING LATE SUNDAY/SUNDAY NIGHT AND CONTINUING TO
GRADUALLY INCREASE THROUGH MONDAY...PERSISTING THROUGH THURSDAY.
TIME FRAME OF GREATEST THREAT OF PRECIP WILL BE MONDAY NIGHT
THROUGH TUESDAY NIGHT.
OTHER MAIN FORECAST ITEM IS THE CONTINUED WARM UP TODAY AND SUNDAY
WITH WARMTH PERSISTING MONDAY BEFORE HIGH TEMPERATURES START
FALLING OFF TUESDAY...WITH HIGHS ONLY IN THE MID 60S TO LOWER 70S
ON THURSDAY AND FRIDAY.
OTHER CONCERNS ARE POTENTIAL FOR SIGNIFICANT AMOUNTS OF RAINFALL
FROM MONDAY NIGHT INTO WEDNESDAY AND SOME POTENTIAL FOR SEVERE
CONVECTION...IN THE WESTERN PORTION OF THE FORECAST AREA LATE
SUNDAY AND SUNDAY NIGHT...AND ACROSS THE AREA MONDAY AND MONDAY
NIGHT.
CHANCES OF ANY PRECIP IN THE AREA ARE LOW FOR TODAY AND TONIGHT
AS AN UPPER RIDGE BUILDING OVER THE MID CONTINENT SHIFTS EASTWARD
TO OVER THE LOCAL AREA LATE TODAY AND TONIGHT RESULTING IN RISING
HEIGHTS AND LARGE SCALE SUBSIDENCE. THE CONVECTION THAT HAS BEEN
OCCURRING DURING THE NIGHT AND EARLY THIS MORNING OVER THE
NORTHERN PLAINS AND UPPER MS VALLEY WILL CONTINUE TO MOVE TO THE
EAST-NORTHEAST OVER THE TOP OF THE BUILDING RIDGE. BY SUNDAY NIGHT
THE UPPER RIDGE WILL HAVE REACHED THE CENTRAL GREAT LAKES AND THE OH
VALLEY REGIONS AS AN UPPER LOW SLOWLY MOVES EAST FROM THE CANADIAN
MARITIMES.
A VERY WARM AIR MASS WAS ACROSS THE HIGH PLAINS FRIDAY UNDER THE
UPPER RIDGE. THIS AIR MASS WILL SPREAD TO THE LOCAL AREA FOR
SUNDAY. DEPENDING ON CLOUD COVER...OF WHICH MUCH WOULD LIKELY BY
CONVECTIVE DEBRIS SPREADING EAST ACROSS THE MS RIVER FROM UPSTREAM
CONVECTION...TEMPERATURES MAY PEAK IN THE UPPER 80S IF THE CIRRUS
DEBRIS CLOUDS ARE NOT TOO THICK. EVEN WITH MORE CLOUDINESS MID 80S
LOOKS PRETTY LIKELY FOR SUNDAY AFTERNOON.
MEANWHILE...MULTIPLE STRONG UPPER WAVES DROPPING INTO AN UPPER
TROUGH EXTENDING FROM WEST OF THE B.C. COAST SOUTHEAST ACROSS THE
PACIFIC NORTHWEST TO THE DESERT SOUTHWEST ARE PROGGED TO CONGEAL
AND FORM AN UPPER LOW TO REACH THE CENTRAL HIGH PLAINS BY SUNDAY
EVENING. INCREASING SOUTH TO SOUTHWEST LOW AND MID LEVEL FLOW
AHEAD OF A SURFACE LOW ASSOCIATED WITH THE UPPER LOW WILL
TRANSPORT SIGNIFICANT MOISTURE FROM THE WESTERN GULF UP ACROSS THE
SOUTHERN PLAINS...MID MO VALLEY AND UPPER MS VALLEY DURING SUNDAY
WITH THE MOISTURE AXIS SHIFTING EAST OVER THE MID MS VALLEY AND
THE UPPER MIDWEST TO OVER IL AND THE WESTERN GREAT LAKES BY MONDAY.
WHILE THE UPPER LOW WILL STILL BE OUT OVER THE CENTRAL PLAINS
LATE SUNDAY AND NOT REACH THE MID MO VALLEY TIL LATER MONDAY
POTENTIAL INSTABILITY WILL BE INCREASING OVER THE LOCAL AREA AND
ANY SMALLER SCALE DISTURBANCES TRAVELING NORTHEASTWARD ACROSS
THE MID MS VALLEY MAY TRIGGER THUNDERSTORMS. GIVEN AMOUNT OF
AVAILABLE CAPE AND LOW LEVEL WIND SHEAR THERE IS THE POTENTIAL
FOR SOME OF THE THUNDERSTORMS THAT MAY DEVELOP TO BE STRONG TO
SEVERE.
WITH THE CORE OF THE WARM AIR DOME SHIFTING TO THE EAST MONDAY
AND MORE CLOUDS AND POSSIBLY MOIST CONVECTION OVER/NEAR THE AREA
TEMPERATURES WILL LIKELY BE HELD DOWN A FEW TO A COUPLE DEGREES
FROM THOSE REACHED SUNDAY.
THE SLOW PROGRESS OF THE UPPER LOW DUE TO BEING IN AN OMEGA BLOCK
TYPE UPPER PATTERN RESULTS IN IT NOT REACHING NEAR/OVER THE LOCAL
AREA UNTIL LATER WEDNESDAY AND WEDNESDAY NIGHT. THIS SLOW MOVEMENT
KEEPS THE THREAT OF THUNDERSTORMS GOING...WITH THE HIGHEST POPS
DURING MONDAY NIGHT THROUGH TUESDAY NIGHT AS THIS IS WHEN THE
HIGHEST THETA E AIR IS IN PLACE WITH SIGNIFICANT CAPE VALUES.
WHILE PRECIPITABLE WATER VALUES ARE NOT EXTREME...GENERALLY AROUND
1.5 INCHES FROM SUNDAY NIGHT INTO WEDNESDAY...THE POTENTIAL FOR
MULTIPLE RAINFALL EVENTS DURING THE PERIOD OF TIME IT TAKES THE
UPPER LOW TO REACH AND EVENTUALLY PASS OVER THE LOCAL AREA DOES
PRESENT THE POSSIBILITY OF SOME 2 TO 3 INCH RAINFALL TOTALS.
SPECIFICS ON WHICH PART OR PARTS OF THE FA WOULD BE MOST PRONE TO
RECEIVING SIGNIFICANT RAINFALL AMOUNTS IS NOT CLEAR AT THIS TIME
SO ALL THAT CAN BE SAID THAT THERE IS THE POTENTIAL.
CHANCES FOR SHOWERS AND SOME THUNDERSTORMS PERSIST WEDNESDAY
THROUGH THURSDAY AS THE UPPER LOW IS TO STILL BE SLUGGISHLY
MOVING EAST TO THE WESTERN GREAT LAKES AND MIDWEST. COOLER AIR
WILL BE DRAWN DOWN ACROSS THE REGION AS THE UPPER FLOW VEERS TO
OUT OF THE NORTHWEST THURSDAY. THIS RESULTS IN HIGHS OF ONLY MID
60S TO LOWER 70S FOR THURSDAY AND FRIDAY. BY THURSDAY NIGHT THE
THREAT OF ANY ADDITIONAL SHOWERS SHOULD HAVE ENDED WITH THE UPPER
LOW OPENING UP TO THE EAST OF THE AREA AND THE LOWER LEVEL FLOW
BECOMING SOMEWHAT ANTICYCLONIC AS A RIDGE OF HIGH PRESSURE
EXTENDING SOUTHWEST FROM ONTARIO DRIFTS EAST ACROSS THE UPPER
MIDWEST AND MID MO VALLEY.
TRS
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 14Z...
* WINDS APPROX 140-160 DEGREES BECOMING MORE EASTERLY 090-120 OR
SO MIDDAY/EARLY AFTERNOON.
* MVFR VSBY REDUCTION POSSIBLE LATE TONIGHT THROUGH DAYBREAK
SUNDAY.
MDB
//DISCUSSION...UPDATED 12Z...
IR IMAGERY EARLY THIS MORNING WAS INDICATING SOME LOW CLOUDS
SLIDING NORTHWEST ACROSS GYY...TOWARDS ORD/MDW. THESE CLOUDS HAVE
SINCE DISSIPATED. PATCHY FOG ALSO DEVELOPED...BUT REMAINED
SOUTHWEST OF THE TAF SITES. REDUCED VSBYS AT VARIOUS AIRFIELDS WAS
ARND 1-2SM. IT APPEARS THIS SHUD LIFT BY 14Z...HOWEVER WITH HIGH
CLOUDS BEGINNING TO APPROACH FROM A DECAYING COMPLEX OF
THUNDERSTORMS IN MINNESOTA OVERNIGHT...MAY SLOW THE RATE OF
IMPROVING VSBYS. WINDS HAVE REMAINED LIGHT EARLY THIS
MORNING...THRU DAYBREAK. GENERALLY VRB WITH SPEEDS LESS THAN 4 KT.
AS THE MORNING PROGRESSES...MIXING WILL INCREASE AND WINDS WILL
BRIEFLY TURN SOUTHEASTERLY. SPEEDS WILL GENERALLY BE 10KT OR LESS
THRU LATE MORNING. THEN IT APPEARS A LAKE BREEZE WILL DEVELOP AND
ALLOW WINDS TO TURN EASTERLY OR BETWEEN A 080-100 DEG RANGE. AT
THIS TIME IT APPEARS OCCASIONAL GUSTS MAY ACCOMPANY THE WIND
SHIFT. HOWEVER IT APPEARS THIS MAY ONLY AFFECT ORD/MDW. FOR GYY
WINDS WILL TURN MORE NORTH/NORTHEASTERLY OR A 010-030 DEG RANGE.
VFR CONDS ARE EXPECTED TO PREVAIL THRU THE DAY TODAY...WITH SCT CLOUDS
NOTED IN A 3-4KFT AGL DECK WITH A CIRRUS SHIELD OVERHEAD AT OR
AROUND 15KFT AGL. THEN AFT SUNSET WINDS DIMINISH AND THEN RELAX
BACK TO THE SOUTHEAST. GUIDANCE HAS BACKED OFF ON PRECIP CHCS
TODAY...HOWEVER SOME SPOTTY SHOWERS MAY STILL DEVELOP. THE
COVERAGE DOES NOT LOOK TOO GREAT...AND HAVE OPTED TO MAINTAIN A
DRY TAF. OVERNIGHT IT APPEARS CONDITIONS BECOME FAVORABLE FOR
PATCHY FOG TO DEVELOP. AT THIS TIME FEEL THE TAF SITES MAY ONLY BE
REDUCED TO ARND 3-4SM...HOWEVER ADDITIONAL MOISTURE WILL POOL INTO
THE NORTHERN IL/NORTHWEST IN AIRFIELDS. THIS MAY AID IN FURTHER
REDUCING VSBYS TO ARND 1SM IN LOCATIONS.
BEACHLER
//ORD AND MDW CONFIDENCE...UPDATED 14Z...
* HIGH CONFIDENCE IN WIND SPEED/DIRECTION TRENDS THROUGH MIDDAY
...MEDIUM-HIGH CONFIDENCE THIS AFTERNOON...SOME CHANCE FOR AN
EAST-NORTHEAST DIRECTION.
* MEDIUM CONFIDENCE IN MVFR VSBY REDUCTION POTENTIAL
OVERNIGHT/SUNDAY MORNING.
MDB
//OUTLOOK FOR ORD/MDW FOR 00Z MONDAY-12Z SATURDAY...UPDATED 12Z...
SUNDAY NIGHT...VFR TRENDING TO PATCHY MVFR. PERIODS OF TSRA.
MONDAY THROUGH WEDNESDAY...PERIODS OF TSRA
THURSDAY...CHC SHRA.
FRIDAY...VFR. NO SIG WX.
BEACHLER
&&
.MARINE...
221 AM CDT
MINIMAL CHANGES FROM PREVIOUS FORECAST. BROAD SFC RIDGE HAS BECOME
CENTERED ACROSS CENTRAL QUEBEC....HOWEVER THIS FEATURE CONTINUES
TO INFLUENCE THE WESTERN GREAT LAKES WITH A LIGHT EAST FLOW TODAY
ACROSS THE LAKE. AS THE SFC RIDGE WILL DRIFT FURTHER AWAY FROM
LAKE MICHIGAN...WINDS WILL GRADUALLY TURN SOUTHEASTERLY. A STALLED
FRONTAL BOUNDARY STRETCHES FROM CENTRAL MINNESOTA EXTENDING
SOUTHEAST THROUGH WESTERN ILLINOIS INTO CENTRAL INDIANA. IT
APPEARS THE BROAD SFC RIDGE WILL KEEP THIS BOUNDARY JUST SOUTH OF
LAKE MICHIGAN...AND MOST LIKELY WEAKEN. A TROUGH OF LOW PRESSURE
OVER THE NORTHERN PLAINS WILL WEAKEN...AS A SECOND AREA OF LOW
PRESSURE DEVELOPS ALONG A SLOW MOVING COLD FRONT IN THE CENTRAL
PLAINS SUNDAY EVENING. PRIOR TO THE FRONTAL BOUNDARIES
ARRIVAL...WINDS SPEEDS WILL GENERALLY BE 10 TO 20 KT. HOWEVER...AN
OCCASIONAL GUSTS TO 25 KT MAY OCCUR THROUGHOUT THE DAY AS A WEAK
GRADIENT IS FORECAST TO DEVELOP OVER THE CENTRAL PORTION OF THE
LAKE.
AS THE CENTRAL PLAINS LOW PRESSURE DEVELOPS...IT WILL LIFT A WARM
FRONT NORTH ACROSS THE CENTRAL PORTIONS OF THE LAKE SUNDAY
NIGHT/EARLY MON. WINDS WILL TURN SOUTHERLY AND INCREASE BEHIND
THIS BOUNDARY. THIS LOW PRESSURE SYSTEM WILL SLOWLY PUSH EAST INTO
THE MID-MISSISSIPPI VALLEY TUE/WED...THEN DRIFT EAST INTO THE OHIO
VALLEY. WITH THE SLOW MOVING FRONTAL BOUNDARY EXPECTED TO BE OVER
THE CENTRAL PORTIONS OF THE LAKE...WINDS NORTH WILL BE NORTHERLY
AND SOUTHERLY TO THE SOUTH. FORECAST GUIDANCE INDICATES THAT A
TIGHTENING GRADIENT ACROSS THE NORTHERN PORTIONS OF THE LAKE IS
LIKELY...WHICH COULD RESULT IN WINDS BETWEEN 15-25 KT MON/TUE. THEN
THE BOUNDARY WILL EVENTUALLY PUSH BACK TO THE SOUTH OF THE LAKE
TOWARDS THE MIDDLE OF THE UPCOMING WEEK.
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 181148
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
648 AM CDT SAT MAY 18 2013
.DISCUSSION...
430 AM CDT
FOCUS OF FORECAST IS ON THE INCREASE IN CHANCES OF SHOWERS AND
THUNDERSTORMS BEGINNING LATE SUNDAY/SUNDAY NIGHT AND CONTINUING TO
GRADUALLY INCREASE THROUGH MONDAY...PERSISTING THROUGH THURSDAY.
TIME FRAME OF GREATEST THREAT OF PRECIP WILL BE MONDAY NIGHT
THROUGH TUESDAY NIGHT.
OTHER MAIN FORECAST ITEM IS THE CONTINUED WARM UP TODAY AND SUNDAY
WITH WARMTH PERSISTING MONDAY BEFORE HIGH TEMPERATURES START
FALLING OFF TUESDAY...WITH HIGHS ONLY IN THE MID 60S TO LOWER 70S
ON THURSDAY AND FRIDAY.
OTHER CONCERNS ARE POTENTIAL FOR SIGNIFICANT AMOUNTS OF RAINFALL
FROM MONDAY NIGHT INTO WEDNESDAY AND SOME POTENTIAL FOR SEVERE
CONVECTION...IN THE WESTERN PORTION OF THE FORECAST AREA LATE
SUNDAY AND SUNDAY NIGHT...AND ACROSS THE AREA MONDAY AND MONDAY
NIGHT.
CHANCES OF ANY PRECIP IN THE AREA ARE LOW FOR TODAY AND TONIGHT
AS AN UPPER RIDGE BUILDING OVER THE MID CONTINENT SHIFTS EASTWARD
TO OVER THE LOCAL AREA LATE TODAY AND TONIGHT RESULTING IN RISING
HEIGHTS AND LARGE SCALE SUBSIDENCE. THE CONVECTION THAT HAS BEEN
OCCURRING DURING THE NIGHT AND EARLY THIS MORNING OVER THE
NORTHERN PLAINS AND UPPER MS VALLEY WILL CONTINUE TO MOVE TO THE
EAST-NORTHEAST OVER THE TOP OF THE BUILDING RIDGE. BY SUNDAY NIGHT
THE UPPER RIDGE WILL HAVE REACHED THE CENTRAL GREAT LAKES AND THE OH
VALLEY REGIONS AS AN UPPER LOW SLOWLY MOVES EAST FROM THE CANADIAN
MARITIMES.
A VERY WARM AIR MASS WAS ACROSS THE HIGH PLAINS FRIDAY UNDER THE
UPPER RIDGE. THIS AIR MASS WILL SPREAD TO THE LOCAL AREA FOR
SUNDAY. DEPENDING ON CLOUD COVER...OF WHICH MUCH WOULD LIKELY BY
CONVECTIVE DEBRIS SPREADING EAST ACROSS THE MS RIVER FROM UPSTREAM
CONVECTION...TEMPERATURES MAY PEAK IN THE UPPER 80S IF THE CIRRUS
DEBRIS CLOUDS ARE NOT TOO THICK. EVEN WITH MORE CLOUDINESS MID 80S
LOOKS PRETTY LIKELY FOR SUNDAY AFTERNOON.
MEANWHILE...MULTIPLE STRONG UPPER WAVES DROPPING INTO AN UPPER
TROUGH EXTENDING FROM WEST OF THE B.C. COAST SOUTHEAST ACROSS THE
PACIFIC NORTHWEST TO THE DESERT SOUTHWEST ARE PROGGED TO CONGEAL
AND FORM AN UPPER LOW TO REACH THE CENTRAL HIGH PLAINS BY SUNDAY
EVENING. INCREASING SOUTH TO SOUTHWEST LOW AND MID LEVEL FLOW
AHEAD OF A SURFACE LOW ASSOCIATED WITH THE UPPER LOW WILL
TRANSPORT SIGNIFICANT MOISTURE FROM THE WESTERN GULF UP ACROSS THE
SOUTHERN PLAINS...MID MO VALLEY AND UPPER MS VALLEY DURING SUNDAY
WITH THE MOISTURE AXIS SHIFTING EAST OVER THE MID MS VALLEY AND
THE UPPER MIDWEST TO OVER IL AND THE WESTERN GREAT LAKES BY MONDAY.
WHILE THE UPPER LOW WILL STILL BE OUT OVER THE CENTRAL PLAINS
LATE SUNDAY AND NOT REACH THE MID MO VALLEY TIL LATER MONDAY
POTENTIAL INSTABILITY WILL BE INCREASING OVER THE LOCAL AREA AND
ANY SMALLER SCALE DISTURBANCES TRAVELING NORTHEASTWARD ACROSS
THE MID MS VALLEY MAY TRIGGER THUNDERSTORMS. GIVEN AMOUNT OF
AVAILABLE CAPE AND LOW LEVEL WIND SHEAR THERE IS THE POTENTIAL
FOR SOME OF THE THUNDERSTORMS THAT MAY DEVELOP TO BE STRONG TO
SEVERE.
WITH THE CORE OF THE WARM AIR DOME SHIFTING TO THE EAST MONDAY
AND MORE CLOUDS AND POSSIBLY MOIST CONVECTION OVER/NEAR THE AREA
TEMPERATURES WILL LIKELY BE HELD DOWN A FEW TO A COUPLE DEGREES
FROM THOSE REACHED SUNDAY.
THE SLOW PROGRESS OF THE UPPER LOW DUE TO BEING IN AN OMEGA BLOCK
TYPE UPPER PATTERN RESULTS IN IT NOT REACHING NEAR/OVER THE LOCAL
AREA UNTIL LATER WEDNESDAY AND WEDNESDAY NIGHT. THIS SLOW MOVEMENT
KEEPS THE THREAT OF THUNDERSTORMS GOING...WITH THE HIGHEST POPS
DURING MONDAY NIGHT THROUGH TUESDAY NIGHT AS THIS IS WHEN THE
HIGHEST THETA E AIR IS IN PLACE WITH SIGNIFICANT CAPE VALUES.
WHILE PRECIPITABLE WATER VALUES ARE NOT EXTREME...GENERALLY AROUND
1.5 INCHES FROM SUNDAY NIGHT INTO WEDNESDAY...THE POTENTIAL FOR
MULTIPLE RAINFALL EVENTS DURING THE PERIOD OF TIME IT TAKES THE
UPPER LOW TO REACH AND EVENTUALLY PASS OVER THE LOCAL AREA DOES
PRESENT THE POSSIBILITY OF SOME 2 TO 3 INCH RAINFALL TOTALS.
SPECIFICS ON WHICH PART OR PARTS OF THE FA WOULD BE MOST PRONE TO
RECEIVING SIGNIFICANT RAINFALL AMOUNTS IS NOT CLEAR AT THIS TIME
SO ALL THAT CAN BE SAID THAT THERE IS THE POTENTIAL.
CHANCES FOR SHOWERS AND SOME THUNDERSTORMS PERSIST WEDNESDAY
THROUGH THURSDAY AS THE UPPER LOW IS TO STILL BE SLUGGISHLY
MOVING EAST TO THE WESTERN GREAT LAKES AND MIDWEST. COOLER AIR
WILL BE DRAWN DOWN ACROSS THE REGION AS THE UPPER FLOW VEERS TO
OUT OF THE NORTHWEST THURSDAY. THIS RESULTS IN HIGHS OF ONLY MID
60S TO LOWER 70S FOR THURSDAY AND FRIDAY. BY THURSDAY NIGHT THE
THREAT OF ANY ADDITIONAL SHOWERS SHOULD HAVE ENDED WITH THE UPPER
LOW OPENING UP TO THE EAST OF THE AREA AND THE LOWER LEVEL FLOW
BECOMING SOMEWHAT ANTICYCLONIC AS A RIDGE OF HIGH PRESSURE
EXTENDING SOUTHWEST FROM ONTARIO DRIFTS EAST ACROSS THE UPPER
MIDWEST AND MID MO VALLEY.
TRS
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 12Z...
* PATCHY FG/HZ S/SW OF ORD/MDW...WILL BURN OFF ARND 14Z.
* VRB WINDS ARND 3-4KT...TURN BRIEFLY SE THEN BACK TO A 080-100
DEG RANGE MIDDAY. SPEEDS INCREASE TO ARND 10KT...WITH OCCASIONAL
GUSTS TO 16KT THRU MIDDAY.
* WINDS TURN SE AFT SUNSET...AND DIMINISH TO ARND 4KT OVERNIGHT.
* PSBL PATCHY FG AND REDUCED VSBYS DEVELOP OVERNIGHT INTO SUN
MORNING.
BEACHLER
//DISCUSSION...UPDATED 12Z...
IR IMAGERY EARLY THIS MORNING WAS INDICATING SOME LOW CLOUDS
SLIDING NORTHWEST ACROSS GYY...TOWARDS ORD/MDW. THESE CLOUDS HAVE
SINCE DISSIPATED. PATCHY FOG ALSO DEVELOPED...BUT REMAINED
SOUTHWEST OF THE TAF SITES. REDUCED VSBYS AT VARIOUS AIRFIELDS WAS
ARND 1-2SM. IT APPEARS THIS SHUD LIFT BY 14Z...HOWEVER WITH HIGH
CLOUDS BEGINNING TO APPROACH FROM A DECAYING COMPLEX OF
THUNDERSTORMS IN MINNESOTA OVERNIGHT...MAY SLOW THE RATE OF
IMPROVING VSBYS. WINDS HAVE REMAINED LIGHT EARLY THIS
MORNING...THRU DAYBREAK. GENERALLY VRB WITH SPEEDS LESS THAN 4 KT.
AS THE MORNING PROGRESSES...MIXING WILL INCREASE AND WINDS WILL
BRIEFLY TURN SOUTHEASTERLY. SPEEDS WILL GENERALLY BE 10KT OR LESS
THRU LATE MORNING. THEN IT APPEARS A LAKE BREEZE WILL DEVELOP AND
ALLOW WINDS TO TURN EASTERLY OR BETWEEN A 080-100 DEG RANGE. AT
THIS TIME IT APPEARS OCCASIONAL GUSTS MAY ACCOMPANY THE WIND
SHIFT. HOWEVER IT APPEARS THIS MAY ONLY AFFECT ORD/MDW. FOR GYY
WINDS WILL TURN MORE NORTH/NORTHEASTERLY OR A 010-030 DEG RANGE.
VFR CONDS ARE EXPECTED TO PREVAIL THRU THE DAY TODAY...WITH SCT CLOUDS
NOTED IN A 3-4KFT AGL DECK WITH A CIRRUS SHIELD OVERHEAD AT OR
AROUND 15KFT AGL. THEN AFT SUNSET WINDS DIMINISH AND THEN RELAX
BACK TO THE SOUTHEAST. GUIDANCE HAS BACKED OFF ON PRECIP CHCS
TODAY...HOWEVER SOME SPOTTY SHOWERS MAY STILL DEVELOP. THE
COVERAGE DOES NOT LOOK TOO GREAT...AND HAVE OPTED TO MAINTAIN A
DRY TAF. OVERNIGHT IT APPEARS CONDITIONS BECOME FAVORABLE FOR
PATCHY FOG TO DEVELOP. AT THIS TIME FEEL THE TAF SITES MAY ONLY BE
REDUCED TO ARND 3-4SM...HOWEVER ADDITIONAL MOISTURE WILL POOL INTO
THE NORTHERN IL/NORTHWEST IN AIRFIELDS. THIS MAY AID IN FURTHER
REDUCING VSBYS TO ARND 1SM IN LOCATIONS.
BEACHLER
//ORD AND MDW CONFIDENCE...UPDATED 12Z...
* MEDIUM CONFIDENCE IN PRECIP REMAINING S/SW OF TAF SITES.
* HIGH CONFIDENCE IN WIND DIR/SPEED FORECAST.
* MEDIUM/HIGH CONFIDENCE IN CLOUD FORECAST.
* MEDIUM CONFIDENCE IN OVERNIGHT PATCHY FOG DEVELOPING.
BEACHLER
//OUTLOOK FOR ORD/MDW FOR 00Z MONDAY-12Z SATURDAY...UPDATED 12Z...
SUNDAY NIGHT...VFR TRENDING TO PATCHY MVFR. PERIODS OF TSRA.
MONDAY THROUGH WEDNESDAY...PERIODS OF TSRA
THURSDAY...CHC SHRA.
FRIDAY...VFR. NO SIG WX.
BEACHLER
&&
.MARINE...
221 AM CDT
MINIMAL CHANGES FROM PREVIOUS FORECAST. BROAD SFC RIDGE HAS BECOME
CENTERED ACROSS CENTRAL QUEBEC....HOWEVER THIS FEATURE CONTINUES
TO INFLUENCE THE WESTERN GREAT LAKES WITH A LIGHT EAST FLOW TODAY
ACROSS THE LAKE. AS THE SFC RIDGE WILL DRIFT FURTHER AWAY FROM
LAKE MICHIGAN...WINDS WILL GRADUALLY TURN SOUTHEASTERLY. A STALLED
FRONTAL BOUNDARY STRETCHES FROM CENTRAL MINNESOTA EXTENDING
SOUTHEAST THROUGH WESTERN ILLINOIS INTO CENTRAL INDIANA. IT
APPEARS THE BROAD SFC RIDGE WILL KEEP THIS BOUNDARY JUST SOUTH OF
LAKE MICHIGAN...AND MOST LIKELY WEAKEN. A TROUGH OF LOW PRESSURE
OVER THE NORTHERN PLAINS WILL WEAKEN...AS A SECOND AREA OF LOW
PRESSURE DEVELOPS ALONG A SLOW MOVING COLD FRONT IN THE CENTRAL
PLAINS SUNDAY EVENING. PRIOR TO THE FRONTAL BOUNDARIES
ARRIVAL...WINDS SPEEDS WILL GENERALLY BE 10 TO 20 KT. HOWEVER...AN
OCCASIONAL GUSTS TO 25 KT MAY OCCUR THROUGHOUT THE DAY AS A WEAK
GRADIENT IS FORECAST TO DEVELOP OVER THE CENTRAL PORTION OF THE
LAKE.
AS THE CENTRAL PLAINS LOW PRESSURE DEVELOPS...IT WILL LIFT A WARM
FRONT NORTH ACROSS THE CENTRAL PORTIONS OF THE LAKE SUNDAY
NIGHT/EARLY MON. WINDS WILL TURN SOUTHERLY AND INCREASE BEHIND
THIS BOUNDARY. THIS LOW PRESSURE SYSTEM WILL SLOWLY PUSH EAST INTO
THE MID-MISSISSIPPI VALLEY TUE/WED...THEN DRIFT EAST INTO THE OHIO
VALLEY. WITH THE SLOW MOVING FRONTAL BOUNDARY EXPECTED TO BE OVER
THE CENTRAL PORTIONS OF THE LAKE...WINDS NORTH WILL BE NORTHERLY
AND SOUTHERLY TO THE SOUTH. FORECAST GUIDANCE INDICATES THAT A
TIGHTENING GRADIENT ACROSS THE NORTHERN PORTIONS OF THE LAKE IS
LIKELY...WHICH COULD RESULT IN WINDS BETWEEN 15-25 KT MON/TUE. THEN
THE BOUNDARY WILL EVENTUALLY PUSH BACK TO THE SOUTH OF THE LAKE
TOWARDS THE MIDDLE OF THE UPCOMING WEEK.
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 180954
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
440 AM CDT SAT MAY 18 2013
.DISCUSSION...
430 AM CDT
FOCUS OF FORECAST IS ON THE INCREASE IN CHANCES OF SHOWERS AND
THUNDERSTORMS BEGINNING LATE SUNDAY/SUNDAY NIGHT AND CONTINUING TO
GRADUALLY INCREASE THROUGH MONDAY...PERSISTING THROUGH THURSDAY.
TIME FRAME OF GREATEST THREAT OF PRECIP WILL BE MONDAY NIGHT
THROUGH TUESDAY NIGHT.
OTHER MAIN FORECAST ITEM IS THE CONTINUED WARM UP TODAY AND SUNDAY
WITH WARMTH PERSISTING MONDAY BEFORE HIGH TEMPERATURES START
FALLING OFF TUESDAY...WITH HIGHS ONLY IN THE MID 60S TO LOWER 70S
ON THURSDAY AND FRIDAY.
OTHER CONCERNS ARE POTENTIAL FOR SIGNIFICANT AMOUNTS OF RAINFALL
FROM MONDAY NIGHT INTO WEDNESDAY AND SOME POTENTIAL FOR SEVERE
CONVECTION...IN THE WESTERN PORTION OF THE FORECAST AREA LATE
SUNDAY AND SUNDAY NIGHT...AND ACROSS THE AREA MONDAY AND MONDAY
NIGHT.
CHANCES OF ANY PRECIP IN THE AREA ARE LOW FOR TODAY AND TONIGHT
AS AN UPPER RIDGE BUILDING OVER THE MID CONTINENT SHIFTS EASTWARD
TO OVER THE LOCAL AREA LATE TODAY AND TONIGHT RESULTING IN RISING
HEIGHTS AND LARGE SCALE SUBSIDENCE. THE CONVECTION THAT HAS BEEN
OCCURRING DURING THE NIGHT AND EARLY THIS MORNING OVER THE
NORTHERN PLAINS AND UPPER MS VALLEY WILL CONTINUE TO MOVE TO THE
EAST-NORTHEAST OVER THE TOP OF THE BUILDING RIDGE. BY SUNDAY NIGHT
THE UPPER RIDGE WILL HAVE REACHED THE CENTRAL GREAT LAKES AND THE OH
VALLEY REGIONS AS AN UPPER LOW SLOWLY MOVES EAST FROM THE CANADIAN
MARITIMES.
A VERY WARM AIR MASS WAS ACROSS THE HIGH PLAINS FRIDAY UNDER THE
UPPER RIDGE. THIS AIR MASS WILL SPREAD TO THE LOCAL AREA FOR
SUNDAY. DEPENDING ON CLOUD COVER...OF WHICH MUCH WOULD LIKELY BY
CONVECTIVE DEBRIS SPREADING EAST ACROSS THE MS RIVER FROM UPSTREAM
CONVECTION...TEMPERATURES MAY PEAK IN THE UPPER 80S IF THE CIRRUS
DEBRIS CLOUDS ARE NOT TOO THICK. EVEN WITH MORE CLOUDINESS MID 80S
LOOKS PRETTY LIKELY FOR SUNDAY AFTERNOON.
MEANWHILE...MULTIPLE STRONG UPPER WAVES DROPPING INTO AN UPPER
TROUGH EXTENDING FROM WEST OF THE B.C. COAST SOUTHEAST ACROSS THE
PACIFIC NORTHWEST TO THE DESERT SOUTHWEST ARE PROGGED TO CONGEAL
AND FORM AN UPPER LOW TO REACH THE CENTRAL HIGH PLAINS BY SUNDAY
EVENING. INCREASING SOUTH TO SOUTHWEST LOW AND MID LEVEL FLOW
AHEAD OF A SURFACE LOW ASSOCIATED WITH THE UPPER LOW WILL
TRANSPORT SIGNIFICANT MOISTURE FROM THE WESTERN GULF UP ACROSS THE
SOUTHERN PLAINS...MID MO VALLEY AND UPPER MS VALLEY DURING SUNDAY
WITH THE MOISTURE AXIS SHIFTING EAST OVER THE MID MS VALLEY AND
THE UPPER MIDWEST TO OVER IL AND THE WESTERN GREAT LAKES BY MONDAY.
WHILE THE UPPER LOW WILL STILL BE OUT OVER THE CENTRAL PLAINS
LATE SUNDAY AND NOT REACH THE MID MO VALLEY TIL LATER MONDAY
POTENTIAL INSTABILITY WILL BE INCREASING OVER THE LOCAL AREA AND
ANY SMALLER SCALE DISTURBANCES TRAVELING NORTHEASTWARD ACROSS
THE MID MS VALLEY MAY TRIGGER THUNDERSTORMS. GIVEN AMOUNT OF
AVAILABLE CAPE AND LOW LEVEL WIND SHEAR THERE IS THE POTENTIAL
FOR SOME OF THE THUNDERSTORMS THAT MAY DEVELOP TO BE STRONG TO
SEVERE.
WITH THE CORE OF THE WARM AIR DOME SHIFTING TO THE EAST MONDAY
AND MORE CLOUDS AND POSSIBLY MOIST CONVECTION OVER/NEAR THE AREA
TEMPERATURES WILL LIKELY BE HELD DOWN A FEW TO A COUPLE DEGREES
FROM THOSE REACHED SUNDAY.
THE SLOW PROGRESS OF THE UPPER LOW DUE TO BEING IN AN OMEGA BLOCK
TYPE UPPER PATTERN RESULTS IN IT NOT REACHING NEAR/OVER THE LOCAL
AREA UNTIL LATER WEDNESDAY AND WEDNESDAY NIGHT. THIS SLOW MOVEMENT
KEEPS THE THREAT OF THUNDERSTORMS GOING...WITH THE HIGHEST POPS
DURING MONDAY NIGHT THROUGH TUESDAY NIGHT AS THIS IS WHEN THE
HIGHEST THETA E AIR IS IN PLACE WITH SIGNIFICANT CAPE VALUES.
WHILE PRECIPITABLE WATER VALUES ARE NOT EXTREME...GENERALLY AROUND
1.5 INCHES FROM SUNDAY NIGHT INTO WEDNESDAY...THE POTENTIAL FOR
MULTIPLE RAINFALL EVENTS DURING THE PERIOD OF TIME IT TAKES THE
UPPER LOW TO REACH AND EVENTUALLY PASS OVER THE LOCAL AREA DOES
PRESENT THE POSSIBILITY OF SOME 2 TO 3 INCH RAINFALL TOTALS.
SPECIFICS ON WHICH PART OR PARTS OF THE FA WOULD BE MOST PRONE TO
RECEIVING SIGNIFICANT RAINFALL AMOUNTS IS NOT CLEAR AT THIS TIME
SO ALL THAT CAN BE SAID THAT THERE IS THE POTENTIAL.
CHANCES FOR SHOWERS AND SOME THUNDERSTORMS PERSIST WEDNESDAY
THROUGH THURSDAY AS THE UPPER LOW IS TO STILL BE SLUGGISHLY
MOVING EAST TO THE WESTERN GREAT LAKES AND MIDWEST. COOLER AIR
WILL BE DRAWN DOWN ACROSS THE REGION AS THE UPPER FLOW VEERS TO
OUT OF THE NORTHWEST THURSDAY. THIS RESULTS IN HIGHS OF ONLY MID
60S TO LOWER 70S FOR THURSDAY AND FRIDAY. BY THURSDAY NIGHT THE
THREAT OF ANY ADDITIONAL SHOWERS SHOULD HAVE ENDED WITH THE UPPER
LOW OPENING UP TO THE EAST OF THE AREA AND THE LOWER LEVEL FLOW
BECOMING SOMEWHAT ANTICYCLONIC AS A RIDGE OF HIGH PRESSURE
EXTENDING SOUTHWEST FROM ONTARIO DRIFTS EAST ACROSS THE UPPER
MIDWEST AND MID MO VALLEY.
TRS
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 09Z...
* POSSIBLE FOG/HAZE DEVELOPING...LINGER THRU DAYBREAK. LOW CLOUDS
MAY ACCOMPANY FOG/HAZE.
* VRB WINDS ARND 5KT OR LESS OVERNIGHT. WINDS TURN BRIEFLY
SOUTHEAST...THEN BACK TO EAST/NORTHEAST WITH A WEAK LAKE BREEZE.
BEACHLER
//DISCUSSION...UPDATED 06Z...
IR IMAGERY EARLY THIS MORNING CONTINUES TO SHOW THINNING CLOUDS
OVER NORTHERN IL/NORTHWEST IN AIRFIELDS. A STALLED FRONTAL
BOUNDARY WAS LOCATED ALONG A FAR NORTHWEST IL TO JUST SOUTH OF JOT
TO FORT WAYNE LINE. ABUNDANT MOISTURE WAS NOTED ALONG AND SOUTH OF
THE BOUNDARY...WHICH IS THE AREA OF GREATEST CONCERN OVERNIGHT FOR
FOG TO DEVELOP. ALREADY A FEW POINTS HAVE OBSERVED VSBYS DROP TO
ARND 2SM. FEEL THAT OVER TIME THIS WILL SPREAD IN COVERAGE...AND
POSSIBLY A FEW POINTS COULD DIP TO ARND 1SM OR LESS BRIEFLY. AT
THIS TIME FEEL THE GREATEST VSBY REDUCTION WILL OCCUR JUST
WEST/SOUTH OF RFD TO JOT. FOR THE TAF SITES IT APPEARS VSBYS MAY
ONLY REDUCE TO ARND 3SM AT RFD/DPA...WHILE ORD/MDW SHUD REMAIN AT
5SM OR BETTER. IN ADDITION TO THE FOG POTENTIAL...LOW STRATUS DECK
MAY TRY TO DEVELOP ARND 08-10Z. GUIDANCE HAS CONTINUED TO SUGGEST
THAT A STRATUS DECK MAY TRY TO DEVELOP WITH CLOUDS ARND 800FT AGL.
FEEL AT THIS TIME THIS IS MORE OF A FEATURE OF ADDTL
MOISTURE...AND HAVE ONLY OPTED TO INCLUDE A MENTION OF FEW008 IN
THE TAF SITES. OTHERWISE WILL RIDE WITH A SCT DECK ARND 2KFT AGL.
WINDS WILL REMAIN VRB THRU THE OVERNIGHT...THEN BRIEFLY TURN
SOUTHEAST FOR ORD/MDW/GYY. WITH SOME HEATING...BY LATE
MORNING/EARLY AFTN...WINDS WILL THEN TURN EAST/NORTHEAST FOR
ORD/MDW AND NORTH/NORTHEAST FOR GYY. IN ADDITION A FEW GUSTS MAY
OCCUR FOR THE TAF SITES CLOSEST TO LAKE MICHIGAN. ELSEWHERE WINDS
WILL REMAIN ARND 10KT FROM THE SOUTHEAST.
AT THIS TIME IT DOES NOT APPEAR ANY ORGANIZED PRECIP/THUNDERSTORMS
ARE EXPECTED...SO HAVE CONTINUED WITH A DRY TAF. OTHERWISE SAT NGT
THRU EARLY SUN...LOOKS FAVORABLE FOR PATCHY FOG TO DEVELOP ONCE
AGAIN. ALTHOUGH THIS SETUP LOOKS MORE FAVORABLE FOR ORD/MDW FOR
SUN MORNING.
BEACHLER
//ORD AND MDW CONFIDENCE...UPDATED 09Z...
* HIGH CONFIDENCE IN WIND DIR/SPEED FORECAST.
* HIGH CONFIDENCE ORD/MDW WILL MAINTAIN VFR CONDS OVERNIGHT.
* MEDIUM CONFIDENCE IN FOG/HAZE DEVELOPING.
* LOW/MEDIUM CONFIDENCE FOG REMAINS WEST/SOUTHWEST OR ORD/MDW.
* MEDIUM CONFIDENCE IN CLOUDS FORECAST SAT AFTN/EVE.
BEACHLER
//OUTLOOK FOR ORD/MDW FOR 12Z SUNDAY-12Z FRIDAY...UPDATED 00Z...
SUNDAY...VFR.
SUNDAY NIGHT THROUGH WEDNESDAY...PERIODS OF TSRA.
THURSDAY...CHC SHRA.
ALLSOPP
&&
.MARINE...
221 AM CDT
MINIMAL CHANGES FROM PREVIOUS FORECAST. BROAD SFC RIDGE HAS BECOME
CENTERED ACROSS CENTRAL QUEBEC....HOWEVER THIS FEATURE CONTINUES
TO INFLUENCE THE WESTERN GREAT LAKES WITH A LIGHT EAST FLOW TODAY
ACROSS THE LAKE. AS THE SFC RIDGE WILL DRIFT FURTHER AWAY FROM
LAKE MICHIGAN...WINDS WILL GRADUALLY TURN SOUTHEASTERLY. A STALLED
FRONTAL BOUNDARY STRETCHES FROM CENTRAL MINNESOTA EXTENDING
SOUTHEAST THROUGH WESTERN ILLINOIS INTO CENTRAL INDIANA. IT
APPEARS THE BROAD SFC RIDGE WILL KEEP THIS BOUNDARY JUST SOUTH OF
LAKE MICHIGAN...AND MOST LIKELY WEAKEN. A TROUGH OF LOW PRESSURE
OVER THE NORTHERN PLAINS WILL WEAKEN...AS A SECOND AREA OF LOW
PRESSURE DEVELOPS ALONG A SLOW MOVING COLD FRONT IN THE CENTRAL
PLAINS SUNDAY EVENING. PRIOR TO THE FRONTAL BOUNDARIES
ARRIVAL...WINDS SPEEDS WILL GENERALLY BE 10 TO 20 KT. HOWEVER...AN
OCCASIONAL GUSTS TO 25 KT MAY OCCUR THROUGHOUT THE DAY AS A WEAK
GRADIENT IS FORECAST TO DEVELOP OVER THE CENTRAL PORTION OF THE
LAKE.
AS THE CENTRAL PLAINS LOW PRESSURE DEVELOPS...IT WILL LIFT A WARM
FRONT NORTH ACROSS THE CENTRAL PORTIONS OF THE LAKE SUNDAY
NIGHT/EARLY MON. WINDS WILL TURN SOUTHERLY AND INCREASE BEHIND
THIS BOUNDARY. THIS LOW PRESSURE SYSTEM WILL SLOWLY PUSH EAST INTO
THE MID-MISSISSIPPI VALLEY TUE/WED...THEN DRIFT EAST INTO THE OHIO
VALLEY. WITH THE SLOW MOVING FRONTAL BOUNDARY EXPECTED TO BE OVER
THE CENTRAL PORTIONS OF THE LAKE...WINDS NORTH WILL BE NORTHERLY
AND SOUTHERLY TO THE SOUTH. FORECAST GUIDANCE INDICATES THAT A
TIGHTENING GRADIENT ACROSS THE NORTHERN PORTIONS OF THE LAKE IS
LIKELY...WHICH COULD RESULT IN WINDS BETWEEN 15-25 KT MON/TUE. THEN
THE BOUNDARY WILL EVENTUALLY PUSH BACK TO THE SOUTH OF THE LAKE
TOWARDS THE MIDDLE OF THE UPCOMING WEEK.
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 180940
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
440 AM CDT SAT MAY 18 2013
.DISCUSSION...
430 AM CDT
FOCUS OF FORECAST IS ON THE INCREASE IN CHANCES OF SHOWERS AND
THUNDERSTORMS BEGINNING LATE SUNDAY/SUNDAY NIGHT AND CONTINUING TO
GRADUALLY INCREASE THROUGH MODAY...PERSISTING THROUGH THURSDAY.
TIME FRAME OF GREATEST THREAT OF PRECIP WILL BE MONDAY NIGHT
THROUGH TUESDAY NIGHT.
OTHER MAIN FORECAST ITEM IS THE CONTINUED WARM UP TODAY AND SUNDAY
WITH WARMTH PERSISTING MONDAY BEFORE HIGH TEMPERATURES START
FALLING OFF TUESDAY...WITH HIGHS ONLY IN THE MID 60S TO LOWER 70S
ON THURSDAY AND FRIDAY.
OTHER CONCERNS ARE POTENTIAL FOR SIGNIFICANT AMOUNTS OF RAINFALL
FROM MONDAY NIGHT INTO WEDNESDAY AND SOME POTENTIAL FOR SEVERE
CONVECTION...IN THE WESTERN PORTION OF THE FORECAST AREA LATE
SUNDAY AND SUNDAY NIGHT...AND ACROSS THE AREA MONDAY AND MONDAY
NIGHT.
CHANCES OF ANY PRECIP IN THE AREA ARE LOW FOR TODAY AND TONIGHT
AS AN UPPER RIDGE BUILDING OVER THE MID CONTINENT SHIFTS EASTWARD
TO OVER THE LOCAL AREA LATE TODAY AND TONIGHT RESULTING IN RISING
HEIGHTS AND LARGE SCALE SUBSIDENCE WITH THE CONVECTION THAT
HAS BEEN OCCURRING DURING THE NIGHT AND EARLY THIS MORNING OVER THE
NORTHERN PLAINS AND UPPER MS VALLEY CONTINUES TO MOVE TO THE EAST-
NORTHEAST OVER THE TOP OF THE BUILDING RIDGE. BY SUNDAY NIGHT THE
UPPER RIDGE WILL HAVE REACHES THE CENTRAL GREAT LAKES AND THE OH
VALLEY REGIONS AS AN UPPER LOW SLOWLY MOVES EAST FROM THE CANADIAN
MARITIMES.
A VERY WARM AIR MASS WAS ACROSS THE HIGH PLAINS FRIDAY UNDER THE
UPPER RIDGE. THIS AIR MASS WILL SPREAD TO THE LOCAL AREA FOR
SUNDAY. DEPENDING ON CLOUD COVER...OF WHICH MUCH WOULD LIKELY BY
CONVECTIVE DEBRIS SPREADING EAST ACROSS THE MS RIVER FROM UPSTREAM
CONVECTION...TEMPERATURES MAY PEAK IN THE UPPER 80S IF THE CIRRUS
DEBRIS CLOUDS ARE NOT TOO THICK. EVEN WITH MORE CLOUDINESS MID 80S
LOOKS PRETTY LIKELY FOR SUNDAY AFTERNOON.
MEANWHILE...MULTIPLE STRONG UPPER WAVES DROPPING INTO AN UPPER
TROUGH EXTENDING FROM WEST OF THE B.C. COAST SOUTHEAST ACROSS THE
PACIFIC NORTHWEST TO THE DESERT SOUTHWEST ARE PROGGED TO CONGEAL
AND FORM AN UPPER LOW TO REACH THE CENTRAL HIGH PLAINS BY SUNDAY
EVENING. INCREASING SOUTH TO SOUTHWEST LOW AND MID LEVEL FLOW
AHEAD OF A SURFACE LOW ASSOCIATED WITH THE UPPER LOW WILL
TRANSPORT SIGNIFICANT MOISTURE FROM THE WESTERN GULF UP ACROSS THE
SOUTHERN PLAINS...MID MO VALLEY AND UPPER MS VALLEY DURING SUNDAY
WITH THE MOISTURE AXIS SHIFTING EAST OVER THE MID MS VALLEY AND
THE UPPER MIDWEST TO THE OVER IL AND THE WESTERN GREAT LAKES BY
MONDAY.
WHILE THE UPPER LOW WILL STILL BE OUT OVER THE CENTRAL PLAINS
LATE SUNDAY AND NOT REACH THE MID MO VALLEY TIL LATER MONDAY
POTENTIAL INSTABILITY WILL BE INCREASING OVER THE LOCAL AREA AND
ANY SMALLER SCALE DISTURBANCES TRAVELING NORTHEASTWARD ACROSS
THE MID MS VALLEY MAY TRIGGER THUNDERSTORMS. GIVEN AMOUNT OF
AVAILABLE CAPE AND LOW LEVEL WIND SHEAR THERE IS THE POTENTIAL
FOR SOME OF THE THUNDERSTORMS THAT MAY DEVELOP TO BE STRONG TO
SEVERE.
WITH THE CORE OF THE WARM AIR DOME SHIFTING TO THE EAST MONDAY
AND MORE CLOUDS AND POSSIBLY MOIST CONVECTION OVER/NEAR THE AREA
TEMPERATURES WILL LIKELY BE HELD DOWN A FEW TO A COUPLE DEGREES
FROM THOSE REACHED SUNDAY.
THE SLOW PROGRESS OF THE UPPER LOW DUE TO BEING IN AN OMEGA BLOCK
TYPE UPPER PATTERN RESULTS IN IT NOT REACHING NEAR/OVER THE LOCAL
AREA UNTIL LATER WEDNESDAY AND WEDNESDAY NIGHT. THIS SLOW MOVEMENT
KEEPS THE THREAT OF THUNDERSTORMS GOING...WITH THE HIGHEST POPS
DURING MONDAY NIGHT THROUGH TUESDAY NIGHT AS THIS IS WHEN THE
HIGHEST THETA E AIR IS IN PLACE WITH SIGNIFICANT CAPE VALUES.
WHILE PRECIPITABLE WATER VALUES ARE NOT EXTREME...GENERALLY AROUND
1.5 INCHES FROM SUNDAY NIGHT INTO WEDNESDAY...THE POTENTIAL FOR
MULTIPLE RAINFALL EVENTS DURING THE PERIOD OF TIME IT TAKES THE
UPPER LOW TO REACH AND EVENTUALLY PASS OVER THE LOCAL AREA DOES
PRESENT THE POSSIBILITY OF SOME 2 TO 3 INCH RAINFALL TOTALS.
SPECIFICS ON WHICH PART OR PARTS OF THE FA WOULD BE MOST PRONE TO
RECEIVING SIGNIFICANT RAINFALL AMOUNTS IS NOT CLEAR AT THIS TIME
ALL THAT CAN BE SAID THAT THERE IS THE POTENTIAL.
CHANCES FOR SHOWERS AND SOME THUNDERSTORMS PERSIST WEDNESDAY
THROUGH THURSDAY AS THE UPPER LOW IS TO STILL BE SLUGGISHLY
MOVING EAST TO THE WESTERN GREAT LAKES AND MIDWEST. COOLER AIR
WILL BE DRAWN DOWN ACROSS THE REGION AS THE UPPER FLOW VEERS TO
OUT OF THE NORTHWEST THURSDAY. THIS RESULTS IN HIGHS OF ONLY MID
60S TO LOWER 70S FOR THURSDAY AND FRIDAY. BY THURSDAY NIGHT THE
THREAT OF ANY ADDITIONAL SHOWERS SHOULD HAVE ENDED WITH THE UPPER
LOW OPENING UP AND THE LOWER LEVEL FLOW BECOMING SOMEWHAT
ANTICYCLONIC AS A RIDGE OF HIGH PRESSURE EXTENDING FROM ONTARIO
DRIFTS EAST ACROSS THE UPPER MIDWEST AND MID MO VALLEY.
TRS
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 09Z...
* POSSIBLE FOG/HAZE DEVELOPING...LINGER THRU DAYBREAK. LOW CLOUDS
MAY ACCOMPANY FOG/HAZE.
* VRB WINDS ARND 5KT OR LESS OVERNIGHT. WINDS TURN BRIEFLY
SOUTHEAST...THEN BACK TO EAST/NORTHEAST WITH A WEAK LAKE BREEZE.
BEACHLER
//DISCUSSION...UPDATED 06Z...
IR IMAGERY EARLY THIS MORNING CONTINUES TO SHOW THINNING CLOUDS
OVER NORTHERN IL/NORTHWEST IN AIRFIELDS. A STALLED FRONTAL
BOUNDARY WAS LOCATED ALONG A FAR NORTHWEST IL TO JUST SOUTH OF JOT
TO FORT WAYNE LINE. ABUNDANT MOISTURE WAS NOTED ALONG AND SOUTH OF
THE BOUNDARY...WHICH IS THE AREA OF GREATEST CONCERN OVERNIGHT FOR
FOG TO DEVELOP. ALREADY A FEW POINTS HAVE OBSERVED VSBYS DROP TO
ARND 2SM. FEEL THAT OVER TIME THIS WILL SPREAD IN COVERAGE...AND
POSSIBLY A FEW POINTS COULD DIP TO ARND 1SM OR LESS BRIEFLY. AT
THIS TIME FEEL THE GREATEST VSBY REDUCTION WILL OCCUR JUST
WEST/SOUTH OF RFD TO JOT. FOR THE TAF SITES IT APPEARS VSBYS MAY
ONLY REDUCE TO ARND 3SM AT RFD/DPA...WHILE ORD/MDW SHUD REMAIN AT
5SM OR BETTER. IN ADDITION TO THE FOG POTENTIAL...LOW STRATUS DECK
MAY TRY TO DEVELOP ARND 08-10Z. GUIDANCE HAS CONTINUED TO SUGGEST
THAT A STRATUS DECK MAY TRY TO DEVELOP WITH CLOUDS ARND 800FT AGL.
FEEL AT THIS TIME THIS IS MORE OF A FEATURE OF ADDTL
MOISTURE...AND HAVE ONLY OPTED TO INCLUDE A MENTION OF FEW008 IN
THE TAF SITES. OTHERWISE WILL RIDE WITH A SCT DECK ARND 2KFT AGL.
WINDS WILL REMAIN VRB THRU THE OVERNIGHT...THEN BRIEFLY TURN
SOUTHEAST FOR ORD/MDW/GYY. WITH SOME HEATING...BY LATE
MORNING/EARLY AFTN...WINDS WILL THEN TURN EAST/NORTHEAST FOR
ORD/MDW AND NORTH/NORTHEAST FOR GYY. IN ADDITION A FEW GUSTS MAY
OCCUR FOR THE TAF SITES CLOSEST TO LAKE MICHIGAN. ELSEWHERE WINDS
WILL REMAIN ARND 10KT FROM THE SOUTHEAST.
AT THIS TIME IT DOES NOT APPEAR ANY ORGANIZED PRECIP/THUNDERSTORMS
ARE EXPECTED...SO HAVE CONTINUED WITH A DRY TAF. OTHERWISE SAT NGT
THRU EARLY SUN...LOOKS FAVORABLE FOR PATCHY FOG TO DEVELOP ONCE
AGAIN. ALTHOUGH THIS SETUP LOOKS MORE FAVORABLE FOR ORD/MDW FOR
SUN MORNING.
BEACHLER
//ORD AND MDW CONFIDENCE...UPDATED 09Z...
* HIGH CONFIDENCE IN WIND DIR/SPEED FORECAST.
* HIGH CONFIDENCE ORD/MDW WILL MAINTAIN VFR CONDS OVERNIGHT.
* MEDIUM CONFIDENCE IN FOG/HAZE DEVELOPING.
* LOW/MEDIUM CONFIDENCE FOG REMAINS WEST/SOUTHWEST OR ORD/MDW.
* MEDIUM CONFIDENCE IN CLOUDS FORECAST SAT AFTN/EVE.
BEACHLER
//OUTLOOK FOR ORD/MDW FOR 12Z SUNDAY-12Z FRIDAY...UPDATED 00Z...
SUNDAY...VFR.
SUNDAY NIGHT THROUGH WEDNESDAY...PERIODS OF TSRA.
THURSDAY...CHC SHRA.
ALLSOPP
&&
.MARINE...
221 AM CDT
MINIMAL CHANGES FROM PREVIOUS FORECAST. BROAD SFC RIDGE HAS BECOME
CENTERED ACROSS CENTRAL QUEBEC....HOWEVER THIS FEATURE CONTINUES
TO INFLUENCE THE WESTERN GREAT LAKES WITH A LIGHT EAST FLOW TODAY
ACROSS THE LAKE. AS THE SFC RIDGE WILL DRIFT FURTHER AWAY FROM
LAKE MICHIGAN...WINDS WILL GRADUALLY TURN SOUTHEASTERLY. A STALLED
FRONTAL BOUNDARY STRETCHES FROM CENTRAL MINNESOTA EXTENDING
SOUTHEAST THROUGH WESTERN ILLINOIS INTO CENTRAL INDIANA. IT
APPEARS THE BROAD SFC RIDGE WILL KEEP THIS BOUNDARY JUST SOUTH OF
LAKE MICHIGAN...AND MOST LIKELY WEAKEN. A TROUGH OF LOW PRESSURE
OVER THE NORTHERN PLAINS WILL WEAKEN...AS A SECOND AREA OF LOW
PRESSURE DEVELOPS ALONG A SLOW MOVING COLD FRONT IN THE CENTRAL
PLAINS SUNDAY EVENING. PRIOR TO THE FRONTAL BOUNDARIES
ARRIVAL...WINDS SPEEDS WILL GENERALLY BE 10 TO 20 KT. HOWEVER...AN
OCCASIONAL GUSTS TO 25 KT MAY OCCUR THROUGHOUT THE DAY AS A WEAK
GRADIENT IS FORECAST TO DEVELOP OVER THE CENTRAL PORTION OF THE
LAKE.
AS THE CENTRAL PLAINS LOW PRESSURE DEVELOPS...IT WILL LIFT A WARM
FRONT NORTH ACROSS THE CENTRAL PORTIONS OF THE LAKE SUNDAY
NIGHT/EARLY MON. WINDS WILL TURN SOUTHERLY AND INCREASE BEHIND
THIS BOUNDARY. THIS LOW PRESSURE SYSTEM WILL SLOWLY PUSH EAST INTO
THE MID-MISSISSIPPI VALLEY TUE/WED...THEN DRIFT EAST INTO THE OHIO
VALLEY. WITH THE SLOW MOVING FRONTAL BOUNDARY EXPECTED TO BE OVER
THE CENTRAL PORTIONS OF THE LAKE...WINDS NORTH WILL BE NORTHERLY
AND SOUTHERLY TO THE SOUTH. FORECAST GUIDANCE INDICATES THAT A
TIGHTENING GRADIENT ACROSS THE NORTHERN PORTIONS OF THE LAKE IS
LIKELY...WHICH COULD RESULT IN WINDS BETWEEN 15-25 KT MON/TUE. THEN
THE BOUNDARY WILL EVENTUALLY PUSH BACK TO THE SOUTH OF THE LAKE
TOWARDS THE MIDDLE OF THE UPCOMING WEEK.
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 180930
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
430 AM CDT SAT MAY 18 2013
.DISCUSSION...
430 AM CDT
FOCUS OF FORECAST IS ON THE INCREASE IN CHANCES OF SHOWERS AND
THUNDERSTORMS BEGINNING LATE SUNDAY/SUNDAY NIGHT AND CONTINUING TO
GRADUALLY INCREASE THROUGH MODAY...PERSISTING THROUGH THURSDAY.
TIME FRAME OF GREATEST THREAT OF PRECIP WILL BE MONDAY NIGHT
THROUGH TUESDAY NIGHT.
OTHER MAIN FORECAST ITEM IS THE CONTINUED WARM UP TODAY AND SUNDAY
WITH WARMTH PERSISTING MONDAY BEFORE HIGH TEMPERATURES START
FALLING OFF TUESDAY...WITH HIGHS ONLY IN THE MID 60S TO LOWER 70S
ON THURSDAY AND FRIDAY.
OTHER CONCERNS ARE POTENTIAL FOR SIGNIFICANT AMOUNTS OF RAINFALL
FROM MONDAY NIGHT INTO WEDNESDAY AND SOME POTENTIAL FOR SEVERE
CONVECTION...IN THE WESTERN PORTION OF THE FORECAST AREA LATE
SUNDAY AND SUNDAY NIGHT...AND ACROSS THE AREA MONDAY AND MONDAY
NIGHT.
CHANCES OF ANY PRECIP IN THE AREA ARE LOW FOR TODAY AND TONIGHT
AS AN UPPER RIDGE BUILDING OVER THE MID CONTINENT SHIFTS EASTWARD
TO OVER THE LOCAL AREA LATE TODAY AND TONIGHT RESULTING IN RISING
HEIGHTS AND LARGE SCALE SUBSIDENCE WITH THE CONVECTION THAT
HAS BEEN OCCURRING DURING THE NIGHT AND EARLY THIS MORNING OVER THE
NORTHERN PLAINS AND UPPER MS VALLEY CONTINUES TO MOVE TO THE EAST-
NORTHEAST OVER THE TOP OF THE BUILDING RIDGE. BY SUNDAY NIGHT THE
UPPER RIDGE WILL HAVE REACHES THE CENTRAL GREAT LAKES AND THE OH
VALLEY REGIONS AS AN UPPER LOW SLOWLY MOVES EAST FROM THE CANADIAN
MARITIMES.
A VERY WARM AIR MASS WAS ACROSS THE HIGH PLAINS FRIDAY UNDER THE
UPPER RIDGE. THIS AIR MASS WILL SPREAD TO THE LOCAL AREA FOR
SUNDAY. DEPENDING ON CLOUD COVER...OF WHICH MUCH WOULD LIKELY BY
CONVECTIVE DEBRIS SPREADING EAST ACROSS THE MS RIVER FROM UPSTREAM
CONVECTION...TEMPERATURES MAY PEAK IN THE UPPER 80S IF THE CIRRUS
DEBRIS CLOUDS ARE NOT TOO THICK. EVEN WITH MORE CLOUDINESS MID 80S
LOOKS PRETTY LIKELY FOR SUNDAY AFTERNOON.
MEANWHILE...MULTIPLE STRONG UPPER WAVES DROPPING INTO AN UPPER
TROUGH EXTENDING FROM WEST OF THE B.C. COAST SOUTHEAST ACROSS THE
PACIFIC NORTHWEST TO THE DESERT SOUTHWEST ARE PROGGED TO CONGEAL
AND FORM AN UPPER LOW TO REACH THE CENTRAL HIGH PLAINS BY SUNDAY
EVENING. INCREASING SOUTH TO SOUTHWEST LOW AND MID LEVEL FLOW
AHEAD OF A SURFACE LOW ASSOCIATED WITH THE UPPER LOW WILL
TRANSPORT SIGNIFICANT MOISTURE FROM THE WESTERN GULF UP ACROSS THE
SOUTHERN PLAINS...MID MO VALLEY AND UPPER MS VALLEY DURING SUNDAY
WITH THE MOISTURE AXIS SHIFTING EAST OVER THE MID MS VALLEY AND
THE UPPER MIDWEST TO THE OVER IL AND THE WESTERN GREAT LAKES BY
MONDAY.
WHILE THE UPPER LOW WILL STILL BE OUT OVER THE CENTRAL PLAINS
LATE SUNDAY AND NOT REACH THE MID MO VALLEY TIL LATER MONDAY
POTENTIAL INSTABILITY WILL BE INCREASING OVER THE LOCAL AREA AND
ANY SMALLER SCALE DISTURBANCES TRAVELING NORTHEASTWARD ACROSS
THE MID MS VALLEY MAY TRIGGER THUNDERSTORMS. GIVEN AMOUNT OF
AVAILABLE CAPE AND LOW LEVEL WIND SHEAR THERE IS THE POTENTIAL
FOR SOME OF THE THUNDERSTORMS THAT MAY DEVELOP TO BE STRONG TO
SEVERE.
WITH THE CORE OF THE WARM AIR DOME SHIFTING TO THE EAST MONDAY
AND MORE CLOUDS AND POSSIBLY MOIST CONVECTION OVER/NEAR THE AREA
TEMPERATURES WILL LIKELY BE HELD DOWN A FEW TO A COUPLE DEGREES
FROM THOSE REACHED SUNDAY.
THE SLOW PROGRESS OF THE UPPER LOW DUE TO BEING IN AN OMEGA BLOCK
TYPE UPPER PATTERN RESULTS IN IT NOT REACHING NEAR/OVER THE LOCAL
AREA UNTIL LATER WEDNESDAY AND WEDNESDAY NIGHT. THIS SLOW MOVEMENT
KEEPS THE THREAT OF THUNDERSTORMS GOING...WITH THE HIGHEST POPS
DURING MONDAY NIGHT THROUGH TUESDAY NIGHT AS THIS IS WHEN THE
HIGHEST THETA E AIR IS IN PLACE WITH SIGNIFICANT CAPE VALUES.
WHILE PRECIPITABLE WATER VALUES ARE NOT EXTREME...GENERALLY AROUND
1.5 INCHES FROM SUNDAY NIGHT INTO WEDNESDAY...THE POTENTIAL FOR
MULTIPLE RAINFALL EVENTS DURING THE PERIOD OF TIME IT TAKES THE
UPPER LOW TO REACH AND EVENTUALLY PASS OVER THE LOCAL AREA DOES
PRESENT THE POSSIBILITY OF SOME 2 TO 3 INCH RAINFALL TOTALS.
SPECIFICS ON WHICH PART OR PARTS OF THE FA WOULD BE MOST PRONE TO
RECEIVING SIGNIFICANT RAINFALL AMOUNTS IS NOT CLEAR AT THIS TIME
ALL THAT CAN BE SAID THAT THERE IS THE POTENTIAL.
CHANCES FOR SHOWERS AND SOME THUNDERSTORMS PERSIST WEDNESDAY
THROUGH THURSDAY AS THE UPPER LOW IS TO STILL BE SLUGGISHLY
MOVING EAST TO THE WESTERN GREAT LAKES AND MIDWEST. COOLER AIR
WILL BE DRAWN DOWN ACROSS THE REGION AS THE UPPER FLOW VEERS TO
OUT OF THE NORTHWEST THURSDAY. THIS RESULTS IN HIGHS OF ONLY MID
60S TO LOWER 70S FOR THURSDAY AND FRIDAY. BY THURSDAY NIGHT THE
THREAT OF ANY ADDITIONAL SHOWERS SHOULD HAVE ENDED WITH THE UPPER
LOW OPENING UP AND THE LOWER LEVEL FLOW BECOMING SOMEWHAT
ANTICYCLONIC AS A RIDGE OF HIGH PRESSURE EXTENDING FROM ONTARIO
DRIFTS EAST ACROSS THE UPPER MIDWEST AND MID MO VALLEY.
TRS
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 06Z...
* POSSIBLE FOG/HAZE DEVELOPING...LINGER THRU DAYBREAK. LOW CLOUDS
MAY ACCOMPANY FOG/HAZE.
* VRB WINDS ARND 5KT OR LESS OVERNIGHT. WINDS TURN BRIEFLY
SOUTHEAST...THEN BACK TO EAST/NORTHEAST WITH A WEAK LAKE BREEZE.
BEACHLER
//DISCUSSION...UPDATED 06Z...
IR IMAGERY EARLY THIS MORNING CONTINUES TO SHOW THINNING CLOUDS
OVER NORTHERN IL/NORTHWEST IN AIRFIELDS. A STALLED FRONTAL
BOUNDARY WAS LOCATED ALONG A FAR NORTHWEST IL TO JUST SOUTH OF JOT
TO FORT WAYNE LINE. ABUNDANT MOISTURE WAS NOTED ALONG AND SOUTH OF
THE BOUNDARY...WHICH IS THE AREA OF GREATEST CONCERN OVERNIGHT FOR
FOG TO DEVELOP. ALREADY A FEW POINTS HAVE OBSERVED VSBYS DROP TO
ARND 2SM. FEEL THAT OVER TIME THIS WILL SPREAD IN COVERAGE...AND
POSSIBLY A FEW POINTS COULD DIP TO ARND 1SM OR LESS BRIEFLY. AT
THIS TIME FEEL THE GREATEST VSBY REDUCTION WILL OCCUR JUST
WEST/SOUTH OF RFD TO JOT. FOR THE TAF SITES IT APPEARS VSBYS MAY
ONLY REDUCE TO ARND 3SM AT RFD/DPA...WHILE ORD/MDW SHUD REMAIN AT
5SM OR BETTER. IN ADDITION TO THE FOG POTENTIAL...LOW STRATUS DECK
MAY TRY TO DEVELOP ARND 08-10Z. GUIDANCE HAS CONTINUED TO SUGGEST
THAT A STRATUS DECK MAY TRY TO DEVELOP WITH CLOUDS ARND 800FT AGL.
FEEL AT THIS TIME THIS IS MORE OF A FEATURE OF ADDTL
MOISTURE...AND HAVE ONLY OPTED TO INCLUDE A MENTION OF FEW008 IN
THE TAF SITES. OTHERWISE WILL RIDE WITH A SCT DECK ARND 2KFT AGL.
WINDS WILL REMAIN VRB THRU THE OVERNIGHT...THEN BRIEFLY TURN
SOUTHEAST FOR ORD/MDW/GYY. WITH SOME HEATING...BY LATE
MORNING/EARLY AFTN...WINDS WILL THEN TURN EAST/NORTHEAST FOR
ORD/MDW AND NORTH/NORTHEAST FOR GYY. IN ADDITION A FEW GUSTS MAY
OCCUR FOR THE TAF SITES CLOSEST TO LAKE MICHIGAN. ELSEWHERE WINDS
WILL REMAIN ARND 10KT FROM THE SOUTHEAST.
AT THIS TIME IT DOES NOT APPEAR ANY ORGANIZED PRECIP/THUNDERSTORMS
ARE EXPECTED...SO HAVE CONTINUED WITH A DRY TAF. OTHERWISE SAT NGT
THRU EARLY SUN...LOOKS FAVORABLE FOR PATCHY FOG TO DEVELOP ONCE
AGAIN. ALTHOUGH THIS SETUP LOOKS MORE FAVORABLE FOR ORD/MDW FOR
SUN MORNING.
BEACHLER
//ORD AND MDW CONFIDENCE...UPDATED 06Z...
* HIGH CONFIDENCE IN WIND DIR/SPEED FORECAST.
* HIGH CONFIDENCE ORD/MDW WILL MAINTAIN VFR CONDS OVERNIGHT.
* MEDIUM CONFIDENCE IN FOG/HAZE DEVELOPING.
* LOW/MEDIUM CONFIDENCE FOG REMAINS WEST/SOUTHWEST OR ORD/MDW.
* MEDIUM CONFIDENCE IN CLOUDS FORECAST SAT AFTN/EVE.
BEACHLER
//OUTLOOK FOR ORD/MDW FOR 12Z SUNDAY-12Z FRIDAY...UPDATED 00Z...
SUNDAY...VFR.
SUNDAY NIGHT THROUGH WEDNESDAY...PERIODS OF TSRA.
THURSDAY...CHC SHRA.
ALLSOPP
&&
.MARINE...
221 AM CDT
MINIMAL CHANGES FROM PREVIOUS FORECAST. BROAD SFC RIDGE HAS BECOME
CENTERED ACROSS CENTRAL QUEBEC....HOWEVER THIS FEATURE CONTINUES
TO INFLUENCE THE WESTERN GREAT LAKES WITH A LIGHT EAST FLOW TODAY
ACROSS THE LAKE. AS THE SFC RIDGE WILL DRIFT FURTHER AWAY FROM
LAKE MICHIGAN...WINDS WILL GRADUALLY TURN SOUTHEASTERLY. A STALLED
FRONTAL BOUNDARY STRETCHES FROM CENTRAL MINNESOTA EXTENDING
SOUTHEAST THROUGH WESTERN ILLINOIS INTO CENTRAL INDIANA. IT
APPEARS THE BROAD SFC RIDGE WILL KEEP THIS BOUNDARY JUST SOUTH OF
LAKE MICHIGAN...AND MOST LIKELY WEAKEN. A TROUGH OF LOW PRESSURE
OVER THE NORTHERN PLAINS WILL WEAKEN...AS A SECOND AREA OF LOW
PRESSURE DEVELOPS ALONG A SLOW MOVING COLD FRONT IN THE CENTRAL
PLAINS SUNDAY EVENING. PRIOR TO THE FRONTAL BOUNDARIES
ARRIVAL...WINDS SPEEDS WILL GENERALLY BE 10 TO 20 KT. HOWEVER...AN
OCCASIONAL GUSTS TO 25 KT MAY OCCUR THROUGHOUT THE DAY AS A WEAK
GRADIENT IS FORECAST TO DEVELOP OVER THE CENTRAL PORTION OF THE
LAKE.
AS THE CENTRAL PLAINS LOW PRESSURE DEVELOPS...IT WILL LIFT A WARM
FRONT NORTH ACROSS THE CENTRAL PORTIONS OF THE LAKE SUNDAY
NIGHT/EARLY MON. WINDS WILL TURN SOUTHERLY AND INCREASE BEHIND
THIS BOUNDARY. THIS LOW PRESSURE SYSTEM WILL SLOWLY PUSH EAST INTO
THE MID-MISSISSIPPI VALLEY TUE/WED...THEN DRIFT EAST INTO THE OHIO
VALLEY. WITH THE SLOW MOVING FRONTAL BOUNDARY EXPECTED TO BE OVER
THE CENTRAL PORTIONS OF THE LAKE...WINDS NORTH WILL BE NORTHERLY
AND SOUTHERLY TO THE SOUTH. FORECAST GUIDANCE INDICATES THAT A
TIGHTENING GRADIENT ACROSS THE NORTHERN PORTIONS OF THE LAKE IS
LIKELY...WHICH COULD RESULT IN WINDS BETWEEN 15-25 KT MON/TUE. THEN
THE BOUNDARY WILL EVENTUALLY PUSH BACK TO THE SOUTH OF THE LAKE
TOWARDS THE MIDDLE OF THE UPCOMING WEEK.
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 180735
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
235 AM CDT SAT MAY 18 2013
.DISCUSSION...
303 PM...MULTIPLE FORECAST CONCERNS THROUGH THE MIDDLE OF NEXT
WEEK INCLUDING CONVECTIVE CHANCES THIS EVENING AND THEN FROM
SUNDAY AFTERNOON THROUGH NEXT WEDNESDAY...IN ADDITION TO
TEMPERATURES...WINDS AND POTENTIAL LAKE BREEZES...AND POTENTIAL
FOR PERIODS OF HEAVY RAIN NEXT WEEK.
IN THE SHORT TERM...CONVECTION CONTINUES TO DEVELOP AND SPREAD
NORTH ACROSS THE SOUTHERN HALF OR SO OF THE CWA WHILE AN OUTFLOW/
WIND SHIFT FROM CONVECTION EARLIER THIS MORNING ACROSS WI
CONTINUES TO MOVE SOUTH OF THE I-80 CORRIDOR AND IS NOW
INTERSECTING WITH A CONVECTIVE OUTFLOW LIFTING NORTH. THIS
BOUNDARY WILL LIKELY AID ADDITIONAL DEVELOPMENT THROUGH THE
AFTERNOON. AS NOTED IN THE MESOSCALE DISCUSSION ABOVE...MAIN
CONCERN WITH ONGOING CONVECTION IS LOCALLY HEAVY RAIN WITH SLOW
STORM MOVEMENT. SHORT TERM GUIDANCE IN GOOD AGREEMENT WITH THIS
ACTIVITY QUICKLY DISSIPATING AFTER SUNSET WITH LINGERING SHOWERS
POSSIBLE INTO THE EARLY OVERNIGHT HOURS.
LITTLE TO FOCUS ADDITIONAL PRECIP DEVELOPMENT FROM LATE TONIGHT
THROUGH MIDDAY SUNDAY AND HAVE MAINTAINED A GENERALLY DRY
FORECAST. WITH LOW LEVEL MOISTURE SLOWLY INCREASING OVER THE
WEEKEND...POSSIBLE FOR ISOLATED SHOWERS BUT EXPECTED COVERAGE TOO
LOW FOR ANY MENTION AT THIS TIME. CONVECTIVE CHANCES THEN BEGIN TO
INCREASE FROM SUNDAY AFTERNOON/EVENING INTO SUNDAY NIGHT.
CONSENSUS SEEMS TO BE FOCUSING ON A MCS DEVELOPING OVER THE PLAINS
SUNDAY AFTERNOON/EVENING AND MOVING INTO THE WESTERN LAKES SUNDAY
NIGHT. STILL TIME TO EVALUATE THIS BUT HAVE MAINTAINED SLIGHT
CHANCE POPS SUNDAY AFTERNOON AND THEN INCREASED POPS THROUGH
SUNDAY EVENING AND OVERNIGHT INTO MONDAY MORNING. AND SHOULD THIS
PAN OUT THEN MONDAY AFTERNOON INTO MONDAY AFTERNOON COULD
POTENTIALLY BE FAIRLY DRY.
AS FOR TEMPERATURES...WITH MUCH OF SUNDAY NOW LOOKING DRY AS WELL
AS MONDAY AFTERNOON POTENTIALLY BEING DRY OR DRY ENOUGH TO ALLOW
GOOD HEATING...HAVE BUMPED TEMPS UP MORE IN LINE WITH THE GEM...
WHICH WAS ONE OF THE BETTER PERFORMING MODELS FOR HIGH TEMPS WITH
THE WARM UP EARLIER THIS WEEK WHICH PUSHES HIGHS FOR BOTH DAYS
INTO THE MID/UPPER 80S AND WOULDN/T BE SURPRISED TO SEE SOME
LOCATIONS TAG 90. WINDS STILL SOUTHEASTERLY SUNDAY WILL LIKELY
KEEP THE IL SHORE COOLER BUT BY MONDAY WINDS INCREASE AND SHOULD
TURN ENOUGH SOUTHWESTERLY TO PREVENT ANY COOLING ALONG THE LAKE.
FORECAST SOUNDINGS SUGGEST WINDS COULD BE GUSTING WELL INTO THE
25-30 MPH RANGE.
DEWPOINTS WILL ALSO BE INCREASING THROUGH THE WEEKEND AND COULD
POTENTIALLY REACH THE UPPER 60S BY SUNDAY AFTERNOON AND ONLY DROP
MODESTLY SUNDAY NIGHT WITH LOWS WELL IN THE 60S. HOWEVER...SHOULD
STRONGER WINDS MATERIALIZE ON MONDAY...LOW LEVEL MIXING WOULD
LIKELY ALLOW SOME AMOUNT OF DRIER AIR TO MIX TO THE SURFACE.
BY MONDAY NIGHT AND BEYOND...TIMING VARIOUS WAVES BECOMES MORE
DIFFICULT AND WHILE THERE WILL BE DRY PERIODS...AT TIMES... HAVE
OPTED TO KEEP LIKELY POPS FOR SHOWERS/TSRA AND THE 12Z ECMWF SHOWS
SEVERAL WAVES TO AFFECT THE REGION DURING THE MIDDLE OF NEXT WEEK.
CLOUD COVER/PRECIP/POTENTIAL FLOW OFF THE LAKE ALL SIGNIFICANTLY
INCREASE TEMPERATURE FORECAST DIFFICULTY AND HAVE GENERALLY GONE
MIDDLE OF THE ROAD ON TEMPS. WITH DEWPOINTS EXPECTED TO STAY IN
THE 60S THROUGH WEDNESDAY MORNING AND PRECIPITABLE WATER VALUES IN
THE 1 TO 1.5 INCH RANGE...WHICH MAY END UP TOO LOW...ROUNDS OF
HEAVY RAIN WILL CERTAINLY BE POSSIBLE. CMS
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 06Z...
* POSSIBLE FOG/HAZE DEVELOPING...LINGER THRU DAYBREAK. LOW CLOUDS
MAY ACCOMPANY FOG/HAZE.
* VRB WINDS ARND 5KT OR LESS OVERNIGHT. WINDS TURN BRIEFLY
SOUTHEAST...THEN BACK TO EAST/NORTHEAST WITH A WEAK LAKE BREEZE.
BEACHLER
//DISCUSSION...UPDATED 06Z...
IR IMAGERY EARLY THIS MORNING CONTINUES TO SHOW THINNING CLOUDS
OVER NORTHERN IL/NORTHWEST IN AIRFIELDS. A STALLED FRONTAL
BOUNDARY WAS LOCATED ALONG A FAR NORTHWEST IL TO JUST SOUTH OF JOT
TO FORT WAYNE LINE. ABUNDANT MOISTURE WAS NOTED ALONG AND SOUTH OF
THE BOUNDARY...WHICH IS THE AREA OF GREATEST CONCERN OVERNIGHT FOR
FOG TO DEVELOP. ALREADY A FEW POINTS HAVE OBSERVED VSBYS DROP TO
ARND 2SM. FEEL THAT OVER TIME THIS WILL SPREAD IN COVERAGE...AND
POSSIBLY A FEW POINTS COULD DIP TO ARND 1SM OR LESS BRIEFLY. AT
THIS TIME FEEL THE GREATEST VSBY REDUCTION WILL OCCUR JUST
WEST/SOUTH OF RFD TO JOT. FOR THE TAF SITES IT APPEARS VSBYS MAY
ONLY REDUCE TO ARND 3SM AT RFD/DPA...WHILE ORD/MDW SHUD REMAIN AT
5SM OR BETTER. IN ADDITION TO THE FOG POTENTIAL...LOW STRATUS DECK
MAY TRY TO DEVELOP ARND 08-10Z. GUIDANCE HAS CONTINUED TO SUGGEST
THAT A STRATUS DECK MAY TRY TO DEVELOP WITH CLOUDS ARND 800FT AGL.
FEEL AT THIS TIME THIS IS MORE OF A FEATURE OF ADDTL
MOISTURE...AND HAVE ONLY OPTED TO INCLUDE A MENTION OF FEW008 IN
THE TAF SITES. OTHERWISE WILL RIDE WITH A SCT DECK ARND 2KFT AGL.
WINDS WILL REMAIN VRB THRU THE OVERNIGHT...THEN BRIEFLY TURN
SOUTHEAST FOR ORD/MDW/GYY. WITH SOME HEATING...BY LATE
MORNING/EARLY AFTN...WINDS WILL THEN TURN EAST/NORTHEAST FOR
ORD/MDW AND NORTH/NORTHEAST FOR GYY. IN ADDITION A FEW GUSTS MAY
OCCUR FOR THE TAF SITES CLOSEST TO LAKE MICHIGAN. ELSEWHERE WINDS
WILL REMAIN ARND 10KT FROM THE SOUTHEAST.
AT THIS TIME IT DOES NOT APPEAR ANY ORGANIZED PRECIP/THUNDERSTORMS
ARE EXPECTED...SO HAVE CONTINUED WITH A DRY TAF. OTHERWISE SAT NGT
THRU EARLY SUN...LOOKS FAVORABLE FOR PATCHY FOG TO DEVELOP ONCE
AGAIN. ALTHOUGH THIS SETUP LOOKS MORE FAVORABLE FOR ORD/MDW FOR
SUN MORNING.
BEACHLER
//ORD AND MDW CONFIDENCE...UPDATED 06Z...
* HIGH CONFIDENCE IN WIND DIR/SPEED FORECAST.
* HIGH CONFIDENCE ORD/MDW WILL MAINTAIN VFR CONDS OVERNIGHT.
* MEDIUM CONFIDENCE IN FOG/HAZE DEVELOPING.
* LOW/MEDIUM CONFIDENCE FOG REMAINS WEST/SOUTHWEST OR ORD/MDW.
* MEDIUM CONFIDENCE IN CLOUDS FORECAST SAT AFTN/EVE.
BEACHLER
//OUTLOOK FOR ORD/MDW FOR 12Z SUNDAY-12Z FRIDAY...UPDATED 00Z...
SUNDAY...VFR.
SUNDAY NIGHT THROUGH WEDNESDAY...PERIODS OF TSRA.
THURSDAY...CHC SHRA.
ALLSOPP
&&
.MARINE...
221 AM CDT
MINIMAL CHANGES FROM PREVIOUS FORECAST. BROAD SFC RIDGE HAS BECOME
CENTERED ACROSS CENTRAL QUEBEC....HOWEVER THIS FEATURE CONTINUES
TO INFLUENCE THE WESTERN GREAT LAKES WITH A LIGHT EAST FLOW TODAY
ACROSS THE LAKE. AS THE SFC RIDGE WILL DRIFT FURTHER AWAY FROM
LAKE MICHIGAN...WINDS WILL GRADUALLY TURN SOUTHEASTERLY. A STALLED
FRONTAL BOUNDARY STRETCHES FROM CENTRAL MINNESOTA EXTENDING
SOUTHEAST THROUGH WESTERN ILLINOIS INTO CENTRAL INDIANA. IT
APPEARS THE BROAD SFC RIDGE WILL KEEP THIS BOUNDARY JUST SOUTH OF
LAKE MICHIGAN...AND MOST LIKELY WEAKEN. A TROUGH OF LOW PRESSURE
OVER THE NORTHERN PLAINS WILL WEAKEN...AS A SECOND AREA OF LOW
PRESSURE DEVELOPS ALONG A SLOW MOVING COLD FRONT IN THE CENTRAL
PLAINS SUNDAY EVENING. PRIOR TO THE FRONTAL BOUNDARIES
ARRIVAL...WINDS SPEEDS WILL GENERALLY BE 10 TO 20 KT. HOWEVER...AN
OCCASIONAL GUSTS TO 25 KT MAY OCCUR THROUGHOUT THE DAY AS A WEAK
GRADIENT IS FORECAST TO DEVELOP OVER THE CENTRAL PORTION OF THE
LAKE.
AS THE CENTRAL PLAINS LOW PRESSURE DEVELOPS...IT WILL LIFT A WARM
FRONT NORTH ACROSS THE CENTRAL PORTIONS OF THE LAKE SUNDAY
NIGHT/EARLY MON. WINDS WILL TURN SOUTHERLY AND INCREASE BEHIND
THIS BOUNDARY. THIS LOW PRESSURE SYSTEM WILL SLOWLY PUSH EAST INTO
THE MID-MISSISSIPPI VALLEY TUE/WED...THEN DRIFT EAST INTO THE OHIO
VALLEY. WITH THE SLOW MOVING FRONTAL BOUNDARY EXPECTED TO BE OVER
THE CENTRAL PORTIONS OF THE LAKE...WINDS NORTH WILL BE NORTHERLY
AND SOUTHERLY TO THE SOUTH. FORECAST GUIDANCE INDICATES THAT A
TIGHTENING GRADIENT ACROSS THE NORTHERN PORTIONS OF THE LAKE IS
LIKELY...WHICH COULD RESULT IN WINDS BETWEEN 15-25 KT MON/TUE. THEN
THE BOUNDARY WILL EVENTUALLY PUSH BACK TO THE SOUTH OF THE LAKE
TOWARDS THE MIDDLE OF THE UPCOMING WEEK.
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 180559
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1259 AM CDT SAT MAY 18 2013
.DISCUSSION...
303 PM...MULTIPLE FORECAST CONCERNS THROUGH THE MIDDLE OF NEXT
WEEK INCLUDING CONVECTIVE CHANCES THIS EVENING AND THEN FROM
SUNDAY AFTERNOON THROUGH NEXT WEDNESDAY...IN ADDITION TO
TEMPERATURES...WINDS AND POTENTIAL LAKE BREEZES...AND POTENTIAL
FOR PERIODS OF HEAVY RAIN NEXT WEEK.
IN THE SHORT TERM...CONVECTION CONTINUES TO DEVELOP AND SPREAD
NORTH ACROSS THE SOUTHERN HALF OR SO OF THE CWA WHILE AN OUTFLOW/
WIND SHIFT FROM CONVECTION EARLIER THIS MORNING ACROSS WI
CONTINUES TO MOVE SOUTH OF THE I-80 CORRIDOR AND IS NOW
INTERSECTING WITH A CONVECTIVE OUTFLOW LIFTING NORTH. THIS
BOUNDARY WILL LIKELY AID ADDITIONAL DEVELOPMENT THROUGH THE
AFTERNOON. AS NOTED IN THE MESOSCALE DISCUSSION ABOVE...MAIN
CONCERN WITH ONGOING CONVECTION IS LOCALLY HEAVY RAIN WITH SLOW
STORM MOVEMENT. SHORT TERM GUIDANCE IN GOOD AGREEMENT WITH THIS
ACTIVITY QUICKLY DISSIPATING AFTER SUNSET WITH LINGERING SHOWERS
POSSIBLE INTO THE EARLY OVERNIGHT HOURS.
LITTLE TO FOCUS ADDITIONAL PRECIP DEVELOPMENT FROM LATE TONIGHT
THROUGH MIDDAY SUNDAY AND HAVE MAINTAINED A GENERALLY DRY
FORECAST. WITH LOW LEVEL MOISTURE SLOWLY INCREASING OVER THE
WEEKEND...POSSIBLE FOR ISOLATED SHOWERS BUT EXPECTED COVERAGE TOO
LOW FOR ANY MENTION AT THIS TIME. CONVECTIVE CHANCES THEN BEGIN TO
INCREASE FROM SUNDAY AFTERNOON/EVENING INTO SUNDAY NIGHT.
CONSENSUS SEEMS TO BE FOCUSING ON A MCS DEVELOPING OVER THE PLAINS
SUNDAY AFTERNOON/EVENING AND MOVING INTO THE WESTERN LAKES SUNDAY
NIGHT. STILL TIME TO EVALUATE THIS BUT HAVE MAINTAINED SLIGHT
CHANCE POPS SUNDAY AFTERNOON AND THEN INCREASED POPS THROUGH
SUNDAY EVENING AND OVERNIGHT INTO MONDAY MORNING. AND SHOULD THIS
PAN OUT THEN MONDAY AFTERNOON INTO MONDAY AFTERNOON COULD
POTENTIALLY BE FAIRLY DRY.
AS FOR TEMPERATURES...WITH MUCH OF SUNDAY NOW LOOKING DRY AS WELL
AS MONDAY AFTERNOON POTENTIALLY BEING DRY OR DRY ENOUGH TO ALLOW
GOOD HEATING...HAVE BUMPED TEMPS UP MORE IN LINE WITH THE GEM...
WHICH WAS ONE OF THE BETTER PERFORMING MODELS FOR HIGH TEMPS WITH
THE WARM UP EARLIER THIS WEEK WHICH PUSHES HIGHS FOR BOTH DAYS
INTO THE MID/UPPER 80S AND WOULDN/T BE SURPRISED TO SEE SOME
LOCATIONS TAG 90. WINDS STILL SOUTHEASTERLY SUNDAY WILL LIKELY
KEEP THE IL SHORE COOLER BUT BY MONDAY WINDS INCREASE AND SHOULD
TURN ENOUGH SOUTHWESTERLY TO PREVENT ANY COOLING ALONG THE LAKE.
FORECAST SOUNDINGS SUGGEST WINDS COULD BE GUSTING WELL INTO THE
25-30 MPH RANGE.
DEWPOINTS WILL ALSO BE INCREASING THROUGH THE WEEKEND AND COULD
POTENTIALLY REACH THE UPPER 60S BY SUNDAY AFTERNOON AND ONLY DROP
MODESTLY SUNDAY NIGHT WITH LOWS WELL IN THE 60S. HOWEVER...SHOULD
STRONGER WINDS MATERIALIZE ON MONDAY...LOW LEVEL MIXING WOULD
LIKELY ALLOW SOME AMOUNT OF DRIER AIR TO MIX TO THE SURFACE.
BY MONDAY NIGHT AND BEYOND...TIMING VARIOUS WAVES BECOMES MORE
DIFFICULT AND WHILE THERE WILL BE DRY PERIODS...AT TIMES... HAVE
OPTED TO KEEP LIKELY POPS FOR SHOWERS/TSRA AND THE 12Z ECMWF SHOWS
SEVERAL WAVES TO AFFECT THE REGION DURING THE MIDDLE OF NEXT WEEK.
CLOUD COVER/PRECIP/POTENTIAL FLOW OFF THE LAKE ALL SIGNIFICANTLY
INCREASE TEMPERATURE FORECAST DIFFICULTY AND HAVE GENERALLY GONE
MIDDLE OF THE ROAD ON TEMPS. WITH DEWPOINTS EXPECTED TO STAY IN
THE 60S THROUGH WEDNESDAY MORNING AND PRECIPITABLE WATER VALUES IN
THE 1 TO 1.5 INCH RANGE...WHICH MAY END UP TOO LOW...ROUNDS OF
HEAVY RAIN WILL CERTAINLY BE POSSIBLE. CMS
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 06Z...
* POSSIBLE FOG/HAZE DEVELOPING...LINGER THRU DAYBREAK. LOW CLOUDS
MAY ACCOMPANY FOG/HAZE.
* VRB WINDS ARND 5KT OR LESS OVERNIGHT. WINDS TURN BRIEFLY
SOUTHEAST...THEN BACK TO EAST/NORTHEAST WITH A WEAK LAKE BREEZE.
BEACHLER
//DISCUSSION...UPDATED 06Z...
IR IMAGERY EARLY THIS MORNING CONTINUES TO SHOW THINNING CLOUDS
OVER NORTHERN IL/NORTHWEST IN AIRFIELDS. A STALLED FRONTAL
BOUNDARY WAS LOCATED ALONG A FAR NORTHWEST IL TO JUST SOUTH OF JOT
TO FORT WAYNE LINE. ABUNDANT MOISTURE WAS NOTED ALONG AND SOUTH OF
THE BOUNDARY...WHICH IS THE AREA OF GREATEST CONCERN OVERNIGHT FOR
FOG TO DEVELOP. ALREADY A FEW POINTS HAVE OBSERVED VSBYS DROP TO
ARND 2SM. FEEL THAT OVER TIME THIS WILL SPREAD IN COVERAGE...AND
POSSIBLY A FEW POINTS COULD DIP TO ARND 1SM OR LESS BRIEFLY. AT
THIS TIME FEEL THE GREATEST VSBY REDUCTION WILL OCCUR JUST
WEST/SOUTH OF RFD TO JOT. FOR THE TAF SITES IT APPEARS VSBYS MAY
ONLY REDUCE TO ARND 3SM AT RFD/DPA...WHILE ORD/MDW SHUD REMAIN AT
5SM OR BETTER. IN ADDITION TO THE FOG POTENTIAL...LOW STRATUS DECK
MAY TRY TO DEVELOP ARND 08-10Z. GUIDANCE HAS CONTINUED TO SUGGEST
THAT A STRATUS DECK MAY TRY TO DEVELOP WITH CLOUDS ARND 800FT AGL.
FEEL AT THIS TIME THIS IS MORE OF A FEATURE OF ADDTL
MOISTURE...AND HAVE ONLY OPTED TO INCLUDE A MENTION OF FEW008 IN
THE TAF SITES. OTHERWISE WILL RIDE WITH A SCT DECK ARND 2KFT AGL.
WINDS WILL REMAIN VRB THRU THE OVERNIGHT...THEN BRIEFLY TURN
SOUTHEAST FOR ORD/MDW/GYY. WITH SOME HEATING...BY LATE
MORNING/EARLY AFTN...WINDS WILL THEN TURN EAST/NORTHEAST FOR
ORD/MDW AND NORTH/NORTHEAST FOR GYY. IN ADDITION A FEW GUSTS MAY
OCCUR FOR THE TAF SITES CLOSEST TO LAKE MICHIGAN. ELSEWHERE WINDS
WILL REMAIN ARND 10KT FROM THE SOUTHEAST.
AT THIS TIME IT DOES NOT APPEAR ANY ORGANIZED PRECIP/THUNDERSTORMS
ARE EXPECTED...SO HAVE CONTINUED WITH A DRY TAF. OTHERWISE SAT NGT
THRU EARLY SUN...LOOKS FAVORABLE FOR PATCHY FOG TO DEVELOP ONCE
AGAIN. ALTHOUGH THIS SETUP LOOKS MORE FAVORABLE FOR ORD/MDW FOR
SUN MORNING.
BEACHLER
//ORD AND MDW CONFIDENCE...UPDATED 06Z...
* HIGH CONFIDENCE IN WIND DIR/SPEED FORECAST.
* HIGH CONFIDENCE ORD/MDW WILL MAINTAIN VFR CONDS OVERNIGHT.
* MEDIUM CONFIDENCE IN FOG/HAZE DEVELOPING.
* LOW/MEDIUM CONFIDENCE FOG REMAINS WEST/SOUTHWEST OR ORD/MDW.
* MEDIUM CONFIDENCE IN CLOUDS FORECAST SAT AFTN/EVE.
BEACHLER
//OUTLOOK FOR ORD/MDW FOR 12Z SUNDAY-12Z FRIDAY...UPDATED 00Z...
SUNDAY...VFR.
SUNDAY NIGHT THROUGH WEDNESDAY...PERIODS OF TSRA.
THURSDAY...CHC SHRA.
ALLSOPP
&&
.MARINE...
206 PM CDT
A SURFACE RIDGE OF HIGH PRESSURE CONTINUES TO BUILD
EAST-SOUTHEASTWARD ACROSS ONTARIO AND THE CENTRAL AND EASTERN LAKES
THIS AFTERNOON. A HYBRID LAKE BREEZE/OUTFLOW BOUNDARY FROM
CONVECTION ACROSS WISCONSIN THIS MORNING HAS PUSHED ACROSS SOUTHERN
LAKE MICHIGAN EARLY THIS AFTERNOON. THIS LED TO A SUBSTANTIAL
INCREASE IN THE WINDS FOR A PERIOD OUT OF THE NORTH-NORTHEAST UP TO
25 TO 30 KT. THESE NORTHEAST WINDS UP TO AROUND 20 KT WILL CONTINUE
FOR THE NEXT FEW HOUR BEFORE SLOWLY EASING AND BECOMING MORE
EASTERLY TONIGHT.
A STORM SYSTEM IS EXPECTED TO TAKE SHAPE ACROSS THE HIGH PLAINS ON
SATURDAY BEFORE IT MOVES EAST-NORTHEASTWARD TOWARDS THE MID MISSOURI
VALLEY BY LATE SUNDAY. THIS SYSTEM LOOKS TO LIFT A WARM FRONT
NORTHWARD ACROSS AT LEAST THE SOUTHERN HALF TO TWO THIRDS OF THE
LAKE THROUGH MONDAY. BEHIND THIS FRONT WINDS LOOKS TO INCREASE OUT
OF THE SOUTH IN THE 15 TO 25 KT RANGE ON MONDAY. IT APPEARS THAT
THIS LOW WILL SLOWLY MOVE EASTWARD ACROSS THE MID MISSISSIPPI VALLEY
INTO MID WEEK AND THEN TO THE OHIO VALLEY LATER IN THE WEEK. THIS
SHOULD ALLOW THIS FRONT TO MOVE BACK SOUTH. DURING THIS TIME...THE
WINDS LOOK TO BECOME MORE NORTHERLY WITH TIME...ESPECIALLY BY MID TO
LATE WEEK AS THE SURFACE LOW PASSES TO THE SOUTH OF THE LAKE. THIS
COULD RESULT IN SOME STRONGER NORTHERLY WINDS BY LATE NEXT WEEK.
KJB
&&
.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 180316
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1016 PM CDT FRI MAY 17 2013
.DISCUSSION...
303 PM...MULTIPLE FORECAST CONCERNS THROUGH THE MIDDLE OF NEXT
WEEK INCLUDING CONVECTIVE CHANCES THIS EVENING AND THEN FROM
SUNDAY AFTERNOON THROUGH NEXT WEDNESDAY...IN ADDITION TO
TEMPERATURES...WINDS AND POTENTIAL LAKE BREEZES...AND POTENTIAL
FOR PERIODS OF HEAVY RAIN NEXT WEEK.
IN THE SHORT TERM...CONVECTION CONTINUES TO DEVELOP AND SPREAD
NORTH ACROSS THE SOUTHERN HALF OR SO OF THE CWA WHILE AN OUTFLOW/
WIND SHIFT FROM CONVECTION EARLIER THIS MORNING ACROSS WI
CONTINUES TO MOVE SOUTH OF THE I-80 CORRIDOR AND IS NOW
INTERSECTING WITH A CONVECTIVE OUTFLOW LIFTING NORTH. THIS
BOUNDARY WILL LIKELY AID ADDITIONAL DEVELOPMENT THROUGH THE
AFTERNOON. AS NOTED IN THE MESOSCALE DISCUSSION ABOVE...MAIN
CONCERN WITH ONGOING CONVECTION IS LOCALLY HEAVY RAIN WITH SLOW
STORM MOVEMENT. SHORT TERM GUIDANCE IN GOOD AGREEMENT WITH THIS
ACTIVITY QUICKLY DISSIPATING AFTER SUNSET WITH LINGERING SHOWERS
POSSIBLE INTO THE EARLY OVERNIGHT HOURS.
LITTLE TO FOCUS ADDITIONAL PRECIP DEVELOPMENT FROM LATE TONIGHT
THROUGH MIDDAY SUNDAY AND HAVE MAINTAINED A GENERALLY DRY
FORECAST. WITH LOW LEVEL MOISTURE SLOWLY INCREASING OVER THE
WEEKEND...POSSIBLE FOR ISOLATED SHOWERS BUT EXPECTED COVERAGE TOO
LOW FOR ANY MENTION AT THIS TIME. CONVECTIVE CHANCES THEN BEGIN TO
INCREASE FROM SUNDAY AFTERNOON/EVENING INTO SUNDAY NIGHT.
CONSENSUS SEEMS TO BE FOCUSING ON A MCS DEVELOPING OVER THE PLAINS
SUNDAY AFTERNOON/EVENING AND MOVING INTO THE WESTERN LAKES SUNDAY
NIGHT. STILL TIME TO EVALUATE THIS BUT HAVE MAINTAINED SLIGHT
CHANCE POPS SUNDAY AFTERNOON AND THEN INCREASED POPS THROUGH
SUNDAY EVENING AND OVERNIGHT INTO MONDAY MORNING. AND SHOULD THIS
PAN OUT THEN MONDAY AFTERNOON INTO MONDAY AFTERNOON COULD
POTENTIALLY BE FAIRLY DRY.
AS FOR TEMPERATURES...WITH MUCH OF SUNDAY NOW LOOKING DRY AS WELL
AS MONDAY AFTERNOON POTENTIALLY BEING DRY OR DRY ENOUGH TO ALLOW
GOOD HEATING...HAVE BUMPED TEMPS UP MORE IN LINE WITH THE GEM...
WHICH WAS ONE OF THE BETTER PERFORMING MODELS FOR HIGH TEMPS WITH
THE WARM UP EARLIER THIS WEEK WHICH PUSHES HIGHS FOR BOTH DAYS
INTO THE MID/UPPER 80S AND WOULDN/T BE SURPRISED TO SEE SOME
LOCATIONS TAG 90. WINDS STILL SOUTHEASTERLY SUNDAY WILL LIKELY
KEEP THE IL SHORE COOLER BUT BY MONDAY WINDS INCREASE AND SHOULD
TURN ENOUGH SOUTHWESTERLY TO PREVENT ANY COOLING ALONG THE LAKE.
FORECAST SOUNDINGS SUGGEST WINDS COULD BE GUSTING WELL INTO THE
25-30 MPH RANGE.
DEWPOINTS WILL ALSO BE INCREASING THROUGH THE WEEKEND AND COULD
POTENTIALLY REACH THE UPPER 60S BY SUNDAY AFTERNOON AND ONLY DROP
MODESTLY SUNDAY NIGHT WITH LOWS WELL IN THE 60S. HOWEVER...SHOULD
STRONGER WINDS MATERIALIZE ON MONDAY...LOW LEVEL MIXING WOULD
LIKELY ALLOW SOME AMOUNT OF DRIER AIR TO MIX TO THE SURFACE.
BY MONDAY NIGHT AND BEYOND...TIMING VARIOUS WAVES BECOMES MORE
DIFFICULT AND WHILE THERE WILL BE DRY PERIODS...AT TIMES... HAVE
OPTED TO KEEP LIKELY POPS FOR SHOWERS/TSRA AND THE 12Z ECMWF SHOWS
SEVERAL WAVES TO AFFECT THE REGION DURING THE MIDDLE OF NEXT WEEK.
CLOUD COVER/PRECIP/POTENTIAL FLOW OFF THE LAKE ALL SIGNIFICANTLY
INCREASE TEMPERATURE FORECAST DIFFICULTY AND HAVE GENERALLY GONE
MIDDLE OF THE ROAD ON TEMPS. WITH DEWPOINTS EXPECTED TO STAY IN
THE 60S THROUGH WEDNESDAY MORNING AND PRECIPITABLE WATER VALUES IN
THE 1 TO 1.5 INCH RANGE...WHICH MAY END UP TOO LOW...ROUNDS OF
HEAVY RAIN WILL CERTAINLY BE POSSIBLE. CMS
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 03Z...
* POTENTIAL FOR SOME FOG/HAZE LATE TONIGHT/EARLY SATURDAY MORNING.
ALLSOPP
//DISCUSSION...UPDATED 03Z...
ISOLATED SPRINKLES LINGERING OVER PARTS OF NORTHERN IL/IN BUT
NOTHING NEAR THE TERMINALS...SO HAVE LET VCSH DROP AS PLANNED. NE
WINDS SHOULD REMAIN VERY LIGHT OVERNIGHT AND INTO SATURDAY
MORNING. IF MID CLOUD DECK THINS OUT SOME OVERNIGHT...LIGHT
FOG/HAZE IS LIKELY TO DEVELOP FOR A COUPLE HOURS AROUND SUNRISE.
SOME PATCHY STRATUS IS POSSIBLE BUT CONFIDENCE LEVEL IS VERY LOW.
PREVAILING WINDS SATURDAY WILL BE ESE BUT LAKE ENHANCEMENT WILL
LIKELY TURN WINDS MORE ENE MID TO LATE AFTERNOON WITH A FEW GUSTS
TO AROUND 15 KT OR SO.
ALLSOPP
PREVIOUS DISCUSSION UPDATED 00Z...
SPRINKLES/LIGHT SHOWERS DISSIPATING EARLY THIS EVENING...OTHERWISE
JUST BROKEN MID AND HIGH CLOUD LAYERS FOR MOST OF THE NIGHT. SOME
MVFR VISIBILITIES MAY DEVELOP LATE TONIGHT AND EARLY SATURDAY AS
WINDS DIMINISH AND LOW LEVEL INVERSION STRENGTHENS. THE LIGHT
SHOWERS LATE THIS AFTERNOON AND EARLY THIS EVENING MAY HAVE ADDED
ENOUGH ADDITIONAL LOW LEVEL MOISTURE TO ALLOW SOME LIGHT FOG AND
HAZE DEVELOP. THIS SHOULD MIX OUT BY MID MORNING.
NEARLY STATIONARY WARM FRONT EXTENDS FROM NEAR MLI TO PNT TO
LAF THIS EVENING...WITH ENE WINDS PREVAILING NORTH OF THE BOUNDARY.
PRESSURE GRADIENT WILL BE WEAKENING AS UPPER LEVEL RIDGE BUILDS
OVER THE REGION AND SURFACE HIGH PRESSURE OVER THE GREAT LAKES
SHIFTS EAST. WINDS WILL GRADUALLY TURN SOUTHEAST OVER MUCH OF
NORTHERN IL AND IN SATURDAY EXCEPT NEAR THE LAKE WHERE ONSHORE
FLOW WILL KEEP WINDS MORE EAST. THEREFORE DONT EXPECT WINDS TO BE
QUITE AS STRONG OR GUSTY SATURDAY AS THEY WERE TODAY. WITH
BUILDING UPPER RIDGE SATURDAY AND OLD WARM FRONTAL BOUNDARY
WASHING OUT...THERE DOESN`T SEEM TO BE MUCH FOCUS FOR CONVECTION
SATURDAY. ALSO BUILDING RIDGE SHOULD KEEP ATMOSPHERE CAPPED.
THEREFORE NOT ANTICIPATING ANY SHOWERS OR THUNDERSTORMS IN THE AREA
SATURDAY.
ALLSOPP
//ORD AND MDW CONFIDENCE...UPDATED 03Z...
* MEDIUM TO HIGH CONFIDENCE IN WIND FORECAST.
* MEDIUM CONFIDENCE IN MVFR VSBY AROUND SUNRISE. LOW CONFIDENCE
IN MVFR CIG DEVELOPING.
ALLSOPP
//OUTLOOK FOR ORD/MDW FOR 12Z SUNDAY-12Z FRIDAY...UPDATED 00Z...
SUNDAY...VFR.
SUNDAY NIGHT THROUGH WEDNESDAY...PERIODS OF TSRA.
THURSDAY...CHC SHRA.
ALLSOPP
&&
.MARINE...
206 PM CDT
A SURFACE RIDGE OF HIGH PRESSURE CONTINUES TO BUILD
EAST-SOUTHEASTWARD ACROSS ONTARIO AND THE CENTRAL AND EASTERN LAKES
THIS AFTERNOON. A HYBRID LAKE BREEZE/OUTFLOW BOUNDARY FROM
CONVECTION ACROSS WISCONSIN THIS MORNING HAS PUSHED ACROSS SOUTHERN
LAKE MICHIGAN EARLY THIS AFTERNOON. THIS LED TO A SUBSTANTIAL
INCREASE IN THE WINDS FOR A PERIOD OUT OF THE NORTH-NORTHEAST UP TO
25 TO 30 KT. THESE NORTHEAST WINDS UP TO AROUND 20 KT WILL CONTINUE
FOR THE NEXT FEW HOUR BEFORE SLOWLY EASING AND BECOMING MORE
EASTERLY TONIGHT.
A STORM SYSTEM IS EXPECTED TO TAKE SHAPE ACROSS THE HIGH PLAINS ON
SATURDAY BEFORE IT MOVES EAST-NORTHEASTWARD TOWARDS THE MID MISSOURI
VALLEY BY LATE SUNDAY. THIS SYSTEM LOOKS TO LIFT A WARM FRONT
NORTHWARD ACROSS AT LEAST THE SOUTHERN HALF TO TWO THIRDS OF THE
LAKE THROUGH MONDAY. BEHIND THIS FRONT WINDS LOOKS TO INCREASE OUT
OF THE SOUTH IN THE 15 TO 25 KT RANGE ON MONDAY. IT APPEARS THAT
THIS LOW WILL SLOWLY MOVE EASTWARD ACROSS THE MID MISSISSIPPI VALLEY
INTO MID WEEK AND THEN TO THE OHIO VALLEY LATER IN THE WEEK. THIS
SHOULD ALLOW THIS FRONT TO MOVE BACK SOUTH. DURING THIS TIME...THE
WINDS LOOK TO BECOME MORE NORTHERLY WITH TIME...ESPECIALLY BY MID TO
LATE WEEK AS THE SURFACE LOW PASSES TO THE SOUTH OF THE LAKE. THIS
COULD RESULT IN SOME STRONGER NORTHERLY WINDS BY LATE NEXT WEEK.
KJB
&&
.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 172358
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
658 PM CDT FRI MAY 17 2013
.DISCUSSION...
303 PM...MULTIPLE FORECAST CONCERNS THROUGH THE MIDDLE OF NEXT
WEEK INCLUDING CONVECTIVE CHANCES THIS EVENING AND THEN FROM
SUNDAY AFTERNOON THROUGH NEXT WEDNESDAY...IN ADDITION TO
TEMPERATURES...WINDS AND POTENTIAL LAKE BREEZES...AND POTENTIAL
FOR PERIODS OF HEAVY RAIN NEXT WEEK.
IN THE SHORT TERM...CONVECTION CONTINUES TO DEVELOP AND SPREAD
NORTH ACROSS THE SOUTHERN HALF OR SO OF THE CWA WHILE AN OUTFLOW/
WIND SHIFT FROM CONVECTION EARLIER THIS MORNING ACROSS WI
CONTINUES TO MOVE SOUTH OF THE I-80 CORRIDOR AND IS NOW
INTERSECTING WITH A CONVECTIVE OUTFLOW LIFTING NORTH. THIS
BOUNDARY WILL LIKELY AID ADDITIONAL DEVELOPMENT THROUGH THE
AFTERNOON. AS NOTED IN THE MESOSCALE DISCUSSION ABOVE...MAIN
CONCERN WITH ONGOING CONVECTION IS LOCALLY HEAVY RAIN WITH SLOW
STORM MOVEMENT. SHORT TERM GUIDANCE IN GOOD AGREEMENT WITH THIS
ACTIVITY QUICKLY DISSIPATING AFTER SUNSET WITH LINGERING SHOWERS
POSSIBLE INTO THE EARLY OVERNIGHT HOURS.
LITTLE TO FOCUS ADDITIONAL PRECIP DEVELOPMENT FROM LATE TONIGHT
THROUGH MIDDAY SUNDAY AND HAVE MAINTAINED A GENERALLY DRY
FORECAST. WITH LOW LEVEL MOISTURE SLOWLY INCREASING OVER THE
WEEKEND...POSSIBLE FOR ISOLATED SHOWERS BUT EXPECTED COVERAGE TOO
LOW FOR ANY MENTION AT THIS TIME. CONVECTIVE CHANCES THEN BEGIN TO
INCREASE FROM SUNDAY AFTERNOON/EVENING INTO SUNDAY NIGHT.
CONSENSUS SEEMS TO BE FOCUSING ON A MCS DEVELOPING OVER THE PLAINS
SUNDAY AFTERNOON/EVENING AND MOVING INTO THE WESTERN LAKES SUNDAY
NIGHT. STILL TIME TO EVALUATE THIS BUT HAVE MAINTAINED SLIGHT
CHANCE POPS SUNDAY AFTERNOON AND THEN INCREASED POPS THROUGH
SUNDAY EVENING AND OVERNIGHT INTO MONDAY MORNING. AND SHOULD THIS
PAN OUT THEN MONDAY AFTERNOON INTO MONDAY AFTERNOON COULD
POTENTIALLY BE FAIRLY DRY.
AS FOR TEMPERATURES...WITH MUCH OF SUNDAY NOW LOOKING DRY AS WELL
AS MONDAY AFTERNOON POTENTIALLY BEING DRY OR DRY ENOUGH TO ALLOW
GOOD HEATING...HAVE BUMPED TEMPS UP MORE IN LINE WITH THE GEM...
WHICH WAS ONE OF THE BETTER PERFORMING MODELS FOR HIGH TEMPS WITH
THE WARM UP EARLIER THIS WEEK WHICH PUSHES HIGHS FOR BOTH DAYS
INTO THE MID/UPPER 80S AND WOULDN/T BE SURPRISED TO SEE SOME
LOCATIONS TAG 90. WINDS STILL SOUTHEASTERLY SUNDAY WILL LIKELY
KEEP THE IL SHORE COOLER BUT BY MONDAY WINDS INCREASE AND SHOULD
TURN ENOUGH SOUTHWESTERLY TO PREVENT ANY COOLING ALONG THE LAKE.
FORECAST SOUNDINGS SUGGEST WINDS COULD BE GUSTING WELL INTO THE
25-30 MPH RANGE.
DEWPOINTS WILL ALSO BE INCREASING THROUGH THE WEEKEND AND COULD
POTENTIALLY REACH THE UPPER 60S BY SUNDAY AFTERNOON AND ONLY DROP
MODESTLY SUNDAY NIGHT WITH LOWS WELL IN THE 60S. HOWEVER...SHOULD
STRONGER WINDS MATERIALIZE ON MONDAY...LOW LEVEL MIXING WOULD
LIKELY ALLOW SOME AMOUNT OF DRIER AIR TO MIX TO THE SURFACE.
BY MONDAY NIGHT AND BEYOND...TIMING VARIOUS WAVES BECOMES MORE
DIFFICULT AND WHILE THERE WILL BE DRY PERIODS...AT TIMES... HAVE
OPTED TO KEEP LIKELY POPS FOR SHOWERS/TSRA AND THE 12Z ECMWF SHOWS
SEVERAL WAVES TO AFFECT THE REGION DURING THE MIDDLE OF NEXT WEEK.
CLOUD COVER/PRECIP/POTENTIAL FLOW OFF THE LAKE ALL SIGNIFICANTLY
INCREASE TEMPERATURE FORECAST DIFFICULTY AND HAVE GENERALLY GONE
MIDDLE OF THE ROAD ON TEMPS. WITH DEWPOINTS EXPECTED TO STAY IN
THE 60S THROUGH WEDNESDAY MORNING AND PRECIPITABLE WATER VALUES IN
THE 1 TO 1.5 INCH RANGE...WHICH MAY END UP TOO LOW...ROUNDS OF
HEAVY RAIN WILL CERTAINLY BE POSSIBLE. CMS
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 00Z...
* SCATTERED SPRINKLES/LIGHT SHOWERS ENDING EARLY EVENING.
* POSSIBLE MVFR CIG/VSBY DEVELOPING LATE TONIGHT/EARLY SATURDAY MORNING.
ALLSOPP
//DISCUSSION...UPDATED 00Z...
SPRINKLES/LIGHT SHOWERS DISSIPATING EARLY THIS EVENING...OTHERWISE
JUST BROKEN MID AND HIGH CLOUD LAYERS FOR MOST OF THE NIGHT. SOME
MVFR VISIBILITIES MAY DEVELOP LATE TONIGHT AND EARLY SATURDAY AS
WINDS DIMINISH AND LOW LEVEL INVERSION STRENGTHENS. THE LIGHT
SHOWERS LATE THIS AFTERNOON AND EARLY THIS EVENING MAY HAVE ADDED
ENOUGH ADDITIONAL LOW LEVEL MOISTURE TO ALLOW SOME LIGHT FOG AND
HAZE DEVELOP. THIS SHOULD MIX OUT BY MID MORNING.
NEARLY STATIONARY WARM FRONT EXTENDS FROM NEAR MLI TO PNT TO
LAF THIS EVENING...WITH ENE WINDS PREVAILING NORTH OF THE BOUNDARY.
PRESSURE GRADIENT WILL BE WEAKENING AS UPPER LEVEL RIDGE BUILDS
OVER THE REGION AND SURFACE HIGH PRESSURE OVER THE GREAT LAKES
SHIFTS EAST. WINDS WILL GRADUALLY TURN SOUTHEAST OVER MUCH OF
NORTHERN IL AND IN SATURDAY EXCEPT NEAR THE LAKE WHERE ONSHORE
FLOW WILL KEEP WINDS MORE EAST. THEREFORE DONT EXPECT WINDS TO BE
QUITE AS STRONG OR GUSTY SATURDAY AS THEY WERE TODAY. WITH
BUILDING UPPER RIDGE SATURDAY AND OLD WARM FRONTAL BOUNDARY
WASHING OUT...THERE DOESN`T SEEM TO BE MUCH FOCUS FOR CONVECTION
SATURDAY. ALSO BUILDING RIDGE SHOULD KEEP ATMOSPHERE CAPPED.
THERFORE NOT ANTICIPATING ANY SHOWERS OR THUNDERSTORMS IN THE AREA
SATURDAY.
ALLSOPP
//ORD AND MDW CONFIDENCE...UPDATED 00Z...
* MEDIUM TO HIGH CONFIDENCE IN WIND FORECAST.
* LOW CONFIDENCE IN SHOWERS NEXT COUPLE HOURS.
* MEDIUM CONFIDENCE IN MVFR VISIBILITY LATE TONIGHT/EARLY SATURDAY
MORNING. LOW CONFIDENCE IN MVFR CIG DEVELOPING.
ALLSOPP
//OUTLOOK FOR ORD/MDW FOR 12Z SUNDAY-12Z FRIDAY...UPDATED 00Z...
SUNDAY...VFR.
SUNDAY NIGHT THROUGH WEDNESDAY...PERIODS OF TSRA.
THURSDAY...CHC SHRA.
ALLSOPP
&&
.MARINE...
206 PM CDT
A SURFACE RIDGE OF HIGH PRESSURE CONTINUES TO BUILD
EAST-SOUTHEASTWARD ACROSS ONTARIO AND THE CENTRAL AND EASTERN LAKES
THIS AFTERNOON. A HYBRID LAKE BREEZE/OUTFLOW BOUNDARY FROM
CONVECTION ACROSS WISCONSIN THIS MORNING HAS PUSHED ACROSS SOUTHERN
LAKE MICHIGAN EARLY THIS AFTERNOON. THIS LED TO A SUBSTANTIAL
INCREASE IN THE WINDS FOR A PERIOD OUT OF THE NORTH-NORTHEAST UP TO
25 TO 30 KT. THESE NORTHEAST WINDS UP TO AROUND 20 KT WILL CONTINUE
FOR THE NEXT FEW HOUR BEFORE SLOWLY EASING AND BECOMING MORE
EASTERLY TONIGHT.
A STORM SYSTEM IS EXPECTED TO TAKE SHAPE ACROSS THE HIGH PLAINS ON
SATURDAY BEFORE IT MOVES EAST-NORTHEASTWARD TOWARDS THE MID MISSOURI
VALLEY BY LATE SUNDAY. THIS SYSTEM LOOKS TO LIFT A WARM FRONT
NORTHWARD ACROSS AT LEAST THE SOUTHERN HALF TO TWO THIRDS OF THE
LAKE THROUGH MONDAY. BEHIND THIS FRONT WINDS LOOKS TO INCREASE OUT
OF THE SOUTH IN THE 15 TO 25 KT RANGE ON MONDAY. IT APPEARS THAT
THIS LOW WILL SLOWLY MOVE EASTWARD ACROSS THE MID MISSISSIPPI VALLEY
INTO MID WEEK AND THEN TO THE OHIO VALLEY LATER IN THE WEEK. THIS
SHOULD ALLOW THIS FRONT TO MOVE BACK SOUTH. DURING THIS TIME...THE
WINDS LOOK TO BECOME MORE NORTHERLY WITH TIME...ESPECIALLY BY MID TO
LATE WEEK AS THE SURFACE LOW PASSES TO THE SOUTH OF THE LAKE. THIS
COULD RESULT IN SOME STRONGER NORTHERLY WINDS BY LATE NEXT WEEK.
KJB
&&
.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 172218
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
518 PM CDT FRI MAY 17 2013
.DISCUSSION...
303 PM...MULTIPLE FORECAST CONCERNS THROUGH THE MIDDLE OF NEXT
WEEK INCLUDING CONVECTIVE CHANCES THIS EVENING AND THEN FROM
SUNDAY AFTERNOON THROUGH NEXT WEDNESDAY...IN ADDITION TO
TEMPERATURES...WINDS AND POTENTIAL LAKE BREEZES...AND POTENTIAL
FOR PERIODS OF HEAVY RAIN NEXT WEEK.
IN THE SHORT TERM...CONVECTION CONTINUES TO DEVELOP AND SPREAD
NORTH ACROSS THE SOUTHERN HALF OR SO OF THE CWA WHILE AN OUTFLOW/
WIND SHIFT FROM CONVECTION EARLIER THIS MORNING ACROSS WI
CONTINUES TO MOVE SOUTH OF THE I-80 CORRIDOR AND IS NOW
INTERSECTING WITH A CONVECTIVE OUTFLOW LIFTING NORTH. THIS
BOUNDARY WILL LIKELY AID ADDITIONAL DEVELOPMENT THROUGH THE
AFTERNOON. AS NOTED IN THE MESOSCALE DISCUSSION ABOVE...MAIN
CONCERN WITH ONGOING CONVECTION IS LOCALLY HEAVY RAIN WITH SLOW
STORM MOVEMENT. SHORT TERM GUIDANCE IN GOOD AGREEMENT WITH THIS
ACTIVITY QUICKLY DISSIPATING AFTER SUNSET WITH LINGERING SHOWERS
POSSIBLE INTO THE EARLY OVERNIGHT HOURS.
LITTLE TO FOCUS ADDITIONAL PRECIP DEVELOPMENT FROM LATE TONIGHT
THROUGH MIDDAY SUNDAY AND HAVE MAINTAINED A GENERALLY DRY
FORECAST. WITH LOW LEVEL MOISTURE SLOWLY INCREASING OVER THE
WEEKEND...POSSIBLE FOR ISOLATED SHOWERS BUT EXPECTED COVERAGE TOO
LOW FOR ANY MENTION AT THIS TIME. CONVECTIVE CHANCES THEN BEGIN TO
INCREASE FROM SUNDAY AFTERNOON/EVENING INTO SUNDAY NIGHT.
CONSENSUS SEEMS TO BE FOCUSING ON A MCS DEVELOPING OVER THE PLAINS
SUNDAY AFTERNOON/EVENING AND MOVING INTO THE WESTERN LAKES SUNDAY
NIGHT. STILL TIME TO EVALUATE THIS BUT HAVE MAINTAINED SLIGHT
CHANCE POPS SUNDAY AFTERNOON AND THEN INCREASED POPS THROUGH
SUNDAY EVENING AND OVERNIGHT INTO MONDAY MORNING. AND SHOULD THIS
PAN OUT THEN MONDAY AFTERNOON INTO MONDAY AFTERNOON COULD
POTENTIALLY BE FAIRLY DRY.
AS FOR TEMPERATURES...WITH MUCH OF SUNDAY NOW LOOKING DRY AS WELL
AS MONDAY AFTERNOON POTENTIALLY BEING DRY OR DRY ENOUGH TO ALLOW
GOOD HEATING...HAVE BUMPED TEMPS UP MORE IN LINE WITH THE GEM...
WHICH WAS ONE OF THE BETTER PERFORMING MODELS FOR HIGH TEMPS WITH
THE WARM UP EARLIER THIS WEEK WHICH PUSHES HIGHS FOR BOTH DAYS
INTO THE MID/UPPER 80S AND WOULDN/T BE SURPRISED TO SEE SOME
LOCATIONS TAG 90. WINDS STILL SOUTHEASTERLY SUNDAY WILL LIKELY
KEEP THE IL SHORE COOLER BUT BY MONDAY WINDS INCREASE AND SHOULD
TURN ENOUGH SOUTHWESTERLY TO PREVENT ANY COOLING ALONG THE LAKE.
FORECAST SOUNDINGS SUGGEST WINDS COULD BE GUSTING WELL INTO THE
25-30 MPH RANGE.
DEWPOINTS WILL ALSO BE INCREASING THROUGH THE WEEKEND AND COULD
POTENTIALLY REACH THE UPPER 60S BY SUNDAY AFTERNOON AND ONLY DROP
MODESTLY SUNDAY NIGHT WITH LOWS WELL IN THE 60S. HOWEVER...SHOULD
STRONGER WINDS MATERIALIZE ON MONDAY...LOW LEVEL MIXING WOULD
LIKELY ALLOW SOME AMOUNT OF DRIER AIR TO MIX TO THE SURFACE.
BY MONDAY NIGHT AND BEYOND...TIMING VARIOUS WAVES BECOMES MORE
DIFFICULT AND WHILE THERE WILL BE DRY PERIODS...AT TIMES... HAVE
OPTED TO KEEP LIKELY POPS FOR SHOWERS/TSRA AND THE 12Z ECMWF SHOWS
SEVERAL WAVES TO AFFECT THE REGION DURING THE MIDDLE OF NEXT WEEK.
CLOUD COVER/PRECIP/POTENTIAL FLOW OFF THE LAKE ALL SIGNIFICANTLY
INCREASE TEMPERATURE FORECAST DIFFICULTY AND HAVE GENERALLY GONE
MIDDLE OF THE ROAD ON TEMPS. WITH DEWPOINTS EXPECTED TO STAY IN
THE 60S THROUGH WEDNESDAY MORNING AND PRECIPITABLE WATER VALUES IN
THE 1 TO 1.5 INCH RANGE...WHICH MAY END UP TOO LOW...ROUNDS OF
HEAVY RAIN WILL CERTAINLY BE POSSIBLE. CMS
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 22Z...
* AREA OF WEAKENING SHOWERS DRIFTING NORTH THROUGH CHICAGO METRO
* WEAKENING OUTFLOW BOUNDARY MOVING THROUGH ORD MAY CAUSE SOME
VARIABILITY IN WIND THROUGH 23Z.
* MVFR CIG/VSBY POSSIBLE LATE TONIGHT/EARLY SATURDAY MORNING.
ALLSOPP
//DISCUSSION...UPDATED 22Z...
AREA OF SHOWERS SOUTH OF A LINE FROM ARR TO VPZ DRIFTING NORTH AND
WEAKENING. SHOWERS WILL AFFECT DPA...MDW...AND GYY BETWEEN 2230Z
AND 0000Z. BACKED OFF ON VISIBILITY RESTRICTION DUE TO WEAK NATURE
OF SHOWERS. SHOWERS SHOULD DISSIPATE BY 00Z. OUTFLOW BOUNDARY
PUSHED NORTH AHEAD OF THE SHOWERS AND CAUSED MDW AND ORD WINDS TO
BRIEFLY GO SE. BOUNDARY IS DYING RAPIDLY IN THE FACE OF STRONG
ONSHORE NE WINDS. WIND DIRECTION WILL VARY A BIT FROM SE TO NE
NEXT HOUR OR TWO BEFORE SETTLING BACK TO ENE FOR THE EVENING.
FROM 18Z...
COMPLEX FORECAST CONTINUES WITH LAKE MICHIGAN HELPING TO PUSH A
FRONTAL BOUNDARY SOUTHWESTWARD ACROSS THE CHICAGO/NW INDIANA METRO
AREA. THIS HAS RESULTED IN A SHIFT TO STEADY NORTHEAST WINDS AT
ORD/MDW/DPA AND GYY SHORTLY WITH SOME GUSTS TO NEAR 20 KT. WINDS
SHOULD STAY NORTHEASTERLY FOR THE NEXT FEW HOURS AND TREND MORE
EASTERLY THROUGH THE AFTERNOON BUT THIS MAY BE SLOWER TO OCCUR
THAN FORECAST. SHRA/TSRA HAS BEGUN TO DEVELOP SOUTH OF THE
TERMINALS AND WILL BE MOVING NORTHWARD THROUGH THE AFTERNOON. ONE
QUESTION IS HOW FAR NORTH IT WILL BE ABLE TO MAKE IT NOW THAT THE
FRONTAL BOUNDARY HAS PUSHED THROUGH THE TERMINALS. AM THINKING
THAT THE BOUNDARY ITSELF MAY ACT TO TRIGGER MORE STORMS BUT THAT
IT WILL NEED TO MOVE FURTHER SOUTH TOWARD/PAST JOT/KC09 WHERE THE
NORTHERN EDGE OF DECENT INSTABILITY EXISTS IN ORDER TO DO SO. WILL
CONTINUE WITH THE IDEA OF THE HIGHEST POTENTIAL AT GYY AND MDW AND
INCLUDE TEMPO TS THERE BY MID AFTERNOON. ORD/DPA/RFD HAVE A CHANCE
AS WELL BUT IT IS MUCH LESS CLEAR WHETHER OR NOT THEY WILL BE
DIRECTLY AFFECTED. WHERE SHRA/TSRA DO PASS OVER THEN BRIEF IFR
VSBY IS POSSIBLE IN HEAVY DOWNPOURS.
SHRA/TSRA ACTIVITY WILL WANE THIS EVENING AND WINDS WILL LIKELY
REMAIN EAST OR EAST-NORTHEAST FOR THE MOST PART BUT MAY TURN
SOUTHEAST OVERNIGHT. BETTER LOW LEVEL MOISTURE WILL BE IN
PLACE..ESPECIALLY IF RAIN CAN FALL...AND MVFR VSBY IS A DECENT
POSSIBILITY TOWARD DAYBREAK. SCT-BKN MVFR CLOUDS MAY ALSO DEVELOP
DURING THIS TIME. EXPECT THAT ANY MVFR VSBY/CIGS WOULD IMPROVE
AFTER DAYBREAK. WINDS WILL CONTINUE TO BE TRICKY WITH A EASTERLY
DIRECTION CONTINUING WITH VARIABILITY LIKELY.
MDB
//ORD AND MDW CONFIDENCE...UPDATED 22Z...
* HIGH CONFIDENCE IN PREVAILING ENE WIND RETURNING TO ORD AND MDW
AFTER SHORT PERIOD OF SE WINDS.
* MEDIUM CONFIDENCE IN SHOWERS REACHING MDW. LOW CONFIDENCE IN ANY
VSBY RESTRICTION.
* LOW CONFIDENCE IN SHOWERS REACHING ORD.
* MEDIUM CONFIDENCE IN MVFR VSBY LATE TONIGHT...LOW CONFIDENCE IN
MVFR CIG POTENTIAL.
ALLSOPP
//OUTLOOK FOR ORD/MDW FOR 00Z SUNDAY-12Z FRIDAY...UPDATED 12Z...
SATURDAY NIGHT...VFR.
SUNDAY THROUGH WEDNESDAY...VFR. PERIODIC CHANCES FOR SHRA/TSRA.
THURSDAY...VFR. PSBL MVFR WITH CHANCE FOR SHRA.
BEACHLER
&&
.MARINE...
206 PM CDT
A SURFACE RIDGE OF HIGH PRESSURE CONTINUES TO BUILD
EAST-SOUTHEASTWARD ACROSS ONTARIO AND THE CENTRAL AND EASTERN LAKES
THIS AFTERNOON. A HYBRID LAKE BREEZE/OUTFLOW BOUNDARY FROM
CONVECTION ACROSS WISCONSIN THIS MORNING HAS PUSHED ACROSS SOUTHERN
LAKE MICHIGAN EARLY THIS AFTERNOON. THIS LED TO A SUBSTANTIAL
INCREASE IN THE WINDS FOR A PERIOD OUT OF THE NORTH-NORTHEAST UP TO
25 TO 30 KT. THESE NORTHEAST WINDS UP TO AROUND 20 KT WILL CONTINUE
FOR THE NEXT FEW HOUR BEFORE SLOWLY EASING AND BECOMING MORE
EASTERLY TONIGHT.
A STORM SYSTEM IS EXPECTED TO TAKE SHAPE ACROSS THE HIGH PLAINS ON
SATURDAY BEFORE IT MOVES EAST-NORTHEASTWARD TOWARDS THE MID MISSOURI
VALLEY BY LATE SUNDAY. THIS SYSTEM LOOKS TO LIFT A WARM FRONT
NORTHWARD ACROSS AT LEAST THE SOUTHERN HALF TO TWO THIRDS OF THE
LAKE THROUGH MONDAY. BEHIND THIS FRONT WINDS LOOKS TO INCREASE OUT
OF THE SOUTH IN THE 15 TO 25 KT RANGE ON MONDAY. IT APPEARS THAT
THIS LOW WILL SLOWLY MOVE EASTWARD ACROSS THE MID MISSISSIPPI VALLEY
INTO MID WEEK AND THEN TO THE OHIO VALLEY LATER IN THE WEEK. THIS
SHOULD ALLOW THIS FRONT TO MOVE BACK SOUTH. DURING THIS TIME...THE
WINDS LOOK TO BECOME MORE NORTHERLY WITH TIME...ESPECIALLY BY MID TO
LATE WEEK AS THE SURFACE LOW PASSES TO THE SOUTH OF THE LAKE. THIS
COULD RESULT IN SOME STRONGER NORTHERLY WINDS BY LATE NEXT WEEK.
KJB
&&
.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 172003
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
303 PM CDT FRI MAY 17 2013
.MESOSCALE DISCUSSION...
201 PM CDT
A CLUSTER OF STORMS IS TRYING TO TAKE SHAPE ACROSS THE SOUTHERN
PORTION OF THE CWA THIS AFTERNOON ALONG A STATIONARY SURFACE
BOUNDARY AND MOISTURE CONVERGENCE AXIS...BUT AT THIS TIME WE ARE NOT
EXPECTING ANYTHING SEVERE TO DEVELOP. LOCALIZED FLOODING WOULD BE
MORE OF A CONCERN. SFC-BASED CAPE VALUES HAVE REACHED SEVERAL
HUNDRED J/KG...BUT DEEP LAYER SHEAR IS VIRTUALLY NONEXISTENT...WITH
BOTH FORECAST AND LATEST ACARS SOUNDINGS FROM ORD SHOWING WINDS
THROUGH MOST OF THE TROPOSPHERE AT 20 KTS OR LESS.
STORMS THAT DO PULSE UP IN THIS LOW SHEAR AND MODERATE CAPE
ENVIRONMENT COULD POSE A HAIL OR WIND THREAT...BUT ACARS -20C
HEIGHTS AROUND 23 KFT PROVIDE AN IDEA OF HOW HIGH 60 DBZ ECHOES
WOULD HAVE TO GET TO SUPPORT SEVERE HAIL...AND STORMS SO FAR HAVE
ONLY BEEN REACHING HALF THAT LEVEL. FAIRLY SATURATED LOW LEVELS IN
FORECAST SOUNDINGS ALSO SUGGEST THE THREAT OF STRONG DOWNBURST WINDS
WOULD NOT BE HIGH. AGAIN...LOCALIZED FLOODING WOULD BE MORE OF A
CONCERN GIVEN THE COMBINATION OF SATURATED SOUNDINGS SOMEWHAT
TROPICAL IN NATURE...SLOW STORM MOTION...MINIMAL SHEAR...THE
PRESENCE OF A FOCUSING BOUNDARY...AND PRECIPITABLE WATER VALUES
AROUND 1.4 INCHES. AT THIS POINT THE STORMS ARE REMAINING GENERALLY
SCATTERED AND DISCRETE...AND HAVE NOT BEEN TRAINING. THESE WILL
CONTINUE TO BE MONITORED FOR ANY CHANGES AS WE PROGRESS THROUGH PEAK
MIDAFTERNOON HEATING.
LENNING
&&
.DISCUSSION...
303 PM...MULTIPLE FORECAST CONCERNS THROUGH THE MIDDLE OF NEXT
WEEK INCLUDING CONVECTIVE CHANCES THIS EVENING AND THEN FROM
SUNDAY AFTERNOON THROUGH NEXT WEDNESDAY...IN ADDITION TO
TEMPERATURES...WINDS AND POTENTIAL LAKE BREEZES...AND POTENTIAL
FOR PERIODS OF HEAVY RAIN NEXT WEEK.
IN THE SHORT TERM...CONVECTION CONTINUES TO DEVELOP AND SPREAD
NORTH ACROSS THE SOUTHERN HALF OR SO OF THE CWA WHILE AN OUTFLOW/
WIND SHIFT FROM CONVECTION EARLIER THIS MORNING ACROSS WI
CONTINUES TO MOVE SOUTH OF THE I-80 CORRIDOR AND IS NOW
INTERSECTING WITH A CONVECTIVE OUTFLOW LIFTING NORTH. THIS
BOUNDARY WILL LIKELY AID ADDITIONAL DEVELOPMENT THROUGH THE
AFTERNOON. AS NOTED IN THE MESOSCALE DISCUSSION ABOVE...MAIN
CONCERN WITH ONGOING CONVECTION IS LOCALLY HEAVY RAIN WITH SLOW
STORM MOVEMENT. SHORT TERM GUIDANCE IN GOOD AGREEMENT WITH THIS
ACTIVITY QUICKLY DISSIPATING AFTER SUNSET WITH LINGERING SHOWERS
POSSIBLE INTO THE EARLY OVERNIGHT HOURS.
LITTLE TO FOCUS ADDITIONAL PRECIP DEVELOPMENT FROM LATE TONIGHT
THROUGH MIDDAY SUNDAY AND HAVE MAINTAINED A GENERALLY DRY
FORECAST. WITH LOW LEVEL MOISTURE SLOWLY INCREASING OVER THE
WEEKEND...POSSIBLE FOR ISOLATED SHOWERS BUT EXPECTED COVERAGE TOO
LOW FOR ANY MENTION AT THIS TIME. CONVECTIVE CHANCES THEN BEGIN TO
INCREASE FROM SUNDAY AFTERNOON/EVENING INTO SUNDAY NIGHT.
CONSENSUS SEEMS TO BE FOCUSING ON A MCS DEVELOPING OVER THE PLAINS
SUNDAY AFTERNOON/EVENING AND MOVING INTO THE WESTERN LAKES SUNDAY
NIGHT. STILL TIME TO EVALUATE THIS BUT HAVE MAINTAINED SLIGHT
CHANCE POPS SUNDAY AFTERNOON AND THEN INCREASED POPS THROUGH
SUNDAY EVENING AND OVERNIGHT INTO MONDAY MORNING. AND SHOULD THIS
PAN OUT THEN MONDAY AFTERNOON INTO MONDAY AFTERNOON COULD
POTENTIALLY BE FAIRLY DRY.
AS FOR TEMPERATURES...WITH MUCH OF SUNDAY NOW LOOKING DRY AS WELL
AS MONDAY AFTERNOON POTENTIALLY BEING DRY OR DRY ENOUGH TO ALLOW
GOOD HEATING...HAVE BUMPED TEMPS UP MORE IN LINE WITH THE GEM...
WHICH WAS ONE OF THE BETTER PERFORMING MODELS FOR HIGH TEMPS WITH
THE WARM UP EARLIER THIS WEEK WHICH PUSHES HIGHS FOR BOTH DAYS
INTO THE MID/UPPER 80S AND WOULDN/T BE SURPRISED TO SEE SOME
LOCATIONS TAG 90. WINDS STILL SOUTHEASTERLY SUNDAY WILL LIKELY
KEEP THE IL SHORE COOLER BUT BY MONDAY WINDS INCREASE AND SHOULD
TURN ENOUGH SOUTHWESTERLY TO PREVENT ANY COOLING ALONG THE LAKE.
FORECAST SOUNDINGS SUGGEST WINDS COULD BE GUSTING WELL INTO THE
25-30 MPH RANGE.
DEWPOINTS WILL ALSO BE INCREASING THROUGH THE WEEKEND AND COULD
POTENTIALLY REACH THE UPPER 60S BY SUNDAY AFTERNOON AND ONLY DROP
MODESTLY SUNDAY NIGHT WITH LOWS WELL IN THE 60S. HOWEVER...SHOULD
STRONGER WINDS MATERIALIZE ON MONDAY...LOW LEVEL MIXING WOULD
LIKELY ALLOW SOME AMOUNT OF DRIER AIR TO MIX TO THE SURFACE.
BY MONDAY NIGHT AND BEYOND...TIMING VARIOUS WAVES BECOMES MORE
DIFFICULT AND WHILE THERE WILL BE DRY PERIODS...AT TIMES... HAVE
OPTED TO KEEP LIKELY POPS FOR SHOWERS/TSRA AND THE 12Z ECMWF SHOWS
SEVERAL WAVES TO AFFECT THE REGION DURING THE MIDDLE OF NEXT WEEK.
CLOUD COVER/PRECIP/POTENTIAL FLOW OFF THE LAKE ALL SIGNIFICANTLY
INCREASE TEMPERATURE FORECAST DIFFICULTY AND HAVE GENERALLY GONE
MIDDLE OF THE ROAD ON TEMPS. WITH DEWPOINTS EXPECTED TO STAY IN
THE 60S THROUGH WEDNESDAY MORNING AND PRECIPITABLE WATER VALUES IN
THE 1 TO 1.5 INCH RANGE...WHICH MAY END UP TOO LOW...ROUNDS OF
HEAVY RAIN WILL CERTAINLY BE POSSIBLE. CMS
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 20Z...
* ISOLD-SCT SHRA/TSRA TO THE WEST AND SOUTH WHICH MAY REACH MDW
LATE AFTERNOON...WITH LOWER CHANCE OF REACHING ORD.
* NORTHEAST WINDS 10-12KT WITH SOME GUSTS NEAR 20 KT AT
TIMES...TRENDING MORE EASTERLY LATE AFTERNOON.
* MVFR CIGS/VSBY POSSIBLE LATE TONIGHT/EARLY SATURDAY MORNING.
MDB
//DISCUSSION...UPDATED 20Z...
BAND OF SCATTERED SHRA/TSRA FROM ENE OF KVYS TO KC09 TO KRZL
CONTINUES TO LIFT NORTHWARD AT 20Z. LAKE REINFORCED BOUNDARY IS
POSITIONED NEAR THE LEADING EDGE OF THE ACTIVITY AND WITH MUCH MORE
STABLE AIR TO ITS NORTH SO THE NORTHWARD PUSH MAY BE LIMITED. WILL
REMOVE TS MENTION FROM MDW WITH THE CHANCE FOR TSRA ONLY AROUND 30
PERCENT IF THAT...WITH A BETTER CHANCE FOR JUST SHRA SO WILL KEEP
TEMPO FOR SHRA FOR NOW. GYY STILL HAS A FAIR CHANCE FOR TSRA GIVEN
THAT THE BOUNDARY ARCS BACK TO THE LAKESHORE JUST TO THE EAST SO
UNSTABLE AIR IS NEARBY...AND OUT FLOW FROM CELLS NEAR IKK MAY PUSH
THAT PORTION OF THE BOUNDARY NORTHWARD SOMEWHAT. CHANCES FOR
SHRA/TSRA AT ORD ARE LOWER...PROBABLY LESS THAN 30 PERCENT SO
REMOVED VCTS MENTION BUT BRIEF SHRA IS POSSIBLE LATE THIS AFTERNOON.
RFD LOOKS TO BE IN A SIMILAR SITUATION BUT WITH A BETTER CHANCE FOR
SHRA AND A REDUCED CHANCE FOR TSRA. ANY BETTER ORGANIZED SHRA/TSRA
THAT DOES PASS OVER A TERMINAL WILL LIKELY DROP VSBY TO IFR FOR A
SHORT PERIOD. WINDS REMAIN A CHALLENGE WITH THE BOUNDARY IN THE AREA
AND POTENTIAL OUTFLOWS FROM CONVECTION. STILL FAVOR THE PREVAILING
NORTHEAST TO EAST DIRECTION THROUGH THE EVENING HOWEVER.
FROM 18Z...
COMPLEX FORECAST CONTINUES WITH LAKE MICHIGAN HELPING TO PUSH A
FRONTAL BOUNDARY SOUTHWESTWARD ACROSS THE CHICAGO/NW INDIANA METRO
AREA. THIS HAS RESULTED IN A SHIFT TO STEADY NORTHEAST WINDS AT
ORD/MDW/DPA AND GYY SHORTLY WITH SOME GUSTS TO NEAR 20 KT. WINDS
SHOULD STAY NORTHEASTERLY FOR THE NEXT FEW HOURS AND TREND MORE
EASTERLY THROUGH THE AFTERNOON BUT THIS MAY BE SLOWER TO OCCUR
THAN FORECAST. SHRA/TSRA HAS BEGUN TO DEVELOP SOUTH OF THE
TERMINALS AND WILL BE MOVING NORTHWARD THROUGH THE AFTERNOON. ONE
QUESTION IS HOW FAR NORTH IT WILL BE ABLE TO MAKE IT NOW THAT THE
FRONTAL BOUNDARY HAS PUSHED THROUGH THE TERMINALS. AM THINKING
THAT THE BOUNDARY ITSELF MAY ACT TO TRIGGER MORE STORMS BUT THAT
IT WILL NEED TO MOVE FURTHER SOUTH TOWARD/PAST JOT/KC09 WHERE THE
NORTHERN EDGE OF DECENT INSTABILITY EXISTS IN ORDER TO DO SO. WILL
CONTINUE WITH THE IDEA OF THE HIGHEST POTENTIAL AT GYY AND MDW AND
INCLUDE TEMPO TS THERE BY MID AFTERNOON. ORD/DPA/RFD HAVE A CHANCE
AS WELL BUT IT IS MUCH LESS CLEAR WHETHER OR NOT THEY WILL BE
DIRECTLY AFFECTED. WHERE SHRA/TSRA DO PASS OVER THEN BRIEF IFR
VSBY IS POSSIBLE IN HEAVY DOWNPOURS.
SHRA/TSRA ACTIVITY WILL WANE THIS EVENING AND WINDS WILL LIKELY
REMAIN EAST OR EAST-NORTHEAST FOR THE MOST PART BUT MAY TURN
SOUTHEAST OVERNIGHT. BETTER LOW LEVEL MOISTURE WILL BE IN
PLACE..ESPECIALLY IF RAIN CAN FALL...AND MVFR VSBY IS A DECENT
POSSIBILITY TOWARD DAYBREAK. SCT-BKN MVFR CLOUDS MAY ALSO DEVELOP
DURING THIS TIME. EXPECT THAT ANY MVFR VSBY/CIGS WOULD IMPROVE
AFTER DAYBREAK. WINDS WILL CONTINUE TO BE TRICKY WITH A EASTERLY
DIRECTION CONTINUING WITH VARIABILITY LIKELY.
MDB
//ORD AND MDW CONFIDENCE...UPDATED 20Z...
* HIGH CONFIDENCE IN SHRA/TSRA REMAINING MAINLY SOUTH OF THE
TERMINALS...LOW-MEDIUM CONFIDENCE IN ACTIVITY NEAR MDW THIS
AFTERNOON...MEDIUM CONFIDENCE THAT SHRA/TSRA POTENTIAL NEAR ORD
IS LOW.
* MEDIUM CONFIDENCE IN WIND TRENDS THROUGH THE PERIOD.
* MEDIUM CONFIDENCE IN MVFR VSBY LATE TONIGHT...LOW CONFIDENCE IN
MVFR CIG POTENTIAL.
MDB
//OUTLOOK FOR ORD/MDW FOR 00Z SUNDAY-12Z FRIDAY...UPDATED 12Z...
SATURDAY NIGHT...VFR.
SUNDAY THROUGH WEDNESDAY...VFR. PERIODIC CHANCES FOR SHRA/TSRA.
THURSDAY...VFR. PSBL MVFR WITH CHANCE FOR SHRA.
BEACHLER
&&
.MARINE...
206 PM CDT
A SURFACE RIDGE OF HIGH PRESSURE CONTINUES TO BUILD
EAST-SOUTHEASTWARD ACROSS ONTARIO AND THE CENTRAL AND EASTERN LAKES
THIS AFTERNOON. A HYBRID LAKE BREEZE/OUTFLOW BOUNDARY FROM
CONVECTION ACROSS WISCONSIN THIS MORNING HAS PUSHED ACROSS SOUTHERN
LAKE MICHIGAN EARLY THIS AFTERNOON. THIS LED TO A SUBSTANTIAL
INCREASE IN THE WINDS FOR A PERIOD OUT OF THE NORTH-NORTHEAST UP TO
25 TO 30 KT. THESE NORTHEAST WINDS UP TO AROUND 20 KT WILL CONTINUE
FOR THE NEXT FEW HOUR BEFORE SLOWLY EASING AND BECOMING MORE
EASTERLY TONIGHT.
A STORM SYSTEM IS EXPECTED TO TAKE SHAPE ACROSS THE HIGH PLAINS ON
SATURDAY BEFORE IT MOVES EAST-NORTHEASTWARD TOWARDS THE MID MISSOURI
VALLEY BY LATE SUNDAY. THIS SYSTEM LOOKS TO LIFT A WARM FRONT
NORTHWARD ACROSS AT LEAST THE SOUTHERN HALF TO TWO THIRDS OF THE
LAKE THROUGH MONDAY. BEHIND THIS FRONT WINDS LOOKS TO INCREASE OUT
OF THE SOUTH IN THE 15 TO 25 KT RANGE ON MONDAY. IT APPEARS THAT
THIS LOW WILL SLOWLY MOVE EASTWARD ACROSS THE MID MISSISSIPPI VALLEY
INTO MID WEEK AND THEN TO THE OHIO VALLEY LATER IN THE WEEK. THIS
SHOULD ALLOW THIS FRONT TO MOVE BACK SOUTH. DURING THIS TIME...THE
WINDS LOOK TO BECOME MORE NORTHERLY WITH TIME...ESPECIALLY BY MID TO
LATE WEEK AS THE SURFACE LOW PASSES TO THE SOUTH OF THE LAKE. THIS
COULD RESULT IN SOME STRONGER NORTHERLY WINDS BY LATE NEXT WEEK.
KJB
&&
.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 172001
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
301 PM CDT FRI MAY 17 2013
.MESOSCALE DISCUSSION...A CLUSTER OF STORMS IS TRYING TO TAKE
SHAPE ACROSS THE SOUTHERN PORTION OF THE CWA THIS AFTERNOON ALONG
A STATIONARY SURFACE BOUNDARY AND MOISTURE CONVERGENCE AXIS...BUT
AT THIS TIME WE ARE NOT EXPECTING ANYTHING SEVERE TO DEVELOP.
LOCALIZED FLOODING WOULD BE MORE OF A CONCERN. SFC-BASED CAPE
VALUES HAVE REACHED SEVERAL HUNDRED J/KG...BUT DEEP LAYER SHEAR IS
VIRTUALLY NONEXISTENT...WITH BOTH FORECAST AND LATEST ACARS
SOUNDINGS FROM ORD SHOWING WINDS THROUGH MOST OF THE TROPOSPHERE
AT 20 KTS OR LESS.
STORMS THAT DO PULSE UP IN THIS LOW SHEAR AND MODERATE CAPE
ENVIRONMENT COULD POSE A HAIL OR WIND THREAT...BUT ACARS -20C
HEIGHTS AROUND 23 KFT PROVIDE AN IDEA OF HOW HIGH 60 DBZ ECHOES
WOULD HAVE TO GET TO SUPPORT SEVERE HAIL...AND STORMS SO FAR HAVE
ONLY BEEN REACHING HALF THAT LEVEL. FAIRLY SATURATED LOW LEVELS IN
FORECAST SOUNDINGS ALSO SUGGEST THE THREAT OF STRONG DOWNBURST WINDS
WOULD NOT BE HIGH. AGAIN...LOCALIZED FLOODING WOULD BE MORE OF A
CONCERN GIVEN THE COMBINATION OF SATURATED SOUNDINGS SOMEWHAT
TROPICAL IN NATURE...SLOW STORM MOTION...MINIMAL SHEAR...THE
PRESENCE OF A FOCUSING BOUNDARY...AND PRECIPITABLE WATER VALUES
AROUND 1.4 INCHES. AT THIS POINT THE STORMS ARE REMAINING GENERALLY
SCATTERED AND DISCRETE...AND HAVE NOT BEEN TRAINING. THESE WILL
CONTINUE TO BE MONITORED FOR ANY CHANGES AS WE PROGRESS THROUGH PEAK
MIDAFTERNOON HEATING.
LENNING
&&
.DISCUSSION...
428 AM CDT
EARLY THIS MORNING A STATIONARY FRONT RAN FROM NE IA...FAR NW AND
NE IL...AND NORTHERN IND. ND...NORTHEAST AND FAR NORTHWEST IL.
BOUNDARY POSITION IS WELL DEFINED BY BOTH WIND PATTERN AND LARGE
DIFFERENCE IN DEW POINTS ON OPPOSITE SIDES OF THE FRONT. AN UPPER
LOW WAS OVER THE EASTERN PORTION OF THE MO-AR BOARDER WHILE
A FEW DISTURBANCES...LIKELY CONVECTIVELY INDUCED...WERE JUST
UPSTREAM OF THE LOCAL FORECAST AREA.
THE FIRST DISTURBANCE WAS MOVING ACROSS FAR NW AND N CENTRAL IL
WITH A SECOND ALONG THE MN-IA BORDER AND A THIRD MOVING OVER THE
MID MO VALLEY FROM NEB E OVER FAR WESTERN IA. THESE DISTURBANCES
PRECEDED AN UPPER LOW MOVING E ALONG THE SD-NEB BOARDER.
THE FIRST DISTURBANCE DID PRODUCE A FEW SHOWERS AND THUNDERSTORMS
AS FAR E AS OVER THE FAR SW PORTION OF THE FA LAST EVENING AND
EARLIER THIS MORNING BUT HAD DISSIPATED AS THEY MOVED E INTO A
CAPPED AREA. THE SECOND DISTURBANCE. THE MAIN AREA OF CONVECTION
THAT HAD BEEN MOVING ACROSS IA HAD ALSO DISSIPATED AS IT MOVED
AWAY FROM THE BETTER ISENTROPIC LIFT RESULTING FROM MODERATELY
STRONG MID LEVEL WAA. THE THIRD DISTURBANCE HAS GENERATED AN
ELONGATED AREA OF THUNDERSTORMS ALONG THE MN-IA BORDER WHERE 30-35
KT SOUTHERLY FLOW IN THE 1.5 TO 3 KM AGL LAYER WAS MAXIMIZING LIFT
IN AN AREA OF RELATIVELY LARGE ELEVATED CAPE N OF THE STATIONARY
FRONT.
LATER TODAY THE CAP IS PROGGED TO BE REMOVED THOUGH FORECAST
TEMPERATURE PROFILES ARE NOT INDICATING AND SIGNIFICANT CAPE
AVAILABLE TO BE REALIZED. IN ADDITION...THE BEST ISENTROPIC LIFT
IS PROGGED TO MOVE ACROSS WI DURING THE DAY. STILL...THERE WILL BE
INCREASING CHANCES OF SHOWERS AND THUNDERSTORMS SPREADING W TO E
ACROSS THE LOCAL AREA DURING THE MORNING AS PERSISTING THROUGH THE
AFTERNOON AND EARLY EVENING AS THE SD-NEB UPPER LOW AND THE MO-AR
UPPER LOW MERGE AND MOVE TO OR SLIGHTLY E OF THE MID MS VALLEY BY
00Z. BEYOND THE FIRST PART OF THIS EVENING CHANCES OF PRECIP ARE
SMALL EXCEPT FOR THE FAR SE PORTION OF THE FA WHICH WILL STILL BE
UNDER THE INFLUENCE OF THE SLOW MOVING UPPER LOW WHICH IS PROGGED
TO BE OVER/NEAR THE LOWER OH VALLEY AT 12Z SAT.
THE UPPER PATTERN WILL BECOME MORE AMPLIFIED OVERNIGHT AND SAT
BEFORE BECOMING ZONAL E OF THE ROCKIES MID NEXT WEEK. WHILE THE
FLOW WILL BE AMPLIFIED THE FLOW WILL BE SLUGGISH AS AN UPPER
TROUGH MOVING OVER THE PACIFIC COAST EARLY THIS MORNING REACHES
THE ROCKIES LATE SAT-SAT NIGHT WHILE ANOTHER UPPER TROUGH OVER THE
N PACIFIC OFF THE B.C. COAST MOVES OVER PAC NW COAST. BY LATE SUN-
SUN NIGHT THE PAIR OF TROUGHS ARE PROGGED TO FORM AN UPPER LOW
OVER THE NORTHERN HIGH PLAINS. THIS UPPER LOW IS TO THEN VERY
SLOWLY MOVE E TO THE UPPER MIDWEST BY WED EVENING WHILE ALSO
GRADUALLY WEAKENING. HOWEVER...A FAIRLY STRONG SURFACE LOW IS
PROGGED TO MOVE E ACROSS THE NORTHERN PLAINS AND UPPER MS VALLEY
BEFORE THE UPPER SYSTEM WEAKENS AS DOES THE SURFACE REFLECTION.
DUE TO THE VERY SLOW EASTWARD PROGRESS OF THE SYSTEM A PROLONGED
PERIOD OF PERSISTENT RELATIVELY STRONG S TO SW LOWER LEVEL FLOW
WILL BE TRANSPORTING A CONTINUOUS STREAM OF MOISTURE FROM THE
WESTERN GULF UP ACROSS THE MID MS VALLEY AND TO THE UPPER MIDWEST
AND WESTERN GREAT LAKES.
WHILE THE MOST LIKELY TIME FRAME FOR RAIN IS LATER MON AND TUE AS
THIS IS WHEN SIGNIFICANT WARM AIR ADVECTION AND RESULTING UVV
ALONG WITH THE ARRIVAL OF ABUNDANT MOISTURE OCCURS...THERE WILL BE
CHANCES OF RAIN IN THE FORECAST FROM SUNDAY NIGHT RIGHT THROUGH
END OF NEXT WEEK...FIRST AS THE UPPER LOW APPROACHES THERE LIKELY
WILL BE SMALLER SCALE SHORT WAVES ROTATING AROUND TO AFFECT THE
LOCAL AREA EARLY IN THE WEEK BEFORE THE UPPER LOW IN OVER THE
AREA...AND THEN AS AN UPPER TROUGH TAKES UP SEMI PERMANENT
RESIDENCE OVER THE GREAT LAKES LATE WEEK.
STRONG WAA OCCURS AHEAD OF THE UPPER LOW DURING SAT AND SUN AND
WITH THE CORE OF THE WARM AIR OVER THE REGION ON SUN. WITH PARTLY
TO MOSTLY SUNNY SKIES TEMPERATURES ARE EXPECTED TO BE INTO THE
MID AND UPPER 80S. INCREASED CLOUDINESS WILL LIMIT HIGH
TEMPERATURES MON TO THE LOWER AND MID 80S. MIDWEEK AS THE UPPER
LOW/TROUGH MOVE OVER AND PAST THE AREA COOLER AIR WILL SPREAD S
AND SE OVER THE AREA. CONSIDERABLE CLOUDINESS AND SHOWERS WILL
KEEP AFTERNOON TEMPERATURES LIMITED TO LOWER AND MID 70S BY WED
AND UPPER 60S AND LOWER 70S ON THU.
TRS
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 20Z...
* ISOLD-SCT SHRA/TSRA TO THE WEST AND SOUTH WHICH MAY REACH MDW
LATE AFTERNOON...WITH LOWER CHANCE OF REACHING ORD.
* NORTHEAST WINDS 10-12KT WITH SOME GUSTS NEAR 20 KT AT
TIMES...TRENDING MORE EASTERLY LATE AFTERNOON.
* MVFR CIGS/VSBY POSSIBLE LATE TONIGHT/EARLY SATURDAY MORNING.
MDB
//DISCUSSION...UPDATED 20Z...
BAND OF SCATTERED SHRA/TSRA FROM ENE OF KVYS TO KC09 TO KRZL
CONTINUES TO LIFT NORTHWARD AT 20Z. LAKE REINFORCED BOUNDARY IS
POSITIONED NEAR THE LEADING EDGE OF THE ACTIVITY AND WITH MUCH MORE
STABLE AIR TO ITS NORTH SO THE NORTHWARD PUSH MAY BE LIMITED. WILL
REMOVE TS MENTION FROM MDW WITH THE CHANCE FOR TSRA ONLY AROUND 30
PERCENT IF THAT...WITH A BETTER CHANCE FOR JUST SHRA SO WILL KEEP
TEMPO FOR SHRA FOR NOW. GYY STILL HAS A FAIR CHANCE FOR TSRA GIVEN
THAT THE BOUNDARY ARCS BACK TO THE LAKESHORE JUST TO THE EAST SO
UNSTABLE AIR IS NEARBY...AND OUT FLOW FROM CELLS NEAR IKK MAY PUSH
THAT PORTION OF THE BOUNDARY NORTHWARD SOMEWHAT. CHANCES FOR
SHRA/TSRA AT ORD ARE LOWER...PROBABLY LESS THAN 30 PERCENT SO
REMOVED VCTS MENTION BUT BRIEF SHRA IS POSSIBLE LATE THIS AFTERNOON.
RFD LOOKS TO BE IN A SIMILAR SITUATION BUT WITH A BETTER CHANCE FOR
SHRA AND A REDUCED CHANCE FOR TSRA. ANY BETTER ORGANIZED SHRA/TSRA
THAT DOES PASS OVER A TERMINAL WILL LIKELY DROP VSBY TO IFR FOR A
SHORT PERIOD. WINDS REMAIN A CHALLENGE WITH THE BOUNDARY IN THE AREA
AND POTENTIAL OUTFLOWS FROM CONVECTION. STILL FAVOR THE PREVAILING
NORTHEAST TO EAST DIRECTION THROUGH THE EVENING HOWEVER.
FROM 18Z...
COMPLEX FORECAST CONTINUES WITH LAKE MICHIGAN HELPING TO PUSH A
FRONTAL BOUNDARY SOUTHWESTWARD ACROSS THE CHICAGO/NW INDIANA METRO
AREA. THIS HAS RESULTED IN A SHIFT TO STEADY NORTHEAST WINDS AT
ORD/MDW/DPA AND GYY SHORTLY WITH SOME GUSTS TO NEAR 20 KT. WINDS
SHOULD STAY NORTHEASTERLY FOR THE NEXT FEW HOURS AND TREND MORE
EASTERLY THROUGH THE AFTERNOON BUT THIS MAY BE SLOWER TO OCCUR
THAN FORECAST. SHRA/TSRA HAS BEGUN TO DEVELOP SOUTH OF THE
TERMINALS AND WILL BE MOVING NORTHWARD THROUGH THE AFTERNOON. ONE
QUESTION IS HOW FAR NORTH IT WILL BE ABLE TO MAKE IT NOW THAT THE
FRONTAL BOUNDARY HAS PUSHED THROUGH THE TERMINALS. AM THINKING
THAT THE BOUNDARY ITSELF MAY ACT TO TRIGGER MORE STORMS BUT THAT
IT WILL NEED TO MOVE FURTHER SOUTH TOWARD/PAST JOT/KC09 WHERE THE
NORTHERN EDGE OF DECENT INSTABILITY EXISTS IN ORDER TO DO SO. WILL
CONTINUE WITH THE IDEA OF THE HIGHEST POTENTIAL AT GYY AND MDW AND
INCLUDE TEMPO TS THERE BY MID AFTERNOON. ORD/DPA/RFD HAVE A CHANCE
AS WELL BUT IT IS MUCH LESS CLEAR WHETHER OR NOT THEY WILL BE
DIRECTLY AFFECTED. WHERE SHRA/TSRA DO PASS OVER THEN BRIEF IFR
VSBY IS POSSIBLE IN HEAVY DOWNPOURS.
SHRA/TSRA ACTIVITY WILL WANE THIS EVENING AND WINDS WILL LIKELY
REMAIN EAST OR EAST-NORTHEAST FOR THE MOST PART BUT MAY TURN
SOUTHEAST OVERNIGHT. BETTER LOW LEVEL MOISTURE WILL BE IN
PLACE..ESPECIALLY IF RAIN CAN FALL...AND MVFR VSBY IS A DECENT
POSSIBILITY TOWARD DAYBREAK. SCT-BKN MVFR CLOUDS MAY ALSO DEVELOP
DURING THIS TIME. EXPECT THAT ANY MVFR VSBY/CIGS WOULD IMPROVE
AFTER DAYBREAK. WINDS WILL CONTINUE TO BE TRICKY WITH A EASTERLY
DIRECTION CONTINUING WITH VARIABILITY LIKELY.
MDB
//ORD AND MDW CONFIDENCE...UPDATED 20Z...
* HIGH CONFIDENCE IN SHRA/TSRA REMAINING MAINLY SOUTH OF THE
TERMINALS...LOW-MEDIUM CONFIDENCE IN ACTIVITY NEAR MDW THIS
AFTERNOON...MEDIUM CONFIDENCE THAT SHRA/TSRA POTENTIAL NEAR ORD
IS LOW.
* MEDIUM CONFIDENCE IN WIND TRENDS THROUGH THE PERIOD.
* MEDIUM CONFIDENCE IN MVFR VSBY LATE TONIGHT...LOW CONFIDENCE IN
MVFR CIG POTENTIAL.
MDB
//OUTLOOK FOR ORD/MDW FOR 00Z SUNDAY-12Z FRIDAY...UPDATED 12Z...
SATURDAY NIGHT...VFR.
SUNDAY THROUGH WEDNESDAY...VFR. PERIODIC CHANCES FOR SHRA/TSRA.
THURSDAY...VFR. PSBL MVFR WITH CHANCE FOR SHRA.
BEACHLER
&&
.MARINE...
206 PM CDT
A SURFACE RIDGE OF HIGH PRESSURE CONTINUES TO BUILD
EAST-SOUTHEASTWARD ACROSS ONTARIO AND THE CENTRAL AND EASTERN LAKES
THIS AFTERNOON. A HYBRID LAKE BREEZE/OUTFLOW BOUNDARY FROM
CONVECTION ACROSS WISCONSIN THIS MORNING HAS PUSHED ACROSS SOUTHERN
LAKE MICHIGAN EARLY THIS AFTERNOON. THIS LED TO A SUBSTANTIAL
INCREASE IN THE WINDS FOR A PERIOD OUT OF THE NORTH-NORTHEAST UP TO
25 TO 30 KT. THESE NORTHEAST WINDS UP TO AROUND 20 KT WILL CONTINUE
FOR THE NEXT FEW HOUR BEFORE SLOWLY EASING AND BECOMING MORE
EASTERLY TONIGHT.
A STORM SYSTEM IS EXPECTED TO TAKE SHAPE ACROSS THE HIGH PLAINS ON
SATURDAY BEFORE IT MOVES EAST-NORTHEASTWARD TOWARDS THE MID MISSOURI
VALLEY BY LATE SUNDAY. THIS SYSTEM LOOKS TO LIFT A WARM FRONT
NORTHWARD ACROSS AT LEAST THE SOUTHERN HALF TO TWO THIRDS OF THE
LAKE THROUGH MONDAY. BEHIND THIS FRONT WINDS LOOKS TO INCREASE OUT
OF THE SOUTH IN THE 15 TO 25 KT RANGE ON MONDAY. IT APPEARS THAT
THIS LOW WILL SLOWLY MOVE EASTWARD ACROSS THE MID MISSISSIPPI VALLEY
INTO MID WEEK AND THEN TO THE OHIO VALLEY LATER IN THE WEEK. THIS
SHOULD ALLOW THIS FRONT TO MOVE BACK SOUTH. DURING THIS TIME...THE
WINDS LOOK TO BECOME MORE NORTHERLY WITH TIME...ESPECIALLY BY MID TO
LATE WEEK AS THE SURFACE LOW PASSES TO THE SOUTH OF THE LAKE. THIS
COULD RESULT IN SOME STRONGER NORTHERLY WINDS BY LATE NEXT WEEK.
KJB
&&
.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 171907
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
207 PM CDT FRI MAY 17 2013
.MESOSCALE DISCUSSION...201 PM CDT
A CLUSTER OF STORMS IS TRYING TO TAKE SHAPE ACROSS THE SOUTHERN
PORTION OF THE CWA THIS AFTERNOON ALONG A STATIONARY SURFACE
BOUNDARY AND MOISTURE CONVERGENCE AXIS...BUT AT THIS TIME WE ARE NOT
EXPECTING ANYTHING SEVERE TO DEVELOP. LOCALIZED FLOODING WOULD BE
MORE OF A CONCERN. SFC-BASED CAPE VALUES HAVE REACHED SEVERAL
HUNDRED J/KG...BUT DEEP LAYER SHEAR IS VIRTUALLY NONEXISTENT...WITH
BOTH FORECAST AND LATEST ACARS SOUNDINGS FROM ORD SHOWING WINDS
THROUGH MOST OF THE TROPOSPHERE AT 20 KTS OR LESS.
STORMS THAT DO PULSE UP IN THIS LOW SHEAR AND MODERATE CAPE
ENVIRONMENT COULD POSE A HAIL OR WIND THREAT...BUT ACARS -20C
HEIGHTS AROUND 23 KFT PROVIDE AN IDEA OF HOW HIGH 60 DBZ ECHOES
WOULD HAVE TO GET TO SUPPORT SEVERE HAIL...AND STORMS SO FAR HAVE
ONLY BEEN REACHING HALF THAT LEVEL. FAIRLY SATURATED LOW LEVELS IN
FORECAST SOUNDINGS ALSO SUGGEST THE THREAT OF STRONG DOWNBURST WINDS
WOULD NOT BE HIGH. AGAIN...LOCALIZED FLOODING WOULD BE MORE OF A
CONCERN GIVEN THE COMBINATION OF SATURATED SOUNDINGS SOMEWHAT
TROPICAL IN NATURE...SLOW STORM MOTION...MINIMAL SHEAR...THE
PRESENCE OF A FOCUSING BOUNDARY...AND PRECIPITABLE WATER VALUES
AROUND 1.4 INCHES. AT THIS POINT THE STORMS ARE REMAINING GENERALLY
SCATTERED AND DISCRETE...AND HAVE NOT BEEN TRAINING. THESE WILL
CONTINUE TO BE MONITORED FOR ANY CHANGES AS WE PROGRESS THROUGH PEAK
MIDAFTERNOON HEATING.
LENNING
&&
.DISCUSSION...
428 AM CDT
EARLY THIS MORNING A STATIONARY FRONT RAN FROM NE IA...FAR NW AND
NE IL...AND NORTHERN IND. ND...NORTHEAST AND FAR NORTHWEST IL.
BOUNDARY POSITION IS WELL DEFINED BY BOTH WIND PATTERN AND LARGE
DIFFERENCE IN DEW POINTS ON OPPOSITE SIDES OF THE FRONT. AN UPPER
LOW WAS OVER THE EASTERN PORTION OF THE MO-AR BOARDER WHILE
A FEW DISTURBANCES...LIKELY CONVECTIVELY INDUCED...WERE JUST
UPSTREAM OF THE LOCAL FORECAST AREA.
THE FIRST DISTURBANCE WAS MOVING ACROSS FAR NW AND N CENTRAL IL
WITH A SECOND ALONG THE MN-IA BORDER AND A THIRD MOVING OVER THE
MID MO VALLEY FROM NEB E OVER FAR WESTERN IA. THESE DISTURBANCES
PRECEDED AN UPPER LOW MOVING E ALONG THE SD-NEB BOARDER.
THE FIRST DISTURBANCE DID PRODUCE A FEW SHOWERS AND THUNDERSTORMS
AS FAR E AS OVER THE FAR SW PORTION OF THE FA LAST EVENING AND
EARLIER THIS MORNING BUT HAD DISSIPATED AS THEY MOVED E INTO A
CAPPED AREA. THE SECOND DISTURBANCE. THE MAIN AREA OF CONVECTION
THAT HAD BEEN MOVING ACROSS IA HAD ALSO DISSIPATED AS IT MOVED
AWAY FROM THE BETTER ISENTROPIC LIFT RESULTING FROM MODERATELY
STRONG MID LEVEL WAA. THE THIRD DISTURBANCE HAS GENERATED AN
ELONGATED AREA OF THUNDERSTORMS ALONG THE MN-IA BORDER WHERE 30-35
KT SOUTHERLY FLOW IN THE 1.5 TO 3 KM AGL LAYER WAS MAXIMIZING LIFT
IN AN AREA OF RELATIVELY LARGE ELEVATED CAPE N OF THE STATIONARY
FRONT.
LATER TODAY THE CAP IS PROGGED TO BE REMOVED THOUGH FORECAST
TEMPERATURE PROFILES ARE NOT INDICATING AND SIGNIFICANT CAPE
AVAILABLE TO BE REALIZED. IN ADDITION...THE BEST ISENTROPIC LIFT
IS PROGGED TO MOVE ACROSS WI DURING THE DAY. STILL...THERE WILL BE
INCREASING CHANCES OF SHOWERS AND THUNDERSTORMS SPREADING W TO E
ACROSS THE LOCAL AREA DURING THE MORNING AS PERSISTING THROUGH THE
AFTERNOON AND EARLY EVENING AS THE SD-NEB UPPER LOW AND THE MO-AR
UPPER LOW MERGE AND MOVE TO OR SLIGHTLY E OF THE MID MS VALLEY BY
00Z. BEYOND THE FIRST PART OF THIS EVENING CHANCES OF PRECIP ARE
SMALL EXCEPT FOR THE FAR SE PORTION OF THE FA WHICH WILL STILL BE
UNDER THE INFLUENCE OF THE SLOW MOVING UPPER LOW WHICH IS PROGGED
TO BE OVER/NEAR THE LOWER OH VALLEY AT 12Z SAT.
THE UPPER PATTERN WILL BECOME MORE AMPLIFIED OVERNIGHT AND SAT
BEFORE BECOMING ZONAL E OF THE ROCKIES MID NEXT WEEK. WHILE THE
FLOW WILL BE AMPLIFIED THE FLOW WILL BE SLUGGISH AS AN UPPER
TROUGH MOVING OVER THE PACIFIC COAST EARLY THIS MORNING REACHES
THE ROCKIES LATE SAT-SAT NIGHT WHILE ANOTHER UPPER TROUGH OVER THE
N PACIFIC OFF THE B.C. COAST MOVES OVER PAC NW COAST. BY LATE SUN-
SUN NIGHT THE PAIR OF TROUGHS ARE PROGGED TO FORM AN UPPER LOW
OVER THE NORTHERN HIGH PLAINS. THIS UPPER LOW IS TO THEN VERY
SLOWLY MOVE E TO THE UPPER MIDWEST BY WED EVENING WHILE ALSO
GRADUALLY WEAKENING. HOWEVER...A FAIRLY STRONG SURFACE LOW IS
PROGGED TO MOVE E ACROSS THE NORTHERN PLAINS AND UPPER MS VALLEY
BEFORE THE UPPER SYSTEM WEAKENS AS DOES THE SURFACE REFLECTION.
DUE TO THE VERY SLOW EASTWARD PROGRESS OF THE SYSTEM A PROLONGED
PERIOD OF PERSISTENT RELATIVELY STRONG S TO SW LOWER LEVEL FLOW
WILL BE TRANSPORTING A CONTINUOUS STREAM OF MOISTURE FROM THE
WESTERN GULF UP ACROSS THE MID MS VALLEY AND TO THE UPPER MIDWEST
AND WESTERN GREAT LAKES.
WHILE THE MOST LIKELY TIME FRAME FOR RAIN IS LATER MON AND TUE AS
THIS IS WHEN SIGNIFICANT WARM AIR ADVECTION AND RESULTING UVV
ALONG WITH THE ARRIVAL OF ABUNDANT MOISTURE OCCURS...THERE WILL BE
CHANCES OF RAIN IN THE FORECAST FROM SUNDAY NIGHT RIGHT THROUGH
END OF NEXT WEEK...FIRST AS THE UPPER LOW APPROACHES THERE LIKELY
WILL BE SMALLER SCALE SHORT WAVES ROTATING AROUND TO AFFECT THE
LOCAL AREA EARLY IN THE WEEK BEFORE THE UPPER LOW IN OVER THE
AREA...AND THEN AS AN UPPER TROUGH TAKES UP SEMI PERMANENT
RESIDENCE OVER THE GREAT LAKES LATE WEEK.
STRONG WAA OCCURS AHEAD OF THE UPPER LOW DURING SAT AND SUN AND
WITH THE CORE OF THE WARM AIR OVER THE REGION ON SUN. WITH PARTLY
TO MOSTLY SUNNY SKIES TEMPERATURES ARE EXPECTED TO BE INTO THE
MID AND UPPER 80S. INCREASED CLOUDINESS WILL LIMIT HIGH
TEMPERATURES MON TO THE LOWER AND MID 80S. MIDWEEK AS THE UPPER
LOW/TROUGH MOVE OVER AND PAST THE AREA COOLER AIR WILL SPREAD S
AND SE OVER THE AREA. CONSIDERABLE CLOUDINESS AND SHOWERS WILL
KEEP AFTERNOON TEMPERATURES LIMITED TO LOWER AND MID 70S BY WED
AND UPPER 60S AND LOWER 70S ON THU.
TRS
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 18Z...
* ISOLD-SCT SHRA/TSRA DEVELOPING SOUTH OF THE TERMINALS NEXT 1-2
HRS...POSSIBLE AT OR NEAR TERMINALS MID AFTERNOON...ESPECIALLY
MDW.
* NORTHEAST WINDS 10-12KT WITH SOME GUSTS NEAR 20 KT AT
TIMES...TRENDING MORE EASTERLY LATE AFTERNOON.
* MVFR CIGS/VSBY POSSIBLE LATE TONIGHT/EARLY SATURDAY MORNING.
MDB
//DISCUSSION...UPDATED 18Z...
COMPLEX FORECAST CONTINUES WITH LAKE MICHIGAN HELPING TO PUSH A
FRONTAL BOUNDARY SOUTHWESTWARD ACROSS THE CHICAGO/NW INDIANA METRO
AREA. THIS HAS RESULTED IN A SHIFT TO STEADY NORTHEAST WINDS AT
ORD/MDW/DPA AND GYY SHORTLY WITH SOME GUSTS TO NEAR 20 KT. WINDS
SHOULD STAY NORTHEASTERLY FOR THE NEXT FEW HOURS AND TREND MORE
EASTERLY THROUGH THE AFTERNOON BUT THIS MAY BE SLOWER TO OCCUR
THAN FORECAST. SHRA/TSRA HAS BEGUN TO DEVELOP SOUTH OF THE
TERMINALS AND WILL BE MOVING NORTHWARD THROUGH THE AFTERNOON. ONE
QUESTION IS HOW FAR NORTH IT WILL BE ABLE TO MAKE IT NOW THAT THE
FRONTAL BOUNDARY HAS PUSHED THROUGH THE TERMINALS. AM THINKING
THAT THE BOUNDARY ITSELF MAY ACT TO TRIGGER MORE STORMS BUT THAT
IT WILL NEED TO MOVE FURTHER SOUTH TOWARD/PAST JOT/KC09 WHERE THE
NORTHERN EDGE OF DECENT INSTABILITY EXISTS IN ORDER TO DO SO. WILL
CONTINUE WITH THE IDEA OF THE HIGHEST POTENTIAL AT GYY AND MDW AND
INCLUDE TEMPO TS THERE BY MID AFTERNOON. ORD/DPA/RFD HAVE A CHANCE
AS WELL BUT IT IS MUCH LESS CLEAR WHETHER OR NOT THEY WILL BE
DIRECTLY AFFECTED. WHERE SHRA/TSRA DO PASS OVER THEN BRIEF IFR
VSBY IS POSSIBLE IN HEAVY DOWNPOURS.
SHRA/TSRA ACTIVITY WILL WANE THIS EVENING AND WINDS WILL LIKELY
REMAIN EAST OR EAST-NORTHEAST FOR THE MOST PART BUT MAY TURN
SOUTHEAST OVERNIGHT. BETTER LOW LEVEL MOISTURE WILL BE IN
PLACE..ESPECIALLY IF RAIN CAN FALL...AND MVFR VSBY IS A DECENT
POSSIBILITY TOWARD DAYBREAK. SCT-BKN MVFR CLOUDS MAY ALSO DEVELOP
DURING THIS TIME. EXPECT THAT ANY MVFR VSBY/CIGS WOULD IMPROVE
AFTER DAYBREAK. WINDS WILL CONTINUE TO BE TRICKY WITH A EASTERLY
DIRECTION CONTINUING WITH VARIABILITY LIKELY.
MDB
//ORD AND MDW CONFIDENCE...UPDATED 18Z...
* HIGH CONFIDENCE IN SHRA/TSRA DEVELOPING SOUTH OF THE TERMINALS
NEXT 1-2 HRS...LOW-MEDIUM CONFIDENCE IN ACTIVITY NEAR MDW THIS
AFTERNOON...LOW CONFIDENCE IN POTENTIAL NEAR ORD.
* MEDIUM CONFIDENCE IN WIND TRENDS THROUGH THE PERIOD.
* MEDIUM CONFIDENCE IN MVFR VSBY LATE TONIGHT...LOW CONFIDENCE IN
MVFR CIG POTENTIAL.
MDB
//OUTLOOK FOR ORD/MDW FOR 00Z SUNDAY-12Z FRIDAY...UPDATED 12Z...
SATURDAY NIGHT...VFR.
SUNDAY THROUGH WEDNESDAY...VFR. PERIODIC CHANCES FOR SHRA/TSRA.
THURSDAY...VFR. PSBL MVFR WITH CHANCE FOR SHRA.
BEACHLER
&&
.MARINE...
206 PM CDT
A SURFACE RIDGE OF HIGH PRESSURE CONTINUES TO BUILD
EAST-SOUTHEASTWARD ACROSS ONTARIO AND THE CENTRAL AND EASTERN LAKES
THIS AFTERNOON. A HYBRID LAKE BREEZE/OUTFLOW BOUNDARY FROM
CONVECTION ACROSS WISCONSIN THIS MORNING HAS PUSHED ACROSS SOUTHERN
LAKE MICHIGAN EARLY THIS AFTERNOON. THIS LED TO A SUBSTANTIAL
INCREASE IN THE WINDS FOR A PERIOD OUT OF THE NORTH-NORTHEAST UP TO
25 TO 30 KT. THESE NORTHEAST WINDS UP TO AROUND 20 KT WILL CONTINUE
FOR THE NEXT FEW HOUR BEFORE SLOWLY EASING AND BECOMING MORE
EASTERLY TONIGHT.
A STORM SYSTEM IS EXPECTED TO TAKE SHAPE ACROSS THE HIGH PLAINS ON
SATURDAY BEFORE IT MOVES EAST-NORTHEASTWARD TOWARDS THE MID MISSOURI
VALLEY BY LATE SUNDAY. THIS SYSTEM LOOKS TO LIFT A WARM FRONT
NORTHWARD ACROSS AT LEAST THE SOUTHERN HALF TO TWO THIRDS OF THE
LAKE THROUGH MONDAY. BEHIND THIS FRONT WINDS LOOKS TO INCREASE OUT
OF THE SOUTH IN THE 15 TO 25 KT RANGE ON MONDAY. IT APPEARS THAT
THIS LOW WILL SLOWLY MOVE EASTWARD ACROSS THE MID MISSISSIPPI VALLEY
INTO MID WEEK AND THEN TO THE OHIO VALLEY LATER IN THE WEEK. THIS
SHOULD ALLOW THIS FRONT TO MOVE BACK SOUTH. DURING THIS TIME...THE
WINDS LOOK TO BECOME MORE NORTHERLY WITH TIME...ESPECIALLY BY MID TO
LATE WEEK AS THE SURFACE LOW PASSES TO THE SOUTH OF THE LAKE. THIS
COULD RESULT IN SOME STRONGER NORTHERLY WINDS BY LATE NEXT WEEK.
KJB
&&
.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 171903
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
203 PM CDT FRI MAY 17 2013
.MESOSCALE DISCUSSION...
201 PM CDT
A CLUSTER OF STORMS IS TRYING TO TAKE SHAPE ACROSS THE SOUTHERN
PORTION OF THE CWA THIS AFTERNOON ALONG A STATIONARY SURFACE
BOUNDARY AND MOISTURE CONVERGENCE AXIS...BUT AT THIS TIME WE ARE NOT
EXPECTING ANYTHING SEVERE TO DEVELOP. LOCALIZED FLOODING WOULD BE
MORE OF A CONCERN. SFC-BASED CAPE VALUES HAVE REACHED SEVERAL
HUNDRED J/KG...BUT DEEP LAYER SHEAR IS VIRTUALLY NONEXISTENT...WITH
BOTH FORECAST AND LATEST ACARS SOUNDINGS FROM ORD SHOWING WINDS
THROUGH MOST OF THE TROPOSPHERE AT 20 KTS OR LESS.
STORMS THAT DO PULSE UP IN THIS LOW SHEAR AND MODERATE CAPE
ENVIRONMENT COULD POSE A HAIL OR WIND THREAT...BUT ACARS -20C
HEIGHTS AROUND 23 KFT PROVIDE AN IDEA OF HOW HIGH 60 DBZ ECHOES
WOULD HAVE TO GET TO SUPPORT SEVERE HAIL...AND STORMS SO FAR HAVE
ONLY BEEN REACHING HALF THAT LEVEL. FAIRLY SATURATED LOW LEVELS IN
FORECAST SOUNDINGS ALSO SUGGEST THE THREAT OF STRONG DOWNBURST WINDS
WOULD NOT BE HIGH. AGAIN...LOCALIZED FLOODING WOULD BE MORE OF A
CONCERN GIVEN THE COMBINATION OF SATURATED SOUNDINGS SOMEWHAT
TROPICAL IN NATURE...SLOW STORM MOTION...MINIMAL SHEAR...THE
PRESENCE OF A FOCUSING BOUNDARY...AND PRECIPITABLE WATER VALUES
AROUND 1.4 INCHES. AT THIS POINT THE STORMS ARE REMAINING GENERALLY
SCATTERED AND DISCRETE...AND HAVE NOT BEEN TRAINING. THESE WILL
CONTINUE TO BE MONITORED FOR ANY CHANGES AS WE PROGRESS THROUGH PEAK
MIDAFTERNOON HEATING.
LENNING
&&
.DISCUSSION...
428 AM CDT
EARLY THIS MORNING A STATIONARY FRONT RAN FROM NE IA...FAR NW AND
NE IL...AND NORTHERN IND. ND...NORTHEAST AND FAR NORTHWEST IL.
BOUNDARY POSITION IS WELL DEFINED BY BOTH WIND PATTERN AND LARGE
DIFFERENCE IN DEW POINTS ON OPPOSITE SIDES OF THE FRONT. AN UPPER
LOW WAS OVER THE EASTERN PORTION OF THE MO-AR BOARDER WHILE
A FEW DISTURBANCES...LIKELY CONVECTIVELY INDUCED...WERE JUST
UPSTREAM OF THE LOCAL FORECAST AREA.
THE FIRST DISTURBANCE WAS MOVING ACROSS FAR NW AND N CENTRAL IL
WITH A SECOND ALONG THE MN-IA BORDER AND A THIRD MOVING OVER THE
MID MO VALLEY FROM NEB E OVER FAR WESTERN IA. THESE DISTURBANCES
PRECEDED AN UPPER LOW MOVING E ALONG THE SD-NEB BOARDER.
THE FIRST DISTURBANCE DID PRODUCE A FEW SHOWERS AND THUNDERSTORMS
AS FAR E AS OVER THE FAR SW PORTION OF THE FA LAST EVENING AND
EARLIER THIS MORNING BUT HAD DISSIPATED AS THEY MOVED E INTO A
CAPPED AREA. THE SECOND DISTURBANCE. THE MAIN AREA OF CONVECTION
THAT HAD BEEN MOVING ACROSS IA HAD ALSO DISSIPATED AS IT MOVED
AWAY FROM THE BETTER ISENTROPIC LIFT RESULTING FROM MODERATELY
STRONG MID LEVEL WAA. THE THIRD DISTURBANCE HAS GENERATED AN
ELONGATED AREA OF THUNDERSTORMS ALONG THE MN-IA BORDER WHERE 30-35
KT SOUTHERLY FLOW IN THE 1.5 TO 3 KM AGL LAYER WAS MAXIMIZING LIFT
IN AN AREA OF RELATIVELY LARGE ELEVATED CAPE N OF THE STATIONARY
FRONT.
LATER TODAY THE CAP IS PROGGED TO BE REMOVED THOUGH FORECAST
TEMPERATURE PROFILES ARE NOT INDICATING AND SIGNIFICANT CAPE
AVAILABLE TO BE REALIZED. IN ADDITION...THE BEST ISENTROPIC LIFT
IS PROGGED TO MOVE ACROSS WI DURING THE DAY. STILL...THERE WILL BE
INCREASING CHANCES OF SHOWERS AND THUNDERSTORMS SPREADING W TO E
ACROSS THE LOCAL AREA DURING THE MORNING AS PERSISTING THROUGH THE
AFTERNOON AND EARLY EVENING AS THE SD-NEB UPPER LOW AND THE MO-AR
UPPER LOW MERGE AND MOVE TO OR SLIGHTLY E OF THE MID MS VALLEY BY
00Z. BEYOND THE FIRST PART OF THIS EVENING CHANCES OF PRECIP ARE
SMALL EXCEPT FOR THE FAR SE PORTION OF THE FA WHICH WILL STILL BE
UNDER THE INFLUENCE OF THE SLOW MOVING UPPER LOW WHICH IS PROGGED
TO BE OVER/NEAR THE LOWER OH VALLEY AT 12Z SAT.
THE UPPER PATTERN WILL BECOME MORE AMPLIFIED OVERNIGHT AND SAT
BEFORE BECOMING ZONAL E OF THE ROCKIES MID NEXT WEEK. WHILE THE
FLOW WILL BE AMPLIFIED THE FLOW WILL BE SLUGGISH AS AN UPPER
TROUGH MOVING OVER THE PACIFIC COAST EARLY THIS MORNING REACHES
THE ROCKIES LATE SAT-SAT NIGHT WHILE ANOTHER UPPER TROUGH OVER THE
N PACIFIC OFF THE B.C. COAST MOVES OVER PAC NW COAST. BY LATE SUN-
SUN NIGHT THE PAIR OF TROUGHS ARE PROGGED TO FORM AN UPPER LOW
OVER THE NORTHERN HIGH PLAINS. THIS UPPER LOW IS TO THEN VERY
SLOWLY MOVE E TO THE UPPER MIDWEST BY WED EVENING WHILE ALSO
GRADUALLY WEAKENING. HOWEVER...A FAIRLY STRONG SURFACE LOW IS
PROGGED TO MOVE E ACROSS THE NORTHERN PLAINS AND UPPER MS VALLEY
BEFORE THE UPPER SYSTEM WEAKENS AS DOES THE SURFACE REFLECTION.
DUE TO THE VERY SLOW EASTWARD PROGRESS OF THE SYSTEM A PROLONGED
PERIOD OF PERSISTENT RELATIVELY STRONG S TO SW LOWER LEVEL FLOW
WILL BE TRANSPORTING A CONTINUOUS STREAM OF MOISTURE FROM THE
WESTERN GULF UP ACROSS THE MID MS VALLEY AND TO THE UPPER MIDWEST
AND WESTERN GREAT LAKES.
WHILE THE MOST LIKELY TIME FRAME FOR RAIN IS LATER MON AND TUE AS
THIS IS WHEN SIGNIFICANT WARM AIR ADVECTION AND RESULTING UVV
ALONG WITH THE ARRIVAL OF ABUNDANT MOISTURE OCCURS...THERE WILL BE
CHANCES OF RAIN IN THE FORECAST FROM SUNDAY NIGHT RIGHT THROUGH
END OF NEXT WEEK...FIRST AS THE UPPER LOW APPROACHES THERE LIKELY
WILL BE SMALLER SCALE SHORT WAVES ROTATING AROUND TO AFFECT THE
LOCAL AREA EARLY IN THE WEEK BEFORE THE UPPER LOW IN OVER THE
AREA...AND THEN AS AN UPPER TROUGH TAKES UP SEMI PERMANENT
RESIDENCE OVER THE GREAT LAKES LATE WEEK.
STRONG WAA OCCURS AHEAD OF THE UPPER LOW DURING SAT AND SUN AND
WITH THE CORE OF THE WARM AIR OVER THE REGION ON SUN. WITH PARTLY
TO MOSTLY SUNNY SKIES TEMPERATURES ARE EXPECTED TO BE INTO THE
MID AND UPPER 80S. INCREASED CLOUDINESS WILL LIMIT HIGH
TEMPERATURES MON TO THE LOWER AND MID 80S. MIDWEEK AS THE UPPER
LOW/TROUGH MOVE OVER AND PAST THE AREA COOLER AIR WILL SPREAD S
AND SE OVER THE AREA. CONSIDERABLE CLOUDINESS AND SHOWERS WILL
KEEP AFTERNOON TEMPERATURES LIMITED TO LOWER AND MID 70S BY WED
AND UPPER 60S AND LOWER 70S ON THU.
TRS
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 18Z...
* ISOLD-SCT SHRA/TSRA DEVELOPING SOUTH OF THE TERMINALS NEXT 1-2
HRS...POSSIBLE AT OR NEAR TERMINALS MID AFTERNOON...ESPECIALLY
MDW.
* NORTHEAST WINDS 10-12KT WITH SOME GUSTS NEAR 20 KT AT
TIMES...TRENDING MORE EASTERLY LATE AFTERNOON.
* MVFR CIGS/VSBY POSSIBLE LATE TONIGHT/EARLY SATURDAY MORNING.
MDB
//DISCUSSION...UPDATED 18Z...
COMPLEX FORECAST CONTINUES WITH LAKE MICHIGAN HELPING TO PUSH A
FRONTAL BOUNDARY SOUTHWESTWARD ACROSS THE CHICAGO/NW INDIANA METRO
AREA. THIS HAS RESULTED IN A SHIFT TO STEADY NORTHEAST WINDS AT
ORD/MDW/DPA AND GYY SHORTLY WITH SOME GUSTS TO NEAR 20 KT. WINDS
SHOULD STAY NORTHEASTERLY FOR THE NEXT FEW HOURS AND TREND MORE
EASTERLY THROUGH THE AFTERNOON BUT THIS MAY BE SLOWER TO OCCUR
THAN FORECAST. SHRA/TSRA HAS BEGUN TO DEVELOP SOUTH OF THE
TERMINALS AND WILL BE MOVING NORTHWARD THROUGH THE AFTERNOON. ONE
QUESTION IS HOW FAR NORTH IT WILL BE ABLE TO MAKE IT NOW THAT THE
FRONTAL BOUNDARY HAS PUSHED THROUGH THE TERMINALS. AM THINKING
THAT THE BOUNDARY ITSELF MAY ACT TO TRIGGER MORE STORMS BUT THAT
IT WILL NEED TO MOVE FURTHER SOUTH TOWARD/PAST JOT/KC09 WHERE THE
NORTHERN EDGE OF DECENT INSTABILITY EXISTS IN ORDER TO DO SO. WILL
CONTINUE WITH THE IDEA OF THE HIGHEST POTENTIAL AT GYY AND MDW AND
INCLUDE TEMPO TS THERE BY MID AFTERNOON. ORD/DPA/RFD HAVE A CHANCE
AS WELL BUT IT IS MUCH LESS CLEAR WHETHER OR NOT THEY WILL BE
DIRECTLY AFFECTED. WHERE SHRA/TSRA DO PASS OVER THEN BRIEF IFR
VSBY IS POSSIBLE IN HEAVY DOWNPOURS.
SHRA/TSRA ACTIVITY WILL WANE THIS EVENING AND WINDS WILL LIKELY
REMAIN EAST OR EAST-NORTHEAST FOR THE MOST PART BUT MAY TURN
SOUTHEAST OVERNIGHT. BETTER LOW LEVEL MOISTURE WILL BE IN
PLACE..ESPECIALLY IF RAIN CAN FALL...AND MVFR VSBY IS A DECENT
POSSIBILITY TOWARD DAYBREAK. SCT-BKN MVFR CLOUDS MAY ALSO DEVELOP
DURING THIS TIME. EXPECT THAT ANY MVFR VSBY/CIGS WOULD IMPROVE
AFTER DAYBREAK. WINDS WILL CONTINUE TO BE TRICKY WITH A EASTERLY
DIRECTION CONTINUING WITH VARIABILITY LIKELY.
MDB
//ORD AND MDW CONFIDENCE...UPDATED 18Z...
* HIGH CONFIDENCE IN SHRA/TSRA DEVELOPING SOUTH OF THE TERMINALS
NEXT 1-2 HRS...LOW-MEDIUM CONFIDENCE IN ACTIVITY NEAR MDW THIS
AFTERNOON...LOW CONFIDENCE IN POTENTIAL NEAR ORD.
* MEDIUM CONFIDENCE IN WIND TRENDS THROUGH THE PERIOD.
* MEDIUM CONFIDENCE IN MVFR VSBY LATE TONIGHT...LOW CONFIDENCE IN
MVFR CIG POTENTIAL.
MDB
//OUTLOOK FOR ORD/MDW FOR 00Z SUNDAY-12Z FRIDAY...UPDATED 12Z...
SATURDAY NIGHT...VFR.
SUNDAY THROUGH WEDNESDAY...VFR. PERIODIC CHANCES FOR SHRA/TSRA.
THURSDAY...VFR. PSBL MVFR WITH CHANCE FOR SHRA.
BEACHLER
&&
.MARINE...
341 AM CDT
RIDGE OF HIGH PRESSURE HAS BECOME CENTERED NEAR JAMES BAY EARLY THIS
MORNING...EXPECTED TO DRIFT SOUTHEAST AND BECOME CENTERED NEAR
WESTERN QUEBEC TONIGHT. SOUTH OF THIS HIGH PRESSURE WAS A STALLED
FRONTAL BOUNDARY THAT STRETCHING ACROSS THE CENTRAL PLAINS INTO THE
OHIO VALLEY. ACROSS THE CENTRAL PLAINS AN AREA OF LOW PRESSURE IS
EXPECTED TO DEVELOP...THIS LOW PRESSURE WILL DRIFT NORTH AND BEGIN
TO LIFT THE STALLED FRONTAL BOUNDARY TO THE NORTH. THE GRADIENT
REMAINS RELATIVELY WEAK ACROSS THE LAKE...AND THIS APPEARS TO REMAIN
THROUGH THIS EVENING AS THE BOUNDARY BEGINS TO APPROACH THE SOUTHERN
PORTION OF THE LAKE. WINDS WILL GENERALLY BE NORTH/NORTHEAST OVER
THE LAKE...FURTHER SOUTH WINDS MAY START EASTERLY THEN BECOME
NORTHEASTERLY. THEN AS THE BOUNDARY SLIDES NORTH ACROSS THE SOUTHERN
PORTION OF THE LAKE...WINDS WILL BECOME EASTERLY. THE GRADIENT DOES
INCREASE MARGINALLY...AND MAY PRODUCE SPEEDS BETWEEN 10 TO 20 KT
SAT. LOW PRESSURE ACROSS THE CENTRAL PLAINS WILL DRIFT NORTH OVER
THE WEEKEND...AND THIS WILL ALLOW THE BOUNDARY TO STEADILY LIFT
NORTH ACROSS THE LAKE. AS THIS OCCURS...WINDS TO THE SOUTH OF THE
BOUNDARY WILL TURN SOUTHEASTERLY. MEANWHILE THE FAR NORTHERN
PORTIONS OF THE LAKE WILL BE NORTHEAST/EAST. EVENTUALLY THE NORTHERN
PORTIONS OF THE LAKE WILL BECOME SOUTHEAST WINDS...BUT THIS DOES NOT
OCCUR UNTIL CLOSER TO SUNDAY MORNING. THE SLOW MOVING LOW PRESSURE
SYSTEM WILL EVENTUALLY REACH THE WESTERN GREAT LAKES...HOWEVER THIS
DOES NOT APPEAR TO OCCUR UNTIL CLOSER TO WED OF NEXT WEEK. AS THE
LOW FINALLY LIFTS NORTHEAST OF LAKE MICHIGAN MID-WEEK...THE FRONTAL
BOUNDARY WILL PUSH SOUTH ACROSS THE LAKE. THIS WILL ALLOW WINDS TO
BECOME NORTHWEST TO NORTH.
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 171805
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
105 PM CDT FRI MAY 17 2013
.DISCUSSION...
428 AM CDT
EARLY THIS MORNING A STATIONARY FRONT RAN FROM NE IA...FAR NW AND
NE IL...AND NORTHERN IND. ND...NORTHEAST AND FAR NORTHWEST IL.
BOUNDARY POSITION IS WELL DEFINED BY BOTH WIND PATTERN AND LARGE
DIFFERENCE IN DEW POINTS ON OPPOSITE SIDES OF THE FRONT. AN UPPER
LOW WAS OVER THE EASTERN PORTION OF THE MO-AR BOARDER WHILE
A FEW DISTURBANCES...LIKELY CONVECTIVELY INDUCED...WERE JUST
UPSTREAM OF THE LOCAL FORECAST AREA.
THE FIRST DISTURBANCE WAS MOVING ACROSS FAR NW AND N CENTRAL IL
WITH A SECOND ALONG THE MN-IA BORDER AND A THIRD MOVING OVER THE
MID MO VALLEY FROM NEB E OVER FAR WESTERN IA. THESE DISTURBANCES
PRECEDED AN UPPER LOW MOVING E ALONG THE SD-NEB BOARDER.
THE FIRST DISTURBANCE DID PRODUCE A FEW SHOWERS AND THUNDERSTORMS
AS FAR E AS OVER THE FAR SW PORTION OF THE FA LAST EVENING AND
EARLIER THIS MORNING BUT HAD DISSIPATED AS THEY MOVED E INTO A
CAPPED AREA. THE SECOND DISTURBANCE. THE MAIN AREA OF CONVECTION
THAT HAD BEEN MOVING ACROSS IA HAD ALSO DISSIPATED AS IT MOVED
AWAY FROM THE BETTER ISENTROPIC LIFT RESULTING FROM MODERATELY
STRONG MID LEVEL WAA. THE THIRD DISTURBANCE HAS GENERATED AN
ELONGATED AREA OF THUNDERSTORMS ALONG THE MN-IA BORDER WHERE 30-35
KT SOUTHERLY FLOW IN THE 1.5 TO 3 KM AGL LAYER WAS MAXIMIZING LIFT
IN AN AREA OF RELATIVELY LARGE ELEVATED CAPE N OF THE STATIONARY
FRONT.
LATER TODAY THE CAP IS PROGGED TO BE REMOVED THOUGH FORECAST
TEMPERATURE PROFILES ARE NOT INDICATING AND SIGNIFICANT CAPE
AVAILABLE TO BE REALIZED. IN ADDITION...THE BEST ISENTROPIC LIFT
IS PROGGED TO MOVE ACROSS WI DURING THE DAY. STILL...THERE WILL BE
INCREASING CHANCES OF SHOWERS AND THUNDERSTORMS SPREADING W TO E
ACROSS THE LOCAL AREA DURING THE MORNING AS PERSISTING THROUGH THE
AFTERNOON AND EARLY EVENING AS THE SD-NEB UPPER LOW AND THE MO-AR
UPPER LOW MERGE AND MOVE TO OR SLIGHTLY E OF THE MID MS VALLEY BY
00Z. BEYOND THE FIRST PART OF THIS EVENING CHANCES OF PRECIP ARE
SMALL EXCEPT FOR THE FAR SE PORTION OF THE FA WHICH WILL STILL BE
UNDER THE INFLUENCE OF THE SLOW MOVING UPPER LOW WHICH IS PROGGED
TO BE OVER/NEAR THE LOWER OH VALLEY AT 12Z SAT.
THE UPPER PATTERN WILL BECOME MORE AMPLIFIED OVERNIGHT AND SAT
BEFORE BECOMING ZONAL E OF THE ROCKIES MID NEXT WEEK. WHILE THE
FLOW WILL BE AMPLIFIED THE FLOW WILL BE SLUGGISH AS AN UPPER
TROUGH MOVING OVER THE PACIFIC COAST EARLY THIS MORNING REACHES
THE ROCKIES LATE SAT-SAT NIGHT WHILE ANOTHER UPPER TROUGH OVER THE
N PACIFIC OFF THE B.C. COAST MOVES OVER PAC NW COAST. BY LATE SUN-
SUN NIGHT THE PAIR OF TROUGHS ARE PROGGED TO FORM AN UPPER LOW
OVER THE NORTHERN HIGH PLAINS. THIS UPPER LOW IS TO THEN VERY
SLOWLY MOVE E TO THE UPPER MIDWEST BY WED EVENING WHILE ALSO
GRADUALLY WEAKENING. HOWEVER...A FAIRLY STRONG SURFACE LOW IS
PROGGED TO MOVE E ACROSS THE NORTHERN PLAINS AND UPPER MS VALLEY
BEFORE THE UPPER SYSTEM WEAKENS AS DOES THE SURFACE REFLECTION.
DUE TO THE VERY SLOW EASTWARD PROGRESS OF THE SYSTEM A PROLONGED
PERIOD OF PERSISTENT RELATIVELY STRONG S TO SW LOWER LEVEL FLOW
WILL BE TRANSPORTING A CONTINUOUS STREAM OF MOISTURE FROM THE
WESTERN GULF UP ACROSS THE MID MS VALLEY AND TO THE UPPER MIDWEST
AND WESTERN GREAT LAKES.
WHILE THE MOST LIKELY TIME FRAME FOR RAIN IS LATER MON AND TUE AS
THIS IS WHEN SIGNIFICANT WARM AIR ADVECTION AND RESULTING UVV
ALONG WITH THE ARRIVAL OF ABUNDANT MOISTURE OCCURS...THERE WILL BE
CHANCES OF RAIN IN THE FORECAST FROM SUNDAY NIGHT RIGHT THROUGH
END OF NEXT WEEK...FIRST AS THE UPPER LOW APPROACHES THERE LIKELY
WILL BE SMALLER SCALE SHORT WAVES ROTATING AROUND TO AFFECT THE
LOCAL AREA EARLY IN THE WEEK BEFORE THE UPPER LOW IN OVER THE
AREA...AND THEN AS AN UPPER TROUGH TAKES UP SEMI PERMANENT
RESIDENCE OVER THE GREAT LAKES LATE WEEK.
STRONG WAA OCCURS AHEAD OF THE UPPER LOW DURING SAT AND SUN AND
WITH THE CORE OF THE WARM AIR OVER THE REGION ON SUN. WITH PARTLY
TO MOSTLY SUNNY SKIES TEMPERATURES ARE EXPECTED TO BE INTO THE
MID AND UPPER 80S. INCREASED CLOUDINESS WILL LIMIT HIGH
TEMPERATURES MON TO THE LOWER AND MID 80S. MIDWEEK AS THE UPPER
LOW/TROUGH MOVE OVER AND PAST THE AREA COOLER AIR WILL SPREAD S
AND SE OVER THE AREA. CONSIDERABLE CLOUDINESS AND SHOWERS WILL
KEEP AFTERNOON TEMPERATURES LIMITED TO LOWER AND MID 70S BY WED
AND UPPER 60S AND LOWER 70S ON THU.
TRS
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 18Z...
* ISOLD-SCT SHRA/TSRA DEVELOPING SOUTH OF THE TERMINALS NEXT 1-2
HRS...POSSIBLE AT OR NEAR TERMINALS MID AFTERNOON...ESPECIALLY
MDW.
* NORTHEAST WINDS 10-12KT WITH SOME GUSTS NEAR 20 KT AT
TIMES...TRENDING MORE EASTERLY LATE AFTERNOON.
* MVFR CIGS/VSBY POSSIBLE LATE TONIGHT/EARLY SATURDAY MORNING.
MDB
//DISCUSSION...UPDATED 18Z...
COMPLEX FORECAST CONTINUES WITH LAKE MICHIGAN HELPING TO PUSH A
FRONTAL BOUNDARY SOUTHWESTWARD ACROSS THE CHICAGO/NW INDIANA METRO
AREA. THIS HAS RESULTED IN A SHIFT TO STEADY NORTHEAST WINDS AT
ORD/MDW/DPA AND GYY SHORTLY WITH SOME GUSTS TO NEAR 20 KT. WINDS
SHOULD STAY NORTHEASTERLY FOR THE NEXT FEW HOURS AND TREND MORE
EASTERLY THROUGH THE AFTERNOON BUT THIS MAY BE SLOWER TO OCCUR
THAN FORECAST. SHRA/TSRA HAS BEGUN TO DEVELOP SOUTH OF THE
TERMINALS AND WILL BE MOVING NORTHWARD THROUGH THE AFTERNOON. ONE
QUESTION IS HOW FAR NORTH IT WILL BE ABLE TO MAKE IT NOW THAT THE
FRONTAL BOUNDARY HAS PUSHED THROUGH THE TERMINALS. AM THINKING
THAT THE BOUNDARY ITSELF MAY ACT TO TRIGGER MORE STORMS BUT THAT
IT WILL NEED TO MOVE FURTHER SOUTH TOWARD/PAST JOT/KC09 WHERE THE
NORTHERN EDGE OF DECENT INSTABILITY EXISTS IN ORDER TO DO SO. WILL
CONTINUE WITH THE IDEA OF THE HIGHEST POTENTIAL AT GYY AND MDW AND
INCLUDE TEMPO TS THERE BY MID AFTERNOON. ORD/DPA/RFD HAVE A CHANCE
AS WELL BUT IT IS MUCH LESS CLEAR WHETHER OR NOT THEY WILL BE
DIRECTLY AFFECTED. WHERE SHRA/TSRA DO PASS OVER THEN BRIEF IFR
VSBY IS POSSIBLE IN HEAVY DOWNPOURS.
SHRA/TSRA ACTIVITY WILL WANE THIS EVENING AND WINDS WILL LIKELY
REMAIN EAST OR EAST-NORTHEAST FOR THE MOST PART BUT MAY TURN
SOUTHEAST OVERNIGHT. BETTER LOW LEVEL MOISTURE WILL BE IN
PLACE..ESPECIALLY IF RAIN CAN FALL...AND MVFR VSBY IS A DECENT
POSSIBILITY TOWARD DAYBREAK. SCT-BKN MVFR CLOUDS MAY ALSO DEVELOP
DURING THIS TIME. EXPECT THAT ANY MVFR VSBY/CIGS WOULD IMPROVE
AFTER DAYBREAK. WINDS WILL CONTINUE TO BE TRICKY WITH A EASTERLY
DIRECTION CONTINUING WITH VARIABILITY LIKELY.
MDB
//ORD AND MDW CONFIDENCE...UPDATED 18Z...
* HIGH CONFIDENCE IN SHRA/TSRA DEVELOPING SOUTH OF THE TERMINALS
NEXT 1-2 HRS...LOW-MEDIUM CONFIDENCE IN ACTIVITY NEAR MDW THIS
AFTERNOON...LOW CONFIDENCE IN POTENTIAL NEAR ORD.
* MEDIUM CONFIDENCE IN WIND TRENDS THROUGH THE PERIOD.
* MEDIUM CONFIDENCE IN MVFR VSBY LATE TONIGHT...LOW CONFIDENCE IN
MVFR CIG POTENTIAL.
MDB
//OUTLOOK FOR ORD/MDW FOR 00Z SUNDAY-12Z FRIDAY...UPDATED 12Z...
SATURDAY NIGHT...VFR.
SUNDAY THROUGH WEDNESDAY...VFR. PERIODIC CHANCES FOR SHRA/TSRA.
THURSDAY...VFR. PSBL MVFR WITH CHANCE FOR SHRA.
BEACHLER
&&
.MARINE...
341 AM CDT
RIDGE OF HIGH PRESSURE HAS BECOME CENTERED NEAR JAMES BAY EARLY THIS
MORNING...EXPECTED TO DRIFT SOUTHEAST AND BECOME CENTERED NEAR
WESTERN QUEBEC TONIGHT. SOUTH OF THIS HIGH PRESSURE WAS A STALLED
FRONTAL BOUNDARY THAT STRETCHING ACROSS THE CENTRAL PLAINS INTO THE
OHIO VALLEY. ACROSS THE CENTRAL PLAINS AN AREA OF LOW PRESSURE IS
EXPECTED TO DEVELOP...THIS LOW PRESSURE WILL DRIFT NORTH AND BEGIN
TO LIFT THE STALLED FRONTAL BOUNDARY TO THE NORTH. THE GRADIENT
REMAINS RELATIVELY WEAK ACROSS THE LAKE...AND THIS APPEARS TO REMAIN
THROUGH THIS EVENING AS THE BOUNDARY BEGINS TO APPROACH THE SOUTHERN
PORTION OF THE LAKE. WINDS WILL GENERALLY BE NORTH/NORTHEAST OVER
THE LAKE...FURTHER SOUTH WINDS MAY START EASTERLY THEN BECOME
NORTHEASTERLY. THEN AS THE BOUNDARY SLIDES NORTH ACROSS THE SOUTHERN
PORTION OF THE LAKE...WINDS WILL BECOME EASTERLY. THE GRADIENT DOES
INCREASE MARGINALLY...AND MAY PRODUCE SPEEDS BETWEEN 10 TO 20 KT
SAT. LOW PRESSURE ACROSS THE CENTRAL PLAINS WILL DRIFT NORTH OVER
THE WEEKEND...AND THIS WILL ALLOW THE BOUNDARY TO STEADILY LIFT
NORTH ACROSS THE LAKE. AS THIS OCCURS...WINDS TO THE SOUTH OF THE
BOUNDARY WILL TURN SOUTHEASTERLY. MEANWHILE THE FAR NORTHERN
PORTIONS OF THE LAKE WILL BE NORTHEAST/EAST. EVENTUALLY THE NORTHERN
PORTIONS OF THE LAKE WILL BECOME SOUTHEAST WINDS...BUT THIS DOES NOT
OCCUR UNTIL CLOSER TO SUNDAY MORNING. THE SLOW MOVING LOW PRESSURE
SYSTEM WILL EVENTUALLY REACH THE WESTERN GREAT LAKES...HOWEVER THIS
DOES NOT APPEAR TO OCCUR UNTIL CLOSER TO WED OF NEXT WEEK. AS THE
LOW FINALLY LIFTS NORTHEAST OF LAKE MICHIGAN MID-WEEK...THE FRONTAL
BOUNDARY WILL PUSH SOUTH ACROSS THE LAKE. THIS WILL ALLOW WINDS TO
BECOME NORTHWEST TO NORTH.
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 171627
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1127 AM CDT FRI MAY 17 2013
.DISCUSSION...
428 AM CDT
EARLY THIS MORNING A STATIONARY FRONT RAN FROM NE IA...FAR NW AND
NE IL...AND NORTHERN IND. ND...NORTHEAST AND FAR NORTHWEST IL.
BOUNDARY POSITION IS WELL DEFINED BY BOTH WIND PATTERN AND LARGE
DIFFERENCE IN DEW POINTS ON OPPOSITE SIDES OF THE FRONT. AN UPPER
LOW WAS OVER THE EASTERN PORTION OF THE MO-AR BOARDER WHILE
A FEW DISTURBANCES...LIKELY CONVECTIVELY INDUCED...WERE JUST
UPSTREAM OF THE LOCAL FORECAST AREA.
THE FIRST DISTURBANCE WAS MOVING ACROSS FAR NW AND N CENTRAL IL
WITH A SECOND ALONG THE MN-IA BORDER AND A THIRD MOVING OVER THE
MID MO VALLEY FROM NEB E OVER FAR WESTERN IA. THESE DISTURBANCES
PRECEDED AN UPPER LOW MOVING E ALONG THE SD-NEB BOARDER.
THE FIRST DISTURBANCE DID PRODUCE A FEW SHOWERS AND THUNDERSTORMS
AS FAR E AS OVER THE FAR SW PORTION OF THE FA LAST EVENING AND
EARLIER THIS MORNING BUT HAD DISSIPATED AS THEY MOVED E INTO A
CAPPED AREA. THE SECOND DISTURBANCE. THE MAIN AREA OF CONVECTION
THAT HAD BEEN MOVING ACROSS IA HAD ALSO DISSIPATED AS IT MOVED
AWAY FROM THE BETTER ISENTROPIC LIFT RESULTING FROM MODERATELY
STRONG MID LEVEL WAA. THE THIRD DISTURBANCE HAS GENERATED AN
ELONGATED AREA OF THUNDERSTORMS ALONG THE MN-IA BORDER WHERE 30-35
KT SOUTHERLY FLOW IN THE 1.5 TO 3 KM AGL LAYER WAS MAXIMIZING LIFT
IN AN AREA OF RELATIVELY LARGE ELEVATED CAPE N OF THE STATIONARY
FRONT.
LATER TODAY THE CAP IS PROGGED TO BE REMOVED THOUGH FORECAST
TEMPERATURE PROFILES ARE NOT INDICATING AND SIGNIFICANT CAPE
AVAILABLE TO BE REALIZED. IN ADDITION...THE BEST ISENTROPIC LIFT
IS PROGGED TO MOVE ACROSS WI DURING THE DAY. STILL...THERE WILL BE
INCREASING CHANCES OF SHOWERS AND THUNDERSTORMS SPREADING W TO E
ACROSS THE LOCAL AREA DURING THE MORNING AS PERSISTING THROUGH THE
AFTERNOON AND EARLY EVENING AS THE SD-NEB UPPER LOW AND THE MO-AR
UPPER LOW MERGE AND MOVE TO OR SLIGHTLY E OF THE MID MS VALLEY BY
00Z. BEYOND THE FIRST PART OF THIS EVENING CHANCES OF PRECIP ARE
SMALL EXCEPT FOR THE FAR SE PORTION OF THE FA WHICH WILL STILL BE
UNDER THE INFLUENCE OF THE SLOW MOVING UPPER LOW WHICH IS PROGGED
TO BE OVER/NEAR THE LOWER OH VALLEY AT 12Z SAT.
THE UPPER PATTERN WILL BECOME MORE AMPLIFIED OVERNIGHT AND SAT
BEFORE BECOMING ZONAL E OF THE ROCKIES MID NEXT WEEK. WHILE THE
FLOW WILL BE AMPLIFIED THE FLOW WILL BE SLUGGISH AS AN UPPER
TROUGH MOVING OVER THE PACIFIC COAST EARLY THIS MORNING REACHES
THE ROCKIES LATE SAT-SAT NIGHT WHILE ANOTHER UPPER TROUGH OVER THE
N PACIFIC OFF THE B.C. COAST MOVES OVER PAC NW COAST. BY LATE SUN-
SUN NIGHT THE PAIR OF TROUGHS ARE PROGGED TO FORM AN UPPER LOW
OVER THE NORTHERN HIGH PLAINS. THIS UPPER LOW IS TO THEN VERY
SLOWLY MOVE E TO THE UPPER MIDWEST BY WED EVENING WHILE ALSO
GRADUALLY WEAKENING. HOWEVER...A FAIRLY STRONG SURFACE LOW IS
PROGGED TO MOVE E ACROSS THE NORTHERN PLAINS AND UPPER MS VALLEY
BEFORE THE UPPER SYSTEM WEAKENS AS DOES THE SURFACE REFLECTION.
DUE TO THE VERY SLOW EASTWARD PROGRESS OF THE SYSTEM A PROLONGED
PERIOD OF PERSISTENT RELATIVELY STRONG S TO SW LOWER LEVEL FLOW
WILL BE TRANSPORTING A CONTINUOUS STREAM OF MOISTURE FROM THE
WESTERN GULF UP ACROSS THE MID MS VALLEY AND TO THE UPPER MIDWEST
AND WESTERN GREAT LAKES.
WHILE THE MOST LIKELY TIME FRAME FOR RAIN IS LATER MON AND TUE AS
THIS IS WHEN SIGNIFICANT WARM AIR ADVECTION AND RESULTING UVV
ALONG WITH THE ARRIVAL OF ABUNDANT MOISTURE OCCURS...THERE WILL BE
CHANCES OF RAIN IN THE FORECAST FROM SUNDAY NIGHT RIGHT THROUGH
END OF NEXT WEEK...FIRST AS THE UPPER LOW APPROACHES THERE LIKELY
WILL BE SMALLER SCALE SHORT WAVES ROTATING AROUND TO AFFECT THE
LOCAL AREA EARLY IN THE WEEK BEFORE THE UPPER LOW IN OVER THE
AREA...AND THEN AS AN UPPER TROUGH TAKES UP SEMI PERMANENT
RESIDENCE OVER THE GREAT LAKES LATE WEEK.
STRONG WAA OCCURS AHEAD OF THE UPPER LOW DURING SAT AND SUN AND
WITH THE CORE OF THE WARM AIR OVER THE REGION ON SUN. WITH PARTLY
TO MOSTLY SUNNY SKIES TEMPERATURES ARE EXPECTED TO BE INTO THE
MID AND UPPER 80S. INCREASED CLOUDINESS WILL LIMIT HIGH
TEMPERATURES MON TO THE LOWER AND MID 80S. MIDWEEK AS THE UPPER
LOW/TROUGH MOVE OVER AND PAST THE AREA COOLER AIR WILL SPREAD S
AND SE OVER THE AREA. CONSIDERABLE CLOUDINESS AND SHOWERS WILL
KEEP AFTERNOON TEMPERATURES LIMITED TO LOWER AND MID 70S BY WED
AND UPPER 60S AND LOWER 70S ON THU.
TRS
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 16Z...
* ISOLATED SHOWERS/THUNDERSTORMS SOUTHWEST OF TERMINALS DEVELOPING
TOWARD MIDDAY. PSBL VCTS THIS AFTERNOON.
* LIGHT AND VARIABLE WINDS TRENDING EASTERLY WITH SPEEDS COMING UP
TO AROUND 10-12 KT.
* CIGS REMAIN VFR...PATCHY MVFR CIGS WITH THUNDERSTORMS.
MDB
//DISCUSSION...UPDATED 16Z...
FORECAST DETAILS REMAIN TRICKY IN TERMS OF WINDS AND TS
POTENTIAL/COVERAGE THROUGH THE AFTERNOON. SURFACE ANALYSIS SHOWS
WEAK LOW PRESSURE OVER EASTERN MISSOURI WITH A SMALLER WEAK
CIRCULATION SUGGESTED BY WIND DIRECTION OBS IN THE RFD-FEP-SQI
AREA. A BOUNDARY IS ALSO ANALYZED FROM NORTHEAST IOWA INTO THE
SOUTHERN CHICAGO METRO AREA. THIS IS HAVING A LARGE IMPACT ON WIND
DIRECTION/SPEED TRENDS. ORD/RFD/DPA/MDW CONTINUE TO FAVOR LIGHT
AND VARIABLE OR EAST TO NORTHEAST WINDS WHERE GYY HAS TRENDED
SOUTHEAST. THIS WILL PROBABLY BE THE TREND FOR THE NEXT SEVERAL
HOURS BEFORE TRENDING MORE EASTERLY WITH A STEADIER SPEED.
IN TERMS OF TS POTENTIAL...HAVE SLOWED VCTS MENTION SLIGHTLY AND
AM STILL EXPECTING ISOLATED TO SCATTERED TS DEVELOPMENT THIS
AFTERNOON. IT STILL APPEARS THAT THE FAVORED AREA WILL BE JUST
SOUTH AND WEST OF THE TERMINALS TOWARD MID AFTERNOON WITH THE
FRONTAL BOUNDARY NEARBY AND AN UPPER LEVEL LOW PASSING TO THE
SOUTH. GYY AND MDW MAY HAVE THE BEST POTENTIAL OVERALL.
MDB
FROM 12Z...
COMPLEX OF THUNDERSTORMS ACROSS NORTHEAST IOWA/WEST CENTRAL
WISCONSIN CONTINUE TO DRIFT NORTHEAST THIS MORNING...AND NOT
EXPECTED TO IMPACT DIRECTLY ANY OF THE NORTHERN IL/NORTHWEST IN
AIRFIELDS. STALLED FRONTAL BOUNDARY REMAINS SOUTHWEST OF THE TAF
SITES THIS MORNING...AND SHOULD ONLY LIFT NORTH SLIGHTLY
THROUGHOUT THE DAY TODAY. CIGS REMAIN VFR WITH BASES GENERALLY
AROUND 8-10KFT AGL. GUIDANCE CONTINUES TO SUGGEST VFR CONDS WILL
PREVAIL FOR MUCH OF THE DAY...PSBLY INTO TONIGHT. WITH THE
BOUNDARY REMAINING SOUTH OF THE TAF SITES...WINDS ARE NOT EXPECTED
TO CHANGE MUCH THROUGHOUT THE DAY/AFTN. WILL REMAIN ARND A 060-090
DEG RANGE WITH SPEEDS SHOWING SOME INCREASE THIS AFTN. IT APPEARS
SOME OCCASIONAL GUSTS MAY OCCUR THIS AFTN...TO 18KT. OTHERWISE
SPEEDS WILL BE ARND 8 TO 12 KT.
THE BEST CHC FOR PRECIP WILL OCCUR SOUTHWEST OF THE TAF SITES THRU
MUCH OF THE MORNING...WITH MINIMAL COVERAGE. BY MIDDAY COVERAGE
SHUD BEGIN TO INCREASE IN SHOWERS/THUNDERSTORMS...HOWEVER IT STILL
APPEARS THE BEST INSTABILITY WILL BE FOCUSED WITH THE BOUNDARY AND
THIS WILL BE JUST WEST/SOUTHWEST OF THE TAF SITES. HOWEVER...HAVE
INCLUDED A MENTION OF VCTS AS SOME STORMS COULD BE RATHER CLOSE TO
THE AIRFIELDS. THEN IT APPEARS ANY PRECIP WILL PUSH BACK TO THE
WEST/SOUTHWEST OF THE AIRFIELDS...WITH A SMALL CHC OF PRECIP
CONTINUING THROUGH THE EVENING HOURS. WINDS WILL EVENTUALLY BEGIN
TO TURN SOUTHEASTERLY ONCE THE BOUNDARY LIFTS OVERHEAD AND TO THE
NORTH OF THE TAF SITES...HOWEVER THIS DOES NOT APPEAR TO OCCUR
UNTIL AFT 05Z SAT.
BEACHLER
//ORD AND MDW CONFIDENCE...UPDATED 16Z...
* LOW CONFIDENCE IN SHRA/TSRA TIMING/COVERAGE.
* MEDIUM-HIGH CONFIDENCE IN WIND SPEED/DIRECTION TRENDS.
* HIGH CONFIDENCE IN PREVAILING VFR CIGS WITH BRIEF MVFR CIGS
POSSIBLE IN TSRA.
MDB
//OUTLOOK FOR ORD/MDW FOR 00Z SUNDAY-12Z FRIDAY...UPDATED 12Z...
SATURDAY NIGHT...VFR.
SUNDAY THROUGH WEDNESDAY...VFR. PERIODIC CHANCES FOR SHRA/TSRA.
THURSDAY...VFR. PSBL MVFR WITH CHANCE FOR SHRA.
BEACHLER
&&
.MARINE...
341 AM CDT
RIDGE OF HIGH PRESSURE HAS BECOME CENTERED NEAR JAMES BAY EARLY THIS
MORNING...EXPECTED TO DRIFT SOUTHEAST AND BECOME CENTERED NEAR
WESTERN QUEBEC TONIGHT. SOUTH OF THIS HIGH PRESSURE WAS A STALLED
FRONTAL BOUNDARY THAT STRETCHING ACROSS THE CENTRAL PLAINS INTO THE
OHIO VALLEY. ACROSS THE CENTRAL PLAINS AN AREA OF LOW PRESSURE IS
EXPECTED TO DEVELOP...THIS LOW PRESSURE WILL DRIFT NORTH AND BEGIN
TO LIFT THE STALLED FRONTAL BOUNDARY TO THE NORTH. THE GRADIENT
REMAINS RELATIVELY WEAK ACROSS THE LAKE...AND THIS APPEARS TO REMAIN
THROUGH THIS EVENING AS THE BOUNDARY BEGINS TO APPROACH THE SOUTHERN
PORTION OF THE LAKE. WINDS WILL GENERALLY BE NORTH/NORTHEAST OVER
THE LAKE...FURTHER SOUTH WINDS MAY START EASTERLY THEN BECOME
NORTHEASTERLY. THEN AS THE BOUNDARY SLIDES NORTH ACROSS THE SOUTHERN
PORTION OF THE LAKE...WINDS WILL BECOME EASTERLY. THE GRADIENT DOES
INCREASE MARGINALLY...AND MAY PRODUCE SPEEDS BETWEEN 10 TO 20 KT
SAT. LOW PRESSURE ACROSS THE CENTRAL PLAINS WILL DRIFT NORTH OVER
THE WEEKEND...AND THIS WILL ALLOW THE BOUNDARY TO STEADILY LIFT
NORTH ACROSS THE LAKE. AS THIS OCCURS...WINDS TO THE SOUTH OF THE
BOUNDARY WILL TURN SOUTHEASTERLY. MEANWHILE THE FAR NORTHERN
PORTIONS OF THE LAKE WILL BE NORTHEAST/EAST. EVENTUALLY THE NORTHERN
PORTIONS OF THE LAKE WILL BECOME SOUTHEAST WINDS...BUT THIS DOES NOT
OCCUR UNTIL CLOSER TO SUNDAY MORNING. THE SLOW MOVING LOW PRESSURE
SYSTEM WILL EVENTUALLY REACH THE WESTERN GREAT LAKES...HOWEVER THIS
DOES NOT APPEAR TO OCCUR UNTIL CLOSER TO WED OF NEXT WEEK. AS THE
LOW FINALLY LIFTS NORTHEAST OF LAKE MICHIGAN MID-WEEK...THE FRONTAL
BOUNDARY WILL PUSH SOUTH ACROSS THE LAKE. THIS WILL ALLOW WINDS TO
BECOME NORTHWEST TO NORTH.
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 171405
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
905 AM CDT FRI MAY 17 2013
.DISCUSSION...
428 AM CDT
EARLY THIS MORNING A STATIONARY FRONT RAN FROM NE IA...FAR NW AND
NE IL...AND NORTHERN IND. ND...NORTHEAST AND FAR NORTHWEST IL.
BOUNDARY POSITION IS WELL DEFINED BY BOTH WIND PATTERN AND LARGE
DIFFERENCE IN DEW POINTS ON OPPOSITE SIDES OF THE FRONT. AN UPPER
LOW WAS OVER THE EASTERN PORTION OF THE MO-AR BOARDER WHILE
A FEW DISTURBANCES...LIKELY CONVECTIVELY INDUCED...WERE JUST
UPSTREAM OF THE LOCAL FORECAST AREA.
THE FIRST DISTURBANCE WAS MOVING ACROSS FAR NW AND N CENTRAL IL
WITH A SECOND ALONG THE MN-IA BORDER AND A THIRD MOVING OVER THE
MID MO VALLEY FROM NEB E OVER FAR WESTERN IA. THESE DISTURBANCES
PRECEDED AN UPPER LOW MOVING E ALONG THE SD-NEB BOARDER.
THE FIRST DISTURBANCE DID PRODUCE A FEW SHOWERS AND THUNDERSTORMS
AS FAR E AS OVER THE FAR SW PORTION OF THE FA LAST EVENING AND
EARLIER THIS MORNING BUT HAD DISSIPATED AS THEY MOVED E INTO A
CAPPED AREA. THE SECOND DISTURBANCE. THE MAIN AREA OF CONVECTION
THAT HAD BEEN MOVING ACROSS IA HAD ALSO DISSIPATED AS IT MOVED
AWAY FROM THE BETTER ISENTROPIC LIFT RESULTING FROM MODERATELY
STRONG MID LEVEL WAA. THE THIRD DISTURBANCE HAS GENERATED AN
ELONGATED AREA OF THUNDERSTORMS ALONG THE MN-IA BORDER WHERE 30-35
KT SOUTHERLY FLOW IN THE 1.5 TO 3 KM AGL LAYER WAS MAXIMIZING LIFT
IN AN AREA OF RELATIVELY LARGE ELEVATED CAPE N OF THE STATIONARY
FRONT.
LATER TODAY THE CAP IS PROGGED TO BE REMOVED THOUGH FORECAST
TEMPERATURE PROFILES ARE NOT INDICATING AND SIGNIFICANT CAPE
AVAILABLE TO BE REALIZED. IN ADDITION...THE BEST ISENTROPIC LIFT
IS PROGGED TO MOVE ACROSS WI DURING THE DAY. STILL...THERE WILL BE
INCREASING CHANCES OF SHOWERS AND THUNDERSTORMS SPREADING W TO E
ACROSS THE LOCAL AREA DURING THE MORNING AS PERSISTING THROUGH THE
AFTERNOON AND EARLY EVENING AS THE SD-NEB UPPER LOW AND THE MO-AR
UPPER LOW MERGE AND MOVE TO OR SLIGHTLY E OF THE MID MS VALLEY BY
00Z. BEYOND THE FIRST PART OF THIS EVENING CHANCES OF PRECIP ARE
SMALL EXCEPT FOR THE FAR SE PORTION OF THE FA WHICH WILL STILL BE
UNDER THE INFLUENCE OF THE SLOW MOVING UPPER LOW WHICH IS PROGGED
TO BE OVER/NEAR THE LOWER OH VALLEY AT 12Z SAT.
THE UPPER PATTERN WILL BECOME MORE AMPLIFIED OVERNIGHT AND SAT
BEFORE BECOMING ZONAL E OF THE ROCKIES MID NEXT WEEK. WHILE THE
FLOW WILL BE AMPLIFIED THE FLOW WILL BE SLUGGISH AS AN UPPER
TROUGH MOVING OVER THE PACIFIC COAST EARLY THIS MORNING REACHES
THE ROCKIES LATE SAT-SAT NIGHT WHILE ANOTHER UPPER TROUGH OVER THE
N PACIFIC OFF THE B.C. COAST MOVES OVER PAC NW COAST. BY LATE SUN-
SUN NIGHT THE PAIR OF TROUGHS ARE PROGGED TO FORM AN UPPER LOW
OVER THE NORTHERN HIGH PLAINS. THIS UPPER LOW IS TO THEN VERY
SLOWLY MOVE E TO THE UPPER MIDWEST BY WED EVENING WHILE ALSO
GRADUALLY WEAKENING. HOWEVER...A FAIRLY STRONG SURFACE LOW IS
PROGGED TO MOVE E ACROSS THE NORTHERN PLAINS AND UPPER MS VALLEY
BEFORE THE UPPER SYSTEM WEAKENS AS DOES THE SURFACE REFLECTION.
DUE TO THE VERY SLOW EASTWARD PROGRESS OF THE SYSTEM A PROLONGED
PERIOD OF PERSISTENT RELATIVELY STRONG S TO SW LOWER LEVEL FLOW
WILL BE TRANSPORTING A CONTINUOUS STREAM OF MOISTURE FROM THE
WESTERN GULF UP ACROSS THE MID MS VALLEY AND TO THE UPPER MIDWEST
AND WESTERN GREAT LAKES.
WHILE THE MOST LIKELY TIME FRAME FOR RAIN IS LATER MON AND TUE AS
THIS IS WHEN SIGNIFICANT WARM AIR ADVECTION AND RESULTING UVV
ALONG WITH THE ARRIVAL OF ABUNDANT MOISTURE OCCURS...THERE WILL BE
CHANCES OF RAIN IN THE FORECAST FROM SUNDAY NIGHT RIGHT THROUGH
END OF NEXT WEEK...FIRST AS THE UPPER LOW APPROACHES THERE LIKELY
WILL BE SMALLER SCALE SHORT WAVES ROTATING AROUND TO AFFECT THE
LOCAL AREA EARLY IN THE WEEK BEFORE THE UPPER LOW IN OVER THE
AREA...AND THEN AS AN UPPER TROUGH TAKES UP SEMI PERMANENT
RESIDENCE OVER THE GREAT LAKES LATE WEEK.
STRONG WAA OCCURS AHEAD OF THE UPPER LOW DURING SAT AND SUN AND
WITH THE CORE OF THE WARM AIR OVER THE REGION ON SUN. WITH PARTLY
TO MOSTLY SUNNY SKIES TEMPERATURES ARE EXPECTED TO BE INTO THE
MID AND UPPER 80S. INCREASED CLOUDINESS WILL LIMIT HIGH
TEMPERATURES MON TO THE LOWER AND MID 80S. MIDWEEK AS THE UPPER
LOW/TROUGH MOVE OVER AND PAST THE AREA COOLER AIR WILL SPREAD S
AND SE OVER THE AREA. CONSIDERABLE CLOUDINESS AND SHOWERS WILL
KEEP AFTERNOON TEMPERATURES LIMITED TO LOWER AND MID 70S BY WED
AND UPPER 60S AND LOWER 70S ON THU.
TRS
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 14Z...
* ISOLATED SHOWERS/THUNDERSTORMS SOUTHWEST OF TERMINALS DEVELOPING
TOWARD MIDDAY. PSBL VCTS THIS AFTERNOON.
* VARIABLE EASTERLY WINDS WINDS ARND 8-10KT...OCCASIONAL GUSTS TO
16-18KT MIDDAY THRU AFTN.
* CIGS REMAIN VFR...PATCHY MVFR CIGS WITH THUNDERSTORMS WEST OF
ORD/MDW.
MDB
//DISCUSSION...UPDATED 12Z...
COMPLEX OF THUNDERSTORMS ACROSS NORTHEAST IOWA/WEST CENTRAL
WISCONSIN CONTINUE TO DRIFT NORTHEAST THIS MORNING...AND NOT
EXPECTED TO IMPACT DIRECTLY ANY OF THE NORTHERN IL/NORTHWEST IN
AIRFIELDS. STALLED FRONTAL BOUNDARY REMAINS SOUTHWEST OF THE TAF
SITES THIS MORNING...AND SHOULD ONLY LIFT NORTH SLIGHTLY
THROUGHOUT THE DAY TODAY. CIGS REMAIN VFR WITH BASES GENERALLY
AROUND 8-10KFT AGL. GUIDANCE CONTINUES TO SUGGEST VFR CONDS WILL
PREVAIL FOR MUCH OF THE DAY...PSBLY INTO TONIGHT. WITH THE
BOUNDARY REMAINING SOUTH OF THE TAF SITES...WINDS ARE NOT EXPECTED
TO CHANGE MUCH THROUGHOUT THE DAY/AFTN. WILL REMAIN ARND A 060-090
DEG RANGE WITH SPEEDS SHOWING SOME INCREASE THIS AFTN. IT APPEARS
SOME OCCASIONAL GUSTS MAY OCCUR THIS AFTN...TO 18KT. OTHERWISE
SPEEDS WILL BE ARND 8 TO 12 KT.
THE BEST CHC FOR PRECIP WILL OCCUR SOUTHWEST OF THE TAF SITES THRU
MUCH OF THE MORNING...WITH MINIMAL COVERAGE. BY MIDDAY COVERAGE
SHUD BEGIN TO INCREASE IN SHOWERS/THUNDERSTORMS...HOWEVER IT STILL
APPEARS THE BEST INSTABILITY WILL BE FOCUSED WITH THE BOUNDARY AND
THIS WILL BE JUST WEST/SOUTHWEST OF THE TAF SITES. HOWEVER...HAVE
INCLUDED A MENTION OF VCTS AS SOME STORMS COULD BE RATHER CLOSE TO
THE AIRFIELDS. THEN IT APPEARS ANY PRECIP WILL PUSH BACK TO THE
WEST/SOUTHWEST OF THE AIRFIELDS...WITH A SMALL CHC OF PRECIP
CONTINUING THROUGH THE EVENING HOURS. WINDS WILL EVENTUALLY BEGIN
TO TURN SOUTHEASTERLY ONCE THE BOUNDARY LIFTS OVERHEAD AND TO THE
NORTH OF THE TAF SITES...HOWEVER THIS DOES NOT APPEAR TO OCCUR
UNTIL AFT 05Z SAT.
BEACHLER
//ORD AND MDW CONFIDENCE...UPDATED 14Z...
* MEDIUM-HIGH CONFIDENCE IN WIND SPEED/DIRECTION TRENDS.
* LOW CONFIDENCE IN SHRA/TSRA TIMING/COVERAGE.
* HIGH CONFIDENCE IN PREVAILING VFR CIGS WITH BRIEF MVFR CIGS
POSSIBLE IN TSRA.
MDB
//OUTLOOK FOR ORD/MDW FOR 00Z SUNDAY-12Z FRIDAY...UPDATED 12Z...
SATURDAY NIGHT...VFR.
SUNDAY THROUGH WEDNESDAY...VFR. PERIODIC CHANCES FOR SHRA/TSRA.
THURSDAY...VFR. PSBL MVFR WITH CHANCE FOR SHRA.
BEACHLER
&&
.MARINE...
341 AM CDT
RIDGE OF HIGH PRESSURE HAS BECOME CENTERED NEAR JAMES BAY EARLY THIS
MORNING...EXPECTED TO DRIFT SOUTHEAST AND BECOME CENTERED NEAR
WESTERN QUEBEC TONIGHT. SOUTH OF THIS HIGH PRESSURE WAS A STALLED
FRONTAL BOUNDARY THAT STRETCHING ACROSS THE CENTRAL PLAINS INTO THE
OHIO VALLEY. ACROSS THE CENTRAL PLAINS AN AREA OF LOW PRESSURE IS
EXPECTED TO DEVELOP...THIS LOW PRESSURE WILL DRIFT NORTH AND BEGIN
TO LIFT THE STALLED FRONTAL BOUNDARY TO THE NORTH. THE GRADIENT
REMAINS RELATIVELY WEAK ACROSS THE LAKE...AND THIS APPEARS TO REMAIN
THROUGH THIS EVENING AS THE BOUNDARY BEGINS TO APPROACH THE SOUTHERN
PORTION OF THE LAKE. WINDS WILL GENERALLY BE NORTH/NORTHEAST OVER
THE LAKE...FURTHER SOUTH WINDS MAY START EASTERLY THEN BECOME
NORTHEASTERLY. THEN AS THE BOUNDARY SLIDES NORTH ACROSS THE SOUTHERN
PORTION OF THE LAKE...WINDS WILL BECOME EASTERLY. THE GRADIENT DOES
INCREASE MARGINALLY...AND MAY PRODUCE SPEEDS BETWEEN 10 TO 20 KT
SAT. LOW PRESSURE ACROSS THE CENTRAL PLAINS WILL DRIFT NORTH OVER
THE WEEKEND...AND THIS WILL ALLOW THE BOUNDARY TO STEADILY LIFT
NORTH ACROSS THE LAKE. AS THIS OCCURS...WINDS TO THE SOUTH OF THE
BOUNDARY WILL TURN SOUTHEASTERLY. MEANWHILE THE FAR NORTHERN
PORTIONS OF THE LAKE WILL BE NORTHEAST/EAST. EVENTUALLY THE NORTHERN
PORTIONS OF THE LAKE WILL BECOME SOUTHEAST WINDS...BUT THIS DOES NOT
OCCUR UNTIL CLOSER TO SUNDAY MORNING. THE SLOW MOVING LOW PRESSURE
SYSTEM WILL EVENTUALLY REACH THE WESTERN GREAT LAKES...HOWEVER THIS
DOES NOT APPEAR TO OCCUR UNTIL CLOSER TO WED OF NEXT WEEK. AS THE
LOW FINALLY LIFTS NORTHEAST OF LAKE MICHIGAN MID-WEEK...THE FRONTAL
BOUNDARY WILL PUSH SOUTH ACROSS THE LAKE. THIS WILL ALLOW WINDS TO
BECOME NORTHWEST TO NORTH.
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 171150
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
650 AM CDT FRI MAY 17 2013
.DISCUSSION...
428 AM CDT
EARLY THIS MORNING A STATIONARY FRONT RAN FROM NE IA...FAR NW AND
NE IL...AND NORTHERN IND. ND...NORTHEAST AND FAR NORTHWEST IL.
BOUNDARY POSITION IS WELL DEFINED BY BOTH WIND PATTERN AND LARGE
DIFFERENCE IN DEW POINTS ON OPPOSITE SIDES OF THE FRONT. AN UPPER
LOW WAS OVER THE EASTERN PORTION OF THE MO-AR BOARDER WHILE
A FEW DISTURBANCES...LIKELY CONVECTIVELY INDUCED...WERE JUST
UPSTREAM OF THE LOCAL FORECAST AREA.
THE FIRST DISTURBANCE WAS MOVING ACROSS FAR NW AND N CENTRAL IL
WITH A SECOND ALONG THE MN-IA BORDER AND A THIRD MOVING OVER THE
MID MO VALLEY FROM NEB E OVER FAR WESTERN IA. THESE DISTURBANCES
PRECEDED AN UPPER LOW MOVING E ALONG THE SD-NEB BOARDER.
THE FIRST DISTURBANCE DID PRODUCE A FEW SHOWERS AND THUNDERSTORMS
AS FAR E AS OVER THE FAR SW PORTION OF THE FA LAST EVENING AND
EARLIER THIS MORNING BUT HAD DISSIPATED AS THEY MOVED E INTO A
CAPPED AREA. THE SECOND DISTURBANCE. THE MAIN AREA OF CONVECTION
THAT HAD BEEN MOVING ACROSS IA HAD ALSO DISSIPATED AS IT MOVED
AWAY FROM THE BETTER ISENTROPIC LIFT RESULTING FROM MODERATELY
STRONG MID LEVEL WAA. THE THIRD DISTURBANCE HAS GENERATED AN
ELONGATED AREA OF THUNDERSTORMS ALONG THE MN-IA BORDER WHERE 30-35
KT SOUTHERLY FLOW IN THE 1.5 TO 3 KM AGL LAYER WAS MAXIMIZING LIFT
IN AN AREA OF RELATIVELY LARGE ELEVATED CAPE N OF THE STATIONARY
FRONT.
LATER TODAY THE CAP IS PROGGED TO BE REMOVED THOUGH FORECAST
TEMPERATURE PROFILES ARE NOT INDICATING AND SIGNIFICANT CAPE
AVAILABLE TO BE REALIZED. IN ADDITION...THE BEST ISENTROPIC LIFT
IS PROGGED TO MOVE ACROSS WI DURING THE DAY. STILL...THERE WILL BE
INCREASING CHANCES OF SHOWERS AND THUNDERSTORMS SPREADING W TO E
ACROSS THE LOCAL AREA DURING THE MORNING AS PERSISTING THROUGH THE
AFTERNOON AND EARLY EVENING AS THE SD-NEB UPPER LOW AND THE MO-AR
UPPER LOW MERGE AND MOVE TO OR SLIGHTLY E OF THE MID MS VALLEY BY
00Z. BEYOND THE FIRST PART OF THIS EVENING CHANCES OF PRECIP ARE
SMALL EXCEPT FOR THE FAR SE PORTION OF THE FA WHICH WILL STILL BE
UNDER THE INFLUENCE OF THE SLOW MOVING UPPER LOW WHICH IS PROGGED
TO BE OVER/NEAR THE LOWER OH VALLEY AT 12Z SAT.
THE UPPER PATTERN WILL BECOME MORE AMPLIFIED OVERNIGHT AND SAT
BEFORE BECOMING ZONAL E OF THE ROCKIES MID NEXT WEEK. WHILE THE
FLOW WILL BE AMPLIFIED THE FLOW WILL BE SLUGGISH AS AN UPPER
TROUGH MOVING OVER THE PACIFIC COAST EARLY THIS MORNING REACHES
THE ROCKIES LATE SAT-SAT NIGHT WHILE ANOTHER UPPER TROUGH OVER THE
N PACIFIC OFF THE B.C. COAST MOVES OVER PAC NW COAST. BY LATE SUN-
SUN NIGHT THE PAIR OF TROUGHS ARE PROGGED TO FORM AN UPPER LOW
OVER THE NORTHERN HIGH PLAINS. THIS UPPER LOW IS TO THEN VERY
SLOWLY MOVE E TO THE UPPER MIDWEST BY WED EVENING WHILE ALSO
GRADUALLY WEAKENING. HOWEVER...A FAIRLY STRONG SURFACE LOW IS
PROGGED TO MOVE E ACROSS THE NORTHERN PLAINS AND UPPER MS VALLEY
BEFORE THE UPPER SYSTEM WEAKENS AS DOES THE SURFACE REFLECTION.
DUE TO THE VERY SLOW EASTWARD PROGRESS OF THE SYSTEM A PROLONGED
PERIOD OF PERSISTENT RELATIVELY STRONG S TO SW LOWER LEVEL FLOW
WILL BE TRANSPORTING A CONTINUOUS STREAM OF MOISTURE FROM THE
WESTERN GULF UP ACROSS THE MID MS VALLEY AND TO THE UPPER MIDWEST
AND WESTERN GREAT LAKES.
WHILE THE MOST LIKELY TIME FRAME FOR RAIN IS LATER MON AND TUE AS
THIS IS WHEN SIGNIFICANT WARM AIR ADVECTION AND RESULTING UVV
ALONG WITH THE ARRIVAL OF ABUNDANT MOISTURE OCCURS...THERE WILL BE
CHANCES OF RAIN IN THE FORECAST FROM SUNDAY NIGHT RIGHT THROUGH
END OF NEXT WEEK...FIRST AS THE UPPER LOW APPROACHES THERE LIKELY
WILL BE SMALLER SCALE SHORT WAVES ROTATING AROUND TO AFFECT THE
LOCAL AREA EARLY IN THE WEEK BEFORE THE UPPER LOW IN OVER THE
AREA...AND THEN AS AN UPPER TROUGH TAKES UP SEMI PERMANENT
RESIDENCE OVER THE GREAT LAKES LATE WEEK.
STRONG WAA OCCURS AHEAD OF THE UPPER LOW DURING SAT AND SUN AND
WITH THE CORE OF THE WARM AIR OVER THE REGION ON SUN. WITH PARTLY
TO MOSTLY SUNNY SKIES TEMPERATURES ARE EXPECTED TO BE INTO THE
MID AND UPPER 80S. INCREASED CLOUDINESS WILL LIMIT HIGH
TEMPERATURES MON TO THE LOWER AND MID 80S. MIDWEEK AS THE UPPER
LOW/TROUGH MOVE OVER AND PAST THE AREA COOLER AIR WILL SPREAD S
AND SE OVER THE AREA. CONSIDERABLE CLOUDINESS AND SHOWERS WILL
KEEP AFTERNOON TEMPERATURES LIMITED TO LOWER AND MID 70S BY WED
AND UPPER 60S AND LOWER 70S ON THU.
TRS
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 12Z...
* ISOLATED SHOWERS/THUNDERSTORMS SOUTHWEST OF TERMINALS THRU
MIDDAY. PSBL VCTS EARLY IN THE AFTN.
* EASTERLY WINDS ARND 8-10KT...OCCASIONAL GUSTS TO 16-18KT MIDDAY
THRU AFTN.
* CIGS REMAIN VFR...PATCHY MVFR CIGS WITH THUNDERSTORMS WEST OF
ORD/MDW.
BEACHLER
//DISCUSSION...UPDATED 12Z...
COMPLEX OF THUNDERSTORMS ACROSS NORTHEAST IOWA/WEST CENTRAL
WISCONSIN CONTINUE TO DRIFT NORTHEAST THIS MORNING...AND NOT
EXPECTED TO IMPACT DIRECTLY ANY OF THE NORTHERN IL/NORTHWEST IN
AIRFIELDS. STALLED FRONTAL BOUNDARY REMAINS SOUTHWEST OF THE TAF
SITES THIS MORNING...AND SHOULD ONLY LIFT NORTH SLIGHTLY
THROUGHOUT THE DAY TODAY. CIGS REMAIN VFR WITH BASES GENERALLY
AROUND 8-10KFT AGL. GUIDANCE CONTINUES TO SUGGEST VFR CONDS WILL
PREVAIL FOR MUCH OF THE DAY...PSBLY INTO TONIGHT. WITH THE
BOUNDARY REMAINING SOUTH OF THE TAF SITES...WINDS ARE NOT EXPECTED
TO CHANGE MUCH THROUGHOUT THE DAY/AFTN. WILL REMAIN ARND A 060-090
DEG RANGE WITH SPEEDS SHOWING SOME INCREASE THIS AFTN. IT APPEARS
SOME OCCASIONAL GUSTS MAY OCCUR THIS AFTN...TO 18KT. OTHERWISE
SPEEDS WILL BE ARND 8 TO 12 KT.
THE BEST CHC FOR PRECIP WILL OCCUR SOUTHWEST OF THE TAF SITES THRU
MUCH OF THE MORNING...WITH MINIMAL COVERAGE. BY MIDDAY COVERAGE
SHUD BEGIN TO INCREASE IN SHOWERS/THUNDERSTORMS...HOWEVER IT STILL
APPEARS THE BEST INSTABILITY WILL BE FOCUSED WITH THE BOUNDARY AND
THIS WILL BE JUST WEST/SOUTHWEST OF THE TAF SITES. HOWEVER...HAVE
INCLUDED A MENTION OF VCTS AS SOME STORMS COULD BE RATHER CLOSE TO
THE AIRFIELDS. THEN IT APPEARS ANY PRECIP WILL PUSH BACK TO THE
WEST/SOUTHWEST OF THE AIRFIELDS...WITH A SMALL CHC OF PRECIP
CONTINUEING THROUGH THE EVENING HOURS. WINDS WILL EVENTUALLY BEGIN
TO TURN SOUTHEASTERLY ONCE THE BOUNDARY LIFTS OVERHEAD AND TO THE
NORTH OF THE TAF SITES...HOWEVER THIS DOES NOT APPEAR TO OCCUR
UNTIL AFT 05Z SAT.
BEACHLER
//ORD AND MDW CONFIDENCE...UPDATED 12Z...
* HIGH CONFIDENCE IN WIND DIR/SPEED.
* MEDIUM CONFIDENCE IN CIGS FORECAST.
* LOW CONFIDENCE IN PRECIP TIMING/COVERAGE.
* MEDIUM CONFIDENCE IN THUNDERSTORMS.
* MEDIUM/HIGH CONFIDENCE IN WIND DIRECTION BECOMING SOUTHEAST
TIMING.
BEACHLER
//OUTLOOK FOR ORD/MDW FOR 00Z SUNDAY-12Z FRIDAY...UPDATED 12Z...
SATURDAY NIGHT...VFR.
SUNDAY THROUGH WEDNESDAY...VFR. PERIODIC CHANCES FOR SHRA/TSRA.
THURSDAY...VFR. PSBL MVFR WITH CHANCE FOR SHRA.
BEACHLER
&&
.MARINE...
341 AM CDT
RIDGE OF HIGH PRESSURE HAS BECOME CENTERED NEAR JAMES BAY EARLY THIS
MORNING...EXPECTED TO DRIFT SOUTHEAST AND BECOME CENTERED NEAR
WESTERN QUEBEC TONIGHT. SOUTH OF THIS HIGH PRESSURE WAS A STALLED
FRONTAL BOUNDARY THAT STRETCHING ACROSS THE CENTRAL PLAINS INTO THE
OHIO VALLEY. ACROSS THE CENTRAL PLAINS AN AREA OF LOW PRESSURE IS
EXPECTED TO DEVELOP...THIS LOW PRESSURE WILL DRIFT NORTH AND BEGIN
TO LIFT THE STALLED FRONTAL BOUNDARY TO THE NORTH. THE GRADIENT
REMAINS RELATIVELY WEAK ACROSS THE LAKE...AND THIS APPEARS TO REMAIN
THROUGH THIS EVENING AS THE BOUNDARY BEGINS TO APPROACH THE SOUTHERN
PORTION OF THE LAKE. WINDS WILL GENERALLY BE NORTH/NORTHEAST OVER
THE LAKE...FURTHER SOUTH WINDS MAY START EASTERLY THEN BECOME
NORTHEASTERLY. THEN AS THE BOUNDARY SLIDES NORTH ACROSS THE SOUTHERN
PORTION OF THE LAKE...WINDS WILL BECOME EASTERLY. THE GRADIENT DOES
INCREASE MARGINALLY...AND MAY PRODUCE SPEEDS BETWEEN 10 TO 20 KT
SAT. LOW PRESSURE ACROSS THE CENTRAL PLAINS WILL DRIFT NORTH OVER
THE WEEKEND...AND THIS WILL ALLOW THE BOUNDARY TO STEADILY LIFT
NORTH ACROSS THE LAKE. AS THIS OCCURS...WINDS TO THE SOUTH OF THE
BOUNDARY WILL TURN SOUTHEASTERLY. MEANWHILE THE FAR NORTHERN
PORTIONS OF THE LAKE WILL BE NORTHEAST/EAST. EVENTUALLY THE NORTHERN
PORTIONS OF THE LAKE WILL BECOME SOUTHEAST WINDS...BUT THIS DOES NOT
OCCUR UNTIL CLOSER TO SUNDAY MORNING. THE SLOW MOVING LOW PRESSURE
SYSTEM WILL EVENTUALLY REACH THE WESTERN GREAT LAKES...HOWEVER THIS
DOES NOT APPEAR TO OCCUR UNTIL CLOSER TO WED OF NEXT WEEK. AS THE
LOW FINALLY LIFTS NORTHEAST OF LAKE MICHIGAN MID-WEEK...THE FRONTAL
BOUNDARY WILL PUSH SOUTH ACROSS THE LAKE. THIS WILL ALLOW WINDS TO
BECOME NORTHWEST TO NORTH.
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 170930
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
430 AM CDT FRI MAY 17 2013
.DISCUSSION...
428 AM CDT
EARLY THIS MORNING A STATIONARY FRONT RAN FROM NE IA...FAR NW AND
NE IL...AND NORTHERN IND. ND...NORTHEAST AND FAR NORTHWEST IL.
BOUNDARY POSITION IS WELL DEFINED BY BOTH WIND PATTERN AND LARGE
DIFFERENCE IN DEW POINTS ON OPPOSITE SIDES OF THE FRONT. AN UPPER
LOW WAS OVER THE EASTERN PORTION OF THE MO-AR BOARDER WHILE
A FEW DISTURBANCES...LIKELY CONVECTIVELY INDUCED...WERE JUST
UPSTREAM OF THE LOCAL FORECAST AREA.
THE FIRST DISTURBANCE WAS MOVING ACROSS FAR NW AND N CENTRAL IL
WITH A SECOND ALONG THE MN-IA BORDER AND A THIRD MOVING OVER THE
MID MO VALLEY FROM NEB E OVER FAR WESTERN IA. THESE DISTURBANCES
PRECEDED AN UPPER LOW MOVING E ALONG THE SD-NEB BOARDER.
THE FIRST DISTURBANCE DID PRODUCE A FEW SHOWERS AND THUNDERSTORMS
AS FAR E AS OVER THE FAR SW PORTION OF THE FA LAST EVENING AND
EARLIER THIS MORNING BUT HAD DISSIPATED AS THEY MOVED E INTO A
CAPPED AREA. THE SECOND DISTURBANCE. THE MAIN AREA OF CONVECTION
THAT HAD BEEN MOVING ACROSS IA HAD ALSO DISSIPATED AS IT MOVED
AWAY FROM THE BETTER ISENTROPIC LIFT RESULTING FROM MODERATELY
STRONG MID LEVEL WAA. THE THIRD DISTURBANCE HAS GENERATED AN
ELONGATED AREA OF THUNDERSTORMS ALONG THE MN-IA BORDER WHERE 30-35
KT SOUTHERLY FLOW IN THE 1.5 TO 3 KM AGL LAYER WAS MAXIMIZING LIFT
IN AN AREA OF RELATIVELY LARGE ELEVATED CAPE N OF THE STATIONARY
FRONT.
LATER TODAY THE CAP IS PROGGED TO BE REMOVED THOUGH FORECAST
TEMPERATURE PROFILES ARE NOT INDICATING AND SIGNIFICANT CAPE
AVAILABLE TO BE REALIZED. IN ADDITION...THE BEST ISENTROPIC LIFT
IS PROGGED TO MOVE ACROSS WI DURING THE DAY. STILL...THERE WILL BE
INCREASING CHANCES OF SHOWERS AND THUNDERSTORMS SPREADING W TO E
ACROSS THE LOCAL AREA DURING THE MORNING AS PERSISTING THROUGH THE
AFTERNOON AND EARLY EVENING AS THE SD-NEB UPPER LOW AND THE MO-AR
UPPER LOW MERGE AND MOVE TO OR SLIGHTLY E OF THE MID MS VALLEY BY
00Z. BEYOND THE FIRST PART OF THIS EVENING CHANCES OF PRECIP ARE
SMALL EXCEPT FOR THE FAR SE PORTION OF THE FA WHICH WILL STILL BE
UNDER THE INFLUENCE OF THE SLOW MOVING UPPER LOW WHICH IS PROGGED
TO BE OVER/NEAR THE LOWER OH VALLEY AT 12Z SAT.
THE UPPER PATTERN WILL BECOME MORE AMPLIFIED OVERNIGHT AND SAT
BEFORE BECOMING ZONAL E OF THE ROCKIES MID NEXT WEEK. WHILE THE
FLOW WILL BE AMPLIFIED THE FLOW WILL BE SLUGGISH AS AN UPPER
TROUGH MOVING OVER THE PACIFIC COAST EARLY THIS MORNING REACHES
THE ROCKIES LATE SAT-SAT NIGHT WHILE ANOTHER UPPER TROUGH OVER THE
N PACIFIC OFF THE B.C. COAST MOVES OVER PAC NW COAST. BY LATE SUN-
SUN NIGHT THE PAIR OF TROUGHS ARE PROGGED TO FORM AN UPPER LOW
OVER THE NORTHERN HIGH PLAINS. THIS UPPER LOW IS TO THEN VERY
SLOWLY MOVE E TO THE UPPER MIDWEST BY WED EVENING WHILE ALSO
GRADUALLY WEAKENING. HOWEVER...A FAIRLY STRONG SURFACE LOW IS
PROGGED TO MOVE E ACROSS THE NORTHERN PLAINS AND UPPER MS VALLEY
BEFORE THE UPPER SYSTEM WEAKENS AS DOES THE SURFACE REFLECTION.
DUE TO THE VERY SLOW EASTWARD PROGRESS OF THE SYSTEM A PROLONGED
PERIOD OF PERSISTENT RELATIVELY STRONG S TO SW LOWER LEVEL FLOW
WILL BE TRANSPORTING A CONTINUOUS STREAM OF MOISTURE FROM THE
WESTERN GULF UP ACROSS THE MID MS VALLEY AND TO THE UPPER MIDWEST
AND WESTERN GREAT LAKES.
WHILE THE MOST LIKELY TIME FRAME FOR RAIN IS LATER MON AND TUE AS
THIS IS WHEN SIGNIFICANT WARM AIR ADVECTION AND RESULTING UVV
ALONG WITH THE ARRIVAL OF ABUNDANT MOISTURE OCCURS...THERE WILL BE
CHANCES OF RAIN IN THE FORECAST FROM SUNDAY NIGHT RIGHT THROUGH
END OF NEXT WEEK...FIRST AS THE UPPER LOW APPROACHES THERE LIKELY
WILL BE SMALLER SCALE SHORT WAVES ROTATING AROUND TO AFFECT THE
LOCAL AREA EARLY IN THE WEEK BEFORE THE UPPER LOW IN OVER THE
AREA...AND THEN AS AN UPPER TROUGH TAKES UP SEMI PERMANENT
RESIDENCE OVER THE GREAT LAKES LATE WEEK.
STRONG WAA OCCURS AHEAD OF THE UPPER LOW DURING SAT AND SUN AND
WITH THE CORE OF THE WARM AIR OVER THE REGION ON SUN. WITH PARTLY
TO MOSTLY SUNNY SKIES TEMPERATURES ARE EXPECTED TO BE INTO THE
MID AND UPPER 80S. INCREASED CLOUDINESS WILL LIMIT HIGH
TEMPERATURES MON TO THE LOWER AND MID 80S. MIDWEEK AS THE UPPER
LOW/TROUGH MOVE OVER AND PAST THE AREA COOLER AIR WILL SPREAD S
AND SE OVER THE AREA. CONSIDERABLE CLOUDINESS AND SHOWERS WILL
KEEP AFTERNOON TEMPERATURES LIMITED TO LOWER AND MID 70S BY WED
AND UPPER 60S AND LOWER 70S ON THU.
TRS
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 06Z...
* ISOLATED SHOWER REMAIN SOUTHWEST OF TERMINALS THRU MID-MORNING.
* PRECIP COVERAGE INCREASES BY MIDDAY...POSSIBLE THUNDERSTORM ARND
19-22Z.
* WINDS REMAIN EASTERLY WITH SPEEDS GENERALLY ARND 10KT OR
LESS...TURNING SOUTHEASTERLY AFT 05Z SAT.
* CIGS REMAIN VFR...POSSIBLE MVFR CIGS IN OR AROUND TSRA/SHRA.
BEACHLER
//DISCUSSION...UPDATED 06Z...
IR IMAGERY EARLY THIS MORNING SHOWS AN AREA OF CLOUDS ACROSS THE
WESTERN GREAT LAKES INTO THE UPPER MIDWEST. SCT SHOWERS/THUNDERSTORMS
ACROSS NORTHCENTRAL IOWA/SOUTHCENTRAL MINNESOTA. THIS PRECIPITATION WAS LOCATED
ALONG A STALLED FRONTAL BOUNDARY THAT STRETCHES EAST/SOUTHEAST
INTO CENTRAL IL/IN. AIRFIELDS ACROSS NORTHERN IL/NORTHWEST IN
REMAIN VFR...WITH SOME CLOUDS OBSERVED AT 8KFT AGL OR HIGHER.
GUIDANCE CONTINUE TO SUGGEST VFR CONDS WILL CONTINUE THROUGH
DAYBREAK...WITH A CONTINUED LIGHT EAST WIND ARND 8KT OR LESS. THE
DIRECTION WILL GENERALLY REMAIN BETWEEN A 060-090 DEG
RANGE...HOWEVER SOME VRB DIRECTIONS MAY OCCUR THRU DAYBREAK AS
SPEEDS WILL BE LESS THAN 5 KT.
THEN IT APPEARS THE BEST CHC FOR PRECIP WILL OCCUR SOUTHWEST OF
THE TAF SITES THRU MUCH OF THE MORNING...WITH MINIMAL COVERAGE. BY
MIDDAY COVERAGE SHUD BEGIN TO INCREASE IN
SHOWERS/THUNDERSTORMS...AND GUIDANCE IS BEGINNING TO SHOW A HIGHER
CONFIDENCE IN TIMING OF 18-22Z. HAVE OPTED TO PLACE A VCSH TO
HANDLE THE BEGINNING COVERAGE AT 16Z...WITH A TEMPO IN A 19-22Z
TIMEFRAME. THIS APPEARS TO BE THE BEST TIME THAT A THUNDERSTORM
WOULD OCCUR. THEN IT APPEARS ANY PRECIP WILL PUSH BACK TO THE
WEST/SOUTHWEST OF THE AIRFIELDS...WITH A SMALL CHC OF PRECIP
CONTINUEING THROUGH THE EVENING HOURS. WINDS WILL EVENTUALLY BEGIN
TO TURN SOUTHEASTERLY ONCE THE BOUNDARY LIFTS OVERHEAD AND TO THE
NORTH OF THE TAF SITES...HOWEVER THIS DOES NOT APPEAR TO OCCUR
UNTIL AFT 05Z SAT.
BEACHLER
//ORD AND MDW CONFIDENCE...UPDATED 06Z...
* HIGH CONFIDENCE IN WIND DIR/SPEED.
* MEDIUM CONFIDENCE IN CIGS FORECAST.
* LOW CONFIDENCE IN PRECIP TIMING/COVERAGE.
* MEDIUM CONFIDENCE IN THUNDERSTORMS.
* MEDIUM/HIGH CONFIDENCE IN WIND DIRECTION BECOMING SOUTHEAST
TIMING.
BEACHLER
//OUTLOOK FOR ORD/MDW FOR 12Z SATURDAY-12Z THURSDAY...UPDATED 00Z...
SATURDAY THROUGH WEDNESDAY...PERIODIC CHANCES FOR SHRA/TSRA...
OTHERWISE...VFR.
KREIN
&&
.MARINE...
341 AM CDT
RIDGE OF HIGH PRESSURE HAS BECOME CENTERED NEAR JAMES BAY EARLY THIS
MORNING...EXPECTED TO DRIFT SOUTHEAST AND BECOME CENTERED NEAR
WESTERN QUEBEC TONIGHT. SOUTH OF THIS HIGH PRESSURE WAS A STALLED
FRONTAL BOUNDARY THAT STRETCHING ACROSS THE CENTRAL PLAINS INTO THE
OHIO VALLEY. ACROSS THE CENTRAL PLAINS AN AREA OF LOW PRESSURE IS
EXPECTED TO DEVELOP...THIS LOW PRESSURE WILL DRIFT NORTH AND BEGIN
TO LIFT THE STALLED FRONTAL BOUNDARY TO THE NORTH. THE GRADIENT
REMAINS RELATIVELY WEAK ACROSS THE LAKE...AND THIS APPEARS TO REMAIN
THROUGH THIS EVENING AS THE BOUNDARY BEGINS TO APPROACH THE SOUTHERN
PORTION OF THE LAKE. WINDS WILL GENERALLY BE NORTH/NORTHEAST OVER
THE LAKE...FURTHER SOUTH WINDS MAY START EASTERLY THEN BECOME
NORTHEASTERLY. THEN AS THE BOUNDARY SLIDES NORTH ACROSS THE SOUTHERN
PORTION OF THE LAKE...WINDS WILL BECOME EASTERLY. THE GRADIENT DOES
INCREASE MARGINALLY...AND MAY PRODUCE SPEEDS BETWEEN 10 TO 20 KT
SAT. LOW PRESSURE ACROSS THE CENTRAL PLAINS WILL DRIFT NORTH OVER
THE WEEKEND...AND THIS WILL ALLOW THE BOUNDARY TO STEADILY LIFT
NORTH ACROSS THE LAKE. AS THIS OCCURS...WINDS TO THE SOUTH OF THE
BOUNDARY WILL TURN SOUTHEASTERLY. MEANWHILE THE FAR NORTHERN
PORTIONS OF THE LAKE WILL BE NORTHEAST/EAST. EVENTUALLY THE NORTHERN
PORTIONS OF THE LAKE WILL BECOME SOUTHEAST WINDS...BUT THIS DOES NOT
OCCUR UNTIL CLOSER TO SUNDAY MORNING. THE SLOW MOVING LOW PRESSURE
SYSTEM WILL EVENTUALLY REACH THE WESTERN GREAT LAKES...HOWEVER THIS
DOES NOT APPEAR TO OCCUR UNTIL CLOSER TO WED OF NEXT WEEK. AS THE
LOW FINALLY LIFTS NORTHEAST OF LAKE MICHIGAN MID-WEEK...THE FRONTAL
BOUNDARY WILL PUSH SOUTH ACROSS THE LAKE. THIS WILL ALLOW WINDS TO
BECOME NORTHWEST TO NORTH.
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 170910
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
410 AM CDT FRI MAY 17 2013
.DISCUSSION...
339 AM CDT
EARLY THIS MORNING A STATIONARY FRONT RAN FROM NE IA...FAR NW AND
NE IL...AND NORTHERN IND. ND...NORTHEAST AND FAR NORTHWEST IL.
BOUNDARY POSITION IS WELL DEFINED BY BOTH WIND PATTERN AND LARGE
DIFFERENCE IN DEW POINTS ON OPPOSITE SIDES OF THE FRONT. AN UPPER
LOW WAS OVER THE EASTERN PORTION OF THE MO-AR BOARDER WHILE
A FEW DISTURBANCES...LIKELY CONVECTIVELY INDUCED...WERE JUST
UPSTREAM OF THE LOCAL FORECAST AREA.
THE FIRST DISTURBANCE WAS MOVING ACROSS FAR NW AND N CENTRAL IL
WITH A SECOND ALONG THE MN-IA BORDER AND A THIRD MOVING OVER THE
MID MO VALLEY FROM NEB E OVER FAR WESTERN IA. THESE DISTURBANCES
PRECEDED AN UPPER LOW MOVING E ALONG THE SD-NEB BOARDER.
THE FIRST DISTURBANCE DID PRODUCE A FEW SHOWERS AND THUNDERSTORMS
AS FAR E AS OVER THE FAR SW PORTION OF THE FA LAST EVENING AND
EARLIER THIS MORNING BUT HAD DISSIPATED AS THEY MOVED E INTO A
CAPPED AREA. THE SECOND DISTURBANCE. THE MAIN AREA OF CONVECTION
THAT HAD BEEN MOVING ACROSS IA HAD ALSO DISSIPATED AS IT MOVED
AWAY FROM THE BETTER ISENTROPIC LIFT RESULTING FROM MODERATELY
STRONG MID LEVEL WAA. THE THIRD DISTURBANCE HAS GENERATED AN
ELONGATED AREA OF THUNDERSTORMS ALONG THE MN-IA BORDER WHERE 30-35
KT SOUTHERLY FLOW IN THE 1.5 TO 3 KM AGL LAYER WAS MAXIMIZING LIFT
IN AN AREA OF RELATIVELY LARGE ELEVATED CAPE N OF THE STATIONARY
FRONT.
LATER TODAY THE CAP IS PROGGED TO BE REMOVED THOUGH FORECAST
TEMPERATURE PROFILES ARE NOT INDICATING AND SIGNIFICANT CAPE
AVAILABLE TO BE REALIZED. IN ADDITION...THE BEST ISENTROPIC LIFT
IS PROGGED TO MOVE ACROSS WI DURING THE DAY. STILL...THERE WILL BE
INCREASING CHANCES OF SHOWERS AND THUNDERSTORMS SPREADING W TO E
ACROSS THE LOCAL AREA DURING THE MORNING AS PERSISTING THROUGH THE
AFTERNOON AND EARLY EVENING AS THE SD-NEB UPPER LOW AND THE MO-AR
UPPER LOW MERGE AND MOVE TO OR SLIGHTLY E OF THE MID MS VALLEY BY
00Z. BEYOND THE FIRST PART OF THIS EVENING CHANCES OF PRECIP ARE
SMALL EXCEPT FOR THE FAR SE PORTION OF THE FA WHICH WILL STILL BE
UNDER THE INFLUENCE OF THE SLOW MOVING UPPER LOW WHICH IS PROGGED
TO BE OVER/NEAR THE LOWER OH VALLEY AT 12Z SAT.
TRS
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 09Z...
* ISOLATED SHOWER REMAIN SOUTHWEST OF TERMINALS THRU MID-MORNING.
* PRECIP COVERAGE INCREASES BY MIDDAY...POSSIBLE THUNDERSTORM ARND
19-22Z.
* WINDS REMAIN EASTERLY WITH SPEEDS GENERALLY ARND 10KT OR
LESS...TURNING SOUTHEASTERLY AFT 05Z SAT.
* CIGS REMAIN VFR...POSSIBLE MVFR CIGS IN OR AROUND TSRA/SHRA.
BEACHLER
//DISCUSSION...UPDATED 06Z...
IR IMAGERY EARLY THIS MORNING SHOWS AN AREA OF CLOUDS ACROSS THE
WESTERN GREAT LAKES INTO THE UPPER MIDWEST. SCT SHOWERS/THUNDERSTORMS
ACROSS NORTHCENTRAL IOWA/SOUTHCENTRAL MINNESOTA. THIS PRECIPITATION WAS LOCATED
ALONG A STALLED FRONTAL BOUNDARY THAT STRETCHES EAST/SOUTHEAST
INTO CENTRAL IL/IN. AIRFIELDS ACROSS NORTHERN IL/NORTHWEST IN
REMAIN VFR...WITH SOME CLOUDS OBSERVED AT 8KFT AGL OR HIGHER.
GUIDANCE CONTINUE TO SUGGEST VFR CONDS WILL CONTINUE THROUGH
DAYBREAK...WITH A CONTINUED LIGHT EAST WIND ARND 8KT OR LESS. THE
DIRECTION WILL GENERALLY REMAIN BETWEEN A 060-090 DEG
RANGE...HOWEVER SOME VRB DIRECTIONS MAY OCCUR THRU DAYBREAK AS
SPEEDS WILL BE LESS THAN 5 KT.
THEN IT APPEARS THE BEST CHC FOR PRECIP WILL OCCUR SOUTHWEST OF
THE TAF SITES THRU MUCH OF THE MORNING...WITH MINIMAL COVERAGE. BY
MIDDAY COVERAGE SHUD BEGIN TO INCREASE IN
SHOWERS/THUNDERSTORMS...AND GUIDANCE IS BEGINNING TO SHOW A HIGHER
CONFIDENCE IN TIMING OF 18-22Z. HAVE OPTED TO PLACE A VCSH TO
HANDLE THE BEGINNING COVERAGE AT 16Z...WITH A TEMPO IN A 19-22Z
TIMEFRAME. THIS APPEARS TO BE THE BEST TIME THAT A THUNDERSTORM
WOULD OCCUR. THEN IT APPEARS ANY PRECIP WILL PUSH BACK TO THE
WEST/SOUTHWEST OF THE AIRFIELDS...WITH A SMALL CHC OF PRECIP
CONTINUEING THROUGH THE EVENING HOURS. WINDS WILL EVENTUALLY BEGIN
TO TURN SOUTHEASTERLY ONCE THE BOUNDARY LIFTS OVERHEAD AND TO THE
NORTH OF THE TAF SITES...HOWEVER THIS DOES NOT APPEAR TO OCCUR
UNTIL AFT 05Z SAT.
BEACHLER
//ORD AND MDW CONFIDENCE...UPDATED 09Z...
* HIGH CONFIDENCE IN WIND DIR/SPEED.
* MEDIUM CONFIDENCE IN CIGS FORECAST.
* LOW CONFIDENCE IN PRECIP TIMING/COVERAGE.
* MEDIUM CONFIDENCE IN THUNDERSTORMS.
* MEDIUM/HIGH CONFIDENCE IN WIND DIRECTION BECOMING SOUTHEAST
TIMING.
BEACHLER
//OUTLOOK FOR ORD/MDW FOR 12Z SATURDAY-12Z THURSDAY...UPDATED 00Z...
SATURDAY THROUGH WEDNESDAY...PERIODIC CHANCES FOR SHRA/TSRA...
OTHERWISE...VFR.
KREIN
&&
.MARINE...
341 AM CDT
RIDGE OF HIGH PRESSURE HAS BECOME CENTERED NEAR JAMES BAY EARLY THIS
MORNING...EXPECTED TO DRIFT SOUTHEAST AND BECOME CENTERED NEAR
WESTERN QUEBEC TONIGHT. SOUTH OF THIS HIGH PRESSURE WAS A STALLED
FRONTAL BOUNDARY THAT STRETCHING ACROSS THE CENTRAL PLAINS INTO THE
OHIO VALLEY. ACROSS THE CENTRAL PLAINS AN AREA OF LOW PRESSURE IS
EXPECTED TO DEVELOP...THIS LOW PRESSURE WILL DRIFT NORTH AND BEGIN
TO LIFT THE STALLED FRONTAL BOUNDARY TO THE NORTH. THE GRADIENT
REMAINS RELATIVELY WEAK ACROSS THE LAKE...AND THIS APPEARS TO REMAIN
THROUGH THIS EVENING AS THE BOUNDARY BEGINS TO APPROACH THE SOUTHERN
PORTION OF THE LAKE. WINDS WILL GENERALLY BE NORTH/NORTHEAST OVER
THE LAKE...FURTHER SOUTH WINDS MAY START EASTERLY THEN BECOME
NORTHEASTERLY. THEN AS THE BOUNDARY SLIDES NORTH ACROSS THE SOUTHERN
PORTION OF THE LAKE...WINDS WILL BECOME EASTERLY. THE GRADIENT DOES
INCREASE MARGINALLY...AND MAY PRODUCE SPEEDS BETWEEN 10 TO 20 KT
SAT. LOW PRESSURE ACROSS THE CENTRAL PLAINS WILL DRIFT NORTH OVER
THE WEEKEND...AND THIS WILL ALLOW THE BOUNDARY TO STEADILY LIFT
NORTH ACROSS THE LAKE. AS THIS OCCURS...WINDS TO THE SOUTH OF THE
BOUNDARY WILL TURN SOUTHEASTERLY. MEANWHILE THE FAR NORTHERN
PORTIONS OF THE LAKE WILL BE NORTHEAST/EAST. EVENTUALLY THE NORTHERN
PORTIONS OF THE LAKE WILL BECOME SOUTHEAST WINDS...BUT THIS DOES NOT
OCCUR UNTIL CLOSER TO SUNDAY MORNING. THE SLOW MOVING LOW PRESSURE
SYSTEM WILL EVENTUALLY REACH THE WESTERN GREAT LAKES...HOWEVER THIS
DOES NOT APPEAR TO OCCUR UNTIL CLOSER TO WED OF NEXT WEEK. AS THE
LOW FINALLY LIFTS NORTHEAST OF LAKE MICHIGAN MID-WEEK...THE FRONTAL
BOUNDARY WILL PUSH SOUTH ACROSS THE LAKE. THIS WILL ALLOW WINDS TO
BECOME NORTHWEST TO NORTH.
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 170841
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
341 AM CDT FRI MAY 17 2013
.DISCUSSION...
339 AM CDT
EARLY THIS MORNING A STATIONARY FRONT RAN FROM NE IA...FAR NW AND
NE IL...AND NORTHERN IND. ND...NORTHEAST AND FAR NORTHWEST IL.
BOUNDARY POSITION IS WELL DEFINED BY BOTH WIND PATTERN AND LARGE
DIFFERENCE IN DEW POINTS ON OPPOSITE SIDES OF THE FRONT. AN UPPER
LOW WAS OVER THE EASTERN PORTION OF THE MO-AR BOARDER WHILE
A FEW DISTURBANCES...LIKELY CONVECTIVELY INDUCED...WERE JUST
UPSTREAM OF THE LOCAL FORECAST AREA.
THE FIRST DISTURBANCE WAS MOVING ACROSS FAR NW AND N CENTRAL IL
WITH A SECOND ALONG THE MN-IA BORDER AND A THIRD MOVING OVER THE
MID MO VALLEY FROM NEB E OVER FAR WESTERN IA. THESE DISTURBANCES
PRECEDED AN UPPER LOW MOVING E ALONG THE SD-NEB BOARDER.
THE FIRST DISTURBANCE DID PRODUCE A FEW SHOWERS AND THUNDERSTORMS
AS FAR E AS OVER THE FAR SW PORTION OF THE FA LAST EVENING AND
EARLIER THIS MORNING BUT HAD DISSIPATED AS THEY MOVED E INTO A
CAPPED AREA. THE SECOND DISTURBANCE. THE MAIN AREA OF CONVECTION
THAT HAD BEEN MOVING ACROSS IA HAD ALSO DISSIPATED AS IT MOVED
AWAY FROM THE BETTER ISENTROPIC LIFT RESULTING FROM MODERATELY
STRONG MID LEVEL WAA. THE THIRD DISTURBANCE HAS GENERATED AN
ELONGATED AREA OF THUNDERSTORMS ALONG THE MN-IA BORDER WHERE 30-35
KT SOUTHERLY FLOW IN THE 1.5 TO 3 KM AGL LAYER WAS MAXIMIZING LIFT
IN AN AREA OF RELATIVELY LARGE ELEVATED CAPE N OF THE STATIONARY
FRONT.
LATER TODAY THE CAP IS PROGGED TO BE REMOVED THOUGH FORECAST
TEMPERATURE PROFILES ARE NOT INDICATING AND SIGNIFICANT CAPE
AVAILABLE TO BE REALIZED. IN ADDITION...THE BEST ISENTROPIC LIFT
IS PROGGED TO MOVE ACROSS WI DURING THE DAY. STILL...THERE WILL BE
INCREASING CHANCES OF SHOWERS AND THUNDERSTORMS SPREADING W TO E
ACROSS THE LOCAL AREA DURING THE MORNING AS PERSISTING THROUGH THE
AFTERNOON AND EARLY EVENING AS THE SD-NEB UPPER LOW AND THE MO-AR
UPPER LOW MERGE AND MOVE TO OR SLIGHTLY E OF THE MID MS VALLEY BY
00Z. BEYOND THE FIRST PART OF THIS EVENING CHANCES OF PRECIP ARE
SMALL EXCEPT FOR THE FAR SE PORTION OF THE FA WHICH WILL STILL BE
UNDER THE INFLUENCE OF THE SLOW MOVING UPPER LOW WHICH IS PROGGED
TO BE OVER/NEAR THE LOWER OH VALLEY AT 12Z SAT.
TRS
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 06Z...
* ISOLATED SHOWER REMAIN SOUTHWEST OF TERMINALS THRU MID-MORNING.
* PRECIP COVERAGE INCREASES BY MIDDAY...POSSIBLE THUNDERSTORM ARND
19-22Z.
* WINDS REMAIN EASTERLY WITH SPEEDS GENERALLY ARND 10KT OR
LESS...TURNING SOUTHEASTERLY AFT 05Z SAT.
* CIGS REMAIN VFR...POSSIBLE MVFR CIGS IN OR AROUND TSRA/SHRA.
BEACHLER
//DISCUSSION...UPDATED 06Z...
IR IMAGERY EARLY THIS MORNING SHOWS AN AREA OF CLOUDS ACROSS THE
WESTERN GREAT LAKES INTO THE UPPER MIDWEST. SCT SHOWERS/THUNDERSTORMS
ACROSS NORTHCENTRAL IOWA/SOUTHCENTRAL MINNESOTA. THIS PRECIPITATION WAS LOCATED
ALONG A STALLED FRONTAL BOUNDARY THAT STRETCHES EAST/SOUTHEAST
INTO CENTRAL IL/IN. AIRFIELDS ACROSS NORTHERN IL/NORTHWEST IN
REMAIN VFR...WITH SOME CLOUDS OBSERVED AT 8KFT AGL OR HIGHER.
GUIDANCE CONTINUE TO SUGGEST VFR CONDS WILL CONTINUE THROUGH
DAYBREAK...WITH A CONTINUED LIGHT EAST WIND ARND 8KT OR LESS. THE
DIRECTION WILL GENERALLY REMAIN BETWEEN A 060-090 DEG
RANGE...HOWEVER SOME VRB DIRECTIONS MAY OCCUR THRU DAYBREAK AS
SPEEDS WILL BE LESS THAN 5 KT.
THEN IT APPEARS THE BEST CHC FOR PRECIP WILL OCCUR SOUTHWEST OF
THE TAF SITES THRU MUCH OF THE MORNING...WITH MINIMAL COVERAGE. BY
MIDDAY COVERAGE SHUD BEGIN TO INCREASE IN
SHOWERS/THUNDERSTORMS...AND GUIDANCE IS BEGINNING TO SHOW A HIGHER
CONFIDENCE IN TIMING OF 18-22Z. HAVE OPTED TO PLACE A VCSH TO
HANDLE THE BEGINNING COVERAGE AT 16Z...WITH A TEMPO IN A 19-22Z
TIMEFRAME. THIS APPEARS TO BE THE BEST TIME THAT A THUNDERSTORM
WOULD OCCUR. THEN IT APPEARS ANY PRECIP WILL PUSH BACK TO THE
WEST/SOUTHWEST OF THE AIRFIELDS...WITH A SMALL CHC OF PRECIP
CONTINUEING THROUGH THE EVENING HOURS. WINDS WILL EVENTUALLY BEGIN
TO TURN SOUTHEASTERLY ONCE THE BOUNDARY LIFTS OVERHEAD AND TO THE
NORTH OF THE TAF SITES...HOWEVER THIS DOES NOT APPEAR TO OCCUR
UNTIL AFT 05Z SAT.
BEACHLER
//ORD AND MDW CONFIDENCE...UPDATED 06Z...
* HIGH CONFIDENCE IN WIND DIR/SPEED.
* MEDIUM CONFIDENCE IN CIGS FORECAST.
* LOW CONFIDENCE IN PRECIP TIMING/COVERAGE.
* MEDIUM CONFIDENCE IN THUNDERSTORMS.
* MEDIUM/HIGH CONFIDENCE IN WIND DIRECTION BECOMING SOUTHEAST
TIMING.
BEACHLER
//OUTLOOK FOR ORD/MDW FOR 12Z SATURDAY-12Z THURSDAY...UPDATED 00Z...
SATURDAY THROUGH WEDNESDAY...PERIODIC CHANCES FOR SHRA/TSRA...
OTHERWISE...VFR.
KREIN
&&
.MARINE...
341 AM CDT
RIDGE OF HIGH PRESSURE HAS BECOME CENTERED NEAR JAMES BAY EARLY THIS
MORNING...EXPECTED TO DRIFT SOUTHEAST AND BECOME CENTERED NEAR
WESTERN QUEBEC TONIGHT. SOUTH OF THIS HIGH PRESSURE WAS A STALLED
FRONTAL BOUNDARY THAT STRETCHING ACROSS THE CENTRAL PLAINS INTO THE
OHIO VALLEY. ACROSS THE CENTRAL PLAINS AN AREA OF LOW PRESSURE IS
EXPECTED TO DEVELOP...THIS LOW PRESSURE WILL DRIFT NORTH AND BEGIN
TO LIFT THE STALLED FRONTAL BOUNDARY TO THE NORTH. THE GRADIENT
REMAINS RELATIVELY WEAK ACROSS THE LAKE...AND THIS APPEARS TO REMAIN
THROUGH THIS EVENING AS THE BOUNDARY BEGINS TO APPROACH THE SOUTHERN
PORTION OF THE LAKE. WINDS WILL GENERALLY BE NORTH/NORTHEAST OVER
THE LAKE...FURTHER SOUTH WINDS MAY START EASTERLY THEN BECOME
NORTHEASTERLY. THEN AS THE BOUNDARY SLIDES NORTH ACROSS THE SOUTHERN
PORTION OF THE LAKE...WINDS WILL BECOME EASTERLY. THE GRADIENT DOES
INCREASE MARGINALLY...AND MAY PRODUCE SPEEDS BETWEEN 10 TO 20 KT
SAT. LOW PRESSURE ACROSS THE CENTRAL PLAINS WILL DRIFT NORTH OVER
THE WEEKEND...AND THIS WILL ALLOW THE BOUNDARY TO STEADILY LIFT
NORTH ACROSS THE LAKE. AS THIS OCCURS...WINDS TO THE SOUTH OF THE
BOUNDARY WILL TURN SOUTHEASTERLY. MEANWHILE THE FAR NORTHERN
PORTIONS OF THE LAKE WILL BE NORTHEAST/EAST. EVENTUALLY THE NORTHERN
PORTIONS OF THE LAKE WILL BECOME SOUTHEAST WINDS...BUT THIS DOES NOT
OCCUR UNTIL CLOSER TO SUNDAY MORNING. THE SLOW MOVING LOW PRESSURE
SYSTEM WILL EVENTUALLY REACH THE WESTERN GREAT LAKES...HOWEVER THIS
DOES NOT APPEAR TO OCCUR UNTIL CLOSER TO WED OF NEXT WEEK. AS THE
LOW FINALLY LIFTS NORTHEAST OF LAKE MICHIGAN MID-WEEK...THE FRONTAL
BOUNDARY WILL PUSH SOUTH ACROSS THE LAKE. THIS WILL ALLOW WINDS TO
BECOME NORTHWEST TO NORTH.
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 170840
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
340 AM CDT FRI MAY 17 2013
.DISCUSSION...
339 AM CDT
EARLY THIS MORNING A STATIONARY FRONT RAN FROM NE IA...FAR NW AND
NE IL...AND NORTHERN IND. ND...NORTHEAST AND FAR NORTHWEST IL.
BOUNDARY POSITION IS WELL DEFINED BY BOTH WIND PATTERN AND LARGE
DIFFERENCE IN DEW POINTS ON OPPOSITE SIDES OF THE FRONT. AN UPPER
LOW WAS OVER THE EASTERN PORTION OF THE MO-AR BOARDER WHILE
A FEW DISTURBANCES...LIKELY CONVECTIVELY INDUCED...WERE JUST
UPSTREAM OF THE LOCAL FORECAST AREA.
THE FIRST DISTURBANCE WAS MOVING ACROSS FAR NW AND N CENTRAL IL
WITH A SECOND ALONG THE MN-IA BORDER AND A THIRD MOVING OVER THE
MID MO VALLEY FROM NEB E OVER FAR WESTERN IA. THESE DISTURBANCES
PRECEDED AN UPPER LOW MOVING E ALONG THE SD-NEB BOARDER.
THE FIRST DISTURBANCE DID PRODUCE A FEW SHOWERS AND THUNDERSTORMS
AS FAR E AS OVER THE FAR SW PORTION OF THE FA LAST EVENING AND
EARLIER THIS MORNING BUT HAD DISSIPATED AS THEY MOVED E INTO A
CAPPED AREA. THE SECOND DISTURBANCE. THE MAIN AREA OF CONVECTION
THAT HAD BEEN MOVING ACROSS IA HAD ALSO DISSIPATED AS IT MOVED
AWAY FROM THE BETTER ISENTROPIC LIFT RESULTING FROM MODERATELY
STRONG MID LEVEL WAA. THE THIRD DISTURBANCE HAS GENERATED AN
ELONGATED AREA OF THUNDERSTORMS ALONG THE MN-IA BORDER WHERE 30-35
KT SOUTHERLY FLOW IN THE 1.5 TO 3 KM AGL LAYER WAS MAXIMIZING LIFT
IN AN AREA OF RELATIVELY LARGE ELEVATED CAPE N OF THE STATIONARY
FRONT.
LATER TODAY THE CAP IS PROGGED TO BE REMOVED THOUGH FORECAST
TEMPERATURE PROFILES ARE NOT INDICATING AND SIGNIFICANT CAPE
AVAILABLE TO BE REALIZED. IN ADDITION...THE BEST ISENTROPIC LIFT
IS PROGGED TO MOVE ACROSS WI DURING THE DAY. STILL...THERE WILL BE
INCREASING CHANCES OF SHOWERS AND THUNDERSTORMS SPREADING W TO E
ACROSS THE LOCAL AREA DURING THE MORNING AS PERSISTING THROUGH THE
AFTERNOON AND EARLY EVENING AS THE SD-NEB UPPER LOW AND THE MO-AR
UPPER LOW MERGE AND MOVE TO OR SLIGHTLY E OF THE MID MS VALLEY BY
00Z. BEYOND THE FIRST PART OF THIS EVENING CHANCES OF PRECIP ARE
SMALL EXCEPT FOR THE FAR SE PORTION OF THE FA WHICH WILL STILL BE
UNDER THE INFLUENCE OF THE SLOW MOVING UPPER LOW WHICH IS PROGGED
TO BE OVER/NEAR THE LOWER OH VALLEY AT 12Z SAT.
TRS
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 06Z...
* ISOLATED SHOWER REMAIN SOUTHWEST OF TERMINALS THRU MID-MORNING.
* PRECIP COVERAGE INCREASES BY MIDDAY...POSSIBLE THUNDERSTORM ARND
19-22Z.
* WINDS REMAIN EASTERLY WITH SPEEDS GENERALLY ARND 10KT OR
LESS...TURNING SOUTHEASTERLY AFT 05Z SAT.
* CIGS REMAIN VFR...POSSIBLE MVFR CIGS IN OR AROUND TSRA/SHRA.
BEACHLER
//DISCUSSION...UPDATED 06Z...
IR IMAGERY EARLY THIS MORNING SHOWS AN AREA OF CLOUDS ACROSS THE
WESTERN GREAT LAKES INTO THE UPPER MIDWEST. SCT SHOWERS/THUNDERSTORMS
ACROSS NORTHCENTRAL IOWA/SOUTHCENTRAL MINNESOTA. THIS PRECIPITATION WAS LOCATED
ALONG A STALLED FRONTAL BOUNDARY THAT STRETCHES EAST/SOUTHEAST
INTO CENTRAL IL/IN. AIRFIELDS ACROSS NORTHERN IL/NORTHWEST IN
REMAIN VFR...WITH SOME CLOUDS OBSERVED AT 8KFT AGL OR HIGHER.
GUIDANCE CONTINUE TO SUGGEST VFR CONDS WILL CONTINUE THROUGH
DAYBREAK...WITH A CONTINUED LIGHT EAST WIND ARND 8KT OR LESS. THE
DIRECTION WILL GENERALLY REMAIN BETWEEN A 060-090 DEG
RANGE...HOWEVER SOME VRB DIRECTIONS MAY OCCUR THRU DAYBREAK AS
SPEEDS WILL BE LESS THAN 5 KT.
THEN IT APPEARS THE BEST CHC FOR PRECIP WILL OCCUR SOUTHWEST OF
THE TAF SITES THRU MUCH OF THE MORNING...WITH MINIMAL COVERAGE. BY
MIDDAY COVERAGE SHUD BEGIN TO INCREASE IN
SHOWERS/THUNDERSTORMS...AND GUIDANCE IS BEGINNING TO SHOW A HIGHER
CONFIDENCE IN TIMING OF 18-22Z. HAVE OPTED TO PLACE A VCSH TO
HANDLE THE BEGINNING COVERAGE AT 16Z...WITH A TEMPO IN A 19-22Z
TIMEFRAME. THIS APPEARS TO BE THE BEST TIME THAT A THUNDERSTORM
WOULD OCCUR. THEN IT APPEARS ANY PRECIP WILL PUSH BACK TO THE
WEST/SOUTHWEST OF THE AIRFIELDS...WITH A SMALL CHC OF PRECIP
CONTINUEING THROUGH THE EVENING HOURS. WINDS WILL EVENTUALLY BEGIN
TO TURN SOUTHEASTERLY ONCE THE BOUNDARY LIFTS OVERHEAD AND TO THE
NORTH OF THE TAF SITES...HOWEVER THIS DOES NOT APPEAR TO OCCUR
UNTIL AFT 05Z SAT.
BEACHLER
//ORD AND MDW CONFIDENCE...UPDATED 06Z...
* HIGH CONFIDENCE IN WIND DIR/SPEED.
* MEDIUM CONFIDENCE IN CIGS FORECAST.
* LOW CONFIDENCE IN PRECIP TIMING/COVERAGE.
* MEDIUM CONFIDENCE IN THUNDERSTORMS.
* MEDIUM/HIGH CONFIDENCE IN WIND DIRECTION BECOMING SOUTHEAST
TIMING.
BEACHLER
//OUTLOOK FOR ORD/MDW FOR 12Z SATURDAY-12Z THURSDAY...UPDATED 00Z...
SATURDAY THROUGH WEDNESDAY...PERIODIC CHANCES FOR SHRA/TSRA...
OTHERWISE...VFR.
KREIN
&&
.MARINE...
228 PM CDT
RIDGING FROM HIGH PRESSURE CENTERED OVER WESTERN ONTARIO EXTENDS
ACROSS LAKE MICHIGAN THIS AFTERNOON. WEAK LOW PRESSURE WILL DEVELOP
AND MOVE UP THE OHIO RIVER VALLEY FRIDAY WITH ADDITIONAL LOW
PRESSURE DEVELOPING ACROSS THE CENTRAL HIGH PLAINS. EAST TO
NORTHEAST FLOW OVERALL WILL CONTINUE ACROSS THE LAKE...WITH ONSHORE
FLOW IN AREAS WHERE THE PRESSURE GRADIENT IS WEAKER CAUSING SOME
ERRATIC DIRECTIONS AT TIMES. STEADIER AND MORE UNIFORM WINDS WILL
DEVELOP WITH TIME THROUGH TOMORROW WITH MORE OF AN EAST TO SOUTHEAST
TREND. THE STRONGEST WINDS WILL OCCUR FRIDAY EVENING/NIGHT
COINCIDENT WITH THE STRONGEST PRESSURE GRADIENT THANKS TO THE LOW
PASSING TO THE SOUTHEAST. THE GRADIENT WEAKENS DURING THE DAY
SATURDAY AS THE LOW DEPARTS TO THE EAST. LOW PRESSURE STRENGTHENS
ACROSS THE CENTRAL/NORTHERN HIGH PLAINS INTO SUNDAY WHICH WILL
GRADUALLY TIGHTEN THE PRESSURE GRADIENT ACROSS THE LAKE. THIS WILL
ALLOW A STEADY SOUTH TO SOUTHEAST WIND TO DEVELOP ACROSS MOST OF THE
LAKE...WITH A MORE EASTERLY DIRECTION ACROSS THE FAR NORTH WHERE A
WARM FRONTAL BOUNDARY IS EXPECTED TO SET UP. THE MAIN LOW WILL
MEANDER NORTHWARD BEFORE BEING PUSHED EASTWARD ACROSS MINNESOTA/IOWA
SOMETIME TUESDAY OR WEDNESDAY WHICH WILL LIKELY PUSH THE FRONTAL
BOUNDARY FURTHER SOUTH ACROSS THE LAKE LEADING TO EAST TO NORTHEAST
WINDS NORTH AND SOUTH TO SOUTHWEST WINDS SOUTH BY MID WEEK. THE MAIN
CONCERN WILL BE THE POTENTIAL FOR INCREASED GUSTINESS ACROSS THE
NORTH AS COLDER AIR SETTLES IN ALLOWING SLIGHTLY INCREASED MIXING.
OTHERWISE...GENERALLY STABLE LOW LEVEL AIR ACROSS THE LAKE WILL KEEP
GUSTS TO A MINIMUM FROM TONIGHT THROUGH THE WEEKEND.
MDB
&&
.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 170557
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1257 AM CDT FRI MAY 17 2013
.DISCUSSION...
930 PM CDT
THE FORECAST FOR TONIGHT HAS BEEN TWEAKED SLIGHTLY...TO CONTINUE
THE EVENING CHANCE OF THUNDER ACROSS THE SOUTHERN FORECAST AREA
THROUGH THE NIGHT...AND TO NUDGE IT NORTH SOME.
THE EVE WATER VAPOR LOOP DEPICTS THE CLOSED UPPER LOW ACROSS
NORTHERN AR EASING ITS WAY NORTHEAST. AT THE SURFACE...THE
PRIMARILY SYNOPTIC FRONT IS NEAR THE LOT/ILX CWA BORDER WITH A
LAKE BREEZE HAVING PUSHED WELL INLAND. BETWEEN THESE TWO A FEW
STORMS GENERATED...IT LOOKED LIKE ON A SLIGHTLY ELEVATED BOUNDARY
JUST NORTH OF THE SURFACE BOUNDARY PER ILX RADAR. THESE MAY FESTER
NORTHEAST ON THE AFOREMENTIONED MULTIPLE AREAS OF LOW-LEVEL
CONVERGENCE FOR SEVERAL MORE HOURS...BUT ANY CG LIGHTNING HAS BEEN
SPORADIC AT BEST AND WOULD EXPECT THAT TREND TO CONTINUE OR
DIMINISH ALTOGETHER. THE HRRR DOES INDICATE THESE SHOWERS TO SORT
OF OSCILLATE ALL THE WAY UP TO FAR NORTHEAST IL THROUGH EARLY
OVERNIGHT.
THE ILX VAD PROFILER INDICATES INCREASING SOUTHERLY FLOW BELOW 3K
FT...NOW UP TO 30 KT. THE LOW-LEVEL JET IS NOT EXPECTED TO
INCREASE MUCH FROM THAT MAGNITUDE AND POINT MORE INTO WESTERN IL.
MOISTURE TRANSPORT IS MORE LIMITED TONIGHT SO NOT EXPECTING AS
MUCH IF ANY ELEVATED CONVECTION...BUT COULD SEE SOME IN WESTERN IL
WHERE A LITTLE MORE THETA-E ADVECTION AND CONVERGENCE AROUND 850MB
IS FORECAST.
THE LAKE BREEZE MADE IMPRESSIVE PROGRESS WSW THROUGH EARLY EVE
AFTER SORT OF A SLOW START. A 30 DEGREE SPREAD AS OF 930 PM EXISTS
ACROSS THE CWA SIMPLY FROM JUST THIS MESOSCALE BOUNDARY. HAVE
ADJUSTED THE HOURLY TEMPERATURE FORECAST TO MEET TRENDS. THE LAV
GUIDANCE HAS VERY LITTLE TEMPERATURE DROP FOR MANY POINTS THROUGH
THE REST OF THE NIGHT...LIKELY DUE TO INCREASING CLOUD COVER.
WHILE CAA OFF THE LAKE LIKELY WILL CREATE A LITTLE MORE DROP THAN
IT ADVERTISES...THIS IS IN LINE WITH THE GOING MINIMUM TEMPERATURE
FORECASTS.
MTF
//PREV DISCUSSION...
259 PM CDT
TODAY`S FORECAST CHALLENGES CONTINUE TO BE DEALING WITH FRONTAL
BOUNDARY CURRENTLY JUST SOUTH OF THE CWA...AND PERIODIC CONVECTIVE
CHANCES THROUGH MID NEXT WEEK.
TODAY AND TONIGHT...
THIS AFTERNOON THE FRONT IS LOCATED JUST NORTH OF QUINCY IL EAST TO
NEAR TERRE HAUTE INDIANA...AND HAS BEEN SLOWLY PUSHING NORTH THIS
AFTERNOON. MODERATE INSTABILITY EXISTS SOUTH OF THE FRONT AND MAY
LIFT INTO FAR SOUTHERN PORTIONS OF THE CWA LATE THIS EVENING BEFORE
FADING NOCTURNALLY. MAINTAINED SLT CHC POPS FOR A FEW HOURS THIS
EVENING WHEN THIS OCCURS...BUT OTHERWISE SHOULD BE FAIRLY QUIET
PERIOD THROUGH TONIGHT.
FRIDAY THROUGH SATURDAY...
COMPACT SHORTWAVE NOTED ON WV IMAGERY THIS AFTERNOON OVER WESTERN
NE/KS WILL CONTINUE ENE INTO WEST CENTRAL WISCONSIN BY FRIDAY
AFTERNOON. AS THIS HAPPENS...SOUTHERLY FLOW INCREASE AT THE SURFACE
AND SHOULD HELP PUSH THE BOUNDARY NORTH ACROSS THE AREA. DEWPOINTS
RISE INTO THE MID 60S AND MODEST INSTABILITY DEVELOPS OUTSIDE OF FAR
NE ILLINOIS WHERE ONSHORE WINDS WILL KEEP CONDITIONS COOLER/MORE
STABLE. THIS INSTABILITY IS UNCAPPED...AND GIVEN THERE IS NO WELL
DEFINED FOCUS FOR THUNDERSTORMS...EXPECT UNORGANIZED/SCATTERED
CONVECTION TO DEVELOP WITHIN THE WARM SECTOR. MID LEVEL LAPSE RATES
ARE PRETTY POOR...SO CONVECTION MAY STRUGGLE AT TIMES AND MAY LIMIT
THE THUNDER CHANCES TO SOME DEGREE. MUCH OF THE SAME IS EXPECTED
SATURDAY SO WILL MAINTAIN THE LOW POPS FOR DIURNALLY DRIVEN TSTORMS.
SUNDAY THROUGH TUESDAY...
THIS PERIOD CONTINUES TO LOOK ACTIVE AS THE OVERALL PATTERN
AMPLIFIES WITH DEEP TROUGHING DEVELOPING ACROSS THE WESTERN
CONUS...AND STRONG RIDGING EAST. THE H85 THERMAL RIDGE BEGINS TO
WORK INTO THE AREA SUNDAY...AS WELL AS DRY AIR ALOFT AND THE EML
LATER IN THE DAY HELPING TO STEEPEN LAPSE RATES ALOFT. NEGATIVELY
TILTED TROUGH IS EXPECTED TO ROUND THE BASE OF THE LONGWAVE TROUGH
SUNDAY LIFTING INTO THE MID MISSOURI VALLEY SUNDAY NIGHT. MODELS ARE
MIXED ON WHETHER OR NOT THE CIN ERODES DURING THE DAYTIME...BUT IF
IT DOES CHANCES WILL BE BEST OVER WESTERN PORTIONS OF THE CWA...SO
HAVE MAINTAINED LOWER POPS. THERE MAY BE A BETTER CHANCE FOR
CONVECTION OVERNIGHT AS A LOW LEVEL JET DEVELOPS JUST TO OUR WEST
WITH LARGE SCALE ASCENT ASSOCIATED WITH AFOREMENTIONED TROUGH.
ON MONDAY...THE GFS INDICATES ANOTHER LOWER AMPLITUDE DISTURBANCE
WILL ROUND THE BASE OF THE LONGWAVE TROUGH AND LIFT INTO THE MID
MISSISSIPPI VALLEY. THIS CONTINUES TO BE A DAY TO KEEP AN EYE ON FOR
SEVERE WEATHER POTENTIAL. MODELS CONTINUE TO ADVERTISE MODERATE TO
STRONG INSTABILITY IN PLACE OVERHEAD WITH MARGINAL SHEAR CONDITIONS
TO SUPPORT SEVERE WEATHER. AS PREVIOUSLY MENTIONED...CONVECTION FROM
THE PREVIOUS NIGHT...CLOUD COVER...AND OTHER SMALL SCALE FEATURES
CANNOT BE RESOLVED THIS FAR OUT AND ADD A CONSIDERABLE AMOUNT OF
UNCERTAINTY. WE SHOULD BEGIN TO GET A BETTER PICTURE THIS WEEKEND SO
STAY TUNED FOR FORECAST UPDATES. DEPENDING ON THE SPEED OF THE
SYSTEM...TUESDAY WILL ALSO HAVE TO BE MONITORED...PERHAPS WITH THE
THREAT MORE FOCUSED ON THE EASTERN PORTIONS OF THE CWA.
IN ADDITION TO THE SEVERE THREAT...MULTIPLE ROUNDS OF THUNDERSTORMS
MOVING ALONG THE SLOW MOVING BOUNDARY SUNDAY NIGHT THROUGH TUESDAY
WILL LEAD TO A INCREASED HEAVY RAIN AND FLOODING THREAT.
FOR TEMPERATURES SUNDAY AND MONDAY...CONTINUE TO LEAN ON THE WARMER
BIAS CORRECTED GEM WHICH HAPPENED TO VERIFY BEST WITH THE
UNSEASONABLY HEAT TUESDAY. DEPENDING ON THE SPEED OF THE
SYSTEM...CURRENT FORECAST TEMPS MAY BE A BIT ON THE COOL SIDE
TUESDAY...PARTICULARLY THE EASTERN CWA. H85 TEMPS OF 16-18C AND H92
TEMPS OF 19-22C SHOULD SUPPORT TEMPERATURES WELL INTO THE 80S AND
WOULDN`T BE SURPRISED TO SEE PLACES HIT 90S THOSE DAYS...BUT WILL
REMAIN A BIT CONSERVATIVE GIVEN THE PRECIP CHANCES AND CLOUD COVER.
DEUBELBEISS
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 06Z...
* ISOLATED SHOWER REMAIN SOUTHWEST OF TERMINALS THRU MID-MORNING.
* PRECIP COVERAGE INCREASES BY MIDDAY...POSSIBLE THUNDERSTORM ARND
19-22Z.
* WINDS REMAIN EASTERLY WITH SPEEDS GENERALLY ARND 10KT OR
LESS...TURNING SOUTHEASTERLY AFT 05Z SAT.
* CIGS REMAIN VFR...POSSIBLE MVFR CIGS IN OR AROUND TSRA/SHRA.
BEACHLER
//DISCUSSION...UPDATED 06Z...
IR IMAGERY EARLY THIS MORNING SHOWS AN AREA OF CLOUDS ACROSS THE
WESTERN GREAT LAKES INTO THE UPPER MIDWEST. SCT SHOWERS/THUNDERSTORMS
ACROSS NORTHCENTRAL IOWA/SOUTHCENTRAL MINNESOTA. THIS PRECIPITATION WAS LOCATED
ALONG A STALLED FRONTAL BOUNDARY THAT STRETCHES EAST/SOUTHEAST
INTO CENTRAL IL/IN. AIRFIELDS ACROSS NORTHERN IL/NORTHWEST IN
REMAIN VFR...WITH SOME CLOUDS OBSERVED AT 8KFT AGL OR HIGHER.
GUIDANCE CONTINUE TO SUGGEST VFR CONDS WILL CONTINUE THROUGH
DAYBREAK...WITH A CONTINUED LIGHT EAST WIND ARND 8KT OR LESS. THE
DIRECTION WILL GENERALLY REMAIN BETWEEN A 060-090 DEG
RANGE...HOWEVER SOME VRB DIRECTIONS MAY OCCUR THRU DAYBREAK AS
SPEEDS WILL BE LESS THAN 5 KT.
THEN IT APPEARS THE BEST CHC FOR PRECIP WILL OCCUR SOUTHWEST OF
THE TAF SITES THRU MUCH OF THE MORNING...WITH MINIMAL COVERAGE. BY
MIDDAY COVERAGE SHUD BEGIN TO INCREASE IN
SHOWERS/THUNDERSTORMS...AND GUIDANCE IS BEGINNING TO SHOW A HIGHER
CONFIDENCE IN TIMING OF 18-22Z. HAVE OPTED TO PLACE A VCSH TO
HANDLE THE BEGINNING COVERAGE AT 16Z...WITH A TEMPO IN A 19-22Z
TIMEFRAME. THIS APPEARS TO BE THE BEST TIME THAT A THUNDERSTORM
WOULD OCCUR. THEN IT APPEARS ANY PRECIP WILL PUSH BACK TO THE
WEST/SOUTHWEST OF THE AIRFIELDS...WITH A SMALL CHC OF PRECIP
CONTINUEING THROUGH THE EVENING HOURS. WINDS WILL EVENTUALLY BEGIN
TO TURN SOUTHEASTERLY ONCE THE BOUNDARY LIFTS OVERHEAD AND TO THE
NORTH OF THE TAF SITES...HOWEVER THIS DOES NOT APPEAR TO OCCUR
UNTIL AFT 05Z SAT.
BEACHLER
//ORD AND MDW CONFIDENCE...UPDATED 06Z...
* HIGH CONFIDENCE IN WIND DIR/SPEED.
* MEDIUM CONFIDENCE IN CIGS FORECAST.
* LOW CONFIDENCE IN PRECIP TIMING/COVERAGE.
* MEDIUM CONFIDENCE IN THUNDERSTORMS.
* MEDIUM/HIGH CONFIDENCE IN WIND DIRECTION BECOMING SOUTHEAST
TIMING.
BEACHLER
//OUTLOOK FOR ORD/MDW FOR 12Z SATURDAY-12Z THURSDAY...UPDATED 00Z...
SATURDAY THROUGH WEDNESDAY...PERIODIC CHANCES FOR SHRA/TSRA...
OTHERWISE...VFR.
KREIN
&&
.MARINE...
228 PM CDT
RIDGING FROM HIGH PRESSURE CENTERED OVER WESTERN ONTARIO EXTENDS
ACROSS LAKE MICHIGAN THIS AFTERNOON. WEAK LOW PRESSURE WILL DEVELOP
AND MOVE UP THE OHIO RIVER VALLEY FRIDAY WITH ADDITIONAL LOW
PRESSURE DEVELOPING ACROSS THE CENTRAL HIGH PLAINS. EAST TO
NORTHEAST FLOW OVERALL WILL CONTINUE ACROSS THE LAKE...WITH ONSHORE
FLOW IN AREAS WHERE THE PRESSURE GRADIENT IS WEAKER CAUSING SOME
ERRATIC DIRECTIONS AT TIMES. STEADIER AND MORE UNIFORM WINDS WILL
DEVELOP WITH TIME THROUGH TOMORROW WITH MORE OF AN EAST TO SOUTHEAST
TREND. THE STRONGEST WINDS WILL OCCUR FRIDAY EVENING/NIGHT
COINCIDENT WITH THE STRONGEST PRESSURE GRADIENT THANKS TO THE LOW
PASSING TO THE SOUTHEAST. THE GRADIENT WEAKENS DURING THE DAY
SATURDAY AS THE LOW DEPARTS TO THE EAST. LOW PRESSURE STRENGTHENS
ACROSS THE CENTRAL/NORTHERN HIGH PLAINS INTO SUNDAY WHICH WILL
GRADUALLY TIGHTEN THE PRESSURE GRADIENT ACROSS THE LAKE. THIS WILL
ALLOW A STEADY SOUTH TO SOUTHEAST WIND TO DEVELOP ACROSS MOST OF THE
LAKE...WITH A MORE EASTERLY DIRECTION ACROSS THE FAR NORTH WHERE A
WARM FRONTAL BOUNDARY IS EXPECTED TO SET UP. THE MAIN LOW WILL
MEANDER NORTHWARD BEFORE BEING PUSHED EASTWARD ACROSS MINNESOTA/IOWA
SOMETIME TUESDAY OR WEDNESDAY WHICH WILL LIKELY PUSH THE FRONTAL
BOUNDARY FURTHER SOUTH ACROSS THE LAKE LEADING TO EAST TO NORTHEAST
WINDS NORTH AND SOUTH TO SOUTHWEST WINDS SOUTH BY MID WEEK. THE MAIN
CONCERN WILL BE THE POTENTIAL FOR INCREASED GUSTINESS ACROSS THE
NORTH AS COLDER AIR SETTLES IN ALLOWING SLIGHTLY INCREASED MIXING.
OTHERWISE...GENERALLY STABLE LOW LEVEL AIR ACROSS THE LAKE WILL KEEP
GUSTS TO A MINIMUM FROM TONIGHT THROUGH THE WEEKEND.
MDB
&&
.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 170303
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1003 PM CDT THU MAY 16 2013
.DISCUSSION...
930 PM CDT
THE FORECAST FOR TONIGHT HAS BEEN TWEAKED SLIGHTLY...TO CONTINUE
THE EVENING CHANCE OF THUNDER ACROSS THE SOUTHERN FORECAST AREA
THROUGH THE NIGHT...AND TO NUDGE IT NORTH SOME.
THE EVE WATER VAPOR LOOP DEPICTS THE CLOSED UPPER LOW ACROSS
NORTHERN AR EASING ITS WAY NORTHEAST. AT THE SURFACE...THE
PRIMARILY SYNOPTIC FRONT IS NEAR THE LOT/ILX CWA BORDER WITH A
LAKE BREEZE HAVING PUSHED WELL INLAND. BETWEEN THESE TWO A FEW
STORMS GENERATED...IT LOOKED LIKE ON A SLIGHTLY ELEVATED BOUNDARY
JUST NORTH OF THE SURFACE BOUNDARY PER ILX RADAR. THESE MAY FESTER
NORTHEAST ON THE AFOREMENTIONED MULTIPLE AREAS OF LOW-LEVEL
CONVERGENCE FOR SEVERAL MORE HOURS...BUT ANY CG LIGHTNING HAS BEEN
SPORADIC AT BEST AND WOULD EXPECT THAT TREND TO CONTINUE OR
DIMINISH ALTOGETHER. THE HRRR DOES INDICATE THESE SHOWERS TO SORT
OF OSCILLATE ALL THE WAY UP TO FAR NORTHEAST IL THROUGH EARLY
OVERNIGHT.
THE ILX VAD PROFILER INDICATES INCREASING SOUTHERLY FLOW BELOW 3K
FT...NOW UP TO 30 KT. THE LOW-LEVEL JET IS NOT EXPECTED TO
INCREASE MUCH FROM THAT MAGNITUDE AND POINT MORE INTO WESTERN IL.
MOISTURE TRANSPORT IS MORE LIMITED TONIGHT SO NOT EXPECTING AS
MUCH IF ANY ELEVATED CONVECTION...BUT COULD SEE SOME IN WESTERN IL
WHERE A LITTLE MORE THETA-E ADVECTION AND CONVERGENCE AROUND 850MB
IS FORECAST.
THE LAKE BREEZE MADE IMPRESSIVE PROGRESS WSW THROUGH EARLY EVE
AFTER SORT OF A SLOW START. A 30 DEGREE SPREAD AS OF 930 PM EXISTS
ACROSS THE CWA SIMPLY FROM JUST THIS MESOSCALE BOUNDARY. HAVE
ADJUSTED THE HOURLY TEMPERATURE FORECAST TO MEET TRENDS. THE LAV
GUIDANCE HAS VERY LITTLE TEMPERATURE DROP FOR MANY POINTS THROUGH
THE REST OF THE NIGHT...LIKELY DUE TO INCREASING CLOUD COVER.
WHILE CAA OFF THE LAKE LIKELY WILL CREATE A LITTLE MORE DROP THAN
IT ADVERTISES...THIS IS IN LINE WITH THE GOING MINIMUM TEMPERATURE
FORECASTS.
MTF
//PREV DISCUSSION...
259 PM CDT
TODAY`S FORECAST CHALLENGES CONTINUE TO BE DEALING WITH FRONTAL
BOUNDARY CURRENTLY JUST SOUTH OF THE CWA...AND PERIODIC CONVECTIVE
CHANCES THROUGH MID NEXT WEEK.
TODAY AND TONIGHT...
THIS AFTERNOON THE FRONT IS LOCATED JUST NORTH OF QUINCY IL EAST TO
NEAR TERRE HAUTE INDIANA...AND HAS BEEN SLOWLY PUSHING NORTH THIS
AFTERNOON. MODERATE INSTABILITY EXISTS SOUTH OF THE FRONT AND MAY
LIFT INTO FAR SOUTHERN PORTIONS OF THE CWA LATE THIS EVENING BEFORE
FADING NOCTURNALLY. MAINTAINED SLT CHC POPS FOR A FEW HOURS THIS
EVENING WHEN THIS OCCURS...BUT OTHERWISE SHOULD BE FAIRLY QUIET
PERIOD THROUGH TONIGHT.
FRIDAY THROUGH SATURDAY...
COMPACT SHORTWAVE NOTED ON WV IMAGERY THIS AFTERNOON OVER WESTERN
NE/KS WILL CONTINUE ENE INTO WEST CENTRAL WISCONSIN BY FRIDAY
AFTERNOON. AS THIS HAPPENS...SOUTHERLY FLOW INCREASE AT THE SURFACE
AND SHOULD HELP PUSH THE BOUNDARY NORTH ACROSS THE AREA. DEWPOINTS
RISE INTO THE MID 60S AND MODEST INSTABILITY DEVELOPS OUTSIDE OF FAR
NE ILLINOIS WHERE ONSHORE WINDS WILL KEEP CONDITIONS COOLER/MORE
STABLE. THIS INSTABILITY IS UNCAPPED...AND GIVEN THERE IS NO WELL
DEFINED FOCUS FOR THUNDERSTORMS...EXPECT UNORGANIZED/SCATTERED
CONVECTION TO DEVELOP WITHIN THE WARM SECTOR. MID LEVEL LAPSE RATES
ARE PRETTY POOR...SO CONVECTION MAY STRUGGLE AT TIMES AND MAY LIMIT
THE THUNDER CHANCES TO SOME DEGREE. MUCH OF THE SAME IS EXPECTED
SATURDAY SO WILL MAINTAIN THE LOW POPS FOR DIURNALLY DRIVEN TSTORMS.
SUNDAY THROUGH TUESDAY...
THIS PERIOD CONTINUES TO LOOK ACTIVE AS THE OVERALL PATTERN
AMPLIFIES WITH DEEP TROUGHING DEVELOPING ACROSS THE WESTERN
CONUS...AND STRONG RIDGING EAST. THE H85 THERMAL RIDGE BEGINS TO
WORK INTO THE AREA SUNDAY...AS WELL AS DRY AIR ALOFT AND THE EML
LATER IN THE DAY HELPING TO STEEPEN LAPSE RATES ALOFT. NEGATIVELY
TILTED TROUGH IS EXPECTED TO ROUND THE BASE OF THE LONGWAVE TROUGH
SUNDAY LIFTING INTO THE MID MISSOURI VALLEY SUNDAY NIGHT. MODELS ARE
MIXED ON WHETHER OR NOT THE CIN ERODES DURING THE DAYTIME...BUT IF
IT DOES CHANCES WILL BE BEST OVER WESTERN PORTIONS OF THE CWA...SO
HAVE MAINTAINED LOWER POPS. THERE MAY BE A BETTER CHANCE FOR
CONVECTION OVERNIGHT AS A LOW LEVEL JET DEVELOPS JUST TO OUR WEST
WITH LARGE SCALE ASCENT ASSOCIATED WITH AFOREMENTIONED TROUGH.
ON MONDAY...THE GFS INDICATES ANOTHER LOWER AMPLITUDE DISTURBANCE
WILL ROUND THE BASE OF THE LONGWAVE TROUGH AND LIFT INTO THE MID
MISSISSIPPI VALLEY. THIS CONTINUES TO BE A DAY TO KEEP AN EYE ON FOR
SEVERE WEATHER POTENTIAL. MODELS CONTINUE TO ADVERTISE MODERATE TO
STRONG INSTABILITY IN PLACE OVERHEAD WITH MARGINAL SHEAR CONDITIONS
TO SUPPORT SEVERE WEATHER. AS PREVIOUSLY MENTIONED...CONVECTION FROM
THE PREVIOUS NIGHT...CLOUD COVER...AND OTHER SMALL SCALE FEATURES
CANNOT BE RESOLVED THIS FAR OUT AND ADD A CONSIDERABLE AMOUNT OF
UNCERTAINTY. WE SHOULD BEGIN TO GET A BETTER PICTURE THIS WEEKEND SO
STAY TUNED FOR FORECAST UPDATES. DEPENDING ON THE SPEED OF THE
SYSTEM...TUESDAY WILL ALSO HAVE TO BE MONITORED...PERHAPS WITH THE
THREAT MORE FOCUSED ON THE EASTERN PORTIONS OF THE CWA.
IN ADDITION TO THE SEVERE THREAT...MULTIPLE ROUNDS OF THUNDERSTORMS
MOVING ALONG THE SLOW MOVING BOUNDARY SUNDAY NIGHT THROUGH TUESDAY
WILL LEAD TO A INCREASED HEAVY RAIN AND FLOODING THREAT.
FOR TEMPERATURES SUNDAY AND MONDAY...CONTINUE TO LEAN ON THE WARMER
BIAS CORRECTED GEM WHICH HAPPENED TO VERIFY BEST WITH THE
UNSEASONABLY HEAT TUESDAY. DEPENDING ON THE SPEED OF THE
SYSTEM...CURRENT FORECAST TEMPS MAY BE A BIT ON THE COOL SIDE
TUESDAY...PARTICULARLY THE EASTERN CWA. H85 TEMPS OF 16-18C AND H92
TEMPS OF 19-22C SHOULD SUPPORT TEMPERATURES WELL INTO THE 80S AND
WOULDN`T BE SURPRISED TO SEE PLACES HIT 90S THOSE DAYS...BUT WILL
REMAIN A BIT CONSERVATIVE GIVEN THE PRECIP CHANCES AND CLOUD COVER.
DEUBELBEISS
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 03Z...
* NELY WINDS 5-10KT OVERNIGHT BECMG SELY TOMORROW MORNING THEN
BACKING ELY IN THE AFTERNOON.
* CHANCE TSRA/SHRA TOMORROW AFTERNOON/EVENING.
KREIN
//DISCUSSION...UPDATED 00Z...
THE LAKE BREEZE HAS FINALLY PUSHED INLAND OF ORD/MDW/GYY AND
SHOULD PUSH THROUGH DPA SOON AS WELL. THIS WILL SET UP ENELY WINDS
OVER NERN IL/NWRN IN...BUT WILL LIKELY NOT IMPACT RFD WHICH SHOULD
REMAIN SELY THROUGH THE NIGHT. HAVE BEEN MONITORING THE
PROGRESSION OF THE LAKE BREEZE BOUNDARY TO THE SOUTHWEST ALONG
WITH ANOTHER WEAK BOUNDARY MOVING NORTHWARD ALONG THE
ILLINOIS/KANKAKEE RIVERS. THIS WEAK BOUNDARY SEPARATES SOUTHERLY
FLOW WITH SLIGHTLY HIGHER DEWPOINTS. WILL NEED TO MONITOR THESE
BOUNDARYS CLOSELY AS THEY APPROACH EACH OTHER FOR ANY SHRA/TSRA
DEVELOPMENT...WHICH BASED ON CURRENT TRACK/TIMING WOULD BE INVOF
KJOT AREA. OTHERWISE THE REMAINDER OF THE NIGHT SHOULD BE QUIET AT
THE TERMINALS. FOCUS WILL THEN SHIFT TO TSRA POTENTIAL TOMORROW
AFTERNOON. LATEST GUIDANCE INDICATES A WARM FRONT LIFTING INTO NRN
IL/IN BY LATE TOMORROW AFTERNOON. MOISTURE POOLING ALONG THE
BOUNDARY AND ISENTROPIC LIFT ALONG THE FRONTAL ZONE WILL PROVIDE
ENOUGH FOCUS TO NECESSATE ADDING A PROB30 GROUP TO THE FORECAST.
TIMING WILL BE THE MAIN QUESTION...BUT GENERALLY EXPECT THE BEST
TIMING TO BE DURG THE LATE AFTERNOON/EARLY EVENING HOURS.
KREIN
//ORD AND MDW CONFIDENCE...UPDATED 03Z...
* MODERATE TO HIGH CONFIDENCE IN WIND TRENDS.
* MODERATE CONFIDENCE IN TSRA/SHRA CHANCES TOMORROW...BUT LOWER
CONFIDENCE IN EXACT TIMING.
KREIN
//OUTLOOK FOR ORD/MDW FOR 12Z SATURDAY-12Z THURSDAY...UPDATED 00Z...
SATURDAY THROUGH WEDNESDAY...PERIODIC CHANCES FOR SHRA/TSRA...
OTHERWISE...VFR.
KREIN
&&
.MARINE...
228 PM CDT
RIDGING FROM HIGH PRESSURE CENTERED OVER WESTERN ONTARIO EXTENDS
ACROSS LAKE MICHIGAN THIS AFTERNOON. WEAK LOW PRESSURE WILL DEVELOP
AND MOVE UP THE OHIO RIVER VALLEY FRIDAY WITH ADDITIONAL LOW
PRESSURE DEVELOPING ACROSS THE CENTRAL HIGH PLAINS. EAST TO
NORTHEAST FLOW OVERALL WILL CONTINUE ACROSS THE LAKE...WITH ONSHORE
FLOW IN AREAS WHERE THE PRESSURE GRADIENT IS WEAKER CAUSING SOME
ERRATIC DIRECTIONS AT TIMES. STEADIER AND MORE UNIFORM WINDS WILL
DEVELOP WITH TIME THROUGH TOMORROW WITH MORE OF AN EAST TO SOUTHEAST
TREND. THE STRONGEST WINDS WILL OCCUR FRIDAY EVENING/NIGHT
COINCIDENT WITH THE STRONGEST PRESSURE GRADIENT THANKS TO THE LOW
PASSING TO THE SOUTHEAST. THE GRADIENT WEAKENS DURING THE DAY
SATURDAY AS THE LOW DEPARTS TO THE EAST. LOW PRESSURE STRENGTHENS
ACROSS THE CENTRAL/NORTHERN HIGH PLAINS INTO SUNDAY WHICH WILL
GRADUALLY TIGHTEN THE PRESSURE GRADIENT ACROSS THE LAKE. THIS WILL
ALLOW A STEADY SOUTH TO SOUTHEAST WIND TO DEVELOP ACROSS MOST OF THE
LAKE...WITH A MORE EASTERLY DIRECTION ACROSS THE FAR NORTH WHERE A
WARM FRONTAL BOUNDARY IS EXPECTED TO SET UP. THE MAIN LOW WILL
MEANDER NORTHWARD BEFORE BEING PUSHED EASTWARD ACROSS MINNESOTA/IOWA
SOMETIME TUESDAY OR WEDNESDAY WHICH WILL LIKELY PUSH THE FRONTAL
BOUNDARY FURTHER SOUTH ACROSS THE LAKE LEADING TO EAST TO NORTHEAST
WINDS NORTH AND SOUTH TO SOUTHWEST WINDS SOUTH BY MID WEEK. THE MAIN
CONCERN WILL BE THE POTENTIAL FOR INCREASED GUSTINESS ACROSS THE
NORTH AS COLDER AIR SETTLES IN ALLOWING SLIGHTLY INCREASED MIXING.
OTHERWISE...GENERALLY STABLE LOW LEVEL AIR ACROSS THE LAKE WILL KEEP
GUSTS TO A MINIMUM FROM TONIGHT THROUGH THE WEEKEND.
MDB
&&
.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 170239 AAA
AFDLOT
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
939 PM CDT THU MAY 16 2013
.DISCUSSION...
930 PM CDT
THE FORECAST FOR TONIGHT HAS BEEN TWEAKED SLIGHTLY...TO CONTINUE
THE EVENING CHANCE OF THUNDER ACROSS THE SOUTHERN FORECAST AREA
THROUGH THE NIGHT...AND TO NUDGE IT NORTH SOME.
THE EVE WATER VAPOR LOOP DEPICTS THE CLOSED UPPER LOW ACROSS
NORTHERN AR EASING ITS WAY NORTHEAST. AT THE SURFACE...THE
PRIMARILY SYNOPTIC FRONT IS NEAR THE LOT/ILX CWA BORDER WITH A
LAKE BREEZE HAVING PUSHED WELL INLAND. BETWEEN THESE TWO A FEW
STORMS GENERATED...IT LOOKED LIKE ON A SLIGHTLY ELEVATED BOUNDARY
JUST NORTH OF THE SURFACE BOUNDARY PER ILX RADAR. THESE MAY FESTER
NORTHEAST ON THE AFOREMENTIONED MULTIPLE AREAS OF LOW-LEVEL
CONVERGENCE FOR SEVERAL MORE HOURS...BUT ANY CG LIGHTNING HAS BEEN
SPORADIC AT BEST AND WOULD EXPECT THAT TREND TO CONTINUE OR
DIMINISH ALTOGETHER. THE HRRR DOES INDICATE THESE SHOWERS TO SORT
OF OSCILLATE ALL THE WAY UP TO FAR NORTHEAST IL THROUGH EARLY
OVERNIGHT.
THE ILX VAD PROFILER INDICATES INCREASING SOUTHERLY FLOW BELOW 3K
FT...NOW UP TO 30 KT. THE LOW-LEVEL JET IS NOT EXPECTED TO
INCREASE MUCH FROM THAT MAGNITUDE AND POINT MORE INTO WESTERN IL.
MOISTURE TRANSPORT IS MORE LIMITED TONIGHT SO NOT EXPECTING AS
MUCH IF ANY ELEVATED CONVECTION...BUT COULD SEE SOME IN WESTERN IL
WHERE A LITTLE MORE THETA-E ADVECTION AND CONVERGENCE AROUND 850MB
IS FORECAST.
THE LAKE BREEZE MADE IMPRESSIVE PROGRESS WSW THROUGH EARLY EVE
AFTER SORT OF A SLOW START. A 30 DEGREE SPREAD AS OF 930 PM EXISTS
ACROSS THE CWA SIMPLY FROM JUST THIS MESOSCALE BOUNDARY. HAVE
ADJUSTED THE HOURLY TEMPERATURE FORECAST TO MEET TRENDS. THE LAV
GUIDANCE HAS VERY LITTLE TEMPERATURE DROP FOR MANY POINTS THROUGH
THE REST OF THE NIGHT...LIKELY DUE TO INCREASING CLOUD COVER.
WHILE CAA OFF THE LAKE LIKELY WILL CREATE A LITTLE MORE DROP THAN
IT ADVERTISES...THIS IS IN LINE WITH THE GOING MINIMUM TEMPERATURE
FORECASTS.
MTF
&&
.PREV DISCUSSION...
259 PM CDT
TODAY`S FORECAST CHALLENGES CONTINUE TO BE DEALING WITH FRONTAL
BOUNDARY CURRENTLY JUST SOUTH OF THE CWA...AND PERIODIC CONVECTIVE
CHANCES THROUGH MID NEXT WEEK.
TODAY AND TONIGHT...
THIS AFTERNOON THE FRONT IS LOCATED JUST NORTH OF QUINCY IL EAST TO
NEAR TERRE HAUTE INDIANA...AND HAS BEEN SLOWLY PUSHING NORTH THIS
AFTERNOON. MODERATE INSTABILITY EXISTS SOUTH OF THE FRONT AND MAY
LIFT INTO FAR SOUTHERN PORTIONS OF THE CWA LATE THIS EVENING BEFORE
FADING NOCTURNALLY. MAINTAINED SLT CHC POPS FOR A FEW HOURS THIS
EVENING WHEN THIS OCCURS...BUT OTHERWISE SHOULD BE FAIRLY QUIET
PERIOD THROUGH TONIGHT.
FRIDAY THROUGH SATURDAY...
COMPACT SHORTWAVE NOTED ON WV IMAGERY THIS AFTERNOON OVER WESTERN
NE/KS WILL CONTINUE ENE INTO WEST CENTRAL WISCONSIN BY FRIDAY
AFTERNOON. AS THIS HAPPENS...SOUTHERLY FLOW INCREASE AT THE SURFACE
AND SHOULD HELP PUSH THE BOUNDARY NORTH ACROSS THE AREA. DEWPOINTS
RISE INTO THE MID 60S AND MODEST INSTABILITY DEVELOPS OUTSIDE OF FAR
NE ILLINOIS WHERE ONSHORE WINDS WILL KEEP CONDITIONS COOLER/MORE
STABLE. THIS INSTABILITY IS UNCAPPED...AND GIVEN THERE IS NO WELL
DEFINED FOCUS FOR THUNDERSTORMS...EXPECT UNORGANIZED/SCATTERED
CONVECTION TO DEVELOP WITHIN THE WARM SECTOR. MID LEVEL LAPSE RATES
ARE PRETTY POOR...SO CONVECTION MAY STRUGGLE AT TIMES AND MAY LIMIT
THE THUNDER CHANCES TO SOME DEGREE. MUCH OF THE SAME IS EXPECTED
SATURDAY SO WILL MAINTAIN THE LOW POPS FOR DIURNALLY DRIVEN TSTORMS.
SUNDAY THROUGH TUESDAY...
THIS PERIOD CONTINUES TO LOOK ACTIVE AS THE OVERALL PATTERN
AMPLIFIES WITH DEEP TROUGHING DEVELOPING ACROSS THE WESTERN
CONUS...AND STRONG RIDGING EAST. THE H85 THERMAL RIDGE BEGINS TO
WORK INTO THE AREA SUNDAY...AS WELL AS DRY AIR ALOFT AND THE EML
LATER IN THE DAY HELPING TO STEEPEN LAPSE RATES ALOFT. NEGATIVELY
TILTED TROUGH IS EXPECTED TO ROUND THE BASE OF THE LONGWAVE TROUGH
SUNDAY LIFTING INTO THE MID MISSOURI VALLEY SUNDAY NIGHT. MODELS ARE
MIXED ON WHETHER OR NOT THE CIN ERODES DURING THE DAYTIME...BUT IF
IT DOES CHANCES WILL BE BEST OVER WESTERN PORTIONS OF THE CWA...SO
HAVE MAINTAINED LOWER POPS. THERE MAY BE A BETTER CHANCE FOR
CONVECTION OVERNIGHT AS A LOW LEVEL JET DEVELOPS JUST TO OUR WEST
WITH LARGE SCALE ASCENT ASSOCIATED WITH AFOREMENTIONED TROUGH.
ON MONDAY...THE GFS INDICATES ANOTHER LOWER AMPLITUDE DISTURBANCE
WILL ROUND THE BASE OF THE LONGWAVE TROUGH AND LIFT INTO THE MID
MISSISSIPPI VALLEY. THIS CONTINUES TO BE A DAY TO KEEP AN EYE ON FOR
SEVERE WEATHER POTENTIAL. MODELS CONTINUE TO ADVERTISE MODERATE TO
STRONG INSTABILITY IN PLACE OVERHEAD WITH MARGINAL SHEAR CONDITIONS
TO SUPPORT SEVERE WEATHER. AS PREVIOUSLY MENTIONED...CONVECTION FROM
THE PREVIOUS NIGHT...CLOUD COVER...AND OTHER SMALL SCALE FEATURES
CANNOT BE RESOLVED THIS FAR OUT AND ADD A CONSIDERABLE AMOUNT OF
UNCERTAINTY. WE SHOULD BEGIN TO GET A BETTER PICTURE THIS WEEKEND SO
STAY TUNED FOR FORECAST UPDATES. DEPENDING ON THE SPEED OF THE
SYSTEM...TUESDAY WILL ALSO HAVE TO BE MONITORED...PERHAPS WITH THE
THREAT MORE FOCUSED ON THE EASTERN PORTIONS OF THE CWA.
IN ADDITION TO THE SEVERE THREAT...MULTIPLE ROUNDS OF THUNDERSTORMS
MOVING ALONG THE SLOW MOVING BOUNDARY SUNDAY NIGHT THROUGH TUESDAY
WILL LEAD TO A INCREASED HEAVY RAIN AND FLOODING THREAT.
FOR TEMPERATURES SUNDAY AND MONDAY...CONTINUE TO LEAN ON THE WARMER
BIAS CORRECTED GEM WHICH HAPPENED TO VERIFY BEST WITH THE
UNSEASONABLY HEAT TUESDAY. DEPENDING ON THE SPEED OF THE
SYSTEM...CURRENT FORECAST TEMPS MAY BE A BIT ON THE COOL SIDE
TUESDAY...PARTICULARLY THE EASTERN CWA. H85 TEMPS OF 16-18C AND H92
TEMPS OF 19-22C SHOULD SUPPORT TEMPERATURES WELL INTO THE 80S AND
WOULDN`T BE SURPRISED TO SEE PLACES HIT 90S THOSE DAYS...BUT WILL
REMAIN A BIT CONSERVATIVE GIVEN THE PRECIP CHANCES AND CLOUD COVER.
DEUBELBEISS
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 00Z...
* ENELY WINDS 5-10KT FOLLOWING LAKE BREEZE PASSAGE.
* SELY WINDS TOMORROW MORNING BACKING ELY IN THE AFTERNOON.
* CHANCE TSRA/SHRA TOMORROW AFTERNOON/EVENING.
KREIN
//DISCUSSION...UPDATED 00Z...
THE LAKE BREEZE HAS FINALLY PUSHED INLAND OF ORD/MDW/GYY AND
SHOULD PUSH THROUGH DPA SOON AS WELL. THIS WILL SET UP ENELY WINDS
OVER NERN IL/NWRN IN...BUT WILL LIKELY NOT IMPACT RFD WHICH SHOULD
REMAIN SELY THROUGH THE NIGHT. HAVE BEEN MONITORING THE
PROGRESSION OF THE LAKE BREEZE BOUNDARY TO THE SOUTHWEST ALONG
WITH ANOTHER WEAK BOUNDARY MOVING NORTHWARD ALONG THE
ILLINOIS/KANKAKEE RIVERS. THIS WEAK BOUNDARY SEPARATES SOUTHERLY
FLOW WITH SLIGHTLY HIGHER DEWPOINTS. WILL NEED TO MONITOR THESE
BOUNDARYS CLOSELY AS THEY APPROACH EACH OTHER FOR ANY SHRA/TSRA
DEVELOPMENT...WHICH BASED ON CURRENT TRACK/TIMING WOULD BE INVOF
KJOT AREA. OTHERWISE THE REMAINDER OF THE NIGHT SHOULD BE QUIET AT
THE TERMINALS. FOCUS WILL THEN SHIFT TO TSRA POTENTIAL TOMORROW
AFTERNOON. LATEST GUIDANCE INDICATES A WARM FRONT LIFTING INTO NRN
IL/IN BY LATE TOMORROW AFTERNOON. MOISTURE POOLING ALONG THE
BOUNDARY AND ISENTROPIC LIFT ALONG THE FRONTAL ZONE WILL PROVIDE
ENOUGH FOCUS TO NECESSATE ADDING A PROB30 GROUP TO THE FORECAST.
TIMING WILL BE THE MAIN QUESTION...BUT GENERALLY EXPECT THE BEST
TIMING TO BE DURG THE LATE AFTERNOON/EARLY EVENING HOURS.
KREIN
//ORD AND MDW CONFIDENCE...UPDATED 00Z...
* MODERATE TO HIGH CONFIDENCE IN WIND TRENDS.
* MODERATE CONFIDENCE IN TSRA/SHRA CHANCES TOMORROW...BUT LOWER
CONFIDENCE IN EXACT TIMING.
KREIN
//OUTLOOK FOR ORD/MDW FOR 12Z SATURDAY-12Z THURSDAY...UPDATED 00Z...
SATURDAY THROUGH WEDNESDAY...PERIODIC CHANCES FOR SHRA/TSRA...
OTHERWISE...VFR.
KREIN
&&
.MARINE...
228 PM CDT
RIDGING FROM HIGH PRESSURE CENTERED OVER WESTERN ONTARIO EXTENDS
ACROSS LAKE MICHIGAN THIS AFTERNOON. WEAK LOW PRESSURE WILL DEVELOP
AND MOVE UP THE OHIO RIVER VALLEY FRIDAY WITH ADDITIONAL LOW
PRESSURE DEVELOPING ACROSS THE CENTRAL HIGH PLAINS. EAST TO
NORTHEAST FLOW OVERALL WILL CONTINUE ACROSS THE LAKE...WITH ONSHORE
FLOW IN AREAS WHERE THE PRESSURE GRADIENT IS WEAKER CAUSING SOME
ERRATIC DIRECTIONS AT TIMES. STEADIER AND MORE UNIFORM WINDS WILL
DEVELOP WITH TIME THROUGH TOMORROW WITH MORE OF AN EAST TO SOUTHEAST
TREND. THE STRONGEST WINDS WILL OCCUR FRIDAY EVENING/NIGHT
COINCIDENT WITH THE STRONGEST PRESSURE GRADIENT THANKS TO THE LOW
PASSING TO THE SOUTHEAST. THE GRADIENT WEAKENS DURING THE DAY
SATURDAY AS THE LOW DEPARTS TO THE EAST. LOW PRESSURE STRENGTHENS
ACROSS THE CENTRAL/NORTHERN HIGH PLAINS INTO SUNDAY WHICH WILL
GRADUALLY TIGHTEN THE PRESSURE GRADIENT ACROSS THE LAKE. THIS WILL
ALLOW A STEADY SOUTH TO SOUTHEAST WIND TO DEVELOP ACROSS MOST OF THE
LAKE...WITH A MORE EASTERLY DIRECTION ACROSS THE FAR NORTH WHERE A
WARM FRONTAL BOUNDARY IS EXPECTED TO SET UP. THE MAIN LOW WILL
MEANDER NORTHWARD BEFORE BEING PUSHED EASTWARD ACROSS MINNESOTA/IOWA
SOMETIME TUESDAY OR WEDNESDAY WHICH WILL LIKELY PUSH THE FRONTAL
BOUNDARY FURTHER SOUTH ACROSS THE LAKE LEADING TO EAST TO NORTHEAST
WINDS NORTH AND SOUTH TO SOUTHWEST WINDS SOUTH BY MID WEEK. THE MAIN
CONCERN WILL BE THE POTENTIAL FOR INCREASED GUSTINESS ACROSS THE
NORTH AS COLDER AIR SETTLES IN ALLOWING SLIGHTLY INCREASED MIXING.
OTHERWISE...GENERALLY STABLE LOW LEVEL AIR ACROSS THE LAKE WILL KEEP
GUSTS TO A MINIMUM FROM TONIGHT THROUGH THE WEEKEND.
MDB
&&
.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 162346
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
646 PM CDT THU MAY 16 2013
.DISCUSSION...
259 PM CDT
TODAY`S FORECAST CHALLENGES CONTINUE TO BE DEALING WITH FRONTAL
BOUNDARY CURRENTLY JUST SOUTH OF THE CWA...AND PERIODIC CONVECTIVE
CHANCES THROUGH MID NEXT WEEK.
TODAY AND TONIGHT...
THIS AFTERNOON THE FRONT IS LOCATED JUST NORTH OF QUINCY IL EAST TO
NEAR TERRE HAUTE INDIANA...AND HAS BEEN SLOWLY PUSHING NORTH THIS
AFTERNOON. MODERATE INSTABILITY EXISTS SOUTH OF THE FRONT AND MAY
LIFT INTO FAR SOUTHERN PORTIONS OF THE CWA LATE THIS EVENING BEFORE
FADING NOCTURNALLY. MAINTAINED SLT CHC POPS FOR A FEW HOURS THIS
EVENING WHEN THIS OCCURS...BUT OTHERWISE SHOULD BE FAIRLY QUIET
PERIOD THROUGH TONIGHT.
FRIDAY THROUGH SATURDAY...
COMPACT SHORTWAVE NOTED ON WV IMAGERY THIS AFTERNOON OVER WESTERN
NE/KS WILL CONTINUE ENE INTO WEST CENTRAL WISCONSIN BY FRIDAY
AFTERNOON. AS THIS HAPPENS...SOUTHERLY FLOW INCREASE AT THE SURFACE
AND SHOULD HELP PUSH THE BOUNDARY NORTH ACROSS THE AREA. DEWPOINTS
RISE INTO THE MID 60S AND MODEST INSTABILITY DEVELOPS OUTSIDE OF FAR
NE ILLINOIS WHERE ONSHORE WINDS WILL KEEP CONDITIONS COOLER/MORE
STABLE. THIS INSTABILITY IS UNCAPPED...AND GIVEN THERE IS NO WELL
DEFINED FOCUS FOR THUNDERSTORMS...EXPECT UNORGANIZED/SCATTERED
CONVECTION TO DEVELOP WITHIN THE WARM SECTOR. MID LEVEL LAPSE RATES
ARE PRETTY POOR...SO CONVECTION MAY STRUGGLE AT TIMES AND MAY LIMIT
THE THUNDER CHANCES TO SOME DEGREE. MUCH OF THE SAME IS EXPECTED
SATURDAY SO WILL MAINTAIN THE LOW POPS FOR DIURNALLY DRIVEN TSTORMS.
SUNDAY THROUGH TUESDAY...
THIS PERIOD CONTINUES TO LOOK ACTIVE AS THE OVERALL PATTERN
AMPLIFIES WITH DEEP TROUGHING DEVELOPING ACROSS THE WESTERN
CONUS...AND STRONG RIDGING EAST. THE H85 THERMAL RIDGE BEGINS TO
WORK INTO THE AREA SUNDAY...AS WELL AS DRY AIR ALOFT AND THE EML
LATER IN THE DAY HELPING TO STEEPEN LAPSE RATES ALOFT. NEGATIVELY
TILTED TROUGH IS EXPECTED TO ROUND THE BASE OF THE LONGWAVE TROUGH
SUNDAY LIFTING INTO THE MID MISSOURI VALLEY SUNDAY NIGHT. MODELS ARE
MIXED ON WHETHER OR NOT THE CIN ERODES DURING THE DAYTIME...BUT IF
IT DOES CHANCES WILL BE BEST OVER WESTERN PORTIONS OF THE CWA...SO
HAVE MAINTAINED LOWER POPS. THERE MAY BE A BETTER CHANCE FOR
CONVECTION OVERNIGHT AS A LOW LEVEL JET DEVELOPS JUST TO OUR WEST
WITH LARGE SCALE ASCENT ASSOCIATED WITH AFOREMENTIONED TROUGH.
ON MONDAY...THE GFS INDICATES ANOTHER LOWER AMPLITUDE DISTURBANCE
WILL ROUND THE BASE OF THE LONGWAVE TROUGH AND LIFT INTO THE MID
MISSISSIPPI VALLEY. THIS CONTINUES TO BE A DAY TO KEEP AN EYE ON FOR
SEVERE WEATHER POTENTIAL. MODELS CONTINUE TO ADVERTISE MODERATE TO
STRONG INSTABILITY IN PLACE OVERHEAD WITH MARGINAL SHEAR CONDITIONS
TO SUPPORT SEVERE WEATHER. AS PREVIOUSLY MENTIONED...CONVECTION FROM
THE PREVIOUS NIGHT...CLOUD COVER...AND OTHER SMALL SCALE FEATURES
CANNOT BE RESOLVED THIS FAR OUT AND ADD A CONSIDERABLE AMOUNT OF
UNCERTAINTY. WE SHOULD BEGIN TO GET A BETTER PICTURE THIS WEEKEND SO
STAY TUNED FOR FORECAST UPDATES. DEPENDING ON THE SPEED OF THE
SYSTEM...TUESDAY WILL ALSO HAVE TO BE MONITORED...PERHAPS WITH THE
THREAT MORE FOCUSED ON THE EASTERN PORTIONS OF THE CWA.
IN ADDITION TO THE SEVERE THREAT...MULTIPLE ROUNDS OF THUNDERSTORMS
MOVING ALONG THE SLOW MOVING BOUNDARY SUNDAY NIGHT THROUGH TUESDAY
WILL LEAD TO A INCREASED HEAVY RAIN AND FLOODING THREAT.
FOR TEMPERATURES SUNDAY AND MONDAY...CONTINUE TO LEAN ON THE WARMER
BIAS CORRECTED GEM WHICH HAPPENED TO VERIFY BEST WITH THE
UNSEASONABLY HEAT TUESDAY. DEPENDING ON THE SPEED OF THE
SYSTEM...CURRENT FORECAST TEMPS MAY BE A BIT ON THE COOL SIDE
TUESDAY...PARTICULARLY THE EASTERN CWA. H85 TEMPS OF 16-18C AND H92
TEMPS OF 19-22C SHOULD SUPPORT TEMPERATURES WELL INTO THE 80S AND
WOULDN`T BE SURPRISED TO SEE PLACES HIT 90S THOSE DAYS...BUT WILL
REMAIN A BIT CONSERVATIVE GIVEN THE PRECIP CHANCES AND CLOUD COVER.
DEUBELBEISS
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 00Z...
* ENELY WINDS 5-10KT FOLLOWING LAKE BREEZE PASSAGE.
* SELY WINDS TOMORROW MORNING BACKING ELY IN THE AFTERNOON.
* CHANCE TSRA/SHRA TOMORROW AFTERNOON/EVENING.
KREIN
//DISCUSSION...UPDATED 00Z...
THE LAKE BREEZE HAS FINALLY PUSHED INLAND OF ORD/MDW/GYY AND
SHOULD PUSH THROUGH DPA SOON AS WELL. THIS WILL SET UP ENELY WINDS
OVER NERN IL/NWRN IN...BUT WILL LIKELY NOT IMPACT RFD WHICH SHOULD
REMAIN SELY THROUGH THE NIGHT. HAVE BEEN MONITORING THE
PROGRESSION OF THE LAKE BREEZE BOUNDARY TO THE SOUTHWEST ALONG
WITH ANOTHER WEAK BOUNDARY MOVING NORTHWARD ALONG THE
ILLINOIS/KANKAKEE RIVERS. THIS WEAK BOUNDARY SEPARATES SOUTHERLY
FLOW WITH SLIGHTLY HIGHER DEWPOINTS. WILL NEED TO MONITOR THESE
BOUNDARYS CLOSELY AS THEY APPROACH EACH OTHER FOR ANY SHRA/TSRA
DEVELOPMENT...WHICH BASED ON CURRENT TRACK/TIMING WOULD BE INVOF
KJOT AREA. OTHERWISE THE REMAINDER OF THE NIGHT SHOULD BE QUIET AT
THE TERMINALS. FOCUS WILL THEN SHIFT TO TSRA POTENTIAL TOMORROW
AFTERNOON. LATEST GUIDANCE INDICATES A WARM FRONT LIFTING INTO NRN
IL/IN BY LATE TOMORROW AFTERNOON. MOISTURE POOLING ALONG THE
BOUNDARY AND ISENTROPIC LIFT ALONG THE FRONTAL ZONE WILL PROVIDE
ENOUGH FOCUS TO NECESSATE ADDING A PROB30 GROUP TO THE FORECAST.
TIMING WILL BE THE MAIN QUESTION...BUT GENERALLY EXPECT THE BEST
TIMING TO BE DURG THE LATE AFTERNOON/EARLY EVENING HOURS.
KREIN
//ORD AND MDW CONFIDENCE...UPDATED 00Z...
* MODERATE TO HIGH CONFIDENCE IN WIND TRENDS.
* MODERATE CONFIDENCE IN TSRA/SHRA CHANCES TOMORROW...BUT LOWER
CONFIDENCE IN EXACT TIMING.
KREIN
//OUTLOOK FOR ORD/MDW FOR 12Z SATURDAY-12Z THURSDAY...UPDATED 00Z...
SATURDAY THROUGH WEDNESDAY...PERIODIC CHANCES FOR SHRA/TSRA...
OTHERWISE...VFR.
KREIN
&&
.MARINE...
228 PM CDT
RIDGING FROM HIGH PRESSURE CENTERED OVER WESTERN ONTARIO EXTENDS
ACROSS LAKE MICHIGAN THIS AFTERNOON. WEAK LOW PRESSURE WILL DEVELOP
AND MOVE UP THE OHIO RIVER VALLEY FRIDAY WITH ADDITIONAL LOW
PRESSURE DEVELOPING ACROSS THE CENTRAL HIGH PLAINS. EAST TO
NORTHEAST FLOW OVERALL WILL CONTINUE ACROSS THE LAKE...WITH ONSHORE
FLOW IN AREAS WHERE THE PRESSURE GRADIENT IS WEAKER CAUSING SOME
ERRATIC DIRECTIONS AT TIMES. STEADIER AND MORE UNIFORM WINDS WILL
DEVELOP WITH TIME THROUGH TOMORROW WITH MORE OF AN EAST TO SOUTHEAST
TREND. THE STRONGEST WINDS WILL OCCUR FRIDAY EVENING/NIGHT
COINCIDENT WITH THE STRONGEST PRESSURE GRADIENT THANKS TO THE LOW
PASSING TO THE SOUTHEAST. THE GRADIENT WEAKENS DURING THE DAY
SATURDAY AS THE LOW DEPARTS TO THE EAST. LOW PRESSURE STRENGTHENS
ACROSS THE CENTRAL/NORTHERN HIGH PLAINS INTO SUNDAY WHICH WILL
GRADUALLY TIGHTEN THE PRESSURE GRADIENT ACROSS THE LAKE. THIS WILL
ALLOW A STEADY SOUTH TO SOUTHEAST WIND TO DEVELOP ACROSS MOST OF THE
LAKE...WITH A MORE EASTERLY DIRECTION ACROSS THE FAR NORTH WHERE A
WARM FRONTAL BOUNDARY IS EXPECTED TO SET UP. THE MAIN LOW WILL
MEANDER NORTHWARD BEFORE BEING PUSHED EASTWARD ACROSS MINNESOTA/IOWA
SOMETIME TUESDAY OR WEDNESDAY WHICH WILL LIKELY PUSH THE FRONTAL
BOUNDARY FURTHER SOUTH ACROSS THE LAKE LEADING TO EAST TO NORTHEAST
WINDS NORTH AND SOUTH TO SOUTHWEST WINDS SOUTH BY MID WEEK. THE MAIN
CONCERN WILL BE THE POTENTIAL FOR INCREASED GUSTINESS ACROSS THE
NORTH AS COLDER AIR SETTLES IN ALLOWING SLIGHTLY INCREASED MIXING.
OTHERWISE...GENERALLY STABLE LOW LEVEL AIR ACROSS THE LAKE WILL KEEP
GUSTS TO A MINIMUM FROM TONIGHT THROUGH THE WEEKEND.
MDB
&&
.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 162211
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
511 PM CDT THU MAY 16 2013
.DISCUSSION...
259 PM CDT
TODAY`S FORECAST CHALLENGES CONTINUE TO BE DEALING WITH FRONTAL
BOUNDARY CURRENTLY JUST SOUTH OF THE CWA...AND PERIODIC CONVECTIVE
CHANCES THROUGH MID NEXT WEEK.
TODAY AND TONIGHT...
THIS AFTERNOON THE FRONT IS LOCATED JUST NORTH OF QUINCY IL EAST TO
NEAR TERRE HAUTE INDIANA...AND HAS BEEN SLOWLY PUSHING NORTH THIS
AFTERNOON. MODERATE INSTABILITY EXISTS SOUTH OF THE FRONT AND MAY
LIFT INTO FAR SOUTHERN PORTIONS OF THE CWA LATE THIS EVENING BEFORE
FADING NOCTURNALLY. MAINTAINED SLT CHC POPS FOR A FEW HOURS THIS
EVENING WHEN THIS OCCURS...BUT OTHERWISE SHOULD BE FAIRLY QUIET
PERIOD THROUGH TONIGHT.
FRIDAY THROUGH SATURDAY...
COMPACT SHORTWAVE NOTED ON WV IMAGERY THIS AFTERNOON OVER WESTERN
NE/KS WILL CONTINUE ENE INTO WEST CENTRAL WISCONSIN BY FRIDAY
AFTERNOON. AS THIS HAPPENS...SOUTHERLY FLOW INCREASE AT THE SURFACE
AND SHOULD HELP PUSH THE BOUNDARY NORTH ACROSS THE AREA. DEWPOINTS
RISE INTO THE MID 60S AND MODEST INSTABILITY DEVELOPS OUTSIDE OF FAR
NE ILLINOIS WHERE ONSHORE WINDS WILL KEEP CONDITIONS COOLER/MORE
STABLE. THIS INSTABILITY IS UNCAPPED...AND GIVEN THERE IS NO WELL
DEFINED FOCUS FOR THUNDERSTORMS...EXPECT UNORGANIZED/SCATTERED
CONVECTION TO DEVELOP WITHIN THE WARM SECTOR. MID LEVEL LAPSE RATES
ARE PRETTY POOR...SO CONVECTION MAY STRUGGLE AT TIMES AND MAY LIMIT
THE THUNDER CHANCES TO SOME DEGREE. MUCH OF THE SAME IS EXPECTED
SATURDAY SO WILL MAINTAIN THE LOW POPS FOR DIURNALLY DRIVEN TSTORMS.
SUNDAY THROUGH TUESDAY...
THIS PERIOD CONTINUES TO LOOK ACTIVE AS THE OVERALL PATTERN
AMPLIFIES WITH DEEP TROUGHING DEVELOPING ACROSS THE WESTERN
CONUS...AND STRONG RIDGING EAST. THE H85 THERMAL RIDGE BEGINS TO
WORK INTO THE AREA SUNDAY...AS WELL AS DRY AIR ALOFT AND THE EML
LATER IN THE DAY HELPING TO STEEPEN LAPSE RATES ALOFT. NEGATIVELY
TILTED TROUGH IS EXPECTED TO ROUND THE BASE OF THE LONGWAVE TROUGH
SUNDAY LIFTING INTO THE MID MISSOURI VALLEY SUNDAY NIGHT. MODELS ARE
MIXED ON WHETHER OR NOT THE CIN ERODES DURING THE DAYTIME...BUT IF
IT DOES CHANCES WILL BE BEST OVER WESTERN PORTIONS OF THE CWA...SO
HAVE MAINTAINED LOWER POPS. THERE MAY BE A BETTER CHANCE FOR
CONVECTION OVERNIGHT AS A LOW LEVEL JET DEVELOPS JUST TO OUR WEST
WITH LARGE SCALE ASCENT ASSOCIATED WITH AFOREMENTIONED TROUGH.
ON MONDAY...THE GFS INDICATES ANOTHER LOWER AMPLITUDE DISTURBANCE
WILL ROUND THE BASE OF THE LONGWAVE TROUGH AND LIFT INTO THE MID
MISSISSIPPI VALLEY. THIS CONTINUES TO BE A DAY TO KEEP AN EYE ON FOR
SEVERE WEATHER POTENTIAL. MODELS CONTINUE TO ADVERTISE MODERATE TO
STRONG INSTABILITY IN PLACE OVERHEAD WITH MARGINAL SHEAR CONDITIONS
TO SUPPORT SEVERE WEATHER. AS PREVIOUSLY MENTIONED...CONVECTION FROM
THE PREVIOUS NIGHT...CLOUD COVER...AND OTHER SMALL SCALE FEATURES
CANNOT BE RESOLVED THIS FAR OUT AND ADD A CONSIDERABLE AMOUNT OF
UNCERTAINTY. WE SHOULD BEGIN TO GET A BETTER PICTURE THIS WEEKEND SO
STAY TUNED FOR FORECAST UPDATES. DEPENDING ON THE SPEED OF THE
SYSTEM...TUESDAY WILL ALSO HAVE TO BE MONITORED...PERHAPS WITH THE
THREAT MORE FOCUSED ON THE EASTERN PORTIONS OF THE CWA.
IN ADDITION TO THE SEVERE THREAT...MULTIPLE ROUNDS OF THUNDERSTORMS
MOVING ALONG THE SLOW MOVING BOUNDARY SUNDAY NIGHT THROUGH TUESDAY
WILL LEAD TO A INCREASED HEAVY RAIN AND FLOODING THREAT.
FOR TEMPERATURES SUNDAY AND MONDAY...CONTINUE TO LEAN ON THE WARMER
BIAS CORRECTED GEM WHICH HAPPENED TO VERIFY BEST WITH THE
UNSEASONABLY HEAT TUESDAY. DEPENDING ON THE SPEED OF THE
SYSTEM...CURRENT FORECAST TEMPS MAY BE A BIT ON THE COOL SIDE
TUESDAY...PARTICULARLY THE EASTERN CWA. H85 TEMPS OF 16-18C AND H92
TEMPS OF 19-22C SHOULD SUPPORT TEMPERATURES WELL INTO THE 80S AND
WOULDN`T BE SURPRISED TO SEE PLACES HIT 90S THOSE DAYS...BUT WILL
REMAIN A BIT CONSERVATIVE GIVEN THE PRECIP CHANCES AND CLOUD COVER.
DEUBELBEISS
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 22Z...
* LAKE BREEZE BOUNDARY TO MOVE THROUGH ORD/MDW BTWN 2230-2300Z.
* WIND TO SHIFT FM ELY-ESELY TO ENELY.
KREIN
//DISCUSSION...UPDATED 18Z...
QUIET CONDITIONS CONTINUE WEATHER WISE AT THE TERMINALS THIS
AFTERNOON AS A SURFACE RIDGE OF HIGH PRESSURE DOMINATES ACROSS THE
WESTERN GREAT LAKES. SHOWER AND THUNDERSTORM ACTIVITY WILL STAY
SOUTH OF THE TERMINALS THIS AFTERNOON ACROSS CENTRAL PORTIONS OF
ILLINOIS...IN CLOSE PROXIMITY TO A STALLED OUT SURFACE BOUNDARY.
LIGHT EASTERLY FLOW IS EXPECTED THROUGH MUCH OF THE PERIOD.
A SERIES OF UPPER LEVEL DISTURBANCES...CURRENTLY ACROSS WESTERN
NEBRASKA AND THE OZARKS VIA WATER VAPOR IMAGERY...ARE EXPECTED TO
PROGRESS EASTWARD ACROSS THE MID MISSISSIPPI VALLEY ON FRIDAY. THIS
WILL LIKELY LEAD TO ADDITIONAL SHOWER AND THUNDERSTORM
DEVELOPMENT...ESPECIALLY FRIDAY AFTERNOON. HOWEVER...AT THIS TIME IT
APPEARS THE BETTER CHANCES WILL BE WEST AND SOUTH OF THE
TERMINALS...SO NO MENTION HAS BEEN ADDED TO THE NEW 30 HOUR ORD
TAF...BUT THIS WILL NEED TO BE WATCHED AS CONVECTIVE ACTIVITY COULD
BE CLOSE TO THE TERMINALS FRIDAY AFTERNOON.
KJB
//ORD AND MDW CONFIDENCE...UPDATED 22Z...
* HIGH FOR ALL FORECAST ELEMENTS.
KREIN
//OUTLOOK FOR ORD/MDW FOR 00Z SATURDAY-12Z THURSDAY...UPDATED 12Z...
FRIDAY NIGHT...SLIGHT CHANCE OF TSRA...OTHERWISE VFR.
SATURDAY...SLIGHT CHANCE OF TSRA...OTHERWISE VFR.
SUNDAY...CHANCE OF TSRA...OTHERWISE VFR.
MONDAY...CHANCE OF TSRA...OTHERWISE VFR.
TUESDAY...CHANCE OF TSRA...OTHERWISE VFR.
WEDNESDAY...CHANCE OF TSRA...OTHERWISE VFR.
RODRIGUEZ
&&
.MARINE...
228 PM CDT
RIDGING FROM HIGH PRESSURE CENTERED OVER WESTERN ONTARIO EXTENDS
ACROSS LAKE MICHIGAN THIS AFTERNOON. WEAK LOW PRESSURE WILL DEVELOP
AND MOVE UP THE OHIO RIVER VALLEY FRIDAY WITH ADDITIONAL LOW
PRESSURE DEVELOPING ACROSS THE CENTRAL HIGH PLAINS. EAST TO
NORTHEAST FLOW OVERALL WILL CONTINUE ACROSS THE LAKE...WITH ONSHORE
FLOW IN AREAS WHERE THE PRESSURE GRADIENT IS WEAKER CAUSING SOME
ERRATIC DIRECTIONS AT TIMES. STEADIER AND MORE UNIFORM WINDS WILL
DEVELOP WITH TIME THROUGH TOMORROW WITH MORE OF AN EAST TO SOUTHEAST
TREND. THE STRONGEST WINDS WILL OCCUR FRIDAY EVENING/NIGHT
COINCIDENT WITH THE STRONGEST PRESSURE GRADIENT THANKS TO THE LOW
PASSING TO THE SOUTHEAST. THE GRADIENT WEAKENS DURING THE DAY
SATURDAY AS THE LOW DEPARTS TO THE EAST. LOW PRESSURE STRENGTHENS
ACROSS THE CENTRAL/NORTHERN HIGH PLAINS INTO SUNDAY WHICH WILL
GRADUALLY TIGHTEN THE PRESSURE GRADIENT ACROSS THE LAKE. THIS WILL
ALLOW A STEADY SOUTH TO SOUTHEAST WIND TO DEVELOP ACROSS MOST OF THE
LAKE...WITH A MORE EASTERLY DIRECTION ACROSS THE FAR NORTH WHERE A
WARM FRONTAL BOUNDARY IS EXPECTED TO SET UP. THE MAIN LOW WILL
MEANDER NORTHWARD BEFORE BEING PUSHED EASTWARD ACROSS MINNESOTA/IOWA
SOMETIME TUESDAY OR WEDNESDAY WHICH WILL LIKELY PUSH THE FRONTAL
BOUNDARY FURTHER SOUTH ACROSS THE LAKE LEADING TO EAST TO NORTHEAST
WINDS NORTH AND SOUTH TO SOUTHWEST WINDS SOUTH BY MID WEEK. THE MAIN
CONCERN WILL BE THE POTENTIAL FOR INCREASED GUSTINESS ACROSS THE
NORTH AS COLDER AIR SETTLES IN ALLOWING SLIGHTLY INCREASED MIXING.
OTHERWISE...GENERALLY STABLE LOW LEVEL AIR ACROSS THE LAKE WILL KEEP
GUSTS TO A MINIMUM FROM TONIGHT THROUGH THE WEEKEND.
MDB
&&
.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 162000
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
300 PM CDT THU MAY 16 2013
.DISCUSSION...
259 PM CDT
TODAY`S FORECAST CHALLENGES CONTINUE TO BE DEALING WITH FRONTAL
BOUNDARY CURRENTLY JUST SOUTH OF THE CWA...AND PERIODIC CONVECTIVE
CHANCES THROUGH MID NEXT WEEK.
TODAY AND TONIGHT...
THIS AFTERNOON THE FRONT IS LOCATED JUST NORTH OF QUINCY IL EAST TO
NEAR TERRE HAUTE INDIANA...AND HAS BEEN SLOWLY PUSHING NORTH THIS
AFTERNOON. MODERATE INSTABILITY EXISTS SOUTH OF THE FRONT AND MAY
LIFT INTO FAR SOUTHERN PORTIONS OF THE CWA LATE THIS EVENING BEFORE
FADING NOCTURNALLY. MAINTAINED SLT CHC POPS FOR A FEW HOURS THIS
EVENING WHEN THIS OCCURS...BUT OTHERWISE SHOULD BE FAIRLY QUIET
PERIOD THROUGH TONIGHT.
FRIDAY THROUGH SATURDAY...
COMPACT SHORTWAVE NOTED ON WV IMAGERY THIS AFTERNOON OVER WESTERN
NE/KS WILL CONTINUE ENE INTO WEST CENTRAL WISCONSIN BY FRIDAY
AFTERNOON. AS THIS HAPPENS...SOUTHERLY FLOW INCREASE AT THE SURFACE
AND SHOULD HELP PUSH THE BOUNDARY NORTH ACROSS THE AREA. DEWPOINTS
RISE INTO THE MID 60S AND MODEST INSTABILITY DEVELOPS OUTSIDE OF FAR
NE ILLINOIS WHERE ONSHORE WINDS WILL KEEP CONDITIONS COOLER/MORE
STABLE. THIS INSTABILITY IS UNCAPPED...AND GIVEN THERE IS NO WELL
DEFINED FOCUS FOR THUNDERSTORMS...EXPECT UNORGANIZED/SCATTERED
CONVECTION TO DEVELOP WITHIN THE WARM SECTOR. MID LEVEL LAPSE RATES
ARE PRETTY POOR...SO CONVECTION MAY STRUGGLE AT TIMES AND MAY LIMIT
THE THUNDER CHANCES TO SOME DEGREE. MUCH OF THE SAME IS EXPECTED
SATURDAY SO WILL MAINTAIN THE LOW POPS FOR DIURNALLY DRIVEN TSTORMS.
SUNDAY THROUGH TUESDAY...
THIS PERIOD CONTINUES TO LOOK ACTIVE AS THE OVERALL PATTERN
AMPLIFIES WITH DEEP TROUGHING DEVELOPING ACROSS THE WESTERN
CONUS...AND STRONG RIDGING EAST. THE H85 THERMAL RIDGE BEGINS TO
WORK INTO THE AREA SUNDAY...AS WELL AS DRY AIR ALOFT AND THE EML
LATER IN THE DAY HELPING TO STEEPEN LAPSE RATES ALOFT. NEGATIVELY
TILTED TROUGH IS EXPECTED TO ROUND THE BASE OF THE LONGWAVE TROUGH
SUNDAY LIFTING INTO THE MID MISSOURI VALLEY SUNDAY NIGHT. MODELS ARE
MIXED ON WHETHER OR NOT THE CIN ERODES DURING THE DAYTIME...BUT IF
IT DOES CHANCES WILL BE BEST OVER WESTERN PORTIONS OF THE CWA...SO
HAVE MAINTAINED LOWER POPS. THERE MAY BE A BETTER CHANCE FOR
CONVECTION OVERNIGHT AS A LOW LEVEL JET DEVELOPS JUST TO OUR WEST
WITH LARGE SCALE ASCENT ASSOCIATED WITH AFOREMENTIONED TROUGH.
ON MONDAY...THE GFS INDICATES ANOTHER LOWER AMPLITUDE DISTURBANCE
WILL ROUND THE BASE OF THE LONGWAVE TROUGH AND LIFT INTO THE MID
MISSISSIPPI VALLEY. THIS CONTINUES TO BE A DAY TO KEEP AN EYE ON FOR
SEVERE WEATHER POTENTIAL. MODELS CONTINUE TO ADVERTISE MODERATE TO
STRONG INSTABILITY IN PLACE OVERHEAD WITH MARGINAL SHEAR CONDITIONS
TO SUPPORT SEVERE WEATHER. AS PREVIOUSLY MENTIONED...CONVECTION FROM
THE PREVIOUS NIGHT...CLOUD COVER...AND OTHER SMALL SCALE FEATURES
CANNOT BE RESOLVED THIS FAR OUT AND ADD A CONSIDERABLE AMOUNT OF
UNCERTAINTY. WE SHOULD BEGIN TO GET A BETTER PICTURE THIS WEEKEND SO
STAY TUNED FOR FORECAST UPDATES. DEPENDING ON THE SPEED OF THE
SYSTEM...TUESDAY WILL ALSO HAVE TO BE MONITORED...PERHAPS WITH THE
THREAT MORE FOCUSED ON THE EASTERN PORTIONS OF THE CWA.
IN ADDITION TO THE SEVERE THREAT...MULTIPLE ROUNDS OF THUNDERSTORMS
MOVING ALONG THE SLOW MOVING BOUNDARY SUNDAY NIGHT THROUGH TUESDAY
WILL LEAD TO A INCREASED HEAVY RAIN AND FLOODING THREAT.
FOR TEMPERATURES SUNDAY AND MONDAY...CONTINUE TO LEAN ON THE WARMER
BIAS CORRECTED GEM WHICH HAPPENED TO VERIFY BEST WITH THE
UNSEASONABLY HEAT TUESDAY. DEPENDING ON THE SPEED OF THE
SYSTEM...CURRENT FORECAST TEMPS MAY BE A BIT ON THE COOL SIDE
TUESDAY...PARTICULARLY THE EASTERN CWA. H85 TEMPS OF 16-18C AND H92
TEMPS OF 19-22C SHOULD SUPPORT TEMPERATURES WELL INTO THE 80S AND
WOULDN`T BE SURPRISED TO SEE PLACES HIT 90S THOSE DAYS...BUT WILL
REMAIN A BIT CONSERVATIVE GIVEN THE PRECIP CHANCES AND CLOUD COVER.
DEUBELBEISS
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 20Z...
* NONE.
KJB
//DISCUSSION...UPDATED 18Z...
QUIET CONDITIONS CONTINUE WEATHER WISE AT THE TERMINALS THIS
AFTERNOON AS A SURFACE RIDGE OF HIGH PRESSURE DOMINATES ACROSS THE
WESTERN GREAT LAKES. SHOWER AND THUNDERSTORM ACTIVITY WILL STAY
SOUTH OF THE TERMINALS THIS AFTERNOON ACROSS CENTRAL PORTIONS OF
ILLINOIS...IN CLOSE PROXIMITY TO A STALLED OUT SURFACE BOUNDARY.
LIGHT EASTERLY FLOW IS EXPECTED THROUGH MUCH OF THE PERIOD.
A SERIES OF UPPER LEVEL DISTURBANCES...CURRENTLY ACROSS WESTERN
NEBRASKA AND THE OZARKS VIA WATER VAPOR IMAGERY...ARE EXPECTED TO
PROGRESS EASTWARD ACROSS THE MID MISSISSIPPI VALLEY ON FRIDAY. THIS
WILL LIKELY LEAD TO ADDITIONAL SHOWER AND THUNDERSTORM
DEVELOPMENT...ESPECIALLY FRIDAY AFTERNOON. HOWEVER...AT THIS TIME IT
APPEARS THE BETTER CHANCES WILL BE WEST AND SOUTH OF THE
TERMINALS...SO NO MENTION HAS BEEN ADDED TO THE NEW 30 HOUR ORD
TAF...BUT THIS WILL NEED TO BE WATCHED AS CONVECTIVE ACTIVITY COULD
BE CLOSE TO THE TERMINALS FRIDAY AFTERNOON.
KJB
//ORD AND MDW CONFIDENCE...UPDATED 20Z...
* HIGH FOR ALL FORECAST ELEMENTS.
KJB
//OUTLOOK FOR ORD/MDW FOR 00Z SATURDAY-12Z THURSDAY...UPDATED 12Z...
FRIDAY NIGHT...SLIGHT CHANCE OF TSRA...OTHERWISE VFR.
SATURDAY...SLIGHT CHANCE OF TSRA...OTHERWISE VFR.
SUNDAY...CHANCE OF TSRA...OTHERWISE VFR.
MONDAY...CHANCE OF TSRA...OTHERWISE VFR.
TUESDAY...CHANCE OF TSRA...OTHERWISE VFR.
WEDNESDAY...CHANCE OF TSRA...OTHERWISE VFR.
RODRIGUEZ
&&
.MARINE...
228 PM CDT
RIDGING FROM HIGH PRESSURE CENTERED OVER WESTERN ONTARIO EXTENDS
ACROSS LAKE MICHIGAN THIS AFTERNOON. WEAK LOW PRESSURE WILL DEVELOP
AND MOVE UP THE OHIO RIVER VALLEY FRIDAY WITH ADDITIONAL LOW
PRESSURE DEVELOPING ACROSS THE CENTRAL HIGH PLAINS. EAST TO
NORTHEAST FLOW OVERALL WILL CONTINUE ACROSS THE LAKE...WITH ONSHORE
FLOW IN AREAS WHERE THE PRESSURE GRADIENT IS WEAKER CAUSING SOME
ERRATIC DIRECTIONS AT TIMES. STEADIER AND MORE UNIFORM WINDS WILL
DEVELOP WITH TIME THROUGH TOMORROW WITH MORE OF AN EAST TO SOUTHEAST
TREND. THE STRONGEST WINDS WILL OCCUR FRIDAY EVENING/NIGHT
COINCIDENT WITH THE STRONGEST PRESSURE GRADIENT THANKS TO THE LOW
PASSING TO THE SOUTHEAST. THE GRADIENT WEAKENS DURING THE DAY
SATURDAY AS THE LOW DEPARTS TO THE EAST. LOW PRESSURE STRENGTHENS
ACROSS THE CENTRAL/NORTHERN HIGH PLAINS INTO SUNDAY WHICH WILL
GRADUALLY TIGHTEN THE PRESSURE GRADIENT ACROSS THE LAKE. THIS WILL
ALLOW A STEADY SOUTH TO SOUTHEAST WIND TO DEVELOP ACROSS MOST OF THE
LAKE...WITH A MORE EASTERLY DIRECTION ACROSS THE FAR NORTH WHERE A
WARM FRONTAL BOUNDARY IS EXPECTED TO SET UP. THE MAIN LOW WILL
MEANDER NORTHWARD BEFORE BEING PUSHED EASTWARD ACROSS MINNESOTA/IOWA
SOMETIME TUESDAY OR WEDNESDAY WHICH WILL LIKELY PUSH THE FRONTAL
BOUNDARY FURTHER SOUTH ACROSS THE LAKE LEADING TO EAST TO NORTHEAST
WINDS NORTH AND SOUTH TO SOUTHWEST WINDS SOUTH BY MID WEEK. THE MAIN
CONCERN WILL BE THE POTENTIAL FOR INCREASED GUSTINESS ACROSS THE
NORTH AS COLDER AIR SETTLES IN ALLOWING SLIGHTLY INCREASED MIXING.
OTHERWISE...GENERALLY STABLE LOW LEVEL AIR ACROSS THE LAKE WILL KEEP
GUSTS TO A MINIMUM FROM TONIGHT THROUGH THE WEEKEND.
MDB
&&
.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 161944
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
244 PM CDT THU MAY 16 2013
.DISCUSSION...
330 AM CDT
SURFACE FRONT LIES JUST SOUTH OF THE CWA THIS MORNING AND PROBABLY
WONT MOVE MUCH THE NEXT COUPLE OF DAYS...ONLY TRENDING SLOWLY
NORTHWARD OVER THE WEEKEND. POPS THE NEXT COUPLE OF DAYS WILL BE A
CHALLENGE AS MAIN BELT OF WESTERLIES IS NORTH OF THE AREA AND UPPER
LOW OVER TEXAS OPENS UP AND MOVES INTO THE OHIO VALLEY LEAVING OUR
CWA IN A REGION OF RELATIVELY WEAK FORCING. CERTAINLY PLAUSIBLE THAT
CONVECTION COULD LIGHT UP NEAR AND JUST NORTH OF THE STALLED OUT
BOUNDARY AT JUST ABOUT ANY POINT THE NEXT COUPLE DAYS WITH THE BEST
CHANCES ACROSS FAR SOUTHERN CWA SLOWLY SPREADING NORTH INTO THE
REMAINDER OF THE AREA LATE FRIDAY INTO EARLY SATURDAY. DOES LOOKS
LIKE WE PRECIP CHANCES WILL DECREASE LATER SATURDAY THROUGH SUNDAY
AS UPPER RIDGE BUILDS INTO THE AREA AND FRONT MOVES NORTH OF THE
REGION.
TEMPERATURES PROBABLY WONT FLUCTUATE MORE THAN A FEW DEGREES FROM
WEDNESDAY`S READINGS TODAY THROUGH SATURDAY. DAILY LAKE BREEZES
SHOULD HOLD TEMPS IN THE 60S ALONG THE LAKE WITH UPPER 70S TO LOW
80S EXPECTED INLAND...THOUGH MORE CLOUD COVER ON FRIDAY COULD KEEP
IT A BIT COOLER INLAND. BIGGER WARM UP IS ANTICIPATED SUNDAY AS H8
TEMPS SORE INTO THE MID TEENS AND 925MB TEMPS GET INTO THE UPPER
TEENS WHICH SHOULD ALLOW TEMPS TO SOAR WELL INTO THE 80S AND
POSSIBLY AROUND 90 WITH ENOUGH SUNSHINE. MODELS SUGGEST THE SRF
GRADIENT WILL BE SOUTHEAST WHICH WOULD KEEP CHICAGO LAKE FRONT AND
NORTH SHORE AREAS COOLER...BUT AT THIS DISTANCE THE DETAILS ON THE
GRADIENT AND RESULTANT WIND FLOW COULD CHANGE SO STAY TUNED.
BIG WESTERN UPPER TROUGH THAT WE`VE BEEN TALKING ABOUT FOR DAYS
STILL LOOKS LIKE IT WILL MOVE TOWARD THE UPPER MISSISSIPPI VALLEY
EARLY NEXT WEEK. AFTER WHAT LOOKS TO BE A COUPLE ACTIVE SEVERE
WEATHER DAYS OUT IN THE CENTRAL CONUS THIS WEEKEND...THE MORE ACTIVE
WEATHER WILL SHIFT EAST INTO OUR AREA EARLY NEXT WEEK. GENERALLY
SPEAKING THE SYNOPTIC PATTERN LOOKS REASONABLY FAVORABLE FOR A
SEVERE WEATHER THREAT IN THE REGION MONDAY AND/OR TUESDAY...BUT
OBVIOUSLY A LOT WILL HINGE ON THE SMALLER SCALE DETAILS THAT WONT BE
RESOLVED FOR DAYS TO COME STILL. OF POTENTIALLY GREATER CONCERN IS
THE THREAT FOR HEAVY RAINFALL AND FLOODING...GFS/ECMWF/GEM ALL SHOW
UPPER LOW CLOSING OFF OVER THE NORTHERN PLAINS AND UPPER MISSISSIPPI
VALLEY DURING THE FIRST HALF OF THE WEEK WITH A WIDE OPEN GULF OF
MEXICO PROVIDING AMPLE MOISTURE. PROBABLY A BIT EARLY TO DO AN ESF
BUT IF THE MODEL REMAIN CONSISTENT THE NEXT RUN OR TWO LATER SHIFTS
MAY NEED TO CONSIDER AN ESF FOR THE THREAT OF MULTIPLE ROUNDS OF
SHOWERS/STORMS DURING THE FIRST HALF OF NEXT WEEK.
IZZI
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 20Z...
* NONE.
KJB
//DISCUSSION...UPDATED 18Z...
QUIET CONDITIONS CONTINUE WEATHER WISE AT THE TERMINALS THIS
AFTERNOON AS A SURFACE RIDGE OF HIGH PRESSURE DOMINATES ACROSS THE
WESTERN GREAT LAKES. SHOWER AND THUNDERSTORM ACTIVITY WILL STAY
SOUTH OF THE TERMINALS THIS AFTERNOON ACROSS CENTRAL PORTIONS OF
ILLINOIS...IN CLOSE PROXIMITY TO A STALLED OUT SURFACE BOUNDARY.
LIGHT EASTERLY FLOW IS EXPECTED THROUGH MUCH OF THE PERIOD.
A SERIES OF UPPER LEVEL DISTURBANCES...CURRENTLY ACROSS WESTERN
NEBRASKA AND THE OZARKS VIA WATER VAPOR IMAGERY...ARE EXPECTED TO
PROGRESS EASTWARD ACROSS THE MID MISSISSIPPI VALLEY ON FRIDAY. THIS
WILL LIKELY LEAD TO ADDITIONAL SHOWER AND THUNDERSTORM
DEVELOPMENT...ESPECIALLY FRIDAY AFTERNOON. HOWEVER...AT THIS TIME IT
APPEARS THE BETTER CHANCES WILL BE WEST AND SOUTH OF THE
TERMINALS...SO NO MENTION HAS BEEN ADDED TO THE NEW 30 HOUR ORD
TAF...BUT THIS WILL NEED TO BE WATCHED AS CONVECTIVE ACTIVITY COULD
BE CLOSE TO THE TERMINALS FRIDAY AFTERNOON.
KJB
//ORD AND MDW CONFIDENCE...UPDATED 20Z...
* HIGH FOR ALL FORECAST ELEMENTS.
KJB
//OUTLOOK FOR ORD/MDW FOR 00Z SATURDAY-12Z THURSDAY...UPDATED 12Z...
FRIDAY NIGHT...SLIGHT CHANCE OF TSRA...OTHERWISE VFR.
SATURDAY...SLIGHT CHANCE OF TSRA...OTHERWISE VFR.
SUNDAY...CHANCE OF TSRA...OTHERWISE VFR.
MONDAY...CHANCE OF TSRA...OTHERWISE VFR.
TUESDAY...CHANCE OF TSRA...OTHERWISE VFR.
WEDNESDAY...CHANCE OF TSRA...OTHERWISE VFR.
RODRIGUEZ
&&
.MARINE...
228 PM CDT
RIDGING FROM HIGH PRESSURE CENTERED OVER WESTERN ONTARIO EXTENDS
ACROSS LAKE MICHIGAN THIS AFTERNOON. WEAK LOW PRESSURE WILL DEVELOP
AND MOVE UP THE OHIO RIVER VALLEY FRIDAY WITH ADDITIONAL LOW
PRESSURE DEVELOPING ACROSS THE CENTRAL HIGH PLAINS. EAST TO
NORTHEAST FLOW OVERALL WILL CONTINUE ACROSS THE LAKE...WITH ONSHORE
FLOW IN AREAS WHERE THE PRESSURE GRADIENT IS WEAKER CAUSING SOME
ERRATIC DIRECTIONS AT TIMES. STEADIER AND MORE UNIFORM WINDS WILL
DEVELOP WITH TIME THROUGH TOMORROW WITH MORE OF AN EAST TO SOUTHEAST
TREND. THE STRONGEST WINDS WILL OCCUR FRIDAY EVENING/NIGHT
COINCIDENT WITH THE STRONGEST PRESSURE GRADIENT THANKS TO THE LOW
PASSING TO THE SOUTHEAST. THE GRADIENT WEAKENS DURING THE DAY
SATURDAY AS THE LOW DEPARTS TO THE EAST. LOW PRESSURE STRENGTHENS
ACROSS THE CENTRAL/NORTHERN HIGH PLAINS INTO SUNDAY WHICH WILL
GRADUALLY TIGHTEN THE PRESSURE GRADIENT ACROSS THE LAKE. THIS WILL
ALLOW A STEADY SOUTH TO SOUTHEAST WIND TO DEVELOP ACROSS MOST OF THE
LAKE...WITH A MORE EASTERLY DIRECTION ACROSS THE FAR NORTH WHERE A
WARM FRONTAL BOUNDARY IS EXPECTED TO SET UP. THE MAIN LOW WILL
MEANDER NORTHWARD BEFORE BEING PUSHED EASTWARD ACROSS MINNESOTA/IOWA
SOMETIME TUESDAY OR WEDNESDAY WHICH WILL LIKELY PUSH THE FRONTAL
BOUNDARY FURTHER SOUTH ACROSS THE LAKE LEADING TO EAST TO NORTHEAST
WINDS NORTH AND SOUTH TO SOUTHWEST WINDS SOUTH BY MID WEEK. THE MAIN
CONCERN WILL BE THE POTENTIAL FOR INCREASED GUSTINESS ACROSS THE
NORTH AS COLDER AIR SETTLES IN ALLOWING SLIGHTLY INCREASED MIXING.
OTHERWISE...GENERALLY STABLE LOW LEVEL AIR ACROSS THE LAKE WILL KEEP
GUSTS TO A MINIMUM FROM TONIGHT THROUGH THE WEEKEND.
MDB
&&
.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 161931
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
231 PM CDT THU MAY 16 2013
.DISCUSSION...
330 AM CDT
SURFACE FRONT LIES JUST SOUTH OF THE CWA THIS MORNING AND PROBABLY
WONT MOVE MUCH THE NEXT COUPLE OF DAYS...ONLY TRENDING SLOWLY
NORTHWARD OVER THE WEEKEND. POPS THE NEXT COUPLE OF DAYS WILL BE A
CHALLENGE AS MAIN BELT OF WESTERLIES IS NORTH OF THE AREA AND UPPER
LOW OVER TEXAS OPENS UP AND MOVES INTO THE OHIO VALLEY LEAVING OUR
CWA IN A REGION OF RELATIVELY WEAK FORCING. CERTAINLY PLAUSIBLE THAT
CONVECTION COULD LIGHT UP NEAR AND JUST NORTH OF THE STALLED OUT
BOUNDARY AT JUST ABOUT ANY POINT THE NEXT COUPLE DAYS WITH THE BEST
CHANCES ACROSS FAR SOUTHERN CWA SLOWLY SPREADING NORTH INTO THE
REMAINDER OF THE AREA LATE FRIDAY INTO EARLY SATURDAY. DOES LOOKS
LIKE WE PRECIP CHANCES WILL DECREASE LATER SATURDAY THROUGH SUNDAY
AS UPPER RIDGE BUILDS INTO THE AREA AND FRONT MOVES NORTH OF THE
REGION.
TEMPERATURES PROBABLY WONT FLUCTUATE MORE THAN A FEW DEGREES FROM
WEDNESDAY`S READINGS TODAY THROUGH SATURDAY. DAILY LAKE BREEZES
SHOULD HOLD TEMPS IN THE 60S ALONG THE LAKE WITH UPPER 70S TO LOW
80S EXPECTED INLAND...THOUGH MORE CLOUD COVER ON FRIDAY COULD KEEP
IT A BIT COOLER INLAND. BIGGER WARM UP IS ANTICIPATED SUNDAY AS H8
TEMPS SORE INTO THE MID TEENS AND 925MB TEMPS GET INTO THE UPPER
TEENS WHICH SHOULD ALLOW TEMPS TO SOAR WELL INTO THE 80S AND
POSSIBLY AROUND 90 WITH ENOUGH SUNSHINE. MODELS SUGGEST THE SRF
GRADIENT WILL BE SOUTHEAST WHICH WOULD KEEP CHICAGO LAKE FRONT AND
NORTH SHORE AREAS COOLER...BUT AT THIS DISTANCE THE DETAILS ON THE
GRADIENT AND RESULTANT WIND FLOW COULD CHANGE SO STAY TUNED.
BIG WESTERN UPPER TROUGH THAT WE`VE BEEN TALKING ABOUT FOR DAYS
STILL LOOKS LIKE IT WILL MOVE TOWARD THE UPPER MISSISSIPPI VALLEY
EARLY NEXT WEEK. AFTER WHAT LOOKS TO BE A COUPLE ACTIVE SEVERE
WEATHER DAYS OUT IN THE CENTRAL CONUS THIS WEEKEND...THE MORE ACTIVE
WEATHER WILL SHIFT EAST INTO OUR AREA EARLY NEXT WEEK. GENERALLY
SPEAKING THE SYNOPTIC PATTERN LOOKS REASONABLY FAVORABLE FOR A
SEVERE WEATHER THREAT IN THE REGION MONDAY AND/OR TUESDAY...BUT
OBVIOUSLY A LOT WILL HINGE ON THE SMALLER SCALE DETAILS THAT WONT BE
RESOLVED FOR DAYS TO COME STILL. OF POTENTIALLY GREATER CONCERN IS
THE THREAT FOR HEAVY RAINFALL AND FLOODING...GFS/ECMWF/GEM ALL SHOW
UPPER LOW CLOSING OFF OVER THE NORTHERN PLAINS AND UPPER MISSISSIPPI
VALLEY DURING THE FIRST HALF OF THE WEEK WITH A WIDE OPEN GULF OF
MEXICO PROVIDING AMPLE MOISTURE. PROBABLY A BIT EARLY TO DO AN ESF
BUT IF THE MODEL REMAIN CONSISTENT THE NEXT RUN OR TWO LATER SHIFTS
MAY NEED TO CONSIDER AN ESF FOR THE THREAT OF MULTIPLE ROUNDS OF
SHOWERS/STORMS DURING THE FIRST HALF OF NEXT WEEK.
IZZI
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 18Z...
* NONE.
KJB
//DISCUSSION...UPDATED 18Z...
QUIET CONDITIONS CONTINUE WEATHER WISE AT THE TERMINALS THIS
AFTERNOON AS A SURFACE RIDGE OF HIGH PRESSURE DOMINATES ACROSS THE
WESTERN GREAT LAKES. SHOWER AND THUNDERSTORM ACTIVITY WILL STAY
SOUTH OF THE TERMINALS THIS AFTERNOON ACROSS CENTRAL PORTIONS OF
ILLINOIS...IN CLOSE PROXIMITY TO A STALLED OUT SURFACE BOUNDARY.
LIGHT EASTERLY FLOW IS EXPECTED THROUGH MUCH OF THE PERIOD.
A SERIES OF UPPER LEVEL DISTURBANCES...CURRENTLY ACROSS WESTERN
NEBRASKA AND THE OZARKS VIA WATER VAPOR IMAGERY...ARE EXPECTED TO
PROGRESS EASTWARD ACROSS THE MID MISSISSIPPI VALLEY ON FRIDAY. THIS
WILL LIKELY LEAD TO ADDITIONAL SHOWER AND THUNDERSTORM
DEVELOPMENT...ESPECIALLY FRIDAY AFTERNOON. HOWEVER...AT THIS TIME IT
APPEARS THE BETTER CHANCES WILL BE WEST AND SOUTH OF THE
TERMINALS...SO NO MENTION HAS BEEN ADDED TO THE NEW 30 HOUR ORD
TAF...BUT THIS WILL NEED TO BE WATCHED AS CONVECTIVE ACTIVITY COULD
BE CLOSE TO THE TERMINALS FRIDAY AFTERNOON.
KJB
//ORD AND MDW CONFIDENCE...UPDATED 18Z...
* HIGH FOR ALL FORECAST ELEMENTS.
KJB
//OUTLOOK FOR ORD/MDW FOR 00Z SATURDAY-12Z THURSDAY...UPDATED 12Z...
FRIDAY NIGHT...SLIGHT CHANCE OF TSRA...OTHERWISE VFR.
SATURDAY...SLIGHT CHANCE OF TSRA...OTHERWISE VFR.
SUNDAY...CHANCE OF TSRA...OTHERWISE VFR.
MONDAY...CHANCE OF TSRA...OTHERWISE VFR.
TUESDAY...CHANCE OF TSRA...OTHERWISE VFR.
WEDNESDAY...CHANCE OF TSRA...OTHERWISE VFR.
RODRIGUEZ
&&
.MARINE...
228 PM CDT
RIDGING FROM HIGH PRESSURE CENTERED OVER WESTERN ONTARIO EXTENDS
ACROSS LAKE MICHIGAN THIS AFTERNOON. WEAK LOW PRESSURE WILL DEVELOP
AND MOVE UP THE OHIO RIVER VALLEY FRIDAY WITH ADDITIONAL LOW
PRESSURE DEVELOPING ACROSS THE CENTRAL HIGH PLAINS. EAST TO
NORTHEAST FLOW OVERALL WILL CONTINUE ACROSS THE LAKE...WITH ONSHORE
FLOW IN AREAS WHERE THE PRESSURE GRADIENT IS WEAKER CAUSING SOME
ERRATIC DIRECTIONS AT TIMES. STEADIER AND MORE UNIFORM WINDS WILL
DEVELOP WITH TIME THROUGH TOMORROW WITH MORE OF AN EAST TO SOUTHEAST
TREND. THE STRONGEST WINDS WILL OCCUR FRIDAY EVENING/NIGHT
COINCIDENT WITH THE STRONGEST PRESSURE GRADIENT THANKS TO THE LOW
PASSING TO THE SOUTHEAST. THE GRADIENT WEAKENS DURING THE DAY
SATURDAY AS THE LOW DEPARTS TO THE EAST. LOW PRESSURE STRENGTHENS
ACROSS THE CENTRAL/NORTHERN HIGH PLAINS INTO SUNDAY WHICH WILL
GRADUALLY TIGHTEN THE PRESSURE GRADIENT ACROSS THE LAKE. THIS WILL
ALLOW A STEADY SOUTH TO SOUTHEAST WIND TO DEVELOP ACROSS MOST OF THE
LAKE...WITH A MORE EASTERLY DIRECTION ACROSS THE FAR NORTH WHERE A
WARM FRONTAL BOUNDARY IS EXPECTED TO SET UP. THE MAIN LOW WILL
MEANDER NORTHWARD BEFORE BEING PUSHED EASTWARD ACROSS MINNESOTA/IOWA
SOMETIME TUESDAY OR WEDNESDAY WHICH WILL LIKELY PUSH THE FRONTAL
BOUNDARY FURTHER SOUTH ACROSS THE LAKE LEADING TO EAST TO NORTHEAST
WINDS NORTH AND SOUTH TO SOUTHWEST WINDS SOUTH BY MID WEEK. THE MAIN
CONCERN WILL BE THE POTENTIAL FOR INCREASED GUSTINESS ACROSS THE
NORTH AS COLDER AIR SETTLES IN ALLOWING SLIGHTLY INCREASED MIXING.
OTHERWISE...GENERALLY STABLE LOW LEVEL AIR ACROSS THE LAKE WILL KEEP
GUSTS TO A MINIMUM FROM TONIGHT THROUGH THE WEEKEND.
MDB
&&
.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 161701
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1201 PM CDT THU MAY 16 2013
.DISCUSSION...
330 AM CDT
SURFACE FRONT LIES JUST SOUTH OF THE CWA THIS MORNING AND PROBABLY
WONT MOVE MUCH THE NEXT COUPLE OF DAYS...ONLY TRENDING SLOWLY
NORTHWARD OVER THE WEEKEND. POPS THE NEXT COUPLE OF DAYS WILL BE A
CHALLENGE AS MAIN BELT OF WESTERLIES IS NORTH OF THE AREA AND UPPER
LOW OVER TEXAS OPENS UP AND MOVES INTO THE OHIO VALLEY LEAVING OUR
CWA IN A REGION OF RELATIVELY WEAK FORCING. CERTAINLY PLAUSIBLE THAT
CONVECTION COULD LIGHT UP NEAR AND JUST NORTH OF THE STALLED OUT
BOUNDARY AT JUST ABOUT ANY POINT THE NEXT COUPLE DAYS WITH THE BEST
CHANCES ACROSS FAR SOUTHERN CWA SLOWLY SPREADING NORTH INTO THE
REMAINDER OF THE AREA LATE FRIDAY INTO EARLY SATURDAY. DOES LOOKS
LIKE WE PRECIP CHANCES WILL DECREASE LATER SATURDAY THROUGH SUNDAY
AS UPPER RIDGE BUILDS INTO THE AREA AND FRONT MOVES NORTH OF THE
REGION.
TEMPERATURES PROBABLY WONT FLUCTUATE MORE THAN A FEW DEGREES FROM
WEDNESDAY`S READINGS TODAY THROUGH SATURDAY. DAILY LAKE BREEZES
SHOULD HOLD TEMPS IN THE 60S ALONG THE LAKE WITH UPPER 70S TO LOW
80S EXPECTED INLAND...THOUGH MORE CLOUD COVER ON FRIDAY COULD KEEP
IT A BIT COOLER INLAND. BIGGER WARM UP IS ANTICIPATED SUNDAY AS H8
TEMPS SORE INTO THE MID TEENS AND 925MB TEMPS GET INTO THE UPPER
TEENS WHICH SHOULD ALLOW TEMPS TO SOAR WELL INTO THE 80S AND
POSSIBLY AROUND 90 WITH ENOUGH SUNSHINE. MODELS SUGGEST THE SRF
GRADIENT WILL BE SOUTHEAST WHICH WOULD KEEP CHICAGO LAKE FRONT AND
NORTH SHORE AREAS COOLER...BUT AT THIS DISTANCE THE DETAILS ON THE
GRADIENT AND RESULTANT WIND FLOW COULD CHANGE SO STAY TUNED.
BIG WESTERN UPPER TROUGH THAT WE`VE BEEN TALKING ABOUT FOR DAYS
STILL LOOKS LIKE IT WILL MOVE TOWARD THE UPPER MISSISSIPPI VALLEY
EARLY NEXT WEEK. AFTER WHAT LOOKS TO BE A COUPLE ACTIVE SEVERE
WEATHER DAYS OUT IN THE CENTRAL CONUS THIS WEEKEND...THE MORE ACTIVE
WEATHER WILL SHIFT EAST INTO OUR AREA EARLY NEXT WEEK. GENERALLY
SPEAKING THE SYNOPTIC PATTERN LOOKS REASONABLY FAVORABLE FOR A
SEVERE WEATHER THREAT IN THE REGION MONDAY AND/OR TUESDAY...BUT
OBVIOUSLY A LOT WILL HINGE ON THE SMALLER SCALE DETAILS THAT WONT BE
RESOLVED FOR DAYS TO COME STILL. OF POTENTIALLY GREATER CONCERN IS
THE THREAT FOR HEAVY RAINFALL AND FLOODING...GFS/ECMWF/GEM ALL SHOW
UPPER LOW CLOSING OFF OVER THE NORTHERN PLAINS AND UPPER MISSISSIPPI
VALLEY DURING THE FIRST HALF OF THE WEEK WITH A WIDE OPEN GULF OF
MEXICO PROVIDING AMPLE MOISTURE. PROBABLY A BIT EARLY TO DO AN ESF
BUT IF THE MODEL REMAIN CONSISTENT THE NEXT RUN OR TWO LATER SHIFTS
MAY NEED TO CONSIDER AN ESF FOR THE THREAT OF MULTIPLE ROUNDS OF
SHOWERS/STORMS DURING THE FIRST HALF OF NEXT WEEK.
IZZI
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 18Z...
* NONE.
KJB
//DISCUSSION...UPDATED 18Z...
QUIET CONDITIONS CONTINUE WEATHER WISE AT THE TERMINALS THIS
AFTERNOON AS A SURFACE RIDGE OF HIGH PRESSURE DOMINATES ACROSS THE
WESTERN GREAT LAKES. SHOWER AND THUNDERSTORM ACTIVITY WILL STAY
SOUTH OF THE TERMINALS THIS AFTERNOON ACROSS CENTRAL PORTIONS OF
ILLINOIS...IN CLOSE PROXIMITY TO A STALLED OUT SURFACE BOUNDARY.
LIGHT EASTERLY FLOW IS EXPECTED THROUGH MUCH OF THE PERIOD.
A SERIES OF UPPER LEVEL DISTURBANCES...CURRENTLY ACROSS WESTERN
NEBRASKA AND THE OZARKS VIA WATER VAPOR IMAGERY...ARE EXPECTED TO
PROGRESS EASTWARD ACROSS THE MID MISSISSIPPI VALLEY ON FRIDAY. THIS
WILL LIKELY LEAD TO ADDITIONAL SHOWER AND THUNDERSTORM
DEVELOPMENT...ESPECIALLY FRIDAY AFTERNOON. HOWEVER...AT THIS TIME IT
APPEARS THE BETTER CHANCES WILL BE WEST AND SOUTH OF THE
TERMINALS...SO NO MENTION HAS BEEN ADDED TO THE NEW 30 HOUR ORD
TAF...BUT THIS WILL NEED TO BE WATCHED AS CONVECTIVE ACTIVITY COULD
BE CLOSE TO THE TERMINALS FRIDAY AFTERNOON.
KJB
//ORD AND MDW CONFIDENCE...UPDATED 18Z...
* HIGH FOR ALL FORECAST ELEMENTS.
KJB
//OUTLOOK FOR ORD/MDW FOR 00Z SATURDAY-12Z THURSDAY...UPDATED 12Z...
FRIDAY NIGHT...SLIGHT CHANCE OF TSRA...OTHERWISE VFR.
SATURDAY...SLIGHT CHANCE OF TSRA...OTHERWISE VFR.
SUNDAY...CHANCE OF TSRA...OTHERWISE VFR.
MONDAY...CHANCE OF TSRA...OTHERWISE VFR.
TUESDAY...CHANCE OF TSRA...OTHERWISE VFR.
WEDNESDAY...CHANCE OF TSRA...OTHERWISE VFR.
RODRIGUEZ
&&
.MARINE...
449 AM CDT
A TROUGH OF LOW PRESSURE WILL CONTINUE TO SHIFT TO THE EASTERN
GREAT LAKES TODAY WHILE HIGH PRESSURE OVER MANITOBA AND ONTARIO
MOVES SOUTHEAST ACROSS THE CENTRAL GREAT LAKES. THIS WILL RESULT
IN WEST WINDS ACROSS THE LAKE BECOMING NORTHWEST AND THEN NORTH
TODAY. SPEEDS SHOULD REMAIN IN THE 10-15 KT RANGE THROUGH THIS
MORNING...BEFORE WINDS SLIGHTLY INCREASE TOWARDS 10 TO 20 KT THIS
AFTERNOON. WITH THE HIGH MOVING TO EASTERN ONTARIO AND THE EASTERN
GREAT LAKES TONIGHT AND FRIDAY...NEW LOW PRESSURE WILL DEVELOP
ACROSS THE CENTRAL PLAINS. THIS WILL RESULT IN A PERSISTENT EAST
TO NORTHEAST DIRECTION ACROSS THE LAKE THROUGH FRIDAY. THIS WILL
CONTINUE FURTHER INTO THE WEEKEND...AS THE HIGH CONTINUES EAST
TOWARDS QUEBEC AND THE LOW PRESSURE REMAINS ACROSS THE CENTRAL
PLAINS. WINDS WILL BEGIN TO BECOME MORE SOUTHERLY LATE IN THE
WEEKEND AS THIS LOW MAKES A SLOW PROGRESSION EAST ACROSS THE
PLAINS.
RODRIGUEZ
&&
.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 161559
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1059 AM CDT THU MAY 16 2013
.DISCUSSION...
330 AM CDT
SURFACE FRONT LIES JUST SOUTH OF THE CWA THIS MORNING AND PROBABLY
WONT MOVE MUCH THE NEXT COUPLE OF DAYS...ONLY TRENDING SLOWLY
NORTHWARD OVER THE WEEKEND. POPS THE NEXT COUPLE OF DAYS WILL BE A
CHALLENGE AS MAIN BELT OF WESTERLIES IS NORTH OF THE AREA AND UPPER
LOW OVER TEXAS OPENS UP AND MOVES INTO THE OHIO VALLEY LEAVING OUR
CWA IN A REGION OF RELATIVELY WEAK FORCING. CERTAINLY PLAUSIBLE THAT
CONVECTION COULD LIGHT UP NEAR AND JUST NORTH OF THE STALLED OUT
BOUNDARY AT JUST ABOUT ANY POINT THE NEXT COUPLE DAYS WITH THE BEST
CHANCES ACROSS FAR SOUTHERN CWA SLOWLY SPREADING NORTH INTO THE
REMAINDER OF THE AREA LATE FRIDAY INTO EARLY SATURDAY. DOES LOOKS
LIKE WE PRECIP CHANCES WILL DECREASE LATER SATURDAY THROUGH SUNDAY
AS UPPER RIDGE BUILDS INTO THE AREA AND FRONT MOVES NORTH OF THE
REGION.
TEMPERATURES PROBABLY WONT FLUCTUATE MORE THAN A FEW DEGREES FROM
WEDNESDAY`S READINGS TODAY THROUGH SATURDAY. DAILY LAKE BREEZES
SHOULD HOLD TEMPS IN THE 60S ALONG THE LAKE WITH UPPER 70S TO LOW
80S EXPECTED INLAND...THOUGH MORE CLOUD COVER ON FRIDAY COULD KEEP
IT A BIT COOLER INLAND. BIGGER WARM UP IS ANTICIPATED SUNDAY AS H8
TEMPS SORE INTO THE MID TEENS AND 925MB TEMPS GET INTO THE UPPER
TEENS WHICH SHOULD ALLOW TEMPS TO SOAR WELL INTO THE 80S AND
POSSIBLY AROUND 90 WITH ENOUGH SUNSHINE. MODELS SUGGEST THE SRF
GRADIENT WILL BE SOUTHEAST WHICH WOULD KEEP CHICAGO LAKE FRONT AND
NORTH SHORE AREAS COOLER...BUT AT THIS DISTANCE THE DETAILS ON THE
GRADIENT AND RESULTANT WIND FLOW COULD CHANGE SO STAY TUNED.
BIG WESTERN UPPER TROUGH THAT WE`VE BEEN TALKING ABOUT FOR DAYS
STILL LOOKS LIKE IT WILL MOVE TOWARD THE UPPER MISSISSIPPI VALLEY
EARLY NEXT WEEK. AFTER WHAT LOOKS TO BE A COUPLE ACTIVE SEVERE
WEATHER DAYS OUT IN THE CENTRAL CONUS THIS WEEKEND...THE MORE ACTIVE
WEATHER WILL SHIFT EAST INTO OUR AREA EARLY NEXT WEEK. GENERALLY
SPEAKING THE SYNOPTIC PATTERN LOOKS REASONABLY FAVORABLE FOR A
SEVERE WEATHER THREAT IN THE REGION MONDAY AND/OR TUESDAY...BUT
OBVIOUSLY A LOT WILL HINGE ON THE SMALLER SCALE DETAILS THAT WONT BE
RESOLVED FOR DAYS TO COME STILL. OF POTENTIALLY GREATER CONCERN IS
THE THREAT FOR HEAVY RAINFALL AND FLOODING...GFS/ECMWF/GEM ALL SHOW
UPPER LOW CLOSING OFF OVER THE NORTHERN PLAINS AND UPPER MISSISSIPPI
VALLEY DURING THE FIRST HALF OF THE WEEK WITH A WIDE OPEN GULF OF
MEXICO PROVIDING AMPLE MOISTURE. PROBABLY A BIT EARLY TO DO AN ESF
BUT IF THE MODEL REMAIN CONSISTENT THE NEXT RUN OR TWO LATER SHIFTS
MAY NEED TO CONSIDER AN ESF FOR THE THREAT OF MULTIPLE ROUNDS OF
SHOWERS/STORMS DURING THE FIRST HALF OF NEXT WEEK.
IZZI
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 16Z...
* NO CONCERNS IN THE NEAR TERM.
KJB
//DISCUSSION...UPDATED 12Z...
QUIET WEATHER CONTINUES AT THE TERMINALS THIS MORNING WITH ONLY
SOME PASSING MID/HIGH LEVEL CLOUD COVER...WITH ANY
SHOWER/THUNDERSTORM ACTIVITY REMAINING WELL TO THE SOUTH. EXPECT
QUIET CONDITIONS TO PERSIST ACROSS THE TERMINALS WITH ANY PRECIP
DEVELOPMENT ONCE AGAIN STAYING AWAY FROM THE TERMINALS.
LIGHT/VARIABLE WINDS WILL BE REPLACED WITH AN EASTERLY LIGHT WIND
BY MID MORNING...CONTINUING THROUGH THE EARLY AFTERNOON BEFORE
LAKE BREEZE INFLUENCE GIVES A STRONGER PUSH OF AN EAST NORTHEAST
WIND. WINDS WILL DIMINISH THIS EVENING...AND HOLD ONTO THIS EAST
NORTHEAST WIND THROUGH THE REMAINDER OF THE FORECAST PERIOD.
RODRIGUEZ
//ORD AND MDW CONFIDENCE...UPDATED 16Z...
* HIGH CONFIDENCE WITH ALL FORECAST ELEMENTS.
KJB
//OUTLOOK FOR ORD/MDW FOR 00Z SATURDAY-12Z THURSDAY...UPDATED 12Z...
FRIDAY NIGHT...SLIGHT CHANCE OF TSRA...OTHERWISE VFR.
SATURDAY...SLIGHT CHANCE OF TSRA...OTHERWISE VFR.
SUNDAY...CHANCE OF TSRA...OTHERWISE VFR.
MONDAY...CHANCE OF TSRA...OTHERWISE VFR.
TUESDAY...CHANCE OF TSRA...OTHERWISE VFR.
WEDNESDAY...CHANCE OF TSRA...OTHERWISE VFR.
RODRIGUEZ
&&
.MARINE...
449 AM CDT
A TROUGH OF LOW PRESSURE WILL CONTINUE TO SHIFT TO THE EASTERN
GREAT LAKES TODAY WHILE HIGH PRESSURE OVER MANITOBA AND ONTARIO
MOVES SOUTHEAST ACROSS THE CENTRAL GREAT LAKES. THIS WILL RESULT
IN WEST WINDS ACROSS THE LAKE BECOMING NORTHWEST AND THEN NORTH
TODAY. SPEEDS SHOULD REMAIN IN THE 10-15 KT RANGE THROUGH THIS
MORNING...BEFORE WINDS SLIGHTLY INCREASE TOWARDS 10 TO 20 KT THIS
AFTERNOON. WITH THE HIGH MOVING TO EASTERN ONTARIO AND THE EASTERN
GREAT LAKES TONIGHT AND FRIDAY...NEW LOW PRESSURE WILL DEVELOP
ACROSS THE CENTRAL PLAINS. THIS WILL RESULT IN A PERSISTENT EAST
TO NORTHEAST DIRECTION ACROSS THE LAKE THROUGH FRIDAY. THIS WILL
CONTINUE FURTHER INTO THE WEEKEND...AS THE HIGH CONTINUES EAST
TOWARDS QUEBEC AND THE LOW PRESSURE REMAINS ACROSS THE CENTRAL
PLAINS. WINDS WILL BEGIN TO BECOME MORE SOUTHERLY LATE IN THE
WEEKEND AS THIS LOW MAKES A SLOW PROGRESSION EAST ACROSS THE
PLAINS.
RODRIGUEZ
&&
.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 161403
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
903 AM CDT THU MAY 16 2013
.DISCUSSION...
330 AM CDT
SURFACE FRONT LIES JUST SOUTH OF THE CWA THIS MORNING AND PROBABLY
WONT MOVE MUCH THE NEXT COUPLE OF DAYS...ONLY TRENDING SLOWLY
NORTHWARD OVER THE WEEKEND. POPS THE NEXT COUPLE OF DAYS WILL BE A
CHALLENGE AS MAIN BELT OF WESTERLIES IS NORTH OF THE AREA AND UPPER
LOW OVER TEXAS OPENS UP AND MOVES INTO THE OHIO VALLEY LEAVING OUR
CWA IN A REGION OF RELATIVELY WEAK FORCING. CERTAINLY PLAUSIBLE THAT
CONVECTION COULD LIGHT UP NEAR AND JUST NORTH OF THE STALLED OUT
BOUNDARY AT JUST ABOUT ANY POINT THE NEXT COUPLE DAYS WITH THE BEST
CHANCES ACROSS FAR SOUTHERN CWA SLOWLY SPREADING NORTH INTO THE
REMAINDER OF THE AREA LATE FRIDAY INTO EARLY SATURDAY. DOES LOOKS
LIKE WE PRECIP CHANCES WILL DECREASE LATER SATURDAY THROUGH SUNDAY
AS UPPER RIDGE BUILDS INTO THE AREA AND FRONT MOVES NORTH OF THE
REGION.
TEMPERATURES PROBABLY WONT FLUCTUATE MORE THAN A FEW DEGREES FROM
WEDNESDAY`S READINGS TODAY THROUGH SATURDAY. DAILY LAKE BREEZES
SHOULD HOLD TEMPS IN THE 60S ALONG THE LAKE WITH UPPER 70S TO LOW
80S EXPECTED INLAND...THOUGH MORE CLOUD COVER ON FRIDAY COULD KEEP
IT A BIT COOLER INLAND. BIGGER WARM UP IS ANTICIPATED SUNDAY AS H8
TEMPS SORE INTO THE MID TEENS AND 925MB TEMPS GET INTO THE UPPER
TEENS WHICH SHOULD ALLOW TEMPS TO SOAR WELL INTO THE 80S AND
POSSIBLY AROUND 90 WITH ENOUGH SUNSHINE. MODELS SUGGEST THE SRF
GRADIENT WILL BE SOUTHEAST WHICH WOULD KEEP CHICAGO LAKE FRONT AND
NORTH SHORE AREAS COOLER...BUT AT THIS DISTANCE THE DETAILS ON THE
GRADIENT AND RESULTANT WIND FLOW COULD CHANGE SO STAY TUNED.
BIG WESTERN UPPER TROUGH THAT WE`VE BEEN TALKING ABOUT FOR DAYS
STILL LOOKS LIKE IT WILL MOVE TOWARD THE UPPER MISSISSIPPI VALLEY
EARLY NEXT WEEK. AFTER WHAT LOOKS TO BE A COUPLE ACTIVE SEVERE
WEATHER DAYS OUT IN THE CENTRAL CONUS THIS WEEKEND...THE MORE ACTIVE
WEATHER WILL SHIFT EAST INTO OUR AREA EARLY NEXT WEEK. GENERALLY
SPEAKING THE SYNOPTIC PATTERN LOOKS REASONABLY FAVORABLE FOR A
SEVERE WEATHER THREAT IN THE REGION MONDAY AND/OR TUESDAY...BUT
OBVIOUSLY A LOT WILL HINGE ON THE SMALLER SCALE DETAILS THAT WONT BE
RESOLVED FOR DAYS TO COME STILL. OF POTENTIALLY GREATER CONCERN IS
THE THREAT FOR HEAVY RAINFALL AND FLOODING...GFS/ECMWF/GEM ALL SHOW
UPPER LOW CLOSING OFF OVER THE NORTHERN PLAINS AND UPPER MISSISSIPPI
VALLEY DURING THE FIRST HALF OF THE WEEK WITH A WIDE OPEN GULF OF
MEXICO PROVIDING AMPLE MOISTURE. PROBABLY A BIT EARLY TO DO AN ESF
BUT IF THE MODEL REMAIN CONSISTENT THE NEXT RUN OR TWO LATER SHIFTS
MAY NEED TO CONSIDER AN ESF FOR THE THREAT OF MULTIPLE ROUNDS OF
SHOWERS/STORMS DURING THE FIRST HALF OF NEXT WEEK.
IZZI
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 14Z...
* NO CONCERNS IN THE NEAR TERM.
KJB
//DISCUSSION...UPDATED 12Z...
QUIET WEATHER CONTINUES AT THE TERMINALS THIS MORNING WITH ONLY
SOME PASSING MID/HIGH LEVEL CLOUD COVER...WITH ANY
SHOWER/THUNDERSTORM ACTIVITY REMAINING WELL TO THE SOUTH. EXPECT
QUIET CONDITIONS TO PERSIST ACROSS THE TERMINALS WITH ANY PRECIP
DEVELOPMENT ONCE AGAIN STAYING AWAY FROM THE TERMINALS.
LIGHT/VARIABLE WINDS WILL BE REPLACED WITH AN EASTERLY LIGHT WIND
BY MID MORNING...CONTINUING THROUGH THE EARLY AFTERNOON BEFORE
LAKE BREEZE INFLUENCE GIVES A STRONGER PUSH OF AN EAST NORTHEAST
WIND. WINDS WILL DIMINISH THIS EVENING...AND HOLD ONTO THIS EAST
NORTHEAST WIND THROUGH THE REMAINDER OF THE FORECAST PERIOD.
RODRIGUEZ
//ORD AND MDW CONFIDENCE...UPDATED 14Z...
* HIGH CONFIDENCE WITH ALL FORECAST ELEMENTS.
KJB
//OUTLOOK FOR ORD/MDW FOR 00Z SATURDAY-12Z THURSDAY...UPDATED 12Z...
FRIDAY NIGHT...SLIGHT CHANCE OF TSRA...OTHERWISE VFR.
SATURDAY...SLIGHT CHANCE OF TSRA...OTHERWISE VFR.
SUNDAY...CHANCE OF TSRA...OTHERWISE VFR.
MONDAY...CHANCE OF TSRA...OTHERWISE VFR.
TUESDAY...CHANCE OF TSRA...OTHERWISE VFR.
WEDNESDAY...CHANCE OF TSRA...OTHERWISE VFR.
RODRIGUEZ
&&
.MARINE...
449 AM CDT
A TROUGH OF LOW PRESSURE WILL CONTINUE TO SHIFT TO THE EASTERN
GREAT LAKES TODAY WHILE HIGH PRESSURE OVER MANITOBA AND ONTARIO
MOVES SOUTHEAST ACROSS THE CENTRAL GREAT LAKES. THIS WILL RESULT
IN WEST WINDS ACROSS THE LAKE BECOMING NORTHWEST AND THEN NORTH
TODAY. SPEEDS SHOULD REMAIN IN THE 10-15 KT RANGE THROUGH THIS
MORNING...BEFORE WINDS SLIGHTLY INCREASE TOWARDS 10 TO 20 KT THIS
AFTERNOON. WITH THE HIGH MOVING TO EASTERN ONTARIO AND THE EASTERN
GREAT LAKES TONIGHT AND FRIDAY...NEW LOW PRESSURE WILL DEVELOP
ACROSS THE CENTRAL PLAINS. THIS WILL RESULT IN A PERSISTENT EAST
TO NORTHEAST DIRECTION ACROSS THE LAKE THROUGH FRIDAY. THIS WILL
CONTINUE FURTHER INTO THE WEEKEND...AS THE HIGH CONTINUES EAST
TOWARDS QUEBEC AND THE LOW PRESSURE REMAINS ACROSS THE CENTRAL
PLAINS. WINDS WILL BEGIN TO BECOME MORE SOUTHERLY LATE IN THE
WEEKEND AS THIS LOW MAKES A SLOW PROGRESSION EAST ACROSS THE
PLAINS.
RODRIGUEZ
&&
.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 161138
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
638 AM CDT THU MAY 16 2013
.DISCUSSION...
330 AM CDT
SURFACE FRONT LIES JUST SOUTH OF THE CWA THIS MORNING AND PROBABLY
WONT MOVE MUCH THE NEXT COUPLE OF DAYS...ONLY TRENDING SLOWLY
NORTHWARD OVER THE WEEKEND. POPS THE NEXT COUPLE OF DAYS WILL BE A
CHALLENGE AS MAIN BELT OF WESTERLIES IS NORTH OF THE AREA AND UPPER
LOW OVER TEXAS OPENS UP AND MOVES INTO THE OHIO VALLEY LEAVING OUR
CWA IN A REGION OF RELATIVELY WEAK FORCING. CERTAINLY PLAUSIBLE THAT
CONVECTION COULD LIGHT UP NEAR AND JUST NORTH OF THE STALLED OUT
BOUNDARY AT JUST ABOUT ANY POINT THE NEXT COUPLE DAYS WITH THE BEST
CHANCES ACROSS FAR SOUTHERN CWA SLOWLY SPREADING NORTH INTO THE
REMAINDER OF THE AREA LATE FRIDAY INTO EARLY SATURDAY. DOES LOOKS
LIKE WE PRECIP CHANCES WILL DECREASE LATER SATURDAY THROUGH SUNDAY
AS UPPER RIDGE BUILDS INTO THE AREA AND FRONT MOVES NORTH OF THE
REGION.
TEMPERATURES PROBABLY WONT FLUCTUATE MORE THAN A FEW DEGREES FROM
WEDNESDAY`S READINGS TODAY THROUGH SATURDAY. DAILY LAKE BREEZES
SHOULD HOLD TEMPS IN THE 60S ALONG THE LAKE WITH UPPER 70S TO LOW
80S EXPECTED INLAND...THOUGH MORE CLOUD COVER ON FRIDAY COULD KEEP
IT A BIT COOLER INLAND. BIGGER WARM UP IS ANTICIPATED SUNDAY AS H8
TEMPS SORE INTO THE MID TEENS AND 925MB TEMPS GET INTO THE UPPER
TEENS WHICH SHOULD ALLOW TEMPS TO SOAR WELL INTO THE 80S AND
POSSIBLY AROUND 90 WITH ENOUGH SUNSHINE. MODELS SUGGEST THE SRF
GRADIENT WILL BE SOUTHEAST WHICH WOULD KEEP CHICAGO LAKE FRONT AND
NORTH SHORE AREAS COOLER...BUT AT THIS DISTANCE THE DETAILS ON THE
GRADIENT AND RESULTANT WIND FLOW COULD CHANGE SO STAY TUNED.
BIG WESTERN UPPER TROUGH THAT WE`VE BEEN TALKING ABOUT FOR DAYS
STILL LOOKS LIKE IT WILL MOVE TOWARD THE UPPER MISSISSIPPI VALLEY
EARLY NEXT WEEK. AFTER WHAT LOOKS TO BE A COUPLE ACTIVE SEVERE
WEATHER DAYS OUT IN THE CENTRAL CONUS THIS WEEKEND...THE MORE ACTIVE
WEATHER WILL SHIFT EAST INTO OUR AREA EARLY NEXT WEEK. GENERALLY
SPEAKING THE SYNOPTIC PATTERN LOOKS REASONABLY FAVORABLE FOR A
SEVERE WEATHER THREAT IN THE REGION MONDAY AND/OR TUESDAY...BUT
OBVIOUSLY A LOT WILL HINGE ON THE SMALLER SCALE DETAILS THAT WONT BE
RESOLVED FOR DAYS TO COME STILL. OF POTENTIALLY GREATER CONCERN IS
THE THREAT FOR HEAVY RAINFALL AND FLOODING...GFS/ECMWF/GEM ALL SHOW
UPPER LOW CLOSING OFF OVER THE NORTHERN PLAINS AND UPPER MISSISSIPPI
VALLEY DURING THE FIRST HALF OF THE WEEK WITH A WIDE OPEN GULF OF
MEXICO PROVIDING AMPLE MOISTURE. PROBABLY A BIT EARLY TO DO AN ESF
BUT IF THE MODEL REMAIN CONSISTENT THE NEXT RUN OR TWO LATER SHIFTS
MAY NEED TO CONSIDER AN ESF FOR THE THREAT OF MULTIPLE ROUNDS OF
SHOWERS/STORMS DURING THE FIRST HALF OF NEXT WEEK.
IZZI
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 12Z...
* NO CONCERNS IN THE NEAR TERM.
* LIGHT/VARIABLE WINDS THIS MORNING BECOMING EASTERLY BY MID
MORNING.
RODRIGUEZ
//DISCUSSION...UPDATED 12Z...
QUIET WEATHER CONTINUES AT THE TERMINALS THIS MORNING WITH ONLY
SOME PASSING MID/HIGH LEVEL CLOUD COVER...WITH ANY
SHOWER/THUNDERSTORM ACTIVITY REMAINING WELL TO THE SOUTH. EXPECT
QUIET CONDITIONS TO PERSIST ACROSS THE TERMINALS WITH ANY PRECIP
DEVELOPMENT ONCE AGAIN STAYING AWAY FROM THE TERMINALS.
LIGHT/VARIABLE WINDS WILL BE REPLACED WITH AN EASTERLY LIGHT WIND
BY MID MORNING...CONTINUING THROUGH THE EARLY AFTERNOON BEFORE
LAKE BREEZE INFLUENCE GIVES A STRONGER PUSH OF AN EAST NORTHEAST
WIND. WINDS WILL DIMINISH THIS EVENING...AND HOLD ONTO THIS EAST
NORTHEAST WIND THROUGH THE REMAINDER OF THE FORECAST PERIOD.
RODRIGUEZ
//ORD AND MDW CONFIDENCE...UPDATED 12Z...
* HIGH CONFIDENCE WITH VFR CONDITIONS.
* HIGH CONFIDENCE WITH WIND SPEED/DIRECTION.
RODRIGUEZ
//OUTLOOK FOR ORD/MDW FOR 00Z SATURDAY-12Z THURSDAY...UPDATED 12Z...
FRIDAY NIGHT...SLIGHT CHANCE OF TSRA...OTHERWISE VFR.
SATURDAY...SLIGHT CHANCE OF TSRA...OTHERWISE VFR.
SUNDAY...CHANCE OF TSRA...OTHERWISE VFR.
MONDAY...CHANCE OF TSRA...OTHERWISE VFR.
TUESDAY...CHANCE OF TSRA...OTHERWISE VFR.
WEDNESDAY...CHANCE OF TSRA...OTHERWISE VFR.
RODRIGUEZ
&&
.MARINE...
449 AM CDT
A TROUGH OF LOW PRESSURE WILL CONTINUE TO SHIFT TO THE EASTERN
GREAT LAKES TODAY WHILE HIGH PRESSURE OVER MANITOBA AND ONTARIO
MOVES SOUTHEAST ACROSS THE CENTRAL GREAT LAKES. THIS WILL RESULT
IN WEST WINDS ACROSS THE LAKE BECOMING NORTHWEST AND THEN NORTH
TODAY. SPEEDS SHOULD REMAIN IN THE 10-15 KT RANGE THROUGH THIS
MORNING...BEFORE WINDS SLIGHTLY INCREASE TOWARDS 10 TO 20 KT THIS
AFTERNOON. WITH THE HIGH MOVING TO EASTERN ONTARIO AND THE EASTERN
GREAT LAKES TONIGHT AND FRIDAY...NEW LOW PRESSURE WILL DEVELOP
ACROSS THE CENTRAL PLAINS. THIS WILL RESULT IN A PERSISTENT EAST
TO NORTHEAST DIRECTION ACROSS THE LAKE THROUGH FRIDAY. THIS WILL
CONTINUE FURTHER INTO THE WEEKEND...AS THE HIGH CONTINUES EAST
TOWARDS QUEBEC AND THE LOW PRESSURE REMAINS ACROSS THE CENTRAL
PLAINS. WINDS WILL BEGIN TO BECOME MORE SOUTHERLY LATE IN THE
WEEKEND AS THIS LOW MAKES A SLOW PROGRESSION EAST ACROSS THE
PLAINS.
RODRIGUEZ
&&
.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 160950
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
450 AM CDT THU MAY 16 2013
.DISCUSSION...
330 AM CDT
SURFACE FRONT LIES JUST SOUTH OF THE CWA THIS MORNING AND PROBABLY
WONT MOVE MUCH THE NEXT COUPLE OF DAYS...ONLY TRENDING SLOWLY
NORTHWARD OVER THE WEEKEND. POPS THE NEXT COUPLE OF DAYS WILL BE A
CHALLENGE AS MAIN BELT OF WESTERLIES IS NORTH OF THE AREA AND UPPER
LOW OVER TEXAS OPENS UP AND MOVES INTO THE OHIO VALLEY LEAVING OUR
CWA IN A REGION OF RELATIVELY WEAK FORCING. CERTAINLY PLAUSIBLE THAT
CONVECTION COULD LIGHT UP NEAR AND JUST NORTH OF THE STALLED OUT
BOUNDARY AT JUST ABOUT ANY POINT THE NEXT COUPLE DAYS WITH THE BEST
CHANCES ACROSS FAR SOUTHERN CWA SLOWLY SPREADING NORTH INTO THE
REMAINDER OF THE AREA LATE FRIDAY INTO EARLY SATURDAY. DOES LOOKS
LIKE WE PRECIP CHANCES WILL DECREASE LATER SATURDAY THROUGH SUNDAY
AS UPPER RIDGE BUILDS INTO THE AREA AND FRONT MOVES NORTH OF THE
REGION.
TEMPERATURES PROBABLY WONT FLUCTUATE MORE THAN A FEW DEGREES FROM
WEDNESDAY`S READINGS TODAY THROUGH SATURDAY. DAILY LAKE BREEZES
SHOULD HOLD TEMPS IN THE 60S ALONG THE LAKE WITH UPPER 70S TO LOW
80S EXPECTED INLAND...THOUGH MORE CLOUD COVER ON FRIDAY COULD KEEP
IT A BIT COOLER INLAND. BIGGER WARM UP IS ANTICIPATED SUNDAY AS H8
TEMPS SORE INTO THE MID TEENS AND 925MB TEMPS GET INTO THE UPPER
TEENS WHICH SHOULD ALLOW TEMPS TO SOAR WELL INTO THE 80S AND
POSSIBLY AROUND 90 WITH ENOUGH SUNSHINE. MODELS SUGGEST THE SRF
GRADIENT WILL BE SOUTHEAST WHICH WOULD KEEP CHICAGO LAKE FRONT AND
NORTH SHORE AREAS COOLER...BUT AT THIS DISTANCE THE DETAILS ON THE
GRADIENT AND RESULTANT WIND FLOW COULD CHANGE SO STAY TUNED.
BIG WESTERN UPPER TROUGH THAT WE`VE BEEN TALKING ABOUT FOR DAYS
STILL LOOKS LIKE IT WILL MOVE TOWARD THE UPPER MISSISSIPPI VALLEY
EARLY NEXT WEEK. AFTER WHAT LOOKS TO BE A COUPLE ACTIVE SEVERE
WEATHER DAYS OUT IN THE CENTRAL CONUS THIS WEEKEND...THE MORE ACTIVE
WEATHER WILL SHIFT EAST INTO OUR AREA EARLY NEXT WEEK. GENERALLY
SPEAKING THE SYNOPTIC PATTERN LOOKS REASONABLY FAVORABLE FOR A
SEVERE WEATHER THREAT IN THE REGION MONDAY AND/OR TUESDAY...BUT
OBVIOUSLY A LOT WILL HINGE ON THE SMALLER SCALE DETAILS THAT WONT BE
RESOLVED FOR DAYS TO COME STILL. OF POTENTIALLY GREATER CONCERN IS
THE THREAT FOR HEAVY RAINFALL AND FLOODING...GFS/ECMWF/GEM ALL SHOW
UPPER LOW CLOSING OFF OVER THE NORTHERN PLAINS AND UPPER MISSISSIPPI
VALLEY DURING THE FIRST HALF OF THE WEEK WITH A WIDE OPEN GULF OF
MEXICO PROVIDING AMPLE MOISTURE. PROBABLY A BIT EARLY TO DO AN ESF
BUT IF THE MODEL REMAIN CONSISTENT THE NEXT RUN OR TWO LATER SHIFTS
MAY NEED TO CONSIDER AN ESF FOR THE THREAT OF MULTIPLE ROUNDS OF
SHOWERS/STORMS DURING THE FIRST HALF OF NEXT WEEK.
IZZI
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 09Z...
* NO CONCERNS IN THE NEAR TERM.
* LIGHT/VARIABLE WINDS THIS MORNING BECOMING EASTERLY BY MID
MORNING.
RODRIGUEZ
//DISCUSSION...UPDATED 06Z...
QUIET AT THE TERMINALS EARLY THIS MORNING WITH THE BULK OF ANY
ACTIVITY OCCURRING SOUTH/SOUTHWEST OF THE TERMINALS...AND EXPECT
THIS TO CONTINUE FOR THE REMAINDER OF THE FORECAST PERIOD WITH
ONLY HIGH LEVEL CLOUD COVER EXPECTED TO MOVE ACROSS THE TERMINALS.
LIGHT AND VARIABLE WINDS WILL BE REPLACED WITH AN EASTERLY LIGHT
WIND BY MID MORNING...CONTINUING THROUGH THE AFTERNOON BEFORE LAKE
BREEZE INFLUENCE GIVES A STRONGER PUSH OF AN EAST NORTHEAST WIND.
WINDS WILL DIMINISH THIS EVENING...AND HOLD ONTO THIS EAST
NORTHEAST WIND.
RODRIGUEZ
//ORD AND MDW CONFIDENCE...UPDATED 09Z...
* HIGH CONFIDENCE WITH VFR CONDITIONS.
* HIGH CONFIDENCE WITH WIND SPEED/DIRECTION.
RODRIGUEZ
//OUTLOOK FOR ORD/MDW FOR 12Z FRIDAY-12Z WEDNESDAY...UPDATED 00Z...
FRIDAY THROUGH TUESDAY...PERIODIC CHANCES FOR SHRA/TSRA WITH
LOCALIZED MVFR CONDITIONS. OTHERWISE...VFR.
KREIN
&&
.MARINE...
449 AM CDT
A TROUGH OF LOW PRESSURE WILL CONTINUE TO SHIFT TO THE EASTERN
GREAT LAKES TODAY WHILE HIGH PRESSURE OVER MANITOBA AND ONTARIO
MOVES SOUTHEAST ACROSS THE CENTRAL GREAT LAKES. THIS WILL RESULT
IN WEST WINDS ACROSS THE LAKE BECOMING NORTHWEST AND THEN NORTH
TODAY. SPEEDS SHOULD REMAIN IN THE 10-15 KT RANGE THROUGH THIS
MORNING...BEFORE WINDS SLIGHTLY INCREASE TOWARDS 10 TO 20 KT THIS
AFTERNOON. WITH THE HIGH MOVING TO EASTERN ONTARIO AND THE EASTERN
GREAT LAKES TONIGHT AND FRIDAY...NEW LOW PRESSURE WILL DEVELOP
ACROSS THE CENTRAL PLAINS. THIS WILL RESULT IN A PERSISTENT EAST
TO NORTHEAST DIRECTION ACROSS THE LAKE THROUGH FRIDAY. THIS WILL
CONTINUE FURTHER INTO THE WEEKEND...AS THE HIGH CONTINUES EAST
TOWARDS QUEBEC AND THE LOW PRESSURE REMAINS ACROSS THE CENTRAL
PLAINS. WINDS WILL BEGIN TO BECOME MORE SOUTHERLY LATE IN THE
WEEKEND AS THIS LOW MAKES A SLOW PROGRESSION EAST ACROSS THE
PLAINS.
RODRIGUEZ
&&
.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 160846
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
346 AM CDT THU MAY 16 2013
.DISCUSSION...
330 AM CDT
SURFACE FRONT LIES JUST SOUTH OF THE CWA THIS MORNING AND PROBABLY
WONT MOVE MUCH THE NEXT COUPLE OF DAYS...ONLY TRENDING SLOWLY
NORTHWARD OVER THE WEEKEND. POPS THE NEXT COUPLE OF DAYS WILL BE A
CHALLENGE AS MAIN BELT OF WESTERLIES IS NORTH OF THE AREA AND UPPER
LOW OVER TEXAS OPENS UP AND MOVES INTO THE OHIO VALLEY LEAVING OUR
CWA IN A REGION OF RELATIVELY WEAK FORCING. CERTAINLY PLAUSIBLE THAT
CONVECTION COULD LIGHT UP NEAR AND JUST NORTH OF THE STALLED OUT
BOUNDARY AT JUST ABOUT ANY POINT THE NEXT COUPLE DAYS WITH THE BEST
CHANCES ACROSS FAR SOUTHERN CWA SLOWLY SPREADING NORTH INTO THE
REMAINDER OF THE AREA LATE FRIDAY INTO EARLY SATURDAY. DOES LOOKS
LIKE WE PRECIP CHANCES WILL DECREASE LATER SATURDAY THROUGH SUNDAY
AS UPPER RIDGE BUILDS INTO THE AREA AND FRONT MOVES NORTH OF THE
REGION.
TEMPERATURES PROBABLY WONT FLUCTUATE MORE THAN A FEW DEGREES FROM
WEDNESDAY`S READINGS TODAY THROUGH SATURDAY. DAILY LAKE BREEZES
SHOULD HOLD TEMPS IN THE 60S ALONG THE LAKE WITH UPPER 70S TO LOW
80S EXPECTED INLAND...THOUGH MORE CLOUD COVER ON FRIDAY COULD KEEP
IT A BIT COOLER INLAND. BIGGER WARM UP IS ANTICIPATED SUNDAY AS H8
TEMPS SORE INTO THE MID TEENS AND 925MB TEMPS GET INTO THE UPPER
TEENS WHICH SHOULD ALLOW TEMPS TO SOAR WELL INTO THE 80S AND
POSSIBLY AROUND 90 WITH ENOUGH SUNSHINE. MODELS SUGGEST THE SRF
GRADIENT WILL BE SOUTHEAST WHICH WOULD KEEP CHICAGO LAKE FRONT AND
NORTH SHORE AREAS COOLER...BUT AT THIS DISTANCE THE DETAILS ON THE
GRADIENT AND RESULTANT WIND FLOW COULD CHANGE SO STAY TUNED.
BIG WESTERN UPPER TROUGH THAT WE`VE BEEN TALKING ABOUT FOR DAYS
STILL LOOKS LIKE IT WILL MOVE TOWARD THE UPPER MISSISSIPPI VALLEY
EARLY NEXT WEEK. AFTER WHAT LOOKS TO BE A COUPLE ACTIVE SEVERE
WEATHER DAYS OUT IN THE CENTRAL CONUS THIS WEEKEND...THE MORE ACTIVE
WEATHER WILL SHIFT EAST INTO OUR AREA EARLY NEXT WEEK. GENERALLY
SPEAKING THE SYNOPTIC PATTERN LOOKS REASONABLY FAVORABLE FOR A
SEVERE WEATHER THREAT IN THE REGION MONDAY AND/OR TUESDAY...BUT
OBVIOUSLY A LOT WILL HINGE ON THE SMALLER SCALE DETAILS THAT WONT BE
RESOLVED FOR DAYS TO COME STILL. OF POTENTIALLY GREATER CONCERN IS
THE THREAT FOR HEAVY RAINFALL AND FLOODING...GFS/ECMWF/GEM ALL SHOW
UPPER LOW CLOSING OFF OVER THE NORTHERN PLAINS AND UPPER MISSISSIPPI
VALLEY DURING THE FIRST HALF OF THE WEEK WITH A WIDE OPEN GULF OF
MEXICO PROVIDING AMPLE MOISTURE. PROBABLY A BIT EARLY TO DO AN ESF
BUT IF THE MODEL REMAIN CONSISTENT THE NEXT RUN OR TWO LATER SHIFTS
MAY NEED TO CONSIDER AN ESF FOR THE THREAT OF MULTIPLE ROUNDS OF
SHOWERS/STORMS DURING THE FIRST HALF OF NEXT WEEK.
IZZI
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 09Z...
* NO CONCERNS IN THE NEAR TERM.
* LIGHT/VARIABLE WINDS THIS MORNING BECOMING EASTERLY BY MID
MORNING.
RODRIGUEZ
//DISCUSSION...UPDATED 06Z...
QUIET AT THE TERMINALS EARLY THIS MORNING WITH THE BULK OF ANY
ACTIVITY OCCURRING SOUTH/SOUTHWEST OF THE TERMINALS...AND EXPECT
THIS TO CONTINUE FOR THE REMAINDER OF THE FORECAST PERIOD WITH
ONLY HIGH LEVEL CLOUD COVER EXPECTED TO MOVE ACROSS THE TERMINALS.
LIGHT AND VARIABLE WINDS WILL BE REPLACED WITH AN EASTERLY LIGHT
WIND BY MID MORNING...CONTINUING THROUGH THE AFTERNOON BEFORE LAKE
BREEZE INFLUENCE GIVES A STRONGER PUSH OF AN EAST NORTHEAST WIND.
WINDS WILL DIMINISH THIS EVENING...AND HOLD ONTO THIS EAST
NORTHEAST WIND.
RODRIGUEZ
//ORD AND MDW CONFIDENCE...UPDATED 09Z...
* HIGH CONFIDENCE WITH VFR CONDITIONS.
* HIGH CONFIDENCE WITH WIND SPEED/DIRECTION.
RODRIGUEZ
//OUTLOOK FOR ORD/MDW FOR 12Z FRIDAY-12Z WEDNESDAY...UPDATED 00Z...
FRIDAY THROUGH TUESDAY...PERIODIC CHANCES FOR SHRA/TSRA WITH
LOCALIZED MVFR CONDITIONS. OTHERWISE...VFR.
KREIN
&&
.MARINE...
205 PM CDT
OVERALL...IT APPEARS TO BE RATHER QUIET ACROSS THE LAKE FOR THE NEXT
COUPLE OF DAYS. A SURFACE RIDGE OF HIGH PRESSURE WILL BUILD IN
ACROSS THE UPPER LAKES ON THURSDAY IN THE WAKE OF A LOW MOVING
EASTWARD ACROSS SOUTHERN QUEBEC. THIS WILL LEAD TO A PERIOD OF
NORTHERLY WINDS ACROSS THE LAKE LATER THURSDAY AND INTO FRIDAY.
HOWEVER...WIND SPEEDS DO NOT LOOK TO GET OVER 20 KT.
IN THE EXTENDED FORECAST PERIOD...LATER THIS WEEKEND AND INTO EARLY
NEXT WEEK...IT APPEARS THAT A POTENT STORM SYSTEM WILL TAKE SHAPE
ACROSS THE PLAINS STATES. THIS SYSTEM LOOKS TO PRODUCE SOME STRONGER
SOUTHERLY FLOW OVER THE LAKE DURING THIS PERIOD ALONG WITH
INCREASING THREATS FOR THUNDERSTORMS INTO EARLY NEXT WEEK.
KJB
&&
.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 160830
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
330 AM CDT THU MAY 16 2013
.DISCUSSION...
330 AM CDT
SURFACE FRONT LIES JUST SOUTH OF THE CWA THIS MORNING AND PROBABLY
WONT MOVE MUCH THE NEXT COUPLE OF DAYS...ONLY TRENDING SLOWLY
NORTHWARD OVER THE WEEKEND. POPS THE NEXT COUPLE OF DAYS WILL BE A
CHALLENGE AS MAIN BELT OF WESTERLIES IS NORTH OF THE AREA AND UPPER
LOW OVER TEXAS OPENS UP AND MOVES INTO THE OHIO VALLEY LEAVING OUR
CWA IN A REGION OF RELATIVELY WEAK FORCING. CERTAINLY PLAUSIBLE THAT
CONVECTION COULD LIGHT UP NEAR AND JUST NORTH OF THE STALLED OUT
BOUNDARY AT JUST ABOUT ANY POINT THE NEXT COUPLE DAYS WITH THE BEST
CHANCES ACROSS FAR SOUTHERN CWA SLOWLY SPREADING NORTH INTO THE
REMAINDER OF THE AREA LATE FRIDAY INTO EARLY SATURDAY. DOES LOOKS
LIKE WE PRECIP CHANCES WILL DECREASE LATER SATURDAY THROUGH SUNDAY
AS UPPER RIDGE BUILDS INTO THE AREA AND FRONT MOVES NORTH OF THE
REGION.
TEMPERATURES PROBABLY WONT FLUCTUATE MORE THAN A FEW DEGREES FROM
WEDNESDAY`S READINGS TODAY THROUGH SATURDAY. DAILY LAKE BREEZES
SHOULD HOLD TEMPS IN THE 60S ALONG THE LAKE WITH UPPER 70S TO LOW
80S EXPECTED INLAND...THOUGH MORE CLOUD COVER ON FRIDAY COULD KEEP
IT A BIT COOLER INLAND. BIGGER WARM UP IS ANTICIPATED SUNDAY AS H8
TEMPS SORE INTO THE MID TEENS AND 925MB TEMPS GET INTO THE UPPER
TEENS WHICH SHOULD ALLOW TEMPS TO SOAR WELL INTO THE 80S AND
POSSIBLY AROUND 90 WITH ENOUGH SUNSHINE. MODELS SUGGEST THE SRF
GRADIENT WILL BE SOUTHEAST WHICH WOULD KEEP CHICAGO LAKE FRONT AND
NORTH SHORE AREAS COOLER...BUT AT THIS DISTANCE THE DETAILS ON THE
GRADIENT AND RESULTANT WIND FLOW COULD CHANGE SO STAY TUNED.
BIG WESTERN UPPER TROUGH THAT WE`VE BEEN TALKING ABOUT FOR DAYS
STILL LOOKS LIKE IT WILL MOVE TOWARD THE UPPER MISSISSIPPI VALLEY
EARLY NEXT WEEK. AFTER WHAT LOOKS TO BE A COUPLE ACTIVE SEVERE
WEATHER DAYS OUT IN THE CENTRAL CONUS THIS WEEKEND...THE MORE ACTIVE
WEATHER WILL SHIFT EAST INTO OUR AREA EARLY NEXT WEEK. GENERALLY
SPEAKING THE SYNOPTIC PATTERN LOOKS REASONABLY FAVORABLE FOR A
SEVERE WEATHER THREAT IN THE REGION MONDAY AND/OR TUESDAY...BUT
OBVIOUSLY A LOT WILL HINGE ON THE SMALLER SCALE DETAILS THAT WONT BE
RESOLVED FOR DAYS TO COME STILL. OF POTENTIALLY GREATER CONCERN IS
THE THREAT FOR HEAVY RAINFALL AND FLOODING...GFS/ECMWF/GEM ALL SHOW
UPPER LOW CLOSING OFF OVER THE NORTHERN PLAINS AND UPPER MISSISSIPPI
VALLEY DURING THE FIRST HALF OF THE WEEK WITH A WIDE OPEN GULF OF
MEXICO PROVIDING AMPLE MOISTURE. PROBABLY A BIT EARLY TO DO AN ESF
BUT IF THE MODEL REMAIN CONSISTENT THE NEXT RUN OR TWO LATER SHIFTS
MAY NEED TO CONSIDER AN ESF FOR THE THREAT OF MULTIPLE ROUNDS OF
SHOWERS/STORMS DURING THE FIRST HALF OF NEXT WEEK.
IZZI
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 06Z...
* NO CONCERNS IN THE NEAR TERM.
* LIGHT/VARIABLE WINDS THIS MORNING BECOMING EASTERLY BY MID
MORNING.
RODRIGUEZ
//DISCUSSION...UPDATED 06Z...
QUIET AT THE TERMINALS EARLY THIS MORNING WITH THE BULK OF ANY
ACTIVITY OCCURRING SOUTH/SOUTHWEST OF THE TERMINALS...AND EXPECT
THIS TO CONTINUE FOR THE REMAINDER OF THE FORECAST PERIOD WITH
ONLY HIGH LEVEL CLOUD COVER EXPECTED TO MOVE ACROSS THE TERMINALS.
LIGHT AND VARIABLE WINDS WILL BE REPLACED WITH AN EASTERLY LIGHT
WIND BY MID MORNING...CONTINUING THROUGH THE AFTERNOON BEFORE LAKE
BREEZE INFLUENCE GIVES A STRONGER PUSH OF AN EAST NORTHEAST WIND.
WINDS WILL DIMINISH THIS EVENING...AND HOLD ONTO THIS EAST
NORTHEAST WIND.
RODRIGUEZ
//ORD AND MDW CONFIDENCE...UPDATED 06Z...
* HIGH CONFIDENCE WITH VFR CONDITIONS.
* HIGH CONFIDENCE WITH WIND SPEED/DIRECTION.
RODRIGUEZ
//OUTLOOK FOR ORD/MDW FOR 12Z FRIDAY-12Z WEDNESDAY...UPDATED 00Z...
FRIDAY THROUGH TUESDAY...PERIODIC CHANCES FOR SHRA/TSRA WITH
LOCALIZED MVFR CONDITIONS. OTHERWISE...VFR.
KREIN
&&
.MARINE...
205 PM CDT
OVERALL...IT APPEARS TO BE RATHER QUIET ACROSS THE LAKE FOR THE NEXT
COUPLE OF DAYS. A SURFACE RIDGE OF HIGH PRESSURE WILL BUILD IN
ACROSS THE UPPER LAKES ON THURSDAY IN THE WAKE OF A LOW MOVING
EASTWARD ACROSS SOUTHERN QUEBEC. THIS WILL LEAD TO A PERIOD OF
NORTHERLY WINDS ACROSS THE LAKE LATER THURSDAY AND INTO FRIDAY.
HOWEVER...WIND SPEEDS DO NOT LOOK TO GET OVER 20 KT.
IN THE EXTENDED FORECAST PERIOD...LATER THIS WEEKEND AND INTO EARLY
NEXT WEEK...IT APPEARS THAT A POTENT STORM SYSTEM WILL TAKE SHAPE
ACROSS THE PLAINS STATES. THIS SYSTEM LOOKS TO PRODUCE SOME STRONGER
SOUTHERLY FLOW OVER THE LAKE DURING THIS PERIOD ALONG WITH
INCREASING THREATS FOR THUNDERSTORMS INTO EARLY NEXT WEEK.
KJB
&&
.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 160551
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1251 AM CDT THU MAY 16 2013
.DISCUSSION...
830 PM CDT
ONLY VERY MINOR TWEAKS MADE TO GOING FORECAST. HELD ON TO
SCATTERED CLOUDS THROUGH THE ENTIRE EVE ACROSS THE FORECAST AREA
WHICH COULD SLOW THE TEMPERATURE DROP SOME...BUT OTHER THAN
THAT MUCH OF THE FORECAST IS ON TRACK.
WATER VAPOR IMAGERY THIS EVE SHOWS THE CLOSED LOW OVER OK SLOWLY
MEANDERING NORTHEAST WITH A SHEARED SHORT WAVE RACING ESE ACROSS
LOWER MI TO NORTHERN IL TO EASTERN IA. THE STATIONARY FRONT AT THE
SURFACE IS DRAPED ACROSS CENTRAL IL JUST SOUTH OF THE FORECAST
AREA. ON THE ILX RADAR THIS BOUNDARY CAN BE SEEN INCHING BACK
NORTHWARD. CONVECTION THAT HAS DEVELOPED ACROSS NORTHERN MO IS ON
THE BEGINNINGS OF THE LOW-LEVEL JET NOSE WHICH WILL ORIENT ITSELF
INTO CENTRAL IL LATER IN THE NIGHT AND IMPROVE CONVERGENCE ATOP
THE LOW-LEVEL BOUNDARY. WITH COLUMN MOISTURE IMPROVING FROM THE
APPROACHING UPPER LOW...AND ELEVATED INSTABILITY OF AROUND 600
J/KG AT THIS POINT PER THE 00Z ILX RAOB...IT DOES LOOK LIKE
ISOLATED TO SCATTERED CONVECTION HAS A DECENT SHOT OF DEVELOPING
TO THE SOUTH OF THE AREA...ESPECIALLY GIVEN THE OBSERVED TRENDS
IN MO ALREADY. EVEN THE SOUTHERN PERIPHERY OF THE SHEARED SHORT
WAVE COULD HELP BE A TRIGGER. SOME OF THIS COULD GRAZE THE FAR
SOUTHERN/SOUTHEASTERN FORECAST AREA. THE SEVERE POTENTIAL IS QUITE
LOW DUE TO LIMITED DEEP LAYER SHEAR AND MARGINAL INSTABILITY. THE
AREA OF STORM CHANCES WAS WELL COVERED IN THE INHERITED FORECAST.
FOR TEMPERATURES...THE DRY LOW-LEVEL AIR MASS AND LIGHT WINDS NORTH
OF THE BOUNDARY INITIALLY POINTED TOWARDS A QUICK TEMPERATURE DROP.
HOWEVER...CLOUDS ASSOCIATED WITH THE MID-LEVEL SPEED MAX AND
FRONTOGENESIS IN THE 700-500MB LAYER LOOK TO SLOW THAT SOME. LAST
VISIBLE IMAGERY SHOWED MID-LEVEL CLOUDS ACTUALLY EXPANDING ACROSS
PORTIONS OF CENTRAL IA. SO HAVE INCREASED SKY COVER...DELAYING
CLEARING ACROSS NORTHERN IL AND FAR NW IN UNTIL LATE. HAVE
ADJUSTED HOURLY TEMPERATURES SOME BUT ALL IN ALL THE MINS STILL
LOOK REASONABLE. HAVE COME UP A DEGREE OR TWO IN CENTRAL AND
SOUTHERN LOCATIONS.
MTF
//PREV DISCUSSION...
513 PM CDT
MINOR UPDATE LATE THIS AFTERNOON TO INCLUDE A SMALL CHANCE FOR A
SHOWER OR SPRINKLES ACROSS NORTHERN ILLINOIS THROUGH EARLY
EVENING. A MID-LEVEL SHORT WAVE AND ASSOCIATED 60 KT 500 MB SPEED
MAX ACROSS WI INTO NORTHEAST IA LOOK TO CONTINUE TO PUSH EASTWARD
MAINLY NORTH OF THE AREA. THE SOUTHERN EXTENSION OF THIS HAS A
NICE 800-900MB CONVERGENCE SIGNATURE AND GENERATING JUST ENOUGH
SATURATION FOR SOME SUSTAINED SHOWERS FROM SOUTHERN WI INTO NW IL
AND EASTERN IA. THESE SHOULD MORE THAN LIKELY DISSIPATE WITH THE
LOSS OF DAYTIME HEATING FURTHER DWINDLING THE INSTABILITY PRESENT.
WHILE THERE HAVE BEEN A FEW LIGHTNING STRIKES NORTHWEST OF THE
QUAD CITIES...THE INSTABILITY ALOFT IS MEAGER SO DO NOT BELIEVE
THOSE WILL BECOME ANY MORE WIDESPREAD. SO WHILE WOULD NOT BE
SURPRISED IF WIDELY ISOLATED SHOWERS OR SPRINKLES HANG TOGETHER
AS THIS WAVE TRACKS ACROSS A GOOD PART OF THE CWA...THINKING THAT
WILL BE AT BEST THE COVERAGE AND EXTENT IN THE FORECAST AREA.
MTF
//PREV DISCUSSION...
241 PM CDT
FORECAST CHALLENGES THIS AFTERNOON MAINLY REVOLVE AROUND PERIODIC
CONVECTIVE CHANCES ASSOCIATED WITH FRONTAL BOUNDARY THAT HAS STALLED
SOUTH OF I-80.
TODAY AND TONIGHT...
MODEST SURFACE RIDGE IS BUILDING ACROSS THE NORTHERN PLAINS INTO
NORTHERN ILLINOIS THIS AFTERNOON WHILE A COLD FRONT HAS SLOWLY
SAGGED SOUTH ACROSS OUR SOUTHERN TIER OF COUNTIES THIS AFTERNOON.
DEWPOINTS POOLING INTO THE LOW 60S AHEAD THE FRONT WITH TEMPS WELL
INTO THE 80S HAS LED TO MODERATE INSTABILITY DEVELOPING JUST TO OUR
SOUTH. AN ELONGATED TROUGH DROPPING ACROSS THE GREAT LAKES THIS
EVENING WILL LEAD TO MODEST HEIGHT FALLS ALOFT ASSISTING DIURNAL
EROSION OF THE CAP TO KICK OFF A FEW THUNDERSTORMS LATE THIS
EVENING. APPEARS THE MAIN THREAT WILL REMAIN SOUTH OF THE CWA NEAR
AN OUTFLOW/EFFECTIVE FRONTAL BOUNDARY CURRENTLY JUST SOUTH OF
BLOOMINGTON EAST TO LAFAYETTE. TRIMMED POPS...LEAVING ONLY SLT CHC
POPS SOUTH OF THE KANKAKEE RIVER TO ACCOUNT FOR SOME UNCERTAINTY.
MANY CONVECTIVE ALLOWING MODELS SUGGEST THAT COVERAGE WILL BE PRETTY
SPARSE...AND GIVEN THE WEAKLY FORCED SETUP...SEEMS REASONABLE.
THURSDAY THROUGH SATURDAY...
CLOSED LOW NOTED ON WV IMAGERY THIS AFTERNOON MOVING INTO SOUTHERN
UTAH WILL CONTINUE EAST ACROSS THE PLAINS THURSDAY. BROAD AREA OF
SURFACE LOW PRESSURE OVER THE PLAINS WILL LEAD TO MOISTURE RETURN
INTO THE UPPER MISSISSIPPI VALLEY AND NORTHERN PLAINS...AND SHOULD
HELP LIFT THE STATIONARY BOUNDARY BACK INTO THE CWA. MEANWHILE...THE
MID LEVEL DISTURBANCE BECOMES MASKED WITHIN THE MID/UPPER LEVEL
RIDGING WHICH IS AMPLIFYING ACROSS THE CENTRAL CONUS. MODEL
SOUNDINGS INDICATE WEAK IF ANY CIN IN PLACE THURSDAY AFTERNOON...SO
WON`T TAKE MUCH IMPETUS FOR THUNDERSTORMS TO DEVELOP. EXPECT MAIN
FOCUS TO BE ALONG THE FRONT AS IT LIFTS NORTH ACROSS THE MISSISSIPPI
VALLEY SOUTHEAST INTO EAST CENTRAL ILLINOIS...AND SHOULD LARGELY BE
DIURNALLY DRIVEN GIVEN OVERALL LACK OF SUPPORT ALOFT. EXPECT BETTER
CHANCES FOR CONVECTION ACROSS ALL BUT FAR NORTHEAST ILLINOIS //WHERE
INSTABILITY IS FORECAST TO BE MUCH WEAKER// ON FRIDAY AS THE
AFOREMENTIONED MID LEVEL DISTURBANCE FINALLY MOVES ACROSS THE AREA.
DETAILS FOR SATURDAY ARE PRETTY MURKY. STILL EXPECT THE MODEST
INSTABILITY ACROSS THE AREA AND CANNOT RULE OUT AFTERNOON
THUNDERSTORMS...THOUGH MID LEVEL RIDGE AXIS MOVING DIRECTLY OVERHEAD
MAY INHIBIT VERTICAL GROWTH...SO CAPPED POPS IN THE SLT CHC
CATEGORY. EACH DAY THIS PERIOD EXPECT AN ONSHORE COMPONENT TO THE
WINDS EITHER SYNOPTICALLY OR DUE TO LAKE BREEZES DEVELOPING...WHICH
WILL MEAN TEMPERATURES QUITE A BIT COOLER ALONG THE LAKE FRONT.
SUNDAY AND MONDAY...
MODELS CONTINUE TO INDICATE A RETURN OF HEAT THIS PERIOD WITH
INCREASING STRONG TO SEVERE THUNDERSTORM CHANCES AS LOW PRESSURE
DEEPENS OVER THE CENTRAL PLAINS AND LIFTS NORTH INTO THE DAKOTAS.
EML BEGINS TO MOVE OVER THE AREA SUNDAY WITH H85 TEMPS INCREASING TO
17-19C PROVIDING A FAIRLY STOUT CAPPED FOR SURFACE BASED CONVECTION.
LOCAL CLIMATOLOGY SHOWS THESE H85 TEMPS WITH H92 TEMPS OF 19-20C
RESULTING IN MEAN TEMPERATURES INTO THE UPPER 80S. BUMPED UP
TEMPERATURES TOWARDS THE BIAS CORRECTED GEM...AND BUMPED DOWN POPS
ACROSS THE CWA SUNDAY...THOUGH STILL MAINTAINED SOME LOW CHANCE/SLT
CHC POPS.
GUIDANCE CURRENTLY INDICATES THAT MONDAY WILL BE THE DAY TO KEEP AN
EYE ON SEVERE WEATHER-WISE...THOUGH HAS BEEN HAVING TROUBLE TIMING
THIS SYSTEM THUS FAR. THAT SAID...MAIN INSTABILITY AXIS IS CURRENTLY
PROGGED TO BE OVERHEAD MONDAY AS A NEGATIVELY TILTED TROUGH LIFTS
INTO THE UPPER MISSISSIPPI VALLEY. MODERATE TO STRONG INSTABILITY
COUPLED WITH MARGINAL SHEAR DEEP LAYER SHEAR INDICATE THE POTENTIAL
FOR SEVERE WEATHER...THOUGH THE USUAL CAVEATS THIS FAR OUT APPLY.
UPSTREAM CONVECTION...CLOUD COVER...AND UNCERTAINTY IN THE TIMING OF
THE UPPER LEVEL DISTURBANCE ALL CLOUD THE PICTURE SOMEWHAT.
DEUBELBEISS
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 06Z...
* NO CONCERNS IN THE NEAR TERM.
* LIGHT/VARIABLE WINDS THIS MORNING BECOMING EASTERLY BY MID
MORNING.
RODRIGUEZ
//DISCUSSION...UPDATED 06Z...
QUIET AT THE TERMINALS EARLY THIS MORNING WITH THE BULK OF ANY
ACTIVITY OCCURRING SOUTH/SOUTHWEST OF THE TERMINALS...AND EXPECT
THIS TO CONTINUE FOR THE REMAINDER OF THE FORECAST PERIOD WITH
ONLY HIGH LEVEL CLOUD COVER EXPECTED TO MOVE ACROSS THE TERMINALS.
LIGHT AND VARIABLE WINDS WILL BE REPLACED WITH AN EASTERLY LIGHT
WIND BY MID MORNING...CONTINUING THROUGH THE AFTERNOON BEFORE LAKE
BREEZE INFLUENCE GIVES A STRONGER PUSH OF AN EAST NORTHEAST WIND.
WINDS WILL DIMINISH THIS EVENING...AND HOLD ONTO THIS EAST
NORTHEAST WIND.
RODRIGUEZ
//ORD AND MDW CONFIDENCE...UPDATED 06Z...
* HIGH CONFIDENCE WITH VFR CONDITIONS.
* HIGH CONFIDENCE WITH WIND SPEED/DIRECTION.
RODRIGUEZ
//OUTLOOK FOR ORD/MDW FOR 12Z FRIDAY-12Z WEDNESDAY...UPDATED 00Z...
FRIDAY THROUGH TUESDAY...PERIODIC CHANCES FOR SHRA/TSRA WITH
LOCALIZED MVFR CONDITIONS. OTHERWISE...VFR.
KREIN
&&
.MARINE...
205 PM CDT
OVERALL...IT APPEARS TO BE RATHER QUIET ACROSS THE LAKE FOR THE NEXT
COUPLE OF DAYS. A SURFACE RIDGE OF HIGH PRESSURE WILL BUILD IN
ACROSS THE UPPER LAKES ON THURSDAY IN THE WAKE OF A LOW MOVING
EASTWARD ACROSS SOUTHERN QUEBEC. THIS WILL LEAD TO A PERIOD OF
NORTHERLY WINDS ACROSS THE LAKE LATER THURSDAY AND INTO FRIDAY.
HOWEVER...WIND SPEEDS DO NOT LOOK TO GET OVER 20 KT.
IN THE EXTENDED FORECAST PERIOD...LATER THIS WEEKEND AND INTO EARLY
NEXT WEEK...IT APPEARS THAT A POTENT STORM SYSTEM WILL TAKE SHAPE
ACROSS THE PLAINS STATES. THIS SYSTEM LOOKS TO PRODUCE SOME STRONGER
SOUTHERLY FLOW OVER THE LAKE DURING THIS PERIOD ALONG WITH
INCREASING THREATS FOR THUNDERSTORMS INTO EARLY NEXT WEEK.
KJB
&&
.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
| 
