838
FXUS63 KLOT 250755
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
255 AM CDT WED MAR 25 2026
KEY MESSAGES
- BREEZY AND MUCH WARMER TODAY WITH A SOMEWHAT ELEVATED
GRASS/BRUSH FIRE RISK THIS AFTERNOON.
- ISOLATED TO SCATTERED THUNDERSTORMS EXPECTED SOUTH OF I-80
TONIGHT, SOME MAY PRODUCE HAIL UP TO AROUND 1" IN DIAMETER.
- POWERFUL COLD FRONT WILL MOVE ACROSS THE AREA THURSDAY WITH
TEMPS IN THE 70S/80S AHEAD IT, FALLING SHARPLY INTO THE
40S/50S BEHIND IT.
- THUNDERSTORMS ARE LIKELY TO DEVELOP NEAR THE FRONT THURSDAY
AFTERNOON, WITH THE HIGHEST CHANCES OF THUNDERSTORMS NEAR AND
SOUTH OF I-80. SOME THUNDERSTORMS WILL PROBABLY BE SEVERE.
DISCUSSION
ISSUED AT 255 AM CDT WED MAR 25 2026
THE WEATHER IS GOING TO GET PRETTY ACTIVE THE NEXT COUPLE OF
DAYS AROUND HERE WITH DRAMATIC TEMPERATURE SWINGS!
TODAY, LOOKS BREEZY AND UNSEASONABLY MILD WITH GUSTY SOUTHWEST
WINDS LIKELY TO HELP PUSH HIGH TEMPS UP TO NEAR, IF NOT INTO,
THE LOWER 70S. THERE WILL HIGH CLOUDINESS AROUND AGAIN TODAY,
BUT LESS PROMINENT THAN TUESDAY, WITH INDICATIONS THAT THERE
COULD BE SOME MODEST DECREASE IN CLOUDINESS THIS AFTERNOON. THIS
IS LIKELY TO HELP DEEPEN THE BOUNDARY LAYER WHICH SHOULD MIX
INTO SOME EXTREMELY DRY AIR OFF THE SURFACE. MADE NO REAL
CHANGES TO FORECAST DEWPOINTS FOR TODAY, KEEPING THEM 5F+ LOWER
THAN NBM, WHICH COULD STILL BE TOO HIGH IF WE SEE A GOOD DEAL OF
SUNSHINE THIS AFTERNOON.
LOW LEVEL MOISTURE RETURN IS UNDERWAY ACROSS THE SOUTHERN PLAINS
WITH 850MB DEWPOINTS AROUND 10C OBSERVED ON SOUNDINGS TUESDAY
EVENING. THIS MOISTURE WILL ADVECT NORTHWARD TODAY, THEN
EASTWARD INTO THE MIDWEST TONIGHT, DRIVEN BY A 50KT WESTERLY
LOW LEVEL JET. LOW AMPLITUDE SHORTWAVE CURRENTLY APPROACHING THE
NORTHERN ROCKIES WILL RACE EASTWARD AND IS PROGGED TO REACH THE
MID-MISSISSIPPI VALLEY TONIGHT. STRONG MOISTURE CONVERGENCE NEAR
THE TERMINUS OF THE LOW LEVEL JET AIDED BY SOME LARGE SCALE
ASCENT FROM THE AFOREMENTIONED SHORTWAVE SHOULD RESULT IN
SCATTERED ELEVATED THUNDERSTORMS DEVELOPING THIS EVENING.
THERE IS SOME SPREAD AMONG GUIDANCE WITH RESPECT TO THE
MAGNITUDE OF ELEVATED INSTABILITY TONIGHT, BUT MOST GUIDANCE
DEPICTS AN AXIS OF 500-1000 J/KG OF MUCAPE NOSING INTO ILLINOIS
ALONG THE LEADING EDGE OF A STRONG ELEVATED MIXED LAYER (EML).
HODOGRAPHS IN THE EFFECTIVE SHEAR LAYER ARE LONG AND STRAIGHT
WITH EFFECTIVE BULK SHEAR OF 40KT+. ASSUMING ELEVATED CAPE OF
500-1000 J/KG IS REALIZED, THEN THERE WOULD BE CONCERN FOR SOME
ELEVATED SUPERCELLS WITH THE POTENTIAL FOR ISOLATED SEVERE
T-STORMS CAPABLE OF LARGE HAIL ACROSS THE ILLIANA REGION
TONIGHT, MAINLY AFFECTING OUR SOUTHERN CWA.
LOTS TO TALK ABOUT WITH THURSDAY'S WEATHER...
FIRST, GUIDANCE IS IN GOOD AGREEMENT ON A STRENGTHENING SURFACE
FRONT BECOMING ESTABLISHED ACROSS NORTHERN IL OR FAR SOUTHERN WI
THURSDAY MORNING. UNFORTUNATELY, THERE ARE SOME VERY MEANINGFUL
DIFFERENCES IN MODELS WITH RESPECT TO WHERE THIS BOUNDARY SETS
UP. THE HRDPS AND NAM ARE FARTHER NORTH WITH THE BOUNDARY
DEVELOPING NORTH OF THE WI BORDER WITH THE ECMWF FARTHEST SOUTH
WITH SFC FRONTOGENESIS TAKING PLACE NEAR I-80 THURSDAY MORNING,
WITH THE GFS IN THE MIDDLE. CLIMO THIS TIME OF YEAR WOULD
CERTAINLY FAVOR THE ECMWF'S FARTHER SOUTH SOLUTION GIVEN THE
STILL VERY COLD LAKE, BUT CONFIDENCE IS PRETTY LOW AT THIS
POINT. WHERE THE FRONT DEVELOPS WILL HAVE HUGE IMPLICATIONS ON
TEMPERATURES AND WHERE THE EVENTUAL SEVERE THREAT WILL
MATERIALIZE THURSDAY AFTERNOON.
SOUTH OF THE STRENGTHENING WARM FRONT, TEMPERATURES ARE LIKELY
TO CLIMB INTO THE UPPER 70S TO MID 80S, WHILE NORTH OF THE
BOUNDARY TEMPERATURES MAY STRUGGLE TO GET OUT OF THE 50S. THAT
TIGHT TEMPERATURE GRADIENT OPENS TO THE DOOR TO HUGE TEMPERATURE
FORECAST BUSTS FOR THURSDAY. FOR NOW, LEANING TOWARD THE
COMPROMISE SOLUTION OF THE GFS IN THE GRIDS, WHICH WOULD ALLOW
MOST OF THE CHICAGO AREA AND MOST OF NORTHERN IL TO AT LEAST
SPEND THE FIRST HALF OF THE DAY IN THE WARM SECTOR WITH TEMPS
CLIMBING INTO THE 70S. IF THE ECMWF SOLUTION PANS OUT, HIGH
TEMPS NEAR AND NORTH OF THE I-88/I-290 CORRIDOR COULD END UP
BEING EASILY 25 DEGREES COLDER THAN CURRENTLY FORECAST, SO STAY
TUNED!
DURING THE AFTERNOON, A WEAK SURFACE LOW IS PROGGED TO RIPPLE
EASTWARD ACROSS NORTHERN IL/SOUTHERN WI INTO SOUTHERN LOWER MI
OR NORTHERN IN BY LATER IN THE AFTERNOON. IN THE WAKE OF THAT
LOW, THE FRONT SHOULD BEGIN TO SURGE SOUTHWARD RESULTING IN A
DRAMATIC TEMPERATURE DROP. IF AREAS NEAR LAKE MICHIGAN DO WARM
WELL INTO THE 70S EARLY TOMORROW, THEN THIS COULD END UP BEING A
PNEUMONIA FRONT WITH A RAPID TEMP DROP GREATER THAN 30F DURING
THE AFTERNOON.
AN USUALLY STRONG EML FOR THIS TIME OF YEAR IS FORECAST TO
OVERSPREAD THE MIDWEST INTO THE LOWER OHIO VALLEY THURSDAY. VERY
STEEP MID LEVEL LAPSE RATES WITHIN THIS EML COMBINED WITH
MODERATE LOW LEVEL MOISTURE SHOULD RESULT IN AN MLCAPE AXIS OF
1500-2000 J/KG ALONG AND AHEAD OF THE COLD FRONT. THE EML WILL
ALSO PROVIDE FOR A STRONG CAPPING INVERSION NEAR ITS BASE, BUT
ASCENT ASSOCIATED WITH THE APPROACHING SHORTWAVE TROUGH, HEATING
OF THE BOUNDARY LAYER, SOME MODEST POOLING OF LOW LEVEL
MOISTURE AHEAD OF THE FRONT, AND CONVERGENCE NEAR THE FRONT
SHOULD BE ENOUGH TO BREACH THE CAP DURING THE MID-LATE
AFTERNOON.
THE FAIRLY STRONG INSTABILITY FOR THIS TIME OF YEAR WILL BE
JUXTAPOSED BENEATH VERY STRONG KINEMATIC FIELD WITH 0-6KM BULK
SHEAR LIKELY TO BE NEAR/ABOVE 60KT, CREATING A POTENTIALLY
EXPLOSIVE SEVERE WEATHER SET-UP. FORECAST HODOGRAPHS ARE LONG
AND STRAIGHT, SUGGESTING A POTENTIAL FOR SUPERCELLS WITH LARGE
TO VERY LARGE HAIL AS THE INITIAL CONVECTIVE MODE. MOST CAMS
SUGGEST A FAIRLY QUICK EVOLUTION TO LINEAR MODE, WHICH GIVEN THE
SHEAR VECTORS FAIRLY PARALLEL TO THE FRONT AND STRONG FRONTAL
FORCING WOULD MAKE SENSE. THE TRANSITION TO LINEAR MODE WOULD
LIKELY LEAD TO A TRANSITION TO MORE OF DAMAGING WIND THREAT.
THERE'S STILL A GOOD DEAL OF UNCERTAINTY ABOUT HOW FAR NORTH
CONVECTIVE INITIATION TAKES PLACE AS WELL AS HOW QUICKLY THE
TRANSITION TO LINEAR MODE TAKES PLACE. THE GREATEST OVERALL
SEVERE RISK IN OUR CWA LOOKS TO BE NEAR/SOUTH OF I-80 AND
PARTICULARLY SOUTH OF THE KANKAKEE RIVER VALLEY. THERE LOOKS TO
BE A COUPLE HOUR WINDOW OF SUPERCELLS CAPABLE OF PRODUCING HAIL
GREATER THAN 2" IN DIAMETER WITH THE TRANSITION TO MORE A
DAMAGING WIND THREAT POTENTIALLY NOT TAKING PLACE UNTIL STORMS
ARE OUT OF OR NEARLY OUT OF OUR CWA.
PRECIPITATION SHOULD END QUICKLY THURSDAY NIGHT, LIKELY ENDING
BEFORE THE COLUMN IS COLD ENOUGH FOR ANY WINTRY PRECIPITATION.
FRIDAY LOOKS QUITE CHILLY WITH HIGHS IN THE 40S, EXCEPT ONLY IN
THE 30S NEAR AND IMMEDIATELY DOWNWIND OF LAKE MICHIGAN. IT STILL
LOOKS AS THOUGH A COLD SNAP WILL BE SHORT WITH A QUICK
MODERATION IN TEMPERATURES TAKING PLACE OVER THE WEEKEND.
- IZZI
AVIATION /06Z TAFS THROUGH 12Z THURSDAY/
ISSUED AT 1246 AM CDT WED MAR 25 2026
EXPECT VFR CONDITIONS WITH PERIODS OF BKN MID TO UPPER-LEVEL
CLOUDS FILTERING OVER THE AREA THROUGH AT LEAST THIS EVENING.
ELEVATED TS FORMING ON A MODEST LLJ SHOULD REMAIN SOUTH OF THE
TERMINALS VERY LATE THIS EVENING INTO THE EARLY MORNING HOURS
THURSDAY. PROB30 TS MAY NEED TO BE INCLUDED AT GYY/MDW WITH
FUTURE TAF CYCLES, ESPECIALLY WITH THE POTENTIAL FOR TS TO
PRODUCE HAIL. MVFR CEILINGS ALSO CANNOT BE RULED OUT EARLY
THURSDAY MORNING AS LOW-LEVEL MOISTURE SURGES NORTHWARD.
ESE/SE WINDS AROUND 5 KNOTS AT TAF ISSUANCE WILL SLOWLY VEER S
THROUGH SUNRISE. RECENT RFD ACARS AND KLOT/TORD/TMDW VWP ALSO
SUPPORT INCLUSION OF LLWS THROUGH SUNRISE WITH A WEAK LLJ
PRODUCES SSE WINDS OF 35 KNOTS AS LOW AS AROUND 1KFT.
WINDS WILL QUICKLY SETTLE SSW AND GUST OVER 20 KNOTS AS DAYTIME
MIXING INTO THE LLJ COMMENCES 13 TO 14Z. FREQUENT SW GUSTS OF
25 KNOTS ARE THEN EXPECTED THIS AFTERNOON, WITH SPORADIC GUSTS
TO 30 KNOTS POSSIBLE LATE IN THE AFTERNOON.
LLWS WAS ALSO ADDED FOR THIS EVENING AS GRADUAL DECOUPLING
LEADS TO SW/SSW WINDS AT OR BELOW 10 KNOTS (SPORADIC GUSTS STILL
POSSIBLE) BENEATH A DEVELOPING 40 KNOT LLJ.
KLUBER
LOT WATCHES/WARNINGS/ADVISORIES
IL...NONE.
IN...NONE.
LM...GALE WATCH FROM THIS AFTERNOON THROUGH THURSDAY MORNING FOR
THE IL AND IN NEARSHORE WATERS.
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