140
FXUS63 KLOT 050554
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
1254 AM CDT THU JUN 5 2025
KEY MESSAGES
- SHOWERS WILL PERSIST THROUGH DAYBREAK FOR AREAS SOUTHEAST OF
INTERSTATE 55.
DISCUSSION
ISSUED AT 330 PM CDT WED JUN 4 2025
THROUGH THURSDAY NIGHT:
MUCH OF OUR FORECAST AREA HAS BEEN BLANKETED BY RAIN, STRATUS, AND
HAZE/LIGHT FOG THROUGHOUT THE DAY TODAY WITH TEMPERATURES STUCK IN
THE 60S ON THE COOL SIDE OF A SLOW-MOVING COLD FRONT THAT HAS SLOWLY
BEEN SAGGING SOUTHWARD ACROSS THE AREA (QUINTESSENTIAL JUNE WEATHER,
RIGHT?). THE RAIN AND STRATUS HAVE HINDERED DESTABILIZATION EFFORTS
IN OUR SOUTHEASTERN COUNTIES, WHICH THE COLD FRONT STILL HASN'T
FULLY PASSED THROUGH AT PRESS TIME. DON'T REALLY EXPECT THINGS TO
CHANGE MUCH THERE OVER THE NEXT FEW HOURS, BUT MID-LEVEL LAPSE RATES
STILL LOOK TO REMAIN STEEP ENOUGH TO SUPPORT A THREAT FOR ISOLATED
EMBEDDED THUNDERSTORMS WITHIN THE BROADER RAIN SHIELD THAT SHOULD
PERSIST ACROSS OUR SOUTHEASTERN CWA THE REMAINDER OF THIS AFTERNOON
AND INTO TONIGHT. PRECIPITABLE WATER VALUES APPROACHING 2" WILL
CONTINUE TO SUPPORT SOAKING RAINFALL ALONG AND JUST BEHIND THE
FRONT, AND LOCALIZED RAINFALL TOTALS IN EXCESS OF 2" COULD END
UP BEING OBSERVED WHEN ALL IS SAID AND DONE. HOWEVER, THE
ANTECEDENT DRYNESS PRIOR TO THIS RAINFALL AND THE PROLONGED
DURATION OF THIS RAINFALL SHOULD LARGELY PRECLUDE ANY NOTABLE
HYDROLOGIC CONCERNS FROM MATERIALIZING.
SURFACE HIGH PRESSURE CENTERED TO OUR NORTH WILL ALLOW FOR
WINDS TO BECOME LIGHT TONIGHT. WITH SKIES ALSO EXPECTED TO CLEAR
OUT A GOOD BIT IN OUR NORTHERN CWA, SOME FOG DEVELOPMENT MAY
OCCUR. FORECAST GUIDANCE IS ACTUALLY MOST BULLISH ON THIS
OCCURRING OUT OVER LAKE MICHIGAN, AND WITH SURFACE WINDS
EXPECTED TO BE OUT OF THE NORTH, WE'LL NEED TO KEEP AN EYE ON
THIS FOG POTENTIALLY BLEEDING INLAND IF IT DOES END UP
DEVELOPING OVER THE LAKE. OTHERWISE, LOW TEMPERATURES TONIGHT
ACROSS OUR FORECAST AREA SHOULD RANGE FROM THE LOW 50S TO LOW
60S.
DURING THE DAYTIME TOMORROW, THE FRONT WILL HAVE STALLED SOUTH
OF OUR FORECAST AREA, THOUGH THERE IS STILL SOME SPREAD IN
MODEL GUIDANCE REGARDING PRECISELY WHERE THE FRONT WILL SET UP
SHOP. MOST GUIDANCE FAVORS THIS FRONT STALLING COMFORTABLY SOUTH
OF OUR FORECAST AREA, BUT A COUPLE OF MODELS HAVE IT STALLING
CLOSE ENOUGH TO OUR SOUTHERN CWA BORDER TO WHERE SOME SHOWERS
AND MAYBE A THUNDERSTORM COULD STILL AFFECT OUR FAR
SOUTHEASTERN COUNTIES WELL AFTER DAYBREAK. HAVE MAINTAINED SOME
LOWER END POPS (UNDER 30%) NEAR AND SOUTH OF THE KANKAKEE RIVER
VALLEY TO ACCOUNT FOR THIS POSSIBILITY.
PARTLY CLOUDY SKIES ARE OTHERWISE EXPECTED ACROSS THE REMAINDER
OF OUR FORECAST AREA TOMORROW, THOUGH LINGERING CANADIAN
WILDFIRE SMOKE MAY CONTINUE TO RESULT IN HAZY SKIES. IT ALSO
APPEARS THAT A GREATER CONCENTRATION OF THIS SMOKE MAY BE
PRESENT AT GROUND LEVEL COMPARED TO PRIOR DAYS, WHICH HAS
WARRANTED THE ISSUANCE OF AN AIR QUALITY ALERT, PER THE REQUESTS
OF THE ILLINOIS ENVIRONMENTAL PROTECTION AGENCY AND THE INDIANA
DEPARTMENT OF ENVIRONMENTAL MANAGEMENT. DAYTIME TEMPERATURES
TOMORROW SHOULD BE WARMER THAN TODAY'S IN MOST LOCATIONS WITH
HIGHS EXPECTED TO END UP IN THE 70S ACROSS MOST OF OUR FORECAST
AREA. BREEZY ONSHORE FLOW, HOWEVER, WILL KEEP LOCATIONS WITHIN A
FEW MILES OF LAKE MICHIGAN MIRED IN THE UPPER 50S OR 60S FOR
ANOTHER DAY.
OGOREK
FRIDAY THROUGH WEDNESDAY:
PERIODIC SHOWER AND THUNDERSTORM CHANCES WILL CONTINUE FOR
PORTIONS OF THE AREA THROUGH THE END OF THE WEEK AS MULTIPLE
DISTURBANCES MOVE WITHIN THE BROADER QUASI-ZONAL FLOW.
THE FIRST OF THESE WAVES IS EXPECTED TO MOVE ACROSS THE MID-
MISSISSIPPI AND OHIO VALLEYS ON FRIDAY. THERE CONTINUE TO BE
DIFFERENCES IN POSITION AND TRACK OF THE WAVE AMONG THE GLOBAL
GUIDANCE, WITH GFS REMAINING FURTHEST NORTH AND BRINGING SHOWERS
INTO SOUTHERN PORTIONS OF THE AREA, WHEREAS THE ECMWF IS WELL
SOUTH OF THE AREA LEADING TO DRY CONDITIONS AREAWIDE. TEND TO
FAVOR THE ECMWF AT THIS RANGE AND HAVE CAPPED SHOWER CHANCES IN
THE 20-40% RANGE (HIGHEST WELL SOUTH OF I-80). SUSPECT FURTHER
REDUCTIONS WILL BE WARRANTED WITH LATER UPDATES.
A SUBSEQUENT WAVE ARRIVES ON SATURDAY WHICH COULD LEAD TO
ADDITIONAL MAINLY ISOLATED SHOWER DEVELOPMENT (~20% CHANCE).
SURFACE HIGH PRESSURE CENTERED OVER THE UP OF MICHIGAN SHOULD
HELP HOLD THIS ACTIVITY TO AREAS MAINLY WEST AND SOUTH OF THE
CHICAGO METRO BUT A STRAY SHOWER CAN'T BE RULED OUT AMIDST
OTHERWISE DRY AND SEASONABLE CONDITIONS.
AN UPPER LOW IS THEN FORECAST TO DEVELOP ACROSS CANADA OVER THE
WEEKEND AND DESCEND TOWARD THE GREAT LAKES REGION EARLY NEXT
WEEK. A COLD FRONT EXTENDING WELL SOUTH OF AN ASSOCIATED SURFACE
LOW IN WESTERN ONTARIO WILL MOVE THROUGH THE AREA ON SUNDAY
LEADING TO SCATTERED THUNDERSTORM CHANCES. DEPENDING ON THE
TIMING OF THE FRONTAL PASSAGE WE WILL HAVE TO KEEP AN EYE ON THE
POTENTIAL FOR SEVERE WEATHER SUNDAY AFTERNOON INTO EARLY
EVENING. AS EMBEDDED WAVES/VORT LOBES ROUND THE CLOSED MID-
UPPER LOW ADDITIONAL SHOWER AND STORM CHANCES MAY CONTINUE ON
MONDAY.
TEMPERATURES WILL REMAIN NEAR SEASONABLE THROUGH THE PERIOD
WITH HIGHS MAINLY IN THE MID-UPPER 70S INLAND FROM THE
LAKESHORE.
PETR
AVIATION /06Z TAFS THROUGH 12Z FRIDAY/
ISSUED AT 1254 AM CDT THU JUN 5 2025
N/NNE WINDS AROUND 5 KNOTS AT TAF ISSUANCE WILL SETTLE NE 10-15
KNOTS TODAY AND UNDER 10 KNOTS TONIGHT.
GRADUAL CLEARING COMBINED WITH LIGHT WINDS AND RAINFALL OVER
THE PAST 24 HOURS WILL PROMOTE LOWER-END VFR TO MVFR BR THROUGH
SUNRISE. SOME RESIDUAL WILDFIRE SMOKE TRAPPED UNDER THE
NOCTURNAL INVERSION MAY ALSO BE CONTRIBUTING TO THE REDUCED
VISIBILITY. VALUES SHOULD IMPROVE TO VFR LEVELS BY MID-MORNING
AS BR ERODES AND HIGHER SMOKE CONCENTRATIONS REMAIN FAVORED TO
THE WEST OF THE CHICAGO TERMINALS.
WHILE CEILINGS ARE EXPECTED TO REMAIN VFR (EXCEPT AT GYY)
THROUGH THE PERIOD, WILL NEED TO MONITOR FOR THE DEVELOPMENT OF
IFR OR LOWER-END MVFR STRATUS OVER WESTERN LOWER MICHIGAN EARLY
THIS MORNING. UPSTREAM TRAJECTORIES WOULD ADVECT/SPREAD THIS
STRATUS ACROSS SOUTHERN LAKE MICHIGAN AND TOWARD THE CHICAGO
TERMINALS DURING THE MORNING HOURS. HAVE MAINTAINED THE
INCLUSION OF SCT010 FOR MUCH OF THE MORNING AT ORD/MDW AS ANY
INCOMING STRATUS DECK OVER LAKE MICHIGAN SHOULD QUICKLY SCATTER
WITH DAYTIME HEATING/MIXING.
KLUBER
LOT WATCHES/WARNINGS/ADVISORIES
IL...AIR QUALITY ALERT UNTIL MIDNIGHT CDT TONIGHT FOR ILZ005-ILZ006-
ILZ012-ILZ013-ILZ020-ILZ021-ILZ103-ILZ104-ILZ105-ILZ106-
ILZ107-ILZ108.
IN...AIR QUALITY ALERT UNTIL MIDNIGHT CDT TONIGHT FOR INZ001-INZ002-
INZ010-INZ011.
LM...NONE.
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