126  
FXUS63 KLOT 061050  
AFDLOT  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL  
550 AM CDT FRI JUN 6 2025  
   
KEY MESSAGES  
 
- LINGERING CANADIAN WILDFIRE SMOKE WILL MAKE FOR POOR AIR  
QUALITY THROUGH THIS EVENING.  
 
- SHOWER AND THUNDERSTORM CHANCES WILL RETURN OVER THE WEEKEND,  
PARTICULARLY LATE SATURDAY-SATURDAY NIGHT AND THEN ON SUNDAY  
AFTERNOON.  
 
 
   
DISCUSSION  
 
ISSUED AT 315 AM CDT FRI JUN 6 2025  
 
THROUGH SATURDAY:  
 
A BROAD UPPER TROUGH CONTINUES TO RESIDE OVER THE CENTRAL CONUS  
WITH A COUPLE OF SHORTWAVES (ONE MOVING ACROSS IA AND THE UPPER  
MIDWEST AND THE OTHER MOVING ACROSS THE SOUTHERN PLAINS)  
TRAVERSING THROUGH THE PATTERN. WHILE BOTH OF THESE SHORTWAVES  
WILL CONTINUE TO EJECT EAST TODAY, THEIR TRAJECTORIES WILL CAUSE  
THEM TO LARGELY MISS OUR AREA RESULTING IN GENERALLY RAIN-FREE  
CONDITIONS THROUGH TONIGHT. HOWEVER, AS THE CLUSTER OF STORMS  
ASSOCIATED WITH THE SOUTHERN WAVE MOVES ACROSS THE MISSISSIPPI  
VALLEY THERE IS A NON-ZERO CHANCE (15-20%) THAT AN ISOLATED  
SHOWER MAY BRUSH OUR FAR SOUTHERN CWA (AREAS ALONG AND SOUTH OF  
US-24) THIS AFTERNOON.  
 
OTHERWISE, THE MAIN FORECAST CONCERN FOR TODAY WILL BE SOME  
LINGERING WILDFIRE SMOKE WHICH WILL LEAD TO POOR AIR QUALITY  
ACROSS PORTIONS OF NORTHERN IL AND NORTHWEST IN THROUGH THIS  
EVENING. AS A RESULT, AN AIR QUALITY ALERT REMAINS IN EFFECT  
UNTIL MIDNIGHT FOR THE CHICAGO METRO AREA AND NORTHWEST IN. THAT  
SAID, SURFACE SMOKE CONCENTRATIONS ARE EXPECTED TO GRADUALLY  
DIMINISH THROUGH THE AFTERNOON SO NOT EXPECTING REDUCED  
VISIBILITIES TO BE MUCH OF AN ISSUE TODAY. OUTSIDE OF THE SMOKE,  
EXPECT PARTLY TO MOSTLY CLOUDY SKIES WITH HIGH TEMPERATURES IN  
THE MID-70S INLAND AND LOWER TO MID- 60S NEAR THE LAKE DUE TO  
LIGHT ONSHORE WINDS.  
 
HEADING INTO SATURDAY, ANY LINGERING WILDFIRE SMOKE IS EXPECTED  
TO ADVECT EAST WHICH SHOULD ALLOW AIR QUALITY TO IMPROVE. WHILE  
MOST OF OUR SATURDAY SHOULD BE DRY, ANOTHER SHORTWAVE TROUGH  
WILL BE EJECTING OUT OF THE NORTHERN ROCKIES AND MOVING INTO THE  
SOUTHERN GREAT LAKES BY SATURDAY EVENING. THUS CHANCES FOR  
SHOWERS (AND PERHAPS AN ISOLATED STORM) WILL INCREASE SATURDAY  
AFTERNOON ESPECIALLY FOR LOCATIONS SOUTH OF I-80. REGARDLESS,  
TEMPERATURES WILL BE SIMILAR TO TODAY WITH HIGHS IN THE MID TO  
UPPER 70S INLAND AND 60S NEAR THE LAKE.  
 
YACK  
 
SATURDAY NIGHT THROUGH THURSDAY:  
 
THE LARGER SCALE WEATHER PATTERN IS EXPECTED TO TURN MORE  
UNSETTLED WITH A FEW PERIODS OF SHOWERS AND STORMS ACROSS THE  
MIDWEST THROUGH THE GREAT LAKES LATER THIS WEEKEND THROUGH EARLY  
NEXT WEEK. WITHIN THIS EVOLVING PATTERN, THERE ARE TWO DISTINCT  
WEATHER SYSTEMS OF INTEREST, BOTH OF WHICH WILL PLAY MAJOR  
ROLES IN DRIVING OUR CHANCES AND TIMING OF SHOWERS AND STORMS  
THROUGH THIS PERIOD. THE FIRST, IS NOTED IN THE WATER VAPOR  
IMAGERY AS A POSITIVELY TILTED IMPULSE (SOUTHWEST TO NORTHEAST  
ORIENTATION) OVER SOUTHERN ID EARLY THIS MORNING, WHILE THE  
SECOND IS CURRENTLY MOVING FROM THE GULF OF ALASKA ONSHORE  
ACROSS FAR NORTHWESTERN BRITISH COLUMBIA CANADA.  
 
THE SOUTHERN ID IMPULSE IS EXPECTED TO TRANSVERSE THE CENTRAL  
ROCKIES LATER TODAY BEFORE SLIDING EASTWARD ACROSS THE CORN BELT  
ON SATURDAY. AS IT DOES, ENSEMBLE GUIDANCE CONTINUES TO COME  
INTO BETTER AGREEMENT IN THE DEVELOPMENT OF A SURFACE WAVE OF  
LOW PRESSURE ALONG THE REMNANT WEST-TO-EAST ORIENTED FRONTAL  
BOUNDARY DRAPED ACROSS MO INTO SOUTHERN IL LATE SATURDAY INTO  
SATURDAY NIGHT AS THE MID-LEVEL SYSTEM MOVES ACROSS THE MID-  
MISSISSIPPI VALLEY. IF THIS OCCURS PAIRED WITH PWATS RISING TO  
OR JUST UPWARDS OF 1.5" (~UP TO 150% OF NORMAL FOR EARLY JUNE),  
A CORRIDOR OF ENHANCED LOW-TO-MID LEVEL DEFORMATION INDUCED  
FRONTOGENESIS MAY FOSTER SOME RATHER EFFICIENT RAINFALL RATES  
(WITH PERHAPS ISOLATED EMBEDDED T-STORMS) JUST NORTH OF THE  
SURFACE LOW TRACK SATURDAY NIGHT. THIS POTENTIAL CONTINUES TO BE  
CORROBORATED BY AN UPWARD TREND IN THE ENSEMBLE PROBABILITIES  
OF 24-HOUR RAINFALL AMOUNTS (QPF) OF 0.5" OR HIGHER. THE PAST  
FEW RUNS OF THE ECMWF ENSEMBLE (EPS) AND THE GFS ENSEMBLE (GEFS)  
FOR EXAMPLE, NOW PEAK THESE PROBABILITIES AROUND 50-60% SOUTH  
OF I-80 AND 30-50% UP TO THE I-88 CORRIDOR.  
 
FOLLOWING SATURDAY NIGHT'S SHOWER AND STORM CHANCES, OUR  
ATTENTION TURNS TO THE DIGGING MID-LEVEL TROUGH/LOW ACROSS THE  
NORTHERN PLAINS AND UPPER MIDWEST BY EARLY SUNDAY. THIS FEATURE  
IS EXPECTED TO SEND A SURFACE COLD FRONT SOUTHEAST ACROSS OUR  
AREA SUNDAY AFTERNOON AND EVENING. TEMPERATURES IN ADVANCE OF  
THIS APPROACHING FRONT SHOULD REACH THE 75-80F RANGE WITH DEW  
POINTS FROM THE UPPER 50S TO LOWER 60S.  
 
SEASONABLY STRONG MID AND UPPER-LEVEL FLOW WILL TRANSLATE TO  
OTHERWISE SUPPORTIVE EFFECTIVE DEEP LAYER BULK SHEAR FOR  
ORGANIZED LATE DAY CONVECTION. HOWEVER, SOME KEY LIMITING  
FACTORS AT THIS TIME INCLUDE: THE PRESENCE OF RATHER LACKLUSTER  
MID-LEVEL LAPSE RATES; ONLY MODEST LARGE SCALE FORCING UNTIL  
EVENING; AND VEERING WINDS IN THE COLD FRONTAL TROUGH REDUCING  
LOW-LEVEL CONVERGENCE. NEVERTHELESS, WE'LL NEED TO CONTINUE TO  
MONITOR THIS FOR A LOW-END/CONDITIONAL SEVERE THREAT (PRIMARILY  
DAMAGING WINDS), PARTICULARLY ACROSS NORTHWESTERN PARTS OF IL.  
CONVECTION WOULD LIKELY BE ON A WEAKENING TREND THROUGH THE  
EVENING AS IT MOVES SOUTHEASTWARD TOWARDS THE I-55 CORRIDOR.  
 
THE UPPER-LEVEL LOW WILL SETTLE OVER THE GREAT LAKES REGION BY  
MONDAY. AS IT DOES, A SERIES OF EMBEDDED COMPACT WAVES ROTATING  
AROUND IT'S SOUTHERN PERIPHERY COULD DRIVE ADDITIONAL DIURNALLY-  
ENHANCED SHOWERS (AND MAYBE A FEW ISOLATED THUNDERSTORMS),  
PARTICULARLY MONDAY AFTERNOON, AND POSSIBLY AGAIN TUESDAY  
AFTERNOON. THEREAFTER, A DEAMPLIFYING MID-LEVEL RIDGE IS  
EXPECTED TO CROSS THE REGION FOR THE SECOND HALF OF NEXT WEEK.  
ACCORDINGLY, THIS WILL SUPPORT A PERIOD OF DRIER AND WARMER  
WEATHER. THUS, AFTER A COOLER START TO THE WEEK, WITH HIGHS IN  
THE LOW TO MID 70S, TEMPERATURES ARE EXPECTED TO REBOUND BACK  
INTO THE 80S MID TO LATE WEEK.  
 
KJB  
 
 
   
AVIATION /12Z TAFS THROUGH 18Z SATURDAY/  
 
ISSUED AT 550 AM CDT FRI JUN 6 2025  
 
THERE ARE NO SIGNIFICANT AVIATION WEATHER CONCERNS ANTICIPATED  
THROUGH THE PERIOD.  
 
THE ONLY ITEM OF NOTE IN THE NEAR TERM WILL BE THE CONTINUED  
HAZY CONDITIONS EARLY THIS MORNING, WITH SOME ASSOCIATED MINOR  
VSBY RESTRICTIONS. THESE HAZY CONDITIONS SHOULD IMPROVE LATER  
THIS MORNING, SO WE ARE CURRENTLY NOT ANTICIPATING ANY VSBY  
RESTRICTIONS FROM MID-MORNING ONWARD. OTHERWISE, EXPECT  
NORTHEASTERLY WINDS THROUGH THE PERIOD, WITH SPEEDS PEAKING  
DURING THE DAY IN THE 7 TO 11 KT RANGE.  
 
SOME MVFR CIGS HAVE RECENTLY DEVELOPED INTO GYY. THESE CIGS MAY  
LINGER FOR A FEW HOURS EARLY THIS MORNING, BUT IMPROVEMENT BACK  
TO VFR IS EXPECTED LATER THIS MORNING.  
 
KJB  
 
 
   
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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