986
FXUS63 KLOT 100744
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
244 AM CDT WED SEP 10 2025
KEY MESSAGES
- MOSTLY DRY WEATHER EXPECTED THE REMAINDER OF THE WORK WEEK
WITH A CONTINUED GRADUAL WARMING TREND.
- UNSEASONABLY WARM WITH A (LESS THAN 30 PERCENT) CHANCE OF
SCATTERED SHOWERS AND SOME THUNDERSTORMS THIS WEEKEND.
DISCUSSION
ISSUED AT 244 AM CDT WED SEP 10 2025
THROUGH THURSDAY:
OTHER THAN PERHAPS AN ISOLATED SPRINKLE NEAR THE IL/WI BORDER
THIS MORNING, DRY AND GENERALLY WARMER WEATHER IS EXPECTED
THROUGH THURSDAY. AREAS ALONG LAKE MICHIGAN WILL EXPERIENCE
COOLER TEMPERATURES WITH ONSHORE WINDS, ESPECIALLY THURSDAY,
THOUGH MOST INLAND AREAS WILL SEE A RETURN OF ABOVE-AVERAGE
SUMMER-LIKE WARMTH.
WEATHER ACROSS THE FORECAST AREA CONTINUES TO BE INFLUENCED BY
OUR POSITION ALONG THE WESTERN PERIPHERY OF AN ELONGATED SURFACE
HIGH PRESSURE RIDGE FROM THE LOWER GREAT LAKES THROUGH NEW
ENGLAND. ALOFT, A NORTH-SOUTH MID-LEVEL SHORT WAVE TROUGH AXIS
WAS EVIDENT ACROSS IL IN MORNING GOES VAPOR IMAGERY, WHILE
ANOTHER SLIGHTLY MORE VIGOROUS WAVE WAS NOTED DIGGING SOUTHEAST
ACROSS THE UPPER MISSISSIPPI VALLEY IN ASSOCIATION WITH A 60 KT
UPPER LEVEL JET STREAK OVER IA. MODEST 15-20 KT SOUTH-
SOUTHWESTERLY FLOW IN THE 925- 850 MB LAYER CONTINUES TO FOCUS
WEAK MOISTURE TRANSPORT INTO THE MN/WI/IA BORDER REGION TO OUR
NORTHWEST EARLY THIS MORNING, WITH REGIONAL RADAR MOSAIC
PAINTING SHOWERS MAINLY NORTH OF THE U.S. 20 CORRIDOR IN
NORTHEASTERN IA. THERE'S ALSO A FEW ELEVATED RETURNS ALONG THE
IL/IN STATE LINE OVER THE SOUTHERN CHICAGO METRO AREA, THOUGH
WITH OBSERVED CLOUD BASES GENERALLY ABOVE 11-12 KFT EXPECT THAT
THESE ARE MOSTLY VIRGA AND ARE EVAPORATING BEFORE REACHING THE
GROUND. CAN'T COMPLETELY RULE OUT A FEW SCATTERED LIGHT
SPRINKLES OCCURRING NEAR THE IL/WI BORDER LATER THIS MORNING AS
THE UPPER MISSISSIPPI WAVE CONTINUES TO ADVANCE SOUTHEAST INTO
OUR REGION, THOUGH FORECAST SOUNDINGS CONTINUE TO DEPICT DRY LOW
LEVELS WHICH SHOULD LARGELY PRECLUDE THESE MAKING IT TO THE
GROUND TO ANY SIGNIFICANT EXTENT.
WITH MODEST BUT PERSISTENT WARM ADVECTION, TEMPERATURES ARE
EXPECTED TO WARM A FEW DEGREES OVER YESTERDAY, WITH HIGHS
RANGING FROM NEAR 80 IN THE NORTH TO THE LOWER 80S SOUTH.
ANOTHER WEAK LAKE BREEZE WILL LIMIT TEMPS TO THE MID-70S ALONG
THE ILLINOIS LAKE MICHIGAN SHORE, WITH SURFACE WINDS ACROSS THE
FORECAST AREA EVENTUALLY FLOPPING FROM SOUTHERLY TO
NORTHEASTERLY THIS EVENING AS A WEAK SURFACE LOW TRACKS DOWN THE
MISSISSIPPI RIVER AND INTO WESTERN IL IN ASSOCIATION WITH THE
UPPER LEVEL SHORT WAVE. IT LOOKS AS IF THIS WILL BE LATE ENOUGH
TO NOT AFFECT AFTERNOON MAX TEMPS, HOWEVER.
THE UPPER LEVEL TROUGH COMPLETES IT'S TRANSIT OF THE AREA
TONIGHT, AND MOVES OFF TO THE EAST OF THE REGION THURSDAY.
SURFACE HIGH PRESSURE BUILDING ACROSS ONTARIO/QUEBEC AND THE
NORTHERN GREAT LAKES WILL PROVIDE SYNOPTIC NORTHEAST SURFACE
FLOW, WHICH WILL MAKE FOR A SOMEWHAT LARGER LAKE COOLING
FOOTPRINT. THERMAL PROFILES ALOFT CONTINUE TO WARM HOWEVER, AND
WITH MOSTLY SUNNY SKIES AFTERNOON HIGHS ARE FORECAST TO RANGE
FROM THE MID-70S ALONG THE LAKE TO THE LOW-MID 80S WITH FARTHER
INLAND EXTENT TO THE SOUTHWEST ACROSS THE CWA.
RATZER
THURSDAY NIGHT THROUGH TUESDAY:
A DEVELOPING REX BLOCK OVER THE NORTHERN ROCKIES INTO CENTRAL
CANADA WILL TRANSITION INTO AN UNBALANCED OMEGA BLOCK ACROSS
THE CENTRAL CONUS AND SOUTHERN CANADA THROUGH EARLY NEXT WEEK.
THIS PATTERN WILL REMAIN ANCHORED BY A STRONG MID-LEVEL RIDGE
CENTERED SOUTHWEST OF HUDSON BAY. MEANWHILE, THE WESTERN (AND
MUCH STRONGER) UPPER-LEVEL LOW IN THE BLOCKING PATTERN WILL
DRIFT FROM THE NORTHERN ROCKIES TO THE SOUTHERN CANADIAN
PRAIRIES.
GUIDANCE CONTINUES TO SUGGEST THAT A PIECE OF ENERGY WILL
BECOME DISLODGED FROM THE WESTERN LOW AND DRIFT ACROSS A
WEAKNESS IN THE MID-LEVEL HEIGHTS ON FRIDAY BEFORE THE MAIN
RIDGE DOMINATES THE OVERALL PATTERN. THE WAVE IS PROGGED TO
TRACK SOMEWHERE ACROSS THE CENTRAL GREAT LAKES REGION FRIDAY
NIGHT INTO SATURDAY, WITH A TRAILING COLD FRONT STALLING NEAR
OR OVER PART OF THE FORECAST AREA ON SUNDAY. AS CAN BE EXPECTED
WITH WEAK WAVES EMBEDDED WITHIN A BROADER BLOCKING PATTERN,
INDIVIDUAL ENSEMBLE AND DETERMINISTIC MODEL MEMBERS HAVE
EXHIBITED A WIDE RANGE OF SPATIAL AND TEMPORAL SOLUTIONS AND
THEIR RESULTANT IMPACTS ON THE LOCAL WEATHER. OVERALL, SOME MID-
LEVEL SHOWERS WITH AN OUTSIDE CHANCE OF AN ISOLATED STORM MAY
BRUSH NORTHEAST ILLINOIS AND NORTHWEST INDIANA LATE FRIDAY NIGHT
INTO SATURDAY MORNING, WITH A SECONDARY AND HIGHLY SHEARED MID-
LEVEL TROUGH BRINGING ANOTHER LOW CHANCE FOR SHOWERS AND STORMS
SATURDAY NIGHT. WITH DRY CONDITIONS THE PAST FEW WEEKS AND THE
ONGOING SEASONAL DECLINE IN EVAPOTRANSPIRATION, IT IS ENTIRELY
POSSIBLE THAT THE LOW-LEVEL MOISTURE PROFILE WILL REMAIN
UNFAVORABLE FOR PRECIP OVER MUCH OF THE AREA. THE MAIN MESSAGE
WILL CONTINUE TO NOTE LOW CHANCES FOR SHOWERS AND PERHAPS A FEW
STORMS OVER THE WEEKEND, BUT FAVOR A DRY FORECAST FOR MUCH OF
THE AREA.
WITH THE LOW-LEVEL THERMAL RIDGE EXTENDING NORTHEASTWARD TOWARD
THE AREA FRIDAY THROUGH THE WEEKEND, AN UNSEASONABLY WARM
PERIOD IS LIKELY WITH DAYTIME HIGHS WELL INTO THE 80S AND
PERHAPS SOME LOW 90S. THE ULTIMATE LOCATION OF THE
AFOREMENTIONED COLD FRONT MAY RESULT IN COOLER CONDITIONS NEAR
THE LAKE BY SUNDAY.
BY THE MIDDLE OF NEXT WEEK THE UPPER RIDGE WILL BREAK DOWN AND
SHIFT SOUTHEAST. SOME INDICATIONS OF MODEST TROUGHING OVER THE
NORTHERN GREAT PLAINS COULD BRING PERIODS OF DECAYING SHOWERS
TOWARD THE AREA LATE MONDAY THROUGH MUCH OF THE WEEK, BUT
CONSENSUS GUIDANCE MAINTAINS A CONTINUED PERIOD WITH LITTLE
RAIN OVER THE NEXT WEEK AND A HALF.
KLUBER
AVIATION /06Z TAFS THROUGH 12Z THURSDAY/
ISSUED AT 1229 AM CDT WED SEP 10 2025
VFR CONDITIONS WILL PERSIST THROUGH THE PERIOD AS MID-LEVEL
CLOUDS AROUND OR ABOVE 10KFT FILTER OVER THE AREA IN RESPONSE TO
A SLOW- MOVING WAVE CROSSING THE SOUTH HALF OF WISCONSIN. SHRA
ASSOCIATED WITH THE WAVE ARE EXPECTED TO REMAIN NORTH OF THE
TERMINALS, THOUGH ISOLATED SPRINKLES CANNOT BE FULLY RULED OUT
(PARTICULARLY AT RFD) THROUGH THIS AFTERNOON AS MID-LEVEL VIRGA
EVAPORATES THROUGH A DRY SUB-CLOUD LAYER.
SSE WINDS UP TO AROUND 5 KNOTS EARLY THIS MORNING WILL
GRADUALLY SHIFT SSW THROUGH SUNRISE. A LAKE BREEZE IS THEN
EXPECTED TO SHIFT WINDS ENE UP TO 10 KNOTS AROUND 20Z AT MDW AND
21Z AT ORD. E OR ENE WINDS WILL THEN PREVAIL THROUGH TONIGHT.
KLUBER
LOT WATCHES/WARNINGS/ADVISORIES
IL...NONE.
IN...NONE.
LM...NONE.
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