702
FXUS63 KLOT 092318
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
618 PM CDT TUE SEP 9 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 226 PM CDT TUE SEP 9 2025
A BROAD TROUGH IS EVIDENT ON WATER VAPOR IMAGERY EARLY THIS
AFTERNOON DIGGING SOUTHEASTWARD INTO THE MIDWEST. SEVERAL,
SMALLER VORTS ARE EMBEDDED WITHIN THIS BROADER TROUGH WITH THE
MOST PROMINENT ONE OVER SOUTHWEST MN/NORTHWEST IA. THE LARGER,
PARENT TROUGH, WITH EMBEDDED VORTS, WILL MOVE ACROSS OUR AREA
LATER TONIGHT AND WEDNESDAY.
AIR MASS OVER OUR AREA IS QUITE DRY WITH PRECIPITABLE WATER OF
ONLY 0.44" ON THE KILX 12Z SOUNDING, WHICH IS RIGHT AROUND THE
DAILY RECORD MIN. THERE IS AN AXIS WITH HIGHER MOISTURE FROM THE
WESTERN CORN BELT NORTHEAST INTO THE UPPER GREAT LAKES, BUT WITH
LOW LEVEL FLOW LARGELY REMAINING SOUTH OR EVEN SOUTHEASTERLY,
THIS AXIS OF GREATER MOISTURE WILL STRUGGLE TO MOVE EASTWARD. AS
THE UPPER TROUGH PROGRESSES EASTWARD, IT WILL ENCOUNTER AND
INCREASINGLY PARCHED AIR MASS. AN INCREASE/THICKENING OF MID-
HIGH LEVEL CLOUDINESS IS EXPECTED TONIGHT WITH CLOUDINESS
LINGERING INTO WEDNESDAY. STRONGER ASCENT, LIKELY FOCUSED NEAR
THE STRONGER SMALLER EMBEDDED VORTS, WILL LIKELY BE ENOUGH FOR
PLENTY OF VIRGA AND PERHAPS SOME SPRINKLES REACHING THE SURFACE
LATE TONIGHT AND POSSIBLY INTO WEDNESDAY. FOR NOW CONFINED THE
SPRINKLE CHANCES IN THE GRIDS TO OUR NORTHWESTERN CWA LATER
TONIGHT, BUT CERTAINLY WOULDN'T BE HARD TO ENVISION THOSE
SPRINKLE CHANCES NEEDING TO BE EXTENDED FARTHER EAST AND INTO
THE DAYTIME HOURS WEDNESDAY.
TEMP FORECAST IS A BIT TRICKY WITH LOW LEVEL THERMAL FIELDS
FAVORING TEMPS WARMING TOWARD IF NOT INTO THE LOWER 80S, THOUGH
EXTENT AND THICKNESS OF CLOUDINESS COULD RESULT IN TEMPS BEING
HELD A FEW DEGREES COOLER, ESPECIALLY NORTHERN/NORTHWESTERN CWA.
SUNSHINE RETURNS THURSDAY AND FRIDAY WHICH SHOULD ALLOW TEMPS TO
CLIMB INTO THE 80S BOTH DAYS, THOUGH WEAK LAKES BREEZES WILL
KEEP TEMPS A BIT COOLER (70S) NEAR THE LAKE BOTH AFTERNOONS.
A HIGHLY AMPLIFIED, BLOCKY, AND FAIRLY WONKY PATTERN IS EXPECTED
TO DEVELOP OVER NORTH AMERICAN THIS WEEKEND WITH HIGHLY
AMPLIFIED UPPER RIDGING OVER THE CENTRAL PART OF THE U.S. MEDIUM
RANGE GUIDANCE HAS THE UPPER RIDGE CENTER VERY NEAR OUR AREA,
WHICH FAVOR DRY, WARM CONDITIONS, HOWEVER, SHORTWAVE TROUGH
DIGGING SOUTH INTO THE EASTERN GREAT LAKES COULD ALLOW A WEAK
COLD FRONT TO MOVE ACROSS OUR AREA LATER IN THE WEEKEND. CAN'T
RULE OUT A SHOWER OR STORM AT SOME POINT THIS WEEKEND, BUT THE
VAST MAJORITY (ALL?) OF THE UPCOMING WEEKEND LOOKS DRY AND VERY
WARM.
- IZZI
AVIATION /00Z TAFS THROUGH 06Z WEDNESDAY/
ISSUED AT 618 PM CDT TUE SEP 9 2025
FORECAST CONCERN FOR THE TERMINALS...
- 10-15% CHANCE FOR A LIGHT SHOWER OR SPRINKLE TONIGHT INTO
WEDNESDAY MAINLY ACROSS NORTHWEST IL.
- LAKE BREEZE TO RESULT IN EASTERLY WIND SHIFT AT CHICAGO
TERMINALS AND GYY WEDNESDAY AFTERNOON.
AN UPPER DISTURBANCE WILL CONTINUE TO PIVOT OVERHEAD TONIGHT
THROUGH WEDNESDAY AFTERNOON WHICH MAY RESULT IN ISOLATED LIGHT
SHOWERS AND/OR SPRINKLES AT TIMES. GIVEN THAT FORECAST
SOUNDINGS SHOW RATHER DRY CONDITIONS BELOW 10000 FT, CONFIDENCE
ON ANY RAIN BEING OBSERVED AT THE TERMINALS IS LOW SO HAVE LEFT
TAFS DRY FOR NOW. THAT SAID, IF ANY SPRINKLES DO MATERIALIZE
HIGHEST POTENTIAL LOOKS TO BE ACROSS NORTHWEST IL WHERE SLIGHTLY
BETTER MOISTURE IS FORECAST.
OTHERWISE, EXPECT THE CURRENT SOUTHWEST WINDS TO BECOME
SOUTHEASTERLY OVER THE NEXT 1-2 HOURS WITH SPEEDS IN THE 5-7 KT
RANGE. DIRECTIONS WILL ONCE AGAIN TURN SOUTH-SOUTHWEST ON
WEDNESDAY, BUT A LAKE BREEZE IS EXPECTED TO MOVE THROUGH THE
CHICAGO TERMINALS AND GYY RESULTING IN AN EASTERLY WIND SHIFT.
WITH THE WEAK WINDS JUST ABOVE THE GROUND AND SIMILAR LAKE AND
LAND TEMPERATURES, THE LAKE BREEZE MAY BE SOMEWHAT SLOW TO
ACTUALLY MOVE THROUGH THE CHICAGO TERMINALS SO EXPECT CHANGES TO
CURRENT FORECAST TO OCCUR AS WE GET CLOSER IN TIME. OUTSIDE OF
THE WINDS VFR CONDITIONS WILL PREVAIL THROUGH THE TAF PERIOD.
YACK
LOT WATCHES/WARNINGS/ADVISORIES
IL...NONE.
IN...NONE.
LM...NONE.
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