663
FXUS63 KLOT 130817
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
317 AM CDT WED MAY 13 2026
KEY MESSAGES
- AFTER A RELATIVELY COOL WEDNESDAY, TEMPERATURES WILL TREND
UPWARD THURSDAY ONWARD.
- SEVERAL ROUNDS OF SHOWERS AND STORMS ARE POSSIBLE IN THE
GENERAL REGION THIS WEEKEND INTO EARLY NEXT WEEK, SOME COULD
BE SEVERE.
DISCUSSION
ISSUED AT 317 AM CDT WED MAY 13 2026
A MUCH COOLER AIRMASS IS MOVING OVERHEAD THIS MORNING ON BREEZY
NORTHWEST WINDS FOLLOWING YESTERDAY EVENINGS COLD FRONTAL
PASSAGE. THIS UNSEASONABLY COOL AIRMASS IN COMBINATION WITH A
GOOD AMOUNT OF STRATO-CU CLOUD COVER WILL RESULT IN HIGH
TEMPERATURES THIS AFTERNOON ONLY TOPPING OUT IN THE LOW TO MID
60S ACROSS INLAND PORTIONS OF NORTHERN IL AND NORTHWEST IN. EVEN
COOLER CONDITIONS ARE EXPECTED ALONG THE LAKE MICHIGAN
LAKESHORE, WHERE READINGS LOOK TO REMAIN IN THE 50S THIS
AFTERNOON AS WINDS VEER OFF THE LAKE.
THE WINDS WILL REMAIN BREEZY THROUGH THE DAY, WITH GUSTS OF
20-25 MPH EXPECTED. WIND SPEEDS ARE THEN SLATED TO ABATE WITH
SUNSET EARLY THIS EVENING, THEN BECOME LIGHT (<5 MPH) OVERNIGHT
AS A SURFACE RIDGE OF HIGH PRESSURE SHIFTS OVERHEAD. LIGHT WINDS
UNDER THIS HIGH, IN COMBINATION WITH CLEARING SKIES THROUGH THE
EVENING, WILL SET THE STAGE FOR ANOTHER CHILLY NIGHT. OVERNIGHT
TEMPERATURES ARE FORECAST TO FALL OFF INTO THE UPPER 30S TO LOW
40S INLAND FROM THE LAKE AND OUTSIDE OF CHICAGO. SOME OF THE
TYPICALLY CLIMATOLOGICALLY FAVORED COOL SPOTS COULD EVEN DROP A
BIT LOWER (INTO THE MIDDLE 30S), POSSIBLY RESULTING IN SOME
PATCHY FROST DEVELOPMENT TOWARDS EARLY THURSDAY MORNING.
FORTUNATELY, AT THIS TIME, IT APPEARS THE FROST THREAT WILL
REMAIN LIMITED, SO WE WILL FORGO A FORMAL MENTION IN THE
FORECAST AT THIS TIME.
FOLLOWING A CHILLY START TO THE DAY ON THURSDAY, INCREASED
SUNSHINE AND A MODERATING AIRMASS THROUGH THE DAY WILL HELP PUSH
INLAND TEMPERATURES BACK INTO THE 60S TO LOW 70S (WARMEST
ACROSS INTERIOR SECTIONS OF NORTHERN IL). HOWEVER, CONTINUED
ONSHORE EASTERLY WINDS ACROSS THE NORTHEASTERN IL LAKE MICHIGAN
SHORE WILL KEEP CONDITIONS ALONG AND NEAR THE LAKE IN THE 50S TO
NEAR 60. DRY WEATHER IS EXPECTED THROUGH THE DAY. HOWEVER,
SCATTERED RAIN SHOWER CHANCES WILL RETURN TO THE FORECAST LATER
THURSDAY NIGHT INTO FRIDAY MORNING AS THE FIRST OF SEVERAL MID-
LEVEL IMPULSES EJECTING OUT OF THE SOUTHWEST CONUS BEGINS TO
MOVE INTO THE CENTRAL CONUS.
WHILE OUR AREA MAY EXPERIENCE A PERIOD OF SHOWERS, AND POSSIBLY
SOME STORMS (ESPECIALLY IN THE SOUTH), THURSDAY NIGHT INTO
FRIDAY, THE MAIN FOCUS FOR POTENTIALLY MORE SUBSTANTIAL SHOWERS
AND THUNDERSTORMS IN OUR AREA WILL BE THIS WEEKEND INTO EARLY
NEXT WEEK. DETERMINISTIC AND ENSEMBLE GUIDANCE REMAIN IN
AGREEMENT THAT A POTENT SURFACE LOW TRACKING EASTWARD ACROSS
SOUTHERN CANADA THROUGH LATE WEEK WILL LAY OUT A WEST-TO-EAST
ORIENTED QUASI-STATIONARY SURFACE FRONTAL BOUNDARY SOMEWHERE
ACROSS THE MIDWEST INTO THE LOWER GREAT LAKES REGION ON
SATURDAY. THIS FRONT MAY BECOME THE FOCUS FOR A FEW OF WAVES OF
SHOWERS AND THUNDERSTORMS THIS THE WEEKEND AS THE AIRMASS SOUTH
OF THE FRONT MOISTENS AND DESTABILIZES. THEREAFTER, A MORE
PRONOUNCED UPPER TROUGH DIGGING INTO THE WESTERN CONUS COULD
DRIVE A STRONGER STORM SYSTEM NORTHEASTWARD FROM THE PLAINS
THROUGH THE UPPER MIDWEST EARLY NEXT WEEK. SUCH A SYSTEM WOULD
SUPPORT VERY WARM AND BREEZY CONDITIONS ACROSS OUR AREA EARLY
NEXT WEEK, ALONG WITH CONTINUED CHANCES OF SHOWERS AND
THUNDERSTORMS, SOME POTENTIALLY SEVERE WITH HEAVY RAINFALL.
STAY TUNED!
KJB
AVIATION /06Z TAFS THROUGH 12Z THURSDAY/
ISSUED AT 1238 AM CDT WED MAY 13 2026
AN OUTFLOW BOUNDARY CURRENTLY CROSSING ORD/MDW WILL BRIEFLY
MAINTAIN NE WINDS UP TO AROUND 15 KNOTS FOR ABOUT AN HOUR. A
PASSING COLD FRONT WILL THEN SHIFT WINDS NW WITH GUSTS UP TO 20
KNOTS THROUGH SUNRISE AND UP TO 20 TO 25 KNOTS THIS MORNING INTO
THE EARLY AFTERNOON. A LAKE-ENHANCED NE WIND SHIFT WITH SPEEDS
UP TO 15 KNOTS IS EXPECTED TO CROSS THE CHICAGO TERMINALS
SOMETIME MID-AFTERNOON THROUGH EARLY EVENING. CONFIDENCE IN THE
EXACT TIMING REMAINS LOW AS THE BOUNDARY MAY STALL NEAR THE
TERMINALS FOR SEVERAL HOURS THIS AFTERNOON. IT IS QUITE POSSIBLE
THAT THIS OCCURS BETWEEN ORD AND MDW, WHICH WOULD LEAD TO A
MID-AFTERNOON PASSAGE AT MDW AND EARLY EVENING PASSAGE AT ORD.
BY LATE EVENING, WINDS WILL SETTLE NW UNDER 5 KNOTS OR BECOME
CALM/VRB.
MID-LEVEL STRATUS NEARING NE ILLINOIS EARLY THIS MORNING WILL
GRADUALLY LOWER, WITH A LARGER AREA OF MVFR STRATUS SLOWLY
MOVING SOUTHWARD ACROSS WISCONSIN. PERIODS OF MVFR CEILINGS
APPEAR LIKELY AT THE TERMINALS FOR SEVERAL HOURS DURING THE
MORNING BEFORE DAYTIME MIXING LIFTS REMAINING STRATUS INTO VFR
LEVELS BY THE AFTERNOON.
KLUBER
LOT WATCHES/WARNINGS/ADVISORIES
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY UNTIL 7 PM CDT THIS EVENING FOR THE IL
NEARSHORE WATERS.
SMALL CRAFT ADVISORY UNTIL 1 AM CDT THURSDAY FOR THE IN
NEARSHORE WATERS.
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