455
FXUS63 KLOT 291130
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
630 AM CDT TUE APR 29 2025
KEY MESSAGES
- A 20% CHANCE FOR A FEW SHOWERS AND STORMS PERSIST EARLY THIS
MORNING, THOUGH THE SEVERE THREAT IS LOW.
- A STORM SYSTEM WILL BRING PERIODS OF SOAKING RAINFALL (WITH
THUNDERSTORMS) TO THE AREA WEDNESDAY THROUGH FRIDAY.
- A BLOCKING PATTERN WILL BUILD INTO THE REGION NEXT WEEK
RESULTING IN ABOVE NORMAL TEMPERATURES AND DRY CONDITIONS
DURING THE FIRST WEEK OF MAY.
DISCUSSION
ISSUED AT 318 AM CDT TUE APR 29 2025
THROUGH WEDNESDAY:
THE SURFACE COLD FRONT IS CURRENTLY SHIFTING EASTWARD TOWARDS
THE MISSISSIPPI RIVER AS OF THIS WRITING. IN ADVANCE OF THIS
FRONT, VERY WARM AND BREEZY CONDITIONS PERSIST ACROSS IL AND IN.
IN FACT, AS OF 3 AM CDT, TEMPERATURES REMAIN IN THE MID TO
UPPER 70S, SOME 10+ DEGREES ABOVE THE NORMAL HIGH TEMPERATURES
FOR LATE APRIL. THESE READINGS WILL DROP BACK INTO LOWER TO MID
60S FOLLOWING THE COLD FRONTAL PASSAGE THIS MORNING.
THERE HAVE BEEN SOME RECENT SUCCESSFUL ATTEMPTS AT SOME ISOLATED
CONVECTIVE DEVELOPMENT (MOST RECENTLY JUST NORTH OF DUBUQUE, IA)
NEAR THE FRONTAL BOUNDARY. IN SPITE OF THIS, LINGERING CAPPING AND
AND RATHER NEBULOUS FORCING FOR ASCENT ALONG THE THE FRONTAL
BOUNDARY HAS LARGELY LEAD TO A DEARTH OF STORMS WITH THE FRONT
EARLY THIS MORNING. WHILE THIS IS LIKELY TO CONTINUE TO BE THE
CASE WITH (AND AHEAD OF) THE FRONT AS IT SLIDES ACROSS NORTHERN
IL EARLY THIS MORNING, A SMALL (~10-20%) CHANCE FOR A FEW ISOLATED
SHOWERS AND STORMS WILL PERSIST PRIOR TO ITS PASSAGE AROUND
DAYBREAK IN THE CHICAGO METRO AREA. IF ANY STORMS ARE ABLE TO
DEVELOP, THE MAIN THREATS WOULD BE SOME OCCASIONAL LIGHTNING AND
POSSIBLY SOME SMALL HAIL.
THE THREAT FOR STORMS WILL QUICKLY END ACROSS MOST OF NORTHERN IL
BY DAYBREAK WITH THE FRONTAL PASSAGE. HOWEVER, FARTHER SOUTH,
PARTICULARLY ACROSS MY EAST CENTRAL IL AND WEST CENTRAL IN
COUNTIES, THE THREAT FOR STORMS MAY PERSIST FOR A FEW MORE HOURS
THIS MORNING (THROUGH LATE MORNING OR SO) BEFORE THE FRONT CLEARS
THIS AREA. FORTUNATELY, IT APPEARS ANY DIURNAL DEVELOPMENT OF
SEVERE STORMS TODAY WILL LARGELY BE FOCUSED TO THE SOUTH AND EAST
OF THE AREA THIS AFTERNOON.
WINDS WILL TURN WEST-NORTHWESTERLY IN THE WAKE OF THE FRONT THIS
MORNING, WITH WIND SPEEDS EXPECTED TO GRADUALLY EASE THROUGH THE
DAY. A COOLER AND MUCH DRIER AIRMASS WILL FILTER INTO THE AREA,
THUS RESULTING IN DRY WEATHER AREAWIDE BY THIS AFTERNOON.
TEMPERATURES WILL BE COOLER TODAY, WITH READINGS EXPECTED TO HOLD
IN THE MID TO UPPER 60S THIS AFTERNOON UNDER PARTLY CLOUDY SKIES.
A SECONDARY PUSH OF COOLER AIR IS EXPECTED THIS EVENING AS SURFACE
HIGH PRESSURE SHIFTS INTO THE WESTERN GREAT LAKES AND SHIFTS THE
WINDS OFF OF LAKE MICHIGAN. THIS IN COMBINATION WITH LIGHT WINDS
TONIGHT SHOULD ALLOW TEMPERATURES TO DROP BACK INTO THE 40S.
WEDNESDAY LOOKS TO START OFF DRY ACROSS THE AREA. HOWEVER,
LATER IN THE DAY RAIN SHOWERS ARE EXPECTED TO DEVELOP NORTHWARD
OVER THE AREA IN ADVANCE OF THE NEXT WEATHER SYSTEM SHIFTING OUT
ACROSS THE PLAINS. THE CHANCES FOR SHOWERS AND THUNDERSTORMS
WILL CONTINUE TO INCREASE FOR THE AREA WITH THE APPROACH OF THIS
WEATHER SYSTEM WEDNESDAY NIGHT INTO THURSDAY. MORE ON THAT
BELOW.
KJB
WEDNESDAY NIGHT THROUGH MONDAY:
LAPSE RATES ARE PROJECTED TO STEEPEN AS THE SURFACE LOW
APPROACHES THE AREA. AS SUCH, INSTABILITY WILL INCREASE
WEDNESDAY NIGHT INTO THURSDAY MORNING WHICH IS EXPECTED TO
INCREASE THE CHANCES FOR THUNDERSTORMS AROUND THE FORECAST AREA.
MODELED DEEP LAYER SHEAR DOES NOT LOOK TOO IMPRESSIVE (LESS
THAN 30 KNOTS), SO THE THREAT OF SEVERE WEATHER IS LOW. IF
ANYTHING, THE BETTER CHANCES COULD BE THURSDAY AFTERNOON WITH
BETTER FORCING ALONG THE SURFACE FRONT. HOWEVER, MOST MODELS ARE
SUGGESTING THAT THE FRONT COULD BE JUST EAST OF OUR FORECAST
AREA, BUT SOMETHING TO MONITOR NONETHELESS. THE ONLY OTHER
IMPACT FROM THIS SYSTEM WILL BE FROM THE HIGH MOISTURE CONTENT
AS IT BRINGS ALMOST 1.5 INCHES OF PRECIPITABLE WATER INTO THE
AREA. FLOODING CONCERNS ARE LIMITED GIVEN THE DRIER ANTECEDENT
CONDITIONS, BUT IT LOOKS LIKE THE NEXT BEST CHANCE FOR
WIDESPREAD SOAKING RAINS.
AS THE SURFACE LOW EXITS TO THE EAST FRIDAY MORNING, DRIER
CONDITIONS ARE EXPECTED TO DEVELOP. ENSEMBLES ARE STILL
SUGGESTING ANOTHER UPPER-LEVEL LONG WAVE TROUGH WILL DROP DOWN
OUT OF CANADA. THERE IS A (20 TO 35 PERCENT) CHANCE FOR SOME
SHOWERS TO DEVELOP AS IT PASSES. THERE SHOULD BE ENOUGH FORCING,
BUT MOISTURE AVAILABLE WOULD BE A LIMITING FACTOR. GENERALLY
DRIER CONDITIONS ARE EXPECTED FRIDAY ESPECIALLY INTO THE
AFTERNOON AND EVENING.
AN UPPER-LEVEL RIDGE WILL DEVELOP OVER THE WEEKEND DRIVING HIGH
PRESSURE AT THE SURFACE AND DRIER CONDITIONS. TEMPERATURES ARE
EXPECTED TO INCREASE NEXT WEEK WITH HIGHS BACK INTO THE 70S AND
POSSIBLY SOME 80S.
DK
AVIATION /12Z TAFS THROUGH 18Z WEDNESDAY/
ISSUED AT 630 AM CDT TUE APR 29 2025
KEY AVIATION MESSAGES FOR THE CURRENT TAF PERIOD:
- BREEZY SOUTHWEST WINDS TURN WEST AND EVENTUALLY NORTHWEST
TODAY AS THEY DIMINISH
- WIND SHIFT AT CHICAGO TERMINALS TO NORTHEAST LATE TUESDAY
AFTERNOON/EVENING
ISOLATED TO SCATTERED SHOWERS CANNOT BE COMPLETELY RULED OUT AS
THE SURFACE COLD FRONT PASSES THROUGH THE REGION THIS MORNING.
HOWEVER, THE CHANCES FOR ANY SHOWER OR THUNDERSTORMS IS AROUND
20 PERCENT, AND THEREFORE KEPT OUT OF THE TAF. DRY AND VFR
CONDITIONS ARE EXPECTED THROUGH THE TAF PERIOD.
SOUTHWEST WIND GUSTS REMAIN STRONG BETWEEN 25 TO 30 KNOTS.
WINDS WILL SLOWLY DIMINISH AND VEER TO THE WEST AND EVENTUALLY
NORTHWEST THROUGH THE DAY. AS ANOTHER BOUNDARY MOVES IN OFF THE
LAKE LATE IN THE AFTERNOON, A WIND CHANGE TO THE NORTHEAST IS
EXPECTED AT CHICAGO TERMINALS (NOT UNTIL CLOSER TO 03Z AT KRFD).
WINDS WILL BECOME LIGHT AND TURN TO THE EAST BEFORE DAYBREAK
TOMORROW.
DK
LOT WATCHES/WARNINGS/ADVISORIES
IL...NONE.
IN...NONE.
LM...GALE WARNING UNTIL 1 PM CDT THIS AFTERNOON FOR WINTHROP HARBOR
IL TO GARY IN.
SMALL CRAFT ADVISORY UNTIL 4 PM CDT THIS AFTERNOON FOR GARY TO
BURNS HARBOR IN-BURNS HARBOR TO MICHIGAN CITY IN.
VISIT US AT WEATHER.GOV/CHICAGO
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