210
FXUS63 KLOT 082324
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
624 PM CDT THU MAY 8 2025
KEY MESSAGES
- TONIGHT WILL BE UNSEASONABLY CHILLY WITH AREAS OF FROST,
ESPECIALLY IN OUTLYING AREAS AWAY FROM CHICAGO AND NORTH OF
I-80.
- A GRADUAL WARMING TREND WILL COMMENCE TOMORROW WITH
UNSEASONABLY WARM TEMPERATURES LASTING THROUGH AT LEAST NEXT
WEEK.
- CHANCES FOR RAIN LOOK SLIM TO NONE UNTIL THE MIDDLE OF NEXT
WEEK.
DISCUSSION
ISSUED AT 156 PM CDT THU MAY 8 2025
THROUGH NEXT WEEK:
THE GREAT LAKES CONTINUES TO BE UNDER THE INFLUENCE OF A
SPRAWLING SURFACE HIGH PRESSURE SYSTEM CENTERED ALONG THE
ONTARIO/QUEBEC BORDERS, LEADING TO UNSEASONABLY COOL CONDITIONS
AND BREEZY NORTH TO NORTHEASTERLY WINDS.
TONIGHT, THE HIGH PRESSURE SYSTEM WILL ELONGATE INTO A SURFACE
PRESSURE RIDGE WHILE GETTING PUSHED SOUTHWARD TOWARD THE GREAT
LAKES. WHILE SURFACE WINDS WILL ONLY GRADUALLY RELAX (AS OUR
AREA WILL REMAIN WITHIN A GRADIENT IN PRESSURE ALONG THE
SOUTHERN PERIPHERY OF THE SURFACE RIDGE) AND A FEW HIGH CLOUDS
MAY SPILL OVER THE REGION AFTER SUNSET, THE STAGE WILL OTHERWISE
BE SET FOR AN UNSEASONABLY CHILLY NIGHT. OVERNIGHT LOWS SHOULD
RANGE FROM THE LOWER 30S NEAR THE WISCONSIN STATE LINE AND
KANKAKEE RIVER VALLEY TO THE UPPER 30S TO AROUND 40 IN THE
CHICAGO METROPOLITAN AREA AND NEAR/SOUTH OF US-24. DID OPT TO
HOIST A FROST ADVISORY MAINLY ALONG/NORTH OF I-88 AND OUTSIDE OF
THE CHICAGO METROPOLITAN AREA WHERE THE COLDEST TEMPERATURES
ARE EXPECTED OVERNIGHT.
TOMORROW, THE SURFACE RIDGE WILL MOVE DIRECTLY OVERHEAD LEADING
TO A QUIET DAY. WITH THE MORNING AND EARLY AFTERNOON HOURS
STILL FAVORED TO FEATURE A NORTHEASTERLY BREEZE, TEMPERATURES
WILL VARY FROM THE UPPER 50S TO LOWER 60S ALONG SHORELINE-
BORDERING COUNTIES TO THE MID TO UPPER 60S WELL INLAND.
ON SATURDAY, THE SURFACE RIDGE WILL SLIDE SOUTH OF OUR AREA AS
AN UPPER-LEVEL RIDGE BEGINS TO BUILD INTO THE UPPER MISSISSIPPI
RIVER VALLY. THE SLACKENING SURFACE PRESSURE GRADIENT LOCALLY
(SOUTH OF A BUILDING SURFACE HIGH PRESSURE SYSTEM TO OUR NORTH)
WILL SET THE STAGE FOR A BACKDOOR COLD FRONT TO RACE DOWN LAKE
MICHIGAN AT SOME POINT DURING THE DAY. AS A RESULT, HIGH
TEMPERATURES IN THE UPPER 70S WILL FALL AT SOME POINT DURING THE
AFTERNOON BEHIND THE FRONT. A FEW SPRINKLES CANNOT BE RULED OUT
ALONG AND AHEAD OF THE FRONT WHERE LOW-LEVEL MOISTURE POOLS.
SUNDAY (MOTHER'S DAY), THE AFOREMENTIONED UPPER-LEVEL RIDGE
WILL STRENGTHEN ACROSS THE GREAT LAKES NORTH OF A CUT-OFF LOW
PRESSURE SYSTEM STALLED NEAR THE GULF COAST. THE NET RESULT WILL
BE A BRIEF "REX" BLOCK, WHICH TYPICALLY LEADS TO A DEARTH OF
IMPACTFUL WEATHER. INDEED, SUNDAY IS SHAPING UP TO BE GORGEOUS
WITH HIGHS IN THE LOWER 80S, LITTLE TO NO WIND, AND SUNNY
SKIES. IN FACT, FORECAST SOUNDINGS ACROSS OUR AREA DEPICT NO
MORE THAN 20KT OF FLOW FROM THE SURFACE TO NEARLY 40KFT ON
SUNDAY, AN UNUSUAL FEAT SHOULD IT VERIFY. OF COURSE, A LAKE
BREEZE SHOULD SURGE INLAND DURING THE AFTERNOON, LEADING TO
COOLER TEMPERATURES SHORE-SIDE. MONDAY LOOKS SIMILARLY BEAUTIFUL
IN SPITE OF A AN INCREASE IN UPPER- LEVEL CLOUDS DURING THE
AFTERNOON.
TUESDAY INTO WEDNESDAY, DEVELOPING UPPER-LEVEL TROUGHING IN THE
NORTHWESTERN UNITED STATES WILL ENCOURAGE THE CUT-OFF LOW
PRESSURE SYSTEM ALONG THE GULF COAST TO LIFT EAST-NORTHEASTWARD
TOWARD THE GREAT LAKES. INCREASING LOW-LEVEL MOISTURE AND
CONTINUED WARM TEMPERATURES WILL HENCE ENCOURAGE DAILY DIURNAL
INSTABILITY, TOGETHER SUPPORTING A RETURN OF CHANCES FOR SHOWERS
AND THUNDERSTORMS. TUESDAY IS CURRENTLY "FAVORED" TO HAVE THE
HIGHEST COVERAGE OF SHOWERS AND STORMS (POPS IN THE 20 TO 40
PERCENT RANGE), THOUGH "REX" BLOCKS DO HAVE A WAY OF BREAKING
DOWN SLOWER THAN ADVERTISED IN MODEL GUIDANCE.
ENSEMBLE MODEL GUIDANCE ADVERTISES A CONTINUATION OF MUCH
ABOVE-AVERAGE TEMPERATURES IN THE 80S AS WELL AS ELEVATED
HUMIDITY LEVELS THROUGH THE REST OF NEXT WEEK. WITH THE PACIFIC
TROUGH EVENTUALLY EJECTING EASTWARD THROUGH THE CENTRAL US, DO
HAVE TO THINK THERE MAY BE A WINDOW OR TWO FOR STRONG TO SEVERE
STORMS IN THE BROAD MIDWEST REGION AT SOME POINT LATE NEXT WEEK.
BORCHARDT
AVIATION /00Z TAFS THROUGH 06Z FRIDAY/
ISSUED AT 624 PM CDT THU MAY 8 2025
ONLY FORECAST CONCERN REMAINS GUSTY NORTHEAST WINDS INTO THIS
EVENING WITH GUSTS INTO THE LOWER/MID 20KT RANGE THROUGH SUNSET.
GUSTS ARE EXPECTED TO QUICKLY DIMINISH AFTER SUNSET, BUT MAY
TAKE A BIT LONGER TO DIMINISH FOR THE CHICAGO TERMINALS.
NORTHEAST WINDS MAINLY UNDER 10KTS ARE THEN EXPECTED TO CONTINUE
THROUGH FRIDAY AFTERNOON, WITH WINDS BECOMING LIGHT SOUTHEAST
FRIDAY EVENING. CMS
LOT WATCHES/WARNINGS/ADVISORIES
IL...FROST ADVISORY FROM 1 AM TO 8 AM CDT FRIDAY FOR ILZ003-ILZ004-
ILZ005-ILZ006-ILZ008-ILZ011-ILZ012.
IN...NONE.
LM...SMALL CRAFT ADVISORY UNTIL 4 AM CDT FRIDAY FOR THE IL AND IN
NEARSHORE WATERS.
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