732
FXUS63 KLOT 071738
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
1238 PM CDT WED MAY 7 2025
KEY MESSAGES
- STRONG WINDS AND MUCH COOLER TEMPS EXPECTED BEHIND A LAKE
ENHANCED COLD FRONT TODAY, THE STRONGEST WINDS AND BIGGEST
TEMPERATURE DROP WILL BE IN CLOSER PROXIMITY TO THE LAKE
MICHIGAN.
- THIS WEEKEND WILL FEATURE MOSTLY SUNNY SKIES, NO RAIN, AND
UNSEASONABLY MILD TEMPERATURES, ALTHOUGH COOLER NEAR THE LAKE.
DISCUSSION
ISSUED AT 343 AM CDT WED MAY 7 2025
THROUGH THURSDAY:
EARLY MORNING SURFACE ANALYSIS DEPICTS A COLD FRONT STRETCHING
ACROSS THE UPPER MIDWEST FROM ROUGHLY NEW ULM MINNESOTA, TO
WAUSAU WISCONSIN AND MACKINAC ISLAND MICHIGAN. FARTHER TO THE
NORTH, STRONG SURFACE HIGH PRESSURE OF 1034 MB WAS BUILDING
SOUTHEAST ACROSS EASTERN MANITOBA AND NORTHERN ONTARIO. THE
COLD FRONT WILL CONTINUE TO PUSH SOUTH INTO THE AREA LATER THIS
MORNING, SURGING DOWN THE COLD AND RELATIVELY FRICTIONLESS
WATERS OF LAKE MICHIGAN MORE QUICKLY THAN OVER INLAND AREAS OF
WI AND NORTHERN IL. THIS WILL RESULT IN THE FRONT PUSHING
SOUTHWEST ACROSS THE CHICAGO AREA AND NORTHWEST INDIANA TOWARD
MIDDAY, AND CONTINUING AT A LITTLE SLOWER PACE ACROSS THE
REMAINDER OF THE FORECAST AREA THROUGH THIS AFTERNOON AND EARLY
EVENING.
AHEAD OF THE FRONT, TEMPERATURES SHOULD ONCE AGAIN RISE INTO
THE MID AND UPPER 70S WEST AND SOUTH OF THE CHICAGO AREA.
WITHIN THE METRO AREA, WHERE THE FRONT ARRIVES EARLIER, WE'LL
LIKELY SEE A GRADIENT FROM LOWER 60S ALONG THE NORTH SHORE TO
THE LOW-MID 70S FARTHER INLAND TOWARD THE WEST AND SOUTH
SUBURBS. THESE HIGH TEMPS WILL LIKELY OCCUR AROUND MIDDAY
HOWEVER, WITH TEMPERATURES THEN DROPPING INTO THE 50S AND 60S
DURING THE AFTERNOON WITH BLUSTERY NORTHEAST WINDS GUSTING AS
HIGH AS 25 TO 30 MPH BEHIND THE FRONT OFF THE LAKE. THE POST-
FRONTAL TEMPERATURE DROP WILL BE LATER IN THE DAY AND LESS
DRAMATIC ACROSS OUR SOUTHERN AND FAR WESTERN CWA COUNTIES.
MODEL GUIDANCE CONTINUES TO INDICATE THE POTENTIAL FOR SOME
CONVECTIVE SHOWERS OR EVEN AN ISOLATED THUNDERSTORM ALONG THE
FRONT THIS AFTERNOON, MAINLY WEST OF ROCHELLE, TOWARD STERLING
AND THE QUAD CITIES AREA, WHERE LOW-50S SURFACE DEW POINTS
LOOK TO POOL AHEAD OF THE FRONT. BEST CHANCES (INCLUDING BETTER
HREF THUNDER PROBABILITIES) LOOK TO BE JUST WEST OF THE CWA,
BUT HAVE MAINTAINED SOME LOW CHANCE (20-25%) SHOWER POPS DURING
THE AFTERNOON IN THESE AREAS. ELSEWHERE, INCREASING HIGH CLOUDS
THIS MORNING WILL MAKE FOR A PARTLY TO MOSTLY CLOUDY DAY.
PARTLY TO MOSTLY CLOUDY SKIES ARE EXPECTED FOR MUCH OF THE AREA
TONIGHT, WITH DECREASING BUT STILL BREEZY NORTHEAST WINDS.
OVERNIGHT LOWS SHOULD DIP INTO THE LOW TO MID 40S FOR THE MOST
PART, THOUGH A FEW UPPER 30S CAN'T BE RULED OUT NEAR THE IL/WI
BORDER WHERE THE BEST CHANCES OF MORE SUBSTANTIAL CLEARING AND
LIGHTER WINDS WOULD BE. BREEZY AND COOLER WEATHER WILL PERSIST
THURSDAY, THOUGH CLOUDS SHOULD GRADUALLY CLEAR OUT FROM THE
NORTH/NORTHEAST TO THE SOUTH AND ALLOW FOR SUNSHINE INTO THE
AFTERNOON. LOW LEVEL THERMAL FIELDS SUPPORT AFTERNOON HIGHS
RANGING FROM THE UPPER 50S ACROSS NORTHEAST ILLINOIS (THOUGH
ONLY IN THE LOWER 50S RIGHT ALONG THE LAKE) TO THE MID TO UPPER
60S ACROSS OUR WESTERN AND SOUTHERN COUNTIES.
RATZER
THURSDAY NIGHT THROUGH TUESDAY:
A LARGE UPPER HIGH WILL ARCH OVER THE CENTRAL PLAINS AND GREAT
LAKES THIS WEEKEND INTO NEXT WEEK BRINGING A STRETCH OF WARMING
TEMPERATURES. COOLER NE WINDS FOLLOWING THIS AFTERNOON'S COLD
FRONT WILL STICK AROUND FOR THURSDAY NIGHT AND FRIDAY. THIS MAY
LEAD TO SOME PATCHY FROST DEVELOPMENT THURSDAY NIGHT,
ESPECIALLY NORTH OF I-88. HOWEVER, SUNNY SKIES AND VERY DRY
CONDITIONS DURING THE DAY ON FRIDAY WILL HELP BRING AFTERNOON
HIGHS INTO THE MIDDLE AND UPPER 60S. THE REAL WARMUP BEGINS THIS
WEEKEND WHEN SURFACE HIGH PRESSURE MOVES TO OUR SOUTH AND MILD
SOUTHERLY LOW LEVEL FLOW WILL WORK OVER THE AREA. SIMILAR TO THE
PAST SEVERAL DAYS, THE NBM CONTINUES TO RESOLVE NOTABLY WARMER
TEMPERATURES THIS WEEKEND THAN MOST AVAILABLE GUIDANCE. IT'S
LIKELY BEING CONTAMINATED BY THE MUCH, MUCH WARMER CMC SUITE.
THE GEPS IS WARMER THAN BOTH THE GEFS AND EPS EACH DAY THIS
WEEK, AND THE SAME GOES FOR THEIR DETERMINISTIC COUNTERPARTS AS
IT RESOLVES MUCH WARMER LOW LEVEL AIR IN THE MIDWEST BENEATH
THE UPPER HIGH THAN OTHER GUIDANCE. AND, LOOKING BACK AT PRIOR
RUNS, THE GEPS HAS BEEN CARRYING A WARM BIAS IN OUR REGION
RECENTLY, EVEN IN THE SHORT TERM. THIS ADDS CONFIDENCE IN THE
NBM BEING TOO WARM THIS WEEKEND. THIS SORT OF
ENVIRONMENT/SYNOPTIC PATTERN IS ONE WHERE MODELS DO SOMETIMES
VERIFY TOO COOL, SO THAT'S MAYBE ONE POINT TOWARD THE WARMER
SOLUTIONS, BUT THERE'S JUST NOTHING OUTSIDE OF THE CMC SUITE
THAT QUITE MATCHES THE NBM AT THE MOMENT. ACCORDINGLY, MADE SOME
ADJUSTMENTS TO COOL THINGS OFF THIS WEEKEND IN THE FORECAST.
OVERALL, THIS WEEKEND IS LOOKING DOWNRIGHT GORGEOUS. HIGHS ON
SATURDAY ARE LOOKING LIKE THE LOWER AND MIDDLE 70S OVER INLAND
AREAS FOLLOWED BY MIDDLE TO UPPER 70S FOR SUNDAY. CONDITIONS
WILL BE KEPT COOLER NEAR THE LAKE THIS WEEKEND, THEN MAINLY ON
THE IL SIDE OF THE LAKE EARLY NEXT WEEK. LAKESIDE TEMPERATURES
OVER THE WEEKEND ARE EXPECTED TO MAX OUT IN THE 60S. ONE FINAL
NOTE ABOUT TEMPERATURES THIS WEEKEND: RECENT ITERATIONS OF THE
DETERMINISTIC EURO AND EPS RESOLVE A BACK DOOR COLD FRONT
PLOWING DOWN THE LAKE SATURDAY EVENING LEADING TO SLIGHTLY
COOLER CONDITIONS ON SUNDAY THAN PREVIOUSLY FORECAST. SO WHEREAS
SUNDAY WAS LOOKING AT LEAST A COUPLE OF DEGREES WARMER THAN
SATURDAY, THE ECMWF SUITE NOW ISN'T SO SURE THAT'LL BE THE CASE.
OTHERWISE, EXPECT LOTS OF SUN, NO RAIN, AND A COMFORTABLE
BREEZE THIS WEEKEND TO ACCOMPANY THE MILD TEMPERATURES.
THE NBM IS CERTAINLY ON THE WARMER SIDE OF AVAILABLE GUIDANCE
FOR EARLY NEXT WEEK AS WELL, ALTHOUGH WITH MUCH LESS CERTAINTY,
DIDN'T BOTHER TO DEVIATE FROM THE NBM BEYOND THE WEEKEND AT THIS
POINT. SCATTERED SHOWER CHANCES WILL RETURN EARLY NEXT WEEK AS
A SUBTROPICAL UPPER LOW PROPAGATES INTO THE REGION FROM THE
SOUTH. IF ENOUGH LOW LEVEL MOISTURE CAN FILL IN, SOME HEAT-
DRIVEN INSTABILITY MAY ENABLE THE DEVELOPMENT OF SOME AFTERNOON
AND EVENING THUNDERSTORMS AT TIMES, ALTHOUGH NO ORGANIZED
CONVECTION IS ANTICIPATED THROUGH THE MIDDLE OF NEXT WEEK.
DOOM
AVIATION /18Z TAFS THROUGH 00Z FRIDAY/
ISSUED AT 1238 PM CDT WED MAY 7 2025
THE MAIN AVIATION WEATHER CONCERNS FOR THE 18Z TAF PERIOD
INCLUDE:
- INCREASINGLY GUSTY NORTHEAST WINDS AFTER 20Z THIS AFTERNOON.
- A CHANCE FOR A PERIOD OF LOWER MVFR CIGS LATE TONIGHT INTO
THURSDAY MORNING.
A LAKE ENHANCED COLD FRONT IS CURRENTLY IN THE PROCESS OF MOVING
ACROSS NORTHERN IL AT THIS TIME. EXPECT NORTHEASTERLY WINDS TO
BECOME INCREASINGLY GUSTY IN THE WAKE OF THIS FRONT AFTER 20Z.
WHILE A BRIEF PERIOD OF GUSTS OF UP TO 30 KT IS POSSIBLE AT THE
CHICAGO TERMINALS THIS AFTERNOON, GUSTS ARE EXPECTED TO SETTLE
INTO THE 20 TO 25 KT RANGE FOR THE REMAINDER OF THE PERIOD.
VFR CONDITIONS ARE EXPECTED THROUGH THIS EVENING. HOWEVER, SOME
LOWER MVFR CIGS (1,200 - 2,000FT) MAY DEVELOP AND MOVE IN OFF
THE LAKE LATE TONIGHT. THESE CIGS WOULD THEN LIKELY PERSIST
THROUGH THE MID-MORNING HOURS OF THURSDAY BEFORE SCATTERING OUT
FOR THE REMAINDER OF THE DAY.
KJB
LOT WATCHES/WARNINGS/ADVISORIES
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY UNTIL 4 AM CDT FRIDAY FOR THE IL AND IN
NEARSHORE WATERS.
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