537
FXUS63 KLOT 072340
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
640 PM CDT WED MAY 7 2025
KEY MESSAGES
- ISOLATED SHOWERS AND PERHAPS A STORM OR TWO MAY DEVELOP DURING
THE LATE AFTERNOON WITHIN A NARROW CORRIDOR EXTENDING FROM LEE
COUNTY, IL TO THE RENSSELAER, IN AREA (ROUGHLY ABOUT 20% CHANCE
AT ANY PARTICULAR LOCATION).
- THIS WEEKEND WILL FEATURE MOSTLY SUNNY SKIES, LIKELY NO RAIN,
AND MILD TO POTENTIALLY UNSEASONABLY MILD TEMPERATURES
(ALTHOUGH IT WILL BE COOLER NEAR LAKE MICHIGAN).
DISCUSSION
ISSUED AT 342 PM CDT WED MAY 7 2025
THROUGH THURSDAY NIGHT:
A LAKE-ENHANCED COLD FRONT CONTINUES TO PUSH INLAND ACROSS
NORTHERN ILLINOIS AND NORTHWEST INDIANA AT THIS HOUR WITH
TEMPERATURES FALLING INTO THE 60S AND 50S AND WINDS TURNING
NORTHEASTERLY AND BECOMING GUSTIER BEHIND IT. GOES VISIBLE
SATELLITE IMAGERY SHOWS THAT SOME CUMULUS HAS STARTED TO BUBBLE
ALONG AND AHEAD OF THIS FRONT, AND AS THIS CUMULUS CONTINUES TO
GROW DEEPER, ISOLATED SHOWERS AND PERHAPS EVEN A STORM OR TWO
MAY EVENTUALLY DEVELOP WITHIN THE NEXT 2-3 HOURS. THIS IS MOST
LIKELY TO OCCUR TO OUR WEST, TOWARDS THE QUAD CITIES AND INTO
EASTERN IOWA, BUT HI-RES MODEL GUIDANCE AND OBSERVATIONAL
TRENDS SUGGEST THAT SOME OF THIS ACTIVITY COULD AFFECT WESTERN
AND/OR SOUTHERN PORTIONS OF OUR FORECAST AREA, WITH WESTERN
PORTIONS OF LEE AND LASALLE COUNTIES LOOKING TO BE BEST
POSITIONED FOR THIS. ANY OF THESE DIURNALLY-INFLUENCED
SHOWERS/STORMS THAT DEVELOP IN OUR CWA SHOULD DWINDLE AWAY BY
SUNSET AS THE FRONT PUSHES THROUGH THE REMAINDER OF OUR FORECAST
AREA. BEYOND THAT TIME, THE BROAD-REACHING INFLUENCE OF A CUT-
OFF UPPER-LEVEL LOW CHURNING OVER THE CENTRAL PLAINS COULD
CAUSE SOME SPITS OF PRECIPITATION TO DEVELOP AND LINGER IN OUR
SOUTHERN CWA TONIGHT INTO TOMORROW MORNING, BUT THE BROADER
SWATH OF PRECIPITATION ASSOCIATED WITH THE UPPER LOW SHOULD
REMAIN TO OUR SOUTH, KEEPING THE ODDS OF MEASURABLE
PRECIPITATION OCCURRING AT ANY ONE LOCATION IN OUR FORECAST
AREA TONIGHT FAIRLY LOW (ROUGHLY 15% OR LESS).
COLD AIR ADVECTION/BREEZY ONSHORE FLOW WILL PERSIST INTO
THURSDAY, LEADING TO COOLER HIGH TEMPERATURES BEING OBSERVED
ACROSS THE AREA. OUR LATEST FORECAST HAS THURSDAY'S HIGHS
REACHING THE UPPER 60S/NEAR 70F ACROSS OUR SOUTHWESTERN CWA BUT
ONLY REMAINING IN THE 50S ALONG THE LAKESHORE AND SEVERAL MILES
INLAND INTO THE CHICAGO METRO. THE CLEARING SKIES AND SLACKENING
WINDS AFTER SUNSET SHOULD PROMOTE DECENT RADIATIONAL COOLING
CONDITIONS THURSDAY NIGHT INTO FRIDAY MORNING, ALLOWING FOR
TEMPERATURES TO FALL INTO THE MID 30S TO LOW 40S ACROSS MUCH OF
THE AREA. THOSE AREAS THAT DO FALL INTO THE MID 30S (CURRENTLY
MOST LIKELY TO OCCUR IN INTERIOR PORTIONS OF NORTHERN ILLINOIS,
ESPECIALLY NEAR THE WISCONSIN STATE LINE) COULD SEE AT LEAST
PATCHY FROST DEVELOP. A FROST ADVISORY MAY NEED TO BE CONSIDERED
FOR SOME OF OUR NORTHERN COUNTIES IF CONFIDENCE IN MORE
WIDESPREAD FROST DEVELOPMENT INCREASES FOR THURSDAY NIGHT/FRIDAY
MORNING.
FRIDAY THROUGH TUESDAY NIGHT:
THE SYNOPTIC WEATHER PATTERN OVER THE CONUS WILL UNDERGO SOME
CHANGES AS WE CLOSE OUT THE WORKWEEK AND GO INTO MOTHER'S DAY
WEEKEND. THE AFOREMENTIONED CENTRAL PLAINS UPPER LOW WILL FIRST
BE ABSORBED INTO A NORTHERN STREAM TROUGH DIGGING INTO THE
NORTHEASTERN CONUS AS THE OMEGA BLOCK THAT HAS BEEN IN PLACE
ACROSS THE COUNTRY THE PAST COUPLE OF DAYS STARTS TO BREAK DOWN.
ANOTHER CLOSED OFF UPPER-LEVEL LOW WILL THEN DEVELOP OVER THE
WESTERN GULF COAST GOING INTO THE WEEKEND WHILE A HIGH-AMPLITUDE
UPPER-LEVEL RIDGE SETS UP ABOVE IT, DISPLACING THE NORTHERN
STREAM JET NORTH OF THE CANADIAN BORDER. AT THE SURFACE, THIS
WILL TRANSLATE TO HIGH PRESSURE HAVING A PRESENCE SOMEWHERE IN
THE MIDWEST FROM LATE WEEK THROUGH THE WEEKEND, WHICH IN TURN
WILL LEAD TO PLENTY OF SUNSHINE BEING OBSERVED ACROSS THE REGION
DURING THIS TIME FRAME.
THE ENSUING SEVERAL CONSECUTIVE DAYS OF AIR MASS WARMING WILL
ALLOW FOR TEMPERATURES HERE TO BOUNCE BACK INTO THE 70S, IF NOT
80S OVER THE WEEKEND INTO EARLY NEXT WEEK. ONE POTENTIAL CAVEAT
IS THAT ANOTHER LAKE-ENHANCED COLD FRONT COULD MAKE AN INLAND
PUSH SOMETIME LATE SATURDAY, TEMPORARILY BRINGING COOLER
TEMPERATURES INTO THE AREA. DEPENDING ON HOW STRONG THE FRONT IS
AND HOW FAR THE FRONT MAKES IT INLAND, IT COULD ALSO CAUSE
SUNDAY'S TEMPERATURES TO END UP BEING A BIT LOWER THAN PRESENTLY
ADVERTISED. ADDITIONALLY, THE NBM STILL APPEARS TO BE RUNNING A
LITTLE WARM ON TEMPERATURES FOR THIS WEEKEND INTO NEXT WEEK DUE
TO THE INFLUENCE OF THE WARM-BIASED CMC-BASED GUIDANCE. FOR
THESE TWO REASONS, HAVE CONTINUED TO NUDGE OUR HIGH TEMPERATURES
OVER THE WEEKEND DOWN A FEW DEGREES FROM THE NBM INITIALIZATION.
REGARDLESS OF HOW EVERYTHING PLAYS OUT, ONSHORE FLOW AND/OR THE
DEVELOPMENT OF LAKE BREEZES WILL TEND TO KEEP HIGH TEMPERATURES
NEAR SOME OR ALL OF THE LAKESHORE SEVERAL DEGREES COOLER THAN
FARTHER INLAND ON BASICALLY EVERY DAY OF THE CURRENT 7-DAY
FORECAST PERIOD.
IF THE AFOREMENTIONED COLD FRONT DOES END UP PUSHING INLAND
SATURDAY AFTERNOON, THEN COULDN'T RULE OUT A SHOWER OR EVEN A
STORM POPPING ALONG IT AS A NORTHERN STREAM SHORTWAVE TROUGH
PASSES TO OUR NORTH AND PROVIDES A GLANCING BLOW OF ASCENT TO
AUGMENT THE CONVERGENCE ALONG THE FRONT. ONLY A MINORITY OF
MEMBERS FROM THE LATEST GEFS AND EPS ENSEMBLE SUITES SUPPORT
SUCH A SCENARIO, SO CONFIDENCE WASN'T HIGH ENOUGH TO JUSTIFY
INTRODUCING MENTIONABLE POPS IN OUR FORECAST GRIDS FOR THIS
POSSIBILITY ON SATURDAY, BUT WE'LL CONTINUE TO MONITOR TRENDS IN
FORECAST GUIDANCE TO SEE IF BOOSTING POPS FOR THIS MAY
ULTIMATELY BE WARRANTED AT SOME POINT. OTHERWISE, THE NEXT
APPRECIABLE CHANCES FOR PRECIPITATION SHOULD COME EARLY TO MID-
WEEK NEXT WEEK AS THE GULF COAST UPPER LOW LIFTS NORTHEASTWARD
TOWARDS THE GREAT LAKES AND MID-ATLANTIC.
OGOREK
AVIATION /00Z TAFS THROUGH 06Z FRIDAY/
ISSUED AT 640 PM CDT WED MAY 7 2025
FORECAST CONCERNS INCLUDE...
GUSTY NORTHEAST WINDS THROUGH THURSDAY AFTERNOON.
MVFR CIGS THURSDAY MORNING.
NORTHEAST WINDS WILL REMAIN GUSTY, INTO THE 20-25KT RANGE
THROUGH THURSDAY AFTERNOON AND THEN DIMINISH WITH SUNSET
THURSDAY EVENING.
MVFR CIGS OFF LAKE MICHIGAN ARE POSSIBLE FOR THE CHICAGO
TERMINALS OVERNIGHT THROUGH MID MORNING THURSDAY WHICH WOULD
LIFT AND THEN SCATTER OUT IN THE LATE MORNING/EARLY AFTERNOON.
CMS
LOT WATCHES/WARNINGS/ADVISORIES
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY UNTIL 4 AM CDT FRIDAY FOR THE IL AND IN
NEARSHORE WATERS.
VISIT US AT WEATHER.GOV/CHICAGO
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