255
FXUS63 KLOT 020851
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
251 AM CST MON MAR 2 2026
KEY MESSAGES
- LOW CHANCE (15%) FOR PATCHY SLICK SPOTS LATE TONIGHT INTO
EARLY TUESDAY MORNING OUTSIDE OF CHICAGO.
- WARMER AND OCCASIONALLY WET WEATHER IS IN STORE FROM THE MID
TO LATE WEEK PERIOD ONWARD. CONFIDENCE IS HIGHER IN MORE
WIDESPREAD RAIN LATE WEDNESDAY NIGHT INTO THURSDAY AND AGAIN
LATE FRIDAY INTO EARLY SATURDAY.
DISCUSSION
ISSUED AT 250 AM CST MON MAR 2 2026
THROUGH TUESDAY NIGHT:
OTHER THAN A FEW LINGERING FLURRIES NEAR AND SOUTH OF US 24,
THE NORTHERN PERIPHERY OF THE DOMINANT BAND OF ACCUMULATING
SNOW, SLEET, AND FREEZING RAIN HAS SHIFTED SOUTH OF THE AREA
EARLY THIS MORNING. PAVEMENT LOOKS MAINLY WET BASED ON WEBCAMS
IN SOUTHERN FORD COUNTY. HOWEVER, WITH TEMPERATURES IN THE UPPER
20S EXPECTED THROUGH DAYBREAK ANY UNTREATED PAVEMENT COULD
BECOME SLICK UNTIL TEMPERATURES WARM ABOVE FREEZING AFTER
DAYBREAK.
LOOKING AHEAD TO THE REST OF THE DAY, THE EXPANSIVE SURFACE
HIGH WILL BEGIN SHIFTING EAST OF THE REGION ALLOWING SURFACE
FLOW TO TREND MORE SOUTHEASTERLY HERE LOCALLY. THIS PAIRED WITH
MUCH OF THE AREA STARING THE DAY UNDER MOSTLY CLEAR SKIES WILL
ALLOW TEMPERATURES TO WARM INTO THE LOW TO MID 40S. ONSHORE
WINDS WILL LIKELY HOLD TEMPERATURES IN THE UPPER 30S ALONG THE
ILLINOIS SHORE AND FARTHER INLAND INTO FAR NORTHEAST ILLINOIS.
DEWPOINTS DROPPED MUCH LOWER THAN EXPECTED YESTERDAY AFTERNOON.
BECAUSE OF THIS, OPTED TO BLEND IN HRRR AND RAP DEWPOINTS TO
LOWER THEM INTO THE TEENS THIS AFTERNOON FOR AREAS NEAR AND
NORTH OF THE ILLINOIS AND KANKAKEE RIVERS. WHILE DEWPOINTS ARE
EXPECTED TO INCREASE SOME THROUGH THE NIGHT, A LOWER STARTING
POINT COULD ALLOW TEMPERATURES TONIGHT TO DROP BELOW FREEZING
IN SOME AREAS OUTSIDE OF CHICAGO.
LOW TO MID-LEVEL WARM ADVECTION AND ISENTROPIC ASCENT IS
EXPECTED LATE TONIGHT INTO EARLY TUESDAY MORNING AHEAD OF AN
APPROACHING SYSTEM. THE RESULTING STEEPENING MID-LEVEL LAPSE
RATES AND SATURATION AND LIFT WITHIN THE DGZ ALOFT COULD SUPPORT
THE DEVELOPMENT OF ISOLATED SHOWERS INTO PARTS OF THE AREA. THE
NAM REMAINS THE MOST BULLISH WITH THIS POTENTIAL, WITH LOWER
COVERAGE (AND EVEN DRY CONDITIONS) DEPICTED AMONGST THE
AVAILABLE HI-RES GUIDANCE. IF TEMPERATURES DO MANAGE TO FALL
BELOW FREEZING, PATCHY SLICK SPOTS COULD DEVELOP WHERE ANY RAIN
MANAGES TO PUNCH THROUGH THE LOWER-LEVEL DRY LAYER. CONFIDENCE
IN THIS OCCURRING REMAINS LOW, HOWEVER, AND HAVE CAPPED FREEZING
RAIN CHANCES AT 15% FOR NOW. THE INCREASED CLOUD COVERAGE COULD
ALSO ALLOW TEMPERATURES TO REMAIN ABOVE FREEZING THROUGH THE
NIGHT, PREVENTING ANY IMPACTS.
MODEL GUIDANCE CONTINUES TO VARY A FAIR AMOUNT IN THE POTENTIAL
COVERAGE OF SHOWERS THROUGH THE REMAINDER OF THE DAY ON
TUESDAY, ESPECIALLY ACROSS NORTHERN ILLINOIS. HAVE MADE SOME
DOWNWARD ADJUSTMENTS IN PRECIPITATION CHANCES FOR AREAS NORTH OF
I-80 THROUGH SUNSET (CAPPED AROUND 30%), WITH THE EXPECTATION
THAT COVERAGE WOULD REMAIN ISOLATED TO WIDELY SCATTERED IF IT
DOES RAIN FARTHER NORTH. SHOWER COVERAGE MAY INCREASE SOME TUESDAY
NIGHT, PARTICULARLY WELL SOUTH OF I-80, WHEN A FEW EMBEDDED
THUNDERSTORMS AND LOCALLY HEAVY RAINFALL (1"+ PWATS) ARE ALSO
POSSIBLE.
PETR
WEDNESDAY THROUGH SUNDAY (AND BEYOND):
ON WEDNESDAY, NCEP PRODUCED DETERMINISTIC AND ENSEMBLE FORECASTS
REMAIN MUCH FASTER/FARTHER NORTH WITH THE NEXT SHORTWAVE AND
ASSOCIATED RAIN CHANCES. WITH THIS BEING SAID, OVER THE PAST FEW
CYCLES, FINALLY DID SEE MOVEMENT IN THE GFS/GEFS SUITE TOWARDS
A GENERAL SOUTHWARD SHIFT IN PROBABILITIES FOR MEANINGFUL
RAINFALL. MEANWHILE, THE ECMWF (EPS) AND UKMET (MOGREPS-G)
ENSEMBLE SYSTEMS HAVE BEEN STEADFAST IN DEPICTING PRIMARILY DRY
CONDITIONS FOR MUCH OF IF NOT THE ENTIRE AREA THROUGH WEDNESDAY
EVENING, INFLUENCED BY SURFACE HIGH PRESSURE OVER THE GREAT
LAKES. THE CANADIAN ENSEMBLE HAS ALSO EXHIBITED A RUN OVER RUN
SOUTHWARD SHIFT IN RECENT CYCLES.
ALL IN ALL, CONSIDERING THE CONSISTENCY OF THE EC AND UK SUITES,
SUSPECT THAT THE MORE AGGRESSIVE NCEP (AND TO A LESSER EXTENT
CANADIAN) DEPICTIONS WILL END UP HAVING BEEN OUTLIERS FROM THIS
LEAD TIME. IT APPEARS THAT IF RAIN DOES OCCUR, A BETTER CHANCE OF
THIS WILL BE FOR LOCALES SOUTH OF I-80, AND THUS CONTINUE TO
MESSAGE THE HIGHEST RAINFALL PROBABILITIES FOR THESE AREAS. IF OUR
HUNCH IS ON THE RIGHT TRACK THOUGH, THE CURRENT NDFD POPS WILL
COME DOWN CONSIDERABLY AREAWIDE IN SUBSEQUENT UPDATES. ASIDE FROM
THE RAINFALL UNCERTAINTIES, CONFIDENCE IS HIGH IN ONSHORE FLOW
KEEPING TEMPS NEAR THE LAKE AND INTO NORTHEAST IL RELATIVELY COOL,
WITH SEASONABLY MILD 50S FARTHER INLAND.
CONFIDENCE IS HIGHER IN SHOWERS BECOMING MORE WIDESPREAD LATE
WEDNESDAY NIGHT INTO THURSDAY, FAVORING LIKELY TO LOWER END
CATEGORICAL POPS (60-80%). THIS IS IN LINE WITH THE FAVORED EC/UK
TIMING OF THE SHORTWAVE EJECTION AND ITS ASSOCIATED WEAK SURFACE
LOW PRESSURE TRACKING ACROSS THE AREA. THE DETERMINISTIC 00Z GFS
AND CANADIAN RUNS ALSO HAPPENED TO BE A REASONABLE APPROXIMATION
OF THIS IDEA. ANOMALOUSLY HIGH PWATS (250-300% OF NORMAL) POINT
TOWARDS THE POTENTIAL FOR HEAVY RAINFALL RATES AT TIMES AND
CORRIDORS OF NOTABLE RAINFALL (WHICH WOULD BE WELCOME COMING OFF
THE EXCEPTIONALLY DRY FEBRUARY AND WORSENING DROUGHT). EMBEDDED
CONVECTION AND OTHER MESOSCALE UNCERTAINTIES MAY STILL YIELD
RELATIVE MINIMA IN OBSERVED RAINFALL DESPITE THE HIGH POPS
FORECAST, THOUGH. THE EXACT SURFACE LOW TRACK ON THURSDAY WILL
DETERMINE TEMPERATURE SPECIFICS, WITH AT LEAST THE IL SHORE STILL
LOOKING TO BE QUITE A BIT COOLER THAN AREAS FARTHER SOUTH/SOUTHWEST.
SURFACE HIGH PRESSURE WILL LIKELY TRANSIT THE AREA THURSDAY NIGHT,
PROBABLY KEEPING RAIN CHANCES FAIRLY MINIMAL. THIS MAY ALSO
POTENTIALLY DELAY A NORTHWARD SURGE OF ANOMALOUS DEW POINTS WITH
A STRONG WARM FRONT UNTIL LATER IN THE DAY ON FRIDAY. TEMPERATURES
SOARING INTO THE 60S TO LOWER 70S AND DEW POINTS IN THE 50S TO
LOWER 60S, TOPPED BY STEEP MID-LEVEL LAPSE RATES AND SEASONABLY
STRONG WIND FIELDS, MAY YIELD SUFFICIENT INSTABILITY AND SHEAR
FOR ORGANIZED STRONG TO SEVERE CONVECTION IN THE AREA FRIDAY
AFTERNOON AND EVENING. HOWEVER, LARGE SCALE FORCING HAS BEEN
TRENDING A BIT MORE NEBULOUS LOCALLY, OWING TO THE MAIN TROUGH
IN THE SOUTHWEST POSSIBLY FAILING TO FULLY EJECT. MID-LEVEL
HEIGHT RISES MAY SERVE AS A LIMITING FACTOR FOR CONVECTIVE
INTENSITY (AND PERHAPS COVERAGE), THOUGH STILL THINK THERE'S
ENOUGH SUPPORT FOR THE HIGH GRIDDED POPS.
A SLOW MOVING COLD FRONT WILL MOVE ACROSS THE AREA SOMETIME ON
SATURDAY, BRINGING AN END TO RAIN CHANCES FOR A FEW DAYS.
TEMPERATURES WILL GENERALLY REMAIN WELL ABOVE AVERAGE THROUGH
EARLY NEXT WORKWEEK. CURRENT MEDIUM TO LONG-RANGE ENSEMBLES
POINT TOWARDS A STRONGER COLD FRONT PASSAGE BRINGING A RETURN TO
COLDER CONDITIONS BY LATER NEXT WEEK/MID-MARCH.
CASTRO
AVIATION /06Z TAFS THROUGH 12Z TUESDAY/
ISSUED AT 1051 PM CST SUN MAR 1 2026
VFR CONDITIONS ARE EXPECTED THROUGH THE TAF PERIOD. EAST-
NORTHEAST WINDS AROUND 5-10 KTS WILL PREVAIL TONIGHT BEFORE
TURNING SOUTHEASTERLY THROUGH MONDAY MORNING. SPEEDS WILL THEN
LIKELY INCREASE INTO THE 10-15 KT RANGE BEFORE EASING AGAIN
MONDAY EVENING.
A DISTURBANCE WILL MOVE ACROSS THE AREA LATE MONDAY NIGHT INTO
TUESDAY MORNING. AT THIS TIME, PRECIPITATION CHANCES THROUGH THE
END OF THE ORD/MDW EXTENDED TAFS IS UNDER ABOUT 25 PERCENT.
HOWEVER, INSTABILITY IS FORECAST TO DEVELOP ALOFT, AND IT'S
POSSIBLE THAT SOME ISOLATED CONVECTIVE ACTIVITY DEVELOPS. IF
THIS OCCURS, SOME NARROW WEST-EAST BANDS OF PRECIPITATION COULD
BECOME HEAVY ENOUGH TO BREAK THROUGH DRY AIR BELOW 10 KFT.
WETBULB TEMPERATURES WOULD BE BELOW FREEZING DURING THIS TIME,
LEADING TO A POTENTIAL FOR SOME VERY SPOTTY FZRA, BUT CHANCES
FOR THIS AGAIN REMAIN QUITE REMOTE AT THIS POINT.
CARLAW
LOT WATCHES/WARNINGS/ADVISORIES
IL...NONE.
IN...NONE.
LM...NONE.
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