607
FXUS63 KLOT 231858
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
158 PM CDT MON MAR 23 2026
KEY MESSAGES
- DRY CONDITIONS WITH A WARMING TREND THROUGH THURSDAY.
- STRONG COLD FRONT WILL BRING ANOTHER ABRUPT END TO
UNSEASONABLE WARMTH LATE THURSDAY/THURSDAY EVENING.
- THUNDERSTORMS ARE POSSIBLE THURSDAY AFTERNOON AND EVENING.
SOME SEVERE THREAT EXISTS, BUT SIGNIFICANT UNCERTAINTY IN
LOCATION EXISTS.
DISCUSSION
ISSUED AT 158 PM CDT MON MAR 23 2026
HIGH PRESSURE IS IN THE PROCESS OF SHIFTING DIRECTLY OVERHEAD
THIS AFTERNOON. EARLIER GUSTY NORTHERLY WINDS WILL CONTINUE TO
EASE, AND A LAKE BREEZE WILL EVENTUALLY SCOOT WESTWARD ACROSS
THE ENTIRE FORECAST AREA THIS AFTERNOON AND EVENING. A WEAK
UPPER-LEVEL IMPULSE CURRENTLY PUSHING ACROSS NEBRASKA WILL
MEANDER INTO THE REGION LATE TONIGHT AND INTO EARLY TUESDAY
MORNING. AS THIS OCCURS, FORECAST SOUNDINGS DEPICT MOISTENING
OCCURRING WITHIN A LAYER OF STEEPENED LAPSE RATES, ROUGHLY
BETWEEN 600 AND 800 MB, AND THIS MATCHES THE CURRENT LOOK ON
SATELLITE TO OUR WEST WITH A MORE CUMULIFORM LOOK TO THE MID-
LEVEL CLOUD LAYER. GIVEN THE PRESENCE OF A FAIRLY STOUT
TEMPERATURE INVERSION IMMEDIATELY ATOP THIS AREA OF CONDITIONAL
INSTABILITY AND PLENTIFUL DRY AIR BELOW 6 KFT, HAVE LEFT THE
FORECAST PRECIPITATION-FREE BUT DID ADD SOME "SILENT" 10 PERCENT
POPS THROUGH THE MORNING.
HIGH PRESSURE WILL CONTINUE TO SHIFT OFF TO OUR EAST ON TUESDAY,
FACILITATING THE RETURN OF SOUTHERLY BREEZES TO THE REGION
THROUGH THE AFTERNOON. DEWPOINT/RH TRENDS REMAIN A BIT TRICKY,
AS LINGERING CLOUD COVER MAY TEMPER DIURNAL MIXING A BIT.
HOWEVER, GIVEN THE PRESENCE OF A VERY DRY AIRMASS OVERHEAD WITH
850 MB DEWPOINTS AROUND -20 C, HAVE ADJUSTED AFTERNOON DEWPOINTS
DOWN A BIT BUT NOT QUITE TO THE MOST AGGRESSIVE GUIDANCE. AT
THIS TIME, SUSTAINED WINDS/GUSTS DO NOT LOOK TO BE STRONG ENOUGH
TO DRIVE AN "ELEVATED" FIRE DANGER.
ANOTHER DISTURBANCE WILL TRAVERSE THE AREA TUESDAY NIGHT AND
WEDNESDAY MORNING, AT THIS TIME SANS FANFARE. WEDNESDAY WILL
LIKELY FEATURE GUSTIER SOUTHWESTERLY WINDS AS THE SURFACE
PRESSURE GRADIENT TIGHTENS AND BOUNDARY LAYER FLOW INCREASES.
DEPENDING ON THE DEGREE OF CLOUD COVER (WHICH REMAINS A BIT IN
QUESTION AT THIS POINT), TEMPERATURES WILL LIKELY PUSH INTO THE
UPPER 60S/NEAR 70 ACROSS A LARGE CHUNK OF THE FORECAST AREA, AND
POSSIBLY INTO THE MID 70S CLOSER TO CENTRAL ILLINOIS. RH VALUES
LOOK A BIT HIGHER COMPARED TO TUESDAY, BUT MAY GET CLOSE TO A
SOMEWHAT MORE ELEVATED FIRE DANGER DUE TO THE INCREASED WINDS
DURING THE AFTERNOON.
THE MAIN FOCUS OF THIS FORECAST REMAINS ON THE THURSDAY
AFTERNOON AND EVENING TIME FRAME AS A STRONG COLD FRONT WILL
BRING THE NEXT CHANCES FOR THUNDERSTORMS TO THE REGION (WITH AT
LEAST SOME SEVERE WEATHER POTENTIAL). SOME RATHER SIGNIFICANT
SPREAD REGARDING THE TIMING OF THE COLD FRONT IS EVIDENT IN
TODAY'S GUIDANCE, WITH THE ECMWF AND GFS GENERALLY IN GOOD
AGREEMENT, BUT NOTABLY FASTER SOLUTIONS ARE ADVERTISED BY THE
LATEST NAM AND CMC/RGEM. THIS WILL HAVE A SIGNIFICANT BEARING ON
THE SCOPE AND EXTENT OF ANY SEVERE THREAT.
IN ADVANCE OF THIS FRONT, UPPER 50S/LOWER 60S DEWPOINTS ARE
FORECAST TO SURGE NORTHWARD THROUGH THE DAY ON THURSDAY. AT THE
SAME TIME, AN EXPANSIVE ELEVATED MIXED LAYER (EML) WITH NOTABLY
STEEPER MID-LEVEL LAPSE RATES WILL SLIDE OVERHEAD. THIS
COMBINATION WILL DRIVE A STEADY INCREASE IN CONDITIONAL
INSTABILITY THROUGH THE DAY, ALTHOUGH GIVEN THE NATURE OF THE
INCOMING EML WITH A FAIRLY WARM BASE, THINGS LOOK DECIDEDLY
CAPPED TO SURFACE BASED CONVECTION THROUGH EARLY AFTERNOON.
EVENTUALLY, THE AFOREMENTIONED COLD FRONT WILL SPILL INTO OUR
REGION FROM THE WEST, AND WILL LIKELY ALSO ACCELERATE DUE SOUTH
OFF THE LAKE. EXACTLY WHERE THIS BOUNDARY SETS UP DURING PEAK
HEATING REMAINS IN QUESTION, BUT GIVEN THE NATURE OF THE PARENT
SURFACE HIGH IN ITS WAKE (NEAR 1040 MB) AND LACK OF A STRONGER
SURFACE LOW NEARBY, THE POTENTIAL CERTAINLY EXISTS FOR A FASTER
FROPA GIVEN THE SHALLOW NATURE OF THIS FRONT AND UNDOUBTEDLY
ENHANCEMENT DUE TO THE COLD LAKE. A BIG TEMPERATURE BUST
POTENTIAL EXISTS, PARTICULARLY NEAR THE LAKE AND NORTH OF I-80
DEPENDING ON THE EXACT FRONT TIMING.
WITHIN ANY REMAINING WARM SECTOR IN OUR AREA WHICH AT THIS TIME
IS MOST LIKELY SOUTH (POSSIBLY WELL SOUTH) OF I-80, MEDIUM
RANGE GUIDANCE HAS GENERALLY BEEN CONSISTENT SHOWING CONVECTIVE
INITIATION THROUGH THE MID-LATE AFTERNOON, BUT IS OBVIOUSLY
CONTINGENT ON LINGERING CAPPING ERODING. IF STORMS CAN FIRE,
THEY WOULD CERTAINLY POSE A SEVERE WEATHER THREAT GIVEN A
STRONGLY-SHEARED ENVIRONMENT. STEEP LOW AND MID-LEVEL LAPSE
RATES, AND 55-65 KTS OF EFFECTIVE DEEP LAYER SHEAR WOULD SUPPORT
UPDRAFT ROTATION, AND A THREAT FOR LARGE HAIL AND DAMAGING
WINDS. HOWEVER, GIVEN THE FORECASTED FORWARD SPEED OF THE COLD
FRONT, STORMS MAY ONLY HAVE A BRIEF PERIOD IN THE FREE WARM
SECTOR, WITH LARGELY EASTERLY STORM MOTIONS EVENTUALLY LIKELY
TO TAKE STORMS OVER AND ATOP THE SURGING FRONTAL ZONE.
OBVIOUSLY, LOTS OF UNCERTAINTIES EXIST AT THIS RANGE. A SLOWER
FROPA WOULD OPEN THE DOOR TO MORE OF AN EXPANSIVE SEVERE WEATHER
THREAT ACROSS THE AREA, WITH A FASTER FRONT (LIKE THE NAM/CMC)
WOULD RELEGATE THE THREAT TO MAINLY OUR FAR SOUTHERN LOCALES,
WITH A HIGH LIKELIHOOD OF CELLS QUICKLY GETTING UNDERCUT.
A MUCH COLDER AIRMASS WILL SPILL INTO THE REGION ON FRIDAY ON
VERY BLUSTERY NORTHERLY WINDS. CAN'T TOTALLY RULE OUT PRECIP
ENDING AS A BRIEF PERIOD OF SNOW THURSDAY NIGHT, BUT GUIDANCE
LARGELY DEPICTS THINGS DRYING OUT PRIOR TO THE ARRIVAL OF SUB-
FREEZING TEMPERATURES.
CARLAW
AVIATION /18Z TAFS THROUGH 00Z WEDNESDAY/
ISSUED AT 1248 PM CDT MON MAR 23 2026
THERE ARE NO SIGNIFICANT AVIATION FORECAST CONCERNS FOR THE
CURRENT TAF PERIOD.
WINDS WILL CONTINUE TO GRADUALLY DIMINISH THROUGH THE REMAINDER
OF THE DAY, EVENTUALLY SHIFTING EASTERLY AS AN INCREASINGLY
DEFINED LAKE BREEZE WORKS ITS WAY INLAND. WINDS SHOULD SETTLE
UNDER 10 KTS AND REMAIN PRIMARILY EAST-OF-SOUTH TONIGHT, BUT
WILL PICK UP A BIT AGAIN WHILE BECOMING MORE SOUTH-SOUTHWESTERLY
TOWARDS DAYBREAK, THEN MORE OR LESS REMAIN THAT WAY THROUGH
MOST OF THE DAYTIME TOMORROW.
VFR CONDITIONS WILL PREVAIL THROUGH THE TAF PERIOD WITH A
LOWER-END CHANCE (~10-15%) THAT ONE OR MORE OF OUR TAF SITES
OBSERVES A FEW FLURRIES OR SPRINKLES TOMORROW MORNING.
OGOREK
LOT WATCHES/WARNINGS/ADVISORIES
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY UNTIL 3 PM CDT THIS AFTERNOON FOR THE IL
NEARSHORE WATERS.
SMALL CRAFT ADVISORY UNTIL 9 PM CDT THIS EVENING FOR THE IN
NEARSHORE WATERS.
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