910
FXUS63 KLOT 260612
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
112 AM CDT THU MAR 26 2026
KEY MESSAGES
- ELEVATED GRASS/BRUSH FIRE THREAT CONTINUES THIS AFTERNOON.
- ISOLATED TO SCATTERED THUNDERSTORMS EXPECTED SOUTH OF I-80
TONIGHT, SOME MAY PRODUCE HAIL UP TO AROUND 1" IN DIAMETER.
- POWERFUL COLD FRONT WILL MOVE ACROSS THE AREA THURSDAY WITH
TEMPS IN THE 70S/80S AHEAD IT, FALLING SHARPLY INTO THE
40S/50S BEHIND IT.
- THUNDERSTORMS ARE LIKELY TO DEVELOP NEAR THE FRONT THURSDAY
AFTERNOON, WITH THE HIGHEST CHANCES OF THUNDERSTORMS NEAR AND
SOUTH OF I-80. THERE IS A LEVEL 3 OUT OF 5 SEVERE THREAT IN
THE REGION WITH LARGE, POSSIBLY DESTRUCTIVE HAIL AND DAMAGING
WINDS THE MAIN THREATS.
DISCUSSION
ISSUED AT 215 PM CDT WED MAR 25 2026
TODAY AND TONIGHT...
AN AREA OF SOMEWHAT ENHANCED MID-LEVEL MOISTURE (NEAR 12-15 KFT
AGL) ACROSS IOWA IS STEADILY TRANSLATING EASTWARD AND WILL
ARRIVE IN OUR SOUTHWEST LOCALES THROUGH MID-LATE AFTERNOON.
WATER VAPOR LOOPS AND MODEL ANALYSES CLEARLY REVEAL A LOW
AMPLITUDE WAVE CENTERED NEAR 850- 700 MB WHICH WILL CONTINUE TO
SLIDE SOUTHEAST ACROSS THE FORECAST AREA THROUGH EARLY EVENING.
GIVEN THE PRESENCE OF STEEP MID-LEVEL LAPSE RATES (AT LEAST IN A
NARROW ZONE ALOFT), THERE IS AT LEAST A LOW POTENTIAL FOR HIGH
BASED CONVECTION TO DEVELOP AS THIS ACTIVITY SCOOTS ACROSS THE
AREA. WITH SIGNIFICANT SUB-CLOUD DRY AIR IN PLACE, IF MORE
SUBSTANTIAL SHOWER (AND ISOLATED THUNDERSTORM) ACTIVITY
MATERIALIZES, SOME STRONG WIND GUSTS AROUND 40 MPH CAN'T BE
RULED OUT, MAINLY ACROSS THE SOUTHWEST THIRD OF THE CWA. HAVE
INTRODUCED SOME SLIGHT CHANCES (MAINLY FOR SHOWERS) TO COVER
THIS POTENTIAL THROUGH EARLY EVENING.
MORE ROBUST CONVECTIVE DEVELOPMENT WILL BE POSSIBLE LATER THIS
EVENING AND INTO THE EARLY OVERNIGHT PERIOD AS A PLUME OF
ENHANCED 925-850 MB MOISTURE PUSHES EAST-NORTHEASTWARD OUT OF
CENTRAL ILLINOIS. INTENSIFYING ISENTROPIC ASCENT AT THE NOSE OF
A SOUTHWESTERLY LLJ SHOULD ALLOW AT LEAST WIDELY SCATTERED
ELEVATED CONVECTION TO BLOSSOM. PRECISELY WHERE THIS OCCURS AND
HOW MUCH MUCAPE IS AVAILABLE REMAINS IN QUESTION DUE TO SOME
LINGERING MODEL SPREAD. THE LATEST NAM HAS TRENDED A BIT FARTHER
SOUTH AND LESS ROBUST WITH THE DEGREE OF 850 MB MOISTENING AND
THUS MUCAPE, MORE IN LINE WITH THE REST OF THE GUIDANCE SUITE.
IN TURN, HAVE GENTLY PUSHED THE HIGHEST THUNDERSTORM CHANCES A
BIT FARTHER SOUTH CLOSER TO THE KANKAKEE RIVER VICINITY AND
POINTS SOUTH. GIVEN AT LEAST MODEST SKINNY CAPE PROFILES AND
RESPECTABLE DEEP LAYER SHEAR WITH STRONG VEERING THROUGH THE
COLUMN, SOME INSTANCES OF MARGINALLY SEVERE HAIL CAN'T BE RULED
OUT WITH THE STRONGEST CORES MAINLY ACROSS OUR FAR SOUTH AND
SOUTHWEST LOCALES AFTER ABOUT 9-10 PM, BUT THIS POTENTIAL
APPEARS LIMITED IN BOTH SCOPE AND LOCATION AT THIS TIME.
ANY ELEVATED CONVECTION SHOULD DIMINISH AND PUSH EAST OF THE
REGION LATE TONIGHT. THIS WILL SET THE STAGE FOR A VERY ACTIVE
PERIOD OF WEATHER THURSDAY AFTERNOON AND EVENING.
THURSDAY...
ONE LINGERING QUESTION MARK WHICH WILL ULTIMATELY HAVE A LARGE
BEARING ON THE PRECISE LOCATION, TIMING, AND GENERAL EVOLUTION
OF THE SEVERE WEATHER THREAT IS THE SPEED/LOCATION OF A VERY
SHARP BACKDOOR COLD FRONT. TODAY'S GUIDANCE STILL REMAINS
SOMEWHAT SPLIT ON THIS, AND IN PARTICULAR HOW QUICKLY THE FRONT
INITIALLY ROLLS OFF THE LAKE AND ACROSS NORTHERN ILLINOIS DURING
THE LATE MORNING AND EARLY AFTERNOON. THE LATEST ECMWF REMAINS
A REASONABLE MIDDLE GROUND SOLUTION, BUT A FASTER SOLUTION LIKE
THE 12Z HRRR/WRFARW/GFS REMAINS VERY MUCH IN PLAY. AS SUCH, THE
HIGH TEMPERATURE FORECAST ACROSS NORTHERN ILLINOIS AND LAKE-
ADJACENT PORTIONS OF NW INDIANA REMAINS UNCERTAIN, WITH A VERY
LARGE "BUST" POTENTIAL. IF THE FRONT ENDS UP SLOWER,
TEMPERATURES IN CHICAGOLAND COULD SURGE INTO THE UPPER 70S
BEFORE FALLING RAPIDLY INTO THE 40S.
BY ABOUT 1 PM/EARLY AFTERNOON, THERE IS DECENT AGREEMENT THAT
THE FRONT WILL BE SOMEWHERE IN THE VICINITY OF A ROCHELLE TO
AURORA TO VALPARAISO LINE AND WILL CONTINUE TO MOVE SOUTHWARD AT
A DECENT CLIP. TO THE SOUTH OF THE BOUNDARY, TEMPERATURES WILL
WARM VERY QUICKLY INTO THE 80S (POSSIBLY MID TO UPPER 80S IN
SPOTS). DEEPER MIXING MAY FACILITATE THE DEVELOPMENT OF STRONGER
SOUTHWESTERLY WIND GUSTS AND HAVE BOOSTED THESE A BIT WITH THIS
FORECAST. THE BASE OF A WARM EML WILL EFFECTIVELY CAP THIS WARM
SECTOR TO CONVECTION UNTIL AT LEAST 2-3 PM, IF NOT EVEN A BIT
LATER THAN THIS. TO THE NORTH OF THE FRONT, MARKEDLY COLDER
CONDITIONS WITH GUSTY NORTHEASTERLY WINDS WILL DEVELOP.
INCREASING UPPER JET DIVERGENCE AND THE ARRIVAL OF A 700 MB
SHORTWAVE MAY ALLOW INITIAL ELEVATED CONVECTIVE CLUSTERS TO
DEVELOP ACROSS NORTHERN ILLINOIS THROUGH MID AFTERNOON.
THROUGH MID-LATE AFTERNOON, THE COLD FRONT WILL CONTINUE TO
PRESS SOUTHWARD, LIKELY IN THE VICINITY OF THE KANKAKEE RIVER
VALLEY BY ABOUT 4 PM OR SO. GRADUALLY-INCREASING LARGE SCALE
ASCENT WILL EVENTUALLY ERODE WHAT LINGERING CAPPING EXISTS TO
THE SOUTH OF THE BOUNDARY AND MOISTENING/COOLING ATOP THE
FRONTAL INVERSION, RESULTING IN WHAT SHOULD BE GENERALLY
EXPLOSIVE THUNDERSTORM DEVELOPMENT ACROSS THE REGION AROUND THIS
TIME PERIOD. THE PRIMARY SEVERE HAZARD DURING THIS TIME AND
INTO THURSDAY EVENING WILL BE FROM LARGE, POSSIBLY VERY LARGE
HAIL, PARTICULARLY FOR ELEVATED CELLS ATOP THE SHALLOW FRONTAL
INVERSION. DEEP LAYER SHEAR IS FORECAST TO BE EXTREME, WITH 1-7
KM SHEAR VALUES APPROACHING 60 TO 80 KNOTS. ADDITIONALLY, MODEST
MUCAPE VALUES AND VERY STRONG STORM- RELATIVE INFLOW WINDS (35+
KNOTS) WILL BE SUPPORTIVE OF VERY WIDE/LARGE UPDRAFTS,
FACILITATING LARGE HAIL GROWTH. EVEN THOUGH MOST STORMS WILL
REMAIN ELEVATED, THERE WILL BE A LOCALIZED DAMAGING WIND GUST
THREAT (HIGH RES GUIDANCE DEPICTS SOME DEGREE OF EVENLY- SPACED
CONVECTIVE ELEMENTS AND ASSOCIATED 50+ KNOT GUST OUTPUT,
SUGGESTING THE POTENTIAL FOR GRAVITY WAVE DAMAGING WIND GUSTS).
REGARDING THE TORNADO POTENTIAL: IT REMAINS UNCLEAR HOW MANY
STORMS WILL FIRE IN THE LINGERING FREE WARM SECTOR. THE
HRRR/RAP/RRFS (WHICH COULD BE A BIT OVERMIXED) DO NOT APPEAR TO
CONVECT AGGRESSIVELY SOUTH OF THE FRONT, POSSIBLY DUE TO A
WARM/DRY PBL. HOWEVER, IF STORMS DEVELOP IN THIS AREA AND REMAIN
DISCRETE OR SEMI-DISCRETE, THERE WOULD BE A TORNADO POTENTIAL
BEFORE THE COLD FRONT ROLLS SOUTH OF THE FORECAST AREA. AT THIS
TIME, THE GREATEST TORNADO THREAT (BASED ON THE LATEST COLD
FRONT TIMING) APPEARS TO BE RELEGATED TO AREAS SOUTH OF ABOUT A
STREATOR TO RENSSELAER LINE, AND THIS AREA WOULD BECOME
INCREASINGLY SMALL WITH TIME. EVEN AGGRESSIVELY RIGHTWARD-MOVING
SUPERCELLS WOULD ALSO LIKELY EVENTUALLY GET UNDERCUT BY THE
SURGING COLD FRONT (AUGMENTED BY THUNDERSTORM OUTFLOW TO THE
NORTH).
SOME LOCALIZED TRAINING OF WEST-EAST MOVING STORMS MAY RESULT IN
LOCALLY HEAVY RAINFALL, BUT THIS DOES NOT APPEAR TO BE A SET UP
FAVORING WIDESPREAD FLASH FLOODING.
ACTIVITY WILL EVENTUALLY END AS THE MAIN ELEVATED INSTABILITY
AXIS IS SHOVED WELL SOUTH OF US THROUGH THE LATE EVENING. RIGHT
NOW, IT LOOKS LIKE PRECIP WILL END PRIOR TO THE ARRIVAL OF SUB-
FREEZING TEMPERATURES AND DO NOT HAVE ANY SNOW MENTION IN THE
GRIDDED FORECAST THURSDAY NIGHT.
FRIDAY AND BEYOND...
BROAD CYCLONIC FLOW WILL DEVELOP ACROSS THE UPPER GREAT LAKES ON
FRIDAY AS A SPRAWLING MID 1030S MB HIGH SPREADS ACROSS THE
CENTRAL CONUS. AN EMBEDDED PERTURBATION WILL DRIFT ACROSS
NORTHERN WISCONSIN AND ACROSS NORTHERN LOWER MICHIGAN ON FRIDAY,
AND SOME GUIDANCE HINTS AT THE POTENTIAL FOR SOME RAIN/SNOW
SHOWER DEVELOPMENT DURING THE AFTERNOON ACROSS NORTHERN
ILLINOIS. BOUNDARY LAYER MOISTURE LOOKS PRETTY MINIMAL IN OUR
AREA, SO HAVE LEFT A DRY FORECAST AT THIS TIME. LINGERING
NORTHWESTERLY BREEZES WILL QUIET DOWN FRIDAY NIGHT AND SATURDAY
MORNING AS THE SURFACE HIGH BUILDS EAST OF THE MISSISSIPPI
RIVER. AFTER A COOL START, SATURDAY LOOKS LIKE A DECENT DAY WITH
TEMPERATURES PUSHING BACK TO AROUND 50. WARMER AND BREEZY
CONDITIONS ARE EXPECTED ON SUNDAY AS THE SURFACE PRESSURE
GRADIENT TIGHTENS IN ADVANCE OF THE NEXT SYSTEM.
FORECAST CONFIDENCE DIMINISHES FOR NEXT WEEK, BUT THE LARGE
SCALE PATTERN GENERALLY LOOKS ACTIVE IN THE REGION AS BROAD
LONGWAVE TROUGHING TO OUR WEST WILL LIKELY GUIDE REPEATED
DISTURBANCES ACROSS THE AREA. AT THE SAME TIME, AN EXPANSIVE
ELEVATED MIXED LAYER (EML) WILL CONTINUALLY EXPAND AND ADVECT
EASTWARD ON INCREASING SOUTHWESTERLY MID-LEVEL FLOW. AS A
RESULT, SHOWER AND THUNDERSTORM CHANCES LOOK LIKE THEY'LL
PERSIST INTERMITTENTLY THROUGH MUCH OF NEXT WEEK.
CARLAW
AVIATION /06Z TAFS THROUGH 12Z FRIDAY/
ISSUED AT 112 AM CDT THU MAR 26 2026
KEY AVIATION MESSAGES THROUGH EARLY FRIDAY MORNING:
- SHARP WIND SHIFT FROM SW TO GUSTY NNE LATE MORNING/EARLY AFTERNOON.
- PERIOD OF SCATTERED ELEVATED TS MID-AFTERNOON INTO EARLY EVENING.
- STRONG NNE WINDS OVER 30 KNOTS THIS EVENING.
- IFR CEILINGS LIKELY THIS EVENING.
WINDS: LIGHT S WINDS WILL PERSIST THROUGH SUNRISE. SW WINDS
WILL BEGIN TO INCREASE AFTER SUNRISE IN RESPONSE TO DAYTIME
MIXING, WITH SPORADIC GUSTS TO AROUND 20 KNOTS POSSIBLE LATE IN
THE MORNING (PARTICULARLY AT MDW/GYY). A STRONG COLD FRONT WILL
SURGE SSW ACROSS ALL SITES ROUGHLY AROUND 17-18Z AND PRODUCE A
SHARP NNE WIND SHIFT WITH GUSTS OVER 20 KNOTS. PRECISE TIMING OF
THE FRONTAL PASSAGE WILL NOT BE CLEAR UNTIL WITHIN A FEW HOURS
PRIOR, SO ANY DELAY IN THE FRONT WILL ALLOW THE PRE-FRONTAL SW
WINDS TO INCREASE FURTHER. BEHIND THE FRONT, NNE WINDS WILL
CONTINUE TO INCREASE THROUGH THE AFTERNOON, YIELDING GUSTS OF 30
TO 35 KNOTS THIS EVENING BEFORE SLOWLY ABATING LATE TONIGHT.
CANNOT RULE OUT SOME ROGUE 40 KNOT GUSTS EARLY TO MID-EVENING.
PRECIP/TS: ISOLATED HIGH-BASED SHRA ARE EXPECTED TO DEVELOP
ACROSS NORTHERN ILLINOIS EARLY THIS AFTERNOON. FAST-MOVING
SCATTERED ELEVATED TS WILL THEN FORM NORTH OF THE COLD FRONT IN
RESPONSE TO A LOW TO MID-LEVEL DISTURBANCE MID TO LATE
AFTERNOON. CURRENT FORECAST TIMING FOR ORD/MDW IS GENERALLY IN
THE 21-00Z WINDOW, WITH LINGERING TS POSSIBLY CONTINUING SOUTH
OF THE CHICAGO METRO INTO MID-EVENING (PROB30 TS MAINTAINED AT
MDW/GYY DURING THIS TIME). OTHERWISE, PERIODS OF LIGHT RA/SHRA
WILL CONTINUE THIS EVENING BEFORE ENDING AFTER MIDNIGHT.
CEILINGS: VFR CONDITIONS WILL CONTINUE WITH SCT/BKN UPPER-LEVEL
CLOUDS LEADING UP TO THE FRONTAL PASSAGE. SCT TO POSSIBLY BKN
HIGH-END MVFR STRATUS WILL THEN BEGIN TO THICKEN AND LOWER WITH
TIME LATE MORNING INTO THE AFTERNOON, YIELDING LOW-END MVFR
CEILINGS BY LATE AFTERNOON. IF TS/SHRA COVERAGE IS MORE
PREVALENT OVER LAKE MICHIGAN LATE IN THE AFTERNOON, IFR CEILINGS
OVER THE LAKE WILL LIKELY BEGIN ADVECTING OVER THE TERMINALS
WHILE TS IS ONGOING. EITHER WAY, CEILINGS SHOULD SETTLE INTO IFR
LEVELS THIS EVENING, THEN SLOWLY LIFT AND/OR BREAK OVERNIGHT.
KLUBER
LOT WATCHES/WARNINGS/ADVISORIES
IL...NONE.
IN...NONE.
LM...GALE WARNING FROM 4 PM THIS AFTERNOON TO 7 AM CDT FRIDAY FOR
THE IL AND IN NEARSHORE WATERS.
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