599
FXUS63 KLOT 010822
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
222 AM CST SUN MAR 1 2026
KEY MESSAGES
- PERIODS OF WET WEATHER ARE PROBABLE DURING THE TUESDAY THROUGH
SATURDAY PERIOD, WHICH MAY INCLUDE A THREAT FOR THUNDERSTORMS
AT TIMES. EXPECT ABOVE AVERAGE TEMPERATURES DURING THIS TIME,
WITH THE BEST CHANCE FOR UNSEASONABLE WARMTH AREAWIDE ON FRIDAY.
DISCUSSION
ISSUED AT 221 AM CST SUN MAR 1 2026
THROUGH MONDAY NIGHT:
AN EXPANSIVE 1036 MB SURFACE HIGH IS DESCENDING ACROSS THE
UPPER MIDWEST EARLY THIS MORNING WHICH WILL ALLOW FOR CONTINUED
NORTHEAST FLOW ACROSS THE LOCAL AREA TODAY. WHILE WINDS HAVE
EASED SOME, CONTINUED ONSHORE FLOW FROM LAKE MICHIGAN WILL
LIKELY HOLD TEMPERATURES IN THE 30S ACROSS THE AREA TODAY WITH
SUB- FREEZING HIGHS POSSIBLE NEAR THE IMMEDIATE LAKESHORE. THE
LAKE EFFECT SNOW POTENTIAL FOR TODAY HAS DIMINISHED OWING TO THE
LOW CLOUD LAYER BEING EVEN THINNER THAN EXPECTED. STILL CAN'T
RULE OUT A FEW FLURRIES AT TIMES TODAY BENEATH ANY THICKER
STRATUS, HOWEVER, NO ACCUMULATION IS EXPECTED.
WARM ADVECTIVE SHOWERS ARE EXPECTED TO QUICKLY EXPAND IN
COVERAGE ACROSS KANSAS THIS AFTERNOON COINCIDENT WITH THE LEFT
EXIT REGION OF THE SOUTHERN STREAM SPLIT UPPER JET. THIS FEATURE
WILL CONTINUE TO TRACK EAST ACROSS MISSOURI INTO CENTRAL
ILLINOIS AND INDIANA THIS EVENING AND OVERNIGHT. WHILE THE
OVERALL TREND HAS BEEN TOWARD THE MAJORITY OF THE AREA REMAINING
DRY THROUGH TONIGHT (OWING TO A DRY LOW-LEVEL AIRMASS IN
PLACE), IT REMAINS POSSIBLE THAT THE NORTHERN PERIPHERY OF THIS
PRECIPITATION GRAZES THE FAR SOUTHERN PORTION OF THE FORECAST
AREA (MAINLY SOUTH OF US 24). THIS WOULD LIKELY BE TIED TO A
SUBTLE EPHEMERAL 850 MB FGEN AXIS POTENTIALLY ENDING UP A BIT
FARTHER NORTH THAT COULD OVERCOME THE DRY LAYER FOR A BRIEF
WINDOW. HAVE ACCORDINGLY HELD ONTO LOW SNOW CHANCES (20% IN
THOSE AREAS) BETWEEN 9 PM AND 6 AM CST TO ACCOUNT FOR THIS.
WHILE LIKELY REMAINING SOUTH OF THE AREA IT DOES LOOK LIKE A
VERY NARROW AXIS OF HEAVIER PRECIPITATION RATES COULD OCCUR ON
THE NORTH SIDE OF THIS SYSTEM, POTENTIALLY FALLING AS A MIX OF
SNOW AND SLEET.
THE CENTER OF THE SURFACE HIGH WILL SHIFT EAST OF THE AREA ON
MONDAY ALLOWING THE SURFACE FLOW TO TURN MORE SOUTHEASTERLY.
THIS WILL BRING A RETURN OF WARMER THAN AVERAGE TEMPERATURES TO
THE AREA WITH HIGHS IN THE LOW TO MID 40S (COOLER UPPER 30S
ALONG THE IL SHORE). LOOKING AHEAD TO MONDAY NIGHT, MODELS
CONTINUE TO TREND SLOWER WITH THE NEXT WEATHER SYSTEM,
POTENTIALLY HOLDING OFF UNTIL CLOSER TO DAYBREAK. WE WILL HAVE
TO KEEP AN EYE ON WHETHER ANY SPOTTY SHOWERS OCCUR DURING THE
PRE-DAWN HOURS. IF SURFACE TEMPERATURES END UP DROPPING BELOW
FREEZING DURING THIS TIME THERE COULD BE PATCHY SLICK SPOTS THAT
DEVELOP. GIVEN THIS IS SUCH A LOW PROBABILITY SCENARIO
(CURRENTLY UNDER 15%), HAVE HELD OFF ON A FORMAL MENTION OF
FREEZING RAIN WITH THIS UPDATE. SEE THE DISCUSSION BELOW FOR
MORE DETAILS ON THE POTENTIALLY MORE ACTIVE PATTERN WE ARE
HEADING INTO.
PETR
TUESDAY ONWARD:
A BROADER ZONAL FLOW REGIME WITH AN EMBEDDED SLOW-MOVING TROUGH
OVER THE CENTRAL ROCKIES EARLY IN THE WEEK WILL TRANSITION TO A
MUCH MORE MERIDIONAL PATTERN HIGHLIGHTED BY DEEP WESTERN
TROUGHING AND EASTERN RIDGING FOR THE SECOND HALF OF THE WEEK.
MEANWHILE, AN EXPANSIVE BERMUDA HIGH WILL FOSTER A PERSISTENT FEED
OF GULF AND CARIBBEAN MOISTURE TOWARD THE CENTRAL CONUS THROUGH
THE PERIOD. THIS WILL ULTIMATELY RESULT IN A SEASONABLY MILD TO AT
TIMES UNSEASONABLY WARM PERIOD WITH SEVERAL ROUNDS OF RAIN AND
LOCALIZED CONVECTION OVER THE AREA. WHILE AXES OF HEAVY RAIN
APPEAR LIKELY OVER THE MID-MISSISSIPPI AND OHIO RIVER VALLEYS, IT
REMAINS TO BE SEEN WHERE THOSE AXES SET-UP AND WHETHER THOSE AXES
ALIGN OVER THE SAME LOCATION AND RESULT IN FLOODING CONCERNS.
INITIALLY, BROAD LOW-LEVEL ISENTROPIC ASCENT COMBINED WITH
MODEST MOISTURE TRANSPORT WILL BRING THE FIRST AREA OF PRECIP
OVER AT LEAST PORTIONS OF THE AREA ON TUESDAY. SOMEWHAT OF A
SPLIT FLOW REGIME AND THE "JUICIEST" LOW LEVEL AIR MASS NEAR A
WARM FRONT ACROSS CENTRAL ILLINOIS AND INDIANA MAY TEND TO FOCUS
ANY HIGHER RAINFALL AMOUNTS SOUTH OF I-80. THERE DOES APPEAR TO BE
A PLAUSIBLE SCENARIO IN WHICH A RELATIVE MINIMA IN RAINFALL OR
CONCEIVABLY LITTLE/NO RAINFALL MATERIALIZES SOMEWHERE NORTH OF
I-80 OR I-88 WHERE POPS ONLY PEAK IN THE LIKELY (~70%) RANGE.
BEYOND THE DAYTIME HOURS OF TUESDAY, THE SPREAD IN THE ENSEMBLE
SUITE, OWING TO THE DIFFERENCES IN THE EVOLUTION OF THE WESTERN
TROUGH, OFFERS LESS CONFIDENCE ON EXACTLY WHEN AND WHERE HEAVY
RAIN AXES DEVELOP. HOWEVER, WITH PWATS AROUND 1.5" (300% OF
NORMAL), ANY PRONOUNCED WAVE EMANATING FROM THE WESTERN TROUGH
WILL INDUCE SUFFICIENT FORCING TO REALIZE FOCUSED AXES OF HEAVY
RAIN. THE GEFS AND TO A LESSER EXTENT THE CANADIAN ENSEMBLE
SYSTEM HAVE REMAINED ON THE FASTER SIDE OF THE GUIDANCE ENVELOPE,
WHICH WOULD ENTAIL RAINY/INCLEMENT CONDITIONS FOR THE TUESDAY
NIGHT-WEDNESDAY EVENING PERIOD AND THEN DRYING OUT ON THURSDAY.
MEANWHILE, IF THE CONSISTENTLY SLOWER SOLUTIONS ADVERTISED BY
ABOUT HALF OF THE ENSEMBLE SUITES (THE ECMWF AND UKMET ENSEMBLES)
PAN OUT, A GOOD CHUNK OF TUESDAY NIGHT AND WEDNESDAY COULD BE DRY
(ESPECIALLY WITH NORTHWARD EXTENT) BEFORE RAIN CHANCES INCREASE
AGAIN LATE WEDNESDAY NIGHT INTO THURSDAY. AS A WHOLE, WHILE WE
CAN'T IGNORE THE CONSISTENT GEFS DEPICTIONS WITH HEAVY RAINFALL
TOTALS FARTHER NORTH TUESDAY NIGHT-WEDNESDAY, THE MIDWEEK FOCUS
MAY VERY WELL REMAIN PRIMARILY ACROSS SOUTHERN SECTIONS OF THE CWA
AND POINTS SOUTH. ON EITHER SIDE OF THE FASTER TO SLOWER SPECTRUM
WITH RESPECT TO RAIN TRENDS WEDNESDAY-THURSDAY, ONSHORE FLOW
FROM LAKE MICHIGAN WILL KEEP TEMPERATURES NOTABLY COOLER WITHIN
RANGE OF THE MARINE LAYER INLAND PROPAGATION THAN FOR LOCALES
FARTHER SOUTH AND WEST.
WE'LL ALSO NEED TO KEEP AN EYE ON THE POTENTIAL FOR MORE
ORGANIZED CONVECTION IN OR AROUND THE AREA THURSDAY PM AND
ESPECIALLY ON FRIDAY AS A LARGE PORTION OF THE WESTERN TROUGH
EJECTS TOWARD THE MID TO UPPER-MISSISSIPPI RIVER VALLEY. EVEN AT
THIS LEAD TIME, THE VARIOUS ENSEMBLE SYSTEMS HAVE A STRIKINGLY
STRONG SIGNAL CENTERED ON FRIDAY FOR A NORTHWARD SURGE OF
ANOMALOUS DEW POINTS IN THE 50S TO POSSIBLY 60F+ IN SPOTS
COINCIDING WITH AN APPROACHING COLD FRONT AND SEASONABLY STRONG
WIND FIELDS. THE OFFICIAL FORECAST INDICATES LIKELY POPS AREA-WIDE
FRIDAY PM THROUGH FRIDAY NIGHT AND SOUTHEAST OF I-55 ON SATURDAY
MORNING, OWING TO A SIZABLE PORTION OF GUIDANCE MEMBERS WITH A
SLOWER COLD FRONT PASSAGE. IN THE WAKE OF THE FRONT, THERE
SHOULD BE A COUPLE DAYS OF QUIETER, BUT STILL MILD WEATHER INTO
THE START OF THE 2ND WEEK OF MARCH.
CASTRO/KLUBER
AVIATION /06Z TAFS THROUGH 12Z MONDAY/
ISSUED AT 1056 PM CST SAT FEB 28 2026
BREEZY NORTHEASTERLY WINDS WILL CONTINUE THROUGH SUNDAY MORNING
BUT THE STRONGEST GUSTS WILL CONTINUE TO GRADUALLY EASE THROUGH
TONIGHT. MVFR CIGS WILL PREVAIL TONIGHT, ALTHOUGH THERE IS SOME
INDICATION CIGS MAY LIFT TO VFR PERIODICALLY TONIGHT INTO
SUNDAY MORNING. AT RFD, VFR WILL LIKELY RETURN OVERNIGHT
TONIGHT. GIVEN THE CONTINUED FLOW OFF THE LAKE, HAVE MAINTAINED
MVFR AT THE CHICAGO-AREA TERMINALS THROUGH MIDDAY SUNDAY, BUT
ADJUSTMENTS MAY BE NEEDED. VFR CONDITIONS ARE EXPECTED SUNDAY
NIGHT WITH WINDS GRADUALLY TURNING SOUTHEASTERLY.
CARLAW
LOT WATCHES/WARNINGS/ADVISORIES
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY UNTIL 3 PM CST THIS AFTERNOON FOR THE IL
AND IN NEARSHORE WATERS.
VISIT US AT WEATHER.GOV/CHICAGO
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