158
FXUS63 KLOT 071151
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
551 AM CST SAT FEB 7 2026
KEY MESSAGES
- QUICK SHOT OF SNOW POSSIBLE TONIGHT OVER FAR NE IL AND NW IN.
- MILDER TEMPERATURES EXPECTED FOR MUCH OF THE UPCOMING WORK
WEEK.
DISCUSSION
ISSUED AT 228 AM CST SAT FEB 7 2026
AFTER OUR MILDEST TEMPERATURE IN NEARLY 3 WEEKS ON FRIDAY, NORTHERLY
WINDS EARLY THIS MORNING CONTINUE TO USHER IN COLDER AIR. SOME
LAKE EFFECT FLURRIES AND A COUPLE OF ISOLATED LIGHT SNOW
SHOWERS ARE STREAMING INLAND INTO NW INDIANA EARLY THIS MORNING.
LOW INVERSION HEIGHTS HAVE BEEN A BIG LIMITING FACTOR IN MORE
ROBUST LAKE EFFECT SNOW AND WITH INVERSION HEIGHTS PROGGED TO
CONTINUE TO LOWER THIS MORNING, LAKE EFFECT THREAT SHOULD END
LATER THIS MORNING. NOT EXPECTING ANY ACCUMULATIONS.
AFTER A MAINLY SUNNY DAY, LOOK FOR HIGH AND EVENTUALLY MID LEVEL
CLOUDINESS TO STREAM INTO THE AREA TOWARD, AND ESPECIALLY AFTER,
SUNSET THIS EVENING. THIS CLOUDINESS IS IN ASSOCIATION WITH A
LOW AMPLITUDE SHORTWAVE TROUGH RIDING THE NORTHWEST FLOW THROUGH
THE REGION TONIGHT. LOOK FOR STRENGTHENING ISENTROPIC ASCENT
TONIGHT IN ADVANCE OF THIS WAVE AS LOW AND MID LEVEL FLOW BACK
ON THE 280-295K THETA SURFACES. LOW LEVEL AIR MASS WILL BE QUITE
DRY, SO IT WILL BE A RACE TO SEE IF THE VIRGA CAN BREAK THROUGH
THE DRY LOW LEVELS BEFORE STRONGEST ISENTROPIC ASCENT SHIFTS
EAST OF THE AREA. THERE HAS BEEN A WESTWARD TREND IN GUIDANCE IN
WHERE THE BREACH OF THE LOW LEVEL DRY AIR WILL TAKE PLACE, WITH
MOST GUIDANCE NOW SUGGESTING A QUICK HIT OF SNOW OVER FAR
NORTHEAST ILLINOIS INTO NORTHWEST INDIANA TONIGHT. IF SNOW DOES
OCCUR IT LOOKS TO BE BRIEF, ONLY LASTING AN HOUR OR TWO, BUT
COULD BE ENOUGH TO COAT THE GROUND. CONFIDENCE IS STILL RATHER
LOW, SO HELD OFF ON LIKELY POPS, BUT DID INTRODUCE SOME HIGH END
CHANCE POPS OVER FAR EASTERN CWA TONIGHT.
LARGE SCALE PATTERN CHANGE IS STILL PROGGED TO TAKE PLACE DURING
THE UPCOMING WORK. THE PERSISTENT HIGH AMPLITUDE RIDGING OVER
WESTERN NORTH AMERICA IS PROGGED TO BREAK DOWN, AND BE REPLACED
BY A LONG WAVE TROUGH. DOWNSTREAM RIDGING OVER CENTRAL AND
EASTERN U.S. LOOKS TO BE MUTED BY LINGERING, PERSISTENT
TROUGHING OVER NEW ENGLAND. THIS WILL RESULT IN A MAINLY ZONAL
FLOW PATTERN WHICH SHOULD KEEP THE VERY COLD AIR TO OUR NORTH
AND EAST, WITH A MODIFIED PACIFIC AIR MASS ACROSS MUCH OF THE
CENTRAL U.S. INTO THE MIDWEST NEXT WEEK.
GUIDANCE HAS CONTINUED THE TREND FROM THE 12Z GUIDANCE OF
KEEPING A SHORTWAVE TUESDAY SOUTH OF OUR AREA. IN THIS SCENARIO,
WE'D LIKELY REMAIN DRY, BUT A WEAK COLD FRONT MOVING ACROSS THE
AREA ALSO LOOKS TO KEEP TEMPS IN CHECK. NBM TEMPS ARE LIKELY TOO
WARM TUESDAY AND WOULD EXPECTED SUBSEQUENT RUNS TO TREND A BIT
COOLER, BUT CONFIDENCE WASN'T HIGH ENOUGH TO LOWER TEMPS OR
REMOVE THE SLIGHT CHANCE POPS JUST YET.
THERE REMAINS A LOT OF UNCERTAINTY WITH A POTENTIAL LATE WEEK
SYSTEM. DIDN'T MAKE ANY CHANGES TO THE POPS OFFERED UP BY THE
NBM, BUT THERE IS A SIGNIFICANT CONTINGENT OF EPS AND GEFS
MEMBERS THAT WOULD KEEP US DRY THROUGH THE MIDDLE-END OF THE
UPCOMING WORK WEEK.
- IZZI
AVIATION /12Z TAFS THROUGH 18Z SUNDAY/
ISSUED AT 551 AM CST SAT FEB 7 2026
FORECAST CONCERN FOR THE TERMINALS...
- NORTHWEST WINDS THIS MORNING BECOMING EASTERLY THIS AFTERNOON.
- 30-40% CHANCE FOR A PERIOD OF SNOW SHOWERS TONIGHT IN FAR
NORTHEAST IL AND NORTHWEST IN WHICH COULD RESULT IN REDUCED
VISIBILITIES AND SOME ACCUMULATIONS.
A SURFACE HIGH CONTINUES TO SETTLE INTO THE GREAT LAKES THIS
MORNING WHICH WILL GENERALLY MAINTAIN VFR CONDITIONS THROUGH THE
TAF PERIOD. THE EXCEPTION HOWEVER WILL IN NORTHWEST IN WHERE
SOME LAKE EFFECT CLOUDS WILL CONTINUE TO STREAM INLAND RESULTING
IN 2500-3500 FT CEILINGS THROUGH THE MORNING BEFORE CLOUDS
SCATTER OUT BY EARLY AFTERNOON. WHILE WIND SPEEDS WILL
GENERALLY BE LIGHT AROUND 5-10 KTS, DIRECTIONS WILL BECOME MORE
EASTERLY TOWARDS MIDDAY BEFORE TURNING SOUTHEASTERLY BY THIS
EVENING WHERE THEY WILL REMAIN FOR THE REST OF THE TAF PERIOD.
HEADING INTO TONIGHT, A SHORTWAVE TROUGH IS EXPECTED TO PIVOT
INTO THE GREAT LAKES AND INTERACT WITH SOME MID-LEVEL MOISTURE
WHICH SHOULD GENERATE SNOW ALOFT. THAT SAID, THE LOWER
ATMOSPHERE IS FORECAST TO BE RATHER DRY WHICH MAY KEEP THE BULK
OF THE SNOW ALOFT AS VIRGA AND/OR FLURRIES. HOWEVER, CONFIDENCE
IS STARTING TO INCREASE (30-40% CHANCE) THAT THE FORCING MAY BE
ABLE TO GENERATE SUFFICIENT SNOW ALOFT TO SATURATE THE LOWER
ATMOSPHERE AND LEAD TO A PERIOD OF SNOW SHOWERS OVERNIGHT ACROSS
FAR NORTHEAST IL AND NORTHWEST IN. IF THIS SATURATION DOES
OCCUR AS GUIDANCE SUGGESTS THEN A 2-3 HOUR PERIOD OF SNOW
SHOWERS COULD MATERIALIZE AROUND MIDNIGHT AND RESULT IN SOME
REDUCED VISIBILITIES (POSSIBLY AS LOW AS 2-3 MILES) AND A
DUSTING TO HALF INCH OF ACCUMULATION. GIVEN SOME LINGERING
UNCERTAINTY IN SNOW COVERAGE AND INTENSITY HAVE OPTED TO
INTRODUCE PROB30S FOR THE CHICAGO AREA TERMINALS (ORD, MDW,
GYY, AND DPA) FOR THIS POTENTIAL WHERE LOW-LEVEL MOISTURE IS
FORECAST TO BE GREATEST.
YACK
LOT WATCHES/WARNINGS/ADVISORIES
IL...NONE.
IN...NONE.
LM...NONE.
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