437
FXUS63 KLOT 070828
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
228 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 /06Z TAFS THROUGH 12Z SUNDAY/
ISSUED AT 1057 PM CST FRI FEB 6 2026
KEY MESSAGES FOR 06Z TAFS:
- BLUSTERY NORTH WINDS GUSTING 20-25 KT GRADUALLY DIMINISH
OVERNIGHT, BECOMING LIGHT AND VARIABLE BY EARLY SATURDAY
AFTERNOON AND LIGHT SOUTHEAST SATURDAY NIGHT.
- LOW PROBABILITY (<25%) FOR A 3-4 HOUR PERIOD OF LIGHT SNOW
TOWARD/AFTER MIDNIGHT SATURDAY NIGHT.
BLUSTERY NORTHERLY WINDS WILL PERSIST INTO THE OVERNIGHT HOURS
IN THE WAKE OF A COLD FRONT. GUSTS 20-25 KT WILL GRADUALLY
DIMINISH PREDAWN, WITH WINDS REMAINING NORTH-NORTHWEST SATURDAY
MORNING. SURFACE HIGH PRESSURE WILL SPREAD ACROSS THE AREA
DURING THE MIDDAY/AFTERNOON HOURS, WHICH WILL RESULT IN A FEW
HOUR PERIOD OF LIGHT AND SOMEWHAT VARIABLE WINDS, WHICH SHOULD
BECOME LIGHT EAST-SOUTHEAST BY SATURDAY EVENING AND INCREASE
INTO THE 5-10 KT RANGE OVERNIGHT.
LINGERING VFR LAKE-INDUCED STRATOCU WILL PERSIST MAINLY AT GYY
OVERNIGHT AND INTO SATURDAY MORNING. OTHERWISE, MAINLY CLEAR
SKIES ARE EXPECTED UNTIL SATURDAY AFTERNOON WHEN INCREASING VFR
HIGH CLOUDS DEVELOP AND EVENTUALLY THICKEN AND LOWER INTO A
MID-DECK SATURDAY EVENING. LOW-LEVELS WILL REMAIN QUITE DRY
ACROSS THE REGION SATURDAY NIGHT, THOUGH THERE REMAINS A SIGNAL
FOR LIGHT SNOW TO DEVELOP NEAR BUT MAINLY NORTH/NORTHEAST OF THE
TERMINALS SATURDAY NIGHT. A SMALL SUBSET OF MODEL RUNS DO DEPICT
DEVELOPMENT OVER THE AREA HOWEVER, THOUGH WHILE THIS CAN'T BE
COMPLETELY DISREGARDED THE CURRENT POTENTIAL (<25%) IS NOT HIGH
ENOUGH TO INCLUDE IN TAFS AT THIS TIME. IF IT WERE TO OCCUR,
TIMING LOOKS TO BE AFTER ABOUT 03Z AT RFD AND AFTER 05Z FOR
CHICAGO SITES.
RATZER
LOT WATCHES/WARNINGS/ADVISORIES
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY UNTIL 3 AM CST EARLY THIS MORNING FOR THE
IL NEARSHORE WATERS.
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