901
FXUS63 KIWX 021622
AFDIWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
1122 AM EST MON FEB 2 2026
KEY MESSAGES
- PATCHY FREEZING DRIZZLE GRADUALLY DIMINISHES THROUGH THE
AFTERNOON, BUT SLICK ROADS MAY PERSIST INTO EARLY EVENING.
- A SYSTEM MAY BRING LIGHT SNOW TO AREAS SOUTH OF US-30 TONIGHT
INTO TUESDAY.
- NOT QUITE AS COLD THIS WEEK WITH HIGHS IN THE 20S AND LOWS IN
THE TEENS TO SINGLE-DIGITS.
UPDATE
ISSUED AT 1106 AM EST MON FEB 2 2026
BROAD WEAK ISENTROPIC ASCENT IN WAKE OF LEAD SHORT WAVE THAT
BROUGHT LIGHT SNOW ACCUMULATIONS TO THE REGION OVERNIGHT SHOULD
BE ENOUGH WHEN COUPLED WITH SHALLOW MOISTURE FOR SOME CONTINUED
PATCHY LIGHT FREEZING DRIZZLE THROUGH EARLY-MID AFTERNOON. AS
WE HEAD INTO LATE AFTERNOON, SOME INDICATIONS IN NEAR TERM MODEL
TIME/HEIGHT AND CROSS SECTIONS THAT DESCENDING MID LEVEL DRY
LAYER SHOULD TEND TO REDUCE DRIZZLE AS A WEAK COOL FRONT
APPROACHES. THE GREATEST LONGEVITY TO PATCHY FREEZING DRIZZLE
MAY BE DOWNWIND OF LAKE MICHIGAN ACROSS SOUTHWEST LOWER
MICHIGAN. A WINTER WEATHER ADVISORY WAS ISSUED EARLIER THIS
MORNING THROUGH 21Z FOR ROUGHLY ALONG AND NORTH OF I-80 CORRIDOR
WHERE GREATEST IMPACTS HAVE BEEN REPORTED. IT IS POSSIBLE
FLURRIES/LIGHT SNOW SHOWER PRECIP TYPE COULD BECOME DOMINANT
AGAIN ACROSS THE NORTHWEST LATER THIS AFTERNOON WITH APPROACH OF
WEAK COLD FRONT. SOME BRIEF EXTENSION IN TIME IS POSSIBLE
DOWNWIND OF LAKE MICHIGAN FOR THE WINTER WEATHER ADVISORY, BUT
WILL ADDRESS THIS IN MORE DETAIL IN NEXT FEW HOURS.
DISCUSSION
ISSUED AT 258 AM EST MON FEB 2 2026
AN 850 MB THETA-E PLUME PAIRED WITH AN AREA OF WAA TRAVERSES THE
AREA TODAY AS A LOW PRESSURE FORMS TO THE NORTH OF THE GREAT LAKES
AND PUSHES AN OCCLUDED FRONT THROUGH. INITIAL REPORTS OUT OF IL
INDICATE AREAS OF FREEZING DRIZZLE MIXING IN WITH SNOW AND THE
MODELS BEAR THIS OUT AS DGZ SATURATION APPEARS TO STRUGGLE,
ESPECIALLY ON THE BACK END OF THE FRONTAL PASSAGE. THE MAIN AREA OF
OMEGA PUSHES THROUGH BETWEEN 9 AND 18Z AND MOST OF THAT APPEARS TO
RESIDE WITHIN THE DGZ, WHICH IS SATURATED, AT LEAST THE BOTTOM PART
OF IT IS AND THAT MAY LOWER SLR. DGZ SATURATION ALREADY APPEARS TO
DROP OFF AROUND 12Z IN WESTERN AREAS AS THE BACKSIDE OF THE MOISTURE
PLUME BEGINS TO MOVE THROUGH FROM WEST TO EAST. A THIN AREA OF LOW
LEVEL MOISTURE REMAINS IN THE LOW LEVELS RESEMBLING STRATUS AND IT
IS QUESTIONABLE IF THERE'S ENOUGH LIFT TO FORCE FREEZING DRIZZLE,
HALTING PRECIPITATION INSTEAD. HOWEVER, THE BACKSIDE OF THE FRONT
APPEARS TO BE THE BEST CHANCE FOR THE FREEZING DRIZZLE, IF IT
OCCURS AT ALL.
BEHIND THIS FRONT, THE VORT MAX CAUSING THE SFC LOW OVER THE
NORTHERN GREAT LAKES DIVES SOUTHEAST AND BRINGS A SHORTWAVE EASTWARD
ALONG ITS SOUTHWESTERN PERIPHERY. THE NAM, DURING THIS TIME, HAS A
BOUNDARY MOVING SOUTHWARD THROUGH MI FROM 12Z TO 21Z TUESDAY.
INVERSION HEIGHTS FROM LAKE ENHANCEMENT APPEAR TO BE MARGINAL AT
ONLY 3 TO 4 KFT AND DELTA TS ARE ONLY 10C. MEANWHILE, THETA-E
INSTABILITY IS ALSO MARGINAL AND THE MOISTURE COLUMN LEAVES A LOT
TO BE DESIRED.
AWAY FROM LAKE MI, THE AFOREMENTIONED SHORTWAVE ALONG THE UPPER
LOW'S PERIPHERY FORCES A LOW PRESSURE SYSTEM THAT, BY TUESDAY,
PHASED LOW PRESSURE IN THE TENNESSEE RIVER VALLEY CREATES A PRECIP
SHIELD THAT COULD GRAZE OUR SOUTHERN TIER OF COUNTIES. MODEL
CERTAINTY HAS ABOUT A 20 PERCENT CHANCE AT 0.5 INCH OR GREATER
SNOWFALL AND THERE IS NOT ONE MODEL THAT IS COMPLETELY DEVOID OF
SNOW ACROSS THE AREA (MANY HAVE 0.1 INCH OF SNOW). THE NAM IS
PRODUCING THE MOST SNOW AT 1 TO 3 INCHES ACROSS OUR SOUTHERN TIER OF
COUNTIES (WHITE TO JAY). THE NORTHERN PERIPHERY OF THE PRECIP SHIELD
IS KNOWN TO RUN INTO SATURATION PROBLEMS, BUT THAT'S USUALLY WHEN
THE SURFACE HIGH IS JUST TO THE NORTH OF THE LOW. THIS TIME THE
SURFACE HIGH IS TRAILING THE LOW, BACK IN THE NORTHERN PLAINS.
IT IS INTERESTING SEEING A GOOD AMOUNT OF MODELS CREATING WHAT
APPEARS TO BE LAKE EFFECT SNOW TUESDAY NIGHT INTO WEDNESDAY, BUT
THERE'S QUITE A BIT OF TYPICAL INGREDIENTS FOR LES THAT ARE MISSING.
TRAJECTORIES APPEAR TO BE MORE NORTHEASTERLY WITH MUCH MORE OF THE
LOW LEVEL MOISTURE JUST WEST OF THE AREA IN LOT'S AREA, WHICH IS
ALSO WHERE THE BETTER THETA-E INSTABILITY RESIDES. THAT IS UNTIL WE
GET TO AFTER 9Z WEDNESDAY AS TRAJECTORIES TAKE A MORE NORTHWESTERLY
DIRECTION. STILL THE THETA-E INSTABILITY IS NOT ALL THAT GREAT AS IT
MOVES ONSHORE DURING THE DAY WEDNESDAY. DELTA TS APPEAR TO BE AROUND
10 TO 15C AND INVERSION HEIGHTS ARE AROUND 4 KFT DURING THIS TIME.
WILL CONTINUE THE SLIGHT CHANCE MENTION, BUT IT DOES APPEAR TO BE
LIGHT SNOW IF IT DOES HAPPEN.
DRY WEATHER FOLLOWS FOR THURSDAY WITH SOME MID LEVEL RIDGING EVIDENT
AND SURFACE PRESSURE PASSING THROUGH.
WE'LL, THEN, HAVE TO WATCH THE THURSDAY NIGHT INTO FRIDAY PERIOD AS
ANOTHER CLIPPER SYSTEM DIVES DOWN THROUGH THE GREAT LAKES REGION.
THE COLD AIRMASS THAT MOVES THROUGH IN CONJUNCTION WITH THAT SYSTEM
IS MUCH COLDER ON THE GFS AND IS CLOSER IN LINED WITH WHAT WE JUST
GOT OUT OF WITH 850 MB TEMPERATURES AROUND -20C. THE AIRMASS BEHIND
THE CLIPPER IS WARMER AND MUCH MORE TRANSIENT ON THE ECMWF SO THAT
BY SUNDAY, WE'RE BACK INTO THE ABOVE FREEZING AIR AT 850 MB (NOT SO
ON THE GFS). IT DOES LOOK POSSIBLE TO SEE A PERIOD OF LES TAKE OVER
LATER FRIDAY INTO SATURDAY. WE ALSO APPROACH COLD WEATHER ADVISORY
WIND CHILLS SATURDAY MORNING AND SO THAT WILL HAVE TO WATCHED.
AVIATION /12Z TAFS THROUGH 12Z TUESDAY/
ISSUED AT 638 AM EST MON FEB 2 2026
MVFR/IFR IN CIGS/VSBYS THROUGH 01Z TUE FOR KSBN AND THROUGH 08Z
TUE FOR KFWA WITH A DISTURBANCE MOVING THROUGH THE AREA FOLLOWED
BY LOWERED CIGS. DID MAKE MENTION OF SOME LIGHT FREEZING DRIZZLE
MIXING IN BEHIND THESE INITIAL SNOW SHOWERS FOR BOTH SITES,
MAINLY BETWEEN 12Z AND 16Z FOR KSBN AND 14Z AND 17Z FOR KFWA.
VFR CONDITIONS LOOK TO RETURN TO KSBN AFTER 01Z TUE AND AFTER
08Z TUE FOR KFWA. WINDS OUT OF THE S-SW VEERING TOWARDS THE
W-SW THROUGH THE TAF PERIOD.
IWX WATCHES/WARNINGS/ADVISORIES
IN...WINTER WEATHER ADVISORY UNTIL 4 PM EST THIS AFTERNOON FOR
INZ005>007.
OH...WINTER WEATHER ADVISORY UNTIL 4 PM EST THIS AFTERNOON FOR
OHZ001-002.
MI...WINTER WEATHER ADVISORY UNTIL 4 PM EST THIS AFTERNOON FOR
MIZ078>081-177-277.
MARINE...NONE.
UPDATE...MARSILI
DISCUSSION...ROLLER
AVIATION...ANDERSEN
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