923
FXUS63 KIWX 040531
AFDIWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
1231 AM EST WED FEB 4 2026
KEY MESSAGES
- COLD TONIGHT WITH LOW TEMPERATURES EXPECTED IN THE SINGLE DIGITS
ABOVE ZERO FOR MANY LOCATIONS.
- LOW CHANCES OF LIGHT SNOW (20-30%) FOR THURSDAY, WITH GREATEST
CHANCES (50-70%) LATE THURSDAY NIGHT INTO FRIDAY.
- TEMPERATURES MODERATE BY FRIDAY, BUT COLDER CONDITIONS RETURN FOR
WEEKEND.
- A MORE SIGNIFICANT MODERATING TEMPERATURE TREND EXPECTED NEXT
WEEK.
DISCUSSION
ISSUED AT 305 PM EST TUE FEB 3 2026
AN UPPER LEVEL SHORT WAVE CONTINUES TO SINK SOUTHEAST ACROSS WEST
CENTRAL ILLINOIS THIS AFTERNOON. DOWNSTREAM STRONGER LOW/MID LEVEL
FRONTOGENESIS FORCING HAS SLIPPED SOUTHEAST OF THE LOCAL AREA AND
SHOULD NO LONGER POSE A CHANCE FOR ANY ADDITIONAL SNOW ACCUMULATION
THIS AFTERNOON/EVENING. OTHERWISE TONIGHT, A WEAK SFC TROUGH/LOW
LEVEL COLD FRONT WILL DROP SOUTHEAST ACROSS THE EASTERN GREAT LAKES
WITH SOME RENEWED LOW LEVEL CAA/DRY AIR ADVECTION. THIS SHOULD ALLOW
FOR PARTLY CLOUDY TO CLEAR SKIES DEVELOPING TONIGHT, AND THIS
COMBINATION OF AT LEAST PARTIAL CLEARING, COLD ADVECTION, AND GOOD
DECOUPLING SHOULD PROMOTE MUCH COLDER TEMPERATURES TONIGHT WITH
SINGLE DIGIT LOWS. SOME CONCERN THAT FAVORED COLD SPOTS COULD REALLY
CRASH THIS EVENING, BUT AGE OF SNOWPACK COULD LIMIT THESE EXTREMES.
IF TEMPS DO DROP OFF MORE THAN FORECAST, WINDS SHOULD BE ON THE
LIGHT SIDE, SO MINIMUM WIND CHILLS SHOULD BE IN CHECK TONIGHT AROUND
ZERO. SOME WEAK LAKE RESPONSE IS EXPECTED TONIGHT GIVEN THE COLD
ADVECTION, BUT WOULD EXPECT THIS TO MANIFEST MORE AS MID-LAKE BAND
GIVEN ANTICIPATED DEVELOPMENT OF LAND BREEZE, WEAKENING FLOW, AND
POSITIONING OF LAKE AGGREGATE TROUGH.
BROAD LOW LEVEL THERMAL TROUGHING WILL REMAIN ANCHORED FROM THE MID
MS VALLEY TO THE EASTERN GREAT LAKES ON WEDNESDAY AS AN EXPANSIVE
LOW LEVEL ANTICYCLONE SETTLES INTO THE REGION. WHILE MAGNITUDE OF
LOW LEVEL THERMAL PROGS ARE NOT NEARLY AS COLD AS POST-FRONTAL
SITUATIONS OF PAST FEW WEEKS, OVERALL POOR MIXING IN THIS SETUP
SHOULD LIMIT HIGHS TO THE 20 TO 25 DEGREE RANGE. THE NEXT LARGE
SCALE UPPER TROUGH WILL SHIFT ACROSS THE WESTERN GREAT LAKES LATE IN
THE DAY WEDNESDAY, BUT MOISTURE PROFILES WILL BE SCANT AND VERY
SHALLOW. APPROACH AND PASSAGE OF THIS TROUGH COULD SHIFT ANY WEAK
MID LAKE CONVERGENT BAND BACK EASTWARD ACROSS SW LOWER MI/NW INDIANA
BUT GIVEN SUCH LIMITED MOISTURE DEPTHS/SHALLOW INVERSION HEIGHTS,
THIS WOULD LIKELY MANIFEST AS JUST SOME LIGHT SNOW SHOWERS OR
FLURRIES.
AN AMPLIFIED LONGWAVE PATTERN PERSISTS INTO THURSDAY WITH A 582 DM
UPPER RIDGE ACROSS WESTERN CONUS AND SEVERAL SMALL SCALE
PERTURBATIONS CARVING OUT NEGATIVE UPPER HEIGHT ANOMALY ACROSS SE
CANADA. GUIDANCE CONTINUES TREND OF DEPICTING TWO SEPARATE NW FLOW
WAVES TOPPING THE RIDGE AND DIVING SOUTHEAST INTO THE REGION, ONE
FOR THURSDAY MORNING, AND THE SECOND FOR LATE THURSDAY NIGHT INTO
EARLY FRIDAY. THE AMPLITUDE OF THIS PATTERN AND EFFECTS FROM THE
AFOREMENTIONED BROAD LOW LEVEL ANTICYCLONE WILL ALLOW FOR LIMITED
LOW/MID LEVEL MOISTURE IN THIS PATTERN. WITH THE FIRST WAVE EARLY
THURSDAY, SOME MASS CONVERGENCE AT NOSE OF A WESTERLY LOW LEVEL JET
AND STRENGTHENING LOW LEVEL WAA COULD ALLOW SOME PROSPECTS OF LIGHT
PRECIP TO REACH AS FAR SOUTH AS US 6 CORRIDOR, BUT CONFIDENCE IN
PRECIP IS LOW AT THIS TIME. BETTER PRECIP CHANCES STILL LOOK TO
BE IN THE LATER THURSDAY NIGHT/FRIDAY PERIOD AS A 150 KNOT
UPPER SPEED MAX DIVES SOUTHEAST ALLOWING BETTER PUSH OF ARCTIC
AIR INTO THE EASTERN GREAT LAKES. STRONGER LOW LEVEL CONVERGENCE
AND BRIEF PERIOD OF STRONG DPVA WITH THE UPPER VORTICITY SHOULD
ALLOW SNOW TO SPREAD ACROSS MUCH OF LOWER MI/NORTHEAST
IN/NORTHWEST OH. DEEP MOISTURE PROFILES WITH BETTER RH IN DGZ
STILL LOOK TO BE OF LIMITED DURATION (2-4 HOURS), BUT A QUICK
INCH OR TWO OF ACCUMULATION IS POSSIBLE EARLY FRIDAY. THIS SETUP
COULD YIELD SOME FLAGS FOR SNOW SQUALL POTENTIAL, BUT THE VERY
LIMITED MOISTURE SETUP MIGHT SUGGEST THAT BETTER RH IN DGZ IS
LOST BY THE TIME STEEPER LOW LEVEL LAPSE RATES AND STRONGER WIND
GUSTS DEVELOP. IF SOME SNOW SQUALL POTENTIAL MATERIALIZES, THIS
MAY BE MAXIMIZED ACROSS THE EASTERN GREAT LAKES.
BELOW NORMAL TEMPS BUILD BACK IN BEHIND THIS SYSTEM FRIDAY NIGHT
INTO SATURDAY, WITH WEAK WARMING TREND THROUGH THE WEEKEND AS MEAN
RIDGE AXIS SLOWLY SHIFTS EASTWARD. THE WILDCARD FOR THE WEEKEND WILL
BE POTENTIAL OF ANY ADDITIONAL NW FLOW WAVES WHILE THE UPPER RIDGE
AXIS IS FAR ENOUGH WEST OF THE AREA. THIS COULD SUPPORT ADDITIONAL
LIGHT SNOW CHANCE AT SOME POINT LATER SATURDAY/EARLY SUNDAY GIVEN
EXPECTED STRONG BAROCLINICITY WITH ANY NW FLOW WAVE, BUT
CONFIDENCE IS ON THE VERY LOW SIDE GIVEN LOW PREDICTABILITY OF
THESE LOW AMPLITUDE PROGRESSIVE WAVES. A SHARPER WARMING TREND
STILL LOOKS TO BE IN STORE FOR NEXT WEEK AS MEDIUM RANGE
GUIDANCE CONSENSUS FAVORS LONGWAVE TROUGHING ACROSS THE WESTERN
CONUS BY MIDDLE OF NEXT WEEK.
AVIATION /06Z TAFS THROUGH 06Z THURSDAY/
ISSUED AT 1230 AM EST WED FEB 4 2026
IN THE MIDDLE OF THIS MID LEVEL TROUGH WITH PLENTY OF VORTICITY, AN
AREA OF SURFACE HIGH PRESSURE MOVES THROUGH TONIGHT, WHICH WOULD
SIGNIFY DRIER AIR. THE PROBLEM IS THAT THERE IS A THIN LAYER OF LOW
LEVEL MOISTURE IDENTIFIABLE IN RAP TIME SECTIONS THAT IS TRAPPED
UNDER THE INVERSION AND IS CONTRIBUTING TO STRATUS CLOUDS OVERHEAD.
MODELS HAVE BEEN INDICATING THAT THE AREA OF 925 MB MOISTURE WOULD
BE DRYING OUT BY NOW, BUT THAT HASN'T BEEN THE CASE SO WILL CONTINUE
TO HOLD ONTO IT USING A TEMPO GROUP FOR THESE FIRST 4 HOURS. THERE
IS ALSO DISAGREEMENT IN MODELS ABOUT WHAT TO DO WITH THE REST OF THE
DAY. DO WE CLOUD UP THE AFTERNOON (NAM/RAP) OR DO WE BREAK IT ALL UP
(LAV)? THERE ARE ALSO SOME LAKE ENHANCED SNOW SHOWERS AROUND IN MI
THAT MAY BE ABLE TO CREATE SOME SNOW AT SBN DURING THE FIRST 9 HOURS
OF THIS TAF PERIOD, BUT BELIEVE IT TO BE WEAK ENOUGH THAT IT CAN BE
LEFT OUT OF THESE TAFS.
A SLIGHT EASTERLY (OF NORTH) COMPONENT OF WIND MAY BE ENOUGH TO
KEEP CLOUDS SOCKED IN THROUGH MUCH OF THIS TAF PERIOD, BUT THAT
LOOKS TO BACK NORTHERLY AND NORTHWESTERLY THIS AFTERNOON AND
EVENING, WHICH WOULD INDICATE THAT IT MAY TAKE UNTIL LATER
WEDNESDAY TO FINALLY SCATTER OUT. BUT EVEN THAT MAY BE DELAYED
WITH FUTURE MODEL ADJUSTMENTS.
IWX WATCHES/WARNINGS/ADVISORIES
IN...NONE.
OH...NONE.
MI...NONE.
MARINE...NONE.
DISCUSSION...MARSILI
AVIATION...ROLLER
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