508
FXUS63 KIWX 011701
AFDIWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
1201 PM EST SUN FEB 1 2026
KEY MESSAGES
- THERE IS A 60 PERCENT CHANCE OF GREATER THAN A HALF INCH OF SNOW
NORTH OF US-6 ON MONDAY FROM A CLIPPER SYSTEM. SLIPPERY TRAVEL IS
POSSIBLE FOR THE MORNING AND EVENING COMMUTES.
- NOT AS COLD THIS WEEK WITH HIGH TEMPERATURES THE 20S THROUGH
THURSDAY.
DISCUSSION
ISSUED AT 232 AM EST SUN FEB 1 2026
GIVEN CLEAR SKIES IN MANY AREAS, FRESH SNOWPACK, AND RADIATIONAL
COOLING WITH SHALLOW LOW LEVEL INVERSIONS, IT'S NOT ALL THAT
SURPRISING THAT FOG WAS FORMING LAST EVENING AND SCATTERED REDUCED
VISIBILITY HAS BEEN OCCURRING ACROSS THE AREA INTO THIS
MORNING. IT IS RELATIVELY SURPRISING GIVEN THE NEGATIVE DEW
POINTS AND THE DRYNESS THAT INDICATES, BUT PROBABLY THE FRESH
SNOW HAS PROVIDED THE NEEDED MOISTURE FOR SUCH AN OCCURRENCE. LOOK
OUT FOR SLICK SPOTS WHERE BLACK ICE HAS FORMED.
MOVING FORWARD, SURFACE HIGH PRESSURE AND MID LEVEL RIDGING
CONTINUES TO KEEP THE AREA DRY TODAY UNDER MOSTLY SUNNY SKIES. ALSO,
850 MB TEMPERATURES WARMING TOWARDS -10C AS OPPOSED TO THE -20C THAT
WE'VE BEEN IN WILL HELP HIGH TEMPERATURES TO ACHIEVE THE LOW TO
MID 20S AS OPPOSED TO STAYING IN THE TEENS THAT WE'VE HAD.
ONE CAN SEE ON THE 850 MB THETA-E PLOT THAT A PLUME MOVES INTO THE
AREA SUNDAY NIGHT INTO MONDAY. THIS COMES INTO THE AREA IN
CONJUNCTION WITH AN OCCLUDED FRONT. WITH THE WARMER TEMPERATURE
COLUMN, THE DGZ IS MUCH HIGHER UP NOW THAN WHAT WE'VE HAD. NAM TIME
SECTIONS MAINLY ACROSS US-30 INDICATE THAT THE BETTER LIFT AND
MOISTURE IS BELOW AND JUST BLEEDING INTO THE UNDERSIDE OF THE DGZ
WHICH WOULD CREATE SOME DENDRITES BUT ALSO BRING IN SOME LOWER SLR
TYPE SNOW CRYSTALS. THE OTHER ISSUE IS THAT THE DGZ DRIES OUT TO
SOMEWHERE AROUND -10 OR -11C DURING THE AFTERNOON SO THAT THE PTYPE
COULD END AS A MIX OF SNOW AND DRIZZLE OR JUST STOP. AFTER THE
OCCLUDED FRONT LEAVES, THERE IS A WEAK INDICATION OF LES/LAKE
ENHANCEMENT AS WELL WITH THETA-E LAPSE RATES RIGHT AROUND 0, SOME
LOW LEVEL CONVERGENCE RIGHT AROUND BERRIEN COUNTY AND SOME LOW LEVEL
MOISTURE TO WORK WITH. DELTA T VALUES ARE WEAK WITH 10 TO 15C, BUT
INVERSION HEIGHTS ARE MARGINAL AT AROUND 6 KFT.
BEHIND THIS SYSTEM, AN UPPER LOW DIVES SOUTHWARD TOWARD THE NORTHERN
GREAT LAKES, WHICH OPENS A PATH FOR A SHORTWAVE TO DIVE
SOUTHEASTWARD FROM THE NORTHERN PLAINS AND INTERACT WITH A LOW
PRESSURE SYSTEM IN THE SOUTHERN PLAINS ALL IN THE RIGHT ENTRANCE
REGION OF AN UPPER JET, WHICH ENHANCES LIFT. THE PLACEMENT OF THIS
LOW GETS THE NORTHERN PERIPHERY OF THE PRECIP SHIELD JUST SOUTH
OF OUR SOUTHERN TIER OF COUNTIES. INSTEAD, THERE LOOKS TO BE A
BOUNDARY DIVING SOUTHWARD THROUGH MI ON TUESDAY AND INTO
WEDNESDAY THAT CREATES LOW LEVEL MOISTURE, LOW LEVEL
CONVERGENCE, AND THERE IS SOME THETA-E INSTABILITY TO WORK WITH
THAT ALLOWS FOR SOME LAKE EFFECT SNOW TO DEVELOP. NAM BUFKIT
SOUNDINGS ONLY SHOW INVERSION HEIGHTS UP TO 3-4 KFT UP AND THAT
JUST NICKS THE DGZ. IT GETS SHALLOWER FOR WEDNESDAY AT MORE
LIKE 2-3 KFT, BUT THAT STILL MAY BE ENOUGH TO CREATE SOME LES.
A BETTER CHANCE FOR DRY WEATHER FOLLOWS FOR LATER WEDNESDAY THROUGH
THURSDAY AS SURFACE HIGH PRESSURE MOVES THROUGH.
FOLLOWING THIS, A CLIPPER-LIKE SYSTEM DIVES INTO THE GREAT LAKES AND
INTRODUCES ANOTHER CHANCE FOR SNOW. THERE ARE VARYING TEMPERATURE
PROFILES FOR THIS TIME PERIOD, BUT IT STILL APPEARS LIKE MOST AREAS
SEE SNOW. THE HANDLING OF THE COLD AIR THAT FOLLOWS BEHIND THIS
CLIPPER APPEARS TO VARY BETWEEN THE ECMWF AND THE GFS WITH ECMWF
HAVING GLANCING BLOW OF SLIGHTLY WARMER AIR THAN WHAT WE'VE HAD.
WHEREAS THE GFS IS MORE IN LINE WITH WHAT WE'VE HAD RECENTLY AND FOR
A LONGER PERIOD OF TIME.
AVIATION /18Z TAFS THROUGH 18Z MONDAY/
ISSUED AT 1155 AM EST SUN FEB 1 2026
QUIET, DRY WEATHER CONTINUES TODAY AS HIGH PRESSURE IS OVER THE
GREAT LAKES. CHANGES ARE COMING THOUGH FOR MONDAY AS A CLIPPER
SYSTEM DROPS IN FROM THE NORTHWEST. SOUTHERLY WINDS SHOULD PICK
UP THIS AFTERNOON TO AROUND 10KTS. CLOUDS ADVECT IN THIS EVENING
AND CEILINGS WILL RAPIDLY DROP OVERNIGHT. EXPECT VFR CEILINGS
UNTIL ABOUT 03Z-06Z MONDAY, THEN IFR CEILINGS AND VISIBILITIES
WILL PREVAIL AFTER 06Z-09Z MONDAY AS LIGHT SNOW BEGINS. AS
MONDAY MORNING PROGRESSES, CEILINGS WILL LIKELY DROP EVEN
FURTHER TO BETWEEN 500-1000 FT. SNOW EXITS THE AREA AROUND THE
END OF THE TAF FORECAST PERIOD, ALTHOUGH LOW CEILINGS WILL
REMAIN THROUGH AT LEAST THE AFTERNOON.
IWX WATCHES/WARNINGS/ADVISORIES
IN...NONE.
OH...NONE.
MI...NONE.
MARINE...NONE.
DISCUSSION...ROLLER
AVIATION...JOHNSON
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