500
FXUS63 KLOT 020256
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
856 PM CST SUN FEB 1 2026
KEY MESSAGES
- A LIGHT COATING TO HALF INCH OF SNOW IS LIKELY (70%+ CHANCE)
TONIGHT INTO EARLY MONDAY MORNING.
- THERE IS A CHANCE (30-40%) FOR FREEZING DRIZZLE FOR A COUPLE
HOURS BEHIND THE SNOW TONIGHT. IF FREEZING DRIZZLE OCCURS SOME
ICY SURFACES MAY MATERIALIZE.
UPDATE
ISSUED AT 856 PM CST SUN FEB 1 2026
THE SHORTWAVE TROUGH IS BEGINNING TO PIVOT INTO NORTHERN IL
THIS EVENING AND WILL CONTINUE THROUGH THE AREA OVERNIGHT.
ASSOCIATED WITH THE SHORTWAVE IS A BAND OF SNOW THAT IS JUST
ENTERING THE I-39 CORRIDOR BUT WILL SPREAD EAST THROUGH THE
EARLY OVERNIGHT HOURS. WHILE ACCUMULATIONS WITH THE SNOW WILL
ONLY BE UP TO A HALF INCH AT WORST, SOME AREAS OF FREEZING
DRIZZLE HAVE DEVELOPED BEHIND THE SNOW IN EASTERN IA AND
SOUTHWEST WI. FORECAST SOUNDINGS FROM ACROSS OUR CWA CONTINUE TO
SHOW CLOUD TOP TEMPERATURES HOVERING IN THE -9 TO -10C RANGE
BEHIND THE SNOW WHICH IS ON THE MORE MARGINAL SIDE FOR FREEZING
DRIZZLE AND MAY SUPPORT MORE POOR QUALITY FLURRIES THAN TRUE
DRIZZLE. COUPLE THIS WITH THE FACT THAT CLOUD BASES SHOULD
HOVER AROUND 1000-1500 FT (IDEALLY WANT 800 FT OR LOWER BASES),
CONFIDENCE IS LOW AS TO HOW FAR EAST THE FREEZING DRIZZLE WILL
GET AND HOW WIDESPREAD IT WILL BE.
THAT SAID, WITH THE FREEZING DRIZZLE ONGOING HAVE OPTED TO
INCLUDE A FORMAL MENTION IN THE FORECAST (30-40% CHANCE). IF
FREEZING DRIZZLE DOES INDEED OCCUR IT WILL LIKELY ONLY LAST 2-3
HOURS AT ANY ONE LOCATION, BUT WILL LIKELY LEAD TO SOME ICY
SURFACES ESPECIALLY IF THEY ARE UNTREATED. GIVEN THE SLIPPERY
TRAVEL THREAT HAVE ALSO ISSUED A SPECIAL WEATHER STATEMENT
THROUGH MIDNIGHT FOR AREAS ALONG AND NORTH OF I-80.
REGARDLESS ON THE COVER OF FREEZING DRIZZLE, PRECIPITATION IS
EXPECTED TO TAPER BY DAYBREAK MONDAY MORNING. WHILE CLOUD COVER
SHOULD GRADUALLY THIN THROUGH THE DAY MONDAY, EXPECT PARTLY TO
MOSTLY CLOUD CONDITIONS TO PREVAIL. THOUGH WITH MODEST WARM
ADVECTION TEMPERATURES SHOULD ONCE AGAIN TOP OUT IN THE UPPER
20S TO AROUND 30 MONDAY AFTERNOON.
YACK
DISCUSSION
ISSUED AT 212 PM CST SUN FEB 1 2026
MID AND HIGH-LEVEL CLOUD COVER CONTINUES TO INCREASE FROM WEST-
TO-EAST IN ASSOCIATION WITH OUR NEXT WEATHER SYSTEM SHIFTING
EASTWARD ACROSS THE MISSISSIPPI VALLEY EARLY THIS AFTERNOON. AN
AREA OF LIGHT SNOW HAS ALSO DEVELOPED WEST OF THE AREA THROUGH
THE MORNING WITHIN A REGION OF DEEPER MOISTURE AND ISENTROPIC
UPGLIDE. WHILE THIS AREA OF LIGHT SNOW IS ATTEMPTING TO SHIFT
EASTWARD INTO WESTERN IL AT THIS TIME, IT IS ALSO FIGHTING
AGAINST DRIER AIR BELOW 10,000 FEET ACROSS NORTHERN IL.
ACCORDINGLY, IT IS GOING TO TAKE TIME FOR THE SNOW TO MAKE
EASTWARD EXTENT INTO THE CHICAGO METRO AREA THIS EVENING, LIKELY
NOT ONSETTING HERE UNTIL SOMETIME AFTER 8 OR 9 THIS EVENING.
EVEN AFTER IT STARTS SNOWING THIS EVENING, RATES ARE EXPECTED TO
REMAIN LIGHT, OWING TO RATHER POOR FORCED ASCENT AND ONLY
MODEST MOISTURE IN THE DGZ. SO, WHY THE POTENTIAL FOR SNOW
TONIGHT IS HIGH (70%+), THE POOR SNOW QUALITY (SMALL FLAKE
SIZES) AND LIGHT RATES IS NOT GOING TO AMOUNT TO MUCH (ONLY A
LIGHT COATING TO AS MUCH AS ONE HALF INCH). THE LIGHT SNOW IS
EXPECTED TO END PRIOR TO DAYBREAK MONDAY MORNING FOR MOST.
FORECAST SOUNDINGS OVERNIGHT INDICATE POOR MOISTURE IN THE DGZ
FOR A PERIOD, WHICH SUGGESTS THERE TO BE A LOW, BUT NON-ZERO,
CHANCE FOR SOME LIGHT FREEZING DRIZZLE. WHILE THE POSSIBILITY
FOR THIS CANNOT BE TOTAL RULED OUT, CLOUD TEMPERATURES MAY
REMAIN JUST COLD ENOUGH (~-10C) TO KEEP ANY LINGERING LIGHT
PRECIPITATION IN THE FORM OF LOW QUALITY SNOW FLAKES OVERNIGHT.
ALSO, THE WINDOW FOR THIS POSSIBILITY ALSO LOOKS LIMITED TO ONLY
A COUPLE HOURS AT ANY GIVEN LOCATION. FOR THESE REASONS, WE
HAVE OPTED TO KEEP THE MENTION OUT OF THE FORECAST AT THIS TIME.
ASIDE FROM THE CHANCE OF A FEW OCCASIONAL FLURRIES FROM A
LINGERING STRATO CU DECK ON MONDAY, CONDITIONS WILL REMAIN
QUIET, WITH HIGHS IN THE MID TO UPPER 20S.
LATE MONDAY NIGHT THROUGH EARLY TUESDAY MORNING, EYES WILL BE
ON THE NEXT MID-LEVEL IMPULSE EXPECTED TO DROP SOUTHEASTWARD
ALONG THE LOWER-LEVEL BAROCLINIC ZONE DRAPED FROM THE DAKOTA'S
INTO THE MIDWEST. AS IT DOES, WE COULD EXPERIENCE ANOTHER
COATING OF SNOW SOMETIME LATE MONDAY NIGHT INTO TO EARLY TUESDAY
MORNING. THE NBM DID NOT OFFER UP ANY POPS FOR THIS PERIOD, BUT
IN COLLABORATION WITH NEIGHBORING OFFICES, WE OPTED TO ADD A
SLIGHT (20%) CHANCE FOR SOME LIGHT SNOW LATE MONDAY NIGHT. AT
THE PRESENT TIME, WE HAVE ONLY ADDED THIS CHANCE TO NORTHWESTERN
PARTS OF IL. ADMITTEDLY, HOWEVER, WE COULD SEE THE NEED FOR
THESE CHANCES TO BE EXPANDED INTO MUCH OF NORTHERN IL WITH
FUTURE FORECAST UPDATES. OTHERWISE, THE MAIN CHANCES FOR SNOW
LATER TUESDAY WITH THIS WAVE ARE EXPECTED TO QUICKLY TRANSITION
TO OUR SOUTHEAST ACROSS THE OHIO VALLEY.
A RATHER MARGINAL LAKE-EFFECT SNOW SET-UP INTO NORTHWEST
INDIANA AND ALONG THE ILLINOIS SHORE WILL THEN BE THE NEXT FOCUS
FOR PRECIP TUESDAY NIGHT INTO WEDNESDAY MORNING. LOW INVERSION
HEIGHTS AND BORDERLINE THERMO PROFILES INDICATE THE PRECIP WILL
BE LIMITED TO ISOLATED TO SCATTERED LIGHT SHOWERS. WE HAVE
MAINTAINED THE GOING CHANCE POPS WITH LITTLE ACCUMULATION DURING
THIS WINDOW.
BROADER NORTHWEST FLOW WILL PERSIST MIDWEEK THROUGH NEXT
WEEKEND. TEMPS WILL MODERATE TO ABOVE FREEZING ON THURSDAY, AND
FRIDAY, WHICH WOULD BE THE FIRST TIME IN AROUND THREE WEEKS FOR
MUCH OF THE AREA. THIS WOULD ALSO COME WITH A POTENTIAL FOR MORE
ACTIVE WEATHER IN THE REGION LATE IN THE WEEK, WITH CHANCES OF
ACCUMULATING SNOW AND PERHAPS MIXED PRECIP. ANOTHER PERIOD OF
COLDER CONDITIONS THEN APPEARS TO BE IN STORE FOR NEXT WEEKEND.
KJB
AVIATION /00Z TAFS THROUGH 06Z TUESDAY/
ISSUED AT 540 PM CST SUN FEB 1 2026
FORECAST CONCERNS FOR THE TERMINALS...
- PERIOD OF SNOW TONIGHT RESULTING IN REDUCED VISIBILITIES AND
SOME ACCUMULATION.
- MVFR CEILINGS TO PERSIST INTO MONDAY MORNING BEFORE IMPROVING
TO VFR MONDAY AFTERNOON.
A SHORTWAVE TROUGH CONTINUES TO PIVOT OUT OF THE UPPER MIDWEST
TOWARDS NORTHERN IL WHICH HAS DEVELOPED AN AREA OF SNOW ACROSS
EASTERN IA AND SOUTHERN MN. WHILE THE LIGHT RADAR ECHOES OVER
NORTHERN IL HAVE RESULTED IN SOME OCCASIONAL FLURRIES, THE TRUE
ACCUMULATING SNOW WITH REDUCED VISIBILITIES IS STILL NEAR THE
MISSISSIPPI RIVER AND WON'T REACH THE TERMINALS UNTIL 03-05Z,
EARLIEST AT RFD. ONCE THE SNOW ARRIVES EXPECT A FEW HOUR PERIOD
OF MVFR TO IFR VISIBILITIES (2-3SM) BEFORE SNOW STARTS TO PUSH
EAST AND TRANSITIONS MORE TO LIGHT SNOW AND FLURRIES FOR THE
REST OF THE OVERNIGHT HOURS. GIVEN PROGRESSIVE NATURE AND MODEST
SNOW RATES, ACCUMULATIONS LOOK TO GENERALLY BE LESS THAN 0.5
INCHES FOR THIS EVENT.
HEADING INTO MONDAY, THE LIGHT SNOW/FLURRIES WILL GRADUALLY COME
TO A CLOSE BY MID-MORNING. HOWEVER, MVFR CEILINGS ARE EXPECTED
TO PREVAIL THROUGH THE LATE MORNING HOURS BEFORE ATTEMPTING TO
LIFT BACK TO A 3000-4000 DECK. HOW QUICKLY CEILINGS RETURNS TO
VFR REMAINS A BIT UNCERTAIN BUT DIDN'T SEE ANY REASON TO ALTER
THE PREVAILING TIME IN THE TAFS AT THIS POINT. REGARDLESS,
CEILINGS SHOULD CONTINUE TO LIFT THROUGH MONDAY AFTERNOON SO VFR
CONDITIONS ARE EXPECTED BY THE END OF THE TAF PERIOD. OTHERWISE,
EXPECT SOUTH-SOUTHWEST WINDS TONIGHT TO BECOME MORE WEST-
NORTHWEST MONDAY MORNING WITH SPEEDS REMAINING AROUND 10-12 KTS.
YACK
LOT WATCHES/WARNINGS/ADVISORIES
IL...NONE.
IN...NONE.
LM...NONE.
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