575
FXUS63 KLOT 060303
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
903 PM CST THU FEB 5 2026
KEY MESSAGES
- A WINTRY MIX WITH SNOW AND FREEZING DRIZZLE OVERNIGHT INTO
EARLY FRIDAY MORNING. LOCALLY HAZARDOUS TRAVEL MAY RESULT.
- A SHARP COLD FRONT WILL RACE THROUGH THE REGION FRIDAY
AFTERNOON. SNOW SHOWERS, INCLUDING SQUALL-LIKE BEHAVIOR, MAY
ACCOMPANY THE FRONT.
- A PERIOD OF NUISANCE LAKE EFFECT SNOW WILL OCCUR IN
NORTHWESTERN INDIANA FRIDAY NIGHT THROUGH SATURDAY.
- A PATTERN SHIFT WILL OCCUR NEXT WEEK TOWARD WARMER, AND
POTENTIALLY WETTER, CONDITIONS.
UPDATE
ISSUED AT 903 PM CST THU FEB 5 2026
PRECIPITATION IS DEVELOPING/SPREADING ACROSS NORTHWEST WI
CURRENTLY AND THIS WILL MOVE ACROSS THE LOCAL AREA OVERNIGHT
INTO EARLY FRIDAY MORNING. THE CURRENT FORECAST REMAINS MAINLY
ON TRACK THOUGH THERE CONTINUES TO BE MINOR SHIFTS IN THE CAM
GUIDANCE, MAINLY WOBBLES TO THE NORTHEAST WITH THE MAIN AREA OF
PRECIP. IF A SLIGHTLY NORTHEAST SHIFT CONTINUES, THIS WOULD
LIKELY ALLOW THE FAR WESTERN/SOUTHWEST CWA TO REMAIN DRY, WHILE
BRINGING THE CHANCE OF FREEZING DRIZZLE FURTHER EAST INTO THE
CHICAGO METRO AREA. SOME OF THE PRECIPITATION MAY ALSO BE
PARTIALLY CONVECTIVE, THUS POCKETS OF FREEZING RAIN WILL BE
POSSIBLE, BUT PERHAPS NOT WIDESPREAD. OPTED TO MAINTAIN THE
FREEZING DRIZZLE MENTION (VS. ADDING FREEZING RAIN) BUT DID
BRING THE FREEZING DRIZZLE ACROSS MUCH OF THE AREA EARLIER THEN
PREVIOUSLY FORECAST. CONFIDENCE REMAINS LOW FOR A WINTER WEATHER
ADVISORY AND OPTED TO MAINTAIN THE SPS AT THIS TIME.
ONE OTHER CHANGE WAS TO INCREASE THE NORTHWEST WINDS MUCH FASTER
FRIDAY MORNING. THE PRECIPITATION DURATION WILL BE SHORT AND AS
IT ENDS FRIDAY MORNING, NORTHWEST WINDS WILL RAPIDLY INCREASE
WITH A PERIOD OF GUSTS INTO THE 35 MPH RANGE POSSIBLE. CMS
DISCUSSION
ISSUED AT 257 PM CST THU FEB 5 2026
A ROBUST UPPER LEVEL JET-STREAK (140+ KT) CURRENTLY OVERTOPPING
THE WESTERN CONUS RIDGE AXIS WILL CARVE OUT A REINFORCING UPPER
TROUGH/LOW ACROSS THE EASTERN GREAT LAKES INTO SATURDAY. AS IT
DOES, AN ACTIVE NORTHWESTERLY FLOW PATTERN WILL REMAIN THE
DOMINANT FEATURE ACROSS OUR REGION. OF PARTICULAR INTEREST WITH
THIS PATTERN IS OUR NEXT CLIPPER-TYPE IMPULSE CURRENTLY NOTED
OVER THE PRAIRIE PROVIDENCES OF CANADA. THIS FEATURE WILL
QUICKLY DIVE SOUTHEAST INTO THE ARROWHEAD REGION OF MN THIS
EVENING, THEN RIGHT INTO OUR AREA BY DAYBREAK FRIDAY MORNING.
THE MAIN CONCERN WITH THIS FEATURE CONTINUES TO BE SHORT, BUT
ILL-TIMED PERIOD OF WINTRY PRECIPITATION EARLY FRIDAY MORNING.
THE WINDOW FOR WINTRY PRECIPITATION FROM THIS WEATHER SYSTEM
WILL REMAIN RATHER SHORT (~3-5 HOURS) LATE TONIGHT THROUGH EARLY
FRIDAY MORNING. PRECIPITATION TYPE WILL BE PROBLEMATIC,
PARTICULARLY WEST-SOUTHWEST OF THE CHICAGO METRO AREA. IN THIS
REGION, LOW-LEVEL WARM AIR ADVECTION IS EXPECTED TO DRIVE THE
NOSE OF A MELTING LAYER OFF THE SURFACE NORTHEASTWARD INTO
NORTHWESTERN AND CENTRAL IL. ALSO, THE SYSTEM TRACK WILL FAVOR
MORE MID-LEVEL DRYING AND POTENTIAL LOSE OF CLOUD ICE WEST-
SOUTHWEST OF THE CHICAGO METRO AREA. ACCORDINGLY, P-TYPES WEST-
SOUTHWEST OF THE METRO WILL FAVOR LIGHT FREEZING RAIN OR DRIZZLE
AND THE POTENTIAL FOR A LIGHT GLAZING OF ICE ON UNTREATED
SURFACES LATE TONIGHT.
ACROSS MOST OF THE NORTHEASTERN IL INTO NORTHWESTERN IN
(INCLUDING MUCH OF THE CHICAGO METRO AREA) THE PRECIPITATION
TYPE LATE TONIGHT INTO EARLY FRIDAY MORNING LOOKS TO BE
PRIMARILY SNOW. WHILE THE WINDOW FOR THIS SNOW WILL AGAIN ONLY
BE 3 TO 5 HOURS, THERE IS CONCERN THAT A "THUMP" OF CONVECTIVE
HEAVY SNOW MAY OCCUR JUST BEFORE DAYBREAK AS MID-LEVEL LAPSE
RATES STEEPEN (7C + PER KM) CONSIDERABLY AS STRONG DYNAMIC
FORCING ALONG THE LOW-LEVEL BAROCLINIC ZONE SETS UP WITHIN THE
EXIT REGION OF THE AFOREMENTIONED UPPER LEVEL JET STREAK. IF
THIS MATERIALIZES, WE COULD ENVISION A QUICK 1-2 INCH SNOWFALL
ACROSS PARTS OF THE METRO AREA IN THE 3 TO 6 AM TIMEFRAME.
WITH THE INCREASING POTENTIAL OF THIS PERIOD OF WINTRY
PRECIPITATION INTO THE EARLY FRIDAY MORNING COMMUTE WE HAVE
OPTED TO INCREASE THE MESSAGING OF THIS EVENT WITH AN SPS AND
THROUGH OUR AFTERNOON FORECAST GRAPHIC PUSH. AT THIS TIME, WE
CANNOT RULE OUT THE NEED FOR A SHORT FUSED WINTER WEATHER
ADVISORY, BUT WILL LET THE EVENING SHIFT GET ANOTHER LOOK.
THE WINTRY PRECIPITATION WILL COME TO A QUICK END FROM
NORTHWEST TO SOUTHEAST AROUND AND JUST AFTER DAYBREAK FRIDAY
MORNING. SURFACE TEMPERATURES WILL WARM INTO 30S LATE IN THE
MORNING, BUT ATTENTION THEN TURNS TO THE PERIOD OF STRONG NORTH-
NORTHWESTERLY WINDS (GUSTS 35 TO 40 MPH) EXPECTED IN THE
AFTERNOON FOLLOWING A COLD FRONTAL PASSAGE. STEEPENING LOW-LEVEL
LAPSE RATES MAY ALSO SUPPORT THE DEVELOPMENT OF SOME AFTERNOON
SNOW SHOWERS.
KJB
FRIDAY NIGHT ONWARD:
FALLING TEMPERATURES BEHIND THE COLD FRONT (850MB VALUES
DROPPING TOWARD -15C OR SO) AND PERSISTENT NORTH TO
NORTHWESTERLY WINDS WILL SUPPORT THE DEVELOPMENT OF PERSISTENT
LAKE EFFECT SNOW SHOWERS ACROSS NORTHWESTERN INDIANA FRIDAY
NIGHT THROUGH EARLY SATURDAY. CONSIDERING THE INNER UPPER-LEVEL
CYCLONIC SHEAR AXIS WILL BE WELL EAST OF OUR AREA BY THEN AND A
SURFACE HIGH WILL BE BUILDING INTO THE GREAT LAKES, INVERSION
HEIGHTS WILL STRUGGLE TO CLIMB BEYOND 5KFT. ACCORDINGLY, THE
LAKE EFFECT SNOW LOOKS MORE LIKE A NUISANCE THAN AN IMPACT, WITH
PERHAPS A FEW INCHES OF SNOW EAST OF GARY BY THE TIME SNOW ENDS
SATURDAY AFTERNOON. ELSEWHERE, SATURDAY WILL BE A BRIEF CHILLY
INTERLUDE WITH HIGHS IN THE 20S. THANKFULLY, THE ARRIVAL OF THE
SURFACE HIGH SHOULD LEAD TO SOMEWHAT LIGHT WINDS.
LOOKING TOWARD NEXT WEEK, A POWERFUL 200KT+ JET STREAK
ORIGINATING FROM THE KAMCHATKA PENINSULA OF RUSSIA WILL SPUR THE
DEVELOPMENT OF AGGREGATE TROUGHING ALONG THE PACIFIC COAST OF
THE US. AS THIS OCCURS, A CUT-OFF LOW PRESSURE SYSTEM WILL
DEVELOP ALONG THE SOUTHWESTERN US/NORTHWESTERN MEXICO BORDER.
THE NET EFFECT WILL BE A SUBSTANTIAL PUSH OF MID-LEVEL WARM AIR
ADVECTION ACROSS THE CENTRAL UNITED STATES, ALLOWING FOR THE
DEVELOPMENT OF COMPOSITE LARGE-SCALE RIDGING THROUGH THE GREAT
LAKES. CONFIDENCE HENCE REMAINS HIGH IN A PERIOD OF ABOVE
AVERAGE TEMPERATURES NEXT WEEK.
ENSEMBLE MODEL GUIDANCE CONTINUES TO EXHIBIT A SIGNAL FOR THE
DEVELOPMENT OF A SYNOPTIC-SCALE CYCLONE SOMEWHERE IN THE CENTRAL
US IN THE FEBRUARY 11-14 TIMEFRAME, THOUGH EXACTLY HOW AND
WHERE WILL LIKELY DEPEND ON THE EVOLUTION OF THE LEADING CUT-OFF
LOW PRESSURE SYSTEM AND ANY EJECTING SHORTWAVES FROM THE
AGGREGATE TROUGHING ALONG THE PACIFIC COAST.
BORCHARDT
AVIATION /00Z TAFS THROUGH 06Z SATURDAY/
ISSUED AT 555 PM CST THU FEB 5 2026
KEY MESSAGES FOR THE 00Z TAFS:
- GRADUALLY LOWERING MVFR CEILINGS THIS EVENING, WITH MVFR
LIKELY TO PREVAIL THROUGH THE REMAINDER OF THE PERIOD.
- PERIOD OF WINTRY PRECIPITATION EXPECTED LATE TONIGHT/EARLY
FRIDAY MORNING. MAINLY SNOW EXPECTED FARTHER EAST INTO THE
CHICAGO AREA SITES, WHILE A MIX OF SNOW/SLEET/FREEZING RAIN IS
MORE LIKELY WITH WESTWARD EXTENT (TOWARD KRFD). BRIEF IFR/LIFR
POSSIBLE EARLY FRIDAY DURING PRECIP ALONG WITH SOME SNOW
ACCUMS.
- WEST-SOUTHWEST WINDS TURN BLUSTERY NORTH-NORTHWEST BEHIND A
STRONG COLD FRONT FRIDAY MORNING. GUSTS 30-35 KTS LIKELY
DURING THE DAY/EARLY EVENING.
A WEAK SURFACE TROUGH WILL MOVE EAST ACROSS THE FORECAST AREA
THIS EVENING, WITH THE MAIN IMPACTS BEING A GRADUALLY LOWERING
MVFR CLOUD DECK AND SOUTHWEST WINDS DIMINISHING AND TURNING WEST-
SOUTHWEST.
ATTENTION THEN TURNS QUICKLY TO A STOUT UPPER-LEVEL DISTURBANCE
CURRENTLY TRACKING QUICKLY SOUTH-SOUTHEAST OUT OF SOUTHERN
MANITOBA. THIS DISTURBANCE IS FORECAST TO TRACK ACROSS THE
TERMINALS FRIDAY MORNING, RESULTING IN THE DEVELOPMENT OF MIX
OF WINTRY PRECIPITATION PREDAWN WITH A BURST OF MODERATE SNOW
THROUGH 8-9 AM. THERMAL PROFILES ARE WARMER THAN WE'VE SEEN IN
A WHILE, SETTING UP THE POTENTIAL FOR A MIX OF SNOW/SLEET INTO
THE CHICAGO METRO SITES, AND A MIX OF FREEING RAIN/SLEET SNOW
FARTHER WEST TOWARD KRFD ALONG THE WESTERN PERIPHERY OF THE
PRECIPITATION BAND. CURRENT HIGH-RES MODEL FORECAST SOUNDINGS
INDICATE CHICAGO TERMINALS WOULD SEE PRIMARILY SNOW, WITH
VISIBILITY POTENTIALLY DROPPING TO LESS THAN A MILE WITH
ACCUMULATIONS OF 1-2", BUT CAN'T RULE OUT SOME SLEET AT TIMES.
SLIGHTLY WARMER TEMPS ALOFT FARTHER TO THE WEST WOULD RESULT IN
MORE SLEET/FREEZING RAIN/FREEZING DRIZZLE AND AN ASSOCIATED
LIGHT GLAZE ON UNTREATED SURFACES AT RFD. STRONG MID-LEVEL
DRYING DEVELOPS IN THE WAKE OF THE DISTURBANCE BY MID-LATE
MORNING WHICH SHOULD QUICKLY END THE MAIN PRECIPITATION THREAT,
THOUGH THERE REMAINS A LOW (10% CHANCE) OF SOME SPOTTY FREEZING
DRIZZLE LINGERING FOR ALL SITES DURING THE MORNING.
A SHARP COLD FRONT IS THEN EXPECTED TO PUSH SOUTH ACROSS THE
TERMINALS BY MID-MORNING, TURNING WINDS NORTH-NORTHWEST WITH
INCREASING SPEEDS/GUSTS. SUSTAINED SPEEDS NEAR 20 KTS AND GUSTS
FREQUENTLY 30-35 KTS ARE EXPECTED THROUGH THE REMAINDER OF THE
DAY. A PERIOD OF CONVECTIVE SNOW SHOWERS APPEAR LIKELY FOR A FEW
HOURS IN THE MID-LATE AFTERNOON, POTENTIALLY WITH SOME BRIEF
MVFR/IFR VISIBILITIES. OTHERWISE, A FEW SCATTERED FLURRIES MAY
LINGER INTO EARLY EVENING FROM A GRADUALLY RISING MVFR DECK.
RATZER
LOT WATCHES/WARNINGS/ADVISORIES
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY FROM 10 AM FRIDAY TO 3 AM CST SATURDAY
FOR THE IL NEARSHORE WATERS.
GALE WARNING FROM NOON FRIDAY TO MIDNIGHT CST FRIDAY NIGHT FOR
THE IN NEARSHORE WATERS.
VISIT US AT WEATHER.GOV/CHICAGO
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