340
FXUS63 KLOT 052057
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
257 PM CST THU FEB 5 2026
KEY MESSAGES
- ANOTHER CLIPPER SYSTEM WILL MOVE THROUGH THE REGION CENTERED
ON DAYBREAK TOMORROW WITH A THREAT FOR A WINTRY MIX. 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.
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 /18Z TAFS THROUGH 00Z SATURDAY/
ISSUED AT 1151 AM CST THU FEB 5 2026
KEY MESSAGES FOR THE 18Z TAF PERIOD:
* MVFR CIGS THROUGHOUT THE PERIOD; INTERMITTENT VFR POSSIBLE
THIS AFTERNOON
* A PUSH OF WINTRY PRECIP TONIGHT INTO EARLY FRIDAY WITH
ASSOCIATED IFR POSSIBLE. MOSTLY SNOW FAVORED IN CHICAGO WITH
A PERIOD OF SLEET OR FREEZING RAIN POSSIBLE, MAINLY WEST OF
CHICAGO
* ADDITIONAL SNOW SHOWERS POSSIBLE AROUND THE LAKE FRIDAY AFTERNOON
MVFR CIGS ARE EXPECTED TO HANG OVERHEAD THROUGHOUT THE PERIOD.
BOUTS OF VFR WILL BE POSSIBLE THIS AFTERNOON BEFORE MVFR TAKES
HOLD AGAIN BY THIS EVENING.
A SYSTEM OF WINTRY PRECIP WILL MOVE OVER THE TERMINALS LATE
TONIGHT INTO FRIDAY MORNING. AT CHICAGO, MOSTLY SNOW IS FAVORED,
BUT A PERIOD OF SLEET WILL ALSO BE POSSIBLE. A PERIOD OF
MODERATE TO HEAVY SNOW WILL EVEN BE POSSIBLE WITH <1SM
VISIBILITIES. CHICAGO SITES MAY SEE A FEW TENTHS OF ACCUMULATION
TO NEAR AN INCH ON THE HIGH END BY THE TIME THE SNOW WRAPS UP
MID-MORNING. SLEET AND FREEZING RAIN CHANCES ARE HIGHER OUT AT
DPA AND ESPECIALLY RFD. IT'S POSSIBLE THAT RFD SEES NO
MEASURABLE SNOW BUT A GLAZE OF ICE INSTEAD. ADDITIONALLY, CIGS
MAY DROP INTO IFR TERRITORY DURING THIS PERIOD.
EXPECT NNW WINDS GUSTING TO AROUND 25 KT DURING THE DAY ON
FRIDAY WITH CONTINUED MVFR CIGS. AN ADDITIONAL PUSH OF SNOW
SHOWERS IS EXPECTED TO DEVELOP OVER THE LAKE AND POSSIBLY BRING
PERIODS OF MVFR SNOW TO ORD, MDW, AND GYY FRIDAY AFTERNOON.
DOOM
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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