770
FXUS63 KLOT 042346
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
546 PM CST WED FEB 4 2026
KEY MESSAGES
- A PAIR OF CLIPPER SYSTEMS WILL RACE THROUGH THE REGION THROUGH
THE END OF THE WEEK. THE FIRST ON THURSDAY WILL BRING A CHANCE
FOR SOME LIGHT SNOW ACCUMULATIONS (LESS THAN A HALF INCH) TO
PARTS OF THE REGION.
- THE SECOND CLIPPER SYSTEM LATE THURSDAY NIGHT INTO FRIDAY
MORNING HAS THE POTENTIAL TO DELIVER A WINTRY MIX TO THE AREA.
- A PATTERN CHANGE TOWARD WARMER TEMPERATURES (HIGHS AND LOWS
BOTH ABOVE FREEZING) MAY MATERIALIZE BY THE MIDDLE OF NEXT
WEEK.
DISCUSSION
ISSUED AT 219 PM CST WED FEB 4 2026
PERSISTENT LOW STRATUS ALONG AND EAST OF I-55 HAS RECENTLY
SHOWED SOME SIGNS OF THINNING AND ERODING ALONG ITS WESTERN
PERIPHERY, AND THIS TREND SHOULD CONTINUE THROUGH THE AFTERNOON.
FARTHER TO THE EAST AND NEAR THE LAKE, CLOUD COVER APPEARS
LIKELY TO REMAIN ENTRENCHED, POTENTIALLY INTO AND THROUGH THE
EVENING. FLURRIES/INTERMITTENT LIGHT SNOW SHOWERS WILL GRADUALLY
FOCUS MAINLY ACROSS NORTHWEST INDIANA AS THE CLOUD-BEARING FLOW
TURNS NORTH TO NORTHWESTERLY.
THE FIRST IN A SERIES OF FAST-MOVING CLIPPER SYSTEMS WILL MOVE
SOUTHWARD OUT OF WISCONSIN TOMORROW MORNING. LARGE SCALE FORCING
LOOKS APPRECIABLE AS THIS FEATURE RAPIDLY SHIFTS ACROSS THE
REGION, WITH 500 MB HEIGHT FALLS ON THE ORDER OF 60-80 M/12
HOURS. WHILE OVERNIGHT GUIDANCE TRENDED DECIDEDLY "WETTER" WITH
THIS SYSTEM, THAT TREND HAS NOT NECESSARILY CONTINUED TODAY,
WITH A WIDE SPREAD IN FORECAST QPF ACROSS BOTH THE HIRES AND
MEDIUM-RANGE GUIDANCE SUITE, ALL OF WHICH SEEMS TO BE TIED TO
THE DEGREE OF LOW-LEVEL DRY AIR IN PLACE. EVEN THE INCOMING 18Z
HRRR APPEARS TO BE TRENDING A BIT LESS BULLISH ON PRECIP
INTENSITY AND COVERAGE. ALL THIS SAID, FORECAST SOUNDINGS EVEN
FROM GUIDANCE THAT DOES NOT FORMALLY PRODUCE PRECIP LOOKS VERY
CLOSE TO SUPPORTING LIGHT SNOW, PARTICULARLY NORTH AND EAST OF
ABOUT A ROCKFORD TO RENSSELAER LINE. GIVEN THE PROGGED ASCENT
WITH THIS FEATURE, HAVE CONTINUED TO INCREASE POPS A BIT
THURSDAY MORNING THROUGH MID AFTERNOON. P-TYPES MAINLY LOOK TO
BE SNOW WITH THIS SYSTEM, AND THE BRIEF-HITTING NATURE AND
GENERAL LACK OF DEEPER LAYERS OF INSTABILITY ARE EXPECTED TO CAP
SNOWFALL ACCUMULATIONS TO LESS THAN A HALF INCH.
AS THE SYNOPTIC SCALE TROUGH PASSES TO OUR SOUTH AND EAST,
FORECAST SOUNDINGS INDICATE A RAPID LOSS OF DEEPER SATURATION
THURSDAY AFTERNOON AND INTO THE EVENING. LINGERING WARM
ADVECTION AND ASSOCIATED MODEST FORCING IS FORECAST TO REMAIN IN
PLACE, WHICH LEADS THE DOOR OPEN TO AT LEAST A LOW CHANCE FOR
PRECIP TO END AS A LITTLE FREEZING DRIZZLE OR VERY LOW-QUALITY
SNOW/DRIZZLE ("SNIZZLE") MIX. AT THIS TIME, MODELED CLOUD
CEILINGS LOOK A BIT TOO HIGH, ALONG WITH SOME SIGNAL THAT THE
900-750 MB LAYER MAY TEND TO DRY OUT WITH TIME THAT WE HAVE
ELECTED TO FORGO A MENTION OF FREEZING DRIZZLE. WILL CONTINUE TO
KEEP A CLOSE EYE ON MODEL TRENDS, HOWEVER.
FAST ON THE HEELS OF THIS SYSTEM, THE NEXT WAVE WILL PIVOT
OVERHEAD LATE THURSDAY NIGHT THROUGH FRIDAY MORNING. THIS WAVE
LOOKS A BIT MORE COMPACT THAN THURSDAY'S CLIPPER, BUT ROUGHLY
SIMILAR IN THE MAGNITUDE OF FORCING, WITH SIGNIFICANT DCVA
FORECAST TO SHIFT ACROSS NORTHEAST ILLINOIS AND NORTHWEST
INDIANA THROUGH FRIDAY MORNING. ADDITIONALLY, GUIDANCE INDICATES
THIS FEATURE WILL ALSO BE ACCOMPANIED BY A PLUME OF SOMEWHAT
STEEPER LAPSE RATES IN THE 850-700 MB LAYER, THE RESULT OF WHICH
CAN BE SEEN IN QPF OUTPUT FROM GUIDANCE LIKE THE ECMWF, WITH
LOCALIZED SWATHS OF HIGHER AMOUNTS OVER A TENTH OF AN INCH.
STILL NOTING A SIGNIFICANT SPREAD IN THE HANDLING OF THE
SOUTHWEST TERMINUS OF THE MAIN PRECIP SHIELD WITH THIS SYSTEM,
HOWEVER. NBM-DELIVERED POPS FOR LATE THURSDAY NIGHT THROUGH
FRIDAY MORNING DID LOOK TOO LOW GIVEN THE LATEST ENSEMBLE
GUIDANCE, SO CONTINUED TO PAINT MID RANGE CHANCE POPS ACROSS THE
NORTHEAST HALF OF THE CWA, TRENDING LOWER FROM THERE WITH
SOUTHWEST EXTENT. P-TYPES COULD END UP BEING A BIT MORE
PROBLEMATIC WITH THIS SYSTEM AS INTENSIFYING W TO WNW LOW-LEVEL
FLOW IS SLATED TO DRIVE AN ABOVE-FREEZING AIRMASS ALOFT INTO
PARTS OF THE AREA EARLY FRIDAY MORNING WHICH BRINGS THE
POTENTIAL FOR SLEET AND FREEZING RAIN INTO THE PICTURE.
IT REMAINS A BIT UNCLEAR JUST HOW FAR NORTHEAST INTO THE REGION
ANY P-TYPE CHANGE OVER TO A WINTRY MIX WILL OCCUR, WITH SOME
DEGREE OF DYNAMIC COOLING LIKELY TO PERSIST ACROSS FAR NE
ILLINOIS, POTENTIALLY MAINTAINING ALL SNOW THERMO PROFILES
CLOSER TO THE LAKE. CHANCES FOR NON-SNOW P-TYPES INCREASE
QUICKLY THE FARTHER INLAND YOU GO, AND HAVE CONTINUED A GENERAL
WINTRY MESS WORDING IN THE GRIDDED FORECAST, BUT WILL NOTE THAT
SIGNIFICANT UNCERTAINTIES DURING THIS PART OF THE FORECAST
REMAIN. IF THE CONVECTIVE NATURE OF PRECIP MATERIALIZES WITH
THIS SYSTEM, COULD ENVISION SOME ROAD IMPACTS AND SUBSEQUENT
TRAVEL ISSUES DURING THE FRIDAY MORNING COMMUTE, BUT UNCERTAINLY
IN THE GENERAL EVOLUTION OF THINGS DURING THIS PERIOD REMAINS
QUITE HIGH.
THE ABOVE-FREEZING PORTION OF THE ATMOSPHERIC COLUMN WILL COOL
THROUGH LATE FRIDAY MORNING. WHILE SURFACE AIR TEMPERATURES MAY
CLIMB ABOVE FREEZING DURING THE AFTERNOON, WET BULB
TEMPERATURES ARE EXPECTED TO REMAIN NEAR TO JUST BELOW FREEZING
THROUGH THE DAY. AS LOW-LEVEL LAPSE RATES STEEPEN IN THE
DEEPENING CAA PUSH, SOME STREAKY SNOW SHOWER ACTIVITY MAY
DEVELOP AS THE TRAILING 850-700 MB VORT MAX ROLLS OVERHEAD.
ADDITIONALLY, HAVE BOOSTED WINDS A BIT ABOVE THE BLENDED
OFFERING AS BOUNDARY LAYER FLOW INCREASES TO AROUND 30 KTS.
CARLAW
A GLANCING BLOW OF ANOTHER POOL OF SEASONABLY COLD AIR WILL
RENDER TEMPERATURES TO FALL THIS WEEKEND. MEAN GEFS/EPS HIGHS
SETTLE INTO THE 20S ON SATURDAY AND WARM TOWARD 30 ON SUNDAY.
WILL NOTE THE NBM, WHICH INFORMS OUR EXTENDED FORECAST, IS
CURRENTLY 4 TO 6 DEGREES WARMER (IF NOT EVEN A BIT MORE) THAN
INPUT ENSEMBLE SUITES. SO, WOULD EXPECT OUR FORECAST HIGHS TO
LOWER AS WE GET CLOSER AND CAN MORE READILY ADJUST THE
TEMPERATURES.
NEXT WEEK:
ENSEMBLE MODEL GUIDANCE REMAINS IN AGREEMENT THAT THE UPPER-
LEVEL FLOW WILL SHIFT FROM A PERSISTENT NORTHWESTERLY FLOW
PATTERN TO MORE OF A SOUTHWESTERLY FLOW PATTERN THROUGH THE
COURSE OF NEXT WEEK. AM STARTING TO SEE A FLY IN THE OINTMENT IN
A MORE PRISTINE PATTERN SHIFT, BEING A CUT-OFF WAVE MEANDERING
ALONG THE US/MEXICO BORDER DURING THE FIRST HALF OF THE WEEK.
WITH THAT SAID, THE SIGNAL REMAINS IN ENSEMBLE MEAN FIELDS FOR
TEMPERATURES TO INCREASE NEXT WEEK WITH HIGHS GENERALLY IN THE
40S AND LOWS GENERALLY NEAR THE FREEZING MARK. THERE IS STILL A
SIGNAL FOR A SYNOPTIC SYSTEM SOMEWHERE IN THE BROAD CENTRAL US
REGION IN THE FEBRUARY 11 TO 14 TIMEFRAME, WHICH WOULD PROBABLY
PRESENT THE NEXT OPPORTUNITY FOR INCLEMENT WEATHER.
BORCHARDT
AVIATION /00Z TAFS THROUGH 06Z FRIDAY/
ISSUED AT 546 PM CST WED FEB 4 2026
AVIATION FORECAST CONCERNS FOR THE 00Z TAFS:
- MVFR CEILINGS SCATTERING OUT FROM NORTHWEST TO SOUTHEAST ACROSS
CHICAGO TERMINALS THIS EVENING.
- PERIOD OF SNOW SHOWERS THURSDAY MORNING/MIDDAY, WITH BRIEF
MVFR CONDITIONS POSSIBLE.
- MVFR CEILINGS LIKELY THURSDAY NIGHT.
A WEAK SURFACE HIGH PRESSURE RIDGE WAS DRIFTING SOUTHEAST ACROSS
THE AREA LATE THIS AFTERNOON. SURFACE WINDS HAVE BECOME LIGHT
AND VARIABLE WITHIN THE RIDGE AXIS, AND WILL EVENTUALLY BECOME
LIGHT SOUTHWEST LATER THIS EVENING. IN ADDITION, THE TRAILING
EDGE OF AN MVFR STRATUS LAYER WAS ALONG/JUST EAST OF A LINE FROM
ROUGHLY KBMI TO KORD AT TAF ISSUANCE TIME. THIS MVFR DECK WILL
SCATTER OUT SLOWLY AT KMDW AND KGYY DURING THE EVENING AS IT
CONTINUES TO DRIFT SLOWLY OFF TO THE EAST-SOUTHEAST.
EVENTUALLY, VFR MID AND HIGH CLOUDS WILL DEVELOP, LOWER AND
THICKEN OVERNIGHT INTO THURSDAY MORNING, IN ADVANCE OF AN UPPER
LEVEL DISTURBANCE DROPPING SOUTHEAST ACROSS THE WESTERN GREAT
LAKES. MODEL FORECASTS DIFFER SOMEWHAT IN HOW EFFECTIVELY TOP-
DOWN SATURATION OCCURS THURSDAY MORNING, THOUGH THE GENERAL
CONSENSUS IS THAT AT LEAST SOME INTERMITTENT LIGHT SNOW/SNOW
SHOWERS WILL DEVELOP AFTER SUNRISE AND PERSIST THROUGH LATE
MORNING/MIDDAY. PERIODS OF MVFR CIG/VIS CONDITIONS ARE POSSIBLE
WITH THIS PRECIPITATION. THERE IS SOME INDICATION IN MODEL
FORECASTS MOST AGGRESSIVE WITH LOW-LEVEL SATURATION THAT THERE
COULD BE SOME PATCHY LIGHT FREEZING DRIZZLE IN THE AFTERNOON AS
MID-LEVEL DRYING LEADS TO LOSS OF SNOWFLAKE GENERATION. THIS IS
OF LOW CONFIDENCE HOWEVER, AND THE MOST LIKELY OUTCOME MAY BE
THAT NO PRECIPITATION LINGERS PAST EARLY AFTERNOON ONCE SNOW
ENDS. THERE IS SOMEWHAT BETTER MODEL AGREEMENT HOWEVER, IN MVFR
CEILINGS THURSDAY EVENING.
SOUTHWEST WINDS MAY BECOME SOMEWHAT BREEZY AFTER SUNRISE,
GUSTING AT LEAST OCCASIONALLY INTO THE 15-20 KT RANGE DURING THE
DAY.
RATZER
LOT WATCHES/WARNINGS/ADVISORIES
IL...NONE.
IN...NONE.
LM...GALE WATCH FROM FRIDAY AFTERNOON THROUGH FRIDAY EVENING FOR
THE IN NEARSHORE WATERS.
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