438
FXUS63 KLOT 060923
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
323 AM CST FRI FEB 6 2026
KEY MESSAGES
- SNOW SHOWERS, WITH SOME SLEET/GRAUPEL, EARLY THIS MORNING.
TRAVEL IMPACTS EXPECTED, MAINLY ACROSS THE CHICAGO METRO AREA
INTO NORTHWEST INDIANA.
- PERIOD OF LAKE EFFECT SNOW FRIDAY NIGHT THROUGH SATURDAY
IN NORTHWEST INDIANA.
- A PATTERN SHIFT WILL OCCUR NEXT WEEK TOWARDS WARMER,
AND POTENTIALLY WETTER, CONDITIONS.
DISCUSSION
ISSUED AT 323 AM CST FRI FEB 6 2026
THROUGH TODAY:
WATER VAPOR IMAGERY THIS MORNING SHOWS A POTENT SHORTWAVE DIVING
SOUTH INTO THE WESTERN GREAT LAKES. AN AREA OF SNOW ASSOCIATED
WITH THIS SHORTWAVE COVERS MUCH EASTERN/SOUTHEASTERN WISCONSIN.
RADAR PRESENTATION OF THIS SNOW DEFINITELY IS CONVECTIVE IN
NATURE, UNSURPRISINGLY GIVEN THE STEEP MID LEVEL LAPSE RATES
ACROSS THE REGION. HAVE SEEN A NUMBER "UNKNOWN PRECIPITATION"
REPORTS FROM AWOS/ASOS SITES ACROSS WISCONSIN, GIVEN THE HIGH
CLOUD BASES AND CONVECTIVE NATURE OF THE PRECIPITATION, SUSPECT
THIS IS GRAUPEL OR SNOW PELLETS.
ANTICIPATE THIS AREA OF SNOW, MIXED AT TIMES WITH GRAUPEL,
SLEET, OR SNOW PELLETS, TO OVERSPREAD ABOUT THE NORTHEAST HALF
OR SO OF OUR CWA DURING THE PREDAWN HOURS, THEN RAPIDLY END FROM
NORTHWEST TO SOUTHEAST DURING THE EARLY-MID MORNING HOURS. MOST
CONCENTRATED AREA OF PRECIP AND HIGHEST AMOUNTS SHOULD END UP
OVER THE CHICAGO METRO AREA INTO EXTREME NORTHWEST INDIANA,
WHEN A QUICK INCH OR SO OF SNOW COULD FALL THIS MORNING.
CERTAINLY POSSIBLE THAT THERE COULD BE SOME HEAVIER BURSTS OF
SNOW WITH THE MORE INTENSE CONVECTIVE ELEMENTS. ROADWAYS
IMPACTS ARE LIKELY DURING THE RUSH HOUR THIS MORNING.
OPTED TO REMOVE FREEZING DRIZZLE FROM THE FORECAST AS LOW LEVELS
SHOULD BE TOO DRY FOR DRIZZLE AND CLOUD BASES TOO HIGH. OPTED TO
MAINTAIN A SLIGHT CHANCE FOR SOME FREEZING RAIN, BUT PLAN TO
DOWNPLAY THAT THREAT IN MESSAGING AS CONVECTION DEEP ENOUGH FOR
PRECIPITATION SHOULD ALSO BE DEEP ENOUGH TO HAVE ICE NUCLEI
PRESENT TO SUPPORT SNOW, GRAUPEL, OR SNOW PELLETS. WHILE SNOW
LOOKS TO HIT AT AN INOPPORTUNE TIME, TOTALS SHOULD BE TOO LIGHT
TO WARRANT A WINTER WEATHER ADVISORY, SO PLAN TO RE-ISSUE AND
FRESHEN UP THE SPECIAL WEATHER STATEMENT.
GUSTY NORTH-NORTHWEST WINDS WILL DEVELOP THIS MORNING AND
CONTINUE THROUGH THE AFTERNOON. WHILE THERE COULD BE A COUPLE
HOURS WITH SOME BREAKS IN THE CLOUDS, STRATOCUMULUS SHOULD FILL
BACK IN THIS AFTERNOON. THE CLOUD COVER MAY TEMPER THE MAGNITUDE
OF THE GUSTS SOME, BUT FORECAST SOUNDINGS DEPICT STEEP LOW LEVEL
LAPSE RATES TAPPING INTO 35-40KT WINDS A FEW THOUSAND FEET OFF
THE DECK. CERTAINLY POSSIBLE WE COULD SEE A COUPLE GUSTS TO 40
MPH TODAY, PARTICULARLY WITH ANY CLEARING/PARTIALLY CLEARING.
- IZZI
TONIGHT THROUGH THURSDAY:
A DEEPENING TROUGH IS EXPECTED TO BE TRAVERSING ACROSS THE
GREAT LAKES TONIGHT INTO SATURDAY WITH NORTHERN IL AND NORTHWEST
IN RESIDING ON THE WESTERN PERIPHERY OF SAID TROUGH. WHILE THE
DRYING MID-LEVELS ON THE BACKSIDE OF THE TROUGH WILL ALLOW
PRECIPITATION TO CONCLUDE FOR MOST OF THE AREA THIS
AFTERNOON/EVENING, INCREASING SURFACE CONVERGENCE OVER SOUTHERN
LAKE MICHIGAN WILL DEVELOP A BAND OF LAKE EFFECT SNOW FOR
PORTIONS OF NORTHWEST AND NORTHERN IN. FORECAST SOUNDINGS SHOW
THE LAKE EFFECT PARAMETERS TO BE DECENT WITH ELS AROUND
5000-5500 FT AND STEEP LOW-LEVEL LAPSE RATES (AROUND 7-8C/KM)
RESIDING WITHIN THE DGZ WHICH COULD ALLOW FOR A LOCALIZED COUPLE
INCHES OF ACCUMULATION ESPECIALLY IN EASTERN PORTER COUNTY NEAR
THE CONVERGENCE AXIS. HOWEVER, WITH ELS EXPECTED TO BE LOWERING
OVERNIGHT AS HIGH PRESSURE BUILDS IN AND NORTHWEST WINDS
PUSHING THE BAND MORE INTO NORTHERN IN THERE IS A PLAY FOR THE
BULK OF ANY ACCUMULATION TO STAY EAST OF OUR AREA. GIVEN THE
FINICKY NATURE OF LAKE EFFECT THERE IS A CHANCE THINGS COULD
SHIFT SLIGHTLY AS WE GET CLOSER, BUT FOR NOW HAVE KEPT OUR
OFFICIAL FORECAST MORE IN LINE WITH THE MORE EASTWARD SOLUTIONS
WITH HIGHEST POPS (30-50%) IN EASTERN PORTER COUNTY AND NORTHERN
IN AND ACCUMULATIONS IN THE 0.5-1.0 INCH RANGE (HIGHEST AGAIN
IN EASTERN PORTER COUNTY).
THE LAKE EFFECT WILL GRADUALLY WANE SATURDAY MORNING WITH HIGH
PRESSURE SETTLING OVERHEAD GIVING AS A QUIET BUT CHILLY SATURDAY
WITH HIGHS IN THE MID TO UPPER 20S. HOWEVER, A SHORTWAVE TROUGH
IS FORECAST TO DIVE ACROSS THE WESTERN GREAT LAKES LATE
SATURDAY NIGHT INTO SUNDAY WHICH MAY LEAD TO A PERIOD OF LIGHT
SNOW SHOWERS AND/OR FLURRIES FOR SOME. WHILE GUIDANCE IS IN GOOD
AGREEMENT ON THE SHORTWAVE TRACK AND TIMING, FORECAST SOUNDINGS
SHOW MOISTURE (ESPECIALLY IN THE MID-LEVELS) MAY BE SOMEWHAT OF
A LIMITING FACTOR AND THUS MOST OF OUR AREA MAY REMAIN DRY.
THAT SAID, GIVEN SOME DECENT LOW-LEVEL MOISTURE AND THE
COMBINATION OF WARM ADVECTION AND ASCENT WITH THE WAVE HAVE
OPTED TO INTRODUCE SOME SLIGHT CHANCE (15- 20%) POPS OVER FAR
NORTHEAST IL AND NORTHWEST IN IN CASE SOME SNOW SHOWERS ARE ABLE
TO MATERIALIZE. REGARDLESS ANY SNOW THAT DOES OCCUR DOESN'T
LOOK TO AMOUNT TO MUCH IN THE WAY OF ACCUMULATIONS ASIDE FROM
MAYBE A LIGHT DUSTING.
HEADING INTO NEXT WEEK, THE NORTHWEST ORIENTED UPPER PATTERN
THAT HAS KEPT US IN COLD THESE PAST FEW WEEKS WILL BEGIN TO
BECOME MORE ZONAL (EAST-WEST ORIENTED) BY MONDAY. THIS SHIFT
WILL ALLOW FOR MORE PERSISTENT PERIODS OF WARM ADVECTION WHICH
IN TURN IS EXPECTED TO ALLOW TEMPERATURES TO MODERATE INTO THE
40S TO NEAR 50 BY THE MIDDLE OF THE WEEK. THE ONLY CAVEAT THOUGH
IS A BAROCLINIC ZONE THAT IS FORECAST TO ESTABLISH ACROSS THE
MID-MISSISSIPPI VALLEY AND WESTERN GREAT LAKES WHICH COULD
RESULT IN A GRADIENT IN TEMPERATURES IF IT WERE TO SET UP
OVERHEAD. ADDITIONALLY, A COUPLE OF SHORTWAVES ARE ALSO FORECAST
TO TRAVERSE THROUGH THE ZONAL FLOW (ONE OVER THE UPPER MIDWEST
AND NORTHERN GREAT LAKES AND THE OTHER OVER THE DEEP SOUTH) AND
MAY KICK OFF SOME PRECIPITATION LATE TUESDAY INTO WEDNESDAY. IF
SUFFICIENT MOISTURE CAN BUILD INTO THE AREA THEN PRECIPITATION
SHOULD INITIALLY START OFF AS RAIN TUESDAY EVENING (WITH PERHAPS
AN ISOLATED THUNDERSTORM GIVEN THE 6-7C/KM LAPSE RATES ALOFT)
BEFORE TRANSITIONING TO SNOW (OR A RAIN/SNOW MIX) AS THE
BAROCLINIC ZONE SHIFTS SOUTH AS A COLD FRONT ON WEDNESDAY. WITH
A LOT OF UNCERTAINTY IN QUALITY OF MOISTURE RETURN TO OUR AREA
HAVE OPTED TO MAINTAIN THE 20-40% POPS LATE TUESDAY THROUGH
WEDNESDAY FOR NOW.
DEPENDING ON HOW FAR SOUTH THE AFOREMENTIONED BAROCLINIC ZONE
GETS WEDNESDAY WILL DETERMINE WHETHER OR NOT ADDITIONAL PERIODS
OF PRECIPITATION WILL OCCUR THROUGHOUT THE REST OF THE WEEK AS
MORE SHORTWAVES PIVOT THROUGH THE REGION. GIVEN HOW GUIDANCE
TENDS TO STRUGGLE WITH BAROCLINIC ZONES (ESPECIALLY 5-7 DAYS
OUT) SAW NO REASON TO CHANGE THE 20-30% POPS OFFERED BY THE NBM
THROUGH THE END OF NEXT WEEK. HOWEVER, DO THINK THAT SOME DRY
PERIODS WILL ALSO BE POSSIBLE ESPECIALLY IF THE BAROCLINIC ZONE
CAN SHIFT FAR ENOUGH SOUTH. REGARDLESS, MORE TYPICAL
TEMPERATURES FOR MID-FEBRUARY ARE FORECAST TO CLOSE OUT NEXT
WEEK WITH HIGHS IN THE 30S TO AROUND 40 AND OVERNIGHT LOWS IN
THE 20S.
YACK
AVIATION /06Z TAFS THROUGH 12Z SATURDAY/
ISSUED AT 1055 PM CST THU FEB 5 2026
KEY MESSAGES FOR THE 06Z TAFS:
- PERIOD OF WINTRY PRECIPITATION EXPECTED EARLY FRIDAY MORNING.
MAINLY SNOW EXPECTED FOR ORD/MDW/GYY, THOUGH CAN'T RULE OUT
SOME SLEET MIXING IN. MORE SLEET MAY MIX AT DPA, WITH FZRA/PL
MORE LIKELY FARTHER WEST TOWARD RFD. IFR VIS/CIGS POSSIBLE.
- WIND SHIFT TO STRONG NNW BY MID-MORNING, WITH GUSTS 30-35 KT.
STRONGEST PUSH OF WINDS MAY FOCUS WEST OF CHICAGO TERMINALS. WINDS
ONLY GRADUALLY DIMINISH AFTERNOON/NIGHT.
- SCATTERED AFTERNOON FLURRIES AND SNOW SHOWERS POSSIBLE FOR
CHICAGO TERMINALS, WITH BRIEF MVFR/IFR VIS POSSIBLE.
A STRONG UPPER LEVEL DISTURBANCE WILL DIG SOUTHEAST ACROSS THE
AREA INTO FRIDAY MORNING, AND IS EXPECTED TO PRODUCE A 3-5 HOUR
PERIOD OF WINTRY PRECIPITATION ACROSS NORTHEAST IL AND NORTHWEST
IN. THERMAL PROFILES ARE WARM ENOUGH FARTHER WEST TOWARD RFD
THAT A MIX OF FZRA/PL IS LIKELY, WHILE A SLIGHTLY COLDER COLUMN
FARTHER EAST INTO THE CHICAGO METRO TAF SITES SHOULD SUPPORT
PRIMARILY SNOW, THOUGH CAN'T RULE OUT SOME MIXING WITH SLEET.
PRECIPITATION MAY BE SOMEWHAT SHOWERY, WITH VARYING INTENSITY.
BRIEF IFR/LIFR VIS POSSIBLE IN PERIODS OF MODERATE SNOW, WITH
ACCUMULATIONS UP TO 1-2" POSSIBLE. PRECIPITATION ENDS QUICKLY
TOWARD MID-MORNING, AS A SHARP COLD FRONT PUSHES SOUTH ACROSS
THE AREA. COOLING OF THE COLUMN BEHIND THE FRONT WILL LIKELY
SUPPORT SCATTERED CONVECTIVE SNOW SHOWERS DURING THE AFTERNOON,
WITH BRIEF MVFR/IFR VSBY REDUCTIONS, ESPECIALLY NEAR THE LAKE
AND FOR GYY. OTHERWISE, MVFR CEILINGS WILL GRADUALLY LIFT
THROUGH THE AFTERNOON AND EARLY EVENING HOURS BEFORE SCATTERING
OUT. A FEW NON-IMPACTFUL FLURRIES MAY SQUEEZE OUT OF THIS DECK
AT TIMES INTO THE EVENING.
SURFACE WINDS ARE EXPECTED TO TURN NORTH-NORTHWEST BEHIND THE
COLD FRONT FRIDAY MORNING, AND BECOME STRONG AND GUSTY. WIND
GUSTS IN THE 30-35 KT RANGE ARE LIKELY DURING THE MORNING AND
EARLY AFTERNOON, WITH A FEW HIGHER GUSTS POSSIBLE ESPECIALLY AT
RFD AS THE AXIS OF STRONGEST WINDS APPEARS TO FOCUS WEST OF THE
CHICAGO METRO. WINDS WILL ONLY GRADUALLY EASE FRIDAY
AFTERNOON/NIGHT.
RATZER
LOT WATCHES/WARNINGS/ADVISORIES
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY FROM 8 AM THIS MORNING TO 3 AM CST
SATURDAY FOR THE IL NEARSHORE WATERS.
GALE WARNING FROM 10 AM THIS MORNING TO MIDNIGHT CST TONIGHT
FOR THE IN NEARSHORE WATERS.
VISIT US AT WEATHER.GOV/CHICAGO
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