249
FXUS63 KLOT 162033
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
233 PM CST SUN FEB 16 2025
KEY MESSAGES
- BITTERLY COLD CONDITIONS ARE EXPECTED SUNDAY NIGHT THROUGH
THURSDAY MORNING.
- THERE'S A LOW (10-20%) CHANCE OF FLUFFY ACCUMULATING SNOW
WELL SOUTH OF I-80 MONDAY AFTERNOON AND EVENING, THEN ANOTHER
CHANCE (30-40%) OF FLUFFY ACCUMULATING SNOW AND ASSOCIATED
TRAVEL IMPACTS AREAWIDE LATE TUESDAY NIGHT THROUGH WEDNESDAY
NIGHT.
- TEMPERATURES WILL GRADUALLY WARM BACK TOWARD AND EVEN ABOVE
NORMAL FOR THIS TIME OF YEAR NEXT WEEKEND AND BEYOND.
DISCUSSION
ISSUED AT 233 PM CST SUN FEB 16 2025
THROUGH MONDAY NIGHT:
A BROAD UPPER-TROUGH CONTINUES TO GRADUALLY WORK ITS WAY
EASTWARD ACROSS THE AREA THIS AFTERNOON WHICH HAS MAINTAINED
SOME LIGHT SNOW SHOWERS AND FLURRIES. WHILE THESE SNOW
SHOWERS/FLURRIES ARE EXPECTED TO PERSIST THROUGH THE EVENING, NO
ACCUMULATION IS EXPECTED TO OCCUR DUE TO THE POOR SNOW QUALITY.
HOWEVER, SOME VISIBILITY REDUCTIONS MAY MATERIALIZE AS
"HEAVIER" SHOWERS MOVE THROUGH. OUTSIDE OF THE FLURRIES, GUSTY
NORTHWEST WINDS WILL PERSIST THROUGH MUCH OF THE NIGHT WITH THE
HIGHEST GUSTS (UPWARDS OF 30 MPH) EXPECTED THROUGH MIDNIGHT.
AS THE SNOW ENDS, SKIES SHOULD CLEAR OUT FAIRLY QUICKLY
ALLOWING TEMPERATURES TO FOLLOW SUITE AND DIP INTO THE LOW
SINGLE DIGITS WITH PORTIONS OF NORTHWEST IL LIKELY TO SEE SUB-
ZERO READINGS. COUPLE THESE TEMPERATURES WITH THE AFOREMENTIONED
WINDS, WIND CHILLS ARE EXPECTED TO BOTTOM OUT IN THE -10F TO -25F
RANGE (COLDEST VALUES ACROSS NORTHWEST IL AND NEAR THE IL-WI
LINE). THEREFORE, A COLD WEATHER ADVISORY REMAINS IN EFFECT
THROUGH MONDAY MORNING FOR THESE WIND CHILLS SO BE SURE TO
BUNDLE UP BEFORE HEADING OUT THE DOOR MONDAY MORNING.
HEADING INTO MONDAY, A SURFACE HIGH WILL BEGIN TO BUILD INTO
THE AREA RESULTING IN DRY CONDITIONS AND MOSTLY TO PARTLY SUNNY
SKIES. DESPITE THE SUN, TEMPERATURES MONDAY AFTERNOON ARE ONLY
EXPECTED TO TOP OUT IN THE LOWER TEENS. WINDS ON MONDAY WILL BE
LIGHTER AS WELL BUT STILL BLUSTERY ENOUGH (GUSTS AROUND 20 MPH)
TO KEEP AFTERNOON WIND CHILLS BELOW ZERO. A SHORTWAVE
DISTURBANCE IS EXPECTED TO DEVELOP ACROSS THE CENTRAL PLAINS
MONDAY AFTERNOON AND MOVE EASTWARD INTO CENTRAL IL MONDAY NIGHT.
WHILE MOST OF OUR AREA WILL REMAIN DRY FROM THIS DISTURBANCE,
THERE IS SOME LOW AND MID-LEVEL MOISTURE FORECAST TO ADVECT INTO
OUR FAR SOUTH AND SOUTHWEST CWA (MAINLY ALONG AND SOUTH OF A
PONTIAC, IL TO FOWLER, IN LINE) RESULTING IN A FEW FLURRIES
AND/OR LIGHT SNOW SHOWERS MONDAY AFTERNOON AND EVENING.
WIDESPREAD ACCUMULATIONS WITH THESE SNOW SHOWERS/FLURRIES ARE
NOT EXPECTED, BUT GIVEN THE BITTERLY COLD AIR MASS A DUSTING OF
SNOW CANNOT BE RULED OUT.
FINALLY, MONDAY NIGHT WILL ALSO BE ANOTHER BITTERLY COLD NIGHT
WITH LOWS FORECAST TO BE NEAR TO BELOW ZERO AREA WIDE. WHILE
WINDS DURING THIS PERIOD ARE EXPECTED TO BE MUCH LIGHTER, WIND
CHILLS ARE STILL FORECAST TO GET INTO THE -15F TO -25F RANGE.
THERE IS ALSO A DECENT SIGNAL FOR SOME LOCATIONS NEAR THE IL-WI
LINE TO GET WIND CHILLS NEAR -30, BUT SINCE THIS IS LOWER
CONFIDENCE (AROUND 30% CHANCE OF OCCURRING) HAVE DECIDED TO HOLD
OFF ON A EXTREME COLD WATCH FOR NOW. REGARDLESS, WILL NEED TO
CONSIDER ANOTHER COLD WEATHER ADVISORY FOR THIS PERIOD ONCE THE
CURRENT ONE EXPIRES.
YACK
TUESDAY THROUGH SUNDAY:
TOWARD THE MIDDLE OF THE WEEK, THE BROAD UPPER-LEVEL LOBE OF THE
POLAR VORTEX POSITIONED OVER THE NORTHERN US IS EXPECTED TO
FRACTURE. ONE SEGMENT WILL RACE NORTHEASTWARD TOWARD SOUTHERN
GREENLAND, WHILE THE OTHER (COMPARATIVELY STRONGER) SEGMENT WILL
CONSOLIDATE OVER THE NORTHERN PLAINS. MEANWHILE, AN UPPER-LEVEL
SHORT-WAVELENGTH TROUGH (CURRENTLY MEANDERING OFF THE COAST OF
BRITISH COLUMBIA) IS EXPECTED TO RIDE THE UPPER-LEVEL WAVE TRAIN
SOUTHEASTWARD INTO THE WESTERN US EARLY THIS WEEK AND THEN LIFT
NORTHEASTWARD TOWARD THE OHIO RIVER VALLEY TOWARD THE MIDDLE OF THE
WEEK. THIS WILL ALL OCCUR AMONGST CONTINUED WELL-BELOW AVERAGE
TEMPERATURES IN OUR REGION.
WHILE THE SURFACE LOW ASSOCIATED WITH THE PACIFIC SHORTWAVE
SHOULD PASS WELL TO THE SOUTH OF OUR AREA (POTENTIALLY AS FAR SOUTH
AS THE GULF COAST), AT LEAST PARTIAL PHASING WITH THE WESTERN UPPER-
LEVEL POLAR LOW MAY ALLOW FOR A SHIELD OF SNOW (AUGMENTED BY LAKE
MOISTURE?) TO EXPAND AS FAR NORTHWEST AS THE LOWER GREAT LAKES IN
THE TUESDAY NIGHT THROUGH WEDNESDAY TIMEFRAME. A QUICK LOOK AT
FORECAST SOUNDINGS DEPICT A FAIRLY CLASSIC COLD-TEMPERATURE HIGH-
RATIO SNOW PROFILE WITH A NEARLY ISOTHERMAL TEMPERATURES FROM THE
SURFACE TO 10KFT LOCATED ENTIRELY WITHIN THE DGZ, WHICH WOULD
SUPPORT ANYWHERE FROM 0.5 TO 1.5" OF FLUFFY SNOW. CONSIDERING SUCH
SURFACE TEMPERATURES ALSO OFTEN RENDER ROAD TREATMENTS LESS
EFFECTIVE, ANY SNOW THAT DOES FALL IN THE TUESDAY NIGHT THROUGH
WEDNESDAY TIMEFRAME MAY BE SURPRISINGLY IMPACTFUL. WITH THAT SAID,
THERE IS NO GUARANTEE ENOUGH PHASING WILL OCCUR TO BRING SNOW TO OUR
REGION, AS CONFIRMED BY ABOUT A THIRD OF ALL ENSEMBLE MEMBERS FROM
THE GEFS, EPS, AND CMCE REMAINING COMPLETELY DRY. BLENDED NBM POPS
OFFER A WIDE SWATH OF 20-40% CHANCES FOR SNOW, HIGHEST ALONG AND
SOUTHEAST OF I-55, WHICH SEEMS FAIR AT THIS RANGE.
TOWARD THE END OF THE WEEK, THE UPPER-LEVEL POLAR LOW (AND
ASSOCIATED POOL OF COLD LOW-LEVEL AIR) WILL SHIFT EASTWARD AS A
SURFACE HIGH PRESSURE SYSTEM BUILDS INTO THE CENTRAL US. SPLIT UPPER-
LEVEL NORTHWESTERLY FLOW TRANSITIONING TO WESTERN-US RIDGING SHOULD
ALLOW FOR A GRADUAL WARMING TREND THROUGH THE WEEKEND AND INTO EARLY
NEXT WEEK. IN FACT, ENSEMBLE MODEL GUIDANCE HAS A STRONG SIGNAL FOR
HIGHS RETURNING TOWARD THE UPPER 30S TO LOWER 40S BY THE END OF THE
MONTH, IF NOT WARMER.
BORCHARDT
AVIATION /18Z TAFS THROUGH 00Z TUESDAY/
ISSUED AT 1108 AM CST SUN FEB 16 2025
FLURRIES AND OCCASIONAL SNOW SHOWERS WILL CONTINUE THROUGH THE
REMAINDER OF THE AFTERNOON, PARTIALLY THANKS TO THE ARRIVAL OF A
SECONDARY UPPER-LEVEL SHORTWAVE FROM IOWA. FOR NOW, WILL
MAINTAIN PREVAILING -SN WITH PROB30 GROUPS FOR LOWER VISIBILITY
THROUGH THE EVENING. TONIGHT, THE BACK EDGE OF STRATUS SHOULD
WORK FROM WEST TO EAST AS THE BACK EDGE OF THE UPPER-LEVEL
CYCLONIC SHEAR AXIS SLIDES OVERHEAD, LEADING TO AN END IN
FLURRIES. NORTHWEST WINDS WILL REMAIN BREEZY WITH OCCASIONAL
GUSTS OF 25-30KT.
TOMORROW, WINDS WILL GRADUALLY EASE AS A SURFACE PRESSURE RIDGE
BUILDS INTO THE REGION. HIGH RESOLUTION GUIDANCE SUCH AS THE
THE HRRR/RAP SUPPORT THE REDEVELOPMENT AND EXPANSION OF A LOW-
LEVEL STRATUS DECK TOMORROW AFTERNOON AS UPPER-LEVEL CLOUDS
THICKEN IN ADVANCE OF THE NEXT WEATHER SYSTEM. FOR NOW, WILL
MAINTAIN SCT020 AND SCT100 THROUGH THE REMAINDER OF THE TAF AND
EVALUATE CIG TRENDS IN LATER FORECAST PACKAGES.
BORCHARDT
LOT WATCHES/WARNINGS/ADVISORIES
IL...COLD WEATHER ADVISORY FROM MIDNIGHT TONIGHT TO 11 AM CST
MONDAY FOR ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-ILZ010-
ILZ011-ILZ012-ILZ013-ILZ019-ILZ020-ILZ103.
IN...NONE.
LM...SMALL CRAFT ADVISORY UNTIL 6 AM CST MONDAY FOR THE IL
NEARSHORE WATERS.
GALE WARNING UNTIL MIDNIGHT CST TONIGHT FOR THE IN NEARSHORE
WATERS.
VISIT US AT WEATHER.GOV/CHICAGO
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