235
FXUS63 KARX 022105
AFDARX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
305 PM CST SUN FEB 2 2025
KEY MESSAGES
- A WINTER WEATHER ADVISORY IS IN EFFECT FOR CLARK AND TAYLOR
COUNTIES FROM MIDNIGHT TONIGHT THROUGH NOON MONDAY. 3 TO 5
INCHES OF SNOW EXPECTED ALONG AND NORTH OF WISCONSIN HIGHWAY
29, AND 1 TO 3 INCHES ACROSS THE REMAINDER OF CLARK COUNTY.
THERE ARE STILL SOME CONCERN THAT THIS ADVISORY MAY HAVE TO
BE EXPAND SOUTH INTO THE INTERSTATE 90 AND 94 CORRIDORS DUE TO
FREEZING DRIZZLE.
- A WINTRY MIX WILL BE POSSIBLE ON WEDNESDAY AND WEDNESDAY NIGHT
AND SOME SNOW ON SATURDAY AND SATURDAY NIGHT. DUE TO
UNCERTAINTIES ON HOW MUCH PHASING WILL OCCUR BETWEEN THE
NORTHERN AND SOUTHERN STREAMS, CONFIDENCE REMAINS LOW ON
PRECIPITATION TYPES AND AMOUNTS.
DISCUSSION
ISSUED AT 304 PM CST SUN FEB 2 2025
THIS AFTERNOON
LOW STRATUS DECK IS FINALLY STARTING TO DIMINISH ALONG ITS
WESTERN AND SOUTHERN FRINGES, ALLOWING FOR SOME FILTERED SUNSHINE
THIS AFTERNOON AS MID TO HIGH CLOUDS CONTINUE TO SPILL INTO THE
AREA. BECAUSE OF THE CLOUDINESS AND ONLY WEAK WARM AIR ADVECTION,
TEMPERATURES HAVE BEEN SUPPRESSED SOMEWHAT, BUT THEY WILL RESPOND
QUICKLY ANYWHERE THAT SEES A BIT OF SUN.
TONIGHT THROUGH MONDAY
ANOTHER ROUND OF WINTER WEATHER IS ON TAP FOR LATER TONIGHT INTO
MONDAY MORNING. MULTIPLE ZONAL FRONTOGENETIC BANDS LOOK TO DEVELOP
AND SLIDE EASTWARD THROUGH THE UPPER MISSISSIPPI VALLEY TONIGHT,
WITH IMPRESSIVE DEEP LIFT THROUGH THE 800-600MB LAYER, MAXIMIZED
AROUND 700MB. MODEST ISENTROPIC LIFT WILL ALSO DEVELOP OVER THE
FORECAST AREA, SO FORCING WITH THIS SYSTEM DEFINITELY LOOKS MORE
IMPRESSIVE THAN SATURDAY NIGHT'S WEAK SYSTEM. PRECIP CHANCES WILL
BEGIN LATE THIS EVENING BUT BECOME HIGHEST AFTER MIDNIGHT BEFORE
TAPERING OFF FROM WEST TO EAST DURING THE MID TO LATE MORNING HOURS
ON MONDAY. EXPECT SOME MORNING COMMUTE IMPACTS WHERE EVER
PRECIPITATION OCCURS.
CONFIDENCE IN PRECIP TYPES AND AMOUNTS REMAINS HIGHEST ACROSS OUR
FAR NORTH (TAYLOR COUNTY) WHERE THERMODYNAMICS AND SATURATION LOOK
TO BE MOST FAVORABLE FOR ALL SNOW THROUGH THE EVENT. ALSO, THE FGEN
SNOW BAND HASN'T REALLY SHIFTED MUCH IN RECENT MODEL RUNS, WHICH
FURTHER LENDS ITSELF TO HIGHER CONFIDENCE. LOOKING LIKE AROUND 3 TO
5 INCHES IN TAYLOR COUNTY WITH LESSER AMOUNTS FURTHER SOUTH. SNOW
RATES COULD APPROACH 1/2" TO NEAR 1" PER HOUR EARLY MONDAY MORNING.
NORTHERN CLARK COUNTY SHOULD ALSO SEE PRIMARILY SNOW, BUT HEADING
SOUTH OF HIGHWAY 29 THERE ARE SOME ADDITIONAL QUESTIONS THAT COME
INTO PLAY SURROUNDING PRECIP TYPE. WHILE FORECAST SOUNDINGS HAVE
BEEN CONSISTENTLY SHOWING ICE NUCLEATION IN THE CLOUD LAYER EARLY ON
DURING THIS EVENT, THERE LOOKS TO BE A DRY LAYER THAT DEVELOPS
BETWEEN ROUGHLY 800-700MB, WITH NEARLY SATURATED CONDITIONS BENEATH
IN THE NEAR-SURFACE LAYER. IF THAT DRIER LAYER REMAINS FAIRLY
SHALLOW, SEEDER-FEEDER PROCESSES COULD COME INTO PLAY AND STILL
ALLOW FOR MAINLY LIGHT SNOW TO REACH THE SURFACE AS FAR SOUTH AS THE
I-90 CORRIDOR. BUT IF THAT DRY LAYER IS TOO DEEP, PRECIPITATION WILL
BE MORE IN LIQUID FORM (DRIZZLE OR FREEZING DRIZZLE DEPENDING ON
SURFACE TEMPERATURES) FOR THE AREA BETWEEN THE I-90 AND I-94
CORRIDORS.
UNFORTUNATELY THIS FORECAST HANGS ON A DELICATE BALANCE BETWEEN A
LOT OF INTRICATE CLOUD AND SATURATION FACTORS THAT AREN'T YET FULLY
KNOWN. IF THE DRIZZLE/FREEZING DRIZZLE SCENARIO PANS OUT, IT DOES
LOOK TO BE A HIGHER AND MORE WIDESPREAD RISK OF ICING THAN SATURDAY
NIGHT BECAUSE OF GREATER MOISTURE AND MORE ROBUST FORCING. THE AXIS
OF POTENTIAL ICE ACCUMULATION LOOKS TO LIE ROUGHLY ALONG THE I-90
CORRIDOR, BUT LIGHT ICING IMPACTS COULD EXTEND A BIT FURTHER NORTH
OR SOUTH DEPENDING ON EXACTLY WHERE THE FGEN BANDS DEVELOP. ICING
AMOUNTS ARE GENERALLY MINOR, BUT SOME SPOTS COULD DEVELOP A LIGHT
GLAZE. FULLY EXPECTING THERE WILL BE AREAS OF SLIPPERY TRAVEL
OVERNIGHT AND INTO MONDAY MORNING, BUT WE LIKELY WON'T KNOW EXACTLY
WHERE UNTIL CLOSER TO EVENT ONSET.
WITH HIGHER CONFIDENCE IN THE AREA OF SNOW, HAVE EXPANDED THE
ADVISORY TO INCLUDE BOTH TAYLOR AND CLARK COUNTIES. IF FREEZING
DRIZZLE THREAT INCREASES BETWEEN THE I-90/94 CORRIDORS, MAY NEED TO
DO A SHORT-NOTICE EXPANSION OF THE ADVISORY TO ENCOMPASS THE LIGHT
ICING THREAT. WILL LET LATER SHIFTS MONITOR THE LATEST TRENDS.
WEDNESDAY INTO WEDNESDAY NIGHT
STILL PLENTY OF UNCERTAINTY ON HOW MUCH PHASING TAKES PLACE
BETWEEN THE SOUTHERN AND NORTHERN STREAMS. IF THESE 2 SYSTEMS DO
INDEED PHASE (25% OF GRAND ENSEMBLE MEMBERS), THESE ENSEMBLE
MEMBERS SHOW THAT THE TRACK OF THE SURFACE LOW WILL TRACK
FURTHER NORTHWEST ACROSS NORTHERN ILLINOIS. THIS RESULTS IN MORE
QPF FOR THE AREA AND A GREATER POTENTIAL FOR A WINTRY MIX SOUTH
OF INTERSTATE 94. THIS INCLUDES A 25 TO 50 PERCENT PROBABILITY
OF 0.01 INCHES OR GREATER OF FREEZING DRIZZLE/FREEZING RAIN.
MEANWHILE, IN THE MEMBERS THAT DO NOT PHASE THE 2 STREAMS (75
PERCENT OF THE GRAND ENSEMBLE SOLUTIONS), THEY HAVE A MUCH
FURTHER SOUTHEAST TRACK OF THE SURFACE LOW IN THE SOUTHERN
STREAM THROUGH THE MID-MISSISSIPPI RIVER VALLEY AND INTO THE
SOUTHERN GREAT LAKES. THIS RESULTS IN FAR LESS QPF. IF
PRECIPITATION DOES OCCUR, IT WOULD BE IN THE FORM OF LIGHT SNOW.
ANY ICING THREAT WOULD REMAIN SOUTHEAST OF OUR FORECAST AREA.
SATURDAY INTO SATURDAY NIGHT
THERE IS PLENTY OF UNCERTAINTY OF HOW MUCH PHASING TAKES PLACE
ACROSS THE UPPER MISSISSIPPI RIVER VALLEY. THE NORTHERN STREAM
IS A BIT FURTHER SOUTH, SO IT LOOKS LIKE MOST OF THE AREA WILL
SEE AT LEAST SOME LIGHT SNOW. IN THE ENSEMBLE MEMBERS WHERE
PHASING DOES INDEED OCCUR, MORE MOISTURE IS BROUGHT NORTHWARD
FROM THE GULF. THIS RESULTS IN MUCH HIGHER SNOW AMOUNTS.
AVIATION /18Z TAFS THROUGH 18Z MONDAY/
ISSUED AT 1154 AM CST SUN FEB 2 2025
PESKY FOG AND LOW STRATUS IS STILL HOLDING ON AT THIS HOUR BUT
THERE IS SOME IMPROVEMENT SEEN JUST UPSTREAM VIA SATELLITE. IF
STRATUS MANAGES TO SCATTER WITHIN THE NEXT FEW HOURS (MORE
LIKELY AT RST), SHOULD SEE A PERIOD OF VFR THIS AFTERNOON INTO
EARLY EVENING.
MAIN FOCUS IS ON ANOTHER SYSTEM THAT WILL BRING MORE WINTRY
PRECIPITATION TO AREAS ROUGHLY NEAR AND NORTH OF I-90 TONIGHT
INTO MONDAY MORNING, WITH HIGHEST LIKELIHOOD (90%) OF SNOW NORTH
OF I-94. BOTH RST AND LSE WILL BE ON THE SOUTHERN FRINGES OF
THIS SYSTEM, BUT MODELS STILL MAINTAIN A FAIRLY DECENT SIGNAL
(30-40% CHANCE) FOR BOTH AIRFIELDS TO SEE LIGHT PRECIP IN THE
FORM OF -SN AND FZDZ/DZ (DEPENDING ON SFC TEMPS) BEGINNING
TOWARDS 06Z. PRECIP CHANCES WILL CONTINUE THROUGH MID-MORNING
ON MONDAY WITH THE POSSIBILITY FOR SOME LIGHT ICING.
CIGS WILL AGAIN BECOME MVFR TO IFR TONIGHT WITH VISIBILITY
IMPACTS FROM ANY LIGHT PRECIPITATION. COULD BE SOME AREAS OF FOG
AGAIN AS WELL.
ARX WATCHES/WARNINGS/ADVISORIES
WI...WINTER WEATHER ADVISORY FROM MIDNIGHT TONIGHT TO NOON CST
MONDAY FOR WIZ017-029.
MN...NONE.
IA...NONE.
DISCUSSION...BOYNE/KURZ
AVIATION...KURZ
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