371
FXUS63 KARX 200915
AFDARX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
315 AM CST TUE JAN 20 2026
KEY MESSAGES
- WIDESPREAD DANGEROUS COLD RETURNS THURSDAY WITH -25F TO -40F
WIND CHILLS POSSIBLE THURSDAY NIGHT THROUGH SUNDAY MORNING.
- SNOWFALL TONIGHT AND WEDNESDAY AFTERNOON/EVENING. HIGHER
ACCUMULATIONS EXPECTED TUESDAY NIGHT WITH A SWATH OF 1"-2"
SOUTH OF I-90 AND A NARROW AXIS TOPPING 3" WITHIN THIS SWATH,
CURRENTLY FAVORED TO OCCUR SOUTH OF US HIGHWAY 18.
- WEDNESDAY AFTERNOON/EVENING BRINGS MINOR (1" OR LESS) SNOW AMOUNTS
BUT POTENTIAL FOR GUSTY WINDS AND GREATLY REDUCED VISIBILITY
AS SNOW FALLS.
DISCUSSION
ISSUED AT 314 AM CST TUE JAN 20 2026
DANGEROUS COLD THURSDAY NIGHT THROUGH SUNDAY MORNING
CYCLONIC FLOW OVER EASTERN NORTH AMERICA CONTINUES OVER THE NEXT 7
DAYS WILL LEAD TO BELOW AVERAGE TEMPERATURES. THE APPROACH OF AN
UPPER LOW THURSDAY/FRIDAY WILL LEAD TO A REINFORCING SURGE OF COLD
AIR SPILLING INTO THE CWA STARTING THURSDAY AFTERNOON. THURSDAY
NIGHT INTO SUNDAY MORNING APPEAR VERY LIKELY TO FEATURE DANGEROUSLY
COLD CONDITIONS WITH WIND CHILLS UNDER -25. SIMILAR TO WHAT HAS BEEN
STATED WITH THE PAST FEW FORECAST UPDATES, TIMING OF THE COLDEST
MORNING IS STILL UNCERTAIN AS THE COLDEST AIR TEMPERATURE MORNING
(SATURDAY) APPEARS LIKELY TO FEATURE VERY LIGHT WINDS. 20.00Z LREF
AND 2 OF THE ENSEMBLES (ECENS/GEFS) THAT MAKE UP THE BROADER
ENSEMBLE POINT TOWARD FRIDAY MORNING WITH A 60-95% CHANCE TO SEE
WIND CHILLS AT LEAST 35 BELOW WHILE CMC ENSEMBLE ALSO KEEPS SIMILAR
PROBABILITIES BOTH FRIDAY AND SATURDAY MORNINGS. GIVEN THESE
PROBABILITIES, AM GROWING INCREASINGLY CONFIDENT IN WARNING-LEVEL
CONDITIONS (10 MINUTES TO FROSTBITE) FRIDAY MORNING. AS FOR SATURDAY
AND SUNDAY MORNINGS, UNCERTAINTY IS A BIT HIGHER GIVEN REDUCED
CONTRIBUTION FROM WIND, BUT ADVISORY-LEVEL (30 MINUTES TO
FROSTBITE) IMPACTS DO APPEAR PROBABLE (65-90% AND 30-60%,
RESPECTIVELY PER 20.00Z LREF). SHOULD THESE TRENDS HOLD, WILL
STRONGLY CONSIDER A LONGER LEAD TIME WATCH IN THE NEXT FEW FORECAST
CYCLES.
2 ROUNDS OF SNOW TONIGHT AND WEDNESDAY AFTERNOON/EVENING
TWO DISTURBANCES IN THE NORTHWESTERLY FLOW ALOFT LOOK TO SWING
SOUTHEAST OUT OF CANADA. FIRST WAVE ARRIVES TONIGHT WHICH SHOULD
LEAD TO A SWATH OF SNOW MAINLY SOUTH OF I-90 WHERE BROAD LIFTING DUE
TO QG ASCENT OCCURS WITHIN THE DGZ. GIVEN PRESENCE OF 925/850MB
FRONTOGENESIS, EXPECT A NARROW AXIS WITHIN THIS SWATH WITH TOTALS OF
3"+. PROGGED LOCATION OF THE SWATH OF SNOW HAS SHIFTED SOUTHWARD
CONSIDERABLY OVER THE PAST 4 RUNS OF THE OPERATIONAL NAM/GFS
BRINGING IT IN LINE WITH OPERATIONAL CMC/EC. SHORT RANGE ENSEMBLES
SHOW A SIMILAR PATTERN WITH A JOG SOUTHWARD SEEN IN 20.00Z HREF.
HAVE THEREFORE FOCUSED HIGHEST POPS AND SNOW AMOUNTS IN NE IA AND
FAR SW WI, CUTTING BOTH DOWNWARD FARTHER NORTH. AS FOR AMOUNTS, WITH
MUCH OF THE SNOW PRODUCING LAYER LIKELY IN THE DGZ, SHOULD GET SNOW
TO LIQUID RATIOS CLOSE TO 20:1 ADJUSTING 20.00Z HREF PROBABILITIES
FOR THIS, THE CHANCE TO EXCEED 3" IS AROUND 60% FOR SOME AREAS SOUTH
OF HIGHWAY 18 IN NE IA AND FAR SW WI. WHILE UNCERTAINTY IS HIGHER
THAN WOULD BE OPTIMAL GIVEN RECENT SHIFT IN PLACEMENT OF THE SNOW
BAND IN GUIDANCE, GIVEN THESE PROBABILITIES AND INTER-OFFICE
COLLABORATION CONCERNS, HAVE ISSUED A WINTER WEATHER ADVISORY FOR
FAYETTE, CLAYTON, AND GRANT COUNTIES. THE GOOD NEWS IS THAT IMPACTS
SHOULD BE AT THE LOW END FOR AN ADVISORY DUE TO LIGHT WINDS AND
HIGHEST SNOW RATES OCCURRING AFTER 6 PM.
SECOND ROUND OF SNOW PRESENTS A DIFFERENT SET OF POTENTIAL IMPACTS.
WITH A BIT STRONGER OF AN UPPER WAVE AND THUS COOLER TEMPERATURES
ALOFT, POTENTIAL FOR A POCKET OF SURFACE-BASED INSTABILITY TO
DEVELOP EXISTS. WITHIN THIS POTENTIALLY UNSTABLE BOUNDARY LAYER,
PROGGED WINDS RAMP UP TO AROUND 40 KNOTS AT 850MB. THUS, WHILE SNOW
AMOUNTS LOOK TO BE MINOR (1" OR LESS) AS THE PERIOD OF SNOWFALL
LOOKS TO BE EVEN SHORTER COMPARED TO TUESDAY, COULD HAVE MODERATE TO
SHORT LIVED HIGH IMPACTS ON DRIVING CONDITIONS DUE TO POTENTIAL FOR
A SHORT BURST OF SNOW, STRONG GUSTS, AND GREATLY REDUCED VISIBILITY.
AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/
ISSUED AT 1138 PM CST MON JAN 19 2026
VFR CONDITIONS WILL PERSIST THROUGH TUESDAY AND THEN THE
VISIBILITIES AND CEILINGS WILL QUICKLY BECOME IFR/MVFR AS SNOW
MOVES INTO THE AREA DURING THE EVENING. THIS SHOULD OCCUR AT
KRST BETWEEN 21.02Z AND 21.03Z AND KLSE BETWEEN 21.04Z AND
21.05Z.
ARX WATCHES/WARNINGS/ADVISORIES
WI...WINTER WEATHER ADVISORY FROM 6 PM THIS EVENING TO 6 AM CST
WEDNESDAY FOR WIZ061.
COLD WEATHER ADVISORY UNTIL 10 AM CST THIS MORNING FOR WIZ017-
029.
MN...NONE.
IA...WINTER WEATHER ADVISORY FROM 6 PM THIS EVENING TO 6 AM CST
WEDNESDAY FOR IAZ029-030.
DISCUSSION...FERGUSON
AVIATION...BOYNE
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