274
FXUS63 KARX 200459
AFDARX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
1059 PM CST THU DEC 19 2024
KEY MESSAGES
- SECOND ROUND OF WIDESPREAD SNOW MOVES IN LATER THIS AFTERNOON
AND COMES TO AN END FROM WEST TO EAST AFTER MIDNIGHT. HIGHEST
AMOUNTS OF 2 TO 4 INCHES ARE LOOKING TO FALL ALONG AND SOUTH
OF I-90 AND THE WINTER WEATHER ADVISORY HAS BEEN EXPANDED
SOUTHWARD TO ACCOUNT FOR THIS TREND.
- COOLER AND DRIER FOR THE WEEKEND.
- WARMING UP FOR NEXT WEEK WITH SEVERAL POTENTIAL ROUNDS OF
SNOW.
DISCUSSION
ISSUED AT 150 PM CST THU DEC 19 2024
THIS AFTERNOON - TONIGHT: SNOW CONTINUES, GRADUALLY ENDS
THIS WAS A CHALLENGING STORM TO NAIL DOWN EVEN AT THE 11TH HOUR
AS THE COMPACT WAVE THAT DROVE OUR ROUND OF HEAVY SNOW THIS
AFTERNOON TOOK A SOUTHERLY TRACK, BRINGING THE AXIS OF HEAVIEST
SNOW FARTHER SOUTH ALONG WITH IT CLOSER TO THE I-90 CORRIDOR.
EARLY AMOUNTS OF 4 TO 7 INCHES HAVE BEEN REPORTED WITHIN THE
CURRENT WARNING OUTLINE. UPSTREAM, A SECONDARY VORT LOBE IS
TIGHTENING ON WATER VAPOR IMAGERY OVER EASTERN SOUTH DAKOTA AND
PREPARING TO EJECT EASTWARD ALONG THE MN/IA BORDER. A NARROW
REGION OF ISENTROPIC ASCENT AND FRONTOGENESIS IS MANIFESTING
ITSELF OVER SOUTHWESTERN MINNESOTA AND PROGGED TO SLIDE ESE THIS
AFTERNOON AND EVENING, AFFECTING MAINLY AREAS SOUTH OF I-90.
DID EXPAND THE WINTER WEATHER ADVISORY SOUTHWARD TO ACCOUNT FOR
THESE LATEST TRENDS, WITH MATCHES THE RECENT MORNING OUTPUTS
FROM THE HRRR AS WELL.
DID DOWNGRADE AREAS NORTH OF I-94 TO AN ADVISORY WITH THIS
SOUTHERN TRACK AND MOST AREAS IN THE WARNING LIKELY WILL ONLY
SEE ANOTHER 1-3 INCHES OF SNOW BEFORE THE STORM SYSTEM DEPARTS
OVERNIGHT. WINDS INCREASE OUT OF THE NORTHWEST LATE TONIGHT INTO
FRIDAY MORNING IN THE WAKE OF THE SURFACE LOW THAT TRACKS
THROUGH THE REGION THIS AFTERNOON AND EVENING. COULD SEE SOME
DRIFTING GIVEN THE LIGHT NATURE OF THE SNOW THAT MAY KEEP ROADS
SLICK INTO THE MORNING HOURS ON FRIDAY.
FRIDAY - SUNDAY: COOLER AND DRIER
LONGWAVE RIDGING BUILDS WEST OF THE REGION FOR THE END OF THE
WEEK AND THE WEEKEND, KEEPING THE THREAT FOR IMPACTFUL WEATHER
AT BAY. WE WILL END THE WEEK ON A COLD NOTE IN THE WAKE OF
TODAY'S SYSTEM WITH HIGH TEMPERATURES FALLING INTO LOW 20S AND
LOWS IN THE SINGLE DIGITS FOR FRIDAY NIGHT. SURFACE HIGH
PRESSURE SLIDES EAST OF THE REGION BY LATE SATURDAY, ALLOWING
FOR WARMER AIR TO RETURN GRADUALLY SUNDAY AND INTO NEXT WEEK.
HIGHS FOR THE NEXT WEEK LOOK TO CLIMB BACK INTO THE MID TO EVEN
UPPER 30S, BUT THE NEW SNOWPACK MAY MODULATE THESE TEMPERATURES
DOWNWARD.
MONDAY: NEXT ROUND OF SNOW
AN ACTIVE ZONAL TO NORTHWESTERLY UPPER LEVEL FLOW USHERS IN
ANOTHER CLIPPER WAVE OFF THE ROCKIES AND THROUGH THE REGION ON
MONDAY. CURRENT TRENDS HAVE BEEN FAVORING THE SYSTEM TO IMPACT
MAINLY WISCONSIN WITH MAJORITY OF THE THE ENSEMBLE MEMBERS
CLUSTERING AROUND 1 TO 2 INCHES FOR SNOW. GIVEN THE FAST-MOVING
NATURE OF THIS SYSTEM, THIS REMAINS A SENSITIVE FORECAST AND
COULD EASILY SHIFT OVER THE NEXT SEVERAL DAYS. THERE IS SOME
SIGNAL FOR ANOTHER ROUND OF PRECIPITATION FOR THE END OF NEXT
WEEK, BUT THERE EXISTS A LARGE SPREAD IN THE GUIDANCE ON IF/WHEN
THAT MIGHT HAPPEN.
AVIATION /06Z TAFS THROUGH 06Z SATURDAY/
ISSUED AT 1059 PM CST THU DEC 19 2024
THE FINAL ROUND OF SNOW FOR THIS EVENT HAS ENTERED OUR
NORTHWEST THIS EVENING. AS IT PASSED THROUGH MINNESOTA,
OBSERVATIONS INDICATED VISIBILITIES GENERALLY REMAINED 1-3SM
WITH THE SNOW, ALTHOUGH THE 20.00Z HREF DOES SUGGEST A 40-60%
PROBABILITY THAT VISIBILITIES COULD DROP BELOW 1SM IN HEAVIER
SNOW, ESPECIALLY IN AREAS NORTH OF I- 90. WINDS INCREASE AND
BECOME NORTHWESTERLY OVERNIGHT, GENERALLY 20-25KT, BUT GUSTS UP
TO 30KT ARE POSSIBLE OVER NORTHEAST IOWA. SNOW EXITS TO THE
SOUTHEAST FRIDAY MORNING AROUND 12-13Z WITH THE MVFR TO IFR
CEILINGS THAT PERSIST OVERNIGHT BECOMING VFR FRIDAY AFTERNOON.
ARX WATCHES/WARNINGS/ADVISORIES
WI...WINTER WEATHER ADVISORY UNTIL 3 AM CST FRIDAY FOR WIZ017-029-
053>055-061.
WINTER STORM WARNING UNTIL 3 AM CST FRIDAY FOR WIZ032>034-
041>044.
MN...WINTER WEATHER ADVISORY UNTIL 3 AM CST FRIDAY FOR MNZ086-087-
094>096.
WINTER STORM WARNING UNTIL 3 AM CST FRIDAY FOR MNZ079-088.
IA...WINTER WEATHER ADVISORY UNTIL 3 AM CST FRIDAY FOR IAZ008>011-
018-019-029-030.
DISCUSSION...SKOW
AVIATION...FALKINHAM
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