685
FXUS63 KARX 222105
AFDARX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
305 PM CST SUN DEC 22 2024
KEY MESSAGES
- FREEZING DRIZZLE AND LIGHT SNOW WILL LIKELY OCCUR LATE TONIGHT
INTO EARLY MONDAY AFTERNOON. WHILE AMOUNTS WILL BE LIGHT,
CONFIDENCE HAS INCREASED (60%) THAT FREEZING DRIZZLE WILL
AFFECT THE MORNING COMMUTE ALONG AND NORTHEAST OF I-94 AND
ALONG I-90 EAST OF THE MISSISSIPPI RIVER.
- WARMER TEMPERATURES IN THE 30S AND POTENTIALLY EVEN THE 40S
RETURN OVER THE NEXT 7 DAYS.
DISCUSSION
ISSUED AT 302 PM CST SUN DEC 22 2024
WINTRY PRECIP OVERNIGHT INTO MONDAY
OVERNIGHT INTO MONDAY, UPPER WAVE, LOCATED OVER MT AS OF 19Z, WILL
ADVANCE EAST-SOUTHEAST TO THE GREAT LAKES, PASSING OVER THE CWA.
AHEAD OF THIS FEATURE, EXPECT LOW LEVEL WAA, CURRENTLY ONGOING, TO
CONTINUE WIT THIS ALSO BRINGING SOME MOISTURE TO THE AREA IN THE
LOW TO MID-LEVELS. WITH QG FORCING HELPING TO GENERATE LIFT AND LOW-
LEVEL UPGLIDE SEEN ON THE 280 AND 285K SURFACES, PRECIP WOULD
SEEMINGLY BE A GOOD BET ACROSS MUCH OF THE AREA. HOWEVER, ISSUE WITH
THE PRECIP EVENT CONTINUES TO BE TROUBLE WITH A DRY AIR INTRUSION
AROUND 700MB, GIVING PROGGED SOUNDINGS, INCLUDING MUCH OF THE 22.12Z
HREF, A BIT OF AN ONION SHAPE WITH A SATURATED DGZ ATOP A DRY LAYER
ATOP SATURATED LOW LEVELS. IN NORTHEAST IOWA AND ADJACENT AREAS OF
MN AND WI, THIS DRY AIR WILL LIKELY EAT INTO BOTH THE ICE
INTRODUCTION ZONE ALOFT AND THE NEAR-SURFACE MOIST LAYER TO PREVENT
MUCH PRECIP FROM OCCURRING, THOUGH IF IT WERE TO OCCUR, IT WOULD
MAINLY BE FREEZING DRIZZLE. FOR AREAS TO THE NORTHEAST - ROUGHLY
BETWEEN A ROCHESTER TO BOSCOBEL LINE AND I-94 - ICE CRYSTALS WILL
STRUGGLE TO SURVIVE THE FALL WHILE LOW LEVEL MOISTURE DEPTH MAY BE
SUFFICIENT FOR FREEZING DRIZZLE TO OCCUR MORE OFTEN COMPARED TO
AREAS TO THE SOUTHWEST, WITH SURFACE TEMPS RISING ABOVE FREEZING
DURING THE DAY LEADING TO A CHANGEOVER TO STRAIGHT DRIZZLE. FOR
AREAS IN OUR FAR NORTHEAST, THIS INTRUSION WILL BE WEAKER BUT STILL
STRONG ENOUGH TO LEAD TO AN INITIAL PERIOD WITH FREEZING DRIZZLE
BEFORE SNOW BECOMES DOMINANT AFTER SUNRISE AS ICE SLOWLY SATURATED
THE MID-LEVEL DRY LAYER.
UNFORTUNATELY, THE TIMING OF THIS FREEZING DRIZZLE, IF IT OCCURS,
WOULD AFFECT THE MORNING COMMUTE AND AREAS ALONG I-90 EAST OF THE
RIVER AND ALONG I-94. THUS, WHILE CONFIDENCE IN IMPACTFUL FREEZING
DRIZZLE IS LOWER THAN WOULD BE COMFORTABLE, HAVE ISSUED A WINTER
WEATHER ADVISORY COVERING NORTH CENTRAL WI, THE I-94 CORRIDOR, AND
VERNON AND RICHLAND COUNTIES. BUFFALO AND TREMPEALEAU MAY NEED TO BE
ADDED BUT CONFIDENCE IN IMPACTS THERE WAS TOO LOW TO OVERRIDE
COLLABORATION CONCERNS WITH THIS UPDATE. THIS MAY CHANGE THIS
EVENING OR OVERNIGHT AS THE SITUATION EVOLVES.
WARMING UP NEXT WEEK
NEXT WEEK BRINGS A GENERAL TREND TOWARD RISING HEIGHTS ALOFT AND
WARMER TEMPERATURES WITH HIGHS IN THE 40S AND 50S. CHRISTMAS UPPER
TROUGH CONTINUES TO FOCUS POTENTIAL IMPACTS TO OUR SOUTHEAST, SO THE
FORECAST REMAINS FREE OF PRECIP FOR THE 24TH AND 25TH. BEYOND
CHRISTMAS, CONFIDENCE IN DETAILS OF THE UPPER PATTERN BECOMES LOW,
PARTICULARLY WITH A SERIES OF THREE UPPER DISTURBANCES DURING THE
LATTER PART OF THE WEEK, WHERE GUIDANCE SPREAD REMAINS LARGE WITH
BOTH TIMING AND POSITION, WHICH WILL HAVE IMPLICATIONS FOR ANY
PRECIP WITH THESE WAVES. THAT SAID, TEMPERATURES ARE WARM ENOUGH
THAT LREF PROBS FOR SNOW ARE UNDER 5 PERCENT, SO HAVE GONE WITH AN
ALL RAIN FORECAST WHILE STICKING WITH NBM POPS.
AVIATION /18Z TAFS THROUGH 18Z MONDAY/
ISSUED AT 1158 AM CST SUN DEC 22 2024
VFR CONDITIONS TODAY. OVERNIGHT, MVFR/IFR CIGS MOVE INTO THE
AREA ROUGHLY BETWEEN 08Z AND 11Z. WINDS WILL BE OUT OF THE SOUTH
TODAY WITH GUSTS BETWEEN 20 AND 25KTS, WITH THE STRONGEST GUSTS
PRIMARILY IN SOUTHEAST MINNESOTA AND NORTHEAST IOWA. WINDS WILL
THEN DIE DOWN THIS EVENING AND INTO THE OVERNIGHT BEFORE
TRANSITIONING TO THE NORTHWEST AS A FRONT MOVES THROUGH THE AREA
MONDAY MORNING. SOME LIGHT SNOW WILL BE POSSIBLE, STARTING
AFTER MIDNIGHT AND LASTING INTO THE MID-MORNING HOURS ON MONDAY.
THERE IS A CHANCE AT SEEING SOME FREEZING DRIZZLE, HOWEVER
CONFIDENCE IS LOW SO DIDN'T MENTION THAT IN THE TAF.
ARX WATCHES/WARNINGS/ADVISORIES
WI...WINTER WEATHER ADVISORY FROM MIDNIGHT TONIGHT TO 3 PM CST
MONDAY FOR WIZ017-029.
WINTER WEATHER ADVISORY FROM 3 AM TO 3 PM CST MONDAY FOR
WIZ034-041>044-053-055.
MN...NONE.
IA...NONE.
DISCUSSION...FERGUSON
AVIATION...CECAVA
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