529  
FXUS63 KARX 230012  
AFDARX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE LA CROSSE WI  
612 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 /00Z TAFS THROUGH 00Z TUESDAY/
 
 
ISSUED AT 549 PM CST SUN DEC 22 2024  
 
AN AREA OF SURFACE LOW PRESSURE OVER NORTHEAST NEBRASKA IS  
FORECAST TO TRACK NORTHEAST TOWARD SOUTHEAST MINNESOTA INTO  
CENTRAL WISCONSIN. FORECAST SOUNDINGS SHOW VFR CEILINGS TODAY  
START, HOWEVER WITH TIME, LOW LEVEL MOISTURE INCREASES ENOUGH  
FOR PATCHY FREEZING DRIZZLE AS THE SURFACE LOW TRACKS THROUGH  
THE REGION...WITH MIXING WITH AND CHANGING TO SNOW. THE HI-RES  
MODELS SHOW VARYING COVERAGES OF SNOW INCLUDING PARTS OF  
SOUTHEAST MN INTO CENTRAL WI OR JUST CENTRAL WI. FOR NOW WITH THE  
WITH THE PRECIPITATION BEING QUITE LIGHT, INCLUDED A PROB30 AT  
BOTH RST/LSE MONDAY MORNING WITH IFR/LIFR CEILINGS. BRISK SOUTH  
WINDS DIMINISH AS THE SURFACE LOW APPROACHES, THEN SHIFTS TO  
THE WEST AND NORTHWEST LATER MONDAY MORNING AND MONDAY  
AFTERNOON.  
 

 
   
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...ZAPOTOCNY  
 
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