822  
FXUS63 KARX 220000  
AFDARX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE LA CROSSE WI  
600 PM CST SAT DEC 21 2024  
   
KEY MESSAGES
 
 
- POTENTIAL FOR LIGHT SNOW AND/OR FREEZING DRIZZLE LATE SUNDAY NIGHT  
INTO MONDAY MORNING. AMOUNTS LOOK TO BE MINIMAL, BUT THE MORNING  
COMMUTE MAY BE AFFECTED IF FREEZING DRIZZLE DOES OCCUR.  
 
- WARMING TREND FOR TUESDAY ONWARD, BUT DETAILS BECOME UNCLEAR  
LATE NEXT WEEK.  
 

 
   
DISCUSSION
 
 
ISSUED AT 327 PM CST SAT DEC 21 2024  
 
POTENTIAL FOR LIGHT SNOW AND/OR FREEZING DRIZZLE LATE SUNDAY NIGHT  
INTO MONDAY MORNING  
 
SUNDAY NIGHT INTO MONDAY MORNING, UPPER WAVE, CURRENTLY OFF THE  
PACIFIC NORTHWEST COAST, WILL ADVANCE OVER THE CWA. WARM, MOIST  
ADVECTION AHEAD OF THIS FEATURE SHOULD SATURATE THE LOW LEVELS  
AND WARM TEMPERATURES TO NEAR - BUT LIKELY BELOW - FREEZING. AS  
THE UPPER WAVE APPROACHES, DRY AIR INTRUSION AROUND 700MB MAY  
DRY OUT THE DGZ WHILE, NEARER TO THE SURFACE, SOME ISENTROPIC  
LIFT ON THE 280/285K SURFACES LOOKS TO CONTINUE, AS SUGGESTED BY  
THE 21.12Z GFS. THE END RESULT FOR MANY LOCATIONS MAY BE  
FREEZING DRIZZLE IF THE MID-LEVEL DRY AIR LEAVES ENOUGH OF THAT  
NEAR SURFACE LAYER SATURATED FOR DROPLETS TO FORM. THE FREEZING  
DRIZZLE POTENTIAL WILL PRIMARILY RESIDE IN SOUTHWEST OF I-94  
WHILE AREAS TO THE NORTHEAST LOOK TO FEATURE DEEPER SATURATION  
AND SNOW FOR MUCH OF THE EVENT. FINALLY, LOCATIONS IN SW WI MAY  
END UP A BIT TOO WARM FOR FREEZING TEMPERATURES TO HANG ON AT  
THE SURFACE DUE TO THE EFFECTS OF AFOREMENTIONED ADVECTION.  
THERE ARE A LOT OF REMAINING UNCERTAINTIES WITH THIS SYSTEM,  
MAINLY CENTERING AROUND WHERE THE DRY AIR INTRUDES AND HOW DEEP  
SAID INTRUSION WILL BE, SO HAVE ENDEAVORED TO KEEP POPS LESS  
THAN 50 PERCENT OUTSIDE OF NORTH CENTRAL WI, WHERE CONFIDENCE IN  
AT LEAST SOME SNOW IS BETTER (60-70%) AND SPREAD MENTIONS OF  
BOTH SNOW AND FREEZING DRIZZLE ACROSS MUCH OF THE AREA. DUE TO  
TIMING, THE MORNING COMMUTE MAY BE IMPACTED, SO HOPEFULLY  
DETAILS WILL BECOME CLEARER OVER THE NEXT DAY.  
 
WARMING TREND AHEAD  
 
PREDICTABILITY ACROSS GUIDANCE BECOMES RELATIVELY LOW THROUGH THE  
REST OF THE FORECAST, WITH POOR AGREEMENT ON TIMING AND PLACEMENT OF  
SEVERAL UPPER WAVES, PARTICULARLY BY LATE NEXT WEEK. HOWEVER,  
GENERAL TREND IS FOR HIGHER HEIGHTS ALOFT WHICH FAVORS A SLOW RETURN  
TO HIGHS IN THE 30S. MAY EVEN SEE SOME TEMPERATURES IN THE 40S  
FRIDAY AND NEXT SATURDAY, BUT NBM INTERQUARTILE RANGES AT THAT TIME  
BEGIN TO APPROACH 10 DEGREES, REFLECTING THE LOW CONFIDENCE IN THE  
EXACT DETAILS OF THE PATTERN BY THAT PORTION OF THE WEEK.  
 

 
   
AVIATION /00Z TAFS THROUGH 00Z MONDAY/
 
 
ISSUED AT 553 PM CST SAT DEC 21 2024  
 
SURFACE HIGH PRESSURE LOCATED OVER THE REGION IS FORECAST TO  
SHIFT EASTWARD OVERNIGHT AND SUNDAY AHEAD OF A SHORTWAVE TROUGH.  
THE FLOW ALOFT IS FROM THE NORTHWEST, HOWEVER THE LOW LEVEL FLOW  
STRENGTHENS FROM THE SOUTHWEST. AN AREA OF MID-CLOUDS HAS BEEN  
OVERSPREADING THE REGION AND THESE WILL CONTINUE TO PUSH  
EASTWARD OVERNIGHT. MEANWHILE, AN AREA OF MVFR STRATUS EXTENDS  
FROM CENTRAL MN INTO CENTRAL IOWA. THE RAP/HRRR BOTH BRING  
MVFR/PATCHY IFR CONDITIONS EASTWARD TOWARD KRST AND THE RAP  
SPREADS THEN EASTWARD ACROSS MUCH OF SOUTHEAST MN AND WI  
OVERNIGHT. CONFIDENCE WAS NOT HIGH ENOUGH TO INCLUDE AT KLSE,  
BUT DID INCLUDE THE MVFR CEILINGS AT KRST THROUGH SUNDAY  
MORNING. LIGHT SOUTHEAST WINDS INCREASE 10 TO 15KTS OVERNIGHT  
INTO SUNDAY WITH SOME GUSTS 20 TO 30KTS SUNDAY AFTERNOON.  
 

 
   
ARX WATCHES/WARNINGS/ADVISORIES
 
 
WI...NONE.  
MN...NONE.  
IA...NONE.  
 

 
 

 
 
DISCUSSION...FERGUSON  
AVIATION...ZAPOTOCNY  
 
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