965  
FXUS63 KARX 151150  
AFDARX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE LA CROSSE WI  
550 AM CST SAT FEB 15 2025  
   
KEY MESSAGES  
 
- A NARROW SNOWFALL BAND MAY PROVIDE AN ADDITIONAL 1" TO 3"  
PRIMARILY LOCALLY FROM NORTHEAST IOWA INTO SOUTHWEST  
WISCONSIN.  
 
- DANGEROUSLY COLD TEMPERATURES FORECASTED THIS WEEK, OVERNIGHT  
INTO THE EARLY MORNINGS. COLDEST WIND CHILLS NEAR -35F ARE  
POSSIBLE MONDAY, TUESDAY, AND WEDNESDAY MORNINGS.  
 
 
   
DISCUSSION  
 
ISSUED AT 323 AM CST SAT FEB 15 2025  
 
THE UPPER LEVEL LOW RESPONSIBLE FOR FRIDAY'S SNOW CAN BE SEEN  
CHURNING THROUGH THE CENTRAL PLAINS ON GOES WATER VAPOR LOOPS.  
GOES DERIVED UPPER LEVEL WINDS SHOW THE DRIVING 100+ KT JET  
STREAK EXTENDING THROUGH THE CONUS FROM SOUTHWEST TO NORTHEAST.  
 
TODAY'S SNOWFALL:  
 
THE LOW LEVEL CYCLONIC FLOW PROGRESSING THROUGH SOUTHERN MINNESOTA  
EARLY THIS MORNING ON 850MB VWPS WILL CONTINUE EAST OVER THE  
FORECAST AREA THIS MORNING. ATTENDANT LOBES OF LOW LEVEL  
FRONTOGENESIS DRIVE POTENTIAL WIDESPREAD ON/OFF LIGHT SNOW  
CHANCES. UPPER LEVEL QG LIFTS NORTHEAST WITH THE MEAN UPPER  
LEVEL TROUGH TODAY, FUSING LOW LEVEL CYCLONIC FLOW OVER THE  
FORECAST AREA WITH THE CYCLONIC FLOW OVER THE CENTRAL PLAINS. AS  
A RESULT, AN ENHANCED BAND OF LOW LEVEL FRONTOGENESIS IS  
LEVERAGED FROM THE SOUTHERN PLAINS THROUGH CENTRAL IOWA. THE  
NORTHEASTERN EXTENT OF THIS BAND REMAINS MURKY, AFFECTING LOCAL  
SNOWFALL LOCATION AND HIGHER AMOUNTS FROM 1" TO 3". BOTH  
FORCING MECHANISMS GRAZE OUR SOUTHERN PERIPHERY THROUGH THE  
AFTERNOON, KEEPING CURRENT CONFIDENCE FOR ACCUMULATING SNOWFALL FROM  
NORTHEAST IOWA INTO SOUTHWEST WISCONSIN.  
 
UPPER LEVEL PLANETARY PROGRESSION FOR COLD:  
 
AS THE UPPER LEVEL WAVE PHASES EAST, AMPLIFIES, AND EVENTUALLY  
OCCLUDES, AN UNPROGRESSIVE PLANETARY PATTERN AMPLIFIES THE UPSTREAM  
RIDGE, ADVECTING AN ARCTIC AIRMASS SOUTH, THROUGH UPPER  
MISSISSIPPI RIVER VALLEY. THIS ANOMALOUS COLD IS CURRENTLY OVER  
NORTHERN MANITOBA WITH RECORD OVERNIGHT POES DERIVED 500MB  
TEMPERATURES OF -45C ACCORDING TO SPC SOUNDING CLIMATOLOGY. THE  
PLANETARY PROGRESSION LEVERAGES THIS SOUTH THROUGH THE NEW WEEK.  
GEFS DYNAMIC TROPOPAUSE AND RAP 1.5 PVU SUGGEST THE BOWLING  
BALL OF 500MB TROPOPAUSE PRESSURE ELONGATES AS IT BATTLES A  
MEAGER UPPER LEVEL RIDGE PUSHING THROUGH THE EASTERN PACIFIC ON  
CURRENT GOES WEST WATER VAPOR IMAGERY. AS A RESULT, THE  
ANOMALOUS LOW DYNAMIC TROPOPAUSE STRETCHES ANTICYCLONICALLY FROM  
NORTHEAST ALBERTA INTO NEW ENGLAND SUNDAY NIGHT INTO MONDAY  
MORNING. WITHIN THE FILAMENT'S CENTER, A LOBE OF LOWER DT  
PRESSURE NEAR 700MB STRETCHES FROM SOUTHEAST SASKATCHEWAN  
THROUGH NORTHERN LAKE HURON, SLIGHTLY NORTH OF THE LOCAL  
FORECAST AREA. THEREFORE, THE SOUTHERN EXTENT OF COLDEST AREA OF  
THE ARCTIC AIRMASS WILL BE POISED TO POTENTIALLY SAG SOUTH,  
POTENTIALLY FURTHER DECREASING LOCAL TEMPERATURES.  
 
COLD ANOMALY AMOUNTS & CONFIDENCE:  
 
DPROG/DT FOR GEFS MEAN DT PRESSURE HAS EXHIBITED THIS SLIGHT  
SOUTHERN SAG, GRAZING LOCAL COUNTIES IN CENTRAL WISCONSIN.  
SIMILAR TO GEFS DYNAMIC TROPOPAUSE DPROG/DT TRENDS, GLOBAL LONG  
TERM ENSEMBLE CLUSTER ANALYSIS PROBABILITIES FOR 850MB  
TEMPERATURES BELOW -30C HAS ALSO ADVECTED FARTHER SOUTH. WHAT  
WAS A QUICK DECREASE IN PROBABILITIES FROM 100% TO ZERO AT THE  
INTERNATIONAL BORDER IN THE 14.12Z RUN PUSHES FARTHER SOUTH INTO  
NORTHERN SOUTH DAKOTA FOR THE 15.00Z RUN. WHICH WOULD BE RECORD  
LOW LEVEL TEMPERATURES IN BISMARCK ACCORDING TO SPC SOUNDING CLIMATOLOGY.  
SIMILARLY, PROBABILITIES IN SURFACE TEMPERATURES BELOW -25F  
HAVE INCREASED SLIGHTLY FARTHER SOUTHEAST IN A NORTHWEST TO  
SOUTHEAST ORIENTED LOBE FROM CENTRAL SASKATCHEWAN INTO THE  
NORTHERN PLAINS.  
 
ACCORDING TO ECMWF EXTREME FORECAST INDEX ABOVE 0.9, THE MOST  
ANOMALOUS COLD IS EXPECTED LOCALLY WEST OF THE MISSISSIPPI  
RIVER VALLEY ON TUESDAY MORNING WITH 1 (ALL MEMBERS ANOMALOUS IN  
5 WEEK MODEL CLIMATE) AS NEAR AS CENTRAL MINNESOTA. HAS  
REMAINED A CONSTANT SIGNAL OVER THE LAST FEW RUNS.  
 
DANGEROUS COLD FORECAST:  
 
WIND CHILLS DROP BELOW -20 TONIGHT INTO SUNDAY MORNING, BELOW  
-30 IN SPOTS SUNDAY NIGHT INTO MONDAY MORNING, BELOW -30 MONDAY  
NIGHT INTO TUESDAY MORNING, NEAR -30 TUESDAY NIGHT INTO  
WEDNESDAY MORNING, AND -25 WEDNESDAY NIGHT INTO THURSDAY  
MORNING. SPREAD BETWEEN LONG TERM ENSEMBLE CLUSTERS OF 5 TO 10  
DEGREES RESULTS IN SOME COUNTIES HOVERING NEAR EXTREME COLD  
WARNING CRITERIA (-35F) PRIMARILY MONDAY AND TUESDAY MORNINGS.  
 
HAVE NOTICED A SLIGHT WARM BIAS OVER THE LAST COUPLE OF  
FORECAST RUNS IN THE NBM DETERMINISTIC. THEREFORE, HAVE BLENDED  
IN NBM ENSEMBLE 50TH PERCENTILE TO DROP OVERNIGHT MINIMUMS BY A  
COUPLE OF DEGREES IN COLLABORATION WITH NEIGHBORS. HAVEN'T  
OPTED FOR ISSUING ANY HEADLINES AT THE CURRENT FORECAST HOUR AS  
SUNDAY MORNING MINIMUM WIND CHILLS ARE ONLY EXPECTED TO  
POTENTIALLY GRAZE COLD WEATHER ADVISORY CRITERIA OF -25F  
PRIMARILY WEST OF THE MISSISSIPPI RIVER VALLEY.  
 
 
   
AVIATION /12Z TAFS THROUGH 12Z SUNDAY/  
 
ISSUED AT 533 AM CST SAT FEB 15 2025  
 
ONGOING WINTER WEATHER SEEN ON SURFACE OBSERVATIONS ORIENTED IN  
A SOUTHWEST TO NORTHEAST LINE THROUGH CENTRAL IOWA. THE  
ACCOMPANYING NARROW GRADIENT OF VISIBILITY REDUCTIONS ARE FROM  
1/2SM TO 5SM. THE ORIENTATION AND PROGRESSION OF THIS LINE EXPECTED  
TO PUSH NEAR AND TOWARDS KLSE OVER THE NEXT COUPLE OF HOURS.  
HAVE ACCOUNTED FOR THIS WITH 2SM -SN PREVAILING WITH TEMPO MVFR  
AT KLSE. NOT HIGH CONFIDENCE GIVEN THE VERY NARROW NATURE OF  
IMPACTS. KRST EXPECTED TO REMAIN ON NORTHERN PERIPHERY OF  
ACCUMULATING SNOWFALL. HOWEVER, LOW LEVEL SATURATION AT 15.12Z  
TAF ISSUANCE HAS SURROUNDED TAF SITE WITH IFR CEILINGS.  
CURRENTLY UNACCOUNTED FOR BUT CONSTANTLY MONITORING.  
 
EVENTUALLY THE NARROW BAND PROGRESSES SOUTHEAST WITH LINGERING,  
LIMITED IMPACT SCATTERED SNOW THROUGH THE END OF THE 15.12Z TAF  
PERIOD.  
 
 
   
ARX WATCHES/WARNINGS/ADVISORIES  
 
WI...WINTER WEATHER ADVISORY UNTIL 6 PM CST THIS EVENING FOR  
WIZ041>044-053>055-061.  
MN...WINTER WEATHER ADVISORY UNTIL 6 PM CST THIS EVENING FOR  
MNZ094>096.  
IA...WINTER WEATHER ADVISORY UNTIL 6 PM CST THIS EVENING FOR  
IAZ008>011-018-019-029-030.  
 
 
 
 
 
DISCUSSION...JAR  
AVIATION...JAR  
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