897  
FXUS63 KFSD 220011  
AFDFSD  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE SIOUX FALLS SD  
611 PM CST SAT DEC 21 2024  
   
KEY MESSAGES  
 
- SUNDAY WILL BE WARMER AND DRY WITH HIGH TEMPERATURES RANGING  
FROM THE FREEZING MARK NEAR THE HIGHWAY 14 CORRIDOR TO THE MID  
40S ALONG THE MISSOURI RIVER.  
 
- THERE IS A 20-30 PERCENT CHANCE OF A WINTRY MIX SUNDAY NIGHT  
ALONG AND EAST OF A LINE FROM MARSHALL TO WORTHINGTON TO  
SPENCER. WHILE ANY ACCUMULATION WILL BE VERY LIGHT, ROADS MAY  
BECOME SLICK, IMPACTING THE MONDAY MORNING COMMUTE.  
 
- TEMPERATURES WILL WARM THROUGH THE UPCOMING WEEK AND BE WELL  
ABOVE LATE DECEMBER NORMALS. SPORADIC 20 PERCENT PRECIPITATION  
CHANCES RETURN THURSDAY INTO NEXT WEEKEND. PRECIPITATION  
COVERAGE AND TYPE WILL DEPEND ON STORM TRACK, BUT SOME  
TEMPERATURES ABOVE FREEZING MAY ALLOW FOR INCREASED RAIN  
CHANCES.  
 
 
   
DISCUSSION  
 
ISSUED AT 238 PM CST SAT DEC 21 2024  
 
TONIGHT...SOUTHERLY BREEZES WILL CONTINUE TONIGHT WITH A TIGHT  
SURFACE PRESSURE GRADIENT ACROSS THE REGION. THIS, IN  
COMBINATION WITH INCREASING MID-HIGH LEVEL CLOUDS WILL KEEP  
TEMPERATURES 10-15 DEGREES WARMER THAN THIS MORNING.  
 
SUNDAY...A 500 HPA CLOSED LOW WILL DROP SOUTHEASTWARD FROM  
CENTRAL MT TO SOUTHERN MN. AT THE SURFACE, LOW PRESSURE WILL  
SKIRT ALONG THE NE/SD BORDER AND ACROSS NORTHERN IA. VERY STRONG  
WARM AIR ADVECTION AHEAD OF THIS SYSTEM WILL ALLOW FOR WELL  
ABOVE NORMAL TEMPERATURES...WITH HIGHS RANGING FROM THE FREEZING  
MARK ALONG HIGHWAY 14 TO THE MID 40S ALONG THE MISSOURI RIVER.  
 
OVERALL, THIS SYSTEM IS QUITE MOISTURE STARVED WITH THE 12Z  
HREF SHOWING NON-ZERO PERCEPTION PROBABILITIES NORTH AND EAST  
OF THE FORECAST AREA. THAT SAID, NEW 12Z DETERMINISTIC GUIDANCE  
(ESPECIALLY THE NAM) IS A BIT MORE BULLISH WITH BRINGING SOME  
PRECIPITATION ACROSS PARTS OF SOUTHWEST MN INTO NORTHWEST IA  
SUNDAY NIGHT.  
 
AS THE LOW-LEVELS BEGIN TO SATURATE, SOUNDINGS SHOW A PROMINENT  
WARM NOSE OF +3 TO +5 CELSIUS AROUND 850 HPA. IF SATURATION  
OCCURS QUICKLY ENOUGH, THIS COULD RESULT IN LIGHT FREEZING  
RAIN/DRIZZLE FOR AREAS ALONG AND EAST OF A LINE FROM MARSHALL TO  
WORTHINGTON TO SPENCER AFTER 9 PM. THERMAL PROFILES EVENTUALLY  
COOL TO BELOW FREEZING ON THE BACKSIDE OF THE DEPARTING LOW,  
ALLOWING ANY REMAINING PRECIPITATION TO CHANGE OVER TO  
SLEET/SNOW. THAT SAID, THERE ARE STILL QUESTIONS CONCERNING  
SATURATION WITHIN THE -12 TO -18 C ICE PRODUCTION LAYER THAT  
COULD WRECK HAVOC ON THE P-TYPE FORECAST. TOTAL LIQUID  
ACCUMULATIONS LOOK TO BE VERY MINIMAL (A COUPLE HUNDREDTHS AT  
BEST), BUT COULD STILL BE ENOUGH TO CREATE SLICK ROADS,  
IMPACTING MONDAY MORNING'S COMMUTE.  
 
MONDAY THROUGH CHRISTMAS DAY...A SOMEWHAT MESSY PROGRESSIVE  
SYNOPTIC FLOW PATTERN WILL KEEP THE IMMEDIATE REGION DRY AND  
WARM. THE COOLEST TEMPERATURES WILL RESIDE ALONG THE HIGHWAY 14  
CORRIDOR INTO SOUTHWEST MINNESOTA, COINCIDENT WITH THE CURRENT  
SNOWPACK, BUT AFTERNOON HIGHS ARE EXPECTED TO TOP THE FREEZING  
MARK REGION WIDE BY CHRISTMAS DAY.  
 
THURSDAY INTO NEXT WEEKEND...12Z MEDIUM-RANGE GUIDANCE (GFS/  
ECMWF) EJECTS A COUPLE OF 500 HPA LOWS INTO THE CENTRAL CONUS  
FROM THE FOUR CORNERS REGION. LARGE RUN-TO-RUN VARIABILITY  
COUPLED WITH TIMING/STRENGTH DIFFERENCES PRECLUDES STRAYING FROM  
NBM POPS, BUT THIS RESULTS IN LOW-CONFIDENCE SPORADIC 20  
PERCENT CHANCES EACH DAY, ESPECIALLY EAST OF I-29. ENSEMBLE  
GUIDANCE HAS BEEN CONSISTENT IN KEEPING TEMPERATURES WELL ABOVE  
LATE DECEMBER NORMALS, SO ANY PRECIPITATION HAS A HIGHER  
PROBABILITY OF FALLING AS RAIN. THOSE WITH HOLIDAY TRAVEL PLANS  
WILL WANT TO MONITOR THE FORECAST FOR CHANGES AS DETAILS BECOME  
CLEARER.  
 
 
   
AVIATION /00Z TAFS THROUGH 00Z MONDAY/  
 
ISSUED AT 546 PM CST SAT DEC 21 2024  
 
VFR CONDITIONS WILL PREVAIL THROUGH THIS PERIOD.  
 
COULD STILL SEE OCCASIONAL 20KT GUSTS IN SOUTHEAST TO SOUTH  
FLOW AT TIMES, MAINLY NEAR AND EAST OF I-29 CORRIDOR LATE  
TONIGHT THROUGH THE DAY SUNDAY.  
 
 
   
FSD WATCHES/WARNINGS/ADVISORIES  
 
SD...NONE.  
MN...NONE.  
IA...NONE.  
NE...NONE.  
 
 
 
 
 
DISCUSSION...ROGERS  
AVIATION...JH  
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