596  
FXUS63 KFSD 201038  
AFDFSD  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE SIOUX FALLS SD  
538 AM CDT TUE MAY 20 2025  
   
KEY MESSAGES  
 
- PERIODS OF RAIN AND ISOLATED THUNDERSTORMS CONTINUE TODAY INTO  
WEDNESDAY. HIGH CONFIDENCE IN MOST LOCATIONS RECEIVING AN  
ADDITIONAL 0.10" TO 0.25" OF RAIN, WITH ANOTHER 0.50" TO 1"  
EXPECTED FOR MUCH OF EAST CENTRAL SOUTH DAKOTA AND SOUTHWEST  
MINNESOTA. WHILE THIS MAY CAUSE SOME LOCAL RISES IN SMALL  
STREAMS AND CREEKS AND OCCASIONAL PONDING OF WATER, FLASH  
FLOODING IS NOT ANTICIPATED.  
 
- THERE WILL BE A LOW END CHANCE OF FUNNEL CLOUDS WITH ANY  
DEVELOPING SHOWERS THROUGH THE JAMES RIVER VALLEY INTO THE  
LOWER MISSOURI RIVER VALLEY THIS AFTERNOON.  
 
- AFTER A BREAK ON THURSDAY, MODERATE (30-60%) RAIN AND  
THUNDERSTORM CHANCES RETURN FOR FRIDAY INTO THE BEGINNING OF  
NEXT WEEK. TEMPERATURES REMAIN SEASONABLY COOL FOR THIS TIME  
OF YEAR.  
 
 
   
DISCUSSION  
 
ISSUED AT 345 AM CDT TUE MAY 20 2025  
 
LITTLE CHANGE TO THE WEATHER PATTERN FOR TODAY AND WEDNESDAY AS  
AN UPPER LEVEL LOW CONTINUES TO ROTATE OVER THE NORTHERN PLAINS  
THROUGH THE PERIOD. INTERMITTENT SHOWERS AND ISOLATED  
THUNDERSTORMS WILL CONTINUE THROUGH THE PERIOD, THOUGH NO SEVERE  
WEATHER IS EXPECTED EITHER DAY WITH A MORE STABLE ATMOSPHERE IN  
PLACE ACROSS THE AREA. OF NOTE, WITH A COLD UPPER LEVEL LOW  
OVERHEAD, THERE IS A LOW END CHANCE OF A FEW FUNNEL CLOUDS (NON-  
SEVERE) IN ANY DEVELOPING SHOWERS THROUGH THE JAMES RIVER  
VALLEY INTO THE LOWER MISSOURI RIVER VALLEY THIS AFTERNOON.  
CURRENT HI- RES GUIDANCE INDICATES A SURFACE TROUGH/LOW LEVEL  
CONVERGENCE ZONE LOCATED OVER THAT AREA IN THE MID TO LATE  
AFTERNOON. THIS LOOKS TO BE COLLOCATED WITH AN ENHANCED AREA OF  
LOW LEVEL VORTICITY AND A ML ENHANCED STRETCHING POTENTIAL.  
WORKING AGAINST IT HOWEVER IS WEAK LOW LEVEL SHEAR AND WEAK  
INSTABILITY. IF A LITTLE MORE INSTABILITY CAN BE ACHIEVED THEN  
FUNNEL FORMATION MAY BE MORE LIKELY. EITHER WAY, THESE FUNNELS  
DO NOT TYPICALLY REACH THE GROUND, BUT IT IS SOMETHING TO BE  
AWARE OF. IN A COLD AIR ADVECTION REGIME, 925 MB TEMPERATURES  
WILL BE MUCH COOLER TODAY WITH HIGHS ONLY IN THE UPPER 40S TO  
MID 50S. THIS WILL THEN LEAD TO A COOLER NIGHT TONIGHT WITH LOWS  
IN THE UPPER 30S. WEDNESDAY WILL BE SIMILAR WITH HIGHS AGAIN IN  
THE UPPER 40S TO MID 50S. RAINFALL COVERAGE WILL BECOME LESS  
THROUGH THE DAY ON WEDNESDAY AS THE SURFACE LOW CONTINUES TO  
MOVE AWAY AND THE UPPER LEVEL LOW WEAKENS. THE GREATER RAIN  
CHANCES (40-60%) WILL BE SITUATED FROM THE INTERSTATE 90  
CORRIDOR AND NORTHWARD. ADDITIONAL RAINFALL AMOUNTS FOR TODAY  
THROUGH WEDNESDAY WILL AVERAGE AROUND 0.10" THROUGH THE MISSOURI  
RIVER VALLEY UP TO IN EXCESS OF 0.50" THROUGH EAST CENTRAL  
SOUTH DAKOTA AND SOUTHWESTERN MINNESOTA. IT WILL CONTINUE TO BE  
BREEZY FOR TODAY AND WEDNESDAY, BEFORE TRENDING DOWNWARD ON  
WEDNESDAY NIGHT.  
 
WE FINALLY GET A BREAK IN THE ACTIVE WEATHER BY THURSDAY AS SURFACE  
HIGH PRESSURE BUILDS INTO THE REGION. IN A LAX SURFACE PRESSURE  
GRADIENT WINDS WILL BE MUCH LIGHTER THAN RECENT DAYS - RUNNING  
GENERALLY 10 TO 15 MPH. WITH THE PREVIOUS SYSTEM EXITING TO THE  
EAST, WE WILL SEE A DECREASE IN CLOUDS, AND WITH A LITTLE MORE  
SUNSHINE HIGHS WILL CLIMB INTO THE LOWER 60S.  
 
UNFORTUNATELY, MODELS AND ENSEMBLES SUPPORT A RETURN TO UNSETTLED  
WEATHER FOR FRIDAY INTO THE BEGINNING OF NEXT WEEK AS UPPER LEVEL  
ENERGY WORKS FROM THE NORTHERN ROCKIES INTO THE NORTHERN PLAINS.  
THIS WILL BRING AN INCREASING CHANCE OF SHOWERS AND ISOLATED  
THUNDERSTORMS THROUGH THE PERIOD. TEMPERATURES LOOK TO REMAIN ON THE  
COOL SIDE OF NORMAL WITH HIGHS IN THE 60S AND LOWS IN THE 30S AND  
40S.  
 
 
   
AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/  
 
ISSUED AT 535 AM CDT TUE MAY 20 2025  
 
PERIODIC SHOWERS WITH MVFR/IFR CONDITIONS THROUGH TODAY, BEFORE  
SHOWERS DIMINISH IN COVERAGE TONIGHT. WHILE SHOWERS WILL NOT BE  
CONTINUOUS AT TERMINALS TODAY, LEFT THEM PREVAILING IN THE TAFS  
BECAUSE OF LOW CONFIDENCE IN TIMING. NORTHERLY WINDS WILL GUST  
AROUND 20 KTS TODAY, THEN DECREASE TONIGHT.  
 
 
   
FSD WATCHES/WARNINGS/ADVISORIES  
 
SD...NONE.  
MN...NONE.  
IA...NONE.  
NE...NONE.  
 
 
 
 
 
DISCUSSION...JM  
AVIATION...JM  
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