155  
FXUS63 KFSD 130344 AAA  
AFDFSD  
 
AREA FORECAST DISCUSSION...UPDATED  
NATIONAL WEATHER SERVICE SIOUX FALLS SD  
1044 PM CDT MON APR 12 2021  
   
UPDATE
 
 
ISSUED AT 1044 PM CDT MON APR 12 2021  
 
SATELLITE DATA LATE THIS EVENING SHOWS WIDESPREAD STRATUS  
CONTINUES TO STREAM INTO THE REGION AND MODELS HAVE BEEN SLOW TO  
PICK UP ON THIS. THUS, INCREASED CLOUD COVER OVERNIGHT AND INTO  
EARLY TUESDAY AND INCREASED LOW TEMPERATURES A FEW DEGREES SINCE  
STRATUS IS CAUSING TEMPERATURES TO FALL MUCH MORE SLOWLY THAN  
PREVIOUSLY EXPECTED.  
 

 
   
SHORT TERM
 
(THIS EVENING THROUGH TUESDAY NIGHT)  
ISSUED AT 253 PM CDT MON APR 12 2021  
 
SURFACE OBSERVATIONS FROM AROUND THE REGION SHOW THE STRONGEST WIND  
SPEEDS HAVE LARGELY DECREASED, WITH A COUPLE SITES STILL FLOATING  
AROUND ADVISORY CRITERIA DUE TO SUSTAINED WINDS. THIS ACTIVITY IS IN  
RESPONSE TO THE TIGHT PRESSURE GRADIENT CAUSED BY THE SURFACE LOW  
OFF TO OUR NORTHEAST AND THE SURFACE HIGH OFF WELL OFF TO OUR  
NORTHWEST, AS WELL AS COLD AIR ADVECTION BRINGING IN SURGES OF  
STRONGER WIND GUSTS. ALOFT, A CUT-OFF UPPER LEVEL LOW CONTINUES TO  
SPIN JUST OFF TO OUR NORTH, AND LOOKING AT RADAR THIS IS PRODUCING  
SCATTERED RAIN/SNOW SHOWERS WHICH ARE STARTING TO SLIDE INTO OUR  
NORTHERN TIER OF COUNTIES. TEMPERATURE PROFILES LOOK TO REMAIN WARM  
ENOUGH FOR OUR LOCATIONS THAT MOST SHOULD STICK TO ONLY SEEING RAIN,  
WHILE A COUPLE LOCATIONS IN FAR EAST-CENTRAL SD AND SW MN COULD SEE  
SOME SNOW OVERNIGHT. DUE TO A BIT OF INSTABILITY IN THE MID-LEVELS  
LEADING TO THEIR CONVECTIVE NATURE, SHOWERS WILL LARGELY BE HIT OR  
MISS, BUT EITHER WAY ONLY VERY LIGHT ACCUMULATIONS (IF ANY) ARE  
EXPECTED.  
 
WHILE WINDS SHOULD DECREASE A BIT THROUGHOUT THE OVERNIGHT PERIOD AS  
THE NOCTURNAL INVERSION ATTEMPTS TO SET UP, THEY WILL LIKELY REMAIN  
BREEZY. AS COLD AIR ADVECTION CONTINUES, LOOK FOR OVERNIGHT LOWS TO  
MAINLY BE IN THE UPPER 20S. HOWEVER, IF THE INVERSION IS ABLE TO SET  
UP, TEMPERATURES COULD GET A BIT COOLER AS MIXING CEASES ALLOWING  
FOR BETTER RADIATIONAL COOLING.  
 
FOR TUESDAY, LOOK FOR MUCH OF THE SAME AS THE UPPER LEVEL LOW DRIFTS  
EASTWARDS. WINDS SHOULD PICK UP AGAIN AS MIXING HEIGHTS RISE, WITH  
AN OVERALL COOLER DAY IN STORE THANKS TO CONTINUED CAA. AFTERNOON  
HIGHS MAY STRUGGLE TO GET OUT OF THE 30S FOR SW MN AND FAR EAST-  
CENTRAL SD, WHILE ELSEWHERE TEMPERATURES WILL LARGELY REMAIN IN THE  
40S. THIS IS LOOKING TO BE THE COLDEST DAY FOR THE NEXT WEEK, WITH  
OUR NORMAL EXPECTED TEMPERATURES NORMALLY IN THE UPPER 50S AND LOWER  
60S. THE UPPER LEVEL LOW WILL LIKELY LEAD TO ANOTHER ROUND OF LIGHT  
CONVECTIVE SNOW SHOWERS ACROSS SW MN, WITH ACCUMULATIONS AGAIN  
LARGELY GOING TO BE HIT OR MISS INTO THE EVENING HOURS. OVERNIGHT,  
AS THE TEMPERATURE PROFILES COOL DOWN, ACCUMULATIONS COULD CREEP UP  
TO A QUARTER INCH BUT ARE EXPECTED TO STAY BELOW HALF AN INCH.  
OTHERWISE, LOOK FOR OVERNIGHT LOWS IN THE 20S.  
   
LONG TERM
 
(WEDNESDAY THROUGH MONDAY)  
ISSUED AT 253 PM CDT MON APR 12 2021  
 
AS OUR PERSISTENT UPPER LEVEL LOW BEGINS TO MIGRATE EASTWARDS,  
ANOTHER UPPER LEVEL IS POISED TO MOVE TOWARDS THE REGION BY THE END  
OF THE WEEK. THIS LEAVES LITTLE OVERALL CHANGE TO OUR AIRMASS, SO  
EXPECT THE COOLER AND DRY AIR TO CONTINUE ON WEDNESDAY LEAVING  
AFTERNOON HIGHS IN THE UPPER 40S AND LOWER 50S. BY THURSDAY, SOME  
WAA IN THE MID-LEVELS COULD RESULT IN AN EVER SO SLIGHTLY WARMER  
DAY, AND THIS LOOKS TO BE THE LEAST WINDY DAY FOR THIS FORECAST  
PERIOD. DURING THE AFTERNOON, THE NEXT APPROACHING UPPER WAVE DOES  
START TO PRODUCE RAINFALL IN CENTRAL SD, WITH MODELS BEGINNING TO  
TREND THIS PRECIPITATION SOUTH OF OUR AREA THROUGHOUT THE DAY ON  
FRIDAY.  
 
ENSEMBLE SOLUTIONS REALLY START TO DIVERGE BY FRIDAY, AS THE PARENT  
GLOBAL MODELS HANDLE OUR TWO (OR THREE) CLOSED OFF UPPER LEVEL LOWS  
DIFFERENTLY. OVERALL, THE THEME FOR THE WEEKEND CONTINUES TO BE  
BELOW AVERAGE TEMPERATURES, WITH A SLIGHT CHANCE FOR PRECIPITATION.  
 

 
   
AVIATION
 
(FOR THE 06Z TAFS THROUGH 06Z TUESDAY NIGHT)  
ISSUED AT 1037 PM CDT MON APR 12 2021  
 
LOW VFR TO MVFR CEILINGS WILL PREVAIL THROUGH AT LEAST MONDAY  
MORNING. AS STRATUS CONTINUES TO SPREAD IN FROM THE NORTHWEST,  
UPSTREAM SATELLITE DATA SHOWS NO SIGNS OF CLEARING BEYOND  
OCCASIONAL BREAKS. GUSTY NORTHWEST WINDS CONTINUE TO WEAKEN BUT  
STILL MAY OCCASIONALLY GUST AS HIGH AS 25 KTS OVERNIGHT. WINDS  
WILL INCREASE AGAIN AFTER SUNRISE.  
 

 
   
FSD WATCHES/WARNINGS/ADVISORIES
 
 
SD...NONE.  
MN...NONE.  
IA...NONE.  
NE...NONE.  

 
 

 
 
UPDATE...BP  
SHORT TERM...APT  
LONG TERM...APT  
AVIATION...BP  
 
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