034  
FXUS63 KFSD 121116  
AFDFSD  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE SIOUX FALLS SD  
516 AM CST TUE DEC 12 2017  
   
SHORT TERM
 
(TODAY AND TONIGHT)  
ISSUED AT 346 AM CST TUE DEC 12 2017  
 
AFTER A VERY COLD MORNING, TEMPERATURES WILL RECOVER TODAY WITH WARM  
AIR ADVECTION IN AN EVOLVING WESTERLY FLOW. MID TO LOW CLOUDS WILL  
SPREAD ACROSS THE AREA FROM WEST TO EAST DURING THE DAY WITH THE  
WARM AIR ADVECTION ALOFT. THE BETTER WARMING WILL BE REALIZED OVER  
OUR WEST, AND WITH POSSIBLE AFTERNOON SUNSHINE HIGHS WILL MAKE IT  
INTO THE LOWER 50S OVER SOUTH CENTRAL SD, TO MID/UPPER 40S THROUGH  
THE JAMES RIVER AND MO RIVER VALLEYS. TO THE EAST WHERE CLOUD COVER  
WILL EXIST FOR MUCH OF THE DAY, LOOKING AT HIGHS IN THE 30S.  
 
TONIGHT, AN UPPER LEVEL SHORTWAVE DROPS OUT OF CANADA AND INTO OUR  
AREA OVERNIGHT, WHILE A SURFACE LOW TRACKS FROM ND TO SOUTHERN MN  
DURING THE NIGHT. THIS WILL PULL A COLD FRONT THROUGH OUR AREA BY  
WEDNESDAY MORNING. RELATED TO THAT, NORTHWESTERLY WINDS WILL BEGIN  
TO PICK UP THE LATTER HALF OF THE NIGHT. THIS WILL RESULT IN A MUCH  
MILDER NIGHT, AND WITH THE BETTER MIXING TEMPERATURES WILL RISE  
LATER IN THE NIGHT. EARLY NIGHT LOWS WILL RANGE FROM THE UPPER 20S  
EAST TO MID 30S OVER SOUTH CENTRAL SD.  
   
LONG TERM
 
(WEDNESDAY THROUGH MONDAY)  
ISSUED AT 346 AM CST TUE DEC 12 2017  
 
WINDS WILL CONTINUE TO INCREASE DURING THE DAY ON WEDNESDAY BEHIND  
THE FRONT, WITH MIXED LAYER WINDS OF 40 TO 45 KTS, AND MAY BE  
LOOKING AT ANOTHER WIND ADVISORY. MODELS ARE STILL PRODUCING SOME  
LIGHT PRECIPITATION WITH THIS SYSTEM, MORE SO OVER SOUTHWESTERN MN,  
AND THERMAL PROFILES SUPPORT SNOW, WITH RAIN MIXING IN AS  
TEMPERATURES RISE INTO THE UPPER 30S TO LOWER 40S. IN ANY EVENT, ANY  
SNOW THAT WOULD ACCUMULATE WOULD BE LESS THAN HALF AN INCH - AGAIN,  
MAINLY OVER SOUTHWESTERN MN.  
 
THE SHORTWAVE TRAIN CONTINUES ON THURSDAY AS ANOTHER WAVE SLIDES  
SOUTHWARD ON A NORTHWESTERLY UPPER LEVEL FLOW. AS IS TYPICAL WITH  
THESE TYPE OF SYSTEMS, MODELS VARYING A BIT IN PLACEMENT OF THE  
FEATURE - AND ASSOCIATED LIGHT PRECIPITATION - BUT CONSENSUS WOULD  
LEAN MORE TOWARD AREAS WEST OF INTERSTATE 29, AND COULD SEE A NEAR  
HALF AN INCH OF SNOW OVER THAT AREA, BEFORE MIXING WITH RAIN IN THE  
AFTERNOON.  
 
NO SURPRISES IN THE LONGER TERM - FRIDAY THROUGH MONDAY - WITH  
PRETTY MUCH THE STATUS QUO CHARACTERIZED BY ABOVE NORMAL  
TEMPERATURES THROUGH THE PERIOD. MODEL DIFFERENCES DO NOT BRING  
CONFIDENCE TO ANY PRECIPITATION TIMING, THOUGH THE OVERALL THEME  
WILL BE FOR MAINLY DRY CONDITIONS INTO THE BEGINNING OF NEXT WEEK.  
 

 
   
AVIATION
 
(FOR THE 12Z TAFS THROUGH 12Z WEDNESDAY MORNING)  
ISSUED AT 514 AM CST TUE DEC 12 2017  
 
NEAR MVFR TO MVFR CEILINGS, GENERALLY FROM ABOUT 2500 FEET TO 3500  
FEET, WILL MOVE FROM WEST TO EAST THIS MORNING INTO THE AFTERNOON.  
AFTER ABOUT 21Z, VFR CONDITIONS ARE EXPECTED. WIND GUSTS FROM THE  
NORTHWEST AROUND 30 MPH WILL BE POSSIBLE AFTER 10Z WEDNESDAY WEST  
OF INTERSTATE 29. THE WINDS WILL BECOME MUCH STRONGER DURING THE  
DAY ON WEDNESDAY.  
 

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

 
 

 
 
SHORT TERM...JM  
LONG TERM...JM  
AVIATION...08  
 
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