753  
FXUS63 KFSD 172335  
AFDFSD  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE SIOUX FALLS SD  
535 PM CST SAT FEB 17 2018  
   
SHORT TERM
 
(THIS EVENING THROUGH SUNDAY)  
ISSUED AT 342 PM CST SAT FEB 17 2018  
 
SKIES WILL REMAIN MOSTLY CLEAR THROUGH THIS AFTERNOON AND EVENING,  
WITH HIGH TEMPERATURES INTO THE 30S FOR MOST. DURING THE EARLY  
OVERNIGHT, A STRONG JET STREAK DEVELOPS OVER NORTH DAKOTA ASSOCIATED  
WITH A ROBUST UPPER-LEVEL SHORTWAVE. THIS WILL PROVIDE THE FORCING  
FOR A STRONG SURFACE LOW WHICH WILL SLIDE EASTWARD THOUGH SOUTH  
DAKOTA SUNDAY MORNING. WINDS WILL BE BREEZY AS THE PRESSURE GRADIENT  
TIGHTENS WITH SOUTH WINDS IN THE 30+ MPH RANGE ARE LIKELY DURING THE  
MORNING HOURS. IT CONTINUES TO LOOK LIKE PRECIPITATION ASSOCIATED  
WITH THIS SYSTEM WILL STAY ALONG AND NORTH OF THE DAKOTAS' MUTUAL  
BORDER. MID-LEVEL CLOUDS WILL BE WIDESPREAD, BUT NO SNOW IS EXPECTED  
UNTIL LATER SUNDAY EVENING.  
   
LONG TERM
 
(SUNDAY NIGHT THROUGH SATURDAY)  
ISSUED AT 342 PM CST SAT FEB 17 2018  
 
ON SUNDAY EVENING, WINTER WEATHER RETURN TO OUR AREA. THE SET-UP FOR  
THIS EVENT IS LESS STRAIGHT FORWARD THAN USUAL, AS MULTIPLE  
SHORTWAVE TROUGHS WILL BE MOVING NORTHEAST THROUGH THE DOWNSTREAM  
SIDE OF A LONGWAVE TROUGH CENTERED OVER THE WESTERN CONUS. SENSIBLE  
WEATHER-WISE, THIS WILL LEAD TO AN EXTENDED PERIOD WITH SNOW,  
FREEZING DRIZZLE, AND SLEET IMPACTING TRAVEL.  
 
SNOW WILL START IN SOUTH CENTRAL SOUTH DAKOTA AND QUICKLY SPREAD  
NORTH AND EAST SUNDAY EVENING, AFFECTING LOCATIONS SUCH AS  
CHAMBERLAIN, BROOKINGS, AND MARSHALL. AFTER MIDNIGHT, A SLEET AND  
FREEZING DRIZZLE MIX DEVELOPS OVER NORTHWEST IOWA, AS ARCTIC AIR  
SURGING SOUTHWARD INTERACTS WILL WARM, MOIST NORTHERLY FLOW INTO A  
WARM FRONT THAT STRETCHES EASTWARD ALONG THE IOWA-MINNESOTA BORDER.  
THERE IS INCREASING CONFIDENCE IN THIS SCENARIO, WITH THE MOST  
RECENT RUNS SHOWING A DEEPER AND COLDER SURFACE LAYER, WHICH COULD  
MAKE SLEET AND ICE PELLETS MORE COMMON. ACCUMULATING SLEET AND AT  
LEAST OF LIGHT COATING OF ICE LOOKS INCREASINGLY LIKELY FOR PLACES  
SUCH AS STORM LAKE AND SPENCER, IA, PERHAPS REACHING AS FAR WEST AS  
SIOUX CITY AND AS FAR NORTH AS I-90 IN SOUTHWEST MINNESOTA. THIS  
WINTRY MIX LOOKS TO LAST UNTIL MONDAY AFTERNOON. MEANWHILE, FOR  
SOUTHEAST SOUTH DAKOTA AND AREAS NORTHWEST OF HWY 60 IN SOUTHWEST  
MINNESOTA, LIGHT SNOW WILL SLOWLY BE ACCUMULATING THROUGHOUT THE  
DAY. ACCUMULATIONS WILL BE HIGHER THE FARTHER WEST ONE MOVES, WITH  
PLACES LIKE HURON AND CHAMBERLAIN, SD SEEING THE BEST CHANCES FOR  
SEVERAL INCHES OF SNOW.  
 
MONDAY NIGHT, ANOTHER ROUND OF SNOW LOOKS TO ADD A COUPLE MORE  
INCHES TO THE TOTALS FROM MONDAY, AS ANOTHER SHORTWAVE TROUGH MOVES  
THROUGH THE UPPER-LEVEL FLOW. THIS BAND OF SNOW SWEEPS EASTWARD  
THROUGH THE REGION INTO TUESDAY MORNING, AFTER WHICH TIME COLDER,  
DRIER AIR AND DECREASING DYNAMICS ENDS SNOWFALL.  
 
TUESDAY AND WEDNESDAY TEMPERATURES WILL BE COLD AS AN ARCTIC SURFACE  
HIGH BUILDS INTO THE REGION, WITH MORNING WIND CHILLS IN THE -20S.  
ON THURSDAY TEMPERATURES WILL MODERATE, WITH HIGHS REACHING AROUND  
FREEZING, WHICH IS CLOSE TO NORMAL THIS TIME OF THE YEAR. ANOTHER  
WINTER SYSTEM IS POSSIBLE ON FRIDAY, BUT GIVEN MODEL DISAGREEMENT,  
CONFIDENCE IS VERY LOW.  
 

 
   
AVIATION
 
(FOR THE 00Z TAFS THROUGH 00Z SUNDAY EVENING)  
ISSUED AT 530 PM CST SAT FEB 17 2018  
 
THE MAIN ISSUE LATER TONIGHT ARE WINDS. A VERY STRONG LOW LEVEL  
JET WILL DEVELOP, MOST ACUTE AT KFSD AND KSUX, BUT ALSO WINDY AT  
KHON. SURFACE WINDS FROM THE SOUTHEAST AND THEN SOUTH, WILL  
FREQUENTLY GUST TO 25 TO 30 KNOTS COUPLED WITH NON CONVECTIVE LOW  
LEVEL WIND SHEAR, AS 50 KNOT WINDS EXIST NOT TOO FAR OFF THE  
SURFACE BETWEEN 1000 AND 1500 FEET AGL. THE WINDS WILL FIRST  
SUBSIDE AT KHON SUNDAY MORNING, THEN ACROSS KFSD AND KSUX SUNDAY  
AFTERNOON. A COLD FRONT WILL THEN MOVE THROUGH KHON BY MID  
AFTERNOON SUNDAY LIKELY USHERING IN MVFR CEILINGS BEHIND THE WIND  
SHIFT.  
 

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

 
 

 
 
SHORT TERM...VANDENBOOGART  
LONG TERM...VANDENBOOGART  
AVIATION...MJ  
 
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