856  
FXUS63 KFSD 242252  
AFDFSD  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE SIOUX FALLS SD  
552 PM CDT THU SEP 24 2020  
   
SHORT TERM
 
(THIS EVENING THROUGH FRIDAY)  
ISSUED AT 308 PM CDT THU SEP 24 2020  
 
SHORTWAVE RIDGING BEHIND THIS MORNING'S UPPER-LEVEL TROUGH PASSAGE  
WILL KEEP SKIES MOSTLY CLEAR AND WINDS RELATIVELY LIGHT THIS EVENING  
AND INTO THE EARLY OVERNIGHT HOURS. AS A SURFACE LOW PRESSURE  
APPROACHES FROM THE WEST, SOUTHERLY WINDS WILL INCREASE OVERNIGHT  
JUST ABOVE THE NOCTURNAL INVERSION ALLOWING SOME BREEZY GUSTS TO  
MIX DOWN WEST OF I-29.  
 
FRIDAY STAYS MOSTLY CLEAR, WITH SURFACE WINDS SWITCHING TO WESTERLY  
AND NORTHWESTERLY THROUGHOUT THE DAYTIME HOURS. GUSTS IN THE 20 TO  
30 MPH RANGE WILL BECOME COMMON BY THE AFTERNOON. HIGH TEMPERATURES  
WILL BE MILD AND IN THE UPPER 70S TO LOW 80S.  
   
LONG TERM
 
(FRIDAY NIGHT THROUGH THURSDAY)  
ISSUED AT 308 PM CDT THU SEP 24 2020  
 
A BROAD LOW-AMPLITUDE TROUGH OVER THE WESTERN CONUS WILL KEEP MILD  
CONDITIONS IN PLACE ON SATURDAY, WITH TEMPERATURES REMAINING ABOUT  
10 DEGREES ABOVE NORMAL. THE WIND PATTERN SATURDAY CLOSELY RESEMBLES  
FRIDAY'S, WITH BREEZY WINDS STARTING AS SOUTHERLY AND SWITCHING TO  
NORTHWESTERLY BY THE EVENING HOURS.  
 
A MORE ROBUST COLD FRONT MOVES THROUGH SATURDAY NIGHT INTO SUNDAY,  
USHERING IN A BIGGER PATTERN CHANGE. MOISTURE IS LACKING WITH THIS  
FEATURE GIVEN THE POLAR ORIGINS, SO VERY LITTLE IF ANY  
PRECIPITATION IS EXPECTED. SUNDAY TEMPERATURES LOWER TO NEAR OR  
JUST BELOW SEASONAL AVERAGES, WHICH COULD FEEL COOL GIVEN THE  
WARMTH AS OF LATE. THE TIGHT PRESSURE GRADIENT ASSOCIATED WITH  
THIS COLD AIR ADVECTION ENCOURAGES DEEPER MIXING, SO AFTERNOON  
GUSTS WILL LIKELY BE IN THE 30 TO 40 MPH RANGE. THIS IS LOWER THAN  
IN RECENT MODEL RUNS, BUT STILL WORTH MONITORING FOR FUTURE WIND  
ADVISORY HEADLINES.  
 
THE COOLDOWN CONTINUES ON MONDAY AS THE UPPER LEVEL TROUGH DEEPENS  
OVER THE MISSISSIPPI RIVER VALLEY. HIGHS WILL BE BELOW SEASONAL  
AVERAGES, WITH LOW TO MID 60S. COLD AIR ALOFT COULD HELP SUPPORT A  
FEW COOL RAIN SHOWERS DURING DAYTIME HEATING, BUT PRECIPITATION  
AMOUNTS WILL BE MINIMAL.  
 
A REINFORCING SHOT OF COLD AIR ARRIVES FROM THE NORTH ON TUESDAY,  
WITH THE RETURN OF GUSTY NORTH WINDS. WEDNESDAY IS FORECAST TO BE  
PARTLY CLOUDY AND COOLER, WITH HIGHS IN THE 50S. WEDNESDAY NIGHT  
BRINGS SOME CLEARING WITH SINKING MOTION IN THE UPPER ATMOSPHERE.  
FROST IS POSSIBLE DURING THIS TIMEFRAME IF CLOUDS CLEAR  
SUFFICIENTLY, WITH LOWS IN THE MID TO UPPER 30S.  
 

 
   
AVIATION
 
(FOR THE 00Z TAFS THROUGH 00Z FRIDAY EVENING)  
ISSUED AT 546 PM CDT THU SEP 24 2020  
 
VFR CONDITIONS EXPECTED THROUGH THE TAF PERIOD. LIGHT  
SOUTHEASTERLY WINDS TONIGHT, WITH SOME GUSTINESS AROUND KHON AFTER  
05Z. IN ADDITION, INCREASING WINDS ALOFT WILL RESULT IN LOW LEVEL  
WIND SHEAR AT KHON. ON FRIDAY, WINDS WILL TRANSITION TO  
NORTHWESTERLY ACROSS THE AREA IN THE AFTERNOON WITH GUSTS AROUND  
20 KTS AT TIMES.  
 

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

 
 

 
 
SHORT TERM...VANDENBOOGART  
LONG TERM...VANDENBOOGART  
AVIATION...JM  
 
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