933  
FXUS63 KFSD 190748  
AFDFSD  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE SIOUX FALLS SD  
248 AM CDT THU OCT 19 2017  
   
SHORT TERM
 
(TODAY AND TONIGHT)  
ISSUED AT 246 AM CDT THU OCT 19 2017  
 
WARM AND WINDY CONDITIONS ARE EXPECTED TO FINISH OUT THIS WORK WEEK.  
GENERALLY, TEMPERATURES WILL AVERAGE NEARLY 15 TO 20 DEGREES ABOVE  
NORMAL, BUT STILL AROUND 5 TO 10 DEGREES BELOW RECORD HIGHS FOR THIS  
TIME OF THE YEAR! HERE'S A LOOK AT THE PRIMARY MODIFICATIONS TO THE  
FORECAST THROUGH NEXT WEEK.  
 
1. INCREASED HIGH AND LOW TEMPERATURES FROM TODAY THROUGH SATURDAY.  
2. INCREASED WIND SPEEDS FRIDAY THROUGH EARLY SATURDAY.  
3. DECREASED AFTERNOON DEW POINTS TODAY.  
4. INCREASED THUNDER POTENTIAL SATURDAY MORNING.  
 
TODAY: EXPECTING A FAIRLY STRONG DIURNAL RECOVERY TODAY FROM  
OVERNIGHT LOWS IN THE UPPER 30S TO LOWER 40S. 925:850 WARM ADVECTION  
CONTINUES THIS MORNING AND WINDS ARE EXPECTED TO INCREASE THROUGH  
THE DAY. HAVE FAVORED THE WARMEST GUIDANCES FROM MAV/MEX/LAMP/CMC  
FOR TODAY WHICH WILL PUSH TEMPERATURES INTO THE MIDDLE AND UPPER  
70S. MODELS HAVE BEEN A BIT GENEROUS ON BOUNDARY LAYER MOISTURE, SO  
WILL MIX DOWN SLIGHTLY DRIER DEW POINTS THIS AFTERNOON AND SLOW  
ARRIVAL OF HIGHER DEW POINTS FROM THE SOUTH.  
 
TONIGHT: WE'LL BEGIN TO SEE A BIT OF AN INCREASE IN CIRRUS AND MID-  
LEVEL CLOUDS OVERNIGHT AS FLOW TURNS SOUTHWESTERLY. SHOULD SEE A  
FAIRLY MIXY OVERNIGHT TIMEFRAME WHICH WILL KEEP LOWS IN THE 50S  
WITH A FEW 60S IN ELEVATED AREAS.  
 
   
LONG TERM
 
(FRIDAY THROUGH WEDNESDAY)  
ISSUED AT 246 AM CDT THU OCT 19 2017  
 
FRIDAY: SHORTWAVE ENERGY LIFTING NORTHEAST INTO THE PLAINS FROM THE  
SOUTHWESTERN US WILL PUSH INTO THE AREA ON FRIDAY. FOR THE MOST  
PART, IT LOOKS LIKE THE ONLY IMPACT FROM THIS WAVE WILL BE IN AN  
INCREASE IN MID-UPPER LEVEL CLOUDS. WITH DEEP UPPER TROUGHING MOVING  
TOWARDS THE NORTHERN ROCKIES AND LEE SIDE TROUGHING DEVELOPING OVER  
THE WESTERN HIGH PLAINS, THE SFC PRESSURE GRADIENT SHOULD STEEPEN  
SIGNIFICANTLY THROUGH THE DAY. MODELS CONTINUE TO SHOW A STRONG LOW  
LEVEL JET PERSISTENT THROUGH THE DAY, UPWARDS OF 40 TO 45 KNOTS AT  
850 MB. DEPENDING ON THE DEPTH OF MIXING, DOWNWARD MOMENTUM  
TRANSFER SHOULD RESULT IN WIND GUSTS UPWARDS OF 40 MPH AT TIMES  
DURING THE DAY.  
 
HAVE CONTINUED TO TREND TOWARDS THE WARMEST GUIDANCE THROUGH THE  
DAY, DESPITE THE THREAT FOR INCREASED MID LEVEL CLOUDS. MIXING  
UPWARDS OF 900-875 MB WILL RESULT IN READINGS IN THE UPPER 70S.  
AGAIN FAVORED THE WARMER GUIDANCE NUMBERS, BUT REMAIN CAUTIOUS  
WITH POTENTIAL CLOUD IMPACTS.  
 
FRIDAY NIGHT - SATURDAY: STRATUS LOOKS TO ARRIVE A BIT LATER THAN  
EARLIER THOUGHT, MORE INTO THE OVERNIGHT TIME FRAME. BROAD WARM  
ADVECTION WILL ALLOW THE POTENTIAL FOR SHOWERS AND EVEN A FEW  
THUNDERSTORMS TO DEVELOP AFTER MIDNIGHT. WITH SFC TROUGHING WELL  
WEST OF THE AREA, EXPECTING OVERNIGHT LOWS TO STRUGGLE TO REACH THE  
50S. ELEVATED INSTABILITY DOES INCREASED ACROSS THE BOARD AS MID-  
LEVEL LAPSE RATES INCREASE SLIGHTLY AFTER 4AM. WILL INCREASE THE  
PROBABILITY OF THUNDER SLIGHTLY. THE AFOREMENTIONED FRONTAL  
BOUNDARY BEGINS TO MOVE THROUGH THE CWA EARLY SATURDAY. FRONTAL  
FORCING MAY BE ENOUGH TO FORCE A LINEAR AREA OF SHOWERS AND  
THUNDERSTORMS ALONG THE BOUNDARY BY MID-MORNING, QUICKLY MOVING  
EASTWARD THROUGH MN/IA BY MID-DAY. WILL TRY TO ADVERTISE A BIT  
MORE THUNDER THAN SHOWERS. BEHIND THE FRONT, TEMPERATURES WILL  
COOL BACK INTO THE 50S AND 60S, WITH A LIMITED DIURNAL CURVE.  
 
SUNDAY - WEDNESDAY: MINIMAL CHANGES FURTHER OUT INTO THE FORECAST.  
WESTERLY MID-LEVEL FLOW CONTINUES SUNDAY AND MONDAY, WITH A  
SEASONALLY STRONG UPPER JET CROSSING THE NORTHERN PLAINS BY MONDAY  
AND MONDAY NIGHT. MODELS ARE A BIT SPLIT, BUT COULD SEE A NEED FOR  
INCREASED POPS LATE MONDAY AND MONDAY NIGHT AS A SHORTWAVE DIPS  
THROUGH THE NORTHERN US PUSHING MORE FAVORABLE JET DYNAMICS  
OVERHEAD. TEMPERATURES MORE TYPICAL OF LATE OCTOBER ARRIVE FOR THE  
MIDDLE OF THE WEEK, WITH HIGHS IN THE 50S AND DRY CONDITIONS.  
 

 
   
AVIATION
 
(FOR THE 06Z TAFS THROUGH 06Z THURSDAY NIGHT)  
ISSUED AT 1026 PM CDT WED OCT 18 2017  
 
VFR CONDITIONS THROUGH THE TAF PERIOD. GUSTY SOUTHERLY WINDS WILL  
ARRIVE BY LATE MORNING INTO THURSDAY EVENING. MODELS SUGGEST LLWS  
AFTER 20/04Z AT ALL TERMINALS, BUT OPTED NOT TO INCLUDE FOR NOW  
DUE TO LOW CONFIDENCE.  
 

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

 
 

 
 
SHORT TERM...DUX  
LONG TERM...DUX  
AVIATION...05  
 
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