882  
FXUS63 KFSD 051030  
AFDFSD  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE SIOUX FALLS SD  
430 AM CST FRI MAR 5 2021  
   
UPDATE
 
 
ISSUED AT 430 AM CST FRI MAR 5 2021  
 
PER OBS AND WEBCAMS, FOG HAS EXPANDED AND BECOME LOCALLY DENSE  
THROUGH SOUTH CENTRAL SD AND THE JAMES RIVER VALLEY. BECAUSE OF  
THAT, HAVE ISSUED A DENSE FOG ADVISORY THROUGH 10 AM FOR THAT  
AREA.  
 

 
   
SHORT TERM
 
(TODAY AND TONIGHT)  
ISSUED AT 333 AM CST FRI MAR 5 2021  
 
SEEING A BIT OF PATCHY FOG ACROSS THE AREA THIS MORNING. EXPECT THIS  
TO DISSIPATE BY MID TO LATE MORNING. OTHERWISE, LOOK FOR A SLIGHTLY  
COOLER DAY AS STRONG LOW PRESSURE OVER THE EASTERN  
CANADA/NORTHEASTERN U.S. DRAWS COOLER AIR INTO THE NORTHERN PLAINS.  
THERE IS QUITE A BIT OF DIFFERENCE BETWEEN GEFS AND ECMWF ENSEMBLES  
REGARDING TEMPERATURES TODAY, BUT WITH TEMPERATURES CONSISTENTLY  
GOING HIGHER THAN NBM DATA OVER THE PAST SEVERAL DAYS, WENT WITH THE  
90TH PERCENTILE FOR HIGHS. THIS PLAYS OUT TO READINGS IN THE LOWER  
50S EAST OF INTERSTATE 29 TO AROUND 60 OVER SOUTH CENTRAL SD AND THE  
JAMES RIVER VALLEY.  
 
FOR TONIGHT, EVEN LIGHTER EAST/SOUTHEASTERLY WINDS MAY BE MORE  
CONDUCIVE FOR FOG FORMATION OVERNIGHT, SO MAY HAVE A LITTLE MORE FOG  
THAN THIS MORNING. LOW TEMPERATURES WILL AGAIN BE IN THE UPPER 20S  
TO LOWER 30S.  
   
LONG TERM
 
(SATURDAY THROUGH THURSDAY)  
ISSUED AT 333 AM CST FRI MAR 5 2021  
 
FOR THE WEEKEND, THE MAIN THEME WILL BE WARMING TEMPERATURES. WHILE  
STAYING ON THE WARMER SIDE OF GUIDANCE FOR SATURDAY, REMAINED  
SOMEWHAT CONSTRAINED WITH A SOUTHEASTERLY LOW LEVEL FLOW - WHICH IS  
NOT TYPICALLY CONDUCIVE FOR THE VERY WARMEST TEMPERATURES. EVEN SO,  
STILL LOOKING AT HIGHS IN THE MID 50S EAST TO NEAR 70 OVER SOUTH  
CENTRAL SD. IT WILL BE BREEZY WITH MIXED LAYER WINDS OF 15 TO 20  
KTS, AND WITH THE WARMER TEMPERATURES THERE WILL BE AN ENHANCED FIRE  
DANGER - REACHING VERY HIGH IN OUR FAR WESTERN COUNTIES. AT THIS  
TIME, THE VERY LOWEST RH VALUES WILL BE FOUND OVER FAR WESTERN  
GREGORY COUNTY WHERE AFTERNOON RH MAY DROP AS LOW AS 20 PERCENT FOR  
A COUPLE HOURS IN THE AFTERNOON. THIS IS THE AREA THAT WILL HAVE TO  
BE MONITORED FOR POSSIBLE FIRE WEATHER HEADLINES IN LATER FORECASTS.  
THE STRONGER WINDS WILL PERSIST INTO SUNDAY OUT AHEAD OF AN  
APPROACHING SURFACE TROUGH WHICH WILL PUSH THROUGH THE AREA ON  
SUNDAY AFTERNOON. AGAIN WENT ON THE HIGH SIDE OF GUIDANCE - CLOSE TO  
THE 75TH PERCENTILE WITH HIGHS IN THE LOWER 60S TO AROUND 70. THIS  
WILL RESULT IN ANOTHER DAY WITH AN ENHANCED FIRE DANGER.  
 
WARM DAYS CONTINUE FOR MONDAY AND TUESDAY OF NEXT WEEK, AND IN  
COORDINATION WITH SURROUNDING OFFICES WENT ABOVE GIVEN NBM GUIDANCE  
WHICH CONTINUED TO LOOK TOO COOL. STILL LOOKING AT THE POTENTIAL FOR  
SOME PRECIPITATION TOWARD THE MIDDLE OF NEXT WEEK AS A WESTERN CONUS  
TROUGH BEGINS TO PUSH TO THE EAST. MODELS STILL HAVE NOT RESOLVED  
THEIR DIFFERENCES SO CONFIDENCE IS LOW WITH REGARD TO ANY ONE  
SOLUTION. AT THIS TIME, IT APPEARS THAT ANY PRECIPITATION WOULD BE  
IN THE FORM OF RAIN, AT LEAST INITIALLY - AND DID INTRODUCE A LITTLE  
THUNDER ON TUESDAY NIGHT WITH MODELS INDICATING SOME INSTABILITY  
ACROSS THE AREA. MODELS THEN TREND TOWARD COOLER TEMPERATURES FOR  
THE END OF THE WEEK.  
 

 
   
AVIATION
 
(FOR THE 06Z TAFS THROUGH 06Z FRIDAY NIGHT)  
ISSUED AT 1022 PM CST THU MAR 4 2021  
 
VFR CONDITIONS CONTINUE THIS EVENING AND THAT MAY BE THE TREND  
THROUGH THE NIGHT. THICK CIRRUS CONTINUES TO HOLD TEMPERATURES UP,  
AND WITH SHALLOW NATURE OF BOUNDARY LAYER MOISTURE, MODEL GUIDANCE  
MAY STILL BE OVERDOING POTENTIAL STRATUS/FOG DEVELOPMENT.  
 
NEVERTHELESS, WILL INCLUDE SOME LOWER CEILINGS AND VISIBILITY WEST  
OF THE JAMES RIVER, BUT IT MAY BE QUITE LOCALIZED.  
 
VFR CONDITIONS WILL PERSIST THROUGH FRIDAY WITH WINDS REMAINING  
RATHER LIGHT AND VARIABLE.  
 

 
   
FSD WATCHES/WARNINGS/ADVISORIES
 
 
SD...DENSE FOG ADVISORY UNTIL 10 AM CST THIS MORNING FOR SDZ038-050-  
052-053-057>060-063>065-068-069.  
 
MN...NONE.  
IA...NONE.  
NE...NONE.  

 
 

 
 
UPDATE...JM  
SHORT TERM...JM  
LONG TERM...JM  
AVIATION...DUX  
 
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