196  
FXUS63 KFSD 180320  
AFDFSD  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE SIOUX FALLS SD  
1020 PM CDT SUN OCT 17 2021  
   
SHORT TERM
 
(THIS EVENING THROUGH MONDAY)  
ISSUED AT 210 PM CDT SUN OCT 17 2021  
 
FORECAST HIGHLIGHTS:  
1. ABOVE NORMAL TEMPERATURES AND CLEAR SKIES CONTINUE THROUGH MONDAY.  
2. FIRE DANGER RISK WILL BE ELEVATED THROUGH MONDAY.  
3. RAIN CHANCES STILL ON TRACK FOR WEDNESDAY.  
4. HIGH PROBABILITY OF COOLER TEMPERATURES TO START NEXT WEEKEND  
 
TODAY: AN ABSOLUTELY BEAUTIFUL SUNDAY AFTERNOON ACROSS THE REGION  
AS TEMPERATURES ARE RISING NEARLY 10 OR MORE DEGREES ABOVE  
NORMAL. WINDS HAVE BEEN A LITTLE SLOW TO INCREASE TODAY, BUT WE'RE  
NOW SEEING SOME MORE PERSISTENT SOUTHERLY BREEZES MIXING DOWN  
LOWER DEW POINT AIR. THIS IS EVEN MORE PROFOUND ACROSS PORTIONS OF  
CENTRAL AND WESTERN NEBRASKA, WHERE THERE COULD BE SOME SIGNALS  
FOR DEW POINTS ON MONDAY.  
 
TONIGHT: WINDS WILL WEAK OVERNIGHT, AND THIS WILL AGAIN ALLOW FOR  
MORE PRONOUNCED COOLING (ESPECIALLY IN VALLEY AND LOWER TERRAIN  
AREAS). WOULD NOT RULE OUT VERY PATCHY VALLEY AND RIVER FOG AT  
TIMES THROUGH DAYBREAK.  
 
MONDAY: THE GREATEST CONCERN ON MONDAY WILL BE FOCUSED ON AFTERNOON  
DEW POINTS AND WINDS, WHICH MAY BOTH COMBINE TO PRODUCE ELEVATED TO  
NEAR CRITICAL FIRE WEATHER CONDITIONS BRIEFLY IN THE AFTERNOON. AN  
INCREASING SPG WILL BEGIN TO PRODUCE SUSTAINED SOUTHERLY WINDS UP TO  
15 KNOTS BY MID-DAY. SOUNDINGS SUGGEST THAT WE MAY MIX AS HIGH AS  
875 MB AT PEAK HEATING, AND WITH A VERY SUBSTANCIAL POOL OF DRY AIR  
ALOFT, WOULD NOT BE SURPRISED AT ALL TO SEE DEW POINTS DROP INTO THE  
LOWER TO MIDDLE 30S. SLIGHTLY DIFFERENT TERRAIN ACROSS CENTRAL AND  
WESTERN NEBRASKA, BUT MANY AREAS SUNDAY AFTERNOON HAVE FALLEN INTO  
THE LOWER 30S THIS AFTERNOON AND THIS COULD PROVIDE A REASONABLE  
SOLUTION FOR TOMORROW. HAVE GENERALLY POPULATED THE 10TH  
PERCENTILE OF NBM FOR DEW POINTS, AND EVEN LOCALLY ADJUSTED  
DOWNWARD SOME. TEMPERATURES WILL MIX INTO THE MIDDLE TO UPPER 70S  
IN MANY LOCATIONS. WHILE I'D LIKE TO SEE A BIT MORE ALIGNMENT IN  
THE LOW LVL WIND FIELDS TO PROMOTE THE STRONGEST GUSTS POTENTIAL,  
WE COULD SEE A COUPLE HOURS WIND WINDS TOWARDS THE 25-27 KNOT  
RANGE (AROUND THE 90TH PERCENTILE OF NBM GUIDANCE). THE POTENTIAL  
FOR THIS MIXING IS APPARENT IN MOST OF THE BETTER MIXING  
MESOSCALE MODELS. PLEASE SEE SEPARATE FIRE WEATHER DISCUSSION  
SECTION FOR POTENTIAL CONCERNS.  
   
LONG TERM
 
(MONDAY NIGHT THROUGH SUNDAY)  
ISSUED AT 210 PM CDT SUN OCT 17 2021  
 
TUESDAY: A LARGE UPPER LOW WILL BEGIN TO DRIFT THROUGH THE CENTRAL  
ROCKIES BY TUESDAY MORNING, WITH SURFACE CYCLOGENESIS TAKING  
PLACE ACROSS THE NEBRASKA PANHANDLE. WINDS MAY STAY QUITE MIXY  
THROUGH THE OVERNIGHT HOURS AND MAY HOLD OVERNIGHT LOW  
TEMPERATURES WELL ABOVE NORMAL. CIRRUS AND MID CLOUDS MAY TRY TO  
DEVELOP DURING THE DAY ON TUESDAY, BUT IF THIS DOESN'T HAPPEN,  
THEN TEMPERATURES MAY NEED TO BE PUSHED EVEN HIGHER.  
 
WEDNESDAY: MOST MEDIUM RANGE GUIDANCE IS IN RELATIVE AGREEMENT WITH  
THE TIMING OF THE DEEPENING UPPER LOW MOVING THROUGH THE PLAINS. THE  
MAIN ISSUES REMAIN WITH THE EXACT TRACK OF THE UPPER CIRCULATION AND  
SFC LOW. SOME TRENDS TODAY TO PULL THESE FEATURES SLIGHTLY FURTHER  
SOUTH, WHICH MAY LEAD TO HIGHER POPS LATE TUESDAY NIGHT AS WARM  
ADVECTION INTENSIFIES. WHILE LOW, THERE MAY BE ENOUGH INSTABILITY  
FOR AN ISOLATED RUMBLE OF THUNDER ALONG THE LOW-LVL FRONTAL BOUNDARY  
EARLY IN THE DAY. THE UPPER LOW PASSES EAST THROUGH THE DAY ON  
WEDNESDAY, WITH THE TROWAL OF THE SYSTEM SLIDING EAST BY THE  
EVENING. HAVE GENERALLY INCREASED POPS ON WEDNESDAY AND INTO  
WEDNESDAY EVENING IN MOST AREAS.  
 
THURSDAY-FRIDAY: QUIET AND MUCH COOLER TEMPERATURES ARRIVE FOR THE  
END OF THE WEEK AS COLDER AIR FILTERS INTO THE NORTHERN US. HIGH  
TEMPERATURES MAY AVERAGE 5 TO 10 DEGREES BELOW NORMAL; A RARITY SO  
FAR THIS OCTOBER. OVERNIGHT LOWS MAY FINALLY BRING A COMPLETE END TO  
THE GROWING SEASON FOR AREAS ALONG AND EAST OF I-29 FRIDAY MORNING.  
 
SATURDAY-SUNDAY: FORECAST CONFIDENCE REALLY BEGINS TO TREND LOWER  
FOR NEXT WEEKEND AND EARLY NEXT WEEK AS THE MID-LVL PATTERN  
TRANSITIONS TOWARDS MORE OF A ZONAL TO SOUTHWEST FLOW PATTERN. GFS  
IS MUCH MORE AMPLIFIED WITH THE UPPER TROUGHING OVER THE WESTERN  
HALF OF THE CONUS, RESULTING IN STRONGER LOW-LVL MOISTURE ADVECTION  
AND HIGHER PRECIPITATION CHANCES AS WE BEGIN THE NEW WEEK. ECMWF IS  
SLOWER AND LESS AMPLIFIED WITH THE UPPER TROUGH. MOST GUIDANCE HINTS  
AT THE IMPACTS OF STRONGER SOUTHEAST TO EAST SURFACE FLOW AND  
INCREASED LOW-LVL MOISTURE, POTENTIALLY LEADING TO STRATUS.  
 

 
   
AVIATION
 
(FOR THE 06Z TAFS THROUGH 06Z MONDAY NIGHT)  
ISSUED AT 1019 PM CDT SUN OCT 17 2021  
 
VFR CONDITIONS THROUGHOUT THE TAF PERIOD. WILL START TO SEE LLWS  
FROM SIOUX FALLS TO HURON FOR A COUPLE HOURS, WEAKENING BELOW  
THRESHOLDS BY 0500 CDT. SOUTHERLY WINDS WILL BECOME GUSTY BY MID-  
MORNING ON MONDAY, WITH GUSTS AS HIGH AS 30 MPH INTO THE  
AFTERNOON.  
 

 
   
FIRE WEATHER
 
 
ISSUED AT 210 PM CDT SUN OCT 17 2021  
 
FIRE WEATHER DANGER IS ANTICIPATED TO BE ELEVATED TO NEAR CRITICAL  
IN SOME AREAS ALONG THE JAMES RIVER VALLEY AND INTO PORTIONS OF  
NORTHWEST IOWA MONDAY AFTERNOON.  
 
MODEL SOUNDINGS CONTINUE TO SHOW POTENTIAL FOR MIXING AOA 875 MB  
AT PEAK HEATING ON MONDAY, WHICH COULD TRANSLATE TO DEW POINTS  
MIXING INTO THE LOWER TO MIDDLE 30S. SUSTAINED WINDS AOA 15 KNOTS,  
MAY TEMPORARILY GUST TOWARDS THE 25 KNOT RANGE IN THE AFTERNOON.  
WHILE GUIDANCE LIKE THE RAP/NAM MAY BE TOO MIXED OUT AND THEREFORE  
TOO DRY AND WINDY IN THEIR 24 HOUR GUIDANCE, THEY DO SHOW THE  
POTENTIAL RH DROP TODAY THAT IS ALREADY HAPPENING ACROSS PORTIONS  
OF CENTRAL AND WESTERN NEBRASKA.  
 
CURRENT RELATIVE HUMIDITY PROJECTIONS DROP AREA ALONG THE JAMES  
RIVER VALLEY AND AREAS OF NW IOWA INTO THE 20 TO 25 PERCENT RANGE  
FOR 1-2 HOURS.  
 
GENERALLY GFDI VALUES REMAIN IN THE HIGH CATEGORY, WITH RFTI  
GUIDANCE INDICATING SLIGHTLY HIGHER POTENTIAL. GIVEN SHORT  
DURATION OF POTENTIAL THRESHOLDS, UNCERTAINTY IN THE WINDS, AND  
THROUGH COLLABORATION WILL HOLD OFF ON ANY WATCH PRODUCT. HOWEVER,  
FUTURE SHIFTS WILL NEED TO MONITOR NEW GUIDANCE FOR ANY STRONGER  
TREND IN WINDS AS THERE COULD BE SOME POTENTIAL FOR A SHORT RFW  
MONDAY AFTERNOON.  
 

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

 
 

 
 
SHORT TERM...DUX  
LONG TERM...DUX  
AVIATION...APT  
FIRE WEATHER...DUX  
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab SD Page
The Nexlab IA Page
The Nexlab MN Page
The Nexlab NE Page Main Text Page