940
FXUS63 KFSD 231920
AFDFSD
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
220 PM CDT WED SEP 23 2026
KEY MESSAGES
- BREEZY SOUTHEAST WINDS ARE ONGOING, MOSTLY WEST OF I-29 TODAY.
FREQUENT GUSTS OF 25-35 MPH ARE EXPECTED WITH ISOLATED GUSTS
TO 40 MPH POSSIBLE.
- SHOWERS AND THUNDERSTORMS DEVELOP OVER CENTRAL SOUTH DAKOTA
LATE THIS AFTERNOON INTO THE EVENING. STORMS WILL SLOWLY
PROGRESS EAST THROUGH THE OVERNIGHT AND INTO THURSDAY
AFTERNOON. THE MAIN CONCERN WILL BE BRIEF HEAVY DOWNPOURS,
THOUGH FLOODING IS NOT EXPECTED.
- THE ACTIVE WEATHER PATTERN CONTINUES BRINGING A HIGH CHANCE
(>60%) OF ADDITIONAL RAIN LATER THURSDAY NIGHT INTO SATURDAY.
- DAYTIME TEMPERATURES REMAIN BELOW NORMAL, BUT SHOULD CLIMB
CLOSER TO NORMAL SATURDAY INTO MONDAY.
DISCUSSION
ISSUED AT 215 PM CDT WED SEP 23 2026
LIGHT RAIN SHOWERS LOCATED ALONG AND SOUTH OF HIGHWAY 20 WILL
CONTINUE TO DRIFT EAST AND TAPER OFF BY EARLY TO MID AFTERNOON
TODAY. HIGHS WILL BE IN THE MID 60S WEST OF I-29 AND IN THE LOW 70S
TO THE EAST WHERE CLOUDS HAVE CLEARED.
LOOKING ALOFT WE HAVE A LOW AMPLITUDE RIDGE CENTERED OVER THE
NORTHERN PLAINS. TO THE WEST OVER THE NORTH CENTRAL ROCKIES A WEAK
JET STREAK IS LIFTING A SHORTWAVE EAST-NORTHEAST. TO THE SOUTHWEST
OVER THE FOUR CORNERS REGION A SECOND SHORTWAVE BEGINS TO SLOWLY
MOVE NORTHEAST. THESE WAVES WILL BE THE DRIVING FORCE BEHIND A FEW
ROUNDS OF SLOW MOVING SHOWERS AND THUNDERSTORMS. LOOKING ALOFT TO
THE EAST WE SEE A REX BLOCK OVER SOUTHERN ONTARIO AND DOWN INTO THE
OHIO VALLEY. THIS BLOCK IS RESPONSIBLE FOR THE SLOW PROGRESSION OF
STORMS OVER THE NEXT 24-48 HOURS. LOOKING AT THE MID-LEVELS MODERATE
THETA-E ADVECTION BRINGS NORTH WARMER AND MOIST AIR THAT POOLS OVER
CENTRAL NEBRASKA, SOUTH DAKOTA, AND NORTH DAKOTA, AHEAD OF THE FIRST
WAVE. BY MID-AFTERNOON THE LLJ BEGINS TO INCREASE AS THE WAVE
ARRIVES WITH A STRONG PUSH OF WAA. FROM THE SOUTHWEST A BAND OF
POSITIVE VORTICITY ADVECTS IN, FURTHER INCREASING DYNAMIC FORCING. A
BAND OF SHOWERS AND THUNDERSTORMS ARE EXPECTED TO FORM ALONG THIS
JUNCTURE IN CENTRAL SOUTH DAKOTA LATE THIS AFTERNOON. SEVERE WEATHER
IS NOT ANTICIPATED, HOWEVER THERE EXISTS ENOUGH SHALLOW INSTABILITY
THAT A FEW STRONGER THUNDERSTORMS MAY PRODUCE BRIEF PERIODS OF HEAVY
RAIN. THIS NORTH/SOUTH BAND OF STORMS WILL SLOWLY PROGRESS EAST
THROUGH THE EVENING AND OVERNIGHT. AROUND SUNRISE THURSDAY STORMS
SHOULD BE ALONG AND WEST OF I-29, AND ENDING OVER CENTRAL SOUTH
DAKOTA. STORMS CONTINUE TO SLOWLY PROGRESS EAST THROUGH MINNESOTA
AND IOWA THE REMAINDER OF THE DAY THURSDAY WITH SHOWERS ENDING FROM
WEST TO EAST THROUGH THE LATE AFTERNOON AND EVENING. HIGHS FOR
THURSDAY WILL ONCE AGAIN BE COOLER THAN AVERAGE FOR THIS TIME OF
YEAR, IN THE LOW 60S EAST OF HIGHWAY 81, AND UPPER 60S TO LOW 70S
WEST.
THROUGH THE COURSE OF THE DAY THURSDAY, THE FOUR CORNERS WAVE WILL
MOVE SLOWLY NORTHEAST. BY LATE THURSDAY EVENING INTO EARLY FRIDAY
MORNING THE REX BLOCK THAT WAS SLOWING EVERYTHING DOWN WILL BEGIN TO
BREAK DOWN. THIS WILL ALLOW THE WAVE TO ACCELERATE NORTHEAST THROUGH
THE OVERNIGHT. WITH IT WILL COME A STRONG PUSH OF WAA AND A STRONG
BAND OF VORTICITY ADVECTION. AS DYNAMIC FORCING INCREASES
SHOWERS AND THUNDERSTORMS WILL FORM ALONG THE LEADING EDGE OF
THESE ELEMENTS. STORMS MOVE NORTH AND INCREASE IN AREAL COVERAGE
THROUGH THE DAY FRIDAY, BECOMING WIDESPREAD. ONCE AGAIN SEVERE
WEATHER IS NOT ANTICIPATED, BUT SOME LIGHTNING AND BRIEF HEAVY
RAIN ARE POSSIBLE. MEANWHILE, A STRONG TROUGH WILL PUSH INTO THE
PACIFIC NORTHWEST THROUGH THE DAY FRIDAY. AS IT EJECTS OUT ONTO
THE NORTHERN PLAINS OVERNIGHT INTO SATURDAY IT WILL BEGIN TO
PUSH THE EXISTING STORMS TO THE EAST. THE STRONG UPPER TROUGH
WILL KEEP PUSHING EVERYTHING OUT OF THE REGION AND STORMS WILL
TAPER OFF FROM WEST TO EAST EARLY SATURDAY AFTERNOON THROUGH THE
EVENING.
AS FAR AS RAINFALL TOTALS ARE CONCERNED, THE GFS, EC, AND CAN
ENSEMBLES HAVE FLUCTUATED A BIT BUT OVER ALL KEEP THE MAIN BAND OF
HIGHER ACCUMULATION FROM ROUGHLY NORTHEAST NEBRASKA INTO SOUTHWEST
MINNESOTA. HIRES GUIDANCE HAS SOME SHIFTS WEST OR EAST TO THE
HEAVIEST BAND BUT FOR THE MOST PART THEY ALIGN WITH THE ENSEMBLES.
LREF PROBABILITIES FROM NOW UNTIL 7PM SATURDAY INDICATE A GREATER
THAN 80% PROBABILITY FOR WIDESPREAD 0.25 INCHES OF RAIN. INCREASING
TOTALS NARROW IN A SIMILAR PATTERN TO THE MODEL GUIDANCE OF HIGHEST
PRECIPITATION, WITH A 40-80% PROBABILITY OF 1 INCH OF TOTAL RAIN.
PLEASE NOTE, ISOLATED POCKETS OF 1+ INCHES ARE ALSO POSSIBLE.
LOCALIZED PONDING IS POSSIBLE, AS WELL AS RISES IN CREEKS AND
STREAMS, BUT RIVER FLOODING IS NOT EXPECTED AT THIS TIME.
SATURDAY OVERNIGHT WILL BE DRY AND SO WILL SUNDAY. BY SUNDAY
AFTERNOON A FEW PEAKS OF SUNSHINE WILL BE POSSIBLE. THANKS TO
CONTINUOUS SOUTHERLY TO SOUTHEASTERLY WINDS AND WAA DURING THIS
TIME, HIGHS WILL GRADUALLY INCREASE FROM FRIDAY ONWARD. FRIDAY WILL
SEE HIGHS IN THE MID TO UPPER 60S. SATURDAY AND SUNDAY WILL SEE
HIGHS IN THE MID 60S TO LOW 70S. ALAS, OUR WARMER AND DRY CONDITIONS
WILL BE SHORT LIVED. BEGINNING MONDAY A SERIES OF WAVES BRINGS MORE
CHANCES FOR RAIN AND THUNDERSTORMS FOR THE FIRST HALF OF THE WEEK.
HIGHS WILL TREND DOWN FROM THE MID 70S TO THE LOW 60S.
AVIATION /18Z TAFS THROUGH 18Z THURSDAY/
ISSUED AT 143 PM CDT WED SEP 23 2026
STRATUS DECK AND MVFR CONDITIONS CURRENTLY ACROSS A MAJORITY OF THE
CWA. PRECIPITATION CURRENTLY IN NORTHEAST NE MOVING INTO NORTHWEST
IA IS ANTICIPATED TO CONTINUE MOVING NORTHEASTWARD THROUGH KSUX AND
THE SURROUNDING AREAS. CURRENT GUIDANCE HAS THE PRECIPITATION TO
DISSIPATE AROUND 22Z. GUSTY WINDS REMAIN FOR THE AFTERNOON INTO THE
EVENING HOURS FOR THE REGION WEST OF I-29 PAIRED WITH THE CURRENT
LOCATION OF THE LLJ.
CONFIDENCE REMAINS LOW IN IMPROVEMENT TO VFR CONDITIONS ALONG THE I-
29 CORRIDOR INCLUDING KFSD/KSUX BETWEEN 20-02Z. BRIEF VFR CONDITIONS
ARE EXPECTED ALONG A SIMILAR CORRIDOR OF I-29 AND EAST BETWEEN 2-8Z
PRECEDING THE NEXT ROUND OF RAIN THURSDAY MORNING. OVERNIGHT
CEILINGS WILL DROP AGAIN DETERIORATING TO IFR CONDITIONS FOR MOST OF
THE CWA ASIDE FROM NORTHWEST IA. NORTHWEST IA INCLUDING KSUX IS
ANTICIPATED TO DROP BACK DOWN TO MVFR CONDITIONS AROUND 13Z.
THE BROAD AREA OF RAIN WILL SLOWLY PROGRESS EAST THROUGH THE
MORNING. SOUTH WINDS AROUND 10-15 KTS SUSTAINED GUSTING OVER 20 WILL
PREVAIL THROUGH THE PERIOD.
FSD WATCHES/WARNINGS/ADVISORIES
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
DISCUSSION...AJP
AVIATION...BP/RAFALSKI
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