596
FXUS63 KFSD 201038
AFDFSD
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
538 AM CDT TUE MAY 20 2025
KEY MESSAGES
- PERIODS OF RAIN AND ISOLATED THUNDERSTORMS CONTINUE TODAY INTO
WEDNESDAY. HIGH CONFIDENCE IN MOST LOCATIONS RECEIVING AN
ADDITIONAL 0.10" TO 0.25" OF RAIN, WITH ANOTHER 0.50" TO 1"
EXPECTED FOR MUCH OF EAST CENTRAL SOUTH DAKOTA AND SOUTHWEST
MINNESOTA. WHILE THIS MAY CAUSE SOME LOCAL RISES IN SMALL
STREAMS AND CREEKS AND OCCASIONAL PONDING OF WATER, FLASH
FLOODING IS NOT ANTICIPATED.
- THERE WILL BE A LOW END CHANCE OF FUNNEL CLOUDS WITH ANY
DEVELOPING SHOWERS THROUGH THE JAMES RIVER VALLEY INTO THE
LOWER MISSOURI RIVER VALLEY THIS AFTERNOON.
- AFTER A BREAK ON THURSDAY, MODERATE (30-60%) RAIN AND
THUNDERSTORM CHANCES RETURN FOR FRIDAY INTO THE BEGINNING OF
NEXT WEEK. TEMPERATURES REMAIN SEASONABLY COOL FOR THIS TIME
OF YEAR.
DISCUSSION
ISSUED AT 345 AM CDT TUE MAY 20 2025
LITTLE CHANGE TO THE WEATHER PATTERN FOR TODAY AND WEDNESDAY AS
AN UPPER LEVEL LOW CONTINUES TO ROTATE OVER THE NORTHERN PLAINS
THROUGH THE PERIOD. INTERMITTENT SHOWERS AND ISOLATED
THUNDERSTORMS WILL CONTINUE THROUGH THE PERIOD, THOUGH NO SEVERE
WEATHER IS EXPECTED EITHER DAY WITH A MORE STABLE ATMOSPHERE IN
PLACE ACROSS THE AREA. OF NOTE, WITH A COLD UPPER LEVEL LOW
OVERHEAD, THERE IS A LOW END CHANCE OF A FEW FUNNEL CLOUDS (NON-
SEVERE) IN ANY DEVELOPING SHOWERS THROUGH THE JAMES RIVER
VALLEY INTO THE LOWER MISSOURI RIVER VALLEY THIS AFTERNOON.
CURRENT HI- RES GUIDANCE INDICATES A SURFACE TROUGH/LOW LEVEL
CONVERGENCE ZONE LOCATED OVER THAT AREA IN THE MID TO LATE
AFTERNOON. THIS LOOKS TO BE COLLOCATED WITH AN ENHANCED AREA OF
LOW LEVEL VORTICITY AND A ML ENHANCED STRETCHING POTENTIAL.
WORKING AGAINST IT HOWEVER IS WEAK LOW LEVEL SHEAR AND WEAK
INSTABILITY. IF A LITTLE MORE INSTABILITY CAN BE ACHIEVED THEN
FUNNEL FORMATION MAY BE MORE LIKELY. EITHER WAY, THESE FUNNELS
DO NOT TYPICALLY REACH THE GROUND, BUT IT IS SOMETHING TO BE
AWARE OF. IN A COLD AIR ADVECTION REGIME, 925 MB TEMPERATURES
WILL BE MUCH COOLER TODAY WITH HIGHS ONLY IN THE UPPER 40S TO
MID 50S. THIS WILL THEN LEAD TO A COOLER NIGHT TONIGHT WITH LOWS
IN THE UPPER 30S. WEDNESDAY WILL BE SIMILAR WITH HIGHS AGAIN IN
THE UPPER 40S TO MID 50S. RAINFALL COVERAGE WILL BECOME LESS
THROUGH THE DAY ON WEDNESDAY AS THE SURFACE LOW CONTINUES TO
MOVE AWAY AND THE UPPER LEVEL LOW WEAKENS. THE GREATER RAIN
CHANCES (40-60%) WILL BE SITUATED FROM THE INTERSTATE 90
CORRIDOR AND NORTHWARD. ADDITIONAL RAINFALL AMOUNTS FOR TODAY
THROUGH WEDNESDAY WILL AVERAGE AROUND 0.10" THROUGH THE MISSOURI
RIVER VALLEY UP TO IN EXCESS OF 0.50" THROUGH EAST CENTRAL
SOUTH DAKOTA AND SOUTHWESTERN MINNESOTA. IT WILL CONTINUE TO BE
BREEZY FOR TODAY AND WEDNESDAY, BEFORE TRENDING DOWNWARD ON
WEDNESDAY NIGHT.
WE FINALLY GET A BREAK IN THE ACTIVE WEATHER BY THURSDAY AS SURFACE
HIGH PRESSURE BUILDS INTO THE REGION. IN A LAX SURFACE PRESSURE
GRADIENT WINDS WILL BE MUCH LIGHTER THAN RECENT DAYS - RUNNING
GENERALLY 10 TO 15 MPH. WITH THE PREVIOUS SYSTEM EXITING TO THE
EAST, WE WILL SEE A DECREASE IN CLOUDS, AND WITH A LITTLE MORE
SUNSHINE HIGHS WILL CLIMB INTO THE LOWER 60S.
UNFORTUNATELY, MODELS AND ENSEMBLES SUPPORT A RETURN TO UNSETTLED
WEATHER FOR FRIDAY INTO THE BEGINNING OF NEXT WEEK AS UPPER LEVEL
ENERGY WORKS FROM THE NORTHERN ROCKIES INTO THE NORTHERN PLAINS.
THIS WILL BRING AN INCREASING CHANCE OF SHOWERS AND ISOLATED
THUNDERSTORMS THROUGH THE PERIOD. TEMPERATURES LOOK TO REMAIN ON THE
COOL SIDE OF NORMAL WITH HIGHS IN THE 60S AND LOWS IN THE 30S AND
40S.
AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/
ISSUED AT 535 AM CDT TUE MAY 20 2025
PERIODIC SHOWERS WITH MVFR/IFR CONDITIONS THROUGH TODAY, BEFORE
SHOWERS DIMINISH IN COVERAGE TONIGHT. WHILE SHOWERS WILL NOT BE
CONTINUOUS AT TERMINALS TODAY, LEFT THEM PREVAILING IN THE TAFS
BECAUSE OF LOW CONFIDENCE IN TIMING. NORTHERLY WINDS WILL GUST
AROUND 20 KTS TODAY, THEN DECREASE TONIGHT.
FSD WATCHES/WARNINGS/ADVISORIES
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
DISCUSSION...JM
AVIATION...JM
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