894
FXUS63 KFSD 290435
AFDFSD
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
1135 PM CDT MON JUL 28 2025
KEY MESSAGES
- SEVERE WEATHER OUTBREAK EXPECTED LATE THIS AFTERNOON INTO THE
EVENING. A FEW SUPERCELLS IN CENTRAL SD WILL LIKELY TRANSITION
INTO A LINE AND BRING HURRICANE FORCE WINDS TO THE AREA.
- MORE THUNDERSTORMS POSSIBLE AGAIN TUESDAY NIGHT INTO
WEDNESDAY. WHILE ISOLATED SEVERE STORMS ARE POSSIBLE,
WIDESPREAD SEVERE WEATHER IS NOT ANTICIPATED.
- A PERIOD OF MAINLY BELOW NORMAL TEMPERATURES IS EXPECTED
WEDNESDAY INTO THE WEEKEND.
DISCUSSION
ISSUED AT 241 PM CDT MON JUL 28 2025
A SURFACE FRONT WILL CONTINUE TO SETTLE SOUTH LATE THIS AFTERNOON
AND BY LATE AFTERNOON BE IN PLACE FROM ROUGHLY WINNER NORTH TOWARDS
CHAMBERLAIN AND MITCHELL INTO NORTHEAST SD. AT THE SAME TIME MORE
UNSTABLE LOW LEVEL AIR THAT WAS PUSHED SOUTH THIS MORNING BY THE
OUTFLOW IS SURGING NORTH AND WILL ALLOW FOR A VERY UNSTABLE
ENVIRONMENT ACROSS AREAS NEAR AND SOUTH OF I-90. THIS FRONT WILL
LIKELY SERVE AS A FOCUS FOR THUNDERSTORM DEVELOPMENT WITH THE
POTENTIAL FOR A FEW SUPERCELLS. MODEL SOUNDINGS HINTING AT ABOUT
4000 TO 5000 J/KG CAPE PROVIDING AMPLE ENERGY TO ANY UPDRAFTS THAT
FORM. LOW LEVEL INFLOW FROM THE SOUTH AND SOUTHEAST FROM ABOUT 850
MB TO THE SURFACE WILL PROVIDE SOME LOW LEVEL SHEAR THAT COULD
SUPPORT AN ISOLATED TORNADO OR TWO ALONG WITH THE THREAT FOR HAIL TO
THE SIZE OF TENNIS BALLS AS WELL AS WINDS TO 75 MPH. THE BEST CHANCE
FOR THIS WILL BE FROM ABOUT 5 PM TO 8 PM. AROUND 8 PM, A SEASONALLY
STRONG UPPER LEVEL JET AROUND 50 TO 80 KNOTS WILL SETTLE SOUTHWARD
AND INCREASE LARGE SCALE SHEAR WHICH SHOULD AID IN PRODUCING
INCREASINGLY STRONG LINEAR SYSTEM CAPABLE OF PRODUCING WIND GUSTS OF
80 TO 90 MPH AS THE STORMS MOVE EASTWARD. EMBEDDED QLCS TORNADO
POTENTIAL WILL EXIST, BUT THE SURFACE TO 3 KM WIND SHEAR VECTORS
RUNNING ABOUT 20-30 KNOTS FROM THE WEST AND SOUTHWEST ARE JUST
MARGINAL FOR THIS THREAT. AS THIS SYSTEM BECOMES LINEAR NEAR AND
EAST OF HIGHWAY 81 THE THREAT FOR LARGER HAIL DECREASES AS WIND
BECOMES THE HIGHEST THREAT. THE LATEST HRRR COMING MORE IN LINE WITH
THIS LINEAR THREAT VS. THE MORE DISORGANIZED CLUSTERS THE MODEL WAS
HINTING AT EARLIER.
IT SHOULD BE NOTED THAT THERE IS STILL SOME DISAGREEMENT AMONGST THE
SHORT TERM, HIGH RESOLUTION MODELS. MOST SUGGEST SEVERE WEATHER, BUT
A BIT MORE DISORGANIZED AND NEVER QUITE DEVELOPING A SOLID LINEAR
SYSTEM. ALL MODELS CONTINUE TO INDICATE SEVERE THUNDERSTORMS HOWEVER
SO IT CONTINUES TO LOOKS LIKE A BUSY EVENING AHEAD. THE LATEST HRRR
IS NOW COMING AROUND TO A MORE LINEAR SYSTEM.
WHILE THE CONVECTIVE COMPLEX THAT DEVELOPS THIS EVENING WILL LIKELY
PUSH MUCH OF THE INSTABILITY SOUTHWARD, ANOTHER WEAK MID LEVEL
SHORTWAVE WILL MOVE INTO THE AREA TUESDAY AFTERNOON AND EVENING.
WITH THE 925-850 MB BOUNDARY NEAR THE MISSOURI RIVER TOWARDS I-90 A
FEW STRONGER UPDRAFTS COULD PRODUCE LOCALLY HEAVY RAIN AND ISOLATED
SEVERE WEATHER. CONFIDENCE IS MODERATE TO LOW AS THIS ACTIVITY WILL
BE SOMEWHAT DEPENDENT UPON THIS EVENINGS ACTIVITY.
RIDGING TO THE WEST AND WEAK NORTHWEST FLOW ALOFT WILL AID IN
SUPPORTING A PERIOD OF BELOW NORMAL TEMPERATURES FROM ABOUT
WEDNESDAY INTO SUNDAY. LOWS WILL GENERALLY BE IN THE 50S TO LOWER
60S WITH HIGHS IN THE 70S TO LOWER 80S. WHILE THE PREDICTABILITY OF
ANY OF THE SMALLER WAVES IS PRETTY LOW THERE IS SOME GENERAL
AGREEMENT THAT LATER IN THE PERIOD TOWARDS SATURDAY AND SUNDAY THE
CHANCES FOR SHOWERS AND THUNDERSTORMS WILL INCREASE AS UPPER LEVEL
RIDGING PUSHES EAST AND WESTERLY FLOW INCREASES.
AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/
ISSUED AT 1135 PM CDT MON JUL 28 2025
A MIX OF VFR TO IFR AS A LINE OF THUNDERSTORMS CONTINUE TO PROGRESS
ACROSS THE COUNTY WARNING AREA. CURRENTLY STORMS ARE LOCATED EAST OF
THE SD/MN/IA BORDER. THESE STORMS HAVE A HISTORY OF PRODUCING VERY
STRONG WIND GUSTS IN EXCESS OF 75 MPH. THESE STORMS WILL CONTINUE TO
PROGRESS EASTWARD AND THE STRONGEST STORMS SHOULD BE EAST OF THE
AREA AROUND 29.09Z. IN ADDITION, LINGERING NON-SEVERE SHOWERS AND
THUNDERSTORMS ALONG AND SOUTH OF I-90. THESE SHOULD MOVE EAST AND
DISSIPATE OVER THE NEXT FEW HOURS.
CEILINGS ARE IMPROVING FROM WEST TO EAST AS THE CLOUDS BEGIN TO
BREAK UP AND MOVE OUT. HOWEVER, DUE TO THE RAIN, PATCHY DENSE FOG
AND/OR LOW STRATUS WILL BE POSSIBLE INTO TUESDAY MORNING. EXPECT
THESE TO BURN OFF SHORTLY AFTER SUNRISE.
WINDS TUESDAY WILL BE NORTHEASTERLY SUSTAINED AT 9-12 KTS WITH GUSTS
TO 20 KTS. WINDS BECOME LIGHT TUESDAY EVENING.
FSD WATCHES/WARNINGS/ADVISORIES
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
DISCUSSION...08
AVIATION...AJP
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