171
FXUS63 KFSD 282329
AFDFSD
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
629 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 /00Z TAFS THROUGH 00Z WEDNESDAY/
ISSUED AT 628 PM CDT MON JUL 28 2025
A MIX OF VFR TO MVFR AS STRONG TO SEVERE THUNDERSTORMS APPROACH FROM
THE WEST. EXPECT CEILINGS TO DEGRADE TO MVFR TO IFR UNDER THE
STRONGER STORMS. THESE STORMS WILL BE CAPABLE OF PRODUCING VERY
STRONG WIND GUSTS IN EXCESS OF 70 MPH, HAIL TO THE SIZE OF GOLF
BALLS, HEAVY DOWN POURS, AND A FEW TORNADOES. AS THESE STORMS TRACK
EAST ACROSS THE REGION WE EXPECT THEY WILL GROW INTO A LARGE LINEAR
SYSTEM THAT WILL TRANSITION TO MORE OF A WIND THREAT. GUSTS OF 80-90
MPH ARE POSSIBLE. THE STORMS QUICKLY MOVE EAST BY EARLY WEDNESDAY
MORNING.
CEILINGS WILL REMAIN MVFR AS SOME FOG AND LOW STRATUS FORM BEHIND
THE STORMS. CONDITIONS IMPROVE AS WE APPROACH MID-DAY AND THE CLOUDS
BEGIN TO BREAK UP.
FSD WATCHES/WARNINGS/ADVISORIES
SD...EXTREME HEAT WARNING UNTIL 8 PM CDT THIS EVENING FOR SDZ050-
052>055-057>071.
HEAT ADVISORY UNTIL 8 PM CDT THIS EVENING FOR SDZ038>040-056.
MN...EXTREME HEAT WARNING UNTIL 8 PM CDT THIS EVENING FOR MNZ098.
HEAT ADVISORY UNTIL 8 PM CDT THIS EVENING FOR MNZ071-072-080-
081-089-090-097.
IA...EXTREME HEAT WARNING UNTIL 8 PM CDT THIS EVENING FOR
IAZ001>003-012>014-020>022-031-032.
NE...EXTREME HEAT WARNING UNTIL 8 PM CDT THIS EVENING FOR NEZ013-
014.
DISCUSSION...08
AVIATION...AJP
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