491
FXUS63 KFSD 101753
AFDFSD
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
1253 PM CDT THU JUL 10 2025
KEY MESSAGES
- PERIODIC STORM CHANCES CONTINUE LATER TODAY INTO FRIDAY. STORMS
THIS EVENING WILL BRING A THREAT OF ALL STORM MODES, AS WELL AS
LOCALLY HEAVY RAIN, MAINLY SOUTH OF HIGHWAY 18. LESS ORGANIZED
STORMS FRIDAY BRING PRIMARILY AN ISOLATED HAIL/WIND THREAT.
- A DRY WEEKEND IS EXPECTED, WITH COOLER TEMPERATURES SATURDAY
WARMING ABOVE NORMAL BY SUNDAY AND MONDAY.
- THE NEXT RISK FOR THUNDERSTORMS RETURNS TO THE REGION LATE
MONDAY INTO TUESDAY. A FEW STRONGER STORMS ARE POSSIBLE, BUT
DETAILS ARE UNCERTAIN.
DISCUSSION
ISSUED AT 325 AM CDT THU JUL 10 2025
TODAY-TONIGHT: ONGOING LINE OF SUB-SEVERE CONVECTION IS IN THE
PROCESS OF EXITING OUR EASTERN COUNTIES, THOUGH MORE STRATIFORM
RAIN AND ISOLATED EMBEDDED THUNDER WILL LINGER FOR A BIT LONGER.
TRAILING MCV NEAR BROOKINGS AS OF 3 AM WILL LIKEWISE SLIDE EAST,
AND SUBSIDENCE IN THE WAKE OF THIS WAVE SHOULD KEEP OUR AREA
MOSTLY DRY THROUGH MIDDAY.
BY THIS AFTERNOON, WILL HAVE TO MONITOR LOCATION OF DIFFUSE
BOUNDARIES LINGERING IN THE WAKE OF THIS MORNING'S CONVECTION,
AS THESE MAY SERVE TO FOCUS BETTER CHANCES FOR DEVELOPMENT LATE
AFTERNOON INTO THIS EVENING AS A WAVE LIFTS NORTHEAST OUT OF
WESTERN NEBRASKA. WHILE THERE ARE SOME DIFFERENCES AMONG THE
HIGH-RES MODELS, ALSO SEE A BROAD CONSENSUS SHOWING A LINE OF
WEAK ELEVATED STORMS NEAR I-90 EARLY- MID AFTERNOON IN RESPONSE TO
WEAK WARM ADVECTION. THE GREATER POTENTIAL FOR STRONG TO SEVERE
STORMS LOOKS TO BE NEAR AND SOUTH OF HIGHWAY 20 CORRIDOR BY LATE
AFTERNOON AS THE ELONGATED WAVE LIFTS NORTHEAST.
STEEP MID-LEVEL LAPSE RATES AND A MOIST BOUNDARY LAYER WILL
CONTRIBUTE TO ABUNDANT INSTABILITY (MLCAPE 2500+ J/KG) ABOVE A
WEAK CAPPING INVERSION. OVERALL MID-LEVEL WINDS ARE ON THE WEAKER
SIDE, BUT MAY BE LOCALLY ENHANCED BY THE APPROACHING WAVE WHICH
WOULD LEAD TO POCKETS OF STRONGER DEEP LAYER SHEAR SUPPORTIVE OF
ORGANIZED STORMS CAPABLE OF LARGE HAIL UP TO GOLF BALL SIZE (MAYBE
LARGER IF A STORM BEGINS ROTATING) AND ISOLATED DAMAGING WINDS OF
60-70 MPH. IF STORMS FIND A WEAK BOUNDARY WITH WHICH TO INTERACT,
A BRIEF TORNADO IS ALSO POSSIBLE. THE WEAK MID LEVEL FLOW WILL
INITIALLY LEAD TO RELATIVELY SLOW STORM MOTIONS WHICH COULD
PROMOTE POCKETS OF HEAVY RAINFALL. HOWEVER, STORMS ARE EXPECTED
TO EVOLVE INTO A SOUTHEASTWARD MOVING PROGRESSIVE LINE BY LATE
EVENING AS THE CLUSTERS BECOME COLD-POOL DOMINANT. THIS SHOULD
CONFINE THE GREATER THREAT OF SEVERE STORMS AND HEAVY RAIN TO THE
FIRST HALF OF THE NIGHT WITH ACTIVITY IN OUR AREA WANING AFTER
04Z-06Z.
FRIDAY-FRIDAY NIGHT: AGAIN IT SEEMS LIKE A RELATIVELY QUIET
MORNING WILL GIVE WAY TO A SLIGHTLY MORE ACTIVE AFTERNOON-EARLY
EVENING, THE LATTER IN RESPONSE TO 2 DISTINCT FEATURES. FIRST, THE
MID-UPPER LEVEL TROUGH SHIFTS SLIGHTLY EAST WITH ANOTHER PIECE OF
ENERGY (PERHAPS A RESIDUAL MCV) SWINGING TOWARD NORTHWEST IOWA IN
THE AFTERNOON. FARTHER TO THE WEST, A DEEPER NORTHERN STREAM
TROUGH AND ASSOCIATED COLD FRONT BEGIN TO PUSH INTO THE EASTERN
DAKOTAS. EACH OF THESE FEATURES LOOKS TO HAVE DECENT INSTABILITY,
THOUGH SHEAR IS MUCH WEAKER THAN THE PRECEDING COUPLE OF NIGHTS SO
LIKELY LOOKING AT MORE DISORGANIZED MULTI-CELL CLUSTERS CAPABLE OF
MARGINAL LARGE HAIL/WIND.
SATURDAY-EARLY MONDAY: THE NORTHERN STREAM TROUGH BRINGS A BRIEF
SHOT OF COOLER AIR INTO THE NORTHERN PLAINS SATURDAY LEADING TO
HIGHS IN THE MID 70S TO MID 80S. THIS TROUGH QUICKLY ERODES AS A
MORE ZONAL FLOW DEVELOPS ACROSS THE NORTHERN CONUS AND WARMER
TEMPERATURES BUILD BACK INTO THE WESTERN PLAINS, AND WE WILL
LIKELY START NEXT WEEK WITH ABOVE NORMAL TEMPERATURES BACK INTO
THE 80S AND 90S (WARMEST WEST OF I-29). RAIN CHANCES THIS WEEKEND
AND INTO EARLY MONDAY ARE LOW.
LATER MONDAY-WEDNESDAY: A STRENGTHENING TROUGH OVER THE ROCKIES
AND HIGH PLAINS DEVELOPS MONDAY, LIFTING NORTHEAST INTO THE UPPER
MIDWEST ON TUESDAY. THIS SHOULD BRING OUR NEXT CHANCE FOR SHOWERS
AND STORMS, AND OVERALL IT LOOKS LIKE A LOW POTENTIAL FOR SEVERE
STORMS WITH WEAK SHEAR ACROSS THE AREA. HOWEVER, ML OUTPUT DOES
HINT A LOW SEVERE PROBABILITIES, ESPECIALLY BY TUESDAY, SO WILL BE
A PERIOD TO MONITOR OVER THE COMING DAYS. THE TROUGH LOOKS TO BE
FOLLOWED BY A MORE PERSISTENT STRETCH OF COOLER WEATHER WITH SOME
LINGERING RAIN CHANCES INTO THE MIDDLE OF NEXT WEEK.
AVIATION /18Z TAFS THROUGH 18Z FRIDAY/
ISSUED AT 1251 PM CDT THU JUL 10 2025
SCATTERED SHOWERS AND STORMS ARE SET TO DEVELOP NEAR AND ALONG THE
MISSOURI RIVER VALLEY THIS AFTERNOON, BRINGING A RISK OF SEVERE
WEATHER AND HEAVY RAINFALL. WITH THAT, THE BEST CHANCES OF
THUNDERSTORM IMPACTS WILL BE FROM KYKN TO KSUX THROUGH THE EVENING
HOURS, AND THUS HAVE A TEMPO GROUP IN KSUX FROM 00Z TO 03Z TO
ACCOUNT FOR THIS. THE STRONGEST STORMS WILL BRING IFR VISIBILITIES
AND THE POTENTIAL FOR SEVERE WIND GUSTS IN EXCESS OF 50 KTS. AFTER
THE STORMS, SHOWERS MAY CONTINUE FOR AREAS MAINLY SOUTH OF
I-90, BUT GUIDANCE VARIES LARGELY REGARDING ANY ACTIVITY THROUGH
THE EARLY MORNING HOURS. WE'LL DRY OUT HEADING INTO FRIDAY
MORNING, WITH ADDITIONAL THUNDERSTORM DEVELOPMENT POSSIBLE ON
KHON'S DOORSTEP JUST AFTER THIS PERIOD.
WINDS WILL BE MAINLY OUT OF THE SOUTHEAST THROUGH THIS EVENING,
BEFORE TURNING LIGHTER AND MORE VARIABLE FRIDAY MORNING. WITH
LESSENING WINDS AND MOISTURE LEFT BEHIND FROM THESE LAST ROUNDS
OF RAIN, CAN'T ENTIRELY RULE OUT SOME PATCHY LIGHT FOG, BUT NOT
ENOUGH CONFIDENCE TO INCLUDE IN THE TAFS AT THIS TIME. WINDS
WILL PICK UP AGAIN LATER FRIDAY MORNING AS A COLD FRONT
APPROACHES AND TURNS WINDS TO THE WEST-NORTHWEST FOR AREAS WEST
OF THE JAMES RIVER AT THE END OF THE PERIOD.
FSD WATCHES/WARNINGS/ADVISORIES
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
DISCUSSION...JH
AVIATION...SAMET
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