971
FXUS63 KFSD 090850
AFDFSD
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
350 AM CDT WED JUL 9 2025
KEY MESSAGES
- ISOLATED THUNDERSTORMS WILL BE POSSIBLE MOSTLY ACROSS PORTION
OF SOUTHCENTRAL SD THIS MORNING. WHILE THESE STORM WILL
LIKELY STAY SUB- SEVERE, SMALLER HAIL WILL BE POSSIBLE.
- A LINEAR MESOSCALE CONVECTIVE SYSTEM (MCS) WILL LIKELY DEVELOP
OVER CENTRAL SD BY WEDNESDAY NIGHT AND PROGRESSES INTO PORTIONS
OF SOUTHEASTERN SD. THE PRIMARY HAZARDS WILL BE DAMAGING
WINDS UP TO 65 MPH AND LARGE HAIL UP TO HALF DOLLAR SIZE.
- ADDITIONAL CHANCES FOR SHOWERS AND STORMS WILL CONTINUE INTO
THE LATE WEEK WITH THE FOCUS BEING BETWEEN THURSDAY AND
FRIDAY. MIXED STORM MODES COULD BRING A VARIETY OF SEVERE
WEATHER RISK, BUT SLOWER STORM MOTIONS MAY ALSO BRING A
LOCALLY HEAVY RAIN RISK.
DISCUSSION
ISSUED AT 348 AM CDT WED JUL 9 2025
TODAY & TONIGHT: TAKING A LOOK ACROSS THE AREA, MOSTLY QUIET
CONDITIONS CONTINUE AS OF 4 AM THIS MORNING. THE FORECAST STILL
REMAINS ON TRACK FOR A FEW ISOLATED THUNDERSTORMS DEVELOPING ACROSS
SOUTHCENTRAL SD THROUGH DAYBREAK AS PIECES OF VORTICITY INTERACT
WITH A 20-30 KT LLJ. HOWEVER, THE SEVERE RISK WITH THIS ACTIVITY
WILL LIKELY STAY ON THE LOWER SIDE WITH ONLY AROUND 500-750 J/KG OF
INSTABILITY TO WORK WITH. AS THE LLJ WEAKENS, SHOULD SEE THIS
ACTIVITY WEAKEN AND DIMINISH BY MID-MORNING. SHIFTING GEARS HERE,
ANOTHER WARM DAY IS AHEAD AS INCREASING SOUTHEASTERLY WINDS AND
INCREASING MID-LEVEL WARM AIR ADVECTION (WAA) LEAD TO TEMPERATURES
IN THE 80S TO LOW 90S WITH THE WARMEST CONDITIONS CLOSEST TO THE
WARM FRONT SITUATED ALONG AND WEST OF THE MISSOURI RIVER VALLEY.
FROM HERE, THE FOCUS TURNS TO OUR NEXT PRECIPITATION CHANCES THIS
EVENING AND OVERNIGHT.
TAKING A LOOK ALOFT, A QUICK MID-LEVEL WAVE WILL PUSH ACROSS THE
STATE AND INTERSECTS THE PREVIOUSLY MENTIONED WARM FRONT TRIGGERING
SEMI-DISCRETE CLUSTERS OF SHOWERS AND THUNDERSTORMS ACROSS WESTERN
AND CENTRAL SD. WHILE THIS DEVELOPING ACTIVITY WILL HAVE ACCESS TO
AN UNSTABLE ENVIRONMENT CHARACTERIZED BY 2000-3000 J/KG OF
INSTABILITY AND 25-35 KTS OF BULK SHEAR, MODEL SOUNDINGS CONTINUES
SHOW A STABILIZING BOUNDARY LAYER AS THIS DEVELOPING ACTIVITY
MOVES INTO OUR CWA. AS A RESULT, MOST HIGH-RESOLUTION GUIDANCE
HAS THIS DEVELOPING MESOSCALE CONVECTIVE SYSTEM (MCS) WEAKENING
AS IT PROGRESSES EASTWARDS TOWARDS THE I-29 CORRIDOR. WITH THIS
IN MIND, THE MAJORITY OF THE SEVERE RISK (IF ANY) WILL LIKELY BE
ISOLATED TO AREAS WEST OF U.S. HIGHWAY-281 WHERE REMNANT
THUNDERSTORMS COULD PRODUCE DAMAGING WINDS UP TO 65 MPH AND HALF
DOLLAR SIZED HAIL. LASTLY, AS THE LLJ STRENGTHENS ACROSS AREAS
EAST OF I-29 OVERNIGHT; SOME POTENTIAL REDEVELOPMENT WILL BE
POSSIBLE MAINLY IN NORTHWESTERN IA. WHILE THIS ACTIVITY WILL
LIKELY BE SUB-SEVERE DUE TO WANING INSTABILITY, CAN'T COMPLETELY
RULE OUT THE POTENTIAL FOR A FEW ADDITIONAL THUNDERSTORMS WITH
SOME SMALLER HAIL.
THURSDAY-FRIDAY: LOOKING INTO THE LATTER PARTS OF THE WEEK, COULD
SEE THE PREVIOUSLY MENTIONED ACTIVITY LINGERING ACROSS AREAS EAST OF
I-29 THROUGH THE MID-MORNING HOURS ON THURSDAY BEFORE THINGS
PROGRESS OUT OF OUR AREA. FROM HERE, QUIETER CONDITIONS TEMPORARILY
RETURN THROUGH THE LATE AFTERNOON AS TEMPERATURES PEAK IN THE 80S TO
LOW 90S FOR THE DAY. MORE SHOWER AND THUNDERSTORM CHANCES WILL
RETURN DURING THE EVENING TO OVERNIGHT HOURS ON THURSDAY AS A
STRENGTHENING SHORTWAVE LIFTS THROUGH OUR AREA AND INTERSECTS A FEW
LINGERING SURFACE BOUNDARIES LEFT BEHIND FROM THE PREVIOUSLY
MENTIONED MCS. WHILE THERE IS STILL SOME UNCERTAINTY REGARDING WHERE
THINGS WILL SET UP, THE HIGH CAPE/LOW SHEAR ENVIRONMENT ASSOCIATED
WITH THIS SYSTEM; WILL LIKELY SUPPORT AN ISOLATED TO SCATTERED
SEVERE RISK WITH STRONGER STORMS POTENTIALLY DEVELOP UP TO 2 INCH
HAIL (HEN EGG) AND DAMAGING WINDS UP TO 70 MPH WITH STRONG COLD
POOLS. AS INSTABILITY WANES OVERNIGHT, SLOWER STORM MOTIONS ALONG
WITH PWATS BETWEEN 1.50 TO 1.75 INCHES (90TH PERCENTILE) WILL
PROMOTE A LOCALLY HEAVY RAINFALL RISK INTO FRIDAY MORNING.
NONETHELESS, WITH THE VARIETY OF CONVECTIVE SCENARIOS ITS STILL A
BIT DIFFICULT TO PIN POINT AN AREA OF FOCUS FOR THE OVERALL SEVERE
RISK AND ANTECEDENT HEAVY RAINFALL THREATS AT THIS TIME.
LASTLY, GIVEN THE INCREASING PRECIPITATION CHANCES; EXPECT
TEMPERATURES TO DECREASE FROM THE 80S AND LOW 90S ON THURSDAY TO
THE 70S TO LOW 80S BY FRIDAY.
SATURDAY ONWARDS: HEADING INTO THE EXTENDED PERIOD, QUIETER
CONDITIONS RETURN TO THE AREA AS SURFACE RIDGING MOVES IN BY
SATURDAY TO REPLACE THE DEPARTING SYSTEM. WITH BACKING SURFACE WIND
PROFILES AND INCREASING WARM AIR ADVECTION (WAA) IN THE MID-LEVELS,
EXPECT TEMPERATURES TO TREND NEAR TO ABOVE NORMAL OVER THE NEXT FEW
DAYS WITH HIGHS INCREASE FROM THE UPPER 70S TO MID 80S BY SATURDAY
TO THE MID 80S TO LOW 90S BY MONDAY. FROM HERE, OUR NEXT SHOWER AND
THUNDERSTORM CHANCES LIKELY RETURN BY TUESDAY AS A COLD FRONT SWINGS
THROUGH THE REGION. WHILE THE SEVERITY OF THIS ACTIVITY IS STILL
UNCERTAIN, SOME OF THE MACHINE LEARNING GUIDANCE HAS STARTED TO SHOW
SOME WEAK SIGNALS FOR STRONGER ACTIVITY SO THIS PERIOD WILL LIKELY
BE ONE TO WATCH MOVING FORWARDS.
AVIATION /06Z TAFS THROUGH 06Z THURSDAY/
ISSUED AT 950 PM CDT TUE JUL 8 2025
ISOLATED SHOWERS/THUNDERSTORMS WILL BE POSSIBLE THROUGH CENTRAL
SD INTO THE JAMES RIVER VALLEY LATE TONIGHT INTO WEDNESDAY
MORNING. ALTHOUGH THIS ACTIVITY COULD APPROACH KHON AND KSUX, AT
THIS TIME GUIDANCE WOULD SUGGEST THAT THIS ACTIVITY WILL REMAIN
WEST OF THE TAF SITES. ANY SHOWERS/STORMS WOULD END BY MID
MORNING ON WEDNESDAY. ADDITIONAL SHOWERS AND THUNDERSTORMS MAY
DEVELOP THROUGH CENTRAL SD ON WEDNESDAY EVENING, AND THIS
ACTIVITY COULD AFFECT KHON TOWARD THE END OF THE TAF PERIOD.
FSD WATCHES/WARNINGS/ADVISORIES
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
DISCUSSION...05
AVIATION...JM
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