172
FXUS63 KFSD 121853
AFDFSD
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
153 PM CDT FRI SEP 12 2025
KEY MESSAGES
- WELL ABOVE NORMAL TEMPERATURES (10+ DEGREES), WILL CONTINUE
THROUGH THE WEEKEND AND INTO EARLY NEXT WEEK. WBGT VALUES
REACH THE MODERATE LEVELS, AND THOSE PARTICIPATING IN OUTDOOR
ACTIVITY SHOULD USE SOME CAUTION.
- CONVECTION CHANCES REMAIN LOW THROUGH SATURDAY AND INTO
SUNDAY, HOWEVER CHANCES DO INCREASE SUNDAY AFTERNOON INTO
SUNDAY NIGHT.
- CONDITIONAL RISKS FOR ISOLATED SEVERE STORMS DEVELOP SUNDAY
AFTERNOON INTO THE EVENING. MARGINAL HAIL AND BRIEF STRONG
WIND GUSTS ARE THE PRIMARY RISKS.
- NEXT REASONABLE RISK FOR RAIN ARRIVE TUESDAY AND CONTINUES
THROUGH WEDNESDAY, WITH COOLER TEMPERATURES THE SECOND HALF
OF NEXT WEEK.
DISCUSSION
ISSUED AT 151 PM CDT FRI SEP 12 2025
THIS AFTERNOON: SHORTWAVE ENERGY MOVING THROUGH EARLY THIS
AFTERNOON WILL CONTINUE TO PUSH MODEST WARM ADVECTION AXIS (AND
COEXISTING RISK OF CONVECTION) EAST OF THE CWA. FURTHER WEST, WE'LL
CONTINUE TO A MID-LVL AND UPPER CLOUD DECK BUILD INTO THE REGION AS
TEMPERATURES RISE INTO THE 80S.
TONIGHT: AN UPPER TROUGH CENTERED OVER THE ROCKIES AND WESTERN CONUS
WILL BEGIN TO SLOWLY DRIFT EASTWARD OVERNIGHT. MODELS REMAIN
CONSISTENT IN A SHORTWAVE TROUGH EJECTING NORTHEAST THROUGH THE
WESTERN HIGH PLAINS AND DAKOTAS OVERNIGHT, BRINGING RISKS OF
CONVECTION TO THOSE AREAS. WHILE THE BULK OF THIS ACTIVITY STAYS
WELL WEST OF THE CWA, WOULDN'T DISCOUNT AN ISOLATE
SHOWER/THUNDERSTORM DEVELOPING IN CENTRAL SOUTH DAKOTA AROUND
DAYBREAK. FURTHER EAST, WE'LL MOSTLY SEE LINGERING MID-UPR CLOUD
COVE OVERNIGHT WITH A SURFACE WARM FRONT DRIFTING NORTHWARD. SOME
MODEST CONVERGENCE ON THE LLJ IN SOUTHERN MINNESOTA COULD DEVELOP AN
ISOLATED SHOWER OVER THE EASTERN CWA, BUT CHANCES TOO LOW TO
INDICATE AT THIS TIME.
SATURDAY: A LARGE DOME OF WARM AIR AT 850MB WILL LIFT NORTHWARD,
WITH TEMPERATURES AT THAT LEVEL BREAKING THE +25C MARK BY DAYBREAK.
COMBINING THIS WARM LAYER WITH MORE MERIDIONAL FLOW OF THE UPPER
TROUGH, THIS SHOULD KEEP CONDITIONS DRY THROUGH THE DAYTIME HOURS OF
SATURDAY. TEMPERATURES WILL HOWEVER PUSH THE UPPER 80S TO LOWER 90S
IN QUITE A FEW AREAS. SOUNDINGS SHOW A BIT OF DRY AIR WITHIN THE
SOUNDINGS, AND GIVEN HOW WE'RE TRENDING TOWARDS A DRIER
(LOWERING GREENNESS) TIME OF THE YEAR, DEW POINTS IN THE
AFTERNOON COULD MIX DOWN A COUPLE DEGREES WITH THE GUSTY
SOUTHERLY WINDS. NEVERTHELESS, HEAT INDEX VALUES MAY APPROACH
THE MIDDLE TO UPPER 90S IN A FEW AREAS.
SATURDAY NIGHT: A SECONDARY SHORTWAVE MOVES NORTHWARD THROUGH THE
PLAINS SATURDAY NIGHT INTO SUNDAY, INDUCING SCATTERED THUNDERSTORMS
IN CENTRAL AND WESTERN DAKOTAS/NEBRASKA OVERNIGHT. WHILE CHANCES
REMAIN LOW, COULD SEE SOME EVENING DEVELOPMENT NEAR A STALLED
FRONTAL BOUNDARY IN SOUTH CENTRAL AND CENTRAL SD EARLY IN THE
EVENING. FURTHER EAST, OVERNIGHT LOW TEMPERATURES WILL BE SLOW TO
DECLINE GIVEN THE PERSISTENT MIXY CONDITIONS.
SUNDAY: GUIDANCE REMAINS IN MODEST TO STRONG AGREEMENT THAT
SCATTERED SHOWERS AND THUNDERSTORMS MAY BE ONGOING EARLY IN THE
PERIOD SUNDAY WEST OF THE JAMES RIVER. SOME UNCERTAINTIES FURTHER
EAST AS WARMING WILL BE DEPENDENT ON MID-LVL CLOUD COVER. HOWEVER
SHOULD TEMPERATURES WARM INTO THE MIDDLE TO UPPER 80S, THEN
POTENTIAL FOR EARLY TO MID AFTERNOON THUNDERSTORM DEVELOPMENT
INCREASES. MODEL SOUNDINGS SHOW QUITE A VARIATION IN BOTH MID-LVL
LAPSE RATES AND BOUNDARY LAYER MOISTURE, RESULTING IN A DECENT
SPREAD OF MLCAPE FROM 800 J/KG TO 1500 J/KG. ADDITIONALLY, IF NEXT
SHORTWAVE APPROACHES TOO EARLY IN THE DAY, THEN ANY SEVERE RISKS MAY
LESSON CONSIDERABLY. HOWEVER, IF ALL THINGS COME TOGETHER IN THE
RIGHT WAY, MODEST SHEAR COMBINED WITH REASONABLE INSTABILITY COULD
LEAD TO AN ISOLATED HAIL OR WIND PRODUCING STORM IN THE AFTERNOON
AND EVENING. THIS MATCHES WELL WITH THE SWODY3 MARGINAL OUTLOOK FOR
THE AREA.
MONDAY-THURSDAY: LOOKING AHEAD TO NEXT WEEK INDICATES THAT WE'LL
CONTINUE TO SEE ABOVE NORMAL TEMPERATURES MONDAY AND TUESDAY AS
THE LONGWAVE RIDGE AXIS REMAINS FOCUSED WEST OF THE ROCKIES.
GUSTY SOUTHERLY WINDS ON MONDAY KEEP TEMPERATURES 10+ DEGREES
ABOVE NORMAL. MORE UNCERTAINTY BUILDS FROM TUESDAY THROUGH
THURSDAY AS ENSEMBLE AND DETERMINISTIC MODELS FAVOR THE UPPER
TROUGH SHIFTING EAST INTO THE PLAINS. LIFT BEGINS IN EARNEST
TUESDAY, WITH BROAD WARM ADVECTION SHOWERS AND THUNDERSTORMS
DEVELOPING. BEYOND TUESDAY, CONFIDENCE LOWERS AS THE EVENTUAL
EVOLUTION OF THE UPPER TROUGH (OPEN WAVE VS CLOSED LOW) GROWS
UNCERTAIN. NEVERTHELESS, POPS REMAIN ELEVATED THROUGH THE MIDDLE
OF THE WEEK WITH GLOBAL ENSEMBLES SUGGESTING OVER 60%
PROBABILITIES OF 0.10" OF PRECIPITATION BY WEDNESDAY INTO
THURSDAY. TEMPERATURES WILL BEGIN TO LOWER BACK TOWARDS NORMAL
LEVELS AT END SECOND HALF OF THE WEEK.
AVIATION /18Z TAFS THROUGH 18Z SATURDAY/
ISSUED AT 1154 AM CDT FRI SEP 12 2025
VFR CONDITIONS CONTINUE TO MOVE THROUGH THE REGION. MID-LVL WAVE
MOVING THROUGH WILL SPARK SCATTERED SHOWERS AND THUNDERSTORMS
ALONG THE BUFFALO RIDGE INTO EARLY AFTERNOON BEFORE SHIFTING
EAST. ELSEWHERE, A BROKEN MID-LVL CLOUD FIELD WILL DEVELOP AS
SURFACE WINDS REMAIN SOUTHEASTERLY.
TONIGHT WILL FEATURE VFR CONDITIONS ONCE AGAIN AS WINDS REMAIN
BREEZY. MID-LVL CLOUDS ARE LIKELY TO CONTINUE INTO SATURDAY
MORNING. LOW PROBABILITIES FOR LLWS DEVELOP NEAR SIOUX CITY.
SATURDAY WILL FEATURE VFR CONDITIONS ONCE AGAIN WITH A GUSTY
SOUTHERLY WIND DEVELOPING BY MID-LATE MORNING.
FSD WATCHES/WARNINGS/ADVISORIES
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
DISCUSSION...DUX
AVIATION...DUX
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