599
FXUS63 KFSD 130801
AFDFSD
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
301 AM CDT SAT SEP 13 2025
KEY MESSAGES
- PATCHY FOG, INCLUDING VISIBILITY BELOW ONE MILE, IS POSSIBLE
TONIGHT NEAR THE BUFFALO RIDGE.
- WELL ABOVE NORMAL TEMPERATURES (10+ DEGREES), WILL CONTINUE
THROUGH THE WEEKEND AND INTO EARLY NEXT WEEK. WBGT VALUES
REACH THE MODERATE LEVELS, ESPECIALLY TODAY, AND THOSE
PARTICIPATING IN OUTDOOR ACTIVITY SHOULD USE SOME CAUTION.
- CONVECTION CHANCES REMAIN LOW INTO SUNDAY MORNING, HOWEVER
CHANCES DO INCREASE SUNDAY AFTERNOON INTO SUNDAY NIGHT. A FEW
STORMS WILL BE POSSIBLE IN CENTRAL SD TONIGHT.
- 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 ARRIVES TUESDAY AND CONTINUES
THROUGH WEDNESDAY, WITH COOLER TEMPERATURES THE SECOND HALF OF
NEXT WEEK.
DISCUSSION
ISSUED AT 300 AM CDT SAT SEP 13 2025
A HOT AND SOMEWHAT HUMID DAY IS AHEAD WITH GUSTY SOUTHERLY WINDS
AROUND 25 MPH. HIGHS WILL GENERALLY BE IN THE UPPER 80S TO LOWER 90S
WITH DEW POINTS IN THE MID TO UPPER 60S. MODEL SOUNDINGS ARE SHOWING
STRONG CAPPING SO NOT ANTICIPATING ANY THUNDERSTORM DEVELOPMENT THIS
AFTERNOON WITH THIS HEAT AND HUMIDITY. THE ONE EXCEPTION WHERE THE
CAPPING INVERSION IS A BIT WEAKER IS IN CENTRAL SD, WEST OF THE
JAMES RIVER, WHERE SOME POTENTIAL FOR DEVELOPMENT WILL BE POSSIBLE
VERY LATE AFTERNOON INTO THE EVENING. THE BETTER CHANCES MOST
CERTAINLY WILL BE LATER IN THE EVENING AND OVERNIGHT AS LOW PRESSURE
DEEPENS TO THE WEST AND MID LEVEL MOISTURE INCREASES NEAR AND WEST
OF THE JAMES RIVER. WHILE A VERY ISOLATED SEVERE STORM WOULD BE
POSSIBLE, THE MAIN THREATS WILL BE LIGHTNING AND LOCALLY HEAVY RAIN.
AN UNSEASONABLY STRONG UPPER LEVEL LOW PRESSURE SWINGS NORTH INTO
WESTERN AND CENTRAL SD ON SUNDAY. A SHOT OF MID LEVEL MOISTURE AND
LIFT SPREAD NORTH INTO CENTRAL SD LATE SUNDAY MORNING INTO THE EARLY
AFTERNOON. EXPECT SHOWERS AND THUNDERSTORMS TO DEVELOP OR MOVE INTO
THE AREA DURING THIS TIME. INSTABILITY AND SHEAR VERY MARGINAL FOR
ANY SEVERE, SO THE THREAT WILL BE VERY LOW. DURING THE EVENING AND
OVERNIGHT HOURS THE MAIN WAVE WILL DRIFT NORTH INTO SOUTHEAST SD AND
SHOULD BRING SCATTERED SHOWERS AND THUNDERSTORMS. MODEL SOUNDINGS ARE
SOMEWHAT INCONCLUSIVE ON THE SEVERE WEATHER THREAT, BUT WITH 1000-
1500 J/KG CAPE SUSPECT AN UPDRAFT OR TWO WILL BRING THE POTENTIAL
FOR 60 MPH WINDS AND QUARTER SIZED HAIL.
MONDAY WILL SEE MID AND UPPER LEVEL RIDGING BUILD INTO THE AREA SO
MORE THAN LIKELY ANY THUNDERSTORM DEVELOPMENT WILL BE SUPPRESSED.
HOWEVER, IT DOES NEED TO BE NOTED THAT AN ENVIRONMENT WILL EXIST
THAT COULD SUPPORT SOME STRONG UPDRAFTS WITH CAPE VALUES OF 2000+
J/KG AND SOME SOLID DIRECTIONAL SHEAR, ALBEIT NOT OVERLY STRONG, IN
THE LOWER LEVELS. SO AGAIN, CAPPING AND MID AND UPPER LEVEL RIDGING
WILL LIKELY KEEP STORMS AT BAY, BUT IF SOMETHING CAN DEVELOP THERE
WOULD BE THE POTENTIAL FOR A SUPERCELL OR TWO, ABOUT A 5% CHANCE.
AS THIS WAVE ROTATES TO THE NORTH A BROAD TROUGH WILL DEVELOP ACROSS
THE NORTHERN PLAINS WEDNESDAY INTO FRIDAY WHICH WILL BRING PERIODIC
CHANCES FOR SHOWERS AND THUNDERSTORMS WITH TEMPERATURES COOLING BACK
TO AROUND OR A BIT BELOW NORMAL. RIGHT NOW TUESDAY NIGHT INTO
WEDNESDAY NIGHT APPEARS TO BE THE BETTER CHANCE FOR SHOWERS AND
STORMS WITH THE EC ENSEMBLE AND GEFS INDICATING ABOUT A 40-60
PERCENT CHANCE FOR A HALF AN INCH OR MORE OF RAIN.
AVIATION /06Z TAFS THROUGH 06Z SUNDAY/
ISSUED AT 1032 PM CDT FRI SEP 12 2025
MID AND HIGH CLOUDS PREVAIL ACROSS THE AREA THROUGH THE PERIOD
WITH VFR CONDITIONS. HI-RES DETERMINISTIC AND ENSEMBLE GUIDANCE
REMAIN KEEN ON MVFR/IFR FOG DEVELOPING NEAR THE BUFFALO RIDGE
LATER TONIGHT AND INTO SATURDAY MORNING AS SOUTHEAST WINDS
BECOME LIGHT TO CALM. NOT EXPECTING ANY IMPACTS TO TAF SITES AT
THIS TIME.
LLJ CONTINUES TO STRENGTHEN THROUGH THE OVERNIGHT HOURS,
LEADING TO LLWS FOR MUCH OF THE AREA EAST OF I-29 AND NEAR/SOUTH
OF I-90. 13.00Z GUIDANCE HAS SHIFTED A TAD FURTHER NORTH WITH
THE NOSE OF THE JET, AND THEREFORE HAVE ADDED LLWS MENTION FOR A
FEW HOURS AT KFSD. CONDITIONS SHOULD IMPROVE QUICKLY AS WE BEGIN
TO MIX TOMORROW MORNING. SOUTHERLY WINDS INCREASE TOMORROW WITH
GUSTS AROUND 20 KNOTS DURING THE DAY.
EXPECT A DRY TAF PERIOD; HOWEVER, HI-RES GUIDANCE SHOWS ISOLATED
SHOWERS AND STORMS ACROSS SOUTH CENTRAL SD TOWARD KHON LATE
TONIGHT TOWARD DAYBREAK SATURDAY AND AGAIN SATURDAY EVENING,
BUT CONFIDENCE IS TOO LOW IN COVERAGE AND POTENTIAL FOR MENTION
AT THIS TIME.
FSD WATCHES/WARNINGS/ADVISORIES
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
DISCUSSION...08
AVIATION...SG
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