321
FXUS63 KFSD 101949
AFDFSD
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
249 PM CDT WED SEP 10 2025
KEY MESSAGES
- MORE FOG IS LIKELY TO DEVELOP TONIGHT MAINLY EAST OF I-29.
SOME AREAS COULD SEE LOCALLY DENSE FOG MAINLY IN SOUTHWEST
MINNESOTA THROUGH MID-MORNING TOMORROW.
- TEMPERATURES WARM TO WELL ABOVE MID-SEPTEMBER NORMALS HEADING
INTO THE WEEKEND AND INTO EARLY NEXT WEEK.
- RAIN/STORM CHANCES INCREASE THIS WEEKEND, WITH A 30-50% CHANCE
WEST OF I-29 LATE SATURDAY AND A 30-50% CHANCE AREA-WIDE
SUNDAY INTO SUNDAY NIGHT.
DISCUSSION
ISSUED AT 245 PM CDT WED SEP 10 2025
WE'RE SEEING A MIX OF CLOUDS AND SUN ACROSS THE AREA AS
TEMPERATURES PEAK IN THE THE MID-70S TO LOW-80S. THE ONLY EXCEPTION
TO THIS SEASONAL WARMTH IS OVER PARTS OF SOUTHWEST MINNESOTA WHERE
STUBBORN LINGERING STRATUS IS HOLDING TEMPERATURES TO MID-60S TO LOW-
70S. THESE CLOUDS WILL CONTINUE DISSIPATING THROUGH THE REMAINDER OF
THE AFTERNOON INTO THE EVENING. WITH THE AMOUNT OF MOISTURE OUT
THERE AND AS CLEARING SKIES ALLOW THE TEMPERATURES TO COOL
QUICKLY TONIGHT, MORE FOG IS EXPECTED TO DEVELOP MAINLY ALONG
AND EAST OF I- 29. THE ONLY LIMITING FACTOR TO FOG DEVELOPMENT
WILL BE HIGHER WINDS TONIGHT THAN COMPARED TO LAST NIGHT. WINDS
WILL BE LIGHTEST EAST OF I-29 HENCE THE BETTER CHANCE OF FOG
DEVELOPMENT THERE. THE BEST CHANCE FOR DENSE FOG OF A QUARTER
MILE VISIBILITY OR LESS LOOKS TO BE OVER SOUTHWEST MINNESOTA.
LOWS TONIGHT DROP TO THE MID-50S TO LOW-60S. AFTER THE MORNING
FOG BURNS OFF TOMORROW, EXPECT PARTLY CLOUDY SKIES THROUGH THE
DAY TOMORROW WITH HIGHS MAINLY IN THE 80S.
A SERIES OF UPPER-LEVEL WAVES WILL MOVE THROUGH THE AREA STARTING
THURSDAY EVENING AND INTO THE WEEKEND. FOR THURSDAY EVENING INTO THE
NIGHT, INSTABILITY WILL BE HIGHEST ALONG AND WEST OF THE JAMES RIVER
(1000-2000 J/KG OF MLCAPE), BUT A STRONG CAP WILL BE IN PLACE, SO
THUNDERSTORM DEVELOPMENT LOOKS UNLIKELY. HOWEVER, THERE WILL BE
ENOUGH WAA AT 850 MB AND A SUFFICIENT LLJ (AROUND 30-35 KTS) TO
TRIGGER ISOLATED SHOWERS THURSDAY NIGHT IN CENTRAL SOUTH DAKOTA
MAINLY WEST OF THE JAMES. ANOTHER WEAK WAVE MOVES IN DURING THE DAY
ON FRIDAY, BUT ONCE AGAIN THE STRONG CAP IN PLACE WILL PREVENT
THUNDERSTORM DEVELOPMENT OVER THE AREA. HEADING INTO FRIDAY EVENING
INTO THE NIGHT, A TROUGH OVER THE PACIFIC NORTHWEST WILL BEGIN TO
MOVE INTO THE NORTHERN ROCKIES/WESTERN HIGH PLAINS. THE BEST UPPER-
LEVEL SUPPORT WILL REMAIN WEST OF THE AREA; HOWEVER, A WEAKER CAP
LOOKS TO BE IN PLACE FOR AREAS WEST OF THE JAMES RIVER AND THUS AN
ISOLATED STORM OR TWO WILL BE POSSIBLE. BULK SHEAR LOOKS TO BE LESS
THAN 30 KTS, SO SEVERE WEATHER LOOKS UNLIKELY AT THIS TIME. THE
AFOREMENTIONED TROUGH WILL CONTINUE TO MOVE TOWARDS OUR AREA
INTO THE WEEKEND BEFORE EVENTUALLY EJECTING TO OUR
NORTH/NORTHEAST AT THE END OF THE WEEKEND. AFTER SOME SCATTERED
SHOWER AND STORM CHANCES SATURDAY EVENING MAINLY WEST OF I-29,
MOST GUIDANCE INDICATES THIS TROUGH EJECTION OCCURRING SOMETIME
BETWEEN SUNDAY INTO MONDAY MORNING, AND ENSEMBLE PROBABILITIES
FOR MEASURABLE RAINFALL SUGGESTS THE GREATEST POTENTIAL HAS
SHIFTED TOWARDS SUNDAY INTO SUNDAY NIGHT. AT THIS POINT IT IS
TOO EARLY TO TELL IF THERE WILL BE SEVERE WEATHER WITH THIS
SYSTEM, BUT IT WILL BE SOMETHING TO KEEP AN EYE ON. AS THE
TROUGH EXITS THE AREA, ANOTHER ONE WILL SWING TOWARDS OUR AREA
INTO NEXT WEEK, POTENTIALLY KEEPING MORE RAIN/STORM CHANCES IN
THE FORECAST.
TEMPERATURE WISE THROUGH THE WEEKEND INTO NEXT WEEK, RIDGING ALOFT
WILL CONTINUE TO BUILD THROUGH THE WEEKEND. THIS WILL ALLOW
TEMPERATURES TO HEAT UP WITH HIGHS WELL INTO THE 80S EXPECTED ON
FRIDAY AND SATURDAY. THERE IS A CHANCE FOR A FEW SPOTS TO REACH THE
LOW-90S SATURDAY AFTERNOON, MAINLY OVER NORTHWEST IOWA. DID BLEND IN
SOME OF THE NBM 50TH PERCENTILE INTO HIGHS FOR THE WEEKEND, AS THE
REGULAR NBM WAS RUNNING TOO WARM DUE TO A WARM-BIAS IN THE GFS.
TEMPERATURES MAY MODERATE SOMEWHAT DURING THE NEXT WORK WEEK DUE TO
MORE TROUGHINESS OVER THE AREA, BUT WE STILL LOOK BE WARMER THAN
AVERAGE THROUGH MID-WEEK.
AVIATION /18Z TAFS THROUGH 18Z THURSDAY/
ISSUED AT 1240 PM CDT WED SEP 10 2025
MORNING FOG HAS DISSIPATED, BUT SOME LOW STRATUS REMAINS ALONG WITH
SOME DEVELOPING MVFR CU TO START THE PERIOD. THESE CLOUDS SHOULD
GRADUALLY LIFT THROUGH THE AFTERNOON, LEADING TO VFR CONDITIONS
AREA- WIDE THIS EVENING. MORE FOG IS EXPECTED TO DEVELOP LATE
TONIGHT INTO EARLY TOMORROW MORNING, THOUGH IT IS NOT EXPECTED
TO BE AS DENSE AS IT WAS THIS MORNING AT LEAST AT THE TAF SITES.
THIS IS DUE TO HIGHER WINDS AND SOME HIGH CLOUD COVER, BUT
VISIBILITIES COULD STILL DROP TO MVFR TO IFR ALONG AND EAST OF
I-29 ESPECIALLY AROUND DAYBREAK TOMORROW. THE BEST CHANCE OF
SEEING DENSE FOG WITH VISIBILITIES A QUARTER MILE OR LOWER WILL
BE OVER SOUTHWEST MINNESOTA. AFTER FOG LIFTS, VFR CONDITIONS ARE
EXPECTED TO END THE PERIOD.
WINDS WILL BE OUT OF THE EAST-SOUTHEAST THROUGH THIS EVENING,
TURNING MORE SOUTHEASTERLY INTO TOMORROW MORNING. STRONGEST GUSTS
THROUGH THE PERIOD (20-25 KTS) WILL BE ALONG AND WEST OF THE JAMES
RIVER THIS AFTERNOON, AND THEN ALONG AND WEST OF I-29 LATE TOMORROW
MORNING.
FSD WATCHES/WARNINGS/ADVISORIES
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
DISCUSSION...SAMET
AVIATION...SAMET
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