355
FXUS63 KFSD 271721
AFDFSD
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
1221 PM CDT WED AUG 27 2025
KEY MESSAGES
- SCATTERED SHOWERS AND STORMS MAY DEVELOP THIS AFTERNOON AND
EVENING. SEVERE WEATHER IS NOT EXPECTED.
- TEMPERATURES RETURN NEAR SEASONAL AVERAGES FOR TODAY AND
THURSDAY, WITH A SLIGHTLY COOLER DAY FRIDAY.
- MORE WIDESPREAD RAIN CHANCES AND COOLER CONDITIONS RETURN BY
FRIDAY NIGHT THROUGH THE UPCOMING HOLIDAY WEEKEND. DETAILS
REMAIN UNCERTAIN HEADING INTO THE WEEKEND SO CONTINUE TO
MONITOR THE LATEST FORECAST.
DISCUSSION
ISSUED AT 316 AM CDT WED AUG 27 2025
NOW THROUGH TONIGHT: ISOLATED TO SCATTERED SHOWERS HAVE DEVELOPED
EARLY THIS MORNING, MAINLY EAST OF I-29 BUT DO ANTICIPATE ADDITIONAL
DEVELOPMENT BACK TO THE WEST TOWARD THE JAMES RIVER VALLEY, ALIGNING
MORE WITH THE ORIENTATION OF THE LLJ AND WAA MOVING THROUGH THE
FORECAST AREA THIS MORNING. CAN'T RULE OUT A FEW ISOLATED RUMBLES OF
THUNDER WITH VERY WEAK INSTABILITY. STARTING OFF MORE MILD THAN THE
LAST COUPLE OF MORNINGS WITH TEMPS IN THE MID 50S TO LOWER 60S.
MID LEVEL SHORT WAVE SLIDES SOUTH THROUGH THE DAY TODAY, WITH THE
UPPER LEVEL JET OVERHEAD. WAA AND SOUTHERLY SURFACE FLOW AIDS IN
WARMING TEMPERATURES UP FROM THE LAST COUPLE OF DAYS, LEADING TO
HIGHS IN THE UPPER 70S TO MID 80S. A BOUNDARY AT THE SURFACE AND
LOWER LEVELS MOVES INTO THE FORECAST AREA THROUGH THE DAY AS WELL,
WHICH WILL BE THE CATALYST ALONG WITH PEAK HEATING FOR SCATTERED
SHOWERS AND STORMS THIS AFTERNOON AND EVENING STRETCHING FROM SOUTH
CENTRAL SD TO SOUTHWESTERN MN. SEVERE WEATHER IS NOT EXPECTED WITH
MOST GUIDANCE SHOWING 1200 J/KG OR LESS OF LONG, SKINNY CAPE AND MID
LEVEL LAPSE RATES AROUND 6 DEG C/KM. WITH BULK SHEAR AROUND 30
KNOTS, CAN'T ENTIRELY RULE OUT A STRONGER STORM PRODUCING SMALL HAIL
(FREEZING LEVELS AROUND 11KFT). RAINFALL AMOUNTS MAY BE QUITE
VARIABLE WITH THE SCATTERED NATURE OF SHOWERS/STORMS, BUT SOME
LOCATIONS COULD SEE A QUARTER OF AN INCH OF RAIN OR MORE.
SHOWER AND STORM CHANCES TAPER OFF THROUGH LATE EVENING AS WE MOVE
AWAY FROM PEAK HEATING. FOG MAY DEVELOP TONIGHT INTO THURSDAY
MORNING WITH LIGHT WINDS ACROSS THE AREA. FOG WOULD BE MORE LIKELY
IN RIVER VALLEYS AND AREAS WHICH RECEIVE RAIN TODAY. LOWS TONIGHT
FALL INTO THE MID 50S TO NEAR 60.
THURSDAY: AFTER ANY MORNING FOG ON THURSDAY, DRY AND SEASONAL
CONDITIONS EXPECTED WITH THE MID/UPPER LEVEL RIDGE AXIS TO THE WEST.
HIGHS AGAIN IN THE MID/UPPER 70S TO MID 80S. THURSDAY NIGHT SHOULD
REMAIN DRY WITH THE WAVE AND JET REMAINING ACROSS WESTERN SD INTO NE
DURING THIS TIME, BUT DO EXPECT AN INCREASE IN CLOUD COVER WITH LOWS
IN THE MID 50S TO NEAR 60.
FRIDAY ONWARD: 27.00Z GUIDANCE SHOWS CONSIDERABLE DISAGREEMENT IN
THE DETAILS OF THE PATTERN FRIDAY THROUGH THE HOLIDAY WEEKEND AND
EARLY NEXT WEEK. FOR FRIDAY, EXPECT AT LEAST ONE MID LEVEL SHORT
WAVE TO MOVE THROUGH THE REGION BEGINNING AS EARLY AS FRIDAY
AFTERNOON, WITH WAA AND A SURFACE LOW LIFTING OUT OF WESTERN SD/NE.
THIS WOULD BRING THE RETURN OF SHOWER AND STORM CHANCES. REGARDLESS
OF TIMING/TRACK OF RAIN CHANCES, FRIDAY LOOKS TO BE A BREEZY AND
SLIGHTLY COOLER DAY.
FOR THE HOLIDAY WEEKEND, GFS AND NAM (THROUGH THE END OF ITS RUN)
KEEP MORE OPEN WAVES TREKKING THROUGH THE NORTHWESTERLY MID LEVEL
FLOW REGIME, CLOSING THE MID LEVEL LOW OFF A BIT LATER AND FURTHER
WEST. MEANWHILE, THE CANADIAN AND ECMWF HAVE LESS DEFINED WAVES, AND
CLOSE OFF THE MID LEVEL LOW A BIT SOONER AND FURTHER EAST. ALL
MODELS KEEP THIS LOW OR SOME SORT OF TROUGH AXIS IN THE VICINITY
THROUGH THE HOLIDAY WEEKEND. ALL THAT TO SAY, DETAILS IN TIMING OF
RAIN CHANCES REMAIN UNCERTAIN, BUT CONDITIONS LOOK PREDOMINATELY
COOL, CLOUDY, BREEZY, AND PERIODICALLY RAINY THROUGH SUNDAY AND INTO
LABOR DAY.
AVIATION /18Z TAFS THROUGH 18Z THURSDAY/
ISSUED AT 1221 PM CDT WED AUG 27 2025
SLIGHTLY BREEZY SOUTHWESTERLY WINDS WILL DECREASE THROUGH THE
AFTERNOON AND EVENING HOURS, BECOMING LIGHT AND VARIABLE. THERE IS A
CHANCE FOR SOME PATCHY DENSE FOG TO DEVELOP OVERNIGHT, ESPECIALLY
OVER CENTRAL SOUTH DAKOTA AND ALONG AND NORTH OF I-90. FOG SHOULD
BEGIN TO BURN OFF SHORTLY AFTER SUNRISE THURSDAY.
KFSD MAY SEE A FEW LIGHT SHOWERS THIS EVENING INTO VERY EARLY
THURSDAY MORNING. SEVERE WEATHER IS NOT EXPECTED. CONFIDENCE IN
SHOWERS ACTUALLY IMPACTING THE TAF SITE IS LOW AND SO COVERED
SHOWER CHANCES WITH A PROB30 GROUP.
FSD WATCHES/WARNINGS/ADVISORIES
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
DISCUSSION...SG
AVIATION...AJP
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