528
FXUS63 KFSD 310738
AFDFSD
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
238 AM CDT SAT MAY 31 2025
KEY MESSAGES
- SCATTERED SHOWERS AND A FEW THUNDERSTORMS MOVE THROUGH AREAS
WEST OF THE JAMES RIVER VALLEY SATURDAY MORNING. SEVERE
WEATHER NOT ANTICIPATED.
- HIGH LEVEL CANADIAN WILDFIRE SMOKE WILL CONTINUE THROUGH THE
WEEKEND. SOME GROUND LEVEL SMOKE OR REDUCED AIR QUALITY IS
POSSIBLE LATER SATURDAY, BUT ESPECIALLY SUNDAY.
- THUNDERSTORM RISKS RETURN LATE MONDAY AFTERNOON AND PEAK
MONDAY NIGHT. SEVERE WEATHER RISKS WILL BE POSSIBLE ESPECIALLY
NORTHWEST OF LINE FROM YANKTON TO SIOUX FALLS TO MARSHALL.
RISKS INCLUDE LARGE HAIL AND LOCALIZED SEVERE WIND.
DISCUSSION
ISSUED AT 235 AM CDT SAT MAY 31 2025
THIS MORNING: COMPACT OPEN LOW PIVOTING SOUTHWARD THROUGH THE
DAKOTAS THIS MORNING. WE'RE ALREADY SEEING HIGH BASED SHOWERS AND
ISOLATED THUNDERSTORMS OVER NORTH CENTRAL SOUTH DAKOTA AS OF
2AM. AS THIS LOW CONTINUES TO TRACK SOUTHWARD THROUGH DAYBREAK,
ADDITIONAL RISKS FOR CONVECTION BUILD INTO AREA MOSTLY WEST OF
THE JAMES RIVER VALLEY. MUCAPE UPWARDS OF 200 TO 500 J/KG WILL
PROMOTE A FEW THUNDERSTORM RISKS.
TODAY: AFOREMENTIONED LOW CONTINUES TO MOVE SOUTHWARD THIS MORNING,
ENTERING NORTHERN NEBRASKA BY MID-LATE MORNING. SHOWERS AND A
FEW THUNDERSTORMS PERSIST THROUGH MID-DAY WEST OF THE JAMES
RIVER, AND AS MUCAPE INCREASES AFTER 10AM, A MORE PREVALENT RISK
FOR NON- SEVERE THUNDERSTORMS CONTINUES ALONG THE MO RIVER
COUNTIES THROUGH 18Z. A DENSE WILDFIRE SMOKE PLUME, MOSTLY
CONTAINED ALOFT, WILL CONTINUE TO TRACK SOUTHWARD THROUGH THE
PLAINS. UPSTREAM OBSERVATIONS NEAR THE CANADIAN BORDER ARE
ALREADY INDICATING SOME VISIBILITY DROPS, WITH LATEST RAP/HRRR
SMOKE GUIDANCE SUGGESTING THAT A CORRIDOR OF SURFACE BASED SMOKE
MOVES INTO CENTRAL SOUTH DAKOTA BY EARLY AFTERNOON, WITH SOME
POTENTIAL FOR LIGHT HAZE FURTHER EAST BY LATE AFTERNOON. AIR
QUALITY IS LIKELY TO DETERIORATE THIS AFTERNOON AND MAY
CONTINUE TO REMAIN AT SLIGHTLY IMPACTFUL LEVELS INTO SUNDAY. ON
FRIDAY, UPPER SMOKE LIMITED HIGH TEMPERATURES BY 1-3 DEGREES
THROUGH THE REGION, SO HAVE LOWERED HIGHS TODAY SLIGHTLY TO
ACCOUNT FOR THE CONTINUED SMOKE.
TONIGHT: WINDS WILL REMAINS QUITE LIGHT OVERNIGHT, AND WITH LOW-LVL
SUBSIDENCE IN PLACE, WILDFIRE SMOKE MAY GET PUSHED DOWNWARD TO THE
SURFACE THROUGH THE NIGHT.
SUNDAY: A LIGHT AND VARIABLE WIND AT DAYBREAK TURNS SOUTHWESTERLY IN
THE AFTERNOON. THE SLOW AND GRADUAL SHIFT OF LOW-UPPER WINDS TO THE
SOUTHWEST IS NOT EXPECTED TO BEGIN UNTIL LATE IN THE DAY ON SUNDAY,
THEREFORE SMOKE ALOFT AS WELL AS SOME INFLUENCE AT THE SURFACE CAN
BE EXPECTED. HIGH TEMPERATURES WARM A FEW MORE DEGREES ON
SUNDAY, PUSHING THE MIDDLE TO UPPER 80S IN MOST LOCATIONS.
MONDAY-MONDAY NIGHT: THE FORECAST REMAINS MUCH THE SAME AS WE START
THE NEW WORK WEEK. WE'LL STILL BE KEENLY FOCUSED ON AN APPROACHING
FRONTAL BOUNDARY THAT SPRAWLS FROM THE SW TO THE NE ACROSS CENTRAL
AND EASTERN SOUTH DAKOTA BY LATE MONDAY AFTERNOON. 00Z GUIDANCE HAS
SHIFTED THE FRONT EVER TO SLIGHTLY FURTHER EAST, FALLING ALONG A
LINE FROM GREGORY TO HURON AND SISSETON BY MID-AFTERNOON. A LOW-LVL
MOISTURE SURGE IS EXPECTED THROUGH THE DAY, WITH MID TO EVEN
UPPER 60 DEWPOINTS INTO A NARROW CORRIDOR ALONG AND AHEAD OF
THIS BOUNDARY. WITH TEMPERATURES RISING INTO THE UPPER 80S TO
LOWER 90S, WE'LL SEE MLCAPE VALUES BETWEEN 2000-3000 J/KG BY
3-4PM. WHILE SOME SLIGHT CAPPING REMAINS IN PLACE NEAR THE
BOUNDARY, CONVECTION SHOULD QUICKLY FORM ALONG THE BOUNDARY INTO
THE LATE AFTERNOON HOURS AS SURFACE CONVERGENCE INCREASES. BY
THE EVENING, DEEPER SYNOPTIC FORCING ARRIVES, ALONG WITH A
STRONGER LLJ THAT SHOULD PROMOTE MORE WIDESPREAD DEVELOPMENT
ALONG AND SOUTH OF THE MISSOURI RIVER INTO NEBRASKA. THANKS TO A
MID-LVL JET SHIFTED WELL WEST OF THE FRONT, EFFECTIVE SHEAR
REMAINS MARGINAL AND MOSTLY LAGS WELL BEHIND THE FRONT INTO THE
EVENING, SUGGESTING SOMEWHAT POOR ORGANIZATION OF CONVECTION AT
TIMES DURING IT'S ONSET. THAT SAID, INITIAL UPDRAFTS SHOULD BE
ABLE TO PRODUCE 1.5" HAIL AND WITH DCAPE AOA 1200 J/KG,
LOCALIZED STRONG WINDS WILL BE POSSIBLE. THE SOUTHEASTWARD
EXTENT OF SEVERE WEATHER MAY BE QUITE LIMITED GIVEN THE POSITIVE
TILT TO THE UPPER TROUGH AND STEERING FLOW SOMEWHAT PARALLEL TO
THE FRONT.
THE FRONT SINKS SOUTHEAST INTO MN/IA OVERNIGHT, AND WITH MID-LVL
FLOW RUNNING NEARLY PARALLEL TO THE BOUNDARY, THE GREATEST
RISKS FOR NEW CONVECTION MAY BE WITHIN THE POST FRONTAL REGIME
INTO THE OVERNIGHT HOURS. WITH INSTABILITY ALSO WEAKENING
QUICKLY AFTER DARK, THE SEVERE WEATHER RISK QUICKLY DIMINISH AS
WELL. NBM 48 HOUR QPF 25/75 PERCENTILES CONTINUES TO SUGGEST A
PRECIPITATION RANGE OF 0.50- 2.0 " IN MOST LOCATIONS, WITH THE
PROBABILITY OF >1.0" ONLY AROUND 50-60%. AREAS WHERE CONVECTION
INITIALLY FORMS (PRIOR TO COLD POOL DEVELOPMENT) MAY STAND THE
GREATEST PROBABILITY OF 2".
TUESDAY: RAINFALL MAY PERSIST THROUGH THE FIRST HALF OF TUESDAY, BUT
SHOULD BEGIN TO WEAKEN OR MOVE AWAY BY THE AFTERNOON.
TEMPERATURES COOL CONSIDERABLY ON TUESDAY, ONLY RISING INTO THE
60S.
WEDNESDAY-FRIDAY: A BROAD TROUGH OVER NORTH AMERICA WILL KEEP
SLIGHTLY COOLER AND UNSETTLED WEATHER IN THE NORTHERN UNITED STATES
THROUGH THE REST OF THE WEEK. OCCASIONAL SHOWERS OR PERHAPS AN
ISOLATED THUNDERSTORM MAY BE POSSIBLE. HOWEVER SEVERE WEATHER RISKS
REMAIN LOW WITH PROBABILITIES OF >1000 J/KG MLCAPE ONLY REACH THE
50% MARK BY NEXT SATURDAY. TEMPERATURES SLOWLY RISE INTO THE LOWER
TO MIDDLE 70S.
AVIATION /06Z TAFS THROUGH 06Z SUNDAY/
ISSUED AT 1035 PM CDT FRI MAY 30 2025
SKIES WILL BE MAINLY CLOUD FREE FOR MOST OF THE AREA THROUGH
THE TAF PERIOD, THOUGH THERE WILL BE A THICK LAYER OF SMOKE
ALOFT. SOME OF THIS SMOKE MAY BEGIN TO MAKE IT TO THE SURFACE BY
SATURDAY, THOUGH AT THIS TIME VISIBILITIES LOOK TO REMAIN IN
THE VFR RANGE. LIGHT NORTHWEST WINDS WILL PREVAIL THROUGH THE
PERIOD.
FSD WATCHES/WARNINGS/ADVISORIES
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
DISCUSSION...DUX
AVIATION...JM
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