652
FXUS63 KFSD 311953
AFDFSD
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
253 PM CDT SAT MAY 31 2025
KEY MESSAGES
- SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS CONTINUE MOVING
SOUTH SOUTH CENTRAL SD INTO THE SOUTHERN JAMES RIVER VALLEY
LATE THIS AFTERNOON. SEVERE WEATHER NOT ANTICIPATED.
- CANADIAN WILDFIRE SMOKE CONTINUES TO FILTER IN THROUGH THE
WEEKEND. SOME GROUND LEVEL SMOKE AND REDUCED AIR QUALITY
CONTINUES TONIGHT, WITH MORE WIDESPREAD IMPACTS SUNDAY.
CONDITIONS BEGIN TO IMPROVE SUNDAY NIGHT.
- THUNDERSTORM RISKS RETURN MONDAY AFTERNOON INTO MONDAY NIGHT.
SCATTERED SEVERE STORMS ARE POSSIBLE ALONG AND WEST OF A TRACY
TO SIOUX FALLS TO YANKTON LINE. RISKS INCLUDE LARGE HAIL AND
LOCALIZED SEVERE WIND.
DISCUSSION
ISSUED AT 251 PM CDT SAT MAY 31 2025
CURRENTS THROUGH SUNDAY NIGHT: SHOWERS AND ISOLATED THUNDERSTORMS
CONTINUE TO PIVOT AROUND THE EASTERN SIDE OF THE MID/UPPER LEVEL
WAVE MOVING THROUGH SOUTH CENTRAL SD AND NORTHERN NE - FOCUSING THE
SHOWERS ACROSS SOUTH CENTRAL SD INTO THE SOUTHERN JAMES RIVER
VALLEY. THIS SHOULD EXIT THE AREA BY MID TO LATE THIS EVENING.
WILDFIRE SMOKE ALOFT AND AT THE SURFACE CONTINUES TO ADVECT INTO THE
AREA, WITH VISIBILITY NEAR THE US HWY 14 CORRIDOR AND NORTHWARD
OCCASIONALLY DROPPING TO 2 MILES OR LESS. THOSE WHO ARE SENSITIVE TO
SMOKE SHOULD LIMIT EXPOSURE. TEMPERATURES HAVE WARMED INTO THE UPPER
70S TO LOWER 80S FOR MOST LOCATIONS. NORTHWESTERLY WIND GUSTS AROUND
20 TO 25 MPH THIS AFTERNOON AND EVENING TAPER OFF TONIGHT.
SMOKY SKIES CONTINUE THROUGH SUNDAY THANKS TO CONTINUED
NORTHWESTERLY FLOW ALOFT. SURFACE SMOKE BEGINS TO DIMINISH FROM WEST
TO EAST DURING THE AFTERNOON AND EVENING AS LOWER LEVEL WINDS SHIFT
WESTERLY WITH MORE IMPROVEMENT THROUGH THE OVERNIGHT HOURS. REDUCED
VISIBILITY AND AIR QUALITY ARE EXPECTED. DESPITE SMOKY SKIES, EXPECT
WARMER TEMPERATURES ON SUNDAY WITH WARMER TEMPERATURES ALOFT IN THE
RIDGE. HIGHS IN THE 80S TO NEAR 90. LOWS TOMORROW NIGHT IN THE LOWER
60S.
MONDAY-MONDAY NIGHT: ATTENTION TURNS TO THE DEVELOPING MID/UPPER
LEVEL TROUGH IN MY AND SURFACE LOW EJECTING OUT OF WY DURING THE DAY
ON MONDAY. A MID LEVEL WAVE AND UPPER LEVEL JET STREAK EJECT OUT
AHEAD OF THE MAIN TROUGH DURING THE DAY MONDAY. 31.12Z GUIDANCE HAS
COME IN FAIRLY SIMILARLY TIMING WISE TO THE 31.00Z RUNS, BUT THERE
STILL SEEMS TO BE 3-6 HOUR DIFFERENCE BETWEEN THE FASTEST (CANADIAN)
AND SLOWER (GFS/NAM) GUIDANCE. REGARDLESS, SURFACE COLD FRONT MOVES
INTO THE US HIGHWAY 28 CORRIDOR BY MID AFTERNOON (3-4 PM). AHEAD OF
THE FRONT, WE'LL SEE DEW POINTS CLIMB INTO THE UPPER 50S AND LOWER
60S WITH TEMPS IN THE 80S TO LOWER 90S WITH SOUTHERLY FLOW. THIS
LEADS TO INCREASED INSTABILITY AT OR ABOVE 2000 J/KG. CAP SHOULD
BEGIN TO BREAK NEAR THE FRONT THROUGH THE AFTERNOON. BROAD SYNOPTIC
FORCING WITH THE 700MB WAVE AND UPPER LEVEL JET STREAK INCREASES AS
WE HEAD THROUGH THE EVENING. HOWEVER, IN SPITE OF THE BROADER
FORCING MOVING IN, SEVERE RISK MAY BE RELATIVELY LIMITED IN TIME (3
PM TO 10 PM OR SO) AS INSTABILITY QUICKLY DROPS OFF LATE IN THE
EVENING. GREATEST SEVERE RISK REMAINS ALONG AND WEST OF A TRACY TO
SIOUX FALLS TO YANKTON LINE. HIGHEST SHEAR VALUES AND LAPSE RATES
REMAIN OFFSET FROM THE HIGHEST INSTABILITY. MAIN THREATS WITH STRONG
TO SEVERE STORMS WOULD BE HAIL TO 1.5" (PING PONG BALL) AND WIND
GUSTS TO 65 MPH WITH DCAPE VALUES AROUND 1000 J/KG.
SHOWERS AND STORMS CONTINUE TO MOVE EAST WITH THE FRONT THROUGH THE
OVERNIGHT HOURS, ALTHOUGH ADDITIONAL DEVELOPMENT BEHIND THE SURFACE
FRONT IS POSSIBLE WITH CONTINUED BROAD SYNOPTIC FORCING AND THE
APPROACH OF THE UPPER LEVEL TROUGH. RAINFALL WITH THIS FRONT SHOULD
BE EFFICIENT WITH FLOW PARALLEL TO THE BOUNDARY AND ROBUST MOISTURE
RETURN. PWAT VALUES AT OR ABOVE 1.5" TO NEAR 2" (WHICH IS IN THE TOP
1% OF VALUES COMPARED TO CLIMATOLOGY). A DEEP WARM CLOUD LAYER NEAR
OR ABOVE 10000 FT AIDS IN WIDESPREAD MODERATE TO HEAVY RAINFALL
POTENTIAL. GIVEN 1 HOURLY FFG RANGING FROM 1.5 TO 2.5+ INCHES IN OUR
AREA - LOWEST IN NORTHWESTERN IA - WIDESPREAD FLASH FLOODING IS NOT
EXPECTED. HOWEVER, HEAVY RAINFALL RATES COULD LEAD TO LOCALIZED
ISSUES ESPECIALLY IN URBAN AREAS. RAINFALL AMOUNTS INTO TUESDAY
MORNING BETWEEN 0.75" AND 2" EXPECTED. CHANCES OF MORE THAN AN INCH
REMAIN MODERATE (40-60%).
TUESDAY: COOLER, CLOUDY, AND RAINY TUESDAY AS THE MID AND UPPER
LEVEL TROUGH CONTINUE TO MOVE EAST AND THE SURFACE FRONT PUSHES
THROUGH IA. HIGHS IN THE 60S TO NEAR 70. BREEZY NORTHWESTERLY WINDS
EXPECTED. ADDITIONAL RAINFALL AMOUNTS OF A TENTH OF AN INCH UP TO AN
INCH - HIGHEST IN SOUTHWESTERN MN AND NORTHWESTERN IA.
WEDNESDAY ONWARD: QUASI ZONAL TO NORTHWESTERLY FLOW DEVELOPS FOR MID
WEEK INTO NEXT WEEKEND. NUMEROUS MID/UPPER LEVEL SHORT WAVES TREK
THROUGH THE NORTHERN AND CENTRAL PLAINS WHICH KEEPS PERIODIC LOW TO
MODERATE (LESS THAN 50%) SHOWER AND STORM CHANCES IN THE FORECAST.
SEVERE STORMS CURRENTLY LOOK UNLIKELY. TEMPERATURES MODERATE CLOSER
TO NORMAL WITH HIGHS IN THE MID AND UPPER 70S AND LOWS IN THE MID
50S.
AVIATION /18Z TAFS THROUGH 18Z SUNDAY/
ISSUED AT 1226 PM CDT SAT MAY 31 2025
AN AREA OF SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS NEAR
KYKN TO KMKA TO KICR CONTINUES TO MOVE SOUTH THIS AFTERNOON.
EXPECT THIS ACTIVITY TO REMAIN EAST OF KFSD AND KSUX, AND HAS
MOVED SOUTH OF KHON. BEGINNING TO SEE MVFR AND LOWER SURFACE
SMOKE MOVE INTO THE US HWY 14 CORRIDOR, WITH THE LOWEST
VISIBILITY OFF IN NORTHERN SD AND ACROSS ND. HAVE INCLUDED MVFR
MENTION AT KHON AND KFSD THIS AFTERNOON, WITH LOWER CONFIDENCE
AT KSUX. SMOKE PREVAILS AT THE SURFACE AND ALOFT THROUGH TONIGHT
AND SUNDAY, WITH CEILINGS REMAINING VFR. COULD SEE MVFR OR LOWER
VISIBILITIES AGAIN SUNDAY.
WINDS TODAY OUT OF THE NORTHWEST MAY GUST AROUND 20 KNOTS. LIGHT
AND VARIABLE WINDS TONIGHT BECOME WEST-SOUTHWESTERLY BY THE END
OF THE PERIOD.
FSD WATCHES/WARNINGS/ADVISORIES
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
DISCUSSION...SG
AVIATION...SG
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