987
FXUS63 KFSD 091133
AFDFSD
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
633 AM CDT WED SEP 9 2026
KEY MESSAGES
- FOG, INCLUDING DENSE FOG WITH VISIBILITY BELOW HALF A MILE,
MAINLY ACROSS NORTHWESTERN IOWA INTO SOUTHWESTERN MN. A DENSE
FOG ADVISORY IS IN EFFECT FOR PORTIONS OF THE AREA UNTIL 9 AM
CDT.
- SEVERE WEATHER POSSIBLE FRIDAY AFTERNOON AND EVENING.
CONFIDENCE REMAINS LOW DUE TO STRONG CAPPING POTENTIAL.
- ADDITIONAL MODERATE TO HIGH CHANCES (50-80 PERCENT) FOR
SHOWERS AND THUNDERSTORMS RETURN SATURDAY NIGHT INTO EARLY
NEXT WEEK. SEVERE RISK IS LOW.
- COOLER CONDITIONS ARRIVE THIS WEEKEND INTO EARLY NEXT WEEK.
UPDATE
ISSUED AT 257 AM CDT WED SEP 9 2026
ONLY CHANGES TO THE FORECAST WERE AREAL EXPANSIONS OF THIS MORNING'S
DENSE FOG ADVISORY.
WE'RE STARTING THE DAY IN THE 50S AND 60S WITH MOSTLY CLEAR SKIES.
DENSE FOG HAS CONTINUED TO EXPAND EARLY THIS MORNING, MAINLY ACROSS
NORTHWESTERN IA INTO ADJACENT AREAS OF NE/SD/MN. DENSE FOG ADVISORY
CONTINUES UNTIL 9 AM FOR PORTIONS OF THE AREA, AS FOG IS EXPECTED TO
LIFT THROUGH THE MORNING HOURS.
OTHERWISE, A PLEASANT SEPTEMBER DAY ON TAP WITH TEMPERATURES IN THE
UPPER 70S TO NEAR 80 FOR MOST OF THE AREA. DRY WITH PLENTY OF
SUNSHINE AND NORTHWESTERLY WINDS, WHICH MAY GUST TO AROUND 20 MPH AT
TIMES. SURFACE HIGH PRESSURE REMAINS OVERHEAD TONIGHT, WITH LOWS
AGAIN THE 50S. CALM TO LIGHT WINDS AND MOSTLY CLEAR SKIES MAY LEAD
TO SOME PATCHY FOG ONCE AGAIN TONIGHT. MORE OF THE SAME, BUT
SLIGHTLY WARMER THURSDAY AS THE SURFACE HIGH SLIDES EAST AND
SOUTHERLY FLOW RETURNS.
DISCUSSION
ISSUED AT 111 PM CDT TUE SEP 8 2026
THE RIGHT ENTRANCE REGION OF THE UPPER LEVEL JET WILL MOVE ACROSS
THE AREA THIS EVENING, HELPING INCREASE CONVERGENCE ALONG THE LOW TO
MID LEVEL BOUNDARY. MUCH DRIER AIR WAS FILTERING IN BEHIND THE
SURFACE FRONT, WITH 30 AND 40 DEGREE DEW POINTS IN CENTRAL SD. WITH
1500-2000 J/KG CAPE AHEAD OF THIS FRONT AND ABOUT 40 KNOTS OF DEEPER
LAYER SHEAR, A FEW STRONGER UPDRAFTS WILL BE POSSIBLE LATER THIS
AFTERNOON. FOR NOW THE BETTER CHANCES APPEAR TO BE FROM NORTHEAST NE
TOWARDS STORM LAKE AND POINTS SOUTH. THE MAIN SEVERE THREAT SHOULD
EXIT THE AREA BY EARLY EVENING AS COOLER AND DRIER AIR SETTLES IN
BEHIND THE EXITING RIGHT ENTRANCE REGION.
WEDNESDAY SHOULD PROVE TO BE A PLEASANT DAY WITH DECREASED HUMIDITY
AND SEASONALLY WARM TEMPERATURES IN THE UPPER 70S TO LOWER 80S.
NORTHWEST WINDS MAY GUST AS HIGH AS 25 MPH, WITH LIGHTER WINDS
ACROSS NORTHWEST IA. HIGH PRESSURE AT THE SURFACE WILL DRIFT ACROSS
THE AREA TONIGHT AND ALLOW FOR SOME COOL MORNING LOWS, MAINLY LOW TO
MID 50S BUT A FEW LOWER SPOTS COULD SEE LOWS AS COOL AS THE UPPER
40S.
UPPER LEVEL TROUGHING DIGS ACROSS THE NORTHERN ROCKIES THURSDAY
WHICH WILL SWING LOWER LEVEL WINDS AROUND TO THE SOUTH, ALLOWING
FOR SLIGHTLY WARMER TEMPERATURES, GENERALLY LOWER TO MID 80S.
AS THIS UPPER LEVEL TROUGH SPREADS ONTO THE PLAINS FRIDAY, AN
ENVIRONMENT THAT POTENTIALLY SUPPORTS SEVERE WEATHER WILL SET UP.
THE CHALLENGE THAT DAY WILL BE BREAKING THE CAP. IF THE CAP CAN BE
BROKEN, 2000-3000 J/KG CAPE ALONG WITH ABOUT 30-40 KNOTS OF DEEP
LAYER SHEAR WOULD SUPPORT A FEW SEVERE UPDRAFTS.
ONCE THIS FRONT MOVES THROUGH FRIDAY NIGHT, MUCH COOLER AIR WILL
SETTLE INTO THE REGION. HIGHS SATURDAY THROUGH MONDAY WILL LIKELY BE
IN THE 70S, WITH SOME 60S POSSIBLE ON SUNDAY. LOWS EACH MORNING
SHOULD BE ROUGHLY 45 TO 55.
SUNDAY INTO SUNDAY NIGHT WILL SEE ANOTHER FAIRLY STRONG TROUGH MOVE
THROUGH WHICH INCREASES WARM AIR ADVECTION AND SHOULD BRING FAIRLY
WIDESPREAD SHOWERS AND THUNDERSTORMS. FOR NOW ANY SEVER WEATHER
LOOKS TO REMAIN VERY ISOLATED.
AVIATION /12Z TAFS THROUGH 12Z THURSDAY/
ISSUED AT 625 AM CDT WED SEP 9 2026
BEGINNING TO SEE SOME IMPROVEMENTS IN VISIBILITY DUE TO FOG THIS
MORNING, ALTHOUGH THERE REMAINS SCATTERED IFR TO LIFR VISIBILITY
ACROSS NORTHWESTERN IA AND ADJACENT AREAS OF NE/SD/MN. FOG
CONTINUES TO MIX OUT THROUGH THE MORNING HOURS, AND EXPECT VFR
CONDITIONS TO RETURN TO THE AREA BY 14-15Z.
WINDS LATER TODAY GUST AROUND 20 KNOTS, GENERALLY OUT OF THE
NORTHWEST. CALM TO LIGHT WINDS RETURN TONIGHT INTO THURSDAY
MORNING, WHICH MAY LEAD TO SOME ADDITIONAL PATCHY FOG
DEVELOPMENT.
FSD WATCHES/WARNINGS/ADVISORIES
SD...DENSE FOG ADVISORY UNTIL 9 AM CDT THIS MORNING FOR SDZ071.
MN...DENSE FOG ADVISORY UNTIL 9 AM CDT THIS MORNING FOR MNZ090.
IA...DENSE FOG ADVISORY UNTIL 9 AM CDT THIS MORNING FOR IAZ002-003-
012>014-020>022-031-032.
NE...DENSE FOG ADVISORY UNTIL 9 AM CDT THIS MORNING FOR NEZ014.
UPDATE...SG
DISCUSSION...08
AVIATION...SG
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