558
FXUS63 KFSD 202314
AFDFSD
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
614 PM CDT TUE OCT 20 2026
KEY MESSAGES
- CHANCES FOR FOG ALONG RIVER VALLEYS AND LOW AREAS RETURN
WEDNESDAY MORNING. AREA MOST LIKELY TO SEE FOG IS THE NORTHERN
JAMES RIVER WITH A 50% PROBABILITY OF VISIBILITY DECREASING TO
2 MILES OR LESS.
- ABOVE TO WELL ABOVE AVERAGE TEMPERATURES CONTINUE. HIGHS IN
THE UPPER 60S AND 70S AND LOWS IN THE 40S AND 50S. AVERAGE
HIGHS FOR MID/LATE OCTOBER ARE UPPER 50S TO LOWER 60S, WITH
AVERAGE LOWS IN THE MID TO UPPER 30S.
- DRY CONDITIONS ARE EXPECTED THROUGH THURSDAY EVENING. LOW (35%
OR LESS) RAIN CHANCES RETURN FRIDAY MORNING WITH MORE
WIDESPREAD AND HIGHER CHANCES (AROUND 50%) THIS WEEKEND.
- WARM, DRY, AND BREEZY CONDITIONS LEAD TO LOCALIZED ELEVATED
FIRE DANGER FOR THE REST OF THIS WEEK.
DISCUSSION
ISSUED AT 313 PM CDT TUE OCT 20 2026
BREEZY SOUTHERLY WINDS WILL GRADUALLY DECREASE THIS AFTERNOON AND
EVENING WITH MOSTLY CLEAR SKIES. LOWS WILL FALL TO THE MID TO UPPER
40S. FOR REFERENCE AVERAGE LOWS THIS TIME OF YEAR ARE IN THE MID
30S. EARLY WEDNESDAY MORNING WINDS WILL BECOME LIGHT, WHICH MAY
ALLOW FOR PATCHY FOG DEVELOPMENT ALONG RIVER VALLEYS AND LOW AREAS.
ESPECIALLY ALONG THE NORTHERN JAMES RIVER VALLEY WHERE PROBABILITY
OF VISIBILITY FALLING TO 2 MILES OR LESS IS AROUND 50%. ANY FOG
DEVELOPMENT WILL BURN OFF BY MID-WEDNESDAY MORNING.
AS FOR THE REST OF WEDNESDAY AN UPPER TROUGH AND SURFACE LOW LOCATED
OVER EASTERN NUNAVUT AND MANITOBA WILL DRAG A COLD FRONT INTO THE
REGION EARLY WEDNESDAY MORNING, CONNECTED TO A SECONDARY WEAK MID-
LEVEL SHORTWAVE AND SURFACE LOW OVER WESTERN SOUTH DAKOTA. AT THE
SAME TIME MODERATE WAA ON SOUTHERLY WINDS WILL BEGIN TO AMPLIFY A
SHALLOW UPPER RIDGE LOCATED OVER THE SOUTH CENTRAL US. AS THIS RIDGE
CONTINUES TO AMPLIFY THROUGH THE DAY IT WILL PUSH BACK AGAINST THE
COLD FRONT CAUSING IT TO STALL OUT, EVENTUALLY WASHING OUT THE FRONT
AND SECONDARY LOW PRESSURE. THIS WILL RESULT IN A DIFFUSE WEAK
SURFACE BOUNDARY. WINDS MAY VARY ALONG THIS BOUNDARY FOR A SHORT
TIME BEFORE BECOMING SOUTHERLY ONCE AGAIN AS A SURFACE HIGH PRESSURE
STRENGTHENS OVER THE CENTRAL MIDWESTERN STATES. BY FRIDAY 200 MB
HEIGHTS WILL BE NEAR TO OR AT MAXIMUM FOR CLIMATOLOGY, AS WILL 700-
500 MB TEMPERATURES. WHAT THIS MEANS IS AT THE SURFACE WE WILL BE
EXPERIENCING ABNORMALLY WARM OCTOBER DAYS. THE NBM CONTINUED SHOWING
A COLD BIAS THIS RUN AND SO COORDINATED WITH NEIGHBORS TO BOOST
HIGHS USING A BLEND OF NBM/NBM90TH. HIGHS WILL RISE INTO THE LOW TO
MID 70S WEDNESDAY, AND THE MID TO UPPER 70S THURSDAY. THERE MAY EVEN
BE A FEW 80S! WHILE THIS IS 10 TO 20 DEGREES F WARMER THAN AVERAGE,
WE ARE STILL MORE THAN 5 DEGREES AWAY FROM TYING OR BREAKING
ANY RECORD HIGHS.
LOOKING NOW TO THE WEST WE SEE A DEEP UPPER TROUGH MOVING ON SHORE
STRETCHING FROM BRITISH COLUMBIA DOWN TO SOUTHERN CALIFORNIA. AS
THIS AND A SERIES OF EMBEDDED SHORTWAVES ON THE WEST SIDE OF THE
RIDGE MOVE EAST THE SPG WILL BEGIN TO TIGHTEN. SOUTHERLY WINDS WILL
INCREASE, GUSTING 15-25 MPH BY THURSDAY AFTERNOON FOR AREAS ALONG
AND WEST OF I-29. EAST OF I-29 GUSTS WILL 15 MPH OR LESS. AS THIS
ENTIRE PATTERN SHIFTS EAST OVERNIGHT GUSTY WINDS WILL SPREAD EAST.
FRIDAY WINDS WILL CONTINUE TO INCREASE, WITH WIDESPREAD GUSTS OF 30
TO 40 MPH. HIGHER GUSTS ARE EXPECTED AS YOU MOVE WEST TOWARD CENTRAL
SOUTH DAKOTA. GUSTS WEST OF THE JAMES RIVER COULD REACH 45+ MPH.
WHILE MINIMUM RELATIVE HUMIDITY VALUES WILL REMAIN ABOVE 40%,
STRONG WINDS AND DRYING GRASSES WILL LEAD TO LOCALLY ELEVATED
FIRE RISK AT TIMES THROUGH THE REMAINDER OF THE WEEK.
IN ADDITION, EARLY FRIDAY MORNING WAA ALONG THE NOSE OF THE LLJ MAY
RESULT IN LIGHT, SCATTERED SHOWERS OVER SOUTH CENTRAL SOUTH DAKOTA
EARLY FRIDAY MORNING MOVING NORTHEAST INTO SOUTHWEST MINNESOTA
AROUND NOON. THESE SHOWERS ARE LIKELY TO BE HIT AND MISS, MEANING
NOT EVERYONE WILL GET RAIN, AND THOSE THAT DO WILL PROBABLY ONLY SEE
A TRACE TO A HUNDREDTH OR TWO. FRIDAY NIGHT INTO SATURDAY AS THE
PREVIOUSLY MENTIONED UPPER TROUGH MOVES INTO THE CENTRAL PLAINS OF
CANADA AND THE US, DRAPING A COLD FRONT DOWN INTO EASTERN COLORADO.
SHOWERS WILL FORM ALONG THE FRONT AND MOVE SOUTHEAST FROM EARLY
SATURDAY MORNING THROUGH SATURDAY EVENING. ONCE AGAIN SHOWERS ARE
EXPECTED TO BE LIGHT, AND COULD BE SPOTTY AT TIMES. A BRIEF BREAK
OVERNIGHT BEFORE A SOUTHERN STREAM UPPER TROUGH MOVES NORTHEAST INTO
THE REGION BRINGING MORE CHANCES FOR RAIN SUNDAY AFTERNOON INTO
MONDAY MORNING. OVERALL TOTALS ARE EXPECTED TO BE LIGHT, WITH AREAS
OF SOUTHEAST SOUTH DAKOTA, NORTHEAST NEBRASKA, AND NORTHWEST IOWA
SEEING AROUND A 60% PROBABILITY OF 0.25 INCHES. PROBABILITIES FALL
OFF QUICKLY FROM THERE, AND MOST WILL ONLY SEE A FEW HUNDREDTHS TO A
TENTH OR SO.
AVIATION /00Z TAFS THROUGH 00Z THURSDAY/
ISSUED AT 613 PM CDT TUE OCT 20 2026
VFR THROUGH THE PERIOD. SOME PATCHY VALLEY FOG WILL BE
POSSIBLE LATE TONIGHT INTO WEDNESDAY MORNING.
FSD WATCHES/WARNINGS/ADVISORIES
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
DISCUSSION...AJP
AVIATION...08
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