482
FXUS63 KFSD 150755
AFDFSD
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
255 AM CDT WED JUL 15 2026
KEY MESSAGES
- HEAT WAVE CONTINUES THROUGH THE WEEKEND. HIGHS IN THE 90S TO
AROUND 100 DEGREES EXPECTED. DEW POINTS REMAIN A BIT BELOW
SEASONAL NORMALS, AIDING IN LOWER RELATIVE HUMIDITY. HOWEVER,
CUMULATIVE NATURE OF THE HEAT COULD LEAD TO SOME HEAT IMPACTS.
- VERY PATCHY MORNING FOG IS POSSIBLE DAILY, BUT WIDESPREAD
DENSE FOG REMAINS UNLIKELY. FOG WILL LIKELY BE CONFINED TO
RIVER VALLEYS AND NEARBY AREAS, BUT COULD REDUCE VISIBILITY
BELOW TWO MILES AT TIMES.
- PRECIPITATION VERY UNLIKELY (LESS THAN 10%) THROUGH SATURDAY
NIGHT. SUNDAY INTO MONDAY CHANCES RISE TO 15-25%, BUT
CONFIDENCE IN TIMING IS VERY LOW.
UPDATE
ISSUED AT 252 AM CDT WED JUL 15 2026
ADDED IN SOME PATCHY AND LOCALLY DENSE FOG TO THE AREA, MAINLY
ACROSS RIVER VALLEYS NEAR AND EAST OF I-29. THROUGH EARLY THIS
MORNING, LOWEST VISIBILITY AS BEEN BRIEFLY BELOW A MILE FOR PORTIONS
OF SOUTHWESTERN MN AND NORTHWESTERN IA WHERE WINDS ARE VERY LIGHT TO
CALM. EXPECT PATCHY AND LOCALLY DENSE FOG TO LINGER THROUGH 8 AM
CDT.
MADE SOME MINOR CHANGES TO THE TEMPS AND DEW POINTS OVER THE NEXT
COUPLE OF DAYS FROM THE NBM BASED ON TRENDS; HOWEVER, NO APPRECIABLE
IMPACTS TO HEAT INDEX VALUES OR HEATRISK. STILL ANTICIPATE HIGHS IN
THE 90S TO NEAR 100 THROUGH THE WEEKEND WITH DRY CONDITIONS THROUGH
SATURDAY. EVEN WITH SLIGHTLY INCREASED HUMIDITY, HEAT INDEX VALUES
REMAIN IN THE 90S TODAY, WITH SOME LOCATIONS AROUND 100 THURSDAY.
CONTINUE TO TAKE PRECAUTIONS TO LIMIT HEAT AND SUN EXPOSURE. KNOW
THE SIGNS AND TREATMENT OF HEAT STROKE AND HEAT EXHAUSTION.
FOR MORE INFORMATION ON THE CLIMATOLOGICAL CONTEXT OF THIS HEAT
WAVE, PLEASE SEE THE CLIMATE SECTION BELOW.
DISCUSSION
ISSUED AT 132 PM CDT TUE JUL 14 2026
OVERALL TRENDS FOR ABOVE NORMAL TEMPERATURES CONTINUES FOR THE NEXT
SEVERAL DAYS. FOR WEDNESDAY AND THURSDAY DID LOWER HIGHS A COUPLE OF
DEGREES AND INCREASE DEW POINTS A COUPLE OF DEGREES GIVEN LATEST
TRENDS/BIAS IN THE GUIDANCE. BASICALLY THE GFS IS TOO HOT AND TOO
LOW OF DEW POINTS AND THAT IS GETTING INCORPORATED INTO THE NBM
GUIDANCE AND PRODUCING A TRACKABLE BIAS. THE OVERALL EFFECTS WILL
NOT BE SIGNIFICANT AS HEAT RISKS REMAIN BELOW ADVISORY CRITERIA WITH
AFTERNOON HEAT INDICES IN THE 90S.
FRIDAY LOOKS LIKE IT COULD BE THE HOTTEST DAY OF THE WEEK AS A WEAK
FRONT SETTLES SOUTH AND SOME ENHANCED MIXING BECOMES POSSIBLE AS
SURFACE WINDS TURN MORE SOUTHWESTERLY. THIS SHOULD BE THE DAY WITH
THE BETTER CHANCE FOR MORE WIDESPREAD HIGHS FROM THE MID 90S TO 103
OR SO.
ON SATURDAY, THE NBM MIGHT BE RUNNING TOO HIGH GIVEN LATEST MOS AND
RAW OUTPUT AS WELL AS THE BIAS CORRECTED DATA. ALL POINT TO LOWER
TEMPERATURES. STILL FAR ENOUGH OUT NOT HIGHLY CONFIDENT ON TIMING OF
THIS WEAKER BOUNDARY. ON THING THAT COULD HAPPEN IS THE FRONT COULD
STALL IN THE AREA AND PRODUCE A LITTLE MOISTURE POOLING AT THE
SURFACE WHICH WOULD BRING HIGHER DEW POINTS. SOMETHING TO WATCH FOR.
STILL SOME HINTS THAT THE UPPER LEVEL RIDGE WILL BREAK DOWN JUST
ENOUGH SUNDAY INTO MONDAY TO ALLOW FOR SOME ISOLATED SHOWER AND
THUNDERSTORM POTENTIAL. THIS CONTINUES TO BE A LOWER CONFIDENCE
SCENARIO, ESPECIALLY IN TERMS OF TIMING.
AVIATION /06Z TAFS THROUGH 06Z THURSDAY/
ISSUED AT 1150 PM CDT TUE JUL 14 2026
MAINLY VFR CONDITIONS WILL CONTINUE THIS TAF PERIOD AS MOSTLY
CLEAR CONDITIONS PERSIST THIS EVENING. SIMILAR TO THE LAST FEW
NIGHT, SOUTHERLY SURFACE WINDS WILL GRADUALLY WEAKEN OVERNIGHT
MAINLY ACROSS NORTHWESTERN IA LEADING TO A FEW PATCHY AREAS OF
FOG. DECIDED TO ADD IN A TEMPO TO KSUX FOR FOG SINCE CONFIDENCE
IS TRENDING HIGHER WITH DEVELOPMENT ACROSS HIGHWAY-20 CORRIDOR.
NONETHELESS, STILL THINKING FOG WILL GRADUALLY ERODE BY MID MORNING.
OTHERWISE, EXPECT SURFACE WINDS TO BECOME MORE SOUTHEASTERLY
AND INCREASE BY WEDNESDAY AFTERNOON WITH GUSTS BETWEEN 15-25 MPH
EXPECTED.
CLIMATE
ISSUED AT 252 AM CDT WED JUL 15 2026
DAILY RECORD HIGHS FOR OUR FOUR CLIMATE SITES (HURON, MITCHELL,
SIOUX FALLS, AND SIOUX CITY) ARE ALL SQUARELY INTO THE 100-110+
RANGE THROUGH THE NEXT WEEK, SO NOT EXPECTING ANY RECORD HIGHS.
RECORD WARM LOWS ARE IN THE UPPER 70S TO LOWER 80S SO AGAIN, NOT
EXPECTED ANY RECORDS HERE EITHER AT THIS TIME.
LOOKING AT THE DURATION OF THE HEAT VIA CONSECUTIVE 90+ DEGREE DAYS,
WE MAY APPROACH THE TOP 10 LIST FOR SOME LOCATIONS IF 90+ DEGREE
HIGHS REMAIN IN PLACE THROUGH EARLY NEXT WEEK. WITH HEAT LOOKING TO
BREAK INTO THE 80S MID TO LATE NEXT WEEK, WE WILL NOT BE ANYWHERE
CLOSE TO THE LONGEST STREAK OF 90S FOR ANY CLIMATE SITES.
LONGEST STREAK (YEAR OF OCCURRENCE):
- HON: 23 DAYS (1941, 1974)
- MHE: 27 DAYS (1936)
- FSD: 19 DAYS (1910)
- SUX: 27 DAYS (1936)
TO BREAK INTO THE TOP 10 LIST, WE'D HAVE TO MATCH OR EXCEED THE
FOLLOWING STREAKS FOR EACH CLIMATE SITES:
- HON: 11 DAYS; OCCURRED 6 TIMES, LAST IN 1991
- MHE: 15 DAYS; OCCURRED 3 TIMES, LAST IN 1964
- FSD: 11 DAYS; OCCURRED 4 TIMES, LAST IN 1989
- SUX: 12 DAYS; OCCURRED 5 TIMES, LAST IN 1955
CURRENT (THROUGH TUESDAY, 7/13) STREAKS ARE:
- HON: 4 DAYS; STREAK BEGAN JULY 10
- MHE: 4 DAYS; STREAK BEGAN JULY 10
- FSD: 2 DAYS; STREAK BEGAN JULY 12
- SUX: 0 DAYS; LAST HIT 90+ ON JULY 8
FSD WATCHES/WARNINGS/ADVISORIES
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
UPDATE...SG
DISCUSSION...08
AVIATION...05
CLIMATE...SG
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