144
FXUS63 KFSD 131125
AFDFSD
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
625 AM CDT MON JUL 13 2026
KEY MESSAGES
- AN EXTENDED STRETCH OF HOT TEMPERATURES CONTINUES INTO THE
UPCOMING WEEKEND. HIGHS IN THE 90S TO 100 DEGREES EXPECTED.
THE CUMULATIVE NATURE OF THE HEAT COULD LEAD TO SOME HEAT
HEALTH CONCERNS.
- PATCHY MORNING FOG IS POSSIBLE EACH MORNING, BUT WIDESPREAD
DENSE FOG REMAINS UNLIKELY. FOG WILL LIKELY BE CONFINED TO
RIVER VALLEYS AND NEARBY AREAS.
- MINIMAL PRECIPITATION IS EXPECTED OVER THE NEXT 7 DAYS, WITH
THE LREF PROBABILITY OF >0.25" INTO NEXT TUESDAY (JULY 21ST)
AT 25% OR LESS.
UPDATE
ISSUED AT 245 AM CDT MON JUL 13 2026
HI-RES GUIDANCE ONCE AGAIN SHOWS SOME PATCHY AND LOCALLY DENSE RIVER
VALLEY FOG POSSIBLE THROUGH THE MONDAY MORNING COMMUTE. FOG
DEVELOPMENT MAY BE MORE TEMPERED THAN PREVIOUS MORNINGS GIVEN OUR
SLIGHTLY BREEZIER SOUTHERLY WINDS. WE'RE STARTING THE MORNING IN THE
MID 60S TO MID 70S.
MINOR CHANGES TO HIGH TEMPERATURES THE NEXT COUPLE DAYS, BUT NO
SIGNIFICANT IMPACTS. HEAT WAVE CONTINUE THROUGH THIS WEEK AND INTO
THE WEEKEND WITH HIGHS IN THE 90S TO LOWER 100S. STILL BELOW HEAT
ADVISORY CRITERIA TODAY AND INTO MID WEEK GIVEN RELATIVELY DRY AIR
IN PLACE; HOWEVER, WILL NEED TO MONITOR FOR POSSIBLE HEADLINES MID
WEEK, ESPECIALLY WITH WARMER TEMPERATURES AND GIVEN THE LONG
DURATION OF THIS HEAT WAVE. WE'LL ALSO BE CONTINUING TO WATCH FOR
POTENTIAL FIRE CONCERNS LATER THIS WEEK AS WELL GIVEN THE LACK OF
MOISTURE AND PERIODIC BREEZINESS.
WITH LOTS OF SUNSHINE, THOSE SPENDING ANY TIME OUTDOORS SHOULD TAKE
PRECAUTIONS TO LIMIT SUN AND HEAT EXPOSURE. KNOW THE SIGNS OF HEAT
ILLNESS AS WELL.
DISCUSSION
ISSUED AT 1250 PM CDT SUN JUL 12 2026
THIS AFTERNOON: ANOTHER HOT DAY ACROSS THE REGION, THOUGH GUSTY
WINDS ARE A BIT SLOW TO DEVELOP TODAY. THIS MAY ULTIMATELY RESULT IN
SLIGHTLY LOWER TEMPERATURES, BUT COULD KEEP HUMIDITY A BIT HIGHER
ALONG AND EAST OF I-29. THAT SAID, HEAT INDEX READINGS PEAK IN THE
LOWER TO MIDDLE 90S.
TONIGHT: MUCH LIKE THE PAST DAYS, WINDS WEAKEN OVERNIGHT, BUT STILL
STAY MIXY. THIS WILL HOLD OVERNIGHT LOW INTO THE UPPER 60S TO LOWER
70S. IT MAY ALSO PREVENT ANY WIDESPREAD FOG DEVELOPMENT OUTSIDE OF
VERY SHELTERED VALLEYS.
MONDAY-TUESDAY: LOW-LVL TEMPERATURES REALLY DO NOT CHANGE ALL THAT
MUCH FOR MONDAY, AND THIS SHOULD RESULT IN A TEMPERATURE FORECAST
VERY SIMILAR TO SUNDAY. BY THE LATE MORNING WE MAY BEGIN TO SEE SOME
STRONGER SOUTHWEST GUSTS FORM ALONG A LINE FROM LAKE ANDES TO
BROOKINGS, HOWEVER THROUGH THE AFTERNOON THOSE WINDS MAY SHIFT A BIT
MORE TO THE SOUTH AND SOUTHEAST. WHAT WILL BE APPARENT HOWEVER IS
THE LOWERING OF AFTERNOON DEWPOINTS WHICH MAY MIX INTO THE MIDDLE TO
UPPER 50S WEST OF I-29 AND MIDDLE 60S EAST OF I-29. RESULTANT HEAT
INDEX NUMBERS PEAK IN THE LOWER TO MIDDLE 90S IN MOST AREAS, WARMEST
WEST OF THE JAMES RIVER. WBGT REMAIN AT THE MODERATE LEVELS
THROUGHOUT THE CWA. BY TUESDAY, THERE IS SOME EVIDENCE THAT 850 MB
TEMPERATURES MAY COOL SLIGHTLY AS SOUTHEASTERLY WINDS AT THE SURFACE
AND ALOFT PULL WEAK COLD ADVECTION NORTHWARD. THIS IS PARTIALLY WHY
RECENT CONSSHORT AND NBM GUIDANCE HAS COOLED HIGH TEMPERATURES
SLIGHTLY ON TUESDAY. WITH DEW POINTS AT PEAK HEATING RANGING
FROM THE MID 50S TO THE LOWER 60S, HEAT INDEX VALUES AGAIN ONLY
TOP INTO THE MIDDLE 90S IN THE WESTERN CWA. WBGT VALUES DO CREEP
UP SLIGHTLY, BUT THE VAST MAJORITY OF THE CWA REMAINS AT
MODERATE LEVELS. GIVEN THE CURRENT HEAT INDEX VALUES REMAINING A
FEW DEGREES BELOW 100, WBGT ONLY IN THE MODERATE RANGE, AND A
25+ DROP IN OVERNIGHT TEMPERATURES FROM AFTERNOON HIGHS, NOT
ANTICIPATING A HEAT ADVISORY AT THIS TIME. HOWEVER, CONTINUE TO
USE EXTRA PRECAUTION IF SPENDING TIME OUTDOORS.
WEDNESDAY-FRIDAY: WE'LL CERTAINLY BEGIN TO SEE THE HOTTEST
TEMPERATURES SHIFT SOUTH AND EAST THROUGH THE END OF THE WORK WEEK.
850MB TEMPERATURES REMAIN CLOSE TO TUESDAY'S LEVELS AROUND 20-22C,
BUT WE'LL ALSO SEE A BIT MORE OF A SURFACE WIND SHIFT TO THE SOUTH.
COMPOUNDING THIS WITH DRY GROUND, AND CONTINUED WARMTH OF SOIL
TEMPERATURES, TEMPERATURES WILL REACH FOR THE 100S ALONG AND WEST OF
THE JAMES RIVER AND INTO THE LOWER 90S FURTHER EAST. THE HEAT DOME
SPREADS EAST FOR THURSDAY AND FRIDAY, PUSHING 850C AIR BETWEEN 24-
28C INTO THE TRI-STATE AREA. THIS LEADS TO INCREASING RISKS FOR
MIDDLE 90S OVER MN/IA, WITH 100S SPREADING TOWARDS THE I-29
CORRIDOR. THE PERSISTENT MIX-DOWN OF DRY AIR EACH AFTERNOON MAY
KEEP HI FROM REACHING EXTREME LEVELS, BUT WILL LIKELY BEGIN TO REACH
HI CRITERIA WEDNESDAY WITH THESE CONDITIONS SPREADING SOUTHEAST
THROUGH FRIDAY. ADVISORIES WILL MOST CERTAINLY BE POSSIBLE IN
THIS TIME FRAME AS WBGT ALSO JUMPS TOWARDS THE HIGH CATEGORIES
AND "MAJOR" HEAT RISK DESIGNATIONS SHIFT SOUTH AS WELL.
SATURDAY-SUNDAY: RECENT MODEL TRENDS CONTINUE TO SLOW THE GRADUAL
PATTERN EVOLUTION DURING THE UPCOMING WEEKEND. THE SLOW APPROACH OF
A SW-NE ORIENTED BOUNDARY MAY ONLY SERVE TO HELP FOCUS DEEPER MIXING
IN THE AFTERNOON. THIS WILL LEAVE MOST OF THE TRI-STATE AREA WELL
UNDER THE THERMAL RIDGE ON SATURDAY, WITH INCREASING POTENTIAL FOR
WIDESPREAD UPPER 90S TO LOWER 100 HIGHS. THE LATEST NBM STILL
MAINTAINS A 12 DEGREE SPREAD IN THE 25/75TH FORECAST, WITH THOSE
75TH PERCENTILE VALUES ALL NEAR OR OVER 100 IN THE CWA. HEAT INDEX
VALUES ARE AGAIN BELOW 100 IN MOST AREAS WITH RH VALUES IN THE 20-
30% RANGE. A TROUGH SINKING INTO THE NORTHERN PLAINS SUNDAY COULD
LEAD TO THE POTENTIAL FOR ISOLATED TO SCATTERED THUNDERSTORMS
INTO SUNDAY, THOUGH LACK OF DEEP MOISTURE MAY LIMIT THIS RISK.
HIGHS DO APPEAR TO LOWER SLIGHTLY SUNDAY AFTERNOON.
PRECIPITATION AMOUNTS OVER THE UPCOMING 7-10 DAYS WILL NOT BE
SIGNIFICANT IN THE AREA. 12Z LREF DATA CONTINUES TO HINT AT VERY
LITTLE RAINFALL AHEAD. THE POTENTIAL OF >0.25" THROUGH TUESDAY JULY
21ST IS ONLY AT 25%.
AVIATION /12Z TAFS THROUGH 12Z TUESDAY/
ISSUED AT 621 AM CDT MON JUL 13 2026
VERY PATCHY VALLEY FOG THIS MORNING, WITH SOME LOCATIONS BRIEFLY
DOWN TO IFR OR LOWER VIS. OTHERWISE, VFR CONDITIONS PREVAIL
THROUGH THE PERIOD. WINDS MAY BE STRONG ENOUGH EARLY TUESDAY
MORNING TO PRECLUDE ANY FOG DEVELOPMENT, BUT CAN'T RULE OUT SOME
PATCHY VALLEY FOG ONCE AGAIN.
SOUTHERLY WINDS THROUGH THE PERIOD. GUSTS AROUND 20-25 KNOTS
WEST OF I-29, STRONGEST THIS AFTERNOON/EVENING AND WEST OF THE
JAMES RIVER. COULD SEE SOME LINGER GUSTS AROUND 15-20 KNOTS INTO
TONIGHT FOR THIS AREA.
FSD WATCHES/WARNINGS/ADVISORIES
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
UPDATE...SG
DISCUSSION...DUX
AVIATION...SG
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