216
FXUS63 KFSD 212351
AFDFSD
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
651 PM CDT TUE JUL 21 2026
KEY MESSAGES
- TEMPERATURES REMAIN BELOW NORMAL FOR THE REST OF THE WORK
WEEK. DEPARTURES FROM NORMAL WILL AVERAGE 5 TO 8 DEGREES BELOW
NORMAL.
- OUTSIDE OF TWO LIGHT RAIN CHANCES EARLY WEDNESDAY AND
THURSDAY NIGHT, MUCH OF THE 7 DAY FORECAST IS DRY.
- TEMPERATURES THIS WEEKEND INTO EARLY NEXT WEEK RISE WELL ABOVE
NORMAL WITH HIGHS WELL INTO THE 90S IN MOST LOCATIONS. HEAT
RELATED HEADLINES MAY BE NEEDED AT TIMES THIS WEEKEND.
DISCUSSION
ISSUED AT 1252 PM CDT TUE JUL 21 2026
THIS AFTERNOON: PLENTY OF COOL AIR ALOFT HAS POURED SOUTHWARD INTO
THE REGION, WITH MORNING STRATO-CU CONTINUING TO SLOWLY MIX UPWARDS.
HIGH TEMPERATURES GIVEN THE CLOUD COVER WILL REMAIN IN THE UPPER
70S TO LOWER 80S. ALOFT, THE INCREASING NORTHWESTERLY FLOW COULD
BRING HIGH LEVEL SMOKE THOUGH THE REGION INTO THE NIGHT.
TONIGHT: SURFACE HIGH PRESSURE DRIFTS INTO THE MIDWEST AND WESTERN
GREAT LAKES REGION OVERNIGHT. WINDS TURN LIGHT AND VARIABLE WHICH,
MAY LEAD TO FAIRLY COOL OVERNIGHT LOWS IN AREAS EAST OF THE JAMES
RIVER. THE LOW-LVL AIRMASS IS FAIRLY DRY, SO FOG PROBABILITIES WILL
REMAIN VERY LOCALIZED TO SHELTERED VALLEYS AND RIVERWAYS.
FURTHER WEST, HIGH LEVEL CLOUDS INCREASE AFTER MIDNIGHT AS MID-
LVL WARM ADVECTION FOCUSES OVER THE WEST RIVER AREAS AND THE
NEBRASKA PANHANDLE. A FEW SPRINKLES TO LIGHT RAIN SHOWERS MAY
REACH THE CENTRAL PORTIONS OF SD INTO THE JAMES RIVER VALLEY BY
DAYBREAK.
WEDNESDAY: A SUBTLE SHORTWAVE DROPS SOUTHEAST FROM THE BLACK HILLS
REGION ACROSS CENTRAL NEBRASKA DURING WEDNESDAY. MUCH OF THE
CWA WILL REMAIN UNDER THE INFLUENCE OF LOW-LVL DRY AIR ADVECTION
FROM THE NORTHEAST DURING THE DAY. WHILE MID-LVL LIFT SPREAD
EAST TOWARDS THE I-29 CORRIDOR, MOST GUIDANCE STRUGGLES TO
PRODUCE MORE THAN SPRINKLES EAST OF I-29, WITH THE BEST LOW-LVL
SATURATION FOCUSED ALONG AND SOUTH OF THE MO RIVER VALLEY. ANY
QPF THAT FALLS WILL BE LIGHT. THE MOST IMPACT FROM THIS SYSTEM
MAY BE INCREASED CLOUD COVER AND TEMPERATURES IN THE 70S AND
80S.
THURSDAY: AFTER ANOTHER NIGHT WITH VARIABLE CLOUD COVER, LIGHT
WINDS, AND COOLER TEMPERATURES, THURSDAY WILL SEE SURFACE WINDS
RETURN BACK TO THE SOUTH EARLY IN THE DAY. WE'LL BE WATCHING ANOTHER
SLIGHTLY STRONGER WAVE CROSS THE ROCKIES DURING THE DAY ON THURSDAY.
MODEL GUIDANCE HAS BEEN A BIT ALL OVER WITH THIS WAVE, WITH THE GFS
AND ABOUT 40% OF IT'S ENSEMBLE MEMBERS STUBBORNLY FURTHER TO THE NE
THAN ALL OF THE OTHER MAJOR MODEL GUIDANCE. THE ECMWF/ICON/GEM/UKMET
AND TO SOME DEGREE NAM FORCE THIS WAVE FURTHER SOUTHEAST BRINGING
THE MAJORITY OF RAIN CHANCES TO WESTERN SD, CENTRAL AND
NORTHERN NE AND WESTERN IOWA. THE LATEST NBM HAS HEDGED A BIT
MORE TOWARDS THE DRIER SOLUTIONS AS MORE DRIER INPUT IS
RECEIVED, AND I CONTINUE TO FAVOR THE GREATEST FOCUS FOR RAIN
ALONG THE MO RIVER VALLEY. THAT SAID, IF THERE IS SOME SHIFT
TOWARDS THE OUTLIER SOLUTIONS, MOISTURE CONVERGENCE COULD BE
ENOUGH TO AT LEAST PRODUCE SOME MEANINGFUL RAIN INTO THURSDAY
NIGHT.
FRIDAY-MONDAY: A 600 DM RIDGE BUILDS THROUGH THE CENTRAL PLAINS
HEADING INTO THE UPCOMING WEEKEND. THIS RIDGE, UNLIKE THE PAST
WEEKS, IT A BIT MORE SUPPRESSED WHICH MAY SERVE TO DELAY THE MOST
INTENSE HEAT INTO THE SECOND HALF OF THE WEEKEND. TEMPERATURES ARE
LIKELY TO SURGE INTO THE 90S SATURDAY AND SUNDAY WITH INITIAL FOCUS
FOR THE HOTTEST TEMPERATURES WEST OF THE JAMES RIVER SATURDAY AND
THEN FURTHER EAST SUNDAY. EVEN WITH THE SLIGHTLY WARM BIASED NBM,
THERE IS SOME POTENTIAL FOR HEAT RELATED HEADLINES THIS WEEKEND.
CONVECTION CHANCES REMAIN LOW FOR SATURDAY, BUT MAY RISE SLIGHTLY ON
THE EDGE OF THE EML LATE SUNDAY. A VERY HOT MONDAY IS ALSO
POSSIBLE WITH A SIMILAR SETUP FOR WEAK FLOW CONVECTION ON THE
EDGE OF THE EML IN THE AFTERNOON EVENING.
AVIATION /00Z TAFS THROUGH 00Z THURSDAY/
ISSUED AT 650 PM CDT TUE JUL 21 2026
LINGERING SCATTERED 5-6KFT AGL CLOUDS AND NORTHERLY WIND GUSTS
WILL SUBSIDE WITH SUNSET. ADDITIONAL MID-HIGH LEVEL CLOUDS WILL
EXPAND EAST OVERNIGHT INTO WEDNESDAY, WITH VARIABLE LIGHT WINDS
(AT OR BELOW 10KT).
LIGHT RAIN SHOWERS/SPRINKLES MAY ACCOMPANY THE THICKER MID-LEVEL
CLOUDS THROUGH PORTIONS OF THE JAMES AND MISSOURI RIVER VALLEYS
LATE TONIGHT INTO EARLY WEDNESDAY AFTERNOON, WITH BETTER CHANCES
REMAINING SOUTH/WEST OF OUR TAF LOCATIONS. CONDITIONS WITHIN ANY
SHOWERS SHOULD REMAIN VFR WITH NO THUNDER EXPECTED.
FSD WATCHES/WARNINGS/ADVISORIES
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
DISCUSSION...DUX
AVIATION...JH
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