292
FXUS63 KFSD 201758
AFDFSD
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
1258 PM CDT WED MAY 20 2026
KEY MESSAGES
- SCATTERED SHOWERS POSSIBLE THIS AFTERNOON MAINLY WEST OF THE
JAMES RIVER VALLEY WITH LIGHT ACCUMULATIONS EXPECTED.
- COOLER CONDITIONS CONTINUE THIS WEEK. ABOVE NORMAL
TEMPERATURES ARE EXPECTED SUNDAY THROUGH WEDNESDAY.
- SHOWERS AND ISOLATED THUNDERSTORMS ARE EXPECTED FROM THURSDAY
EVENING THROUGH FRIDAY NIGHT. SEVERE WEATHER NOT EXPECTED.
HOWEVER, SOME ENSEMBLE GUIDANCE SUGGESTS ABOUT A 40 PERCENT
CHANCE FOR A HALF AN INCH OR MORE OF RAIN DURING THIS TIME.
DISCUSSION
ISSUED AT 1257 PM CDT WED MAY 20 2026
A WEAK WAVE AND MID LEVEL MOISTURE AROUND THE DGZ MOVES IN TONIGHT,
BRINGING A SMALL THREAT FOR SHOWERS. MOST LOCATIONS WILL SEE A
FAIRLY STOUT DRY LAYER BELOW THE INCOMING MOISTURE WHICH WILL
SEVERELY LIMIT RAINFALL POTENTIAL. ONE EXCEPTION MAY BE WEST OF THE
JAMES RIVER LATE THIS AFTERNOON AND EARLY THIS EVENING WHEN A LITTLE
WEAK INSTABILITY DEVELOPS DURING PEAK HEATING WHICH COULD SUPPORT
ISOLATED SHOWERS THERE.
LIFT AND VERY WEAK INSTABILITY MOVES IN ON THURSDAY AHEAD OF THE
NEXT WAVE. THE CHANCES FOR RAINFALL REMAINS VERY LIMITED WITH THIS.
OTHERWISE EXPECTING PARTLY TO MOSTLY CLOUDY SKIES AND HIGHS IN THE
60S.
THURSDAY NIGHT INTO FRIDAY WILL SEE WARM ADVECTION AND UPPER LEVEL
SUPPORT SPREAD INTO THE AREA. MOST OF THURSDAY NIGHT WILL SEE THE
BETTER CHANCES REMAIN TO THE SOUTH OF THE MISSOURI RIVER, BUT AFTER
MIDNIGHT CHANCES WILL INCREASE. FOR THE MOST PART, SHOWERY AND VERY
ISOLATED THUNDERSTORMS WILL BE INSTABILITY DRIVEN NEAR AND EAST OF I-
29, WHILE WEST OF I-29 BETTER UPPER LEVEL SUPPORT FOR RAINFALL WILL
BE THE DRIVING FACTOR. WHILE THE CONVECTIVE PORTION IS OF COURSE A
LITTLE LESS PREDICTABLE, ASSUMING SOME CONVECTIVE COMPONENT DOES
DEVELOP A FEW LOCATIONS COULD SEE 1-2" OF RAIN. MANY OF THE LATEST
MODELS ARE EACH INDICATING SWATHS ABOUT 20-40 MILES WIDE OF 1-2"
AMOUNTS. WHAT ALSO APPEARS TO BE FAIRLY CONSISTENT IS THAT
ESPECIALLY WEST OF HIGHWAY 81 IS WHERE THE MOST CONSISTENT
SUGGESTIONS FOR A MORE WIDESPREAD QUARTER TO THREE QUARTERS OF AN
INCH OF RAIN IS POSSIBLE.
MOST OF THE LIFT WILL DRIFT NORTHEAST ON SATURDAY WITH A FEW SPRINKLES
POSSIBLE IN THE MORNING. OTHERWISE A MILD DAY WITH HIGHS MOST IN THE
60S TO LOWER 70S.
MODEL SOUNDINGS HINTING AT SOME WEAK, SURFACE BASED INSTABILITY ON
SUNDAY AFTERNOON AND EVENING WHICH MAY ALLOW FOR AN ISOLATED
THUNDERSTORM TO DEVELOP. WITH SOME DRY LOW LEVELS AND WEAK SHEAR
GUSTY WINDS WOULD LIKELY BE THE MAIN THREAT IF ANYTHING CAN DEVELOP.
CONFIDENCE IN THIS IS LOW FOR NOW.
BY MONDAY STRONGER SOUTHERLY FLOW SETS UP AN CONTINUES THROUGH THE
MIDDLE OF THE WEEK. HIGH TEMPERATURES IN THE 80S SHOULD BE COMMON.
WITH UPPER LEVEL RIDGING IN PLACE MONDAY THROUGH WEDNESDAY AND VERY
LITTLE UPPER LEVEL ENERGY EXPECTED TO MOVE THROUGH THE AREA MOSTLY
DRY CONDITIONS ARE EXPECTED. SOME HINTS OF SOME SUPPORT WEDNESDAY
INTO THURSDAY SO WILL HAVE TO SEE IF THIS COMES TO FRUITION.
AVIATION /18Z TAFS THROUGH 18Z THURSDAY/
ISSUED AT 1204 PM CDT WED MAY 20 2026
VFR THROUGH THE PERIOD. A FEW SHOWERS WILL BE POSSIBLE MAINLY
WEST OF THE JAMES RIVER LATE THIS AFTERNOON INTO THE EVENING. A
FEW SPRINKLES WILL BE POSSIBLE ELSEWHERE.
FSD WATCHES/WARNINGS/ADVISORIES
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
DISCUSSION...08
AVIATION...08
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