985
FXUS63 KFSD 261748
AFDFSD
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
1248 PM CDT SUN APR 26 2026
KEY MESSAGES
- SHOWERS AND ISOLATED THUNDERSTORMS EXPECTED TO DEVELOP THROUGH
THE AFTERNOON HOURS AND LIFT NORTHEAST. BRIEF MODERATE RAIN
MAY BE POSSIBLE. THIS ACTIVITY WILL PERSIST INTO THE OVERNIGHT
HOURS.
- CONTINUED CONDITIONAL AND VERY LOW CHANCES FOR ISOLATED
STRONG STORMS BOTH THIS EVENING, BUT PERHAPS AGAIN TOWARDS
DAYBREAK MONDAY. LOW RISKS FOR MARGINAL HAIL, A FEW STRONG
WIND GUSTS POSSIBLE.
- AFTER RAIN ENDS MONDAY AFTERNOON AN EXTENDED PERIOD OF COOLER
THAN NORMAL TEMPERATURES WILL CONTINUE THROUGH THE WEEK WITH
ONLY MINOR RAIN CHANCES LATE WEDNESDAY.
- WARMER TEMPERATURES RETURN BY NEXT WEEKEND WITH HIGH
TEMPERATURES AROUND 10 DEGREES ABOVE NORMAL IN THE 70S.
DISCUSSION
ISSUED AT 1242 PM CDT SUN APR 26 2026
THIS AFTERNOON: SCATTERED SHOWERS AND EMBEDDED THUNDERSTORMS
CONTINUE TO DEVELOP AND LIFT NORTHWARD THIS AFTERNOON. DRIVEN BY A
COMBINATION OF MODERATE DPVA AND BROAD WARM ADVECTION. ELEVATED
INSTABILITY IS SLOWLY CRAWLING NORTHWARD, BUT DOESN'T SEEM TO EXTEND
MUCH PAST I-90. THIS MAY LIMIT OVERALL PRECIPITATION RATES AS THIS
ACTIVITY MOVES NORTHEAST, BUT WITH PWAT VALUES NEAR THE 90TH
PERCENTILE, POCKETS OF MODERATE RAINFALL WILL STILL BE POSSIBLE.
PORTIONS OF NW IOWA HAVE SEEN A BIT MORE CLEARING TODAY, BUT
WITH CLOUDS INCREASING, THAT WARM-UP AND LOW-LVL LAPSE RATE
INCREASE MAY DIMINISH.
THIS EVENING AND OVERNIGHT: QUESTIONS STILL REMAIN ON THE DEGREE OF
ELEVATED INSTABILITY THAT CAN ADVECT NORTHWARD BOTH THIS EVENING AND
THEN AFTER MIDNIGHT. INITIAL WAVE OF VORTICITY IS EXPECTED TO
TRACK INTO SW MINNESOTA VERY EARLY THIS EVENING, LEAVING A BIT OF A
LULL IN FORCING FOR A FEW HOURS. TRAILING INSTABILITY ALONG WITH
SOME SHARPENING MID-LVL LAPSE RATES COULD STILL LEAD TO THE
DEVELOPMENT OF A STRONGER MARGINAL HAILER OR TWO SOUTH OF I-90
THROUGH SUNSET (FOCUSED IN A SECTOR FROM VERMILLION TO SPENCER
SOUTHWARD), BUT FOCUS FOR DEVELOPMENT REMAINS UNCERTAIN. A FEW CAMS
DO ALSO SUGGEST THE EDGE OF THE WARM SECTOR APPROACHES HIGHWAY 20,
WHICH COULD SUPPORT A WIND GUST TRANSPORTING DOWNWARD IN ANY
STRONGER STORM.
AS MULTIPLE MCS DEVELOP OVER THE CENTRAL AND SOUTHERN PLAINS AS EVEN
STRONGER UPPER TROUGHING ENTERS THE REGION, WE MAY BEGIN TO SEE A
WEAK SFC LOW TRY TO DEVELOP OVER NORTHEASTERN NEBRASKA WITH A
NORTHWARD EXTENDED INVERTED TROUGH. SHORT TERM GUIDANCE (MAINLY
NAM/RAP) SHOW SOME PERSISTENT NORTHWARD ADVECTION OF ELEVATED
INSTABILITY (800-1200 J/KG) AHEAD OF THIS FEATURE ALONG AND EAST OF
I-29. OTHER MODELS (GFS/EC) SUGGEST WEAKER LAPSE RATES WITH ONLY 300-
600 J/KG MUCAPE. THOUGHTS ARE THAT WHILE THE LLJ BEGINS TO VEER OFF
TO THE NW, THERE MAY BE ENOUGH CONVERGENCE COMBINED WITH DPVA
TO INDUCE SCATTERED THUNDERSTORMS AFTER 2AM. AN ISOLATED HAILER
COULD BE POSSIBLE, BUT SEVERE WEATHER RISKS REMAIN ON THE LOWER
SIDE.
MONDAY: THE AFOREMENTIONED INVERTED TROUGH WILL TURN TOWARDS A COLD
FRONT EARLY IN THE DAY AND SURGE EAST. LATEST CAMS HAVE SPED UP THE
BOUNDARY JUST ENOUGH TO KEEP ANY RENEWED SFC BASED CONVECTION ALONG
OR JUST EAST OF THE CWA BY LATE MORNING. FURTHER WEST, AS THE UPPER
TROUGH OPENS UP AND PASSES THROUGH THE CENTRAL PLAINS AND TOWARD THE
UPPER MS RIVER VALLEY, WE'LL BEGIN TO SEE A DEFORMATION AREA OF RAIN
DEVELOP IN CENTRAL SD. THIS PRECIPITATION WILL DRAG IT'S FOOT
EASTWARD DURING THE DAY, POTENTIALLY DISSIPATING BY TIME IT REACHES
I-29 BY MID-AFTERNOON. ADDITIONALLY, DEEPENING SURFACE LOW
PRESSURE INDUCED A STRONGER SPG THROUGH THE DAKOTAS, AND WHEN
COMBINED WITH STRONG LOW-LVL COLD ADVECTION WE SHOULD SEE WIND
GUSTS APPROACH THE 30 TO 40 MPH RANGE THROUGH THE DAY BEFORE
SETTLING IN THE EVENING. DAYTIME HIGHS MAY TAKE PLACE EARLY IN
THE DAY WITH FALLING TEMPERATURES IN THE AFTERNOON. HAVE
ADJUSTED THE NBM DIURNAL TEMPERATURES TREND TO ACCOUNT FOR
AFTERNOON CLOUDS AND COLD ADVECTION.
PRECIPITATION TOTALS: AMOUNTS HAVE TAPERED OFF SLIGHTLY OVER THE
PAST 24 HOURS, POTENTIALLY INDICATING LESS INSTABILITY FURTHER
NORTH, BUT ALSO SOME REDIRECTION OF MOISTURE AFTER DARK FROM
CONVECTION IN THE SOUTHERN PLAINS. NEVERTHELESS THE PROBABILITY OF
AN ADDITIONAL 1" OF RAIN BREAKS THE 75% MARK IN AREAS ALONG AND
NORTH OF I-90. THERE ARE ALSO SOME STRIPES OF 50% PROBABILITY OF 2"+
OF RAIN TOWARDS THE MADISON, BROOKINGS, AND MARSHALL AREAS IN HREF
GUIDANCE. AVERAGE TOTALS BASED ON THE 25/75TH PERCENTILE LIKELY RUN
BETWEEN 0.50" AND 1.5" WITH POCKETS OF HIGHER NUMBERS.
TUESDAY-THURSDAY: WE'LL REMAIN IN A DOMINANT TROUGHING PATTERN FOR
MUCH OF THE REMAINDER OF THE WORK WEEK. LONG WAVE TROUGHING
CENTERED OVER HUDSON BAY WILL KEEP NORTHWESTERLY FLOW ALOFT IN
THE TRI-STATE AREA. THE RESULT WILL BE TEMPERATURES NEAR TO
SLIGHTLY BELOW NORMAL AT TIMES, ALONG WITH A LOW CHANCE (30%)
OF SHOWERS BY WEDNESDAY NIGHT INTO THURSDAY.
FRIDAY-SUNDAY: THE GOOD NEWS IS THAT IT APPEARS THE MID-LVL PATTERN
MAY BREAK SLIGHTLY BY THE END OF THE WEEK AS LONG WAVE RIDGING MOVES
OUT OF THE WEST COAST AND TOWARDS THE PLAINS BY THE WEEKEND. MEDIUM
RANGE DETERMINISTIC AND ENSEMBLE GUIDANCE STILL REMAINS A BIT SPLIT
IN THIS POTENTIAL, WITH QUITE A BIT OF SPREAD IN ENSEMBLE GUIDANCE.
NBM 25/75TH SPREAD APPROACHES 10-15 DEGREES BY SUNDAY, SUGGESTING A
RANGE FROM THE MID 60S (SHOULD RIDGE BE SLOWER TO ADVECT EAST), TO
THE UPPER 70S AND 80S BY SUNDAY (IF RIDGE MOVE EAST FASTER). AT
THIS POINT THE NBM MEAN IN THE LOWER 70S SEEMS APPROPRIATE.
AVIATION /18Z TAFS THROUGH 18Z MONDAY/
ISSUED AT 1242 PM CDT SUN APR 26 2026
SCATTERED SHOWERS CONTINUE TO BREAK OUT EARLY THIS AFTERNOON,
WITH A VARIABLE CEILING FROM VFR TO MVFR IN MOST LOCATIONS.
SHOWERS BUILD NORTHWARD THROUGH MID-AFTERNOON AND WILL BECOME
FAIRLY WIDESPREAD BY LATE AFTERNOON AND EVENING. MVFR TO LOCALLY
IFR CEILINGS ARE LIKELY, WITH VISIBILITY RESTRICTIONS ONLY IN
MODERATE RAINFALL.
MORE UNCERTAINTY BUILDS DURING THE OVERNIGHT HOURS AS A WEAK
FRONT DEVELOPS THROUGH THE HEART OF THE CWA. CEILINGS MAY FALL
AND BRIEF BOUTS OF FOG COULD DEVELOP NEAR THIS BOUNDARY.
HOWEVER BY 10Z WE SHOULD SEE RENEWED SHOWERS AND THUNDERSTORMS
DEVELOP (MOSTLY EAST OF THE JAMES RIVER AND I-29) MOVING
EASTWARD INTO MONDAY MORNING. A COLD FRONT BEGINS TO SWEEP
EASTWARD MONDAY MORNING TURNING WINDS FROM EAST TO NORTHWEST BY
MID-DAY WITH GUSTS OVER 30 KNOTS.
FSD WATCHES/WARNINGS/ADVISORIES
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
DISCUSSION...DUX
AVIATION...DUX
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