546
FXUS63 KFSD 270549
AFDFSD
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
1249 AM CDT MON APR 27 2026
KEY MESSAGES
- AREAS OF PATCHY FOG HAVE DEVELOPED MAINLY NEAR THE MISSOURI
RIVER VALLEY. LOCALLY DENSE FOG WILL BE POSSIBLE THROUGH
SUNRISE SO BE SURE TO USE EXTRA CAUTION ON THE ROADS EARLY
THIS MORNING.
- SCATTERED SHOWERS AND THUNDERSTORMS CONTINUE TO BE POSSIBLE
THIS MORNING. CAN'T RULE OUT AN ISOLATED STRONG TO SEVERE
STORM WITH QUARTER SIZED HAIL AS THE MAIN THREAT, BUT CHANCES
REMAIN VERY LOW.
- 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.
UPDATE
ISSUED AT 851 PM CDT SUN APR 26 2026
THE FORECAST FOR TONIGHT REMAINS ON TRACK. AN AREA OF STEADY
RAIN DRIVEN BY A WAVE OF MID-LEVEL VORTICITY IS CONTINUING TO
LIFT SLOWLY NORTHEASTWARD. FARTHER SOUTH IN ITS WAKE, THE AIR IS
A BIT DRIER, BUT MORE SCATTERED ACTIVITY LOOKS TO DEVELOP
THROUGH THE REST OF THIS EVENING AS WARM AIR ADVECTION
CONTINUES. A NOSE OF AROUND 250-500 J/KG OF ELEVATED
INSTABILITY IS STARTING TO CREEP INTO THE HIGHWAY 20 CORRIDOR,
AND WILL CONTINUE TO LIFT TOWARDS THE I-90 CORRIDOR (STAYING
MAINLY NEAR AND EAST OF I-29 AS IT DOES).
NEAR AND AFTER MIDNIGHT, NAM/RAP SOUNDINGS INDICATE AROUND
1000-1200 J/KG OF CAPE REACHING THE HIGHWAY 20 CORRIDOR, WHILE
MOST OTHER GUIDANCE KEEPS THIS A BIT LOWER TOWARDS THE 500-750
J/KG RANGE. AS THIS OCCURS, A SECONDARY PUSH OF MID-LEVEL
VORTICITY ALONG WITH A SURFACE LOW MOVING NORTHWARD ACROSS
EASTERN NEBRASKA INTO SOUTHEASTERN SOUTH DAKOTA WILL LEAD TO
ADDITIONAL SHOWERS AND ISOLATED THUNDERSTORMS DEVELOPING
OVERNIGHT. SURFACE BASED THUNDERSTORMS WILL BECOME INCREASINGLY
HARD TO COME BY OVER THE NEXT COUPLE OF HOURS AS LOW LEVEL AIR
BEGINS TO WARM A TOUCH JUST ABOVE THE SURFACE AND BEGINS TO CAP
ANY POTENTIAL FOR SURFACE CONVECTION. THIS WILL MEAN THE THREAT
FOR DAMAGING WINDS WILL BE VERY LOW FROM THIS POINT FORWARD.
SO WITH ELEVATED CONVECTION EXPECTED, HAIL UP TO THE SIZE OF A
QUARTER REMAINS THE MAIN THREAT. THIS WILL STILL BE A VERY
ISOLATED THREAT ESPECIALLY FOR THE REST OF THE EVENING AS TALL
AND THIN CAPE PROFILES INDICATE WEAK VERTICAL MOTION WITHIN ANY
THUNDERSTORM, PREVENTING ANY HAILSTONES FROM GETTING TOO LARGE.
AS WE HEAD INTO THE LATE NIGHT TIME FRAME, THE AFOREMENTIONED
SECONDARY PUSH OF MID LEVEL VORTICITY MOVING OVERHEAD WILL COOL
THE MID LEVELS A BIT AND STEEPEN LAPSE RATES TO AROUND 7-7.5
C/KM. THIS COULD BETTER SUPPORT HAIL UP TO THE SIZE OF
QUARTERS ESPECIALLY IF INSTABILITY SHOWN BY THE RAP/NAM CAN BE
REALIZED, BUT STILL, THIS THREAT REMAINS LOW.
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 /06Z TAFS THROUGH 06Z TUESDAY/
ISSUED AT 1244 AM CDT MON APR 27 2026
AREAS OF FOG HAVE DEVELOPED MAINLY NEAR THE MISSOURI RIVER
VALLEY AND THIS WILL CONTINUE TO BE POSSIBLE THROUGH DAYBREAK
MONDAY. OTHERWISE SCATTERED SHOWERS AND A FEW STORMS REMAIN POSSIBLE
INTO MONDAY MORNING. CEILINGS HAVE MAINLY DROPPED TO MVFR AND IFR TO
LOCALLY LIFR LEVELS NEAR AND WEST OF I-29, AND THESE LOWER CEILINGS
ARE EXPECTED TO SPREAD EASTWARD OVER THE NEXT FEW HOURS. WE'LL
SEE CEILINGS VERY SLOWLY LIFT THROUGH THE DAY ON MONDAY,
RETURNING TO VFR CONDITIONS FOR MOST AREAS BY THE END OF THE
PERIOD.
WINDS WILL BE PICKING UP FROM THE NORTHWEST THROUGH THE DAY ON
MONDAY AS A COLD FRONT SWINGS THROUGH THE AREA FROM WEST TO EAST.
PEAK GUSTS HAVE TRENDED DOWN SOMEWHAT ACCORDING TO RECENT GUIDANCE,
BUT COULD STILL GUSTS UPWARDS OF 30 TO 35 KTS THIS AFTERNOON. AREAS
WITHIN THE HIGHER ELEVATIONS OF THE COTEAU DES PRAIRIES OF
SOUTHWEST MINNESOTA AND EAST-CENTRAL SOUTH DAKOTA COULD GUSTS
UP TO 40 KTS LATE THIS AFTERNOON/EARLY EVENING.
FSD WATCHES/WARNINGS/ADVISORIES
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
UPDATE...SAMET
DISCUSSION...DUX
AVIATION...SAMET
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