545
FXUS63 KFSD 121140
AFDFSD
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
640 AM CDT SUN APR 12 2026
KEY MESSAGES
- ELEVATED TO CRITICAL FIRE DANGER IS EXPECTED TODAY. A RED FLAG
WARNING HAS BEEN ISSUED FOR MANY AREAS ALONG AND WEST OF I-29
WHERE CONFIDENCE IS HIGHEST IN CRITICAL FIRE DANGER CONDITIONS
BEING MET. THE WARNING IS IN EFFECT FROM NOON TO 7PM TODAY.
- MONDAY BRINGS THE BEST CHANCES (30-60%) FOR STRONG TO SEVERE
STORMS. HOWEVER, THERE REMAIN UNCERTAINTY REGARDING THE LOCATION
IN WHERE STORMS DEVELOP. CONTINUE TO CHECK THE FORECAST FOR THE
LATEST UPDATES.
- CHANCES (30-50%) FOR SHOWERS AND STORMS LOOK TO PERSIST THROUGH
THE REST OF THE WEEK. DETAILS REMAIN UNCERTAIN AT THIS TIME.
UPDATE
ISSUED AT 345 AM CDT SUN APR 12 2026
A COUPLE OF CHANGES FOR TODAY. FIRST, LATEST SPC OUTLOOK FOR TODAY
HAS REMOVED THE MARGINAL (LEVEL 1 OF 5) FROM THE EASTERN PORTIONS
OF OUR FORECAST AREA TODAY. THIS ALIGNS WITH OUR THINKING AS WE
SHOULD BE MORE PREVALENT SUBSIDENCE IN THE WAKE OF A SUBTLE WAVE
SLIDING THROUGH THIS MORNING, WHICH SHOULD PRECLUDE ADDITIONAL
STORM DEVELOPMENT THIS AFTERNOON.
AS A RESULT, OUR PRIMARY CONCERN FOR TODAY REMAINS ELEVATED TO
CRITICAL FIRE WEATHER AND THE COVERAGE OF A RED FLAG WARNING.
MODELS CONTINUE TO SUPPORT A DEEP UNIDIRECTIONAL SOUTHWEST TO
WEST FLOW BY MIDDAY, WITH SIGNIFICANT DRYING EXPECTED TO MIX TO
THE SURFACE, ESPECIALLY IN THE SOUTHWEST QUADRANT OF OUR FORECAST
AREA (ALONG/SOUTH OF I-90 AND ALONG/WEST OF I-29). THIS SCENARIO
IS OFTEN HANDLED WELL BY THE HRRR/RAP DURING THIS TIME OF YEAR, SO
HAVE BLENDED SOME OF THESE SOLUTIONS INTO OUR WINDS AND DEW POINTS
(RELATIVE HUMIDITY) FOR THIS AFTERNOON. THIS INCREASED CONFIDENCE
IN SEEING SEVERAL HOURS OF RED FLAG CONDITIONS AS FAR EAST AS I-29
BUT GENERALLY SOUTH OF SD HWY 34, SO HAVE EXPANDED THE RED FLAG
WARNING AS FAR EAST AS MINNEHAHA/LINCOLN/UNION COUNTIES IN SD AND
DIXON COUNTY NEBRASKA. MAY STILL NEED FURTHER EXPANSION INTO
PORTIONS OF SOUTHWEST MN AND FAR NORTHWEST IA, BUT CONFIDENCE IS
LOWER THAT THE TIMING OF CRITICAL HUMIDITY LEVELS AND WINDS IN
THESE AREAS WOULD SUFFICIENTLY OVERLAP, SO WILL LET THE DAY SHIFT
CONTINUE TO ASSESS AND EXPAND IF NEEDED.
DISCUSSION
ISSUED AT 300 PM CDT SAT APR 11 2026
WARM ADVECTIVE RAIN SHOWERS HAVE PUSHED OFF TO THE EAST THIS
AFTERNOON. HOWEVER, MOIST LOW LEVELS HAS KEPT LOW LEVEL STRATUS
AROUND. THIS HAS KEPT HIGH TEMPERATURES IN THE MID 40S TO MID 60S,
WARMEST ACROSS SOUTH CENTRAL SOUTH DAKOTA. THIS IS DUE TO WINDS
TAKING ON A SOUTH/SOUTHWEST COMPONENT ACROSS SOUTH CENTRAL SOUTH
DAKOTA, RESULTING IN CLEARING THE STRATUS ACROSS THIS AREA. BREEZY
WINDS WILL BE PERSISTENT THOUGH AND LAST THROUGH THE OVERNIGHT
HOURS. WITH BREEZY WINDS AND STRATUS IN PLACE, ONLY HAVE LOW
TEMPERATURES FALLING TO THE 50S ACROSS THE AREA. THERE REMAINS THE
POSSIBILITY OF A ROUGE STORM OR TWO LATE TONIGHT. SHOULD A STORM
DEVELOP, IT WOULD BE ACROSS PARTS OF NORTHWEST IOWA. THIS SEEMS
UNLIKELY (15% CHANCE) AS OF NOW AS WARM AIR ADVECTION (WAA)
STRENGTHEN ALOFT WITHOUT ADVECTING SUFFICIENT MOISTURE WITH IT. THIS
WILL LEAD TO AN INCREASING CAP ABOVE THE MOIST STABLE LATER. IF A
STORM CAN FORM, THEN IT WOULD HAVE THE POTENTIAL TO BE STRONG TO
SEVERE GIVEN SUFFICIENT
LOW LEVEL WINDS WILL TURN WESTERLY FOR THE DAY TOMORROW AND REMAIN
BREEZY. HIGH TEMPERATURES LOOK TO SIGNIFICANTLY WARM INTO THE UPPER
70S AND AND LOW 80S ACROSS THE AREA. WITH DRIER WESTERLY FLOW IN
PLACE, HUMIDITY LEVELS WILL DROP, RESULTING IN CRITICAL FIRE DANGER
BEING REACHED. MORE DETAILS CAN BE FOUND IN THE FIRE WEATHER
DISCUSSION BELOW. THE WESTERLY WINDS WILL ADVECT DRIER AIR INTO THE
AREA THROUGHOUT THE DAY. HOWEVER, GUIDANCE IS PERSISTENT IN SHOWING
THIS DRIER AIR SHOVING THE BETTER LOW LEVEL MOISTURE ALL THE WAY
DOWN TO PORTIONS OF NORTHWEST IOWA. THIS MOISTURE BOUNDARY WOULD BE
THE LOCATION FOR A ROUGE STORM TO DEVELOP ON. HOWEVER, A WEAK
SHORTWAVE TROUGH WILL ALREADY BE EAST OF THE AREA, PROMOTING
SUBSIDENCE ON ITS BACKSIDE. THUS, SUNDAY LOOKS TO BE MOSTLY DRY
THOUGH THERE REMAINS THE OUTSIDE CHANCE (15-30%) THAT A FEW SHOWERS
OR STORMS DEVELOP ALONG AND SOUTHEAST OF THIS BOUNDARY. ANY FIRE
DANGER WILL COME TO AN END DURING THE EVENING HOURS AS THE BOUNDARY
LAYER STABILIZES. WAA WILL RESTRENGTHEN ALOFT AHEAD OF AN INCOMING
EXIT REGION OF AN UPPER LEVEL JET TIED TO A SHORTWAVE TROUGH.
MOISTURE LOOKS SCARCE ABOVE 900MB AND WITH THE WAA STRENGTHENING THE
LOW LEVEL INVERSION. AGAIN, THE POTENTIAL FOR ANY SHOWERS REMAINS
LOW AT 15% OR LESS THROUGH THE NIGHT. IF A STORM IS ABLE TO FORM, IT
COULD BE STRONG TO SEVERE. LOW TEMPERATURES WILL FALL TO THE 40S AND
50S OVERNIGHT.
MONDAY LOOKS TO HAVE THE HIGHEST CHANCES FOR STRONG TO SEVERE STORMS
AS MEDIUM RANGE GUIDANCE IS IN DECENT AGREEMENT IN A SHORTWAVE
TROUGH PUSHING THROUGH THE NORTHERN PLAINS. THE MASS RESPONSE TO
THIS WAVE WILL RESULT IN SOUTHERLY RETURN FLOW AND MOISTEN DEW
POINTS ACROSS THE FORECAST AREA. WITH MID LEVEL LAPSE RATES TO ABOVE
8C/KM ALOFT. THIS WILL RESULT IN THE POTENTIAL FOR LARGE BUOYANCY.
THERE REMAINS SOME UNCERTAINTY THOUGH AS SOME OF THE GUIDANCE SHOWS
THE BULK OF THE MOISTURE GETTING ADVECTED TO THE EAST OF THE AREA.
THIS POSSIBILITY WOULD HAPPEN IF THE SURFACE LOW RACES EAST OF THE
AREA AND AND INTRODUCES WESTERLY SURFACE WINDS ON ITS BACK SIDE. IF
THE INCOMING SHORTWAVE IS SLOWER ALOFT, THEN THE SURFACE LOW WILL
NOT QUICKLY RACE OFF TO THE EAST AND THUS LEAVE A BROADER WARM
SECTOR ACROSS THE AREA. THE OTHER COMPONENT TO POTENTIAL SEVERE
WEATHER IS THE CAP. LATEST GUIDANCE CONTINUES TO SUPPORT A STRONG
CAP ABOVE THE WARM SECTOR. AT THIS TIME, THE LONGER RANGE CAMS SUCH
AS THE RRFS, NAM3KM, AND FV3 DO SHOW CONVECTION FIRING ALONG THE
WARM FRONT. BUT, THIS FRONT IS JUST NORTH OF THE AREA. WITH THE MEAN
WIND REMAINING OUT OF THE SOUTHWEST, THESE STORMS WOULD QUICKLY PUSH
OFF TO THE NORTHEAST. LATEST REFS ALSO SUGGESTS THIS SOLUTION AS
WELL AS CONVERGENCE IS STRONGEST ALONG THE WARM FRONT NORTH OF THE
FORECAST AREA. AS OF NOW, ONLY THE DETERMINISTIC EURO, EURO
ENSEMBLE, AND AIFS (AI EURO) SHOW THE WARM FRONT REMAINING DRAPED
ACROSS I-90 AND THUS PRODUCING CONVECTION MONDAY AFTERNOON. THINK
THE CURRENT SPC DAY 3 OUTLOOK REMAINS VALID GIVEN THIS REMAINING
UNCERTAINTY.
THE WARM SECTOR LOOKS GET SHOVED FURTHER SOUTH AND EAST OF THE
FORECAST AREA ON TUESDAY. WHILE THE MAIN WAVE WILL EJECT OUT OF THE
ROCKIES ON THIS DAY, KEEPING SEVERE STORM CHANCES AROUND. IF THE
BOUNDARY REMAINS OFF TO THE SOUTH AND EAST, THEN STORMS CHANCES
WOULD BE LOWER. IF THE BOUNDARY REMAINS ACROSS THE FORECAST AREA,
THEN STORM CHANCES WOULD INCREASE ACROSS THE AREA. TOUGH TO SAY WHICH
SOLUTION IS CORRECT AT THIS TIME BUT SOMETHING TO KEEP AN EYE ON
OVER THE NEXT FEW DAYS. THE UPPER LEVEL PATTERN DIVERGES TOWARDS THE
MIDDLE AND END OF NEXT WEEK BUT ADDITIONAL CHANCES FOR SHOWERS AND
STORMS REMAIN POSSIBLE. ASIDE FROM RAIN CHANCES, HIGH TEMPERATURES
LOOK TO REMAIN ABOVE AVERAGE IN THE 70S AND 80S THROUGH FRIDAY.
AVIATION /12Z TAFS THROUGH 12Z MONDAY/
ISSUED AT 640 AM CDT SUN APR 12 2026
NARROW AREA OF HIGH-BASED SHOWERS/THUNDERSTORMS MOVING THROUGH
EAST CENTRAL SD EARLY THIS MORNING SHOULD LIFT NORTH OF KBKX BY
13Z-14Z. FARTHER SOUTHEAST, AN AREA OF MVFR STRATUS LINGERS IN
NORTHWEST IOWA, MAINLY EAST OF KSUX THOUGH CANNOT RULE OUT A BRIEF
MVFR CEILING. PROBABILITY IS LOW, THOUGH, AND KEPT THE KSUX TAF
VFR FOR NOW. DRY WEATHER WITH VFR CONDITIONS WILL BECOME MORE
PREVALENT BY 15Z-16Z THROUGHOUT THE FORECAST AREA, WITH SOUTHWEST
TO WEST WINDS GUSTING 25-30KT AT TIMES THROUGH SUNSET. WINDS WILL
DROP OFF QUICKLY AFTER SUNSET, BECOMING LIGHT/VARIABLE OVERNIGHT.
FIRE WEATHER
ISSUED AT 345 AM CDT SUN APR 12 2026
TODAY WILL START OFF RATHER HUMID WITH AREAS OF GUSTY WINDS ALONG
AND EAST OF U.S. HIGHWAY 81 IN RESPONSE TO STRONG SOUTH-SOUTHWEST
FLOW ABOVE THE SURFACE. AS THE DAY PROGRESSES, A WEAK BOUNDARY
WILL SLIDE EAST ACROSS SOUTHEAST SOUTH DAKOTA INTO NORTHWEST IOWA,
TURNING SURFACE WINDS MORE TO THE SOUTHWEST AND WEST. BY MIDDAY,
DEEPER MIXING WILL PULL MUCH DRIER AIR TO THE SURFACE IN AREAS
WEST OF THIS BOUNDARY AS TEMPERATURES CLIMB INTO THE 70S TO LOWER
80S. AS A RESULT, RELATIVE HUMIDITY LEVELS ALONG AND SOUTH OF THE
I-90 CORRIDOR AND AT LEAST AS FAR EAST AS I-29 WILL FALL BELOW
CRITICAL LEVELS, REACHING 17 TO 22 PERCENT IN THE MID TO LATE
AFTERNOON. DEEPER MIXING WILL ALSO SUPPORT OCCASIONAL STRONGER
WIND GUSTS, REACHING 30 TO 35 MPH AT TIMES IN THESE AREAS. THESE
CONDITIONS ARE EXPECTED TO LAST FOR SEVERAL HOURS, SUPPORTING
EXPANSION OF THE RED FLAG WARNING EAST TO INCLUDE A PORTION OF
I-29 (MINNEHAHA TO UNION COUNTY SOUTH DAKOTA) AS WELL AS DIXON
COUNTY NEBRASKA.
THERE IS SOME POTENTIAL THAT CRITICAL CONDITIONS MAY OVERLAP FOR
MORE THAN AN HOUR OR TWO IN SOME AREAS EAST OF I-29. HOWEVER,
CONFIDENCE IS CURRENTLY NOT HIGH ENOUGH TO EXPAND THE RED FLAG
WARNING INTO AREAS EAST OF I-29. TRENDS WILL BE MONITORED
THROUGHOUT THE DAY, AND FURTHER EXPANSION OF THE WARNING IS
POSSIBLE.
FSD WATCHES/WARNINGS/ADVISORIES
SD...RED FLAG WARNING FROM NOON TODAY TO 7 PM CDT THIS EVENING FOR
SDZ050-052-053-057>071.
MN...NONE.
IA...NONE.
NE...RED FLAG WARNING FROM NOON TODAY TO 7 PM CDT THIS EVENING FOR
NEZ013.
UPDATE...JH
DISCUSSION...MEYERS
AVIATION...JH
FIRE WEATHER...JH
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