911
FXUS63 KFSD 130926
AFDFSD
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
426 AM CDT SUN APR 13 2025
KEY MESSAGES
- LOW HUMIDITY AND STRONG NORTHWEST WINDS THIS AFTERNOON AND
EVENING WILL LEAD TO NEAR CRITICAL TO CRITICAL FIRE DANGER.
THE MOST CRITICAL CONDITIONS WILL BE NEAR AND WEST OF I-29
WHERE A RED FLAG WARNING IS IN EFFECT.
- STRONG NORTHWEST WINDS PERSIST THROUGH MUCH OF TONIGHT AND
INTO MONDAY. GUSTS AS HIGH AS 50 MPH ARE EXPECTED IN SOUTH
CENTRAL SOUTH DAKOTA, AND A WIND ADVISORY HAS BEEN ISSUED
THIS AFTERNOON THROUGH LATE TONIGHT.
- COLDER WITH SCATTERED RAIN SHOWERS MONDAY AFTERNOON. ISOLATED
LIGHTNING AND TINY HAIL ARE POSSIBLE, WITH A VERY LOW (<20%)
POTENTIAL FOR SNOW TO MIX WITH RAIN IN THE HIGHEST ELEVATIONS.
- MODERATE (40-50%) CHANCES FOR RAIN AND SOME THUNDERSTORMS
THURSDAY-THURSDAY NIGHT. HOWEVER, DETAILS ON TIMING AND
LOCATION OF GREATER CHANCES ARE STILL UNCERTAIN.
DISCUSSION
ISSUED AT 420 AM CDT SUN APR 13 2025
TODAY-TONIGHT: INCREASING NORTHWEST WINDS, AND THEIR IMPACT ON
FIRE WEATHER CONDITIONS, WILL BE THE MAIN STORY THROUGH THE NEXT
24 HOURS. WEAK SURFACE BOUNDARY EXTENDS FROM NORTHEAST NEBRASKA
INTO FAR WESTERN MINNESOTA EARLY THIS MORNING. HOWEVER, ATTENTION
WILL BE ON THE MID-UPPER LEVEL WAVE DRIVING AN AREA OF SHOWERS
IN NORTH DAKOTA, AND THE ASSOCIATED PUSH OF COLD ADVECTION WHICH
IS FORECAST TO PUSH INTO EASTERN SOUTH DAKOTA/NEBRASKA BY MIDDAY.
THIS COLD ADVECTION WILL SUPPORT MIXING BEYOND 800MB, RESULTING
IN STRONGER WINDS AND DRIER AIR WORKING TO THE SURFACE THROUGH
THE AFTERNOON. SOUTH CENTRAL SOUTH DAKOTA WILL SEE THE STRONGEST
WINDS AND DRIEST AIR IN OUR FORECAST AREA, WITH GUSTS EXCEEDING
40KT/45-50MPH AND DEW POINTS FALLING INTO THE LOWER 20S. THOUGH
TEMPERATURES WILL BE COOLER THAN POINTS FARTHER EAST, HUMIDITY
LEVELS STILL FALL TO AROUND 20 PERCENT BY LATE AFTERNOON. FROM
THE JAMES RIVER VALLEY EAST TOWARD THE I-29 CORRIDOR, THE DRIEST
AIR WILL BE A LITTLE SLOWER TO ARRIVE BUT WILL STILL COINCIDE
WITH WIND GUSTS TOPPING 30KT/35MPH. THUS HAVE TRANSITIONED THE
FIRE WEATHER WATCH TO A RED FLAG WARNING STARTING AT 1 PM, WITH
A SLIGHT EASTWARD EXPANSION TO INCLUDE MADISON AND SIOUX FALLS.
HUMIDITY LEVELS WILL BE SLOW TO RECOVER AS STOUT MIXING PERSISTS
INTO THE EVENING. THUS HAVE EXTENDED SOUTHERN PORTIONS OF THE
RED FLAG WARNING FARTHER INTO THE EVENING, ENDING AREAS SOUTH OF
I-29 AT 10 PM. EVEN AS THE HUMIDITY LEVELS RISE, STRONG WINDS
ARE EXPECTED TO PERSIST TONIGHT, AND MAY EVEN INCREASE FURTHER
IN RESPONSE TO A SECONDARY SURGE OF COLD ADVECTION DURING THE
EVENING. HAVE ISSUED A WIND ADVISORY THIS AFTERNOON THROUGH 4
AM MONDAY FOR SOUTH CENTRAL SOUTH DAKOTA WHERE CONFIDENCE IN AT
LEAST ADVISORY LEVEL WINDS IS HIGHEST. HOWEVER, LATER SHIFTS
MAY CONSIDER EXPANSION FOR THE OVERNIGHT HOURS IF MORE MODELS
JOIN THE RAP AND ARW IN SHOWING 50+KT ATOP THE MIXED LAYER
FARTHER EAST THROUGH THE MISSOURI RIVER VALLEY TONIGHT.
MONDAY-MONDAY EVENING: THIS WILL BE A MUCH COLDER AND RAW DAY,
AT LEAST RELATIVELY SPEAKING, WITH HIGHS ONLY IN THE UPPER 40S
AND 50S AND GUSTY NORTHWEST WINDS CONTINUING. A TRAILING WAVE
DROPPING SOUTHEAST ACROSS THE REGION MONDAY AFTERNOON COMBINED
WITH LOW CONVECTIVE TEMPERATURES AND WEAK INSTABILITY ABOVE THE
MIXED LAYER WILL PRODUCE SCATTERED SHOWERS, POSSIBLY LINGERING
INTO THE EARLY EVENING AS THE WAVE DEPARTS NORTHWEST IOWA. THE
WEAK INSTABILITY MAY NOT ONLY RESULT IN ISOLATED THUNDER, BUT
THE COLD TEMPERATURES ALOFT COULD SUPPORT SMALL HAIL/GRAUPEL. IN
ADDITION, THE "WARM" LAYER WILL BE RELATIVELY SHALLOW ACROSS THE
HIGHER ELEVATIONS OF THE BUFFALO RIDGE IN SOUTHWEST MINNESOTA,
AND POSSIBLY OVER THE COTEAU DES PRAIRIES IN EAST CENTRAL SOUTH
DAKOTA. WOULD NOT BE SURPRISED TO SEE A RAIN/SNOW MIX IN THESE
AREAS DESPITE AMBIENT TEMPERATURES AWAY FROM THE SHOWERS IN THE
40S.
TUESDAY-WEDNESDAY: WEAK RIDGING ALOFT WILL BRING MORE MILD AND
DRY CONDITIONS TO THE REGION MIDWEEK WITH DAYTIME HIGHS WARMING
BACK INTO THE UPPER 50S-MID 60S TUESDAY, AND MOSTLY IN THE 70S
BY WEDNESDAY. LIGHTER WINDS TUESDAY WILL BRING A BRIEF RESPITE
FROM THE ELEVATED FIRE DANGER, BUT ELEVATED CONDITIONS WILL
RETURN WITH BREEZY SOUTHERLY FLOW ON WEDNESDAY.
THURSDAY-THURSDAY NIGHT: WHILE UNCERTAINTY LINGERS IN HOW THE
PATTERN WILL EVOLVE THROUGH THE LATE WEEK PERIOD, WE ARE
STARTING TO SEE SOME CONSENSUS FAVORING AN UPPER LOW DIGGING
SOUTHWARD THROUGH THE INTERMOUNTAIN WEST ON THURSDAY WHILE A
NORTHERN STREAM WAVE SLIDES INTO THE NORTHERN PLAINS/SOUTHERN
CANADA BY FRIDAY. AN APPROACHING UPPER LEVEL JET AND ASSOCIATED
SHORTWAVE IN THE SOUTHWEST FLOW WILL SUPPORT INCREASING CHANCES
FOR SHOWERS AND SOME THUNDERSTORMS LATER THURSDAY INTO THURSDAY
NIGHT. ENSEMBLE JOINT PROBABILITY FOR MUCAPE > 500J/KG AND SHEAR
> 30KT REACH 50-70% ACROSS NORTHWEST IOWA LATE THURSDAY, AND
DETERMINISTIC MODELS LIKEWISE SHOW GROWING AGREEMENT IN AN
OVERLAPPING AREA OF INSTABILITY AND SHEAR IN OUR SOUTHEAST
COUNTIES. SPC OUTLOOKS HAVE INTRODUCED A 15% OUTLINE FOR SEVERE
STORMS IN THIS AREA IN THE DAY 5 OUTLOOK AS WELL, SO NOW WOULD
BE THE TIME TO REVIEW YOUR SEVERE WEATHER PREPARATIONS.
FRIDAY-SATURDAY: THE BROADER ENSEMBLE BECOMES A BIT MORE
MUDDLED, BUT DETERMINISTIC MODELS FAVOR A STRONGER NORTHERN
STREAM TROUGH IMPACTING THE UPPER MIDWEST WHILE THE SOUTHERN
STREAM LOW REMAINS CLOSED OFF OVER THE DESERT SOUTHWEST.
PRECIPITATION CHANCES APPEAR LIMITED AFTER THE THURSDAY NIGHT
ACTIVITY MOVES EAST, WITH TEMPERATURES TRENDING CLOSER TO
SEASONAL NORMALS FOR A COUPLE OF DAYS AFTER THE ROLLER COASTER
WE'LL BE ON FROM TODAY THROUGH THURSDAY.
AVIATION /06Z TAFS THROUGH 06Z MONDAY/
ISSUED AT 1038 PM CDT SAT APR 12 2025
VFR CONDITIONS ARE EXPECTED FOR THE TAF PERIOD. HIGH LEVEL CIRRUS
PERSISTS ACROSS THE REGION LATE THIS EVENING. AT THE SURFACE, A WEAK
BOUNDARY REMAINS DRAPED ACROSS THE AREA, INCLUDING JUST ABOUT OVER
KFSD. WINDS ARE OUT OF THE SOUTH/SOUTHEAST EAST OF THE BOUNDARY AND
OUT OF THE NORTHEAST WEST OF THE BOUNDARY. MARGINALLY BREEZY WINDS
PERSIST SOUTH OF THE BOUNDARY BUT SHOULD WEAKEN DURING THE OVERNIGHT
HOURS.
A FEW HOURS OF LOW LEVEL WIND SHEAR (LLWS) ARE EXPECTED AT KSUX
TONIGHT ALONG WITH THE POTENTIAL FOR LIGHT RAIN SHOWERS ALONG
HIGHWAY-14, INCLUDING KHON. FOR NOW, CONFIDENCE IS NOT HIGH ENOUGH
TO INCLUDE LIGHT RAIN AS A PREVAILING GROUP SO HAVE ADDED IT VIA A
PROB30 GROUP.
THE BOUNDARY WILL PUSH THROUGH THE AREA DURING THE MORNING HOURS
TOMORROW, TURNING WINDS TO OUT OF THE NORTHWEST IN ITS WAKE. WINDS
WILL STRENGTHEN ONCE AGAIN WITH GUSTS UP TO 25-40 KNOTS EXPECTED FOR
THE AFTERNOON HOURS. THE STRONGEST WINDS WILL RESIDE ALONG AND WEST
OF I-29. HOWEVER, WINDS WILL REMAIN STRONG THROUGH THE EVENING HOURS
TO END THE TAF PERIOD.
FIRE WEATHER
ISSUED AT 420 AM CDT SUN APR 13 2025
NEAR CRITICAL TO CRITICAL FIRE WEATHER CONDITIONS (VERY HIGH TO
EXTREME GRASSLAND FIRE DANGER) WILL BE WIDESPREAD ACROSS THE
AREA TODAY THANKS TO STRONG NORTHWEST WINDS AND DRY AIR. THE
MOST CRITICAL CONDITIONS, WITH A POTENTIAL FOR WIND GUSTS 45 TO
50 MPH AND HUMIDITY LESS THAN 20 PERCENT, WILL BE FOCUSED WEST
OF THE JAMES RIVER VALLEY IN SOUTH CENTRAL SOUTH DAKOTA.
HOWEVER, LOCATIONS AS FAR EAST AS THE I-29 CORRIDOR WILL STILL
SEE GUSTS UP TO 40 MPH AND HUMIDITY AS LOW AS 25 PERCENT. THUS A
RED FLAG WARNING HAS BEEN ISSUED WHERE THE FIRE WEATHER WATCH
WAS IN EFFECT, WITH A SLIGHT EXPANSION EAST TO INCLUDE MADISON
AND SIOUX FALLS SOUTH DAKOTA. AT THIS TIME, WIND SPEEDS ACROSS
SOUTHWEST MINNESOTA/NORTHWEST IOWA ARE FORECAST TO BE SLIGHTLY
LOWER AND HUMIDITY LEVELS SLIGHTLY HIGHER, THOUGH NEAR CRITICAL
CONDITIONS ARE STILL EXPECTED.
UNLIKE TYPICAL WINDY DAYS, THE STRONG/GUSTY WINDS WILL PERSIST
THROUGHOUT TONIGHT AND HUMIDITY WILL BE SLOWER TO RECOVER,
ESPECIALLY SOUTH OF THE I-90 CORRIDOR. THEREFORE THE RED FLAG
WARNING HAS BEEN EXTENDED UNTIL 10 PM THIS EVENING FOR NORTHEAST
NEBRASKA AND THOSE PORTIONS OF SOUTHEAST SOUTH DAKOTA SOUTH OF
I-90. WHILE WIND GUSTS OF 40 TO 45 MPH REMAIN POSSIBLE THROUGH
THE DAY MONDAY, COLDER TEMPERATURES WILL RESULT IN LESS CRITICAL
HUMIDITY LEVELS (30-50%) WITH SCATTERED AFTERNOON RAIN SHOWERS
EXPECTED.
FSD WATCHES/WARNINGS/ADVISORIES
SD...RED FLAG WARNING FROM 1 PM THIS AFTERNOON TO 10 PM CDT THIS
EVENING FOR SDZ050-063>071.
RED FLAG WARNING FROM 1 PM THIS AFTERNOON TO 8 PM CDT THIS
EVENING FOR SDZ038-052>055-057>062.
WIND ADVISORY FROM 1 PM THIS AFTERNOON TO 4 AM CDT MONDAY FOR
SDZ050-052-057>059-063-064.
MN...NONE.
IA...NONE.
NE...RED FLAG WARNING FROM 1 PM THIS AFTERNOON TO 10 PM CDT THIS
EVENING FOR NEZ013-014.
DISCUSSION...JH
AVIATION...MEYERS
FIRE WEATHER...JH
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