096
FXUS63 KFSD 251734
AFDFSD
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
1234 PM CDT WED JUN 25 2025
KEY MESSAGES
- MULTIPLE ROUNDS OF SHOWERS AND THUNDERSTORMS CAPABLE OF
PRODUCING HEAVY RAINFALL WILL OCCUR DURING THE NEXT 36-48
HOURS. HIGHEST POTENTIAL FOR HEAVY RAINFALL WILL OCCUR TONIGHT
INTO THURSDAY MORNING.
- WIDESPREAD AMOUNTS OF 1 TO 3" ARE POSSIBLE, WITH SEVERAL
INDICATORS OF HEAVY RAIN OF 3 TO 5" FOCUSED THROUGH NE
NEBRASKA, NW IOWA, AND ADJACENT AREAS OF MN/SD.
- THERE IS SOME RISK FOR SMALL STREAMS AND CREAKS TO RISE OVER
THEIR BANKS, AS WELL AS LOCALIZED URBAN STREET FLOODING. AREA
RIVER FORECAST CONTINUE TO SUGGEST SOME FLOODING POTENTIAL,
BUT RECENT DROUGHT MAY SUPPRESS HIGHER LEVEL POTENTIAL.
- WEDNESDAY NIGHT, THERE IS POTENTIAL FOR STRONG TO SEVERE
THUNDERSTORMS TO FORM ALONG THE BOUNDARY. RISKS INCLUDE HEAVY
DOWNPOURS, WIND GUSTS TO 60 MPH, AND LARGE HAIL TO AN INCH IN
DIAMETER. THOUGH UNLIKELY, A TORNADO IS POSSIBLE.
- A BRIEF BREAK IN THE RAIN FRIDAY AND SATURDAY BEFORE
THUNDERSTORM CHANCES RETURN SUNDAY.
DISCUSSION
ISSUED AT 354 AM CDT WED JUN 25 2025
TODAY: TODAY, DESPITE THE RAIN, HIGHS WILL WARM INTO THE 70S AND 80S
THANKS TO PERSISTENT WAA. THE FORECAST REMAINS LARGELY ON TRACK
FOR 36-48 HOURS OF WIDESPREAD, PERIODICALLY HEAVY RAIN FALL. A
MID-LEVEL WAVE HAS MOVED NORTH OUT OF WESTERN NEBRASKA INTO
CENTRAL SOUTH DAKOTA AND WILL CONTINUE TO MOVE NORTHEASTWARD
THROUGH THE DAY TODAY. WITH IT COMES A STRONG PUSH OF WAA AND A
VORTICITY MAX THAT IS TRIGGERING SHOWERS AND THUNDERSTORMS.
THESE STORMS WILL PROGRESS NORTHEASTWARD WITH THE WAVE,
EXPANDING IN COVERAGE TO INCLUDE THE MAJORITY OF THE COUNTY
WARNING AREA BY DAYBREAK. AS THE DAY CONTINUES, ELEVATED
INSTABILITY OF 1000-1500 J/KG CAPE AND MARGINAL 0-6 KM BULK
SHEAR OF LESS THAN 30 KTS COULD SPAWN AN OCCASIONAL STRONGER
THUNDERSTORM. BUT THE GREATER RISK FOR STRONG TO SEVERE
THUNDERSTORMS WILL COME THIS EVENING.
THROUGH THE DAY TODAY, WAA WILL CONTINUE TO PULL WARM, MOISTURE RICH
AIR NORTHWARD INTO THE REGION INCREASING INSTABILITY, AND POOLING
AGAINST THE WEST-TO-EAST ORIENTATED FRONT. THE 0-6 BULK SHEAR
INCREASES AS THE LLJ PICKS UP AND THE MAIN UPPER WAVE BEGINS TO LIFT
NORTHEASTWARD FROM CENTRAL SOUTH DAKOTA INTO SOUTHWESTERN MINNESOTA.
THE AREA OF GREATEST CONVERGENCE, JUST TO THE SOUTH OF BOUNDARY,
WILL SERVE AS THE FOCUS FOR STRONG TO SEVERE THUNDERSTORM INITIATION
WEDNESDAY EVENING AND INTO THE OVERNIGHT. LOW LEVEL LAPSE RATES ARE
STEEP, BUT THERE IS A DEEP WARM LAYER (10-12 THOUSAND FEET). THIS
LEADS ME TO BELIEVE THE PRIMARY THREAT WILL BE DAMAGING WIND GUSTS
TO 60 MPH, AND QUARTER SIZED HAIL. THOUGH UNLIKELY, A TORNADO CANNOT
BE RULED OUT. THESE ARE IN ADDITION TO THE HEAVY RAINFALL THAT ANY
STORM WILL BE CAPABLE OF PRODUCING.
THERE REMAINS SOME QUESTION ON HOW FAR NORTH THE 925-850 MB FRONT
WILL BE PUSHED. THIS WILL GREATLY IMPACT WHERE THE HIGHEST RAIN
TOTALS, AND WHERE THE GREATEST SEVERE THREAT WILL BE. SOME OF THE
MODELS IN THE 00Z RUN HAVE FLIP-FLOPPED FROM THE PREVIOUS FORECAST.
THERE STILL REMAINS TWO SCENARIOS. IN THE FIRST SCENARIO, THE ECMWF
AND THE NAM NEST INDICATE THE FRONT WILL MOVE FURTHER NORTH.
(PREVIOUSLY THE NAM HAD A MORE SOUTHERLY TRACK) IF THIS IS THE CASE
THE HEAVIER RAINFALL WILL BE SOUTHEAST OF A ROUGH LINE FROM WAGNER-
SALEM-TRACY. THE SECOND SCENARIO IS SHOWN BY THE GFS AND CANADIAN
THAT INDICATE THE FRONT WILL REMAIN FARTHER SOUTH. (PREVIOUSLY THE
GFS HAD A MORE NORTHERLY TRACK) SHOULD THIS SCENARIO PLAY OUT, THE
HEAVIEST RAIN WILL FALL SOUTHEAST OF A ROUGH LINE FROM YANKTON-
LUVERNE-JACKSON. OVERALL, ENSEMBLE GUIDANCE INDICATES A SLIGHT TREND
NORTH IN THE HEAVIEST PRECIPITATION. IF THIS TREND HOLDS, THE MOST
LIKELY SCENARIO WOULD BE SCENARIO ONE.
WHEN IT'S ALL SAID AND DONE, WIDESPREAD TOTALS OF 1-3 INCHES ARE
EXPECTED ACROSS THE REGION. AS MENTIONED PREVIOUSLY, HIGHER AMOUNTS
ARE POSSIBLE BUT WILL BE HIGHLY DEPENDENT ON WHERE THE FRONT
SETTLES. AREAS OF NORTHEASTERN NEBRASKA, EXTREME SOUTHEASTERN SOUTH
DAKOTA, NORTHWESTERN IOWA, AND SOUTHWESTERN MINNESOTA COULD SEE
TOTALS CLOSER TO 3-5 INCHES, WITH POCKETS OF HIGHER POSSIBLE. THIS
RAISES THE QUESTION OF FLOODING. THIS MORNING'S STORMS ARE MORE
LIKELY TO RESULT IN SOME LOCALIZED PONDING AND URBAN STREET
FLOODING. AS WE CONTINUE INTO TONIGHT WITH THE POTENTIALLY STRONGER
THUNDERSTORMS, WE MAY BEGIN TO SEE SMALL CREEKS AND STREAMS OVERRUN
THEIR BANKS. SOME LOCALIZED FLASH FLOODING IS POSSIBLE. THANKS TO
THE RECENT DRY WEATHER, OUR RIVERS ARE AT OR BELOW NORMAL FOR THIS
TIME OF YEAR. WHILE THERE WILL LIKELY BE RIVER RISES, MOST SHOULD
REMAIN BELOW FLOOD STAGE. A FEW MAY COME CLOSE TO MINOR FLOOD STAGE,
BUT IT'S TOO EARLY TO TELL WHAT RIVERS MAY REACH THAT POINT. WITH
THE UNCERTAINTY IN THE LOCATION OF THE HEAVIEST RAINFALL, HAVE OPTED
NOT TO ISSUE A FLOOD WATCH TONIGHT AFTER COLLABORATION WITH
NEIGHBORS.
THURSDAY-NEXT WEEK: THURSDAY SHOWERS WILL LINGER THROUGH THE EARLY
AFTERNOON BEFORE TAPERING OFF IN THE EVENING. HIGHS WILL REACH THE
70S TO 80S WITH THE WARMEST TEMPERATURES ALONG THE MISSOURI RIVER
VALLEY. FRIDAY, FLOW ALOFT BECOMES WEST-SOUTHWESTERLY, DRYING THINGS
OUT. A STRONG PUSH OF WAA WILL HELP WARM HIGHS INTO THE 80S AND 90S.
BY SATURDAY THE FLOW ALOFT BECOMES MORE WESTERLY, KEEPING US DRY AND
WARM DURING THE DAY. HIGHS ARE EXPECTED TO CLIMB INTO THE 90S. A
SHORT WAVE WILL MOVE NORTH OF THE REGION SATURDAY NIGHT, BRINGING
ANOTHER ROUND OF SHOWERS AND THUNDERSTORMS FOR SATURDAY NIGHT INTO
SUNDAY. FOR THE FIRST HALF OF NEXT WEEK, A RIDGE OF HIGH PRESSURE
WILL MOVE INTO THE REGION. SUNDAY THROUGH WEDNESDAY TEMPERATURES
WILL BE SEASONABLY WARM, IN THE 80S.
AVIATION /18Z TAFS THROUGH 18Z THURSDAY/
ISSUED AT 1230 PM CDT WED JUN 25 2025
A MIX OF MVFR AND IFR CEILINGS CONTINUE TO MOVE ACROSS THE
REGION EARLY THIS AFTERNOON. A FEW BREAKS HAVE DEVELOP SOUTH OF
I-90, SO TEMPORARY RISES INTO VFR LEVELS IS POSSIBLE. SCATTERED
SHOWERS WILL PERSIST AT TIMES, BUT FOCUS FOR STRONGER CONVECTION
BEGINS TO INCREASE OVER NORTHWEST IOWA AND NORTHERN NEBRASKA BY
MID-AFTERNOON.
THOUGH THE NIGHT, ADDITIONAL CONVECTION IS LIKELY THROUGH THE
REGION, HOWEVER A HIGH DEGREE OF UNCERTAINTY LINGERS OUTSIDE OF
THE AREA FROM NORTHERN NEBRASKA TO SOUTHERN MINNESOTA. A
SECONDARY ARE OF CONVECTION MAY DEVELOP NEAR OR JUST SOUTH OF
HIGHWAY 14 OVERNIGHT. GENERALLY MVFR TO IFR CEILINGS WILL BE
EXPECTED WITH BRIEF REDUCTIONS TO VISIBILITY IN CONVECTION NEAR
1 MILE AT TIMES.
FSD WATCHES/WARNINGS/ADVISORIES
SD...NONE.
MN...NONE.
IA...FLOOD WATCH FROM 4 PM CDT THIS AFTERNOON THROUGH THURSDAY
AFTERNOON FOR IAZ013-014-020>022-031-032.
NE...FLOOD WATCH FROM 4 PM CDT THIS AFTERNOON THROUGH THURSDAY
AFTERNOON FOR NEZ013-014.
DISCUSSION...AJP
AVIATION...DUX
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