515
FXUS63 KFSD 020808
AFDFSD
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
308 AM CDT THU JUL 2 2026
KEY MESSAGES
- SCATTERED STRONG THUNDERSTORMS ARE POSSIBLE IN SOUTHWEST MN
AND NORTHWEST IA DURING THROUGH THE MORNING. THE STRONGEST
STORMS WILL BE CAPABLE OF DAMAGING WINDS TO 60 MPH AND QUARTER
SIZED HAIL.
- CONCERNS ARE GROWING FOR MORE WIDESPREAD SEVERE STORMS THIS
EVENING INTO FRIDAY MORNING AND AGAIN FRIDAY INTO SATURDAY
WITH ONE OR MORE OVERNIGHT STORM COMPLEXES POSSIBLE. AN
ENHANCED RISK (LEVEL 3 OF 5) HAS BEEN INTRODUCED FOR PART OF
THE AREA TODAY.
- MULTIPLE ROUNDS OF RAIN AND STORMS OVER THE NEXT FEW DAYS,
COMBINED WITH RECENT RAINFALL, MAY LEAD TO GROWING CONCERNS OF
LOCALIZED FLASH FLOODING AND MINOR RIVER FLOODING THROUGH THE
END OF THE WEEK.
UPDATE
ISSUED AT 308 AM CDT THU JUL 2 2026
CONVECTION NEVER REALLY GOT GOING YESTERDAY EVENING NOR OVERNIGHT.
WITH THE LLJ CONTINUING TO IMPINGE ON THE AREA THIS MORNING,
SCATTERED THUNDERSTORMS REMAIN POSSIBLE OVER PARTS OF NORTHWEST IA
AND NORTHEAST NE. HOWEVER, WITH A FREEZING LEVEL AT 13 KFT AGL, CAPE
VALUES OF ABOUT 1000 J/KG AND DEEP LAYER SHEAR VALUES AROUND 30
KNOTS, THE SEVERE WEATHER THREAT THROUGH THE MORNING IS VERY
LIMITED. THE MAIN THREAT WILL BE HAIL TO THE SIZE OF QUARTERS AND
WIND GUSTS O 50 TO 60 MPH.
THE BETTER THREAT FOR SEVERE WEATHER WILL COME DURING THE LATE
EVENING AND OVERNIGHT HOURS. THIS IS IN RESPONSE TO AN UPPER LEVEL
WAVE INCREASING THE LLJ ACROSS THE AREA. MODEL SOUNDINGS INDICATE
FAIRLY DEEP INSTABILITY, LIKELY AROUND 3000 J/KG, HOWEVER SHEAR
VALUES ARE NOT OVERLY IMPRESSIVE. THE QUESTION WILL COME FOR TONIGHT
WHETHER OR NOT ANY LINEAR SEGMENT THAT DEVELOPS TO THE NORTHWEST OF
THE AREA WILL SEE THE OUTFLOW RACE AHEAD OR IF THE MCS CAN MAINTAIN
A MORE COHERENT UPDRAFT CYCLE THROUGH THE NIGHT. IF THE MCS CAN
REMAIN MORE ORGANIZED, WINDS TO 75 MPH AND LOCALLY HEAVY RAIN WILL
BE POSSIBLE. IF THE MCS BECOMES A BIT MORE OUTFLOW DOMINANT, THEN
GUSTY WINDS TO 60 MPH WILL BE POSSIBLE WITH HEAVY RAIN POSSIBLY
BECOMING MORE OF A THREAT. WITH HOW POORLY THE LATEST MODELS ARE
HANDLING THE CURRENT EARLY MORNING CONVECTION, CONFIDENCE ON
TONIGHT'S ACTIVITY REMAINS PRETTY LOW.
FRIDAY AND ESPECIALLY FRIDAY CONTINUES TO SHOW A FAIRLY CONSISTENT
AND DECENTLY AGREED UPON WAVE EXPECTED TO MOVE THROUGH AS WINDS
ALOFT TURN A BIT MORE WESTERLY. THIS WILL BE ANOTHER GOOD CHANCE FOR
SEVERE WEATHER AND HEAVY RAIN.
FOR THE 4TH OF JULY, THE GOOD NEWS IS THAT TRENDS ARE SUGGESTING WE
MAY SEE MAINLY DRY CONDITIONS. THE BAD NEWS IS THIS IS STILL FAIRLY
FAR OUT WHEN DEALING WITH DAILY THUNDERSTORM THREATS SO THERE IS
STILL SOME ROOM FOR ERROR.
DISCUSSION
ISSUED AT 240 PM CDT WED JUL 1 2026
SKIES HAVE MOSTLY CLEARED OUT FROM LAST NIGHT'S STORMS EXCEPT OVER
PORTIONS OF NORTHWEST IOWA WHERE CLOUDS LINGER FROM REMNANT SHOWERS
THAT MOVED THROUGH DURING THE MID MORNING HOURS. THIS IS ALSO WHERE
A BOUNDARY IS ROUGHLY LOCATED THAT WILL BE THE FOCUS FOR STRONGER
CONVECTION TO DEVELOP LATE THIS AFTERNOON INTO THE EARLY EVENING.
THE LATEST HRRR RUNS HAVE BEEN TRENDING CONVECTIVE INITIATION
FARTHER WEST INTO NORTHEAST NEBRASKA, AND THIS IS LIKELY BECAUSE
THOSE AREAS HAVE CLEARED QUICKER AND HAVE THUS BEEN ABLE TO
DESTABILIZE MORE EFFICIENTLY WHEREAS CLOUDS HAVE LINGERED OVER
PORTIONS OF NORTHWEST IOWA. LATEST MESOANALYSIS SHOWS AROUND
1500-2000 J/KG OF MLCAPE THAT WILL INCREASE INTO THE AFTERNOON
IN AN UNCAPPED ENVIRONMENT. A WEAK WAVE WILL ALSO MOVE ACROSS
THE AREA AND HELP DEVELOP SHOWERS AND STORMS BY ABOUT 4-5 PM.
DUE TO THE LACK OF CIN ACROSS A FAIRLY LARGE AREA, THERE IS A
CHANCE THAT NUMEROUS THUNDERSTORMS QUICKLY DEVELOP AROUND THE
OVER THE HIGHWAY 20 CORRIDOR OF NORTHWEST IOWA AND FAR NORTHEAST
NEBRASKA. IF WE GET NUMEROUS STORMS DEVELOPING AT ONCE, STORMS
MAY BE COMPETING FOR THE STRONGEST UPDRAFT AND THUS LOWERING THE
OVERALL SEVERE THREAT. BUT IF CONVECTION REMAINS MORE ISOLATED,
STORMS INITIALLY WILL BE CAPABLE OF 2 INCH DIAMETER HAIL AND
DAMAGING WIND GUSTS TO 70 MPH. A TORNADO CANNOT BE RULED OUT IF
A STORM CAN GET ROOTED TO THE BOUNDARY. STORMS WILL PUSH
EASTWARD AND GROW NORTHWARD THROUGH THE EVENING AND POSSIBLY
MERGE INTO ORGANIZED CLUSTERS WHICH WILL ENHANCE THE DAMAGING
WIND THREAT TO GREATER THAN 70 MPH AS STORMS PUSH INTO NORTHERN
IOWA AND SOUTHERN MINNESOTA. THESE STRONGER STORMS WILL EXIT THE
AREA AROUND MIDNIGHT, BUT ADDITIONAL WEAKER SHOWERS AND
THUNDERSTORMS WILL CONTINUE TO DEVELOP OVERNIGHT OVER NORTHWEST
IOWA ALONG THE BOUNDARY AS THE LOW LEVEL JET FEEDS MORE MOISTURE
INTO THE AREA. THE MAIN THREAT WITH THIS WOULD BE IF THESE
SHOWERS/STORMS TRAIN OVER THE SAME AREA, IT COULD RESULT IN
MINOR FLASH FLOODING.
TROUGHING OVER THE WESTERN US WILL CONTINUE TO SEND UPPER WAVES
THROUGH THE REGION HEADING INTO THE DAY ON THURSDAY AND FRIDAY. A
VERY WEAK WAVE ON THURSDAY MORNING MAY SET OFF A FEW SHOWERS AND
STORMS ALONG A BOUNDARY OVER EASTERN NEBRASKA AND WESTERN IOWA, BUT
GUIDANCE IS IN FAIRLY GOOD AGREEMENT THAT THE MORE INTENSE
PARTS OF THIS CONVECTION WILL REMAIN SOUTH OF THE AREA. HEADING
INTO THURSDAY AFTERNOON, DAYTIME HEATING SHOULD RESULT IN THE
CAP ERODING ESPECIALLY OVER PORTIONS OF SOUTH-CENTRAL SOUTH
DAKOTA, WHICH MAY ALLOW FOR ISOLATED SUPERCELLS TO DEVELOP GIVEN
THE 40-45 KTS OF BULK SHEAR THAT WILL BE IN PLACE. WITH LAPSE
RATES AROUND 7.5-8 C/KM, LARGE HAIL TO 2 INCHES IN DIAMETER WILL
BE THE MAIN THREAT WITH THESE STORMS, ALONG WITH 70 MPH
STRAIGHT-LINE WIND GUSTS. THE TORNADO THREAT LOOKS LOW, THOUGH
THERE MAY BE BRIEF WINDOW IN THE EARLY EVENING AS THESE STORMS
MOVE EAST WHERE THE LOW LEVEL JET CAN HELP INCREASE 0-1 KM SRH
BEFORE STORMS TURN MORE ELEVATED HEADING INTO THE LATER EVENING
HOURS. THIS AFTERNOON SUPERCELL THREAT IS A CONDITIONAL ONE AS
OVERALL FORCING WILL BE WEAK.
THE MAIN THREAT FOR SEVERE STORMS WILL ARRIVE OVERNIGHT THURSDAY
INTO FRIDAY AS A STRONGER WAVE EJECTS ACROSS THE NORTHERN
PLAINS TOWARDS THURSDAY EVENING AND FIRES UP ISOLATED TO
SCATTERED THUNDERSTORMS OVER WESTERN SOUTH DAKOTA. THESE
THUNDERSTORMS LOOK TO DEVELOP INTO EITHER AN ORGANIZED LINE OR
INTO A FEW LINEAR CLUSTERS AND THEN PROGRESS THROUGH OUR AREA
FROM WEST TO EAST DURING THE OVERNIGHT TIME FRAME. DUE TO THE
LINEAR NATURE OF THESE STORMS, DAMAGING STRAIGHT-LINE WINDS TO
70+ MPH WILL BE THE MAIN SEVERE WEATHER THREAT WITH THIS ROUND.
IF STORMS FORM INTO A FEW DIFFERENT CLUSTERS AND TRAIL ONE
ANOTHER (THUS MOVE OVER THE SAME AREA MULTIPLE TIMES), WILL
ALSO HAVE TO WATCH OUT OF A THREAT FOR FLASH FLOODING THURSDAY
NIGHT/FRIDAY MORNING. YET ANOTHER WAVE MOVES THROUGH THE AREA ON
FRIDAY, WHICH WILL LIKELY FORM MORE STRONG TO SEVERE
THUNDERSTORMS ESPECIALLY IN THE AFTERNOON AND EARLY EVENING
HOURS. UNCERTAINTY IN HOW STORMS EVOLVE THURSDAY NIGHT AND
DIFFERENCES AMONGST GUIDANCE PRECLUDES DETAILS ON THE EXACT
THREATS FOR FRIDAY, BUT CERTAINLY KEEP UP TO DATE WITH THE
LATEST FORECAST ESPECIALLY IF YOU HAVE OUTDOOR PLANS FOR THE
JULY FOURTH WEEKEND. SPEAKING OF JULY FOURTH, THE DAY ITSELF
WILL FEATURE ANOTHER WAVE PASSING THROUGH THE REGION; HOWEVER,
UNCERTAINTY REMAINS HIGH ON WHERE ANY STORMS DEVELOP. THE
01.12Z GEFS KEEPS THE BEST CHANCES OF RAIN NEAR AND SOUTH OF THE
MISSOURI RIVER VALLEY WHILE THE EC ENSEMBLE KEEPS IT EAST OF
THE AREA. BOTTOM LINE, THERE WILL BE AT LEAST A BROAD AREA OF 20-40%
POPS IN PLACE ESPECIALLY HEADING INTO SATURDAY NIGHT UNTIL THE
SPREAD IN GUIDANCE CAN BE BETTER RESOLVED. FROM SUNDAY ONWARDS,
THE ACTIVE UPPER PATTERN MAY RELAX A BIT AS UPPER RIDGING TRIES
TO BUILD IN OVER THE INTERMOUNTAIN WEST.
AVIATION /06Z TAFS THROUGH 06Z FRIDAY/
ISSUED AT 1222 AM CDT THU JUL 2 2026
GENERALLY VFR THROUGH THE PERIOD. SOME LOW CONFIDENCE PATCHY FOG
COULD RESULT IN MVFR CONDITIONS. OTHERWISE SCATTERED
THUNDERSTORMS ARE EXPECTED ACROSS NORTHWEST IA LATE TONIGHT
INTO THURSDAY MORNING. A LARGER COMPLEX OF POTENTIALLY SEVERE THUNDERSTORMS
WILL BE POSSIBLE THURSDAY EVENING WITH THE BETTER CHANCES NORTH
OF I-90 AND WEST OF I-29.
FSD WATCHES/WARNINGS/ADVISORIES
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
UPDATE...08
DISCUSSION...SAMET
AVIATION...08
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