840
FXUS63 KFSD 012002
AFDFSD
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
302 PM CDT WED JUL 1 2026
KEY MESSAGES
- SCATTERED STRONG TO SEVERE THUNDERSTORMS ARE POSSIBLE LATE
THIS AFTERNOON AND EVENING MAINLY NEAR AND EAST OF THE I-29
CORRIDOR. THE STRONGEST STORMS WILL BE CAPABLE OF DAMAGING
WINDS TO 70+ MPH AND/OR 2 INCH DIAMETER HAIL. A TORNADO OR TWO
CANNOT BE RULED OUT.
- BEYOND THIS EVENING'S THREAT, CONCERNS ARE GROWING FOR MORE
WIDESPREAD SEVERE STORMS THURSDAY EVENING INTO FRIDAY AND
AGAIN FRIDAY INTO SATURDAY WITH ONE OR MORE OVERNIGHT STORM
COMPLEXES POSSIBLE.
- 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.
- ABOVE NORMAL TEMPERATURES CONTINUE THROUGH THE REST OF THIS
WEEK AND INTO THE WEEKEND, WITH HUMIDITY INCREASING DAILY.
HOWEVER, WE'LL REMAIN BELOW HEAT ADVISORY LEVELS.
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 /18Z TAFS THROUGH 18Z THURSDAY/
ISSUED AT 1249 PM CDT WED JUL 1 2026
ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS WILL REDEVELOP
LATE THIS AFTERNOON AND EVENING ESPECIALLY NEAR AND EAST OF I-29.
STORMS WILL BE CAPABLE OF DAMAGING WINDS, LARGE HAIL, AND POSSIBLY A
TORNADO. THE BETTER CHANCES OF SEVERE WEATHER WILL BE NEAR AND EAST
OF MINNESOTA/IOWA HIGHWAY 60. THE THREAT FOR SEVERE THUNDERSTORMS
ENDS LATE THIS EVENING, WITH ADDITIONAL SHOWERS AND ISOLATED
NON- SEVERE THUNDERSTORMS CONTINUING TO BE POSSIBLE OVERNIGHT IN
NORTHWEST IOWA. OTHERWISE, PATCHY FOG, SOME LOCALLY DENSE, WILL
DEVELOP TONIGHT AS WINDS TURN LIGHT OVER TOP THE WET GROUNDS.
THE BETTER CHANCE FOR FOG WILL BE JUST WEST OF THE EDGE OF THE
CLOUDS ASSOCIATED WITH THE OVERNIGHT STORMS, SO THERE IS A BIT
OF UNCERTAINTY AS TO WHETHER OR NOT WE'LL GET FOG AT KFSD GIVEN
THAT THE SITE WILL LIKELY BE EITHER JUST WEST OF THOSE HIGH
CLOUDS OR UNDER THEM. STILL, THERE WAS ENOUGH CONFIDENCE TO
INCLUDE MVFR VISIBILITIES AT THE KFSD SITE EARLY THURSDAY
MORNING. ANY FOG SHOULD DIMINISH AFTER THE 02.14 TO 02.15Z TIME
FRAME AND LEAD TO VFR CONDITIONS THROUGH THE REMAINDER OF THE
PERIOD.
WINDS WILL PICK UP A BIT OUT OF THE SOUTHWEST OVER NORTHWEST IOWA
AND SOUTHWEST MINNESOTA THROUGH THE EARLY AFTERNOON, BUT ONLY
GUSTING AS HIGH AS AROUND 20 KTS. STRONGER WIND GUSTS WILL BE
POSSIBLE IN ANY THUNDERSTORM THAT DEVELOPS LATE THIS AFTERNOON
THROUGH THE EVENING. WINDS WILL TURN LIGHT AND VARIABLE OVERNIGHT
ACROSS THE AREA, BUT THEN START PICKING UP OUT OF THE SOUTHEAST TO
END THE PERIOD.
FSD WATCHES/WARNINGS/ADVISORIES
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
DISCUSSION...SAMET
AVIATION...SAMET
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page