012
FXUS63 KFSD 280306
AFDFSD
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
1006 PM CDT SAT JUN 27 2026
KEY MESSAGES
- ISOLATED STRONG TO SEVERE THUNDERSTORMS ARE POSSIBLE
ESPECIALLY WEST OF I-29 TONIGHT. LARGE HAIL UP TO GOLF BALL IN
SIZE AND 65 MPH WILL BE THE MAIN THREAT. STORMS LOOK TO
GENERALLY WEAKEN WITH EASTWARD EXTENT.
- A HEAT ADVISORY HAS BEEN ISSUED FOR SOME AREAS SUNDAY INTO
MONDAY, AND FURTHER ADJUSTMENTS TO HEADLINES ARE POSSIBLE IN
THE COMING DAYS.
- SUMMER HEAT AND HUMIDITY IS EXPECTED SUNDAY INTO NEXT WEEK.
DAILY HEAT INDICES OF 95 TO 105 DEGREES WILL LEAD TO MAJOR TO
LOCALLY EXTREME HEAT RISK AT TIMES. BEGIN PLANNING NOW TO
REDUCE THE RISK OF HEAT ILLNESS AND IMPACTS.
- AN ACTIVE PATTERN THROUGH THE WEEK LEADS TO PERIODIC MODERATE
CHANCES FOR SHOWERS AND STORMS. UNCERTAINTY IN THE TIMING OF
RAIN ALSO BRINGS LOWER CONFIDENCE IN DAYTIME HIGH
TEMPERATURES.
UPDATE
ISSUED AT 956 PM CDT SAT JUN 27 2026
A BROKEN LINE OF STRONG THUNDERSTORMS EXTENDS ACROSS
MOST OF WESTERN SOUTH DAKOTA AND INTO THE NORTHERN NEBRASKA
PANHANDLE THIS EVENING. THESE WILL BE THE STORMS TO WATCH AS THEY
GRADUALLY LIFT NORTHEASTWARD THROUGH THE NIGHT AIDED BY A
STRENGTHENING LOW LEVEL JET. LATEST SOUNDINGS STILL SHOW A
STRONG CAPPING INVERSION IN PLACE OVER OUR AREA THROUGH THE
NIGHT, BUT THE CAP WILL BE THE WEAKEST ALONG THE US HIGHWAY 14
CORRIDOR IN EASTERN SOUTH DAKOTA ESPECIALLY CLOSER TO THE JAMES
RIVER VALLEY LATE THIS EVENING. SO THIS AREA LOOKS TO HAVE THE
BETTER CHANCES OF WIND GUSTS OF 60-65 MPH, BUT THIS THREAT STILL
APPEARS TO BE ISOLATED DUE TO THE OVERALL STRONG CAP.
FARTHER SOUTH ALONG THIS LINE OVER NORTHERN NEBRASKA IS A
CLUSTER OF THUNDERSTORMS WITH EMBEDDED SUPERCELL STRUCTURES THAT
IS CAPABLE OF QUARTER TO GOLF BALL SIZED HAIL. THESE STORMS
WILL BE WATCHED CLOSELY AS WELL AS THEY LIFT TOWARDS SOUTH-
CENTRAL SOUTH DAKOTA LATER AROUND MIDNIGHT AS THIS WILL BE IN
AN AREA OF HIGHER INSTABILITY. HOWEVER, THE SAME CAPPING ISSUES
REMAIN AND SO THIS THREAT FOR LARGE HAIL WILL ALSO REMAIN
ISOLATED. INSTABILITY AND SHEAR WILL GRADUALLY LESSEN WITH
EASTWARD AND ESPECIALLY NORTHEASTWARD EXTENT, AND THUS THE
STORMS WILL CONTINUE WEAKENING AS THEY PUSH EASTWARD HEADING
INTO EARLY SUNDAY MORNING. HOWEVER, STORMS WILL STILL BE CAPABLE
OF SMALL HAIL AND WIND GUSTS TO 40 MPH BY THE TIME THEY REACH
THE I-29 CORRIDOR AND POINTS EAST.
THERE IS AN ALTERNATE, BUT LESS LIKELY SCENARIO WHERE THE STORMS ARE
ABLE TO MAINTAIN THEIR STRENGTH AS THEY PUSH ACROSS THE AREA THROUGH
THE NIGHT AND BRING 60-65 MPH WINDS AND LARGE HAIL TO A WIDER SWATH
OF THE AREA. GIVEN THE STRONG CAP ALREADY DISCUSSED, THIS
SCENARIO IS UNLIKELY, BUT IF STORMS CAN TAKE FULL ADVANTAGE OF A
POTENTIAL 40-50 MPH LLJ, THIS CAN'T BE ENTIRELY RULED OUT. THE
GREATER THREAT FOR SEVERE WEATHER IN THIS ALTERNATE SCENARIO
WOULD BE NEAR AND SOUTH OF I-90 WHERE THERE WILL BE GREATER
INSTABILITY AND THE STRONGEST LLJ.
TIMING-WISE, LOOK FOR THE STORMS TO START MOVING INTO THE AREA
AROUND MIDNIGHT AND REACH THE I-29 CORRIDOR BY 3-5 AM AND THEN
EXITING THE AREA OFF TO OUR EAST BY 7-9 AM. ONE OTHER THING TO NOTE
IS THAT THOUGH THE STORMS WILL BE QUICK-MOVING, SOME GUIDANCE
INDICATES A NARROW, BUT LONG SWATH OF A QUICK 2-4" OF RAIN WITH
THESE STORMS WHICH COULD RESULT IN SOME MINOR URBAN FLOODING.
DISCUSSION
ISSUED AT 1248 PM CDT SAT JUN 27 2026
THE FIRST CONCERN WILL BE THE POTENTIAL FOR THUNDERSTORMS TONIGHT.
THE CURRENT RUN OF MODELS IS REALLY PUSHING FOR A STRONG CAPPING
INVERSION, WHICH STRENGTHENS THROUGH THE NIGHT. THIS SUGGESTS THAT
TAPPING INTO THE DEEPER INSTABILITY MAY BE IMPOSSI.BLE. ABOVE THIS
CAPPING INVERSION SOME MOISTURE AND WEAK (500 J/KG) INSTABILITY MAY
ALLOW FOR SOME ACCAS SHOWERS AND THUNDERSTORMS LATE TONIGHT INTO
SUNDAY MORNING, BUT ANY SEVERE THREAT WOULD BE VERY LIMITED. WILL
NEED TO SEE SOME FAIRLY LARGE CHANGES IN THE UPCOMING DATA AND MODEL
RUNS FOR THE SEVERE THREAT TO BECOME MORE PREVALENT. IF A STORM CAN
TAP INTO THE LOWER, DEEPER INSTABILITY (2500-3000 J/KG) A VERY
ISOLATED THREAT FOR HAIL TO THE SIZE OF GOLF BALLS IS POSSIBLE.
VERY WARM AIR AND A CONTINUED STRENGTHENING CAPPING INVERSION
BARRELS NORTH ON SUNDAY, WHICH SHOULD SHUT DOWN CONVECTIVE CHANCES
THROUGH ABOUT MONDAY NIGHT. LATER SUNDAY NIGHT INTO MONDAY MORNING
SOME PATCHY ELEVATED SHOWERS OR STORMS WILL BE POSSIBLE BUT FOR NOW
CONFIDENCE IS TOO LOW AND WILL KEEP CHANCES AT 20 PERCENT OR LESS.
CONCERNS FOR HEAT RAMP UP SUNDAY BUT ONE BIG QUESTION MARK REMAINS,
STRATUS. THE LATEST RUN OF THE NAM HAS SOME FAIRLY DEEP AND
WIDESPREAD STRATUS THAT WOULD REALLY BITE INTO THE AFTERNOON HEAT
INDICES. FOR NOW CONFIDENCE IS NOT HIGH ENOUGH TO DROP THE HEAT
ADVISORY BUT WILL NEED TO MONITOR THE TRENDS OF THIS STRATUS AS WELL
AS THE TRENDS OF THE DEW POINTS. THE NEAREST 70+ DEW POINT IN SOUTH
CENTRAL NE AND SURFACE WINDS ARE EXPECTED TO REMAIN SOUTHEAST INTO
SUNDAY MORNING.
MONDAY MAY PROVE TO BE THE HOTTER MORE HUMID DAY WITH LESS CHANCE
FOR STRATUS. EXPANDED THE HEAT ADVISORY INTO PARTS OF SOUTHWEST MN
TO COVER THE POTENTIAL FOR MORE WIDESPREAD HEAT INDICES ABOVE 100.
MONDAY DOES LOOK TO BE WINDY WHICH WILL HELP TAKE THE EDGE OFF OF
THE HEAT A TOUCH.
OTHERWISE, TUESDAY THROUGH SATURDAY WILL HAVE SOUTHWEST FLOW ALOFT
WITH THE STRONGER UPPER LEVEL RIDGING JUST TO THE EAST OF THE AREA.
THIS WILL ALLOW PERIODIC WAVES TO MOVE THROUGH THE AREA WITH OFF AND
ON THREATS FOR SHOWERS AND THUNDERSTORMS. MORE THAN LIKELY THIS
UPPER LEVEL PATTERN WILL KEEP THE EXTREME HEAT AT BAY MOST OF THE
DAYS, BUT STILL SEE HIGHS FROM THE UPPER 80S TO MID 90S. BUT WITH
THESE THREATS FOR SHOWERS AND THUNDERSTORMS WILL COME "UNEXPECTED"
OUTFLOW BOUNDARIES AND STRATUS AT TIMES SO THERE WILL BE SOME
VARIABILITY IN WHICH DAYS ARE HOTTEST AND WHICH ARE LESS HOT.
AVIATION /00Z TAFS THROUGH 00Z MONDAY/
ISSUED AT 628 PM CDT SAT JUN 27 2026
2500 TO 3500 FT STRATUS WILL SINK TO MORE WIDESPREAD IFR AND MVFR
CEILINGS OVERNIGHT INTO SUNDAY MORNING. ASIDE FROM STRATUS AND
A GUSTY SOUTHEAST WIND, SCATTERED SHOWERS AND THUNDERSTORMS ARE
LIKELY TO SPREAD EASTWARD NEAR AND NORTH OF THE I-90 CORRIDOR
OVERNIGHT. A FEW STRONG TO SEVERE STORMS WITH LARGE HAIL AND
DAMAGING WIND GUSTS ARE MORE LIKELY NEAR AND NORTH OF THE
HIGHWAY 14 CORRIDOR (NEAR HURON) AFTER 06Z. MODEL FORECAST
SOUNDINGS HAVE FAIRLY HIGH CONFIDENCE IN WINDS WEAKENING AND STRATUS
LIFTING AND ERODING AROUND MID DAY SUNDAY.
CLIMATE
ISSUED AT 410 AM CDT SAT JUN 27 2026
SUMMER HEAT BUILDS INTO THE AREA FROM SUNDAY THROUGH MUCH OF
NEXT WEEK. THIS WILL LEAD TO A POTENTIAL FOR A FEW TEMPERATURE
RECORDS TO BE TIED, OR POSSIBLY BROKEN:
CURRENT RECORD HIGHS:
MONDAY (06/29): KFSD(101|2002) KSUX(100|2022)
CURRENT RECORD WARM LOWS:
MONDAY (06/29): KFSD(77|2020) KSUX(80|1931) KHON(75|2020)
FSD WATCHES/WARNINGS/ADVISORIES
SD...HEAT ADVISORY FROM 1 PM SUNDAY TO 9 PM CDT MONDAY FOR SDZ062-
066-067-069>071.
HEAT ADVISORY FROM 1 PM TO 9 PM CDT SUNDAY FOR SDZ060-061-065-
068.
MN...HEAT ADVISORY FROM 1 PM TO 9 PM CDT MONDAY FOR MNZ072-080-081-
089-090-098.
IA...HEAT ADVISORY FROM 1 PM SUNDAY TO 9 PM CDT MONDAY FOR
IAZ001>003-012>014-020>022-031-032.
NE...HEAT ADVISORY FROM 1 PM SUNDAY TO 9 PM CDT MONDAY FOR NEZ013-
014.
UPDATE...SAMET
DISCUSSION...08
AVIATION...BP
CLIMATE...JH
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