999
FXUS63 KFSD 190109
AFDFSD
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
809 PM CDT FRI SEP 18 2026
KEY MESSAGES
- ISOLATED THUNDERSTORMS OVER NORTHEAST NEBRASKA, NORTHWEST
IOWA, AND SOUTHWEST MINNESOTA WILL CONTINUE TO PUSH NORTHEAST.
IT REMAINS POSSIBLE A STORM COULD BECOME STRONG PRODUCING
MARGINALLY SEVERE HAIL, BRIEF HEAVY RAIN, AND WIND GUSTS TO
55-60 MPH.
- FOG HAS BEGUN TO FORM AND WILL CONTINUE INTO SATURDAY MORNING.
PATCHY DENSE FOG IS POSSIBLE ALONG RIVERS, STREAMS, VALLEYS,
AND LOW AREAS. FOG WILL BE SLOW TO BURN OFF, AND MAY LINGER
INTO LATE SATURDAY MORNING TO EARLY AFTERNOON.
- BELOW NORMAL TEMPERATURES WILL PERSIST THROUGH NEXT WEEK.
ADDITIONAL RAIN CHANCES WILL CONTINUE INTO EARLY NEXT WEEK,
BUT THUNDER CHANCES ARE LOW AND SEVERE WEATHER IS NOT
EXPECTED.
UPDATE
ISSUED AT 804 PM CDT FRI SEP 18 2026
CURRENTLY ISOLATED SHOWERS AND THUNDERSTORMS ARE ONGOING OVER
NORTHEAST NEBRASKA, NORTHWEST IOWA, AND SOUTHWEST MINNESOTA. THERE
REMAINS A LOW RISK (AROUND 5%) THAT ONE OR TWO OF THESE STORMS COULD
BECOME STRONG TO SEVERE. MAIN RISKS ARE MARGINALLY SEVERE HAIL,
BRIEF HEAVY RAINFALL, AND WIND GUSTS TO 55-60 MPH. CONFIDENCE IN
SEVERE STORM DEVELOPMENT IS LOW AS SURFACE HEATING HAS CEASED SINCE
THE SUN SET AND THE LOWER LEVELS HAVE BEGUN TO STABILIZE. THESE
STORMS WILL PROGRESS EAST OUT OF THE CWA AROUND OR SHORTLY AFTER
MIDNIGHT.
LOW STRATUS TO FOG HAS BEGUN TO DEVELOP AND IS EXPECTED TO BECOME
WIDESPREAD ACROSS THE CWA AS WINDS BECOME LIGHT AND VARIABLE. LOW
AREAS, RIVER AND STREAM BEDS, AND VALLEYS COULD SEE BRIEF PERIODS OF
DENSE FOG. BE PREPARED FOR RAPIDLY CHANGING VISIBILITY CONDITIONS
TONIGHT AND INTO SATURDAY MORNING. OVERNIGHT CLOUDS ARE EXPECTED TO
DEEPEN, WHICH WILL SLOW DOWN FOG DISSIPATION INTO THE LATE MORNING
TO EARLY AFTERNOON.
A SECOND WAVE WILL WORK THROUGH THE REGION EARLY SATURDAY MORNING.
SHOWERS AND THUNDERSTORMS ARE EXPECTED TO DEVELOP OVER NORTHEAST
NEBRASKA, SOUTHEAST SOUTH DAKOTA, NORTHWEST IOWA, AND INTO
SOUTHWEST MINNESOTA AFTER 4 AM. STORMS ARE NOT EXPECTED TO BE
SEVERE AS THE ENVIRONMENT IS PRETTY WORKED OVER AT THIS POINT.
HOWEVER, SHOULD SOMETHING LIFT OFF THE 850 MB LAYER IT WILL HAVE
500-1000 J/KG TO WORK WITH. MOST LIKELY THESE WILL PRODUCE
BRIEF HEAVY RAIN, BUT AN ISOLATED STRONGER STORM COULD PRODUCE
WIND GUSTS UP TO 55 MPH AND SMALL HAIL. THESE WILL MOVE
NORTHEAST AND DISSIPATE THROUGH LATE SATURDAY MORNING. THE REST
OF SATURDAY SHOULD BE MOSTLY DRY, THOUGH CLOUDY AND ON THE
DREARY SIDE. HIGHS ARE ONLY EXPECTED TO CLIMB INTO THE 60S WITH
A FEW LOW 70S POSSIBLE OVER NORTHWEST IOWA.
DISCUSSION
ISSUED AT 1251 PM CDT FRI SEP 18 2026
SHOWER AND THUNDERSTORM CHANCES WILL LIKELY COME IN TOW WAVES
TONIGHT, BUT FOCUSED ON MOSTLY NORTHWEST IA AND NORTHEAST NE. THE
FIRST WILL BE LATE AFTERNOON AND EARLY EVENING, CENTERED AROUND THE
POTENTIAL FOR SOMETHING CLOSE TO SURFACE BASED IF ENOUGH HEATING CAN
OCCUR. THE WARM NOSE IS CURRENTLY WORKING TOWARDS SIOUX CITY WITH
WAYNE NE AT 85 DEGREES AND A 73 DEW POINT. LATEST SOUNDINGS SUGGEST
SURFACE HEATING INTO THE UPPER 80S WILL BE NEEDED TO BREAK THE CAP.
THE BEST CHANCE FOR THIS SHOULD BE SOUTH OF AN ELK POINT TO OKOBOJI
LINE. IF THE CAP CAN BREAK CAPE VALUES AROUND 2500 J/KG ARE EXPECTED
WITH MARGINAL SHEAR AND A FREEZING LEVEL AROUND 14000 FEET AGL. THIS
WOULD SUPPORT WIND GUSTS TO 65 MPH AND POTENTIALLY AN ISOLATED
TORNADO IF A STORM CAN BECOME ROOTED IN THE BOUNDARY LAYER. THE
LATEST HRRR RUNS SUGGEST THAT SURFACE BASED DEVELOPMENT MAY TOUGH TO
COME BY WITH SLIGHTLY ELEVATED STORMS DEVELOPING CLOSER TO JACKSON
AND OKOBOJI ABOUT 23-0Z.
LATER THIS EVENING AND EARLY OVERNIGHT A WAVE MOVES NORTHEAST FROM
NE AND MAY BRING ANOTHER THREAT FOR SHOWERS AND STORMS. CURRENTLY
THESE SHOULD NOT BE SEVERE WITH MARGINAL SHEAR AND INSTABILITY
EXPECTED.
WEAK NORTH TO NORTHEAST FLOW DEVELOPS AT THE SURFACE TONIGHT AND
CONTINUES THROUGH SATURDAY. MODEL SOUNDINGS SHOWING A SATURATED LOW
LEVEL AIR MASS IN PLACE TONIGHT INTO SATURDAY MORNING, SHALLOWEST
NEAR THE MISSOURI RIVER AND DEEPEST NEAR HIGHWAY 14. GIVEN THE
WEAKER, COOL FLOW SUSPECT THAT FOG WILL BECOME FAIRLY WIDESPREAD
WITH SOME LOCALLY DENSE. GIVEN THE COOLER NORTHERLY FLOW, THIS FOG
WILL BE SLOW TO LIFT ON SATURDAY MORNING AND WILL LIKELY BECOME A
STRATUS LAYER THROUGH THE DAY SATURDAY, LEADING TO A COOL AND CLOUDY
DAY.
A SLOW MOVING LOW PRESSURE WILL MOVE ONTO THE PLAINS SUNDAY INTO
MONDAY BRINGING THE NEXT THREAT FOR RAIN AND ISOLATED THUNDERSTORMS.
FOR NOW SEVERE WEATHER LOOKS VERY UNLIKELY. HEAVY RAIN ALSO LOOKS A
BIT UNLIKELY WITH CAPE VALUES PRETTY LOW. COULD SEE SOME EXTENDED
PERIODS OF MODERATE RAINFALL, BUT UNLIKELY TO MAKE A PUSH TOWARDS
ANY FLASH FLOODING WITH RIVER FLOODING ALSO PRETTY LOW.
BROAD UPPER LEVEL RIDING WILL BUILD INTO THE AREA BEHIND THE SLOW
MOVING LOW PRESSURE, WITH TEMPERATURES EXPECTED TO WARM BUT REMAIN A
BIT BELOW NORMAL. THE MODELS ARE VERY DISAGREEABLE ON SOME WEAK
UPPER LEVEL ENERGY MID WEEK NEXT WEEK SO CONFIDENCE ON RAINFALL IS
LOW.
AVIATION /00Z TAFS THROUGH 00Z SUNDAY/
ISSUED AT 648 PM CDT FRI SEP 18 2026
LOW STRATUS AND PATCHY DENSE FOG OVERLAY MOST OF THE CWA
RESULTING IN MVFR TO LIFR CEILINGS. THESE CONDITIONS ARE
EXPECTED TO PREVAIL FOR THE MAJORITY OF THE PERIOD. WINDS WILL
BECOME LIGHT AND VARIABLE THIS EVENING AND REMAIN SO THROUGH
MID-DAY SATURDAY. FOG IS EXPECTED TO EXPAND ACROSS MUCH OF THE
CWA. THE COMBINATION OF LIGHT WINDS AND INCREASING CLOUD DEPTHS
WILL SLOW FOG DISSIPATION DOWN THROUGH THE LATE MORNING TO
EARLY AFTERNOON. SATURDAY AFTERNOON CEILINGS BEGIN TO IMPROVE
BUT WILL LIKELY REMAIN MVFR FOR THE MOST PART.
SCATTERED SHOWERS ARE ON GOING OVER PORTIONS OF NORTHWEST IOWA AND
SOUTHWEST MINNESOTA. THERE IS POTENTIAL AN ISOLATED STORM MAY BECOME
STRONG PRODUCING MARGINALLY SEVERE HAIL AND WIND GUSTS. THIS ROUND
OF STORMS MOVES EAST WITH THE SURFACE LOW AROUND MIDNIGHT.
FSD WATCHES/WARNINGS/ADVISORIES
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
UPDATE...AJP
DISCUSSION...08
AVIATION...AJP
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page