986
FXUS63 KFSD 162349
AFDFSD
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
649 PM CDT SAT MAY 16 2026
KEY MESSAGES
- HIGH BASED SPRINKLES MAY DEVELOP NEAR HIGHWAY 20 INTO THIS
EVENING WITH ISOLATED LIGHTNING STRIKES.
- THUNDERSTORMS INCREASE IN COVERAGE TONIGHT INTO EARLY SUNDAY.
WEAKENING STORM CLUSTERS MAY PRODUCE MARGINALLY SEVERE HAIL
AND BRIEF 60 MPH WIND GUSTS BETWEEN 10PM AND 5AM.
- A SIGNIFICANT SEVERE WEATHER EPISODE IS POSSIBLE SUNDAY
AFTERNOON INTO SUNDAY NIGHT. VERY LARGE HAIL, STRAIGHT LINE
WINDS, AND SEVERAL TORNADOES, POSSIBLY STRONG, WILL BE
POSSIBLE. THIS RISK MAY EXTEND INTO VERY EARLY MONDAY.
- IF YOU HAVE OUTDOOR PLANS SUNDAY AFTERNOON THROUGH MONDAY, THE
TIME IS NOW TO PREPARE AND HAVE ALTERNATIVE PLANS IN PLACE.
DISCUSSION
ISSUED AT 101 PM CDT SAT MAY 16 2026
THIS AFTERNOON: WE CONTINUE TO SEE A PLEASANT SATURDAY AFTERNOON
ACROSS THE REGION WITH A LIGHT TO EASTERLY WIND PREVAILING.
TEMPERATURES ARE GRADUALLY RISING TOWARDS THE 80S, BUT HUMIDITY
REMAINS VERY LOW IN THE 15 TO 20% RANGE. WEAK WARM ADVECTION TO OUR
SOUTH WILL BEGIN TO STREAM ELEVATED ACCAS OVERHEAD, PERHAPS WITH A
SPRINKLE OR TWO BY EARLY EVENING. THIS ACTIVITY IS BASED WELL
ALOFT AOA 600 MB, WITH SOUNDINGS SHOWING MINIMAL POTENTIAL FOR
DEEPENING. ANY SURFACE BASED CONVECTION WILL REMAIN WELL SOUTH
OF THE CWA WITH THE FRONTAL BOUNDARY STUCK NORTH OF I-80.
TONIGHT: EASTERLY LOW-LVL FLOW WILL KEEP THE RISK FOR CONVECTION
LOWER THROUGH THE EVENING HOURS AS A GRADUAL NORTHWARD ADVANCEMENT
OF THE SURFACE FRONT BEGINS TO OUR SOUTH. WE'LL BEGIN TO SEE
CONVECTION FORM ALONG AND SOUTH OF THIS BOUNDARY EXTENDING FROM
WESTERN NEBRASKA INTO WESTERN IOWA LATE THIS EVENING. THIS
ACTIVITY WILL BE PULLED NORTHWARD BY A STRONGER SHORTWAVE
LIFTING OUT OF THE CENTRAL ROCKIES INTO THE PLAINS. THE
ADVANCEMENT OF A LOW- LVL FRONT AND STRONG THETA-E ADVECTION
WILL BRING THE RISK FOR ELEVATED THUNDERSTORMS TO THE TRI-STATE
AREA AFTER 10PM WITH ONE MORE CLUSTERS OF STORMS (OR POTENTIALLY
AN MCV) THAT FORM TO OUR SOUTHWEST TRACKING TOWARDS THE AREA
THROUGH DAYBREAK. MUCAPE PLOTS AND SOUNDINGS AHEAD OF THIS
CONVECTION CONTINUE TO LOOK MARGINAL, WITH MID-LVL LAPSE RATES
AROUND 7 C/KM AND STORMS LIKELY TO BE STRONGLY ELEVATED OR
MARGINALLY SEVERE. AT THIS POINT THE GREATEST SEVERE WEATHER
RISK WOULD BE SOUTH OF I-90 AND PERHAPS MORE FOCUSED ALONG THE
MO RIVER AND HIGHWAY 20 CORRIDORS. ONE THING TO WATCH WOULD BE
THE POTENTIAL FOR ANY MCV THAT DEVELOPS TO BRING WAKE LOW
CONDITIONS, OR STRONG EVAPORATIVE COOLING WINDS NORTHEAST AS
CONVECTION WANES. SOME HIGH-RES GUIDANCE SUPPORTS POCKETS OF 50+
MPH WINDS MOVING NORTHEAST WITH THE WEAKENING CONVECTION.
SUNDAY-SUNDAY NIGHT:
THE KEY TAKEAWAYS FOR SUNDAY CONTINUE TO BE:
1. CONVECTIVE DEBRIS, STRATUS, AND AN EML MAY BE PROBLEMATIC AND
COULD MAKE THIS FORECAST CONDITIONAL.
2. IF STORMS GET ROOTED INTO THE BOUNDARY LAYER, THERE IS NO
SHORTAGE OF SPIN POTENTIAL INTO THE EARLY OVERNIGHT AND TORNADIC
ACTIVITY BECOMES AN INCREASED CONCERN.
3. IF DISCRETE MODE IS SHORT LIVED AND STORMS TURN LINEAR, THEN
DURATION OF THREAT IN ANY ONE AREA MAY BE INTENSE BUT BRIEF.
THE MESOSCALE PICTURE MAY BE QUITE CLOUDY TO START SUNDAY.
CONSIDERABLE STRATUS WILL BE PRESENT IN THE AREA AND WE'LL ONLY
GET A BETTER PICTURES OF WHERE THE COLD FRONT/INVERTED TROUGH
AND ASSOCIATED WARM FRONT WILL BE POSITIONED THROUGH THE
MORNING. MOST OF THE MORNING IS LIKELY TO REMAIN QUIET, WITH
SOME RENEWED CONVECTION POSSIBLE IN SW SOUTH DAKOTA/WESTERN
NEBRASKA ON THE NOSE OF THE UPPER JET ENTERING THE PLAINS. SOME
CAMS DO HAVE THIS MOSTLY ELEVATED CONVECTION BRUSHING THE NW
EDGE OF THE CWA BY 18Z. FURTHER EAST, IT MAY TAKE INTO THE MID-
AFTERNOON HOURS FOR CLOUDS TO THIN AND THE WARM FRONT TO JUMP
NORTHWARD (IF IT DOES). A STUBBORN EML WILL ALSO REMAIN WITHIN
THE 600-700 MB. GUIDANCE IS STILL VERY BULLISH ON THE RAPID
NORTHWARD ADVECTION OF 2000-3000 MLCAPE NORTHWARDS TOWARDS
HIGHWAY 14 AND WEST TO HIGHWAY 281 BY 21-00Z. THE INCREASING
CAPE WILL BE AIDED BY THE ARRIVAL OF 8.5-9 C/KM 700:500 LAPSE
RATES, AND ONCE THE NEXT WAVE OF MID- LVL VORTICITY ARRIVES,
SCATTERED CONVECTION MAY QUICKLY DEVELOP ALONG THE FRONTAL
BOUNDARY STRETCHING NEAR HWY 281 AFTER 20Z. A SECOND AREA OF
CONVECTION MAY FORM FURTHER SOUTH ALONG THE DRY LINE
INTERSECTION IN EASTWARD NEBRASKA AND TRACK NORTHEAST INTO THE
EVENING. SOME UNCERTAINTY PERSISTS ON HOW DISCRETE STORMS WILL
REMAIN OR IF THEY WILL QUICKLY TURN LINEAR AS THEY EXPAND AND
SLIDE EAST/NORTHEAST INTO THE EVENING AND EARLY OVERNIGHT.
SUPERCELLS WITH VERY LARGE HAIL (2-3") AND AN INCREASED TORNADIC
RISK WILL BE POSSIBLE INITIALLY, BUT IF LINEAR TRENDS DEVELOP,
LINE SEGMENTS WITH STRAIGHT LINE WINDS/EMBEDDED TORNADOES MAY
BECOME A POSSIBILITY AS STORMS TRACK EAST NORTHEAST TOWARDS I-29
AND MN/IA. THE DEGREE OF LOW- LVL HELICITY/SHEAR COMBINED WITH
INCREASING 0-1KM CAPE APPROACHING 100-200 J/KG AND CRITICAL LCL
VALUES ALONG AND SLIGHTLY EAST OF I-29 IS PARTICULARITY
CONCERNING HEADING INTO THE EVENING AND CONTINUES TO SUPPORT THE
10-15% TORNADO PROBABILITIES BY SPC. IN FACT, STP VALUES PUSH
5+ ALONG PORTIONS OF I-29 BETWEEN SF/SC BY 00Z. MOST OF THE
RECENT CAMS SUPPORT THE LINEAR LINES MOVING EAST OF THE CWA BY
MIDNIGHT WITH LOWER RISKS INTO DAYBREAK MONDAY.
MONDAY: THERE IS BETTER AGREEMENT IN TODAY'S GUIDANCE PUSHING THE
EFFECTIVE BOUNDARY EAST OF THE CWA BY MONDAY MORNING. THAT SAID,
INCOMING SHORTWAVE ENERGY MAY PULL ELEVATED INSTABILITY AND
INCREASED LAPSE RATES BACK WEST OF THE BOUNDARY BY MID-LATE
AFTERNOON. THIS COULD PLACE AREAS OF NW IOWA UNDER THE RISK OF
ELEVATED HAILERS FOR A PERIOD OF TIME. FOR NW IOWA, THIS COULD
ALSO BE THE TIME WHERE THE MOST BENEFICIAL RAINFALL MAY ALSO
TAKE PLACE. FURTHER WEST, SIGNIFICANT COOLDOWN IS EXPECTED AS
TEMPERATURES STRUGGLE TO CLIMB THROUGH THE 50S.
TUESDAY-FRIDAY: QUIET AND COOLER THAN NORMAL TEMPERATURES ARE
EXPECTED THROUGH THE MIDDLE OF THE WEEK AS HIGHS CLIMB BACK THROUGH
THE 60S BY THURSDAY. ANOTHER TROUGH MOVES THROUGH THE PLAINS BY THE
END OF THE WEEK HOWEVER A LACK OF DEEP MOISTURE PREVENTS ANY
SIGNIFICANT SEVERE WEATHER RISK. THE LATEST AI LEARNING GUIDANCE
SUGGESTS LESS THAN 5% PROBABILITIES OF ANY SEVERE STORM AT THIS
TIME.
AVIATION /00Z TAFS THROUGH 00Z MONDAY/
ISSUED AT 648 PM CDT SAT MAY 16 2026
VFR CONDITIONS BEGIN THE TAF PERIOD. LIGHT EAST/NORTHEAST WINDS WITH
A FEW GUSTS UP TO ABOUT 25 KNOTS PERSIST EARLY THIS EVENING. WINDS
WILL NOT ONLY PERSIST BUT STRENGTHEN THROUGH THE EVENING HOURS WITH
GUSTS PEAKING AT ABOUT 30 KNOTS OVERNIGHT. STORMS THAT HAVE
DEVELOPED ALONG I-80 EARLY THIS EVENING WILL BEGIN TO PUSH
NORTH/NORTHEASTWARDS. THESE SHOWERS AND STORMS WILL PERSIST THROUGH
THE NIGHT. LARGE HAIL AND STRONG WINDS COULD ACCOMPANY THE STRONGEST
STORMS. CEILINGS WILL BE LOWERING THROUGHOUT THE NIGHT THOUGH ANY
CEILING THAT DROPS BELOW VFR LEVELS WILL ONLY OCCUR IN SHOWERS AND
STORMS. MORE WIDESPREAD MVFR CEILINGS WILL PUSH INTO THE AREA
TOMORROW MORNING AS WINDS BEGIN TO TURN SOUTHEASTERLY. CEILINGS MAY
LOWER TO IFR LEVELS ALONG AND WEST OF THE JAMES RIVER. A FEW SHOWERS
COULD CONTINUE THROUGH THE MORNING HOURS AS WELL. CEILINGS LOOK TO
LIFT BACK TO VFR LEVELS SOUTH OF I-90 TOMORROW AFTERNOON, ESPECIALLY
ALONG AND EAST OF THE JAMES RIVER. THIS LOOKS TO RESULT IN NEW
THUNDERSTORM DEVELOPMENT TO END THE TAF PERIOD.
FSD WATCHES/WARNINGS/ADVISORIES
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
DISCUSSION...DUX
AVIATION...MEYERS
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page