024
FXUS63 KFSD 150845
AFDFSD
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
345 AM CDT FRI MAY 15 2026
KEY MESSAGES
- RELATIVE HUMIDITY AND WIND GUSTS AROUND 25 MPH ALONG HIGHWAY
14 LEAD TO CRITICAL FIRE DANGER. RED FLAG WARNING IN EFFECT
TODAY 9 AM TO 6 PM CDT. ELEVATED TO NEAR CRITICAL FIRE
CONDITIONS ELSEWHERE DUE TO VERY LOW HUMIDITY.
- SHOWER AND THUNDERSTORM CHANCES RETURN THIS AFTERNOON AND
EVENING, MAINLY ACROSS NORTHWESTERN IOWA. A FEW STORMS MAY BE
STRONG TO SEVERE BETWEEN 4 AND 9 PM. MAIN THREATS HAIL TO 2
INCHES AND WIND GUSTS TO 75 MPH. HAVE A WAY TO RECEIVE
WARNINGS!
- SIGNIFICANTLY HIGHER THUNDERSTORM RISKS DEVELOP SATURDAY NIGHT
THROUGH MONDAY. STRONG TO SEVERE STORMS POSSIBLE OVERNIGHT
SATURDAY INTO EARLY SUNDAY. POTENTIAL FOR WIDESPREAD SEVERE
STORMS REMAINS FOCUSED SUNDAY AFTERNOON AND EARLY EVENING.
MONITOR THE FORECAST AND REVIEW SEVERE WEATHER PLANS NOW!
UPDATE
ISSUED AT 318 AM CDT FRI MAY 15 2026
NO CHANGES TO THE FORECAST INTO THIS MORNING. FORECAST FOR TODAY'S
FIRE CONCERNS REMAIN ON TRACK AS WELL, WITH RED FLAG WARNING IN
EFFECT TODAY FOR AREAS ALONG AND NORTH OF US HWY 14 - MORE DETAILS
IN THE FIRE WEATHER SECTION OF THIS DISCUSSION. CHANGES WERE MADE TO
TONIGHT WITH INCREASING SEVERE RISK; DETAILS BELOW.
INCREASED POPS IN NORTHWESTERN IA FOR THIS AFTERNOON AND EVENING TO
ACCOUNT FOR CONVECTIVE INITIATION. SOME OF THE 15.00Z CAMS (NAM
NEST, ARW) BREAK THE CAP WITH THE FRONT AS FAR WEST AS THE SD/IA
BORDER AND AS EARLY AS 3 PM. HOWEVER, OTHER GUIDANCE LIKE THE 15.06Z
RAP AND 15.00Z FV3 ARE AS LATE AS 6-7 PM WITH INITIATION AND KEEP IT
MORE LOCALIZED TO THE FRONT IN OUR FAR SOUTHEASTERN COUNTIES. HRRR
TRENDS ARE ALSO MAINTAINING A LATER AND MORE EASTERLY INITIATION
THROUGH THE 15.06Z RUN. BASED ON THIS AND THE TRENDS IN THE HREF,
THINK THAT THE GREATEST SEVERE THREAT FOR OUR AREA WILL BE FROM
ROUGHLY 4 TO 9 PM THIS EVENING, AS NEARLY ALL GUIDANCE HAS STORMS
EXITING OUR AREA BY 9-10 PM. DURATION OF SEVERE THREAT IS HIGHLY
DEPENDENT ON WHERE AND WHEN CONVECTION INITIATES.
MAIN THREATS ARE LARGE HAIL TO 2 INCHES IN DIAMETER AND WIND GUSTS
UP TO 75 MPH. WITH INCREASING SHEAR AND STEEP MID LEVEL LAPSE RATES,
EXPECT HAIL TO BE THE MAIN THREAT WITH ANY OF THE MORE DISCRETE AND
ISOLATED CELLS. AS THE FRONT MOVES EAST ACROSS NORTHWESTERN IA THIS
AFTERNOON AND EVENING, 0-6KM SHEAR VECTORS BECOME MORE PARALLEL TO
THIS BOUNDARY, SUPPORTING UPSCALE GROWTH AND INCREASING WIND THREAT
WITH GUSTS TO 75 MPH POSSIBLE. BIGGEST UNCERTAINTY WITH TODAY'S
SEVERE THREAT BOILS DOWN TO WHERE AND WHEN THE CAP BREAKS. SECONDARY
CONCERN IS OUR MOISTURE RETURN, IMPACTING THE INSTABILITY. TRENDS IN
OBSERVATIONS WILL NEED TO BE CLOSELY MONITORED TODAY.
CONCERNS FOR STRONG TO SEVERE STORMS CONTINUE THROUGH THE EARLY PART
OF NEXT WEEK. MORE DETAILS BELOW.
DISCUSSION
ISSUED AT 158 PM CDT THU MAY 14 2026
18
THIS AFTERNOON: SYNOPTICALLY DRIVEN STRONG SOUTHWESTERLY WIND
GUSTS OF 30 TO 45 MPH CONTINUE TO DEVELOP AHEAD OF A SURFACE
FRONT MOVING EASTWARD GRADUALLY. WE'VE HAD QUITE A FEW REPORTS
OF ELEVATED DUST AS WELL AS BLOWING DUST IMPACTING WEST TO EAST
ROADWAYS THIS AFTERNOON. WHILE WIDESPREAD VISIBILITY REMAINS
ABOVE 5 MILES, VERY HIGHLY LOCALIZED VISIBILITY MAY DROP BELOW 1
MILE IN HIGHER GUSTS. WHILE TEMPERATURES ARE SLOWER TO RESPOND
TODAY WITH THE CLOUD COVER, WE'RE STILL HEADED TOWARDS CRITICAL
FIRE DANGER. SEE SEPARATE DISCUSSION FOR MORE DETAILS.
OTHERWISE, A FEW LINGERING HIGH BASED SHOWERS WILL REMAIN OVER
NW IOWA INTO THE LATE AFTERNOON, WITH ISOLATED SHOWER/TSRA
POSSIBLE ALONG THE AFOREMENTIONED FRONT MOVING EAST THROUGH
SUNSET.
TONIGHT: THE FRONTAL BOUNDARY WILL SLIDE INTO THE EASTERN CWA AFTER
DARK TONIGHT WITH SOME PERSISTENCE OF MID-LVL CLOUDS ALONG IT.
ELSEWHERE, WINDS DO TURN LIGHT AND VARIABLE AS TEMPERATURES
COOL INTO THE UPPER 40S AND 50S.
FRIDAY-FRIDAY NIGHT: WE'LL BEGIN TO SEE GRADUAL SHIFTS IN THE MID-
LVL PATTERN ON FRIDAY AS ZONAL FLOW DEVELOPS. TWO CONCERNS ON
FRIDAY, ONE BEING MARGINAL RFW CONDITIONS ALONG THE HIGHWAY 14
CORRIDOR IN THE AFTERNOON, AND THE SECOND BEING POTENTIAL CONVECTION
FORMING ALONG SURFACE CONVERGENCE ZONE OVER EASTERN NEBRASKA AND
WESTERN/NORTHWESTERN IOWA LATE IN THE AFTERNOON. SOUNDINGS ALONG
THE HIGHWAY 20 CORRIDOR SHOW SOME INHIBITION LINGERING AT MID-
AFTERNOON, BUT DISSIPATING AS CONVECTIVE TEMPS IN THE LOW 90S ARE
MET. WITH MID-LVL FLOW INCREASING LATE IN THE DAY, JUST ENOUGH
FORCING ON THE BOUNDARY COULD FORCE ISOLATED TO SCATTERED STORMS
ALONG AND SOUTH OF HIGHWAY 20 IN THE EVENING. MLCAPE AROUND 1000-
1500 J/KG COULD SUPPORT MARGINALLY SEVERE HAIL FOR A FEW HOURS
AS STORMS WILL TRACK SOUTHEAST WITH THE MEAN FLOW AWAY FROM THE
CWA. FURTHER NORTH, WEAKER LOW-LVL FLOW SHOULD PREVENT
WIDESPREAD CONVECTION FROM FORMING INTO SATURDAY MORNING, BUT
IT'S ALSO A NON-ZERO CHANCE.
SATURDAY: THE VAST MAJORITY OF THE DAYTIME HOURS OF SATURDAY IS
ANTICIPATED TO BE DRY AS BRIEF MID-LVL RIDGING SLIDES THROUGH THE
AREA. THE SURFACE FRONT THAT PASSES THROUGH THE AREA TODAY WILL
SETTLE NEAR OR NORTH OF I-80 BUT MAY MAKE A SLOW RETREAT NORTHWARD
IN THE AFTERNOON. BY EARLY EVENING DEEPER SYNOPTIC LIFT ASSOCIATED
WITH AN UPPER TROUGH EJECTING OUT OF THE CENTRAL ROCKIES WILL FOCUS
LOW-LVL CONVERGENCE AND STRONG THETA-E ADVECTION SOUTH OF I-90 OR
TOWARDS HIGHWAY 20. THIS IS WHERE SOME UNCERTAINTY BEGINS TO GROW
IN THE FORECAST. MODELS HAVE SOME VARIABILITY ON THE NORTHWARD
EXTENT OF SURFACE BASED ACTIVITY BUT STRONGLY SUPPORT ELEVATED STORM
DEVELOPMENT ACROSS NORTHERN NEBRASKA EASTWARD INTO NORTH CENTRAL
IOWA. THERE MAY BE SOME POTENTIAL GIVEN 40 KNOTS EFFECTIVE SHEAR,
FOR A FEW SUPERCELLS WITH VERY LARGE HAIL TO FORM INITIALLY. LATER
IN THE EVENING A POTENTIAL MCS MAY TRY TO FORM OVER NORTHERN
NEBRASKA AND LIFT NORTHEAST THROUGH THE NEARLY 1500 J/KG MUCAPE
BRINGING BOTH A RISK FOR VERY LARGE HAIL BUT SOME MODEST STRONG WIND
RISKS INTO THE TRI-STATE AREA INTO DAYBREAK. POCKETS OF HEAVY
RAIN WILL BE POSSIBLE IN THIS THUNDERSTORM ACTIVITY.
SUNDAY: WHILE SOME CONSIDERABLE UNCERTAINTIES REMAIN ON SUNDAY,
THERE CONTINUES TO BE INCREASED POTENTIAL FOR IMPACTFUL AND
POTENTIALLY WIDESPREAD SEVERE WEATHER IN THE AREA. AS ALLUDED TO
IN WEDNESDAY'S DISCUSSION, THE GREATEST UNCERTAINTY CONTINUES
TO REVOLVE AROUND THE EXTEND OF THE NORTHWARD ADVECTION OF THE
WARM SECTOR INTO THE PLAINS DURING THE DAY. OVERNIGHT AND
MORNING CONVECTION MAY PLAY A LARGE ROLE IN THIS PROCESS, BUT
ENSEMBLE DATA HAS TRENDED TOWARDS INSTABILITY SHIFTING FURTHER
NORTH OVER THE PAST 24 HOURS, EVEN SHOWING MLCAPE EXCEEDING 3000
J/KG OVER PORTIONS OF NW IOWA BY LATE AFTERNOON. THE OTHER
LIMITATION WE'LL NEED TO MONITOR IS THE EML THAT REMAINS IN
PLACE FOR MUCH OF THE DAYTIME HOURS ONCE MORNING CONVECTION
PASSES. A STUBBORN WARM LAYER CONTINUES TO PRESENT ITSELF IN
SOUNDINGS NEAR 700 MB DEEP INTO THE AFTERNOON, BUT THOUGHTS ARE
THE AMPLITUDE OF THE SLIGHTLY NEGATIVELY TILTED TROUGH MAY BE
ENOUGH TO OVERCOME THIS LIMITATION. GIVEN THE MAGNITUDE OF BULK
SHEAR, SUPPORTIVE MID- LVL LAPSE RATES, LOW-LVL HELICITY AND
BUOYANCY THERE IS CERTAINLY POTENTIAL FOR A HIGHER END SEVERE
WEATHER DAY WELL INTO THE EVENING/OVERNIGHT HOURS WHICH INCLUDES
ALL MODES. THIS THOUGHT IS BACKED UP BY AI-LEARNING OUTLOOK
PRODUCTS AND CIPS ANALOGS THAT SUPPORT A SIGNIFICANT SEVERE
WEATHER POTENTIAL. STILL QUITE A FEW ISSUES TO WORK THOUGH AND
PLENTY OF TIME FOR THINGS TO CHANGE, BUT IT'S TIME TO REALLY
START MONITORING THE FORECAST IF PLANS EXIST ON SUNDAY OR SUNDAY
NIGHT.
MONDAY: UNCERTAINTY GROWS FURTHER ON MONDAY AS MODELS DIVERGE ON THE
POSITIONING OF A COLD FRONT AND HOW FAR EAST IT MAY TRACK. ENSEMBLES
OF THESE MODELS ARE ALSO SPLIT WITH THE GFS SHOVING THE EFFECTIVE
BOUNDARY EAST. THE ECMWF/CMC BOTH STALL THE FRONT OVER THE EASTERN
CWA AND ALLOW IT TO RETREAT WESTWARD AS A SECONDARY TROUGH LIFT OUT
OF THE CENTRAL PLAINS. THESE DRASTICALLY DIFFERENT SCENARIOS MEAN A
BIG DIFFERENCE IN SEVERE WEATHER RISKS ESPECIALLY EAST OF I-29
MONDAY AFTERNOON AND EVENING.
QPF TOTALS: A WIDE ARRAY OF POTENTIAL QPF TOTALS REMAIN WITH THIS
SYSTEM WITH NBM CONTINUING TO SPREAD LOW PROBABILITIES OF HIGHER QPF
TOTALS, BUT EXPRESSING A WIDE ARRAY OF 10/90TH PERCENTILE POTENTIAL
BETWEEN 0.25-2". CONVECTION WILL ULTIMATELY DRIVE THE HIGHEST
TOTALS, AND WOULD NOT BE SURPRISED TO SEE POCKETS OF 2"+ BY
MONDAY EVENING.
TUESDAY-THURSDAY: BEHIND THIS TROUGH, COOLER WEATHER WILL ARRIVE
THROUGH THE MIDDLE OF THE WEEK WITH MINIMAL HAZARDS EXPECTED.
AVIATION /06Z TAFS THROUGH 06Z SATURDAY/
ISSUED AT 1208 AM CDT FRI MAY 15 2026
VFR CONDITIONS ARE EXPECTED TO PREVAIL WITH MOSTLY CLEAR SKIES
FOR THE DURATION OF THE PERIOD. WINDS ARE LIGHT AND VARIABLE
THROUGH FRIDAY MORNING BEFORE BECOMING WESTERLY FOR I-90 AND
NORTH. AREAS TO THE SOUTH WILL BE MORE SOUTHERLY. A SURFACE
BOUNDARY PASSES THROUGH AFTER 00Z SATURDAY, TURNING WINDS TO THE
NORTH. WINDS BECOME BREEZY IN THE AFTERNOON WITH 15-25 KT
GUSTS, HIGHEST NEAR AND NORTH OF HIGHWAY 14.
CHANCES FOR THUNDERSTORMS INCREASE AFTER OOZ SATURDAY. SOME STORMS
COULD BE STRONG TO SEVERE PRODUCING 2 INCH HAIL AND 60 MPH WIND
GUSTS. AREA MOST LIKELY TO SEE STRONG STORMS IS NORTHWEST IOWA,
ESPECIALLY ALONG AND SOUTH OF HIGHWAY 20. AREAS TO THE NORTH ARE NOT
LIKELY TO SEE ANY PRECIPITATION. STORMS SHOULD BE SOUTHEAST OF THE
AREA SHORTLY AFTER 06Z.
FIRE WEATHER
ISSUED AT 334 AM CDT FRI MAY 15 2026
VERY DRY CONDITIONS CONTINUE TODAY WITH RELATIVE HUMIDITY VALUES
AROUND AND BELOW 25% AREA WIDE. WINDS REMAIN LIGHT OVER MUCH OF THE
AREA, ALTHOUGH GUSTS TO 25 MPH ARE EXPECTED THROUGH THE DAY ALONG
AND NORTH OF US HIGHWAY 14. A FEW GUSTS TO 25 MPH ARE POSSIBLE FOR
PARTS OF SOUTH CENTRAL SD, BUT THESE ARE EXPECTED TO BE BRIEF LATE
THIS AFTERNOON. THIS COMBINATION LEADS TO NEAR CRITICAL AND CRITICAL
FIRE CONDITIONS. RED FLAG WARNING WILL BE IN EFFECT FOR THE US HWY
14 CORRIDOR AND NORTHWARD WHERE CONFIDENCE IN NEAR CRITICAL TO
CRITICAL CONDITIONS IS HIGHEST FROM 9 AM TO 6 PM CDT.
RAIN AND STORM CHANCES RETURN TO PORTIONS OF THE AREA TONIGHT. LOW
HUMIDITY SATURDAY (AROUND AND LESS THAN 25%) THROUGH THE MID TO LATE
AFTERNOON WITH BREEZY CONDITIONS (GUSTS TO 25 MPH) MAY LEAD TO
ELEVATED TO NEAR CRITICAL CONDITIONS FOR A BRIEF WINDOW.
WIDESPREAD RAIN AND STORM CHANCES RETURN TO THE REGION SATURDAY
NIGHT THROUGH MONDAY, TEMPERING WIDESPREAD CONCERNS.
FSD WATCHES/WARNINGS/ADVISORIES
SD...RED FLAG WARNING FROM 9 AM THIS MORNING TO 6 PM CDT THIS
EVENING FOR SDZ038>040.
MN...RED FLAG WARNING FROM 9 AM THIS MORNING TO 6 PM CDT THIS
EVENING FOR MNZ071-072.
IA...NONE.
NE...NONE.
UPDATE...SG
DISCUSSION...DUX
AVIATION...AJP
FIRE WEATHER...SG
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