955
FXUS63 KFSD 181144
AFDFSD
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
644 AM CDT MON MAY 18 2026
KEY MESSAGES
- PATCHY DRIZZLE THROUGH MID MORNING WILL LEAD TO SOME REDUCED
VISIBILITY. USE CAUTION AND KEEP HEADLIGHTS ON THROUGH THE
MORNING COMMUTE.
- SHOWERS AND ISOLATED THUNDERSTORMS RETURN TO THE AREA BY
EARLY THIS AFTERNOON, CONTINUING THROUGH THIS EVENING INTO
TONIGHT.
- A FEW STORMS ALONG AND SOUTHEAST OF A WAYNE TO SHELDON TO
WINDOM LINE MAY BE STRONG TO SEVERE LATE THIS AFTERNOON INTO
THIS EVENING. CONFIDENCE IN THIS RISK IS LOW.
- COOL CONDITIONS PREVAIL THIS WEEK. DRY WEATHER EXPECTED MID
WEEK. ANOTHER ROUND OF STORMS IS POSSIBLE THURSDAY THROUGH
FRIDAY.
UPDATE
ISSUED AT 304 AM CDT MON MAY 18 2026
TEMPERATURES THIS MORNING RANGE FROM THE MID 40S TO THE MID 60S FROM
WEST TO EAST. LOWS TONIGHT FALL TO THE UPPER 30S TO MID 50S,
ALTHOUGH AREAS WEST OF THE JAMES RIVER MAY STAY A BIT WARMER THAN
THE UPPER 30S IF STRATUS LINGERS LONGER INTO THE OVERNIGHT HOURS, AS
SOME MODELS HINT AT. STILL SEEING BREEZY WINDS WITH GUSTS TO 30 MPH
AT TIMES.
FOCUS SHIFTS TO THE NEXT WAVE PROGGED TO MOVE OUT OF THE ROCKIES
LATE THIS AFTERNOON THROUGH TONIGHT, AS WELL AS THE PRECEDING WAA
AND WEAK VORTICITY LOBE. EXPECT SCATTERED SHOWERS AND ISOLATED
THUNDERSTORMS TO DEVELOP THIS MORNING ACROSS NE AND LIFT NORTHWARD
INTO OUR AREA BY THE AFTERNOON HOURS. SHOWERS AND ISOLATED STORMS
CONTINUE THROUGH THE EVENING/OVERNIGHT HOURS, TAPERING DOWN FROM
WEST TO EAST AS THE 700MB TROUGH MOVES ACROSS THE AREA.
A FEW ISOLATED STRONG TO SEVERE STORMS ARE POSSIBLE ALONG AND
SOUTHEAST OF A LINE FROM WAYNE TO SHELDON TO WINDOM, MAINLY FROM 4
TO 9 PM. CONFIDENCE IS LOW IN THE CHANCES FOR SEVERE WEATHER, AS
THERE ARE A FEW QUESTIONS. ONE, HOW MUCH DO SKIES CLEAR DURING THE
DAY, ESPECIALLY WITH LATEST GUIDANCE SHOWING STRATUS REMAINING IN
PLACE THROUGH THE EARLY AFTERNOON? TWO, DEPENDING ON CLOUD COVER,
HOW MUCH CAN THE ATMOSPHERE RECOVER FROM YESTERDAY'S STORMS?
FINALLY, WHERE DO ANY BOUNDARIES END UP TODAY, AND HOW QUICKLY DOES
THE ELEVATED FRONT MOVE EAST?
IF WE ARE ABLE TO GET A STRONGER STORM OR TWO TO DEVELOP, HAIL TO
PING PONG BALL SIZE (1.5") AND WIND GUSTS TO 60 MPH ARE THE MAIN
THREATS. IF WE HAVE A SURFACE BOUNDARY OR GET A SURFACE BASED STORM
(MORE LIKELY IF WE'RE ABLE TO CLEAR OUT TODAY), A TORNADO CANNOT BE
RULED OUT, ALTHOUGH RISK IS LOW. HEAVY RAIN IN THUNDERSTORMS MAY
CAUSE SOME LOCALIZED FLOODING ISSUES IF STORMS TRACK OVER THE SAME
AREAS WHICH RECEIVED HEAVY RAIN OVER THE WEEKEND. STAY AWARE FOR
POSSIBLE WARNINGS LATER TODAY.
DISCUSSION
ISSUED AT 120 PM CDT SUN MAY 17 2026
THE SHORT-TERM CONVECTIVE OUTLOOK PRESENTS A HIGHLY VOLATILE
SPRING SEVERE WEATHER SETUP. LATEST SURFACE ANALYSIS SHOWS A
COMPLEX PATTERN, ANCHORED BY A STRONG 994 MB LOW OVER NORTHWEST
KS. AN INVERTED TROUGH EXTENDED NORTH OF THE LOW THROUGH
CENTRAL SD, WHILE A WELL-DEFINED WARM FRONT STRETCHED NORTHEAST
OF THE LOW INTO EAST CENTRAL NE. A WEAKER LOW WAS ALSO NOTED IN
NORTH CENTRAL NE. VISIBLE SATELLITE IMAGERY REVEALED STABLE
WAVE CLOUDS ADVANCING NORTHEAST OVER FAR NORTHEAST NE AND
EXTREME SE SD, AHEAD OF THE ADVANCING WARM FRONT. REGIONAL
RADAR IMAGERY SHOWED A COMPLEX OF STRONG TO SEVERE STORMS OVER
NORTH CENTRAL NE. THIS STORM COMPLEX IS FORECAST BY SHORT RANGE
GUIDANCE TO CONTINUE TRACKING EAST THIS AFTERNOON, INTENSIFYING
AS INTERACTS WITH THE RICHER LOW- LEVEL MOISTURE POOL NEAR AND
SOUTH OF THE WARM FRONT.
MODERATE TO STRONG INSTABILITY WILL BE IN PLACE OVER THE
SOUTHERN TO EASTERN CWA BY LATE AFTERNOON WITH MLCAPE NEARING
3000 J/KG. IN ADDITION, DEEP LAYER SHEAR WILL INCREASE TO AROUND
50 KT, COINCIDENT WITH A MID LEVEL SPEED MAX EJECTING FROM THE
DEEP UPPER TROUGH TO OUR WEST. AS THE SYSTEM EVOLVES OVER THE
NEXT SEVERAL HOURS, IT APPEARS THE INGREDIENTS FOR A SIGNIFICANT
SEVERE WEATHER EVENT WILL BE MOST FAVORED OVER THE SOUTHERN TO
EASTERN CWA. AHEAD OF THE MAIN CONVECTIVE LINE, SOME CAMS SHOW
SUPERCELL DEVELOPMENT ALONG THE NORTHWARD ADVANCING WARM FRONT.
THESE STORMS WOULD PRESENT A RISK OF VERY LARGE HAIL (2"+) AND
TORNADOES. GIVEN THE AMOUNT OF LOW LEVEL SRH/CURVED HODOGRAPHS
PRESENT, A COUPLE STRONG TORNADOES ARE POSSIBLE. THE CONVECTIVE
CLUSTER CURRENTLY ENTERING OUR FAR SOUTHWEST CWA SHOULD
STRENGTHEN AS IT SHIFTS EAST, WITH AN INITIAL HAIL AND TORNADO
THREAT TRANSITIONING TO A DAMAGING STRAIGHT LINE WIND THREAT
(70+ MPH) AS IT GROWS UPSCALE INTO A SQUALL LINE/QLCS. SOME
LINE-EMBEDDED QLCS TORNADOES ARE POSSIBLE, ESPECIALLY FOR ANY
LINE SEGMENTS THAT BECOME ORIENTED NORTH/SOUTH OR
NORTHWEST/SOUTHEAST, GIVEN SOUTHWESTERLY 0-3 KM SHEAR VECTORS.
TIMING FROM LATEST HIGH-RES GUIDANCE SUGGESTS THIS ACTIVITY
EXITS TO THE EAST OF OUR CWA LATE THIS EVENING.
PRECIPITATION AMOUNTS WILL VARY SIGNIFICANTLY BASED ON CONVECTIVE
TRACKS, THOUGH NBM GUIDANCE AND HREF PROBABILITY MATCH MEAN
FIELDS PROJECT A WIDESPREAD 0.50 TO 1.50 INCHES OF RAINFALL,
PARTICULARLY ACROSS NORTHWEST IOWA AND SOUTHWEST MINNESOTA. ON
MONDAY, THE COLD FRONT FINALLY PUSHES INTO THE AREA. INSTABILITY
AND SHEAR ARE FORECAST TO BE MUCH LOWER THAN TODAY, HOWEVER,
THERE WILL BE A CONDITIONAL RISK OF SEVERE STORMS OVER THE
EASTERN CWA DURING THE LATE AFTERNOON TO EVENING, IF THE AIRMASS
CAN DESTABILIZE SUFFICIENTLY AHEAD OF THE FRONT. SPC'S DAY 2
OUTLOOK INDICATES AS MARGINAL RISK (LEVEL 1 OF 5), FOR OUR MN
AND IA COUNTIES.
BEHIND THE DEPARTING UPPER WAVE, QUASI-ZONAL FLOW SETS UP FOR
TUESDAY AND WEDNESDAY, YIELDING QUIET CONDITIONS AND SEASONALLY
COOL HIGH TEMPERATURES MODERATING FROM THE UPPER 50S TUESDAY TO
MID-UPPER 60S WEDNESDAY.
THE NEXT UPPER WAVE MOVES IN FOR THE THURSDAY TO FRIDAY PERIOD,
HOWEVER GULF MOISTURE REMAINS CUTOFF AHEAD OF THIS SYSTEM.
EVALUATING THE ECMWF EXTREME FORECAST INDEX (EFI) REVEALS NO
SIGNIFICANT CLIMATOLOGICAL ANOMALIES FOR PRECIPITATION OR WIND
ACROSS THE UPPER MIDWEST DURING THIS PERIOD, REINFORCING THE
THE IDEA OF A LOW-IMPACT SYSTEM FOR OUR AREA. THE CURRENT
FORECAST STICKS CLOSELY TO THE NBM CONSENSUS, MAINTAINING BROAD
20-30 PERCENT PROBABILITIES FOR LIGHT RAIN FOR LATE THURSDAY
INTO SATURDAY.
BY LATE THIS WEEK AND ESPECIALLY THIS WEEKEND, TEMPERATURES
WILL EMBARK ON A STEADY UPWARD TRAJECTORY, AS THE MID LEVEL FLOW
BACKS WEST, THEN SOUTHWEST. THE CLIMATE PREDICTION CENTER (CPC)
6-10 DAY OUTLOOK FAVORS ABOVE-NORMAL TEMPERATURES ACROSS THE
NORTHERN PLAINS AND UPPER MIDWEST, WHICH SUPPORTS BLENDED
GUIDANCE HIGH TEMPERATURES REACHING WELL INTO THE 80S ON
SUNDAY.
AVIATION /12Z TAFS THROUGH 12Z TUESDAY/
ISSUED AT 632 AM CDT MON MAY 18 2026
MVFR TO IFR CEILINGS PERSIST THIS MORNING, AND ARE EXPECTED TO
DO SO THROUGH THE PERIOD. LOWEST CEILINGS OVERALL ARE NEAR AND
EAST OF I-29. HAVE SEEN PATCHY TO WIDESPREAD DRIZZLE THIS
MORNING WITH THE LOW CEILINGS, AND GUIDANCE IS HANDLING THIS
POORLY THIS MORNING. HAVE SEEN VISIBILITY ALSO DOWN TO MVFR AND
IFR; DRIZZLE LINGERS THROUGH THE MID MORNING. SHOWERS AND
ISOLATED STORMS RETURN TO THE AREA BY EARLY THIS AFTERNOON,
CONTINUING THROUGH THIS EVENING. TRIED TO NARROW CONVECTIVE
TIMING AS MUCH AS POSSIBLE WITH LATEST TRENDS, BUT EXPECT
FURTHER REFINEMENT. WITH SLIGHTLY HIGHER CONFIDENCE IN TSRA
POTENTIAL FOR NORTHWESTERN IA, INCLUDED MENTION. HOWEVER, STILL
LOW ENOUGH CONFIDENCE IN TIMING/OCCURRENCE AT THE TERMINAL TO
EXCLUDE FROM PREVAILING GROUP FOR NOW.
WINDS THROUGH THE PERIOD REMAIN CLOSE TO NORTHWESTERLY, WITH
GUSTS 20 TO 30 KNOTS.
A FEW THUNDERSTORMS ALONG/SOUTHEAST OF KLCG-KSHL-KMWM MAY BE
STRONG TO SEVERE WITH LARGE HAIL AND STRONG WINDS, BUT
CONFIDENCE IS LOW.
FSD WATCHES/WARNINGS/ADVISORIES
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
UPDATE...SG
DISCUSSION...ILX/25
AVIATION...SG
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