484
FXUS63 KFSD 181728
AFDFSD
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
1228 PM CDT WED MAR 18 2026
KEY MESSAGES
- A STRONG WARMING TREND IS ON THE WAY INTO THE WEEKEND. THE
DEGREE OF WARMING HOWEVER WILL BE DETERMINED BY HOW QUICKLY
SNOW MELTS.
- FOG, POSSIBLY DENSE, MORE LIKELY TO DEVELOP THURSDAY MORNING,
FOCUSED PRIMARILY ALONG THE HIGHER ELEVATIONS OF THE COTEAU
DES PRAIRIES BUT COULD EXTEND TO THE JAMES RIVER.
- DEPENDING ON FINE FUEL MOISTURE (GRASS AND BRUSH), FIRE
CONDITIONS MAY BECOME ELEVATED ALONG THE MISSOURI RIVER
VALLEY FRIDAY AND SATURDAY.
DISCUSSION
ISSUED AT 1219 PM CDT WED MAR 18 2026
THIS AFTERNOON: WINDS CONTINUE TO SLOWLY TURN TO THE WEST THIS
AFTERNOON, USHERING IN STEADILY WARMER TEMPERATURES. WE'RE SEEING A
GOOD RESPONSE TO THE WARMTH AT THE SURFACE AS TEMPERATURES SURGE
TOWARDS THE 60S AND 70S ALONG AND SOUTHWEST OF THE JAMES RIVER.
AREAS WITH MORE SNOW COVER ARE SLOWER TO RESPOND, BUT STILL QUICKLY
RISING INTO THE 40S AND 50S, A GOOD INDICATION OF THE POWER OF MID-
MARCH SUN.
TONIGHT: UPR-MID LEVEL CLOUDS WILL PERSIST THROUGH THE EVENING AND
OVERNIGHT HOURS AS THE CWA REMAINS UNDER MID-LVL NORTHWESTERLY FLOW
ALOFT AND SLIGHTLY SOUTH OF A BUILDING UPPER JET. THESE CLOUDS WILL
HELP TEMPERATURES STAY NEAR THE FREEZING MARK, AND COULD EVEN STAY
IN THE 40S IN SOME AREAS. HIGH RESOLUTION GUIDANCE AGAIN HINTS AT
LOW STRATUS/FOG DEVELOPMENT ALONG THE RIDGE AREAS BY DAYBREAK
THURSDAY. WHILE THE NAM BASED SOLUTION MAY BE TOO AGGRESSIVE, WE'RE
ALSO SEEING SIGNALS OF SNOWMELT FOG DEVELOPING IN ADDITIONAL MODEL
DATA. SHOULD FOG DEVELOP, IT COULD TURN DENSE RATHER QUICKLY AND
ADVISORIES MAY BE NEEDED AS FAR WEST AS THE JAMES RIVER VALLEY.
THURSDAY-SATURDAY: THE WEATHER FOR THE END OF THE WEEK WILL BE
DOMINATED BY A LARGE 592DM UPPER RIDGE CENTERED OVER THE FOUR
CORNERS REGION. THE EXPANSION OF THIS RIDGE EASTWARD WILL ALLOW
CLIMATOLOGICALLY SIGNIFICANT LOW-LVL TEMPERATURES TO ADVECT
EASTWARD. AS NOTED YESTERDAY, MINIMAL CHANGE IN MEDIUM RANGE MODELS
WHEN IT COMES TO THE OVERALL SIGNIFICANCE OF THE AIRMASS, WITH ESAT
DATA INDICATING THAT 850MB TEMPERATURES APPROACH THE 90TH AND THEN
EXCEED THE 99TH PERCENTILE OF CLIMATOLOGY CENTERED AROUND MID-
MARCH BY THE WEEKEND. AT THE SURFACE, TEMPERATURES WILL BE MOST
IMPACTED BY LINGERING SNOW COVER, WET GROUNDS, AND DEPTH OF
MIXING BUT ARE STILL EXPECTED TO SURGE INTO THE 70S BY FRIDAY,
AND 70S AND 80S ON SATURDAY. THESE TEMPERATURES MAY APPROACH OR
EXCEED RECORD VALUES, WITH THE GREATEST POTENTIAL FOCUSED
AROUND FRIDAY AFTERNOON.
THE RISE IN TEMPERATURES AND ADVECTION OF DRIER LOW-LVL AIR THROUGH
THE PLAINS MAY INTRODUCE SOME MINOR FIRE DANGER RISKS. HOWEVER,
SURFACE WINDS REMAIN LESS THAN RFW CRITERIA FRIDAY AND SATURDAY, AND
MAY ONLY PRODUCE ELEVATED CONDITIONS NEAR THE MISSOURI RIVER VALLEY
REGION.
SATURDAY NIGHT: ONE MINOR VARIANCE IN THE MEDIUM RANGE FORECAST
CONTINUES TO BE THE TIMING OF A STRONGER COLD FRONT SURGING
SOUTHWARD THROUGH THE PLAINS SATURDAY AFTERNOON AND EVENING. TIMING
DIFFERENCES IN MODEL DATA ARE PRODUCING A 10+ DEGREE RANGE IN THE
25/75TH PERCENTILE TEMPERATURES AT 7PM SATURDAY, MOSTLY NORTH OF I-
90. WINDS BEHIND THE PASSAGE OF THIS SATURDAY NIGHT MAY GUST
BETWEEN 30-40 MPH BASED ON THE 35 KNOTS OF WIND AT THE TOP OF THE
SHALLOW MIXED LAYER OVERNIGHT. LREF HISTOGRAM DATA WOULD SUGGEST AT
LEAST A 35% PROBABILITY OF >30 MPH WINDS. POPULATED NBM GUIDANCE IS
LIKELY TOO LOW, AND HEADING TOWARDS THE 75TH PERCENTILE IS
REASONABLE GIVEN THE STRONG COLD ADVECTION BEHIND THE FRONT.
SUNDAY-TUESDAY: A BRIEF SPELL OF NEAR NORMAL TEMPERATURES ARRIVES
FOR SUNDAY AND MONDAY AS HIGH PRESSURES MOVES INTO THE GREAT LAKES
EARLY NEXT WEEK. HOWEVER, LATEST MODEL TRENDS PROJECT A PERIOD OF
FAST NORTHWEST TO WESTERLY FLOW INTO NEXT WEEK, KEEPING THE REGION
SUSCEPTIBLE TO A ROLLER COASTER RIDE OF TEMPERATURES AND PERIODIC
WINDY DAYS INTO THE MIDDLE OF THE WEEK. AT THIS TIME, NO LARGE
IMPACTFUL SYSTEMS ARE EXPECTED.
AVIATION /18Z TAFS THROUGH 18Z THURSDAY/
ISSUED AT 1152 AM CDT WED MAR 18 2026
VFR CONDITIONS EXPECTED TO CONTINUE INTO THE OVERNIGHT HOURS AS
A WEAK WESTERLY WIND DEVELOPS. AFTER SUNSET, WINDS WILL AGAIN
TURN LIGHT AND VARIABLE. DEPENDING ON THE DEGREE OF MID-UPR
CLOUDS THAT DEVELOP, A FAST DROP IN TEMPERATURES COMBINED WITH
SNOW MELT MAY LEAD TO RAPID FOG FORMATION AFTER MIDNIGHT. AREAS
WHERE CONFIDENCE IS HIGHEST ARE GENERALLY ALONG THE HIGHER
ELEVATIONS OF THE COTEAU, BUT COULD SEE FOG FORM AS FAR WEST AS
THE JAMES RIVER. WILL PUSH VISIBILITY DOWN TOWARDS 1/2 MILE AT
FSD/HON, BUT COULD SEE DENSE FOG AT TIMES AFTER 3AM TO MID-
MORNING BEFORE WESTERLY WINDS INCREASE.
CLIMATE
ISSUED AT 1220 PM CDT WED MAR 18 2026
EXTREMELY WARM AIR WILL TRY TO MOVE EASTWARD LATE THIS WEEK INTO
THIS WEEKEND. THESE TEMPERATURES MAY RESULT IN THE TOP 10
EARLIEST 75 AND 80 DEGREE HIGHS AT LONG TERM CLIMATE LOCATIONS.
HERE IS A LOOK AT RECORDS FOR FRIDAY AND SATURDAY
RECORD HIGH TEMPERATURES:
MARCH 20:
KFSD: 73/2022, KSUX: 79/2015, KHON: 75/1911, KMHE: 77/1994
MARCH 21:
KFSD: 83/1910, KSUX: 85/1910, KHON: 84/1907, KMHE: 88/1907
RECORD HIGH MINIMUM TEMPERATURES:
MARCH 21:
KFSD: 49/1938, KSUX: 48/2012, KHON: 45/1938
FSD WATCHES/WARNINGS/ADVISORIES
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
DISCUSSION...DUX
AVIATION...DUX
CLIMATE...DUX
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