422
FXUS63 KFSD 180220
AFDFSD
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
920 PM CDT TUE MAR 17 2026
KEY MESSAGES
- LIGHT SNOW AND A WINTRY MIX SLIDES SOUTH LATE THIS EVENING
ALONG AND EAST OF I-29. CALM WEATHER RETURNS TONIGHT.
- A STRONG WARMING TREND IS ON THE WAY INTO THE WEEKEND. THE
DEGREE OF WARMING HOWEVER WILL BE DETERMINED BY HOW QUICKLY
SNOW MELTS. IF ALL POTENTIAL IS REALIZED, THEN RECORDS MAY BE
BROKEN FRIDAY AND SATURDAY.
- DEPENDING ON FINE FUEL MOISTURE (GRASS AND BRUSH), FIRE
CONDITIONS MAY BECOME ELEVATED ALONG THE MISSOURI RIVER VALLEY
TOWARD THE WEEKEND.
UPDATE
ISSUED AT 916 PM CDT TUE MAR 17 2026
FORECAST FOR TONIGHT INTO WEDNESDAY REMAINS LARGELY ON TRACK.
HAVE HAD A COUPLE OF REPORTS OF FREEZING DRIZZLE THIS EVENING
ACROSS NORTHWESTERN IA AS PRECIPITATION (SNOW AND SOME SLEET)
CONTINUES TO MOVE SOUTH. THIS SHOULD TAPER OFF OVER THE NEXT
HOUR OR SO, BUT COULD LEAD TO ADDITIONAL SLICK SPOTS ON
UNTREATED OR ELEVATED SURFACES.
GFS/NAM AND SOME HI-RES DERIVATIVES CONTINUE TO SHOW PATCHY TO
WIDESPREAD FOG ACROSS THE AREA TONIGHT. HOWEVER, A FEW QUESTIONS
WITH THIS POTENTIAL. FIRST, IF TEMPERATURES RISE A FEW MORE
DEGREES BUT NOT ABOVE FREEZING, THINK THAT MOST AREAS EAST OF
THE JAMES SHOULD BE OKAY. SECOND, MANY AREAS WEST OF I-29 HAVE
DEW POINT DEPRESSIONS OF 5 OR MORE, WHICH COULD MAKE IT HARD TO
GET ANY FOG. FINALLY, CLOUDS MAY LINGER A BIT LONGER INTO THE
OVERNIGHT, WHICH MAY ALSO LIMIT EXTENT. SOMETHING TO KEEP AN EYE
ON INTO THE EARLY OVERNIGHT HOURS, BUT STILL HAVE LOW CONFIDENCE
IN DEVELOPMENT.
DISCUSSION
ISSUED AT 1205 PM CDT TUE MAR 17 2026
THIS AFTERNOON: LOW-LVL WARM ADVECTION CONTINUES TO PASS
THROUGH THE REGION THIS AFTERNOON. LIGHT SNOW CONTINUES TO MOVE
EAST INTO MN/IA THIS AFTERNOON, LEAVING LIGHT ACCUMULATIONS IN
IT'S WAKE. THE PASSAGE OF THE 850 MB TROUGH SIGNALS THE ARRIVAL
OF >0C TEMPERATURES ALOFT, ALSO SUGGESTING THAT A FEW LINGERING
CONVECTIVE SHOWERS COULD PRODUCE A WINTRY MIX AS THEY MOVE EAST
OF I-29 THROUGH LATE AFTERNOON. ANY WINTRY MIX ON TOP OF LIGHT
SNOW SHOULDN'T ADD ANY ADDITIONAL TRAVEL HAZARDS.
TONIGHT: WINDS WILL REMAIN LIGHT AND VARIABLE TO WESTERLY THROUGH
THE OVERNIGHT HOURS AS A SURFACE WARM FRONT BEGINS TO MOVE
EASTWARD. EARLY EVENING LOW TEMPERATURES MAY BE POSSIBLE, WITH A
FLATTENED OR REVERSED DIURNAL CURVE DEVELOPING AFTER 3AM AS LOW-LVL
WARM ADVECTION INCREASES. WITH INCREASING LOW-LVL MOISTURE FROM SNOW
MELT, WE MAY HAVE TO WATCH FOR FOG DEVELOPMENT BY DAYBREAK. NAM
BASED MODELS ARE VERY BULLISH ON THIS IDEA, BUT OFTEN OVER
SATURATE A COLD NEAR SURFACE LAYER.
WEDNESDAY-THURSDAY: A BUILDING MID-LVL RIDGE OVER THE SOUTHWESTERN
US WILL PLAY AN IMPORTANT ROLE THROUGH THE MIDDLE AND END OF THE
WEEK, PUSHING IMPACTFUL WEATHER TO OUR NORTHWEST, WHILE ALLOWING
BROAD AND INTENSE LOW-LVL WARM ADVECTION TO STREAM INTO THE PLAINS.
THE PASSAGE OF A SUBTLE SHORTWAVE MOVING THROUGH NORTHWEST FLOW ON
WEDNESDAY WILL INDUCE A WARMER SOUTHWESTERLY SURFACE FLOW. A SLIGHT
INCREASE IN MID-UPR CLOUD COVER MAY TEMPER HIGHS SLIGHTLY, BUT THE
LATEST GUIDANCE CONTINUES TO INDICATE HIGHS PUSHING INTO THE 40S AND
50S WEDNESDAY, WITH POTENTIAL FOR THE 50S AND 60S IN MOST AREAS
THURSDAY. FORECAST WILD CARDS INCLUDE THE POTENTIAL OF INCREASING
STRATUS OVER THE MELTING SNOW PACK ALONG WITH WET GROUND THAT COULD
ACTUALLY LIMIT THE SURFACE WARMING. THAT SAID THURSDAY'S HIGH
TEMPERATURES MAY HAVE THE MOST VARIANCE AND IT'S POSSIBLE
FORECAST TEMPERATURES MAY COOL, ESPECIALLY ALONG AND EAST OF A
LINE FROM HURON TO SIOUX FALLS TO SPENCER. WE'RE ALREADY SEEING
MODELS CATCH ONTO THE LINGERING IMPACTS OF SNOW COVER, AND
FUTURE TEMPERATURE FALLS MAY CONTINUE. ONE THING TO NOTE IS HOW
INDIVIDUAL MODELS ARE HANDLING THE CURRENT SNOW DEPTH. SEVERAL
MODELS ARE NOT INITIALIZING WELL WITH SNOW DEPTH (ESPECIALLY
EAST OF I-29), AND MAY BE ERODING THE PACK TOO QUICKLY THROUGH
THURSDAY.
FRIDAY-MONDAY: A 592DM RIDGE WILL CONTINUE TO BUILD OVER THE FOUR
CORNERS REGION THROUGH THE END OF THE WEEK, SURGING A
CLIMATOLOGICALLY SIGNIFICANT SURGE OF LOW-LVL TEMPERATURES EASTWARD
THROUGH THE PLAINS. ESAT TABLES FROM THE NAEFS/GEFS/EC WOULD ALL
INDICATE THAT BOTH THE 700:500 MB RIDGE HEIGHTS ARE ALL AT THE EDGE
OF THE 30 YEAR CLIMATOLOGY CENTERED AROUND MID-MARCH. LOW-LVL
TEMPERATURE EXTREMES ARE ALL AOA THE 99TH PERCENTILE ALONG THE
WESTERN HIGH PLAINS AND LOWER TOWARDS THE 90TH PERCENTILE TOWARDS
THE GREAT LAKES. WITH THE INCREASE IN SOUTHERLY SURFACE FLOW FRIDAY
AND SATURDAY, THE BIGGEST QUESTIONS WILL BE HOW MUCH SNOW LINGERS,
ANY STRATUS POTENTIAL, AND IMPACTS OF WET GROUND ON TEMPERATURES.
THE LATEST NBM CONTINUES TO NARROW DOWN THE TEMPERATURE SPREADS IN
THE 25/75TH PERCENTILE) ON FRIDAY BELOW 5 DEGREES IN MOST AREAS, BUT
DOES MAINTAIN A NEARLY 10 DEGREE SPREAD OVER SW MINNESOTA. SATURDAY
IS THE DAY THAT THINGS REALLY GET INTERESTING, BUT ALSO VERY
CHALLENGING TO FORECAST. MOST MEDIUM RANGE DETERMINISTIC AND
ENSEMBLE GUIDANCE PRODUCES STRONG GUSTY SOUTHWEST WINDS THROUGH THE
DAYTIME HOURS OF SATURDAY. THESE WINDS, INTERTWINED WITH THE AXIS OF
THE LOW-LVL THERMAL RIDGE, HAVE THE POTENTIAL TO SURGE AFTERNOON
HIGH TEMPERATURES WELL INTO THE 70S AND INTO THE 80S. THE 13Z NBM
CONTINUES TO SHOW AN EXTREME LEVEL OF SPREAD IN THE 25/75TH
PERCENTILE DATA WITH POTENTIAL ALL THE WAY FROM THE UPPER 50S TO
LOWER 60S TO THE UPPER 70S AND LOWER 80S. THE 10/90TH SPREAD OF THE
NBM IS OVER 25 DEGREES IN MOST AREAS. DETERMINISTIC MODELS ARE NEAR
THE EDGE OF ALL OF THE ENSEMBLES, AND THOSE SIMILAR CONCERNS OF SNOW
COVER, CLOUDS, AND WET GROUND CONTINUE. IF ALL THE STARS ALIGN,
RECORDS WILL CERTAINLY BE POSSIBLE FRIDAY AND SATURDAY, MAKING
THE BLIZZARD OF LAST WEEKEND A MEMORY.
THERE IS ALSO SOME POTENTIAL FOR A STRONGER COLD FRONT TO SINK
SOUTHWARD LATE SATURDAY INTO SUNDAY, WHICH IS LEADING TO A BIT MORE
SPREAD IN ENSEMBLE GUIDANCE. THIS FRONT, MOSTLY LIMITED IN
MOISTURE, COULD PRODUCE VERY LIGHT RAIN TO SNOW INTO SUNDAY ALONG
WITH COOLING TEMPERATURES CONSIDERABLY. COOL AND DRY CONDITIONS
CONTINUE INTO MONDAY AS HIGHS SETTLE BACK INTO THE 40S.
AVIATION /00Z TAFS THROUGH 00Z THURSDAY/
ISSUED AT 634 PM CDT TUE MAR 17 2026
MVFR AND LOCALLY IFR CONDITIONS CONTINUE TO IMPROVE THROUGH THE
LATE EVENING AND TONIGHT. AN AREA OF LIGHT SNOW/WINTRY MIX
CONTINUES TO MOVE SOUTH ACROSS AREAS EAST OF I-29, BUT EXPECT
THIS TO DIMINISH THROUGH THE EVENING HOURS.
SOME GUIDANCE, MAINLY GFS/NAM AND THE ASSOCIATED HI-RES MODELS
SHOW WIDESPREAD FOG DEVELOPING WEST OF I-29 TONIGHT; HOWEVER,
WITH LOWER CONFIDENCE WILL AGAIN OMIT MENTION AT THIS TIME AND
MONITOR TRENDS. WINDS DO BECOME LIGHT AND VARIABLE, WITH SOME
LLWS PREDOMINANTLY ALONG/NORTH OF I-90.
VFR CONDITIONS EXPECTED WEDNESDAY, ALTHOUGH SOME GUIDANCE SHOWS
LOW VFR TO MVFR STRATUS RETURNING BUT CONFIDENCE IS LOW.
CLIMATE
ISSUED AT 1205 PM CDT TUE MAR 17 2026
EXTREMELY WARM AIR WILL TRY TO MOVE EASTWARD LATE THIS WEEK INTO
THIS WEEKEND. 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.
UPDATE...SG
DISCUSSION...DUX
AVIATION...SG
CLIMATE...DUX
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