657
FXUS63 KFSD 141721
AFDFSD
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
1221 PM CDT TUE APR 14 2026
KEY MESSAGES
- PATCHY AND LOCALLY DENSE FOG CONTINUES THROUGH THIS MORNING.
VISIBILITY BELOW ONE MILE IN DENSE FOG. FOG DISSIPATES LATER
THIS MORNING.
- PERIODIC CHANCES (20-60%) FOR SHOWERS AND THUNDERSTORMS
CONTINUE THIS WEEK. ISOLATED STRONG TO SEVERE STORMS ARE POSSIBLE
LATE THIS AFTERNOON THROUGH WEDNESDAY EAST OF IOWA/MINNESOTA
HIGHWAY 60, ALTHOUGH CONFIDENCE IS LOW IN POTENTIAL.
- ELEVATED TO NEAR CRITICAL FIRE DANGER IS EXPECTED THURSDAY
WITH A BREAK FROM RAINFALL, MUCH WARMER TEMPERATURES, STRONG
WINDS, AND LOW HUMIDITY. WINDS MAY LEAD TO ELEVATED
CONDITIONS FRIDAY, ALTHOUGH SHOWER AND STORM CHANCES MAY
TEMPER CONCERNS.
UPDATE
ISSUED AT 329 AM CDT TUE APR 14 2026
FOG AND VERY LOW STRATUS CONTINUE TO DEVELOP EARLY THIS MORNING. SO
FAR, MOST VISIBILITY HAS REMAINED ABOVE 2 MILES OUTSIDE THE
CHAMBERLAIN AREA (WHERE VISIBILITY AT THE TIME OF THE DISCUSSION IS
DOWN TO AROUND 1/4 SM). MODEL PROBABILITIES DO SHOW MODERATE (30-
60%) CHANCES AREAS ALONG THE BUFFALO RIDGE AND ACROSS NORTHWESTERN
IA TO FALL BELOW 1 MILE THROUGH THIS MORNING SO WILL CONTINUE TO
MONITOR FOR POTENTIAL HEADLINES. FOG SHOULD MIX OUT THROUGH THE
MORNING HOURS. ALSO SEEING SOME RETURNS ON RADAR OUT ACROSS CENTRAL
SD, BUT HAVE NOT SEEN ANY PRECIPITATION REPORTS, LIKELY DUE TO THE
STOUT DRY LAYER BETWEEN THE MID CLOUDS AND THE SURFACE/STRATUS.
FORECAST REMAINS ON TRACK FOR THE REST OF TODAY AND INTO WEDNESDAY.
SPC HAS EXPANDED THE MARGINAL (LEVEL 1 OF 5) RISK BACK TOWARD IA/MN
STATE HWY 60 FOR BOTH TODAY AND WEDNESDAY. SOME UNCERTAINTY IN
DEVELOPMENT AND TIMING, AS GUIDANCE STILL MOSTLY KEEPS THE BETTER
FORCING OFF TO THE SOUTHEAST. HOWEVER, RECENT RUNS OF LARGER SCALE
DETERMINISTIC MODELS ARE SHIFTING THE SURFACE AND LOW LEVEL FRONTS
FURTHER NORTH TODAY, SHIFTING THAT INSTABILITY AXIS WITH IT.
ADDITIONALLY, STORMS WILL NEED TO OVERCOME THE CAP ONCE AGAIN.
STORMS LATE TODAY MAY MOVE OUT OF EASTERN NE INTO OUR FORECAST AREA,
AND WOULD BE CAPABLE OF LARGE HAIL TO 1.5 INCHES (PING-PONG BALL
SIZED) AND WIND GUSTS TO 65 MPH. IF THERE IS A LOW LEVEL OR SURFACE
BOUNDARY IN PLAY, A TORNADO IS POSSIBLE. CAN'T RULE OUT A STRONGER
STORM INTO TUESDAY NIGHT. FOR WEDNESDAY, WILL HAVE TO WAIT AND SEE
HOW TODAY PLAYS OUT WITH CONVECTION WITH THE BETTER INSTABILITY
AGAIN OFF TO OUR SOUTH AND EAST.
DISCUSSION
ISSUED AT 238 PM CDT MON APR 13 2026
SCATTERED THUNDERSTORMS ARE SET TO DEVELOP OVER THE NEXT
FEW HOURS, BRINGING THE POTENTIAL FOR A FEW SEVERE STORMS WITH LARGE
HAIL, DAMAGING WINDS, AND PERHAPS A TORNADO OR TWO. AS OF 2 PM,
A SURFACE LOW IS LOCATED OVER NORTHERN NEBRASKA WITH A WARM
FRONT EXTENDING NORTHEAST OF IT ACROSS FAR SOUTHEASTERN SOUTH
DAKOTA INTO NORTHWEST IOWA. DEW POINTS IN THE 60S HAVE BEEN
GRADUALLY SPREADING NORTHWARD, AND THESE HIGHER DEW POINTS ARE
EXPECTED TO REACH THE I-90 CORRIDOR OVER THE NEXT COUPLE OF
HOURS. THIS BOUNDARY WILL BE THE FOCUS OF INITIAL STORM
DEVELOPMENT, WITH THESE STORMS HAVING ACCESS TO 35-50 KTS OF
EFFECTIVE BULK SHEAR AND 1500-2000 J/KG OF MLCAPE. THERE ARE
QUESTIONS THOUGH ON HOW MUCH SOME HIGH CLOUDS HAVE LIMITED THE
AREA FROM REACHING FULL HEATING POTENTIAL, BUT IF A STORM CAN
GET GOING THEN STEEP MID LEVEL LAPSE RATES OF 7.5-8.5 DEGREES
C/KM AND MOSTLY STRAIGHT, ELONGATED HODOGRAPHS WILL FAVOR LARGE
HAIL TO AROUND 2 INCHES IN DIAMETER OR LARGER. THE SECONDARY
THREAT WILL BE DAMAGING WIND GUSTS UP TO 70 MPH. IF A STORM CAN
GET ROOTED TO THE AFOREMENTIONED SURFACE WARM FRONT, THEN A
TORNADO OR TWO WILL ALSO BE POSSIBLE. CAN'T RULE OUT A STRONG
TORNADO EITHER, PRIMARILY OVER SOUTHWEST MINNESOTA. AS THE LOW
PRESSURE SYSTEM DRIFT ACROSS THE AREA, A FEW ADDITIONAL SHOWERS
AND STORMS LOOK TO DEVELOP FARTHER SOUTH ACROSS NORTHWEST IOWA
(DOWN TO ABOUT IA HIGHWAY-3, OR JUST NORTH OF US HIGHWAY-20)
WITHIN THE WARM SECTOR AROUND SUNSET. THESE STORMS COULD ALSO BE
ON THE STRONG TO SEVERE SIDE, WITH AN ISOLATED INSTANCE OF
QUARTER SIZED HAIL AND 60 MPH AS THE THREATS.
SHOWERS AND STORMS WILL EXIT OFF TO OUR EAST BY THE MID
EVENING HOURS, LEAVING MOSTLY QUIET CONDITIONS IN ITS WAKE. A FEW
SHOWERS MAY DEVELOP IN CENTRAL SOUTH DAKOTA PRIOR TO DAYBREAK
TUESDAY, BUT DRY AIR SHOULD WIN OUT AND PREVENT MOST IF NOT ALL OF
THIS FROM REACHING THE GROUND. PATCHY FOG WILL ALSO BE POSSIBLE
BY EARLY TUESDAY MORNING ACROSS PORTIONS OF NORTHWEST IOWA AND
SOUTHWEST MINNESOTA AS WINDS TURN LIGHT AND VARIABLE OVERNIGHT
AND AMPLE MOISTURE REMAINS IN PLACE. TEMPERATURES TONIGHT DROP
MAINLY IN THE 40S, THOUGH SOME 50S ARE POSSIBLE IN OUR
EASTERNMOST AREAS. LOW CHANCES FOR SHOWERS CONTINUE INTO THE DAY
ON TUESDAY, BUT ACTIVITY IS EXPECTED TO REMAIN SPOTTY AT BEST
AS RAIN CONTINUES TO BATTLE A DRY SUB CLOUD LAYER. HIGHS WILL
RANGE FROM THE 60S NORTHWEST TO 70S SOUTHEAST. RAIN CHANCES LOOK
TO INCREASE TUESDAY NIGHT INTO WEDNESDAY AS TWO SHORTWAVE
TROUGHS IMPACT OUR AREA. THE BEST CHANCES OF RAIN AND STORMS
LOOK TO BE OVER NORTHWEST IOWA AND ADJACENT AREAS OF NEBRASKA,
SOUTH DAKOTA, AND MINNESOTA. AT THIS TIME, SEVERE WEATHER LOOKS
UNLIKELY WITH THIS SYSTEM AS THE BETTER INSTABILITY LOOKS TO BE
OFF TO OUR SOUTH AND EAST.
RAIN AND STORMS EXIT OFF TO OUR EAST BY WEDNESDAY NIGHT, LEADING TO
A DRY THURSDAY. WINDS LOOK TO INCREASE ON THURSDAY ESPECIALLY WEST
OF I-29 CLOSER TO A DEEPENING SURFACE LOW, AND WINDS MAY TAKE ON A
SOUTHWESTERLY COMPONENT ESPECIALLY IN SOUTH CENTRAL SOUTH DAKOTA.
THIS COULD LEAD TO ANOTHER DAY WITH HIGHER FIRE DANGER AS
TEMPERATURES WILL BE WARM AND RELATIVE HUMIDITY VALUES DROP TO 25%
OR BELOW MAINLY ALONG AND WEST OF THE JAMES RIVER. STILL SOME
UNCERTAINTY INTO HOW BREEZY THE WINDS WILL BE, SO KEEP UP TO DATE
WITH THE LATEST FORECAST. NOT TOO MUCH TIME TO LOOK INTO THE
EXTENDED FORECAST GIVEN THE NEAR TERM SEVERE WEATHER THREAT, BUT
GUIDANCE IS IN FAIRLY GOOD AGREEMENT THAT THE WESTERN TROUGH
WILL BEGIN TO MOVE INTO OUR AREA BY THE END OF THE WORK
WEEK/EARLY WEEKEND. THIS COULD BRING MORE RAIN AND STORMS TO OUR
AREA ON FRIDAY AND THEN COLDER WEATHER INTO SATURDAY AS
GUIDANCE INDICATES A STRONGER PUSH OF COLD AIR ADVECTION BEHIND
THIS SYSTEM.
AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/
ISSUED AT 1218 PM CDT TUE APR 14 2026
VFR CONDITIONS EXPECTED THIS AFTERNOON INTO THIS EVENING WITH
NORTHERLY WINDS TURNING LIGHT AND VARIABLE INTO TONIGHT. A FEW
THUNDERSTORMS WILL MOVE TOWARDS THE HIGHWAY 20 CORRIDOR IN NORTHWEST
IOWA BY DAYBREAK INTO WEDNESDAY MORNING, THOUGH UNCERTAINTY REMAINS
ON JUST HOW FAR NORTH THESE STORMS WILL MAKE IT. ENOUGH CONFIDENCE
TO AT LEAST INCLUDE A PROB30 GROUP AT KSUX FOR -TSRA, BUT TRENDS
WILL BE MONITORED. WINDS WILL REMAIN MOSTLY LIGHT AND VARIABLE INTO
THE DAY ON WEDNESDAY.
FSD WATCHES/WARNINGS/ADVISORIES
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
UPDATE...SG
DISCUSSION...SAMET
AVIATION...SAMET
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