018
FXUS63 KFSD 071150
AFDFSD
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
650 AM CDT FRI AUG 7 2026
KEY MESSAGES
- AREAS OF FOG WILL CONTINUE THROUGH MID-MORNING. LOCALLY DENSE
PATCHES COULD LEAD TO VISIBILITIES AS OF A MILE OR LESS AT
TIMES.
- SCATTERED SHOWERS WITH ISOLATED THUNDERSTORMS WILL CONTINUE
THROUGH LATE MORNING ESPECIALLY ACROSS SOUTHWESTERN MN BE
POSSIBLE. IF A STRONGER STORM DEVELOPS, GOLF BALL SIZED HAIL
AND DAMAGING WINDS UP TO 60 MPH WOULD BE THE PRIMARY THREATS.
- A SOMEWHAT UNSETTLED WEATHER PATTERN WITH LOW PREDICTABILITY
WILL BEGIN TO BRING DAILY RISKS FOR THUNDERSTORMS INTO NEXT
WEEK. A FEW OF THESE MAY BE STRONG TO SEVERE.
UPDATE
ISSUED AT 358 AM CDT FRI AUG 7 2026
TAKING A LOOK ACROSS THE AREA, THE FORECAST REMAINS ON TRACK WITH
THE MAIN FOCUS BEING ON THE DEVELOPING FOG AND SHOWERS. STARTING
WITH FOG, ELEVATED DEW POINTS AND A SLIGHTLY WARMER AIR MASS ALOFT
HAVE LED TO SOME ADVECTION FOG DEVELOPING THIS MORNING. WHILE
COVERAGE IS MOSTLY PATCHY, THERE COULD BE A FEW LOCALLY DENSE AREAS
MAINLY ALONG OUR WATERWAYS AND LOW-LYING AREAS WHERE VISIBILITIES AS
LOW AS 1 MILE WILL BE POSSIBLE. WITH THIS MIND, MAKE SURE TO DRIVE
WITH CAUTION WHEN MAKING THOSE MORNING COMMUTES. SHIFTING TO OUR
PRECIPITATION CHANCES, WE CONTINUE TO SEE SCATTERED SHOWERS WITH
ISOLATED THUNDERSTORMS DEVELOPING THIS MORNING MAINLY IN RESPONSE TO
A NOCTURNAL LLJ AND BITS OF ISENTROPIC LIFT AHEAD OF A COLD FRONT.
WHILE WE COULD SEE THIS ACTIVITY FESTER ACROSS PARTS OF THE AREA
OVER THE NEXT SEVERAL HOURS, MOST GUIDANCE CONTINUE TO HIGHLIGHT
PORTIONS OF SOUTHWESTERN MN AS THE MAIN AREA OF CONCERN FOR ANYTHING
STRONGER AS THE COLD FRONT APPROACHES. IF A STRONGER STORM OR TWO
CAN GET GOING, THE MAIN CONCERNS WOULD BE LARGE HAIL UP TO GOLF BALL
SIZE AND DAMAGING WINDS UP TO 60 MPH. NONETHELESS, WITH THE FAIRLY
PROGRESSIVE NATURE OF THE FRONT; THE WINDOW FOR ANY STRONGER
ACTIVITY WOULD BE NARROW MAYBE 2-4 HOURS AT MOST WITH THE FOCUS
BEING BETWEEN 6AM-10AM. LASTLY, SHOULD SEE QUIETER CONDITIONS RETURN
INTO THE EARLY AFTERNOON WITH HIGHS MAINLY IN THE LOW TO UPPER 80S
EXPECTED.
DISCUSSION
ISSUED AT 202 PM CDT THU AUG 6 2026
THIS AFTERNOON: WEAK TROUGHING SLIDING THROUGH THE REGION THIS
AFTERNOON HAS KEPT A NARROW CORRIDOR OF MID-LVL MOISTURE STRETCHING
FROM NORTHERN NEBRASKA INTO WESTERN MINNESOTA. THIS MOISTURE,
CONFINED WITHIN AN AREA WHERE H850 MB FLOW 30-40 KNOTS, MAY
EVENTUALLY LEAD TO ISOLATED HIGH BASED SHOWERS OR THUNDERSTORMS
LATER THIS AFTERNOON. CONFIDENCE ON DEVELOPMENT REMAINS LOW, AND
WILL KEEP POPS BELOW 20% ATTM. ELSEWHERE, SOUTHERLY WINDS ARE
INCREASING, FINALLY MIXING OUT LOW-STRATUS AND FOG. HIGH
TEMPERATURES CLIMB INTO THE UPPER 80S WEST OF THE JAMES RIVER TO THE
LOWER 80S FURTHER EAST.
TONIGHT: TWO CONCERNS IN THE OVERNIGHT PERIOD. FIRST OF ALL,
SOUTHERLY WINDS SHOULD CONTINUE TO TRANSPORT LOW-LVL MOISTURE
NORTHWARD, PUSHING DEW POINTS INTO THE MID-60S. SHOULD WINDS
WEAKEN SUFFICIENTLY AND TEMPERATURES DROPS NOT BE OVERLY
IMPACTED BY WIDESPREAD WILDFIRE SMOKE ALOFT, THEN AREAS OF FOG
MAY ONCE AGAIN DEVELOP ALONG AND SOUTH OF I-90. HREF
PROBABILITIES FOCUS A 70% PROBABILITY OF <1 MILE VISIBILITY
ALONG AND SOUTHEAST OF A LINE FROM YANKTON TO WINDOM. HOWEVER,
IF THE SECOND CONCERN WE'LL DISCUSS NEXT TAKES PLACE, THEN THOSE
FOG PROBABILITY MAY DROP SIGNIFICANTLY.
THAT SECOND CONCERN IS A RISK FOR ELEVATED CONVECTION BY DAYBREAK.
THE PESKY QUASI-NORTHWEST FLOW HAS THE POTENTIAL TO BRING SUBTLE MID-
LVL VORTICITY INTO THE AREA BY DAYBREAK. GUIDANCE IS ALL OVER
THE PLACE, WHICH IS TYPICAL IN THIS SETUP, SUGGESTING EITHER
MINIMAL TO NO CONVECTION, OR FAIRLY WIDESPREAD STORM
DEVELOPMENT. FROM A PARAMETER PERSPECTIVE INCOMING CAA AOA
850:700 MB WILL CREATE A STEEPENED MID-LVL LAPSE RATE, BUT ALSO
PUSH MUCAPE OVER 2000 J/KG. SHEAR REMAINS A BIT MARGINAL AOA 20
KNOTS, SUGGESTING CONVECTION MAY STAY A BIT LESS ORGANIZED.
HOWEVER ANALOG SOUNDINGS INDICATE POTENTIAL FOR GOLF BALL HAIL
WITH FREEZING LEVELS NEAR 11K FT AGL, WITH SOME MODEST MID-LVL
DRY AIR ALSO SUGGESTING A FEW STRONGER WIND GUSTS THAT MAY MAKE
IT THROUGH THE STABLE BOUNDARY LAYER. IF THIS THREAT DEVELOPS
STORMS WOULD PUSH SOUTHEAST WITH THE MEAN FLOW AND EXIT LATE
MORNING.
FRIDAY: THE INITIAL MORNING CONVECTION WILL PRECEDE A COLD FRONT
THAT WILL PUSH SOUTHEAST DURING THE DAY. TEMPERATURES BEHIND THIS
FRONT WILL NOT BE ALL THAT COOL, WITH HIGHS AGAIN CLIMBING INTO THE
LOWER TO MIDDLE 80S. THE REST OF THE DAY AND EVENING WILL BE QUIET.
AFTER MIDNIGHT HOWEVER, SOME GUIDANCE IS SHOWING ANOTHER WAVE MOVING
THROUGH CENTRAL SD AND INTO NE. SHOULD THIS WAVE DEVELOP, THERE MAY
BE SUFFICIENT CONVERGENCE ON THE LLJ TO INDUCE SCATTERED
CONVECTION IN CENTRAL AND SOUTH CENTRAL SOUTH DAKOTA AFTER 3AM.
ISOLATED HAIL WILL BE THE MOST LIKELY RISK WITH THESE STORMS.
SATURDAY/SUNDAY: THERE REMAINS QUITE A BIT OF UNCERTAINTY HEADING
INTO THE UPCOMING WEEKEND GIVEN THE SYNOPTIC FLOW PATTERN.
SATURDAY MORNING CONVECTION SHOULD CONTINUE TO PUSH AWAY FROM
THE CWA IN THE MORNING HOURS, WHICH WOULD SUGGEST STABILIZATION
IN THE TRI-STATE AREA FOR THE REST OF THE DAY. HOWEVER THE
NOCTURNAL IGNITION OF THE LLJ WOULD POSE SOME RISK FOR RENEWED
ELEVATED STORMS INTO SUNDAY MORNING SOUTH OF I-90. THERE SEEMS
TO BE A BIT MORE AGREEMENT BY LATE SUNDAY INTO MONDAY AS A
STRONGER WAVE MOVES THROUGH THE DAKOTAS LATE IN THE EVENING.
DEPENDING ON THE DEGREE OF INSTABILITY IN THE REGION, THIS COULD
SERVE AS A REASONABLE SETUP FOR A NOCTURNAL MCS GIVEN THE
INTENSIFYING 850MB SOUTHERLY FLOW AND INCREASED MID-LVL
WESTERLIES. CONTINUE TO MONITOR SEVERE WEATHER OUTLOOK RISKS
INTO MONDAY MORNING.
MONDAY-WEDNESDAY: THERE WILL REALLY BE NO CHANGE IN THE FORECAST
INTO THE MIDDLE OF THE WEEK AS THE REGION REMAINS UNDER SLIGHT
NORTHWESTERLY FLOW ALOFT. THIS FLOW WILL KEEP A PERSISTENT RISK FOR
DAILY CONVECTION, THOUGH WITH EXTREMELY LOW CONFIDENCE AND
PREDICTABILITY UNTIL A DAY OR SO BEFORE. TEMPERATURES MAY FALL
BACK SLIGHTLY INTO THE LOWER TO MIDDLE 80S NEAR THE SEASONAL
NORMALS.
AVIATION /12Z TAFS THROUGH 12Z SATURDAY/
ISSUED AT 642 AM CDT FRI AUG 7 2026
A MIX OF CONDITIONS CONTINUES THIS MORNING MAINLY DUE TO FOG AND
SCATTERED SHOWERS AND THUNDERSTORMS. SHOULD SEE THE FOG GRADUALLY
ERODE BY MID-MORNING WITH THE RETURN OF DIURNAL HEATING. ANY
LINGERING SHOWER/THUNDERSTORM ACTIVITY WILL CONTINUE TO PROGRESS
EASTWARDS WITH THE COLD FRONT THROUGH THE MORNING HOURS WITH
MAINLY VFR CONDITIONS RETURNING BY EARLY AFTERNOON. OTHERWISE,
SOUTHERLY SURFACE WINDS WILL BECOME MORE NORTHWESTERLY BEHIND
THE PREVIOUSLY MENTIONED FRONT WITH WIND GUSTS BETWEEN 20-30 MPH.
FSD WATCHES/WARNINGS/ADVISORIES
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
UPDATE...05
DISCUSSION...DUX
AVIATION...05
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