490
FXUS63 KFSD 090528
AFDFSD
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
1228 AM CDT THU JUL 9 2026
KEY MESSAGES
- PATCHY DENSE FOG IS POSSIBLE INTO THURSDAY MORNING. BE
PREPARED FOR RAPIDLY CHANGING VISIBILITY AS YOU MAKE YOUR WAY.
- HIGH TEMPERATURES REMAIN ON TRACK TO RISE TO THE 90S TO 100
DEGREE MARK TOWARDS THIS WEEKEND AND INTO EARLY NEXT WEEK.
- THIS WEEKEND AND MOST OF NEXT WEEK ARE EXPECTED TO BE MAINLY
DRY.
UPDATE
ISSUED AT 910 PM CDT WED JUL 8 2026
THE SLOW MOVING QUASI-STATIONARY FRONT FROM THE PAST COUPLE OF DAYS
HAS PUSHED OFF TO THE SOUTHEAST, TAKING OUR SEVERE WEATHER CHANCES
WITH IT. LIGHT NORTHERLY SURFACE WINDS BEHIND THE FRONT HAVE BEGUN
TO COOL THE BOUNDARY LAYER. AS COOLING CONTINUES AN INVERSION WILL
QUICKLY SET IN OVER MUCH OF THE REGION. THIS WILL WORK TO TRAP THE
MOISTURE FROM RECENT RAIN NEAR THE SURFACE. AS WE ENTER THE EARLY
HOURS OF THURSDAY MORNING SURFACE TEMPERATURES ARE EXPECTED TO FALL
TO, OR VERY NEAR TO, THE DEW POINT TEMPERATURES. PATCHY, DENSE FOG
IS LIKELY TO DEVELOP IN RESPONSE, ESPECIALLY ALONG AND EAST OF THE
JAMES RIVER VALLEY. ENSEMBLE PROBABILITIES OF VISIBILITY DECREASING
BELOW 5 MILES IS LOW AT AROUND 30%. HOWEVER, PLEASE ENSURE YOU ARE
PREPARED FOR RAPIDLY CHANGING CONDITIONS. AFTER SUNRISE WINDS WILL
BECOME NORTHEAST TO EAST BUT WILL REMAIN LIGHT. WITH LITTLE MIXING
OCCURRING AS A RESULT, FOG MAY HANG ON UNTIL THE MIDDLE OF THE
MORNING.
THURSDAY WILL BE DRY WITH HIGHS CLIMBING TO AROUND AVERAGE FOR THIS
TIME OF YEAR, IN THE LOW TO MID 80S. THURSDAY EVENING A FAST MOVING
SHORT WAVE COULD BRING RAIN CHANCES TO THE REGION. UNCERTAINTY
REMAINS HIGH AS MOST GUIDANCE HAS THE STORMS EITHER SPLITTING AND
GOING AROUND OUR CWA, OR DISSIPATING RAPIDLY AS THEY MOVE EAST FROM
CENTRAL SOUTH DAKOTA. OVERALL DYNAMICS ARE WEAK, AND SO IF STORMS DO
FORM THE RISK FOR SEVERE WEATHER IS LOW. FRIDAY DURING THE DAY LOOKS
TO BE DRY AND MOSTLY SUNNY WITH HIGHS IN THE MID 80S TO LOW 90S WEST
OF THE JAMES RIVER VALLEY.
THIS WEEKEND A STRONG, HIGH AMPLITUDE HIGH PRESSURE RIDGE WILL BUILD
OVER THE CENTRAL UNITED STATES. THIS RIDGE WILL PERSIST FOR MUCH OF
THE FOLLOWING WEEK. HIGHS DURING THIS TIME WILL BE SEASONABLY WARM
FOR JULY, IN THE 90S WITH A FEW 100S SPRINKLED IN. DEW POINTS WILL
BE IN THE 60S WITH LOW 70S POSSIBLE OVER NORTHWEST IOWA. AS WE HAVE
ENTERED PEAK GROWING SEASON, DEW POINTS MAY BE INFLUENCED BY
EVAPOTRANSPIRATION (AKA CORN SWEAT), RESULTING IN LOCALIZED HIGHER
HUMIDITY. POTENTIALLY DANGEROUS HEAT INDEX VALUES MAY BE POSSIBLE AT
TIMES. PLEASE ENSURE YOU ARE PROPERLY HYDRATED AND TAKE BREAKS OUT
OF THE HEAT. THE FORECAST FOR THIS TIME IS EXPECTED TO REMAIN MOSTLY
DRY.
DISCUSSION
ISSUED AT 208 PM CDT WED JUL 8 2026
A FEW LIGHT RAIN SHOWERS PERSIST ACROSS MAINLY NORTHWEST IOWA THIS
AFTERNOON. A SURFACE TROUGH AND ASSOCIATED COLD FRONT CONTINUE TO
TRACK THROUGH THE FORECAST AREA EARLY THIS AFTERNOON. THE MID LEVEL
CLOUDS ASSOCIATED WITH THESE LIGHT RAIN SHOWERS CONTINUE TO SIT OVER
MAINLY NORTHWEST IOWA AND SURROUNDING LOCATIONS. THIS HAS PREVENTED
LOCATIONS IN THIS AREA FROM HEATING OUT. THE COOLER TEMPERATURES
LOOK TO ALSO DELAY NEW CONVECTIVE DEVELOPMENT AS THE COLD FRONT
PUSHES INTO THIS AREA. STILL, THESE CLOUDS LOOK TO CLEAR/BREAK UP
ENOUGH TO ALLOW ADEQUATE INSTABILITY TO DEVELOP WITH A MAGNITUDE UP
TO ABOUT 2,000 J/KG OVER THE COURSE OF THE AFTERNOON TIMEFRAME.
VERTICAL SHEAR VALUES WILL BE ON THE WEAKER SIDE OF THINGS WITH A
MAGNITUDE OF ROUGHLY 20-30 KNOTS. LATEST HI-RES GUIDANCE SHOWS THAT
A SMALL, BI-MODAL SEVERE WEATHER EVENT IS ON THE TABLE FOR THIS
AFTERNOON AND EVENING. STORMS LOOK TO DEVELOP ON BOTH THE PRE-
FRONTAL TROUGH AND TRAILING COLD FRONT. STORM DEVELOPMENT LOOKS TO
TAKE PLACE ACROSS MAINLY NORTHWEST IOWA AND ADJACENT AREAS THIS
AFTERNOON WITH A TIMEFRAME FROM FROM ABOUT 4 PM TO 10 PM. WITH THE
COLD FRONTAL FORCING, STORMS LOOK TO GROW INTO A LINE AS THEY PUSH
OUT OF THE AREA THIS EVENING. WHILE VERTICAL SHEAR MAGNITUDES WILL
BE ON THE LOWER SIDE, HODOGRAPHS SHOW A WEAK BUT CLASSIC VEER-BACK
PROFILE. WITH WEAK COLD ADVECTION ALOFT, LAPSE RATES WILL STEEPEN
JUST A BIT MORE AND ALLOW FOR A LARGE HAIL THREAT. SOUNDINGS DO SHOW
SLIGHTLY MORE SATURATED PROFILES IN THE HAIL GROWTH ZONE (HGZ) WHICH
WILL TONE DOWN THE HAIL THREAT A BIT, WITH SOME OF THE LARGEST
STONES GROWING UP TO HALF DOLLAR SIZE. DCAPE VALUES WILL BE
SUFFICIENT WITH VALUES UP TO 800 TO 1,000 J/KG, KEEPING A DAMAGING
WIND THREAT IN PLACE WITH THE STRONGEST GUSTS UP TO 65 MPH. THE
LARGE HAIL THREAT WILL COME WITH THE INITIAL STORM DEVELOPMENT
BEFORE TRANSITIONING TO A DAMAGING WIND THREAT AS STORMS GROW
UPSCALE. POCKETS OF MODERATE TO HEAVY RAINFALL COULD RESULT IN
LOCALIZED PONDING IN LOW LYING/URBAN AREAS AS STORMS ROLL THROUGH.
THE STORM THREAT WILL END THIS EVENING, LEAVING MOSTLY QUIET
CONDITIONS FOR THE OVERNIGHT HOURS. LOW TEMPERATURES WILL FALL TO
THE 60S.
SEASONABLE AND MOSTLY DRY CONDITIONS WILL RETURN FOR THE END OF THE
WEEK WITH HIGH TEMPERATURES REMAINING IN THE 80S TO JUST TOUCHING
90F. WINDS WILL BE LIGHT, MAKING FOR A PLEASANT THURSDAY AND FRIDAY.
HEIGHTS BEGIN TO RISE ALOFT ON SATURDAY, BEGINNING TO WARM
TEMPERATURES WITH HIGHS RISING TO THE 80S AND 90S. SUNDAY WILL KICK
OFF THE FIRST DAY OF NEAR TO ABOVE NORMAL TEMPERATURES AS MEDIUM
RANGE AND ENSEMBLE GUIDANCE SHOW A 600 DAM RIDGE BUILDING INTO THE
NORTHERN PLAINS. THIS RIDGE LOOKS TO PERSIST THROUGH THE FIRST HALF
OF NEXT WEEK, BRINING HOT AND HUMID CONDITIONS WITH IT. THE
ENSEMBLES SHOW A 60-100% CHANCE FOR HIGHS TO EXCEED 90F SUNDAY
THROUGH TUESDAY NEAR AND WEST OF I-29. CHANCES FOR EXCEEDING 100F
DROP TO 40-70% FOR THE SAME PERIOD OF TIME WITH TUESDAY HAVING THE
HIGHEST PROBABILITIES. THE ENSEMBLES ALSO SHOW A BROAD 40-100%
CHANCE FOR DEW POINTS TO EXCEED 60F AS WELL. ALL THESE PROBABILITIES
TO SAY THAT HOT AND HUMID CONDITIONS ARE EXPECTED LATE THIS WEEKEND
AND INTO EARLY NEXT WEEK. A FEW ENSEMBLE MEMBERS SHOW THE RIDGE
BEGINNING TO FLATTEN NEXT WEDNESDAY WHICH COULD BEGIN TO TREND
TEMPERATURES DOWN. THERE REMAINS UNCERTAINTY REGARDING HOW LONG THE
RIDGE REMAINS STRONG SO SOMETHING TO KEEP AN EYE ON HEADING
FORWARD.
AVIATION /06Z TAFS THROUGH 06Z FRIDAY/
ISSUED AT 1227 AM CDT THU JUL 9 2026
SCATTERED WEAK THUNDERSTORMS ARE ONGOING ALONG AND SOUTH OF HIGHWAY
20 IN NORTHWEST IOWA AT TIME OF ISSUANCE. WHILE THESE STORMS ARE NOT
EXPECTED TO BECOME SEVERE, THEY MAY PRODUCE WIND GUSTS TO 45 MPH.
STORMS WILL CONTINUE TO MOVE SOUTHEAST AND CLEAR OUT OF THE AREA IN
THE NEXT COUPLE OF HOURS.
A MIX OF VFR AND MVFR IS EXPECTED FOR THE FIRST HALF OF THE PERIOD.
LOW TO MID-LEVEL CLOUDS ARE EXPECTED TO LINGER INTO THURSDAY
MORNING. WINDS ARE LIGHT AND VARIABLE. PATCHY DENSE FOG IS EXPECTED
TO FORM, ESPECIALLY EAST OF THE JAMES RIVER VALLEY. BRIEF PERIODS OF
IFR VISIBILITY AND CEILINGS ARE POSSIBLE. WINDS REMAIN LIGHT AND
VARIABLE THOUGH MOST OF THURSDAY. AS A RESULT FOG MAY LINGER INTO
THE MID-MORNING HOURS BEFORE DAYTIME HEATING BURNS IT OFF. VFR
CONDITIONS ARE THEN EXPECTED TO PREVAIL FOR THE REMAINDER OF THE
PERIOD.
FSD WATCHES/WARNINGS/ADVISORIES
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
UPDATE...AJP
DISCUSSION...MEYERS
AVIATION...AJP
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