420
FXUS63 KFSD 090802
AFDFSD
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
302 AM CDT THU JUL 9 2026
KEY MESSAGES
- FOG, INCLUDING LOCALLY DENSE FOG, CONTINUES THROUGH THE
THURSDAY MORNING COMMUTE. BE PREPARED FOR RAPIDLY CHANGING
VISIBILITY INTO MID MORNING, WHICH MAY DROP BELOW TWO MILES AT
TIMES.
- HIGH TEMPERATURES REMAIN ON TRACK TO RISE TO THE 90S TO 100
DEGREE MARK TOWARDS THIS WEEKEND AND INTO EARLY NEXT WEEK. BE
PREPARED TO ALTER OUTDOOR PLANS TO REDUCE RISK OF HEAT
ILLNESS.
- MOSTLY DRY CONDITIONS ARE EXPECTED INTO EARLY NEXT WEEK.
UPDATE
ISSUED AT 301 AM CDT THU JUL 9 2026
FOG AND STRATUS ARE EXPANDING OVER THE FORECAST AREA THIS MORNING,
CONTINUING INTO THE MID MORNING HOURS. THROUGH 2:30 AM CDT,
VISIBILITY REMAINS AT OR ABOVE 4 MILES, BUT GUIDANCE CONTINUES TO
SHOW SOME LOW (35% CHANCE OR LESS) PROBABILITY OF VISIBILITY FALLING
BELOW 2 MILES. MAY SEE SOME BRIEF VISIBILITY BELOW ONE MILE IF SOME
HI-RES GUIDANCE IS TO BE BELIEVED. CAMS REMAIN CONSISTENT ON SOME
ADDITIONAL SHOWER DEVELOPMENT LATER THIS MORNING FOR NORTHWESTERN
IA. CONFIDENCE IS LOW BUT CAN'T RULE OUT A SPRINKLE WITH THE STRATUS.
CONDITIONS TODAY ARE EXPECTED TO REMAIN DRY WITH HIGHS IN THE UPPER
70S TO UPPER 80S AND A MIX OF CLOUDS AND SUN. A TROUGH IS EXPECTED
TO MOVE INTO THE WESTERN DAKOTAS/NE LATER THIS AFTERNOON THROUGH
TONIGHT. MUCH OF THE GUIDANCE SPLITS THE BETTER FORCING AROUND OUR
FORECAST AREA, WITH THE CAMS FOLLOWING SUIT (TAKING CONVECTION
EITHER NORTH OR SOUTH), OR SHOWING CONVECTION WEAKEN ON APPROACH.
WITH THAT, CAN'T ENTIRELY RULE OUT AN ISOLATED SHOWER/STORM THROUGH
SOUTH CENTRAL SD INTO THE MO RIVER VALLEY LATE THIS EVENING INTO
TONIGHT IF SOMETHING CAN MOVE INTO OUR AREA FROM THE WEST. IF THIS
OCCURS, SEVERE WEATHER IS NOT EXPECTED WITH THE LACK OF SHEAR.
SHOWERS MAY LINGER INTO FRIDAY MORNING AS THE SUBTLE WAVE MOVES
SOUTH OF THE AREA, BUT CONFIDENCE IN COVERAGE IS LOW (LESS THAN 20%).
FOCUS FOR THE FORECAST REMAINS ON THE HEAT BUILDING IN FOR THE
WEEKEND AND EARLY NEXT WEEK. ENSEMBLE PROBABILITIES OF HIGHS
EXCEEDING 95 DEGREES SUNDAY INTO EARLY NEXT WEEK REMAIN MODERATE TO
HIGH (OVER 55%) FOR AREAS ALONG AND WEST OF I-29. IF YOU HAVE
OUTDOOR PLANS, BE PREPARED TO ALTER THEM TO REDUCE THE RISK OF HEAT
ILLNESS.
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...SG
DISCUSSION...MEYERS
AVIATION...AJP
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