765
FXUS63 KFSD 011654
AFDFSD
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
1154 AM CDT FRI AUG 1 2025
KEY MESSAGES
- SURFACE SMOKE WILL CONTINUE TO CAUSE MINOR VISIBILITY IMPACTS
AND HEALTH HAZARDS TO SENSITIVE GROUPS INTO SATURDAY.
- CHANCE FOR SHOWERS/STORMS TOWARD CENTRAL SD TODAY WILL SLOWLY
NUDGE EAST THROUGH THE WEEKEND, REMAINING WEST OF I-29 THROUGH
SATURDAY, THEN WORKING INTO SOUTHWEST MN AND NORTHWEST IA LATER
SATURDAY NIGHT-SUNDAY. THE RISK FOR SEVERE WEATHER THROUGH
SUNDAY IS LOW.
- ANOTHER CHANCE WILL COME TUESDAY NIGHT INTO WEDNESDAY. THIS
PERIOD MAY BRING A GREATER POTENTIAL FOR STRONG TO SEVERE
STORMS, SO SOMETHING TO KEEP AN EYE ON.
DISCUSSION
ISSUED AT 355 AM CDT FRI AUG 1 2025
TODAY-TONIGHT: WATCHING AN AREA OF STORMS MOVING INTO CENTRAL SD
ALONG AN ELEVATED WARM FRONT. THIS ACTIVITY MAY PUSH INTO OUR FAR
WESTERN COUNTIES BY AROUND DAYBREAK, BUT MINIMAL INSTABILITY EAST
OF THE MISSOURI RIVER WILL LIMIT EASTWARD EXTENT. THIS ACTIVITY IS
EXPECTED TO WANE BY MID-LATE MORNING.
OTHERWISE SUBTLE RIDGING ALOFT REMAINS TO OUR WEST, DISRUPTED BY
A CONVECTION-INDUCED WAVE WHICH MAY BRING SOME RAIN/STORM CHANCES
TO AREAS WEST OF TO MAYBE NEAR THE JAMES RIVER. SIMILAR TO THIS
MORNING, INSTABILITY IS RATHER WEAK OUTSIDE OF OUR FAR WESTERN
COUNTIES AND SHEAR IS ALSO ON THE WEAK SIDE. AS A RESULT, THINK
THE POTENTIAL FOR SEVERE STORMS IS LOW, WHICH IS SUPPORTED BY THE
LATEST SPC DAY 1 OUTLOOK WHICH GRAZES WESTERN PORTIONS BRULE AND
GREGORY COUNTIES WITH A MARGINAL (LEVEL 1 OF 5) RISK.
ASIDE FROM THE RAIN/STORM CHANCES IN OUR WEST, TODAY'S WEATHER
WILL AGAIN BE DOMINATED BY DIFFUSE SMOKE ROTATING INTO THE AREA
AROUND THE PROMINENT SURFACE HIGH OVER MINNESOTA. SIMILAR TO
YESTERDAY, WE WILL LIKELY SEE MINOR VISIBILITY RESTRICTIONS AT
TIMES, ALONG WITH AIR QUALITY THAT IS UNHEALTHY, ESPECIALLY FOR
SENSITIVE GROUPS (ORANGE AIR QUALITY INDEX). TEMPERATURES REMAIN
BELOW NORMAL FOR THE START OF AUGUST WITH HIGHS IN THE 70S AND DEW
POINTS "ONLY" IN THE 50S-LOWER 60S.
SATURDAY-MONDAY: WEAK FLOW IN THE MID-UPPER LEVELS IS EXPECTED
THROUGH THIS PERIOD, WITH A MODEST (50-70KT) UPPER LEVEL JET TO
OUR SOUTH SATURDAY, AND A WEAKENING JET TOPPING THE JET OVER THE
CENTRAL ROCKIES SUNDAY INTO MONDAY. AS THE SURFACE HIGH SLOWLY
SLIDES EAST, A MORE SOUTHERLY SURFACE FLOW WILL BEGIN TO BRING AN
INCREASE IN LOW LEVEL HUMIDITY AGAIN, ESPECIALLY BY SUNDAY-MONDAY.
SUBTLE WAVES MAY INTERACT WITH THIS UNSTABLE AIR MASS THAT SLOWLY
EXPANDS EAST TO BRING PERIODIC CHANCES FOR SHOWERS AND STORMS.
HOWEVER, THE WEAK FLOW ALOFT WILL LIMIT SHEAR AND ASSOCIATED
SEVERE STORM POTENTIAL. SOME MACHINE LEARNING PROJECTIONS SHOW A
LOW SEVERE THREAT PERHAPS FLIRTING WITH OUR FAR WESTERN COUNTIES
SUNDAY, SO WILL HAVE TO MONITOR TRENDS THERE, BUT FOR NOW THE LACK
OF SHEAR WILL LIKELY INHIBIT ORGANIZED STRONG TO SEVERE CONVECTION
IN OUR AREA.
TUESDAY-THURSDAY: THE MID-WEEK PERIOD WILL SEE THE MID-UPPER LEVEL
RIDGE SLIDE INTO THE PLAINS, WITH WEAK WAVES SLIDING ACROSS THE
NORTHERN PLAINS AROUND THE TOP OF THE RIDGE. SOME SOLUTIONS DO
BRING AN INCREASE IN SHEAR AT TIMES DURING THIS PERIOD, AND WHILE
AGREEMENT IS NOT GREAT, THERE IS MODERATE CONSENSUS FOCUSED ON THE
TUESDAY NIGHT-WEDNESDAY PERIOD WHERE WE MAY SEE SHEAR/INSTABILITY
SUPPORTIVE OF SOME STRONGER STORMS.
THE UPPER RIDGE WILL ALSO ALLOW WARMER/MORE SEASONABLE AIR (HIGHS
IN THE 80S-LOWER 90S) TO RETURN TO THE REGION, WITH HUMIDITY ALSO
MORE TYPICAL OF EARLY AUGUST (DEW POINTS IN THE 60S TO PERHAPS
LOWER 70S AT TIMES).
AVIATION /18Z TAFS THROUGH 18Z SATURDAY/
ISSUED AT 1153 AM CDT FRI AUG 1 2025
THE MAIN CONCERNS THROUGH THIS PERIOD WILL BE SLIGHTLY REDUCED
VISIBILITIES IN SMOKE. OVERALL THE VISIBILITY SHOULD BE BETWEEN
4 TO 6 MILES AT MOST LOCATIONS. LATER TONIGHT SCATTERED SHOWERS
AND ISOLATED THUNDERSTORMS WILL MOVE INTO CENTRAL SD WITH THE
BETTER CHANCES FROM ABOUT 10Z THROUGH 15Z.
FSD WATCHES/WARNINGS/ADVISORIES
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
DISCUSSION...JH
AVIATION...08
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