249 FXUS63 KFSD 050742 AFDFSDArea Forecast Discussion National Weather Service Sioux Falls SD 242 AM CDT Fri Sep 5 2025
.KEY MESSAGES...
- Fall-like temperatures in the 50-60s today. Afternoon clouds may produce some isolated sprinkles to light showers north of I-90.
- Breezy afternoon winds will gust between 25-35 mph with strongest winds west of I-29.
- Lows Saturday morning will fall to the mid 30s along and north of I-90. Patchy frost may be possible.
- Next week there are some chances for showers and thunderstorms, though many details are unknown at this time.
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.DISCUSSION... Issued at 240 AM CDT Fri Sep 5 2025
TODAY: Northwesterly flow from the surface through the upper levels will bring down strong CAA throughout the day. Temperatures in the mid-levels will cool through the day, decreasing to 2-6 degrees C. Despite good mixing through approximately the 800 mb layer, these cooler temperatures will only allow highs to rise to the upper 50s to low 60s. We`ll begin the day with partly cloudy skies but as we enter the afternoon hours clouds will increase as moisture from Canada is bought south on a shortwave associated with a large upper low spinning over eastern Canada. Weak instability above the mixed layer will allow clouds to build into towering cumulus, resulting in afternoon mostly cloudy skies. While we do not expect much to come from these clouds, a roughly 5000 ft deep saturated layer may result in a few isolated sprinkles to light showers north of I-90. In addition, with winds well aligned through the depth of the column, we can expect stronger gusts to reach the surface as we reach peak mixing this afternoon. Northwesterly gusts of of 30-35 mph can be expected for areas west of I-29. Areas to the east can expect slightly lower gusts of 20-25 mph. Winds will decrease after sunset, becoming light and variable overnight. Lows are expected to fall to the upper 30s to low 40s.
THE WEEKEND: Surface high pressure settles over the region for the weekend. Though flow aloft remains primarily northwesterly, some weak subsidence aloft will help warm the mid-levels back into the 8-12 degree C range for Saturday. Good mixing again will help us tap into those slightly warmer temperatures and warm our surface highs into the 60s. Diurnal winds will be slightly breezy with gusts generally 20 mph or less. As we lose afternoon heating those winds will become light and variable. With mostly clear skies, maximum radiational cooling will be achieved. Lows for Saturday will dip into the mid 30s to low 40s. Isolated pockets of frost are possible along north of I-90. Tender outdoor plants may need to be taken inside or covered. Sunday the surface high shifts east, turning our winds southerly. WAA at the surface and in the mid-levels helps warm highs into the upper 60s and low 70s. Winds overnight remain a little more mixy as a surface low pressure begins to move east out of Wyoming. This will help overnight lows stay out of frost range, in the mid 40s to low 50s.
NEXT WEEK: By Monday morning the low pressure will be over western South Dakota and an associated warm front will lift north through the region. This may act to trigger some isolated showers and thunderstorms Monday morning. Monday afternoon into Tuesday morning the main mid to upper wave will pass over the region, bringing renewed chances for thunderstorms. A moderately unstable thermodynamic profile may allow for some of these storms to be on the strong side. Though, there is very low agreement on long range guidance to speculate on the details at this time. Periodic waves keep storm chances in the forecast for the second half of next week. Highs will be warmer, in the upper 70s to low 80s for Monday through Thursday.
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.AVIATION /06Z TAFS THROUGH 06Z SATURDAY/... Issued at 1001 PM CDT Thu Sep 4 2025
Scattered mid-lvl clouds continue through the overnight hours as northwesterly winds slowly subside.
Low-mid lvl clouds build in from the north by mid to late morning of Friday. Initially some high end MVFR ceilings may develop, but will quickly lift into VFR levels through the afternoon. A very low probability of sprinkles may form by mid- afternoon. Gusts over 20 knots may be possible through the afternoon.
Ceilings slowly dissipate with the loss of daytime heating in the evening, leaving a light and variable wind into Friday night.
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.FSD WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. IA...None. NE...None.
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DISCUSSION...AJP AVIATION...Dux
NWS FSD Office Area Forecast Discussion