textproduct: Sioux Falls

KEY MESSAGES

- Patchy fog is possible tonight near and east of I-29. Any fog that does develop should burn off by mid morning.

- Dry conditions and seasonable temperatures will prevail through the rest of the weekend.

- Shower and storm chances return Monday night into Wednesday. An isolated strong to severe storm is possible in portions of southeast South Dakota Monday evening, if storms can develop.

UPDATE

Issued at 851 PM CDT Sat Aug 1 2026

No significant changes to the forecast this cycle. Winds tonight will become light and variable to calm. Areas along and east of I-29 look the most likely to become calm. Here patchy fog may form early Sunday morning, mainly along low areas and water ways. Fog should burn off by mid-morning. Lows for tonight will be in the mid 50s to low 60s over central South Dakota.

Surface high pressure moves off to the east Sunday morning turning winds to the south. During the day a lee trough will form along the eastern side of the northern Rockies and then push to the east as an upper wave deepens over the MT/ND/CAN border. This will work to induce a strong 40-50 kt LLJ and compress the surface pressure gradient. At the surface this will translate into strengthening winds through Sunday afternoon. Along and west of I-29 gusts will be 20-30 kts. Winds to the east will be generally less than 20 kt for most of the day. Highs will be warmer for Sunday, in the 80s to low 90s.

As the larger system slowly moves east overnight the strong winds will progress east as well. Monday 20-30 kt gusts become widespread across the region. Highs will climb once again into the 80s and low 90s. Monday late afternoon and into the overnight chances for showers and thunderstorms return. However, there remains high uncertainty in the strength and coverage of storms. This is mainly due to the best instability and mid-level lapse rates being off set from the best deep layer shear. In addition, model soundings indicate the environment will be strongly capped. For more on storm chances please see the Discussion below.

DISCUSSION

Issued at 216 PM CDT Sat Aug 1 2026

High pressure continues to push through the forecast area this afternoon. This has allowed for high temperatures to warm to the upper 70s and 80s while winds remain light. These pleasant conditions will persist for the rest of today. Winds will remain elevated through the night as low level pressure gradients tighten as the surface high pressure system passes off to the southeast. Some fog is possible for locations east of I-29 tonight where the lightest winds will reside.

Sunday will be a slightly warmer day with high temperatures warming to the 80s to low 90s. The low level pressure gradients will tighten a bit more for the day, resulting in southerly gusts up to 20-35 mph. The strongest gusts will occur west of I-29, an especially west of the James River. After a breezy Summer day, an incoming upper level wave will result in a strengthening low level jet for the evening and overnight hours. This will keep winds elevated through the night and low temperatures on the low side with lows only falling to the upper 50s and 60s. A few locations could see lows bottom out around 70F.

The next chance for showers and thunderstorms look to return to the area on Monday. Some uncertainty remains as a cold front will be situated west/northwest of the forecast area. Storms could develop on the front during the afternoon and evening timeframe but this potential is uncertain as a stout elevated mixed layer (EML) will be in place, creating a large cap. The latest REFS supports this as it shows a straight 100% chance for convective inhibition (CIN) values of -100 J/kg or less. However, some of the latest models show the front pushing through the forecast area during the overnight hours, which could lead to some convective development along the elevated portion of the front. Tough to say if this potential convection will be strong to severe as even the elevated portion of the front may reside just ahead of the greater vertical shear. Something to watch over the next day or two. Otherwise, Monday will be near to above seasonable with highs in the 80s to low 90s.

The elevated front will slowly push through the rest of the forecast area on Tuesday. With continued shortwaves passing over the elevated front, rain looks to persist along the front for the entirety of Tuesday. The ensembles support this as they show a 30-70% chance for rainfall totals to exceed a tenth of an inch near and south of I-90. Any appreciable instability looks to reside southeast of the forecast area, which should keep severe storm chances at bay. Can't rule out a stray rumble of thunder though. Widespread cloud cover and rain will keep temperatures cooler, down to the 70s across the area.

Some light rain could continue through Wednesday before completely exiting the area. Wednesday will see highs below average again in the 70s before highs warm back up to near seasonable in the 80s to low 90s on Thursday, Friday, and Saturday. Chances for rain are uncertain for the end of next week due to the increasing variance in the upper level pattern. But if latest trends of broad troughing over the Northern Plains holds, then rain chances could perhaps increase as we get closer to this period of time.

AVIATION /00Z TAFS THROUGH 00Z MONDAY/

Issued at 615 PM CDT Sat Aug 1 2026

VFR conditions are expected to prevail for the duration of the period. Winds will become light and variable overnight. Patchy fog may develop as a result, mostly along water ways and low areas. Fog should burn off by mid-morning.

Skies will be mostly clear, but will be obscured partially by wildfire smoke. Smoke should remain aloft and not impact flight operations. Early Sunday morning winds will become southerly and begin to increase over central South Dakota. Stronger winds spread east through the day, gusting 20-30 kts for areas along and west of I-29. The strongest gusts are expected over central South Dakota. To the east gusts are much lower at 20 kts or less. Gusty winds continue through the end of the period.

FSD WATCHES/WARNINGS/ADVISORIES

SD...None. MN...None. IA...None. NE...None.