textproduct: Sioux Falls

KEY MESSAGES

- Winds increase through the day today, reaching 25-35 mph along and west of I-29 this afternoon. Gusty winds gradually spread east through the evening and overnight.

- Dry conditions and seasonably warm temperatures continue today into mid-afternoon Monday.

- 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 430 AM CDT Sun Aug 2 2026

Though not as evident on satellite this morning, surface obs and webcams do support development of patchy fog, mainly confined to river valleys from around Yankton on the Missouri River into northwest Iowa. Fog may be locally dense with visibility 1/2 mile or less, but most areas should remain above 1-3 miles.

With increasing southeast to south winds today, feel we could see another day of temperatures exceeding NBM guidance and have nudged highs up a few degrees, especially west of I-29 where deeper mixing will be favored. That said, still seeing broad coverage of smoke aloft, so did not push highs too far with concerns that smoke could limit temps from reaching their full potential. With the surface ridge lingering near to east of IA/MN Highway 60 into this afternoon, these areas should see less favorable mixing, so did not deviate from the NBM in our eastern counties.

Still looking at a conditional severe risk Monday evening as the cold front pushes in, though strength of a capping inversion remains a concern that could limit storm development. If storms can form as depicted by a few of the CAMs, isolated damaging winds would be the main threat. Hail size may be limited by the warm mid-levels, though marginally severe hail could occur with the strongest updrafts given steep mid-level lapse rates. Again, that is all contingent on the front providing enough forcing to break the cap, and as such, confidence in timing and location of potential storms is low.

Little change through the mid-week period, though trends have shifted lingering rain chances slightly south for Wednesday with low (20-30%) chances focused along the Highway 20 corridor.

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 /18Z TAFS THROUGH 18Z MONDAY/

Issued at 1232 PM CDT Sun Aug 2 2026

VFR conditions are expected for the TAF period. Light southeasterly winds begin the TAF period. The southeasterly winds will remain elevated through the overnight hours as the low level jet (LLJ) strengthens aloft. This will result in low level wind shear (LLWS) for locations along and west of the James River tonight. The LLWS will come to an end in the morning hours but breezy southerly winds with gusts up to 20-35 knots will end the period.

Isolated valley fog is possible tonight mainly across parts of northwest Iowa where winds are weakest.

FSD WATCHES/WARNINGS/ADVISORIES

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