textproduct: Sioux Falls

KEY MESSAGES

- Isolated thunderstorms may form across south central South Dakota and north central Nebraska after midnight, bringing low risks for hail. Widespread severe weather is not anticipated.

- Considerable uncertainty remains in the forecast for much of the upcoming 5 days, with relatively low, but not zero, risks for rain each day.

- Severe weather risks also remain uncertain, with some focus for stronger storms Saturday night, late Sunday into Sunday night, and again Monday night into Tuesday

- Temperatures remain near seasonal normals into mid-week, with potential cooler weather late next week.

DISCUSSION

Issued at 105 PM CDT Fri Aug 7 2026

THIS AFTERNOON: Convection earlier this morning continues to move east and away from the area early this afternoon. A cool front also continues to push southeast, already well into NW Iowa. Behind this boundary, periods of very low stratus with drizzle have been reported. As stronger dry air advection moves southeast, we should continue to see stratus erode. Temperatures with all the cloud cover have been stuck in the upper 60s to lower 70s, with a small areas ahead of the front in the lower 80s. As long as clouds clear by mid-afternoon, there should be enough time for highs to still reach the upper 70s to lower 80s.

TONIGHT: High level wildfire smoke will continue to leave a milky sky overhead. However we've seen little impact on overnight lows with this smoke, so with the continued dry air advection southward this afternoon and evening, we are likely to see low temperatures in the lower 50s by Saturday morning. One area to watch after midnight will be in central Nebraska into central South Dakota, as guidance continues to hint as a subtle wave entering the Dakotas. This wave should induce a stronger LLJ which in return may produce enough focused convergence for a few stronger thunderstorms. The general track of any strong activity should be south southeast along the elevated instability axis into east central Nebraska. Nevertheless, if a storm could develop near Gregory County, 1.5" hail would be the main risk.

SATURDAY: Forecast confidence remains lower for Saturday regarding precipitation chances. Guidance is quite split on where the axis of stronger low-lvl jet convergence will drift through the day. Most of this uncertainty is due to poor model resolution of any weak vorticity passing through the 700:500 layer. Some models keep the best lift bottled up south of the Missouri River with an MCS moving towards western Iowa. Others have a wave further north, pushing the LLJ towards I-29 by mid-day and leaving a few lingering showers and clouds overhead into the afternoon. What fairly certain is that MUCAPE will struggle to lift northeast, keeping any very isolated severe weather risk focused along or south of the MO river into mid- day. By the late afternoon and evening, the instability pool does drift northward, however soundings also show a fairly stout capping layer overhead that should inhibit convection given weak and transient lift. One note: If we do end up with at least a thick mid- lvl cloud field over the heart of the CWA by mid-day, then high temperatures could be significantly impacted and convection risks lower even further. Rain chances may continue Saturday night, though focus moreso over Iowa and western Minnesota as the LLJ redevelops and interactions with a developing elevated frontal boundary. Confidence is very low with these precipitation risks.

SUNDAY: Any nocturnal convection Saturday night could play a role in redevelopment on Sunday. Again though, the myriad of potential small shortwaves moving through the NW flow is problematic with model guidance which shows a wide range of solutions. Some guidance shows a mostly dry day and night with subsidence and high pressure moving through. Others maintain a surface and elevated frontal boundary in the area, with increasing lift late in the day and some isolated strong to severe storms. Given the spread in models, low probabilities spread through the evening and early overnight models continues to be the best way to suggest the potential at this stage.

MONDAY-THURSDAY: There will really be no change in the forecast into the middle of the week as the region remains under slight northwesterly flow aloft. This flow will keep a persistent risk for daily convection, though with extremely low confidence and predictability until a day or so before. There continues to be some focus for lift around the Monday night/Tuesday and again Wednesday night and Thursday timeframe where an MCS could form. Temperatures may fall back slightly into the lower to middle 80s near the seasonal normals, with potential for a larger cooldown by next weekend.

AVIATION /18Z TAFS THROUGH 18Z SATURDAY/

Issued at 1150 AM CDT Fri Aug 7 2026

Frontal boundary continues to slide southeast early this afternoon. Immediately preceding the passage of the front we continue to see IFR ceilings and even drizzle move southeast. Continued mixing behind the boundary will erode this stratus fairly quickly, but cloud cover will spread southeast into NW Iowa this afternoon. Northwest winds may gust to 20-25 mph at times into early evening.

Clear skies are expected overnight, with lingering wildfire smoke aloft. Mid-lvl clouds form over south central SD after midnight, with this area of clouds and potential sprinkles/showers moving northeast towards I-29 by mid-late morning. VFR conditions are likely.

FSD WATCHES/WARNINGS/ADVISORIES

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