textproduct: Sioux Falls

KEY MESSAGES

- Thunderstorm risks continue to remain low into the overnight hours, with some focus along or north of Highway 14, and northwest Iowa after midnight. Marginal hail and 60 mph winds would be the main risks any any storm.

- Late Sunday evening into Monday could be a focus point for strong to severe convection in western into central South Dakota. While uncertain, one or two clusters of severe storms may develop.

- Nearly daily precipitation risks will continue well into next week, however chances remain low due to the high uncertainty in the forecast.

DISCUSSION

Issued at 123 PM CDT Sat Aug 8 2026

THIS AFTERNOON: We're continuing to watch a slowly northeastward advancing mid-lvl cloud deck early this afternoon. This cloud layer marks the advancing edge of moisture (and instability) advecting within the 850:700 mb layer. A parcel lifted from this level still appears to be fighting a bit of inhibition, which will keep only very low PoPs in the forecast as this moves northeast. Elsewhere, wildfire smoke aloft remains quite thick, and may have slight impacts on high temperatures this afternoon.

TONIGHT: The forecast remains somewhat uncertain this evening and overnight, though there are at least better signals for where convection may form after dark today. Latest short term guidance points to two distinct areas of focus. One near the SD/ND border into west central Minnesota where current AC field ends up by sunset. The initiation of at least a 25 to 35 knot LLJ should be enough to develop a few storms. It's possible that a minor shortwave could also drop southeast after midnight helping push this activity towards Highway 14 and SW Minnesota by daybreak. A second area to watch will be northwest and north central Iowa where slightly stronger LLJ convergence develops. Any activity that forms should pass along the far eastern CWA by 12Z. Realistic MUCAPE between 1500-2000 J/KG with 20-25 knots of shear may produce a few stronger storms with large hail.

SUNDAY: A continued uncertain forecast remains for Sunday. Morning convection should weaken by mid-morning as the LLJ weakens and any activity pushes east of the CWA. In it's wake, there remains no strong triggering mechanisms for any convection further west and low- lvl and surface flow may turn more northeasterly by mid-day. Nevertheless while we may see CAPE values push 2500-3000 J/KG, HREF probabilities of less than 100 J/KG CIN remain only around 25%, suggesting that surface based convection may be hard to come by. Wildfire smoke will again be quite thick on Sunday, and have lowered temperatures a degree or two. Though the ongoing drought may also counter act some of those limiting effects.

SUNDAY NIGHT: Slightly increased PoPs arrive late Sunday evening into Monday as there seems to be some mid-lvl vorticity moving through the region. While highly uncertain on the track, this could at least pose some risks for stronger convection forming early in the evening in western SD/ND on the nose of an increasing LLJ. This convection will be initially surface based and capable of very large hail. There are some hints that these storms could congeal and begin to produce a bit more wind as they reach central SD. The limiting factor in the eastward progression could be a very dry sub 600 mb layer as these storms reach the James River valley.

MONDAY-WEDNESDAY: The first half of the week continues to look very uncertain given the quasi-zonal or slightly northwest flow pattern aloft. It's certainly possible one or more of these days will feature a rain chance, but these are all dependent on any weak eddy in the flow. There continues to be some consistency again today on one of these waves arriving Monday evening into Tuesday and again into Wednesday morning. The available instability would suggest at least a continued low-risk for a severe storm or two, though wind shear continues to be borderline. Temperatures remain near their seasonal normals in the lower to middle 80s.

THURSDAY-FRIDAY: No changes in this portion of the forecast, where mid-lvl flow flattens and becomes westerly. PoPs will be elevated into Thursday as a cold front may pass through the region. There continues to be growing signs of a slight cooldown into the weekend.

AVIATION /18Z TAFS THROUGH 18Z SUNDAY/

Issued at 1214 PM CDT Sat Aug 8 2026

VFR conditions continue at mid-day Saturday. We'll see a band of mid-lvl clouds move northeast through the area this afternoon. These clouds mark the leading edge of deeper instability. While most areas will stay dry, cannot rule out a high based shower or virga along this passing cloud band.

With persistent south winds, VFR conditions will continue overnight, with isolated to scattered thunderstorm risks north of Highway 14 and in portions of NW Iowa after midnight. Currently, the risks to HON/FSD/SUX remain low.

FSD WATCHES/WARNINGS/ADVISORIES

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