textproduct: Sioux Falls

KEY MESSAGES

- Isolated strong to severe storms are possible mainly Wednesday afternoon along and east of a Spencer to Sioux City line. Ping pong ball sized hail and 60 mph winds will be the main threats.

- Elevated to near critical fire danger is expected Thursday with a break from rainfall, much warmer temperatures, strong winds, and low humidity. Winds may lead to elevated conditions Friday, although shower and storm chances may temper concerns.

- Strong to severe storms will be possible again on Friday, though uncertainty in the timing of a cold frontal passage leads to a lower confidence forecast regarding the extent of the severe weather threat. As of now, areas near and east of I-29 are favored for stronger storms.

DISCUSSION

Issued at 233 PM CDT Tue Apr 14 2026

Radar is picking up on a stripe of showers extending from roughly Marshall, MN to Gregory, SD this afternoon, but most of this will not be reaching the ground due high cloud heights and dry air beneath said clouds. Scattered showers and storms will continue to develop off to our south and west over the next hour or so where the greater surface moisture is. Can't entirely rule out an elevated thunderstorm over northwest Iowa as soundings show a few hundred J/kg of CAPE lifted from around 750 mb this afternoon, but likely not enough for severe weather. However, small hail would be possible with mid level lapse rates around 7-7.5 C/km and 50-60 kts of 0-6 km bulk shear if a thunderstorm can develop.

A boundary will be lifting northward across the region late tonight into Wednesday morning. The NAMNest is the fastest with this boundary arrival, bringing in storms to the Highway 20 corridor just before sunrise Wednesday, but this remains an outlier. What's more likely to occur is showers and storms not developing until the afternoon as the boundary continues drifting northward and instability increases due to daytime heating. Isolated strong to severe storms will be possible given mid level lapse rates greater than 8 C/km and bulk shear in the 45-55 kt range. The main threat with any of these afternoon storms would be large hail up to ping pong ball in size followed by damaging wind gusts to 60 mph. If we do get morning showers or storms tomorrow, then that may limit the ability for the atmosphere to recover in the afternoon, thus less afternoon instability. The best chance of an isolated severe storm Wednesday afternoon will be roughly along and east of a Spencer to Sioux City line. Any storms will push east of the area heading into Wednesday evening as the surface low and upper wave move out of the area.

We are dry for Thursday, but this may come with the potential for critical fire danger in parts of the area. Southwesterly winds look to return for areas mainly along and west of I-29, which will help drop relative humidity values down to 25% and below Thursday afternoon. With temperatures in the 80s and winds gusting to 25 to 30 mph, a very high fire danger can be expected for most of the area. Uncertainty remains on how strong the winds will get and how far east these stronger winds make it, and if the grasses are starting to green up enough to prevent more widespread fire weather concerns. With that, held off on fire weather headlines for now until certainty grows.

The main western US trough that has been helping to send all these impulses across the area over the past couple of days will finally move eastward heading into Friday, pushing a strong cold front into the area. Ahead of the front, warm and moister air will be favorable for thunderstorms, some of which could be strong to severe mainly east of I-29. Timing of the cold front will play a role in how much coverage of storms can be expected, with a faster passage meaning a lower threat and a slower passage leading to a greater threat of stronger storms. One thing is for more certain is the colder air that will follow this system, with lows expected to drop below freezing for most of the area by Saturday morning. This means some rain with this system may at least briefly turn to snow as the precipitation exits the area, but confidence is very low on this potential. Either way, expect much cooler temperatures heading into the Friday night through Sunday morning time frame. After this push of colder air, ridging aloft looks to return and thus a quick warming trend looks possible into early next week.

AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/

Issued at 1218 PM CDT Tue Apr 14 2026

VFR conditions expected this afternoon into this evening with northerly winds turning light and variable into tonight. A few thunderstorms will move towards the Highway 20 corridor in northwest Iowa by daybreak into Wednesday morning, though uncertainty remains on just how far north these storms will make it. Enough confidence to at least include a PROB30 group at KSUX for -TSRA, but trends will be monitored. Winds will remain mostly light and variable into the day on Wednesday.

FSD WATCHES/WARNINGS/ADVISORIES

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