textproduct: Des Moines

KEY MESSAGES

- Scattered shower and thunderstorm chances return early Saturday morning, mainly over northern Iowa.

- More widespread strong to severe thunderstorms are forecast Saturday after 12pm, mainly for areas along and south of I-80. Primary concerns are large hail, gusty winds, and flash flooding. A tornado or two is possible in far southern Iowa.

SHORT TERM /THROUGH SUNDAY/

Issued at 243 PM CDT Fri Jun 12 2026

After a very active period across central Iowa, we've been given a short break before severe weather returns on Saturday.

The severe weather risk on Saturday is complexified by the 850mb Low Level Jet (LLJ) that sets up tonight, leading to two potential scenarios for how tomorrow will play out. Guidance is split on how strong the jet is, which means it's also split on whether elevated thunderstorms can fire in the early morning hours in Nebraska before moving across northern Iowa just after sunrise. Some of the CAMs are firing storms with this LLJ and pushing them across northern Iowa. If this ends up being the scenario that plays out, the atmosphere in northern Iowa will be unable to recover for storms Saturday afternoon. Some stronger storms in the early morning could produce small hail and gusty winds. This would also limit the severe risk to areas along and south of I-80 in the afternoon.

The other scenario is if we have a weaker LLJ and storms don't form early Saturday morning. Through the day Saturday, the atmosphere would be able to destabilize and the severe risk would be brought as far north as the US-20 corridor. REFS guidance shows surface-based CAPE values between 1300 and 2500 J/kg, while the HREF is more aggressive with CAPE exceeding 3000 J/kg.

Another somewhat limiting factor in the severe risk for tomorrow is the amount of directional shear. Guidance suggests speed shear will be sufficient with values of 38kts in southern Iowa and values approaching 50kts farther north. The shear is unidirectional, however, which greatly limits the tornado risk in both scenarios. Directional shear in far southern Iowa looks a bit better, so the threat isn't quite zero, the area is just very limited. This leads to the severe hazards being limited to large hail and damaging wind gusts. As has been the case with many of the recent severe events, flash flooding is also a concern due to recent heavy rains.

As for timing, the peak window for severe weather looks to be after 2pm. As the storms progress, they will move to the east-southeast as a cold front pushes them out of Iowa. Storms look to exit the area around or just after 10pm, though a post-frontal shower or two is still in the mix.

To round out the weekend, Sunday looks to be cooler, dry and a bit breezy. Winds will be out of the northwest around 15 to 20mph across northern Iowa, with speeds of 10 to 15mph across central and southern Iowa. Gusts through the day will range from 20 to 25mph.

LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/

Issued at 243 PM CDT Fri Jun 12 2026

Cooler temperatures are forecast Sunday night through the end of next week. Much of the area will stay below 85 degrees each day, with a slight warming trend towards the end of next week. Lows Sunday night into Monday will bottom out in the high 40s to low 50s before gradually warming each night. The overall pattern looks much less active, save for a few passing shortwaves. Specifics on those will be addressed in the coming days.

AVIATION /18Z TAFS THROUGH 18Z SATURDAY/

Issued at 1223 PM CDT Fri Jun 12 2026

VFR conditions to prevail through the end of this TAF period. Skies will remain clear the rest of Friday. Winds will shift from a west wind to a south wind around 23z under 12kts. Ceilings are expected to remain VFR with Saturday morning showers and storms moving into western Iowa. PROB30s have been introduced at MCW, FOD and ALO to represent this. Additional showers and storms will be possible towards the end of this TAF period but confidence is too low to issue PROB30s at this time.

DMX WATCHES/WARNINGS/ADVISORIES

None.