textproduct: Des Moines

KEY MESSAGES

- Today/Monday is favoring drier conditions with capping in place to limit if not prevent storms. However, similar to yesterday/Sunday, if storms can develop late this afternoon or early this evening, a few severe storms with large hail, gusty winds, and locally heavy rainfall are possible.

- High pressure drifts southward through the Great Lakes into the Ohio Valley, which pushes rain and storm chances west of the state through Wednesday. Highs above normal in the 80s.

- Storm chances look to return late in the week.

SHORT TERM /THROUGH TUESDAY/

Issued at 124 AM CDT Mon Jun 1 2026

Monitoring ongoing convection over western Iowa that is just beginning to push into our forecast area. Storms west of a Sac to Cass County line have had warnings the last few hours with hail reports up to an inch with radar indicating larger sized hail. SPC mesoanalysis shows these storms have 2000 J/kg of MUCAPE and effective shear around 30 knots. They are also moving slowly around 15 to 20 mph. There are several storms lined up west to east and while they are not moving due east, will have to watch for repeat rounds of rainfall if they occur over our forecast area with the heavy rainfall parameters favorable with precipitable water values around 1.5 inches and deep warm cloud depths. WPC just recently issue mesoscale precipitation discussion 291 that highlights the risk of flash flooding as well. To the north, another storm cluster is pushing in from the Spencer area, which had a wind gust to 45 mph around 1230am. These storms are expected to remain below severe limits as the outflow boundary has already pushed out ahead of this cluster. Outside of the next few hours when storms are expected to be their strongest to possibly severe, it is expected that the storms over Iowa will trend downward through sunrise as the low level jet (LLJ) is forecast to veer and point over Missouri the rest of the night.

Thereafter, forecast soundings show a warm capping layer aloft, which should suppress storm develop through much of the afternoon. Thus, the daylight hours today will have a good deal of sunshine and it will be warm. As was the case on Sunday, the question becomes whether there is enough forcing to overcome the cap. If so and storms are able to develop, there will be sufficient instability with mixed layer CAPE values between 1500 and 2500 J/kg and deep layer shear near 30 knots (RAP) to a bit above (NAM/GFS). However, it remains unclear what the forcing will be for storms tonight with the LLJ focused west of the state. The omega block pattern remains over the CONUS and there is subtle shortwave energy approaching the top of the ridge axis, which will be center over roughly the Iowa Nebraska border late today. So, that is a possible mechanism. Looking at convective allowing models (CAMs) for possible scenarios, they generally show storms trying to develop late this afternoon or early this evening over some portion of western Iowa. The exception is the RRFS (both cores) that initiate storms over south central Iowa. This would seem less likely given that it would be more removed from the shortwave energy just discussed. If storms can form and sustain for any appreciable time in the evening, gusty winds, large hail, and heavy rainfall will be the main hazards. Much farther west of the state, storms are forecast to develop on the High Plains and push towards the state as a mesoscale convective system (MCS). This is expected to weaken as it nears Iowa with drier air pushing into the state and also outrunning the LLJ axis.

After any storms dissipate tonight/Monday night, attention will be on a zone of high pressure dropping south from Hudson Bay over the Great Lakes region on Tuesday. With drier easterly flow pushing into the state, this will also shunt the higher moisture axis west of Iowa providing for dry and warm conditions on Tuesday.

LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/

Issued at 253 PM CDT Sun May 31 2026

Warm conditions continue this week with highs in the 80s. A Great Lakes high looks to keep conditions dry Tuesday into Wednesday with storm chances returning later in the week as the upper ridge finally breaks down. By the end of the week, temperatures may warm further as southwest flow kicks in with additional storm chances into the weekend.

AVIATION /18Z TAFS THROUGH 18Z TUESDAY/

Issued at 1219 PM CDT Mon Jun 1 2026

VFR conditions prevail today, with calm to light winds today. Wind direction will be variable today, then prevailing generally out of the east this afternoon and evening. A few scattered showers and storms may develop over western Iowa this afternoon, but aren't expected to impact terminals at this time.

DMX WATCHES/WARNINGS/ADVISORIES

None.