textproduct: Des Moines

KEY MESSAGES

- Early morning thunderstorms are forecast once again on Thursday morning, then scattered thunderstorm chances last through Thursday afternoon and evening. Strong wind, hail, and heavy rain are the main concerns with these storms.

- Additional thunderstorms are possible overnight and early Friday morning and will depend on how the Thursday storms evolve. These storms could be severe with pockets of heavy rain as well.

- The pattern remains active with storms chances through the weekend and early next week.

SHORT TERM /THROUGH THURSDAY NIGHT/

Issued at 142 PM CDT Wed Aug 12 2026

Morning thunderstorms across Iowa are pushing east with clearing occurring quickly across western and central Iowa. Temperatures have recovered into the mid 80s this afternoon, though morning convection has helped to keep temperatures a few degrees cooler today. A weak boundary across northern Missouri will see convection bubble through this afternoon, however capping in place should keep Iowa dry.

This evening a shortwave will ride across the thermal ridge from South Dakota and Nebraska with the MCS expected to reach Iowa early Thursday morning. As the MCS reaches Iowa it is expected to ride along the instability gradient (2000+ J/kg MLCAPE) as the weak Missouri boundary lifts north back into Iowa overnight. There are two main areas of uncertainty with the Thursday morning MCS in Iowa: location and strength. Current expectation for the MCS is to travel across central Iowa with the main bowing segment along roughly the I- 80 corridor, however this placement will depend on how far north the instability axis lifts into the state. Strength is also uncertain. This will be the third night in a row with the potential for overnight or early morning storms across Iowa. While the previous two nights have had less upper level support, tonight's complex is supported by an upper level shortwave that makes a stronger MCS more likely. As it reaches Iowa the continued intensity will be driven primarily by how far north instability axis can lift to feed the complex. Current data suggests the low level jet will reach northern Missouri with the boundary being push just north of the jet into Iowa. MLCAPE of 2000+ CAPE will be in place with mid level lapse rates around 7 C/km. There is plenty of moisture in place with PWATs of 1.5-2+". While the MCS should be fairly progressive, ribbons of 2- 3+" are possible and could cause ponding or minor flooding.

This morning convection will help to squash the thermal ridge, shoving the heat south with highs in the upper 70s to low 80s in northern to central Iowa on Thursday while southern Iowa still warms to near 90. After a daytime lull, afternoon convection is expected to develop along the lingering boundary with less capping across the area. Further redevelopment is anticipated overnight Thursday into Friday morning, though placement is less certain and will depend on where outflow boundaries from earlier round of convection and the low level jet set up. The east-west orientation of convection Thursday afternoon and again overnight will be less progressive and could result in hydro concerns with training storms over the same locations. This will need close monitoring with PWATs remaining around 2" along with those deep warm cloud layers.

LONG TERM /FRIDAY THROUGH TUESDAY/

Issued at 142 PM CDT Wed Aug 12 2026

Overnight convection lingers into Friday morning with continued hydro concerns into the day. The pattern remains active through the weekend and upcoming week as wave continue to ride across the thermal ridge in this "ring of fire" set up. Repeated rounds of convection will rely on earlier rounds for both placement and strength. A few lulls in convection are possible next week, but timing out which days this may occur is difficult at this time range.

AVIATION /18Z TAFS THROUGH 18Z THURSDAY/

Issued at 1252 PM CDT Wed Aug 12 2026

Morning storms have exited east of the area with skies clearing quickly behind. Scattered cumulus may develop this afternoon but VFR conditions are expected. Overnight storms will reach western Iowa, moving across Iowa in the early morning through the end of the TAF period. Confidence in occurrence is fairly high and -TSRA was included at all sites, but timing and location could shift and adjustments in later issuances are possible.

DMX WATCHES/WARNINGS/ADVISORIES

None.