textproduct: Des Moines

KEY MESSAGES

- Storms diminishing over southern Iowa early this morning. Locally heavy rainfall still possible. Additional storms may occur late this afternoon and evening.

- Mostly dry Sunday!

- Another round of strong storms possible Tuesday.

SHORT TERM /THROUGH SUNDAY/

Issued at 148 AM CDT Sat Aug 15 2026

Low pressure is located over northeast Kansas this morning with a warm front extending east through central Missouri. Strong theta-e advection is occurring north of the surface boundary and has led to a broad are of thunderstorms over far southeast Iowa and into northern Missouri. The current setup resembles frontal type of Maddox heavy rainfall setup with the warm moist air overrunning the primary boundary with weak ridging and weaker flow aloft. So far, heavy rainfall has been falling in the northeast quad of the low level jet speed convergence zone, which also matches the Maddox heavy rain conceptual model.

The low level jet (LLJ) and the attendant MUCAPE axis will lift north more into Iowa over the next several hours which will lead the the thunderstorm focus to lift north as well. The LLJ will then veer more eastward by 12z with the precipitation migrating east as well. The mid-level lapse rates are weak and approaching moist adiabatic lapse rates with values currently at 6 C/km or less. While that does limit the parcel accelerations for stronger updrafts, higher PWAT values are greater than 2 inches and the 850 mb dew point is 16C or greater, are leading to more saturated profiles and deeper warm cloud depths. This is leading to warm rain processes and efficient rainfall under these storms. A few areas with heavy rainfall remain possible over southern Iowa the next several hours but fortunately, most of those areas have miss out on the recent heavy rainfall. This will help mitigate some of the flooding potential. The Flood Watch for flash flooding remains in effect until 10 am this morning but with the diminishing threat, have consolidated the hydrology discussion here. Rises along streams

Much of the precipitation will diminish this morning as the kinematic forcing moves east. A broad stratus deck with cloud bases less than 1000 ft, may be slow to erode along with hazy conditions from the residual fog. This may limit high temperatures today pending how long the clouds hold. Additional thunderstorms are possible again later this afternoon and evening as a boundary moves in the state as Canadian high pressure extends farther south. The mid-level lapse rates will remain quite modest and the overall threat for severe weather is low. The potential for efficient rainfall producing storms will persist but these storms should be more progressive with less chance for training of storms, so limiting the overall heavy rain threat, compared what has occurred recently. High pressure arrives on Sunday and should finally bring a dry day!

LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/

Issued at 153 PM CDT Fri Aug 14 2026

At this point, Sunday looks drier as a drier air mass advects in as evident by PWATs dropping to near 1" across central and north. Looking into next week periodic shower and thunderstorm chances will continue to be possible, however, it appears that these will be more seasonal, compared to the past week.

AVIATION /12Z TAFS THROUGH 12Z SUNDAY/

Issued at 619 AM CDT Sat Aug 15 2026

Scattered showers and thunderstorms are lingering over southern Iowa early in the period but will continue to diminish. A broad area of LIFR/IFR stratus is in place over much of Iowa along with areas of IFR/MVFR fog. These conditions will gradually improve today. Additional thunderstorms are possible again later this afternoon and evening. The wind will be mainly light while transitioning from southeast to northwest. A return to VFR could return late this evening but there remains potential form more MVFR stratus late tonight.

DMX WATCHES/WARNINGS/ADVISORIES

Flood Watch until 10 AM CDT this morning for IAZ044>050- 057>062-070>075-081>086-092>097.