textproduct: Des Moines

KEY MESSAGES

- Scattered thunderstorms remain possible into the overnight with the focus over north central Iowa.

- A few funnel clouds remain possible this afternoon. A localized damaging wind gusts and locally heavy rain may occur.

- Drier conditions to start the work week.

SHORT TERM /THROUGH SUNDAY/

Issued at 246 PM CDT Sat Jul 4 2026

Thunderstorms have developed along an instability ribbon over north central Iowa this afternoon. Very weak surface flow combined with 0- 3 km CAPE values of 100+ J/kg has created a favorable environment for vertical stretching of horizontal vortex tubes. This has led to numerous reports of funnel clouds. The LCL levels are around 1000 meters or less and several funnels have been close to half way down to the ground. There have been a report of at least one brief tornado over northwest Iowa. These are landspouts and very weak and form during the updraft phase of thunderstorm development. At the current location of the storms, these will not be detectable on radar other than the location of new updrafts. Otherwise, weak deep layer flow has led to very slow storm motions leading to locally heavy rainfall occurring under these storms. Already have measure amounts exceeding 2 inches near Emmetsburg and Garner. Finally, there remains the potential for damaging wind gusts remains with very little deep layer shear present and a mid-level dry layer, leading to wind development with collapsing storms. The hail threat is low with vertically stacked storms and any ice falling through heavy rain and undergoing substantial melting.

Water vapor imagery is showing short wave energy moving into central South Dakota this afternoon. That may lead to additional thunderstorm development later this afternoon and may help sustain some convection into the overnight. An attendant damaging wind and heavy rain threat will persist with any storms. Precipitation chances will linger into Sunday mainly east of Interstate 35 with generally dry conditions west as the short wave energy begins to pass to the east.

LONG TERM /SUNDAY NIGHT THROUGH SATURDAY/

Issued at 246 PM CDT Sat Jul 4 2026

Drier conditions are expected to start the week. The next short wave arrives late Tuesday night into Wednesday and will bring thunderstorm chances to northern Iowa. Westerly/zonal flow will persist the rest of the week with another embedded short wave passage around Friday.

AVIATION /00Z TAFS THROUGH 00Z MONDAY/

Issued at 646 PM CDT Sat Jul 4 2026

VFR conditions are expected to prevail throughout this TAF period. However, low end chances for fog and thunderstorms exist this evening. Latest trends have overnight thunderstorms <30% chance of occurring, though the highest chances are at the northern terminals. Given low chances for precip, clearing skies and high humidity left behind this evening will increase the chances for fog by 9z-11z. That said, any fog is expected to be patchy and there is low confidence on exact locations so have not included it in this issuance. Overall impacts tomorrow are minimal, but there is decent confidence in a cumulus layer developing in the late morning, though total coverage is uncertain.

DMX WATCHES/WARNINGS/ADVISORIES

None.