textproduct: Des Moines

KEY MESSAGES

- Another chance of severe thunderstorms this morning with damaging wind being the primary threat. Isolated instances of large hail and locally heavy rainfall are also possible.

- Hot and humid conditions continue through today with heat indices nearing or just exceeding 100 degrees across southern and portions of central Iowa.

- More shower and storm chances tonight and tomorrow, with additional shower and storm chances through the weekend. Locally heavy rain and severe weather is possible, but details will be better assessed with time.

SHORT TERM /THROUGH THURSDAY/

Issued at 315 AM CDT Wed Aug 12 2026

Showers and thunderstorms are again expected this morning and severe weather is possible. A cluster of storms in southern South Dakota/northern Nebraska is currently ongoing and moving towards Iowa, with an expected arrival in western Iowa in the early morning hours. As has been the case the past several nights, there is no clear-cut solution with how things will evolve. The devil lies in the details. Mesoanalysis shows a deeply unstable environment across Iowa with a strong CAPE gradient farther to the west. This cluster is expected to ride the CAPE gradient to the southeast, though it has to fight mid-level convective inhibition. RAP analysis shows the Low Level Jet (LLJ) is just now beginning to nose into Iowa. Deterministic models show the jet strengthening around 7am/12z this morning. As it does this, the cluster would be energized and begin to build towards the northeast into central Iowa. Another part of the uncertainty comes from a lack of moisture return. Moisture transport shows some signal in the mid-levels, and mesoanalysis hints at better moisture transport with the still-strengthening LLJ. Another solution that would bring storms even farther north is if storms are enhanced by shortwave energy ahead of the main cluster. If everything materializes, there is a decent signal for a damaging wind threat with this cluster as it moves through Iowa. Compared to previous nights, confidence is much higher in the evolution of storms.

Once storms clear the area, which should be around mid to late morning, with the potential to be as late as 1pm/18z, hot and humid conditions are expected with heat indices again approaching the 100 degree mark. There is more uncertainty in terms of heat than in previous days, as storms are progged to track farther south than in previous nights over the area forecast to be warmest, which could lessen heat indices. Once again, atmospheric recovery is expected through the day today, though capping is still going to be in place to inhibit storms during the daytime hours. Otherwise, storm chances once again return tonight driven by a shortwave that will move over the area. Confidence with storms tonight looks much higher than previous nights have been given a more pronounced shortwave. Severe wind gusts are not out of the question with this setup, however the signal for heavy and excessive rainfall looks the greatest with decent moisture return and PWATs over 2 across the area. There is still some disagreement with the specific location of where the heaviest rain will fall. At the very least, flash flooding would be a concern over any cities/towns.

Thursday looks to bring cooler temperatures to much of the state, save for far southern Iowa. with temperatures in the upper 80s across the south, and upper 70s to low 80s across north and central Iowa. It may not be as dry, however, with the potential for showers and thunderstorms through the day for at least some part of the state along a boundary that looks to set up across central Iowa.

LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/

Issued at 249 PM CDT Tue Aug 11 2026

Active weather persists into Thursday night as another shortwave traverse into the Plains, The SPC currently highlights the southern CWA in a Marginal Risk (Level 1 of 5) for Thursday. The active pattern remains in place through Saturday, maintaining low-end severe storm probabilities. A more robust cold front will finally sweep through the region on Sunday, bringing a cooler and drier airmass. Highs look to top out in the upper 70s in northern Iowa to lower 80s in southern Iowa.

AVIATION /12Z TAFS THROUGH 12Z THURSDAY/

Issued at 641 AM CDT Wed Aug 12 2026

Main aviation focus is on the showers and storms ongoing and expected to move through most of the area this morning. Convective evolution has not followed previous expectations particularly well and CAMs are still a bit varied on their evolution from here, though many are not capturing current trends well either. This being said, timing in current TAFs may still need further adjustments as KOTM is seeing the new storm development out ahead of the main line, and other sites will eventually see the main line come through, though the extent and severity of which remains to be seen. Generally expecting some amount of thunderstorms to affect KFOD and KDSM and probably KALO with time if storms can hold together with additional new development also possible in that area. KMCW remains further north and will likely only see a shower or two if anything unless things trend more north. Storms could have gusty and erratic winds associated with them, and should they become more organized again, these winds could become severe. Storms clear the area by mid morning to midday with dry conditions behind through the rest of the daytime. There are more widespread storm chances again overnight into Thursday morning but will be addressed in future issuances. Behind the storms, winds will largely be out of the east and light under 10-12 knots.

DMX WATCHES/WARNINGS/ADVISORIES

None.