textproduct: Des Moines

KEY MESSAGES

- Hot and humid today with heat index of 100-105+ this afternoon. A heat Advisory is in effect from noon - 8pm.

- Strong to severe storms are expected this afternoon and evening. Damaging wind and hail are the main hazards, along with pockets of heavy rain. There is a low tornado threat mainly in northeast Iowa.

- Cooler temperatures in the low 80s this week behind the cold front.

SHORT TERM /THROUGH TONIGHT/

Issued at 301 AM CDT Mon Jul 20 2026

The upper level shortwave through has made it to North Dakota and northern Minnesota overnight with a cold front trailing to the southwest. The low level jet has increased ahead of the shortwave, fueling overnight convection that has push across South Dakota and into southern Minnesota early this morning. The LLJ has brought a plume of moisture back into the upper midwest and convection is traveling along this gradient. Expect storms to continue moving to the southeast through the morning, clipping parts of northeast Iowa towards sunrise. While this cluster of storms produced severe winds earlier, is has since diminished in intensity. This trend is expected to continue this morning with the LLJ weakening through sunrise. Even so, a few stronger gusts are possible.

Conditions clear out behind these morning storms in northern Iowa with strong theta e advection into the area. This will make for another hot and humid day, the hottest of the recent warm spell. Heat indicies this afternoon are expected to reach 100-105+ across most of Iowa. The approaching shortwave should help to push wildfire smoke back east of the area for most of today.

Storms are expect to develop on the cold front that will make it to northern Iowa by this afternoon. A few isolated airmass thunderstorms are possible on remnant outflow boundaries in northern to northeast Iowa midday into the early afternoon ahead of the main front. Instability builds with strong theta e advection into the area and MLCAPE reaches 3000+ J/kg in northeast Iowa by the afternoon. There is 50+ kts of 0-6 km shear to organize updrafts, with initial supercell and cluster thunderstorms anticipated before growing upscale along the front. Lapse rates are modest at 6-7 C/km, diminished by warmer mid level temperatures. In northeast Iowa 0-1 km SRH reaches 100-200 m2/s2 with 0-3 km SRH 300+ m2/s2. This increased the tornado potential in that part of the state, especially as storms initiate. Low level CAPE is somewhat lacking at under 100 J/kg for 0-3 km which may inhibit the low level stretching potential. As storms grow upscale and push into central and southern Iowa this evening wind will be the primary hazard. The cold front finally sinks south of the area early Tuesday morning. Pockets of heavy rain are possible with storms owing to PWATS around 2" and warm cloud depths of 3500+ m. Dry antecedent conditions and mature crops should mitigate most hydro concerns.

LONG TERM /TUESDAY THROUGH SUNDAY/

Issued at 318 PM CDT Sun Jul 19 2026

Showers and thunderstorms will likely carry primarily a wind threat into the night, before decreasing near/after sunrise. With the front through the majority, if not all of Iowa, northwest flow and cool advection will spread across Iowa, leading to slightly cooler temperatures and drier air. With this shift in the flow, HRRR smoke guidance indicates the return of wildfire smoke into Iowa from Minnesota, leading to additional hazy skies and at least some possible lowering of visibilities. Surface high pressure though will lead to dry conditions through the rest of the day as this feature descends across the Central Plains and through much of Wednesday. Conditions will remain comfortable through midweek as northwest flow remains, with temperatures largely in the upper 70s to 80s and dewpoints in the 50s to low 60s. A weak wave skimming southwest Iowa Wednesday evening looks to bring returning chances for rain and possible thunderstorms, while additional waves riding the upper level flow follow this activity that will bring additional periods of active weather through late work week. Details regarding these systems will be better known in the coming days. Ridging then builds over the southwestern CONUS that will slowly influence temperatures through the weekend as highs gradually return into the 90s.

AVIATION /06Z TAFS THROUGH 06Z TUESDAY/

Issued at 1152 PM CDT Sun Jul 19 2026

MVFR vsbys have been in and out in eastern terminals due to smoke, so kept mentions going until thunderstorms arrive after 10z. Trends have been as follows for precipitation:

- KMCW now only may be impacted by the morning storms, so have removed the afternoon Prob30 group.

- Have added a Prob30 group to KFOD for start of storms after 20z and to KDSM for storms after 00z

- Trended stronger for storms at KALO in the afternoon with prevailing -TSRA and a Prob30 window showing the arrival of severe storms. This is the terminal where there is the highest confidence for storms both in the morning and especially the afternoon.

- Added thunderstorm mentions to KOTM in the final 6 hours.

DMX WATCHES/WARNINGS/ADVISORIES

Heat Advisory from noon today to 8 PM CDT this evening for IAZ004>007-015>017-023>028-033>039-044>050-057>062-070>075- 081>086-092>097.