textproduct: Des Moines

KEY MESSAGES

- Another hot and humid day is in store for Iowa, with highs in the upper 80s to low 90s and heat indices nearing 100 degrees. - Storm chances return, with the most likely window overnight tonight into Friday morning.

SHORT TERM /THROUGH FRIDAY/

Issued at 219 AM CDT Thu Jul 2 2026

Hot and humid conditions continue with some limited relief from the heat. Ongoing convection early this morning will help limit temperatures, particularly across northern Iowa. High temperatures across the state are forecast to be in the upper 80s to low 90s. The continued abundance of gulf moisture will lead to dewpoints in the low to mid 70s. This will push heat indices near the triple digit mark, especially in the southern portion of the state. For now, the Extreme Heat Warning will continue, but will need to be reassessed later due to potential impacts from overnight thunderstorms.

Today looks to be shower and thunderstorm free as we remain capped. A shortwave is expected to pass through and a few brief windows exist for storms to develop in the afternoon and into the evening, particularly in northwest Iowa. Confidence in widespread development during this window is low, however, despite ample CAPE (upwards of 2500 J/kg). Shear looks to be pretty limited depending on the model, although during the daytime hours it looks most favorable in the north and northwest portions of the state (35-40 kts). Of note, the HRRR sees this portion of the state as uncapped and is quite aggressive with convection in the early afternoon and into the evening. Other models are holding strong with capping. Given how things have played out with capping the past several days in addition to potential recovery challenges from overnight convection, confidence is higher with staying capped through most of the day.

Of higher confidence is an MCS which is expected to move through Thursday evening and overnight from South Dakota. Some variability exists here, too. CAMs are split on the placement of the MCS and how far south it reaches. Similar to what happened a few nights ago, the Low Level Jet (LLJ) will have kicked in as the MCS enters our area and will keep the MCS from diving to the south, aided in part by the ridge which has not yet broken down. Confidence is highest in the MCS forming and moving through the area, although there is less confidence in strength as it reaches Iowa. Should the MCS reach our area, guidance points at the potential for gusts ranging from 60-70 mph. Guidance is much more split on how far east the potential for damaging winds will be.

The final piece of the never-ending puzzle is the threat for heavy rain. Precipitation chances are once again highest across northern Iowa. Widespread flooding concerns are quite limited for the moment. That said, PWAT values are hovering around 2" and repeated heavy rainfall over the same general areas would lead to the potential for localized flooding concerns.

Moving into Friday, there is potential for it to be active once again in the evening and overnight. Initially, it looks like there is more potential for an overnight MCS, but the formation of this MCS depends on atmospheric recovery following morning convection farther to the west.

LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/

Issued at 257 PM CDT Wed Jul 1 2026

As we get into Friday and the holiday weekend, uncertainty increases given so many convective scenarios that will play out prior. However, the upper level pattern will be trending more zonal with continued moisture advection and warm temperatures working up into the state. This pattern will be conducive for continued rain and thunderstorm chances persisting into the weekend and potentially the Independence Day holiday. It seems unlikely the state of Iowa will be completely spared from thunderstorms Friday into Saturday. Therefore, the most important takeaway is to stay tuned to the forecast as it will be evolving into the weekend. The hot and humid temperatures will also persist into Friday and Saturday. Another heat headline may be needed on Friday, but given uncertainty of convective trends through the next 48 hours have decided to hold off during this shift. Independence Day looks a tad cooler, but will also be driven by the persistent thunderstorm chances through the end of the week and into the weekend.

AVIATION /12Z TAFS THROUGH 12Z FRIDAY/

Issued at 607 AM CDT Thu Jul 2 2026

VFR conditions are expected to prevail at all sites through this TAF period. In the immediate term, thunderstorms may impact KMCW but conditions are expected to remain VFR and they should pass fairly early in the period. Otherwise, later today PROB30 mentions were added at KFOD, KMCW, and KALO for thunderstorms that may develop. Lower confidence exists for thunderstorms in this timeframe, and this may be adjusted with amendments if confidence increases. Otherwise, the potential for widespread thunderstorms exists at the end of this TAF period, but confidence in timing and placement is too low to mention this far out.

DMX WATCHES/WARNINGS/ADVISORIES

Extreme Heat Warning until 10 PM CDT this evening for IAZ059>062-072>075-082>086-092>097.