textproduct: Des Moines

KEY MESSAGES

- Hot and humid conditions continue both today and tomorrow with a low (20%) chance for isolated showers and thunderstorms until sunset.

- The heat looks to linger through the weekend before a pattern change takes place, leading to relatively cooler temperatures and increased precipitation chances.

SHORT TERM /THROUGH FRIDAY NIGHT/

Issued at 208 PM CDT Thu Jul 16 2026

Currently, scattered cumulus have formed across Iowa. GOES imagery has the highest coverage across the western part of the state. This afternoon, there is a low (20%) for showers and potentially an isolated non-severe thunderstorm. This is caused mainly by the high that has been over us for the past several days moving just outside of our area, allowing for subtle forcing to arrive.

Today's forecast is very similar to yesterday's. High temperatures will be in the upper 80s to low 90s with dewpoints around 70. Like yesterday, temperatures have been poked down a degree or two. In a similar fashion, dewpoints were poked up a degree or two. This leads to heat index values in the upper 90s across the state. This afternoon, there are low chances for popcorn thunderstorms. Today's lapse rates are decent with ample CAPE, although the lack of any shear will dampen the severe threat and will lead to storms being either slow-moving or stationary. Some deterministic model soundings hint at the potential for gusty winds as thunderstorms collapse, however nothing is progged at more than 30 mph. Furthermore, limited forcing will lead to low chances for storm development in the first place.

Thunderstorm chances decrease after sunset as instability wanes. Unlike previous nights, cloud cover is expected across the south. Naturally, this will lower the potential for fog tonight. Tomorrow, dewpoints are forecast to be a degree or two higher, with temps reaching into the low 90s across most of the state. Heat indices around the 100 degree mark are expected. The most notable feature for tomorrow's forecast is the potential for showers and thunderstorms. A weak moisture plume is shoved into southern and southeastern Iowa which will aid in thunderstorm development. Forcing will still be limited, but a small area of potential vorticity will advect into Iowa from Missouri and provide some amount of forcing. CAPE and moisture will once again be plentiful. Despite all of this, thunderstorm development is still expected to be very isolated and "popcorn-y" with very little shear to steer thunderstorms.

Tomorrow night, temperatures look to be even warmer (in the mid 70s) which could have implications on overnight recovery from heat, even if we remain below criteria for any headlines. Cloud cover is forecast to be less than tonight, which could lead to the potential for fog to return if dewpoints over-perform in the nighttime hours.

LONG TERM /SATURDAY THROUGH WEDNESDAY/

Issued at 208 PM CDT Thu Jul 16 2026

The high continues to be pinched off as an upper level ridge builds over the western CONUS this weekend and early next week. Uncertainty lies in how quickly this happens. LREF clusters hint that we could be out from under the ridge as soon as Sunday night/Monday, although it is most likely that we stay under it or on the edge through the day Monday. A surge of warmer air enters the area this weekend just before the ridge translates away from us, leading to the potential for the highest temperatures of this stretch to end the weekend. The Extreme Forecast Index (EFI) is keying in on this, highlighting part of Iowa as having above normal temperatures. With this still being several days out, it is a trend to monitor. Of note, long-term deterministic models key in on this as well. In tandem, uncomfortably warm low temperatures are being forecast for the same time period.

Once we are out of the ridge's area of influence, we get into a northwesterly flow regime which leads to a change of pattern and increased potential for shower and thunderstorm chances across the region at times next week.

AVIATION /18Z TAFS THROUGH 18Z FRIDAY/

Issued at 1212 PM CDT Thu Jul 16 2026

VFR conditions are expected to prevail at all terminals this period. Scattered cumulus are present around Iowa and are expected to dissipate after sunset tonight. There is a low (20%) chance for showers and thunderstorms between 18z and 02z, though low confidence in storms impacting any one terminal leads to no mention in the TAF. Otherwise, winds will be light and variable with a low potential for fog to develop across northern Iowa tonight.

DMX WATCHES/WARNINGS/ADVISORIES

None.