textproduct: Des Moines

KEY MESSAGES

- Hot and dry conditions continue this week, with steady warming expected each day. Heat indices in the upper 90s to near 100F.

- Patchy fog possible again overnight into early Tuesday, mainly in low lying areas and over the eastern portions of the state.

- Showers and thunderstorms may return to the area late this week and weekend.

SHORT TERM /THROUGH WEDNESDAY NIGHT/

Issued at 226 PM CDT Mon Jul 13 2026

Our 500 mb ridge has now fully arrived overhead today and will remain there through the work week. The coincident surface high pressure has kept conditions status quo with another day of warm and dry summer weather. Our subtle daily increase in temperatures is on pace again today, with values across the area around 1 to 2 degrees higher than they were this time yesterday. Dewpoint temperatures are also similar, if not slightly higher, today compared to yesterday, generally in the mid 60s to near 70 and highest in northern and northeastern Iowa.

With the marginally higher dewpoints, and yet another night of efficient radiational cooling, model guidance is once again signaling for some patchy fog by Tuesday morning. This is expected to be fairly isolated, favoring low-lying areas where temperatures will be locally cooler and the eastern portions of the state where winds will be calm. Fog will likely be shallow, and will dissipate after a few hours of sunshine and surface heating.

We won't see much change to the weather tomorrow and Wednesday. Our surface high pressure remains in place overhead, resulting in widespread subsidence and dry conditions. There aren't any real strong pushes of moisture or temperature advection into the area, so any inputs into the airmass will be locally driven. Temperatures will continue to creep up a degree or two each day as more thermal energy is added to the airmass with each day of heating. Dewpoints will remain status quo, if not increasing slightly as soils and crops transfer more moisture to the air. The warmer 850 mb temperatures rounding the 850 mb ridge overhead will start to inch southward into northern Iowa, but these areas also have slightly higher moisture content, limiting thermal mixing and the transfer of warmer temperatures aloft down to the surface. That said, that higher moisture content from northern into eastern Iowa will lead to apparent temperatures in the upper 90s to near 100. Areas farther south and west will see similar or slightly warmer ambient temperatures, but the lower dewpoints will keep heat indices relatively cooler in the mid 90s.

Although the heat advisory criteria of 105F likely won't be reached Tuesday or Wednesday, conditions will still feel hot and muggy regardless. An excellent point from the morning discussion is that the calm to light winds will cause the air to feel more stagnant and likely hotter than if it were windier, further adding to the already uncomfortably warm conditions. Therefore, if spending long periods of time outdoors, make sure to drink plenty of water and take frequent breaks in the shade or A/C!

LONG TERM /THURSDAY THROUGH SUNDAY/

Issued at 226 PM CDT Mon Jul 13 2026

The dry spell is expected to continue through at least the latter half of the week as a deep ridge continues to dominate the midwest. Highs by the end of the week will top out in the mid 90s with dew points pushing the upper 60's to lower 70's. The primary source of the surface moisture will be crop evapotranspiration; due to a lack of external moisture advection, dew points should cap out in the lower 70s on Thursday.

Southwesterly flow returns to central Iowa toward the weekend, bringing a push of deeper moisture to the area. Highs will remain in the mid 90s with dew points creeping just above 70 degrees. Friday and Saturday currently offer the highest probability for heat indices over 100 degrees, though values are still forecast to remain below headline criteria. However, multiple days of heat indices nearing 100F and little relief with overnight lows in the mid 70s may warrant heat headline discussion later this week. Additionally, a passing shortwave interacting with this deeper moisture will bring a chance for scattered showers and storms Friday afternoon and night. Severe weather is unlikely due to minimal vertical wind shear, so any storms that develop will be pulse-like in nature.

For those looking for a break in the heat, model guidance hints that the powerful ridge will shift south and west by Sunday, allowing for northwestern flow to enter Central Iowa. Model guidance also suggests that organized convection will be possible Sunday and onward. Convective trends will be something to watch as we near the weekend.

AVIATION /18Z TAFS THROUGH 18Z TUESDAY/

Issued at 1229 PM CDT Mon Jul 13 2026

VFR conditions prevail through the day. Patchy fog will once again be possible overnight, but like previous nights, impacts will be isolated. Have mentioned 6SM BR at KALO and KOTM to account for this potential, as chances look best in the eastern portions of the state.

DMX WATCHES/WARNINGS/ADVISORIES

None.