textproduct: Des Moines

KEY MESSAGES

- Hot and humid today and tomorrow. Heat peaks on Monday, with a Heat Advisory across the entire forecast area from noon to 8pm.

- Two rounds of storms are possible on Monday: The first in the morning and again in the later afternoon through the evening. Severe storms are expected and may produce damaging winds, along with hail and heavy rain. There is also a low tornado threat, highest in northeast Iowa.

- Cooler temperatures return into midweek in the upper 70s to 80s and dry until Wednesday evening

SHORT TERM /THROUGH MONDAY NIGHT/

Issued at 318 PM CDT Sun Jul 19 2026

A look at surface conditions this afternoon per GOES satellite imagery shows a blanket of smoke covering much of roughly the eastern third to half of Iowa, but especially into Wisconsin and Illinois where it is notably thicker. This is thanks to an area of high pressure that is centered over the Great Lakes, which is moving this lingering wildfire smoke from the Ohio Valley into Iowa from the southeasterly flow. Sites such as Mason City, Waterloo and Ottumwa were reporting visibility values anywhere between 2-5 statute miles due to this smoke, with light wind also reported. This smoke per guidance is expected remain over these areas due to little change in the flow pattern, before gradually departing through Monday morning given an expected pattern change. The Iowa Department of Natural Resources has issued an Air Quality Alert through 11am Monday for the eastern half of Iowa due to this smoke. Those especially sensitive to smoke should limit time spent outdoors as needed. Outside of the smoke, seeing a streak of clouds over southwest Iowa that is associated with pooling theta e advection against the dominant area of high pressure. The instability gradient in this strip of clouds is indicating values generally less than 1000-2000 J/kg, paired with weak flow that will allow for clouds to remain in this area, along with a very low chance for a diurnally driven isolated shower or storm into the early evening. A larger area of clouds moving across northwest Iowa from decaying morning convection over the Dakotas will allow for a general increase in upper level cloud cover across Iowa, along with the development of scattered diurnally driven cumulus, but shouldn't hinder highs today from reaching forecast values in the mid 80s to low 90s, warmest south.

Into this evening, the high pressure system will slowly dive further southeast out of the region, with attention turning to a rather potent shortwave over southern Canada that is expected to move east/southeast to the Upper Midwest into Monday morning. Ahead of this feature, a boundary will extend down through Minnesota and into northern Iowa, which per guidance will bring the next chance for showers and thunderstorms. Latest CAM guidance has slowed the arrival of this boundary, with dry conditions likely holding on until near/after sunrise when scattered showers and storms push into northern Iowa. While the better forcing is located further north and east of the state, should still see enough lift near the boundary to allow for elevated storm development that will be aided by environmental conditions of shear around 30-40 knots and MUCAPE values around 1000-2000 J/kg to produce sub severe to isolated severe wind gusts and small hail. Could also see localized areas of efficient rainfall with this activity, given PWATS around 1.75-2 inches and high warm cloud depths, leading to rainfall amounts up to an inch and potentially locally higher amounts.

This activity is only the first round of storms for the day, as additional activity is expected to occur into the afternoon and especially through the evening/overnight. Before we get into those details, lets discuss the setup. The low-level flow will increase out of the southwest, increasing theta-e advection across the entire forecast area, which will bring much warmer and humid air into the region. Despite the morning storm potential in northern Iowa, should see a window of returning dry conditions and decreasing clouds in these areas that will allow for temperatures to increase substantially into the mid to upper 90s over much of Central Iowa, paired with dewpoints through the 70s. This will allow for heat indices to top out in the 100-105 degree range across the forecast area into the afternoon, with high enough confidence resulting in the coordination and issuance of a Heat Advisory that is in effect from noon to 8pm. Heat safety measures need to be practiced to avoid negative impacts from these conditions.

The hot and humid conditions, paired with the closer proximity of better mid and upper level support from the deepening trough traveling southeast across the Midwest will lead to returning chances for scattered showers and thunderstorms into Iowa with and near the surface boundary later in the afternoon and especially evening/overnight. Regarding the specific details, could see initial isolated storm development just ahead of the boundary around mid- afternoon over northern Iowa, followed by more scattered activity by evening. Model guidance has been struggling to agree on how fast this boundary sinks through the area, with variations of the front anywhere from north central to south central Iowa after sunset. While timing details will need to be watched over very closely, the environment regardless of position of this front will be more than conducive for strong and even severe thunderstorm development as organization takes place, given instability values over 4000 J/kg and shear values around 50-60 knots, along with steeper lapse rates near 7-7.5 C/km. The main hazard of concern remains damaging wind gusts, especially later on as storms congeal into a line, though large hail initially is possible, as well as a few tornadoes mainly in northeast Iowa given closer proximity to the surface low. Heavy rain is also expected at times due to PWATS around 2-2.25 inches and warm cloud depths over 15 kts, with rainfall amounts in spots possible up to 1-2 inches and slightly higher amounts in localized areas. However, the flooding threat is minimal given antecedent dry conditions and the expected progressive movement of any storms.

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 /00Z TAFS THROUGH 00Z TUESDAY/

Issued at 641 PM CDT Sun Jul 19 2026

MVFR vsbys in the east due to near surface smoke. Smoke will linger through the TAF period, but vsby reductions less certain due to showers and storms. Have left as VFR for now with Prob30 groups reflecting storm arrival. 4 kft cumulus deck common throughout the period.

For storm confidence, the early morning arrival will affect northeast terminals most, with a second round developing somewhere over northern Iowa after 20z. Confidence in impacts with the first round is decreasing and the second round may be delayed in time in the 06z issuance. Confidence remains low for storms at KDSM.

DMX WATCHES/WARNINGS/ADVISORIES

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