textproduct: Des Moines

KEY MESSAGES

- Generally quiet weather for the upcoming week, with daily high temperatures in the upper 70s to mid-80s.

- Decent rain chances (around 50%) late Sunday night and Monday, otherwise only low and spotty chances for most of the week.

- Early signs of a somewhat more active weather pattern next weekend, with a return of more persistent rain chances but any details still unclear at this range.

SHORT TERM /THROUGH MONDAY/

Issued at 1237 PM CDT Sat Aug 22 2026

An omega blocking pattern is attempting to set up across North America, but is not fully entrenched. At 500 MB a large ridge is entrenched across the southern High Plains and over toward the Four Corners region, bringing near-record warmth to parts of that area, and extending far northward into Central Canada. Meanwhile, two troughs are present with the western one just coming ashore over the U.S. Pacific Northwest, while downstream, another trough is digging from Hudson Bay down across Ontario and into the U.S. Great Lakes region. Iowa currently lies beneath the brisk northwesterly steering flow between the ridge and the eastern trough. At the surface, a large high pressure area is spilling down from the Canadian plains into the Midwest, heralding relatively quiet and comfortable weather for Iowa this weekend. High temperatures will range in the upper 70s to lower 80s both today and Sunday, with dewpoints generally in the 50s and 60s. This will make for a glorious weekend for most late summer outdoor activities. Tonight into early Sunday, as the ridge settles across Iowa and winds to light to calm beneath virtually clear skies, we should radiate nicely with temperatures falling into the 50s in much of the state. Some guidance outputs light fog around sunrise Sunday, however, most does not and given relatively dry soils and more organized winds right off the deck, as well as the sparsity of wispy fog that occurred this morning, do not believe probability or impacts are sufficient to justify adding it to the forecast for Sunday morning.

During the day on Sunday, the Pacific Northwest 500 MB trough will begin to move east northeastward around the periphery of the High Plains ridge, which will begin to flatten the northward part of the ridge and allow a subtle shortwave impulse to overtop it ahead of the main trough. This shortwave will move over or near Iowa on Sunday night into Monday and bring a return of rain chances to our forecast area. Initially, there will be substantial dry air to overcome per forecast soundings, so while a few model solutions attempt to bring isolated showers into our western and southwestern counties late in the day Sunday, have held POPs out until later Sunday night when saturation may achieve sufficient depth to support rain chances. These chances will then continue during the day Monday before fading out as the shortwave moves away to the east. Instability will be very limited with this system so while scattered showers and isolated thunderstorms are forecast, severe weather is not currently anticipated.

LONG TERM /MONDAY NIGHT THROUGH FRIDAY/

Issued at 1237 PM CDT Sat Aug 22 2026

By Monday night the eastern 500 MB trough will have shifted over Quebec, while the western one crosses from Saskatchewan into Manitoba, then subsequently shifts east southeastward into the Lake Superior region by Wednesday. In Iowa this will be concurrent with a very light surface pressure/flow pattern, resulting in nebulous low rain chances at times from Monday night into Wednesday. As the 500 MB trough moves over Lake Superior, it will help push a large surface high pressure area down the northern High Plains and Midwest during this time, later bringing relatively comfortable and dry weather from around Wednesday night through Friday. The onset of the influence of this surface ridge will take the form of a modest trough, pushing through ahead of the main mid-level shortwave sometime around Tuesday night. Differences in timing and the sharpness of the trough lead to a high variability in model solutions, however, there does appear to be some potential for good destabilization on Tuesday afternoon/evening and also potential for moderate deep-layer (0-6 KM) shear of perhaps 30-35 KT or so. Again, there is significant variability in these solutions and much will depend on diurnal timing, but it is possible if the trough has enough low-level convergence and comes through during peak diurnal heating time, there may be a narrow window of opportunity for pulse storms with a severe weather threat late Tuesday. A more likely scenario, however, is that the trough comes through overnight with much less instability and/or weaker shear, or that the trough is too weak and low-level convergence is not sufficient to support stronger updrafts, or both. By next weekend, the 500 MB pattern should begin to shift just a bit, with the ridge flattening and shifting a bit toward the southwestern U.S., while a more zonal flow pattern sets up across the northern CONUS and Iowa. This would favor a somewhat more active weather regime in our region, with persistent rain chances likely returning. Of course that is still a week-plus out, but something to keep an eye on in the coming days.

AVIATION /18Z TAFS THROUGH 18Z SUNDAY/

Issued at 1221 PM CDT Sat Aug 22 2026

TAFs are VFR with no aviation impacts anticipated. There is a very low chance (<20%) of shallow fog around sunrise Sunday, but both probability and coverage/impact if it were to occur are too low for any TAF mention.

DMX WATCHES/WARNINGS/ADVISORIES

None.