textproduct: Des Moines

KEY MESSAGES

- Quiet weather continues today with highs in upper 70s to lower 80s. Areas of patchy morning fog remain possible.

- Rain chances return Sunday night into Monday morning (40- 50%), mainly across western Iowa. Severe weather is not anticipated.

- 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 218 AM CDT Sun Aug 23 2026

Saturday was arguably the best day in August so far! Highs climbed into the upper 70s to lower 80s across the state with dew points generally in the 50s and 60s making for a pleasant afternoon. Surface high pressure remains in place across the Central Plains this morning, keeping conditions calm across the Upper Midwest. With the high ushering dry air across central iowa, skies remain mostly clear tonight allowing for efficient radiational cooling. Lows overnight are expected to drop into the upper 50s across southern Iowa and lower 50s north. Given clear skies and calm winds, areas of patchy fog remain possible overnight- primarily along low lying river valleys, with minimal impacts as fog should remain fairly wispy. As we head into late morning, fog will burn off and cloud cover will increase from western Iowa ahead of our next incoming disturbance.

The 500 MB trough centered over Ontario will begin shifting eastward, flattening the northern edge of the Four Corners ridge that has been anchored for past few days. Consequently, short range guidance indicates a shortwave emerging off the Rockies, pushing unsettled weather across the High Plains Sunday afternoon and evening. This will allow rain chances to return to western and central Iowa as early as Sunday night. The main forecast challenge is the timing of initial rain onset, as forecast soundings show a very dry layer in the lower to mid levels. While short range guidance attempts to introduce showers into western Iowa as early as Sunday afternoon, precipitation chances were kept out of the daytime forecast due to the strong signal of dry air keeping initial returns as virga. Overnight, a strengthening LLJ will push into western iowa, enhancing low level moisture transport and saturating the column top down. The highest precipitation chances (40-50%) will align near the jet axis, with chances dropping of eastward toward the Des Moines to Davenport corridor (30-10%) where the deep layer saturation is harder to achieve. If the jet shifts further east, rain chances will need to bumped up accordingly. Rain chances gradually diminish into Monday afternoon. Severe Weather is not anticipated with this round due to negligible instability, with activity expected to remain mostly showers and an isolated storm or two.

LONG TERM /MONDAY NIGHT THROUGH SATURDAY/

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 /12Z TAFS THROUGH 12Z MONDAY/

Issued at 646 AM CDT Sun Aug 23 2026

VFR conditions will prevail with light winds. Added in a Prob30 for rain at KFOD for late in the planning period. Impacts with rain are expected to be low with a low chance of thunder.

DMX WATCHES/WARNINGS/ADVISORIES

None.