textproduct: Des Moines

KEY MESSAGES

- Showers and thunderstorms in the west this afternoon slowly move eastward with time tonight. More widespread rain/storms are then expected late tonight into early Friday morning. There is a chance for some gusty winds but the overall chance for severe storms is low tonight. There is a potential for heavy rain Thursday night into Friday morning.

- Additional rain and thunderstorms are possible on Friday midday into the evening, with an isolated threat for severe weather, especially in southeast Iowa.

- Breezy conditions are expected Friday afternoon with wind gusts reaching up to 40-45mph.

- Relatively cooler and quiet weather is then forecast Saturday through at least Monday.

SHORT TERM /THROUGH FRIDAY NIGHT/

Issued at 252 PM CDT Thu Jul 30 2026

Surface high pressure continues to drift eastward this afternoon as the first in a series of shortwaves moves into the area. Radar returns have slowly crept into Crawford and Sac counties over the last several hours with returns also diminishing as they creep eastward, thanks to dry air in the low to mid levels. As time goes on, profiles do start to saturate so it is possible western to northwestern counties do start to see some light rain this afternoon to early evening as the first shortwave pushes east into tonight. Prior to saturation occurring, profiles show the inverted V soundings so an isolated strong wind gust remains possible with the shower activity as it reaches our western area, but overall the severe threat remains low this afternoon with limited CAPE/Shear in the bulk of the area. As this saturation occurs, these showers will then likely percolate across portions of western and into northern and central Iowa through the evening posing mainly a heavy rain threat as they will be slow moving. The bulk of this rain initially looks to fall in western Iowa, just outside of our area.

Attention then turns towards the activity developing in NE/SD this afternoon, as these are the storms we are monitoring as they near our area late tonight. Although there remains some overall agreement in storms diminishing in intensity as they reach into our area late tonight/overnight, there is less confidence in the track of the storms with some recent guidance sinking them southwest, others right through the area, and then even less acquirement amongst CAMS in timing with many suggesting a slower evolution while others still have most activity through between 06-12Z (1AM to 7AM). There remains some idea of the storms congealing into a line but should they dive southwest, there may then be a spatial break between the diminishing line of storms and the percolating activity closer to the low (more on this in a minute). The timing and strength of this next line of storms has many implications on the going forecast in 1) QPF/rain amounts/locations of the highest rain amounts, and 2) the severe threat to follow on Friday. We'll get back to this in a second. What we do know is by late tonight cyclogenesis occurs with a surface low developing around the IA/SD/NE border. The parent upper trough and related surface low both cross through the area through the day Friday, finally departing the state by early Saturday morning. There is likely to be a break in the activity between the line late tonight/overnight and the additional activity developing in the deformation zone on the backside of the low tomorrow. If there is enough of a break (e.g. the faster solution noted above), there is a conditional severe threat that may develop in southern to especially southeast Iowa Friday later afternoon to early evening provided some clearing can occur. Sufficient 0-3 CAPE and low LCLs could combine with the backing flow to create a tornado threat, or at the very least some funnel cloud potential in addition to a wind threat with any storms that can develop. Gradient winds on the back side of the low are expected to increase through the afternoon Friday with gusts to around 30-45 mph, so it wouldn't take much to get an even stronger gust with a storm. If the slower solution noted above occurs, this could potentially increase rain amounts, but it makes destabilization much harder and thus decreases the severe threat Friday afternoon. Rain amounts largely remain in the 1-3" range, the highest totals looking to be in portions of northern to eastern Iowa, though isolated higher amounts are certainly possible in localized areas and should they get closer to the 3-5" range, especially if in an urban area, this could lead to some heightened flash flood concerns. The location of these higher rain amounts remains uncertain, however, with the increasing variability in location/timing of the showers/storms through the rest of the day/night tonight into Friday morning. See the HYDROLOGY section below for some additional details in the Hydro threat.

LONG TERM /SATURDAY THROUGH WEDNESDAY/

Issued at 252 PM CDT Thu Jul 30 2026

Drier conditions return on Saturday as an upper ridge starts to build back into the area. Temperatures remain cooler for the season and in the 70s Saturday to 80s into early next week making for another pleasant stretch. The next chances for precipitation start to move in midweek as upper troughing returns with several rounds possible as waves move through the overarching upper level pattern. Details will continue to be fine-tuned as we get closer.

AVIATION /18Z TAFS THROUGH 18Z FRIDAY/

Issued at 1245 PM CDT Thu Jul 30 2026

VFR conditions ongoing to start the TAF period though clouds will continue to move in and ceilings to decrease through the afternoon into evening, but mainly VFR. Showers/storms are still expected to cross through the area with the bulk of the activity between 06 and 12Z, but with some showers/storms lingering beyond in the east or developing ahead in the west. Although confidence in rain impacting the terminals at some point during the night is pretty high, there is less confidence in the visibility impacts and extent of thunder so kept previous prob30 groups for lower visby conditions/TSRA but refined timing a bit to reflect current guidance. Models are hinting at near widespread IFR ceilings moving in 08-12Z and lingering until 15-18Z or beyond in especially the north/northeast. Although IFR signal is decent, extent of low clouds is less certain (e.g. FL004 vs FL009) so started with touching IFR (FL010) but refinements are likely in future issuances. Some additional showers/storms may then redevelop through the afternoon Friday, just beyond the end of this TAF period, with gradient winds also becoming gusty. Some additional gusty and erratic winds are possible with storms that occur tonight/overnight but are not reflected in TAFs themselves.

HYDROLOGY

Issued at 252 PM CDT Thu Jul 30 2026

Risk of flash flooding (initially) and subsequent river flooding returns to our CWA late in the work week due to aforementioned heavy rain potential. For the flash flood risk, the most likely QPF scenario would mainly confine flash flood concerns to urban areas, where ponding or lower-end flash flooding may occur. Crops in the rural areas are well into their growth which tends to significantly increase infiltration capacity. Three potential nuances are (1) slightly elevated soil moisture percentiles from central into northeast IA, which would increase the risk of runoff in rural areas; (2) intense rainfall rates may increase the risk of increased runoff in rural areas; (3) rainfall that overachieves vs. QPF would increase the flash flood risk even in rural areas. Rural rain amounts that exceed ~3-4 inches over a few hours would especially increase the risk.

River flood risk depends significantly on rainfall amounts, location and timing. Presently the most likely scenario is moderate to significant within-bank rises on many streams with a few river forecast points possibly reaching action stage, but remaining below flood stage. Rainfall that overachieves vs. QPF would result in higher stages, with more forecast points reaching minor flooding, along with some isolated moderate river flooding.

DMX WATCHES/WARNINGS/ADVISORIES

None.