textproduct: Des Moines

KEY MESSAGES

- Warm and mostly dry conditions continue today. Highs in the 80s continue into the weekend.

- Scattered shower/storm chances (20 to 30%) return to the western and southwestern portions of the area overnight into early Friday morning, then again Friday afternoon and evening. The potential for severe weather looks low at this time. - Additional scattered shower and storm chances (20 to 30%) persist into the weekend, although much of this activity should remain west of the area.

SHORT TERM /THROUGH FRIDAY NIGHT/

Issued at 311 AM CDT Thu May 28 2026

After multiple nights of scattered showers and sub-severe storms, northern Iowa finally gets to join the rest of the state in having a dry and uneventful night. Surface high pressure has begun to build over the Great Lakes region, which now spills into Iowa early this morning. Current surface winds are fairly light, but a subtle shift from south southeast to northeast in northeastern Iowa is a sign of this drier air mass trying to work it's way into Iowa. The expansion of this Great Lakes high into Iowa will have a notable influence on our forecast over the days to come, particularly in regards to rain chances.

Through the day Today, the high pressure over the Great Lakes will generally dominate the surface flow pattern. This will keep a persistent stream of dry air at the surface, inhibiting precipitation over most of Iowa through the day. A stripe of weak instability (~500 J/kg) over western Iowa is causing some shower/storm development in CAM guidance this afternoon, but a deeper look into model soundings shows very dry profiles and a shallow unstable layer sitting atop of a well-mixed boundary layer. These profiles suggest some scattered cumulus development under the high clouds today, and maybe even some virga, but not expecting hydrometeors to reach the ground before evaporating. Otherwise, highs will once again reach the mid 80s under partly cloudy skies.

An increasing gulf moisture stream will push northeastward into southwest Iowa tonight into early Friday morning, which will work to saturate the mid and upper levels. Easterly flow from the surface high will keep the low levels dry, but the surface high's influence won't be as strong over western Iowa. As a result, we'll see increasing rain chances (~20%) over far southwestern Iowa by early Friday morning, as the weak lift and instability saturates down through the dry low levels. Breezy winds may occur as this saturation occurs, but with only a few hundred J/kg of MUCAPE and minimal shear Friday morning, not anticipating any severe weather.

Our Great Lakes surface high will try to hold off the encroaching moisture stream as it attempts to bring better saturation into Iowa on Friday. The strength of the high on Friday will greatly dictate how far east rain chances get, with some of the 00z CAM guidance suggesting we could see scattered showers/storms as far east as central Iowa Friday afternoon and evening. However, some of the 06z guidance that has been rolling in has already backed off on the eastward extent of rain Friday, suggesting the dry air from the high pressure may win out. Typically in these cases, we see the high pressure and east southeasterly flow win out over the moisture advection, especially in weakly forced scenarios like this one. The wild card will be if any instability will be able to take advantage of the increasing moisture content, leading to isolated or scattered convection. Fortunately, if any showers or storms do occur, the instability values still look low (< 1000 J/kg) and wind shear still weak, so the potential for organized storms and severe weather looks minimal at this time.

LONG TERM /SATURDAY THROUGH WEDNESDAY/

Issued at 225 PM CDT Wed May 27 2026

Remarkably similar mid-80s highs are expected through the end of the period, though confidence decreases after Monday. The moisture axis mentioned above will remain just west of our area until Sunday, keeping some potential precipitation chances over west/southwest Iowa into Saturday. On Sunday, a shortwave embedded within the western longwave will pivot across the high plains. It is likely this will be too far west to create any meaningful shear, but may be enough to bring the moisture axis farther into Iowa. GEFS SBCAPE probabilities increase significantly Sunday and beyond, and more QPF outliers show up in the NBM members Sunday night and afterwards (though an overall dry pattern will likely still dominate). Ensembles suggest the omega block pattern will begin to break down early next week, and the exact evolution of how the ridge breaks down and the longwave finally ejects will determine whether our hazards for next week are garden variety single cell thunderstorms or stronger, more organized storms.

AVIATION /06Z TAFS THROUGH 06Z FRIDAY/

Issued at 1036 PM CDT Wed May 27 2026

VFR conditions will persist through the period. Scattered cirrus overnight may become BKN at times on Thursday. Light wind overnight the becoming east/southeast around 10 kts by mid to late morning.

DMX WATCHES/WARNINGS/ADVISORIES

None.