textproduct: Des Moines

KEY MESSAGES

- Shower and non-severe thunderstorm activity continues early this morning, diminishing around day- break.

- Warm, breezy and dry conditions expected during the day today with highs in the 80s and southerly winds gusting around 25 to 30 mph at times.

- Additional shower and thunderstorm chances (20 to 30%) over northwest into north central Iowa this evening. A few stronger storms could produce gusty winds or hail, mainly in northwest Iowa.

SHORT TERM /THROUGH TUESDAY/

Issued at 229 AM CDT Mon May 25 2026

Rain and thunderstorms continue to develop along the nose of a healthy 40 to 50 kt low level jet (LLJ) currently positioned over western Iowa early this morning. Storms have very much been of the "general" variety, as the activity in our forecast area has been pulsey and disorganized. Looking at the current environment over Iowa, this makes sense. The effective shear is negligible (20 kts or less), and instability is meager (less than 500 J/kg). Instability and shear values improve farther north and west nearer to the center of the jet, resulting in a few strong to severe storms with gusty winds and hail closer to Sioux Falls. Through the rest of the morning, the jet will slowly pivot east into Iowa, bringing the slightly better instability (~1000 J/kg) and shear (~30 to 40 kts) with it. That said, both variables will also be waning as time goes on, and generally lag behind the current activity, so still expecting storms to remain sub-severe through the night. If anything, some 30 to 40 kt winds could be mixed down with storms from the jet aloft.

The jet and coincident low level pressure gradient will end up over central Iowa during the day today, which will bring breezy conditions as the boundary layer mixes during the day. Wind gusts of 25 to 30 mph will be possible, especially through mid-day when the gradient will be strongest. The Monday morning jet eventually diminishes by this evening, but another LLJ will begin to develop similar to last nights, oriented over the Plains and nosed into northwest Iowa again. This will keep the moisture feed into the state today into tonight, as well as more chances for showers and thunderstorms.

Today/tonight's setup will be very similar to last nights, with a swath of better instability (2000+ J/kg) and marginal deep layer shear (25 to 35 kts) co- located with the jet. Like last night, there won't be much for forcing mechanisms, which is causing inconsistencies for convective initiation in model guidance, ranging from late afternoon to late evening. If storms do go over northwest Iowa in the late afternoon or early evening, gusty winds and hail would once again be the main threats. The later in the night it gets, the more the instability will diminish but the stronger the LLJ will get, increasing the potential for storms but decreasing potential severity. Therefore, once again we will see scattered showers and storms firing along the nose of the jet, mainly in the evening and over northwest into north central Iowa, with the strongest storms likely being earlier in the evening. One main difference tonight compared to last night, however, is that the jet will be pushing northward through the night (rather than pivoting eastward) which will likely lift any shower/storm activity northward through Tuesday morning. The storm prediction center has trimmed the marginal risk for severe weather (level 1 of 5) westward this morning, with only portions of Emmet, Palo Alto, and Kossuth counties remaining in the severe weather outlook and the rest of central and northern Iowa in a general thunder outlook.

Aside from the shower/storm activity over northwest into northern Iowa, mostly dry conditions are expected through much of the area this Memorial Day. Temperatures remain warm to start out the week, as southerly flow at the surface and thermal15ridging aloft brings warmer air into Iowa. Highs today are expected to reach the low 80s southeast to upper 80s northwest, with a more widespread area of mid to upper 80 temperatures expected on Tuesday. After a breezier day on Monday, winds will be lighter on Tuesday, with dry conditions expected across the state.

LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/

Issued at 228 PM CDT Sun May 24 2026

The moisture axis responsible for Monday's storms will be ushered north by the building ridge. The blocking pattern still favors highs in the 80s, and now trends favor the moisture profile keeping southwest of the area for most of this week. Models diverge on how to handle the arrival of high pressure this weekend, which will affect where the moisture pool will move. A more eastward shift like the ECMWF's would mean active weather, whereas a more centered, faster solution like the GFS spells an extension of seasonal, dry conditions.

AVIATION /12Z TAFS THROUGH 12Z TUESDAY/

Issued at 627 AM CDT Mon May 25 2026

Isolated showers and storms linger over central Iowa early this morning, but should continue to diminish through the next few hours. Skies begin to clear out with breezy south southwesterly winds today. Winds will be strongest through mid- day, sustained around 12 to 18 kts, gusting up to around 28 kts. Otherwise, VFR conditions prevail. There is a low chances for an isolated shower or thunderstorm in northwest Iowa this evening, but not anticipating any impacted terminals at this time.

DMX WATCHES/WARNINGS/ADVISORIES

None.