textproduct: Des Moines

KEY MESSAGES

- Frost Advisory in effect until 8am this morning. Dry and cooler today with additional frost potential tonight.

- Low chance (30-40%) for showers Friday, then more widespread showers and thunderstorms Saturday into Sunday, with highest potential over southern Iowa (50-60%)

SHORT TERM /THROUGH THURSDAY NIGHT/

Issued at 408 AM CDT Wed May 6 2026

Dry and cool conditions are common across the forecast area early this morning, with satellite imagery depicting a stream of mid to upper level clouds across much of Central Iowa, while a broader area of mid level clouds is dropping south across Minnesota, with its southern extent just touching the IA border. The broad synoptic pattern features a large area of troughing over the Upper Midwest into Canada that has more or less moved very little over the past few days, while further west, an area of surface high pressure is currently sitting over Montana/western Dakotas and extending its influence into the Central Plains. Continued cold air advection from northwest flow into Iowa is keeping cooler conditions overhead, with current temperatures in the upper 30s in northern and western Iowa, and warmer in the south in the 40s. Mostly clear skies and temperatures expected to bottom out in the low to mid 30s over northern Iowa may still allow for some areas of frost development through sunrise, hence the continuation of the current Frost Advisory over this area until 8am this morning. As the aforementioned high pressure moves closer to the state through today, will see the continuation of dry conditions and cooler temperatures, with forecast highs in the 50s. Boundary layer mixing is expected later this morning into the afternoon, with the presence of low level dry air leading to breezy conditions as gusts up to 20- 25 mph are expected, especially north. Winds relax into this evening through early Thursday, becoming variable in direction as the area of surface high pressure drops further south/southeast across the Central Plains. Overnight lows turn chilly once again, though more widespread with values in the mid to upper 30s. Regarding frost potential, there remains the potential in patchy cloud cover that would limit frost formation, but is still possible. Will be keeping an eye on trends, with the possible issuance of additional frost headlines later today. Stay tuned for updates.

A shift to low level southwesterly flow through the morning is expected to allow for a push of warmer air into Iowa, with forecast highs in the mid to upper 60s by the afternoon. Theta-e advection from this southwesterly flow increases dew points in the upper 30s to low 40s over south/southeast Iowa, creating a subtle boundary as drier air remains north/west. A close look at model soundings shows an impressive layer of keep mixing all the way up to around 3km, leading to very dry air overhead, along with cumulus development given elevated instability and some mid-level moisture. Have therefore decreased dewpoints, especially northwest with this forecast package, which has also lowered RH values as minimum values drop into the low 20s, though likely lower given the degree of airmass drying that short-range guidance is indicating. These conditions may lead to at most some concern for elevated fire weather conditions in northwest Iowa, though rather isolated in nature given increasing greenup of fuels. The weak boundary slowly shifts south into Thursday evening, with a low level wave passing through as well that models are indicating some development of showers mainly east of I-35, but especially over IL/WI where forcing and moisture is maximized. With the presence of dry air overhead as mentioned earlier, it would seem unlikely that any hydrometeors would be able to reach the ground, so have left the forecast dry at this time and will continue to monitor.

LONG TERM /FRIDAY THROUGH TUESDAY/

Issued at 408 AM CDT Wed May 6 2026

As ridging builds west into Friday, mid-level northwest flow persists into Iowa, while another shortwave and attendant surface low developing east of the Rockies moves into the region. Models generally keep this system over Missouri, with its northern periphery into southern Iowa where forcing for lift is suggested to develop rain showers later in the morning and through the afternoon before moving off east out of the area. Little instability over this area could lead to some thunder, but otherwise little in the way of storm development is expected with this activity at this time. Temperatures will remain warmer as highs are expected to reach into the upper 60s to low 70s.

Dry conditions and warmer temperatures are expected to start the weekend, with long range guidance showing more widespread chances for showers and storms into Saturday evening/early Sunday, especially over southern Iowa, and highs reaching through the 70s, warmest south. Instability values under 500 J/kg should limit any potential for severe weather with this activity. As the boundary departs into Sunday, temperatures will be slightly cooler with highs in the 60s. High pressure dropping through the region into the start of the next work week keeps conditions on the quiet side, then turns rainy again by early Tuesday as another area of low pressure arrives into the Midwest.

AVIATION /12Z TAFS THROUGH 12Z THURSDAY/

Issued at 634 AM CDT Wed May 6 2026

Areas of mid level clouds are expected through this afternoon, before decreasing this evening, outside of lingering upper level clouds. VFR conditions are generally expected, with lowest ceilings expected through this afternoon at times down to around 5kft across most if not all sites. Winds out of the northwest will increase this morning and into the afternoon, with gusts peaking at 15-20 knots, before turning light and variable this evening.

DMX WATCHES/WARNINGS/ADVISORIES

Frost Advisory until 8 AM CDT this morning for IAZ004>007- 015>017-023>028.