textproduct: Des Moines

KEY MESSAGES

- Frost and Freeze headlines remain through sunrise this morning, then improving temperatures in the low to mid 60s.

- Light shower activity possible in northeast half of Iowa late tonight into Sunday morning. Dry the remainder of the day.

- Increasing potential for showers and storms later Monday, with isolated strong/severe storms possible south into the evening.

SHORT TERM /THROUGH SUNDAY NIGHT/

Issued at 332 AM CDT Sat May 2 2026

A quiet but chilly early morning is panning out largely as expected, with much of the area under clear skies and light winds, leading to efficient radiational cooling and temperatures plummeting into the 30s. Values are coldest over northern to central Iowa in the 32-36 degree range. Clouds that were overhead the state yesterday are still lingering over southeastern Iowa though, which has led to temperatures much warmer yet in the 40s. Despite this, the expectation is that these stubborn clouds should slowly track southeast out of the area over the next hour or so, allowing for temperatures to drop rather quickly into the 30s before sunrise occurs. Therefore have made no change to current frost/freeze headlines this morning, which will remain in effect until 8am. Winds shift westerly into this afternoon as the area of surface high pressure centered over eastern Nebraska shifts south out of the area through the day, with mostly sunny skies through the afternoon that will lead to warming temperatures in the low to mid 60s. Surface winds shift further southwest into the night through Sunday morning, allowing for warm air advection to increase into Iowa. Overnight lows for this reason, along with increasing cloud cover will allow for milder low temperatures in the upper 40s to low 50s.

The shift to WAA is a response ahead of the next shortwave within the midlevel northwest flow pattern, which is expected to descend across the Midwest by Sunday. A trailing cold front related to this wave is expected to reach into northwest Iowa in the early morning hours, dropping southeastward across the state before making a full passage by the early afternoon. Notable forcing for lift ahead of the front, along with some saturation in the mid-levels is featured, which CAM guidance continues to try generating reflectivities late tonight through mid-morning Sunday, mainly over the northeast half of the state. However, a closer look at model soundings shows the presence of a deep layer of pronounced low level dry air that is lingering from the high pressure that departed the state earlier in the day, which will likely greatly limit rainfall potential at the surface. Sprinkles or very light rain in areas where better precipitation loading could occur, at best, would be possible, but otherwise most areas should remain dry. Despite the shift to northwesterly surface winds behind the departing front into the afternoon, incoming 850mb temperatures with the approaching western CONUS ridge will allow for highs to reach into the upper 60s to low 70s. There remains a signal for redevelopment of showers and even some storms into the evening, but by then the front is well south into northern to central Missouri, so any potential for additional activity continues to diminish and have left the forecast dry for the remainder of the day. Otherwise, another area of high pressure will quickly pass across the state through the evening, leading to gradually shifting winds back southwesterly into Monday, keeping overnight lows on the milder side in the mid to upper 40s.

LONG TERM /MONDAY THROUGH FRIDAY/

Issued at 332 AM CDT Sat May 2 2026

The warming trend will peak Monday as the warm air settles overhead, with highs expected to top out in the mid to upper 70s. While conditions are expected to remain dry through the afternoon, a stronger system dropping across the Upper Midwest will send another cold front across Iowa through the day, which will eventually lead to shower and storm development by the evening. Model guidance indicates development of this shower/storm activity to occur largely over southern and eastern Iowa, where the better saturation and forcing near the boundary is located per NAM, though comparison with the GFS/Euro has this boundary placed over north central Iowa by the evening. Certainly some timing differences that will need to be sorted out over the next few days, though it is safe to say at this time that at least somewhere in Iowa will see showers and storms to some degree. There is the inclusion of a Marginal Risk for isolated severe storms in far southern Iowa into Missouri/Illinois in the SPC Day 3 outlook, which is reasonable considering the presence of instability values around 1000-1500 J/kg and shear values over 35 knots in these areas.

By Tuesday, this boundary is suggested to stall somewhere over southern Iowa or northern Missouri, with an overall decreasing trend in activity through the morning before redevelopment is indicated in the afternoon to evening as peak heating occurs. Overall uncertainty in exact coverage and timing is present this far out considering the inconsistency in guidance earlier in the week with this boundary, so will be something to keep an eye on. Otherwise, high temperatures will be several degrees lower as values are only expected in the upper 50s across the forecast area. The pattern by midweek is trending on the cool side, with additional rain chances as a deepening longwave trough arrives over the Central Plains. It is worth noting though that there is no signal for severe weather at this time with this activity, given the instability axis being shunted much further south of the state.

AVIATION /12Z TAFS THROUGH 12Z SUNDAY/

Issued at 627 AM CDT Sat May 2 2026

VFR conditions are expected across the terminals through the period. Mostly clear skies are expected through the afternoon, followed by increasing clouds expanding northwest to southeast by the evening. There is a low potential for sprinkles or light rain showers mainly over the eastern terminals after 03-06z, though with low confidence have continued to leave out at this time and will continue to assess through today. Winds will be out of the west/northwest for much of the day, then shifting southwesterly late in the period, before shifting further northwesterly near the end of the period as the boundary passes through, with occasional gusts up to 10-15 knots. LLWS is also expected between 06-12z across most sites before dissipating.

DMX WATCHES/WARNINGS/ADVISORIES

Freeze Warning until 8 AM CDT this morning for IAZ004>007- 015>017-023>028-033>037-044>047. Frost Advisory until 8 AM CDT this morning for IAZ038-039- 048>050-057>062-070>075-081>086-092>097.