textproduct: Des Moines

SHORT TERM /THROUGH SATURDAY/

Issued at 226 PM CDT Thu Oct 8 2026

The current upper level pattern has the region placed under northwest flow aloft with a trough over the Great Lakes and most of western CONUS under a ridge. At the surface, Canadian high pressure is allowing for mostly clear skies, dewpoints in the 30-40s, and light and variable winds.

Going into tonight, model agreement is increasing for scattered showers and thunderstorms to track east-southeast from 02z to 15z, mainly north of I-80. The upper level flow is expected to become more zonal as the surface high moves east and is replaced by a weak surface low. In conjunction with this low, a decent nocturnal LLJ (20-30kts) will pivot into the southwestern part of the state and lift a warm front across the state. As this happens, there is good agreement that a swath of enhanced theta-e advection will provide sufficient lift and instability for showers to develop. Most models are depicting MUCAPE values of 500-1200 J/Kg. This would allow most showers and storms that develop to produce 0.10" to 0.5" of rain, which matches the HREF probability of areas east of I-35 and north of I-80 seeing 0.5" rain being around 40%. There are a few models that are depicting a low probability higher end scenario (especially the NAM) where the LLJ pivots more directly overhead of the state allowing for higher values of MUCAPE (~2500 J/Kg). This has led the SPC to issue a day 1 Marginal risk for hail over the northern half of the CWA where a few instances of severe hail could be possible in the strongest updrafts overnight. This scenario would also have the possibility of seeing a narrow zone of 1-2" of rain. However, this solution is less likely given the dry air that would need to be overcome for this to come to fruition.

Going into Friday, lingering showers in the northern and eastern counties will lead to delayed warming with highs only expected to reach mid 70s. Whereas elsewhere, southerly winds, a northward moving surface boundary, and a building ridge will allow temperatures to rise into the low 80s. Winds will also increase in the afternoon to 10-15 mph with gusts up to 20 mph.

Focus then shifts to Saturday as the remnants of tropical cyclone Isaias will drift northward before pushing off to the east on Sunday. While not directly impacting Iowa, it will cause the weak ridging to stick around on Saturday for southeastern Iowa. At the same time, a broad surface low pressure system is expected to traverse trough the Dakotas leading to a tighter pressure gradient at the surface in northern and western Iowa. This will result in stronger surface winds from the south in the northwestern portion of the state. Winds around 20-30 mph with gusts up to 40 mph are likely. Elevated fire weather concerns will be probable given dewpoints in the 40-50s and minimum RH values in the 30-40 percent range. Given that this area received less rain in the month of September than the rest of the state and that croplands have cured, this will be something to monitor closely in the next couple of days.

LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/

Issued at 226 PM CDT Thu Oct 8 2026

On Sunday, temperatures will be in the upper 70s to low 80s with winds lessening as the surface low pressure system moves off toward the Great Lakes. Going into Monday, the upper level flow will once again turn zonal as the remnants of tropical cyclone Isaias pushes off into the Atlantic.

There will be slight chances for light precipitation on Monday in the far northern counties as a shortwave moves across Manitoba/Ontario; however, being so far disconnected from the greatest lift has led precipitation chances to be less than 20%. Temperatures on Tuesday and Wednesday should be pleasant and fall-like with highs in the mid 60s to low 70s before southwesterly flow aloft returns mid-week and a large trough digs over the western US. Effects from this trough are uncertain at this time due to model differences, but will be something to monitor over the weekend into next week.

AVIATION /06Z TAFS THROUGH 06Z SATURDAY/

Issued at 1122 PM CDT Thu Oct 8 2026

Prevailing VFR conditions are expected through this TAF period. Showers and thunderstorms are ongoing across central and northwestern Iowa, although that are fairly concentrated in area. Brief MVFR CIG/VIS are possible with overnight showers and storms. This activity has been handled as PROB30 mentions at northern sites with prevailing mentions at KFOD, KDSM and KOTM through the first part of the period before storms clear off to the north and east through the morning. Wind gusts are expected to increase slightly during the daytime hours before dropping out after sunset. Winds will be out of the east/southeast through the day.

DMX WATCHES/WARNINGS/ADVISORIES

None.