textproduct: Des Moines

KEY MESSAGES

- Showers and thunderstorms are likely tonight into Friday morning across central portions of Iowa. Severe weather and widespread heavy rain is not anticipated.

- Warmer Friday and Saturday. Breezy and dry on Saturday, with elevated fire weather concerns.

- Rain chances return to northern Iowa around Monday, then perhaps more widespread toward the middle of next week but details remain unclear at that range.

SHORT TERM /THROUGH FRIDAY NIGHT/

Issued at 225 AM CDT Thu Oct 8 2026

Radiative cooling is well underway tonight, with lows dipping into the lower 50s and a few upper 40s. Some patchy and shallow fog may develop in the next several hours, but cirrus shreds streaming into the state may offset the cooling by early morning. Fog is most likely in our western counties where calm winds are observed, and it will have several more hours of mostly clear skies. Highs during the day today will again be in the 70s, but avoided increasing the forecast much higher than NBM due to the extra cirrus today and continued cool 850mb temps.

Most of the CAMs and global models are honing in on the occurrence of showers and storms from 3z tonight to 15z tomorrow. A small surface low will move across the plains this evening and as it does so will produce a decent LLJ as well as start to lift a warm front across the state. This warm air advection will mainly be elevated, but will bring with it a pool of 700-850mb moisture. As it lifts in the late evening, the exit region of the LLJ will provide lift for the moist parcels in the 700-850mb layer. MUCAPE in this layer looks to be around ~500 J/kg and perhaps as high as 1000 J/kg initially. The severe weather threat is low, but not zero. 1-6km shear is forecast to be ~35-40 knots across the CAMs, and may be enough to help sustain a stronger updraft with small hail, at least initially, though lapse rates are poor overall. Also, the surface to 850mb layer will be relatively dry and could increase evaporative cooling and make for gustier downdrafts. Still, CAMs suggest all wind gusts will be subsevere. QPF is a bit of a wild card with a few of the usual culprit CAMs (NAM/Canadian) showing a thin swath of over 1" of rain in central Iowa. This is the upper end scenario given all the dry air that needs to be overcome, and many of the other models forecast a more reasonable 0.1-0.5" swath.

Friday may be a bit warmer again, resembling the warm air advection pattern of this past Tuesday after the rain moves out and the surface warm front advances north. Most models have the boundary somewhere near the DSM metro, oriented NW to SE across the central part of the state. Highs in the low to mid 80s on the south side of the boundary and highs in the mid to upper 70s on the north side are expected at this time. The temperature gradient across the warm front will be something to monitor as residual outflow, cloud cover, and differences in mixing could all be contributors. Some gusty winds may also happen given the efficient mixing down of fairly strong 850mb winds that actually maintain intensity through the daytime. Gusts of 20-25 mph across the state are expected.

LONG TERM /SATURDAY THROUGH WEDNESDAY/

Issued at 1253 PM CDT Wed Oct 7 2026

The remnants of tropical cyclone Isaias, which is predicted to make landfall along the central Gulf coast sometime around Friday night, will drift northward up the Mississippi River valley on Saturday and Saturday night, before shunting off to the east on Sunday. As it approaches the midwest, its primary effects including clouds and rain will remain southeast of our area, but it will pinch off the weak 500 MB ridging in place prior to its passage, resulting in lighter mid-level flow over Iowa. It may also cause a slackening of the low-level pressure gradient and winds in our southeastern counties on Saturday. Our northwestern counties, however, will reside closer to the broad surface low pressure trough slowly approaching from the High Plains, and within a tighter pressure gradient resulting in stronger winds in those areas. This will be enhanced by deeper surface-layer mixing evidenced by forecast soundings, which support peak gusts in the 35-40 KT range around Estherville and farther north and west. Have maintained a forecast in that range, and also trended dewpoints downward by several degrees given the efficient mixing anticipated as well as recent model tendencies for overforecasting daytime moisture. The combination of gusty winds and relatively low RH may support some elevated fire weather concerns Saturday in areas with cured fuels, namely most croplands. This concern will be monitored over the next few days.

As the remnants of Isaias move eastward away from Iowa on Sunday, the surface trough will continue to slowly approach and the pressure gradient and mixing depth will decrease, leading to more modest south southwest breezes and slightly less warm temperatures Sunday afternoon, but still peaking in the upper 70s. By Monday morning, another pattern change will be underway as a 500 MB low develops near the Pacific coast of southern California, while a northern stream 500 MB trough moves quickly near the central U.S./Canada border. As the latter feature scoots by to our north it will spread clouds and rain across the Dakotas, Minnesota, and Wisconsin that may just scrape northern Iowa where low (20-30%) POPs are maintained. Of possibly greater sensible weather impact is that the passage of this mid-level trough will also cause the surface trough, which had been creeping over the High Plains for several preceding days, to surge quickly southeastward through Iowa during the day and into Monday evening. This will bring brisk northerly breezes Monday night followed by a quick passage of surface high pressure on Tuesday. A somewhat more active weather pattern is expected thereafter as the southwestern U.S. 500 MB low evolves, however, model depictions of this evolution and particularly the degree of phasing between that system and the northern stream is quite erratic at this range, and will leave resolution of any details for the coming days.

AVIATION /12Z TAFS THROUGH 12Z FRIDAY/

Issued at 626 AM CDT Thu Oct 8 2026

VFR conditions are expected to prevail through the TAF period. The biggest point of impacts and uncertainty is the chance for showers and thunderstorms Thursday night. Chances are highest at KFOD, but impacts are also possible at KALO/KDSM/KMCW. Uncertainty in location and timing is too high for inclusion anywhere besides KFOD. Winds at 2kft will approach 25 knots towards 12z tomorrow over calm surface winds, but the resulting LLWS is too marginal for inclusion at this time.

DMX WATCHES/WARNINGS/ADVISORIES

None.