textproduct: Des Moines

KEY MESSAGES

- Slow warming trend this week, with highs in the mid/upper 60s today and Monday eventually climbing into the mid/upper 70s by Thursday and Friday.

- The forecast is dry through the work week, with rain chances returning sometime next weekend.

SHORT TERM /THROUGH TUESDAY NIGHT/

Issued at 103 PM CDT Sun Oct 18 2026

A broad 500 MB ridge covers most of the central and southern U.S. today, with a trough passing by far to the north across Canada and flattening the ridge a bit over Iowa. Meanwhile, a weak southern stream trough is crossing the SOCAL/Arizona/far northwestern Mexico region. At the surface, a large high pressure area is centered roughly over the Ohio River valley while a broad low pressure trough has developed along the High Plains to our west. The pressure gradient between these systems lies across Iowa, resulting in gusty southerly breezes this afternoon. Skies remain clear under the influence of the 500 MB ridge and with Gulf moisture cut off, while diurnal mixing is maintaining low dewpoints in the upper 30s. Within this regime temperatures are once again overachieving a bit today, and are likely to peak in the mid to upper 60s this afternoon.

Tonight, the surface trough over the High Plains will get squeezed out by a succeeding high pressure area moving along the U.S./Canada border. This will slacken the pressure gradient over Iowa, along with diurnal decoupling, and allow our winds to diminish after sunset but not go completely calm for the most part. Even so, with clear skies overnight radiational cooling will allow temperatures to fall into the lower 40s in most of our area by sunrise Monday, and a few spots could dip into the upper 30s. On Monday the northern surface high will merge with the Ohio River valley high to form an even larger ridge over the Great Lakes region that will dominate the surface pattern for a couple of days. During this time, the 500 MB southern stream trough currently over the extreme southwestern U.S. will become somewhat discombobulated as it drifts slowly northeastward toward the Midwestern states. As it does so, it will spit out shreds of vorticity and bring increased moisture aloft, resulting in mid/high level clouds spreading over Iowa from late Monday onward. These may have a slight dampening effect on temperatures, both daytime warming and overnight cooling, however the clouds are likely to be both high and generally thin, mitigating these effects. Meanwhile, a few model solutions still try to put out spotty sprinkles or light showers, but forecast soundings indicate a deep and substantial dry layer above the surface and have maintained POPs below 10% for now.

LONG TERM /WEDNESDAY THROUGH SATURDAY/

Issued at 103 PM CDT Sun Oct 18 2026

Between Wednesday and Wednesday night the weakened 500 MB trough axis will finally cross Iowa, bringing somewhat thicker mid/high level clouds. However, the trough will be largely washed out by that time and a deep near-surface dry layer will persist, once again reducing any rain chances. Thereafter, a high-amplitude ridging pattern will build across the central U.S., with the axis stretching all the way from Mexico up to Hudson Bay by Thursday evening. This will maintain dry and notably warmer weather at the end of the work week. Both Thursday and Friday high temperatures will likely range in the mid to upper 70s, and a few areas could even touch 80 degrees.

By Friday, even as the 500 MB ridge axis moves over Iowa, a deep trough will build over the western U.S. and subsequently slide northeastward into the Upper Midwest, shunting the preceding ridge southeastward and bringing a return of rain chances followed eventually by a surface trough/cool front through Iowa. While this general scenario is likely to occur, long-range models still vary considerably in the details of the evolution, timing and magnitude of any rain chances, strength of the surface trough, etc. As such, persistent low (20-30%) rain chances are forecast next weekend but it is likely these will eventually narrow to a shorter period of higher POPs as confidence in timing increases later this week.

AVIATION /18Z TAFS THROUGH 18Z MONDAY/

Issued at 1221 AM CDT Sun Oct 18 2026

VFR conditions will continue for the foreseeable future. Gusty breezes this afternoon will diminish around sunset and be light from the south tonight through Monday.

DMX WATCHES/WARNINGS/ADVISORIES

None.