textproduct: Des Moines

KEY MESSAGES

- Very cold this morning, with daily record low temperatures a near certainty. See climate section below for record temperature values.

- Friday will be more mild, with highs approaching 30 degrees and a light dusting of snow crossing far northern Iowa.

- Chances for accumulating snowfall late Saturday through Saturday night have increased to 50-70% across most of the area. Amounts are still uncertain, but there is the potential for several inches in some area. The relatively short duration of the event limits potential for higher amounts, but in any event, travel impacts are increasingly likely.

DISCUSSION

Issued at 205 AM CST Thu Dec 4 2025

A large surface high pressure area has settled across the region overnight, bringing clear skies and light winds that are allowing temperatures to fall well below zero this morning. Wind chill values of around 15 to 25 below zero are anticipated, but any readings reaching advisory levels are marginal and fleeting thus no advisory has been issued. Even so, it will be very cold and anyone venturing outside should take appropriate precautions. The high pressure area will slide off to the southeast today, allowing for a return of modest south breezes by this afternoon and bringing relatively milder weather on Friday.

Meanwhile, on the synoptic scale, a large gyre is spinning over Hudson Bay and a string of shortwave impulses rounding its western periphery will cross western and southern Canada and the Midwestern U.S. this weekend into early next week, making for a more active weather pattern in our area. The leading impulse in the approaching train is currently located over the Alberta/Saskatchewan border and will eventually cross Minnesota and northern Iowa on Friday. A reflective surface low will cross Minnesota during the day Friday, bringing light to moderate snow north of Iowa and likely just scraping our far northern counties with a quick shot of light snow. Have increased POPs to 30-50% roughly north of Highway 18, mainly Friday morning, but expected accumulations are very light at only a few tenths of an inch or so.

A deeper and somewhat more robust trough will cross the region late Saturday through Saturday night, and long-range model solutions have been picking up on this feature for many days now but with varying solutions as to timing and latitudinal extent. With it now only being 2-3 days away the model suite is achieving better resolution and we have a better idea of how things will play out. By Saturday afternoon the 500 MB wave will be crossing eastern South Dakota and Nebraska, with a surface trough extending along the southern High Plains from the Texas panhandle up to the Nebraska/Kansas border. The broad forcing for ascent associated with the shortwave will overlay a band of frontogenetical forcing in the northern/northeastern hemisphere of the developing surface cyclone, generating a swath of snow that will cross our forecast area around Saturday night. The EC has been the most consistent in its track for this storm, with accumulating snow focused across about the northeastern two thirds of Iowa, while the GFS has been more erratic and the NAM has so far been taking things more over the southwestern half of Iowa. In any event, the probability of snowfall in our area is increasing and we are now carrying 50-70% POPs on Saturday evening/night accordingly. Amounts are still uncertain due to variations in the location, elevation and magnitude of frontogenetical forcing as well as the larger storm track, but it is fair to assume a few inches of snow will affect at least portions of the area. The system will be moving through pretty quickly though, which should limit the potential for higher accumulations. We will be closely watching this system over the next couple of days as some travel impacts are likely from late Saturday into early Sunday. The wave train will then continue into the first half of next week, with several more impulses expected between Monday and at least Wednesday, but the details during that time are hazy at this range.

AVIATION /06Z TAFS THROUGH 06Z FRIDAY/

Issued at 1042 PM CST Wed Dec 3 2025

Little change from previous forecast with the wind continue to diminish overnight. Some guidance is beginning to hint at fog potential over northern Iowa later tonight but at this time it appears unlikely given temperature and dew points spreads. The wind will switch from northwest to southerly during the day Thursday. The wind may become gusty at times by the afternoon over the north. Steering flow change during this time does still bring the potential of the Nebraska/South Dakota stratus to move into northern Iowa during the late afternoon and evening with KFOD/KMCW potentially being impacted. Still confidence remains low enough to not introduce MVFR cigs at this time.

CLIMATE

Issued at 205 AM CST Thu Dec 4 2025

Forecast and Record Low Temperatures for Select Central Iowa Cities...

=============================================== | Wednesday | Period | | Forecast Record/ | of | City | Low Year | Record | =============================================== Des Moines -9 -6/1886 1878- Lamoni -5 2/1991* 1897- Mason City -14 -9/1991 1903- Ottumwa -5 1/2005* 1923- Waterloo -12 -7/1991 1895- ===============================================

*Record occurred in multiple years

DMX WATCHES/WARNINGS/ADVISORIES

None.