textproduct: Des Moines

KEY MESSAGES

- Strong winds will cause blowing snow impacts this morning, especially from the Des Moines metro area northward and eastward where a Winter Weather Advisory is now in effect until noon.

- More snow is likely on Monday, especially across the southern/southeastern half of Iowa. Light to moderate accumulations are possible with the highest amounts near the Missouri border.

- Much of this week will be substantially colder than what has previously been experienced this season, especially today and even more so around Thursday. Lows Thursday morning will fall well below zero across the area, albeit with light winds.

DISCUSSION

Issued at 314 AM CST Sun Nov 30 2025

Snowfall has ended across the area overnight, necessitating the end of the Winter Storm Warning. However, strong northwest winds continue with a tight surface pressure gradient in place and gusts to near 35 MPH being reported. This is blowing the fresh deep snow pack, resulting in moderate visibility reductions to around 2-4 miles in some areas, and also blowing snow back over roadways and prolonging dangerous travel conditions. In light of this, have opted to replace much of the warning, generally from around the Des Moines metro northward and eastward to our CWA borders, with a Winter Weather Advisory for blowing snow until noon today. As the low pressure system moves away to our east, taking the tighter pressure gradient with it, winds will gradually diminish from west to east this morning allowing the blowing snow to abate and roads to be re-cleared.

Later today and tonight a surface high pressure area will slide across Iowa, bringing nearly calm winds this evening and supporting much colder temperatures. However, the temperature forecast after sunset tonight is complicated by questions about cloud cover, not only how much will persist from this morning right through the day, but also how quickly high clouds will move in from the west tonight ahead of the next storm system. Have maintained a temperature forecast close to the previous package for tonight, but short-term adjustments will likely be needed based on observational trends.

Late tonight a broad 500 MB trough will swing southeastward over the northern High Plains, and subsequently cross Iowa and the Midwest from Monday to Monday night. While broad forcing for ascent in the leading flank of the advancing trough will support redevelopment of clouds and snow, there are significant differences between this system and the one we experienced over the last couple of days. It is substantially weaker in terms of being an open trough rather than a deepening closed low. There is little low-level reflection as the surface pressure pattern will be loose and nebulous. Surface winds will remain light on Monday, and moisture will be much more limited than the previous system with QPF only about 10 percent of what fell the last two days. All that being said, there are still potential impacts to consider. A ribbon of pronounced frontogenetical forcing around 650 MB will help to focus the broader lift and generate a broad band of snowfall roughly oriented from southwest to northeast, but translating east northeastward across the region. Most model solutions take this zone of snowfall across southern and eastern Iowa during the day on Monday. In addition, forecast soundings depict a very deep dendritic growth zone for much of the event, although the transient band of frontogenetical forcing is mostly located above the DGZ and not within it. Even so, given the temperature profile and deep growth zone, snow- to-liquid ratios will be considerably higher with the Monday system. Thus while QPF is only 0.1-0.2 inches across our central to southern counties, SLRs of 15 or 20 to one are anticipated, resulting in potential snow accumulations of 2-4 inches. This does not qualify as a winter storm by any stretch, particularly with it being a relatively long duration accumulation and with light winds. However, coming fast on the heels of the previous heavy snow and on the first work/school day for many returning from the Thanksgiving holiday break, impacts may exceed those typical of such an event.

From late Monday night through the rest of the week the forecast is generally quiet and cold. There is a low chance (around 20%) of light snow Tuesday night into Wednesday, but it appears to be low impact at this point. Thursday will be very cold with a surface high pressure area moving through. Morning lows will be well below zero, potentially around 10 below zero in the north, and Thursday afternoon highs only in the low to mid-teens. However, winds will be light during this time so wind chills will likely not reach advisory criteria. Additional snow chances return toward the end of the week, but are nebulous at this range.

AVIATION /12Z TAFS THROUGH 12Z MONDAY/

Issued at 542 AM CST Sun Nov 30 2025

Scattered areas of low clouds and BLSN are affecting the area early this morning, producing MVFR ceilings and visibilities at some terminals. As gusty NW winds gradually diminish this the BLSN/reduced vsbys will end. However, trends in cloud cover are more inscrutable and periodic ceilings will likely continue at least until midday if not beyond, though heights will gradually rise to VFR by the afternoon. Have indicated these trends and uncertainties in the 12Z TAFs, but amendments are likely today. Toward the end of the TAF period, overnight into Monday morning, additional low stratus/fog may develop particularly across northern Iowa, and have signaled this in the FOD/MCW/ALO TAFs. Snow will then move in after 12Z Monday and produce more widespread lowered conditions during the day, but this will be addressed in future TAF issuances.

DMX WATCHES/WARNINGS/ADVISORIES

Winter Weather Advisory until noon CST today for IAZ007-017- 025>028-036>039-047>050-059>062-073>075.