textproduct: Des Moines

KEY MESSAGES

- Winter Weather Advisory for 1 to 4" of snow Saturday. Locally higher amounts possible.

- Cold Weather Advisory follows Saturday night and Sunday morning. Wind chills as low as -30 expected north.

- Mild weather builds in the first half of the work week.

DISCUSSION

Issued at 229 PM CST Fri Dec 12 2025

A thermal front has moved across the state today and temperatures were starting to slide into the teens in northwest Iowa. Precipitation was sparse along the front, with most of it closer to the parent low to the northeast of the state. Midlevel cloudiness will replace the low level stratus at least for a time tonight. The last gasp of energy along the northwest flow pattern arrives tonight. A notable change has been a warming of the midlevels compared to yesterday, taking some of the profile out of the DGZ. This is due to the strong downslope flow with wind speeds up to around 70kts. This reduces the SLRs below 20:1, increasing confidence in snowfall amounts remaining under 4 inches for much of the Advisory area. There will be locally higher amounts embedded as the weak fgen band generates lift in the DGZ. Omega values generally remain below -5, but midlevel Q vectors intensify as the clipper reaches southeast Iowa, increasing synoptic forcing. Some ice pellets could mix in on the southwest flank of the snow as ice introduction aloft is lost, but the drops will fall towards the cold low-levels, causing freezing before they reach the surface.

Temperatures plummet as clouds are pulled away and an arctic high approaches. Cold northwest flow will drop temperatures below zero statewide. There will be a window of wind chills as low as -30 degrees in the north, the window for this being short due to the high settling overhead, calming winds. A Cold Weather Advisory was issued for Saturday night/Sunday morning to reflect when these dangerous wind chill values will occur.

An upper level ridge will break this stagnant northwest flow pattern in the early week. Temperatures over 40 degrees will work to erode the snowpack. Flow will switch to zonal during the second half of the week which will open up the chance for a more active pattern with the Pacific moisture in play.

AVIATION /00Z TAFS THROUGH 00Z SUNDAY/

Issued at 553 PM CST Fri Dec 12 2025

Occasional flurries are expected this evening, otherwise ceilings will remain at or just above MVFR criteria before lowering once again into Saturday with the next passing system. Light to moderate snow is expected to expand northwest to southeast after midnight, with the highest probabilities (around 80%) at KFOD, KDSM, and KOTM between 12 to 18z before gradually tapering off. This snow will lead to periods of low vsbys and ceilings resulting in MVFR/IFR conditions. Winds will also be slightly breezy out of the north/northwest with gusts up to 15+ knots.

DMX WATCHES/WARNINGS/ADVISORIES

Cold Weather Advisory from 6 PM Saturday to 10 AM CST Sunday for IAZ004>007-015>017-023>028-033>039-045>050-059>062-073>075- 084>086-095>097. Winter Weather Advisory from midnight tonight to 3 PM CST Saturday for IAZ023-033>036-044>048-058>060. Winter Weather Advisory from 3 AM to 3 PM CST Saturday for IAZ049-061-062-073>075-085-086-097.