textproduct: Des Moines

KEY MESSAGES

- Increasing clouds and chance for a light freezing drizzle in northern Iowa tonight into early Wednesday.

- Light snow/flurries north and east on Wednesday. Accumulations will be minimal. Light snow may briefly flip to light freezing drizzle in east central Iowa.

- Cold front Wednesday night into Thursday will cool temperatures Thursday and Friday. Steady warming through the weekend and above normal temperatures by next week.

DISCUSSION

Issued at 216 PM CST Tue Dec 30 2025

Light snow/flurries drifted over northern Iowa this morning, but have all but departed to the east early this afternoon. These flakes were associated with a subtle wave oscillating around the back side of a 500 mb trough currently parked over the northeastern CONUS. Weak theta-e advection and mid-level forcing was able to squeeze out a few flakes, although accumulations were negligible. Behind this wave a plume of low level moisture is oozing southward, bringing a broad area of stratus to the state through today and tonight. The low level moisture will continue to increase through the night, introducing some freezing drizzle potential to northern Iowa late tonight into early Wednesday morning. Lift will be fairly weak, and shear is unidirectional, which may not be overly favorable for drizzle production. Likewise, the saturated layer does fade in and out, as dry air from the southeast combats the increasing moisture from the north. However, soundings do indicate brief periods of roughly 1 km of moisture depth, which could squeeze out a light mist/drizzle should any turbulence develop. It's far from a high confidence scenario, but have included some freezing drizzle mention across northern Iowa in collaboration with surrounding offices.

Mid-level forcing will increase over Iowa again on Wednesday morning as another subtle shortwave brings more precipitation chances to the state. While surface moisture will be sufficient with this systems passage, snow chances will be limited to the northern and northeastern portions of the forecast area where better mid-level moisture will be available as well. Areas farther south and east will be too dry to achieve deep saturation and falling precipitation. There will be some concern along the edges of the deeper saturation (around east central and north central Iowa) where ice introduction may be lost for a brief time. There will also be some weak lift in the low levels through this period, introducing more risk for light snow to flip over to a freezing drizzle. This is far from a high confidence scenario, but certainly something we will be watching for through the day tomorrow, especially with it being New Year's Eve.

A cold front will eventually drop southward behind the wave Wednesday evening, bringing drier low level air and colder air into the state. This will drop temperatures into the single digits north to teens south with wind chills in the single digits Wednesday night into Thursday morning. Temperatures remain cool to seasonal Thursday through Saturday, but then begin to warm again on Sunday as the persistent 500 mb trough over the eastern CONUS begins to lift off and allow ridging to fill in from the west. The forecast looks mostly dry Thursday through the weekend, but will continue to watch for any other subtle waves, especially given the northwest flow pattern overhead.

AVIATION /00Z TAFS THROUGH 00Z THURSDAY/

Issued at 523 PM CST Tue Dec 30 2025

Main aviation impacts tonight will be from MVFR stratus encroaching from the north. In addition, surface winds will shift from southwest to northwest this evening. There is low potential for freezing drizzle to develop to the NE, possibly impacting MCW and ALO. Chance is too low to mention in TAFs at this time, but this will need monitoring for updates if it does develop.

DMX WATCHES/WARNINGS/ADVISORIES

None.