textproduct: Des Moines

KEY MESSAGES

- Light wintry precipitation possible this afternoon and early this evening from around Mason City to Waterloo and more so points northeast of this area. Potential accumulations of a light glaze of ice or dusting of snow.

- Colder on New Year's Day, but temperatures moderating to above normal by Sunday into next week with mainly dry conditions

DISCUSSION

Issued at 137 PM CST Wed Dec 31 2025

Upper level GOES-East water vapor imagery shows a ridge over the western CONUS with a closed low off of the California coast that will slowly move eastward through the end of this week. There is a plume of moisture flowing over top of this ridge and into our region in the fast, 130 knot 250mb northwesterly flow. A shortwave trough can easily be seen in this imagery and is just northeast of Lake Superior. A surface cold front is trailing back to its west and is the feature of interest for our potential light wintry precipitation over our northeastern forecast area from around Mason City to Waterloo this afternoon into early this evening. However, there are several forecast parameters that are marginal and bring into question whether it will occur. First, the ice introduction layer may or may not have saturate, depending on the model, though it can be stated with confidence that there is a gradient in ice introduction/drier air over the same Mason City to Waterloo area. If ice introduction is achieved, then flurries or light snow would result, which seems to fit with current surface observations, mPINGs, and reported road conditions in Minnesota. If there is no ice introduction, then freezing drizzle may result. Forecast soundings show that saturation is elevated above the surface and around a 1km in depth for a few hours at most. While low and mid- level thermodynamics and upper level kinematics are favorable for lift, the saturated layer shows a lack of lift with neutral to weak subsidence in forecast soundings. Lastly, there is some degree of wind shear, but that becomes more unidirectional as the boundary moves through the area. Therefore, have trimmed back areal extent of freezing drizzle mentioned in the forecast with updates this morning and have maintained that thinking and forecast into this afternoon. Any icing, if it were to occur, would be a hundreth or two as drier air pushes in and dries out the column.

As the cold front clears the state tonight, temperatures will fall into the single digits and teens above zero by New Year's Day morning. Another subtle, fast moving shortwave will slip into and through the region on Thursday, but the moisture profiles are insufficient with lots of dry air in the mid-levels for any snow over our forecast area. The jet stream and shortwave trough train will trek a bit farther northeast through the first weekend of 2026, though the aforementioned closed low off the California coast will slide across into the central or southern Plains. Moisture return this far north looks unlikely so not expecting any significant precipitation through the weekend as temperatures moderate to normal by Saturday and above normal by Sunday. The West Coast ridge axis pushes over the central US early next week while at the same time deamplifying, which may allow the jet stream to bring light precipitation chances closer to the northern border of the state. As the the flow becomes more southwesterly late in the week, this presents a more opportune setup for precipitation and something to watch in the coming days.

AVIATION /00Z TAFS THROUGH 00Z FRIDAY/

Issued at 525 PM CST Wed Dec 31 2025

A wide band of low stratus clouds is progressing southward across the region this evening and will bring multiple hours of MVFR ceilings to the TAFs, with bases anywhere from around FL013-FL030 at times. These low ceilings will then clear out from north to south, breaking up or rising to VFR last at DSM and OTM somewhere around 08-10Z. Have indicated these trends in the 00Z TAFs, but amendments may be needed tonight based on short-term observational and satellite trends. Once the ceilings to break up and/or rise above FL030, VFR conditions are then expected for the remainder of the TAF period.

DMX WATCHES/WARNINGS/ADVISORIES

None.