Widespread dense fog into Christmas Day; major winter storm possible this weekend
Very mild temperatures on Tuesday released lots of moisture from our snowpack into the surface boundary layer. Now we are set up for widespread fog to thicken overnight.
Dense Fog Advisories have been posted for most of Minnesota and about the northwestern half of Wisconsin for Tuesday night well into Christmas morning. Visibilities are likely to drop to or below a quarter of a mile at times.
In the Twin Cities, the advisory is scheduled to be in effect from 9 p.m. Christmas Eve until 11 a.m. Christmas morning.
Not included in the advisory are northwestern Minnesota from around Fergus Falls northward and Rock County in the southwest corner.
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Mild Christmas temperatures with drizzle and mixed precipitation
High temperatures on Christmas Day should be mainly in the 30s. Southeastern Minnesota could warm into the low 40s.
The forecast high for the Twin Cities is 40, which would be warmer than what we had for Thanksgiving (28) and Halloween (36). The record high for Christmas is 51.
Low clouds and the mild temperatures are likely to generate some drizzle and sprinkles for about the southern half of Minnesota on Christmas Day.
Northern Minnesota will be a bit cooler and should get a variety of light snow and mixed wintry precipitation.
Accumulating snow into Thursday
Light snow will continue in parts of northern Minnesota Wednesday night into Thursday. Accumulations of a few inches are likely, mainly in northwestern and north central Minnesota.
Major weekend snowstorm possible
A storm is forecast to develop over New Mexico later this week and then deepen dramatically into a significant winter storm as it races northeast on the weekend.
The timing, track and snowfall amounts cannot be estimated at this early time. However, forecast models have been getting more consistent with pointing a plowable southwest-to-northeast band of heavy snow in our general direction.
Current models are bringing snow into southwestern Minnesota on Saturday and zooming it northeastward toward northeastern Minnesota and northwestern Wisconsin during the day.
The current GFS model plots out one possible outcome of snowfall for Minnesota from Wednesday through the end of Sunday. Snow would likely still be falling in the northeastern part of that band at that time. The small number over Minneapolis is for 9.0 inches of snow if that forecast worked out exactly.
What has me more concerned than just the potential snowfall amounts is that the pressure gradient will become very strong as the deepening low crosses Minnesota. That means lots of wind with blowing and drifting by Saturday night and into Sunday. Even lesser amounts of snow could be blown into near-whiteout conditions.
This is likely to become a high-impact storm somewhere in our part of the world. Regardless of the exact track, some areas of the Upper Midwest are likely to get significant snowfall and blizzard or near-blizzard conditions in open areas.
At this point as of Christmas Eve, I just want to leave you with a heads up of our potential weekend weather. Much might change. But this could easily become the kind of storm that requires some planning and adaptation if you are going to travel.
Cooler next week
Cooler air blowing in from Canada after the storm passes will return us to more normal temperatures for late December.