Coldest morning of the season; accumulating snow again on Tuesday

Biting cold air greeted morning shoppers hastening their pre-Christmas chores.  The temperature dropped to 27 degrees below zero at Fosston, Minn., and wind chill readings were in the 40 to 45 below zero range in some places of western Minnesota.

Exposed flesh can freeze in a matter of minutes with those low wind chill readings. Winds drop off tonight and we set up for perhaps the coldest night of the season, leading us into Christmas.

A small area of very light snow was passing across the eastern Twin Cities Metro late this afternoon.  These clouds have little water content and will fade shortly after dark.

Screen capture of very light snow on radar at 3:20 p.m.  Image: Wunderground.com

I’ve been exploring the output of a number of computer models, plus looking at current conditions. Very cold air is likely to settle over eastern Minnesota tonight. Nearly calm winds, clear skies and fresh snow cover are perfectly aligned for temperatures approaching 30 below zero.

The regional computer model from the Duluth National Weather Service run this morning shows pockets of temperatures at 30 below zero around 2 a.m. on Tuesday. This is the model’s forecast, not the official NWS forecast.

Surface temperatures at 2 a.m. from the Duluth National Weather Service forecast model.

Click on image to closely examine the forecast of readings of 30 below zero.

This visible satellite image  from this afternoon shows a wedge of the Plains extending into south central Minnesota with little or no snow cover. Image:NOAA

Our next weather-maker is in the upstream wind flow pattern moving across Montana.  Snow will increase in coverage through the Dakotas overnight.

Infrared image from 3 p.m. Coldest cloud tops enhanced in blue. Image:NOAA

With the likelihood of up to a 20 to 1 snow to water ratio (due to relatively cold air) some places could tally up to 5 inches of snow with this system. The National Weather Service has issued a Winter Weather Advisory for Tuesday and Christmas Eve. Travel conditions will deteriorate from west to east during the day.

Weather graphic LaCrosse, Wi

The snow pushes through western Wisconsin on Tuesday evening. Arctic air is not expected in the wake of the snow. Temperatures on Christmas Day should be just a tad shy of the seasonal normals.

Use caution when taking to the roadways Tuesday and Tuesday night.

High temperatures forecast for Christmas day.

Colder air arrives for Thursday, but Friday and Saturday are not likely to be particularly bitter if you wish to enjoy the freshly fallen snow or ice skate.  Another blast of icy air arrives Sunday.

Here’s a look ahead to the expected lows on Monday.

Low temperatures forecast by NOAA/NWS next Monday, Dec. 30.