Upgrade to Winter Storm Warning for major southeast Michigan cities

The winter storm watch issued early this morning has been upgraded to a winter storm warning for some areas, meaning the likelihood of heavy snow is growing.

Winter storm warning criteria at this time of mid-winter is six inches or more of snow possible, or slightly lesser snow and some freezing rain ice accumulation. The winter storm warning area could have either of those weather scenarios. Right now one-tenth to two-tenths of an inch of ice accumulation from freezing rain is possible in the heavy snow area. If the ice accumulation does occur, it will be at the expense of a couple of inches of snow.

Either way the weather goes, we are going to have dangerous driving conditions eventually Thursday.

Eventually is an important word I want to emphasize. As I noted in my morning update on the snow and freezing rain forecast, the main period of heavy winter precipitation is slower than yesterday’s thought. The winter storm warning now goes into effect at 3 p.m. Thursday, showing the expected later timing of the most significant snow. The winter storm warning now also expires a little later at 3 a.m. Friday.

Winter Storm Warning in pink and Winter Weather Advisory in purple.

The winter storm warning is in effect from the southwest Michigan border counties to Battle Creek, Jackson, Hillsdale, Coldwater, Adrian, Ann Arbor, the entire Detroit area, Oakland County and St. Clair County.

The official snow forecast from the National Weather Service is four to eight inches of snow in the winter storm warning area. The warning area also can expect one-tenth to two-tenths of an inch of ice accumulation from freezing rain and sleet. A few of the best computer models show six to seven inches of snow will be common. An isolated nine inch amount is possible.

The purple shaded area from Kalamazoo to Lansing to Flint to Sanilac County is a winter weather advisory for three to five inches of snow.

The one important tend I want you to grasp is the delayed timing of the heaviest precipitation. There will be a round of lighter snow and brief freezing rain Thursday morning across all of the southern half of Lower Michigan, but the heavy snow will occur late in the afternoon and Thursday evening.