National Weather Services Sets New Criteria for Calling Winter Storm Warnings

We're about to 'Winter Storm Warning' season here in Michigan, meaning those warnings could pop up at any time. And the National Weather Service has completely revamped its criteria for issuing Winter Storm Warnings throughout the United States.

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How Does the NWS Determine When a Winter Storm Warning is Issued?

The National Weather uses predicted snowfall amounts when determining whether or not a Winter Storm Warning is warranted. This means that the predicted snowfall would have to meet a certain threshold in order to trigger a warning.

The National Weather Service operates 122 offices throughout the United States. Previously, each of those offices set their own thresholds for the amount of predicted snow that would trigger a warning. According to Fox Weather, each of those offices covers jurisdictions that cover 10 to 20 counties, with some counties split between offices, based on geographical layout.

National Weather Service Offices Establish New Guidelines

Under the National Weather Service's new guidelines, all local NWS offices will follow snowfall thresholds assigned to them by the main NWS office. This shift is supposedly going to mean Winter Storm Warnings will be issued on a more consistent basis.

The interactive map below is color coded by region, with each color designating different snowfall thresholds that will be used in order to trigger a warning.

Michigan Will Use Three Different Snowfall Thresholds

As you can see in this interactive map on the National Weather Service's website, there are three snowfall amounts for Michigan counties that will be used in order to generate a Winter Storm Warning.

In Genesee County and the surrounding counties of Shiwassee, Lapeer, Tuscola, Livingston, Oakland, and Saginaw, seven inches will be used as the threshold amount. If the forecast calls for seven inches or more, a warning will be issued.

Along the shoreline of Lake Michigan, Northwest Michigan, and in the Northern Upper Peninsula, eight inches will be required to trigger a Winter Storm Warning.  In five counties in the Southern UP that border Wisconsin, only six inches will need to be in the forecast in order for a warning to be issued.