Minor Change to Snowfall Criteria for Winter Storm Watches/Warnings Effective This Winter

Effective immediately, the National Weather Service Duluth MN Forecast Office will implement new Winter Storm Watch/Warning Criteria for Heavy Snow across its County Warning Area of responsibility. This is part of a national effort to remove non-meteorological discontinuities across County Warning Areas and to better align watch/warning snowfall criteria to the local climatology of the region. 

Historically the National Weather Service Duluth MN County Warning Area snowfall criteria was partitioned into different 12- hour and 24- hour criteria. The new criteria will no longer be dependent on the time-frame of the snowfall, allowing for a more event-driven approach to messaging. This new paradigm maintains and encourages the ability to issue or withhold watches and warnings in anticipation of expected impacts or lack thereof.

The new Winter Storm Watch/Warning Criteria for Heavy Snow will be the following:

* 6 inches of snowfall during a winter storm event for zones listed in Table 1

* 7 inches of snowfall during a winter storm event for zones listed in Table 2

* 8 inches of snowfall during a winter storm event for zones listed in Table 3

Table 1: Universal Geographic Codes (UGC): Weather Zones included in the 6 inch Warning Snowfall Criteria 

_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

MNZ010: Koochiching

MNZ018: North Itasca

MNZ026: South Itasca

MNZ025: North Cass

MNZ033: South Cass

MNZ034: Crow Wing

MNZ035: North Aitkin

MNZ036: South Aitkin

MNZ011: North St Louis

MNZ012: Northern Cook/Northern Lake

MNZ019: Central St Louis

MNZ037: Carlton/South St Louis

MNZ038: Pine

WIZ001: Douglas

WIZ006: Burnett

WIZ007: Washburn

WIZ008: Sawyer

WIZ009: Price

Table 2: Universal Geographic Codes (UGC): Weather Zones included in the 7 inch Warning Snowfall Criteria 

_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

MNZ020: Southern Lake/North Shore

MNZ021: Southern Cook/North Shore

WIZ003: Bayfield

WIZ004: Ashland

Table 3: Universal Geographic Codes (UGC): Weather Zones included in the 8 inch Warning Snowfall Criteria 

_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

WIZ004: Iron

A map of the criteria across the entire Contiguous United States can be found at this link: www.weather.gov/snow-criteria

There will be no changes to the Winter Weather Advisory snowfall criteria. 

For any questions, please contact: 

Joseph Moore, Warning Coordination Meteorologist 

joseph.moore@noaa.gov, 218-729-6483 x726