New Experimental Winter Storm Warning Snowfall Criteria for the 2022-23 Winter Season

...The National Weather Service Gray Forecast Office Will Test New Experimental Winter Storm Warning Snowfall Criteria for the 2022-23 Winter Season...

Beginning this winter season the National Weather Service Gray Forecast Office will test a change to the Winter Storm Warning Snowfall Criteria in its County Warning Area of responsibility. The reason for the change is to better align warning snowfall criteria to the local climatology of the region.

Historically the National Weather Service Gray County Warning Area snowfall criteria has been the following:

6 inches of snow in 12 hours or
8 inches of snow in 24 hours

The snowfall warning criteria was the same across the entire County Warning Area. This meant that the warning level snowfall criteria was the same in coastal areas and the interior mountains. There is a significant difference in annual snowfall amounts between these two geographic areas.

The new experimental criteria for this winter season will be based on local snowfall climatology to better align Winter Storm Warnings to what is normal for certain regions. Based on this approach it will limit over warning in regions that are used to more snowfall.

The experimental Winter Storm Warning Snowfall Criteria will be the following:

6 inches of snowfall during a winter storm event

UGC Forecast Zone Number	Weather Forecast Zone Name
NHZ005	Southern Grafton
NHZ006	Southern Carroll
NHZ007	Sullivan
NHZ008	Merrimack
NHZ009	Belknap
NHZ010	Strafford
NHZ011	Cheshire
NHZ012	Eastern Hillsborough
NHZ013	Interior Rockingham
NHZ014	Coastal Rockingham
NHZ015	Western & Central Hillsborough
MEZ014	Southern Somerset
MEZ018	Interior York
MEZ019	Central Interior Cumberland
MEZ020	Androscoggin
MEZ021	Kennebec
MEZ022	Interior Waldo
MEZ023	Coastal York
MEZ024	Coastal Cumberland
MEZ025	Sagadahoc
MEZ026	Lincoln
MEZ027	Knox
MEZ028	Coastal Waldo

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

8 inches of snowfall during a winter storm event

UGC Forecast Zone Number	Weather Forecast Zone Name
NHZ001	Northern Coos
NHZ002	Southern Coos
NHZ003	Northern Grafton
NHZ004	Northern Carroll
MEZ007	Northern Oxford
MEZ008	Northern Franklin
MEZ009	Central Somerset
MEZ012	Southern Oxford
MEZ013	Southern Franklin
MEZ014	Southern Somerset
MEZ033	Interior Cumberland Highlands

Table 2: Universal Geographic Codes (UGC): Weather Zones included in the 8 inch Warning Snowfall Criteria

Image 1: Proposed Experimental Event Snowfall Criteria Map for the Gray County Warning Area

Image 2: Maine Public Forecast Zone Numbers Image 3: New Hampshire Public Forecast Zone Numbers

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

Evaluation of this experiment will take place in the Spring of 2023 to determine if these changes will become official policy for the winter of 2023-24.

For any questions, please contact:

Donald Dumont, Warning Coordination Meteorologist

Donald.Dumont@noaa.gov, 207-688-3221 ext. 223

or

Hendricus Lulofs, Meteorologist in Charge

Hendricus.lulofs@noaa.gov, 207-688-3221 ext. 222