The Winter Storm Severity Index (WSSI) is created by screening the National Digital Forecast Database (NDFD) for winter weather elements and combining those data with non-meteorological or static information datasets (e.g., climatology, land-use, urban areas). It creates a graphical depiction of anticipated overall impacts to society due to winter weather.

The WSSI provides a classification of the overall expected severity of winter weather using the following terminology: “none,” “limited,” “minor,” “moderate,” “major,” and “extreme.”The WSSI is updated every 2 hours at 0100 UTC, 0300 UTC, etc… and provides forecasts for 24-hour periods covering Day 1, 2, and 3, as well as a 72-hour forecast encompassing the full Day 1-3 period.

There are six subcomponents of the WSSI, with the overall impact being the maximum value of any subcomponent. The specific subcomponents are Snow Load, Snow Amount, Ice Accumulation, Blowing Snow, Flash Freeze, and Ground Blizzard. For the overall impact and subcomponents, the layers contain separate Day 1, 2, and 3 24-hour forecasts and a 72-hour forecast encompassing the full 3-day period.

Link to graphical webpage: https://www.wpc.ncep.noaa.gov/wwd/wssi/wssi.php

Link to data download: https://www.wpc.ncep.noaa.gov/wwd/wssi/gis/shp/

Link to metadata

Questions/Concerns about the service, please contact the IDP-GIS team.

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