The winter weather products

What the Winter Storm Severity Index, the winter precipitation probabilities and the Day 3 to 7 hazards each measure.

The routes and fields are on the winter weather reference.

WSSI, the Winter Storm Severity Index. WPC’s forecast of how much disruption winter weather may cause, not how much falls: the same 6 inches of snow rates higher where it rarely snows. It comes as an overall category plus the components behind it, for three 24 hour days. The published components are snow_amount, snow_load (weight of snow on trees and power lines), ice_accumulation and blowing_snow.
PWPF, the Probabilistic Winter Precipitation Forecast. WPC’s chance that a 24 hour period brings at least a given amount: 4, 8 or 12 inches of snow, or 0.01, 0.10 or 0.25 inch of freezing rain accretion (“ice” here means freezing rain, which is what the product measures).
Day 3 to 7 hazards, winter only. WPC’s medium range hazards outlook, keeping only heavy_snow, freezing_rain and hazardous_cold. It is a set of labelled areas with dates; WPC attaches no probability to it.