About Snow Cover
Snow Mask or Snow Cover refers to a data layer used to mark areas where snow is present, so wildfire risk/fire spread modeling can treat those areas differently. Snow data is used in Technosylva products to account for the fire-suppressing and fuel-modifying effects of snowpack.
When an area is snow-masked, Technosylva’s model can raise 1-hour dead fuel moisture (DFM) to saturated values and suppress fire spread, meaning little or no fire risk is shown there. Areas above a threshold (snow depth greater than 2 cm) are treated as snow-covered.
Data Sources
The data source for snow varies by geography: customers within the contiguous United States (CONUS) historically received snow cover derived from the Snow Data Assimilation System (SNODAS). However, if snow data is stale, the mask may still show snow after rapid melt, which can understate real fire risk in areas where snow has already melted.
Beginning in 2026, Technosylva has therefore upgraded how snow cover is represented in the daily wildfire risk forecasts. The static, satellite-based snow mask previously used has been replaced with hourly, forecast-driven snow modeling from Technosylva's own Weather Research and Forecasting (WRF) model. SNODAS will be retained as an independent reference for periodic verification.
Similarly, soil moisture now comes from WRF’s hourly forecast rather than NASA's Short-term Prediction and Transition Center – Land Information System (SPoRT-LIS), removing another external dependency from the data pipeline. This increases robustness, adds dynamic forecast capabilities, and contributes to more representative risk computations.
Outside CONUS
Customers outside CONUS receive a Technosylva-calculated product derived from Visible Infrared Imaging Radiometer Suite (VIIRS) surface reflectance data.
Visible Infrared Imaging Radiometer Suite Snow Cover (VIIRS)
VIIRS Snow Cover is a Technosylva-calculated snow cover product for areas outside the contiguous United States, derived from the NASA/NOAA Suomi NPP Visible Infrared Imaging Radiometer Suite (VIIRS) daily surface reflectance data (VNP09GAv002). The product combines the Normalized Difference Snow Index (NDSI), a data collection confidence flag band, and a water body mask to classify snow-covered pixels.
Source: VNP09GAv002 — VIIRS/NPP Surface Reflectance Daily L2G Global 1 km and 500 m SIN Grid, Version 2
Temporal resolution: 1 day
Spatial resolution: 500 m x 500 m
Coverage: Outside CONUS