Numerical Weather and Snowpack Prediction at the Colorado Avalanche Information Center

The Colorado Avalanche Information Center (CAIC) is the oldest public avalanche forecast program in the United States. As a state-funded program, the mission of the CAIC is to provide avalanche information, education and promote research for the protection of life, property and the enhancement of the state's economy. Since 1950 avalanches have killed more people in Colorado than any other natural hazard, and in the United States, Colorado accounts for one-third of all avalanche deaths. CAIC performs a dual purpose of forecasting and public education to achieve this mission.

The seasonal Colorado mountain snowpack is directly affected by weather at all times. As such, accurately forecasting weather is an important component to successfully predicting snowpack stability. In 2011, CAIC purchased computer hardware for the sole purpose of providing in-house numerical weather prediction (NWP) guidance using The Weather Research and Forecasting (WRF) model. A double nested (12km-4km grid spacing) domain system is centered over the Colorado mountains. The system generates 84-hour forecasts four times daily initialized with NOAA's Local Analysis and Prediction System (LAPS) analyses and constrained by forecast lateral boundary conditions derived from the NOAA North American Model (NAM). A variety of products are derived from the WRF model output including standard surface and upper air maps. In addition, hourly point forecasts include text and graphical displays such as vertical time-height cross-sections and wind roses. All NWP products are integrated into the operational CAIC web site (http://colorado.gov/avalanche), which includes daily human forecaster updates of mountain weather and snowpack conditions for ten regional mountain zones.

A new endeavor for 2013 is to investigate the utilization of a snowpack evolution model, called SNOWPACK, developed at the Switzerland-based WSL Institute for Snow and Avalanche Research SLF. The SNOWPACK model simulates snowpack layering and characteristics such as density, temperature, and crystal type using a set of meteorological inputs. Initial SNOWPACK model implementation at CAIC during the past winter season used actual meteorological measurements from a limited number of mountain tower observations locations. For the upcoming winter season, WRF model output will be used to drive the SNOWPACK model; hence, providing much wider areal coverage of snowpack characteristics.

The paper will discuss WRF model applications pertaining to the CAIC mission of improving the forecasting and public education mission. Preliminary SNOWPACK model products will be presented.