Author: Gabrielle Antonioli

Understanding the Spatial Variability of Snowfall in a Mountain Catchment

Integral to the understanding of a snowpack in a given area, whether from the standpoint of a practitioner, avalanche forecaster, or hydrologist, is an understanding of how storms flow across the terrain of interest, and the subsequent impact that terrain has on snowfall.  A central question of spatial variability at the catchment scale is, given a specific storm or weather pattern, how much snow is falling, and where is it falling? This research involves correlating upper atmospheric jet stream flow at the 500 millibar (mb) level, 700 mb local effects, and snow water equivalent (SWE) amounts collected across a large segment of Hyalite Canyon, a watershed 23 kilometers south of Bozeman, Montana.  Specifically, we collect field data using storm boards located in representative spots at different elevations in sub-canyons branching from the primary watershed.  Field SWE amounts are compared to two snow telemetry (SNOTEL) stations located in the canyon, and kriged to produce interpolated SWE maps.  A large portion of storms flows of interest to forecasters in this area are primarily either southwest or northwest in direction, thus storm cycles where divided into these two categories.  High-alpine catchments represent snow reservoirs, though they often are too remote or lack proper instrumentation for detailed snow cover monitoring and analysis. Hyalite Canyon, located in the Northern Gallatin Range of Montana, provides an ideal area to study storm flow across terrain and the effects of orography with relation to spatial variability of SWE. Hyalite Canyon has SNOTEL sites: Shower Falls located at 2,469 meters, Lick Creek located at 2,091 meters, and one Gallatin National Forest Avalanche Center weather station at 3,043 meters, all of which are useful for meteorological data and extrapolating orographic flow at the 700 mb height.   Additionally, it serves as an essential water resource for the Gallatin Valley, supplying domestic water

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