Lundquist et al.

This is an article about the ability to predict peak snow and snow water content (SWE) accumulation early in the season. This can be helpful to water planners. I came across this in a webinar that had four excellent presentations and one was related to this article.  Here is the link to the recording of that presentation. You may want to watch and listen to the recording of that webinar. The overall conclusion is that predictability from early-season snowfall is greatest where it is coldest which usually means high latitudes. That is not surprising but some may find the methodology of quantifying the degree of predictability to be interesting. A lot of detail is provided for the U.S. West but Figure 2 shows it is true across North America.

Abstract

SNOwpack TELemetry observations and model simulations both demonstrate that the fractional contribution of October through December (early season) snowfall to peak snow accumulation in North America increases with latitude due to both colder temperatures and Pacific storm tracks focusing further north earlier in the season. Early season snowfall also makes up greater than 60 percent of peak accumulation in interior low-precipitation locations leeward of mountains, particularly those that are subject to strong, warm winds and midwinter snow loss. Early season snow observations show promise in predicting peak snow water equivalent in locations where large-scale ocean-atmosphere patterns similarly influence fall and winter conditions, and in northern maritime locations where winter temperatures are warm enough that rain on snow and midwinter melt occur. Because climate change is likely to increase the extent of midwinter melt, the latter relationship is expected to become important over more locations in the future.

Key Points

• Fall snow contributes more to peak snow at colder and more northerly locations
• Fall snow can be used to predict peak snow where large scale ocean and atmosphere patterns influence annual snowfall variations
• Fall snow regulates cold content, which in warm regions may tip a snowpack between lasting or ablating midwinter, influencing peak snow

Plain Language Summary

Across North America, snow accumulates from October until the following spring. Early season snow, defined as the snow that accumulates by the end of December, is a greater fraction of total snow accumulation at higher latitudes and at colder locations. Early season snow accumulation can be used to predict peak snow accumulation. Predictions are more skillful at locations where fall precipitation is correlated with winter precipitation because more snow at the end of December indicates that weather patterns are favorable for greater than average snowfall to continue. Predictions also have skill at warmer northern locations where more snow on the ground early season increases the likelihood that mixed rain-snow events add water to the snowpack rather than melting the snow. Predictions at warm southern locations do not have skill because winter and spring snowfall is highly variable, and frequently little to no snow has accumulated by the end of December.

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