Weather Patterns for Significant Snowfall Events in Prince William Sound, AK, Part 2

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Sunday, 4 January 2015
Kristy C. Carter, University of South Carolina, Columbia, SC; and J. A. Nelson Jr. and T. C. Chen

This project is part 2 of a research study focusing on the patterns leading to large snowfall events for three cities in Prince William Sound, AK. Despite their close proximity, Cordova, Thompson Pass, and Valdez, AK vary in snowfall accumulation during large snowfall events. Snowfall data was collected for all three cites and cases were selected based on variations in snowfall occurring at each of the sites on the same day. Each case was analyzed using the North American Regional Reanalysis (NARR) data with common atmospheric variables studied at both the surface and aloft. The Weather Research and Forecasting (WRF) model was run for specific cases to further investigate the synoptic evolution at a higher resolution. Reanalysis of the cases from Cordova, Thompson Pass and Valdez did not reveal any clear cause for varying snowfall amounts among the three cities. WRF output was looked at for more evidence.

A Climatology of snowfall events was put together for each city based on data availability. Preliminary results from the Valdez climatology study indicate the greatest frequency of large snowfall events (>12in) occur between December and February despite the typical winter season running from October through March. Preliminary results also show years with fewer large snowfall events coincide with warmer sea surface temperatures in the Pacific Ocean associated with the PDO. Reanalysis of the top twenty cases resulted in the placement of the cases into distinct categories based on the location of the surface low pressure and 500mb height pattern. This allows forecasters to identify these events and sea surface temperature anomalies in the Pacific such that the potential severity of snowstorms may be anticipated on a seasonal timescale.

Snowfall distribution in Southern Alaska during large events is complex and likely dependent on several small-scale factors. Output from high resolution WRF simulations will provide further insight into factors that may contribute to differences in precipitation patterns over Prince William Sound.