14B.4 Microphysics sensitivity studies of a heavy snowfall event in South Central Alaska

Thursday, 27 January 2011: 2:15 PM
615-617 (Washington State Convention Center)
James A. Nelson Jr., NOAA/NWSFO, Anchorage, AK

Successive winter storms worked their way through the North Pacific and into South Central Alaska during a period of March 4th-12th, the most significant of these in regards to impact to the communities of South Central Alaska was on the 8th and 9th of March 2010. Snow totals up to 35 inches were reported over a 24 hour period along with strong winds in excess of 40 mph. Periods of blowing snow caused white out conditions across Kachemak Bay and in parts of Anchorage on the 9th of March. The heavy snow and strong winds resulted in two avalanches on the Seward Highway on either side of Girdwood. According to reports, there were more than a 100 vehicles in distress and 24 accidents. In Homer, city schools closed and numerous car accidents occurred as well.

Although the high impact event was well advertised, precipitation amounts and resultant snowfall amounts were not well represented. Output from a high resolution WRF model is explored to determine the sensitivity of precipitation amount forecasts to changes in the microphysics schemes in the complex terrain of the Chugach Mountains of South Central Alaska. The National Weather Service Forecast Office in Anchorage is currently using a high resolution (3km) WRF model run to assist in daily forecasts, but it is not objectively known if the current configuration is best able to capture these high impact snowfall events.

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