Summary Avalanche Forecast for Olympics and Washington Cascades
Northwest Weather and Avalanche Center Seattle Washington
1142 AM PST Wed Mar 10 2010
The NWAC program is administered by the USDA-Forest Service and operates out of the National Weather Service Forecast Office in Seattle. NWAC services are made possible by important collaboration and support from a variety of federal, state and private cooperators.
WAZ 513-518-519-019-042-501-502
Avalanche Forecast
OLYMPICS
Wednesday: Moderate avalanche danger above 4000 feet and low below. Avalanche danger gradually increasing late Wednesday.
Wednesday night: Increasing considerable avalanche danger above 4000 feet and moderate below.
Thursday and Thursday night: Increasing high avalanche danger above 5000 feet and considerable below.
WASHINGTON CASCADES NEAR AND WEST OF THE CREST
Wednesday and Wednesday night: Moderate avalanche danger above 4000 feet and low below. Avalanche danger gradually increasing Wednesday night.
Thursday and Thursday night: Increasing high avalanche danger above 5000 feet and considerable below Thursday. Further increasing high avalanche danger above 4 to 5000 feet and considerable below Thursday night.
WASHINGTON CASCADES EAST OF THE CREST
Wednesday and Wednesday night: Moderate avalanche danger above 5000 feet and low below. Avalanche danger gradually increasing Wednesday night.
Thursday and Thursday night: Increasing considerable avalanche danger below 7000 feet Thursday. Further increasing high avalanche danger above 5000 feet and considerable below Thursday night.
Snowpack Synopsis
Weak frontal passages Sunday night and again Tuesday night have deposited generally shallow amounts of cold unconsolidated snow amounting to 4 to 8 inches in most areas. The new snow has fallen over generally hard crust surfaces or settled old snow. The new snow may have covered hoar frost that formed during clearing periods last weekend. The new snow in most areas is unconsolidated and therefore lacks the ability to fail as a slab avalanche.
There may be a few isolated areas of unstable snow, mainly higher elevations near ridges where triggered avalanches could be possible.
However, the current snow pack structure should quickly become unstable when loaded with heavy snowfall with strong winds such is expected beginning Wednesday night in the Olympics and the Cascades Thursday.
Backcountry travelers should be alerted to the expected significant increase in danger over the next few days.
Wednesday and Wednesday night
Light snow showers will end by midday, giving way to some sunshine along with high clouds and light winds. This should allow for a slow decrease in danger, mainly later Wednesday as isolated unstable layers settle. Any sunshine received during the afternoon could make wet snow avalanches possible on steeper south facing slopes where extra caution is advised.
Increasing strong winds Wednesday night and increasing snow in the Olympics spreading to the Cascades late night should lead to an increasing danger. New unstable layers will form over weak existing snow. The greatest danger increase overnight is expected in the Olympics where heavier snowfall is expected.
Thursday and Thursday night
Very strong winds and moderate to heavy snow along with a slight warming trend is expected in all areas Thursday. This should cause a significant increase in danger in all areas, especially higher elevations where strongest winds are expected. New increasingly deep unstable layers should form, especially on lee slopes at higher elevations where natural or triggered slab avalanches will be likely. Backcountry travel on steep open slopes at higher elevations is not recommended Thursday.
Further warming and moderate snow and very strong winds Thursday night should lead to a further increasing danger.
NWAC weather data and forecasts are also available by calling 206-526-6677 for Washington, 503-808-2400 for the Mt Hood area, or by visiting our Web site at www.nwac.us. Remember that these avalanche forecasts apply to back country avalanche terrain below 7000 feet outside of developed and operating ski areas or highways.
The NWAC program is administered by the USDA-Forest Service. NWAC forecasts, data and avalanche or mountain weather information are made possible by partnerships between the Forest Service and many important cooperators, including the National Weather Service, Washington State Department of Transportation, Washington State Parks and Recreation Commission, Washington Snowparks and Snowmobile Grants, National Park Service, Ski Washington, Pacific Northwest Ski Area Association, the Friends of the Avalanche Center and others.
This forecast is prepared for cooperators and users of the NWAC, as an aide to tranportation and recreational operations, and to help promote public safety in the NW mountains.
Kramer/Northwest Weather and Avalanche Center Seattle Washington