Summary Avalanche Forecast for Olympics and Washington Cascades
Northwest Weather and Avalanche Center Seattle Washington
1219 PM PST Fri Nov 20 2009
In order to provide a better and more complete avalanche forecast on a regular basis, the primary avalanche forecasts will be issued between 11 AM and 12 PM PST on a daily basis, with updates issued whenever significant deviations occur. The timing and the products will be adjusted as necessary during the upcoming winter in order to produce the best possible avalanche information.
WAZ-513-518-519-018-042-501-502
Avalanche Forecast
OLYMPICS- WASHINGTON CASCADES NEAR AND WEST OF THE CREST-
Friday and Friday night: Considerable avalanche danger above 5000 feet and moderate below, gradually increasing late Friday and Friday night.
Saturday morning: Slightly decrease danger becoming considerable above 6000 feet and moderate below.
Saturday afternoon and night: Increasing avalanche danger becoming considerable above 4 to 5000 feet and moderate below.
Outlook Sunday: Further increasing danger becoming considerable above 4000 feet and moderate below.
WASHINGTON CASCADES EAST OF THE CREST
Friday and Friday night: Considerable avalanche danger above 6000 feet and moderate below, slightly increasing late Friday.
Saturday morning: Decreasing moderate avalanche danger below 7000 feet.
Saturday afternoon and night: Increasing avalanche danger becoming considerable above 5 to 6000 feet and moderate below.
Outlook Sunday: Further slight increasing danger becoming considerable above 5000 feet and moderate below.
Snowpack Synopsis
Significant warming occurred early Thursday along with decreasing precipitation over most areas. The exception was the extreme north Cascades and Olympics that received heavy amounts of wet snow. This produced a widespread increase in danger Thursday causing a significant avalanche cycle. The current danger level has diminished markedly as of early Friday.
The main current concern is from areas of wind deposited snow at higher elevations where a considerable danger remains. Otherwise, settling wet snow is gradually refreezing and has consolidated greatly over the past day.
Friday and Friday night
Gradually increasing light to moderate rain or snow cooling and becoming mostly snow late Friday and Friday night. This should allow for old snow layers to refreeze and begin to build some shallow new snow layers on mainly lee slopes at higher terrain.
Increasing caution is urged later Friday, especially on steeper open slopes receieving the greatest new snow amounts, such as on the volcanic peaks.
Saturday and Saturday night
A brief break between weather systems should allow for decreasing winds early Saturday and a slight decrease in danger. Increasing light to moderate snow at cooling temperatures and increasing winds later Saturday and Saturday night is expected to cause an increasing danger. New unstable wind slab layers are expected to develop late Saturday on lee slopes in higher terrain.
Sunday and Sunday night
Moderate to heavy snow showers, especially along the west slope areas along with strong crest level winds is expected to cause a further increasing danger. Increasingly deep unstable wind slab layers are expected through Sunday, especially on northeast through southeast facing slopes at higher elevations.
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.
Kramer/Northwest Weather and Avalanche Center Seattle Washington