915 AM PST WED DEC 19 2007 && ZONE AVALANCHE FORECASTS * OLYMPICS- WASHINGTON CASCADES NEAR AND WEST OF THE CREST- ...AVALANCHE WARNING FOR WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT... High avalanche danger above 4000 feet and considerable danger below 4000 feet Wednesday. Avalanche danger slightly decreasing Wednesday night. Further decreasing danger Thursday becoming considerable above 4000 feet and moderate below. Further slowly decreasing danger Thursday night. * MT HOOD AREA- ...AVALANCHE WARNING FOR WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT... High avalanche danger above 5000 feet and considerable danger below 5000 feet Wednesday. Avalanche danger slightly decreasing Wednesday night. Further decreasing danger Thursday becoming considerable above 5000 feet and moderate below. Further slowly decreasing danger Thursday night. * EAST SLOPES WASHINGTON CASCADES- Increasing considerable avalanche danger above 4000 feet and moderate below Wednesday. Avalanche danger slightly decreasing Wednesday night. Further decreasing danger Thursday becoming considerable above 5000 feet and moderate below. Further slowly decreasing danger Thursday night. SNOWPACK ANALYSIS Additional heavy snowfall Tuesday and again early Wednesday has deposited an additional 10 to 20 inches of new snow. Along with periods of slight warming overnight Tuesday and very strong winds this has caused a significantly increased avalanche danger. Some 2 to 4 feet or more of new snow has accumulated in the Olympics, most west slope areas of the Cascades and Mt Hood area over the past five days. This heavy snowfall along with very strong winds at times should overburden numerous buried weak layers from previous storm snow or weaknesses near the early December rain crust. These conditions should make natural or triggered avalanches likely. Slides of 2 to 4 feet or more are likely Wednesday and travel in avalanche terrain is not recommended. The main concern remains the weakness at or just above the early December rain crust now buried some 2 to 4 feet below the surface in most areas near or west of the crest. Light snowfall of low density snow or surface hoar that developed over this crust early last week has now been loaded by the increasingly deep storm snow layers. This was evident by results on previously uncontrolled slopes at Crystal Mountain Tuesday where widespread 2 foot slabs were releasing on the crust. While most of these were triggered by explosives one patroller triggered a 2 to 3 foot slab after the slope settled from his weight on slope near the ridge. A climber is missing after triggering a slide and being caught in Edith Basin above Paradise on Mt Rainer Tuesday. An early morning snowpit Wednesday in the area revealed the weak layer at the crust when failure occurred about 4 feet down on the crust with compression test 5 and Rutschblock 4. Slides not initiating down to the crust may begin in more shallow storm layer weaknesses but likely step down to the crust layer, making some large and very dangerous slides possible. Travel on lower angled slopes away from steeper slopes above and on windward ridges is recommended. A similar but shallower structure might be expected along the Cascade east slopes where a slightly lower danger is expected. However, triggered slab avalanches are probable on steeper lee slopes above about 4000 feet where the greatest danger is expected. WEDNESDAY AND WEDNESDAY NIGHT A very strong frontal passage is expected midday Wednesday. This should bring heavy snow and very strong crest level winds through the day Wednesday. This should cause a significant increase in the avalanche danger with mostly unstable snow developing above 4000 feet. Travel in avalanche terrain is not recommended above these elevations Wednesday. Decreasing snow and winds Wednesday night should begin to allow for a slowly decreasing danger. THURSDAY AND THURSDAY NIGHT Cooler temperatures and decreasing light to moderate snow showers with diminishing winds are expected Thursday. This should allow for a slowly decreasing danger as recently formed unstable layers begin to settle and consolidate. However, continued deeply buried weak layers should maintain the possibility of some large triggered slides, possibly 3 to 5 feet deep or more. Backcountry travelers are urged to use extra caution and avoid steep open slopes. &&