900 AM PST MON DEC 3 2007 && ZONE AVALANCHE FORECASTS * OLYMPICS- ...AVALANCHE WARNING MONDAY... Extreme avalanche danger above about 5000 feet and high below Monday. High avalanche danger above about 5000 feet and considerable below Monday night. Considerable avalanche danger above about 5000 feet and moderate below Tuesday and Tuesday night. * WASHINGTON CASCADES- ...AVALANCHE WARNING MONDAY... Extreme avalanche danger above about 4000 feet and high below Monday. High avalanche danger above about 4000 feet and considerable below Monday night. Considerable avalanche danger above about 4000 feet and moderate below Tuesday and Tuesday night. * MT HOOD AREA- ...AVALANCHE WARNING MONDAY... Extreme avalanche danger above about 5000 feet and high below Monday. High avalanche danger above about 5000 feet and considerable below Monday night. Considerable avalanche danger above about 5000 feet and moderate below Tuesday and Tuesday night. SNOWPACK ANALYSIS The general snow pack structure in most areas until Saturday was something like 1-2 feet of slightly consolidated snow from late November, over weak faceted snow or hoar frost from mid November, over shallow firmer snow or crusts from early in the season. This structure is ideal for instability. A similar though shallower structure would have been expected east of the crest. An increasing very strong southwest flow began to be seen over the Northwest on Sunday. An initial strong storm crossed the Olympics and Cascades on Sunday. This is being followed by an extremely strong storm on Monday. This storm has tropical origins and is being accompanied by very strong southwest crest level winds and extremely heavy snow generally changing to rain with warming temperatures. New 24 hour snowfall on Monday morning ranges from 1-2 feet at sites near and west of the Cascades crest. This follows the 1-1.5 feet of 24 hour snowfall that was seen Sunday morning. Heavy snow has changed to heavy rain at many sites on Monday morning but this is being delayed east of the crest where cold air is trapped near the surface. Many reports confirm that a widespread major avalanche cycle is occurring late Sunday and Monday. Direct and indirect reports of instability are available on the Turns All Year and FOAC web sites. The Stevens Pass highway was closed in Tumwater Canyon Monday morning due to avalanches across the road. The Snoqualmie DOT avalanche crew reported 1-2 widespread fractures Monday morning. The Paradise road crew reported that their snow blower was causing 300-400 yard fractures on Sunday. The Hurricane Ridge road was closed due to avalanches across the road on Sunday. Terrain and vegetation may be anchoring a shallow snowpack at low elevations especially east of the Cascade crest. But note that avalanches that begin at higher elevations may run into run out zones with much less snow cover. MONDAY AND MONDAY NIGHT Continued very strong crest level winds, heavy snow or rain with high snow levels should be seen on Monday. Natural or human triggered avalanches remain likely on Monday. Destructive avalanches will remain most possible on steep slopes that did not release on Sunday. Avalanches and consolidation may stabilize other slopes. We do not recommend back country travel near avalanche terrain on Monday unless on site evaluation determines that a lesser degree on danger. Avalanche danger may begin to decrease late Monday as snow or rain intensities decrease and temperatures cool and avalanches and consolidation stabilize many slopes. TUESDAY AND TUESDAY NIGHT Decreasing but still strong west southwest crest level winds, orographic snowfall and slowly lowering snow levels are expected on Tuesday. Several inches to perhaps a foot of snowfall is possible at higher elevations. This may build some local new slab layers on steep lee slopes at higher elevations. Human triggered slab avalanches may be probable on such slopes. At lower elevations the cooler temperatures and consolidated snow should result in a significantly decreasing avalanche danger. These trends should generally continue into Tuesday night. &&