900 AM PST SUN DEC 23 2007 && ZONE AVALANCHE FORECASTS * OLYMPICS, WASHINGTON CASCADES NEAR AND WEST OF THE CREST- ...AVALANCHE WARNING SUNDAY TO MONDAY MORNING... Avalanche danger becoming high above 4000 feet and considerable below Sunday and continuing to Monday morning. Avalanche danger decreasing Monday afternoon and evening becoming considerable above 4000 feet and moderate below. * EAST SLOPES WASHINGTON CASCADES- Avalanche danger becoming high above 5000 feet and considerable below Sunday and continuing to Monday morning. Avalanche danger decreasing Monday afternoon and evening becoming considerable above 5000 feet and moderate below. * MT HOOD AREA- ...AVALANCHE WARNING SUNDAY TO MONDAY MORNING... Avalanche danger becoming high above 5000 feet and considerable below Sunday and continuing to Monday morning. Avalanche danger decreasing Monday afternoon and evening becoming considerable above 5000 feet and moderate below. SNOWPACK ANALYSIS A stormy period brought about 4-7 feet of heavy snowfall to sites near and west of the crest over the last week. Many natural and triggered avalanches, triggered snowpack settlements (whumpfing) and propagating cracks were reported during that time especially from the ski areas. Some of these avalanches were as deep as several feet to the weakened crust from early December or even to the ground. A day of lighter winds and little snowfall was seen Friday. Most sites near and west of the crest received about 4-5 inches of snow Saturday although Mt Baker recorded 15 inches. These conditions Friday and Saturday have allowed the snowpack to settle and slightly stabilize in most areas. Note that the heavier snowfall at Mt Baker will make new surface slabs layers more likely in that area. Back country reports for Friday and Saturday on the Friends of the Avalanche Center and Turns All Year web sites do not indicate any avalanches although skiers were sticking mostly to lower angle slopes. However some signs of instability were still observed such as triggered whumpfing. The Crystal Mountain ski area avalanche crew reported minimal avalanche control results with explosives in their back country areas on Friday and Saturday. The break in the weather on Friday allowed searchers to find and recover the body of the missing snowshoer in Edith Creek Basin near Paradise. This person was caught in a triggered avalanche last Tuesday. DETAILED FORECAST SUNDAY A very strong front will cross the Olympics and Cascades Sunday afternoon. This should cause strong increasing southwest crest level winds and heavy snowfall with a warming trend Sunday. The snow and warming trend should help build potential deep new slab layers on lee slopes. A change to rain should be seen in many areas by Sunday afternoon. These new heavier rain and snow layers will not be well supported by previous hoar frost or low density layers. This should cause an avalanche cycle by late Sunday. Natural or triggered avalanches should be likely may entrain deeper layers. We do not recommend backcountry travel near avalanche terrain Sunday. SUNDAY NIGHT TO MONDAY MORNING More moderate to heavy orographic snowfall should be seen Sunday night to Monday morning with a cooling trend. Convergence effects may continue to enhance snowfall near Stevens and Snoqualmie Monday morning. This weather should build or maintain storm cycle slab layers on lee slopes. We do not recommend backcountry travel near avalanche terrain through Monday morning. MONDAY AFTERNOON AND EVENING Decreasing west winds, decreasing snow showers, and much cooler temperatures are expected Monday afternoon and evening. This should allow new layers to begin to stabilize. New slab layers are most likely to linger on lee north to southeast slopes at higher elevations. Human triggered avalanches may remain probable later Monday. Avoiding avalanche terrain late Monday should still be a good plan since little time will have elapsed since the storm and new layers may not have completely stabilized. &&