Northwest Weather and Avalanche Center Seattle Washington Avalanche Forecast 1208 PM PST Fri Mar 04 2011 Remember that these forecasts apply to back country avalanche terrain below 7000 feet and not to developed ski areas or highways. Zone Avalanche Forecast East slopes WA Cascades - north of Stevens Pass, East slopes WA Cascades - between Stevens and Snoqualmie Pass, East slopes WA Cascades - between Snoqualmie and White Pass, East slopes WA Cascades - south of White Pass Forecast Friday: Considerable avalanche danger above 5000 feet and moderate below. Danger significantly increasing by Friday night. Saturday: High avalanche danger above 6000 feet and considerable below gradually decreasing. Danger further gradually decreasing Saturday night. Sunday: Considerable avalanche danger above 5000 feet and moderate below further gradually decreasing. Danger further gradually decreasing Sunday night. Snowpack Analysis The latest weather and avalanche cycle began last weekend. Strong southwest winds and warmer denser snowfall were seen Sunday-Monday. Strong southeast to southwest winds and warmer denser snowfall were seen again on Wednesday. Total snowfall since last weekend is in the 2-3 foot range at sites east of the Cascade crest. The winds and the periods of warmer denser snowfall helped build wind and soft slab layers and cause many natural and triggered avalanches during this period. Periods of lower density snowfall and graupel showers between the storms provided temporary weak layers. Generally decreasing winds, decreasing snow and cooler temperatures were seen Thursday. This should have begun to allow recent layers to partly stabilize. Note that areas east of the crest are more likely to have persistent weak layers than near and west of the crest. Buried hoar frost layers from mid to late February are more likely to be persisting in this area. A back country skier near Leavenworth last Tuesday reported snow pack collapsing due to these layers. Snow pits to check for this layer should be especially worthwhile east of the crest. Detailed Forecasts Friday A front should approach the Northwest on Friday. This should cause increasing southwest winds, increasing clouds, and warmer temperatures. Some light snow should be seen by the afternoon. But this should not cause great change in snow conditions. Previous soft or wind slab layers are most likely to linger on lee slopes. This should be north to southeast slopes at higher elevations. The front should cross the Cascades on Friday night. This should cause further increasing southwest winds and heavier snowfall with warmer temperatures. Several inches of snow should be common by Saturday morning with deeper wind transported accumulations on lee slopes. This should build significant new soft or wind slab layers on lee slopes by Saturday morning. This should also be mainly north to southeast slopes at higher elevations. Saturday Southwest winds and snow showers should decrease on Saturday with cooler temperatures. But wind transport may further slightly build new soft or wind slab layers for awhile on Saturday morning on lee slopes. This should continue to be mainly north to southeast slopes at higher elevations but is possible on other aspects. Travel in avalanche terrain at higher elevations is not recommended Saturday morning. Light snow showers mainly near and west of the crest or at higher elevations should mostly end by Saturday afternoon. New and recent layers should partly stabilize by Saturday afternoon. This should cause a lower avalanche danger by Saturday afternoon and night. Sunday A cool day with few if any snow shower and fairly light winds is indicated for Sunday. This should allow new and recent soft or wind slab layers to further partly stabilize. Careful snow pack evaluation and cautious route finding should still be essential on Sunday. Remember that snow pits to check for persistent weak layers such as the buried hoar frost from mid to late Feburary should be espeically worth while east of the crest. Good snow conditions seem likely on lower or sheltered slopes. Backcountry travelers should be aware that elevation and geographic distinctions are approximate and that a transition zone between dangers exists. Remember there are avalanche safe areas in the mountains during all levels of avalanche danger. Contact local authorities in your area of interest for further information.