0800 AM PST THU JAN 24 2008 && ZONE AVALANCHE FORECASTS * OLYMPICS, WASHINGTON CASCADES, MT HOOD AREA- MODERATE avalanche danger below 7000 feet through Friday with greatest danger on west and southwest exposures near higher ridges and near the Cascade passes. Greatest danger gradually shifting onto north through east exposures at higher elevations Friday night and early Saturday. SNOWPACK ANALYSIS Slow snowpack settlement this week has allowed for slow stabilization of the upper part of the snowpack and a very slow reduction of the avalanche danger in most areas. Also, weak surface crust formation has also helped to reduce the danger on sun exposed areas. However, very cold temperatures have made any stabilization a very slow process and strong near surface temperature gradients are continuing to facet the snow near last Mondays crust, as well as weakening and faceted much of the top 1-2 feet of near surface snow, with weak low density recycled powder the result. Also, strong east to northeast winds early this week created some shallow but unstable wind slabs and accentuated the danger on west and southwest exposures, where human triggered slides or isolated hard slabs are possible, especially on lee slopes near higher ridges and near the Cascade passes. With intermittent clearing also producing sporadic surface hoar mid-late last week, some buried surface hoar may also exist under these recent wind slabs and this may result in some sensitive though relatively local instabilities. As a result, recent weather has developed highly variable snow conditions, primarily dependent on exposure: on wind exposed terrain, previous strong high winds scoured many windward slopes down to relatively stable old crusts or wind hardened surfaces. On adjacent steeper lee terrain near higher ridges and near the Cascade passes, these winds may have produced some sensitive wind slabs ranging from 6 inches to about 2 feet, with some of these slabs deposited over weak layers of buried surface hoar or some lower density snow over the crust formed in mid-January. However, in wind sheltered areas, some relatively stable powder or recycled powder has developed, though some cross loading by recent winds may have produced local shallow slabs on steeper terrain to the lee of minor ridges. Finally, on sun exposed and wind sheltered terrain, especially at higher elevations, solar radiation has produced a thin trap crust that is resulting in challenging travel conditions. All in all, the past, current and expected weather have produced and should maintain a snowpack structure that will be highly susceptible to a significant danger increase whenever more normal wintertime snowfall returns to the region. Current forecast models indicate that while a relatively weak disturbance passing mostly west of the region on Thursday should not affect the current danger, a more significant danger increase is likely this weekend when moderate snowfall and increasing winds should load a very weak snowpack structure. DETAILED FORECASTS THURSDAY, THURSDAY NIGHT Although some areas of low clouds or fog at lower elevations along the Cascade east slopes may result in some light showers or flurries Thursday morning, primarily near the Columbia River Gorge, in most other areas of the Cascades and Olympics variable mid and high clouds should spread southward on Thursday. However, considerable sunshine or filtered sunshine is still likely in most locations with only a chance of flurries or light snow showers in the Mt Hood area Thursday afternoon and evening where briefly increased clouds are likely. Along with generally decreasing winds Thursday afternoon and continued relatively light ridgetop winds and low freezing levels, this weather should have little affect on the current danger. However, the continued relatively cold weather in most locations should help to maintain some unstable slabs through a weak and weakening bond to last weeks crust, especially on wind loaded west and southwest exposures where increasing caution is advised. A slow clearing trend with light winds and low freezing levels Thursday night should have little affect on the current danger, but should once again allow for further faceting and weakening within the upper part of the snowpack as well as further and more widespread surface hoar formation. These potential weak layers should be monitored in the days ahead as they may become important factors in increasing the avalanche danger when future snow loading is received. FRIDAY, FRIDAY NIGHT Mostly fair skies and cold temperatures Friday morning should be followed by mostly sunny weather and slightly warmer temperatures Friday afternoon, especially in the south. This weather should have little effect on the overall moderate danger, with some relatively shallow wind slabs continuing, mainly on west through southwest exposures. Increasing high clouds and slowly increasing ridgetop winds late Friday and early Saturday should not affect the current danger significantly, but should begin to shift the greatest danger onto north through east exposures near higher ridges where generally weaker and more faceted snow layers are likely. Also, this weather should promote further surface hoar growth while allowing for continued faceting and weakening of much of the near surface snow structure. All in all, these snowpack developments should set the table for a significant increase in the danger over the weekend when increasing snow and strengthening winds should load and stress a variety of potential weak layers. &&