145 PM PST FRI JAN 11 2008 && ZONE AVALANCHE FORECASTS * OLYMPICS, WASHINGTON CASCADES- High avalanche danger above 4 to 5000 feet and considerable below gradually and briefly decreasing later Friday afternoon and evening. Danger slowly increasing later Friday night and Saturday morning and becoming high above 5 to 6000 feet and considerable below. Danger slowly decreasing Saturday afternoon and night and becoming considerable above 4 to 5000 feet and moderate below. * MT HOOD AREA- High avalanche danger above 5 to 6000 feet and considerable below gradually and briefly decreasing later Friday afternoon and evening. Danger slowly increasing later Friday night and Saturday morning and becoming high above 5 to 6000 feet and considerable below. Danger slowly decreasing Saturday afternoon and night and becoming considerable above 4 to 5000 feet and moderate below. * SUNDAY OUTLOOK- Avalanche danger continuing to slowly decrease Sunday morning, becoming considerable above 5000 feet and moderate below. Danger slowly increasing Sunday afternoon and significantly increasing Sunday night and early Monday, becoming high above 4 to 5000 feet and considerable below. SNOWPACK ANALYSIS In all areas, increasingly large wind slabs and several recent weak layers that developed during periods of cool showery weather and diminished winds earlier this week were loaded by heavy amounts of higher density snowfall or rain late Wednesday through Friday morning. With new snowfall amounts ranging from around 8 to over 20 inches during the past 24 hours ending this morning and over 30 inches since snowfall began late Wednesday along with water equivalents of 1 to over 2.5 inches during the past 36 hours, this created and maintained a generally high avalanche danger below 7000 feet in all areas through mid-day Friday. Although reports of true back country conditions have been sparse and primarily confined to highway and within developed ski area avalanche control programs, these reports indicated a significantly unstable snow structure in the upper part of the deepening Northwest snowpack Friday morning with easy ski triggered slides and some sympathetic slides up to 1-2 feet. Although most reported avalanches involved only the most recently deposited 1-2 feet of wind transported snow received since Thursday morning, significant fracture propagation was reported in slides that did release and these quickly ran long distances, entraining considerable amounts of near surface snow. With generally decreasing showers and winds late Friday morning and early afternoon, the snowpack has started the process of slow stabilization. However, with the amounts of recent loading this should be a relatively slow process. As a result, back country travel in avalanche terrain is still not recommended Friday afternoon, and travelers should confine travel to lower angled terrain not connected to steeper terrain above until the recent snowfall has had more of a chance to further settle and stabilize. While most avalanches may initially involve only the most recent 1 to 2 feet of wind transported snow received Thursday afternoon and night, surface slides that do release may trigger some deeper slides reaching the buried weak layers formed early this week, with potential fracture depths reaching up to 3 to 6 feet or more. Although recently increasing snowpack settlement and densification of the overall snowpack structure is diminishing the potential for climax slides releasing to the ground, the recent warming and very large amounts of loading are helping to maintain this possibility, especially along the Cascade east slopes where a generally weaker snow structure exists all the way to ground. Potential triggers for larger slide releases to more deeply buried weak layers should apply particularly to, but not exclusively to, larger loads, such as cornice falls, snowmobilers, and larger groups. DETAILED FORECASTS FRIDAY In most areas, moderate to heavy showers and winds slowly decreased later Friday morning and mid-day, and moderate showers and winds early Friday afternoon should be followed by decreasing light showers and some partial clearing later Friday afternoon. The morning snowfall helped maintain the current mostly unstable snowpack structure and associated high danger below 7000 feet through mid-day, especially on north, northeast and east exposures. However, with moderate temperatures and diminished winds and less loading expected Friday afternoon and evening, slow snowpack settlement is likely and recent wind slabs should begin to slowly stabilize, especially at lower and mid elevations. This should produce a slow decrease in the danger Friday afternoon and evening. However, colder temperatures at higher elevations should make settlement a slower process, especially on lee slopes where some larger human triggered wind slabs should remain likely. FRIDAY NIGHT, SATURDAY Increasing winds, slow warming and increasing light snow expected to develop Friday night should lead to gradually increasing avalanche danger by early Saturday, with moderate rain or snow, moderate winds and further slight warming Saturday morning expected to further increase the danger. While smaller amounts of snowfall are expected than with recent storms, the new snow which does fall should be deposited over some lower density snow received during decreasing winds Friday afternoon and this should make human triggered avalanches probable to likely, especially at higher elevations on wind loaded terrain. Moderate showers and winds should gradually decrease Saturday afternoon and this should allow for a slow decrease in the danger as new wind slabs settle. SATURDAY NIGHT, SUNDAY, SUNDAY NIGHT Further decreasing light showers and winds are expected Saturday night along with low freezing levels. With partly sunny skies, light winds and continue low freezing levels expected Sunday morning, this weather should allow for a continued slowly decreasing danger Saturday night into Sunday morning as slow settlement and stabilization of both recent slabs and the snowpack as a whole continue. However, rising freezing levels and increasing winds should accompany increasing high clouds Sunday afternoon, with strengthening winds, further warming and light rain or snow slowly spreading southward Sunday night into early Monday. While relatively light precipitation amounts are expected in most areas prior to early Monday, the warming and winds should still lead to a gradual increase in the danger mid-late Sunday with a more significant increase expected on Monday as a strong storm moves southward over the region. &&