0930 AM PST FRI DEC 21 2007...AMD && ZONE AVALANCHE FORECASTS * OLYMPICS, WASHINGTON CASCADES NEAR AND WEST OF THE CREST- ...AVALANCHE WATCH FOR SATURDAY AFTERNOON AND NIGHT... High avalanche danger above 5000 feet and considerable danger below slightly and briefly decreasing Friday and becoming high above 6000 feet and considerable below. Danger gradually increasing Friday night and Saturday morning, further increasing Saturday afternoon and becoming high above 3 to 4000 feet and considerable below later Saturday afternoon and night. * MT HOOD AREA- ...AVALANCHE WATCH FOR SATURDAY AFTERNOON AND NIGHT... High avalanche danger above 5 to 6000 feet and considerable danger below slowly and briefly decreasing Friday and becoming high above 6000 feet and considerable below. Danger gradually increasing Friday night and Saturday morning, further increasing Saturday afternoon and becoming high above 4000 feet and considerable below later Saturday afternoon and night. * EAST SLOPES WASHINGTON CASCADES- Considerable avalanche danger below 7000 feet slightly decreasing Friday. Danger gradually increasing Friday night and Saturday morning, and further increasing Saturday afternoon and night, becoming high above 5 to 6000 feet and considerable below late Saturday. * SUNDAY OUTLOOK- ...AVALANCHE WATCH FOR MID-LATE SUNDAY... Briefly and slightly decreasing danger Sunday morning, but danger increasing again Sunday afternoon and becoming high below 7000 feet late Sunday into early Monday. SNOWPACK ANALYSIS Although briefly decreasing winds and snowfall have allowed for a slight danger decrease from the recent avalanche warning situation, significant weak layers remain buried in a continuing scary and quasi-continental snowpack structure. This structure consists of large amounts of recent slightly higher density snow received this past week lying over smaller amounts of lower density snow from last week, all over a weak and increasingly faceted crust formed in early December. This faceting and associated temperature gradients near the crust have now reduced the crust to a mostly decomposed and rather weak granular structure in many areas while allowing for an increasingly poor bond between the crust and the overlying large amounts of recent snow. Additionally, buried weak layers of surface hoar are interspersed with some weaker low density layers above the crust. Finally, in areas where winds and snowfall decreased overnight, some very low density snow and surface hoar have been reported early Friday morning. Obviously this apparently more stable and fluffy snow structure near the surface is masking some very substantial and deeply buried instabilities. As a result, high danger continues above about 5 to 6000 feet in steeper avalanche terrain of the Olympics, Mt Hood area and Washington Cascades near and west of the crest, with a slightly lower but still considerable avalanche danger at lower elevations and along the Cascade east slopes. Back country travelers should exercise significant caution in avalanche terrain with travel not recommended on steeper wind loaded slopes at higher elevations. Field reports from many areas continue to indicate a dangerous snowpack structure, with both human and explosive triggered large slabs being reported during the past few days. Slab depths have ranged from a few feet up to 6-7 feet, with most larger slides releasing on either the decomposed old crust or the ground. Good fracture propagation has been noted as well as sympathetic releases and resulting avalanches quickly running full path and beyond. Also, many reports of shooting cracks and sudden snowpack settlement (whomping) continue, indicating significant collapse of overlying slabs on one or more buried weak layers. As a result of all of these weather and snowpack conditions, back country travel in avalanche terrain is still not recommended at higher elevations on Friday. All back country travelers, whether their mode of travel is by ski, snowboard, snowmobile or snowshoe, are urged to confine travel to more gentle and/or tree covered terrain until the recent large amounts of new snow have had a chance to further settle and stabilize. It should also be noted that the snowshoer who triggered and was caught by a slab avalanche near Edith Basin above Paradise on Mt Rainier on Tuesday remains missing; hopefully better weather will aid searching efforts today. It is important to re-emphasize that although a recent decrease in winds in some areas may make the current new snow surface very attractive, this surface is masking a variety of buried weaknesses which may need only a little added stress to release. While slow snowpack stabilization should occur Friday, several episodes of heavy loading over the weekend should bring further significant danger increases mid-late Saturday and again mid-late Sunday. Although most avalanche activity should involve only the most recently deposited snow releasing on lower density snow or some surface hoar, this weather should maintain the potential for some very large slab slides that may still involve all of the recent snow down to the old early December crust, especially in areas not experiencing recent avalanche activity. DETAILED FORECASTS FRIDAY, FRIDAY NIGHT Partly to mostly cloudy skies with light showers Friday morning should be followed by mostly cloudy skies and occasional light snow or light snow showers Friday afternoon. However, along with generally decreased winds and cold temperatures, this should allow for a slight and slow decrease in the danger on Friday as the recent large amounts of new snow slowly settle and begin to strengthen. Unfortunately, this strengthening process should be much slower near the already faceted old crust where some larger temperature gradients are likely to persist. Increasing winds and slowly increasing light snow late Friday should be followed by stronger winds, some warming and increasing snowfall early Saturday. This should produce a gradual increase in the danger later Friday into early Saturday. SATURDAY, SATURDAY NIGHT...AMENDED Light snow should spread to most areas and increase later Saturday morning, with moderate to occasionally heavy snow likely Saturday afternoon along with strong winds and a brief and limited warming trend. This weather should produce generally increasing avalanche danger with both human and naturally triggered avalanches becoming increasingly likely later Saturday, especially above 3 to 4000 feet in the Olympics and Cascades near and west of the crest. Although expected slide activity should primarily involve only the most recently deposited new snow releasing on the lower density snow or surface hoar from Friday, the potential for isolated deep and very dangerous slides involving all of the new snow since early December should continue. The developing danger should be accentuated on north through east exposures near higher ridge lines along with some loading on west exposures near the Cascade passes. SUNDAY, SUNDAY NIGHT After a brief decrease in showers and winds allow for a slight decrease in the avalanche danger Sunday morning, increasing snow, strengthening winds, and brief warming should produce generally high danger below 7000 feet in most areas. Further unstable slabs are expected on a variety of aspects and slope angles, with some very sensitive slabs likely developing. More shooting cracks, local whomping and sympathetic and remotely triggered slides should become increasingly likely by later Sunday, along with a continuing potential for additional large slab releases to either the old early December crust or the ground. As a result, back country travel in avalanche terrain is not recommended Sunday afternoon and night and travelers are urged to exercise considerable caution in all areas. &&