0845 AM PST FRI DEC 14 2007 && ZONE AVALANCHE FORECASTS * OLYMPICS, WASHINGTON CASCADES NEAR AND WEST OF THE CREST FROM MT RAINIER NORTHWARD- Moderate avalanche danger above 5000 feet and low below Friday morning. Danger slowly increasing Friday afternoon and night, becoming considerable above 4 to 5000 feet and moderate below early Saturday. Danger continuing to slowly increase on Saturday, becoming high above 5 to 6000 feet, considerable from 4 to 5000 feet and moderate below late Saturday, except locally considerable on smooth, wind loaded terrain below 4000 feet. Greatest danger developing on northeast through southeast exposures mid-late Saturday. * WASHINGTON CASCADES NEAR AND WEST OF THE CREST SOUTH OF MT RAINIER, MT HOOD AREA- Moderate avalanche danger above 5000 feet and low below Friday. Danger slowly increasing Friday night, becoming considerable above 5 to 6000 feet and moderate below early Saturday. Danger continuing to slowly increase on Saturday, becoming considerable above 4 to 5000 feet and moderate below late Saturday, with greatest danger developing on southeast through northeast exposures. * EAST SLOPES WASHINGTON CASCADES- Moderate avalanche danger above 6000 feet and low below Friday. Danger slowly increasing Friday night, becoming considerable above 5 to 6000 feet and moderate below early Saturday. Danger continuing to slowly increase on Saturday, becoming considerable above 4 to 5000 feet and moderate below late Saturday, with greatest danger on higher terrain near the crest. * SUNDAY OUTLOOK- ...AVALANCHE WATCH FOR SUNDAY... Danger slowly increasing early Sunday and substantially increasing mid-late Sunday, becoming high above 4 to 5000 feet and considerable below. Back country travel in avalanche terrain is not recommended on Sunday, and travelers should use increasing caution in avalanche terrain and route selection on Saturday. SNOWPACK ANALYSIS In all areas, the mid-lower part of the current still relatively shallow snowpack structure consists of the old refrozen and increasingly hard old crust from the flooding rain event of early December over multiple old melt-freeze snow layers from mid-late November. During the past week several weak weather systems in the recent cool northwesterly flow have deposited anywhere from several inches to a foot or more of generally low density snow, depending on location, all of which overlie and are weakly bonded to the generally hard walkable old crust surface. Also, as a result of some intermittent clearing, this new snow may be interspersed with some weak surface hoar layers that may be buried in some locations. Finally, with the recent cool temperatures some faceting and weakening of the snowpack structure at the interface of the old crust and the new snow has occurred. The most recent but limited wind transport near higher ridges has probably produced pockets of generally shallow wind slabs on southeast and east exposures above about 5000 feet; however on other exposures and at lower elevations, generally light winds during recent snowfall are combining with vegetative and terrain anchors and a lack of cohesive slabs to produce a mostly stable snowpack structure and generally low avalanche danger. All in all, the snowpack appears rather similar to the one preceding the heavy snow, rain and substantial avalanche activity that occurred throughout much of the Northwest in early December. And the forecasts for the next few days indicate that increasingly heavy loading of this potentially very unstable snow structure once again appears likely. Fortunately, the increasing danger should be primarily driven by heavy snow and wind loading rather than rain. DETAILED FORECASTS FRIDAY Mostly cloudy skies and occasional light snow or snow showers are likely in most areas on Friday, with slightly heavier showers likely in the north. Along with a limited rise in freezing levels, this weather should maintain the current avalanche danger for much of Friday. However, gradually increasing winds Friday afternoon should begin to create more cohesive but still shallow slabs on lee slopes, mainly north and northeast exposures near higher ridgelines and west facing slopes near the passes. FRIDAY NIGHT, SATURDAY, SATURDAY NIGHT Increasing light to moderate snow should spread southward Friday night becoming moderate early Saturday, heaviest from about Mt Rainier northward. Along with increased winds and lowering freezing levels, this should produce gradually increasing danger as slowly deepening and more cohesive slabs are deposited over a variety of weak snow layers over the early December crust. Although moderate showers should slightly decrease later Saturday morning, increasing showers, moderate to strong winds and continued cool temperatures should create a further danger increase Saturday afternoon as gradually larger wind slabs are created, especially on southeast through northeast exposures. As a result, increasing caution and proper route selection is advised, with back country travelers urged to perform stability tests prior to venturing onto steeper avalanche terrain. SUNDAY, SUNDAY NIGHT After briefly decreasing showers early Sunday, increasing light to moderate snow should spread over most areas later Sunday morning, with moderate to heavy snowfall expected to develop Sunday afternoon and night. Along with strong winds and only a slight and brief rise in freezing levels, this weather should produce a further increase in the danger as an increasingly sensitive snowpack spreads to progressively lower elevations. While expected slides should initially involve only the most recently deposited new snow since Saturday, as loading continues mid-late Sunday expected avalanches may step down to and involve all of the new snow over the early December crust. Both natural and human triggered slides should become increasingly likely by later Sunday, with slab depths ranging up to 2 to 4 feet or more. As a result, back country travel in avalanche terrain is not recommended on Sunday with safest travel on windswept ridges or lower angle terrain not connected to steeper slopes above. &&