0830 AM PST Friday, March 07, 2003 ZONE AVALANCHE FORECASTS..... OLYMPICS...WASHINGTON CASCADES NEAR AND WEST OF THE CREST.... ..................AVALANCHE WARNING.................... High avalanche danger above 4000 feet and considerable below Friday, with greatest danger on southeast through northeast facing slopes. Slightly decreasing danger late Friday through early Saturday, mainly north and central Cascades. Danger increasing significantly Saturday and becoming high to extreme above 3 to 4000 feet and high below late Saturday into early Sunday. MT HOOD AREA..... ..................AVALANCHE WARNING.................... High avalanche danger above 4 to 5000 feet and considerable below Friday and Friday night, with greatest danger on southeast through northeast facing slopes. High danger above 5000 feet and considerable below Saturday morning, increasing significantly later Saturday afternoon and night and becoming high to extreme above 4 to 5000 feet and high below. EAST SLOPES WASHINGTON CASCADES..... ..................AVALANCHE WATCH......................... High avalanche danger above 5000 feet and considerable below Friday, with greatest danger on southeast through northeast facing slopes. Slightly decreasing danger later Friday, mainly north and central Cascades. Danger increasing significantly Saturday and becoming high above 4 to 5000 feet and considerable below. SUNDAY OUTLOOK............. ................AVALANCHE WATCH..................... High to extreme avalanche danger above about 4000 feet and high below Sunday morning, decreasing slightly mid-late Sunday and becoming high above 4 to 5000 feet and considerable below. SNOWPACK ANALYSIS..... In most areas, increasingly large amounts of new snow have loaded a variety of weaker layers or recent sun crusts during the past 48 hours, with two day totals now ranging from about 16 inches to over 50 inches. Along with some graupel layers that were received during heavy showers, these weak layers include some surface hoar from Monday night, some older lower density snow received last weekend that has persisted on sun shaded terrain, and some older faceted snow above an old crust from mid-February. Loading of these weak layers by strong wind transport of the heavy new snowfall amounts has resulted in a significant increase in the avalanche danger. In most areas a high avalanche danger and storm related soft slabs of 1-3 feet are likely above about 4 to 5000 feet, especially on wind loaded southeast through northeast exposures. These soft wind slabs may release on graupel, surface hoar or thin sun crusts, and some isolated deeper avalanches may step down to faceted snow layers above the old rain crust formed several weeks ago--especially on shaded northeast through northwest exposures. Field reports from many areas indicate that most slides are involving mainly the most recently deposited snow, with slabs of 1-2 feet releasing rather easily by both ski testing and explosive control. However these reports indicate that most slides are not running long distances yet. Although slightly less snowfall was reported along the Cascade east slopes since Wednesday, moderate amounts of new snow combined with strong ridge top winds have still produced a substantially increased danger, especially above 5000 feet where high danger is expected and human triggered slabs are likely. Back country travelers should note that the buried surface hoar may make some slabs quite sensitive, while the cold temperatures and strong winds have probably produced rather cohesive and brittle wind slabs. Hence some avalanches on previously sun and wind sheltered terrain may be triggered from lower angled slopes (surface hoar as the weak layer), some fractures may propagate considerable distances (a very cohesive slab structure), and wind transported snow is likely to have been deposited lower than normal on lee- slope starting zones. FRIDAY...FRIDAY NIGHT..... Heaviest rain and snow showers should slowly shift southward Friday, with heaviest snowfall and strongest winds likely in the southern Washington and northern Oregon Cascades Friday afternoon and night. However, moderate snowfall in the north and moderate to heavy snowfall in the south should still produce additional stress on existing wind slabs and buried weak layers, thus maintaining the generally high danger above about 4 to 5000 feet and considerable danger below into Friday afternoon in the north and through Friday night in the south. Significant 1-2 ft natural or human-triggered wind slabs should remain likely above 4 to 5000 feet and probable below, particularly on heavily loaded northeast through southeast exposures where some larger slabs up to 2 to 4 ft or more are probable. Briefly decreasing showers and winds late Friday-especially in the north and central Cascades- should allow for a slight and relatively brief decrease in the danger Friday night and early Saturday as loading rates decrease and recent wind slabs start to settle. SATURDAY...SATURDAY NIGHT....SUNDAY MORNING... Moderate rain or snow should spread northward again Saturday, becoming moderate to heavy Saturday night into Sunday morning. Along with rising freezing levels and slowly strengthening winds this should produce a significant increase in the avalanche danger on Saturday as heavier dense snow or rain is deposited over recent lower density snow and a variety of weak layers. High to extreme avalanche danger is expected later Saturday, and widespread natural or human triggered avalanches should become increasingly likely on most aspects and slope angles late Saturday into Sunday morning. Shifting winds near the Cascade passes should also spread the danger to a variety of slope exposures. With the warming, increased snow density and the loading, some large destructive avalanches are possible, with slab fractures of 3 to 5 feet or more involving all of the snow down to the rain crust from mid-February and some of these slides running long distances. As a result, travel in avalanche terrain should be avoided. SUNDAY AFTERNOON AND NIGHT.... Decreasing and more showery precipitation is expected Sunday afternoon and night, along with gradually lowering freezing levels. This should allow for a slight decrease in the danger from the recent high to extreme as recent slabs begin to settle and stabilize and wet surface snow starts to refreeze. However generally high danger should persist above 4 to 5000 feet- especially on northeast through southeast exposures-with considerable danger below.