####018005161#### WWUS86 KSEW 051911 SABWA Summary Avalanche Forecast for Olympics and Washington Cascades Northwest Weather and Avalanche Center Seattle Washington 1111 AM PST Mon Mar 05 2012 This forecast applies to back country avalanche terrain below 7000 feet and does not apply to developed ski areas or highways. Avalanche Forecast Olympics, Washington Cascades near and west of the crest north of Stevens Pass Monday and Monday night: Considerable avalanche danger above 4000 feet and moderate below early Monday increasing and becoming high on lee slopes above 5000 feet and considerable elsewhere Monday afternoon and night. Little change in the danger Monday night. Tuesday and Tuesday night: High avalanche danger on lee slopes above 5000 feet and considerable elsewhere with a local danger increase on sun exposed slopes during the late morning and afternoon. Little change in the danger Monday night. Washington Cascades near and west of the crest from Stevens Pass southward Monday and Monday night: Moderate avalanche danger below 7000 feet increasing significantly on Monday and becoming high on lee slopes above 5000 feet and considerable elsewhere late Monday. Little change in the danger Monday night. Tuesday and Tuesday night: High avalanche danger on lee slopes above 5000 feet and considerable elsewhere with a local danger increase on sun exposed slopes during the late morning and afternoon. Slightly decreasing danger Tuesday night. Washington Cascades east of the crest Monday and Monday night: Moderate avalanche danger below 7000 feet increasing Monday and becoming considerable above 5000 feet and on lee slopes above 4000 feet and moderate elsewhere. Slightly decreasing danger expected later Monday night. Tuesday and Tuesday night: Considerable avalanche danger on lee slopes above 5000 feet and moderate elsewhere with a local danger increase on sun exposed slopes during the late morning and afternoon. Slightly decreasing danger Tuesday night. Snowpack Synopsis Following significant new snowfall early last week, a combination of warming and precipitation mid-late last week produced either numerous wet loose or wet slab avalanches, strong settlement of the old snowpack, or some percolation channels or rain runnels, along with an overall very slow decrease in the danger late Saturday into Sunday morning as warm but unstable near suface snow slowly settled. Substantial breakable or semi-breakable crusts also formed that now overlie the older weaker snow in many areas above about 4 to 5000 feet with some wet weak surface snow developing at lower elevations. These near surface snow conditions produced recent trap crusts and very challenging travel in the back country over the weekend when wet loose and isolated wet slabs occurred. Most recently a strong storm moved into the Olympics and northern WA Cascades overnight, producing increasing winds and moderate snow fall amounts at lowering freezing levels and increasingly strong winds. This has produced generally increased avalanche danger in the north and Olympics, with further increasing danger likely spreading southward on Monday as the front moves over the remainder of the region. Monday and Monday night Increasing moderate to occasionally heavy rain or snow should spread southward over the region on Monday, along with strong ridgetop winds and dramatic cooling. This should produce an increasing considerable to high avalanche danger...especially on higher elevation lee terrain...where new human triggered wind slabs should become likely to very likely. Also, some weak new cornice formations are expected that should be avoided. Although slowly decreasing showers are likely later Monday night, cold temperatures and moderate winds should help limit any danger decrease. Tuesday and Tuesday night Light snow showers should end Tuesday morning with clearing skies spreading southward later Tuesday morning and afternoon. However, cold temperatures should slow snowpack stabilization and help maintain current elevated dangers...especially on lee slopes, while increasing solar effects are likely to produce a local danger increase on sun exposed terrain. Although light winds and clear skies Tuesday night should allow for a slightly decreasing danger at lower and mid elevations, moderate winds near higher ridges should help maintain unstable wind slabs on higher elevation lee terrain. NWAC weather data and forecasts are also available by calling 206-526-6677 for Washington, 503-808-2400 for the Mt Hood area, or by visiting our Web site at www.nwac.us. Moore/Northwest Weather and Avalanche Center Seattle Washington References 1. http://www.nwac.us/