Northwest Weather and Avalanche Center Seattle Washington Avalanche Forecast 1159 AM PST Mon Feb 28 2011 Note that this is archived for reference purposes in relation to an accident on Feb 28. This bulletin was issued around noon so the previous days forecast would be more relevant. That is not available, but the forecast is probably less relevant here than in other incidents. The burial and close call was within a ski area and involved an off-duty patroller who would have been familiar with the conditions and the terrain. Technically this does not even apply within ski areas, but the accident on the 28th was in a somewhat out of the way area and this forecast most likely does apply to conditions at the time. Remember that these forecasts apply to back country avalanche terrain below 7000 feet and not to developed ski areas or highways. Mt Hood area Forecast AVALANCHE WARNING MONDAY AND TUESDAY Monday: High avalanche danger below 7000 feet. Danger gradually decreasing Monday night. Tuesday: High avalanche danger above 5000 feet and considerable below. Snowpack Analysis The biggest snow producing storm of the season is upon us! This storm began late Saturday and Saturday night, depositing the initial 6 to 12 inches of snow at cold temperatures with increasing winds. Temperatures rose some 10 degrees F Sunday in most areas with an additional 1 to 2 feet of snow deposited by Monday morning over the Mt Hood areas. Thus far some 20 to 40 inches of snow has fallen in about 36 hours during this storm with very strong winds in most locations. Wind sensors on Mt Hood just above 7000 feet were averaging 70 mph early Monday morning! These strong winds have made it difficult to get accurate snowfall data as snow study plots have been disturbed by the winds. All this new snow has been deposited on an existing very weak snow pack, consisting of 1 to 3 feet or more of gradually settling, but relatively low density snow received last week. In addition to the generally weak underlying snow, there have been many reports of recent avalanches involving a hoar frost layer that became buried over a week ago as well as weak faceted snow layers over thin sun crusts on many previously sun exposed slopes. A successful search and rescue effort found two lost backcountry skiers in the central Washington Cascades near Stevens Pass Sunday afternoon. Fortunately, this had a good outcome, however there was evidence of fresh natural avalanches in the area with estimated crown depths of 5 feet, likely down to the known buried hoar frost layer. There is now an additional 2 to 3 feet of snow load on these layers! Given the strong winds and white out conditions over the past 36 hours, there has been little to no recent avalanche information reported in the Mt Hood area. Also note that some slides that begin in surface layers may step down to more deeply buried crust layers making possible very large and destructive avalanches. The current avalanche conditions remain very dangerous and travel in avalanche terrain is not recommended. Detailed Forecasts Monday and Monday night Moderate to heavy snowfall at gradually cooling temperatures with strong ridge top winds changing to moderate snow showers late Monday and further cooling. The new snow deposits will add additional loads to an already very stressed snowpack. This should maintain or increase the already very high avalanche danger. triggered or natural avalanches should remain likely. We are highly encouraging any would be back country travelers to avoid avalanche terrain until these conditions improve. Decreasing winds and snowfall with further cooling late Monday and Monday night should begin to allow for a slow decrease in danger. Tuesday and Tuesday night Cloudy with light winds and cool temperatures early Tuesday should allow for a further slow decrease in danger. However increasing winds and gradual warming along with increasing light rain or snow is expected by late morning in the Mt Hood area. Rain, snow and winds should further increase Tuesday afternoon and night causing an increasing danger by late Tuesday.