Special Avalanche Statement issued 300 PM PDT Friday 24 May 2013
…Potentially dangerous avalanche conditions from Mt. Rainier to Mt. Hood over Memorial Day weekend…
Recent Weather and Snowpack: An upper level low pressure system and a very cool and unstable air mass moved over the Northwest on Tuesday and lingered throughout the week.
Snow levels dipped below 4000 ft earlier in the week with 1 to 2 ft of snow accumulation mainly in the central and south Cascades (including eastern slopes) and the Mt. Hood area through Friday morning. Less snowfall and more settlement has occurred in the North Cascades and Olympics. Cool temps and mostly cloudy skies have allowed for slow storm snow settlement late this week.
Avalanche reports were few and far between this week. WSDOT avalanche control at Chinook Pass Thursday PM produced minimal results with ski cuts of the roughly 12 in. of new snow.
Weather Outlook: The cold upper low should weaken over the weekend with a slight warming trend. Scattered light to moderate snow showers could produce light additional snow accumulations. The west slopes should remain mostly cloudy this weekend with more sunshine over the eastern Cascade slopes.
Avalanche Concerns: Poor or even dangerous snow and avalanche conditions are possible at higher elevations, including the volcanoes in the central and south Cascades and Mt. Hood area where the heaviest of snow fell this week. Careful snowpack evaluation, cautious route finding and conservative decision making will be essential for a safe holiday weekend in the back country.
Storm slab avalanches are still possible on varied aspects at higher elevations where new snow has not completely settled. Loose wet snow avalanches will become more likely over the weekend during sunbreaks and warming, especially on solar aspects during the late morning and afternoon hours.
If you begin to sink into the snow surface more than a few inches or notice widespread pinwheeling or natural avalanches, be prepared to alter your travel plans.
This statement will be updated as warranted.
D'Amico/USFS NW Weather and Avalanche Center