Today's and yesterday's warnings in reverse chronological order.
A relatively benign spring snowpack evolution in the Northwest during the past month or so is expected to change significantly this week. Rain at slowly rising freezing levels Tuesday into early Wednesday should be followed by sustained high freezing levels reaching 13,000 to 15,000 feet later Wednesday through Saturday. Consequently, rainwater weakening and lubricating of near surface snow Tuesday should be rapidly followed by increasing amounts of meltwater percolating into and weakening progressively deeper snowpack layers. Combined with some early winter faceting and weakening of several layers near the ground, this sudden and sustained warming of the Northwest snowpack should result in a significant spring avalanche cycle, with some slides possibly involving all of this past winter’s snowcover.
An increasing moderate to considerable avalanche danger from rain on Tuesday should precede a considerable to locally high danger expected to develop in many areas mid-late Wednesday through Saturday. As a result, back country travelers from climbers to snowmobilers, skiers to snowboarders, hikers to snowshoers, should all exercise increasing caution in avalanche terrain Tuesday and Wednesday, with travel in steeper avalanche terrain not recommended Thursday through Saturday, especially on slopes not experiencing recent avalanche activity. Travelers should be especially cautious on slopes with overhanging cornices or below icefalls, which may become very active later this week, and may be the trigger for some of the larger slide releases expected.
This statement will be updated as conditions warrant.
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Backcountry travelers should be aware that elevation and geographic distinctions are approximate and that a transition zone between dangers exists. Remember there are avalanche safe areas in the mountains during all levels of avalanche danger. Contact local authorities in your area of interest for further information.
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
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