West Slopes South - South of I-90 to Columbia River
NWAC avalanche forecasts apply to backcountry avalanche terrain in the Olympics, Washington Cascades and Mt Hood area. These forecasts do not apply to developed ski areas, avalanche terrain affecting highways and higher terrain on the volcanic peaks above the Cascade crest level.
A ridge of high pressure predominated for most of the time period from October 23 - November 1. Warmer temperatures melted or consolidated much of the snow that accumulated during a mid-October storm cycle.
A pronounced trough across the Pacific Northwest is bringing a series of cold low-pressure systems across our region. Cold flow from interior northern Canada passes around Vancouver Island, where it picks up Pacific moisture. The first low which is currently spinning off the coast of Washington today is slowly cutting off moisture as it moves south. This initial system brought 17" to Mt. Baker, just shy of a foot at Hurricane Ridge, Mt. Rainier and Mt. Hood and 3-6" for the Cascade Passes and Crystal Mountain. Higher elevations near the Cascade Passes received significantly more (such as the top of Alpental received 14" according to the Alpental website). This storm has brought cold, interior air into the lowlands through the Frasier River Gap in British Columbia.
Moderate snow showers will be tapering to light snow showers tonight in most locations, with up to a quarter inch of additional precipitation expected in favored locations in the South Cascades west of the Crest. Hood will receive an additional .25-.5" of snow water. Mostly cloudy conditions will persist Saturday with light westerly winds allowing for isolated and light snow showers throughout the day. Southerly winds will increase ahead of a second low-pressure system which will head into Washington State Saturday night, spreading a second shot of moderate to heavy snow Saturday night and Sunday to the Central and South Cascades and Hood with lighter snow reaching Hurricane Ridge and the North Cascades.
Snow levels will remain below 2000 ft in the Washington Cascades throughout the weekend and will be in the 3000-4000 foot range on Mt Hood.
Drier weather will arrive Sunday night and continue into early next week. The cold airmass will begin to moderate Monday afternoon with much warmer air arriving Tuesday and driving a strong temperature gradient across the Cascades. Expect strong easterly flow through the passes at this time. The next storm system is not anticipated to arrive until later in the week.
Given the recent heavy snowfall in parts of our forecast zones, expect the potential for avalanches at higher elevations as conditions for storm slab and loose dry avalanches (primarily) will be present this weekend where anchoring is insufficient.
Please see Forest's blog post regarding early-season avalanches.
As the winter season rapidly approaches, the Northwest Avalanche Center is preparing once again to provide daily mountain weather and avalanche forecasts for the Olympics and Cascades. Preparations include outreach events, office maintenance, standard training, administrative tasks, weather station installation and repair, and preliminary forecasting for program cooperators such as the National Park Service, Washington State DOT and Pacific Northwest Ski Area Association.
At this time we will continue to monitor snow and avalanche conditions and we will begin issuing regular mountain weather and avalanche forecasts when sufficient snow has accumulated at moderate and lower elevations to create potential avalanche danger. The NWAC will issue information regarding this schedule as soon as it is available.