BACKCOUNTRY AVALANCHE FORECAST FOR THE OLYMPICS WASHINGTON CASCADES AND MT HOOD AREA NORTHWEST WEATHER AND AVALANCHE CENTER SEATTLE WASHINGTON 130 PM PST TUE FEB 10 2009 NWAC Program administered by: USDA-Forest Service with cooperative funding and support from: Washington State Department of Transportation National Weather Service National Park Service Washington State Parks and Recreation Commission Pacific Northwest Ski Area Association Friends of the Avalanche Center and other private organizations. This forecast applies to back country avalanche terrain below 7000 feet and does not apply to highways or operating ski areas. WAZ513-518-519-019-042-501-502-ORZ011-111700- && ZONE AVALANCHE FORECASTS * OLYMPICS- * WASHINGTON CASCADES NEAR AND WEST OF THE CREST- * STEVENS SNOQUALMIE WHITE PASSES- Tuesday morning: Low avalanche danger below 7000 feet. Tuesday afternoon through Wednesday: Moderate avalanche danger above 4000 feet and low below. * EAST SLOPES WASHINGTON CASCADES- * MT HOOD AREA- Tuesday morning: Low avalanche danger below 7000 feet. Tuesday afternoon through Wednesday: Moderate avalanche danger above 5000 feet and low below. SNOWPACK ANALYSIS Alternating periods of light snow and cool or mild temperatures have been seen so far in February. This should have caused slight stabilizing in most areas. The last significant snow was the 6-12 inches of snowfall that was reported about 28 January at sites near and west of the crest. An exception is the 9 inches of snow reported from the Mt Baker area the past 3 days. Winds and snow transport in that area may have created some new shallow slab layers on lee slopes. This should be mainly on north to southeast facing slopes at higher elevations. I have not seen a report of any avalanches for several days. A general upper snow structure on north slopes might be varied crusts, near surface facets, or recent snow, over layers from the storm in late January, over firm or hard snow from the mid January inversion or early January rain episode. Some isolated buried facets are reported adjacent to crusts in the upper snowpack or on the firm or hard snow from early or mid January. But the facets layers do not seem to be widespread and seem dormant at this time. Snow on other aspects in the upper snow pack should be more homogeneous due to recent occasional mild weather and lack of snowfall. Corn snow conditions have been reported at times recently on south aspects. A shallow snowpack is reported at moderate or lower elevations east of the crest. Local near surface or faceting on the early to mid January crust might be more possible but no recent avalanches seem to have been reported in that area as well. DETAILED FORECASTS TUESDAY AND TUESDAY NIGHT Increasing crest level winds and increasing snow is expected by Tuesday afternoon. Crest level winds should become south to southeast and pass winds should become east by Tuesday afternoon. Snowfall intensities should remain light in the north to central Cascades but become light to moderate in the Olympics and south Cascades. This should lead to a slight avalanche danger increase mainly in the Olympics and south Cascades. This should be mainly on lee northwest to north east slopes at higher elevations where new shallow soft or wind slab layers would be most likely to form. Back country travelers should use caution near steep avalanche terrain by Tuesday afternoon. WEDNESDAY AND WEDNESDAY NIGHT Crest level winds should decrease and light snow showers should end Wednesday morning with cool temperatures. The cool temperatures would allow new shallow wind or soft slab layers to linger on lee slopes. This should continue to be mainly lee northwest to north east slopes at higher elevations. Back country travelers should continue to use caution near steep terrain on Wednesday. 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. Also note that field snowpack information is often available on the FOAC website at www.avalanchenw.org, and weather and avalanche glossaries for commonly used terms in the forecasts can be found on the NWAC education page. Ferber/Northwest Weather and Avalanche Center $$