000 WWUS86 KSEW 112134 SABNW MOUNTAIN WEATHER FORECAST FOR THE OLYMPICS WASHINGTON CASCADES AND MT HOOD AREA NORTHWEST WEATHER AND AVALANCHE CENTER SEATTLE WASHINGTON 130 PM PST WED FEB 11 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 is prepared primarily for federal, state and private snow safety programs in Washington and Northern Oregon. WAZ513-518-519-019-042-501-502-ORZ011-121700- && WEATHER SYNOPSIS FOR WEDNESDAY AND THURSDAY A northwest flow over the northeast Pacific Ocean should maintain a storm track that mostly misses the Northwest the next few days. A series of weak low pressure system should move southeast over the Northwest coastal waters to the Oregon California border area. The first weakening low moved past on Tuesday. A weak front moved out of this low and across the Northwest. This caused some moderate crest level winds and snowfall. NWAC weather stations near and west of the crest received about 3-10 inches of low density snowfall with the most at Paradise and Mt Hood. The first low is moving into the Oregon California border area on Wednesday. However some moisture circulating around the low is over eastern Washington and causing some lower clouds from about Snoqualmie to Mt Hood. But a weak ridge and weak surface high pressure should move over the Northwest most of Wednesday evening and Thursday morning. This should cause light crest level winds, decreasing clouds and a slight rise in freezing levels in the Olympics and Cascades. A second weak low should follow the storm track and move southeast over the Northwest coastal waters Thursday afternoon and night. Flow over the Northwest is indicated to remain weak but the low may spread some moisture mainly to the Mt Hood area and further south Thursday night. && WEATHER FORECAST FOR WEDNESDAY AND THURSDAY *OLYMPICS- Wednesday afternoon: Mostly sunny. Wednesday night: Mostly clear. Thursday morning: Increasing high clouds. Thursday afternoon and night: Mostly cloudy with chance of light snow. *WASHINGTON CASCADES NEAR AND WEST OF THE CREST- *CASCADE PASSES INCLUDING STEVENS, SNOQUALMIE AND WHITE PASSES- Wednesday afternoon: Mostly sunny except some clouds below about 4-5000 feet at Snoqualmie. Wednesday night: Mostly clear except some lower clouds Snoqualmie. Thursday morning: Increasing high clouds. Thursday afternoon and night: Mostly cloudy with chance of light snow mainly south part. *EAST SLOPES WASHINGTON CASCADES- Wednesday afternoon: Mostly sunny except areas low clouds below about 4-5000 feet. Wednesday night: Mostly clear except local low clouds below about 4-5000 feet. Thursday: Increasing high clouds. Thursday night: Mostly cloudy with chance of light snow mainly south part. *MT HOOD AREA- Wednesday afternoon: Partly cloudy. Wednesday night: Mostly clear. Thursday morning: Increasing high clouds. Thursday afternoon and night: Increasing light snow. && SNOW LEVELS-CASCADE MTNS 1000 ft N to S Wed morn FREEZING LEVELS 2500 ft N, 3500 ft S Wed aft Lowering Wed night 1000 ft N to S Thu morn SNOW LEVELS 2000 ft N to S Thu aft Lowering Thu night SNOW LEVEL-OLYMPIC MTNS 1000 ft Wed morn FREEZING LEVELS 3000 ft Wed aft Lowering Wed night 1000 ft Thu morn SNOW LEVELS 2000 ft Thu aft Lowering Thu night Cascade Snow/Freezing Levels refer to the northern Washington Cascades (N) through Mt Hood area (S). Central Washington Cascade snow levels (typically near Snoqualmie Pass) are normally midway between indicated N and S levels. Note that surface snow/freezing levels are common near the passes during easterly pass flow and may result in multiple snow/freezing levels. && 24 HOUR FORECAST OF PRECIPITATION IN INCHES OF WATER EQUIVALENT ENDING AT 4AM THU FRI *HURRICANE RIDGE0 LT .10 *MT BAKER 0 LT .10 *WASHINGTON PASS0 LT .10 *STEVENS PASS 0 LT .10 *SNOQUALMIE PASS0 LT .10 *MISSION RIDGE 0 LT .10 *CRYSTAL MTN 0 LT .10 *PARADISE 0 LT .10 *WHITE PASS 0 LT .10 *MT HOOD LT .10 .25 && WINDS IN MILES PER HOUR (MPH) *CASCADE PASS LEVEL WINDS E 5-10 Wed aft Light variable Wed night to Thu morn E 5-10 Thu aft and eve *FREE WINDS AT 5000 FT E 5-10 Wed aft Light variable Wed night SW 5-10 Thu morn SW 5-15 Thu aft and eve *FREE WINDS AT 9000 FT E-NE 5-10 Wed aft NW 10-15 Wed night W 10-15 Thu morn SW 1015 Thu aft and eve && EXTENDED WEATHER SYNOPSIS FOR FRIDAY THROUGH SUNDAY The second weak low should move into the Oregon California border area on Friday. Higher surface pressure should begin to build over Canada. Weak flow should be seen over the Northwest. This should cause partly or mostly cloudy weather over the Olympics and north Cascades and maintain some light snow showers over the south Cascades and mainly the Mt Hood area. Yet a third weak low is indicated by the US GFS model to follow the storm track southeast over the Northwest coastal waters on Saturday and Sunday. This system is indicated to be a bit further offshore. Weak flow should continue over the Northwest. The surface high pressure over Canada and the offshore low should also cause offshore surface flow. This should limit the threat of light snow to the south Cascades and Mt Hood area Saturday and Sunday. EXTENDED FORECAST FOR FRIDAY THROUGH SUNDAY Friday and Friday night: Partly or mostly cloudy Olympics and north Cascades and light snow showers ending south Cascades. Saturday and Saturday night: Partly cloudy with slight chance of light snow showers. Sunday and Sunday night: Partly or mostly cloudy north and cloudy south with chance of light snow showers mainly south part. *SNOW LEVELS 1-2000 ft N to S Fri to Sun lowest morning hours and highest afternoon hours. 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. Ferber/Northwest Weather and Avalanche Center $$