MOUNTAIN WEATHER FORECAST FOR THE OLYMPICS WASHINGTON CASCADES AND MT HOOD AREA NORTHWEST WEATHER AND AVALANCHE CENTER SEATTLE WASHINGTON 200 PM PST MON FEB 9 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-ORZ011-101700- && WEATHER SYNOPSIS FOR MONDAY AND TUESDAY An approaching upper trough is moving onshore Monday afternoon causing increasing showers across southwest Washington and northwest Oregon. Showers associated with this trough passage should increase over the southern Washington Cascades and Mt Hood area through this evening with weaker snow showers increasing in the north as well. The established strong northwest jet stream in the eastern north Pacific should maintain a storm track that mostly misses the Pacific Northwest, taking developing low pressure systems towards California through the forecast period. Showers should end overnight through early Tuesday between passing systems. The next low pressure system upstream is expected to take a similar track towards California later Tuesday. However, some moisture associated with this storm is expected to provide another round of generally light precipitation at low freezing levels Tuesday afternoon and night. The Mt Hood area and southern volcanoes should get the most precipitation out of this passing system with less in the Cascade passes due to southerly flow as the moisture passes. High pressure should rebuild over the region by early Wednesday causing showers to end. && WEATHER FORECAST FOR MONDAY AND TUESDAY * OLYMPICS- Monday afternoon: Light snow showers. Monday night: Light snow showers ending with partial clearing. Tuesday morning: Light snow developing. Tuesday afternoon and evening: Light to occasionally moderate snow. Tuesday night: Snow changing to light snow showers. * WASHINGTON CASCADES NEAR AND WEST OF THE CREST- * CASCADE PASSES INCLUDING STEVENS, SNOQUALMIE AND WHITE PASSES- Monday afternoon and evening: Light snow showers increasing, especially in the south. Monday night: Light snow showers ending. Tuesday morning: Increasing mid and high clouds. Tuesday afternoon: Light snow developing. Tuesday night: Light to occasionally moderate snow, heaviest volcanoes. Snow changing to light snow showers late. * EAST SLOPES WASHINGTON CASCADES- Monday afternoon: Light snow showers. Monday night. Light snow showers ending with clearing. Tuesday: Increasing mid and high clouds. Tuesday afternoon and evening: Occasional light snow. Tuesday night: Light snow possibly moderate at times south part. Snow changing to snow showers late. * MT HOOD AREA- Monday afternoon and night: Increasing light to briefly moderate snow showers. Tuesday morning: Cloudy with light snow beginning late morning. Tuesday afternoon and night: Increasing snow becoming light to moderate. && SNOW LEVELS-CASCADE MTNS near sea level N, 1000 ft S Monday afternoon near sea level N and S Monday night and Tuesday morning 500 ft N, 1000 ft S Tuesday afternoon near sea level N and S Tuesday night SNOW LEVEL-OLYMPIC MTNS 1000 ft Monday afternoon Near sea level Monday night and Tuesday morning 1000 ft Tuesday afternoon Near sea level Tuesday 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 TUE WED * HURRICANE RIDGE LT .10 LT. 25 * MT BAKER LT .25 LT .25 * WASHINGTON PASS LT .25 LT .25 * STEVENS PASS LT .25 LT .25 * SNOQUALMIE PASS LT .25 LT .25 * MISSION RIDGE LT .10 LT .25 * CRYSTAL MTN LT .25 LT .25 * PARADISE LT .25 .25 * WHITE PASS LT .25 LT .25 * MT HOOD LT .25 .25-.5 && WINDS IN MILES PER HOUR (MPH) * CASCADE PASS LEVEL WINDS W 5-15 Monday midday and afternoon W 5-15 Monday night through early Tuesday morning E 0-10 late Tuesday morning E 5-15 Tuesday afternoon and night * FREE WINDS AT 5000 FT W-NW 10-20 Monday afternoon and night W-SW 10-20 Tuesday morning S-SW 15-25 Tuesday afternoon S-SW 10-20 Tuesday night * FREE WINDS AT 9000 FT W-NW 15-25 Monday afternoon and night W 15-25 Tuesday SW 20-30 N and C, SW 30-40 S Tuesday afternoon SW 10-20 N and C, W-SW 20-30 Tuesday night && EXTENDED WEATHER SYNOPSIS FOR WEDNESDAY THROUGH FRIDAY Showers should end by Wednesday morning as upper level high pressure rebuilds over the area. Weak flow and high pressure should dominate later Wednesday and through Friday. This should maintain light winds and partly cloudy conditions and remaining cool. The main storm track should continue to cause developing storms offshore to head southeast well offshore and move inland across central and southern California through the extended period. EXTENDED FORECAST FOR WEDNESDAY THROUGH FRIDAY Wednesday morning: Light snow showers ending. Wednesday afternoon and night: Becoming partly cloudy. Thursday and Friday: Mostly sunny days and fair nights. * SNOW LEVELS 1-2000 ft N and S Wednesday morning * FREEZING LEVELS 1-3000 ft N and S Wednesday afternoon through Friday 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. Kramer/Northwest Weather and Avalanche Center $$