130 PM PST TUE DEC 4 2007 WEATHER SYNOPSIS FOR TUESDAY AND WEDNESDAY An upper level trough of low pressure is gradually rotating across the Pacific Northwest Tuesday afternoon and should exit the region by later Wednesday. This feature is maintaining light to moderate showers mainly along the west slope areas at slowly lowering freezing levels and with gradually diminishing westerly flow. The flow and precipitation are expected to continue to slowly decrease through Tuesday night along with further gradual cooling. This should allow for decreasing precipitation Tuesday evening and night. As the upper trough rotates through the area early Wednesday the strongest flow and precipitation remain towards the north Washington Cascades with gradually diminished precipitation southward towards Mt Hood. Light showers and further cooling are expected Wednesday afternoon before ending overnight as high pressure continues to build offshore. A strong upper level ridge of high pressure is expected to develop and dominate the eastern north Pacific Wednesday night into the extended period. This should produce a cool northerly flow with clearing and light winds developing late Wednesday into the extended period. WEATHER FORECAST FOR TUESDAY AND WEDNESDAY * OLYMPICS- Tuesday afternoon and night: Light to moderate rain or snow showers at further lowering snow levels heaviest west Olympics. Wednesday morning: Light to occasionally moderate rain or snow showers with a decreasing trend. Wednesday afternoon and night: Occasional light snow showers ending late with gradual clearing and cool. * WASHINGTON CASCADES NEAR AND WEST OF THE CREST- Tuesday afternoon and night: Light to moderate rain or snow showers at further lowering snow levels heaviest north Cascades. Wednesday morning: Light rain or snow showers with a decreasing trend, except light to moderate showers north Cascades. Wednesday afternoon and night: Occasional light snow showers ending late with gradual clearing and cool. * CASCADE PASSES, INCLUDING STEVENS, SNOQUALMIE AND WHITE PASSES- Tuesday afternoon and night: Light to moderate rain or snow showers at further lowering snow levels. Wednesday morning: Light rain or snow showers with a decreasing trend, except light to moderate showers north Cascade passes. Wednesday afternoon and night: Occasional light snow showers ending late with gradual clearing and cool. * EAST SLOPES WASHINGTON CASCADES- Tuesday afternoon and night: Further decreasing light rain or snow showers heaviest north to central part at further lowering snow levels. Wednesday morning: Occasional light rain or snow showers. Wednesday afternoon and night: Occasional light snow showers ending late with gradual clearing and cool. * MT HOOD AREA- Tuesday night: Decreasing light to moderate rain or snow showers at further lowering snow levels. Wednesday morning: Light to briefly moderate rain or snow showers. Wednesday afternoon and night: Occasional light snow showers ending late with gradual clearing and cool. SNOW LEVELS-CASCADE MTNS 5000 ft N, 5500 ft C, 6500 ft S Tue aft 3500 ft N and C, 4500 ft S Tue night 2500 ft N and C, 3000 ft S Wed morn 2000 ft N and C, 2500 ft S Wed aft 1000 ft N and C, 1500 ft S Wed night SNOW LEVELS-OLYMPIC MTNS 5000 ft Tue aft 3500 ft Tue night 3000 ft Wed morn 1500 ft Wed aft 1000 ft Wed 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 WED THU * HURRICANE RIDGE .5-.75 LT .25 * MT BAKER 1.5-2 .25-.5 * WASHINGTON PASS .75-1 .25 * STEVENS PASS 1 .25 * SNOQUALMIE PASS .75-1 .25 * MISSION RIDGE .25 LT .25 * CRYSTAL MTN .5-.75 LT .25 * PARADISE .75 .25 * WHITE PASS .5-.75 LT .25 * MT HOOD .75 .25 WINDS IN MILES PER HOUR (MPH) * CASCADE PASS LEVEL WINDS W 10-20 Tue aft with higher gusts W 5-15 Tue night and Wed W 0-10 Wed night * FREE WINDS AT 5000 FT WSW 30-40 Tue aft and eve WSW 20-30 Tue night and early Wed W 10-20 Wed aft WNW 5-15 Wed night * FREE WINDS AT 9000 FT WSW 35-50 Tue aft and eve W 25-40 Tue night and early Wed NW 15-25 Wed aft N-NW 5-15 Wed night EXTENDED WEATHER SYNOPSIS FOR THURSDAY THROUGH SATURDAY A strong upper level ridge of high pressure should dominate the eastern north Pacific Thursday through Saturday. Thos should produce cool and dry northerly flow over the region with generally clear skies. The ridge is expected to extend inland over B.C. Friday and Saturday causing cold and dry northeast flow aloft over the Pacific Northwest. Winds through the extended period should remain relatively light with freezing levels lowering through the period to near sea level. EXTENDED FORECAST FOR THURSDAY THROUGH SATURDAY Mostly fair and dry with light winds Thursday through Saturday. * FREEZING LEVELS Near sea level1000 ft N, 1-2000 ft S Thu Near sea level500 ft N and S Fri and Sat