200 PM PST WED DEC 19 2007 WEATHER SYNOPSIS FOR WEDNESDAY AND THURSDAY A fast moving and strong frontal system moved across the Cascades Wednesday morning bringing heavy precipitation and strong winds to all the mountain stations in the area. The surface and upper level feature are moving across Vancouver Island Wednesday afternoon. Strong and moist flow behind the front should maintain orographic showers along the west slope areas overnight and into early Thursday. The broad upper level trough over the eastern north Pacific that has been spinning these systems across the region is gradually expected to shift inland Thursday. This should usher in very cool air and continued but decreasing showers through midday Thursday. A brief upper ridge should build offshore later Thursday to cause a diminishing cool northwesterly flow across the area. This should allow for further cooling and diminishing showers, mainly near the crest. Weak northwest flow Thursday night should allow for some partial clearing and light winds with freezing levels near sea level. WEATHER FORECAST FOR WEDNESDAY AND THURSDAY * OLYMPICS- Wednesday afternoon and night: Light to moderate snow showers, heaviest west part. Thursday morning: Light to occasionally moderate snow showers early Thursday, gradually decreasing. Thursday afternoon and night: Diminishing light snow showers, becoming partly cloudy overnight. * WASHINGTON CASCADES NEAR AND WEST OF THE CREST-CASCADE PASSES INCLUDING STEVENS, SNOQUALMIE AND WHITE PASSES- Wednesday afternoon and night: Moderate to heavy snow showers, gradually decreasing overnight. Thursday: Light to occasionally moderate snow showers early Thursday, gradually decreasing. Thursday afternoon and night: Diminishing light snow showers, becoming partly cloudy overnight. * EAST SLOPES WASHINGTON CASCADES- Wednesday afternoon and evening: Light to moderate snow showers, mainly near the crest. Wednesday night: Diminishing light snow showers. Thursday: Cool with occasional light snow showers early and partial clearing late. Thursday night: Partly cloudy, light winds and cool. * MT HOOD AREA- Wednesday afternoon: Moderate to occasionally heavy rain or snow showers and very windy. Wednesday night: Light to moderate snow showers. Thursday: Light to occasionally moderate snow showers, gradually decreasing late afternoon. Thursday night: Diminishing light snow showers, becoming partly cloudy overnight. SNOW LEVELS-CASCADE MTNS 2000 ft N, 3000 ft C, 3500 ft S, Wednesday aft 1500 ft N, 2500 ft S Wednesday night 1000 ft N, 1500 ft S Thursday Sea level N, 500 ft S Thursday night SNOW LEVELS-OLYMPIC MTNS 3000 ft Wednesday aft 1500 ft Wednesday night 1000 ft Thursday Sea level Thursday 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 RIDGE .5 .25 * MT BAKER 1.5 .25-.5 * WASHINGTON PASS .75 .25 * STEVENS PASS .75-1 .25-.5 * SNOQUALMIE PASS 1-1.5 .25-.5 * MISSION RIDGE .25-.5 LT .25 * CRYSTAL MTN .75-1 .25 * PARADISE 1 .25-.5 * WHITE PASS .75 .25 * MT HOOD 1-1.5 .5 WINDS IN MILES PER HOUR (MPH) * CASCADE PASS LEVEL WINDS W 10-20 Wed aft W 5-15 Wed night and Thur W 0-10 Thur night * FREE WINDS AT 5000 FT S-SW 30-40 N, W-SW 35-50 S Wed aft W-SW 20-30 N, W 25-40 S Wed night W 15-30 N and C, W 25-35 S Thur morn W-NW 10-20 Thur aft and night * FREE WINDS AT 9000 FT SW 50-70 Wed aft W-SW 35-50 Wed night W 25-40 Thur morn NW 25-35 Thur aft and night EXTENDED WEATHER SYNOPSIS FOR FRIDAY THROUGH SUNDAY A ridge of high pressure is expected to move across the area Friday to allow for a period of light winds cool temperatures and partly cloudy skies. Another frontal system is expected to approach the area Saturday morning spreading increasing cloud and light precipitation over the forecast region during the morning hours. The front should reach the Cascades Saturday afternoon causing increasing winds and moderate to heavy precipitation at relatively low but gradually rising snow levels. Strong and moist westerly flow behind the front Saturday night through early Sunday should maintain orographic snow showers along the west slope areas as well as a likely convergence zone forming to affect the central areas. Another strong system is expected to move into the area Sunday night. This system is currently expected to cause very windy conditions with moderate to heavy precipitation and moderately rising snow levels Sunday night, especially in the Mt Hood area. EXTENDED FORECAST FOR FRIDAY THROUGH SUNDAY Friday: Partly cloudy with a few light snow showers, mainly early. Saturday: Increasing light to moderate rain or snow in the Olympics early. Rain and snow spreading to the Cascades and becoming moderate to heavy Saturday midday. Moderate showers Saturday afternoon and night, heaviest in the central Cascades in convergence. Sunday: Decreasing showers early. Increasing light rain or snow Sunday evening. Rain or snow becoming heavy Sunday night and windy. * SNOW LEVELS Near sea level N, 1-2000 ft S Fri 1500 ft N, 3000 ft C, 3500 ft S Sat 1500 ft N, 3000 ft S Sat night and Sun 3000 ft N, 3500 ft C, 6000 ft S Sun night