215 PM PST WED JAN 9 2008 WEATHER SYNOPSIS FOR WEDNESDAY AND THURSDAY Moist westerly flow Wednesday maintained orographic showers over most west slope areas early Wednesday before diminishing late morning and early afternoon at most sites. The break should be brief Wednesday afternoon and evening as yet another front in this active pattern rapidly approaches the Pacific Northwest. This next disturbance is racing eastward with the high cloud shield already nearing the coast by early Wednesday morning. Winds should back to southerly and increase early Wednesday night with precipitation beginning in the Olympics early Wednesday night. Precipitation should spread to the Cascades and increase late Wednesday night and early Thursday morning. Freezing levels are expected to rise with this strong system overnight and early Thursday. Easterly flow should develop across the Cascade passes Wednesday night and shift again to westerly with the frontal passage, expected early Thursday morning. Following the frontal passage, strong westerly flow should maintain heavy orographic precipitation along the west slopes areas through the day Thursday with little change in freezing levels expected behind the front. Another wave associated with the upper level trough should renew or maintain the moderate to heavy precipitation Thursday night into early Friday. WEATHER FORECAST FOR WEDNESDAY AND THURSDAY * OLYMPICS- Wednesday evening and night: Light rain or snow evening, increasing overnight becoming moderate. Thursday: Further increasing rain or snow Thursday morning becoming moderate to heavy. Rain or snow changing to showers later Thursday morning. Moderate rain or snow showers Thursday afternoon slightly decreasing Thursday evening. Thursday night: Increasing rain or snow showers becoming moderate to heavy, heaviest over the west part. * WASHINGTON CASCADES NEAR AND WEST OF THE CREST- * CASCADE PASSES, INCLUDING STEVENS, SNOQUALMIE AND WHITE PASSES- Wednesday afternoon and evening: Cloudy with showers ending. Wednesday night: Light rain or snow developing Wednesday night, increasing overnight becoming moderate. Thursday: Further increasing rain or snow Thursday morning becoming moderate to heavy. Rain or snow changing to showers later Thursday morning. Moderate to heavy rain or snow showers Thursday afternoon and evening. Thursday night: Moderate to heavy rain or snow showers, heaviest in the central part in likely convergence zone. * EAST SLOPES WASHINGTON CASCADES- Wednesday night: Increasing clouds with light snow developing late night. Thursday: Moderate rain or snow morning, changing to showers late morning. Thursday afternoon: Light to moderate rain or snow showers, mainly nearer the crest. Thursday night: Light to moderate rain or snow showers. * MT HOOD AREA- Wednesday afternoon and evening: Cloudy with scattered showers. Wednesday night: Light rain or snow developing Wednesday night, increasing overnight becoming moderate. Thursday: Further increasing rain or snow Thursday morning becoming moderate to heavy. Rain or snow changing to showers later Thursday morning. Moderate to heavy rain or snow showers Thursday afternoon and evening. Thursday night: Moderate to heavy rain or snow showers. SNOW LEVELS-CASCADE MTNS 1000 ft N, 2000 ft S Wed aft and evening 1500 ft N, 2500 ft C, 3000 ft S Wed night 1500 ft N, 3000 ft C, 4000 ft S early Thurs morn 3000 ft N, 3500 ft C, 4000 ft S later Thur morn thru Thur night SNOW LEVELS-OLYMPIC MTNS 1500 ft Wed aft 3000 ft Wed night 3500 ft Thur morn thru Thur 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 .25-.5 .5-.75 * MT BAKER .75 1-1.5 * WASHINGTON PASS .25 .5-.75 * STEVENS PASS .25-.5 .75 * SNOQUALMIE PASS .5 1 * MISSION RIDGE LT .25 .25 * CRYSTAL MTN .25-.5 .75 * PARADISE .5 1 * WHITE PASS .25-.5 .75 * MT HOOD .5 1-1.5 WINDS IN MILES PER HOUR (MPH) * CASCADE PASS LEVEL WINDS W 0-10 Wed aft E 5-15 Wed night and early Thur morn W 10-20 later Thur morn W 5-15 Wed aft and night * FREE WINDS AT 5000 FT S-SW 5-15 N and C, SW 10-20 S Wed aft and eve S-SW 30-40 Wed night W-SW 35-50 Thur morn W 25-35 N and C, W-SW 30-50 S Thur aft SW 20-30 N, W-SW 25-35 C and S Thur night * FREE WINDS AT 9000 FT W-NW 15-25 Wed mid morn and aft SW 30-45 Wed night W-SW 40-60 Thur morn W 30-50 later Thur morn thru Thur night EXTENDED WEATHER SYNOPSIS FOR FRIDAY THROUGH SUNDAY The strong westerly jet stream in the eastern north Pacific should maintain strong showers behind a frontal passage expected to pass the Cascade crest Thursday morning. The showers should continue in the moderate to heavy category through early Friday. The flow and moisture should decrease later Friday to allow for a brief break. A brief ridge of high pressure should maintain light winds and partly mostly cloudy conditions later Friday through early Saturday. Another weaker frontal passage is expected Saturday morning. This should renew a period of moderate precipitation at rising freezing levels. A ridge of high pressure should build more strongly over the area later Saturday through Sunday to allow for lighter winds and mainly high clouds. EXTENDED FORECAST FOR FRIDAY THROUGH SUNDAY Friday morning: Moderate to heavy rain or snow showers and gradually decreasing. Friday afternoon and evening: Partly to mostly cloudy. Saturday: Light to moderate rain or snow early Saturday, changing to showers late morning. Decreasing showers with partial clearing Saturday afternoon. Sunday: Partly cloudy. Increasing clouds late with rain or snow developing Olympics Sunday night. * SNOW LEVELS 25-3500 ft N, 3-4000 ft S Friday 35-4500 ft N, 5-6000 ft S early Saturday 25-3500 ft N, 45-5500 ft S later Saturday 3-4000 ft N, 7-9000 ft S early Sunday 5-7000 ft N, 7-9000 ft S late Sunday