200 PM PST WED FEB 27 2008 WEATHER SYNOPSIS FOR WEDNESDAY AND THURSDAY A weak upper level trough moving across the region Wednesday coupled with a weak frontal band combined to cause a brief period of generally light precipitation earlier Wednesday that mainly affected the Stevens to Snoqualmie Pass areas. Precipitation has ended over most NWAC stations Wednesday afternoon as the feature continues eastward. Considerable low level moisture remains however and with weak onshore flow there could be a few more light showers through Wednesday night. Any shower activity should be light and mainly confined to the central Cascade passes. Little if any precipitation expected to reach the Mt Hood area. Freezing levels should lower modestly through Wednesday night. A few showers may linger early Thursday morning before clearing once again returns to the mountain areas of the northwest as upper level high pressure rebuilds offshore. A high pressure ridge should gain strength offshore Thursday causing clearing in northwest flow aloft, decreasing winds and gradually rising freezing levels through Thursday night. WEATHER FORECAST FOR WEDNESDAY AND THURSDAY OLYMPICS- Wednesday afternoon and eve: Decreasing light rain or snow showers. Wednesday night: Rain or snow showers ending with partial clearing. Thursday morning: Partly cloudy. Thursday afternoon: Mostly sunny with variable high clouds. Thursday night: Mostly fair with high clouds. * WASHINGTON CASCADES NEAR AND WEST OF THE CREST- * CASCADE PASSES, INCLUDING STEVENS, SNOQUALMIE AND WHITE PASSES- Wednesday afternoon and eve: Occasional light rain or snow showers. Wednesday night: Scattered light rain or snow showers. Thursday morning: Mostly cloudy with showers ending. Thursday afternoon: Mostly sunny with variable high clouds. Thursday night: Mostly fair with high clouds. * EAST SLOPES WASHINGTON CASCADES- Wednesday afternoon and eve: Partly cloudy with a chance of light rain or snow showers, mainly higher elevations nearer the crest. Wednesday night: Scattered light rain or snow showers higher elevations. Thursday morning: Partly cloudy with showers ending. Thursday afternoon: Mostly sunny with variable high clouds. Thursday night: Mostly fair with high clouds. * MT HOOD AREA- Wednesday afternoon and eve: Partly cloudy with a slight chance of light rain or snow showers. Wednesday night: Mostly cloudy. Thursday morning: Partly cloudy. Thursday afternoon: Mostly sunny with variable high clouds. Thursday night: Mostly fair with high clouds. SNOW LEVELS-CASCADE MTNS 4500 ft N, 5000 ft C, 6000 ft S Wed aft and eve 4000 ft N, 4500 ft C, 8000 ft S Wed night FREEZING LEVELS-CASCADE MTNS 4500 ft N, 6000 ft C, 9500 ft S early Thur 6500 ft N, 8000 ft C, 10,000 ft S late Thur SNOW LEVELS-OLYMPIC MTNS 5000 ft Wed aft and night FREEZING LEVELS-OLYMPIC MTNS 6500 ft Thur morn 7500 ft Thur aft and 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 LT .10 0 * MT BAKER LT .10 0 * WASHINGTON PASS LT .10 0 * STEVENS PASS LT .10 0 * SNOQUALMIE PASS LT .10 0 * MISSION RIDGE LT .10 0 * CRYSTAL MTN LT .10 0 * PARADISE LT .10 0 * WHITE PASS 0 0 * MT HOOD 0 0 WINDS IN MILES PER HOUR (MPH) * CASCADE PASS LEVEL WINDS W 5-15 Wed aft to Thur morn W 0-10 Thur midday Var 0-10 Thur aft E 0-10 Thur night * FREE WINDS AT 5000 FT W 10-20 Wed aft and eve W-NW 5-15 Thur W-SW 5-15 Thur aft and eve S-SW 5-15 Thur night * FREE WINDS AT 9000 FT W 25-35 N, W-NW 15-25 S Wed aft and eve NW 20-30 N, NW 10-20 S Wed night and Thur morn W-SW 10-20 Thur aft W-SW 15-25 Thur night EXTENDED WEATHER SYNOPSIS FOR FRIDAY THROUGH SUNDAY The upper level ridge should move east of the area during the morning Friday. This should allow an approaching frontal system offshore to spread increasing clouds over the area early Friday with strengthening winds. A strong frontal passage is expected midday Friday over the Olympics and Friday afternoon across the Cascades and Friday evening over the Mt Hood area. This front should bring moderate to heavy precipitation at lowering snow levels and strong winds beginning in the Olympics and north Washington Cascades midday Friday and shifting southward during the afternoon. An upper trough passage is expected Saturday morning accompanied by strong and moist westerly flow. This should maintain strong orographic precipitation along the west slope areas. A secondary wave and associated band of moisture should renew the moderate to heavy precipitation during the day Saturday. Very strong westerly flow and abundant moisture Saturday night into early Sunday should maintain the precipitation, especially along the west slopes with precipitation being mostly blocked and shadowed along the east slopes. A rebuilding ridge should allow for drying and partial clearing later Sunday through Sunday night along with diminishing winds. EXTENDED FORECAST FOR FRIDAY THROUGH SUNDAY Friday morning: Increasing clouds with light rain or snow developing Olympics and north Washington Cascades. Friday afternoon and night: Increasing moderate to heavy rain or snow especially near and west of the crest with lowering snow levels. Saturday through Saturday night: Renewed moderate to heavy snow mainly near and west of the crest with further lowering snow levels. Sunday morning: Decreasing light to moderate snow showers. Sunday afternoon and night: Becoming partly cloudy or mostly fair. * SNOW LEVELS Friday morn: 5000 ft N, 6500 ft S Friday afternoon: 4500 ft N, 5500 ft S and lowering Friday night: 2500 ft N and S Saturday and Sunday: 1-2000 ft N and S