200 PM PST TUE MAR 4 2008 WEATHER SYNOPSIS FOR TUESDAY AND WEDNESDAY High pressure is rebuilding offshore Tuesday afternoon producing a shift to north and northeasterly flow over the mountain areas of the Pacific Northwest. This is allowing for gradual clearing Tuesday afternoon following the strong westerly flow overnight that has now diminished and with it any residual showers that ended Tuesday morning. The ridge should gradually shift towards the coast later Tuesday causing further slow drying with showers ending by late morning over most mountain areas. As the flow becomes increasingly northerly late Tuesday clouds should decrease with some partial clearing during the afternoon hours. The strengthening upper ridge should near the coast during the day Wednesday as it moves eastward. This should allow for mostly sunny conditions Wednesday. Freezing levels should begin rather low Wednesday but by late Wednesday warm air under the ridge should cause significant warming by afternoon. The ridge should keep weather fair and mild with light winds Wednesday night. WEATHER FORECAST FOR TUESDAY AND WEDNESDAY * OLYMPICS- Tuesday afternoon: Decreasing clouds becoming mostly sunny. Tuesday night: Mostly clear. Wednesday: Mostly sunny with warming and light winds. Wednesday night: Fair and mild. * WASHINGTON CASCADES NEAR AND WEST OF THE CREST- * CASCADE PASSES, INCLUDING STEVENS, SNOQUALMIE AND WHITE PASSES- Tuesday afternoon: Decreasing clouds becoming partly to mostly sunny. Tuesday night: Mostly clear. Wednesday: Mostly sunny with warming and light winds. Wednesday night: Fair and mild. * EAST SLOPES WASHINGTON CASCADES- Tuesday afternoon: Decreasing clouds becoming mostly sunny. Tuesday night: Mostly clear. Wednesday: Mostly sunny with warming and light winds. Wednesday night: Fair and mild. * MT HOOD AREA- Tuesday afternoon: Decreasing clouds becoming partly to mostly sunny. Tuesday night: Mostly clear. Wednesday: Mostly sunny with warming and light winds. Wednesday night: Fair and mild. FREEZING LEVELS-CASCADE MTNS 2000 ft N, 3000 ft S Tuesday aft and night 2500 ft N and S Wednesday morn 6000 ft N, 8000 ft S Wednesday aft 8000 ft N, 8500 ft S Wednesday night FREEZING LEVELS-OLYMPIC MTNS 3000 ft Tuesday aft and night 4000 ft Wednesday morn 7000 ft Wednesday aft 8500 ft Wednesday 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 0 0 * MT BAKER 0 0 * WASHINGTON PASS 0 0 * STEVENS PASS 0 0 * SNOQUALMIE PASS LT .10 0 * MISSION RIDGE 0 0 * CRYSTAL MTN 0 0 * PARADISE LT .25 0 * WHITE PASS LT .10 0 * MT HOOD LT .25 0 WINDS IN MILES PER HOUR (MPH) * CASCADE PASS LEVEL WINDS W 5-15 Tue aft and eve E 0-10 Tue night E 5-15 Wed and Wed night * FREE WINDS AT 5000 FT N-NW 5-15 Tue aft and eve NE 5-15 Tue night E-NE 5-15 Wed and Wed night * FREE WINDS AT 9000 FT N-NW 15-25 Tue aft and eve NE 10-20 Tue night N-NE 5-15 Wed and Wed night EXTENDED WEATHER SYNOPSIS FOR THURSDAY THROUGH SATURDAY A strong upper level ridge of high pressure should be centered over western Washington and Oregon Thursday morning and gradually move east of the Cascades by late Thursday. This should maintain fair skies and high freezing levels Thursday with light winds. A weak trough should move through the area Friday to cause increasing southwest flow and increasing clouds. However, little or no precipitation is expected early Friday, just increasing high and mid level clouds. A deeper trough of low pressure and associated frontal system is expected to move across the area Friday night or early Saturday morning. This should cause further increasing south to southwest crest level winds, lowering freezing levels and increasing precipitation overnight Friday. Strong west flow at crest level is expected behind the frontal passage during the morning Saturday. This should maintain orographic precipitation along the west slope areas with a possible convergence zone affect the central Cascade pass areas. Showers should gradually decrease late Saturday as flow decreases and becomes more northwesterly. EXTENDED FORECAST FOR THURSDAY THROUGH SATURDAY Thursday: Mostly sunny during the day with mostly clear skies overnight. Friday: Increasing clouds with light rain or snow developing late Friday or Friday evening. Friday night and early Saturday: Moderate to occasionally heavy rain or snow changing to showers early Saturday. Saturday: Moderate snow showers early, decreasing to light snow showers afternoon. Saturday night: Showers ending with clearing. * FREEZING LEVELS Thur: 7-9000 ft N, 8-10,000 ft S Fri morn: 4-5000 ft N, 6-7000 ft S * SNOW LEVELS Fri aft and night: 3-4000 ft N and S Sat: 1-2000 ft N, 15-2500 ft S