130 PM PST MON MAR 3 2008 WEATHER SYNOPSIS FOR MONDAY AND TUESDAY A broad ridge is over the northeast Pacific Ocean and Northwest Monday. A vigorous front will make its way over the ridge and across the Northwest on Monday. The front should cross the Olympics Monday late morning and the Cascades Monday early afternoon. This will be accompanied by increasing southwest to west crest level flow and increasing precipitation on Monday in the Olympics and Cascades. A period of west crest level flow following the front should carry a cooler slightly unstable air mass across the Northwest on Monday afternoon and evening. This should cause a period of orographic snow at lower snow levels. Convergence effects should enhance snow in the north to central Cascades Monday afternoon and evening. The ridge and a dry air mass should rebuild over the northeast Pacific Ocean on Tuesday with surface high pressure building over the Northwest. This should cause snow showers to end on Tuesday morning. Clearing should be seen in most areas by Tuesday afternoon and evening. WEATHER FORECAST FOR MONDAY AND TUESDAY * OLYMPICS- Monday midday: Increasing moderate to heavy snow heaviest southwest part. Monday afternoon and evening: Moderate to heavy snow showers heaviest west part. Monday night: Snow showers decreasing. Tuesday morning: Light snow showers ending. Tuesday afternoon: Decreasing clouds becoming mostly sunny. Tuesday night: Mostly clear. * WASHINGTON CASCADES NEAR AND WEST OF THE CREST- * CASCADE PASSES, INCLUDING STEVENS, SNOQUALMIE AND WHITE PASSES- Monday midday: Increasing moderate to heavy snow north to central and increasing light to moderate snow passes and south. Monday afternoon and evening: Moderate to heavy snow showers north to central part and light to moderate snow showers south part. Monday night: Snow showers decreasing. Tuesday morning: Light snow showers ending. Tuesday afternoon: Decreasing clouds becoming mostly sunny. Tuesday night: Mostly clear. * EAST SLOPES WASHINGTON CASCADES- Monday midday: Increasing light to moderate snow north to central and increasing light snow south. Monday afternoon and evening: Light to moderate snow showers north to central part and light snow showers south part. Monday night: Snow showers decreasing. Tuesday morning: Light snow showers mainly at higher elevations ending becoming mostly sunny. Tuesday afternoon: Mostly sunny. Tuesday night: Mostly clear. * MT HOOD AREA- Monday midday: Increasing light to moderate snow. Monday afternoon and evening: Light to moderate snow showers. Monday night: Snow showers beginning to decrease. Tuesday morning: Light snow showers ending. Tuesday afternoon: Decreasing clouds becoming mostly sunny. Tuesday night: Mostly clear. SNOW LEVELS-CASCADE MTNS 2000 ft N, 2500 ft C, 5000 ft S Mon morn 2000 ft N, 3000 ft S Mon aft and eve 1000 ft N, 2000 ft Tue morn FREEZING LEVELS 2000 ft N, 3000 ft S Tue aft and eve SNOW LEVELS-OLYMPIC MTNS 2000 ft Mon morn 2500 Mon aft and eve 1500 ft Tue morn FREEZING LEVELS 3000 ft Tue aft and eve 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 TUE WED * HURRICANE RIDGE .5-.75 LT .10 * MT BAKER .75-1 LT .10 * WASHINGTON PASS .5-.75 LT .10 * STEVENS PASS .75 LT .10 * SNOQUALMIE PASS .75-1 LT .25 * MISSION RIDGE LT .25 0 * CRYSTAL MTN .25-.5 LT .10 * PARADISE .5-.75 LT .10 * WHITE PASS .25-.5 LT .10 * MT HOOD .25-.5 LT .10 WINDS IN MILES PER HOUR (MPH) * CASCADE PASS LEVEL WINDS W 5-15 Mon midday W 15-30 Mon aft and eve W 10-20 Tue morn W 5-15 Tue aft and eve * FREE WINDS AT 5000 FT SW 20-30 Mon midday W 30-50 Mon aft and eve W 15-30 Tue morn strongest south part NW 5-15 Tue aft and eve * FREE WINDS AT 9000 FT W 40-50 Mon midday W 40-60 Mon aft and eve NW 25-50 Tue morn strongest south part NW 20-30 Tue aft and eve EXTENDED WEATHER SYNOPSIS FOR WEDNESDAY THROUGH FRIDAY The upper ridge and dry air mass should shift to over the Northwest coastal waters on Wednesday and to over the Northwest on Thursday. A weak front is now indicated to dissipate over the Northwest coastal waters Thursday. This should cause weak crest level winds, fair weather and gradually rising freezing levels in the Olympics and Cascades. An initial weakening front is now indicated to move over the ridge and the Northwest on Friday. This should be accompanied by increasing crest level flow in the Olympics and Cascades and increasing light precipitation later Friday. It seems that computer models have been rather inconsistent regarding the pattern late this week however. EXTENDED FORECAST FOR WEDNESDAY THROUGH FRIDAY Wednesday and Thursday: Mostly sunny days and mostly clear nights. Friday: Increasing clouds with light rain or snow later Friday. * FREEZING LEVELS Wed morn: 2000 ft N, 3000 ft S Wed aft and eve: Rising to about 5000 ft N, 7000 ft S Thu: 6-7000 ft N, 7-8000 ft S possibly near the surface Cascades passes and east slopes night and morning hours SNOW LEVELS Fri: 4-5000 ft N, 5-6000 ft S possibly near the surface Cascades passes and east slopes