130 PM PST MON DEC 3 2007 WEATHER SYNOPSIS FOR MONDAY AND TUESDAY The ridge that was over the Northwest until a couple days ago has been undercut by an extremely strong, moist southwest flow. This is leading to extreme weather conditions in the Olympics and Cascades! The second of 2 weather systems in the southwest flow will move over the Olympics and Cascades on Monday. This weather system has a tropical origin. This will maintain very strong crest level winds and very heavy precipitation at many sites at high snow levels Monday. A gradual erosion of the surface cold air mass east of the crest and near the lower Cascade passes has occurred Monday. Sites at lower elevations east of the crest such as Lake Wenatchee are now apparently experiencing rain. The poorly defined front should cross the Washington Cascades in the late afternoon or early evening. The front may take a little longer to reach the Mt Hood area. Crest level winds and showers should decrease following the front Monday night. A cooler decreasing west southwest flow with less moisture should be seen on Tuesday. This should cause slowly decreasing orographic showers on Tuesday with slowly lowering snow levels. Some convergence is indicated Tuesday evening by the MM5 model in the Glacier Peak area. WEATHER FORECAST FOR SATURDAY AND SUNDAY * OLYMPICS- Monday afternoon: Heavy rain or snow. Monday night: Decreasing light to moderate rain or snow showers. Tuesday morning: Moderate to heavy rain or snow showers heaviest west Olympics with lowering snow levels. Tuesday afternoon and evening: Light to moderate rain or snow showers at further lowering snow levels heaviest west Olympics. * WASHINGTON CASCADES NEAR AND WEST OF THE CREST- Monday afternoon: Heavy rain or snow. Monday night: Decreasing light to moderate rain or snow showers. Tuesday morning: Moderate to heavy rain or snow showers north and moderate rain or snow showers south with lowering snow levels. Tuesday afternoon and evening: Light to moderate rain or snow showers at further lowering snow levels possibly heaviest near Glacier Peak in convergence. * CASCADE PASSES, INCLUDING STEVENS, SNOQUALMIE AND WHITE PASSES- Monday afternoon: Heavy rain or snow. Monday night: Decreasing light to moderate rain or snow showers. Tuesday morning: Moderate to heavy rain or snow showers north passes and moderate rain or snow showers south passes with lowering snow levels. Tuesday afternoon and evening: Light to moderate rain or snow showers at further lowering snow levels. * EAST SLOPES WASHINGTON CASCADES- Monday afternoon: Moderate to heavy rain or snow. Monday night: Decreasing light to moderate rain or snow showers. Tuesday morning: Moderate rain or snow showers heaviest north part with lowering snow levels. Tuesday afternoon and evening: Light rain or snow showers heaviest north to central part at further lowering snow levels. * MT HOOD AREA- Monday afternoon: Moderate to heavy rain or snow. Monday night: Decreasing light to moderate rain or snow showers. Tuesday: Moderate rain or snow showers with lowering snow levels. Tuesday evening: Light to moderate rain or snow showers at further lowering snow levels. SNOW LEVELS-CASCADE MTNS 7000 ft N, 8000 ft C, 10000 ft S Mon midday 7000 ft N, 7500 ft C, 8000 ft S Mon aft 6000 ft N, 6500 ft C, 7000 ft S Mon eve 5500 ft N, 6000 ft C, 6500 ft S Tue morn 3500 ft N, 4000 ft C, 4500 ft S Tue aft 1500 ft N, 2500 ft C, 3000 ft S Wed morn, except near the surface Cascade passes Mon early morning, rising to free air levels Mon midday and afternoon. SNOW LEVELS-OLYMPIC MTNS 8500 ft Mon midday 7000 ft Mon aft 6500 ft Mon eve 5500 ft Tue morn 3000 ft Tue aft 2000 ft Wed morn 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 2-3 1 * MT BAKER 3-4 1.5-2 * WASHINGTON PASS 2-3 1 * STEVENS PASS 3-4 1 * SNOQUALMIE PASS 3-4 1 * MISSION RIDGE 1 .25-.5 * CRYSTAL MTN 3-5 .5 * PARADISE 3 1.5 * WHITE PASS 2 .75 * MT HOOD 2-3 .75 WINDS IN MILES PER HOUR (MPH) * CASCADE PASS LEVEL WINDS E 5-10 Mon morn W 5-10 Mon aft W 10-15 Mon night and Tue morn W 15-20 Tue aft and eve * FREE WINDS AT 5000 FT SW 70-90 Mon morn SW 60-80 Mon aft and eve WSW 40-60 Tue morn WSW 30-50 Tue aft and eve * FREE WINDS AT 9000 FT SW 90-110 Mon morn SW 80-100 Mon aft and eve WSW 60-80 Tue morn WSW 40-60 Tue aft and eve EXTENDED WEATHER SYNOPSIS FOR WEDNESDAY THROUGH FRIDAY Rather benign weather is expected in the extended forecast in contrast to the current conditions. A ridge should begin to build over the northeast Pacific Ocean on Wednesday. This should cause a cooler west northwest flow over the Northwest. Light orographic snow showers should end in the Olympics and Cascades Wednesday morning. The ridge should further build over the northeast Pacific Ocean on Thursday and Friday causing a drier cool north flow to the Northwest. EXTENDED FORECAST FOR WEDNESDAY THROUGH FRIDAY Light orographic snow showers ending Wednesday morning. Partly or mostly cloudy Wednesday afternoon and evening. Partly cloudy Thursday and Friday. * SNOW LEVELS 1-2000 ft N, 2-3000 ft S Wed Near sea level N, 1-3000 ft S Thu and Fri