100 PM PST TUE JAN 1 2008 WEATHER SYNOPSIS FOR TUESDAY AND WEDNESDAY A very strong flow and unstable air mass moved over the Northwest last weekend and this caused more orographic snowfall in the Olympics and Cascades. However the flow rapidly decreased and the air mass stabilized as an upper ridge began to move over the Northwest Monday. This brought clearing weather Monday. A trough should begin to become re-established in the Gulf of Alaska on Tuesday and help cause a front to move closer to the Northwest coast. This should cause south southwest flow aloft and clouds to increase especially over the Olympics and north Cascades on Tuesday. The increasing flow aloft and higher surface pressure east of the crest should bring local increasing strong southeast winds over some mountaintops and ridges on Tuesday, east winds in the passes and gusty east winds west approaches to the passes. Computer models also indicate some fairly high freezing levels in the warm air sector ahead of the front. So some warmer temperatures should be seen at higher elevations Tuesday. But the east winds should maintain cooler temperatures in the lower Cascade passes. The front should reach the Olympics Wednesday early morning and the Cascades Wednesday late morning. This should bring increasing precipitation mainly to the volcanic peaks. Continued higher surface pressure east of the crest should help limit precipitation in the Cascade passes on Wednesday. A short wave ridge, decreasing moisture and continued higher surface pressure east of the crest should reduce light showers on Wednesday night. WEATHER FORECAST FOR TUESDAY AND WEDNESDAY * OLYMPICS- Tuesday: Increasing mid and high clouds. Local increasing strong southeast wind higher elevations. Tuesday night: Increasing light to moderate rain or snow. Wednesday: Moderate to heavy snow. Wednesday night: Decreasing light snow showers most locations. * WASHINGTON CASCADES NEAR AND WEST OF THE CREST- * CASCADE PASSES, INCLUDING STEVENS, SNOQUALMIE AND WHITE PASSES- Tuesday: Increasing high clouds becoming cloudy north and mostly cloudy south. Local increasing strong southeast wind along the crest, increasing east winds passes, and gusty east winds west approaches to the passes. Tuesday night: Cloudy with increasing light rain or snow north Cascades. Wednesday: Increasing snow becoming moderate to heavy volcanic peaks and light to moderate passes. Wednesday night: Decreasing light snow showers most locations. * EAST SLOPES WASHINGTON CASCADES- Tuesday: Increasing high clouds becoming mostly cloudy north and partly cloudy south. Tuesday night: Cloudy with increasing light rain or snow north Cascades. Wednesday: Increasing snow becoming light to moderate most locations. Wednesday night: Decreasing light snow showers higher elevations and partial clearing lower elevations. * MT HOOD AREA- Tuesday: Increasing high clouds becoming partly cloudy. Local increasing strong southeast wind higher elevations by afternoon. Tuesday night: Cloudy with possible continued strong southeast wind higher elevations. Wednesday: Increasing snow becoming light to moderate. Wednesday night: Decreasing light snow showers. FREEZING LEVELS-CASCADE MTNS 3000 ft N, 4000 ft C, 5000 ft S Tue morn 6000 ft N, 7000 ft C, 8000 ft S Tue aft and eve SNOW LEVELS 2000 ft N, 5000 ft C, 7000 ft S Tue night 2000 ft N, 3000 ft C, 4000 ft S Wed morn through eve...except remaining at the surface Cascade passes and east slopes Tuesday and Wednesday. FREEZING LEVELS-OLYMPIC MTNS 7000 ft Tue SNOW LEVELS 4000 ft Tue night 2500 ft Wed morn through 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 WED THU * HURRICANE RIDGE .25-.5 .5 * MT BAKER .25-.5 .75-1 * WASHINGTON PASS LT .25 .25-.5 * STEVENS PASS LT .25 .25-.5 * SNOQUALMIE PASS LT .25 .25-.5 * MISSION RIDGE 0 .25-.5 * CRYSTAL MTN LT .25 .25-.5 * PARADISE LT .25 .75 * WHITE PASS LT .25 .25-.5 * MT HOOD LT .10 .5 WINDS IN MILES PER HOUR (MPH) * CASCADE PASS LEVEL WINDS E 10-20 Tue morn E 15-25 Tue aft E 10-20 Wed morn E 5-15 Wed aft and eve * FREE WINDS AT 5000 FT SE 20-30 Olympics, SE 15-25 Cascades Tue morn SE 30-40 Olympics, SE 20-30 Cascades Tue midday SE 40-50 Olympics, SE 20-30 Cascades Tue aft and eve SW 30-40 Olympics, SW 20-30 Cascades Wed morn SW 15-30 Wed aft and eve * FREE WINDS AT 9000 FT SSW 40-50 Olympics, SSW 20-30 Cascades Tue morn SSW 50-60 Olympics, SSW 30-40 Cascades Tue midday SSW 60-70 Olympics, SSW 40-60 Cascades Tue aft SSW 60-70 Tue eve SW 50-60 Wed morn SW 30-40 Wed aft and eve EXTENDED WEATHER SYNOPSIS FOR THURSDAY THROUGH SATURDAY Another front is indicated to cross the Northwest Thursday afternoon. This should help cause increasing winds and precipitation Thursday. Higher surface pressure east of the crest may help maintain cooler temperatures and limit precipitation in the passes. The main flow from the trough in the Gulf is indicated to shift toward California Friday and Saturday. Another weak front is indicated to cross the Northwest Friday afternoon. This should cause increasing precipitation again Friday. A shortwave moving out of the trough and across the Northwest should enhance showers Saturday. Higher surface pressure east of the crest may continue to help maintain cooler temperatures and limit precipitation in the passes Friday and Saturday. EXTENDED FORECAST FOR THURSDAY THROUGH SATURDAY Thursday: Light snow in the morning becoming light to moderate in the afternoon and evening possibly remaining limited Cascade passes. Friday: Light snow in the morning becoming light to moderate in the afternoon and evening possibly remaining limited Cascade passes. Saturday: Moderate snow showers mainly midday and afternoon possibly remaining limited Cascade passes. . * SNOW LEVELS 25-3500 ft N, 4-6000 ft S Thu 25-3500 ft N and S Fri 2-3000 ft N and S Sat...except mostly near the surface Cascade passes and east slopes Thursday to Saturday.