200 PM PST MON JAN 28 2008 WEATHER SYNOPSIS FOR MONDAY AND TUESDAY A cold upper level trough has quickly moved east of the area Monday afternoon making way for a fast approaching frontal system moving in from the west. Bands of convergent enhanced showers affected from Stevens Pass to Mt Rainier early Monday before dissipating by late morning. Showers have tapered to a more scattered variety by Monday afternoon. A strong Pacific frontal system is spreading high clouds across the Olympics Monday afternoon with precipitation not far behind. Precipitation should begin early Monday night as the front approaches and gradually increase by early Tuesday. The frontal passage is expected sometime about 5 to 7 am Tuesday across the Cascades causing a period of heavy precipitation at slightly rising freezing levels but still remaining very low. Behind the front later Tuesday morning, continued strong westerly flow should maintain moderate precipitation at cooling temperatures through the day Tuesday. A broad upper level trough and moderate westerly flow Tuesday night should maintain periods of moderate precipitation with the heaviest along the west slopes areas and towards the south of the forecast area, such as Mt Hood where the flow should be stronger. WEATHER FORECAST FOR MONDAY AND TUESDAY * OLYMPICS- Monday aft: Cloudy with occasional light snow showers. Monday evening: Increasing light snow. Monday night: Increasing light to moderate snow. Tuesday morning: Moderate to heavy snow. Tuesday late morning through Tuesday night: Light to moderate snow showers. * WASHINGTON CASCADES NEAR AND WEST OF THE CREST- Monday aft: Cloudy with occasional light snow showers. Monday evening: Light snow developing by late evening and gradually increasing. Monday night: Increasing light to moderate snow. Tuesday morning: Moderate to heavy snow changing to showers late morning. Tuesday aft and night: Moderate snow showers. * CASCADE PASSES, INCLUDING STEVENS, SNOQUALMIE AND WHITE PASSES- Monday aft: Cloudy with occasional light snow showers. Monday evening: Light snow developing by late evening and gradually increasing. Monday night: Increasing light to moderate snow. Tuesday morning: Moderate to heavy snow changing to showers late morning. Tuesday aft and night: Moderate snow showers. * EAST SLOPES WASHINGTON CASCADES- Monday afternoon and evening: Cloudy with light snow showers. Monday night: Increasing light to occasionally moderate snow, mainly near the crest. Tuesday morning: Moderate snow early changing to showers late morning. Tuesday aft and night: Light snow showers. * MT HOOD AREA- Monday aft: Cloudy with light snow showers. Monday evening: Light snow developing by late evening and gradually increasing. Monday night: Increasing light to moderate snow. Tuesday morning: Moderate to heavy snow changing to showers late morning. Tuesday aft and night: Moderate snow showers. SNOW LEVELS-CASCADE MTNS Near sea level N, 500 ft C and S Mon aft and night 500 ft N, 1000 ft C and S early Tue 500 ft N and S Tue aft Near sea level Tue night SNOW LEVELS-OLYMPIC MTNS 500 ft Mon aft and night 1500 ft Tue morn 1000 ft Tue aft 500 ft Tue 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 TUE WED * HURRICANE RIDGE .5 .5 * MT BAKER .5 1 * WASHINGTON PASS .25 .5-.75 * STEVENS PASS .5-.75 .75-1 * SNOQUALMIE PASS .5-.75 1 * MISSION RIDGE .25 .25-.5 * CRYSTAL MTN .5-.75 .5-.75 * PARADISE .5-.75 .75-1 * WHITE PASS .5 .75 * MT HOOD .5-.75 1-1.5 WINDS IN MILES PER HOUR (MPH) * CASCADE PASS LEVEL WINDS W 5-15 Mon aft and night E 0-10 late Mon night and early Tue W 15-30 late Tue morn W 10-20 Tue aft W 5-15 Tue night * FREE WINDS AT 5000 FT SW 10-20 N, SW 20-30 S Mon aft SW 20-30 N and C, SW 35-50 S Mon night S-SW 30-40 N, 35-50 C, SW 40-55 S early Tue morn SW 25-40 late Tue morn SW 15-25 N, SW 20-30 C, W 30-40 S Tue aft W-SW 15-25 N and C, W 20-30 S Tue night * FREE WINDS AT 9000 FT W 20-30 Mon aft SW 30-45 Mon night SW 40-60 early Tue morn W-SW 35-50 late Tue morn W 25-35 Tue aft and night EXTENDED WEATHER SYNOPSIS FOR WEDNESDAY THROUGH FRIDAY Cool and moist northwest flow is expected Wednesday along with embedded short wave disturbances. This should maintain snow showers at low snow levels Wednesday. A brief short wave ridge should move over the Pacific Northwest late Wednesday with weak surface high pressure building over the areas. This should cause decreasing light snow showers late Wednesday becoming scattered in nature. Another strong front should move across the area in strong westerly flow early Thursday morning. This strong system should renew heavy snow at low freezing levels and very strong winds early Thursday morning. Moderate to heavy showers in strong flow behind the frontal passage should persist through the day Thursday before tapering Thursday night. Continued moderate westerly flow Friday under a broad upper trough should maintain moderate snow showers at continued low snow levels much of Friday. EXTENDED FORECAST FOR WEDNESDAY THROUGH FRIDAY Wednesday: Periods of light to occasionally moderate snow showers, gradually decreasing late. Thursday: Increasing heavy snow early Thursday. Moderate snow showers Thursday afternoon, slowly decreasing Thursday night. Friday: Periods of light to moderate snow showers. * SNOW LEVELS Near sea level 1000 ft N to S Wed 1-3000 ft N and S Thur 500-1500 ft N and S Fri