130 PM PST THU JAN 3 2008 WEATHER SYNOPSIS FOR THURSDAY AND FRIDAY A surface low pressure center is moving north to northeastward and is heading for Vancouver Island Thursday afternoon. This system has rapidly deepened through the day Thursday and is producing very strong crest level southerly winds being recorded at several NWAC weather stations. Heavy precipitation is falling over the Mt Baker area, light to moderate precipitation over the Mt Rainier areas and little or no precipitation over the Cascade passes and Mt Hood area as of Thursday afternoon. The frontal and associated with this system should spread across the area overnight bringing increasing precipitation and continued very strong winds in areas exposed to the southerly direction, such as the volcanoes. Freezing levels have risen through Thursday afternoon in most exposed locations, with the exception of the passes where strong easterly surface winds are maintaining very cool temperatures. This environment that is favorable for storm development is the result of the broad upper level trough of low pressure centered over the eastern north Pacific. This pattern is expected to produce another strong storm Friday with similar results. Under this pattern of predominantly southerly upper level flow, the Cascade passes are receiving less precipitation with greater precipitation over the volcanic peaks. A brief break is expected later Thursday night and early Friday ahead of a strongly developing deep low pressure center. This next system is expected to deepen and approach the area from the west Friday morning. Increasing very strong crest level southerly winds are expected Friday with slightly rising freezing levels and increasing moderate precipitation becoming heavy at times over the volcanic peaks. The upper level trough of low pressure along the coast should maintain very strong and moist southwest flow to maintain periods of moderate precipitation Friday night into early Saturday at significantly lowering freezing levels. WEATHER FORECAST FOR THURSDAY AND FRIDAY * OLYMPICS- Thursday afternoon and evening: Moderate to heavy snow Thursday afternoon and evening, heaviest along the south slopes. Thursday night: Decreasing light rain or snow showers, except moderate along south slopes. Friday morning: Increasing rain or snow becoming moderate late morning, except moderate to heavy south slopes. Friday afternoon and night: Periods of moderate snow and very windy. * WASHINGTON CASCADES NEAR AND WEST OF THE CREST- Thursday afternoon and evening: Light to moderate rain or snow becoming moderate to heavy evening, heaviest volcanoes. Thursday night: Decreasing light rain or snow showers, except light to moderate volcanoes. Friday morning: Increasing rain or snow becoming moderate late morning, except moderate to heavy volcanoes. Friday afternoon and night: Periods of moderate snow and very windy. * CASCADE PASSES, INCLUDING STEVENS, SNOQUALMIE AND WHITE PASSES- Thursday afternoon and evening: Light snow at times becoming light to moderate late evening and early night. Thursday night: Decreasing light snow showers. Friday: Increasing light snow early, becoming light to occasionally moderate late. Friday night: Light to moderate snow. * EAST SLOPES WASHINGTON CASCADES- Thursday afternoon and evening: Snow becoming light to occasionally moderate. Thursday night: Decreasing light snow showers. Friday morning: Increasing snow in the south spreading north and becoming light to moderate late morning and afternoon. Friday night: Periods of light snow and very windy. * MT HOOD AREA- Thursday afternoon and evening: Increasing light rain or snow developing by evening. Thursday night: Moderate to heavy rain or snow early night, decreasing to snow showers late. Friday morning: Increasing rain or snow becoming moderate to heavy late morning. Friday afternoon and night: Periods of moderate to heavy snow and very windy. SNOW LEVELS-CASCADE MTNS 3500 ft N, 4500 ft C and S Thur aft 2500 ft N and C, 3500 ft S Thur night 4000 ft N, 4500 ft C, 4500 ft S Fri morn 2500 ft N, 3000 ft C and S Fri aft 2000 ft N and S Fri night ...except remaining at the surface Cascade passes and east slopes Thursday and Friday, but briefly rising to free air levels near midnight Thursday. SNOW LEVELS-OLYMPIC MTNS 4500 ft Thur aft 3500 ft Thur night 4500 ft Fri morn 3500 ft Fri aft 2000 ft Fri 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 FRI SAT * HURRICANE RIDGE .25 .25-.5 * MT BAKER 1 1 * WASHINGTON PASS .25-.5 .5 * STEVENS PASS .25-.5 .25-.5 * SNOQUALMIE PASS .25-.5 .5 * MISSION RIDGE .25-.5 .25 * CRYSTAL MTN .5 .5-.75 * PARADISE .5-.75 .75 * WHITE PASS .25-.5 .5 * MT HOOD .5 .75-1 WINDS IN MILES PER HOUR (MPH) * CASCADE PASS LEVEL WINDS E 10-20 Thur evening W 5-15 Thur night E 10-20 Fri E 5-15 Fri aft and night * FREE WINDS AT 5000 FT S-SW 40-60 Thur aft and night S 25-35 N, S-SW 30-50 C and S Fri morn S 30-40 N, S-SW 35-55 C, SW 50-70 S Fri aft and night * FREE WINDS AT 9000 FT SW 50-70 Thur aft and night S-SW 40-60 Fri morn SW SW 50-70 Fri aft and night EXTENDED WEATHER SYNOPSIS FOR SATURDAY THROUGH MONDAY An upper level trough of low pressure to expected to be along the coastal region early Saturday. This should shift the flow to more southwesterly and should be very strong. Significant moisture rotating around the trough should maintain periods of moderate to heavy precipitation through Saturday at lowering freezing levels. A gradually rebuilding upper level ridge well offshore Sunday should shift the greatest flow, strongest winds and precipitation to the south. This should allow for light winds and decreasing showers over the Olympics and Washington Cascades with continued moderate winds and precipitation over the Mt Hood area into Sunday night. By Monday weak flow under an upper ridge should allow for clearing with light winds. EXTENDED FORECAST FOR SATURDAY THROUGH MONDAY Saturday: Moderate to heavy snow, except light in the passes and heaviest over the volcanic peaks. Sunday: Light snow showers Olympics and Washington Cascades, light to moderate snow Mt Hood. Monday: Partly cloudy and light winds Olympics and Washington Cascades, light snow showers Mt Hood. * SNOW LEVELS 2-3000 ft N and S Sat sfc-1000 ft N and S Sun and Mon