215 PM PST THU FEB 7 2008 WEATHER SYNOPSIS FOR THURSDAY AND FRIDAY In the wake of a strong frontal passage early Thursday morning, very strong westerly flow is directing moist and somewhat unstable air into the Olympics and Washington Cascades Thursday afternoon. This is producing moderate to heavy orographic snowfall at slightly cooler temperatures that is even spilling over to the east slope areas. The very strong westerly jet stream cranked up the wind speeds early Thursday with several NWAC telemetry stations reporting gusts over 100 mph Thursday. Flow has diminished somewhat by Thursday afternoon but is expected to increases overnight Thursday and early Friday morning. Coupled with abundant low level moisture, this should maintain moderate to heavy precipitation over the west slope areas of the Olympics, Cascades as well as the over the volcanic peaks through mid day Friday. This flow pattern may also allow a convergence zone to form overnight Thursday and early Friday to enhance precipitation over the central Washington Cascades, centered on about Stevens Pass. Warm frontal moisture from the next approaching weather system should cause increasing steady precipitation at rising freezing levels Friday afternoon and night. The snow level should rise above the Snoqualmie Pass level but remain just below Stevens and White Pass Friday night. WEATHER FORECAST FOR THURSDAY AND FRIDAY * OLYMPICS- Thursday aft: Very windy with moderate to heavy snow showers heaviest west slopes. Thursday night: Continued very windy with moderate snow showers heaviest west Olympics. Friday: Light to moderate snow showers early. Friday afternoon and night: Increasing moderate snow becoming moderate to occasionally heavy rain or snow late. * WASHINGTON CASCADES NEAR AND WEST OF THE CREST- * CASCADE PASSES, INCLUDING STEVENS, SNOQUALMIE AND WHITE PASSES- Thursday aft: Windy with moderate to heavy snow showers. Thursday night: Moderate to heavy snow showers. Friday morning: Moderate to heavy snow showers. Friday afternoon: Decreasing light to moderate snow showers. Friday night: Increasing moderate rain or snow. * EAST SLOPES WASHINGTON CASCADES- Thursday aft: Windy with moderate snow showers especially higher elevations. Thursday night: Light to moderate snow showers especially higher elevations. Friday: Light to occasionally moderate snow showers and windy. Friday night: Increasing light to moderate rain or snow. * MT HOOD AREA- Thursday aft: Very windy with heavy snow showers. Thursday night: Moderate snow showers. Friday morning: Light to moderate snow showers. Friday afternoon: Increasing light to moderate snow showers. Friday night: Increasing moderate rain or snow. SNOW LEVELS-CASCADE MTNS 1500 ft N, 2500 ft S Thu aft thru Fri morn 1500 ft N, 2500 ft C, 4000 ft S Fri aft 3500 ft N, 4000 ft C, 5000 ft S late Fri night SNOW LEVELS-OLYMPIC MTNS 2000 ft Thu aft and night 1500 ft Fri morn 3500 ft Fri aft 4000 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 1 .75 * MT BAKER 1.5 1 * WASHINGTON PASS .75-1 .75-1 * STEVENS PASS 1-1.5 1-1.5 * SNOQUALMIE PASS 1.5 1-1.5 * MISSION RIDGE .25-.5 .5 * CRYSTAL MTN .5-.75 .5-.75 * PARADISE 1 1 * WHITE PASS 1 .75 * MT HOOD 1.5 .75-1 WINDS IN MILES PER HOUR (MPH) * CASCADE PASS LEVEL WINDS W 15-25 Thu aft thru Fri morn W 10-20 Fri aft and night * FREE WINDS AT 5000 FT W 30-40 Thu aft and eve W 35-50 Thu night and Fri morn W 25-35 Fri mid day, strongest Mt Hood W 20-30 Fri aft, W 35-45 Mt Hood W-SW 10-20 N, W 20-30 C, W-NW 30-40 S Fri night * FREE WINDS AT 9000 FT W 40-60 Thu aft and night W-NW 40-60 Fri thru Fri night EXTENDED WEATHER SYNOPSIS FOR SATURDAY THROUGH MONDAY Following a warm frontal passage Friday night most areas should see decreasing precipitation during the day Saturday as the warm front lifts northward. However freezing levels should rise Saturday as strong southwest flow brings warmer air over the area. The associated cold front is expected to move across the Pacific Northwest Saturday night causing increasing winds and rain or snow. Orographic snowfall is expected Sunday at lowering freezing levels. Light to moderate snow showers should continue Sunday night and decrease Monday as a ridge of high pressure moves across the area. The next front should bring renewed precipitation at rising freezing levels late Monday night and early Tuesday. EXTENDED FORECAST FOR SATURDAY THROUGH MONDAY Saturday morning: Moderate rain or snow, heaviest north and central Cascades, light rain or snow south part. Saturday afternoon: Decreasing light rain or snow, except moderate north. Saturday night: Increasing moderate to heavy rain or snow. Sunday: Moderate orographic snow showers. Sunday night: Light orographic snow showers. Monday: Cloudy with occasional light snow showers. Monday night: Increasing light to moderate rain or snow late. * SNOW LEVELS 4-5000 ft N, 45-6000 ft S Sat except 1-2000 ft N, 3-4000 ft S Sun and early Mon 3-4000 ft N, 4-6000 ft S late Mon and rising