200 PM PST WED JAN 2 2008 WEATHER SYNOPSIS FOR WEDNESDAY AND THURSDAY A series of deep upper level low pressure systems are expected to develop well offshore and spawn frontal systems to pass across the Pacific Northwest over the next several days. This should continue to keep the active weather pattern that persisted through late December going as we move into 2008. A frontal band extends from the north Cascades through northwest Oregon Wednesday afternoon. This band is producing continued but generally light precipitation over most NWAC sites near or west of the crest Wednesday afternoon. This frontal system is expected to continue moving east overnight to allow for a brief break between disturbances through early Thursday. Another developing upper level low and associated surface low is expected to develop well offshore of Oregon Thursday and begin moving north to northeastward. This should increase the south to southwest flow across the Pacific Northwest Thursday with very strong winds developing and increasing precipitation at rising freezing levels. The heaviest precipitation should begin over the Mt Hood area Thursday morning and shift northward through Thursday afternoon and night. Continued easterly pass flow should maintain locally lower freezing levels with snow levels remaining at the surface. The strong southerly crest levels flow Thursday should also maintain the heaviest precipitation over the volcanic peaks while limiting the precipitation amounts along the crest. WEATHER FORECAST FOR WEDNESDAY AND THURSDAY * OLYMPICS- Wednesday afternoon and evening: Light to moderate rain or snow showers, gradually decreasing. Wednesday night: Decreasing light snow showers. Thursday: Increasing light rain or snow Thursday morning becoming moderate to heavy afternoon and evening, heaviest along the south slopes. Thursday night: Light to moderate rain or snow showers, heaviest south slopes. * WASHINGTON CASCADES NEAR AND WEST OF THE CREST- * CASCADE PASSES, INCLUDING STEVENS, SNOQUALMIE AND WHITE PASSES- Wednesday afternoon and evening: Mostly light to occasionally moderate rain or snow showers. Wednesday night: Decreasing light snow showers most locations. Thursday: Increasing light rain or snow Thursday morning in the south gradually shifting northward late morning and afternoon and increasing. Rain or snow becoming moderate in the passes and heavy over the volcanic peaks late afternoon and evening. Thursday night: Light to moderate snow passes and moderate to heavy rain or snow volcanic peaks. Rain or snow gradually decreasing late Thursday night. * EAST SLOPES WASHINGTON CASCADES- Wednesday afternoon and night: Decreasing light snow showers higher elevations and partial clearing lower elevations. Thursday: Cloudy with snow developing in the south early and spreading to the north by afternoon and gradually increasing. Light to moderate snow showers late. Thursday night: Decreasing light snow showers with partial clearing. * MT HOOD AREA- Wednesday afternoon and evening: Increasing light to moderate rain or snow. Wednesday night: Decreasing light rain or snow showers. Thursday: Moderate to heavy rain or snow early decreasing midday. Increasing rain or snow Thursday afternoon and evening becoming moderate to heavy. Thursday night: Decreasing light rain or snow showers. SNOW LEVELS-CASCADE MTNS 2500 ft N, 3500 ft C and S Wed aft and night 2000 ft N, 4500 ft C, 5000 ft S Thur 3000 ft N, 3500 ft C, 4000 ft S Thur night ...except remaining at the surface Cascade passes and east slopes Wednesday and Thursday. SNOW LEVELS-OLYMPIC MTNS 3000 ft Wed aft and night 4000 ft Thur morn 3500 ft Thur aft and 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 THU FRI * HURRICANE RIDGE .5 .5 * MT BAKER .75 1 * WASHINGTON PASS .25-.5 .5 * STEVENS PASS .25-.5 .25-.5 * SNOQUALMIE PASS .5-.75 .25-.5 * MISSION RIDGE LT .25 .25-.5 * CRYSTAL MTN .5 .5 * PARADISE .5-.75 .5 * WHITE PASS .25-.5 .25-.5 * MT HOOD .75 .75-1 WINDS IN MILES PER HOUR (MPH) * CASCADE PASS LEVEL WINDS E 5-15 Wed aft and eve E 10-20 Thur E 5-15 Thur night * FREE WINDS AT 5000 FT S-SW 1-20 N, SW 15-30 C, SW 25-35 S Wed aft and eve S-SW 10-20 N and C, S-SW 25-35 S Wed night S-SE 25-35 N, S-SW 30-50 CC and S Thur morn S-SW 40-60 Thur aft and night * FREE WINDS AT 9000 FT SW 30-40 Wed aft and eve SW 25-35 Wed night and early Thur SW 40-60 Thur late morn and aft SW 50-70 Thur night EXTENDED WEATHER SYNOPSIS FOR FRIDAY THROUGH SUNDAY Another deep upper level and surface low pressure system should develop well offshore of the Pacific Northwest Friday. This should renew the strong south flow across the region and maintain moderate precipitation at times. The main heavier precipitation associated with the system Friday should move inland to the south of the forecast area towards northern California. Freezing levels should lower Friday as the low pressure spreads inland. Another developing wave and associated frontal band should move across the area Saturday morning. This should cause increasing precipitation at further lowering freezing levels and a period of very strong winds early Saturday. Gradually decreasing showers are expected later Saturday in the wake of the frontal passage. A cool showery pattern is expected Sunday with a return to very low freezing levels and decreasing winds. EXTENDED FORECAST FOR FRIDAY THROUGH SUNDAY Friday: Light snow in the morning becoming light to moderate in the afternoon and evening. Precipitation limited in the passes and heaviest over the volcanic peaks. Saturday: Moderate to heavy snow, except light in the passes and heaviest over the volcanic peaks. Sunday light to moderate snow showers. * SNOW LEVELS 25-3500 ft N, 3-4000 ft S Fri 2-3000 ft N and S Sat 1-2000 ft N and S Sun...except at the surface Cascade passes and east slopes Friday to early Saturday.