130 PM PST SAT DEC 22 2007 WEATHER SYNOPSIS FOR FRIDAY AND SATURDAY An active pattern over the northeast Pacific Ocean should carry a steady progression of fronts across the Northwest the next several days. This should bring continued significant snow accumulations to the Olympics and Cascades! Increasing southwest flow over the Northwest should carry a front to the Olympics Saturday morning and the Cascades Saturday midday. This should be accompanied by increasing crest level winds, increasing snow, and a rise in snow levels. The snow level change should be most significant in the Cascade passes when the front moves past and causes cool east winds change to warmer west winds. A short period of weak orographic showers and slightly lower snow levels should be seen Saturday afternoon and evening following the front. Weak convergence may enhance these showers near Stevens and Snoqualmie. A brief relative break should be seen Saturday night and Sunday morning while a shortwave ridge and temporary surface high pressure move over the Northwest. Increasing southwest flow should carry another stronger front to the Olympics Sunday midday and the Cascades Sunday afternoon. This should cause another period of stormy weather with increasing crest level winds, increasing moderate to heavy snow, and a larger rise in snow levels. A change to rain should be expected at the lower Cascade passes Sunday afternoon with some freezing rain most likely at Snoqualmie. A better period of moderate to heavy orographic showers and lowering snow levels should be seen Sunday night. Stronger convergence may enhance the showers at Stevens and Snoqualmie. WEATHER FORECAST FOR FRIDAY AND SATURDAY * OLYMPICS- Saturday midday: Moderate to heavy rain or snow. Saturday afternoon and evening: Decreasing light to moderate rain or snow showers. Sunday morning: Light rain or snow early morning becoming moderate late morning. Sunday afternoon: Moderate to heavy rain or snow. Sunday night: Moderate to heavy snow showers. * WASHINGTON CASCADES NEAR AND WEST OF THE CREST- * CASCADE PASSES, INCLUDING STEVENS, SNOQUALMIE AND WHITE PASSES- Saturday midday: Increasing moderate to heavy snow except light to moderate snow in the passes. Saturday afternoon and evening: Decreasing light to moderate snow showers. Sunday morning: Light rain or snow early morning becoming moderate late morning remaining snow in the passes. Sunday afternoon: Moderate to heavy rain or snow with a change to rain in the passes and some freezing rain most likely Snoqualmie. Sunday night: Moderate to heavy rain or snow showers. * EAST SLOPES WASHINGTON CASCADES- Saturday midday: Increasing light to moderate snow. Saturday afternoon and evening: Decreasing light to moderate snow showers mainly near the crest. Sunday morning: Light rain or snow early morning becoming light to moderate late morning. Sunday afternoon: Moderate snow. Sunday night: Moderate snow showers especially near the crest. * MT HOOD AREA- Saturday midday: Increasing moderate rain or snow. Saturday afternoon and evening: Decreasing light to moderate rain or snow showers. Sunday morning: Light rain or snow early morning becoming moderate late morning. Sunday afternoon: Moderate to heavy rain or snow. Sunday night: Moderate to heavy snow showers. SNOW LEVELS-CASCADE MTNS 2000 ft N, 2500 ft C, 4500 ft S Sat aft 1500 ft N, 2000 ft C, 3000 ft S Sat eve 1500 ft N, 2500 ft C, 4000 ft S Sun early morn 2000 ft N, 4000 ft C, 8000 ft S Sun late morn 4000 ft N, 6000 ft C, 8500 ft S Sun aft Lowering Sun eve 1000 ft N, 2000 ft S Mon morn, remaining at the surface Cascade passes and east slopes Sun morn, rising to free air levels Sun aft. SNOW LEVELS-OLYMPIC MTNS 3500 ft Sat aft 2000 ft Sat eve 2500 ft Sun early morn 5000 ft Sun late morn 4000 ft Sun aft Lowering Sun eve 1500 ft Mon morn 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 SUN MON * HURRICANE RIDGE .5 1 * MT BAKER 1.5 1.5 * WASHINGTON PASS .5 1 * STEVENS PASS .5-.75 1-1.5 * SNOQUALMIE PASS .75 1-1.5 * MISSION RIDGE .25 .25-.5 * CRYSTAL MTN .5 .75-1 * PARADISE .75 1.5 * WHITE PASS .5 1 * MT HOOD .75 1.5 WINDS IN MILES PER HOUR (MPH) * CASCADE PASS LEVEL WINDS E 5-10 Sat midday W 10-20 Sat aft W 5-15 Sat eve Light variable Sun morn E 10-15 Sun midday W 10-20 eve * FREE WINDS AT 5000 FT SW 30-50 Sat midday W 20-40 Sat aft W 15-30 Sat night and Sun morn SW 30-50 Sun aft W 20-40 Sun night * FREE WINDS AT 9000 FT SW 40-60 Sat midday W 30-50 Sat aft W 25-40 Sat night and Sun morn SW 40-60 Sun aft W 30-50 Sun night EXTENDED WEATHER SYNOPSIS FOR MONDAY THROUGH WEDNESDAY A short wave in the active pattern should move over the Northwest on Monday morning. This should help maintain orographic snow showers and a possible convergence near Stevens and Snoqualmie. Another relative break should be seen Monday afternoon and evening. Another front is indicated to move over the Northwest on Tuesday afternoon. This should cause increasing crest level winds and increasing moderate to heavy snow. This should be followed by moderate to heavy orographic snow showers Tuesday night and Wednesday morning. Orographic snow showers should decrease and become light by later Wednesday. At this time it looks like the active pattern is going to continue through the end of the month which should make December 2007 a memorable month! EXTENDED FORECAST FOR MONDAY THROUGH WEDNESDAY Monday morning: Light to moderate orographic snow showers. Monday afternoon and evening: Light snow showers mostly ending. Tuesday morning: Increasing light snow. Tuesday afternoon: Moderate to heavy snow. Tuesday night and Wednesday morning: Moderate to heavy orographic snow showers. Wednesday afternoon and evening: Orographic snow showers decreasing and becoming light. * SNOW LEVELS 5-1500 ft N, 1-2000 ft S Mon through Wed