130 PM PST SAT JAN 12 2008 WEATHER SYNOPSIS FOR SATURDAY AND SUNDAY An upper ridge is beginning to amplify over the west US. First a moderate front will move through the ridge and over the Northwest on Saturday. This caused increasing crest levels winds and increasing snow Saturday morning at most sites. The front should crossed the Olympics about sunrise and the Cascades Saturday late morning. Cool offshore surface flow in advance of the front caused snow in the Cascade passes Saturday morning. A rapidly falling snow level should help cause snow following the front at the higher Cascade passes Saturday afternoon but a little rain seems likely at Snoqualmie. A stabilizing air mass and minimal onshore surface flow following the front should limit showers Saturday afternoon and evening. The upper ridge, surface high pressure and dry air mass should continue to build over the west US and Northwest on Sunday. This should cause lighter crest level winds, fair weather and rising freezing levels on Sunday. WEATHER FORECAST FOR SATURDAY AND SUNDAY * OLYMPICS- Saturday afternoon: Light to moderate rain or snow showers. Saturday evening: Light snow showers ending with partial clearing. Sunday: Mostly sunny. Sunday night: Mostly clear with increasing high clouds early Monday. * WASHINGTON CASCADES NEAR AND WEST OF THE CREST- Saturday afternoon: Light to moderate rain or snow showers. Saturday evening: Light snow showers ending with partial clearing. Sunday: Mostly sunny. Sunday night: Mostly clear with increasing high clouds north part early Monday. * CASCADE PASSES, INCLUDING STEVENS, SNOQUALMIE AND WHITE PASSES- Saturday afternoon: Light snow showers except light rain showers Snoqualmie. Saturday evening: Light snow showers ending with partial clearing. Sunday: Mostly sunny. Sunday night: Mostly clear. * EAST SLOPES WASHINGTON CASCADES- Saturday afternoon: Light snow showers mainly higher elevations. Saturday evening: Light snow showers higher elevations ending with partial clearing. Sunday: Mostly sunny. Sunday night: Mostly clear. * MT HOOD AREA- Saturday afternoon: Light to moderate rain or snow showers. Saturday evening: Light snow showers ending with partial clearing. Sunday: Mostly sunny. Sunday night: Mostly clear. SNOW LEVELS-CASCADE MTNS 4000 ft N, 5000 ft S Sat midday except surface Cascade passes and east slopes 3000 ft N, 4000 ft S Sat aft rising to free air levels Cascade passes and east slopes 2000 ft N, 3000 ft S Sat eve FREEZING LEVELS 3000 ft N, 4000 ft S Sun morn 6000 ft N, 8000 ft S Sun aft and eve SNOW LEVELS-OLYMPIC MTNS 4500 ft Sat midday 3500 ft Sat aft 2500 ft Sat eve FREEZING LEVELS 3500 ft Sun morn 7000 ft Sun aft and eve 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 .25-.5 0 * MT BAKER .5-.75 0 * WASHINGTON PASS .25 0 * STEVENS PASS .25 0 * SNOQUALMIE PASS .5 0 * MISSION RIDGE LT .25 0 * CRYSTAL MTN .25-.5 0 * PARADISE .5 0 * WHITE PASS .25 0 * MT HOOD .75 0 WINDS IN MILES PER HOUR (MPH) * CASCADE PASS LEVEL WINDS E 5-10 Sat midday W 5-15 Sat aft and eve W 0-10 Sun morn E 5-15 Sun aft and eve * FREE WINDS AT 5000 FT SW 25-35 Sat midday WSW 20-30 Sat aft WSW 15-20 Sat eve W 10-15 Sun morn SW 10-15 Sun aft SW 20-30 N, SW 10-20 Sun night * FREE WINDS AT 9000 FT SW 35-45 Sat midday W 35-45 Sat aft W 25-35 Sat eve W 20-30 Sun morn W 15-25 Sun aft SW 30-40 N, SW 10-20 S Sun night EXTENDED WEATHER SYNOPSIS FOR MONDAY THROUGH WEDNESDAY The significant pattern change should continue into the extended period. An upper short wave and front is indicated to move over the building ridge and over the Northwest on Monday. This should cause further increasing clouds and increasing precipitation Monday with lowering snow levels. A shift to cool northwest flow aloft but with a rapidly stabilizing air mass should cause some light snow showers Monday evening. The large ridge should continue to build over the US coastal waters with high surface pressure over the Northwest on Tuesday and Wednesday. This should start a period of up to a few days of fair weather. Offshore surface flow should cool the Cascade passes. EXTENDED FORECAST FOR MONDAY THROUGH WEDNESDAY Monday: Increasing clouds and increasing moderate rain or snow north and light rain or snow south. Monday evening: Light snow showers decreasing and ending with partial clearing. Tuesday and Wednesday: Mostly sunny days and mostly clear nights. * SNOW LEVELS 4-6000 ft N, 6-8000 ft S Mon morn except surface Cascade passes and east slopes 1-2000 ft N, 3-5000 ft S Mon aft and eve except free air levels passes FREEZING LEVELS Near sea level N and S Tue Rising to 4-6000 ft N, 6-8000 ft S Wed except remaining near the surface Cascade passes and east slopes