130 PM PST SUN JAN 20 2008 WEATHER SYNOPSIS FOR SUNDAY AND MONDAY A trough of low pressure is continuing to exit the forecast area towards the south Sunday afternoon. Light snow showers are diminishing over most NWAC stations Monday afternoon with the exception of Hurricane Ridge, where increasing northeast winds are creating upslope snow showers along the northern Olympics. These showers should end over the next few hours as clearing drier air moves into the region from the north. The showers should end in the south early Sunday night as the disturbance moves away. This trough is expected to extend westward off the northern California coast by Monday morning and form a new upper low pressure center that should continue southward along the California coast. Meanwhile upper ridging and strong surface high pressure should build inland across B.C. This should cause strong northeast flow over the Pacific Northwest from Sunday night through Monday, ushering in some very cold and dry air. Skies should clear overnight Sunday and early Monday with strong easterly flow developing across the Cascades and through the passes. Easterly flow should diminish Monday night with continued clear and clod weather. WEATHER FORECAST FOR SUNDAY AND MONDAY * OLYMPICS- Sunday afternoon and evening: Light snow showers ending Sunday evening. Sunday night: Partly cloudy early becoming mostly fair and cold late with strong east winds developing. Monday: Sunny and cold with strong east winds. Monday night: Mostly fair. * WASHINGTON CASCADES NEAR AND WEST OF THE CREST- CASCADE PASSES INCLUDING STEVENS, SNOQUALMIE, WHITE PASSES- Sunday afternoon and evening: Partial clearing in the north. Continued occasional light snow showers central and south, ending by evening with partial clearing. Sunday night: Partly cloudy early becoming mostly fair and cold late with strong east winds developing. Monday: Sunny and cold with strong east winds. Monday night: Mostly fair. * EAST SLOPES WASHINGTON CASCADES- Sunday afternoon and evening: Showers ending in the north with partial clearing. Continued occasional light snow showers central and south, ending by evening with partial clearing from the north. Sunday night: Partly cloudy early becoming mostly fair and cold late with strong east winds developing. Monday: Sunny and cold with strong east winds. Monday night: Mostly fair. * MT HOOD AREA- Sunday afternoon and evening: Light snow showers, ending by evening with partial clearing. Sunday night: Partly cloudy early becoming mostly fair and cold late with strong east winds developing. Monday: Sunny and cold with strong east winds. Monday night: Mostly fair. SNOW LEVELS-CASCADE MTNS Near sea level N, 1000 ft S Sun aft Near sea level N and S Sun night through Mon night SNOW LEVELS-OLYMPIC MTNS 1000 ft Sun aft Near sea level Sun night through Mon 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 MON TUE * HURRICANE RIDGE LT .25 0 * MT BAKER LT .10 * WASHINGTON PASS LT .10 0 * STEVENS PASS LT .10 0 * SNOQUALMIE PASS LT .10 0 * MISSION RIDGE LT .25 0 * CRYSTAL MTN LT .10 0 * PARADISE LT .10 0 * WHITE PASS LT .10 0 * MT HOOD LT .25 0 WINDS IN MILES PER HOUR (MPH) * CASCADE PASS LEVEL WINDS E 5-15 Sun aft and eve E 15-25 with higher gusts Sun night and Mon morn E 10-20 with higher gusts Mon aft and night * FREE WINDS AT 5000 FT E-NE 15-30 Sun aft and eve E 25-35 Sun night, strongest S E 20-30 N and C, E 35-50 S Mon morn E 10-20 N and C, E 35-50 S Mon aft and eve E 5-15 N and C, E-SE 20-35 S Mon night * FREE WINDS AT 9000 FT E-NE 15-25 Sun aft and eve E 30-40 Sun night and early Mon E 35-50 Mon mid-morn and aft E-NE 15-30 N, 30-40 S Mon night EXTENDED WEATHER SYNOPSIS FOR TUESDAY THROUGH THURSDAY The strong upper ridge over the northeast Pacific should be dominant Tuesday through Wednesday. This should maintain dry cool northerly flow aloft through Wednesday producing mostly fair skies. Easterly crest level winds should weaken on Tuesday and Wednesday. A short wave disturbance is expected to move southward along the B.C. coast Thursday. This should spread increasing high clouds over the region Thursday with light snow showers at low snow levels developing Thursday night. EXTENDED FORECAST FOR TUESDAY THROUGH THURSDAY Tuesday and Wednesday: Mostly sunny days and mostly clear nights. Thursday: Increasing high clouds. Thursday night: Light snow developing in the north and spreading southward. * FREEZING LEVELS Near sea level N and S Tue 1-2000 ft Olympics, near sea level Cascades Wed * SNOW LEVELS Near sea level-1000 ft N and S Thursday