245 PM PST WED DEC 12 2007 WEATHER SYNOPSIS FOR WEDNESDAY AND THURSDAY The Pacific Northwest remains under a cool and relatively weak northwesterly flow aloft as a result of the ridge of high pressure centered over the eastern North Pacific. This is maintaining cool and mostly cloudy conditions along with period light showers as weak impulses transit the region. Little change in this pattern is expected until Friday after the upper ridge begins moving eastward. In the mean time another weak weather disturbance should allow for increasing light showers Wednesday evening, mainly in the north part with less affect in the south. The next disturbance is expected to bring slightly greater precipitation to the mountain areas later Thursday and Thursday night. This system should produce periods of light precipitation except possibly moderate at times in the northwest Washington Cascades where the system should be stronger. This disturbance should also maintain low snow levels with briefly enhanced westerly flow at crest levels Thursday afternoon and evening. WEATHER FORECAST FOR WEDNESDAY AND THURSDAY * OLYMPICS- Wednesday afternoon: Mostly cloudy with a chance of light snow showers. Wednesday evening and night: Increasing light snow showers. Thursday: Decreasing snow showers early Thursday. Increasing light to occasionally moderate snow showers Thursday afternoon and evening. Thursday night: Snow showers ending with partial clearing. * WASHINGTON CASCADES NEAR AND WEST OF THE CREST- CASCADE PASSES- INCLUDING STEVENS, SNOQUALMIE AND WHITE PASSES- Wednesday afternoon: Mostly cloudy with a chance of light snow showers. Wednesday evening and night: Increasing light snow showers. Thursday: Decreasing snow showers early Thursday. Increasing light to occasionally moderate snow showers Thursday afternoon and evening. Thursday night: Snow showers ending with partial clearing. * EAST SLOPES WASHINGTON CASCADES- Wednesday afternoon: Partly cloudy. Wednesday evening and night: Increasing light snow showers, mainly nearer the crest and north part. Thursday: Decreasing snow showers early Thursday. Increasing light snow showers Thursday afternoon and evening. Thursday night: Snow showers ending with partial clearing. * MT HOOD AREA- Wednesday afternoon and evening: Partly cloudy. Wednesday night: Chance of a few light snow showers. Thursday: Decreasing snow showers early Thursday. Increasing light snow showers Thursday afternoon and evening. Thursday night: Light snow showers. SNOW LEVELS-CASCADE MTNS 1000 ft N, 1500 ft C, 2000 ft S Wed through Thur 1000 ft N, 2000 ft C, 2500 ft S Thur eve and night SNOW LEVELS-OLYMPIC MTNS 1500 ft Wed and Wed night 2000 ft Thur 2500 ft Thur 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 LT .10 LT .25 * MT BAKER LT .25 .25 * WASHINGTON PASS LT .10 LT .25 * STEVENS PASS LT .10 LT .25 * SNOQUALMIE PASS LT .10 LT .25 * MISSION RIDGE 0 LT .10 * CRYSTAL MTN LT .10 LT .25 * PARADISE LT .10 LT .25 * WHITE PASS LT .10 LT .10 * MT HOOD LT .10 LT .10 WINDS IN MILES PER HOUR (MPH) * CASCADE PASS LEVEL WINDS W 5-10 Wed and Thur E 0-10 Thur night * FREE WINDS AT 5000 FT W-NW 10-20 N, C and S Wed aft and eve W-NW 10-20 N and C, NW 15-30 S Thur morn SW 10-20 N, W 20-30 C, W-NW 15-25 S Thur aft W-NW 10-20 Thur night * FREE WINDS AT 9000 FT NW 25-35 Wed aft through Thur morn W-NW 20-30 Thur aft NW 20-30 Thur night EXTENDED WEATHER SYNOPSIS FOR FRIDAY THROUGH SUNDAY The upper ridge is expected to approach the coast early Friday and gradually shift inland during the day Friday. This should allow for an offshore frontal system to spread increasing southwest flow over the region as well as increasing precipitation later in the day Friday at only slightly rising freezing levels. A frontal passage is expected Friday night and this should cause a period of moderate precipitation and strong crest level winds. Westerly flow behind the front should maintain light to moderate orographic precipitation along the west slope areas Saturday at lowering freezing levels. A brief break in action is expected Saturday night and early Sunday as a short wave ridge of high pressure transits the area. A stronger disturbance is expected to move into the area late Sunday to cause strong winds and moderate to heavy precipitation later Sunday night. EXTENDED FORECAST FOR FRIDAY THROUGH SUNDAY Friday morning: Mostly cloudy with light showers at times mainly in the Olympics and north Cascades. Friday afternoon and night: Light to moderate snow. Saturday morning: Light to moderate snow showers along the west slopes and becoming partly cloudy east slopes. Saturday afternoon and evening: Decreasing showers west slopes and becoming partly cloudy. Sunday: Partly cloudy early. Increasing light snow north part and Olympics by afternoon. Sunday night: Increasing moderate snow Olympics and west slope areas with light snow east slopes. * SNOW LEVELS 500 to 1000 ft N, 15-3000 ft S early Friday 2-3000 ft N and C, 3-4500 ft S late Friday 15-2500 ft N and C, 2-3000 ft S Saturday thru Sunday