130 PM PST WED FEB 13 2008 WEATHER SYNOPSIS FOR WEDNESDAY AND THURSDAY After a brutal period of unrelenting and very stormy weather for most of the early part of February, a brief respite should develop for much of the Northwest Wednesday afternoon through most of Thursday. Following passage of a narrow front and associated moderate upper trough that passed through the area Tuesday afternoon and night, moderate to strong upper ridging building about 500 miles offshore early Wednesday morning brought decreasing showers to most areas mid-late Wednesday morning. Although a moderate onshore flow at the surface has helped to maintain light showers near and west of the Cascade crest through mid-day, light to moderate northerly winds should bring generally decreasing showers and slow clearing to most areas mid-late Wednesday afternoon. As the ridge moves closer to the coast overnight and Thursday morning, mostly fair skies are expected to spread into most areas along with some patchy fog developing overnight in lower valleys. However, some high clouds are expected to spill over the ridge around mid-day, with further mid and high clouds expected in the north Thursday afternoon and night along with variable high clouds in the south as the first of several weak disturbances passes by mainly to the north. This mid and upper level cloudiness should also be accompanied by a significant warming trend, especially in the south where freezing levels should approach 8-9000 ft by early Friday. WEATHER FORECAST FOR WEDNESDAY AND THURSDAY * OLYMPICS- Wednesday afternoon: partly cloudy with showers ending early-mid Wednesday afternoon becoming partly sunny later afternoon Wednesday night and Thursday morning: clouds decreasing becoming mostly fair except for few areas of fog developing lower valleys late night and early morning hours Thursday afternoon: variable mid and high clouds Thursday night: variable mid and high clouds increasing * WASHINGTON CASCADES NEAR AND WEST OF THE CREST- * CASCADE PASSES, INCLUDING STEVENS, SNOQUALMIE AND WHITE PASSES- Wednesday afternoon: mostly cloudy early-mid afternoon with light showers decreasing, becoming partly cloudy with widely scattered flurries further decreasing late afternoon Wednesday night and Thursday morning: clouds decreasing becoming mostly fair except for some patchy fog lower valleys early morning hours Thursday afternoon: considerable sunshine through variable mid and high clouds north and variable high clouds south; much warmer south Thursday night: variable mid and high clouds increasing north; warm with variable high clouds continuing south * EAST SLOPES WASHINGTON CASCADES- Wednesday afternoon: partly to mostly sunny Wednesday night and Thursday morning: mostly fair except for some patchy fog lower valleys Thursday afternoon: variable mid and high clouds north and variable high clouds south; much warmer south Thursday night: variable mid and high clouds increasing north; warm with variable high clouds continuing central and south * MT HOOD AREA- Wednesday afternoon: partly to mostly cloudy with scattered light showers early-mid afternoon becoming partly to mostly sunny late afternoon Wednesday night and Thursday morning: clouds decreasing becoming mostly fair except for some patchy fog lower valleys Thursday afternoon: much warmer with variable high clouds Thursday night: warm with variable high clouds SNOW LEVELS-CASCADE MTNS 1000 ft N, 1500 ft S Wednesday afternoon through Thursday morning 1000 ft N and C, 3000 ft S mid-day Thursday 1000 ft N and C, 3500 ft S Thursday afternoon 1000 ft N, 2000 ft C, 7500 ft S Thursday night, rising further early Friday SNOW LEVELS-OLYMPIC MTNS 2000 ft Wednesday afternoon through Thursday morning 2500 ft Thursday afternoon 7000 ft Thursday night, rising further early Friday 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 0 * MT BAKER LT .25 0 * WASHINGTON PASS LT .10 0 * STEVENS PASS LT .10 0 * SNOQUALMIE PASS LT .25 0 * MISSION RIDGE LT .10 0 * CRYSTAL MTN LT .10 0 * PARADISE LT .25 0 * WHITE PASS LT .25 0 * MT HOOD LT .25 0 WINDS IN MILES PER HOUR (MPH) * CASCADE PASS LEVEL WINDS W 10-15 with higher gusts early Wednesday afternoon W 5-15 later Wednesday afternoon W 0-10 Wednesday night Variable 0-10 Thursday morning W 5-10 Thursday afternoon Variable 0-10 Thursday night * FREE WINDS AT 5000 FT N-NW 15-25 early Wednesday afternoon N 10-20 later Wednesday afternoon and night N-NW 10-20 Thursday morning W-NW 15-25 N, N 5-15 S Thursday afternoon W-NW 15-20 N, 10-15 S Thursday night * FREE WINDS AT 9000 FT N 15-30 Cascades, 20-40 Olympics Wednesday afternoon N 15-25 Cascades, 20-35 Olympics Wednesday night N-NW 15-30 Cascades, 20-40 Olympics Thursday morning N-NW 20-40 Thursday afternoon N-NW 15-30 Thursday night EXTENDED WEATHER SYNOPSIS FOR FRIDAY THROUGH SUNDAY A moderate and split upper trough and surface front moving mostly north of the area across BC should spread increasing clouds and some light rain or snow to north-central Washington Friday morning, with light rain or snow expected from about Snoqualmie Pass northward Friday afternoon and some light showers reaching as far south as Mt Rainier or White Pass later Friday afternoon and evening. However, most amounts should be relatively minor, with heaviest precipitation expected in the northern Washington Cascades. Although the precipitation should be accompanied by gradually and slightly lowering freezing levels, any snowfall received should be confined to elevations above about 4000 feet in the north, 5000 ft in the central and 6- 7000 feet in the southern Washington Cascades, with mainly increased clouds and a chance of widely scattered light showers reaching the Mt Hood area. A briefly cooler northwesterly flow ahead of more strongly building upper ridging offshore should follow the weak trough early Saturday and bring slightly lowered freezing levels and generally decreasing showers Saturday morning. However, as the upper ridge becomes more firmly established just offshore mid-late Saturday, substantial warming should spread over the region along with clearing skies and generally light winds. Freezing levels should reach the highest of the year and highest since last October late Saturday and Sunday as the ridge moves slowly over the area later Saturday night and early Sunday and into eastern Washington by late Sunday. Although mostly sunny skies and light ridgetop winds should accompany the warmth for a glimpse of almost spring like conditions in many areas, an increasing easterly flow across the Cascade passes may provide some cooler conditions there. EXTENDED FORECAST FOR FRIDAY THROUGH SUNDAY Friday morning: increasing clouds spreading southward with light rain or snow developing Olympics and northern Washington Cascades Friday afternoon and night: cooling with light rain or snow north, occasional light rain or snow central and a considerable mid and high clouds with a few showers reaching as far south as Mt Rainier Saturday morning: cool with decreasing clouds and showers Saturday afternoon: partly to mostly sunny and much warmer Saturday night and Sunday: mostly fair and warm with light winds * SNOW LEVELS 1-3000 ft N, 6-8000 ft C, 7-9000 ft S early Friday 2-4000 ft N, 4-6000 ft C, 6-8000 ft S late Friday 2-4000 ft N, 3-5000 ft S early Saturday * FREEZING LEVELS 6-8000 ft N, 10-12,000 ft S late Saturday 8-10,000 ft N, 11-13,000 ft s early Sunday 8-10,000 ft N and S late Sunday