215 PM PST THU JAN 24 2008 WEATHER SYNOPSIS FOR THURSDAY AND FRIDAY Only a pinch of snow for over a week, Has allowed sun and settling the snowpack to tweak. But while the hazards diminished its by no means gone. And the week ahead will make slabs live on. Following a period thats been cold and clear, The upper part of our pack still inspires some fear. Weak layers include lots of facets and hoar, Which have set the stage for danger and more. All thats needed are wind and some snow, And avalanches galore will be ready to go. The weekend ahead looks ripe for this mix, So use caution and wisdom while out for your kicks. Sensitive slabs with whomps and cracking, Will indicate instabilitys not lacking Releasing on facets or a buried crust, The future snowpack is not one you should trust. While expected avalanches may initially be small, Its not only big ones that need a 911 call. Route selection is crucial when the dangers get high, For those that dont care, the statistics dont lie. So when you head out the door and into the white, Update all the time the world in your sight. Moving thru terrain changes snowpack and weather, And demands brain use for safe travel together. A moderate but narrow upper trough is passing slowly southward about 150-200 miles off the northern Oregon coast early Thursday afternoon as it heads toward the currently preferred trough position just off the central California coast. Although in most areas all but briefly increased mid and high clouds associated with the weather disturbance should remain offshore as the disturbance slides further to the south and southwest later Thursday afternoon, slightly increased circulation around the trough is expected to lift some of the moisture from the current California low northward mid-late Thursday. This weather situation should produce variable mid and high clouds and some filtered sunshine over most mountain locations in Washington Thursday afternoon, along with relatively low freezing levels and a continuing temperature inversion, especially near the Cascade passes where a moderate but cold east winds exists. However, the slightly moister southerly flow with the low should also spread a little more moisture northward in north-central Oregon and produce a chance of light snow showers later Thursday afternoon and evening in the Mt Hood area. Meanwhile at lower elevations along the east slopes of the southern Washington Cascades Thursday morning, some trapped low level moisture in the southern Columbia River Basin should maintain a chance of flurries or occasional light snow below about 2-3000 feet in areas affected by Columbia Gorge outflow. As the offshore disturbance sinks further southward overnight and early Friday to reinforce the upper low off the central California coast, associated clouds and any flurries in the Mt Hood area should retreat southward with the low with variable mid and high clouds decreasing in the remainder of the region Thursday afternoon and evening. Brief upper ridging and a drier northerly flow should produce a return to mostly fair but cool weather in most areas on Friday, with trapped cold air persisting in most locations along the Cascade east slopes and near the Cascade passes, along with some areas of low clouds or fog. WEATHER FORECAST FOR THURSDAY AND FRIDAY * OLYMPICS- Thursday afternoon: variable high clouds decreasing Thursday night: mostly fair and cold Friday: mostly fair and continued cool Friday night: increasing high clouds * WASHINGTON CASCADES NEAR AND WEST OF THE CREST- Thursday afternoon: variable mid and high clouds decreasing in the north but continued partly to mostly cloudy south Thursday night: variable high clouds decreasing in the north with clearing spreading southward overnight Friday: few high clouds, otherwise mostly fair and slightly warmer higher terrain, especially south Friday night: increasing high clouds north otherwise mostly fair and a little warmer south, especially higher elevations * CASCADE PASSES, INCLUDING STEVENS, SNOQUALMIE AND WHITE PASSES- Thursday afternoon: continued cool with variable mid and high clouds decreasing in the north but continued partly to mostly cloudy south Thursday night: cold with variable high clouds decreasing in the north and clearing spreading southward overnight Friday: few high clouds, otherwise mostly fair and cold Friday night: increasing high clouds north otherwise mostly fair and cold * EAST SLOPES WASHINGTON CASCADES- Thursday afternoon: continued cool with variable mid and high clouds slowly decreasing in the north later Thursday but continued mostly cloudy south Thursday night: cold with variable high clouds decreasing in the north and slow clearing spreading southward overnight; areas of low clouds persisting lower valleys Friday: few high clouds, otherwise mostly fair and cold most areas, with areas of low clouds or fog lower valleys Friday night: increasing high clouds north otherwise mostly fair and cold except for continued areas of low clouds or fog lower valleys * MT HOOD AREA- Thursday afternoon: clouds increasing and lowering with chance light snow showers late Thursday night: mostly cloudy with flurries or light showers early, then decreasing clouds and showers overnight Friday: few high clouds, otherwise mostly fair and slightly warmer higher terrain Friday night: few high clouds north otherwise mostly fair and a little warmer FREEZING LEVELS-CASCADE MTNS Sea level N and C, 1000 ft S Friday afternoon Sea level N and C, 6000 ft S Friday night, except freezing levels remaining at the surface Cascade east slopes and passes through Friday night FREEZING LEVELS-OLYMPIC MTNS Sea level Thursday afternoon through Friday morning 2500 ft Friday afternoon Sea level Friday 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 FRI SAT * HURRICANE RIDGE 0 0 * MT BAKER 0 0 * WASHINGTON PASS 0 0 * STEVENS PASS 0 0 * SNOQUALMIE PASS 0 0 * MISSION RIDGE 0 0 * CRYSTAL MTN 0 0 * PARADISE 0 0 * WHITE PASS 0 0 * MT HOOD 0 LT .10 WINDS IN MILES PER HOUR (MPH) * CASCADE PASS LEVEL WINDS E 10-20 with higher gusts early Thursday afternoon E 5-15 with occasional higher gusts mid-late Thursday afternoon through Friday morning E 5-10 Friday afternoon E 5-15 Friday night, increasing early Saturday * FREE WINDS AT 5000 FT SE 10-20 N, 15-25 C and S and S 15-25 Olympics mid-day E-SE 10-20 Thursday afternoon E 10-15 Thursday night Variable 5-15 Friday morning W 5-15 N, S 5-10 S Friday afternoon SW 5-15 Friday night * FREE WINDS AT 9000 FT SE 10-20 Thursday afternoon E 5-15 Thursday night N 10-20 N, E 5-10 S Friday morning W 15-25 N, SW 10-20 S Friday afternoon W 20-40 N, 15-25 C and SW 10-20 S Friday night, increasing early Saturday EXTENDED WEATHER SYNOPSIS FOR SATURDAY THROUGH MONDAY A moderate to strong upper trough should spread increasing clouds and winds over the region Saturday morning, with light snow developing mid-day as the associated southerly flow ahead of the low pulls moisture northward from the still strong California low. Moderate to strong ridgetop winds should accompany increasing moderate snow mid-late Saturday afternoon and night as the associated front moves over the area. The front should also be accompanied by slow cooling, with any warming early Saturday very slight and limited to the south. Behind the front early Sunday, the upper level trough should slowly move over the area Sunday morning. While this should maintain light to moderate showers and bring further cooling, most of the energy with the trough is expected to sink southward into south-central Oregon. A secondary upper and surface trough should move over the area late Sunday into early Monday for a slight increase in shower activity, heaviest in the south. Brief and very weak upper ridging should move quickly over the area mid-day Monday and bring a decrease in showers. A strong upper and surface disturbance should then approach the area late Monday before heading mainly southeastward toward south-central Oregon just offshore. While the brunt of this disturbance is expected over south-central Oregon and northern California, the disturbance should still spread increasing winds and increasing moderate snow over most areas late Monday night through early-mid Tuesday at continued low freezing levels before the main energy drives southward. Most recent forecast models now indicate that the following upper trough should drive primarily to the south of the area behind the front, it should still produce light to moderate shower activity in most areas Tuesday afternoon and evening, heaviest in the southern Washington Cascades, Mt Hood area and along the Cascade east slopes in return flow around the low. EXTENDED FORECAST FOR SATURDAY THROUGH MONDAY Saturday morning: increasing clouds with light snow developing later morning in the Olympics and mid-day Cascades Saturday afternoon: light to moderate snow increasing late Saturday night: moderate snow Sunday morning: snow decreasing and becoming light to moderate showers Sunday afternoon: light showers Sunday night and Monday morning: light to moderate showers, heaviest south Monday afternoon: light showers decreasing Monday night: increasing snow becoming moderate to occasionally heavy overnight, heaviest in the south and in the Olympics * SNOW LEVELS Sea level to 500 ft N, 3-5000 ft S early Saturday Sea level to 500 ft N, 1-3000 ft S Saturday afternoon and night Sea level N and C, 500-1500 ft S Sunday morning, except snow levels at the surface Cascade passes and east slopes Saturday, rising to near free air levels early Sunday Sea level N and S Sunday afternoon and night Sea level N and S Monday