200 PM PST TUE FEB 12 2008 WEATHER SYNOPSIS FOR TUESDAY AND WEDNESDAY A weakening cold front is moving into the Olympics and north Washington Cascades Tuesday afternoon. A ridge of high pressure provided a nice morning over the Cascades Tuesday with sunshine and mild temperatures. The front should usher in some light to moderate precipitation along with lowering freezing levels behind the front. The front is looking rather unimpressive on satellite imagery however. Other than some good cooling with and behind the front, not a great deal of water is expected out of it. It looks more like a garden variety front as opposed to what we have experienced of late. The front should transit the Cascades by late Tuesday evening followed by some moderate west to northwest flow through Tuesday night. This should maintain a period of light to moderate orographic precipitation along the west slopes through early Wednesday. The flow also looks conducive to developing a convergence zone Tuesday evening through early Wednesday. With the flow becoming more northwesterly at crest level the convergence affects may initiate over Stevens Pass but have more prolonged affect over Snoqualmie Pass. A rebuilding ridge offshore Wednesday should cause a further shift to northwest then northerly flow later Wednesday allowing for further cooling and gradual drying. Under the building ridge offshore, showers diminish rapidly over most areas by later Wednesday morning. The convergence zone may linger longer into Wednesday midday. Weakening north to northwest flow should allow for further clearing Wednesday night, light winds and remaining cool. WEATHER FORECAST FOR TUESDAY AND WEDNESDAY * OLYMPICS- Tuesday early afternoon: Increasing moderate rain or snow. Tuesday night: Light to moderate snow showers, gradually diminishing. Wednesday morning: Decreasing light snow showers. Wednesday afternoon and night: Becoming partly cloudy. * WASHINGTON CASCADES NEAR AND WEST OF THE CREST- * CASCADE PASSES, INCLUDING STEVENS, SNOQUALMIE AND WHITE PASSES- Tuesday afternoon: Increasing light to moderate rain or snow in the north and light rain or snow developing in the south. Tuesday evening and night: Light to moderate snow showers, heaviest Stevens to Snoqualmie Passes. Wednesday morning: Decreasing light snow showers, except possibly light to moderate Snoqualmie Pass in convergence. Wednesday afternoon and night: Showers ending and becoming partly cloudy. * EAST SLOPES WASHINGTON CASCADES- Tuesday afternoon: Increasing clouds with light rain or snow north to central. Tuesday night: Light snow showers mainly higher elevations, ending late. Wednesday: A few light showers higher terrain Wednesday morning otherwise becoming partly cloudy. Wednesday night: Becoming mostly fair. * MT HOOD AREA- Tuesday afternoon : Increasing clouds. Tuesday evening: Increasing light to moderate rain or snow. Tuesday night: Light snow showers. Wednesday morning: Snow showers ending becoming partly cloudy. Wednesday afternoon and night: Partly cloudy. SNOW LEVELS-CASCADE MTNS 3500 ft N, 5000 ft C, 6500 ft S Tue aft 2500 ft N, 3000 ft C, 4000 ft S Tue night 1000 ft N, 1500 ft S Wed morn through Wed night SNOW LEVELS-OLYMPIC MTNS 5000 ft Tue aft 2500 ft Tue night 1500 ft Wed morn through Wed 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 WED THU * HURRICANE RIDGE .25-.5 LT .10 * MT BAKER .5 LT .25 * WASHINGTON PASS .25-.5 LT .10 * STEVENS PASS .5 LT .25 * SNOQUALMIE PASS .5-.75 LT. 25 * MISSION RIDGE LT .25 LT .10 * CRYSTAL MTN .25-.5 LT .25 * PARADISE .25-.5 LT. 25 * WHITE PASS .25 LT .25 * MT HOOD .25-.5 LT .25 WINDS IN MILES PER HOUR (MPH) * CASCADE PASS LEVEL WINDS W 10-20 Tue aft through Wednesday aft W 5-10 Wednesday night * FREE WINDS AT 5000 FT S-SW 20-30 N SW 20-30 C, W 15-25 S Tue midday W 20-30 Tue aft W-NW 15-30 Tue night and Wed morn N-NW 10-20 Wed aft N 5-15 Wed night * FREE WINDS AT 9000 FT SW 30-40, W-SW 25-35 C, W 20-30 S Tue late morn and midday W 30-45 Tue aft and eve NW 20-35 Tue night, strongest Mt Hood NW 20-30 Wed morn N-NW 15-25 Wed aft N 10-20 Wed night EXTENDED WEATHER SYNOPSIS FOR THURSDAY THROUGH SATURDAY A ridge of high pressure in the upper atmosphere should dominate the flow pattern in the eastern north Pacific off the Washington and northern Oregon coast through much of the extended period. Weak flow Thursday under the ridge should allow for only high clouds and light winds. The ridge extends inland gradually late Thursday and early Friday to allow for warmer air and rising freezing levels but only some mid level and high clouds. The ridge flattens slightly later Friday to allow for slightly greater westerly flow however the main storm track is expected to remain north of the forecast area. Only increasing higher clouds are expected later Thursday and Friday. The ridge gains strength offshore Saturday to allow for clearing and rising freezing levels later Saturday. The dry period appears to be with us into early next week as well. EXTENDED FORECAST FOR THURSDAY THROUGH SATURDAY Thursday: Partly or mostly cloudy especially near and west of the crest with mainly high clouds. Friday: Mostly cloudy north Cascades and Olympics, partly cloudy south Cascades. Saturday: Becoming partly cloudy * SNOW LEVELS FREEZING LEVEL 1-3000 ft N, 2-4000 ft S early Thur 2-4000 ft N, 6-8000 ft S late Thur 4-6000 ft N, 8-10,000 ft S Fri 3-5000 ft N, 8-10,000 ft S early Sat 5-7000 ft N, 8-10,000 ft S late Sat