200 PM PST MON DEC 31 2007 WEATHER SYNOPSIS FOR MONDAY AND TUESDAY A very strong west to northwest flow through Sunday over the Northwest, with a jet stream of 170 knots and unstable air mass, caused more orographic snowfall. New snow amounts range from about 6-18 inches on Monday morning. However the flow rapidly decreased and the air mass stabilized Monday morning. This caused light snow showers to end with clearing Monday morning. A little break from all the recent snowfall should be seen Monday afternoon and Tuesday. An upper ridge should move from over the Northwest coastal waters Monday afternoon to over the Cascades Tuesday morning. This should cause a rise in freezing levels. Some fairly strong southeast Cascade crest level winds may be seen Tuesday. Building surface pressure east of the crest should also help bring east winds and cooler temperatures to the passes, and some possible windy conditions to the lower Cascade west slopes. Moisture from an approaching front should bring increasing high clouds to the Olympics and Cascades later Tuesday. Some light precipitation should be expected in the Olympics Tuesday night. WEATHER FORECAST FOR MONDAY AND TUESDAY * OLYMPICS- Monday afternoon: Mostly sunny. Monday night: Mostly clear. Tuesday: Partly cloudy with increasing strong southeast winds over ridges. Tuesday night: Light rain or snow developing. * WASHINGTON CASCADES NEAR AND WEST OF THE CREST- * CASCADE PASSES, INCLUDING STEVENS, SNOQUALMIE AND WHITE PASSES- Monday afternoon: Mostly sunny. Monday night: Mostly clear. Tuesday: Partly cloudy north and partly sunny south with increasing southeast winds along the crest and east winds passes. Tuesday night: Mostly cloudy north and partly cloudy south with southeast winds along the crest and east winds passes. * EAST SLOPES WASHINGTON CASCADES- Monday afternoon: Mostly sunny. Monday night: Mostly clear. Tuesday: Partly cloudy north and partly sunny south. Tuesday night: Mostly cloudy north and partly cloudy south. * MT HOOD AREA- Monday afternoon: Mostly sunny. Monday night: Mostly clear. Tuesday: Partly sunny with increasing southeast winds higher elevations and east winds near the gorge. Tuesday night: Partly cloudy with southeast winds higher elevations and east winds near the gorge. SNOW LEVELS-CASCADE MTNS Near sea level Mon morn FREEZING LEVEL 1000 ft N, 1500 ft C, 4000 ft Mon aft and eve 3000 ft N, 6000 ft C, 7000 ft S Tue morn 6000 ft N, 7000 ft C, 8000 ft S Tue aft and eve except remaining at the surface Cascade passes and east slopes Tuesday. SNOW LEVELS-OLYMPIC MTNS Near seal level Mon morn FREEZING LEVEL 2000 ft Mon aft and eve 7000 ft Tue morn 6000 ft Tue aft and eve 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 TUE WED * HURRICANE RIDGE LT .10 LT .10 * MT BAKER LT .10 0 * WASHINGTON PASS LT .10 0 * STEVENS PASS LT .10 0 * SNOQUALMIE PASS LT .10 0 * MISSION RIDGE 0 0 * CRYSTAL MTN LT .10 0 * PARADISE LT .10 0 * WHITE PASS LT .10 0 * MT HOOD LT .10 0 WINDS IN MILES PER HOUR (MPH) * CASCADE PASS LEVEL WINDS W 10-20 Mon morn Light variable Mon midday E 5-10 Mon aft and eve E 15-25 Tue and Tue eve * FREE WINDS AT 5000 FT NW 10-20 Mon morn Light variable Mon midday SE 5-15 Mon aft and eve SE 20-30 Olympics, SE 15-25 Cascades Tue morn SE 40-50 Olympics, SE 20-30 Cascades Tue aft and eve * FREE WINDS AT 9000 FT NW 20-30 Mon morn NW 10-20 Mon midday W 5-15 Mon aft and eve SW 30-40 Olympics, SW 25-35 Cascades Tue morn SW 50-60 Olympics, SW 40-50 Cascades Tue aft and eve EXTENDED WEATHER SYNOPSIS FOR WEDNESDAY THROUGH FRIDAY An upper trough should become re-established in the Gulf of Alaska starting Wednesday. A series of low pressure systems should move through the Gulf with fronts beginning to cross the Northwest each day or so. The first weakening front should cross the Olympics Wednesday morning and the Cascades Wednesday midday. This should cause increasing precipitation mainly in the Olympics and on the volcanic peaks with limited precipitation in the Cascade passes. The main flow is currently indicated to be over Oregon and California on Thursday and Friday, with limited onshore surface flow. Therefore weak or moderate fronts should be expected on Thursday and Friday. East winds may keep snow level locally lower in the Cascade passes. EXTENDED FORECAST FOR WEDNESDAY THROUGH FRIDAY Wednesday morning: Light to moderate rain or snow Olympics and light rain or snow developing Cascades. Wednesday afternoon and evening: Moderate rain or snow mainly volcanic peaks and light rain or snow Cascade passes. Thursday: Light rain or snow in the morning becoming moderate in the afternoon and evening but possibly remaining limited Cascade passes. Friday: Light rain or snow in the morning becoming moderate in the afternoon and evening but possibly remaining limited Cascade passes. * SNOW LEVELS 2-3000 ft N, 3-5000 ft S Wed 2-3000 ft N, 35-4500 ft S Thu 2-3000 ft N, 3-4000 ft S Fri...except mostly near the surface Cascade passes and east slopes Wednesday to Friday.