115 PM PDT MON DEC 10 2007 WEATHER SYNOPSIS FOR MONDAY AND TUESDAY A strong upper level ridge of high pressure centered about 300 miles off the Washington coast Monday is providing cool and generally clear conditions over all the mountains of the region. The ridge is producing a moderate northerly flow aloft and a weak to moderate north to northeast flow at crest level with weak easterly flow through the Cascade passes. A weak disturbance moved through the ridge Sunday through early Monday producing a period of generally light snowfall. The upper ridge is expected to weaken, flatten and gradually tilt over the Pacific Northwest by early Tuesday. This should allow for some warmer air aloft affecting the higher elevations along with increasing high clouds from offshore disturbances spreading into the area throughout the day Tuesday. As the ridge flattens and moves inland later Tuesday the upper flow should become northwesterly ushering in a weakening frontal system Tuesday night. This front should weaken rapidly as it moves inland overnight Tuesday but may provide a brief period of light showers as it transits the area, especially over the northwest Washington Cascades and Olympics. Freezing levels should lower rapidly with the weak frontal passage late Tuesday night and therefore any precipitation should fall at low freezing levels. WEATHER FORECAST FOR MONDAY AND TUESDAY * OLYMPICS- Mostly sunny Monday afternoon. Increasing high clouds Monday night. Mainly high Cloudiness early Tuesday. Clouds lowering Tuesday afternoon with a few light snow showers Tuesday night. * WASHINGTON CASCADES NEAR AND WEST OF THE CREST- Mostly sunny Monday afternoon. Increasing high clouds Monday night. Mainly high Cloudiness early Tuesday. Clouds lowering Tuesday afternoon with a few light snow showers Tuesday night, mainly north part. * CASCADE PASSES, INCLUDING STEVENS, SNOQUALMIE AND WHITE PASSES- Mostly sunny Monday afternoon. Increasing high clouds Monday night. Mainly high Cloudiness early Tuesday. Clouds lowering Tuesday afternoon with a few light snow showers Tuesday night. * EAST SLOPES WASHINGTON CASCADES- Mostly sunny Monday afternoon. Increasing high clouds Monday night. Mainly high Cloudiness early Tuesday. Clouds lowering Tuesday afternoon with a chance of a few light snow showers Tuesday night. * MT HOOD AREA- Mostly sunny Monday. Fair Monday night. Increasing high clouds early Tuesday with gradual warming. Mainly high Cloudiness later Tuesday and Tuesday night. SNOW LEVELS-CASCADE MTNS 1000 ft N, 1500 ft S Monday afternoon 1000 ft N, 2000 ft S Monday night 1500 ft N, 5500 ft S early Tuesday 2000 ft N, 6000 ft S late Tuesday, except snow levels lowering to near the surface Cascade passes and east slopes Monday through Tuesday SNOW LEVELS-OLYMPIC MTNS 3500 ft Monday afternoon 5000 ft Monday night 6000 ft early Tuesday 2500 ft late Tuesday 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 0 LT .10 * MT BAKER LT .10 LT .10 * WASHINGTON PASS 0 LT .10 * STEVENS PASS LT .10 LT .10 * SNOQUALMIE PASS LT .10 LT .10 * MISSION RIDGE 0 0 * CRYSTAL MTN 0 LT .10 * PARADISE 0 LT .10 * WHITE PASS 0 0 * MT HOOD 0 0 WINDS IN MILES PER HOUR (MPH) * CASCADE PASS LEVEL WINDS E 0-10 Monday afternoon E 5-15 Monday night and Tuesday E 0-10 Tuesday afternoon and night * FREE WINDS AT 5000 FT E-SE 5-15 Monday afternoon and night S-SW 5-15 early Tuesday W 5-15 Tuesday afternoon W 10-20 Tuesday night * FREE WINDS AT 9000 FT N-NE 15-25 Monday afternoon N 10-20 Monday night N-NW 10-20 Tuesday morning W 20-30 Tuesday afternoon NW 20-30 Tuesday night EXTENDED WEATHER SYNOPSIS FOR WEDNESDAY THROUGH FRIDAY Cool northwesterly flow aloft is expected over the Pacific Northwest Wednesday and Thursday carrying weak weather disturbances across the region. These systems are not expected to produce much in the way of precipitation however. One weak system should exit the region early Wednesday with a dryer northwesterly flow developing later Wednesday causing cool and partly cloudy conditions. Another very weak disturbance should maintain the chance of a few light showers Thursday and mostly cloudy conditions and remaining very cool. The latest model runs are indicating that the ridge should remain strong enough to shunt a developing system further north than earlier anticipated. If this scenario plays out, Friday should be only a cloudy day with light amounts of precipitation if any. The frontal system is expected to move through but maybe as late as Saturday night. As run to run inconsistencies play out, stay tuned for details as the ridge breaks down and stronger Pacific storms once again return to the region. EXTENDED FORECAST FOR WEDNESDAY THROUGH FRIDAY Mostly cloudy with a few light snow showers ending Wednesday morning. Mostly cloudy Thursday with a chance of light snow showers, mainly north part. Increasing clouds late Thursday with light snow developing in the north and Olympics Friday and Friday night. * SNOW LEVELS Sea level to 1000 ft N, 1-2000 ft C and S Wednesday and Thursday 500 to 1000 ft N, 15-3000 ft S early Friday 2-4000 ft N and C, 4-6000 ft S late Friday