145 PM PST SUN FEB 24 2008 WEATHER SYNOPSIS FOR SUNDAY AND MONDAY As a strong and deep upper low moves eastward across northern California early Sunday, increased moisture in a weak southerly flow to the north of the low combined with a very weak and almost stationary upper low over northern Washington to produce mostly cloudy skies, relatively cool temperatures and occasional light rain or snow in most areas Sunday morning. As the upper lows move slowly eastward Sunday afternoon and night, this should produce partly cloudy skies with decreasing light showers, light winds and continued relatively low freezing levels. Moderate upper ridging offshore should move onshore and slowly strengthen on Monday. Combined with a very weak upper disturbance moving across the top of the slowly building ridge, this should lift some residual moisture bands from the old California low northward Monday morning, with diminishing showers and some partial clearing spreading northward behind the weak shower bands Monday afternoon. By late Monday the ridge is expected to amplify along the west coast. This should allow for further clearing and a brief return to mostly fair skies, light winds and slightly rising freezing levels. WEATHER FORECAST FOR SUNDAY AND MONDAY * OLYMPICS- Sunday afternoon: clouds and light showers decreasing Sunday night: partly cloudy Monday morning: partly sunny Monday afternoon: partly cloudy with scattered light showers Monday night: decreasing clouds becoming mostly fair * WASHINGTON CASCADES NEAR AND WEST OF THE CREST- * CASCADE PASSES, INCLUDING STEVENS, SNOQUALMIE AND WHITE PASSES- Sunday afternoon: clouds and light showers decreasing Sunday night: partly cloudy Monday morning: partly cloudy with light showers spreading northward Monday afternoon: partly cloudy with scattered light showers ending south and decreasing north Monday night: decreasing clouds becoming mostly fair * EAST SLOPES WASHINGTON CASCADES- Sunday afternoon: clouds and light showers decreasing Sunday night: partly cloudy Monday morning: partly cloudy with light showers spreading northward, mainly higher terrain near the crest Monday afternoon: partly cloudy with scattered light showers ending south and decreasing north Monday night: decreasing clouds becoming mostly fair * MT HOOD AREA- Sunday afternoon through Monday morning: partly to mostly cloudy with scattered light showers Monday afternoon: partly sunny with scattered light showers ending Monday night: decreasing clouds becoming mostly fair SNOW LEVELS-CASCADE MTNS 3500 ft N and S Sunday afternoon 3000 ft N, 4000 ft S Sunday night 2000 ft N, 2500 ft C, 4000 ft S Monday morning 3000 ft N and S mid-day Monday 3500 ft N and S Monday afternoon 3500 ft N, 4500 ft S Monday night SNOW LEVELS-OLYMPIC MTNS 3500 ft Sunday afternoon through Monday evening 4000 ft later Monday 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 MON TUE * HURRICANE RIDGE LT .10 LT .10 * MT BAKER 0 LT .10 * WASHINGTON PASS LT .10 LT .10 * STEVENS PASS LT .10 LT .10 * SNOQUALMIE PASS LT .10 LT .10 * MISSION RIDGE LT .10 LT .10 * CRYSTAL MTN LT .10 LT .10 * PARADISE LT .10 LT .10 * WHITE PASS LT .10 LT .10 * MT HOOD LT .10 LT .10 WINDS IN MILES PER HOUR (MPH) * CASCADE PASS LEVEL WINDS E 5-15 Sunday afternoon E 0-10 Sunday night Variable 0-10 Monday * FREE WINDS AT 5000 FT SE 5-15 Sunday afternoon Variable 5-10 N, SW 5-15 S Sunday night W-SW 5-10 N, 10-20 S Monday morning SW 5-15 Cascades, 10-20 Olympics Monday afternoon S-SW 10-15 Cascades, 15-25 Olympics Monday night * FREE WINDS AT 9000 FT E 5-15 N, SW 5-15 C and S Sunday afternoon Variable 5-15 N, W 10-15 C and S Sunday night W-NW 5-15 N, 10-20 C and 15-25 S Monday morning SW 5-15 N and C, W 10-15 S mid-day Monday SW 5-15 Monday afternoon SW 10-20 Cascades, 15-25 Olympics Monday night EXTENDED WEATHER SYNOPSIS FOR TUESDAY THROUGH THURSDAY As the moderate upper ridge shifts eastward mid-late Tuesday, mostly fair skies Tuesday morning should give way to increasing clouds, increasing winds, rising freezing levels and some light rain or snow from about Mt Rainier northward Tuesday afternoon as a weak warm front moves onshore. Briefly decreasing light rain or snow are expected late Tuesday afternoon and evening as the warm front lifts north of the area, but this should be followed by increasing light rain or snow later Tuesday night and Wednesday morning as a weak cold front pushes across the region. The cold front should also be accompanied by moderate winds and generally lowering freezing levels. Following the front, a weak to moderate upper trough should maintain light to moderate showers at further lowering freezing levels Wednesday afternoon before decreasing and more northwesterly winds result in decreasing showers Wednesday night and early Thursday. A moderate upper ridge should approach the coast Thursday morning and slowly move across western Washington Thursday afternoon through early Friday. This should produce clearing skies, gradually rising freezing levels, and decreasing and relatively light winds. Extended forecast models continue to indicate that the ridge should be forced eastward by a moderate to strong front and several associated upper and surface troughs mid-late Friday into Saturday. If correct, moderate rain or snow at rapidly lowering freezing levels and strengthening winds later Friday should be followed by periods of moderate to heavy orographic snowfall at low freezing levels and moderate to strong winds on Saturday. EXTENDED FORECAST FOR TUESDAY THROUGH THURSDAY Tuesday morning: variable high clouds otherwise mostly fair Tuesday afternoon: increasing clouds with light rain or snow developing, mainly Mt Rainier northward Tuesday night: clouds and light rain or snow briefly decreasing, then increasing early Wednesday Wednesday morning: increasing light rain or snow Wednesday afternoon: light rain or snow showers Wednesday night and Thursday morning: partly to mostly cloudy with light showers decreasing Thursday afternoon and night: clouds decreasing becoming mostly fair and warmer * SNOW LEVELS 2-4000 ft N, 4-6000 ft S early Tuesday 4-6000 ft N, 6-8000 ft S late Tuesday 3-5000 ft N, 4-6000 ft S early Wednesday 2-4000 ft N, 3-5000 ft S late Wednesday 1-3000 ft N and S early Thursday 3-5000 ft N, 6-8000 ft S late Thursday...except snow levels locally lower Cascade passes Tuesday, rising to near free air levels early-mid Wednesday morning