####018007890#### WWUS86 KSEW 291556 SABNW MOUNTAIN WEATHER FORECAST FOR THE OLYMPICS WASHINGTON CASCADES AND MT HOOD AREA NORTHWEST WEATHER AND AVALANCHE CENTER SEATTLE WASHINGTON 700 AM PST THU JAN 29 2009 NWAC Program administered by: USDA-Forest Service with cooperative funding and support from: Washington State Department of Transportation National Weather Service National Park Service Washington State Parks and Recreation Commission Pacific Northwest Ski Area Association Friends of the Avalanche Center and other private organizations. This forecast is prepared primarily for federal, state and private snow safety programs in Washington and Northern Oregon. WAZ513-518-519-019-042-501-502-ORZ011-301700- && WEATHER SYNOPSIS FOR THURSDAY AND FRIDAY A building upper level ridge well offshore is shunting Pacific frontal systems mainly north of the forecast area. The southern portion of a warm front is draped over the Pacific Northwest Thursday morning but affecting mainly the north to central areas with cloud cover and a little light precipitation. The ridge should gain strength and gradually shift to the coast late Thursday then inland Friday. This should push the clouds further north and cause significantly rising freezing levels and diminishing northwest winds through the day Thursday into early Friday. Clouds and winds should increase through the day Friday as an approaching cold front makes its way towards the area. The ridge should weaken Friday as a short wave trough moves over the area Friday night. The main energy should remain north of the forecast area but moderate precipitation is expected over the north part late Friday with lowering freezing levels. Little precipitation is expected to reach the Mt Hood area with this front as that should be about the southern extent of the fronts impact. The front should bring much cooler air into the area however Friday night with freezing levels dropping fast. Precipitation should change to showers late Friday night with the main precipitation again remaining in the north part. && WEATHER FORECAST FOR THURSDAY AND FRIDAY *OLYMPICS- Thursday: Mostly cloudy with a chance of a few light rain or snow showers. Thursday night: Partly cloudy and mild with light winds. Friday: Increasing clouds with light rain or snow developing by midday or early afternoon. Friday evening and night: Increasing light to occasionally moderate snow changing to showers late. *WASHINGTON CASCADES NEAR AND WEST OF THE CREST- *CASCADE PASSES, INCLUDING STEVENS SNOQUALMIE WHITE PASSES- Thursday morning: Mostly cloudy with a chance of light snow showers, mainly north part. Thursday afternoon: Partly cloudy with mainly high clouds. Thursday night and Friday morning: Variable high clouds. Friday late morning and midday: Increasing clouds becoming mostly cloudy. Friday afternoon: Light rain or snow developing in the north and cloudy central and south. Friday night: Light to moderate snow north, light rain or snow central part and a chance of rain or snow south. *EAST SLOPES WASHINGTON CASCADES- Thursday and Thursday night: Mostly mid and high clouds north part, variable high clouds central and south. Friday: Variable high clouds. Clouds increasing north part late day. Friday night: Occasional light snow north part and cloudy central and south. *MT HOOD AREA- Thursday: Mostly sunny and warm with variable high clouds. Thursday night: Mostly fair and warm. Friday: Variable high clouds and warm. Friday night: increasing clouds with a chance of rain or snow late. && SNOW LEVELS-CASCADE MTNS 1500 ft N, 5000 ft S Thursday morning FREEZING LEVELS-CASCADE MTNS 7000 ft N, 10,000 ft C, 11,000 ft S Thursday afternoon and night SNOW LEVELS-CASCADE MTNS 6000 ft N, 10,000 ft S Friday morning 3000 ft N, 8000 ft S Friday afternoon 1500 ft N, 2500 ft S Friday night SNOW LEVELS-OLYMPIC MTNS 2000 ft Thursday morning FREEZING LEVELS-OLYMPIC MTNS 7000 ft Thursday afternoon 9500 ft Thursday night SNOW LEVELS-OLYMPIC MTNS 6000 ft Friday morning 3500 ft Friday afternoon 1500 ft 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 RIDGELT .10 .25 *MT BAKER LT .10 .25-.5 *WASHINGTON PASSLT .10 .25 *STEVENS PASS LT .10 .25 *SNOQUALMIE PASSLT .10 .25 *MISSION RIDGE 0 LT .25 *CRYSTAL MTN LT .10 LT .25 *PARADISE LT .10 .25 *WHITE PASS 0 LT .25 *MT HOOD 0 LT .25 && WINDS IN MILES PER HOUR (MPH) *CASCADE PASS LEVEL WINDS W 5-15 Thursday through Thursday night E 0-10 Friday W 5-15 Friday afternoon W 10-20 Friday night *FREE WINDS AT 5000 FT W-NW 15-25 N, N-NW 10-15 S Thursday N-NW 5-15 Thursday night and early Friday morning SW 15-25 N, W-SW 10-20 S late Friday morning SW 20-30 N, W 15-25 S Friday afternoon W 15-25 Friday night *FREE WINDS AT 9000 FT NW 35-50 N, N-NW 15-25 S Thursday morning W-NW 25-35 N, NW 10-20 S Thursday afternoon and night W 30-40 N, NW 10-20 S Friday morning W 35-50 N, W 25-35 S Friday afternoon W-NW 35-50 Friday night && EXTENDED WEATHER SYNOPSIS FOR FRIDAY THROUGH SUNDAY A strong upper ridge should move across the area Friday and weaken. This should allow for a mostly fair and mild day Friday. An approaching frontal system should spread increasing clouds over the area later Friday. A strong cold frontal passage is expected Friday night. This front will be moving over the weakening ridge with the strongest part of the front cross to the north of the forecast region. Therefore the heaviest precipitation Friday night and early Saturday should be in the north Washington Cascades with gradually less precipitation received to the south and only light amounts reaching the Mt Hood area. Freezing levels should drop rapidly with the onset of precipitation and continue to lower Friday night and early Saturday along with strong winds, being strongest in the north part. Weakening flow and gradual drying should cause orographic snowfall to diminish through the day Saturday. High pressure should rebuild over the area late Saturday and Sunday. This should cause gradual clearing with light winds and remaining cool from late Saturday through Sunday. EXTENDED FORECAST FOR FRIDAY THROUGH SUNDAY Friday: Increasing high clouds north part and fair south and warm. Increasing clouds all area late Friday Friday night: Increasing moderate to briefly heavy snow in the north, moderate snow central and light snow south. Saturday: Light snow showers north and central part west slopes gradually decreasing. Becoming partly cloudy south part. Sunday: Cool with chance of light snow showers north and only variable high clouds central and south. *SNOW LEVELS 1-2000 ft N, 1-2000 ft S Saturday and Sunday && NWAC weather data and forecasts are also available by calling 206-526-6677 for Washington, 503-808-2400 for the Mt Hood area, or by visiting our Web site at www.nwac.us. Kramer/Northwest Weather and Avalanche Center $$