MOUNTAIN WEATHER FORECAST FOR THE OLYMPICS WASHINGTON CASCADES AND MT HOOD AREA NORTHWEST WEATHER AND AVALANCHE CENTER SEATTLE WASHINGTON 130 PM PST SUN FEB 8 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-ORZ011-091700- && WEATHER SYNOPSIS FOR SUNDAY AND MONDAY Current global models indicate a consistency in the long wave pattern over the eastern north Pacific. A strong northwest jet stream currently over the eastern north Pacific should be maintained for the near future. This is causing the upper level flow to split offshore sending the strongest energy diving southeast offshore towards California while the weak northern portions of systems move across the Pacific Northwest. In general, this should produce generally light amounts of precipitation at increasingly cool temperatures as systems head southeast offshore. The current conditions Sunday afternoon see an upper level closed low pressure system centered over southern California while the next upstream trough is approaching the area off the coast. A cold upper low is moving across the Gulf of Alaska. The system off the coast has spread increasing clouds over the area Sunday afternoon with the cloud deck having lowered to about 10,000 feet in the Mt Rainier and Mt Hood area per the latest camera views. The weak northern portion of the cold front offshore should pass later Sunday night and early Monday. This should spread generally light precipitation over the region Sunday night and early Monday. The main energy with this system should head to the Sierras of California late tonight and early Monday. The cold air upstream in the northeastern Pacific should reach the area with the upper trough that should pass our area later Monday. This should cause the air mass to destabilize as the cold air aloft reaches the region, producing showery precipitation at low freezing levels. A brief increase in onshore flow behind the trough later Monday and a possible convergence zone may produce a brief period of moderate precipitation in the central area. The Pacific Northwest should be between systems Monday night and see showers diminishing overnight. && WEATHER FORECAST FOR SUNDAY AND MONDAY * OLYMPICS- Sunday afternoon: Clouds lowering with a chance of light snow. Sunday evening: Increasing light snow. Sunday night: Increasing light to occasionally moderate snow, heaviest west part. Monday: Light snow showers. Monday night: Light snow showers gradually decreasing. * WASHINGTON CASCADES NEAR AND WEST OF THE CREST- * CASCADE PASSES INCLUDING STEVENS, SNOQUALMIE AND WHITE PASSES- Sunday afternoon: Increasing clouds mid level clouds. Sunday evening: Increasing light snow. Sunday night: Increasing light to occasionally moderate snow, heaviest south volcanoes. Monday: Light snow showers, possibly moderate central area afternoon or evening in convergence. Monday night: Light snow showers gradually decreasing. * EAST SLOPES WASHINGTON CASCADES- Sunday afternoon and evening: Increasing mid and high clouds. Sunday night: Increasing light snow. Monday: Light snow showers. Monday night. Light snow showers ending with clearing. * MT HOOD AREA- Sunday afternoon: Clouds lowering. Sunday evening: Increasing light snow. Sunday night: Increasing light to occasionally moderate snow. Monday: Light snow showers. Monday night: Occasional light snow showers. && SNOW LEVELS-CASCADE MTNS 3000 ft N, 3500 ft S Sunday afternoon and evening 1500 ft N to S Sunday night 500 ft N, 1000 ft S Monday morning near sea level N, 1000 ft S Monday afternoon near sea level N and S Monday night SNOW LEVEL-OLYMPIC MTNS 3000 ft Sunday afternoon 2000 ft Sunday night 1000 ft Monday Near sea level Monday afternoon and 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 .25 LT. 25 * MT BAKER LT .25 LT .25 * WASHINGTON PASS LT .25 LT .25 * STEVENS PASS LT .25 LT .25 * SNOQUALMIE PASS LT .25 LT .25 * MISSION RIDGE LT .10 LT .10 * CRYSTAL MTN LT .25 LT .25 * PARADISE LT .25 LT .25 * WHITE PASS LT .25 LT .25 * MT HOOD .25 LT .25 && WINDS IN MILES PER HOUR (MPH) * CASCADE PASS LEVEL WINDS E 5-15 Sunday afternoon W 0-10 Sunday night and early Monday morning W 10-20 Monday midday and afternoon W 5-15 Monday night * FREE WINDS AT 5000 FT S-SW 10-20 Sunday afternoon SW 10-20 Sunday night W 10-20 N and C, W 15-30 S Monday W-NW 10-20 Monday afternoon and night * FREE WINDS AT 9000 FT SW 15-25 Sunday afternoon and night W-NW 20-30 Monday W 15-25 Monday night && EXTENDED WEATHER SYNOPSIS FOR TUESDAY THROUGH THURSDAY Another developing low pressure system should form offshore and head towards California Tuesday. Some moisture from this system should move inland across the region during the day Tuesday to cause increasing light precipitation with moderate precipitation making it over the southern parts of the forecast area. Drying should be seen Wednesday as the system moves towards California. A temporary ridge should rebuild over the area Thursday between systems, resulting in decreasing clouds but remaining cool with light winds. EXTENDED FORECAST FOR TUESDAY THROUGH THURSDAY Tuesday morning: Increasing clouds. Tuesday afternoon to Wednesday morning: Increasing mostly light to occasionally moderate snow heaviest Olympics and Mt Hood areas. Wednesday afternoon and night: Decreasing light snow showers. Thursday: Becoming mostly sunny. * SNOW LEVELS Near sea level-1000 ft N, 1-2000 ft S Tuesday through Thursday 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 $$