A storm system will push inland today with light warm frontal precipitation beginning this morning, increasing in the afternoon, and intensifying further Sunday night. Snow levels will creep up to mid-elevations west of the Cascade crest approaching 4500-5000' for the Mt Baker area by sunset, and 5000-5500' for the West South zone and the Olympics, and 6500-7000' for Mt Hood. Colder air along the eastern slopes of the Cascades combined with cool easterly flow will keep snow levels around 3000-3500' once precipitation gets going today for the Cascade Passes and along the east slopes. Look for strong S-SE ridgeline winds in many areas in the afternoon.
Temperatures/snow levels will hold at these levels until a cold front passes through after midnight. A switch to WSW winds Sunday night will mix out the colder air along the east slopes of the Cascades and bring about a period of 4000-4500' snow levels across the region (a bit cooler for East North) as steady precipitation turns to showers.
A ridge of high pressure will build over the inland NW on Monday with a brief but notable drying trend taking place. Freezing levels will pop back up for areas west of the Cascade crest to 5000-7000'. We're entering a progressive weather pattern with systems every 24 hours or so. The next system is on tap Monday night.
Weather Forecast
Olympics
West North
West Central
West South
Stevens Pass
Snoqualmie Pass
East North
East Central
East South
Mt. Hood
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Sunday
Light rain and snow developing and becoming light to moderate in the afternoon, heaviest southern slopes of the Olympics. Strong ridgeline winds.
Sunday
Night
Stormy with moderate rain and snow becoming light to moderate showers around midnight. Strong ridgeline winds.
Sunday
Cloudy in the morning with light rain and snow developing late morning/mid-day, and becoming moderate in the afternoon. Winds becoming strong in the afternoon.
Sunday
Night
Stormy with moderate to occasionally heavy rain and snow becoming moderate showers after midnight. Strong ridgeline winds.
Sunday
Cloudy in the morning with light rain and snow developing late morning/mid-day, and becoming light to occasionally moderate in the afternoon. Winds increasing and becoming moderate in the afternoon.
Sunday
Night
Stormy with moderate to occasionally heavy rain and snow becoming light to moderate showers after midnight. Strong ridgeline winds.
Sunday
Cloudy in the morning with light rain and snow developing during the morning, and becoming light to moderate in the afternoon. Winds increasing and becoming moderate in the afternoon.
Sunday
Night
Stormy with moderate to occasionally heavy rain and snow becoming light to moderate showers after midnight. Strong ridgeline winds.
Sunday
Cloudy in the morning with light rain and snow developing late morning/mid-day, and becoming light to occasionally moderate in the afternoon. Light to moderate E winds at Pass level and SE at ridgeline increasing in the afternoon.
Sunday
Night
Stormy with moderate rain and snow becoming light to moderate showers after midnight. Moderate E Pass level winds/SE winds at ridgeline becoming moderate to Strong W winds after midnight.
Sunday
Cloudy in the morning with light rain and snow developing late morning/mid-day, and becoming light to occasionally moderate in the afternoon. Light to moderate E winds at Pass level and SE at ridgeline increasing in the afternoon.
Sunday
Night
Stormy with moderate to occasionally heavy rain and snow becoming light to moderate showers after midnight. Moderate E Pass level winds/SE winds at ridgeline becoming moderate to Strong W winds after midnight.
Sunday
Cloudy in the morning with light rain and snow developing mid-day, and becoming light to occasionally moderate in the afternoon. Winds increasing and becoming moderate in the afternoon.
Sunday
Night
Stormy with moderate rain and snow becoming light to occasionally moderate showers after midnight. Strong ridgeline winds.
Sunday
Cloudy in the morning with light rain and snow developing late morning/mid-day, and becoming light to occasionally moderate in the afternoon. Winds increasing and becoming moderate in the afternoon.
Sunday
Night
Stormy with moderate rain and snow becoming light to occasionally moderate showers after midnight. Strong ridgeline winds.
Sunday
Cloudy in the morning with light rain and snow developing late morning, and becoming light to occasionally moderate in the afternoon. Winds increasing and becoming moderate in the afternoon.
Sunday
Night
Stormy with moderate rain and snow becoming light to occasionally moderate showers after midnight. Strong ridgeline winds.
Sunday
Cloudy in the morning with light rain and snow developing during the morning, and becoming light to moderate in the afternoon. Winds increasing and becoming moderate to strong in the afternoon.
Sunday
Night
Stormy with moderate to occasionally heavy rain and snow becoming light to moderate showers after midnight. Strong ridgeline winds.
The NWAC program is administered by the USDA-Forest Service and operates from the National Weather Service Forecast Office in Seattle. NWAC services are made possible by important collaboration and support from a wide variety of federal, state and private cooperators.
The 5000’ temperature forecast does not imply a trend over the 12 hr period and only represents the max and min temperatures within a 12 hr period in the zone. The 6-hr snow level forecast, the forecast discussion, and weather forecast sections may add detail regarding temperature trends.
The snow level forecast represents the general snow level over a 6 hr time period. Freezing levels are forecast when precipitation is not expected.
*Easterly or offshore flow is highlighted with an asterisk when we expect relatively cool east winds in the major Cascade Passes. Easterly flow will often lead to temperature inversions and is a key variable for forecasting precipitation type in the Cascade Passes. Strong easterly flow events can affect terrain on a more regional scale.
Ridgeline winds are the average wind speed and direction over a 6 hr time period.
The wind forecast represents an elevation range instead of a single elevation slice. The elevation range overlaps with the near and above treeline elevation bands in the avalanche forecast and differs per zone.
Wind direction indicates the direction the wind originates or comes from on the 16-point compass rose.
Water Equivalent (WE) is the liquid water equivalent of all precipitation types; rain, snow, ice pellets, etc., forecast to the hundredth of an inch at specific locations. To use WE as a proxy for snowfall amounts, start with a snow to water ratio of 10:1 (10 inches of snow = 1 inch WE). Temperatures at or near freezing will generally have a lower ratio (heavy wet snow) and very cold temperatures can have a much higher ratio (dry fluffy snow).