Today will mark the end of our recent stretch of mild and dry weather. Mostly sunny skies will give way to increasing high clouds over the Olympics and north Cascades in the afternoon as a Pacific frontal system approaches. Freezing levels will still be quite high, 8000' in the north and 11,000' down near Mt Hood and mid-mountain temperatures will be in the 40s and 50s. However, ridgeline and alpine winds will increase today as the front approaches.
A sharp front will pass through Tuesday night with gusty winds and steady precipitation quickly turning to showers with the frontal passage. Snow levels will plummet by sunrise to near 2000' for the Olympics and Mt Baker area and 2500-3000' for areas further south and east. The northwest Cascades stand to pick up the most precipitation/snowfall through mid-morning Wednesday with a short-lived convergence zone affecting the mountain Loop Highway. Showers will become scattered in the afternoon and mostly focused on the west slopes of the Cascades with drier conditions likely along the east slopes of the Cascades.
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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Tuesday
Mostly sunny, becoming mostly cloudy mid to late afternoon. Moderate ridgeline winds.
Tuesday
Night
Light to occasionally moderate rain and snow becoming showers after midnight. Sharp cooling trend. Moderate to occasionally strong ridgeline winds.
Tuesday
Mostly sunny, becoming partly sunny with increasing high clouds in the afternoon. Moderate to occasionally strong ridgeline winds.
Tuesday
Night
Light to moderate rain and snow developing in the evening becoming showers after midnight. Sharp cooling trend. Moderate to occasionally strong ridgeline winds.
Tuesday
Mostly sunny, becoming partly sunny with increasing high clouds in the afternoon. Moderate ridgeline winds.
Tuesday
Night
Light to moderate rain and snow developing in the evening becoming showers after midnight. Sharp cooling trend. Moderate to occasionally strong ridgeline winds.
Tuesday
Mostly sunny. Increasing high clouds late in the afternoon. Moderate ridgeline winds.
Tuesday
Night
Cloudy in the evening then light to occasionally moderate rain and snow developing around midnight, becoming shower late. Sharp cooling trend after midnight. Moderate to occasionally strong ridgeline winds.
Tuesday
Mostly sunny. Increasing high clouds late in the afternoon. Pass level and ridgeline W winds becoming moderate in the afternoon.
Tuesday
Night
Cloudy in the evening then light to occasionally moderate rain and snow developing around midnight, becoming shower late. Sharp cooling trend after midnight. Moderate to occasionally strong W ridgeline and Pass level winds.
Tuesday
Mostly sunny. Increasing high clouds late in the afternoon. Pass level and ridgeline W winds becoming moderate in the afternoon.
Tuesday
Night
Cloudy in the evening then light to occasionally moderate rain and snow developing around midnight, becoming shower late. Sharp cooling trend after midnight. Moderate to occasionally strong W ridgeline and Pass level winds.
Tuesday
Mostly sunny, becoming partly sunny with increasing high clouds in the afternoon. Moderate to occasionally strong ridgeline winds.
Tuesday
Night
Cloudy in the evening then light to occasionally moderate rain and snow developing around midnight, becoming shower late. Sharp cooling trend after midnight. Moderate to occasionally strong ridgeline winds.
Tuesday
Mostly sunny. Increasing high clouds late in the afternoon. Moderate ridgeline winds.
Tuesday
Night
Cloudy in the evening then light to occasionally moderate rain and snow developing around midnight, becoming shower late. Sharp cooling trend after midnight. Moderate to occasionally strong ridgeline winds.
Tuesday
Mostly sunny. Increasing high clouds late in the afternoon. Ridgeline winds becoming moderate in the afternoon.
Tuesday
Night
Cloudy in the evening then light to occasionally moderate rain and snow developing around midnight, becoming shower late. Sharp cooling trend after midnight. Moderate to occasionally strong ridgeline winds.
Tuesday
Mostly sunny. Ridgeline winds becoming moderate in the afternoon.
Tuesday
Night
Cloudy in the evening then light to occasionally moderate rain and snow developing around midnight, becoming shower late. Sharp cooling trend 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).