Another unseasonably warm and sunny day is in store as we edge closer to the official first day of Spring. The upper level ridge that's been over the West Coast for several days will begin to flatten today, and freezing levels will slip below 10,000' across the area before sunset. Mid-mountain temperatures will still be quite warm, generally peaking in the low to mid-50s. Westerly onshore flow will increase in the afternoon, so dewpoints and RHs will creep upwards over the Olympics, west slopes of the Cascades and Passes.
Overnight, temperatures will remain mild but we'll start to see W-SW ridgeline winds increase as a weak frontal system approaches. High clouds will begin to increase overnight as well. Low clouds pushing in from the coast may bump up against the western foothills by sunrise on Wednesday but are unlikely to make it further inland.
A thickening high overcast will take hold by Wednesday afternoon as the weak frontal system nears the coast. While we'll stay dry for another day, expect continued moderate W-SW ridgeline winds and freezing levels to dip another notch into the 6500-7500' range. Onshore flow will cool the west slopes of the Cascades and Olympics by several degrees on Wednesday, while the east slopes of the Cascades and Mt. Hood stay a few degrees warmer.
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. Light to occasionally moderate ridgeline winds.
Tuesday
Night
Mostly clear in the evening, then partly cloudy with increasing high clouds after midnight. Light to occasionally moderate ridgeline winds.
Tuesday
Mostly sunny. Light to occasionally moderate ridgeline winds.
Tuesday
Night
Mostly clear in the evening, then partly cloudy with increasing high clouds after midnight. Ridgeline winds increasing to moderate after midnight.
Tuesday
Mostly sunny. Light to occasionally moderate ridgeline winds.
Tuesday
Night
Mostly clear in the evening, then partly cloudy with increasing high clouds after midnight. Ridgeline winds increasing to moderate after midnight.
Tuesday
Mostly sunny. Light to occasionally moderate ridgeline winds.
Tuesday
Night
Mostly clear in the evening, then partly cloudy after midnight. Moderate ridgeline winds.
Tuesday
Mostly sunny. Light to occasionally moderate W ridgeline and Pass level winds.
Tuesday
Night
Mostly clear in the evening, then partly cloudy with increasing high clouds after midnight. Moderate W ridgeline winds. Light to moderate W Pass level winds
Tuesday
Mostly sunny. Light to occasionally moderate W ridgeline and Pass level winds.
Tuesday
Night
Mostly clear in the evening, then partly cloudy after midnight. Moderate W ridgeline winds. Light to moderate W Pass level winds
Tuesday
Mostly sunny. Light to occasionally moderate ridgeline winds.
Tuesday
Night
Mostly clear in the evening, then partly cloudy with increasing high clouds after midnight. Light to occasionally moderate ridgeline winds.
Tuesday
Mostly sunny. Ridgeline winds increasing to moderate in the afternoon.
Tuesday
Night
Mostly clear. A few high clouds after midnight. Moderate ridgeline winds.
Tuesday
Mostly sunny. Light to occasionally moderate ridgeline winds.
Tuesday
Night
Mostly clear. A few high clouds after midnight. Moderate ridgeline winds.
Tuesday
Mostly sunny. Ridgeline winds increasing to moderate in the afternoon.
Tuesday
Night
Mostly clear. A few high clouds after midnight. Moderate 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).