We're kicking off another balmy early April day with mostly sunny skies and temperatures well above freezing. A slight change in the weather will start to take hold this afternoon as a cool low pressure system off the NW British Columbia coast begins to push inland. This weather feature will send a few clouds our way, and also an uptick in westerly ridgeline winds this afternoon.
That change will accelerate overnight into Tuesday morning as the low traverses inland and an upper trough briefly digs over the inland NW. We'll see a few low clouds push along the west slopes of the Cascades near and north of I-90 along with a slight chance of a light shower, but the bigger story will be the increase in westerly winds. Strong westerly ridgeline winds will ramp up overnight, becoming occasionally extreme along the east slopes of the Cascades by early Tuesday morning. There will be a brief cooling trend, focused mainly on the northern zones overnight, pushing freezing levels down into the 3000-5000' range.
The trough's influence will begin to wane on Tuesday afternoon, and we'll see winds slowly ease off during the day. Look for a fair bit of sunshine with perhaps some low clouds for West North/West Central, and with freezing levels rebounding to 5500-7500' Tuesday afternoon.
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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Monday
Mostly sunny in the morning, partly to mostly sunny in the afternoon. Light ridgeline winds becoming light to moderate in the afternoon.
Monday
Night
Partly cloudy. Moderate ridgeline winds.
Monday
Mostly sunny in the morning, partly to mostly sunny in the afternoon. Light to occasionally moderate ridgeline winds increasing in the afternoon.
Monday
Night
Partly to mostly cloudy with a slight chance of light showers overnight. Moderate ridgeline winds.
Monday
Mostly sunny in the morning, partly to mostly sunny in the afternoon. Light ridgeline winds becoming light to moderate in the afternoon.
Monday
Night
Partly to mostly cloudy with a slight chance of light showers overnight. Moderate ridgeline winds.
Monday
Mostly sunny with a few high clouds in the afternoon. Light ridgeline winds becoming light to moderate in the afternoon.
Monday
Night
Mostly clear. Moderate to strong ridgeline winds.
Monday
Mostly sunny in the morning, partly to mostly sunny in the afternoon. Light W Pass level and ridgeline winds becoming light to moderate in the afternoon.
Monday
Night
Partly cloudy. Moderate W ridgeline and Pass level winds.
Monday
Mostly sunny with a few high clouds in the afternoon. Light W Pass level and ridgeline winds becoming light to moderate in the afternoon.
Monday
Night
Partly cloudy. Moderate W Pass level winds, occasionally strong at ridgeline.
Monday
Mostly sunny with a few high clouds in the afternoon. Light to occasionally moderate ridgeline winds increasing in the afternoon.
Monday
Night
Mostly clear. Strong ridgeline winds.
Monday
Mostly sunny with a few high clouds in the afternoon. Light to occasionally moderate ridgeline winds increasing in the afternoon.
Monday
Night
Mostly clear. Strong ridgeline winds.
Monday
Mostly sunny with a few high clouds in the afternoon. Light to occasionally moderate ridgeline winds increasing in the afternoon.
Monday
Night
Mostly clear. Moderate to strong ridgeline winds.
Monday
Mostly sunny with a few high clouds in the afternoon. Light to occasionally moderate ridgeline winds increasing in the afternoon.
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).