An upper low positioned offshore will lead to showers and a fair amount of cloud cover over the region today. An upper level disturbance rotating up from northern Oregon today should help focus an area of showers in the south WA Cascades later this morning and then the central Cascades this afternoon. The air mass is marginally unstable, so we'll see scattered convective showers elsewhere in the afternoon and early evening. Look for an increase in afternoon/overnight westerly ridgeline winds as onshore flow increases. Snow levels will be around 3500-4000' today with freezing levels 4000-5000', warmest along the east slopes of the Cascades.
The upper low will transition to an open trough tonight as it shifts inland on Tuesday. This will position the PNW on the backside of the trough, translating to cool and showery weather, especially near and west of the Cascade crest, with more sunshine further east of the crest. Showers and clouds will likely be concentrated in the central Cascades Tuesday.
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 cloudy with scattered light to occasionally moderate rain and snow showers. Light to occasionally moderate ridgeline winds.
Monday
Night
Mostly cloudy with scattered light rain and snow showers. Light to moderate ridgeline winds.
Monday
Partly sunny to mostly cloudy with scattered light to occasionally moderate rain and snow showers. Light to occasionally moderate ridgeline winds.
Monday
Night
Mostly cloudy with scattered light rain and snow showers. Light to moderate ridgeline winds.
Monday
Mostly cloudy with scattered light to occasionally moderate rain and snow showers, heaviest in the afternoon. Light to occasionally moderate ridgeline winds.
Monday
Night
Mostly cloudy with scattered light to moderate rain and snow showers. Light to moderate ridgeline winds.
Monday
Mostly cloudy with scattered light to occasionally moderate rain and snow showers, heaviest late morning through mid-day. Light to occasionally moderate ridgeline winds.
Monday
Night
Mostly cloudy with scattered light to moderate rain and snow showers. Light to moderate ridgeline winds.
Monday
Mostly cloudy with scattered light to occasionally moderate rain and snow showers, heaviest in the afternoon. Light to occasionally moderate W ridgeline and Pass level winds.
Monday
Night
Mostly cloudy with scattered light to moderate rain and snow showers. Light to occasionally moderate W ridgeline and Pass level winds.
Monday
Mostly cloudy with scattered light to occasionally moderate rain and snow showers, heaviest in the afternoon. Light to occasionally moderate W ridgeline and Pass level winds.
Monday
Night
Mostly cloudy with scattered light to moderate rain and snow showers. Moderate W ridgeline and Pass level winds.
Monday
Partly sunny to mostly cloudy with scattered light to occasionally moderate rain and snow showers, more widespread in the afternoon. Light to occasionally moderate ridgeline winds.
Monday
Night
Mostly cloudy with scattered light rain and snow showers. Light to moderate ridgeline winds.
Monday
Partly sunny to mostly cloudy with scattered light to occasionally moderate rain and snow showers, more widespread in the afternoon. Light to occasionally moderate ridgeline winds.
Monday
Night
Mostly cloudy with scattered light rain and snow showers. Moderate ridgeline winds.
Monday
Partly sunny to mostly cloudy with scattered light to occasionally moderate rain and snow showers, more widespread in the afternoon. Light to occasionally moderate ridgeline winds.
Monday
Night
Mostly cloudy with scattered light rain and snow showers. Light to moderate ridgeline winds.
Monday
Mostly cloudy with scattered light to occasionally moderate rain and snow showers. Moderate ridgeline winds.
Monday
Night
Mostly cloudy with scattered light rain and snow showers. Light to 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).