An atmospheric river has narrowed with the E-W axis of moisture lingering over central and northern Washington. This will bring generally moderate precipitation to the west slopes of the Cascades through the day, with moisture gradually decreasing in southern portions of the forecast region by the afternoon as a ridge begins to expand northward. This will also continue to in further elevate snow lines within the 5500-8500 ft range (cooler in the north). Winds continue to decrease with ridgeline areas favored by W flow in the moderate range.
Precipitation mostly ends from Mt Rainier southward Monday evening and becomes light further north. In these areas snow lines will be 7000-8000 ft.
Tuesday will be mostly dry under the influence of the ridge of high pressure. Expect sunny skies with 8500-11000 ft freezing levels over most of the forecast region. Some clouds and showers will linger near the Canadian border in the morning hours.
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
Decreasing periods of light rain.
Monday
Night
Decreasing periods of light rain.
Monday
Moderate to occasionally heavy rain.
Monday
Night
Periods of generally light rain.
Monday
Moderate to heavy rain.
Monday
Night
Periods of light rain. Light to moderate ridgeline winds.
Monday
Periods of moderate rain in the morning, becoming light in the afternoon.
Monday
Night
Periods of light rain end overnight.
Monday
Moderate to heavy rain decreasing in the afternoon. Light to moderate ridgeline and light W wind at the Pass.
Monday
Night
Periods of light rain taper overnight. Light to moderate ridgeline and light W wind at the Pass.
Monday
Moderate rain decreases in the afternoon. Moderate ridgeline and light to moderate W wind at the Pass.
Monday
Night
Periods of light rain taper overnight. Light to moderate ridgeline and light W wind at the Pass.
Monday
Periods of light rain and highest elevation snow. Moderate ridgeline winds.
Monday
Night
Periods of light rain. Moderate ridgeline winds.
Monday
Periods of light rain. Moderate ridgeline winds.
Monday
Night
Light rain in the evening near the Cascade Crest. Otherwise partly cloudy. Decreasing moderate ridgeline winds.
Monday
Periods of light rain. Moderate ridgeline winds.
Monday
Night
Partly cloudy.
Monday
Moderate rain in the morning becomes light overnight. 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).