A low center that tracked into southern British Columbia early Thursday is associated with a shortwave feature that brings moderate rain and snow into the Pacific Northwest Thursday morning before precipitation tapers and becomes light and showery in the afternoon. The heaviest precipitation will be in the Mt Baker area, enhanced by moderate SSW ridgeline winds. Low-level E winds through the mountain gaps should drag snow levels down to the 3000-4000 ft range, whereas areas further west experience snow levels around 5000 ft (even 6000 ft further south around Mt Rainier). As ridgeline winds shift WSW in the afternoon, expect snow levels to rise in the passes as well.
A warm front lifts NE across Washington State, bringing a band of mostly light rain and higher elevation snow, but expect steadier moderate precipitation around Mt Baker. Southern portions of the forecast region dry out overnight, while areas further north remain wet. The trailing cold front pushes steady moderate rain and higher-elevation snow into the Olympics and sustains precipitation in the Mt Baker area Friday morning, with lighter precipitation elsewhere. The moderate precipitation spreads throughout the region in the afternoon as the cold front arrives with increasing light to moderate SW and SSW ridgeline winds and snow levels rising to 5000-6500 ft in most areas.
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Thursday
Light rain and higher elevation snow tapers to light and occasional showers. Moderate ridgeline winds become mostly light in the afternoon.
Thursday
Night
Periods of. light rain and higher elevation snow. Increasing light to moderate ridgeline winds.
Thursday
Heavy rain and higher-elevation snow in the morning become light and showery in the afternoon. Moderate ridgeline winds become mostly light in the afternoon.
Thursday
Night
Increasing moderate to heavy rain and higher elevation snow. Moderate ridgeline winds redevelop in the evening hours.
Thursday
Moderate rain and higher-elevation snow in the morning become light and showery in the afternoon. Moderate ridgeline winds become mostly light in the afternoon.
Thursday
Night
Increasing moderate rain and higher elevation snow.
Thursday
Moderate rain and higher-elevation snow become light and showery in the afternoon.
Thursday
Night
Mostly light rain and higher-elevation snow (moderate at Paradise) taper overnight.
Thursday
Light to moderate rain and snow becomes light and showery by mid-morning. Light ridgeline and E wind at the Pass.
Thursday
Night
Decreasing light rain and higher elevation snow. Light ridgeline and E wind at the Pass.
Thursday
Moderate rain and snow become light and showery by mid-morning. Light to moderate ridgeline and mostly light E wind at the Pass.
Thursday
Night
Decreasing light rain and higher elevation snow. Mostly light ridgeline and E wind at the Pass.
Thursday
Decreasing light to moderate rain and snow becomes light and showery in the afternoon.
Thursday
Night
Periods of light rain and snow.
Thursday
Light to moderate rain and snow in the morning becomes light and showery by late morning as snow levels rise.
Thursday
Night
Periods of light rain and higher elevation snow.
Thursday
Light to moderate rain and snow in the morning becomes light and showery by late morning as snow levels rise.
Thursday
Night
Periods of light rain and higher elevation snow, primarily during the evening hours.
Thursday
Decreasing light rain and snow become showery by late morning. Moderate ridgeline winds.
Thursday
Night
Light rain and snow in the evening, then mostly cloudy skies overnight. 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).