Warm frontal moisture associated with an atmospheric river event will lift over the area today bringing heavy precipitation generally to the west slopes of the Cascades and S slopes of the Olympics and more moderate amounts for the Cascade Passes and along the east slopes of the Cascades. Heavier precipitation has already come to an end for the Mt Hood area. In the afternoon, areas south of Stevens Pass will see precipitation rates decrease as the warm frontal band shifts north.
Snow levels have begun to rise as well. Cool east flow will help slow snow level rises in the Cascade Passes and along the east slopes of the Cascades, with milder snow levels to the west. Stevens Pass and along the east slopes of the Cascades near and north of Hwy 2 should generally hold onto snow below 4000-4500' not only through Thursday but also Thursday night while 6000-8000' snow levels flood the rest of the region. The cooler east slopes of the Cascades will continue to gradually warm on Friday.
Successive waves of moisture will pass through Thursday night and Friday, but they are generally not expected to be as heavy as today. The exception will be for the S slopes of the Olympics and the northwest Cascades where moderate to heavy precipitation will continue.
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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Thursday
Stormy with strong winds and moderate to heavy rain and snow, heaviest south slopes of the Olympics.
Thursday
Night
Stormy with strong winds and moderate rain and snow, heaviest south slopes of the Olympics.
Thursday
Stormy with moderate to strong winds and moderate to heavy rain and snow.
Thursday
Night
Stormy with moderate to strong winds and moderate to occasionally heavy rain and snow.
Thursday
Stormy with moderate to strong winds and moderate to heavy rain and snow.
Thursday
Night
Stormy with moderate to strong winds and moderate to occasionally heavy rain and snow.
Thursday
Stormy with moderate to strong winds and moderate to occasionally heavy rain and snow. Rain and snow becoming lighter in the afternoon.
Thursday
Night
Periods of light to moderate rain and snow overnight. Moderate ridgeline winds.
Thursday
Moderate rain and snow this morning, becoming light to occasionally moderate in the afternoon. Moderate E-SE ridgeline and Pass level winds.
Thursday
Night
Periods of light to occasionally moderate rain and snow overnight. Moderate ridgeline winds. Moderate E-SE ridgeline and Pass level winds.
Thursday
Moderate rain and snow this morning, becoming light to occasionally moderate in the afternoon. Moderate E-SE ridgeline and Pass level winds.
Thursday
Night
Periods of light to occasionally moderate rain and snow overnight. Moderate ridgeline winds. Moderate E-SE ridgeline and Pass level winds.
Thursday
Moderate rain and snow this morning, becoming light to occasionally moderate in the afternoon. Moderate ridgeline winds.
Thursday
Night
Periods of light to occasionally moderate rain and snow overnight. Moderate ridgeline winds.
Thursday
Moderate rain and snow this morning, becoming light to occasionally moderate in the afternoon. Moderate ridgeline winds.
Thursday
Night
Periods of light to occasionally moderate rain and snow overnight. Moderate ridgeline winds.
Thursday
Moderate rain and snow this morning, becoming light to occasionally moderate in the afternoon. Moderate ridgeline winds.
Thursday
Night
Periods of light to occasionally moderate rain and snow overnight. Moderate ridgeline winds.
Thursday
Cloudy with light to occasionally moderate rain and snow this morning, becoming light in the afternoon. Moderate to strong ridgeline winds.
Thursday
Night
Periods of light rain and snow 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).