Very active weather continues for the next 36 hours. On Thursday, a Post-frontal W flow behind Wednesday night's frontal passage will bring locally intense convective rain and snow showers to areas near and west of the Cascades Crest. With cooler air moving in aloft, expect increased convection, higher snow-to-liquid ratios, and periods of graupel. Moderate WSW winds will continue to buffet the region.
A developing storm system focuses more of the precipitation on the southern Cascades and the Olympics as we head late in the day. That moderate to heavy precipitation will spread northward during the evening hours as a warm and cold frontal package moves onshore with moderate to locally strong WSW winds. Expect a bump in snow levels to 3000-4500 ft. WSW winds continue on Friday with post-frontal vigorous showers. A pulse moving north along a stalled frontal boundary in the southern portion of the forecast region could bring some heavier sustained snowfall to southern portions of the forecast region in the afternoon.
The west slopes of the Cascades can expect 1-2 ft of snow through the end of the work week above the rain-snow line. The east slopes of the Cascades and Hurricane Ridge can expect 6-18".
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
Light to moderate rain and snow showers. Decreasing light to moderate ridgeline winds.
Thursday
Night
Moderate rain and snow peaking during the evening. Moderate ridgeline winds.
Thursday
Moderate convective rain and snow showers. Light to moderate ridgeline winds.
Thursday
Night
Moderate to heavy rain and snow. Moderate ridgeline winds.
Thursday
Decreasing moderate rain and snow showers. Decreasing moderate ridgeline winds.
Thursday
Night
Moderate to heavy rain and snow. Moderate ridgeline winds.
Thursday
Decreasing moderate rain and snow showers. Decreasing moderate ridgeline winds.
Thursday
Night
Moderate to heavy rain and snow. Moderate ridgeline winds.
Thursday
Moderate convective rain and snow showers become generally light by the afternoon. Light to moderate ridgeline and light W wind at the Pass.
Thursday
Night
Increasing moderate rain and snow. Light to moderate ridgeline and light W wind at the Pass could shift E at times overnight.
Thursday
Moderate convective rain and snow showers become generally light by the afternoon. Decreasing moderate ridgeline and light to moderate W wind at the Pass.
Thursday
Night
Increasing moderate to heavy rain and snow. Moderate ridgeline and light W wind at the Pass could switch E at times overnight.
Thursday
Decreasing light rain and snow showers. Moderate ridgeline winds.
Thursday
Night
Increasing light to moderate rain and snow. Moderate ridgeline winds.
Thursday
Decreasing light rain and snow showers. Moderate ridgeline winds.
Thursday
Night
Increasing light to moderate rain and snow. Moderate ridgeline winds.
Thursday
Decreasing light rain and snow showers. Moderate ridgeline winds.
Thursday
Night
Increasing mostly light rain and snow. Moderate ridgeline winds.
Thursday
Moderate convective rain and snow showers. Moderate to strong ridgeline winds.
Thursday
Night
Moderate to heavy rain and snow showers. Moderate to strong 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).