Thursday features the final day of our split flow pattern and dry weather as we eagerly anticipate a major weather pattern. The ridge axis of a transient ridge of high pressure shifts south into Oregon on Thursday, opening the door to increasing light WSW ridgeline winds. A subtle shortwave embedded in that ridge is bringing some high- and mid-level clouds, which should provide filtered sunshine (and possibly obscured skies) in the morning, with better chances of full sunshine midday into the early afternoon.
A weak frontal system approaches from the northwest on Thursday evening, spreading light rain and snow into the Olympics Mt Baker areas during the early morning hours. This light precipitation eases southeastward through Friday morning, reaching Snoqualmie Pass by 10 AM, and Mt Hood late in the day. Snow levels hover around 3000 ft in the morning, but bump up to around 3500 ft in the afternoon. Mt Baker stands to receive the most precipitation with around 0.5" of water equivalent, with the cold front reaching this region late in the day.
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
A mix of sunshine, filtered sunshine, and obscured skies.
Thursday
Night
High clouds lower and thicken with light snow developing in the early morning hours.
Thursday
A mix of sunshine, filtered sunshine, and obscured skies.
Thursday
Night
High clouds lower and thicken with light snow developing in the early morning hours.
Thursday
A mix of sunshine, filtered sunshine, and obscured skies.
Thursday
Night
High clouds lower and thicken.
Thursday
A mix of sunshine, filtered sunshine, and obscured skies.
Thursday
Night
Increasing clouds.
Thursday
A mix of sunshine, filtered sunshine, and obscured skies.
Thursday
Night
Increasing clouds. Increasing light ridgeline winds. Light W wind at the Pass.
Thursday
A mix of sunshine, filtered sunshine, and obscured skies.
Thursday
Night
Increasing clouds. Light to moderate ridgeline winds. Light W wind at the Pass.
Thursday
A mix of sunshine, filtered sunshine, and obscured skies.
Thursday
Night
Increasing clouds. Light to moderate ridgeline winds.
Thursday
A mix of sunshine, filtered sunshine, and obscured skies.
Thursday
Night
Increasing clouds. Light to moderate ridgeline winds.
Thursday
A mix of sunshine, filtered sunshine, and obscured skies.
Thursday
Night
Increasing clouds. Light to moderate ridgeline winds.
Thursday
A mix of sunshine, filtered sunshine, and obscured skies.
Thursday
Night
Mostly clear, then increasing clouds 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).