A ridge of high pressure dominates the region, keeping all but very low clouds and very high clouds at bay.
Depending on your trailhead it could be cold and even socked in to start on Thursday. Rest assured, it's much sunnier and warmer above. With easterly flow, the low clouds and fog hold strong in the eastern forecast zones and Stevens/Snoqualmie Pass. West of the crest and near Mt Hood, morning fog remains more limited and should burn off and become patchy. While freezing levels soar as the ridge shifts inland, air temperatures only top out in the upper 30s to low 40s.
Clouds begin to increase, thicken, and lower overnight ahead of a fast-moving storm with precipitation beginning before daybreak in the Olympics. The main frontal band should bring a round of precipitation from 4-10 AM with moderate to strong SW winds. Most locations west of the Cascade Crest start as rain, but E flow is likely to keep the passes "wet" snow before the mid-morning frontal passage. Snow levels could bump up to 3500 ft just behind the front before re-descending to 3000 ft in the central Cascades as a moist NW flow brings moderate snow showers. We'll have to monitor the timing and strength of a Puget sound convergence zone likely to form between Stevens and Snoqualmie Passes later in the day, just as precipitation is starting to slow down.
We're expecting 2-8" of snow by the end of the day Friday for the west slopes and passes with 1-4" for the east slopes.
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
Warm with increasing high clouds. Valley fog is possible in some areas.
Thursday
Night
Mild. High clouds lower and thicken with a chance of light rain and snow in the early morning hours with moderate ridgeline winds developing.
Thursday
Warm with increasing high clouds.
Thursday
Night
Mild. High clouds lower and thicken. Moderate ridgeline winds develop overnight.
Thursday
Warm with increasing high clouds.
Thursday
Night
Mild. High clouds lower and thicken. Moderate ridgeline winds develop by morning.
Thursday
Warm with increasing high clouds.
Thursday
Night
Mild. High clouds lower and thicken. Moderate ridgeline winds develop overnight.
Thursday
High clouds. Warm above 5000 ft, but chilly below. Light to occasionally moderate ridgeline and E winds at the Pass.
Thursday
Night
High clouds lower and thicken. Light ridgeline and E winds at the Pass.
Thursday
High clouds. Warm above 5000 ft, but chilly below. Low cloud likely below 4000 ft. Moderate ridgeline and light to moderate E winds at the Pass.
Thursday
Night
High clouds lower and thicken. Light ridgeline and E winds at the Pass.
Thursday
High clouds. Warm above 6000 ft, but chilly below.
Thursday
Night
High clouds lower and thicken. Inversion conditions.
Thursday
Increasing high clouds. Warm above 5500 ft, but chilly below. Low cloud deck in the 2000-4000 ft range.
Thursday
Night
High clouds lower and thicken. Low cloud deck in the 2000-4000 ft range.
Thursday
Increasing high clouds. Warm above 5500 ft, but chilly below. Low cloud deck in the 2000-4000 ft range.
Thursday
Night
High clouds lower and thicken. Low cloud deck in the 2000-4000 ft range.
Thursday
Increasing high clouds. Warm above 5500 ft, but chilly below.
Thursday
Night
High clouds lower and thicken. Low cloud deck in the 2000-4000 ft range.
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).