Inactive weather continues across the Pacific Northwest through the end of the work week. A blocking high centered 500-1000 miles off of Vancouver Island continues to force the jetstream north to Alaska. A stationary cutoff low to the south of the high helps maintain the pattern. Thursday morning starts with clear skies and temperatures in the 20s for most mountain locations. Weak inversions exist in some locations, particularly colder mountain valleys where temperatures have dropped into the 10s in some locations. Dry northerly flow remains over the region. Meanwhile, descending air associated with the high to our west should warm mid and upper elevations to the west of the Cascade Crest with afternoon freezing levels in these locations rising to 5000-7500 ft. Meanwhile, the cold pool to the east of the Cascades continues to thicken and strengthen. Easterly flow keeps this cold air streaming through the mountain gaps. Easterly gradients peak Thursday night, with moderate E flow.
Under clear skies, temperatures should cool off in most locations Thursday night. Friday looks similar to Thursday, but upper-level flow turns NWerly as a trough begins to slide down the Canadian Rockies. Temperatures warm further with freezing levels about 2000 ft higher than Thursday throughout the region. High clouds may begin to arrive later 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
Mostly sunny.
Thursday
Night
Mostly clear with a weak inversion.
Thursday
Mostly sunny with a few high clouds in the morning.
Thursday
Night
Mostly clear with a weak inversion.
Thursday
Mostly sunny.
Thursday
Night
Mostly clear with a weak inversion.
Thursday
Mostly sunny.
Thursday
Night
Mostly clear with a weak inversion.
Thursday
Mostly sunny. Light to occasionally moderate ridgeline and E winds at the Pass.
Thursday
Night
Mostly clear with a weak inversion. Light to moderate ridgeline and E winds at the Pass.
Thursday
Mostly sunny. Light to moderate ridgeline and E winds at the Pass.
Thursday
Night
Mostly clear with a weak inversion. Light to moderate ridgeline and E winds at the Pass.
Thursday
A few high clouds in the morning, then becoming mostly sunny.
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).