The Pacific Northwest enters an extended period of relatively mild and unusually benign weather pattern as we start the work week.
The weak shortwave trough that brushed the area Sunday night exits the region to the south and east. This feature brings some mid-level cloud cover that should pass pass through the central and southern Cascades during the morning hours. Low cloud cover lingering in the Puget Sound lowlands below 5000 ft should also gradually dissipate. Expect partly to mostly sunny skies across the region by the afternoon. Most NWAC stations range from the upper 20s to mid-30s early Monday morning - quite mild for early December. Temperatures should rise slightly by mid-day as a begins to build offshore, but a low-level shift to light E flow should begin a cooling trend along the E slopes of the Cascades and for low levels in the mountain gaps.
Expect mostly clear skies Monday night as the ridge expands and shifts toward the coast on Tuesday for mostly sunny skies. Expect a seasonably chilly start along the E slopes of the Cascades with milder air west of the Cascade Crest. Freezing levels should rise to around 9000 ft over the Olympics by the afternoon. Expect more variable temperatures for the Cascades with multiple freezing levels and much cooler temperatures for the east slopes and passes. In the passes, you might start the day below freezing at Pass level with an increasing E wind becoming moderate strength by mid-morning, so dress warmly. Temperatures may rise as you ascend to higher elevations.
Weather Forecast
Olympics
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Stevens Pass
Snoqualmie Pass
East North
East Central
East South
Mt. Hood
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Monday
Hurricane Ridge sits near the top of a 5000 ft cloud deck. The cloud deck should break up during the afternoon. Light ridgeline winds.
Monday
Night
Mostly clear. Light ridgeline winds.
Monday
Mostly sunny with low clouds in the valleys. Light ridgeline winds.
Monday
Night
Mostly clear. Light ridgeline winds.
Monday
Mostly sunny with low clouds in the valleys. Light ridgeline winds.
Monday
Night
Mostly clear. Light ridgeline winds.
Monday
Mostly to partly cloudy below 5000 ft in the morning, with sunny skies above. Low clouds gradually decrease as the day progresses. Light ridgeline winds.
Monday
Night
Mostly clear. Light ridgeline winds.
Monday
Mostly cloudy early with the peaks above the cloud deck, then becoming partly cloudy to mostly sunny. Light ridgeline and very light W wind shifting E at the pass around mid-morning.
Monday
Night
Mostly clear. Light ridgeline winds and increasing light E winds at the Pass.
Monday
Mostly cloudy early with the peaks above the cloud deck, then becoming partly cloudy in the afternoon. Light ridgeline and very light W wind shifting E at the pass around mid-morning.
Monday
Night
Mostly clear. Light ridgeline winds and increasing light E winds at the Pass.
Monday
Mostly sunny. Light ridgeline winds.
Monday
Night
Mostly clear. Light ridgeline winds.
Monday
Partly cloudy early, then becoming mostly sunny. Light ridgeline winds.
Monday
Night
Mostly clear. Light ridgeline winds.
Monday
Partly cloudy early, then becoming mostly sunny. Light ridgeline winds.
Monday
Night
Mostly clear. Light ridgeline winds.
Monday
Mostly cloudy early, then becoming mostly sunny by late morning. Low clouds may linger much of the day below 5000 ft. Light 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).