A departed trough gets replaced by an expanding offshore high pressure to bring us some dry and increasingly very mild weather this weekend.
NW winds aloft have relented gradually Friday night, but continue to bring some moderate to locally strong winds to locations near and east of the Cascade Crest through the morning hours. Low-level W flow should gradually decrease, spawning some sprinkles/flurries from Snoqualmie Pass to the Canadian border to gradually decrease. Very weak convergence also lingers just north of Highway 2.
The expanding high pressure combined with a gradual shift toward easterly low-level flow by the evening should dry the region out by the afternoon; low clouds get replaced by a mix of high clouds and sunshine. Full sunshine should be more common across southern Washington and Northern Oregon.
The high pressure has already started warming temperatures at upper levels in the Mt. Hood area where freezing levels have risen above the highest chairlifts (with a low-level inversion likely to remain through the morning hours). The Olympics can expect a rise in temperatures during the afternoon. Elsewhere, freezing levels should skyrocket overnight as high clouds increase. Shallow inversions maintain cooler air at low elevations as low clouds form in the valleys.
Inversions mostly dissipate Sunday morning with filtered sunshine and freezing levels relatively steady into the 7500-10000 ft range.
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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Saturday
A few low clouds dissipate early, then filtered sunshine with a mix of mid and high-layer clouds.
Saturday
Night
A mix of thin high and mid-level clouds. Inversion developing with low cloud and fog in the lowlands.
Saturday
Mostly cloudy in the morning with partial clearing in the afternoon.
Saturday
Night
A mix of thin high and mid-level clouds. Inversion developing with low cloud and fog in the lowlands.
Saturday
Mostly cloudy in the morning with partial clearing in the afternoon.
Saturday
Night
A mix of thin high and mid-level clouds. Inversion developing with low cloud and fog in the lowlands.
Saturday
Mostly cloudy in the morning with mostly clear skies and filtered sunshine by the afternoon. Strong ridgeline winds early in the day near the Cascade Crest.
Saturday
Night
Mostly clear skies with some high clouds. Inversion developing with low cloud and fog in the lowlands.
Saturday
Mostly cloudy in the morning with partial clearing in the afternoon. Light W wind switching east late in the day at the Pass.
Saturday
Night
A mix of thin high and mid-level clouds. Inversion developing with low cloud and fog in the lowlands. Light E wind at the Pass.
Saturday
Mostly cloudy in the morning with partial clearing in the afternoon. Light W wind switching east late in the day at the Pass. Strong ridgeline wind gusts early in the day.
Saturday
Night
A mix of thin high and mid-level clouds. Inversion developing with low cloud and fog in the lowlands. Light E wind at the Pass.
Saturday
Partly cloudy in the morning, then becoming mostly clear with filtered sunshine in the afternoon. Strong ridgeline wind gusts early in the day.
Saturday
Night
A mix of thin high and mid-level clouds. Inversion developing.
Saturday
Partly cloudy in the morning, then becoming mostly clear with filtered sunshine in the afternoon. Strong ridgeline wind gusts early in the day.
Saturday
Night
A mix of thin high and mid-level clouds. Inversion developing.
Saturday
Partly cloudy in the morning, then becoming mostly clear with filtered sunshine in the afternoon. Strong ridgeline wind gusts early in the day.
Saturday
Night
Mostly clear skies with some high clouds. Inversion developing.
Saturday
Low clouds banked against the west slopes of Mt. Hood. Otherwise mostly sunny. Strong ridgeline wind gusts early in the day.
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).