A ridge of high pressure will dominate Pacific Northwest weather through Thursday. A stable atmosphere combined with low relative humidities up to 10,000 ft should combine to limit the low-level afternoon cumulus development seen on Tuesday. Thin high clouds will move in from the west with some filtering of the sunlight expected by the afternoon for the Olympics and Mt. Baker. Wednesday started a few degrees warmer in most mountain locations than Tuesday. The exception is in cold valley locations where clear skies and light winds helped the cold air settle in. Washington Pass started the morning in the single digits with a modest inversion.
Temperates continue to moderate across the region Wednesday night as a warm front lifts into British Columbia. Mid and high clouds thicken somewhat across the region as a splitting front approaches the area and ridgeline winds remain light. Light E flow develops through the mountain gaps.
The closed low associated with the splitting front moves south toward California while a weak front ahead of a subtle trough brushes the area on Thursday. Expect a chance of very light rain/snow for the Olympics and a slight chance for Mt. Baker. Expect mostly light SW winds ahead of the front with S winds possibly getting into the moderate range for Mt. Baker. Obscured skies should cover NW Washington with filtered sunshine in most other areas. Temperatures should be slightly warmer than Wednesday and near seasonal norms.
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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Wednesday
Filtered sunshine.
Wednesday
Night
Increasing thin mid-level and high clouds.
Wednesday
Mostly sunny in the morning with filtered sunshine in the afternoon.
Wednesday
Night
Increasing thin mid-level and high clouds.
Wednesday
Mostly sunny.
Wednesday
Night
Increasing thin mid-level and high clouds.
Wednesday
Mostly sunny.
Wednesday
Night
Increasing thin mid-level and high clouds.
Wednesday
Mostly sunny. Light ridgeline and W wind at the Pass.
Wednesday
Night
Increasing thin mid-level and high clouds. Light ridgeline and E wind at the Pass.
Wednesday
Mostly sunny. Light to occasionally moderate ridgeline and light W wind at the Pass.
Wednesday
Night
Increasing thin mid-level and high clouds. Light ridgeline and E wind at the Pass.
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).