A broad ridge of high pressure continues to dominate our weather on Friday, featuring sunny skies and unseasonably mild temperatures. Modest low-level inversions in some deeper valleys and mountain gaps should un-invert by about 10 AM as full sunshine in most areas helps to mix the atmosphere. Expect light ridgeline winds for the northern half of the Cascades, but light to moderate ridgeline winds in some areas near the Cascade Crest from White Pass south to Mt Hood. Any cloudcover should be relegated to areas adjacent to the Canadian border and a low stratus deck below 500 ft in the Puget Sound Lowlands that mixes out as the day progresses. Expect little in the way of change Friday night as the ridge slides eastward, but low-level E flow increases slightly, strengthening the low-level cold pool somewhat east of the Cascade Crest.
Saturday starts sunny, but high clouds move in from the west during the mid-day hours and start to lower and thicken late in the day as an offshore trough drifts towards our nearshore waters. Ridgeline winds should decrease relative to Friday and the direction shifts from SW to SSW.
Throughout the next 36 hours, freezing levels will range between 7000 and 11000 ft, with the warmest temperatures in the southern Cascades.
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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Friday
Sunny and warm.
Friday
Night
Clear and mild.
Friday
A few mid-level clouds to start, then sunny and warm.
Friday
Night
Clear and mild.
Friday
Sunny and warm.
Friday
Night
Clear and mild.
Friday
Sunny and warm.
Friday
Night
Clear and mild. Light ridgeline and E wind at the Pass.
Friday
Sunny and warm. Light ridgeline and E wind at the Pass.
Friday
Night
Clear and mild. Light ridgeline and E wind at the Pass.
Friday
Sunny and warm. Light ridgeline and E wind at the Pass.
Friday
Night
Clear and mild.
Friday
Sunny and warm.
Friday
Night
Clear and mild.
Friday
Sunny and warm.
Friday
Night
Clear and mild.
Friday
Sunny and warm.
Friday
Night
Clear and mild.
Friday
Sunny and warm. Decreasing light to moderate ridgeline winds.
Friday
Night
Clear and mild. Light to moderate 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).