The high pressure nearly parked over our region for a week gradually retreats southeastward through Saturday, opening the door to a storm system impacting the region on Sunday.
The retreating high pressure allows freezing levels to gradually lower from the 9000-10500 ft range today to the 6000-8500 ft range on Saturday. While areas west of the Cascade Crest continue to enjoy these warm temperatures, locations up to around 4000-4500 ft on the east slopes of the Cascades remain under the influence of a strong inversion with temperatures in the 10s and low 20s early Friday morning at low elevations and temperatures in the 40s above. You'll really want to bundle up if you're heading to one of the passes as decreasing moderate winds driven by an easterly pressure gradient continue to usher the cold air through the mountain gaps creating windchill near 0F. Light to moderate SW winds continue to ride over the inversion but have yet to mix down. With a cloud deck insulating in the surface from warming over eastern Washington, don't expect significant mixing of this inversion layer on Friday. It may take until Saturday afternoon as SW winds and low-level pressure gradients begin to increase further ahead of the next frontal system for the inversion to weaken.
Expect sunny/clear skies over the next 36 hours with high clouds becoming more widespread by Saturday.
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
Mostly sunny with some high clouds. Shallow low-level inversion mixing out by the afternoon.
Friday
Night
Mostly clear with some high clouds. Strengthening low-level inversion.
Friday
Mostly sunny with some high clouds. Shallow low-level inversion mixing out by the afternoon.
Friday
Night
Mostly clear with some high clouds. Strengthening low-level inversion.
Friday
Mostly sunny with some high clouds. Shallow low-level inversion mixing out by the afternoon.
Friday
Night
Mostly clear with some high clouds. Strengthening low-level inversion.
Friday
Mostly sunny with a few high clouds. Shallow low-level inversion mixing out by the afternoon.
Friday
Night
Mostly clear with some high clouds. Strengthening low-level inversion.
Friday
Mostly sunny with high clouds at times. Shallow low-level inversion mixing out by the afternoon. Decreasing light to occasionally moderate E winds at the Pass.
Friday
Night
Mostly clear with some high clouds. Strong low-level inversion. Decreasing light E winds at the Pass.
Friday
Mostly sunny with high clouds at times. Shallow low-level inversion mixing out by the afternoon. Decreasing moderate E winds at the Pass.
Friday
Night
Mostly clear with some high clouds. Strong low-level inversion. Decreasing light to occasionally moderate E winds at the Pass.
Friday
Mostly sunny with high clouds at times. Very strong inversion slightly decreasing in strength by the afternoon.
Friday
Night
Mostly clear with some high clouds. Very strong low-level inversion.
Friday
Mostly sunny with a few high clouds. Very strong inversion slightly decreasing in strength by the afternoon.
Friday
Night
Mostly clear with some high clouds. Very strong low-level inversion.
Friday
Mostly sunny with high clouds at times. Very strong inversion slightly decreasing in strength by the afternoon.
Friday
Night
Mostly clear with some high clouds. Very strong low-level inversion.
Friday
Mostly sunny. Inversion slightly decreasing in strength by the afternoon.
Friday
Night
Mostly clear with some high clouds. Strong low-level inversion.
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).