High pressure continues to dominate as the high-pressure center shifts onshore over Oregon today. With the high pressure centered on our region, expect increased sinking air and the highest freezing levels our region has experienced since last weekend. In most areas, freezing levels will rise to around 10,000 ft Thursday night and Friday morning before decreasing slightly during the afternoon. Thin high clouds may be present over Washington State on Thursday and they should become more widespread on Friday.
A surface high pressure over the Columbia Basin will drive moderate E flow through the mountain gaps on Thursday. Low clouds and low-elevation temperatures in the teens and low twenties should continue to get sucked through the mountain gaps with a strong inversion in place east of the Cascades. The inversion should moderate by the afternoon but will strengthen once again Thursday night.
The high-pressure center shifts SE toward the Great Basin on Friday. More SWerly winds aloft will help temperatures moderate east of the Cascade Crest during the day on Friday, but the inversion will still keep low-level temperatures cold in the morning.
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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Thursday
Mostly sunny with thin high clouds. Inversion mixing out by late morning with low clouds decreasing in deep valleys by the afternoon.
Thursday
Night
Clear with thin high clouds. Inversion re-forming along with low clouds in deep valleys.
Thursday
Mostly sunny with thin high clouds. Inversion mixing out by late morning with low clouds decreasing in deep valleys by the afternoon.
Thursday
Night
Clear with thin high clouds. Inversion re-forming along with low clouds in deep valleys.
Thursday
Mostly sunny with thin high clouds. Inversion mixing out by late morning with low clouds decreasing in deep valleys by the afternoon.
Thursday
Night
Clear with thin high clouds. Inversion re-forming along with low clouds in deep valleys.
Thursday
Mostly sunny with thin high clouds. Inversion mixing out by late morning with low clouds decreasing in deep valleys by the afternoon.
Thursday
Night
Clear with thin high clouds. Inversion re-forming along with low clouds in deep valleys.
Thursday
Mostly sunny with thin high clouds. Inversion mixing out and low cloud dissipating at Pass level by late morning. Light to occasionally moderate E wind at the Pass.
Thursday
Night
Clear with thin high clouds. Inversion re-forming along with low clouds in deep valleys. Decreasing light E wind at the Pass.
Thursday
Mostly sunny with thin high clouds. Inversion mixing out by late morning. Moderate E wind at the Pass.
Thursday
Night
Clear with thin high clouds. Inversion re-forming along with low clouds in deep valleys. Decreasing light to moderate E wind at the Pass.
Thursday
Mostly sunny with thin high clouds. Strong inversion mixing out by late morning with low clouds possibly decreasing in deep valleys during the afternoon.
Thursday
Night
Clear with thin high clouds. Inversion re-forming along with low clouds in deep valleys.
Thursday
Mostly sunny with thin high clouds. Strong inversion mixing out by late morning with low clouds possibly decreasing in deep valleys during the afternoon.
Thursday
Night
Clear with thin high clouds. Inversion re-forming along with low clouds in deep valleys.
Thursday
Mostly sunny with thin high clouds. Strong inversion mixing out by late morning with low clouds possibly decreasing in deep valleys during the afternoon.
Thursday
Night
Clear with thin high clouds. Inversion re-forming along with low clouds in deep valleys.
Thursday
Sunny. Inversion mixing out by late morning with low clouds possibly decreasing in deep valleys during the afternoon.
Thursday
Night
Clear with a few high clouds by morning. Inversion re-forming along with low clouds in deep valleys.
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).