A ridge of high pressure remains centered over the region and will shift only slightly eastward through Wednesday. The result will be a gradual evolution of the weather pattern, thanks to a shift to SW winds aloft, which brings milder air into the region. However, the cold air pool east of the Cascades remains difficult to displace. The resulting battleground between the air mass occurs near the Cascade Crest and the mountain gaps in horizontal space, but also in the vertical dimension. Expect below-freezing temperatures below 5000-6000 ft near and east of the Cascade Crest, with temperatures firmly above freezing up until 11-12,500 ft within the thick tongue of warm air spilling over the top.
Don't expect much change in the pattern Saturday night or Sunday, but the cold pool may thin slightly. The freezing level top might drop around 1,000 ft by Wednesday. Expect periods of high clouds to increase over the northern half of Washington State on Tuesday and linger over similar areas through Wednesday, with mostly sunny skies farther south.
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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Tuesday
Increasing high clouds. Mild.
Tuesday
Night
Thin, high clouds in the evening, then clearing overnight.
Tuesday
Mostly sunny to start, then increasing high clouds. Mild.
Tuesday
Night
Thin high clouds. Mild.
Tuesday
Mostly sunny to start, then increasing high clouds. Mild.
Tuesday
Night
Thin high clouds. Mild.
Tuesday
Mostly sunny. Mild.
Tuesday
Night
Mostly clear.
Tuesday
Mostly sunny to start, then increasing high clouds by late morning. Warm above 5000-6000 ft, cold below. Decreasing moderate to strong ridgeline and light to moderate E winds at the Pass.
Tuesday
Night
Thin high clouds. Warm above 5000-6000 ft, cold below. Decreasing mostly light ridgeline and E wind at the Pass.
Tuesday
Mostly sunny to start, then increasing high clouds by late morning. Warm above 5000-6000 ft, cold below. Decreasing light to moderate ridgeline and E wind at the Pass.
Tuesday
Night
Thin high clouds. Warm above 5000-6000 ft, cold below. Decreasing light to moderate ridgeline and E wind at the Pass.
Tuesday
Mostly sunny to start, then increasing high clouds by late morning. Warm above 5000-6000 ft, cold below.
Tuesday
Night
Thin high clouds. Warm above 5000-6000 ft, cold below.
Tuesday
Mostly sunny to start, then increasing high clouds by late morning. Warm above 5000-6000 ft, cold below.
Tuesday
Night
Thin high clouds. Warm above 5000-6000 ft, cold below.
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).