The Pacific Northwest will experience dry, mostly sunny weather Tuesday through Wednesday, sitting in a quiescent wedge between more active weather to the north, west, and south. Monday's weak trough has lifted north into British Columbia, taking the last of the precipitation with it before 7 AM. Partly cloudy skies remain banked against the west slopes of the Cascades before 10 AM. Meanwhile, a closed low drops southward well offshore, entering the orbit of a stronger closed low spinning off the coast of California. High cloud cover associated with this system will bring filtered sunshine to Mt Hood and areas of southern Washington, mainly south of Highway 12, on Tuesday. Although a shift to E and SE ridgeline winds has been slower than forecast to materialize, we still expect this to occur by late Tuesday morning, peaking Tuesday afternoon. Most of these winds will be light, but expect moderate gusts at times around Mt Hood. The split flow pattern favors a gradual overall warming trend, with the wind direction accelerating warming in areas west of the Cascade Crest.
The split in the flow widens Tuesday night, fully clearing skies. ESE ridgeline winds gradually ease, allowing for weak low-level cold air pooling east of the Cascade Crest. These shallow inversions will keep freezing levels low through the mountain gaps.
After a cool start for most areas Wednesday morning, a tongue of a ridge moving into the area will push freezing levels to around 5500-6000 ft by the afternoon in areas above pockets of cold pool that linger east of the Cascade Crest.
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
Partly cloudy before 10 AM, then mostly sunny skies.
Tuesday
Night
Mostly clear.
Tuesday
Partly cloudy before 10 AM, then mostly sunny skies.
Tuesday
Night
Mostly clear skies.
Tuesday
Partly cloudy before 10 AM, then mostly sunny skies.
Tuesday
Night
Mostly clear skies.
Tuesday
Mostly sunny with filtered sunshine at times south of Highway 12.
Tuesday
Night
Mostly clear skies.
Tuesday
Mostly sunny. Light ridgeline winds. Variable winds at the Pass shift E and remain light at the Pass.
Tuesday
Night
Mostly clear. Light ridgeline and E wind at the Pass.
Tuesday
Mostly sunny. Light ridgeline winds. Variable winds at the Pass shift E and remain light at the Pass.
Tuesday
Night
Mostly clear. Light ridgeline and E wind at the Pass.
Tuesday
A few clouds early, then mostly sunny skies in the afternoon.
Tuesday
Night
Mostly clear. Inversions strengthening.
Tuesday
Mostly sunny skies.
Tuesday
Night
Mostly clear.
Tuesday
Mostly sunny with filtered sunshine south of highway 12.
Tuesday
Night
Mostly clear.
Tuesday
Filtered sunshine with obscured skies at times. Increasing 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).