The Pacific NW remains dominated by a cold trough over the western US. A number of smaller-scale circulation centers dictate the weather across the region, leading significant variability. A circulation center in eastern Idaho extends a deformation band of light snowfall northwest all the way into the Washington Pass area. This band of snow should be slow to exit the area and may bring an additional 1-4" of snow to Washington Pass and Mazama. E winds re-develop as this circulation drifts east later in the day. Another circulation center over southern Oregon gradually shifts northward bringing light snowfall to Mt. Hood from mid-morning through the evening hours with light snow shifting into areas of Washington south of I-90 during the evening hours as well. The original low weakening offshore continues to bring some very light snow showers into the southern Olympics.
Expect partially clearing skies later Sunday night into Monday morning before some instability convective showers develop as some moisture rotates into the region during the afternoon hours.
Temperatures remain cold, but with better chances for sunshine at times Monday and Tuesday expect freezing levels to rise to around 3000 ft during the afternoon hours, but any precipitation will remain frozen above around 1500 ft.
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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Sunday
Partly cloudy.
Sunday
Night
Mostly cloudy with a chance of light snow at times.
Sunday
Mostly cloudy with a slight chance of light snow.
Sunday
Night
Partly cloudy.
Sunday
Partly cloudy to mostly cloudy.
Sunday
Night
Partly cloudy.
Sunday
Mostly cloudy with clouds increasing late in the day.
Sunday
Night
Periods of light snow.
Sunday
Mostly cloudy. Light ridgeline and W switching E winds at the Pass.
Sunday
Night
Mostly cloudy. Light ridgeline and E wind at the Pass.
Sunday
Mostly cloudy. Light ridgeline and W switching E winds at the Pass.
Sunday
Night
Mostly cloudy. Light ridgeline and E wind at the Pass.
Sunday
Light to occasionally moderate snow.
Sunday
Night
Mostly cloudy.
Sunday
A few snow flurries in the morning, then becoming mostly cloudy.
Sunday
Night
Mostly cloudy with a few snow flurries.
Sunday
Partly cloudy in the morning, then becoming mostly cloudy.
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).