Sunday will be a quiet, transitional day. Mid-level moisture streams into the region in the form of a pervasive cloud deck ahead of a warm front rounding an offshore ridge. Snowfall arrives in the Olympics by mid-morning and spreads into the Cascades during the afternoon. Expect an abrupt jump in snow levels once the warm front lifts over the region from south to north Sunday night. Light generally E or SE winds near the Cascade Crest in advance of the front shift SSW behind it, ushering much warmer air. Snow levels jump from less than 3000 ft to around 7000-9000 ft behind the front. The central and northern Washington Cascades can expect moderate snowfall accumulations before this transition occurs. We're generally expecting more than 0.5" of water equivalent for Paradise and also Snoqualmie Pass northward on Sunday night.
Moisture continues to stream into the same general areas on a warm, moist, and brisk WSW, bringing another 0.5-1" of precipitation on Monday. Precipitation amounts remain light south of Mt Rainier and along the east slopes of the Cascades. Ridgeline winds ramp up into the moderate range for many areas late Sunday night and sustain on Monday. Expect strong gusts in exposed terrain near and 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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Sunday
Mid-level clouds lower and thicken with light to occasionally moderate rain and snow increasing through the afternoon.
Sunday
Night
Periods of light rain and snow.
Sunday
High clouds lower and thicken with a slight chance of snow late in the day.
Sunday
Night
Increasing moderate snow changing to rain at lower and middle elevations. Increasing moderate ridgeline winds.
Sunday
Increasing moderate-to-heavy snow transitioning to rain at lower and middle elevations. Increasing moderate ridgeline winds.
Sunday
Night
Increasing moderate-to-heavy snow transitioning to rain at lower and middle elevations. Increasing moderate ridgeline winds.
Sunday
High clouds lower and thicken with light snow developing in the afternoon.
Sunday
Night
Periods of light rain and snow (moderate at Paradise). Rapidly rising snow levels. Increasing moderate ridgeline winds.
Sunday
High clouds lower and thicken. Light snow develops in the afternoon. Increasing light ridgeline and E wind at the Pass.
Sunday
Night
Moderate rain and snow. Rapidly rising snow levels. Increasing moderate ridgeline and light W or variable wind at the Pass.
Sunday
High clouds lower and thicken. Light snow develops in the afternoon. Increasing light ridgeline and E wind at the Pass.
Sunday
Night
Moderate rain and snow. Rapidly rising snow levels. Increasing moderate ridgeline and light W or variable wind at the Pass.
Sunday
High clouds lower and thicken. Light snow develops late in the day.
Sunday
Night
Increasing light snow changing to rain at lower elevations. Increasing moderate ridgeline winds.
Sunday
High clouds lower and thicken. Light snow develops in the afternoon.
Sunday
Night
Increasing light-to-moderate snow changing to rain at lower and middle elevations. Increasing moderate ridgeline winds.
Sunday
High clouds lower and thicken. Light rain and snow develop in the afternoon.
Sunday
Night
Increasing light snow changing to rain at most elevations. Increasing moderate ridgeline winds.
Sunday
Periods of very light rain and snow from late morning onward.
Sunday
Night
Periods of very light rain and snow. Rapidly rising snow levels. Increasing moderate ridgeline winds may become strong.
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).