Unseasonably warm weather continues, with each system arriving on the SW flow, lifting a warm front across our region and then a cold front.
Friday afternoon's frontal passage leaves light post-frontal rain and higher-elevation snow showers in the evening, tapering overnight. Expect brisk WSW winds behind the front, accelerating down the east slopes of the Cascades, helping scour lingering cold air east of the crest and raising snow levels at Washington Pass and along the east slopes.
Temperatures peak on Saturday as a warm front brushes the region. A few hours of rain and high-elevation snow begin near Mount Rainier early in the morning and into the north Cascades by late morning, with precipitation exiting north into Canada by the evening. As the day progresses, filtered sunshine expands northward, reaching Snoqualmie Pass by afternoon. Winds will be light in most areas, but pick up into the moderate range during the afternoon for the Olympics and Mt Baker areas ahead of the trailing cold front. This front stalls over the Olympics, with southerly flow focusing precipitation on the southern portions of the range while the Cascades stay mostly dry until the early morning areas when precipitation starts up around Mt Baker. Conditions turn slightly cooler as the front progresses eastward, with snow levels starting near 5,000 ft and lowering later in the day following the frontal passage and associated SSW to WSW wind shift. Before the wind shift, expect moderate to strong ridgeline winds in the Mt Baker area with light to moderate winds in most other areas.
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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Friday
Night
A few showers are possible in the early evening, then mostly cloudy skies.
Saturday
A band of rain and high elevation snow moves through early in the day, then mostly cloudy skies. Moderate ridgeline winds develop in the afternoon.
Friday
Night
Decreasing light rain and higher elevation snow showers.
Saturday
A band of light to moderate rain and higher elevation snow moves through in the late morning through early afternoon hours, coinciding with a period of moderate ridgeline winds.
Friday
Night
Decreasing light rain and higher elevation snow showers.
Saturday
A band of rain and higher elevation snow moves through in the late morning hours.
Friday
Night
Decreasing light rain and higher elevation snow showers.
Saturday
A band of mostly light rain and higher-elevation snow moves through early in the day, then skies mostly clear, leaving filtered sunshine.
Friday
Night
Light rain and higher elevation snow showers taper or end. Light to moderate ridgeline winds. Light W winds shift E at the Pass overnight.
Saturday
A band of mostly light rain and higher-elevation snow moves through in the mid-morning hours, then skies mostly clear, leaving filtered sunshine. Light ridgeline and E wind at the Pass.
Friday
Night
Light rain and higher elevation snow showers taper or end. Moderate ridgeline winds. Light W winds shift E at the Pass overnight.
Saturday
A band of mostly light rain and higher-elevation snow moves through in the mid-morning hours, then skies mostly clear, leaving filtered sunshine. Light ridgeline and E wind at the Pass.
Friday
Night
Light rain and snow showers mainly during the evening hours. Decreasing light to moderate ridgeline winds.
Saturday
A band of mostly light rain and higher-elevation snow moves through in the mid-morning hours, then skies mostly clear, leaving filtered sunshine. Light ridgeline and E wind at the Pass.
Friday
Night
A band of light rain and snow moves through in the midday hours.
Saturday
A few sprinkles or flurries through mid-morning, then skies mostly clear, leaving filtered sunshine.
Friday
Night
Light rain and snow showers mainly during the evening hours. Decreasing moderate ridgeline winds.
Saturday
A few sprinkles or flurries early, then skies mostly clear, leaving filtered sunshine.
Post-frontal light rain and snow showers continue Sunday evening. A weakening low-pressure center tracking into southern British Columbia on Monday will bring a round of light precipitation to our region Monday through the evening hours. The ridge rebuilds overnight, bringing dry, warm sunny weather starting Tuesday.
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).