We'll see a near repeat of Saturday as a cold upper low rotates snow showers inland today. Showers will become more widespread and will feature some pulses of higher snowfall rates in the afternoon and early evening thanks to a cold unstable air mass, daytime heating, and a weak upper level disturbance. Most areas should see a few inches of low density snow before sunset, with the Olympics, closer to the low, once again serving up a more moderate serving of new snow. Snowfall amounts will taper quickly the further east of the Cascade crest.
The upper low will slowly sink south tonight and Monday and colder air from the interior of British Columbia will start to seep out of the Fraser Valley and along the east slopes of the Cascades. We may see a more focused area of snow showers for the western Cascades of Whatcom and Skagit Counties tonight as onshore flow combines with Fraser Outflow, but otherwise snow showers will become isolated overnight.
On Monday, expect slightly chillier temperatures with widespread teens for daytime highs at mid-elevations and single digits or colder at upper elevations. We'll see more pop-up daytime light showers in the afternoon, except slightly cloudier and steadier light snow along the east slopes of the Cascades with light upslope flow.
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
Cloudy with light to occasionally moderate snow showers. Light to moderate ridgeline winds.
Sunday
Night
Cloudy with light to occasionally moderate snow showers. Light ridgeline winds.
Sunday
Cloudy with scattered light snow showers in the morning, then light to occasionally moderate snow showers in the afternoon. Light to moderate ridgeline winds.
Sunday
Night
Cloudy with light to occasionally moderate snow showers. Light to moderate ridgeline winds.
Sunday
Cloudy with scattered light snow showers in the morning, then light to occasionally moderate snow showers in the afternoon. Light to moderate ridgeline winds.
Sunday
Night
Cloudy with light to occasionally moderate snow showers. Light ridgeline winds.
Sunday
Mostly cloudy with scattered light snow showers in the morning, then light to occasionally moderate snow showers in the afternoon. Moderate ridgeline winds.
Sunday
Night
Cloudy with light to occasionally moderate snow showers in the evening, then mostly cloudy with scattered light showers late evening. Light to moderate ridgeline winds.
Sunday
Mostly cloudy with scattered light snow showers in the morning, then light to occasionally moderate snow showers in the afternoon. Light to moderate W ridgeline winds, light W winds at Pass level.
Sunday
Night
Cloudy with light to occasionally moderate snow showers in the evening, then mostly cloudy with scattered light showers late evening. Light to moderate W ridgeline winds, light E winds at Pass level.
Sunday
Mostly cloudy with scattered light snow showers in the morning, then light to occasionally moderate snow showers in the afternoon. Light to moderate W ridgeline winds, light W winds at Pass level.
Sunday
Night
Cloudy with light to occasionally moderate snow showers in the evening, then mostly cloudy with scattered light showers late evening. Light to moderate W ridgeline winds, light E winds at Pass level.
Sunday
Mostly cloudy with isolated light snow showers in the morning near the Cascade crest and partly sunny further east. Light to occasionally moderate snow showers in the afternoon, showers more widespread near the Cascade crest. Light ridgeline winds.
Sunday
Night
Cloudy with light to occasionally moderate snow showers in the evening, then mostly cloudy with scattered light showers late evening. Light to moderate ridgeline winds.
Sunday
Mostly cloudy with isolated light snow showers in the morning near the Cascade crest and partly sunny further east. Light to occasionally moderate snow showers in the afternoon, showers more widespread near the Cascade crest. Light to moderate ridgeline winds.
Sunday
Night
Cloudy with light to occasionally moderate snow showers in the evening, then mostly cloudy with scattered light showers late evening. Light to moderate ridgeline winds.
Sunday
Mostly cloudy with isolated light snow showers in the morning near the Cascade crest and partly sunny further east. Light to occasionally moderate snow showers in the afternoon, showers more widespread near the Cascade crest. Moderate ridgeline winds.
Sunday
Night
Cloudy with light to occasionally moderate snow showers in the evening, then mostly cloudy with scattered light showers late evening. Light to moderate ridgeline winds.
Sunday
Mostly cloudy with isolated light snow showers in the morning, then light to occasionally moderate snow showers in the afternoon. Moderate to occasionally strong ridgeline winds.
Sunday
Night
Cloudy with light to occasionally moderate snow showers in the evening, then mostly cloudy with scattered light showers late evening. 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).