High to extreme avalanche danger exists in the mountains. Please check the avalanche forecast before traveling to or recreating in the mountains.
The atmospheric river impacting our region continues to deal our region its most powerful impacts throughout the day on Monday. Satellite imagery early Monday morning shows a stream of moisture originating west of the Hawaiian Islands that feeds moisture into our region. Very heavy rain and snow developed Sunday night and should continue from the mountain loop area southward. A cold front drops SE across Washington state today. In advance of it, precipitation rates of 0.1-0.25" per hour are expected through around 3 PM in the central Washington Cascades and should extend into the evening hours for Mt. Hood. Mt. Baker may get some light to moderate precipitation as rain and snow spill slightly back northward into the area before the front moves through. Very strong downslope winds continue in favored areas along the east slopes of the Cascades.
Moderate showers, heavy convergence activity, and rapidly cooling temperatures will be the story Monday night. Convergence appears to focus on areas from the mountain loop to just north of Snoqualmie Pass and the Salmon La Sac region. With rapidly increasing snow water ratios, this could result in over a foot of fresh snow overnight in some parts of the central Washington Cascades.
On Tuesday, a shortwave trough approaches and should bring slightly more convective snow showers with more convergence, potentially focusing slightly southward into the Snoqualmie Pass area. Another foot of snow is possible in areas favored by convergence with snow levels around 1000-2000 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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Monday
Light to moderate rain and snow tapering to light showers.
Monday
Night
Light snow showers.
Monday
Light to moderate rain and snow increasing during the mid-day hours and becoming showery in the afternoon.
Monday
Night
Light to occasionally moderate snow showers, heaviest southern part.
Monday
Very heavy rain and snow becoming heavy showers and convergence late in the day.
Monday
Night
Moderate snow showers, heavy in convergence bands. Moderate to strong ridgeline winds.
Monday
Very heavy rain and snow at Paradise, heavy rain and snow at White Pass, and moderate to heavy rain and snow at Crystal. Moderate ridgeline winds in most areas, but expect strong to very strong ridgeline winds near the Cascade Crest and White Pass.
Monday
Night
Light to moderate rain and snow showers changing to all snow showers.
Monday
Very heavy rain and snow becoming heavy showers and convergence late in the day. Increasing light W winds at the Pass. Moderate ridgeline winds with strong gusts.
Monday
Night
Moderate snow showers with heavy convergence likely at times. Light to moderate W winds at the Pass. Moderate to strong ridgeline winds.
Monday
Very heavy rain and snow. Light to moderate W winds at the Pass. Moderate to strong ridgeline winds.
Monday
Night
Moderate snow showers with heavy convergence likely at times. Moderate W winds at the Pass. Moderate to strong ridgeline winds.
Monday
Moderate to heavy rain and snow becoming showery late in the day.
Monday
Night
Light snow showers.
Monday
Very heavy rain and snow with strong ridgeline winds, western part. Moderate to heavy rain and snow with very strong to extreme ridgeline winds, eastern part.
Monday
Night
Moderate rain and snow showers, locally heavy in convergence bands and strong winds, western part. Light rain and snow showers with strong to very strong ridgeline winds, eastern part.
Monday
Heavy rain and snow. Moderate to strong ridgeline winds.
Monday
Night
Light to moderate rain and snow showers changing to all snow showers.
Monday
Heavy rain and snow. Very strong ridgeline winds.
Monday
Night
Heavy rain and snow in the early tapering to light to moderate snow showers. Strong 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).