An offshore ridge combined with northerly flow aloft will keep the Pacific Northwest dry and chilly on Monday. Inversions formed overnight in many locations as light winds enabled the cold air to sink into valley locations. Some locations such as Mazama are below zero, while many low-elevation stations near and east of the Cascade Crest are reporting single-digit temperatures and may be slow to warm up today. Mid and upper-elevation locations are already warmer than this time yesterday and should continue to moderate on Tuesday. At 5000 ft most areas should warm into the 20s by the afternoon, but lower elevations along the east slopes of the Cascades (particularly north of I-90) may not make it out of the 10s. Sunny skies give way to high clouds Monday afternoon with continued mostly cloudy weather overnight. A weak wave rounding the back of the offshore ridge on NW flow could bring some very light snow to the Mt. Baker area Monday night along with moderate W winds for some locations near and east of the Cascade Crest. These winds will maintain through Tuesday.
Tuesday will be milder than Monday as the flattening offshore high continues to drift towards the west coast. Another weak wave could bring some very light snow to the west slopes of the northern Cascades during the mid-day hours with widespread mid and high clouds in other areas. The southern portions of the region could see some above-freezing temperatures by the afternoon.
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
Sunny in the morning with mid and high-level clouds increasing during the afternoon.
Monday
Night
Mostly cloudy.
Monday
Sunny in the morning with mid and high-level clouds increasing during the afternoon.
Monday
Night
Mostly cloudy with a chance of light snow overnight.
Monday
Sunny in the morning with mid and high-level clouds increasing during the afternoon.
Monday
Night
Mostly cloudy.
Monday
Sunny in the morning with mid and high-level clouds increasing during the afternoon.
Monday
Night
Mostly cloudy.
Monday
Sunny in the morning with mid and high-level clouds increasing during the afternoon. Light ridgeline and E wind at the Pass.
Monday
Night
Mostly cloudy. Light ridgeline and E or variable wind at the Pass.
Monday
Sunny in the morning with mid and high-level clouds increasing during the afternoon. Light ridgeline and E wind at the Pass.
Monday
Night
Mostly cloudy. Light ridgeline and E or variable wind at the Pass.
Monday
Sunny in the morning with mid and high-level clouds increasing during the afternoon.
Monday
Night
Mostly cloudy with a few flurries possible.
Monday
Sunny in the morning with mid and high-level clouds increasing during the afternoon.
Monday
Night
Mostly cloudy.
Monday
Sunny in the morning with mid and high-level clouds increasing late in the day.
Monday
Night
Mostly cloudy.
Monday
Sunny in the morning with mid and high-level clouds increasing late in the day. Moderating temperatures.
Monday
Night
Mostly cloudy and milder with a low-level inversion.
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).