We'll see a battle of air masses today with milder air to the west of the Cascade crest and some of the coldest temperatures of the winter near and to the east of the Cascade crest. Mild air is trying to nose its way inland this morning and aloft - place like the top of Crystal and even Camp Muir on Mt Rainier are warmer than most other sites across the Cascades. Most NWAC weather stations are in the teens with even a few single digits, with of course the cold temp winner of Washington Pass base where it's below zero F.
We'll likely see freezing levels "pop" this afternoon to free air-freezing levels over the Olympics, the western half of the West South and Mt Hood as an upper level ridge of high pressure noses over the area. That should coincide with easterly flow backing off this afternoon, and areas like Snoqualmie and White Pass experiencing moderate easterly ridgeline winds should winds decrease and become westerly this afternoon. We'll also see some high clouds sneaking in from the NW today, making for a period of filtered sunshine near the Canadian border Monday afternoon.
A dry shortwave will pass over the area late tonight brining a brief increase in high clouds but skies should clear out once again on Tuesday. This upper level feature will also kick up NW winds, so expect moderate ridgeline winds in most areas approaching strong in the alpine on Tuesday.
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
Mostly sunny in the morning, then partly sunny with high clouds and filtered sunshine in the afternoon. Light ridgeline winds.
Monday
Night
Mostly cloudy in the evening, then becoming mostly clear after midnight. Moderate ridgeline winds.
Monday
Mostly sunny in the morning, then partly to mostly sunny with high clouds and filtered sunshine in the afternoon. Light to occasionally moderate ridgeline winds.
Monday
Night
Mostly cloudy in the evening, then becoming mostly clear late. Moderate ridgeline winds.
Monday
Mostly sunny in the morning, then partly to mostly sunny with high clouds and filtered sunshine in the afternoon.
Monday
Night
Mostly cloudy in the evening, then becoming mostly clear late. Moderate ridgeline winds.
Monday
Mostly sunny. Occasional high clouds in the afternoon. Milder western half of the zone including Mt Rainier and Mt Helens, cooler eastern part including Crystal and White Pass. Light to moderate ridgeline winds, strongest near White Pass this morning.
Monday
Night
Mostly cloudy in the evening, then becoming mostly clear late. Moderate ridgeline winds.
Monday
Mostly sunny. Occasional high clouds in the afternoon. Light to moderate E ridgeline winds becoming W this afternoon. Light E winds at Pass level.
Monday
Night
Mostly cloudy in the evening, then becoming mostly clear late. Moderate W ridgeline winds and light to moderate W at Pass level.
Monday
Mostly sunny. Occasional high clouds in the afternoon. Moderate E ridgeline winds becoming light W this afternoon. Light to moderate E winds at Pass level.
Monday
Night
Mostly cloudy in the evening, then becoming mostly clear late. Moderate W ridgeline winds and light to moderate W at Pass level.
Monday
Mostly sunny in the morning, then partly to mostly sunny with high clouds and filtered sunshine in the afternoon. Light to occasionally moderate ridgeline winds.
Monday
Night
Mostly cloudy in the evening, then becoming mostly clear late. Moderate ridgeline winds.
Monday
Mostly sunny. Occasional high clouds in the afternoon. Light to occasionally moderate ridgeline winds.
Monday
Night
Mostly cloudy in the evening, then becoming mostly clear late. Moderate ridgeline winds.
Monday
Mostly sunny. Occasional high clouds in the afternoon. Light to occasionally moderate ridgeline winds.
Monday
Night
Becoming mostly cloudy in the evening, then becoming mostly clear late. Moderate ridgeline winds.
Monday
Sunny. Moderate ridgeline winds this morning easing in the afternoon.
Monday
Night
Becoming mostly cloudy in the evening, then becoming mostly clear late. Moderate ridgeline winds becoming strong after midnight.
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).