Colder air has begun to settle along the western side of the Cascades, with mid and high-level clouds moving in from the south. A SW-NE oriented band of precipitation has positioned itself east of the Cascade crest and will continue lifting NE through Monday morning. Mt Hood is seeing the heaviest precipitation so far, while areas farther north have yet to see snow reach the ground.
Two separate weather systems will shape conditions on Monday:
First, the track of the SW-NE precipitation band will determine snowfall totals for this morning. It could bring very light snow as far north as Snoqualmie Pass, but mostly focused to the south and east. East of the Cascades could see up to a few inches of snow from this system.
Second, a cold low-pressure system digging offshore will begin pushing colder air and precipitation in from the NW this afternoon. This system will reach the Olympics in the late afternoon, reaching the central Cascades by the evening hours. Snow levels will steadily fall through Monday and Monday night, potentially dropping as low as 500 feet across western Washington. However, there is fairly minimal moisture with this system, so low-elevation areas will likely only see a trace of snow.
Mountain passes should be more efficient at squeezing out snow, with up to a few inches possible by Tuesday. Ridgeline winds are expected to increase this evening and overnight as the system moves through.
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 cloudy. Light to occasionally moderate snow showers. Light to moderate ridgeline wind, increasing in the afternoon.
Monday
Night
Mostly cloudy and cold, with light to occasionally moderate snow showers. Light to moderate ridgeline wind.
Monday
Mostly cloudy. Light to occasionally moderate snow showers. Light to moderate ridgeline wind, increasing in the afternoon.
Monday
Night
Mostly cloudy and cold, with light to occasionally moderate snow showers. Light to moderate ridgeline wind.
Monday
Mostly cloudy. Light to occasionally moderate snow showers. Light to moderate ridgeline wind, increasing in the afternoon.
Monday
Night
Mostly cloudy and cold, with light to occasionally moderate snow showers. Light to moderate ridgeline wind.
Monday
Mostly cloudy. Light to occasionally moderate snow showers. Light to moderate ridgeline wind, increasing in the afternoon.
Monday
Night
Mostly cloudy and cold. Light to moderate snow, with light to moderate ridgeline wind.
Monday
Mostly cloudy. Light to occasionally moderate snow showers. Light Pass level wind, and SW at ridgeline.
Monday
Night
Cloudy and cold, with light snow showers. Light Pass level wind, and SW at ridgeline.
Monday
Mostly cloudy. Light to occasionally moderate snow showers. Light Pass level wind, and light to moderate SW at ridgeline.
Monday
Night
Cloudy and cold, with light snow showers. Light to moderate Pass level wind, and SW at ridgeline.
Monday
Mostly cloudy, with a chance of light snow in the morning.
Monday
Night
Mostly cloudy, with periods of clearing. Cold, with a chance of light snow.
Monday
Cloudy, with a chance of light snow showers in the morning. Light to moderate ridgeline wind.
Monday
Night
Cloudy and cold, with light to moderate snow. Light to moderate ridgeline wind.
Monday
Cloudy, with a chance of light snow showers in the morning. Light to moderate ridgeline wind.
Monday
Night
Cloudy and cold, with light to moderate snow. Light to moderate ridgeline wind.
Monday
Cloudy. Light to moderate snow, with lowering snow levels through the day. Light to moderate ridgeline wind.
Monday
Night
Cloudy and cold, with light to moderate snow. Light to moderate ridgeline wind.
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).