A compact Low-pressure system continues to approach the region this morning spreading several bands of light to moderate precipitation out ahead of it. These waves of rain and snow should reach most mountain locations before 8 am. This isn't a particularly wet storm, and its fast-moving track will limit the amount of precipitation we receive. The Low should move quickly over the Olympics and Mt Hood during the day before exiting the region to the south overnight. A cold front associated with the storm will cause snow levels to quickly drop during the morning hours. So, even if precipitation begins as rain, expect temperatures to cool and snow to return for all but the lower elevation trailheads. Winds out ahead of the storm should peak for locations near Mt Baker, Mission Ridge, and Crystal Mt this morning before decreasing in the afternoon. Areas more in line with the Low's track like Mt St Helens and Mt Hood could experience very strong winds and stormy conditions all day long.
As the storm exits overnight, our upper airflow will turn more northerly allowing for a few isolated showers to continue along the west slopes of the Cascades. These showers should be heaviest between the Mt Loop highway and I-90 where a short-lived Puget Sound Convergence Zone could swing across the area. By Tuesday morning, we're left with mostly cloudy skies, northerly winds, and a few isolated showers.
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 rain and snow in the morning becoming snow showers in the afternoon. Moderate WSW winds decreasing.
Monday
Night
Mostly cloudy with a few snow flurries possible. Light N winds.
Monday
Light rain and snow becoming showers in the afternoon. Moderate to strong S winds in the morning decreasing dramatically during the day and becoming more northerly.
Monday
Night
Cloudy with isolated snow showers. Light N winds.
Monday
Light to occasionally moderate rain and snow. Light to moderate SW winds decreasing and turning WNW.
Monday
Night
Cloudy with scattered snow showers. Light to moderate NW winds.
Monday
Light to moderate rain and snow. Heaviest near Mt St Helens and Mt Adams. Moderate SW winds decreasing and becoming WNW.
Monday
Night
Cloudy with isolated snow showers. Light to moderate NW winds.
Monday
Light to occasionally moderate rain and snow. Light to moderate W winds increasing in the afternoon.
Monday
Night
Cloudy with isolated snow showers. Light to moderate W winds.
Monday
Light to occasionally moderate rain and snow. Light to moderate W winds.
Monday
Night
Cloudy with scattered showers. Light to moderate NW winds.
Monday
Cloudy with scattered showers. Light to moderate westerly winds increasing in the afternoon.
Monday
Night
Cloudy with isolated snow showers. Moderate NNW winds.
Monday
Cloudy with scattered showers heaviest near the crest. Moderate W winds becoming NW in the afternoon.
Monday
Night
Mostly cloudy with isolated showers especially near the crest. Moderate NNW winds.
Monday
Cloudy with scattered showers. Moderate to strong W winds decreasing and becoming NW in the afternoon.
Monday
Night
Cloudy with isolated showers near the crest. Light to moderate NNW winds.
Monday
Light to occasionally moderate rain and snow. Very strong W winds decreasing in the afternoon.
Monday
Night
Cloudy with scattered showers. Moderate to strong NW winds turning NNW and decreasing.
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).