A frontal system will slowly move through the region today. The front will pass through the Cascades just after the noon hour, weakening as it does. This system has a north-south orientation and will spread light to moderate precipitation over to the east slopes of the Cascades during the daylight hours. Cool easterly flow through the Cascade Passes will help keep snow levels below Pass level by drawing on much colder air over the east side of the state.
After the front pushes through this afternoon, the associated deep surface low off the north of Vancouver Island will begin to fill and drift south towards the Washington coast tonight before passing inland Thursday morning. The low should rotate significant post-frontal showers into the west slopes of the Cascades and Mt Hood through mid-day tomorrow. Snow levels will begin to creep up for many areas, settling around 4000' late tonight into Thursday as the air mass becomes more mixed. There's a fair bit of uncertainty as to how this surface low will track, which will affect the snow levels on Thursday.
Showers will become scattered by Thursday afternoon as weak upper-level ridging builds overhead.
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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Wednesday
Light to moderate rain and snow showers. Strong winds.
Wednesday
Night
Light to moderate rain and snow showers.
Wednesday
Moderate to occasionally heavy snow becoming showers in the afternoon. Strong winds.
Wednesday
Night
Moderate rain and snow showers.
Wednesday
Moderate to occasionally heavy snow becoming showers in the afternoon. Strong winds.
Wednesday
Night
Moderate to occasionally heavy rain and snow showers.
Wednesday
Moderate to occasionally heavy snow becoming showers in the afternoon. Strong winds.
Wednesday
Night
Moderate to occasionally heavy rain and snow showers, heaviest Paradise area.
Wednesday
Moderate snow becoming showers in the afternoon. Moderate east winds at Pass level.
Wednesday
Night
Moderate rain and snow showers. Moderate east winds becoming west overnight at Pass level.
Wednesday
Moderate to occasionally heavy snow becoming showers in the afternoon. Moderate east winds at Pass level.
Wednesday
Night
Moderate rain and snow showers. Moderate east winds becoming west overnight at Pass level.
Wednesday
Light to moderate snow becoming scattered showers in the afternoon.
Wednesday
Night
Light snow showers.
Wednesday
Light to moderate snow becoming scattered showers in the afternoon.
Wednesday
Night
Light snow showers.
Wednesday
Light to moderate snow becoming scattered showers in the afternoon.
Wednesday
Night
Light rain and snow showers.
Wednesday
Moderate snow becoming showers in the afternoon. Strong 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).