A weak north-south oriented frontal band will cross the area today, passing through the Cascade around 11 am. The parent low is curling towards SE Alaska and this system will fall apart as it passes inland. Strong SE winds seen in the Passes and up to ridgeline especially at places like Crystal Mt overnight have eased as the front moves inland. Slightly higher precipitation totals are expected down near Mt Hood where a secondary wave is forming along the old frontal boundary. Light post-frontal showers in westerly flow will keep light showers along the west slopes of the Cascades predominately from the mountain loop highway and south to Mt Rainier/Crystal Mt through this afternoon.
Strong upper level ridging will build offshore tonight leading to a drying trend. Areas of low clouds will form east of the Cascades and lap against the lower slopes and likely start to infiltrate the Cascade Passes before daybreak as offshore flow increases once again.
Another weakening frontal system will approach on Saturday. This will increase cool offshore flow and mute any warming associated with the ridge outside of the Olympics and potentially the northwest Cascades. Look for low clouds along the east slopes of the Cascades and in the Cascade Passes. High clouds will spread over all areas in advance of the system in 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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Friday
Light to occasionally moderate rain and snow this morning, then isolated light showers mid-day onward. Partly sunny in the afternoon.
Friday
Night
Partly to mostly clear.
Friday
Light to occasionally moderate rain and snow this morning, then cloudy scattered light showers mid-day onward.
Friday
Night
Partly cloudy.
Friday
Light to occasionally moderate rain and snow this morning, then cloudy scattered light showers mid-day onward.
Friday
Night
Partly to mostly clear.
Friday
Light to occasionally moderate rain and snow this morning, then mostly cloudy with scattered light showers mid-day onward.
Friday
Night
Partly to mostly clear.
Friday
Light to occasionally moderate rain and snow this morning, then cloudy with scattered light showers mid-day onward. Moderate east winds at Pass level becoming west mid-day.
Friday
Night
Partly to mostly clear. Areas of low clouds possible. Light winds at Pass level.
Friday
Light to occasionally moderate rain and snow this morning, then cloudy with scattered light showers mid-day onward. Moderate east winds at Pass level becoming west mid-day.
Friday
Night
Partly to mostly clear. Areas of low clouds possible. Light winds at Pass level.
Friday
Light rain and snow this morning, then cloudy with isolated light showers mid-day onward.
Friday
Night
Partly to mostly clear. Areas of low clouds forming.
Friday
Light rain and snow this morning, then cloudy with isolated light showers mid-day onward.
Friday
Night
Mostly clear. Areas of low clouds forming.
Friday
Light rain and snow this morning, then mostly cloudy with isolated light showers mid-day onward.
Friday
Night
Mostly clear. Areas of low clouds forming.
Friday
Light to occasionally moderate rain and snow this morning, then isolated light showers mid-day onward. Partly sunny in the afternoon.
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).