A deep upper low centered over south-central Canada will continue to bring the coldest air of the season to the region. Some NWAC stations are starting Friday below zero, while many stations are in the single digits and teens. Several systems will bring both lowland and mountain snow before temperatures begin to moderate early next week.
The first system is associated with an upper low moving south into central California. A surface low sits just off the Oregon coast. And an arctic front is draped along the Cascades, spilling very cold air from the interior through the mountain gaps on a moderate easterly low-level flow. A band of light to moderate snow should continue on Friday from Mt. Hood to just north of the Mt. Rainier area, possibly lifting slightly northward into the Snoqualmie area by afternoon.
As this initial system dissipates today, it will be replaced by a developing low tracking toward the mouth of the Columbia River where it is expected to arrive early Saturday morning. It should bring increasing E winds into the moderate to strong range along the Cascade Crest and through the mountain gaps. The frontal system should increase moderate to locally heavy snow to the central and south Washington Cascades and Mt. Hood. Snow should be lighter in the northern Cascades.
With high snow ratios, some areas like Paradise and Mt. Hood should expect 1-2 ft of snow through the day on Saturday.
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
Cold. Mostly cloudy with periods of light snow.
Friday
Night
Cold. Increasing light to moderate snow.
Friday
Cold. Mid-level clouds with a chance of snow flurries.
Friday
Night
Cold. Cloudy with light snow developing after midnight.
Friday
Cold. Cloudy with a chance of light snow flurries.
Friday
Night
Cold. Cloudy in the evening with light snow developing after midnight.
Friday
Cold. Moderate snow at Paradise and White Pass; light snow at Crystal.
Friday
Night
Cold. Moderate to heavy snow at Paradise; moderate snow at White Pass and Crystal.
Friday
Cold. Cloudy with a chance of light snow or snow flurries. Light E winds at the Pass.
Friday
Night
Cold. Cloudy in the evening with light snow developing. Light to occasionally moderate E winds at the Pass.
Friday
Cold. Cloudy with a chance of light snow or snow flurries. Light to moderate E winds at the Pass.
Friday
Night
Cold. Increasing light snow. Moderate E winds at the Pass.
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).