An upper-level front brings widespread light to moderate snowfall as it passes from W to E across the region early Thursday morning. In advance of the surface cold front, more showery precipitation moves in during the mid-morning hours. E gradients maintain slightly cooler E flow through the mountain gaps, likely maintaining snowfall at Snoqualmie Pass level until the frontal passage mid-afternoon. Once winds shift W, expect a bump in snow levels to 3000-3500 ft with W or WNW flow behind the front focusing moderate convergence precipitation on Snoqualmie and Stevens Passes. Elsewhere, light snow showers decrease during the evening hours. Winds increase behind the front, particularly for the mountain gaps and E slopes of the Cascades. In these locations expect moderate winds and strong gusts. A weak secondary frontal feature brings a chance for some light snow showers across the mountains of northern Washington State during the early morning hours.
An approaching front maintains the moderate W winds through the mountain gaps and E slopes of the Cascades on Friday. Cool air with 2000-3000 ft snow levels is in place as light snow trickles into most areas on Friday.
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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Thursday
Decreasing light rain and snow showers.
Thursday
Night
Periods of light snow.
Thursday
Light rain and snow. Decreasing moderate ridgeline winds.
Thursday
Night
Decreasing light snow showers in the evening. Light snow develops in the early morning hours. Light to occasionally moderate ridgeline winds.
Thursday
Light rain and snow.
Thursday
Night
Decreasing light snow showers in the evening. Light snow develops in the early morning hours.
Thursday
Light to moderate rain and snow (heaviest at Paradise).
Thursday
Night
Light snow showers.
Thursday
Light to moderate rain and snow. Increasing light ridgeline and light E winds at the Pass switching W late in the day.
Thursday
Night
Light snow showers (moderate with convergence possible through the evening hours). Moderate ridgeline and light W wind at the Pass.
Thursday
Light to moderate rain and snow. Increasing light ridgeline and light E winds at the Pass switching W late in the day.
Thursday
Night
Light snow showers (moderate with convergence possible through the evening hours). Moderate ridgeline and light occasionally moderate W wind at the Pass.
Thursday
Light snow or snow showers.
Thursday
Night
Light snow showers near the Cascade Crest. Moderate ridgeline winds.
Thursday
Light rain and snow become showery by the afternoon. Light ridgeline winds become moderate.
Thursday
Night
Light snow showers near the Cascade Crest. Moderate ridgeline winds with strong gusts.
Thursday
Light rain and snow become showery by the afternoon. Increasing light ridgeline winds become light to moderate in the afternoon.
Thursday
Night
Light snow showers near the Cascade Crest. Moderate ridgeline winds.
Thursday
Moderate rain and snow become showery by late morning. Moderate ridgeline winds with strong gusts.
Thursday
Night
Light snow showers at times. Moderate to strong ridgeline 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).