Dribs and drabs of moisture continue for the west slopes of the Cascades on Thursday. Initially the source of the moisture will be lingering post-frontal flow from a departed system, bringing the final stages weakening convergence to the Mt Baker area early in the day. Moderate to locally strong W and NW ridgeline winds will continue to target the southern Cascades and particularly Mt Hood, but should gradually decrease throughout the day. A flattened or "dirty" ridge moves into the area, drying out the southern half of the Cascades, while limited moisture rides over the ridge for areas further north. Snow levels rise as the day progresses from 3000 to 3500 ft. The east slopes of the Cascades should experience better chances of sunshine with partly to mostly cloudy skies.
The ridge expands slightly Thursday night, limiting chances of light precipitation to the northern Olympics and Mt Baker area. With plenty of cloud cover over the area and some warm air advection, 5000 ft temperatures only drop into the upper 20s to low 30s.
A modest frontal system sags SE on Friday. In the morning, expect some light rain and snow for the Olympics and northern half of the Washington Cascades, expanding throughout the region as the day progresses. Snow levels should be in the 4000-5000 ft range, but thanks to increasing light to moderate E flow, they might be slightly lower for the Cascade passes.
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
Mostly cloudy with a few rain or snow showers.
Thursday
Night
Cloudy with a slight chance of rain and snow showers.
Thursday
Light rain and snow early, then a mostly cloudy with a chance of rain or snow showers in the afternoon.
Thursday
Night
Cloudy with a chance of light rain and snow showers.
Thursday
Mostly cloudy with decreasing chances of light rain and snow showers.
Thursday
Night
Thursday
Mostly cloudy with slight chances of light rain and snow showers. Decreasing moderate ridgeline winds near the Cascade Crest.
Thursday
Night
Mostly cloudy.
Thursday
Mostly cloudy with decreasing chances of light rain and snow showers. Decreasing light to moderate ridgeline and light W wind at the Pass.
Thursday
Night
Mostly cloudy. Light ridgeline winds. Light W winds switch E at the Pass.
Thursday
Mostly cloudy with decreasing chances of light rain and snow showers. Decreasing light to moderate ridgeline and light W wind at the Pass.
Thursday
Night
Mostly cloudy. Light ridgeline winds. Light W winds switch E at the Pass.
Thursday
Partly to mostly cloudy.
Thursday
Night
Mostly cloudy.
Thursday
Partly to mostly cloudy. Moderate ridgeline winds in some areas.
Thursday
Night
Partly to mostly cloudy.
Thursday
Partly to mostly cloudy. Moderate ridgeline winds in some areas.
Thursday
Night
Partly to mostly cloudy.
Thursday
Mostly cloudy with isolated showers possible on the west slopes of Mt Hood. Strong ridgeline winds decrease into the moderate range during the afternoon hours.
Thursday
Night
Partly to mostly cloudy. Moderate 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).