A weak upper-level disturbance will approach from the WSW today as the ridge dominating our recent weather shifts to the east. The result will be a transition day with increasing high and mid-level clouds. A low-level push of onshore flow will maintain fairly widespread low-level stratus clouds (below around 3000 ft) to the west of the Cascade Crest. Freezing levels continue to descend throughout the day as well. Do expect a diurnal increase in temperatures at lower elevations during the mid-day hours, particularly in areas where the higher clouds are slower to thicken and along the east slopes of the Cascades where WSW winds are warming and drying as they descend off the Cascades. Expect moderate ridgeline winds for Mt Hood, but mostly light winds elsewhere.
The upper-level disturbance arrives late Wednesday evening with light rain and snow above 4000-5000 ft. Precipitation peaks in the early morning hours along the west slopes of the Cascades, with only a few dribs and drabs making it into the immediate lee of the Cascade Crest. Expect light to moderate W or SW ridgeline winds across the region.
A drying trend develops on Thursday as attention shifts to a closed low off the Oregon coast. Winds decrease and shift more southerly as the day progresses. Snow levels remain in the 4000-4500 ft range.
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
Partly to mostly cloudy with high clouds and filtered sunshine through mid-day and some low clouds below 3000 ft, then becoming cloudy with a high overcast in the afternoon.
Wednesday
Night
Cloudy with light rain and snow developing from late evening onward.
Wednesday
Partly to mostly cloudy with high clouds and filtered sunshine through mid-day and some low clouds below 3000 ft, then becoming cloudy with a high overcast in the afternoon.
Wednesday
Night
Cloudy with light rain and snow developing from late evening onward.
Wednesday
Partly to mostly cloudy with high clouds and filtered sunshine through mid-day and some low clouds below 3000 ft, then becoming cloudy with a high overcast in the afternoon.
Wednesday
Night
Cloudy with light rain and snow developing from late evening onward.
Wednesday
Partly to mostly cloudy with high clouds and filtered sunshine through mid-day and some low clouds below 3000 ft, then becoming cloudy with a high overcast in the afternoon.
Wednesday
Night
Cloudy with light rain and snow developing from late evening onward.
Wednesday
Partly to mostly cloudy with high clouds and filtered sunshine through mid-day and some low clouds below 3000 ft, then becoming cloudy with a high overcast in the afternoon. Light ridgeline and W wind at the Pass.
Wednesday
Night
Cloudy with light rain and snow developing from late evening onward. Increasing light to occasionally moderate ridgeline and light W wind at the Pass.
Wednesday
Partly to mostly cloudy with high clouds and filtered sunshine through mid-day and some low clouds below 3000 ft, then becoming cloudy with a high overcast in the afternoon. Light ridgeline and W wind at the Pass.
Wednesday
Night
Cloudy with light rain and snow developing from late evening onward. Increasing moderate ridgeline and light W wind at the Pass.
Wednesday
Partly to mostly cloudy with high clouds and filtered sunshine through mid-day, then becoming cloudy with a high overcast in the afternoon.
Wednesday
Night
Cloudy with a chance of light rain and snow from late evening onward.
Wednesday
Partly to mostly cloudy with high clouds and filtered sunshine through mid-day, then becoming cloudy with a high overcast in the afternoon.
Wednesday
Night
Cloudy with a chance of light rain and snow from late evening onward.
Wednesday
Partly to mostly cloudy with high clouds and filtered sunshine through mid-day, then becoming cloudy with a high overcast in the afternoon.
Wednesday
Night
Cloudy with a chance of light rain and snow from late evening onward.
Wednesday
Partly to mostly cloudy with high clouds and filtered sunshine through mid-day, then becoming cloudy with a high overcast in the afternoon. Moderate ridgeline winds.
Wednesday
Night
Cloudy with light rain and snow developing in the late evening. 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).