A weak frontal system will battle an upper level ridge parked offshore over the next 24 hours. The result will be some drippy conditions from the central Cascades and northward to the Mt Baker area early this morning today and generally clearer and sunnier conditions the further south and/or east. The frontal system will pass into British Columbia tonight, pushing some light precipitation into the same central/northern Cascade areas tonight and an increase in high clouds elsewhere. Snow/freezing levels will also follow the same north to south trend, with much higher freezing levels to the south. One notable feature will be the moderate to strong NW ridgeline winds seen in most areas as this system rides up and over the ridge. Winds will generally increase this afternoon and stay strong through Wednesday morning.
On Wednesday, low/mid level moisture will try to hang on along the west slopes of the Cascades but as the ridge builds offshore, most areas should see more sun than clouds in the afternoon except perhaps the northwest Cascades. The air mass will rapidly warm on Wednesday with freezing levels pushing to near 10,000' for most areas.
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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Tuesday
Partly cloudy becoming mostly cloudy in the afternoon.
Tuesday
Night
Cloudy with becoming cloudy in the afternoon with periods of light rain. Winds becoming strong.
Tuesday
Mostly cloudy in the morning, becoming cloudy in the afternoon with periods of light rain or snow.
Tuesday
Night
Cloudy with periods of light rain or snow. Increasing ridgeline winds.
Tuesday
Partly sunny in the morning, becoming cloudy in the afternoon with periods of light rain or snow.
Tuesday
Night
Cloudy with periods of light rain or snow. Increasing ridgeline winds.
Tuesday
Mostly sunny. Increasing high clouds and filtered sunshine in the afternoon.
Tuesday
Night
Cloudy. Chance of light rain or snow. Strong ridgeline winds.
Tuesday
Mostly sunny with areas of low clouds in the morning. Cloudy with a chance of very light rain or snow in the afternoon. Light west winds at Pass level, moderate NW winds at ridgeline.
Tuesday
Night
Cloudy with periods of light rain or snow. Light to moderate west winds at Pass level. Moderate to strong NW ridgeline winds.
Tuesday
Mostly sunny with areas of low clouds in the morning. Cloudy in the afternoon. Light west winds at Pass level, moderate NW winds at ridgeline.
Tuesday
Night
Cloudy with periods of light rain or snow. Moderate west winds at Pass level. Moderate to strong NW ridgeline winds.
Tuesday
Mostly cloudy in the morning, becoming cloudy in the afternoon. Chance of light rain or snow near the Cascade crest in the afternoon. Moderate to strong ridgeline winds.
Tuesday
Night
Cloudy with periods of light rain or snow near the Cascade crest. Moderate to strong ridgeline winds.
Tuesday
Partly to mostly sunny in the morning, becoming mostly cloudy in the afternoon with increasing high clouds. Increasing ridgeline winds.
Tuesday
Night
Cloudy. Strong ridgeline winds.
Tuesday
Mostly sunny in the morning, becoming mostly cloudy in the afternoon with increasing high clouds. Increasing ridgeline winds.
Tuesday
Night
Cloudy. Moderate to strong ridgeline winds.
Tuesday
Mostly sunny in the morning, becoming partly sunny in the afternoon with filtered sunshine and high clouds. Increasing ridgeline winds.
Tuesday
Night
Cloudy with high overcast. 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).