Look for a slow cooling trend in all areas today and tonight as the upper level ridge that dominated our weather over the last few days is replaced by a weak frontal system currently hung up over southern British Columbia this morning. As this frontal boundary slowly meanders southward, lower clouds along with light rain and snow should develop over the Olympics and northwest Cascades later this morning, but precipitation will hold off for areas further south. Low clouds also stuck over eastern Washington and near and east of the Cascade Passes will be slow to mix out today. Widespread high clouds over the region this morning with should pass through later this morning leaving at least partly sunny skies for the central and southern Washington Cascades and Mt Hood. Moderate to strong westerly ridgeline winds will develop over the central/northern Washington Cascades and slowly spread further south later today and Monday night.
A trailing upper level shortwave will kick the frontal boundary inland Monday night through Tuesday morning, spreading light precipitation further south. Showers will become more scattered Tuesday morning and decrease further in the afternoon. Weak upper-level ridging quickly building along the coast on Tuesday afternoon will help trap low level clouds in place despite the decrease in shower activity. Snow levels will settle into the 4000-5000' range on Tuesday with lighter winds overall.
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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Monday
Mostly cloudy in the morning, then becoming cloudy with light rain and snow developing mid-day.
Monday
Night
Cloudy wiith light rain and snow showers.
Monday
Mostly cloudy in the morning, then becoming cloudy with light to occasionally moderate rain and snow developing mid-day.
Monday
Night
Cloudy with light to occasionally moderate rain and snow showers.
Monday
Mostly cloudy in the morning. Becoming cloudy in the afternoon with light rain and snow developing late.
Monday
Night
Cloudy with light to occasionally moderate rain and snow showers.
Monday
Mostly cloudy with high clouds this morning, then mostly sunny with periods of high clouds.
Monday
Night
Cloudy with light rain and snow showers.
Monday
Mostly cloudy with high clouds this morning, then partly sunny this afternoon. Areas of low clouds near and east of the Pass. Variable winds at Pass level, moderate west winds at ridgeline.
Monday
Night
Cloudy with light rain and snow showers. Light west winds in the Passes, moderate at ridgeline.
Monday
Mostly cloudy with high clouds this morning, then partly sunny this afternoon. Areas of low clouds near and east of the Pass. Variable winds at Pass level, moderate west winds at ridgeline.
Monday
Night
Cloudy with light to occasionally moderate rain and snow showers. Light west winds in the Passes, moderate to strong at ridgeline.
Monday
Mostly cloudy with high clouds this morning, then partly sunny this afternoon. Areas of low clouds and valley fog. Moderate to strong ridgeline winds.
Monday
Night
Cloudy with light rain and snow showers.
Monday
Mostly cloudy with high clouds this morning, then partly to mostly sunny this afternoon. Areas of low clouds and valley fog. Moderate to strong ridgeline winds.
Monday
Night
Cloudy with light rain and snow showers. Moderate to strong ridgeline winds.
Monday
Mostly cloudy with high clouds this morning, then mostly sunny this afternoon. Areas of low clouds and valley fog.
Monday
Night
Cloudy with light rain and snow showers. Moderate to strong ridgeline winds.
Monday
Mostly cloudy with high clouds this morning, then mostly sunny this afternoon.
Monday
Night
Cloudy. Chance of light rain and snow showers late.
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).