High clouds will slowly lower today as a Pacific frontal system approaches. There's a strong temperature gradient across the Cascades, with much colder temperatures and lower freezing levels on the east side of the Cascades and in the Cascade Passes. Light rain and snow will develop first for the Olympics and spread into the northwest Cascades by this afternoon. These same areas, including the West South for areas like Crystal mountain, will see the strongest southerly winds today.
The precipitation spreads inland overnight but the more moderate precipitation remains focused on the Olympics and northwest Cascades until after midnight. A trailing upper level trough will finally kick the frontal boundary through early Sunday morning with post-front showers following in the afternoon. Look for a slight bump in snow levels Sunday mid-day as milder Pacific air mixes in the Passes and to the East.
Much wetter and increasingly mild weather is on tap Sunday night through Tuesday.
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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Saturday
Cloudy with light rain and snow developing mid-day. Strong winds.
Saturday
Night
Light to moderate rain and snow overnight. Strong to extreme winds.
Saturday
Overcast with high clouds in the morning, then cloudy with light rain and snow developing in the afternoon. Increasing strong winds during the day.
Saturday
Night
Moderate rain and snow overnight. Strong winds.
Saturday
Overcast with high clouds, with clouds slowly lowering during the day. Cooler east side of the zone near the crest. Winds increasing and becoming strong during the day.
Saturday
Night
Light to moderate rain and snow overnight. Strong winds.
Saturday
Overcast with high clouds, with clouds slowly lowering during the day. Cooler east side of the zone near the crest. Winds increasing and becoming strong during the day.
Saturday
Night
Light to occasionally moderate rain and snow developing overnight. Strong winds.
Saturday
Overcast with high clouds, with clouds slowly lowering during the day. Light to moderate easterly winds at Pass level and ridgelines.
Saturday
Night
Light to occasionally moderate rain and snow developing overnight. Light to moderate east winds at Pass level and S winds at ridgeline.
Saturday
Overcast with high clouds, with clouds slowly lowering during the day. Moderate easterly winds at Pass level and ridgelines.
Saturday
Night
Light to occasionally moderate rain and snow developing overnight. Light to moderate east winds at Pass level and S winds at ridgeline.
Saturday
Mostly cloudy with high clouds and filtered sunshine this morning, then overcast in the afternoon.
Saturday
Night
Light to occasionally moderate rain and snow developing overnight.
Saturday
Mostly cloudy with high clouds and filtered sunshine this morning, then overcast in the afternoon.
Saturday
Night
Light to occasionally moderate rain and snow developing overnight.
Saturday
Mostly cloudy with high clouds and filtered sunshine this morning, then overcast in the afternoon.
Saturday
Night
Light rain and snow developing overnight.
Saturday
Mostly cloudy with high clouds and filtered sunshine this morning, then overcast in the afternoon.
Saturday
Night
Light to occasionally moderate rain and snow developing overnight. Winds increasing.
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).