A shortwave ridge of high pressure brings a dry day as it transits the region. Expect a cool start with temperatures in the 10s and 20s at NWAC stations. Easterly low-level flow and southerly winds aloft should gradually increase throughout the day as a frontal system tied to a deep Aleutian Low approaches the region from the west. The E flow combined with a significant cold air pool east of the Cascades should keep the east slopes and passes cool while temperatures moderate significantly for the Olympic mountains and to a lesser extent Paradise and Mt. St. Helens. After a mostly clear start to the day, high clouds should also begin to filter sunlight across the region in the afternoon.
Clouds lower and thicken overnight with rain and snow arriving late Saturday night or early Sunday morning. Snow levels are well below pass level and the Cascade foothills may start off as snow. Easterly flow peaks in the moderate range overnight, but expect some strong winds in exposed locations in the Snoqualmie, Crystal, White Pass, and east Central Cascades. The frontal passes Sunday morning, switching flow to the SW as E flow becomes light. Snow continues in the light to moderate range on Sunday.
By late Sunday, the system should bring around a foot of snow to Mt. Hood and Paradise, 6-12" to Mt. Baker, 4-8" to the Cascade Passes, and 2-6" for the east slopes of the Cascades.
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
Mostly clear in the morning with high and mid-level clouds increasing in the afternoon. Light winds.
Saturday
Night
Clouds lowering and thickening with light rain and snow developing in the early morning hours. Milder. Moderate winds.
Saturday
Mostly clear with high clouds increasing late in the day. Light winds.
Saturday
Night
Increasing clouds, lowering and thickening after midnight. Ridgeline winds increasing into the moderate range.
Saturday
Mostly clear with high clouds increasing late in the day. Light winds.
Saturday
Night
Increasing clouds, lowering and thickening after midnight with a chance of light snow developing late. Ridgeline winds increasing into the moderate range.
Saturday
Mostly clear with high clouds increasing throughout the day. Milder at Paradise in the afternoon. Crystal and White Pass stay cool. Light winds.
Saturday
Night
Increasing clouds, lowering and thickening after midnight with light snow developing late. Ridgeline winds increasing into the moderate range.
Saturday
Mostly clear with high clouds increasing late in the day. Cool. Light 5000 ft and easterly pass-level winds increasing into the moderate range late in the day.
Saturday
Night
Saturday
Mostly clear with high clouds increasing late in the day. Cool. Light winds. Light 5000 ft and easterly pass-level winds increasing into the moderate range in the afternoon.
Saturday
Night
Saturday
Mostly clear with high clouds increasing late in the day. Cool. Light winds.
Saturday
Night
Saturday
Mostly clear with high clouds increasing late in the day. Cool. Light winds.
Saturday
Night
Saturday
Mostly clear with high clouds increasing throughout the day. Cool. Light winds.
Saturday
Night
Saturday
Mostly clear with high clouds increasing in the morning and mid-level clouds increasing late in the day. Light ridgeline winds increasing into the moderate range late in the day.
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).