The very wet and active weather pattern continues, with moisture streaming in over the top of an offshore ridge. Systems continue to arrive daily with only brief relative lulls between pulses.
Sunday will be a stormy, wet day in the mountains. It features a surface feature tracking toward the Olympic Peninsula. Out ahead of it a warm front continues to bring moderate to heavy rain and higher elevation snow throughout the region on SW winds as snow levels rise to 5000-7000 ft. The low tracks over the northern Cascades by late afternoon, bringing a shift to WSW or W winds, decreasing precipitation, and subtle cooling. Rain or snow shower activity becomes light, and snow levels drop 500-1000 ft.
Monday ushers in the bulk of the atmospheric river event. The strongest moisture feed reaches the coast Monday morning and the Cascades by mid-day, spreading increasing heavy to very heavy precipitation across the region. The heaviest precipitation is likely to take aim on the central and southern Cascades, but the northern Cascades will get plenty. Rainfall amounts should be in the 1-3" range for most areas on Monday, with moderate to strong WSW ridgeline winds bringing plenty of moisture (0.75-1.5" of precipitation) over to the east slopes of the ranges. Snow levels peak late in the day in the 5500 to 8500 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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Sunday
Light rain and snow. Light to moderate ridgeline winds.
Sunday
Night
Periods of light rain and snow. Light to moderate ridgeline winds.
Sunday
Moderate to occasionally heavy rain and snow.
Sunday
Night
Light rain and snow showers.
Sunday
Moderate to heavy rain and snow. Moderate ridgeline winds.
Sunday
Night
Light rain and snow showers. Decreasing moderate ridgeline winds.
Sunday
Moderate to heavy rain and snow. Moderate ridgeline winds.
Sunday
Night
Light rain and snow showers. Decreasing moderate ridgeline winds.
Sunday
Moderate to occasionally heavy rain and snow. Moderate ridgeline and light E wind at the Pass switches W late in the day.
Sunday
Night
Light rain and snow showers. Moderate ridgeline and light W wind at the Pass.
Sunday
Moderate to occasionally heavy rain and snow. Moderate ridgeline and light E wind at the Pass switches W late in the day.
Sunday
Night
Mostly light rain and snow showers. Moderate ridgeline and light to moderate W wind at the Pass.
Sunday
Periods of light to moderate snow. 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).