A cold upper low continues to drift slowly southward well off the Washington coastline. A disturbance centered just offshore of the California/Oregon border provides dynamic support for clouds Monday morning. A band of clouds lines the coastal waters of Oregon and Washington while a 9000 ft cloud deck continues to thicken over the southern parts of our forecast region and will lift northward throughout the day. Sunshine from the central Washington Cascades northward will gradually transition to mid-level clouds throughout the day. Some light snow showers should develop for Mt. Hood and the southern Washington Cascades. Mt. Hood may pick up 1-4" of snow by the end of the day with additional disturbances rotating around the primary low producing similar amounts Monday night and another 1-2" on Tuesday. The additional disturbances may spread very light snow shower activity more broadly across the mountains of Washington State.
Chilly temperatures Monday morning should quickly moderate, bringing above-freezing temperatures up to 3000-4000 ft by the early afternoon throughout the region (3000 ft snow levels for areas receiving precipitation). Monday night should be cool, but not as cold as Sunday night with clouds limiting radiational cooling. Tuesday should once again moderate with snow levels around 3000 ft. Light E winds through the mountain gaps will continue through the forecast period.
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 sunny in the morning with mid-level clouds increasing in the afternoon.
Monday
Night
Mostly cloudy.
Monday
Mostly sunny in the morning with mid-level clouds increasing in the afternoon.
Monday
Night
Mostly cloudy.
Monday
Mostly sunny early, then mid-level clouds increasing from mid-morning onwards.
Monday
Night
Mostly cloudy.
Monday
Cloudy with a chance of light snow showers in the afternoon.
Monday
Night
Mostly cloudy with a chance of light snow showers.
Monday
Mostly sunny early, then mid-level clouds increasing from late morning onwards.
Monday
Night
Mostly cloudy.
Monday
Mostly sunny early, then mid-level clouds increasing from mid-morning onwards.
Monday
Night
Mostly cloudy.
Monday
Mostly sunny early, then mid-level clouds increasing from mid-morning onwards.
Monday
Night
Mostly cloudy.
Monday
Mostly sunny early, then mid-level clouds increasing from mid-morning onwards.
Monday
Night
Mostly cloudy.
Monday
Cloudy with a chance of light snow showers in the afternoon.
Monday
Night
Mostly cloudy with a chance of light snow showers.
Monday
Cloudy with light snow showers developing and increasing during the afternoon.
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).