An upper-level low over the Pacific Northwest maintains a cool and unsettled weather pattern, bringing more isolated snow showers to most parts of the region. WNW winds focus those snow showers near and west of the Cascade Crest. Moderate ridgeline winds can be found near and east of the Cascade Crest from I-90 southward. Strong winds can be expected further south around Mt. Hood. These areas with the strongest upslope component can expect more snow accumulations and Mt Hood could pick up 2-4" of snow during the day with significant blowing snow. Snow levels rise from around 500 ft to 2000 ft by the afternoon as daytime heating triggers some increasing convection and more widespread mostly cloudy skies. Expect more sunshine east of the Cascade Crest, but still some cloud build-up.
Snow shower activity peaks with a weak disturbance on the backside of the trough Monday evening and mostly decreases overnight. Most areas near and west of the Cascade crest can expect 1-3" of snow. However, expect some locally higher snow amounts for Mt. Hood and in areas of convergence in the central Washington Cascades.
Tuesday should be similar to Monday even more isolated snow shower activity along with decreasing ridgeline winds.
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 isolated snow showers in the afternoon.
Monday
Night
Isolated snow showers.
Monday
Isolated snow showers. More sun than clouds in the morning, then becoming mostly cloudy in 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).