The Pacific Northwest is in the warm sector of a storm with very mild temperatures west of the Cascades and near or below-freezing temperatures further east. Moderate to strong E winds are peaking early this morning with acceleration into the foothills of the Cascades downing some trees and branches in places like North Bend and Enumclaw. Light shower activity associated with a weak warm front should taper early Wednesday morning. Most areas will experience a break in the action with a frontal precipitation band currently over the Olympics and approaching I-5, bringing a period of temporarily moderate precipitation rates as it moves into the Cascades during the late morning through early afternoon hours. Precipitation should become showery late in the day as SSW flow continues to feed moisture into the region. Precipitation type remains tricky for the Cascade Passes, with 3500 ft snow levels likely for today while snow levels will be closer to 5500-6500 ft further west.
This pattern continues with some decrease in precipitation during the evening hours with snow levels likely to drop slightly to 3000 ft in the passes. Expect precipitation to increase into the moderate to occasionally heavy range overnight for favored portions of the Olympics, Mt Baker area, Mt St. Helens, and Mt Dallas.
Rain and snow shower activity taper on Thursday as a ridge builds across the interior. Precipitation is most likely to linger for the Olympics Mt Baker areas with partial sunshine gradually returning in other areas. Temperatures remain anomalously warm for late December.
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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Wednesday
Light to moderate rain and high-elevation snow.
Wednesday
Night
Moderate rain and snow.
Wednesday
Light rain and high-elevation snow become moderate by late morning.
Wednesday
Night
Moderate to possibly heavy rain and snow.
Wednesday
Light rain and high-elevation snow become moderate by late morning.
Wednesday
Night
Increasing light rain and higher elevation snow.
Wednesday
Increasing light rain and snow may become moderate on the volcanoes.
Wednesday
Night
Light rain and higher elevation snow become moderate for the volcanoes overnight.
Wednesday
Increasing light rain, snow, or wintry mix. Moderate ridgeline and light to moderate E wind at the Pass.
Wednesday
Night
Periods of light rain, snow, or wintry mix. Light ridgeline and light E winds at the Pass.
Wednesday
Increasing light rain, snow, and wintry mix. Mostly rain at the Pass. Decreasing moderate to strong ridgeline and light to moderate E wind at the Pass.
Wednesday
Night
Periods of light rain, snow, and wintry mix. Light ridgeline and light E winds at the Pass.
Wednesday
Increasing periods of light snow.
Wednesday
Night
Periods of light snow.
Wednesday
Increasing light rain, snow, and wintry mix.
Wednesday
Night
Periods orf light rain, snow, and wintry mix.
Wednesday
Periods of light rain, snow, and wintry mix.
Wednesday
Night
Periods of light rain, snow, and wintry mix.
Wednesday
Periods of light to moderate rain and higher elevation snow. Moderate ridgeline winds.
Wednesday
Night
Periods of light rain and 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).