A moisture-laden low and associated warm front will impact the Pacific Northwest today and tonight with heavy precipitation and rising snow levels. The low sits just south of the mouth of the Columbia River early Saturday morning. It tracks NE across the region, crossing the central Washington Cascades during the afternoon hours. A moderate to heavy precipitation shield extends north of the low, with wrap-around moisture on the back side of the low. The tricky part of the forecast will be how rapidly some pockets of sub-freezing temperatures near and east of the Cascade Crest get scoured out by the very mild SW winds aloft that are bringing the copious moisture. In the central Cascades, some of that cold air cold hold on around Stevens Pass until 10 AM or noon, but it will hold on through the evening hours around Washington Pass with a warm end to the system overnight. The other point of uncertainty is how much of the moisture will reach Mt Baker. Some of the models keep the majority of the precipitation staying just south of the volcano.
Expect a subtle break in the action late Saturday and early in the evening hours, between the first low and a secondary shortwave re-invigorating rainfall Saturday night. Sunday should be one of the milder days in recent January history with some areas experiencing mostly dry weather as the moisture feed focuses on SW British Columbia. Most model forecasts do have clouds and some light showers lingering across our region.
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
Light to moderate rain.
Saturday
Night
Moderate rain.
Saturday
Rain and highest elevation snow becoming moderate to heavy.
Saturday
Night
Heavy rain and highest elevation snow.
Saturday
Moderate to occasionally heavy rain and highest elevation snow.
Saturday
Night
Heavy rain and highest elevation snow.
Saturday
Moderate to heavy rain and highest elevation snow (very heavy at Paradise).
Saturday
Night
Moderate to heavy rain and highest elevation snow (heaviest at Paradise).
Saturday
A wintry mix in the morning hours transitions to all rain. Light ridgeline and E wind at the Pass.
Saturday
Night
Moderate rain. Light ridgeline and E wind at the Pass.
Saturday
Heavy rain with a slight chance of freezing rain at middle elevations early in the day. Moderate ridgeline and light to moderate E wind at the Pass.
Saturday
Night
Heavy rain. Moderate ridgeline and light to moderate E wind at the Pass.
Saturday
Increasing light to moderate rain, snow, and freezing rain. Rising snow levels.
Saturday
Night
Moderate to heavy rain, snow, and freezing rain. Rising snow levels.
Saturday
Moderate rain mixing with freezing rain or snow at times early in the day.
Saturday
Night
Moderate to heavy rain, snow, and freezing rain. Rising snow levels.
Saturday
Moderate rain mixing with freezing rain or snow at times early in the day.
Saturday
Night
Moderate to heavy rain, snow, and freezing rain. Rising snow levels.
Saturday
Moderate to heavy rain and high-elevation snow. Strong ridgeline winds.
Saturday
Night
Moderate to heavy rain and high-elevation 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).