An atmospheric river continues to bring very heavy rain and snow to the region. In the past 48 hours, Mt. Baker has picked up nearly 5" of water equivalent, while most other areas have picked up 1-3". E flow kept Snoqualmie Pass snow through the night, and the pass has picked up 20" of snow with temperatures hovering right at 32 degrees as of 7 AM. The moisture onslaught will continue throughout the day into the evening. A warm front crossing the region this morning will continue to push snow levels higher and gradually win the battle against the cooler east flow. We expect Snoqualmie to transition to rain at pass level during the mid-moring hours and the snow line to retreat quickly to higher elevations (6500 ft) by afternoon. Stevens should see the transition during mid-day or early afternoon hours. The forecast is particularly tricky because we don't expect a wind shift, so the cold pool east of the Cascade Crest has to erode enough that the east flow just isn't cool enough. That cooler air is dense and hard to move!
The moisture feed should focus most heavily from central Washington south to Mt. Hood, but Mt. Baker will still get plenty of water. 1-3" of water equivalent can be expected during daylight hours with moderate SW winds. A strong cold front should pass after midnight Tuesday night ends the atmospheric river and brings a rapid decrease in the heavy precipitation, but not before some of the heaviest precipitation rates are expected Tuesday evening. The frontal passage also comes with a cool-down and mid-elevations could see moderate to locally heavy snow showers and convergence by Wednesday morning.
Expect light to moderate snow showers decreasing on Wednesday with temperatures continuing to plummet with snow levels dropping to pass level or below.
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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Tuesday
Heavy rain and high elevation snow. Strong wind gusts at ridgelines.
Tuesday
Night
Very heavy rain and high elevation snow transitioning to rain and snow showers after midnight. Strong wind gusts at ridgelines.
Tuesday
Heavy rain and high elevation snow. Strong wind gusts at ridgelines.
Tuesday
Night
Heavy rain and high elevation snow. Cooling with rain and snow tapering to showers toward morning. Strong wind gusts at ridgelines.
Tuesday
Heavy rain and high elevation snow. Strong wind gusts at ridgelines.
Tuesday
Night
Heavy rain and high elevation snow. Cooling with rain and snow tapering to showers toward morning. Strong wind gusts at ridgelines.
Tuesday
Heavy rain and high elevation snow. Strong wind gusts at ridgelines.
Tuesday
Night
Heavy rain and high elevation snow. Cooling with rain and snow tapering to showers toward morning. Strong wind gusts at ridgelines.
Tuesday
Heavy rain and snow. Snow level rising in the afternoon. Strong wind gusts at ridgelines. Light E winds at pass level.
Tuesday
Night
Heavy rain and high elevation snow. Cooling with rain and snow tapering to showers toward morning. Strong wind gusts at ridgelines. Light E winds switching to moderate W at pass level.
Tuesday
Heavy rain and snow. Snow level rising throughout the day. Strong wind gusts at ridgelines. Decreasing light to moderate E winds at pass level.
Tuesday
Night
Heavy rain and high elevation snow. Cooling with rain and snow tapering to showers toward morning. Strong wind gusts at ridgelines. Light E winds switching to moderate W at pass level.
Tuesday
Heavy snow in the morning, then heavy rain and snow in the afternoon. Strong wind gusts at ridgelines.
Tuesday
Night
Heavy rain and high elevation snow. Cooling with rain and snow tapering to showers toward morning. Strong wind gusts at ridgelines.
Tuesday
Heavy rain and high elevation snow. Strong wind gusts at ridgelines.
Tuesday
Night
Heavy rain and high elevation snow. Cooling with rain and snow tapering to showers toward morning. Strong wind gusts at ridgelines.
Tuesday
Heavy rain and high elevation snow. Strong wind gusts at ridgelines.
Tuesday
Night
Heavy rain and high elevation snow. Cooling with rain and snow tapering to showers toward morning. Strong wind gusts at ridgelines.
Tuesday
Heavy rain and highest elevation snow. Strong ridgeline winds.
Tuesday
Night
Heavy rain and high elevation snow. Cooling after midnight with rain and snow tapering to showers toward morning. Strong 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).