The final major storm in an unrelenting train off the Pacific will approach the area on Tuesday, lifting a warm front over western Washington. Following a cool start on Tuesday with post-frontal snow showers winding down, light precipitation ahead of the approaching warm front has reached the Washington Coast. Light snowfalls should gradually fill in across NW Washington during the morning hours, then increase into the moderate to heavy range in the afternoon in these same areas during the afternoon, while moving light precipitation into other areas of Washington. Increasing E low-level flow will allow some of this light precipitation to spill onto the E slopes of the Cascades. Increasing SSW or S ridgeline for the Hurricane Ridge and Mt. Baker areas should become moderate and strong, respectively, from late morning onwards.
The storm reaches peak precipitation intensity Tuesday evening and overnight where areas favored by SSW can expect very heavy snowfall rates, tapering with a frontal passage in the early morning hours. E flow through the passes should keep the passes cool and we don't expect a wind shift with the frontal passage, just a decrease in E flow. Light to moderate post-frontal showers should end relatively quickly on Tuesday over Washington State. Mt. Hood should see a delay in the onset and the end of the storm with heavier precipitation late Tuesday night and Wednesday morning before tapering off in the afternoon.
Overall, the storm is likely to bring 1-2 ft of snow to many areas of the Cascades with the most expected at Mt. Baker, Paradise, Snoqualmie Pass, and Washington Pass.
An incoming upper trough will likely bring a disturbance with some light to moderate snow moving into the Olympics and Mt. Hood area during the afternoon.
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
Light rain and snow in the morning becoming moderate to heavy in the afternoon. Ridgeline winds becoming moderate to strong.
Tuesday
Night
Heavy rain and snow in the evening, decreasing overnight.
Tuesday
Light rain and snow developing in the morning and becoming heavy in the afternoon. Ridgeline winds increasing to strong by the afternoon.
Tuesday
Night
Very heavy rain and snow decreasing slightly in the early morning hours.
Tuesday
Periods of light rain and snow, increasing and possibly becoming moderate late in the day.
Tuesday
Night
Heavy rain and snow.
Tuesday
Periods of light rain and snow, increasing and possibly becoming moderate late in the day.
Tuesday
Night
Heavy rain and snow at Paradise and Crystal with moderate rain and snow at White Pass.
Tuesday
Periods of light rain and snow, increasing late in the day. Light E winds at pass level.
Tuesday
Night
Moderate rain and snow. Light E winds at pass level.
Tuesday
Periods of light rain and snow, increasing and possibly becoming moderate late in the day. W pass-level wind switching to E early in the day and increasing in the light-moderate range during the afternoon.
Tuesday
Night
Heavy rain and snow. Decreasing moderate E winds at pass level.
Tuesday
Periods of light snow, increasing and possibly becoming moderate late in the day.
Tuesday
Night
Heavy snow.
Tuesday
Periods of light rain and snow, increasing and possibly becoming moderate late in the day.
Tuesday
Night
Heavy rain and snow.
Tuesday
Partly to mostly cloudy in the morning with light rain and snow developing late in the day.
Tuesday
Night
Moderate rain and snow.
Tuesday
Mostly cloudy with increasing ridgeline winds with strong gusts in the afternoon.
Tuesday
Night
Moderate rain and snow developing in the overnight hours.
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).