An atmospheric river that peaked in the strong category early this morning continues to send copious amounts of precipitation into the region. Precipitation rates reached 0.5"/hr in the North Cascades last night (Bolt Creek) and Mt Baker picked up just shy of 4.0" of water in a 12hr period. Snow levels have also peaked in the 8,500-10,000ft range.
Today wind speeds generally ratchet back down and we'll see precipitation rates slow comparatively. The orientation of the flow shifts ever so slightly to be SSW'ly, putting the southern Washington Volcanoes in the cross hairs and keeps all of the western Washington Cascades in the action. As the main current notches west the passes might be on the edge of the heavier precipitation later. Expect lighter and more showery rain for the eastern Cascades and other areas in the lee by afternoon.
Cooler air filters in slowly from the NW behind the main flow as the front inches east tonight. We'll see gradually lowering snow levels from this afternoon through the day on Wednesday.
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 to moderate rain showers.
Tuesday
Night
Light rain showers.
Tuesday
Moderate to heavy rain showers. Strong ridgeline winds in the morning.
Tuesday
Night
Moderate rain showers.
Tuesday
Moderate to heavy rain.
Tuesday
Night
Moderate to heavy rain.
Tuesday
Heavy rain on SW slopes of the volcanoes, moderate rain showers at Crystal and White Pass. Strong winds on exposed ridgelines.
Tuesday
Night
Moderate rain showers.
Tuesday
Moderate rain showers.
Tuesday
Night
Light to moderate rain showers.
Tuesday
Moderate to heavy rain showers. Strong winds in the morning.
Tuesday
Night
Light to moderate showers.
Tuesday
Moderate rain. Decreasing ridgeline winds.
Tuesday
Night
Light to moderate rain with high elevation snow.
Tuesday
Moderate rain with strong winds in areas like Mission Ridge.
Tuesday
Night
Light rain showers.
Tuesday
Light to moderate rain showers.
Tuesday
Night
Light to moderate rain showers.
Tuesday
Moderate to heavy rain showers at times. Strong 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).