An atmospheric river will send pulses of moisture, mostly in the form of rain, over the PNW over the next few days. Freezing levels will hover near 11,000-12,000 feet near Mt Hood, where they'll see no precipitation, to 9000' over the south WA Cascades, and 7000-8000' over the north and central WA Cascades, where we'll see several inches of water over this period. This first pulse will focus moderate precipitation today towards the central Cascades, becoming somewhat lighter in the afternoon. We'll see cloudy conditions along the west slopes of the Cascades and Passes, transition to partly sunny skies along the eastern slopes further from the Cascade crest. Mt Hood will see some filtered sunshine today as the frontal boundary slightly sags south.
The next pulse will bring heavier rain tonight into Wednesday morning, before becoming relatively lighter on Wednesday afternoon. Westerly winds will oscillate between moderate and strong over this time period, and increase in strength as you approach alpine areas. Not to beat a dead horse, but it's not a very pleasant forecast for those who enjoy good snow conditions and nice weather.
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
Cloudy with light to moderate rain. Moderate to strong ridgeline winds.
Tuesday
Night
Moderate rain. Strong ridgeline winds.
Tuesday
Cloudy with light to moderate rain. Moderate to strong ridgeline winds.
Tuesday
Night
Moderate to occasionally heavy rain. Strong ridgeline winds.
Tuesday
Cloudy with moderate to occasionally heavy rain, heaviest in the morning. Moderate ridgeline winds.
Tuesday
Night
Moderate to occasionally heavy rain. Strong ridgeline winds.
Tuesday
Cloudy with moderate rain, heaviest western areas, lighter Crystal area. Moderate ridgeline winds.
Tuesday
Night
Light to moderate rain, heaviest western parts, lighter Crystal area. Strong ridgeline winds.
Tuesday
Cloudy with moderate to occasionally heavy rain, heaviest in the morning. Moderate W Pass level and ridgeline winds.
Tuesday
Night
Moderate to occasionally heavy rain. Moderate to strong W Pass level and ridgeline winds.
Tuesday
Cloudy with moderate to occasionally heavy rain, heaviest in the morning. Moderate to strong W Pass level and ridgeline winds.
Tuesday
Night
Moderate to occasionally heavy rain. Moderate to strong W Pass level and ridgeline winds.
Tuesday
Cloudy with light rain and high elevation snow this morning, then chance of rain near the Cascade crest in the afternoon. Partly sunny eastern parts of the zone. Strong ridgeline winds.
Tuesday
Night
Cloudy with light to moderate rain and high elevation snow near the crest, mostly cloudy eastern parts of the zone. Strong ridgeline winds.
Tuesday
Cloudy with light to moderate rain and high elevation snow this morning, then chance of rain near the Cascade crest in the afternoon. Partly sunny eastern parts of the zone. Strong ridgeline winds.
Tuesday
Night
Cloudy with light to moderate rain and high elevation snow near the crest, mostly cloudy eastern parts of the zone. Strong ridgeline winds.
Tuesday
Cloudy with light rain and high elevation snow this morning, then chance of rain near the Cascade crest in the afternoon. Partly sunny eastern parts of the zone. Strong ridgeline winds.
Tuesday
Night
Cloudy with light rain and high elevation snow near the crest, mostly cloudy eastern parts of the zone. Strong ridgeline winds.
Tuesday
Mostly sunny this morning, then partly sunny with filtered sunshine. Strong ridgeline winds.
Tuesday
Night
Partly cloudy with high clouds. 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).