While it's generally dry and clear across the mountains this morning, that will change. A warm front will lift north from Oregon spreading clouds and eventually precipitation across the region. Rain and snow should arrive at Mt Hood, Mt St Helens, and Mt Adams first thing. It will slowly work its way northward eventually reaching areas near and north of I90 in the afternoon. Low level E-SE winds should help turn this moisture into more significant snow showers for areas east of the Cascade crest.
The bulk of the moisture and warmer temperatures arrive this evening. Snow levels will creep up the hillsides. Even though this isn't a particularly warm storm, these are the highest snow levels we've seen in quite some time. Things get even trickier in the Passes. Easterly flow should help moderate some of the incoming warm air, but unfortunately, the cold air pool east of the Cascades doesn't look very deep. As a result, you should see rain at Snoqualmie Pass and mixed precipitation at Stevens and White Passes.
Winds and precipitation ramp up in the wee hours of Monday morning as the trailing cold front meanders toward the mountains. As it does so, snow levels quickly fall back below Pass and most trailhead locations. An interesting feature Monday could be a Puget Sound Convergence Zone focussed towards this Mt Baker area. This may bring a band of locally heavy snowfall in that 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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Sunday
Increasing clouds with light precipitation developing. Light to moderate S winds.
Sunday
Night
Rain and snow. Moderate to strong SW winds.
Sunday
Increasing clouds with precipitation developing later in the day. SSE winds becoming light to moderate.
Sunday
Night
Rain and snow could be heavy at times. Moderate to strong and gusty S winds.
Sunday
Increasing clouds with precipitation developing in the afternoon. Winds becoming S moderate.
Sunday
Night
Rain and snow, could be heavy at times. Moderate S winds becoming SW.
Sunday
Increasing clouds with rain and snow developing late morning. Heaviest near the southern volcanoes. Light to moderate SE winds.
Sunday
Night
Rain and snow could be heavy at times, especially near the volcanoes. Moderate SW winds.
Sunday
Increasing clouds with precipitation developing late in the day. Light E flow at pass level. SE ridgline winds becoming light to moderate/
Sunday
Night
Rain and snow. Light to moderate E flow at pass level. Light to moderate S winds becoming SW.
Sunday
Increasing clouds with precipitation developing in the afternoon. Light to moderate E flow at pass level. SE rideline winds becoming moderate.
Sunday
Night
Rain and snow could be occasionally heavy at times. Light E flow at pass level. Moderate SE winds becoming SW.
Sunday
Increasing clouds with precipitation developing in the afternoon. Light to moderate SSE winds.
Sunday
Night
Rain and snow with warming temperatures. Moderate S winds decreasing slightly.
Sunday
Increasing clouds with precipitation developing in the afternoon. Light to moderate S winds increasing.
Sunday
Night
Rain and snow showers. Moderate to strong and gusty SW winds decreasing slightly.
Sunday
Increasing clouds with precipitation developing mid morning. S winds becoming moderate.
Sunday
Night
Rain and snow showers. Moderate to strong and gusty SW winds decreasing slightly.
Sunday
Increasing clouds with precipitation developing in the morning. SW winds increasing throughout the day and becoming moderate to strong.
Sunday
Night
Rain and snow, could be heavy at times. Strong and gusty SW winds increasing overnight.
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).