We're in a very active pattern with frontal passages every 12-18 hours. The frontal system currently impacting our region is associated with an offshore low. The front arcs across the northern Olympics and into the southern Cascades to start the work week and brings moderate rain and snow to much of the region. Snow levels range from 2000-3000 ft with E flow lowering snow levels slightly through the mountain gaps and east of the Cascade Crest. This also allows the precipitation to spill over onto the east slopes of the Cascades. The steadier precipitation ends from SW to NE as the front lifts away from the area, replaced with some light rain and snow showers for the afternoon.
The forecast becomes more uncertain heading into Monday night and Tuesday. A weak front lifting northeast spreads a band of light to moderate rain and snow to the southern and central Cascades, mainly during the overnight hours. Southerly winds aloft continue with low-level E flow.
A stronger warm front approaches the region during the day on Tuesday with precipitation spreading from SW to NE across the area. Precipitation becomes moderate to heavy by the afternoon for much of the region as snow levels rise to 2500-4000 ft for the central and northern Cascades and 4000-6500 ft for the southern Cascades and Olympics. SW ridgeline winds will also become moderate to strong late in the day.
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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Monday
Moderate snow early quickly tapering to light snow showers. Moderate ridgeline winds are possible at times early.
Monday
Night
Cloudy with occasional light snow showers.
Monday
Moderate snow tapering to light snow showers by the afternoon. Moderate ridgeline winds at times through the morning hours.
Monday
Night
Cloudy with occasional light snow showers.
Monday
Moderate snow tapering to light snow showers by the afternoon. Moderate ridgeline winds at times through the morning hours.
Monday
Night
Cloudy with occasional light snow showers.
Monday
Moderate rain and snow early, becoming mostly light and showery by the afternoon. Moderate ridgeline winds through the morning hours.
Monday
Night
Light rain and snow showers transition to light rain and snow overnight.
Monday
Light to moderate snow through mid-morning, tapers to light snow showers for the remainder of the day. Light ridgeline and E wind at the Pass.
Monday
Night
Mostly cloudy with light snow developing in the early morning hours. Increasing light ridgeline and E wind at the Pass.
Monday
Light to moderate snow through mid-morning, tapers to light snow showers for the remainder of the day. Decreasing light to moderate ridgeline and E wind at the Pass.
Monday
Night
Mostly cloudy with light snow developing in the early morning hours. Increasing light ridgeline and E wind at the Pass.
Monday
Light snow transitions to occasional light snow showers by the afternoon.
Monday
Night
Mostly cloudy with a chance of light snow.
Monday
Light to moderate snow becomes showery by the afternoon. Decreasing light to moderate ridgeline winds.
Monday
Night
Mostly cloudy in the evening with light snow developing overnight.
Monday
Light to moderate snow through mid-morning, then becoming showery. Decreasing light to moderate ridgeline winds.
Monday
Night
Mostly cloudy in the evening with light snow developing overnight.
Monday
Moderate rain and snow early, transition to light showers by the afternoon. Decreasing moderate ridgeline winds.
Monday
Night
Light rain and snow showers transition to moderate rain and snow by the overnight hours. Increasing light to moderate 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).