The Pacific Northwest lies at the western edge of a broad, deep, and cold trough over the western US. Some enhanced convection has developed with a weak boundary near the Washington Coast with NW flow aloft guiding this cellular convection toward Mt Hood and Mt St Helens. These areas could pick up 2-5" of low-density snowfall on Tuesday, mostly during the morning hours. Isolated snow showers should increase during the afternoon hours for the mountains further north as daytime heating destabilizes the atmosphere with unusually cold temperatures aloft. Snow levels should rise from around 1000 ft in the morning to around 2000 ft during the afternoon.
Isolated snow showers in some areas during the early evening hours should dissipate as the exiting trough enables a ridge to move into the area. The ridge should provide mostly dry weather through Wednesday, however, an approaching warm front will bring increasing high cloud cover to the area. Light rain and snow may develop for Mt Hood by the end of the day as SSW winds increase in coastal areas.
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
Partly to mostly cloudy skies with isolated snow showers.
Tuesday
Night
Mostly clear with increasing high clouds.
Tuesday
Partly to mostly cloudy with isolated snow showers.
Tuesday
Night
Partly cloudy in the evening with isolated snow showers or flurries, then becoming mostly clear.
Tuesday
Partly to mostly cloudy skies with isolated snow flurries in the morning and isolated snow showers in the afternoon.
Tuesday
Night
Partly cloudy with isolated snow flurries in the evening, then becoming mostly clear.
Tuesday
Partly to mostly cloudy skies with increasing chances for snow showers as the day progresses.
Tuesday
Night
Mostly clear with high clouds increasing overnight.
Tuesday
Partly to mostly cloudy with isolated snow flurries in the morning and isolated snow showers in the afternoon. Light ridgeline and W wind at the Pass.
Tuesday
Night
Mostly clear. Light ridgeline and W wind at the Pass.
Tuesday
Partly to mostly cloudy with isolated snow flurries in the morning and isolated snow showers in the afternoon. Light ridgeline and W wind at the Pass.
Tuesday
Night
Mostly clear. Light ridgeline and W wind at the Pass.
Tuesday
Chilly start. Mostly sunny skies in the morning give way to partly cloudy skies with isolated snow showers in the afternoon.
Tuesday
Night
Isolated snow showers in the early evening, then mostly clear skies.
Tuesday
Mostly sunny in the morning with partly cloudy skies and isolated snow showers in the afternoon.
Tuesday
Night
Mostly clear skies.
Tuesday
Mostly sunny in the morning with partly cloudy skies and isolated snow showers in the afternoon.
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).