We'll remain in cool NW flow today with an upper-level feature enhancing shower activity and winds in the afternoon. Mountain temperatures have dropped precipitously following the passage of a frontal boundary and atmospheric river event overnight. Snow levels this morning are between 1500-2000' and upper mountain station temperatures have plummeted into the teens. Along with scattered showers this morning, convergence zone activity will be focused into the central Cascades today, first around the Mountain Loop to Snoqualmie Pass area and then focusing more on the I-90 corridor in the afternoon and early evening. Shower activity will increase for all areas this afternoon. Westerly ridgeline winds will be strong for most areas today, pushing to extreme along the central and south east slopes of the Cascades and in alpine areas south of Mt Rainier to Mt Hood.
The flow will begin to turn northerly tonight, cutting off the shower activity from north to south. A clearing trend will begin later tonight with upper-level ridging building offshore. Tomorrow should be partly to mostly sunny with much lighter winds and cool freezing levels for late February. High clouds will begin to create filtered sunshine in the afternoon as the next Pacific frontal system in NW flow aloft approaches.
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
Mostly cloudy with scattered light snow showers becoming cloudy with light to occasionally moderate snow showers in the afternoon. Increasing ridgeline winds.
Tuesday
Night
Mostly cloudy in the evening with isolated light snow showers becoming partly cloudy overnight.
Tuesday
Mostly cloudy with scattered light snow showers becoming cloudy with light to moderate snow showers in the afternoon. Increasing ridgeline winds.
Tuesday
Night
Mostly cloudy in the evening with scattered light snow showers becoming partly cloudy overnight.
Tuesday
Cloudy with moderate snow showers. Strong ridgeline winds.
Tuesday
Night
Cloudy in the evening with scattered light to occasionally moderate snow showers becoming partly cloudy overnight. Ridgeline winds decreasing overnight.
Tuesday
Cloudy with light to occasionally moderate snow showers increasing to moderate in the afternoon. Heaviest showers Paradise and White Pass areas. Strong ridgeline winds.
Tuesday
Night
Cloudy in the evening light to occasionally moderate snow showers becoming mostly cloudy late. Ridgeline winds decreasing overnight.
Tuesday
Cloudy with moderate snow showers. Strong west wind at ridgeline and Pass level.
Tuesday
Night
Cloudy in the evening with scattered light to occasionally moderate snow showers becoming partly cloudy overnight. Ridgeline and Pass winds decreasing overnight.
Tuesday
Cloudy with light to moderate snow showers in the morning increasing to moderate to occasionally heavy in the afternoon. Strong west wind at ridgeline and Pass level.
Tuesday
Night
Cloudy in the evening with light to moderate snow showers becoming mostly cloudy late. Ridgeline and Pass winds decreasing overnight.
Tuesday
Cloudy with scattered light snow showers in the morning increasing to light to occasionally moderate in the afternoon. Strong ridgeline winds decreasing in the afternoon.
Tuesday
Night
Mostly cloudy in the evening with scattered light snow showers becoming partly cloudy overnight.
Tuesday
Cloudy with light snow showers, occasionally moderate near the Cascade crest in the morning increasing in the afternoon. Strong to extreme ridgeline winds.
Tuesday
Night
Cloudy in the evening with light snow showers, occasionally moderate near the Cascade crest, becoming partly cloudy overnight. Ridgeline winds decreasing overnight.
Tuesday
Cloudy with light snow showers, occasionally moderate near the Cascade crest in the morning increasing in the afternoon. Strong to extreme ridgeline winds.
Tuesday
Night
Cloudy in the evening with light snow showers, occasionally moderate near the Cascade crest, becoming partly cloudy overnight. Ridgeline winds decreasing overnight.
Tuesday
Mostly cloudy with scattered light rain and snow showers in the morning, becoming cloudy with light to occasionally moderate snow showers in the afternoon. Fewer clouds east-side of the mountain. Strong to extreme winds.
Tuesday
Night
Cloudy in the evening with light to moderate snow showers, becoming mostly cloudy late. Ridgeline winds decreasing 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).