A complex winter storm system is tracking toward southern Vancouver Island on Thursday. A band of moderate snow lifts NE across the region Thursday morning, ahead of an occluded front. The heavier precipitation targets the central and southern Cascades during the late morning through evening hours as the system's warm sector passes through. This will create some complex weather for the passes as low-level E flow intensifies, keeping the pass levels cold, while warmer air moves in above 4500 ft. This makes the risk for freezing rain during peak precipitation from around 3 PM to 7 PM before the front pushes through and the flow switches westerly. This westerly flow brings decreasing light to moderate rain and snow, transitioning to all snow as snow levels drop to and then remain around 1500 ft by Friday morning. With an upper trough offshore and sustained light to moderate WSW flow, expect snow showers to bring substantial accumulations to the W slopes of the Cascades Thursday night and Friday.
We're expecting 6-10" snow totals for areas above the rain/snow line on Friday, but rain or freezing rain will eat into snow totals below 4500-6500 ft for the central and southern Cascades. The southern Cascades should pick up the most snowfall Thursday night, with up to 5-15" of snow, and 3-8 further north. Friday will bring another 4-10" of snow for many locations across the Cascades.
Weather Forecast
Olympics
West North
West Central
West South
Stevens Pass
Snoqualmie Pass
East North
East Central
East South
Mt. Hood
Use dropdown to select your zone
Thursday
Increasing light to moderate snow, potentially mixing with rain late in the day. Increasing moderate ridgeline winds.
Thursday
Night
Decreasing light snow showers.
Thursday
Increasing heavy snow. A chance for a changeover to rain late in the day. Moderate ridgeline winds, strong gusts.
Thursday
Night
Deacreasing light to moderate snow showers. Decreasing moderate ridgeline winds.
Thursday
Increasing moderate snow. A chance for a changeover to rain late in the day. Ridgeline winds increasing into the moderate range by mid-morning.
Thursday
Night
Heavy rain and snow transition to light snow showers overnight. Decreasing moderate ridgeline winds.
Thursday
Heavy rain and snow. Ridgeline winds increasing into the moderate range by mid-morning.
Thursday
Night
Heavy rain and snow transition to light snow showers overnight. Moderate ridgeline winds.
Thursday
Light snow becoming modetate to heavy by mid-morning and potentially mixing with rain or freezing rain late in the day. Increasing light to moderate ridgeline and E wind at the Pass.
Thursday
Night
Moderate to heavy rain, snow, and freezing rain in the evening, transitions to moderate snow showers overnight. Moderate ridgeline and W wind at the Pass.
Thursday
Moderate snow becoming heavy by mid-morning and mixing with rain or freezing rain late in the day. Moderate ridgeline and light to moderate E wind at the Pass.
Thursday
Night
Moderate to heavy rain, snow, and freezing rain in the evening, transitions to moderate snow showers overnight. Moderate ridgeline and light to moderate E wind switches W wind at the Pass by around 7 PM.
Thursday
Light snow becomes moderate to heavy by late morning. Increasing light to moderate ridgeline winds.
Thursday
Night
Moderate snow transitions to light snow showers overnight. Moderate to strong ridgeline winds.
Thursday
Light snow becomes moderate to heavy by late morning. Increasing moderate ridgeline winds.
Thursday
Night
Heavy rain, snow, and freezing rain transition to light, mostly light snow showers overnight. Moderate to strong ridgeline winds.
Thursday
Increasing moderate snow becomes heavy by mid-morning, and mixes with rain or freezing rain late in the day. Increasing light to moderate ridgeline winds.
Thursday
Night
Heavy rain and snow transition to light to moderate snow showers overnight. Moderate ridgeline winds, strong gusts.
Thursday
Increasing heavy rain and snow. Increasing moderate to strong ridgeline winds.
Thursday
Night
Heavy rain and higher elevation snow decreases overnight as snow levels drop below ski area bases. 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).