The deep and cold upper level trough that has delivered cold temperatures and snow showers all week is starting slide to the east as it shifts inland. One final upper level shortwave will slide down the backside of the trough today in NW flow aloft, bringing light snow to the mountains once again. A Puget Sound convergence zone, currently pegged around Snohomish County Thursday morning will drift southward towards I-90 by late morning as the upper level feature veers the low-level wind field to more W-NW by this afternoon. Expect occasionally moderate snowfall rates in and near the convergence zone today with up to 6 inches of snow possible from the Mtn Loop area, Stevens and Snoqualmie Passes areas and with lighter snowfall amounts likely elsewhere. WNW winds will kick up this afternoon for the central Cascades into the moderate-strong range and strong winds down at Mt Hood will increase further this afternoon.
Snow showers will taper off tonight. Low level clouds will linger along the west slopes of the Cascades and Mt Hood, partially trapped by a weak upper level ridge building offshore.
A stronger Pacific frontal system offshore will begin to spread high level clouds over the region from mid-day onward. Freezing levels will stay on the cool side during the short term.
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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Thursday
Cloudy with occasional light snow showers.
Thursday
Night
Mostly cloudy with a few light snow showers possible in the evening.
Thursday
Cloudy with light snow showers decreasing in the afternoon.
Thursday
Night
Mostly cloudy with a few light snow showers possible in the evening.
Thursday
Light to occasionally moderate snow showers becoming scattered in the afternoon. Moderate to strong ridgeline winds.
Thursday
Night
Cloudy with a chance of snow showers in the evening.
Thursday
Cloudy with light snow showers from mid-morning onward.
Thursday
Night
Mostly cloudy with a chance of snow showers in the evening.
Thursday
Light to occasionally moderate snow showers becoming scattered in the afternoon. Moderate to strong ridgeline and Pass level westerly winds.
Thursday
Night
Cloudy with a chance of snow showers in the evening. Moderate west winds at Pass level becoming variable overnight.
Thursday
Light to occasionally moderate snow showers developing. Moderate to strong ridgeline and Pass level westerly winds.
Thursday
Night
Cloudy with a chance of snow showers in the evening. Moderate west winds at Pass level becoming variable overnight.
Thursday
Cloudy with light snow showers from mid-morning onward.
Thursday
Night
Mostly cloudy with a chance of snow showers in the evening.
Thursday
Cloudy with light snow showers near the Cascade crest. Moderate ridgeline winds increasing in the afternoon.
Thursday
Night
Mostly cloudy with a chance of snow showers in the evening.
Thursday
Cloudy with light snow showers near the Cascade crest. Moderate ridgeline winds increasing in the afternoon.
Thursday
Night
Mostly cloudy with a chance of snow showers in the evening.
Thursday
Cloudy with light snow showers starting late morning. Moderate to strong ridgeline winds increasing in the afternoon.
Thursday
Night
Mostly cloudy with a chance of snow showers in the evening.
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).