The end of the work week will bring mostly dry weather with a shift from cool to warm. The trough that settled over the area Wednesday night has brought a chilly start to Thursday, with 5000 ft temperatures in the upper 10s to mid-20s. Decreasing mostly light W winds are banking low clouds against the west slopes of the Cascades. The majority of the post-frontal showers and convergence banding has tapered off, but some areas from Snoqualmie Pass northward could still experience a few flurries or a brief snow shower. Snow showers could linger into the afternoon around Mt. Baker, although most models favor them ending.
The air mass stabilizes throughout the day on Thursday as the upper trough slides eastward, with a subtle ridge replacing it. Freezing levels rise up to 3000-6000 ft by the afternoon, with more warming in the southern portions of the forecast region. Under clear skies, temperatures should cool slightly overnight, despite the overall warming trend. Light E flow develops around 11 PM, delaying the onset of above-freezing temperatures in some lower elevation areas near and east of the Cascade Crest early Friday (creating an inversion), but spring daytime warming mixes this out by mid-morning. Freezing levels peak around 6000 ft in the north, 7500 ft in the central Cascades, and 10,500 ft on Mt Hood by late Friday.
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
Partly cloudy skies give way to mostly sunny skies with a few high clouds. Milder in the afternoon.
Thursday
Night
Mostly clear.
Thursday
Mostly cloudy to start with clouds decreasing. Isolated snow showers possible at times throughout the day.
Thursday
Night
Mostly clearing skies.
Thursday
A few snow showers or flurries early, then gradually clearing low cloud with mostly sunny skies by late in the day.
Thursday
Night
Mostly clear.
Thursday
A few low clouds early, then mostly sunny skies.
Thursday
Night
Mostly clear.
Thursday
Partly cloudy early with a few snow flurries, then trending towards full sunshine. Light ridgeline and W wind at the Pass.
Thursday
Night
Mostly clear. Light ridgeline. Light W wind at the Pass switches E overnight.
Thursday
Partly cloudy early with a few snow flurries, then trending towards full sunshine. Light ridgeline and W wind at the Pass.
Thursday
Night
Mostly clear. Light ridgeline. Light W wind at the Pass switches E overnight.
Thursday
Mostly sunny.
Thursday
Night
Mostly clear.
Thursday
A few clouds early in the west, then mostly sunny. Occasional moderate ridgeline winds early in the day.
Thursday
Night
Mostly clear.
Thursday
Mostly sunny, with a cool start then milder.
Thursday
Night
Mostly clear.
Thursday
Some low clouds banked against the west slopes of Mt Hood early. Otherwise, mostly sunny skies.
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).