The first two days of spring will give us a taste of the spring-like weather. The remnants of a NW-SE oriented trough start the day mostly cloudy, but expect increasing influence from a weak high pressure over British Columbia to bring partly to mostly sunny skies by the afternoon. Mountain temperatures started cooler in southern portions of the forecast region with freezing levels around 3500-4000 ft in the central and northern Washington Cascades. A weak low over SE Washington could rotate some very light precipitation into the Mission Ridge and some weak convergence in the NE Olympics could bring some lingering showers through mid-morning, before the high gains full traction. Freezing levels rise to around 5000-5500 ft across the region by the afternoon, but there's a 20% chance of isolated showers south of the I-90 corridor in the afternoon associated with a weak surface trough extending northward from California.
The surface trough dissipates by the evening, leaving mostly clear skies Tuesday night. Temperatures remain mild with clear skies getting the freezing levels down to 3000 ft in some areas. Freezing levels rise back up to around 5500 ft by Wednesday afternoon with another chance for isolated showers as a weak shortwave trough approaches.
Expect light E winds Tuesday and Tuesday night with a shift back westerly early Wednesday.
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
Isolated rain/snow showers before 8 AM, then decreasing clouds with mostly sunny skies in the afternoon.
Tuesday
Night
Mostly clear.
Tuesday
Mostly cloudy to start, then becoming partly to mostly sunny by the afternoon.
Tuesday
Night
Mostly clear.
Tuesday
Mostly cloudy in the morning, becoming partly to mostly sunny by the afternoon.
Tuesday
Night
Mostly clear.
Tuesday
Partly cloudy with isolated afternoon rain/snow showers possible over the higher terrain.
Tuesday
Night
Mostly clear.
Tuesday
Mostly cloudy skies give way to partial sunshine. Light ridgeline winds. W winds switch E by mid-morning at the Pass.
Tuesday
Night
Mostly clear. Light ridgeline and E wind at the Pass.
Tuesday
Mostly cloudy skies give way to partial sunshine. A slight chance of an afternoon rain/snow shower. Light ridgeline winds. W winds switch E by mid-morning at the Pass.
Tuesday
Night
Mostly clear. Light ridgeline and E wind at the Pass.
Tuesday
Mostly sunny.
Tuesday
Night
Mostly clear.
Tuesday
Mostly cloudy skies give way to mostly sunny skies.
Tuesday
Night
Mostly clear.
Tuesday
Mostly cloudy skies to start, then becoming partly cloudy. A chance of very isolated rain/snow showers over the higher terrain in the afternoon.
Tuesday
Night
Mostly clear.
Tuesday
Mostly clear. A chance of very isolated rain/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).