A strong storm relative to late March is currently bearing down on the PNW with warm frontal precipitation spreading over the area. Precipitation rates should be highest this morning as snow levels rise from 2500-3000' over the WA Cascades to 4000-4500', with slightly higher freezing levels down near Mt Hood. Precipitation forecasts continue to range from 0.35-1.00" for today, with the higher totals for Mt Baker/Mt Rainier/Mt St Helens, and the Crystal area. Above the rain-line, 4-12" of snow will likely accumulate today. The back edge of the frontal system will pass through a bit faster, meaning a quicker transition from steady precipitation to showers in the afternoon along with the potential for sunbreaks. Most areas will see moderate winds, but the Olympics, Mt Hood and Crystal Mt area will see strong winds for much of the day.
Showers will taper off overnight and become lighter and more scattered. The low pressure system will drift towards the WA coast tonight and Thursday. We'll have a cool unstable air mass overhead on Thursday, and convective showers will fire up over the mountains in the afternoon. Some showers will be heavy at times and contain graupel. Freezing levels will rise to 4500-5500' but snow levels will fall to around 3500' during showers.
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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Wednesday
Light to moderate rain and snow through early afternoon, then mostly cloudy with light to occasionally moderate rain and snow showers. Strong ridgeline winds.
Wednesday
Night
Mostly cloudy with light to occasionally moderate rain and snow showers. Moderate ridgeline winds.
Wednesday
Moderate rain and snow through mid-afternoon, then mostly cloudy with light to occasionally moderate rain and snow showers. Moderate ridgeline winds.
Wednesday
Night
Mostly cloudy with light to occasionally moderate rain and snow showers. Moderate ridgeline winds.
Wednesday
Light to moderate rain and snow through mid-afternoon, then mostly cloudy with light to occasionally moderate rain and snow showers. Moderate ridgeline winds.
Wednesday
Night
Mostly cloudy with light to occasionally moderate rain and snow showers. Moderate ridgeline winds.
Wednesday
Moderate rain and snow through mid-afternoon, occasionally heavy Mt Rainier and Mt St Helens area, then mostly cloudy with light to occasionally moderate rain and snow showers. Moderate ridgeline winds, locally strong Crystal Mt area.
Wednesday
Night
Mostly cloudy with light to occasionally moderate rain and snow showers. Moderate ridgeline winds.
Wednesday
Light to occasionally moderate rain and snow through mid-afternoon, then mostly cloudy with light to occasionally moderate rain and snow showers. Moderate Pass level and ridgeline SE winds becoming SW late in the afternoon.
Wednesday
Night
Mostly cloudy with light to occasionally moderate rain and snow showers. Light to moderate ridgeline and Pass level W-SW winds.
Wednesday
Light to moderate rain and snow through mid-afternoon, then mostly cloudy with light to occasionally moderate rain and snow showers. Moderate Pass level and ridgeline SE winds becoming SW late in the afternoon.
Wednesday
Night
Mostly cloudy with light to occasionally moderate rain and snow showers. Moderate ridgeline and Pass level W-SW winds.
Wednesday
Light to occasionally moderate rain and snow through mid-afternoon, then mostly cloudy with light to occasionally moderate rain and snow showers. Moderate ridgeline winds.
Wednesday
Night
Mostly cloudy with scattered light rain and snow showers. Periods of moderate ridgeline winds.
Wednesday
Light to occasionally moderate rain and snow through mid-afternoon, then mostly cloudy with light to occasionally moderate rain and snow showers. Moderate ridgeline winds.
Wednesday
Night
Mostly cloudy with scattered light rain and snow showers. Moderate ridgeline winds.
Wednesday
Light to occasionally moderate rain and snow through mid-afternoon, then mostly cloudy with light to occasionally moderate rain and snow showers. Moderate ridgeline winds.
Wednesday
Night
Mostly cloudy with scattered light rain and snow showers. Moderate ridgeline winds.
Wednesday
Moderate rain and snow through mid-afternoon, then mostly cloudy with light to occasionally moderate rain and snow showers. Strong ridgeline winds.
Wednesday
Night
Mostly cloudy with light to occasionally moderate rain and snow showers. 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).