A relatively weak and narrow atmospheric river has taken aim at Vancouver Island this morning. The main band of precipitation is clipping the Olympic Mountains and North Cascades setting up quite a difference between these areas and the rest of our forecast region. Near and under this fire hose you'll find very storm conditions with periods of heavy rain and snow combined with very strong and gusty southerly winds.
A bit of precipitation is spilling further south than initially expected this morning. Don't be surprised if you encounter very light drizzle near Stevens or Snoqualmie Pass to start the day. However, all this moisture will lift north mid-morning relegating any showers to places adjacent to the main event like the East North and West Central zones. Strong winds will be more common across the entire region. Expect gusty ridgeline winds, with the strongest wind speeds near Hurricane Ridge, Mt Baker, Mt Saint Helens, and Mt Hood. While most places should stay cloudy on Saturday, overcast skies could thin a bit in the southern zones and near Mt Hood. This could result in filtered sunshine or maybe even some sun breaks.
This evening, the trough associated with the atmospheric river digs further south and becomes more N-S oriented. This should lift the bulk of the precipitation north of the border. However, ridgelines winds will remain strong and gusty. On Sunday, the trough splits in half as the storm tries to push inland. This will limit the available moisture for our region. Weather models still disagree about when exactly the system will move onshore. While there are still plenty of details to work out, it's a safe bet that areas further north have a better chance at significant precipitation in the afternoon than locations further south.
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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Saturday
Stormy, particularly in the western part of the range. Moderate and gusty SSW winds becoming stronger in the afternoon.
Saturday
Night
Stormy mainly in the western part of the range. Moderat to strong and gusty SSW winds increasing.
Saturday
Very stromy with periods of heavy precipitation and very strong and gusty winds.
Saturday
Night
Rain and snow, mainly near Mt Baker and Canadian border. Showers elsewhere. Strong and gusty S winds.
Saturday
Rain and snow mainly in the northern portion of the zone. A few light showers elsewhere in the morning. Moderate and gusty SSW winds becoming stronger in the afternoon.
Saturday
Night
Cloudy with a few very isolated showers possible. Moderate and gusty SSW winds becoming stronger overnight.
Saturday
Cloudy in the morning with a few sprinkles possible in the norther part of the zone. Clouds may become thinner or provide sun breaks in the afternoon. Moderate and gusty SW winds becoming stronger in the afternoon.
Saturday
Night
Mostly cloudy. Moderate and gusty SW winds becoming stronger overnight.
Saturday
Cloudy with a few sprinkles possible in the morning. Light to moderate WSW winds.
Saturday
Night
Mostly cloudy. Light to moderate WSW winds at ridgecrest with very light east flow at pass level.
Saturday
Cloudy with a few sprinkles possible in the morning. Light to moderate WSW winds becoming moderate W in the afternoon.
Saturday
Night
Cloudy. Light to moderate W ridgeline winds with very light E flow at pass level.
Saturday
Cloudy with light precipitation mainly in the western and northern portions of the zone. Moderate and gusty SW winds becoming stronger in the afternoon.
Saturday
Night
Mostly cloudy. Moderate and gusty SW winds becoming stronger overnight.
Saturday
Cloudy in the morning. Clouds thinning with a few sun breaks possible in the afternoon, particularly in the eastern part of the zone. Moderate to strong and gusty SW winds.
Saturday
Night
Mostly cloudy. Moderate and gusty SW winds becoming stronger overnight.
Saturday
Cloudy in the morning. Clouds may thin in the afternoon with a few sun breaks possible. Moderate and gusty SW winds increasing.
Saturday
Night
Mostly cloudy. Moderate and gusty SW winds increasing.
Saturday
Mostly cloudy in the morning with generally high overcast. Clouds could thin in the afternoon with sun breaks possible. Strong and gusty winds decreasing slightly in the afternoon.
Saturday
Night
Mostly cloudy. Moderate to strong and gusty SW wind increasing overnight.
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).