An upper low off Heida Guay continues to spin light snow showers into the Pacific Northwest. SW winds shift to the SSW as the day progresses. This shift has led to moderate ridgeline winds and slightly more vigorous snow shower activity in the Mt. Baker vicinity which we expect to continue throughout the day and overnight. However, we're only expecting 2-4" of snow for Mt. Baker and the southern Olympics today with lighter amounts in all other areas. Expect mostly cloudy skies in the morning to give way to partly cloudy skies in most areas by the afternoon.
A weak ridge centered over the Rockies expands slightly Saturday night bringing in mostly dry conditions, with only a few light snow flurries lingering for Mt. Baker and the Olympics.
However, active weather returns to the region on Sunday as a developing low moves into the area on SW flow as it rotates around the parent low off Heida Guay. Light precipitation should spread into the southern Cascades during the morning hours, becoming moderate for Mt. Hood during the afternoon with light snow spreading throughout the ranges by the end of the day. Snow levels rise to 2500-3000 ft in the afternoon with increasing low-level E flow as SW winds increase into the moderate range in southern parts of the region.
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).