A cool upper trough continues to dig southward over the region continues to bring significant snowfall to the region on Sunday. The radar on Sunday morning showers scattered snow showers north of Stevens Pass with more sustained snow showers from Mt. Rainier Southward. A strong convergence has dropped southward from Stevens and appears relatively stationary over Snoqualmie Pass, which could receive 10-12" of snowfall during the day. While we think the heaviest snowfall is over at Stevens Pass, 4-6" of snow remain a possibility and some models have a Vancouver Island convergence zone picking up snowfall rates here in the afternoon. Ridgeline winds become stronger further south. Expect exposed areas south of Snoqualmie Pass to receive strong wind gusts throughout the day. Mt. Hood can expect moderate to heavy snow and significant wind.
The trough axis shifts slightly east of the region Sunday night with upper-level flow gradually shifting more northerly. Snow showers should become light in the central Cascades, but moderate snow showers continue in southern parts of the forecast region with some potential for convergence in the Mt. Rainier area. Fraser River outflow increases overnight, bringing the potential for an upslope snowfall event on the north slopes of the Olympics that could bring Hurricane 6-12" Sunday night and Monday. With increasingly cold air aloft and supported by the Fraser River outflow at low levels, expect continued cooling and low-density snowfall.
Snow showers across the region should be generally light on Monday with an additional 2-5" possible at Mt. Hood.
Weather Forecast
Olympics
West North
West Central
West South
Stevens Pass
Snoqualmie Pass
East North
East Central
East South
Mt. Hood
Use dropdown to select your zone
Sunday
Light snow showers.
Sunday
Night
Moderate snow possible with upslope N winds and accumulations down to just above sea level.
Sunday
Light snow showers.
Sunday
Night
Light snow showers.
Sunday
Light snow showers in the north with moderate and locally intense snow showers in convergence bands focused on the southern part.
Sunday
Night
Light snow showers, heaviest in weakening convergence possible southern part.
Sunday
Light to moderate snow showers. Strong ridgeline wind gusts near the Cascade Crest.
Sunday
Night
Light snow showers, locally moderate in convergence bands.
Sunday
Moderate snow showers, locally intense in convergence bands. Light to occasionally moderate W winds at the Pass.
Sunday
Night
Light snow showers. Light W winds at the Pass.
Sunday
Moderate to heavy snow showers, locally intense in convergence bands. Light to moderate W winds at the Pass.
Sunday
Night
Light snow showers with convergence possible. Light W winds at the Pass.
Sunday
Light snow showers.
Sunday
Night
Decreasing light snow showers.
Sunday
Generally light snow showers may be moderate in convergence spillover near the Cascade Crest.
Sunday
Night
Light snow showers and convergence spillover mainly near the Cascade Crest.
Sunday
Light snow showers. Strong ridgeline wind gusts.
Sunday
Night
Very light snow showers near the Cascade Crest.
Sunday
Moderate to at times heavy snow. Strong ridgeline wind gusts.
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).