A winter storm finally brings an end to our prolonged period of warm and dry weather Sunday. A warm front lifting north across the region this morning may produce a few showers in the mountains, particularly near Mt Baker. However, for other locations, Sunday will be a generally dry day and any precipitation should be minimal. A very pronounced cold front will start to swing through the Pacific Northwest late this afternoon and evening. Ahead of the front expect wind speeds to increase dramatically. Strong S-SW ridgeline winds will develop for most areas by the end of the day. As the front passes overhead, several hours of moderate to heavy precipitation will bring significant rain and snow to the mountains. While snow levels may begin between 4000 and 5000 ft, they should plummet during the evening and bring snow to well below pass levels by the early morning. These initial bands of precipitation should easily make it over the Cascade crest and impact locations further east. After the cold front passes winds should become more westerly and continue to push light to moderate snow up into the west slopes and passes.
By very early Monday morning a Puget Sound Convergence Zone will take aim at the central Cascades and likely focus most of its moisture between Hwy 2 and I90. Under this narrow band of heavier snow, significant accumulations will be possible. For other locations, northwesterly winds and plenty of lingering low-level moisture will keep the snow falling in the mountains. This generally unsettled weather pattern should persist as we head into the first part of the week.
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
Rain and snow. Very strong SW winds developing in the afternoon.
Sunday
Night
Snow showers with snow levels rapidly lowering. Moderate to strong W winds decreasing over night.
Sunday
Moderate rain and snow, increasing in the afternoon. SSW winds becoming very strong in the afternoon.
Sunday
Night
Light to moderate snow, becoming showery overnight. Strong W winds.
Sunday
Moderate rain and snow particularly in the northern half of the zone. Moderate to strong SW winds increasing in the afternoon.
Sunday
Night
Moderate rain and snow with snow levels rapidly lowering. Moderate to strong W winds.
Sunday
Overcast with a few sprinkles in the northern part of the zone. SW winds becoming strong in the afternoon.
Sunday
Night
Light to moderate precipitation with rapidly lowering snow levels. Strong W winds.
Sunday
Overcast with rain and snow increasing in the afternoon. Light easterly flow at pass level maintaining shallow inversions. SW ridge top winds becoming moderate in the afternoon.
Sunday
Night
Moderate rain and snow with rapidly lowering snow levels. East flow quickly ending with a short-lived bump in temperatures. Strong W winds.
Sunday
Overcast with rain and snow increasing in the afternoon. Light easterly flow at pass level will maintain shallow temperature inversions. Chance of freezing rain at Pass level this afternoon. Moderate to strong SW ridgetop winds.
Sunday
Night
Rain and snow, heavy at times. East flow quickly turning westerly with a slight bump in temperatures. Snow levels quickly lowering overnight bringing snow below Pass level. Strong W winds increasing overnight.
Sunday
Overcast with occasional showers. SW winds becoming strong in the afternoon.
Sunday
Night
Light to moderate snow with lowering snow levels. Moderate W winds becoming strong.
Sunday
Overcast with a few sprinkles near the crest. Moderate W winds becoming strong.
Sunday
Night
Light to occasionally moderate rain and snow with rapidly lowering snow levels. Strong to very strong W winds increasing overnight.
Sunday
Overcast. Moderate west winds becoming strong in the afternoon.
Sunday
Night
Light to occasionally moderate rain and snow. Snow levels quickly lowering. Strong W winds increasing overnight.
Sunday
Overcast with clouds thickening and lowering. Winds increasing significantly in the afternoon. Moderate to strong WSW ridgetop winds.
Sunday
Night
Rain and snow, heavy at times. Snow levels quickly dropping. Very strong W 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).