A frontal system with a surface low center near Heida Guay pivots southeastward during the day on Saturday. In advance of the front, temperatures remain well below normal, but have warmed 10-15F from this time yesterday morning. Most areas have temperatures in the low 10s. SW winds ahead of the front should allow temperatures to moderate. Warming will be more significant in southern parts of the region. Areas from around I-90 southward could see 5000 ft temperatures briefly above freezing during the early afternoon hours while temperatures remain in the mid to upper 20s further north. Clouds lower and thicken across the region with light snow developing during the afternoon hours for the Olympics and Mt Baker area as the frontal system parallels the coastline by dusk.
Snow spreads from NW to SE overnight, increasing in intensity. With dry air across the region, expect snow down to 2000 ft or lower with snow levels dropping as the front moves through in the early morning hours. SSW winds ramp up in advance of the front into the moderate to locally strong range. Mt. Baker will be favored for precipitation totals with heavy snowfall and winds potentially exceeding forecast numbers in the vicinity of the ski area.
Post-frontal westerlies increase behind the front on Sunday and peak during the mid-day hours. Moderate snow showers in the morning decrease during the afternoon, but convergence focused around the mountain loop will maintain moderate to locally heavys snowfall in this area. By late in the day, snow levels should be between 0-500 ft. Expect 10-15" of snow by late Sunday for the west slopes of the Cascades with 2-8" for the east slopes of the Cascades. Snow to water ratios will be high with the cold teperatures.
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
High clouds lower and thicken with light snow developing during the afternoon.
Saturday
Night
Increasing light snow becomes moderate overnight.
Saturday
High clouds lower and thicken with light snow developing during the afternoon.
Saturday
Night
Increasing heavy snow. Moderate ridgeline winds may be strong at times.
Saturday
High and mid-level clouds thicken.
Saturday
Night
Snowfall increases during the evening, becoming heavy overnight. Increasing moderate ridgeline winds.
Saturday
High and mid-level clouds thicken.
Saturday
Night
Light snow becomes moderate (Crystal and White Pass) or heavy (Paradise) overnight. Moderate ridgeline winds.
Saturday
High and mid-level clouds thicken. Light ridgeline and E winds at the Pass.
Saturday
Night
Light snow develops in the evening and becomes moderate to heavy overnight. Light to moderate ridgeline and light E wind at the pass.
Saturday
High and mid-level clouds thicken. Light ridgeline and E winds at the Pass.
Saturday
Night
Light snow develops in the evening and becomes heavy overnight. Light to moderate ridgeline and light E wind at the pass.
Saturday
High and mid-level clouds thicken.
Saturday
Night
Increasing light to moderate snow.
Saturday
High and mid-level clouds thicken. Moderate ridgeline winds.
Saturday
Night
Increasing light snow may be moderate at times (western part). Moderate ridgeline winds may be strong at times overnight.
Saturday
Sunny to start, then high clouds lower and thicken.
Saturday
Night
Light snow develops overnight.
Saturday
Sunny to start, then high clouds lower and thicken. Ridgeline winds become moderate by the afternoon.
Saturday
Night
Cloudy in the evening with moderate snow overnight. Moderate ridgeline winds become strong.
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).