An upper-level low drifting toward the northern California coastline has ejected another wave of moisture northward. Moisture wrapping around the upper-level low is moving into the southern half of our forecast region from the SE. Moisture should increase throughout the morning hours and reach as far north as highway 2 by late afternoon. A very pronounced cold pool exists east of the Cascades with temperatures in the single digits in cold valley locations. With moderate E flow through the mountain gaps, many areas near and east of the passes have pronounced inversion conditions. Areas west of the Cascade crest are milder, but the contrast between the air masses should decrease on Sunday as the weak disturbance mixes the air masses slightly and E flow through the mountain gaps should gradually decrease. Expect strong winds at places like Crystal Mountain and White Pass to decrease into the moderate range by late in the day. Easterly winds should shift to the WSW for Mt. Hood as the disturbance lifts north of the area.
Snow should decrease during the evening hours and taper to flurries overnight, generally remaining in the same areas. Through tonight, we expect up to 3" of low-density snow for Stevens Pass southward in Washington state with 2-6" for Mt. Hood.
Monday should be a relatively quiet day with light winds and upper-level flow shifting to the NNW. A few snow showers could dust parts of the west slopes of the Cascades.
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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Sunday
Mostly cloudy for the northern Olympics with periods of light snow for the southern and eastern Olympics. Milder.
Sunday
Night
Mostly cloudy to start, then becoming clear overnight.
Sunday
Filtered sunshine. Milder.
Sunday
Night
Mostly clear.
Sunday
A mix of mid-level clouds and sunshine in the morning, then becoming mostly cloudy by the afternoon.
Sunday
Night
Mostly cloudy in the evening, then mostly clear overnight.
Sunday
Cloudy with periods of light snow developing.
Sunday
Night
Mostly cloudy with light snow in the evening, tapering overnight.
Sunday
Clouds thickening in the morning with light snow at times during the afternoon. Light to moderate ridgeline and E wind at the Pass.
Sunday
Night
Light snow at times during the evening, then becoming partly cloudy overnight. Light ridgeline and E wind at the Pass.
Sunday
Clouds thickening in the morning with light snow at times during the afternoon. Light to moderate ridgeline and E wind at the Pass.
Sunday
Night
Light snow at times during the evening, then becoming partly cloudy overnight. Light ridgeline and E wind at the Pass.
Sunday
Mostly clear with high and mid-level clouds increasing during the afternoon. Cold, with inversions during the morning hours.
Sunday
Night
Clearing skies. Cold.
Sunday
Clouds lowering and thickening during the morning. Light snow at times during the afternoon.
Sunday
Night
Light snow at times during the evening, then becoming partly to mostly cloudy 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).