Cold, clear/sunny weather continues thanks to a blocking high-amplitude ridge offshore. An upper-level disturbance slides down the backside of the ridge into the Pacific Northwest Sunday morning. This disturbance is associated with an uptick in wind speeds mainly above 6500 ft and a shift in direction from NW to NE. Windspeeds in the low 20s and 10s have been recorded from the upper stations at Crystal Mountain and Mt Hood Meadows, respectively. These winds should ease as the day progresses. The added ventilation generally helped decrease the strength of any inversions by mixing the atmosphere, so most locations have temperatures that are slightly warmer than on Saturday morning.
Increasing offshore pressure gradients will gradually increase low-level E winds through places like Snoqualmie Pass over the next 24 hours with these light to moderate gap winds likely peaking Sunday mid-day or afternoon. These winds will also focus the coldest air on the E slopes of the Cascades, but areas further west that are influenced by the E flow should also remain far chillier, likely creating stronger inversions and some temperatures dropping into the single digits in deep valley locations. These east winds peak mid-day on Monday. Afternoon freezing levels should be around 2000-3000 ft on Sunday. However, afternoon freezing levels on Monday vary from 1500 ft E of the Cascade Crest to 7500 ft over the Olympics as the offshore ridge gradually moves onshore keeping the sunny, dry pattern going.
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
Sunny with a chilly start, then moderating.
Sunday
Night
Clear and cool.
Sunday
Sunny. A low-level inversion is possible in the morning hours.
Sunday
Night
Clear and cold. Low-level temperature inversions are likely.
Sunday
Sunny and cool. A low-level inversion is possible in the morning hours.
Sunday
Night
Clear and cold. Low-level temperature inversions are likely.
Sunday
Sunny and cool. A low-level inversion is possible in the morning hours.
Sunday
Night
Clear and cold. Low-level temperature inversions are likely.
Sunday
Sunny and cool. A low-level inversion is possible in the morning hours. Light ridgeline and E wind at the Pass.
Sunday
Night
Clear and cold. Low-level temperature inversion is likely. Increasing light to occasionally moderate ridgeline and E wind at the Pass.
Sunday
Sunny and cool. A low-level inversion is possible in the morning hours. Light to occasionally moderate ridgeline and E wind at the Pass.
Sunday
Night
Clear and cold. Low-level temperature inversion is likely. Increasing light to moderate ridgeline and E wind at the Pass.
Sunday
Cold with some mid-level clouds early, then full sun. A low-level inversion is likely at times.
Sunday
Night
Clear and cold. Low-level temperature inversion is likely.
Sunday
Sunny and cold. A low-level inversion is possible in the morning hours.
Sunday
Night
Clear and cold. Low-level temperature inversion is likely.
Sunday
Sunny and cold. A low-level inversion is possible in the morning hours.
Sunday
Night
Clear and cold. Low-level temperature inversion is likely.
Sunday
Sunny and cool. A low-level inversion is possible in the morning hours.
Sunday
Night
Clear and cold. Low-level temperature inversion likely.
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).