A weak upper level disturbance positioned offshore pushed clouds over the region last night. With the cloud cover, low temperatures in Passes and low-lying areas are generally a few degrees warmer than yesterday morning. While there's still temperature inversions and easterly flow in the Passes, breezy W-SW ridgeline winds can be found in most locations. The upper trough will pass through this afternoon, briefly switching the low-level flow to westerly, mixing up the lower levels and producing a more uniform set of freezing levels across the mountains. The best chance to squeeze out a few flurries will be in the Mt Hood area this afternoon. There should be a fair bit of sunshine mixing in this afternoon across the mountains.
The upper level ridge will rebuild over the area tonight, and slide inland on Tuesday. High cloud cover from a splitting N-S oriented frontal system will begin to spill over the area late tonight, and increase on Tuesday. Offshore flow will increase once again on Tuesday, making for a tricky freezing level forecast. Freezing levels and temperatures will cooler on the east-side, but with E-SE winds increasing, the Passes will likely once again be the battleground between cooler and milder air. Light precipitation will hold off until Tuesday night and Wednesday.
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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Monday
Mostly cloudy this morning, then partly sunny in the afternoon. Light to moderate ridgeline winds.
Monday
Night
Mostly cloudy in the evening, becoming overcast with high and mid clouds thickening after midnight. Light to moderate ridgeline winds.
Monday
Mostly cloudy this morning, then partly sunny in the afternoon. Light to moderate ridgeline winds.
Monday
Night
Mostly cloudy in the evening, becoming overcast with high and mid clouds thickening after midnight. Light to moderate ridgeline winds.
Monday
Mostly cloudy this morning, then partly sunny in the afternoon. Light to moderate ridgeline winds.
Monday
Night
Mostly cloudy in the evening, becoming overcast with high and mid clouds thickening after midnight. Light to moderate ridgeline winds.
Monday
Mostly cloudy this morning, then partly sunny in the afternoon. Light to moderate ridgeline winds.
Monday
Night
Mostly cloudy in the evening, becoming overcast with high and mid clouds thickening after midnight. Light to moderate ridgeline winds.
Monday
Mostly cloudy this morning, then partly sunny in the afternoon. Light E winds at Pass level becoming W in the afternoon. Light to moderate W ridgeline winds.
Monday
Night
Partly to mostly cloudy in the evening, then high and mid clouds thickening after midnight. Light to moderate E winds at Pass level. Light to moderate W ridgeline winds.
Monday
Mostly cloudy this morning, then partly sunny in the afternoon. Light E winds at Pass level becoming W in the afternoon. Moderate W ridgeline winds.
Monday
Night
Partly to mostly cloudy in the evening, then high and mid clouds thickening after midnight. Light to moderate E winds at Pass level. Light to moderate W ridgeline winds.
Monday
Mostly cloudy this morning, then partly sunny in the afternoon. Light to moderate ridgeline winds.
Monday
Night
Partly cloudy. Increasing high and mid clouds late. Light to moderate ridgeline winds.
Monday
Mostly cloudy this morning, then partly sunny in the afternoon. Moderate ridgeline winds.
Monday
Night
Partly cloudy. Increasing high and mid clouds late. Moderate ridgeline winds.
Monday
Mostly cloudy this morning, then partly sunny in the afternoon. Moderate ridgeline winds.
Monday
Night
Partly cloudy. Increasing high and mid clouds late. Moderate ridgeline winds.
Monday
Partly to mostly cloudy. A chance of light rain or snow in the afternoon. Moderate ridgeline winds.
Monday
Night
Partly to mostly cloudy in the evening, then high and mid clouds thickening after midnight. Light to moderate ridgeline 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).