High pressure is firmly in control over the western U.S, with dry, clear and warm conditions over the region. Mid and upper mountain temperatures are well above freezing, with some sites over 50F(!) this morning for the second day in a row. Valley fog on the west slide and fog/stratus along the eastern slopes will continue today with stronger inversions, less mixing for the lower elevations along the east slopes. Low clouds and fog will nip at the Cascade Passes all day as well. We'll see some high clouds this afternon make for passing periods of filtered sun. SE-S winds will be breezy in the Passes, Mt Hood and areas near and east of the Cascade crest.
Even though the low clouds persist in these areas, it's an even thinner layer of moisture. It feels strange to highlight relative humidity (RH), but it's very dry above the low-level inversions, with some stations reporting RHs in the 10-20% range - keep the chapstick handy!
More of the same tonight with high freezing levels, mostly clear skies, temperature inversions, and low clouds and valley fog. The upper level ridge will begin to break down on Friday. Temperatures will still be quite mild, but freezing levels will lower very slowly during the day, with some scattered high clouds starting to roll in during Friday afternoon. Offshore flow will weaken and day-time inversions should be weaker along the east slopes of the Cascades, and low clouds may actually clear out of the Passes.
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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Thursday
Mostly sunny, with a few high clouds and periods of filtered sunshine in the afternoon. Light to occasionally moderate ridgeline winds.
Thursday
Night
Mostly clear with a few high clouds. Areas of valley fog. Moderate ridgeline winds.
Thursday
Mostly sunny, with a few high clouds and periods of filtered sunshine in the afternoon. Areas of valley fog. Light to occasionally moderate ridgeline winds.
Thursday
Night
Mostly clear with a few high clouds. Areas of valley fog. Light to moderate ridgeline winds.
Thursday
Mostly sunny, with a few high clouds and periods of filtered sunshine in the afternoon. Areas of valley fog. Light to occasionally moderate ridgeline winds.
Thursday
Night
Mostly clear with a few high clouds. Areas of valley fog. Light to moderate ridgeline winds.
Thursday
Mostly sunny, with a few high clouds and periods of filtered sunshine in the afternoon. Areas of valley fog and low clouds near and east of White Pass. Moderate ridgeline winds.
Thursday
Night
Mostly clear with a few high clouds. Areas of valley fog. Light to moderate ridgeline winds.
Thursday
Mostly sunny upper slopes with a few high clouds and periods of filtered sunshine in the afternoon. Cooler with areas of fog and low clouds at Pass level. Light to moderate E-SE Pass and ridgeline winds.
Thursday
Night
Mostly clear with a few high clouds. Cooler with areas of fog and low clouds at Pass level. Light to moderate E-SE Pass and ridgeline winds.
Thursday
Mostly sunny upper slopes with a few high clouds and periods of filtered sunshine in the afternoon. Cooler with areas of fog and low clouds at Pass level. Light to moderate E-SE Pass and ridgeline winds.
Thursday
Night
Mostly clear with a few high clouds. Cooler with areas of fog and low clouds at Pass level. Light to moderate E-SE Pass and ridgeline winds.
Thursday
Mostly sunny upper slopes with a few high clouds and periods of filtered sunshine in the afternoon. Areas of valley fog and low clouds. Light to moderate ridgeline winds.
Thursday
Night
Mostly clear upper slopes with a few high clouds. Areas of valley fog and low clouds. Light to moderate ridgeline winds.
Thursday
Mostly sunny upper slopes with a few high clouds and periods of filtered sunshine in the afternoon. Areas of valley fog and low clouds. Moderate ridgeline winds.
Thursday
Night
Mostly clear upper slopes with a few high clouds. Areas of valley fog and low clouds. Light to moderate ridgeline winds.
Thursday
Mostly sunny upper slopes with a few high clouds and periods of filtered sunshine in the afternoon. Areas of valley fog and low clouds. Moderate ridgeline winds.
Thursday
Night
Mostly clear upper slopes with a few high clouds. Areas of valley fog and low clouds. Light to moderate ridgeline winds.
Thursday
Mostly sunny with a few high clouds and periods of filtered sunshine in the afternoon. Areas of valley fog and low clouds surrounding lowlands. Moderate ridgeline winds.
Thursday
Night
Mostly clear with a few high clouds. Areas of valley fog and low clouds surrounding lowlands. 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).