0845 Update: Cloud conditions West North and West Central today.
We'll be dry and mild over the next few days with strong upper level ridging offshore. There are a few caveats that come along with the dry weather. For today, a weak upper level feature passing through in NW flow aloft will keep strong NW winds at ridgeline and in the alpine blowing through at least early afternoon. With these winds, Mazama, WA in the Methow Valley saw an amazing 27F degree jump in 2 hours early this morning thanks to strong downsloping and adiabatic warming (warming through compression). Further south, Mt Hood is basking in the mild air with 50F temperatures found in the 5000-7000' range. Along the west slopes of the Cascades north of I-90, low clouds can be found generally in the valleys and western edge of most zones below 5000'. In areas with low clouds, if you push above ~5000' you should find mostly sunny conditions and a stiff wind. There will be some cooler temperatures briefly ushered in over the north Cascades as well, look for lowering freezing levels and falling mid-mountain temperatures in the afternoon hours.
On Friday, the offshore flow (east winds) will begin to ramp up. Freezing levels and mountain temperatures will still be mild, but slightly lower than Thursday. The warmest temperatures will be found west of the Cascade crest for areas like Mt Baker, Paradise, Mt Pilchuck and the Olympic Range. Slightly cooler temps and breezy E-SE ridgeline winds will occur in the afternoon near the Cascade crest, especially near and west 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 areas of low clouds.
Thursday
Night
Mostly clear.
Thursday
Partly to mostly sunny with low clouds in valleys to mid-mountain eastern part of the zone, mostly cloudy with widespread low clouds western portion of the zone. Cooling trend in the afternoon.
Thursday
Night
Partly cloudy with areas of low clouds.
Thursday
Partly to mostly sunny with low clouds in valleys to mid-mountain eastern part of the zone, mostly cloudy with widespread low clouds western portion of the zone. Cooling trend in the afternoon.
Thursday
Night
Partly cloudy with areas of low clouds.
Thursday
Mostly sunny with areas of low clouds western part of the zone. Moderate to strong ridgeline winds.
Thursday
Night
Mostly clear. Patchy areas of low clouds and fog.
Thursday
Mostly sunny with areas of low clouds this morning. Moderate to strong NW ridgeline winds. Light to moderate W ridgeline winds at Pass level.
Thursday
Night
Mostly clear. Patchy areas of low clouds and fog.
Thursday
Mostly sunny with areas of low clouds this morning. Strong NW ridgeline winds. Moderate W Pass level winds.
Thursday
Night
Mostly clear. Patchy areas of low clouds and fog.
Thursday
Mostly sunny with some low clouds near the Cascade crest. Strong ridgeline winds decreasing in the afternoon. Cooling trend in the afternoon.
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).