Southerly flow aloft is generally not a high-confidence forecast scenario, and that pattern is playing out now and over the next 24-36 hours. Upper level shortwaves ejecting from an upper low offshore will pass from south to north over the area today, tonight and on Sunday, bringing a round of light to moderate precipitation each time along with bursts of S-SE winds.
Snow levels along the west slopes of the Cascades and Olympics will generally be in the 5000-5500' this morning. Cold air along the east slopes of the Cascades has moderated, but it's still just cold enough for snow levels of 2000-3000' near and north of I-90, and milder further south. However, there are pockets of freezing rain along the eastern slopes and valleys. That freezing rain potential extends to Cascade passes, especially Snoqualmie and White, and to a lesser extent Stevens this morning. The Stampede Pass weather station has been reporting freezing rain for several hours.
The precipitation will pass north today, continuing the longest and heaviest for the Mt Baker area. We'll see sunbreaks and freezing levels pop a bit in the afternoon for most other areas.
We'll do it again tonight and Sunday with additional shortwaves rotating north and the same forecast uncertainties play out. Precipitation looks a bit heavier for the south WA Cascade and Mt Hood Saturday night.
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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Saturday
Light to moderate rain and snow turning to light showers this afternoon. Moderate to strong ridgeline winds.
Saturday
Night
Light to occasionally moderate rain and snow. Moderate ridgeline winds.
Saturday
Light to moderate rain and snow turning to showers late this afternoon. Moderate to strong ridgeline winds, strongest in the afternoon.
Saturday
Night
Light to occasionally moderate rain and snow. Moderate ridgeline winds.
Saturday
Light to moderate rain and snow turning to mostly cloudy skies with scattered light showers this afternoon. Moderate ridgeline winds.
Saturday
Night
Light to occasionally moderate rain and snow. Moderate ridgeline winds.
Saturday
Light to moderate rain and snow turning to mostly cloudy skies with scattered light showers this afternoon. Areas of freezing rain possible near White Pass. Moderate ridgeline winds.
Saturday
Night
Light to occasionally moderate rain and snow with a chance of freezing rain near White Pass. Moderate ridgeline winds.
Saturday
Light to occasionally moderate rain, snow or freezing rain this morning. Mostly cloudy with scattered light showers this afternoon. Moderate E pass level winds and S-SE ridgeline winds.
Saturday
Night
Light to occasionally moderate rain and snow, with a chance of freezing rain. Moderate E pass level winds and S-SE ridgeline winds.
Saturday
Light to occasionally moderate rain, snow or freezing rain this morning. Mostly cloudy with scattered light showers this afternoon. Moderate E pass level winds and S-SE ridgeline winds.
Saturday
Night
Light to occasionally moderate rain and snow, with a chance of freezing rain. Moderate E pass level winds and S-SE ridgeline winds.
Saturday
Light to occasionally moderate rain or snow this morning. Mostly cloudy with isolated light showers this afternoon. Moderate ridgeline winds.
Saturday
Night
Light to occasionally moderate rain and snow. Moderate ridgeline winds.
Saturday
Light to occasionally moderate rain or snow this morning with pockets of freezing rain. Mostly cloudy with isolated light showers this afternoon. Moderate ridgeline winds.
Saturday
Night
Light to occasionally moderate rain and snow with pockets of freezing rain. Moderate ridgeline winds.
Saturday
Light to occasionally moderate rain or snow this morning with pockets of freezing rain. Mostly cloudy with isolated light showers this afternoon. Moderate ridgeline winds.
Saturday
Night
Light to occasionally moderate rain and snow. Moderate ridgeline winds.
Saturday
Light to occasionally moderate rain or snow this morning. Mostly cloudy with isolated light showers this afternoon. Moderate to strong ridgeline winds.
Saturday
Night
Light to occasionally moderate rain and snow. Moderate to strong 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).