We're in for a stormy pattern over the next 36 hours with plenty of twists and turns to keep us on our feet. An occluded front passed north overnight dropping a few inches of snow, localized freezing rain, and forcing relatively warmer air (20s) near and above ridgelines along the Washington Cascades. Much colder air remains entrenched at lower elevations on both sides of the crest. An amazing 25F degree W to E difference is occurring at 5000' at the Stevens Pass resort as the easterly flow and SW winds aloft battle it out. Snow will be heaviest in the Mt Baker area this morning with strong southerly winds. A mix of snow and occasional freezing rain may occur near and west of Stevens and Snoqualmie Passes with continued periods of freezing rain for White Pas this morning. The Mt Hood area will be the relatively mild spot today with snow levels around 5000-5500'.
The low-pressure system hanging off of our coast will merge with a digging upper level trough to re-invigorate precipitation across the west slopes of the Cascades and Mt Hood later this morning. Mid-day to afternoon snowfall rates look very heavy, in the 1-3"/hr range. The trough will pass through the Cascades this afternoon with a switch from east Pass level winds to westerly around the 3 o'clock hour. We'll see a relative bump in snow levels, most pronounced over the south Washington Cascades late this afternoon and less noticeable further north. Westerly winds will become extreme for these same areas this afternoon and evening.
Post-frontal snow showers should wind down quickly later Wednesday evening as the flow begins to reverse to easterly again. The exception will be the Mt Hood area where warm frontal moisture will begin lifting north from the next system. Warm frontal moisture will bring moderate snow to the Mt Hood area and the south Washington Cascades on Thursday with lighter snow further north. Strong SE ridgeline winds are expected for the Hood area, and south/central WA Cascades.
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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Wednesday
Light snow and rain. Periods of moderate ridgeline winds.
Wednesday
Night
Light scattered snow showers.
Wednesday
Moderate to occasionally heavy snow through early afternoon, then becoming light to moderate showers. Strong winds this morning becoming lighter this afternoon.
Wednesday
Night
Light scattered snow showers.
Wednesday
Light to occasionally moderate snow and localized freezing rain, becoming moderate to heavy mid-day. Strong ridgeline winds increasing in the afternoon.
Wednesday
Night
Light to moderate snow showers in the evening, becoming light scattered snow showers after midnight. Strong ridgeline winds decreasing after midnight.
Wednesday
Light to occasionally moderate snow and localized freezing rain mainly near White Pass, becoming moderate to heavy mid-day. Strong ridgeline winds increasing in the afternoon.
Wednesday
Night
Light to moderate snow showers in the evening, becoming light scattered snow showers after midnight. Strong ridgeline winds decreasing after midnight.
Wednesday
Light to occasionally moderate snow and localized freezing rain, becoming moderate to heavy mid-day. Moderate E winds in the Passes, strong W ridgeline winds increasing in the afternoon.
Wednesday
Night
Light to moderate snow showers in the evening, becoming light scattered snow showers after midnight. Strong W ridgeline and Pass level winds decreasing after midnight.
Wednesday
Light to occasionally moderate snow and localized freezing rain, becoming moderate to heavy mid-day. Moderate E winds in the Passes, strong W ridgeline winds increasing in the afternoon.
Wednesday
Night
Light to moderate snow showers in the evening, becoming light scattered snow showers after midnight. Strong W ridgeline and Pass level winds decreasing after midnight.
Wednesday
Light to moderate snow. Moderate ridgeline winds.
Wednesday
Night
Light scattered snow showers heaviest in the evening. Moderate ridgeline winds.
Wednesday
Light snow increasing in the afternoon to moderate. Moderate ridgeline winds becoming strong.
Wednesday
Night
Light scattered snow showers heaviest in the evening. Strong ridgeline winds decreasing after midnight.
Wednesday
Light snow increasing in the afternoon to moderate wintry mix. Moderate ridgeline winds becoming strong.
Wednesday
Night
Light scattered snow showers heaviest in the evening. Strong ridgeline winds decreasing after midnight.
Wednesday
Light rain and snow, with a chance of localized freezing rain this morning. Heavy rain and snow in the afternoon. Strong to extreme 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).