A disorganized frontal boundary is moving through the area this morning with a frontal passage expected in the Cascades around 9 am. As the parent low stays stationary off the coast of British Columbia and begins to weaken, storm totals look slightly less impressive. Precipitation amounts have been lowered a notch versus yesterday's forecast. As colder air is replaced with relatively milder Pacific air behind the front, snow levels will bump up to 3500-4000' for the Washington Cascades late this morning through mid-afternoon and up to 5500' for Mt Hood. Post-frontal westerlies are still expected to be strong behind the front this afternoon and evening. Winds may be too strong for a well-defined convergence zone later today, but if one does form it's most likely to hang up north up Hwy 2 into the Mt Loop Hwy corridor through this evening.
Showers will taper off across the area from south to north beginning this evening and continuing overnight. We are in a progressive weather pattern with another front arriving Wednesday afternoon before we can truly dry out. An occluded front will begin to move into the region from the southeast affecting the Olymipcs and Mt Hood in the afternoon. Meaningful precipitation for the rest of the area will likely hold off until Wednesday night. Snow levels will drop to 3000' across the Cascade Passes as easterly offshore flow cranks up in the afternoon.
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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Tuesday
Mostly cloudy with scattered light rain and snow showers.
Tuesday
Night
Mostly cloudy with isolated rain and snow showers.
Tuesday
Light to occasionally moderate rain and snow becoming light to occasionally moderate showers late morning.
Tuesday
Night
Light to occasionally moderate snow showers tapering off after midnight.
Tuesday
Light to occasionally moderate rain and snow becoming light to occasionally moderate showers late morning.
Tuesday
Night
Light to occasionally moderate snow showers tapering off after midnight.
Tuesday
Light to occasionally moderate rain and snow becoming light to occasionally moderate showers late morning.
Tuesday
Night
Scattered light rain and snow showers tapering off after midnight.
Tuesday
Light to occasionally moderate rain and snow becoming light to occasionally moderate showers late morning. Moderate east winds becoming strong westerlies at Pass level by mid-day.
Tuesday
Night
Light to occasionally moderate snow showers tapering off in the evening. Strong west winds at Pass level decreasing after midnight.
Tuesday
Light to occasionally moderate rain and snow becoming light to occasionally moderate showers late morning. Moderate east winds becoming strong westerlies at Pass level by mid-day.
Tuesday
Night
Scattered light rain and snow showers tapering off after midnight. Strong west winds at Pass level decreasing after midnight.
Tuesday
Light rain and snow becoming light to occasionally moderate showers late morning.
Tuesday
Night
Scattered light rain and snow showers tapering off after midnight.
Tuesday
Light rain and snow becoming light to occasionally moderate showers late morning.
Tuesday
Night
Scattered light rain and snow showers tapering off in the evening.
Tuesday
Light rain and snow becoming light to occasionally moderate showers late morning.
Tuesday
Night
Scattered light rain and snow showers tapering off in the evening.
Tuesday
Light to occasionally moderate rain and snow becoming light to occasionally moderate showers late morning.
Tuesday
Night
Scattered light rain and snow showers tapering off in the evening.
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).