Tonight:
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Colder Canadian air moves into eastern Washington, reaching the Lower Columbia Basin overnight.
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Moisture from the central Pacific system enters SW Oregon as a warm front, lifting north into central Oregon.
Wednesday:
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The central Pacific system undercuts the ridge, bringing precipitation.
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Central Oregon experiences initial snow, with rising snow levels (3000 to 4500 feet) by afternoon.
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The front progresses northward, spreading precipitation across the forecast area and stalling overnight.
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Areas from Madras northward mainly experience snow, while lower elevations see a mix of rain and snow.
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Wednesday Night – Thursday:
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Elevations below 1000-1500 feet with a rain and snow mix, becoming mostly snow by Thursday morning.
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A return to a mix is expected by midday and afternoon.
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Precipitation along the stalled front decreases late Thursday, tapering off to showers by Thursday night.
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Snow Accumulations and Alerts:
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The complex system leads to varying snow accumulations.
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Winter Storm Watches, Warnings, and advisories are in effect, especially in the Oregon and southern Washington Cascades.
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Travel difficulties are possible from White Pass southward.