Over the next 36 hours, a frontal system moves into our region, rounding the top of a high-pressure system off the California coastline.
The warm front will impact the region today through this evening. The radar shows light rain and snow across SW Washington and NW Oregon on Wednesday morning. This moisture should continue in these same general areas, shifting into the Mt. Rainier area during the afternoon. Mt. Hood could pick up 1-2" of snow, but elsewhere minor accumulations are expected.
Easterly low-level flow could bring several hours of freezing rain to Snoqualmie Pass, Stevens Pass and areas just east of the passes as the precipitation moves in Wednesday evening. Overnight, light to moderate rain and snow increasingly becomes an all rain event as rain/snow lines rise to 6000-8000 ft and the cold front approaches.
The cold front arrives Thursday morning with a period of moderate WSW winds a good westerly surge of wind behind it. Rain rates should be in the moderate to strong range as the front passes, tapering to rain and snow showers as slightly cooler mid-level air arrives in the afternoon. Modest convergence could develop in the Stevens Pass vicinity during the afternoon as brisk W winds very slowly decrease.
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
Increasing light rain and snow showers. Rising snow levels.
Wednesday
Night
Increasing light rain and highest elevation snow.
Wednesday
Mostly cloudy with a chance of very light rain or snow.
Wednesday
Night
Light rain and snow becoming light to moderate overnight.
Wednesday
Mostly cloudy.
Wednesday
Night
Increasing light rain and snow becoming light to moderate overnight.
Wednesday
Mostly cloudy in the morning with light rain or snow possible in the afternoon.
Wednesday
Night
Increasing light to occasionally moderate rain and snow.
Wednesday
Mostly cloudy. Increasing light E winds at the Pass.
Wednesday
Night
Increasing light rain and snow. Freezing rain may be possible at times. Light E winds at the Pass.
Wednesday
Mostly cloudy. Increasing light E winds at the Pass.
Wednesday
Night
Light rain and snow becoming light to moderate overnight. Freezing possible near and east of the Pass. Light E winds at the Pass.
Wednesday
Partly cloudy.
Wednesday
Night
Light rain and snow developing.
Wednesday
Mostly cloudy.
Wednesday
Night
Increasing light rain and snow, possibly mixing with freezing rain at times.
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).