10:20 AM update: adjusted water numbers for Mt. Baker, Stevens Pass, and Salmon La Sac on Thursday.
A trough exits the region on Monday Morning. Light post-frontal snow showers and weakening convergence over the Cascades decrease with 1-3" of low-density additional accumulation along the west slopes and a trace to an inch along the east slopes before the offshore high pressure cuts off the shower activity by late morning. Expect partly cloudy skies by mid-day for the west slopes of the Cascades with mostly sunny skies developing further east. Temperatures start in the upper 10s to mid-20s but should rise into the upper 20s to low 30s by the afternoon.
A weak warm front moves north, brushing the Olympics in the evening perhaps the Mt. Baker overnight with some very light rain or snow. This will moderate temperatures west of the Cascade Crest as E flow develops through the mountain gaps.
The warm front lingers near the Canadian Border on Thursday with very light rain and snow remaining over the northern Cascades and Olympics, with a weak cold front approaching the coast late in the day. Temperatures should be warm with freezing levels rising to 4500-7500 ft the southern Cascades with snow levels rising to 3000-4500 ft further north. Temperatures will be slower to warm along the east slopes of the Cascades and E winds through the mountain gaps peak in the moderate range.
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
Snow flurries in the morning, then becoming partly cloudy with high clouds increasing.
Wednesday
Night
Periods of very light rain or snow.
Wednesday
A few snow showers in the morning, then becoming partly cloudy.
Wednesday
Night
Increasing clouds with very light rain or snow overnight.
Wednesday
A few snow showers in the morning, then becoming partly cloudy.
Wednesday
Night
Increasing clouds with very light rain or snow possible overnight.
Wednesday
A few snow showers in the morning, then becoming partly cloudy.
Wednesday
Night
Increasing clouds with a slight chance of sprinkles or snow flurries.
Wednesday
A few snow showers in the morning, then becoming partly cloudy. Moderate ridgelinewinds quickly becoming light. Decreasing light W winds at the Pass.
Wednesday
Night
Increasing clouds with a slight chance of sprinkles or snow flurries.
Wednesday
A few snow showers in the morning, then becoming partly cloudy. Moderate ridgeline and W winds at the Pass quickly becoming light.
Wednesday
Night
Increasing clouds with a slight chance of sprinkles or snow flurries.
Wednesday
A few snow flurries early then becoming mostly sunny.
Wednesday
Night
Increasing high clouds.
Wednesday
A few snow flurries early then becoming mostly sunny.
Wednesday
Night
Increasing high clouds.
Wednesday
A few snow flurries early then becoming mostly sunny.
Wednesday
Night
Increasing high clouds.
Wednesday
Periods of light snow or showers early then becoming partly cloudy to mostly sunny. Moderate ridgeline winds becoming light.
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).