Temperatures remain unseasonably cold, but nearly all NWAC stations have warmed in the last 24 hours with some stations in the Mt. Rainier area warming by 20F since this time on Saturday. A series of shortwave troughs will keep the snowfall going in the mountains. The first is rotating NE around an offshore low and will bring periods of generally light snow to our mountains. WSW flow above 6000 ft will favor Paradise, Mt. St. Helens, the southern Olympics, and Mt. Hood where 3-6" of snow can be expected on Sunday. At the surface, E flow will keep areas near and east of the Cascade crest quite chilly with wind chills near zero.
A stronger disturbance with a well-defined surface low approaches tonight and reaches our coastline late Monday. This system should bring moderate to heavy snowfall to our region. Snoqualmie Pass southward will be favored with another 1-2 ft of snow expected Sunday night through Monday. Areas further north can expect 6-15". Moderate to strong WSW ridgeline winds will increase throughout the day on Monday with the potential for very strong winds at Mt. Hood.
Temperatures should continue to moderate throughout the forecast period.
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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Sunday
Cloudy with periods of light snow increasing throughout the day.
Sunday
Night
Periods of light snow.
Sunday
Cloudy with snow flurries in the morning. Light snow likely developing late in the day.
Sunday
Night
Light snow.
Sunday
Cloudy with snow flurries in the morning. Light snow developing in the afternoon.
Sunday
Night
Light to occasionally moderate snow.
Sunday
Light to moderate snow, heaviest at Paradise, lightest at Crystal.
Sunday
Night
Heavy snow at Paradise, moderate snow at White Pass, and light to moderate snow at Crystal.
Sunday
Cloudy with snow flurries in the morning. Light snow developing in the afternoon. Light to occasionally moderate E wind at the Pass.
Sunday
Night
Light to moderate snow. Light to moderate E wind at the Pass.
Sunday
Cloudy with snow flurries in the morning. Light snow developing in the afternoon. Light to moderate E wind at the Pass.
Sunday
Night
Light snow becoming moderate. Moderate E wind at the Pass.
Sunday
Cloudy with a chance of snow flurries.
Sunday
Night
Cloudy with periods of light snow.
Sunday
Cloudy with snow flurries in the morning. Light snow developing in the afternoon.
Sunday
Night
Increasing light to occasionally moderate snow.
Sunday
Periods of light snow.
Sunday
Night
Light snow becoming moderate.
Sunday
Moderate snow. Moderate to strong 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).