Updated 0745 to adjust the wind forecast for Mt. Hood.
The polar express seems to be right on schedule this year...Merry Christmas!
Snow showers continue to rotate around a cold trough sitting over the region today. 5000 ft temperatures should struggle to get out of the teens in most of our mountain locations today as cold air continues to filter into the mountains. Lowland locations will increasing find temperatures dropping as Fraser river outflow moves very cold air from interior Canada across W Watcom County and toward the northern Olympics. This could bring some increasing upslope snowfall to the northern Olympics today and tonight. Scattered snows showers should bring anywhere from a few inches east of the Cascade Crest to 3-10" near and west of the Cascade Crest today. Snowfall should be light with intense squalls at times. Snow to water ratios will be high.
A second lobe of the trough swings toward our area overnight, accompanied by a relatively weak and newly-formed surface low. The surface low should reach the mouth of the Columbia river by early Sunday morning with snowfall still piling up, but decreasing slightly lower across Washington State. As the low tracks south of most of our mountain locations, it should allow the really cold air to our north to move in more forcefully at all elevations, bringing temperatures down to 0F in some of our mountain locations. Light snow showers continue on Sunday in most areas. Saturday night and Sunday, Mt. Hood can expect the highest snowfall amounts. Perhaps 4-8" of snowfall during both 12-hour time perids.
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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Saturday
Decreasing light to moderate snow showers, but increasing upslope snowfall along the north edge of the range.
Saturday
Night
Light upslope snowfall increasing to moderate overnight.
Saturday
Increasing moderate snow showers.
Saturday
Night
Decreasing light to moderate snow showers.
Saturday
Decreasing moderate snow showers.
Saturday
Night
Light snow showers.
Saturday
Moderate snow showers at Crystal and White Pass; light snow showers at Crystal. Moderate ridgeline winds at Crystal and White Pass decreasing.
Saturday
Night
Moderate snow showers at Paradise; light at White Pass.
Saturday
Light to moderate snow showers. Light W wind at the Pass.
Saturday
Night
Decreasing light snow showers. Light E wind at the Pass.
Saturday
Moderate snow showers. Light W wind at the Pass.
Saturday
Night
Decreasing light to moderate snow showers. Light E wind at the Pass.
Saturday
Light to occasionally moderate snow showers.
Saturday
Night
Decreasing light snow showers.
Saturday
Light to moderate snow showers western part; light eastern part. Strong ridgeline wind gusts possible during the morning hours.
Saturday
Night
Decreasing light snow showers.
Saturday
Light to occasionally moderate snow showers.
Saturday
Night
Decreasing light snow showers.
Saturday
Moderate snow showers. Strong ridgeline wing gusts likely, particularly during the morning hours.
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).