A very active pattern continues across the Pacific Northwest. A potent frontal system continues to push through the Mt Hood area between 7 and 8 AM this morning. The primary frontal band continues to bring very heavy snowfall. A vigorous push of moist westerly flow has produced a wide and heavy convergence band currently situated from Highway 90 to Highway 2. This band should continue to maintain heavy snowfall in this region for much of the morning hours. Temperatures peaked in the upper 20s and low 30s for the west slopes of the Cascades during the early morning hours but will drop several more degrees as the post-frontal air mass ushers in slightly cooler temperatures. W ridgeline winds will be most intense (strong to extreme) at Mt Hood, but will remain in the moderate range for exposed locations along the E slopes of the Cascades and through the mountain gaps.
Saturday evening will be a relative break in the action as post-frontal showers become universally light.
However, in the early morning hours, a warm front begins lifting northward. Precipitation increases first around Mt Hood and then into the southern Washington Volcanoes. The package of heavy precipitation peaks Sunday morning as snow levels rise rapidly. E flow through the mountain gaps will create a messy transition at Snoqualmie Pass just before the wind shifts westerly around 10 AM. Expect very heavy rain and high-elevation snow for Paradise southward to Mt Hood with the warmup impacting all areas, but Washington Pass likely stays all snow.
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Decreasing light to moderate snow showers. Decreasing light to moderate ridgeline winds.
Light snow showers in the evening. Light snow developing overnight. Light 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).