An impressive plume of warm, moisture laden air pushes in today. The leading edge of the firehose comes in with a SW orientation and stays with us for a while. Mt Hood and the adjacent southern volcanoes should get a solid brush of precipitation this morning. Moderate to heavy precipitation rates should quickly settle into the west side of the Olympics and Cascades during the day with a focus on the northern part of the range. Ridgetop winds should increase notably by afternoon as the storm lays in. Overnight temperatures dropped into the mid 20's and even upper teens in the eastern Cascade valleys, which may mix in and help slow the changeover from snow to rain from about Stevens pass and northeast-ward. Elsewhere, snow levels rise rapidly to 7,500-9,000ft by noon.
The heaviest precipitation and strongest winds should occur during the overnight period and last well into the day Tuesday. We could see sustained ridgetop winds of 40-55mph with rainfall rates exceeding .25"/hr in many favored west side locations. The firehose may stall out as it whiplashes and reloads, resulting in increased precipitation totals through Tuesday. Snow levels remain in the 8,000-9,000ft range until Tuesday afternoon when cooler air begins to filter in on the backside of the feature. The North Cascades may start seeing snowfall back down at 5,000ft or so by the end of the day.
Weather Forecast
Olympics
West North
West Central
West South
Stevens Pass
Snoqualmie Pass
East North
East Central
East South
Mt. Hood
Use dropdown to select your zone
Monday
Light rain, increasing to moderate rain with moderate Southerly winds.
Monday
Night
Very heavy rain with moderate to strong ridgetop winds.
Monday
Light precipitation in the morning then becoming moderate to heavy during the day. Snow changing to rain early. Increasingly strong ridgetop winds.
Monday
Night
Very heavy rain with moderate to strong ridgetop winds.
Monday
Light precipitation in the morning, then moderate to heavy during the day. Increasing ridgetop winds.
Monday
Night
Very heavy rain with moderate to strong ridgetop winds.
Monday
Moderate rain with increasing ridgetop winds. Rain could be heavy at times in favored locations.
Monday
Night
Moderate rain showers, could be heavy in favored locations.
Monday
Light snow and wintry mix, becoming mostly rain by afternoon and increasing.
Monday
Night
Heavy rain with moderate to strong ridgetop winds.
Monday
Light precipitation as a wintry mix early, then becoming mostly rain and increasing.
Monday
Night
Heavy rain with moderate to strong ridgetop winds.
Monday
Light snow, increasing to heavy snow and rain by the end of the day.
Monday
Night
Heavy snow and rain with moderate to strong ridgetop winds.
Monday
Light snow and rain, becoming mostly rain by the end of the day.
Monday
Night
Heavy rain with strong ridgetop winds.
Monday
Light to moderate rain and snow.
Monday
Night
Light to moderate rain showers.
Monday
Moderate to heavy rain with moderate ridgetop 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).