8am Update: Corrected Snoqualmie/Stevens Precipitation Forecasts for today
A convergence zone pummeled Snoqualmie Pass and the I-90 corridor last night, doing most of its damage during the early morning hours with snowfall rates exceeding several inches/hr and 12-18" of snow overnight with the higher totals above Pass level. Heavy snowfall in this band extended well east side of Snoqualmie Pass. Generally 4-8" fell elsewhere with the most higher total for the Mountain Loop, Stevens, Paradise, and Mt Hood.
Scattered snow showers will continue this morning, with locally more intense showers near the Convergence zone near the I-90 corridor. While most of the damage has been done, the convergence zone and scattered snow showers will continue through mid-day. Strong upper-level ridging is building offshore with a drying trend in store for the region. Look for sunny skies as you travel east of the Cascades east, a mix of sun and clouds near the crest, and mostly cloudy with low clouds trapped to the west.
We'll have a dry Friday night as the ridge quickly traverses inland. Easterly winds and offshore pressure gradients will quickly increase overnight, with gusty winds developing in the Passes late as a storm approaches. Snow will develop for the Olympics Saturday morning and spread inland during the day, with precipitation likely becoming intense for the Cascades around sunset. This will be a snow event during the day but the Olympics will see a rising rain/snow line. A warm-up will occur Saturday night and Sunday as the storm really slams into the region.
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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Friday
Mostly cloudy with isolated light snow showers, becoming partly to mostly sunny in the afternoon.
Friday
Night
Partly cloudy early, becoming cloudy with increasing high clouds late evening.
Friday
Mostly cloudy with scattered light snow showers, becoming partly to mostly cloudy in the afternoon.
Friday
Night
Partly cloudy in the evening, then cloudy with increasing high clouds after midnight.
Friday
Mostly cloudy with scattered light to occasionally moderate snow showers through mid-day, becoming partly to mostly cloudy in the afternoon. Moderate ridgeline winds easing during the morning.
Friday
Night
Partly cloudy in the evening, then cloudy with increasing high clouds after midnight.
Friday
Mostly cloudy with scattered light to occasionally moderate snow showers through mid-day, becoming partly to mostly cloudy in the afternoon. Moderate ridgeline winds easing during the morning.
Friday
Night
Partly cloudy in the evening, then cloudy with increasing high clouds after midnight.
Friday
Mostly cloudy with scattered light to occasionally moderate snow showers through mid-day, becoming partly to mostly cloudy in the afternoon. Light to moderate ridgeline winds easing during the morning.
Friday
Night
Partly cloudy in the evening, then cloudy with increasing high clouds after midnight. Moderate east Pass level winds developing after midnight.
Friday
Cloudy with light to occasionally moderate snow showers through mid-day, becoming mostly cloudy in the afternoon. Moderate ridgeline winds easing during the morning.
Friday
Night
Partly cloudy in the evening, then cloudy with increasing high clouds after midnight. Moderate east Pass level winds developing after midnight.
Friday
Mostly cloudy with isolated light snow showers near the Cascade crest, becoming partly to mostly sunny mid-day. Moderate ridgeline winds easing during the morning.
Friday
Night
Mostly clear in the evening, becoming cloudy with increasing high clouds after midnight.
Friday
Mostly cloudy with scattered light snow showers, except occasionally moderate near Snoqualmie Pass in the morning. Becoming partly to mostly sunny mid-day. Moderate ridgeline winds easing during the day.
Friday
Night
Mostly clear in the evening, becoming cloudy with increasing high clouds after midnight.
Friday
Mostly cloudy with isolated light snow showers near the Cascade crest, becoming partly to mostly sunny mid-day. Moderate ridgeline winds easing during the day.
Friday
Night
Mostly clear in the evening, becoming cloudy with increasing high clouds after midnight.
Friday
Mostly cloudy with scattered light to occasionally moderate snow showers through mid-day, becoming partly to mostly cloudy in the afternoon. Moderate to strong ridgeline winds easing slowly during the day.
Friday
Night
Partly cloudy in the evening, then cloudy with increasing high clouds after midnight.
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).