A ridge builds further into the region as it amplifies on Thursday, bringing partly cloudy skies to the region in the morning with increasing sunshine in the afternoon. Temperatures above 5000 ft increased for many NWAC stations in the early morning hours on Thursday, a sign of the increasing influence of the high pressure. Lower elevation locations remained colder, setting up an inversion for as we head into Thursday morning. West of the Cascade Crest, the inversion should mix out as sunshine warms the lower atmosphere.
A cold air pool east of the Cascade Crest remains stronger and combines with increasing moderate E flow through the mountain gaps to keep the passes cooler today. Temperatures may get into the mid-30s at Snoqualmie Pass during the middle of the day, while at comparable elevations further west, temperatures will be in the upper 40's to lower 50's.
The E flow should peak Thursday evening as a weakening frontal system approaches. Light rain and snow should spread throughout the region during the early morning hours on Friday with a cold frontal passage around 7-9 AM on Friday. Snoqualmie Pass may start as snow or a rain/snow mix, but the shift to W flow behind the front should quickly bump snow levels up to 5500 ft. Light post-frontal rain and snow showers will gradually decrease during the morning hours. The weak system should generally bring around 0.25" of water equivalent with some areas getting as much as 0.50". Partial sunshine should re-emerge late in the day.
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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Thursday
Partly cloudy in the morning, then mostly sunny in the afternoon.
Thursday
Night
Becoming mostly cloudy in the evening. Light rain and snow at the highest elevations developing overnight.
Thursday
Partly cloudy early with decreasing clouds throughout the day.
Thursday
Night
Mostly clear to start, then becoming mostly cloudy in the late evening with light rain and high elevation snow developing after midnight.
Thursday
Partly cloudy early with decreasing clouds throughout the day.
Thursday
Night
Mostly clear to start, then becoming partly cloudy in the late evening with light rain and high elevation snow developing after midnight.
Thursday
Partly cloudy early with decreasing clouds throughout the day.
Thursday
Night
Mostly clear to start, then becoming partly cloudy in the late evening with light rain and high elevation snow developing after midnight.
Thursday
Partly cloudy early with decreasing clouds throughout the day.
Thursday
Night
Mostly clear to start, then becoming partly cloudy in the late evening with light rain and high elevation snow developing after midnight.
Thursday
Partly cloudy early with decreasing clouds throughout the day.
Thursday
Night
Mostly clear to start, then becoming partly cloudy in the late evening with light rain and high elevation snow developing after midnight.
Thursday
Partly cloudy early with decreasing clouds throughout the day.
Thursday
Night
Mostly clear in the evening, then increasing clouds with light rain and snow developing in the early morning hours.
Thursday
Partly cloudy early with decreasing clouds throughout the day.
Thursday
Night
Mostly clear in the evening, then increasing clouds with light rain and snow developing in the early morning hours.
Thursday
Partly cloudy early with decreasing clouds throughout the day.
Thursday
Night
Mostly clear in the evening, then increasing clouds with light rain and high elevation snow developing in the early morning hours.
Thursday
Partly cloudy early with decreasing clouds throughout the day.
Thursday
Night
Mostly clear with clouds increasing after midnight and a chance of light rain or snow developing by morning.
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).