A weak warm front lifting northward over western Washington on Sunday is associated with a weak circulation center offshore and on the downstream side of a trough digging southward toward California. The warm front has moderate precipitation along the coast, but anything east of I-5 is very light. Most areas west of the Cascade Crest should pick up a dusting of snow today with Mt. Baker and Hurricane Ridge likely to pick up an inch or so. The warm front brings subtle warming west of the Cascade crest, combining with subtle high pressure working in from the interior to help increase E flow. E gradients increase through Sunday evening driving light to moderate E flow through the passes, then relax overnight. Expect inversion conditions to develop in many areas on Sunday night with strong radiational cooling and decreasing wind throughout the region. a cold air pool east of the Cascades, and low-level east flow through the mountain gaps.
The inversion conditions are likely to weaken or potentially mix out as high pressure strengthens aloft and brings subtle additional warming on Monday. Expect mostly sunny skies with light winds to make for very nice weather on Monday.
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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Sunday
Periods of light rain and snow through early afternoon, then partial clearing late in the day.
Sunday
Night
Partly cloudy early, then becoming mostly clear. Low cloud possible in the valleys.
Sunday
Periods of light rain and snow.
Sunday
Night
Partly cloudy early, then becoming mostly clear.
Sunday
Periods of light rain and snow, then partial clearing late in the day.
Sunday
Night
Mostly clear.
Sunday
Periods of light rain and snow ending around mid-morning. Then mostly sunny skies developing in the afternoon.
Sunday
Night
Mostly clear. Low cloud possible in the valleys.
Sunday
Mostly cloudy in the morning, then partial sunshine in the afternoon. Increasing light E wind at pass level.
Sunday
Night
Mostly clear aloft with low cloud and inversion conditions likely. Decreasing light E flow at pass level.
Sunday
Mostly cloudy in the morning with a chance of light rain or snow, then partial sunshine in the afternoon. Increasing light to moderate E wind at pass level.
Sunday
Night
Mostly clear aloft with low cloud and inversion conditions likely. Decreasing light to moderate E flow at pass level.
Sunday
Mostly cloudy with the chance of light snow greatest in the afternoon.
Sunday
Night
Gradually clearing skies.
Sunday
Mostly cloudy in the morning, then partial sunshine in the afternoon. Low cloud lingering in valleys.
Sunday
Night
Mostly clear aloft with low clouds in the valleys.
Sunday
Mostly cloudy in the morning, then becoming mostly sunny by late afternoon. Low cloud lingering in valleys.
Sunday
Night
Mostly clear aloft with low clouds in the valleys.
Sunday
Decreasing mid-level clouds with mostly sunny conditions developing from mid-morning onwards.
Sunday
Night
Mostly clear aloft with low clouds in the valleys.
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).