A weak shortwave centered off the Pacific Northwest coastline lifts NE and brings cloudy conditions on Tuesday with some chances for light rain or showers. Temperatures remain unseasonably mild for late January, but most areas cooled slightly overnight and remain on average 5F cooler than Monday. A frontal boundary sits over southern Washington with a narrow band of light rain. This boundary lifts northward through the day as a warm front with a band of precipitation. South of the warm front, expect a transition to light showers and increasing E winds as the day progresses.
Cloudy conditions remain with cloudy skies Monday evening and isolated shower activity. A deep offshore low well off the coast pushes an associated frontal system toward the coast overnight with increasing moderate to locally strong S winds ahead of it. Light rain spreads into our region overnight.
Wednesday brings the atmospheric river of moisture into our region. The southerly flow aloft focuses the precipitation on the volcanoes. Easterly low-level flow peaking early in the day allows significant spillover onto the east slopes of the Cascades. Mission Ridge could benefit from both the southerly and easterly flow components and could pick up over an inch of rain. Other areas can expect 0.25-1" of precipitation. Snow levels should range from 6000-8500 ft.
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Tuesday
Cloudy with a chance of very light rain showers.
Tuesday
Night
Cloudy with increasing light rain. Moderate ridgeline winds become strong.
Tuesday
Light rain showers taper early, then re-develop in the afternoon. Otherwise, cloudy skies.
Tuesday
Night
Cloudy with light rain developing in the early morning hours. Increasing moderate ridgeline winds.
Tuesday
Cloudy with a chance of very light rain or showers lifting northward from late morning onwards.
Tuesday
Night
Cloudy with light rain developing in the early morning hours.
Tuesday
Cloudy with periods of light rain in the morning, transitioning to showers by late morning. Otherwise, cloudy skies.
Tuesday
Night
Cloudy with light rain developing overnight. Increasing moderate ridgelin winds.
Tuesday
Cloudy with light rain or showers from mid-day onwards. Light ridgeline winds may become moderate late in the day. Increasing light E wind at the Pass.
Tuesday
Night
Cloudy a chance of light rain developing in the early morning hours. Increasing moderate ridgeline and light to moderate E wind at the Pass.
Tuesday
Cloudy with a chance of light rain or showers from mid-morning onwards. Light ridgeline winds and E wind at the Pass may become moderate late in the day.
Tuesday
Night
Cloudy with light rain developing in the early morning hours. Increasing moderate ridgeline and E wind at the Pass.
Tuesday
Cloudy with a chance of very light rain or showers in the afternoon. Moderate ridgeline winds early in the day.
Tuesday
Night
Cloudy with a few rain showers in the early evening. Moderate ridgeline winds.
Tuesday
Cloudy with a chance of very light rain or showers from mid-morning onwards. Light ridgeline winds become moderate.
Tuesday
Night
Cloudy with a slight chance of rain in the early morning hours. Moderate ridgeline winds.
Tuesday
Cloudy with periods of light rain transitioning to showers.
Tuesday
Night
Cloudy with a chance of light rain in the early morning hours. Increasing light to moderate ridgeline winds.
Tuesday
Cloudy with periods of light rain transitioning to showers. Light ridgeline winds become moderate.
Tuesday
Night
Cloudy with a chance of light rain mainly after midnight. Increasing moderate 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).