We are in for another unseasonably warm and mostly sunny day with highs in the 50s and even a few 60s, but showers and thunderstorms will start to creep into the forecast along the west slopes of the Cascades and Olympics during the day. We should see scattered showers or isolated thunderstorms develop mid-day through the afternoon along the west slopes of the Cascades, but the main action will begin during the evening as a frontal system approaches the coast. The front will take advantage of other atmospheric conditions, like a relatively humid and unstable air mass to produce a widespread area of showers and potentially severe thunderstorms late this afternoon through the evening. Showers/thunderstorms should fire up first west of the Cascade crest this afternoon and move from south to north over the area. The Passes and east slopes of the Cascades should see some of this activity as well, although it's unclear how far east of the crest the heavier showers/T-storms will push. Some thunderstorms may produce hail, and strong gusty winds. Make sure you're not caught out in these storms later today and tonight.
Showers will become less intense later tonight as the front pushes through and we'll see a slow cooling trend. A stacked upper low offshore will drift closer on Thursday, keeping showers in the forecast with low certainty on timing. There will be a chance of afternoon thunderstorms on Thursday, but if they do develop, they'll be less intense than Wednesday evening.
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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Wednesday
Mostly sunny in the morning, then partly sunny with a chance of showers or thunderstorms in the afternoon. Light to moderate ridgeline winds.
Wednesday
Night
Moderate to heavy showers or thunderstorms in the evening, then lighter showers after midnight. Thunderstorms may produce hail and strong gusty winds.
Wednesday
Mostly sunny in the morning, then partly sunny with a chance of showers or thunderstorms in the afternoon. Light to moderate ridgeline winds.
Wednesday
Night
Moderate to heavy showers or thunderstorms developing in the evening, then lighter showers late tonight. Thunderstorms may produce hail and strong gusty winds.
Wednesday
Mostly sunny in the morning, then partly sunny with a chance of showers or thunderstorms in the afternoon. Light to moderate ridgeline winds.
Wednesday
Night
Moderate to heavy showers or thunderstorms in the evening, then lighter showers after midnight. Thunderstorms may produce hail and strong gusty winds.
Wednesday
Mostly sunny in the morning, then partly sunny with a chance of showers or thunderstorms in the afternoon. Moderate ridgeline winds.
Wednesday
Night
Moderate to heavy showers or thunderstorms in the evening, then lighter showers after midnight. Thunderstorms may produce hail and strong gusty winds.
Wednesday
Mostly sunny with passing high clouds. Slight chance of a shower or thunderstorm in the afternoon. Light to moderate SE ridgeline and E Pass level winds.
Wednesday
Night
Moderate to locally heavy showers or thunderstorms in the evening, then lighter showers after midnight. Thunderstorms may produce hail and strong gusty winds.
Wednesday
Mostly sunny with passing high clouds. Slight chance of a shower or thunderstorm in the afternoon. Light to moderate SE ridgeline and E Pass level winds.
Wednesday
Night
Moderate to locally heavy showers or thunderstorms in the evening, then lighter showers after midnight. Thunderstorms may produce hail and strong gusty winds.
Wednesday
Mostly sunny with passing high clouds. Slight chance of a shower or thunderstorm in the afternoon. Light to moderate ridgeline winds.
Wednesday
Night
Moderate showers or thunderstorms developing in the evening, heaviest near the Cascade crest, then lighter showers late tonight. Thunderstorms may produce hail and strong gusty winds.
Wednesday
Mostly sunny with passing high clouds. Slight chance of a shower or thunderstorm in the afternoon. Light to moderate ridgeline winds.
Wednesday
Night
Moderate showers or thunderstorms developing in the evening, heaviest near the Cascade crest, then lighter showers late tonight. Thunderstorms may produce hail and strong gusty winds.
Wednesday
Mostly sunny with passing high clouds. Slight chance of a shower or thunderstorm in the afternoon. Light to moderate ridgeline winds.
Wednesday
Night
Moderate showers or thunderstorms in the evening, heaviest near the Cascade crest, then lighter showers after midnight. Thunderstorms may produce hail and strong gusty winds.
Wednesday
Mostly sunny in the morning, then partly sunny with a chance of showers or thunderstorms in the afternoon. Light to moderate ridgeline winds.
Wednesday
Night
Moderate to heavy showers or thunderstorms in the evening, then lighter showers after midnight. Thunderstorms may produce hail and strong gusty 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).