One river in western Washington is drawing the attention of forecasters as a second strong Pacific system lines up behind Friday’s rain. The Skokomish River near Potlatch could rise above flood stage when heavy rain falls on high snow levels over the Olympic Mountains, according to NWS Seattle, and a watch for Mason County is in place from late Thursday night, Nov. 12, through late Saturday night, Nov. 14.
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Of all the rivers in the area, only this one is singled out. In its afternoon forecast discussion, issued at 2:43 p.m. PST on Nov. 12, the Seattle office said river flooding is not expected on the other rivers in the area over the next seven days.
The watch for Mason County and the Olympics
The watch product, issued at 2:56 p.m. PST on Nov. 12, covers a portion of northwest Washington that includes Mason County and the city of Shelton. It says flooding caused by excessive rainfall continues to be possible and that excessive runoff may flood rivers, creeks, streams and other low-lying, flood-prone spots. The forecast discussion lists the zone as Olympia and Southern Puget Sound, the Olympics and Southern Hood Canal.
NWS Seattle’s own forecast discussion says the potential for flooding on the Skokomish River continues, with periods of heavy rainfall from Friday through the weekend. The watch text adds the detail behind the concern: heavy rain combined with high snow levels could push the river near Potlatch above flood stage.
Rainfall totals from the south slopes to the coast
The rain arrives in two pulses. Friday brings rain spreading inland in the mid to late morning and afternoon, around a tenth to a quarter inch for most areas. The bigger push is the frontal system forecast for Saturday and Sunday, Nov. 14 and 15, which adds another 1 to 3 inches along the coast and 0.50 to 1.00 inches in the interior, per the Seattle office.
The Olympics’ south slopes are where the river is fed, and the watch text calls for 3 to 4.5 inches of rain there between early Friday and early Sunday. Because that is several times the interior figure of half an inch to an inch, a basin that touches the south slopes can run high while Seattle and Tacoma stay merely wet.
The reason one river gets the attention is geography and time. Rain falling on the Olympics’ south slopes at snow levels high enough to keep precipitation as rain sends water straight to the streams rather than storing it as snow, and the Skokomish is the river the Seattle office keeps naming. Its forecast discussion flags potential for flooding on the Skokomish across Friday and the weekend, covering the rain pulse on Friday and the stronger system after it.
Friday’s rain is the warm-up, not the main event. The forecast discussion describes another strong Pacific frontal system poised to hit the Pacific Northwest on Saturday and Sunday, which is why the watch runs through late Saturday night rather than ending after the first round. A river that has already taken Friday’s tenth to quarter inch across most areas, and several inches on the Olympic south slopes, enters the Saturday system with less room to absorb more.
Gusts, snow levels and the Monday cool-down
Rain is not the only hazard from the second system. Forecasters see the potential for strong wind gusts of 40 to 50 mph along the coast, while interior areas should see gusts of 30 to 40 mph, with winds peaking Saturday night. Snow levels are high enough through the weekend to let rain, rather than snow, fall on the Olympic slopes, which is what pushes runoff into the river.
The relief comes Monday, Nov. 16, when snow levels lower to around 4,000 feet with only light snow amounts in the mountains. At that point the threat to the Skokomish becomes one of recession, not a new surge.
The watch window gives a firm schedule. It begins late Thursday night, Nov. 12, so that Friday morning’s rain arrives with the watch already in effect, and it ends late Saturday night, Nov. 14, just as the Saturday-night wind peak passes. Sunday, Nov. 15 still carries rain from the same frontal system, so the river’s response can lag the watch’s end, which is a timing question the Seattle office’s later updates will settle. The product text spells out when the watch begins and ends, so it is also the first place a change would show.
Nationally, the Weather Prediction Center’s Nov. 12 discussion has a front moving onshore over the West Coast on Friday and rain with embedded thunderstorms through Saturday. Readers can check the NWS Seattle office page and the Weather Prediction Center for any change to the watch or its end time. The open question is whether the Skokomish actually crosses flood stage near Potlatch, a call the forecasters left as a possibility rather than a prediction.
This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.
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