NOAA flags a heavy-rain risk for the Pacific Northwest from Nov. 14 to 17 as rivers could rise

NOAA’s Climate Prediction Center has flagged a risk of heavy rain for the Pacific Northwest from Nov. 14 to 17, with a stronger moderate tier over southwest Oregon on Nov. 14 and 15. The outlook, issued at 3 p.m. EST on Nov. 6, sets up a stretch in which rivers already nudged upward by earlier storms could rise further if the rain delivers. Local coverage had pointed to a Nov. 11 to 15 window, and that timing has since moved.

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Two things changed between those versions. The dates slid later, and the moderate heavy-rain category retreated from the northern end of the region, leaving Washington and northern Oregon under a slight risk while the stronger signal settled farther south. Readers working from older coverage should plan around the later dates.

The Climate Prediction Center’s Nov. 6 hazards outlook

The hazards outlook was signed by forecaster Thomas Collow and covers Nov. 14 to 20. It places a moderate risk of heavy precipitation over southwest Oregon and northern and central California on Nov. 14 and 15, where the strongest signals show three-day totals above 1 to 2 inches. A slight risk of heavy precipitation stretches across the West Coast through Nov. 17. Collow’s discussion says probabilities for integrated vapor transport above 250 kg/m/s along the coast have ticked up, the moisture-flux measure forecasters use to spot atmospheric rivers, though the outlook never uses that term itself.

The moderate category was removed from the northern Pacific Northwest, a call based on 20 to 30 percent probabilities that three-day rainfall tops the 85th climatological percentile. Moderate high-elevation snow risk was also pulled from the Cascades and now sits over the Klamath and Sierra Nevada ranges, with only a slight snow risk left for the Cascades through Nov. 17. A moderate wind risk covers coastal Washington, Oregon and much of California on Nov. 14 and 15.

KATU’s read of the earlier Nov. 11 to 15 signal

Meteorologist Matt Gontarek wrote in a KATU forecast, updated at 10:05 a.m. on Nov. 6, that NOAA’s Climate Prediction Center was already showing an increased risk of heavy precipitation for parts of the Pacific Northwest on Nov. 11 to 15, with an extended outlook pointing to heavy high-elevation Cascade snow on Nov. 11 to 17. He said the heaviest rain could target the Coast Range and Cascades, and that prolonged runoff could send rivers rising downstream. Snow levels, he added, could climb above 6,000 feet if warm air rides in with the moisture, or fall to roughly 4,500 to 5,000 feet if colder air follows.

The station said it could issue StormTracker 2 Weather Alert Days if flood advisories or warnings become necessary, and described the outlook as a signal worth watching as the date approaches rather than a guaranteed major rain event. It also said the track, strength and duration of the atmospheric river would decide the outcome, with higher elevations possibly receiving much more rain than the Willamette Valley floor.

The article labels itself “Pattern recognition, not an exact forecast,” and offers no rainfall totals or river levels.

Rivers and the Portland office’s uncertainty

The National Weather Service in Portland said in a forecast discussion issued at 9:34 p.m. PST on Nov. 4 that a midweek system could pair higher vapor transport aloft with longer-lasting precipitation, a combination that could support more substantial rainfall accumulations. Rain from earlier systems should raise background river levels, which could leave rivers prone to flooding if the midweek rainfall comes in heavy. The same discussion put the odds of 40 mph gusts at 30 to 40 percent along the coast and 5 to 15 percent along the Interstate 5 corridor, and said uncertainty over the system’s location and intensity remains high.

Farther south, NWS Reno wrote on Nov. 6 that a stronger Pacific storm could bring heavier rain, Sierra snow and gusty winds across the Nov. 14 and 15 weekend, and that the signal had been relatively consistent. That matches the dates in the Climate Prediction Center product, which suggests one storm system is behind both sets of forecasts.

The Weather Prediction Center keeps a separate days 3 to 7 hazards page, issued Nov. 5 and valid for Nov. 8 to 12. Its text does not describe regional rain or snow areas, which appear only on a map graphic, so it neither confirms nor contradicts the earlier Nov. 11 timing.

The Portland discussion remains the latest local word on river flooding, and it is two days older than the Climate Prediction Center outlook. No river forecast in the reviewed material names a crest or a specific stream, so how far rivers climb after Nov. 14 depends on rainfall totals that Collow’s outlook does not yet provide.

This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.

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