Climate Prediction Center Issues Atmospheric River Outlook: Moderate Risk of Heavy Rain, Mountain Snow and Coastal Winds on West Coast Nov. 12-15
The Climate Prediction Center of the National Oceanic and Atmospheric Administration (NOAA) issued its Probabilistic Hazards Outlook at 3 p.m. Eastern on November 4, valid November 12 to 18. The outlook says a highly amplified mid-level low pressure system will encroach on the West Coast during week two, promoting onshore flow consistent with atmospheric river activity, with elevated chances of heavy precipitation, high winds and high-elevation heavy snowfall, and possible flooding over the Pacific Northwest and northern California.
For November 12 to 15, the outlook posts a moderate risk of heavy precipitation for parts of the Pacific Northwest and northern and central California; a moderate risk of heavy high-elevation snow across the Klamath and Sierra Nevada mountains; and a moderate risk of high winds across coastal portions of Washington, Oregon and much of California. A slight risk of heavy precipitation, heavy high-elevation snow and high winds extends across the West Coast into parts of the Desert Southwest, Great Basin and Southern Rockies through November 18, and a slight risk of high winds also covers parts of the Northern and Central Appalachians, the Lower Great Lakes, the Upper Mid-Atlantic and the Northeast on November 12.
The center said models now better identify at least two periods of enhanced moisture intrusion, one beginning late in week one and another during the early portion of week two, though models still vary on timing, strength and spatial extent. Ensemble tools indicate 30 to 50 percent chances of precipitation amounts exceeding the 85th climatological percentile, with the highest probabilities of amounts exceeding one and two inches focused from central California northward to western Washington. Because of day-to-day volatility in the raw tools and uncertainty in the evolving height pattern, no high-risk designations were posted.
The favored persistence of strong troughing for the entirety of week two supports the potential for atmospheric river activity of longer duration through mid-November, the outlook said, and excess precipitation over burn-scarred areas may trigger localized flooding. The outlook, issued by forecaster Nick Novella, advises the public to consult local National Weather Service forecast offices for short-range forecasts and region-specific information. (Source: National Oceanic and Atmospheric Administration)
Source: National Oceanic and Atmospheric Administration
Published by GSM · USA (original Chinese edition)
Photo: 图：卫星视角下的 Sierra Nevada 山脉积雪（2025年10月16日），该山脉被气候预测中心列入高海拔强雪中风险区。CSU/CIRA 与 NOAA 影像，公共领域，经 Wikimedia Commons。 / Photo: Satellite view of snow over the Sierra Nevada (October 16, 2025), a range the Climate Prediction Center placed under a moderate risk of heavy high-elevation snow. CSU/CIRA and NOAA imagery, public domain, via Wikimedia Commons.
