ATMOSPHERIC RIVER THREATENS WEST COAST WITH HEAVY RAIN, MOUNTAIN SNOW, POWER OUTAGES, AND DANGEROUS SURF

NOAA forecasts multiple Pacific storm systems affecting California, Oregon, and Washington from November 13 through November 18, 2026, with elevated risks of flooding, damaging winds, hazardous coastal conditions, and significant snowfall across western mountain ranges.

November 11, 2026

A developing series of powerful Pacific storm systems is expected to bring widespread precipitation, strong coastal winds, and mountain snowfall to the western United States beginning Friday, November 13, with the greatest initial impacts forecast across portions of California, Oregon, and Washington. The National Oceanic and Atmospheric Administration (NOAA) has identified an elevated risk of atmospheric river activity as an amplified upper-level weather pattern channels moisture toward the West Coast. Forecast guidance indicates that successive disturbances will affect the region through the weekend and into the following week, increasing concerns about localized flooding, hazardous travel, power outages, and dangerous surf along exposed coastal areas.

The NOAA Climate Prediction Center issued its initial key message on November 2 and updated the assessment on November 6, identifying a moderate risk of heavy precipitation across southwestern Oregon and northern and central California for November 14–15. The agency assigned the event a 40–60 percent probability of meeting its heavy-precipitation hazard criteria in those areas, while a broader slight risk of 20–40 percent extended through November 17 across portions of the West Coast, Southwest, Great Basin, and Southern Rockies. A moderate risk of high winds was also identified for coastal portions of Washington, Oregon, and California during November 14–15, with the potential for additional wind impacts extending farther inland.

The latest Weather Prediction Center forecast, issued at 2:20 a.m. Eastern Standard Time on November 11, confirms that multiple rounds of rain and mountain snow are expected from California to Washington during the November 14–18 period. The agency identifies an amplified atmospheric pattern featuring a broad upper-level trough over the western United States, supporting the movement of Pacific disturbances and associated moisture into the region. This pattern is expected to sustain unsettled conditions beyond the arrival of the first major storm, allowing additional systems to develop and move inland before the atmosphere returns to a more stable configuration.

Atmospheric rivers are long, relatively narrow corridors of concentrated water vapor transported through the atmosphere, frequently carrying enormous quantities of moisture from oceanic regions toward continental landmasses. When these corridors encounter coastal mountains and other elevated terrain, the approaching air is forced upward, cools, and releases moisture as rain or snow. The resulting precipitation can become particularly intense along windward mountain slopes, where terrain amplifies atmospheric lifting and concentrates rainfall over relatively small geographical areas.

These weather systems are an important component of the water cycle across western North America, delivering substantial precipitation to rivers, reservoirs, forests, and mountain snowpacks. Their consequences depend upon the intensity and duration of moisture transport, the position of associated frontal boundaries, atmospheric temperatures, and the condition of the ground before precipitation begins. Strong atmospheric rivers can deliver beneficial water supplies while simultaneously producing destructive flooding when rainfall exceeds the capacity of rivers, drainage systems, and surrounding terrain to absorb or transport the additional water.

The November 2026 forecast involves more than a single moisture plume reaching the coastline. NOAA anticipates a succession of low-pressure systems and upper-level disturbances moving across the northeastern Pacific, creating repeated opportunities for heavy precipitation and strong winds. The extended duration is important because rainfall from an initial storm can increase soil moisture and streamflow before another system arrives. Additional precipitation falling onto already wet ground may produce faster runoff, particularly in steep terrain, low-lying communities, and watersheds vulnerable to rapid changes in water levels.

Forecast confidence is strongest regarding the development of an active storm pattern across the western United States, while the exact placement and intensity of the heaviest precipitation remain subject to changes as the individual systems approach. The timing of atmospheric fronts, their north-to-south movement, and the availability of moisture will determine which communities experience the greatest impacts. NOAA’s probabilistic outlooks identify regions where hazardous conditions are more likely, rather than guaranteeing that every location within those regions will experience flooding, damaging winds, or significant snow accumulation.

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CALIFORNIA, OREGON, AND WASHINGTON FACE DIFFERENT STORM HAZARDS

California is among the states expected to receive substantial precipitation as the Pacific storm sequence develops. Northern and central portions of the state are included in NOAA’s moderate heavy-precipitation risk for November 14–15, with additional rainfall possible during the following days. Forecast discussions indicate that the initial frontal systems will carry Pacific moisture into coastal areas and interior valleys, while accompanying colder air will lower snow levels across the Sierra Nevada and northern California mountain ranges.

The Sierra Nevada is expected to experience a different set of conditions as temperatures decline and precipitation changes from rain to snow at higher elevations. NOAA has identified a moderate risk of heavy mountain snowfall for November 14–15, followed by a broader slight risk extending through November 17. Snow accumulation will depend upon the altitude of the freezing level, the strength of individual disturbances, and the amount of moisture available as colder air moves inland. Higher mountain passes and exposed transportation corridors may become difficult to navigate when snowfall combines with reduced visibility and gusty winds.

Southern California is also expected to experience periods of unsettled weather. The National Weather Service office serving Los Angeles and surrounding communities forecasts several opportunities for light to moderate rainfall beginning Thursday night or Friday, followed by additional precipitation during Sunday night through Monday and another potential disturbance around Wednesday. Although these forecasts do not establish the same level of widespread flooding risk identified farther north, they indicate that the storm sequence may affect much of California through repeated periods of rain, cooler conditions, and coastal hazards.

For Oregon, the developing system represents a combination of inland precipitation, mountain snow, strong winds, and significant coastal hazards. The National Weather Service office in Medford identified a stronger storm system approaching around Friday and Saturday, with rain, high-elevation snowfall, gusty winds, and dangerous surf expected across portions of southern Oregon and adjacent northern California. Forecast guidance also indicates that additional disturbances may affect the region during the following week, extending the period of unsettled weather beyond the initial frontal passage.

The Pacific coastline faces particularly significant wave conditions. A November 10 National Weather Service discussion from Medford projected long-period ocean swells reaching approximately 25 feet in coastal waters, with breaking surf potentially reaching 30 to 35 feet along exposed beaches during Saturday’s peak. Such conditions could produce dangerous wave run-up, substantial beach inundation, localized coastal erosion, and hazardous conditions near jetties, rocky shorelines, and harbor entrances. The forecast identifies a major swell originating from a developing storm system near the western Aleutian Islands, demonstrating how distant Pacific weather systems can generate coastal hazards well beyond the locations experiencing their strongest winds.

The Portland National Weather Service office reported that an atmospheric river was already affecting far northwestern Oregon and southwestern Washington on November 10, carrying a band of rain into the Pacific Northwest and British Columbia. The office anticipated a temporary period of drier weather during Wednesday and Thursday before another storm system arrived Friday and continued into the weekend. This sequence indicates that the region’s atmospheric activity is developing through several distinct systems, rather than a single storm arriving simultaneously across all three West Coast states.

Washington remains within the broader area of concern, especially along exposed coastal locations and higher terrain. The Olympic Peninsula and Cascade Mountains are susceptible to enhanced precipitation when moist Pacific air encounters steep topography. The Weather Prediction Center’s November 11 excessive-rainfall discussion identified a marginal risk of excessive rainfall across portions of the Olympic Peninsula for the November 14–15 period, indicating a localized flash-flood concern associated with the expected precipitation.

Across the Pacific Northwest, mountain snowfall and coastal rainfall may occur simultaneously because precipitation type changes with elevation and atmospheric temperature. Lower valleys and coastal communities may experience sustained rain while mountain highways receive snow or mixed precipitation. Strong winds accompanying the frontal systems can compound travel difficulties by reducing visibility, affecting vehicle handling, and increasing the risk of falling tree limbs or damaged electrical equipment. These combined hazards create operational concerns for transportation agencies, emergency services, and electrical utilities throughout the affected region.

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FLOODING, POWER INFRASTRUCTURE, AND THE EXTENDED PACIFIC STORM PATTERN

One of the primary concerns associated with the approaching weather systems is the possibility that heavy precipitation will overwhelm local drainage networks and cause rivers or streams to rise rapidly. Atmospheric-river rainfall can create particularly difficult conditions in mountainous regions because runoff moves quickly through steep watersheds and concentrates in valleys below. Urban environments face additional risks when intense precipitation exceeds storm-drain capacity, while communities near rivers and flood-prone roadways may encounter hazardous water accumulation even when rainfall amounts differ considerably across the surrounding region.

The National Weather Service’s rainfall outlooks distinguish between the probability of heavy precipitation and the probability of excessive rainfall capable of producing flash flooding. Those categories describe different hazards. A location may receive a substantial amount of rain without experiencing a flash flood, while a shorter period of intense rainfall over vulnerable terrain can produce dangerous runoff. The November forecasts therefore require attention to both the broader Climate Prediction Center heavy-precipitation risks and the Weather Prediction Center’s more geographically focused excessive-rainfall assessments.

Areas affected by previous wildfires deserve particular attention because burned watersheds can experience rapid runoff, debris flows, and sediment movement when intense rainfall reaches exposed slopes. Vegetation loss, altered soil properties, and unstable surface material can reduce a hillside’s ability to absorb precipitation or resist erosion. Conditions vary according to the severity and age of a burn scar, but the approach of sustained Pacific rainfall makes these locations important subjects for localized National Weather Service and emergency-management monitoring.

Strong winds introduce another important threat. Pacific low-pressure systems can produce substantial pressure differences along the coast and across mountain ranges, driving gusts capable of damaging trees, utility lines, and exposed structures. When trees are rooted in saturated soil, prolonged rainfall may increase their susceptibility to being uprooted during strong wind events. Electrical outages can follow when trees or branches strike distribution lines, while damage to substations and other infrastructure may complicate restoration efforts during prolonged storms.

NOAA’s November 6 forecast specifically warned that the approaching systems could produce power outages associated with high winds. The agency advised residents in affected areas to monitor local forecasts, prepare for potential interruptions to electricity, and exercise caution during travel. The warning does not establish that widespread outages are inevitable, but it identifies an operational risk that becomes more consequential when strong winds, heavy rainfall, and mountain snow occur during the same storm sequence.

Coastal transportation and maritime operations face additional challenges. Powerful waves can make exposed beaches, harbor entrances, and coastal roads dangerous even when communities farther inland receive limited precipitation. Long-period swells generated by distant storms can arrive with enough energy to produce sudden wave run-up, catching people near the shoreline without warning. Hazardous seas also affect fishing vessels, commercial shipping, recreational boating, and emergency-response operations. The forecast for exceptionally high surf in southern Oregon demonstrates why coastal hazards must be assessed independently of rainfall totals.

The longer-range outlook indicates that unsettled conditions may continue across the western United States into late November. An updated NOAA Climate Prediction Center discussion dated November 11 identifies a slight risk of heavy precipitation across portions of southwestern Oregon and California on November 19 and again from November 22–25. The agency also identifies a slight risk of heavy snowfall across higher elevations of the Klamath Mountains and Sierra Nevada during those periods, along with high-wind risks affecting much of California, Nevada, and additional western states. The forecast reflects a persistent upper-level trough over the eastern Pacific, allowing additional disturbances to move inland and sustain periods of rain, mountain snow, and strong winds beyond the initial atmospheric-river event.

The extended outlook makes an important forecast distinction. The strongest atmospheric-river signal is concentrated before November 18, with model probabilities for enhanced integrated water vapor transport declining after approximately November 15. NOAA therefore did not identify a moderate atmospheric-river-related precipitation risk for the November 18–24 period. The continued hazards are associated with a persistent upper-level trough and multiple low-pressure disturbances rather than a confirmed continuation of the initial atmospheric-river event.

The November 10 outlook also identifies continued activity across the central United States as disturbances emerging from the western trough move eastward and contribute to new surface low-pressure systems. This demonstrates that the developing Pacific storm pattern has implications beyond California, Oregon, and Washington. Although the immediate atmospheric-river concern is concentrated along the West Coast, the upper-level circulation supporting those systems can influence weather across much of the country as individual disturbances progress inland.

The current outlook is also occurring during a period of strong El Niño conditions in the tropical Pacific. El Niño can influence the position and strength of atmospheric circulation patterns across North America, particularly during the colder months, when changes in tropical Pacific temperatures affect the distribution of heat and convection. These relationships are relevant to seasonal forecasting, but determining the contribution of El Niño to any individual November storm requires analysis of the specific atmospheric conditions responsible for its development. The immediate hazards identified by NOAA are supported by observed and modeled Pacific pressure systems, moisture transport, and upper-level circulation.

For residents across the affected states, the practical significance lies in the combination of hazards rather than any single forecast measurement. Rainfall can create flooding or hazardous driving conditions in valleys and coastal communities, snow can disrupt higher-elevation highways, powerful winds can damage infrastructure, and large ocean swells can threaten coastal locations. The precise extent of those impacts will depend upon where individual disturbances make landfall and how their intensity changes during the forecast period.

Local National Weather Service offices will remain the primary sources for location-specific warnings and advisories as the systems approach. Travelers crossing higher elevations should monitor winter-weather alerts and changing road conditions, while residents in flood-prone areas should follow local emergency instructions and avoid entering flooded roadways. Coastal communities should pay particular attention to high-surf and marine warnings, and households in areas vulnerable to wind-related power outages should maintain access to emergency supplies and reliable weather information.

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TRJ CONCLUSION

The developing atmospheric-river threat represents a significant period of unsettled weather for the western United States, with NOAA identifying elevated precipitation, wind, mountain-snow, and coastal hazards across California, Oregon, and Washington. The most concentrated initial risks are forecast for November 14–15, particularly across southwestern Oregon and northern and central California, while additional disturbances could extend hazardous conditions into the following week.

The forecast is supported by multiple federal meteorological assessments, including the Climate Prediction Center’s probabilistic hazards outlook, the Weather Prediction Center’s extended forecast discussion, and regional National Weather Service analyses. These sources establish a coherent picture of an active Pacific storm pattern capable of delivering substantial moisture to coastal and mountainous terrain. The anticipated impacts will vary geographically, with some communities facing flooding concerns, others experiencing significant snowfall, and exposed coastal areas confronting dangerous waves and strong winds.

The November 10 and 11 forecasts also establish that the strongest atmospheric-river conditions are expected earlier in the event, while additional Pacific disturbances may sustain rain, snow, and wind threats through November 24. Continued monitoring will be necessary as atmospheric models refine the position and strength of individual systems, particularly in regions where terrain can amplify precipitation and increase the potential for hazardous runoff.

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TRJ VERDICT

The West Coast is preparing for an active and potentially hazardous period of Pacific storms, with NOAA identifying an elevated risk of heavy precipitation, mountain snowfall, damaging winds, and coastal flooding concerns during the middle of November 2026. California, Oregon, and Washington face different combinations of these hazards, making local weather conditions and emergency advisories especially important as the systems approach.

The atmospheric-river threat demonstrates the considerable power of moisture transport across the Pacific Ocean. When concentrated water vapor interacts with strong weather systems and the mountainous terrain of western North America, substantial precipitation can develop over relatively short periods, creating conditions capable of disrupting communities, transportation networks, and critical infrastructure.

The most important development is the prospect of repeated storms affecting the region before earlier systems have fully cleared. Additional precipitation falling across already wet watersheds, combined with high winds and changing snow levels, can complicate emergency response and increase the consequences of individual weather events. The possibility of exceptionally dangerous surf along portions of the Oregon coast adds another serious hazard to the developing situation.

With the strongest initial hazards forecast for November 14–15 and additional unsettled weather possible through November 24, residents across the affected states should remain attentive to updated forecasts, travel advisories, flood warnings, and local emergency instructions.

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National Oceanic and Atmospheric Administration (NOAA), National Weather Service, Weather Prediction Center. (November 11, 2026). Extended Forecast Discussion. Issued at 2:20 a.m. EST. Forecast period: November 14–18, 2026. College Park, Maryland. (Free Download)

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National Oceanic and Atmospheric Administration (NOAA), National Weather Service, Climate Prediction Center. (November 11, 2026). U.S. Week-2 Hazards Outlook. Issued at 3:00 p.m. EST. Forecast period: November 19–25, 2026. Forecaster: Anthony Artusa. (Free Download)

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National Oceanic and Atmospheric Administration (NOAA), National Weather Service, Portland Weather Forecast Office. (November 11, 2026). Portland, Oregon: Official Weather Forecasts, Watches, Warnings, and Advisories. Hazard map updated at 10:52 a.m. PST. (Free Download)

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National Oceanic and Atmospheric Administration (NOAA), National Weather Service, Weather Prediction Center. (November 11, 2026). Excessive Rainfall Discussion. Issued at 11:01 a.m. EST. Includes the marginal excessive-rainfall risk for Washington’s Olympic Peninsula during November 14–15, 2026. (Free Download)

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