863 FXUS05 KWBC 171231 PMD90D Prognostic Discussion for Long-Lead Seasonal Outlooks NWS Climate Prediction Center College Park MD 830 AM EDT Thu Sep 17 2026 SUMMARY OF THE OUTLOOK FOR NON-TECHNICAL USERS El Niño conditions are present, as represented in current oceanic and atmospheric observations. El Niño is strengthening, with a greater than 90 percent chance of a very strong event this fall and winter. The October-November-December (OND) 2026 Temperature Outlook favors above normal temperatures for much of Alaska as well as most areas west of the Rockies, nearly all areas east of the Mississippi River, and the northcentral states in-between. The highest probabilities (greater than 50 percent) of above normal temperatures are forecast across Southeast Alaska, the Northern Great Basin, and the vicinity of North Dakota and northwestern Minnesota. The OND 2026 Precipitation Outlook depicts enhanced probabilities of above normal precipitation amounts from the southern half of California east-northeastward across most of the Four Corners region and Great Plains, much of the Mississippi and Tennessee Valleys, the Southeast, and the Mid-Atlantic. The greatest chances (higher than 60 percent) for above normal precipitation are indicated for parts of the eastern Gulf Coast region and Southeast coast. A modest tilt in the odds towards above normal precipitation is depicted from portions of southcentral Alaska eastward through much of Southeast Alaska. Modest tilts towards below normal precipitation amounts are favored over the Aleutians, interior portions of Mainland Alaska, interior portions of the northwestern CONUS, and parts of the Great Lakes region. Equal chances (EC) are forecast for areas where probabilities for each category of seasonal mean temperatures and seasonal accumulated precipitation amounts are expected to be similar to climatological probabilities. BASIS AND SUMMARY OF THE CURRENT LONG-LEAD OUTLOOKS Note: For Graphical Displays of the Forecast Tools Discussed Below See: http://www.cpc.ncep.noaa.gov/products/predictions/90day/tools/briefing CURRENT ATMOSPHERIC AND OCEANIC CONDITIONS El Niño strengthened over the past month, with sea surface temperature (SST) anomalies exceeding +3.0°C in the eastern equatorial Pacific. The latest weekly Niño index value for Niño-3.4 was +2.0°C, and for Niño-3 the index value was +2.8°C. The equatorial subsurface temperature index (average from 180°-100°W) remained steady during August, reflecting a deeper-than-average thermocline. Subsurface temperature anomalies were significant, reaching +10.0°C at depth. Low-level westerly wind anomalies and upper-level easterly wind anomalies extended from the western to east-central equatorial Pacific. Convection and rainfall were enhanced from the central to eastern Pacific and were suppressed over Indonesia. The traditional and equatorial Southern Oscillation indices were significantly negative. Collectively, the coupled ocean-atmosphere system reflected a strengthening El Niño. PROGNOSTIC DISCUSSION OF SST FORECASTS The CPC Official El Niño Southern Oscillation (ENSO) Outlook, which synthesizes multiple models from North America and abroad, indicates El Niño will continue to strengthen through the end of the year. During the October-November-December (OND) 2026 season, there is a 75% chance of a historic event that would exceed the strength of previous El Niño events dating back to 1950 (+2.5°C or more for a 3-month RONI value). With an event of this magnitude, the chances of experiencing impacts consistent with El Niño are larger, but they are not guaranteed. In summary, El Niño is strengthening, with a greater than 90% chance of a very strong event during the Northern Hemisphere fall and winter 2026-27. PROGNOSTIC TOOLS USED FOR U.S. TEMPERATURE AND PRECIPITATION OUTLOOKS Newer RONI ENSO composites derived from the current and forecast state of ENSO were strongly utilized due to the magnitude of this El Niño event. Analogs of the "Big Three" El Niño's were also considered in making the temperature outlooks throughout the fall and winter. Dynamical model forecasts from the North American Multi-Model Ensemble (NMME), the Climate Forecast System version 2 (CFSv2), and the Copernicus (C3S) multi-model ensemble system were also used for the first six leads when they are available, as was the objective, historical skill-weighted consolidation and Calibration, Bridging, and Merging (CBaM) guidance, that combines both dynamical and statistical forecast information. Analysis of antecedent conditions such as extratropical SST anomalies and sea ice extent were considered where appropriate. At later leads, decadal trends in temperature and precipitation were increasingly relied upon in creating the seasonal outlooks. PROGNOSTIC DISCUSSION OF OUTLOOKS - OND 2026 TO OND 2027 TEMPERATURE The seasonal temperature outlooks for this fall and winter rely heavily on the high likelihood of a very strong El Niño. In most cases, the presence of a very strong El Niño would overwhelm contributions from climatic modes of mid to high-latitude variability, such as the Arctic Oscillation (AO) or North Atlantic Oscillation (NAO). There are two factors that make the current situation unique. The first factor is the presence of a fairly strong, negatively phased Pacific Decadal Oscillation (PDO), with the August PDO index value of -1.11 . The "€œBig Three"€ historical El Niño's since 1950 include the warm events of 1982-83, 1997-98, and 2015-16, all of which occurred when the PDO phase was positive, leading to constructive interference. This time, however, the PDO phase is negative and may dampen the typical impacts of a strong El Niño in certain areas. The second factor involves the large region of warmer-than-normal SSTs that is typically present in the Gulf of Alaska during strong El Niños. The current situation shows a significant westward shift in these warmer SSTs, which may allow for slightly cooler water to influence portions of the U.S. West coast. In addition, even with the possibility of one or more cold air outbreaks across the northwestern quarter of the Lower 48 states, it is unlikely that this will have much of an impact on the average temperature for a 90-day season. With the above considerations in mind, the October-November-December (OND) 2026 temperature outlook favors above normal mean temperatures over most of the western, northern, and eastern Contiguous U.S. (CONUS). This is based on much of the dynamical and statistical temperature guidance, including the hybrid CBaM output. Adjustments rendered to the OND outlook made last month include an expansion of modest probabilities of above normal temperatures across most of the Southeast, which is reasonable given the typical El Niño cool signal doesn't usually show up in this region until December. Over the Northern CONUS, the 40-50 percent probabilities favoring relative warmth were extended eastward across the Great Lakes and Northeast, with October and November warmth also supported by longer-term trends. Over the Pacific Northwest coastal region, probabilities favoring warmer-than-normal temperatures were tempered a bit in response to potential influences from a negative PDO. In Alaska, most of the models and tools support above normal temperatures over much of the central and eastern Mainland, the North Slope, and Southeast Alaska, with the highest probabilities (50-60 percent) favored over Southeast Alaska. A broad area of Equal Chances (EC) of above, near, and below normal temperatures is depicted from the southern Rockies eastward across the southern Plains and into the Lower Mississippi Valley, based on weak and/or conflicting signals. From late fall to early spring (November-December-January (NDJ 2026-27) to February-March-April (FMA 2027), the outlooks showcase a classic El Niño signature featuring increased chances of above normal temperatures over many areas west of the Rockies, and over northern and central portions of the country east of the Rockies. The highest chances (50-60 percent) for above normal temperatures are indicated over interior portions of the Northwest and along much of the northern tier of states. Over the Southwest, the modest tilt towards relative warmth gradually gives way to EC. For much of the Southeast, a region of near normal temperatures is introduced during NDJ and continues through the FMA season. This reflects competing influences between the cooler El Niño signal during winter and milder historical trends. By March-April-May (MAM 2027), the current El Niño is forecast to weaken significantly, possibly becoming ENSO-neutral later in the spring. Anomalous warmth is expected to return to the Southeast by this time, with much of the East favoring above normal temperatures with the highest chances of 50-60 percent depicted from the Lower Great Lakes eastward to the Northeast coast. Relative warmth is also favored to extend westward across the Dakotas, Northern Rockies, and Pacific Northwest. From April-May-June (AMJ 2027) through the remaining leads, the temperature outlooks are based primarily on long-term historical trends and feature widespread above normal temperatures. For Alaska temperatures, widespread above normal temperatures are favored over the central and eastern Mainland, Southeast Alaska, and the North Slope for the first three leads, OND 2026 through DJF 2026-27. This is supported by most of the dynamical and statistical guidance, the hybrid CBaM output, and trends. The greatest probabilities are indicated over Southeast Alaska, and range from 50-60 percent. Relatively warm mean temperatures are favored over the state for the remaining leads, with the exception of EC over western portions of Alaska during MJJ, JJA, and JAS 2027, in part due to the effects of sea ice and cooler SSTs. PRECIPITATION El Niño composites highlight a robust wet signal across the southern and central CONUS in OND, primarily from the Four Corners region eastward across the southern Plains to the Southeast coast. Modest extensions of this wet signal extend westward across the southern half of California, northward over the Great Plains into portions of South Dakota, and northward along the Eastern Seaboard to include the Upper Mid-Atlantic region. Maximum probabilities for above normal precipitation range from 60-70 percent over parts of the Southeast, which is well supported by a large number of models and tools, and is reasonable given the current and predicted strength of El Niño. Two relatively modest signals for below normal precipitation are depicted over the interior northwestern CONUS and the Great Lakes region, consistent with historical El Niño events and many of the objective tools. From NDJ 2026-27 through FMA 2027, the precipitation outlooks are heavily based on ENSO composites, with adjustments rendered according to dynamical and statistical model guidance. The wet signal across the southern and central CONUS, and extending northward along the Atlantic coast into New England, is the dominant precipitation signal this fall and winter, and is associated in large part with the mean position of the subtropical jet stream and the mean storm track. Probabilities favoring wetter-than-normal conditions increase across California, reaching a maximum of 50-60 percent near the coast during DJF, JFM, and FMA. These probabilities may be increased further in the next set of seasonal outlooks, to be released in mid-late October, pending reassessment of the latest model forecasts. The favored area of above normal precipitation is expected to reach as far north as central Oregon, and possibly farther north given the intensity of this current El Niño event. Over the southern Plains, probabilities for above normal precipitation reach a maximum of 40-50 percent, increasing across much of the Gulf and Southeast coasts to a maximum of 70-80 percent over southern Georgia and northern Florida. The two areas of modestly favored below normal precipitation over the interior Northwest and Great Lakes region are expected to persist but remain rather weak through FMA 2027. During March-April-May (MAM) 2027, the El Nino signal is expected to weaken considerably with the dominant and contiguous wet signal over the southern and central CONUS forecast to split into three separate, and less widespread, regions: one over California and the Southwest, another over the Upper Midwest/eastern Dakotas, and the third encompassing much of the Gulf and Atlantic coasts. The token dry signal favored over the Great Lakes during the fall and winter disappears, and the below normal precipitation region over the interior Northwest begins to expand in spatial extent from MAM to JJA 2027, heavily influenced by decadal trends. In addition, the precipitation anomalies typically associated with El Niño are forecast to gradually wane during the spring. For the summer and early fall of 2027, long-term precipitation trends play a large role in the outlooks. In Alaska, newer ENSO composites were used for the fall and winter, followed by dynamical model output; for subsequent seasons decadal precipitation trends formed the basis of the outlooks. In OND 2026, small areas of slightly favored below normal precipitation are depicted over portions of the Central Interior and the Aleutians, while above normal precipitation is slightly favored from the southeastern Alaska Mainland to the northern Panhandle region. In NDJ, the two dry signals consolidate into one larger one that extends from the southwestern Mainland to the Central Interior, and above normal precipitation continues over Southeast Alaska, the latter being a common occurrence during warm events. By DJF, composites show a widespread dry signal over most of the Mainland, which continues through FMA but weakens significantly by MAM 2027. The Southeast Alaska wet signal remains throughout these seasons, though waxes and wanes in coverage. The precipitation outlooks from AMJ 2027 onward are based on longer-term precipitation trends, with the primary and most durable signal being above normal precipitation favored over much of the southern coast of Alaska. FORECASTER: Anthony Artusa The Climatic normals are based on conditions between 1991 and 2020, following the World Meterological Organization convention of using the most recent 3 complete decades as the climatic reference period. The probability anomalies for temperature and precipitation based on these new normals better represent shorter term climatic anomalies than the forecasts based on older normals. For a description of of the standard forecast tools - their skill- and the forecast format please see our web page at http://www.cpc.ncep.noaa.gov/products/predictions/long_range/tools.html (Use Lower Case Letters) Information on the formation of skill of the CAS forecasts may be found at: http://www.cpc.ncep.noaa.gov/products/Soilmst_Monitoring/US/Outlook/outlook.shtm l (use lowercase letters) Notes - These climate outlooks are intended for use prior to the start of their valid period. Within any given valid period observations and short and medium range forecasts should be consulted. This set of outlooks will be superseded by the issuance of the new set next month on Oct 15 2026 1991-2020 base period means were implemented effective with the May 20, 2021 forecast release. $$