733 FXUS05 KWBC 161231 PMD90D Prognostic Discussion for Long-Lead Seasonal Outlooks NWS Climate Prediction Center College Park MD 830 AM EDT Thu Oct 16 2025 SUMMARY OF THE OUTLOOK FOR NON-TECHNICAL USERS A La Nia Advisory was issued in early October as conditions representing the cold phase of the El Nio Southern Oscillation (ENSO) have developed. The expectations are for a relatively weak and short lived event through winter 2025-2026 before easing back to ENSO-neutral by early Spring. The most common La Nia impacts contribute to the outlook during the late autumn and winter months. The temperature outlook for Nov-Dec-Jan (NDJ) 2025-2026 favors above-normal seasonal mean temperatures for much of the contiguous U.S. (CONUS) with the exception of most of the northern tier of the country where Equal-Chances (EC) of either of the three categories is forecast. The highest odds of warmer than normal conditions are located in the Southwest, southern High Plains, and coastal areas of northwestern Alaska. Below-normal seasonal mean temperatures are favored for the Alaska Panhandle. There is an elevated likelihood of above-normal seasonal precipitation amounts for the Pacific Northwest and northern California eastward to the northern Rockies and Plains and western Great Lakes in the NDJ 2025-2026 precipitation outlook. Drier-than-normal conditions are most likely for the southern tier of the U.S. from the Southwest eastward to southern Texas and the Southeast. For Alaska, above-normal precipitation is favored for western areas of the state and below-normal precipitation is favored for the Alaska Panhandle. 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 La Nia conditions exist in the tropical Pacific Ocean as shown by both oceanic and atmospheric indicators. Below-normal sea surface temperatures (SSTs) exist along the equator from 160 E to near the South America coast. Within this area are regions of SST anomalies less than -0.5 degrees C. The latest weekly value of the Nino3.4 SST index is -0.3 degrees C. The most recent ocean heat content values indicate colder than normal water from the surface to about 175 meters in depth from 150 W to 90 W indicating a reservoir to maintain La Nia conditions from the ocean perspective. Anomalous convection and lower- and upper-level winds in the tropical Pacific atmosphere are consistent with La Nia conditions. Another area of anomalous SSTs is present in the north Pacific Ocean where a large region of above-normal temperatures exists from near Japan eastward to the central North America coast. The largest departures at this time are centered along the Date Line from approximately 30 - 50 degrees N. A current review of snow cover across the northern hemisphere indicates lots of variability across the domain with substantial areas of both positive and negative snow cover anomalies present. The status of the land surface state across the CONUS shows the majority of the CONUS and Hawaii under at least abnormally dry conditions with severe, extreme and exceptional drought present for much of the western CONUS, parts of the Ohio Valley, mid-Mississippi Valley, and New England. The Quasi-Biennial Oscillation (QBO) is currently in its easterly phase and will remain so throughout the winter into Spring 2026. PROGNOSTIC DISCUSSION OF SST FORECASTS The CPC objective, skill weighted consolidation and North American Multi-Model Ensemble (NMME) Nino3.4 SST outlooks are consistent in forecasting continuing La Nia conditions into the late winter before transitioning to ENSO-neutral in early Spring 2026. ENSO-neutral is favored to continue through Spring into Summer 2026. PROGNOSTIC TOOLS USED FOR U.S. TEMPERATURE AND PRECIPITATION OUTLOOKS Physical subseasonal to seasonal (S2S) climate drivers considered in these set of outlooks include the current La Nia conditions and associated potential winter impacts, the state of the QBO and its relationship with La Nia and the stratospheric polar vortex, and coastal SSTs in some areas. Above-normal SSTs across the northern Pacific ocean are also considered in preparing the outlook. The NMME and C3S dynamical model ensemble systems and their participant models were utilized as well as statistical forecast tools and long term temperature and precipitation trends. PROGNOSTIC DISCUSSION OF OUTLOOKS - NDJ 2025 TO NDJ 2026 TEMPERATURE The NDJ 2025-2026 temperature outlook favors above-normal seasonal mean temperatures for much of the CONUS with the exception of most of the northern tier of the country where Equal-Chances (EC) of either of the three categories is forecast. This is consistent with the majority of the statistical, hybrid (CBaM), and dynamical model guidance. The highest odds of warmer than normal conditions in the CONUS are located in the Southwest and the southern High Plains where the above tools, La Nia impacts and long term trends align. For Alaska, later sea ice formation and consequently positive temperature trends support elevated odds for above-normal temperatures for much of the northern and western areas of the state. Potential La Nia impacts, primarily later in the season, along with NMME dynamical model support favors a slight tilt to below-normal temperatures for the Alaska Panhandle. EC is forecast across much of the northern tier of the CONUS due to favored high variability over this three month season. The evolution of the temperature outlooks from Dec-Jan-Feb (DJF) 2025-2026 through Feb-Mar-Apr (FMA) 2026 depict enhanced odds for below-normal temperatures from parts of the Pacific Northwest eastward across the northern Rockies, northern Plains, upper Mississippi Valley, and the far western Great Lakes. Maximum coverage of favored below-normal temperatures occurs during Jan-Feb-Mar (JFM) and FMA 2026. This area recedes during Mar-Apr-May (MAM) 2026. Highlighted favored warmer than normal temperatures across much of the CONUS forecast in NDJ 2025-2026 decreases in coverage and likelihood over this same period. More modest probabilities for favored above-normal temperatures are confined to the southern tier and much of the East Coast of the CONUS during JFM and FMA 2026. Later in MAM 2026, elevated odds of above-normal temperatures increase in coverage across both the western CONUS and Eastern Seaboard. The forecasts over the period from late autumn through winter and early Spring 2026 described above are based on a number of factors and considerations. These include typical La Nia impacts across the seasons of DJF 2025-2026 through FMA 2026. Given retraction of the East Asian jet (on average) and potential subsequent ridging/blocking in the north Pacific Ocean, troughing and colder than normal conditions often impact eastern Alaska as well as much of the western and north-central CONUS. Also, in these seasons long-term temperature trends are neutral or negative in some of these areas. For the central U.S., statistical forecast tools are consistent with a significant weakness or absence in the forecast of warmer than normal conditions indicated by most of the NMME and C3S dynamical model ensemble systems - most likely an overrepresentation of positive temperature trends in this region where observed trends do not indicate this. Two additional considerations when preparing the outlook included the (1) current abnormally warm north Pacific SSTs and (2) how the current easterly phase of the QBO may impact the strength of the stratospheric polar vortex. Extratropical SSTs can change very quickly due to variations in the storm track and so typically are not a reliable predictor of climate variability. With La Nia conditions in place, typical anomalous ridging or blocking in the north Pacific could lead to some persistence of these positive SSTs in some regions. Although highly uncertain, any impact would most likely be consistent with typical La Nia temperature anomalies (i.e. potentially colder than average temperatures in areas of the north-central CONUS). The stratospheric polar vortex is weaker typically during winters when both La Nia and an easterly QBO phase are in place - which is favored to be the case this year. A weaker stratospheric polar vortex can lead to Sudden Stratospheric Warming (SSW) events and a more meridional or wavy jet stream in general. This makes it more likely for Arctic air outbreaks consistent with a negative Arctic Oscillation (AO) and so potential cold air penetrating the northern Hemisphere continental areas. Even if this is the case, Arctic air can enter either the western or eastern hemisphere. Nevertheless, this set of conditions does slightly elevate the potential for colder temperatures in the central and eastern U.S., so also supports favored below-normal temperatures in the upper Midwest and the considerable area of EC in the interior central CONUS and parts of the Northeast during JFM and FMA 2026. For Alaska, the outlooks over this period highlight an enhanced likelihood for above-normal temperatures for northern and western coastal areas of the state. Favored below-normal temperatures increase in coverage from that depicted in NDJ 2025-2026 in the Alaska Panhandle to include parts of southeastern Mainland Alaska in DJF 2025-2026, JFM 2026 and FMA 2026 with the maximum extent in coverage forecast for the latter two seasons. The outlooks from Apr-May-Jun (AMJ) 2026 onwards are based on the ENSO-OCN forecast tool which is based on the "perfect prog" forecast from the CPC Nio3.4 SST consolidation (ENSO component) and long term temperature trends (Optimal Climate Normal). Given the ENSO-neutral forecast from this guidance, the forecast maps are primarily based on long term temperature trends. PRECIPITATION For precipitation, there is an elevated likelihood of above-normal seasonal precipitation amounts for the Pacific Northwest and northern California eastward to the northern Rockies, Plains and western Great Lakes during the NDJ 2025-2026 season. Drier-than-normal conditions are most likely for the southern tier of the U.S. from the Southwest eastward to southern Texas and the Southeast. For Alaska, above-normal precipitation is favored for western areas of the state and below-normal precipitation for the Alaska Panhandle. Moving through the winter seasons to early Spring 2026, the evolution of the precipitation outlooks from NDJ 2025-2026 through FMA 2026 shows a continuation of favored above-normal precipitation across the northern tier eastward to the Great Lakes through JFM 2026 with an extension to include the Ohio Valley from DJF 2025-2026 through FMA 2026. Highest odds for above-normal precipitation are for the northern Rockies and High Plains especially during DJF 2025-2026. Common La Nia impacts and evolution supported by statistical, hybrid, and dynamical model forecast guidance form the basis for these outlooks. Above normal SSTs in the north Pacific are used to increase coverage somewhat beyond typical La Nia impacts during NDJ 2025-2026, primarily in November. For below-normal precipitation, forecast coverage and probabilities increase along the southern tier of the U.S. and maximize during JFM and FMA 2026. La Nia and associated NMME and C3S model guidance support these outlooks. Both these signals (wetter and drier) recede during the MAM 2026 season. For Alaska, the outlooks over this period continue to highlight an enhanced likelihood for above-normal precipitation for western areas of the state with below-normal precipitation favored for both areas in southeastern Mainland Alaska and the Alaska Panhandle during DJF 2025-2026 and JFM 2026. Similar to temperature, the outlooks from Apr-May-Jun (AMJ) 2026 onwards are based on the ENSO-OCN forecast tool which is based on the "perfect prog" forecast from the CPC Nio3.4 SST consolidation (ENSO component) and long term precipitation trends (Optimal Climate Normal). Given the ENSO-neutral forecast from this guidance, the forecast maps are primarily based on long term precipitation trends. FORECASTER: Jon Gottschalck 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 Nov 20 2025 1991-2020 base period means were implemented effective with the May 20, 2021 forecast release. $$