535 FXUS07 KWBC 181331 PMD30D Prognostic Discussion for Monthly Outlook NWS Climate Prediction Center College Park MD 300 PM EST Thu Dec 18 2025 30-DAY OUTLOOK DISCUSSION FOR JANUARY 2026 The January 2026 Monthly Temperature and Precipitation Outlooks are constructed by considering the La Nia base state, as well as dynamical climate models and integrated statistical tools. Equatorial sea surface temperatures (SSTs) remain below average across the Central and East-Central Pacific Ocean, with SST departures in the Nio 3.4 region reaching -0.7 degrees C. These below-average SSTs have persisted since September 2025, and we are firmly within weak La Nia territory. Furthermore, atmospheric anomalies over the tropical Pacific Ocean are consistent with La Nia, consequently, we expect La Nia teleconnections during January 2026. In contrast, the Madden-Julian Oscillation (MJO) remains more uncertain, as models suggest destructive interference from a strong Kelvin Wave may hinder its re-emergence. The January 2026 Outlooks are primarily shaped by the La Nia background state, dynamical climate models, local SST anomalies, sea ice, and land surface conditions (where appropriate). An experimental multiple linear regression (MLR) tool which estimates the influences of the El Nio Southern Oscillation (ENSO), MJO, and decadal trends is utilized, as is a consolidation that includes influence of ENSO, decadal trends, and calibrated North American Multi-Model Ensemble (NMME) output. Weeks 3-4 forecasts from the Global Ensemble Forecast System version 12 (GEFSv12), the European Centre for Medium-Range Weather Forecasts (ECMWF), and Coupled Forecast System version 2 (CFSv2) models that cover the period to about mid-January were also considered. Impacts from the MJO, along with land surface variables such as snow cover, will be re-evaluated at the end of the month for the updated version of this Outlook. The January 2026 Temperature Outlook features increased chances of below-normal temperatures for much of Mainland Alaska, all of Southeast Alaska, and stretching from the Northern Rockies to the Upper Mississippi Valley. Above-normal temperatures are more likely for the Southern Tier of the Contiguous United States (CONUS), covering much of the Southwest, Four Corners, Southern Plains, Southeast, and Mid-Atlantic. Equal Chances (EC) of above-, near-, and below-normal temperatures are forecast for Western and Northern Alaska, the Northwest, much of Northern and Central California, the Central Plains, Great Lakes, and New England. A mid-level height pattern typical of La Nia has been established and is forecast to persist into at least mid-January per week 3-4 dynamical models. A blocking high has been a significant feature over the North Pacific and Aleutians, with downstream mid-level low pressure residing over eastern Alaska and portions of the Northwest. Above-average mid-level heights cover much of the Southern Tier and Eastern CONUS. The pattern reflected in the January 2026 Temperature Outlooks is consistent with La Nia expectations, though it has been modified based on available guidance. Probabilities for below-normal temperatures are highest over Southeast Alaska and adjacent areas of southeastern Mainland Alaska, reaching 50 to 60%, given consistency among various tools. Monthly forecasts for Alaska from NMME, C3S, and CFSv2 align with shorter-term week 3-4 forecasts in favoring these cooler conditions. Probabilities are also enhanced, reaching 50 to 60%, over Southern New Mexico, Texas, Louisiana, and Florida. This is driven by strong agreement between dynamical models and higher-probability signals in the shorter-term week 3-4 forecasts. While decadal trends and certain tools like the CFSv2 tilt toward above-normal temperatures over the Northern Coast of Alaska, EC is indicated because early to mid-January is forecast to be at least slightly below-normal, and sea ice is present along the coast. Similarly, while La Nia often brings below-normal temperatures to the Northern Tier of the CONUS, sometimes including the Northwest, the NMME, C3S, and CFSv2 monthly outlooks are generally above-normal along the western third of the country. Furthermore, should the MJO become more coherent, it could introduce more variability, such as cooler temperatures in the West, though this influence is currently highly uncertain. EC is thus favored over much of the West and Northwest as we cannot discount the possibility of cooler air extending further West and South. Similarly, models are warm over the central CONUS, however, it is not unheard of during January and La Nia years to see cold air intrusions reach further South, as such we tilt toward EC over the central CONUS and will re-assess in the monthly update. In addition, uncertainty is high in the central CONUS in a consolidation of statistical tools (which include influence of trend and ENSO), and NMME, which adds to our uncertainty here. Finally, guidance was mixed and inconsistent over the Great Lakes and New England, which also led to a tilt toward EC. Because this La Nia is currently weak, increased variability and uncertainty are possible for some regions, which also supports EC. While some regions in the January Temperature Outlook remain uncertain due to the variability of weak La Nia teleconnections, the precipitation pattern is more consistent across various tools, closely resembling the expected La Nia signature. Above-normal precipitation is favored for the Northwest, Northern Rockies, Great Lakes, and much of the Ohio and Middle Mississippi Valleys. Western Alaska also leans above-normal. Drier conditions are more likely across the Southwest, Southern Plains, and much of the Southeast. A weak tilt toward below-normal precipitation is also indicated over much of the southern coast of Mainland Alaska and all of Southeast Alaska. While the NMME and C3S favor below-normal precipitation up much of the West Coast, reaching into the Northwest in some models, recent forecasts from CFSv2 tilt above-normal for the month of January over the Northwest. Moreover, week 3 and week 4 dynamical models forecast at least 40 to 50% chances of above-normal precipitation over the Northwest. As such, we have minimized the region of below-normal precipitation forecast by some of the multi-model ensembles, confining it more to southeastern California. Given the uncertainty regarding how far South the moisture may reach, much of California is designated as EC. Above-normal precipitation is also indicated for the Great Lakes, Ohio Valley, and parts of the Middle and Lower Mississippi Valleys and the Tennessee Valley , which is a typical La Nia signature. These two areas of above-normal precipitation are connected by a weak (33 to 40%) chance of above-normal precipitation that is supported by the NMME and C3S. The below-normal precipitation favored over the southern tier is consistent with models and La Nia, though some uncertainty exists over parts of Texas and Louisiana as it is currently unclear how far south any above-normal precipitation might reach. Finally, over Alaska, decadal trends and La Nia support the forecast for below-normal precipitation over the southern coast of the Mainland and Southeast Alaska, while dynamical models like the NMME, C3S, and CFSv2 favor above-normal precipitation for much of the western Mainland. FORECASTER: Johnna Infanti The climatic normals are based on conditions between 1991 and 2020, following the World Meteorological Organization convention of using the most recent 3 complete decades as the climate 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. The next monthly outlook...for Feb ... will be issued on Thu Jan 15 2026. These outlooks are based on departures from the 1991-2020 base period. $$