Prognostic Discussion for Monthly Outlook NWS Climate Prediction Center College Park MD 300 PM EST Fri Jan 31 2025 30-DAY OUTLOOK DISCUSSION FOR FEBRUARY 2025 The updated monthly temperature and precipitation outlooks for February 2025 are based primarily on WPC’s Week-1 temperature and precipitation forecasts, two-week GEFS and European Prediction System (EPS) ensemble mean temperature and precipitation dynamical forecasts, CPC’s Week-2 and Weeks 3-4 temperature and precipitation outlooks, subseasonal GEFS/CFSv2 guidance, the most recent runs of the monthly CFSv2 temperature and precipitation forecasts, and on weak La Niña composites. In addition, the latest information regarding the Madden Julian Oscillation (MJO), snow cover, Great Lakes ice coverage, and the latest 30-day temperature and precipitation observations were also considered. The updated temperature outlook for February 2025 calls for increased chances of below normal temperatures over southeastern Alaska, and from the Pacific Northwest and the northern half of California eastward across portions of the Intermountain region and far northern Rockies, the northern third of the Great Plains, northern portions of Minnesota and Wisconsin, and the Upper Peninsula of Michigan. This is based on a subjective consensus of the various official outlooks and model runs noted earlier that comprise the monthly time period. Above normal temperature chances are elevated for much of the southern and eastern contiguous U.S. (CONUS). Maximum probabilities of 60-70% are depicted over Florida and portions of Georgia and South Carolina. In the eastern CONUS, this is consistent with MJO lagged temperature composites with the enhanced convective phase propagating through the Maritime Continent region. However, it is noted that the composites also show a trend towards colder temperatures in the East towards the end of February. The widespread coverage of favored above normal temperatures across much of the CONUS is supported by historical La Niña composites, the CFSv2, and the subseasonal GEFS-CFSv2 temperature guidance. Above normal temperatures are also favored over approximately the northern and western halves of Mainland Alaska, based on GEFS and EPS 2-meter temperature anomalies through the first half of February, the CFSv2 model, and GEFS-CFSv2 subseasonal temperature guidance. Equal Chances (EC) of below, near, and above normal temperatures are favored for remaining areas where models and tools displayed weak and/or conflicting signals. The updated precipitation outlook for February 2025 depicts increased chances of above normal precipitation from northern and central California and the Pacific Northwest eastward across the northern Intermountain region to eastern Montana. Maximum probabilities of 60-70% are indicated for the Coastal Ranges and Cascades of the Pacific Northwest, extending southward across the Klamath range and northern and central Sierras of California. This broad pattern of favored above normal precipitation is generally consistent with historical La Niña precipitation composites. For the West Coast area, anywhere from 3-8+ inches of precipitation (liquid equivalent) is predicted to fall within the first week of February associated with atmospheric river activity. Chances favoring above normal precipitation are also elevated across most of the Mississippi Valley, the Great Lakes region, Ohio and Tennessee Valleys, most of the Appalachians, and interior portions of the Northeast and Mid-Atlantic. Maximum probabilities of 50-60% are depicted from the vicinity of the Mississippi-Ohio River Confluence northeastward across most of the eastern half of the Great Lakes region. This is consistent with much of the objective model guidance and La Niña composites, and denotes the expected location of the mean storm track. Odds favoring below normal precipitation are enhanced for eastern Arizona, most of New Mexico, western and southern portions of Texas, and much of the Southern Atlantic region. These favored areas of relative dryness are commonly observed during La Niña winters, though the indicated spatial coverage of below normal precipitation is significantly reduced relative to moderate or strong La Niña composites. Maximum odds of 50-60% favoring below normal precipitation are indicated over southern Florida. For Alaska, a combination of dynamical model guidance and La Niña composites slightly favors above normal precipitation chances over northern, central, and western Mainland Alaska, continuing southwestward across much of the Aleutians, and below normal precipitation chances over parts of southcentral and southeastern Mainland Alaska. Equal Chances (EC) of below, near, and above normal precipitation is favored for remaining areas where models and tools displayed weak and/or conflicting signals. —- The 0.5-month lead message for the February 2025 outlooks is shown below: —- The long-awaited transition from a neutral El Niño Southern Oscillation (ENSO) to a weak La Niña finally occurred during December 2024, with the latest weekly value of the Oceanic Niño Index (ONI) of -0.7C for the Niño 3.4 region. Below-average sea-surface temperatures (SSTs) now dominate the central and east-central Pacific with significant subsurface cooling to a depth of 100-200 meters. Broad expanses of enhanced (suppressed) tropical convection are noted over the vicinity of Indonesia (Date Line), with persistently enhanced low-level trade winds over the western and central near-equatorial Pacific. La Niña conditions are expected to persist through the Feb-Mar-Apr (FMA) 2025 season with odds of 59 percent, followed by a nearly equally likely transition to ENSO-neutral starting in Mar-Apr-May (MAM) 2025. In addition to La Niña being the expected primary driver of the atmospheric circulation pattern in February, there is significant forcing associated with the Arctic Oscillation (AO) and the Madden-Julian Oscillation (MJO). The AO index has been negative during the past two weeks, which has likely contributed to the current cold snap across the central and eastern contiguous U.S. (CONUS). The AO index is forecast to transition toward its positive phase in the next 2 weeks, which may signify at least a brief reprieve from the persistent influence of Arctic air masses over this portion of the country. In the tropics, the convectively enhanced phase of the MJO is currently in the Western Hemisphere, near the interface of Realtime Multivariate MJO (RMM) Phases 8 and 1. During the past 10-14 days, there has been a very significant increase in amplitude of the MJO signal, though there has been little eastward propagation. Most RMM-based MJO Index forecasts predict a high-amplitude MJO accelerating to phase speeds more consistent of a convectively-coupled Kelvin Wave, as the signal traverses the remainder of the Western Hemisphere, Africa, the Indian Ocean, and reaches the Maritime Continent during the next two-week period. Historically, an MJO signal propagating eastward across the Indian Ocean and Maritime Continent favors a warm response downstream over the central and eastern CONUS towards the end of January, but this is contradicted by most dynamical model guidance which favors the continuation of below normal temperatures across this region. Other considerations for the February outlooks include coastal SSTs, sea and lake ice, and snow cover. At the present time, near to primarily above normal SSTs prevail near the West Coast of the CONUS, the western and central Gulf Coast, and near the southwest coast of Alaska. Below normal SSTs are observed near the coast of the Northeast CONUS. Most of the Alaska coast as far south as Kuskokwim Bay (Southwest Alaska) is dominated by sea ice. Over the Lower 48 states, the Great Lakes remain mostly ice-free as of mid-January, with relatively shallow Lake Erie being the most likely to freeze over during the next few weeks. Current snow cover is widespread across the northern and central CONUS, with associated radiational cooling helping to keep surface temperatures lower over this area. The monthly Temperature and Precipitation Outlooks for February are based on historical La Niña composites and regressions and the secondary forcings described above, as well as on dynamical and statistical model support. Dynamical support is derived from dynamical model suites including the North American Multi-Model Ensemble (NMME), Copernicus Climate Suite (C3S), and from the Climate Forecast System version 2 (CFSv2) dynamical model. Statistical support comes largely from a combined ENSO-OCN tool, and to a lesser degree the Canonical Correlation Analysis (CCA). CPC’s official outlooks for Weeks 3-4, and monthly and submonthly temperature and precipitation guidance from the Global Ensemble Forecast System (GEFS), CFSv2, and European Centre for Medium-Range Weather Forecasts (ECMWF) models are also used in the preparation of the February Outlooks, though it is important to note that these forecasts only cover the first half of February. The February 2025 Temperature Outlook features elevated odds of above normal temperatures over the vicinity of the Four Corners states/Southwest, southern Plains, Lower Mississippi and Tennessee Valleys, the Southeast, Upper Ohio Valley, most of the Appalachians, Mid-Atlantic, and Northeast. Probabilities of above normal temperatures reach 50 to 60 percent over parts of the southern Rockies. This broad pattern is characteristic of part of the typical cold season La Niña signature, and is supported by available models and tools such as the dynamical consolidation (NMME CON), NMME Probability Anomaly Correlated (PAC) calibrated forecasts, C3S, and recent runs of the CFSv2. Below normal temperature chances are enhanced from the Pacific Northwest eastward across much of Montana, the Northern and Central Plains, and the Upper Mississippi Valley. This is supported by the statistical consolidation (Stat CON), recent runs of the CFSv2, the ENSO-OCN tool which combines influences of ENSO and trends, and the ECMWF and Deutscher Wetterdienst (DWD, German model) which are constituents of the Copernicus model Suite (C3S). Other constituents such as the United Kingdom Met Office (UKMO) and Meteo-France models appear to be too warm overall. This broad area of favored anomalous cold is also very typical of classic wintertime La Niña events. In Alaska, many tools support some variation on the classic La Niña theme which is characterized by increased chances for below normal mean temperatures across southcentral and southeast Alaska, and increased chances for above normal mean temperatures confined to northwest portions of the Mainland. The February 2025 Precipitation Outlook features elevated odds for above normal precipitation from the Pacific Northwest eastward across the Northern Intermountain region and Northern Rockies to the northern High Plains. This is generally associated with the Pacific jet stream as it traverses much of the northern CONUS. One of the few dissenting opinions comes from the Stat CON (specifically the CCA input) which favors below normal precipitation across the Pacific Northwest and was discounted for this particular forecast. Above normal precipitation chances are also increased for much of the Mississippi Valley, Tennessee and Ohio Valleys, Great Lakes region, central and northern Appalachians, and interior portions of the Mid-Atlantic and Northeast. Probabilities of above normal precipitation reach 50 to 60 percent percent from the central Great Lakes region southwestward towards the Missouri Bootheel. This second region of favored anomalous storminess is associated with a typical meandering of the jetstream across this region and the resulting mean storm track, and is consistent with many of the precipitation tools. Approximately half of the available tools forecast above normal precipitation reaching the Northeast and Mid-Atlantic coasts, and while this is certainly reasonable with individual cyclonic systems, the La Niña storm track on average tends to be shifted farther inland. There are enhanced odds of below normal precipitation from far southern California generally eastward across much of the Four Corners region, the central and southern High Plains, much of Texas, far southern Mississippi Valley, and a large portion of the Southeast as far north as the Tidewater area of southeastern Virginia. Probabilities reach 50 to 60 percent over the vicinity of the Rio Grande Valley, and also most of Florida, southeastern Georgia, and nearby parts of South Carolina. This broad region of favored drier than normal conditions is consistent with the typical La Niña footprint, and is well supported by many tools, such as the Stat and NMME CONs and the CFSv2 to name a few. Over Alaska, above normal precipitation chances are elevated over most of the Mainland north of the Alaska Range, with a sliver of slightly enhanced below normal precipitation chances over parts of southcentral and southeastern Mainland Alaska. These predicted anomalies are generally consistent with mean surface high pressure and mid-level ridging over the Gulf of Alaska during La Niña events. FORECASTER: Anthony Artusa 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 Mar ... will be issued on Thu Feb 20 2025 These outlooks are based on departures from the 1991-2020 base period. $$