647 FXUS07 KWBC 282000 PMD30D Prognostic Discussion for Monthly Outlook NWS Climate Prediction Center College Park MD 300 PM EST Fri Feb 28 2025 30-DAY OUTLOOK DISCUSSION FOR MARCH 2025 The March 2025 Monthly Temperature and Precipitation Outlooks are updated with input from the Climate Prediction Center (CPC) Extended Range and Subseasonal Outlooks, dynamical model guidance for week 2 and weeks 3-4, background climate states such as the Madden Julian Oscillation (MJO) and El Nio Southern Oscillation (ENSO), recent Climate Forecast System version 2 (CFSv2) monthly forecasts of temperature and precipitation, and experimental monthly forecasts of temperature and precipitation from extended runs of the Global Ensemble Forecast System version 12 (GEFSv12) and the European Centre for Medium-Range Weather Forecasts (ECMWF) models. A La Nia Advisory is still in effect. The latest weekly sea surface temperature (SST) departures reached -0.5 degrees Celsius in the Nio 4 region and -0.3 degrees Celsius in the Nio 3 region over the last week. This is a weak La Nia event, so while we may expect some of the typical impacts, we also expect greater variability in temperature and precipitation during the month or season. The MJO has begun to weaken and stall in Phase 8, retreating back into the unit circle, due to destructive interference with equatorial Rossby wave activity and the low-frequency base state, however, dynamical model forecasts of the Realtime Multivariate MJO (RMM) index favor the return of eastward propagation of the signal, but this is also weak and there is uncertainty in models on the strength of the MJO, with GEFS favoring a stronger MJO and ECWMF keeping the MJO rather weak. Given the weakness of these drivers as well as the variability seen in shorter term forecasts, we expect a fairly transient pattern through at least the first half of March. In the near-term forecast period (i.e. the 6-10 day and 8-14 day forecasts through about mid-March), an active, transient pattern is expected which would bring variable weather to the Contiguous United States (CONUS). In the 6-10 day period, the mean mid-level height pattern favors below normal heights across much of the eastern CONUS to the Pacific Northwest, with near normal heights favored over the West and Central CONUS. An active southern stream and associated shortwave troughing add to the transient forecast for early March. The pattern is less progressive into the week-2 period, but still active and complex. This transient pattern in the first half of March adds some uncertainty to the monthly forecast. In the Weeks 3-4 period (through approximately the end of March), models favor mid-level troughing over Alaska and the Northwest, and weak ridging over the South and East with the ridge axis favored to be off the East Coast. Overall, the March forecast is complex and variability is expected, particularly in the first half of the month. The updated March 2025 Temperature Outlook features below normal temperatures over the Northwest and approximately the northern half of California, and the southern two-thirds of Alaska. Above normal temperatures are favored over the Northern Plains, central CONUS, and southern U.S. including the Gulf States and parts of the southern Mid-Atlantic. Troughing is expected throughout much of the month over the West, leading to the favored below normal temperatures over parts of the West Coast. The area of below normal temperatures is additionally supported by the typical La Nia teleconnection, even though the La Nia is weak. Forecasts for above normal temperatures have also been fairly consistent over the North-Central, Central, and Southern CONUS, which leads to relatively enhanced probabilities over these regions. A significant swing in the pattern and temperatures is expected early in March over Alaska, where shorter term forecasts favor a rapid swap from above normal temperatures to below normal temperatures as troughing moves into the region, which then remains consistent into the Weeks 3-4 period. As the above normal temperatures appear to be shorter lived over Alaska, the overall March forecast has a tilt toward below normal. Swings in temperatures are also expected in the short term (early March) over the East, with periods of below normal temperatures possible, particularly for the Northeast. This gives way to ridging and above normal temperatures by the middle to end of March. Despite the variability in early March, much of the southern half of the East Coast is favored to be above normal given the forecasts for the mid to end of March given weaker signals for below normal temperatures, while Equal Chances (EC) of above, near, and below normal temperatures are favored for the Northeast where some periods of below normal temperatures are more strongly forecasted. In contrast to temperatures, model forecasts have been more consistent on the precipitation signals. Mid-level troughing and onshore flow supports enhanced probabilities of above normal precipitation over parts of California and the Northwest, though there is some uncertainty on how far south the above normal precipitation will reach given dynamical models and the La Nia teleconnection that support below normal precipitation over southern California. Thus, EC of above, near, and below normal precipitation are appropriate over southern California, despite the early March above normal precipitation signal that covers much of the state. Above normal precipitation is also favored over the Great Lakes and parts of northern New England, as supported by dynamical models, and the La Nia teleconnection. Most dynamical models favor above normal precipitation over Alaska and it is the climatologically driest time of year for precipitation, as such a tilt toward above normal is indicated over much of the state. Below normal precipitation is favored over the Southwest and Southern Plains given model consistency, though most models also tilt toward below normal over the Gulf Coast and Florida consistent with what we might expect from La Nia. However, there is a chance for above normal precipitation over the Gulf States in the short term, so EC is favored. EC is also favored over the Northern Plains given weak and inconsistent signals among models and tools. ****************************************************************************** ***** Previous mid-month discussion below ***** ****************************************************************************** A number of extratropical drivers are present that may impact the March 2025 temperature and precipitation patterns over the U.S. La Nia conditions continue in the Equatorial Pacific, and sea surface temperature (SST) anomalies were -0.3 degrees Celsius below normal in the Nio3.4 region during the past week, and reached -0.7 degrees Celsius below normal in the Nio4 region. La Nia conditions are expected to persist in the near term before transitioning to El Nio Southern Oscillation (ENSO) neutral during the spring. In addition to the potential La Nia impacts, the Madden Julian Oscillation (MJO) may have some bearing on the forecast. There has been coherent MJO activity since the beginning of 2025, and though dynamical model forecasts of the Realtime Multivariate MJO (RMM) index for the short term favor a slowed and erratic evolution of the MJO signal due to a strong equatorial Rossby wave, eastward propagation is forecast to resume near the beginning of March. Finally, the Arctic Oscillation (AO) is forecast to become positive in the last week of February, though this is followed by forecasts of a sharp drop to near neutral to start the month of March, which may lead to a more transient pattern to start the month. Though we expect some lingering impacts of the La Nia through the month of March, these other noted influences are also considered for the March 2025 Temperature and Precipitation Outlooks, which may modify the canonical La Nia pattern. Short term Outlooks through the end of February depict a progressive flow pattern. In the mean, the mid-level flow pattern favors ridging over the west and neutral to below normal 500 hPa heights over the East, which leads to a warm end to February over the western half of the Contiguous United States (CONUS). However, the mid-level height pattern is expected to be progressive as we end the month of February and move into early March. As March begins, the mid-level height pattern is forecast to weaken and retrograde, leading to variable heights over the East and below normal heights eroding away the ridging over the western half of the CONUS. This appears to continue into the Weeks 3-4 Period (through Mid-March), and models forecast troughing over the Northern part of the CONUS and Alaska, and ridging over the South. However, there is considerable uncertainty of the extent of troughing into the lower 48 with some models containing the below normal heights more to the North over Canada, and others depicting it reaching further South. This leads to uncertainty over the northern third of the CONUS particularly for temperature. The March 2025 Temperature Outlook favors below normal temperatures over southeastern Alaska and the Northwest. Above normal temperatures are indicated over northern Alaska and from the Southwest to the Southeast. This somewhat resembles a typical La Nia teleconnection pattern for March, which would bring below normal temperatures to southern Alaska and the northern tier of the CONUS and above normal temperatures to the South, as well as monthly CFSv2 forecasts of temperatures. Multi-Model Ensemble forecasts of monthly temperatures, such as the North American Multi-Model Ensemble (NMME) and Copernicus Climate Suite (C3S), support the below normal temperatures over southeastern Alaska and the Northwest, but tilt toward above normal temperature probabilities over the eastern two-thirds of the CONUS, including the Northern Plains and New England. However, given the progressive but below normal 500 hPa height pattern expected in the beginning of March and differences in the southward extent of the mid-level height pattern in week 3-4 models, Equal Chances (EC) of above, near, and below normal temperatures are favored for the Central and Northern Plains to the northern half of the East Coast where there is higher uncertainty and models differed. Probabilities of below normal temperatures are enhanced where the impact of La Nia, cooler temperatures possible from MJO, and where the trough that is expected to retrograde in early March are expected to lead to below normal temperatures. In contrast, above normal temperatures are indicated over much of the southern tier, and are (relatively) stronger. Models and tools support the probabilities of above normal temperatures along the South, as does the typical La Nia teleconnection and mid-level ridging that is comparatively more stationary. Tools were comparatively more consistent when considering the precipitation pattern over the U.S. for March. As has been fairly common the last few months, models tend toward a La Nia like pattern for precipitation, which is found in most models. This is very apparent in NMME and C3S, which broadly favor weak above normal precipitation over central and northern Alaska, the Northwest, and Great Lakes to the northern parts of Gulf States, and below normal precipitation over the South coast of Alaska, the Southwest, Southern Great Plains, and western Gulf Coast. The March Precipitation Outlook also broadly favors this pattern, indicating above normal precipitation over much of Mainland Alaska, the Northwest and Great Lakes to Southeast and below normal precipitation over the Southwest and Southern Plains, but there are some differences given expected intra-month variability. In particular, equal chances of above, near, and below normal precipitation are favored over the South coast of Alaska given short term forecasts for above normal precipitation that may outweigh the below normal signal. Similar arguments are in place for the Gulf Coast, which is typically below normal during La Nia, but is appearing to be more variable in the shorter term forecasts, thus EC is favored for the eastern Gulf Coast. EC is also favored over the Northern Plains, despite some models such as CFSv2 indicating weak chances of above normal precipitation, due to uncertainty in remaining tools and relatively stronger signals over the Northwest and Great Lakes. 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 Apr ... will be issued on Thu Mar 20 2025 These outlooks are based on departures from the 1991-2020 base period. $$