Prognostic Discussion for Monthly Outlook NWS Climate Prediction Center College Park MD 300 PM EST Sat Feb 29 2020 30-DAY OUTLOOK DISCUSSION FOR MARCH 2020 The updated March temperature and precipitation outlooks have been adjusted primarily from dynamical model forecast guidance from across multiple time scales and resulted in the need to make large changes from the mid-month previously released March outlook. The favored large scale 500-hPa height pattern depicts on average predominately the influence of Pacific air into the CONUS. Mean troughing near and over the far western CONUS, anomalous west-southwesterly flow and mean ridging and positive 500-hpa height departures across the central and eastern CONUS are most likely for much of March 2020. This is consistent from the short-range to Week 3-4 forecast time scale. The March temperature outlook favors above-normal monthly mean temperatures for the eastern two-thirds of the CONUS with the highest probabilities stretching from the lower Mississippi Valley to the lower Great Lakes. Troughing to the north of Alaska and negative 500-hPa height departures and strongly elevated odds for above-normal precipitation favor below-normal temperatures for the southern half of Alaska and the Alaska Panhandle, extending southward to the northern Pacific Northwest. There remains slightly increased odds for above-normal temperatures for the north slope of Alaska. An expected highly varying pattern across the far western CONUS along with varying forecast signals over the course of the month make EC or "Equal-chances" for either below-, near- or above-normal temperatures" the best forecast for much of the far western CONUS. For precipitation, variations in dynamical model guidance across time scales from the beginning of the month to the end of the month complicate the forecast of monthly total precipitation amounts. During the first week of March, heavy precipitation is favored for an area centered across the Tennessee Valley favoring elevated odds for above-normal precipitation in this region. Model predictions support this area remaining just north of the Gulf coast with a tight gradient in precipitation so slightly elevated odds for below-normal precipitation remain forecast in this area. Troughing entering the southern West coast and migrating into the western CONUS during Week-2 favors above-normal precipitation for parts of California and the Southwest. Potential phasing with the northern polar jet stream favors above-normal precipitation for the far northern great Plains, upper Midwest and Great Lakes during Weeks 2-3. A strong Pacific jet impacting Alaska favors high odds for above-normal precipitation for much of Alaska during March 2020. There are slightly elevated odds for below-normal precipitation for areas of the central Plains due to a high likelihood of no precipitation during the first week of March and only modest odds of above-normal precipitation through mid and later portions of the month. Although confidence is generally low in this region, monthly model integrations support this forecast. ******************************************************************************* **** Previous discussion from the mid-month March outlook release is below **** ******************************************************************************* The March temperature and precipitation outlooks depict limited forecast coverage and only modestly elevated probabilities from that expected from climatology due to above-average uncertainty - a result of a number of factors. This is true for both monthly mean temperatures and monthly total precipitation amounts and for both above- and below-normal tercile categories. In the Tropics, the MJO, although active, is being affected by other subseasonal coherent tropical variability (i.e., atmospheric Kelvin wave and Equatorial Rossby wave activity), so forecasts of its evolution by common guidance (e.g., RMM index) are non-canonical and varied in nature. Constructive and destructive interference of these other tropical modes can make it difficult to have high forecast confidence and fully interpret observed and forecast amplitude and eastward propagation of the main MJO envelope. Most RMM forecasts, however, do indicate varying degrees of forecast amplitude and eastward propagation over the next few weeks across the Pacific Ocean into the Western Hemisphere. In fact, at the current time, a strong enhanced convective anomaly has been in place across the west-central Pacific Ocean along the equator. The March temperature and precipitation outlooks do utilize some MJO predictive information from both lagged and conterminous composite as well as a multi-linear regression forecast tool that targets temperature and precipitation contributions from the MJO. Week 3-4 dynamical model guidance from both the CFS and ECMWF monthly prediction systems are also utilized to aid prediction during the first half of March as well as monthly integrations from the CFS for the entire month of March. The monthly NMME forecasts are not considered due to considerably outdated initial conditions used for their March predictions. The higher than average uncertainty (potential and strength of any teleconnection from the MJO and weak signals from both statistical forecast tools and dynamical model guidance results in a large region of "Equal Chances" (EC) across the forecast domain for both temperature and precipitation. Above-normal monthly mean temperatures are favored for parts of northern and western Alaska due to strong long term positive temperature trends primarily linked to reduced sea ice coverage in nearby waters. Some signals from dynamical model guidance support favored above-normal temperatures for California, Nevada and parts of neighboring states at only modest probability departures from the region's climatological odds. Both the MJO and dynamical model guidance serve as the forecast basis for elevated odds of below-normal temperatures for the central and southern Plains, Ohio Valley, Southeast and mid-Atlantic regions. For precipitation, prospects of a pattern favoring below-normal temperatures across parts of the eastern CONUS also favors below-normal precipitation for parts of the central and northern Mississippi Valley, Ohio Valley and Great Lakes. The most likely region of enhanced odds for above-normal precipitation resides along the Gulf and south Atlantic coasts. Forecast ridging and a potential northward shifted storm track favors below-normal precipitation for Arizona and the West Coast as well as the Alaska Panhandle. Consensus of dynamical model guidance favors above-normal monthly total precipitation amounts for northern and western Alaska during March 2020. FORECASTER: Jon Gottschalck The climatic normals are based on conditions between 1981 and 2010, 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 19 2020 These outlooks are based on departures from the 1981-2010 base period. $$