Prognostic Discussion for Monthly Outlook NWS Climate Prediction Center College Park MD 300 PM EDT Wed Jun 30 2021 30-DAY OUTLOOK DISCUSSION FOR JULY 2021 The updated outlook of temperature and precipitation for July 2021 reflects the official outlooks from WPC, CPC, and NHC, latest model guidance, soil moisture conditions, and the status of well-known climate oscillations. Dry conditions are forecast to continue across much of the western and northern CONUS, further supporting an outlook favoring above normal temperatures from the Southwest to the Northwest and eastward to the Great Lakes and Northeast. The highest odds are across the northern Intermountain West, where outlooks from the short-term to Week 4 all highlight enhanced odds for below normal precipitation, continuing to tip the feedback cycle toward above normal temperatures. Early frontal activity, combined with favored above normal precipitation (as indicated in many models), backed by recent above normal soil moisture, favors below normal temperatures across the Southern Great Plains and portions of the Southeast, except Florida. Across the Southwest, an early moisture surge is likely to bring rains to southern Arizona and New Mexico. The latest CFS runs indicate a push of moisture into the Great Basin during the middle of the month, but that signal is weaker in recent ECMWF runs, so slightly enhanced odds of above normal precipitation, or EC, is the resultant outlook for much of California, Nevada, and portions of Utah. Below normal precipitation is favored to continue across the Pacific Northwest and Northern Rockies, with the first two weeks likely to be dry. Below normal precipitation is also favored for portions of the Northeast as there is little chance for moisture to stream northward. Across the Southeast, early frontal activity and the potential for tropical moisture favor above normal precipitation. An MJO signal moving into phases 3 and 4 would tend to reduce tropical activity across the Gulf of Mexico, so that mitigates the odds across the Southeast and Gulf Coast. The Southern Great Plains are likely to remain wet due to a combination of moisture from the Southwest and the western end of a frontal boundary. -------------- Previous discussion follows ---------------- The July 2021 outlook was prepared based on dynamical model and statistical forecast guidance, current soil moisture/drought conditions, potential impacts from the MJO, and newly derived long term trends from the 1991-2020 base period. ENSO neutral is likely to continue through the outlooks period. The MJO may also influence the climate pattern. Model predictions for MJO indicate a strengthening over Africa and the western Indian Ocean, though there is another area of upper-level divergence over the Western Pacific. If the signal emerges, it would increase the variability throughout the month. That potential resulted in some lower probabilities for some regions, as explained below. Drought is largely entrenched over the western CONUS and Northern Plains, and the summer months are prime months when current soil moisture values can impact temperature and precipitation in following months. Above normal temperatures are favored along the Rockies and across the West, with the highest odds in the Great Basin and Four Corners region. The deeply entrenched drought, long-term trends, and numerical guidance (dynamical models and statistical tools) all indicate above normal temperatures are most likely. For the Pacific Northwest and Northern Rockies, an active MJO could result in more variable conditions, so the odds are more modest in those regions. Sea surface temperatures are also likely to be below normal near the California coast, moderating odds there as well. Equal chances for above, near, and below normal are indicated across the Southern Plains, Middle and Lower Mississippi Valleys, and portions of the Southeast. Temperature trends as indicated in the OCN are not as strong there. The suite of dynamical model guidance from the NMME, C3S, and CFS all indicate a relative relaxation of probabilities for above normal temperatures, while some statistical tools favor below normal temperatures, so the mixed indications from the tools result in EC. For the Great Lakes and Northeast, trends, dynamical model guidance, and statistical tools are all largely in agreement for above normal temperatures. Across Alaska, the signals are a bit more mixed as summer trends are not as strong as winter trends, and some NMME models indicate below normal temperatures. More recent model runs and some statistical tools (SST-CA and ENSO-OCN) support higher odds over southern Mainland and eastern Alaska in the outlook. Above normal precipitation is indicated from the Gulf Coast to the Ohio Valley, consistent with dynamical model guidance, though the guidance has shown variability in recent runs for the Carolinas and Florida, so odds in those places are low. Statistical tools and dynamical models show a consistent signal for below normal precipitation from the Pacific Northwest to the Northern Plains, though an active MJO could introduce short-term wetness in mid to late July (however this would be very atypical), so below-normal precipitation is still favored, but probabilities are lower along the coast. Some dynamical models indicate wetness into the Four Corners region, but half of the statistical tools (CCA and SST-CA) do not. The precipitation OCN shows a weak wet signal from Central California to Oklahoma in a broad swath, though amounts are low and the pattern is not similar to other tools, so equal chances is indicated in the outlook. NMME, C3S, and statistical tools support above-normal precipitation for western mainland Alaska. FORECASTER: Matthew Rosencrans 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 Aug ... will be issued on Thu Jul 15 2021 These outlooks are based on departures from the 1991-2020 base period. $$