Extended Forecast Discussion NWS Weather Prediction Center College Park MD 151 PM EDT Fri Jul 01 2022 Valid 12Z Mon Jul 04 2022 - 12Z Fri Jul 08 2022 ...19Z Update... Only minor changes from the overnight forecast, as the 00Z/06Z guidance continued to show good agreement overall (GFS and ECMWF closer to the ensemble means than the Canadian and UKMET). Upper low over the northeastern Pacific Monday will slowly fill as a strong upper ridge builds over the southern Rockies into the Plains late next week. Northwest flow aloft from the Upper Midwest to the central Appalachians will support chances of heavy rainfall from organized convection, thus maintaining the Slight Risk of Excessive Rainfall in the experimental outlooks. Fracasso ...Overview... A persistent upper level high looks to be in place next week over the south-central and southeastern U.S. in a common summer pattern, causing hot temperatures across much of the central CONUS. The storm track will thus remain farther north, with a reloading upper low across the eastern Pacific/Northwest U.S. and shortwaves and periods of troughing through the rest of the northern tier, though by the latter part of the week ridging could build into the northern Rockies/High Plains. At the surface, a quasi-stationary frontal boundary draped from the north-central Plains to the Mid-Atlantic will focus showers and storms, with some locally heavy rainfall. ...Guidance Evaluation/Predictability Assessment... Recent model guidance remains in good agreement with the synoptic pattern described above especially through the middle of next week, and a blend of the deterministic 12Z ECMWF, CMC, and UKMET and the 18Z GFS worked well for the first half of the WPC medium range forecast. By Thursday-Friday, the 12Z CMC becomes different from consensus with an eastern Canada/northeastern U.S. trough, with its axis east of the agreeable GFS/ECMWF solutions. Thus phased out the CMC in favor of the GEFS and ECMWF ensemble mean guidance by the latter part of the period, but maintained a majority of the operational GFS/ECMWF considering their good agreement on the large scale. However, the smaller scale features like individual shortwaves show considerably more variability from model to model, which will likely take until the short range period to resolve. Unfortunately this is a pattern in which these mesoscale features matter greatly particularly for QPF placement and amounts, so continue to follow updates to the forecast for changes going forward. ...Sensible Weather and Hazards... Scattered showers and storms are likely across much of the U.S. at times next week, with enhanced totals in the vicinity of a couple of frontal boundaries stretching generally west to east across the northern half of the country. Parts of the Northwest into the northern High Plains could see moderate to heavy rainfall into Monday as a strong shortwave passes nearby. Downstream, potentially heavy rainfall is forecast to focus over parts of the Midwest and shifting toward the Central Appalachians as well Monday-Tuesday with the possibility of mesoscale convective systems and high rainfall rates where there is abundant moisture and instability. Slight Risks of excessive rainfall are in place for those areas in the WPC experimental Excessive Rainfall Outlook for days 4-5. Scattered thunderstorms are also likely in the Southeast through the week, and some Mid-Atlantic to Northeast rain events are possible as well dependent on frontal positions. Meanwhile monsoonal moisture could persist through much of the week with southwesterly flow from the eastern Pacific, leading to mainly diurnally driven showers and storms over the Four Corners states. The greatest concern for temperatures will be with heat expected to build again across the central U.S. by early next week in response to a strengthening upper level ridge. Highs of 10-15 degrees above normal are forecast for the central Plains to Middle Mississippi Valley, equating to temperatures in the mid 90s to low 100s. Southern Plains locations will see a slightly hotter trend as well, but with less extreme anomalies. Warmer than average temperatures may build into the northern Rockies to northern Plains by Thursday-Friday. Meanwhile the West is forecast to be cooler than normal in response to troughing aloft, but should moderate closer to normal as the period progresses. The East is likely to be near average temperature-wise. Tate Additional 3-7 Day Hazard information can be found on the WPC medium range hazards outlook chart at: https://www.wpc.ncep.noaa.gov/threats/threats.php WPC medium range 500mb heights, surface systems, weather grids, quantitative precipitation, experimental excessive rainfall outlook, winter weather outlook probabilities and heat indices are at: https://www.wpc.ncep.noaa.gov/medr/5dayfcst500_wbg.gif https://www.wpc.ncep.noaa.gov/medr/5dayfcst_wbg_conus.gif https://www.wpc.ncep.noaa.gov/5km_grids/5km_gridsbody.html https://www.wpc.ncep.noaa.gov/qpf/day4-7.shtml https://www.wpc.ncep.noaa.gov/#page=ero https://www.wpc.ncep.noaa.gov/wwd/pwpf_d47/pwpf_medr.php?day=4 https://www.wpc.ncep.noaa.gov/heat_index.shtml