Extended Forecast Discussion NWS Weather Prediction Center College Park MD 300 AM EDT Sat Jul 02 2022 Valid 12Z Tue Jul 05 2022 - 12Z Sat Jul 09 2022 ...Overview... A persistent upper level ridge/high looks to be in place next week over the southern tier of the U.S. in a common summer pattern, with ridging building farther northward in the Rockies/High Plains and 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 generally west to northwest flow with embedded shortwaves across the rest of the northern tier. This flow pattern and a quasi-stationary frontal boundary draped from the north-central Plains to the Mid-Atlantic will focus showers and storms, with some organized convection and 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 12Z/18Z GFS worked well for the first half of the WPC medium range forecast. Increasing but relatively minor differences were seen around Thursday, such as the 12Z GFS becoming somewhat different with broad troughing in eastern Canada as it was more aggressive with a shortwave in south-central Canada than other guidance. Reasonably larger scale differences also arise by Friday-Saturday with the eastern Pacific trough/low, with the 12Z/18Z GFS runs holding the low offshore while the ECMWF and CMC bring troughing into the Northwest by then. The WPC forecast favored the latter cluster, so the model blend lessened the amounts of GFS runs in favor of the agreeable GEFS and ECMWF ensemble mean guidance by the latter part of the period, but maintained a majority of the operational guidance considering the reasonable agreement on the large scale. The new 00Z GFS is faster than the previous runs and more in line with other guidance, though the 00Z GEFS mean shows that a slower track is still possible. Also, overall 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. Northwesterly flow aloft and abundant moisture and instability will create a favorable pattern for mesoscale convective systems and high rainfall rates for a broad area from the northern Plains/Midwest/Upper Great Lakes into the Ohio Valley and Appalachians to the East Coast. There is a Slight Risk in the day 4 WPC experimental Excessive Rainfall Outlook in the central Appalachians where this activity could focus, and heavy rain causing flash flooding could certainly persist into day 5 and beyond but with considerable uncertainty in the placement of heavy rain amounts. 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 moist 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 hot temperatures as well, but with less extreme anomalies. Warmer than average temperatures are likely to build into the northern Rockies to northern Plains by Thursday-Saturday. Meanwhile the West is forecast to be cooler than normal in response to troughing aloft initially, but should moderate closer to normal and even above normal in the Desert Southwest and California by the latter part of next week. 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