Extended Forecast Discussion NWS Weather Prediction Center College Park MD 1150 AM EDT Fri Aug 09 2019 Valid 12Z Mon Aug 12 2019 - 12Z Fri Aug 16 2019 ...Overview and Guidance/Predictability Assessment... Generally quasi-zonal flow is expected to prevail early next week across the CONUS, with embedded shortwaves tracking through and some indication of troughing along the West Coast. This trough is least amplified in the EC solutions. By midweek, more amplified flow begins rebuilding as a deeper trough pushes into the Northwest and ridging centered in the Southern Plains is expected to strengthen by Thu/Fri. This would likely lead to troughing downstream in the eastern U.S. Model guidance, particularly the GEFS and EC means, are in pretty good alignment with the pattern, so a multi-model blend was able to be used early on. The 00Z CMC by day 5/Wed pushes more energy into the eastern U.S. trough, deepening it more than other guidance into day 6/7. On the other hand, the GFS deterministic runs, particularly the 06Z run, flatten out that trough. Thus, the ECMWF and GEFS means made up the bulk of the forecast later in the period. Overall not many changes were needed to the overnight fronts/pressures forecast. ...Weather Highlights/Threats... Widespread rain and thunderstorms are expected around a low pressure system from the Northern Plains into the Upper Midwest and Ohio Valley early in the workweek ahead of a shortwave. Gulf moisture flowing into the vicinity of that front as it pushes into the Southeast will lead to scattered showers and thunderstorms there. Temperature-wise, above average temperatures are forecast in the southern tier underneath the upper high, leading to the likelihood of excessive heat and widespread record high minimum temperatures. Meanwhile the northwestern and north-central CONUS will generally have below average high temperatures. Tate Additional 3-7 Day Hazards information can be found on the WPC medium range hazards chart at: https://www.wpc.ncep.noaa.gov/threats/threats.php WPC medium range 500mb heights, surface systems, weather grids, quantitative precipitation, 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/wwd/pwpf_d47/pwpf_medr.php?day=4 https://www.wpc.ncep.noaa.gov/heat_index.shtml