Extended Forecast Discussion NWS Weather Prediction Center College Park MD 219 AM EDT Fri Aug 09 2019 Valid 12Z Mon Aug 12 2019 - 12Z Fri Aug 16 2019 ...Guidance/Predictability Assessment and Weather Highlights/Threats... Models and ensembles agree in showing general zonal upper flow over the northern tier of the lower 48 states early next week. There is a trend towards amplification mid-later next week with development of troughs/height falls to push convection focusing surface frontal passages through an unsettled Northwest and Northeast, with height rises in between over the north-central U.S. and the re-emergence of a hot southern Plains closed upper high. This seems reasonable. However, the models continue to offer significant embedded system timing differences Monday to Friday, albeit with some favorable forecast clustering showing decent shortwave trough/height falls progression from the northern Rockies Monday eastward over the Midwest/Great Lakes to the Northeast into midweek. This seems likely to drive a lead/wavy surface frontal system and the best convective rainfall potential focus/threat southward across the central and eastern states this period, eventually working later week into the southern Plains/South/Southeast. The South and Southeast ahead of this front will remain quite hot through much of the period beneath upper ridging, especially over the southern Plains under the closed upper high. Pre-frontal maximum and minimum temperatures are forecast to be 5 to 10+ deg above normal. This would result in a threat for widespread record high minimum temperatures in the quite moist and hot summer airmass. The WPC medium range product suite was primarily derived from a broad composite blend of the National Blend of Models with the latest GFS/ECMWF and GEFS/NAEFS/ECMWF ensemble means Monday before transitioning Tuesday to mainly just the ensemble means Wednesday to Friday. Schichtel 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