Extended Forecast Discussion NWS Weather Prediction Center College Park MD 137 AM EDT Thu Aug 15 2019 Valid 12Z Sun Aug 18 2019 - 12Z Thu Aug 22 2019 ...Guidance/Predictability Assessment and Weather Highlights/Threats... A stationary Southeast front lingers into early next week to pool deep moisture. While a threat of locally heavy rainfall remains, recent ECMWF runs in particular seem over zealous to spin-up and track northward small scale convective systems with heavy QPF. Guidance then overall agrees to build upper ridging over the Southwest and U.S. southern tier that may support some daily record high minimum/maximum temperatures. Meanwhile, an upper trough will dig within northern stream flow off British Columbia and the Pacific Northwest. A series of dynamic ejecting shortwaves in this flow will progress downstream over southern Canada and the U.S. northern tier to force wavy frontal systems down across the north-central U.S., Midwest/Great Lakes, the Ohio Valley/Northeast and Mid-Atlantic. Pooled moisture and instability will favors periods of enhanced convection, with a cell training risk as the fronts stall into the hot summer airmass underneath. Given uncertainties and recent run-run continuity issues with deterministic guidance, the WPC medium range product suite was mainly derived from the GEFS/ECMWF ensemble means. 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