Extended Forecast Discussion NWS Weather Prediction Center College Park MD 1151 AM EDT Tue Aug 13 2019 Valid 12Z Fri Aug 16 2019 - 12Z Tue Aug 20 2019 ...Overview and Guidance/Predictability Assessment... Upper ridging is forecast to build again into the Southwest near the New Mexico/Texas border early next week as troughing digs down into the Northeast Pacific offshore British Columbia. Broad cyclonic flow will persist over southeastern Canada and through the Great Lakes/Northeast but with generally above average heights. The models/ensembles have converged toward a similar idea of the high-latitude flow out of Alaska/NW Canada that determines the shape/strength of the Northeast Pacific troughing. The 00Z runs of the GFS/ECMWF and their ensemble means (slight preference toward 00Z NAEFS vs the 00Z GEFS mean) offered a good starting point amid lingering uncertainty in system details. This will feature a stationary boundary in the Southeast, a defined front moving through Canada and the northern tier, and western Canada troughing toward the Northwest. ...Weather Highlights/Threats... Heavy rain potential will persist from late this week through the weekend from the lower Mississippi Valley eastward in the vicinity of the stalled front in some areas, but otherwise scattered rain/storms will be likely for the central/northeastern Gulf Coast. ECMWF appears to be overzealous on precipitation due in part to a nearly stationary mid-level reflection but still aligns with the highest probabilities of heavier rain. To the north, shortwave along the front may favor heavier rain through the Corn Belt out of the short range Friday. Thereafter, highest rain chances will push eastward into the Ohio Valley and eastern states as weak troughing settles through the Great Lakes. Temperatures will be above normal in the Southwest/Southern Plains and into the Ohio Valley/Mid-Atlantic/Southeast for much of the period. Some daily record highs will be possible over Texas this weekend and perhaps Arizona next Tuesday as the ridging expands. Cooler than normal temperatures are favored in the Northwest into Montana and the northern Plains as cooler air pushes in over the weekend. Fracasso 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