Extended Forecast Discussion NWS Weather Prediction Center College Park MD 256 AM EDT Wed Sep 04 2019 Valid 12Z Sat Sep 07 2019 - 12Z Wed Sep 11 2019 ...Record heat to continue for the Lower Mississippi Valley/Gulf Coast this weekend... ...Overview... Upper ridging will remain anchored over the Lower Mississippi Valley and Southeast this weekend and into next week. The West will see lead troughing Saturday lift through the Great Basin Sunday as reinforcing troughing comes into the Pac NW. With rising heights over the Great Lakes/Northeast as Dorian exits, this will take western systems eastward along the US/Canadian border. By next Wednesday, troughing may linger along the west coast. ...Guidance Evaluation and Preferences... Blend of the 12Z/18Z GFS and 12Z ECMWF/UKMET offered a good starting point for most of the CONUS Sat-Mon as a front pushes off the east coast but stops across the Tennessee Valley due to ridging to its south. For Mon-Tue, GFS/ECMWF were close to their means with the exiting High Plains low pressure that should move ENE into the Great Lakes. In the West, uncertainty increases by next Tue/Wed due to upstream timing/amplitude differences in the guidance. This area has been much less predictable than elsewhere in recent days and the GEFS mean and ECMWF ensemble mean become out of phase by next Wednesday. Prefer to side more with the ECMWF ensemble mean which favors continued (maybe reinforced) troughing along the west coast rather than ridging per just the recent GEFS mean. ...Sensible Weather... A potent cold front will bring fall-like temperatures (10-20F below average) to the High Plains/Upper Midwest this weekend as many places rise only into the upper 50 and 60s. The Southern tier of the CONUS from Texas eastward to Florida will generally see well above average temperatures in the mid-90s to around 100F that are forecast to tie or break record highs. The heat may temper only a bit next week as temperatures stay in the middle and upper 90s from Texas to Georgia. Much of the West will see below average temperatures under upper troughing. Rainfall will dive through the Plains/Corn Belt this weekend with additional rainfall moving into the Northwest. As the cold front moves eastward early next week, rain will advance in tandem through the northern tier states. Questions remain in how much moisture will lift out of NW Mexico into the Southwest/Four Corners region next week. The GFS/GEFS runs have been wetter than the ECMWF/ECMWF ensembles so a middle ground solution was depicted in the QPF progs for now especially along/north of I-40 in AZ/NM. 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