Extended Forecast Discussion NWS Weather Prediction Center College Park MD 217 AM EDT Thu Sep 05 2019 Valid 12Z Sun Sep 08 2019 - 12Z Thu Sep 12 2019 ...Record heat to continue for the Lower Mississippi Valley/Gulf Coast into next week... ...Overview... Upper ridging will remain anchored over the Lower Mississippi Valley and Southeast into next week. The West will see a series of upper troughs moving through the region with southwest flow across the Plains. Low pressure emerging from the West early in the week should track eastward along the US/Canadian border to the east coast around next Thursday. ...Guidance Evaluation and Preferences... The 12Z/18Z GFS and 12Z ECMWF offered reasonable clustering near their respective ensemble means and each other through the period. The 12Z UKMET/Canadian differed mostly in the West and upstream over the northeastern Pacific and were not preferred. Blended approach remedied any timing/track/amplitude differences among the GFS/ECMWF deterministic runs. ...Sensible Weather... Fall-like temperatures (10-15F below average; highs in the 60s) over the High Plains/Upper Midwest Sunday will moderate only slightly through the week (5-10F below average). 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, especially on Sunday but still continuing through at least Wednesday. Much of the West will see below average temperatures under upper troughing, with lowest anomalies tending to be over north-central areas and the northern Rockies. Rainfall will mostly favor the northern areas from the Pacific Northwest eastward as the frontal system moves toward the Great Lakes and then Northeast by later next week. Pockets of heavier rain may be possible across the High Plains into the western Great Lakes region around the surface low and in advance of the warm front. In the Mid-Atlantic region, stalling front late this weekend into early Monday may help expand an area of generally light rain before high pressure to the north moves in by Tuesday. In the Southwest, moisture out of Mexico will likely lead to a daily chance of mountain showers/storms that could move into desert valley locations (southern Arizona and portions of New Mexico) and perhaps into extreme western Texas. 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