Extended Forecast Discussion NWS Weather Prediction Center College Park MD 1136 PM EDT Thu Sep 05 2019 Valid 12Z Mon Sep 09 2019 - 12Z Fri Sep 13 2019 ...Record heat to continue for the Lower Mississippi Valley/Gulf Coast next week... ...Overview... Upper ridging will remain anchored over the Lower Mississippi Valley and Southeast next week, with additional positive height anomalies diving southeastward out of far NW Canada to Hudson Bay. The West will see a series of upper troughs moving through the region with the lead system weakening into the Great Lakes Tuesday. Another system exiting the West late Wednesday into Thursday may be more robust. ...Guidance Evaluation and Preferences... A blend of the 18Z GFS and 12Z ECMWF/Canadian formed a good consensus cluster near the ensemble means through the period. The exception during the medium range may be over the Northeast around Wed/Thu as the 18Z GFS (and 12Z run) was much quicker/deeper with the surface low pressure as a result of phasing in a northern stream shortwave. Ensemble consensus suggested this was not likely as the members showed rather zonal flow with little amplitude. GFS runs were in the deepest 10% of the ensemble members with this feature and was not preferred. However, by next Friday, that system will exit the CONUS and the 18Z GFS again fit the consensus with deepening low pressure through the High Plains into the Upper Midwest. This may be a precursor to a pattern change over the West perhaps due to the upstream extratropical transition of Typhoon Lingling and Tropical Storm Faxai which may lead to deep troughing in the Bering Sea and ridging downstream into western North America. ...Sensible Weather... The Southern tier of the CONUS from east Texas eastward to the Florida panhandle will generally see well above average temperatures in the upper 90s to lower 100s F that are forecast to tie or break record highs. Much of the West and Northern Rockies/High Plains will see below average temperatures in a generally stormy/wet pattern. Mild temperatures, about 5-10F above average, are favored for the mid-Mississippi Valley eastward through the Ohio/Tennessee Valleys to the south of a frontal boundary. Rainfall will be mostly confined to northern areas along the storm track. 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 Mon-Tue. Another chance of widespread rain with embedded heavier elements will be possible next Thu/Fri from eastern Montana into Minnesota as low pressure deepens over the Plains. 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. Chances of rain should decrease though the week there. 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