Extended Forecast Discussion NWS Weather Prediction Center College Park MD 210 AM EDT Fri Jul 10 2020 Valid 12Z Mon Jul 13 2020 - 12Z Fri Jul 17 2020 ...Overview and Guidance/Predictability Assessment... Intense summertime heat will shift from the Southwest to the East Coast next week as the jet stream lifts into Canada. Troughing in the Northeast Monday is forecast to weaken as the upper high migrates from NM/TX to the Lower Mississippi Valley around Wednesday. Ensembles remain in good agreement on the pattern shift and expanding upper ridge, with relatively smaller differences among the deterministic models. A blend of the recent 12Z/18Z guidance offered a good starting point for most areas with a trend toward about half ensemble weighting by next Thu/Fri due to differences in system timing out of the Pacific. Quasi-zonal flow suggests lower predictability for smaller wavelength features but those should be fairly weak. ...Weather Pattern/Hazard Highlights... Front over the East Coast will slowly lift northeastward on Tuesday, opening southwesterly flow that will bring in the very warm/hot temperatures toward the end of the week, especially over the Mid-Atlantic where mid to upper 90s are possible next Thursday. A weak cold front over the Great Lakes may skirt through the Northeast Thu-Fri and hold back temperatures to only a few degrees above normal. A more vigorous front on Monday will push through the Northern Plains and Upper Midwest with a chance of showers/thunderstorms and locally heavy rain. The unsettled weather will continue along to the south of the boundary (central Plains/Corn Belt/western Great Lakes) with generally dry conditions elsewhere over the CONUS except Florida. Temperatures near and above record highs are likely over the Southwest/Texas on Monday with widespread 100+ readings. As the upper ridge moves and expands eastward, above normal temperatures will be likely from the Rockies to the East Coast, centered along I-70 (~Denver to Baltimore). Widespread mid-90s to low 100s are likely with higher heat indices. Overnight temperatures may only fall into the mid 70s to near 80 in urban areas. 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