Extended Forecast Discussion NWS Weather Prediction Center College Park MD 228 AM EDT Sun Jul 12 2020 Valid 12Z Wed Jul 15 2020 - 12Z Sun Jul 19 2020 ...Hot temperatures to continue into next weekend for much of the CONUS... ...Overview and Guidance/Predictability Assessment... Classic summertime upper high will meander over the southern Plains and lower Mississippi Valley into next weekend. Models/ensembles show excellent agreement in the lower latitudes with a weakness off California and another off Florida that will weaken in time. Jet stream will be relegated to along the U.S./Canadian border with an increasingly zonal flow, lowering predictability in shortwave timing. Closed upper low over northern Saskatchewan/Manitoba is forecast to slowly drift northeastward over Hudson Bay with its associated cold front moving through the northern tier of the Lower 48. As heights rise across the mid-latitudes, frontal features will become less defined between the hot/humid air mass south of about 40N and the warm air mass to its north. The 12Z GFS (and to a lesser extent the GEFS) was most different from the otherwise good consensus of the 12Z ECMWF/Candian/UKMET after Wednesday due to its different handling of Pacific/Gulf of Alaska energy (slower and farther north) and its 18Z run was still away from the best consensus. However, including a minority weighting was acceptable to modulate the other models. Otherwise, trended toward a blend of the ECMWF/Canadian and the GEFS/ECMWF ensemble means by the start of next weekend with an expansive area > 588dam heights. ...Weather Pattern/Hazard Highlights... Cold front will push through the Great Lakes Wednesday with a chance of showers/thunderstorms and locally heavy rain. The unsettled weather will continue along and to the south of the boundary Ohio Valley/Midwest and eventually to the Northeast/Mid-Atlantic) but with overall modest rainfall amounts. Generally dry conditions are expected elsewhere over the CONUS except Florida which will see afternoons showers/storms and perhaps over the southern Rockies on the west side of the upper high. Temperatures near and above record highs are likely over parts of New Mexico and Texas on Wednesday with widespread 100+ readings. This will continue an already hot July with many locations experiencing their hottest start to the month (e.g., San Antonio). Above normal temperatures are likely from the Rockies to the East Coast much of next week into the weekend with the largest anomalies over West Texas as well as around the Great Lakes (5-10 deg above normal). Widespread mid-90s to low 100s are likely with higher heat indices from Oklahoma eastward to the Southeast. A few hotter days are likely for the Northeast/Mid-Atlantic into the upper 80s to mid 90s. Overnight temperatures may only fall into the mid 70s to near 80 in urban areas under the influence of the upper high. 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