Extended Forecast Discussion NWS Weather Prediction Center College Park MD 1249 PM 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 lower 48 United States... ...Overview and Guidance/Predictability Assessment... A stronger than average warm core ridge 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. The jet stream will be relegated to its usual July position along the U.S./Canadian border with increasingly zonal/west-to-east flow, leading to lower 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 mid-level heights rise across the Mid-Latitudes, frontal features will become less defined between the hot/humid air mass south of about 40N and the less hot/warm air mass to its north. Outside of the 06Z GFS at times, there was a reasonably good agreement in the deterministic and ensemble mean guidance. However, including a minority weighting of the 06z GFS was acceptable to account for uncertainty. The preference for fronts/pressures/winds/500 hPa heights started with an even blend of the 06z GFS, 00z Canadian, 00z UKMET, and 00z ECMWF. Slowly incorporated the 00z NAEFS/ECMWF ensemble mean solutions with time to help deal with lingering differences within the deterministic guidance, ending up with a near even weighting of the deterministic and ensemble mean guidance by next Sunday. ...Weather Pattern/Hazard Highlights... A 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 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. The relative lack of rainfall across the West and Plains during the next week in combination with summertime heat is expected to worsen/expand drought conditions in those areas. Temperatures will be close to average across the West, including the Desert Southwest. Temperatures rise to near and above record highs over parts of New Mexico and Texas into 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 east of the Rockies with the largest anomalies migrating from West Texas through the Central Plains, Great Lakes, and eventually the Northeast next weekend (5-10 deg above normal). Widespread highs in the mid-90s to low 100s are likely with higher heat indices from Oklahoma eastward to the Southeast with an increase in highs into the low to mid 90s with time for areas near the Great Lakes and Northeast. Roth/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