Extended Forecast Discussion NWS Weather Prediction Center College Park MD 207 AM EDT Sat Jul 18 2020 Valid 12Z Tue Jul 21 2020 - 12Z Sat Jul 25 2020 ...Hot temperatures for the Northeast/Mid-Atlantic through early next week... ...Overview and Weather/Hazard Highlights... A relatively strong and broad subtropical ridge is forecast to remain in place across the CONUS southern tier during the extended forecast period, while an active and progressive setup persists across the northern tier. By late next week, the pattern is expected to amplify a bit, with a ridge strengthening across the eastern half of the U.S. and a trough developing along the West Coast. Positive 500 hPa height anomalies are initially expected to be in place across the Mid-Atlantic and Northeast on Tue, shifting into the Atlantic Wed. The ridge will promote above average temperatures, with highs forecast to be 5 to 10 deg F above normal across portions of the Mid-Atlantic and Northeast (a continuation of even hotter temperatures during the short range). Farther west, a wave of low pressure is forecast to develop along a frontal boundary and move across the Midwest and Great Lakes Tue-Wed, and the Northeast on Thu. This low pressure system along with a mid/upper-level shortwave are expected to produce areas of scattered to numerous showers and thunderstorms, with locally heavy rains possible from the Midwest to the Eastern Seaboard. By Thu-Fri the next shortwave is likely to be moving across the Rockies, accompanied by another potential wave of low pressure, and areas of convection are possible across the Midwest along a lingering stationary/warm front. Lastly, a broad area of moisture and convection is forecast to drift westward across the Gulf of Mexico next week, and may bring some increase in shower/thunderstorm activity to southwestern portions of Florida and then to the central/western Gulf Coast by late next week. ...Guidance/Predictability Assessment... Overall, model/ensemble guidance showed relatively good consensus at the larger scales. The 12Z ECMWF/18Z GFS showed sufficient consensus to base the forecast heavily on a blend of those solutions during days 3-4 (Tue-Wed). After that, large scale agreement remained relatively good. Some differences were evident with the amplitude of upper-level troughing off the Northeast coast late next week, and with the degree of troughing along the West Coast. In general, increasing weight on the ECENS/GEFS ensemble means through time served to depict a good middle ground with respect to these differences, and to smooth out some of the finer-scale details with less predictability at those time scales. Ryan 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