Extended Forecast Discussion NWS Weather Prediction Center College Park MD 1200 PM EDT Tue Jul 16 2019 Valid 12Z Fri Jul 19 2019 - 12Z Tue Jul 23 2019 ...Guidance/Predictability Assessment... The WPC medium range product suite was prmarily derived from a blend of the 06 UTC GEFS mean, 00 UTC NAEFS/ECMWF ensemble means, and WPC continuity. Latest guidance still depicts a fair amount of uncertainty through the extended period; therefore, followed suite to the previous forecast and utilized a compromise of the NAEFS and ECWMF ensemble means. Again, the ECMWF and GEFS mean clustered reasonably well with this preferred solution that offers a fairly well established larger scale pattern with much less certainty with embedded smaller scale impulses and local convective focus. ...Overview and Weather Highlights/Threats... There is a significant threat for dangerously hot and humid conditions later this week/weekend into early next week within an expansive sector of the nation. Later week hot upper ridging will encompass much of the Southwest and south-central portions of the Rockies and central and eastern U.S. By early next week, upper ridging/heat is expected to build up through the west-central states and begin to moderate downstream into the east-central U.S. with upper trough amplification. Some locations may tie or set new daily high minimum records. Heat indices will be around 105 to 115F, which may lead to some future issuance of heat advisories. Overtop, a quasi-zonal mean flow pattern develops over the northern-tier of the U.S. late week and for the weekend. A prolonged series of impulses/trough energies will pass over southern Canada and through the U.S. northern tier states with uncertain individual system amplitudes and timings. Showers and thunderstorms capable of producing locally heavy convection/MCS activity will sporadically develop and propagate within a wavy frontal/baroclinic zone across the north-central states, Midwest/Great Lakes and Northeast/Mid-Atlantic. Multiple rounds of rain/high rain rates may lead to locally excessive rainfall as the moisture and instability pools along the slow moving and wavy main frontal boundary. Although the model spread for QPF is not as high as previous cycles, it still lower confidence on where and when the highest amounts occur. Guidance continues to suggest the max QPF occurs over the Upper Mississippi Valley and Great Lakes this weekend that spreads into the east-central states early next week with flow amplification. Schichtel 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