Extended Forecast Discussion NWS Weather Prediction Center College Park MD 208 PM EST Sat Nov 21 2020 Valid 12Z Tue Nov 24 2020 - 12Z Sat Nov 28 2020 ...Overview and Guidance Evaluation... Much uncertainty and model spread remain the main theme across the central to eastern U.S. for the middle of next week as global models continue to struggle with the details of interaction between the northern stream energy forecast to move across the northern Plains and the southern stream energy across the central Plains. The ECMWF shows run-to-run flip-flop between favoring the northern and southern stream development while the GFS tends to favor northern stream development. The 00Z CMC was similar to the 00Z ECMWF idea of favoring southern stream development. The latest 12Z guidance including the GFS and the UKMet now favor the southern stream development. The WPC medium range product suite was derived from blending the 06 UTC GFS/GEFS mean, the 00 UTC ECMWF/ECMWF ensemble mean together with a smaller portion from the CMC. This yielded a solution in line with recent guidance trends and continuity. ...Sensible Weather and Hazards... There is a decent guidance signal that a separated southern stream shortwave trough/low aloft and surface low pressure system will produce a swath of moderate to locally heavy precipitation from the southern Plains/mid-lower MS Valley Tue-Wed before reaching the East Coast on Thu with decreasing intensity. Farther north, moderate wintry precipitation including some snow will also be possible this period from the upper Midwest, the upper Great Lakes, and across northern New England under more northern stream system influence. Over the Northwest, it remains the case that progressive but energetic flow aloft will deliver another round of unsettled weather through midweek next week as a series of fronts approach/reach the region. Persistent rain and higher elevation snow are expected with highest totals over Coastal and Cascade Ranges and a secondary maximum into the Rockies. The interior section of the Northwest should catch a break late next week before the next surge of moisture reaches northwestern Washington. The supporting trough energies aloft early next week may be followed by more flow separated/amplified systems mid-later next week that could dig organized precipitation into the Great Basin toward the central to southern Rockies. Meanwhile, it appears that return moisture from the Gulf of Mexico will promote enhanced rainfall later next week across the Deep South. Kong/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