Extended Forecast Discussion NWS Weather Prediction Center College Park MD 300 AM EDT Wed Oct 02 2019 Valid 12Z Sat Oct 05 2019 - 12Z Wed Oct 09 2019 ...Overview and model uncertainty assessment... Global models are in very good agreement on the speed and evolution of the upper-level trough forecast to move across the northern tier states during the weekend. By early next week, models appear to show an increasing potential for the pattern to become more amplified, resulting in higher uncertainty in the forecasts from early to the middle of next week. One area to monitor will be in the eastern U.S. where both the GFS and ECMWF have indicated cyclogenesis in some previous runs. However, there continues to be considerable run-to-run variability regarding this potential system. In addition, their ensemble means still do not indicate any signs of an East Coast cyclone. Another area of uncertainty will be over the Pacific Northwest from early to the middle of next week as the next upper trough arrives. The ECMWF has been showing the tendency for an upper low to form offshore while the GFS is much more progressive in bringing the trough onshore. The WPC forecast package was primarily derived from a composite blend of the 18 UTC GFS and the 12 UTC ECMWF, with increasing emphasis on their ensemble means for day 6 and 7 to handle the increasing uncertainty. This yielded generally good continuity with the previous WPC forecast package, but with a faster progression of the upper trough and surface cold fronts across the Pacific Northwest toward the middle of next week. ...Weather Pattern Highlights/Threats... An upper trough working its way into the northern Plains will bring a round of showers across the Midwest and Great Lakes during the weekend. As the trailing cold front forecast to slow down, there is an increasing chance for precipitation to linger across the southern Plains into the Tennessee Valley during the weekend. There is some potential for heavy rain to train across the Tennessee Valley as well. General rain is forecast to move through the East Coast early next week and off the coast by Wednesday. Temperatures across the country will be less extreme by the weekend and lasting through midweek next week with readings staying within 12 degrees from normal. The western U.S. upper trough will bring scattered rain/high elevation snow to the Pacific Northwest and northern Rockies through midweek next week. Meanwhile, tropical moisture north of a tropical low will bring a good chance of thunderstorms across Florida. The heaviest rains are expected to stay in the Gulf of Mexico through midweek next week. Kong 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