Extended Forecast Discussion NWS Weather Prediction Center College Park MD 300 AM EDT Thu Oct 03 2019 Valid 12Z Sun Oct 06 2019 - 12Z Thu Oct 10 2019 ...Overview and model uncertainty assessment... Global deterministic guidance this evening shows fairly good agreement on the synoptic pattern beginning on Sunday with a trough moving into the eastern U.S. and a ridge moving across the northern Rockies. The ECMWF continues to depict a more amplified pattern than other guidance, which leads to lower predictability across the U.S. toward the middle of next week, reaching the northern Plains by Thursday. On the other hand, the GFS has been showing more run-to-run consistency on the next upper trough moving into the northwestern U.S. next Tuesday and Wednesday. The Canadian model agrees with this scenario. This would bring a cold front fairly quickly across the Pacific Northwest and then into the Plains during midweek next week. The WPC forecast package was primarily derived from a composite blend of the 18Z GFS and the 12Z ECMWF, together with a smaller percentage from the 12Z Canadian model. More of the ensemble means from the 18Z GEFS and the 12Z EC mean were incorporated for Days 5 to 7 with higher emphasis on the 18Z GEFS due to its better run-to-run consistency on handling the upper trough over the western U.S. ...Weather Pattern Highlights/Threats... A fairly strong low pressure system should be tracking north of the Great Lakes on Sunday, bringing a reinforcing shot a cool air from Canada into the region with blustery winds. The trailing cold front is expected to slow down slightly as it heads toward the Appalachians with some locally heavy rainfall possible later on Sunday. More general rainfall is expected for the East Coast on Monday before the front moves off the coast on Tuesday. Over the Pacific Northwest, precipitation associated with the next upper trough is expected to arrive on Tuesday. Scattered higher elevation snowfall is expected to reach the northern Rockies Tuesday night to Wednesday. The cold air behind the upper trough will drive a cold front quickly into the Plains by Thursday. Scattered showers are expected to form ahead of the front over the central Plains on Thursday. Temperatures across the country will be less extreme by next week. However, the reinforcing cold air behind the upper trough could drop temperatures to near 20 degrees below normal over the northern Rockies on Wednesday. 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