Extended Forecast Discussion NWS Weather Prediction Center College Park MD 156 AM EST Thu Nov 12 2020 Valid 12Z Sun Nov 15 2020 - 12Z Thu Nov 19 2020 ***Additional rounds of rain and mountain snow for the northwestern U.S. next week, and relatively uneventful weather east of the Rockies*** ...Overview... An upper level trough over the Upper Midwest early Sunday, along with a strong surface low over the Great Lakes, will then cross the Northeast U.S. through Monday with a cold front exiting the East Coast. By this time, an upper ridge should briefly build across the Rockies and western High Plains, before the next trough and storm system approaches from the eastern Pacific by mid-week. ...Guidance Evaluation/Preferences... The deterministic guidance is in relatively good agreement through the weekend on the synoptic scale pattern, and then the ECMWF becomes stronger with the upper trough crossing near the East Coast compared to the model consensus, similar to earlier runs. Significant differences come into play across the West Coast region by Tuesday and Wednesday with the arrival of the next trough. The 00Z GFS is faster to bring height falls to the West Coast, whereas the CMC and ECMWF are both considerably slower. In addition, both the CMC and ECMWF bring a reinforcing shortwave trough to the East Coast by midweek, in contrast to building heights portrayed by the GFS. Given the earlier 00Z ECMWF run from Wednesday morning was closer to continuity compared to the 12Z run and more in line with the latest ensemble means, the 00Z run was given greater weighting in the forecast. The WPC front/pressures forecast also incorporated the GFS and some previous WPC continuity through Day 5, and more EC mean and NAEFS mean was used for early next week to account for increasing model spread, with below average confidence for days 6 and 7. ...Sensible weather and hazards... Unsettled weather is expected from northern California to Washington state during much of this time as two additional storm systems approach the region, with an atmospheric river event possible late Monday and into Tuesday. This will equate to a few inches of rainfall for the lower elevations near the Coast, and 1-2 feet of snow for the higher elevations of the Cascades and slightly less for the northern Rockies. Temperatures are expected to moderate after the recent cold spell, with readings returning to slightly above climatological averages for this region. In contrast, the eastern U.S. will likely see temperatures fall to, or slightly below, mid-November averages by early next week as the upper trough replaces the Bermuda high. An addition round of rain is likely ahead of the next front, albeit much lighter than what is ongoing now along the East Coast, followed by much drier conditions as a large surface high builds in from the Plains. Hamrick 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