Extended Forecast Discussion NWS Weather Prediction Center College Park MD 355 PM EST Mon Nov 09 2020 Valid 12Z Thu Nov 12 2020 - 12Z Mon Nov 16 2020 ...Tropical Storm Eta may threaten portions of Florida as it meanders over the eastern Gulf of Mexico... ...Active weather expected over the northwestern CONUS... ...Overview... An active storm track will be in place across the northeast Pacific with both a northern and southern stream component to the mid- to upper-level flow. The upper-level ridge axis that is currently in place near the East Coast is expected to be shunted a little farther to the east over the western Atlantic as shortwave energy approaches from the Plains for the end of the workweek, though ridging may build back into the Southeast by the weekend. Troughing is forecast to move into the central U.S. over the weekend as its amplitude weakens. Tropical Storm Eta is initially forecast to move slowly through the eastern Gulf of Mexico, but its track after that remains uncertain. ...Guidance Evaluation/Preferences... The progressive, initially dual stream flow in the medium range period has generally lower predictability than the more amplified pattern seen recently. However, model guidance was in fair agreement through the period. A blend mainly focused on the 06Z GFS and 00Z ECMWF deterministic runs was used for the WPC fronts/pressures forecast early in the period. One area where there is still model disagreement is with a low pressure system and shortwave moving through the eastern Pacific toward the Northwest around Fri; the 00Z CMC in particular seemed particularly deep and fast with this system, while the 00Z UKMET was weak and fast. Thus leaned more toward the GFS and EC solutions. By early next week, incorporated some of the EC and GEFS ensemble means to reduce reliance on the smaller-scale details of any particular model. The WPC forecast followed the National Hurricane Center track for Tropical Storm Eta. Any potential landfall over Florida during the second half of the week remains highly uncertain in position and timing. GFS and GEFS ensemble members have persistently shown Eta recurving back southwestward into the Gulf, with no Florida landfall. The 00Z EC ensemble members generally had a bimodal solution, with some members tracking a surface low across Florida Thu/Fri getting picked up by the front ahead of the upper trough, while some followed a solution similar to the GFS suite. The deterministic 00Z ECMWF also had a weak storm moving across northern Florida early in the medium range period, but the new 12Z ECMWF run now came in with Eta moving westward and no Florida landfall. See the National Hurricane Center for updates and additional information pertaining to this storm. ...Weather/Hazards Highlights... The western U.S. trough will result in below normal temperatures for much of the interior West through Thu, before a gradual moderating trend commences. An extended period of unsettled weather is forecast for the Northwest by the end of the week and beyond, with heavy mountain snows in the Cascades, Sierra Nevada, and northern portions of the Rockies. Lower elevation rain is likely especially in the Pacific Northwest as there is potential for an atmospheric river to take aim at the region and possibly cause multiple inches of rain. Tropical Storm Eta could cause heavy rainfall and tropical-storm-force winds in portions of Florida during the medium range period if it does end up approaching or making landfall, but this remains uncertain as discussed above. Regardless, tropical moisture streaming into a frontal boundary could cause heavy rainfall in the southern Mid-Atlantic and Southeast through the end of the workweek. Then, another round of rain is forecast for parts of the central over the weekend to the eastern U.S. early next week ahead of another frontal system. Warmer than normal temperatures are expected for the Eastern Seaboard especially Thu, while warm temperatures continue across the Southern Plains to Southeast through Sun. Tate/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 Hazards: - Heavy precipitation across portions of the Northern/Central Plains, the Great Basin, the Northern/Central Rockies, California, and the Pacific Northwest, Thu-Mon, Nov 12-Nov 16. - Heavy rain across portions of the Southeast and the Mid-Atlantic, Thu, Nov 12. - Heavy rain across portions of the Central/Southern Appalachians, the Tennessee Valley, the Mid-Atlantic, the Southeast, the Great Lakes, and the Ohio Valley, Sat, Nov 14. - Heavy rain across portions of the Great Lakes, the Mid-Atlantic, the Northeast, and the Central Appalachians, Sun, Nov 15. - Flooding possible across portions of the Southeast, the Great Lakes, the Mid-Atlantic, the Southern Appalachians, and the Upper Mississippi Valley. - Much below normal temperatures across portions of the Great Basin, the Northern Rockies, and the Northern Plains, Thu, Nov 12. 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