Extended Forecast Discussion NWS Weather Prediction Center College Park MD 144 AM EST Tue Nov 10 2020 Valid 12Z Fri Nov 13 2020 - 12Z Tue Nov 17 2020 ***Tropical Storm Eta tracks slowly across eastern Gulf and may affect central Gulf Coast later this week*** ***Strong low pressure system will likely affect the Pacific Northwest by Friday and into Saturday*** ...Pattern Description... An active storm track will be in place across the northeast Pacific with both a northern and southern stream component to the mid-upper level flow, and a powerful storm system is likely to affect the Pacific Northwest around Friday night. The upper-level ridge axis that is currently in place near the East Coast is expected to be suppressed a bit over the western Atlantic as shortwave energy approaches from the Plains and erodes the ridge. A central U.S. upper ridge with troughs near the East Coast and West Coast appears likely by the end of the forecast period Tuesday. Tropical Storm Eta is initially forecast to move slowly across the eastern Gulf of Mexico, but its track after that remains uncertain owing to weak steering flow. ...Guidance Evaluation/Preferences... The progressive, initially dual stream flow on Friday and into the weekend has generally lower predictability than the more amplified pattern seen recently. There was good overall agreement among the GFS/ECMWF and their respective ensemble means for much of the forecast period. However, it is worth noting that both the 12Z and 00Z runs of the CMC and UKMET are stronger and faster with the Pacific storm system for the end of the week, and did not have as much ensemble support. A blend mainly focused on the 18Z GFS and 12Z ECMWF deterministic runs and their respective means was used for the WPC fronts/pressures forecast, with higher percentages of the ensemble means by early next week. The WPC forecast followed the National Hurricane Center track for Tropical Storm Eta. Any potential landfall over the Florida Panhandle for the end of the week remains highly uncertain in both position and timing. The 12Z ECMWF and its mean are the closest to the track, whereas the UKMET is well to the south with no U.S. landfall and the GFS/CMC dissipate is prior to reaching land, mainly owing to increased shear and cooler sea surface temperatures over the northern Gulf. ...Sensible weather and hazards... A potentially high impact storm system will likely affect the Pacific Northwest in the Friday-early Saturday time period. Given the potential for a sub-980 mb low approaching Vancouver Island, British Columbia, this would not only result in widespread heavy rain for the lower elevations, but also damaging winds and very hazardous marine conditions. This would also produce blizzard conditions in the Cascades and perhaps even the northern Rockies. The trend has been for a stronger storm, so this is something that will be need to be monitored closely over the next several days. The cold front approaching the eastern U.S. on Sunday will likely lead to another round of widespread rainfall from the southern Appalachians to the Northeast U.S., although not quite as heavy as the rainfall expected during the short-term forecast period. Tropical Storm Eta could cause some heavy rainfall and tropical-storm-force winds for portions of the Florida Panhandle and the central Gulf Coast for the end of the week if it does end up approaching or making landfall, but this is still a low confidence forecast and things will very likely change in future updates. No major temperature extremes are expected with readings mainly within 10 degrees of climatological averages for most of the nation. 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