Extended Forecast Discussion NWS Weather Prediction Center College Park MD 159 PM EST Sun Nov 08 2020 Valid 12Z Wed Nov 11 2020 - 12Z Sun Nov 15 2020 ...Tropical Storm Eta could affect portions of Florida while heavy rain is possible over the Eastern Seaboard... ...Cold and unsettled weather forecast for much of the West... ...Overview... A broad upper-level trough is forecast to be situated over western and central parts of the U.S. through the end of the week, eventually shifting its axis slightly eastward by next weekend. The Bermuda high and a subtropical ridge over the East should cause anomalously warm temperatures there, while the West will see below normal temperatures moderating to near normal late week. Meanwhile, Tropical Storm Eta may strengthen to a hurricane and impact portions of Florida during the short range period, then meander slowly through the eastern Gulf of Mexico during the latter half of the week. ...Guidance Evaluation/Preferences... Model guidance continues to show good agreement with the overall trough pattern gradually shifting eastward through the week. Even smaller-scale shortwaves moving through the trough were generally well-clustered in model guidance through Thu. By Fri, notable model differences arise with the flow coming into the Northwest. The 00Z UKMET and to a lesser extent the 00Z CMC bring significantly more energy than other guidance and spin up deep surface lows, and it did not seem prudent have such a deep solution at this time. Differences in the timing and amplitude of shortwaves continue from there, as the 00Z ECMWF continues to show a more potent trough than other guidance in the central U.S. by the weekend, but the position has varied considerably from run to run. Thus, the medium range mass field forecast transitioned from a multi-model deterministic blend of the 00Z/06Z guidance at the beginning of the period (removing the CMC and UKMET by Fri) toward a blend which favored the 06Z GEFS and 00Z EC ensemble means by the weekend. The means were well clustered and this served to reduce discrepancies from individual models. The WPC forecast followed the National Hurricane Center track for Tropical Storm Eta. In general, slower movement is expected over the eastern Gulf compared to yesterday's and previous forecasts. Any potential landfall over Florida during the second half of the week remains highly uncertain in position and timing, with model and ensemble guidance showing a myriad of solutions from landfall in the Florida Big Bend to a recurve southwestward staying over the Gulf. See the National Hurricane Center for updated information on Eta. ...Weather/Hazard Highlights... After causing potentially hurricane conditions in southern Florida during the short range period, what is currently Tropical Storm Eta is forecast to move into the eastern Gulf of Mexico midweek onward. Some rain and hazardous marine conditions could spread into the western Florida peninsula regardless of landfall, but the worst conditions would depend on if, where, and when the cyclone makes landfall. Tropical moisture from Eta and moisture from the Atlantic are expected to combine in the vicinity of a slow-moving cold front over the Eastern Seaboard, causing a broad area of moderate to locally heavy rainfall. The heaviest rainfall totals are forecast for the Appalachians eastward toward the Mid-Atlantic and portions of the Northeast Wed/Thu, with some rain lingering in the Carolinas in particular for the end of the week. Another round of precipitation is possible over the central to eastern U.S. over the weekend ahead of another frontal system. In the West, precipitation is likely to increase by Fri and into the weekend, with the potential for heavy snow in higher elevations of the Cascades and Northern Rockies as well as persistent lower elevation rain. Generally cooler than normal conditions should continue underneath the upper troughing especially Wed/Thu, with moderating temperatures for the late week. On the other hand, much above normal temperatures will occur in the East given the ridging east of the trough. Record-setting warmth is possible especially Wed in the Eastern Seaboard, and dozens to hundreds of warm low temperatures could set daily records as the week progresses. Tate 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