Extended Forecast Discussion NWS Weather Prediction Center College Park MD 158 PM EST Sun Nov 07 2021 Valid 12Z Wed Nov 10 2021 - 12Z Sun Nov 14 2021 ...Robust Midwest/Great Lakes Low mid-later week... ...Multiple rounds of precipitation into the Pacific Northwest later in the week... ...Pattern Overview... Upper ridging to the southwest of California as well as over the Canadian archipelago favors troughing over the central to eastern CONUS later this week into the weekend. This favors a deepening central states cyclone that will lift northeastward through the Midwest/Great Lakes into Canada Thu-Sat. Milder air over much of the Lower 48 will trend cooler with time as the attendant cold front sweeps eastward, favoring a widespread swath of modest to locally heavy rain across much of the East. On the northwest side of the low pressure, some wrap-around snow is likely over parts of the Dakotas/Upper Midwest/Great Lakes and central/northern Appalachians next weekend. Upstream, there is a growing guidance signal bringing a long fetch plume of Pacific moisture into the Pacific Northwest, especially later this week. Favorable flow should focus heavy rains and elevation snows over the Olympics and Cascades. ...Guidance/Predictability Assessment... Guidance continues to illustrate a reasonably similar larger scale pattern evolution, but with continued uncertainty in timing, track, and strength of the embedded systems including run-to-run continuity issues. Given uncertainty in recent trends, a composite blend was a prudent starting point that largely downplayed more seemingly errant deterministic runs including the 06Z GFS and at times the 00Z ECMWF. General overlap between many GEFS and ECMWF ensembles favored using the National Blend of Models for most grids with enhancements to its QPF overall, especially around the Great Lakes next weekend but also in the East with the surface low/front. ...Weather/Hazards Highlights... Amplifying upper pattern will support surface cyclogenesis over the Upper Midwest late Wed into Thu as Gulf moisture streams northward along and ahead of the cold front. Surface wave development out of the lower Mississippi Valley could act to enhance rainfall from the southern Appalachians northward into the Northeast. As the system moves into Canada, backside cold air flow by next Friday will likely support some snow over the Dakotas/Upper Midwest/Great Lakes and into the northern/central Appalachians. This could be the first accumulating snow of the season for some areas of northern Minnesota into the eastern Dakotas. Temperatures will be near to above normal early in the week, with possible record highs ahead of the front on Friday in the Mid-Atlantic, but trending cooler by week's end especially into the Southeast (relative to typical mid-November values there). Please see WPC links below for all the details in graphical format. Upstream, there is a growing guidance signal bringing several rounds of rain and mountain snow to the Pacific Northwest, especially later this week. Favorable flow should focus heavy rains and elevation snows over the Olympics and Washington Cascades. Fracasso/Schichtel Additional 3-7 Day Hazard information can be found on the WPC medium range hazards outlook 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