Extended Forecast Discussion NWS Weather Prediction Center College Park MD 143 AM EST Mon Nov 08 2021 Valid 12Z Thu Nov 11 2021 - 12Z Mon Nov 15 2021 ...Robust Midwest/Great Lakes Low into later this week... ...Multiple rounds of precipitation into the Pacific Northwest later this week... ...Pattern Overview... It remains the case that upper ridging to the southwest of California as well as over the Canadian archipelago favors amplified 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, wrap-around and then lake effect snow is likely over the Dakotas/Upper Midwest/Great Lakes late week and then the central/northern Appalachians. 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 and forecast clustering has improved slightly Thu into Fri. A composite blend of the GFS/ECMWF/Canadian/UKMET seems reasonable, is in line with the NBM and GEFS/NAEFS/ECMWF ensemble means and maintains good WPC continuity in this time frame. However, continued uncertainty in timing, track, and strength of the embedded systems including run-to-run continuity issues remains evident starting later Fri and onward. Given uncertainty in recent trends, the WPC product suite was derived from a composite blend of still compatible guidance from GEFS/NAEFS and ECMWF ensembles and the National Blend of Models. ...Weather/Hazards Highlights... Amplifying upper pattern will support surface cyclogenesis over the Upper Midwest 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 subsequently with cold flow off the 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. 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