Extended Forecast Discussion NWS Weather Prediction Center College Park MD 1232 AM EDT Sat Oct 19 2019 Valid 12Z Tue Oct 22 2019 - 12Z Sat Oct 26 2019 ...Upper Midwest/Great Lakes storm early next week... ...Wet Southern to Eastern U.S. to include effect from remnants of T.S. Nestor... ...Northern then Central Rockies Heavy Snow... ...Guidance/Uncertainty Assessment and Weather Highlights/Threats... It remains the case that an amplified and generally progressive flow pattern will support several significant weather systems over the lower 48 states next week. A closed upper low/trough will lift from the MS Valley through eastern North America early to mid next week. Deep surface cyclogenesis into the Upper Midwest/Great Lakes will act to ramp up winds and rain with wrap-back wet snow while forcing a lead frontal system and a return of Gulf moisture to combine with upper support to fuel a widespread swath of heavy rain/convection over the Eastern Seaboard. Pre-frontal activity and runoff issues over the Northeast may be significantly enhanced by interaction with an extratropical coastal low associated with current Tropical Storm Nestor. Recent model solutions indicate a trend toward curving a weakening cyclone back into New England. The pattern meanwhile reloads upstream as upper impulses/jet energies/height falls work progressively inland over the Northwestern U.S. early-mid next week that carve out another amplified central U.S. upper trough mid-later next week. A series of systems/frontal passages offer a risk of Northern then Central Rockies heavy snow. Below normal temperatures will sweep down through the interior West/Rockies then Central U.S. Temperatures will become 10-15 degrees below normal over the north-central states as the post-frontal high surges southward. Lead Gulf of Mexico moisture returning into the central Gulf Coast and lower MS/TN Valleys then into the Appalachians/Eastern Seaboard should fuel widespread enhanced rain/convection with potential for runoff issues. The WPC medium range product suite was primarily derived from a composite of reasonably well clustered guidance from the 18 UTC GFS/GEFS, the 12 UTC ECMWF/ECMWF ensemble mean and the National Blend of Models in a pattern with above normal forecast predictability. This guidace blend acts to mitigate lingering timing/strength variance to maintain good WPC system/pattern continuity. Schichtel 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