Extended Forecast Discussion NWS Weather Prediction Center College Park MD 1200 PM EDT Fri Oct 18 2019 Valid 12Z Mon Oct 21 2019 - 12Z Fri Oct 25 2019 ...Upper Midwest/Great Lakes Storm... ...Potential Tropical Cyclone Sixteen to threaten the Northeast... ...Heavy rain and mountain snow from the Cascades to the North-Central Rockies... ...Guidance/Uncertainty Assessment and Weather Highlights/Threats... 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 Plains 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 across the east-central states. Activity over the Northeast may also be significantly enhanced by interaction/merging with a Mid-Atlantic frontal wave with the current Potential Tropical Cyclone Sixteen. Recent model solutions indicate a trend toward curving a weakening cyclone back into New England by next Tuesday. 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 heavy rain and mountain snow from the Cascades to North-Central Rockies. 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 may fuel enhanced rain/convection, with modest precipitation inland over the east-central states including the possibility of wrap-around snows for a cooling Upper Midwest by late next week. The WPC medium range product suite was primarily derived from a composite blend of reasonably well-clustered guidance from the 06Z GFS/00Z ECMWF/00Z UKMET/00Z Canadian Monday and Tuesday in a pattern with above normal forecast uncertainty. For later next week, more of the 06Z GEFS and 00Z ECMWF ensemble means were used. The 06Z GFS appears much too fast with the frontal progression across the Plains. The 06Z GEFS was slower than than its deterministic solution, while the ECMWF was slower than its ensemble mean and the GFS solutions. Kong/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