Extended Forecast Discussion NWS Weather Prediction Center College Park MD 140 AM EDT Mon Oct 15 2018 Valid 12Z Thu Oct 18 2018 - 12Z Mon Oct 22 2018 ...Pattern Overview and Guidance/Predictability Assessment... Models/ensembles continue to show good agreement on the longwave pattern over the lower 48 through the weekend into next week. With upper ridging over British Columbia and Florida, troughing will be favored through the northern tier east of the Rockies with a closed low lingering across the Southwest. This will take a couple cold fronts out of western Canada and through the Great Lakes/Northeast into the Southeast. A multi-model deterministic blend sufficed for the forecast Thu-Sat. By Sunday, the lead front will be offshore the Northeast/Mid-Atlantic with high pressure over the Plains and the next front dipping southeastward. Models diverge on timing of this front and strength across Canada but a trend toward the ensembles should minimize error. In the Southwest, the closed low will likely meander westward per the consensus with ridging moving eastward into WA/OR/ID. ...Weather Highlights/Threats... Below average temperatures will continue late this week into next Monday for the Southwest through the southern Plains (especially Texas) northeastward through the Ohio Valley into the Northeast/Mid-Atlantic. On the warm side of the southern stationary front, Florida will see warm/hot temperatures that may tie/break record highs at some locations. Upper ridging across the Pacific Northwest (WA/OR/ID into western Montana) will also lead to continued above average temperatures for that region. The southern/central Texas coast will see the most organized rainfall this period along an inverted trough and just to the northwest of a stationary boundary in the western Gulf. The lingering upper low in the Southwest will support rain/snow showers mostly focused on/along the higher terrain while a stationary front across Florida will keep daily shower/storm chances in the forecast. The rest of the lower 48 looks to be largely dry with some generally light rain/snow showers around the Lakes and into the Northeast along/ahead of the cold front Friday/Saturday. Fracasso WPC medium range 500 mb heights, surface systems, weather grids, quantitative precipitation, winter weather outlook probabilities and heat indexes are found 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