Extended Forecast Discussion NWS Weather Prediction Center College Park MD 137 AM EDT Sun Oct 14 2018 Valid 12Z Wed Oct 17 2018 - 12Z Sun Oct 21 2018 ...Pattern Overview... Upper ridging over British Columbia and Florida will favor progressive troughing through the northern tier east of the Rockies with a closed low in the Southwest. A couple Canadian fronts with limited moisture will swing through the Great Lakes/Northeast later this week into the weekend with a renewed push of cooler air. Florida will remain warm/hot with scattered showers/storms and the Pacific Northwest should see above average temperatures and dry conditions. ...Guidance/Predictability Assessment... A multi-model deterministic blend (GFS/ECMWF/Canadian) sufficed for the Wed-Fri period as models showed generally good consensus with respect to the upper low lingering across the Southwest and with amplifying shortwave energy crossing the Great Lakes. For Sat/Sun, one point of contention among the guidance becomes how much erosion/flattening of the western North American ridge occurs as shortwave energy exits the northeastern Pacific. The ECMWF and its ensembles have mostly been more aggressive with flattening the ridge while the GFS/GEFS have maintained it, though the latest ECMWF guidance was closer to the GFS/GEFS than previous cycles. In the east, GFS/Canadian were much stronger with the upper trough and surface low exiting the Northeast but a blend of the solutions with more ensemble weighting proved to be a reasonable compromise for now. ...Weather Highlights/Threats... Below average temperatures will continue late this week into the weekend for the Southwest through the southern Plains (especially Texas) northeastward through the Ohio Valley into the Northeast. On the warm side of the stationary front, Florida will see warm/hot temperatures that may tie/break record highs at some locations but the chance of showers/storms will remain for much of the state. Precipitation will be generally light except for the Texas coast just to the northeast of the lingering front along an inverted trough. This signal has been steady for several model/ensemble cycles (roughly Victoria to Brownsville). Upper low in the Southwest will support rain/snow showers for at least the higher elevations though its focus keeps shifting with the small changes in the shape of the upper low per the models. The rest of the lower 48 will be largely dry with some generally light rain/snow showers around the Lakes and into the Northeast along/ahead of the cold front next weekend. 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