Extended Forecast Discussion NWS Weather Prediction Center College Park MD 1047 AM EST Wed Nov 13 2019 Valid 12Z Sat Nov 16 2019 - 12Z Wed Nov 20 2019 ...Pattern Overview and Guidance/Predictability Assessment... Upper pattern will transition toward western troughing and eastern quasi-zonal flow in about a week, after two successive systems lift northeastward along the East Coast. In the West, upper ridging will weaken as it slides eastward atop a closed upper low moving away from Baja California. This will pave the way for a Pacific shortwave to dig through interior California as downstream heights rise in response. Off the Southeast coast, the models have come into better agreement with mostly some timing differences as the surface low looms offshore. Another system upstream will act to kick this lead shortwave along by the end of the weekend, but reinforce the surface boundary along the Gulf Stream. This may develop another low off the NC coast by early next week, though models continue to struggle with intensity/depth of this next system. In the West, the leading front into Washington will weaken in favor of a stronger shortwave on its heels. The ECMWF continues to be the most aggressive with this feature digging it farther southwest than the other guidance. GFS is better in line with the ensembles but given how much upstream ridging is forecast to build into the Gulf of Alaska, the ECMWF solution cannot be ruled out completely. This would carry a cold front through the Great Basin into the Four Corners region by next Wednesday. Across the board, the WPC blend uses the ECMWF and prior 2 runs of the GFS, along with previous WPC continuity and ensemble mean guidance (ECENS and GEFS). Due to greater differences as noted above later in the period, both in the East and the West, more ensemble mean weighting was used by the middle of next week. ...Weather Highlights/Threats... Below average temperatures in the East will slowly moderate back toward more typical mid-November values by early next week. Much of the West will have temperatures above normal by 5-15 degrees through this weekend, cooling early next week with the arrival of the next upper trough. The system off the Southeast/Mid-Atlantic coast should keep the heaviest rains offshore but should be close enough to produce at least showers along the I-95 corridor. Heavier rain is possible right along the coast of North Carolina. The strong pressure gradient between the low and the sfc high over New England will lead to windy conditions along the coast. The precipitation shield will move northward into New England early next week where temperatures may be cold enough for some snow in higher elevations. Several systems out of the Pacific will maintain a rather wet period for at least coastal Washington/Oregon and the Cascades, with less rain/snow along and just west of the Continental Divide. With increased troughing toward the Southwest next week, some light precipitation will be possible late Tue into Wed though this depends heavily on the evolution of the Western U.S. trough digging southward next week. Santorelli/Fracasso 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