Extended Forecast Discussion NWS Weather Prediction Center College Park MD 200 AM EST Fri Dec 06 2019 Valid 12Z Mon Dec 09 2019 - 12Z Fri Dec 13 2019 ...Heavy rain potential for Mid-South to Northeast early next week... ...Well below normal temperatures over the northern Plains/Upper Midwest early-mid week... ...Pattern Overview and Guidance/Predictability Assessment... The pattern aloft by early-mid next week will highlight a closed vortex over Hudson Bay as troughing/cyclonic flow rotates underneath from a chilled and unsettled north-central to northeastern U.S. This is supported by an amplified upstream ridge aloft on the North American West Coast. A southern stream flow meanwhile features shortwave trough ejection from the Southwest Monday to the Southern Plains Tuesday that then phases with a more dominant northern stream. Recent GFS/ECMWF runs are trending to a compromise amplitude and progression solution that is becoming increasingly consistent with their latest ensembles. A composite 00 UTC model/ensemble solution still also suggests that gradual rounding of the West Coast ridge later next week would let increased eastern Pacific impulse energy/moisture work inland from the Northwest/Rockies to the Plains. This may also set the tone for robust east-central U.S. upper trough amplification to keep an eye on heading into next weekend. ...Weather Highlights/Threats... Over the West...a building West Coast upper ridge should keep most of the West dry through early next week beyond some lingering Rockies snows in northwest flow. The pattern should become more wet and elevation snowy for especially the Pacific Northwest, but also inland to the Rockies as shortwave energies round the northern part of the ridge mid-later week. There is a strong signal for heavy rainfall over a broad area from the Mid-South to the northern Mid-Atlantic and southern/eastern New England Monday/Monday night with frontal approach and support aloft. Locally heavy snow is possible in the comma head of this low over the Upper Midwest Sunday night through Monday with potential Lake Superior enhancement. Lake effect snow should spread across the remainder of the Great Lakes Monday into Tuesday in the wake of the low which is particularly cold. Polar plunges are expected behind the cold front with temperature anomalies of 15 to 25 degrees below normal centered over the Upper Midwest with reinforcing shots of cold air. 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