Extended Forecast Discussion NWS Weather Prediction Center College Park MD 115 PM EST Fri Jan 31 2020 Valid 12Z Mon Feb 03 2020 - 12Z Fri Feb 07 2020 ...Heavy Rainfall Threat for the South/Southeast/Appalachians Wednesday/Thursday... ...Overview and Guidance/Predictability Assessment... An amplified shortwave/closed low will dig over the Great Basin Monday, ejecting into the Central U.S. by later Tuesday. Models indicate this feature splitting into northern/southern stream pieces of energy, with the northern part tracking towards the Great Lakes by Thursday. Meanwhile, the southern piece of energy should be reinforced by additional upstream western U.S. energy resulting in amplified broad troughing over the Central U.S. into late next week. This would favor development of an emerging heavy rainfall threat across the South/Southeast/Appalachians as a induced series of frontal waves and increasingly deep and inland surge of Gulf of Mexico moisture combine with upper support. SPC also forecasts a severe weather risk with this system. Confidence is above normal and building in the large scale/synoptic flow pattern and main threats, but closer to average on the flow details past midweek. Accordingly, the WPC medium range product suite was mainly derived from the latest GFS/ECMWF Mon-Wed before adding significant input from the consistent ECMWF ensemble mean next Thu-Fri. ...Weather/Hazard Highlights... Potent trough/low energies digging over the Great Basin Monday will bring some rain but mainly widespread snows that should be heavy in the favored terrain/mountains from the Central Great Basin into the Central and Northern Rockies. Moisture return ahead of the upper trough and surface cold front will bring showers and thunderstorms from the lower Mississippi Valley to the Southeast, Appalachians and up through the Mid-Atlantic to the Northeast Tuesday-Friday. Frontal wave development and leading/increasing Gulf moisture inflow suggest a threat for heavy rainfall especially across the South/Southeast and Appalachians/southern Mid-Atlantic. On the north side of the precipitation shield, sufficient cold air may be in place for wintry precipitation from parts of the Midwest/Mid-Mississippi Valley to the Northeast. Meanwhile, persistent onshore flow should bring another round of heavy precipitation to the Pacific Northwest mid-later next week, with heavy mountain snowfalls that will working inland to the northern Rockies later next week. Temperatures next week will range from upwards of 15-30F above average from the south-central Plains to the Mid-Atlantic, with these temps trending back towards normal through the week as a main wavy cold front gradually makes its way eastward. Out west, temperatures begin below normal, but should increase back to normal or even slightly above normal by the end of the week as upper level ridging builds in aloft. Santorelli/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