Extended Forecast Discussion NWS Weather Prediction Center College Park MD 141 AM EST Sun Jan 31 2021 Valid 12Z Wed Feb 03 2021 - 12Z Sun Feb 07 2021 ...Potent midweek CA system to progress to the Plains/Midwest/Northeast later week... ...Guidance/Predictability Assessment... The WPC medium range product suite was primarily derived from a composite blend of the GFS/ECMWF, GEFS/ECMWF ensemble means and the National Blend of Models. Blend weightings in favor of the well clustered models days 3/4 (Wed/Thu) transition to mainly the still reasonably compatible ensemble means by next weekend amid growing forecast spread. ...Weather/Threats Highlights... For the deep cyclone near New England, wintry precipitation inland should gradual taper off into Wednesday, but some areas along or offshore the coast should continue to experience brisk to strong winds into Thursday as the cyclone will be slow to depart. A strong upper trough driving through CA Wed will support a period of enhanced moisture/rains and mountain snows, with activity spreading across the south-central Great Basin/Rockies with system progression. Variance with the extent of digging still leads to subsequent ejection differences. Model differences grow downstream along with uncertain stream phasing/central U.S. storm genesis mid-later next week. It is expected that as the energy comes out of the West and Rockies, a deepening low or lows to the lee of the Rockies will lift toward the Great Lakes. Leading warm air advection and moisture return on the backside of the departing high will allow deepening Gulf moisture interact with the favorable dynamics and forcing. This will fuel an expanding area of moderate to locally heavier precipitation across the east-central U.S. Enhanced wrap-back snows can be expected near and to the north of the main cyclone track over the north-central to northeastern U.S.. However, low support aloft/phasing details remain uncertain. Upstream, another batch of wintry precipitation is forecast to track down over the Northwest and then the northern and central Rockies late week associated with a polar front with approach of new digging upper trough energies. Frontal surges, lead ejecting waves and main upper trough amplification back over the central U.S. next weekend may favor some uncertain modest swaths of snows from the Midwest/OH Valley to the Appalachians and the Northeast, including some lake effect enhancement and focus. Schichtel Additional 3-7 Day Hazard information can be found on the WPC medium range hazards outlook 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