Extended Forecast Discussion NWS Weather Prediction Center College Park MD 147 AM EST Tue Feb 04 2020 Valid 12Z Fri Feb 07 2020 - 12Z Tue Feb 11 2020 ...Heavy snow risk across New England... ...Pattern Overview and Guidance/Predictability Assessment... Eastern U.S. troughing will push a cold front off the East coast early on day 3 (Friday), with another quick shortwave following through the Tennessee/Ohio Valleys. After this, upper level ridging should build initially across the Southeast by Sunday, while out west a vigorous shortwave/closed low drops down the West coast. Another shortwave will reach the Pacific Northwest coast on Day 7/Tuesday. Confidence is above average in the overall pattern, though details still need to be worked out especially towards the end of the period. For the Eastern U.S. system, models show relatively good agreement so a composite blend of the ECMWF/GFS worked well for days 4 and 5. Out west, there remains some differences in timing of the closed low dropping southward along the West coast, especially by days 6 and 7/Monday and Tuesday. The ECMWF has been rather consistent the past 3 runs in showing this low center off the coast of southern California, though is the farthest west with the low. While the 18z/Feb 3 run of the GFS shows good placement with the overall guidance consensus, the run to run consistency of the evolution of this system has been rather poor. Thus, an ensemble mean approach seems most appropriate at this time, with smaller contributions from the GFS/ECMWF for definition. ...Weather/Hazard Highlights... Heavy rainfall at the end of the short range period will have pushed off the East coast by the start of the medium range period, though heavy snows will continue across parts of the interior northeast and northern New England through at least Friday. The second shortwave, crossing the Appalachians this weekend, may bring a period of light accumulating snows to parts of the southern/central Appalachians on Saturday, and again to the Northeast on Sunday. Impulses rounding the top of Western U.S. ridging will bring possibly heavy snowfall to the higher terrain of the Pacific Northwest into the northern/central Rockies Friday and Saturday. Meanwhile, rainfall will shift southward with the closed low across California, while return flow ahead of the system out of the Gulf of Mexico will increase precipitation chances across the parts of the southern Plains/Lower Mississippi Valley early to mid next week. Temperatures across the CONUS through the medium range period should be fairly close to average (give or take 5-10 degrees). A general warming trend is expected across the Eastern U.S., while temperatures should trend cooler out west. The central U.S. should be near normal through the entire period. Santorelli 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