Extended Forecast Discussion NWS Weather Prediction Center College Park MD 114 AM EDT Tue Apr 09 2019 Valid 12Z Fri Apr 12 2019 - 12Z Tue Apr 16 2019 ...Major winter storm tracking across the Upper Great Lakes Fri... ...Heavy rainfall threat from eastern Texas/Lower Mississippi Valley northeastward during the weekend to Monday... ...Overview and Guidance Assessment/Preferences... The medium range period starts with the tail end of the central US major cyclone moving through the upper Great Lakes Fri and then across the border into Canada Fri night, when the event winds down over the US. The models and ensembles remain clustered so a consensus based approach continues to be preferred. Also on Fri, the system that will become a producer of widespread precipitation in the lower MS Valley with flooding potential digs south across the Great Basin towards the southwest, with a closed 500 mb low possibly near the NM/AZ border at 12z Sat. The system moves east afterward on to the southern Plains and lower MS Valley by Sun morning, a bit faster than the prior cycle's dominant cluster of solutions. Low pressure forms at the surface and moves steadily northeast towards the Ohio Valley, with the system occluding and a new low forming near the mid Atlantic coast and proceeding northeast near or off the New England coast early next week. The 12z ECMWF/12z ECMWF mean solutions show a slower progression of the upper trough than the GFS runs this weekend into early next week and remain preferred. The 18z GEFS mean was an intermediate solution and given a minority weighting to hedge the timing. The guidance shows the arrival of upstream Pacific energy into the Northwest by around day 5 Sun and into the northern Rockies on day 6 Mon, possibly reaching the high plains day 7 Tue 16 Apr. The 12z ECMWF/12z Canadian/18z GFS models all show differing timing and phasing of the upper trough, so much greater weighting was given to the respective ensemble means, although greater weighting was given to the ECMWF Ensemble Mean for this forecast cycle. ...Weather Highlights/Hazards... Consensus still displays a high potential for heavy snowfall and strong winds--leading to a period of blowing snow and possible blizzard conditions into the Upper Great Lakes Fri. Some strong to severe convection will be possible farther south/southeast in the warm sector in the Ohio Valley Thu. The late week/early weekend system digging into the West will spread light valley rain and high elevation snow across the region. This system will lead to a heavy rainfall threat from eastern Texas and the Lower Mississippi Valley region into the Appalachians, Mid-Atlantic and southern New England, and possibly including the Ohio Valley. The highest forecast rainfall amounts are centered over the lower MS Valley. The Pacific Northwest and northern Rockies should see additional precipitation after the late week system in association with frontal systems moving onshore and inland. The cold temperature anomalies will be over the Rockies/Plains Fri-Sat, behind the initial Great Lakes storm (peaking 20-25 degrees below normal in the central to northern central Plains. Also during Fri-Sat expect above normal temperatures over the East, especially for morning lows which may be 10-20F above normal in the upper Ohio valley/Appalachians Fri and coastal mid Atlantic to southern New England Sat. Expect readings to moderate over much of the Lower 48 early next week, with slightly below normal temps under the Rockies upper trough and above normal in return flow in the southern to central Plains. Petersen 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