Extended Forecast Discussion NWS Weather Prediction Center College Park MD 1152 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 Friday... ...Heavy rainfall threat from eastern Texas/Lower Mississippi Valley northeastward during the weekend to Monday... ...Overview and Guidance Assessment/Preferences... The robust storm system over the Great Lakes region will continue to lift north and east into Canada spreading wintry precipitation along with it. As the central low pressure exits/weakens the wind speeds will begin to relax over the northern U.S. Meanwhile, a system will exit the Southwest/Southern Rockies this weekend bringing widespread rain to much of eastern Texas, Lower Mississippi and western Tennessee Valley with the potential for excessive rainfall and flash flooding. A surface low is expected to form along the boundary and aid in the progressive track toward the Ohio Valley. Model guidance suggest that this system will occlude, with a new low forming near the mid Atlantic coast and proceeding northeast near or off the New England coast early next week. Multiple shortwaves moving onshore the Pacific Northwest over the course of the coming week will bring precipitation to the coasts of Washington and Oregon and elevated snow to the Cascades. This energy will translate over into the Northern High Plains. The latest runs of the GFS have been faster/east than the rest of the operational solutions. Although the trend over the last few cycles have favored a more progressive track as it reaches the eastern U.S., the GFS has been too quick. As such the use and weighting of it was relatively light early on and negligible after Sunday. The CMC, UKMET and the ECWMF were much better clustered over most of the CONUS and picked up more details of the system leaving the Great Basin and entering the Southern/Central Plains. ...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 Friday. Some strong to severe convection will be possible farther south/southeast in the warm sector in the Ohio Valley Thursday. The 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 Friday-Saturday, behind the initial Great Lakes storm (peaking 20-25 degrees below normal in the central to northern Central Plains. Also during Friday-Saturday 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 Saturday. 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. Campbell 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