Extended Forecast Discussion NWS Weather Prediction Center College Park MD 1110 AM EST Tue Mar 05 2019 Valid 12Z Fri Mar 08 2019 - 12Z Tue Mar 12 2019 ...A Stormy Pattern with Multiple Hazards Continues over the Nation... ...Model Guidance Evaluation and Preferences... The WPC medium range product suite was mainly derived from a composite blend of well clustered guidance from the latest GFS/ECMWF and GEFS/ECMWF ensemble means in a stormy pattern with above normal forecast predictability. Adjusted blend weightings gradually from model guidance to the ensmebles over time consistent with gradually growing forecast spread. ...Weather Highlights and Hazards... A lead system works through and the east-central then eastern states Friday into Saturday that offers modest but widespread moisture/precipitation potential. This will include some snow/ice threat potential to the north of an associated wavy front and modest coastal low as moisture spreads over slow to recede cold/dammed high pressure. Meanhwhile, heavy snows will likely continue on Friday focusing into favored terrain of the Intermountain West and Rockies as the strong Pacific disturbance crosses the region. Total snowfall amounts on the order of 1 to 2 feet are possible across parts of the central and northern Rockies, before easing this weekend in a pattern with secondary northern stream energies and associated cold surge works down through the West. Ample mid-upper level trough energy moving out of the West will lead to cyclo/frontogenesis over the central U.S. Widespread rain and thunderstorms are then slated to develop from the Gulf Coast to the Ohio Valley and southern Appalachians this weekend as a rich supply of Gulf moisture surges northward ahead of a strong cold front from the surface low. The heaviest rainfall is likely from eastern Texas and Tennessee Valley/Mid-south to the southern Appalachians, where heavy rains/repeat cells are likely to lead to some flooding issues. There is a significant threat for heavy wrapping snow/ice and a corridor of blizzard conditions across parts of the northern plains, Upper Midwest, and western Great Lakes region. Another facet to this deep low will be potential for strong to severe thunderstorms to develop in the warm sector that the Storm Prediction Center is currently monitoring. Upstream, the pattern again favors amplified mid-upper level trough development off the west coast this weekend. This will support modest precipitation over the Pacific Northwest but more ample height falls and cooling are slated for California and the Southwest early next week. This would enhance precipitation focus, though current forecast amounts are mainly moderate. Additional widespread rain may then develop across the s-central U.S. in about a week as the system works into the region to spawn another sound of cyclo/frontogenesis. 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