Extended Forecast Discussion NWS Weather Prediction Center College Park MD 918 AM EDT Sun Mar 10 2019 Valid 12Z Wed Mar 13 2019 - 12Z Sun Mar 17 2019 ...Heavy Snow/Wind Threat for the North-Central U.S. Wednesday and Thursday... ...Heavy Rain/Strong Thunderstorm Threat from the South-Central Plains/MS Valley to the Mid-South/Southeast Wednesday to Friday... ...Overview... An amplified flow pattern will remain quite active Wed/Thu as another central U.S. system heads toward the Great Lakes with a potpourri of weather threats typical of a robust late winter/early spring storm. This will spread a large area of potentially heavy rain/severe convection and runoff threat from the central/southern Plains through the Mid-South/Southeast as marginally cold air to the north supports a heavy snow/wind threat for the north-central Rockies/Plains and Upper Midwest. By next weekend, the pattern appears much quieter with high pressure forecast to dominate the western/central parts of the lower 48 as broad troughing lingers in the east with most unsettled flow over a cooled Northeast and wet Florida near a stalled trailing front. ...Guidance and Uncertainty Assessment... Deterministic and ensemble guidance remain unusually well clustered into next weekend and a composite blend seems to offer a very reasonable forecast that maintains excellent WPC continuity. Predictability in this pattern is quite high. ...Weather Highlights and Hazards... The main system of interest in the medium range will lift out of southeastern CO Wed morning as precipitation expands in coverage eastward, focused from eastern portions of the southern/central Plains and mid-lower MS Valley to the TN Valley Wed. This will include a risk of severe weather given height falls/jet dynamics/diffluence aloft and lower atmospheric inflow/convergence. To the east, a lead frontal boundary will lift northward as a warm front and bring widespread rains and embedded convection to AL/GA/TN/KY then south-central Appalachians Thu/Fri. To the north, enough cold air will support heavy snow on the northwest/north side of the surface low that will occur with strong winds (possible blizzard conditions). Heavy cold rains will fall to the southeast of the surface low over some areas that will have received significant snow in the short term (i.e. ND/SD/MN intersection). The surface low will depart through southern Canada Friday as colder air is dragged in behind it across the Great Lakes, enhancing lake-effect snows. This activity may be reinforced with weekend approach of shortwave energy digging well to the lee of an amplifying western Canadian upper ridge. Fracasso/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