Extended Forecast Discussion NWS Weather Prediction Center College Park MD 155 AM EST 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... Pattern will start quite active in the medium range Wed/Thu as another central CONUS system heads toward the Great Lakes with a potpourri of weather threats typical of a robust 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. ...Guidance and Uncertainty Assessment... Most of the GFS/ECMWF deterministic/ensemble guidance clustered well through the period so that a blend could be utilized through about Friday. For next weekend, preferred a mostly ensemble-based solution given disagreement on the shape/details of the upper trough in the east as well as back over the Southwest. ...Weather Highlights and Hazards... Main system of interest in the medium range will lift out southeastern Colorado Wednesday morning as precipitation expands in coverage eastward, focused on the central/southern Plains (northern Texas northward) Tue/Wed. To the east, boundary across the Gulf will lift northward as a warm front and bring widespread rainfall and embedded convection into the Mississippi/Tennessee Valley Wednesday then into Alabama/Georgia/southern Appalachians Thursday into early Friday. The potential for several inches of rain exists over a large area that will be further refined over the next few days. To the north, cold enough air will support snow on the northwest/north side of the surface low that will occur with strong winds (i.e., possible blizzard conditions). A cold rain (perhaps over an inch to an inch and a half) will fall to the southeast of the surface low over some areas that have received significant snow in the short term (e.g., 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. Temperatures will remain below average in the west but moderate by next weekend as upper ridging slowly noses into the area. In the east, seasonable temperatures Wednesday will warm up ahead of the central states' system by Thursday into Friday, only to retreat back to near or just below climo values by next weekend. 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