Extended Forecast Discussion NWS Weather Prediction Center College Park MD 1100 AM EST Fri Mar 08 2019 Valid 12Z Mon Mar 11 2019 - 12Z Fri Mar 15 2019 ...North-Central U.S. Heavy Snow Threat... ...South-Central U.S. to Mid-South/Southeast Heavy Rain/Convection Threat... ...Overview... Deep mid-upper level troughing near California Monday will head eastward through the Southeast/Mexico Tuesday then northeastward over the central to east-central U.S. midweek through next Friday atop building ridging into the Southeast U.S./Cuba. In this pattern, yet another robust late winter storm will lift out of the Southwest Tuesday toward the Upper Midwest by Thursday. This will likely lead to another round of heavy snow and high winds across the north-central U.S. with heavy rain and strong convection focused from the South-Central U.S. to the Mid-South/Southeast. Slow movement of the cold front along the Gulf Coast may increase the threat of locally heavy rain with the potential for multiple inches of rain and flooding concerns given rather wet antecedent conditions. By next Thu/Fri, the surface low will exit through the Great Lakes and southern Ontario into Quebec but its attendant cold front will slow as it runs into the ridging to the east and becomes oriented near-parallel to the upper flow. Additional height falls upstream through the unsettled/wintry Great Basin and Rockies through mid-late week will also act to slow the trough progression eastward along the Gulf Coast. ...Guidance and Uncertainty Assessment... The 00 UTC GFS/ECMWF and GEFS/ECMWF ensemble mean have converged on a more well clustered solution days 3-7 and a composite was used as a starting template for the WPC medium range product suite today. ...Weather Highlights and Hazards... Snow will exit New England Monday though lake-enhanced snow will persist on the windy backside flow around the exiting deep low until a surface high builds in by Tuesday. Areas of rain and thunderstorm activity will persist across the Gulf Coast region along/ahead of a frontal boundary. Colder than average temperatures will persist over much of the western states on the order of 5-15F below climo. Temperatures in the east will be a bit more variable--near average early in the week, but trending milder later in the week ahead of the central Plains system. Main system of interest in the medium range will start in the West/Southwest with precipitation moving through Southern California and the Southwest Deserts. Precipitation will expand in coverage from New Mexico eastward, focused on the central/southern Plains from KS southward to northern Texas Tue/Wed as the surface low deepens from New Mexico into southwestern Kansas. Front across the Gulf will lift northward as the low heads toward Minnesota by Thursday morning which will bring widespread rainfall and embedded convection into the Mississippi/Tennessee Valley. The potential for several inches of rain exists over a large area that will be further refined over the next several days. Atmospheric and ensemble signals were notable even at this lead time. 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). 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