Extended Forecast Discussion NWS Weather Prediction Center College Park MD 111 AM EST Fri Mar 08 2019 Valid 12Z Mon Mar 11 2019 - 12Z Fri Mar 15 2019 ...Active weather pattern for the central states through next week with additional snow possible for the High Plains/Upper Midwest... ...Heavy rain quite possible over the Southeast/TN Valley late next week... ...Overview... The work week next week will feature yet another robust late winter storm lifting out of the Southwest Tuesday toward the Upper Midwest by Thursday. This will likely lead to another round of snow across the High Plains with rain/convection focused across the Southeast and Tennessee Valley. Slow movement of the cold front along the Gulf Coast may increase the threat of locally heavy rain with the potential for several inches of rain and flooding concerns given rather wet antecedent conditions. ...Guidance and Uncertainty Assessment... Deep troughing near California at the start of the period Monday will head eastward then northeastward atop building ridging into Cuba. Ensembles have been split on the timing of this evolution with the GEFS members quicker than the ECMWF and Canadian ensembles. Most recent 12Z and 18Z GEFS have trended slower with the progression while the ECMWF/Canadian ensembles remained steady. With the 18Z FV3-GFS nearer to the 12Z ECMWF than the operational 18Z GFS, placed much more emphasis on the 12Z ECMWF-led cluster that included the UKMET and Canadian with the 12Z ECMWF ensemble mean and 12Z NAEFS mean. 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 Great Basin on Wednesday will also act to slow the trough progression eastward along the Gulf Coast. Ensembles were in good agreement in the east overall but differed on the details including possible surface wave development along the cold front. ...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 but QPF was kept lower than any given model given timing/detail uncertainty. 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). Fracasso 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