Extended Forecast Discussion NWS Weather Prediction Center College Park MD 200 AM EST Thu Feb 06 2020 Valid 12Z Sun Feb 09 2020 - 12Z Thu Feb 13 2020 ...Heavy rain threat for parts of the Southern Plains/Lower Mississippi Valley to the Tennessee Valley next week... ...Overview and Guidance/Predictability Assessment... Upper pattern will shift next week toward western troughing and a resurgence of the subtropical ridge over Cuba. A lead shortwave dropping through the Northwest to begin the period (Sunday) will likely deepen into a closed low by Monday over southern California. As this weakens and lifts northeastward into the Southern Plains next Tuesday into Wednesday, a heavy rain threat will expand over the Southern Plains/Lower Mississippi Valley to the Tennessee Valley along a slow moving frontal boundary. Yet another shortwave is forecast to sink southward out of British Columbia around next Tuesday into the Northwest, reinforcing the western trough. A deterministic blend (between the GFS/ECMWF/CMC) worked well for the Sun-Mon period. Thereafter, uncertainty begins to increase with respect to the evolution of the system in the Southwest (how quickly it may lift northeastward) as well as the details of reinforcing energy into the Northwest. Beyond day 4, slowly began increasing the ensemble means into the blend. Confidence remains above average in the overall pattern, though details remain expectedly less clear by the latter half of the period. ...Weather/Hazard Highlights... Weak high pressure will settle into the Northeast on Sunday before another front from the Great Lakes moves into the region Monday. This may bring a band of accumulating snow to parts of the Upper Midwest/Upper Great Lakes on Sunday and possibly northern New England into Monday. The western U.S. closed low will sink through California on Sunday to bring light to modest rain and mountain snows to parts of Calfirnia and the Great Basin/central/southern Rockies. As the upper low moves into the Southwest and ridging increases over the Gulf, a frontal boundary will settle across the mid-Mississippi and Tennessee Valleys. Gulf moisture will increase initially into the Southern Plains/Lower Mississippi Valley Monday and then spread northward and eastward into the Tennessee Valley by Tuesday into Wednesday, with another surge of moisture moving into the same region next Wednesday into Thursday. Convectively-enhanced rainfall supports a locally heavy rain threat in these areas. Some snow is possible on the northern edge of the precipitation shield from the mid-Mississippi Valley to the Midwest, but any kind of accumulation remains in question. The second shortwave dropping into the Northwest next Tuesday into Wednesday will bring another round of possibly heavy mountain snows, which drop into the Rockies/Four Corners Wednesday into Thursday. Santorelli 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