Extended Forecast Discussion NWS Weather Prediction Center College Park MD 104 AM EST Wed Feb 05 2020 Valid 12Z Sat Feb 08 2020 - 12Z Wed Feb 12 2020 ...Heavy rain threat possible from parts of the Southern Plains/Lower Mississippi Valley to the Tennessee Valley... ...Overview and Guidance/Predictability Assessment... Upper troughing will be exiting the Northeast as a quick shortwave follows across the Ohio Valley on Saturday. Meanwhile, out west, a shortwave over the Pacific Northwest this weekend will drop southward across the Great Basin, eventually spinning up a potentially deep closed low over Southern California/the Southwest by Monday next week. This could set up a heavy rain threat for the end of the period (next Tue into Wed) from the Lower Mississippi Valley to the Tennessee Valley. A deterministic blend (between the ECMWF/GFS/CMC) worked well for days 3 and 4, trending towards more ensemble mean guidance towards the end of the period as timing/evolution differences arise with the Southwestern upper low. Confidence remains above average in the overall pattern, though details remain less clear, especially towards the end of the period. ...Weather/Hazard Highlights... The shortwave crossing the Appalachians this weekend may lay down minor accumulating snow parts of the southern/central Appalachians Saturday into Sunday. It may also bring a rain/snow mix to parts of the Mid-Atlantic and coastal New England. Several frontal systems out of the Northeast Pacific will bring modest to possibly heavy snowfall to the mountains of the Pacific Northwest into the northern/central Rockies on Saturday. As the front sinks southward through the West, rain and mountain snow will push through California and the Great Basin. By early next week, as the upper low moves through the Southwest, Gulf moisture will increase initially into the Southern Plains/Lower Mississippi Valley, spreading north and east into the Tennessee Valley by Tuesday into Wednesday along a nearly stationary frontal boundary. Convectively-enhanced rainfall may support a locally heavy rain threat in these areas. Snow is possible on the northern edge of the precipitation shield from the Mid-Mississippi Valley across the Ohio Valley, but any possible accumulation amounts at this point remain very uncertain. Temperatures in the East will trend warmer through the period, with daytime highs 5 to 15 degrees above normal returning by the middle of next week. Out West, temperatures trend cooler as troughing moves through the region, and the Central U.S. should stay near normal through the entire period. 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