Extended Forecast Discussion NWS Weather Prediction Center College Park MD 1100 AM EST Sat Feb 16 2019 Valid 12Z Tue Feb 19 2019 - 12Z Sat Feb 23 2019 ...Multi-day threat of heavy rain for the Tennessee Valley to Southern/Central Appalachians, with wintry precipitation likely on the northern edge in the Ohio Valley/Mid-Atlantic... ...Cold weather will persist in the western to central U.S., with unsettled weather coming into the Southwest... ...Overview... Troughing in the western U.S. will be persistent during the medium range period, reinforced by shots of renewed energy. This feature plus the unyielding upper high in the western Atlantic will create a favorable pattern for heavy precipitation in the southeastern U.S. ...Guidance/Predictability Assessment and Preferences... Model guidance is generally rather agreeable in the large scale pattern of potent upper troughs/height falls progressing overtop a northeast Pacific ridge that then dig sharply southward to reinforce a western U.S. mean trough. Another mid/upper-level trough will eject from the Southwest to Northeast Tue-Thu, which guidance also seems to handle well. The medium range suite was derived from a multi-model blend of the operational 00Z and 06Z GFS, the 00Z ECMWF, and the 00Z EC ensemble and GEFS means, with more of a deterministic component than normal by day 6-7 due to the good model agreement and to maintain details of strength. The CMC was excluded from the blend, however, as by day 4-5 a trough in the Gulf of Alaska became more progressive than other models, which negatively affected the downstream features. ...Weather Highlights/Hazards... Heavy precipitation in the southeastern U.S. will be the main story across the CONUS next week. Lead deep layered and anomalously moist southwest flow channeled from the Southern Plains to the East will act to sustain a Southeast ridge and fuel multi-day threats of heavy rain/training from the Lower Mississippi/Tennessee Valleys to the Southern/Central Appalachians. On the northern edge, a cold surface high and cold air damming in the Mid-Atlantic region is expected, leading to frozen precipitation. Potentially heavy snow and ice is a possibility from the Middle Mississippi Valley to Ohio Valley and northern Mid-Atlantic region. With anomalously low heights in the western U.S., much below average temperatures will prevail for the western and central U.S. A surface low is progged to make its way into California on day 5 (Thu) and move throughout the Southwest the next couple of days, which will lead to enhanced precipitation for the Southwest, including higher elevation snow. Tate/Schichtel WPC medium range 500mb heights, surface systems, weather grids, quantitative precipitation and winter weather outlook probabilities are found 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