Extended Forecast Discussion NWS Weather Prediction Center College Park MD 1045 AM EST Mon Jan 04 2021 Valid 12Z Thu Jan 07 2021 - 12Z Mon Jan 11 2021 ...Overview... A progressive synoptic pattern will persist over the CONUS through next weekend with repeating activity arriving into the Pacific Northwest. By Thursday there will be a southern system tracking east over the Mid-South states with increasing confidence that it will slide east off the Carolina coast Friday/Saturday, before turning northeast off the Eastern Seaboard. In the West, a series of systems persists, producing continued/additional coastal rain and mountain snow for northern California and western Oregon/Washington. By the weekend into next Monday, a system crossing Texas and the central Gulf coast looks to provide a focus for potentially heavy rainfall. ...Guidance/Predictability Assessment... Global guidance continues to depict varied solutions with the succession of shortwave features out of the Pacific and how the northern/southern portions of the waves will evolve. Preference remains with the ECMWF with the 00Z run later in its northern/southern stream interaction with the East Coast system on Friday night/Saturday which keeps the surface portion of the system offshore. Other guidance is a little farther north with this system on Days 4/5, so there was only minor inclusion of the 06Z GFS/00Z UKMET/CMC for those days. For the southern trough this weekend the 00Z ECMWF and CMC were a little farther south than the 06Z GFS, so some inclusion of these deterministic solutions were included in Day 6/7 to go along with the 00Z ECENS/06Z GEFS means. There is decent potential for surface cyclogenesis along the Texas and central Gulf Coast Sunday/Monday. ...Weather/Threats Highlights... The Pacific Northwest will continue to see systems arrive about every other day through the period with the heaviest precip in the medium range expected on Friday. This weekend into next week, the best focus for heavier amounts will be in Canada and the Alaska panhandle. Low pressure in the lower Mississippi Valley Thursday will move eastward as an expanding area of rain precedes the front (and some snow on the north side of the system in the marginally cold air mass). As the system reaches the coast, it will turn northeastward and spread some rain/snow over the Carolinas and southern Mid-Atlantic region Fri-Sat and again likely offshore of New England Sat-Sun. Next system out of the Interior West will tap the Gulf for moisture into the Texas and Louisiana coasts next Sunday into Monday. This could lead to a heavy rain threat for east-central Texas to the central Gulf Coast Sunday into Monday. Temperatures will be well above normal along the Canadian border by about 10-25 degrees, especially for overnight lows, through next week. Modestly above normal temperatures can be expected for most of the rest of the CONUS into late next week with a general cooling pattern toward modestly below normal temperatures, especially over Texas, as successive lows track farther south. Jackson Additional 3-7 Day Hazard information can be found on the WPC medium range hazards outlook 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