Extended Forecast Discussion NWS Weather Prediction Center College Park MD 1105 AM EST Sun Jan 03 2021 Valid 12Z Wed Jan 06 2021 - 12Z Sun Jan 10 2021 ...Overview... A progressive synoptic pattern will persist over the CONUS through next weekend with activity focused on the Pacific Northwest. By midweek, there will be an exiting system off New England while a southern system over the south-central Plains shifts east, possibly lifting northeastward along/off the Northeast coast Friday/Saturday. In the West, a series of systems persists, producing notable coastal rain and mountain snow north from northern California. An even farther south tracking system may cross Texas on Sunday. Temperatures will generally be near to above normal thanks to continued influx of Pacific air that will keep arctic air in Canada though a succession of farther tracking systems would allow more seasonable air to push down the central CONUS. ...Guidance/Predictability Assessment... Global guidance continues to depict varied solutions with the succession of shortwave features out of the Pacific and whether the northern or southern portions of the waves will dominate. The key with south-central Plains/Mid-South low is potential interaction with northern stream energy descending from the Great Lakes Thursday, interacting with the low over the Mid-Atlantic Friday night as indicated by the 00Z ECMWF and UKMET or if it remains a southern stream low as indicated by the 06Z GFS/CMC. Despite this being a change to consensus, preference for now is with the ECMWF/UKMET solutions through Day 5. Uncertainty then increases for Days 6/7 with the resulting trough pattern/surface low pattern in the Northeast. For now, broad troughing is forecast for the Northeast for next weekend with inclusion of the somewhat similar 00Z ECENS mean and 06Z GEFS mean. Next weekend, the 00Z ECMWF/GFS are in decent agreement with a farther south tracking low over the Desert Southwest to Texas (while the CMC is farther inland/north) with the GFS a little more progressive. ...Weather/Threats Highlights... The Pacific Northwest will continue to see systems arrive about every other day through Days 3-7 with the heaviest likely on Friday. Multi-day precipitation totals should exceed several inches in many areas (especially west of the Cascades) with considerable snowfall in the Cascades. Expect windy conditions and variable snow levels (though not too low) as the systems move through. Low pressure in the Southern Plains 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 may turn northeastward and spread some rain/snow over the Mid-Atlantic region Fri-Sat into New England Sat-Sun. The preferred 00Z ECMWF solution favors a more out to sea track, but uncertainty remains. Influx of of Gulf moisture ahead of the far southern low track next weekend would set up a heavy rain threat for east-central Texas Sunday. 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 to modestly below normal temperatures 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