Extended Forecast Discussion NWS Weather Prediction Center College Park MD 150 AM EST Sun Jan 03 2021 Valid 12Z Wed Jan 06 2021 - 12Z Sun Jan 10 2021 ...Overview... Active pattern will remain for much of the lower 48 into next weekend. Exiting system off New England Wednesday will give way to a southern system through the rest of the week, which may lift northeastward along the coast by next Saturday. In the West, a series of systems will show little respite from the coastal rain and mountain snow. Temperatures will generally be near to above normal thanks to an influx of Pacific air that will keep arctic air in Canada. ...Guidance/Predictability Assessment... Models continue to struggle with the flow out of the Pacific and how much the northern vs southern portions of the waves will dominate. In the central/eastern states, consensus between the GFS/ECMWF/Canadian offered good continuity with the low exiting Arkansas early Thursday and off the Virginia coast by early Saturday. Ensemble means were just a bit quicker overall so maintained a majority deterministic blend to next Saturday before any agreement in the West was lost. There, the 12Z ECMWF was most different from the GFS/Canadian and ensembles, which favored more troughing or an upper low near the Four Corners Fri-Sat. Uncertainty increases markedly by next Sunday with little agreement overall. ...Weather/Threats Highlights... The Pacific Northwest will see the brunt of the precipitation during the period with a string of systems, about one every other day, coming ashore. Multi-day precipitation totals should exceed several inches in many areas (even lower elevations 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. Heaviest totals may be on Wednesday and perhaps by next weekend. 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. Strength/track/structure of the system will play a big role in the details but remain unclear. 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 east of the Rockies and north of the Southeast. The exception area could be the east-central states depending on the low track and intensity of the main wave of concern crossing the CONUS next week. The interior West should see near to slightly below normal temperatures in the active pattern, perhaps slipping into Texas by next weekend. Fracasso 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