Extended Forecast Discussion NWS Weather Prediction Center College Park MD 1026 AM EST Sat Jan 02 2021 Valid 12Z Tue Jan 05 2021 - 12Z Sat Jan 09 2021 ...Weather Pattern Overview... Somewhat progressive flow over CONUS outside of the Northeast will maintain a stormy pattern over the Pacific Northwest through the week with at least one system crossing the country. Over the Northeast, downstream blocking over the northern Atlantic (Labrador Sea) will stall a system just off New England through the middle of next week until a trailing upper trough merges into it Wednesday and ejects it northeast through Thursday. A Pacific system crossing inland from the Pacific Northwest coast Monday night will trek eastward out of the central Plains to the East Coast Wednesday to Friday night with uncertainty to the speed, timing, and latitude gain while it's along the coast. Relatively mild Pacific air will dominate the CONUS through the week, keeping arctic air in Canada at least into Friday. ...Guidance/Predictability Assessment... With a relatively complicated pattern comprised of shorter wavelength western features and merging eastern features, a blended solution again offered a reasonable starting point with the focus on the CONUS crossing system through the period. The 00Z ECMWF remained better clustered with the ensemble means, though there is notable divergence in solutions for a western trough (with little precipitation impact) by Wednesday night. However, used more deterministic model weight than normal for this uncertainty as to not wash out the features that at least maintain decent continuity considering the pattern. ...Weather/Threats Highlights... An area of low pressure lingering near/off New England Tuesday into Wednesday will bring at least some light to modest precipitation (and dreary January weather) to eastern New England depending on its proximity to the coast and structure. A slow exodus could prolong oceanic affects at the least, but perhaps remain a coastal threat as well. The Pacific Northwest will see the brunt of the precipitation next week 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. By later in the week, low pressure in the Southern Plains moving eastward will promote an area of expanding rain and perhaps some snow on the north side of the system in the marginally cold air mass. Temperatures will be well above normal along the Canadian border by about 10-20 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. 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