Extended Forecast Discussion NWS Weather Prediction Center College Park MD 155 AM EST Wed Feb 03 2021 Valid 12Z Sat Feb 06 2021 - 12Z Wed Feb 10 2021 ...Major Arctic Outbreak for the Central and Eastern U.S... ...Pattern Overview and Guidance/Predictability Assessment... Guidance still to show remarkably good agreement for the flow pattern evolution through medium range time scales. This is highlighted aloft by an amplified eastern Pacific/Alaskan ridge and a deep longwave trough centering over the central/eastern U.S., with an anomalous closed low north of the Great Lakes. This allows significant intrusions of Arctic air overspread and hold a firm grip on central and eastern U.S. much below normal temperatures. The upper trough may begin to flatten by next midweek as more progressive flow emerges from the Pacific. Considering the better than average guidance clustering, the WPC medium range product suite was derived from a composite blend of the 18 UTC GFS/GEFS, 12 UTC ECMWF/UKMET/Canadian/ECMWF ensemble mean and the 01 UTC National Blend of Models, albeit with increasing emphasis on the ensembles by day 6/7 (next Tue/Wed) consistent with gradually decreasing system predictability. This maintains good WPC product continuity and latest 00 UTC model and ensemble guidance overall seems well in line with this scenario. ...Weather/Threats Highlights... Lead energetic low pressure exiting New England Saturday and cyclonic flow/cold surge out from the Great Lakes offers some lingering enhanced snows, including lake effect, along with blustery/windy conditions on the backside. Meanwhile upstream, expect upslope snows over the northern Rockies as shortwaves cross over the region and as potent Arctic blasts surge southward. This energy and subsequent systems will dive into an amplified central U.S. upper trough position this weekend into next week and produce periodic snow swaths in the reinforced Arctic air. A lingering lead front over the Southeast/FL should focus Superbowl weekend showers/thunderstorms. A Southeast coast low developing off the front should lift northward Sunday/Monday and spread precipitation across the cooling Appalachians/Mid-Atlantic and Northeast to include an interior snow/ice threat. There is uncertainty with phasing of this low and mid/upper level energy. Impulses running on the base of the upper trough early-mid next week offer potential for swaths of overrunning precipitation including a snow/ice threat deeper into the cold post-frontal airmass over much of the south-central states and Southeast where modest amounts have an enhanced impact. Schichtel 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