Extended Forecast Discussion NWS Weather Prediction Center College Park MD 158 PM EST Sun Jan 16 2022 Valid 12Z Wed Jan 19 2022 - 12Z Sun Jan 23 2022 ...Cooled South to East Coast Snow/Ice Threat with frontal/coastal low genesis late week... ...Pattern Overview... A series of impulses will carve out and reinforce a broad mean trough over the central and eastern states during the extended period while the upper ridge amplifies offshore the West Coast. The leading shortwave will track over the Great Lakes region into the Northeast by Thursday with one behind it digging into the South Friday and then pulling offshore the Mid-Atlantic/Southeast region Saturday. This pattern will be conducive for precipitation to spread across the higher terrain of the Northern and Central Rockies through Friday and precipitation to span from Texas/western Gulf Coast, Deep South, Southeast to the Mid-Atlantic and push eastward beyond the weekend into next early next week. ...Guidance/Predictability Assessment and Weather Highlights/Hazards... Previously, it was noted that there is significant forecast spread and run to run uncertainty with this latter feature and associated mid-winter weather focus with frontal wave/coastal low genesis. The 06Z/12Z guidance continues to have notable spread on the placement/track of the secondary shortwave feature. In turn, the QPF placement varies significantly as well, especially across the Gulf states, Southeast and Southern Appalachia. To combat these differences, a general blend of the GFS/GEFS mean/CMC/ECWMF/EC ensemble means were used through all time periods. This provide a middle ground approach and helped maintain continuity from the previous forecast cycle. There is good agreement with an organized low pressure system set to dig into the north-central U.S. and subsequently track moving eastward along the U.S./Canadian border through Thursday. This should bring some snow to the Great Lakes then northern New England, with locally higher totals expected near typical lake enhancement areas as cold high pressure sweeps down across the central and eastern U.S. in the wake of the low in a pattern with above normal predictability for these features. As the Arctic blast reaches the southern tier states a wavy cold front will encounter Gulf moisture to fuel an emerging area of precipitation up from the South/Southeast. This pattern will be favorable for an enhanced swath of overrunning snow/ice on the northern periphery of activity later in the week. This wave may develop into a robust coastal low/winter storm that tracks up the East Coast. Meanwhile, The West could see some light precipitation through the period, particularly over the Pacific Northwest and into the Northern Rockies as weakening systems cross the region, with mainly dry conditions elsewhere. Campbell/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