Extended Forecast Discussion NWS Weather Prediction Center College Park MD 1149 PM EST Sun Jan 16 2022 Valid 12Z Thu Jan 20 2022 - 12Z Mon Jan 24 2022 ...Cooled Deep South to East Coast Snow/Ice threats with uncertain wave genesis pattern... ...Guidance/Predictability Assessment and Weather Highlights/Hazards... Major model differences persist in a data sensitive pattern with rampant run to run continuity issues days 3-7. Instead of chasing uncertain shortwaves, the WPC medium range product suite was primarily derived from the 01 UTC National Blend of Models and a composite blend of the 18 UTC GEFS/12 UTC ECMWF ensemble means whose reasonably compatible solutions lessen detail consistent with a pattern with lower than normal embedded system predictability. Manual adjustments were applied to incorporate as much WPC system continuity as feasible. ...Pattern Overview and Weather Highlights/Threats... A deepened low and wrapping snows/winds is slated to exit the Northeast Day 3/Thu as a massive Arctic high spreads across much of the central and eastern CONUS. Cold air flow also favor lake effect snow. A continuing series of uncertain impulses will carve out and reinforce the large mean upper trough over the central and eastern U.S. through this forecast period, digging downstream of an amplified upper ridge position just offshore the West Coast. This pattern will be conducive for periods with snow to spread across the Northern and Central Rockies Thu/Fri, and beyond that for uncertain periods of shortwave/frontal wave enhanced precipitation to span from Texas/western Gulf Coast through the Deep South and Southeast to the Mid-Atlantic/East Coast. This includes threats for snow/ice on the northern periphery of activity across the South/Southeast and potentially up the Appalachians/East Coast to the U.S. northern tier/Northeast given the extent of cold air intrusions and with uncertain systems rotating through the mean upper trough position. However, ample forecast spread and continuity issues limits predictability of particular system threats days 4-7. 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