Extended Forecast Discussion NWS Weather Prediction Center College Park MD 200 AM EST Fri Jan 29 2021 Valid 12Z Mon Feb 01 2021 - 12Z Fri Feb 05 2021 ...Winter Storms over the East early next week and from the West to the Midwest/Northeast mid-later next week... ...Weather Pattern Overview and Guidance/Predictability Assessment... The is a strong guidance signal for an amplified and stormy flow pattern over the nation next week. A major lead winter storm/coastal low with favorable upper support is expected develop and lift up the East Coast into Monday/Tuesday and Canadian Maritimes next midweek to present a significant threat for heavy snow/unsettled weather from the northern and central Appalachians/Mid-Atlantic to New England and the Maritimes. WPC medium range guidance in the period was primarily derived from a composite blend of reasonably well clustered overall guidance from ensemble supported latest GFS/ECMWF/UKMET/Canadian and National Blend of Models. WPC product continuity was well maintained. Well upstream, additional amplified upper trough energies may also dig into the West midweek and subsequently progress across the Rockies and Plains/Midwest/Northeast later next week. Forecast spread increases over time, but suspect widespread wintry conditions including a focus for heavy terrain/mountain snows across the West/Rockies midweek will translate to downstream deep cyclogenesis over the Plains/Midwest/Great Lakes later week. WPC medium range guidance in the period was increasingly derived from a composite blend of the GEFS and especially ECENS ensemble means that seem to more reasonably support recent guidance trends/amplification, with less focus on the deterministic models and biases. WPC product continuity was reasonably well maintained. ...Weather/Threats Highlights... An upper trough and leading frontal system will bring moderate to heavy rain/mountain snow to the Pacific Northwest and central West Coast with the heavy precipitation focus concentrating over the central West Coast/Sierra Nevada into early next week. Progression of the upper trough will spread more moderate amounts of precipitation across a majority of the West into midweek, though favored terrain may significantly enhance locally. Currently expect the north-central states and vicinity to see the best potential for meaningful snowfall as low pressure evolves over the central U.S. Also winds could become fairly strong with sufficient development of this system. A leading warm sector heavy convection/rainfall pattern may develop over the east-central U.S onward with system progression after midweek. Overall the guidance consensus has been fairly stable in depicting the best potential for meaningful (potentially significant) snowfall from the Lower Great Lakes/northern Ohio Valley region through the interior Mid-Atlantic/central Appalachians and into the Northeast. The latest Winter Weather Outlook shows moderate to high probabilities across the interior mid-Atlantic/Appalachians while probabilities increased slightly this cycle for areas along the I-95 corridor from Washington, DC to Philadelphia. It will likely take a ways into the short range time frame to resolve more precisely the locations of the rain-snow line/transition zone and axis of heaviest snowfall. Some areas along or offshore the coast may see a period of brisk to strong winds. Farther south expect the highest rainfall totals with some moderate to heavy activity over or near the southern Mid-Atlantic early in the forecast period as a warm front moves in from the south and coastal low pressure develops. 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