Extended Forecast Discussion NWS Weather Prediction Center College Park MD 307 PM EST Mon Feb 24 2020 Valid 12Z Thu Feb 27 2020 - 12Z Mon Mar 02 2020 ...Overview and Guidance/Predictability Assessment... An amplified mid-upper level pattern highlighted later this week by a ridge over the West and a trough over the East will shift eastward over the weekend in a rather quiet pattern. An exiting system at the short range/medium range interface (Thu) will continue to slowly move into Quebec and Atlantic Canada Fri-Sat. Well upstream, a potent Pacific system will move into WA/OR Saturday. There is a growing guidance signal and forecaster confidence to dig this system sharply through the cooling West/Southwest Sun into Mon in a separating southern stream flow split. Plains cyclogenesis and frontogensis early next week offers an emerging precipitation threat as Gulf moisture returns inland into the wettened mid-lower MS Valley and vicinity. There is also some risk for snow/ice on the northern periphery of the expanding precipitation shield. Overall, a WPC composite blend of the generally compatable GFS/ECMWF and GEFS/ECMWF ensemble means seems to produce a good forecast starting point through medium range time scales consistent with predictability. ...Weather/Hazard Highlights... An exiting deep lead low will support lingering heavy snow over northern New England Thu. Wrap-around flow over the Great Lakes will also support a several day period of snow focused downwind of Lakes Ontario and Erie. Accumulations could be significant for the Tug Hill Plateau. There may also be room for clipper low snows Friday for the OH Valley/Appalachians, but guidance is quite varied. Temperatures trend much cooler behind these systems, generally for a couple days, before rebounding toward average. By contrast, the West will see generally mild/warm days Thu-Sat with some potential record highs in California. Dry conditions Thu into Friday will be replaced by increasing coverage of light to terrain enhanced rain/snow with potent system development/passage. Temperatures will trend cooler as the system moves in, pushing the milder air east of the Rockies next week. Schichtel Additional 3-7 Day Hazards information can be found on the WPC medium range hazards chart at: https://www.wpc.ncep.noaa.gov/threats/threats.php Hazards: - Heavy precipitation across portions of the Pacific Northwest and the Northern Great Basin, Sat, Feb 29. - Heavy rain across portions of the Middle Mississippi Valley, the Lower Mississippi Valley, and the Southern Plains, Mon, Mar 2. - Heavy snow across portions of the Northeast and the Great Lakes, Thu-Fri, Feb 27-Feb 28. - Heavy snow across portions of the Northeast, Thu, Feb 27. - Flooding possible across portions of the Southeast. - Flooding occurring or imminent across portions of the Lower Mississippi Valley, the Tennessee Valley, the Middle Mississippi Valley, the Southern Appalachians, the Southeast, the Southern Plains, and the Ohio Valley. - Flooding likely across portions of the Southeast. - Much below normal temperatures across portions of the Central Appalachians, the Northern Plains, the Tennessee Valley, the Middle Mississippi Valley, the Southern Appalachians, the Upper Mississippi Valley, the Great Lakes, and the Ohio Valley, Thu-Sat, Feb 27-Feb 29. - Much below normal temperatures across portions of the Southeast, Thu-Fri, Feb 27-Feb 28. - Heavy precipitation across portions of the Alaska Panhandle and mainland Alaska, Thu, Feb 27. - High winds across portions of mainland Alaska and the Aleutians, Sat-Sun, Feb 29-Mar 1. - Much below normal temperatures across portions of mainland Alaska, Thu-Mon, Feb 27-Mar 2. - Much below normal temperatures across portions of far northern mainland Alaska, Thu-Fri, Feb 27-Feb 28. 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