Extended Forecast Discussion NWS Weather Prediction Center College Park MD 227 AM EDT Sun Mar 22 2020 Valid 12Z Wed Mar 25 2020 - 12Z Sun Mar 29 2020 ...Active pattern from the Southwest northeastward to the Northeast... ...Guidance/Predictability Assessment... The upcoming medium range upper flow pattern will feature cold troughing across the western U.S. with zonal to southwesterly flow over the central/eastern U.S overtop an amplified Gulf of Mexico to Florida upper ridge. In this flow, a series of progressive shortwaves and associated/complex surface based systems will traverse through the active southern stream, bringing episodes of organized precipitation with warm lead southern tier flow. The WPC medium range product suite valid Wed/Thu was primaily derived from a composite blend of well clustered guidance from the latest GFS/GEFS mean and ECMWF/ECMWF ensembles. Leaned mostly on the ECMWF, GEFS mean and especially the ECMWF ensemble mean Fri-Sun, mainly given this composite favors more organized surface low/system developmemt associated with the ejection of a main/dynamic upper trough from the Southwest through the central then northeastern U.S. Forecast predictability in this pattern over the next week seems to be gradually increasing overall beyond smaller scale details. ...Weather/Hazard Highlights... Expect an active wintry pattern for much of the West next week as broad areas of moderate rains and terrain enhanced snows periodically overspread the region with approach and passage of several lead systems and eventual upper trough amplification. Highest totals for the period should be over the Sierra Nevada while favored terrain along much of the West Coast. The Great Basin/Southwest and Rockies will see episodes of organized precipitation as well, especially with main system passage. Ejecting lead system energy offers potential for a swath of rain/convection from the Mid-Atlantic/Northeast through midweek with low/frontal system passage and moderate lead return moisture inflow. Progressive flow nature should limit heavy rainfall/runoff issue potential. This system could produce another round of accumulating snows for portions of the Northeast with coastal low developments. A potentially deeper low pressure system across the central U.S. Fri into the weekend would produce broad areas of showers and thunderstorms from the Central Plains/Mid-Mississippi Valley to the eastern U.S. The system also has some potential to produce some severe warm sector fueled thunderstorms as per latest SPC Day 4-8 Convective Outlook/Discussion. The heaviest rainfall risk may focus over the OH Valley and vicinity given system organization/depth and deeper moisture influx/instability. There is also an increasing guidance signal for a threat of a swath of heavy snow from the Upper Midwest/Great Lakes to the Northeast on the northern tier of the wrapping/expanding precipitation shield. 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 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