Extended Forecast Discussion NWS Weather Prediction Center College Park MD 156 PM EST Tue Mar 03 2020 Valid 12Z Fri Mar 06 2020 - 12Z Tue Mar 10 2020 ...Guidance/Predictability Assessment and Weather/Hazard Highlights... An amplifying upper trough over the OH Valley/Mid-Atlantic Fri may close off a low off the Northeast by Sat. This favors coastal cyclogenesis with development of a deep low a couple hundred miles off Cape Cod. There remains plenty of forecast spread, especially concerning placement of the low, which has implications for weather along the Northeast Coast. This low offers a threat for dangerous maritime conditions, with high winds and moderate wrapback snows slated for a cooling Northeast. Meanwhile, the passage of an eastern Pacific upper trough/height falls over the Northwest into the weekend would support rains/terrain enhancing snows. Additional energies dropping southward upstream will amplify troughing aloft and act to develop a closed low well off the West Coast by Sun. The biggest forecast consideration for this system continues to be that recent GFS runs including the latest 12 UTC version that are even quicker to eject lead energies inland to the Southwest Sun and are noticeably flatter with the wave as it progresses over the Rockies then east-central U.S. early next week. The somehwat slower and more amplified solution presented by the ECMWF/UKMET/CMC remain better supported by GEFS/ECMWF ensemble means. This solution could support a swath of modest precipitation/mountain snows over southern CA and the Southwest/Rockies. There is also a reasonable signal for subsequent Plains development whose emerging/lead return flow from the Gulf of Mexico could fuel an expanding rain/strong convection pattern with best focus eminating out from the eastern Plains/MS Valley. A Canadian cold air surge into the north-central states would also support some risk of heavier snows from the Upper Midwest into the Great Lakes early next week. The WPC medium range product suite was produced from a composite of the compatable GFS/CMC/ECMWF/UKMET for Fri/Sat. The 00/12 UTC ECMWF seems the best fit with GEFS/ECMWF ensembles Sun-Tue, so I used that blend for that period. 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