Extended Forecast Discussion NWS Weather Prediction Center College Park MD 310 AM EDT Thu Mar 26 2020 Valid 12Z Sun Mar 29 2020 - 12Z Thu Apr 02 2020 ...Great Lakes to Northeast storm threat Sun-Mon... ...Heavy rain for the South Mon-Tue then coastal low development up the East Coast Wed-Thu... ...Periodic wet flow into the Pacific Northwest next week... ...Guidance/Predictability Assessment and Weather/Hazard Highlights... Several significant weather concerns materialize during the medium range period. A lead deep low will track from the Great Lakes to the Northeast Sun before transitioning to a coastal storm off New England and the Canadian Maritimes Monday. A GFS/ECMWF and GEFS/ECENS mean blend seems reasonable. A lead rain swath underneath along with Great Lakes/Northeast heavy snows are expected. The Pacific Northwest should see several periods of moderate to terrain enhanced precipitation next week, albeit in a series of features within highly uncertain flow from the northeast Pacific. Highest totals this period will be along favored Olympics/Cascades terrain. Guidance remains all over the place with pattern evolution, but WPC progs were mainly derived from the more consistent ECMWF ensemble mean. Meanwhile, southern stream upper trough passage may focus/organize system development across the South then coastal low development up along the East Coast. Enhanced rainfall as a result of deeper Gulf moisture advected northward may develop over the South, but details and confidence on timing/rainfall and other impacts are much below normal. Expect wrapping Atlantic moisture to also fuel organized rains up the East coast. The deepening low also offers some late period potential for snows from the central Appalachians to the interior Northeast. WPC progs were primarily derived from the more consistent ECMWF ensemble mean, deeper model trends and WPC continuity. Unseasonably warm conditions are expected over the South ahead of the initial system could result in daily records for highs/lows into Sunday. 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