Extended Forecast Discussion NWS Weather Prediction Center College Park MD 1210 PM EDT Fri Apr 12 2019 Valid 12Z Mon Apr 15 2019 - 12Z Fri Apr 19 2019 ...Another major spring storm next week to bring risk of heavy rainfall/flooding from the mid-lower Mississippi Valley/Ohio Valley along some risk of lead severe weather south and wrapback snows north... ...Guidance Preferences and Predictability Assessment... A deep lead short range system will exit through New England Monday as our weather emphasis returns to the West. Models and ensembles overall cluster reasonably well Monday into Wednesday and a preferred composite blend continues maintains good WPC continuity in showcasing the track of a series of dynamic mid-upper level shortwave troughs/height falls and associated swaths of enhanced but progressive precipitation from the eastern Pacific inland across the West/Rockies with a substantial heavy mountain snow threat. Energies then emerge within another pattern favorable for major storm genesis over the Plains into midweek. Models and ensembles have not been as aligned with recent runs with subsequent storm timing/details into later next week, but the overall signal for significant storm genesis remains quite strong. The latest GFS and ECMWF deterministic runs trended faster overnight, but have now retreated back slower to offer better continuity with yesterdays WPC forecast again. This is albeit with a shift a bit more northwestaward that could portend a better opportunity for wintery precipitation over a marginally coolded Upper Midwest/Great Lakes into next Friday considering most solutions do still wrap up quite a deep surface low/frontal system and cooling northern stream frontal drape overtop. Interestingly, the GEFS individual ensemble members uncharacteristically cluster slower than the GFS/ECMWF while ECMWF ensemble members uncharacteristically cluster more progressive than the GFS/ECMWF. Overall, WPC has trended back slower versus our overnight continuity most now in line with the deterministic GFS/ECMWF into Thursday and next Friday. ...Weather Highlights/Hazards... Significant precipitation will again increase by Wednesday into Thursday across the Mississippi/Missouri Valleys into the Great Lakes as low pressure strengthens over Oklahoma/Kansas. Multi-inch rainfall totals are probable (enhanced in embedded convection) in some locations of the warm sector and perhaps to the north/northeast of the low with additional northern stream support. Temperatures to the north/northwest of the low may only be marginally cold enough for snow depending on the amount of cooler air behind a Canadian cold front. Temperatures will largely be within 10 degrees of average values for mid-April but with a slower moderation over parts of the Dakotas/Minnesota owing to the melting of near-term snow cover. 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