Extended Forecast Discussion NWS Weather Prediction Center College Park MD 213 AM EDT Thu Apr 11 2019 Valid 12Z Sun Apr 14 2019 - 12Z Thu Apr 18 2019 ...Heavy Rainfall Threat for the Mid-Lower Mississippi/Ohio Valleys this weekend and again in the middle of next week... ...Weather Highlights/Hazards and Guidance/Predictability Assessment... An upper trough crosses the southern Plains through the mid-lower MS/OH Valleys this weekend, bringing widespread rains with potential of excessive rainfall, flash flooding, and strong to severe lead warm sector convection over the South. The potent low and precipitation shield will track over the Northeast Monday, with the trailing cold front moving across the southeast and offshore into the Gulf of Mexico and western Atlantic. A blend of the 18z GFS/18z GEFS Mean/12z ECMWF/12z ECMWF Ensemble Mean was used due to good clustering of these solutions. Meanwhile upstream, models/ensembles overall agree to bring another potent mid-upper level trough/ample height falls/frontal precipitation into the West Coast Sunday. The upper trough amplifies with time as it crosses the Great basin Monday and into the Rockies Tuesday. Height falls on the high plains induces cyclogenesis with a renewed return flow of deepening Gulf moisture and ascent leading to enhanced rainfall in eastern OK/TX extending downstream into the lower MS Valley. Given a similar cyclone track and upper level trough track, similar areas hit by rain this weekend are expected to received additional rains in the middle of next week. This could result in a renewed flooding/flash flooding threat across eastern OK/TX into the lower MS Valley. The models spread grows for this system as the ensemble means have more emphasis on low pressure along the wavy front further north in the Midwest while the operational GFS/ECMWF heave more emphasis on low pressure under the southern stream portion of the upper trough Wed 17 Apr to Thu 18 Apr. An equal blend of the 12z GFS/12z ECMWF models/ 18z GEFS/12z ECMWF Ensemble means was used to mitigate the differences until better agreement develops. The developing western trough leads to an area of below normal temperatures in the northwest and northern Rockies Mon 15 Apr that expands southeast across the Great Basin and then central Rockies Tue and then the Plains Wed, with readings commonly several degrees below average. The building west coast ridge leads to warm temperatures in CA/OR/WA next Thu. The southerly flow east of the central US storm leads to an area of above normal temperatures near the east coast next Wed 17 Apr-Thu 18 Apr. Petersen 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