Extended Forecast Discussion NWS Weather Prediction Center College Park MD 235 PM EDT Sun Jun 21 2020 Valid 12Z Wed Jun 24 2020 - 12Z Sun Jun 28 2020 ...Guidance/Predictability Assessment... Models and ensembles still suffer from run-run continuity issues through medium range time scales. Guidance initializations have seemed especially sensitive to data across the Northern/Northeast Pacific and with connections from Mexico and the western Gulf of Mexico. However, forecast spread with latest guidance has decreased some, bolstering forecast confidence a bit. Accordingly, a seemingly reasonable composite blend of the latest UTC GFS/GEFS mean and ECMWF/ECMWF ensemble mean along with the 13 UTC National Blend of Models was primarily used to derived the WPC medium range product suite. ...Overview and Weather/Hazard Highlights... A closed upper low held south of Hudson Bay midweek gradually weakens while ejecting over eastern Canada Friday-Sunday. Height falls across the Ohio Valley/Northeast will drive a cold front underneath over the Eastern U.S. Wednesday/Thursday with showers and thunderstorms likely along and ahead of the boundary from the Mid-Atlantic to the South. Upper level energy combined with the stalled trailing portion of the moisture pooling front supports a period of focused convection from the Southern Plains to the Lower Mississippi Valley. The best chance for heavy rainfall may be near the Texas Gulf Coast region Wednesday into Thursday. Unsettled weather should continue into the weekend across the South as the trailing boundary lingers and eventually weakens. Meanwhile out West, upper level ridging dominates across the Southwest much of the period with early period ridging across the Northwest/Rockies keeping temperatures above normal. A progressive upper level trough will push a frontal system from the Northwest to the northern Rockies Wednesday/Thursday then across the Plains Friday. The most organized precipitation and some strong thunderstorms are likely ahead of the trough and lead surface warm front as it lifts from the northern Rockies/Plains to the Upper Midwest late week, with additional showers and storms also developing by next weekend from the Central Plains/Mid-Mississippi Valley out through the Midwest/Great Lakes/Northeast. Uncertain troughing reinforcement that may arrive back over the Northwest next weekend may help moderate temperatures back towards normal. Schichtel/Santorelli 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