Extended Forecast Discussion NWS Weather Prediction Center College Park MD 419 PM EDT Wed Jun 24 2020 Valid 12Z Sat Jun 27 2020 - 12Z Wed Jul 01 2020 ...Guidance/Predictability Assessment... An amplified upper level trough set to robustly dig down through the West Coast would act to eject a lead low/trough from the Southwest to the north-central U.S. this weekend into next midweek. Downstream upper level ridging over the central U.S. should meanwhile favor upper trough development from the Northeast through the East. The 00 UTC ECMWF seems the closest deterministic model match with the GEFS/ECMWF ensemble means. These emphasize amplified flow over the lower 48 well into next week and a favored composite blend along with the National Blend of Models should tend to mitigate forecast uncertainties with system timing/interactions and convective focus. WPC continuity is reasonably well maintained. ...Overview and Weather/Hazard Highlights... Cold frontal progression should focus showers and potentially strong storms from the Northeast to the Ohio Valley/mid-Mississippi Valley this weekend along with some locally heavy downpours. Showers and storms will continue to linger next week down across much of the South/Southeast states along the slow/trailing front and with upper trough amplification. Upstream, a potent cold front will dive through the West this weekend into next week and focus some showers and storms. Given flow amplitude and lead Southwest system ejection, activity will also spread out across the Rockies into the north-central states over the period with height falls/instability and moisture. Potential upper low development over the West brings a threat for heavy precipitation with models indicating the best chance for this across western Montana Sunday and Monday. Significant height falls and cooling temperatures should allow precipitation to fall as snow across the highest elevations of the northern Rockies. Temperatures across the West will trend cooler with a period of temperature anomalies 10 to 15+ degrees below normal possible across portions of the Great Basin early next week. Downstream, expect a defined lead warming trend across the Central U.S. with the best chance for much above normal temperatures across the north-central U.S. 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 Hazards: - Heavy rain across portions of the Northern Plains and the Northern Rockies, Sun-Tue, Jun 28-Jun 30. - Heavy rain across portions of the Central Plains, the Middle Mississippi Valley, the Upper Mississippi Valley, and the Northern Plains, Tue-Wed, Jun 30-Jul 1. - Heavy rain across portions of the Southeast, the Middle Mississippi Valley, the Lower Mississippi Valley, the Mid-Atlantic, and the Tennessee Valley, Wed, Jul 1. - Heavy rain across portions of the Central Appalachians, the Tennessee Valley, the Middle Mississippi Valley, the Southern Appalachians, the Great Lakes, and the Ohio Valley, Sat-Sun, Jun 27-Jun 28. - Heavy rain across portions of the Tennessee Valley, the Middle Mississippi Valley, the Southern Appalachians, the Upper Mississippi Valley, the Great Lakes, and the Ohio Valley, Mon-Tue, Jun 29-Jun 30. - Heavy rain across portions of the Northeast and the Great Lakes, Sat, Jun 27. - Flooding possible across portions of the Middle Mississippi Valley, the Great Lakes, and the Upper Mississippi Valley. - Flooding occurring or imminent across portions of the Mid-Atlantic, the Upper Mississippi Valley, and the Northern Plains. - Flooding likely across portions of the Middle Mississippi Valley and the Upper Mississippi Valley. - High winds across portions of the Central Rockies, the Central Great Basin, California, the Northern Great Basin, and the Southwest, Sun, Jun 28. - Much above normal temperatures across portions of the Central Plains, the Upper Mississippi Valley, and the Northern Plains, Sun-Mon, Jun 28-Jun 29. - Heavy rain across portions of western mainland Alaska, Sat-Sun, Jun 27-Jun 28. - High winds across portions of western coastal Alaska, Sat, Jun 27. 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