Extended Forecast Discussion NWS Weather Prediction Center College Park MD 233 AM EDT Tue Jun 25 2019 Valid 12Z Fri Jun 28 2019 - 12Z Tue Jul 02 2019 ...Overview and Guidance/Predictability Assessment... An initially deep closed upper low is forecast to slowly but steadily move through the Pacific Northwest and then into British Columbia late this week and weekend before weakening. Upper ridging will build downstream over the High Plains into the western Great Lakes while troughing in eastern Canada (Hudson Bay) will dig into the Northeast over the weekend. Along the Gulf Coast, an inverted trough will develop and move westward as an upper high settles into AZ/NM. The latest deterministic models offer a reasonably well-clustered starting point for the Fri-Sun period. Thereafter, incorporated the GEFS/ECMWF ensemble means which smoothed out smaller-scale timing and amplitude differences for the lower 48. ...Weather Highlights/Threats... The amplified upper low and lingering troughing will favor cooler than average temperatures in most of the West (especially Pacific Northwest into the Great Basin/Intermountain West) and scattered rain/storms with some very high elevation snow on Friday. Temperatures initially 5-15 deg F below average will moderate back toward typical late-June values by next week as heights rise. Temperatures in the northern Plains/Upper Midwest will be 5-10 deg F above average (80s to mid 90s), but with a daily risk of showers/storms with locally heavy downpours in the vicinity of a warm front. The Northeast will see warm/hot temperatures Fri/Sat be replaced by cooler temperatures and a drier air mass by next week as a front sinks through the region. The Southeast and lower MS Valley/Gulf Coast region will see a daily chance of showers/storms in typical summertime fashion, but that may be enhanced via the upper trough as it moves westward and lower-level moisture increases from the Gulf. Fracasso 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