Extended Forecast Discussion NWS Weather Prediction Center College Park MD 244 AM EDT Sun Jun 23 2019 Valid 12Z Wed Jun 26 2019 - 12Z Sun Jun 30 2019 ...Overview and Guidance/Predictability Assessment... An upper low is forecast to slowly but steadily move into Washington and then lift into British Columbia later this week with building ridging downstream over the High Plains into the western Great Lakes. Troughing in eastern Canada will likely dip into the Northeast next weekend as in inverted trough develops along the central Gulf coast. The latest deterministic models offered a reasonably well-clustered starting point for the Wed-Fri period. Thereafter, trended to a blend of the 12Z ECMWF/ECENS mean and the 18Z GEFS mean which smoothed out timing/amplitude differences over the lower 48 as the upper high settled into AZ/NM. ...Weather Highlights/Threats... Upper low 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. Temperatures initially 5-15 deg F below average will moderate back toward typical late-June values by next weekend as the upper low moves into Canada. Temperatures in the northern Plains/Upper Midwest will be 5-10 deg F above average (80s and some low 90s) but with a risk of showers/storms in the vicinity of a warm front. The Northeast will see a bit cooler temperatures next weekend as a front slips south/east of 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 as the upper trough moves westward later in the week into the weekend. 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