Extended Forecast Discussion NWS Weather Prediction Center College Park MD 241 AM EDT Sat Jun 22 2019 Valid 12Z Tue Jun 25 2019 - 12Z Sat Jun 29 2019 ...Overview... An upper low is forecast to slowly rotate into Washington next week as upper ridging expands over the High Plains. To the east, a lead system will lift northeastward through New England as its cold front stalls and then dissipates over the Southeast. Upper ridging initially over the Gulf of Mexico will be replaced by an inverted upper trough by next Fri/Sat. ...Guidance/Predictability Assessment... A blend of the deterministic 12Z GFS/ECMWF/Canadian and 18Z GFS offered a good starting point for the Tue-Thu forecast. Solutions continue to converge with the lead system exiting the Great Lakes/Northeast as the UKMET was the only one displaced from the otherwise good consensus. In the Pacific Northwest, upstream differences over Alaska have essentially vanished and a consensus approach served well as the upper low wobbles into Washington next Thursday or so before turning northeastward into British Columbia. Trend toward more ensemble mean weighting acted to maintain good continuity. Farther east, a trough may wrap around the initial/lead system by next Fri/Sat into the Northeast in an otherwise low-amplitude flow. To the south, the GFS-based guidance continues to be a bit more defined with the upper trough near the Gulf Coast than the ECMWF-based guidance. ...Weather Highlights/Threats... Much of the West will see below normal temperatures on the order of 5-10 deg F under the approaching upper trough. Contrastingly, areas from the High Plains to the Northeast will see near to above normal temperatures (up to about +5 to +10 deg F anomalies) from especially Wed onward. Southern Plains to the Southeast will see 90s most days with a sprinkling of showers/storms during the afternoons, enhanced initially by the weak front and then later by the upper trough. Precipitation will be quite scattered in nature over the East/South due to a lack of concentrated forcing and deep moisture. In the Pacific Northwest, the upper low will bring in showers (and some very high elevation snow) that will gradually expand over the northern Plains to the Upper Midwest later in the week. Along the Gulf Coast, there is potential for locally heavy rain depending on the details of the upper trough. Otherwise, typical diurnally-driven storms will be common. The Southwest will stay dry as the upper high settles near the AZ/NM border. 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