Extended Forecast Discussion NWS Weather Prediction Center College Park MD 231 AM EDT Fri Jun 21 2019 Valid 12Z Mon Jun 24 2019 - 12Z Fri Jun 28 2019 ...Overview... Troughing will continue to be favored in the Pacific Northwest next week as an upper low slowly sinks southeastward then eastward. To the east, a lead system will lift northeastward through the Great Lakes as heights rise in its wake. Upper ridging is forecast to slide westward across the Gulf of Mexico and into the Mexican plateau and far western Texas/southern New Mexico. ...Guidance/Predictability Assessment... Deterministic blend of the latest 12Z/18Z guidance offered a good starting point for the Mon/Tue forecast. Differences in timing with the eastern system (slower ECMWF/Canadian vs quicker GFS/UKMET) were smoothed out given wavering trends in recent model cycles. By Tue into Wed, models/ensembles show increasing divergence in solutions off the west coast, stemming from how mid-level energy over Alaska on Monday either lingers over the high latitudes or drops down on the southwest side of the lead upper low off Washington on Tue/Wed. In these highly uncertain flow regimes with divergent solutions, agreement among the models is rather useless and often fleeting. Rather than getting caught up with the latest deterministic guidance, opted to rely more on the ensemble means which aligned well with continuity in order to prevent undesirable waffling in the forecast. The GFS/ECMWF/Canadian solutions were all plausible yet quite different, but the eventual outcome may very well be "none of the above." Farther east, ensembles were in good agreement on moving the weak trough eastward along with its surface cold front. ...Weather Highlights/Threats... Much of the West from WA/OR/NorCal eastward through the Great Basin will see below normal temperatures on the order of 5-15 deg F. Areas from the High Plains to the Northeast will see near to above normal temperatures (up to about +5 to +10 deg F anomalies) but generally not near record maxes. Cold front will not bring in much colder air to the East but rather a bit drier (briefly). Southern Plains to the Southeast will see 90s most days with a sprinkling of showers/storms during the afternoons. Precipitation forcing will be best on Monday along/ahead of the cold front in the Corn Belt/Midwest and mid/lower-Mississippi Valley. Scattered showers/storms will push eastward with the front but generally with less coverage Tue/Wed. In the West, upper low will bring in some showers (and still some very high elevation snow) that will gradually expand over the Plains to the Upper Midwest later in the week as the trough and cold front move eastward. 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