Extended Forecast Discussion NWS Weather Prediction Center College Park MD 248 PM EDT Wed Jun 10 2020 Valid 12Z Sat Jun 13 2020 - 12Z Wed Jun 17 2020 ...Overview... Over the West, deep troughing over the weekend should relax around Mon but be reinforced by additional energy toward midweek. Meanwhile, an upper low may become cut off from northern stream flow in the East, while ridging persists in between, over the Plains and Midwest. ...Guidance/Predictability Assessment... Model guidance was generally in agreement with the trough/ridge/trough pattern early in the medium range period, and a blend of 00Z ECMWF/UKMET/CMC and 00Z/06Z GFS deterministic runs sufficed. Notable model differences arose around Mon onward in the East, as the GFS and GEFS mean were faster than ECMWF and ECENS mean with moving the upper low eastward; this was particularly pronounced in the 6Z run. The CMC began clustered more toward the EC suite and then became a middle ground with its trough axis, while the UKMET at day 5 was in between the GFS/EC as well. There is also some question regarding if and when the upper low splits from the northern stream flow, with the CMC not calling for a split until later than other models. For now, leaned toward the slower 00Z EC solutions, especially the mean, but did not go with it outright. The 12Z GFS came in faster like the 6Z run, so it is possible that a trend for a faster moving low is forming. In the West, a general model blend worked as the initial energy moves northeastward into south-central Canada and another upper low approaches from the Pacific. The initial front in the western/central U.S. is forecast to dissipate in favor of a front ahead of the energy coming from the Pacific. Then around Tue, the interaction of those upper lows gets complicated with the deterministic models, and transitioned toward the means for that area late in the period. ...Weather/Hazard Highlights... Temperatures 10 to 20 degrees above normal are expected Sat in the Northern High Plains ahead of the initial front crossing the West, but warm temperature anomalies of 5 to 15 degrees should persist over the Central High Plains throughout the period and build toward the Midwest Tue/Wed. Behind the western front, cool temperatures with highs 10 to 15 degrees below average are forecast for the West Coast to Northern Rockies this weekend before moderating. With the upper low influence as well as a front lingering near the Atlantic coast, temperatures should be a few degrees below normal over the Mid-Atlantic through the period. Rainfall over the CONUS should be generally light through the medium range period, though portions of the Eastern Seaboard could be the exception. Given the upper low overhead and a stalled front along the Atlantic Coast, the Carolinas and Mid-Atlantic may see heavy rainfall for the first half of next week. Rainfall amounts and placement will depend greatly on track of those features. For example, with the slow track of the upper low in the 00Z ECMWF, rainfall amounts in portions of the Mid-Atlantic accumulated to over 8 inches in the EC. Though this is exceptionally high, it is an example of the rainfall potential with a slower-moving low. Southern Florida could see enhanced rainfall with plenty of tropical moisture. The northwestern and north-central U.S. should see a couple of rounds of light to modest precipitation with fronts moving through. The precipitation should mainly fall as rain, but light snow is possible in the highest peaks. Tate 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