Extended Forecast Discussion NWS Weather Prediction Center College Park MD 205 AM EDT Sun Jun 07 2020 Valid 12Z Wed Jun 10 2020 - 12Z Sun Jun 14 2020 ...Overview and Guidance/Predictability Assessment... Upon the exit/demise of Cristobal around midweek, the upper pattern will trend toward an omega block configuration with troughs along the west and east coasts by next weekend. The models/ensembles were in good agreement overall with this evolution with some expected detail differences. Preferred to rely mostly on the 12Z ECMWF which has been fairly consistent the past several runs notwithstanding the flow out of the Pacific late in the period. Added input from the GFS/Canadian/UKMET formed a good starting point but trended toward a majority ensemble mean weighting by next weekend as uncertainty increased especially in the West. For Wed-Fri, combination of Cristobal and a deep western trough will produce a robust system out of the Upper Midwest into Ontario with a weakening cold front moving into the East. Central pressure around 980mb would approach or possibly break monthly low sea level pressure records over northern WI and the U.P. of Michigan. GFS has been on the quicker side but has trended slower, more in line with continuity/NHC. Ocean system near Bermuda may attempt to retrograde westward/northwestward toward the Mid-Atlantic/Northeast as either an occluded or subtropical entity, or perhaps just a weak surface trough. Cresting upper high would tug it back to the coast but incoming/reinforcing upper trough out of the Great Lakes/southern Ontario would then guide it back northward/northeastward (dependent on timing of each system). NHC will continue to monitor this system. By next weekend, flow out of the Pacific trends deeper, but the 12Z ECMWF was quite aggressive in developing an upper low near the CA coast. Though a few ensemble members show such a system, preferred to maintain a digging trough that maintains some slow eastward motion (via the ensemble means which were quicker than the ECMWF but slower than the GFS). In the East, amplified upstream flow suggests troughing may be in no hurry to move past 80W, stalling at least a portion of the surface front near the East Coast. ...Weather/Hazard Highlights... Temperatures will shift eastward through the period as the cool weather initially over the Plains Wednesday moves to the Midwest/eastern Great Lakes by the weekend. Warmer temperatures initially over the West will move through the Rockies later in the week and to the High Plains by the end of the period where 80s/90s will be common from the Dakotas to Texas. The Southwest will see a few days of very hot temperatures where the lower deserts will again push toward 110F in the Valley of the Sun. Precipitation will be focused around the exiting low pressure (ex-Cristobal) and attendant cold front Wednesday moving to the East on Thursday with the trailing front again igniting at least some scattered showers. Expect some more showers and maybe a storm over the South and Gulf Coast as the front settles there. Much more uncertainty lies in the rainfall forecast for next weekend over the East Coast depending on the orientation of the upper flow and surface boundary. Ensembles do show an increase in rainfall farther north by next Sat-Sun into the Mid-Atlantic/Northeast. Over the West, lead front on Wed will bring minimal rain to the area but that will likely change by later in the week into the weekend as digging upper troughing could increase rainfall for at least parts of WA/OR. 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