Extended Forecast Discussion NWS Weather Prediction Center College Park MD 249 AM EDT Wed Aug 19 2020 Valid 12Z Sat Aug 22 2020 - 12Z Wed Aug 26 2020 ...Hot temperatures to continue for much of the West into next week... ...Overview and Weather/Hazard Highlights... Strong upper ridging over the Southwest will meander in place while a trough over the east-central U.S. slowly weakens. The ridge will promote continued well above normal temperatures in areas along and west of the Rockies and to some degree into the Plains as well. Expect some record high values this weekend (more isolated next week) throughout the Great Basin southward to the Colorado River Valley/Southwest with temperatures 5-12 degrees above normal. Some isolated showers/storms will dot the landscape over the Rockies each day but the larger focus for rainfall will be in the Gulf of Mexico and adjacent areas. A stalled front ahead of the east-central U.S. upper trough will dissipate this weekend but its moisture will remain in the northeast Gulf and in less abundant form over the eastern states. Areas from the northern Gulf into Florida have the best chance of an inch or so of rain each day depending on thunderstorm propagation/mobility. Tropical features described below may also produce enhanced rainfall over some areas near the Gulf. To the north, at least a couple northern tier U.S.-southern Canada waves/fronts should bring transient rainfall to areas between the Northern Plains and Northeast. Temperatures outside the West will be near to above normal except for a few degrees cooler than normal over the Southeast this weekend and perhaps the Upper Midwest by the end of the period. ...Tropical Features... In the East Pacific, the latest National Hurricane Center forecast expects Hurricane Genevieve to weaken as the system turns northwestward into colder waters. With the upper high to its northeast, then east, some reflection of Genevieve's remnants may extend toward the California coast but without retaining much moisture. In the Atlantic basin, NHC outlooks continue to advertise a high likelihood of development from a broad area of low pressure near 45W. Per the 17Z NHC/WPC tropical coordination call and the most common signal among latest model/ensemble guidance, anticipate this feature to move west-northwest just north of Cuba and into the eastern Gulf of Mexico early next week. Note that the full solution envelope becomes quite broad by next Mon-Tue, ranging between the Bahamas (or even a bit to the east) and the Gulf. In addition a feature originating from the western Caribbean may emerge into the western Gulf with the full array of guidance also quite diverse with its specifics. It also remain a possibility that either or both of these systems may weaken or even dissipate before nearing any U.S. coastal areas. Please consult latest NHC products for further information. ...Guidance/Predictability Assessment... An operational model consensus provided a reasonable starting point for about the first half of the period, though the 12Z UKMET was much quicker with Genevieve and farther north with the lead system Sat/Sun moving out of the Upper Midwest. With the 12Z ECMWF quicker in the Northeast but much weaker over the Bahamas with the potential tropical feature, increased weighting of its ensemble mean to temper the uncertainty. By next Tue/Wed, ensembles become blurred with the evolution of low pressure out of the northern Plains, appearing much slower than the deterministic GFS/ECMWF/Canadian due to increased spread. Maintained a majority deterministic weight to keep the pattern progressive with low pressure moving to the Great Lakes. However, confidence is low over much of the CONUS by then especially near/around the Gulf. Fracasso/Rausch 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