Extended Forecast Discussion NWS Weather Prediction Center College Park MD 258 AM EDT Fri Aug 23 2019 Valid 12Z Mon Aug 26 2019 - 12Z Fri Aug 30 2019 ...Weather Pattern Overview... Broad cyclonic flow aloft is expected across the northern tier of the nation for much of the upcoming week as an upper level low develops over southern Canada and then Hudson Bay. This is expected to result in a broad upper level trough over the northern Plains and extending to the Great Lakes with a Canadian surface high in place. Upper level ridging extending from Texas to California is expected to continue through midweek, and also across the western Atlantic Ocean. ...Model Guidance Evaluation... Models and ensemble means are in relatively good agreement at the beginning of the forecast period, with the GFS a little more amplified with the trough axis over the northern Plains. The 00Z ECMWF has trended more in line with the model consensus regarding the evolution of the upper low over Manitoba by Tuesday compared to its 12Z run, which was a bit farther south. Noteworthy model differences become apparent across British Columbia by Tuesday regarding timing and amplitude of shortwave energy in northwest flow, with the ECMWF supporting more of a ridge axis and the CMC and GFS indicating a shortwave trough. This leads to uncertainties in timing of cold front passage across the Plains and then the Ohio Valley. There is also a growing model signal for a potential tropical disturbance to pass between the East Coast and Bermuda on Tuesday, and the National Hurricane Center will have additional information on that. ...Sensible Weather... A hint of fall is expected across the north-central U.S. next week with high temperatures generally 5 to 15 degrees below normal, which equates to readings topping out in the middle 60s to middle 70s for much of this region. It should continue feeling like the middle of summer from Texas to the Great Basin and the Desert Southwest with temperatures 5 to 15 degrees above normal, with the greatest anomalies expected early next week across western Texas and New Mexico. High temperatures could exceed 110 degrees across the lower elevations of southern Arizona and southeast California on Monday and Tuesday. Areas of moderate to locally heavy rainfall will be possible ahead of the cold front crossing the Upper Midwest and Great Lakes region early in the week, with possible convective complexes that may produce 2 inches of rainfall through early Tuesday. For midweek and beyond, model uncertainty reduces confidence in placement of heaviest rainfall areas. However, there is a good chance of a corridor of enhanced rainfall across the central Plains later in the week near the trailing end of the front. Hamrick 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