Extended Forecast Discussion NWS Weather Prediction Center College Park MD 1154 AM EDT Sun May 19 2019 Valid 12Z Wed May 22 2019 - 12Z Sun May 26 2019 ...Overall Weather Pattern... It remains evident that the upper level pattern across the continental U.S. will stay amplified and slow to change next week. A hot upper level ridge over the southeast U.S. becomes anchored over the region and gradually becomes stronger for the second half of the upcoming work week. Across the western U.S., a large scale upper trough will be dominant as multiple shortwave perturbations keep conditions cool and unsettled/wet. This will also be slow to move given the expected development of an omega block type pattern upstream over the eastern Pacific. Lead main weather features include a strong low pressure system for the Plains and Upper Midwest mid-week, followed by weaker lows and slow moving fronts from the Southwest to the Northeast U.S. later in the week on the western and northern periphery of the Southeast ridge. ...Models and Preferences... The 06 UTC GFS and 00 UTC ECMWF/UKMET seem in good agreement Wed-Fri and a composite seems reasonable. By next weekend, the GFS still shows weaker upper level ridging expanding from the southeastern U.S. compared to the guidance consensus and especially the ECMWF. The GFS has more run to run continuity issues than the ECMWF. Given uncertainties and trends, the WPC product suite was derived from compatable 06 UTC GEFS/00 UTC ECMWF ensemble means and 00 UTC ECMWF. ...Weather Highlights and Hazards... The main things that will make weather headlines for the second half of the week and extending into next weekend will be the anomalous heat and humidity building across the southeastern quadrant of the nation, the unseasonably cool weather expected for the interior western U.S. and northern plains, and the ongoing threat of heavy rainfall and potential severe weather eminating from the central U.S. High temperatures are forecast to be on the order of 10 to 15 degrees above late May averages from the Midwest to the Southeast U.S., with the hottest readings expected for the Friday to Sunday time period. There is a good chance that the first 100 degree temperatures of the season could be realized across inland portions of southern Georgia and South Carolina. The opposite will hold true for the unsettled western U.S. under the influence of the upper level trough and periods of widespread but more modest precipitation/elevation snows, with daytime highs of 15 to 25 degrees below normal for mid-week, and then moderating to 5 to 15 degrees below normal by the end of the forecast period. Heavy rain will likely be an issue again for parts of the central plains and Midwest with the stalled frontal boundary in place for the end of the week and into the weekend. There are some differences in the model placements of the heaviest QPF axis, but the consensus is for the heaviest rain to develop from northern Texas to Iowa with the potential for flash flooding. Strong to severe thunderstorms are also likely in this same general area. D. Hamrick/Schichtel 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