Extended Forecast Discussion NWS Weather Prediction Center College Park MD 304 AM EDT Thu May 31 2018 Valid 12Z Sun Jun 3 2018 - 12Z Thu Jun 7 2018 ...Record heat expected across the southern Plains... Guidance and uncertainty assessment ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ The forecast period begins on Sunday with an eastern Pacific trough, upper level ridge over Texas, and both a northern and southern stream trough over the Upper Midwest and East Coast, respectively. The trough over the eastern U.S. becomes more firmly established through the middle of next week, and the upper ridge over the southern plains continues to govern the weather pattern over the central U.S. Shortwave disturbances crossing the northern tier of the nation around the ridge axis will be the main foci for precipitation. The guidance is in excellent agreement regarding the persistent upper level ridge over Mexico and the southern plains through the entire forecast period, with the 00Z ECMWF indicating the greatest northward extent across the Plains. Greater differences reside in the flow across the northern tier of the nation by the Tuesday to Thursday time period. The 00Z GFS is initially more amplified with the eastern U.S. upper low, whilst the 00Z ECMWF keeps the upper low over the Mid-Atlantic region longer. The CMC is much farther north with the closed low over eastern Canada. For the northwestern U.S. trough, differences emerge as shortwave energy ejects eastward across Montana and the Dakotas, and these details should become more refined with future model runs. Weather Highlights and Threats ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ The best prospects for noteworthy precipitation across the continental U.S. will be from the Great Lakes to New England in association with the upper low and trough, along with a surface low developing offshore. Right now, it appears the heaviest rainfall from the oceanic low will be over the open waters of the western Atlantic. Another area of concentrated showers and storms is expected across the Dakotas and the Upper Midwest by the middle of next week as a disturbance crosses near the Canadian border. In the temperature department, the heat wave across Texas and Oklahoma is forecast to continue going into next week after a brief and minor abatement on Sunday north of Interstate 20. Widespread highs exceeding 100 degrees are expected as far north as Kansas early next week, and a few locations may approach 110 degrees over western Texas. Some record high temperatures are likely during this time. Above normal temperatures are also expected across the Rockies and extending northward across the north-central U.S. Some relief from the hot weather can be found for the Northeast U.S. and the Pacific Northwest, which will be under the influence of the upper level troughs. Temperatures near or slightly below average can be expected for those regions. WPC medium range forecasts of 500 mb heights, surface systems, weather grids, quantitative precipitation, and winter weather outlook probabilities can be found at: http://www.wpc.ncep.noaa.gov/medr/5dayfcst500_wbg.gif http://www.wpc.ncep.noaa.gov/medr/5dayfcst_wbg_conus.gif http://www.wpc.ncep.noaa.gov/5km_grids/5km_gridsbody.html http://www.wpc.ncep.noaa.gov/qpf/day4-7.shtml http://www.wpc.ncep.noaa.gov/wwd/pwpf_d47/pwpf_medr.php?day=4 D. Hamrick