Extended Forecast Discussion NWS Weather Prediction Center College Park MD 1122 AM EDT Wed May 30 2018 Valid 12Z Sat Jun 02 2018 - 12Z Wed Jun 06 2018 ...Record heat expected across the southern Plains... Guidance and uncertainty assessment ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Latest model and ensemble guidance offer a reasonably well clustered range of solutions this weekend into day5/Monday in a pattern with average predictability. Guidance spread increases thereafter, with 06/18 UTC GFS runs notable outliers. Recent ECMWF trends have been toward stronger systems moving through Canada and WPC progs have been shaded in that direction. Overall though, WPC continuity was well maintained with a composite blend of the 00 UTC GFS/ECMWF/ECMWF ensemble mean and the favorably trending 06 UTC GEFS, but opted to drop the GFS days 6/7 amid growing forecast spread/uncertainty. Canadian ensembles offer this general scenario, but recent UKMET/Canadian determinitsic runs have been less consistent. Weather Highlights and Threats ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Shortwaves reinforcing an upper trough in the East should support lingering wet weather for the Mid-Atlantic and the Southeast into the weekend. A lingering surface front from the western Atlantic and Southeast to the southern plains remains a focus for deeper moisture pooling and some heavier local convective downpours next week, albeit with main low genesis offshore. Upstream, an amplifying trough position over the Northwest should generate some late season rainfall and some cooling. A less certain stream of ejecting energy/height falls will also support an extended pattern favorable for locally heavy convection/rainfall over the Plains/Midwest with low/front genesis to include some risk of severe weather as per SPC. The dominant focus of the temperature forecast will be on a multi-day Texas heat wave expected to persist into Sunday whose influence may extend at times northward into the central Plains and eastward into the western Gulf coast. Hot afternoon readings in the 100-110F range should be most common in the lower Rio Grande, with Saturday setting up to be the hottest day. Record warm values for high and low temperatures will be reached/exceeded during this time frame. The southward suppression of the heat in Texas with time from Sunday onward occurs as a front settles southward and ridging aloft over the area slowly weakens. Schichtel 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