Extended Forecast Discussion NWS Weather Prediction Center College Park MD 1200 PM EDT Sat Jun 02 2018 Valid 12Z Tue Jun 05 2018 - 12Z Sat Jun 09 2018 ...Heat wave from the Desert Southwest to the south-central U.S... ...Pattern overview and guidance/predictability evaluation... Model and ensemble guidance offer a similar and persistent larger scale pattern over the nation as highlighted aloft by significant mean troughs off the northwestern U.S. and downstream over the East that sandwich an amplified/hot Southwest/s-central us ridge. Recent guidance has trended a bit toward a bit more amplitude and pattern longevity. This trend seems reasonable. The depiction and interactions of a multitude of mid-smaller scale systems embedded with the flow however is proving to be quite problematic days 3-7 and forecast uncertainty with these is producing significant run to run model issues. This is particularly evident with disturbances tracking across the northern tier of the U.S. around the northern periphery of the upper ridge and into the eastern us mean trough position. These disturbances and associated height falls will become a local focus for potentially heavy rainfall. Overall, the WPC medium range product suite was primarily derived from a composite blend of the 00 UTC GFS/ECMWF and 00 UTC GEFS/NAEFS/ECMWF ensemble means. 00 UTC guidance seemed to cluster best overall and maintain max continuity in this pattern. ...Weather highlights and hazards... Precipitation can be expected from the north-central states to New England with the upper low and trough, along with a surface low developing offshore. 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. Model guidance is also signaling possible mesoscale convective systems (MCS) developing from the south-central plains and propagating southeast in northwest flow aloft early in the week. A potent mid-upper level ridge over the southwest to south-central U.S. will support a heat wave from the Desert Southwest to the south-central U.S where daily maximum temperature records will be threatened. 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 Schichtel