Extended Forecast Discussion NWS Weather Prediction Center College Park MD 233 AM EDT Fri May 01 2020 Valid 12Z Mon May 04 2020 - 12Z Fri May 08 2020 ...Record heat for parts of the southern tier of the CONUS lingers into next week... ...Guidance/Predictability Assessment... A brokered upper ridge between Mexico and northwestern North America (Alaska/Yukon/British Columbia) will favor troughing in the eastern North Pacific as well as over the eastern third of the CONUS. With the separation between the upper ridge centers, quasi-zonal flow will meander in between from the Pacific Northwest through the Plains and into the eastern troughing. The models/ensembles mostly agree on the fairly stagnant pattern but the quicker flow leads to no better than average confidence with individual system details. The 12Z ECMWF was the preferred deterministic model but the others added some needed smoothing to the forecast. The 12Z/18Z GFS runs seemed too deep in the Upper Midwest on Tuesday given the upper pattern, and was discounted but not tossed out completely as other solutions may have been too weak. Trend has been for a much flatter system to push out of the Southeast (not Mid-Atlantic) around next Wed as the troughing over Hudson Bay sinks southward. By the end of next week, the pattern resembles that of mid-winter with a front perhaps all the way through mainland Florida and minimal precipitation for what can be the wettest month of the year for areas from the Southern Plains into the Ohio Valley/Mid-Atlantic. Trended toward nearly all ensemble mean weighting by next Fri amid too much uncertainty out of the Pacific. ...Weather/Hazard Highlights... Record heat will continue to be the main impact into at least early next week. Temperatures 10-20F above normal over the Southern Plains will migrate westward through the Southwest and into California by the end of the week as the upper ridge builds along the West Coast/120W. By contrast, much of the east, and especially around the Great Lakes/Northeast, will see cooler than normal temperatures more typical of early April (about 5-10F below normal). Cold front may push all the way to southern Florida by the end of the week though in a very modified state. Precipitation will generally be limited to around the lead system out of the Rockies/Plains Monday-Tuesday as it flattens into the Southeast and streaks eastward. Weakening area of low pressure over the Northern Plains will carry an enhanced area of showers through the Great Lakes Tue before diminishing in favor of the southern portion over the central Appalachians eastward. Exiting low out of Maine Monday will maintain a showery/breezy pattern for the start of the week in northern New England. Some snow showers are still possible in the highest elevations. Precipitation will be rather scant by the end of the week CONUS-wide. Fracasso 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