Extended Forecast Discussion NWS Weather Prediction Center College Park MD 345 PM EDT Thu Jul 04 2019 Valid 12Z Sun Jul 07 2019 - 12Z Thu Jul 11 2019 ...Overview and Guidance/Predictability Assessment... The most persistent feature of the medium range is a closed mid level anticyclone over the southern Plains and southwest. The models indicate an initial longwave trough over the Pacific northwest that retreats up into Canada days 4-5..The 06z GFS was slower/more amplified with the trough and not given any weighting in the forecast. An upper trough over the northeast bringing cooling and drying. The trailing front makes is south across the mid Atlantic and southeast, eventually all the way into northern Florida next Wed and Thu before dissipating. The 06z GFS/00z Canadian and 00z ECMWF all differ on the timing/phasing of waves progressing across the northern Rockies/Plains/upper MS Valley/Great Lakes, so confidence is low on the progression of waves and corresponding timing of wave-triggered convection in the northern states. Also, the 00z ECMWF differed considerably in the timing/amplitude of waves across the northern US, so low confidence exists in any one model or model run. Consequently, with good agreement among the models days 3-4 among the GFS/UKMET/CMC and their respective ensemble means, a consensus approach was favored. Starting on day 5 (Tue), deterministic solutions began to diverge substantially, so the approach was to use a blend of continuity and the 00z NAEFS Mean, along with the 00z ECMWF Ensemble Mean and 06z GEFS Ensemble Mean. ...Weather Highlights/Threats... The frontal boundary crossing the central/eastern U.S. through much of the forecast period will focus areas of scattered to numerous showers and thunderstorms across portions of the Central/Northern Plains, Ohio/Tennessee Valleys, and the Southeast/Mid-Atlantic through the middle of next week. Models show a signal for areas of heavy rainfall ahead of the approaching cold front and lee trough along the immediate Southeast U.S. coastline from Sunday through Tuesday, and then further south in Florida Wednesday and Thursday. A renewed threat of more clusters of convection should develop across the Northern Plains and Upper Midwest Mon-Wed and Great Lakes Thu as the next shortwave/frontal system crosses the region. Temperatures should be relatively close to seasonal norms across much of the CONUS through the medium range. Cooler temperatures (highs 5 to 8 deg F below average) are forecast across portions of the West early next week as the upper-level shortwave crosses the region. Above normal temperatures are forecast across much of the southern Plains to the southwest under the dominant upper high. Petersen 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 Hazards: - Heavy rain across portions of the Upper Mississippi Valley and the Northern Plains, Mon-Tue, Jul 8-Jul 9. - Heavy rain across portions of the Lower Mississippi Valley, Tue-Thu, Jul 9-Jul 11. - Heavy rain across portions of the Southeast and the Mid-Atlantic, Sun-Thu, Jul 7-Jul 11. - Severe weather across portions of the Northern Plains, Mon, Jul 8. - Flooding occurring or imminent across portions of the Northern/Central Plains, the Middle/Lower Mississippi Valley, and the Ohio Valley. - Flooding likely across portions of the Northern/Central Plains and the Upper/Middle Mississippi Valley. - Excessive heat across portions of the Lower Mississippi Valley, Sun-Thu, Jul 7-Jul 11. 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