Extended Forecast Discussion NWS Weather Prediction Center College Park MD 300 AM EDT Thu Jul 01 2021 Valid 12Z Sun Jul 04 2021 - 12Z Thu Jul 08 2021 ...Heat across the interior Northwest and northern Plains will linger into next week but should further moderate... ...Threat of heavy rain lingers near the Gulf Coast into next week as Tropical Storm Five could impact Florida by midweek... ...Overview and Guidance/Predictability Evaluation... The large scale pattern is forecast to evolve into a more typical summer regime after this weekend as an amplified upper trough over the northeastern states lifts away into the Canadian Maritimes, and the westerlies in the wake remains confined to southern Canada and northern tier of the U.S. Elsewhere, a seasonably strong upper ridge will prevail over the Southwest through the period and a weakness with possible embedded low should evolve over the southern Plains into northern Mexico during Monday-Wednesday. Meanwhile, Tropical Depression Five in the tropical Atlantic is forecast to strengthen into a tropical storm and could track across the Florida Peninsula during the middle of next week. Latest model and ensemble guidance continues with the recent trend toward faster ejection of the East Coast upper trough through this weekend. There is now good model agreement on clearing skies across the Mid-Atlantic states on Sunday as the departing trough brings only some showers across new England. Behind the upper trough, there is rather good model agreement on the subsequent synoptic evolution across the U.S. through the remainder of the medium range period. The general consensus calls for the upper ridge to flatten out into a zonal flow across the northern tier states as the next upper trough approaches the Pacific Northwest during the early to middle of next week. Farther south, the model/mean blend has been indicating the presence of a subtle subtropical trough/upper weakness over the southern Plains to northern Mexico. This feature tends to focus the heaviest rains to fall in the vicinity of the western Gulf Coast through much of the medium range period. Meanwhile, the National Hurricane Center continues to monitor the future progress of Tropical Depression (T.D.) Five currently over the tropical Atlantic. The latest forecast track calls for the possibility of the T.D. to intensify and track across the Florida Peninsula midweek as a tropical storm. The WPC medium-range forecasts were based on a general compromise of the 12Z EC mean, 18Z GEFS, the 12Z CMC mean, together with some of their deterministic components. ...Weather Highlights/Hazards... The historic heat wave over the Pacific Northwest will be less intense than it has been over recent days but triple-digit heat is still likely on Sunday before moderating mostly into the 90s further into next week. A portion of this heat will spread into the northern Plains on Sunday before slightly cooler air arrives behind a cold front on Monday. Some rain showers over the northern Rockies may offer slight relief to the heat but they will do little to ease the growing drought concern over much of the western U.S. During midweek, a low pressure wave developing near the Montana-Canadian border could help to focus areas of heavier rainfall across the northern Plains but confidence in the specifics is relatively low at this time. Farther south, some late-day monsoonal type showers and thunderstorms are likely each day over the central to southern Rockies through the medium range period. Across the Northeast into the Mid-Atlantic, clearing skies behind the departing upper trough will help promote another heat wave to build on Monday and continue through midweek ahead of a cold front. Scattered showers and thunderstorms are expected to develop ahead of the front across the Great Lakes before moving into parts of the Northeast. Farther south, the trailing cold front from the departing upper trough is expected to stall near the Gulf Coast on Sunday with areas of moderate to heavy rainfall to the south of the front. With time the heaviest rainfall should gravitate toward the western half of the Gulf Coast and nearby areas ahead of the upper weakness/low forecast to develop over/near Texas. Meanwhile, interests near the eastern Gulf should monitor the latest National Hurricane Center products for the future progress of Tropical Depression Five into next week. The latest forecast track calls for the possibility of the T.D. to intensify and track across the Florida Peninsula midweek as a tropical storm. Temperature-wise, clouds and rainfall over the southern half of the Plains will keep that region below normal for highs during the period with some minus 5-10F or so anomalies. High pressure behind the Gulf Coast front should provide moderately below normal morning lows to portions of the eastern half of the country during the weekend. Kong/Rausch Additional 3-7 Day Hazard information can be found on the WPC medium range hazards outlook 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