219 FXUS02 KWBC 070627 PMDEPD Extended Forecast Discussion NWS Weather Prediction Center College Park MD 227 AM EDT Fri Aug 7 2026 Valid 12Z Mon Aug 10 2026 - 12Z Fri Aug 14 2026 ...Heat wave wanes in Southwest early next week, while heat threat expands across the Central and Southeastern U.S.... ...Multi-day heavy rainfall potential for Ohio Valley and Central Appalachians early next week... ...Overview... Two distinct troughs, one over the Northeast Pacific and another over Hudson Bay will promote stormy conditions from the Central to Eastern U.S. next week. Meanwhile, an upper ridge centered over the Southwest will weaken as it shifts east into the Southern/Central Plains and Deep South where another heat wave may develop. ...Guidance/Predictability Assessment... The latest deterministic and ensemble mean guidance appear to be in reasonably good agreement regarding the overall synoptic evolution of the 500 mb pattern during the medium range period. The ECAIFS is the only outlier, particularly early in the period, with it notably amplifying a West Coast trough and displaying a weaker ridge in the Southwest compared to the other models. A general model blend consisting of the available deterministic guidance was used in the days 3 and 4 blends with greater weighting given to the GFS and Euro. The GEFS and ECENS were introduced to the blend beginning on day 5 and increased in weighting through the end of the period, to mitigate growing differences in the evolution of the East Coast trough. The CMCE was introduced to the blend on day 6 and continued through the end of the period as well. ...Weather/Hazards Highlights... A long surface front draped across the northern tier on Monday will slowly drift south over the next few days. Thunderstorms and heavy rainfall will focus around this boundary, with some potential for a multi-day heavy rainfall event unfolding over parts of the Ohio Valley and Central Appalachians between Monday and Wednesday. To the South, a ridge in the Southwest will degrade and shift eastward beginning early next week. This will lead to renewed moist, southerly flow into the Southern Plains, Gulf Coast and Southeast, where heat indices could reach 105 to 115 degrees in some places for multiple days. Overnight temperatures in the 70s will offer little to no relief for those without adequate cooling and/or hydration. Temperatures begin to cool across the Northern Plains Upper Midwest and Great Lakes next week as the surface front descends into the Midwest and East Coast. A retreating ridge to the east should reinvigorate moist southerly flow into the Southwest, which will likely promote increased monsoonal activity next week. Isolated instances of flash flooding will be possible, especially over vulnerable surfaces such as slot canyons and dry washes. Kebede 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 forecast, excessive rainfall outlook, winter weather outlook probabilities, heat indices and Key Messages 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/#page=ero https://www.wpc.ncep.noaa.gov/wwd/pwpf_d47/pwpf_medr.php?day=4 https://www.wpc.ncep.noaa.gov/heat_index.shtml https://www.wpc.ncep.noaa.gov/#page=ovw $$