Extended Forecast Discussion NWS Weather Prediction Center College Park MD 242 PM EDT Wed Aug 7 2024 Valid 12Z Sat Aug 10 2024 - 12Z Wed Aug 14 2024 ...Excessive Heat lingers over portions of Texas and the central Gulf Coast this weekend into next week... ...Overview... The remnants of Debby will be exiting northern New England at the start of the period, pushed out via an incoming Great Lakes upper low. This will bring in a cooler/drier air mass to much of the Northeast/Mid-Atlantic this weekend into early next week. Upstream over the West and central states, upper ridging centered over Texas will maintain monsoonal flow over the Southwest this weekend into next week with heat concerns persisting from Texas to the central Gulf Coast. Minor troughing over the Pacific Northwest will linger through the period. ...Guidance/Predictability Assessment... The 06Z/12Z GFS/ECMWF and their ensemble means offered reasonable clustering through the period, and a blend of their solutions (along with the 00Z UKMET/Canadian to start) was a good starting point. Lower predictability lied in the surface temperatures near the lingering frontal boundary, especially over the Plains as the front wavers N-S. Generally the NBM was a decent starting point. ...Weather/Hazards Highlights... For the Saturday ERO, kept a small Marginal Risk outline for far northern New England as remnant Debby will be very nearly out of the picture. To the west, monsoonal moisture on the western side of the ridge will keep a wet and unsettled pattern in place from the Four Corners region northward into the Rockies/High Plains through this weekend. Marginal EROs were maintained and expanded a bit for much of the Southwest/Four Corners for Days 4/5. Guidance continues to agree on organized activity Saturday/Sunday that originates in the lee of the CO Rockies and tracks southeastward over portions of southern KS/much of OK into the Ozarks. Marginal Risks are in effect for both Days 4 and 5 as a result, but expanded a bit based on the latest CSU Machine Learning ERO first guess which should account for some displacement errors/bias. Wavy front over the Southeast could touch off some isolated heavier rain fall where rainfall from Debby has resulted in fully saturated soils that may only partially recover by then. Above seasonal normal temperatures persist over Texas to the central Gulf coast this weekend into next week down stream of a ridge axis over west Texas. HeatRisk values will be at Moderate to Major levels with some isolated Extreme values. Below normal temperatures over the central U.S. persists behind a cold front this weekend/Monday before return flow brings temps back toward normal. Fracasso/Jackson 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 (QPF), excessive rainfall outlook (ERO), winter weather outlook (WWO) probabilities, heat indices, and Key Messages can be accessed from: 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