Extended Forecast Discussion NWS Weather Prediction Center College Park MD 254 AM EDT Thu Jul 4 2024 Valid 12Z Sun Jul 07 2024 - 12Z Thu Jul 11 2024 ***Major heatwave continues for the lower elevations of California and the Desert Southwest into next week, and Beryl approaches southern Texas Sunday into Monday*** ...Overview... An intense and prolonged heatwave is forecast to impact much of California and extending into the lower elevations of the Desert Southwest through the middle of next week, and also extending into the Intermountain West. Meanwhile, the track and intensity of tropical cyclone Beryl will bear close watching as it will likely track close to or over southern Texas by late Sunday into Monday. Meanwhile, a quasi-stationary front across the eastern U.S. will serve as a focusing mechanism for showers and storms south of the boundary across the Deep South and Southeast/Mid-Atlantic region, and this will be ahead of an upper level trough that is expected to build across the Northern Plains and Upper Midwest. Hot and humid conditions will also continue for much of the southern states and extending to the East Coast. ...Guidance/Predictability Assessment... The 00Z model guidance suite indicates very good overall synoptic scale agreement across the Continental U.S. going into the weekend, and better agreement on the massive upper ridge building over the West Coast. The guidance suggests this ridge should slowly move east over the southern Intermountain West by next Tuesday and Wednesday. Meanwhile, a general trough axis situated over the north-central U.S. should be anchored in place by another ridge axis over the western Atlantic Ocean, with a somewhat blocky pattern developing. A general deterministic model blend sufficed as a good starting point in the forecast process for the weekend, and then increased the ensemble means to about 40% by next Wednesday/Thursday. The latest forecast from the National Hurricane Center has tropical cyclone Beryl tracking across the western Gulf of Mexico, and making landfall just south of Brownsville, Texas Sunday night. The GFS guidance remains on the northern side of the track, and the UKMET/ECMWF/CMC near or just south of the track. It is interesting to note recent runs of the ICON and JMA models take the storm farther east and affect the central and eastern coast of Texas, but these solutions are not currently favored. The QPF for Beryl during the Sunday-early Tuesday time period was primarily derived from 40% ECMWF/20% ECENS/20% CMC/20% previous WPC. Beryl's track will continue to be closely monitored over the next several days, and the NHC has additional information pertaining to this. ...Weather/Hazards Highlights... Going into the Day 4 period Sunday, the official NHC track of Beryl has it making landfall just to the south of Brownsville, Texas, and a slower forward motion. Given this forecast track, rain and embedded thunderstorms would be increasing in coverage across Deep South Texas through the day Sunday into Sunday night, with the potential for some 3+ inch totals by 12Z Monday south of Corpus Christi. Therefore, a Slight Risk area is maintained for the Day 4 ERO for this area, and a broader Marginal Risk area extending farther northward along the Texas coast to account for periods of heavy rainfall with the outer rain bands. Farther to the north across the Central Plains, a Slight Risk area is also maintained for central Oklahoma into southern Kansas, with increasing model support for development of some MCS activity northeast of a surface low and and upper trough. Heavy rainfall concerns continue going into Monday across the Lower Rio Grande area of Texas as Beryl moves farther inland and weakens. There is still some notable model differences regarding the placement of the higher QPF, but given forecast heavy rain the day prior and the NHC track, a Slight Risk is planned for the new Day 5 ERO for portions of Deep South Texas and extending farther inland. This is subject to change as the forecast track becomes more certain and the models get a better handle on the situation. A separate Marginal Risk is also planned for Day 5 near the Red River Valley of TX/OK and into Arkansas and Missouri for additional MCS activity. Scattered showers and storms are likely to persist across much of the Gulf Coast, Deep South, and the East Coast states going into the middle of next week with a moist and unstable airmass remaining in place. Major heat will continue to make weather headlines for the West Coast states, with 100+ degree high temperatures extending to northern Washington for the entire forecast period. Highs will likely reach the 110s for the lower elevations of inland California, southern Nevada, and southern Arizona, with some 120s possible for the normally hotter locations. Some of this extreme heat will likely expand eastward to include much of the Intermountain West, including Utah and Idaho where some triple digits readings are expected. Numerous daily records are likely to be established during this prolonged and dangerous heat event, with major to extreme heat stress conditions. Even Wyoming and Montana get above average temperatures by next Wednesday/Thursday as the upper ridge slowly moves inland across the Rockies. Elsewhere, seasonal levels of heat and humidity can be expected most days for the southern and eastern parts of the country, although there will likely be some days that reach heat advisory criteria in some areas. Hamrick 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