Extended Forecast Discussion NWS Weather Prediction Center College Park MD 212 AM EDT Sat Jul 03 2021 Valid 12Z Tue Jul 06 2021 - 12Z Sat Jul 10 2021 ...Elsa is forecast to impact Florida and the Southeast through the middle of next week with heavy rainfall and potential for high winds... ...Repeating heavy rain is likely to persist over southern Texas through much of next week as low pressure lingers... ...Overview... A summer pattern persists through next week as the main jet stream/westerlies meander over the northern U.S. and southern Canada. An upper ridge over the Desert Southwest is forecast to strengthen, while a weak upper trough/low merely drifts southwest over Texas and into northern Mexico, and a fairly low amplitude trough will be centered around the Great Lakes region. Additionally, what is currently Hurricane Elsa is forecast to impact Florida and the Southeast through the middle of next week. ...Guidance/Predictability Evaluation... Guidance remains reasonably agreeable with the mid-latitude pressure pattern described above except for continued uncertainty with the track/timing/strength of Elsa. A deterministic model blend of the 18Z GFS, and 12Z ECMWF/UKMET sufficed for Days 3-5. The main differences outside of Elsa are with the timing and amplitude of shortwave trough ejecting east from the Pacific Northwest/southwest Canada. The 00Z GFS is now the fastest with this low ejection, just slightly ahead of the 12Z ECMWF. The 12Z CMC was the largest outlier of the deterministic guidance with this feature by re-amplifying it off the Pacific Northwest, making it the slowest solution by far, so it was limited in the blend. Regarding Elsa, the deterministic GFS and CMC are the strongest with the GFS west of the Florida Peninsula and the CMC east (the CMC has also slowed considerably from being by far the fastest model). The ECMWF and its ensembles are still weaker with the system with track generally east of Florida while the GFS/GEFS are generally west. The UKMET is still similar to GFS, just a bit weaker, farther east, and slower. The GFS remains steady for multiple days have been steady with similar track, though it has shifted farther west into the Gulf. A more westward track is expected with a stronger Elsa (currently a hurricane), so it continues to work well to follow NHC's forecasts for Elsa's track and strength for the QPF. ...Weather Highlights/Hazards... An upper low/trough drifts southwest over southern Texas into northern Mexico through next week making for a repeating heavy rain threat there each day of the next workweek, with multi-inch totals expected with totals over a foot likely (though the heaviest looks to be just south of the Rio Grande. Farther west, late-day monsoonal type showers and thunderstorms are likely to continue through Wednesday over the Central/Southern Rockies. Heavy rainfall, flooding, and high winds are potential threats where Elsa tracks. Timing and strength of Elsa still have considerable uncertainty, but the heavy rain threat is more for the western Florida Peninsula Tuesday and across north Florida to eastern Georgia/South Carolina coast Wednesday. Periods of rain are forecast along and ahead of a front moving through the week from the north-central to northeastern CONUS, and tropical moisture from Elsa may help increase rain totals in the Mid-Atlantic and Northeast in the latter part of the week depending on its track. The heat wave persists over the western CONUS through next week as ridging restrengthens with max temperature anomalies of generally 10 to 15 degrees above normal for the Northwest/northern Great Basin, challenging several daily high temperature record, mostly in the northern Great Basin Tuesday and Wednesday. Temperatures will generally be a few degrees lower than average in the south-central U.S./Texas through the week due to cloudiness and rain from the persistent upper level disturbance there. Jackson 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