Extended Forecast Discussion NWS Weather Prediction Center College Park MD 521 PM EDT Fri Jul 02 2021 Valid 12Z Mon Jul 05 2021 - 12Z Fri Jul 09 2021 ...Elsa may impact Florida and the Southeast Atlantic Coast early to mid-next week with heavy rainfall and potential for high winds... ...Repeating heavy rain is likely to persist over southern Texas as low pressure lingers through much of next week... ...Overview... A summer-like pattern sets up for next week as the main jet stream/westerlies meander over the northern U.S. and southern Canada. A strengthening upper ridge is forecast over the Desert Southwest and Four Corners states, while a weak upper trough/low slowly sinks south in and around Texas, and a fairly low amplitude trough will be centered around the Great Lakes region. Additionally, what is currently Hurricane Elsa has the potential to cross Florida and move up the Southeast Coast early to midweek. ...Guidance/Predictability Evaluation... Guidance remains reasonably agreeable with the midlatitude pattern described above (with the main exception of the track/timing/strength of Elsa). A mainly deterministic model blend of the 00Z/06Z GFS and 00Z UKMET and ECMWF sufficed for early in the period. By the latter part of the week, models generally show a shortwave moving across southwestern Canada, but with some differences in the details. The 00Z CMC was the largest outlier of the deterministic guidance with this feature, so it was not used, and minor timing and strength differences in the other deterministic guidance were able to be taken care of by incorporating some of the agreeable GEFS and EC ensemble means later in the period. Regarding Elsa, a large amount of model spread remains, though some guidance may be starting to converge on a track into the eastern Gulf of Mexico like the current forecast from the National Hurricane Center shows. The GFS runs for multiple days have been steady with a track similar to that, though with some timing differences. And many members of the 00Z EC ensemble now show low centers taking that similar track, after almost all members stayed east of Florida in the western Atlantic yesterday. However, the 00Z and now the 12Z deterministic ECMWF still have Elsa weakening before entering the Gulf, as does the UKMET. The 00Z CMC has a stronger system but fast and east. Thus, plenty of spread remains. A more westward track is expected with a stronger Elsa (currently a hurricane), so it worked well to follow NHC's forecasts for Elsa's track and strength. ...Weather Highlights/Hazards... An upper low/trough sets up over Texas making for a heavy rain threat there each day of the next workweek, with multi-inch totals likely. Farther west, late-day monsoonal type showers and thunderstorms are likely Monday into Wednesday over the Central/Southern Rockies. Heavy rainfall, flooding, and high winds are potential threats where Elsa tracks. Timing and strength of Elsa have considerable uncertainty, but there is a heavy rain threat for portions of the Florida Peninsula Monday into Tuesday and across the Georgia and Carolina coast Wednesday with Elsa. 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 now looks to persist over the western CONUS through next week as ridging lingers and restrengthens with max temperature anomalies of 10 to 20 degrees above normal for the Northwest, with a handful of daily record high temperatures mostly in the Great Basin. Temperatures will generally be a few degrees cooler than average in the south-central U.S./Texas through the week with cloudiness and rain from the persistent upper level disturbance there. Tate/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 Hazards: - Heavy rain across portions of central and southern Texas and southwestern Louisiana, Mon-Thu, Jul 5-Jul 8. - Heavy rain across portions of the Mid-Missouri Valley and the Upper Mississippi Valley, Tue, Jul 6. - Heavy rain across portions of the Southeast and the Carolinas, Tue-Wed, Jul 6-Jul 7. - Flooding possible across portions of the Central Plains and the Middle Mississippi Valley. - Flooding occurring or imminent across portions of the Central and Southern Plains, the Great Lakes, and the Middle Mississippi Valley. - Flooding likely across portions of the Central and Southern Plains and the Middle Mississippi Valley. - High winds across portions of the Southeast, Tue-Wed, Jul 6-Jul 7. - Much above normal temperatures across portions of the Interior Northwest, the northern Great Basin, and the Northern Rockies, Mon-Fri, Jul 5-Jul 9. - Much above normal temperatures across portions of the Northern High Plains, Wed-Thu, Jul 7-Jul 8.