Extended Forecast Discussion NWS Weather Prediction Center College Park MD 339 PM EDT Tue Jun 07 2022 Valid 12Z Fri Jun 10 2022 - 12Z Tue Jun 14 2022 ...Dangerous/Record heat for the Southwest/Central Great Basin to Texas Friday into the Weekend... 18Z Update: The 12Z model guidance, along with the 00Z ECMWF, is in very good synoptic scale agreement through the majority of the forecast period. Some minor differences become apparent with the CMC by early next week with a slightly more amplified and progressive solution across the East Coast region. By next Tuesday, the GFS is stronger with the closed low exiting the Northern Rockies, but still close to the ensemble means regarding placement. The southern U.S. upper ridge and the accompanying heat is probably the most confident part of the forecast. In terms of QPF, there is a stronger signal for heavier rain across central Idaho and into western Montana this weekend as deeper moisture from the Pacific advects inland. The previous forecast discussion is appended below for reference. /Hamrick ...Overview and Model Guidance Evaluation/Preferences... Lingering zonal flow will trend toward increased troughing into the East/Northeast and western Canada/Northwest U.S. as upper ridging builds into the Southwest late this week into the weekend. This will favor a cooler and wetter period for much of the East late this week into the early part of the weekend with extreme heat for portions of Texas to the Southwest/Central Great Basin, and a generally warm/hot pattern for much of the rest of the West. A frontal boundary over the Southeast and Mid-South will act as a focus for more organized rain/thunderstorms in addition to a weekend wave of deepened low pressure moving along the Mid-Atlantic/Northeast. The guidance remained in overall good agreement with a blend of the 12Z/18Z GFS/ECMWF/UKMET/Canadian forming a reasonable starting point and details that has good ensemble support. By early next week, there remain differences in how quickly moderating upper troughing moves into the West, with best clustered guidance from the GFS/ECMWF and GEFS/ECMWF ensemble mean emphasized. The 01 UTC National Blend of Models also offers an adequate middle-ground solution overall, especially with temperatures. Newer 00 UTC guidance remain in line with this scenario, but have overall trended a bit more amplified with the flow and that may be reasonable. ...Sensible Weather/Threat Highlights... For Fri, heavy rain potential will lie over the Mid-South (where SPC highlights a chance for severe weather) as moisture intersects the frontal boundary over some areas that have been relatively wet the past week. The system will progress eastward then northeastward to the coast, spreading rain and most organized heavy storms into the Mid-Atlantic and Northeast Fri-Sat where it has been relatively dry as of late and also along the trailing front over the Southeast. Meanwhile, much of the West should stay dry until late week and the weekend when Pacific system energies work inland to bring some enhanced moisture and rainfall to the Pacific Northwest and onward across the northern Intermountain West/Rockies. Downstream system progression would add enhanced convective potential to the northern Plains/Upper Midwest into early next week. Temperatures will be near to below normal over much of the East due to clouds and increased rain chances, but it will be hot and dry over Texas and the Southwest/central Great Basin. With strong ridging in place by Friday, temperatures will soar into the 100s and 110s over the lower deserts which will be 10-20 degrees above normal at what is typically near the hottest time of the year in that part of the CONUS. This will challenge daily records for many locations from I-80 southward and especially focused over southern Nevada into Arizona and southeastern California. Excessive Heat Watches are in place for parts of this region for later this week through the weekend. Low temperatures will be quite warm as well, only dipping into the 70s and 80s for many locations in the Southwest. Schichtel 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 Hazards: - Heavy rain across portions of the Middle Mississippi Valley, the Lower Mississippi Valley, the Ohio Valley, and the Tennessee Valley, Fri, Jun 10. - Heavy rain across portions of the Mid-Atlantic and the Central Appalachians, Sat, Jun 11. - Severe weather across portions of the Southeast, the Lower Mississippi Valley, the Southern Plains, and the Tennessee Valley, Fri, Jun 10. - Flooding possible across portions of the Central Plains, the Southern Plains, the Northern Rockies, and the Northern Great Basin. - Flooding occurring or imminent across portions of the Upper Mississippi Valley and the Northern Plains. - Flooding likely across portions of the Central Plains and the Northern Plains. - Excessive heat across portions of California, Fri-Sat, Jun 10-Jun 11. - Excessive heat across portions of the Central Great Basin, California, and the Southwest, Fri-Sun, Jun 10-Jun 12. - Excessive heat across portions of the Lower Mississippi Valley and the Southern Plains, Fri-Tue, Jun 10-Jun 14. - High winds across portions of the Central Rockies, the Central Great Basin, the Northern Rockies, the Northern Great Basin, and the Southwest, Sun-Mon, Jun 12-Jun 13. WPC medium range 500mb heights, surface systems, weather grids, quantitative precipitation, experimental excessive rainfall outlook, 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/#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