Extended Forecast Discussion NWS Weather Prediction Center College Park MD 404 PM EDT Mon Jun 07 2021 Valid 12Z Thu Jun 10 2021 - 12Z Mon Jun 14 2021 ...Locally Heavy Rainfall Thursday and Friday from the Tennessee/Ohio River Valleys to the Central Appalachians and Mid-Atlantic... ...Much Above Normal Temperatures for the North-Central U.S Late This Week and Weekend.... ...Guidance/Predictability Evaluation... The latest model guidance offers average to above average predictability for the Nation during the medium range period (Thursday-Monday) and is driven by the amplified upper level pattern featuring a western U.S. trough with ridging across the southern to central U.S. and some troughing becoming established over the Northeast this weekend. The main difference from previous WPC continuity was with placement/movement of shortwave energy through the Rockies into southern Canada along with track of low pressure at the surface. Much of the guidance now lifts this energy north into south-central Canada Friday-Saturday, when previous model runs hinted at a closed low making its way eastward across the Great Lakes. For the 00z cycle of guidance, the only deterministic solution still advertising this was the UKMET (and thus it was not used in WPCs blend for today), but the new 12z model came in better agreement with the consensus, adding some confidence in this adjustment to continuity. The 06z GFS also slowed down it's progression of Eastern Pacific troughing and is now more in line with the ECMWF and the CMC with keeping the main trough axis off the West Coast by day 7. WPC favored a blend of the deterministic runs (ECMWF/CMC/GFS) through day 4, increasing weighting of the ensemble means thereafter but only to a 50/50 ensemble mean/deterministic blend by day 7. Aside from what's mentioned above, this maintained good continuity with the previous WPC forecast. ...Weather Highlights/Hazards... Upper level ridging building through the central U.S. will favor much above normal temperatures from the southern High Plains into the northern Rockies and northern Plains Thursday and then again through the weekend to early next week (brief reprieve expected on Friday). Departures above normal could reach 15F to 20F, locally higher, with highs well into the 90s. These values may approach or exceed both daytime highs and warm morning low records, especially on Thursday and also Friday morning, for some locations. Locally heavy rainfall capable of producing flash flooding will be possible Thursday and Friday across portions of the Ohio Valley to the Mid-Atlantic as moisture and lift associated with a weak upper level feature traverses the region. Its eventual interaction with a more substantial cold front dropping south will shunt the moisture southward this weekend. For this upcoming weekend, unsettled weather and higher precipitation chances will be confined to the Southeast U.S. along the residual frontal boundary as well as portions of the Pacific Northwest as a few waves of low pressure move onshore. Santorelli/Taylor 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 Central/Southern Appalachians, the Mid-Atlantic, and the Ohio Valley, Thu-Fri, Jun 10-Jun 11. - Severe weather across portions of the Central Plains and the Northern Plains, Thu, Jun 10. - Flooding possible across portions of the Southern Plains. - Flooding occurring or imminent across portions of the Southern Plains and the Northern Rockies. - Much above normal temperatures across portions of the Great Basin, the Northern/Central Plains, and the Northern/Central Rockies, Sat-Mon, Jun 12-Jun 14. - Much above normal temperatures across portions of the Central Plains, the Central Rockies, the Northern Plains, the Great Lakes, the Southern Rockies, the Middle Mississippi Valley, the Upper Mississippi Valley, and the Southern Plains, Thu, Jun 10. 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