Extended Forecast Discussion NWS Weather Prediction Center College Park MD 125 AM EDT Mon Aug 06 2018 Valid 12Z Thu Aug 09 2018 - 12Z Mon Aug 13 2018 ...Record heat for the interior Northwest Thursday/Friday... ...Pattern Overview and Guidance/Predictability Assessment... The dominant upper high in the west will be pushed over as an upper low over the northeastern Pacific finally moves northeastward into southern British Columbia. In the east, troughing will be reinforced this weekend as a potential upper low sinks toward the Ohio Valley. The models/ensembles were in very good agreement overall and a majority deterministic blend was used for the period. ...Weather Highlights and Hazards... Near or above record high temperatures are forecast for much of the interior Northwest Thursday/Friday ahead of the upper low with 100s widespread east of the Cascades and through the Snake Valley in Idaho and also the Missouri River Valley in Montana. Light precipitation will be confined to coastal/northern/higher elevation areas of Washington as the best upper support travels through Canada. Heavier convective precipitation is likely in the deeper moisture on the eastern side of the upper high from NM/CO/AZ eastward to the southern Plains. Several inches of rain over a few days appears likely which may lead to localized flooding. Precipitation will accompany and precede a frontal boundary as it pushes through the Great Lakes and into the Northeast via afternoon storms. Another front will linger across the U.S. southern tier during the period which will help spark afternoon showers/storms and locally heavy rainfall in the warm/humid airmass. As the trough digs southward out of the Great Lakes, more widespread precipitation may be favored to its east along the Appalachians to the I-95 corridor. Fracasso WPC medium range 500 mb heights, surface systems, weather grids, quantitative precipitation, winter weather outlook probabilities and heat indexes are found 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