Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 1255 PM EDT Thu Aug 09 2018 Valid 00Z Fri Aug 10 2018 - 00Z Sun Aug 12 2018 ...Unsettled wet weather across eastern & southern tier of U.S. with a lingering heavy rainfall threat across the South through Friday... ...Near record-breaking heat likely out West... ...Monsoonal moisture will bring an elevated heavy rainfall/flash flood risk to portions of the Southwest and southern Rockies... Much of the southern tier of the U.S. will be in a wet pattern through the end of the week near and ahead of a stalling frontal boundary ahead of an elongated upper level disturbance. As a surface low lifts northeast through New England a cold front will pass through the Northeast while the trailing end slows from the Mid-Atlantic to the Central/Southern Plains. Moisture streaming northward over the boundary will initiate widespread convection and lead to afternoons which are below average for early to mid August. Afternoon temperatures on Sunday could lead to record cool high temperatures across northwest Texas near Wichita Falls. As convection potentially repeats at the same location, the risk for flash flooding increases. Monsoonal moisture rounding the base of a strong upper level ridge over the western U.S. will keep mainly diurnally driven showers and thunderstorms in the forecast across the Southwest through the rest of the work week. Heavy rainfall and localized flash flooding will be possible, especially along the favored terrain. WPC has a slight risk for excessive rainfall in effect for portions of Arizona, New Mexico, and from Northeast Texas to northern Alabama today, then primarily from Arizona to central Texas this weekend. With a strong ridge anchored over the West temperatures will continue to rise, especially for parts of the Pacific Northwest, Intermountain West and the Northern High Plains. Hot and dry conditions are expected from the interior Pacific Northwest to eastern Montana. Record breaking temperatures in the 90s and 100s in the afternoon , with 60s and 70s expected overnight persist through Friday, which are as much as 10 to 20 degrees above normal for early to mid August. Excessive Heat Warnings and Heat Advisories are in effect across southern California, southern Nevada, and from Washington and Oregon to Montana. Ongoing wildfires combined with the heat continue to cause poor air quality issues. The hot and dry conditions will only exacerbate the fire weather concerns out West, particularly for those areas already dealing with wildfires. The passage of a cold front should relieve the heat across the Pacific Northwest and Northern Continental Divide on Saturday, with heat relief expected for Montana expected on Sunday. Roth/Campbell Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php