Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 341 AM EDT Fri Sep 06 2013 Valid 12Z Fri Sep 06 2013 - 12Z Sun Sep 08 2013 ***Hot temperatures to continue for the Southwest and the Central and Southern Plains*** ***Strong upper low bringing heavy rains and thunderstorms to the Pacific Northwest*** ***Cooler and drier air expected to continue for the Eastern U.S.*** A large upper ridge of high pressure is expected to prevail over the center of the nation through the weekend with very warm to downright hot temperatures expected from the Desert Southwest east out across the Central and Southern Plains. Some monsoonal moisture will be conducive for some scattered showers and thunderstorms over the Southwest U.S., but it should remain very dry out across most of the Central and Southern Plains. Farther to the north and west, a slow-moving upper low moving inland across Washington and Oregon this morning along with an associated frontal system will yield a widespread area of showers and thunderstorms. The main focus will initially be on the Pacific Northwest, but there will gradually be an eastward advance of the shower and thunderstorm activity by Saturday involving the Northern Rockies and then out into the northern High Plains on Sunday. Locally heavy rainfall is expected especially today and Saturday for some of the higher terrain of the Pacific Northwest and the Northern Rockies including the Cascades and the Bitterroots. This may result in areas of flash flooding, and there will also locally be a threat for severe weather as this system moves slowly east the next few days. In the wake of the system, especially over the Pacific Northwest, expect cooler temperatures to arrive. The same front attendant to this system is expected to stall out farther south over the Great Basin late in the weekend, and this will at least support scattered showers and thunderstorms elsewhere over the Intermountain West. Over the Southeast U.S., a weak front settling southward will be gradually dissipating by Saturday, allowing drier air though to filter south all the way to the Gulf Coast. There will be some widely scattered showers and thunderstorms along the immediate Gulf Coast and across Florida. Elsewhere, relatively cool high pressure moving across the Ohio Valley, Mid-Atlantic and Northeast will advance eastward and gradually move offshore by late in the weekend. A new cold front though will be dropping southeast across the Midwest and the Great Lakes region Saturday and Sunday and this will usher in a reinforcing shot of cool and dry air from Canada. There should be some scattered showers and thunderstorms with this next front. The remainder of the East though will continue to be dry. Orrison Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php