Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 416 PM EDT Thu Oct 01 2015 Valid 00Z Fri Oct 02 2015 - 00Z Sun Oct 04 2015 ...Flash flooding expected over portions of the Southeast and Mid-Atlantic States... ...Rain expected for much of the Intermountain West and Pacific Northwest... A stalled frontal boundary will persist along the East Coast through the short range forecast period. A surface low will develop along the front off the Georgia/Florida coast tonight. As an upper-level low deepens over the Southeast, the surface low will slowly move westward over the next couple days, moving into South Carolina by Saturday morning and into Georgia by Saturday afternoon. The combination of the surface low, frontal boundary, and a plume of moisture streaming westward into the Southeast from Hurricane Joaquin, will result in a period of very heavy rainfall over portions of the Southeast and southern Mid-Atlantic states. Widespread heavy rainfall will result in a significant threat of flash flooding across these areas through the next few days. Through Saturday evening, Hurricane Joaquin is forecast to remain offshore. Please refer to the latest products from the National Hurricane Center for details on the forecast for Hurricane Joaquin. An upper-level trough will move into the western U.S. from the Pacific this evening. As the associated surface frontal system moves across the tonight and Friday, scattered to numerous showers will occur across much of the Intermountain West. An additional upper-level disturbance will move into the Pacific Northwest Friday evening, bringing showers to the Pacific Northwest, which will then spread additional rains across the northern Intermountain West on Saturday. Rain is forecast to mix with snow at the highest elevations of Wyoming, Idaho, and Montana. Scattered showers and thunderstorms will also be possible through Saturday across the Plains, as a weakening frontal boundary lingers east of the Rockies, and moisture flowing into the region interacts with this front as well as upper-level disturbances passing through the region. Ryan Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php