Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 339 AM EDT Thu Apr 21 2016 Valid 12Z Thu Apr 21 2016 - 12Z Sat Apr 23 2016 ...Flash flooding possible for portions of the Gulf Coast and Lower Mississippi valley... ...Warm temperatures expected to continue today for the northwestern U.S... The eastern third of the CONUS will have scattered to widespread showers and thunderstorms through the end of the week as low a pressure system tracks east of the Mississippi River and with a cold front dropping south of of Canada in its wake. Showers and thunderstorms may still result in locally heavy rainfall through this morning for portions of the western Gulf Coast, and lower/middle Mississippi Valley -- and flash flooding is a continued possibility. Drier air will move into the area as the cold front passes, which will greatly reduce the chances for precipitation for much of the Gulf states on Friday and Saturday. Rain and thunderstorms will continue across the East on Friday as the front approaches the coast by Friday evening. Most areas east of the Appalachians have 0.25 to 0.75 inch forecast over the next couple of days. Nearly 2 inches of rainfall is expected just offshore of the Carolinas. Unseasonably warm temperatures will persist today across the Pacific Northwest with high temperatures forecast to be 10 to 25 degrees above average. Showers will begin to move into the coastal Northwest by this afternoon as a front approaches. Showers and possibly a few thunderstorms will expand into the Intermountain West on Friday, with snow at the highest elevations. Much of the West Coast could see 1 to 2 inches of rain by this weekend. Temperatures will cool down by late Friday as the front sweeps through. Campbell Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php