Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 346 AM EDT Sat Oct 17 2015 Valid 12Z Sat Oct 17 2015 - 12Z Mon Oct 19 2015 ...Flash flooding possible for portions of the southwestern U.S... ...A mix of rain and snow showers is expected for portions of the Great Lakes and Northeast... The western U.S. will remain wet through the short range forecast period. A slow-moving upper-level disturbance will move northeastward today from the Southwest into the central Rockies. A moist and unstable air mass in place across the entire region will combine with the upper-level disturbance to produce scattered to numerous showers and thunderstorms across much of the western U.S. Rain may be heavy at some locations, and flash flooding is possible across portions of the southwestern U.S. An upper-level trough and the associated surface frontal system will move onshore in California and Oregon later today, and this will move into the interior western states by Sunday, providing continued support for numerous showers and thunderstorms through the weekend and into early Monday. A weakening frontal boundary will bring showers and thunderstorms to southern Florida today and Sunday. Showers and thunderstorms are forecast to be the most numerous across the Florida Keys today, before becoming more scattered in nature on Sunday. A deep upper-level trough will bring well below average temperatures to much of the eastern half of the U.S. today. Afternoon high temperatures are forecast to be 5 to 20 degrees below normal. The coldest temperatures are expected across portions of the Upper Great Lakes and the Northeast, where high temperatures may remain in the 30s for some areas. A series of upper-level disturbances crossing the Great Lakes and Northeast today and Sunday will cause scattered areas of precipitation. Due to the cold temperatures, this precipitation will fall as a mix of rain and snow showers. Snowfall accumulations should generally be light for most areas, with 1-3 inches expected across portions of northern Maine. Rain and snow showers should taper off Sunday evening Ryan Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php