Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 340 AM EDT Tue Oct 20 2015 Valid 12Z Tue Oct 20 2015 - 12Z Thu Oct 22 2015 ...Flash flooding possible today and Wednesday from portions of the southwestern U.S. to the southern High Plains... ...Severe thunderstorms possible today across portions of the southwestern U.S... An upper-level low across the southwestern U.S. and a stationary frontal boundary draped across the higher terrain of Utah and Colorado will combine with a moist and unstable air mass to produce scattered to numerous showers and thunderstorms today and Wednesday across much of the Four Corners region. The upper-level low will drift eastward by Wednesday afternoon into early Thursday, causing showers and thunderstorms to spread east into portions of the southern and central High Plains. Heavy rain will be possible both today and Wednesday, which may result in a threat of flash flooding for some areas. Additionally, the Storm Prediction Center is forecasting a marginal to slight risk of severe thunderstorms today across portions of the southwestern U.S. A low pressure system will move across the central/northern plains today/tonight and into the Upper Great Lakes by Wednesday morning. This system will bring scattered showers and possibly a few thunderstorms generally along a warm front across portions of the Midwest and Great Lakes through Wednesday. The surface low will move across southern Ontario and into Quebec by Thursday as showers develop along the warm front across the northeastern U.S. Across northern Maine, the air mass may be cold enough north of the warm front to support a mix of rain and snow Wednesday night into Thursday morning. Ryan Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php