Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 233 AM EST Thu Mar 10 2016 Valid 12Z Thu Mar 10 2016 - 12Z Sat Mar 12 2016 ...Heavy rain and threat of flash flooding will continue today for the lower Mississippi valley... ...Heavy rain possible for portions of northern California... ...Warm temperatures expected to persist today for the Mid-Atlantic and Northeast... A large and anomalous upper-level low will continue to drift slowly eastward over northern Mexico today. East of the low, a plume of tropical moisture will continue to stream northward into the Mississippi valley and the southern plains, where it will interact with a stationary frontal boundary to produce widespread rain and thunderstorms. Moisture, instability, and upper-level dynamics will be greatest across the lower Mississippi valley and portions of the southern plains, and this is where the potential will continue for very heavy rainfall with the potential for more flash flooding. The axis of showers and thunderstorms will shift only slightly eastward on Friday, with many of the same areas once again seeing a threat of heavy rain and flash flooding. The plume of showers will extend across the Ohio valley today and into the Northeast, ahead of a cold front. Colder air in place across northern New England will cause precipitation to fall as snow or a mix of rain and snow for some areas Friday night . The cold front will move offshore Friday morning, bringing an and to precipitation across the northeastern U.S. A cold front and a plume of Pacific moisture will stream into the Pacific Northwest and northern California today, bringing rain and high elevation snow. The heaviest and most widespread rain is expected to fall across northern California, where flooding is possible for some areas. A second low pressure system will approach the West Coast on Friday, bringing a continuation of rain and mountain snows. The track of this system will be farther south than the first. Thus, rain and mountain snow are forecast to fall over central and even southern California as well as the Great Basin and Intermountain region. This system will move into the Four Corners region by Saturday morning. Also by this time, yet another cold front will approach the coast, bringing rain and snow as far south as northern California. Lastly, temperatures will be well above average once again today across the Mid-Atlantic and Northeast. Afternoon high temperatures in these areas are forecast to be 15 to 30 degrees above average. Ryan Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php