Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 355 AM EDT Wed Apr 08 2020 Valid 12Z Wed Apr 08 2020 - 12Z Fri Apr 10 2020 ...Unsettled weather to continue across the Southwest with heavy mountain snow, heavy valley and coastal rain, and the potential for flash flooding over southern California... ...Severe weather and flash flooding possible for the Ohio Valley into parts of the Mid-Atlantic before a strong cold front clears the region on Thursday... ...Significant snow possible for interior northern New England on Thursday, plummeting temperatures arrive late week... The anomalously deep upper-level low that has doused California with rain and mountain snowfall the last few days will continue to slowly progress through the Desert Southwest through week's end. A cold front ahead of the deep upper low will inch its way towards the Lower Colorado River Valley this morning. Pacific moisture streaming into southern California will bring the threat of excessive rainfall into the region, which could lead to flash flooding over the interior desert. In the higher elevations, more than of foot of snow is expected most notably along the southern Sierra Nevada. By Wednesday evening precipitation should edge farther east into Arizona and southwestern Utah. The upper-low is forecast to weaken by Thursday causing precipitation to become more widely scattered and taper off across the Southwest, although a few spotty showers cannot be ruled out. Farther east, showers and thunderstorms will be common as a pair of frontal systems traverse the eastern half of the country. As the episode of severe weather in the eastern Ohio Valley finishes early this morning, another frontal wave will once again raise the severe weather threat farther south into the western Ohio Valley, central Mississippi Valley, and Tennessee Valley on today before a strong cold front arrives from the west Wednesday night. The Storm Prediction Center has both an Enhanced and Slight Risks for severe weather in these regions for later today. The strong front is forecast to sweep through the eastern U.S. on Thursday with strong thunderstorms possible across the Mid-Atlantic states in the morning hours. Meanwhile, a chance for showers and thunderstorms will be present in the western Gulf Coast region Thursday evening. As the strong cold front moves rapidly off the East Coast on Thursday, a low pressure system is forecast to rapidly intensify near the New England coast. In response to this rapid deepening, winds will pick up across New England with accumulating snow likely to develop across the northern tier of the region. Winter storm Watches have been issued for northern Maine as snowfall accumulations over a foot are possible. When gusty winds are paired with heavy snowfall, the potential exists for treacherous travel and whiteout conditions. In addition, some lake-effect snow will likely develop on Thursday downwind from the lower Great Lakes on the back side of the low pressure system. Meanwhile, a cold Canadian air mass will race across much of the eastern two-thirds of the country in wake of the strong cold front. Temperatures in portions of the Central Plains could wake up to temperatures near freezing come Friday morning. Mullinax Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php