Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 258 AM EDT Thu Apr 18 2019 Valid 12Z Thu Apr 18 2019 - 12Z Sat Apr 20 2019 ...Risk of severe thunderstorms and flash flooding from the Gulf Coast to the Ohio River Valley today, shifting to the East Coast on Friday... ...Warmer and generally dry over the West, with the next round of precipitation arriving in the Northwest on Friday... A low pressure system will move east from the Mississippi River Valley today, to the East Coast by Friday Night. This will deliver widespread rain to much of the eastern half of the U.S. over the next couple days with many locations likely to receive over an inch of rainfall. The primary surface low will shift from the Mid South, near Arkansas, today to the central Appalachians later on Friday. A trailing cold front will sweep across much of the Gulf Coast and Southeast. Ahead of the low and associated cold front, a warm, humid air mass will push well inland, supporting the development of thunderstorms as far north as the Great Lakes and Mid Atlantic. Some of the thunderstorms will be severe. The greatest risk of severe weather is in the Gulf Coast states today, and in the Southeast Atlantic Coast states from Virginia to Florida on Friday. The main threats with the severe storms will be damaging wind gusts and several tornadoes; some of the tornadoes in the South today and tonight could be strong. For more detailed information on the severe weather threat, refer to Storm Prediction Center forecasts. The thunderstorms and areas of heavy rain will also pose a risk for flash flooding over much of the eastern half of the U.S. in the next couple days, gradually shifting east with the low pressure system. Flash flooding will be most likely today in the Lower and Middle Mississippi River Valley; some locations could receive several inches of rain in a few hours. The risk of flash flooding on Friday should extend along most of the U.S. East Coast, from the northern border with Canada south to Georgia. Meanwhile, across the West, today should be relatively warm and dry with the warmth continuing into Friday in most areas. Temperatures will be 10 to 20 degrees on a widespread basis. The next front will begin to arrive in the Northwest tonight and Friday, with increasing chances of precipitation. Fairly high snow levels will generally prevent snow other than in the highest elevations behind the cold front. Lamers Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php