Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 414 AM EDT Wed Mar 17 2021 Valid 12Z Wed Mar 17 2021 - 12Z Fri Mar 19 2021 ...A rapidly intensifying low pressure system is expected to bring widespread thunderstorms across the Deep South with dangerous severe weather likely today... ...Threat of excessive rainfall will expand into the mid-Mississippi Valley today... ...Critical fire weather threat along the Rio Grande River Valley today... A low pressure system is currently rapidly intensifying over the mid-section of the country. Under this active and volatile weather pattern, an outbreak of strong to severe thunderstorms is forecast to rapidly expand across the Deep South today. The area that will be under the highest threat for dangerous severe weather will be from the lower Mississippi Valley eastward later today into this evening ahead of a dynamic cold front. In addition, heavy rain associated with thunderstorm clusters is expected to expand in coverage across the mid-Mississippi Valley today as the intensifying low pressure system approaches from the west. Some of the heavy rain and severe thunderstorms should reach the interior Southeast tonight. The entire storm system will move at a relative quick pace through the central and eastern U.S. during the next couple of days. The threat of severe weather will then shift into the Southeast on Thursday as heavy rain spreads across the central Appalachians into the northern Mid-Atlantic and the southern New England coast by Thursday night. Meanwhile, a cold air mass associated with a high pressure system could change the heavy rain into a period of snow with increasingly blustery northerly winds early on Friday across the central Appalachians to southern England as the entire storm systems will be moving out into the Atlantic. In the mean time, accumulating snow and rapidly strengthening winds are expected across the central High Plains to the Oklahoma and Texas Panhandles this morning into early this afternoon on the back side of the intensifying storm where Blizzard Warnings are in effect. In the Southern Plains, critical fire weather threat is shifting into the Rio Grande River Valley today. Elsewhere, the Pacific Northwest and the northern half of California can expect precipitation chances to increase by Thursday morning as an upper-level low and a frontal system move slowly toward the region. Some mountain snows should then reach the Intermountain region and the Sierra Nevada by early on Friday. Kong Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php