Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 354 PM EDT Tue Mar 20 2018 Valid 00Z Wed Mar 21 2018 - 00Z Fri Mar 23 2018 ...Snow expected from the Ohio Valley into Appalachians and the Mid-Atlantic northward into New England... ...Severe thunderstorms expected parts of the Southeast and Florida... ...Heavy rain with the potential of flash flooding for California... Another coastal low/nor'easter is underway as the surface low located in the Carolinas will move into the Atlantic by tonight. Meanwhile, a swath of precipitation will move across the Ohio Valley into the Appalachians, Mid-Atlantic, and Northeast. For today, the rain/snow line will stretch from New Jersey southward into the Washington DC metro area through southern Virginia. North of that line, areas will experience mostly snow especially throughout the Ohio Valley and central Appalachians. Along the rain/snow line, mixed precipitation in the form of rain, sleet, and snow will occur. Across the Carolinas and southern Virginia, rain and thunderstorms will be possible. As the low moves along the coast tonight, the rain/snow line will shift to the east--with snow spreading across most of the Mid-Atlantic and coastal areas of the Northeast and New England. Snow will continue across these regions through Wednesday as the low tracks northward along the East Coast; however, parts of coastal New England can expect precipitation to change over to rain by Wednesday afternoon. On Thursday, most of the precipitation will be in the form of snow in the New England region as the low treks northward towards the Canadian maritimes. Snow may linger by Thursday evening in the interior of New England but the significant snowfall will come to an end at that point. For more information on snowfall for this event, please see WPC's winter weather products. Meanwhile, as the strong cold front from the coastal low pushes south and east across coastal Georgia/South Carolina and northern/central Florida, thunderstorms will continue to fire along the boundary. These storms have already produced severe weather and are expected to continue to do so through this evening. Consequently, SPC has issued an enhanced risk of severe thunderstorms from coastal South Carolina through central Florida through this evening. The front will move into southern Florida by tonight--with thunderstorms following, albeit not expected to be severe. As the East Coast experiences the fourth nor'easter in 3 weeks, the West Coast will also have a very active period of weather throughout the short term period. An impressive axis of moisture will set up along the central/southern California coast--bringing a long duration flooding event to the state. Heavy rainfall has already begun and will continue through Thursday along the southern California coast. Burn scars from previous fires will give way to flash flooding across southern California--in addition to mudslides and debris flows. Because of this, a high risk of excessive rainfall is in effect for Wednesday. A moderate risk will also be in effect for Thursday as additional heavy rainfall is expected. Heavy snow is also expected for the Sierra Nevada mountain range through Thursday night--with snowfall accumulations 2 to 4 feet expected and localized amounts up to 5 feet! Winter storm warnings are in effect for these areas of the mountain range. Reinhart Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php