Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 312 AM EST Wed Jan 27 2021 Valid 12Z Wed Jan 27 2021 - 12Z Fri Jan 29 2021 ...Light to moderate snow to blanket parts of the Northeast and southern New England through Wednesday morning... ...Excessive heavy lower elevation rain to bring dangerous flash flood risk to coastal California tonight and into Wednesday... ...Extreme snowfall amounts expected across the Sierra Nevada through Thursday... Scattered to widespread rain is expected to move through parts of the South, Southeast and Tennessee Valley/Mid-Atlantic region today and into Thursday morning as a low pressure system tracks toward the Southeast. With cold Canadian air settling in over the central U.S. behind the cold front, snow will spread from the Mid-Mississippi Valley to the Mid-Atlantic as a low pressure system tracking through the Central Rockies exits into the Plains and advances toward the Tennessee Valley and Appalachians by Wednesday. Both systems are expected to move offshore on Thursday. Snow may linger across parts of the Northeast while any lingering precipitation to the south quickly tapers off. A general 2 to 4 inches, with locally higher amounts can be expected, especially in the mountains. Winter Weather Advisories have been issued for the area. Snow could mix with rain through the southern Mid-Atlantic early on Thursday as the area of low pressure strengthens and continues to dash eastward into the Atlantic. For the West, moderate to heavy rainfall will spread across central and southern California as a robust Pacific front moves inland. Deep moisture will be directed onshore and will help produce several inches of rain along the coast and lower elevations. Flash flooding and debris flow near recent burn scars may occur. WPC has highlighted part of this region as having a Moderate Risk for excessive rainfall. Mountain snow will likely be heavy at times across the Sierra Nevada. Several feet of snow (as much as 10 feet) will add up through Thursday night, with road closures and travel delays very likely. Numerous locations have Winter Storm Warnings and Winter Weather Advisories in effect. Blizzard Warnings are also in effect for part of the Sierra Nevada. A Flash Flood Watch has been posted as well. Over the next three days, as much as 10 to 15 inches of rain could fall along the central California coast roughly between Monterey and Santa Barbara. This amount of rain in a 72-hour period is very rare for this region, with an annual exceedance probability of only 2 percent. Campbell/Snell Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php