Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 249 PM EST Wed Nov 21 2018 Valid 00Z Thu Nov 22 2018 - 00Z Sat Nov 24 2018 ...Heavy rain likely in parts of California through Friday which could lead to flash flooding, mudslides, and debris flows over recent burn scars... ...Significant snowfall accumulations expected in the mountains of the Northwest and California... ...Unseasonably cold temperatures will move into the Northeast by Thursday... A wet couple of days is in store for much of the Western U.S. as a series of upper level systems move through. Heavy rainfall is likely to continue through Friday across portions of California and the Pacific Northwest with rain reaching inland across the lower elevations of the Great Basin and Intermountain West as well. Excessive rainfall is a concern, especially across California where heavy rains over recent burn scars may lead to flash flooding, debris flows, and mudslides. WPC has highlighted much of the region in a marginal to slight risk on the Days 1 and 2 excessive rainfall outlooks and flash flood watches are also in effect across interior portions of Northern California. In addition to the rainfall threat, heavy snowfall is likely in the higher terrain of the Cascades, Sierras, and Intermountain West where as much as 2 to 3 feet is possible. Winter storm warnings, watches, and advisories are in effect for some locations. The other big weather story is the arctic chill expected to move over the Northeast U.S. just in time for Thanksgiving. Temperatures on Thursday and Friday will struggle to get out of the teens and 20s across New England and the 30s in the Mid-Atlantic states, with wind chills making it feel even colder. These values are as much as 20 to 40 degrees below normal and both record lows and highs could be challenged or broken for dozens of locations. On the backside of the cold front, heavy snow squalls may continue through this evening for parts of the Great Lakes. A deep upper level trough moving into the Central U.S. on Friday will allow for increased rain chances along the western and central Gulf Coast and into the lower/middle Mississippi Valley. Locally moderate to heavy rainfall is possible, especially near a developing surface low moving along the western Gulf Coast on Friday. Santorelli Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php