Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 256 PM EST Thu Nov 29 2018 Valid 00Z Fri Nov 30 2018 - 00Z Sun Dec 02 2018 ...Heavy precipitation is expected over large portions of the West going into the weekend including very heavy snow for the Sierra-Nevada and the Rockies... ...A new winter storm will begin to impact portions of the northern Plains and upper Midwest by this weekend... ...Severe weather and heavy rainfall are likely across areas of the southern Plains, lower Mississippi Valley and Gulf Coast states... A wet, active pattern is expected to continue through the weekend for the Western U.S., particularly in California and also areas downstream across the Rockies. A vigorous upper low and associated frontal system is currently bringing heavy rainfall with embedded thunderstorms across California, along with heavy snow over the higher terrain of the Sierra-Nevada. This will continue through tonight with lighter precipitation across the Pacific Northwest. However, as the aforementioned upper low and front move farther inland going through Friday, precipitation will increase across the Great Basin and also the central Rockies while still persisting across central and southern California. As this system exits out toward the southern Plains by Friday night, there will already be a new storm system arriving across the Pacific Northwest which will bring another round of heavier precipitation to especially southwest Oregon and northern California Friday night and Saturday. A new round of heavy snowfall is expected over the Sierra-Nevada and also portions of the Cascades. In fact, multi-day snowfall totals through Saturday are expected to be in excess of 2 feet locally. Between the two systems impacting the West, there are numerous winter storm warnings and advisories in effect to address the winter weather hazards. Also, because of the heavy rainfall, there are concerns for some flash flooding in California and especially in and around the burn scar areas. In fact, the Weather Prediction Center has highlighted a Slight Risk of excessive rainfall for these areas. By late Friday, a quasi-stationary front will be draped across the Ohio Valley southwestward to the lower Mississippi Valley. This will become an increasing focus for showers and thunderstorms and especially as low pressure deepens in the lee of the southern Rockies by Friday evening. The aforementioned front will begin to lift north as a warm front Friday night and Saturday. Deep southerly flow ahead of a cold front advancing east across Texas will send copious amounts of moisture from the Gulf of Mexico northward across the lower Mississippi Valley. This coupled with a destabilizing airmass will set the stage for heavy rain and severe weather across portions of the southern Plains and lower Mississippi Valley late Friday and into early Saturday. In fact, the Storm Prediction Center has highlighted an Enhanced Risk of severe thunderstorms for these areas. On Saturday, the heavy rainfall and severe weather threat will shift east to include the Ohio Valley, Tennessee Valley and the central and eastern Gulf Coast states. Farther north, heavy snow is expected to develop across the northern Plains along with north-central Nebraska by Friday night. On Saturday, heavy snow will impact the South Dakota and Nebraska border region along with adjacent areas of the upper Midwest. Winter storm watches are already in effect in anticipation of this next winter storm. Above average temperatures are expected to gradually shift from the Plains and Midwest to the Eastern U.S. this weekend, with temperatures locally over 20 degrees above normal over the Ohio Valley and the lower to middle Mississippi Valley region. Meanwhile, all of the unsettled weather moving through the West will result in temperatures being below normal and especially over the Rockies by Sunday. Orrison Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php