Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 352 PM EST Tue Dec 22 2015 Valid 00Z Wed Dec 23 2015 - 00Z Fri Dec 25 2015 ...Flash flooding threat exists from the central/eastern Gulf Coast up along the Appalachians... ...Severe thunderstorms likely from the Arklatex to points west of the Appalachians... ...Heavy snow in the forecast across the higher terrain over the western U.S... ...Temperatures 25 to 35 degrees above normal possible from the Mississippi River eastward... The upper pattern through Christmas Eve shows a broad trough extending from the West Coast to the Appalachians while a ridge dominates the Eastern Seaboard and western Atlantic. A series of embedded disturbances will track from southwest to northeast, each being a conduit for moderate/heavy rainfall. Expect the eastern third of the nation to be quite wet, particularly from the central/eastern Gulf Coast up along the southern/central Appalachians. Recent forecasts indicate the possibility of 2 to 5 inches of rainfall through Thursday evening with isolated higher amounts likely. With that said, a multi-day excessive rainfall outlook covers these regions given the enhanced threat for flash flooding. Besides the hydrologic threats, severe thunderstorms are likely from the Arklatex to locations west of the Appalachians. Per recent Storm Prediction Center outlooks, an enhanced risk for tornadoes, wind, and hail exists over areas of the lower Mississippi Valley, mid-South, and Tennessee Valley. An active storm track carrying multiple systems from the northeastern Pacific into the Pacific Northwest and Upper Intermountain West will maintain cool and unsettled conditions through Christmas Eve. Snow levels should gradually lower as a strong upper trough digs into northwestern California by Thursday morning. The persistence of onshore flow and strong lift via each Pacific disturbance will spread abundant precipitation over much of the western U.S. Lower elevations are likely to remain rain throughout the event with wintry precipitation across interior valleys and mountain locales. The Cascades can expect 2 to 3 feet of snow through Thursday while other adjacent ranges should see slightly lower amounts in the 1 to 2 foot range. Given the deep amplified flow across the country, temperature anomalies are quite impressive, particularly with the warmth. Recent forecasts indicate daily temperatures could reach 25 to 35 degrees Fahrenheit above normal range from the Mississippi River eastward. This is especially the case north of interstate 40. This could bring high temperatures on Christmas Eve into the 70s as far north as New York City with 60s up to northern Vermont. Just as impressively, the overnight lows on Thursday morning should be in the 60s all the way up to the lower Ohio Valley and Mid-Atlantic. Rubin-Oster Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php