Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 320 AM EST Fri Dec 20 2013 Valid 12Z Fri Dec 20 2013 - 12Z Sun Dec 22 2013 ***Bad weather expected over much of the Central U.S.*** ***Significant warming trend for the Eastern U.S.*** ***Another storm system moving into the Pacific Northwest*** The weather pattern over the Southern Plains to the Midwest states will be quite active for Friday and into the weekend. A strong frontal boundary will separate a maritime tropical airmass from a polar continental airmass. This boundary is expected to extend from northern Texas northeastward to the northern Ohio Valley and into central New England. Multiple waves of low pressure along the front will help to generate periods of mainly light precipitation. There will be a very big difference in temperature across this boundary. An upper level trough approaching from the Desert Southwest will move eastward and energize the frontal boundary and associated surface trough by early Saturday. These systems are expected to merge over the Southern Plains and allow for an anomalous surge of moisture from the Gulf of Mexico ahead of the main cold front. Widespread heavy rainfall is expected from Arkansas to Ohio where numerous flood watches are in effect. Farther to the south, a severe weather threat exists for Saturday and Saturday night over the Deep South and Central Gulf Coast with increasing wind shear aloft and greater instability. Elsewhere across the United States, a major warm-up will be enjoyed by many from the Deep South to the Northeast U.S. before the cold front arrives by the end of the weekend. Strong southerly flow around a surface high off the Atlantic coast will bring temperatures up well into the 60s and 70s for many areas, along with increasing humidity. Record high temperatures are possible in some areas. Over the Pacific Northwest, another shortwave moving inland from the Pacific Ocean will bring another round of steady precipitation to Western Canada, Washington, Oregon, and the Northern Rockies. D. Hamrick Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php