Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 405 PM EDT Wed Mar 28 2018 Valid 00Z Thu Mar 29 2018 - 00Z Sat Mar 31 2018 ...Heavy rain should begin to move out of the western Gulf states and the lower Mississippi Valley by Thursday night... ...Arctic air is expected to reach the northern Plains with steady snow across Montana and northern High Plains on Friday... An upper-level trough currently lifting out of the southern Rockies will soon merge with another broader upper-level trough dropping into the central Plains. This interaction will keep a couple of active boundaries to move very slowly eastward across the southern Plains into the lower Mississippi Valley, resulting in heavy rain and possibly severe thunderstorms to persist across these areas for the next couple of days. As the broader upper-level trough pushes further toward the south and east, the active boundaries and the associated heavy rainfall will begin to move faster eastward into the central Gulf states and then into the southern Appalachians Thursday night. This trough-front interaction will also initiate the deepening of a low pressure system which will ride up along a cold front and then accelerate northeastward across the Ohio Valley Thursday night and into northern New England on Friday. Rain will be the primary precipitation type along the Eastern Seaboard ahead of the cold front which should have adopted a steady eastward motion as it moves toward the Atlantic on Friday. Temperatures will rebound quickly into the 70's and 80's during the day on Thursday and Friday across the Mid-Atlantic while cooler 50's and 60's should prevail across the Northeast. Showers and thunderstorms along the Eastern Seaboard ahead of the cold front are not expected to be severe. The rain could end as wintry precipitation from the lower Great Lakes into the central Appalachians Friday morning. As the broard upper trough dips south and east toward the eastern U.S., colder air from Canada will penetrate further into the northern and central Plains during the next couple of days. The outer boundary of the cold air is forecast to become nearly stationary along the eastern slopes of the Rockies on Thursday as a colder surge of arctic air from Canada reaches the northern Plains Thursday night. Temperatures are expected to plunge as much as 30 degrees below normal during the day on Friday near the Canadian border as steady snow is forecast to develop across Montana Friday morning behind an arctic cold front. A low pressure system forming along the front will then spread the snow eastward into the northern Plains as the day progresses on Friday. The rest of the western U.S. should remain dry with a gradual warming trend. Kong Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php