The energy for this storm is projected to drop south from the Pacific Northwest and strengthen as it enters the southern Plains. From there, it swings east and develops a negative tilt as it pushes northeast into the East Coast. The development of a negative tilt means the highest vorticity values at the 500 millibar level are positioned to the southeast. This is observed in the upper left hand panel of the above forecast image, which is valid for the night just before President's Day. Typically, negatively-tilted storm systems are watched in the spring, when cold air can run aloft and provoke stronger thunderstorms than positively-tilted storm systems. As you might guess, positively-tilted storm systems have their highest vorticity values tilted towards the Southwest. The presence of a negatively-tilted winter storm would likely increase precipitation totals as cold air runs aloft and convective snow bands are enhanced. Thundersnow would naturally be more widespread in the presence of cold air aloft.