More active weather is expected in the Southeast on Monday as a frontal boundary extending from southern Louisiana through the Southeast becomes nearly stationary.The frontal boundary will pull warm, gulf moisture into the Southeast and kick up more rain and scattered thunderstorms in the Gulf Coast States through the afternoon. Daytime heating and unstable atmospheric conditions will support a marginal threat for severe weather activity across the Gulf Coast States.While, warm and active weather continues to the south of the frontal boundary in the Southeast, cold weather will continue to grip areas to the north of the boundary. Temperatures across the Midwest, Northeast, Eastern Valleys and the Mid-Atlantic will remain below normal. Cold temperatures over the nation's mid-section will support snow showers in parts of the Central and Northern Plains as disturbances from the West move eastward.In the West, a cold front from the West Coast will move through the Intermountain West, bring snow showers and strong wind to the Central Basin. Moist onshore flow will continue to stream across the Northwest Coast, creating more chances for rain and high elevation snow in the Pacific Northwest and northern California.Temperatures in the Lower 48 states Sunday ranged from a morning low of -12 degrees at Tomahawk, Wis., to a high of 91 degrees at Plant City, Fla.