Tropical System Moving through the Caribbean; Heavy Rain in the Plains Across the Mid-South; Dangerous Heat in the West - Tropical Storm Isaias is impacting the Greater Antilles. Heavy rain with life-threatening flash flooding and mudslides are expected in Puerto Rico and the U.S. Virgin Islands through Friday. Meanwhile, heavy rain will also be possible in portions of the Plains to the Tennessee Valley. Finally, Excessive heat warnings are in effect for the Northwest and Southwest.