Unsettled weather persists across the Northeast and Central U.S today......Hazardous heat possible across South Florida and South Texas this week......Significant flash flooding possible across portions of East Texas intothe Gulf States tomorrow and Friday...Several focused areas of stormy and unsettled weather can be expectedtoday across the central and eastern parts of the Lower 48 as a series offrontal systems gradually migrate eastward. Along the Eastern Seaboard,coastal low pressure located over the southern DelMarVa will maintainlocally heavy rainfall chances over Eastern Long Island and Coastal NewEngland through tomorrow morning, with 2-3" of rain and isolated flashflooding possible as the storm wraps up offshore. Much of this activity inthe Northeast will remain steady stratiform rainfall, with the bulk ofrobust thunderstorms being confined to parts of the Mid-Atlantic andSoutheast. Thunderstorm coverage will be more widespread across the Plainsstates this afternoon as a very warm and moist Gulf of Mexico airmass isdrawn northward ahead of a weak cold front. Severe weather is the bigstory there, as the Storm Prediction Center has an Enhanced Risk (level3/5) of severe thunderstorms across the Texas Panhandle and SouthernKansas. The same Gulf airmass will set the stage for a bout of unusually early hotweather in South Florida and Texas, with heat indices exceeding 100degrees possible. Owing to the combination of oppressive heat indices andforecast record warm overnight temperatures in these areas, majorheat-related impacts are possible with this round of hot weather throughthe work week according to experimental NWS HeatRisk guidance.The forecast remains on track for widespread heavy rainfall acrossportions of East Texas and West Mississippi tomorrow as repeatthunderstorm complexes track across the region, where a Moderate Risk(level 3/4) is in effect. Areal averages of 3 to 5 inches of rainfall isforecast for the Moderate Risk area, and locally higher amounts will bepossible, which suggests numerous instances of flash flooding are likelyas the region is very sensitive to any additional rainfall. The threat isexpected to roll into Friday with another Moderate Risk depicted oversouthern Mississippi and Alabama, as the environment is ripe for continuedthunderstorm development.