Heavy rain and flash flooding concerns across the northern Plains tothe upper Midwest......Focus for record hot temperatures will shift into the Mid-Atlantic bySaturday......Heat building over much of the West...Tropical Storm Alberto made landfall in Mexico this morning and continuesto spiral rainfall into South Texas, which will slowly diminish intoFriday. Some of the tropical moisture from Alberto will be drawn northwardand energize the scattered showers and thunderstorms from the southernHigh Plains to the Four Corners heading into the weekend. Theseshowers/storms will be more numerous during the late afternoon to earlyevening hours in these areas, and there is a Slight Risk of excessiverainfall in this area late this afternoon and again on Friday. Meanwhile,the National Hurricane Center continues to monitor the potential oftropical cyclone formation over the western Atlantic near the Bahamas as atropical wave moves west-northwestward in the general direction ofnortheastern Florida and coastal Georgia. Locally modest rainfall withsome breezy winds may affect this region later tonight through Friday.Across the northern Plains to the upper Midwest, rainfall will increaseover the area through Friday to the north of a frontal boundary. Rounds ofrain, heavy at times, over already saturated soils will increase thethreat for flash flooding. A Moderate risk of excessive rainfall has beenhighlighted for eastern South Dakota into southern Minnesota throughSaturday morning. Farther east, scattered thunderstorms are likely acrossthe Great Lakes region and the Northeast near and north of the easternextent of the front. Some severe thunderstorms are also possible per theStorm Prediction Center.The heat will continue to set records in parts of the Northeast with ashift into the Mid-Atlantic this weekend. Afternoon high temperatures andwarm overnight lows will challenge and exceed daily records for manylocations in the Ohio Valley eastward. Heat index readings are expected topeak from 100 to 105 degrees in many locations, and Heat Advisories are ineffect from Ohio to New Jersey. Those without access to reliable airconditioning are urged to find a way to cool down as very warm overnighttemperatures (only in the 70s) will prevent natural cooling and allow theheat danger to build over time indoors without air conditioning.Temperatures may be lower and less hazardous at the coast if/where seabreezes form. On Friday, cooler air will filter into northern New Englandbehind a slowly-moving cold front, but temperatures south of the boundarywill soar into the middle/upper 90s Friday and especially Saturday. Thesetemperatures may be the highest observed in several years for somelocations. In much of the West (West Coast and Great Basin/DesertSouthwest), temperatures will continue to heat up each day with 90s and100s quite prevalent by Saturday. Some daily record highs may bechallenged in Northern California into Oregon.