Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 356 PM EDT Wed Jun 19 2024 Valid 00Z Thu Jun 20 2024 - 00Z Sat Jun 22 2024 ...Heavy rain/flooding and gusty winds will continue at least through this evening in South Texas associated with Tropical Storm Alberto... ...Heavy rain and flash flooding concerns increase for the north-central U.S. later Thursday into Friday... ...A heat wave will persist over the Great Lakes, Ohio Valley, and the Northeast into late week... Tropical Storm Alberto has formed in the far western Gulf of Mexico and is forecast to make landfall in Mexico around Thursday morning. Alberto will have impacts extending into southern Texas north of its center of circulation, including tropical-storm-force winds and storm surge continuing through tonight and heavy rain/flooding concerns. These hazards are likely to be enhanced by surface troughing near the Gulf Coast that focuses the ample tropical moisture. Rainfall amounts of 5 to 10 inches are expected into South Texas, which could produce considerable flash and urban flooding along with new and renewed river flooding. Thus a Moderate Risk is in place in the Excessive Rainfall Outlook through tonight, with a Slight Risk in place for Thursday for South Texas. While Alberto should weaken rapidly over the higher terrain of Mexico on Thursday and reduce winds, the tropical moisture will stream north and trigger showers and thunderstorms across the southern High Plains and Four Corners region on Thursday and Friday, where Marginal to Slight Risks of excessive rainfall are highlighted. Meanwhile over the western Atlantic, moisture associated with a tropical wave could reach northeastern Florida and coastal Georgia Thursday night to Friday morning. Though the north-central U.S. is seeing a relative break in heavy rainfall today behind a cold front, renewed support for thunderstorms with heavy rain is likely there Thursday into Friday. Upper-level energy and the front stalling and drifting north will reinvigorate storms in central to northern parts of the Plains and Mississippi Valley into the Midwest. Moderate Risks of excessive rainfall have been introduced for eastern South Dakota into parts of Minnesota and western Wisconsin on Thursday into Friday, meaning numerous flash floods are likely. Antecedent conditions there are wet because of previous rainfall, so this contributes to flooding concerns. Farther east, scattered thunderstorms are likely across the Great Lakes region and Northeast. Marginal to Slight Risks are delineated each day from the Storm Prediction Center (mainly for the threat of severe wind but with some low chances for hail), and Marginal Risks of excessive rainfall are in place as well. All these rain and thunderstorm areas are taking place along the periphery of an upper ridge/heat dome that edges from the Mid-Atlantic into the Mid-South over the next couple of days, producing a record-breaking heat wave across the Great Lakes, Northeast, and Mid-Atlantic. Afternoon high temperatures and warm overnight lows will challenge daily records and even some monthly and all-time records. Heat index readings are expected to peak from 100 to 105 degrees in many locations. Those without access to reliable air conditioning are urged to find a way to cool down. Record warm overnight temperatures will prevent natural cooling and allow the heat danger to build over time indoors without air conditioning. Temperatures may be lower and less hazardous closer to the coast if/where sea breezes form. By Friday, conditions should improve over New England behind a cold front, but temperatures well into the 90s and higher heat indices are forecast to continue across the Ohio Valley to Mid-Atlantic. Meanwhile, cooler than average highs are likely into the southern High Plains with the clouds and rain forecast, but temperatures over the West will gradually rise above normal Thursday and Friday. Tate Graphics available at https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php