Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 445 AM EDT Tue Jun 18 2024 Valid 12Z Tue Jun 18 2024 - 12Z Thu Jun 20 2024 ...Significant heavy rain/flash flooding threat with gusty winds well ahead of Potential T.C. One expected to impact southern Texas on Wednesday... ...More rounds of heavy rain and severe thunderstorms expected for the northern Plains and upper Midwest today before shifting south into the central Plains on Wednesday... ...A heat wave will persist over the Great Lakes, Ohio Valley and the Northeast through midweek... ...Late-season wet snow continues across the high-elevations of the northern Rockies today before tapering off early on Wednesday... An active weather pattern continues across the U.S. mainland. This weather pattern that features snow, heat, heavy rain, severe thunderstorms, strong winds, and fire weather is now bringing Potential Tropical Cyclone One in the midst. A low pressure system currently intensifying along a frontal boundary is fostering another round of heavy rain and severe thunderstorms across the northern Plains into the upper Midwest early this morning. The potent upper trough and the associated dome of cold air have continued to result in a round of late-season wet snow across the higher-elevations of the northern Rockies together with rather strong wind gusts. With less potent jet stream energy behind this system, the low pressure system will quickly eject into southern Canada by this evening, bringing the inclement weather across the northern Plains to an end by Wednesday morning. However, a sharp front trailing south and southwest from the low center will likely trigger an axis of heavy rain and severe thunderstorms from the central Plains to the upper Midwest by tonight into Wednesday morning. From Wednesday into Thursday morning, the rain/storms should gradually become more scattered in nature across the central Plains as a cool high pressure system passes to the north. This high pressure system will also push the widely scattered showers and embedded thunderstorms farther east into the lower Great Lakes and interior New England through Thursday morning. In stark contrast to the cool, windy, rainy and even snowy weather in the West, a heat wave will settle and persist across the Great Lakes, Ohio Valley and the Northeast through the next few days. Forecast highs today and Wednesday will reach into the mid- to upper 90s, even the century mark Wednesday and Thursday afternoon at the hottest locations in interior northern New England. Widespread, numerous record-tying/breaking high temperatures are possible. Additionally, morning lows will remain in about the mid-70s, at record-tying/breaking levels, providing little relief from the heat overnight. The early arrival of this magnitude of heat, the duration, abundant sunshine, and lack of relief overnight will increase the danger of this heatwave beyond what the exact temperature values would suggest. This is especially true for those without adequate air conditioning, which becomes more of a concern for locations further north that are not as accustomed to periods of persistent heat. Another big weather story over the next couple of days will be in the Gulf of Mexico where the National Hurricane Center has already initiated advisories on Potential Tropical Cyclone One. An elongated upper trough digging into the southern Plains and northeastern Mexico has already drawn a plume of tropical moisture northward into the central Gulf Coast region. This upper trough will be instrumental in drawing the tropical moisture well north of the center of PTC One into southern Texas mainly on Wednesday as PTC One tracks west toward northern Mexico. An axis of very heavy rain may develop just inland of the Texas coastline behind a coastal front with dynamic support from the elongated upper trough. This pattern could result in locally heavy rainfall in excess of 10 inches near or just inland of the lower to middle Texas coast which would result in significant flash flooding. The heavy rain is forecast to push farther inland across the Rio Grande Valley early on Thursday. In addition to the heavy rainfall, some coastal flooding along with tropical-storm-force winds can be expected up the Texas coast on Wednesday. See the latest advisory from the National Hurricane Center for additional detailed updates. Meanwhile, fire danger across the Four Corners region should gradually ease over the next few days with the arrival of slightly cooler air followed by the arrival of moisture from the northern edge of Potential Tropical Cyclone One. Kong/Putnam Graphics available at https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php