Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 346 AM EDT Thu Jul 11 2019 Valid 12Z Thu Jul 11 2019 - 12Z Sat Jul 13 2019 ...Tropical threat looming over the northern Gulf of Mexico... ...The risk of very heavy rainfall and significant flash flooding will be increasing along the central Gulf Coast and the lower Mississippi Valley by the end of the week and into the weekend... ...Severe thunderstorms, locally heavy rain and some flash flooding will be possible today across the lower Great Lakes, upper Ohio Valley, and the central and northern Mid-Atlantic region... An area of low pressure over the northern Gulf of Mexico will be strengthening through the end of the week over the warm waters of the northern Gulf of Mexico while moving slowly westward. The National Hurricane Center (NHC) is forecasting this system to develop into a tropical storm Thursday night, and into a hurricane Friday night as the system approaches coastal areas of southern Louisiana. The slow movement of this system will result in a long duration heavy rainfall threat along the central Gulf Coast and inland through the lower Mississippi Valley through the weekend and into early next week. Flash flooding and river flooding will become increasingly likely, some of which may be significant, especially along and east of the track of the system. Please refer to the latest NHC forecast advisory for the latest information on this system. Meanwhile, another low pressure system moving across the Great Lakes will drive a cold front eastward across the lower Great Lakes and Ohio Valley today, and then across the Mid-Atlantic and Northeast through Friday. This will drive a rather large area of showers and thunderstorms across these areas which will include a threat for severe thunderstorms today across especially the lower Great Lakes, upper Ohio Valley and the northern half of the Mid-Atlantic. Locally very heavy rainfall and some flash flooding will be possible. Cooler weather is expected behind the cold front, with highs in the 70s to lower 80s over the western Great Lakes today, and the eastern Great Lakes and interior portions of the Northeast on Friday. A new cold front meanwhile ejecting out of the Northwest will be advancing east across the northern Plains and the Midwest by Saturday, and this will bring a threat of locally heavy showers and thunderstorms to these areas as well.. Elsewhere, increasingly hot temperatures are expected across the western United States going through the end of the week and into the weekend as high pressure strengthens over the Four Corners region. For today and Friday, high temperatures in the 90s will be commonplace, with temperatures locally exceeding 110 degrees across the Desert Southwest. Over the weekend, there will also be just a hint of some monsoonal moisture lifting north from the Gulf of California and adjacent areas of mainland Mexico, and this will scattered afternoon and evening showers and thunderstorms over the Four Corners region. Orrison Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php