Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 354 AM EDT Sat Jun 29 2024 Valid 12Z Sat Jun 29 2024 - 12Z Mon Jul 01 2024 ...Severe thunderstorm and heavy rain threat enters the lower Great Lakes and northern Mid-Atlantic today before sliding to the East Coast on Sunday... ...Unsettled weather remains throughout parts of the southern Rockies and Southwest over the next few days, while wet weather returns to the upper Midwest by Monday... ...Dangerously hot conditions will continue from parts of the southern Plains to the Southeast this weekend... A surface low pressure system currently crossing the upper Great Lakes and anticipated to swing through southeast Canada this weekend will help push a cold front into the lower Great Lakes by tonight. This cold front is expected to spark scattered strong to severe thunderstorms from the Ohio Valley to the lower Great Lakes and northern Mid-Atlantic, with damaging wind gusts and a few tornadoes the most likely weather hazards, particularly from eastern Ohio to central Pennsylvania. Heavy rain may also lead to instances of flash flooding throughout this region and into the interior Northeast. As the cold front nears the East Coast on Sunday, another round of robust thunderstorms are possible between the Southeast and New England, with some storms containing frequent lightning and gusty winds. This same frontal boundary will also be responsible for isolated to widely scattered thunderstorms extending westward across the mid-Mississippi Valley, central/southern Plains, and southern Rockies this weekend. The slow-moving nature of thunderstorms over the sensitive terrain of the southern Rockies and Southwest will create additional daily chances for flash flooding through at least early next week. More specifically, parts of northern New Mexico, southern Colorado, and southeast Arizona are most likely to be dealing with thunderstorms producing intense rainfall rates this weekend. The next upper-level trough to traverse the Intermountain West is forecast to spark thunderstorms across the northern High Plains on Sunday prior to spreading rainfall chances into the upper Midwest on Monday. Heavy rain is not welcome for much of the upper Mississippi and middle Missouri valleys as ongoing river flooding continues. However, the threat for another round of organized thunderstorms capable of containing intense rainfall rates and severe weather has prompted a Slight Risk (level 2/4) of Excessive Rainfall to be issued for much of the region on Monday. Dangerously high heat and humidity is forecast to continue across the south-central and southeastern U.S. through the start of July. High temperatures into the mid-to-upper 90s and low 100s can be expected, with heat index values up to 110 degrees throughout the lower Mississippi Valley and parts of the southern Plains. Overnight temperatures will not offer much relief and only dip into the low 80s and upper 70s. In fact, the warm overnight temperatures are forecast to break dozens of daily records and potentially a few June monthly records from the southern Plains to Mid-Atlantic. Much cooler weather and below average temperatures are forecast to follow high pressure as it builds southward from the northern Plains today to the Midwest and Great Lakes on Sunday. Comfortable high temperatures in the 70s with mostly sunny skies can be anticipated across these locations. Snell Graphics available at https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php