Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 400 AM EDT Sat Jun 03 2017 Valid 12Z Sat Jun 03 2017 - 12Z Mon Jun 05 2017 ...Strong to possibly severe thunderstorms are expected to move across the Northern Tier during the weekend... ...Heavy rain over parts of Texas could lead to flash flooding... Some unusual changes in the synoptic pattern is in store especially for the northeastern U.S. during the next few days. First of all, a frontal system associated with an occlusion-like low pressure system is currently pushing showers and thunderstorms into the upper Midwest this Saturday morning. With a blocky pattern already in place across much eastern Canada, this system is forecast to dip southeastward across the Great Lakes on Sunday and will begin to interact with an upper-level low and a cool air mass surging down from James Bay. This complex interaction will strengthen the low pressure system as it heads towards New England Monday morning. Showers and thunderstorms are expected to advance well ahead of the low pressure center reaching western New England on Sunday and possibly into Maine on Monday. Meanwhile, typical summer heat will continue across the Deep South. An upper-level low will support the formation of showers and thunderstorms over the southern Plains today. Some thunderstorms could be heavy enough to result in flash flooding over parts of Texas today. As the upper-level low drifts slowly to the east, showers and thunderstorms will shift slightly to the east each day, reaching the Mississippi Valley and the interior Southeast on Sunday, before heading northeastward into the Appalachians on Monday as the upper-level low begins to merge with the low pressure system over the Great Lakes. Out West, a front will begin to form the Intermountain Region on Sunday before heading steadily across the northern Rockies and the northern High Plains on Monday. Showers and thunderstorms will begin to develop over parts of the area overnight Saturday into much of Sunday. Kong Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php