Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 400 AM EDT Thu May 27 2021 Valid 12Z Thu May 27 2021 - 12Z Sat May 29 2021 ...A low pressure system will bring strong to severe thunderstorms from the central Plains eastward toward the central/southern Appalachians into Friday... ...The same low pressure system will bring moderate to heavy rain for parts of the Northeast and possibly severe thunderstorms for the Mid-Atlantic by the Memorial Day weekend... A developing low pressure system currently in the central High Plains will be the main weather maker for the central and eastern U.S. as we head into the Memorial Day weekend. Showers and thunderstorms will generally expand eastward into the Midwest today ahead of the low pressure center while additional thunderstorms clusters are expected to form across the central Plains today ahead of a cold front. Some of these thunderstorms are expected to become severe. In addition, heavy downpours from the thunderstorms could result in flash flooding. By later on Friday, the low pressure system is forecast to move across the central Appalachians. Showers and thunderstorms over the Ohio and Tennessee Valley early on Friday will move to much of the East Friday night near the advancing cold front. Thunderstorms over the Mid-Atlantic could be severe Friday night. Meanwhile, moderate to heavy rain is forecast to develop across southern New England early on Saturday as new low pressure center is forecast to form off Long Island. A strong cold front trailing off a deep Canadian low pressure system will pass through the Northeast overnight. Ahead of the front warm temperatures and shortwave instability are expected to aid the development of showers and thunderstorms, some of which may become severe and produce damaging winds. Behind the cold front a high pressure system in southern Canada is forecast to build and spread east, transporting colder arctic air south into the northern Great Plains, Midwest, and Northeast. On Thursday and Friday, daily highs across these regions will likely drop as much as 15 to 20 degrees below normal into the 50s and 60s. Out in the Pacific Northwest, a low pressure system moving onshore Thursday morning will bring widespread rain to the area, with mixed precipitation and even some wet snow possible in the northern Cascades. As the system moves inland the rain is forecast to expand eastward into the northern Rockies, some of which may transition into wet snow at higher elevations overnight as temperatures drop behind a cold front. The northern Cascades could see wet snow lingering into Friday morning as well. Kong Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php