Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 358 PM EDT Sat Mar 25 2017 Valid 00Z Sun Mar 26 2017 - 00Z Tue Mar 28 2017 ...There is a slight risk of severe thunderstorm over parts of the Lower/Middle Mississippi Valley/Central Gulf Coast/Tennessee Valley... ...Heavy rain possible over parts of the Tennessee Valley/Southern Appalachians... ...Rain/freezing rain possible over parts of the Upper Great Lakes and the Northeast... An strong low pressure system over the Middle Mississippi Valley will move northeastward across the Ohio Valley, weakening somewhat as it reaches the Great Lakes region Sunday night into Monday. Moisture from the Gulf of Mexico will stream northward into the Ohio Valley and pool along the associated stationary frontal boundary spanning eastward from the low into the Mid-Atlantic. Showers and thunderstorms will result, developing along and ahead of the potent cold front over the Middle/Lower Mississippi Valley that will move eastward to the Eastern Ohio Valley/Eastern Gulf Coast by Sunday. The Storm Prediction Center has outlined a portion of the Lower Mississippi Valley along the Gulf Coast as being in a slight risk for severe thunderstorm activity this afternoon/overnight. Please refer to their website for more information: www.spc.ncep.noaa.gov. Meanwhile any precipitation that occurs on the north side of the west-to-east oriented northern frontal boundary will be in the cold sector, and may result in some freezing rain across the Upper Great Lakes tonight/Sunday morning, and across the far northeast over the next couple of days. As this low pressure system progresses eastward, a secondary system over the southern Plains will strengthen, with the surface frontal systems merging during the day Sunday. This second system will bring yet another surge of warm unstable air into the central and southern Plains Sunday afternoon, strengthening as it shifts eastward toward the Mississippi River Valley Sunday night. These showers and thunderstorms are expected to continue spreading towards the Atlantic Coast as the system progresses Northeastward Monday into Tuesday as well. Once again, the Storm Prediction Center has outlined central Oklahoma and northeast Texas as being in a Slight and Enhanced region for severe weather development Sunday into Sunday night due to the strong instability related to this system. Meanwhile, an upper-level trough over the West Coast will move eastward to the Plains by Sunday evening. The system will produce rain and higher elevation snow over parts of the Pacific Northwest/California eastward to parts of the Northern Rockies/Great Basin that will move into parts of the Central/Southern Rockies and the Northern High Plains by Sunday morning. In addition, the rain and higher elevation snow will come to an end over parts of the Pacific Northwest/California into the Northern Rockies/Great Basin overnight Saturday into Sunday morning. By Sunday afternoon, rain and higher elevation snow will begin again over parts of the Pacific Northwest/California into Sunday evening as additional upper-level energy moves onshore over the West. Additionally, energy in the upper-level trough moving eastward across the Southwest/Southern Rockies will develop low pressure over the Southern High Plains overnight Saturday moving eastward to the Southern Plains by Sunday evening. The system will produce rain and higher elevation snow over parts of the Central Rockies/Central High Plains on Sunday morning. On Sunday afternoon into Sunday evening, showers and thunderstorms will develop over parts of the Southern/Central Plains. Ziegenfelder Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php