Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 348 AM EDT Sun Jun 24 2018 Valid 12Z Sun Jun 24 2018 - 12Z Tue Jun 26 2018 ...Increasing chances for severe thunderstorms across the center of the country on Sunday... ...Flash flooding concerns should generally focus over vast sections of the central U.S. into the Middle Mississippi Valley... ...Well below average temperatures expected to follow an upper low moving from the Northern/Central Rockies into the Upper Midwest... ...Locally heavy rainfall possible across south Florida and the coastal Carolinas... A sharpening upper trough currently traversing across the Central Rockies will eventually emerge over the adjacent High Plains by this evening. With a very moist and unstable air mass in place across the central U.S., widespread convection should unfold during the height of the diurnal heating cycle. Evolving thunderstorms will likely be severe weather producers based on the latest Storm Prediction Center outlook. As of early this morning, an Enhanced Risk stretches over the Oklahoma/Texas panhandles into parts of central Oklahoma and Kansas. All severe hazards are possible with damaging winds and large hail being the main concerns although a few tornadoes cannot be ruled out. Gradually a broader wind threat should extend over locations to the east during the overnight hours as the storms take on a more progressive mode. By the following day, the parent surface low will track into Iowa with the threat for severe weather accompanying this relocation. In addition to the severe aspects of this dynamic upper trough, flash flood concerns will be widespread over a majority of the central U.S. Slow movement of individual thunderstorm clusters or areas of repeat activity should provide mechanisms to enhance the flash flood potential on Sunday. Additionally, many pockets of the outlook area have seen heavy rainfall the past week with recent totals around 300-600 percent above normal for mid/late June. As a result, rapid runoff with these heavy precipitation producing thunderstorms could lead to numerous hydrologic issues. While the initial threat begins across the middle of the country on Sunday, it should translate into the Middle Mississippi Valley and back into Missouri thereafter. With a slow-moving upper low carrying a path from the Northern/Central Rockies toward the Upper Midwest the next couple of days, below average temperatures will follow suit. Extensive cloud cover underneath the low center should ensure highs will hold in the 60s across the higher terrain and 70s into the north-central U.S. which is roughly 10 to 15 degrees below climatology. Farther east, the Great Lakes should see similar departures as a secondary cold front sags southward from Ontario. On the flip side, the warmest conditions should prevail across the western U.S. in advance of a potent cold front pushing inland. This should raise the mercury to near the century mark across the Central Great Basin on Monday. Elsewhere, a combination of abundant moisture in place with local sea breeze effects should spread heavy rainfall over sections of south Florida. Heaviest amounts are likely to focus over southwestern Florida out toward the Everglades. Farther north, unsettled conditions are forecast to prevail over the coastal Carolinas on Monday. This is in response to a series of disturbances overriding a stalled frontal zone extending offshore. Otherwise, conditions should begin to improve over the northeastern U.S. to start the week as a surface ridge drops down from Ontario. Rubin-Oster Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php