Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 300 PM EDT Sat May 18 2019 Valid 00Z Sun May 19 2019 - 00Z Tue May 21 2019 ...Severe thunderstorms and some flash flooding are expected across portions of the Plains, Mississippi Valley and Ohio Valley... ...Much cooler than average temperatures will continue for much of the Western U.S. and Northern Plains... An area of low pressure will develop over the Plains today and push northeast into the Great Lakes on Sunday. Meanwhile, a reinforcing shot of cold air will arrive into the west and lead to renewed low pressure development in the southern Plains on Monday. This will lead to several rounds of rain and thunderstorms along an active frontal zone. The first will spread from the Plains and Mississippi Valley today and tonight, into the Great Lakes and Ohio Valley on Sunday. The second round is expected in the central and southern Plains on Monday. Severe weather is likely with some of the thunderstorms, with damaging winds, large hail and tornadoes all possible. The risk will be highest on Monday in parts of Kansas, Oklahoma and Texas, when a significant severe weather event will be possible. The thunderstorms may also produce areas of flash flooding, particularly in the Upper Midwest today and tonight, and in the Plains on Monday. There is both a Moderate Risk of severe thunderstorms and flash flooding in parts of the Plains on Monday. As the reinforcing cold front arrives in the West tonight, precipitation chances will increase across much of the region. The colder air will enable snow to fall at the higher elevations. The snow accumulation is likely to exceed 12 inches in the highest elevations from the Sierra Nevada into much of the Intermountain West, particularly in ranges above 8000 feet. Some snow will also be possible in lower elevations of the Northern High Plains from eastern Montana and Wyoming into the western Dakotas. Much of the Eastern U.S. from the Mid Atlantic into the Southeast will see temperatures warmer than average and generally dry weather, with highs reaching into the 90s in some areas. Further north, parts of the Northeast may see some showers and thunderstorms, with temperatures also likely above average. To the north and west of the low pressure track and active frontal zone, temperatures will remain cooler than average from the West into much of the Northern Plains and Upper Midwest. High temperatures will be significantly below average, over 30 degrees in some areas, in the northern Plains. Lamers Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php