Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 458 AM EDT Sat May 16 2015 Valid 12Z Sat May 16 2015 - 12Z Mon May 18 2015 ...Spring storm to bring strong to severe storms throughout much of the Great Plains today along with possible flash flooding from Texas into Oklahoma... ...Gusty winds and heavy rain, likely ending as snow, for the northern plains on Sunday... An expansive upper level storm system currently approaching the central Rockies will reach the southern and central High Plains today, likely resulting in a large area of thunderstorms extending from southern Texas to the U.S-Canadian border. These thunderstorms will have the potential to become severe, as highlighted by a moderate risk forecast by the Storm Prediction Center. Southerly flow out ahead of the system's cold front will draw warm and humid conditions northward from the Gulf of Mexico helping to provide ample instability...one necessary ingredient for severe weather. Flash flooding will also be possible as these storms organize later this afternoon from portions of central and northern Texas into central and eastern Oklahoma. Flash flooding rains will also be possible across portions of the central Gulf Coast and Lower Ohio Valley. Cold air to the west of the departing storm system will continue to allow locally heavy snow for the highest elevations of the Colorado and Wyoming Rockies today, with scattered thundershowers elsewhere across the West. The severe threat is expected to spread into the Upper Mississippi River Valley on Sunday with scattered thunderstorms extending down ahead the cold front into Texas, where the front and heavy rainfall will be slow to move. Low pressure associated with the storm system will strengthen while tracking from Nebraska to Minnesota, allowing winds to pick up in intensity, likely containing gusts between 30 and 40 mph to the northwest of the surface low across the northern plains during the day. These winds will also act to draw much colder air southward, likely allowing a changeover from heavy rain to heavy snow for North Dakota, with some light accumulations expected through Monday morning. As some of the heat and humidity from the center of the country spreads eastward, folks to the east of the Appalachians will begin to notice more summer-like conditions outside this weekend, along with a chance of thunderstorms. The exception to thunderstorms is expected to be across the coastal Carolinas, where high pressure will act to stabilize the atmosphere both today and Sunday. Otto Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php