Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 344 AM EDT Wed May 18 2016 Valid 12Z Wed May 18 2016 - 12Z Fri May 20 2016 ...Severe thunderstorms possible for parts of Texas... ...Heavy rain possible over portions of Texas and Louisiana... ...Temperatures will be 10 to 20 degrees below average from the Central Appalachians westward to the Central/Southern Rockies and Southern Plains... The southern Plains will be in a wet pattern through the end of the week. A deep upper-level trough will slowly track into the southern Plains while a steady southeast flow transports Gulf of Mexico moisture through the Southern Plains and into portions of the Desert Southwest. Widespread showers and thunderstorms will initiate along a nearly stationary boundary. High rainfall rates will likely occur over this region, which in turn, will increase the threat for flash flooding - excessive rainfall outlooks have been issued for portions of the southern Plains for today and Thursday. The Big Bend area of Texas into Southern Texas will be in a favorable environment for more organized convection today - the Storm Prediction Center has highlighted this area as having a slight risk for severe storms. The threat area will shift slightly westward for tomorrow as the upper level dynamics consolidate over Western Texas. Numerous rounds of showers and thunderstorms will likely train (move through the same area) over a broad area of Texas and western Louisiana on Thursday, which will maintain the elevated risk for rapid runoff and flash flooding. Numerous showers and thunderstorms will move through the Southeast today as a frontal boundary pushes through the Eastern U.S. Much of the Mid-Atlantic, Southeast and southern states will persist in having below normal temperatures. Many locations will have afternoon highs up to 20 degrees cooler than those typical for mid-May. A cold front will push through the northwestern states today and into the Intermountain West by Thursday afternoon. As it crosses the northern Rockies, it will strengthen resulting in much cooler temperatures infiltrating the region. The above normal temperatures will quickly moderate before turning below normal. Campbell Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php