Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 358 AM EDT Tue May 17 2016 Valid 12Z Tue May 17 2016 - 12Z Thu May 19 2016 ...Severe thunderstorms possible for most of Texas... ...Heavy rain possible over portions of Texas and Oklahoma... ...Temperatures will be 10 to 20 degrees below average from the Central Appalachians westward to the Central/Southern Rockies and Southern Plains... An upper-level low will sink southward over the Great Basin and into the Desert Southwest by midweek. Scattered to widespread showers and thunderstorms are forecast for the northern Intermountain West southward to the Great Basin/Southwest and eastward to the middle and lower Mississippi valley. Higher elevations of Utah, Wyoming and Colorado will likely have snow over the next few days. Unstable conditions over the southern Plains today will be conducive for strong to severe thunderstorm, particularly for Texas. Most of the state has a slight risk per the Storm Prediction Center, with an enhanced threat for the Hill country and adjacent counties. Heavy rain will be possible across this region as well, as slow storm motion is anticipated along the nearly stationary boundary that sets up over the area. Excessive rainfall outlooks encompass portions of Texas and Oklahoma today and tomorrow. Another Pacific system will track across the northwestern states on Wednesday and move inland to the Intermountain West on Thursday. Showers and thunderstorms will begin to spread from the Pacific Northwest to the northern Rockies Wednesday evening into Thursday. Snow is forecast in the Cascades with this system. Rain developing over parts of the Ohio valley will expand eastward into the Mid-Atlantic today as a weak boundary moves through the Great Lakes region - it will become absorbed into the precipitation shield moving eastward from the Mississippi Valley by this evening. Additionally, showers and thunderstorms will develop over parts of the Southeast through Wednesday as well along a sinking frontal boundary. Portions of the Eastern Seaboard could potentially be in a rather wet pattern by this coming weekend. An area of low pressure will develop along the Carolinas and will deepen as it lifts north and east further offshore. Wrap around moisture will be directed toward the coastal areas. Noticeably cooler temperatures will stick around for the southern and Mid-Atlantic states - many areas will have afternoon temperatures of 10 to 20 degrees below the mid-May averages. Campbell Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php