Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 358 AM EDT Wed May 15 2013 Valid 12Z Wed May 15 2013 - 12Z Fri May 17 2013 ...A threat for severe thunderstorms exists across Central Texas on Wednesday... ...Unsettled conditions should persist from the Middle Mississippi Valley into the Ohio Valley along a stalled front... A slow-moving upper trough ejecting out of the Southern High Plains is expected to continue fueling numerous showers and thunderstorms this morning across Central Texas. The better activity should occur during the peak heating of the day as the air further destabilizes. Additionally, some of the storms may become locally severe as indicated by the Storm Prediction Center outlook. As the entire system gradually makes its way toward the north and east, convection should spread toward the Ozarks and Lower Mississippi Valley. One limiting factor is the fact there is no identifiable region of surface convergence over the region as much of the activity is being driven by the mid-level disturbance itself. The other region of active weather across the country is with a stalled frontal zone stretching from the Central Plains through the Middle Mississippi Valley and into the Ohio Valley. A surface anticyclone positioned across the Southeastern U.S. will continue to draw abundant Gulf moisture northward given the broad clockwise flow. Moisture intercepting this stationary front should drive periods of light to moderate rainfall throughout the period. Weak mid-level impulses emerging off the Front Range of the Rockies will provide additional focus for pockets of stronger convection. Such unsettled conditions are expected to continue through late in the work week as the boundary does not move a whole lot the next 48 to 60 hours. To the south of this frontal zone, abundant warmth is forecast with highs soaring into the 80s. However, this is in stark contrast to the near 100 degree readings seen yesterday over the Middle Mississippi Valley and Upper Midwest. Elsewhere, an occluded system working its way through New England this afternoon and evening will bring increasing chances for widespread rainfall. While a bulk of the activity should wind down by Thursday morning, an upper trough overhead will keep scattered showers possible over Upper New England through Thursday night. Looking out west, a series of Pacific systems tracking inland is forecast to bring scattered showers over the region. Overall moisture content is limited so the expected rainfall amounts are rather light. Rubin-Oster Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php