Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 346 AM EDT Wed Jul 17 2013 Valid 12Z Wed Jul 17 2013 - 12Z Fri Jul 19 2013 ...90 degrees or higher for many from the East Coast to the Plains today and Thursday... ...Slow improvement for western Texas into the Southwest, but continued cool and wet... The upper level pattern continues to feature a large upper level ridge over the eastern U.S. and a weakening closed upper level low over New Mexico, while the jet stream remains up north across southern Canada. The ridge is expected to expand westward through Thursday which will cause widespread heat for a large portion of the country. While this heat wave is nothing unusual for the middle of the summer, it will affect a large portion of the lower 48 with some locations flirting with 100 degrees across South Dakota and portions of Arkansas for Thursday. Scattered, diurnally driven showers and thunderstorms will be possible from the Great Lakes down into the Southeast and Florida, with the rest of the U.S. affected by the heat staying generally rain-free. Across the Southwest, the upper low will continue to weaken which should reduce the magnitude of widespread heavy rain and flash flooding, although flood concerns will remain across western Texas into New Mexico today. While temperatures beneath the clouds and wet weather will remain below average, high temperatures should get much closer to average by the end of the week. There is an end to the heat in sight though, as a cold front begins to drop south on Friday, bringing relief to much of the northern Plains along with a good chance of thunderstorms, with the potential for localized very heavy rain. Otto Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php