Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 209 PM EDT Mon Jul 15 2013 Valid 00Z Tue Jul 16 2013 - 00Z Thu Jul 18 2013 ...Heat wave to expand across much of the Midwest and the eastern U.S. through the middle of the week... ...Cool and wet weather with some potential for flash flooding is expected for the southern High Plains... A strong subtropical ridge of high pressure currently focused over the eastern U.S. will continue foster an expansive area of hot and humid weather over the next several days. In fact, the ridge of high pressure should tend to nose westward through the middle of the week across the Midwest and even out into the Plains states which will allow for the hot temperatures to expand in coverage and ultimately cover a rather large part of the central and eastern U.S. this week. The upper level low over Texas and Oklahoma is forecast to slowly drift west, reaching New Mexico by Wednesday morning and then gradually weakening. Moderate to locally heavy rainfall already impacting much of the southern Plains will tend to continue the next several days. The rainfall will be impacting drought-strict areas of the region, but there is some potential for flash flooding given locally very heavy rainfall rates which may result in some runoff problems. The rain and extensive cloud cover will also keep temperatures across the region quite cool for this time of the year, with some areas over 20 degrees below their average July temperatures. This moisture will also be advancing westward into the central and southern Rockies and portions of the Southwest, where it will promote additional afternoon and evening shower and thunderstorm activity. Across the East, temperatures will warm further and become downright hot, with temperatures reaching well into the 90's the next several days as the aforementioned subtropical ridge continues to build westward. The strong ridging will tend to suppress shower and thunderstorm activity for much of the East, but there will be scattered showers and thunderstorms across the Gulf Coast states. As low pressure tracks northeastward from southwestern Canada, it will take a cold front slowly across the north-central U.S. but the front will do little to cool off locations in its wake. Scattered thunderstorms are expected near the boundary in and around the upper Mississippi Valley through Tuesday where the greatest moisture and instability will be present, but widespread heavy totals are not forecast. Orrison Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php