Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 331 PM EDT Fri Jul 19 2013 Valid 00Z Sat Jul 20 2013 - 00Z Mon Jul 22 2013 ***Heat wave for the Eastern U.S. abating this weekend*** ***Showers and storms over the Southern Rockies*** ***Strong and severe storms from Ohio Valley to the Northeast*** The heat and humidity that has been affecting the Eastern U.S., including the Mid-Atlantic, Northeast, Ohio Valley, and Midwest states, is forecast to abate by Sunday when a cold front arrives. Heat advisories and a few excessive heat warnings are in effect from Wisconsin all the way to southern New England. A large upper level ridge and sinking air in the lower atmosphere are causing the hot conditions. The upper level low and associated trough that has been making a rather anomalous transcontinental retrogression westward is now over northwest Mexico. This feature should gradually weaken and move towards the Baja California peninsula by Friday evening. This, in conjunction with the monsoonal flow, will help generate scattered showers and thunderstorms for much of the Four Corners region for the weekend Elsewhere, strong to severe thunderstorms are expected to develop from North Dakota eastward to the Upper Great Lakes and New England. This is where a cold front will begin moving towards the southeast and bring badly needed relief to those affected by the ongoing heat wave. The showers and storms should reach the East Coast by Saturday night, and this will mark the beginning of a welcomed pattern change for the Eastern U.S. D. Hamrick Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php