Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 346 PM EDT Thu Jul 18 2013 Valid 00Z Fri Jul 19 2013 - 00Z Sun Jul 21 2013 ***Heat wave for the Eastern U.S. abating by Saturday*** ***Showers and storms over the Southern Rockies*** ***Showers and storms near Canadian border with a cold front*** The heat and humidity is here for a few more days for the Eastern U.S., including the Mid-Atlantic, Northeast, Ohio Valley, and Midwest. Heat advisories and a few excessive heat warnings are in effect from parts of the Upper Midwest all the way to southern New England. A large upper level ridge and sinking air in the lower atmosphere are causing the hot conditions. Although this is the hottest weather so far this season, it is less than the extreme heat observed last summer over these areas. Relief is in sight by this weekend as the upper level ridge breaks down and a cold front approaches from the Great Lakes. The upper level low and associated trough that has been making a rather anomalous transcontinental retrogression westward is now over southern Arizona and 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 to numerous showers and thunderstorms for much of the Four Corners region for the remainder of the week. Elsewhere, strong to severe thunderstorms are a good possibility 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, 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