Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 350 PM EDT Thu Jul 21 2016 Valid 00Z Fri Jul 22 2016 - 00Z Sun Jul 24 2016 ...There is a slight risk of severe thunderstorms from the Great Lakes to New England through Saturday morning... ...There is a slight risk of severe thunderstorms over the northern High Plains/Upper Mississippi valley through Friday morning... ...Heavy rain possible over parts of the Northern Plains, Upper and Middle Mississippi valley... ...Oppressive Heat over central U.S. will spread into the East through the weekend... A dome of high pressure over most of the southern and central tier of the country will maintain the oppressive heat wave through the weekend. Many locations will have apparent temperatures around 105 to 112 degrees F, which will be approximately 10 to 15 degrees above normal for the third week of July. Numerous heat advisories and warning are in effect from the Gulf states northward to the northern Plains and Upper Midwest. Tropical moisture streaming northward from the Gulf of Mexico, combined with strong daytime heating, will aid in producing showers and thunderstorms from parts of the Western Gulf Coast to the Southeast on Friday. Additionally, showers and thunderstorms will develop over parts of the Southwest/Eastern Great Basin and parts of the Central/Southern Rockies on Thursday and Friday afternoon into late evening due to monsoonal moisture and daytime heating. A front extending from eastern Canada through the Upper Great Lakes to the Central Plains and westward to the northern Rockies will advance eastward through the weekend. Showers and thunderstorms are expected to develop along and ahead of the boundary - some of the storms may become severe. Periods of heavy rain and flash flooding may also be possible. By Friday morning, showers and thunderstorms will develop along and ahead of the front associated with the wave of low pressure moving eastward out of the Northern Rockies/High Plains that will expand into parts of the Northern Plains by Friday evening. Onshore flow off the Pacific Ocean will help generate rain over parts of the Pacific Northwest through Friday evening. Campbell Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php