Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 400 PM EDT Fri Jun 17 2016 Valid 00Z Sat Jun 18 2016 - 00Z Mon Jun 20 2016 ...Cool and pleasant weather returns to the eastern U.S. as heat culminates to record levels in the Desert Southwest...excessive heat in the central Plains as well... ...Scattered thunderstorms expected for the Deep South over the weekend... ...Showers and thunderstorms expected for the northern Rockies into the northern Plains before cooler air arrives... The weather pattern across U.S. this weekend will be dominated by a strengthening high pressure cell aloft, which signifies the building of the heat over a significant part of the country. In particular, heat advisories and excessive heat warnings are in effect for a good portion of the central Plains down into the Deep South and parts of the Southeast, as well as much of the southwestern U.S. In fact, high temperatures could approach record levels in Arizona on Sunday with readings soaring well up into the 110's. Meanwhile, heat indices are expected to be in the 110's as well in parts of the central Plains. Showers and thunderstorms will keep temperatures at bay in the Deep South as a cold front continues to drop unusually far south into Florida by Sunday. In contrast, unusually cool air for this time of the year is spreading southward from the Northeast into the eastern U.S. This will provide fine and pleasant conditions across much of the eastern U.S. this weekend. Over the Northwestern part of the country, an upper-level low is pushing farther eastward into the northern Rockies. A low pressure center is expected to form in Montana. Showers and thunderstorms are forecast to form in the high terrain of western Montana late Saturday and spread eastward into the northern Plains on Sunday. This will be followed by cooler conditions as a cold front moves across the region. Kong Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php