Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 400 PM EDT Sat Jun 18 2016 Valid 00Z Sun Jun 19 2016 - 00Z Tue Jun 21 2016 ...Cool and pleasant weather continues for the East Coast as heat culminates to record levels in the Desert Southwest... ...Areas of thunderstorms expected for the Deep South... ...Showers and thunderstorms expected for the northern Plains into the Great Lakes before cooler air arrives... A high pressure cell aloft, signifying very warm temperatures at the surface, continues to strengthen and build eastward across the mid-section of the country. In particular, heat advisories are in effect for parts of the central Plains down into the Deep South with excessive heat warnings in effect for 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 to near 120 degrees! Meanwhile, heat indices are expected to reach the 110's 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 through Florida. In contrast, cool air for this time of the year continues to spread southward along the Eastern Seaboard. This will provide quite a fine and pleasant weekend across much of the eastern U.S. By Monday, temperatures are expected to rebound to near or above normal levels. Over the northwestern part of the country, an upper-level low is pushing farther eastward into the Intermountain region. A low pressure center forming in Montana is expected to spread showers and thunderstorms eastward across the northern Plains on Sunday. Some of the thunderstorms could become severe Sunday afternoon and evening. By Monday, the cold front associated with the low pressure system is expected to reach the Great Lakes with showers and thunderstorms extending down into central Plains. Cooler air will once again spread into the northern Plains behind the cold front. Kong Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php