Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 333 AM EDT Tue Aug 24 2021 Valid 12Z Tue Aug 24 2021 - 12Z Thu Aug 26 2021 ...Hot and humid throughout much of the central and eastern United States, with dangerous heat returning to the Southwest by Wednesday... ...Scattered showers and a few severe thunderstorms possible from the northern and central Plains into the Midwest over the next few days... Sultry conditions are expected throughout much of the central and eastern U.S. through at least Thursday as an expansive and relatively strong ridge of high pressure builds across the south-central part of the country. As a result, dangerously hot weather is once again possible over the Lower Mississippi Valley. Excessive Heat Warnings have been issued for the Mississippi Delta region, where heat indices look to soar into the 110-115F range. Heat Advisories extend into eastern sections of the central and southern Plains, as well as northward into the Middle Mississippi Valley. Above average temperatures are forecast nearly everywhere east of the Rockies (the lone exception being the Northern Plains) as highs reach into the upper-80s and 90s for most locations early this week. Meanwhile, highs may reach the triple digits across parts of Kansas and Oklahoma today. While only a handful of daily high temperatures records are at risk of breaking, a plethora of warm minimum temperature records could fall thanks to high humidity levels keeping overnight temperatures very warm. These warm nighttime temperatures in the 70s can be particularly dangerous for those without access to proper air conditioning. Unfortunately, the large dome of upper level high pressure will continue to deflect cold fronts attempting to usher in a cooler and more refreshing airmass found to the north, keeping much of the South and east-central U.S. hot and muggy this last full week of August. Not to be left out, the Southwest will also begin to see dangerous heat build back into the forecast by Wednesday as the aforementioned ridge stretches into the region. Afternoon high temperatures may reach up to 115F on Wednesday, which has triggered Excessive Heat Watches to be issued for southwest California and southern Arizona. Elsewhere, two separate rounds of showers and storms are set to impact the north-central United States over the next few days. The first wave associated with an approaching cold front is already responsible for a line of severe thunderstorms entering central Minnesota this morning. These thunderstorms may continue to progress east-southeast throughout the day today and potentially produce damaging wind gusts and isolated tornadoes across the Upper Midwest. A few isolated severe thunderstorms could develop farther south and into the Central Plains along the cold front as well. By Wednesday, the same frontal boundary is expected to lift north as a warm front over the Central Plains as an approaching upper level trough enters the Northern Rockies. This could spell more chances for isolated severe storms throughout the northern and central Plains. While heavy rain could cause localized flash flooding, much of this section of the country from the northern High Plains to the Upper Midwest is experiencing severe to exceptional drought and will likely welcome every drop of rain that falls. Farther south and east, typical widely scattered summer thunderstorms are forecast across the Southeast and Gulf Coast, with the main hazard associated with heavy rain. The slow movement of these storms could lead to isolated instances of flash flooding. Snell Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php