Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 341 PM EDT Mon Aug 23 2021 Valid 00Z Tue Aug 24 2021 - 00Z Thu Aug 26 2021 ...Tropical Depression Henri to become post-tropical later today and track over southern New England this evening; threat for flash flooding to persist into the overnight hours... ...Dangerous heat forecast across the Lower Mississippi Valley, with hot and humid weather expanding across much of the central and eastern United States as well... ...Scattered showers and a few severe thunderstorms possible from the northern and central Plains into the Midwest... Tropical Depression Henri continues to drench parts of the Northeast this afternoon. Areas of heavy showers and thunderstorms have led to the issuance of several Flash Flood Warnings with potentially more areas of flash flooding likely to transpire this evening. WPC maintains a Moderate Risk (level 3/4) of excessive rainfall between southeast New York and portions of interior New England. Flood Watches also remain in effect through this evening. Henri will become a post-tropical storm later this afternoon while drifting east across southern New England later this evening. By Tuesday afternoon, all associated hazards with Henri will exit stage right into the northwest Atlantic Ocean with mostly dry conditions a "sight for sore eyes" on Wednesday. Sultry conditions are expected throughout much of the central and eastern U.S. through midweek as an expansive and relatively strong ridge of high pressure builds across the south-central part of the CONUS. As a result, dangerously hot weather is possible over the Lower Mississippi Valley. Excessive Heat Warnings have been issued for the Mississippi Delta region, where heat indices look to range between 110-115F. Heat Advisories extend into eastern Oklahoma and Kansas, as well as northward into the Middle Mississippi Valley. Above average temperatures are forecast nearly everywhere east of the Rockies (lone exception being the northern High Plains) as highs reach into the upper-80s and 90s for most locations early this week. 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 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 cooler and more refreshing humidity levels to the north, keeping much of the South and east-central U.S. hot and muggy into the second half of the week. Elsewhere, an area of low pressure and its associated frontal boundaries are forecast to swing across the Northern Plains and Upper Great Lakes between today and Wednesday morning. Scattered showers and a few severe thunderstorms are possible throughout the northern/central Plains and Midwest, with much of the activity on Tuesday located over the Upper Midwest and Great Lakes. By Wednesday afternoon, a new wave of low pressure figures to produce more spotty thunderstorms, some of which could be severe, in the northern and central High Plains. Farther west, Red Flag Warnings and Fire Weather Watches for much of Wyoming, southwestern South Dakota, and northwestern Nebraska due to the combination of gusty winds and low relative humidity. There are also Air Quality Alerts in place for parts of the Intermountain West and Pacific Northwest due to ongoing bouts of wildfire smoke in these areas. Mullinax Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php