Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 338 AM EDT Mon Aug 23 2021 Valid 12Z Mon Aug 23 2021 - 12Z Wed Aug 25 2021 ...Tropical Depression Henri to linger across New England today and continue producing heavy rain that could result in numerous flash flood events... ...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 across the northern and central Plains into the Midwest over the next couple of days... After making landfall along the coast of Rhode Island yesterday, the center of Tropical Depression Henri has now pushed inland over the Northeast and continues to produce instances of moderate to heavy rainfall. Henri is expected to continue weakening today, while very slowly drifting back toward the east over southern New England. The main hazard associated with Henri today will be the threat of flash, urban, and river flooding. Additional rainfall amounts of 1 to 3 inches may fall over regions that have already seen several inches of rain in the last 24 hours, leading to added flooding concerns. WPC has issued a Moderate Risk (level 3/4) of excessive rainfall between southeast New York and Rhode Island, including Long Island. Flash Flood Watches are also in effect. Henri and all associated hazards are expected to exit the region on Tuesday. High heat and humidity are expected to swelter much of the central and eastern U.S. through midweek as a large and relatively strong ridge of high pressure is anticipated to build across the south-central section of the country. As a result, dangerously hot weather is possible over the Lower Mississippi Valley. Excessive Heat Warnings have been issued for the ArkLaMiss region, where heat indices could approach the 110-115F range. Heat Advisories extend into eastern Oklahoma and Kansas, as well as the Middle Mississippi Valley. Above average temperatures are forecast nearly everywhere east of the Rockies (outside North Dakota and the northern High Plains) as highs reach into the upper-80s and 90s for most locations early this week. Only a few daily high temperatures records are at risk of breaking, but numerous warm minimum temperature records could fall thanks to high humidity keeping overnight temperatures very warm. These warm nighttime temperatures can be particularly dangerous for those without access to proper air conditioning. Otherwise, an area of low pressure and 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. Farther west, Red Flag Warnings and Fire Weather Watches extend from northwest Colorado across much of Wyoming and into western South Dakota due to the combination of gusty winds and low relative humidity. Snell Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php