Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 335 PM EDT Tue Jul 27 2021 Valid 00Z Wed Jul 28 2021 - 00Z Fri Jul 30 2021 ...Excessive Heat Warning over parts of the Northern High Plains; Heat Advisory over parts of the Lower Mississippi Valley/Southern Plains, Northern/Central Plains, and the Northern High Plains... ...There is a Slight Risk of excessive rainfall over parts of the Upper Midwest/Upper Great Lakes Wednesday through early Thursday and for the Southeast through Wednesday morning... ...There is a Slight Risk of severe thunderstorms over parts of the Upper Midwest and the Lower Great Lakes through Wednesday morning... Hot conditions will persist across portions of the Northern High Plains, Central and Southeast U.S. - this vast area has Heat Advisories in place from central Montana to central Georgia with pockets of Excessive Heat Warnings over northeast Oklahoma, eastern Montana and north-central Wyoming, as well as, Excessive Heat Watches over parts of Minnesota and Iowa. Daily temperatures will rise into the upper 90s to low 100s. Several regions have Air Quality Alerts due to Canadian wildfires and the wildfires over the Northwest into the Northern Rockies. The hot and dry airmass over the West has weakened the impact of the Southwest Monsoon but there will be an uptick expected in the risk for excessive rainfall by Friday. Showers and thunderstorms will continue over the Southwest, Central/Southern Rockies, and Great Basin through Thursday, becoming more diurnal. Marginal Risk areas are in effect through Thursday and a Slight Risk is in effect for parts of Arizona on Friday. A front extending from the Northeast, across the Great Lakes and into the Northern High Plains will have multiple waves of low pressure traverse through this boundary as it sags southward. This boundary will provide focus for showers and thunderstorms to develop near it and some may become severe. SPC has issued a Slight Risk of severe thunderstorms over parts of the Upper Midwest and the Lower Great Lakes through Wednesday morning; frequent lightning, strong wind gusts, hail, and minimal risk of tornadoes are possible. This threat will translate to the Upper Great Lakes/Upper Mississippi Valley on Thursday. Heavy rainfall and flash flooding will also accompany these severe storms. WPC has a Slight Risk for excessive rainfall in effect. Another front extending from the Mid-Atlantic region across the Ohio/Tennessee Valleys into the Northern Plains will begin to weaken. Tropical moisture will pool over the Southeast, Lower Mississippi Valley and the Southern Plains and will aid in the development of showers and thunderstorms as pulses of energy pass through in the mid/upper atmosphere. Periods of heavy rain are expected and may lead to an increase risk for flash flooding. Campbell Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php