Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 352 AM EDT Wed Aug 21 2024 Valid 12Z Wed Aug 21 2024 - 12Z Fri Aug 23 2024 ...There is a Slight Risk of excessive rainfall over parts of the Southwest and Great Basin on Wednesday and expanding into parts of the Central/Southern Rockies on Thursday... ...There is a Slight Risk of severe thunderstorms over parts of the Northern High Plains on Wednesday... ...There are Excessive Heat Warnings and Heat Advisories over parts of the Southern Plains... A front over the Northern Rockies will move slowly eastward to the Northern Plains by Friday. The boundary will produce showers and severe thunderstorms over northeastern Montana and northwestern North Dakota. Therefore, the SPC has issued a Slight Risk (level 2/5) of severe thunderstorms over parts of the Northern High Plains through Thursday morning. The hazards associated with these thunderstorms are frequent lightning, severe thunderstorm wind gusts, hail, and a minimal threat of tornadoes. However, there is an increased threat of severe thunderstorm wind gusts 65 knots or greater. In addition, an upper-level low over the Northeast will help create rain with an embedded thunderstorm over parts of the Northeast through Thursday. Moreover, upper-level energy over the Middle Mississippi Valley will move southeastward to the Southeast, developing a weak upper-level low by Thursday evening. With ample moisture over the area, showers and thunderstorms will develop over parts of the Southeast through Friday. Furthermore, monsoonal moisture and upper-level energy will aid in producing showers and thunderstorms with heavy rain over parts of Arizona and southern Utah. Therefore, the WPC has issued a Slight Risk (level 2/4) of excessive rainfall over parts of the Southwest and Great Basin through Thursday morning. The associated heavy rain will create mainly localized areas of flash flooding, with urban areas, roads, small streams, low-lying areas, narrow canyons/gullies, and burn scars the most vulnerable. On Thursday, the monsoonal moisture will extend farther northward over the area. Likewise, the upper-level energy and monsoonal moisture will produce showers and thunderstorms with heavy rain over parts of southeastern Utah, northern Arizona, southwestern Colorado, and northwestern New Mexico. Therefore, the WPC has issued a Slight Risk (level 2/4) of excessive rainfall over parts of the Southwest, Great Basin, and Central/Southern Rockies from Thursday through Friday morning. The associated heavy rain will create mainly localized areas of flash flooding, with urban areas, roads, small streams, low-lying areas, narrow canyons/gullies, and burn scars the most vulnerable. Moreover, as the front over the Northern High Plains moves eastward on Thursday, showers and strong to severe thunderstorms will develop over parts of the Northern/Central Plains and the Central High Plains. Therefore, the SPC has issued a Marginal Risk (level 1/5) of severe thunderstorms over parts of the Northern/Central Plains and the Central High Plains from Thursday into Friday morning. The hazards associated with these thunderstorms are frequent lightning, severe thunderstorm wind gusts, hail, and a minimal threat of tornadoes. Elsewhere, as upper-level low moves southward along the Northwest Coast will develop rain over parts of the Pacific Northwest through Friday. Meanwhile, an upper-level high over the Southern Plains will allow high temperatures to be in the upper 90s and low 100s, with dew points in the upper 60s and low 70s, prompting Excessive Heat Warnings and Advisories over parts of the Southern Plains. Additionally, with low temperatures in the lower 80s and upper 70s, little relief from the heat will occur overnight. Therefore, people spending more time or effort outdoors or in a building without cooling in areas with heat warnings are still at an increased risk of heat-related illness. Ziegenfelder Graphics available at https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php