Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 347 AM EDT Thu Aug 22 2024 Valid 12Z Thu Aug 22 2024 - 12Z Sat Aug 24 2024 ...Record heat continues into the end of the week across the Southern Plains... ...There is a Slight Risk of excessive rainfall over parts of the Southwest, Great Basin, and Central/Southern Rockies on Thursday... ...Record cold develops across California Friday into Saturday... ...There are Excessive Heat Warnings and Heat Advisories over parts of the Southern Plains... A front over the Pacific Northwest Coast will move slowly eastward to the Northern High Plains to the Great Basin and then into Southeastern California by Saturday. The boundary will be on the leading edge of an upper-level trough, bringing colder temperatures in the mid-70s to California. The associated upper-level low will develop rain over parts of the Pacific Northwest and Northern California through Saturday. Furthermore, monsoonal moisture and upper-level energy will aid in producing 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 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. The threat of excessive rainfall will decrease slightly over the Four Corners Region on Friday. However, there will still be a threat of heavy rain. Therefore, the WPC has issued a Marginal Risk (level 1/4) of excessive rainfall over parts of the Southwest, Great Basin, and Central/Southern Rockies from Friday into Saturday morning. The associated heavy rain will create localized areas of flash flooding, affecting low-lying areas, narrow canyons/gullies, and burn scars that experience rapid runoff with heavy rain. Additionally, a second front extending from the Northern Plains to the Great Basin will move northward as a warm front over the Northern Tier States by Saturday. On Thursday, the boundary will produce showers and thunderstorms over parts of the Northern/Central Plains into parts of the Upper Mississippi Valley. The showers and thunderstorms will expand into parts of the Upper Great Lakes and Middle Mississippi Valley on Friday. Moreover, another upper-level low over the Northeast will help create rain with an embedded thunderstorm over parts of the Northeast through late Thursday night. Further, an area of upper-level energy moving into the Southeast will develop a weak upper-level low by Thursday evening. With ample moisture over the area and a lingering boundary, showers and thunderstorms will develop over parts of the Southeast through Saturday. Additionally, upper-level energy trapped under an upper-level high and moisture moving northward off the Gulf of Mexico will create scattered showers and thunderstorms over parts of the Southern Plains through Saturday. Meanwhile, the 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