Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 333 AM EDT Mon Jul 21 2025 Valid 12Z Mon Jul 21 2025 - 12Z Wed Jul 23 2025 ...Dangerous heat wave to expand across the Central Plains, Mississippi Valley, and Southeast through mid-week... ...Thunderstorms to pose a flash flood threat in portions of the Southwest, Northwest, Midwest, Mid-South, and Southeast... ...Severe storms are likely in parts of the Midwest; Unseasonably cooler & comfortable conditions in the Northeast... The "Dog Days of Summer" are in full swing for most of the eastern two-thirds of the Lower 48. This is brought about by a strengthening heat dome originating over the Deep South that builds in over the Mississippi and Ohio Valleys by mid-week. Expect some localized daily record highs to be broken in the Southeast, with an even larger swath of daily record warm minimum temperatures. Heat indices from the Central Plains to the Southeast will range between 100-110F each day, with some locations reaching as high as 115F. For Monday, HeatRisk shows an expansive area of Major Impacts that are most common in the Southeast and Lower Mississippi Valley. By Tuesday, much of the Deep South on north through the Middle Mississippi Valley and into the Lower Missouri River Valley see Major Impacts according to HeatRisk. Extreme Heat Warnings are in place for parts of the Central Plains and Lower-to-Middle Mississippi Valley, while an expansive list of Heat Advisories spans from South Dakota on south and east to the Florida Peninsula. Look for the heat dome to expand east into the Great Lakes by Wednesday and Thursday. WPC continues to carry Key Messages for this impending heat wave. Please visit www.weather.gov/safety/heat for more information on tips for how to stay cool and safe when dealing with oppressive heat. Precipitation across the continental U.S. will be largely driven due to a "Ring of Fire" upper-level ridge pattern over the Southern U.S. and a series of disturbances traversing the northern tier of the U.S.. This ridge of high pressure is channeling rich Gulf moisture north into the Upper Midwest and ahead of an approaching cold front. There is also a pool of anomalous moisture and a stalled front over the Tennessee and Ohio Valleys today. WPC issued a Slight Risk (threat level 2/4) for flash flooding in portions of the Ohio and Tennessee Valleys today, with a Slight Risk in place for parts of the Upper Midwest on Tuesday. There are Flood Watches in effect for parts of the Middle Mississippi and Ohio Valleys through this afternoon. Meanwhile, there is also anomalous moisture over the Northwest and northern Rockies today. Thunderstorms could produce locally heavy rainfall amounts in parts of Washington and Oregon (east of the Cascades) and into the heart of Montana, prompting the issuance of a Marginal Risk (threat level 1/4) for flash flooding. The Southwest and Southeast also sport Marginal Risks for flash flooding today and Tuesday given the modest moisture and instability present. Speaking of instability, many of the aforementioned storms in the Northern Plains and Midwest have the potential to be severe today and Tuesday. The Storm Prediction Center (SPC) has a Slight Risk (threat level 2/4) in place over eastern Montana today, then over parts of the eastern Dakotas and central Minnesota on Tuesday. Isolated severe storms are also possible in the Central Plains and Southeast each day. Damaging winds and large hail are the primary modes of severe weather, although the Northern Plains could also contend with some tornadoes. Elsewhere, regions expecting cooler than normal temperatures and a more tranquil weather pattern to start the week are the Desert Southwest and Northeast. The Northeast will witness unusually cool and comfortable temperatures for late July with some communities in northern New England struggling to get above 70 degrees. This period of cool/comfortable conditions in the Northeast will be short lived as sultry conditions return by the second half of the work-week. Mullinax Graphics available at https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php