747 FXUS01 KWBC 222000 PMDSPD Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 358 PM EDT Tue Sep 22 2026 Valid 00Z Wed Sep 23 2026 - 00Z Fri Sep 25 2026 ...Significant Heavy Rainfall/Flooding Threat across New Mexico and the Southern High Plains through Thursday... ...Heavy Rainfall/Flooding Threat across portions of the Ohio Valley, Mid-Atlantic, and Central/Southern Appalachians through Wednesday... A upper-level low/trough will dig into the Southwest and interact with both the Pacific and Gulf moisture, leading to showers and thunderstorms across portions of the Four Corners and the Southern/Central Plains/Rockies. The combination of deep tropical moisture, sufficient instability, and upper-level forcing will lead to high rainfall rates and excessive rainfall across portions of the Four Corners and western Texas tonight. Additionally, WPC maintains a Moderate Risk (at least 40% chance) of excessive rainfall for southern New Mexico, while a broader area of Slight Risk (at least 15% chance) covers much of New Mexico. The flash flooding threat is expected to increase on Wednesday, as the primary shortwave energy lifts northward through New Mexico. Therefore, the Marginal and Slight Risk for excessive rainfall will expand into the Central Plains, while a broad area of Moderate Risk will encompass much of eastern New Mexico. The southwest moisture will gradually transport northeastward along a slow-moving boundary, bringing showers and thunderstorms across the Northern/Central Plains into the Upper Midwest by late Wednesday into Thursday. Furthermore, a upper-level troughing over the Great Lakes will gradually shift eastward toward the Mid-Atlantic and Northeast, while the frontal boundary will settle southward across the Southern Plains into the Southeast, Ohio Valley, and Mid-Atlantic. A developing coastal low offshore will help maintain low-level moisture ahead of the slow-moving frontal boundary, supporting period of showers and thunderstorms from portions of the Ohio Valley/Mid-Atlantic into the Appalachians and Southeast. Pockets of elevated instability may develop along the frontal boundary, leading to severe thunderstorm concerns across the Southeast. Additionally, slow storm motions and efficient warm moisture will lead to locally high rainfall rates within the strongest storms, leading to flash flooding concerns over portions of the Ohio Valley/Mid-Atlantic and Southeast. By Wednesday, the boundary over the Mid-Atlantic and Ohio Valley will move further south, but shortwave troughs will reinforce another round of showers and thunderstorms across the area. This will lead to another day of flash flooding concerns over the Mid-Atlantic and Ohio Valley, especially over areas where soil remains saturated from previous rainfall. Further south, a moist and unstable airmass will persist across southern Florida leading to scattered to numerous showers and thunderstorms, with locally heavy downpours possible through Thursday. Temperature-wise, a strong surface high will bring colder than average temperatures across the northern/central Plains into the Mid-Atlantic and Northeast behind the frontal boundary, while the southern Plains into the Southeast will remain warm and humid. Kebede/Oudit Graphics available at https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php $$