Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 339 AM EDT Thu May 29 2025 Valid 12Z Thu May 29 2025 - 12Z Sat May 31 2025 ...There is a Slight Risk of excessive rainfall over parts of the Mid-Atlantic, Central Appalachians, and Ohio Valley on Friday... ...There is a Slight Risk of severe thunderstorms over parts of the Southern Plains and the Southeast on Thursday and the Southeast to the Mid-Atlantic on Friday... A wave of low-pressure south of Long Island will move eastward out over the Atlantic by Friday. A second wave of low pressure over Georgian Bay, Ontario, Canada, will dissipate by Friday morning. The areas of low pressure will draw moisture off the Atlantic over the Northeast into the Great Lakes, producing rain over parts of the Great Lakes and Northeast on Thursday. A third wave of low pressure develops over the Southern Plains on Thursday, moves northeastward to the northern Mid-Atlantic by Friday evening, then moves over New England by Saturday. Moisture will surge northward over the Southern Plains as upper-level energy moves across Texas, producing showers and severe thunderstorms. Therefore, the SPC has issued a Slight Risk (level 2/5) of severe thunderstorms over parts of the Southern Plains through Friday morning. The hazards associated with these thunderstorms are frequent lightning, severe thunderstorm wind gusts, hail, and a few tornadoes. However, there is an increased risk of hail, two inches or greater, over the region. Similarly, moisture will move northeastward out of the Gulf of America as another area of upper-level energy moves across the Southeast, creating showers and severe thunderstorms. Therefore, the SPC has issued a Slight Risk (level 2/5) of severe thunderstorms over parts of the Southeast through Friday morning. The hazards associated with these thunderstorms are frequent lightning, severe thunderstorm wind gusts, hail, and a few tornadoes. Moreover, an upper-level low over the Central Plains/Middle Mississippi Valley will trigger showers and thunderstorms over parts of the Central Plains/Middle Mississippi Valley and Ohio/Tennessee Valleys. On Thursday, showers and thunderstorms will develop over the Central Rockies. On Friday, as the third wave of low pressure over the Ohio Valley moves into the Mid-Atlantic, showers and thunderstorms will develop with heavy rain over parts of the Ohio Valley, Central Appalachians, and Mid-Atlantic. Therefore, the WPC has issued a Slight Risk (level 2/4) of excessive rainfall over parts of the Ohio Valley, Central Appalachians, and Mid-Atlantic from Friday through Saturday morning. The associated heavy rain will create mainly localized areas of flash flooding, with urban areas, roads, small streams, and low-lying areas the most vulnerable. The cold front, associated with the third wave of low pressure, will cause showers and severe thunderstorms over parts of the Southeast and the Mid-Atlantic region. Therefore, the SPC has issued a Slight Risk (level 2/5) of severe thunderstorms over parts of the Southeast to the Mid-Atlantic from Friday into Saturday morning. The hazards associated with these thunderstorms are frequent lightning, severe thunderstorm wind gusts, hail, and a few tornadoes. Furthermore, showers and thunderstorms will develop over parts of the Great Lakes and Ohio Valley on Friday, and rain will also fall over parts of the Northeast. Meanwhile, a front over the Pacific Northwest on Thursday moves eastward to the Northern High Plains into the Great Basin by Friday morning, dissipating by Friday evening. The system will produce scattered rain over parts of the Northwest, expanding into the Northern Intermountain Region by Thursday evening. Overnight Thursday, showers and thunderstorms will develop over the Northern/Central Rockies. In addition, showers and thunderstorms will develop over the Southern Plains on Friday through Saturday morning. Moreover, showers and thunderstorms will develop overnight Friday over the Central/Southern Rockies. Elsewhere, an upper-level low over Southern California will slowly move southwestward over Northwestern Mexico by Friday evening, and a ridge of high pressure will develop over California and into the Great Basin on Friday morning. The upper-level ridging will allow temperatures to rise into the low hundreds, prompting Heat Advisories and Extreme Heat Warnings over parts of California on Friday. Ziegenfelder Graphics available at https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php