789 FXUS01 KWBC 241826 PMDSPD Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 225 PM EDT Sun Aug 24 2025 Valid 00Z Mon Aug 25 2025 - 00Z Wed Aug 27 2025 ...There is a Slight Risk of excessive rainfall over parts of the Sierra Nevada Mountains, Central/Southern High Plains, and Great Basin on Sunday... ...There is a Slight Risk of excessive rainfall over parts of the Southwest, Central/Southern Rockies, and Central/Southern Plains on Monday... ...There are Extreme Heat Warnings and Heat Advisories along the West Coast and just inland... A front extending from the Lower Great Lakes/Ohio Valley to the Lower Mississippi Valley/Southern Plains will advance eastward off the East Coast and most of the Gulf Coast and into the Southern Plains by Tuesday. The front will produce showers and thunderstorms over the Lower Great Lakes and Central/Southern Appalachians, and rain in parts of the Great Lakes on Sunday and Monday. Showers and thunderstorms will also develop over parts of the Southeast through Tuesday. Moreover, monsoonal moisture, diurnal heating, and upper-level impulses will produce showers and thunderstorms over Central/Southern California, the Southwest, the Great Basin, the Central/Southern Rockies, and the Central/Southern High Plains on Sunday. Heavy rain will develop over parts of the Central/Southern High Plains and a second area over parts of the Southwest on Sunday. Therefore, the WPC has issued a Slight Risk (level 2/4) of excessive rainfall over the Central/Southern High Plains, as well as the Southwest, through Monday morning. The associated heavy rain will primarily create localized areas of flash flooding, with urban areas, roads, small streams, and low-lying areas being the most vulnerable. Showers and thunderstorms will develop over parts of Central/Southern California on Sunday. Heavy rain will develop over parts of the Sierra Nevada Mountains. Therefore, the WPC has issued multiple areas for Slight Risk (level 2/4) of excessive rainfall over the Sierra Nevada Mountains through Monday morning. The associated heavy rain will primarily create localized areas of flash flooding, with urban areas, roads, small streams, and low-lying areas being the most vulnerable. For Tuesday, showers and thunderstorms are expected to develop over parts of Oregon, interior California, the Great Basin, the Southwest, and the Central/Southern Rockies, as well as the Central/Southern Plains. Heavy rain will develop over parts of the Central/Southern Rockies. Therefore, the WPC has issued a Slight Risk (level 2/4) of excessive rainfall over the Central/Southern Plains from Tuesday through Wednesday. The associated heavy rain will primarily create localized areas of flash flooding, with urban areas, roads, small streams, and low-lying areas being the most vulnerable. Another area of showers and thunderstorms will develop over parts of the Central/Southern Plains with heavy rain on Tuesday. Therefore, the WPC has issued a Slight Risk (level 2/4) of excessive rainfall over the Southwest from Tuesday through Wednesday. The associated heavy rain will create mainly localized areas of flash flooding, with urban areas, roads, small streams, and low-lying areas being the most vulnerable. Meanwhile, an upper-level high over the Southwest into the Central/Southern Rockies will aid in creating a heat wave across much of the Western U.S. through the weekend, with the most intense and long-lasting heat across the Desert Southwest into the San Joaquin Valley. Extreme Heat Warnings and Watches are in effect from portions of Arizona through Washington State. This type of heat will be dangerous, posing a threat to anyone without effective cooling and adequate hydration. Numerous daily high temperature records are likely to be broken. For many areas, there will be little nighttime relief from the extreme heat, with overnight lows remaining well above normal. Numerous nighttime temperature records are likely. Extreme heat is dangerous even at night when temperatures do not cool down. Without air conditioning or cooling, the body cannot recover, increasing the risk of heat-related illnesses. Stay informed and take steps to protect yourself from heat-related illnesses. For information on staying cool and safe, visit www.weather.gov/safety/heat. As temperatures rise, limit outdoor activity, stay hydrated, and ensure access to air-conditioning and other cooling areas. Ziegenfelder Graphics available at https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php $$