Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 158 PM EDT Wed Sep 17 2025 Valid 00Z Thu Sep 18 2025 - 00Z Sat Sep 20 2025 ...Coastal low will continue to exit the Mid-Atlantic and southern New England... ...Rounds of heavy rain and possible severe thunderstorms across the northern/central Plains and Mississippi Valley through the next couple of days... ...Tropical moisture from Mario pushes into the Southwest... ...Below average temperatures likely where wet weather occurs next two days, otherwise above average temperatures expected across much of the CONUS with heat building across the Midwest... The coastal storm over the the eastern shores of Virginia will continue to weaken over land but will continue to bring chances for showers and thunderstorms through tonight into early Thursday. By Thursday afternoon, the system gradually moves off the coast, bringing lower chances for showers near the Mid-Atlantic coast but a cold front will bring chances for scattered showers across the Northeast early Friday morning. The upper-low over the Central U.S. will continue to bring chances for showers and thunderstorms through Friday. In addition, an occlusion is anticipated to form over the Mississippi Valley and Central Plains, adding support for heavy rainfall potential over the mid-section of CONUS. With sufficient moisture and unstable environment, Storm Prediction Center has highlighted most of the Central Plains and parts of the Mississippi Valley with a Marginal Risk (level 1/5) for Severe Thunderstorms, as well as a Slight Risk (level 2/5) for parts of Southern Colorado and south-central High Plains. Areas highlighted under the Slight Risk are not limited to showers and thunderstorms, as hail, gusty winds, and low-probability tornadoes are possible. In addition, due to enhanced rainfall rates, Weather Prediction Center has placed parts of Western and Central Dakota under a Slight Risk (level 1/4) for Excessive Rainfall with possible flash flooding and localized flooding. Post tropical Mario continues to bring some tropical moisture near southern coastal California, promoting scattered showers and thunderstorms through Thursday. The storm will gradually weaken as it moves further inland but scattered showers, with chances of occasional heavy rainfall, will continue to move across the Southwest. With rainfalls totals expected to reach 1-3" and rainfall rates >1"/hr, there is a chance for flash flooding and localized urban flooding. Overall, any rainfall amount across the Southwest and central Rockies will be beneficial, as these areas have been notably dry. A general half an inch of rain can be expected to gradually work its way up the southern half of California through late Thursday night into Friday morning with higher amounts across wind-facing terrains. By late Friday, residual showers will move over Arizona and southern New Mexico. In addition to rainfall, the upper-level low over the Plains will continue to bring below normal temperatures over the Central and Northern Plains through Friday but the rest of CONUS will generally experience between 10-15 degrees above normal, especially over the upper and middle Mississippi Valley. Temperatures are expected to build into the 90s in the Midwest as the upper-level ridge becomes more prominent. By Thursday, temperatures over the Southwest begin to cool to 5-10 degrees below normal. Tropical moisture from the Caribbean Sea will continue to bring numerous widespread scattered showers (with occasional heavy downpour of 2-3"/hr) and thunderstorms over southeast Florida, with the Keys seeing the heaviest rainfall through the end of the week. With the ample deep layer moisture, Weather Prediction Center does have a Marginal Risk (level 1/4) for Excessive Rainfall over part of southeast Florida with potential for flash flooding. Winds will become breezy and gusty today but should ease by Thursday, as shower activity continues through Friday. Oudit Graphics available at https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php