Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 332 AM EDT Fri Sep 19 2025 Valid 12Z Fri Sep 19 2025 - 12Z Sun Sep 21 2025 ...Lingering moisture from Mario will continue to lead to the risk of flash flooding in California, the Great Basin, and the Southwest Friday... ...An upper trough over the central U.S. will bring scattered to widespread storms with a threat for isolated flash flooding the next couple of days... ...Much above average, hot temperatures for the last weekend of Summer across much of the eastern U.S... Lingering moisture and remnant energy from former Tropical Storm Mario will continue to bring heavy rain producing storms to portions of California, the Great Basin, and the Southwest today (Friday). An isolated threat for flash flooding exists broadly along the higher terrain surrounding the central valleys of California eastward through the central Great Basin and into the Southwest. A more concentrated threat of flash flooding is expected along the central Sierra Nevada where favorable upslope flow will help further enhance rainfall totals, and a Slight Risk of Excessive Rainfall (level 2/4) is in effect. The heavier rainfall and threat for flash flooding should subside into the evening hours. Storm chances on Saturday will shift a bit north arcing from the northern Great Basin eastward into the central Rockies while lingering for the Southwest. These storms are expected to remain more scattered with lighter rainfall totals. To the east, an upper trough and accompanying slowly progressing surface frontal system will provide the focus for scattered to widespread showers and thunderstorms across much of the Midwest/Mississippi Valley and central/southern Plains the next couple of days. Periodic shortwaves rounding the broader upper trough will help lead to multiple rounds of storms, with moisture in place for moderate to locally heavy rainfall. Some isolated flash flooding is possible, with a focus on the Upper Mississippi Valley southwest to the central Plains on Friday, and portions of the central/southern Plains and adjacent Ozarks on Saturday. Elsewhere, some scattered storms will be possible ahead of a sagging cold front through the southern Mid-Atlantic/central Appalachians/Upper Ohio Valley Saturday. Widely scattered storms will also be possible across the Gulf Coast/Southeast/Florida and into the southern Appalachians. A Pacific system will begin to bring moderate to heavy rainfall to the Pacific Northwest by late Saturday and into the day Sunday. Forecast high temperatures will be above average and rather hot across much of the eastern U.S. for the last weekend of the Summer. Highs into the upper 80s to mid-90s are expected from the Mid-Atlantic/Southeast west through the lower Great Lakes/Ohio Valley, Tennessee Valley, Mississippi Valley, and into the southern Plains/Texas. These temperatures are upwards of 15 degrees above average across the Lower Great Lakes and Ohio/Tennessee Valleys. Southern New England will also see well above average temperatures for Friday with highs into the upper 70s to low 80s. Temperatures will be much cooler and a bit below average north of a cold front across the Interior Northeast/New England and the Upper Great Lakes, with highs mainly in the 60s. Lows Saturday and Sunday morning are expected to fall into the upper 20s to mid-30s across the Interior Northeast/New England and Frost/Freeze related Advisories/Warnings are in place. The sagging cold front is also expected to bring cooler highs to southern New England and portions of the Mid-Atlantic Saturday as temperatures drop into the 60s and 70s. The northern/central Plains will be a bit cool Friday with highs in the 60s before temperatures rebound into the 70s Saturday. In the West, forecast highs the next couple of days are below average across California and portions of the Great Basin as a lingering upper-low and widespread precipitation keep temperatures mainly in the 70s. The Four Corners region and Southwest will be closer to average, as highs rise into the 70s and 80s, with 90s for the Desert regions. Further north, much above average highs are expected across the Pacific Northwest and northern Great Basin/Rockies, with highs in the upper 70s to mid-80s. Putnam Graphics available at https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php