Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Wed Aug 13 2025 18:10:18 AWUS01 KWNH 131810 FFGMPD MAZ000-NHZ000-VTZ000-CTZ000-NYZ000-NJZ000-PAZ000-140000- Mesoscale Precipitation Discussion 0927 NWS Weather Prediction Center College Park MD 208 PM EDT Wed Aug 13 2025 Areas affected...Northeast PA...Northern NJ...Southeast NY...Southern New England Concerning...Heavy rainfall...Flash flooding possible Valid 131808Z - 140000Z SUMMARY...Increasing coverage of heavy showers and thunderstorms may produce isolated to scattered areas of flash flooding going through early this evening. DISCUSSION...The early afternoon GOES-E visible satellite imagery along with radar shows a gradual expansion of shower and thunderstorm activity occurring across areas of northeast PA and southeast NY. This convection is forming within an increasingly moist and unstable airmass that is currently characterized by MLCAPE values of 1000 to 2000 J/kg and PWs of generally near 1.75 inches. Meanwhile, there is some upper-level support with the approach of an upstream vort center over northern PA which coupled with localized orographics and additional diurnal heating should favor additional expansion of heavy shower and thunderstorm activity over the next several hours which will include areas farther east eventually inclusive of northern NJ, the northwest suburbs of New York City, and adjacent areas of southern New England. Rainfall rates with the stronger storms will be capable of reaching 1.5 to 2.5 inches/hour, and with slow cell-motions and some concerns for localized backbuilding and training of convective cells, some rainfall totals by this evening may reach 3 to 4+ inches. This is generally supported by the 12Z HREF guidance. The antecedent conditions across much of the region are on the dry side, and this will mitigate the flash flood threat to an extent. However, with such high rainfall rate potential and the localized storm totals that may occur, there may be some isolated to scattered flash flooding concerns. This will especially be the case near areas of more rugged terrain such as the Poconos and Catskills, along with any of the more urbanized locations to the northwest of New York City and across southern New England. Orrison ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!9fDd8jSDjRgfW5Fk6LwTG4L9XjIxiNXUHagBbH6WsG2upyGby22f4yc1wrSTRm2bKh8e= _ly2h57bo7DeSV2bqFftXYI$ for graphic product... ATTN...WFO...ALY...BGM...BOX...BTV...CTP...GYX...OKX...PHI... ATTN...RFC...RHA...TAR...NWC... LAT...LON 43657338 43497218 42507219 41807271 41257366=20 40897475 41037599 41497634 41827601 42297536=20 42907444=20 =3D =3D =3D To unsubscribe from WX-STORM and you already have a login, go to https://lists.illinois.edu and use the "Unsubscribe" link. Otherwise email Chris Novy at cnovy@cox.net and ask to be removed from WX-STORM. --- SBBSecho 3.28-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .