Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Thu Sep 25 2025 18:56:38 AWUS01 KWNH 251856 FFGMPD MEZ000-MAZ000-NHZ000-RIZ000-VTZ000-CTZ000-NYZ000-NJZ000-PAZ000-260050- Mesoscale Precipitation Discussion 1136 NWS Weather Prediction Center College Park MD 255 PM EDT Thu Sep 25 2025 Areas affected...northern Mid-Atlantic into southern New England Concerning...Heavy rainfall...Flash flooding possible Valid 251854Z - 260050Z Summary...Training axes of heavy rain are expected from the northern Mid-Atlantic region into southern New England through the late afternoon and evening. Hourly rainfall of 1 to 2+ inches may result in localized flash flooding with a focus on any urban centers. Discussion...Radar imagery at 1845Z helped identify a pair of MCVs over the Northeast, embedded within areas of largely stratiform rain from portions of PA into New England. One vortex over central PA and the other near Albany, NY, were tied to surges of higher rainfall rates, with MRMS-derived values between 1 and 2 inches in an hour at times. These two features were located along the northern edges of a region of elevated CAPE with 500-1500 MUCAPE identified on 18Z SPC mesoanalysis data. The environment was characterized by anomalous moisture with PW values of roughly 1.7 to 2.0 inches (2 to 3 standardized anomalies above the mean for late September), supportive of hourly rainfall locally in excess of 2 inches. As a cold front over central NY/PA and the aforementioned mesoscale waves continue to advance downstream, interaction with 500-1000 J/kg MLCAPE from southeastern PA into far southern New England will support an increase in rainfall coverage and rates from the northern Mid-Atlantic into southern New England. Some breaks in cloud cover noted on visible imagery over southeastern PA into NJ may help to locally increase instability through better surface heating, yielding greater potential for higher intensity rainfall. While individual cell motions should remain progressive toward the NE, alignment of convective axes with the southwesterly deep-layered steering flow will promote training and locally 1 to 2+ inches of rain in an hour at times. These locally higher rates could result in a relatively quick accumulation of rainfall totaling 2 to 3+ inches through 01Z. Localized flash flooding may occur as a result, especially if overlap occurs with impervious urban areas. Otto ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!7qyxmCwKpVstv3jN3fWwdyMQipUMRXzIhAqbmAEL2oR2LO2905s5-kjeFo6cNeEXp8M6= 6v4dkwIDL3tkbvHKIqKkVYQ$ for graphic product... ATTN...WFO...ALY...BGM...BOX...BTV...CTP...GYX...OKX...PHI... ATTN...RFC...RHA...TAR...NWC... LAT...LON 44247137 43667053 43137030 42647034 42237087=20 41847183 41297270 40817343 40227422 39927557=20 39917773 40897709 42027600 42747491 43117379=20 43807248=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) .