Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sat Sep 06 2025 17:14:02 AWUS01 KWNH 061713 FFGMPD MAZ000-NHZ000-VTZ000-CTZ000-NYZ000-NJZ000-PAZ000-DEZ000-MDZ000-062300- Mesoscale Precipitation Discussion 1054 NWS Weather Prediction Center College Park MD 113 PM EDT Sat Sep 06 2025 Areas affected...northern Mid-Atlantic into southern New England Concerning...Heavy rainfall...Flash flooding possible Valid 061712Z - 062300Z Summary...A couple areas of flash flooding will be possible from the northern Mid-Atlantic region into southern New England through 23Z. Areas of short term training will be capable of hourly rainfall from 1 to 2+ inches and spotty 3 inch totals. Given dry antecedent conditions, the flash flood threat appears to be mostly urban in nature. Discussion...17Z observations placed a cold front stretching from NH/VT into southern NY, eastern PA and central MD. Surface moisture ahead of this boundary has increased since 12Z with dewpoints in the low to mid-70s from southeastern PA into parts of NJ as layered PW imagery showed a swath of deep layered moisture advecting northeastward from the lower MS Valley. 17Z SPC mesoanalysis data showed estimated PWs of 1.5 to 1.7 inches and filtered sunshine has helped to increase MLCAPE into the 1000-2000 J/kg range. Recent visible satellite and radar imagery showed the beginning stages of convective development along the front from northeastern MD into northwestern NJ. There is sufficient vertical shear for organized storms with both organized and ordinary cells likely containing forward speeds between 20-35 kt toward the northeast/east-northeast. Largely unidirectional flow from just above the surface to the tropopause was oriented parallel to the front which would normally be supportive of training. However, a steady 10-15 kt progression of the cold front is forecast which should limit training to mesoscale waves along the front and/or thunderstorm related outflow that cause convection to align with the mean wind. This situation could support 1 to 2+ inches of rain in an hour or less. Given much of the region has been dry over the past 1-2 weeks, the flash flood threat should remain mostly tied to overlap of heavy rain with the urban I-95 corridor and/or some of the surrounding more flash flood prone areas. Otto ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!8Qkd-zBGYYOiMWeSPgxat76eAuBOHHfvjx4z8EbgPUM1lrzCg9G-l9NdmffKtzi7DqYK= u1C2X4utZIE1WrYEr-Y0x4Y$ for graphic product... ATTN...WFO...ALY...BGM...BOX...CTP...GYX...LWX...OKX...PHI... ATTN...RFC...RHA...TAR...NWC... LAT...LON 43037179 42157189 40887301 39907419 39517521=20 39337605 39437645 39877631 40777521 41777425=20 42947297=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) .