Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Thu Jul 31 2025 17:56:06 AWUS01 KWNH 311755 FFGMPD RIZ000-CTZ000-NYZ000-NJZ000-312345- Mesoscale Precipitation Discussion 0834 NWS Weather Prediction Center College Park MD 155 PM EDT Thu Jul 31 2025 Areas affected...Northern NJ...Southern NY & Long Island...CT... Concerning...Heavy rainfall...Flash flooding likely Valid 311755Z - 312345Z SUMMARY...Slow moving thunderstorms with rates up to 2"/hr and multiple rounds pose local 2-5" totals and possible flash flooding. DISCUSSION...17z Surface analysis shows the stationary front has been further reinforced by southerly sea-breeze off the NY Bight as well as outflow boundary and easterly flow north of the front. Temperatures into the low 90s and Tds in the low to mid-70s across N NJ/Long Island with solid deep layer moisture profiles supports a very unstable environment in the warm sector with 1500-2000 J/kg of MLCAPE analyzed; combined with 1.9-2" total PWats that remain near .8-1" in the Sfc-850mb layer noted in CIRA LPW. The solid directional convergence at the surface has resulted in a few clusters of cells developing from N NJ across LI. The combination will allow for efficient rainfall production with 2-2.5"/hr. Deep layer flow suggests slow east-northeast cell motions, but convergence from outflow and frictional effects near coasts suggest somewhat chaotic motions that may allow for some cells to redevelop in place allowing for increased duration. 17z WoFS members denote this sort of interaction with slow motions across E Long Island resulting in some increased overall totals up to 2-5" between the 50th and 90th 6hr percentiles. This is in agreement with recent HRRR and 12z Hi-Res CAM solutions to provide moderate confidence toward this cell motion environment. Proximity to urban locations and limited infiltration is likely to result in localized flash flooding/rapid inundation conditions, across LI, S NY and southern CT, though precise locations of enhanced totals will remain elusive to lock down, resulting in a scattered nature to the flooding pattern across the area of concern through the evening hours. Mid to upper-level shortwave feature upstream will continue to press eastward across Upstate NY; this should keep southerly flow backed in the low levels and increased DPVA/divergence aloft may allow for additional thunderstorms to develop north and west toward 23z and may seek out remaining unstable air parcels across the area of concern and may track through areas already affected with the initial rounds.=20=20 Gallina ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!9sHLf1jem3DVQ1ubWcT2zw6a1CJSDhzUf5seWTIFQmzlv2Cm2jlACVFxN5mlt-qDOnuc= pHSpWFZfCaIR_BRnSZoMl6o$ for graphic product... ATTN...WFO...ALY...BOX...OKX...PHI... ATTN...RFC...RHA...TAR...NWC... LAT...LON 41967296 41937223 41747190 41277185 41007190=20 40747261 40607306 40557340 40537441 40927478=20 41337457 41617423 41857369=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) .