Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Mon Jun 26 2023 22:58:13 AWUS01 KWNH 262258 FFGMPD MAZ000-CTZ000-NYZ000-NJZ000-PAZ000-270300- Mesoscale Precipitation Discussion 0591 NWS Weather Prediction Center College Park MD 656 PM EDT Mon Jun 26 2023 Areas affected...Eastern PA...Northern NJ...Southern NY...Western CT/MA Concerning...Heavy rainfall...Flash flooding likely Valid 262255Z - 270300Z Summary...Additional localized totals of 1-3" expected over the next several hours. Isolated to scattered instances of flash flooding are likely. Discussion...A dominate cluster of thunderstorms has consolidated across northern NJ/southern NY and surroundings, as moderate to strong low-level moisture transport and divergence aloft (lift) allow updraft longevity (and subsequent training/repeating of heavy rainfall rates). The mesoscale environment is currently characterized by MU CAPE of 500-2000 J/kg, PWATs of 1.7-1.9 inches (above the 90th percentile and nearing the max moving average, per OKX sounding climatology), and effective bulk wind shear of 20-30 kts. This parameter space should continue to support at least scattered thunderstorm activity over the next several hours, despite the notable reduction in surface-based instability over the past several hours (decreasing by 600-1200 J/kg, per EMC RAP analysis). MRMS indicates that as much as 2-4 inches of rainfall has already occurred across portions of far eastern PA, northern NJ, and southern NY over the past 6 hours, and corresponding FFG had already been as low as 1-2" (and is certainly even lower now, given the rainfall that has occured). Given the latest observational trends, it is expected that some localities will see an additional 1-3 inches of rainfall over the next several hours (through 03z) with convection gradually dissipating into the evening hours. While the HREF did a pretty good job with the start of this event (with regard to timing and intensity of convection), it has largely decoupled from reality over the past several hours by insisting that convection would consolidate over eastern PA. The subsequent HRRR runs are doing a better job, and generally depict the expectation for an additional localized 1-3 inches (though still biased a bit too far southwest of ongoing trends as well). Given the rainfall that has already occurred, additional isolated to scattered instances of flash flooding are considered likely. Churchill ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!4VcewKkaxfUWujoVrA5UO1kCChmmgRugb7DSLbIGRjT1rj3CNFIh0Eo6lVGGfIwqwnZy= PPw0sUiC6fEYicz8sKCTLg0$ for graphic product... ATTN...WFO...ALY...BGM...BOX...OKX...PHI... ATTN...RFC...MARFC...NERFC...NWC... LAT...LON 42777413 42707275 41507295 41077343 40817402=20 40527436 40237520 40717572 41677514 41747502=20 =20=20=20=20=20=20=20=20=20=20=20=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 3.14-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .