Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sun Jul 02 2023 20:36:57 AWUS01 KWNH 022036 FFGMPD MAZ000-CTZ000-NYZ000-NJZ000-PAZ000-030200- Mesoscale Precipitation Discussion 0623 NWS Weather Prediction Center College Park MD 436 PM EDT Sun Jul 02 2023 Areas affected...Southeastern Upstate NY...Eastern PA...Northern NJ....Western MA...Northwest CT... Concerning...Heavy rainfall...Flash flooding possible Valid 022035Z - 030200Z SUMMARY...Slow moving/stationary cells along frontal/deformation zone capable of localized 1.5-2.5" totals; while faster but stronger cells capable of sub-hourly totals of 1-2" pose similar flash flooding concerns in terrain and or urban corridor later. DISCUSSION...20z surface analysis shows a stationary frontal zone with numerous weak surface inflections dotted along it across southern Upstate NY into western MA. It is also generally collated with deeper layer deformation zone from 850-700mb resulting in some deeper layer convergence but more of a weakening steering flow zone at the apex of fairly southwest to west-southwest moisture transport. High Theta-E rich environment is filtered weakly to pool along the frontal zone and some filtered solar input has increased the instability for some weak thunderstorms to potentially develop along it. RADAR suite denotes this is becoming enhanced by the rapid approach of a mature shortwave/MCV across N Central NY...as such, the convergence is sufficient for narrow but moisture rich updrafts for localized heavy rainfall along it for the next few hours as the MCV progresses eastward. Increased insolation over the Catskills and N NJ has resulted into pockets of further enhanced instability up to 2000 J/kg which may further increase potential for higher rates up to 1.5"/hr. In weak steering, this is probable to result in a widely scattered spots of 1.5-2.5" totals over a 1-3hr period. Lower FFG values may be exceeded so a few incidents of localized flash flooding are possible through this evening. Further south across E PA into N NJ, deeper overall moisture and slightly better insolation has resulted in stronger updraft strength, especially given enhanced speed/directional convergence in the 925-850mb layer along/head of the MCV. As such, stronger and deeper thunderstorms, some with weak rotation will have capability for more intense rain-rates/efficiency...perhaps up to 2-2.5"/hr (given the 2+" total Pwats and effective 20-25kts moisture flux convergence). However, being further south; the steering flow is much stronger and westerly likely reducing duration at any given location. Still, the HRRR 15minute rainfall totals suggest 1-1.25" are possible and this may be enough (given overall up to 2" totals) for prone areas to experience low-end flash flooding conditions, especially along the I-95 corridor or the lower FFG values across N NJ in the more complex terrain. So like further north in S Upstate, a few widely scattered incidents of flash flooding are considered possible. Gallina ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!9-9z2nNLbfxSMrszOjX9CVhVERcSibjubWEyl04La4pvJHOZniKCzz63oHmJiG6AE66P= ZZCKOEtfYNzMb0FXAIJE4Ps$ for graphic product... ATTN...WFO...ALY...BGM...BOX...CTP...OKX...PHI... ATTN...RFC...MARFC...NERFC...NWC... LAT...LON 42837484 42787393 42547256 42277220 41857241=20 41447343 40687419 40267463 39857518 39887652=20 40957708 41597717 42457721 42837621=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) .