Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Fri Aug 04 2023 00:42:43 AWUS01 KWNH 040042 FFGMPD MAZ000-VTZ000-NYZ000-PAZ000-040630- Mesoscale Precipitation Discussion 0852 NWS Weather Prediction Center College Park MD 841 PM EDT Thu Aug 03 2023 Areas affected...Central and Eastern Upstate NY...Adj Northeast PA...Vermont... Concerning...Heavy rainfall...Flash flooding possible Valid 040045Z - 040630Z SUMMARY...Scattered incidents of slow/stationary thunderstorms ahead of approaching cold front may produce localized 2-3" totals and possible flash flooding DISCUSSION...Evening isolated thunderstorm(s) have been producing highly focused heavy rainfall with 2.5"/hr rates due to notable rotation in the updraft supporting enhanced localized moisture flux inducing flash flooding across Addision county VT denoted by MRMS Flash unit stream flow near 1000 cfs/mi with cell still lingering continuing flooding risk but the updraft is weakening a bit losing some of the strength/rotation to maintain moisture flux and rates. Into the overnight period, greater coverage of thunderstorms and therefore potential for a few additional instances of localized flash flooding is increasing into the overnight period. A potent shortwave has dug through SW Quebec with a trailing mid-level trof across the western St. Lawrence Valley with strong thunderstorms across E Ontario, starting to press into Upstate New York. RAP analysis and CIRA LPW shows the leading edge of deeper moisture living through the Catskills into the Hudson Valley and Interior New England, while a wedge of enhanced moisture resides along/ahead of the trailing cold front associated with the Quebec shortwave. This is resulting in confluent moisture streams across the central Mohawk Valley into the Hudson Valley, concurrent with favorable low level moisture convergence. This is starting to spark a few additional pre-frontal thunderstorms across NY that are expected to be equally slow moving due to backed low level flow and response to approaching stronger height-falls. Total PWats to 1.5" and 1000-1500 J/kg of MLCAPE (uncapped) suggests environment will remain conducive for stronger updrafts and with moisture flux convergence, should be capable of 1.5-2"/hr rates.=20 Cell motions should limit overall duration, but streaks of 2-3" totals are possible across NY into VT. Given 1hr FFG values in the region run about 1-2", scattered incidents of flash flooding are considered possible. Recent runs of the HRRR and RAP also denote an inflection of the 850mb confluence zone across central NY, supporting short-term favorable back-building thunderstorm environment, generally parallel to the mean steering flow (even as it will increase after leading edge of height-falls wash through). This suggests a few spots of 3"+ totals are probable through the early overnight period; though an additional spot of 4" can not be ruled out.=20 Gallina ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!6ExgaMcEdFLKmzVcdc0wFnx8cMwl2yuhTlnTKnSovCnO6Q0T2MdskFdJJptGTL_tlAGA= VHQ4uqI3Fl1NoU3tAeJ37kE$ for graphic product... ATTN...WFO...ALY...BGM...BTV...BUF... ATTN...RFC...MARFC...NERFC...NWC... LAT...LON 45157244 44847180 43077286 41957363 41787451=20 41827548 42037657 43067772 43537705 44077648=20 44507604 44977530 45117394=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) .