Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Wed Jul 31 2024 16:23:30 AWUS01 KWNH 311623 FFGMPD MEZ000-MAZ000-NHZ000-VTZ000-NYZ000-312230- Mesoscale Precipitation Discussion 0766 NWS Weather Prediction Center College Park MD 1223 PM EDT Wed Jul 31 2024 Areas affected...portions of Upstate New York into central and northern New England Concerning...Heavy rainfall...Flash flooding possible Valid 311630Z - 312230Z Summary...Showers and thunderstorms will expand in coverage and lift northward through the evening. Rainfall rates of 1-2+"/hr are likely, which through repeated rounds could produce 2-3" of rain with locally higher amounts. Flash flooding is possible. Discussion...The regional radar mosaic this afternoon shows a rapid expansion of convective development blossoming across New England and Upstate New York. These thunderstorms are developing within favorable thermodynamics characterized by PWs measured by GPS and morning U/A soundings of 1.75 to 2 inches, nearing the daily record according to the SPC sounding climatology, and MLCAPE that has climbed to around 1000 J/kg. Into this environment, forcing for ascent is impinging from the south and west through weak vorticity maxima embedded within the flow and the broad mid-level trough axis approaching from PA to drive height falls. Additionally, a jet streak positioned to the northeast is leaving its favorable RRQ over New England to additionally enhance deep layer lift. Rainfall rates within this fresh convection have generally remained around 1"/hr, but increasing glaciation noted in the GOES-E day cloud phase imagery collocated with increasing lightning cast probabilities indicates updrafts are strengthening and rainfall rates should quickly follow. The CAMs are in good agreement that convection will expand, although the exact placement of what will be primarily scattered cells or multi-cells through 20-25 kts of bulk shear is uncertain. This is reflected by modest 1"/6hrs EAS probabilities, but high(>80%) and moderate(>30%) neighborhood probabilities for 1" and 3", respectively, in 6 hours. There is high confidence that convection will expand as thermodynamic advection continues from the south pushing PWs to broadly over 2" and SBCAPE to nearly 2000 J/kg in much of New England and Upstate NY. These cells will generally lift northward progressively on 0-6km mean winds of 15-20 kts, but the widespread coverage should result in multiple rounds in many areas. Additionally, nearly unidirectional flow noted in morning soundings suggests brief training is possible along narrow N-S corridors. Rain rates will likely reach 1-2"/hr in most of these cells, and the HRRR 15-min accumulation product suggests locally 0.75"+ of rain is possible this evening which indicates brief intense rates to 3"/hr are possible. These axes of enhanced training are where the heaviest rainfall is expected, and this is most likely from far eastern Upstate NY into much of VT where 2-3" of rain is possible. FFG across the region has been compromised from recent heavy rainfall, and there are some local minimums of less than 1.5"/3hrs in the Green Mountains and Northeast Kingdom of Vermont. This area is generally sensitive anyway due the terrain features supporting rapid runoff when rates become intense, but the antecedent rain has made the area even more vulnerable. The generally progressive nature will be somewhat inhibiting to impacts, but where any short-duration training or repeated rounds can occur, instances of flash flooding will be possible. Weiss ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!7Gx4JBLyxXCis3QuuHXeomwH4hmjj6jdaPxirNCDGefoFs_UGPqbPDL0o1Pc-gFlCX_W= AAqN205drZZYstTbaasdrkI$ for graphic product... ATTN...WFO...ALY...BOX...BTV...GYX... ATTN...RFC...NERFC...NWC... LAT...LON 45357189 45257096 45107019 44617028 44087068=20 43527152 43257207 42827239 42437277 42207338=20 42577393 43267425 44157421 45147397=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 3.20-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .