Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sat Jul 29 2023 13:15:30 AWUS01 KWNH 291315 FFGMPD NYZ000-291900- Mesoscale Precipitation Discussion 0810 NWS Weather Prediction Center College Park MD 914 AM EDT Sat Jul 29 2023 Areas affected...Much of Upstate New York... Concerning...Heavy rainfall...Flash flooding possible Valid 291315Z - 291900Z SUMMARY...Slow moving potentially repeating thunderstorms downstream of approaching shortwave pose localized possible flash flooding incidents through late morning/early afternoon. DISCUSSION...GOES-E WV suite depicts a well defined shortwave crossing Lake Erie and the Ontario Peninsula with a well defined anticyclonically curved cirrus shield indicative of continued favorable upper-level divergent pattern aloft for convective/system maintenance. At the surface a well defined surface low resides below the shortwave in Lake Erie with a sharp well defined stationary front extending due east through the Mohawk Valley into central VT/NH. This frontal zone/shear zone extends though a fairly deep layer with enhanced moisture pooled along it. CIRA LPW denotes .8-1" values across W NY that extends to the 850-700mb layer, though overall total moisture remains above average at 1.75 range or about 1.5-2 standard deviation from normal. Lapse rates are modest given the deep layer moisture, but early morning clearing downstream supports 1000-1500 J/kg of MLCAPE and in a weakly capped or uncapped environment, convection is breaking out along and just north of the frontal boundary across north-central Upstate New York.=20 Given the vigor of inflow/flux is generally oblique to the orientation of the deeper frontal zone, moisture flux convergence is weak to moderate and so rainfall efficiency is a bit limited but still capable of 1.5"/hr at least initially for the initial central NY to E NY cells. This will change rapidly with the approach of the shortwave and low level cyclone, backing and increasing flow will allow for stronger directional convergence with similar 15-20kts of mid-level flow too, so short-term rates could perk up to 1.75-2"/hr nearer the surface cyclone as it approaches. So, the concern is the mean steering flow is parallel to the boundary and should support solid opportunities for redevelopment and repeating thunderstorm tracks across much of west-central to east-central Upstate NY, spotty 2-3" totals are expected. If there is some good news, this axis has been relatively dry over the last 1-2 weeks and may be able to have some beneficial infiltration, but given the potential for multiple rounds, the first may saturate the upper soils and limit infiltration for the upstream cells, that are likely to be a bit more intense and could have a bit more runoff. As such, spots of flash flooding are considered possible through late morning into early afternoon.=20=20=20=20 Gallina ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!__pTyesFiJmVTi3wB8IAqVtozmyxy0kRdKK_6-OASvjgI1DjbpP8ZtCe5Ab6KkreO43W= TBFNrTUXMiFasoeiXz7LvsA$ for graphic product... ATTN...WFO...ALY...BGM...BTV...BUF... ATTN...RFC...MARFC...NERFC...OHRFC...NWC... LAT...LON 44477565 44447410 44077356 43357339 42637371=20 42447504 42397726 42447850 42487913 43007914=20 43387885 43427701 43777643 44137633=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) .