Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Fri Jul 07 2023 16:22:05 AWUS01 KWNH 071622 FFGMPD MEZ000-MAZ000-NHZ000-VTZ000-NYZ000-072215- Mesoscale Precipitation Discussion 0653 NWS Weather Prediction Center College Park MD 1220 PM EDT Fri Jul 07 2023 Areas affected...Northern New England...Central NY Concerning...Heavy rainfall...Flash flooding likely Valid 071620Z - 072215Z SUMMARY...Widespread thunderstorms producing hourly rainfall rates >2"/hr are likely to cause flash flooding in areas with sensitive soils or in poor drainage spots this afternoon. 30-minute rainfall rates could top 2"/hr in the most intense cells. DISCUSSION...Northern New England lies beneath the diffluent right-entrance region of a jet streak that is centered over Quebec this afternoon. Meanwhile, a frontal system is approaching from the west, acting as a trigger for thunderstorm development later this afternoon. Storms are forming well in advance of the front thanks to excellent surface based heating that transpired this morning. Convective temps throughout the region are being easily surpassed with dew points also ranging from the upper 60s to low 70s. The aforementioned surface heating will continue to further destabilize the atmosphere to where as much as 1,000-2,000 J/kg of MLCAPE will be at these storms disposal. PWATs are also on the rise, eclipsing 1.75" for much of the region this afternoon. PWATs this high are near the 97.5 climatological percentile across northern ME/NH. RAP soundings across portions of the highlighted at-risk region show RH values between 80-90% and warm cloud layers as deep as 11kft. RAP guidance also shows sampled forecast soundings to contain fairly uniform WSW wind profiles. While storm motions are slightly faster than their southern/western neighbors in MPD #652, these uniform winds out of the WSW are favorable for training convection. Corfidi Upshear vectors are also 10-15 knots, which suggest some opportunity for backbuilding. This can be done via the upshear vectors, or also by persistent upslope into orthogonally favored mountain ranges. Regardless on the method, this setup favors multiple rounds of thunderstorms in an environment that can produce prolific rainfall rates. Per BTV, up to 2.5" of rainfall were near Keene Valley, NY with rainfall rates approaching an astonishing 5"/hr. This does not mean each storm will produce totals that high in an hour, but it is an indicator that the instantaneous rates can be exceptional within these storms and could prompt flash flooding well inside of 1-hr FFGs. Speaking of which, 1-hr FFGs across the vast majority of northern New England are capped at 2". Given the rainfall rates observed in the early convection to the west, flash flooding is likely to occur across portions of the region this afternoon. Areas with sensitive soils and in more urbanized communities are most prone to flash flooding. Mullinax ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!8n7wXi67DUaCTgBXlj6bCqkZD48IjiaOOOCTkhdUn3ruERJMmF8KaEqX2HR55EU5vFDg= B7siX2FkD7AjZ_bSQa-fI8I$ for graphic product... ATTN...WFO...ALY...BTV...CAR...GYX... ATTN...RFC...NERFC...NWC... LAT...LON 47516925 47396807 46836749 46186753 45266862=20 43927098 43877103 43047238 42777304 42147411=20 42487415 43807320 45017295 45107236 45247159=20 45697073 46857006=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) .