Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Tue Jul 30 2024 05:42:33 AWUS01 KWNH 300542 FFGMPD MEZ000-NHZ000-VTZ000-301100- Mesoscale Precipitation Discussion 0757 NWS Weather Prediction Center College Park MD 141 AM EDT Tue Jul 30 2024 Areas affected...Eastern VT...Northern NH...Northwest ME... Concerning...Heavy rainfall...Flash flooding likely Valid 300540Z - 301100Z SUMMARY...Stronger thunderstorms directly under upper low will limit cell motions with some potential for further development in proximity and additional potential for flash flooding over the next few hours. DISCUSSION...Regional RADAR mosaic denotes a band of thunderstorms has developed within the northern Connecticut River Valley.=20 Highly anomalous and fairly symmetric mid-level closed low has wobbled through Northern New England but appears to be slipping eastward. This has brought the core of colder air aloft overhead steepening the lapse rates; concurrently RAP analysis supported by regional VWP suite has shown a backing of low-level flow with 15-20kts of 850-700mb southwesterly flow angling through the Connecticut River Valley both providing some low level warm advection, further enhancing unstable environment but also moisture flux as noted by the CIRA LPW sfc-850 and 850-700mb layers with values of .75 and .4-.5" in each layer respectively.=20 Thunderstorms in the northern valley have utilized the enhanced unstable air and with the flux have generated a few observations of 2"/hr, which in complex terrain is producing MRMS FLASH signals of 250-500 cfs/smi, quite indicative of ongoing flash flooding. As the closed low continues to lift north-northeast, low-level advection should maintain ample moisture/unstable air given 1000 J/kg of upstream CAPEs, while cell motions will be less than 5kts, eventually turning more northeastward across central NH into NW ME, with increasing southwesterly flow increasing with the north-northeastward exiting upper low. Winds will increase from 20-25kts in the low levels with some increasingly unidirectional 850-500mb flow to support potential repeating/cross tracks of thunderstorms with 1.5"/hr rates in short terms across S VT, central NH into NW ME. Closer to the upper-low across NE VT/N NH, cells will remain fairly stationary (~5kts). It is uncertain, if low-level winds are southerly enough to replenish instability/moisture flux to maintain more than a few more updraft cycles, but an additional hour or so is likely to maintain rates over 1.5"/hr and continue to produce likely flash flooding in the near term. Gallina ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!5kczedfpVbEz1Xly1GG8cfSv6PD6u0PMERGX4JB9tl7-2UwYIVSuE29BvJ7Ki6Qwi-iT= eATPiRIEi814KHd-kQ3n5mA$ for graphic product... ATTN...WFO...BTV...GYX... ATTN...RFC...NERFC...NWC... LAT...LON 45527018 45396983 45026970 44507004 43887063=20 43267120 43267229 43497260 44237262 44897225=20 45217154 45497093=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) .