Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Fri Jul 21 2023 21:42:38 AWUS01 KWNH 212142 FFGMPD MEZ000-MAZ000-NHZ000-RIZ000-VTZ000-CTZ000-NYZ000-220330- Mesoscale Precipitation Discussion 0783 NWS Weather Prediction Center College Park MD 541 PM EDT Fri Jul 21 2023 Areas affected...New England...Northeast NY... Concerning...Heavy rainfall...Flash flooding likely Valid 212145Z - 220330Z SUMMARY...Multiple Bands of slow moving, strong thunderstorms with up to 2"/hr rates. Continue to pose likely scattered incidents of flash flooding through early overnight period.=20 DISCUSSION...GOES-E WV suite depicts a highly dynamic mid to upper level pattern over SE Canada into New England. The main core of the upper low is pivoting along the far eastern extent of Ontario along the Quebec boarder with strong secondary trof digging through the St. Lawrence Valley toward N VT by the end of the forecast period. Moisture is a bit reduced relative to further south-east across New England, but strong 850-700mb convergence has increased overall values up to 1.5" due to slightly drier mid-level. However, this does steepen lapse rates to strengthen instability and updraft vigor and with moist low levels in strong convergence, thunderstorms will be capable of intense rates up to 1.75"/hr. As such spots of 1.5-2.5" are possible mainly across far NE NY into VT after 23-01z, before instability wanes with loss of daytime heating.=20=20 Further southeast within the broader southwesterly flow of larger scale cyclone, very strong thunderstorms with impressive anvils and broader than normal updraft/downdraft cores for New England continue to progress slowly across S NH, central MA with a few trailing cells into E Long Island. A subtle shortwave is slipping northeast through S VT, shearing along the way aiding vertical ascent, while also strengthening confluent southwest to south-southwest low level flow. The effective warm conveyor has much deeper, rich moisture with 1.5 to 1.7" total Pwats and slightly warmer lower profiles for similar stronger instability signals to maintain these stronger cores. Rain rates of 1.5-2" still remain, but as the wave shears and lifts north, the winds should abate ever so slightly. This has a positive affect for favorable upwind/flanking line redevelopment as well as slows forward propagation; both increasing rainfall duration. As such, scattered to numerous spots of 2-3" are possible across SE NH, MA into CT, RI), with some suggestion of even spots to near 4" by 03z. All considered, both areas are likely to continuing seeing incidents of flash flooding, while a spot or two of considerable flash flooding are possible in S and SE New England, especially if occurring in/near urban centers.=20=20 Gallina ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!4I3IpHObwZOyG17QIfiVKU3wi4T7j98YaQZJJGSigDlAG8LtncZdOVSHRofz0L2roFEq= CFIbIjgrnSKmBOEBJ7RxTbE$ for graphic product... ATTN...WFO...ALY...BOX...BTV...GYX...OKX... ATTN...RFC...NERFC...NWC... LAT...LON 45417058 44237043 42617056 41867057 41207085=20 40957169 40947246 41477339 42617347 43177333=20 43637378 44067491 44417542 44837540 45137481=20 45107245 45167165=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) .