Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Mon Jul 10 2023 02:56:22 AWUS01 KWNH 100256 FFGMPD MAZ000-CTZ000-NYZ000-NJZ000-100830- Mesoscale Precipitation Discussion 0682 NWS Weather Prediction Center College Park MD 1055 PM EDT Sun Jul 09 2023 Areas affected...Southeast NY...Long Island...Much of CT...Far Southwest MA... Concerning...Heavy rainfall...Flash flooding likely Valid 100300Z - 100830Z SUMMARY...Very slow moving & regenerative bands along/north of the surface low poses likely flash flooding tonight. Due to training, localized totals may exceed 5" through 09z, potentially across dense urban areas with life-threatening flooding conditions possible. DISCUSSION...A precarious localized very heavy rainfall event is starting to take shape across SE NY/Long Island and southern CT.=20 02z surface analysis denotes the developing low is near the mouth of Raritan Bay. Aloft the mid-level the digging shortwave trof over W PA is starting to tilt negatively to strengthen low level cyclogenesis over the Catskills/Lower Hudson Valley sharpening deep layer moisture convergence along deformation trough along/north of the surface low. Tds in the low 70s and total PWat values nearing 2"; however, the directional and speed convergence is also increasing with VWP already perking up to 20kts with backed surface flow suggests 45-60 degrees of convergence.=20=20 Combined with RAP analysis supporting enhanced ribbon of unstable air across Western Long Island as high as 1000 J/kg, this will support deeper thunderstorm activity with 1.5-1.75"/hr.=20 Deep layer flow above 700mb is mainly south enough to support slow (10-15kts) of northward cell motion with limited (less than 5) eastward propagation expected over the next few hours.=20 Convergence to the south will support backbuilding as well. As such, there is growing consensus of an axis of enhanced rainfall totals up to 5" through 09z. The vast majority of Hi-Res CAMs all point to those 5-7" in some location within the MPD through 09z, though precise location relative to urban centers remains difficult to pinpoint, current observational trends suggest best placement will be across SE NY, SW CT. Best redevelopment (less persistent heavy rainfall) across portions of Western to Central Long Island. Additional downstream thunderstorms along the warm front may pose local 1-3" totals ahead of the main line across E Long Island and SE CT, not likely rising to the flash flooding potential, but may help to condition the area for later this morning.=20=20 Gallina ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!960hlTqtCnY-e-lR5WzQrRlr46g8j8Y8uKdgpWMFlVH64t6IcxIpeTRbgw7QUJC8iOhb= P1_X91tQSahCfmYUOxbWQ34$ for graphic product... ATTN...WFO...ALY...BOX...OKX... ATTN...RFC...MARFC...NERFC...NWC... LAT...LON 42187352 41947284 41737248 41437212 41117200=20 40767231 40637299 40517346 40597404 41107406=20 41677424 42057392=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) .