Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Mon Dec 11 2023 07:46:32 AWUS01 KWNH 110744 FFGMPD MEZ000-MAZ000-RIZ000-CTZ000-111342- Mesoscale Precipitation Discussion 1198 NWS Weather Prediction Center College Park MD 243 AM EST Mon Dec 11 2023 Areas affected...Eastern New England Concerning...Heavy rainfall...Flash flooding possible Valid 110742Z - 111342Z Summary...An uptick in rainfall rates is expected across portions of eastern New England now into early Monday. This should result in an increasing flood threat over portions of eastern ME...with additional localized impacts also possible over RI into eastern MA. Discussion...Heavy rain will continue across eastern New England through the overnight and into Monday morning. The cold front will continue to make eastward progress across southern New England, with the heaviest rainfall generally along and just ahead of the front. With strengthening low level convergence and a few hundred J/KG of CAPE to work with would expect to see an uptick in rainfall rates from now through 12z as the front moves east across RI and eastern MA. Latest HRRR guidance supports hourly rainfall getting into the 0.5"-0.75" range, with 3 hour rainfall approaching 1.5". These amounts seem reasonable and will probably stay just below FFG values...with the progressive nature of the front preventing more widespread and significant impacts. Nonetheless, additional rainfall will locally exceed 2", bringing event total rainfall over 3" in spots...which may be enough to result in some urban and small stream flooding. A second relative maximum in rainfall amounts over the next six hours is expected over eastern ME. The coastal front will be more stationary in nature here...resulting in a bit longer duration of higher rainfall rates. The low level jet will continue to increase tonight into early Monday, resulting in impressive low level convergence. This convergence, along with ample mid and upper level forcing, will help overcome the lack of instability...with hourly rainfall expected to locally exceed 0.5" and potentially approach 0.75"/hr after 09z. The 03z-05z HRRR runs have been very consistent in producing 2-3" of rain over eastern ME in the 08z-14z time frame...with 3 hourly amounts locally exceeding 1.5". This is in addition to the 1-2" of rain that has already fallen across this area. Rainfall of the forecast magnitude may begin to locally approach and/or exceed 3 hourly FFG...which combined with longer duration event total rainfall forecast to start exceeding 3"...suggests we should see an uptick in flooding impacts by later tonight into Monday morning. It should be noted that the area of heaviest rain will be quite narrow...focused along and just to the north of the strong coastal front. In general think recent HRRR runs likely have a pretty good handle on rainfall rates/totals and the axis most likely to be impacted. Chenard ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!4HJGzyBGrG_ltY5IP1_aeGaPPFI_rf8ZyKJpPhNECS1IGFfHhDRMzVyxeDGxaID6txrv= Wp1NGgAyqyEhDXmD49QkWUE$ for graphic product... ATTN...WFO...BOX...CAR...GYX...OKX... ATTN...RFC...NERFC...NWC... LAT...LON 45656779 45606747 45326739 44846765 44266851=20 43716908 42656962 42267013 41947046 41567089=20 41257164 41317202 41577210 42067179 42487134=20 42797076 43397007 43686996 43986985 44436953=20 45016893 45596817=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) .