Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Mon Dec 18 2023 14:05:33 AWUS01 KWNH 181405 FFGMPD MEZ000-MAZ000-NHZ000-RIZ000-VTZ000-CTZ000-NYZ000-182003- Mesoscale Precipitation Discussion 1207 NWS Weather Prediction Center College Park MD 904 AM EST Mon Dec 18 2023 Areas affected...Much of the Northeast Concerning...Heavy rainfall...Flash flooding likely Valid 181403Z - 182003Z SUMMARY...Heavy rains will continue to overspread much of the interior of the Northeast going through the midday hours. Numerous areas of flash flooding can be expected given the wet antecedent conditions. DISCUSSION...Widespread areas of heavy rainfall continue to surge well up across the interior of the Northeast as a very strong area of low pressure continues to organize and lift north-northeastward up across coastal areas of the northern Mid-Atlantic and into southern New England. The morning satellite presentation of the deepening cyclone is quite impressive with strongly divergent flow aloft seen in association with a coupled upper jet structure. Very strong warm air advection and moisture transport aided by a powerfully strong south-southeast low-level jet of 60 to 90 kts around the eastern flank of the low center just northwest of New York City is working in tandem with the enhanced deep layer ascent for the widespread heavy rainfall and efficiently high rainfall rates. There is a nose of modest instability riding up across coastal areas of southeast NY and Long Island which is gradually shifting up into adjacent areas of southern New England. MUCAPE values of 250 to 500 J/kg are noted up across this region with the instability rather closely aligned with a warm front that has advanced well inland. Some of the heaviest rainfall rates are associated with some strongly forced convective elements east of the low center that are riding up across eastern Long Island and into much of central/eastern CT and RI. Over the next couple of hours, these stronger convective elements advancing into southern New England will be capable of producing 1 to 1.5"/hour rainfall rates. Meanwhile, farther inland over New England including areas of VT/NH and ME, the rainfall rates will be more modest, but will be quite efficient and capable of reaching or exceeding a 0.50"/hour given such strong warm air advection/isentropic lift and Atlantic moisture transport. The persistence of these rates over very sensitive ground conditions with wet/saturated soils will encourage enhanced runoff concerns. Some areas of snowmelt over the Green and White Mountains will only aggravate the runoff potential. The orographically favored areas of southern VT, and especially NH and into western ME will be favored going through midday and early afternoon for an additional 2 to 4 inches of rain locally. Numerous areas of flash flooding are expected over the next several hours as the rains continue to lift northeast across the region, and this will include areas of urban flash flooding. Orrison ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!9xND60WKm3_s1taPZr4AeQWteLoGNk-ZpDM12uOEDEdkrf5ZFP3zG-eVeLk2VjRR88bm= uc78tige2FvGPnR3eg9Cxag$ for graphic product... ATTN...WFO...ALY...BOX...BTV...CAR...GYX...OKX... ATTN...RFC...NERFC...NWC... LAT...LON 46386912 46266821 45786769 45306763 44706778=20 44046938 42817061 41727106 41167155 40827199=20 40707287 41787432 43507440 44577369 44997258=20 45267134 46117014=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) .