Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Wed Dec 27 2023 21:31:10 AWUS01 KWNH 272131 FFGMPD NYZ000-NJZ000-PAZ000-DEZ000-MDZ000-VAZ000-DCZ000-280330- Mesoscale Precipitation Discussion 1224 NWS Weather Prediction Center College Park MD 430 PM EST Wed Dec 27 2023 Areas affected...Portions of the Mid-Atlantic Concerning...Heavy rainfall...Flash flooding likely Valid 272130Z - 280330Z Summary...Widespread rainfall this evening, some of which will be locally heavy, will pose a flooding risk for portions of the Mid-Atlantic. Total rainfall amounts of 1-2", locally higher, are expected. Discussion...An area of low pressure organizing off the North Carolina coast is expected to lift northeast up the Mid-Atlantic coast this evening, interacting with an existing warm front draped along the coast from Virginia to southern New England. An impressive moisture plume, characterized by PWs in excess of 1-1.25" (2-3 standard deviations above normal), will overspread the region aided by 850 mb flow between 30-40 kts out of the southeast. A narrow corridor of prolonged low level convergence is expected to set up from eastern MD and Delaware through northern New Jersey this evening, producing widespread rainfall. Hourly rain totals are expected to generally remain under 1" (supported by the latest HREF) and will likely peak in the 0.5-0.75" range this evening. However, the relatively prolonged period of moderate/heavy rainfall and favorable dynamics are expected to produce a swath of 1-2" (locally higher to 3") through late evening. The latest HREF shows high probabilities for at least 2" (70-80 percent) and a slight (10 percent) signal for 3" totals. This rainfall will fall over areas that are extremely wet and saturated due to recent heavy rainfall events (14-day rainfall departures are 200-300 percent of normal) and over the more urbanized corridor in the Mid-Atlantic. Of particular concern is portions of eastern PA and central/northern New Jersey where flash flood guidance is very low (1-hr FFG as low as 0.5" and 6-hr FFG as low as 1-1.5") and HREF neighborhood probabilities to exceed the 3-hr and 6-hr FFG are above 50 percent. The expected rainfall this evening over the very sensitive ground conditions is likely to cause excessive runoff and at least scattered instances of flooding through this evening. Taylor ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!7xKmS31gBal_x_3IbQhPrYK26o_9vc2qUWKCmGyPS9GssCkta7MVHnDksEo61iSXaUao= qTrc-SEgr0yytNtQIFIjwNc$ for graphic product... ATTN...WFO...AKQ...ALY...BGM...CTP...LWX...OKX...PHI... ATTN...RFC...MARFC...NERFC...NWC... LAT...LON 41817463 40817380 39537412 38297515 37837635=20 38217744 39377720 40397708 41577673=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) .