Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Mon Sep 11 2023 15:58:51 AWUS01 KWNH 111558 FFGMPD MEZ000-MAZ000-NHZ000-RIZ000-VTZ000-CTZ000-NYZ000-NJZ000-PAZ000-DEZ000-MDZ00= 0-112155- Mesoscale Precipitation Discussion 1058 NWS Weather Prediction Center College Park MD 1157 AM EDT Mon Sep 11 2023 Areas affected...northern Mid-Atlantic to southern/central New England Concerning...Heavy rainfall...Flash flooding possible Valid 111556Z - 112155Z Summary...Isolated to scattered areas of flash flooding are expected to develop this afternoon from portions of the northern Mid-Atlantic into southern/central New England. Efficient rainfall with 1-3 inches in an hour or less can be expected, but coverage of these higher rates will likely stay low across the region. Discussion...Water vapor imagery at 1530Z showed a deamplifying mid-level shortwave trough extending from east-central NY into east-central VA, tracking toward the ENE. Visible imagery showed expanding and maturing Cu across a broad section of the Northeast into the Delmarva Peninsula. The 12Z OKX sounding was fairly representative of the environment across the northern Mid-Atlantic into southern New England showing a 1.8 inch PWAT, a 12.7 kft wet bulb zero height and a relatively tall/skinny CAPE profile with little to no CIN, supportive of the potential for efficient rainfall. Selected regional rainfall reports from earlier this morning showed rainfall rates of 0.5 to 1 inch in 15-30 minutes, working within an estimated 500-1000 J/kg MLCAPE (per SPC mesoanalysis data). Several mesoscale circulations were noted out ahead of the mid-level trough axis aiding ascent but daytime heating will be a large contributor to the development of showers/thunderstorms later today. It is expected that filtered solar insolation through varying degrees of cloud cover will support an increasing coverage of MLCAPE into the early/middle afternoon with recent RAP forecasts indicating 500-1500 J/kg from the eastern Delmarva Peninsula into NJ and southern to central New England through 18Z. Forcing ahead of the synoptic-scale mid-level trough and mesoscale vorticity maxima out ahead will aid in the development of scattered showers and thunderstorms, some of which could be slow moving. Southwesterly cell motions from warm-topped showers may only average 5-15 kt forward speed, allowing for rainfall rates between 1-3 in/hr, although 1 to 3 inches in less than an hour will be likely for a few cells as well. These higher end sub-hourly rates will especially be true where cell alignment occurs with the steering flow, allowing for short term training. Increased flash flood potential will exist over urban areas and where overlap occurs from heavy rain which fell over the past few days. Otto ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!8aGB4D6MMEGWsYK6FqybRCkfNRQljQtcfsuaG5v6nltBHhBV_fujK93-Z5yr1HF4LgFI= YZDSAZU7mQHzEYsRC7HeDX8$ for graphic product... ATTN...WFO...AKQ...ALY...BOX...GYX...OKX...PHI... ATTN...RFC...MARFC...NERFC...NWC... LAT...LON 44057126 43437012 41957066 41307136 40817218=20 40317350 39247402 38527480 38277517 38517560=20 39277559 39967543 40857499 41337457 41957362=20 42657303 43207233 43577201=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) .