Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sun Jul 16 2023 14:46:52 AWUS01 KWNH 161446 FFGMPD CTZ000-NYZ000-NJZ000-PAZ000-DEZ000-MDZ000-VAZ000-NCZ000-DCZ000-162045- Mesoscale Precipitation Discussion 0746 NWS Weather Prediction Center College Park MD 1045 AM EDT Sun Jul 16 2023 Areas affected...Portions of the Mid-Atlantic Coastal Plain Concerning...Heavy rainfall...Flash flooding likely Valid 161445Z - 162045Z SUMMARY...Additional rounds of heavy showers and thunderstorms will be expected over the next several hours. More areas of flash flooding are expected and especially over areas that have already seen heavy rainfall over the last 12 to 24 hours. DISCUSSION...The latest surface analysis shows a well-defined trough axis stretching from south-central VA northeastward up along and just east of the I-95 corridor including southeast PA and northern NJ. This is providing an axis of persistent low-level convergence and is also helping to maintain a pool of deep tropical moisture and moderate instability across the Mid-Atlantic coastal plain. MLCAPE values remain as high as 1500+ J/kg and with PWs that are very high and deeply tropical in nature as seen in 12Z RAOB data and CIRA-ALPW data plots. PWs are locally as high as 2.2 to 2.4 inches and the depth of the warm cloud layer seen in the 12Z IAD RAOB sounding was impressively high with a WBZ height seen at over 15,000 feet. The proximity of additional vort energy lifting northeast across the Mid-Atlantic coastal plain coupled with relatively focused surface moisture convergence near the aforementioned trough should work in tandem with the available instability for a gradual expansion of convection over the next several hours. Cloud cover may tend to temper the boundary layer instability to an extent, but sufficient levels of solar insolation and vertical shear should promote at least broken bands of semi-organized convection. An additional key facilitator of convection for this afternoon will also be the arrival of fairly strong right-entrance region upper-level jet dynamics ahead of the approaching Great Lakes upper trough. Given the extremely efficient warm rain environment that is in place as noted in the 12Z RAOB data, the rainfall rates with the additional convective clusters over the next several hours will be capable of being very high and locally reaching 2 to 3+ inches/hour. Additional localized rainfall amounts of as much as 4 to 6 inches will be possible where any of these areas of convection train over the same area. Given the very heavy rainfall totals that have already occurred locally over the last 12 to 24 hours, and the resulting soil saturation, these additional rainfall totals are likely to result in more areas of flash flooding which could locally be significant. This will include at least portions of the I-95 corridor stretching from Richmond, VA through the eastern suburbs of Washington D.C. and up through the Philadelphia and New York City metropolitan areas. Orrison ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!5mL1O8N4ZTDnJ0q0A0ga8pWk7Yh8NqpI8DDT7Mw_1h4H-U5h2HiOOS0fmnojqG7hiTVd= hojBS50dGud_aUDpwOzNt6Q$ for graphic product... ATTN...WFO...AKQ...LWX...OKX...PHI... ATTN...RFC...MARFC...NERFC...SERFC...NWC... LAT...LON 41277391 41077332 40377354 39487414 38187490=20 37027580 36537676 36677793 37317840 38177794=20 39217658 39947572 40977468=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) .