Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Thu Apr 27 2023 12:18:20 AWUS01 KWNH 271218 FFGMPD FLZ000-ALZ000-MSZ000-LAZ000-271815- Mesoscale Precipitation Discussion 0211 NWS Weather Prediction Center College Park MD 816 AM EDT Thu Apr 27 2023 Areas affected...Southeast LA...Central/Southern MS...Western/Southern AL...Western FL Panhandle Concerning...Heavy rainfall...Flash flooding possible Valid 271215Z - 271815Z SUMMARY...Heavy showers and thunderstorms may tend to expand a bit further in coverage going through midday. Some isolated instances of flash flooding will be possible. DISCUSSION...The radar imagery overall is showing a general expansion of shower and thunderstorm activity down across the central Gulf Coast region and extending a bit farther north up across areas of central/southern MS and gradually approaching western and southern AL. The activity is being driven by upstream shortwave energy traversing the Lower MS Valley and interacting with a quasi-stationary front draped near the Gulf Coast. Multiple waves of low pressure are noted along the front with one wave over southeast LA and another one over far southern MS. These waves of low pressure are combining with a nose of moderate instability with MLCAPE values of 1000 to 2000 J/kg and a fair amount of vertical shear (effective bulk shear of ~40 kts) to result in several semi-organized clusters of strong convection, including a few notable supercells, with very heavy rainfall rates. PWs are on the order of 1.5 to 1.6 inches which is about 1.5 standard deviations above normal, and this coupled with the instability and general storm organization should yield some rainfall rates that approach or locally exceed 2 inches/hour. Radar and satellite trends suggest areas of southeast LA through much of southern MS, and into parts of western and southern AL will see the greatest concentration of convection at least over the next few hours. Toward midday and the early afternoon hours, parts of the western FL Panhandle will also likely get into a threat of more organized convection. The HRRR guidance does suggest locally as much as 3 to 4 inches of rain going through early midday. The 06Z HREF guidance does show some low-end probabilities for seeing 3-hour FFG exceedance, and 6-hour amounts exceeding the 5-year ARI values. This coupled with the high rainfall rates in general suggest at least a threat for some isolated instances of flash flooding over the next few hours, and especially around the more sensitive urban areas. Orrison ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!-moMXHu_Kru_dUOFguopZBnqxg1TA1BUzWZwE7oPahhEhlMj1hbOxM1aeuVO4E7y4UFF= v1WpQB2k9Q2LoJlj8e_p4g4$ for graphic product... ATTN...WFO...BMX...JAN...LCH...LIX...MOB...TAE... ATTN...RFC...LMRFC...SERFC...NWC... LAT...LON 32728797 32518660 31908586 31338579 30508635=20 30238813 29638992 29539125 29949157 30699049=20 31308998 32048953=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) .