Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Tue Mar 28 2023 05:57:44 AWUS01 KWNH 280557 FFGMPD FLZ000-ALZ000-MSZ000-LAZ000-281000- Mesoscale Precipitation Discussion 0142 NWS Weather Prediction Center College Park MD 157 AM EDT Tue Mar 28 2023 Areas affected...Central Gulf Coast Concerning...Heavy rainfall...Flash flooding possible Valid 280600Z - 281000Z SUMMARY...Increasing coverage of efficient heavy rainfall producing thunderstorms. Rates of 2.5"/hr at times and slow motions may result in a few widely scattered incidents of flash flooding/urban flooding are possible due to mergers, repeat tracks. DISCUSSION...A few thunderstorms have become congealed into a larger complex across E Washington Parish, Pearl River and Harrison counties in LA/MS. Recent VWP suite and short-term HRRR/RAP solutions suggest increased confluent veering in the 925-850mb layer along and south of the synoptic stationary front that crosses central AL toward the coastal counties of MS and near I-10 across S LA. SWIR 3.9um also depicts a NW to SE weakly defined boundary/axis from around BTR to MSY, possibly related to an old outflow boundary from earlier convection. The veered low level flow appears to be utilizing the axis for orthogonal convergence/ascent to maintain and expand convective coverage within this unstable environment. Surface Tds in the Mid-70s, co-aligned with 850 moisture strip (12-13C) along the coast will allow for shallow but efficient rainfall production given the 20-25kt ascent/moisture flux. This should allow for rates of 2.5"/hr with the cores and given the broadening coverage, repeating/merging are possible to enhance locally short-term totals. Cell motions are likely to be driven by dry air/cold pool generation at about 5-15kts. Ahead of this cluster, onshore flow appears to be strengthening over the last hour or so in observations and frictional speed convergence has sprouted numerous thunderstorms along the sea-breeze as far east as western FL panhandle. Given the forcing is stationary, regenerative updrafts just ashore of the coast, along with the aforementioned slow moving cells from the west may allow for hours of pulses of heavy rainfall resulting in localized rapid inundation concerns in typical poor drainage areas prone to flooding, especially in urban locales. Still, very high FFG, higher infiltrating soils are likely to limit the coverage to a few widely scattered incidents of flooding where mergers occur, mainly if they overlap with those known prone urban locations.=20 Gallina ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!8IwAURpeqGtgTBMSvGDTkb3LcLLGY67YjZiDUEn0LtnIh7x_Zftp8iqgZ3vG00wMqw2L= K-2kHvB3gm9_do1t71Ut8Zs$ for graphic product... ATTN...WFO...JAN...LIX...MOB... ATTN...RFC...LMRFC...SERFC...NWC... LAT...LON 31078764 31028704 30808650 30318651 30158751=20 30028852 29968884 29678923 29698982 29859042=20 30259061 30619015 30978894=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) .