Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Wed Mar 01 2023 20:53:09 AWUS01 KWNH 012053 FFGMPD TNZ000-MSZ000-ARZ000-TXZ000-020230- Mesoscale Precipitation Discussion 0079 NWS Weather Prediction Center College Park MD 352 PM EST Wed Mar 01 2023 Areas affected...Central & Southern Arkansas...Southwestern Tennessee...Northern Mississippi... Concerning...Heavy rainfall...Flash flooding possible Valid 012100Z - 020230Z SUMMARY...Individual fast moving but efficient supercells capable of quick (subhourly) 1-2" totals pose localized isolated flash flooding risk before thunderstorms expand in coverage and likely align favorably for repeating training after 00-01z time frame.=20 Broader axis of 2-3" totals should increase risk for flash flooding in coverage and magnitude. DISCUSSION...20z surface analysis depicts a weak wave near RUE in central AR moving along a SW to NE frontal zone, from N TX to Lake Michigan, in association with weak shortwave feature that activated convection this morning in northeast TX. This wave will continue to exit, while stronger upper-level jet support/nose of wave aloft continues to advance from the west in north Texas. VWP out of SHV depicts increasing low level flow that generally matches nose of low to mid-level moisture noted in CIRA LPW loop. Surface Tds in upper 60s to near 70 in spots along increasing moisture to 800mb is suggesting total available moisture of 1.5", with some increasing moisture convergence at the intersection near the the surface to boundary layer. SPC MCD 215 supports discrete supercells with severe parameters; in addition, the strong shear profiles will enhance isallobaric moisture flux convergence at the updraft. While steep lapse rates and hail generation are likely to rob from some of the intense rainfall generation, CAMS also support sufficient efficiency to support 2-2.5"/hr rates after initiation in the 21-23z time period. Cell motions are likely to be quick given deep layer shear as well likely to limit duration at any given point; however, HRRR runs suggest peak intensity totals of 1.2-1.5" in 15 minutes are likely with the cores. Rates of this magnitude are likely to result in increased runoff and possible localized flash flooding concerns in the short-term. An overlap with a narrow swath of reduced soil capacity from Polk to Pulaski to Crittenden counties in AR (last week's thunderstorms), may increase this risk but even drier than normal grounds are likely to not to absorb this intensity even across S AR. In the longer term after 00-01z... Low level jet will continue to strengthen and veer with time, and with the front flattening more east-west across AR into W TN should still support favor expanding isentropic ascent.=20 Decoupling boundary layer near/just after night-fall likely to result in increased elevated storm development across a broader S AR into TN/MS likely resulting in overall convective coverage.=20 Rain rate intensity may diminish slightly but given deeper layer flow a more favorable axis for training is probable to result, especially with a favorable back-building regime given 850mb south-southwest LLJ. However, there remains some uncertainty to the latitude of this training axis being dependent on the individual cells interaction/enhancement of the frontal zone in the region potentially crossing SW TN or Northern MS. Irrespective of placement, this axis should be broader in nature than the discrete cells prior to 00z resulting in a swath of 2-3" totals with maybe a very isolated 4" possible through 03z. As such, the potential for flash flooding will increase with greater areal coverage, but still remains uncertain to consider flash flooding possible with this discussion. Gallina ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!7xuzu8qtOVIZt_8Na1Ppctp7TsYNydrNEsLO_cbxgTE4HupK7petNh6OnB7HOEOC0Ogh= mVkuguVn1TrkYGDzThIBDvo$ for graphic product... ATTN...WFO...JAN...LZK...MEG...SHV... ATTN...RFC...ABRFC...LMRFC...SERFC...NWC... LAT...LON 35758926 35318831 34418831 33768913 33299146=20 33239335 33579427 34439436 35359274=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) .