Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Fri Mar 17 2023 01:01:48 AWUS01 KWNH 170101 FFGMPD TNZ000-MSZ000-LAZ000-ARZ000-TXZ000-OKZ000-170700- Mesoscale Precipitation Discussion 0113 NWS Weather Prediction Center College Park MD 900 PM EDT Thu Mar 16 2023 Areas affected...Ark-La-Tex Region into Portions of the Mid-South Concerning...Heavy rainfall...Flash flooding possible Valid 170100Z - 170700Z Summary...Isolated instances of flash flooding are possible into the overnight hours across the Ark-La-Tex and adjacent portions of the Mid-South with 1-2"+ of additional rainfall (over soils that are already locally saturated). Discussion...A relatively narrow line of deep convection is organizing across the Ark-La-Tex late this evening (having evoloved from earlier discrete supercells and multicell clusters). Some threat for flash flooding is expected to develop ahead of this line of thunderstorms, as rainfall totals from earlier this afternoon/evening are already locally in excess of 1" across the region (per MRMS 6-hourly estimates). The mesoscale enviorment ahead of this line is currently characterized by precipitable water values of 1.2-1.6 inches (above the 90th percentile per SHV sounding climatology), wide-ranging MU CAPE of 500-3000 J/kg (with the highest values over TX) and deep layer (0-6 km) shear of 50-60 kts. A very strong low-level jet (850 mb winds of 30-60 kts) will continue to facilitate ample moisture transport into the area from the south-southwest ahead of the front, and strong shear should continue to organize convection linearly as well (while likely becoming more progressive over time). Hourly rainfall rates with some of the remaining discrete convection has been as high as 1-2"/hr, and embedded mesocyclones along the convective line will likely continue to remain capable of those rates into the overnight hours (with quick hourly totals of 0.5-1.0" more common outside of embedded cores). Given the earlier rainfall and somewhat already saturated antecedent conditions, an isolated flash flood threat is expected to develop (particularly where any embedded mesocyclones are able to result in brief localized training along southern portions of the line). That places the highest risk for flash flooding over the Ark-La-Tex itself (with 18z HREF neighborhood exceedance probabilities as high as 20-40%), but a localized threat may also extent northeastward into portions of the Mid-South as well (as earlier rainfall was more widespread across this region, and those antecedent conditions and relatively low flash flood guidance may make up for the lack of instability). The threat of flash flooding should gradually come to an end from west to east as the line of convection (and the associated cold front) moves across the region. Churchill ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!_xx136Yn7wz8V6sZovvbQQWIEsSjdNyM9RfI69kV3N4nR8Jjr5wr8FDVz3bBdmckqHBd= ebcFhsjlWdOOR0gb1Tfz2L4$ for graphic product... ATTN...WFO...EWX...FWD...HGX...JAN...LCH...LZK...MEG...SHV... TSA... ATTN...RFC...ABRFC...LMRFC...WGRFC...NWC... LAT...LON 35429159 35329029 35078980 34448978 33769004=20 33329094 32779149 31879212 31199303 30669420=20 30509581 30739745 31639779 32139722 32769640=20 33399572 34129495 34819427 35169306=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) .