Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Mon Jan 08 2024 22:22:05 AWUS01 KWNH 082221 FFGMPD ALZ000-MSZ000-LAZ000-090420- Mesoscale Precipitation Discussion 0003 NWS Weather Prediction Center College Park MD 520 PM EST Mon Jan 08 2024 Areas affected...South-Central/Southeast LA...Southern MS...West-Central/Southwest AL Concerning...Heavy rainfall...Flash flooding likely Valid 082220Z - 090420Z SUMMARY...Areas of very heavy rainfall from training clusters of showers and thunderstorms will likely impact areas of south-central LA through southern MS heading well through the evening hours. Numerous areas of flash flooding are generally considered to be likely, and this may include a locally significant urban flash flood threat. Areas of west-central to southwest AL will see a similar concern later tonight. DISCUSSION...Very cold convective tops are seen in GOES-East IR satellite imagery overspreading areas of south-central LA as a cluster of very heavy showers and thunderstorms moves northeastward in off the Gulf of Mexico. St. Mary Parish in particular is seeing some of the heaviest rains currently, but this activity is expected to grow upscale and maintain a strong level of organization as it expands off to the northeast over the next several hours across adjacent areas of south-central to southeast LA and gradually through southern MS. In addition to well-defined concerns for severe weather heading through the evening hours, the evolving convective threat will include increasing concerns for very heavy rainfall and resulting areas of flash flooding. A low-level jet of 60+ kts will be driving very strong warm air advection and moisture transport in off the Gulf of Mexico as a warm front arrives from the south-southwest and allows for the arrival of a much more unstable airmass. This coupled with strong synoptic scale forcing and enhanced shear profiles will yield clusters of discrete convection including supercells that in time will tend to merge/organize into more linear segments capable of training over the same area. Rainfall rates are expected to increase as stronger instability arrives this evening and coincides with enhanced IVT values. PWs are forecast to rise to 1.5 to 1.75 inches, with impressively convergent and strong IVT vectors with magnitudes reaching upwards of 1000 to 1250+ kg/m/s in the 00Z to 06Z time frame. A consensus of the 12Z NAM/GFS solutions in conjunction with the wind fields from the 12Z HREF guidance would suggest an axis along and adjacent a line from New Orleans, LA (MSY) through Hattiesburg, MS (PIB) would be the main corridor for the strongest atmospheric moisture transport and heaviest rainfall potential going through the evening hours. The heaviest rainfall rates should gradually focus over areas of southern MS where the 12Z HREF supports some 20% to 40% probabilities of rainfall rates reaching 2 to 3 inches/hour. Storm totals in general from south-central LA through southern MS are expected to be on the order of 3 to 6 inches, with some isolated 8+ inch amounts possible in southern MS where there will be a more organized concern for cell-training which is strongly supported in recent runs of the experimental WoFS guidance. Numerous areas of flash flooding are generally considered to be likely, and this may include a locally significant urban flash flood threat for some of the major metropolitan areas including New Orleans, LA early this evening, and gradually areas downstream over southern MS including Hattiesburg. Later tonight, areas of west-central to southwest AL will need to be closely monitored for similar rainfall and flash flooding concerns. Orrison ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!64Mm0m-J2vC-cIM-zZtjRU2OfsL3YilK3yLbYKJHGwipo1CCbYRJojFcXQZAo39QrTa4= z3dA7eTVlmO3U68XV-PtFvU$ for graphic product... ATTN...WFO...BMX...JAN...LCH...LIX...MOB... ATTN...RFC...LMRFC...SERFC...NWC... LAT...LON 33018941 32778826 32048777 31048795 30148853=20 29608931 29419005 29529093 29829164 30299208=20 30959217 31739177 32609078=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) .