Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Wed Dec 14 2022 04:13:42 AWUS01 KWNH 140413 FFGMPD LAZ000-TXZ000-140915- Mesoscale Precipitation Discussion 1160 NWS Weather Prediction Center College Park MD 1113 PM EST Tue Dec 13 2022 Areas affected...Upper Texas Coast into Central & Southwest Louisiana... Concerning...Heavy rainfall...Flash flooding possible Valid 140415Z - 140915Z SUMMARY...As shortwave exits, mid-level steering flattens to slow cell motions and allow for increased duration for thunderstorms capable of 1.5"/hr. Localized totals in excess of 4" pose localized flash flooding risk overnight. DISCUSSION...GOES-E WV suite denotes a subtle shortwave along the interface of the warm conveyor belt lifting through the Delta Region of E AR. Its exit, is slowly reducing and veering low level flow which is becoming increasingly oriented to the ongoing convective line from KAQV back toward the Houston Metro area.=20 This is in response to slight shortwave ridging across SE TX associated with the subtropical jet. As such, 500-1000 thickness pattern is broadening across S LA, reducing forward propagation for deeper convective cells. While moisture flux is reducing above the boundary layer due to the veering, etc, solid surface southerly response remains fairly strong and orthogonal to the boundary maintaining convective support. The airmass off the Gulf Coast is fairly unstable and is warm/moist with Tds in the 70s to mid 70s. MLCAPEs of 1500-2000 J/kg will support stronger updrafts, but modest moisture flux from only sfc to boundary layer, should limit some of the rainfall efficiency toward 1-1.5"/hr perhaps rarely reaching 2"/hr with transient subtle waves supporting cell rotation.=20 Favorable Upstream shortwave energy is still approaching with solid upper level divergence to support redevelopment upstream toward Houston. While steering flow is strong for quick cell motions, the steering is fairly unidirectional to the orientation to the active convective line/convergence axis to support some repeating. As such, some locations of 2.5-3.5" totals remain possible through the overnight period.=20=20 Recent heavy rainfall over the last 7 days has increased shallow soil saturation levels. NASA SPoRT 0-40cm soil saturation ranges from 60-80% which is in the 80th percentile for this time of of year. So while overall rates are at or slightly below rapidly rebounding 1 to 3hr FFG values (2-3 and 3-4" respectively), given slower propagation may still pose scattered flash flooding risk over the overnight period and is considered possible. Gallina ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!8-l-OW7LaY0Fg_8PY1wpWrHLFh-uia6GmHzQoBv6_hr_PxWmk5t91ggIIB0dHOtWyULr= jNQ7jtISFhLskLxNVeZ-8cA$ for graphic product... ATTN...WFO...HGX...JAN...LCH...SHV... ATTN...RFC...LMRFC...WGRFC...NWC... LAT...LON 31849265 31829201 31639159 30979181 30269276=20 29969370 29499512 29379588 29979590 31129435=20 31449378 31629335=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) .