Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Tue Jan 24 2023 19:52:18 AWUS01 KWNH 241952 FFGMPD LAZ000-TXZ000-250110- Mesoscale Precipitation Discussion 0048 NWS Weather Prediction Center College Park MD 251 PM EST Tue Jan 24 2023 Areas affected...Upper TX Coast into Southwest LA... Concerning...Heavy rainfall...Flash flooding possible Valid 241950Z - 250110Z SUMMARY...Possible isolated incidents of flash flooding continue in vicinity of the I-10 corridor as the surface low deepens and shifts east-northeast this evening into overnight ... DISCUSSION...RADAR Mosaic depicts strong thunderstorms in proximity to the rapidly deepening surface low near DWH along the warm front to the east across the northern Houston Metro-suburbs with convergence bands along the cold front and western gulf confluence trof intersecting near Fort Bend county. Strong surface winds in the 20-25kt range with ~45-60 degrees of convergence of upper 60s to low 70s Tds, combined with slowly veering 925-850mb moisture stream out of the western Gulf across the low is supporting very strong ascent and moisture flux to support 2.5"/hr rates, with 2.77" reported at DWH in the last hour. Mid to upper level RAP analysis supported by GOES-E WV depicts the nose of best diffluence aloft at this weak inflection upstream of the surface low, showing signs of outpacing the best wave. This should support a few more hours of this strong convergence with similar rates across the Houston Metro into far SE TX. Thereafter, this inflection/best dynamic ascent will shift north and east of the surface wave and LLJ will veer narrowing the warm sector/onshore flow. While this restriction in warm sector is sizable, remaining unstable air in proximity to the warm front that is slowly lifting into SW LA will still support 1.5-2"/hr rates but cells should become more progressive reducing time window for southwest to northeast moving cells to train. As such, totals will diminish a bit toward the 2-3" range verses the 3-4" range expected over SE TX. HRRR 15 & 18z runs help to confirm this by depicting 15 minute totals still in the 1-1.25" range and moving quickly to result in maybe 30 minutes of intense rainfall. This should result in highly localized high run-off, but may not expand in a broad enough area to pose larger areal incidents in neighboring watersheds for all but low-end and urban style flash flooding.=20 This should further diminishing after 01-02z into south-central LA, as warm sector will likely be narrowed further with instability only remaining as MUCAPE isentropically ascended though the veering 850mb LLJ. The HRRR has been performing well over the last few runs, generally a little slow but faster than normal bias, providing additional confidence to its solution unfolding over the next few hours. Given recently dry soil conditions per LIS data from NASA SPoRT, flash flooding is considered possible, with best chances earlier and further west, but still remain non-zero well after 23z Gallina ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!7g5ypQjB1VrcktLMiMPqZBn2uXWqNoAPx3ImRTOaP0lJEa16QX7NvAaO1q6rqTvWdfVM= VX9l_F4PvizMMW7_EtfVgag$ for graphic product... ATTN...WFO...HGX...LCH...SHV... ATTN...RFC...LMRFC...WGRFC...NWC... LAT...LON 31589253 30909190 29899205 29619264 29729359=20 29429465 28979589 29399640 30559558 31359428=20 =20=20=20=20=20=20=20=20=20=20=20=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) .