Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Tue May 09 2023 23:20:56 AWUS01 KWNH 092320 FFGMPD TXZ000-100430- Mesoscale Precipitation Discussion 0248 NWS Weather Prediction Center College Park MD 720 PM EDT Tue May 09 2023 Areas affected...South-central Texas... Concerning...Heavy rainfall...Flash flooding possible Valid 092320Z - 100430Z SUMMARY...Potential for slow moving strong thunderstorms for localized possible flash flooding in late evening into early overnight hours. DISCUSSION...Deep layer closed low/shortwave feature is stacked across Medina county. 23z mesoanalysis and GOES-E visible imagery depict areas in the eastern and southeastern quadrant of the deep low are trying to moderate after stabilized environment though the afternoon. Return easterly flow off the unstable western Gulf and filtered afternoon sunshine has brought temperatures back into the upper 70s and low 80s over upper 60s and low 70s dew points, combined with moist profiles through depth (700mb RH between 70-90%) with some modest mid-level lapse rates support some increasing band of unstable air to form across the area of concern. Visible stable wave clouds continue to erode across the area suggesting reducing inhibition while a few cells have been breaking out in areas of maximized convergence both aloft (near the upper low from McMullen to Bexar county or near frictional/coastal convergence boundary in Bee to Calhoun counties.=20 RAP/HRRR analysis and forecast sounding/instability suggest this narrow area between will continue to maintain with some mid-level advection from the more unstable area (south of LRD to NQI). Weak but confluent steering flow should allow for slow forward propagation while leaving upstream inflow areas unobstructed to feed moisture flux convergence for stronger updraft maintenance particularly after 00z when low level flow strengthens (from 20kts to over 35kts). Given deep layer moisture profiles, total PWats of 1.75" may allow for initially 1.5-1.75"/hr rates but slowly increase with strengthening of LLJ to up to 2". Given slow motions/propagation to the east from the upper low and favorable divergent outflow aloft (right entrance to diffluent jet, even if weak), localized storm totals of 3-5" are possible through 06z.=20 This is of particular concern given recent heavy rainfall and saturated ground conditions dotted across the region from the last few days. As such localized flash flooding is considered possible late this evening into the overnight. The greatest uncertainty will remain with the available instability for the strength/maintenance of the updrafts to produce intense enough rainfall rates, given this flash flooding is considered possible. However, if conditions remain favorable, there is potential upscale growth if the latent heat release can=20 feed back on strengthening the mid-level low and upper-level outflow jet. Therefore, maintaining inflow of moist/unstable air to maintain the complex after 04z...as such will continue to monitor closely for any update. Gallina ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!_nPK3zc5Zw424eU_h7_UTlzTjJPEc5JUYMPbfeD1IbzL-P_Qx1IUG8NgLM5yPmZbjIR7= 0jxsZxK4mP4gAgL8Oln_Cdg$ for graphic product... ATTN...WFO...CRP...EWX...HGX... ATTN...RFC...WGRFC...NWC... LAT...LON 30349704 30139669 29709646 29349652 28959673=20 28479718 27909773 27759827 28019886 28499872=20 29029873 29839867 30309768=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) .