####018000595#### PENA01 KWNH 021200 @UHPISF000CN MPDSUM@V2.0@0101700060@12020524@@0NMCGPHMPD b@!' `' ` @ & B7)p&PNAM02@@|NO MDs ARE CURRENTLY IN EFFECT @@d&MESOSCALE DISCUSSION SUMMARY GRAPHIC @@d& OF ALL VALID MESOSCALE DISCUSSIONS AT @@d& TIME OF PRODUCT CREATION:@@d& ISSUED 05/02/2024 1415Z @@ dNOAA/NWS/NCEP@@d WEATHER PREDICTION CENTER @@d FOR COLOR VERSION SEE: @@d WWW.WPC.NCEP.NOAA.GOV @####018004291#### AWUS01 KWNH 021418 FFGMPD LAZ000-TXZ000-022000- Mesoscale Precipitation Discussion 0209 NWS Weather Prediction Center College Park MD 1017 AM EDT Thu May 02 2024 Areas affected...Central to Upper TX Coast...Southwest LA... Concerning...Heavy rainfall...Flash flooding likely Valid 021415Z - 022000Z SUMMARY...Significant flash flooding ongoing across southeast Texas. While rates and areal coverage is expected to decrease through the morning, high rain rates of 3"/hr and training over the next few hours will pose additional areas of new considerable flooding through the early afternoon. DISCUSSION... Leading edge...Louisiana... GOES-E Visible/10.3um IR loop along with RADAR mosaic, depicts a mature/intense MCS with well defined MCV over the Piney Woods of E Texas moving into west-central LA with well defined bow extended southward to the Sabine Pass/BPT. These bows have solid southeasterly inflow with surface Tds in the mid 70s, while boundary layer to 700mb moisture is pooled through the central LA coast feeding northwest into the complex. Fairly saturated deep profile from LCH still retains over 2000 J/kg of CAPE, to maintain strong updrafts. However, forward propagation may limit overall rainfall totals, but given 2-3"/hr rates, initially, post frontal shield precipitation should maintain modest rain-rates (.5"/hr) to allow for streaks of 2-4" totals across Southwest LA, favoring further south where moisture convergence will maximize in proximity to the higher Theta-E/more unstable Gulf air. Southeast Texas including Houston... While MCS cold pool is pressing the leading edge eastward, there is currently a solid balance between weaker southward push of the cold pool and southerly over-running ascent pattern that lays more perpendicular to the outflow boundary. As such, an east-west linear feature with embedded elements tracking more eastward have resulted in greatest risk of considerable/significant flash flooding over the last few hours. This is likely to maintain with 2-3"/hr rates over the next few hours with very slow southward drift across Liberty/E Harris into Chambers county with spots of additional 3-6" probable through to late morning/early afternoon. GOES-Visible imagery shows the westward edge of the outflow boundary is starting to become more shallow. However, the old rear-inflow jet convergence axis developed a secondary convective area, that generated a second cold pool that is dropping south to reinforce and steepen the depth of the cold pool and likely increase boundary layer to 850mb moisture convergence. Additionally, VWP and GOES low level AMVs suggest weak veering and confluence along this upwind edge as well. This strongly hints at upstream new development over the next hour or so, as the area has ample untapped/unstable and highly saturated low level moisture (with sfc/850mb PW over 1"). This should allow for rates of 2.5-3"+/hr rates but there is uncertainty of duration. This uncertainty is driven by the strength of the upstream cold pool undercutting and pressing best convergence southward into the Gulf, reducing overall duration and therefore totals. This is the ideal scenario and may result in localized 2-4" totals and spotty flash flooding; however, there are model and observational trends in RADAR/satellite imagery that may be much worst cast scenarios. Worst case evolution would result from the development of a meso-low generation along the initial outflow boundary in proximity to the western Houston suburbs or points westward in Austin/Colorado county that may stall southward cell motions allowing for efficient 3"/hr rate cells to remain relatively stationary for a few hours with spot totals of 6-10" by early afternoon...which would result in significant/ considerable flash flooding. Gallina ...Please see www.wpc.ncep.noaa.gov for graphic product... ATTN...WFO...CRP...EWX...HGX...LCH...SHV... ATTN...RFC...LMRFC...WGRFC...NWC... LAT...LON 31749268 30959188 29619192 29659368 29189476 28539630 29769715 30359703 30529645 30699461 30959392 31479351 31739310 ####018000739#### PENA01 KWNH 021200 @UHPISF000CN MPDSUM@V2.0@0101700060@12020524@@0NMCGPHMPD b@!' `' ` @ & B7)p&PNAM02@@BS~}}|{|z{zz{|~~}}|||}{|{|~@@S@@S@@x0209 @@d&MESOSCALE DISCUSSION SUMMARY GRAPHIC @@d& OF ALL VALID MESOSCALE DISCUSSIONS AT @@d& TIME OF PRODUCT CREATION:@@d& ISSUED 05/02/2024 1418Z @@ dNOAA/NWS/NCEP@@d WEATHER PREDICTION CENTER @@d FOR COLOR VERSION SEE: @@d WWW.WPC.NCEP.NOAA.GOV @