


Flash Flood Guidance
Issued by NWS
Issued by NWS
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958 AWUS01 KWNH 150508 FFGMPD TXZ000-151100- Mesoscale Precipitation Discussion 0692 NWS Weather Prediction Center College Park MD 108 AM EDT Tue Jul 15 2025 Areas affected...Southern Edwards Plateau...Rio Grande Valley of South-Central Texas... Concerning...Heavy rainfall...Flash flooding possible Valid 150510Z - 151100Z SUMMARY...Low confidence, but potentially additional 2-4" over saturated/sensitive grounds again tonight. Back-building/training would be the driver to localized possible flash flooding overnight. DISCUSSION...KDFX RADAR and GOES-E SWIR animations show a strong roll cloud/outflow boundary surging northward through the Rio Grande Valley into the Southern Edwards Plateau given slightly more mid to upper-level dry air relative to prior days. However, the parent MCV remains further south over N Nuevo Leon and there is a remaining mid-level vorticity center across the Lower Pecos Valley that remains a pivot along the stubborn positive tilt trough back across the Red River and eventually the Lower Ohio River Valley. This convection is also along the leading edge of the return moisture up the Rio Grande Valley with VWP noting a steady increase and alignment of 925-700mb flow along the river at 20-30kts, providing solid moisture flux with total PWats up to 2". As the surge slowly veers toward the mid-level vorticity center in the Pecos Valley and is reinforced from the south, the orientation of the eastern side of the outflow boundary is becoming fairly stationary west to east, but even slightly backed low-level flow will support stronger upwind convergence and potential for back-building and slow northeastward expansion given WAA regime. This is a similar evolution to overnight last night; though value of moisture are slightly lower and there is a loss of stronger SW to NE oriented boundary to the shortwave to the northeast (now in OK not Northwest TX). Still, there are sufficient models including the RRFS and ARW suite that support this evolution with 2"/hr rates and within the training bands potentially small areal totals of 2-4" across already saturated soils (where FFG values are less than 1.5"/hr and less than 2"/3hs. These rates over this hydrologic environment may suggest a likely FF scenario...however, with reduced moisture values and much lower confidence, will only carry the flash flooding possible tag on this MPD. Gallina ...Please see www.wpc.ncep.noaa.gov for graphic product... ATTN...WFO...EWX...SJT... ATTN...RFC...FWR...NWC... LAT...LON 30840023 30759961 30319912 29569925 29089950 28579993 28670051 29130090 29530109 30080120 30610096