AWUS01 KWNH 031138 FFGMPD TXZ000-031700- Mesoscale Precipitation Discussion 0577...Corrected NWS Weather Prediction Center College Park MD 738 AM EDT Thu Jul 03 2025 Corrected for areas affected Areas affected...Portions of West Texas from the Big Bend through the Edwards Plateau Concerning...Heavy rainfall...Flash flooding possible Valid 031134Z - 031700Z Summary...Showers and thunderstorms are expected to increase in coverage this morning and move slowly across parts of West Texas. Rainfall rates at times may reach 1-2"/hr, leading to 1-3" of rain. Flash flooding is possible. Discussion...The GOES-E IR imagery this morning shows an expanding area of cooling cloud tops over the Mexican state of Coahuila in response to a potent shortwave lifting northward over the Serranias del Burro. These cooling cloud tops are associated with intensifying convection approaching the Big Bend of Texas, and although reflectivity over the area is sparse at this time, the GOES-E GREMLIN radar emulation appears to match the IR imagery quite nicely showing higher reflectivity lifting towards the international border. At the same time, showers have begun to develop across the Edwards Plateau in response to a plume of increasing MUCAPE of 1000-2000 J/kg collocated with PWs that are analyzed by the SPC RAP to be 1.8 to 2.2 inches, or above the 99th percentile, thanks in part to a connection to tropical moisture associated with Tropical Storm Flossie over the Eastern Pacific noted via the ALPW products. Although the CAMs are struggling to resolve the ongoing activity, and admittedly are not exceptionally aggressive with rainfall the next few hours, the environment and evolution support heavy rainfall through the morning. Low-level S/SE flow measured at 850mb on the VWPs at both DFX and MAF are around 20 kts, which is helping to transport the elevated PWs northward, and this flow may be locally accelerated downstream of the approaching shortwave. This will help to further improve the local thermodynamic environment, while at the same time leading to locally enhanced convergence into the mean wind which is generally around 10 kts. This evolution suggests that storms will increase in coverage (with additional ascent provided via the shortwave itself) and then move slowly/chaotically as Corfidi vectors veer strongly to the right of the mean wind and bulk shear remains minimal. Although the CAMs are not initializing very well, the accompanying HREF and REFS ensemble solutions do indicate increasing coverage of 10-30% probabilities for 1"/hr rates, leading to 1-3" of rain with isolated higher amounts. FFG across the region is highly variable due a wide variation in 7-day rainfall, but in some places the 3-hr FFG is as low as 1.5 inches, and 0-40cm soil moisture just north of the international border is above the 95th percentile. This indicates that some areas are locally vulnerable to rapid runoff, so as storms spread northward and expand/intensify, instances of flash flooding could result. Weiss ...Please see www.wpc.ncep.noaa.gov for graphic product... ATTN...WFO...EWX...MAF...SJT... ATTN...RFC...FWR...NWC... LAT...LON 32390144 32240056 31970032 31319998 30569973 29989966 29399983 28950014 28870061 29200124 29440185 29150266 28960313 28870351 29080407 29500445 29710463 30180465 30640416 31200337 31350324 32100231