Flash Flood Guidance
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Issued by NWS
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179 AWUS01 KWNH 281819 FFGMPD TXZ000-282330- Mesoscale Precipitation Discussion 0195 NWS Weather Prediction Center College Park MD 218 PM EDT Sun Apr 28 2024 Areas affected...Texas Triangle... Concerning...Heavy rainfall...Flash flooding possible Valid 281820Z - 282330Z SUMMARY...New development across areas affected this morning with some training elements pose possible scattered flash flooding incidents this afternoon into evening. DISCUSSION...18z surface analysis denotes a surface low near BKD with a well defined dry-line extending southward through the Hill Country toward South Texas just west of Laredo. GOES-E Visible imagery shows low level cloud streets coming off the western Gulf increasing deep layer moisture while also advecting higher theta-E/unstable air across areas that were fairly cloud covered with this morning`s weakening MCS. Aloft, favorable right entrance to leaving 110kt jet streak across N OK/KS accompanied by solid cyclonic curvature is providing weak but sufficient divergence aloft and DPVA to back low level flow into the dry line while ascending northward in proximity to the I-35 corridor from San Antonio to Dallas. The sufficient ascent and increasingly uncapped environment moving in from the south has provided sufficient ascent for new development with strong ascent and frequent lightning. CIRA LPW and RAP analysis suggest a slug of remaining 700mb moisture through this axis which has increased overall total PWATs to 1.75" in the axis and given modest 25-30kts of low level influx, will allow for efficient rainfall production. Rates of 1.5-1.75"/hr initially should increase with arrival of Gulf moisture surge later this afternoon with cores capable of 2-2.5"/hr. Deep layer flow is also a concern with respect to potential flooding given north-northeast cell motions generally a tad east of parallel to the dry line. This may allow for some training cells resulting in spots of 2-4". Currently, cells are along the axis where 1-3" fell this morning and are slowly recovering. As such, intersections of rainfall at this rate over wet grounds provide potential for scattered incidents of flash flooding this afternoon. Gallina ...Please see www.wpc.ncep.noaa.gov for graphic product... ATTN...WFO...EWX...FWD...HGX... ATTN...RFC...WGRFC...NWC... LAT...LON 32959631 32779575 31999547 31369557 30509602 29679672 28969760 28839853 29709862 32039756 32699693