Flash Flood Guidance
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Issued by NWS
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581 AWUS01 KWNH 290117 FFGMPD TXZ000-290600- Mesoscale Precipitation Discussion 0339 NWS Weather Prediction Center College Park MD 916 PM EDT Tue May 28 2024 Areas affected...Rolling Plains into Big Country of Northwest Texas... Concerning...Heavy rainfall...Flash flooding possible Valid 290115Z - 290600Z SUMMARY...Cell mergers and training along with ample moisture flux for up to 2"/hr rates and 2-3+" may pose localized flash flooding through early overnight period. DISCUSSION...RAP analysis and 01z surface map suggest a weak FGEN boundary/pressure trough across Northwest Texas that has a pool of enhanced instability along it, with CAPE over 1500 J/kg. Earlier cluster of thunderstorms has evolved into a fast moving outflow boundary across western OK before angling back southwestward across the Rolling Plains into the Big Country intersecting with the W-E developing boundary and instability pool. As such, recent convective development has sprouted with overshooting tops rapidly cooling and congealing to a broad line of sub -60C cloud tops in 10.3um GOES-E IR. RADAR notes generally chaotic cell motions given broad deep layer confluence zone per VWP network and RAP analysis fields. Tds in the low 60s with LPW depicting an enhanced axis of moisture from sfc to 700 across south-east TX toward this area allowing for total PWAT values to be in the 1.4" range per GPS network. Given deep layer flux convergence, and updraft strength has supported increased rainfall rates up to 1.5-1.75". Cell mergers and slow motions may allow for some localized 2-3" totals in 1-2hrs; and while the area has been recently dry, this is still in the range of 1-3hr FFG values. Hi-Res CAMs have performed poorly this evening with the overall evolution. However, recent WoFS runs (a majority of members) have maintained some these cells for a few hours likely feeding off the local instability maxima noted. As such, mean rainfall totals suggest a more reasonable 2-3" totals, though hint at localized values of 3- 4" when looking at 90th percentile of the last few cycles. This provides some confidence in reaching totals that would result in localized flash flooding. As such, flash flooding is considered possible through the early overnight period before the cluster moves further east into a more stable environment. Gallina ...Please see www.wpc.ncep.noaa.gov for graphic product... ATTN...WFO...FWD...LUB...MAF...SJT... ATTN...RFC...WGRFC...NWC... LAT...LON 33610107 33380001 33259922 33049843 32519810 31899846 31809917 32060023 32630132 33310165