Flash Flood Guidance
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Issued by NWS
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483 AWUS01 KWNH 281521 FFGMPD FLZ000-281930- Mesoscale Precipitation Discussion 1080 NWS Weather Prediction Center College Park MD 1120 AM EDT Sat Sep 28 2024 Areas affected...Southwest Florida Concerning...Heavy rainfall...Flash flooding possible Valid 281520Z - 281930Z SUMMARY...Training convection tracking northeast into the west coast of Florida is producing rates to 2.5 inches per hour. Flash flooding is possible, especially in urban areas. DISCUSSION... The remnant trailing front behind Helene is nearly stationary across central Florida this morning. Localized convergence zones have developed within the broader frontal boundary that have been forcing storms that have a history of producing rainfall rates to 2.5 inches per hour. While each individual cell is moving along at around 20 mph, the redevelopment of convection is resulting in multiple cells moving across urban and flood-prone areas. PWAT values to 2.5 inches are draped across the Ft. Myers area, with a distinct moisture boundary over the Tampa area. SBCAPE values are over 2,500 J/kg with MUCAPE over 3,000 J/kg already. These very high values of both moisture and instability will support additional thunderstorm development into the afternoon across the Florida Gulf Coast. HiRes guidance has been variable on how long the storms will last, but given the ample moisture and instability both in place and will continue to be advected in from the Gulf, it appears probable that the storms capable of heavy rainfall rates will continue in this region. Given some of the CAMs guidance that are struggling to depict the activity going on right now are the drier solutions, have opted to favor the wetter guidance such as the 12Z HRRR and ARW for the near-term forecast. Wegman ...Please see www.wpc.ncep.noaa.gov for graphic product... ATTN...WFO...MFL...TBW... ATTN...RFC...SERFC...NWC... LAT...LON 28258185 27958140 27528123 26688140 26358172 26398198 26508229 27558281 27808287 28108287 28198256