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