285
AWUS01 KWNH 172332
FFGMPD
FLZ000-GAZ000-ALZ000-180230-

Mesoscale Precipitation Discussion 0284
NWS Weather Prediction Center College Park MD
731 PM EDT Fri May 17 2024

Areas affected...far southeastern Alabama, southern Georgia,
northern Florida, and portions of the Florida Panhandle

Concerning...Heavy rainfall...Flash flooding possible

Valid 172330Z - 180230Z

Summary...A couple of linear convective complexes are still posing
a flash flood threat, although the overall risk should decrease
somewhat over the next 3-4 hours.

Discussion...Ongoing convection continues to be oriented in a
couple of WSW-ENE bands - 1) just north of Valdosta, GA and 2)
another extending from near Marianna to near DeFuniak Springs, FL.
 These bands remain oriented roughly parallel to steering flow
aloft, supporting localized training of storms and areas of 1-2
inch/hr rain rates.  Over the last hour or so, an increase in
southward propagation has occurred, which has lessened rain rates
from the nearly 3 inches/hr noted across far southeastern Alabama
earlier in the afternoon.  The pre-convective airmass is still
plenty moist/unstable (1.8-2.1 inch PW values and strong
instability - highest across the Florida Panhandle).  The
orientation of storms and continued heavy rain rates should
support at least an isolated flash flood risk over the next 2-3
hours, although this risk should be tempered somewhat by higher
FFGs with southward and eastward extent (exceeding 3 inches/hr in
most areas).

Another potentially negating factor for a larger-scale flash flood
threat will be movement of storms toward a less unstable airmass
across northern Florida (~1000 J/kg MLCAPE), with a continued
weakening of instability due to nocturnal boundary layer cooling.
Storms should continue in this environment for at least 3-4 more
hours, although models suggest that a weakening trend should occur
with time as storms continue their eastward trek.  Some flash
flood potential remains, although this threat should lessen with
time and likely depend on renewed convective development much
later in the night across Louisiana/Mississippi (after 10Z).

Cook

...Please see www.wpc.ncep.noaa.gov for graphic product...

ATTN...WFO...FFC...JAX...MOB...TAE...

ATTN...RFC...SERFC...NWC...

LAT...LON   31908249 31068129 29918265 30038566 31218636
            31728463