848
AWUS01 KWNH 081933
FFGMPD
FLZ000-GAZ000-090130-

Mesoscale Precipitation Discussion 0595
NWS Weather Prediction Center College Park MD
332 PM EDT Mon Jul 08 2024

Areas affected...northeast FL...southeast GA

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

Valid 081930Z - 090130Z

Summary...Extreme rainfall rates of 2-4"/hr may result in
localized totals of 5"+. Isolated to scattered instances of flash
flooding are possible.

Discussion...Deep convection is firing along the sea breeze
circulation this afternoon over southeast GA and northeast FL,
evident via GOES-East infrared imagery with impressively cold
cloud tops of -80deg C. Given near record levels of tropospheric
moisture content (precipitable water values of 2.3-2.6 inches)
with very slow storm motions (850-300 mb mean wind of 5 kts or
less), extreme rainfall rates of 2-4"/hr are being realized with
the strongest updrafts. While effective bulk shear of less than 20
kts should generally prevent meaningful organization and limit
storm longevity, a tropical upper-tropospheric trough (TUTT) to
the east is allowing for some upper-level divergence on the
western periphery of a ~70 kt sub-tropical jet streak. This subtle
feature (combined with the aforementioned tropical-like
tropospheric moisture) could allow for some repeating and
backbuilding of these impressive rates. This is also evidenced by
HREF 40-km neighborhood exceedance probabilities of 30-50% for the
5" threshold, which is near or above the corresponding (6-hr)
Flash Flood guidance (generally 4.0-5.0"). As a result, isolated
to scattered instances of flash flooding are possible (with
particular concern for low-lying, urbanized terrain).

Churchill

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

ATTN...WFO...CHS...JAX...TAE...

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

LAT...LON   32198133 31748099 30898133 29838146 30218282
            31088313