894
AWUS01 KWNH 270946
FFGMPD
NCZ000-SCZ000-GAZ000-TNZ000-ALZ000-271300-

Mesoscale Precipitation Discussion 0332
NWS Weather Prediction Center College Park MD
545 AM EDT Mon May 27 2024

Areas affected...northern AL...norhtern GA...southern Middle/East
TN and surrounding portions of NC/SC

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

Valid 270945Z - 271300Z

Summary...Heavy showers and thunderstorms in association with a
decaying convective complex may produce additional 1-2"/hr rates
(with additional localized totals of 1-3")

Discussion...Remnants of a QLCS (quasi-linear convective system)
are propagating southeast through portions of the TN Valley into
the Southeast early this morning, producing hourly accumulations
of 1-2" from northern AL into southern Middle/East TN and far
northern GA. The most efficient convection has been ongoing over
northern AL specifically, as west-to-east training cells were able
to develop ahead of the primary QLCS propagation (resulting in
some localized totals of 2-4" over the past 2-3 hours). The
mesoscale environment is characterized by ML CAPE of 750-2250 J/kg
(highest over northern AL), PWATs of 1.3-1.8" (near the 90th
percentile, per SPC sounding climatology), and impressive deep
layer (0-6 km) shear of 50-60 kts.

Hi-res CAMs have done a decent job with the evolution of the QLCS
overnight, but the 00z HREF overall has had a low bias with QPF
(as the HREF PMM hardly had over an inch of rain depicted across
northern AL through 09z). More recent runs of the HRRR, however,
have been picking up on the subtle convective trends much better,
and the latest 08z run depicts an additional 1-2" (and locally up
to 3") through 13z. While an approaching cold front will
eventually bring an end to the showers later this morning, this
front is still significantly displaced towards the northwest
(draped near the Mid-South), which will allow for additional
backbuilding of showers supportive of 1"/hr (and locally higher)
rates for at least a few more hours (as 25-35 kt LLJ continues to
usher in moderate moisture transport/flux from the southwest).
Given the already saturated soils across much of the area,
additional widely scattered instances of flash flooding are
possible.

Churchill

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

ATTN...WFO...BMX...FFC...GSP...HUN...MRX...

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

LAT...LON   35588362 34848286 33998409 33508575 33418777
            34138808 34788705 35198520