568
AWUS01 KWNH 092217
FFGMPD
TXZ000-100330-

Mesoscale Precipitation Discussion 0251
NWS Weather Prediction Center College Park MD
616 PM EDT Thu May 09 2024

Areas affected...Heart of Texas into Southeast Texas...

Concerning...Heavy rainfall...Flash flooding likely

Valid 092215Z - 100330Z

SUMMARY...Upscale growth of super cells into larger cluster; while
ingesting much higher/deeply unstable moist air for increasing
rainfall efficiency sub-hourly totals of 1.5"+  and with some
repeating a swath of 2-4" probable.  As such, flash flooding is
becoming increasingly likely along this axis, especially further
southeast.

DISCUSSION...Surface analysis denotes a surface low near MKN with
a cold front dropping in from the north across northern TX under
influence of ongoing convection further north; while the dryline
is starting to advance out of the central Hill country.  A
shortwave aloft is nearly vertical to the surface low but starting
to lift northeast within the influence of the right entrance of a
90kt 3H jet across eastern OK.  With the favorable divergence
aloft, pressure falls are directing surface to boundary layer flow
directly into the the surface low with northeasterly flow out of
Northeast TX, easterly flow out of the Piney Woods (both with low
to mid 70s Tds) and this morning`s slightly higher Theta-E air
with Tds over the mid-70s lifting northwest across the coastal
plain and is seen by a nice enhanced cu boundary from near CFD/UTS
both east and south.

As such, moisture flux convergence has slowly been increasing and
starting to aid in expansion of a pair of discrete super cells
moving southeast out of Bosque and Johnson counties.  Overshooting
tops are below -70C given ingest of said 4000 J/kg MLCAPE.
Currently, cells are still in severe mode, but have been
moistening the mid-level profiles allowing for further expansion
and upscale growth within the favorable dynamics aloft.  Hi-Res
CAMS including the HRRR have been performing well and suggest a
transition of higher rainfall efficiency within the next hour or
so. HRRR 15-minute and WoFS 5-minute rainfall suggest potential
for very intense rainfall to accompany the hail with 1.5" totals
accumulated very quickly.  Given rotation to the cells, mean
steering flow is deflected southeastward along the deepening
moisture axis and will slow to about 20-25kts per Bunker Right
Moving Propagation vectors. This will allow for increased duration
with hourly rates of 2-3"/hr becoming increasingly possible
through and after 00z, especially after intersecting the higher
Gulf moisture into Southeast TX.  Thinking WoFS and HRRR solutions
are on target with a swath of 2-4" probable with 90th percentile
suggesting 5" is attainable through 03z, especially if crossing
areas recently affected in the upper Trinity River Valley...making
the potential for flash flooding increasingly likely after 00z.

Gallina

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

ATTN...WFO...FWD...HGX...SHV...

ATTN...RFC...WGRFC...NWC...

LAT...LON   32409648 31979489 31349452 30489528 30279640
            30699719 31159794 31879841 32319754