Mesoscale Precipitation Discussion 0088
NWS Weather Prediction Center College Park MD
554 AM EST Fri Mar 08 2024

Areas affected...Central LA through Central MS...

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

Valid 081055Z - 081645Z

SUMMARY...Veering upstream wind profile within broad warm
advection pattern should favor back-building development with
potential for training thunderstorms through early morning period.
 Streaks of 2-4" totals and incidents of flash flooding are
considered possible

DISCUSSION...CIRA Sfc-850mb LPW analysis depicts a broad
triangular wedge of enhanced moisture across the northwestern Gulf
angled across southeast TX and western/central LA.  VWP and RAP
analysis shows increasingly confluent/veering LLJ nosing across
northeast LA into west-central MS at this time, providing solid
40-45kts of WAA isentropic ascent across a flat frontal zone
across N LA into northeast MS at this time.  Slow increase in
higher theta-E air (and Tds into the 70s) will continue to
encroach northeastward with broad ascent along and southeast of
approaching/amplifying mid-level shortwave out of central TX.  
Analysis also suggest weakening capping across this higher Theta-E
air where MLCAPE are ticking up over 1000 J/kg across southeast
TX.

GPS total PWat values have risen to 1.7" across this area and with
strong WAA/ascent and proximity to modest instability, increasing
convective activity will continue to expand at the nose of the LLJ
over the next few hours, slowly back-building into the richer/more
unstable air after 12z.  Rates of 1.5"/hr should build to 1.75",
though cell motions of 30kts or greater should limit any one
particular cell resulting in significant totals.   However, with
the approach of the wave, low level confluence will start to
become more unidirectional through a greater depth and favor some
upstream redevelopment/convergence.  This should allow for
potential for training thunderstorms from the 12-18z time period
across central LA into central MS.

There still remain some modest uncertainty in the latitude of
convective initiation upstream, be it closer to the slowly sagging
frontal zone across E TX/NW LA or on the initial outflow
boundaries from ongoing/early developing convection across LA into
MS.  Still, the potential for a streak or two of 2-4" totals may
result in a a few incidents of localized flash flooding. 
Potential is ever so slightly higher across Carroll parish, LA to
Holmes to Lowndes county, MS where upper soil conditions are that
ever so slightly more saturated due to prior heavy rainfall over
the 7 days per AHPS and NASA SPoRT LIS products.

Gallina

ATTN...WFO...BMX...JAN...LCH...LIX...SHV...

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

LAT...LON   33698951 33438859 32598837 31998885 31528993
            31279084 30809322 31039420 31889377 32859176
            33249101 33599036