Mesoscale Precipitation Discussion 0166
NWS Weather Prediction Center College Park MD
1258 PM EDT Sat May 09 2026

Areas affected...Southern LA...Far Southeast TX..

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

Valid 091700Z - 092230Z

SUMMARY...Continued flash flooding potential with over-running in
southern LA.  New convection across SE TX/W LA may be more
pulse-like with cell mergers capable of a very quick 2" burst.

DISCUSSION...Regional RADAR mosaic and surface observations depict
orthogonal ascent from the core of the moisture axis (TPW at
2-2.15") over cold pool centered over SE LA.  Surface easterlies
further help sharped the boundary with additionally rain-cooled
air from the over-running convection, as such a few more hours of
scattered isentropic convection will likely occur.  The
orientation of the ascent streamers will allow for narrow streaks
of enhanced totals with values of 2-3.5" probable, falling over
areas already affected with 2-3" so far this morning.  However,
the parent shortwave from the northern stream now, well displaced
into the Southeast over AL/GA, is still sliding east-southeast and
the moisture axis and remaining weak LLJ will continue to drift
southeastward relative to the current activity further into the
Bayous of S central and SE LA.

However, upstream energy in the form of a strengthening right
entrance region to a 100kt 3H jet streak can be seen by well
defined anticyclonically curved upper cirrus pattern over far E TX
into NW LA at this time.  At the surface the old outflow boundary
remains weakly defined across west-central to central LA and will
likely remain the focus of some convective activity. 
Unfortunately, the influence of the downstream shortwave is
pooling away the main warm-conveyor belt and there only remains a
narrow pocket of enhanced surface to 850 and to 700mb per CIRA LPW
with drier air mixing in aloft.  This helps with some increased
instability as 2000 J/kg of MLCAPE pool exists across E TX. 
Weaker flow into the complex, even with backing low level flow
responding to the divergence aloft, suggests convective mode may
be a bit more pulse-like with scattered clusters and propagation
along collapsing outflow boundaries through the afternoon.  The
amount of moisture should allow for solid efficiency with spots of
2-2.5"/hr (similar totals) possible across SE TX and West-central
LA.   Flash flooding will remain an isolated potential given
recent heavy rainfall, wetter soils (especially east in LA) or
over urban locales.  As such, while the coverage and overall
intensity is reducing; the risk of a few incidents of flash
flooding remain across the MPD area of concern through late
afternoon.

Gallina

ATTN...WFO...LCH...LIX...SHV...

ATTN...RFC...FWR...ORN...NWC...

LAT...LON   31389302 31089232 30719144 30359070 30079019
            29668970 29168963 28929013 29089129 29709306
            30059433 30909437 31289399