Mesoscale Precipitation Discussion 0023
NWS Weather Prediction Center College Park MD
425 PM EST Tue Jan 23 2024

Areas affected...Eastern TX...Northwest LA...Southern/Central AR

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

Valid 232125Z - 240325Z

SUMMARY...Additional rounds of heavy rainfall going into the
evening hours will drive an increasing threat for areas of flash
flooding as the ground conditions continue to become increasingly
saturated and more sensitive.

DISCUSSION...The latest radar and satellite imagery continues to
show a broken axis of heavy rainfall, with some embedded areas of
stronger convection, impacting the broader Arklatex region. Recent
radar trends have also been showing an uptick in convective
concentration farther south over areas of southeast TX.
Strengthening warm air advection and moisture transport heading
through the evening hours will work in tandem with the arrival of
additional upper-level shortwave energy/jet dynamics and a nose of
modest instability for additional rounds of heavy rainfall
including some locally organized areas of convection that will be
capable of producing heavier rainfall rates.

Recent runs of the RAP/HRRR guidance support the nose of a 30 to
40+ kt southerly low-level jet riding north up through eastern TX,
northern LA, and central/southern AR over the next several hours
which will help drive an axis of 1.5+ inch PWs through these
areas. While the bulk of the moisture transport is originating
from the Gulf of Mexico, the latest CIRA-ALPW data actually does
show the upstream transport of moisture in the 700/500 mb layer
coming from the eastern Pacific Ocean, and this confluence of dual
moisture source regions will tend to favor a more efficient setup
for heavy rainfall heading through the evening hours.

Rainfall rates should tend to increase a bit more as this corridor
of moisture transport and somewhat greater pooling of instability
focuses across southeast TX and noses into adjacent areas of the
Lower MS Valley. Some rates may reach or locally exceed 1" to
1.5"/hour with the stronger convective cells. Generally the
heaviest focus of rainfall and any organized areas of convection
should tend to be along and a little east of a quasi-stationary
front draped across the region.

The 12Z HREF guidance and recent runs of the HRRR support
additional rainfall totals of 2 to 4 inches by the mid to late
evening hours. These additional rains falling on areas that have
already seen heavy rain over the last 24+ hours, and thus
increasingly saturated and more sensitive ground conditions, will
result in an increased threat for areas of flash flooding heading
through the evening hours.

Orrison

ATTN...WFO...EWX...FWD...HGX...JAN...LCH...LZK...SHV...

ATTN...RFC...ABRFC...LMRFC...WGRFC...NWC...

LAT...LON   34959231 34849145 34249118 32989151 32049233
            31159355 30289540 29279709 29519755 30149728
            30769671 31369591 32449481 34199374 34779299