968
AWUS01 KWNH 041556
FFGMPD
LAZ000-TXZ000-042000-

Mesoscale Precipitation Discussion 0395
NWS Weather Prediction Center College Park MD
1156 AM EDT Tue Jun 04 2024

Areas affected...Central Eastern TX...Northern & Central LA...

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

Valid 041600Z - 042000Z

SUMMARY...Some lingering potential for redevelopment and repeating
along the upwind edge of weakening overnight MCS.  Rates up to
2"/hr and spots of 2-3+" over saturated ground conditions pose
possible scattered incidents of flash flooding.

DISCUSSION...GOES-WV and Visible imagery suite depicts a trio of
well defined mid-level circulations across N MO, central AR and NW
AL; all within a broad area of troughing through the Mississippi
River Valley.  The central AR is the youngest of the trio and
still has very impressive dynamic appearance with inner core
center while southern quadrant mature convective complex drops
through eastern TX into northwestern LA.  RADAR and Visible
imagery note the cold pool has push the outflow boundary well
eastward though the upwind side still remains in closer proximity
to ongoing upglide convection along and south of I-20 in E TX.
This upwind edge remains exposed to a tight gradient of higher
theta-E air and recent VWP and Vis loop depicts this area well
with increase of 925-850mb southerly (30-35kt) inflow and tracer
low level flat strato-cu field lifting northeast out of the
western Gulf.  This has increased surface moisture convergence
with nearly orthogonal ascent with invigorating thunderstorm
activity in recent hour or so.  The air is very moist with 850mb
Tds approaching 20C with MLCAPE values of 2500-3000 J/kg,
supportive of further convective activity.

The balance of cold pool generation and stronger outflow and
shallower steep isentropic surfaces versus maintaining near
surface based development at the edge of the outflow boundary
remains the highest uncertainty.  Trends favor the outflow
boundary winning even outracing cells in Rusk/Panola county,
leaving lingering elevated cells that can produce 1-2"/hr with
some training elements; but that would likely be shorter-lived at
diurnal minimum and expected weakening 850mb LLJ.  However, the
q-axis orthogonal to the instability gradient and cells near
Henderson/Cherokee county, suggest some flanking line development
may maintain for the next few hours, as it propagates south.

Hi-Res CAMs mostly didn`t resolve/assimilate the ongoing complex
and those that did such as the recent HRRR continue to follow
traditional bias of convective weakening at this time of day.
While this is expected, there does remain a short-window of time
that storm scale interaction/wind flows should maintain a heavy
rainfall risk along and downstream of the upwind edge of the
complex across the Piney Woods into western LA.  Unfortunately,
this also aligns with fully saturated ground/soil conditions and
flooded rivers to suggest high run-off potential for these cells
producing 1.5-2"/hr which may result in possible localized flash
flooding through the early afternoon hours.

Gallina

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

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

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

LAT...LON   32729449 32639319 32419246 31999216 31249211
            30709267 30599367 30799468 31229527 31849558
            32499551