519
AWUS01 KWNH 301824
FFGMPD
LAZ000-ARZ000-TXZ000-OKZ000-310015-

Mesoscale Precipitation Discussion 0347
NWS Weather Prediction Center College Park MD
223 PM EDT Thu May 30 2024

Areas affected...Northeast TX...Northwest LA...Southeast OK...Ext
Southwest AR...

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

Valid 301820Z - 310015Z

SUMMARY...Slow moving thunderstorms ahead of dual squall lines
with ample deep layer moisture to support 1.5-2"/hr rates with
cell mergers/repeating and short-term training elements to support
spots of 3-4" in short duration maintaining likely environment for
scattered flash flooding through the late afternoon/evening.

DISCUSSION...GOES-E WV depicts a broad cirrus shield with
excellent outflow features/transverse banding along all directions
denoting the MCS lies at the apex of synoptic scale ridge.
Overshooting cooling/tops break through the canopy along the
leading eastern edg and southern hemisphere.  Regional RADAR
mosaic highlights the forcing boundaries/effective frontal
features well with the decaying MCV across central OK.  At the
surface, the effective warm frontal zone extends from convective
cluster near NOLA bisecting LA into SE OK/NE TX along the Red
River. Tds south of the Red River are generally 5 degrees warmer
into the low and mid-70s though a nose of enhanced upper 60s
exists north into NE OK.  The front intersects older outflow NW of
Paris, TX with a strong 1017mb meso-high near TKI/F00, that
refocuses the frontal zone near a more defined meso-low near XBI
before mid-level dry air mixing is allowing the cold front to
surge southeast out of Northwest TX.  As such, a large area of
unstable (2000-3000 J/kg) of MLCAPE exists across the area of
concern with solid streamline confluence to maintain active
squall-line features.  Total PWats of 1.75 nearing 2" exist at the
base of the old outflow boundary.  Flux of 5-15kts per VWP through
the boundary layer will support 2"/hr rates, perhaps slightly
higher along the strongest isentropic ascent of the bow echo;
though duration will likely limit overall totals.

As the OK MCV has been decaying, forward propagation and larger
scale flow is reducing forward motions and only the stronger dry
air mixing along the SW backside of the MCV is driving faster cell
motions.  RADAR and GOES-Vis shows  warm sector over-turning as
well with scattered cells developing with higher concentration
along/south of the effective warm front.  This will given an
opportunity for pre-soaking soils with 1-2" spots and allow for
cell mergers as bow(s) reach/collide with time across NE TX into
far NW LA.   This will allow for spots of 3-4" and perhaps an
isolated spot of 5" through the afternoon and into the evening
hours resulting in scattered incidents of flash flooding.

Upstream bow/meso-low will track again over areas recently flooded
along and north of the DFW metro, so this area will once again but
under threat of an additional 1-2" compounding flash flooding
ongoing through this area as well.

Southeast Oklahoma...effective occluded front/TROWAL line
confluence/convergence but surface based thunderstorms (with
slightly lower instability) will be very slow moving across the
area with some inner updrafts/downdraft tracking more northward
allowing for short-term repeating and enhanced streaks of 2-4"
totals also enhancning risk for flash flooding and have drawn the
MPD northward to account for this potential.

Gallina

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

ATTN...WFO...FWD...OUN...SHV...TSA...

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

LAT...LON   35829550 35489482 34149448 33439364 32619325
            32049370 31709468 31579572 31609678 31959797
            32529835 33009805 33279781 33659688 34139628
            35579621