AWUS01 KWNH 311818
FFGMPD
MSZ000-LAZ000-TXZ000-010015-

Mesoscale Precipitation Discussion 1109
NWS Weather Prediction Center College Park MD
218 PM EDT Thu Oct 31 2024

Areas affected...Central & Southern LA...Southeast TX...Ext
Southwest MS...

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

Valid 311820Z - 010015Z

SUMMARY...Potential for a widely scattered incident or two of
flash flooding is possible through late afternoon into early
evening hours.

DISCUSSION...A potent autumn cyclone and associated cold front are
pressing across the central portion of the U.S, while a strong
ridge remains entrenched over the Southeast.  As such, a solid
core of return moisture across the central Gulf with total
Precipitable water over 2.25" is lifting north across Louisiana
and starting to interact/consolidate within the warm sector ahead
of the approaching cold front.  However, stronger mid to upper
level jet remains well enough north that front is starting stretch
and flatten from east to west under these low to mid-level
shearing forces.  Moderately clear skies throughout the morning
into peak heating across the warm sector has brought temps into
the mid-80s over low to mid-70s Tds, resulting in a moderately
unstable environment across SE TX into much of central and
southern LA with MLCAPEs reaching 1500 J/kg, though nearing 2000
J/kg further west.  This disparity is mainly driven by steepening
lapse rates and drying mid-levels above 700mb per CIRA LPW and RAP
analysis; while profiles are more satuated through depth in the
core of the q-axis from Vermillion to Rapides parish in central
LA.

Divergence is maximized at the entrance of the upper-level jet in
proximity to a weak surface inflection along the pre-frontal
convergence axis/effective cold front across NW LA, extending
northward into AR; while weaker flow exists across the Gulf Coast
proper, the overall confluence through depth (mainly directional)
is resulting in solid deep layer convergence.  GOES-E and regional
RADAR mosaic has noted a solid increase in convective coverage and
intensity along the q-axis as well as a few upstream clusters in
SE TX from Houston to the Sabine River.  Effective bulk shear is
modest to weak but sufficient for some organized structures and
with deep layer flow from the southwest to the northeast (and
convergent) cell motions may support occasional repeating/training
profiles of these clusters. This is likely to be required to
overcome dry conditions and high FFG values across much of the
area.  Still, available moisture and solid flux should result in
efficient rainfall production as updrafts broaden in time, adding
to localized duration and potential for 2" sub-hourly totals.=20

While FFG values are 3-5"/1-3hrs across the area of concern, 12z
HREF neighborhood probability of 3"/6hrs (mainly bolstered
3"/3hrs) is greater than 50% from Brazoria county, TX to West
Feliciana parish, LA with greater than 25% from Sabine River to
St. Landry with greatest potential in Evangeline parish.  This
still may only result in widely scattered, low-end instance or two
of localized flash flooding; however there are a few prone urban
centers along that axis where scattered spots of 3-4" may occur.=20
As such, flash flooding is considered possible this afternoon but
mainly after 21z into this evening.=20=20

Gallina

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!=
DZ3fjg!6n-ejLEnHOG6PoqUDNYEN2ZRXHoBotOpuW1NlaIqP3yng_onEqAHjYo__yKqqnTlUZ12=
1by6IcIG56sR0lS4QZBKW7g$  for graphic product...

ATTN...WFO...HGX...JAN...LCH...LIX...SHV...

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

LAT...LON   32279173 31729101 30779125 29389127 29649367=20
            29189471 28949525 28999595 29639600 29979574=20
            30639496 31499402 31919331 32189273=20

=3D =3D =3D
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