AWUS01 KWNH 091105
FFGMPD
LAZ000-TXZ000-091600-

Mesoscale Precipitation Discussion 1144
NWS Weather Prediction Center College Park MD
605 AM EST Sat Nov 09 2024

Areas affected...Southeast TX...Western LA...

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

Valid 091100Z - 091600Z

SUMMARY...Slow moving, highly efficient cells along the front will
continue to produce pockets of heavy rainfall and totals capable
of inducing localized flash flooding. Scattered totals over 3-5"
remain possible.

DISCUSSION...Deep layer convergence through the warm sector over
the northern Gulf and southern LA continues to drive convective
development along the slowing/approaching cold fronta across SE
TX. Strong upper-level divergence at the inflection of the
cyclonically curved jet with maximized diffluence aloft as further enhanced/expanded convective development and isentropic ascent
along and east of the triple point northeast of JAS, TX. CIRA LPW
shows enanced surface to 700mb moisture through the warm sector
though stronger 700-500 moisture along the northern coreo of
Rafael remains distant enough for stronger WAA ascent later today.
So with some weak steepening of lapse rates, modest instability
remains in proximity of the Sabine River Valley to the triple
point and should help to maintain updraft strength and focus
moisture flux convergence to support 2-2.5"/hr rates. Duration of
heavy rainfall may be more limited further north towad the
entrance of the jet/divergence maxima as it slides away with the
speed max with time. Spots of 2-4" across west-central to
north-central LA may result in possible flash flooding over the
next few hours.

Furhter south, the east-southeast surface to 850mb flow
decelerates into a col/weak surface wave near BPT. As such,
similar deep layer moisture convergence and slightly enahnced
surface based CAPE of ~1500 J/kg (due to proximity to the warmer
Gulf) is providings stronger updraft strength. Due to proximity
of slower low to midlevel flow, cells have been a bit more
stationary/slow moving with time and some suggestion of upstream
redevelopment toward the south may allow for some repeating;
duration may continue to result in very localized but intense
rainfall up to 2.5"/hr and localized totals of 3-5" over the next
few hours. Given higher natural FFG values (only locally reduced
due to 5-8" totals over Hardin, E Liberty and NW Jefferson
counties), flash flooding from similar cells may continue risk for
flash flooding.

Gallina

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

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

LAT...LON 32749283 32599214 32029213 31029271 29919333
29709366 29439446 29149487 28989532 29809504
30979455 32399364

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AWUS01 KWNH 262358
FFGMPD
MSZ000-LAZ000-ARZ000-TXZ000-270500-

Mesoscale Precipitation Discussion 1194
NWS Weather Prediction Center College Park MD
658 PM EST Thu Dec 26 2024

Areas affected...southeastern TX into western LA

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

Valid 262356Z - 270500Z

SUMMARY...Training and repeating of thunderstorms will continue a
flash flood threat from southeastern TX into western LA through
05Z. Rainfall rates of 1-2 in/hr and localized totals of 2-4
inches can be expected.

DISCUSSION...Regional radar imagery at 2330Z across the South
showed a line of thunderstorms extending from northwestern LA into
the Piney Woods of southeastern TX with a second line extending
from Jasper/Newton counties to roughly Matagorda Bay. These storms
were occurring just ahead of a pre-frontal trough/wind shift
located east of a cold front moving through east-central TX. SPC
mesoanalysis data from 23Z showed PWATs of 1.4 to 1.7 inches
coincident with the thunderstorm axis and MLCAPE of 500-2000 J/kg
from the central TX/LA border to the mid TX coast. Favorable shear
profiles ahead of a potent mid-level vorticity max (over north TX)
have supported supercells with enhanced rainfall rates while mean
steering flow from the southwest has resulted in areas of training
and/or repeating rounds of heavy rain from the northern TX/LA
border into the southeastern TX Coastal Plain.

Over the next 3-5 hours, the best upper level support (PVA, upper diffluence/divergence) will shift eastward from the Arklatex into
northern LA/southern AR. However, RAP forecasts of instability
show only a small pocket of 500-1000 MUCAPE just ahead of the
mid-level low center which should be steadily tracking east
through the first half of tonight. Due to lower instability
profiles, a lower end flash flood threat will exist for these
northern locations where strong forcing will should be balanced by
a fairly progressive translation of heavy rain toward the east and
limited instability.

Farther south, a lack of height falls for the Gulf Coast region
should result in a slower eastward progression of heavy rain. It
is here where greater instability is forecast to reside within the
warm sector (500-1500 J/kg MLCAPE). 850 mb winds of 40-60 kt from
the southwest and similarly oriented mean steering flow will allow
for areas of training and repeating thunderstorms capable of 1-2
in/hr (perhaps locally above 2 in/hr) due to a slower eastward
progression to the axis of thunderstorms. 2-4 inches of rain over
a roughly 2 hour window is expected to result in a couple of areas
of flash flooding through 05Z from southeastern TX into western LA.

Otto

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

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

LAT...LON 33949177 33509109 32649100 31619139 30769200
29699292 29499407 29039513 29219549 30059521
31439447 32449392 33769307

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