AWUS01 KWNH 261057
FFGMPD
LAZ000-TXZ000-261655-

Mesoscale Precipitation Discussion 0732
NWS Weather Prediction Center College Park MD
656 AM EDT Fri Jul 26 2024

Areas affected...Portions of Eastern TX into West-Central and
Southwest LA

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

Valid 261055Z - 261655Z

SUMMARY...Additional areas of heavy rainfall should tend to
continue this morning across areas of eastern TX and west-central
to southwest LA. Flash flooding will remain likely including
continued concerns for locally considerable urban flash flooding.

DISCUSSION...The early-morning GOES-E IR satellite imagery shows a
rather impressive cold-topped convective wedge (with tops to -60
to -65 C) near the upper TX coast and generally advancing east of
Galveston Bay to the immediate offshore waters, However, radar
imagery does show some of the heavier showers and thunderstorms
with this still impacting some inland areas of southeast TX, with
the activity also encroaching on southwest LA.

An elongated axis of vort energy is noted along much of the middle
and upper TX coast and up across interior areas of eastern TX
around the eastern flank of a broader mid-level trough over the
southern Plains. This energy is interacting with a very deep
tropical airmass and axis of stronger instability that is pooled
up across the northwest Gulf of Mexico and inland to some extent
over far southeast TX and far southwest LA. In fact, MLCAPE values
of 1500 to 2500 J/kg are noted across these areas with PWs of 2.0
to 2.25 inches.

The ongoing convection is likely to continue going through the
morning hours given the set-up which is also being facilitated by
favorable right-entrance region upper-level jet dynamics and a
convergent southerly low-level jet of 20 to 30 kts that is nosed
up along to the TX/LA border.

Generally the focus for the heaviest rainfall totals in near-term
going through at least mid-morning should continue to be over
areas of far southeast TX which over the next 1 to 3 hours will
likely include portions of the Beaumont-Port Arthur vicinity, but
this convection is expected to advance into some areas of
southwest LA, and eventually the Lake Charles vicinity may come
under impacts from this convection. Some of the rainfall rates
with these cells are likely to reach 2 to 3 inches/hour. Galveston
Airport in the last hour (4AM to 5AM CDT) alone reported 2.38
inches as these storms crossed through.

Additional areas of heavy rain are also noted farther north away
from the coast across parts of eastern TX and into west-central LA
where antecedent conditions are already quite wet and locally
saturated from recent heavy rainfall. High streamflows are noted
more regionally also via the latest USGS gauge data.

Therefore, with the potential for an additional 3 to 5+ inches of
rain locally this morning, and the sensitive ground conditions,
additional areas of flash flooding are likely.

Orrison

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

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

LAT...LON 32019350 31809281 31189243 30399238 29679263
29599344 29339437 28809551 28989604 29549595
30159575 30819518 31689421
--- SBBSecho 3.20-Linux
* Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (21:1/175)

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

$$
--- SBBSecho 3.20-Linux
* Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (21:1/175)