AWUS01 KWNH 180935
FFGMPD
LAZ000-TXZ000-181400-

Mesoscale Precipitation Discussion 0647
NWS Weather Prediction Center College Park MD
534 AM EDT Thu Jul 18 2024

Areas affected...Hill Country of Texas east through the Piney
Woods

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

Valid 180934Z - 181400Z

Summary...A corridor of thunderstorms with heavy rainfall will
continue to drop southward through the morning along a nearly
stationary front. These thunderstorms will contain rainfall rates
of 2-3"/hr, which could produce locally more than 4" of rain.
Flash flooding is possible.

Discussion...The regional radar mosaic early this morning
indicates an expanding line of thunderstorms from far western
Louisiana through central Texas. These storms are developing along
a stationary front which should sag slowly southward as a weak
cold front later this morning. North of this boundary, a potent
shortwave noted in WV imagery and in SPC RAP Differential
Vorticity fields is spinning southward, enhancing lift in a region
already favorable through isentropic upglide of a modest LLJ and
beneath a subtle mid-level deformation axis. Thermodynamics across
Texas remain supportive of heavy rainfall, with PWs measured by
GPS of 1.9 to 2.1 inches collocated with MUCAPE exceeding 2000
J/kg. The overlap of ascent into this airmass is providing the
favorable conditions for increasing thunderstorm development, and
recent radar-estimated rain rates from KGRK WSR-88D have been as
high as 2.5"/hr.

The CAMs this morning all offer differing solutions to the
evolution of this convection, but while spatial coverage and
footprint vary, the intensity is well aligned among the various
models which increases confidence in a heavy rain event. The 850mb
LLJ is already beginning to slowly veer as noted in regional VWPs,
and is expected to become westerly by late morning. This will
limit the isentropic ascent and slowly reduce moisture transport
northward, but will also then become more aligned to the advancing
front, helping to turn the mean cloud-layer 0-6km winds parallel
to the front as well. Additionally, the propagation vectors will
become increasingly anti-parallel to the mean flow as the LLJ
veers, suggesting continued backbuilding of echoes to the SW and
along the front into the greater instability. With both HREF and
REFS probabilities for 2"/1hr accumulations reaching 40%, this
could result in 2-3" of rain along the boundary, with locally 4+"
possible as noted by the neighborhood probabilities. The
discussion area was drawn to somewhat emulate the EAS
probabilities which are highest across the Hill Country, Balcones
Escarpment, and along portions of I-35.

Recent rainfall across this region has generally been below normal
the last 7 days according to AHPS, but locally, NASA SPoRT 0-10cm
RSM is above 70%. This indicates that some infiltration of heavy
rain is likely, which is reflected by the higher FFG and
corresponding 3-hr FFG exceedance probabilities peaking at just
10-20%. However, the favorable setup for training of 2-3"/hr rain
rates could still overwhelm soils, especially in urban areas or
the across any more sensitivesoils, leading to rapid runoff and
instances of flash flooding.

Weiss

ATTN...WFO...EWX...FWD...HGX...LCH...SHV...SJT...

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

LAT...LON 31969389 31959322 31719285 30559369 30129502
29899686 29939839 30429957 30880043 31290077
31570017 31709930 31719830 31789713 31819532

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AWUS01 KWNH 031228
FFGMPD
TXZ000-031826-

Mesoscale Precipitation Discussion 0968
NWS Weather Prediction Center College Park MD
827 AM EDT Tue Sep 03 2024

Areas affected...much of Texas

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

Valid 031226Z - 031826Z

Summary...Areas of flash flooding are likely to continue through
at least the early afternoon hours (18Z/1p CDT).

Discussion...Much of Texas remains under the influence of broad
mid/upper difluence associated with a mid-leel wave over the
TransPecos. Additionally, low-level convergence continues in the
vicinity of a surface front subjectively analyzed from near JCT
eastward through central Louisiana near ESF. Across most of the
discussion area, the combination of 2+ inch PW values,
orographic/frontal confluence, weak inhibition, and at least 1000
J/kg MUCAPE was contributing to deep convection. The strongest
updrafts were located across the southern 1/3rd of Texas where
instability was strongest. Meanwhile, weak steering flow was
contributing to slow storm motions, and spots of 1-2.5 inch/hr
rain rates were occasionally observed - highest near deeper
convection across south Texas.

The ongoing scenario should continue to support scattered
instances of flash flooding throughout the day today. Further
compounding potential runoff issues are antecedent rainfall, which
has totaled 2-8 inches over the past 24 hours across broad parts
of Texas Midland to Abilene and in more localized spots near Del
Rio and along the Texas Coast. Areas of FFG exceedance are
expected throughout the day as deep convection lingers and
continues to result in spots of 1-2.5 inch/hr rain rates through
at least the early afternoon. In the near term, the greatest
concern for flash flood potential resides near Del Rio (where deep
convection was resulting in near 3 inch/hr rates over FFGs between
0.25-1.5 inch/hr) and across a large part of west-central Texas
where lighter rainfall continues and FFGs are between 0-1 inch/hr.

Slight risk areas are valid for much of the discussion area in the
D1 Excessive Rainfall Outlook, and expansions of that risk to
cover more of south Texas are anticipated at or before the 16Z
Outlook Update.

Cook

ATTN...WFO...CRP...EWX...FWD...HGX...LUB...MAF...OUN...SJT...

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

LAT...LON 33479778 33139704 32479689 31509744 30749750
30089734 29389646 28849589 27909632 27439733
27539951 28650052 29840109 31620133 33060056
33359945
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AWUS01 KWNH 041222
FFGMPD
TXZ000-041821-

Mesoscale Precipitation Discussion 0974
NWS Weather Prediction Center College Park MD
821 AM EDT Wed Sep 04 2024

Areas affected...south Texas through the middle Texas coast

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

Valid 041221Z - 041821Z

Summary...Persistent onshore flow was contributing to scattered
areas of heavy rainfall especially along coastal areas near Corpus
Christi. Isolated instances of flash flooding are expected to
continue through 18Z/1p CDT today.

Discussion...Deep, slow-moving convection continues to drift
onshore from northwestern Gulf of Mexico waters into the
discussion area. The onshore flow regime is being maintained due
to a weak surface low near Brownsville and east-southeasterly
850mb flow on the northeastern side of that cyclone. That
enhancement of low-level flow was maintaining strong buoyancy
(1500 J/kg MLCAPE) along and just inland from Texas coastal areas,
while low-level convergence was promoting continued updrafts amid
a very moist airmass (2.5+ inch PW values). This regime was
continuing to support local 1-3 inch/hr rain rates at times
especially with more persistent convection as noted with
convection near Port Aransas and just north of Brownsville.

The ongoing scenario supporting flash flooding will evolve very
slowly today. Spots of 1-3 inch/hr rain rates remain likely as
convection slowly streams westward toward Texas coastal areas
today. These heavier rain rates could also materialize as far
north as the Galveston area as well. FFG thresholds vary
spatially, and generally range from 1.5-3.5 inches/hr.
Isolated/localized flash flood potential is expected to persist
through at least 18Z today in this regime, with the most
pronounced threat existing where 1) >1 hour of heavier rainfall
persists and/or 2) in low-lying/sensitive areas.

Cook

ATTN...WFO...BRO...CRP...HGX...LCH...

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

LAT...LON 29899443 29479412 28739523 28229646 27159711
26169708 25819715 25769774 26399870 27419880
28479787 29529608
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