474
FXUS64 KBRO 121952
AFDBRO

Area Forecast Discussion
National Weather Service Brownsville TX
252 PM CDT Wed Jun 12 2024

...New SHORT TERM, LONG TERM, MARINE...

.SHORT TERM...
(Tonight through Thursday night)
Issued at 133 PM CDT Wed Jun 12 2024

It`s hot again this afternoon with heat index values from 105 to 110
degrees in many areas. A weak sea breeze is under way over the
coastal counties. That, said, the weather tonight will be quiet and
warm with lows in the mid 70s to near 80. Skies will be partly
cloudy with light winds. Patchy, light fog/haze could develop over
the Northern Ranchlands late tonight.

H5 ridging upstream will build over the Southwest United States and
will topple east into North Texas. That will leave a weakness over
the Northwest Gulf and Northern Gulf Coast in general. Isolated Gulf
showers will remain. The pressure gradient and surface winds will
remain light to moderate onshore. PWAT is progged to increase to 2
inches or better tomorrow, likely supporting a more robust sea
breeze. SPC has maintained a general thunderstorm outlook for our
coastal counties on Thursday. Skies will be partly cloudy except
mostly cloudy with the sea breeze. High temps will run from the mid
90s to near the century mark. Heat index values will again be in the
105 to 110 degree range, just shy of heat advisory criteria.

Thursday night should again be quiet under partly cloudy to mostly
clear skies and light winds as the toppling mid-level ridge makes
its presence felt. Low temps will be in the mid 70s to near 80. The
moon will be a waxing crescent, a couple of days away from first
quarter. Rip current risk should remain low for a couple more
days.

&&

.LONG TERM...
(Friday through next Wednesday)
Issued at 133 PM CDT Wed Jun 12 2024

Ridging aloft stretching from most of Northern Mexico into the
Southern Plains will primarily dominate the synoptic pattern
through Saturday across our CWA. A general subsident flow albeit
not quite as strong as in recent days and weeks will keep most of
the CWA dry through Saturday, especially for areas west of I-69C.
East of I-69C, there will remain a slight chance to low chance
for mainly seabreeze diurnal convection. By Sunday, an inverted
trough axis begins to advance westward across the central Gulf and
Bay of Campeche. In response, the ridging aloft across our CWA
will begin to weaken and retrograde westward. A gradual moistening
up of the tropospheric column will ensue on Sunday. As the
inverted trough axis slowly moves into the W Gulf on Monday and
across our CWA on Tuesday and Wednesday, deep layer tropical
moisture with PWATS as high as 2.8-2.9 inches will overspread most
of the CWA. If verified, these PWATs would be record levels for
the date. The next question is how will rainfall chances be
affected by any tropical cyclone development.

Both deterministic and ensemble guidance continue to come into
better agreement with tropical cyclone development across the Bay
of Campeche during the Sunday night to Wednesday period. The
consensus guidance solution is the development of a tropical
storm. A ridge aloft is expected to expand and build from Northern
Mexico into the Southern Plains and MS Valley region by Tuesday
and Wednesday. This should tend to keep the core of the tropical
cyclone track well to our south. As a result, the most likely
landfall at this time points to somewhere between Tampico and
Veracruz. This guidance is in line with the NHC/WPC day 7 spot
location of 22.5N 96.5W next Wed. NHC has increased their TC
probabilities now to 30% and would expect these probabilities to
continue to increase over the next several days given the trend in
the NWP guidance.

For now will go with POPs increasing to chance to likely category
for most of the CWA beginning on Sunday with the peak rain chances
on Tuesday and Wednesday. For now, rainfall amounts of 1-3 inches
with locally higher amounts will be possible between Monday and
Wednesday. One caveat to this will be if this system further
intensifies. In this scenario, the heavier rainbands would be
most likely remain south of the Rio Grande Valley, thus limiting
QPF amounts for us. Will not get too cute with this, especially
since we are dealing with a Day 6-7 forecast. Just something for
later shifts to consider.

Besides the mostly beneficial rain (due to our below normal
rainfall situation), other impacts will be increased rips and the
potential for minor coastal flooding. The ESTOFS guidance
depicted these increasing water levels for the Mon-Wed timeframe.
This is quite reasonable given the long fetch of E/SE gradient
flow of 20-25 kts (with pockets of 30 kts) that will develop
across the southwestern one-third of the Gulf. A nearly
perpendicular angle of incoming large swells will increase the rip
risk to high for early next week.

High temperatures through the weekend will generally be close to
or just slightly above normal. Heat indices will overall remain
mainly in the 105-110 range through the weekend which is just
below heat advisory criteria. A slow cooling trend is expected as
we head into the Mon-Wed timeframe given the increased cloud
cover and higher rain chances. Did have to lower the NBM high
temperatures for Tue and Wed as they were just far too warm given
these expected cloudier and rainier conditions.

&&

.AVIATION...
(18Z TAFS)
Issued at 1157 AM CDT Wed Jun 12 2024

VFR conditions at the TAF sites now with light to moderate east
southeast winds. As was the case yesterday, low level cumulus
streets (4 to 4.5 kft) cover the eastern 2/3 of the CWA. There is
a bit more low level moisture today, and the sea breeze is
already underway, pushing a convergence line and enhanced low
level cumulus into the coastal counties. May see few to sct mid
to upper clouds later today as viewed moving south on satellite.
Radar has been quiet this morning. For the rest of the day and
tonight, will plan on continued VFR conditions with a weak
pressure gradient. Some of the guidance hints at brief coastal
MVFR mid tomorrow morning, but this would be brief and will not
emphasize in the new TAF set.

&&

.MARINE...
Issued at 133 PM CDT Wed Jun 12 2024

Tonight through Thursday night...Generally light to moderate east to
southeast winds and low to moderate seas will prevail through
Friday, courtesy of a weak pressure gradient. Isolated showers and
thunderstorms will pop up periodically over the Gulf waters.

Friday through next Wednesday...A weak to occasionally moderate
easterly flow will prevail through Sat across the Lower Texas
coastal waters as weak high pressure remains anchored across the
Northern Gulf and Deep South. The initial swells due to a
developing long moderate to strong E/SE fetch that will be
developing across the southern and central Gulf will begin to
arrive in our coastal waters by Sun. As discussed above, TC
development is becoming a growing possibility for the Sun night
through Wed timeframe across the Bay of Campeche. As a result, we
anticipate long period swells to increase in intensity through
Wed as they continue to impact the coastal waters. Overall seas
are expected to reach as high as 10 ft (or possibly higher) by Tue
and Wed. Widespread small craft advisories will likely be
required for the Mon-Wed period. Numerous showers and embedded
thunderstorms will prevail from Sun thereafter.

&&

.PRELIMINARY POINT TEMPS/POPS...
BROWNSVILLE             96  80  95  79 /  10  10  30  10
HARLINGEN               97  76  97  74 /  10  10  30   0
MCALLEN                100  80  98  78 /  10   0  20   0
RIO GRANDE CITY        100  79  99  77 /  10   0  10   0
SOUTH PADRE ISLAND      88  83  87  82 /  10  10  30  10
BAYVIEW/PORT ISABEL     92  80  92  78 /  10  10  30   0

&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...None.
GM...None.
&&

$$

SHORT TERM...54-BHM
LONG TERM....80-MB
AVIATION...54-BHM