282
FXUS64 KBRO 122321 AAA
AFDBRO

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
621 PM CDT Wed Jun 12 2024

...New AVIATION...

.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
low 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...
(00Z TAFS)
Issued at 622 PM CDT Wed Jun 12 2024

Another fair evening for landing and takeoffs at area
terminals...with the only slight fly in the ointment a few
stronger gusts from the sea breeze coupled with late afternoon
thermals (pulses) that should end soon after sunset from east to
west. Minor convection across the Coastal Bend should dissipate as
sunset arrives, and not impact any of the Valley airports this
evening.

So...current forecast holds nicely with winds laying down and
skies clear...though expect patches of few-scattered MVFR
cumulus/fractus later tonight into early Thursday morning. Light
east winds arrive by late morning and the usual scattered to
perhaps broken low VFR conditions should follow, and have added a
TEMPO group to Brownsville for high MVFR during the post-sunrise
hours.

The next question is sea breeze induced showers. Models are fairly
bearish...but we`re also watching precipitable water values rise
above 1.8 which could be sufficient for a short period of isolated
showers from late morning through early afternoon, especially
along/east of IH-69E. Confidence is low, however...so elected to
hold at VCSH rather than a TEMPO or PROB30 group at this point.
Whatever develops should dry out quickly by mid afternoon as the
sea breeze and general drier air overtakes the column...so expect
similar skies to today...ranging from low VFR to 6-7K few-
scattered fair weather cumulus. Expect another round of sea
breeze/afternoon thermals so included gusts around 20
knots...though would not surprise to see a couple of higher gusts
to 25+ knots due to the thermal mixing. All wind directions will
be from the east (080-110 degrees from north).



&&

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

&&

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

$$


AVIATION...52-Goldsmith