232
FXUS64 KBRO 152325 AAA
AFDBRO

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
625 PM CDT Sat Jun 15 2024

...New AVIATION...

.SHORT TERM...
(Tonight through Sunday night)
Issued at 157 PM CDT Sat Jun 15 2024

Quiescent weather conditions will be the theme through the short
term forecast period as influences from a sfc high over the Gulf of
Mexico remains intact. Additionally, the region will sit in between
an emerging/strengthening 594-597 dam heat dome over the eastern
U.S. and a Sonoran heat ridge over northern and western Mexico, and
portions of the Desert Southwest.

Warm and muggy nights, and very warm to hot and humid afternoons
will persist. Overnight lows tonight and Sunday night are expected
to hold in the mid 70s to near 80F degrees. Meanwhile, on Sunday,
daytime highs are expected to climb into the upper 90s to lower
100s. With dewpoint (Td) temperatures in the upper 60s to mid 70s,
heat indices on Sunday are expected to fall just below Heat Advisory
and maybe even Special Weather Statement (SPS) criteria with values
ranging between the 105-111F.

Coinciding with max sfc based differential heating and associated
with a plume of deep tropical moisture over the eastern Gulf, a few
of the hi-res Convecting Allowing Models (CAMs) are hinting at the
possibility of a few pop-up diurnal showers and thunderstorms on
Sunday as winds continue out of the east-southeast. Most of the
activity is expected to stay offshore. However, there is a low, yet,
non-zero probability of a shower or storm reaching inland Sunday
afternoon/evening. For now, have low grade 20% PoPs along and east
of I-69E increasing to 40% over the barrier island including South
Padre Island (SPI) and the near shore Gulf Waters, and 50-60% over
the offshore Gulf Waters. Otherwise, expect for dry and tranquil
weather conditions to prevail through Sunday night.

&&

.LONG TERM...
(Monday through next Saturday)
Issued at 157 PM CDT Sat Jun 15 2024

The main concern in the long term forecast remains the high
uncertainty of tropical development in the Bay of Campeche/SW Gulf
of Mexico. The uncertainty resides first on the development of a
broad low pressure area over the SW Gulf which current NHC
Tropical Weather Outlook suggest not until early next week.
Second uncertainty is if a tropical cyclone (TC) can form within
the broad circulation and now this may not occur until the middle
of next week according to the latest model analysis and NHC
discussions. Environmental conditions from the Western Caribbean
Sea east to the Bay of Campeche/SW Gulf are expected to become
favorable for TC development (Doesn`t mean a TC is imminent)
somewhere within the Central American Gyre thus NHC continues to
message a 50 percent chance of TC development in the next 7 days.

Synoptic pattern for the long term continues to show the Western
Gulf of Mexico and the eastern two-thirds of Texas residing
between the strong Bermuda Ridge extending eastward to the East
U.S. coast and the Pacific Sub-tropical ridge noted over West-
central Mexico. The low pressure weakness between the ridges will
be an area for moisture transport northward leading to increasing
rain chances despite any tropical development. Models continue to
show a substantial surge of tropical moisture heading north
spreading across the western Gulf and along the Lower Texas Monday
night and over Deep South Texas Tuesday. The peak of the moisture
surge at this time is likely Wednesday-Thursday and slowly
tapering off (not ending) Friday and Saturday. Deterministic model
PoP Guidance from NBM/ECMWF/Canadian as well as Ensemble models
indicate anomalous precipitable water values around 3 standard
deviations from normal or 2.25-2.8 inches. Weather Prediction
Center (WPC) days 1-7 Total QPF values are now in the range of 2-5
inches with the higher amounts along and east of I-69C. The WPC
Day-5 (12Z Wed-12Z Thu) Excessive Rainfall Forecast shows the
entire Texas coast including all of Deep South Texas in a Slight
Risk of exceeding Flash Flood guidance which remains rather high.
Confidence is low on widespread flooding at this time, but with
the amount of moisture content forecast any slow moving
thunderstorm could dump 2-4 inches in short amount of time which
will pose a threat of local ponding and flooding of streets and
low-lying areas. To reiterate NBM and other deterministic models
continue to show rainfall beginning as early as Monday night
across the coastal regions spreading inland Tuesday. The bulk of
the widespread substantial and beneficial rainfall is shown for
Wednesday-Thursday with a continued good chance of scattered
showers and thunderstorms Friday and Saturday.

As for temperatures, highly variable due to the uncertainty of cloud
cover and total areal coverage of rainfall any given day. Will trend
potentially slightly lower than the NBM and may trend close to the
GFS (Wed and Thu)  where temperatures may finally lower to normal
(low to upper 90s). Lows may struggle to lower outside of any rain
cooled air so will maintain NBM trends of 75-80 degrees.

Beach conditions to say the least but need to watch the most is the
uncertainty. The increase of unsettled weather around mid to late in
the week will increase the threat for increased rip current threat,
high surf, coastal flooding and of course heavy rainfall along with
some periods of gusty winds.

&&

.AVIATION...
(00Z TAFS)
Issued at 622 PM CDT Sat Jun 15 2024

Mostly clear skies and moderate east-southeast winds prevail
across Deep South Texas early this evening. Easterly winds will
remain light overnight into Sunday morning with brief gustiness
between 19-24Z as the sea breeze moves inland. VFR conditions are
expected for the next 24 hours.

&&

.MARINE...
Issued at 157 PM CDT Sat Jun 15 2024

Tonight through Sunday Night...Favorable marine conditions are
expected to prevail through Sunday night, as a weak sfc pressure
gradient remains in place over the Lower Texas Coast. Light to
moderate winds and seas are expected along with an isolated to
scattered threat for showers and thunderstorms.

Monday through Saturday...Marine conditions in the long term
with become increasingly unsettled as showers and thunderstorms
increase in aerial coverage and the pressure gradient strengthens.
What is uncertain is the potential for Tropical Cyclone (TC) in
the Bay of Campeche or SW Gulf of Mexico. See the long term
discussion for more details. Otherwise, a strengthening pressure
gradient over the northern and western Gulf of Mexico is expected
through midweek as strong high pressure along the eastern U.S.
coast combines with developing broad low pressure over the
Southern Gulf and over SE Mexico. Winds and seas may approach
Small Craft Advisory conditions as early as Tuesday and continue
through much of the week. Mariners are urged to monitor the latest
coastal forecast and discussions due to the increase of
thunderstorm chances all of next week at a minimum.

&&

.PRELIMINARY POINT TEMPS/POPS...
BROWNSVILLE             80  95  79  96 /   0  20  30  50
HARLINGEN               76  97  76  97 /   0  10  20  40
MCALLEN                 79  99  79 100 /   0  10  10  30
RIO GRANDE CITY         78 100  78 100 /   0   0   0  10
SOUTH PADRE ISLAND      83  88  82  88 /  10  20  40  60
BAYVIEW/PORT ISABEL     80  92  79  93 /  10  20  30  60

&&

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

$$

SHORT TERM...23-Evbuoma
LONG TERM....59-GB
AVIATION...63-KC