-- Discussion containing changed information from previous version are highlighted. --
179
FXUS64 KBRO 222342 AAA
AFDBRO

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
642 PM CDT Sat Jun 22 2024

...New AVIATION...

.SHORT TERM...
(Tonight through Sunday night)
Issued at 221 PM CDT Sat Jun 22 2024

Key Messages:

- There is a 40% chance of tropical cyclone development near the Bay
of Campeche over the next 48 hours.

- Elevated seas and tides will result in a high risk of rip currents
and minor coastal flooding issues along the Lower Texas beaches.

The latest radar and satellite imagery depict mostly cloudy skies
and widely scattered showers and thunderstorms associated with a
broad area of low pressure near the Bay of Campeche. The 12Z BRO
sounding measured precipitable water values of 2.48", well above
sounding climatology normals for mid June. Our region remains just
along the southern periphery of the mid/upper level ridge, which is
centered over the Southern Plains. While subsidence may play a
factor in precipitation chances over the period over the Northern
Ranchlands, precipitable water values are expected to increase and
will likely result in unsettled weather as the tropical disturbance
tracks west toward Mexico tomorrow.

Expect waves of light to moderate showers and isolated thunderstorms
to continue through Sunday night as Deep South Texas remains within
well established easterly flow, allowing for persistent tropical
moisture to steadily stream in. Given the high moisture content in
place, locally heavy rainfall cannot be ruled out with some of the
more robust showers and thunderstorms. Nuisance flooding issues may
occur during periods of heavy rain, especially over flood-prone or
low-lying areas. Rainfall amounts will range from half an inch to
just under two inches, with the highest amounts generally closer to
the immediate coast and across the Rio Grande Valley through Sunday
night.

The latest high res guidance indicates the broad area of low
pressure will move into Mexico sometime tomorrow, limiting the
potential for any further development over the Gulf of Mexico. The
latest observations indicate winds near the core of the low pressure
are around or just below 30 knots. Regardless of any development
over the next 24 hours, an uptick in wind speeds over Gulf waters
will result in elevated seas along the Lower Texas beaches. A high
risk of rip tides and minor coastal flooding cannot be ruled out
through this evening, and once again tomorrow with high tide. A
gradual improvement should begin by late tomorrow afternoon into
tomorrow night.

&&

.LONG TERM...
(Monday through next Saturday)
Issued at 221 PM CDT Sat Jun 22 2024

Key Messages:

- Rain Chances Lower after Monday

- Modest Heat returns, Heat Advisories possible late week

-Coastal/Marine Condition improve

Trends for the long term is for decreasing rain chances to normal
seasonal sea breeze activity along with increasing temperatures.
Mid-range model solutions are showing the Central American Gyre
(CAG) weakening as it drifts west with a large 500mb ridge
building over Texas midweek with the center intensifying as it
settles over West Texas/SW Desert.

Although the tropical disturbance currently over the SW Gulf should
be well inland over Mexico Monday there will remain plenty of
residual moisture over Deep South Texas.  Daytime differential
heating and sufficient instability should be enough to produce
scattered to possible numerous showers and a couple thunderstorms
Monday. Moisture content remains relatively deep (sfc-600mb mean RH
70+ percent and rich (pwats 2-2.4 inches)to allow for heavy rain
potential. Can not rule out a few efficient rain producers even with
WPC QPF rather marginal in the 0.25-0.50 range. Any slower moving
shwr/tstm will still be capable of dropping 1-2 inches in a hours
time.

For the rest of the week Tuesday-Saturday with mid-level high
pressure building north and west of the region and a continue low
level moist southeasterly flow there will be a daily battle between
subsidence from the ridge or a daily recycling of moisture.  NBM and
deterministic models are in good agreement showing overnight Marine
streamer showers transitioning to daily sea breeze convection which
is very typical for late June.  Daily POPs to range from 15-30 with
the higher end chances either Wed or Thu depending on if a weak vort
lobe shown rotating around the mid-level ridge enhances the sea
breeze.

Temperature trends as mentioned are likely to go up, albeit slowly,
with higher rain chances receding. Expect near normal temperatures
Mon-Wed, with slightly above normal Thu-Saturday. Heat index begin
to climb up with possible short-lived heat advisories by the end of
the week. Low temperatures do not show much variation remaining in
the 75-80+ degree range for the week.

&&

.AVIATION...
-- Changed Discussion --
(00Z TAFS)
Issued at 634 PM CDT Sat Jun 22 2024

Generally moderate northeast to east winds prevail across Deep
South Texas early this evening. Latest BRO radar indicates a few
moderate to heavy bands of brief downpours moving across the lower
RGV, resulting in brief IFR/MVFR conditions. This activity is
expected to move west across the mid to upper Valley and impact
MFE between 01-03Z. Periods of light to moderate SHRA and
isolated -TSRA will continue through the next 24 hours. The main
threats will be locally heavy rain and gusty winds...and lightning
with any thunderstorms. Expect ceilings to fluctuate between VFR
and MVFR, and reduced visibility to IFR levels with more robust
showers. Otherwise, winds will remain out of the northeast to
southeast around 5 to 10 knots with occasional gusts to around
15-20 knots.
-- End Changed Discussion --

&&

.MARINE...
Issued at 221 PM CDT Sat Jun 22 2024

Tonight through Sunday night...An area of low pressure near the Bay
of Campeche continues to track westward toward Southern Mexico,
resulting in persistent moderate winds and seas over the Gulf of
Mexico. The NHC indicates a 40% chance of tropical development over
the next 48 hours, which may result in higher winds and seas than
currently forecast. A Small Craft Advisory is in effect for the Gulf
waters through Sunday afternoon as seas build in response to
increasing winds. Otherwise, expect scattered showers and
thunderstorms through Sunday night.

Monday through Saturday...Tropical disturbance should be inland
Monday with coastal and marine conditions steadily improving.
Surface high pressure becomes anchored over the northeast Gulf of
Mexico and combine with a thermal low over interior Mexico. A
steady state moderate to fresh southeast wind and moderate to
slight sea is expected. Exercise caution may become a daily
occurrence over the Gulf at night and on the Laguna Madre during
the day.

&&

.PRELIMINARY POINT TEMPS/POPS...
BROWNSVILLE             78  90  80  92 /  80  80  50  60
HARLINGEN               76  90  76  92 /  80  70  40  50
MCALLEN                 78  90  78  93 /  70  80  40  50
RIO GRANDE CITY         76  88  77  91 /  60  80  40  50
SOUTH PADRE ISLAND      82  86  82  87 /  80  70  50  50
BAYVIEW/PORT ISABEL     78  88  79  90 /  80  70  40  50

&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...Coastal Flood Advisory until 7 PM CDT this evening for TXZ351-
     354-355-451-454-455.

     High Rip Current Risk through Sunday morning for TXZ451-454-455.

GM...Small Craft Advisory until 1 PM CDT Sunday for GMZ150-155-170-
     175.

&&

$$

SHORT TERM...22-Garcia
LONG TERM....59-GB
AVIATION...63-KC