981
FXUS64 KBRO 050546
AFDBRO

Area Forecast Discussion
National Weather Service Brownsville TX
1246 AM CDT Sat Oct 5 2024

...New AVIATION...

.SHORT TERM...
(Tonight through Saturday night)
Issued at 324 PM CDT Fri Oct 4 2024

Key Message:
* A rainy day for much of the populated RGV Saturday with potential
  for nuisance flooding along and east of IH-69E

Near term (through sunset): Forecast is working out nicely so far
this afternoon...as front edge of weak cyclonic circulation moved
onshore and combined with daytime heating to kick off scattered to
locally numerous showers.  Rain has spread farther west due to the
heating and expect this situation to continue through sunset.
Individual cells are producing an estimated 0.25 to 0.5" and reduced
visibility to 1-2 miles, but are moving at 15-20 mph and should
not cause anything more than nuisance ponding for the late
afternoon commute.

Remainder of short term (tonight through Saturday
night)...Developing divergence between two weak short waves...one
nearing Coahuila Mexico and the other east of Tamaulipas...will re-
start overnight rainfall after this afternoon`s activity fades out.
In terms of sensible weather...have kept isolated mention near the
coast but ended everything else inland through just after midnight.
As daybreak approaches...the combination of diurnal instability over
the Gulf waters with low level convergence (slight land breeze) will
aid development and movement of more coverage of rain onshore...and
locations from Brownsville to Los Fresnos to Port Mansfield should
see the next round between 5 and 7 AM Saturday.

As for Saturday...all indications suggest the prime period for
rainfall...including locally heavy bursts...will be from daybreak
through 1 PM. Heaviest rain will favor the coast with a gradual
decrease in intensity farther inland (toward IH-69C) and less
coverage as well. interestingly, if clouds are thinner across the
upper Valley/Brush Country/Rio Grande Plains we could see scattered
thunderstorms by afternoon.  Farther east, the rain will taper off
and could completely end by mid to late afternoon, but have
maintained scattered mention as a buffer...even though a pocket of
isolated appeared in the blended data.  Something to look for as the
situation evolves.

Total rainfall forecast through 7 PM is generally in the 1.5 to 2.5
inch range, potentially higher near Port Mansfield and South
Padre Island. If we see any flooding with 1 to 2 feet of water in
poor drainage locations, it will favor areas along/east of IH-69E
in Cameron and Willacy where training cells are most likely to
occur.

For Saturday night...the rain should end in most areas.  Have kept a
buffer of isolated through mid evening, then expect partly cloudy
skies with seasonable temperatures overnight with the only chance of
rain pinned to the coast toward daybreak.  Note that the rain
forecast near the coast is subject to change, as the GFS model has
been persistent on building a mini-500 mb ridge in east Texas with
northerly flow shoving the deeper moisture well south into the Gulf
and southern Tamaulipas.  Should this occur, even the coast would be
dry to start Sunday.

Lastly...have reverted the afternoon Coastal Flood Advisory to a
Coastal Flood Statement.  Wave energy at both buoy 42020 and 42002
remain rather paltry with wave heights at 3 feet and dominant period
between 5 and 6 seconds. So...even though observed water levels are
running over 1 foot above predicted and may reach 1.3 to 1.4 feet at
high tide (6 PM), our local decision matrix suggests a statement -
which means water nearing the dunes at narrow beaches north of the
city, and remaining some 50 feet shy of them in the city. So...while
beach will be "lost" to use...still some available to place
equipment on.  Rip currents are sitting on moderate which can be
dangerous to those unaware...but no statement yet and with Saturday
being pretty wet, not too concerned but swimmers should still be on
guard.

&&

.LONG TERM...
(Sunday through next Friday)
Issued at 324 PM CDT Fri Oct 4 2024

A surface low pressure system over the southwestern Gulf of Mexico
will continue to support isolated to scattered showers and
thunderstorms Sunday, with rain chances diminishing through the day.
A strengthening mid-level ridge over the Southwestern US will shift
further east into Texas early next week, as the surface low over the
Gulf moves further offshore. This will likely facilitate the passage
of a weak frontal boundary Monday, ushering in drier air and
slightly cooler low temperatures. Some isolated showers and
thunderstorms are possible along the seabreeze Monday, primarily in
Cameron County. Rain chances are expected to remain near zero
through the remainder of the forecast as high pressure and
subsidence sets up across Texas.

High temperatures look to remain in the upper 80s to low 90s through
the period. Low temperatures Sunday night look to be in the low 70s
across most of the CWA, falling to the upper 60s Monday night. Some
gradual cooling through the week is likely thanks to persistent
northerly surface winds. By the end of the period, low temperatures
are expected to be in the low to mid 60s.

&&

.AVIATION...
(06Z TAFS)
Issued at 1245 AM CDT Sat Oct 5 2024

Through 06z Sunday....

Key Aviation IDSS messages for the 06z TAF cycle:

* Rain showers, some heavy at times, with embedded thunder, will
  continue into the day on Saturday

* Clouds and rain showers will result in cigs/vsbys being reduced to
  mainly MVFR-IFR levels, with LIFR levels also possible

Latest GOES-16 satellite imagery and doppler radar depicts extensive
cloudiness over the area with waves of rain showers with some
embedded thunder moving inland from offshore. Conditions were IFR as
of this update at KHRL and KMFE with cigs between 500-1,000 feet
AGL. A batch of heavy rain showers are moving out of KHRL at this
time. KBRO was reporting VFR conditions.

Satellite, radar, and model trends suggest that the area will remain
socked in extensive cloudiness with rounds of rain showers through
much of the 06z TAF period. These clouds and rain showers are
associated with a a low pressure system meandering over the western
Gulf of Mexico. Over the next 6-9 hours, have VCSH and TEMPO groups
to reflect the chances of showers and MVFR to IFR conditions.

Beyond that timeframe, or during the day on Saturday, have Prob30
groups to reflect the continued chances for showers and embedded
thunderstorms. Should any showers or storms move over a TAF site, it
will have the capabilities of reducing cigs/vsbys down to MVFR-LIFR
levels. Otherwise, expect for VFR conditions to be in place with
VCSH around.

Winds will be light and variable to calm, if not out of the north-
northeast at around 5 kts. During the day on Saturday, winds will be
out of the north-northeast 5-10 kts.

&&

.MARINE...
Issued at 324 PM CDT Fri Oct 4 2024

Now through Saturday night: The main issue is messy conditions
due to numerous showers and isolated thunderstorms for much of the
period, especially between midnight and noon tonight/Saturday.
This could produce Caution conditions as well as gusts to 25 knots
or so, as well as plenty of choppy wind waves. With the
convection and moderate northeast gradient, raised combined seas
to 4 feet for most of this period. Boating/fishing not recommended
through Saturday...but conditions may become favorable on Laguna
Madre and perhaps the nearshore waters early Sunday, especially if
the drier GFS solution verifies.

Sunday through Wednesday Night: An area of surface low pressure
over the Southwestern Gulf of Mexico Sunday is expected to move
east through the early part of the period. The NHC has a 50%
chance for tropical cyclone development over the next 7 days
associated with this system. While the system will likely be
traveling away from the Lower Texas Coast, a slight uptick in
winds could be possible if the low strengthens Sunday or Monday.
This low will likely produce light to moderate winds and moderate
to enhanced seas through the early part of the period. Small Craft
Should Exercise Caution headlines may be needed through Tuesday.
By mid week, lighter winds and more moderate seas are expected to
return along the Lower Texas Coast.

&&

.PRELIMINARY POINT TEMPS/POPS...
BROWNSVILLE             85  76  87  75 /  80  40  60  20
HARLINGEN               85  72  87  71 /  90  30  60  10
MCALLEN                 87  75  90  73 /  70  20  50  10
RIO GRANDE CITY         87  73  89  71 /  70  20  40  10
SOUTH PADRE ISLAND      84  79  85  80 /  80  50  60  20
BAYVIEW/PORT ISABEL     85  75  87  75 /  90  30  60  20

&&

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

$$

SHORT TERM...52-Goldsmith
LONG TERM....60-BE
AVIATION...23-Evbuoma/69-Kamba