403
FXUS64 KBRO 102027
AFDBRO

Area Forecast Discussion
National Weather Service Brownsville TX
327 PM CDT Mon Jun 10 2024

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

.SHORT TERM...
(Tonight through Tuesday night)
Issued at 327 PM CDT Mon Jun 10 2024

Boundary driven convection with sea breeze interaction are affecting
the CWA today (we are in a general thunderstorm category outlook
area). Another southward moving pulse may move into the area
evening, but most, if not all, convection should be finished by late
evening. Look for another warm and muggy night. Overnight low temps
will be in the mid 70s to near 80 degrees Fahrenheit with light east
to southeast winds and partly cloudy skies.

Tuesday will feature a similar setup compared to today. Low level
moisture will again be high (PWAT today at KBRO was 2.15 inches) and
should support late morning to early afternoon sea breeze formation.
Due to the weakness over North Central Texas, convection may again
fire to our north overnight and send an outflow boundary south
toward deep South Texas and the Rio Grande Valley. The NAM12 shows
just that type of scenario playing out. Have left the 20 to 30
percent pop area in for tomorrow reflecting at least sea breeze
activity. However, we are in a general thunderstorm category outlook
area for Tuesday and ultimate coverage could increase.

Still on the leeward side of a temporarily weakened sub-tropical
heat dome and ridge axis over North Central Mexico and the Southwest
United States, temperatures will remain above average. That said,
daytime high temps will be in the mid to upper 90s to near or
slightly above the century mark inland west. This will be a few
degrees above average. Accordingly, most CWA heat index values will
be in the 105 to 110 degree range on Tuesday, with a small chance
for some areas to briefly near or reach heat advisory criteria.

Anticyclonic flow over the Gulf will support light east to southeast
winds in the short term as well as isolated periodic Gulf showers.
Wave heights will remain low supporting a low risk of rip currents.


&&

.LONG TERM...
(Wednesday through next Monday)
Issued at 327 PM CDT Mon Jun 10 2024

Key Messages
* Still hot, but closer to mid June averages each day and night

* Isolated to scattered sea-breeze and boundary-driven late
  morning through late afternoon showers and storms, but not
  enough rain to make a prolonged dent in heat

* Rip currents will become moderate by Friday through the weekend,
  posing a danger to unaware swimmers in otherwise favorable surf

The big picture is still hot and generally rain-free, though a
gradual pattern change aloft will help bring some sea-breeze
activity each day through Thursday...and generally easterly flow
in the low levels will continue to remove the hazy skies and bring
more typical tropical azure blue skies with each passing day.

As for that rain...the better chances on land continue to favor
Wednesday and Thursday as additional weak short waves dive
southward on the east side of the north-south axis 500 mb ridge
initially centered over New Mexico through Chihuahua Mexico and
southwest to Sinaloa/Baja. By Friday, that ridge "tips" over and
expands eastward, extending from the lower Mississippi Valley
through most of Texas and out to Baja...which will push any short
waves rotating around the ridge well east of the area. This
should put an end to mentionable rain on land, though isolated
showers will be possible over the warm Gulf waters where hints of
higher moisture remain.

Any sea breeze driven rains will follow diurnal trends which means
morning to around noon on the island and jumping inland soon
after, leaving the beaches mainly sunny with distant cumulus
towers 20-60 nautical miles out. Of course, any southward-moving
boundaries from activity to our north could change the situation,
as was the case today.

The dry air should hold through at least Sunday, but the forecast
becomes more uncertain Sunday night and Monday as the ridge breaks
ito two pieces, one recentering over Baja and the other along the
southeast U.S. coast. As the east coast ridge strengthens a bit,
it will tend to send at least some of the deep tropical plume of
moisture affecting Florida for the rest of this week westward into
the central Gulf late Sunday...and perhaps nosing toward the
entire Texas coast by next Monday.

This is where uncertainty really grows as models are in different
camps and the question remains just how far west the plume can
move...especially since the 500 mb trough (acting like a Tropical
Upper Tropospheric Trough, or TUTT) has a north-south axis and the
west side, which would include the coast, could stay dry for at
least the first day or two next week. The latest National Blend of
Models is more bullish with the approach of deep layer moisture,
and thus has Monday in a 20-40 percent chance of tropical showers
and perhaps a thunderstorms for all but the Rio Grande Plains. The
blend accounts for multiple permutations...so expect this part of
the forecast to change over the next several days.

As for temperatures...the overall atmosphere remains above average
based on traditional parameters such as 1000-850 and 1000-500 mb
thickness, 850 mb temperatures, etc...but the pattern is less
favorable for the blast furnace effect that we saw for much of the
past six weeks. Therefore, have temperatures sitting 1-2 degrees
above average (upper 90s east, 100-102 west) for mid June by day
but right around average each morning with light winds and mainly
clear skies. Still...with temperatures still on the slightly
higher side after a searing hot start to June...our average values
through mid June will end up at or near the hottest on record.

Finally...with the beach offering another weekend of relief...and
azure blue skies with increasing easterly swell...the danger of
moderate pure rip currents lurks as surf temperatures will be in
the inviting mid 80s. Poor swimmers are urged to be near
lifeguards and only venture in to waist or knee deep during this
time.

&&

.AVIATION...
(18Z TAFS)
Issued at 1125 AM CDT Mon Jun 10 2024

An outflow boundary is moving through the CWA from north to
south. It should pass to the south in another two to three hours.
There has been some convection over northeast Kenedy County and
the adjacent coast already, and isolated convection is becoming
evident south of the RG. Interaction with the sea breeze is a bit
of a wild card right now, but that could also contribute to some
storms around the TAF terminals this afternoon. Drier air behind
the boundary is clearing things out, which should happen later
today after the local convection ends. Other than low clouds
thickening ahead of the boundary and supporting MVFR ceilings, VFR
will otherwise be expected. There could be some cloud to ground
lighting within these afternoon storms.

&&

.MARINE...
Issued at 327 PM CDT Mon Jun 10 2024

Now through Tuesday night...High pressure over the north-central
Gulf of Mexico and a weak pressure gradient over the region will
produce light to moderate east to southeast winds and generally low
seas through the forecast. Convection over the Gulf will be more
active this week, with periodic isolated showers and thunderstorms
along the lower Texas coast.

Wednesday through Saturday night...Other than periodic isolated to
scattered showers and a few thunderstorms much of the time (mainly
from late night through early afternoon), winds/seas begin on the
light/slight side before increasing a bit by Saturday as easterly
swell gets going between the weak ridge in the northern Gulf and
weak low in the southwest Gulf.

&&

.PRELIMINARY POINT TEMPS/POPS...
BROWNSVILLE             80  96  79  96 /  10  30   0  20
HARLINGEN               77  97  76  97 /  10  30   0  20
MCALLEN                 79 100  78  99 /  20  20   0  10
RIO GRANDE CITY         78 100  78  99 /  30  10   0  10
SOUTH PADRE ISLAND      82  87  81  87 /  10  30  10  20
BAYVIEW/PORT ISABEL     79  92  78  92 /  10  30   0  20

&&

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

$$

SHORT TERM...54-BHM
LONG TERM....52-Goldsmith