607
FXUS64 KBRO 101641 AAB
AFDBRO

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
1141 AM CDT Mon Jun 10 2024

...New AVIATION...

.SHORT TERM...
(Today through Tuesday)
Issued at 319 AM CDT Mon Jun 10 2024

Key Messages:

* Still very warm and humid, but cooler and near seasonable today
  and Tuesday as Deep South Texas and the RGV get a reprieve from
  the most intense heat

* Moderate to pockets of major HeatRisk today; Moderate with pockets
  of minor Heat Risk Tuesday

* Day-to-day chances for an isolated thunderstorm or two today and
  Tuesday; 20-40% chance today and 20-30% chance on Tuesday

* Outside of thunderstorm chances, favorable marine conditions will
  continue through Tuesday with light winds yielding light seas

The main weather concerns during the short term forecast period will
continue to focus on the very warm to hot and humid conditions as
well as day-to-day chances for an afternoon/evening thunderstorm or
two.

Global deterministic forecast models and their ensembles continue to
depict the southward advancement of a sfc cold front sagging into
central Texas through today. Meanwhile, the 500 mb Sonoran heat
ridge which briefly weakened over the weekend, will begin to
strengthen/re-emerge over the northwestern parts of Mexico into the
4-Corners region through Tuesday.

Given the large-scale setup, our local forecast area will be
placed east of the ridge axis and on the leeward side of the
strengthening 500 mb ridge. This will result in slightly cooler
temperatures (near normal levels) through the short term forecast
period as the core of the hottest temperatures (most intense heat)
will be located across parts of the western U.S. Despite it still
will being very warm and humid across Deep South Texas and the
Rio Grande Valley through Tuesday, the slight cool down to more
seasonable levels and reprieve from the heat serves as good news
for the region.

H850 temps sampled between 19-22C will translate to sfc daytime
highs in the mid to upper 90s. This coupled with dewpoints (Td) in
the mid to upper 70s will result in peak heat indices ranging
between 107-113F degrees before a potential sea breeze kicks in
later this afternoon.

Given that these level temperatures will not persist for more
than two hours, a Heat Advisory is not needed. However, a Special
Weather Statement (SPS) may be needed for Inland Cameron, Hidalgo,
Starr, Inland Willacy, Inland Kenedy, and Brooks Counties today.
So slightly cooler than Sunday and cloud coverage will also be key
in addition to the timing of the potential sea breeze.

The other concern for today is convection potential. Multiple CAMs,
global deterministic models and ensembles are signaling for the
potential for some isolated showers and thunderstorms developing
late this afternoon into this evening. Despite not having a strong
shortwave overhead, precipitable water (PWAT) values approaching 2
inches combined with the possibility of a sea breeze developing as
winds shift more out of the east could create enough surface
convergence in a buoyant environment to break the cap and ignite
showers and thunderstorms.

Have 20-40% Pops across the region for later this afternoon and
evening. The Storm Prediction Center (SPC) has placed the entire
area under a General Risk for thunderstorms today. The best timing
for any thunderstorms will be between 4-9 PM CDT. Otherwise,
expect for rain-free conditions to continue with ideal weather,
especially for the beachgoers.

Tonight, any left over storms should be winding down giving way to
another warm and muggy night. Overnight lows are progged to be in
the mid 70s to near 80F.

Tuesday will feature a similar setup to today. Still on the leeward
side of the aforementioned 594 dam sub-tropical Sonoran heat dome
and ridge axis, temperatures will remain closer to seasonable
levels. That said, daytime highs are expected to be in the mid to
upper 90s. Heat indices are expected to be slightly cooler than
today given that dewpoint temperatures (Td) will be slightly lower
(under Heat Advisory and SPS criteria).

Once again there are some indications amongst computer models
that suggest the potential for additional isolated afternoon and
evening showers and thunderstorms. PWAT values remain elevated
between 1.5 to 2 inches. This coupled with the potential for
another sea breeze developing could help to ignite showers and
thunderstorms Tuesday afternoon/evening.

For now, have 20-30% PoPs for the eastern half of the area (that
is Brooks and Hidalgo Counties and points east). The Storm
Prediction Center (SPC) has the entire area outlooked once again
under a General Risk for thunderstorms on Tuesday. Will continue
to monitor trends. Otherwise, expect for rain-free conditions to
continue with ideal weather, especially for the beachgoers.

&&

.LONG TERM...
(Tuesday night through Sunday)
Issued at 319 AM CDT Mon Jun 10 2024

The persistent mid-level ridge returns across Texas through the
remainder of the long term period, while broad low pressure
settles across the Central Gulf. Most model guidance brings a
500mb low and shortwave around the ridge from the panhandle to the
Gulf during the week, and generally keep Deep South Texas to the
west of the feature, but do increase moisture through the long
term with a weak pressure gradient. Robust PWATs between 1.8 and 2
inches begin rolling in each afternoon, generally near to
slightly above the 90th percentile for PWATs in mid June.

In a light wind regime with increased Gulf moisture, expect the
sea breeze to develop every day, clipping highs across coastal
counties a little and limiting peak Heat Indices. Highs still
reach 95-102 east to west, with lows generally 74-79. Have blended
the NBM with NBM50 Thursday into Monday, which keeps highs more
in line with recent MOS trends and plays off the easterly to
perhaps ENE flow Thursday through Saturday. The only day at the
moment to potentially briefly creep back toward Heat Advisory
criteria is Monday afternoon across the coastal counties.

Overall, the pattern looks very summer-like, with the chance of
streamer showers offshore toward the coast each morning and
isolated convection along the sea breeze each afternoon. NBM has
caught on to the streamer showers maybe a little too well, but not
as bullish on the sea breeze. Have nudged offshore and coastal
POPs down a little for streamers and bumped inland POPs up each
afternoon with the sea breeze, but kept it isolated until
confidence improves.

&&

.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 319 AM CDT Mon Jun 10 2024

Now through Tuesday...High pressure and a weak pressure gradient
will result in favorable marine conditions today through Tuesday.
Light east-southeasterly winds will result in light seas. There is a
chance of an isolated shower or thunderstorm developing on during
the afternoon/evening hours on both Monday and Tuesday.

Tuesday Night through Sunday...A weak pressure gradient maintains
generally light southeasterly to easterly flow through the long
term period resulting in seas of 2 to 3 feet. Broad low pressure
gradually builds across the Central Gulf, increasing the chance of
streamer showers and isolated convection through the weekend.

&&

.PRELIMINARY POINT TEMPS/POPS...
BROWNSVILLE             95  79  95  78 /  30  10  30   0
HARLINGEN               96  76  96  75 /  30  10  20  10
MCALLEN                 98  79  99  78 /  40  30  20  10
RIO GRANDE CITY         98  78  98  77 /  20  30  10  10
SOUTH PADRE ISLAND      87  82  86  81 /  30  10  30  10
BAYVIEW/PORT ISABEL     92  79  91  78 /  30  10  30  10

&&

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

$$

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