052
FXUS64 KBRO 061753 AAB
AFDBRO

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
1253 PM CDT Thu Jun 6 2024

...New AVIATION...

.SHORT TERM...
(Today through Friday)
Issued at 332 AM CDT Thu Jun 6 2024

Key Messages:

* Continued Hot Today and Friday with Record to Near Record-Breaking
  Temperatures Developing This Afternoon

* Heat Advisory in effect from 1PM-8PM CDT today for All of Deep
  South Texas and the Rio Grande Valley with the exception of the
  island counties

* Major HeatRisk (level 3 of 4) continues

* Marine Conditions become More Favorable Tonight into Friday along
  with Very Low Rain Chances

The main weather headline through the short term forecast period
will continue to be the heat. According to the latest large-scale
500 mb upper air analysis, the local forecast area is on the eastern
edge a heatwave taking place over the western U.S. as a massive and
anomalously strong 591 dam heat dome is situated over the Desert
Southwest. Deterministic forecast models/ensembles show this heat
dome shifting eastward over Texas on Friday, however, in a somewhat
weaker state as the heatwave/500 mb pattern out West breaks down
slightly thanks to periods of shortwave energies/impulses helping to
compromise the pattern a bit.

That said, strong differential surface heating with a strong ridge
overhead will increase dewpoint depression and allow for any low
level clouds to scour out by this afternoon. With 850 mb
temperatures sampled between 23-26C, 1.5 to 2.5 STDEVs above normal,
sfc temperatures will have no trouble climbing once again into the
upper 90s to lower 100s across Deep South Texas and the Rio Grande
Valley this afternoon. Marry this with dewpoint (Td) temperatures in
the mid to upper 70s, and heat indices will range from 109-116F this
today. Given the situation, a Heat Advisory has been issued for all
of Deep South Texas and the Rio Grande Valley with the exception of
the island counties of Cameron, Willacy, and Kenedy from 1PM-8PM CDT
today. Inland Cameron, Willacy, Kenedy, Counties along with Brooks,
Hidalgo, and Starr Counties are areas that are expected to see the
highest heat indices. Lastly, the expected high temperatures later
this afternoon are expected to be record or near record-breaking.
Brownsville and Harlingen have the best chances for either tying or
setting a new record today (see Climate Section below).

Tonight will feature another warm and muggy night with overnight low
temperatures in the mid 70s to near 80F degrees. Narrowing dewpoint
depressions given the copious amounts of low level moisture tonight,
will allow for low level clouds to increase in coverage once
again.

Friday will feature another very warm to hot day, though not as hot
as today given that the aforementioned heat dome/500 mb pattern
weakens some (as highlighted above earlier). Humidity levels are not
expected to be as strong as today neither. That said, max heat
indices will be weaker on Friday than today with values ranging from
103-111F.

&&

.LONG TERM...
(Friday Night through Wednesday)
Issued at 332 AM CDT Thu Jun 6 2024

The center of broad 500 mb high pressure will migrate from the
Lone Star State, to the north-central Gulf of Mexico, and then to
northwest Mexico, but will remain the dominant weather feature
over the BRO CWFA. Although dry weather will prevail through a
majority of the period, isolated convection is possible Monday and
Tuesday, but confidence in this occurring is not high at this time.

Temperature-wise, well above normal daytime highs will continue to
be the norm. However, slightly cooler values, when compared to
recent trends, will result in a HEAT ADVISORY not anticipated each
day, with heat indices more likely to be discussed in a daily SPECIAL
WEATHER STATEMENT.

&&

.AVIATION...
(18Z TAFS)
Issued at 1243 PM CDT Thu Jun 6 2024

Persistent smoke/soot from the last of agricultural burning in
southeast Mexico...as well as Central American
wildfires...combined with increasing low level inversion(s) and
lighter winds associated with surface high pressure ridge
settling over the Valley have brought back visibility-reducing
haze/smog that was fairly thick this morning as pockets of IFR
visibility developed. That, along with potential for IFR
ceilings...is the primary concern for the overnight.

Persistence, therefore, is the best option for the overnight and
early Friday morning forecast. After the usual brief uptick in
easterly winds late this afternoon/early this evening, which
should keep haze at bay, expect haze to return as winds lay down
soon after sunrise. Despite a bit more easterly component aloft
(as well as across the smokier areas to our south), stagnant air
is still here (note another day of "Unhealthy" air quality) so
have lowered visibility to the edge of IFR (3 statute miles)
especially for the Lower Valley terminals, mainly after 1 AM.
Ceilings will form up as well but there is some uncertainty on the
duration of such...and exactly how low they drop to. High IFR/low
MVFR seems the best bet (900 to 1500 feet) which should continue
through 8 or 9 AM...then lift to high MVFR/low VFR to close out
the forecast window.

Winds will increase a little but still remain below 10 knots
through late morning. This should be enough to improve visibility
but not by too much...and would not surprise to see 6 miles
continue through lunchtime.

&&

.MARINE...
(Today through Friday)
Issued at 332 AM CDT Thu Jun 6 2024

With the aforementioned 591 dam sub-tropical ridge moving
overhead, marine conditions are expected to become more favorable
tonight and Friday. Light to moderate winds and seas today will
give way to light seas tonight into Friday. A moderate risk for
rip currents is expected today. However, the risk becomes a low
risk for rip currents tonight and on Friday.

(Friday Night through Wednesday)
Light to moderate winds and low to moderate seas will occur along
the Lower Texas Coast through the period with high pressure in
control over the western Gulf of Mexico. Neither Small Craft
Should Exercise Caution nor Small Craft Advisory are anticipated
to be needed.

&&

.CLIMATE...
Issued at 332 AM CDT Thu Jun 6 2024

Record Highs for today June 6, 2024

Brownsville 98F in 2018 (Forecast High is 99F)
Harlingen 100F in 2019 (Forecast High is 100F)
McAllen 103F in 2018 (Forecast High is 101F)

&&

.PRELIMINARY POINT TEMPS/POPS...
BROWNSVILLE             98  79  97  79 /  10   0  10   0
HARLINGEN              100  76  99  75 /  10   0  10   0
MCALLEN                101  79 101  78 /  20   0  10   0
RIO GRANDE CITY        100  78 101  76 /  10  10   0   0
SOUTH PADRE ISLAND      88  81  88  81 /  10   0  10  10
BAYVIEW/PORT ISABEL     94  79  93  78 /  10   0  10   0

&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...Heat Advisory until 8 PM CDT this evening for TXZ248>255-351-
     353>355.

GM...None.
&&

$$

AVIATION...52-Goldsmith