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729
FXUS64 KBRO 250548 AAB
AFDBRO

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
1248 AM CDT Sat May 25 2024

...New AVIATION...

.SHORT TERM...
(Tonight through Saturday night)
Issued at 315 PM CDT Fri May 24 2024

Key Messages:

* Excessive, Dangerous, Record-Breaking Heat Likely on Saturday
* Triple digit highs likely for Brownsville, Harlingen, and McAllen
  on Saturday
* Heat Indices between 110-120F is likely on Saturday
* High Risk for Rip Currents to continue through Saturday

With the local forecast area on the northern edge of a persistent
591 dam sub-tropical heat dome, this dangerous heat episode is
expected to continue through the short term forecast period.

Another abnormally warm and muggy night for late May is expected
with overnight low temperatures holding in the lower 80s. A
relatively tight pressure gradient over the area will result in
breezy conditions/onshore flow continuing through tonight between
10-20 mph.

Triple digit heating is likely on Saturday across almost all of Deep
South Texas (outside of the coast areas) as global deterministic
forecast models are suggesting H850 temps ranging between 21-27C,
which is 2-3 standard deviations above normal for late May
standards. This will translate to daytime highs on Saturday between
100-105F for almost all of Deep South Texas and the Rio Grandee
Valley including Brownsville, Harlingen, and McAllen. Couple this
with dewpoint values in the mid 70s to near 80F and we`re going to
have heat indices (Real Feel Temperatures) ranging between 110-120F
degrees. An Excessive Heat Warning will likely be issued later this
afternoon/evening for Saturday for much of Deep South Texas. A Heat
Advisory will likely be issued for much of Deep South Texas for
tonight due to overnight low temperatures expected to be in the
lower 80s.

Saturday night will feature another abnormally warm and muggy night
with overnight lows in the lower 80s and dewpoints in the mid 70s to
near 80F. Breezy conditions could continue with a relatively tight
pressure gradient inn place yielding in a continuation of
onshore/southeast winds 10-20 mph.

With these level temperatures expected for Saturday, record daytime
highs are likely to be broken over Brownsville, Harlingen, and
McAllen (see Climate section below for more details). Record high
minimum temperatures for tonight and Saturday night could be in
jeopardy as well (see Climate section below for more details).

&&

.LONG TERM...
(Sunday through next Friday)
Issued at 315 PM CDT Fri May 24 2024

Key Messages:

- Dangerous heat will continue through at least Tuesday, including
  Memorial Day.

- There will be an extreme risk of heat-related impacts,
  especially for those that do not stay hydrated or take frequent
  breaks in the shade/indoors.

- Moderate to high risk of rip currents will exist through
  Memorial Day.

Triple-digit temperatures and heat indices will persist through
early next week across Deep South Texas as mid/upper level ridging
centered over Mexico prevails. Meanwhile, well established low
level southerly to southeasterly flow will maintain elevated dew
points. High temperatures will likely reach 100-104 degrees along
the I-69 corridor to around 110 degrees across the Rio Grande
Plains on Sunday and Memorial Day. Heat indices will range from
112 to 122 degrees across the region each afternoon as dew points
remain elevated. Along the Lower Texas beaches and coastal
portions of Cameron, Willacy, and Kenedy counties, high
temperatures will range from the upper 80s to upper 90s. However,
in combination with the high humidity, "feels like" temperatures
will be over 100 degrees... including South Padre Island. Daily
record high temperatures will likely be tied or broken through
Memorial Day.

There will be little to no relief overnight as low temperatures
only fall to around 79 degrees across the Northern Ranchlands to
the low to mid 80s across the Rio Grande Valley. Daily record
highest low temperatures will continue to be broken each morning
through at least Tuesday morning. Morning heat index values in the
low 80s to mid 90s each day will make for unseasonably hot
mornings for those attending any early morning outdoor events this
weekend.

All in all, the very warm nights and dangerously hot days will
cause heat illnesses for anyone who is not acclimated to the heat
or does not take proper precautions against the heat. The NWS
HeatRisk tool indicates an extreme risk of heat-related impacts to
those spending any time outdoors.

Fortunately, there looks to be some relief from the oppressive
heat next week. The mid/upper level ridge looks to weaken
slightly, which will allow for the passage of weak embedded
shortwaves. Slightly lower high temperatures and more seasonable
heat indices are expected Tuesday through Friday. While the hope
is to receive some much needed rainfall, if anything cloud cover
will help with the afternoon heat. The best chances for any rain
look to be Monday and Tuesday afternoon/evening, should any
convection develop off the Sierra Madre.

&&

.AVIATION...
-- Changed Discussion --
(06Z TAFS)
Issued at 1236 AM CDT Sat May 25 2024

The region can expect MVFR ceilings overnight through a few hours
after sunrise with VFR conditions for Saturday afternoon hours.
There is a medium to high probability (60-80%) that MVFR ceiling
to return between 02-05Z Saturday evening. Light to moderate winds
overnight become moderate to gusty Saturday afternoon with gusts
from the southeast to south at 25-30 knots.
-- End Changed Discussion --

&&

.MARINE...
Issued at 315 PM CDT Fri May 24 2024

Tonight through Saturday night...A High Risk for Rip Currents
will continue for the area beaches along the Lower Texas Coast
till 7 PM CDT on Saturday. Moderate winds via a relatively tight
pressure gradient will result in SCEC conditions during the day on
Saturday.

Sunday through next Friday...Moderate winds and moderate seas will
prevail through the period. Small Craft Exercise Caution
conditions will continue through next week along the Laguna Madre
and Gulf waters due to an enhanced pressure gradient. A brief
Small Craft Advisory cannot be ruled out during the afternoon
hours as wind speeds increase.

&&

.CLIMATE...
Issued at 315 PM CDT Fri May 24 2024

Record High Minimums for tonight

Brownsville 81F in 2019
Harlingen 80F in 2016
McAllen 79F in 2019

Record Daytime Highs for Saturday May 25, 2024

Brownsville 97F in 2018
Harlingen 97F in 2018
McAllen 103F in 1989

&&

.PRELIMINARY POINT TEMPS/POPS...
-- Changed Discussion --
BROWNSVILLE             83 100  83  99 /   0   0   0   0
HARLINGEN               80 100  80 101 /   0   0   0   0
MCALLEN                 81 105  82 104 /   0   0   0  10
RIO GRANDE CITY         80 107  81 107 /   0   0   0  10
SOUTH PADRE ISLAND      83  88  83  88 /   0   0   0   0
BAYVIEW/PORT ISABEL     81  95  82  94 /   0   0   0   0
-- End Changed Discussion --

&&

.BRO WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --
TX...Heat Advisory until 11 AM CDT this morning for TXZ248>255-353.

     Excessive Heat Warning from 11 AM this morning to 7 PM CDT this
     evening for TXZ248>255-353.

     Heat Advisory until 7 PM CDT this evening for TXZ351-354-355.

     High Rip Current Risk through this evening for TXZ451-454-455.

GM...None.
-- End Changed Discussion --
&&

$$

SHORT TERM...23
LONG TERM....22
AVIATION...59-GB