869
FXUS64 KBRO 181126 AAA
AFDBRO

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
626 AM CDT Sat May 18 2024

...New AVIATION...

.SHORT TERM...
(Today through Sunday)
Issued at 325 AM CDT Sat May 18 2024

The short-term forecast period starts today and will mark the onset
of another stretch of very warm to hot, humid, hazy, and dry
conditions. Latest LAPS/MSAS surface analysis depicts a sfc high
pressure system building into the area in the wake of a departed
frontal boundary and shortwave. This sfc feature will result in
increased subsidence over the region which will yield dry and
tranquil weather conditions.

As far as the warmth/heat, forecast models and ensembles continue to
depict 500 mb geopotential heights rising to between 591-591 dam as
a broad, elongated sub-tropical heat dome stretching from the
eastern Pacific to the Caribbeans strengthen. 1000-500 mb
thicknesses are expected to increase to about 582 dam today and 585
dam on Sunday. With 850 mb temperatures expected to climb to
between 22-24C on both days, high temperatures will range from the
low/mid 90s to near 100F both today and Sunday. With dewpoints in
the 70s, heat indices are expected to range from 100-110F. While
heat indices look to fall just below Heat Advisory criteria, the NWS
HeatRisk tool suggest that any heat related impacts will be confined
to most individuals sensitive to heat.

Warm and muggy conditions will continue Saturday night with
overnight lows in the mid 70s to near 80F with similar dewpoint
values. Some patchy mist/fog is possible along with haze as light
winds and copious amounts of low level moisture will result in
narrow dewpoint depressions.

&&

.LONG TERM...
(Sunday night through Friday)
Issued at 325 AM CDT Sat May 18 2024

Mid-level ridging will build over Texas through the period leading
to warming temperatures through the period. At the surface, steady
southeast winds, breezy at times, will allow for plenty of low-level
moisture flow to move into the region and thus keeping the air very
humid. The combination of lack of deep moisture and subsidence will
maintain rain-free conditions across Deep South Texas through the
long term.

Temperatures are expected in the triple digits across the Rio Grande
Plains Monday afternoon with mid to upper 90s across the rest of the
area, except for the 80s near the coast. The triple digits will
expand eastward through the week, reaching the I-69c/US 77 corridor
on Tuesday. High humidity combined with the hot surface temperatures
will lead to "feels like" temperatures exceeding 110 degrees in
several locations and Heat Advisories may be needed on Monday.
However, Heat Advisories will be more likely Tuesday through next
Saturday as the heat indices over 111 degrees are more widespread on
those days. The latest NBM suggests that the max heat index at 116
degrees for a few locations Friday and next Saturday afternoon.
Thus, a possible Excessive Heat Warnings and Watches might be needed
during that time. Overnight temperatures each night will remain warm
with lows falling into the upper 70s to low 80s.

There is a Moderate to Major risk of heat-related impacts for anyone
without effective cooling and/or adequate hydration with heat
indices ranging up to around 111 degrees for Monday and Tuesday. By
midweek, appears to pose an Extreme heat risk with heat indices
111- 116 degrees across much of Deep South Texas. This level of
rare and/or long-duration extreme heat with little to no overnight
relief affects anyone without effective cooling and/or adequate
hydration.

&&

.AVIATION...
(12Z TAFS)
Issued at 625 AM CDT Sat May 18 2024

Through 12z Sunday.....Latest surface analysis and satellite imagery
reveals clearing skies overhead and to our west as a frontal
boundary continues to shift southeast and in its wake a sfc high
builds into the region. Latest obs at the terminals indicate mainly
VFR conditions with the exception of KHRL (IFR due to ceilings of
800 feet AGL).

Through this morning, expect for mainly VFR conditions to take
place, though there could be instances of MVFR to IFR conditions. As
we shift into this afternoon, expect for VFR conditions to be the
dominant/main flight category over the terminals. Later tonight,
expect for MVFR conditions to return to the terminals.

Light and variable winds this morning will become more east-
northeast at 5-10 kts later this morning and afternoon. Later this
evening/tonight, expect for winds to trend towards light and
variable to calm.

&&

.MARINE...
Issued at 325 AM CDT Sat May 18 2024

Today through Sunday: Light to moderate winds will yield low to
moderate seas today through Sunday. While marine conditions are
mainly favorable through Sunday, there remains a "Moderate Risk"
for rip currents along the are beaches through Sunday.

Sunday night through Wednesday: Weak to moderate onshore flow with
moderate seas of generally 3 to 4 ft will persist through Monday. A
locally enhanced pressure gradient could lead to Small Craft Caution
conditions on the Laguna Madre and the nearshore Gulf waters each
afternoon into the early evening hours, Tuesday through late
week.

&&

.PRELIMINARY POINT TEMPS/POPS...
BROWNSVILLE             92  79  94  79 /  10   0   0   0
HARLINGEN               93  75  95  75 /   0   0   0   0
MCALLEN                 97  77  99  78 /   0   0   0   0
RIO GRANDE CITY         98  77  98  77 /   0   0   0   0
SOUTH PADRE ISLAND      85  80  84  80 /  10   0   0   0
BAYVIEW/PORT ISABEL     89  77  89  77 /   0   0   0   0

&&

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

$$

SHORT TERM...23-Evbuoma
LONG TERM....63-KC
AVIATION...23-Evbuoma