309
FXUS64 KBRO 080820
AFDBRO

Area Forecast Discussion
National Weather Service Brownsville TX
320 AM CDT Wed May 8 2024

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

.SHORT TERM...
(Today through Thursday)
Issued at 319 AM CDT Wed May 8 2024

Key Messages:

- Unseasonable heat, including triple-digit temperatures and heat
index values, are expected across Deep South Texas.

- A Heat Advisory is in effect for portions of the region this
afternoon, and will likely be needed again on Thursday.

- Those spending a prolonged period outside will need to take
necessary heat precautions to avoid heat-related illnesses.

- Moderate risk of rip currents through Thursday.

The hottest days of the week are expected today and tomorrow across
all of Deep South Texas. Forecast model soundings reveal a sharp
inversion at 850mb as westerly winds transport much more subsident
air overhead, keeping the higher moisture content (humidity) in
place near the surface. Additionally, model guidance suggests 850mb
temperatures will continue to increase each afternoon, measuring
around 24-27C this afternoon and 27-29C Thursday afternoon, which
will further promote unseasonably hot afternoon temperatures.

Well established low level southerly to southeasterly flow will
maintain high dew points along the coast each afternoon, but the
presence of a dryline across the western half of the region will
allow for drier air to filter in. Dew points will range from the mid
to upper 70s east of the dryline to upper 40s and 50s west of the
dryline. While the hottest temperatures will be observed generally
west of the dryline, the lower dew points will result in heat index
values measuring closer the ambient temperature. Conversely,
temperatures will be a few degrees lower (but still quite hot and in
the triple-digits) east of the dryline, but the higher dew points
will result in heat index values 10-15 degrees above the ambient
temperature.

For this afternoon, high temperatures will range from the upper 90s
across the Lower RGV to around 108 degrees across the Rio Grande
Plains. The dryline is expected to push as far east as US-281 this
afternoon and presence of higher humidity along/east of US-281 will
yield heat index values ranging from 110-114 degrees. As a result, a
Heat Advisory is in effect for inland Cameron, inland Willacy,
inland Kenedy, Hidalgo, and Brooks counties this afternoon. Daily
records for May 8th may be tied or broken at Brownsville (95 in
2020), Harlingen (99 in 2003), and McAllen (100 in 2019).

Thursday will be the hottest day of the short-term period. Daily
records for May 9th will likely be  tied or broken as well at
Brownsville (97 in 1998), Harlingen (100 in 1998), and McAllen (103
in 1998). Probabilistic guidance indicates there is a high chance
(70% or greater) that most of Deep South Texas will observe a high
temperature of 100 degrees or higher. The current forecast calls for
temperatures ranging from 100 degrees across the Lower RGV to around
109 degrees across the Rio Grande Plains. Fortunately, high res
model guidance suggest the dryline will push as far east as the I-69
corridor on Thursday, which would temper the heat index values for a
large portion of Deep South Texas. Still, portions of Cameron,
Willacy, and Kenedy counties will likely realize heat index values
ranging from 110-114 degrees Thursday afternoon as dew points remain
in the upper 60s to low 70s. A Heat Advisory will likely be needed
once again Thursday afternoon.

Remember to take the necessary precautions against the heat to limit
the risk of heat-related impacts and illnesses. Never leave children
or pets in vehicles, drink plenty of fluids to stay hydrated, and
take frequent breaks if spending a prolonged period outside.

&&

.LONG TERM...
(Thursday night through Tuesday)
Issued at 319 AM CDT Wed May 8 2024

A weak cold front across the Hill Country Thursday evening is
expected to push southward and move into Deep South Texas late
Thursday night into Friday morning. In the wake of the front,  more
seasonal temperatures are expected Friday and into the weekend.
Daytime high temperatures will be in the upper 80s to low 90s Friday
into Sunday. Overnight lows Friday and Saturday night are expected
to be in the low to mid 70s. Light east to southeast winds Thursday
night will become northeast on Friday with the frontal passage.
Easterly winds Saturday and Saturday night are expected to become
southeasterly on Sunday as the boundary retreats northward as a warm
front and lingers across the area.

Abundant moisture combined increased forcing and ample instability
could support a slight chance for showers and thunderstorms along
the weak cold front Friday. Additional, weak overrunning will
support isolated to scattered showers and thunderstorms across the
area on Saturday. Onshore flow with increased moisture and
instability could again support a slight chance of showers and
thunderstorms Sunday and Monday. Temperatures gradually warm through
the middle of next week.

&&

.AVIATION...
(06Z TAFS)
Issued at 1225 AM CDT Wed May 8 2024

MVFR ceilings, with intermittent periods of IFR ceilings, will
prevail through the mid morning hours on Wednesday at all TAF
sites. The development of patchy fog may result in visibility
falling to around 3-5SM through 13-14Z. Improvement to VFR
ceilings will occur from west to east, around 16Z for MFE, and
around 18-19Z for HRL and BRO. Another round of MVFR ceilings is
expected after 03-05Z. Otherwise, southeast winds around 10-15
knots with occasional gusts around 20-25 knots will prevail
through the TAF period.

&&

.MARINE...
Issued at 319 AM CDT Wed May 8 2024

Today through Thursday...Generally favorable marine conditions will
prevail with light to moderate southeast winds and moderate seas.
Brief periods of Small Craft Exercise Caution conditions will be
possible each afternoon, especially across the Laguna Madre and
northern Gulf waters as the pressure gradient tightens.

Thursday night through Tuesday...Light to moderate winds and
moderate seas are likely Thursday night. Stronger northeasterly
winds will develop behind a cold front Friday will likely require
Small Craft Exercise Caution or Small Craft Advisories by Friday
afternoon. Winds are expected to diminish Friday night as high
pressure settles across the region. Light to moderate winds and
moderate seas will prevail along the Lower Texas through the rest
of the period.

&&

.PRELIMINARY POINT TEMPS/POPS...
BROWNSVILLE             97  79 101  76 /   0   0   0   0
HARLINGEN              100  78 106  75 /   0   0   0   0
MCALLEN                103  78 107  77 /   0   0   0   0
RIO GRANDE CITY        105  77 109  74 /   0   0   0  10
SOUTH PADRE ISLAND      86  79  88  78 /   0   0   0   0
BAYVIEW/PORT ISABEL     95  78  98  76 /   0   0   0   0

&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...Heat Advisory from 1 PM this afternoon to 7 PM CDT this evening
     for TXZ250-251-253>255-353.

GM...None.
&&

$$

SHORT TERM...22-Garcia
LONG TERM....63-KC
AVIATION...22-Garcia