Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 172338 AAA

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
638 PM CDT Thu May 17 2018

.DISCUSSION...Updated for latest aviation discussion below.

.AVIATION...Satellite images and surface observations indicate
clear skies across the CWA early this evening. Expect VFR
conditions across the Rio Grande valley tonight into Friday as the
500mb ridge across northeast Mexico and southwest Texas continues
to provide subsidence across the area.

.PREV DISCUSSION... /issued 249 PM CDT Thu May 17 2018/
SHORT TERM (Tonight through Friday Night):
Hot, hot and more hot for the short term as the H5 ridge remains
in the region. Southeast winds will continue to drift across the
region due to a surface low developing in SE Colorado. This will
keep llvl winds up overnight, with breezy conditions expected
tomorrow. Increased onshore flow will start to bring the humidity
back into south Texas, decreasing the dry heat and increasing the
humid heat. With the increase in moisture along the coast, coastal
areas will see highs only in the low 90s, but heat index values
will still reach right around 100. Moisture will also mean a few
more clouds around Brownsville during the afternoon. Inland areas
will see continued drier conditions, so Highs will reach near 100
From McAllen and west, with the heat index 100 to 105.

LONG TERM (Saturday through Thursday):
Initialized with the superblend, and made only minor adjustments
to high temperatures to reflect the ongoing warmer weather.
Upstream ridging will start to break down over the area Friday and
Saturday, allowing a more southwest mid level flow to set up over
head, which should persist much of the long term with persistent
troughing upstream over the Southwest. High pressure will remain
in control at the surface, supporting continued onshore winds,
breezy at times Saturday and Sunday in response to a tighter
gradient with Plains lower pressure. Temperatures will continue an
above normal trend. A sea breeze may develop on Sunday, with
short wave energy moving through the upper flow Sunday night,
kicking off isolated convection to the west of the CWA, which
could drift east into the upper valley overnight. That will be the
main potential for rain in this long term. Modest ridging will
remain overhead or just east over the northwest Gulf, lending
broad stability to the weather for much of the long term.

MARINE (Now through Friday night): Southeast breezes will remain
elevated in the short term, with gradually rising winds as low
pressure develops in SE Colorado. Winds will be around 15 knots
overnight for the marine areas, before increasing to near 20kts
for the laguna tomorrow and tomorrow night offshore. Advisories
becoming more likely for tomorrow for the Laguna Madre, especially
north of the Port Mansfield Cut. Increasing winds will push
swells upwards to 5 to 6 feet tomorrow.

Saturday through Tuesday night: Small craft should exercise
caution conditions for winds will be possible Saturday through
Sunday night, and wave heights will also fall into that range,
although a few seven footers on the Gulf may push conditions into
small craft advisory territory. A low pressure system over the
southern High Plains Saturday, combined with high pressure over
the Gulf, will set up and maintain a gradient supportive of
stronger southeast winds. High pressure will replace the low
pressure system late in the weekend as it moves northeast toward
the upper Midwest, allowing the pressure gradient to relax and
winds and seas to decrease to mdt. Wind direction will remain
persistently southeast.



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