Area Forecast Discussion
Issued by NWS Brownsville, TX
FXUS64 KBRO 290528 AAA
Area Forecast Discussion...UPDATED
National Weather Service BROWNSVILLE TX
1228 AM CDT MON AUG 29 2016
.DISCUSSION...Updated for latest aviation discussion below.
.AVIATION...Current satellite imagery looks all clear over Deep
South Texas and the Rio Grande Valley, while surface instrumentation
indicates light and variable winds. These VFR conditions will hold
through the remainder of the overnight hours. Tomorrow, weak surface
low pressure over the western Gulf of Mexico will produce winds that
will veer all day with scattered cloudiness overhead. The mention of
precipitation has been removed from the TAFs for tomorrow due to
only isolated convection anticipated at the aerodromes. Tranquil
conditions with light and variable winds will return after sunset
.PREV DISCUSSION... /issued 927 PM CDT SUN AUG 28 2016/
DISCUSSION...Dropped the majority of the rain chances for tonight
and lowered the chance of rain Monday. With the lower rain
chances Monday temperatures were raised 2 to 5 degrees CWA wide.
With the diurnal cooling cycle well underway and the dissipation
of today`s weak seabreeze all showers and clouds have dissipated.
Deep South Texas is situated between a weaken Mid/upper level over
the Northwest Gulf of Mexico and another mid level low over Baja
California. This is producing a confluent upper air pattern and
providing a dry northwest to west flow above 700mb. Limited
moisture through the atmospheric column as well as no upper
support and limited surface forcing provided by daytime heating
and sea breeze warrants a lowering of pops for tonight and Monday.
Have leaned towards the GFS which is looks more reasonable under
this pattern. Temperatures Monday should be very similar of what
was recorded this weekend with lower 100s in the Mid and Upper
Valleys and mid to upper 90s in the Lower RGV under a mostly sunny
to partly cloudy day. Updated zones are out.
PREV DISCUSSION... /issued 632 PM CDT SUN AUG 28 2016/
DISCUSSION...Updated for latest aviation discussion below.
AVIATION...VFR and light ENE to light and variable winds
expected through Monday. isolated to scattered showers or even a
thunderstorm is possible along the sea breeze front Monday between
17-21Z in the vicinity of KBRO and KHRL then 19-23Z at KMFE.
PREV DISCUSSION... /issued 250 PM CDT SUN AUG 28 2016/
SHORT TERM (Now through Monday night): Upper trough continues to
spin off the East Texas coast, wrapping moisture around the east
side away from south Texas. This has minimized the seabreeze
convection again today, but more moisture is noted areawide due to
increased cloud cover. Models finally have this trough dissipating
during the next 24 hours, with general easterly flow develop at all
layers aloft. Tomorrow`s forecast is highly dependent on whether
this moisture will return to the region before peak heating ends.
GFS is pessimistic on deeper moisture returning until after sunset,
while EC, NAM, and UK bring moisture in sooner. Will continue to
lean toward a wetter forecast for tomorrow, with shower and a few
thunderstorms developing starting on the seabreeze late morning.
Steering flow looks fairly weak, so any activity will become more
outflow dominated quickly, so activity will remain scatter areawide
most of the afternoon. Activity wanes overnight with loss of
heating, but shower activity remains active for the marine areas,
with a few showers moving inland right along the coast.
Long Term (Tuesday through Sunday): Keeping an eye on AL99 near the
Florida Keys, which will be moving into the Southeast Gulf in the
short term. The National Hurricane Center forecast calls for a high
chance of the system strengthening and curving north and then north
east toward the Northeast Gulf during the beginning of the long
term. Thus, the system is currently not expected to play a big role
in the local weather.
A weak mid level low over East Texas will lose some definition by
Tuesday as it drifts south toward the CWA. The GFS seems to keep a
587 decameter low offshore in the West Gulf east of the CWA Tuesday
into Wednesday, before drifting it south of the area Wednesday
night. This will definitely generate some convection over the marine
areas. The ECMWF solution is similar, but perhaps shifted a bit more
to the west. The ECMWF 12 hour precip guidance is slightly higher
than that of the GFS. QPF totals for the episode range up to an inch
along the coast, but locally higher amounts will be possible A
northeast to east wind flow will accompany the unsettled conditions
through much of the week. Upstream ridging will eventually move into
the area from the west, late in the week, with high pressure
filtering down from the north to reestablish a more southeast wind
and more stability by the end of the week.
Now through Monday night...Weak pressure gradient will continue
to produce light winds, which in turn keeps seas calmer through
the next 36 hours. Seas remain 1 to 2 feet, with light onshore
flow during the day and nearly calm winds overnight. An increase
in shower activity is forecast starting late tonight as moisture
arrives from the northeast, sparking scattered showers.
Tuesday through Friday...The local surface pressure gradient will
remain weak initially, resulting in generally light winds and low
seas. The synoptic pattern will favor light to moderate northeast to
east winds. A small swell component will develop late Tuesday,
driven in part by the favorable fetch direction and in part by the
winds associated with a low pressure center moving into the
Northeast Gulf, bumping wave heights up a foot or so, into moderate
territory. Instability resulting from a mid level disturbance moving
into the area will help trigger showers and thunderstorms Tuesday
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