Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 300541 AAA
AFDBRO

Area Forecast Discussion...UPDATED
National Weather Service BROWNSVILLE TX
1241 AM CDT TUE AUG 30 2016

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

.AVIATION...Satellite imagery shows cloudiness around 7k feet
trying to sneak across the Rio Grande River and over the
aerodromes, with this cloudiness already being reflected in the
surface observation at MFE. All the major airports may be
affected before the night is over, with light and variable winds
also prevailing. Tomorrow, veering winds and scattered clouds are
anticipated with weak surface low pressure along the Lower Texas
Coast. The proximity of a disturbance in the middle layers of the
atmosphere will generate convection during the afternoon hours,
and a TEMPO has been added for this. Outside of the convection,
VFR will prevail through a majority of the next 24 hours.
&&

.PREV DISCUSSION... /issued 904 PM CDT MON AUG 29 2016/

DISCUSSION...Even with the evening sounding showing a little bit
more moisture rain chances will be limited tonight with low
confidence for 50 percent coverage Tuesday.

Mid level low circulating over the NW Gulf is shown by the latest
GFS and ECMWF to move farther offshore the middle Texas coast
with the overall circulation becoming broader and weaker with
time. This will keep our CWA and especially the RGV on the western
side of the low which maintains a deep northwest flow over the
region. The low level flow becomes a little more favorable as some
additional gulf moisture advects inland with deeper easterly flow
to 800mb. The overall moisture content increases later tonight
into Tuesday as the broad low edges closer to the area, however
upper support is lacking and surface convergence via sea breeze
has not materialized the last few days so confidence in 50 percent
coverage Tuesday is fading. For tonight have reduced pops across
much of the CWA keeping slight chances over the northern border
and chances over the northeast Coastal waters. Have also reduced
cloud cover overnight...we may see an increase in high (thin)
clouds but not low clouds. Will defer a lowering of rain chances
for Tuesday to the overnight shift giving them a new suite of
models to review. New set of zones out soon.

PREV DISCUSSION... /issued 701 PM CDT MON AUG 29 2016/

DISCUSSION...Updated for latest aviation discussion below.

AVIATION...Northeast winds to diminish this evening becoming
light north to northwest overnight. VFR conditions to prevail with
mostly clear skies. Isolated to scattered showers and
thunderstorms are anticipated tomorrow morning east of Padre
Island then developing over inland areas Tuesday afternoon. There
is low confidence of this convection impacting the terminal sites
so just mentioning VCTS at this time.

PREV DISCUSSION... /issued 259 PM CDT MON AUG 29 2016/

SHORT TERM (Now through Tuesday Night): north to northeast flow
continues through much of the atmospheric column over deep south
TX in response to a tropical upper tropospheric (TUTT) low about
200 miles south of south central Louisiana. Early this afternoon,
the BRO WSR-88D was showing isolated/scattered showers/thunderstorms
developing over the northeast portion of the forecast area with
isolated showers over the southwest from Zapata to Rio Grande
City.

The TUTT low will slowly move southwestward through the period
bringing increasing chances of showers/thunderstorms to the Rio
Grande Valley, especially late tonight/Tuesday. Short-term models
are not generating copious amounts of rainfall over the forecast
area through the end of the period, though with dynamics increasing
area-wide and precipitable water values hanging around 2.0 inches,
will not be surprised if a few locations pick up 1 to 3 inches by
sunrise Wednesdsay morning. This would be beneficial rain for a
large majority of the forecast area. Due to increased cloud cover
and precipitation on Tuesday, high temperatures have already been
trended downward closer toward seasonal normals. Overnight lows both
nights should generally be near or just slightly above normal.

LONG TERM (Wednesday through Monday): The Tropical Upper
Tropospheric Trough (TUTT) low will drift southward along the
Lower Texas coast Wednesday and east of the Tamaulipas coast early
Thursday. The combination of deep moisture /precipitable water
values of 2.0 to 2.3 inches/ and energy rotating around the TUTT
low should support scattered to numerous showers and thunderstorms
on Wednesday into early Wednesday night. Lingering moisture and
instability continues across the area late Wednesday night into
Thursday. Isolated to scattered showers and thunderstorms will
possible Wednesday night mainly across the Lower Valley and area-
wide on Thursday due to daytime heating. Sea breeze activity
should support isolated showers and thunderstorms on Friday. Mid-
level ridging builds across Deep South Texas by the weekend.
Isolated sea breeze convection expected Saturday through Monday.
An elevated risk of rip currents will be possible Wednesday and
Thursday due to perpendicular flow combined with some of the
swell.

High temperatures Wednesday will be held into the low to mid 90s due
to the increase in rain chances and cloud cover. High temperatures
will gradually rise each day with triple digits returning to the
mid/upper Valley as soon as the weekend. Overnight low temperatures
will generally be in the mid to upper 70s each night.

MARINE (Now through Tuesday): Buoy 42020 reported north-northwest
winds around 12 knots with seas around 2.3 feet with a period of 5
seconds at 1400 CDT/1900 UTC. For the adjacent coastal waters of
Deep South Texas and the Rio Grande Valley, a weak pressure gradient
over the western Gulf of Mexico will produce generally light winds
and low seas throughout the forecast period. The southwestward
progression of a disturbance in the middle layers of the atmosphere
over the northwest Gulf will lead to an increase in showers and
thunderstorms, especially tonight and Tuesday.

Wednesday through Saturday: Light to occasionally moderate east to
northeast winds will prevail along the lower Texas coast. Swell will
arrive from the broad northeast flow around an upper level system
and from the tropical cyclone in the east central Gulf of Mexico.
Seas and swell should quickly improve by late week as the tropical
system is forecast to accelerate into the northeast Gulf of
Mexico.
&&

.BRO Watches/Warnings/Advisories...None.
&&

$$

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