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Area forecast discussion...updated 
National Weather Service Brownsville Texas
641 am CDT Monday Sep 1 2014

Discussion...updated for latest aviation discussion below.


Aviation...patchy light fog and passing low clouds will continue
across portions of deep south Texas for the next couple of hours.
Will mention a tempo group through 13z for bro/hrl and mfe for
brief MVFR conditions. Otherwise...VFR conditions expected for
the next 24 hours. A more stable air mass will prevail across
area today resulting in isolated convection for later today.
However...can not rule out a stray rain showers/thunderstorms and rain but will not mention
for this taf cycle due to low confidence. Light southeast winds
less than 6 knots now will gradually increase to around 15 knots
with gusts around 21 knots in the afternoon.


Previous discussion... /issued 436 am CDT Monday Sep 1 2014/

Short term.../now through Tuesday...the 500mb trough across deep
south Texas continues to weaken as middle to upper level ridging begins
to build into the region from the west. The 00z bro sounding is
showing precipitable water value of 1.94 inches with light deep east
to southeast flow. The latest kbro radar reflectivity indicates
isolated showers across the extreme southern portions of the Lower
Texas Gulf waters extending down along the Mexican coastline of

Lingering tropical moisture...light onshore flow and daytime heating
should support some sea breeze convection. All of the latest short
range model guidance suggest slight probability of precipitation across the area today and
tonight. Due to the limited pop coverage for today...will not
mention any locally heavy rainfall. High temperatures will reach
range from the lower 90s at the beach to the upper 90s and triple
digits across the west. Low temperatures tonight will be generally
in the upper 70s to around 80 degrees. Moisture begins to surge into
the region by late tonight resulting in isolated convection across
the coastal waters and the coastal counties.

Rain chances increase across the Rio Grande Valley and deep south
Texas on Tuesday as a tropical wave/broad area of low pressure moves
across the southwestern Gulf of Mexico. Environmental conditions are
expected to be conducive for some development as this disturbance
moves west across the southwestern Gulf of Mexico. The National
Hurricane Center currently gives this feature a 60 percent chance of
developing in the next 48 hours. Please refer to the latest
statements and outlooks from the National Hurricane Center
concerning the progress of this tropical disturbance.

Precipitable water values between 2.0 to 2.2 inches and relative humidity values
increase over 65 percent at 1000 to 500mb will support scattered to
chance convection on Tuesday. High temperatures on Tuesday will be a
couple of degrees lower than today courtesy of the increasing cloud
cover and rain chances. Also due to better the better rain chances
and higher atmospheric moisture content...there is a possibility of
heavy rainfall and the potential for minor nuisance flooding on
Tuesday. Will lean towards a blend of the previous forecast and the
super blend for probability of precipitation and temperatures through the forecast

Long period swells will continue to impact surf the conditions along
the Lower Texas coast today. A high risk of rip currents continues
at the beaches of South Padre Island and Boca Chica Beach through
this evening. The high rip current risk will likely continue
along the Lower Texas coast through the rest of the forecast period.

Long term.../Tuesday night through Sunday/...the main concern in
the longer range period will be the eventual track and destination
of the surface low now emerging off of the Yucatan Peninsula
heading to the west northwest pushing across the southwestern
Gulf of mex. The bulk of the longer range model guidance wants to
keep this feature on a general west northwest track with the
center moving inland roughly near the Tampico area Tuesday
night/early Wednesday morning. This west northwest movement is
maintained through the next couple of days as broad 500 mb ridging
builds over the southern states. If this surface low remains
fairly broadly organized with a large swath of deeper layer tropical
moisture associated with it then a fairly broad area of tropical
rains will likely spread across deep south Texas and northeastern
Mexico resulting in more widespread rainfall totals. If the system
becomes better organized as it tracks across the southwestern
Gulf then the bulk of the precipitation may be more concentrated further
south which would miss much of the rgv. At this time am going with
the scenario with a more broadly defined surface low/trough which
would result in better conv chances for the region.

The European model (ecmwf) and GFS probability of precipitation are fairly similar in increasing probability of precipitation Tuesday
night through Thursday as the tropical moisture associated with the
broad surface low surges west and northwest over the region
through middle week. The deeper layer moisture values start to
diminish gradually over the area as the weekend approaches and
will gradually trend down the conv chances into next Saturday and
Sunday as the deep layer tropical moisture feed shifts west and
north around the west side of the southern 500 mb ridge axis.

Since the longer range model guidance is in pretty good agreement
in the handling of this tropical disturbance have opted to go with
a general model blend of the European model (ecmwf) and the GFS for both probability of precipitation and
temperatures through day 7. The maximum temperatures will likely be suppressed a bit
Wednesday adn Thursday as the conv chances maximum out over the area. Will then
trend the temperatures up a bit later as the conv chances fade a bit and a
little more diurnaly heating is expected during the afternoon

Overall confidence in the longer range forecast wording is on the
increase as the model guidance starts to gel towards a similar
solution. Run to run consistency with the GFS mex MOS has also
been pretty stable over the last several runs keeping the highest
probability of precipitation for Wednesday and Thursday. through Tuesday...current surface observations along
the Lower Texas coast and buoy data indicate light to moderate
southeast flow continuing over the Bay and Gulf waters early this
morning with offshore seas around 4 feet. A tropical disturbance
will move west-northwest across the southwestern Gulf of Mexico
today through Tuesday. The environment may be more conducive for
further development as this system moves west-northwest across the
southwest Gulf. There is high chance for tropical development at
this time. This will likely increase swells building seas over the
Gulf waters by later this afternoon. Small craft exercise caution
conditions likely by Tuesday afternoon. Seas of 3 to 5 feet expected
through Tuesday along the Lower Texas Gulf waters.

Tuesday night through Friday...the longer range marine forecast
will be highly dependent on the level of development with the SW
Gulf surface low. A stronger surface low would result in much
higher Gulf seas/winds. For now will go with seas reaching up to
Small Craft Advisory levels Wednesday and Wednesday night with the seas diminishing during the
latter half of the week as the pgf weakens as the tropical low
pushes inland over northern Mexico and dissipates.


Preliminary point temps/pops...
Bayview/Port Isabel 92 81 91 79 / 20 20 50 40
Brownsville 94 79 93 78 / 20 20 50 50
Harlingen 96 78 94 77 / 20 20 50 40
McAllen 98 79 96 78 / 20 10 50 30
Rio Grande City 99 80 98 78 / 10 10 40 30
South Padre Island 89 81 88 80 / 20 20 50 40


Bro watches/warnings/advisories...
Texas...high rip current risk through this evening for txz251-256-257.



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