Area Forecast Discussion
Issued by NWS Brownsville, TX
FXUS64 KBRO 211136 AAA
Area Forecast Discussion...UPDATED
National Weather Service BROWNSVILLE TX
636 AM CDT THU JUL 21 2016
.DISCUSSION...Updated for latest aviation discussion below.
.AVIATION...VFR conditions will be the prevailing flight category
today through tonight. An isolated shower or thunderstorm is
possible with areal coverage is expected to be limited
maintaining vicinity wording between 16-22Z. Confidence is above
average on the rain coverage with near average conditions on
timing of the east to west movement of the seabreeze convection.
.PREV DISCUSSION... /issued 336 AM CDT THU JUL 21 2016/
SHORT TERM (Today through Friday): A weak tropical wave is noted
across Bay of Campeche tracking west into Southern Mexico.
Associated tropical moisture is moving into Northeast Mexico and
just skimming Deep South Texas. The dominate expansive ridge of
high pressure continues to suppress the deepest moisture to our
south keeping overnight marine convection very limited. Latest
short range models suggest convection to be sparse across the CWA
with best chances along the counties bordering the Rio Grande
River. Only subtle lift from the sea breeze and daytime heating
should allow for spotty showers or an isolated thunderstorm to
form late morning and early afternoon. Have decided to cut back on
areal coverage as well as rain probabilities for today. Friday`s
forecast shows little to no change with the deepest tropical
moisture residing to our south and over the Gulf with another weak
tropical wave moving across the Bay of Campeche. Any convection
that forms will once again favor the Lower and Middle Valley along
and just north of the river. The rest of the forecast parameters,
temps and wind, will see little change of what has been occurring
the last several days. McAllen`s century mark streak should remain
intact through the short term. Light winds overnight become a
slight breeze during the afternoon and early evening hours.
Long Term (Friday Night through Wednesday): An expansive 594 plus
dam mid level ridge will initially sprawl from the West Coast all
the way to the mid Mississippi Valley. High pressure will in turn
dominate the Gulf of Mexico, while tropical activity remains muted.
This overall pattern will remain persistent through the long term,
as per long range models.
Characteristics of the daily forecast will include slightly warmer
than normal temps. Went with the model consensus here, but added a
degree to reflect the above average readings. Afternoon heat index
values will be 100 to 105 degrees for most areas with some areas
like Starr County registering values from 105 to 110 degrees. Plenty
of sunshine will occur in any case. A light to moderate south
southeast wind will arise during the day, though a daily seabreeze
will sometimes briefly back winds more to the east and will provide
some gustiness to the breeze as it it moves through. Rain chances
will center around late night to early morning coastal streamer
showers moving in from the Gulf, and a daily late morning to
afternoon sea breeze moving inland with showers and even a tstm or
two. Rain chances for these two events were kept in the 20 to 30
percent range. Total rain amounts from passing convection will
generally be light, though brief moderate downpours will be possible.
There may be others, but one inverted trough will move west from the
western Atlantic and across the north Gulf from roughly Monday
through Friday of next week. There could be some precip enhancement
late next week as the trough moves overhead, but the models don`t
seem to be picking up on much currently.
Today through Friday...Gentle to moderate east to southeast winds
and a slight to moderate sea to persist through Friday. Broad high
pressure extending across the Northern Gulf and lower pressure
stretching across the Yucatan peninsula will continue to interact
maintaining the subtle weak flow. An occasional shower or isolated
thunderstorm is possible anytime with mainly the Southern coastal
waters seeing the majority of the convection with the passage of
weak tropical waves across the Bay of Campeche.
Friday Night through Monday...Broad mid level ridging will sprawl
across the southwest United States from west to east, extending into
the lower half of the Mississippi Valley. This will in turn continue
to support high pressure over the northern Gulf of Mexico. The
southwest Gulf will remain relatively quiet during the long term.
The result will be light to moderate south southeast winds and low
seas of mainly two to three feet through Monday. Landward moving
showers will be possible late each night, continuing into the
morning hours before dissipating.
.PRELIMINARY POINT TEMPS/POPS...
BAYVIEW/PORT ISABEL 93 80 93 79 / 30 10 20 10
BROWNSVILLE 95 78 95 79 / 30 10 20 10
HARLINGEN 97 76 97 77 / 20 10 20 10
MCALLEN 100 78 100 78 / 20 10 20 10
RIO GRANDE CITY 101 76 102 78 / 20 10 10 10
SOUTH PADRE ISLAND 89 81 90 81 / 30 20 20 10
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