667
FXUS64 KBRO 290042 AAA
AFDBRO

Area Forecast Discussion...UPDATED
National Weather Service BROWNSVILLE TX
742 PM CDT Wed Sep 28 2016

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

&&

.AVIATION...Deep Tropical moisture remains in place over the
region as indicated by the 00z BRO sounding with a PWAT of around
2.4 inches. This deeper layer moisture will combine with weak
surface troffing extending down south along the Mexico coastline
to maintain the threat of some isold/sct shower activity over the
next 24 hours. For now will go with mainly VFR conditions
throughout the next 24 hours with brief potential reductions of
ceilings/vsbys down to MVFR levels. Drier air will start filtering
into the region late in the TAF period which will erode away any
marginal ceilings and will reduce the conv potential.

&&

.PREV DISCUSSION... /issued 258 PM CDT Wed Sep 28 2016/

..Cruising into Comfortable Weather to Close September 2016

SHORT TERM (Now through Thursday Night):  After most of a month
where record warm temperatures dominated and will probably end up at
or just above in several Valley locations when all is said and done
Friday, the final days are quite welcome relief...including today
and Tuesday but also Thursday and especially Thursday night when
the coolest overnight temperatures since early May by the time
folks roll out of bed for work and school on Friday.

First, the Lower Valley, mainly southeast Cameron County, needs to
get through one more late afternoon/evening of pesky clouds and a few
showers that continue to rotate onshore from the Cameron/Willacy
County line southwest into Brownsville. The axis is sitting on the
edge of enough low level moisture, but cloud cover has kept heating
at a minimum and below convective temperature (88) which is keeping
coverage to isolated/scattered at most.  Elsewhere, mixed layer
clouds and nothing more than a few sprinkles have been observed in
the Lower and Mid Valley, with partly sunny skies across the Brooks
through Zapata ranchlands where low level dry air dominates and dew
points have fallen into the low to mid 60s.

For the overnight, have held onto slight chance/scattered showers
in the southeast corner of the area based on current trends and just
enough moisture and low level forcing to keep a mention there.
Farther west and north, skies should range from mostly clear (north)
to partly cloudy (mid Valley) with light winds, and temperatures
will respond accordingly and fall close to seasonal averages (upper
60s to around 70) by daybreak Thursday.

For Thursday and Thursday night, the meriodionally broadening 500 mb
trough centered over the Ohio Valley (Kentucky) but expanding south
into the northern Gulf will help push deep dry air into south Texas
Thursday and into northeastern Mexico Thursday night. This will
bring increasing sunshine (with fair weather cumulus and a few
cirrus above) farther south, reaching most of the RGV by afternoon.
Any residual morning precipitation will shift offshore by noon or
so, with Boca Chica and perhaps South Padre still with a few
raindrops.  Temperatures will recover but only back into the upper
80s to lower 90s with the cooler start, light northerly flow, and
time of year as these readings will be at or a touch above normal.

A fantastic night Thursday night for evening activities, leading to
a wonderful daybreak Friday as skies clear everywhere and northerly
flow, albeit light, brings the lowest dewpoints since May and
allows low temperatures to ease into the 60s in all areas except
along the coast and Valley urban centers.  In fact, would not
surprise to see a few 60/upper 50s across wind-protected
ranchlands...so this might be the first night after a long sweaty
spell to open the windows and take in the fresh air.

LONG TERM (Friday through Wednesday):A small taste of fall can be
expected in the long term...with high pressure aloft and at the
surface bringing much drier air into the Valley. No rainfall is
expected through the period, however a small vorticity max and
quick moving upper level impulse will skirt across the edge of the
RGV to the south. This will bring some middle level moisture and
likely an increase in clouds. Otherwise...the dry air will allow
for pleasantly cool overnight lows conditions for the region as
northerly flow dominates the pattern. However...the drier air will
also allow for warmer highs.

The pattern will shift by early nest week with more
southerly flow noted in the lower atmosphere. However...the upper
level pattern will still have a northern component. Temperatures
will also begin a warming trend as the moisture begins to
increase.

MARINE:

Tonight through Thursday Night: Light to moderate north to
northeast winds persist through Thursday and seas are held in
check, likely dipping to between 2 and 3 feet in most waters
through the period. Of course, the showers, some with brief
downpours, will make boating/fishing less pleasurable into
Thursday morning mainly south of Mansfield in the Gulf but that
will change markedly by Thursday night.

By Thursday night, the building surface ridge from north to south
Texas will help kick up north/northeast winds across the Gulf, and
caution levels (15-19 knots) are certainly a possibility but for now
have held just below (14 gust 17 knots).  Held seas at 3 feet with
the increase, but 4 feet in range of possibility so a Friday morning
trip may face moderate conditions over the Gulf.  The same can`t be
said for Laguna Madre, which will be fantastic with a light to fresh
breeze and nothing more than a light or moderate chop under clear
skies.

Friday through Monday...High pressure aloft and at the surface
will be in control of the weather pattern through the forecast
period. Light to moderate N to NE winds will generally be in place
with seas in the 1 to 3 feet range.

&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...None.
GM...None.
&&

$$

This product is also available on the web at:
HTTP://WEATHER.GOV/RGV

Short Term...60
Long Term...66