Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 141137 AAA

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
637 AM CDT Sat Oct 14 2017

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


.AVIATION...Patchy to widespread fog has developed across the
deep south Texas early this morning causing visbys to bounce up
and down. While mainly MVFR conditions are expected, a few brief
IFR visbys cannot be ruled out over the next one to two hours as
winds remain light and moisture levels remain high. Conditions
will improve rapidly once daytime mixing occurs. VFR conditions
and light ESE winds are expected through the afternoon.


.PREV DISCUSSION... /issued 425 AM CDT Sat Oct 14 2017/

SHORT TERM (Today through Sunday): A few isolated streamer showers
have been moving through the coastal waters early this morning with
a few of them running up the beaches of South Padre Island and a
little farther in land towards Brownsville. Any shower activity will
remain largely hit and miss though the morning hours today with high
pressure aloft retrograding over the region and drier air beginning
to filter in. A few showers or even an isolated storm cannot be
ruled out during the heat of the afternoon and along any seabreeze
boundary. Meanwhile, winds will be light through day from the east
and southeast, with high temps in the upper 80s near the coast to
lower and mid 90s along and west of I-69E/HWY 77 corridor.

Dry weather and more variable winds will continue into Saturday night
as Deep South Texas remains between an approaching cold to the north
and coastal troughing approaching from the Central Gulf of Mexico.
Overall dry weather is expected Saturday night although the trough
will bring increasing moisture over the offshore waters and some
showers will be possible although have left POPs low for now.

For Sunday, a sharp H5 trough will dig across the Central Plains and
help drive the cold front through Deep South Texas and the RGV
during the day. Meanwhile, the increase in moisture from the
developing surface coastal low over the Gulf will allow for chances
for showers and some isolated thunderstorms through the day Sunday,
with the best chances being over the coastal areas and Mid to Lower
RGV. Precip chances could also be higher across the Western
Ranchlands as the front interacts with the higher terrain of the
Mexican Plateau. Temps will be a few degrees cooler on Sunday as due
to the increase of clouds ands precip.

LONG TERM (Sunday Night through Friday): A strong 500 mb trough
axis will dig across the central and eastern portion of the lower
48 states late Sun. As this trough pushes towards the east coast
it will push a cold front through the RGV late Sun and Sun night.
This will allow a cooler and drier airmass to build into the
region this coming work week which will result in temperatures
dropping down closer to climo for October. Weak to moderate
500 mb ridging will then build in over the U.S./Mexico border
region which will allow the temps to moderate somewhat through
Fri. Surface ridging over the eastern half of the country will
also allow for a return of a more east to southeasterly low level
flow on Thurs and Fri which will allow for the temps to warm up
somewhat and for the dewpoints to climb. The best moisture
advection with this upcoming fropa will occur late Sun/early Mon
and the ECMWF and GFS guidance is in good agreement with over pops
for this period. So will go with a blend of these two model sets
for the fropa.

Some weakness in the 500 mb ridging will develop over the RGV
Thurs and Fri while some deeper moisture advects north from the
southwestern Gulf of Mex. This may allow for some conv to develop
mainly over the marine locations. For now will leave these as
silent pops for know and will see how future runs handle it.

The ECMWF and GFS temp guidance is also in good agreement in the
degree of CAA reflected after the front in addition to the gradual
warmup shown later this coming work week. So will go with a blend
of the two model sets for temps through Day 7.

Overall confidence in the longer range forecast period is above
average due to the good model agreement.

MARINE (Now through Sunday): Broad high pressure across the
Northern Gulf will keep light east to southeast winds over the Lower
Texas Coastal Waters today with seas still generally around 3 feet
or less. Meanwhile, a low pressure system will begin to develop over
the central Gulf and move towards Texas. Winds Saturday into Sunday
will be come light and variable over the offshore waters before
becoming northerly as the surface trough moves west. Winds will then
increase as a cold front moves through the Lower Texas Coastal
Waters on Sunday with winds increasing to moderate in the afternoon
and small craft may need to exercise caution. Seas will also
increase through the day Sunday with 3 to 5 ft waves expected.

Sunday Night through Wednesday Night: The PGF over the lower TX
Bay and Gulf waters will likely push the Gulf conditions well up
into SCA levels starting Sun Night and continuing through Tues.
The PGF will then weaken around midweek as the surface ridge over
the eastern states shifts further east.




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