Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 091143 AAA

Area Forecast Discussion...UPDATED
National Weather Service BROWNSVILLE TX
543 AM CST Mon Jan 9 2017

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


.AVIATION...Mostly clear skies with light and variable winds
prevail across Deep South Texas and the Rio Grande Valley this
morning. VFR conditions expected today as a tightening pressure
gradient produces breezy onshore winds. Borderline VFR/MVFR
conditions are expected late tonight.


.PREV DISCUSSION... /issued 429 AM CST Mon Jan 9 2017/

SHORT TERM (Today through Tuesday): Surface high pressure is centered
across the Virginia and North Carolina region and extending
southwest into the Gulf of Mexico this morning. Light and variable
winds prevail across Deep South Texas with temperatures currently
ranging from the upper 30s at Zapata to the mid 50s near the coast.
Brownsville radar indicates some streamer activity across the Gulf
Waters. Some light patchy fog will be possible this morning as
temperatures cool to near the dewpoints.

Southeast winds will steadily increase today with warm air advection
in full swing. High temperatures today will mainly be the low to mid
70s under a mix of sun and clouds. Low temperatures tonight will
range from the upper 50s across the west to the mid 60s along the
coast. Warmer temperatures can be expected on Tuesday with highs
across much of the area in the low to mid 80s. Tuesday will also be
fairly breezy as lower pressure upstream interacts with higher
pressure across the Gulf of Mexico. Additionally, the warm and moist
winds from the south and southeast will pass over the much cooler
nearshore waters which may produce periods of dense sea fog along
the coast. However, the gusty winds may limited or prevent
widespread dense sea fog from developing.

LONG TERM (Tuesday Night through Sunday): A fairly zonal 500 mb
pattern will prevail over the RGV through Thursday allowing temps
to increase to well above January climo. As the weekend approaches
a series of 500 mb closed lows will dig southeast across the
U.S./Mexico border region building a ridge axis over the
southeastern states and the Gulf of Mexico. The best mid level
dynamics and deeper layer moisture values will remain located to
the north of the RGV as this series of troughs pull a cold front
down towards the region late in the forecast period. Will maintain
some low end conv pops as the weekend approaches as enough
instability may interact with the approaching troughs to help fire
off some isold/sct conv.

The ECMWF and GFS models are in good agreement in warming up temps
quickly through around Sat with CAA increasing on Sun and Mon as
the cold front works its way through the area. The ECMWF and GFS
models start to differ in the timing of the passage of the 500 mb
troughs moving into the border region late in the forecast period.
Accordingly the GFS indicates stronger CAA occurring mainly for
Sunday and Monday. Otherwise pretty good agreement shows up for
forecast temps through Sat.

The ECMWF is a little drier than the GFS pops for the upcoming
weekend period as the GFS tries to pool a little better moisture
values. Will go with a general model blend for pops through Sun.

Overall forecast wording confidence is above average up through
Sat and drops down to only average for Sun.

The returning warm s-se low level flow blowing over the cooler bay
and Gulf waters will set the stage for potential marine fog near
the coastline and will include this in the forecast at least
through Thurs.

MARINE (Now through Tuesday): Buoy 42020 reported South-southeast
winds around 14 knots with seas near 3.9 feet at 0250 am CST.
Favorable marine conditions expected today as surface high pressure
continues to move east. Lower pressure across the Central Plains
will interact with surface high pressure extending across the Gulf
tonight and Tuesday. This will result in a tightening pressure
gradient along the Lower Texas coast with Small Craft Advisory
conditions developing over the Gulf waters tonight and Tuesday.
Additionally, the warm and moist winds from the south and southeast
will pass over the much cooler nearshore waters which may produce
periods of dense fog across the Laguna Madre and across the Gulf of
Mexico waters east of Padre Island out to at least 20 nautical

Tuesday Night through Friday Night: 500 mb troffing moving across
the central Plains States will maintain a series of surface low
pressure areas over the mid section of the country. These surface
lows will interact with a broad surface ridge over the
southeastern States and the Gulf of Mexico to maintain a pretty
strong PGF. This will likely maintain SCEC/SCA marine conditions
mainly across the Gulf waters through the latter half of this




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