Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 110527 AAC
AFDBRO

Area Forecast Discussion...UPDATED
National Weather Service BROWNSVILLE TX
1127 PM CST Tue Jan 10 2017

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

&&

.AVIATION...VFR conditions will prevail through the entire
period with winds being the main aviation concern. A strong low
level jet between 925 and 850 mb will continue overnight with winds
increasing again Wednesday morning and afternoon. With lighter
surface winds late this evening, low level wind shear has been
added to the forecast overnight with current model data showing 40
knot winds between 1000 and 1500 feet across the Rio Grande
Valley. Wind shear issues will likely not improve until surface
winds increase shortly after 14Z and become strong again in the
afternoon.

&&

.PREV DISCUSSION... /issued 802 PM CST Tue Jan 10 2017/

DISCUSSION...Updated for latest aviation discussion below.

AVIATION...Have amended the TAFs to include low level wind shear
with current model data showing 40 knots between 1000 and 1500
feet across the Rio Grande Valley. The low level jet is not
expected to weaken much overnight, so wind shear will likely not
improve until surface winds increase after 14Z.

PREV DISCUSSION... /issued 622 PM CST Tue Jan 10 2017/

DISCUSSION...Updated for latest aviation discussion below.

AVIATION...VFR conditions will likely prevail through the entire
period with winds being the main aviation concerns. Winds are
beginning to lighten this evening with decreasing daytime heating
after sunset, but will pick up again Wednesday. A low level jet
between 925 and 850 mb will strengthen overnight with winds
increasing Wednesday morning and afternoon. Low level wind shear
will range from 20 to 25 knots overnight below 2000 feet, but have
not mentioned in the TAFs at this point, as it is expected to
remain below 30 knots.

PREV DISCUSSION... /issued 401 PM CST Tue Jan 10 2017/

SHORT TERM (Tonight through Wednesday Night): The models did not
disappoint on the strength of the winds this afternoon with both
Brownsville and Harlingen reporting wind gusts of 40-45 mph.  Winds
do slowly decouple this evening but remain somewhat gusty overnight.
Strong pressure gradient persist into Wednesday as Front Range Low
pressure deepens and combines with broad surface ridge anchored over
the Gulf. The low level jet strengthens and broadens overnight into
with models suggesting 45 knots at 925mb. Daytime heating Wednesday
will allow for thermal mixing of these higher winds which will
produce another windy day across much of the Lower and Mid RGV.
Above average confidence and a wider expanse of the stronger winds
will warrant the issuance of a wind advisory for Hidalgo, Cameron
and Willacy counties for 11am-5pm Wednesday.

1000-500mb thickness and 850mb temperatures continue to rise as the
southerly winds deepen. The maximum temperatures the last few days
have exceeding model guidance numbers and do not see why this should
not happen again Wednesday. Forecast calls for very warm
temperatures tomorrow as much as 12-18 degrees above normal.
Dewpoints have shown some resilience and have been lower then what
the models have been suggesting which is likely due to the downward
mixing of drier air aloft. As a result have not seen any sea fog
developing and confidence is low if any will form within the
stronger wind regime or until dew points inch upward. Will maintain
the patchy fog at this time along the immediate coast and let later
shifts monitor for any changes. Also, overnight lows will be
slightly lower with guidance catching on the lower numbers.

LONG TERM (Thursday through Tuesday): Much more amplified pattern
setting up starting Thursday as The H5 ridge across the gulf
shifts west and the next trough dives down the spine of the
Rockies. The ridge remains the more dominant of the two Thursday
with high temperatures still in the 80s. Rain chances begin to
increase starting Friday as the trough to the west begins to shift
upper flow from the southwest, tapping some Pacific moisture at
midlevels. Expect a slight chances for showers each day, mainly as
streamer showers during the morning and seabreeze-type showers
developing in the afternoon. Models trying to come to a solution
regarding the ejecting trough, moving it into the central plains
later Sunday. Even with differing tracks for the upper low, the
lower level effects remains similar, as it drags a surface front
into the region Monday or Tuesday. Temperatures will not change
much with the front, but may focus rain chances and bring a better
chance for thunder each afternoon.

MARINE:
Now through Wednesday: Buoy 42020 reported South winds around 21
knots with seas near 8 feet at 300 pm CST. The pressure gradient
remains strong and will maintain higher seas overnight with some
slight lowering of the wind possibly. Winds over the Laguna are
likely to lower this evening but are expected to increase once
again before noon Wednesday. Small craft advisories for the Gulf
waters 20-60nm east of Padre island have been extended until noon
Wednesday and are likely to be extended again with no expected
diminishing of the southerly fetch. Also, a SCA is issued for the
Southern portions of the Laguna Madre for Wednesday.

Thursday through Sunday: Southeast winds remain consistent through
the weekend as low pressure begins to build in the central plains.
Winds will generally remain in the 10 to 15 knot range all
weekend, keeping wave heights around 4 to 5 feet. Expect a small
chance for rainfall each night as streamer showers begin to
develop in nocturnal marine instability.

&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...Wind Advisory from 11 AM to 5 PM CST Wednesday for TXZ253>257.

GM...Small Craft Advisory for winds from noon to 6 PM CST Wednesday
     for GMZ130-132.

     Small Craft Advisory for hazardous seas until noon CST Wednesday
     for GMZ170-175.

&&

$$

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

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