Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 180603 AAB

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
103 AM CDT Mon Sep 18 2017

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


.AVIATION...Mainly VFR conditions are expected across the TAF
locations overnight although a few low level clouds may be hit and
miss at times across KHRL and KMFE. Meanwhile, some isolated
field fog will be possible if winds become light enough, but
current thinking is that any MVFR visbys will be brief if fog
develops. Otherwise, winds will be southerly overnight and early
this morning, before becoming more easterly due to the seabreeze,
with some possible convection in the afternoon.


.PREV DISCUSSION... /issued 729 PM CDT Sun Sep 17 2017/

DISCUSSION...Updated for latest aviation discussion below.

AVIATION...The afternoon sea breeze boundary has pushed well
inland over the RGV and continues moving west sparking a few short
lived showers this evening. This will allow a fairly stable
marine layer to push inland over the region decreasing the conv
throughout the late evening and overnight hours. The return of
the daytime heating tomorrow will help generate the afternoon sea
breeze which may fire off some isold conv again during the later
hours of the current TAF period. However these patches of conv
will likely be too sparse to justify mentioning in the RGV TAFs.
Although patchy fog will be possible around the RGV from around
09-13z Monday morning as the surface dewpoints gradually
increase... will not mention fog in the current TAF package as any
fog that forms will likely be too short lived to seriously impact
aviation conditions. Expect overall VFR conditons to prevail for
the upcoming 24 hours for the RGv airports.

PREV DISCUSSION... /issued 306 PM CDT Sun Sep 17 2017/

SHORT TERM (Tonight through Monday Night): 500mb ridge across the
western Gulf of Mexico and south Texas will provide subsidence
across the CWA in general tonight into Monday. However...low to mid
level moisture across portions of northeast Mexico and the western
Gulf of Mexico will allow convection to continue to develop across
the coastal waters tonight into Monday. In addition...isolated
showers and thunderstorms will develop across the coastal sections
of the CWA Monday as the seabreeze front develops along the lower
Texas coast and moves inland.

LONG TERM (Tuesday through Sunday): A quick look down the model
road shows that a 590 or so decameter mid level ridge will set up
shop and maintain a presence over the west Gulf and the CWA for
much of the long term. Some weakening will occur toward the end of
the period, but even then there will be nothing really
significant supplanting the ridge to make a difference. High
pressure over the southeast United States will extend into the
north Gulf during this period as well, maintaining an overall
anticyclonic synoptic scale circulation across much of the basin.
A positive tilt long wave trough will deepen and elongate over the
southwest United States late in the week, weakening and
reorienting the overhead ridge slightly, but the overall effects
seem otherwise uncertain. By opening up the west Gulf to reduced
capping, the model guidance allows thunderstorm chances to
increase a skosh, but the mid levels would dry out more with what
would then be a north flow aloft.

That said, the southwest Gulf will remain convectively active
and, when supported by the anticipated persistent southeast wind
pattern, enhanced moisture will be no stranger to the lower Texas
coast. Thus, maintained the persistent inherited 20 percent pops
over the marine areas. Sea breezes will be a regular visitor to
the coastal counties this week, though not explicitly mentioned
every day. Not much variation in temps will be expected, running a
few degrees above normal, that is 90s to near 100 by day and 70s
by night. A mix of clouds and sun and a light to moderate
southeast wind will round out the particulars.

MARINE: Tonight through Monday night: Seas were near 2 feet with
north to northeast winds near 8 knots at buoy019 and near 3 feet
with southeast winds near 12 knots at buoy002. In addition...winds
were south near 2 knots at buoy045. Light to moderate southeast
winds will prevail across the coastal waters tonight with surface
high pressure across the northern Gulf of Mexico. The pressure
gradient will remain weak across the western Gulf of Mexico
Monday. Light east to southeast winds will prevail across the
coastal waters Monday. Winds will increase slightly offshore the
lower TX coast Mon night.

Tuesday through Friday night: High pressure will remain in control,
supporting light to moderate southeast winds and low to moderate
seas throughout. Intervals of light to moderate isolated showers.




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