Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 230615 AAB

Area Forecast Discussion...UPDATED
National Weather Service BROWNSVILLE TX
115 AM CDT Fri Sep 23 2016

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

.AVIATION...Satellite images and surface observations indicate a
few high clouds across portions of the CWA late tonight. Expect
VFR conditions to prevail the rest of tonight into Friday morning
as the 500mb ridge across central and east Texas continues to
provide subsidence across deep south TX.

.PREV DISCUSSION... /issued 659 PM CDT Thu Sep 22 2016/
DISCUSSION...Updated for latest aviation discussion below.

AVIATION...The afternoon CU field is dissipating...with generally
quiet weather expected. However...deep layer moisture is slowly
returning...and some isolated coastal showers could push their way
onshore overnight. However...chances and confidence remain too low
to warrant mention in TAFs. Winds will shift back to the SSE and
become light and variable overnight. A brief MVFR cig is possible
near daybreak.

PREV DISCUSSION... /issued 239 PM CDT Thu Sep 22 2016/

SHORT TERM (Now through Friday night): Quiet weather at the
moment during these first few hours of astronomical autumn across
the CWA. Shower activity is noticeably absent over land areas at
this time. On the larger scale, the seasonally strong upper-level
trough approaching the Great Basin has nudged the TX upper high
eastward a bit, with center now analyzed over the north-central
part of the state. This, in turn, has allowed the lift associated
with a weak inverted mid-level trough rotating around its southern
periphery to largely pass north of the CWA and into the Middle
Texas Coast, per current satellite imagery. Weak surface pressure
gradient has kept winds light and variable with sea-breeze slow to
develop. Can`t rule out a stray shower or thunderstorm through the
early evening, but moisture aloft is progged to decrease overnight
as drier air behind the short-wave trough filters in. More SE-SSE
flow at the surface also becomes re-established. A few streamer
showers over the coastal waters are possible, but rest of the area
should be precip- free overnight with min temps once again in the
mid-upper 70`s across the area.

No major changes in the sensible weather for Friday.  With the
inverted trough out of the picture, high pressure aloft will still
be in control of our weather.  Combined with SSE winds, max temps
will remain several degrees above normal for this time of year.
Precipitable water is progged to range from 1.5" western areas to
about 2" at the coast.  Some differences between latest GFS and NAM
guidance on precip chances for Friday, with GFS mostly indicating
single-digit PoP`s and NAM in the 20% range, especially nearer the
coast.  Will follow NAM`s trend for coastal areas and keep only
silent PoP`s inland.  Any showers over land should end with the loss
of daytime heating on Friday, with a isolated showers again possible
offshore overnight.

LONG TERM (Saturday through Thursday): 500mb trough across the
western United States Friday will move eastward Saturday. Surface
low pressure will develop on the lee side of the Rockies Saturday
and moisture will pool along and ahead of a weak cold front draped
across the central United States. Showers and thunderstorms will
increase in coverage to the north and west of the CWA Sunday and
move into deep south TX Sun night as the front moves through
central TX into south TX. Will increase rain chances for the Rio
Grande valley and the northern ranchlands Sun night into Monday as
the frontal boundary moves across the lower TX coast Monday. The
rest of the forecast period appears to provide at least a slight
chance of rain even though the GFS and the ECMWF have introduced
different model solutions for Tuesday and Wednesday compared to
yesterday. The GFS progs drier air filtering into the western
portions of the CWA while a weak area of low pressure develops
across the western Gulf of Mexico and moves towards the lower TX
coast Wednesday. The ECMWF is now advertising elevated convection
across portions of southwest TX with an upper level low developing
across northern Mexico/west TX Monday and meandering across the
southwest U.S. through the rest of the forecast period. Will
mention a slight chance to chance of showers and isolated
thunderstorms through the middle of next week hoping that the
global models have a better handle of the synoptic pattern.

Now through Friday night: Buoy 42020 reporting light west winds
of 2-4 knots with seas about 2 feet with as of 14 CDT/19 UTC.
Surface high pressure will resume control of the weather pattern
beginning tonight with SSE winds becoming established and
generally persisting at 10-15KT. Winds on the Gulf waters may
briefly approached SCEC criterion by Friday night but seas will
remain on the low side at 2-3 ft. through the period.

Saturday through Tuesday...Moderate southeast winds will prevail
across the coastal waters Fri night and Saturday with low pressure
across the Texas panhandle and high pressure across the northeast
Gulf of Mexico. The pressure gradient will increase slightly Sat
night and moderate to strong southeast winds will develop Sat
night and continue into Sunday. A weak cold front is expected to
move through the lower TX coast Monday. Small craft advisories may
be needed for the offshore waters Sun night and portions of the
coastal waters Monday as the front moves offshore.



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