Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 191730 AAB

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
1230 PM CDT Tue Sep 19 2017

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


.AVIATION...Cumulus streak producing sct to bkn VFR conditions to
continue through the afternoon then slowly dissipating in the
evening. Isolated convection developing along the streaks moving
north with the general southerly flow but showing a slow westward
drift. One or two showers and maybe an isolated thunderstorm to
briefly impact mainly KBRO and KHRL with lower probabilities at
KMFE. Stratus to reform overnight mostly around sunrise with a few
embedded showers moving in from the Gulf. Light southeast wind
with a few gusts around 15 knots this afternoon becoming less than
10 knots overnight.


.PREV DISCUSSION... /issued 642 AM CDT Tue Sep 19 2017/

DISCUSSION...Updated for latest aviation discussion below.

AVIATION...Onshore flow has brought some MVFR cigs and -SHRA to
KBRO early this morning. Any MVFR conditions will only last
briefly however, with mainly VFR conditions expected through the
day. There may be some seabreeze or afternoon convection possible,
however that will remain too hit and miss to warrant mention in
the TAFS. Otherwise, gusty SE winds will be noted through the
afternoon before winds decouple later in the day.

PREV DISCUSSION... /issued 340 AM CDT Tue Sep 19 2017/

SHORT TERM (Now through Wednesday): Not many changes to the short
term forecast over the next 36 hours. High pressure aloft in the mid
levels will continue to keep the forecast status quo as lower level
moisture, generally below 700mb, allows for isolated nocturnal
streamer showers over the Gulf. As such have maintained POPs at 20%
over the Gulf waters and coastal areas this morning, with some
afternoon chances pushing farther into Lower and Middle RGV and
portions of the northern Ranchlands. However, the H5 ridge and
subsidence will limit the growth of showers/storms today with any
convective activity remaining hit and miss in nature. Heading into
Wednesday, the ridge appears to flatten and elongate over Texas and
Northern Mexico as a deepening low pressure system develops over the
NW U.S. With the ridge weakening slightly and low level moisture
still in place, have just a general mention of slight chance POPs
for showers/isolated storms. Meanwhile, temps will continue to run a
bit above normal under the influence of the high pressure system.

LONG TERM (Wednesday Night through Monday): Mid-level ridging
will remain generally in place over the western Gulf of Mexico and
south Texas through much of the period. Some weakening of the 500mb
ridge overhead will occur during the period, as a weak mid-level low
drifts over the Gulf of Mexico. Surface high pressure across the
southeast United States extending into the northern Gulf of Mexico
will maintain south to southeast winds across the area. Low level
moisture (precipitable waters waffling between 1.75 to 2 inches)
will support a slight chance of marine showers in the morning and
afternoon seabreeze convection each day. Will continue to lean
towards the drier MEX numbers for POPS through the period.
Temperatures are expected to remain a few degrees above normal
across deep south Texas through the forecast period. High
temperatures each day will range from the upper 80s at the beaches,
low to mid 90s near the coast and the upper 90s to around 100 inland
with a mix of sun and clouds. Heat index values expected between 100
to 105 degrees each afternoon. Overnight low temperatures will
generally be in the 70s under partly to mostly cloudy skies.

MARINE (Now through Wednesday): Broad surface high pressure over
the eastern Gulf of Mexico will interact with weak low pressure over
portions of the Southern/Central Plains states. The resultant
surface pressure gradient will generally maintain light to moderate
southeast winds and low to moderate seas through mid week.

Wednesday Night through Saturday...High pressure across the Gulf
will produce light to moderate onshore winds and low to moderate
seas through the period. A few showers and thunderstorms are
expected to develop along the coast from time to time.




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