Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 162357

Area Forecast Discussion
National Weather Service Brownsville TX
557 PM CST Thu Feb 16 2017

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


.AVIATION...High clouds continue across the region as the large
500mb low steadily moves into West Texas this evening with
moisture increasing ahead of it. As moisture fills in
across the region...cigs will deteriorate from VFR to MVFR or
possibly lower. This system will move across Texas through the
overnight hours with a large area of ascent expected as it lifts
across the region. Showers will begin to develop during the early
morning hours...with better chances for SHRA and even some -TSRA
possible mainly after 12Z. This low will generally shift north and
east quickly through the day...with precip ending in the afternoon
as winds shift to the west and southwest.


.PREV DISCUSSION... /issued 252 PM CST Thu Feb 16 2017/

SHORT TERM (Tonight through Friday night): 500mb low/trough across
northern Mexico extending into the eastern Pacific Ocean off the
western Mexican coast this afternoon will move eastward tonight as
surface high pressure across the northwest Gulf coast moves
eastward. Low to mid level moisture will quickly increase across the
CWA tonight into Friday...mainly across the coastal sections. This
will provide a chance of showers and a slight chance of
thunderstorms...mainly elevated...late tonight into early Friday. A
weak coastal low will develop along the lower Texas coast Fri
morning and move northeast Fri afternoon bringing drier air into the
western portions of the CWA Fri afternoon and the eastern portions
of the CWA Fri evening bringing an end to rain chances from west to
east. Temperatures will return to above normal tonight and continue
through the short term. South to southwest winds Friday will allow
temperatures to climb into the 80s...especially across the western
portions of the Rio Grande valley and northern ranchlands...Fri

LONG TERM (Saturday through Thursday): For Saturday, a strong
upper ridge will translate across deep south TX in advance of a
large and vigorous upper trough moving onshore over southern
CA/Baja Mexico. As the ridge moves eastward aloft, a low level
warm air advection pattern will be in place across deep south TX
that will cause high temperatures to rise to well above normal
into the mid 80s to lower 90s. On Sunday, the center of the
vigorous upper trough approaching from the west will generally be
located over the southwest US/northwest Mexico with strong
southerly flow setting across the Rio Grande Valley at the leading
edge of the trough. The general instability of the atmosphere
coupled with some diffluence aloft and daytime heating will lead
to chances of showers and thunderstorms mainly over the northwest
third of the forecast area Sunday afternoon.

Sunday night still looks to be the most interesting portion of the
extended forecast as a strong front pushes southeastward into the
forecast area and interacts with surface dew points in the upper
60s and CAPE values reaching 2,400+ j/kg. Heavy rain is still a
distinct possibility for numerous locations across deep south TX
Sunday night into Monday morning, with most, if not all,
locations receiving some amount of precipitation. Chances of
precipitation will begin to decrease through the day on Monday as
drier air filters into the region behind the surface cold front
and upper dynamics decrease as the upper trough begins to push
offshore. Variably cloudy skies combined with cooler air brought
into the area behind the front will keep highs on Monday in the
upper 70s to mid 80s.

On Tuesday, the upper trough will move into the northwest Gulf
with some wrap-around moisture on the backside of the trough
causing some showers/weak thunderstorms to linger along the coast.
Will see similar high temperatures compared to those reached on
Monday. Chances of precipitation should generally end area- wide
Tuesday night as shortwave ridging/northwest flow develop over the
region. High temperatures on Wednesday will remain above normal
and mainly in the lower/mid 80s area-wide. Will see some
additional warming on Thursday out west with high temperatures
reaching into the upper 80s...otherwise lower/mid 80s elsewhere.

MARINE (Tonight through Friday night): Seas were near 2 feet with
east winds near 4 knots at buoy020 early this afternoon. Light
southeast winds will prevail across the coastal waters tonight with
surface high pressure across the northwest Gulf of Mexico moving
eastward. Surface low pressure will develop across the lower Texas
coast Fri morning and winds will shift to the south and southwest
and increase Friday as the pressure gradient increases across the
northwest Gulf of Mexico. Light southwest winds will prevail across
the Laguna Madre and light to moderate south to southwest winds will
prevail across the offshore waters on Friday. Once the coastal low
lifts northeast...winds will veer to the southeast but will be light
as the pressure gradient weakens in the wake of the low.

Saturday through Tuesday: Fair conditions with modest winds/seas
to prevail Saturday as strong high pressure is in place over the
waters. For Sunday, a strong low pressure system approaching the
lower Texas coast waters will bring windy conditions with
building seas. Small Craft Advisories may be needed for the Laguna
Madre and other bay waters through the day on Sunday. A strong
front will move across the waters late Sunday night into Monday
morning bringing widespread showers and thunderstorms along with
continued elevated seas. Winds will begin to diminish somewhat on
Tuesday as the strong front moves into the central Gulf, however
seas may remain elevated through Tuesday.




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