Area Forecast Discussion
Issued by NWS Brownsville, TX

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373
FXUS64 KBRO 211808 AAB
AFDBRO

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
108 PM CDT Tue Mar 21 2017

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

&&

.AVIATION...Primarily VFR the next 24 hours. NAM guidance hints
at very brief excursions into MVFR ceiling territory right around
dawn Wednesday, with the base of an isothermal layer just below 3
kft on the forecast sounding at BRO, but did not incorporate into
the current TAF set for now due to uncertainty. Otherwise, quiet
weather will occur through 24 hours with upstream mid level
ridging and Gulf high pressure the main synoptic features. Light
southeast winds Wednesday morning will become moderate and gusty
by late morning with scattered low CU along the coast, possible
becoming broken, but above 3 kft.

&&

.PREV DISCUSSION... /issued 634 AM CDT Tue Mar 21 2017/

DISCUSSION...Updated for latest aviation discussion below.

AVIATION...Clear skies and light southeast winds prevail across
Deep South Texas this morning. VFR conditions expected to
continue for the next 24 hours with a very dry atmosphere in
place. Surface winds will once again become breezy later this
morning into the afternoon due to high pressure and low pressure
interaction. Southeast winds will gradually diminish after sunset
this evening.

PREV DISCUSSION... /issued 423 AM CDT Tue Mar 21 2017/

SHORT TERM (Today through Wednesday): High presssure at the surface
and aloft will maintain very warm and dry conditions across Deep
South Texas through the short-term. Very dry air (especially above
925 mb) will mix down today with dewpoints away from the coast
dropping into the mid to upper 50s. The interaction of surface high
pressure over the Gulf and lower pressure across west Texas will
support breezy south-southeast winds today. High temperatures today
will be in upper 80s to lower 90s (except for the low to mid 80s
near the coast) due to combination of abundant sunshine and a drier
airmass in place. Southeast winds will gradually diminish after
sunset this evening. Low temperatures tonight will be in the 60s
across most of the area under partly cloudy skies. Patchy fog will
be possible late tonight across portions of the northern ranchlands.
Wednesday will be a repeat of today with plenty of sunshine and high
temperatures in the 80s to lower 90s. Breezy southeast winds will
develop again on Wednesday due to the tight pressure gradient.

LONG TERM (Wednesday Night through Monday): 500 mb ridging will
prevail over TX on Wed Night into early Thurs. A strong closed low
will then move into the south central Plains states late Thurs
through Fri Night. This closed low will then exit the region early
Sat which will allow some shallow 500 mb ridging to build into the
area on Sat and Sat Night. Another short wave/closed low will then
move over the south central Plains states on Sun exiting the
region on Mon. This steady progression of 500 mb troughs/closed
lows moving from west to east will push a couple of frontal
systems across the central and northern portions of TX through the
longer range period. But these cold fronts appear to be too weak
to make their way through the RGV providing any kind of
significant CAA. Solid low level WAA and elevated 1000-500 mb
thickness values will persist throughout the longer range period
which will maintain overall temps well above climo for late March.

Overall moisture advection ahead of these systems remains very
limited and expect only some slgt chc pops on Fri with the
approach and passage of the 500 mb closed low.

The ECMWF and the GFS model guidance are in better agreement
through Day 7 for temps and pops versus yesterdays model runs with
the GFS coming more in line with the warmer solution indicated by
the ECMWF. Overall confidence in the forecast wording through Day
7 is above average today.

MARINE (Now through Wednesday): Buoy 42020 reported south winds
around 14 knots with gusts near 16 knots and seas of 2.6 feet with a
period of 5 seconds at 03 CDT/08 UTC. Surface high pressure over the
Gulf of Mexico and lower pressure across west Texas will maintain
moderate winds and low to moderate seas through the short term.
Winds on the Laguna Madre will become elevated today and Wednesday
resulting in small craft exercise caution conditions each afternoon.

Wednesday Night through Saturday Night...The PGF will strengthen
along the lower TX coastline ahead of the low pressure system
moving into the south central Plains states starting Wed Night
and Thurs. This will likely result in stronger S-SE surface winds
along the lower TX coastline with these stronger winds persisting
into the weekend. SCA conditions will be likely mainly for the
Gulf waters into Sat. SCEC to marginal SCA conditions will be
possible across the Laguna Madre mainly for Thurs and Fri.

&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...None.
GM...None.
&&

$$

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