Area Forecast Discussion
Issued by NWS Brownsville, TX
FXUS64 KBRO 230550 AAB
Area Forecast Discussion...UPDATED
National Weather Service BROWNSVILLE TX
1250 AM CDT TUE AUG 23 2016
.DISCUSSION...Updated for latest aviation discussion below.
.AVIATION...Mostly clear skies and light southeast winds prevail
across deep south Texas early this morning. VFR conditions
expected to continue through the next 24 hours as a 500mb ridge
builds overhead and provides subsidence across deep south Texas.
Light southeast winds overnight will become breezy by mid morning.
.PREV DISCUSSION... /issued 640 PM CDT MON AUG 22 2016/
DISCUSSION...Updated for latest aviation discussion below.
AVIATION...Satellite images and surface observations indicate
mostly clear skies across the CWA early this evening. Expect VFR
conditions to prevail the rest of the evening into early Tuesday
morning as the 500mb ridge across the northern Gulf of Mexico
extending westward into south Texas provides subsidence across
deep south TX.
PREV DISCUSSION... /issued 255 PM CDT MON AUG 22 2016/
SHORT TERM (Tonight through Tuesday Night): East to west
elongated mid level ridge axis lies along the northern Gulf coast.
The center of moderately strong 596dm ridge settles over Louisiana
Tuesday. This will continue a hot, dry and breezy period which
began today as the short reprieve of rain has shifted north.
As the ridge continues to builds westward mid and upper layers will
continue to dry out. Surface moisture will become shallow as
subsidence increases with precipitable water values falling to about
85 percent of normal. The only feature worth mentioning is a well
define Tropical Upper Tropospheric Trough (TUTT) low north of the
Yucatan Peninsula. GFS/ECMWF direct this upper low to the WSW into
Northeast Mexico. The best we can do is isolated convection over the
coastal waters. Temperatures to inch upward a degree or two Tuesday
which is slightly above normal while overnight lows might be a few
degrees not as warm with clear skies and diminishing overnight
LONG TERM (Wednesday through Monday): "Big bubble, no trouble"
will be the rule to close out the work week, as well advertised
back edge of subtropical 500 mb ridge extends to all of south
Texas and maintains a solid slug of very dry air by late August
standards across the region. Despite lower atmospheric
temperatures, full sunshine and slightly lower afternoon humidity
should allow maximum temperatures to reach the common 96/99/102
(Brownsville/Harlingen/McAllen) each day through Friday.
Temperatures across the Upper Valley/Rio Grande Plains may be a
couple degrees lower given the soaking rains of recent days,
though the dry air and hot sunshine will evaporate much of it.
Through the period, surface winds gradually diminish, leaving just
a freshening afternoon breeze each afternoon Thursday and Friday.
The near calm winds overnight and the lengthening darkness will
allow low temperatures to get nearly comfortable with readings in
the low to mid 70s away from pavement and the coast, so just a bit
nicer for that morning run or school bus wait.
By Friday, the ridge lifts further into the southeast U.S. with
the last day of westward extension into Texas. On Saturday, that
westward extension is gone, allowing an easterly wave or Tropical
Upper Tropospheric Trough (TUTT) type feature to edge across the
northern and central Gulf. Initial plumes of moisture may have
enough oomph to reach the eastern portion of the area which would
assist a sea breeze with very light flow to start the day. Cross
section from the GFS not very bullish on deep moisture, so left
forecast as is with only slight chances jumping from the coast and
to around US 77 or just west by afternoon.
Things get more interesting Sunday and Monday. GFS/ECMWF eases
the TUTT feature to the entire Texas coast by midday, and with
low level winds backing to the east/northeast showers and a few
storms may develop over the Gulf and repeatedly rotate onshore,
not just early but for the entire day. How far inland they can get
remains to be seen, and deeper moisture struggles to get beyond
the mid Valley. For this reason, kept 20/30 percent chances as
forecast, and only slightly lowered temperatures back into the
lower to upper 90s from east to west (100 far west) for now.
Model differences show up a little bit on Monday, with the GFS
bodily moving the feature onshore along with deep tropical
moisture, while the ECMWF waits until the end of day to do so. The
ECMWF also has a closed low, something that may need to be watched
given the still very warm Gulf waters beyond the shelf. For now,
just nudged chances up to the higher end chance due to uncertainty
on Day 7, but with additional clouds and likely more coverage
took temperatures down a few degrees by day, and up a hair in the
MARINE: (Now through Tuesday Night)...A broad weak surface high
pressure over the Eastern Gulf of Mexico becomes centered just off
the Mississippi Delta. This weak ridge will combine with equally
weak lower pressure over the Bay of Campeche producing a lighter
then normal southeast wind and seas regime. A tropical Upper
Tropospheric Trough (TUTT Low)is seen rotating just north of the
Yucatan Peninsula. This upper low expected to move into Northeast
Mexico later Tuesday this feature may combine with some limited
low level moisture to produce isolated showers or a thunderstorms
later tonight and Tuesday.
Wednesday through Saturday night: If you`ve got boating or
fishing plans, this is your forecast - at least through Saturday
morning. The last of moderate winds and somewhat nuisance wind
chop go away over the Gulf on Wednesday, with light winds and
slight seas the rule thereafter. Laguna Madre winds may perk up
again Wednesday afternoon to 15-17 knots but remain below 15 knots
thereafter. As for precipitation? Nothing on the horizon until
Friday night and Saturday; increasing coverage becomes a
possibility by late Saturday night.
This product is also available on the web at: