Area Forecast Discussion
Issued by NWS Brownsville, TX
FXUS64 KBRO 232356 AAA
Area Forecast Discussion...UPDATED
National Weather Service BROWNSVILLE TX
656 PM CDT Fri Sep 23 2016
.DISCUSSION...Updated for latest aviation discussion below.
.AVIATION...VFR conditions expected for the next 24 hours as mid
level ridging over the middle Mississippi River Valley into east
Texas continues to provide subsidence across deep south Texas.
Light southeast winds with some passing low clouds are expected
tonight. Southeast winds will become moderate and gusty by
Saturday afternoon. A limited amount of shower activity
will be focused mostly over the Gulf waters, though a few cells
could move ashore along the coast.
.PREV DISCUSSION... /issued 328 PM CDT Fri Sep 23 2016/
SHORT TERM (Tonight through Saturday Night): H5 ridging will
remain the dominant player in the short term, holding court over
the lower Mississippi Valley and East Tx even as mid level
troughing elongates north to south over the high plains.
Associated high pressure will remain over the North and West Gulf.
The omega field shows lift and sfc convergence, which will keep
persistent precipitation over the Northwest Gulf east of the CWA,
but that is where most of it should stay through the short term.
Overnight streamer showers along the coast will be part of the
Gulf convective activity through the short term.
Look for light south southeast winds tonight under mostly clear
skies, except for few to scattered morning low clouds. Overnight low
temperatures will run from the mid 70s to near 80. Streamer showers
may increase in coverage along the coast toward morning.
Partly cloudy to mostly sunny skies will develop by Saturday aftn,
with moderate winds out of the south southeast to south. Gusts into
20 to 25 mph territory will be possible in response to interaction
with lower pressure upstream over West Texas. Aftn high temperatures
will range from the mid 90s to near the century mark, with heat
index values across most areas ranging from 103 to 108. Kept coastal
county pops at a mentionable 20 percent since higher moisture will
push closer to the coast and move northwest to north along the coast
tonight and Saturday.
Saturday night should again be mostly clear with early morning low
clouds, light south southeast winds and overnight low temperatures
from the mid 70s to near 80. Streamer showers will again develop
LONG TERM (Sunday through Friday): The longer range pattern
continues to show a pretty major 500 mb trough axis digging into
the central plains states. Both the GFS and the ECMWF shear this
trough into two pieces with the northern portion pushing off
towards the Great Lakes by next Monday with the southern portion
closing off over the Desert Southwest and Northwestern Mexico
early next week. The position of this closed 500 mb low will help
maintain a good supply of deeper layer moisture and instability to
much of Texas next week. Both the GFS and the ECMWF are also in
good agreement in retrograding the southern portion of the 500 mb
trough axis further west later next week which allows a ridge axis
to form up over Texas and the rest of the southern plains states.
This will should tend to help stabilize and dry out the atms
towards next weekend. At the surface the passage of the deep 500
mb trough axis to our north will pull a cold front into Deep South
TX early next week which will help focus the surface convergence
over the region which in turn maintains the better conv chcs.
This boundary will likely stall somewhere near the RGV area which
will help provide better focus for continued conv through at
least mid week. The deeper layer moisture values then tend to drop
off later next week as the old boundary weakens/dissipates and the
mid level ridge axis strengthens.
Despite the decent agreement of the broad 500 mb features in both
the ECMWF and the GFS bigger differences show up between the two
models concerning mainly the conv chcs. The GFS is slower with the
advent of the better pops next week in comparison to the ECMWF.
Overall temp trends are also problematic due to the differences
between the two models in how far south the cold front will push
before stalling. So for now the overall confidence level in the
longer term solution is only average.
MARINE: (Tonight through Saturday night)...High pressure will
reign over the Northwest Gulf through Saturday night, producing
moderate southeast winds and low to mdt seas. Slightly stronger
winds will be possible over the Laguna Madre and nearshore Gulf
waters Saturday afternoon, but will not reach exercise caution
levels. Isolated to scattered showers and a few thunderstorms will
be possible through the period.
Sunday through Wednesday Night...Surface ridging over the lower
Texas marine areas will gradually give way to a more easterly to
northerly direction as the cold front discussed in the longer
range forecast segment pushes offshore of the coastline. The PGF
will strengthen up enough to possibly reach into SCEC criteria
later in the marine forecast period. However overall confidence it
somewhat low for sustained long term SCA conditions due to the
lack of confidence in where the old front will stall. For now will
hold conditions below SCA levels.
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