Area Forecast Discussion
Issued by NWS Brownsville, TX
FXUS64 KBRO 280541 AAB
Area Forecast Discussion...UPDATED
National Weather Service BROWNSVILLE TX
1141 PM CST Sun Nov 27 2016
.DISCUSSION...Updated for latest aviation discussion below.
.AVIATION...Southerly winds in the 1000-5000 foot range continue to
increase over much of South Texas in advance of a strengthening
low pressure over the Rockies. Low level wind shear will be the
main aviation impact tonight with speeds forecast to reach between
40-45 knots overnight and into early Monday. Southerly flow is
also allowing for gulf moisture to increase with some patchy MVFR
cigs flowing quickly south to north. Probabilities are low at the
3 TAF sites for extended periods of MVFR cigs so will continue to
trend with a higher confidence of VFR as the predominate condition
overnight but can not rule out an hour or two of MVFR between
06-10Z. For Monday winds to start off breezy to windy then
gradually veer and diminish with sky conditions becoming clear
with much drier air mixing to the surface.
.PREV DISCUSSION... /issued 620 PM CST Sun Nov 27 2016/
DISCUSSION...Updated for latest aviation discussion below.
AVIATION...VFR conditions are expected tonight in the vicinity of
the three terminals while IFR ceilings have a higher probability
of occurrence across the Northern and portions of the Western
Ranchlands. A low level jet is in the beginning stages of
development and is expected to strengthen between 40-45 knots by
12Z Monday. Low level wind shear was added to the latest TAFs to
accommodate for these stronger winds. Stronger surface winds are
likely Monday morning from the S-SW with a gradual west to east
diminishing Monday afternoon.
PREV DISCUSSION... /issued 254 PM CST Sun Nov 27 2016/
SHORT TERM (Tonight through Monday Night):
Light to moderate south winds under mostly clear skies will be on
tap tonight, with low temperatures ranging from the mid 60s across
the Ranchlands and Brush Country to the lower 70s along the coast.
A weak cold front across Northwest texas will edge closer to South
South to southwest winds will increase through about noon on Monday,
supporting a very warm day with inland temperatures ranging from the
upper 80s to lower 90s. Capping southwest flow aloft will also help
trap heat at lower levels. Temperatures by early aftn will approach
and even reach record highs. Cloud cover will be middling, though a
few upper clouds along the tail end of a jet streak over central
Texas may be present, and some low CU will undoubtedly develop near
the coast, but it might be tough with the winds out of the south.
By Mon afternoon a weakening front will be approaching the northern
boundary of the CWA and will push part way into the CWA by evening,
shifting winds to northeast for some, but perhaps not all areas. Dry
air will be behind the front and no rain is forecast locally. Any
convection will be farther to the north and/or well offshore.
High pressure over South Texas will shift east Mon night, allowing a
weak return flow to develop. Higher dew point air will push inland.
Low ceilings and some fog may develop as winds drop to light with a
better onshore component.
LONG TERM (Tuesday through Sunday):
With the large-scale H5 trough across the central US, the local
pattern will be getting a lot more active during the extended
period. The next lobe starts to rotate around the bottom of the
trough on Tuesday, keeping winds aloft from the southwest and
keeping any semblance of a front from passing through the region.
Winds Tuesday will be light and variable, so the lack of a
southwesterly sfc flow will keep temperatures from soaring like
Monday, but will still rise into the upper 80s. Record highs
Tuesday are less in jeopardy, as records are all in the lower 90s.
The big changes arrive later Wednesday night as an autumn cold
front sweeps across the region. Since dry air has been already
infiltrating the mid and upper levels, the front will have
considerable trouble producing showers as it passes. have limited
rain chances to the immediate coast and offshore between midnight
and dawn Wednesday. The bigger change will be in the temperatures,
as cool north winds sweep in behind the front, hold temperatures
right around 70 degrees the entire day Wednesday. High pressure
sweeps into south Texas quickly on Wednesday, with clear skies
expected by sunset. This will provide good radiational cooling
that night for temperatures to fall to the upper 40 and lower 50s.
Thursday looks to be a beautiful day with mostly clear skies and
temperatures in the 70s.
Everything changes starting Friday as the next upper trough drops
rapidly into souther California. This keeps southwesterly flow
aloft going, but introduces a swath of moisture from the Pacific
into the region. At the surface, a coastal trough will
develop during the day Friday and is forecast to continue through
the weekend. As vorts rotate around the trough to the west and
speed northeastward across south Texas, strong overrunning will
develop areas of light rain areawide. This pattern will hold firm
through the weekend, just in time for my son`s birthday party. The
trough will also draw another shot of colder air southward later
Saturday into Sunday, with high temperatures struggling to reach
the 60s on Sunday.
Now through Monday night: Updated the CWF for SCA conditions on
the Laguna starting at midnight, supplementing the SCA already out
for the Gulf beginning at 6 pm. Winds on the Gulf are already in
SCEC territory and are trending up. The plains low is still
deepening this aftn, which will support elevated marine winds
through tonight and Mon morning. The highest 1/3 wave heights are
progged to build to eight feet through Monday. The plains low will
move northeast while a trailing cold front in Northwest Texas
moves closer. Winds will settle down dramatically Monday afternoon
and evening as the front pushes into the CWA and stalls. As a
result of the front not pushing offshore, winds may never really
shift direction over the Gulf in the short term.
Tuesday through Thursday:
The main focus of the extended forecast is the arrival of the next
cold front. Tuesday, winds will decrease as the front approaches
and the gradient relaxes. The long fetch of easterly flow will
keep seas in the 3 to 5 foot range. The cold front then will blast
through the coastal waters around dawn Wednesday, switching winds
to the northwest at 20 to 25 knots. Small craft advisories are all
but set for the day Wednesday, but will need to monitor if any
stronger winds may develop in case a Gale Warning may be needed.
Seas will jump up to 7 to 9 feet offshore, with some swells
possibly reaching 11 or 12 feet just after sunrise Wednesday. Now
the surface high pressure will be moving quickly into the
northwest Gulf Wednesday night, so any advisories will be fairly
short lived, and should last no longer than dawn Thursday. Marine
conditions will quickly improve during the day Thursday. Looking
out further for next weekend, marine conditions look to be much
more agitated as a coastal trough develops locally, with gusty
onshore flow and rough seas expected.
GM...Small Craft Advisory for winds until 9 AM CST Monday for GMZ130-
Small Craft Advisory until 6 PM CST Monday for GMZ150-155-170-
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