Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 071156 AAA

Area Forecast Discussion...UPDATED
National Weather Service BROWNSVILLE TX
556 AM CST Wed Dec 7 2016

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


.AVIATION...A weak cold front has moved through the region
overnight with IFR to MVFR cloud cover filling in behind the weak
boundary. The lower cloud decks are expected to rise slightly but
overall MVFR to prevail at the local terminals. Patches of light
rain or drizzle develop later this morning and afternoon but
coverage is expected to be sparse so no mention in the TAFs at
this time. Light north to northeast winds today gradually
increase Thursday morning as a stronger surge of colder air surges


.PREV DISCUSSION... /issued 408 AM CST Wed Dec 7 2016/

SHORT TERM (Today through Thursday):
The challenge for today will be what impact on temperatures will
the initial cold front currently moving through the RGV as of this
writing. For tomorrow the challenge is when will the pressure
gradient increase ushering in the much colder air.

Surface analysis shows the polar front moving into Cameron County as
of 3 am with the overnight patchy dense fog lifting into a low
stratus deck. One can argue this is the initial surge of the much
advertised polar/arctic front, but the coldest air is associated
with a strong surface high pressure area (1048mb) which is still
located over the Canadian prairies. This surface ridge is expected to
push southward over the next 24-36 hours gradually strengthening the
pressure gradient. The onset of the colder and windy conditions
looks to be slightly delay but overall we can still anticipate a
steady fall in temperatures and an increase in the north winds along
with increasing chances of rain Thursday.

As for today, the passage of the front and the gradual thickening of
the low clouds as south winds between 925-850mb overrun the shallow
northeast surface winds today`s temperatures will likely have a
difficult time reaching expected previous forecast and the latest
guidance Maximums. Have already lowered numbers 3 to 5 degrees but
this may not be enough with 30s and 40s noted over North and Central
Texas. Rain chances albeit light might also see a better chance as
the clouds begin to thicken and the overrunning strengthens as a
coastal trough develops later in the afternoon. Steady temperatures
are anticipated for the overnight period until the surface ridge
makes it surge into the CWA around sunrise. The pressure gradient
(thus the winds) peak Thursday afternoon with a chilly blustery RGV
winter day anticipated. Temperatures begin to fall in the morning
but could be delayed across the RGV until Noon with an accelerated
drop during the afternoon hours once the coastal trough strengthens
as surface ridge builds into South Texas increasing the coverage of
light rain and drizzle.

LONG TERM (Thursday Night through Tuesday):
Gusty north winds continue Thursday night as gradient remains
tight between departing front and lagging strong sfc high
pressure. Cold pool will be at its strongest Thursday night,
bringing lows down into the mid 30s across the ranchlands. Breezes
will be enough to further lower wind chill readings into the upper
20s. Friday will remain cold as the cold air advection continues
to pour in, while weak overrunning keeps skies cloudy with some
light rain possible along the coast from a weak coastal trough.
Slightly milder conditions return starting Saturday as the coastal
trough dissipates and southeast flow starts to bring back Gulf
moisture. This is brief as models continue to bring another cold
front through the region later in the weekend. GFS and Canadian
are faster with the front, arriving Mondya around midnight, while
the EC is slower, with the front arriving Monday around noon.
Front is more of a Pacific front than the previous front, so
temperatures will not plunge nearly as low, with highs Monday and
Tuesday still in the 70s.

Now through Thursday: Initial weak cold front moving through the
coastal waters will produce a light to moderate northeast wind and
a moderate sea. As a strong surface high pressure ridge builds
south into Texas tonight and Thursday north winds to increase
steadily. Gale conditions are expected to develop Thursday and are
now anticipated to impact the Laguna Madre south of Port
Mansfield. The deteriorating conditions could be delayed until mid
to late morning but once they begin improvement is not likely
until Saturday.

Thursday night through Saturday: Gusty north winds will continue
behind the front, with 20 to 25 oknot winds continuing through
Saturday midnight. Seas will start the period around 12 feet and
slowly falling to 7 feet Friday night. Good mixing of the marine
layer should bring continuous gale force gusts through about noon
Friday. Moderate onshore flow develops during the weekend, with
cotntinued agitated seas near Advosiry criteria both days.


BAYVIEW/PORT ISABEL  73  61  62  42 /  20  30  60  50
BROWNSVILLE          75  62  63  42 /  20  30  60  50
HARLINGEN            73  58  59  41 /  10  30  60  50
MCALLEN              73  57  58  40 /  10  30  60  40
RIO GRANDE CITY      69  54  55  38 /  10  20  60  40
SOUTH PADRE ISLAND   73  63  64  45 /  10  30  60  50


GM...Gale Watch from Thursday morning through Thursday evening for

     Gale Watch from Thursday morning through Thursday evening for



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