Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 211126 AAA

Area Forecast Discussion...UPDATED
National Weather Service BROWNSVILLE TX
626 AM CDT Fri Oct 21 2016

.DISCUSSION...Showers continue to move steadily southward with the
front which is well south of the Rio Grande. Latest HRRR has
trended with all showers remaining south of the river this
morning so have decided to drop the mention of the showers. Will
hang on to the clouds with slow clearing in the Valley.
Temperatures will be tricky with not much cold air advection
developing as of this time so confidence is low for the RGV to
see only the lower 80s. zones out soon.


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


.AVIATION...The cold front along with showers and thunderstorms
are well south of the three regional airports. Any MVFR cigs will
be right along the Rio Grande River for the next few hours with
general VFR conditions anticipated for all areas the rest of the
day. VFR cigs will be slow to erode especially across the south
with drier air mixing to the surface and breaking up the overcast
this afternoon. Stronger north-northwest winds gusting 20-25
knots, mainly near the coast, to gradually become north-northeast
this evening and lower considerably.


.PREV DISCUSSION... /issued 452 AM CDT Fri Oct 21 2016/

SHORT TERM (Today through Saturday):
Finally the cold front has passed through Deep South Texas and is
currently clearing the mouth of Rio Grande. The front is losing
some of its punch as the mid level trough over the central
portions of the country quickly moves east but, high pressure will
be building southward allowing for a fresh northerly wind and
drier and cooler air to overspread the CWA as expected. No more
100 degree days (this week) at Mcallen, that makes 90 so far this
year, with at least a 15 to 20 degree cool down in the west and 10
degrees in the east. Scattered showers and isolated thunderstorms
along the leading edge of the front will continue to drift south
with front with only a small chance of additional rain across the
lower valley this morning. Models continue to indicated the
baroclinic zone in the vicinity of the lower valley maintaining a
slight chance of rain through at least mid morning and a slow
clearing of clouds this afternoon.

Surface ridging makes its farthest southern approach spreading along
the coastal bend and the coastal plains tonight before tracking east
Saturday. Clear skies and light northerly winds most locations
tonight allow temperatures to drop into the 50s most locations with
lower 60s across the Lower Valley and along the immediate coast
as some patchy cloudiness and slightly higher winds hang in.

As mentioned surface ridge shifts east with surface winds already
returning from the east by the afternoon. Drier air aloft to mix
through any remaining surface moisture with a fairly dry and clear
and  mild day after the nice cool morning. One concern is across the
Lower Valley where the NAM, more than the GFS, show an increase in
low level moisture which might lead to increasing clouds in the
afternoon. Confidence in an mostly cloudy afternoon is low so will
continue with mostly sunny to partly cloudy.

LONG TERM (Saturday Night through Thursday): Surface ridge
continues to sweep off into the southeastern us over the weekend,
with southeasterly flow returning by Sunday morning. Best moisture
reaches region Monday and Tuesday, in decent timing with the
adjustment of the H5 ridge aloft out of the region. Will continue
to indicate a small chance for showers Monday and Tuesday, but
chances remain thin with the lack of a substantial surface forcing
mechanism. By Wednesday, the next upper ridge shifts into the
region from the west, introducing more dry air aloft and
increasing subsidence. The latter half of the week will be similar
to earlier this week, with ample moisture trapped in the lowest
few thousand feet. This will bring daytime CU field through the
afternoons, with a minimal chance for a shower or two if the
seabreeze can get organized enough. Otherwise temperatures will
remain slightly above normal, reaching the upper 80s to lower 90s
each afternoon, while lows fall into the upper 60s to around 70.

Now through Friday: Winds are peaking this morning as the
pressure gradient is reaching its peak behind the front. Seas will
continue to build also peaking by mid morning. As high pressure
builds along the coastal bend by this evening a gradual lowering
of the northerly winds is expected. Small craft advisory
conditions persist much of the day with winds lowering over the
Laguna around mid day and offshore this evening. Higher seas may
linger through the overnight period with a possible extension of
the SCA. Much improved conditions Saturday as high pressure
spreads east and weakens.


BAYVIEW/PORT ISABEL  79  64  83  70 /  10   0   0  10
BROWNSVILLE          81  63  85  68 /  10   0   0  10
HARLINGEN            81  58  84  65 /  10   0   0  10
MCALLEN              82  59  87  66 /  10   0   0  10
RIO GRANDE CITY      82  56  86  64 /  10   0   0   0
SOUTH PADRE ISLAND   80  70  82  73 /  10   0   0  10


GM...Small Craft Advisory for winds until 4 PM CDT this afternoon for

     Small Craft Advisory until 7 PM CDT this evening for GMZ150-155-



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