Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 172332 AAA

Area Forecast Discussion...UPDATED
National Weather Service BROWNSVILLE TX
632 PM CDT Mon Oct 17 2016

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


.AVIATION...VFR conditions to prevail once again at the TAF sites
as drier conditions continue over the Rio Grande Valley. Some MVFR
to IFR vsbys and lower cigs to develop over the Northern portions
of Deep South Texas as a stronger inversion and slightly better
moisture is available for some fog and stratus formation.
Probabilities remain low for KMFE to see lower conditions and if
they do it should be brief just around sunrise and last for one to
two hours at most. winds to decouple after sunset with light
southeast winds to prevail until Tuesday late morning when the
Southeast winds increase to moderate levels.


.PREV DISCUSSION... /issued 317 PM CDT Mon Oct 17 2016/

SHORT TERM (Tonight through Tuesday Night): No break from the
heat for the RGV in the short term period as a stable 500 mb ridge
remains in place over the Gulf of Mexico and the southeastern
States through tomorrow night. The 1000-500 mb thicknesses remain
about the same on Tuesday as models expected for today. So with
the pattern remaining pretty status quo over the region expect a
persistence forecast for high temps for Tues. Record highs for
tomorrow may be a bit more out of reach versus today with 97/101
and 104 the records for 10/18 for Brownsville...Harlingen and
McAllen respectively.

The latest MAV temp guidance is on the cooler side of the latest
MET and ECMWF numbers. Persistence seems to favor the warmer
ECMWF numbers and will go closer to these in the short term.

Deep layer moisture will remain pretty limited over the region
through tonight and tomorrow but then starts to encroach a little
bit from the east for Tuesday night mainly across the marine
locations. Accordingly will maintain the mention of slgt chc pops
near the coastline and offshore for tomorrow night.

Fog will likely be an issue across the northern tier of counties
tonight due to the combination of the light surface winds and
relatively high surface dewpoints. So will include a mention of
patchy fog here for tonight mainly for the Falfurrias and
Hebbronville areas.

LONG TERM (Wednesday through Monday): Unseasonably warm and dry
weather will continue into the beginning of the long term period.
Mid level ridging overhead will start to shift east Wednesday as a
short wave trough digs into the plains, though southeast winds will
continue until an approaching cold front gets closer. A building
ridge over the Pacific Northwest will bolster underlying maritime
polar high pressure there like mercury rising in a thermometer. The
high pressure will begin to spill southeast Wednesday, triggered by
a progressive shortwave trough moving into the high plains and the
eastward movement of the ridge itself.  A cold front will then push
into Texas late Wednesday in advance of the ridge.

Some moisture will continue to be drawn north along the Northeast
Mexican coast to provide local coastal shower activity Wednesday
night, but low to mid level moisture will also pool along and ahead
of the front moving into North Texas Wednesday night, increasing
Thursday before the front moves through the CWA during the day. The
front will support a chance of showers and thunderstorms across the
area Thursday, and will arrive in deep South Texas and the RGV in
time to keep high temperatures from rising above the upper 80s or
around 90.

A slight chance of showers will linger Thursday night, with lows in
the 60s, as drier and cooler air filters into deep South Texas in
the wake of the front, and as ridging builds over the Southwest
United States. High temperatures Friday will be in the 80 to 85
degree range with light north winds. The coldest night will be
Friday night with overnight lows dipping into the 50s for much of
the area except the immediate coast. Temperatures overall will be
much more seasonable from Friday through Monday, with a slow warming
trend beginning Saturday during the day under full sunshine.

MARINE (Tonight through Tuesday Night): Surface high pressure
over the southeastern states and the Gulf of Mexico will remain in
place throughout the short term period along the lower Texas
coastline. This will maintain light to moderate southeast winds
and low to moderate Gulf swells. With status quo conditions
persisting along the coast no SCA conditions expected through
Tuesday night.

Wednesday through Saturday...H5 ridging will shift over the
Southeast United States on Wednesday as a short wave trough digs
into the plains, with high pressure at the surface and over the
North Gulf. Light to moderate southeast winds will prevail initially
and wave heights will be low to moderate with an easterly swell
component. Coastal showers will move north along the coast. The
leading edge of a cold front will push into North Texas on
Wednesday, and southeast winds will begin to weaken. Winds will veer
to east Wednesday night as the gradient weakens and upstream high
pressure flattens the pressure field. Winds will shift to north
Thursday morning, with the front moving through the Brownsville area
around mid day, and will increase through the afternoon behind the
front, reaching small craft advisory criteria by Thursday evening as
the tightest portion of the gradient moves over the coast. Strong
north winds will then persist through Friday. Wave heights will
build to eight or nine feet offshore most of Friday, and will
outlast winds in terms of being in SCA territory, as winds will
decrease below 20 knots late Friday evening while seas will hang on
above seven feet offshore until some time Friday night. Isolated to
scattered showers and thunderstorms will accompany the front as it
moves through.


BAYVIEW/PORT ISABEL  76  95  77  88 /  10  10  10  20
BROWNSVILLE          76  96  76  91 /  10  10  20  20
HARLINGEN            73  98  74  92 /   0   0  10  20
MCALLEN              74 100  76  96 /   0   0  10  20
RIO GRANDE CITY      72  98  74  94 /   0   0   0   0
SOUTH PADRE ISLAND   80  92  80  84 /  10  10  10  20




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