Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 150909
AFDBRO

Area Forecast Discussion
National Weather Service Brownsville TX
409 AM CDT Tue Aug 15 2017

.SHORT TERM (Today through Wednesday): Mid-level high pressure
anchored over the northern Gulf combined with very dry air above
850mb will lead to another hot and dry day across Deep South Texas.
Breezy winds are expected again this afternoon with gusts reaching
30 mph at times, as a strong pressure gradient continues at the
surface. Decided to update dew points as model guidance continues to
underdo persistent daytime mixing, which has more-reasonably
produced forecast heat indices ranging from 105 to 110F today. A
slight surge of moisture is noted on the experimental and non-
operational GOES-16 derived Total Precipitable Water satellite
imagery along the coast, but think upper level cirrus will keep
ambient temperatures this afternoon below Heat Advisory criteria
when combined with expected dew points. Tonight, conditions will be
muggy with temperatures dropping to around 80F for most locations.

Wednesday, forecast is similar to today with high temperatures
reaching the upper 90s east of Highway 281/I-69C and several degrees
above 100 in the Mid to Upper Valley. Precipitation chances remain
very low Wednesday as moisture will be confined to the sfc to 850mb.
Some guidance tries to bring in higher moisture from the Gulf,
especially the ECMWF, with Precipitable Water values nearing 2.00",
but abundant dry air in the mid levels will make it very difficult
for convection to develop. Have kept 5% PoPs out west and 10% near
the coast.

.LONG TERM (Wednesday Night through Monday): 500mb subtropical
ridge across the southeast United States and eastern Gulf of
Mexico Wednesday will build westward into Texas Thursday. The
upper level ridge becomes elongated across the south-central and
southeast U.S. Friday. Some convection is progged to develop
around the periphery of the subtropical ridge Friday into
Saturday. In addition...an inverted 500mb trough over the
southeast Gulf of Mexico Saturday is progged to move westward
across the central and western Gulf of Mexico Sunday into Monday.
This will provide some isolated seabreeze convection Friday
through Monday.
&&

.MARINE (Now through Wednesday): Tight surface pressure gradient
will bring moderate to strong southeast winds again this morning
through evening with winds around 20 knots over the Laguna Madre and
near 20 knots over the Gulf late tonight. Have issued a Small Craft
Advisory for Winds on the Laguna Madre from 10 AM to 9 PM CDT. Small
craft should also exercise caution this afternoon in the nearshore
(0 to 20nm) Gulf waters. Winds will be breezy again Wednesday
afternoon with seas ranging from 3 to 6 feet.

Wednesday Night through Saturday...Moderate to strong southeast
winds will prevail across the coastal waters Wed night as low
pressure across northwest Texas and high pressure across the
eastern Gulf of Mexico provides a strong pressure gradient across
the lower TX coast. The pressure gradient weakens slightly across
the western Gulf of Mexico Thursday. Moderate southeast winds
should prevail across the lower TX coast Thursday. Surface high
pressure across the northern Gulf of Mexico Friday will provide
light to moderate southeast winds across the western Gulf of
Mexico. The pressure gradient will remain weak across the western
Gulf of Mexico Saturday.
&&

.PRELIMINARY POINT TEMPS/POPS...
BAYVIEW/PORT ISABEL  95  82  93  82 /  10  10  10  10
BROWNSVILLE          96  80  95  81 /  10   0  10  10
HARLINGEN            99  78  99  81 /  10   0  10  10
MCALLEN             103  81 102  81 /  10   0  10  10
RIO GRANDE CITY     105  79 103  81 /  10   0  10   0
SOUTH PADRE ISLAND   89  83  89  83 /  10  10  10  10
&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...None.
GM...Small Craft Advisory for winds from 10 AM this morning to 9 PM
     CDT this evening for GMZ130-132-135.
&&

$$

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