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Area Forecast Discussion (AFD)

Issued by Brownsville/Rio Grande Valley, TX (BRO)

FXUS64 KBRO 162021

Area Forecast Discussion
National Weather Service Brownsville TX
321 PM CDT Thu Aug 16 2018

.SHORT TERM (Tonight through Friday night): Persistence looks to 
be the best forecast the next 36 hours with high pressure aloft 
and at the surface dominating. Atmosphere remains rather dry 
especially around 925mb with the mid to upper level ridge expected
to strengthen over Texas Friday. To say the least, rain chances 
are zero inland and near zero over the coastal waters and just 
like today, cumulus field will be limited to mainly the eastern 
half of the CWA. Increased subsidence and nearly full sunshine 
will maintain above-normal temperatures with highs Friday ranging
from 95 to 105 and lows tonight and Friday night 74 to 81. Main 
concern tomorrow, if any, is the very high heat indices. Daytime 
mixing of the drier air aloft will be just enough to lower day 
time dew points, limiting the heat indices between 106 and 110 
degrees, or just below advisory levels.

.LONG TERM (Saturday through Thursday): The overall weather
pattern will be fairly persistent, even going through the long
term period, with mid-level high pressure center slowly moving 
westward into the Desert Southwest, but still dominating the 
region with hot and rain-free conditions. At the surface, high 
pressure over the Gulf waters will maintain moderate southeast 
winds, with some strong winds along the coast Sunday into Monday 
with a stronger pressure gradient. A few seabreeze showers will be
possible, but the (slightly) better chances of rain will be well 
offshore the Gulf waters through the weekend. Models bring a 
relatively deep trough into the Central U.S. early next week with 
a weakening cold front into Southeast Texas. Uncertainty exists
regarding how far south it will progress, especially given the 
time of year. Though, if the boundary moves south enough, an 
increase of moisture may bring some precipitation into Deep South 
Texas around mid week.

Temperatures will be near normal to slightly above normal this 
weekend. Highs will range from the upper 90s to around 100F in the
Lower Valley to around 105 in the Upper Valley. Temperatures may 
drop a few degrees next week with possible increasing cloud cover.


.MARINE (Now through Friday night): Surface high pressure builds 
over the western gulf and into the coastal waters Friday weakening 
the pressure gradient slightly. Some gusts Friday afternoon will 
approach 20 knots but overall wind regime should be one notch 
lower. Seas should respond to the lower wind field with wind waves
gradually dropping to 3 feet or less by Friday night. An isolated
shower may be possible over the outer coastal water but rain 
chances are near zero as you approach the shore line.

Saturday through Thursday: Surface high pressure over the eastern
Gulf waters will maintain moderate southeast winds through the
weekend and into next week. The pressure gradient will tighten
this weekend with possible Small Craft Advisories for winds Sunday
into Monday. Seas will also build to 4 to 6 feet in response
across the Gulf waters. The gradient will then relax next week 
with models bringing a possible front into Southeast Texas by mid 


BAYVIEW/PORT ISABEL  79  95  79  95 /   0   0   0  10 
BROWNSVILLE          79  99  79  96 /   0   0   0  10 
HARLINGEN            77 100  77 100 /   0   0   0  10 
MCALLEN              80 103  80 102 /   0   0   0  10 
RIO GRANDE CITY      77 103  76 104 /   0   0   0   0 
SOUTH PADRE ISLAND   80  86  80  91 /   0   0   0  10 




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Short Term...59
Long Term...65