Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 190840

Area Forecast Discussion
National Weather Service Brownsville TX
340 AM CDT Tue Sep 19 2017

.SHORT TERM (Now through Wednesday): Not many changes to the short
term forecast over the next 36 hours. High pressure aloft in the mid
levels will continue to keep the forecast status quo as lower level
moisture, generally below 700mb, allows for isolated nocturnal
streamer showers over the Gulf. As such have maintained POPs at 20%
over the Gulf waters and coastal areas this morning, with some
afternoon chances pushing farther into Lower and Middle RGV and
portions of the northern Ranchlands. However, the H5 ridge and
subsidence will limit the growth of showers/storms today with any
convective activity remaining hit and miss in nature. Heading into
Wednesday, the ridge appears to flatten and elongate over Texas and
Northern Mexico as a deepening low pressure system develops over the
NW U.S. With the ridge weakening slightly and low level moisture
still in place, have just a general mention of slight chance POPs
for showers/isolated storms. Meanwhile, temps will continue to run a
bit above normal under the influence of the high pressure system.

.LONG TERM (Wednesday Night through Monday): Mid-level ridging
will remain generally in place over the western Gulf of Mexico and
south Texas through much of the period. Some weakening of the
500mb ridge overhead will occur during in the period, as a weak
mid-level low drifts over the Gulf of Mexico. Surface high
pressure across the southeast United States extending into the
northern Gulf of Mexico will maintain south to southeast winds
across the area. Low level moisture (precipitable waters waffling
between 1.75 to 2 inches) will support a slight chance of marine
showers in the morning and afternoon seabreeze convection each
day. Will continue to lean towards the drier MEX numbers for POPS
through the period. Temperatures are expected to remain a few
degrees above normal across deep south Texas through the forecast
period. High temperatures each day will range from the upper 80s
at the beaches, low to mid 90s near the coast and the upper 90s to
around 100 inland with a mix of sun and clouds. Heat index values
expected between 100 to 105 degrees each afternoon. Overnight low
temperatures will generally be in the 70s under partly to mostly
cloudy skies.


.MARINE (Now through Wednesday): Broad surface high pressure over
the eastern Gulf of Mexico will interact with weak low pressure over
portions of the Southern/Central Plains states. The resultant
surface pressure gradient will generally maintain light to moderate
southeast winds and low to moderate seas through mid week.

Wednesday Night through Saturday...High pressure across the Gulf
will produce light to moderate onshore winds and low to moderate
seas through the period. A few showers and thunderstorms are
expected to develop along the coast from time to time.


BAYVIEW/PORT ISABEL  93  79  93  79 /  20  20  20  10
BROWNSVILLE          93  79  93  79 /  20  20  20  10
HARLINGEN            97  78  97  78 /  20  10  20  10
MCALLEN             100  80 100  79 /  20  10  20  10
RIO GRANDE CITY     101  78 101  78 /  10  10  10  10
SOUTH PADRE ISLAND   88  81  88  81 /  20  20  20  10




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Short Term...69
Long Term...63
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