Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 221958
AFDBRO

Area Forecast Discussion
National Weather Service Brownsville TX
258 PM CDT Thu Jun 22 2017

.Short Term (Tonight through Friday Night): Main story and
challenge is the extreme record heat today and anticipated high
heat indices expected Friday. Monthly and all-time record Maximums
being threatened this afternoon. Downsloping south to southwest
winds and the influence of the western ridge are combining to
produce the dangerous heat. A strong pressure gradient has
developed today and is expected to persist tonight and Friday as
departing tropical storm Cindy, high pressure over the Gulf and a
thermal low over west Texas all combine producing the gusty winds.
The persistent stronger winds will keep temperatures elevated
tonight with minimums anticipated to remain in the 80s. Winds are
expected to turn south to southeast Friday which will in turn
increase the dew points but not lower temperatures substantially.
Heat indices are indicated to range between 110-115 degrees across
several locations across the RGV and Western Ranch lands and
possibly stretch northward which will likely warrant a heat
advisory for Friday afternoon. Another very warm and sultry night
is in store for Friday night with the moisture deepening and
pooling in advance of front nearing the northern Gulf coast.
Streamer showers could develop after midnight over the gulf and
could make their way towards the coast by sunrise.

.Long term (Saturday through Thursday): Look for a broad 500 hPa
trough across the upper Midwest with anchoring ridges centered over
northwest Mexico and Florida. A shallow weakness will be over the
west Gulf stretching from the Bay of Campeche to Louisiana. A
northward extension of the ridge over northwest Mexico into the
Pacific Northwest will translate slowly east while deeper troughing
develops over the the eastern Great Lakes, which will also shift
slowly east. The mid level over deep South Texas and the RGV will
scarcely be altered. This means that a summer pattern of weak to
moderate east to southeast winds will prevail. Ample moisture, with
pwat values forecast to be around two inches near the coast and near
an inch and a half inland, will ensure a mix of clouds and sun,
warm, slightly above average temperatures and a regular supply of
showers and mostly garden variety thunderstorms. Some of this will
be diurnally driven sea breeze convection, but moisture moving up
the northeast coast of Mexico from what is the cauldron of the
southwest Gulf will provide late night and early morning streamer
activity. The weakness aloft will certainly not act very strongly to
suppress this activity over the next week. High temperatures may
tend to be less extreme than they have been recently due to
increased cloud cover and the presence of shower activity, but heat
index values may still be near the century mark in the afternoons.

&&

.Fire weather...Modest relative humidity recovery tonight with
southerly flow remaining gusty. Pressure gradient remains strong
for Friday with humidity levels inching upward as wind direction
turns more southeast. Min RH drops between 25-45 percent in the
afternoon with 20ft winds ranging between 15-20 mph, with higher
gusts, enough to maintain an elevated threat for fire weather
conditions.

&&

.MARINE:
Tonight through Friday Night: Pressure gradient will continue to
strengthen tonight as high pressure builds across the Gulf of
Mexico and combines with Low pressure over West Texas and the
remnants of Tropical Depression Cindy. Small Craft advisory
conditions to continue or develop tonight mainly over the Gulf
waters with exercise caution conditions over the Laguna tonight
before increasing to SCA Friday mid-morning. Conditions gradually
improve Friday night as a weak front approaches the northern gulf
coast weakening the pressure gradient.

Saturday through Tuesday: Light to moderate east to southeast winds
and low to moderate seas as the Gulf returns to a seasonal
pattern.

&&

.PRELIMINARY POINT TEMPS/POPS...
BAYVIEW/PORT ISABEL  81  94  80  90 /   0   0  20  20
BROWNSVILLE          81  98  80  93 /   0   0  20  20
HARLINGEN            80 100  79  94 /   0   0  20  20
MCALLEN              82 103  81  95 /   0   0  10  30
RIO GRANDE CITY      80 106  79  96 /   0   0  10  30
SOUTH PADRE ISLAND   82  90  82  87 /   0   0  20  20

&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...High Rip Current Risk until 7 PM CDT this evening for TXZ251-256-
     257.

GM...Small Craft Advisory for winds until 7 PM CDT this evening for
     GMZ130-132-135.

     Small Craft Advisory from 7 PM this evening to 7 PM CDT Friday
     for GMZ150-155-170-175.

&&

$$

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