Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 241914
AFDBRO

Area Forecast Discussion
National Weather Service Brownsville TX
214 PM CDT Sat Jun 24 2017

.Short Term (Now through Sunday night): The change in the weather
pattern has begun to evolve this afternoon as the H5 ridge gets
pushed westward by the inverted trough moving into the western
Gulf. GOES16 PW imagery shows the arrival of the deeper moisture,
with current pw values around 1.8, with a swath of 2.0 values just
offshore. Morning sounding still showed that moisture was held
down in the lowest roughly 9000 feet, so shower activity has
remained widely scattered. Lightning activity has only just now
begun to spark as the day progresses, but will remain minimal for
the remainder of the afternoon. The first wave of showers will
drift westward through the evening, decreasing with the loss of
daytime heating. A few showers are possible again tonight right
along the coast as streamer shower start to form offshore and
drift inland. Sunday will bring a more numerous showers as the
moisture continues to sweep inland, and begins to infiltrate into
the higher levels of the atmosphere. Light winds are noted at all
levels tomorrow, so showers will become more outflow dominant.
Steering flow will be minimal as well, so a few pockets of
heavier rainfall may occur as showers meander their way across
the region. Shower activity will wane tomorrow evening, with
another round of nocturnal showers drifting into the coastal areas
from the Gulf.

.Long term (Monday through Saturday):

Look for a broad 500 hPa trough across the upper Midwest
initially, with a sturdy ridge centered over northwest Mexico
extending north along the Rockies. A somewhat weaker ridge will
lie over Florida. A shallow mid level weakness will be over the
west Gulf stretching from the Bay of Campeche to Louisiana. The
ridge over the West will translate slowly east, forcing high
pressure at the surface ahead of it and out into the northwest
Gulf. That will keep winds more from the northeast to east Mon
into Tuesday, but by Tuesday night winds should veer to southeast
while high pressure shifts farther east. The ridge over the West
will be replaced by a transiting mid level trough, while the
Bermuda ridge will amplify, with high pressure building into the
Gulf. 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. The latest
ECMWF and GFS temp guidance numbers are pretty close. Both reflect
the marine nature of the convection and both tend to be slightly
drier inland. Winds will pick up a bit late in the week as the
strength of the Florida ridge builds and surface high pressure
ridges more strongly westward across the north Gulf.

&&

.MARINE:
Now through Sunday night: Marine conditions continue to improve
today as the effects of TS Cindy wane. Winds have decreased to
around 10 knots, while seas are currently around 5 feet with a
short 5 second period. Conditions will continue to improve through
the next 36 hours as winds remain in the 10 to 15 knot range. Seas
will continue to relax, reaching around 3 feet by sunrise Sunday.
Showers will continue to develop, especially overnight tonight as
deeper Gulf moisture moves in from the southeast.

Monday through Thursday: Light to moderate east winds Monday and
Tuesday will become southeast afterward as high pressure builds
over the Gulf. Low to moderate seas through the period. Isolated
to scattered marine showers will persist.

&&

.PRELIMINARY POINT TEMPS/POPS...
BAYVIEW/PORT ISABEL  78  88  77  88 /  30  30  50  60
BROWNSVILLE          77  92  76  90 /  30  40  30  50
HARLINGEN            76  93  75  91 /  20  40  30  50
MCALLEN              77  95  76  92 /  20  50  30  60
RIO GRANDE CITY      77  94  75  93 /  10  40  20  50
SOUTH PADRE ISLAND   79  85  78  86 /  30  30  50  60

&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...None.
GM...None.
&&

$$

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