Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 231942
AFDBRO

Area Forecast Discussion
National Weather Service Brownsville TX
242 PM CDT Fri Jun 23 2017

.Short Term (Now through Saturday night): A break in the
oppressive heat is noted moving into the short term as the
summertime H5 ridge finally gets nudged back to the west. During
the next 24 hours, the inverted trough currently along the Yucatan
Peninsula will move west across the western Gulf, drawing much
more moisture into south Texas. With less stable air in the region
and more moisture, shower activity will have an easier time
bubbling up in this deep summertime heat. Tomorrow the first wave
of moisture arrives, but still looks limited to fairly close to
the surface. This will allow only smaller showers, which will
nudge up against the still-present cap and precipitate out
quickly. For the most part, showers will be widely scattered and
brief, so not a full washout for the day Saturday. Increased
moisture and cloud cover will help subdue the epic heat locally,
with highs Saturday a good 6 to 10 degrees lower than the
oppressive heat of Friday.

.Long term (Sunday through Friday): Look for a broad 500 hPa
trough across the upper Midwest with a sturdy ridge centered over
northwest Mexico extending north into the Pacific Northwest. 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 Sun and Monday, but by Tuesday 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. Not much change will be
noticed locally with a steady southeast wind by around Tuesday and
thereafter. 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 Saturday night: Small Craft Advisory for the Gulf
waters just ended, as winds decreased to around 15 knots, while
seas hover just under the 7 foot level. Advisories do continue
through sunset for the Laguna Madre, as winds continue to reach 20
knots. Conditions will improve area wide overnight tonight as
winds relax due to decreasing local gradient across the northwest
Gulf. Seas should fall to around 5 feet by sunrise, with winds
around 10 knots. The main new feature of the marine forecast is
the arrival of deeper Gulf moisture from the southeast, which will
bring a better chance for rain showers and a few thunderstorms
starting after midnight tonight through around noon, and
developing again after midnight Saturday night.

Sunday through Wednesday: Light to moderate northeast to east
winds through Tues. as Plains high pressure moves into the
northwest Gulf, then southeast winds as high pressure shifts east.
Low to moderate seas.

&&

.PRELIMINARY POINT TEMPS/POPS...
BAYVIEW/PORT ISABEL  81  90  78  89 /  20  20  30  40
BROWNSVILLE          80  93  77  91 /  20  20  30  50
HARLINGEN            80  95  76  93 /  10  30  30  50
MCALLEN              81  96  77  94 /  10  40  20  50
RIO GRANDE CITY      79  99  77  95 /  10  30  10  50
SOUTH PADRE ISLAND   82  87  79  87 /  20  20  30  50

&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...Heat Advisory until 5 PM CDT this afternoon for TXZ248>257.

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

&&

$$

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