Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 180606 AAB

Area Forecast Discussion...UPDATED
National Weather Service BROWNSVILLE TX
106 AM CDT SUN SEP 18 2016

.DISCUSSION...Updated for latest aviation discussion below.


.AVIATION...High pressure in the middle layers of the atmosphere
will prevail across deep south Texas and the Rio Grande Valley
through the next 24 hours. Mostly clear skies with light and
variable winds will continue overnight. Southerly winds
will develop later this morning then becoming southeast and gusty
this afternoon. VFR conditions are generally expected through


.PREV DISCUSSION... /issued 641 PM CDT SAT SEP 17 2016/

DISCUSSION...Updated for latest aviation discussion below.

AVIATION...Breezy SE winds will lessen after sunset and become
light and variable overnight. Gusty conditions will return on
Sunday...with southerly winds in the morning becoming more SE
through the day. High pressure is in control of the weather and
VFR conditions are generally expected.

PREV DISCUSSION... /issued 246 PM CDT SAT SEP 17 2016/

SHORT TERM (Now through Sunday night): H5 ridge continues to
build aloft as active pattern remains well to the north. WV
imagery shows swath of drier air across south Texas, with only a
few lower-topped showers trying to pop up along the seabreeze in
Kenedy and Willacy Counties. Showers will remain isolated along
and east of the seabreeze as it progresses slowly westward into
north Hidalgo and Starr Counties. Southerly sfc flow is impeding
the seabreeze progression further south, which should keep the
seabreeze from reach beyond the BRO-HRL corridor and out of
southern Hidalgo County. Tonight, winds decrease again to light
and variable, with minimal cloud cover. Persistence is the
forecast for lows, with upper 70s most areas, near 80 around MFE
and along the immediate coast. Sunday will be similar to today, as
the H5 ridge dominates the region. Instability will be limited to
llvl seabreeze features, and will again have trouble moving inland
and will have limited moisture fuel. Rain chances focused offshore
before noon, and right along the seabreeze after noon. Persistence
for temps again tomorrow, with mid 90s along the I-69E corridor,
upper 90s for the ranchlands, and 100 (again) for KMFE.

LONG TERM (Monday through Saturday): The forecast period begins
with a broad 500 mb ridge centered over much of Texas, which will
subsequently influence the CWA. Most precipitation will be held
offshore Monday, though the wetter ECMWF wants to support higher
pops over land too. Moving into the meat of the work week, mid
level ridging will retreat slightly to the west, allowing rain
chances to increase in general, with the ECMWF favoring better
chances on Tuesday until the GFS achieves better parity for
Wednesday through the end of the work week. A specific trigger is
difficult to discern, but one consideration would be higher
moisture over the southern half of the Gulf being forecast to edge
farther north, providing juice for a more active sea breeze. Winds
too will be more easterly the first half of the week, supporting
the sea breeze theme. That said, guidance supports higher rain
chances, chance category, along the coast through the entire
week. precipitable water values will be modest through about
midweek however, between an inch and a half and an inch and three
quarters, so isolated to scattered showers may not pack a lot of
punch, but by Thursday the forecast PWAT will increase to a more
robust two inches, with winds increasing slightly from the
southeast, perhaps giving scattered convection a better chance at
delivering locally heavier rainfall. Used a model consensus, since
variations did not seem extreme or outlying, resulting in general
acceptance and continuation of the inherited fcst. Above normal
temps will continue to be the norm through the period.

Now through Sunday night...Marine forecast is also persistence
for the short term, as neither sfc high nor sfc low wants to claim
the northwest Gulf during the next 36 hours. With light gradient
comes winds less than 10 knots, which keeps Gulf waters swells 2
feet or less, and keeps Laguna chop to a minimum.

Monday through Thursday...Mid level ridging over Texas and North
Mexico along with high pressure over the lower Mississippi Valley
Monday will yield weak winds and low seas across the lower Texas
Coast. Light to moderate northeast to east winds will develop as
ridging aloft and surface high pressure over the North Gulf
control the weather over the area. Winds will eventually start to
veer to southeast around mid week as high pressure shifts farther
east. Wave heights will continue low to moderate through the
period. Marine convective activity will increase periodically,
partly due to instability over the Southwest Gulf.


.BRO Watches/Warnings/Advisories...


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