Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 161743 AAB

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
1243 PM CDT Fri Mar 16 2018

...18z Aviation Update...

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


.AVIATION...Generally, VFR conditions can be expected this
afternoon. Winds will generally be south or south southeast
throughout the cycle. Winds should generally stay less than 25kt.
Tonight a low stratus deck will again develop over our three
terminals with IFR conditions possible prior to sunrise. There is
also a signal for fog, however, at this time winds will remain
high enough to keep impacts rather minimal. Flight categories
should improve begin to improve by mid morning Saturday.


PREV DISCUSSION... /issued 351 AM CDT Fri Mar 16 2018/

SHORT TERM (Today through Saturday):
The heat and humidity build to get the weekend underway as zonal-
ridging flow at 500 mb holds forth. Tightly wrapped deep
atmospheric low sweeps through Kansas today but dampens rapidly
while moving into the Mississippi Valley tonight and opens into a
shear axis farther east. The wrapped system has little influence
on the Valley`s weather today, and a weak shear axis riding
through the ridge north of the Valley allows us to only "wave" to
any light precipitation that passes through east Texas on

For sensible weather, expect the usual suspects in this situation:
late night through mid morning low clouds, breaking slowly through
noon than clearing out by early to mid afternoon with mainly clear
skies (through some patchy high clouds) during the evening. With
pressure gradient gradually weakening under the flat ridge aloft
expect fresh afternoon breezes but not much more, favoring the lower
Valley.  Lighter winds in the Upper Valley/Ranchlands may briefly
downslope this afternoon with lesser opportunity Saturday, though
atmosphere warms up to match. Afternoon highs will surpass 90
along/west of US 281 both days, with hottest temperatures along the
Rio Grande.  Dewpoints should dip into the 54 to 58 degree range
across portions of Starr, Jim Hogg, and Zapata County this afternoon
with humidity falling below 30 percent.  For the busy beaches this
time of year, expect morning clouds giving way to sunny afternoons
with temperatures nearing 80 and no more than a fresh southeast
breeze as marine layer, though weakening, keeps stronger winds
inland from the coast.

Overnight lows will be where they are this morning:  upper 60s to
around 70 for just about everyone.

LONG TERM (Saturday Night through Thursday):
The long-stable H5 trough across the western US continues to break
apart later in the weekend, throwing lobes across the US. The
next lobe sweeps across northern Texas during the day Sunday, with
a leading stretched vort lobe sweeping ahead and to the south of
it. The northern lobe will also help the dryline make a push into
south Texas. While this would present a reasonable chance for
showers during the late afternoon, there is great capping across
Deep South Texas still, which will be very hard to overcome, even
during peak heating. Will keep a small chance nearer the coast,
where moisture is a bit deeper and may tap a possible seabreeze
instead. The next cold front arrives Monday morning across the
area. Again, capping is still strong, so the front will pass by
dry, but will bring drier air quickly into the region. Models are
starting to hint at the front also bringing gusty north winds
through the day Monday, while would bring a higher threat for
wildfire. This is also a good set up for compressional heating, so
highs in the low 90s becoming a better threat as well, and may
spike further. Northerly flow continues through the middle of next
week, with warm conditions continuing and mostly clear skies.

Now through Saturday: With NOAA Buoy 42020 back in business, more
data are available to assess. Wind conditions have been on the edge
of advisory levels but overall are sitting pretty at "caution"
levels (15 to 20 knots with higher gusts) and the offshore seas have
built to 6 feet overnight.  Expect these conditions to slowly
improve through the day, but will maintain caution wording for the
offshore waters to cover any early morning boating/fishing trips
especially given the steepness of the waves which are driving the
combined seas (4 to 5 foot wind waves at the buoy...very unfavorable
for passengers on small craft fishing trips). Wind waves will likely
remain a nuisance issue over the Gulf waters through Saturday even
as combined seas subside and winds diminish.

By Saturday afternoon, those seas should be down near 3 feet and
winds around 10 knots as the gradient slackens further.

Sunday through Tuesday: The approach of the dryline toward the
western Valley will keep the gradient weak on Sunday, producing
southerly flow around 10 knots. Seas remain around 3 feet, mainly
generated by the longer fetch across the Gulf. Monday, the next
cold front sweeps into the northwest Gulf. Winds are not expected
to elevate considerably with the initial passage, remaining around
10 knots. Seas will actually decrease through the day Monday,
lowering to around 2 feet. A secondary surge of north winds
arrives on Tuesday, jumping winds to 15 knots during the
afternoon. This will push seas upwards to 4 to 5 feet during the




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