Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 252344 AAA

Area Forecast Discussion...UPDATED
National Weather Service BROWNSVILLE TX
644 PM CDT WED MAY 25 2016

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


.AVIATION...stratus layer at MVFR levels already impacting KBRO.
this lower layer should continue to spread north and west with all
airports seeing Mvfr conditions before midnight. the lower cigs to
persist through mid morning thursday. convection over the Mexico
mountains slowly propagating eastward. Higher confidence of
showers making into areas west of I-69C possibly working towards
KMFE between 04-10z with lower confidence of any storms making
their way to khrl and kbro. There is some indication /low
confidence/ that convection could persist much of the night
impacting the 3 air terminals a few hours either side of Sunrise
Thursday. Southeast winds to remain at least 10 to 18 knots
tonight increasing 15 to 25 knots thursday.


.PREV DISCUSSION... /issued 258 PM CDT WED MAY 25 2016/

SHORT TERM (Tonight through Thursday Night):
A strong 500-mb closed
low will be continue moving east into SoCal tonight and will move
into the Four Corners area by midday Thurs.  Upper-level ridging
which was in place over the area for past several days has already
begun flattening in response to this...allowing some high clouds to
stream in from the E. Pacific.  Short-range guidance in good
agreement that a lead impulse will approach the western CWA early
this evening.  With plentiful moisture in place, this should lead to
a round of mainly scattered thundershowers over the western zones,
possibly in combination with storms moving off the higher terrain in
Mexico. These are already apparent this afternoon in IR imagery
and lightning data.

SPC maintains the western CWA in Marginal Risk for severe
thunderstorms, but will not mention in grids at this time to remain
consistent with neighboring office.  Also some uncertainty about
whether there will be enough dynamic forcing to break cap. May have
to keep an eye on localized heavy rain potential in that area,
though, as steering flow will be relatively light. Lighter/more
isolated rainfall expected farther east.  Upper impulse should be
clear of the area offshore by early Thursday morning for a bit of a
lull in precip chances until Thursday evening into the overnight
when the next wave...associated with base of the main upper
low/trough...moves overhead.  Model consensus seems to keep most QPF
north of the CWA.  Western half of CWA in marginal risk for severe
so that will need to be monitored as well.

Max temps will lower a bit on Thurs due to the increased cloud cover
and slightly lower heights.  Heat indices should correspondingly be
a bit lower as well, topping out in the 100-105 range across most of
the CWA.

LONG TERM (Friday through Wednesday):
The agitated pattern continues through the weekend into early next
week due to an active swly flow aloft. During the day Friday, the
initial H5 trough will be passing by to the north, with smaller
impulses sweeping around the southern periphery. Each of these
impulses will enhance the possibility of shower and thunderstorm
activity across the region, generally sweeping west to east. The
region will be in the midst of a significant moisture plume, noted
by PW values around 2 inches. On Saturday, weak ridging buckles
briefly along the Gulf coast, reducing instability. Models note
that moisture lowers slightly, which will lead to a smaller but
still a slight chance for showers. On Sunday, the ridge moves to
the central Gulf, with more impulses moving into the region and
increased moisture. While the individual impulses cannot be timed
to a specific point of the day, we will still have high moisture
and considerable daytime heating (highs in the 90s every day) to
activate the seabreeze at a minimum. Have pushed the PoP chances
upwards well into the chance category Sunday through Wednesday.

Now through Thursday Night: The tightening PGF between surface
high offshore southeastern CONUS and surface low emerging over the
central Plains states...and the thermal low over interior of
Mexico...will keep winds on a gradually increasing trend next 24
hours. This trend will lead to more adverse marine developing by
Thursday evening with Small Craft Advisory for winds (and possibly
seas) likely. Showers and storms should stay mainly isolated over
the offshore waters.

Friday through Sunday: Breezy conditions will continue into Friday
due to interaction between Low pressure passing through kansas and
broad high pressure across the eastern seaboard. Winds are
forecast to reach around 20 knots during the day, with some
possible higher gusts. Seas will remain agitated, running near 7
feet through the day, likely necessitating advisories for all
marine zones. Over the weekend, the gradient relaxes a bit due to
an area of low pressure disturbing the ridge off the SC coast.
Winds will relax to 10 to 15 knots, but seas will only slowly
recede due to the long fetch of southeast winds across the western
gulf. Seas will likely remain 5 to 6 feet all weekend.


BAYVIEW/PORT ISABEL  80  91  79  90 /  30  20  20  20
BROWNSVILLE          78  90  79  91 /  30  20  20  20
HARLINGEN            78  93  79  93 /  30  30  30  20
MCALLEN              78  94  79  93 /  40  30  30  20
RIO GRANDE CITY      78  96  77  98 /  50  30  30  20
SOUTH PADRE ISLAND   80  85  79  83 /  30  20  20  20


.BRO Watches/Warnings/Advisories...


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