Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 190007 AAA

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
707 PM CDT Tue Apr 18 2017

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


.AVIATION...Very isolated convection north of KMFE is expected to
weaken/dissipate around or shortly after 01z with the atmosphere
slowly stabilizing as daytime heating wanes. Models suggest a low
probability and short duration of MVFR cigs overnight with
central areas along the 69C/281 corridor seeing the best chances.
Patches of MVFR vsby may develop over the air fields, especially
KHRL and KMFE, due to the wet ground and limited cloud cover much
of the night. VFR conditions prevail Wednesday along with light
southeast winds.


.PREV DISCUSSION... /issued 256 PM CDT Tue Apr 18 2017/

SHORT TERM (Tonight through Wednesday Night): Still somewhat
unsettled weather in store for the next 24 hours. Convection has
been slow to initiate early this afternoon due to stabilization in
the wake of the mesoscale convective system that formed along the
coast, and subsequently moved eastward into the Gulf, early this
morning. However, a few cells are popping up in Kenedy County as
of this writing, along what appears to be a sea-breeze boundary,
with the cells moving generally to the SSW. PoP`s from recent
model runs have been much lower (generally 20% or less) through
tomorrow. Have blended in the newer guidance with the going
forecast. Am wary to go too far with cutting rain/thunder chances,
with moisture still in good supply (PW around 1.5"), especially
in the eastern counties. Boundary interactions also still
possible. Not expecting much in the way of severe weather, though
a rogue storm could still produce wind gusts up to 40mph and some
small hail.

Convection should shut down pretty quickly by around sunrise, with a
mainly quiet evening in store.  After midnight, some increase in
"wrap-around" lower-mid level moisture is indicated by both the NAM
and GFS, as the 500-mb low reforms over the western Gulf south of
the border, as it is nudge by upper ridging building across central
TX.  Despite a slug of drier air expected to move in between 700-
500mb, a isolated showers and thunderstorms may occur along the
immediate coast.  Overnight low temps will be in the upper 60s to
around 70.  Can`t rule out some patchy fog for inland areas where
the ground is still wet, but not confident enough to mention in

For Wednesday, N-NE flow aloft develops on the front side of the
aforementioned ridge, with slow drying taking place at upper levels.
Looks like the plume of low-mid level moisture will hang around at
least through the first part of the day, though, except far west.
With temps along Hwy. 77 rising into the upper 80s, looks like
another pretty decent setup for some sea-breeze convergence around
mid-day. Models are only hinting at this, but went above MOS
guidance PoP`s with the ingredients mentioned. Whatever does develop
would seem to shut down around mid-afternoon, as subsidence aloft
increases. As ridging aloft takes hold and by Wednesday night, rain
chances finally become nil with lows again in the upper 60s to low
70s. Went ahead and put in patchy fog for the Northern Ranchlands as
winds become light and forecast RH`s approach 100%.

LONG TERM (Thursday through Tuesday): Ridging aloft will be
building into the region to start the long term as the shortwave
pulls away. Plenty of mid-level dry air will be in place and with
no expected weather features, the forecast will remain rain-free
both Thursday and Friday. Meanwhile, temperatures will warm into
the mid 80s to mid 90s given lower moisture levels and plenty of
sunshine, with lows still running above normal.

Heading into the weekend, a cold front is progged to quickly drop
south though Deep South Texas sometime late Saturday morning or
into the afternoon. The mid-level storm system and surface low
will pass well to the north, across Oklahoma and Arkansas. As
such, the better upper level support/dynamics will not be in place
and the cold front will be more trailing in nature. Meanwhile,
the mid-levels still appear to be rather dry, with little in the
way as any significant moisture return ahead of the frontal
boundary. However, the front will be moving through during the
optimal daytime heating period. Some showers and thunderstorms
will be possible, but have left them at slight to chance POPs.
The front will move through and exit the RGV by early Sunday with
temperatures noticeably cooler as readings fall back to near or
even a bit below normal to start the new work week.

The cooler temps won`t last long however, as strong surface high
pressure and a ridge of high pressure aloft build in quickly
behind the cold front with temps already rebounding on Tuesday as
dry weather continues.


Now through Wednesday night: The threat of thunderstorms
continues for the coastal waters, mainly later tonight into
Wednesday morning. Gusty winds, locally agitated seas, and perhaps
small hail are possible with stronger cells. Outside of
thunderstorms, SE winds of 10-15 knots and seas of 3-4 feet will
be the rule.

Thursday through Saturday: High pressure over the Northeastern
Gulf will keep light to moderate southeast winds and low to
moderate seas in place through Friday. A cold front will sweep
through the Lower Texas Coastal Waters on Saturday bringing some
chances for showers and thunderstorms. Strong surface high
pressure will build into the region later on Saturday with the
surface pressure gradient tightening and marine conditions
becoming hazardous.


BAYVIEW/PORT ISABEL  71  85  72  85 /  20  20   0   0
BROWNSVILLE          70  86  71  86 /  10  20  10   0
HARLINGEN            69  87  70  88 /  10  20   0   0
MCALLEN              70  90  71  91 /  10  20   0   0
RIO GRANDE CITY      69  90  70  92 /  10  10   0   0
SOUTH PADRE ISLAND   73  80  74  79 /  20  30  10   0




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