617 
FXUS64 KBRO 221538 AAB
AFDBRO

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
1038 AM CDT Sat Jun 22 2019

.DISCUSSION...KBRO is showing some isolated shower/storm 
development just south of the Rio this morning. With the northerly
track expected to be in the mid/lower valley, went ahead and 
bumped POPs a little for at least some mention through the 
afternoon hours. With cloud cover remaining quite persistent, 
decided to drop maxTs just slightly. There is still a small window
for heat advisory conditions this afternoon, so all headline 
products are left unchanged for now. Updates out shortly. 

&&

.PREV DISCUSSION... /issued 627 AM CDT Sat Jun 22 2019/ 

DISCUSSION...Updated for latest aviation discussion below.

AVIATION...Little change made to previous set of TAF's; just
added some more detail, where appropriate. Southwest flow aloft
still expected to keep multi-layered clouds in the picture 
through much of today. Current surface observations indicate 
patches of MVFR ceilings, but hard to get a fix on areal extent 
due to obscuration by higher clouds on satellite. At any rate, 
the lower clouds will gradually scatter out/rise to VFR this 
morning. Winds become breezy to gusty as well. Overnight MVFR 
cloud decks have been more stubborn of late than guidance would 
suggest, so have included at all TAF sites from 04Z onward.

PREV DISCUSSION... /issued 438 AM CDT Sat Jun 22 2019/ 

SHORT TERM (Now through Sunday): More hot, humid, and breezy 
weather is on tap for Deep South Texas and the Rio Grande Valley for 
the weekend.  Continued SW flow at mid-to-upper levels of the 
troposphere will keep multi-layered clouds overhead today, before 
thinning out overnight and into Sunday.  Overall, expecting high 
temps today to be similar to yesterday's observed values.  Most 
areas will see negligible chances for rain.  Will keep isolated 
coverage over western three counties this evening and Sunday evening 
to account for any storms that may be able to survive off of the 
higher terrain in Mexico. Can't completely rule out a "sprinkle" 
elsewhere (as some saw on Friday), but thinking that it wouldn't 
be enough to measure.

Another Heat Advisory will be needed for all areas away from the 
immediate coast today, from noon until 7 PM CDT.  Not completely 
confident on meeting duration (2+ hours of at least 111F heat index) 
everywhere with the sometimes thicker cloud cover.  On the other 
hand, temps still managed to hit 97F at BRO yesterday and 99F at 
MFE, plus mixing may be slightly inhibited by the cloud cover, which 
should maintain those oppressive dewpoints in the 75-79F range much 
of the afternoon, especially across the more-populated RGV.

High clouds thin a bit overnight, per model time-height sections, 
but with winds staying up at 10-15mph, record high minimum 
temperatures may occur again.  More of the same on Sunday; not much 
change in H85 temps or 1000-500mb heights, but a little less cloud 
cover may heat things up another degree or two.  Heat Advisory again 
appears likely.

And last, but not least:  There is a moderate risk of rip currents 
at area beaches today.  Overall wave heights in the surf zone should 
be mitigated by cooler Gulf-side water temps (around 75F).  A longer-
period swell (10-12 sec) is beginning to show up in buoy data.  So 
far, amplitude is only running 1-2 ft., but will need to monitor 
this.

LONG TERM (Sunday night through Friday): Heading into the work-
week, mid-level synoptic flow will be out of the southwest across
Deep South Texas, as a deep trough and associated lee surface low
traverse across the Central U.S., and a broad high lingers over
the Central Gulf waters. Meanwhile across the CWA, low-level flow
will remain rather strong due to a tight gradient between 
a surface trough over West Texas and high pressure over the NE 
Gulf. Modest moisture advection should allow for isolated rain 
chances on Monday, though most locations will remain dry with a
lack of upper-level support and mid-level dry air. On Tuesday,
steering flow becomes zonal across the Central U.S., with a split
high across the Central Gulf and also over Chihuahua/Sonora Mexico.
This will create a weakness over South Texas and provide an 
uptick in rain chances. Surface flow becomes a bit weaker and 
backs to the ESE, so a seabreeze may be enough to get some 
convection developing, nonetheless. The GFS still remains much 
drier than the wetter ECMWF solution, which develops a weak 500mb 
low over Deep South Texas. MEX (GFS) MOS guidance has consistently
ranged from 15 to 20% across the CWA, whereas the ECX has ranged 
from 30 to 50% across the Mid Valley. Decided to keep rain 
chances mostly unchanged, as model blends and confidence remains 
about the same.

For the second half of the week, cannot rule out an isolated
thunderstorm, but much drier and shallower air will keep coverage
low through early Friday. 1000 to 500mb thicknesses also decrease
through this period, so afternoon high temperatures are expected 
to come down to near normal, hopefully providing some relief from 
the excessive heat the past several days. By the end of the week, 
models bring a weak, inverted mid-level trough and upper-level
closed low westward into the Western Gulf of Mexico, which may 
bring an increase of moisture and rain chances for this weekend.

MARINE (Now through Sunday): Hazardous marine conditions persist 
at least through Sunday morning.  Pressure gradient between a high 
over the SE U. S. and low-pressure over the continental interior 
will continue to drive fresh SSE winds.  A Small Craft Advisory 
(SCA) for Winds is in effect from 10 AM to 7 PM today on the Laguna 
Madre.  Current SCA for the Gulf has been extended through 7 AM on 
Sunday, as persistent SE fetch is beginning to build swell, along 
with the locally generated wind waves.  Seas on the outer Gulf 
waters may reach 8 ft. tonight.  Gradient weakens a little on 
Sunday, but seas remain elevated.  Expect Exercise Caution on the 
Laguna and SCA for the 20-60nm waters again, at a minimum.

Sunday night through Friday: As the 500mb trough axis moves east
into the Eastern U.S., the associated surface gradient will begin
to weaken and marine conditions should begin to improve across the
Western Gulf of Mexico. Advisory-level winds and seas may linger 
into Monday, but they should improve by Tuesday and Wednesday. 
Modest low-level moisture and weak mid-level flow across the 
marine areas may be enough for some isolated showers and storms. 
Rain chances increase next weekend with an upper-level trough 
moving westward towards the Lower to Middle Texas Coast.

&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...Heat Advisory until 7 PM CDT this evening for TXZ248>255-353.

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

     Small Craft Advisory until 7 AM CDT Sunday for GMZ150-155-170-
     175.

&&

$$

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HTTP://WEATHER.GOV/RGV

Short Term Update...Frye-55