Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 270606 AAC
AFDBRO

Area Forecast Discussion...UPDATED
National Weather Service BROWNSVILLE TX
106 AM CDT FRI MAY 27 2016

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

.AVIATION...Satellite images and surface observations indicate
mostly high clouds across the CWA late tonight. Ceilings were near
11000ft at KMFE. Expect MVFR conditions to develop early Friday
morning as low to mid level moisture remains high across portions
of the Rio Grande valley allowing low clouds to develop. Isolated
to scattered showers are expected to develop across southern and
eastern portions of the CWA the rest of tonight as a weak upper
level shortwave trough moves eastward across the area. VFR
conditions will prevail Friday as westerly winds aloft bring some
drier air into the western portions of the CWA FRI afternoon.
&&

.PREV DISCUSSION... /issued 921 PM CDT THU MAY 26 2016/
DISCUSSION...00Z sounding indicated a strong cap over Deep South
Texas this evening and the current LAPS data confirms this with
the cap strengthening over the last few hours. Elevated cape will
likely wane as evening cooling continues. Isolated thunderstorms
over the Sierra Madre are diminishing as they move towards the Rio
Grande River and into the more stable air mass. Lightning activity
is decreasing with only a few anvil showers impacting the Western
Ranch lands. With this mentioned have reduced the areal coverage
and lowered rain chances for the overnight period. Everything else
remains intact.

Marine...will let the sca for the Laguna expire at 10 pm but
continue for offshore waters with seas exceeding 7 feet and winds
still hovering around 20 knots.

PREV DISCUSSION... /issued 639 PM CDT THU MAY 26 2016/

DISCUSSION...Updated for latest aviation discussion below.

AVIATION...low level inversion in place strengthens overnight
with low clouds developing and spreading northwest. MVFR cigs to
develop later this evening and into the overnight period
persisting through mid morning Friday. there is a low chance of
convection moving into the region from the mountains of Mexico
overnight but with the strengthening inversion showers and
thunderstorms will be isolated at best and might not impact any of
the air terminals. KMFE will have the best chance to see some
convection with confidence below average. strong surface winds
slowly diminish this evening with occasional gusts to 23 knots
before midnight. south to southeast winds increasing once again
friday with gusts up to 25 knots.

PREV DISCUSSION... /issued 255 PM CDT THU MAY 26 2016/

SHORT TERM (Tonight through Friday Night):
500mb trough and upper low is centered over the 4 corners with
subtropical high centered over southern Mexico. a deep
southwesterly flow to persist across South Texas through Friday
allowing for weak impulses to traverse the region. High pressure
to build northward into Deep south Texas Friday night as the upper
trough lifts northeast.

Rain chances continue on the low end of chance the next 24-36 hours
as the trough axis remains to the west of the area. As for strong to
severe thunderstorms later today and tonight the atmosphere has
become very unstable with SB capes between 4-5K j/kg...however there
remains a moderately strong cap in place over the region. The cap
will have a tendency to weaken as the daytime heating continues and a
weak disturbance approaches the rio grande plains later this
evening. With this said will maintain the 20-40 percent pops for
tonight with highest readings in the west and lower chances in the
east. SPC is maintaining a marginal risk of severe thunderstorms for
the western third of the CWA so can not rule out one or two storms
approaching severe limits if the cap weakens enough.  For Friday the
entire CWA is in a marginal risk as the upper trough swings through
the state. most of the significant energy is depicted to move north
of our CWA so the lower end pops still looks good at this time.

Breezy to windy conditions continue into the evening before modest
decoupling takes place late tonight. Surface low pressure over the
Southern and Central Plains continues to provide a strong pressure
gradient along the Lower Texas Coast. The strong southerly flow to
resume Friday with another windy day as gusts approach 30 mph along
the coastal counties. Temperatures to continue near or slightly
above normal with the multi-layered clouds decks. The wind tonight
coupled with the clouds will make for another muggy and much above
normal overnight lows with lower 80s along the coast and the Rio
Grande Valley.

LONG TERM (Saturday through Thursday):Brief H5 ridging will build
across Deep South Texas during the Day Saturday as the Friday
trough eject northeastward. While this will take most of the
instability, cannot rule out a small shower or two during the
afternoon during peak heating along the seabreeze. This ridging
will be short-lived, as the next trough drops down the Pacific
Coast, with southwesterly flow aloft bringing in smaller impulses.
While the timing of the individual impulses cannot yet be pinned
down, the conditions are prime for any of these impulses to spark
showers and thunderstorms. These storms will have ample moisture
available, as PW reading are forecast to be near 2 inches through
most of the upcoming week. Have raised forecast back to chance
thunderstorms, mainly focusing on each afternoon during peak
heating, but storms could conceivably fire anytime in this humid
regime. Daytime highs will reach into the 90s each day, with lows
only falling to the upper 70s.

MARINE:
Now through Friday: Deepening low pressure over the
central and southern plains has allowed for the pressure gradient
along the Lower Texas coast to strengthen. Winds have increase to
small craft advisory levels over the Laguna this afternoon and are
just shy of criteria offshore. The gradient to remain strong through
Friday night until an upper level trough moves to the east. Small
Craft advisories are posted for the Laguna through 10 pm and for the
offshore waters through 7 pm Friday.  Advisories for the Laguna may
be needed once again Friday late morning and afternoon.

Saturday through Monday: Marine conditions will begin to slowly
improve Saturday as the sfc low in Kansas weakens and lifts to the
NE. This will allow the pressure gradient to relax, bringing
winds down to 10 to 15 knots each day. The long SE fetch across
the Gulf remains through the weekend, so sea heights will slowly
fall into early next week, not reaching 4 feet or less until
Monday.
&&

.BRO Watches/Warnings/Advisories...
TX...None.
GM...Small Craft Advisory until 7 PM CDT this evening for GMZ150-155-
     170-175.
&&

$$

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