Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 222342 AAA
AFDBRO

Area Forecast Discussion...UPDATED
National Weather Service BROWNSVILLE TX
642 PM CDT SUN MAY 22 2016

.DISCUSSION...Updated for latest /00z/ aviation discussion below.

&&

.AVIATION...In general, same forecast different day. With the
expectation that convection well east of the Lower Valley
terminals will remain far enough offshore that boundaries will
have little to work on well after sunset, have generally
maintained the current forecast with just minor tweaks to ceiling
(a little lower) and wind (also a little lower) based on latest
GFS-20 soundings as well as current low level winds which are at
or below 15 knots on the Brownsville release.

A pocket of LIFR to VLIFR visibility dropped onto the Harlingen
field early this morning, and while that can`t be ruled out again
tonight don`t have the confidence to make a highly localized by
highly influential forecast for early morning landings this time
around. Instead, gave a nod and dropped to 2 statute miles for a
four hour window around daybreak.

Otherwise, southeast gradient increases just a hair on Monday
which should produce a little more gustiness by afternoon. As for
cloud cover, today was more broken than scattered and based on
persistence and Monday`s time-height cross sections elected to go
broken for prevailing with TEMPO scattered conditions, all VFR.
The continued advection of whatever is left from spring agricultural
burning in Mexico and Central America will keep plenty of haze
around, but expect visibility after mixing begins to once again
rise to 8 statute miles or so.
52/BSG

&&

.PREV DISCUSSION... /issued 235 PM CDT SUN MAY 22 2016/

SHORT TERM (Tonight through Monday Night): Generally a more tranquil
period during the next 36 hours as H5 ridge dominates Texas,
deflecting systems into the Central Plains. A few showers trying to
develop ATTM along the weak seabreeze, fueled by still ample sfc
moisture. This is being held back from significant development by
dry capping air above H7, so any showers that do form this afternoon
will be brief. Moisture decreases overnight tonight aloft, further
solidifying the cap. Have kept out PoP chances tonight and tomorrow
as a result. Temperatures tonight only fall to the upper 70s as
summertime humidity becomes entrenched in the region. Highs tomorrow
are a reasonable blend of models, sticking near the current
temperature trends from the past several days, reaching a degree or
two above normal.

LONG TERM (Tuesday through Sunday): At the beginning of the
period, strong upper level high pressure will be centered over
west central old Mexico with a ridge axis extending north-
northeast across northeast old Mexico/southwest Texas. The upper
ridging will continue to keep a lid on any shower/thunderstorm
development across deep south Texas as noted at the end of the
short term period. At the same time, strong subsidence associated
with the upper ridging will bring somewhat higher
heights/thicknesses for higher temperatures that will already have
been at somewhat above normal values for the preceding day or two.
This will simply lead to hot and humid conditions. Precipitation-
free, as well as hot and humid, conditions with above normal
temperatures will continue into Wednesday as the upper high to our
south transitions to east central old Mexico with the extending
upper ridge axis moving over the lower Texas coast.

On Thursday, the upper ridge looks to move east of deep south
Texas into the western Gulf of Mexico and begins to break down as
a broad upper trough over the western U.S. begins to slowly dig
southward toward the U.S./Mexico border. Will reintroduce low chances
of precipitation to the forecast for Thursday in the form of sea
breeze induced showers/thunderstorms mainly over the east half of
the forecast area during the day. Low chances of
showers/thunderstorms are then possible Thursday afternoon/evening
across mostly western portions of the forecast area as convection
forms over the Sierra Madre and propogates eastward toward the
valley. Somewhat lower heights/thicknesses will allow temperatures
to cool a little bit on Thursday and settle in around near normal
values...but it will still be hot and humid. Low chances of
precipitation will hang around for all of the Rio Grande Valley
into Friday while temperatures remain near normal as the broad
trough of low pressure over the western U.S. continues to dig
southward.

For Saturday and Sunday, a ridge of high pressure reasserts itself
over northeast old Mexico/deep south Texas once again with
precipitation-free conditions expected. Temperatures will rise to
somewhat above normal values again through the weekend due to the
building high pressure for more hot and humid weather.

MARINE Now through Monday night: Broad sfc high across the
eastern third of the nation will provide a long fetch of
southeasterly flow across the western Gulf. With low pressure along
the lee of the Rockies, flow will remain modest through the next 36
hours, with winds around 15kts. This and the long fetch will
continue to agitate seas, with wave heights of 4 to 5 feet.

Tuesday through Sunday: Small Craft Exercise Caution and/or
Small Craft Advisories are likely to be needed for the Lower
Texas coastal waters through the period to account for strong
winds and rough seas as a relatively tight pressure gradient
remains in place.

&&

.BRO Watches/Warnings/Advisories...
TX...None.
GM...None.
&&

$$

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