Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 092343 AAA
AFDBRO

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
643 PM CDT Sun May 9 2021

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

&&

.AVIATION...VFR conditions will prevail through most of the night
with south to southeasterly winds backing off slightly. MVFR
ceilings will develop early Monday morning and last only for a few
hours before lifting back to VFR for the rest of the TAF period
as southeasterly winds become gusty again.

&&

.PREV DISCUSSION... /issued 221 PM CDT Sun May 9 2021/

SHORT TERM (Now through Monday Night): A surface trough over
northeastern Mexico is interacting with a surface high off the
Southeastern US coast with windy conditions, especially along
coastal counties, continuing into early evening. A Wind Advisory
remains in effect into early evening for Cameron and Willacy
counties. The surface gradient will weaken a bit this evening into
tonight with winds expected to decrease across the area, though
breezy conditions will continue into Monday evening. A dryline
over western portions of the CWA this afternoon will retreat
westward allowing dewpoint values to rise overnight. This,
combined with southerly winds, will lead to a warm and sticky
night with temperatures falling only into the mid to upper 70s.

On Monday, a midlevel subtropical ridge begins to nudge northward
into the Valley with warm temperatures expected once again. Daytime
highs will reach the triple digits out west with 90s to the east and
80s along the coast. While the temperatures do not stray to far from
seasonal norms, elevated dewpoints will cause heat indices jump into
the 100-110 range across much of Deep South Texas and the Rio Grande
Valley. Monday night, rain and thunderstorm chances will increase
out west ahead of an approaching cold from that will be draped
across central Texas. A midlevel shortwave rotating through South
Texas may be enough to fire off a thunderstorm complex to the west
of the region, drifting into northwestern portions of the CWA
overnight. Monday night temperatures will continue to be warm and
muggy with lows in the mid to upper 70s.

LONG TERM (Tuesday through Sunday): The weather pattern will be
unsettled across south Texas Tuesday through Thursday as a 500mb
trough across the west-central United States Tuesday makes it way
eastward across the southern plains Wednesday and into the east-
central U.S. Thursday. At the surface...a weak cold front will move
into south Texas Tues night and move into the Rio Grande Valley Wed
morning. Both the GFS and ECMWF prog a MCS feature developing north
of the CWA Tues afternoon/evening and propagating the convective
boundary into deep south Texas Tues night. There is a marginal
threat of severe thunderstorms across most of south Texas in the
latest day 3 SPC outlook so will mention strong winds and small
hail with isolated strong to severe storms Tues night. In
addition...will mention heavy rainfall with some of these storms
as rainfall amounts of 1 to 2 inches can be expected with these
isolated strong to severe thunderstorms. Rain chances are expected
to continue Wednesday before diminishing Thursday into Thursday
night but showers and thunderstorms will be mainly elevated as
surface high pressure prevails across the south-central U.S.
Wednesday into Thursday. Low to mid level moisture is expected to
remain relatively high across northeast Mexico Thursday through
the rest of the week into the weekend and this warrants a mention
of a slight chance of rain across portions of the Rio Grande
Valley Thurs night into Friday as a weak 500mb shortwave trough
moves into west Texas Friday. Greater rain chances are expected on
Saturday as the upper level trough moves eastward across
southwest Texas. Some rain chances will linger across the CWA
Sunday but west to northwest flow aloft should provide some
subsidence in the wake of the 500mb shortwave trough.

MARINE (Now through Monday night): Small Craft advisories continue
for the Laguna until 7 pm this evening and offshore waters through
at least 10 pm as moderate to strong southerly winds continue thanks
to a tight pressure gradient. Tonight, the the gradient begins to
weaken slightly though moderate winds will continue into Monday with
seas slowly lowering. SCEC conditions will be likely tonight and
possibly into Monday as winds remain elevated across the coastal
waters.

Tuesday through Friday...Light to moderate southeast winds will
prevail across the coastal waters Tuesday before a weak cold front
moves offshore the lower Texas coast early Wednesday morning.
Winds will shift initially to the north and increase Wed morning
before veering to the east to northeast and diminishing Wed
afternoon. Surface high pressure will build into the northwest
Gulf of Mexico Thursday. Moderate to strong northeast winds will
prevail across the western Gulf of Mexico Thursday. The pressure
gradient should weaken across the lower Texas coast Friday. Expect
light northeast winds across the coastal waters Friday to veer to
the east and increase Fri Night as the surface ridge as the east-
central United States moves eastward.

&&

.PRELIMINARY POINT TEMPS/POPS...
BAYVIEW/PORT ISABEL  76  88  76  87 /   0   0  10  10
BROWNSVILLE          77  90  78  91 /   0   0  10  10
HARLINGEN            77  93  77  92 /   0   0  10  20
MCALLEN              78  96  78  95 /   0  10  10  20
RIO GRANDE CITY      76 100  77 100 /   0  10  20  30
SOUTH PADRE ISLAND   76  80  76  81 /  10   0  10  10

&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...High Rip Current Risk until 8 PM CDT this evening for TXZ256-257-
     351.

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

     Small Craft Advisory until 10 PM CDT this evening for GMZ150-155-
     170-175.

&&

$$

This product is also available on the web at:
HTTP://WEATHER.GOV/RGV

Aviation Update...69-Farris


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