Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 302338 AAA

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
638 PM CDT Sat May 30 2020

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


.AVIATION...Multi-layered cloud decks and light winds prevail
across deep south Texas this evening. BRO radar indicates some
ongoing convection, mainly west of the RGV Aerodromes, moving
westward across the western portions of the CWA. Otherwise, VFR
conditions are expected tonight into Sunday morning with VCSH
possible at times. Rain chances increase by mid-morning with the
best opportunity for convection between 17z to 22z at BRO and HRL
and 18z to 23z for MFE. Added a PROB30 group to indicate the best
times for convection on Sunday. Otherwise, VFR conditions and
generally light northeast to east winds are expected through the
period. However, brief MVFR/IFR conditions and gusty winds will be
possible in convection.


.PREV DISCUSSION... /issued 242 PM CDT Sat May 30 2020/

SHORT TERM (Now through Sunday Night): The 500mb low has stopped
moving south and is currently spinning over NC Mexico (centered over
Zacatecas/San Luis Potosi). A stationary front off the coast has
dissipated however a low pressure trough is analyzed over the
Western Gulf with light northeast-north winds west of the trough.
The southern extent of the 500mb low and sfc trough somewhat removed
from the Lower Texas coast are likely factors in reducing the areal
coverage of pops  thus far today. Isolated convection is beginning
to fire across all areas of the CWA with this trend likely to
continue the remainder of the afternoon with peak heating and
greatest instability over the next few hours.

Have no doubts that rain/convection chances will ramp up later
tonight and Sunday with deterministic models showing the mid-level
low beginning to move north.  As this move takes place moisture
transport/advection increases with pwats increasing from morning
minimums of 1.7 inches to 2 inches or greater Sunday afternoon. This
tropical moisture emanates from the Bay of Campeche and could
possibly tap some added moisture from Invest 91E just south of the
Gulf of Tehuantepec.  Mid-upper divergence increases over NE Mexico,
S Texas and the Western Gulf of Mexico with 500-250mb layer
southerly winds maxing at 45-60kts Sunday. Convection may favor
lining up along the surface trough over the Gulf with best rain
chances and highest rainfall total along the coastal counties.
Surface high pressure over N TX and Oklahoma to expand eastward
allowing for sfc-700mb winds to veer east possibly edging the West
Gulf trough closer to the coast which may result in potentially
higher rainfall amounts. At this time 1-2 inches are possible with
locally higher amounts of up to 4 inches in the east and 1/2 to 1+
inches in the west.

Temperatures continue a few degrees below normal for tonight and
Sunday with conditions remaining rather humid.

LONG TERM (Monday through Saturday): The 500mb low is expected
to slide west across northern Mexico and generally rotate around
the building mid-level ridge of high pressure developing across
the south central US. A system developing across Central America
slowly takes shape into the southwestern Gulf of Mexico and drops
model confidence a bit beyond Wednesday and into next weekend.
There should be plenty of tropical moisture advecting north
through the week, with surface high pressure in control across the
eastern Gulf of Mexico, continuing light easterly to
southeasterly flow.

The best chance of rain remains Monday and Tuesday due to the
strongest upper level support, with more diurnally driven or
seabreeze initiated chances Wednesday through Saturday. PWAT
values remain high between 1.8 to 2.1 inches, especially along the
coast, Monday through Wednesday. The bulk of the rainfall will
reside along the coast and RGV and may be locally heavy at times,
especially Monday into Tuesday. Temperatures continue below
normal, into the upper 80s and gradually warm back toward normal.
Again, the end of the long term could look a bit different
depending on what happens in the southwestern and western Gulf.

Marine (Now through Sunday Night): Low pressure trough just east
of the lower Texas coastal waters maintains a light northerly
flow tonight. As surface high pressure current over North Texas
and Oklahoma extends east Sunday and Sunday night winds to veer
East to southeast remaining light Sunday becoming moderate Sunday
night. Showers and thunderstorms to increase in coverage late
tonight with numerous activity Sunday.

Monday through Saturday: High pressure continues across the
eastern Gulf of Mexico, keeping generally light easterly to
southeasterly winds across the lower Texas coast through the long
term period. A system developing across Central America slowly
takes shape into the southwestern Gulf of Mexico late this week or
into next weekend. The combination of continued easterly flow and
low pressure into the southern Gulf could build seas into next
weekend. The chance of showers and thunderstorms continues each
day, with the strongest or heaviest storms likely on Monday and




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