Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 140455 AAB
AFDBRO

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
1155 PM CDT Fri Apr 13 2018

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

&&

.AVIATION...Breezy south southeast winds will diminish tonight as
the tail end of a cold front, now moving into south Texas, makes
its way toward and through the CWA in the predawn to near dawn
hours. MVFR ceilings will prevail near the coast until then, with
light, patchy fog. A fairly rapid frontal passage will induce a
wind shift to northwest and north at the TAF sites around 10 to
12z Sunday morning. Brief strong and gusty north winds will
materialize around sunrise behind the front, but will settle down
to breezy north by mid morning and, despite a few showers and
maybe a rumble of thunder immediately along the front, skies will
clear rapidly to sunny by mid day with strong dry air advection.

&&

.PREV DISCUSSION... /issued 705 PM CDT Fri Apr 13 2018/

DISCUSSION...Updated for latest aviation discussion below.

AVIATION...Comms issues currently impacting "longline"
transmission of METAR`s from BRO and MFE. Otherwise, have kept
trends of 18Z TAF issuance largely intact, with just some minor
adjustments to the arrival time of a cold front at the Rio Grande
Valley aerodromes. Prior to that, expecting MVFR CIG`s to develop
at all terminals by around 04Z, lowering to IFR at BRO (and
possibly HRL) after midnight, per MOS and SREF guidance. Light
rain showers may accompany the frontal passage. VFR with gusty NNW
winds should prevail for the remainder of the daylight hours on
Saturday beyond about 15Z.

DISCUSSION...Updated for latest marine discussion below.

MARINE...Winds have a been a bit slow to subside on the Laguna
Madre early this evening, so have extended the Small Craft
Advisory for Winds through 10 pm CDT.

PREV DISCUSSION... /issued 301 PM CDT Fri Apr 13 2018/

SHORT TERM (Now through Saturday Night): Gusty south winds
continue across the eastern portions of deep south Texas early
this afternoon due to the interaction of high pressure over the
Gulf and lower pressure inland. Latest satellite imagery and
surface observations indicate sunny skies and very warm to hot
temperatures, especially across the west, as dry line moves across
the CWA. Inland temperatures will continue to climb into the 90s
across the area through late this afternoon. The approach of a dry
line and then a cold front later today from upstream will allow
the surface winds will veer to southwest or west in those areas
through late afternoon. Winds will tend to decrease area wide this
evening, between the retreating Gulf air mass and the approaching
cold front.

The cold front is expected to move into the northern ranchlands
after midnight and off the lower Texas coast around dawn. Isolated
to scattered showers and a rumble of thunder will be possible mainly
along the front after midnight tonight through late Saturday
morning. The Storm Prediction Center /SPC/ has the extreme northern
ranchlands under a marginal risk of severe thunderstorms for tonight
with most of deep south Texas in a general thunderstorm area. The
main threats from any thunderstorms that develop tonight will be
small hail and gusty winds. Some showers may linger over the Gulf
waters through Saturday afternoon. Low temperatures tonight will be
in the 60s under mostly cloudy skies. Slightly cooler and much
drier air will move into the region on Saturday. High temperatures
Saturday will be in the lower 80s, with clearing skies by late
morning to early afternoon. Relative humidity values will crash
Saturday afternoon, with values in the 20 percent or less range
for most areas away from the coast. See the fire weather
discussion below for concerns there. Temperatures will be well
below normal across the area Saturday night under clear skies. Low
temperatures are expected to fall into the 40s inland and into
the low to mid 50s along the Rio Grande river and near the
beaches.

LONG TERM (Sunday through Friday): 500mb ridge across the western
United States Sunday will provide subsidence across south Texas
through the rest of the weekend into early next as the upper level
ridge moves eastward across the central U.S. Monday. At the
surface...surface high pressure across the central U.S. Monday will
move eastward Tuesday as surface low pressure develops across the
lee side of the Rockies. This will provide breezy to windy
conditions across the Rio Grande valley Tuesday. A weak cold front
is progged to move into central Texas Wednesday and moisture is
expected to increase across south TX Wed night into Thursday as the
front stalls north of the CWA. This will provide a slight chance of
showers and thunderstorms...mainly across the northern
ranchlands...Thursday and Friday.

MARINE (Now through Saturday Night): Buoy 42020 reported south-
southeast winds around 19 knots gusting to around 23 knots with
seas slightly under 5.9 feet with a period of 7 seconds at 03
CST/09 UTC. Marine observation platforms across the Laguna Madre
indicate south winds continue between 20 to 25 knots with higher
gusts. A tight pressure gradient along the coast and over the
adjacent Gulf waters this afternoon will maintain breezy south
winds with ongoing small craft advisory conditions. Elevated winds
and rough seas should continue tonight on the Gulf waters, but
winds should settle down late in the evening. Have extended the
Small Craft Advisory until 1 am for the Gulf waters due to
elevated seas. A cold front will bring strong north winds and
advisory conditions to the Gulf waters Saturday morning around
dawn to mid day, and possibly on the Laguna Madre as well.

Sunday through Wednesday...Light northwest winds will prevail
across the coastal waters Sunday as surface high pressure settles
across the lower Texas coast Sun afternoon. Winds will veer to the
southeast and increase as the surface high pressure across the
western Gulf of Mexico moves eastward and the pressure gradient
increases across the lower TX coast. Light to moderate southeast
winds will prevail across the western Gulf Monday as a result. The
pressure gradient is expected to continue to increase Tuesday
with low pressure developing along the lee side of the Rockies.
Winds will increase and veer to the south and southeast Tuesday
before weakening Wednesday as a weak cold front moves into central
TX Wed afternoon. Small craft advisories may be needed for the
offshore waters Mon night and will likely be needed for all of
the coastal waters Tuesday and offshore waters Tues night.

FIRE WEATHER (Saturday)...Dry air will continue to move into the
region from the west this afternoon, and particularly Saturday
afternoon in the wake of a Saturday morning cold front. Though not
quite dry enough nor strong enough winds this afternoon, north
winds at 20 feet behind the cold front will be around 15 mph with
relative humidity values in the mid teens and with cured fuels,
reaching elevated to critical fire weather criteria. A Fire
Weather Watch remains in effect for the counties west of the I69E.

&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...Fire Weather Watch from 11 AM CDT Saturday through Saturday
     afternoon for TXZ248>250-252-253.

GM...Small Craft Advisory for winds from 6 AM to 7 PM CDT Saturday
     for GMZ130-132-135.

     Small Craft Advisory until 7 PM CDT Saturday for GMZ150-155-170-
     175.

&&

$$

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