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Area Forecast Discussion (AFD)

Issued by Brownsville/Rio Grande Valley, TX (BRO)

FXUS64 KBRO 212339 AAA

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
539 PM CST Mon Jan 21 2019

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

.AVIATION...Winds will be the main challenge in the TAF period.
Breezy winds tonight will become strong tomorrow, and there is a
good chance that a wind advisory will be needed for a period of
time on Tuesday for the BRO and HRL aerodromes. Otherwise, VFR to
MVFR is anticipated through the next 24 hours. 

.PREV DISCUSSION... /issued 229 PM CST Mon Jan 21 2019/ 

SHORT TERM (Tonight through Tuesday Night): 500mb trough across the 
western United States tonight will move eastward Tuesday allowing 
low to mid level moisture to increase across east Texas Tues 
afternoon and across south Texas Tues night as the upper trough 
moves across west Texas. This will allow scattered to numerous 
showers with isolated thunderstorms to develop across the eastern 
portions of the CWA late Tues night before a cold front moves 
through the area early Wed morning. At the surface...the pressure 
gradient will continue to increase across the lower Texas coast 
tonight into Tuesday as low pressure continues to deepen across the 
Texas panhandle before moving northeast across the southern plains 
Tuesday. In addition...a strong low level jet will develop across 
the lower Texas Tues morning. Wind advisories will likely be needed 
for the coastal counties of the CWA tomorrow. Breezy to windy 
conditions will prevail across the rest of deep south TX Tuesday. 
Temperatures will be above normal tonight through Tuesday before 
cooler air arrives early Wed morning with the cold front.

LONG TERM (Wednesday through Monday): Rain chances will lingering
into Wednesday morning as a cold front continues to move off the
lower Texas coast. The best chance of showers will mainly be 
along the coast with some enhancement over the Gulf waters. High
temperatures on Wednesday are expected to remain in the mid to
upper 50s with breezy to windy north winds, especially near the 
coast. Rain chances end during the day from west to east as the 
500 mb short wave passes overhead with dry air filtering into the
region. Low temperatures Wednesday night are forecast to fall 
into upper 30s to near 40 degrees under mostly clear skies. Wind 
chill values may drop into the mid to upper 30s with modest light 
north winds. Surface high pressure spreads across the region on 
Thursday as temperatures slowly recover. A series of weak 
reinforcing surface high pressure systems, Friday morning and 
Sunday morning, will allow cool morning and mild afternoon 
temperatures to persist. High temperatures are expected to be 
mainly in the 60s each day and low temperatures each night should 
generally be in the 40s.

MARINE (Tonight through Tuesday night): Seas were near 3 feet with 
south to southeast winds near 18 knots at buoy020 early this 
afternoon. Strong south to southeast winds will develop across the 
coastal waters tonight as the pressure gradient continues to 
increase with deepening low pressure across the Texas/Oklahoma 
panhandles and high pressure across the eastern United States. Will 
go ahead and issue small craft advisories for the offshore waters 
tonight through Tues afternoon and for the bay waters late tonight 
through Tues afternoon as strong south winds continue across the 
coastal waters Tuesday. Winds should begin to diminish across the 
coastal waters Tues night as the pressure gradient weakens ahead of 
a cold front approaching the coastal bend. Light to moderate south 
winds will prevail across the western Gulf of Mexico Tues night but 
small craft advisories will likely need to be extended offshore for 
high seas. 

Wednesday through Saturday night: Ongoing strong northerly winds
will continue through the day on Wednesday as high pressure builds
into the area. Gusts to gale force will be possible mainly Wednesday
morning in the wake of the cold front. Winds and seas should fall
below small craft advisory conditions by Thursday as surface high
pressure spreads over the northwest Gulf. Modest onshore flow is
expected to prevail through the rest of the period. 

FIRE WEATHER...While 20 foot winds will be increasing to 15 to 25 
knots across the eastern portions of the CWA Tuesday 
afternoon...relative humidity values will range between 50 and 60
percent which is above Red Flag warning criteria so no fire 
weather watch is needed for tomorrow. If relative humidity values 
are lower than currently forecast for Tuesday...then a fire danger
statement may be needed for the coastal counties of deep south 
Texas Tues afternoon.

Models continue to indicated that post frontal conditions on 
Wednesday will be dry, with relative humidity values across inland
areas falling to the 20s Wednesday afternoon. Winds at 20 feet 
over those inland areas are forecast to be in the 10 to 15 mph 
range. These conditions, combined with cured fine fuels, will 
enhance the threat of erratic wildfire behavior and the potential 
for wildfire growth and spread. it's too early to say if Red Flag 
Warning criteria will be achieved; it appears marginal for now, 
but conditions will be monitored.

GM...Small Craft Advisory for winds from midnight tonight to 6 PM CST 
     Tuesday for GMZ130-132-135.

     Small Craft Advisory until 6 PM CST Tuesday for GMZ150-155-170-


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