Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 231907 AAB
AFDBRO

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
107 PM CST Wed Jan 23 2019

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

&&

.AVIATION...VFR conditions have finally developed for all
terminals of Deep South Texas this afternoon. Winds are still a
bit gusty with some locations hitting 25-30 knots. This will
gradually improve around sunset. As we decouple, winds will become
light and variable. As mentioned, we are currently VFR and we
expect to remain VFR through this cycle.

&&


PREV DISCUSSION... /issued 441 AM CST Wed Jan 23 2019/

SHORT TERM (Today through Thursday): A cold front advances through
Deep South Texas this morning as a mid-level trough settles eastward
across the CONUS. A pre-frontal trough of low pressure out ahead of
the cold front has allowed widely scattered light rain to work into
a few western and northwestern zones overnight. Expect rain chances
to pick up slightly across the northern ranchlands and coastal
counties as the front pushes through, likely drying out from west to
east with the frontal passage. Any rainfall looks to remain light.

The flip side of strong southerly winds yesterday turns northerly
behind the front into the early afternoon hours, with a short fused
Wind Advisory now in effect across coastal counties. Advisory will
likely need to be trimmed to immediate coast near mid morning, with
strongest winds remaining along the shoreline and offshore.
Dewpoints behind the front drop into the 20s and 30s, creating an
elevated concern for erratic fire behavior or wildfire growth until
winds begin to decrease later this afternoon into this evening. A
Rangeland Fire Discussion has been issued for all of inland Deep
South Texas into this afternoon. Burning of any kind should be
avoided.

Temperatures prior to the front in the low 70s will fall into the
low and mid 50s by mid to late morning. Afternoon high temperatures
rebound into the upper 50s in the ranchlands and possibly low 60s in
the RGV. With clearing skies and calming winds, evening and
overnight temperatures will drop steadily into the 30s across the
board. Traditionally cooler spots, like Zapata and Armstrong, could
even dip toward freezing overnight for a short period. Abundant
sunshine with more zonal flow aloft and southeasterly surface winds
will allow Thursday highs to approach the upper 60s and low 70s.

LONG TERM (Thursday Night through Tuesday): A very large and deep
500 mb trough axis will remain carved out over most of the lower
48 states from late Thurs into the upcoming weekend. Several weak
vortices will rotate around the base of this trough axis
throughout late Fri/early Sat. This will maintain overall temps
close to late January climo for the RGV with pretty limited
moisture levels persisting through Fri Night. An onshore low level
flow will then push the atms moisture levels back up throughout
the day Sat as a stronger 500 mb trough axis digs across the
Desert SW/TX and northern Mexico Sat and Sun. The approach and
passage of the short wave will increase the PVA over the region.
In addition, the passage of this trough will enhance some coastal
surface troffing along the lower TX coastline late Sat/Sun which
will boost up the conv chcs during the weekend. This 500 mb
trough axis will push offshore of the Deep South TX coastline
late Sun which will shut down the coastal surface troffing and
will shift the better moisture values offshore. A series of 500 mb
short waves will then dig into the central Plains states late
Mon/early Tues of next week. This will push a pretty strong but
dry cold front through the region Mon Night resulting in
increasing CAA Tues/Wed.

Both the ECMWF and GFS 500 mb fields are in pretty good agreement
through Day 7/8 so overall confidence in the longer range forecast
wording is above average. The GFS/ECMWF forecast temps are in
good agreement through Day 7. The longer range forecast pops
differ a bit in overall timing for Sat/Sun with the ECMWF holding
onto the pops into Sun a bit longer than the GFS.

MARINE (Now through Thursday): Cold front sweeps through the
coastal waters by mid morning with strong northerly winds in tow.
Gale force winds and gusts are expected into this afternoon, with
Gale Warnings in effect until Noon for the Laguna Madre and 6 pm for
all Gulf of Mexico waters. A Small Craft Advisory for Winds is in
effect for the Laguna Madre this afternoon. Winds and seas begin to
improve this evening and tonight, with small craft hazards likely
continuing for Gulf of Mexico waters. Thursday will see continued
improvement as much lighter winds begin to shift southerly once
again.

Thursday Night through Sunday Night: Surface ridging over the Gulf
Coast region will maintain a light to moderate onshore flow
pattern through Sat. The strengthening surface coastal troffing
expected this weekend may push the winds and seas up close to SCA
levels from late Sat into Sun.

Fire Weather...Have issued a Rangeland Fire Discussion concerning
potential erratic fire behavior and wildfire growth late this
morning into this afternoon. Winds at 20 feet behind the front
increase and persist at 15 to 20 mph into this afternoon while
relative humidity values drop into the 20s across much of Deep South
Texas. Any rainfall overnight or with the front have been very light
and would have little effect on cured fuels. Winds continue to
diminish into this afternoon, effectively ending any fire weather
headlines, while more dry air filters into the region. Light winds
are expected on Thursday as well, with continued dry air. Red Flag
Warning criteria will likely not be met today and unlikely for
Thursday. Burning of any kind is strongly discouraged.

&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...None.
GM...Small Craft Advisory for winds until 6 PM CST this evening for
     GMZ130-132-135.

     Gale Warning until 6 PM CST this evening for GMZ150-155-170-175.

&&

$$

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