Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 191126 AAA
AFDBRO

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
626 AM CDT Thu Apr 19 2018

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

&&

.AVIATION...Surface observations and satellite imagery indicate a
mix of low to mid level cloud decks across deep south Texas this
morning. Latest surface analysis shows a weak cold front
approaching deep south Texas. A mix of MVFR/IFR conditions will
continue across the area through mid morning. VFR conditions
expected to return late this morning into the afternoon as
northeast winds increase. MVFR ceilings may develop across the
Rio Grande Valley by late in the period.

&&

.PREV DISCUSSION... /issued 432 AM CDT Thu Apr 19 2018/

SHORT TERM (Today through Friday): Latest surface analysis shows a
weak cold front approaching deep south Texas. Satellite imagery and
surface observations indicate mostly cloudy skies with some patchy
fog across the region this morning. The front will slowly move south
across the area this morning and push further southward this
afternoon. Moisture will continue to pool ahead and along the
approaching front. The 00z BRO sounding indicated a Precipitable
Water value of 0.97 inches. The combination of increasing low level
moisture and the lift associated with the front will support
isolated showers across the area today. High temperatures today will
range from the mid 70s along the beaches to the low to mid 80s
inland. Mostly cloudy skies are expected tonight with low
temperatures in the 60s. Isolated showers will be possible across
the far western portions of the area tonight. Isolated showers and
thunderstorms and slightly warmer temperatures are expected on
Friday as a warm front moves northward. High temperatures Friday
will be in the 80s, except for the mid 70s at the beaches.

LONG TERM (Friday Night through Wednesday): A large 500 mb closed
low from the Desert Southwest will push east towards the central
and southern Plains states this weekend. As this closed low moves
steadily eastwards this weekend, a mild cold front will sag into
the RGV early Sun resulting in some light northerly surface winds
over the region. The northerly surface flow Sun will be pretty
short lived as the 500 mb closed low makes steady progress to our
east which will allow the low level flow to shift around back from
the E to SE on Mon. After the closed 500 mb moves on to the east
weak ridging will build over the region on Tues and Wed.

Moisture return over the RGV is pretty limited ahead of the
approaching 500 mb closed low with the best moisture values
located to our north closer to the center of the closed low.
However enough moisture may move into the region interacting with
the divergence aloft ahead of the closed low to allow a small
window of conv this weekend. So will maintain some mention of low
end pops.

After the passage of the 500 mb low, overall moisture values
remain pretty low through Day 7, especially in the GFS. However
the ECMWF shows more moisture advecting into the region late
Tues/Wed. This sudden increase in the moisture and associated pops
in the ECMWF looks questionable and will maintain only a mention
of slight chc pops for the time being and will see how future runs
of both the GFS and ECMWF try to deal with this scenario.

For temps, the ECMWF is taking a warmer bias versus the GFS
through Day 7. The last few runs of the GFS MEX MOS temps shows
this model nudging a bit closer to the warmer ECMWF numbers. So
will maintain a general model blend for temps through Wed.

Overall confidence in the longer range forecast wording is above
average at this time.

MARINE: (Now through Friday): Latest observation from Buoy 42020 as
of 320 am CDT indicated East winds around 6 knots and seas around 4
feet. A weak cold front will move into the lower Texas coastal
waters this morning. This will allow northeast winds to increase to
Small Craft Exercise Caution levels later this morning into the
afternoon. The pressure gradient will weaken tonight resulting in
winds diminishing. Moderate east to southeast winds and moderate
will prevail on Friday as a warm front advances northward.

Friday Night through Monday Night: With the approach of the
large 500 mb closed low from the west, a moderate tyo strong
surface low will develop across the central portion of the
country. This will strengthen the PGF along the lower TX coastline
possibly resulting in some maringal SCEC/SCA conditions for
either the Bay or Gulf waters Fri Night/Sat. The PGF will then
weaken as a surface cold front reaches and moves through the
region late Sat into Sun. Light to moderate N-NE surface flow will
move in behind the fropa Sun. However the PGF in the wake of the
frontal passage appears to remain weak enough maintaining winds
and seas below SCA levels for Mon/Mon Night.

&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...None.
GM...None.
&&

$$

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

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