Area Forecast Discussion
Issued by NWS Brownsville, TX
FXUS64 KBRO 251203
Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
603 AM CST Sat Feb 25 2017
.DISCUSSION...Updated for latest aviation discussion below.
.AVIATION...Drier air filtering into the RGV from the north and
northeast will maintain VFR conditions throughout most of the
upcoming TAF period. The low level flow will become more E-SE
later today into tonight which will allow the low level dewpoints
to increase steadily. This will allow some lower level cld decks
to form up later this evening and tonight possibly reducing the
ceilings down to MVFR levels.
.PREV DISCUSSION... /issued 422 AM CST Sat Feb 25 2017/
SHORT TERM (Now through Sunday): The dry cold front has finally
cleared through the RGV with all of the surface obs from around
the region indicating light northeast winds early this morning.
The airmass moving in behind this front will usher in cooler and
drier air over the region today finally bringing an end to the
current record/near record heat that has been impacting the RGV.
The relief from the heat will be somewhat short lived as the E-SE
low level flow will return pretty quickly later tonight and
Sunday which will allow the WAA to increase pretty quickly. The
low level dewpoints will also be on the increase as the flow
returns from the Gulf of Mex allowing values to reach back into
the 60s by Sun across the eastern counties.
The short term temp guidance is in decent agreement through Sun with
the GFS MAV going with the coolest numbers through tomorrow with the
NAM and ECMWF showing better agreement on a slightly warmer
solution. Will opt for a blend of the NAM and ECMWF guidance since
the GFS appears to be the odd model out.
Enough low level moisture may return on Sun to interact with some
weak 500 mb PVA to allow some isold showers to potentially form
tomorrow. Will opt to maintain some 10-20% pops on Sun as the
NAM/GFS and ECMWF guidance all maintain this trend.
LONG TERM (Sunday Night through Friday): The forecast period
begins with a building 500 mb ridge across the eastern Gulf of
Mexico. The mid level ridge moves over the Central Gulf and flattens
by Midweek. A 500 mb trough moving over the High Plains into the
Central Plains will push a cold front across Deep South Texas late
Wednesday. Slight differences continue between the GFS/ECMWF and
timing of the front remains uncertain. A near zonal flow aloft
prevails Thursday then the mid level flow backs to the west-
southwest by Friday. An overrunning patten develops late Thursday
and continues into Friday. Again, differences continue between
the GFS/ECWMF with pops late in the period.
The pressure gradient relaxes on Monday as a surface trough moves
into the mid Valley. This feature will support lighter winds and
building heat. High temperatures Monday will range from the 80s
along the coast to the low to mid 90s inland. Tuesday should the
hottest day of the week with high temperatures in the 90s away from
the beaches, some triple digits are possible along the river across
the upper Valley. Overnight low temperatures will range from the
lower 70s along the coast to the mid 60s across the ranchlands. A
cold front will approach and move through the region by late
Wednesday. Due to model differences, high temperatures could still
reach the lower 90s across portions of the Mid and Upper Valley
before the front moves through. Slightly below to near normal
temperatures will prevail across the area Thursday and Friday with
abundant cloud cover and increasing rain chances. Will maintain the
previous forecast rain chances Thursday through Friday. High
temperatures Thursday and Friday will generally remain in the 70s
with ovenight low temperatures in the 50s across the west and
lower 60s near the coast.
MARINE (Now through Sunday): Buoy020 currently reports a NNE wind
of 21g25kts with swells around 6 feet. Stronger NE surface winds in
the wake of the dry front now pushing south will linger across
the lower TX Gulf waters this morning keeping the Gulf waters up
near SCA levels. Accordingly have extended the SCA for the Gulf
through Noon today. The PGF will then start to decrease later
today with a moderate E-SE flow returning later tonight into Sun.
The E-SE flow may strengthen enough on Sun to possibly reach near
SCEC levels. However strong SCA conditions are not expected after
Sunday Night through Thursday: Moderate winds and seas will continue
across the coastal waters Sunday night. Marine conditions improve
Monday and Tuesday as the pressure gradient relaxes along the Lower
Texas coast. Winds will shift to the north/northwest and increase
with seas building Wednesday night into Thursday due to the passage
of a cold front. Small craft should exercise caution condition will
likely develop by Thursday across all or portions of the Lower Texas
GM...Small Craft Advisory until noon CST today for GMZ150-155-170-175.
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