Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 211941

Area Forecast Discussion
National Weather Service BROWNSVILLE TX
241 PM CDT WED SEP 21 2016

.SHORT TERM (Tonight through Thursday Night):  Morning sounding
recorded a PW value of 1.62, but all moisture remains trapped
below 10000 feet. A couple showers have been trying to form this
afternoon in peak heating, but the dry capping air is not letting
showers get vertical development to hold together. Models continue
to show a slight increase in moisture overnight tonight aloft, but
not enough to introduce significant cloud cover, or to let temps
falls below the upper 70s. Conditions will be similar tomorrow,
with best moisture confined close to the sfc, while drier air
remains capping aloft. Some models are somewhat more optimistic in
bringing moisture into the northeastern zones, so have upped
seabreeze possibilities for Kenedy and Brooks counties to near 30
percent, as it will take very little forcing to get showers going
with better moisture. But for most of the region, conditions will
be hot and dry, with temps in the upper 90s and lower 100s.

.LONG TERM (Friday through Wednesday):  The longer range 500 mb
pattern will be dominated by a large and deeply digging trough that
will push across the central portion of the lower 48 states. As this
trough axis digs into the central portion of the country it is
expected to potentially close off over the central plains states
or the upper midwest by next Monday and Tuesday. The strength of
this trough axis and the slowness of its eastward movement will
set the stage for the first fall cold front passage across the RGV
late in the forecast period. Both the ECMWF and the GFS runs
indicate pretty decent moisture advection occurring ahead of this
500 mb trough axis which will likely in better pops late in the
forecast period.

The ECMWF and the GFS both agree in the general shift in the 500 mb
pattern with the ridge across the central plains states being
replaced by the large trough/closed 500 mb low throughout the longer
range period. However the models disagree in the overall placement
of the central plains trough axis/closed low. The ECMWF digs the
trough axis more deeply and further west early next week while the
GFS keeps the trough positioned more northeastwards towards the
Great Lakes region. Despite this difference in the placement of the
500 mb trough the Model temps and pops from both the ECMWF and the
GFS are in relatively good agreement showing a little lower temps
and higher pops for the RGV late in the period.

Will go with a general 50/50 blend of the guidance from both the
ECMWF and the GFS through day 7. Despite the model
to run comparisons of the GFS MEX MOS temps and pops show pretty
good consistency over the last several runs. So overall confidence
in the current longer range forecast is above average at this time.


.MARINE: Now through Thursday night...Marine conditions remain
tranquil as weak pressure gradient continues across the northwest
gulf. Winds will increase slightly starting Thursday evening as
low pressure deepens across the southern Rockies. Winds will
increase to around 15 knots, which will nudge sea swells up to
around 3 feet.

Friday through Monday night...Moderate surface ridging will
persist over the Gulf of Mexico throughout the rest of this week
and the weekend. At this time a cold front looks to move off of
the lower Texas coastline late Monday/Monday night resulting in
moderate north to northeast winds across the bay and gulf waters.
However the PGF after the front will not likely be strong enough
to result in SCA conditions.


.BRO Watches/Warnings/Advisories...


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