Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 160030 AAA

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
630 PM CST Wed Nov 15 2017

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


.AVIATION...The atmosphere remains marginally primed for stratus
and some patchy fog to form overnight. VFR conditions to prevail
through the evening with stratus starting to form after midnight.
A weak cold front over Central Texas moves into South Central
Texas by early Thursday allowing for winds to become light and
variable and gulf moisture to pool south of the front. This should
lead to MVFR cigs and light fog formation initially along the
281/I69C corridor then spreading near the coast around sunrise.
Conditions could worsen an hour either side of sunrise with low
probabilities of IFR cigs/vsby when winds are lightest. With light
to calm winds through the morning locations that have lower
ceilings will be slow to break out until southerly winds begin to
increase. VFR conditons should prevail through the afternoon with
broken ceilings at around 4k feet.


.PREV DISCUSSION... /issued 253 PM CST Wed Nov 15 2017/

SHORT TERM (Tonight through Thursday Night):

500 mb ridging will remain in entrenched over Mexico and the
western Gulf coastline throughout the end of the workweek. This
will maintain a pretty stable atms in place over the RGV limiting
the conv potential somewhat. Some deeper layer moisture and
instability will move into the coastal regions of the RGV which
may interact with some daytime heating to increase the chcs of
some isold showers tomorrow. Accordingly will maintain some slgt
chc pops for Thurs.

Otherwise above normal temps and the potential for fog will be the
main forecast issues throughout the short term period.  The
combination of boundary layer moisture values and light surface
winds will likely set the stage once again for late night/early
morning fog for much of the region especially across the northern
and western regions. Will include a mention of this in the upcoming
forecast update but will leave out any mention of dense fog as
numerical guidance tends to reflect only a pretty small window for
fog formation.

Because of the persistent 500 mb ridging in combination with the
pretty strong diurnal heating effects will lean on the high side of
the short term temp guidance especially for tomorrows highs. Min
temps will be a general blend of the NAM/GFS and ECMWF numbers.

LONG TERM (Friday through Wednesday):

Upper level ridging will continue for the beginning of the long
term period. With a southerly return flow, expect continued above
average temperatures right through the first part of the upcoming
weekend. A cold frontal boundary will begin to drop southward
toward the Rio Grande Valley by late Saturday and especially early

As the front passes, mid and upper levels will be somewhat dry so
POPs will remain limited at the moment as the front or prefrontal
trough moves through. Winds will veer northwesterly and
eventually northeasterly behind the frontal boundary. Temperatures
will respond and Sunday/Monday will be around (or perhaps
slightly below average?).

Globals diverge as we head toward Thanksgiving. Both ECMWF and GFS
show another strong frontal boundary developing upstream, however,
evolution and synoptic features are not well resolved at this
time. ECMWF is a little less progressive as a cutoff low drops
southward through the TX Hill Country where GFS develops a surface
low right along the natural baroclinic zone across the northwest
GoMex. Regardless, this period looks to be around or slightly
below average Temperature wise and some intermittent shower
activity will be possible.



(Tonight through Thursday Night):

Surface ridging holding in
place over the southeastern States throughout the short range period
will maintain a pretty persistent onshore southeasterly low level.
This will keep moderate Gulf swells and pretty low Bay conditions.
No SCA conditions expected through Thurs Night.

(Friday through Tuesday Night):

Marine conditions will start off rather benign with only light to
moderate winds and seas. However, as a cold frontal boundary
surges southward, winds and seas will build. Small Craft
Advisories will be probably be needed Sunday and Sunday night as
winds pick up to 25kt and seas increase to 8 ft or higher. There
will be some improvement early next week, however, with a large
surface fetch across the Gulf, think seas will remain moderate.




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