Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 230333 AAA
AFDBRO

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
1033 PM CDT Sun Oct 22 2017

.DISCUSSION...Updated for aviation and marine discussions below.

&&

.AVIATION...Skies have cleared across McAllen/Miller by mid
evening but continued northeast flow off the still warm Gulf is
keeping dewpoints in the lower 70s for now in the Lower Valley and
pesky MVFR ceilings are likely to hang a bit longer in the
Brownsville and Harlingen areas through midnight or so. Latest
runs of the GFS/NAM eventually showing the drier air winning out
with surface winds finally backing northerly by 07-09Z and that
should clear the clouds away and bring the comfortable dewpoints
in to allow for a comfortable but still mild start to Monday.

Clear skies with light winds for the remainder of the period
through 00Z/October 24.
52/BSG

&&

.MARINE...Initial surge behind "front" is over and winds have
diminished...with Laguna Madre sustained winds in the 10 to 15
knot range with a few gusts just above that. Gulf winds a bit
trickier with no local buoy data available the best guess is an
extrapolation from Buoy 42019 (south of Freeport) with winds
closer to caution range (15 to 20 knots). Seas are more difficult
still as the initial surge there which had neared 9 feet has
dipped below 6 feet. Buoy 42002 250 mile east of SPI meanwhile
popped over 12 feet most recently...likely due to a Gale-force
surge late this afternoon. With direction from the East-Northeast
along with a swell period of 9 seconds expect some residuals to
reach the waters overnight.

Bottom line? Expect 7 to possibly 8 foot seas at least across the
southern leg overnight so advisories hold here. For Laguna Madre,
even if there is a brief surge of drier air from the north between
midnight and 3 AM, don`t expect speeds to be much more than 15
knots. May keep caution wording to be safe but advisory has been
cancelled with this issuance.
52/BSG

&&

.PREV DISCUSSION... /issued 405 PM CDT Sun Oct 22 2017/

SHORT TERM (Tonight through Monday Night): The cold front is just now
arriving into the BKS/HBV areas, with modest northeasterly breezes
in its wake. Precipitation is currently limited to the immediate
front and offshore, but is beginning to be aided by the seabreeze
drifting inland. Shower activity will continue along the front as is
moves southward, reaching near the river right around 5PM. Skies
behind the front are clear, with dry north winds at the surface and
nwy winds aloft, so temperatures will be able to drop considerably
overnight tonight into the upper 50s and low 60s. Monday will be
completely clear, with high pressure in control. Highs will rise
into the 80s, but will be a much drier atmosphere. Another night of
clear skies tomorrow night will good radiational cooling will see
temps fall into the 50 areawide.

LONG TERM (Tuesday through Sunday): The 500 mb pattern over the
lower 48 state will start with a sharp ridge axis over the western
third of the area with deep troffing prevailing over the central
and eastern states. This configuration will continue through Tues
and Wed with the western ridge axis breaking down later this week
as another deep trough axis digs into the central portions of the
country from Thurs on through the weekend. This will maintain a
steady progression of much cooler and drier Canadian airmasses
pushing into the RGV through next weekend. No significant moisture
return is expected until next weekend and will maintain some pops
mainly for the eastern portions of the RGV ahead of the weekend
fropa.

Pretty decent agreement shows up with the ECMWF and the GFS for
temps and pops through next Fri with bigger disagreements showing
up for the weekend mainly for temps with the ECMWF coming in
cooler versus the GFS numbers. This cooler bias is due to the
ECMWF wanting to hold the strong 500 mb trough axis over the
southern Plains states longer than the GFS.

Overall confidence in the forecast wording is above average
through Friday and near average for the weekend.

MARINE (Now through Monday Night): The front is already half way
through the coastal waters, outracing the onshore component.
Winds behind the front have been reaching advisory criteria, so
will be pushing the advisory forward to start now, and continue
into tomorrow morning. High pressure will move into the NW Gulf
tomorrow, bringing lighter winds and allowing seas to relax
through the day.

Tuesday through Friday Night...The steady progression of Canadian
airmasses throughout this week will likely maintain near SCEC/SCA
conditions across the lower TX Bay and Gulf waters as the PGF
remains pretty strong. The best marine conditions this week will
be confined to late Wed/early Thurs when the PGF appears to be the
weakest ahead of the weekend cold front.

&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...None.
GM...Small Craft Advisory until 7 AM CDT Monday for GMZ150-155-170-
     175.

&&

$$

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