Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 120541 AAA
AFDBRO

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
1241 AM CDT Sat Aug 12 2017

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

.AVIATION...MVFR may temporarily affect MFE within the next few
hours, otherwise VFR will prevail at the aerodromes tonight with
light surface winds. Tomorrow, VFR will continue with scattered
cloudiness. Convection, even isolated, is not expected due to the
domination of mid-level high pressure.
&&

.PREV DISCUSSION... /issued 721 PM CDT Fri Aug 11 2017/

DISCUSSION...Allowed last of the coastal hazards (Rip Current
Statement) to expire at 6 PM. While the threat remained moderate
through sunset, the downward trend and thinning daytime swimming
crowds timed out well with the expiration. Threat should continue
to dip overnight and Saturday...and while there could be a few
pockets where longshore/rip is a little bit more active the day
should feature low waves and currents, perfect timing for what
will be another crowded weekend with heat in full force inland.
52/BSG

AVIATION...For the 00Z forecast, all quiet on the Valley front as
after a couple of days of northeast winds (and one wet day with
the outer arm of distant circulation around Franklin on Thursday),
today was largely benign once again. With deep dry air continuing
across the region, the only issues are wind and perhaps the usual
brief MVFR early morning deck at McAllen/Miller.

For the overnight, mainly clear except for that aforementioned
deck most likely during the pre-dawn to daybreak hours at Miller
airport - with light winds. The start of a minor "wind machine"
situation arrives Saturday, and introduced southeasterly gusts
above 20 knots for the afternoon at all three sites. Dry air above
and below the rising inversion should keep cumulus fields to FEW-
SCT at most, with raising ceilings in line with mixing heights,
all well into VFR range.
52/BSG

MARINE...Currently carrying 2 to 3 foot seas on Saturday but may
need to lower pending trends. Buoy 42002 (about 250 miles east of
South Padre) was near calm and with the center of the surface high
relatively close to the coast tonight into Saturday morning would
not surprise to see 2 to 2.3 foot combined seas for much of
Saturday in the Gulf. That will change Saturday night and Sunday
as the center of the ridge shifts slowly east and southeasterly
flow picks up, slowly rebuilding seas mainly in the form of wind
wave vs. swell.
52/BSG

PREV DISCUSSION... /issued 239 PM CDT Fri Aug 11 2017/

SHORT TERM (Now through Saturday night): Moisture remains
persistent across the region this afternoon, as noted by PW values
this morning still at 2 inches and current GOES PW imagery. Main
issue today with any convection is a small pocket of dry air at
midlevel and east winds aloft shearing the seabreeze apart.
Showers will remain isolated along the immediate coast the rest of
the day before dissipating with loss of heating. GOES imagery
does show the swath of drier air just offshore starting to rotate
into the region. Once this arrives tonight, drawn in by the
southward shifting H% ridge, convection will have an exceedingly
difficult time breaking through the cap. With this in mind, went
ahead and pulled rain chances from the forecast for tonight
through tomorrow night. With the strengthening of the midlevel
ridge, compressional heating will be on the upswing starting
tomorrow. This pushes highs into the upper 90s and low 100s, with
heat index readings 108 to 111 Saturday afternoon.

LONG TERM (Sunday through Friday): A 593 decameter high will be
parked over south Texas Sunday, with 1014 mb high pressure over
the Gulf. This pattern will persist quite well through the long
term. Though can`t rule out a stray afternoon or coastal shower,
rain chances will be muted in the long term, and for now have gone
with a dry long term forecast. Seasonal weather will continue
from the short into Sunday and thereafter, with light to moderate
onshore (southeast) winds and a mix of clouds and sun each day.
Temperatures will be a few degrees above normal on avg., with heat
index values typically in the 103 to 108 degree range for much of
the area for a few hours each afternoon.

MARINE:
Now through Saturday night: Swells have settled around the 4 foot
height today, but the main difference is the reduction of the long
wave period, which fell from 10 seconds last night to 7 seconds
now. Both wave action and period will continue to decrease as
Gulf waters stabilize after Franklin. High pressure will shift to
the northern Gulf, keeping the gradient relaxed, with resulting
onshore flow 10 knots or less through the first half of the
weekend.

Sunday through Wednesday: Mid level ridging overhead and surface
high pressure over the Gulf will support moderate to fresh
southeast to south winds and moderate seas. Diurnal effects will
promote small craft should exercise caution conditions on the
Laguna during the day, with similar conditions off and on during
both day and night on the Gulf waters.
&&

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

$$

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