Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 130544 AAA

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
1244 AM CDT Sun Aug 13 2017

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

.AVIATION...Brief degraded conditions are possible again tonight
at MFE near sunrise. Otherwise, VFR will prevail at the three
major aerodromes. Tomorrow, VFR will continue with scattered
higher cloudiness and breezy surface winds.

.PREV DISCUSSION... /issued 709 PM CDT Sat Aug 12 2017/

DISCUSSION...Updated for latest /00Z/ aviation discussion below.

AVIATION...Overall a fairly easy forecast, with wind the primary
concern for Sunday afternoon takeoffs and landings. Enhanced early
evening southeast breezes will quiet down by 9 or 10 PM but there
should still be some periodic freshness through the
night...generally at or above 8 knots. That should keep the
possibility for IFR ceilings near nil at McAllen/Miller toward and
just after daybreak Sunday...a condition that was a little
surprising early this morning but perhaps from a final remnant of
the moisture from Thursday afternoon rains combined with very
light winds.

Thus, continued to mention the "McAllen MVFR" for the predawn
hours as a TEMPO broken group...and did go in the low MVFR
category (below 1500 feet) even though it could be closer to 1800
feet...time will tell. Otherwise, expect a brief period of broken
higher MVFR a couple hours after sunrise at Harlingen and
Brownsville. Soon after, the wind machine kicks in with gusts
above 20 knots by 10 AM or so, and this should help mix out the
clouds to scattered low VFR before noon. By afternoon, with
moisture even thinner at the base of the mixing layer, expect
little more than FEW and elected to keep Clear conditions for
McAllen during the balance of the afternoon. Winds will pick up
more by mid to late afternoon as enhancements arrive with the sea
breeze. Not forecasting 30 knots at this point but 26-28 knots in
reason and have added. Bottom line? Gusty `thermals` will cause
some difficulties for smaller aircraft landings and perhaps
takeoffs as well.

PREV DISCUSSION... /issued 243 PM CDT Sat Aug 12 2017/

SHORT TERM (Now through Sunday night): Morning sounding reported
PW value of 1.96, but this is all trapped in the lowest 4000 feet
of the atmosphere. This has led to scattered daytime CU field
with no precipitation, even along the sea breeze. Mid level
ridging continues across most of Texas, further enhancing the
capping in the atmosphere. Abundant sunshine will bring another
day of hot temperatures tomorrow, with highs again in the upper
90s and low 100s. Dew point temperatures in the mid 60s inland and
low to mid 70s closer to the coast will equate to heat index
readings of 108 to 112 during peak heating hours tomorrow. The
mostly clear skies tomorrow will also allow breezy conditions to
mix to the surface, with winds of 15 to 20 mph with higher gusts,
especially right along the coast.

LONG TERM (Monday through Saturday): A broad 590 decameter height
ridge will be parked over south Texas Monday, with 1012 mb high
pressure over the Gulf. This pattern will persist quite well
through the week. Storm activity will increase over the Plains
into mid week as a short wave trough rolls out of the western
United States, but little effect will be noticed locally. Slight
rain chances pop up here and there through the week, but will
remain mainly muted in the long term. Seasonal weather (except
for above average temperatures) will continue from the short term
into Monday and thereafter, with light to mdt onshore (southeast)
winds and a mix of clouds and sun each day. Temperatures will be
a few degrees above normal on average, with heat index values
typically in the 105 to 110 degree range for much of the area for
a few hours each aftn. A transiting inverted trough will awaken
increased convection over the southwest Gulf late in the week,
with coastal shower and subsequent daily sea breeze activity
increasing Friday and Saturday.

Now through Sunday night): Seas have leveled off offshore around
3 feet during the past 24 hours, with wave period between 6 and 7
seconds. Wave action will remain consistent through the next 36
hours as southeast flow remains elevated. Winds tomorrow should
reach the 15 to 20 knot range for the Laguna Madre, so small craft
will need to exercise caution during the afternoon. Winds are
forecast to remain in the 10 to 15 knot range tonight and tomorrow
night for all zones.

Monday through Thursday: 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.



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