Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 171718 AAB

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
1118 AM CST Sat Feb 17 2018

...18z Aviation Update...

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


.AVIATION...VFR conditions expected this afternoon across our Deep
South TX terminals. Southerly winds will continue to be rather
gusty through around sunset. Winds should drop off between 5-10kts
overnight. More low stratus/fog is expected to develop tonight.
Think MFE will stay low stratus, BRO will be low stratus plus fog.
HRL is a little tricky with fog as the best signal is just east
of the terminal. Regardless, IFR conditions are expected given the
aforementioned low stratus. Improvement will again occur by mid
morning on Sunday. Similar to today, winds will increase by the


PREV DISCUSSION... /issued 428 AM CST Sat Feb 17 2018/
SHORT TERM (Now through Sunday): Satellite and radar images
indicate elevated convection across north Texas early this morning
behind a stationary frontal boundary draped across south TX.
Moisture will pool along the front today and tonight before the
front retreats as a warm front Sunday. Will continue to mention
isolated showers across northern portions of the CWA today through
Sunday. Patchy fog will linger across the coastal sections this
morning and redevelop across the same areas tonight. Temperatures
will continue to be unseasonably warm today through Sunday.

LONG TERM (Sunday Night through Friday): The beginning of the
work week will start off very warm and windy with the upper-level
ridge having retreated back eastward near the Bahamas and a
digging trough moving into the Four Corners region. At the
surface, a deep low will develop in the Central Plains with a
1040mb high moving southeastward out of Canada. The pressure
gradient will tighten on Monday along the lower Texas coast with
the low-level jet strengthening to 35 to 45 knots just off the
surface. Afternoon mixing will likely lead to wind gusts exceeding
40 mph at times, especially along the coastal counties. Low-level
winds out of the S to SSW from the surface to 700mb will also
cause strong downsloping and warm air advection across Deep South
Texas. Have increased daytime highs a few degrees to the upper
80s and low 90s in the Upper Valley. Warm temperatures are
expected on Tuesday as well, but mid and upper level clouds may
keep highs down a few degrees.

The next cold front will approach the area Wednesday morning and
possibly move through in the afternoon. Model timing differences
make this forecast fairly difficult with the GFS now bringing the
front through early afternoon and the ECMWF late in the evening
and a bit weaker. Decided to trend slightly on the GFS side, which
falls closely with the guidance from the Weather Prediction
Center, so temperatures were dropped a few degrees up north. But
temperatures may warm up enough along the river, so kept those
values in tact from the previous forecast. Confidence is higher on
precipitation chances as decent coastal troughing and deeper
moisture moving overhead. Thunderstorms will be possible with
abundant instability and mid-level lapse rates of around 7 to 7.5
C/km per model soundings. Temperatures behind the front will be
cooler on Thursday, but still only a few degrees below normal for
late February. Conditions should improve Friday and Saturday as
the mid-level ridge moves back westward into the Central Gulf and
southwest flow at the surface returns.

MARINE (Now through Sunday): Seas were 3 to 4 feet with south
winds near 7 knots offshore the lower Texas coast early this
morning. Light to moderate south to southeast winds will prevail
across the coastal waters with surface high pressure across the
eastern Gulf of Mexico and a stationary frontal boundary across
south Texas. The pressure gradient will remain weak across the lower
TX coast tonight before increasing slightly on Sunday. Light
southeast winds will prevail across the western Gulf tonight before
increasing on Sunday. Marine fog will linger across portions of the
Laguna Madre and the nearshore waters today and areas of dense fog
will return across the same area tonight.

Sunday night through Friday: The PGF will start to strengthen
on Sun and Mon as the strong surface low pressure system develops
over the central Plains states. These stronger southerly winds
will tend to be suppressed somewhat as both the current Bay and
Gulf water temps remain pretty cool in the upper 50s. However,
marginal SCEC/SCA conditions could be possible in the longer range
period especially for the Gulf Waters.


GM...Dense Fog Advisory until noon CST today for GMZ130-132-135-150-



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