Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 211737 AAB
AFDBRO

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
1137 AM CST Tue Feb 21 2017

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

&&

.AVIATION...A dry cold front has moved into the Lower Rio Grande
Valley and will push offshore this afternoon with gusty northwest
winds behind it. Strong subsidence will limit any precipitation
chances with VFR conditions prevailing the next 24 hours. Some
indications have possible fog development overnight with surface
high pressure developing overhead and variable light winds, but
moisture will likely be too low across the area.

&&

.PREV DISCUSSION... /issued 550 AM CST Tue Feb 21 2017/

DISCUSSION...Updated for latest aviation discussion below.

AVIATION...Southwest winds have begun to increase this morning
ahead of an approaching dry cold front...as such fog formation
has not materialized. The winds will increase and shift to the
northwest later this morning and become gusty. Winds will
decrease after sunset. VFR conditions will prevail...however fog
may develop given the calm winds expected Tuesday night.

PREV DISCUSSION... /issued 359 AM CST Tue Feb 21 2017/

SHORT TERM (Now through Wednesday): The strong H5 low will
continue to move across Northeast Texas this morning into
Louisiana through the day. This will keep Deep South Texas in a
region of strong subsidence. Meanwhile...the concurrent surface
low will follow a similar path as the mid level low and pass
north of the region into and along the Northern Gulf coastline.
As the low passes...a dry front will sweep through the region.
Winds this morning will quickly shift from southwest to northwest
and increase in speed.

In addition to the subsidence...a very dry airmass will filter in
behind the front. Aided by clear skies...this will cause temps to
rapidly warm above normal Valley-wide. High will be in the mid to
upper 80s for much of the areas...with lower 90s possible in the
Mid to Upper RGV.

The dry air will be a concern today with humidity values
plummeting into the teens from Zapata County all the way east
towards the coastal areas. Coupled with the higher winds
today...erratic fire behavior will be a concern. Indeed...
conditions may near red flag warning criteria this afternoon,
however, I am not overly confident that one will be needed.
Although fuels remain cured...the widespread rainfall from Sunday
night should help mitigate the effect. Will instead go with a Fire
Danger Statement this morning and allow the oncoming shift to
monitor conditions.

Winds will quickly decouple after sunset tonight, and high
pressure both aloft and at the surface will settle across the
region. Under clear skies and calm conditions...temperatures will
fall into the 50s.

High pressure and dry air will bringing even warmer highs on
Wednesday. Winds will be much lighter and fire danger will not be
as high.

LONG TERM (Wednesday night through Monday): This is a dry time
of year, and the outlook period will live up to that expectation.
In addition, temperatures will continue to run roughly 5 to 10
degrees above average. As overhead ridging shifts farther east
Wednesday night, lower pressure in the plains will take over from
lower pressure over the Gulf, resulting in strengthening southeast
to south winds winds on Thursday. Most areas of the CWA, except
for the immediate coast, will get into the 90s. A dry cold front
will approach Thursday night, and will push through on Friday with
north winds becoming moderate. Afternoon high temperatures will
still be around 90, with the ranchlands and brush country shaving
a few degrees off of that mark as cooler air will be sufficient
to temper the higher readings across the northern portion of the
CWA. High pressure will continue to surge over the area Friday
night and Saturday, with low pop showers developing along the
front as it pushes offshore. High temperatures on Saturday will
be slightly cooler, in the mid 80s, and that trend will continue
into Sunday. High pressure will spread over the area Saturday
night and Sunday with winds shifting to east and then southeast
under the zonal mid level pattern aloft and the building high
pressure over the Gulf. Coastal showers will develop Monday amid
return flow, return flow into a midwest U.S. storm system. High
temperatures will creep upward on Monday, into the upper 80s.
High pressure over the Gulf will help keep the onshore flow
established into the first couple of days of the week.

MARINE:
Now through Wednesday: Winds at Buoy 42020 have increased from
the SSW to around 15 knots with seas near 4 feet. Surface low
pressure will deepen and move east across the Northwestern Gulf
coastline today. As the low moves east...it will bring a dry
front through the Lower Texas Coastal Waters early this morning...
with winds quickly increasing from the NW at around 20-25 knots.
A SCA for winds will be issued for the Gulf waters east of Padre
Island starting this mrng. Due to the offshore wind direction...
seas will generally remain below advisory criteria. Surface high
pressure will build in this evening...with improving marine
conditions.

Wednesday night through Friday night: Northeast winds will veer
around to southeast Wednesday night as high pressure slips east
and pressures fall in the southern high plains. No issues are
expected for Thursday, as lower pressure hangs on over the Gulf
under a retreating upper low, but winds will strengthen Thursday
night through Friday, approaching or reaching small craft should
exercise caution criteria, due to a by then tighter pressure
gradient. Seas will remain moderate given the more southerly wind
direction. On Friday night, winds weaken but will then shift to
northeast and strengthen with a surge of plains high pressure,
and will be around 20 knots offshore Saturday morning, right at
small craft advisory criteria. This time seas will build over the
Gulf, reaching 4 to 7 feet Saturday and Saturday night as winds
remain fresh northeast to east.

&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...None.
GM...Small Craft Advisory for winds until 6 PM CST this evening for
     GMZ170-175.

     Small Craft Advisory for winds until noon CST today for GMZ150-
     155.

&&

$$

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