Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 122049

Area Forecast Discussion
National Weather Service Brownsville TX
249 PM CST Sun Feb 12 2017

.SHORT TERM (Tonight through Monday Night): An approaching upper-level
low and a stalled out cold front will bring a return of rain chances
to Deep South Texas over the next 36 hours.  However, latest model
runs now keep even more of the bulk of the "action" to the north of
the area and/or delay it until Tuesday daytime.  For the moment,
another breezy to gusty and warm day is in progress, with temps at
MFE once again flirting with record highs for the date.

The 500-mb low is evident on water-vapor imagery just now making its
eastward turn north of the Baja Spur.  Low-to mid-level moisture is
progged to continue increasing across through tonight as a cold
front moves from Central TX into south TX this evening before it
stalls.  Showers still expected to develop to the north and west of
the area tonight and possibly move into extreme northern and western
portions of the CWA late tonight into early Monday as the frontal
boundary nears.  Patchy fog again on tap across eastern portions of
the CWA late tonight into early Monday morning, with more coverage
over Cameron and Willacy counties.  With surface winds staying up in
the 6-8KT range, not anticipating widespread dense fog.

For Monday, the H5 low lifts NE into the NM Bootheel region.  RH
deepens up to about 700mb.  However, precip will tend to lift back
northward through the day, along with the frontal boundary, as
surface low tries to become better-organized over the higher terrain
of Coahuila state in Mexico.  Left in a mention of thunder Monday
afternoon, but confidence in this is reduced.  Temps will be a few
degrees cooler than today but still in the 80s area-wide.

Things could become a little more interesting Monday night, as a 35-
40KT low-level jet at H85 develops ahead of a pre-frontal trough,
with the surface low tracking to the NE, but not passing through the
CWA.  Best QPF tracks north along with the surface low.  Some
instability is progged to develop, especially late, with MLCAPE
around 1000 J/kg over the eastern CWA and 0-6km bulk shear in the
40KT range.  However, model prog soundings showing that there will
be a decent cap that would have to be overcome for any storms to
become surface-based.  Perhaps that is why model PoP`s have trended
down a bit (at least through 12Z Tuesday).  So some thunder is
possible after midnight Monday night, but won`t play up severe
threat at this point, especially with SPC Day 2 Outlook placing the
Marginal Risk area well to the NW.

.LONG TERM (Tuesday through Sunday): On Tuesday, an upper level
low pressure system will move eastward across north Texas. A
strong surface cold front associated with the low pressure system
will push southeast through the forecast area through the day.
Because the passage of the front will phase with daytime heating,
especially in the afternoon closer to the coast, there may be
enough instability with the front to generate some strong
thunderstorms that may bring some heavy rain and gusty winds to
near 50 mph. High temperatures over the coastal counties ahead of
the front look to reach into the lower 80s with the northen
counties closer to the front earlier in the day topping out in the
mid/upper 70s. Depending on the timing, the front should push
completely offshore by sunset.

Tuesday night into Wednesday, a dry, northerly, low level cold air
advection pattern will prevail over deep south TX as a broad area
of surface high pressure builds over much of northern TX/OK. High
temperatures on Wednesday will stall somewhat below normal in the
mid/upper 60s. On Thursday, the low level flow becomes more
easterly with a little bit of temperature recovery occurring from
Wednesday. Highs on Thursday should be fairly close to normal, for
a change, and will generally run from near 70 at the coast with
70 to 75 inland. Additional temperature recovery is slated for
Friday as southeast to south flow across the region leads to high
temperatures in the mid 70s to the lower 80s.

For Saturday, short-wave ridging looks to prevail across the
region ahead of a large, negatively tiled, upper level low
pressure system approaching from the southwest US/northwest
Mexico. High temperatures will end up well above normal again and
reach into the mid/upper 80s for most areas. For next Sunday, the
medium range models differ on timing/strength details, however
they are showing the strong trough ejecting out of the southwest
U.S. into west TX/western CO. South to southwest flow over deep
south TX ahead of the trough will bring increased moisture to the
region once again with chances of showers/thunderstorms entering
the forecast. Highs on Sunday are tentatively set to stay well
above normal.


.MARINE (Tonight through Monday Night): Latest ob from Buoy 020
reports E winds around 10KT with seas of 3 ft. Some obs from
around the Laguna Madre indicating SCEC-level winds currently;
this wording may need to be added for a few hours with the 3:30pm
Coastal Waters Forecast issuance. Light to moderate ESE winds are
expected overnight. Persistent ESE swell will keep Gulf seas up
around 4 ft. until SE winds pick up to 15-20KT over the Gulf
waters tomorrow night as the gradient tightens ahead of an
approaching surface low. SCEC is likely as seas build to 6 ft.
Potential for a SCA will need to be monitored.

Tuesday through Friday: South winds will be in place across the
waters for much of the day Tuesday before a strong front moves
offshore across the waters late Tuesday afternoon/evening. The
strong front will bring a rapid veering of the winds to the
northwest. The main surge of north winds behind the front will
arrive right around midnight Tuesday night, with winds increasing
to around 25 knots. Seas will build up to around 7 feet for the
Gulf waters and bring a significant chop to the Laguna. Hazardous
seas associated with the frontal passage will necessitate Small
Craft Advisories through about sunset Wednesday. A modest
northeast to east wind will prevail Thursday as high pressure
moves into the northwest Gulf with seas subsiding to 2 to 3 feet.
On Friday, modest southeast onshore winds will keep seas low at
around 1 to 2 feet.




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