Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 280532

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
1132 PM CST Mon Feb 27 2017

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


.AVIATION...Satellite images and surface observations indicate low
to mid level clouds across the central and eastern portions of the
CWA late tonight. Ceilings were near 900ft at KBRO and KPIL to near
1800ft at KMFE. Visibilities were near 4SM with fog at KPIL to near
6SM with haze at KMFE. Expect MVFR to IFR conditions to continue to
develop across portions of the Rio Grande valley and northern
ranchlands late tonight into early Tues morning as low level
moisture under the 850mb thermal inversion allows low clouds/patchy
fog to continue to develop. VFR conditions will prevail after 15Z
Tuesday as low clouds/fog lift and burn off as mixing increases with
diurnal heating.


.PREV DISCUSSION... /issued 516 PM CST Mon Feb 27 2017/

DISCUSSION...Updated for latest aviation discussion below.

AVIATION...Satellite images and surface observations indicate a
few mid to high level clouds across the northeast portions of the
CWA early this evening. Ceilings were near 1900ft at KT65. Expect
VFR conditions to prevail this evening before MVFR to IFR
conditions develop late tonight into early Tues morning as low
clouds/patchy fog develop as moisture remains high just below the
low level thermal inversion across deep south Texas.

PREV DISCUSSION... /issued 257 PM CST Mon Feb 27 2017/
SHORT TERM (Now through Tuesday night): Upper level pattern
remains fairly stable around the Gulf Coast as H5 ridge builds
into the region from the west. At the surface, considerable
southerly flow continues as flow sweeps toward an approaching cold
front from the north. With the capping inversion set around 3000
feet, moisture trapped underneath will provide ample cloud cover
overnight tonight, while the low level jet caught under the cap
will keep surface breezes elevated through the night. Tomorrow,
the cap will continue to hold moisture close to the surface,
keeping cloud cover through most of the morning. The llvl jet will
start to mix to the surface late morning, with winds exceeding 20
knots through the afternoon. The higher winds expected Tuesday
versus Monday will help thin out clouds a little earlier in the
afternoon. A weak trough will try to build into the western zones
in the afternoon, bringing lighter due south winds. This will
bring a chance for drier air to mix to the surface and letting
temperatures jump into the upper 90s. The winds will remain breezy
overnight again Tuesday night before the front begins to encroach
the northern ranchlands before sunrise Wednesday.

LONG TERM (Wednesday through Monday): A cold front is forecast
to move through the area on Wednesday. The front will bring a
quick shot of rain Wednesday afternoon as it passes through,
followed by a cooler, cloudier and wetter period for the latter
half of the week.

The Wednesday cold front should arrive in time for the modified
maritime polar airmass behind it to take the edge off afternoon high
temperatures, with forecast values in the mid 80s. As has been the
recent trend, upper dynamics will be weak or lacking, so weather
should be limited to showers and a possible thunderstorms along the
front as it moves through from dawn to early afternoon. Strong, 1029
mb high pressure will settle over East Texas Wednesday night and
will begin shifting east on Thursday. Most of deep South Texas will
clear Wednesday night, though a few clouds may remain near the Lower
Valley along the coast.

As high pressure shifts east, the low level northeast winds will
continue on Thursday and Friday, being overrun by west southwest
flow aloft. Winds aloft would have to be a bit more from the
northwest to allow for a rapid clearing. Despite the removal of
the high pressure center toward the East Coast, a coastal trough
will help maintain nearby low level convergence and cloudy skies,
except for the possibility of some clearing across the ranchlands
and brush country, along with enhanced rain chances Thursday
through Sunday. This will also help keep temperatures a little
more reasonable, and closer to normal, than they have been.
Thursday night and Friday should be the coolest days of the
period, with 50s Thursday night and 60s on Friday. The game will
not end on Sunday, however. The old front will push north as a
warm front on Sunday, with coastal showers developing then as well
as on Monday. The next front will be on the way for a Tuesday
morning fropa, according to the ECMWF, and a skosh slower by the

Coastal concerns: The arrival of a cold front late Wednesday will
produce strong north northeast winds Wednesday night into Thursday,
along with offshore wave heights of up to 8 feet. Winds will remain
in an unfavorable northeast direction through Thursday, when the
formation of a coastal trough will help bolster northeast to east
winds again, also rebuilding seas to 10 feet late Friday into Sat.
Predicted tides during this interval are forecast to rise to above
one foot above mean lower low water around each mid afternoon from
Thursday through Sunday. The addition of another foot to foot and a
half of swell water on top of high tides will produce a total tide
of two feet or more, enough to produce overwash on the beaches and
minor coastal flooding.

Now through Tuesday night: Southeast flow continues as high
pressure to the east funnels winds northward toward the next
approaching cold front. Winds will remain a consistent 15kts for
the Gulf waters tonight into tomorrow. Daytime heating near shore
will help mix gustier winds to the surface for the Laguna Madre
Tuesday, with winds increasing to near 20 knots. Advisories may be
needed during the afternoon hours. The long southeast fetch
across the open Gulf waters will allow seas to continue to rise
tomorrow to around 5 feet.

Wednesday through Saturday: Conditions will improve briefly and
slightly Wed. morning ahead of a cold front arriving in the late
afternoon or early evening. However, in the wake of the front, poor
marine conditions will prevail in general through the remainder of
the forecast period. Small craft advisory conditions will develop by
Wednesday evening, with north northeast winds becoming strong by
midnight and building seas to 8 feet offshore by Thursday morning.
Conditions will improve slightly Thursday, but small craft advisory
conditions will still be possible and conditions will still be rough
for mariners due to elevated winds and seas. A coastal trough will
form Thurs. night into Fri. in the wake of the front, reinvigorating
northeast to east winds and building seas to 10 feet by Fri. night.
Winds will veer to southeast and weaken on Saturday, but high seas
will linger during the day.




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