Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 161156 AAA

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
556 AM CST Fri Feb 16 2018

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

.AVIATION...Satellite images and surface observations indicate
some low clouds across central and eastern portions of the CWA
this morning. Ceilings were near 700ft at KBRO/KHBV to near 1200ft
at KBKS/KEBG/KMFE. Expect MVFR to IFR conditions through 15Z
before the low clouds lift and burn off with diurnal heating. In
addition...a low level jet at 2000-3000ft will provide low level
wind shear across the lower Texas coast this morning before winds
mix down with diurnal heating. Expect VFR conditions to prevail
across the Rio Grande valley after 15Z with the 500mb ridge across
the Gulf of Mexico providing subsidence across the area. MVFR to
IFR conditions will return tonight as low clouds/fog develops
across the area as a weak cold front moves into south TX and

.PREV DISCUSSION... /issued 444 AM CST Fri Feb 16 2018/
SHORT TERM (Now through Saturday): 500mb ridge across the Gulf of
Mexico will continue to provide subsidence across south Texas
today as a weak cold front moves into central TX this afternoon.
Temperatures will be unseasonably warm today with southerly winds
and mostly clear skies. The front is expected to move into south
TX tonight and stall north of the CWA. The boundary will allow
moisture to pool across the northern ranchlands tonight into
Saturday and isolated showers will develop along the front so will
continue to mention a slight chance of rain across the northern
CWA. The front may move into the northern ranchlands Saturday as
the upper level ridge across the Gulf flattens out and a 500mb
shortwave trough moves eastward across the southern plains Sat
afternoon. Temperatures will continue to be unseasonably warm
Saturday but cloud cover will limit diurnal heating a degree or
two. Will see patchy fog across the coastal sections of deep south
TX this morning with areas of fog developing late tonight across
the lower TX coast.

LONG TERM (Saturday Night through Thursday): 500mb low pressure
system near Baja California will slowly open up into a broad
trough on Sunday, continuing southwest flow over South Texas
through much of the long term period with high pressure moving
westward into the central Gulf. A series of storm systems at the
surface will move across the central and eastern U.S. with the
first one bringing a weakening front into South Texas on Sunday.
Most model guidance indicates the front will stall just to the
north of the CWA with the NAM bringing it slightly further south
into portions of the area. Winds may shift briefly to the east
before southerly flow strengthens Sunday night into Monday. Best
moisture convergence will be in the northern Ranchlands near the
boundary, so have kept PoPs fairly low across the lower RGV and
coastal areas with 20 to 30% in the northern counties.
Southeasterly flow will continue to bring warm, moist air across
the region, so high and low temperatures will be well above normal
into the mid to upper 80s Monday and Tuesday. As a deep low
develops in the Plains, the pressure gradient will strengthen
along the lower Texas coast and bring breezy to windy conditions.
Wind Advisories may be needed with wind gusts possibly reaching 40
mph across the coastal counties Monday afternoon. Moisture remains
shallow and predominantly below 850mb, but a few isolated showers
could initiate as weak impulses move through the mid-level flow.

The next cold front will come mid-week with a 1040mb high moving
southeastward into the Great Lakes. At this point, the front will
likely be strong enough to move through the area, bringing cooler
temperatures and much better rain chances Wednesday afternoon
and Thursday. Temperatures will struggle to reach the 70s on
Thursday with coastal troughing bringing low clouds and
precipitation. Have kept the mention of thunder with the frontal
passage as there will be some instability ahead of the boundary
with warm temperatures and moist dew points. There is some
uncertainty by the end of the week, as several of these coastal
troughs this season have persisted a bit longer than predicted.
Therefore, will stick with a model blend for day 7.

MARINE (Now through Saturday): Seas were near 4 feet with south
to southeast winds near 16 knots offshore the lower Texas coast
early this morning. Light to moderate south to southeast winds
will prevail across the coastal waters today with surface high
pressure across the northeast Gulf of Mexico and a weak cold front
across central TX. The front will stall across south TX tonight
and light southeast winds will prevail across the lower TX coast.
The pressure gradient will remain weak across the western Gulf of
Mexico Saturday and light south to southeast winds will continue
to prevail across the coastal waters. Will likely see marine fog
linger across portions of the Laguna Madre and the nearshore
waters today through Sat morning.

Saturday night through Wednesday: Moderate winds and seas will
continue through the long term period as a series of storm systems
develop in the Plains and tighten the pressure gradient along the
lower Texas coast. Strong southeast flow near the coast Sunday
afternoon and Monday will prompt small craft to exercise caution
with Small Craft Advisories possible. Seas will remain elevated
from 4 to 7 feet. A cold front will move through on Wednesday,
shifting winds to the north with increasing rain chances.

GM...Dense Fog Advisory until 8 AM CST this morning for GMZ130-132-


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