Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 161156 AAA
AFDBRO

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
556 AM CST Wed Jan 16 2019

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

&&

.AVIATION...Poor flying conditions this morning are likely to
persist through the afternoon with a pesky coastal trough and
surface inversion remaining intact but slowly weakening. LIFR cigs
and IFR vsby this morning to slowly and gradually improve through
the afternoon with potential lower end MVFR conditions during the
afternoon hours. Ceilings and visibilities to lower once again
later tonight with IFR to LIFR anticipated. Surface winds are
expected to be light from the west this morning turning southeast
in the afternoon.

&&

.DISCUSSION...Updated for latest marine discussion below.

&&

.MARINE...Dense sea fog is observed by web cameras and local
observing platforms along the Lower Texas coast. Visibilities have
dropped below one mile in some locations across the Laguna Madre
and portions of the near shore Gulf waters. A dense fog advisory
has been issued until 10 am.

&&

.PREV DISCUSSION... /issued 408 AM CST Wed Jan 16 2019/

SHORT TERM (Today through Thursday): Coastal trough lingers but
continues to weaken as surface high pressure shifts east. Isentropic
upglide is trending weaker with the southerly thermal advection
weakening as winds veer a bit more southwest and with boundary layer
flow becoming more parallel to the pressure surfaces. Condensation
pressure deficits at the 295K level remain relative narrow so some
lingering light rain and drizzle is still possible mainly along the
coastal counties this morning before tapering off this afternoon. In
the mid layers a weak disturbance has passed to the east with modest
dry layer developing between 700-400mb which should maintain a
surface inversion over much of the CWA. Even with south winds
becoming established later this afternoon, albeit light, the thick
lower cloudiness is expected to hang around all day with maybe a few
breaks in the overcast out west late in the day. With all this said
temperatures will  have a tough time recovering with GFS/EC guidance
trending lower on highs. A blend of the guidance with a bit more
weight from the NAM has lowered today`s highs into the low to mid
60s.

Tonight just a cloudy night with some patchy fog developing late
with plenty of low level moisture in place and light southerly winds
expected. Temperatures to fall very slowly overnight due to the
blanket of clouds and the light southerly flow. For Thursday
expecting warmer conditions but still clouds lingering with the
southerly flow becoming more established. A weak disturbance in the
persistent southwest flow aloft may be enough to spark a few showers
in the east during the afternoon hours but these should not amount
to much and most locations should remain dry. Highs to rebound back
into the 70s but have kept highs in slightly below guidance with the
expected overcast conditions.

LONG TERM (Thursday Night through Tuesday): Southwesterly flow
will be over head Thursday night ahead of our next upper level
wave and surface cold frontal boundary. At the surface southerly
return flow around the western side of high pressure building over
the Florida Peninsula will help continue to increase boundary
layer moisture across the region into early Friday. Within this
rich low level flow, a few isolated to widely scattered showers
will be possible...though these should be on the light side given
the shallow depth.

As the trough begins to translate eastward across the high plains
of TX/OK...a cold front will begin to slide through the region
late Friday and especially early Saturday morning. Along and ahead
of the front expect some increase in rain chances, however, the
QPF isn`t currently overly impressive in any of the globals. Think
most of the region will experience some type of shower activity,
however, the better chances will be offshore where the highest QPF
signal resides.

Behind the front, drier air will rush southward clearing skies by
later afternoon Saturday. Temperatures will need to be monitored
carefully on Saturday as any upward adjustment may lead to more
of a fire weather concern, especially as winds may gust to near
30mph during the day on Saturday (perhaps more if we can
effectively warm and consequently mix stronger winds aloft to the
surface). The real cool down holds off until early next week
(Sunday and Monday AM) as surface high pressure begins to settle
into South TX. Globals have been trending higher with the
overnight low Sunday/Monday AM. We`ll need to pay close attention
to surface winds during this time as this will dictate the light
freeze potential (more easterly flow will be a warmer flow and may
be a limiting factor).

A brief warm up is expected by Monday afternoon and especially
Tuesday ahead of our next strong cold frontal boundary due into
the region toward the end of this forecast period on Wednesday.
The origin of this front is the northeast Pacific so not expecting
an exceptional cool down, but it should be noticeable after a warm
Tuesday. Left POPs low at this time as GEM and ECM are showing a
little something, however, this appears to be a similar frontal
passage as expected this weekend with much of the precipitation
likely developing/staying offshore.

MARINE (Today through Thursday): Pressure gradient to slacken today
as the coastal trough weakens. Winds and seas to lower through
tonight. Surface high pressure settles to the east Thursday with
light southeast winds and low seas becoming established.

(Thursday Night through Tuesday): Marine conditions start off very
benign on Thursday evening and into early Friday. This, however,
is short lived as winds and seas begin to increase out a head of
our next strong cold front due into the region on Saturday.
Indeed, by midday Saturday winds will have transitioned to a
northwesterly flow and increase to around 30 knots with frequent
gusts over Gale force expected. This should help build seas to
around 12 to 13 feet at times in our offshore waters before seas
finally begin to subside late Sunday and especially into the day
Monday as high pressure begins to settle into the region.

Beyond Monday, marine conditions will become somewhat tranquil,
however, like before, this too will only be short lived as winds
again increase on Tuesday ahead of our next strong cold front due
into the region by midweek.

&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...None.
GM...Dense Fog Advisory until 10 AM CST this morning for GMZ130-132-
     135-150-155.

&&

$$

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