Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 101746 AAB
AFDBRO

Area Forecast Discussion...UPDATED
National Weather Service BROWNSVILLE TX
1146 AM CST Tue Jan 10 2017

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

&&

.AVIATION...Strong south winds will continue to mix down from the
850mb jet over the next couple of hours. However...models
indicate that the jet will begin to weaken by mid afternoon...with
winds generally decreasing this evening. Another low level jet
will develop overnight and gusty south winds will develop during
the mid to late morning hours Wednesday. VFR conditions will
generally prevail...although some MVFR cigs may develop overnight.


&&

.PREV DISCUSSION... /issued 545 AM CST Tue Jan 10 2017/

DISCUSSION...Updated for latest aviation discussion below.

AVIATION...Mostly clear skies prevail across Deep South Texas and
the Rio Grande Valley this morning. VFR conditions expected for
the next 24 hours with only some sct cumulus later this morning
into the afternoon. Breezy south winds will develop after 15z
with gusts remaining just below 35 knots late this morning into
the afternoon. Winds will gradually diminish to around 10 knots
this evening under mostly clear skies.

PREV DISCUSSION... /issued 418 AM CST Tue Jan 10 2017/

SHORT TERM (Today through Wednesday): (Now through Wednesday): The
main forecast issues through the short term will be above normal
temperatures and breezy conditions across the area. Surface high
pressure across the Mid- Atlantic states extending into the Gulf
of Mexico will interact with lower pressure upstream. A strong low
level jet with 925-850mb winds around 40 knots is expected to at
least partially mix of these winds to the surface today. The
limiting factors will depend on the amount of cloud cover that
develops and effects from the cooler marine layer. Peak winds
today should remain just below wind advisory criteria (sustained
30+mph).

Breezy and very warm today with high temperatures mainly in the low
to mid 80s which is 10-15 degrees above normal. Highs will be in the
70s along the coast due to the cooler shelf waters. Mild tonight
with low temperatures generally in the 60s under mostly clear skies.
Very warm and breezy conditions will continue on Wednesday with near
record heat possible with high temperatures away from the coast in
the mid to upper 80s.

Brownsville radar indicates some ongoing streamer activity across
the Gulf waters. Will mention isolated showers across the Gulf
waters this morning. Otherwise, dry conditions will prevail across
Deep South Texas and the Rio Grande Valley through the period.
Additionally, the warm and moist south and southeast winds moving
over much cooler nearshore waters may produce periods of sea fog
along the coast. However, the gusty winds may limited or prevent
widespread dense sea fog from developing.

LONG TERM (Wednesday Night through Monday)...The longer range
period will be dominated by a West Coast 500 mb trough axis
digging south and southeast later this week. This trough axis will
close off over the West Coast with the mid level low reaching NW
Mexico by late Fri/early Sat. This closed low will then kick out
to the northeast reaching OK by Mon. As this closed low digs south
and southeast 500 mb ridging will in turn build over the Gulf
Coast region into Saturday. This ridge axis will eventually shift
east on Sun and Mon as the closed low approaches from the west. As
this closed low clears the region to the north and northeast a
fairly mild cold front will move through the area on Tues allowing
a little cooler airmass to move in place over the RGV. Ahead of
this fropa WAA and increasing 1000-500 mb thickness values will
dominate the region pushing the temps to levels well above climo
for January.

The bulk of the best moisture advection will tend to pool the
deeper moisture values to the north and east of the 500 mb closed
low. This will tend to keep the better pops out of the RGV.
However...some 20 to 30 % pops cannot be ruled out as the large
500 mb closed low gets closer to the region increasing the
divergence aloft a bit.

The latest GFS and ECMWF runs indicate that the longer range
models are coming into better agreement this morning versus that
last several days. The biggest differences today is the final
positioning of the 500 mb closed low as it lifts out to the
northeast this weekend with the ECMWF showing a more northward
positioned closed low versus the GFS. The ECMWF and GFS MOS
Guidance indicate pretty good agreement with both temps and pops
with the ECMWf having a bit of a warmer bias mainly for high
temps. Will go close to a model blend through Day 7 for both the
temps and pops.

Overall forecast confidence is above average throughout early next
week due to the better model to model agreement in the longer
range period. Run to run consistency with the GFS MEX MOS is also
pretty stable for both the temps and pops.

Record high temps will be threatened throughout much of the
upcoming longer range period for the RGV area.

MARINE (Now through Wednesday): Buoy 42020 reported South winds
around 18 knots with seas near 6.2 feet at 0250 am CST. Lower
pressure across the Central Plains will interact with surface high
pressure extending across the Gulf today through Wednesday. This
will support a tightening pressure gradient along the Lower Texas
coast with winds approaching to near small craft advisory levels.
The cooler Laguna Madre and Gulf waters should prevent maximum
mixing of stronger winds to reach the surface. Exercise Caution
conditions are more likely for today with some winds and seas
possibly reaching Small Craft Advisory conditions tonight and
Wednesday across the Gulf waters as the pressure gradient
strengthens further. Additionally, higher dewpoint air will spread
over cooler nearshore waters which may allow for the development of
some sea fog.

Wednesday night through Saturday Night...An elongated surface low
pressure and frontal system extending northeast over the Mid Miss
River Valley will interact with a broad surface high pressure
area centered over the western Atlantic will maintain a moderate
to strong PGF over the lower TX marine locations. This will likely
keep the lower TX Gulf winds and seas elevated up to near
SCEC/SCA levels throughout the latter half of this week and into
the weekend. Some isolated to sct marine conv will be possible
later in the work week as the 500 mb west coast closed low gets
closer to the coastline.

&&

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

&&

$$

This product is also available on the web at:
HTTP://WEATHER.GOV/RGV

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