Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 102313 AAA

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
513 PM CST Sat Mar 10 2018

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


.AVIATION...Restricted ceilings and visibility will develop
tonight, particularly in the HRL and BRO areas, when south winds
winds become light and while high dew points prevail. The
degraded, IFR conditions will persist through mid morning when a
cold front will sweep across the area. Skies will remain cloudy,
but VFR conditions will return around noon. Moderate to breezy
north winds will develop in the afternoon.


.PREV DISCUSSION... /issued 330 PM CST Sat Mar 10 2018/

SHORT TERM (Tonight through Sunday Night): Light southerly flow
continues across the area as low pressure remains across west Texas.
Temperatures have increased into the upper 80s and will continue
into the lower 90s for most areas. Latest radar imagery shows a
seabreeze boundary moving inland, which is pulling temperatures back
down after passage. Southerly flow returns tonight, and with
dewpoint temps still in the mid 60s, fog formation is still a
possibility. Most area will see light vis reductions, but a few
areas, mainly rural grassy areas, may see some locally dense fog
right around sunrise. Sunday will see southerly to southwesterly
flow set up again, remaining generally below 10kts through the day.
The cold front will sweep into the region, with timing expected late
morning for the northern ranchlands, to later afternoon for the
lower valley and the island. Winds will jump to 15 to 20 knots from
the north, drawing much drier air into the region. A few showers are
possible along the front Sunday afternoon, especially along the coast
along any merger between the front and any seabreeze. Moisture aloft
is fairly limited, so strengthening of any showers is not

LONG TERM (Monday through Saturday): The 500 mb trough that is
digging southeast out of NW US will be exiting the south central
states on Mon allowing much cooler and drier surface high pressure
to spread over the RGV. Pretty high amplitude 500 mb ridging will
prevail over the western states while a very deep closed low
remains in place over the Great Lakes region. The 500 mb ridging
over the western States will start shifting gradually east through
the end of the work week allowing for the temps to slowly warm
through the extended period. Expect overall temps to remain near
to below climo through Thurs with near to above normal temps
expected this weekend as a surface low is expected to develop over
the central Plains States which will help increase the WAA over
the RGV.

Overall the longer range models have good agreement for temps and
pops up through Wed and then diverge somewhat. The GFS pulls a
pretty strong 500 mb short wave underneath the base of the ridge
axis that shifts over the central Plains states. Accordingly the
GFS ramps up pops a bit higher for Thurs/Fri with the passage of
this short wave and also shows lower overall temps due to the
better pops and thicker cld cover. The ECMWF only shows a fairly
weak short wave moving through the region with somewhat limited
moisture advection.

Overall confidence is above average through Wed and then drops off
to near to below average from Thurs onwards due to the model
differences. Both long range models have been stubborn from run to
run in holding on to their differing opinions. Will opt for a
general model blend from the GFS and ECMWF through Day 7.

MARINE (Now through Sunday night): Light southerly flow continues
tonight, remaining around 10 knots. This will allow seas to relax
further, with wave heights around 3 feet. Light south and southwest
flow begins the day tomorrow, in advance of the next cold front.
Seas will initially start at 2 to 3 feet. Conditions will deteriorate
quickly once the front arrives, which is currently expected between
3 and 6 PM. North winds will jump to 20 to 25 knots with a few
higher gusts, especially overnight Sunday night. This will bring
considerable churn along the nearshore, with wave heights of 8 to 10
feet expected. The front may spark a few showers Sunday evening, but
most activity will remain along the immediate and be brief. Small
Craft Advisories will likely begin Sunday midafternoon for all zones
and last into the extended periods.

Monday through Thursday Night: SCA conditions will likely persist
for the lower TX Gulf waters into Mon and Mon Night as the post
fropa PGF remains pretty strong. Calmer marine conditions will
return on Tues, Wed and Thurs as the center of the Canadian
surface ridge drops further south over the Gulf Coast region and
allows for a more light to moderate E-SE flow to return. The PGF
Thurs Night may strengthen enough to possibly push back up close
to SCA levels as a surface low develops over the central Plains
states which will interact with the broad and strong surface high
that will be centered over the Gulf Coast region.




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