Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 121741 AAB

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
1241 PM CDT Mon Mar 12 2018

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


.AVIATION...Northerly winds continue to breeze through around 15
knots, which will continue through most of the rest of the
afternoon. Cloud cover is confined to around 15000 feet today, and
will continue to overspread the region. Winds will decrease
overnight as high pressure moves into the region, bringing L/V
conditions all night. A lower cloud deck, roughly around 5000
feet, will shift back into the region overnight, but cigs below
this are not anticipated. High clouds and light easterly flow
continues into the day Tuesday.


.PREV DISCUSSION... /issued 610 AM CDT Mon Mar 12 2018/

DISCUSSION...Updated for latest aviation discussion below.

AVIATION...The cloudiness that dominated at 12k feet only six
hours ago continues, but has been undercut by a 5k to 6k layer
advecting underneath. Surface winds will diminish today as the
mid-level cloudiness continues. A further diminishing of winds
is anticipated tonight as the clouds persist. No precipitation
is expected. Overall, VFR is predicted through the next 24 hours.

PREV DISCUSSION... /issued 354 AM CDT Mon Mar 12 2018/

SHORT TERM (Now through Tuesday):  What was deemed not expected 24
hours ago was achieved spectacularly on Sunday: record high
temperatures (95 at BRO, 97 at HRL, 101 at MFE) were recorded at the
three major airports due to the slow progression of a cold front
through Deep South Texas and the Rio Grande Valley producing the
expected downsloping effect off of the neighboring high terrain in
Mexico. Temperatures like that are not expected during the short
term portion of the forecast with surface high pressure producing a
sustained and much cooler northerly to northeasterly flow. Mostly
cloudy skies are also anticipated, with a west-northwest to east-
southeast mid-level flow out of Mexico advecting clouds over the BRO
CWFA. However, rainfall is not forecast.

On a side and related note, the Rip Current Statement for a High
Risk of rip currents will remain in effect for the local beaches
until around sunset this evening due to Spring Break activities in
the area.

LONG TERM (Tuesday Night through Sunday): No major changes in the
long-term. Still appears that the only day with mentionable
precipitation chances will be Thursday, adding to the dearth of
rain across the region of late. March is climatologically one of
the drier months to begin with, and precipitation roughly west of
I-69C has been <25% of normal over the past two weeks. Fine fuels
have dried considerably over the past couple of days as well.
That being said, no obvious fire danger days stick out in the
progs through this weekend, but conditions will need to be

On Tuesday night, partly cloudy skies, surface high pressure, and
light onshore flow should yield low temps generally in the 50s F.
This is near or just below normal for the populated RGV. Not
really much change for Wednesday, except that flow at upper levels
flattens in response to the de-amplification of upstream ridging.
Easterly winds should keep afternoon temperatures similar to those
expected on Tuesday. SE return flow finally begins to set up
Wednesday night.

Models still having some issues resolving scenario for Thursday
regarding possible light precip associated with a mid-upper level
shortwave trough. Not surprising given the progged low-amplitude
wave in brisk zonal flow. GFS (which has been fairly consistent in
its scenario over the past couple days of runs) brings a fast-
moving vort lobe over Deep South Texas. While the best column
moisture passes by to the north, time-height sections indicate
some decent vertical motion around mid-day, along with
precipitable water values climbing to well above normal at
1.5-1.6". 00Z NAM run shows a similar position to the wave at the
end of its run at 12Z Thu. ECMWF had been indicating an even more
damped and further north wave relative to the GFS, but quick
glance at its 00Z run shows a solution fairly similar to the 00Z
GFS, with a 30% PoP for BRO. All that being said, will nudge
PoP`s back up a bit for daytime Thursday, but hold at slight
chance levels for land areas with some chance coverage offshore.
Even with the cloud cover, temps begin a recovery in the renewed
SE flow.

For Friday and beyond, after the wave exits, moderate zonal
flow/flat ridging aloft on Friday transitions to SW flow by the
weekend as deep WCONUS low moves inland. Low-levels remain fairly
moist, but this moisture is bottled up below 850-900mb, so no
precip is expected. So a series of warm, breezy (especially
eastern counties) days are in store for Friday through Sunday.
Winds may gust to 30+mph at times. 90+ degree max temps will be
common west of Hwy. 77/I-69E. A modest Pacific cold front may
arrive on Monday, but that is just beyond the end of this forecast

MARINE (Now through Tuesday):  Buoy 42019 reported north winds
around 23 knots gusting to around 27 knots with seas slightly under
6 feet with a period of 6 seconds at 02 CDT/07 UTC. Strong winds and
rough seas continue along the Lower Texas Coast at this time. A
Small Craft Advisory (SCA) for Winds remains in effect for the
Laguna Madre through late this morning, with a Small Craft
Advisory also in effect for the Gulf of Mexico waters from 0 to 60
nautical miles offshore until around sunset this evening.
Improved marine conditions are expected tonight and especially on
Tuesday as high pressure prevails. However, Small Craft Exercise
Caution may be needed for a portion of the Gulf of Mexico waters
tonight due to seas.

Tuesday Night through Saturday: Light to moderate onshore flow
through Wednesday with seas generally 3 ft. or less. Winds veer SE
Wednesday night and strengthen, with Small Craft Exercise
Caution (SCEC; 15 to 20 knots)-level winds possible by Thursday
afternoon. Elevated SSE winds continue through Saturday, with
periods of SCEC and/or SCA`s likely. Gulf seas gradually build to
near 5 ft.


TX...High Rip Current Risk until 7 PM CDT this evening for TXZ251-256-

GM...Small Craft Advisory until 7 PM CDT this evening for GMZ150-155-



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