Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 160537 AAA

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
1237 AM CDT Sun Apr 16 2017

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

.AVIATION...VFR/MVFR conditions are expected at the aerodromes.
Breezy winds on Sunday will be bookended by light winds tonight
and tomorrow night.

.PREV DISCUSSION... /issued 624 PM CDT Sat Apr 15 2017/

DISCUSSION...Updated for latest aviation discussion below.

AVIATION...Satellite images and surface observations indicate
mostly mid to high level clouds across the CWA early this evening.
Ceilings were near 1400ft at KT65 to near 4700ft at KBRO. Expect
VFR conditions to prevail the rest of the evening into early Sun
morning as a 500mb ridge across south Texas provides subsidence
across the area. Some MVFR conditions may develop early Sunday
morning as low clouds develops across portions of the Rio Grande
valley and northern ranchlands with low level moisture.

PREV DISCUSSION... /issued 250 PM CDT Sat Apr 15 2017/
Short Term (Now through Sunday night): Generally zonal flow
continues at midlevels, sweeping impulses through the Southern US.
Weak ridging ahead of the next buckle currently overhead,
bringing fair conditions to the valley. Moisture is trapped
underneath dry capping layer around 7000 feet, so daytime CU field
not getting any further vertical development. Skies should be
mostly clear overnight as heating wanes. Took out mention of fog,
as cap remains elevated and winds remain around 10 knots. Easter
Sunday will be similar to today, with partly to mostly cloudy
skies through the day. Highs will again jump into the mid 80s.
Most of the region will again see mostly clear skies Sunday night,
but some more active weather may reach the western counties
around or after midnight. The next impulse sweeps out of the Four
Corners region into the Big Bend region Sunday evening. This will
likely activate some thunderstorm along the dryline in West Texas,
and along some of the mountains in Mexico. Steering flow during
the period will be from the west, so most of the tstm activity
will likely remain off to the north. If any outflow boundaries can
drift further south, a few thunderstorms may reach the
northwestern ranchlands, mainly after midnight. Stronger
thunderstorms are not out of the question, but the lack of better
dynamics to the north, lack of daytime heating, and surface
forcing from the dryline remaining in West Texas should inhibit
stronger formations this far east.

LONG TERM (Monday through Saturday): General thunderstorms will
remain a possibility Monday as weak impulses move through the mid
levels. Residual convection following Sunday night activity may
linger inland Mon morning, but thinking that any new development
will fire on a sea breeze boundary during the day. Another impulse
moving across from the west will fire convection over the front
range Monday later in the day, toward late evening, as potential
vorticity is conserved with vertical stretching of the column
coming off the mountains. May see some stronger storms moving from
west to east make it into the Mid and Upper Valley. Once the
atmosphere is worked over, will need to wait until mid Tuesday for
daytime heating to trigger remnant convection as the mid level
impulse lifts across East Texas.

The models are in fair agreement, with the focus of the rain
chances being Monday through Tuesday morning, after which ridging
from the west begins to take control. The differences arise most
noticeably out west. The ECMWF is a little more gung-ho with pops
Monday and Tuesday for the Upper Valley, by roughly a category,
and even lingers a slight chance of rain over the Lower Valley
early Wednesday. The GFS allows higher temperatures to develop
Wed through Fri, again out west due to a forecast of sunny skies,
before the ECMWF catches up. A mid level ridge building in from
the west will indeed make for more settled conditions after Tues,

A mid level trough will dig southeast from the Pacific Northwest
on Thursday, while ridging builds over the West Coast. A mid level
low will bottom out over Oklahoma on Fri, with a front trailing
to the south and southwest. Rain chances will start to pick up
again over deep South Texas on Saturday as the front nears the
Texas coast and pushes through over the weekend.

Now through Sunday night: Modest southeast flow will continue
through the next 36 hours due to strong southeastern US surface
ridge not being opposed by significant low pressure to the west.
This will keep winds generally 10 to 15 knots through the period.
The long fetch around the ridge across the Gulf will continue to
produce seas around 4 feet, with a period between 6 and 8 seconds,
which will continue through Sunday night. No rain expected for
the marine zones in the short term.

Monday through Thursday night: Moderate southeast winds and seas
will prevail. The Bermuda High will build, with high pres. extending
west across the North Gulf. The persistent high pres. will maintain
an anticyclonic, southeast wind, and the absence of or actual
distance of significant Plains storm systems will temper local wind
strength to under small craft advisory criteria.



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