Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 201738
AFDBRO

Area Forecast Discussion
National Weather Service Brownsville TX
1138 AM CST Tue Feb 20 2018

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

&&

.AVIATION...Winds have likely already hit their peak for the day,
as WSR-88D Velocity Wind Profile showing a slow decreasing trend
over the past hour in the SSE winds a few thousand feet off the
deck. Sustained winds have been edging down recently, but remain
gusty (up to 30 knots), and that should continue through much of
the afternoon. High-end MVFR ceilings should become VFR within the
next hour or two.

Very moist air up to about 020, with drier air above, should lead
to a return of low clouds tonight. Fairly high confidence on IFR
CIG`s moving into BRO around midnight, but lower confidence
further inland where MVFR likely to prevail. CIG`s expected to
begin lifting by mid-morning on Wednesday as SE winds pick up
again. Can`t rule out a stray shower overnight, either, but effect
would be short-lived and low-impact.

&&

.PREV DISCUSSION... /issued 1001 AM CST Tue Feb 20 2018/

DISCUSSION...Updated for latest marine discussion below.

MARINE...Cancelled Small-Craft Advisory (SCA) for the Gulf
waters early, with even far offshore buoys indicating seas of 6-7
feet and wave-model guidance showing a definitive subsiding trend
the remainder of the day. Maintained Small-Craft Exercise Caution
on all of the Lower Texas Coastal Waters, for remnant seas of 4-6
ft. on the Gulf and winds on the Laguna Madre already in the
15-20 knot range. Bumped up wind grids on the Laguna to account
for this as well. Will have to monitor for a possible short-fuse
SCA there this afternoon, but will hold off issuance for now.
Thanks to CRP for marine coordination this morning.

PREV DISCUSSION... /issued 550 AM CST Tue Feb 20 2018/

DISCUSSION...Updated for latest aviation discussion below.

AVIATION...Multiple cloud layers continue to sweep across the
region this morning, keeping lowest cloud layer from thickening.
Expect the lowest layer, around 1000 feet, so continue fluctuating
btwn SCT and BKN through midmorning before lifting. Morning
sounding showed low level jet still in the vicinity, with 35 knot
winds at 1000 feet. This has kept surface winds at 15 knots
overnight. Breezes will again rise during the day today, but the
gradual shifting of the llvl jet further offshore will limit
mixing of stronger winds to the surface over land areas this
afternoon.

PREV DISCUSSION... /issued 359 AM CST Tue Feb 20 2018/

SHORT TERM (Now through Wednesday): The highly amplified
midlevel pattern remains in place across the US through the next
36 hours, with a trough along the Rockies and ridging centered
just off Florida. This is inducing the next area of low pressure
dropping into the Texas Panhandle. Breezy southeast winds will
dominate again today, but not quite as brisk as yesterday. Highs
will again reach the upper 80s areawide. The next cold front will
slowly drop southward across Texas today, bringing an increasing
chance for showers and thunderstorms tonight into tomorrow
morning. The front will stall just off to the north, holding most
of the precipitation to the northern and western valley. While
best dynamics remain off to the north, still some midlevel
impulses that may be able to enhance showers to spark some thunder
near the front. The weakening front will still be in the region
Wednesday, but a lack of upper level support will keep rain
chances minimized through sunset.

LONG TERM (Wednesday Night through Monday): 500mb trough across
the western United States and a 500mb ridge across the southeast
U.S. Wednesday will continue to provide a southwest flow aloft
across the state Thursday and Friday before the upper trough moves
across the central U.S. Saturday. At the surface...a weak cold
front moves into south Texas Wednesday before stalling just north
of the CWA Wed night. Showers and thunderstorms will develop along
the front and move into the northern ranchlands Wed night. The
convective boundary will lift northward Thursday and rain chances
will diminish across the CWA Thursday into Thurs night as the
front washes out and lifts northward. The focus for convection
will remain well to the north of the Rio Grande valley Friday
before another cold front moves through south TX Saturday. Will
not mention any rain chances Friday and Fri night and mention a
slight chance of showers and thunderstorms Saturday. Elevated
convection is expected to develop across the CWA Sat night in the
wake of the front. The rest of the forecast period is dependent on
the frontal boundary draped across the area as the GFS and the
ECMWF differ on the location of the front with the ECMWF farther
north than the GFS. Will mention a slight chance to chance of
showers or thunderstorms through the rest of the weekend into
early next week as low to mid level moisture remains high across
northeast Mexico/deep south TX through Monday.

MARINE (Now through Wednesday): Marine conditions still
producing higher swells across the Gulf waters this morning.
Advisories will remain in effect for the open Gulf through noon,
when seas will relax to 4 to 6 feet. The cold front will encroach
on the marine areas after sunset, with lighter winds expected into
the day Wednesday. With the front in the vicinity, some shower
and thunderstorm activity is expected, especially later tonight.

Wednesday night through Saturday...Light to moderate southeast
winds will prevail across the coastal waters Wed night into
Thursday as a weak cold front across south Texas allows the
pressure gradient to weaken across the lower TX coast. Winds
should increase slightly from the southeast Thurs night into
Friday as the pressure gradient increases slightly as the front
weakens and retreats northward. Moderate southeast winds will
prevail across the western Gulf of Mexico Friday and increase Fri
night before veering to the south on Saturday. Small craft
advisories may be needed for the offshore waters Fri night into
Saturday.

&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...None.
GM...None.
&&

$$

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