Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 232300

Area Forecast Discussion
National Weather Service Brownsville TX
600 PM CDT Mon Apr 23 2018

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


.AVIATION...VFR ceilings expected to continue through Tuesday
afternoon with high pressure in place and some thinning of mid-
level clouds expected overnight. Chance of fog remains too low to
include into the TAFs at this time and will be monitored for
mainly BRO and HRL early Tuesday morning.


.PREV DISCUSSION... /issued 239 PM CDT Mon Apr 23 2018/

SHORT TERM (Now through Tuesday Night): Quiet weather will
prevail with surface high pressure in place over the NW Gulf of
Mexico and flat ridging/zonal flow aloft. Mid-level cloud is
progged to continue thinning into the evening with some high
cirrus continuing to stream by overnight. GFS and HRRR hinting
that a shortwave trough aloft may speed by in the moderately fast
zonal flow and initiate some convection over the Mexican plateau
this evening. Guidance keeps any QPF south of the Rio Grande so
will just insert some silent 10% PoP`s.

The combination of near-surface moisture and light winds may
allow some patchy, shallow fog to develop across mainly eastern
portions of the Rio Grande Valley and northern Ranchlands during
the wee hours of Tuesday morning. Signals in the model guidance
are mixed on this, though. Will retain the inherited areas and
expand northward to match up with WFO/CRP. Not really expecting
visibilities to fall below about 3SM anywhere, though. Overnight
lows will range from the mid-upper 60s along the Rio Grande to
around 60 near Falfurrias and Sarita.

Moderate southeast surface flow returns by mid-day Tuesday as
surface high center moves offshore. Moisture in the atmospheric
column thins out somewhat, so skies should be sunnier than today.
This should in turn allow afternoon temps to nudge up from today`s
readings, with mid-upper 80s along the Hwy. 77/I-69E corridor and
low-mid 90s far west. Partly cloudy and mild on Tuesday night, as
dewpoints creep up into the mid-upper 60s on continued SE flow.
No precipitation is expected, though.

LONG TERM (Wednesday through Monday): Quiet weather will continue
Wednesday, with a short wave trough digging south over the
central high Plains and an underlying cold front moving south over
central and south Texas. A mid level ridge will be positioned
over the Southwest United States with surface high pressure over
the northwest Gulf. The weak cold front will push across the area
late Wednesday night to Thursday morning, with just enough
moisture, instability, and lift to potentially generate a few non-
severe thunderstorms late Wednesday night through Thursday
morning. The ECMWF appears a little more aggressive with rainfall
for the upper valley Wednesday night as the front pushes toward
the coast around dawn Thursday morning.

Once the front clears the area Thursday, high pressure will build
in, with light onshore flow into Friday. As high pressure shifts
east, winds will return to southeast. The rich low level return
moisture combined with westerly mid level flow with embedded
minor perturbations over northern Mexico may keep the threat of
isolated convection in the picture through the weekend. Daytime
high temps will be near normal Thursday through the weekend as
increased cloud cover and onshore flow temper the heat.

Now through Tuesday Night: Favorable boating conditions are
expected through the short-term. Buoy 42020 reported northeast
winds of 10-12 knots with seas of 2-3 feet and a period of 5
seconds as 1:50 PM CDT. Surface high pressure will prevail across
the western Gulf of Mexico through Tuesday night. A weak pressure
gradient will support light east to southeast winds, becoming more
moderate Tuesday night, and low seas around 2 feet through the

Wednesday through Saturday night: Light to moderate east to
southeast winds and low to moderate seas will prevail Wednesday
through Wednesday night. Winds will turn to light northeast or
east late Wednesday night or Thursday morning as a weak cold
front passes across the area, bringing the possibility of a few
showers to the marine areas. Winds will then remain light to
moderate northeast to east with low to moderate seas through
Saturday night as high pressure spreads over the northwest Gulf.
Advisory condition chances will be low during this period.




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